The present invention relates to a toothbrush.
　This application claims priority based on Japanese Patent Application No. 2018-246150 filed in Japan on December 27, 2018, the contents of which are incorporated herein by reference.
Background technology
[0002]
　While the percentage of people at the age of 80 who have 20 teeth is about 50%, the percentage of elderly caries (root caries) is increasing. Root caries is caries of dentin exposed by gingival recession, but since dentin has a higher composition ratio of organic components than enamel, caries progresses quickly. One of the causes of the gingival recession is overbrushing, in which brushing is performed with a brushing pressure larger than the appropriate value.
[0003]
　Since the brushing pressure is defined by the load / flocking area, reducing the brushing pressure can be achieved by at least one of reducing the load and increasing the flocking area. To reduce the load, a toothbrush with specifications designed to tilt the neck part above the flocked surface in advance so that the neck part bends when brushing and the neck part becomes straight when brushing, and a toothbrush with a small diameter. There are commercially available toothbrushes with soft specifications using the above, and toothbrushes with specifications that make it difficult for force to be applied to the flocked portion by arranging the center of gravity of the grip portion closer to the rear end of the handle. Further, for increasing the flocked area, a toothbrush or the like having a wide head width is commercially available. However, in these specifications, although it is possible to reduce the brushing pressure, it is difficult to make all users recognize the appropriate brushing pressure at the same level and control the brushing pressure.
[0004]
　In addition, although the proper brushing method is instructed at the dentist's office, it is difficult to deal with it by oneself because it is not clear how much force is applied. It turns out that there are not a few users who do not.
[0005]
　Therefore, as a means for making the user recognize the appropriate brushing pressure, for example, the toothbrush disclosed in Patent Document 1 can be mentioned. The toothbrush disclosed in Patent Document 1 is arranged between the head portion and the grip portion, and has a two-beam structure of a rear beam to which compressive stress is applied and a facial beam to which tensile stress is applied during normal use. There is.
[0006]
　In this toothbrush, when the user grips the grip, the rear beam to which a compressive force exceeding the determined force is applied is elastically buckled and convex downward from an upwardly convex arc. Invert to a circular arc. As described above, the toothbrush disclosed in Patent Document 1 can make the user recognize that the appropriate brushing pressure has been exceeded by reversing the rear beam.
Prior art literature
Patent documents
[0007]
Patent Document 1: Japanese Patent Application Laid-Open No. 6-504937
Outline of the invention
Problems to be solved by the invention
[0008]
　However, in the toothbrush disclosed in Patent Document 1 described above, when an excessive brushing load is applied, the rear beam is deformed in a direction approaching the facial beam, so that the amount of deformation of the rear beam is limited and general purpose. The sex is not enough. In addition, if the rear beam comes into contact with the facial beam when an excessive brushing load is applied, the usability deteriorates.
[0009]
　The present invention has been made in consideration of the above points, and an object of the present invention is to provide a toothbrush capable of recognizing an appropriate brushing pressure with high versatility and good usability.
Means to solve problems
[0010]
　According to the first aspect of the present invention, a head portion provided on the distal end side in the long axis direction and having a fluffed surface, a grip portion arranged on the rear end side of the head portion, and the fluffed surface and the grip portion. It has a neck portion arranged between the two, and a sensing portion for detecting that the external force in the first direction orthogonal to the flocked surface exceeds a predetermined value is provided on the rear end side of the flocked surface. The sensing unit has a displacement amount of the head portion when a load is applied to the head portion to the back surface side opposite to the flocked surface in the first direction, and a repulsive force generated according to the displacement amount. In relation to the above, the repulsive force is changed from an increase to a decrease at the first threshold value according to the increase in the displacement amount, and the displacement amount is larger than the first threshold value at the second threshold value. When the decrease of the repulsive force is stopped and the repulsive force is A when the displacement amount is the first threshold value and B is the repulsive force when the displacement amount is the second threshold value, B / A is used. Toothbrushes are provided characterized in that the values ​​represented are 0.3 or more and 0.9 or less.
[0011]
　Further, in the toothbrush according to one aspect of the present invention, the repulsive force A is 1.0 N or more and 5.0 N or less.
[0012]
　Further, in the toothbrush according to one aspect of the present invention, where C is the displacement amount at the first threshold value and D is the displacement amount at the second threshold value, the value represented by DC is , 0 mm or more and 1.5 mm or less.
[0013]
　Further, in the toothbrush according to one aspect of the present invention, the displacement amount C is 28 mm or less.
[0014]
　Further, in the toothbrush according to one aspect of the present invention, the sensing unit is characterized in that when the displacement amount exceeds the second threshold value, the repulsive force is increased according to the increase in the displacement amount. And.
[0015]
　Further, in the toothbrush according to one aspect of the present invention, the rate of increase of the repulsive force from the displacement amount at the second threshold value to the displacement amount of the head portion of 4 mm is 0.015 or more. It is characterized by being.
[0016]
　Further, in the toothbrush according to one aspect of the present invention, the sensing unit applies a load to the back surface side to stop the decrease of the repulsive force at least, and then releases the load after the release. The relationship between the displacement amount and the repulsive force is characterized by maintaining the same relationship as before the load is applied.
[0017]
　Further, in the toothbrush according to one aspect of the present invention, the sensing portion connects the first region on the distal end side of the sensing portion and the second region on the rear end side of the sensing portion. With the displacement of the head portion to the back side opposite to the flocked surface in the first direction due to the external force exceeding the threshold value, the inverted portion jumps, buckles and reverses, and the inverted portion. The inverted portion is provided with an elastically deformed portion that is arranged with a gap between the portion and the portion, connects the first region and the second region, and elastically deforms at least up to the external force in which the inverted portion jumps, buckles, and reverses. The portion is characterized in that it is located between the outer contour on the flocked surface side and the outer contour on the back surface side of the elastically deformed portion in the side view seen in the long axis direction and the direction orthogonal to the first direction. And.
　Further, in the toothbrush according to one aspect of the present invention, the path in which the elastically deformed portion is deformed by the external force in the first direction and the path in which the inverted portion is deformed by the external force in the first direction do not interfere with each other. It is characterized by being provided.
[0018]
　Further, in the toothbrush according to one aspect of the present invention, the elastically deformed portion and the inverted portion are arranged with a gap in the second direction orthogonal to the first direction and the major axis direction, respectively. It is characterized by that.
[0019]
　Further, in the toothbrush according to one aspect of the present invention, the inverted portion has a convex shape toward the back surface when the external force in the first direction is equal to or less than the predetermined value, and the external force in the first direction is the predetermined value. It is characterized in that when the value is exceeded, it is inverted into a convex shape toward the flocked surface side.
[0020]
　Further, in the toothbrush according to one aspect of the present invention, the inverted portion has a groove portion extending in the second direction on at least one of the flocked surface side and the back surface side in the region including the apex of the convex shape. It is characterized by that.
[0021]
　Further, in the toothbrush according to one aspect of the present invention, the inverted portion is formed of a hard resin, and a part of the elastically deformed portion is formed of a resin having a hardness different from that of the hard resin. It is characterized by.
[0022]
　Further, in the toothbrush according to one aspect of the present invention, the gap is a through hole extending in the first direction.
The invention's effect
[0023]
　INDUSTRIAL APPLICABILITY The present invention can provide a toothbrush capable of recognizing an appropriate brushing pressure with high versatility and good usability.
A brief description of the drawing
[0024]
FIG. 1 is a view showing an embodiment of the present invention and is a front view of the toothbrush 1.
FIG. 2 is a cross-sectional view of the toothbrush 1 cut along a plane including a center in the width direction.
FIG. 3 is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the width direction.
FIG. 4 is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the long axis direction.
FIG. 5 is a partial front view of the periphery of the sensing portion 70 in the rigid portion 70H.
FIG. 6 is a partial side view of the periphery of the sensing portion 70 in the rigid portion 70H.
FIG. 7 is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the major axis direction to explain that the inverted portion has been inverted.
FIG. 8 is a diagram showing the relationship between the pushing amount (mm) measured by the autograph tester and the bending repulsive force (N).
FIG. 9 is a perspective view showing a sensing portion 70 of the toothbrush 1.
Embodiment for carrying out the invention
[0025]
　Hereinafter, embodiments of the toothbrush of the present invention will be described with reference to FIGS. 1 to 9.
　It should be noted that the following embodiments show one aspect of the present invention, do not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of ​​the present invention. Further, in the following drawings, in order to make each configuration easy to understand, the scale and number of each structure are different from the actual structure. Further, in the following description, the side orthogonal to the flocked surface in the side view will be the vertical direction, the flocked surface side will be the upper side, and the back side opposite to the flocked surface will be the lower side. In addition, the vertical direction, the upper side, and the lower side are names used only for explanation, and do not limit the actual positional relationship and direction in the present invention.
[0026]
　FIG. 1 is a front view of the toothbrush 1. FIG. 2 is a cross-sectional view of the toothbrush 1 cut along a plane including the center in the width direction (vertical direction in FIG. 1).
[0027]
　The toothbrush 1 of the present embodiment has a head portion 10 arranged on the tip side in the long axis direction (hereinafter, simply referred to as the tip side) and having hair bundles (not shown) implanted, and the length of the head portion 10. The neck portion 20 extended to the rear end side in the axial direction (hereinafter, simply referred to as the rear end side), the sensing portion 70 extending to the rear end side of the neck portion 20, and the rear end side of the sensing portion 70. It includes an extended grip portion 30 (hereinafter, the head portion 10, the neck portion 20, the grip portion 30, and the sensing portion 70 are collectively referred to as a handle body 2).
[0028]
　The toothbrush 1 of the present embodiment is a molded body in which a hard portion H formed of a hard resin and a soft portion E formed of a soft resin are integrally molded. The hard portion H constitutes at least a part of each of the head portion 10, the neck portion 20, the grip portion 30, and the sensing portion 70. The soft portion E constitutes a part of each of the grip portion 30 and the sensing portion 70 (details will be described later).
[0029]
[Head portion 10] The
　head portion 10 has a flocked surface 11 on one side in the thickness direction (direction orthogonal to the paper surface in FIG. 1). Hereinafter, the flocked surface 11 side in the thickness direction will be the front side in the front direction, the side opposite to the flocked surface will be the back side, and the direction orthogonal to the thickness direction and the long axis direction will be the width direction (or as appropriate). , Side direction). A plurality of flocked holes 12 are formed on the flocked surface 11. Hair follicles (not shown) are planted in the hair-planting holes 12.
[0030]
　The width of the head portion 10, that is, the length in the width direction parallel to the flocked surface 11 on the front side and orthogonal to the long axis direction (hereinafter, simply referred to as width) is not particularly limited, and is, for example, 7 mm or more and 13 mm or less. Is preferable. When it is at least the above lower limit value, a sufficient area for planting hair bundles can be secured, and when it is at least the above upper limit value, operability in the oral cavity can be further improved.
[0031]
　The length of the head portion 10 in the major axis direction (hereinafter, simply referred to as a length) is not particularly limited, and is preferably 10 mm or more and 33 mm or less, for example. When the length of the head portion 10 is not less than the above lower limit value, a sufficient area for planting hair bundles can be secured, and when it is not more than the above upper limit value, the operability in the oral cavity can be further enhanced. The boundary between the neck portion 20 and the head portion 10 in the major axis direction in the present embodiment is a position where the width of the neck portion 20 is the minimum value from the neck portion 20 toward the head portion 10.
[0032]
　The length of the head portion 10 in the thickness direction (hereinafter, simply referred to as thickness) can be determined in consideration of the material and the like, and is preferably 2.0 mm or more and 4.0 mm or less. When the thickness of the head portion 10 is at least the above lower limit value, the strength of the head portion 10 can be further increased. When the thickness of the head portion 10 is not more than the above upper limit value, the reachability to the back of the molars can be enhanced and the operability in the oral cavity can be further enhanced.
[0033]
　A hair bundle is a bundle of a plurality of hairs. The length (hair length) from the flocked surface 11 to the tip of the hair bundle can be determined in consideration of the hair waist and the like required for the hair bundle, and is, for example, 6 to 13 mm. All hair bundles may have the same hair length or may be different from each other.
[0034]
　The thickness (hair bundle diameter) of the hair bundle can be determined in consideration of the hair waist and the like required for the hair bundle, and is, for example, 1 to 3 mm. All hair bundles may have the same hair bundle diameter or may be different from each other.
[0035]
　As the hair that constitutes the hair bundle, for example, the diameter of the hair gradually decreases toward the tip of the hair, and the tip of the hair is sharpened (tapered hair). Examples include the same hair (straight hair). Examples of straight hair include those having a flat surface substantially parallel to the flocked surface 11 and those having hemispherically rounded hair tips.
[0036]
　The material of the hair is, for example, polyamide such as 6-12 nylon (6-12NY), 6-10 nylon (6-10NY), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT). ), Polyester such as polyethylene terephthalate (PEN) and polybutylene terephthalate (PBN), polyolefins such as polypropylene (PP), polyolefin-based elastomers, and elastomer resins such as styrene-based elastomers. These resin materials can be used alone or in combination of two or more. Further, as the hair, a polyester hair having a multi-core structure having a core portion and at least one layer or more of a sheath portion provided on the outside of the core portion can be mentioned.
[0037]
　The cross-sectional shape of the hair is not particularly limited, and may be a circular shape such as a perfect circle or an ellipse, a polygonal shape, a star shape, a three-leaf clover shape, a four-leaf clover shape, or the like. The cross-sectional shapes of all hairs may be the same or different.
[0038]
　The thickness of the hair can be determined in consideration of the material and the like, and when the cross section is circular, it is, for example, 6 to 9 mil (1 mil = 1/1000 inch = 0.025 mm). Further, in consideration of usability, brushing feeling, cleaning effect, durability and the like, a plurality of hairs having different thicknesses may be used in any combination.
[0039]
[Neck portion 20]
　The length of the neck portion 20 is preferably 40 mm or more and 70 mm or less in terms of operability.
　As an example, the width of the neck portion 20 is formed so as to gradually increase from the position where the minimum value is obtained to the rear end side. The neck portion 20 in the present embodiment is formed so as to gradually increase from the position where the width becomes the minimum value toward the rear end side. Further, the neck portion 20 is formed so that the thickness gradually increases from the position where the thickness becomes the minimum toward the rear end side.
[0040]
　The width and thickness of the neck portion 20 at the minimum position are preferably 3.0 mm or more and 4.5 mm or less. If the width and thickness of the neck portion 20 at the minimum position is equal to or more than the above lower limit value, the strength of the neck portion 20 can be further increased. And the operability in the oral cavity can be further improved. The width and thickness of the neck portion 20 formed so as to gradually increase toward the rear end side from the position where the minimum value is obtained can be appropriately determined in consideration of the material and the like.
[0041]
　The front side of the neck portion 20 in the side view is inclined toward the front side toward the rear end side. The back side of the neck portion 20 in the side view is inclined toward the back side toward the rear end side. The neck portion 20 is inclined in a direction in which the distance from the center in the width direction increases toward the rear end side in the front view.
[0042]
　The boundary between the neck portion 20 and the sensing portion 70 in the present embodiment is the position of the tip of the neck side 20 where the elastically deformed portion 90 described later is provided. Here, the width expands from the neck portion 20 toward the grip portion 30 with an arcuate contour in both front view and side view, and the position of the center of curvature of the arc coincides with the changed position in the long axis direction. There is. More specifically, the boundary between the neck portion 20 and the sensing portion 70 is one with the position in the major axis direction in which the center of curvature changes from the outside of the arcuate contour to the center side in the width direction in the front view shown in FIG. I am doing it. Further, the boundary between the neck portion 20 and the sensing portion 70 coincides with the position in the major axis direction in which the center of curvature changes from the outside of the arcuate contour to the center side in the thickness direction in the side view shown in FIG. There is.
[0043]
[Grip portion 30] The
　grip portion 30 is arranged along the long axis direction. As shown in FIG. 1, the length of the grip portion 30 in the width direction gradually narrows toward the rear end side from the boundary with the sensing portion 70, and then extends at a substantially constant length. As shown in FIG. 2, the length of the grip portion 30 in the thickness direction gradually narrows from the boundary with the sensing portion 70 toward the rear end side, and then extends at a substantially constant length.
[0044]
　The boundary between the sensing portion 70 and the grip portion 30 in the present embodiment is the position of the tip of the grip portion side 30 on which the elastically deformed portion 90 described later is provided. Here, the width is reduced from the sensing portion 70 toward the grip portion side 30 by an arcuate contour in both front view and side view, and the position of the center of curvature of the arc coincides with the changed position in the long axis direction. ing. More specifically, the boundary between the sensing portion 70 and the grip portion 30 is the position in the long axis direction in which the center of curvature changes from the center side in the width direction to the outside of the arcuate contour in the front view shown in FIG. Match. Further, the boundary between the sensing portion 70 and the grip portion 30 coincides with the position in the major axis direction in which the center of curvature changes from the center side in the thickness direction to the outside of the arcuate contour in the side view shown in FIG. ..
[0045]
　The length in the width direction of the grip portion 30 gradually narrows from the boundary with the sensing portion 70 toward the rear end side, and then becomes a substantially constant length. The positions in the long axis direction are the same so that the length gradually narrows from the boundary with the sensing unit 70 toward the rear end side and then becomes a substantially constant length.
[0046]
　The grip portion 30 has a soft portion 31E in the center in the width direction on the front side. The soft portion 31E constitutes a part of the soft portion E. The soft portion 31E gradually narrows from the boundary with the sensing portion 70 toward the rear end side in the front view, and then extends at a substantially constant length. In front view, the side edge of the soft portion 31E and the lateral edge of the grip portion 30 in the width direction are formed at a substantially constant distance.
[0047]
　The grip portion 30 has a hard portion 30H. The hard portion 30H constitutes a part of the hard portion H. The hard portion 30H has a recess 31H in which a part of the soft portion 31E is embedded on the front side. The recess 31H gradually narrows from the boundary with the sensing portion 70 toward the rear end side in the front view, and then extends at a substantially constant length.
[0048]
　A part of the soft portion 31E protrudes from the hard portion 30H exposed on the front side. The other soft portion 31E is substantially flush with the hard portion 30H exposed on the front side.
[0049]
　The grip portion 30 has a soft portion 32E in the center in the width direction on the back surface side (see FIGS. 1 and 2). The soft portion 32E constitutes a part of the soft portion E. The soft portion 32E has substantially the same outer contour as the outer contour of the soft portion 31E when viewed from the front. That is, the soft portion 32E gradually narrows toward the rear end side from the boundary with the sensing portion 70, and then extends at a substantially constant length. In the rear view, the side edge of the soft portion 32E and the lateral edge of the grip portion 30 in the width direction are formed at a substantially constant distance.
[0050]
　The hard portion 30H has a recess 32H (see FIG. 2) in which a part of the soft portion 32E is embedded on the back surface side. The recess 32H gradually narrows from the boundary with the sensing portion 70 toward the rear end side in the rear view, and then extends at a substantially constant length.
[0051]
　A part of the soft portion 32E protrudes from the hard portion 30H exposed on the back surface side. The other soft portion 32E is substantially flush with the hard portion 30H exposed on the front side.
[0052]
　Since the soft portion 31E is provided on the front side of the grip portion 30 and the soft portion 32E is provided on the back side, the grip property when gripping the grip portion 30 is improved.
[0053]
[Sensing unit 70] The
　sensing unit 70 senses that the external force in the first direction orthogonal to the flocked surface 11 exceeds a predetermined value (hereinafter, external force threshold value). The sensing unit 70 increases the displacement amount by increasing the relationship between the displacement amount of the head unit 10 when a load is applied to the back surface side of the head unit 10 in the thickness direction and the repulsive force generated according to the displacement amount. Accordingly, the repulsive force is changed from increasing to decreasing at the first threshold value, and the decrease of the repulsive force is stopped at the second threshold value where the displacement amount is larger than the first threshold value (details will be described later).
[0054]
　As shown in FIG. 1, the sensing portion 70 has a reversing portion 80 and an elastic deformation portion 90 that connect a neck portion 20 on the distal end side of the sensing portion 70 and a grip portion 30 on the rear end side of the sensing portion 70. doing.
[0055]
　FIG. 3 is a cross-sectional view of the sensing portion 70 cut in a plane parallel to the thickness direction and the width direction. FIG. 4 is a cross-sectional view of the sensing portion 70 cut along a plane parallel to the thickness direction and the long axis direction.
　As shown in FIG. 3, the elastically deformed portions 90 are provided with gaps S on both sides of the reversing portion 80 in the width direction. The gap S is formed by a through hole K penetrating in the thickness direction. As shown in FIG. 1, the through hole K is formed in a rectangular shape in a plan view extending in the long axis direction.
[0056]
　By providing the gap S, the reversing portion 80 can be inverted (easily inverted) without interfering with the surrounding structure. Further, since the deformation of the reversing portion 80 does not follow the deformation of the elastic deforming portion (because it does not interfere), the functional roles (described later) of the reversing portion 80 and the elastic deforming portion 90 can be made independent. This makes it possible to increase the degree of freedom in design for obtaining the following effects, for example. For example, vibration / sound when the reversing unit 80, which will be described later, is reversed can be clearly generated. Further, if the gaps S are communicated with both sides of the reversing portion 80 in the thickness direction so as not to interfere with the reversing behavior of the reversing portion 80, the above effect is further improved. By widening the gap S in the thickness direction, the vector of the load applied to the brush portion (brush) during brushing, the direction in which the gap opens, and the direction in which the reversing portion 80 and the elastically deforming portion 90 are deformed become parallel ( (See FIG. 7), for example, it becomes easy to link the generation of vibration / sound due to inversion with the brushing load. Further, if the gap S is penetrated between the front side and the back side by the through hole K, for example, the movable region of the elastically deformed portion 90 which is responsible for the bending function of the toothbrush skeleton with respect to the load at the time of brushing can be further expanded. (The tensile behavior on the front surface and the compression behavior on the back surface due to bending are less likely to be hindered). When the through hole K does not exist between the elastically deformed portion 90 and the inverted portion 80, the movable region of the elastically deformed portion 90 becomes narrow. In this case, the reversing unit 80 is not given an opportunity to reverse in an appropriate load range, and the reversing unit 80 inverts before reaching an appropriate load range, or does not invert even in an appropriate load range. is assumed. On the other hand, by providing the through hole K between the elastically deformed portion 90 and the reversing portion 80, it is possible to control the "external force threshold" at which the reversing portion 80, which will be described later, reverses, in a finer range. .. The gap S does not have to penetrate in the thickness direction, and may be formed, for example, by a closed cavity extending in the major axis direction inside the elastically deformed portion 90. Further, it may be formed by a recess (described later) that opens on the front side or the back side.
[0057]
　Each elastically deformed portion 90 has a hard portion 90H and a soft portion 90E. As shown in FIG. 1, the hard portion 90H and the soft portion 90E connect the rear end of the neck portion 20 and the front end of the grip portion 30. As shown in FIGS. 3 and 4, between the pair of elastically deformed portions 90, a recess (recess) 71 that opens on the front side and a recess (recess) 72 that opens on the back side are provided. The bottoms of the recess 71 and the recess 72 on both ends in the width direction are connected to the through hole K, respectively. A reversing portion 80 is exposed and provided at the bottom of the recess 71 and the center in the width direction in the recess 72. By providing the recesses 71 and 72, for example, the movable region of the elastically deformed portion that bears the bending function of the toothbrush skeleton with respect to the load during brushing can be further expanded, and the bending anisotropy in the thickness direction can be improved. The recesses between the pair of elastically deformed portions 90 may not penetrate in the thickness direction, and may be opened in only one of the thickness directions. Further, for example, a closed cavity extending in the long axis direction may be formed inside the elastic deformation portion 90, and the cavity may be sandwiched in the center to form a pair of elastic deformation portions in the width direction.
[0058]
　In the pair of elastically deformed portions 90, the ends of the soft portions 90E in the major axis direction are connected to each other in the width direction on both the front side and the back surface side. The soft portions 90E of the pair of elastically deformed portions 90 are provided around the oval recesses 71 and 72 when viewed from the front. The rear end side of the soft portion 90E is connected to the soft portion 31E of the grip portion 30.
[0059]
　Since the soft portion 90E is connected in the width direction on both the front end side and the rear end side of the elastically deformed portion 90, stress is less likely to be concentrated on the end of the inverted portion 80 even if the inversion is repeated, and the bending is less likely to occur. Further, since the soft portion 90E is connected in the width direction, the amount of heat possessed by the soft resin (elastomer) during injection molding increases, so that the adhesiveness between the neck portion 20 and the sensing portion 70 (the neck portion 20 and the elastically deformed portion 90) is enhanced. .. Further, since the soft portions 90E are connected in the width direction on both the front end side and the rear end side of the elastic deformation portion 90, the anisotropy in the sensing portion 70 is increased, and for example, the pair of elastic deformation portions 90 moves during brushing. On the other hand, it becomes possible to bend without twisting in the thickness direction.
[0060]
　FIG. 5 is a partial front view of the sensing portion 70 around the hard portion 70H. FIG. 6 is a partial side view of the sensing portion 70 around the hard portion 70H.
　As shown in FIG. 5, the hard portion 70H is formed in a rectangular shape in a plan view connecting the hard portion 20H which is the neck portion 20 and the hard portion 30H of the grip portion 30 in the long axis direction.
[0061]
　As shown in FIG. 6, the front end side of the hard portion 70H is connected to the hard portion 20H by a curved surface 73H having an arc shape in a side view. The rear end side of the front side of the hard portion 70H is connected to the hard portion 30H by a curved surface 74H having an arc shape in a side view. The arc centers of the curved surfaces 73H and 74H are located on the front side of the hard portion 70H in the side view. The tip end side of the hard portion 70H on the back surface side is connected to the hard portion 20H by a curved surface 75H having an arc shape in a side view. The rear end side of the hard portion 70H on the back surface side is connected to the hard portion 30H by a curved surface 76H having an arc shape in a side view. The arc centers of the curved surfaces 75H and 76H are located on the back side of the hard portion 70H in the side view.
[0062]
　When the curved surfaces 73H to 76H do not exist, stress may be concentrated on the boundary between the front end side of the hard portion 70H and the hard portion 20H and the boundary between the rear end side of the hard portion 70H and the hard portion 30H. On the other hand, the presence of the curved surfaces 73H to 76H alleviates the concentrated stress. Further, due to the presence of the curved surfaces 73H to 76H, both the elastic deforming portion 90 and the front end side and the rear end side of the reversing portion 80 can be flexibly deformed (the elastic deforming portion 90 that triggers the reversal). The degree of deformation can be sensed in more detail).
[0063]
　The hard portion 70H has through holes 73 provided on both sides of the reversing portion 80 in the width direction. The through holes 73 extend in the major axis direction, respectively. The length of the through hole 73 in the major axis direction is such that the distal end side end portion of the through hole 73 is separated from the hard portion 20H and the rear end side end portion of the through hole 73 is separated from the hard portion 30H. As shown in FIG. 3, of the through holes 73, a soft portion 90E is provided near the hard portion 90H in the width direction, and a through hole K is formed near the inverted portion 80 in the width direction.
[0064]
　In the hard portion 70H, 90H is arranged on both sides in the width direction with the reversing portion 80 as the center via the through holes 73, so that even if a load is applied and the elastic deforming portion 90 is deformed, the shape of the reversing portion 80 is formed. Can be maintained. When the hard portion H constituting the toothbrush 1 over the entire length is bent, the reversing portion 80 of the sensing portion 70 is inverted in an attempt to release the accumulated strain energy. For example, when the hard portion 70H is connected to the neck portion 20 and the grip portion 30 only by the reversing portion 80, the energy cannot be stored and the portion is immediately inverted. When the reversing portion 80 is integrally injection-molded with the first region A1 and the second region A2, which will be described later, the neck portion 20, the grip portion 30, and the hard portion 70H, the accumulated strain energy is efficiently transferred to the reversing portion. Can be communicated.
[0065]
　The hard portion 90H is formed outside the hard portion 70H in the width direction with respect to the through hole 73. As shown in FIG. 3, the hard portion 90H has a substantially rectangular cross-sectional shape. The hard portion 90H is embedded in the soft portion 90E. Since the hard portion 90H is embedded in the soft portion 90E, the stress applied to the hard portion 90H can be relaxed from the viewpoint of strength. Further, the elastic behavior of the elastically deformed portion 90 can be controlled from the viewpoint of the degree of bending of the toothbrush 1 with respect to the load. Further, the bending anisotropy of the sensing portion 70 is increased, and for example, it is possible to bend the elastic deformation portion 90 without twisting in the thickness direction with respect to the movement during brushing.
[0066]
　Examples of the material of the hard portion H include a resin having a flexural modulus (JIS7171) of 1500 MPa or more and 3500 MPa or less, and examples thereof include polyacetal resin (POM). The flexural modulus of the hard portion H is more preferably 2000 MPa or more and 3500 MPa or less. By using a material having a high elastic modulus (for example, POM), even if the shape is made thin or thin, when an excessive load is applied, jumping buckling occurs and vibration is generated. Further, by using a material having a high elastic modulus, it is possible to quickly return to the initial state (a state in which the bending of the elastically deformed portion 90 is released) after buckling occurs.
[0067]
　As the material of the soft portion E, a material having a shore hardness A of 90 or less is preferable, and a shore hardness A is preferably 90 or less, in that the load when jumping buckling occurs is close to the recommended brushing load value. Those of 50 to 80 are more preferable. Examples of the soft resin include elastomers (for example, olefin-based elastomers, styrene-based elastomers, polyester-based elastomers, polyurethane-based thermoplastic elastomers, etc.) and silicones. A styrene-based elastomer is preferable because it has excellent miscibility with a polyacetal resin.
[0068]
　As shown in FIG. 5, the reversing portion 80 extends in the long axis direction in the front view, and the first region A1 on the distal end side of the through hole 73 in the hard portion 70H and the second region A1 on the rear end side of the through hole 73. It is connected to the area A2. The reversing portion 80 has a first stable state (hereinafter, first) shown in FIG. 4 in which an external force to the back surface side is not applied to the head portion 10 (or an external force equal to or lower than a predetermined external force threshold value described later is applied). In the state (referred to as a state), it is formed in a substantially V shape in a side view that gradually inclines toward the back surface side from both ends in the long axis direction toward the center. That is, in the first state, the reversing portion 80 is formed in a convex shape on the back surface side where the center in the major axis direction is the apex.
[0069]
　For example, when an external force to the back surface side is applied to the head portion 10 while the grip portion 30 is gripped, when the magnitude of the external force is in the first state equal to or less than a predetermined external force threshold value, the sensing unit 70 may use the sensing unit 70. The elastically deformed portion 90 and the inverted portion 80 are elastically deformed according to the magnitude of the external force.
[0070]
　That is, when an external force to the back surface side is applied to the head portion 10, the sensing portion 70 has a displacement amount of the head portion 10 according to the magnitude of the external force and a repulsive force (deflection repulsive force) generated according to the displacement amount. ), The repulsive force is changed from an increase to a decrease at the first threshold value according to the increase in the displacement amount of the head portion 10, and the displacement amount of the head portion 10 is larger than the first threshold value. At the threshold value, the decrease in repulsive force is stopped.
[0071]
　When the magnitude of the external force exceeds a predetermined external force threshold value and the displacement amount of the head portion 10 exceeds the first threshold value, the elastically deformed portion 90 responds to the magnitude of the external force exceeding the external force threshold value. It is elastically deformed. On the other hand, when the magnitude of the external force exceeds a predetermined external force threshold value and the displacement amount of the head portion 10 exceeds the first threshold value, the reversing portion 80 has a neck as shown by a two-dot chain line in FIG. When the portion 20 is deformed, it jumps, buckles, and inverts to a second stable state (hereinafter referred to as a second state). In the second state, the reversing portion 80 is reversed in a direction in which it gradually inclines toward the front side toward the center and becomes a substantially inverted V-shape in side view. In the second state, the reversing portion 80 is formed in a convex shape on the front side where the center in the major axis direction is the apex.
[0072]
　When the reversing unit 80 shifts from the first state to the second state, the energy stored in the reversing unit 80 is released by the time the reversing unit 80 reaches the second state, so that the displacement amount of the head unit 10 increases. The repulsive force decreases. Further, since the reversing portion 80 is in a stable state when it is in the second state, the decrease in the repulsive force is stopped.
[0073]
　That is, when the magnitude of the external force exceeds a predetermined external force threshold value, the elastically deformed portion 90 elastically deforms, so that the bending strength of the sensing portion 70 is secured, and the inverted portion 80 starts from the first state. It jumps, buckles, reverses, and enters the second state. Further, since the through hole K is provided between the reversing portion 80 and the elastically deforming portion 90, the reversing portion 80 and the elastically deforming portion 90 can be deformed independently of each other, and the reversing portion 80 can be easily inverted. Become. That is, since the through hole K is provided when a brushing load is applied, the reversing portion 80 can be flexed after only the elastic member 90 is first flexed without hindering each other's deformation behavior. It should be noted that the space between the reversing portion 80 and the elastically deforming portion 90 does not necessarily have to penetrate, and a gap S may be formed.
[0074]
　The user who grips the grip portion 30 joins the back surface of the head portion 10 due to the vibration and the decrease in the repulsive force when the reversing portion 80 jumps, buckles and flips, and shifts from the first state to the second state. It is possible to detect that the external force to the side is in an overbrushing state that exceeds the external force threshold value.
[0075]
　Even after the reversing portion 80 jumps from the first state, buckles and reverses to the second state, an external force is applied to the head portion 10, and the increased displacement amount of the head portion 10 is larger than the first threshold value. When the large second threshold value is exceeded, the repulsive force increases in a state where the reversing portion 80 in which the decrease in the repulsive force is stopped at the second threshold value is formed in a convex shape on the front side in the second state. Since the repulsive force increases in the state where the reversing portion 80 is formed in a convex shape on the front side in the second state, the continuous brushing pressure behavior is quickly restored even if the external force applied to the head portion 10 decreases. It is possible to suppress the occurrence of operational problems. Therefore, the user who grips the grip portion 30 has a repulsive force in which the displacement amount of the head portion 10 is reduced beyond the first threshold value, and then the displacement amount of the head portion 10 is the second threshold value. Therefore, the change in the repulsive force is sensed in two stages with the repulsive force at which the decrease has stopped, and it is possible to more accurately detect the overbrushing state. When an external force (load) to the back surface side is applied to the sensing unit 70, at least after stopping the decrease in the repulsive force, when the load is released, the displacement amount of the head unit 10 after release. The relationship between and repulsive force maintains the same relationship as before the load was applied.
[0076]
　Here, assuming that the repulsive force when the displacement amount of the head portion 10 is the first threshold value is A (N) and the repulsive force when the displacement amount is the second threshold value is B (N), B / A. The values ​​represented by are preferably 0.3 or more and 0.9, and more preferably 0.65 or more and 0.85 or less. When the value represented by B / A is less than 0.3, the attenuation from the repulsive force A to the repulsive force B is large, which may impair the usability. Further, when the displacement amount of the head portion 10 increases beyond the second threshold value, the repulsive force increases significantly, which may impair the usability. When the value represented by B / A exceeds 0.9, the attenuation from the repulsive force A to the repulsive force B is small, and it may not be possible to recognize that the overbrushing state is present. Therefore, by setting the value represented by B / A to 0.3 or more and 0.9 or less, the displacement amount of the head portion 10 increases beyond the second threshold value without impairing the usability. It is possible to fully recognize the repulsive force and detect that it is in an overbrushing state.
[0077]
　The repulsive force A is preferably 1.0 N or more and 5.0 N or less, more preferably 1.5 N or more and 4.0 N or less, and preferably 1.5 N or more and 3.0 N or less. More preferred. If the repulsive force A is less than 1.0 N, sufficient cleaning force may not be obtained. If the repulsive force A exceeds 5.0 N (about 500 g), it may cause harm to the gingiva. Therefore, by setting the repulsive force A to 1.0 N or more and 5.0 N or less, a sufficient cleaning force can be secured and the harmfulness to the gingiva can be suppressed. Further, the value of the repulsive force A is set to a value within the above-mentioned preferable range and not exceeding the recommended brushing pressure described later.
[0078]
　Assuming that the displacement amount of the first threshold value is C (mm) and the displacement amount of the second threshold value is D (mm), the values ​​represented by DC are 0 mm or more and 1.5 mm or less. Is more preferable, and it is more preferably 0 mm or more and 1.0 mm or less, and further preferably 0 mm or more and 0.5 mm or less. When the value represented by DC exceeds 1.5 mm, the displacement amount of the head portion 10 exceeds the first threshold value and the repulsive force decreases, and then the displacement amount of the head portion 10 becomes the second. The amount of displacement until the repulsive force increases beyond the threshold value becomes large, and the synergistic effect of recognizing the change in the repulsive force in two steps may diminish. That is, there is a possibility that the sharp change in the repulsive force when the first threshold value is exceeded may be felt dull. Therefore, by setting the value represented by DC to 0 mm or more and 1.5 mm or less, the repulsive force can be changed in two stages at a short distance without impairing the usability, and the overbrushing state is achieved. You can accurately sense that.
[0079]
　The displacement amount C of the first threshold value is preferably 28 mm or less. If the displacement amount C exceeds 28 mm, the amount of bending during brushing becomes large, and it becomes difficult for the user to clean the oral cavity. Therefore, by setting the displacement amount C to 28 mm or less, it is possible to secure the role of oral cleaning. The displacement amount C of the first threshold value is more preferably 24 mm or less. Further, the lower limit of the displacement amount C is more preferably 10 mm or more. By setting the lower limit of the displacement amount C to 10 mm or more, the brushing load applied to the gingiva can be relaxed. Further, the repulsive force up to the displacement amount C preferably increases in proportion to the displacement amount, and the proportional relationship does not change even when the displacement amount C is approached (the degree of increase in the repulsive force does not become loose). Is more preferable. Specifically, the rate of increase in the repulsive force for each displacement amount of 1 mm up to the displacement amount C is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.09 or more. As a result, in the region up to the displacement amount C that reaches the upper limit pressure, the pressure assumed by the user is easily reflected in the repulsive force as it is, so that the brushing load can be appropriately controlled. If the degree of increase in the repulsive force gradually becomes loose in the vicinity of the displacement amount C, the user may unintentionally continue brushing at a pressure near the upper limit.
[0080] [0080]
　Starting from the displacement amount D of the second threshold value, the rate of increase in the repulsive force until the displacement amount of the head portion 10 becomes 4 mm is preferably 0.015 or more. When the rate of increase in the repulsive force from the displacement amount D of the second threshold value to the displacement amount of the head portion 10 becomes 4 mm is less than 0.015, the increase in the repulsive force after the reversing portion 80 is reversed is small and used. The feeling may be impaired. Therefore, by setting the rate of increase of the repulsive force from the displacement amount D of the second threshold value to the displacement amount of the head portion 10 of 4 mm to 0.015 or more, the usability is maintained even after the reversing portion 80 is inverted. It is possible to continue brushing without damaging it.
[0081]
　The reversing portion 80 has a groove portion 81 in the center in the long axis direction on the front side, that is, in a region including the apex of the convex shape. The reversing portion 80 has a groove portion 82 in the center in the long axis direction on the back surface side, that is, in a region including the apex of the convex shape. The grooves 81 and 82 extend in the width direction. The groove portion 81 is formed in an arc shape in a side view in which the center of the arc is arranged on the front side. The groove portion 82 is formed in an arc shape in a side view in which the center of the arc is arranged on the back surface side. When the groove portions 81 and 82 are not provided in the reversing portion 80, stress is uniformly generated in the entire reversing portion 80, and jumping buckling is less likely to occur. On the other hand, when the grooves 81 and 82 are provided in the reversing portion 80, stress is intensively generated in the grooves 81 and 82, and jumping buckling is likely to occur.
[0082]
　The radius of the arc-shaped grooves 81 and 82 when viewed from the side is preferably 1 mm or more and 2 mm or less. If the radius of the groove portions 81 and 82 is less than 1 mm, the reversing portion 80 may not be inverted. When the radius of the groove portions 81 and 82 exceeds 2 mm, the vibration of the reversing portion 80 at the time of reversing becomes small, and it may be difficult to detect that the reversing portion 80 is in the overbrushing state.
[0083]
　As for the depth of the groove portions 81 and 82, it is preferable that the groove portion 81 is deeper than the groove portion 82. When the groove portion 82 is deeper than the groove portion 81, the reversing portion 80 is less likely to reverse even when the magnitude of the external force exceeds a predetermined external force threshold value. Further, when the groove portion 81 is deeper than the groove portion 82, the reversing portion 80 can be guided so as to be more likely to jump and buckle on the front side.
　It should be noted that the configuration may be such that both the groove portions 81 and 82 are not provided, but the groove portion 82 is not provided and only the groove portion 81 is provided.
[0084]
　Since the inversion portion 80 is provided with the groove portions 81 and 82 in the region including the convex apex, the region including the convex apex is thinner than the other regions. Therefore, the strain energy accumulated by the deformation of the reversing portion 80 due to the external force exceeding the external force threshold value can be instantly released from the groove portions 81 and 82 as the starting point, and the reversing portion 80 can be inverted. Further, by adjusting the positions of the groove portions 81 and 82 in the thickness direction, it is possible to adjust the position where the reversing portion 80 reverses from the first state to the second state.
[0085]
　Further, since the groove portions 81 and 82 are formed in an arc shape in a side view, for example, as compared with the case where the groove portions 81 and 82 are formed in a V shape on two intersecting planes, the inverted portion 80 including the groove portions 81 and 82 is formed. The stress concentration at the apex can be relaxed even when the apex moves in the thickness direction.
[0086]
　The external force threshold value of the external force applied to the head portion 10 on the back surface side is, for example, an upper limit value of an appropriate brushing pressure. This external force threshold value corresponds to the first threshold value in the displacement amount of the head portion 10 described above.
[0087]
　As shown in FIG. 4, the angle θ at which the reversing portion 80 is tilted with respect to the plane parallel to the major axis direction and the width direction is preferably 5 degrees or more and 11 degrees or less, and 7 degrees or more and 11 degrees. It is more preferably less than or equal to the degree. When the inclination angle θ is less than 5 degrees, the reversing portion 80 jumps and deforms without buckling, which may make it difficult to detect the overbrushing state. When the inclination angle θ exceeds 11 degrees, the reversing section 80 jumps and buckles due to the overbrushing pressure, making it difficult to flip, or when the flipping section buckles and flips, the flipping section 80 jumps and buckles. It may break and lose its reversibility.
[0088]
　The thickness of the reversing portion 80 is preferably 1 mm or more and 2 mm or less, excluding the groove portions 81 and 82. If the thickness of the reversing portion 80 is less than 1 mm, although it is deformed, it does not jump and buckle, and it may be difficult to detect that it is in an overbrushing state. If the thickness of the reversing portion 80 exceeds 2 mm, the reversing portion 80 jumps and buckles due to the overbrushing pressure, making it difficult to reverse, or the reversing portion 80 breaks when the reversing portion 80 jumps and buckles and reverses. And there is a possibility that the reversibility will be lost.
[0089]
　Assuming that the maximum thickness of the reversing unit 80 is T (mm) and the maximum thickness of the sensing unit 70 is t (mm), an excessive brushing load is applied by specifying a value expressed in T / t. At this time, it becomes possible to control the ease of reversing of the reversing unit 80 and its timing (external force threshold value). The value represented by T / t is preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. When the value represented by T / t is less than 0.05, the reversing part 80 also deforms in a form that follows the bending of the sensing part 70 (elastic deformation part 90), but it does not jump and buckle, so that it is overbrushed. It can be difficult to detect the condition. If the value represented by T / t exceeds 0.35, the reversible portion 80 jumps and buckles due to the overbrushing pressure, making it difficult to flip, or jumps and buckles and breaks when flipped. Therefore, there is a possibility that the reversibility of the inversion unit 80 will be lost.
[0090]
　That is, by setting T / t within the above range, the bending strength of the reversing portion 80 becomes flexible at a constant ratio with respect to the elastic deforming portion 90, and the bending strength of the elastic deforming portion 90 that bears the handle skeleton is delayed. It becomes possible to operate the reversing portion 80 slightly. This makes it possible to control the ease of reversing of the reversing unit 80 and the timing (external force threshold value) that triggers the reversing of the reversing unit 80 even when an excessive brushing load is applied.
[0091]
　As shown in FIG. 3, assuming that the maximum width of the reversing unit 80 is L (mm) and the maximum width of the sensing unit 70 is W (mm), by specifying a value represented by L / W, for example, When an excessive brushing load is applied, it becomes possible to control the ease of reversing of the reversing unit 80 and its timing (external force threshold value). The values ​​represented by L / W are preferably 0.05 or more and 0.35 or less, and more preferably 0.10 or more and 0.35 or less. When the value represented by L / W is less than 0.05, the reversing part 80 also deforms in a form that follows the bending of the sensing part 70 (elastic deformation part 90), but it does not easily jump and buckle, and is in an overbrushing state. It can be difficult to perceive that. When the value represented by L / W exceeds 0.35, the inverted portion 80 is less likely to be deformed and inverted due to the bending of the handle body 2 that occurs in the range of normal brushing. Therefore, there is a possibility that the reversing portion 80 jumps and buckles due to the overbrushing pressure, making it difficult to reverse, or when the reversing portion 80 jumps and buckles and reverses, it breaks and the reversibility of the reversing portion 80 is lost. .. That is, by setting L / W within the above range, the bending strength of the reversing portion 80 becomes flexible at a constant ratio with respect to the elastic deforming portion 90, and the bending strength of the elastic deforming portion 90 that bears the handle skeleton is delayed. It becomes possible to operate the reversing portion 80 slightly. Therefore, even when an excessive brushing load is applied, it is possible to control the ease of reversing of the reversing unit 80 and the timing (external force threshold value) that triggers the reversing of the reversing unit 80.
[0092]
　The length of the reversing portion 80 in the major axis direction is preferably 15 mm or more and 30 mm or less, more preferably 15 mm or more and 25 mm or less, and further preferably 15 mm or more and 20 mm or less. The position of the tip side end portion of the reversing portion 80 is the position of the tip end side end portion of the through hole 73. The position of the rear end side end portion of the reversing portion 80 is the position of the rear end side end portion of the through hole 73. When the length of the reversing part 80 in the major axis direction is less than 15 mm, the reversing part 80 jumps and buckles under normal brushing pressure, making it difficult to reverse and jumping buckling, which is necessary. It may not be possible to cause deformation. When the length of the reversing part 80 in the long axis direction exceeds 30 mm, the displacement required for jumping and buckling becomes very large, so that the usability is greatly reduced and the deformation behavior of the reversing part 80 is elastically deformed. There is a possibility that the behavior will be the same as that of the part 90.
[0093]
　The reversing portion 80 is located between the outer contour of the flocked surface side 11 and the outer contour of the back surface side of the elastically deformed portion 90 in the side view. More specifically, the position of the reversing portion 80 in the thickness direction is such that the reversing portion 80 does not protrude from the thickness of the elastically deformed portion 90 in the side view so as not to form the outermost outer shell of the toothbrush. For example, it is possible to prevent the reversing portion from coming into contact with the user during use. Specifically, it is preferable that the elastically deformed portion 90 is on the back side rather than the position where the thickness is halved. When the position in the thickness direction of the reversing portion 80 is on the back side of the position where the thickness of the sensing portion 70 is halved, the apex of the reversing portion 80 is in the second state when the reversing portion 80 is inverted. Can reduce the possibility that the elastically deformed portion 90 protrudes from the front surface of the elastically deformed portion 90 and comes into contact with the user's finger. Further, since the reversing portion 80 is arranged on the back surface side from the position where the thickness of the elastically deformed portion 90 is halved, the back surface side is compressed more than the front side when the reversing portion 80 is bent, for example. , The energy that triggers the inversion is likely to be accumulated, and the strain energy can be efficiently transferred to the inversion unit 80.
[0094]
　By setting the flexural modulus to 1500 MPa or more, the reversing portion 80 forming a part of the hard portion H can jump and buckle to detect that it is in an overbrushing state. Further, by setting the flexural modulus of the reversing portion 80 to 3500 MPa or less, it is possible to prevent the reversible portion 80 from losing its reversibility due to breakage when it jumps and buckles and reverses. Further, by using a material having a specified flexural modulus, vibrations due to jumping and buckling are intensively generated in a short time and become sharp (sharp, large). As a result, the user can easily detect that it is overbrushing.
[0095]
　The moving distance of the convex apex in the thickness direction when the inverted portion 80 jumps and buckles is preferably 0.2 mm or more and 5.0 mm or less. If the moving distance of the apex in the thickness direction is less than 0.2 mm, the vibration at the time of jumping and buckling becomes small, and it may be difficult to detect the overbrushing state. When the moving distance of the apex in the thickness direction exceeds 5.0 mm, the reversible portion 80 jumps and buckles due to the overbrushing pressure, making it difficult to flip, or when the flipping buckles and flips. There is a possibility that it will break and the reversibility of the reversing portion 80 will be lost. If the moving distance of the reversing portion 80 is within the above range when the jumping buckling occurs, the vibration generated by the jumping buckling occurs intensively in a short time and becomes sharp (sharp, large). As a result, the user can easily detect that it is overbrushing.
[0096]
　The thickness of the hard portion 90H in the elastically deformed portion 90 is preferably 2.0 mm or less, and the width is preferably larger than the thickness. When the thickness of the hard portion 90H is 2.0 mm or less, the hard portion 90H is in a plane stress state, so that the hard portion 90H is less likely to generate internal stress. As a result, even if it is deformed, it is less likely to break, and it becomes possible to sufficiently store the energy required for the inversion of the inversion portion 80.
[0097]
　Further, in the toothbrush 1 of the present embodiment, since the reversing portion 80 and the elastic deforming portion 90 are arranged with a gap in the width direction, the sensing portion 70 is more easily deformed to the front side and the back side, and the length is long. It is possible to obtain a plane stress state in which there is almost no deformation in the axial direction and the width direction. That is, in the toothbrush 1 of the present embodiment, the direction in which the reversing portion 80 and the elastic deforming portion 90 are deformed is the thickness direction separated from each other in the width direction, and the toothbrush 1 does not exist on the same plane. In other words, the path in which the elastically deformed portion 90 is deformed by the external force in the thickness direction and the path in which the reversing portion 80 is deformed by the external force in the thickness direction are provided in a non-interfering manner. Therefore, in the toothbrush 1 of the present embodiment, the elastic deforming portion 90 and the reversing portion 80 are less likely to be constrained by each other and can be deformed, so that the energy required for reversing the reversing portion 80 can be more sufficiently stored. , Stress is intensively generated in the reversing portion 80 (particularly the groove portions 81 and 82), and sharp jump buckling is developed.
[0098]
　Further, in the toothbrush 1 of the embodiment, since the toothbrush 1 is suppressed from being shaken in the width direction, the bending in the thickness direction due to brushing can be transmitted to the reversing portion 80 without loss. Further, by arranging the inversion portion 80 and the elastic deformation portion 90 in the width direction, the bending of the elastic deformation portion 90 and the inversion of the inversion portion 80 can be made independent and the timing can be shifted. If the elastically deformed portion 90 and the inverted portion 80 are arranged in the thickness direction, the roles of the elastically deformed portion 90 and the inverted portion 80 may be hindered from each other.
[0099]
　As described above, in the toothbrush 1 of the present embodiment, the displacement amount of the head portion 10 when a load is applied to the back surface side in the thickness direction of the head portion 10, and the repulsive force generated according to the displacement amount. When the displacement amount is less than or equal to the first threshold value, the repulsive force is increased according to the increase in the displacement amount, and when the displacement amount is larger than the first threshold value and less than or equal to the second threshold value, the displacement amount is increased. A sensing unit 70 is provided to reduce the repulsive force as the displacement increases, and the values ​​represented by B / A are 0.3 or more and 0.9 or less, so that the repulsion is achieved with high versatility and good usability. It is possible to fully recognize the force and detect that it is in an overbrushing state.
[0100]
[Deformation example of the sensing unit 70] In the
　above embodiment, the configuration in which the sensing unit 70 has the elastic deformation unit 90 and the reversing unit 80 are exemplified, but the configuration is not limited to this, and for example, due to an external force in the thickness direction. It may have a configuration having both a function of elastic deformation and a function of jumping and buckling.
[0101]
　FIG. 9A is a front view showing a modified example of the sensing unit 70. FIG. 9B is a side view showing a modified example of the sensing unit 70. 9 (c) is a right side view of FIG. 9 (a). In FIGS. 9A to 9C, the neck portion 20 and the grip portion 30 are not shown.
　As shown in FIG. 9A, the sensing unit 70 of the modified example is formed in a rectangular shape in front view. The sensing unit 70 has a recess 70a that opens on the front side. As shown in FIG. 9B, the sensing unit 70 has an arcuate curved surface 70b having a convex shape on the back side in a side view. In the side view, the center of curvature of the curved surface 70b is located on the front side in the thickness direction further than the end portion in the major axis direction of the curved surface 70b. The center of curvature of the curved surface 70b in the side view is located at the center of the sensing portion 70 in the long axis direction. The crossing angle (crossing angle of a small value) between the tangent of the curved surface 70b and the straight line parallel to the long axis direction in the side view is 0 ° (that is, parallel) at the center of the long axis direction. The crossing angle between the tangent of the curved surface 70b and the straight line parallel to the long axis direction in the side view gradually increases from the center in the long axis direction toward the end. Since the center of curvature of the curved surface 70b is located on the front side in the thickness direction from the long axis direction end of the curved surface 70b in the side view, the tangent line of the curved surface 70b and the straight line parallel to the long axis direction are formed in the side view. The intersection angle of is an acute angle or 0 °. The bottom surface of the recess 70a in a side view is a curved surface 70b and a curved surface 70d arranged on the front side with a constant width.
[0102]
　As shown in FIG. 9C, the sensing unit 70 has an arcuate curved surface 70c having a convex shape on the back side when viewed from the right side. In the right side view, the center of curvature of the curved surface 70c is located on the front side in the thickness direction with respect to the widthwise end portion of the curved surface 70c. The center of curvature of the curved surface 70c in the right side view is located at the center of the sensing portion 70 in the width direction. The crossing angle (small value crossing angle) between the tangent of the curved surface 70c and the straight line parallel to the width direction in the right side view is 0 ° (that is, parallel) at the center of the width direction. The crossing angle between the tangent of the curved surface 70c and the straight line parallel to the width direction in the right side view gradually increases from the center in the width direction toward the end. Since the center of curvature of the curved surface 70c is located on the front side in the thickness direction from the widthwise end of the curved surface 70c in the right side view, the tangent line of the curved surface 70c and the straight line parallel to the width direction are formed in the right side view. The intersection angle of is an acute angle or 0 °. The bottom surface of the recess 70a in the right side view is a curved surface 70c and a curved surface 70e arranged on the front side with a constant width.
　As the material of the sensing unit 70 of the modified example, the above-mentioned hard resin, soft resin, metal or the like can be used. In the above sensing unit 70, the length and width in the long axis direction are not limited, but the maximum thickness is 5 mm or less. Further, in order to easily cause jump buckling, it is preferable to provide a through groove 70f indicated by a two-dot chain line extending in the long axis direction at the center position in the width direction of the sensing portion 70 and penetrating in the thickness direction. ..
[0103]
　In the sensing unit 70 having the above configuration, when an external force is transmitted through the neck portion 20 and the surface is deformed to the back side, a curved surface 70b having a convex shape on the back side in side view and a curved surface having a convex shape on the back side in right side view. Since it has 70c and has a large bending strength toward the back surface in the thickness direction, it is elastically deformed as an elastically deformed portion by an external force equal to or less than the external force threshold value. On the other hand, since the sensing unit 70 has a maximum thickness of 5 mm or less and is thin, when an external force exceeding the external force threshold value is transmitted, the sensing unit 70 jumps and buckles as an inverted portion and reverses to a convex arc shape on the front side. As described above, the sensing unit 70 of the modified example can have both the function of elastically deforming by an external force in the thickness direction and the function of jumping and buckling without providing the elastically deformed portion and the reversing portion separately. ..
[0104]
[Examples]
　Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples, and may be appropriately modified and carried out without departing from the gist thereof. can.
[0105]
(Examples 1 to 9, Comparative Examples 1 to 4)
　Samples of Examples 1 to 9 and Comparative Examples 1 to 4 were prepared according to the specifications shown in [Table 1]. Example 4 is a sample of a toothbrush that does not have a soft portion of a sensing portion with respect to the sample of Example 1. Example 6 has no inversion portion with respect to the sample of Example 1, the proximal end is located in the second region on the rear end side of the sensing portion, and the first region on the distal end side of the sensing portion. It has a first engaging portion extending in the long axis direction toward the second region and a second engaging portion having a base end located in the first region and extending in the long axis direction toward the second region. When the external force in one direction is equal to or less than the threshold value, the external force is separated in the first direction, and the external force exceeding the threshold value is applied to the back surface side opposite to the flocked surface in the first direction. This is a sample that engages with the displacement of the head portion and the relative positional relationship in the first direction is reversed. Example 7 is a toothbrush sample in which the radius of the groove portions 81 and 82 of the inversion portion is changed from 1.5 mm to 2 mm with respect to the sample of Example 1. Example 9 is a sample of a toothbrush having a sensing portion of the modified example shown in FIG. 9 with respect to the sample of Example 1. In Comparative Example 1, "Tekiatsu-kun" manufactured by Wada Precision Dental Research Co., Ltd. was used as a sample. In Comparative Example 3, a toothbrush in which the gap S was filled with a soft resin was used as a sample with respect to the sample of Example 1. The flocked parts of the samples other than Comparative Example 1 had the same specifications as the Clinica Advantage Habrush manufactured by Lion Corporation.
[0106]
[Test method] For
　each sample, the grip portion 30 side was fixed from the boundary between the sensing portion 70 and the grip portion 30 so that the flocked surface of the head portion was horizontal. A test was conducted in which a load was applied to the flocked surface of the head portion on the back side in the thickness direction. For each test, an autograph tester (AGS-H, manufactured by SHIMADZU) was used as an evaluation device. In the test, when the finger contact portion on the most tip side of the grip portion of the toothbrush was chucked, the center of the front view of the flocked surface in the head portion was pushed by the presser at a test speed of 100 mm / min, and the inverted portion was inverted. The pushing amount (displacement amount of the head portion) and the load (repulsive force) were measured. The test was carried out three times for each sample, and the average value was used.
[0107]
[Evaluation method] A
　questionnaire was conducted after using each sample for one week. The survey was conducted by 10 panelists. There are five questionnaire items: "awareness of vibration", "feeling of use immediately after vibration", "harmfulness to gums", "feeling of plaque falling in the mouth", and "operability in the mouth". So, each was evaluated on a 7-point scale. The average score obtained in each sample was used as the evaluation result and is shown in [Table 1]. In each evaluation, a case where the average score exceeded 4.0 was regarded as a pass (OK), and a case where the average score was 4.0 or less was regarded as a fail (NG). Details of each evaluation item are described below.
[0108]
-Awareness
　of vibration An evaluation axis for whether or not the user notices the vibration of the sensing unit that occurs when the repulsive force A is attenuated to the repulsive force B. The vibration referred to here means a short-time and sharp (sharp, large) vibration generated by jumping buckling.
　For this vibration, it is very difficult to understand (1 point), very difficult to understand (2 points), slightly difficult to understand (3 points), neither (4 points), slightly easy to understand (5 points), very easy to understand (5 points). It was evaluated on a 7-point scale (6 points) and very easy to understand (7 points).
[0109]

　-Usage feeling immediately after vibration This is an evaluation axis for the usability immediately after vibration generated from the sensing unit. If the attenuation from the repulsive force A to the repulsive force B does not interfere with the series of toothpaste behaviors, the feeling of use is good, and if it becomes a major obstacle, the feeling of use is bad.
　Very bad (1 point), very bad (2 points), slightly bad (3 points), neither (4 points), slightly good (5 points), very good (6 points), for this feeling of use. It was evaluated on a 7-point scale, which was very good (7 points).
[0110]
・ Harmfulness to the gums
　Immediately before the vibration generated from the sensing part occurs, and in the process up to that point (up to the first threshold value), the evaluation axis of whether or not there is harmfulness to the gums due to toothpaste behavior. be.
　For this reason, there is very (1 point), some (2 points), some (3 points), neither (4 points), almost none (5 points), no (6 points), and none at all. It was evaluated on a 7-point scale of (7 points).

The scope of the claims
[Claim 1]
　It has a head portion provided on the tip side in the long axis direction and having a fluffed surface, a grip portion arranged on the rear end side of the head portion, and a neck portion arranged between the fluffed surface and the grip portion. and,
　on the rear end side of the flocked surface, sensing unit external force is sensed that exceeds a predetermined value in the first direction is provided perpendicular to the bristle face,
　the sensing unit,
　the second to the head portion The relationship between the displacement amount of the head portion when a load is applied to the back surface side opposite to the flocked surface in one direction and the repulsive force generated according to the
　displacement amount is increased in the displacement amount. Accordingly, the repulsive force is changed from increasing to decreasing at
　the first threshold value, the decrease of the repulsive force is stopped at the second threshold value where the displacement amount is larger than the first threshold value, and the
　displacement amount is stopped. Assuming that the repulsive force when the first threshold value is A and the repulsive force when the displacement amount is the second threshold
　value is B, the value represented by B / A is 0.3 or more. A toothbrush characterized by being 0.9 or less.
[Claim 2]

　The toothbrush according to claim 1, 　wherein the repulsive force A is 1.0 N or more and 5.0 N or less .
[Claim 3]
　Wherein C the displacement amount in the first threshold value, the displacement amount in the second threshold value when is D,
　the value represented by D-C is, 0 mm or more and 1.5mm or less,
　claims The toothbrush according to 1 or 2.
[Claim 4]

　The toothbrush according to claim 3, 　wherein the displacement amount C is 28 mm or less .
[Claim 5]

　The toothbrush according to any one of claims 1 to 4, 　wherein the sensing unit increases the repulsive force in response to an increase in the displacement amount when the displacement amount exceeds the second threshold value .
[Claim 6]

　The toothbrush according to claim 5, 　wherein the rate of increase in the repulsive force is 0.015 or more until the displacement amount of the head portion reaches 4 mm, starting from the displacement amount at the second threshold value .
[Claim 7]
　When the sensing unit
　applies a load to the back surface side, stops the decrease of the repulsive force at least, and then releases the load, the relationship between the displacement amount after the release and the repulsive force applies the load.
　The toothbrush according to any one of claims 1 to 6 , which maintains the same relationship as before .
[Claim 8]
　The sensing unit connects
　the first region on the tip side of the sensing unit and the second region on the rear end side of the sensing unit, and the first is generated by the external force exceeding the threshold value. With the displacement of the head portion to the back surface side opposite to the flocked surface in the direction, the reversing portion that jumps, buckles and reverses, and the reversing portion are
　arranged with a gap between them and the first region. connecting a second region and, until the external force for inverting at least the reversing unit hopping seat yielded an elastic deformation part for elastically deformed,
　the inverting section, said long axis direction and the first direction
　The toothbrush according to any one of claims 1 to 7, which is located between the outer contour on the flocked surface side and the outer contour on the back surface side in the elastically deformed portion in a side view viewed in an orthogonal direction .
[Claim 9]

　The toothbrush according to claim 8 　, wherein the path in which the elastically deformed portion is deformed by the external force in the first direction and the path in which the inverted portion is deformed by the external force in the first direction are provided in a non-interfering manner .
[Claim 10]

　The toothbrush according to claim 8 or 9, 　wherein the elastically deformed portion and the inverted portion are arranged with a gap in a second direction orthogonal to the first direction and the major axis direction, respectively .
[Claim 11]

　The toothbrush according to claim 10 　, wherein the gap is a through hole extending in the first direction .
[Claim 12]
　The inverted portion has a convex shape toward the back surface when the external force in the first direction is equal to or less than the predetermined value, and has a convex shape toward the flocked surface side when the external force in the first direction exceeds the predetermined value.
　The toothbrush according to claim 10 or 11 , which is inverted to .
[Claim 13]

　The toothbrush according to claim 12, 　wherein the inverted portion has a groove portion extending in the second direction on at least one of the flocked surface side and the back surface side in a region including the apex of the convex shape .
[Claim 14]
　The toothbrush according to any one of claims 8 to 13, 　wherein the inverted portion is formed of a hard resin, and
　a part of the elastically deformed portion is formed of a resin having a hardness different from that of the hard resin.