Title of invention: Method and apparatus for manufacturing outer panel having character line
Technical field
[0001]
　The present invention relates to a manufacturing method and a manufacturing apparatus for an outer panel having a character line.
Background technology
[0002]
　For example, a door outer panel, a fender panel, a side panel, a hood outer panel, a back door outer panel and the like are known as outer panel of a vehicle body of an automobile. In recent years, providing a sharp character line on an outer panel, particularly an outer panel on the side surface of a vehicle body, is often used as one means for realizing an exterior design having high designability.
[0003]
　The character line is a convex ridge line (bent surface) formed by being sandwiched between at least two surfaces of the outer panel. In addition, the character line being sharp means that the radius of curvature of the curved surface is small, for example, 10 mm or less, or that the sandwiching angle that is the smaller angle of the two angles formed by the extended surfaces of the two surfaces is For example, it means a small value of 150° or less.
[0004]
　It is known that when a character line is provided on an outer panel by press working such as drawing or bulging, a line deviation, which is a poor quality of the outer panel surface, occurs.
[0005]
　14A and 14B are cross-sectional views that schematically and chronologically explain the occurrence of line misalignment. FIG. 14A shows the initial stage of molding, and FIG. 14B shows the state after completion of molding. Two black circles in FIG. 14B indicate two R stops of the character line 4a which is a curved surface. 14A and 14B, the blank 3 shows the center position in the plate thickness direction.
[0006]
　As shown in FIG. 14A and FIG. 14B, the outer panel 4 having the character line 4a is formed by pressing the blank 3 by drawing or stretching using the punch 1, the blank holder (not shown) and the die 2. It is manufactured by
[0007]
　As shown in FIG. 14A, in the initial stage of forming, the character line forming convex portion 1a provided in the punch 1 first comes into contact with the blank 3 at the initial blank contact portion, and the initial bending which is a local and minute concave portion. The part (also called bending tendency) 3a is generated. The initial bent portion 3a is a portion which should be a bent surface of the character line when the molding is completed.
[0008]
　In the stretch forming or the draw forming, the blank inflow amount into the punch 1 and the die 2 differs depending on the part of the blank 3. Therefore, a difference in tension acting on each of at least two surfaces constituting the character line is inevitably generated. Due to this difference in tension, the initial bent portion 3a moves and shifts from the convex portion 1a as the press working progresses. Therefore, the initial bent portion 3a remains as a recess 4a-2 substantially along the vicinity of the character line 4a-1 actually formed on the outer panel 4a when the forming is completed.
[0009]
　As described above, the line deviation is a phenomenon in which the initial bent portion 3a generated in the initial stage of molding is displaced from the original position in the molding process and is displaced, and remains even after the completion of molding. When the degree of line deviation, that is, the amount of movement of the initial bending portion 3a that occurs during the molding process is large, highlight folds are found at the line deviation occurrence part in the highlight surface inspection of the outer panel of the finished vehicle, and the outer surface quality It becomes defective.
[0010]
　The line shift is particularly likely to occur when the character line is sharp as described above. In recent years, the exterior design that has a sharp character line on the whole body has been widely used. For this reason, the line deviation is likely to occur.
[0011]
　Further, the line deviation is unlikely to occur in a high-strength steel blank having a tensile strength of 440 MPa or more, and tends to occur in a mild steel blank having a tensile strength of about 270 or 340 MPa.
[0012]
　For example, in the overhang molding of a door outer panel having a character line, the height and interval of the bead for preventing material inflow provided in the mold are made different depending on the parts of the mold as a measure for line deviation. However, a sufficient line shift suppressing effect has not been obtained.
[0013]
　Furthermore, the line deviation is sensory-evaluated visually by an inspector of the completed vehicle. Therefore, an error is inevitably included in the line shift inspection. Therefore, the applicant of the present invention has proposed a method for quantitatively evaluating the line deviation according to Patent Document 1.
[0014]
　In this method, first, the distribution of curvature (second-order differential coefficient of cross-sectional profile) is obtained based on the cross-sectional profile of the outer panel, and the second-order differential coefficient of curvature (fourth-order differential coefficient of cross-sectional profile) is obtained. Then, the value H [mm −3 ] at the peak of the second derivative of the curvature appearing at the line deviation occurrence portion, and the deviation width L [mm] between the position corresponding to the peak and the R stop position of the character line design value. And the amount of line deviation is quantitatively determined with the evaluation parameter S=L×|H| 1/3 . The quantitative evaluation result of the line deviation amount by the evaluation parameter S shows a high correlation with the sensory evaluation result by the inspector.
[0015]
　Patent Document 2 discloses a method of press forming a rear side outer panel having a character line using a punch, a split die having a first die and a second die, and a blank holder.
[0016]
　This method press-molds a portion including a character line on a blank with a first die and a punch. Next, while the formed character line is constrained by the first die and the punch, the remaining portion of the blank is press-formed by the second die and the punch. In this way, the character line is formed while suppressing the line deviation.
[0017]
　Patent Document 3 discloses a method of press-molding an outer panel having a sharp character line from a blank using a press die including a punch, a die and a blank holder.
[0018]
　In this method, a lining layer made of an elastic material is provided at the deepest valley line portion of the concave portion for forming the character line of the die, which is opposed to the convex portion for forming the character line of the punch. Then, the blank is formed while elastically deforming the lining layer at the forming bottom dead center where the punch comes closest to the die. As a result, the distribution of bending moments in the blank at the bottom dead center of molding is reduced, and the occurrence of line deviation is suppressed.
Prior art documents
Patent literature
[0019]
Patent Document 1: International Publication No. 2016/021685 Pamphlet
Patent Document 2: Japanese Patent Application Laid-Open No. 2008-100240
Patent Document 3: Japanese Patent Application Laid-Open No. 2015-96271
Summary of the invention
Problems to be Solved by the Invention
[0020]
　In the invention disclosed in Patent Document 2, when the constraint force of the character line by the second die is increased, the movement of the blank is suppressed when the part other than the character line is molded. Therefore, in a portion other than the character line, the blank is bent and the inflow is insufficient, so that defective molding is likely to occur. This molding failure is particularly likely to occur when molding a three-dimensionally curved character line.
[0021]
　Further, in the invention disclosed in Patent Document 2, since it is necessary to use a split die having a first die and a second die, the die cost increases.
[0022]
　Further, in the invention disclosed in Patent Document 2, a dividing line (split surface) between the first die and the second die may appear on the surface of the molded rear side outer panel. For this reason, there is a possibility that an outer plate surface quality defect different from the outer plate surface quality defect due to the line deviation may occur.
[0023]
　The invention disclosed in Patent Document 3 suppresses the occurrence of line deviation by elastically deforming the lining layer provided at the deepest valley line portion in the character line molding concave portion of the die at the molding bottom dead center. Therefore, it is possible to surely suppress the movement of the initial bent portion at the molding bottom dead center and its vicinity. However, it is not possible to suppress the movement of the initial bent portion other than the bottom dead center of the forming and its vicinity, that is, the movement of the initial bent portion in the forming process. Therefore, it is not possible to obtain a sufficient effect of suppressing the line deviation.
[0024]
　The present invention has been made in view of these problems of the conventional technique, and when manufacturing an outer panel having a character line by press working, it is accompanied by a large increase in die cost and defective molding. The purpose is to suppress or substantially eliminate line deviation.
Means for solving the problem
[0025]
　In order to suppress the line deviation, it is effective to (i) eliminate the generated initial bent portion and (ii) not move the generated initial bent portion in the molding process. The present inventors have conducted extensive studies from such a viewpoint, and as a result, obtained the findings A to D listed below with respect to the item (ii), and completed the present invention.
[0026]
(A) For a punch used for drawing or stretch forming, a high surface pressure generating portion that gives a high surface pressure to the blank and a surface pressure that the high surface pressure generating portion gives to the blank from the start of forming to the completion of forming. There is also a low surface pressure generating part that gives a low surface pressure to the blank.
[0027]
　For example, the convex portion for character line molding and the punch shoulder R portion are high surface pressure generating portions, and the low pressure is generated at the punch top and punch vertical wall portion excluding the convex portion for character line molding and the punch shoulder R portion. It is a department.
[0028]
　By partially increasing the coefficient of static friction with the blank in the high surface pressure generating portion of the punch and the peripheral region thereof, the frictional force between this region of the punch and the blank increases during press forming. This makes it difficult for the initial bent portion to move during the process of forming the character line.
[0029]
　For example, by increasing the coefficient of static friction with the blank in the convex portion for character line forming of the punch, movement in the vicinity of the initial bending portion can be suppressed, and by increasing the coefficient of static friction with the blank in the punch shoulder R portion, the initial bending The movement of the entire blank including the part can be suppressed.
[0030]
　As a result, the occurrence of line deviation in the outer panel having the character line can be suppressed or substantially eliminated.
[0031]
(B) Examples of the following (B1) and (B2) are examples of means for increasing the coefficient of dynamic friction with the blank in the high surface pressure generating portion of the punch and the peripheral region thereof.
　(B1) Particles having a Vickers hardness of 700 HV or more are provided in the high surface pressure generating portion of the punch and the peripheral area thereof.
　(B2) Protrusions are provided on the high surface pressure generating portion of the punch and the peripheral region thereof by appropriate means.
[0032]
(C) The means exemplified in the items (B1) and (B2) is an inner surface which is a non-designed surface of the outer panel in order to prevent deterioration of the design (beauty) of the outer surface of the outer panel to be molded. Perform on punches that come into contact with.
[0033]
(D) During press molding, the blank character line molding portion is not strongly constrained by the punch and die. For this reason, it is possible to prevent the occurrence of molding defects such as bending of the blank and insufficient inflow in portions other than the character line.
[0034]
　The present invention is as listed below.
(1) By using a punch and a blank holder and a die facing the punch and the blank holder, and pressing a blank arranged between the punch and the blank holder and the die by drawing or stretching. A method for manufacturing an outer panel having a character line that is a curved surface sandwiched between two surfaces,
　wherein the punch includes a convex portion for forming the curved surface at a punch top and a punch shoulder R portion. The
　surface pressure given to the blank by at least one of the convex portion and the punch shoulder R portion is equal to the surface pressure applied to the blank at the time of the press working.
　Coefficient of static friction with the blank in the first portion of the punch including at least one of the convex portion and the punch shoulder R portion is higher than the surface pressure applied to the punch. A method for manufacturing an outer panel having a character line, which is larger than the coefficient of static friction with the blank in the second portion.
[0035]
(2) The difference between the coefficient of static friction of the first portion with the blank and the coefficient of static friction of the second portion with the blank is 0.05 or more, and the outer panel having the character line according to item 1. Panel manufacturing method.
[0036]
(3) The static friction coefficient is a coefficient of static friction in a direction in which a recess formed in the blank when the convex portion first hits the blank moves in a molding process. Manufacturing method of board panel.
[0037]
(4) The method for manufacturing an outer panel having a character line according to any one of items 1 to 3, wherein at least one of the convex portion and the punch shoulder R portion has particles having a Vickers hardness of 700 HV or more.
[0038]
(5) The character according to item 4, wherein the punch includes a particle fixing portion having a holding layer that holds the particles, and the particle fixing portion is provided on at least one of the convex portion and the punch shoulder R portion. A method for manufacturing an outer panel having a line.
[0039]
(6) The method for manufacturing an outer panel having a character line according to item 4 or 5, wherein the embedding rate of the particles is 50 to 80%.
　However, the filling rate is calculated as (height of the holding layer/average particle diameter of the particles)×100 (%).
[0040]
(7) The method for manufacturing an outer panel having a character line according to item 6, wherein the average particle size of the particles is 5 to 600 μm.
[0041]
(8) The method for manufacturing an outer panel having a character line according to item 6 or 7, wherein the particle ratio of the fixed particles is 5 to 20%.
　However, the particle ratio is calculated as (total volume of the particles/volume of the particle fixing portion)×100 (%).
[0042]
(9) The method for manufacturing an outer panel having a character line according to any one of items 5 to 8, wherein the particle fixing portion is replaced with another particle fixing portion according to operating conditions.
[0043]
(10) The method for manufacturing an outer panel having a character line according to any one of items 4 to 9, wherein the particles come into contact with a non-designed surface which is an inner surface of the outer panel in the blank.
[0044]
(11) The method for manufacturing an outer panel having a character line according to any one of items 1 to 3, wherein at least one of the convex portion and the punch shoulder R portion has a protrusion.
[0045]
(12) The method for manufacturing an outer panel having a character line according to item 11, wherein the height of the protrusion is 0.02 to 0.10 mm.
[0046]
(13) The method for manufacturing an outer panel having a character line according to item 11 or 12, wherein the protrusion is in contact with a non-designed surface which is an inner surface of the outer panel in the blank.
[0047]
(14) A punch and a blank holder, and a die facing the punch and the blank holder are provided,
　and a blank arranged between the punch and the blank holder and the die is subjected to press working by drawing or stretching.
　Is a device for manufacturing an outer panel having a character line that is a curved surface sandwiched by at least two surfaces, wherein the punch has a convex portion for molding the curved surface at the top of the punch and a punch shoulder R. And
　a surface pressure applied to the blank at the time of the press working by at least one of the convex portion and the punch shoulder R portion is such that the remaining portion of the punch excluding the convex portion and the punch shoulder R portion is the press working portion.
　The static friction coefficient with the blank in the first portion of the punch, which is higher than the surface pressure applied to the blank at times and further includes at least one of the convex portion and the punch shoulder R portion, excludes the first portion. An apparatus for manufacturing an outer panel having a character line, which has a larger static friction coefficient with the blank in the second portion of the punch.
Effect of the invention
[0048]
　According to the present invention, when producing an outer panel having a character line, particularly a sharp character line by press working, without significantly increasing the die cost, while suppressing the occurrence of molding defects, The line shift can be suppressed or substantially eliminated.
Brief description of the drawings
[0049]
FIG. 1 is an exploded perspective view showing an example of a manufacturing apparatus before starting molding.
FIG. 2 is a cross-sectional view showing the configuration of the manufacturing apparatus according to the first embodiment.
FIG. 3 is an enlarged view of a particle fixing part provided on the top of the punch.
FIG. 4 is an explanatory diagram showing a situation in which a punch is looked up from below.
FIG. 5 is an explanatory diagram showing an operation of the manufacturing apparatus 1.
FIG. 6 is an explanatory diagram showing an operation of the manufacturing apparatus 1.
FIG. 7 is an explanatory diagram showing an operation of the manufacturing apparatus 1.
FIG. 8 is a cross-sectional view schematically showing the configuration of a manufacturing apparatus 1 of another mode.
FIG. 9A is an explanatory diagram showing an arrangement of a plurality of protrusions provided, and FIG. 9B is an explanatory diagram showing dimensions of the protrusions.
FIG. 10 is a graph showing the relationship between the nominal surface pressure and the friction coefficient depending on the presence or absence of protrusions.
11A is a plan view showing a region A in which particles are provided in Example 1, and FIG. 11B is a cross-sectional view taken along the line AA of FIG. 11A.
FIG. 12 is a graph showing the results of Example 1.
FIG. 13 is a graph showing the results of Example 2.
FIG. 14A and FIG. 14B are cross-sectional views for schematically explaining the occurrence of line deviation.
MODE FOR CARRYING OUT THE INVENTION
[0050]
　The present invention will be described. In the following description, the case where the outer panel is a door outer panel is taken as an example. The present invention is not limited to door outer panels, and is similarly applied to outer panel panels such as fender panels, side panels, hood outer panels, and back door outer panels.
[0051]
　FIG. 1 is an exploded perspective view showing an example of the manufacturing apparatus 1 before the start of molding.
　As shown in FIG. 1, the manufacturing apparatus 1 includes a punch 2, a blank holder 4 and a die 3.
[0052]
　The die 3 is arranged to face the punch 2 and the blank holder 4. The punch 2, the blank holder 4 and the die 3 are subjected to press forming by drawing or stretch forming on a blank (not shown) arranged between the punch 2 and the blank holder 4 and the die 3 to form a door outer panel ( (Not shown) is manufactured.
[0053]
　The blank is a metal blank and is exemplified by a steel plate. The blank is not limited to a steel plate, and may be an industrial pure aluminum plate, an aluminum alloy plate, an industrial pure titanium plate, a titanium alloy plate, or the like.
[0054]
　The door outer panel includes a character line that is a bent surface (ridgeline) sandwiched by at least two surfaces. The door outer panel may include multiple character lines.
[0055]
　As the character line, in a cross section where the character lines are orthogonal to each other, for example, a sharp character line whose curvature radius is, for example, 10 mm or less, or two angles formed by two surfaces extending from the two surfaces forming the ridge line Among them, a sharp character line having a small sandwiching angle of 150° or less is exemplified. Since these sharp character lines are likely to cause line deviation during press molding, the effect of the present invention can be advantageously obtained.
[0056]
　The punch 2 has a high surface pressure generating portion. The high surface pressure generating portion applies a high surface pressure to the blank from the start of molding the blank to the completion of molding. For example, at least one of the convex portion 2b for character line forming and the punch shoulder R portion 2c is a high surface pressure generating portion. The punch 2 may have a plurality of convex portions 2b.
[0057]
　The punch 2 has a low surface pressure generating portion. The low surface pressure generating portion is a portion obtained by removing the high surface pressure generating portion from the punch 2, and is a residual portion 2d except for the convex portion 2b and the punch shoulder R portion 2c from the punch top portion 2a and the punch vertical wall portion 2e. The low surface pressure generating section applies a surface pressure lower than the surface pressure applied to the blank by the high surface pressure generating section 10 between the start of forming the blank and the completion of forming the blank.
[0058]
　In the manufacturing apparatus 1, the coefficient of static friction μ1 with the blank in the first portion of the punch 2 including at least one of the convex portion 2b and the punch shoulder R portion 2c is the second portion of the punch 2 excluding the first portion. Is larger than the static friction coefficient μ2 with the blank.
[0059]
　Therefore, the frictional force generated between the first portion and the blank increases. As a result, the first portion can prevent the initial bent portion generated in the blank due to the initial contact with the punch 2 from moving and deviating from the original position in the forming process, and suppressing line deviation in the door-outer panel, Or it can be virtually eliminated.
[0060]
　Specifically, when the static friction coefficient of the convex portion 2b is increased, the line deviation suppressing effect is exhibited not only at the time when the molding bottom dead center is reached, but also between the initial hit and the molding bottom dead center. .. Further, since the surface pressure applied to the punch shoulder R portion 2c is higher than the surface pressure of the convex portion 2b for forming the character line, when the static friction coefficient of the punch shoulder R portion 2c is increased, the line at the time when the bottom dead center of the forming is reached. The deviation suppressing effect is greater than that of the conventional technology.
[0061]
　Therefore, at least one of the convex portion 2b and the punch shoulder R portion 2c may be increased in static friction coefficient μ1, but the static friction coefficient μ1 is also increased in the region near at least one of the convex portion 2b and the punch shoulder R portion 2c. May be.
[0062]
　For example, in the case of (a) the convex portion 2b, the range within 100 mm of the character line or the range in which the surface pressure during molding is 2 MPa or more, and (b) the punch shoulder R portion 2c, during molding. The coefficient of static friction μ1 may be increased in the range where the surface pressure is 2 MPa or more.
[0063]
　The difference between the static friction coefficient μ1 of the first portion with the blank and the static friction coefficient μ2 of the second portion with the blank is preferably 0.05 or more, more preferably 0.10 or more, and further preferably It is 0.15 or more. As a result, it is possible to reliably suppress the line shift in the outer panel having the character line.
[0064]
　The static friction coefficients μ1 and μ2 of the first and second portions are static friction coefficients in the direction in which the initial bent portion (recess) generated in the blank when the convex portion 2b first hits the blank moves in the forming process. This is preferable because the range in which the coefficient μ1 is increased can be reduced and an increase in the manufacturing cost of the punch 2 can be suppressed.
[0065]
　Next, means 1 and 2 for increasing the static friction coefficient μ1 of the first portion with the blank will be described.
[0066]
(Means 1)
　FIG. 2 is a sectional view showing the structure of the manufacturing apparatus 1. In the following description of the means 1, the case where the particles are provided on the convex portion 2b of the punch 2 is taken as an example, but the situation is the same when the particles are provided on the punch shoulder R portion 2c of the punch 2.
[0067]
　The manufacturing apparatus 1 has a punch 2 as an upper die and a die 3 as a lower die facing the punch 2. The manufacturing apparatus 1 has a blank holder 4 that holds the blank S on the side of the punch 2 and above the die 3. The punch 2 is supported by a lifting mechanism (not shown) so that it can be lifted and lowered.
[0068]
　FIG. 3 is an enlarged view of the particle fixing portion 5 provided on the punch top portion 2a. In FIG. 3, the size of the particle fixing portion 5 is exaggerated with respect to the punch 2 in order to facilitate understanding of the function of the particle fixing portion 5.
[0069]
　As shown in FIG. 3, the particle fixing portion 5 has particles 5 a and a holding layer 5 b for fixing the particles 5 a to the punch 2. As shown in FIG. 2, the particle fixing portion 5 has a convex shape that conforms to the shape of the punch top portion 2 a when it is provided on the punch 2.
[0070]
　FIG. 4 is an explanatory diagram showing a situation in which the punch 2 is looked up from below.
　As shown in FIG. 4, the punch 2 has a shape extending along the X direction of FIGS. The particle fixing portion 5 also has a shape extending along the X direction of FIGS. 2 and 4 in accordance with the shape of the punch top portion 2a.
[0071]
　The particle fixing portion 5 is provided so as to form the convex portion 2b provided on the punch top portion 2a. The position of the convex portion 2b corresponds to the position where the character line is formed on the door outer panel, which is a product.
[0072]
　On the other hand, the upper surface of the die 3 is provided with a die recess 3a corresponding to the shape of the punch top 2a of the punch 2. The position of the lowermost end of the die recess 3a coincides with the position where the character line is formed on the door outer panel, which is a product.
[0073]
　When the punch top 2a contacts the blank S, an initial bent portion is formed. The punch top 2a and the die recess 3a form a character line on the door outer panel.
[0074]
　The shapes of the punch 2 and the die 3 are not limited to the shapes shown in FIGS. 1 to 4, and may be appropriately changed depending on the shape of the door outer panel to be manufactured. For example, the manufacturing apparatus 1 shown in FIGS. 1 to 4 forms one character line, but when forming a plurality of character lines, the character line forming convex portion 2b of the punch portion 2a and the die concave portion 3a are formed. A plurality of lower ends are also provided.
[0075]
　5 to 7 are explanatory views showing the operation of the manufacturing apparatus 1 according to the embodiment over time. In FIGS. 5 to 7, the particle fixing portion 5 is omitted.
　In the punch 2, a negative portion of the punch 2 (hereinafter, referred to as “punch attaching/detaching portion 6 ”) corresponding to a portion where the particle fixing portion 5 is provided is detachably attached to the punch body 7.
[0076]
　The particle fixing portion 5 is provided on the surface of the punch attaching/detaching portion 6 which is detachable from the punch body 7. Therefore, the particle fixing portion 5 is detachably arranged on the punch 2 through the attachment/detachment of the punch attaching/detaching portion 6.
[0077]
　Since the punch 2 is composed of the punch attaching/detaching portion 6 and the punch main body 7, for example, the particle fixing portion may be used in accordance with the wear condition of the particles 5a of the particle fixing portion 5, the hardness of the blank S, the shape of the character line, and the like. 5 can be easily replaced with another punch attachment/detachment section 6 provided with No. 5 or another punch attachment/detachment section 6 having a particle fixing section having different types of particles.
[0078]
　As a result, the replacement time can be significantly shortened as compared with the replacement of the punch 2 itself, and the productivity can be improved. The configuration in which the particle fixing portion 5 is attachable to and detachable from the punch 2 is not limited to the form described above.
[0079]
　The particles 5a of the particle fixing portion 5 may have any Vickers hardness of 700 HV or more and are not particularly limited. By providing the particle sticking portion 5 on the punch 2, the frictional force between the punch 2 and the blank S at the time of press molding is increased as compared with the case where press molding is performed using a punch having no particle sticking portion 5. You can
[0080]
　Thereby, the movement of the material in the character line forming part of the blank S can be suppressed. Therefore, the amount of movement of the initial bent portion formed in the initial stage of press molding becomes small, and the line deviation of the character line can be suppressed or substantially eliminated.
[0081]
　If the Vickers hardness of the particles 5a is less than 700 HV, it becomes difficult for the particles 5a to be caught in the blank S during press molding, and the frictional force between the punch 2 and the blank S becomes insufficient. Therefore, the Vickers hardness of the particles 5a is 700 HV or higher, preferably 1500 HV or higher, and more preferably 2000 HV or higher.
[0082]
　The particles 5a are appropriately selected according to the hardness of the blank S. For example, fused alumina (2100HV), silicon carbide (25000HV), boron carbide (2750HV), ceramic (2800HV), diamond (9000HV), etc. are used as the particles 5a.
[0083]
　The particles 5a are fixed to the surface of the punch attaching/detaching portion 6 via the holding layer 5b. The method for fixing the particles 5a is not particularly limited, and examples thereof include electrodeposition coating and welding. In electrodeposition coating, the punch attaching/detaching portion 6 is immersed in a liquid layer containing the particles 5a, and a voltage is applied to the portion where the punch attaching/detaching portion 6 is immersed.
[0084]
　When the particles 5a are welded, the surface of the particles 5a is plated with metal and the particles 5a are directly brazed to the surface of the punch attaching/detaching part 6. In this case, the wax plays the role of the retaining layer 5b.
[0085]
　The width of the particle fixing portion 5 (width in the Y direction in FIGS. 2 and 4) is such that the line deviation is suppressed by the frictional force between the punch 2 and the blank S, the type of particles, the hardness, the embedding rate, or the blank S. It may be appropriately determined according to the steel type, the hardness, the shape of the character line, and the like.
[0086]
The embedding ratio
　of the particles 5a in the particle fixing portion 5 is preferably 50 to 80%. This embedding ratio is a ratio of the height H of the retaining layer 5b to the average particle diameter D of the particles 5a, and is calculated as (height H of the retaining layer 5b/average particle diameter D of the particles 5a)×100(%). R. The embedding rate is an index indicating the height of the particles 5a protruding from the holding layer 5b.
[0087]
　When the filling rate is less than 50%, the height of the particles 5a protruding from the holding layer 5b is increased, and the frictional force between the punch 2 and the blank S is improved. However, the input load on each particle 5a becomes large.
[0088]
　As a result, the particles 5a easily fall off the holding layer 5b, and the particles 5a easily wear. Therefore, in order to improve the wear resistance of the particle fixing portion 5, the embedding rate is preferably 50% or more, more preferably 55% or more, and further preferably 60% or more.
[0089]
　On the other hand, when the embedding rate exceeds 80%, the number of particles 5a buried in the holding layer 5b increases, and the frictional force between the particle fixing portion 5 and the blank S cannot be sufficiently increased. Therefore, the embedding rate is preferably 80% or less, more preferably 75% or less, and further preferably 70% or less.
[0090]
　A method for measuring the height H of the holding layer 5b will be described. In the plan view of the punch 2 shown in FIG. 4, the entire length of the convex portion 2b is W, the starting end position of the convex portion 2b is 0, and the ending position of the convex portion 2b is W. At this time, a range of ±2.0 mm from the 0.25 W position, the 0.50 W position, and the 0.75 W position in the projecting portion extending direction (X direction in FIG. 4) is set as the observation point.
[0091]
　With respect to these observation points, an optical microscope sample having a cross section perpendicular to the convex portion 2b was prepared, and the observation points (in the extension direction of the convex portion ±) were observed at the cross sections at the 0.25 W position, the 0.50 W position and the 0.75 W position. Observe a range of 2.0 mm). At each observation location, the height of the holding layer 5b (in the direction perpendicular to the punch surface) was measured at 20 points each, and the height of the holding layer 5b was obtained as an average value of 60 points in total.
[0092]
　Next, a method for measuring the average particle size of the particles 5a will be described. In the plan view of the punch 2 shown in FIG. 4, the entire length of the convex portion 2b is W, the starting end position of the convex portion 2b is 0, and the ending position of the convex portion 2b is W. At this time, the protrusions 2b are respectively located at positions -2 mm, -1 mm, 0 mm, 1 mm, and 2 mm from the 0.25 W position, the 0.50 W position, and the 0.75 W position in the protrusion extending direction (X direction in FIG. 4). An optical microscope sample having a cross section perpendicular to is prepared, and a visual field of 100 to 400 times is observed with the optical microscope.
[0093]
　The average value of the particle diameters of the particles 5a at the 15 cross sections of these observation points is defined as the average particle diameter of the particles 5a. The average value of the long side and the short side of each particle 5a is defined as the particle size. The particle size of the particles 5a overlapping the observation point is not measured and is not included as a value.
[0094]
　Although FIG. 4 shows a case where the convex portion 2b is a straight line in a plan view, the convex portion 2b may be a three-dimensional curved line.
[0095]
The average particle size of the
　particles 5a is preferably 5 to 600 μm. If the average particle size of the particles 5a is less than 5 μm, the frictional force between the punch 2 and the blank S may be insufficient depending on the operating conditions such as the hardness difference between the particles 5a and the blank S and the shape of the character line. Therefore, the average particle diameter of the particles 5a is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 50 μm or more.
[0096]
　On the other hand, if the average particle diameter of the particles 5a exceeds 600 μm, each particle 5a of the particle fixing portion 5 during press molding of the blank S may be depending on operating conditions such as the hardness difference between the particles 5a and the blank S and the shape of the character line. There is a possibility that the input load on the particle 5a becomes too large and the particles 5a easily fall off the holding layer 5b. Therefore, the average particle diameter of the particles 5a is preferably 600 μm or less, more preferably 500 μm or less, and further preferably 400 μm or less.
[0097]
　In the punch 2 shown in FIG. 4, since the convex portions 2b extend linearly along the X direction, the cross sections for measuring the grain size are parallel to each other. However, for example, when the convex portion 2b has a curved shape or a shape that is curved three-dimensionally, the cross sections at the 0.25W position, the 0.50W position, and the 0.75W position intersect each other. There are also things to do.
[0098]
The particle ratio of the
　particle fixing portion 5 is preferably 5 to 20%. The particle ratio is an index showing the density of particles in a certain region, and is calculated as (total volume of particles 5a in particle fixing portion 5/volume of particle fixing portion 5)×100(%). R.
[0099]
　If the particle ratio is less than 5%, the number of particles 5a is too small, and the frictional force between the punch 2 and the blank S is insufficient depending on the operating conditions such as the hardness difference between the particles 5a and the blank S and the shape of the character line. May occur. Therefore, the particle ratio of the particle fixing portion 5 is preferably 5% or more, more preferably 8% or more, and further preferably 10% or more.
[0100]
　On the other hand, when the particle ratio exceeds 20%, the number of the particles 5a in the particle fixing portion 5 is too large, and depending on the operating conditions such as the hardness difference between the particles 5a and the blank S and the shape of the character line, the particles 5a may be separated from each other. Clogging may occur easily. If clogging occurs between the particles 5a, the frictional force between the punch 2 and the blank S becomes insufficient. Therefore, the particle ratio of the particle fixing portion 5 is preferably 20% or less, more preferably 10% or less, and further preferably 15% or less.
[0101]
　The manufacturing apparatus 1 is configured as described above. Next, a method of manufacturing an outer panel having a character line using the manufacturing apparatus 1 will be described.
　First, the blank S is arranged between the die 3 and the pad 4. At this time, the blank S is arranged such that the non-designed surface side of the blank S that appears in the appearance (designed surface) and the surface that does not appear in the appearance (non-designed surface) faces the punch 2 side.
[0102]
　Next, the punch 2 is lowered. At this time, the convex portion 2b of the punch 2 first comes into contact with the blank S, so that the blank S has an initial bent portion that causes a line deviation. FIG. 5 shows a case where the convex portion 2b first contacts the blank S.
[0103]
　Then, as shown in FIG. 6, the punch 2 is further lowered. As a result, the punch 2 descends while the particle fixing portion 5 including the convex portion 2b is in contact with the blank S. Therefore, the particles 5a of the particle fixing portion 5 are caught in the blank S.
[0104]
　Therefore, the frictional force between the particle fixing portion 5 and the blank S is higher than the frictional force obtained when the conventional punch having no particle fixing portion 5 is used. In this state, the punch 2 descends.
[0105]
　As a result, the movement of the material in the character line forming portion of the blank S is suppressed. As a result, the initial bent portion formed in the initial stage of press molding becomes difficult to move, and the line shift of the character line is suppressed.
[0106]
　In this state, as shown in FIG. 7, the punch 2 is moved to the molding bottom dead center to form a character line on the blank S. Since the particle fixing portion 5 of the punch 2 contacts the non-designed surface of the blank S, the eaves caused by the contact with the particles 5a do not appear in the appearance of the product.
[0107]
　In this way, according to the manufacturing apparatus 1, it is possible to suppress the line shift, which is determined to be defective in the outer surface quality of the door outer panel in the highlight surface inspection of the completed vehicle, as compared with the related art.
[0108]
　Further, the particles 5a are fixed only on the punch 2 side, and the particles 5a are not provided on the die 3 side. Therefore, a large restraining force that completely restrains the character line forming portion of the blank S does not occur during press forming.
[0109]
　As a result, in press molding of a portion other than the character line molding portion, molding defects such as bending of the blank and insufficient inflow do not easily occur. Therefore, an outer panel having a three-dimensionally curved character line, such as a door outer panel, can be manufactured.
[0110]
　FIG. 8: is sectional drawing which shows the structure of the manufacturing apparatus 1 of another form typically.
　In the above description, the punch 2 is composed of the punch attaching/detaching portion 6 and the punch main body 7 as an example. However, as shown in FIG. 8, the punch attaching/detaching portion 6 and the punch main body 7 may be integrally configured. In the manufacturing apparatus 1, for example, the holding layer 5b may be attached or applied to the surface of the punch top 2a, and the particles 5a may be fixed to the holding layer 5b so as to be dispersed to form the particle fixing portion 5.
[0111]
(Means 2)
　Next, means 2 will be described. The means 2 is different from the means 1 in that the projections 8 are used instead of the particles 5a of the means 1 as means for increasing the static friction coefficient μ1 of the first portion with the blank.
[0112]
　A plurality of protrusions 8 are provided on the first portion of the punch 2. FIG. 9A is an explanatory diagram showing an example of the arrangement of the plurality of protrusions 8 provided, and FIG. 9B is an explanatory diagram showing an example of the dimensions of the protrusions 8. The unit of dimensions in FIGS. 9A and 9B is mm.
[0113]
　The plurality of protrusions 8 may be formed by any means, but for example, it is desirable to form the protrusions by masking a normal punch and then etching the punch in order to suppress an increase in manufacturing cost of the punch.
[0114]
　As shown in FIG. 9A, the plurality of projections 8 are provided in the first portion in a grid pattern with a center distance of 0.80 mm. Further, as shown in FIG. 9B, a chromium plating layer 9 having a target thickness of 20 μm is formed on the protrusion 8 formed on the first portion. The target value of the height of the protrusion 8 is 0.06 mm, and the target value of the diameter of the protrusion 8 is 0.11 mm. The chromium plating layer 9 increases the hardness of the protrusion 8.
[0115]
　By providing these projections 8 on the first portion of the punch 2 so as to contact the inner surface which is the non-designed surface of the door outer panel in the blank S, the appearance quality of the outer surface which is the designed surface of the door outer panel is improved. It is possible to prevent the line deviation in the door outer panel while preventing the deterioration.
[0116]
　As illustrated in FIGS. 9A and 9B, the protrusions 8 have a height of 0.02 to 0.10 mm, a diameter of 0.05 to 0.15 mm, and a density of 5×10 5 to 5×10 6 pieces/m. 2. Satisfying the center distance of the adjacent protrusions 8: 0.5 to 1.0 mm ensures the line deviation in the outer panel while preventing the deterioration of the appearance quality of the outer surface which is the design surface of the door outer panel. It is desirable because it can be suppressed.
[0117]
　A sliding test mold having minute protrusions 8 was prepared and a flat plate sliding test was performed to measure the coefficient of static friction. The conditions of the sliding test are summarized below.
・Material: 0.7 mm
thick mild steel plate ・Shape of protrusion 8: Diameter 0.11 mm, height 0.06 mm
[0118]
・Arrangement of protrusions 8: Lattice shape with a center distance of 0.7 mm
・Mold shape: 40 mm × 30 mm Extraction in 30 mm direction
・Extraction conditions: Length 300 mm
・Test (nominal) surface pressure: Surface pressure generated in actual molding Was set from FEM analysis.
[0119]
　FIG. 10 is a graph showing the relationship between the nominal surface pressure and the coefficient of static friction depending on the presence or absence of the protrusion 8.
[0120]
　As shown in the graph of FIG. 10, the static friction coefficient μ2 is about 0.10 to 0.15 in a normal flat plate mold (without protrusions), whereas it is about 0.30 when the minute protrusions 8 are provided. The static friction coefficient μ1 increases. If the height of the protrusion 8 is 5% or less with respect to the plate thickness t of the blank, it is possible to prevent the deterioration of the appearance quality of the outer surface which is the design surface of the door outer panel.
[0121]
　In the above description, the upper die 2 is movable and the lower die 3 is fixed, but the upper die 2 may be fixed and the lower die 3 may be movable. The upper die may be the die 3 and the lower die may be the punch 2.
[0122]
　That is, the manufacturing apparatus is not limited to the configuration shown in FIGS. 1 to 8, and the location where the coefficient of static friction is increased by the particles 5a and the projections 8 is at least one of the convex portion 2b of the punch top portion 2a and the punch shoulder R portion 2c. If it is provided in the first portion of the punch 2 that includes the punch 2, it is possible to suppress the misalignment of the character line of the door outer panel while suppressing the occurrence of molding defects such as bending and insufficient inflow.
　Next, the present invention will be described more specifically with reference to Examples.
Example 1
[0123]
　Under the die conditions listed below and the conditions of the means 1 shown in Table 1, the punches 2 for evaluating the line deviation shown in FIGS. (TS270 MPa grade hot-dip galvannealed steel sheet, plate thickness 0.7 mm, length 400 mm, width 200 mm) is press-molded and the evaluation parameter S=L×|H| 1/3 described in Patent Document 1 is used. The amount of line deviation was quantitatively evaluated.
[0124]
[Mold conditions]
-BHF 20 tons
-Press speed 10 mm/s
-Lubrication
-Punch first part: Area A in FIGS. 11A and 11B
-Particle 5a
[0125]
[table 1]

[0126]
　The results are shown in the graph of FIG. Since the evaluation parameter S value is calculated using the deviation width L [mm], a small S value means a small line deviation amount.
　As shown in the graph of FIG. 12, when the evaluation parameter S value of the conventional flat plate is 1, the evaluation parameters S were improved to about 0.9 in the invention examples 1 and 2.
[0127]
　Furthermore, sensory evaluation by visual inspection was performed on Examples 1 and 2 of the present invention. Also in the sensory evaluation, it was confirmed that the line shifts of Examples 1 and 2 of the present invention were suppressed.
Example 2
[0128]
　Using the manufacturing apparatus 1 in which the means 1 is replaced with the means 2, FEM is performed with the above-described line deviation evaluation mold under the test conditions shown in Table 2, and the evaluation parameter S=L×| The amount of line deviation was quantitatively evaluated using H│ 1/3 . As described in paragraph 0116, those skilled in the art can adjust the static friction coefficient by appropriately selecting the height, the diameter, the density, the center distance between the adjacent protrusions, and the like.
[0129]
[Table 2]

[0130]
　In this FEM analysis, the friction coefficient of the punch shoulder R portion 2c in the vicinity of the convex portion 2b of the punch 2 is partially increased by forming the protrusion 8, and the movement of the initial bent portion of the blank with the convex portion 2b is increased. The amount (deviation amount) was calculated.
[0131]
　In this analysis, the coefficient of static friction was set to 0.10.
[0132]
　13A and 13B are graphs showing analysis results. FIG. 13A shows the evaluation result when the projection 8 is provided on the convex portion 2b, and FIG. 13B shows the evaluation result when the projection 8 is provided on the punch shoulder R portion 2c.
[0133]
　As shown in the graphs of FIGS. 13A and 13B, when the evaluation parameter S value of the reference flat plate (static friction coefficient 0.10) is set to 1, in Examples 1 to 3 of the present invention in which the static friction coefficient of the high surface pressure portion is increased. , The evaluation parameter S was significantly improved.
Explanation of symbols
[0134]
1 Manufacturing Equipment
2 Punch
2a Punch Top
2b Convex
2c Punch Shoulder R
2d Residual
2e Punch Vertical Wall
3 Die
3a Recess
4 Blank Holder
5 Particle Fixing
5a Particle
5b Retaining Layer
6 Punch Attachment/Detachment
7 Punch Body
8 Protrusion
9 Chrome plating layer
S Blank

The scope of the claims
[Claim 1]
　A punch and a blank holder and a die facing the punch and the blank holder are used, and a blank arranged between the punch and the blank holder and the die is subjected to press forming by drawing or bulging to obtain two a method of manufacturing a skin panel with a character line which is bent surface sandwiched by a surface,
　the punch has a protrusion for forming the bending surface punch top, provided with a punch shoulder R portion,
　the convex Pressure applied to the blank at the time of the press working by at least one of the punch portion and the punch shoulder R portion is the surface pressure applied to the blank by the remaining portion of the punch excluding the convex portion and the punch shoulder R portion during the press working. The
　coefficient of static friction with the blank in the first portion of the punch, which is higher than the pressure and further includes at least one of the convex portion and the punch shoulder R portion, is equal to that of the second portion of the punch excluding the first portion. The manufacturing method of the outer panel having a character line, which is larger than the coefficient of static friction with the blank in the portion.
[Claim 2]
　The outer panel having a character line according to claim 1, wherein the difference between the coefficient of static friction of the first portion with the blank and the coefficient of static friction of the second portion with the blank is 0.05 or more. Production method.
[Claim 3]
　The outer panel having a character line according to claim 1 or 2, wherein the coefficient of static friction is a coefficient of static friction in a direction in which a recess formed in the blank when the protrusion first contacts the blank moves in a molding process. Manufacturing method.
[Claim 4]
　The method for manufacturing an outer panel having a character line according to claim 1, wherein at least one of the convex portion and the punch shoulder R portion has particles having a Vickers hardness of 700 HV or more.
[Claim 5]
　The character line according to claim 4, wherein the punch includes a particle fixing portion having a holding layer that holds the particles, and the particle fixing portion is provided on at least one of the convex portion and the punch shoulder R portion. A method of manufacturing an outer panel having the same.
[Claim 6]
　The method for manufacturing an outer panel having a character line according to claim 4 or 5, wherein an embedding rate of the particles is 50 to 80%.
　However, the filling rate is calculated as (height of the holding layer/average particle diameter of the particles)×100 (%).
[Claim 7]
　7. The method for manufacturing an outer panel having a character line according to claim 6, wherein the particles have an average particle size of 5 to 600 μm.
[Claim 8]
　8. The method for manufacturing an outer panel having a character line according to claim 6, wherein the particle ratio of the fixed particles is 5 to 20%.
　However, the particle ratio is calculated as (total volume of the particles/volume of the particle fixing portion)×100 (%).
[Claim 9]
　9. The method for manufacturing an outer panel having a character line according to claim 5, wherein the particle fixing portion is replaced with another particle fixing portion according to operating conditions.
[Claim 10]
　The method for manufacturing an outer panel having a character line according to any one of claims 4 to 9, wherein the particles are in contact with a non-designed surface which is an inner surface of the outer panel in the blank.
[Claim 11]
　4. The method for manufacturing an outer panel having a character line according to claim 1, wherein at least one of the convex portion and the punch shoulder R portion has a protrusion.
[Claim 12]
　The method for manufacturing an outer panel having a character line according to claim 11, wherein the height of the protrusion is 0.02 to 0.10 mm.
[Claim 13]
　The said projection is a manufacturing method of the outer panel which has the character line of Claim 11 or 12 which contacts the non-designed surface which is the inner surface of the said outer panel in the said blank.
[Claim 14]
　A punch and a blank holder and a die facing the punch and the blank holder are provided,
　and at least a blank arranged between the punch and the blank holder and the die is subjected to press working by drawing or bulging, thereby at least An apparatus for manufacturing an outer panel having a character line which is a curved surface sandwiched by two surfaces,
　wherein the punch comprises a convex portion for molding the curved surface and a punch shoulder R portion at the punch top. The
　surface pressure that at least one of the convex portion and the punch shoulder R portion gives to the blank at the time of the press working is such that the remaining portion of the punch excluding the convex portion and the punch shoulder R portion is the blank at the time of the press working.
　Coefficient of static friction with the blank in the first portion of the punch including at least one of the convex portion and the punch shoulder R portion is higher than the surface pressure applied to the punch. An apparatus for manufacturing an outer panel having a character line, which is larger than the coefficient of static friction with the blank in the second portion of the above.