[0001]
　The present invention has a dedendum shape capable of reducing the bending stress generated at the tooth root when the power transmission to high strength gear.
Background technique
[0002]
　Gear, industrial, agricultural, is an essential mechanical components for industrial machinery and automobiles to be used in the construction and other industries. Because these gears to be used in severe conditions exposed to high loads, the bending stress generated in the tooth, there is a risk that breakage of the teeth occurs.
[0003]
　In the most common gear cutting as the manufacturing method of the gear, greatly affects the dedendum shape dedendum bending strength, is uniquely determined by the edge shape of the hob. Usually, in order to increase the dedendum bending strength, but as large as possible the roundness of the cutting edge of the hob, when the rounding is too large, the adverse effect on the engagement of the teeth during use of the gear because will come out, the improvement of dedendum bending strength due to the change of the cutting edge shape is limited.
[0004]
　Meanwhile, gears made by forging and powder metallurgy or the like, teeth within a range that does not interfere with the addendum of the mating gear, are possible design freedom of dedendum shape than the gear made by gear cutting it may be possible to produce an excellent gear based on the bending strength. Japanese Patent No. 5520374 (Patent Document 1), a vehicle for transmission that is produced by hot forging consists of free-form surface root surface to maximize the minimum radius of curvature at the tooth drop point, the gear is disclosed. According to Patent Document 1, the stress concentration is relaxed by the maximum a minimum radius of curvature, dedendum bending strength is a, improved.
[0005]
　Further, Japanese Patent 2015-1248 (Patent Document 2), toward the tooth surface from the tooth bottom, first involute portion, an arc portion, a second involute portion, third involute portion, and the tooth surface connecting curved portion having a gear is disclosed. According to Patent Document 2, to equalize the stress variation range of the so-called partial Reversed state of tensile and compressive stresses occurring in the tooth bottom side area, so that the maximum stress amplitude position is not to occur in the tooth bottom center or the vicinity thereof of course that the same may be, the maximum stress amplitude position can prevent occurring across tooth bottom side area, it is possible to improve the durability of the teeth, there is a.
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　However, Patent Document 1, the dedendum shape, is not specified positions radius of curvature is minimized. In cross section, and when the position where the curvature radius is minimum in the vicinity root circle, danger sectional position determined by the 30 ° tangent method of Hofer (hereinafter, simply referred to as "dangerous cross position") in the vicinity compared with the cases, and even the smallest radius of curvature is the same, the generated bending stress varies greatly. That is, the position where the curvature radius is minimum, there is less fear dedendum bending strength than gears made by gear cutting. In Patent Document 2, the tooth gap bottom near the center is, since the curvature radius of involute curve which changes, there is a possibility that the curvature occurs breakage at a point other than near the tooth bottom center is the largest, tooth root flexural strength there may not be sufficiently obtained.
[0007]
　The present invention was made in view of the above circumstances, to reduce the bending stress generated at the tooth root when power transmission, to achieve high strength, and to provide a high strength gear.
Means for Solving the Problems
[0008]
　In order to solve the above problems, the present inventors have found that in cross section, the tooth tip segment, the tooth surface segment, dedendum line, and the high strength gear having a sequentially continuous tooth form tooth bottom line, the dedendum which can reduce the bending stress generated in the (portion indicated by the dedendum line) was examined the shape of the tooth root line. As a result, in particular, relates to the dedendum line, and the radius of curvature at a particular position (dangerous cross position), the shape of the tooth root line itself, and the radius of curvature at a position other than the specific position, the maximum radius of curvature and the minimum curvature by adding the relationship between the radius, the improvement for, reducing the bending stress generated in the tooth root, it is possible to obtain a high strength gear superior in turn dedendum bending strength, to obtain a knowledge that.
[0009]
　The high strength inventors, the addition of improvements in further for tooth bottom line in the vicinity of hazardous cross-sectional position, and further reduce the bending stress generated in the tooth, which is excellent in further dedendum bending strength and thus it can be obtained gear, to obtain a knowledge that.
[0010]
　Based on the above findings, the present inventors have completed the invention. Its gist is as follows.
[0011]
　[1] In cross section, the tooth tip segment, the tooth surface segments, a high strength gear having a dedendum line, and sequentially continuous tooth form tooth bottom segment, risk cross-section defined by 30 ° tangent method of Hofer the maximum radius of curvature at the position, the first radius of curvature to the connection point is a boundary point between the tooth surface lines and the tooth root line segments or decreased is constant danger sectional position, and, the danger second radius of curvature to the connecting point from the cross-sectional position is the boundary point between the dedendum line and the tooth bottom line segments or decreased is constant, within the dedendum line, the danger sectional position there is a point radius of curvature smaller than, within the dedendum line, the maximum radius of curvature is equal to or less than 3 times the minimum radius of curvature, a part the dangerous section position of the arc, and the arc is extends on both sides of the danger section positions, and wherein the high strength gear
[0012]
　[2] based on the above-mentioned danger sectional position, that the arc in the tooth tip line direction and the dedendum line direction, 0.05 times or more of the respective modules in the tooth height direction dimension, extends wherein the high strength gear according to [1].
[0013]
　[3] a gear according to the above [1] or [2], which consists of an iron-based alloy.
Effect of the invention
[0014]
　The high strength gear according to the present invention, in particular the shape of the dedendum segment in cross section, and the radius of curvature at a particular position (dangerous cross position), the shape of the tooth root line itself, at a position other than the specific position radius of curvature, the relationship between the maximum curvature radius and the minimum radius of curvature, are making improvements on. Further, a high strength gear according to the present invention, furthermore, is also added to improve the dedendum line in the vicinity of hazardous sectional position. As a result, according to the high strength gear according to the present invention, to reduce the bending stress generated in the tooth root, it is possible to increase the turn dedendum bending strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015]
FIG. 1 is a diagram showing the tooth profile segments of a conventional gear made by gear cutting.
Is a diagram illustrating a tooth profile line of the high strength gear according to FIG. 2 embodiment.
[Figure 3] was compared dedendum bending strength is a diagram showing the tooth profile segments of various gears (prior art).
[Figure 4] were compared dedendum bending strength is a diagram showing the tooth profile segments of various gears (invention example).
[5] were compared dedendum bending strength is a diagram showing the tooth profile segments of various gears (Comparative Example).
DESCRIPTION OF THE INVENTION
[0016]
　Hereinafter, an embodiment of a high strength gear according to the present invention in detail. The following embodiments are not intended to limit the present invention. The constituent elements of the above embodiments, those skilled person that can be easily replaced, or substantially the same. Moreover, various forms included in the embodiment, a person skilled in the art can arbitrarily combined within obvious limits.
[0017]

　herein, high strength gear units (the tooth tip, the tooth surface, tooth and tooth bottom) of the tooth normal plane of the wheel (hereinafter, if the referred to simply as "sectional" shape at a), in a state in which teeth protruding upward, is defined as follows. The tooth surface segment means a segment in contact with the mating gear in transmitting torque meshing with the mating gear, the case of the external teeth is a convex line segment inside the case of the internal convex, outwardly. The tooth tip line, connecting the left and right upper end of the tooth surface segment of one tooth, convex in the same direction as the tooth surface segment refers to arcuate segment formed of a part of the addendum circle . The dedendum line of the tooth surface segment refers to a segment continuing the lower end. The tooth bottom line, both ends of the different dedendum line segments, contiguous with one end opposite to the aforementioned tooth surface segment, a convex in the same direction as the tooth surface segment, from a portion of the tooth bottom circle It refers to arcuate segment made.
[0018]
　To improve the dedendum bending strength of the gear, it is effective to reduce the maximum bending stress exerted on the tooth. Usually, in sectional view, the tooth root bending stress becomes maximum near dangerous cross-sectional position, decreases as the distance from the dangerous section position. However, even some distance away from the dangerous section position, if the radius of curvature is too small, occur extreme stress concentration, sometimes dedendum bending stress at that position is maximized. That is, assuming that appropriate control of the maximum bending stress, the improved dedendum bending strength of the gear, it is effective to set an appropriate radius of curvature in accordance with the distance from the dangerous section position.
[0019]
　Accordingly, the present inventors have in cross section, with the maximum curvature radius at high risk sectional position might dedendum bending stress is maximum, towards both the tooth surface and tooth root danger sectional position in the tooth root line so as to both the radius of curvature is without or decreased change, also than risk sectional position within dedendum line in the presence of a partial radius of curvature is small, it does not occur more extreme stress concentration according to the maximum radius of curvature less than 3 times the minimum radius of curvature (preferably 2 times or less) if, it is possible to sufficiently reduce the maximum bending stress, which leads to an improvement of dedendum bending strength, and I obtained the findings.
[0020]
　Further, the present inventors have found that in terms of the segment curvature near dangerous section position is an involute curve gradually changes, in order to reduce the overall while somewhat averaging the stress amplitude in the tooth base region, risk sectional position It was also thought to be as large as possible a radius of curvature at. However, if the line segment near the danger sectional position is involute curve, varying the extreme radius of curvature as the distance from the dangerous section position, the stress amplitude is maximized at the other points is not a dangerous section position location found that it appears. Therefore, the present inventors have near dangerous cross-sectional position, by the area radius of curvature rather than the involute curve does not change, the stress amplitude without presence monkey that the other points of maximum bending further dedendum it is possible to improve the strength, to obtain a knowledge that. Hereinafter, the high strength gear according to the present embodiment (typical example shown in FIG. 2) will be described in comparison with the gear (typical example shown in FIG. 1) according to a conventional embodiment.
[0021]

　FIG 1 is a diagram showing the tooth profile segments of a conventional spur gear which is manufactured by gear cutting (sectional view). More specifically, in the example shown in the figure, 1.25 modules, the number of teeth 36, Namiha the tooth profile, the transition coefficient 0, the helix angle 0 °, and have a pressure angle as 20 °, tooth rounded tooth root is the cutting edge R of the hob and 0.38 times the module so as large as possible is not adverse effect on the engagement of the teeth and. Tooth segment shown in the figure, arc-shaped tooth tip line 11 (convex upward), the tooth surface segment 12 is involute curve (the convex upward), dedendum segment 13 is a trochoid curve ( convex) below, and a de-arc-shaped tooth bottom line 14 (convex upward). Incidentally, the boundary point between the tooth surface segment 12 and the tooth root line 13 is a first connection point X0, a boundary point between the dedendum segment 13 and the tooth bottom segment 14 is the second connection point Y0 .
[0022]
　In the example shown in FIG. 1, it relates dedendum segment 13, the radius of curvature at the vicinity of the first connection point X0 is approximately 1.2 mm, the radius of curvature toward from said position near to the tooth bottom segment 14 is smaller , the radius of curvature at the vicinity of the second connection point Y0 was about 0.6 mm. Furthermore, the curvature radius at risk sectional position in the figure was about 0.7 mm.
[0023]

　FIG. 2 is a spur gear, a diagram showing the tooth profile of the high strength gear according to the present embodiment (sectional view). High strength gear shown in the figure, has tooth tip line 21, the tooth surface segment 22, tooth root line 23, and sequentially continuous teeth tooth bottom segment 24. Addendum line 21 and tooth surface segment 22 shown in the figure is the same as the addendum line 11 and tooth surface segment 12 shown in FIG. Dedendum segment 23 shown in FIG. 2, with continuous smoothly with the tooth surface segment 22 at a first connection point X1, a curve leading to smooth the tooth root line 24 at a second connection point Y1. Here, continuous and is smoothly, two line segments tangent to each other means that equal in coupling point.
[0024]
　Further, in the example shown in FIG. 2, the radius of curvature is greatest at risk sectional position determined by the 30 ° tangent method of Hofer. That is, in the example shown in FIG. 2 relates dedendum segment 23, the radius of curvature of a hazardous sectional position is at most 0.8 mm.
[0025]
　Further, in the example shown in FIG. 2, in the first to the connection point X1 (the area including the point A1) radius of curvature which is the boundary point between the tooth surface segment 22 and the tooth root line 23 from danger sectional position is constant there or decreased, and either a second connection point Y1 to (a region including the point B1) radius of curvature which is the boundary point between the dedendum line 23 and the tooth bottom segment 24 from danger sectional position is constant or it has decreased.
[0026]
　Furthermore, in the example shown in FIG. 2, the dedendum line 23, there is a point curvature radius is smaller than the risk sectional position, the dedendum line 23, three times the maximum radius of curvature of the minimum radius of curvature and it has a following. That relates dedendum line 23, the curvature at the vicinity of the first connection point X1 radius, and the radius of curvature at the vicinity of the second connection point Y1 is the smallest, both met about 0.5mm It was. Therefore, as described above, the curvature radius of 0.8mm at risk sectional position for a (maximum), in the tooth base line 23, 1.6 times the maximum radius of curvature minimum radius of curvature (3 times or less) It has become.
[0027]
　In addition, in the example shown in FIG. 2, the details are not shown, danger sectional position is a part of a circular arc, and the arc extends on both sides of the danger section position.
[0028]
　Having the configuration described above, the high strength gear shown in FIG. 2, in sectional view, the radius of curvature at the likely risk cross-sectional position dedendum bending stress is maximum with the maximum, from the danger sectional position both the radius of curvature toward the both tooth surfaces and tooth root is without or decreased change, also than risk sectional position within dedendum line in the presence of a partial radius of curvature is small, the more extreme stress concentration occur lest than three times the minimum radius of curvature of the maximum radius of curvature at the tooth root line has (preferably 2 times or less) and. The high strength gear shown in the figure, a near dangerous cross-sectional position, and a region where the radius of curvature does not change. Therefore, according to the high strength gear, set the appropriate radius of curvature in accordance with the distance from the dangerous section position, moreover, since the stress amplitude is dangerous section position the point of maximum, dedendum bending strength it can be improved.
[0029]
　Incidentally, the tooth profile from the danger sectional position to the first connection point X1 shown in FIG. 2, and, for the tooth profile from the danger sectional position to the second connection point Y1 shown in FIG. 2, an arc is that it includes a dangerous cross position if the end point no other arcs on either side of the arc (radius of curvature does not change) even if being formed, involute curve (curvature radius changes) may be are formed. However, an arc containing dangerous cross position, in contact with the other arc or involute curve, it is a requirement that the tangent of the two curves coincide. By tangential both curves are identical, it is possible to suppress breakage at that point, it is possible to further improve the dedendum bending strength.
[0030]
　In the example shown in FIG. 2 as a reference arc, a risk sectional position including the risk sectional position, the tooth tip line direction and the tooth root line direction, 0.05-fold, respectively module tooth depth dimension above, it is preferable to extend. Here, the module refers to a value obtained by dividing the number of teeth pitch diameter of the gear. The arc two directions modules 0.05 times or more, dedendum bending stress does not become maximum at other points is not a non-hazardous sectional position if extended, it is possible that.
[0031]
　Furthermore, the gear of the material shown in FIG. 2 may be an iron-based alloy. Here, the iron-based alloy, iron as a main component, an alloy containing other elements, such as carbon steel, alloy steel, hardened steel, nitriding steel, stainless steel, maraging steel, invar, kovar , sendust, and a speaker gel Aizen like.
[0032]

　The present inventors have found that in order to study the influence of dedendum shape on dedendum bending strength, the magnitude of the bending stress generated at the tooth root when the gear used (during power transmission) It was estimated by the finite element method analysis. In addition, analysis conditions were as follows. That is, to fix the rotation of the spur gear having a tooth profile shown in FIGS. 1 and 2, force is applied in the vicinity of the tip of the any one of the teeth. Position plus force, on a straight line and the cylindrical surface and the tooth surface with a diameter of 46.5mm with the same central axis as the central axis of the gear intersect the direction of the force was a direction perpendicular to the tooth surface. Gear is assumed to be made of steel, and the Young's modulus 207GPa, an elastic body of Poisson's ratio 0.3, was analyzed as a plane strain state. Incidentally, the applied force for the tooth width 100 mm, was 35 kN.
[0033]
　Results of the finite element analysis for a conventional gear illustrated in Figure 1 made by gear cutting, the maximum value of the maximum principal stress occurring in the tooth root is estimated to be 502MPa. In contrast, for the high strength gear according to the present embodiment shown in FIG. 2, the maximum value of the maximum principal stress is estimated to be 469MPa. Thus, for the high strength gear according to the present embodiment, the greatest radius of curvature of the dangerous section position near and extreme order partial radius of curvature is small there is no maximum value of the maximum principal stress is suppressed, and Conceivable.
[0034]
　By the above, according to the high strength gear according to the present embodiment, assuming that appropriate control of the maximum bending stress, upon improved dedendum bending strength of the gear, suitably according to the distance from the dangerous section position by setting the a radius of curvature, it is possible to suppress the maximum bending stress generated in the tooth root during power transmission, it is possible to realize a high strength of the thus gear.
Example
[0035]
　As described above, the high strength gear according to the present embodiment (typical example shown in FIG. 2) is, with respect to the gear according to the conventional form (typical example shown in FIG. 1), it is demonstrated that achieve the application desired effect and although, in the following, further detailed comparison of these forms. Incidentally, dedendum shape of the high strength gear according to the present embodiment is not limited to the examples shown below.
[0036]
　As described above, in order to examine the influence of dedendum shape on dedendum bending strength, the magnitude of the bending stress generated at the tooth root when the gear used (during power transmission) was estimated by finite element analysis. 3 to 5, respectively, were compared dedendum bending strength is a diagram showing the tooth profile segments of various gears (sectional view) (Figure 3: the conventional example, FIG. 4: Inventive Example, FIG. 5 comparative example). The broken line in these figures are all a line at an angle of tooth center line and 30 °, position risk cross-section this line is in contact with (the portion indicated by the tooth surface line of the figure) tooth surface is a position. Further, in FIGS. 3-5, the point X0, a point X2 ~ point X8 each represent a first connection point, the point Y0, point Y2 ~ point Y8 each represent a second connection point, the point A3, point A4, the point A7 indicate the point included in the region from the danger section respectively positioned to the first connection point X3, X4, X7, point B2, the point B2 ', the point B3, the point B4, the point B5, point B6 the second connection point from the danger sectional position respectively Y2, Y3, Y4, Y5, indicates a point included in the region up to Y6, the point C2 indicates the point at risk sectional position.
[0037]
　Example shown in FIG. 3 (a) (prior art 1) is an example that has been prepared in gear cutting (example shown in FIG. 1), 1.25 modules, the number of teeth 36, Namiha the tooth profile, metastasis coefficient 0, the helix angle 0 °, and the pressure angle is set to 20 °, tooth and tooth root in a range no adverse effect on the engagement of the teeth rounded of the edge R of the possible larger as hobs module It was 0.38 times. Further, as discussed above, relates dedendum line, the radius of curvature at the vicinity of the first connection point X0 is approximately 1.2 mm, the radius of curvature becomes smaller toward the tooth bottom line from the position near the radius of curvature at the vicinity of the second connection point Y0 was about 0.6 mm. Furthermore, the curvature radius at risk sectional position in the figure was about 0.7 mm.
[0038]
　Example shown in FIG. 3 (b) (prior art 2), the addendum line and tooth surface segment is the same as the example shown in FIG. 3 (a), is different from the shape of the tooth root line. Between the addendum line termination dangerously sectional position is involute curve. With a radius of curvature of about 0.7mm in the vicinity of the tip segment end, the radius of curvature becomes larger toward the dangerous section position, the radius of curvature of a hazardous sectional position was 0.8 mm. Between danger sectional position to B2 is involute curve. The radius of curvature becomes smaller toward the dangerous section located in B2, the radius of curvature in the vicinity B2 was about 0.6 mm. Between B2 to B2 'is a circular arc, the radius of curvature was 0.6 mm. Between B2 'to the second connection point (dedendum line termination) Y2 is involute curve. The radius of curvature toward the tooth bottom line terminations B2 'decreases, the radius of curvature at the tooth bottom segment near the end was about 0.3 mm.
[0039]
　Figure 4 (a) ~ (c) and 5 (a), the example shown in (b) (Inventive Example 1 to 3 and Comparative Examples 1 and 2), the addendum line and tooth surface line segment, FIG. 3 it is identical to the example shown in (a), is different from the shape of the tooth root line. 5 example shown in (c) (Comparative Example 3), although the addendum line and tooth surface segment is the same as the example shown in FIG. 3 (a), (shown) of the one tooth flank line end (the first connection point X8) and (not shown) end of the other tooth surface line segment, without going through the tooth bottom line, are connected by a single arc to share tangent at a connection point ing.
[0040]
　Next, the analysis conditions were as follows. That is, to fix the rotation of the spur gear having a tooth profile shown in FIGS. 3 to 5, force is applied in the vicinity of the tip of the any one of the teeth. Position plus force, on a straight line surface and the tooth surface of the cylinder of diameter 46.5mm having the same central axis as the central axis of the gear intersect the direction of the force was a direction perpendicular to the tooth surface. Gear is assumed to be made of steel, and the Young's modulus 207GPa, an elastic body of Poisson's ratio 0.3, was analyzed as a plane strain state. Incidentally, the applied force for the tooth width 100 mm, was 35 kN. Under these conditions, the estimated maximum value of the maximum principal stress in the tooth root of (MPa), from the result to determine the ratio of a conventional example of the maximum value of the maximum principal stress in the tooth root. Table 1 of the above analysis conditions, shows the analysis results in Table 2.
[0041]
[Table 1]

[0042]
[Table 2]

[0043]
　As shown in Tables 1 and 2, together with the the present invention Example 1 3 (FIG. 4 (a) (c)) are all to be the maximum radius of curvature of a dangerous section position, teeth danger sectional position both the radius of curvature toward the both surfaces and tooth root is without or decreased change, also than risk sectional position within dedendum line in the presence of a partial radius of curvature is small, occur more extreme stress concentration It has a maximum radius of curvature at the tooth root line than 3 times the minimum radius of curvature so as not. Also, the 3 Invention Example 1, a near dangerous cross-sectional position, and a region where the radius of curvature does not change. Thus, the 3 Invention Example 1, by setting the appropriate radius of curvature in accordance with the distance from the dangerous section position, moreover, since the stress amplitude is dangerous section position the point of maximum, the conventional example 1, the maximum value of the maximum principal stress is greatly reduced with respect to 2, it can be seen that the improvement in the dedendum bending strength is achieved.
[0044]
　In contrast, for Comparative Example 1 3 (FIG. 5 (a) ~ (c)) is, radius of curvature at risk sectional position is at a maximum, the maximum curvature radius is less than 3 times the minimum radius of curvature, and since the radius of curvature that there is a change, it does not satisfy any of, no application predetermined tooth profile. Therefore, the 3 Comparative Example 1 is not the maximum value of the maximum principal stress is greatly reduced relative to the prior art examples 1 and 2, it is seen that the improvement in the dedendum bending strength is not achieved.
[0045]
　From the above results, according to the gear having a present predetermined dedendum shape, inhibition of dedendum bending stress was demonstrated. The present invention is not only a spur gear, helical gear, internal gear, a bevel gear, worm gear, can also be widely applied to a dedendum shape such as a hypoid gear. Further, the tooth surfaces of the gears of the present invention is not limited to the involute curve may be any curve. Furthermore, the gear material of the present invention may be any one, for example, can be used initially as metal or resin ferrous alloy.
DESCRIPTION OF SYMBOLS
[0046]
　11 and 21 the addendum line
　12, 22 tooth surface segments
　13 and 23 dedendum segment
　14, 24 tooth bottom line
　A1, A3, A4, A7 points included in the area from dangers sectional position to the first connection point
　B1, B2, B2 ', B3 , B4, B5, B6 point included in the region from the danger sectional position to the second connection point
　a point in the C2 danger sectional position
　X0 ~ X8 first connection point
　Y0 ~ Y7 second of the connection point

[Claim 1]
　In cross section, the tooth tip segment, the tooth surface segment, dedendum line, and a high strength gear having a sequentially continuous tooth form tooth bottom line,
　the curvature at risk sectional position determined by the 30 ° tangent method of Hofer radius is the maximum,
　the first radius of curvature to the connecting point or decreased is constant from the danger sectional position is a boundary point between the dedendum line and the tooth surface segment, and the danger section second radius of curvature to the connecting point or decreased is constant from the position which is the boundary point between the tooth bottom segment and the dedendum line,
　within the dedendum line, curvature than the dangerous section position there is a point having a small radius,
　in said tooth root line, the maximum radius of curvature is equal to or less than 3 times the minimum radius of curvature,
　the dangerous section position a portion of the arc, and the arc the danger section and wherein the extending on either side of the position, high strength gear.
[Claim 2]
　The basis of the risk sectional position, the arc is the tooth top line direction and the tooth root line direction, 0.05 times or more of the respective modules in the tooth depth direction dimension extends above [1] high strength gear according to.
[Claim 3]
　High strength gear according to claim 1 or 2, characterized by comprising the iron-based alloy.