Differential gear mechanism and design method thereof

Abstract

The invention provides a differential gear mechanism and a design method thereof. In the differential gear mechanism of the present disclosure, a reference pressure angle of each side gear tooth of a side gear and a reference pressure angle of each pinion tooth of a pinion gear increase from an intermediate portion of a tooth trace toward an inner end side and from the intermediate portion toward an outer end side, and the reference pressure angle of each side gear tooth of the side gear and the reference pressure angle of each pinion tooth of the pinion gear increase from the intermediate portion toward the outer end side. The tooth thickness of the pitch cone of the side gear decreases from the intermediate portion of the tooth trace toward the inner end side and increases from the intermediate portion toward the outer end side. The tooth thickness of the pitch cone of the pinion gear increases from the intermediate portion of the tooth trace toward the inner end side and decreases from the intermediate portion toward the outer end side.

Description

Technical Field

[0001] This disclosure relates to a differential gear mechanism comprising a pair of side gears and a plurality of pinions meshing with the pair of side gears, and a design method thereof. Background Technology

[0002] Conventionally, differential gears are known that consist of a spur bevel gear, which is rotatable and supported by a pinion shaft fixed to a housing, and a pair of spur gears meshing together (for example, see Patent Document 1). In this differential gear, to ensure the wall thickness of the inner end of the pinion (the end near the center of the differential gear), the inner end of the pinion's tooth root is inclined such that the pinion's tooth root cone is located near the tooth tip cone. Furthermore, the inner end of the tooth tip of the spur gear is inclined such that the spur gear's tooth tip cone is located near the tooth root cone, extending along the inner end of the pinion's tooth root.

[0003] Furthermore, conventionally known differential mechanisms include a pinion shaft fixed to a housing, a bevel gear (i.e., a pinion) supported by the pinion shaft and capable of rotation, and a pair of bevel gears (i.e., a pair of side gears) meshing with the pinion (for example, see Patent Document 2). In this differential mechanism, to suppress the reduction in strength of the side gears and shorten the axial length of the differential mechanism, the outer end of the tooth root (the end near the outer periphery) of each side gear is inclined such that the tooth root cone of the side gear is located near the tooth tip cone. Additionally, the outer end of the tooth tip of the pinion is inclined such that the tooth tip cone of the pinion is located near the tooth root cone, extending along the outer end of the tooth root of the side gear.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-048903

[0005] Patent Document 2: Japanese Patent Application Publication No. 2014-185666

[0006] However, as described in Patent Document 1, when the inner end of the pinion's tooth root is inclined such that the pinion's tooth root cone is located near the tooth tip cone, the tooth root thickness of the pinion's teeth becomes smaller at the inner end of the pinion (the end on the center side of the differential gear), thus reducing the pinion's strength. Therefore, without implementing certain countermeasures, it is difficult to ensure the pinion's strength and to reduce the pinion's diameter to achieve miniaturization of the differential gear. Furthermore, as described in Patent Document 2, when the outer end of the side gear's tooth root is inclined such that the side gear's tooth root cone is located near the tooth tip cone, the tooth root thickness of the side gear (differential mechanism) becomes smaller at the outer end of the side gear, thus reducing the side gear's strength. Therefore, without implementing certain countermeasures, it is difficult to ensure the side gear's strength and to shorten the axial length of the differential mechanism along the side gear's axial direction. Summary of the Invention

[0007] Therefore, the main objective of this disclosure is to ensure the strength of the side gears and pinions in a differential gear mechanism comprising a pair of side gears and a plurality of pinions meshing with the pair of side gears, and to miniaturize the differential gear mechanism.

[0008] The differential gear mechanism disclosed herein includes: a pair of bevel gears, each having multiple side gear teeth, and a pair of bevel gears, each having multiple pinion teeth, meshing with the pair of side gears. The outer end of the tooth root of each side gear is inclined such that its tooth root cone is located closer to its tooth tip cone. The inner end of the tooth tip of each side gear is inclined such that its tooth tip cone is located closer to its tooth root cone. The inner end of the tooth root of each pinion is inclined such that its tooth root cone is located closer to its tooth tip cone. The outer end of the tooth tip of each pinion is inclined such that its tooth tip cone is located closer to its tooth root cone. The angle between the radius line at the node of the side gear tooth and the tangent to the tooth profile, i.e., the reference pressure angle, and the angle between the radius line at the node of the pinion tooth and the tangent to the tooth profile, i.e., the reference pressure angle, are determined by the relationship between the tooth line and the tooth profile. In a reference side gear, the reference pressure angle increases from the middle portion of the tooth line encompassing the inner end of the tooth tip of the side gear tooth and the outer end of the tooth tip of the pinion tooth towards the inner end, and the reference pressure angle increases from the middle portion towards the outer end. Compared to a reference side gear, the tooth thickness of the side gear on the pitch cone decreases from the middle portion towards the inner end and increases from the middle portion towards the outer end. In a reference pinion, the tooth thickness of the pinion on the pitch cone increases from the middle portion towards the inner end and decreases from the middle portion towards the outer end.

[0009] Furthermore, the design method of the differential gear mechanism disclosed herein is a design method for a differential gear mechanism. In the aforementioned differential gear mechanism, it includes: a pair of bevel gears, each having multiple side gear teeth; and a pair of bevel gears, each having multiple pinion teeth, meshing with the pair of side gears. The outer end of the tooth root of the side gear is inclined such that its tooth root cone is located closer to the tooth tip cone of the side gear. The inner end of the tooth tip of the side gear is inclined such that its tooth tip cone is located closer to the tooth root cone of the side gear. The inner end of the tooth root of the pinion is inclined such that its tooth root cone is located closer to the tooth tip cone of the pinion. The outer end of the tooth tip of the pinion is inclined such that its tooth tip cone is located closer to the tooth root cone of the pinion. In the aforementioned design method, the angle formed between the radius line passing through the node of the side gear tooth and the tangent of the tooth profile, i.e., the reference pressure angle, and the radius line passing through the node of the pinion tooth are... The angle between the line and the tangent of the tooth profile, i.e., the reference pressure angle, increases from the middle portion of the tooth line encompassing the inner end of the tooth tip of the side gear tooth and the outer end of the tooth tip of the pinion tooth in the tooth line direction towards the inner end, and further increases from the middle portion towards the outer end. The intersection line between the tooth surface and the pitch cone of the side gear tooth is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle is constant in the tooth line direction. Compared to this reference side gear... Compared to a reference pinion where the tooth thickness on the pitch cone of the aforementioned side gear decreases as it approaches the inner end from the middle portion and increases as it approaches the outer end from the middle portion, and the line of intersection between the tooth surface of the pinion and the pitch cone is a straight line passing through the center and the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone of the aforementioned pinion increases as it approaches the inner end from the middle portion and decreases as it approaches the outer end from the middle portion. Attached Figure Description

[0010] Figure 1 This is a simplified structural diagram showing the differential gear mechanism of this disclosure.

[0011] Figure 2 This is a partial sectional view showing the differential gear mechanism of this disclosure.

[0012] Figure 3 It is a graph showing the relationship between the cone distance at the side gear and pinion of the differential gear mechanism of this disclosure and the reference pressure angle.

[0013] Figure 4 This is a graph showing the relationship between the cone distance at the side gear of the differential gear mechanism of this disclosure and the tooth thickness on the pitch cone.

[0014] Figure 5 This is a graph showing the relationship between the cone distance at the pinion and the tooth thickness on the pitch cone in the differential gear mechanism of this disclosure.

[0015] Figure 6 This is a graph showing the relationship between the cone distance at the side gear and the tooth thickness at the tooth root of the differential gear mechanism of this disclosure.

[0016] Figure 7 This is a graph showing the relationship between the cone distance at the pinion and the tooth thickness at the tooth root in the differential gear mechanism of this disclosure.

[0017] Figure 8 This is an enlarged view showing the main parts of the differential gear mechanism of this disclosure.

[0018] Figure 9 This is an enlarged view showing the main parts of the differential gear mechanism of this disclosure.

[0019] Figure 10 This is an illustrative diagram illustrating the tooth tip that may be generated at the pinion of the differential gear mechanism of this disclosure.

[0020] Figure 11 This is an illustrative diagram illustrating the undercut that may occur at the pinion of the differential gear mechanism of this disclosure.

[0021] Figure 12 This is a simplified structural diagram showing the meshing state between the side gear and the pinion in the differential gear mechanism of this disclosure.

[0022] Figure 13 This is a diagram illustrating the steps for adjusting the pressure angle at the pinion of the differential gear mechanism of this disclosure.

[0023] Figure 14 This is a diagram illustrating the pressure angle adjustment at the side gear and pinion of the differential gear mechanism of this disclosure.

[0024] Figure 15 This is a diagram illustrating the pressure angle adjustment at the side gear and pinion of the differential gear mechanism of this disclosure.

[0025] Figure 16 This is a diagram illustrating the steps for adjusting the pressure angle at the pinion of the differential gear mechanism of this disclosure. Detailed Implementation

[0026] Next, with reference to the accompanying drawings, the manner in which the invention is carried out will be described.

[0027] Figure 1 This is a perspective view showing the differential gear mechanism 1 of this disclosure. Figure 2These figures show partial cross-sectional views of the main components of the differential gear mechanism 1. The differential gear mechanism 1 shown in these figures comprises a differential gear mounted in a vehicle along with a differential ring gear and differential housing (not shown). The differential gear mechanism 1 includes a pair of side gears 2 and multiple (in this embodiment, for example, 2-4) pinions 3 that mesh with each pair of side gears 2. The pair of side gears 2 are respectively fixed to corresponding drive shafts (not shown). Furthermore, each pinion 3 has a corresponding pinion shaft inserted into it, which is supported by the differential housing and extends radially in a manner orthogonal to the axial direction of the pair of side gears 2. Thus, each pinion 3 is rotatable thanks to its support by the differential housing via its pinion shaft.

[0028] Each side gear 2 is a bevel gear, such as Figure 1 and Figure 2 As shown, it includes a plurality of side gear teeth 20 extending radially from a center O passing through the axis of each side gear 2 and each pinion 3 of the differential gear mechanism 1, and a plurality of tooth roots 25 located between adjacent side gear teeth 20. Figure 2 As shown, each side gear tooth 20 includes a pair of tooth surfaces 21 formed with reference to a spherical involute curve, and a tooth tip 23 formed between the pair of tooth surfaces 21. In this embodiment, the outer end portion 25o of the tooth root 25 of each side gear 2 (in) Figure 2 The region (the area on the outer periphery of the side gear 2) of the boundary B2 is inclined such that the tooth root cone RC2 of the side gear 2 is located on the side of the tooth tip cone TC2 of the side gear 2. As a result, the reduction of the wall thickness of the outer periphery of the side gear 2 can be suppressed, and the reduction of the strength of the side gear 2 can be suppressed.

[0029] Each of the small gears 3 is a bevel gear, such as Figure 1 and Figure 2 As shown, it includes a plurality of pinion teeth 30 formed in a radial pattern extending from the center O of the differential gear mechanism 1, and a plurality of tooth roots 35 located between adjacent pinion teeth 30. Figure 2 As shown, each pinion tooth 30 includes a pair of tooth surfaces 31 formed with reference to a spherical involute curve, and a tooth tip 33 formed between the pair of tooth surfaces 31. In this embodiment, the inner end portion 35i of the tooth root 35 of each pinion 3 (in Figure 2The region (near the center O side) of the boundary B3 is inclined such that the root cone RC3 of the pinion 3 is located near the tip cone TC3 of the pinion 3. This suppresses the reduction in wall thickness at the inner end (the end near the center O side) of the pinion 3, effectively ensuring its strength. Furthermore, when the axes of the side gear 2 and the pinion 3 are aligned in their meshing state, the tooth profile of one gear is formed by hobbing the tooth profile of the other, and they are in a conjugate relationship when meshed.

[0030] In addition, such as Figure 2 As shown, the inner end portion 23i of the tooth tip 23 of each side gear tooth 20 is formed to extend along the inner end portion 35i of the tooth root 35 of the pinion 3. That is, the inner end portion 23i of the tooth tip 23 of each side gear tooth 20 is inclined such that the tooth tip cone TC2 of that side gear 2 is located on the side closer to the tooth root cone RC2. Furthermore, as... Figure 2 As shown, the outer end portion 33o of the tooth tip 33 of each pinion tooth 30 is formed to extend along the outer end portion 25o of the tooth root 25 of the side gear 2. That is, the outer end portion 33o of the tooth tip 33 of each pinion tooth 30 is inclined such that the tooth tip cone TC3 of the pinion 3 is located on the side near the tooth root cone RC3.

[0031] Here, as Figure 2 As shown, when the outer end 25o of the tooth root 25 of the side gear 2 is inclined to a position closer to the tooth tip cone TC2 than the tooth root cone RC2 of the side gear 2, the tooth thickness at the tooth root of each side gear tooth 20 decreases at the outer periphery of the side gear 2, thus reducing the strength of each side gear tooth 20 and consequently the side gear 2. Therefore, in order to shorten the axial length of the differential gear mechanism 1 in the axial direction of the side gear 2 (drive shaft), it is necessary to suppress the reduction in strength of each side gear tooth 20, i.e., the side gear 2, while the outer end 25o of the tooth root 25 is inclined towards the tooth tip 23.

[0032] Furthermore, when the inner end 35i of the tooth root 35 of the pinion 3 is inclined such that the tooth root cone RC3 of the pinion 3 is located near the tooth tip cone TC3, the tooth root thickness of each pinion tooth 30 becomes smaller at the inner end (the end on the center O side) of the pinion 3, resulting in a decrease in the strength of each pinion tooth 30 and even the pinion 3 itself. Therefore, in order to reduce the diameter of the pinion 3 and thus miniaturize the differential gear mechanism 1, it is necessary to suppress the decrease in strength of each pinion tooth 30, i.e., the pinion 3, while maintaining the inclination of the inner end 35i of the tooth root 35 towards the tooth tip 33.

[0033] Based on these understandings, the inventors conducted focused research to ensure the strength of each lateral gear 2 and each pinion 3, and to miniaturize the differential gear mechanism 1. In this process, they focused on the pressure angle at the node of the lateral gear tooth 20, i.e., the reference pressure angle (the angle between the radius line at that node and the tangent to the tooth surface (tooth profile)) and the pressure angle at the node of the pinion tooth 30, i.e., the reference pressure angle (the angle between the radius line at that node and the tangent to the tooth surface (tooth profile)). Furthermore, in the differential gear mechanism 1, the inventors varied the reference pressure angles of the lateral gear tooth 20 and the pinion tooth 30 (hereinafter referred to as "reference pressure angle α") in the direction of extension of the tooth line (hereinafter referred to as "tooth line direction"), which is the line of intersection between the pitch cone PC2 of the lateral gear 2 and the tooth surface 21 of the lateral gear tooth 20, and the line of intersection between the pitch cone PC3 of the pinion 3 and the tooth surface 31 of the pinion tooth 30.

[0034] That is, in differential gear mechanism 1, such as Figure 3 As shown, the reference pressure angle α of each side gear tooth 20 and each pinion tooth 30 gradually increases from the middle portion M of the tooth line towards the inner end side (center O side), and gradually increases from the middle portion M towards the outer end side (outer peripheral side of the side gear 2). In this embodiment, the middle portion M of the tooth line is a point determined near the midpoint of the tooth line, and includes the range S in the tooth line direction between the inclined inner end 23i of the tooth tip 23 of the side gear tooth 20 and the inclined outer end 33o of the tooth tip 33 of the pinion tooth 30, that is, the meshing between the side gear tooth 20 and the pinion tooth 30 is defined only by the tooth tip cone TC2 of the side gear 2 and the tooth tip cone TC3 of the pinion 3. Figure 2 The range S is within the area between the two double-dotted lines. In this embodiment, the range S is approximately 40%–60% of the meshing range between the side gear tooth 20 and the pinion tooth 30, centered on the middle portion M, in the tooth line direction.

[0035] Furthermore, the middle part M can also be the midpoint of the tooth line. Additionally, in Figure 2In the example, the inner end portion 23i of the tooth tip 23 of the side gear 2 is located closer to the center O in the tooth line direction than the outer end portion 33o of the tooth tip 33 of the pinion tooth 30, but it is not limited to this. For example, the inner end portion 23i of the tooth tip 23 of the side gear 2 may also extend to the outer peripheral side (opposite to the center O) in the tooth line direction than the outer end portion 33o of the tooth tip 33 of the pinion tooth 30. In this case, the intermediate portion M can also be determined to be included within the above-mentioned range S. Furthermore, the position of the outer peripheral end portion of the inner end portion 23i in the tooth line direction and the position of the end portion of the outer end portion 33o closer to the center O in the tooth line direction may coincide. In this case, the intermediate portion M coincides with the position of the outer peripheral end portion of the inner end portion 23i in the tooth line direction and the position of the end portion of the outer end portion 33o closer to the center O in the tooth line direction.

[0036] Furthermore, in the differential gear mechanism 1, in addition to making the reference pressure angle α as... Figure 3 In addition to the variation in the tooth line direction as shown, the tooth thickness (circular arc tooth thickness) of the side gear 2 on the pitch cone PC2 is also determined as follows: Figure 4 As shown by the solid line, with reference to the gear on the reference side (refer to...). Figure 4 Compared to the dotted line in the diagram, the tooth thickness decreases as it approaches the inner end (center O side) from the middle part M, and increases as it approaches the outer end (outer circumference side of side gear 2) from the middle part M. Furthermore, in the differential gear mechanism 1, the tooth thickness (circumferential tooth thickness) of the pinion 3 on the pitch cone PC3 is determined as follows: Figure 5 As shown by the solid line, with reference to the pinion (reference). Figure 5 Compared to the dotted line in the middle, the tooth thickness increases as it moves from the middle part M towards the inner end, and decreases as it moves from the middle part M towards the outer end.

[0037] A reference spur gear is a straight bevel gear in which the line of intersection between the tooth surface and the pitch cone of the spur gear is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle α is constant in the tooth line direction. In the reference spur gear, the cross-section obtained by cutting the spur gear tooth with a spherical surface centered on the center of the differential gear mechanism is enlarged or reduced along the axis of the reference spur gear by a similarity ratio corresponding to the distance from the center (radius of the sphere). Similarly, a reference pinion is a straight bevel gear in which the line of intersection between the pinion tooth surface and the pitch cone of the pinion gear is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle α is constant in the tooth line direction. In the reference pinion, the cross-section obtained by cutting the pinion tooth with a spherical surface centered on the center of the differential gear mechanism is enlarged or reduced along the axis of the reference pinion by a similarity ratio corresponding to the distance from the center (radius of the sphere). Furthermore, the middle portion of the tooth line in the reference side gear and the reference pinion is defined at a point near the midpoint of the tooth line and is contained within the range S between the inclined inner end of the tooth tip of the side gear tooth and the inclined outer end of the tooth tip of the pinion tooth in the tooth line direction. Moreover, the middle portion M of the side gear 2 and the pinion 3 coincides with the middle portion of the reference side gear and the reference pinion.

[0038] Therefore, as Figure 6 As shown by the solid line, this is the case where the reference pressure angle α and the tooth thickness on the pitch cone PC2 were not adjusted (refer to...). Figure 6 Compared to the dotted line in the diagram, the tooth thickness (arc tooth thickness) at the outer end 25o (outer end side than boundary B2) of the tooth root 2 of the side gear 2 is larger. Additionally, as... Figure 7 As shown by the solid line, this is the case where the reference pressure angle α and the tooth thickness on the pitch cone PC3 were not adjusted (refer to...). Figure 7 Compared to the dotted line in the diagram, the tooth thickness (arc tooth thickness) at the inner end 35i (more inner than the boundary B3) of the pinion 3 is larger.

[0039] Therefore, as Figure 8 As shown, at the inner end of the side gear 2 (the end on the center O side), the tooth thickness di2 of the tooth root of the side gear tooth 20 can be sufficiently ensured, and, as Figure 9 As shown by the dashed line, the tooth thickness do2 at the root of the side gear tooth 20 can be increased at the outer periphery of the side gear 2. Additionally, as... Figure 9 As shown, at the outer end of the pinion 3, the tooth thickness do3 at the root of the pinion tooth 30 can be sufficiently ensured, and as... Figure 8 As shown by the dashed line, the tooth thickness di3 of the root of the pinion tooth 30 can be increased at the inner end of the pinion 3. As a result, the strength of the side gear 2 and the pinion 3 can be well ensured, and the axial length of the differential gear mechanism 1 in the axial direction of the side gear 2 and the diameter of the pinion 3 can be reduced, thereby miniaturizing the differential gear mechanism 1.

[0040] However, in the side gear teeth 20 and pinion teeth 30, which cause the reference pressure angle α and the tooth thickness on the pitch cones PC2 and PC3 to vary in the tooth line direction, in the region where the reference pressure angle α is relatively large, such as Figure 10 As shown by the dashed line, there is a possibility of tooth tip ( Figure 10 Example of pinion tooth 30). Furthermore, in the side gear teeth 20 and pinion teeth 30, where the reference pressure angle α and the tooth thickness on the pitch cones PC2 and PC3 vary in the tooth line direction, in the region where the reference pressure angle α is relatively small, such as... Figure 11 As shown by the dashed line, root cutting may occur at the tooth root. Figure 11 Example of pinion tooth 30).

[0041] Furthermore, the tips and roots of the side gear teeth 20 and pinion teeth 30 are cut at... Figure 12 Any region among the first, second, third, and fourth regions A1, A2, A3, and A4 can potentially be generated. For example... Figure 12 As shown, the first region A1 is located on the inner end side of the middle part M (including the middle part M, which is a plane orthogonal to the tooth line direction) in the tooth line direction, and is located on the side of the pitch cones PC2 and PC3 of the side gear 2 and pinion 3, respectively, near the tooth tip cone TC2 of the side gear 2 and the tooth root cone RC3 of the pinion 3. The second region A2 is located on the inner end side of the middle part M in the tooth line direction, and is located on the side of the tooth root cone RC2 and tooth tip cone TC3 of the side gear 2 and PC3, respectively, near the tooth line cone M.

[0042] The third region A3 is located on the outer end side of the middle part M in the tooth line direction, and on the side of the tooth tip cone TC2 of the side gear 2 and the tooth root cone RC3 of the pinion 3, compared to the pitch cones PC2 and PC3. The fourth region A4 is located on the inner end side of the middle part M in the tooth line direction, and on the side of the tooth root cone RC2 of the side gear 2 and the tooth tip cone TC3 of the pinion 3, compared to the pitch cones PC2 and PC3. Moreover, in at least any of the first to fourth regions A1-A4, if tooth tipping or undercutting occurs on the side gear tooth 20 or the pinion tooth 30, the tooth height and meshing rate of the side gear tooth 20 and the pinion tooth 30 cannot be well ensured.

[0043] Based on these, in the differential gear mechanism 1, the aforementioned reference pressure angle α and the tooth thickness adjustment on the pitch cone PC3 result in, for example, the formation of a tooth tip on the pinion tooth 30 in the second region A2 on the inner end side of the inclined outer end 33o of the tooth tip 33 (excluding the pinion tooth 30). Within this second region A2, the pressure angle (the angle between the radius line passing through a point on the tooth surface 21 of each side gear tooth 20 and the tangent of the tooth surface (tooth profile)) at the tooth surface 21 of each side gear tooth 20 and the tooth surface 31 of each pinion tooth 30 is adjusted. In this case, as... Figure 13 As shown, the pressure angle at the tooth surface 31 included in the second region A2 of each pinion tooth 30 is, in the tooth line direction, closer to the inner end side than the middle part M, and is related to the second reference pinion (refer to...). Figure 13 Compared to the dashed line, the pressure angle is adjusted so that as it moves from the pitch cone PC3 of the pinion 3 toward the tooth tip cone TC3 side of the pinion 3, the pressure angle decreases.

[0044] Compared to the aforementioned reference pinion, the second reference pinion is configured to make the reference pressure angle α such that... Figure 3 As shown, this adjustment increases both from the middle portion M towards the inner end and from the middle portion M towards the outer end. Figure 13 As shown, the pressure angle on the tooth surface of each pinion at the inner end of the second reference pinion is larger than the pressure angle on the tooth surface of the middle part M. Additionally, as... Figure 14 As shown, the adjustment amount (hereinafter referred to as "pressure angle adjustment amount") δ of the pressure angle of the pinion 3 in the second region A2 is zero on the pitch cone PC3. In the tooth line direction, closer to the inner end side than the middle part M, the adjustment amount is determined to be a negative value that decreases (increases in absolute value) as it approaches the tip cone TC3 of the pinion 3 from the pitch cone PC3. Furthermore, Figure 14 The horizontal axis represents the rotation angle of pinion 3. Figure 15 (The same applies).

[0045] Furthermore, regarding the side gear 2, which is conjugate with the pinion 3, the pressure angle on the tooth surface 21 included in the second region A2 of each side gear tooth 20 is adjusted such that, in the tooth line direction, at the inner end side of the middle part M, compared to the second reference side gear, the pressure angle decreases as it approaches the tooth root cone RC2 side of the side gear 2 from the pitch cone PC2. Relative to the aforementioned reference side gear, the second reference side gear is equipped with a reference pressure angle α such that... Figure 3 As shown, this adjustment increases from the middle part M towards the inner end and from the middle part M towards the outer end. The pressure angle on the tooth surface of each gear tooth at the inner end of the second reference side gear is also larger than the pressure angle on the tooth surface of the middle part M. Furthermore, as... Figure 14As shown, the pressure angle adjustment δ of the side gear 2 in the second region A2 is zero on the pitch cone PC2. In the tooth line direction, closer to the inner end of the middle part M, the pressure angle adjustment δ is determined to be a negative value that decreases (increases in absolute value) as it approaches the tooth root cone RC2 of the side gear 2 from the pitch cone PC2. As a result, the tooth tip of the pinion tooth 30 in the second region A2 can be eliminated, ensuring good tooth height and meshing ratio of the side gear tooth 20 and the pinion tooth 30. Furthermore, the middle part of the tooth line in the second reference side gear and the second reference pinion coincides with the middle part of the reference side gear and the reference pinion, and the middle part M of the side gear 2 and the pinion 3.

[0046] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC2, for example, in the aforementioned third region A3 on the outer end side of the inclined inner end portion 23i of the tooth tip 23 (excluding the side gear tooth 20), a tooth tip is generated on the side gear tooth 20. Figure 14 As shown, the pressure angle adjustment δ of the side gear 2 and pinion 3 in the third region A3 is determined to be a negative value that decreases (in absolute value increases) as it approaches the tooth tip cone TC2 of the side gear 2 and the tooth root cone RC3 of the pinion 3 from the pitch cones PC2 and PC3. Therefore, the pressure angle on the tooth surface 21 of each side gear tooth 20 in the third region A3 is adjusted such that, compared to the second reference side gear, the pressure angle decreases as it approaches the tooth root cone RC2 of the side gear 2 from the pitch cone PC2 of the side gear 2. Similarly, the pressure angle on the tooth surface 31 of the third region A3 of each pinion tooth 30 is adjusted such that, in the tooth line direction, it decreases towards the tip cone TC3 of the pinion 3 from the pitch cone PC3 towards the tip cone TC3 of the pinion 3, compared to the second reference pinion, at the outer end side of the middle part M. As a result, the tip of the lateral gear tooth 20 in the third region A3 can be eliminated, and the tooth height and meshing ratio of the lateral gear tooth 20 and the pinion tooth 30 are well ensured.

[0047] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC3, for example, in the aforementioned third region A3 on the outer end side of the inner end 35i of the tooth root 35 of the pinion 3, where undercutting occurs at the root of the pinion tooth 30, such as... Figure 15 As shown, the pressure angle adjustment δ within the range of the third region A3 is zero on the pitch cone PC3. In the tooth line direction, closer to the outer end of the middle part M, the pressure angle adjustment δ is determined to be a positive value that increases as it approaches the tooth tip cone TC2 of the side gear 2 and the tooth root cone RC3 of the pinion 3 from the pitch cones PC2 and PC3. Therefore, as... Figure 16As shown, the pressure angle on the tooth surface 31 of the third region A3 of each pinion tooth 30 is adjusted such that, in the tooth line direction, at the outer end side of the middle part M, it is aligned with the aforementioned second reference pinion (refer to...). Figure 16 Compared to the dashed line in the diagram, the pressure angle increases from the pitch cone PC3 of the pinion 3 towards the root cone RC3 of the pinion 3. Similarly, the pressure angle on the tooth surface 21 included in the third region A3 of each side gear tooth 20 is adjusted such that, in the tooth line direction, at the outer end of the middle part M, compared to the second reference side gear, the pressure angle increases from the pitch cone PC2 of the side gear 2 towards the tip cone TC2 of the side gear 2. As a result, undercutting of the pinion tooth 30 in the third region A3 can be eliminated, ensuring good tooth height and meshing ratio of the side gear teeth 20 and the pinion teeth 30.

[0048] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC2, for example, in the second region A2 described above, which is located on the inner side of the inclined outer end 25o of the tooth root 25 of the side gear 20, undercut occurs at the tooth root of the side gear 20. Figure 15 As shown, the pressure angle adjustment δ in the second region A2 is a positive value that increases as it approaches the root cone RC2 of the side gear 2 and the tip cone TC3 of the pinion 3, located closer to the inner end of the tooth line than the middle part M. Therefore, the pressure angle on the tooth surface 21 of each side gear tooth 20 in the second region A2 is adjusted such that, compared to the second reference side gear, the pressure angle increases as it approaches the root cone RC2 of the side gear 2, located closer to the inner end of the tooth line than the middle part M. Similarly, the pressure angle on the tooth surface 31 of each pinion tooth 30 in the second region A2 is adjusted such that, compared to the second reference pinion, the pressure angle increases as it approaches the tip cone TC3 of the pinion 3, located closer to the inner end of the tooth line than the middle part M. As a result, the root undercut of the lateral gear tooth 20 in the second region A2 can be eliminated, and the tooth height and meshing rate of the lateral gear tooth 20 and the pinion tooth 30 can be well ensured.

[0049] Furthermore, as a result of adjusting the reference pressure angle α and the tooth thickness on the pitch cone PC3, for example, in the fourth region A4, which includes the outer end 33o of the inclined formation of the tooth tip 33 of the pinion tooth 30, if a tooth tip is generated on the pinion tooth 30, the same as in the case where a tooth tip is generated on the pinion tooth 30 in the second region A2, the pressure angle on the tooth surface 31 included in the fourth region A4 of each pinion tooth 30 is such that, in the tooth line direction, on the outer end side of the middle part M, the pressure angle decreases as it approaches the tooth tip cone TC3 side of the pinion 3 from the pitch cone PC3 of the pinion 3 compared to the second reference pinion. Furthermore, the pressure angle on the tooth surface 21 encompassed by the fourth region A4 of each side gear tooth 20 is such that, in the tooth line direction, at the outermost end of the middle portion M, compared to the aforementioned second reference side gear, the pressure angle decreases as it approaches the tooth root cone RC2 of the side gear 2 from the pitch cone PC2. As a result, the tooth tip of the pinion tooth 30 in the fourth region A4 can be eliminated, effectively ensuring the tooth height and meshing ratio of the side gear tooth 20 and the pinion tooth 30.

[0050] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC2 results in, for example, in the first region A1, which includes the inclined inner end 23i of the tooth tip 23 of the side gear tooth 20, where a tooth tip is generated on the side gear tooth 20, similar to the case where a tooth tip is generated on the side gear tooth 20 in the third region A3. The pressure angle on the tooth surface 21 included in the first region A1 of each side gear tooth 20 should be such that, in the tooth line direction, closer to the inner end than the middle portion M, the pressure angle decreases compared to the second reference side gear as it approaches the tooth tip cone TC2 side of the side gear from the pitch cone PC2 of the side gear 2. Similarly, the pressure angle on the tooth surface 31 included in the first region A1 of each pinion tooth 30 should be such that, in the tooth line direction, closer to the inner end than the middle portion M, the pressure angle decreases compared to the second reference pinion as it approaches the tooth root cone RC3 side of the pinion 3 from the pitch cone PC3 of the pinion 3. As a result, the tooth tip of the lateral gear tooth 20 in the first region A1 can be eliminated, and the tooth height and meshing rate of the lateral gear tooth 20 and the pinion tooth 30 can be well ensured.

[0051] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC2 results in, for example, undercutting at the root of the side gear tooth 20 in the fourth region A4, which includes the inclined outer end 25o of the tooth root 25 of the side gear 2, similar to the undercutting at the root of the side gear tooth 20 in the second region A2. This allows the pressure angle on the tooth surface 21 included in the fourth region A4 of each side gear tooth 20 to increase as the pressure angle increases from the pitch cone PC2 of the side gear 2 towards the tooth root cone RC2 of the side gear 2 in the tooth line direction, compared to the second reference side gear, at the outermost end of the middle portion M. Furthermore, the pressure angle on the tooth surface 31 encompassed by the fourth region A4 of each pinion tooth 30 is such that, in the tooth line direction, at the outermost end of the middle portion M, compared to the aforementioned second reference pinion, the pressure angle increases from the pitch cone PC3 of the pinion 3 towards the tip cone TC3 of that pinion 3. As a result, undercutting of the tooth root of the lateral gear tooth 20 in the fourth region A4 can be eliminated, effectively ensuring the tooth height and meshing ratio of the lateral gear tooth 20 and the pinion tooth 30.

[0052] Furthermore, the adjustment of the reference pressure angle α and the tooth thickness on the pitch cone PC3 results in, for example, undercutting occurring at the root of the pinion tooth 30 in the first region A1, which includes the inner end 35i of the tooth root 35 of the pinion 3, similar to the undercutting at the root of the pinion tooth 30 in the third region A3. The pressure angle on the tooth surface 31 of each pinion tooth 30 in the first region A1 is such that, in the tooth line direction, it increases as it moves from the pitch cone PC3 of the pinion 3 towards the tooth root cone RC3, compared to the second reference pinion, located further inside the tooth from the middle portion M. Similarly, the pressure angle on the tooth surface 21 of each side gear tooth 20 in the first region A1 is such that, in the tooth line direction, it increases as it moves from the pitch cone PC2 of the side gear 2 towards the tooth tip cone TC2, located further inside the tooth from the middle portion M, compared to the second reference side gear. As a result, the root undercut of the pinion tooth 30 in the first region A1 can be eliminated, and the tooth height and meshing rate of the side gear tooth 20 and the pinion tooth 30 can be well ensured.

[0053] Furthermore, the aforementioned intermediate part M is capable of operating within the aforementioned range S ( Figure 2The range between the two double-dotted lines is arbitrarily determined. Furthermore, the intermediate portion M is not limited to a point on the tooth line; it can also be a portion with a specified length in the tooth line direction. Furthermore, in the differential gear mechanism 1, the tooth profiles of each side gear tooth 20 and each pinion tooth 30 before the adjustment based on the pressure angle adjustment amount δ are formed by a spherical involute curve, but are not limited to this. That is, the tooth profiles of each side gear tooth 20 and each pinion tooth 30 before the adjustment based on the pressure angle adjustment amount δ can also be formed, for example, by a figure-eight tooth profile curve, a cycloidal curve, etc. Additionally, when designing the aforementioned side gear 2 and pinion 3, the tooth thickness can be adjusted after the adjustment of the reference pressure angle α and the pressure angle adjustment based on the pressure angle adjustment amount δ.

[0054] [Summary of Implementation Methods]

[0055] As explained above, the differential gear mechanism of this disclosure includes: a pair of bevel gears (2) each having a plurality of side gear teeth (20), and a plurality of pinions (3) each having a plurality of pinion teeth (30) meshing with the pair of side gears (2). In the differential gear mechanism (1), the outer end (25o) of the tooth root (25) of the side gear (2) is inclined to the side of the tooth root cone (RC2) of the side gear (2) located near the tooth tip cone (TC2) of the side gear (2), and the inner end (23i) of the tooth tip (23) of the side gear (20) is inclined to the side of the tooth tip cone (TC2) of the side gear (2). The cone (TC2) is located on the side of the tooth root cone (RC2) of the aforementioned side gear (2). The inner end (35i) of the tooth root (35) of the aforementioned pinion (3) is inclined to the side of the tooth tip cone (TC3) of the aforementioned pinion (3). The outer end (33o) of the tooth tip (33) of the aforementioned pinion tooth (30) is inclined to the side of the tooth root cone (RC3) of the aforementioned pinion (3). The angle formed between the radius line at the node of the aforementioned side gear tooth (20) and the tangent of the tooth profile is also the reference pressure angle (α). The reference pressure angle (α) is the angle between the radius line at the node of the pinion tooth (30) and the tangent of the tooth profile. As the reference pressure angle (α) increases from the middle part (M) of the tooth line between the inner end (23i) of the tooth tip (23) of the side gear tooth (20) and the outer end (33o) of the tooth tip (33) of the pinion tooth (30) towards the inner end, the reference pressure angle (α) increases from the middle part (M) towards the outer end. The intersection line between the tooth surface and the pitch cone of the side gear tooth is a straight line passing through the center of the differential gear mechanism and is... Compared to a reference side gear where the reference pressure angle is constant in the tooth line direction, the tooth thickness of the side gear (2) on the pitch cone (PC2) decreases as it approaches the inner end from the middle part (M) and increases as it approaches the outer end from the middle part (M). Furthermore, the intersection line between the tooth surface of the pinion tooth and the pitch cone is a straight line passing through the center and the reference pressure angle is constant in the tooth line direction. Compared to a reference pinion where the reference pressure angle is constant in the tooth line direction, the tooth thickness of the pinion (3) on the pitch cone (PC3) increases as it approaches the inner end from the middle part (M) and decreases as it approaches the outer end from the middle part (M).

[0056] In the differential gear mechanism disclosed herein, the outer end of the tooth root of the spur gear, the inner end of the tooth tip of the spur gear, the inner end of the tooth root of the pinion gear, and the outer end of the tooth tip of the pinion gear are inclined. Therefore, the wall thickness of the inner end of the pinion gear can be ensured, and the axial length of the differential gear mechanism in the axial direction of the spur gear is shortened. Furthermore, the reference pressure angle of the spur gear teeth and the reference pressure angle of the pinion gear teeth increase from the middle portion of the tooth line towards the inner end, and increase from the middle portion towards the outer end. Thus, compared to a reference spur gear, the tooth thickness of the spur gear on the pitch cone decreases from the middle portion towards the inner end and increases from the middle portion towards the outer end. This ensures sufficient tooth thickness at the inner end (the end near the center) of the spur gear, and compared to a reference spur gear where the reference pressure angle is constant in the tooth line direction, increases the tooth thickness at the outer end (the end on the outer periphery) of the spur gear. Furthermore, compared to the reference pinion, the tooth thickness of the pinion on the pitch cone increases from the middle portion towards the inner end and decreases from the middle portion towards the outer end. This ensures sufficient tooth thickness at the outer end of the pinion (the end near the outer periphery of the side gear). Moreover, compared to the reference pinion where the reference pressure angle is constant in the tooth line direction, the tooth thickness at the inner end of the pinion (the end near the center of the differential gear mechanism) is increased. As a result, the strength of both the side gear and the pinion is well ensured, and the axial length of the differential gear mechanism in the axial direction of the side gear is shortened, and the diameter of the pinion is reduced, thus miniaturizing the differential gear mechanism. Furthermore, the middle part of the tooth line can be arbitrarily determined within the range defined only by the tooth tip cone of the side gear and the tooth tip cone of the pinion in the tooth line direction, i.e., the meshing between the side gear teeth and the pinion teeth. It can be a point on the tooth line or a specified length can be ensured in the tooth line direction.

[0057] Alternatively, it can be configured such that, in the tooth line direction, the first region (A1) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2) and tooth root cone (RC3) of the side gear (2) and the pinion (3) than the pitch cone (PC2, PC3) of the side gear (2) and the tooth root cone (RC3) of the pinion (3), and the first region (A1) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2, PC3) of the side gear (2) in the tooth line direction. The second region (A2) on the tooth root cone (RC2) and the tooth tip cone (TC3) side of the pinion (3), the third region (A3) on the tooth tip cone (TC2) and the tooth root cone (RC3) side of the side gear (2) that is closer to the outer end side than the middle part (M) and closer to the pitch cone (PC2, PC3) than the side gear (2), and the third region (A3) on the tooth root cone (TC2) and the tooth root cone (RC3) side of the pinion (3) that is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3) than the side gear (2), and the third region (A3) on the tooth root cone (TC2) and the tooth tip cone (RC3) side of the pinion (3) that is closer to the outer ... line direction that is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3). In at least one of the fourth regions (A4) on the side of the root cone (RC2) of the side gear (2) and the tip cone (TC3) of the pinion (3), compared to the second reference side gear whose reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface (21) of the side gear tooth (20) increases from the pitch cone (PC2, PC3) toward the side gear (C3). 2) The pressure angle on the tooth surface (31) of the pinion tooth (30) decreases as it approaches the tooth tip cone (31) or tooth top cone (32) from the pitch cone (PC2, PC3) towards the tooth top cone (TC3) or tooth bottom cone (RC3) of the pinion (3).

[0058] This eliminates the sharp tips of the spur gear teeth or pinion teeth, ensuring good tooth height and meshing rate of the spur gear teeth and pinion teeth.

[0059] Furthermore, it can also be configured such that, in the tooth line direction, the first region (A1) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2) and tooth root cone (RC3) side of the side gear (2) and pinion (3) than the pitch cone (PC2, PC3) of the side gear (2) and pinion (3), and the first region (A1) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2, PC3) of the side gear (3) in the tooth line direction. The second region (A2) on the tooth root cone (RC2) and the tooth tip cone (TC3) side of the pinion (3), the third region (A3) on the tooth tip cone (TC2) and the tooth root cone (RC3) side of the side gear (2) that is closer to the outer end side than the middle part (M) and closer to the pitch cone (PC2, PC3) than the side gear (2), and the third region (A3) on the tooth root cone (TC2) and the tooth root cone (RC3) side of the pinion (3) that is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3) than the side gear (2), and the third region (A3) on the tooth root cone (TC2) and the tooth tip cone (RC3) side of the pinion (3) that is closer to the outer ... line direction that is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3). In at least one of the fourth regions (A4) on the side of the root cone (RC2) of the side gear (2) and the tip cone (TC3) of the pinion (3), compared to the second reference side gear where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface (21) of the side gear tooth (20) increases from the pitch cone (PC2, PC3) toward the side gear (C3). 2) The pressure angle on the tooth surface (21) of the pinion tooth (30) increases from the pitch cone (PC2, PC3) towards the tip cone (TC3) or the root cone (RC3) of the pinion (3). Compared with the second reference pinion, the pressure angle on the tooth surface (21) of the pinion tooth (30) increases from the pitch cone (PC2, PC3) towards the tip cone (TC3) or the root cone (RC3) of the pinion (3).

[0060] This eliminates root undercut of the lateral gear teeth or pinion teeth, ensuring good tooth height and meshing rate of the lateral gear teeth and pinion teeth.

[0061] The design method of the differential gear mechanism disclosed herein is a design method of a differential gear mechanism (1). The differential gear mechanism (1) includes: a pair of bevel gears (2) each having multiple side gear teeth (20), and a pair of bevel gears (3) each having multiple pinion teeth (30), which mesh with the pair of side gears (2). The outer end (25o) of the tooth root (25) of the side gear (2) is inclined to the side of the tooth root cone (RC2) of the side gear (2) located near the tooth tip cone (TC2) of the side gear (2). The inner end (23i) of the tooth tip (23) of the side gear teeth (20) is inclined to the side of the tooth tip cone (TC2) of the side gear (2). The tooth tip cone (TC2) of the side gear (2) is located on the side of the tooth root cone (RC2) of the side gear (2). The inner end (35i) of the tooth root (35) of the pinion (3) is inclined to the side of the tooth tip cone (TC3) of the pinion (3) compared to the side of the tooth root cone (RC3) of the pinion (3). The outer end (33o) of the tooth tip (33) of the pinion tooth (30) is inclined to the side of the tooth root cone (RC3) of the pinion (3) compared to the side of the tooth tip cone (TC3) of the pinion (3). In the above design method, the radius line passing through the node of the side gear tooth (20) is aligned with... The angle between the tangents of the tooth profile, i.e., the reference pressure angle (α), and the angle between the radius line passing through the node of the pinion tooth (30) and the tangent of the tooth profile, i.e., the reference pressure angle (α), increase from the middle part (M) of the tooth line included between the inner end (23i) of the tooth tip (23) of the side gear tooth (20) and the outer end (33o) of the tooth tip (33) of the pinion tooth (30) in the tooth line direction towards the inner end side and from the middle part (M) towards the outer end side. The intersection line between the tooth surface and the pitch cone of the side gear tooth is a straight line passing through the center of the differential gear mechanism and the upper... Compared to a reference side gear where the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone (PC2) of the side gear (2) decreases as it approaches the inner end from the middle part (M) and increases as it approaches the outer end from the middle part (M). Furthermore, the intersection line between the tooth surface of the pinion tooth and the pitch cone is a straight line passing through the center. Compared to a reference pinion where the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone (PC3) of the pinion (3) increases as it approaches the inner end from the middle part (M) and decreases as it approaches the outer end from the middle part (M).

[0062] According to the above method, the strength of the side gear and the pinion can be well ensured, and the axial length of the differential gear mechanism in the axial direction of the side gear and the diameter of the pinion can be reduced, thereby miniaturizing the differential gear mechanism.

[0063] Alternatively, it can be configured such that, in the tooth line direction, the first region (A1) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2) and tooth root cone (RC3) of the side gear (2) and the pinion (3) than the pitch cone (PC2, PC3) of the side gear (2) and the tooth root cone (RC3) of the pinion (3), and the tooth tip cone (TC2) of the side gear (2) is located closer to the inner end side than the middle portion (M) and closer to the tooth tip cone (TC2, PC3) of the side gear (3) in the tooth line direction. The second region (A2) on the side of the bottom cone (RC2) and the tooth tip cone (TC3) of the pinion (3), the third region (A3) on the side of the tooth tip cone (TC2) and the bottom cone (RC3) of the side gear (2) and the pinion (3) in the tooth line direction, which is closer to the outer end side than the middle part (M) and closer to the pitch cone (PC2, PC3), and the third region (A3) on the side of the tooth tip cone (TC2) and the pinion (3) in the tooth line direction, which is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3). In at least one of the fourth regions (A4) on the tooth root cone (RC2) of the aforementioned side gear (2) and the tooth tip cone (TC3) of the aforementioned pinion (3), compared to the second reference side gear where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface (21) of the side gear tooth (20) is such that it increases from the pitch cone (PC2, PC3) toward the side gear (2) The pressure angle on the tooth surface (31) of the pinion tooth (30) decreases as it approaches the inner end from the middle portion and the outer end from the middle portion, compared to the second reference pinion where the reference pressure angle increases as it approaches the inner end from the middle portion and the outer end from the middle portion.

[0064] Furthermore, it can also be configured such that the first region (A1) is located in the tooth line direction closer to the inner end side than the middle part (M) and closer to the tooth tip cone (TC2) and tooth root cone (RC3) side of the side gear (2) and the pinion (3) than the pitch cone (PC2, PC3) of the side gear (2) and the tooth root cone (RC3) of the pinion (3), and the tooth root of the side gear (2) is located in the tooth line direction closer to the inner end side than the middle part (M) and closer to the tooth root of the side gear (2) than the pitch cone (PC2, PC3). The second region (A2) on the tooth tip cone (TC3) side of the cone (RC2) and the pinion (3), the third region (A3) on the tooth tip cone (TC2) and the tooth root cone (RC3) side of the side gear (2) that is closer to the outer end side than the middle part (M) and closer to the pitch cone (PC2, PC3) than the pitch cone (PC2, PC3) in the tooth line direction, and the third region (A3) on the tooth root cone (RC3) side of the side gear (2) that is closer to the inner end side than the middle part (M) and closer to the pitch cone (PC2, PC3) in the tooth line direction. In at least one of the fourth regions (A4) on the tooth root cone (RC2) of the aforementioned side gear (2) and the tooth tip cone (TC3) of the aforementioned pinion (3), compared to the second reference side gear where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface (21) of the aforementioned side gear tooth (20) increases from the pitch cone (PC2, PC3) toward the side gear (2) The pressure angle on the tooth surface (21) of the pinion tooth (30) increases from the pitch cone (PC2, PC3) towards the tooth tip cone (TC2) or the tooth root cone (RC3) of the pinion (3). Compared with the second reference pinion where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface (21) of the pinion tooth (30) increases from the pitch cone (PC2, PC3) toward the tooth tip cone (TC3) or the tooth root cone (RC3) of the pinion (3).

[0065] Furthermore, the invention disclosed herein is not limited to the above-described embodiments in any way, and various modifications can be made within the scope of this disclosure. Moreover, the above-described embodiments are merely one specific method of the technical solution described in this part of the invention description, and do not limit the elements of the technical solution described in this part of the invention description.

[0066] Industrial availability

[0067] The invention disclosed herein can be used in the manufacturing industry of differential gear mechanisms comprising a pair of side gears and a plurality of pinions meshing with the pair of side gears.

Claims

1. A differential gear mechanism, comprising: a pair of bevel gears, each having a plurality of lateral gear teeth; and a plurality of bevel gears having a plurality of pinion teeth, each having a plurality of pinion teeth, meshing with the pair of lateral gears, wherein... In the differential gear mechanism The outer end of the tooth root of the side gear is inclined such that the tooth root cone of the side gear is located on the side closer to the tooth tip cone of the side gear. The inner end of the tooth tip of the side gear is inclined such that the tooth tip cone of the side gear is located on the side closer to the tooth root cone of the side gear. The inner end of the tooth root of the pinion is inclined such that the tooth root cone is located on the side closest to the tooth tip cone of the pinion. The outer end of the tip of the pinion tooth is inclined such that the tip cone of the pinion is located on the side closest to the root cone of the pinion. The reference pressure angle is the angle formed between the radius line at the node of the side gear tooth and the tangent to the tooth profile, and the reference pressure angle is the angle formed between the radius line at the node of the pinion tooth and the tangent to the tooth profile. The reference pressure angle increases from the middle portion of the tooth line in the tooth line direction between the inner end of the tooth tip of the side gear tooth and the outer end of the tooth tip of the pinion tooth, towards the inner end, and further increases from the middle portion towards the outer end. Compared to a reference side gear, where the line of intersection between the tooth surface and the pitch cone of the side gear is a straight line passing through the center of the differential gear mechanism and the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone of the side gear decreases as it approaches the inner end from the middle portion and increases as it approaches the outer end from the middle portion. Furthermore, compared to a reference pinion, where the line of intersection between the tooth surface and the pitch cone of the pinion is a straight line passing through the center and the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone of the pinion increases as it approaches the inner end from the middle portion and decreases as it approaches the outer end from the middle portion.

2. The differential gear mechanism according to claim 1, wherein, The tooth profile includes a first region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth tip cone of the side gear and the tooth root cone of the pinion than the pitch cone of the side gear and the pinion; a second region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth root cone of the side gear and the tooth tip cone of the pinion than the pitch cone; a third region located in the tooth line direction that is closer to the outer end side than the middle portion and closer to the tooth tip cone of the side gear and the tooth root cone of the pinion than the pitch cone; and a third region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth root cone of the side gear and the pinion than the pitch cone of the side gear. In at least one region of the fourth region on the tooth tip cone side, compared to a second reference side gear where the reference pressure angle increases from the middle portion toward the inner end side and from the middle portion toward the outer end side, the pressure angle on the tooth surface of the side gear decreases from the pitch cone toward the tooth root cone side or the tooth tip cone side of the side gear. Furthermore, compared to a second reference pinion where the reference pressure angle increases from the middle portion toward the inner end side and from the middle portion toward the outer end side, the pressure angle on the tooth surface of the pinion decreases from the pitch cone toward the tooth tip cone side or the tooth root cone side of the pinion.

3. The differential gear mechanism according to claim 1, wherein, The tooth profile includes a first region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth tip cone of the side gear and the tooth root cone of the pinion than the pitch cone of the side gear and the pinion; a second region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth root cone of the side gear and the tooth tip cone of the pinion than the pitch cone; a third region located in the tooth line direction that is closer to the outer end side than the middle portion and closer to the tooth tip cone of the side gear and the tooth root cone of the pinion than the pitch cone; and a third region located in the tooth line direction that is closer to the inner end side than the middle portion and closer to the tooth root cone of the side gear and the pinion than the pitch cone of the side gear. In at least one region of the fourth region on the tooth tip cone side, compared to a second reference side gear where the reference pressure angle increases from the middle portion toward the inner end side and from the middle portion toward the outer end side, the pressure angle on the tooth surface of the side gear tooth increases from the pitch cone toward the tooth root cone side or the tooth tip cone side of the side gear. Furthermore, compared to a second reference pinion where the reference pressure angle increases from the middle portion toward the inner end side and from the middle portion toward the outer end side, the pressure angle on the tooth surface of the pinion tooth increases from the pitch cone toward the tooth tip cone side or the tooth root cone side of the pinion.

4. A design method for a differential gear mechanism, wherein, The differential gear mechanism includes: a pair of bevel gears, each having multiple lateral gear teeth, and a pair of pinions, each having multiple pinion teeth, meshing with the pair of lateral gears. The outer end of the tooth root of each lateral gear is inclined such that its tooth root cone is located closer to its tooth tip cone than the tooth root cone of the lateral gear. The inner end of the tooth tip of each lateral gear is inclined such that its tooth tip cone is located closer to its tooth root cone than the tooth tip cone of the lateral gear. The inner end of the tooth root of each pinion is inclined such that its tooth root cone is located closer to its tooth tip cone than the tooth root cone of the pinion. The outer end of the tooth tip of each pinion is inclined such that its tooth tip cone is located closer to its tooth root cone than the tooth tip cone of the pinion. In the design method, The reference pressure angle is formed between the radius line passing through the node of the side gear tooth and the tangent to the tooth profile, and the reference pressure angle is formed between the radius line passing through the node of the pinion tooth and the tangent to the tooth profile. The reference pressure angle increases from the middle portion of the tooth line in the tooth line direction between the inner end of the tooth tip of the side gear tooth and the outer end of the tooth tip of the pinion tooth, towards the inner end, and further increases from the middle portion towards the outer end. Compared to a reference side gear, where the line of intersection between the tooth surface and the pitch cone of the side gear is a straight line passing through the center of the differential gear mechanism and the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone of the side gear decreases as it approaches the inner end from the middle portion and increases as it approaches the outer end from the middle portion. Furthermore, compared to a reference pinion, where the line of intersection between the tooth surface and the pitch cone of the pinion is a straight line passing through the center and the reference pressure angle is constant in the tooth line direction, the tooth thickness on the pitch cone of the pinion increases as it approaches the inner end from the middle portion and decreases as it approaches the outer end from the middle portion.

5. The design method of the differential gear mechanism according to claim 4, wherein, The tooth lines are defined as follows: a first region located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; a second region located on the tooth line direction located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; a third region located on the tooth line direction located on the outer end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; and a third region located on the tooth line direction located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion. In at least one region of the fourth region at the tip cone side, compared to a second reference side gear where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface of the side gear decreases from the pitch cone toward the root cone side or the tip cone side of the side gear; and compared to a second reference pinion where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface of the pinion decreases from the pitch cone toward the tip cone side or the root cone side of the pinion.

6. The design method of the differential gear mechanism according to claim 4, wherein, The tooth lines are defined as follows: a first region located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; a second region located on the tooth line direction located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; a third region located on the tooth line direction located on the outer end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion; and a third region located on the tooth line direction located on the inner end side of the gear relative to the middle portion and on the tooth root cone side of the side gear and the pinion relative to the pitch cone side of the side gear and the pinion. In at least one region of the fourth region at the tip cone side, compared to a second reference side gear where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface of the side gear increases from the pitch cone toward the root cone side or the tip cone side of the side gear; and compared to a second reference pinion where the reference pressure angle increases from the middle portion toward the inner end and from the middle portion toward the outer end, the pressure angle on the tooth surface of the pinion increases from the pitch cone toward the tip cone side or the root cone side of the pinion.

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