Differential gear mechanism and method for designing it

Abstract

In a differential gear mechanism of the present disclosure, the reference pressure angle of each axle shaft gear tooth of an axle shaft gear and the reference pressure angle of each pinion tooth of a pinion increase from an intermediate section of the flank line towards the inner end and increase from the intermediate section towards the outer end, and the tooth thickness on the rolling cone of the axle shaft gear decreases from the intermediate section of the flank line towards the inner end and increases from the intermediate section towards the outer end compared to a reference axle shaft gear, and the tooth thickness on the rolling cone of the pinion gear increases from the intermediate section of the flank line towards the inner end and decreases from the intermediate section towards the outer end compared to a reference pinion gear.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a differential gear mechanism comprising a pair of axle shaft gears and a plurality of pinions meshing with the pair of axle shaft gears, and a method for designing the same. BACKGROUND

[0002] A differential gear is known in which pinions, which are straight bevel gears mounted by a pinion shaft fixed to a housing, mesh with a pair of axle shaft gears (see, for example, patent literature 1). In this differential gear, to increase the thickness of an inner end section of each pinion (an end section on the middle side of the differential gear), inner end sections of the tooth roots of the pinion are inclined such that they are positioned closer to the tip cone of the pinion than the root cone of the pinion. Inner end sections of the tooth tips of the gear teeth of each axle shaft gear are inclined such that they are positioned closer to the root cone of the axle shaft gear than the tip cone of the axle shaft gear and extend along the inner end sections of the tooth roots of each pinion.

[0003] A differential gear mechanism is known with a pinion shaft fixed to a housing, pinions that are bevel gears rotatably mounted by the pinion shaft, and a pair of axle shaft gears that are bevel gears meshing with the pinions (see, for example, patent literature 2). In this differential gear mechanism, to shorten the axial length of the differential gear mechanism while preventing a reduction in the strength of the axle shaft gears, the outer end sections (end sections on the outer circumferential side) of the tooth roots of each axle shaft gear are inclined such that they are positioned closer to the tip cone of the axle shaft gear than the root cone of the axle shaft gear. The outer end sections of the tooth tips of the pinion teeth of each pinion are inclined such that they are positioned closer to the root cone of the pinion gear than the tip cone of the pinion gear and extend along the outer end sections of the tooth roots of each axle shaft gear. CITATION LIST PATENT LITERATURE Patent Literature 1: JP 2005-048903 A Patent Literature 2: JP 2014-185666 A SUMMARY OF INVENTIONAL PROBLEMS

[0004] However, if the inner end sections of the tooth roots of each pinion are inclined such that they are positioned closer to the head cone than the base cone of the pinion, as described in patent literature 1, the tooth thickness of the pinion tooth roots decreases at the inner end section (the end section on the middle side of the differential gear) of the pinion, resulting in a reduction of the pinion's strength. Consequently, unless a measure is taken, it is difficult to reduce the diameter of the pinion teeth to make the differential gear more compact while maintaining the pinion's strength.In the case where the outer end sections of the tooth roots of each axle gear are inclined such that they are positioned closer to the head cone than the base cone of the axle gear, as described in patent literature 2, the tooth thickness of the tooth roots on an outer end section of the axle gear (of the differential mechanism) decreases, resulting in a reduction of the axle gear's strength. Consequently, unless a measure is taken, it is difficult to shorten the axial length of the differential mechanism in the axial direction of the axle gears while maintaining the strength of the axle gears.

[0005] The present disclosure is mainly intended to reduce the size of a differential gear mechanism comprising a pair of axle shaft gears and a plurality of pinions meshing with the pair of axle shaft gears, while satisfactorily maintaining the strength of the axle shaft gears and the pinions in the differential gear mechanism. SOLUTIONS FOR PROBLEMS

[0006] A differential gear mechanism of the present disclosure is a differential gear mechanism with a pair of axle shaft gears, each of which is a bevel gear with a plurality of axle shaft gear teeth, and a plurality of pinions, each of which is a bevel gear with a plurality of pinion teeth and meshes with the pair of axle shaft gears, in which outer end sections of tooth roots of each axle shaft gear are inclined such that they are positioned closer than a root cone of the axle shaft gear to a head cone of the axle shaft gear, inner end sections of tooth heads of the axle shaft gear teeth are inclined such that they are positioned closer than the head cone of the axle shaft gear to the root cone of the axle shaft gear, inner end sections of tooth roots of each pinion are inclined such that they are positioned closer than a root cone of the pinion to a head cone of the pinion, outer end sections of tooth heads of the pinion teeth are inclined such thatthat they are positioned closer to the pinion's root cone than the pinion's head cone, a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth, and a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth, increasing in a flank line direction towards an inner end and increasing from the intermediate section towards an outer end, and a tooth thickness on a pitch cone of each axle shaft gear compared to a reference axle shaft gear.in which a line of intersection between a tooth flank of an axle shaft gear tooth and a rolling cone is a straight line passing through a center of the differential gear mechanism, and the reference pressure angle is constant in the flank line direction, decreases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end, and a tooth thickness on a rolling cone of each pinion compared to a reference pinion, in which a line of intersection between a tooth flank of a pinion tooth and a rolling cone is a straight line passing through the center, and the reference pressure angle is constant in the flank line direction, increases from the intermediate section towards the inner end and decreases from the intermediate section towards the outer end.

[0007] A method for designing a differential gear mechanism of the present disclosure is a method for designing a differential gear mechanism with a pair of axle shaft gears, each of which is a bevel gear with a plurality of axle shaft gear teeth, and a plurality of pinions, each of which is a bevel gear with a plurality of pinion teeth and meshes with the pair of axle shaft gears, in which outer end sections of tooth roots of each axle shaft gear are inclined such that they are positioned closer than a root cone of the axle shaft gear to a head cone of the axle shaft gear, inner end sections of tooth heads of the axle shaft gear teeth are inclined such that they are positioned closer than the head cone of the axle shaft gear to the root cone of the axle shaft gear, inner end sections of tooth roots of each pinion are inclined such that they are positioned closer than a root cone of the pinion to a head cone of the pinion.and outer end sections of the tooth heads of the pinion teeth are inclined such that they are positioned closer to the base cone of the pinion than the head cone of the pinion, a method of increasing a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth, and a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth, from an intermediate section of a flank line contained between the inner end section of the tooth head of the axle shaft gear tooth and the outer end section of the tooth head of the pinion tooth, in a flank line direction towards an inner end and from the intermediate section towards an outer end,and a decrease in tooth thickness on a rolling cone of each axle gear from the intermediate section towards the inner end and an increase in tooth thickness on the rolling cone of the axle gear from the intermediate section towards the outer end compared to a reference axle gear in which a line of intersection between a tooth flank of an axle gear tooth and a rolling cone is a straight line passing through a center of the differential gear mechanism, and the reference pressure angle is constant in the flank line direction, and an increase in tooth thickness on a rolling cone of each pinion from the intermediate section towards the inner end and a decrease in tooth thickness on the rolling cone of the pinion from the intermediate section towards the outer end compared to a reference pinion in which a line of intersection between a tooth flank of a pinion tooth and a rolling cone is a straight line passing through the center,and the reference pressure angle is constant in the flank line direction. BRIEF DESCRIPTION OF DRAWINGS Fig. Figure 1 is a schematic configuration diagram representing a differential gear mechanism of the present disclosure. Fig. Figure 2 is a partial cross-sectional view representing the differential gear mechanism of the present disclosure. Fig. Figure 3 is a diagram illustrating the relationship between the cone spacing and the reference pressure angle for axle shaft gears and pinions of the differential gear mechanism of the present disclosure. Fig. Figure 4 is a diagram illustrating the relationship between the cone spacing and the tooth thickness on the rolling cone in the axle shaft gears of the differential gear mechanism of the present disclosure. Fig. Figure 5 is a diagram illustrating the relationship between the cone spacing and the tooth thickness on the rolling cone in the pinions of the differential gear mechanism of the present disclosure. Fig. Figure 6 is a diagram illustrating the relationship between the cone spacing and the tooth thickness of feet in the axle shaft gears of the differential gear mechanism of the present disclosure. Fig. Figure 7 is a diagram illustrating the relationship between the cone spacing and the tooth thickness of feet in the pinions of the differential gear mechanism of the present disclosure. Fig. Figure 8 is an enlarged view showing an essential part of the differential gear mechanism of the present disclosure. Fig. Figure 9 is an enlarged view representing an essential part of the differential gear mechanism of the present disclosure. Fig. 10 is an explanatory view that represents a sharpening that may occur on the pinions of the differential gear mechanism of the present disclosure. Fig. Figure 11 is an explanatory view illustrating a foot undercut that may occur on the pinions of the differential gear mechanism of the present disclosure. Fig. Figure 12 is a schematic configuration diagram showing a toothed state of one of the axle shaft wheels and one of the pinions in the differential gear mechanism of the present disclosure. Fig. Figure 13 is a diagram illustrating a process for adjusting the pressure angle in the pinions of the differential gear mechanism of the present disclosure. Fig. Figure 14 is a diagram illustrating a pressure angle adjustment dimension in the axle shaft gears and pinions of the differential gear mechanism of the present disclosure. Fig. Figure 15 is a diagram illustrating a pressure angle adjustment dimension in the axle shaft gears and pinions of the differential gear mechanism of the present disclosure. Fig. Figure 16 is a diagram illustrating a process for adjusting the pressure angle in the pinions of the differential gear mechanism of the present disclosure. DESCRIPTION OF EXECUTION FORMS

[0008] Next, an embodiment for carrying out the invention of the present disclosure will be described with reference to the drawings.

[0009] Fig. Figure 1 is a perspective view representing a differential gear mechanism 1 of the present disclosure. Fig. Figure 2 is a partial cross-sectional view showing an essential part of the differential gear mechanism 1. The differential gear mechanism 1, shown in these drawings, is contained within a differential gear that is mounted on a vehicle together with a differential ring gear, a differential housing, etc. (not shown). The differential gear mechanism 1 has a pair of axle shaft gears 2 and a plurality of (in the present embodiment, for example, two to four) pinions 3, each meshing with the pair of axle shaft gears 2. Each of the pair of axle shaft gears 2 is fixed to a corresponding drive shaft (not shown). Through each pinion 3 is inserted the corresponding of a plurality of pinion shafts, each of which is supported by the differential housing and extends radially at right angles to the axial direction of the pair of axle shaft gears 2.Thus, each pinion 3 is rotatably mounted through the differential housing via the pinion shaft.

[0010] As in Fig. 1 and Fig. As shown in Figure 2, each axle shaft gear 2 is a bevel gear and has a plurality of axle shaft gear teeth 20, each configured to extend radially from the center O of the differential gear mechanism 1, through which the axes of the axle shaft gears 2 and the pinion 3 pass, and a plurality of tooth roots 25, each located between the adjacent axle shaft gear teeth 20. As shown in Fig. As shown in Figure 2, each axle shaft gear tooth 20 has a pair of tooth flanks 21, each formed based on a spherical involute curve, and a tooth tip 23 formed between the pair of tooth flanks 21. In the present embodiment, an outer end section 25o of each tooth root 25 of each axle shaft gear 2 (a region closer to the outer circumference of the axle shaft gear 2 than a boundary B2 in Fig. 2) inclined so that it is positioned closer than the base cone RC2 of the axle shaft gear 2 to the head cone TC2 of the axle shaft gear 2. This can prevent a reduction in the thickness of an outer circumferential section of each axle shaft gear 2, thus preventing a reduction in the strength of the axle shaft gear 2.

[0011] Each pinion 3 is a bevel gear and, as in Fig. 1 and Fig. Figure 2 shows a plurality of pinion teeth 30, each configured to extend radially from the center O of the differential gear mechanism 1, and a plurality of tooth bases 35, each located between the adjacent pinion teeth 30. As shown in Fig. As shown in Figure 2, each pinion tooth 30 has a pair of tooth flanks 31, each formed based on a spherical involute curve, and a tooth head 33 formed between the pair of tooth flanks 31. In the present embodiment, an inner end section 35i of each tooth root 35 of each pinion 3 (a region closer to the center O than a boundary B3 in Fig. 2) inclined such that it is positioned closer than the base cone RC3 of the pinion 3 to the head cone TC3 of the pinion 3. This prevents a reduction in the thickness of an inner end section (an end section on the side of the center O) of each pinion 3, so that the strength of the pinion 3 is satisfactorily maintained. For each axle shaft gear 2 and each pinion 3, the tooth profile of one of them is formed by creating it using the tooth profile of the other, with the axes of both being allowed to coincide with their positions in a meshed state. Each axle shaft gear 2 and each pinion 3 are in a conjugate relationship with each other while in meshing.

[0012] As in Fig. As shown in Figure 2, an inner end section 23i of the tooth head 23 of each axle shaft gear tooth 20 is designed such that it extends along the inner end section 35i of each tooth root 35 of each pinion 3. That is, the inner end section 23i of the tooth head 23 of each axle shaft gear tooth 20 is inclined such that it is positioned closer to the root cone RC2 than the head cone TC2 of the axle shaft gear 2. Furthermore, as shown in Fig. As shown in Figure 2, an outer end section 33o of the tooth head 33 of each pinion tooth 30 is designed such that it extends along the outer end section 25o of each tooth root 25 of each axle shaft gear 2. That is, the outer end section 33o of the tooth head 33 of each pinion tooth 30 is inclined such that it is positioned closer to the root cone RC3 than the head cone TC3 of the pinion 3.

[0013] Here, as in Fig. As shown in Figure 2, if the outer end sections 25o of the tooth roots 25 of each axle shaft gear 2 are inclined such that they are positioned closer than the root cone RC2 of the axle shaft gear 2 to the tip cone TC2, the tooth thickness of the root of each axle shaft gear tooth 20 decreases at the outer circumferential section of the axle shaft gear 2, resulting in a reduction of the strength of each axle shaft gear tooth 20 and thus of the axle shaft gear 2. Therefore, to shorten the axial length of the differential gear mechanism 1 in the axial direction of the axle shaft gears 2 (the drive shafts), it is necessary to prevent a reduction in the strength of each axle shaft gear tooth 20, i.e., of each axle shaft gear 2, by inclined the outer end sections 25o of the tooth roots 25 towards the tooth tips 23.

[0014] In the case where the inner end sections 35i of the tooth roots 35 of each pinion 3 are inclined such that they are positioned closer than the root cone RC3 of the pinion 3 to the tip cone TC3, the tooth thickness of the root of each pinion tooth 30 decreases at the inner end section (the end section on the side of the center O) of the pinion 3, resulting in a reduction of the strength of each pinion tooth 30 and thus of the pinion 3. Therefore, in order to reduce the diameter of each pinion 3, thereby making the differential gear mechanism 1 more compact, it is necessary to prevent a reduction in the strength of each pinion tooth 30, i.e., of each pinion 3, by inclined the inner end sections 35i of the tooth roots 35 towards the tooth tips 33.

[0015] Based on this, the present inventors have conducted intensive studies to make the differential gear mechanism 1 more compact while satisfactorily maintaining the strength of each axle shaft gear 2 and each pinion 3. In this process, the present inventors focused on the reference pressure angle, which is the pressure angle at a pitch point of each axle shaft gear tooth 20 (the angle formed by the radial line and the tangent to the tooth flank (tooth profile) passing through the pitch point), and the reference pressure angle, which is the pressure angle at a pitch point of each pinion tooth 30 (the angle formed by the radial line and the tangent to the tooth flank (tooth profile) passing through the pitch point).In the differential gear mechanism 1, the present inventors have modified the reference pressure angle of each axle shaft gear tooth 20 and the reference pressure angle of each pinion tooth 30, which coincide in the extension direction of the flank line (the line of intersection between the rolling cone PC2 of each axle shaft gear 2 and each tooth flank 21 of each gear tooth 20 and the line of intersection between the rolling cone PC3 of each pinion 3 and each tooth flank 31 of each pinion tooth 30) (hereinafter referred to as the “flank line direction”) (hereinafter referred to as the “reference pressure angle α”).

[0016] That is, in the differential gear mechanism 1, as in Fig. As shown in Figure 3, the reference pressure angle α of each axle shaft gear tooth 20 and each pinion tooth 30 gradually increases from an intermediate section M of the flank line towards the inner end (towards the center O) and gradually increases from the intermediate section M towards the outer end (towards the outer circumference of each axle shaft gear 2). In the present embodiment, the intermediate section M of the flank line is a point located near the midpoint of the flank line such that it lies in the flank line direction between the inclined inner end section 23i of the tooth tip 23 of each axle shaft gear tooth 20 and the inclined outer end section 33o of the tooth tip 33 of each pinion tooth 30, i.e., in a region S (the region between the double-dotted dashed lines in Figure 3). Fig. 2), in which the engagement of the axle shaft gear teeth 20 and the pinion teeth 30 is defined solely by the head cone TC2 of each axle shaft gear 2 and the head cone TC3 of each pinion 3. In the present embodiment, the region S comprises approximately 40 to 60% of the engagement area of ​​the axle shaft gear teeth 20 and the pinion teeth 30 in the flank line direction, with the intermediate section M in the middle.

[0017] The intermediate segment M can be the midpoint of the flank line. In the example of Fig. The inner end sections 23i of the tooth tips 23 of the axle shaft gears 2 are positioned closer to the center O than the outer end sections 33o of the tooth tips 33 of the pinion teeth 30 in the flank line direction, but are not restricted to it. For example, the inner end sections 23i of the tooth tips 23 of the axle shaft gears 2 can extend beyond the outer end sections 33o of the tooth tips 33 of the pinion teeth 30 in the flank line direction towards the outer circumferential side (the side opposite the center O). In this case, the intermediate section M can also be defined such that it is contained within the region S. Furthermore, the position of the outer circumferential end of each inner end section 23i in the flank line direction can coincide with the position of the end of each outer end section 33o on the side of the center O in the flank line direction.In this case, the intermediate section M coincides with the position of the outer circumferential end of each inner end section 23i in the flank line direction and the position of the end of each outer end section 33o on the side of the center O in the flank line direction.

[0018] Furthermore, in the differential gear mechanism 1, in addition to a change in the reference pressure angle α in the flank line direction, as in Fig. 3 is shown as if by a solid line in Fig. As specified in section 4, the tooth thickness (circular tooth thickness) of each axle shaft gear 2 on the rolling cone PC2 is set such that, compared to a reference axle shaft gear (see a dashed line in Fig. 4) decreases from the intermediate section M towards the inner end (towards the center O) and increases from the intermediate section M towards the outer end (towards the outer circumference of the axle shaft gear 2). In the differential gear mechanism 1, as shown by a solid line in Fig. 5, the tooth thickness (circular tooth thickness) of each pinion 3 on the rolling cone PC3 is set such that, compared to a reference pinion (see a dashed line in Fig. 5) increases from the intermediate section M towards the inner end and decreases from the intermediate section M towards the outer end.

[0019] The reference axle gear is a straight bevel gear in which the line of intersection between the tooth flank of each axle gear tooth and the rolling cone is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle α is constant in the flank line direction. In the reference axle gear, a cross-section of an axle gear tooth, cut along a spherical surface centered on the center of the differential gear mechanism, is enlarged or reduced along the axis of the reference axle gear in a similarity ratio corresponding to the distance from the center (the radius of the spherical surface). The reference pinion is a straight bevel gear in which the line of intersection between the tooth flank of each pinion tooth and the rolling cone is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle α is constant in the flank line direction.In the reference pinion, a cross-section of a pinion tooth, cut along a spherical surface centered on the center of the differential gear mechanism, is enlarged or reduced along the axis of the reference pinion in a similarity ratio corresponding to the distance from the center (the radius of the spherical surface). An intermediate flank line segment in the reference axle shaft gear and the reference pinion is a point located near the midpoint of the flank line such that it lies between an inclined inner end segment of the tooth tip of each axle shaft gear tooth and an inclined outer end segment of the tooth tip of each pinion tooth in the flank line direction (within the region S). The intermediate segment M of each axle shaft gear 2 and each pinion 3 coincides with the intermediate segment of the reference axle shaft gear and the reference pinion.

[0020] Consequently, as indicated by a solid line in Fig. As specified in 6, the tooth thickness (circular tooth thickness) of the feet at the outer end sections 25° (on the outer end side of the boundary B2) of the tooth roots 25 of each axle shaft gear 2 is larger than if the reference pressure angle α and the tooth thickness on the rolling cone PC2 are not adjusted (see a dashed line in Fig. 6) As seen through a solid line in Fig. As specified in figure 7, the tooth thickness (circular tooth thickness) of the feet at the inner end sections 35i (on the inner end face of the boundary B3) of the tooth roots 35 of each pinion 3 will be larger than if the reference pressure angle α and the tooth thickness on the rolling cone PC3 are not adjusted (see a dashed line in figure 7). Fig. 7).

[0021] Thus, it is like a dotted line in Fig. As indicated in 9, it is possible to increase the tooth thickness do2 of the foot of each axle shaft gear tooth 20 on the outer circumferential section of each axle shaft gear 2, while, as in Fig. As shown in Figure 8, the tooth thickness di2 of the root of each axle shaft gear tooth 20 is sufficiently maintained in the inner end section (the end section on the side of the center O) of the axle shaft gear 2. As indicated by a dotted line in Fig. As indicated in 8, it is possible to increase the tooth thickness di3 of the foot of each pinion tooth 30 at the inner end section of each pinion 3, while, as in Fig. As shown in Figure 9, the tooth thickness do3 of the root of each pinion tooth 30 at the outer end section of the pinion 3 is sufficiently maintained. Consequently, it is possible to make the differential gear mechanism 1 more compact by shortening the axial length of the differential gear mechanism 1 in the axial direction of the axle shaft gears 2 and reducing the diameter of the pinions 3, while satisfactorily maintaining the strength of the axle shaft gears 2 and the pinions 3.

[0022] On the other hand, on the axle shaft gear teeth 20 and the pinion teeth 30, which are modified in the flank line direction with respect to the reference pressure angle α and the tooth thicknesses on the rolling cones PC2 and PC3, as indicated by a dashed line in Fig. As indicated in 10, a sharpening occurs in areas where the reference pressure angle α is relatively large ( Fig. 10 represents a pinion tooth 30). Furthermore, on the axle shaft gear teeth 20 and the pinion teeth 30, which are modified with respect to the reference pressure angle α and the tooth thicknesses on the rolling cones PC2 and PC3 in the flank line direction, as indicated by dashed lines in Fig. As stated in section 11, undercutting at the feet occurs in areas where the reference pressure angle α is relatively small ( Fig. 11 represents a pinion tooth 30).

[0023] Furthermore, a tapering and an undercut of the axle shaft gear teeth 20 and the pinion teeth 30 can be achieved in each first, second, third and fourth area A1, A2, A3 and A4 in Fig. 12 occur. As in Fig. As shown in Figure 12, the first region A1 is a region closer to the inner end than the intermediate section M in the flank line direction (a plane containing the intermediate section M and orthogonal to the flank line direction) and closer to the head cone TC2 of the axle shaft gear 2 and the base cone RC3 of the pinion 3 than the rolling cones PC2 and PC3 of the axle shaft gear 2 and the pinion 3. The second region A2 is a region closer to the inner end than the intermediate section M in the flank line direction and closer to the base cone RC2 of the axle shaft gear 2 and the head cone TC3 of the pinion 3 than the rolling cones PC2 and PC3.

[0024] The third region A3 is located closer to the outer end than the intermediate section M in the flank line direction and closer to the head cone TC2 of the axle shaft gear 2 and the base cone RC3 of the pinion 3 than the rolling cones PC2 and PC3. The fourth region A4 is located closer to the inner end than the intermediate section M in the flank line direction and closer to the base cone RC2 of the axle shaft gear 2 and the head cone TC3 of the pinion 3 than the rolling cones PC2 and PC3. If a tapering or undercut has occurred on the axle shaft gear teeth 20 or the pinion teeth 30 in at least one of the first to fourth regions A1 to A4, the tooth depth and the contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 cannot be satisfactorily maintained.

[0025] Based on this, in the differential gear mechanism 1, if a taper has occurred on each pinion tooth 30 in the second region A2 on the inner end face, which does not include the inclined outer end section 33o of the tooth tip 33 of the pinion tooth 30, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC3, as described above, the pressure angles on each tooth flank 21 of each axle shaft gear tooth 20 and each tooth flank 31 of each pinion tooth 30 (the angle formed by the radial line and the tangent to the tooth flank (tooth profile) passing through a point on the tooth flank 21 or 31) are adjusted within the range of the second region A2. In this case, as described in Fig. Figure 13 shows the pressure angle on each tooth flank 31 contained in the second area A2 of each pinion tooth 30, adapted so that it extends from the rolling cone PC3 of the pinion 3 towards the head cone TC3 of the pinion 3 on the inner end face of the intermediate section M in the flank line direction compared to a second reference pinion (see a dashed line in Fig. 13) decreases.

[0026] The second reference pinion is the reference pinion described above, whose reference pressure angle α is adapted such that it increases from the intermediate section M towards the inner end and increases from the intermediate section M towards the outer end, as shown in Fig. 3 is shown. As in Fig. As shown in Figure 13, the pressure angle on the tooth flank of each pinion tooth on the inner end face of the second reference pinion is greater than the pressure angle on the tooth flank at the intermediate section M. As shown in Fig. As shown in Figure 14, the adjustment range of the pressure angle (hereinafter referred to as the "pressure angle adjustment range") δ of each pinion 3 in the second area A2 on the rolling cone PC3 is zero and is set to a negative value on the inner end face of the intermediate section M in the flank line direction, decreasing (increasing in absolute value) from the rolling cone PC3 towards the head cone TC3 of the pinion 3. The horizontal axis in Fig. 14 represents the rotation angle of each pinion 3 (the same applies to Fig. 15).

[0027] Furthermore, for each axle shaft gear 2, in a conjugate relationship with each pinion 3, the pressure angle on each tooth flank 21 contained in the second region A2 of each axle shaft gear tooth 20 is adjusted such that it decreases from the rolling cone PC2 of the axle shaft gear 2 towards the base cone RC2 of the axle shaft gear 2 on the inner end face of the intermediate section M in the flank line direction compared to a second reference axle shaft gear. The second reference axle shaft gear is the reference axle shaft gear described above, whose reference pressure angle α is adjusted such that it increases from the intermediate section M towards the inner end and from the intermediate section M towards the outer end, as shown in Fig. Figure 3 shows that the pressure angle on the tooth flank of each axle shaft gear tooth on the inner end face of the second reference axle shaft gear is also larger than the pressure angle on the tooth flank at the intermediate section M. As shown in Fig. As shown in Figure 14, the pressure angle adjustment dimension δ of each axle shaft gear 2 in the second region A2 on the rolling cone PC2 is zero and is set to a negative value on the inner end face of the intermediate section M in the flank line direction, decreasing (increasing in absolute value) from the rolling cone PC2 towards the base cone RC2 of the axle shaft gear 2. As a result, a tapering of the pinion teeth 30 in the second region A2 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained. The intermediate section of the flank line in the second reference axle shaft gear and the second reference pinion coincides with the intermediate section of the reference axle shaft gear and the reference pinion and the intermediate section M of the axle shaft gears 2 and the pinion 3.

[0028] In the event that a tapering has occurred on each axle shaft gear tooth 20 in the third region A3 on the outer end face, which does not include the inclined inner end section 23i of the tooth head 23 of the axle shaft gear tooth 20, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC2, as described in Fig. As shown in Figure 14, the pressure angle adjustment dimension δ of each axle shaft gear 2 and each pinion 3 in the third region A3 on the outer end of the intermediate section M is set to a negative value in the flank line direction, decreasing (increasing in absolute value) from the rolling cones PC2 and PC3 towards the head cone TC2 of the axle shaft gear 2 and the base cone RC3 of the pinion 3. Consequently, the pressure angle on each tooth flank 21 contained in the third region A3 of each axle shaft gear tooth 20 is adjusted such that it decreases on the outer end of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the base cone RC2 of the axle shaft gear 2, compared to the second reference axle shaft gear.Similarly, the pressure angle on each tooth flank 31 contained in the third region A3 of each pinion tooth 30 is adjusted such that it decreases on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the head cone TC3 of the pinion 3 compared to the second reference pinion. As a result, a tapering of the axle shaft gear teeth 20 in the third region A3 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0029] Furthermore, in the case that an undercut at the base of each pinion tooth 30 in the third area A3 on the outer end face, which does not include the inner end section 35i of each tooth root 35 of the pinion 3 has occurred, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC3, as in Fig. As shown in Figure 15, the pressure angle adjustment dimension δ within the span of the third area A3 on the rolling cone PC3 is zero and is set to a positive value on the outer end of the intermediate section M in the flank line direction, increasing from the rolling cones PC2 and PC3 towards the head cone TC2 of the axle shaft gear 2 and the base cone RC3 of the pinion 3. Consequently, as shown in Fig. As shown in Figure 16, the pressure angle on each tooth flank 31 contained in the third area A3 of each pinion tooth 30 is adjusted such that it is on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the base cone RC3 of the pinion 3 compared to the second reference pinion (see a dashed line in Figure 16). Fig. 16) increases. Likewise, the pressure angle on each tooth flank 21 contained in the third region A3 of each axle shaft gear tooth 20 is adapted such that it increases on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the head cone TC2 of the axle shaft gear 2 compared to the second reference axle shaft gear. As a result, undercutting of the roots of the pinion teeth 30 in the third region A3 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0030] Furthermore, in the case that an undercut at the root of each axle shaft gear tooth 20 in the second region A2 on the inner end face, which does not include the inclined outer end section 25o of each tooth root 25 of each axle shaft gear 2 has occurred, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC2, as in Fig. As shown in Figure 15, the pressure angle adjustment dimension δ in the second region A2 is set to a positive value, which increases on the inner end face of the intermediate section M in the flank line direction from the rolling cones PC2 and PC3 towards the base cone RC2 of the axle shaft gear 2 and the tip cone TC3 of the pinion 3. Consequently, the pressure angle on each tooth flank 21 contained in the second region A2 of each axle shaft gear tooth 20 is adjusted such that it increases on the inner end face of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the base cone RC2 of the axle shaft gear 2 compared to the second reference axle shaft gear.Similarly, the pressure angle on each tooth flank 31 contained in the second region A2 of each pinion tooth 30 is adapted such that it increases on the inner end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the head cone TC3 of the pinion 3 compared to the second reference pinion. As a result, undercutting of the roots of the axle shaft gear teeth 20 in the second region A2 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0031] Furthermore, in the case that a taper has occurred on each pinion tooth 30 in the fourth region A4 on the outer end face, which includes the inclined outer end section 33o of the tooth head 33 of the pinion tooth 30, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC3, as in the case that a taper has occurred on each pinion tooth 30 in the second region A2, the pressure angle on each tooth flank 31, which is contained in the fourth region A4 of each pinion tooth 30, on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the head cone TC3 of the pinion 3 can be reduced compared to the second reference pinion.Furthermore, the pressure angle on each tooth flank 21, contained in the fourth region A4 of each axle shaft gear tooth 20, can be reduced on the outer end of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the base cone RC2 of the axle shaft gear 2 compared to the second reference axle shaft gear. As a result, a tapering of the pinion teeth 30 in the fourth region A4 can be eliminated, so that the tooth depth and the contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0032] In the event that a taper has occurred on each axle shaft gear tooth 20 in the first region A1 on the inner end side, which includes the inclined inner end section 23i of the tooth head 23 of the axle shaft gear tooth 20, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC2, as in the event that a taper has occurred on each axle shaft gear tooth 20 in the third region A3, the pressure angle on each tooth flank 21, which is contained in the first region A1 of each axle shaft gear tooth 20, on the inner end side of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the head cone TC2 of the axle shaft gear compared to the second reference axle shaft gear.Furthermore, the pressure angle on each tooth flank 31, contained in the first region A1 of each pinion tooth 30, can be reduced on the inner end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the base cone RC3 of the pinion 3 compared to the second reference pinion. As a result, a tapering of the axle shaft gear teeth 20 in the first region A1 can be eliminated, so that the tooth depth and the contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0033] Furthermore, in the event that an undercut has occurred at the root of each axle shaft gear tooth 20 in the fourth region A4 on the outer end face, which includes the inclined outer end section 25o of each tooth root 25 of the axle shaft gear 2, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC2, as in the event that an undercut has occurred at the root of each axle shaft gear tooth 20 in the second region A2, the pressure angle on each tooth flank 21, which is contained in the fourth region A4 of each axle shaft gear tooth 20, on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the base cone RC2 of the axle shaft gear compared to the second reference axle shaft gear, can be increased.Furthermore, the pressure angle on each tooth flank 31 contained in the fourth region A4 of each pinion tooth 30 can be increased on the outer end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the head cone TC3 of the pinion 3 compared to the second reference pinion. As a result, undercutting of the roots of the axle shaft gear teeth 20 in the fourth region A4 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0034] In the event that an undercut has occurred at the root of each pinion tooth 30 in the first region A1 on the inner end face, which includes the inner end section 35i of each tooth root 35 of the pinion 3, for example as a result of the adjustment of the reference pressure angle α and the tooth thickness on the rolling cone PC3, as in the event that an undercut has occurred at the root of each pinion tooth 30 in the third region A3, the pressure angle on each tooth flank 31, which is contained in the first region A1 of each pinion tooth 30, on the inner end face of the intermediate section M in the flank line direction from the rolling cone PC3 of the pinion 3 towards the base cone RC3 of the pinion 3 can be increased compared to the second reference pinion.Furthermore, the pressure angle on each tooth flank 21 contained in the first region A1 of each axle shaft gear tooth 20 can be increased on the inner end face of the intermediate section M in the flank line direction from the rolling cone PC2 of the axle shaft gear 2 towards the head cone TC2 of the axle shaft gear 2 compared to the second reference axle shaft gear. As a result, undercutting of the pinion teeth 30 in the first region A1 can be eliminated, so that the tooth depth and contact ratio of the axle shaft gear teeth 20 and the pinion teeth 30 are satisfactorily maintained.

[0035] It is noted that the intermediate section M is as desired within the area S (the area between the two double-dotted dashed lines in Fig.2) can be determined. The intermediate section M is not restricted to a point on the flank line and can have a predetermined length in the flank line direction. Furthermore, in the differential gear mechanism 1, the tooth profiles of each axle shaft gear tooth 20 and each pinion tooth 30 are formed by spherical involute curves before being adapted by the pressure angle adjustment factor δ, but are not limited to them. That is, the tooth profiles of each axle shaft gear tooth 20 and each pinion tooth 30, before being adapted by the pressure angle adjustment factor δ, can be formed, for example, by octoid curves, trochoid curves, or the like. When designing the axle shaft gears 2 and the pinions 3, the tooth thickness adjustment can be carried out after adjusting the reference pressure angle α and adjusting the pressure angle by the pressure angle adjustment factor δ. <Zusammenfassung der Ausführungsform>

[0036] As described above, a differential gear mechanism of the present disclosure is a differential gear mechanism (1) with a pair of axle shaft gears (2), each of which is a bevel gear with a plurality of axle shaft gear teeth (20), and a plurality of pinions (3), each of which is a bevel gear with a plurality of pinion teeth (30) and meshes with the pair of axle shaft gears (2), wherein outer end sections (25o) of tooth roots (25) of each axle shaft gear (2) are inclined such that they are positioned closer than a root cone (RC2) of the axle shaft gear (2) to a head cone (TC2) of the axle shaft gear (2), and inner end sections (23i) of tooth heads (23) of the axle shaft gear teeth (20) are inclined such that they are positioned closer than the head cone (TC2) of the axle shaft gear (2) to the root cone (RC2) of the axle shaft gear (2). are positioned, inner end sections (35i) of tooth bases (35) of each pinion (3) are inclined,that they are positioned closer than a base cone (RC3) of the pinion (3) to a head cone (TC3) of the pinion (3), outer end sections (33o) of tooth heads (33) of the pinion teeth (30) are inclined such that they are positioned closer than the head cone (TC3) of the pinion (3) to the base cone (RC3) of the pinion (3), a reference pressure angle (α) which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth (20), and a reference pressure angle (α) which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth (30), from an intermediate section (M) of a flank line that is between the inner end section (23i) of the tooth head (23) of the axle shaft gear tooth (20) and the outer end section (33o) of the tooth head (33) of the pinion tooth (30) is included,in the flank line direction towards an inner end and from the intermediate section (M) towards an outer end, and a tooth thickness on a rolling cone (PC2) of each axle shaft gear (2) compared to a reference axle shaft gear in which a line of intersection between a tooth flank of an axle shaft gear tooth and a rolling cone is a straight line passing through a center of the differential gear mechanism, and the reference pressure angle in the flank line direction is constant, decreases from the intermediate section (M) towards the inner end and increases from the intermediate section (M) towards the outer end, and a tooth thickness on a rolling cone (PC3) of each pinion (3) compared to a reference pinion in which a line of intersection between a tooth flank of a pinion tooth and a head cone is a straight line passing through the center, and the reference pressure angle in the flank line direction is constant,from the intermediate section (M) towards the inner end increases and from the intermediate section (M) decreases towards the outer end.

[0037] In the differential gear mechanism of the present disclosure, the outer end sections of the tooth roots of the axle shaft gears, the inner end sections of the tooth tips of the axle shaft gear teeth, the inner end sections of the tooth roots of the pinions, and the outer end sections of the tooth tips of the pinion teeth are inclined, thus allowing the thickness of the inner end sections of the pinions to be increased and the axial length of the differential gear mechanism to be shortened in the axial direction of the axle shaft gears. The reference pressure angle of the axle shaft gear teeth and the reference pressure angle of the pinion teeth increase from the intermediate section of the flank line towards the inner end and increase from the intermediate section towards the outer end.Therefore, the tooth thickness on the rolling cone of each axle gear is reduced from the intermediate section towards the inner end and increased from the intermediate section towards the outer end, so that the tooth thickness of the roots of the axle gear teeth at the outer end section (the end section on the outer circumferential side) of the axle gear can be increased compared to the reference axle gear, in which the reference pressure angle in the flank line direction is constant, while the tooth thickness of the roots of the axle gear teeth at the inner end section (the end section on the middle side) of the axle gear is sufficiently maintained.Furthermore, the tooth thickness on the rolling cone of each pinion is increased from the intermediate section towards the inner end and decreased from the intermediate section towards the outer end, so that the tooth thickness of the pinion teeth's roots at the inner end section (the end section on the middle side of the differential gear mechanism) of the pinion can be increased compared to the reference pinion, where the reference pressure angle in the flank line direction is constant, while the tooth thickness of the pinion teeth's roots at the outer end section of the pinion (the end section on the outer circumferential side of the axle shaft gear) is sufficiently maintained.Consequently, it is possible to make the differential gear mechanism more compact by shortening its axial length in the axial direction of the axle gears and reducing the diameter of the pinions, while satisfactorily maintaining the strength of the axle gears and pinions. It is noted that the intermediate section of the flank line can be defined as desired in the flank line direction between the inclined inner end section of the tooth tip of each axle gear tooth and the inclined outer end section of the tooth tip of each pinion tooth, i.e., within the area where the engagement of the axle gear teeth and the pinion teeth is defined solely by the tip cone of the axle gear and the tip cone of the pinion, and can be a point on the flank line or have a predetermined length in the flank line direction.

[0038] In at least one of a first region (A1) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the rolling cones (PC2, PC3) of the axle shaft gear (2) and the pinion (3), of a second region (A2) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), of a third region (A3) in the flank line direction closer to the outer end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the Rolling cones (PC2, PC3),and a fourth area (A4) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a pressure angle on a tooth flank (21) of each axle shaft gear tooth (20) from the rolling cone (PC2, PC3) towards the base cone (RC2) or the head cone (TC2) of the axle shaft gear (2) can decrease compared to a second reference axle shaft gear, in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end, and a pressure angle on a tooth flank (31) of each pinion tooth (30) can decrease from the rolling cone (PC2, PC3) towards the head cone (TC3) or the base cone (RC3) of the pinion (3) compared to a second reference pinion,in which the reference pressure angle increases from the intermediate section towards the inner end and decreases from the intermediate section towards the outer end.

[0039] This can eliminate the need for a tapering of the axle shaft gear teeth or the pinion teeth, so that the tooth depth and contact ratio of the axle shaft gear teeth and the pinion teeth are satisfactorily maintained.

[0040] Furthermore, in at least one of a first region (A1) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the rolling cones (PC2, PC3) of the axle shaft gear (2) and the pinion (3), a second region (A2) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a third region (A3) in the flank line direction closer to the outer end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the Rolling cones (PC2, PC3),and a fourth area (A4) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a pressure angle on a tooth flank (21) of each axle shaft gear tooth (20) from the rolling cone (PC2, PC3) towards the base cone (RC2) or the head cone (TC2) of the axle shaft gear (2) compared to a second reference axle shaft gear in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end, and a pressure angle on a tooth flank (21) of each pinion tooth (30) can increase from the rolling cone (PC2, PC3) towards the head cone (TC3) or the base cone (RC3) of the pinion (3) compared to a second reference pinion,in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end.

[0041] This can eliminate undercutting of the feet of the gear teeth or pinion teeth, so that the tooth depth and contact ratio of the axle shaft gear teeth and the pinion teeth are satisfactorily maintained.

[0042] A method for designing a differential gear mechanism of the present disclosure is a method for designing a differential gear mechanism (1) with a pair of axle shaft gears (2), each of which is a bevel gear having a plurality of axle shaft gear teeth (20), and a plurality of pinions (3), each of which is a bevel gear having a plurality of pinion teeth (30) and meshing with the pair of axle shaft gears (2), in which outer end sections (25o) of tooth roots (25) of each axle shaft gear (2) are inclined such that they are positioned closer than a root cone (RC2) of the axle shaft gear (2) to a head cone (TC2) of the axle shaft gear (2), and inner end sections (23i) of tooth heads (23) of the axle shaft gear teeth (20) are inclined such that they are positioned closer than the head cone (TC2) of the axle shaft gear (2) to the root cone (RC2) of the axle shaft wheel (2) are positioned, inner end sections (35i) of tooth roots (35) of each pinion (3) are inclined,that they are positioned closer than a base cone (RC3) of the pinion (3) to a head cone (TC3) of the pinion (3), and outer end sections (33o) of tooth heads (33) of the pinion teeth (30) are inclined such that they are positioned closer than the head cone (TC3) of the pinion (3) to the base cone (RC3) of the pinion (3), which method is an increase of a reference pressure angle (α), which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth (20), and a reference pressure angle (α), which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth (30), from an intermediate section (M) of a flank line,which is contained in the flank line direction between the inner end section (23i) of the tooth head (23) of the axle shaft gear tooth (20) and the outer end section (33o) of the tooth head (33) of the pinion tooth (30), in the direction of an inner end and from the intermediate section (M) in the direction of an outer end, and a decrease in tooth thickness on a rolling cone (PC2) of each axle shaft gear (2) from the intermediate section (M) in the direction of the inner end and an increase in tooth thickness on the rolling cone (PC2) of the axle shaft gear (2) from the intermediate section (M) in the direction of the outer end compared to a reference axle shaft gear in which a line of intersection between a tooth flank of an axle shaft gear tooth and a rolling cone is a straight line passing through a center of the differential gear mechanism, and the reference pressure angle in the flank line direction is constant,and includes increasing the tooth thickness on a rolling cone (PC3) of each pinion (3) from the intermediate section (M) towards the inner end and decreasing the tooth thickness on the rolling cone (PC3) of the pinion (3) from the intermediate section (M) towards the outer end compared to a reference pinion, in which a line of intersection between a tooth flank of a pinion tooth and a rolling cone is a straight line passing through the center, and the reference pressure angle is constant in the flank line direction.

[0043] According to this method, it is possible to make the differential gear mechanism more compact by shortening the axial length of the differential gear mechanism in the axial direction of the axle shaft wheels and reducing the diameters of the pinions, while satisfactorily maintaining the strength of the axle shaft wheels and the pinions.

[0044] In at least one of a first region (A1) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the rolling cones (PC2, PC3) of the axle shaft gear (2) and the pinion (3), of a second region (A2) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), of a third region (A3) in the flank line direction closer to the outer end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the Rolling cones (PC2, PC3),and a fourth area (A4) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a pressure angle on a tooth flank (21) of each axle shaft gear tooth (20) from the rolling cone (PC2, PC3) towards the base cone (RC2) or the head cone (TC2) of the axle shaft gear (2) can be reduced compared to a second reference axle shaft gear in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end, and a pressure angle on a tooth flank (31) of each pinion tooth (30) can be reduced from the rolling cone (PC2, PC3) towards the head cone (TC3) or the base cone (RC3) of the pinion (3) compared to a second reference pinion,in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end, are reduced.

[0045] Furthermore, in at least one of a first region (A1) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the rolling cones (PC2, PC3) of the axle shaft gear (2) and the pinion (3), a second region (A2) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a third region (A3) in the flank line direction closer to the outer end than the intermediate section (M) and closer to the head cone (TC2) of the axle shaft gear (2) and the base cone (RC3) of the pinion (3) than the Rolling cones (PC2, PC3),and a fourth area (A4) in the flank line direction closer to the inner end than the intermediate section (M) and closer to the base cone (RC2) of the axle shaft gear (2) and the head cone (TC3) of the pinion (3) than the rolling cones (PC2, PC3), a pressure angle on a tooth flank (21) of each axle shaft gear tooth (20) from the rolling cone (PC2, PC3) towards the base cone (RC2) or the head cone (TC2) of the axle shaft gear (2) compared to a reference axle shaft gear in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end, and a pressure angle on a tooth flank (21) of each pinion tooth (30) can be increased from the rolling cone (PC2, PC3) towards the head cone (TC3) or the base cone (RC3) of the pinion (3) compared to a second reference pinion,in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end.

[0046] The invention of the present disclosure is in no way limited to the embodiments described above, and it is understood that various modifications within the scope of the present disclosure are possible. Furthermore, the embodiment described above is merely a specific embodiment of the invention described in the section "SUMMARY OF THE INVENTION" and does not limit the elements of the invention described in the section "SUMMARY OF THE INVENTION". COMMERCIAL APPLICABILITY

[0047] The invention of the present disclosure can be used in the production industry, etc., of a differential gear mechanism with a pair of axle shaft wheels and a plurality of pinions that mesh with the pair of axle shaft wheels. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2005-048903 A

[0003] JP 2014-185666 A

[0003]

Claims

[1] Differential gear mechanism comprising a pair of axle shaft gears, each of which is a bevel gear with a plurality of axle shaft gear teeth, and a plurality of pinions, each of which is a bevel gear with a plurality of pinion teeth and meshes with the pair of axle shaft gears, wherein outer end sections of the tooth roots of each axle gear are inclined such that they are positioned closer than a base cone of the axle gear to a head cone of the axle gear, inner end sections of the tooth heads of the axle shaft gear teeth are inclined so that they are positioned closer to the base cone of the axle shaft gear than the head cone of the axle shaft gear, The inner end sections of the tooth bases of each pinion are inclined such that they are positioned closer than a base cone of the pinion to a head cone of the pinion. outer end sections of the tooth heads of the pinion teeth are inclined so that they are positioned closer to the base cone of the pinion than the head cone of the pinion, a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth, and a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth, increasing from an intermediate section of a flank line contained between the inner end section of the tooth tip of the axle shaft gear tooth and the outer end section of the tooth tip of the pinion tooth in a flank line direction towards an inner end and increasing from the intermediate section towards an outer end, and a tooth thickness of a rolling cone of each axle shaft gear compared to a reference axle shaft gear, in which a line of intersection between a tooth flank of an axle shaft gear tooth and a rolling cone is a straight line passing through the center of the differential gear mechanism, and the reference pressure angle is constant in the flank line direction, decreasing from the intermediate section towards the inner end and increasing from the intermediate section towards the outer end, and a tooth thickness on a rolling cone of each pinion compared to a reference pinion, in which a line of intersection between a tooth flank of a pinion tooth and a head cone is a straight line passing through the center, and the reference pressure angle is constant in the flank line direction, increasing from the intermediate section towards the inner end and decreasing from the intermediate section towards the outer end. [2] Differential gear mechanism according to claim 1, wherein in at least one of a first region in the flank line direction closer to the inner end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones of the axle shaft gear and the pinion, a second region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, a third region in the flank line direction closer to the outer end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones, and a fourth region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones,a pressure angle on a tooth flank of each axle shaft gear tooth from the rolling cone towards the root cone or the tip cone of the axle shaft gear compared to a second reference axle shaft gear, in which the reference pressure angle increases from the intermediate section towards the inner end and decreases from the intermediate section towards the outer end, and a pressure angle on a tooth flank of each pinion tooth from the rolling cone towards the tip cone or the root cone of the pinion compared to a second reference pinion, in which the reference pressure angle increases from the intermediate section towards the inner end and decreases from the intermediate section towards the outer end. [3] Differential gear mechanism according to claim 1, wherein in at least one of a first region in the flank line direction closer to the inner end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones of the axle shaft gear and the pinion, a second region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, a third region in the flank line direction closer to the outer end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones, and a fourth region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones,a pressure angle on a tooth flank of each axle shaft gear tooth from the rolling cone towards the root cone or the tip cone of the axle shaft gear compared to a second reference axle shaft gear, in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end, and a pressure angle on a tooth flank of each pinion tooth from the rolling cone towards the tip cone or the root cone of the pinion compared to a second reference pinion, in which the reference pressure angle increases from the intermediate section towards the inner end and from the intermediate section towards the outer end. [4] Method for designing a differential gear mechanism comprising a pair of axle gears, each of which is a bevel gear having a plurality of axle gear teeth, and a plurality of pinions, each of which is a bevel gear having a plurality of pinion teeth and meshing with the pair of axle gears, wherein outer end sections of tooth roots of each axle gear are inclined such that they are positioned closer than a root cone of the axle gear to a head cone of the axle gear, inner end sections of tooth heads of the axle gear teeth are inclined such that they are positioned closer than the head cone of the axle gear to the root cone of the axle gear, inner end sections of tooth roots of each pinion are inclined such that they are positioned closer than a root cone of the pinion to a head cone of the pinion, and outer end sections of tooth heads of the pinion teeth are inclined such thatthat they are positioned closer to the base cone of the pinion than the head cone of the pinion, including: Increasing a reference pressure angle, which is an angle defined by a radial line and a tangent to a tooth profile passing through a pitch point of each axle shaft gear tooth, is formed, and a reference pressure angle, which is an angle formed by a radial line and a tangent to a tooth profile passing through a pitch point of each pinion tooth, from an intermediate segment of a flank line contained between the inner end segment of the tooth tip of the axle shaft gear tooth and the outer end segment of the tooth tip of the pinion tooth, in a flank line direction towards an inner end and from the intermediate segment towards an outer end; and Decreasing the tooth thickness on a rolling cone of each axle shaft gear from the intermediate section towards the inner end and increasing the tooth thickness on the rolling cone of the axle shaft gear from the intermediate section towards the outer end compared to a reference axle shaft gear in which a line of intersection between a tooth flank of an axle shaft gear tooth and a rolling cone is a straight line passing through a center of the differential gear mechanism, and the reference pressure angle is constant in the flank line direction; and increasing the tooth thickness on a rolling cone of each pinion from the intermediate section towards the inner end and decreasing the tooth thickness on the rolling cone of the pinion from the intermediate section towards the outer end compared to a reference pinion in which a line of intersection between a tooth flank of a pinion tooth and a rolling cone is a straight line passing through the center.and the reference pressure angle is constant in the flank line direction. [5] Method for designing the differential gear mechanism according to claim 4, wherein in at least one of a first region in the flank line direction closer to the inner end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones of the axle shaft gear and the pinion, of a second region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, of a third region in the flank line direction closer to the outer end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones, and a fourth area in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, a pressure angle on a tooth flank of each axle shaft gear tooth from the rolling cone towards the base cone or the head cone of the axle shaft gear compared to a second reference axle shaft gear in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end, and a pressure angle on a tooth flank of each pinion tooth from the rolling cone towards the head cone or the base cone of the pinion compared to a second reference pinion in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end, is decreased. [6] Method for designing the differential gear mechanism according to claim 4, wherein in at least one of a first region in the flank line direction closer to the inner end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones of the axle shaft gear and the pinion, of a second region in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, of a third region in the flank line direction closer to the outer end than the intermediate section and closer to the head cone of the axle shaft gear and the base cone of the pinion than the rolling cones, and a fourth area in the flank line direction closer to the inner end than the intermediate section and closer to the base cone of the axle shaft gear and the head cone of the pinion than the rolling cones, a pressure angle on a tooth flank of each axle shaft gear tooth from the rolling cone towards the base cone or the head cone of the axle shaft gear compared to a second reference axle shaft gear in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end, and a pressure angle on a tooth flank of each pinion tooth from the rolling cone towards the head cone or the base cone of the pinion compared to a second reference pinion in which the reference pressure angle increases from the intermediate section towards the inner end and increases from the intermediate section towards the outer end.

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