Insertion guide of shaft

Abstract

The invention provides an insertion guide for a shaft, which can restrain the sealing performance of an oil seal from being reduced. The insertion guide (a) is provided with a cylindrical large-diameter section having a first axis as a center line, a cylindrical small-diameter section having a smaller diameter than the large-diameter section, and a cylindrical connection section that connects an outer edge section on the small-diameter section side of the large-diameter section and an outer edge section on the large-diameter section side of the small-diameter section. (b) The difference between the radius of the inner peripheral side of the small-diameter portion and the radius of the largest outer peripheral side of the insertion small-diameter portion of the intermediate shaft is determined according to the pre-design of the assemblability when the intermediate shaft is inserted into the small-diameter portion, (c) the radius of the inner peripheral side of the connection portion varies within the range between the minimum diameter and the maximum diameter in the circumferential direction with the first axis as the center line, and (c) the radius of the inner peripheral side of the connection portion varies within the range between the minimum diameter and the maximum diameter in the circumferential direction with the second axis as the center line. The minimum diameter is larger than the radius of the inner peripheral side of the small-diameter part, and the maximum diameter is smaller than the radius of the inner peripheral side of the large-diameter part.

Description

Technical Field

[0001] This invention relates to an insertion guide for a shaft that is fitted after the shaft passes through an oil seal. Background Technology

[0002] A shaft insertion guide is known that allows the shaft to be inserted through the inner circumference of a cylindrical oil seal and then engaged. For example, the insertion guide described in Patent Document 1 is such a device. The insertion guide described in Patent Document 1 comprises a cylindrical large-diameter portion centered on the axis of the insertion guide, a cylindrical small-diameter portion centered on the same axis, and a cylindrical connecting portion connecting the outer edge of the small-diameter portion of the large-diameter portion to the outer edge of the large-diameter portion of the small-diameter portion. In this configuration, the connecting portion is disc-shaped and does not extend in the axial direction. In this configuration, the disc-shaped connecting portion and the large-diameter portion are supported by the small-diameter portion protruding in the axial direction.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-71190 Summary of the Invention

[0004] However, when using the insertion guide described in Patent Document 1, where a shaft is inserted through its small-diameter portion for assembly, the small-diameter portion may deflect radially due to the low rigidity of the connecting portion supporting the small-diameter portion and the large-diameter portion. "Rigidity" refers to the ability to resist deformation under bending or torsional forces. If the small-diameter portion deflects radially, it reduces the centering accuracy of the shaft and damages the oil seal inserted before shaft fitting, potentially reducing the sealing performance of the oil seal after shaft assembly. "Centering" refers to the operation required when assembling components attached to various devices, adjusting position or positioning to make the connecting parts coaxial.

[0005] The present invention was made against the background described above, and its object is to provide an insertion guide for a shaft that can suppress the reduction of the sealing performance of an oil seal.

[0006] The present invention relates to an insertion guide for a shaft, which engages after the shaft is inserted through the inner circumference of a cylindrical oil seal, wherein (a) it comprises a cylindrical large-diameter portion centered on an axis, a cylindrical small-diameter portion centered on the axis and having a smaller diameter than the large-diameter portion, and a cylindrical connecting portion connecting the outer edge of the small-diameter portion to the outer edge of the large-diameter portion; (b) the difference between the radius of the inner circumference of the small-diameter portion and the radius of the largest outer circumference of the shaft when inserted into the small-diameter portion is determined based on a pre-designed assemblability when the shaft is inserted into the small-diameter portion; and (c) in the circumferential direction centered on the axis, the radius of the inner circumference of the connecting portion varies within a range between a predetermined minimum diameter and a predetermined maximum diameter, wherein the predetermined minimum diameter is greater than or equal to the radius of the inner circumference of the small-diameter portion, and the predetermined maximum diameter is less than or equal to the radius of the inner circumference of the large-diameter portion.

[0007] Invention Effects

[0008] According to the shaft insertion guide of the present invention, (a) it comprises a cylindrical large-diameter portion centered on an axis, a cylindrical small-diameter portion centered on the axis and having a smaller diameter than the large-diameter portion, and a cylindrical connecting portion connecting the outer edge portion of the small-diameter portion in the large-diameter portion to the outer edge portion of the large-diameter portion in the small-diameter portion; (b) the difference between the radius of the inner circumference of the small-diameter portion and the radius of the largest outer circumference of the shaft through the small-diameter portion is determined based on the pre-designed assemblability when the shaft is inserted through the small-diameter portion; (c) in the circumferential direction centered on the axis, the radius of the inner circumference of the connecting portion varies within a range between a predetermined minimum diameter and a predetermined maximum diameter, wherein the predetermined minimum diameter is greater than or equal to the radius of the inner circumference of the small-diameter portion, and the predetermined maximum diameter is less than or equal to the radius of the inner circumference of the large-diameter portion. By having a connecting portion whose radius varies within the range between the minimum and maximum diameter on the inner circumferential side of the circumferential connecting portion as described in (c) above, the rigidity of the connecting portion supporting the small-diameter portion protruding in the axial direction is improved compared to the case without such a connecting portion. If the rigidity of the connecting portion and the large-diameter portion is improved, the small-diameter portion is less likely to deflect radially when assembled by inserting the shaft through the small-diameter portion of the guide member. Therefore, the centering accuracy of the shaft is easily improved when assembled by inserting the shaft through the small-diameter portion of the guide member. Consequently, when assembling the shaft, damage to the oil seal is suppressed, and the sealing performance of the oil seal after shaft assembly is prevented from decreasing. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating the differential gear and intermediate shaft that are fitted together using the insertion guide according to an embodiment of the present invention. The diagram shows the state of the intermediate shaft before assembly.

[0010] Figure 2 yes Figure 1 The diagram shows a perspective view of the insertion guide.

[0011] Figure 3 This is an explanation Figure 2 The diagram shows the shape of the insertion guide. Figure 3 (a) is along Figure 2 The diagram shows the direction of arrow X. Figure 3 (b) is Figure 3 (a) shows a cross-sectional view at section line Y.

[0012] Figure 4 This is an explanation Figure 1 The diagram shows the assembly state of the differential gear and the intermediate shaft.

[0013] Figure 5 This is a perspective view of the insertion guide involved in the comparative example. Figure 5 (a) is a comparative example 1 in which the connecting part is a disk shape and does not extend in the direction of the first axis. Figure 5 (b) is a comparative example 2 in which the radius of the inner circumference of the connection does not change in the circumferential direction but only in the direction of the first axis. Detailed Implementation

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the parts are not necessarily depicted accurately. In this specification, "circumferential direction centered on the first axis CL1" and "radial direction centered on the first axis CL1" are abbreviated as "circumferential direction" and "radial direction," respectively.

[0015] Example

[0016] Figure 1 This is a diagram illustrating the differential gear 10 and intermediate shaft 40 engaged using the insertion guide 30 according to an embodiment of the present invention, showing the state of the intermediate shaft 40 before assembly.

[0017] A differential gear 10 is mounted on a vehicle 90. The differential gear 10 is a known type of differential gear capable of rotating about a first axis CL1. The differential gear 10 is supported by a housing 50, which is a non-rotating component. The differential gear 10 includes a pair of side gears 10s and a differential pinion 10p, both meshing with the pair of side gears 10s. The rotational center lines of the pair of side gears 10s are both the first axis CL1. A meshing portion 10d is provided on the inner circumference of the pair of side gears 10s.

[0018] The intermediate shaft (= intermediate drive shaft) 40 is a cylindrical shaft centered on the second axis CL2. The intermediate shaft 40 transmits driving torque during the movement of the vehicle 90 and absorbs changes in length along the second axis CL2 caused by the vertical movement of the vehicle 90, etc., through connection with a constant velocity joint (not shown). Along the second axis CL2, the intermediate shaft 40 has, from its front end side, a shaft portion 40a, a shaft portion 40b, and a shaft portion 40c. The radius Ris[m] of the outer periphery of shaft portion 40b is smaller than the radius of the outer periphery of shaft portion 40c, and the radius of the outer periphery of shaft portion 40a is smaller than the radius Ris of the outer periphery of shaft portion 40b. The radius Ris is the largest outer periphery radius among the shaft portions into which the guide member 30 (described later) is inserted. Stepped portions are formed between shaft portions 40a and 40b, and between shaft portions 40b and 40c. A fitting portion 40d is provided on the shaft portion 40a, which serves as the front end of the intermediate shaft 40. In addition, the intermediate shaft 40 is equivalent to the "shaft" in this invention, and the radius Ris is equivalent to the "radius of the largest outer periphery of the small diameter portion inserted into the shaft" in this invention.

[0019] The insertion guide 30 is used, for example, when the intermediate shaft 40 is assembled to the side gear 10s of the differential gear 10.

[0020] A cylindrical opening 50o, centered on the first axis CL1, is provided at one end of the housing 50. The oil seal 20 is inserted with its outer circumferential surface pressing against the inner circumferential surface of the opening 50o. The oil seal 20 is a known type of oil seal made of a material that is easily elastically deformable, such as rubber. The radius Ro[m] of the inner circumferential side of the oil seal 20 is smaller than the radius Ris in a manner that ensures the sealing performance of the oil seal 20 when the intermediate shaft 40 is fitted to the side gear 10s of the differential gear 10. That is, when the intermediate shaft 40 is fitted to the side gear 10s of the differential gear 10, the inner circumferential portion 20i of the oil seal 20 presses against the shaft portion 40b of the intermediate shaft 40. The inner circumferential surface of the insertion guide 30 is mounted in contact with the outer circumferential surface of the opening 50o.

[0021] Figure 2 yes Figure 1 The insertion guide 30 is shown in perspective. The insertion guide 30 is formed, for example, by stamping a plate-like body.

[0022] The insertion guide 30 includes a disc-shaped portion 30a, a large-diameter portion 30b, a connecting portion 30c, a small-diameter portion 30d, and a tapered portion 30e, all centered on a first axis CL1. The large-diameter portion 30b is cylindrical, centered on the first axis CL1. The small-diameter portion 30d is cylindrical, smaller than the large-diameter portion 30b, and centered on the first axis CL1. The connecting portion 30c is cylindrical, connecting the outer edge of the small-diameter portion 30d in the large-diameter portion 30b to the outer edge of the large-diameter portion 30b in the small-diameter portion 30d. The disc-shaped portion 30a is a disc-shaped portion extending outwards from the outer edge of the large-diameter portion 30b on the side opposite to the small-diameter portion 30d. The tapered portion 30e connects to the outer edge of the small-diameter portion 30d on the side opposite to the large-diameter portion 30b, and its opening gradually widens as it extends towards the side opposite to the large-diameter portion 30b. The disc portion 30a, the large-diameter portion 30b, the connecting portion 30c, the small-diameter portion 30d, and the tapered portion 30e are connected in a bent state.

[0023] A mounting hole 30a1 is provided in the disc portion 30a. By inserting a bolt or other fastener into the mounting hole 30a1 and fastening it to a fastening hole (not shown) provided in the housing 50, the guide member 30 is installed in the housing 50.

[0024] Figure 3 This is an explanation Figure 2 The diagram showing the shape of the insertion guide 30, (a) is along... Figure 2 The diagram shown is an observation of the direction of arrow X, (b) is Figure 3 (a) shows a cross-sectional view at section line Y.

[0025] As described above, the opening of the tapered portion 30e gradually widens as it extends towards the side opposite to the large-diameter portion 30b. The radius Re[m] of the inner circumference of the opening portion of the tapered portion 30e is greater than the radius Rd[m] of the inner circumference of the small-diameter portion 30d. The radius Rb[m] of the inner circumference of the large-diameter portion 30b is greater than the radius Rd of the inner circumference of the small-diameter portion 30d. In the circumferential direction, the radius Rc[m] of the inner circumference of the connecting portion 30c varies periodically within the range between the minimum diameter Rmin[m] (above radius Rd and below radius Rb) and the maximum diameter Rmax[m].

[0026] The minimum diameter Rmin is a defined diameter that is greater than or equal to the radius Rd and less than the maximum diameter Rmax. The maximum diameter Rmax is a defined diameter that is greater than or equal to the minimum diameter Rmin and less than or equal to the radius Rb. Furthermore, "radius Rb," "radius Rc," and "radius Rd" respectively correspond to "the radius of the inner circumference of the large-diameter portion," "the radius of the inner circumference of the connecting portion," and "the radius of the inner circumference of the small-diameter portion" in this invention. "Minimum diameter Rmin" and "maximum diameter Rmax" respectively correspond to "the defined minimum diameter" and "the defined maximum diameter" in this invention. The minimum diameter Rmin will be described later. Thus, in the connecting portion 30c, portions protruding towards the small-diameter portion 30d and outwards are formed at equal angular intervals (every 60 degrees in this embodiment) in the circumferential direction. In the vertical direction, the radius Rc of the lowermost part Plow of the connecting portion 30c is the minimum diameter Rmin.

[0027] The length of the first axis CL1 in the disk portion 30a is La [m]. The length of the first axis CL1 in the large diameter portion 30b is Lb [m]. The length of the first axis CL1 in the connecting portion 30c is Lc [m]. The length of the first axis CL1 in the small diameter portion 30d is Ld [m]. The length of the first axis CL1 in the tapered portion 30e is Le [m].

[0028] Figure 4 This is an explanation Figure 1 The diagram shows the state of the differential gear 10 and the intermediate shaft 40 when they are assembled. Figure 4 This indicates that during assembly, the intermediate shaft 40 is inserted through the opening of the tapered portion 30e of the insertion guide 30, and further inserted into the small-diameter portion 30d until it contacts the oil seal 20. Figure 4 After the intermediate shaft 40 is inserted through the inner circumference 20i of the oil seal 20, the fitting portion 40d on the front end side of the intermediate shaft 40 engages with the fitting portion 10d. Figure 4 The diagram shows the case where the intersection angle θ [deg] between the centerline of the intermediate shaft 40 (i.e., the second axis CL2) and the centerline of the insertion guide 30 (i.e., the first axis CL1) is at its maximum value. The intersection angle θ is the angle (≤90 [deg]) between the second axis CL2 and the first axis CL1. Figure 4 In the middle shaft 40, the side opposite to the front end shaft portion 40a tilts upwards. Figure 4 In the middle section, the minor diameter portion 30d does not bend radially. That is, the centerline of the minor diameter portion 30d coincides with the first axis CL1.

[0029] The ratio obtained by dividing the multiple of the difference ΔR1 (=Rd-Ris) between the inner circumference radius Rd of the minor diameter 30d and the outer circumference radius Ris of the intermediate axis 40 by the length Ld of the minor diameter 30d (=2×ΔR1 / Ld=2(Rd-Ris) / Ld) is set as tan(θ1). Thus, tanθ, which is the tangent of the crossing angle θ, is subject to the following relation (1) holding.

[0030] tanθ≤2(Rd-Ris) / Ld=tan(θ1)…(1)

[0031] Furthermore, the ratio obtained by dividing the difference between the inner circumference radius Re of the opening portion of the cone 30e and the inner circumference radius Rd of the small diameter portion 30d (=Re-Rd) by the length Le of the cone 30e (=(Re-Rd) / Le) is sufficiently greater than tan(θ1).

[0032] From here, we will explain the minimum diameter Rmin. The ratio obtained by dividing the difference ΔR2 (=Rmin-Rd) between the minimum diameter Rmin and the radius Rd of the inner circumference of the small diameter portion 30d by the length Lc of the connecting portion 30c (=ΔR2 / Lc=(Rmin-Rd) / Lc) is set as tan(θ2).

[0033] When tan(θ1)≤tan(θ2) holds, the cross angle θ is restricted by relation (1).

[0034] When tan(θ2)<tan(θ1) holds, the cross angle θ is restricted by the following relation (2).

[0035] tanθ≤2(Rmin-Ris) / (Lc+Ld)<tan(θ1)…(2)

[0036] In this embodiment, the case where tan(θ2) < tan(θ1) is described.

[0037] In the vertical direction, the lowest position of the inner circumference 20i of the oil seal 20 is set as the lowest position P1. For example... Figure 4 As shown, at the lowest position P1, the oil seal 20 is in contact with the intermediate shaft 40. In the vertical direction, the uppermost position of the inner circumference 20i of the oil seal 20 is defined as the uppermost position P2. (As shown...) Figure 4 As shown, at the uppermost position P2, the oil seal 20 is not yet in contact with the intermediate shaft 40, but it comes into contact with the intermediate shaft 40 by further insertion into the intermediate shaft 40.

[0038] exist Figure 4 In this state, the intermediate shaft 40 tilts upwards only at an angle θ, thus the force exerted by the intermediate shaft 40 at the lowest position P1 on the inner circumference 20i of the oil seal 20 is greater than that at the uppermost position P2. That is, in Figure 4 In the state where the cross angle θ is zero, the force exerted by the intermediate shaft 40 on the inner circumference 20i of the oil seal 20 is weaker at the uppermost position P2, while the force exerted by the intermediate shaft 40 on the inner circumference 20i of the oil seal 20 is stronger at the lowermost position P1. Thus, the force exerted by the intermediate shaft 40 on the inner circumference 20i of the oil seal 20 deviates due to the cross angle θ. Therefore, at the lowermost position P1, compared to the uppermost position P2, the intermediate shaft 40 is more likely to damage the oil seal 20 when it is inserted through the inner circumference 20i of the oil seal 20. If the oil seal 20 is damaged, the sealing performance of the oil seal 20 after the intermediate shaft 40 is assembled may be reduced.

[0039] To prevent the intermediate shaft 40 from damaging the oil seal 20, it is only necessary to set the cross angle θ as small as possible so that the force of the intermediate shaft 40 pressing the inner circumference 20i of the oil seal 20 does not deviate. That is, the centering accuracy can be improved by making the angle θ1 [deg] or angle θ2 [deg] smaller.

[0040] From here, we will study how to limit the crossing angle θ by reducing the angle θ1.

[0041] First, one could consider reducing the angle θ1 by decreasing the difference ΔR1 (=Rd-Ris). However, if the difference ΔR1 is reduced too much, the intermediate shaft 40 will have difficulty inserting into the minor diameter portion 30d, resulting in reduced assemblability. Therefore, the difference ΔR1 needs to be set above the predetermined value in the design, which ensures assemblability is within the allowable range. "Assemblability" refers to the operability of assembly, i.e., the ease of assembly.

[0042] Next, it is possible to reduce the angle θ1 by increasing the length Ld. However, if the length Ld is increased, the small diameter portion 30d may easily deflect radially. If the small diameter portion 30d deflects radially, the crossing angle θ may increase even if the length Ld is extended. Therefore, it is necessary to extend the length of the small diameter portion 30d and prevent it from deflecting radially. That is, it is necessary to improve the rigidity of the connecting portion 30c and the large diameter portion 30b that support the small diameter portion 30d.

[0043] like Figure 4As shown, in the insertion guide 30 of this embodiment, the radius Rc of the inner circumferential side of the connecting portion 30c varies periodically within the range between the minimum diameter Rmin and the maximum diameter Rmax in the circumferential direction. With this structure of the connecting portion 30c, compared to the structure of the connecting portion of the insertion guide involved in the comparative example described later, the rigidity of the connecting portion 30c and the large diameter portion 30b, which support the small diameter portion 30d protruding in the direction of the first axis CL1, is improved. Therefore, even if the small diameter portion 30d is extended in the direction of the first axis CL1, the small diameter portion 30d is less likely to deflect radially when the intermediate shaft 40 is inserted through the small diameter portion 30d for assembly. Furthermore, to improve rigidity, it is possible to consider, for example, increasing the thickness of the plate-like body formed by stamping the insertion guide 30; however, if this is done, the energy efficiency of the vehicle 90, such as fuel economy and electrical efficiency, decreases as the weight of the insertion guide 30 increases.

[0044] Figure 5 The following is a perspective view of the insertion guide involved in the comparative example. (a) is a comparative example 1 in which the connecting part does not extend in the direction of the first axis CL1 and is in the form of a disc. (b) is a comparative example 2 in which the radius of the inner circumference of the connecting part does not change in the circumferential direction but only in the direction of the first axis CL1.

[0045] exist Figure 5 In Comparative Example 1 shown in (a), the connecting portion is disc-shaped. Therefore, compared to this embodiment, the connecting portion supporting the small-diameter portion and the large-diameter portion have low rigidity, making the small-diameter portion prone to radial deflection. Figure 5 (b) In Comparative Example 2, the radius of the inner circumferential side of the connecting portion does not change in the circumferential direction but only in the direction of the first axis CL1. Therefore, in Comparative Example 2, the rigidity of the connecting portion supporting the small diameter portion and the large diameter portion is higher than that of Comparative Example 1, but lower than that of this embodiment. Thus, in Comparative Examples 1 and 2, the rigidity of the connecting portion supporting the small diameter portion and the large diameter portion is lower than that of this embodiment. Therefore, when the intermediate shaft 40 is inserted through the small diameter portion of the guide member for assembly, the small diameter portion is more prone to radial deflection compared to this embodiment.

[0046] From here, we will study how to limit the crossing angle θ by reducing the angle θ2.

[0047] Angle θ2 can be reduced by decreasing the difference ΔR2 (=Rmin-Rd). For example, by setting the minimum diameter Rmin to be the same as the radius Rd, angle θ2 can be set to zero. Alternatively, increasing the length Lc of the connecting portion 30c to reduce angle θ2 would increase the weight of the insertion guide 30.

[0048] According to this embodiment, (a) it includes a cylindrical large-diameter portion 30b centered on the first axis CL1, a cylindrical small-diameter portion 30d smaller than the large-diameter portion 30b centered on the first axis CL1, and a cylindrical connecting portion 30c that connects the outer edge of the small-diameter portion 30d side of the large-diameter portion 30b to the outer edge of the large-diameter portion 30b side of the small-diameter portion 30d; (b) the difference ΔR1 between the inner circumferential radius Rd of the small-diameter portion 30d and the maximum outer circumferential radius Ris of the small-diameter portion 30d through which the intermediate shaft 40 is inserted is determined based on the pre-design of assemblability when the intermediate shaft 40 is inserted through the small-diameter portion 30d; (c) in the circumferential direction, the inner circumferential radius Rc of the connecting portion 30c varies within the range between the minimum diameter Rmin and the maximum diameter Rmax, wherein the minimum diameter Rmin is greater than or equal to the inner circumferential radius Rd of the small-diameter portion 30d, and the maximum diameter Rmax is less than or equal to the inner circumferential radius Rb of the large-diameter portion 30b. By incorporating a connecting portion 30c, as described in (c) above, where the radius Rc of the inner circumferential side of the connecting portion 30c varies within the range between the minimum diameter Rmin and the maximum diameter Rmax, the rigidity and strength of the connecting portion 30c and the large diameter portion 30b, which support the small-diameter portion 30d protruding in the direction of the first axis CL1, are improved compared to the case without such a connecting portion 30c. If the rigidity of the connecting portion 30c and the large-diameter portion 30b is improved, the small-diameter portion 30d is less likely to deflect radially when the intermediate shaft 40 is inserted through the small-diameter portion 30d of the guide member 30 for assembly. Therefore, the centering accuracy of the intermediate shaft 40 is easily improved when the intermediate shaft 40 is inserted through the small-diameter portion 30d of the guide member 30 for assembly. Consequently, damage to the oil seal 20 is suppressed when assembling the intermediate shaft 40, and the reduction in the sealing performance of the oil seal 20 after the intermediate shaft 40 is assembled is suppressed. Furthermore, after the intermediate shaft 40 is assembled to the differential gear 10, the natural vibration coefficient of the insertion guide 30 is increased by improving the rigidity of the connecting portion 30c and the large diameter portion 30b supporting the small diameter portion 30d. Therefore, abnormal sounds or vibrations caused by resonance are less likely to occur during vehicle 90 operation. Moreover, by increasing the strength of the connecting portion 30c and the large diameter portion 30b supporting the small diameter portion 30d, cracks at the boundary between the small diameter portion 30d and the connecting portion 30c or the small diameter portion 30d detaching from the connecting portion 30c are suppressed during vehicle 90 operation.

[0049] According to this embodiment, the radius Rc of the inner circumferential side of the connecting portion 30c changes periodically in the circumferential direction. When it changes periodically, the rigidity variation of the connecting portion 30c and the large-diameter portion 30b in the circumferential direction is smaller compared to when it does not change periodically. Therefore, even if the centerline of the intermediate shaft 40, i.e., the second axis CL2, deviates from or intersects the first axis CL1, which serves as the centerline of the insertion guide 30, in any direction (up, down, left, right), the small-diameter portion 30d is less likely to deflect radially. Therefore, it is easier to improve the centering accuracy of the intermediate shaft 40 when it is assembled by inserting the intermediate shaft 40 through the small-diameter portion 30d of the insertion guide 30.

[0050] According to this embodiment, (a) in the assembled state, in the direction of the vertical line, the radius Rc of the inner circumference of the lowermost part Plow of the connecting portion 30c is the minimum diameter Rmin, and (b) in the cross-section of the first axis CL1, tan(θ2) is less than tan(θ1). As a method for inserting the intermediate shaft 40 through the small diameter portion 30d, there is a method of inserting it while sliding it, with the lowermost part of the end portion of the intermediate shaft 40 in contact with the lowermost part Plow of the inner circumference of the small diameter portion 30d. In this method, when tan(θ2) is less than tan(θ1), the crossing angle θ is more easily limited and becomes smaller compared to cases where this condition is not met. Therefore, due to the crossing angle θ, the force of the intermediate shaft 40 pressing against the inner circumference 20i of the oil seal 20 is less likely to deviate, thereby suppressing damage to the oil seal 20.

[0051] Furthermore, the above are embodiments of the present invention. The present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from its spirit.

[0052] In the foregoing embodiment, the intermediate shaft 40 is engaged with the side gear 10s of the differential gear 10, but the application of the present invention is not limited thereto.

[0053] In the foregoing embodiment, the radius Rc of the inner circumference of the connecting portion 30c varies periodically, but the present invention is not limited thereto. For example, the radius Rc of the inner circumference of the connecting portion 30c may also vary non-periodically. Even in this manner, compared to the case where the radius Rc of the inner circumference of the connecting portion 30c does not change, the rigidity of the connecting portion 30c supporting the small-diameter portion 30d and the large-diameter portion 30b is improved.

[0054] In the aforementioned embodiment, the radius Rc of the inner periphery of the connecting portion 30c at the bottommost Plow is set such that relation (2) holds, but for example, it can also be set such that the difference ΔR2 is zero.

[0055] That is, the minimum diameter Rmin can also be the same as the radius Rd of the inner circumference of the small diameter portion 30d. When the minimum diameter Rmin and the radius Rd of the inner circumference of the small diameter portion 30d are the same, the cross angle θ is more easily limited compared to the case where they are not the same. As a result, the force of the intermediate shaft 40 pressing the inner circumference 20i of the oil seal 20 is less likely to deviate due to the cross angle θ, thereby suppressing damage to the oil seal 20.

[0056] In the foregoing embodiment, the insertion guide 30 is provided with a disc portion 30a and a tapered portion 30e, but the present invention can also be applied to a form without these. For example, in a form without the disc portion 30a, it is sufficient to provide a radially penetrating mounting hole in the large-diameter portion 30b and a radially protruding fastening hole in the opening 50o of the housing 50, and to insert a bolt or other fastener into the mounting hole and fasten it to the fastening hole in the opening 50o.

[0057] Symbol Explanation

[0058] 20 - Oil seal, 20i - Inner circumference, 30 - Insertion guide, 30b - Large diameter section, 30c - Connecting section, 30d - Small diameter section, 40 - Intermediate shaft (shaft), CL1 - First axis (axis), Lc - Length (length of the connecting section in the axis direction), Ld - Length (length of the small diameter section in the axis direction), Plow - Bottommost part (bottommost part of the connecting section), Rc - Radius (radius of the inner circumference of the connecting section), Rd - Radius (radius of the inner circumference of the small diameter section), Ris - Radius (radius of the largest outer circumference of the small diameter section of the shaft), Rmax - Maximum diameter (specified maximum diameter), Rmin - Minimum diameter (specified minimum diameter), ΔR1 - Difference (difference between the radius of the inner circumference of the small diameter section and the radius of the outer circumference of the shaft), ΔR2 - Difference (difference between the minimum diameter and the radius of the inner circumference of the small diameter section).

Claims

1. A shaft insertion guide that engages with a cylindrical oil seal after the shaft has passed through its inner circumference, characterized in that, It comprises a cylindrical large-diameter portion centered on an axis, a cylindrical small-diameter portion centered on the axis and having a smaller diameter than the large-diameter portion, and a cylindrical connecting portion connecting the outer edge of the small-diameter portion of the large-diameter portion to the outer edge of the large-diameter portion of the small-diameter portion. The difference between the radius of the inner circumference of the small-diameter portion and the radius of the largest outer circumference of the shaft when it passes through the small-diameter portion is determined based on the pre-designed assemblability when the shaft passes through the small-diameter portion. In the circumferential direction with the axis as the center line, the radius of the inner circumference of the connecting part varies within a range between a specified minimum diameter and a specified maximum diameter, wherein the specified minimum diameter is above the radius of the inner circumference of the small diameter part, and the specified maximum diameter is below the radius of the inner circumference of the large diameter part.

2. The shaft insertion guide according to claim 1, characterized in that, The radius of the inner circumference of the connecting part changes periodically in the circumferential direction with the axis as the center line.

3. The shaft insertion guide according to claim 1, characterized in that, In the assembled state, the radius of the inner circumference of the lowest part of the connecting portion in the vertical direction is the minimum diameter. In the cross-section of the first axis, the ratio obtained by dividing the difference between the minimum diameter and the inner circumference of the small diameter portion by the length of the connecting portion in the direction of the first axis is less than the ratio obtained by dividing the multiple of the difference between the inner circumference of the small diameter portion and the radius of the largest outer circumference of the small diameter portion through which the shaft passes by by the length of the small diameter portion in the direction of the first axis.

4. The shaft insertion guide according to any one of claims 1 to 3, characterized in that, The minimum diameter is the same as the radius of the inner circumference of the small diameter portion.

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