Shaft insertion guide

Abstract

This invention provides a shaft insertion guide that can suppress the deterioration of the sealing performance of oil seals. [Solution] The insertion guide 30 comprises (a) a cylindrical large-diameter portion 30b with the first axis CL1 as its centerline, a cylindrical small-diameter portion 30d having a smaller diameter than the large-diameter portion 30b, and a cylindrical connecting portion 30c that connects the outer edge of the large-diameter portion 30b on the small-diameter portion 30d side with the outer edge of the small-diameter portion 30d on the large-diameter portion 30b side, and (b) the radius Rd on the inner circumference side of the small-diameter portion 30d and the largest outer diameter portion through which the small-diameter portion 30d is inserted in the intermediate axis 40. The difference ΔR2 (=Rd-Ris) from the circumferential radius Ris is predetermined in the design based on the ease of assembly when the intermediate shaft 40 is inserted into the small diameter section 30d, and (c) in the circumferential direction with the first axis CL1 as the center line, the inner circumferential radius Rc of the connecting section 30c changes within the range between the minimum diameter Rmin, which is greater than or equal to the inner circumferential radius Rd of the small diameter section 30d, and the maximum diameter Rmax, which is less than or equal to the inner circumferential radius Rb of the large diameter section 30b.

Description

Technical Field

[0004] , , , , ,

[0001] The present invention relates to an insertion guide for a shaft, which is fitted after inserting the shaft through an oil seal.

Background Art

[0002] There is known an insertion guide for a shaft, which is fitted after inserting the shaft through the inner peripheral portion of a cylindrical oil seal. For example, the insertion guide described in Patent Document 1 is such an example. The insertion guide described in Patent Document 1 includes a cylindrical large-diameter portion having the axis of the insertion guide as its center line, a cylindrical small-diameter portion having the axis as its center line, and a cylindrical connecting portion connecting the outer edge portion on the small-diameter portion side in the large-diameter portion and the outer edge portion on the large-diameter portion side in the small-diameter portion. The connecting portion in this aspect is a disk shape that does not extend in the axial direction. In this aspect, the small-diameter portion protruding in the axial direction is supported by the disk-shaped connecting portion and the large-diameter portion.

Prior Art Documents

Patent Documents

[0003] <000且017>

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, when the shaft is inserted through the small-diameter section and assembled using the insertion guide described in Patent Document 1, the small-diameter section may bend radially due to the low rigidity of the connecting section supporting the small-diameter section and the large-diameter section. "Rigidity" refers to the degree of resistance to deformation under bending and torsional forces. If the small-diameter section bends radially, the accuracy of shaft alignment will decrease, potentially damaging the oil seal inserted before fitting the shaft, and reducing the sealing performance of the oil seal after shaft assembly. "Alignment" is a necessary operation when assembling components attached to various devices, which involves adjusting or positioning the connecting parts so that they are coaxial.

[0005] This invention was made against the above circumstances, and its objective is to provide a shaft insertion guide that can suppress the deterioration of the sealing performance of an oil seal. [Means for solving the problem]

[0006] The gist of the present invention is a shaft insertion guide for fitting a shaft after it has been inserted into the inner circumference of a cylindrical oil seal, comprising: (a) a cylindrical large-diameter portion with the axis as its centerline; a cylindrical small-diameter portion having a smaller diameter than the large-diameter portion with the axis as its centerline; and a cylindrical connecting portion connecting the outer edge of the large-diameter portion on the small-diameter side of the large-diameter portion to the outer edge of the small-diameter portion on the large-diameter side of the small-diameter portion; (b) the difference between the inner radius of the small-diameter portion and the largest outer radius of the shaft through which the small-diameter portion is inserted is predetermined by design based on the ease of assembly when the shaft is inserted into the small-diameter portion; and (c) in the circumferential direction with the axis as its centerline, the inner radius of the connecting portion changes within a range between a predetermined minimum diameter which is greater than or equal to the inner radius of the small-diameter portion and a predetermined maximum diameter which is less than or equal to the inner radius of the large-diameter portion. [Effects of the Invention]

[0007] According to the shaft insertion guide of the present invention, (a) a cylindrical large-diameter portion with the axis as its centerline, a cylindrical small-diameter portion having a smaller diameter than the large-diameter portion with the axis as its centerline, and a cylindrical connecting portion that connects the outer edge of the large-diameter portion on the small-diameter side of the large-diameter portion to the outer edge of the small-diameter portion on the large-diameter side of the small-diameter portion, (b) the difference between the inner radius of the small-diameter portion and the largest outer radius of the shaft through which the small-diameter portion is inserted is predetermined by design based on the ease of assembly when inserting the shaft into the small-diameter portion, and (c) in the circumferential direction with the axis as its centerline, the inner radius of the connecting portion changes within a range between a predetermined minimum diameter which is greater than or equal to the inner radius of the small-diameter portion and a predetermined maximum diameter which is less than or equal to the inner radius of the large-diameter portion. As described in (c) above, by providing a connection portion in which the radius on the inner side of the connection portion changes within a range between the minimum and maximum diameters in the circumferential direction, the rigidity of the connection portion and the large diameter portion that support the small diameter portion protruding in the axial direction is improved compared to the case where such a connection portion is not provided. When the rigidity of the connection portion and the large diameter portion is improved, the small diameter portion becomes less likely to bend radially when the shaft is inserted through the small diameter portion of the insertion guide and assembled. As a result, the accuracy of centering the shaft when the shaft is inserted through the small diameter portion of the insertion guide and assembled is improved. This suppresses damage to the oil seal when the shaft is assembled and suppresses the deterioration of the sealing performance of the oil seal after the shaft is assembled. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates a differential gear and an intermediate shaft that are fitted together using an insertion guide according to an embodiment of the present invention, and illustrates the state of the intermediate shaft before assembly. [Figure 2] Figure 1 is a perspective view of the insertion guide. [Figure 3] This diagram illustrates the shape of the insertion guide shown in Figure 2, where (a) is a view in the direction of arrow X in Figure 2, and (b) is a cross-sectional view at the cutting line Y shown in Figure 3(a). [Figure 4]This diagram illustrates the assembly of the differential gear and intermediate shaft shown in Figure 1. [Figure 5] The images show perspective views of insertion guides relating to comparative examples, where (a) is Comparative Example 1, in which the connecting portion is disc-shaped and does not extend in the first axial direction, and (b) is Comparative Example 2, in which the radius on the inner circumference of the connecting portion does not change in the circumferential direction but changes in the first axial direction. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part 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" will be simply referred to as "circumferential direction" and "radial direction," respectively. [Examples]

[0010] Figure 1 is a diagram illustrating the differential gear 10 and intermediate shaft 40 fitted together using the insertion guide 30 according to an embodiment of the present invention, and illustrates the state of the intermediate shaft 40 before assembly.

[0011] The differential gear 10 is mounted on the vehicle 90. The differential gear 10 is a well-known differential gear that can rotate around a first axis CL1. The differential gear 10 is supported by a case 50, which is a non-rotating member. The differential gear 10 has a pair of side gears 10s and a differential pinion 10p that meshes with both of the pair of side gears 10s. The rotational centerlines of the pair of side gears 10s are both the first axis CL1. A fitting portion 10d is provided on the inner circumference of the pair of side gears 10s.

[0012] The intermediate shaft 40 is a cylindrical shaft with the second axis CL2 as its centerline. The intermediate shaft 40 transmits driving torque while the vehicle 90 is running and absorbs changes in length in the direction of the second axis CL2 due to vertical movement of the vehicle 90 by being connected to a constant velocity coupling (not shown). In the direction of the second axis CL2, the intermediate shaft 40 has, in order from the tip side, a shaft portion 40a, a shaft portion 40b, and a shaft portion 40c. The outer radius Ris [m] of the shaft portion 40b is smaller than the outer radius of the shaft portion 40c, and the outer radius of the shaft portion 40a is smaller than the outer radius Ris of the shaft portion 40b. The radius Ris is the largest outer radius of the shaft portions of the intermediate shaft 40 through which the small diameter portion 30d of the insertion guide 30 (described later) is inserted. The space between shaft portion 40a and shaft portion 40b, and the space between shaft portion 40b and shaft portion 40c, are stepped. A fitting portion 40d is provided on shaft portion 40a, which is the tip side of the intermediate shaft 40. The intermediate shaft 40 corresponds to the "shaft" in this invention, and radius Ris corresponds to the "largest outer radius through which the small diameter portion is inserted in the shaft" in this invention.

[0013] The insertion guide 30 is used, for example, when assembling the intermediate shaft 40 to the side gear 10s of the differential gear 10.

[0014] In the direction of the first axis CL1, a cylindrical opening 50o is provided at one end of the case 50, with the first axis CL1 as its centerline. The oil seal 20 is fitted in such a way that its outer surface is pressed against the inner surface of the opening 50o. The oil seal 20 is a well-known oil seal made of a material that is easily elastically deformable, such as rubber. The inner circumference of the oil seal 20 has a radius Ro [m]. The radius Ro is smaller than the radius Ris so that the sealing performance of the oil seal 20 is ensured when the intermediate shaft 40 is assembled to the side gear 10s of the differential gear 10. That is, when the intermediate shaft 40 is assembled to the side gear 10s of the differential gear 10, the inner circumference 20i of the oil seal 20 is pressed against the shaft portion 40b of the intermediate shaft 40. The inner surface of the insertion guide 30 is attached so as to be in contact with the outer surface of the opening 50o.

[0015] Figure 2 is a perspective view of the insertion guide 30 shown in Figure 1. The insertion guide 30 is formed, for example, by press-forming a plate-like body.

[0016] The insertion guide 30 comprises a disc portion 30a, a large-diameter portion 30b, a connecting portion 30c, a small-diameter portion 30d, and a tapered portion 30e, with the first axis CL1 as its centerline. The large-diameter portion 30b is cylindrical with the first axis CL1 as its centerline. The small-diameter portion 30d is cylindrical with the first axis CL1 as its centerline and has a smaller diameter than the large-diameter portion 30b. The connecting portion 30c is cylindrical, connecting the outer edge of the large-diameter portion 30b on the small-diameter portion 30d side and the outer edge of the small-diameter portion 30d on the large-diameter portion 30b side. The disc portion 30a is disc-shaped, connected to the outer circumference from the outer edge of the large-diameter portion 30b opposite to the small-diameter portion 30d. The tapered portion 30e is connected to the outer edge of the small-diameter portion 30d opposite to the large-diameter portion 30b, and the opening gradually widens as it extends away from 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.

[0017] The disk portion 30a is provided with a mounting hole 30a1. By inserting a fastener such as a bolt into the mounting hole 30a1 and fastening it to a fastening hole (not shown) provided in the case 50, the insertion guide 30 is attached to the case 50.

[0018] FIG. 3 is a diagram for explaining the shape of the insertion guide 30 shown in FIG. 2. (a) is a view seen in the direction of arrow X shown in FIG. 2, and (b) is a cross-sectional view taken along the cutting line Y shown in FIG. 3(a).

[0019] As described above, as the tapered portion 30e extends to the side opposite to the large-diameter portion 30b, the opening gradually widens. The radius Re [m] on the inner peripheral side at the opening portion of the tapered portion 30e is larger than the radius Rd [m] on the inner peripheral side of the small-diameter portion 30d. The radius Rb [m] on the inner peripheral side of the large-diameter portion 30b is larger than the radius Rd on the inner peripheral side of the small-diameter portion 30d. In the circumferential direction, the radius Rc [m] on the inner peripheral side of the connecting portion 30c varies periodically within a range between a minimum diameter Rmin [m] that is equal to or greater than the radius Rd and a maximum diameter Rmax [m] that is equal to or less than the radius Rb. The minimum diameter Rmin is a predetermined diameter that is equal to or greater than the radius Rd and less than the maximum diameter Rmax, and the maximum diameter Rmax is a predetermined diameter that exceeds the minimum diameter Rmin and is equal to or less than the radius Rb. Note that "radius Rb", "radius Rc", and "radius Rd" respectively correspond to "the radius on the inner peripheral side of the large-diameter portion", "the radius on the inner peripheral side of the connecting portion", and "the radius on the inner peripheral side of the small-diameter portion" in the present invention. "Minimum diameter Rmin" and "maximum diameter Rmax" respectively correspond to "predetermined minimum diameter" and "predetermined maximum diameter" in the present invention. The minimum diameter Rmin will be described later. Thus, in the connecting portion 30c, portions that project toward the small-diameter portion 30d side and project outwardly are formed at equal angular intervals in the circumferential direction (in this embodiment, at every 60 [deg]). In the direction of the vertical line, the radius Rc at the lowermost portion Plow of the connecting portion 30c is the minimum diameter Rmin.

[0020] The length in the direction of the first axis CL1 in the disk portion 30a is La [m]. The length in the direction of the first axis CL1 in the large-diameter portion 30b is Lb [m]. The length in the direction of the first axis CL1 in the connecting portion 30c is Lc [m]. The length in the direction of the first axis CL1 in the small-diameter portion 30d is Ld [m]. The length in the direction of the first axis CL1 in the tapered portion 30e is Le [m].

[0021] FIG. 4 is a diagram for explaining the state at the time of assembling the differential gear 10 shown in FIG. 1 and the intermediate shaft 40. FIG. 4 shows a state in which, at the time of assembly, the intermediate shaft 40 is inserted from the opening portion of the tapered portion 30e of the insertion guide 30, and further the small-diameter portion 30d is inserted and contacts the oil seal 20. After the state shown in FIG. 4, the intermediate shaft 40 is inserted through the inner peripheral portion 20i of the oil seal 20, and then the fitting portion 40d on the tip side of the intermediate shaft 40 is fitted to the fitting portion 10d. In FIG. 4, a case where the intersection angle θ [deg] between the second axis CL2, which is the center line of the intermediate shaft 40, and the first axis CL1, which is the center line of the insertion guide 30, is at its maximum value is shown. The intersection angle θ is the angle (≦90 [deg]) at which the second axis CL2 intersects the first axis CL1. In FIG. 4, the side opposite to the shaft portion 40a on the tip side of the intermediate shaft 40 is inclined upward. In FIG. 4, it is assumed that the small-diameter portion 30d is not bent in the radial direction. That is, it is assumed that the center line of the small-diameter portion 30d coincides with the first axis CL1.

[0022] The ratio (=2×ΔR1 / Ld = 2(Rd - Ris) / Ld) obtained by dividing the multiple of the difference ΔR1 (=Rd - Ris) between the inner peripheral radius Rd of the small-diameter portion 30d and the outer peripheral radius Ris of the intermediate shaft 40 by the length Ld of the small-diameter portion 30d is defined as tan(θ1). Then, tanθ, which is the tangent of the intersection angle θ, is restricted so that the following relational expression (1) holds. tanθ ≦ 2(Rd - Ris) / Ld = tan(θ1) ··· (1)

[0023] In addition, the ratio obtained by dividing the difference (= Re - Rd) between the inner peripheral radius Re at the opening of the tapered portion 30e and the inner peripheral radius Rd of the small-diameter portion 30d by the length Le of the tapered portion 30e (= (Re - Rd) / Le) is made sufficiently larger than tan(θ1).

[0024] Here, the minimum diameter Rmin will be described. The ratio obtained by dividing the difference ΔR2 (= Rmin - Rd) between the minimum diameter Rmin and the inner peripheral radius Rd of the small-diameter portion 30d by the length Lc of the connecting portion 30c (= ΔR2 / Lc = (Rmin - Rd) / Lc) is defined as tan(θ2).

[0025] When tan(θ1) ≤ tan(θ2) holds, the crossing angle θ is restricted by the relational expression (1).

[0026] When tan(θ2) < tan(θ1) holds, the crossing angle θ is restricted by the following relational expression (2). tanθ ≤ 2(Rmin - Ris) / (Lc + Ld) < tan(θ1) ···(2)

[0027] In this embodiment, it will be described assuming that tan(θ2) < tan(θ1) holds

[0028] In the vertical direction, the lowermost position of the inner peripheral portion 20i of the oil seal 20 is referred to as the lowermost position P1. As shown in FIG. 4, at the lowermost position P1, the oil seal 20 is in contact with the intermediate shaft 40. In the vertical direction, the uppermost position of the inner peripheral portion 20i of the oil seal 20 is referred to as the uppermost position P2. As shown in FIG. 4, at the uppermost position P2, the oil seal 20 is not yet in contact with the intermediate shaft 40, but will come into contact with the intermediate shaft 40 when the intermediate shaft 40 is further inserted.

[0029] In the state shown in Figure 4, the intermediate shaft 40 is tilted upward by the intersection angle θ, resulting in a greater pressing force from the intermediate shaft 40 against the inner circumference 20i of the oil seal 20 at the lowest position P1 compared to the uppermost position P2. In other words, in the state shown in Figure 4, compared to the case where the intersection angle θ is zero, the pressing force from the intermediate shaft 40 against the inner circumference 20i of the oil seal 20 is weaker at the uppermost position P2, while at the lowest position P1, the pressing force from the intermediate shaft 40 against the inner circumference 20i of the oil seal 20 is stronger. Thus, the pressing force from the intermediate shaft 40 against the inner circumference 20i of the oil seal 20 is uneven due to the intersection angle θ. Therefore, compared to the uppermost position P2, the intermediate shaft 40 is more likely to damage the oil seal 20 when inserting it into the inner circumference 20i of the oil seal 20 at the lowest position P1. If the oil seal 20 is damaged, the sealing performance of the oil seal 20 may be reduced after the intermediate shaft 40 is assembled.

[0030] To reduce the likelihood of the intermediate shaft 40 damaging the oil seal 20, the intersection angle θ should be made as small as possible so that there is no bias in the force with which the intermediate shaft 40 presses against the inner circumference 20i of the oil seal 20. In other words, the accuracy of the centering should be improved by making angles θ1[deg] and θ2[deg] smaller.

[0031] From here, we will consider limiting the intersection angle θ by reducing the angle θ1.

[0032] First, one might consider reducing the angle θ1 by decreasing the difference ΔR1 (=Rd-Ris). However, if the difference ΔR1 is made too small, it becomes difficult to insert the intermediate shaft 40 through the small diameter section 30d, reducing the ease of assembly. Therefore, the difference ΔR1 must be at or above a predetermined value set in the design so that the ease of assembly remains within an acceptable range. "Ease of assembly" refers to the ease of assembly, or in other words, the ease of assembly.

[0033] Next, it is conceivable to reduce the angle θ1 by increasing the length Ld. However, increasing the length Ld may cause the small-diameter section 30d to bend more easily in the radial direction. If the small-diameter section 30d bends radially, increasing the length Ld may actually increase the intersection angle θ. Therefore, it is necessary to increase the length Ld of the small-diameter section 30d and prevent the small-diameter section 30d from bending radially. In other words, the rigidity of the connecting section 30c and the large-diameter section 30b that support the small-diameter section 30d must be increased.

[0034] As shown in Figure 4, in the insertion guide 30 of this embodiment, the radius Rc on the inner circumference side of the connecting portion 30c changes periodically in the circumferential direction, within the range between the minimum diameter Rmin and the maximum diameter Rmax. With this configuration of the connecting portion 30c, the rigidity of the connecting portion 30c and the large diameter portion 30b that support the small diameter portion 30d protruding in the direction of the first axis CL1 is improved compared to the configuration of the connecting portion of the insertion guide of the comparative example described later. As a result, even if the small diameter portion 30d is made longer in the direction of the first axis CL1, the small diameter portion 30d is less likely to bend radially when the intermediate shaft 40 is inserted through the small diameter portion 30d and assembled. In order to increase rigidity, for example, the thickness of the plate-like body on which the insertion guide 30 is formed by press working could be increased, but if this is done, the energy efficiency of the vehicle 90, such as fuel consumption and electricity consumption, will decrease due to the increase in the weight of the insertion guide 30.

[0035] Figure 5 is a perspective view of an insertion guide according to a comparative example, where (a) is Comparative Example 1, in which the connecting portion is disc-shaped and does not extend in the direction of the first axis CL1, and (b) is Comparative Example 2, in which the radius on the inner circumference of the connecting portion does not change in the circumferential direction but changes in the direction of the first axis CL1.

[0036] In Comparative Example 1 shown in Figure 5(a), the connecting portion is disc-shaped. Therefore, compared to this embodiment, the smaller diameter portion is more prone to radial bending due to the lower rigidity of the connecting portion supporting the smaller diameter portion and the larger diameter portion. In Comparative Example 2 shown in Figure 5(b), the radius on the inner circumference of the connecting portion does not change in the circumferential direction but changes in the direction of the first axis CL1. Therefore, in Comparative Example 2, the rigidity of the connecting portion supporting the smaller diameter portion and the larger diameter portion is higher than in Comparative Example 1, but lower than in this embodiment. Thus, in both Comparative Example 1 and Comparative Example 2, the rigidity of the connecting portion supporting the smaller diameter portion and the larger diameter portion is lower than in this embodiment, so when the intermediate shaft 40 is inserted through the smaller diameter portion of the insertion guide and assembled, the smaller diameter portion is more prone to radial bending than in this embodiment.

[0037] From here, we will consider limiting the intersection angle θ by reducing the angle θ2.

[0038] One way to reduce the angle θ2 is to reduce the difference ΔR2 (=Rmin-Rd). For example, by making the minimum diameter Rmin the same as the radius Rd, the angle θ2 can be set to zero. However, increasing the length Lc of the connection part 30c in order to reduce the angle θ2 would lead to an increase in the weight of the insertion guide 30.

[0039] According to this embodiment, (a) a cylindrical large-diameter portion 30b with a first axis CL1 as its centerline, a cylindrical small-diameter portion 30d having a smaller diameter than the large-diameter portion 30b with a first axis CL1 as its centerline, and a cylindrical connecting portion 30c that connects the outer edge of the large-diameter portion 30b on the small-diameter portion 30d side with the outer edge of the small-diameter portion 30d on the large-diameter portion 30b side, (b) the difference ΔR1 between the inner circumference radius Rd of the small-diameter portion 30d and the largest outer circumference radius Ris through which the small-diameter portion 30d is inserted in the intermediate shaft 40 is predetermined by design based on the ease of assembly when the intermediate shaft 40 is inserted into the small-diameter portion 30d, and (c) in the circumferential direction, the inner circumference radius Rc of the connecting portion 30c changes within a range between a minimum diameter Rmin which is greater than or equal to the inner circumference radius Rd of the small-diameter portion 30d and a maximum diameter Rmax which is less than or equal to the inner circumference radius Rb of the large-diameter portion 30b. As described in (c) above, by providing a connecting portion 30c in which the radius Rc on the inner side of the connecting portion 30c changes within the range between the minimum diameter Rmin and the maximum diameter Rmax in the circumferential direction, the rigidity and strength of the connecting portion 30c and the large diameter portion 30b that support the small diameter portion 30d protruding in the direction of the first axis CL1 are improved compared to the case in which such a connecting portion 30c is not provided. When the rigidity of the connecting portion 30c and the large diameter portion 30b is improved, the small diameter portion 30d becomes less likely to bend radially when the intermediate shaft 40 is inserted into the small diameter portion 30d of the insertion guide 30 and assembled. Therefore, the accuracy of centering the intermediate shaft 40 when the intermediate shaft 40 is inserted into the small diameter portion 30d of the insertion guide 30 and assembled is improved. As a result, damage to the oil seal 20 when the intermediate shaft 40 is assembled is suppressed, and the deterioration of 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 rigidity of the connecting portion 30c and the large-diameter portion 30b that support the small-diameter portion 30d of the insertion guide 30 is improved, which increases the natural frequency of the insertion guide 30. As a result, abnormal noises and vibrations due to resonance are less likely to occur while the vehicle 90 is in motion. In addition, the improved strength of the connecting portion 30c and the large-diameter portion 30b that support the small-diameter portion 30d prevents cracks from forming at the boundary between the small-diameter portion 30d and the connecting portion 30c, and prevents the small-diameter portion 30d from detaching from the connecting portion 30c while the vehicle 90 is in motion.

[0040] In this embodiment, the radius Rc on the inner side of the connecting portion 30c changes periodically in the circumferential direction. When it changes periodically, the change in rigidity of the connecting portion 30c and the large-diameter portion 30b in the circumferential direction is smaller compared to when it does not. As a result, even if the second axis CL2, which is the center line of the intermediate shaft 40, is misaligned and intersects the first axis CL1, which is the center line of the insertion guide 30, in any direction (up, down, left, or right), the small-diameter portion 30d is less likely to bend radially. Therefore, the accuracy of centering the intermediate shaft 40 when the intermediate shaft 40 is inserted into the small-diameter portion 30d of the insertion guide 30 and assembled is easier to improve.

[0041] According to this embodiment, (a) in the assembled state, the radius Rc on the inner circumference side of the connection portion 30c at the lowest Plow of the connection portion 30c in the vertical direction is the minimum diameter Rmin, and (b) in the cross-section of the first axis CL1, tan(θ2) is smaller than tan(θ1). One method of inserting the intermediate shaft 40 into the small diameter portion 30d is to slide it in while the lowest part of the tip of the intermediate shaft 40 is in contact with the lowest Plow on the inner circumference side of the small diameter portion 30d. In this method, when tan(θ2) is smaller than tan(θ1), the intersection angle θ is more likely to be limited and reduced compared to the case where it is not. As a result, the force with which the intermediate shaft 40 presses against the inner circumference portion 20i of the oil seal 20 is less likely to be uneven due to the intersection angle θ, and damage to the oil seal 20 is suppressed.

[0042] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit.

[0043] In the above-described embodiment, the intermediate shaft 40 was fitted to the side gear 10s of the differential gear 10, but the application of the present invention is not limited to this.

[0044] In the above-described embodiment, the radius Rc on the inner circumference side of the connecting portion 30c was periodically changing, but the present invention is not limited to this. For example, the radius Rc on the inner circumference side of the connecting portion 30c may be periodically changing. Even in such an embodiment, the rigidity of the connecting portion 30c supporting the small diameter portion 30d and the large diameter portion 30b is increased compared to the case where the radius Rc on the inner circumference side of the connecting portion 30c is not changing.

[0045] In the above-described embodiment, the inner circumference radius Rc of the connection portion 30c at the lowest Plow was set such that relation (2) holds, but for example, the difference ΔR2 may be set to zero. That is, the minimum diameter Rmin may be the same as the inner circumference radius Rd of the small diameter portion 30d. When the minimum diameter Rmin is the same as the inner circumference radius Rd of the small diameter portion 30d, the intersection angle θ is more easily restricted compared to when it is not. As a result, the force with which the intermediate shaft 40 presses against the inner circumference portion 20i of the oil seal 20 is less likely to be biased due to the intersection angle θ, thereby suppressing damage to the oil seal 20.

[0046] In the above-described embodiment, the insertion guide 30 was configured to include a disc portion 30a and a tapered portion 30e, but the present invention is also applicable to configurations that do not include these portions. For example, in a configuration that does not include a disc portion 30a, a mounting hole that penetrates radially is provided in the large-diameter portion 30b, and a fastening hole is provided radially in the opening 50o of the case 50, and a fastener such as a bolt is inserted through the mounting hole and fastened to the fastening hole provided in the opening 50o. [Explanation of symbols]

[0047] 20: Oil seal, 20i: Inner circumference, 30: Insertion guide, 30b: Large diameter section, 30c: Connection section, 30d: Small diameter section, 40: Intermediate shaft, CL1: First axis, Lc: Length (length of the connection section in the axial direction), Ld: Length (length of the small diameter section in the axial direction), Plow: Bottom (bottom of the connection section), Rc: Radius (radius on the inner circumference side of the connection section), Rd: Radius (radius on the inner circumference side of the small diameter section), Ris: Radius (the largest outer radius on the shaft through which the small diameter section is inserted), Rmax: Maximum diameter (predetermined maximum diameter), Rmin: Minimum diameter (predetermined minimum diameter), ΔR1: Difference (difference between the inner circumference radius of the small diameter section and the outer circumference radius of the shaft), ΔR2: Difference (difference between the minimum diameter and the inner circumference radius of the small diameter section)

Claims

1. A shaft insertion guide, which is fitted after the shaft is inserted through the inner circumference of a cylindrical oil seal, It comprises a cylindrical large-diameter portion with the axis as its centerline, a cylindrical small-diameter portion having a smaller diameter than the large-diameter portion with the axis as its centerline, and a cylindrical connecting portion that connects the outer edge of the large-diameter portion on the small-diameter side of the large-diameter portion to the outer edge of the small-diameter portion on the large-diameter side, The difference between the inner radius of the small diameter portion and the largest outer radius of the shaft through which the small diameter portion is inserted is predetermined in the design based on the ease of assembly when the shaft is inserted into the small diameter portion. In the circumferential direction with the aforementioned axis as the centerline, the radius on the inner circumference of the connecting portion changes within a range between a predetermined minimum diameter which is greater than or equal to the radius on the inner circumference of the small diameter portion and a predetermined maximum diameter which is less than or equal to the radius on the inner circumference of the large diameter portion. A shaft insertion guide characterized by the following.

2. In the circumferential direction with the aforementioned axis as the centerline, the radius on the inner side of the connection portion changes periodically. The shaft insertion guide according to feature 1.

3. In the assembled state, the radius of the inner circumference of the connection part at the lowest point of the connection part in the direction of the vertical 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 radius of the small diameter portion by the length of the connecting portion in the first axial direction is smaller than the ratio obtained by dividing the multiple of the difference between the inner radius of the small diameter portion and the largest outer radius through which the small diameter portion is inserted in the shaft by the length of the small diameter portion in the first axial direction. The shaft insertion guide according to feature 1.

4. The minimum diameter is the same as the radius of the inner circumference of the small diameter portion. A shaft insertion guide according to any one of features 1 to 3.

Images