A sealing structure for a constant velocity universal joint, and a constant velocity universal joint equipped with this sealing structure.

Abstract

This prevents grease from leaking out of the constant velocity universal joint due to repeated bending and stretching of the boot. [Solution] The outer circumferential surface 15a of the outer joint member 15 in the constant velocity universal joint 10 is provided with a first annular groove 31 in the portion to which the boot 22 is attached by attaching the boot band 23. The inner surface 26a of the band attachment portion 26 of the boot 22 is provided with a second annular groove 33 located away from the first annular groove 31 toward the bellows 25. The outer circumferential surface 15a of the outer joint member 15 is provided with a flow passage 34 that allows grease to flow from the inner space of the second annular groove 33 toward the inner space 25a of the bellows.

Description

Technical Field

[0001] The present invention relates to a seal structure of a constant velocity joint and a constant velocity joint provided with this seal structure.

Background Art

[0002] A constant velocity joint enables the transmission of rotational power at a constant speed between two shafts, a driving side and a driven side, and is incorporated and used in power transmission systems such as automobiles and various industrial machines. This constant velocity joint usually includes an outer joint member having a cup portion and an inner joint member disposed in the inner space of the outer joint member (cup portion), and is used in a state where the inner space of the outer joint member is filled with a lubricant such as grease. Further, in order to prevent external leakage of this lubricant and intrusion of foreign matter into the constant velocity joint, the opening of the outer joint member is covered with a cylindrical boot formed of an elastic material such as rubber or resin. One end of the boot is fixed to the outer joint member by a boot band, and the other end of the boot is fixed to a shaft connected to the inner joint member by the same boot band. As a result, both the fixing portion of the boot to the outer joint member and the fixing portion of the boot to the shaft are in a close contact state, and the fixing portion can be sealed.

[0003] By the way, in this type of constant velocity joint, when the constant velocity joint rotates (power transmission) while taking an operating angle, the portion between the bellows (bellows part) of the boot and the boot band mounting portion (band mounting portion) of the boot is repeatedly bent and stretched, so that a so-called "pumping action" may occur in the grease in the inner space of the bellows (hereinafter referred to as "bellows inner space") (see, for example, FIGS. 10 to 13 of Patent Document 1). In this case, the grease enters the space between the band mounting portion of the boot and, for example, the shaft (close contact region) due to the pumping action. As a result, the grease infiltrates into the groove portion of the shaft located radially inside the band mounting portion, and when the groove portion is filled with the grease, a situation may occur where the grease leaks out from the groove portion to the outside of the constant velocity joint. The above-described phenomenon can similarly occur in the space between the band mounting portion and the outer joint member (close contact region).

[0004] Therefore, Patent Document 1 proposes providing a non-contact area (gap) on the side of the boot closer to the bellows than the axial end of the band attachment portion of the boot, in which the outer surface of the shaft and the inner surface of the boot do not come into contact even when the bellows are bent or straightened (see Figure 2 of Patent Document 1).

[0005] Furthermore, Patent Document 1 proposes providing a projection at a position away from the axial end of the band mounting portion of a constant velocity universal joint toward the bellows, thereby providing a non-contact area between the shaft and the boot on the side closer to the bellows than the axial end of the band mounting portion, and providing a contact area between the shaft and the boot on the side closer to the bellows than this non-contact area (see Figure 4 of Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5051334 [Overview of the project] [Problems that the invention aims to solve]

[0007] As shown in Figure 2 of Patent Document 1, providing a non-contact area is expected to suppress the pumping action on the grease. Furthermore, as shown in Figure 4 of Patent Document 1, if both a non-contact area and a contact area are provided between the band mounting portion and the bellows, the repeated bending and straightening motion of the bellows is suppressed in the contact area by the indentation of the protrusion, thereby suppressing the pumping action. In addition, even if grease gets between the protrusion and the boot and penetrates to the band mounting portion side, the non-contact area provided in front of the band mounting portion (bellows side) acts as a grease reservoir, which is expected to suppress further penetration of grease.

[0008] However, as shown in Figure 2 of Patent Document 1, simply providing a non-contact area, while effective in delaying grease intrusion, is not sufficient to completely prevent grease intrusion due to the pumping action. Furthermore, even when both a non-contact area and a contact area are provided, as shown in Figure 4 of Patent Document 1, the pumping action cannot be sufficiently suppressed. As a result, grease can continuously intrude into the non-contact area, filling it with grease and ultimately leading to grease intrusion into the band attachment area.

[0009] In view of the above circumstances, the technical problem to be solved by the present invention is to prevent the grease inside the constant velocity universal joint from leaking out due to repeated bending and stretching of the boot of the constant velocity universal joint. [Means for solving the problem]

[0010] The aforementioned problem is solved by the sealing structure of the constant velocity universal joint according to the present invention. In other words, this seal structure is for solving the above problems and comprises a shaft connected to an outer joint member of a constant velocity universal joint or an inner joint member of the constant velocity universal joint, a boot covering the outer circumference of the outer joint member or the outer circumference of the shaft, and a boot band that attaches the boot to the outer joint member or the shaft by being attached to the outer circumference of the boot, wherein the outer surface of the outer joint member or the outer surface of the shaft has a first annular groove in the portion to which the boot is attached by the attachment of the boot band, the boot comprises a band mounting portion that is attached to the first annular groove via the boot band, and a bellows integrally formed with the band mounting portion, and in a seal structure capable of sealing the space between the first annular groove and the band mounting portion, the inner surface of the band mounting portion has a second annular groove provided at a position away from the first annular groove toward the bellows, and the outer surface of the outer joint member or the outer surface of the shaft has a flow passage that enables the flow of grease from the inner space of the second annular groove toward the inner space of the bellows.

[0011] As described above, in the seal structure according to the present invention, when a first annular groove is provided on the outer circumferential surface of the outer joint member or shaft in the portion to which the boot is attached by mounting a boot band, a second annular groove is provided at a position away from the first annular groove towards the bellows side of the boot. Furthermore, a flow passage is provided that allows grease to flow from the inner space of the second annular groove toward the bellows internal space of the boot. By providing the second annular groove and the flow passage in this way, even if grease enters between the outer joint member or shaft and the boot due to the pumping action described above, the second annular groove, which is provided at a position away from the first annular groove towards the bellows side, can capture the grease that has entered from the bellows internal space side without leakage. Since the second annular groove is provided with a flow passage that connects to the bellows internal space, the grease captured in the second annular groove can be released into the bellows internal space through the flow passage. This prevents grease from entering the first annular groove, thus preventing the first annular groove from being filled with grease and the grease from leaking into the external space of the constant velocity universal joint.

[0012] Another solution is a sealing structure that can seal the space between the first annular groove and the band mounting portion, wherein the inner surface of the band mounting portion is provided with a second annular groove provided at a position away from the first annular groove toward the bellows, and a flow passage that allows grease to flow from the inner space of the second annular groove toward the inner space of the bellows.

[0013] As described above, in the seal structure according to the present invention, when a first annular groove is provided on the outer circumferential surface of the outer joint member or shaft in the portion to which the boot is attached by mounting a boot band, a second annular groove is provided at a position away from the first annular groove towards the bellows side of the boot. Furthermore, a flow passage is provided in the boot, outer joint member, or shaft that allows grease to flow from the inner space of the second annular groove toward the bellows space of the boot. By providing the second annular groove and the flow passage in this way, even if grease enters between the outer joint member or shaft and the boot due to the pumping action described above, the second annular groove, which is provided at a position away from the first annular groove towards the bellows side, can capture the grease that has entered from the side of the bellows space without leakage. And since the second annular groove is provided with a flow passage that connects to the bellows space, the grease captured in the second annular groove can be released into the bellows space through the flow passage. This prevents grease from entering the first annular groove, thus preventing the first annular groove from being filled with grease and leaking out into the external space of the constant velocity universal joint.

[0014] In the sealing structure of a constant velocity universal joint having the above configuration, the flow passage may be provided on the outer surface of the outer joint member at a position in the circumferential direction different from any of the plurality of track grooves provided on the inner circumference of the outer joint member.

[0015] With this configuration, when the flow passage is provided on the outer circumferential surface of the outer joint member, the flow passage can be provided at a position different in the circumferential direction from any of the multiple track grooves provided on the inner circumference of the outer joint member, thereby avoiding the relatively thin-walled portion of the outer joint member. Therefore, it is possible to suppress the reduction in strength of the outer joint member due to the provision of the flow passage and ensure the necessary strength.

[0016] In the sealing structure of a constant velocity universal joint having the above configuration, the second annular groove may be positioned such that at least the opening edge of the second annular groove on the first annular groove side overlaps with the boot band in the axial direction.

[0017] By positioning the second annular groove in the aforementioned location, at least a portion of the second annular groove can be positioned inside the area where the boot band is attached (band attachment area). When the boot band is attached, the band attachment area deforms inward. Therefore, having the opening edge of the second annular groove directly below (inside) the band attachment area causes the band attachment area to bite into the opening edge due to deformation, resulting in a stronger seal against the surface (outer surface) of the outer joint member or shaft including the second annular groove. Thus, the sealing surface pressure in this contact area can be increased, making it possible to further improve sealing performance.

[0018] In the sealing structure of a constant velocity universal joint having the above configuration, all of the flow passages may be arranged to be rotationally symmetric with respect to the axis of the constant velocity universal joint.

[0019] When considering the effective discharge of grease from the annular groove, it is desirable to provide multiple flow passages. On the other hand, since a constant velocity universal joint is a rotating body, the more flow passages are provided, the greater the risk of disrupting the rotational balance of the constant velocity universal joint. In this regard, as described above, by providing multiple flow passages on the outer joint member or shaft so that all flow passages are rotationally symmetrical, it is possible to maintain the rotational balance of the constant velocity universal joint.

[0020] Furthermore, the seal structure described above prevents grease from leaking out of the constant velocity universal joint due to repeated bending and stretching of the boot of the constant velocity universal joint. Therefore, it is possible to suitably provide a constant velocity universal joint equipped with the above-described seal structure. [Effects of the Invention]

[0021] According to the present invention, it is possible to prevent the grease inside the constant velocity universal joint from leaking to the outside due to repeated bending and stretching of the boot of the constant velocity universal joint. [Brief explanation of the drawing]

[0022] [Figure 1]Cross-sectional view of a fixed constant velocity joint according to a first embodiment of the present invention. [Figure 2] Cross-sectional view showing an outer joint member and a boot of a first seal structure according to a first embodiment. [Figure 3] View of an annular groove and an axial groove as seen from the direction of arrow A in FIG. 2. [Figure 4] Cross-sectional view of a first seal structure in a first embodiment. [Figure 5] Cross-sectional view of a first seal structure according to a second embodiment of the present invention. [Figure 6] Cross-sectional view of a first seal structure according to a third embodiment of the present invention. [Figure 7] Cross-sectional view showing an outer joint member and a boot of a first seal structure according to a fourth embodiment of the present invention. [Figure 8] View of the outer joint member as seen from the direction of arrow B in FIG. 7. [Figure 9] Cross-section of a first seal structure in a fourth embodiment. [Figure 10] Cross-sectional view of a first seal structure according to a fifth embodiment of the present invention. [Figure 11] Cross-sectional view of a first seal structure according to a sixth embodiment of the present invention.

Embodiments for Carrying out the Invention

[0023] Hereinafter, a seal structure of a constant velocity joint according to the present invention will be described with reference to the drawings.

[0024] In the following embodiments, the constant velocity universal joint to which the seal structure according to the present invention is applied is exemplified as a fixed constant velocity universal joint incorporated into the drive shaft of an automobile, which connects two shafts, a drive side and a driven side, and has a structure that transmits rotational torque at a constant speed regardless of the operating angle of the two shafts. The seal structure according to the present invention is applicable to any form of fixed constant velocity universal joint, and specific examples include Zeppa type constant velocity universal joints and undercut-free type constant velocity universal joints. The seal structure according to the present invention is not limited to fixed types, but is also applicable to sliding type constant velocity universal joints such as double offset type constant velocity universal joints, cross groove type constant velocity universal joints and tripod type constant velocity universal joints.

[0025] Figures 1 to 4 show a first embodiment of the present invention. Figure 1 shows a cross-sectional view of a constant velocity universal joint according to this embodiment. The constant velocity universal joint 10 is mainly composed of an outer joint member 15 having cup portions 13 and stem portions 14, which are arranged on the outboard side (wheel side) of a drive shaft and have arc-shaped track grooves 11 extending in the axial direction AX formed at multiple locations in the circumferential direction of a spherical inner circumferential surface 12; an inner joint member 18 having arc-shaped track grooves 16 extending in the axial direction AX in conjunction with the track grooves 11 of the outer joint member 15 and formed at multiple locations in the circumferential direction of a spherical outer circumferential surface 17; a plurality of balls 19 interposed between the track grooves 11 of the outer joint member 15 and the track grooves 16 of the inner joint member 18 to transmit torque; and a cage 20 arranged between the spherical inner circumferential surface 12 of the outer joint member 15 and the spherical outer circumferential surface 17 of the inner joint member 18 to hold the balls 19.

[0026] One end of the rotating shaft (here, a shaft acting as an intermediate shaft) 21 is connected to the inner joint member 18, for example, by spline fitting. The other end of this rotating shaft 21 is connected to the inner joint member of a sliding constant velocity universal joint (not shown in the figure), for example, by spline fitting.

[0027] Furthermore, the constant velocity universal joint 10 further comprises a boot 22 that covers the outer circumference of the outer joint member 15 and the outer circumference of the rotating shaft 21, and boot bands 23 and 24 that are attached to predetermined locations on the outer circumference of the boot 22.

[0028] The boot 22 integrally comprises a bellows 25 with a corrugated shape, a first band mounting portion 26 located at the large-diameter end of the boot 22, and a second band mounting portion 27 located at the small-diameter end of the boot 22. The bellows internal space 25a (the inner space of the bellows 25) is filled with grease (not shown in the figure) as a lubricant. This ensures the required lubrication at the sliding portion of the constant-velocity universal joint 10 when the rotating shaft 21 rotates relative to the outer joint member 15 while taking an operating angle within a predetermined range.

[0029] The first band mounting portion 26 has a first mounting recess 28 for the corresponding boot band (hereinafter referred to as "first boot band") 23 on its outer circumference, and is attached to the outer surface 15a of the outer joint member 15 (cup portion 13) by mounting (tightening) the first boot band 23. The second band mounting portion 27 has a second mounting recess 29 for the corresponding boot band (hereinafter referred to as "second boot band") 24 on its outer circumference, and is attached to the outer surface 21a of the rotating shaft 21 by mounting (tightening) the second boot band 24.

[0030] The boot 22 can take any form, as long as the constant velocity universal joint to which it is attached (in this embodiment, the fixed constant velocity universal joint 10 shown in Figure 1) has the function of rotating while taking an operating angle within a predetermined range. For example, if the boot 22 has a bellows-shaped bellows 25 as shown in Figure 1, the form and material of the bellows 25 only need to be set so as to ensure flexibility that can follow the above-mentioned behavior of the constant velocity universal joint 10. For example, the boot 22 having the bellows 25 can be integrally formed from rubber or resin. In this case, as the rubber that can be used for the boot 22, a rubber with a surface hardness of Hs50 or higher and Hs70 or lower is preferred. Specific examples include chloroprene rubber, silicone rubber, or HNBR. Alternatively, as the resin that can be used for the boot 22, a resin with a surface hardness of HD38 or higher and HD50 or lower is preferred. Specific examples include thermoplastic polyester elastomers or compositions containing thermoplastic polyester elastomers. These are merely examples, and any material can be used as long as it can function as a boot 22 (bellows 25).

[0031] The first boot band 23 and the second boot band 24 can also be configured in any way as long as they can secure the boot 22 to the outer joint member 15 or the rotating shaft 21 by tightening. Specific examples include low-profile bands, omega bands, or one-touch bands.

[0032] Next, the seal structure 30 between the outer joint member 15 and the boot 22 (hereinafter referred to as the "first seal structure") will be described in detail.

[0033] As shown in Figures 2 to 4, an annular groove (hereinafter referred to as the "first annular groove") 31 extending in the circumferential direction of the outer joint member 15 is provided on the outer circumferential surface 15a of the outer joint member 15 where the first band mounting portion 26 is attached. In this embodiment, the first annular groove 31 is provided on the opening side of the outer circumferential surface 15a of the cup portion 13, and annular projections 32a and 32b are provided at both ends of the axial direction AX of the first annular groove 31.

[0034] As shown in Figures 2 and 3, the inner surface (inner circumferential surface) 26a of the first band mounting portion 26 has an annular projection 26b formed opposite to the first annular groove 31, and an annular groove (hereinafter referred to as "second annular groove") 33 formed at a position further away from the annular projection 26b towards the bellows 25.

[0035] Furthermore, a flow passage 34 is formed on the outer circumferential surface 15a of the outer joint member 15, which allows grease to flow from the inner space of the second annular groove 33 toward the inner space 25a of the bellows.

[0036] As shown in Figure 4, the annular projection 26b of the first band mounting portion 26 is fitted between the two projections 32a and 32b of the first annular groove 31.

[0037] The second annular groove 33 is an annular groove formed on the inner circumferential surface 26a of the first band mounting portion 26, along its circumferential direction. As shown in Figure 4, the second annular groove 33 is located away from the first annular groove 31 towards the bellows 25. Specifically, the second annular groove 33 is located adjacent to the projection 32b on the bellows 25 side in the axial direction AX.

[0038] The second annular groove 33 has a flat bottom surface 33a and a pair of opening edges 33b1 and 33b2 that are provided so as to sandwich the bottom surface 33a. In this specification, the space enclosed by the bottom surface 33a and the opening edges 33b1 and 33b2 is referred to as the inner space of the second annular groove 33.

[0039] In the second annular groove 33, it is preferable that at least the opening edge 33b1 on the side of the first annular groove 31 of the pair of opening edges 33b1 and 33b2 is positioned to overlap with the first boot band 23 in the axial direction AX. In this embodiment, as shown in Figure 4, both of the pair of opening edges 33b1 and 33b2 are positioned to overlap with the first boot band 23.

[0040] The depth dimension of the second annular groove 33 is preferably set to 0.1 mm or more and 5.0 mm or less. The width dimension of the second annular groove 33 (dimension along the axial direction AX) is preferably set to 0.5 mm or more and 5.0 mm or less. The depth dimension and width dimension of the second annular groove 33 are not limited to this embodiment.

[0041] As shown in Figures 2 to 4, the flow passage 34 is composed of a linear axial groove 35 along the axial direction AX of the outer joint member 15. One end of the flow passage 34 reaches a projection 32b related to the first annular groove 31, but does not penetrate the projection 32b. As shown in Figure 4, this one end of the flow passage 34 overlaps with the second annular groove 33. As a result, the flow passage 34 and the second annular groove 33 are in communication so that grease can flow through them. On the other hand, the other end of the flow passage 34 reaches the open end 15b of the cup portion 13 of the outer joint member 15 so as to connect with the bellows internal space 25a.

[0042] As shown in Figure 4, the axial groove 35 of the flow passage 34 is formed at a predetermined position on the outer circumferential surface 15a so as to penetrate the outer joint member 15 in the axial direction AX, from the side surface 33b of the second annular groove 33 on the bellows 25 side to the open end 15b of the outer joint member 15.

[0043] Furthermore, in this embodiment, when the axial groove 35 is viewed from the radial direction of the constant velocity universal joint 10, it extends in a direction along the axial direction of the constant velocity universal joint 10. In other words, the flow passage 34 (axial groove 35) extends in a direction perpendicular to the second annular groove 33. Also, the cross-section of the axial groove 35 in a direction perpendicular to the longitudinal direction is rectangular.

[0044] The axial grooves 35 of the flow passage 34 can be formed by any processing means, but considering processing efficiency (production efficiency) and processing costs, it is desirable to form them by plastic deformation. In particular, by forming the axial grooves 35 by rolling as a plastic deformation process, for example, when rolling a spline (not shown) provided on the outer circumference of the stem portion 14 of the outer joint member 15, the axial grooves 35 can be formed in the same process as the spline, thus avoiding an increase in the number of processes and processing costs.

[0045] The depth dimension of the axial groove 35 is preferably set to 0.1 mm or more and 5.0 mm or less. The width dimension of the axial groove 35 (the dimension in the direction along the circumferential direction of the outer joint member 15) is preferably set to 0.5 mm or more and 5.0 mm or less. The depth dimension and width dimension of the axial groove 35 are not limited to this embodiment.

[0046] In this embodiment, one axial groove 35 serving as a flow passage 34 is provided on the outer circumferential surface 15a of the outer joint member 15. However, this is not limited to this configuration, and multiple flow passages 34 may be formed on the outer circumferential surface 15a of the outer joint member 15. In this case, it is preferable that the flow passages 34 are provided at predetermined positions on the outer circumferential surface 15a that correspond to positions different in the circumferential direction from any of the multiple track grooves 11 provided on the inner circumference of the outer joint member 15. More preferably, the flow passages 34 (axial grooves 35) are provided at predetermined positions on the outer circumferential surface 15a that correspond to the circumferential intermediate positions of a pair of adjacent track grooves 11, 11 among the multiple track grooves 11 (neither shown in the figure). As previously described, this configuration of flow passages 34 is applicable not only to fixed constant velocity universal joints but also to sliding constant velocity universal joints such as tripod-type constant velocity universal joints.

[0047] Furthermore, from the viewpoint of rotational balance, it is preferable that all of the multiple flow passages 34 (axial grooves 35) are arranged to be rotationally symmetric with respect to the axis of the constant velocity universal joint 10 (not shown). Specifically, it is preferable that all of the flow passages 34 (axial grooves 35) are formed with the same shape and dimensions and extend in the same direction, and that all of the flow passages 34 are arranged with the same circumferential spacing between adjacent flow passages 34 in the circumferential direction.

[0048] As shown in Figure 4, the annular projection 26b of the first band mounting portion 26 fits into the first annular groove 31, and the inner circumferential surface 26a of the first band mounting portion 26 and the outer circumferential surfaces of each projection 32a, 32b are in close contact, thereby sealing the space between the first annular groove 31 and the annular projection 26b. Furthermore, in this embodiment, in addition to the outer circumferential surfaces of each projection 32a, 32b, the outer circumferential surface 15a of the outer joint member 15 adjacent to each projection 32a, 32b in the axial direction AX is also in close contact with the inner circumferential surface 26a of the first band mounting portion 26.

[0049] Between the rotating shaft 21 and the second band mounting portion 27 of the boot 22, a first annular groove 36, projections 37a, 37b, a second annular groove 38, and an axial groove 39 serving as a flow passage 34 may also be provided on the rotating shaft 21, similar to the first seal structure 30 (see Figure 1). In this case, the rotating shaft 21, the second band mounting portion 27 and second mounting recess 29 of the boot 22, the second boot band 24, the first annular groove 36, projections 37a, 37b, the second annular groove 38, and the axial groove 39 constitute the seal structure 40 between the rotating shaft 21 and the boot 22 (hereinafter referred to as the "second seal structure"). The possible forms, arrangements, various dimensions, and processing methods of the second annular groove 38 are the same as those of the second annular groove 33 of the first seal structure 30. Similarly, the possible forms, number, arrangements, various dimensions, and processing methods of the axial groove 39 are the same as those of the axial groove 35 of the first seal structure 30.

[0050] The effects and benefits of the seal structure according to this embodiment will be explained below, using the first seal structure 30 as an example, as shown in Figure 4. The first seal structure 30 consists of an outer joint member 15, a first band mounting portion 26 and a first mounting recess 28 of the boot 22, a first boot band 23, a first annular groove 31, protrusions 32a and 32b, a second annular groove 33, and a flow passage 34.

[0051] When the constant velocity universal joint 10 equipped with the first seal structure 30 shown in Figure 1 is in operation, the portion of the boot 22 between the bellows 25 and the first band mounting portion 26 is repeatedly bent and stretched in the radial direction of the joint, which can cause a so-called "pumping action" to occur in the grease in the bellows internal space 25a.

[0052] In this case, the grease is pumped into the contact area between the first band mounting portion 26 of the boot 22 and the outer joint member 15, or, in the configuration shown in Figure 4, the contact area between the inner circumferential surface 26a of the first band mounting portion 26 and the outer circumferential surface of the projection 32b on the bellows 25 side (see the flow direction indicated by arrow d1 in Figure 4). Therefore, in a conventional seal structure (a seal structure without the second annular groove 33 and the flow passage 34), it is possible that the grease may penetrate as far as the first annular groove 31 located radially inward of the first band mounting portion 26.

[0053] In the first seal structure 30, a second annular groove 33 is provided on the inner circumferential surface 26a of the first band mounting portion 26 at a position away from the first annular groove 31 of the outer joint member 15 toward the bellows 25 side, and a flow passage 34 is provided in the outer joint member 15 that allows grease to flow from the inner space of the second annular groove 33 toward the inner space 25a of the bellows of the boot 22.

[0054] By providing the second annular groove 33 and the flow passage 34 in this way, even if grease enters the contact area between the outer joint member 15 and the boot 22 due to the pumping action described above, the second annular groove 33, which is located closer to the bellows 25 than the first annular groove 31, can capture the infiltrating grease without leakage. Since the flow passage 34, which is connected to the bellows internal space 25a, is connected to this second annular groove 33, the grease captured in the second annular groove 33 can be released into the bellows internal space 25a via the flow passage 34 (see the flow in the direction indicated by arrow d2 in Figure 42). As a result, the infiltration of grease into the first annular groove 31 can be prevented with a high probability.

[0055] Based on the above effects, the first seal structure 30 according to this embodiment makes it possible to prevent grease from leaking from between the first band mounting portion 26 and the outer joint member 15 into the external space of the constant velocity universal joint 10.

[0056] Furthermore, by providing a second annular groove 33 separately from the first annular groove 31, the second annular groove 33 can be designed to be suitable for capturing grease and discharging it into the bellows internal space 25a via the axial groove 35. On the other hand, the first annular groove 31 can be designed to be suitable from the viewpoint of improving the sealing performance of the first band mounting portion 26 by tightening the first boot band 23. Thus, it is possible to design each annular groove 31 and 33 to be optimally suited to their respective purposes.

[0057] Furthermore, as shown in Figure 1, if multiple flow passages 34 (axial grooves 35) are formed as the first seal structure 30, the grease discharge capacity per axial groove 35 can be reduced, so the depth and width dimensions of the axial grooves 35 can be reduced. This makes it possible to suppress the reduction in strength of the outer joint member 15 due to the provision of axial grooves 35. In addition, if these multiple axial grooves 35 are provided at predetermined positions on the outer circumferential surface 15a corresponding to positions different in the circumferential direction from each track groove 11 (in this case, the circumferential intermediate position between adjacent track grooves 11), the axial grooves 35 can be provided in the relatively thicker parts of the outer joint member 15. This also makes it possible to suppress the reduction in strength of the outer joint member 15 due to the provision of axial grooves 35.

[0058] Furthermore, the second seal structure 40 formed between the rotating shaft 21 and the boot 22 is also provided with the same grease recirculation structure (second annular groove 38 and axial groove 39 as a flow passage 34) as the first seal structure 30, and therefore can enjoy the same effects as the first seal structure 30.

[0059] Figure 5 shows a second embodiment of the present invention. The first seal structure 30 in this embodiment differs from the first embodiment in the shape of the first annular groove 31, the manner in which the outer joint member 15 and the first band mounting portion 26 are in close contact, and the position of the second annular groove 33.

[0060] In the first seal structure 30 according to this embodiment, the first annular groove 31 does not have the protrusions 32a and 32b in the first embodiment at both ends in the axial direction AX. The first annular groove 31 has a bottom portion 31c which is configured as a concave curved surface in cross-sectional view. In this first seal structure 30, the outer peripheral surfaces 15a of the first annular groove 31, which have a constant outer diameter, located on both sides in the axial direction AX, and the inner peripheral surface 26a of the first band mounting portion 26 are in close contact with each other.

[0061] The second annular groove 33 is provided such that only the opening edge 33b1 on the side of the first annular groove 31 overlaps with the first boot band 23, out of a pair of opening edges 33b1 and 33b2. The flow passage 34 is formed on the outer circumferential surface 15a of the outer joint member 15 such that one end of the flow passage 34 overlaps with the second annular groove 33 formed at this position.

[0062] Other configurations in this embodiment are the same as in the first embodiment. Components common to the first embodiment in this embodiment are denoted by the same reference numerals as in the first embodiment. In this embodiment, not only the first seal structure 30 but also the second seal structure 40 may be configured in the same manner as described above.

[0063] Figure 6 shows a third embodiment of the present invention. In this embodiment, the second annular groove 33 of the first seal structure 30 is formed on the inner circumferential surface 26a of the first band mounting portion 26 such that both of the pair of opening edges 33b1 and 33b2 do not overlap with the first boot band 23. The other configurations in this embodiment are the same as those in the second embodiment described above.

[0064] Figures 7 to 9 show a fourth embodiment of the present invention. In the first seal structure 30 of this embodiment, the first annular groove 31 of the outer joint member 15 has two protrusions 32a and 32b, similar to the first embodiment.

[0065] Furthermore, the first band mounting portion 26 has an annular projection 26b on its inner surface (inner circumferential surface) 26a, a second annular groove 33 formed at a position away from the annular projection 26b toward the bellows 25, and a flow passage 34 that allows grease to flow from the inner space of the second annular groove 33 toward the inner space 25a of the bellows.

[0066] The flow passage 34 is composed of a linear axial groove 35 extending along the axial direction AX. One end of the flow passage 34 is connected to one opening edge 33b2 of the second annular groove 33. The other end of the flow passage 34 is connected to the bellows internal space 25a.

[0067] As shown in Figure 9, the second annular groove 33 of the first band mounting portion 26 is positioned such that both of its pair of opening edges 33b1 and 33b2 overlap with the first boot band 23.

[0068] Other configurations in this embodiment are the same as in the first embodiment. Components common to the first embodiment in this embodiment are denoted by the same reference numerals as in the first embodiment. The second seal structure 40 between the rotating shaft 21 and the boot 22 may also be configured in the same manner as the first seal structure 30.

[0069] Figure 10 shows a fifth embodiment of the present invention. In this embodiment, unlike the fourth embodiment, the first annular groove 31 of the outer joint member 15 does not have projections 32a and 32b. The first annular groove 31 has a concave curved bottom portion 31c in cross-sectional view. Other configurations in this embodiment are the same as in the fourth embodiment. Components common to the first embodiment in this embodiment are denoted by the same reference numerals as in the first embodiment. The second seal structure 40 between the rotating shaft 21 and the boot 22 may also be configured in a manner similar to the first seal structure 30.

[0070] Figure 11 shows a sixth embodiment of the present invention. In the second annular groove 33 of the first seal structure 30 in this embodiment, of the pair of opening edges 33b1 and 33b2, only the opening edge 33b1 on the first annular groove 31 side is provided in a position that overlaps with the first boot band 23. The other configurations in this embodiment are the same as in the fifth embodiment. The second seal structure 40 between the rotating shaft 21 and the boot 22 may also be configured in a manner similar to the first seal structure 30.

[0071] Furthermore, the present invention is not limited to the configuration of the above embodiments, nor is it limited to the effects described above. The present invention can be modified in various ways without departing from the spirit of the invention.

[0072] In the above embodiment, the axial groove 35 of the flow passage 34 is shown to extend parallel to the axis of the constant velocity universal joint 10 when viewed in cross-section in a virtual plane including the axis of the constant velocity universal joint 10 (as seen in the cross-section of Figure 2, etc.). However, the present invention is not limited to this configuration. For example, although not shown, the axial groove 35 may extend at an angle with respect to the axis of the constant velocity universal joint 10 when viewed in cross-section as shown in Figure 2, etc., or it may have an arc shape.

[0073] In the above embodiment, an example was shown in which the dimensions of the axial groove 35 are constant along its entire length, but the present invention is not limited to this configuration. For example, the width dimension or depth dimension of the axial groove 35 may increase or decrease as it moves from the second annular groove 33 side toward the bellows 25 side. [Explanation of Symbols]

[0074] 10. Constant velocity universal joint 15. Outer joint member 15a Outer surface 18. Inner joint member 21. Rotating axis (shaft) 21a Outer surface 22 Boots 23 First Boot Band 24 Second Boot Band 25 Bellows 25a Bellows interior space 26 First band attachment section 26a Inner surface 26b Annular projection 27 Second band attachment section 30 First seal structure 31, 36 First ring groove 33, 38 Second annular groove 33b1 Opening edge 33b2 Opening edge 34 Distribution path 40 Second seal structure

Claims

1. The universal joint comprises a shaft connected to the outer joint member or the inner joint member of the universal joint, a boot covering the outer circumference of the outer joint member or the shaft, and a boot band that attaches the boot to the outer joint member or the shaft by being fitted around the outer circumference of the boot. The outer circumferential surface of the outer joint member or the outer circumferential surface of the shaft is provided with a first annular groove in the portion to which the boot is attached by mounting the boot band. The boot comprises a band mounting portion that is fitted into the first annular groove via the boot band, and a bellows integrally formed with the band mounting portion. The band mounting portion has an annular projection that fits into the first annular groove, In a sealing structure capable of sealing the space between the first annular groove and the annular projection, The inner surface of the band mounting portion is provided with a second annular groove located away from the first annular groove toward the bellows side, A sealing structure for a constant velocity universal joint, characterized in that the outer surface of the outer joint member or the outer surface of the shaft is provided with a flow passage that allows grease to flow from the inner space of the second annular groove toward the inner space of the bellows.

2. The universal joint comprises a shaft connected to the outer joint member or the inner joint member of the universal joint, a boot covering the outer circumference of the outer joint member or the shaft, and a boot band that attaches the boot to the outer joint member or the shaft by being fitted around the outer circumference of the boot. The outer circumferential surface of the outer joint member or the outer circumferential surface of the shaft is provided with a first annular groove in the portion to which the boot is attached by mounting the boot band. The boot comprises a band mounting portion that is fitted into the first annular groove via the boot band, and a bellows integrally formed with the band mounting portion. The band mounting portion has an annular projection that fits into the first annular groove, In a sealing structure capable of sealing the space between the first annular groove and the annular projection, The sealing structure for a constant velocity universal joint is characterized in that the inner surface of the band mounting portion comprises a second annular groove provided at a position away from the first annular groove toward the bellows side, and a flow passage that enables the flow of grease from the inner space of the second annular groove toward the inner space of the bellows.

3. The sealing structure according to claim 1, wherein the flow passage is provided on the outer surface of the outer joint member at a position different in the circumferential direction from any of the plurality of track grooves provided on the inner circumference of the outer joint member.

4. The seal structure according to any one of claims 1 to 3, wherein the second annular groove is disposed at a position in which at least the opening edge of the second annular groove on the side of the first annular groove overlaps with the boot band in the axial direction.

5. The seal structure according to any one of claims 1 to 3, wherein all of the flow passages are arranged to be rotationally symmetric with respect to the axis of the constant velocity universal joint.

6. A constant velocity universal joint characterized by comprising the seal structure described in any one of claims 1 to 3.

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