Attachment structure for constant-velocity universal joint boot

Abstract

This attachment structure for a boot is obtained by fitting an annular protrusion section 26, provided on the inner peripheral surface of a large-diameter cylindrical part 21 (fixing part A) of the boot 20, to a first annular groove 8, provided on the outer peripheral surface 6a of a boot fixed part B of an outer joint member 2, and securely fastening the outer peripheral surface of the fixing part A with a boot band 24 in a state in which annular protrusions 10 provided on both sides of the first annular groove 8 in the axial direction are pressed against the inner peripheral surface of the fixing part A, and thereby attaching and fixing the fixing part A to the boot fixed part B. Support parts 11 which contact and support the inner peripheral surface 21a of the fixing part A from outside the range of the band width of the boot band 24 are provided on the outer peripheral surface of the boot fixed part B, and are disposed on both sides of the boot band 24 in the axial direction.

Description

Boot mounting structure for constant velocity universal joint

[0001] The present invention relates to a mounting structure for a cylindrical boot (a boot for a constant velocity universal joint) made of an elastic material such as rubber or resin and used as a sealing member for a constant velocity universal joint.

[0002] As is well known, automobiles equipped with a drive source such as an engine or an electric motor on a chassis include a power transmission device for transmitting the output of the drive source to drive wheels. An example of this type of power transmission device is a drive shaft including a fixed-type constant velocity universal joint and a sliding-type constant velocity universal joint arranged at a distance in the vehicle width direction, and a shaft member connecting inner joint members of the two constant velocity universal joints so as to be able to transmit torque.

[0003] In the drive shaft described above, between the shaft member and the outer joint member of the fixed-type constant velocity universal joint, and between the shaft member and the outer joint member of the sliding-type constant velocity universal joint, tubular boots (constant velocity universal joint boots) formed of an elastic material such as rubber or resin and functioning as sealing members are provided, respectively. Cylindrical fixing portions are provided at one and the other axial ends of the boots, and these fixing portions are fastened by, for example, a metal band-shaped member called a boot band, to be attached and fixed to boot fixing portions provided on the outer joint member and the shaft member, which are the members to which the boots are attached. This prevents the lubricant filled inside the joint from leaking out and the intrusion of foreign matter into the joint.

[0004] As shown in FIGS. 15A to 15C , Patent Document 1 listed below discloses a boot mounting structure in which an annular convex portion 113 provided on an inner peripheral surface 112 of a fixing portion 111 of a boot 110 is fitted into an annular groove 102 provided on an outer peripheral surface of a boot fixed portion 101 of an outer joint member 100, and the fixing portion 111 is fastened with a boot band 115. An annular protrusion 103 is provided on both axial sides (one axial side and the other axial side) of the annular groove 102 of the boot fixed portion 101, and when the fixing portion 111 of the boot 110 is arranged on the outer periphery of the boot fixed portion 101 of the outer joint member 100 (see FIG. 15B ) and then the bottom surface of a band groove 114 provided on the outer periphery of the fixing portion 111 of the boot 110 is tightened with a boot band 115, the fixing portion 111 of the boot 110 elastically contracts in diameter and the annular protrusion 103 bites into the inner circumferential surface 112 of the fixing portion 111 of the boot 110 (see FIG. 15C ). This is said to improve the pull-out strength and sealing performance of the fixing portion 111 of the boot 110.

[0005] Patent No. 3333310

[0006] In the above-described boot mounting structure, it is preferable to set the height of the annular protrusion 103 so that, when the boot band 115 is tightened, the annular protrusion 103 reliably bites into the inner peripheral surface 112 of the fixed portion 111 and the inner peripheral surface 112 of the fixed portion 111 is in close contact with the outer peripheral surface 104 of the boot fixed portion 101 of the outer joint member 100. To achieve this mounting structure, it is necessary to tightly tighten the fixed portion 111 of the boot 110 with the boot band 115. However, due to the structure of the constant velocity universal joint, there are cases where it is difficult to tightly tighten the fixed portion 111 of the boot 110 (i.e., it is necessary to use a boot band 115 with a weak tightening force). In such cases, the mounting state shown in Fig. 15C cannot be achieved, and the following problems are likely to occur.

[0007] First, the outer diameter of the annular protrusion 103 provided on the boot fixed portion 101 is generally set larger than the inner diameter of the fixing portion 111 so that the annular protrusion 103 is press-fitted (pressed against) the inner peripheral surface 112 of the fixing portion 111 when the fixing portion 111 of the boot 110 is placed on the outer periphery of the boot fixed portion 101. If the outer diameter of the annular protrusion 103 were equal to or smaller than the inner diameter of the fixing portion 111, wrinkles would form in the fixing portion 111 of the boot 110 when the fixing portion 111 of the boot 110 is tightened with the boot band 115, causing localized reductions in the contact surface pressure of the fixing portion 111 against the boot fixed portion 101, making it difficult to ensure the desired sealing performance.

[0008] When the fixing portion 111 of the boot 110 is disposed on the outer periphery of the boot fixed portion 101 under the dimensional relationship in which the outer diameter of the annular projection 103 is set larger than the inner diameter of the fixing portion 111 of the boot 110, the fixing portion 111 of the boot 110 elastically deforms into a "drum-like" shape in which its axial center is located radially outward of both axial ends, as shown by the solid line in Fig. 16A. Even if the fixing portion 111 of the boot 110 (the groove bottom of the band groove 114 provided on the outer periphery thereof) is tightened with a boot band 115 in this state, if the tightening force of the boot band 115 is weak, it is difficult for the boot band 115 to contact the groove bottom of the band groove 114 over substantially the entire band width, as shown in Figs. 16B and 16C.

[0009] When the constant velocity universal joint rotates with an operating angle, the axial central region of the boot 110 (the bellows portion provided therein) repeatedly bends and expands and contracts, and as a result, a force as indicated by the black arrows in Figure 16C acts on the boot band 115 that fastens the fixed portion 111. Therefore, if the fastening force of the boot band 115 is insufficient, the boot band 115 will tilt in the axial direction, resulting in a decrease in the contact force of the annular protrusion 103 with the fixed portion 111 of the boot 110 and a decrease in sealing performance due to misalignment of the boot band 115 in the axial direction.

[0010] Therefore, the main object of the present invention is to ensure high sealing performance in a boot mounting structure in which the fixing portion of the boot is fixed to the boot fixing portion of the mounting target member by tightening the boot band, even if the tightening force of the boot band is somewhat weak.

[0011] In order to achieve the above object, the present invention provides a boot mounting structure for a constant velocity universal joint, which comprises a boot for a constant velocity universal joint, the boot being formed into a cylindrical shape from an elastic material, and having an annular protrusion on the inner peripheral surface of a fixed portion of a boot mounting member fitted into a first annular groove on the outer peripheral surface of the fixed portion of the boot, and annular protrusions on the outer peripheral surface of the fixed portion on both axial sides of the first annular groove being pressed against the inner peripheral surface of the fixed portion, and a band groove on the outer peripheral surface of the fixed portion being tightened with a boot band, the boot being mounted and fixed to the fixed portion by the boot being fixed, and wherein the outer peripheral surface of the fixed portion is provided with support portions that contact and support the inner peripheral surface of the fixed portion outside the band width of the boot band, the support portions being located on both axial sides of the boot band. Note that "outside the band width of the boot band" refers to outside the "band width (range) of the boot band" indicated by symbol Wa in Figure 3.

[0012] If the above-mentioned support portions are provided on the outer surface of the boot fixed portion on both axial sides of the boot band (on one axial side and the other axial side of the boot band), the ends of the inner surface of the fixing portion of the boot for a constant velocity universal joint (hereinafter simply referred to as the "boot") on one axial side and the other axial side can be contact-supported, respectively.Therefore, when the fixing portion of the boot is placed on the outer periphery of the boot fixed portion of the boot attachment member, or when the fixing portion of the boot elastically contracts and deforms in diameter as the boot band is tightened, it is possible to prevent as much as possible the outer surface of the fixing portion of the boot from becoming "drum-shaped" as shown in Figure 16A, etc., and to maintain the outer surface of the fixing portion as a cylindrical surface with a constant diameter. In this case, even if the tightening force of the boot band is somewhat weak, after tightening the boot band, the entire inner peripheral surface of the boot band, including both ends in the band width direction, can be brought into contact with the bottom surface of the band groove provided on the outer peripheral surface of the fixing portion of the boot, so that even if a force that tilts the boot band in the axial direction acts on the boot band, the boot band is less likely to tilt in the axial direction or to shift in position in the axial direction. Therefore, it is possible to prevent the tight contact between the inner peripheral surface of the fixing portion of the boot and the outer peripheral surface of the part to which the boot is fixed from being released, and a high level of sealing can be ensured.

[0013] When the support portion is provided on the outer peripheral surface of the fixed portion of the boot, a second annular groove can be provided on the outer peripheral surface of the fixed portion of the boot between the annular protrusion and the support portion. In this case, when the outer peripheral surface of the fixed portion of the boot is tightened with a boot band, a portion of the material of the fixed portion (specifically, the material of the portion of the fixed portion facing the second annular groove) can be forced into the second annular groove. In particular, by positioning one end of the second annular groove outside and the other end within the band width of the boot band, respectively, a portion of the material of the fixed portion that moves as the boot band is tightened can be allowed to escape to the outside in the band width direction of the boot band. This reduces the reaction force (elastic restoring force) generated at the fixed portion as the boot band is tightened, thereby improving the tightening ability of the boot band.

[0014] Furthermore, when the second annular groove is provided on the outer peripheral surface of the boot fixed part, it is preferable that one end of this annular groove in the groove width direction is located outside and the other end is located within the groove width range of the band groove, respectively. This makes it possible to optimize the contact state between the inner peripheral surface of the fixing part of the boot and the outer peripheral surface of the boot fixed part, thereby preventing a decrease in sealing performance.

[0015] In the above configuration, when the outer peripheral surface of the fixing portion of the boot is not fastened with the boot band, the axial width of the annular convex portion may be W, the groove width of the first annular groove may be W1, and the groove width of the second annular groove may be W2, so that the relationship W2<W<W1 may be satisfied. In this way, when the fixing portion of the boot is attached to the outer periphery of the boot-receiving portion of the boot-attached member, the annular convex portion provided on the inner periphery of the fixing portion is prevented from being erroneously fitted into the second annular groove, and the annular convex portion can be properly fitted into the first annular groove. Once the annular convex portion is fitted into the first annular groove, the relative axial positioning of the boot and the mounting member can be completed, making it easier to tighten the boot band with precision.

[0016] In the above configuration, when the outer circumferential surface of the fixing portion of the boot is not fastened by the boot band, the axial width of the annular convex portion is W, the groove width of the first annular groove is W1, and the groove width of the second annular groove is W2, the relationship W2 < W1 < W may be satisfied. This increases the adhesion between the boot and the member to which it is attached, and is expected to improve sealing performance.

[0017] In order to suppress the reaction force generated in the fixed portion of the boot when the boot band is tightened and to improve the tightening ability of the boot band, it is preferable to make the annular convex portion non-contact with the groove bottom of the first annular groove and to make the inner surface of the fixed portion of the boot non-contact with the groove bottom of the second annular groove.

[0018] In the above configuration, the outer diameter of the support portion may be set to be (slightly) larger than the outer diameter of the annular protrusion. This reduces the possibility of the annular protrusions of two adjacent outer joint parts coming into contact with each other and causing defects such as scratches on the annular protrusions when transporting a plurality of outer joint parts provided with the annular protrusions or the like (outer joint parts without boots attached).

[0019] In addition to a first annular groove into which the annular protrusion provided on the fixing portion of the boot is fitted, a second annular groove disposed between the annular protrusion and the support portion can be provided on the outer peripheral surface of the fixed portion of the boot. In this case, at least one of the first annular groove and the second annular groove can be formed so that its cross-sectional shape is a plane-symmetrical V-shape on an axis-orthogonal plane passing through the center of the annular groove in the groove width direction.

[0020] In the boot mounting structure according to the present invention, the object of boot mounting can be provided with a marking that allows visual confirmation that the fixing portion of the boot is correctly positioned axially relative to the object of boot mounting, thereby enabling the boot to be mounted easily and accurately to the object of boot mounting.

[0021] The boot fixed portion can be provided on the outer joint member of the constant velocity universal joint or on a shaft member connected to the inner joint member of the constant velocity universal joint so as to be able to transmit torque. That is, the present invention can be applied to a boot mounting structure for the outer joint member, as well as to a boot mounting structure for the shaft member. The outer joint member can have a bottomed, bowl-shaped cup portion having a plurality of axially extending track grooves formed on its inner peripheral surface, and the boot fixed portion can be provided on the cup portion at a position shifted toward the opening from the joint center.

[0022] Furthermore, the present invention can be applied regardless of whether the elastic material forming the boot is a rubber material or a resin material, that is, regardless of whether the boot is a so-called rubber boot or a resin boot.

[0023] As described above, according to the present invention, in a boot mounting structure for a constant velocity universal joint, in which the fixing portion of the boot is mounted and fixed to the boot fixed portion of the mounting target member by tightening the boot band, it is possible to ensure high sealing performance even if the tightening force of the boot band is somewhat weak.

[0024] 6A , 6B, 6C, 6D, 6E, 6F, 6G, 6G, 6H, 6H, 6I, 6J ... 1 is a plan view of the omega band after tightening. FIG. 2 is a plan view of the low profile band before tightening. FIG. 3 is a plan view of the low profile band after tightening. FIG. 4 is an enlarged cross-sectional view of a portion where a step is provided in the boot fixed portion of the outer joint member in the boot attachment structure according to another embodiment of the present invention. FIG. 5 is a cross-sectional view showing a state where the fixing portion of the boot is positioned at an incorrect axial position with respect to the boot fixed portion. FIG. 6 is a cross-sectional view conceptually showing an outer joint member provided with a marker portion in the boot attachment structure according to an embodiment of the present invention. FIG. 7 is a cross-sectional view conceptually showing an outer joint member provided with a marker portion in the boot attachment structure according to an embodiment of the present invention. FIG. 8 is a cross-sectional view conceptually showing an outer joint member provided with a marker portion in the boot attachment structure according to an embodiment of the present invention. FIG. 9 is a cross-sectional view conceptually showing an outer joint member provided with a marker portion in the boot attachment structure according to an embodiment of the present invention.14A is a diagram conceptually showing a state immediately before the fixing portion shown in FIG. 14A is tightened with a boot band. FIG. 15A is a schematic cross-sectional view for explaining a conventional boot mounting structure, showing a state before the fixing portion of the boot is arranged on the outer periphery of the fixed portion of the boot. FIG. 16A is a diagram showing a state after the fixing portion of the boot has been arranged on the outer periphery of the fixed portion of the boot shown in FIG. 15A and before the boot band is tightened. FIG. 17A is a schematic cross-sectional view for explaining problems of the conventional boot mounting structure, showing a state after the fixing portion of the boot has been arranged on the outer periphery of the fixed portion of the boot. FIG. 18A is a diagram showing a state before the fixing portion of the boot is tightened with a boot band. FIG. 19A is a diagram showing a state after the fixing portion of the boot has been tightened with a boot band.

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] FIG. 1 is a longitudinal cross-sectional view of a constant velocity universal joint (boot-equipped constant velocity universal joint) employing a boot mounting structure according to one embodiment of the present invention. More specifically, it is a longitudinal cross-sectional view of the constant velocity universal joint in a state where the operating angle is 0°. The constant velocity universal joint 1 shown in the figure is a fixed-type constant velocity universal joint that allows only relative angular displacement between two shafts (a drive shaft and a driven shaft) to be connected, and includes an outer joint member 2, an inner joint member 3, a plurality of balls 4, and a cage 5. This fixed-type constant velocity universal joint 1 constitutes, for example, an automobile drive shaft together with a sliding-type constant velocity universal joint (not shown), and is disposed on the drive wheel side (outboard side) when the drive shaft is installed in the automobile. In FIG. 1, the left side of the drawing is the outboard side, and the right side is the inboard side. In the following description, the outboard side is also referred to as the "one axial side," and the inboard side is also referred to as the "other axial side."

[0027] The outer joint member 2 integrally includes a cup portion 6 shaped like a bowl with a bottom and a shaft portion 7 extending axially from the bottom of the cup portion 6. A plurality of arc-shaped outer track grooves 2a are formed at equal intervals in the circumferential direction on the inner peripheral surface (spherical inner peripheral surface) of the cup portion 6. Although not shown in the figure, the internal space of the cup portion 6 is filled with a lubricant such as grease.

[0028] The inner joint member 3 has a spherical outer peripheral surface, on which a plurality of arc-shaped inner track grooves 3a are formed at equal intervals in the circumferential direction and which form pairs with the outer track grooves 2a of the outer joint member 2. The inner joint member 3 has axial holes that open at both end surfaces, and one axial end of the shaft member 15 is spline-fitted into this axial hole. An annular groove is formed on the outer peripheral surface of the shaft member 15, and a retaining ring is attached to this annular groove. The shaft member 15 is prevented from coming off from the inner joint member 3 by engaging the retaining ring with the inner joint member 3 in the axial direction.

[0029] The balls 4 are interposed between the paired outer track grooves 2 a and inner track grooves 3 a to transmit torque between the two joint members 2, 3. An annular cage 5, which is disposed between the spherical inner peripheral surface of the outer joint member 2 and the spherical outer peripheral surface of the inner joint member 3, holds the balls 4 at intervals in the circumferential direction.

[0030] A boot (constant velocity universal joint boot) 20, which is formed into a cylindrical shape from a resin material whose main ingredient is a thermoplastic elastomer and functions as a sealing member, is provided between the outer joint member 2 and the shaft member 15. The boot 20 is formed into a predetermined shape by blow molding, for example, press blow molding, and integrally includes: a large-diameter cylindrical portion 21 provided at one axial end and attached and fixed to the cup portion 6 of the outer joint member 2; a small-diameter cylindrical portion 22 provided at the other axial end and attached and fixed to the large-diameter portion 16 of the shaft member 15; and a bellows portion 23 provided between the large-diameter cylindrical portion 21 and the small-diameter cylindrical portion 22. The bellows portion 23 elastically flexes and expands / contracts as the outer joint member 2 and the inner joint member 3 (the shaft member 15 connected thereto) undergo relative angular displacement.

[0031] The large-diameter cylindrical portion 21 of the boot 20 is attached and fixed to the cup portion 6 of the outer joint member 2 by fastening its outer circumferential surface (the bottom surface of the annular band groove 21 b provided therein) with a boot band 24. Moreover, the small-diameter cylindrical portion 22 of the boot 20 is attached and fixed to the large-diameter portion 11 of the shaft member 10 by fastening its outer circumferential surface (the bottom surface of the annular band groove provided therein) with a boot band 25. By attaching the boot 20 to the outer joint member 2 and the shaft member 11 in the above manner, leakage of the lubricant filled in the internal space of the cup portion 6 (inside the joint) and entry of foreign matter into the inside of the joint are prevented as much as possible.

[0032] Known bands such as the one-touch band shown in Figures 8A and 8B, the omega band shown in Figures 9A and 9B, or the low-profile band shown in Figures 10A and 10B can be used as the boot bands 24, 25. The boot bands 24, 25 may be the same type of boot band or different types of boot bands.

[0033] A one-touch band is a band in which a tightening force is generated by bending (folding) a lever member 32 along the band body 31 to reduce the diameter of the annular band body 31, and then fastening the overlapping lever member 32 and band body 31 with a fastener 33. The tightening force of this band is determined by the inner diameter of the band body 31 and is therefore essentially unadjustable. An omega band is a band in which a tightening force is generated by crimping a clamp portion 35 of a band body 34 in an annular rolled state into an omega (Ω) shape. The tightening force of this band can be adjusted depending on the amount of crimping of the clamp portion 35. A low-profile band is a band in which a tightening force is generated by hooking one end 37 of the band body 36 onto a hook portion 38 provided on the outer periphery of the band body 36. Like a one-touch band, the tightening force of this band is determined by the inner diameter of the band body 36 and is therefore essentially unadjustable.

[0034] In this constant velocity universal joint 1, a boot mounting structure according to an embodiment of the present invention is applied to mounting the large diameter cylindrical portion 21 of the boot 20 to the cup portion 6 of the outer joint member 2. Therefore, the large diameter cylindrical portion 21 of the boot 20 corresponds to the "fixing portion (A)" referred to in the present invention, and the portion of the cup portion 6 to which the large diameter cylindrical portion 21 is fixed corresponds to the "boot fixed portion (B)" referred to in the present invention. Below, with reference to Figures 2 to 4, a boot mounting structure according to an embodiment of the present invention will be described in detail.

[0035] 3 and 4A, the inner peripheral surface 21a of the large-diameter cylindrical portion 21 of the boot 20 is provided with an annular convex portion 26 that protrudes inward. The inner peripheral surface of the large-diameter cylindrical portion 21 is not provided with any convex or concave portions other than the annular convex portion 26, and the inner peripheral surface of the large-diameter cylindrical portion 21 is formed as a cylindrical surface with a constant diameter except for the portion where the annular convex portion 26 is provided. Furthermore, the outer peripheral surface of the large-diameter cylindrical portion 21 is provided with an annular band groove 21b that accommodates the boot band 24. The distance Wb between the inner wall surfaces 21c and 21d that form the band groove 21b (groove width of the band groove 21b) is set to be a predetermined amount larger than the band width Wa of the boot band 24 (Wb>Wa).

[0036] As shown in FIG. 4A , a first annular groove 8 and two second annular grooves 9, located on either axial side of the first annular groove 8, are formed in the outer peripheral surface 6a of the boot fixed portion B of the cup portion 6 and spaced apart in the axial direction. The first annular groove 8 has a groove width W1 greater than the groove width W2 of the second annular groove 9 (W1 > W2), and a groove depth greater than the groove depth of the second annular groove 9. The axial region between the first annular groove 8 and the two second annular grooves 9 forms an annular protrusion 10 that protrudes radially outward beyond the annular grooves 8, 9. In this embodiment, the outer diameter end of the annular protrusion 10 is formed on the outer peripheral surface 6a of the cup portion 6, and therefore is located at the same radial position as the outer peripheral surface 6a of the cup portion 6. The outer diameter Db of the annular protrusion 10 is set to be larger by a predetermined amount than the inner diameter Da of the inner peripheral surface 21a of the large-diameter cylindrical portion 21 of the boot 20 (Db > Da).

[0037] 3 and 4C , the two annular protrusions 10 are provided so that their entirety is located within the range of the band width Wa of the boot band 24 (and the groove width Wb of the band groove 21b that accommodates the boot band 24) that tightens the large diameter cylindrical portion 21. On the other hand, each second annular groove 9 is provided so that one end 9a in the groove width direction is located outside the range of the band width Wa of the boot band 24 (and the groove width Wb of the band groove 21b) and the other end 9b in the groove width direction is located within the range of the band width Wa of the boot band 24 (and the groove width Wb of the band groove 21b).

[0038] The outer peripheral surface 6a of the boot fixed portion B is provided with support portions 11 that contact and support the inner peripheral surface 21a of the large-diameter cylindrical portion 21 of the boot 20 outside the band width Wa of the boot band 24. These support portions 11 are arranged on both axial sides of the boot band 24. In this embodiment, the outer peripheral surface 6a of the cup portion 6 that is continuous with the second annular groove 9 on one axial side constitutes the one-side support portion 11, and the outer peripheral surface 6a of the cup portion 6 that is continuous with the second annular groove 9 on the other axial side constitutes the other-side support portion 11. Therefore, in this embodiment, when the first annular groove 8 and two second annular grooves 9 having predetermined groove widths and groove depths are formed at predetermined axial positions on the outer peripheral surface 6a of the cup portion 6, two annular protrusions 10 and two support portions 11 are simultaneously obtained. The first annular groove 8 and the second annular groove 9 are formed, for example, by turning, which is a type of machining.

[0039] 4A , the large-diameter cylindrical portion 21 of the boot 20 and the cup portion 6 of the outer joint member 2 having the above-described configuration are coaxially arranged, and then the two are moved relatively close to each other. As shown in FIG. 4B , the large-diameter cylindrical portion 21 of the boot 20 is positioned as the fixing portion A on the outer periphery of the boot-fixed portion B of the cup portion 6. At this time, the entire annular protrusion 26 provided on the inner circumferential surface 21 a of the large-diameter cylindrical portion 21 is fitted into the first annular groove 8 provided in the boot-fixed portion B. Therefore, the axial width W of the annular protrusion 26 (the axial width W of the annular protrusion 26 before the boot band 24 is tightened) is set smaller than the groove width W1 of the first annular groove 8 (W<W1) but larger than the groove width W2 of the second annular groove 9 (W>W2). In other words, the widths are set so that the relational expression (inequality) W2<W<W1 holds. In this case, when the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 is disposed on the outer periphery of the boot-fixed portion B of the cup portion 6, it is possible to prevent the entire annular protrusion 26 from fitting into the second annular groove 9. Therefore, the relative axial positioning of the fixing portion A with respect to the boot-fixed portion B can be performed with high accuracy.

[0040] Furthermore, since the outer diameter Db of the annular protrusion 10 provided on the boot fixed portion B of the cup portion 6 is larger than the inner diameter Da of the inner surface 21a of the large diameter cylindrical portion 21 of the boot 20 (Db > Da), when the large diameter cylindrical portion 21 of the boot 20 is positioned on the outer periphery of the boot fixed portion B, the annular protrusion 10 is pressed against the inner surface 21a of the large diameter cylindrical portion 21 of the boot 20.

[0041] After the large-diameter cylindrical portion 21 of the boot 20 is positioned on the outer periphery of the boot fixed portion B of the cup portion 6 in the manner described above, a boot band 24 is positioned on the outer periphery of the large-diameter cylindrical portion 21 as shown in FIG. 4C, and this boot band 24 is used to tighten the outer periphery of the large-diameter cylindrical portion 21 (the bottom surface of the band groove 21b provided therein).

[0042] 3 , support portions 11 that contact and support the inner peripheral surface 21 a of the large diameter cylindrical portion 21 of the boot 20 are provided on the outer peripheral surface of the boot fixed portion B provided in the cup portion 6 of the outer joint member 2 outside the range of the band width Wa of the boot band 24, and these support portions 11 are arranged on both axial sides of the boot band 24 to support one and the other axial ends of the inner peripheral surface 21 a of the large diameter cylindrical portion 21. According to this configuration, when the large diameter cylindrical portion 21 of the boot 20 is arranged on the outer periphery of the boot fixed portion B of the cup portion 6 (see FIG. 4B ), it is possible to prevent the outer peripheral surface of the large diameter cylindrical portion 21 of the boot 20 (groove bottom surface of the band groove 21 b) from becoming “drum-shaped” as shown in FIG. 16A etc., and to maintain the outer peripheral surface of the large diameter cylindrical portion 21 as a cylindrical surface with a constant diameter.

[0043] In this case, even if the tightening force of the boot band 24 is somewhat weak, after tightening the boot band 24, the entire inner circumferential surface of the boot band 24, including both ends of the boot band 24 in the band width direction, can be brought into contact with the outer circumferential surface of the large-diameter cylindrical portion 21. Therefore, even if a force that tilts the boot band 24 in the axial direction acts on the boot band 24, the boot band 24 is less likely to tilt in the axial direction or to become displaced in the axial direction. Therefore, even when the omega band shown in FIGS. 9A and 9B is used as the boot band 24, or even when the one-touch band shown in FIGS. 8A and 8B or the low-profile band shown in FIGS. 10A and 10B is used as the boot band 24, which are difficult to obtain a higher tightening force than the omega band, the inner circumferential surface 21 a of the large-diameter cylindrical portion 21 of the boot 20 and the outer circumferential surface of the boot-fixed portion B of the cup portion 6 can be properly brought into close contact with each other, ensuring the required high sealing performance.

[0044] 3 and other figures, two second annular grooves 9 are provided on the outer peripheral surface 6a of the boot fixed portion B of the cup portion 6 so as to be located on both axial sides of the first annular groove 8, and one end 9a and the other end 9b in the groove width direction of each second annular groove 9 are located outside and within the band width Wa of the boot band 24, respectively, so that a portion of the material of the large-diameter cylindrical portion 21 that flows as the boot band 24 is tightened can be allowed to escape to the outside in the band width direction of the boot band 24 (see the black arrows in FIG. 4D ). This reduces the reaction force (elastic restoring force) generated in the large-diameter cylindrical portion 21 of the boot 20 as the boot band 24 is tightened, thereby further improving the tightening ability of the boot band 24.

[0045] 4D , when a tightening force F is applied to the large-diameter cylindrical portion 21 of the boot 20 to reduce its diameter, the inner circumferential surface 21 a of the large-diameter cylindrical portion 21 of the boot 20 is pressed strongly against the outer circumferential surface 6 a of the boot-fixed portion B of the cup portion 6, so that the annular protrusion 10 pressed against the inner circumferential surface 21 a of the large-diameter cylindrical portion 21 sinks into the large-diameter cylindrical portion 21, and a portion of the wall of the large-diameter cylindrical portion 21 (the portion facing the second annular groove 9) enters the second annular groove 9, forming a bulge (protuberance) on the large-diameter cylindrical portion 21 that can axially engage with the second annular groove 9, as shown in FIGS. 3 and 4D . From the above, when the boot band 24 is tightened, a concave-convex fitting portion that axially engages the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 and the boot-fixed portion B of the cup portion 6 is formed, thereby increasing the pull-out strength of the large-diameter cylindrical portion 21 of the boot 20.

[0046] If the wall of the large-diameter cylindrical portion 21 of the boot 20 comes into contact with the groove bottoms of the first annular groove 8 and the second annular groove 9 when the boot band 24 is tightened, a reaction force generated in the large-diameter cylindrical portion 21 as the boot band 24 is tightened increases, resulting in poor tightening of the boot band 24. Therefore, the groove depth (volume) of the first annular groove 8 and the second annular groove 9 is set so that the wall of the large-diameter cylindrical portion 21 does not come into contact with the groove bottoms of the first annular groove 8 and the second annular groove 9 during and after tightening of the boot band 24. Therefore, after tightening of the boot band 24, as shown in FIG. 3 , a gap exists between the groove bottoms of the first annular groove 8 and the second annular groove 9 and the large-diameter cylindrical portion 21 of the boot 20.

[0047] When the cup portion 6 is provided with the first annular groove 8 and the two second annular grooves 9 disposed on both axial sides thereof, the thickness (volume) of the cup portion 6 is reduced compared to when these annular grooves 8, 9 are not provided, which raises concerns about a reduction in the strength of the cup portion 6. In this regard, as shown in Figure 2, the boot fixed portion B is a portion of the cup portion 6 that is shifted toward the other axial side (the opening side of the cup portion 6) from the thinnest portion, which is on the axis-orthogonal plane P passing through the joint center O, and is thicker than the thinnest portion. The first annular groove 8 and the second annular groove 9 are provided in this boot fixed portion B, so that the adverse effect on the strength of the cup portion 6 due to the reduction in volume of the cup portion 6 is suppressed.

[0048] 3 and 4C , the one end 9 a and the other end 9 b in the groove width direction of each second annular groove 9 are respectively located outside and within the range of the band width Wa of the boot band 24, and are also respectively located outside and within the range of the band width Wb of the band groove 21 b that accommodates the boot band 24. In contrast to this configuration, if both the one end 9 a and the other end 9 b of one of the two second annular grooves 9 (the second annular groove 9 on the left side of the paper in FIG. 5 ) are located within the range of the groove width Wb of the band groove 21 b (and further within the range of the band width Wa of the boot band 24), as shown in FIG. 5 , the tightening force of the boot band 24 acts directly on the support portion 11 and the two annular protrusions 10 on the left side of the paper, but does not act on the support portion 11 on the right side of the paper. In this case, the contact pressure between the inner peripheral surface 21a of the large diameter cylindrical portion 21 of the boot 20 and the outer peripheral surface 6a of the cup portion 6 becomes uneven in the axial direction, which may make it impossible to ensure the desired sealing performance.

[0049] 3, when a second annular groove 9 is provided on the outer peripheral surface 6a of the boot fixed portion B of the cup portion 6 between the annular protrusion 10 and the support portion 11 in the axial direction, it is preferable that one end 9a and the other end 9b of (each) second annular groove 9 in the groove width direction be located outside and within the band width Wa of the boot band 24, respectively, and be located outside and within the band width Wb of the band groove 21b that accommodates the boot band 24, respectively. This allows the inner peripheral surface 21a of the large-diameter cylindrical portion 21 of the boot 20 to be in proper contact with the outer peripheral surface 6a of the cup portion 6, ensuring the desired sealing performance.

[0050] Fig. 6A is a partially enlarged cross-sectional view of the boot fixed portion of the outer joint member in a boot mounting structure according to another embodiment of the present invention, and Fig. 6B is a view showing a state in which the fixing portion of the boot arranged on the outer periphery of the boot fixed portion shown in Fig. 6A is fastened with a boot band. In this embodiment, the cross-sectional shapes of the first annular groove 8 and the second annular groove 9 provided in the boot fixed portion B of the cup portion 6 of the outer joint member 2 differ from those of the embodiments described above.

[0051] Specifically, the first annular groove 8 is formed by an inclined surface 8a inclined at an angle θ with respect to the axial direction (the outer peripheral surface 6a of the cup portion 6), and an arcuate surface 8b of a radius of curvature R disposed adjacent to the other axial side of the inclined surface 8a and connecting the small-diameter side end of the inclined surface 8a to the outer peripheral surface 6a of the cup portion 6. The second annular groove 9 is formed by an inclined surface 9a inclined at an angle θ with respect to the axial direction, like the inclined surface 8a forming the first annular groove 8, and an arcuate surface 9b disposed so as to connect the small-diameter side end of the inclined surface 9a to the outer peripheral surface 6a of the cup portion 6, and having the same radius of curvature as the radius of curvature R of the arcuate surface 8b. The inclination angle θ of the inclined surfaces 8a, 9a is set to be equal to or greater than 25° and equal to or less than 30°.

[0052] The first annular groove 8 and the second annular groove 9 are formed by turning the outer peripheral surface 6a of the boot mounting portion B of the cup portion 6, and the cross-sectional shapes of both annular grooves 8, 9 correspond to the cross-sectional shape of the turning tip. More specifically, the arcuate surfaces 8b, 9b correspond to the radiused shape of the nose of the turning tip, and the inclined surfaces 8a, 9a correspond to the inclination of the turning tip.

[0053] Furthermore, since the arrangement of the inclined surfaces 8a and arcuate surfaces 8b that constitute the first annular groove 8 is the same as the arrangement of the inclined surfaces 9a and arcuate surfaces 9b that constitute the second annular groove 9, the turning process for forming the annular grooves 8, 9 is performed, for example, by moving a turning tip inclined at a predetermined angle with respect to the outer peripheral surface 6a of the cup portion 6 in stages from the bottom side (one axial side) of the cup portion 6 to the opening side (the other axial side) of the cup portion 6, and forming the annular grooves 8, 9 in the following order: second annular groove 9 on one axial side → first annular groove 8 → second annular groove 9 on the other axial side. Therefore, the shape of the annular grooves 8, 9 in this embodiment is easy to process in a turning process and is advantageous in suppressing an increase in the cost of the constant velocity universal joint 1.

[0054] Fig. 7A is a partially enlarged cross-sectional view of the boot fixed portion of the outer joint member in a boot mounting structure according to another embodiment of the present invention, and Fig. 7B is a view showing the state in which the fixing portion of the boot arranged on the outer periphery of the boot fixed portion shown in Fig. 7A is fastened with a boot band. In this embodiment, the cross-sectional shapes of the first annular groove 8 and the second annular groove 9 provided in the boot fixed portion B of the cup portion 6 are changed from those shown in Fig. 6.

[0055] Specifically, each of the first annular groove 8 and the second annular groove 9 is formed in a V-shape (a V-shape that is plane-symmetrical with respect to a plane orthogonal to the axis passing through the center of the annular groove in the groove width direction) formed by a pair of inclined surfaces inclined at an angle θ in opposite directions relative to the axial direction and an arc surface that smoothly connects the small-diameter side ends of both inclined surfaces and has a curvature radius R. The inclination angle θ of the inclined surfaces is set to 25° or more and 30° or less, similar to the embodiment shown in Fig. 6 and other figures.

[0056] The annular grooves 8, 9 are formed by turning the outer peripheral surface 6 a of the boot-mounted portion B of the cup portion 6, and the cross-sectional shapes of the annular grooves 8, 9 correspond to the cross-sectional shapes of the turning tips. That is, the arcuate surfaces correspond to the rounded shape of the nose of the turning tips, and the inclined surfaces correspond to the inclination of the turning tips. In this case, the turning process for forming the annular grooves 8, 9 is performed, for example, by moving the turning tip stepwise from the bottom side to the opening side of the cup portion 6 or from the opening side to the bottom side of the cup portion 6 to form the annular grooves 8, 9 in the axial arrangement order, i.e., one second annular groove 9 → first annular groove 8 → other second annular groove 9.

[0057] Therefore, the annular grooves 8, 9 of the present embodiment have even better workability in turning, which increases the degree of freedom in designing the turning process performed in the manufacturing process of the outer joint member 2, thereby contributing to shortening the cycle time of the turning process and ultimately reducing the turning cost.

[0058] The embodiment shown in Figures 6 and 7 also employs a configuration similar to that of the embodiment shown in Figure 3. That is, in the embodiment shown in Figures 6 and 7, the outer peripheral surface 6a of the boot fixed portion B of the cup portion 6 is provided with support portions 11 that contact and support the inner peripheral surface 21a of the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 outside the band width Wa of the boot band 24, and these support portions 11 are provided on both sides of the boot band 24, and the outer peripheral surface 6a of the boot fixed portion B of the cup portion 6 is provided with a first annular groove 8 and two second annular grooves 9, located on both axial sides of the first annular groove 8, spaced apart in the axial direction, and each second annular groove 9 is arranged so that one end 9a in the groove width direction is located outside the band width Wa of the boot band 24 and the other end 9b in the groove width direction is located within the band width Wa of the boot band 24. Therefore, the boot mounting structure according to this embodiment can also enjoy the same effects (merits) as the boot mounting structure of the first embodiment described above.

[0059] The boot mounting structure (constant velocity universal joint 1 employing the same) according to the embodiment of the present invention described above can be modified as appropriate without departing from the gist of the present invention.

[0060] For example, in the embodiment described above, as shown in Fig. 4A , the support portion 11 provided on the boot fixed portion B of the cup portion 6 is disposed at the same radial position as the outer diameter end of the annular protrusion 10 (the outer diameter of the support portion 11 is the same as the outer diameter Db of the annular protrusion 10), but the support portion 11 may be disposed slightly radially outward or inward from the outer diameter end of the annular protrusion 10. That is, it is sufficient that the support portion 11 is disposed so as to contact and support the inner circumferential surface 21a (ends on one and the other axial sides) of the large-diameter cylindrical portion 21 of the boot 20 after the boot band 24 is fastened, and it is not necessary for the support portion 11 to be in contact with the inner circumferential surface 21a of the large-diameter cylindrical portion 21 when the large-diameter cylindrical portion 21 of the boot 20 is disposed on the outer periphery of the boot fixed portion B (for example, the stage shown in Fig. 4B ) or while the large-diameter cylindrical portion 21 is being fastened with the boot band 24.

[0061] FIG. 11 shows an enlarged view of a specific example in which the outer diameter Dc of the support portion 11 is made different from the outer diameter Db of the annular protrusion 10. In FIG. 11 , the outer diameter Dc of the support portion 11 is set slightly larger than the outer diameter Db of the annular protrusion 10. Specifically, the outer diameter Dc of the support portion 11 is set larger than the outer diameter Db of the annular protrusion 10 by 0.01 mm or more and 0.3 mm or less. In other words, in this embodiment, the relationship 0.01 mm≦(Dc−Db)≦0.3 mm is established. By setting the outer diameter Dc of the support portion 11 slightly larger than the outer diameter Db of the annular protrusion 10 in this way, it is possible to reduce the possibility of the annular protrusions 10 of adjacent outer joint parts 2 coming into contact with each other and causing defects such as scratches on the annular protrusions 10 when transporting a plurality of outer joint parts 2 provided with the annular protrusions 10 (outer joint parts 2 without the boots 20 attached).

[0062] In the embodiment described above, as shown in Fig. 4A , the relationship W2 < W < W1 is established between the axial width W of the annular protrusion 26 provided on the large diameter cylindrical portion 21 of the boot 20 serving as the fixing portion A and the groove width W1 of the first annular groove 8 and the groove width W2 of the second annular groove 9 provided on the boot fixing portion B of the cup portion 6. Therefore, when the large diameter cylindrical portion 21 of the boot 20 is disposed on the outer periphery of the boot fixing portion B of the cup portion 6, it is possible to prevent the entire annular protrusion 26 from fitting into the second annular groove 9. However, it cannot be denied that there is a possibility that a part of the tip side of the annular protrusion 26 may fit into the second annular groove 9, causing the large diameter cylindrical portion 21 of the boot 20 to be positioned at an incorrect axial position with respect to the boot fixing portion B, as shown in Fig. 12 .

[0063] 13A to 13D may be provided on the boot fixed part B. This marking part Q is a part that allows visual confirmation that the fixing part A of the boot 20 is correctly positioned in the axial direction relative to the boot fixed part B, and it is important that the marking part Q is provided on the boot fixed part B on the axial outside of the normal attachment position of the fixing part A (here, on the bottom side of the cup part 6).

[0064] 13A is an example where the mark portion Q is formed by an annular groove 41 provided on the outer peripheral surface 6a of the cup portion 6, Fig. 13B is an example where the mark portion Q is formed by a stepped surface 42 provided on the cup portion 6, Fig. 13C is an example where the mark portion Q is formed by a roughened surface portion (a portion formed to be rougher than other portions) 43 provided on the outer peripheral surface 6a of the cup portion 6, and Fig. 13D is an example where the mark portion Q is formed by a colored portion (a portion given a color different from other portions) 44 formed on the outer peripheral surface 6a of the cup portion 6. It is also possible to adopt, as the mark portion Q, something other than the annular groove 41, stepped surface 42, roughened surface portion 43, and colored portion 44 described above.

[0065] In the embodiment described above, as shown in Fig. 4A , in order to accurately position the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 relative to the cup portion 6 (boot fixed portion B) of the outer joint member 2 in the axial direction, the relationship W2 < W < W1 is established between the axial width W of the annular protrusion 26 provided on the inner circumferential surface 21 a of the large-diameter cylindrical portion 21 (the axial width W of the annular protrusion 26 before the boot band 24 is fastened) and the groove width W1 of the first annular groove 8 and the groove width W2 of the second annular groove 9 provided in the boot fixed portion B. However, the magnitude relationship between W and W1 in this relationship may be reversed. That is, in the boot mounting structure according to the present invention, the widths W, W1, and W2 may be set so as to satisfy the relationship W2 < W1 < W, as shown in Fig. 14A .

[0066] 14B , when the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 is positioned in the axial direction with respect to the boot fixed portion B of the cup portion 6 and then the large-diameter cylindrical portion 21 of the boot 20 is tightened with the boot band 24, the annular convex portion 26 of the boot 20 comes into line contact with the opening edge of the first annular groove 8 (the end of the annular protrusion 10 on the first annular groove 8 side) in the initial stage of tightening of the boot band 24, so that the annular protrusion 10 of the cup portion 6 can be tightly fitted into the large-diameter cylindrical portion 21 (annular convex portion 26) of the boot 20. This increases the adhesion between the large-diameter cylindrical portion 21 (fixing portion A) of the boot 20 and the cup portion 6 (fixed portion B) of the outer joint member 2, thereby improving the sealing performance of the boot 20. Although not shown in the figure, as the tightening of the large diameter cylindrical portion 21 by the boot band 24 progresses, the contact pattern of the large diameter cylindrical portion 21 (fixing portion A) of the boot 20 with the boot fixed portion B becomes approximately the same as that shown in Figure 6B.

[0067] In the embodiment described above, the second annular grooves 9 are provided on both axial sides of the first annular groove 8, but the second annular grooves 9 may be provided only on one or the other axial side of the first annular groove 8. In other words, it is sufficient that the second annular grooves 9 are provided on at least one of the axial sides of the first annular groove 8, and the number of second annular grooves 9 provided is also optional. However, it is important that the second annular groove 9 is large enough to allow the material of the fixing portion A (boot 20) that flows as the fixing portion A of the boot 20 is tightened with the boot band to efficiently enter, while not causing a problem of a decrease in strength due to a decrease in volume of the member to which the boot is attached.

[0068] Furthermore, the cross-sectional shapes of the first annular groove 8 and the second annular groove 9 are not limited to the shapes described in detail with reference to Figures 4A, 6A, and 7A, and can be set arbitrarily. For example, various groove shapes are applicable, such as a shape in which the inclined surface is arranged on the axially opposite side of Figure 6A, a trapezoidal shape, a rectangular shape, or an R-shape. Furthermore, when multiple second annular grooves 9 are provided, the cross-sectional shapes of the grooves do not necessarily have to be the same and may be different from each other. However, considering processability, it is preferable that the cross-sectional shapes of the first annular groove 8 and the second annular groove 9 be the same.

[0069] The boot mounting structure according to the present invention can also be applied when fastening the small-diameter cylindrical portion 22 of the boot 20 (as the fastening portion A) to the large-diameter portion 16 (see FIG. 1) of the shaft member 15 (as the boot-receiving portion B) by tightening the small-diameter cylindrical portion 22 with a boot band 25. The boot mounting structure according to the present invention can also be applied when a so-called rubber boot is used as the boot 20 instead of the so-called resin boot described above. The rubber boot is molded using a rubber material whose main raw material is, for example, chloroprene rubber (CR), silicone rubber, or hydrogenated nitrile rubber (HNBR).

[0070] The boot mounting structure according to the present invention can also be applied to fixed constant velocity universal joints other than the constant velocity universal joint (fixed constant velocity universal joint) shown in Fig. 1, and sliding constant velocity universal joints that allow both axial and angular displacement of the two shafts to be connected. Examples of sliding constant velocity universal joints include double offset (DOJ) types, tripod (TJ) types, and cross groove (LJ) types. In sliding constant velocity universal joints, the cup portion of the outer joint member is formed in a cylindrical shape with a bottom, and a linear outer track groove extending in the axial direction is formed on the inner peripheral surface of the cup portion.

[0071] REFERENCE SIGNS LIST 1 Constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 Ball 5 Cage 6 Cup portion 8 First annular groove 9 Second annular groove 10 Annular protrusion 11 Support portion 15 Shaft member 20 Boot (boot for constant velocity universal joint) 21 Large diameter cylindrical portion 21a Inner peripheral surface 21b Band groove 22 Small diameter cylindrical portion 24, 25 Boot band 26 Annular convex portion A Fixing portion B Boot fixed portion Q Mark portion W Axial width of annular convex portion W1 Groove width of first annular groove W2 Groove width of second annular groove

Claims

1. A mounting structure for a boot for a constant velocity universal joint, which is formed in a cylindrical shape from an elastic material and has an annular convex portion provided on the inner peripheral surface of a fixing portion of a boot to be attached to a member, is fitted into a first annular groove provided on the outer peripheral surface of a boot fixed portion of a member to which the boot is attached, and annular protrusions provided on both axial sides of the first annular groove on the outer peripheral surface of the boot fixed portion are pressed against the inner peripheral surface of the fixing portion, and a band groove provided on the outer peripheral surface of the fixing portion is tightened with a boot band, wherein the fixing portion is mounted and fixed to the boot fixed portion, wherein a support portion is provided on the outer peripheral surface of the boot fixed portion that contacts and supports the inner peripheral surface of the fixing portion outside the band width range of the boot band, and the support portion is arranged on both axial sides of the boot band.

2. A mounting structure for a boot for a constant velocity universal joint as described in claim 1, wherein a second annular groove is provided on the outer peripheral surface of the boot fixed portion, between the annular protrusion and the support portion, and one end and the other end in the groove width direction of the second annular groove are located outside and within the band width range of the boot band, respectively.

3. A mounting structure for a boot for a constant velocity universal joint as described in claim 1, wherein a second annular groove is provided on the outer peripheral surface of the boot fixed portion, between the annular protrusion and the support portion, and one end and the other end in the groove width direction of the second annular groove are respectively located outside and within the groove width range of the band groove.

4. A mounting structure for a boot for a constant velocity universal joint as described in claim 2 or 3, wherein when the axial width of the annular convex portion when the outer peripheral surface of the fixed portion is not tightened by the boot band is W, the groove width of the first annular groove is W1, and the groove width of the second annular groove is W2, the relationship W2 < W < W1 is satisfied.

5. A mounting structure for a boot for a constant velocity universal joint as described in claim 2 or 3, wherein when the axial width of the annular convex portion when the outer peripheral surface of the fixed portion is not tightened by the boot band is W, the groove width of the first annular groove is W1, and the groove width of the second annular groove is W2, the relationship W2 < W1 < W is satisfied.

6. A mounting structure for a boot for a constant velocity universal joint as described in claim 2 or 3, wherein the annular convex portion is not in contact with the groove bottom of the first annular groove, and the inner surface of the fixing portion is not in contact with the groove bottom of the second annular groove.

7. A mounting structure for a boot for a constant velocity universal joint as claimed in any one of claims 1 to 3, wherein the outer diameter of said support portion is made larger than the outer diameter of said annular projection.

8. A mounting structure for a boot for a constant velocity universal joint as described in claims 1 to 3, wherein a second annular groove is provided on the outer peripheral surface of the boot fixed portion, and is positioned between the annular protrusion and the support portion, and at least one of the first annular groove and the second annular groove has a cross-sectional shape that is V-shaped and symmetrical with respect to an axially perpendicular plane passing through the center of the groove width direction.

9. A mounting structure for a boot for a constant velocity universal joint as described in any one of claims 1 to 3, in which a marking portion is provided on the member to which the boot is attached, which enables visual determination that the fixing portion is correctly positioned in the axial direction relative to the boot fixed portion.

10. A mounting structure for a boot for a constant velocity universal joint as claimed in any one of claims 1 to 3, wherein the boot fixed portion is provided on an outer joint member of the constant velocity universal joint.

11. A mounting structure for a boot for a constant velocity universal joint as described in claim 10, wherein the outer joint member has a cup portion having a plurality of track grooves formed on its inner peripheral surface extending in the axial direction, and the boot fixed portion is provided at a position on the cup portion shifted toward the opening side from the center of the joint.

12. A mounting structure for a boot for a constant velocity universal joint as claimed in any one of claims 1 to 3, wherein the boot fixed portion is provided on a shaft member connected to the inner joint member of the constant velocity universal joint so as to be capable of transmitting torque.

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