Fixed constant velocity universal joint

Abstract

This invention provides a fixed constant velocity universal joint that reduces the cost of machining the track groove on the outer joint member, improves machining quality, and reduces weight. [Solution] This fixed constant velocity universal joint 1 includes a front track in which the track groove 6 of the outer joint member 2 and the track groove 8 of the inner joint member 3 form a predetermined shape so that the wedge angle α0 with respect to the ball 4 opens toward the opening when the operating angle is 0°, and a rear track in which the track groove 7 of the outer joint member 2 and the track groove 9 of the inner joint member 3 form a predetermined shape so that the wedge angle β0 with respect to the ball 4 opens toward the rear when the operating angle is 0°. In the track groove 7 of the outer joint member 2, a relief portion Tr is formed in the range 7h that is further inward than the axial position of the ball 4 at the maximum operating angle θ, and in the range between the radial position leaving the contact point L of the ball 4 and the spherical inner circumferential surface 2a, and the radial dimension E of the relief portion Tr is greater than the radial dimension F of the chamfered portion Tc provided between the spherical inner circumferential surface 2a and the track groove 7.

Description

[Technical Field]

[0001] The present invention relates to a fixed type constant velocity universal joint that is used, for example, in power transmission systems of automobiles and various industrial machines, and allows only angular displacement between two shafts, a driving shaft and a driven shaft. [Background Art]

[0002] For example, the front drive shaft of an automobile generally incorporates a sliding type constant velocity universal joint on the inboard side (differential side), which has a relatively small maximum operating angle but can achieve axial displacement while allowing for an operating angle, and incorporates a fixed type constant velocity universal joint on the outboard side (wheel side) that can achieve a large operating angle but does not displace in the axial direction in consideration of steering of the wheels.

[0003] As fixed type constant velocity universal joints, Rzeppa type constant velocity universal joints (also referred to as BJ type) and undercut free type constant velocity universal joints (also referred to as UJ type) have been conventionally known. In recent years, lightweight and compact 8-ball type fixed constant velocity universal joints have been proposed and put into practical use (see, for example, Patent Document 1). In addition, counter track type fixed constant velocity universal joints with higher performance than the 8-ball type have been proposed and put into practical use (see, for example, Patent Document 2).

[0004] A counter-track type fixed constant velocity universal joint has a structure in which some of the track grooves among the multiple track grooves arranged on the inner circumferential surface of the outer joint member and the outer circumferential surface of the inner joint member are replaced with track grooves that open in the opposite direction to the axial direction of the so-called wedge angle. More specifically, as shown in Figures 12 and 13, this type of fixed constant velocity universal joint 101 comprises an outer joint member 102, an inner joint member 103, a ball 104, and a retainer 105. On the inner circumferential surface of the outer joint member 102, a first track groove 106 extending in an arc shape along the axial direction and a second track groove 107 also extending in an arc shape along the axial direction are alternately formed in the circumferential direction. On the outer circumferential surface of the inner joint member 103, a first track groove 108 extending in an arc shape along the axial direction and a second track groove 109 also extending in an arc shape along the axial direction are alternately formed in the circumferential direction.

[0005] Here, if we define O11 as the center of curvature of the ball trajectory centerline x11 of the first track groove 106 formed in the outer joint member 102, and O12 as the center of curvature of the ball trajectory centerline y11 of the first track groove 108 formed in the inner joint member 103, then, as shown in Figure 12, the center of curvature O11 is offset from the joint center Oj towards the opening side of the outer joint member 102, and the center of curvature O12 is offset from the joint center Oj towards the back side (cup bottom side) of the outer joint member 102. The amount of offset of each center of curvature O11 and O12 with respect to the joint center Oj is equal. In this case, the first track groove 106 of the outer joint member 102 and the first track groove 108 of the inner joint member 103 constitute a so-called front track, and with the operating angle at 0°, the wedge angle α10 with respect to the ball 104, determined by the shape, dimensions, and positional relationship of the first track grooves 106 and 108, is open toward the opening side of the outer joint member 102. The operating angle referred to here is the angle between the rotational centerline of the outer joint member 102 and the rotational centerline of the inner joint member 103 (the same applies hereinafter in this specification).

[0006] On the other hand, if the curvature center of the ball trajectory centerline x12 of the second track groove 107 formed in the outer joint member 102 is O13, and the curvature center of the ball trajectory centerline y12 of the second track groove 109 formed in the inner joint member 103 is O14, then as shown in Figure 13, the curvature center O13 is offset to the rear side of the outer joint member 102 with respect to the joint center Oj, and the curvature center O14 is offset to the opening side of the outer joint member 102 with respect to the joint center Oj. The amount of offset of each curvature center O13 and O14 with respect to the joint center Oj is equal. In this case, the second track groove 107 of the outer joint member 102 and the second track groove 109 of the inner joint member 103 constitute a so-called rear track, and with the operating angle at 0°, the wedge angle β10 relative to the ball 104, determined by the shape, dimensions, and positional relationship of the second track grooves 107 and 109, opens towards the inner side of the outer joint member 102.

[0007] The term "ball trajectory centerline" as used herein refers to the trajectory traced by the center of a ball as it moves along a track groove. Therefore, the inclination of the track groove is the same as the inclination of the ball trajectory centerline, and the arc-shaped or straight shape of the track groove is the same as the arc-shaped or straight shape of the ball trajectory centerline. The same meaning will be used in the following descriptions of this specification.

[0008] With the fixed constant velocity universal joint 101 according to the above configuration, the axial force component acting on the ball 104 is in opposite directions for the front track and the rear track, so the axial force component acting on the retainer 105 through the ball 104 cancels out. Therefore, it is possible to reduce the contact pressure of the spherical fitting portion between the outer joint member 102 and the retainer 105, and between the inner joint member 103 and the retainer 105, thereby suppressing the loss of transmitted torque. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 3859267 [Patent Document 2] Japanese Patent Publication No. 2003-329052 [Overview of the project] [Problems that the invention aims to solve]

[0010] Incidentally, in this type of constant velocity universal joint, when assembling the inner joint member, retainer, and ball into the outer joint member, it is necessary to tilt the assembly of the inner joint member, retainer, and ball to an angle greater than the maximum operating angle. Therefore, the length of the track groove on the inner side of the outer joint member is set to a dimension greater than the length required to achieve the maximum operating angle. Consequently, when machining the track groove on the inner side of the outer joint member, there is a risk of interference with the cup bottom, which is an unmachined surface, or with the surface of the track groove, which is a machined surface, when the machining tool is close, requiring high-precision adjustment.

[0011] Furthermore, in the front track, where the wedge angle α10 with respect to the ball 104 is configured to open toward the opening side of the outer joint member 102, the track groove 106 becomes shallower towards the rear side of the outer joint member 102 compared to the opening side (Figure 12). On the other hand, in the rear track, where the wedge angle β10 with respect to the ball 104 is opened toward the rear side of the outer joint member 102, the depth of the track groove 107 increases from the opening side to the rear side of the outer joint member 102 (Figure 13). In other words, in the counter track type fixed constant velocity universal joint 101, the track groove 107 on the rear side of the outer joint member 102 that forms the rear track is deeper than the track groove 106 on the rear side of the outer joint member 102 that forms the front track. Therefore, in particular when machining the inner region of the track groove 107 of the outer joint member 102 that forms the rear track, there is concern about interference with the cup bottom, which is a non-machined surface, or with the surface of the track groove 107, which is a machined surface, when the machining tool is close, requiring even more precise adjustment.

[0012] For example, it might seem that shifting the position of the cup bottom towards the back could reduce the probability of interference with the bottom. However, this method would lead to an extension of the axial dimension of the outer joint member 102 and an increase in the cup volume, which would in turn lead to increased weight and material costs, making it impractical. It might also seem that reducing the movement speed of the machining tool when it is close to the workpiece could avoid sudden interference with the surface of the track groove 107, which is the workpiece surface, resulting in high machining resistance. However, this method would lead to an increase in machining time, which in turn leads to increased machining costs, making it impractical.

[0013] In view of the above circumstances, this specification aims to provide a fixed constant velocity universal joint that reduces the cost of machining the track groove of the outer joint member, improves the machining quality, and reduces weight. [Means for solving the problem]

[0014] The aforementioned problem is solved by the fixed constant velocity universal joint according to the present invention. Specifically, this constant velocity universal joint comprises an outer joint member having a plurality of track grooves extending in the axial direction formed on its spherical inner circumferential surface and an opening side and an inner side spaced apart in the axial direction, an inner joint member having a plurality of track grooves extending in the axial direction formed on its spherical outer circumferential surface, a plurality of torque transmission balls arranged one by one between the track grooves of the radially opposing outer joint member and the track grooves of the inner joint member, and a retainer for holding the balls, wherein the track grooves of the outer joint member and the track grooves of the inner joint member are arranged in a predetermined shape such that the wedge angle with respect to the ball opens toward the opening side when the operating angle is 0°. In a fixed constant velocity universal joint further comprising a front track and a rear track such that the track groove of the outer joint member and the track groove of the inner joint member form a predetermined shape so that the wedge angle with respect to the ball opens toward the rear when the operating angle is 0°, a relief portion is formed in the track groove of the outer joint member in a range toward the rear of the axial position of the ball at the maximum operating angle, in the range between the radial position where the ball contact point remains and the spherical inner circumferential surface, and the radial dimension of the relief portion is greater than the radial dimension of the chamfer provided between the spherical inner circumferential surface and the track groove.

[0015] The term "maximum operating angle" here refers to the maximum operating angle guaranteed for a fixed constant velocity universal joint to be usable in a vehicle or other vehicle while mounted on it, and is the angle that is predetermined by the design for each product type.

[0016] To achieve the aforementioned objectives, the inventors, based on the above-mentioned study results and findings regarding the outer joint member of a fixed constant velocity universal joint, arrived at a novel idea: to set a range of track grooves in which the ball rolls only when the assembly of the inner joint member, retainer, and ball is assembled into the outer joint member, and which is not used during operation. In other words, torque load does not need to be considered, and only the contact point of the ball is secured. This led to the present invention. Details of the study results and findings in the development process leading to the present invention will be described later.

[0017] The fixed constant velocity universal joint described above makes it possible to realize a fixed constant velocity universal joint that reduces the cost of machining the track groove of the outer joint member, improves machining quality, and reduces weight.

[0018] Furthermore, in the fixed constant velocity universal joint according to the present invention, a relief portion may be formed in the track groove of the outer joint member constituting the rear track, in a range that is further back than the axial position of the ball at the maximum operating angle, and in a range between the radial position where the ball contact point remains and the spherical inner circumferential surface.

[0019] Thus, in a counter-track type fixed constant velocity universal joint, by providing a relief portion in the track groove of the outer joint member constituting the rear track within the predetermined range described above, interference with the bottom of the cup and interference with the surface of the track groove, which is the machined surface, can be more reliably avoided. As a result, it becomes possible to stably produce a fixed constant velocity universal joint that reduces the cost of machining the track groove of the outer joint member, improves machining quality, and reduces weight.

[0020] Further, in the fixed type constant velocity universal joint according to the present invention, among the track grooves of the outer joint member constituting the front track, the relief portion may be formed in a range on the deeper side than the axial position of the ball at the maximum operating angle, between the radial position leaving the contact point of the ball and the spherical inner circumferential surface.

[0021] As described above, by providing the relief portion in the above-described predetermined range not only in the track grooves constituting the rear track but also in the track grooves constituting the front track, interference with the cup bottom and interference with the surface of the track groove that is a processed surface can be more reliably avoided, making it possible to stably produce the fixed type constant velocity universal joint that achieves the above-described cost reduction for track groove processing of the outer joint member, improvement in processing quality, and weight reduction.

[0022] Further, a fixed type constant velocity universal joint in which the total number of balls is 6 or more is suitable for achieving a fixed type constant velocity universal joint that achieves cost reduction for track groove processing of the outer joint member, improvement in processing quality, and weight reduction.

Effects of the Invention

[0023] As described above, according to the fixed type constant velocity universal joint according to the present invention, it is possible to achieve cost reduction for track groove processing of the outer joint member, improvement in processing quality, and weight reduction.

Brief Description of Drawings

[0024] [Figure 1] It is a front view of a fixed type constant velocity universal joint according to an embodiment of the present invention [Figure 2] It is an A-A cross-sectional view (cross-sectional view of a front track) of the fixed type constant velocity universal joint shown in FIG. 1. [Figure 3] It is a B-B cross-sectional view (cross-sectional view of a rear track) of the fixed type constant velocity universal joint shown in FIG. 1. [Figure 4] (a) is an enlarged cross-sectional view of a main portion of the track groove of a rear track when there is no relief portion, and (b) is a C-C cross-sectional view of the deeper side portion of the track groove shown in FIG. 4(a). [Figure 5]Figure 4(a) is an enlarged cross-sectional view of a key part showing an example of the machining method of the track groove. [Figure 6] This is an enlarged cross-sectional view of a key part showing the state in which the machining tool interferes with the bottom of the cup section at the back when in close proximity. [Figure 7] This is an enlarged cross-sectional view of a key area showing the state in which the machining tool interferes with the far end of the track groove when in close proximity. [Figure 8] Figure 4(a) is an enlarged cross-sectional view of a key part showing the adjustable range of the relief portion in the track groove. [Figure 9] (a) is an enlarged cross-sectional view of the main part showing the machined surface of the track groove of the outer joint member shown in Figure 3, (b) is a DD cross-sectional view of the track groove shown in Figure 9(a), and (c) is a GG cross-sectional view of the track groove shown in Figure 9(a). [Figure 10] Figure 1 is a perspective view of the outer joint member. [Figure 11] (a) is an enlarged cross-sectional view of the main part of the track groove showing a modified example of the relief section shown in Figure 3, and (b) is an HH cross-sectional view of the track groove shown in Figure 11(a). [Figure 12] This is a cross-sectional view of the front track of a conventional counter-track type fixed constant velocity universal joint. [Figure 13] Figure 12 is a cross-sectional view of the rear track of a fixed constant velocity universal joint. [Modes for carrying out the invention]

[0025] One embodiment of the present invention will be described based on the drawings.

[0026] First, the basic configuration of the fixed constant velocity universal joint 1 according to this embodiment will be explained based on Figures 1 to 3. This fixed constant velocity universal joint 1 is a so-called counter track type fixed constant velocity universal joint, and has a higher operating angle compared to the fixed constant velocity universal joint 101 shown in Figures 12 and 13. This fixed constant velocity universal joint 1 comprises an outer joint member 2, an inner joint member 3, a ball 4, and a retainer 5. On the inner circumferential surface of the outer joint member 2, a first track groove 6 extending along the axial direction and a second track groove 7 also extending along the axial direction are alternately formed in the circumferential direction. On the outer circumferential surface of the inner joint member 3, a first track groove 8 extending along the axial direction and a second track groove 9 also extending along the axial direction are alternately formed in the circumferential direction.

[0027] Of these, the first track groove 6 formed in the outer joint member 2, as shown in Figure 2, consists of a first arc-shaped portion 6a formed along the spherical portion 2a (corresponding to the spherical inner circumferential surface of the outer joint member according to the present invention) formed between each track groove 6, 7 on the inner circumferential surface of the outer joint member 2, and a second arc-shaped portion 6b located on the opening side of the outer joint member 2 relative to the first arc-shaped portion 6a and curving in the opposite direction from the first arc-shaped portion 6a. The first arc-shaped portion 6a and the second arc-shaped portion 6b are smoothly connected. If the center of curvature of the ball trajectory center line x1 of the first track groove 6 that passes through the first arc-shaped portion 6a is taken as O1, and the partial center of curvature that passes through the second arc-shaped portion 6b is taken as O2, then the center of curvature O2 is located radially outward of the outer joint member 2. The centers of curvature O1 and O2 are offset axially towards the opening side with respect to the joint center Oj.

[0028] As shown in Figure 2, the first track groove 8 formed in the inner joint member 3 consists of a first arc-shaped portion 8a formed along the spherical portion 3a (corresponding to the spherical inner circumferential surface of the inner joint member according to the present invention) formed between each track groove 8, 9 on the inner circumferential surface of the inner joint member 3, and a second arc-shaped portion 8b located on the opening side of the outer joint member 2 relative to the first arc-shaped portion 8a and curving in the opposite direction from the first arc-shaped portion 8a. The first arc-shaped portion 8a and the second arc-shaped portion 8b are smoothly connected. The ball trajectory centerline of the first track groove 8 of the inner joint member 3 is not shown in the figure, but is formed in a shape that is mirror-image symmetrical with respect to the first track groove 6 of the outer joint member 2 and the joint center plane P when the operating angle is 0°.

[0029] In this case, the first track groove 6 of the outer joint member 2 and the first track groove 8 of the inner joint member 3 constitute the front track, and with the operating angle at 0°, the wedge angle α0 relative to the ball 4, determined by the shape, dimensions, and positional relationship of the first track grooves 6 and 8, is open toward the opening side of the outer joint member 2.

[0030] On the other hand, the second track groove 7 formed in the outer joint member 2, as shown in Figure 3, consists of a first arc-shaped portion 7a formed along the spherical portion 2a of the outer joint member 2, and a second arc-shaped portion 7b located on the opening side of the outer joint member 2 relative to the first arc-shaped portion 7a, and curving toward the opposite side from the first arc-shaped portion 7a. The first arc-shaped portion 7a and the second arc-shaped portion 7b are smoothly connected. If the center of curvature of the ball trajectory center line x2 of the second track groove 7 that passes through the first arc-shaped portion 7a is taken as O3, and the partial center of curvature that passes through the second arc-shaped portion 7b is taken as O4, then the center of curvature O4 is located radially outward of the outer joint member 2. The center of curvature O3 is offset axially toward the inner side relative to the joint center Oj, and the center of curvature O4 is offset axially toward the opening side relative to the joint center Oj.

[0031] As shown in Figure 3, the second track groove 9 formed in the inner joint member 3 consists of a first arc-shaped portion 9a formed along the spherical portion 3a of the inner joint member 3, and a second arc-shaped portion 9b located on the opening side of the outer joint member 2 relative to the first arc-shaped portion 9a, and curving in the opposite direction from the first arc-shaped portion 9a. The first arc-shaped portion 9a and the second arc-shaped portion 9b are smoothly connected. The ball trajectory centerline of the second track groove 9 of the inner joint member 3 is not shown, but it is formed in a shape that is mirror-image symmetrical with respect to the second track groove 7 of the outer joint member 2 and the joint center plane P when the operating angle is 0°.

[0032] In this case, the second track groove 7 of the outer joint member 2 and the second track groove 9 of the inner joint member 3 constitute a rear track, and with the operating angle at 0°, the wedge angle β0 relative to the ball 4, determined by the shape, dimensions, and positional relationship of the second track grooves 7 and 9, is open towards the rear side of the outer joint member 2.

[0033] In the fixed constant velocity universal joint 1 with the above-described configuration, the first track groove 6 and the second track groove 7 of the outer joint member 2 are composed of second arc-shaped portions 6b and 7b that are curved at the opening end so that the centers of curvature O3 and O4 are located radially outward of the outer joint member 2. As a result, the ball 4 does not fall out of the track grooves 6 and 7, and a further increase in operating angle can be achieved compared to the configurations shown in Figures 12 and 13.

[0034] Next, before describing the characteristic configuration of the fixed constant velocity universal joint 1 according to this embodiment, we will first explain the results of the studies and findings from the development process that led to the above-described characteristic configuration.

[0035] As described above, when installing the ball 4, the inner joint member 3 of the assembly of the inner joint member 3, ball 4, and retainer 5 needs to be tilted to an angle greater than the maximum operating angle θ. Therefore, the lengths of the track grooves 6 and 7 on the rear side of the outer joint member 2 are set to a length greater than the length required to achieve the maximum operating angle θ. The basic form of the track grooves 7 on the rear side of the outer joint member 2 will be described in detail with reference to Figure 4. Figure 4(a) is an enlarged cross-sectional view of the main part of the track groove 17 of the rear track in the outer joint member 2 of the counter track type fixed constant velocity universal joint 1 according to this embodiment, assuming that the relief portion Tr (details to be described later), which is a characteristic configuration of the present invention, is absent. Figure 4(b) is a cross-sectional view of the rear portion of the track groove 17 shown in Figure 4(a).

[0036] When the fixed constant velocity universal joint is angled, the ball 4 located on the inner side of the outer joint member will be further in the axial position when the ball 4 is installed than when it is at the maximum operating angle θ. Therefore, as shown in Figure 4(a), the length required for installing the ball 4 in the track groove 17 is set to be larger than the length required to achieve the maximum operating angle θ (the length corresponding to θ / 2). In the machining of the track groove 17 of the outer joint member 2 (grinding, hardened steel cutting), there are problems of interference with the cup bottom 2b of the outer joint member 2, which is the non-machined surface, and interference with the surface of the track groove 17, which is the machined surface, when the machining tool T (see Figure 5) is close, requiring high-precision adjustment.

[0037] Next, with reference to Figure 5, the machining of the track groove of the outer joint member will be described in detail. As an example of machining, for example, the machining tool T is rotationally driven in a fixed position. The outer joint member 2 is held in a chuck (not shown) and oscillates on a plane (neither shown) with a predetermined inclination angle around the joint center Oj. From the state shown in Figure 5, when the machining tool T is rotationally driven and the outer joint member 2 held in the chuck oscillates, the machining tool T approaches the outer joint member 2 in the direction of the arrow, contacts the far end of the track groove 17, and begins machining. Due to the machining area and volume of the far end of the track groove 17 near the point of proximity of the machining tool T, there are concerns about increased machining load and reduced tool life.

[0038] Refer to Figures 6 and 7 for further explanation of interference issues when machining tools are in close proximity. As shown in Figure 6, when in close proximity, there is concern about interference between the machining tool T and the cup bottom 2b on the inner side of the outer joint member 2 (the area where interference is a concern is hatched in Figure 6). Also, as shown in Figure 7, when in close proximity, there is concern about interference between the machining tool T and the inner end 17c of the track groove 17 on the inner side of the track groove 17 (the area where interference is a concern is hatched in Figure 7). The inner end 17c of the track groove 17 is located slightly closer to the opening than the cup bottom 2b. As described above, the inner end 17c of the track groove 17 and the bottom 2b of the cup are positioned very close to the inner circumference of the cup portion of the outer joint member 2. Therefore, when the machining tool T is in close proximity, there are problems of interference with the cup bottom 2b, which is a non-machined surface, and interference with the surface of the inner end 17c of the track groove 17, which is a machined surface. Furthermore, since we want to improve machining efficiency by increasing the feed rate just before machining, high-precision adjustment is required.

[0039] In particular, in the counter-track type fixed constant velocity universal joint 1, the track groove 7(17) on the rear side of the outer joint member 2 that forms the front track is deeper than the track groove 6 on the rear side of the outer joint member 2 that forms the front track (see Figures 2 and 3). Therefore, when machining the rear region of the track groove 7(17) of the outer joint member 2 that forms the rear track, there is a greater concern about interference with the cup bottom 2b, which is the non-machined surface, and with the surface of the track groove 7(17), which is the machined surface, when the machining tool T is close, and we focused on the fact that even more precise adjustment is required.

[0040] Therefore, as shown in Figure 8, we focused on the hatched area 17h within the track groove 17, which is the area between the radial position where the ball 4 remains and the spherical inner surface, and the area necessary for assembling the ball 4, from the axial position of the ball 4 at the maximum operating angle θ, which is near the location of the machining tool T. (That is, the area located radially towards the center of the track groove 17, closer to the contact point L.) After much consideration of this area 17h of the track groove 17, we arrived at a new idea: to set this area 17h as the area of ​​the track groove 17 where the ball 4 rolls only when assembling the inner joint member 3, ball 4, and retainer 5 into the outer joint member 2, and which is not used during travel. In other words, it is an area where torque does not need to be applied, and only the contact point of the ball 4 is secured. Based on this, as shown in Figure 9, the first characteristic configuration of the present invention is that a relief portion (Tr) is formed in the track groove (7) of the outer joint member (2) in the range necessary for assembling the ball (4) beyond the axial position of the ball (4) at the maximum operating angle (θ), in the range between the radial position where the contact point (L) of the ball (4) remains and the spherical portion (2a) (7h), and the second characteristic configuration is that the radial dimension (E) of the relief portion (Tr) is larger than the radial dimension (F) of the conventional chamfered portion (Tc).

[0041] Next, the characteristic configuration of this embodiment will be specifically described with reference to Figures 9 and 10. Figure 9(a) is an enlarged cross-sectional view of the main part showing the machined surface of the second track groove 7, which constitutes the rear track, among the track grooves 6 and 7 provided in the outer joint member 2 of the fixed constant velocity universal joint 1 according to this embodiment. Figure 9(b) is a DD cross-sectional view of the track groove 7 shown in Figure 9(a), and Figure 9(c) is a GG cross-sectional view of the track groove 7 shown in Figure 9(a). Figure 10 is a perspective view of the outer joint member 2 of the fixed constant velocity universal joint 1 according to this embodiment.

[0042] Figure 9(a) shows the trajectory of the contact point L of the ball 4 in the track groove 7. In Figure 9(a), the dashed line located radially towards the center from the bottom of the track groove 7 corresponds to the trajectory of the contact point L described above. Thus, a relief portion Tr is formed in the track groove 7 in the area radially towards the center from the contact point L of the ball 4, and in the area 7h (the cross-hatched area in Figure 9(a)) that is further inward than the axial position of the ball 4 at the maximum operating angle θ (length corresponding to θ / 2) required for the installation of the ball 4. The hatched portion of the track groove 7 is the machined surface Mt of the track groove 7. Thus, the radially outer end of the relief portion Tr is formed at the radial position Sr that leaves the contact point L of the ball 4, and the radially inner end of the relief portion Tr reaches the spherical portion 2a.

[0043] Since the radially outer end of the relief portion Tr is at a radial position Sr that leaves the contact point L of the ball 4, the axial region in which the relief portion Tr is formed is included in the range 7h of the track groove 7, which is not used during driving, and in which the ball 4 rolls only when the inner joint member 3, ball 4, and retainer 5 are assembled into the outer joint member 2, as shown in Figure 9(a). In other words, the axial region in which the relief portion Tr is formed is a region in which torque does not need to be applied and only the contact point of the ball 4 is secured.

[0044] Furthermore, as shown in Figures 9(b) and 9(c), the radial dimension E of the relief portion Tr is greater than the radial dimension F of the chamfered portion Tc, which has a substantially constant width and is provided over the entire axial area between the spherical portion 2a of the outer joint member 2 and the track groove 7. Thus, the relief portion Tr has a different configuration from the conventional chamfered portion Tc.

[0045] Furthermore, with the fixed constant velocity universal joint 1 having the above configuration, by providing a relief portion Tr, unnecessary interference between the machining tool T and the outer joint member 2 (for example, the hatched cup bottom portion 2b in Figure 6, or the far end portion 17c of the hatched track groove 17 in Figure 7) can be avoided. In addition, by providing the relief portion Tr in a range 7h of the track groove 7 where torque load does not need to be considered and only the ball contact point can be secured, the torque load capacity of the fixed constant velocity universal joint 1 can be secured. Thus, with the fixed constant velocity universal joint 1 according to this embodiment, it is possible to reduce the cost of machining the track groove of the outer joint member, improve machining quality, and reduce weight while securing torque load capacity.

[0046] Furthermore, the relief portion Tr according to this embodiment is connected to the chamfered portion Tc at its inner end, with the opening end positioned slightly inward from the axial position of the ball 4 at the maximum operating angle θ. The relief portion Tr has a shape in which the radial dimension E increases as it moves from the opening side to the inner side of the outer joint member 2. Figure 9(a) illustrates the case where the cross-sectional shape of the relief portion Tr is arc-shaped. In this embodiment, the relief portion Tr has a shape in which the circumferential dimension increases as it moves from the opening side to the inner side of the outer joint member 2 (see Figure 10). By adopting such a shape, the shape of the relief portion Tr and its processing can be simplified.

[0047] Although one embodiment of the present invention has been described above, the fixed constant velocity universal joint according to the present invention may also be configured in ways other than those described above, without departing from the spirit of the invention.

[0048] Figure 11(a) is an enlarged cross-sectional view of the main part of the outer joint member 2 showing a modified example of the relief portion Tr according to the present invention, and Figure 11(b) is a cross-sectional view of HH in Figure 11(a).

[0049] As shown in Figure 11(a), the relief portion Tr of the track groove 7 of the outer joint member 2 in this modified example differs from the relief portion Tr shown in Figure 9 in that its radial dimension E is constant over its entire axial range. Of course, in this modified example as well, the relief portion Tr is formed in the range of the track groove 7 that is radially towards the center of the contact point L of the ball 4, and in the range 7h that is further into the joint than the axial position of the ball 4 at the maximum operating angle θ (length corresponding to θ / 2) necessary for assembling the ball 4. Furthermore, the radial dimension E of the relief portion Tr is larger than the radial dimension F of the chamfered portion Tc provided between the spherical portion 2a of the outer joint member 2 and the track groove 7 (see Figures 11(b) and 9(c)).

[0050] Of course, the shape of the relief portion Tr is not limited to the examples given above. For example, the relief portion Tr can take any shape, as long as it does not negate the spirit of the present invention, such as a shape in which the radial dimension increases at a constant rate from the opening side to the back side (a tapered cross-sectional shape).

[0051] Furthermore, the above description illustrates a case where the relief portion Tr according to the present invention is provided in a predetermined range 7h of the track groove 7 (second track groove 7) that constitutes the rear track among the track grooves 6 and 7 of the outer joint member 2. However, of course, the relief portion Tr may also be provided in the same range as the second track groove 7 among the track groove 6 (first track groove 6) that constitutes the front track.

[0052] Furthermore, while the above explanation illustrates the application of the present invention to a fixed constant velocity universal joint 1 with eight balls 4, it is of course not limited to this. It is also possible to apply the present invention to a fixed constant velocity universal joint with more than eight balls 4 (for example, ten balls). Alternatively, it is also possible to apply the present invention to a fixed constant velocity universal joint with fewer than eight balls 4 (for example, six balls).

[0053] Furthermore, while the above explanation illustrates contact points (L) based on an angular contact shape for the track grooves 6 and 7 of the outer joint member 2, this is by no means the only option. A circular contact shape can also be applied to the track grooves 6 and 7 of the outer joint member 2. [Explanation of symbols]

[0054] 1. Fixed constant velocity universal joint 2. Outer joint member 2a Spherical part (spherical inner peripheral surface) 2b Cup bottom 3. Inner joint member 3a Spherical part (spherical outer peripheral surface) 4 balls 5 Cage 6. Track groove (front track) of the outer joint member 6a, 6b Arc-shaped part 7. Track groove (rear track) of the outer joint member 7a, 7b Arc-shaped part 7h range 8. Track groove (front track) of the inner joint member 8a, 8b Arc-shaped part 9. Track groove (rear track) of the inner joint member 9a, 9b Arc-shaped part 17 Track groove (rear track) of the outer joint member 17c Back end 17h range 101 Fixed constant velocity universal joint 102 Outer joint member 103 Inner joint member 104 Ball 105 Retainer 106 Track groove (front track) of outer joint member 107 Track groove (rear track) of outer joint member 108 Track groove (front track) of the inner joint member 109 Track groove (rear track) of the inner joint member E Radial dimension (relief portion) F Radial dimension (chamfered portion) L Ball contact point Mt machined surface O1,O2,O3,O4,O11,O12,O13,O14 Center of curvature Oj joint center P joint center plane Sr radial position T processing tool Tc chamfered section Tr Escape Department x1, x2, x11, x12 Ball trajectory centerline (outer joint member) y11, y12 Ball trajectory centerline (inner joint member) α0,β0,α10,β10 wedge angle θ Maximum working angle

Claims

1. Multiple track grooves extending in the axial direction are formed on the spherical inner surface, and the outer joint member has an opening side and an inner side that are spaced apart in the axial direction, An inner joint member having multiple track grooves extending axially formed on its spherical outer surface, Multiple torque transmission balls are positioned one at a time between the track grooves of the outer joint member and the track grooves of the inner joint member, which face each other radially. The system comprises a retainer for holding the ball, A front track in which the track groove of the outer joint member and the track groove of the inner joint member form a predetermined shape such that the wedge angle with respect to the ball opens toward the opening when the operating angle is 0°, In a fixed constant velocity universal joint, further comprising a rear track in which the track groove of the outer joint member and the track groove of the inner joint member form a predetermined shape such that the wedge angle with respect to the ball opens toward the rear when the operating angle is 0°, In the track groove of the outer joint member, a relief portion is formed in the range behind the axial position of the ball at the maximum operating angle, between the radial position where the contact point of the ball remains and the spherical inner circumferential surface. A fixed constant velocity universal joint characterized in that the radial dimension of the relief portion is greater than the radial dimension of the chamfered portion provided between the spherical inner surface and the track groove.

2. The fixed constant velocity universal joint according to claim 1, wherein the relief portion is formed in the track groove of the outer joint member constituting the rear track, in a range that is further back than the axial position of the ball at the maximum operating angle, and in a range between the radial position where the contact point of the ball remains and the spherical inner circumferential surface.

3. The fixed constant velocity universal joint according to claim 2, wherein the relief portion is formed in the track groove of the outer joint member constituting the front track, in a range that is further back than the axial position of the ball at the maximum operating angle, and in a range between the radial position where the contact point of the ball remains and the spherical inner circumferential surface.

4. A fixed constant velocity universal joint according to any one of claims 1 to 3, wherein the total number of balls is six or more.

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