Fixed constant velocity universal joint

Abstract

The track groove (7) of the outer joint member (2) has a guide surface (71) for guiding the ball (4). Between the spherical inner peripheral surface (6) of the outer joint member (2) and the guide surface (71), a chamfered portion (30) having an arc-shaped cross-sectional shape in a direction orthogonal to the axial direction is formed. The chamfered section (30) of the outer joint member (2) is connected to the guide surface (71) at an edge-shaped connection point (E1), and the angle [epsilon] between the tangent line of the guide surface (71) at the connection point (E1) and the tangent line of the chamfered section (30) is 0 DEG < [epsilon] < = 15 DEG.

Description

Technical Field

[0001] The present invention relates to a fixed constant velocity universal joint for power transmission of motor vehicles and various industrial machines. Background Art

[0002] In a drive shaft used in a power transmission system of a motor vehicle, a sliding constant velocity universal joint is often coupled to the inner side (center side in the vehicle width direction) of an intermediate shaft, and a fixed constant velocity universal joint is often coupled to the outer side (end side in the vehicle width direction). Here, the sliding constant velocity universal joint allows both angular displacement and axial relative movement between two shafts, and the fixed constant velocity universal joint allows angular displacement between two shafts but does not allow axial relative movement between two shafts.

[0003] As fixed constant velocity universal joints, there are known: a constant velocity universal joint of a non-crossed raceway groove type (see Patent Document 1), in which raceway grooves provided on a spherical inner peripheral surface of an outer coupling member and a spherical outer peripheral surface of an inner coupling member are not inclined in the circumferential direction, and a plane including a ball track center line of each raceway groove and a coupling center is in the same direction as an axis of the coupling; and a constant velocity universal joint of a crossed raceway groove type (see Patent Document 2), in which a plane including a ball track center line of each raceway groove and a coupling center is inclined in the circumferential direction with respect to an axis of the coupling. The latter is more expensive than the former, but since axial forces in a direction opposite to that of balls act on pocket portions adjacent to each other in the circumferential direction of a cage, it has an advantage that it is possible to suppress contact forces between a spherical outer peripheral surface of the cage and a spherical inner peripheral surface of the outer coupling member and between a spherical inner peripheral surface of the cage and a spherical outer peripheral surface of the inner coupling member 3 to achieve high efficiency.

[0004] In conventional fixed constant velocity universal joints, the maximum working angle is usually 50° or less (about 47° in a ball cage type constant velocity universal joint and about 50° in a non-undercut type constant velocity universal joint), but in recent fixed constant velocity universal joints for drive shafts, in order to improve the turning performance and small turning performance of a vehicle, there are an increasing number of cases where a larger maximum working angle exceeding 50° is required regardless of the non-crossed raceway groove type and the crossed raceway groove type.

[0005] In a fixed constant velocity universal joint, if a relatively large maximum operating angle is obtained, the contact ellipse generated by contact with the balls tends to overflow toward the shoulder of the raceway groove. Therefore, when a high torque is applied, excessive edge loads are generated on the shoulder of the raceway groove, and the shoulder of the raceway groove may be deformed. The deformation of the shoulder of the raceway groove causes abnormal noise and vibration. As a countermeasure to this problem, as disclosed in Patent Document 1, it is effective to continuously form an R-shaped raceway chamfer along the boundary between the inner diameter spherical surface portion of the outer ring and the raceway groove so that the raceway chamfer is smoothly connected to the raceway groove and the spherical inner peripheral surface.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-164106

[0009] Patent Document 2: Japanese Patent No. 5885997 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] On the other hand, when mass-producing the outer coupling member, it is difficult to smoothly connect the raceway chamfer to the raceway groove and the spherical inner peripheral surface of the outer coupling member or the spherical outer peripheral surface of the inner coupling member in view of machining errors and the like. If intentional implementation is desired, there is a problem that the manufacturing cost, such as the need for finish machining of the raceway chamfer, increases.

[0012] Therefore, an object of the present invention is to provide a fixed constant velocity universal joint that can suppress deformation of the shoulder of the raceway groove of the outer coupling member under high torque load at low cost.

[0013] Means for Solving the Problems

[0014] The fixed constant velocity universal joint of the present invention completed based on the above insights includes: an outer joint member having a plurality of raceways formed on a spherical inner peripheral surface, and having an open side and an inner side separated in the axial direction; an inner joint member having a plurality of raceways formed on a spherical outer peripheral surface; balls disposed between the raceways of the outer joint member and the corresponding raceways of the inner joint member; and a cage having pockets for receiving the balls and fitted to the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member. The raceway of the outer joint member has a guiding surface for guiding the balls, and a chamfer portion having an arc-shaped cross-sectional shape in a direction orthogonal to the axial direction is formed between the spherical inner peripheral surface of the outer joint member and the guiding surface. It is characterized in that the chamfer portion of the outer joint member is connected to the guiding surface at an edge-shaped connection point, and the angle ε between the tangent of the guiding surface at the connection point and the tangent of the chamfer portion is set to 0° < ε ≤ 15°.

[0015] In the case of this fixed constant velocity universal joint, measures, machining, etc. for smoothly connecting the guiding surface of the raceway and the chamfer portion are not required. Therefore, the manufacturing cost of the outer joint member can be reduced. In addition, by setting the angle ε between the tangent of the guiding surface at the connection point and the tangent of the chamfer portion within the range of 0° < ε ≤ 15°, even when transmitting high torque, excessive edge loads will not be generated due to contact with the balls at the shoulders of the raceways. Therefore, deformation, etc. at the shoulders of the raceways of the outer joint member can be suppressed, thereby avoiding the generation of abnormal noise and vibration.

[0016] Preferably, the radius of curvature R of the chamfer portion is in the range of 3.0 mm ≤ R ≤ 9.0 mm. If the radius of curvature R of the chamfer portion is less than 3 mm, the chamfer amount becomes small, so the effect of alleviating the edge load is insufficient and the effect of suppressing the deformation of the shoulder is reduced. If the radius of curvature R exceeds 9 mm, the edge of the connection point becomes sharp and it is difficult to keep the angle ε below 15°.

[0017] Preferably, the raceway of the outer joint member has a portion where the center line of the ball track is an arc.

[0018] The radius of curvature of the chamfer portion may be non-uniform in the axial direction.

[0019] The chamfer portion may be provided at a position closer to the inner side than the center of curvature of the center line of the ball track.

[0020] The center of curvature of the center line of the ball track and the center of curvature of the spherical inner peripheral surface may be offset in the axial direction.

[0021] The radius of curvature of the chamfer portion may be uniform in the axial direction.

[0022] The chamfered portion can be provided over the entire axial length of the raceway groove of the outer coupling member.

[0023] The amount of displacement in the axial direction between the center of curvature of the ball track center line and the center of curvature of the spherical inner peripheral surface can be 0.

[0024] As a fixed constant velocity universal joint, a fixed constant velocity universal joint as follows can be used: the plane including the ball track center line of the raceway groove of the outer coupling member and the coupling center is inclined with respect to the axis of the coupling, and the inclination directions of the raceway grooves adjacent in the circumferential direction are formed to be opposite to each other, and the ball track center line of the raceway groove of the inner coupling member is formed to be mirror-symmetrical with the ball track center lines of the pair of raceway grooves of the outer coupling member with respect to the plane including the coupling center and orthogonal to the axis of the coupling in the state of a working angle of 0°.

[0025] Advantages of the Invention

[0026] According to the present invention, it is possible to suppress deformation of the shoulder of the raceway groove of the outer coupling member under a high torque load at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a longitudinal sectional view of a fixed constant velocity universal joint according to a first embodiment of the present invention.

[0028] Figure 2 is a right side view of the above fixed constant velocity universal joint.

[0029] Figure 3 is Figure 1 a cross-sectional view in which one ball and the raceway groove on the P-P line are enlarged.

[0030] Figure 4 is an enlarged view showing Figure 3 the spherical inner peripheral surface and the raceway groove of the outer coupling member shown.

[0031] Figure 5 is an enlarged view showing Figure 4 region C in

[0032] Figure 6 is a longitudinal sectional view of the outer coupling member.

[0033] Figure 7A is Figure 6 a cross-sectional view taken along the A-A line in

[0034] Figure 7B is Figure 6 a cross-sectional view taken along the B-B line in

[0035] Figure 8 is a longitudinal sectional view of the above-mentioned fixed constant velocity universal joint that obtains the maximum working angle.

[0036] Figure 9A is a partial longitudinal sectional view of the fixed constant velocity universal joint of the first embodiment.

[0037] Figure 9B is a right side view of the fixed constant velocity universal joint of the first embodiment.

[0038] Figure 10A is a partial longitudinal sectional view of the outer coupling member of the above-mentioned fixed constant velocity universal joint.

[0039] Figure 10B is a right side view of the outer coupling member of the above-mentioned fixed constant velocity universal joint.

[0040] Figure 11A is a left side view of the inner coupling member of the above-mentioned fixed constant velocity universal joint.

[0041] Figure 11B is a top view showing the outer peripheral surface of the inner coupling member of the above-mentioned fixed constant velocity universal joint.

[0042] Figure 11C is a right side view of the inner coupling member of the above-mentioned fixed constant velocity universal joint.

[0043] Figure 12 is a partial longitudinal sectional view showing the details of the raceway groove of the outer coupling member.

[0044] Figure 13 is a longitudinal sectional view showing the details of the raceway groove of the inner coupling member.

[0045] Figure 14 is a longitudinal sectional view of the outer coupling member.

[0046] Figure 15A is Figure 14 a sectional view taken along line A'-A' in

[0047] Figure 15B is Figure 14 a sectional view taken along line B'-B' in Specific Embodiments

[0048] Hereinafter, based on Figures 1 to 15A 、 Figure 15B the embodiments of the present invention will be described.

[0049] Figure 1 is a longitudinal sectional view of the fixed constant velocity universal joint 1 of the first embodiment, Figure 2is a right side view thereof (illustrations of the protective cover 20 and the protective cover band 21 are omitted). This constant velocity universal joint 1 is a ball cage type constant velocity universal joint, and the outer coupling member 2, the inner coupling member 3, the torque transmitting balls 4 (hereinafter simply referred to as balls), and the cage 5 are the main constituent elements. As the fixed constant velocity universal joint 1, a non-undercutting type constant velocity universal joint can also be used.

[0050] As Figure 1 and Figure 2 shown, the outer coupling member 2 has a cup-shaped mouth portion 2a that is open at one axial end and closed at the other axial end, and a shaft portion 2b that projects from the other axial end of the mouth portion 2a. In the following description, the one axial end side of the mouth portion 2a is referred to as the open side, and the other axial end side is referred to as the inner side. The inner peripheral surface 6 of the mouth portion 2a is formed in a spherical shape. The inner coupling member 3 is housed inside the mouth portion 2a of the outer coupling member 2, and its outer peripheral surface 8 is spherical.

[0051] On the spherical inner peripheral surface 6 of the outer coupling member 2, a plurality of (for example, 8) raceway grooves 7 are formed at equal intervals in the circumferential direction and along the axial direction. On the spherical outer peripheral surface 8 of the inner coupling member 3, a plurality of (for example, 8) raceway grooves 9 that are opposed to the raceway grooves 7 of the outer coupling member 2 are formed at equal intervals in the circumferential direction and along the axial direction. Between the raceway grooves 7 of the outer coupling member 2 and the raceway grooves 9 of the inner coupling member 3, a plurality of (for example, 8) balls 4 that transmit torque are assembled respectively. A cage 5 that holds the balls 4 is disposed between the spherical inner peripheral surface 6 of the outer coupling member 2 and the spherical outer peripheral surface 8 of the inner coupling member 3. The balls 4 are housed in the pocket portions 5a of the cage 5. The spherical outer peripheral surface 12 of the cage 5 is slidably fitted to the spherical inner peripheral surface 6 of the outer coupling member 2, and the spherical inner peripheral surface 13 of the cage 5 is slidably fitted to the spherical outer peripheral surface 8 of the inner coupling member 3.

[0052] In order to represent the form and shape of the raceway grooves extending in the axial direction, in this specification, terms such as the ball track center line are used. The ball track center line refers to the locus described by the center of the ball 4 when the ball 4 disposed in the raceway groove moves along the raceway groove.

[0053] The centers of curvature of the spherical inner peripheral surface 6 of the outer coupling member 2 and the spherical outer peripheral surface 8 of the inner coupling member 3 are respectively located on the coupling center O. The centers of curvature of the spherical outer peripheral surface 12 of the cage 5 that is fitted to the spherical inner peripheral surface 6 of the outer coupling member 2 and the spherical inner peripheral surface 13 of the cage 5 that is fitted to the spherical outer peripheral surface 8 of the inner coupling member 3 are also located on the coupling center O.

[0054] The raceway groove 7 of the outer coupling member 2 has an arcuate ball track center line X, and the raceway groove 9 of the inner coupling member 3 has an arcuate ball track center line Y. The center of curvature O1 of the ball track center line X of the outer coupling member 2 and the center of curvature O2 of the ball track center line Y of the raceway groove 9 of the inner coupling member 3 are offset by an equal distance f in the opposite axial directions with respect to the coupling center O. Thus, when the fixed constant velocity universal joint 1 obtains a working angle, the balls 4 are always guided to the plane that bisects the angle (working angle) formed by the two axes of the outer coupling member 2 and the inner coupling member 3, and the rotational torque is transmitted between the two shafts at a constant speed.

[0055] In this way, the center of curvature O1 of the raceway groove 7 of the outer coupling member 2 and the center of curvature O2 of the raceway groove 9 of the inner coupling member 3 are offset by an equal distance in the axial direction with respect to the coupling center O. Therefore, the opposing raceway grooves of the outer coupling member 2 and the inner coupling member 3 are wedge-shaped that expand from the inner side of the outer coupling member 2 toward the opening side. Each ball 4 is received in the wedge-shaped raceway groove, and torque is transmitted between the outer coupling member 2 and the inner coupling member 3. A cage 5 is assembled to keep all the balls 4 on the plane that bisects the working angle.

[0056] Figure 3 It is a Figure 1 transverse sectional view showing an enlarged view of a ball and a raceway groove on the P - P line of Figure 3 As shown, the raceway groove 7 of the outer coupling member 2 and the raceway groove 9 of the inner coupling member 3 each have guide surfaces 71, 91 for guiding the balls 4. The cross-sectional shape of the guide surfaces 71, 91 is formed into an elliptical shape or a pointed arch shape. The balls 4 are in angular contact with the guide surface 71 of the raceway groove 7 of the outer coupling member 2 at two points C1, C2, and are in angular contact with the guide surface 91 of the raceway groove 9 of the inner coupling member 3 at two points C3, C4. Therefore, the balls 4 contact the guide surfaces 71, 91 on the side surfaces of the raceway grooves 7, 9 that are slightly away from the bottoms of the raceway grooves 7, 9. The angle (contact angle α) formed by the straight lines passing through the center Ob of the ball 4 and each contact point C1, C2, C3, C4 and the straight line passing through the center Ob of the ball 4 and the coupling center O [refer to Figure 1 is preferably set to 30° to 45°. It should be noted that the cross-sectional shapes of the raceway grooves 7, 9 can also be set to arcuate shapes, and the contact between the raceway grooves 7, 9 and the balls 4 can be set to annular contact.

[0057] As Figure 1As shown, internal splines 16 (the splines include serrations as well. The same applies hereinafter) are formed in the inner diameter hole 15 of the inner coupling member 3. By fitting the external splines 19 of the shaft 17 to the splines 16, the inner coupling member 3 and the shaft 17 are joined in a torque-transmissible manner. The inner coupling member 3 and the shaft 17 are axially positioned by a snap ring 18. A corrugated protective cover 20 is fitted to the outer periphery of the outer coupling member 2 and the outer periphery of the shaft 17 connected to the inner coupling member 3. Both ends of the protective cover 20 are fastened and fixed to the outer coupling member 2 and the shaft 17 by protective cover bands 21 and 22. Grease as a lubricant is sealed inside the coupling covered by the protective cover 20.

[0058] Figure 4 is an enlarged view showing Figure 3 a cross-sectional view of the spherical inner peripheral surface 6 and the raceway groove 7 of the outer coupling member 2 shown in Figure 5 is an enlarged view showing Figure 4 the cross-sectional view of the region C in

[0059] As Figure 4 shown, a convex arc-shaped chamfered portion (raceway chamfer) 30 with a radius of curvature R is formed between the spherical inner peripheral surface 6 of the outer coupling member 2 and the guide surface 71 of the raceway groove 7. As Figure 5 shown, the chamfered portion 30 and the guide surface 71 of the raceway groove 7 are not smoothly continuous, and there is an edge at the connection point E1 between the two. In addition, the angle ε between the tangent T1 of the guide surface 71 of the raceway groove 7 and the tangent T2 of the chamfered portion 30 at the connection point E1 is greater than 0° and 15 degrees or less (0° < ε ≤ 15°). In the present embodiment, an edge E2 is also provided between the chamfered portion 30 and the spherical inner peripheral surface 6 of the outer coupling member 2, but the chamfered portion 30 and the spherical inner peripheral surface 6 may be smoothly continuous in such a way that they have a common tangent.

[0060] The outer coupling member 2 is manufactured through main processes such as cold forging of steel → heat treatment → finish machining of the spherical inner peripheral surface 6 and the raceway groove 7. Hereinafter, each process will be briefly described.

[0061] In cold forging, the spherical inner peripheral surface 6, the raceway groove 7, and the chamfered portion 30 are respectively formed by a die. At the time of this cold forging, the connection point between the chamfered portion 30 and the guide surface 71 of the raceway groove 7 is formed as an edge. Therefore, at the stage of the intermediate product before finish machining after cold forging, there is also an edge portion between the chamfered portion 30 and the guide surface 71 of the raceway groove 7.

[0062] Heat treatment is applied to the spherical inner peripheral surface 6 and the surface of the raceway groove 7 (guide surface 71). Through this heat treatment, a hardened layer (not shown) is formed on the spherical inner peripheral surface 6 and the surface of the raceway groove 7. As the heat treatment, for example, induction hardening can be used. Finish machining is a process for finish machining the spherical inner peripheral surface 6 and the guide surface 71 of the raceway groove 7 within a specified tolerance range while retaining the hardened layer, and either or both of cutting and grinding are performed as finish machining. By performing finish machining on the guide surface 71 of the spherical inner peripheral surface 6 and the raceway groove 7 in this way, the guide surface 71 of the spherical inner peripheral surface 6 and the raceway groove 7 of the final product becomes a finish-machined surface (cutting surface or grinding surface). Since the chamfered portion 30 is not finish-machined, the chamfered portion 30 of the final product becomes a forged surface.

[0063] As in the present embodiment, by forming an edge portion between the raceway groove 7 and the inner surface of the chamfered portion 30 at the time of cold forging, it is not necessary to smoothly connect the forming portion of the raceway groove 7 of the mold and the forming portion of the chamfered portion 30. Therefore, it is possible to achieve a low cost of mold production and simplify the cold forging process. In addition, this edge portion does not disappear with the finish machining of the raceway groove 7, and after finish machining, an edge-shaped connection point E1 (ε > 0°) is formed between the guide surface 71 of the raceway groove 7 and the chamfered portion 30. Therefore, during finish machining, it is not necessary to perform machining such as smoothly connecting the guide surface 71 of the raceway groove 7 and the chamfered portion 30. In this way, it is not necessary to take measures, machining, etc. for smoothly connecting the guide surface 71 of the raceway groove 7 and the chamfered portion 30, so that the manufacturing cost of the outer coupling member 2 can be reduced.

[0064] In addition, the present invention has been verified, and as a result, it has been found that if the angle ε (hereinafter referred to as the angle between tangents) between the tangent T1 of the guide surface 71 at the connection point E1 and the tangent T2 of the chamfered portion 30 is controlled to be 15 degrees or less, even when transmitting high torque, excessive edge load will not be generated at the shoulder of the raceway groove 7 due to contact with the ball 4, and deformation at the shoulder of the raceway groove 7 of the outer coupling member 2 can be suppressed. Based on the above understanding, the angle ε between the tangents at the connection point E1 is preferably set within the range of 0° < ε ≤ 15°.

[0065] As described in Patent Document 1, heretofore, it has been common technical knowledge that the guide surface 71 of the raceway groove 7 and the chamfered portion 30 should be continuously formed in a smoothly connected manner. In contrast, in the present invention, a low cost is achieved by deliberately retaining an edge-shaped connection point E1 between the guide surface 71 of the raceway groove 7 and the chamfered portion 30. On the other hand, by finding the range of the angle ε between the tangents of the connection point E1 that can prevent the generation of excessive edge load, it is characterized in terms of both cost and strength.

[0066] The radius of curvature R of the chamfer portion 30 is preferably 3 mm or more and 9 mm or less. If the radius of curvature R is less than 3 mm, the chamfer amount becomes small, so that the effect of mitigating the edge load is insufficient and the effect of suppressing the deformation of the shoulder is reduced. If the radius of curvature R exceeds 9 mm, the edges of the connection points E1 (and the connection points E2) become sharp, and it becomes difficult to keep the angle ε between the tangents below 15°.

[0067] Figure 6 is a longitudinal sectional view of the outer joint member 2. Figure 7A shows Figure 6 a sectional view taken along line A - A of Figure 7B shows Figure 6 a sectional view taken along line B - B of

[0068] As Figure 7A and Figure 7B shown, in the outer joint member 2 of the constant velocity joint 1 of the ball cage type, the center of curvature O1 of the ball track center line X (radius of curvature Ro) of the raceway groove 7 is axially offset from the center of curvature O of the spherical inner peripheral surface 6 (radius of curvature Ros). Therefore, the depth (Ha, Hb) of the raceway groove 7 becomes shallower toward the inner side (Ha < Hb). Along with this, the angle δ between the spherical inner peripheral surface 6 and the guide surface 71 of the raceway groove 7 changes axially, and the angle δ becomes larger toward the inner side. Therefore, it is difficult to form the chamfer portion 30 with a uniform radius of curvature R. Therefore, in the constant velocity joint 1 of the ball cage type, it is reasonable to make the radius of curvature R of the chamfer portion 30 non-uniform axially. Specifically, the radius of curvature R of the chamfer portion 30 is increased more toward the inner side. Thus, even when the radius of curvature R of the chamfer portion 30 changes axially, it is also preferable that the angle ε between the tangents at the connection point E1 be in the range of 0° < ε ≤ 15° in the entire axial region of the chamfer portion 30. Further, in this entire region, the radius of curvature R of the chamfer portion 30 is preferably 3 mm or more and 9 mm or less.

[0069] Figure 8 is a longitudinal sectional view showing the state when the fixed constant velocity joint 1 attains the maximum working angle θmax (about 47°). As Figure 8 shown, in the state of attaining a high working angle, the inner ball 4 (in Figure 6(not shown in the figure) Torque is transmitted in the region where the depth of the raceway groove 7 is shallow. Therefore, inside the raceway groove 7, the contact ellipse generated by contact with the ball 4 easily overflows from the raceway groove 7, and the generation of edge loads becomes a problem. Therefore, it is preferable to form a chamfered portion 30 in at least the region inside the curvature center O1 of the ball track center line X of the raceway groove 7 of the outer coupling member 2 (the region inside the plane including the curvature center O1 and orthogonal to the axis N-N), where the angle ε between the tangents is in the range of 0° < ε ≤ 15°. In this case, in the chamfered portion 30 in the region on the opening side with respect to the curvature center O1 of the raceway groove 7, in addition to setting the angle ε between the tangents to 0° < ε ≤ 15°, it may also be set to ε > 15°. Further, in the region on the opening side with respect to the curvature center O1 of the raceway groove 7, instead of providing the chamfered portion 30, the guide surface 71 of the raceway groove 7 may be directly connected to the spherical inner peripheral surface 6.

[0070] Next, Figure 9A , Figures 9B to 15A , Figure 15B This represents the second embodiment of the present invention. The fixed constant velocity universal joint of the first embodiment has non-crossing raceway grooves in which the raceway grooves of the outer coupling member and the inner coupling member are in the same direction as the axis of the coupling in the plane including the ball track center lines X, Y of the respective raceway grooves and the coupling center O. However, the fixed constant velocity universal joint of the second embodiment is a fixed constant velocity universal joint with a cross-raceway groove form.

[0071] As Figure 9A and Figure 9B shown, this fixed constant velocity universal joint 1 has the same main structure as that of the first embodiment, including an outer coupling member 2, an inner coupling member 3, balls 4, and a cage 5. As Figure 10A , Figure 10B , Figure 11A , Figure 11B , Figure 11C shown, a plurality of (e.g., 8) raceway grooves 7, 9 formed on the spherical inner peripheral surface 6 of the outer coupling member 2 and the spherical outer peripheral surface 8 of the inner coupling member 3 are inclined in the circumferential direction with respect to the axis N-N of the coupling, and the inclination directions are opposite to each other in the circumferentially adjacent raceway grooves 7A, 7B and 9A, 9B. And one ball 4 is arranged at each intersection of the paired raceway grooves 7A, 9A and 7B, 9B of the outer coupling member 2 and the inner coupling member 3. Details of the raceway grooves 7, 9 will be described later.

[0072] As Figure 9AAs shown, the raceway groove 7 of the outer coupling member 2 has a ball track center line X. The raceway groove 7 is composed of a first raceway groove portion 7a having an arc-shaped ball track center line Xa with the coupling center O as the center of curvature and a second raceway groove portion 7b having a linear ball track center line Xb. The ball track center line Xb of the second raceway groove portion 7b is smoothly connected to the ball track center line Xa of the first raceway groove portion 7a as a tangent. It should be noted that the raceway groove 7 of the outer coupling member 2 may also be provided only with an arc-shaped portion composed of the ball track center line Xa with the coupling center O as the center of curvature.

[0073] On the other hand, the raceway groove 9 of the inner coupling member 3 has a ball track center line Y. The raceway groove 9 is composed of a first raceway groove portion 9a having an arc-shaped ball track center line Ya with the coupling center O as the center of curvature and a second raceway groove portion 9b having a linear ball track center line Yb. The ball track center line Yb of the second raceway groove portion 9b is smoothly connected to the ball track center line Ya of the first raceway groove portion 9a as a tangent. It should be noted that the raceway groove 9 of the inner coupling member 3 may also be provided only with an arc-shaped portion composed of the ball track center line Ya with the coupling center O as the center of curvature.

[0074] By arranging the centers of curvature of the ball track center lines Xa and Ya of the first raceway groove portions 7A and 9A at the coupling center O on the axis N - N of the coupling, the depth of the raceway groove can be made uniform and the machining can be made easy. The cross-sectional shape of the raceway grooves 7 and 9 is formed into an elliptical shape or a pointed arch shape, and the guide surfaces 71 and 91 of the raceway grooves 7 and 9 are in contact with the balls 4 at a so-called angular contact (refer to Figure 3 ) at a contact angle (about 30° to 45°). Therefore, the balls 4 are in contact with the guide surfaces 71 and 91 on the side surfaces of the raceway grooves 7 and 9 slightly away from the bottom of the raceway grooves 7 and 9.

[0075] Based on Figure 10A and Figure 10B , the state in which the raceway groove 7 of the outer coupling member 2 is inclined in the circumferential direction with respect to the axis N - N of the coupling will be described in detail. Figure 10A It shows a partial longitudinal section of the outer coupling member 2, Figure 10B and shows the right side surface of the outer coupling member 2. The raceway groove 7 of the outer coupling member 2 is marked with reference numerals 7A and 7B for the raceway grooves due to the different inclination directions. As Figure 10AAs shown, the plane M including the center line X of the ball track having the raceway groove 7A and the coupling center O is inclined at an angle γ with respect to the axis N - N of the coupling. Also, although not shown in the drawing, for the raceway groove 7B adjacent to the raceway groove 7A in the circumferential direction, the plane M including the center line X of the ball track having the raceway groove 7B and the coupling center O is inclined at an angle γ with respect to the axis N - N of the coupling in a direction opposite to the inclination direction of the raceway groove 7A. In the present embodiment, the entire region of the center line X of the ball track of the raceway groove 7A, that is, both the center line Xa of the ball track of the first raceway groove portion 7a and the center line Xb of the ball track of the second raceway groove portion 7b are formed on the plane M. However, it is not limited thereto, and a mode in which only the center line Xa of the ball track of the first raceway groove portion 7a is included in the plane M may also be implemented. Therefore, the plane M including at least the center line Xa of the ball track of the first raceway groove portion 7a and the coupling center O is inclined in the circumferential direction with respect to the axis N - N of the coupling, and it is sufficient that the inclination directions are opposite to each other in the circumferentially adjacent first raceway groove portions 7a.

[0076] Here, reference numerals for the raceway grooves are added. When referring to the entire raceway groove of the outer coupling member 2, the reference numeral 7 is used, for the first raceway groove portion, the reference numeral 7a is used, and for the second raceway groove portion, the reference numeral 7b is used. Also, when distinguishing raceway grooves with different inclination directions, the reference numerals 7A and 7B are used, for each first raceway groove portion, the reference numerals 7Aa and 7Ba are used, and for the second raceway groove portion, the reference numerals 7Ab and 7Bb are used. For the raceway grooves of the inner coupling member 3 described later, reference numerals are also assigned in the same manner.

[0077] Next, based on Figure 11A 、 Figure 11B 、 Figure 11C , the state in which the raceway groove 9 of the inner coupling member 3 is inclined in the circumferential direction with respect to the axis N - N of the coupling will be described in detail. Figure 11B represents the outer peripheral surface of the inner coupling member 3, Figure 11A represents the left side surface of the inner coupling member 3, Figure 11C represents the right side surface. For the raceway groove 9 of the inner coupling member 3, reference numerals 9A and 9B are used for the raceway grooves due to the difference in their inclination directions. As Figure 11BAs shown, the ball track center line Y of the ball track groove 9A and the plane Q of the coupling center O are inclined at an angle γ with respect to the axis N-N of the coupling. And, although not shown, for the ball track groove 9B adjacent to the ball track groove 9A in the circumferential direction, the plane Q of the ball track center line Y of the ball track groove 9B and the coupling center O is inclined at an angle γ with respect to the axis N-N of the coupling in the direction opposite to the inclination direction of the ball track groove 9A. Considering the workability of the constant velocity universal joint 1 and the spherical width F of the closest side of the ball track groove of the inner coupling member 3, the inclination angle γ is preferably 4° to 12°. In addition, similar to the aforementioned outer coupling member, in the present embodiment, the entire region of the ball track center line Y of the ball track groove 9A, that is, both the ball track center line Ya of the first ball track groove portion 9a and the ball track center line Yb of the second ball track groove portion 9b are formed on the plane Q. However, it is not limited thereto, and a mode in which only the ball track center line Ya of the first ball track groove portion 9a is included in the plane Q may also be implemented. Therefore, at least the plane Q including the ball track center line Ya of the first ball track groove portion 9a and the coupling center O is inclined in the circumferential direction with respect to the axis N-N of the coupling, and the inclination directions thereof are opposite to each other in the circumferentially adjacent first ball track groove portions 9a. The ball track center line Y of the ball track groove 9 of the inner coupling member 3 is formed to be mirror-symmetrical with the ball track center line X of the pair of ball track grooves 7 of the outer coupling member 2 with respect to the plane P including the coupling center O in the state of the working angle of 0°.

[0078] Based on Figure 12 The details of the ball track groove as observed from the longitudinal section of the outer coupling member 2 will be described. Figure 12 The partial longitudinal section is a cross-sectional view observed in the plane M including the ball track center line X of the ball track groove 7A of the aforementioned Figure 10A and the coupling center O. Therefore, strictly speaking, it is not a longitudinal cross-sectional view of the plane including the axis N-N of the coupling, but a cross-section inclined at an angle γ. The ball track groove 7A of the outer coupling member 2 is shown in Figure 12 , but the ball track groove 7B is only inclined in the direction opposite to that of the ball track groove 7A, and the other structures are the same as those of the ball track groove 7A, so the description thereof is omitted.

[0079] On the spherical inner peripheral surface 6 of the outer coupling member 2, a raceway groove 7A is formed along the axial direction. The raceway groove 7A has a ball track center line X, and the raceway groove 7A is composed of a first raceway groove portion 7Aa having an arc-shaped ball track center line Xa with the coupling center O as the center of curvature (without misalignment in the axial direction) and a second raceway groove portion 7Ab having a linear ball track center line Xb. And, at the end A on the opening side of the ball track center line Xa of the first raceway groove portion 7Aa, the linear ball track center line Xb of the second raceway groove portion 7Ab is smoothly connected as a tangent line. That is, the end A is the connection point of the first raceway groove portion 7Aa and the second raceway 7Ab. Since the end A is located at a position closer to the opening side than the coupling center O, the linear ball track center line Xb of the second raceway 7Ab connected as a tangent line at the end A on the opening side of the ball track center line Xa of the first raceway 7Aa is formed to approach the axis N - N of the coupling as it approaches the opening side [refer to Figure 9A . Thereby, the effective raceway length at the maximum working angle can be ensured, and the wedge angle can be suppressed from becoming too large.

[0080] As Figure 12 shown, let the straight line connecting the end A and the coupling center O be L. The axis N' - N' of the coupling projected onto the plane M [refer to Figure 10A containing the ball track center line X of the raceway groove 7A and the coupling center O is inclined at an angle γ with respect to the axis N - N of the coupling, and let the angle formed by the perpendicular line K at the coupling center O of the axis N' - N' and the straight line L be β'. The above-mentioned perpendicular line K lies on the plane P that contains the coupling center O in the state of the working angle of 0° and is orthogonal to the axis N - N of the coupling. Therefore, the angle β formed by the straight line L with respect to the plane P that contains the coupling center O in the state of the working angle of 0° and is orthogonal to the axis N - N of the coupling satisfies the relationship sinβ = sinβ' × cosγ.

[0081] Similarly, based on Figure 13 the longitudinal section of the inner coupling member 3 is used to illustrate the details of the raceway groove. Figure 13 The longitudinal section is a cross-sectional view observed in the plane Q containing the ball track center line Y of the raceway groove 9A of the aforementioned Figure 11B and the coupling center O. Therefore, similar to Figure 12 , strictly speaking, it is not a longitudinal cross-sectional view of the plane containing the axis N - N of the coupling, but a cross-section inclined at an angle γ. The raceway groove 9A of the inner coupling member 3 is shown in Figure 13 , but the raceway groove 9B is only inclined in the direction opposite to that of the raceway groove 9A, and the other structures are the same as those of the raceway groove 9A, so the description thereof is omitted.

[0082] On the spherical outer peripheral surface 8 of the inner coupling member 3, a raceway groove 9A is formed along the axial direction. The raceway groove 9A has a ball track center line Y, and the raceway groove 9A is composed of a first raceway groove portion 9Aa having an arc-shaped ball track center line Ya with the coupling center O as the center of curvature (without misalignment in the axial direction) and a second raceway groove portion 9Ab having a linear ball track center line Yb. And, at the inner end B of the ball track center line Ya of the first raceway groove portion 9Aa, the ball track center line Yb of the second raceway groove portion 9A is smoothly connected as a tangent line. That is, the end B is the connection point of the first raceway groove portion 9Aa and the second raceway groove portion 9Ab. Since the end B is located on the inner side of the coupling center O, the linear ball track center line Yb of the second raceway groove 9Ab connected as a tangent line at the inner end B of the ball track center line Ya of the first raceway groove portion 9Aa is formed to approach the axis N-N of the coupling as it goes inward [refer to Figure 3 of (A)]. Thereby, the effective raceway length at the maximum working angle can be ensured, and the wedge angle can be suppressed from becoming too large.

[0083] As Figure 13 shown, let the straight line connecting the end B and the coupling center O be J. The axis N'-N' of the coupling projected onto the plane Q [refer to Figure 11B including the ball track center line Y of the raceway groove 9A and the coupling center O is inclined by γ with respect to the axis N-N of the coupling, and the angle formed by the perpendicular line K to the coupling center O on the axis N'-N' and the straight line J is set as β'. The above-mentioned perpendicular line K is located on the plane P that includes the coupling center O in the state of the working angle of 0° and is orthogonal to the axis N-N. Therefore, the angle β formed by the straight line J with respect to the plane P that includes the coupling center O in the state of the working angle of 0° and is orthogonal to the axis N-N of the coupling has the relationship of sinβ = sinβ'×cosγ.

[0084] Next, the angles β formed by the straight lines L and J with respect to the plane P that includes the coupling center O in the state of the working angle of 0° will be described. When obtaining the working angle θ, the ball 4 moves by θ / 2 with respect to the plane P that includes the coupling center O of the outer coupling member 2 and the inner coupling member 3 and is orthogonal to the axis N-N of the coupling. The angle β is determined according to 1 / 2 of the working angle with high usage frequency, and the range of the raceway groove contacted by the ball 4 is determined within the range of the working angle with high usage frequency. Here, the working angle with high usage frequency is defined. First, the common angle of the coupling refers to the working angle generated in a fixed constant velocity universal joint of the front drive shaft when the steering wheel is in a straight-ahead state in a motor vehicle when one person is riding on a horizontal and flat road surface. The common angle is usually selected and determined between 2° and 15° according to the design conditions of each vehicle model.

[0085] Moreover, the working angle with a high usage frequency refers to the working angle generated by the fixed constant velocity universal joint when the above-mentioned motor vehicle is on a curved road during continuous driving, etc., rather than the high working angle generated during a right turn or left turn at an intersection, etc. This is also determined according to the design conditions of each vehicle model. The working angle with a high usage frequency aims at a maximum of 20°. Accordingly, the angle β formed by the straight lines L and J with respect to the plane P orthogonal to the coupling center O including the working angle of 0° and with respect to the axis N-N of the coupling is set to 3° to 10°. However, the angle β is not limited to 3° to 10° and can be appropriately set according to the design conditions of the vehicle model. By setting the angle β to 3° to 10°, it can be applied to various vehicle models.

[0086] Based on the above-mentioned angle β, in Figure 12 , the end A of the ball track center line Xa of the first raceway groove portion 7Aa becomes the center position of the ball when it moves axially to the most open side at the working angle with a high usage frequency. Similarly, in the inner coupling member 3, in Figure 13 , the end B of the ball track center line Ya of the first raceway groove portion 9Aa becomes the center position of the ball when it moves axially to the innermost side at the working angle with a high usage frequency. Due to such a setting, within the range of the working angle with a high usage frequency, the ball 4 is located in the first raceway groove portions 7Aa and 9Aa of the outer coupling member 2 and the inner coupling member 3 and the 7Ba and 9Ba with opposite inclination directions (refer to Figure 10A , Figure 10B , Figure 11A , Figure 11B , Figure 11C ). Therefore, forces in opposite directions act on the pocket portion 5a adjacent to the ball 4 in the circumferential direction of the cage 5, and the cage 5 is stabilized at the position of the coupling center O (refer to Figure 9A ). As a result, the contact force between the spherical outer peripheral surface 12 of the cage 5 and the spherical inner peripheral surface 6 of the outer coupling member 2, and the contact force between the spherical inner peripheral surface 13 of the cage 5 and the spherical outer peripheral surface 8 of the inner coupling member 3 are suppressed, and the coupling operates smoothly under high loads and high-speed rotations, torque loss and heat generation are suppressed, and durability is improved.

[0087] In the fixed-side constant velocity universal joint 1 of the second embodiment described above, a chamfer portion 30 having an arc-shaped cross-sectional shape in a direction orthogonal to the axial direction is also formed between the spherical inner peripheral surface 6 of the outer coupling member 2 and the guide surface 71 of the raceway groove 7 (refer to Figure 4 ). Moreover, the chamfer portion 30 of the outer coupling member 2 is connected to the guide surface of the raceway groove 7 at the edge-shaped connection point E1, and the angle ε between the tangent of the guide surface 71 at the connection point and the tangent of the chamfer portion 30 is set in the range of 0° < ε ≤ 15°. At this time, the radius of curvature R of the chamfer portion 30 is preferably 3 mm or more and 9 mm or less.

[0088] Figure 14 It is a longitudinal sectional view of the outer coupling member 2 in the fixed constant velocity universal joint 1 with a cross-raceway groove type. Figure 15A Indicates Figure 14 the cross-section A'-A', Figure 15B Indicates Figure 14 the cross-section B'-B'.

[0089] As Figure 15A and Figure 15B shown, in the outer coupling member 2 of the constant velocity universal joint 1 with a cross-raceway groove type, the center of curvature of the ball track center line X (curvature radius Ro) of the raceway groove 7 coincides with the center of curvature of the spherical inner peripheral surface 6 (curvature radius Ros), that is, the coupling center O. Therefore, the depth (Ha, Hb) of the raceway groove 7 is uniform in the axial direction (Ha = Hb). Along with this, the angle δ between the spherical inner peripheral surface 6 and the raceway groove 7 is constant in the axial direction, so that the chamfer portion 30 can be formed with a uniform curvature radius R. Therefore, in the constant velocity universal joint 1 with a cross-raceway groove type like the second embodiment, it is preferable that the curvature radius R of the chamfer portion 30 is constant in the axial direction. In this case, it is preferable that the curvature radius R of the chamfer portion 30 is set to a constant value in the range of 3 mm or more and 9 mm or less.

[0090] In the second embodiment, the chamfer portion 30 is formed over the entire axial length of the raceway groove 7. In contrast, similarly to the first embodiment, the chamfer portion 30 that makes the angle ε between the tangents in the range of 0° < ε ≤ 15° may be formed only on the inner side (more inward than the curvature center O1) of the raceway groove 7 of the outer coupling member 2 where the ball 4 generates a high load at a high working angle.

[0091] In the fixed constant velocity universal joint of the above embodiments, the case where the number of balls 4 is 8 has been described, but it is not limited thereto. The number of balls can be appropriately implemented as 6 to 10 or more.

[0092] In addition, in the fixed constant velocity universal joint of the second embodiment, the case where the ball track center line Xb of the second raceway groove portion is linear has been described, but it is not limited thereto. In short, as long as it has a shape different from the shape of the ball track center line Xa of the first raceway groove portion and can achieve a high working angle by increasing the effective raceway length, it can be set to an appropriate shape. For example, it can also be elliptical or linear. In addition, the first raceway groove portion and the second raceway groove portion are not limited to a single arc respectively, and may be formed by a plurality of arcs in consideration of the raceway groove depth and the like. Moreover, although the case where the raceway grooves are arranged at equal intervals in the circumferential direction is shown, they may also be arranged at unequal intervals. In addition, the case where the inclination angle γ of the first raceway groove with respect to the axis N-N of the coupling is equal in all the raceway grooves is shown, but it is not limited thereto, and the inclination angle γ may also be formed into unequal angles in the paired first raceway grooves of the outer coupling member and the inner coupling member and other paired first raceway grooves. In short, as long as each inclination angle is set so that the axial forces of the balls acting on all the pocket portions in the circumferential direction of the cage are in overall balance. In addition, although the angular contact embodiment in which the raceway groove contacts the ball with a contact angle is shown, it is not limited thereto, and it may also be set to an annular contact in which the cross-sectional shape of the raceway groove is circular.

[0093] The present invention is not limited by any of the foregoing embodiments, and can of course be further implemented in various ways without departing from the gist of the present invention. The scope of the present invention is shown by the technical solution, and also includes all changes within the meaning equivalent to that described in the technical solution and within the scope.

[0094] Description of reference numerals:

[0095] 1 Fixed constant velocity universal joint

[0096] 2 Outer coupling member

[0097] 3 Inner coupling member

[0098] 4 Ball

[0099] 5 Cage

[0100] 5a Pocket

[0101] 6 Spherical inner peripheral surface

[0102] 7 Raceway groove

[0103] 8 Spherical outer peripheral surface

[0104] 9 Raceway groove

[0105] 30 Chamfered portion

[0106] 71 Guide surface

[0107] 91 Guide surface

[0108] E1 connection point

[0109] Center of O coupling

[0110] Center of curvature of O1

[0111] Center of curvature of O2

[0112] Radius of curvature of the R chamfer part.

Claims

1. A fixed constant velocity universal joint, comprising: an outer joint member having a plurality of raceways formed in a spherical inner peripheral surface, and having an open side and an inner side separated in the axial direction; an inner joint member having a plurality of raceways formed in a spherical outer peripheral surface; balls disposed between the raceways of the outer joint member and the corresponding raceways of the inner joint member; and a cage having pockets for receiving the balls and engaged with the spherical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, wherein the raceways of the outer joint member have guide surfaces for guiding the balls, and a chamfer portion having an arc-shaped cross-sectional shape in a direction orthogonal to the axial direction is formed between the spherical inner peripheral surface of the outer joint member and the guide surfaces, and characterized in that, the chamfer portion of the outer joint member is connected to the guide surface at an edge-shaped connection point, and an angle ε between a tangent of the guide surface at the connection point and a tangent of the chamfer portion is set to 0° < ε ≤ 15°.

2. The fixed constant velocity universal joint according to claim 1, wherein, a radius of curvature R of the chamfer portion is 3.0 mm ≤ R ≤ 9.0 mm.

3. The fixed constant velocity universal joint according to claim 1, wherein, the raceways of the outer joint member have portions where the center line of the ball track is an arc.

4. The fixed constant velocity universal joint according to claim 3, wherein, the radius of curvature of the chamfer portion is non-uniform in the axial direction.

5. The fixed constant velocity universal joint according to claim 3, wherein, the chamfer portion is provided at a position closer to the inner side than the center of curvature of the center line of the ball track.

6. The fixed constant velocity universal joint according to any one of claims 3 to 5, wherein, the center of curvature of the center line of the ball track is axially offset from the center of curvature of the spherical inner peripheral surface.

7. The fixed constant velocity universal joint according to claim 3, wherein, the radius of curvature of the chamfer portion is uniform in the axial direction.

8. The fixed constant velocity universal joint according to claim 3, wherein, the chamfer portion is provided over the entire axial length of the raceways of the outer joint member.

9. The fixed constant velocity universal joint according to claim 3, 7 or 8, wherein, an amount of axial offset between the center of curvature of the center line of the ball track and the center of curvature of the spherical inner peripheral surface is 0.

10. The fixed constant velocity universal joint according to claim 9, wherein, a plane including the center line of the ball track of the raceways of the outer joint member and the joint center is inclined with respect to the axis of the joint, and the inclination directions are opposite to each other in the circumferentially adjacent raceways, the center lines of the ball tracks of the raceways of the inner joint member are formed to be mirror-symmetrical with respect to the center lines of the ball tracks of the paired raceways of the outer joint member with respect to a plane including the joint center and orthogonal to the axis of the joint in a state of a working angle of 0°.

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