Automatic ball incorporation method for constant-velocity universal joint

Abstract

This automatic ball incorporation method comprises an assembly installation step S1, a tilting step S3, and an insertion step S4. In the tilting step S3, a pocket 5a of a cage 5 is exposed to an opening end part of an outer joint member 2 by tilting a tilting member 14 toward a spherical surface part 6 formed between two track grooves 7 adjacent to each other in a circumferential direction in the outer joint member 2.

Description

Automatic Ball Incorporation Method for Constant Velocity Universal Joint

[0001] The present invention relates to an automatic ball incorporation method for a constant velocity universal joint.

[0002] For example, in the front drive shaft of an automobile, a sliding constant velocity universal joint with a relatively small maximum operating angle but capable of axial displacement while taking an operating angle is usually incorporated on the inboard side (differential side), and on the outboard side (wheel side), since the wheel is steered, a fixed constant velocity universal joint that can take a large operating angle but does not displace axially is incorporated.

[0003] As fixed constant velocity universal joints, the Zeppa type constant velocity universal joint (also called BJ type) and the undercut-free type constant velocity universal joint (also called UJ type) are known. For example, as the Zeppa type constant velocity universal joint, there are, for example, those of the 6-ball type (see Patent Document 1) and the 8-ball type (see Patent Document 2).

[0004] Recently, for the purpose of improving the environmental performance of automobiles and achieving further high efficiency, a fixed constant velocity universal joint of the track groove cross type has been proposed (see Patent Document 3). The constant velocity universal joint of the track groove cross type has an arc-shaped ball track center line with a curvature center having no axial offset with respect to the joint center for the track grooves of the outer joint member and the inner joint member, and a plane including this ball track center line and the joint center is inclined in the circumferential direction with respect to the axis of the joint, and this inclination direction is made opposite between the track groove of the outer joint member and the track groove of the inner joint member. And this constant velocity universal joint can achieve high efficiency with less torque loss and heat generation by alternately reversing the inclination directions of the track grooves of the outer joint member and the inner joint member in the circumferential direction.

[0005] As a conventional method for assembling a constant velocity universal joint, Patent Document 1 discloses an automated assembly method for a Zeppa-type constant velocity universal joint using six balls. This automated assembly method comprises a reference ball insertion step, an inner assembly assembly step, and a ball assembly step. Specifically, in the reference ball insertion step, the inner assembly, which consists of an inner joint member (inner ring) and an inner cage fitted to its outside, is aligned with the track groove of the inner joint member and the pocket of the cage, and then a reference ball is inserted into one of the pockets. Next, in the inner assembly assembly step, with the reference ball in one of the pockets positioned on the outside of the outer joint member (outer ring), the pockets formed on both sides of the cage's axis are aligned with opposing protrusions formed between the track grooves of the outer joint member, and the inner assembly is fitted into the outer joint member so that their axes are perpendicular to each other. Subsequently, the inner assembly is rotated by a certain angle in the circumferential direction of the outer joint member, and then the inner assembly is tilted into the outer joint member so that it is coaxial with the outer joint member, and the reference ball is fitted into one of the paired track grooves of the inner and outer joint members.

[0006] Then, in the ball assembly process, while the reference ball is still fitted into the track groove, the inner assembly is tilted relative to the outer joint member, exposing a pocket at a 120° phase relationship with the reference ball from the open end of the outer joint member. The ball is then inserted into the exposed pocket. After that, the inner assembly is returned to its original position, and the ball is fitted into the corresponding track groove of the outer joint member. The process of inserting balls into the remaining pockets is then carried out sequentially while tilting the inner assembly.

[0007] JP-A No. 62-37519 Patent No. 3859267 Patent No. 5138449

[0008] The assembly method disclosed in Patent Document 1 is based on the assembly of a Zeppa-type constant velocity universal joint in which the track grooves of the inner joint member and the track grooves of the outer joint member are not inclined in the circumferential direction. Therefore, with the assembled body incorporated into the outer joint member, the assembled body is tilted such that the track groove of the inner joint member is raised relative to the track groove of the outer joint member, thereby exposing the cage pockets positioned between these track grooves to the open end of the outer joint member.

[0009] However, when incorporating a ball into a track groove crossing type constant velocity universal joint, it was found that because the track grooves of the inner joint member and the outer joint member are inclined in the circumferential direction, tilting the assembly in the same way as before does not sufficiently expose the cage pocket to the open end of the outer joint member, making it impossible to incorporate the ball.

[0010] The present invention has been made in view of the above circumstances, and aims to address the technical challenge of suitably incorporating balls when manufacturing a track groove crossing type constant velocity universal joint.

[0011] The present invention is for solving the above problems and comprises an outer joint member having multiple track grooves extending in the axial direction formed on its spherical inner circumferential surface and an open side and an inner side spaced apart in the axial direction; an inner joint member having multiple track grooves formed on its spherical outer circumferential surface that are paired with the track grooves of the outer joint member; multiple balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; and a cage having a spherical outer circumferential surface and a spherical inner circumferential surface that holds these balls and fits into the spherical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member. An automatic ball assembly method for assembling the ball into a track groove intersecting constant velocity universal joint, wherein the track groove of the outer joint member consists of a first track groove portion (7a) located on the inner side and a second track groove portion (7b) located on the opening side, the first track groove portion (7a) has an arc-shaped ball trajectory centerline (Xa) having a curvature center (Oo1) offset in the axial direction with respect to the joint center (O), and at least the plane (M) containing the ball trajectory centerline (Xa) and the joint center (O) is inclined with respect to the joint axis (N-N) and the direction of inclination is circumferential The ball trajectory centerline (Xb) of the second track groove (7b) is formed in opposite directions to adjacent first track grooves (7a) in the same direction, and when the ball trajectory centerline (Xb) of the second track groove (7b) is projected onto the plane (M), the ball trajectory centerline (Xb) has a straight portion, and this straight portion is formed to be inclined so as it approaches the axis (N-N) of the joint as it moves toward the opening side, and the end (A) of the ball trajectory centerline (Xa) of the first track groove (7a) is located toward the opening side of the joint center (O), and the ball trajectory of the second track groove (7b) is located at this end (A) The core wire (Xb) is connected, and the ball trajectory centerline (Y) of the track groove of the inner joint member is formed in mirror image symmetry with the ball trajectory centerline (X) of the paired track groove of the outer joint member, with respect to a plane (P) that includes the joint center (O) and is perpendicular to the axis (N-N) of the joint when the operating angle is 0°, and the assembly is assembled by fitting the spherical outer surface of the inner joint member into the spherical inner surface of the cage and fitting the assembled assembly into the spherical inner surface of the outer joint member, and tilting the axis of the inner joint member with respect to the axis of the outer joint member by a tilting member,The invention comprises a tilting step of exposing the pocket of the cage to the open end of the outer joint member, and an insertion step of inserting a ball into the pocket of the cage exposed to the open end of the outer joint member, wherein the tilting step involves tilting the tilting member toward a spherical portion formed between two circumferentially adjacent track grooves in the outer joint member, thereby exposing the pocket of the cage in the assembly to the open end of the outer joint member.

[0012] As described above, according to the present invention, in the tilting step, the tilting member is tilted toward the spherical portion formed between the two track grooves, rather than toward the track groove of the outer joint member. This allows the cage pocket in the assembly to be exposed at the open end of the outer joint member. Therefore, in the insertion step, the ball can be suitably inserted into the exposed pocket.

[0013] In the ball automatic assembly method having the above configuration, in the insertion step, the ball may be inserted into the pocket exposed at the open end of the outer joint member by moving the ball along an insertion direction that is inclined with respect to the tilting direction from the tilting member toward the spherical portion of the outer joint member. This allows the ball to be suitably inserted into the pocket of the cage.

[0014] In the ball automatic assembly method having the above configuration, in the tilting step, two pockets adjacent in the circumferential direction in the cage are exposed to the open end of the outer joint member, and in the insertion step, the ball may be inserted into each of the two pockets.

[0015] With this configuration, the two pockets in the cage can be exposed to the open end of the outer joint member in a single tilting step. This allows two balls to be inserted into the pockets in a single insertion step, making it possible to manufacture the outer joint member efficiently.

[0016] According to the present invention, it is possible to suitably incorporate balls when manufacturing a track groove crossing type constant velocity universal joint.

[0017] Figure 1A shows a fixed constant velocity universal joint, and is a partial longitudinal cross-sectional view of the fixed constant velocity universal joint. Figure 1B shows a fixed constant velocity universal joint of Figure 1A, viewed from the axial direction. Figure 2A shows a partial longitudinal cross-sectional view of the outer joint member of the fixed constant velocity universal joint of Figure 1. Figure 2B shows a front view of the outer joint member of Figure 2A, viewed from the axial direction. Figure 3A shows a front view of the inner joint member of the fixed constant velocity universal joint of Figure 1, viewed from one side in the axial direction. Figure 3B shows a side view of the inner joint member of the fixed constant velocity universal joint of Figure 1, viewed from the outer circumference. Figure 3C shows a rear view of the inner joint member of the fixed constant velocity universal joint of Figure 1, viewed from the other side in the axial direction. Figure 1A shows a partial longitudinal cross-sectional view showing details of the track groove of the outer joint member. Figure 1A is a longitudinal cross-sectional view showing details of the track groove of the inner joint member. This is a flowchart of the automatic ball assembly method. This is a perspective view showing the assembly process. This is a perspective view showing the tilting member mounting process. This is a perspective view showing the tilting process. This is a perspective view showing the tilting process. This is a plan view showing the insertion process. This is a side view showing the insertion process. This is a perspective view showing a comparative example of the tilting process.

[0018] Embodiments of the present invention will be described below with reference to the drawings.

[0019] First, the basic configuration of the fixed constant velocity universal joint of the track groove crossing type according to this embodiment will be explained with reference to Figures 1 to 5. The fixed constant velocity universal joint 1 mainly consists of an outer joint member 2, an inner joint member 3, a ball 4, and a cage 5.

[0020] Eight track grooves 7 are formed on the spherical inner surface of the outer joint member 2, and eight track grooves 9 are formed on the spherical outer surface of the inner joint member 3 (see Figure 1B). On the inner surface of the outer joint member 2, spherical portions 6 remain between the track grooves 7 in the circumferential direction, and on the outer surface of the inner joint member 3, spherical portions 8 remain between the track grooves 9 in the circumferential direction (see Figure 1A). The center of curvature of the spherical portions 6 on the inner surface of the outer joint member 2 and the center of curvature of the spherical portions 8 on the outer surface of the inner joint member both coincide with the joint center O. One ball 4 is placed between each of the radially opposing track grooves 7 and 9. The cage 5 has a spherical outer surface 12 that fits into the spherical portions 6 on the inner surface of the outer joint member 2, a spherical inner surface 13 that fits into the spherical portions 8 on the outer surface of the inner joint member 3, and eight pockets 5a that each hold one ball 4. The cage 5 has a pair of annular portions 5b and 5c provided on both sides of the pocket 5a in the axial direction, and a column portion 5e connecting the pair of annular portions 5b and 5c in the axial direction (see Figures 1A and 7). At the axial end of the inner surface of the cage 5, in the illustrated example, a cylindrical surface 5d centered on the axis N-N is provided on the inner surface of one of the annular portions 5c.

[0021] In the following, the opening side (right side in Figure 1A) of the cup-shaped outer joint member 2 in the axial direction will be referred to as the "joint opening side," and the opposite side (left side in Figure 1A) will be referred to as the "joint rear side." Furthermore, in order to accurately describe the form and shape of the track grooves 7 and 9, such as their inclination and curvature, this specification will use the term "ball trajectory centerline." Here, the ball trajectory centerline refers to the trajectory traced by the center of a ball as it moves along the 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.

[0022] As shown in Figure 1A, the track groove 7 of the outer joint member 2 has a ball trajectory centerline X. The track groove 7 consists of a first track groove section 7a having an arc-shaped ball trajectory centerline Xa and a second track groove section 7b having a linear ball trajectory centerline Xb. The curvature center of the ball trajectory centerline Xa of the first track groove section 7a (the center of the sphere containing all the ball trajectory centerlines Ya) Oo1 is offset axially by f toward the joint opening side with respect to the joint center O (the intersection of the plane P containing the centers of the eight balls 4 and the axis N-N when the operating angle is 0°). The ball trajectory centerline Xa of the first track groove section 7a and the ball trajectory centerline Xb of the second track groove section 7b are smoothly continuous. That is, the ball trajectory centerline Xb of the second track groove section 7b coincides with the tangent to the ball trajectory centerline Xa of the first track groove section 7a at the joint opening side end.

[0023] The track groove 9 of the inner joint member 3 has a ball trajectory centerline Y. The track groove 9 consists of a first track groove section 9a having an arc-shaped ball trajectory centerline Ya and a second track groove section 9b having a straight ball trajectory centerline Yb. The curvature center of the ball trajectory centerline Ya of the first track groove section 9a (the center of the sphere containing all the ball trajectory centerlines Ya) Oi1 is offset axially by f on the far side of the joint with respect to the joint center O. The ball trajectory centerline Ya of the first track groove section 9a and the ball trajectory centerline Yb of the second track groove section 9b are smoothly connected. That is, the ball trajectory centerline Yb of the second track groove section 9b coincides with the tangent to the ball trajectory centerline Ya of the first track groove section 9a at the far end of the joint.

[0024] The cross-sectional shapes of the track grooves 7 and 9 are formed in an elliptical or Gothic arch shape. The track grooves 7 and 9 and the ball 4 make contact with a contact angle (approximately 30° to 45°), resulting in so-called angular contact. Therefore, the ball 4 is in contact with the side surface of the track grooves 7 and 9, slightly away from the groove bottom. Alternatively, the cross-sectional shapes of the track grooves 7 and 9 may be made into an arc shape, resulting in so-called circular contact between the track grooves 7 and 9 and the ball 4.

[0025] As shown in Figures 2A, 2B, and 3A to 3C, the track grooves 7 and 9 of the outer joint member 2 and the inner joint member 3 are inclined circumferentially with respect to the axial direction (the N-N direction of the joint axis). Adjacent track grooves in the circumferential direction are inclined in opposite directions with respect to the axial direction. Track grooves 7 and 9 facing each other in the radial direction are inclined in opposite directions with respect to the axial direction, and one ball 4 is placed at each of their intersections.

[0026] Based on Figures 2A and 2B, the track grooves 7 of the outer joint member 2 will be described in detail. The track grooves 7 of the outer joint member 2 are designated as track grooves 7A and 7B, respectively, due to their different inclination directions. Furthermore, the entire track groove of the outer joint member 2 is designated as 7, with the first track groove portion designated as 7a and the second track groove portion as 7b. Additionally, to distinguish between track grooves with different inclination directions, they are designated as 7A and 7B, with the first track groove portions designated as 7Aa and 7Ba, and the second track groove portions as 7Ab and 7Bb, respectively. The track grooves of the inner joint member 3, which will be described later, are designated in a similar manner.

[0027] As shown in Figure 2A, the plane M containing the ball trajectory centerline X of the track groove 7A (more specifically, the plane containing the ball trajectory centerline Xa of the first track groove portion 7Aa of the track groove 7A and its center of curvature) is inclined by an angle γ with respect to the axis N-N of the joint. Furthermore, the track groove 7B adjacent to the track groove 7A in the circumferential direction (not shown in the figure) has a plane containing the ball trajectory centerline X of the track groove 7B (more specifically, the plane containing the ball trajectory centerline Xa of the first track groove portion 7Ba of the track groove 7B and its center of curvature) that is inclined by an angle γ with respect to the axis N-N of the joint in the opposite direction to the inclination of the track groove 7A.

[0028] As shown in Figures 2A and 2B, the spherical portion 6 of the outer joint member 2 is formed between two adjacent track grooves 7A and 7B in the circumferential direction. Due to the difference in the inclination of the track grooves 7A and 7B as described above, the width dimension of the spherical portion 6 in the circumferential direction is not constant along the axial direction. The spherical portion 6 has different width dimensions at one edge 6a and the other edge 6b in the axial direction. That is, the spherical portion 6 has a first edge 6a with a smaller width dimension in the circumferential direction and a second edge 6b with a larger width dimension in the circumferential direction.

[0029] As shown in Figures 2A and 2B, in two adjacent spherical portions 6A and 6B in the circumferential direction, the positional relationship between the first edge 6a and the second edge 6b is reversed between one spherical portion 6A and the other spherical portion 6B. That is, one spherical portion 6A has the first edge 6a on the joint opening side, while the other spherical portion 6B has the second edge 6b on the joint opening side. Similarly, one spherical portion 6A has the second edge 6b on the joint-back side, while the other spherical portion 6B has the first edge 6a on the joint-back side.

[0030] Next, the track grooves 9 of the inner joint member 3 will be described in detail based on Figures 3A to 3C. The track grooves 9 of the inner joint member 3 are labeled as track grooves 9A and 9B, respectively, due to the difference in their inclination direction. As shown in Figure 3B, the plane Q containing the ball trajectory centerline Y of track groove 9A (more specifically, the plane containing the ball trajectory centerline Ya of the first track groove portion 9Aa of track groove 9A and its center of curvature) is inclined by an angle γ with respect to the joint axis N-N. The track groove 9B adjacent to track groove 9A in the circumferential direction is not shown in the figure, but the plane Q containing the ball trajectory centerline Y of track groove 9B (more specifically, the plane containing the ball trajectory centerline Ya of the first track groove portion 9Ba of track groove 9B and its center of curvature) is inclined by an angle γ with respect to the joint axis N-N in the opposite direction to the inclination direction of track groove 9A. The ball trajectory centerline Y of each track groove 9 of the inner joint member 3 is formed in a mirror image symmetric with the ball trajectory centerline X (see Figure 1A) of the track groove 7 of the outer joint member 2, which is radially opposite, with respect to a plane P that includes the joint center O and is perpendicular to the joint axis N-N, when the operating angle is 0°.

[0031] As shown in Figures 3A to 3C, the spherical portion 8 of the inner joint member 3 is formed between two adjacent track grooves 9A and 9B in the circumferential direction. Due to the difference in inclination of the track grooves 9A and 9B as described above, the width dimension of the spherical portion 8 in the circumferential direction is not constant along the axial direction. The spherical portion 8 has different width dimensions at one edge 8a and the other edge 8b in the axial direction. That is, the spherical portion 8 has a first edge 8a with a smaller width dimension in the circumferential direction and a second edge 8b with a larger width dimension in the circumferential direction.

[0032] As shown in Figures 3A to 3C, in two adjacent spherical portions 8A and 8B in the circumferential direction, the positional relationship between the first edge 8a and the second edge 8b is reversed between one spherical portion 8A and the other spherical portion 8B. That is, one spherical portion 8A has the first edge 6a on one end side in the axial direction of the inner joint member 3, while the other spherical portion 6B has the second edge 6b on the same side. Similarly, one spherical portion 6A has the second edge 6b on the other end side in the axial direction of the inner joint member 3, while the other spherical portion 6B has the first edge 6a on the same side.

[0033] Based on Figure 4, the details of the track groove 7A of the outer joint member 2 will be explained. Figure 4 is a cross-sectional view of the track groove 7A of Figure 2A as seen in a plane M that includes the ball trajectory centerline X. Therefore, strictly speaking, Figure 4 is not a longitudinal section view in a plane that includes the axis N-N of the joint, but rather a section inclined by an angle γ. Figure 4 shows the track groove 7A of the outer joint member 2, but the track groove 7B is the same as the track groove 7A except that the inclination direction is opposite, so its explanation will be omitted.

[0034] The track groove 7A consists of a first track groove section 7Aa having an arc-shaped ball trajectory centerline Xa with a curvature center offset axially with respect to the joint center O, and a second track groove section 7Ab having a linear ball trajectory centerline Xb. The linear ball trajectory centerline Xb of the second track groove section 7Ab smoothly connects to the joint opening side end of the ball trajectory centerline Xa of the first track groove section 7Aa. In the illustrated example, since the connection point A of the ball trajectory centerlines Xa and Xb is located on the joint opening side of the joint center O, the linear ball trajectory centerline Xb is inclined to approach the joint axis N-N (see Figure 1A) as it approaches the joint opening side. This ensures the effective track length at the maximum operating angle and suppresses excessive wedge angle. Figure 1A shows the track grooves 7 and 9 with an inclination angle γ of 0°.

[0035] As shown in Figure 4, let L be the straight line connecting the connection point A of the ball trajectory centerlines Xa and Xb to the joint center O. The axis of the joint N'-N' projected onto the plane M (see Figure 2A) containing the ball trajectory centerline X of the track groove 7A is inclined by γ with respect to the joint axis N-N, and let β' be the angle between the perpendicular K at the joint center O of the axis N'-N' and the straight line L. The above perpendicular K lies on the plane P that includes the joint center O when the operating angle is 0° and is perpendicular to the joint axis N-N. Therefore, the angle β that the straight line L makes with respect to the plane P that includes the joint center O when the operating angle is 0° and is perpendicular to the joint axis N-N is given by sinβ = sinβ' × cosγ.

[0036] Similarly, the details of the track groove 9A will be explained based on the longitudinal section of the inner joint member 3, as shown in Figure 5. The longitudinal section in Figure 5 is a cross-sectional view taken in plane Q that includes the ball trajectory center line Y of the track groove 9A in Figure 3B, as described above. Therefore, as with Figure 4, strictly speaking, it is not a longitudinal section in a plane that includes the joint axis N-N, but rather a cross-section that is inclined by an angle γ. Figure 5 shows the track groove 9A of the inner joint member 3, but the track groove 9B is the same as the track groove 9A except that the inclination direction is opposite, so its explanation will be omitted.

[0037] The track groove 9A consists of a first track groove section 9Aa having an arc-shaped ball trajectory centerline Ya with a curvature center offset axially with respect to the joint center O, and a second track groove section 9Ab having a linear ball trajectory centerline Yb. The linear ball trajectory centerline Yb of the second track groove section 9Ab smoothly connects to the joint-side end of the ball trajectory centerline Ya of the first track groove section 9Aa. In the illustrated example, since the connection point B of the ball trajectory centerlines Ya and Yb is located further back in the joint than the joint center O, the linear ball trajectory centerline Yb is inclined to approach the joint axis N-N (see Figure 1A) as it moves further back in the joint. This ensures the effective track length at the maximum operating angle and prevents the wedge angle from becoming excessive. As mentioned above, Figure 1A shows the track grooves 7 and 9 with an inclination angle γ of 0°.

[0038] As shown in Figure 5, let R be the line connecting the connection point B of the ball trajectory centerlines Ya and Yb to the joint center O. The joint axis N'-N' projected onto the plane Q (see Figure 3B) containing the ball trajectory centerline Y of the track groove 9A is inclined by γ with respect to the joint axis N-N. Let β' be the angle between the perpendicular K at the joint center O of axis N'-N' and the line R. The perpendicular K mentioned above lies on the plane P that includes the joint center O when the operating angle is 0° and is perpendicular to the joint axis N-N. Therefore, the angle β that the line R makes with respect to the plane P that includes the joint center O when the operating angle is 0° and is perpendicular to the joint axis N-N is given by sinβ = sinβ' × cosγ.

[0039] Next, we will explain the angle β that the lines L and R make with respect to a plane P that includes the joint center O and is perpendicular to the joint axis N-N when the operating angle is 0°. When the operating angle θ is taken, the ball 4 moves by θ / 2 with respect to a plane that includes the joint center O and is perpendicular to the axis of the outer joint member 2 (or inner joint member 3). The angle β is determined from half of the frequently used operating angle, and the range of the track groove that the ball 4 contacts within the range of the frequently used operating angle is determined. Here, we define the frequently used operating angle. First, the normal operating angle of the joint is the operating angle that occurs in a fixed constant velocity universal joint of the front drive shaft when the steering is in the straight position in a car with one occupant on a horizontal, flat road surface. The normal operating angle is selected and determined according to the design conditions of each vehicle type. Furthermore, the frequently used operating angle refers not to the high operating angle that occurs when the vehicle makes a right or left turn at an intersection, for example, but rather to the operating angle that occurs in a fixed constant-velocity universal joint when continuously driving on curved roads. This is also determined according to the design conditions for each vehicle type, but it is larger than the normal operating angle. In this embodiment, the angle β is set in the range of 8° to 12°. This ensures the length of the track groove and joint strength of the outer joint member in particular, and prevents the generation of abnormal noises.

[0040] Due to the angle β described above, in Figure 4, the connection point A between the ball trajectory centerline Xa of the first track groove 7Aa and the ball trajectory centerline Xb of the second track groove 7Ab becomes the center position of the ball when it moves furthest towards the opening along the axial direction at the most frequently used operating angle. Similarly, in the inner joint member 3, in Figure 5, the connection point B between the ball trajectory centerline Ya of the first track groove 9Aa and the ball trajectory centerline Yb of the second track groove 9Ab becomes the center position of the ball when it moves furthest towards the inner side along the axial direction at the most frequently used operating angle. With these settings, in the range of the most frequently used operating angles, the ball 4 is located in the first track grooves 7Ba and 9Ba (see Figures 2A, 2B, and 3A-3C) of the outer joint member 2 and inner joint member 3, with the inclination direction opposite to that of the first track grooves 7Aa and 9Aa.

[0041] Next, a ball automatic incorporation method (ball incorporation process), which is carried out in one step of the manufacturing method of the above fixed constant velocity joint 1, will be described.

[0042] As shown in FIG. 6, this method includes an assembly incorporation process S1, a tilting member mounting process S2, a tilting process S3, an insertion process S4, and a return process S5.

[0043] The assembly incorporation process S1 is a process of incorporating an assembly AS formed by combining an inner joint member 3 and a cage 5 into the inside of an outer joint member 2 by using an incorporation device (not shown). As shown in FIG. 7, the assembly AS is configured by externally fitting the cage 5 onto the inner joint member 3. Specifically, the assembly AS is configured by fitting a spherical surface portion 8 of the spherical outer peripheral surface of the inner joint member 3 onto the spherical inner peripheral surface 13 of the cage 5. In this assembly AS, the inner joint member 3 and the cage 5 are positioned such that the track groove 9 in the inner joint member 3 and the pocket 5a of the cage 5 overlap.

[0044] In the assembly incorporation process S1, the spherical outer peripheral surface 12 of the cage 5 of the assembly AS is fitted onto the spherical surface portion 6 of the spherical inner peripheral surface of the outer joint member 2. Also, in the assembly incorporation process S1, the assembly AS is inserted into the inside of the outer joint member 2 such that the central axis line CL1 of the inner joint member 3 in the assembly AS and the central axis line CL2 of the outer joint member 2 coincide.

[0045] In the assembly incorporation process S1, the assembly AS is inserted into the opening of the outer joint member 2 fixed to the fixing member, and the spherical outer peripheral surface 12 of the cage 5 in the assembly AS is brought into contact with the spherical surface portion 6 of the outer joint member 2. At this time, the track groove 9 of the inner joint member 3 and the track groove 7 of the outer joint member 2 face each other, and the circumferential position of the assembly AS with respect to the outer joint member 2 is adjusted so that the pocket 5a of the cage 5 is positioned between these track grooves 7 and 9.

[0046] As shown in FIG. 8, in the tilting member mounting step S2, a tilting member 14 for changing the posture of the assembly AS is mounted on the assembly AS. The tilting member 14 is constituted by a metal cylindrical member, but the material and shape of the tilting member 14 are not limited to this embodiment. The tilting member 14 is inserted into the inner joint member 3 in the assembly AS. The tilting member 14 is mounted on the assembly AS such that its central axis CL3 is parallel to the central axis CL2 of the outer joint member 2.

[0047] Next, in the tilting step S3, the posture of the assembly AS is changed by tilting the tilting member 14 mounted on the assembly AS in a predetermined direction by a tilting device (not shown). In the tilting step S3, the tilting member 14 changes its posture from the reference posture shown in FIG. 8 to the tilted posture shown in FIG. 9. While the tilting member 14 changes its posture from the reference posture to the tilted posture, the assembly AS is tilted with respect to the outer joint member 2. Thereby, the central axis CL1 (see FIG. 7) of the inner joint member 3 can be tilted with respect to the central axis CL2 (see FIG. 8) of the outer joint member 2, and the pocket 5a of the cage 5 in the assembly AS can be exposed at the opening end of the outer joint member 2.

[0048] FIG. 10 shows the tilting direction (hereinafter referred to as the “tilting direction”) of the tilting member 14 when the posture of the tilting member 14 is changed from the reference posture to the tilted posture. That is, the tilting direction TD of the tilting member 14 is set in the direction toward the spherical surface portion 6 in the outer joint member 2. More specifically, the tilting direction TD is set with respect to a spherical surface portion 6A having a first edge portion (an edge portion having a small width dimension in the circumferential direction) 6a on the joint opening side. In other words, it is set along a straight line connecting the central axis CL3 of the tilting member 14 and the circumferential central position 6a1 of the first edge portion 6a of this spherical surface portion 6A. A part of the tilting member 14 is held by the tilting device, and the tilting device operates the tilting member 14 such that the upper part of the tilting member 14 tilts along the tilting direction TD.

[0049] As described above, changing the orientation of the tilting member 14 also changes the orientation of the assembly AS. Specifically, the inner joint member 3 in the assembly AS is directly manipulated by the tilting member 14, causing a portion of it (the portion on the tilting direction TD side) to be pushed down into the outer joint member 2, while the other portion opposite to this portion (the portion opposite to the tilting direction TD) rises so that it is exposed from the open end of the outer joint member 2.

[0050] In the combined body AS, the cage 5 changes its orientation in response to the change in the orientation of the inner joint member 3. That is, since the spherical portion 8 of the inner joint member 3 and the spherical inner circumferential surface 13 of the cage 5 are in contact, when the inner joint member 3 is moved by the operation of the tilting member 14, the spherical portion 8 of the inner joint member 3 slides against the spherical inner circumferential surface 13 of the cage 5. As the inner joint member 3 slides, a part of the cage 5 (the part on the tilting direction TD side) is pushed down into the interior of the outer joint member 2 together with the inner joint member 3, and another part (the part opposite to the tilting direction TD) rises so that it is exposed from the open end of the outer joint member 2.

[0051] As a result of the change in posture (tilting) of the combined body AS as described above, the cage 5 in the combined body AS will be in a state where two pockets 5a are exposed from the open end of the outer joint member 2, as shown in Figures 9 and 10.

[0052] The insertion step S4 is the step of inserting the ball 4 into the exposed pocket 5a of the cage 5 after the tilting step S3. As shown in Figures 11 and 12, in the insertion step S4, the ball 4 is moved along a predetermined insertion direction ID by the pushing member 15.

[0053] The pushing member 15 is configured in a cylindrical or cylindrical shape, but is not limited to this shape. Driven by an actuator (not shown), the pushing member 15 can reciprocate between the standby position shown in Figures 11 and 12 and the pushing position in which the ball 4 is pushed into the pocket 5a of the cage 5 in the assembly AS.

[0054] As shown in Figure 11, the insertion direction ID of the ball 4 is set in a direction that is inclined at a predetermined angle with respect to the tilting direction TD in a plan view. That is, the reference line BL is defined as the straight line connecting the center position 6a1 of the first edge 6a on the spherical portion 6 (6A) of the outer joint member 2, which is oriented by the tilting direction TD, and the circumferential center position 5e1 of the column portion 5e between the two exposed pockets 5a, and the insertion direction ID of the ball 4 is set in a direction that is inclined at an angle θ1 with respect to this reference line BL. Note that the reference line BL is set to coincide with the tilting direction TD. In this embodiment, the inclination angle θ1 of the insertion direction ID is, for example, 22.5°, but the present invention is not limited to this angle. This inclination angle θ1 can be changed according to the total number of balls 4 incorporated into the fixed constant velocity universal joint 1.

[0055] As shown in Figure 12, the insertion direction ID is set to a direction that is inclined at an angle θ2 with respect to the horizontal direction in a side view. This inclination angle θ2 is preferably 30° or more and 40° or less. As a result, the ball 4 moves from a position above the cage 5 of the combination AS toward the pocket 5a which is diagonally downward.

[0056] In insertion step S4, the ball 4 is pressed by the pushing member 15 and guided to the pocket 5a along the insertion direction ID by a guide member (not shown). The ball 4 is inserted into the pocket 5a and engages with the track groove 9 of the corresponding inner joint member 3. In this embodiment, two balls 4 are inserted into the two pockets 5a of the cage 5 in a single insertion step S4. The insertion of the two balls 4 may be done simultaneously, or one ball 4 may be inserted into one pocket 5a first, and then the other ball 4 may be inserted into the other pocket 5a.

[0057] Once the insertion of the two balls 4 into the two exposed pockets 5a is complete, the return process S5 is executed. In the return process S5, the tilting member 14 returns from the tilted position to the reference position. As a result, the assembly AS returns to the initial position (reference position) before tilting shown in Figure 8. At this time, the balls 4 inserted into the pockets 5a engage with the corresponding track grooves 7 of the outer joint member 2.

[0058] When the tilting member 14 returns to its reference position, the tilting step S3, insertion step S4, and return step S5 are repeatedly performed to insert the balls 4 into the other pockets 5a that do not yet have balls 4 inserted. The method is completed when all the balls 4 have been inserted into the pockets 5a.

[0059] Figure 13 shows a comparative example in which the pocket 5a of the cage 5 in the assembly AS cannot be exposed during the tilting process S3. In this comparative example, the tilting direction TD of the tilting member 14 is different from that of the above embodiment. That is, the tilting direction TD is set toward the track groove 7 (7A) in the outer joint member 2. When the tilting member 14 and the assembly AS are tilted along this tilting direction TD, as shown in Figure 13, only a part of the pocket 5a of the cage 5 in the assembly AS is exposed, and the entire pocket cannot be exposed. For this reason, in this comparative example, the ball 4 cannot be inserted into the pocket 5a.

[0060] According to the ball automatic assembly method of this embodiment described above, for a track groove crossing type fixed constant velocity universal joint 1, the tilting member 14 attached to the inner joint member 3 of the combination body AS is changed along the tilting direction TD, thereby changing the orientation of the cage 5 of the combination body AS, and allowing the two pockets 5a in the cage 5 to be suitably exposed from the opening of the outer joint member 2 (tilting step S3). Furthermore, with this method, two balls 4 can be inserted into the two pockets 5a of the cage 5 in a single insertion step S4, making it possible to efficiently manufacture the fixed constant velocity universal joint 1.

[0061] Furthermore, the present invention is not limited to the configuration of the above embodiments, nor is it limited to the effects described above. The present invention can be modified in various ways without departing from the spirit of the invention.

[0062] In the above embodiment, a method of incorporating eight balls 4 into a fixed constant velocity universal joint 1 was illustrated, but the present invention is not limited to this configuration. The present invention can also be applied when six balls 4 are incorporated into a fixed constant velocity universal joint 1.

[0063] 1 Fixed constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 Ball 5 Cage 5a Pocket 6 Spherical portion (spherical inner surface) of the outer joint member 7 Track groove of the outer joint member 7a First track groove portion 7b Second track groove portion 8 Spherical portion (spherical outer surface) of the inner joint member 9 Track groove of the inner joint member 9a First track groove portion 9b Second track groove portion 12 Spherical outer surface of the cage 13 Spherical inner surface of the cage 14 Tilting member M Plane containing the ball trajectory centerline N Axis of the joint O Center of the joint Oo1 Center of curvature of the first track groove P Plane perpendicular to the axis of the joint S1 Assembly process S3 Tilting process S4 Insertion process X Ball trajectory centerline of the track groove of the outer joint member Xa Centerline of the ball trajectory in the first track groove Xb Centerline of the ball trajectory in the second track groove Y Centerline of the ball trajectory in the track groove of the inner joint member Ya Centerline of the ball trajectory in the first track groove Yb Centerline of the ball trajectory in the second track groove

Claims

1. An automatic ball assembly method for assembling balls into a track groove crossing type constant velocity universal joint, comprising: an outer joint member having multiple track grooves extending axially formed on its spherical inner surface and having an opening side and a back side spaced apart in the axial direction; an inner joint member having multiple track grooves formed on its spherical outer surface that are paired with the track grooves of the outer joint member; multiple balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member to transmit torque; and a cage having a spherical outer surface and a spherical inner surface that holds the balls and fits onto the spherical inner surface of the outer joint member and the spherical outer surface of the inner joint member, wherein the balls are assembled into the track groove crossing type constant velocity universal joint, The track groove of the outer joint member consists of a first track groove portion (7a) located on the inner side and a second track groove portion (7b) located on the opening side. The first track groove portion (7a) has an arc-shaped ball trajectory centerline (Xa) with a curvature center (Oo1) offset axially with respect to the joint center (O). At least the plane (M) containing the ball trajectory centerline (Xa) and the joint center (O) is inclined with respect to the joint axis (N-N), and the direction of this inclination is opposite to that of adjacent first track groove portions (7a) in the circumferential direction. The track groove (7b) is formed in such a direction that when the ball trajectory centerline (Xb) of the second track groove (7b) is projected onto the plane (M), the ball trajectory centerline (Xb) has a straight portion, and this straight portion is formed to be inclined so as it approaches the axis (N-N) of the joint as it moves toward the opening side, the end (A) of the ball trajectory centerline (Xa) of the first track groove (7a) is located toward the opening side from the joint center (O), and the ball trajectory centerline (Xb) of the second track groove (7b) is connected to this end (A). The ball trajectory centerline (Y) of the track groove of the inner joint member is formed in mirror image symmetry with the ball trajectory centerline (X) of the paired track groove of the outer joint member, with respect to a plane (P) that includes the joint center (O) and is perpendicular to the axis (N-N) of the joint when the operating angle is 0°, and the assembly is assembled by fitting the spherical outer surface of the inner joint member into the spherical inner surface of the cage and then fitting the assembled assembly into the spherical inner surface of the outer joint member; and the tilting step is performed by tilting the axis of the inner joint member with respect to the axis of the outer joint member using a tilting member, thereby exposing the pocket of the cage to the open end of the outer joint member.An automatic ball assembly method for a constant velocity universal joint, comprising: an insertion step of inserting a ball into a pocket of the cage exposed at the open end of the outer joint member, wherein in the tilting step, the tilting member is tilted toward a spherical portion formed between two circumferentially adjacent track grooves in the outer joint member, thereby exposing the pocket of the cage in the assembly to the open end of the outer joint member.

2. The method for automatically assembling a ball into a constant velocity universal joint according to claim 1, wherein in the insertion step, the ball is moved along an insertion direction that is inclined with respect to the tilting direction from the tilting member toward the spherical portion of the outer joint member, thereby inserting the ball into the pocket exposed at the open end of the outer joint member.

3. The ball automatic assembly method according to claim 1 or 2, wherein in the tilting step, two circumferentially adjacent pockets in the cage are exposed to the open end of the outer joint member, and in the insertion step, the ball is inserted into each of the two pockets.

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