Constant velocity joint

Abstract

To provide a constant velocity joint capable of suppressing noise and vibration generated when a ball held by a ball groove is released from a locked state.SOLUTION: As a radius of curvature Ro2 of a second outer ball groove 22b in cutting an outer ball groove 22 of an outer race 12 constituting a second groove portion 32 at a face vertical to a center line CL1 is larger than a radius of curvature Ro1 of a first outer ball groove 22a constituting a first groove portion 30, a load applied to a ball 16 at a second groove portion 32 side can be reduced under a condition that high torque is applied to a constant velocity joint 10 and the load applied to the ball 16 is increased. As a result, noise and vibration generated in releasing of the lock of the ball 16 of the second groove portion 32 can be suppressed.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a constant velocity joint mounted on a vehicle.

Background Art

[0002] There is known a constant velocity joint including a cup-shaped outer race provided with a plurality of outer ball grooves on an inner peripheral surface, an inner race provided with a plurality of inner ball grooves on an outer peripheral surface and disposed inside the outer case, a plurality of balls interposed between the outer ball grooves and the inner ball grooves for torque transmission, and a cage for holding the plurality of balls. The constant velocity joint described in Patent Document 1 is such a joint.

[0003] Patent Document 1 discloses a structure having a first groove portion in which an opening angle formed by the intersection of a tangent line between the outer ball groove and the ball and a tangent line between the inner ball groove and the ball opens toward the cup opening side of the outer race, and a second groove portion in which the opening angle opens toward the cup bottom side (the bottom side of the cup) of the outer race, in a reference state where the center lines of the outer race and the inner race are located on a straight line and the joint angle is zero (deg).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the force with which the outer ball groove and the inner ball groove push out the balls is determined by the product of the load applied between the balls and each ball groove (ball groove load) and the opening angle (ball groove load × opening angle). In a constant velocity joint as described in Patent Document 1, in the high joint angle region, when the opening angle of the second groove portion crosses zero (deg), each ball groove cannot push out the balls and the balls are locked. At this time, if the load applied to the balls increases, there is a risk of abnormal noise and vibration occurring when the balls are unlocked.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a constant velocity joint capable of suppressing abnormal noise and vibration generated when the balls sandwiched between the ball grooves are released from the locked state.

Means for Solving the Problems

[0007] The gist of the first invention is as follows: (a) a cup-shaped outer race provided with a plurality of outer ball grooves on its inner peripheral surface, an inner race provided with a plurality of inner ball grooves on its outer peripheral surface and disposed inside the outer race, a plurality of balls interposed between the outer ball grooves and the inner ball grooves for torque transmission, and in a reference state where the joint angle at which the center lines of the outer race and the inner race are on the same straight line is zero degrees, a first groove portion formed by the intersection of the tangent line between the outer ball groove and the ball and the tangent line between the inner ball groove and the ball, the opening angle of which opens toward the cup opening side of the outer race, and a second groove portion the opening angle of which opens toward the cup bottom side of the outer race. When the joint angle formed by the intersection of the center line of the outer race and the center line of the inner race becomes a predetermined angle or more, the opening angle in the second groove portion is configured to cross zero. A constant velocity joint, wherein (b) the radius of the arc of the outer ball groove of the outer race forming the second groove portion is formed larger than the radius of the arc of the outer ball groove forming the first groove portion when the outer ball groove is cut by a plane perpendicular to the center line of the outer race, and (c) the radius of the arc of the inner ball groove of the inner race forming the second groove portion is formed larger than the radius of the arc of the inner ball groove forming the first groove portion when the inner ball groove is cut by a plane perpendicular to the center line of the inner race, and it is characterized by satisfying at least one of them.

[0008] The gist of the second invention is that in the first invention, (a) when the outer ball groove of the outer race forming the second groove portion is cut by a plane perpendicular to the center line of the outer race, the radius of the arc of the outer ball groove is formed larger than the radius of the arc of the outer ball groove forming the first groove portion, and (b) when the inner ball groove of the inner race forming the second groove portion is cut by a plane perpendicular to the center line of the inner race, the radius of the arc of the inner ball groove is formed larger than the radius of the arc of the inner ball groove forming the first groove portion.

Effect of the Invention

[0010] According to the first invention, since at least one of the following is satisfied: the radius of the arc of the outer ball groove of the outer race forming the second groove portion is formed larger than the radius of the arc of the outer ball groove forming the first groove portion when the outer ball groove is cut by a plane perpendicular to the center line of the outer race, and the radius of the arc of the inner ball groove of the inner race forming the second groove portion is formed larger than the radius of the arc of the inner ball groove forming the first groove portion when the inner ball groove is cut by a plane perpendicular to the center line of the inner race, under the condition that a high torque is applied to the constant velocity joint and the load on the balls becomes large, the load on the balls on the second groove portion side can be reduced. As a result, the abnormal noise and vibration generated when the balls in the second groove portion are unlocked can be suppressed. Further, when the joint angle becomes a predetermined angle or more, the second groove portion is configured such that the opening angle in the second groove portion crosses zero, so that the balls in the second groove portion are locked within a range including an opening angle of zero. At this time, even when the torque applied to the constant velocity joint is in a high torque state, the load applied to the balls on the second groove portion side is reduced, so that abnormal noise and vibration generated when the balls in the second groove portion are unlocked can be suppressed.

[0011] According to the second invention, since the radius of the arc of the outer ball groove of the second groove portion is larger than the radius of the arc of the outer ball groove of the first groove portion, and the radius of the arc of the inner ball groove of the second groove portion is larger than the radius of the arc of the inner ball groove of the first groove portion, when a high torque is applied to the constant velocity joint, the load applied to the balls on the second groove portion side can be effectively reduced.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

Embodiment

[0015] FIG. 1 is an assembly drawing (perspective view) showing the internal structure of a constant velocity joint 10 of a vehicle to which the present invention is applied. The constant velocity joint 10 is provided between two rotating shafts and is a well-known constant velocity universal joint that transmits rotation between these rotating shafts even when the angle (joint angle) formed by these two rotating shafts changes.

[0016] The constant velocity joint 10 includes an outer race 12 formed in a cup shape, an inner race 14 disposed inside the outer race 12, a plurality (six in this embodiment) of balls 16 interposed between the outer race 12 and the inner race 14 for torque transmission, and a cage 18 that holds these plurality of balls 16 in a non-detachable manner from an outer ball groove 22 (described later) of the outer race 12 and an inner ball groove 24 (described later) of the inner race 14.

[0017] The outer race 12 is provided so as to be integrally rotatable together with a rotating shaft 20 connected to the outer race 12. The outer race 12 is formed in a cup shape with an opening on the side opposite to the portion where the rotating shaft 20 is connected. A plurality (six in this embodiment) of outer ball grooves 22 equal in number to the balls 16 are provided on the inner peripheral surface 12a (see FIG. 3) of the cup-shaped portion of the outer race 12. The outer ball grooves 22 are formed along the direction of the center line CL1 of the outer race 12 from the opening side of the cup shape of the outer race 12 toward the inner side (or the bottom side) of the cup shape. The plurality of outer ball grooves 22 are formed at equal angular intervals on the inner peripheral surface 12a of the outer race 12.

[0018] The inner race 14 has an annular shape and is disposed inside the cup-shaped portion of the outer race 12. The inner race 14 is rotatable about a center line CL2 passing through the center of the annular shape. On the outer peripheral surface 14a (see FIG. 3) of the inner race 14, a plurality (six in this embodiment) of inner ball grooves 24 equal in number to the outer ball grooves 22 are formed. The inner ball grooves 24 are formed along the direction of the center line CL2. The plurality of inner ball grooves 24 are formed at equal angular intervals in the circumferential direction of the inner race 14. Incidentally, spline teeth for spline fitting with a rotation shaft (not shown) are formed on the inner peripheral surface of the inner race 14.

[0019] The ball 16 is formed in a spherical shape made of a metal material. The ball 16 is interposed between the outer ball groove 22 of the outer race 12 and the inner ball groove 24 of the inner race 14. One ball 16 is disposed between the outer ball groove 22 and the inner ball groove 24 respectively. The ball 16 is swingable (rollable) along the groove shapes of the outer ball groove 22 and the inner ball groove 24.

[0020] The ball 16 has a function of torque-transmitting the torque transmitted from one of the outer race 12 and the inner race 14 to the other. When torque is transmitted, the ball 16 rotates about the respective center lines CL1, CL2 (hereinafter referred to as the center line CL when not distinguishing between them) together with the outer race 12 and the inner race 14. At this time, the ball 16 is swung along the groove shapes of the outer ball groove 22 and the inner ball groove 24 according to the joint angle θ of the constant velocity joint 10. The joint angle θ corresponds to the intersection angle of the center line CL1 and the center line CL2, with the reference state where the center line CL1 of the outer race 12 and the center line CL2 of the inner race 14 are in a straight line being zero [deg].

[0021] The cage 18 is formed in an annular shape, and both its inner circumferential surface and outer circumferential surface are formed in smooth curved surfaces. The cage 18 is interposed between the outer race 12 and the inner race 14 in the radial direction centered on the center line CL. The cage 18 is formed with pockets 26 for holding the balls 16 in a non-detachable manner, and the number of the pockets 26 is the same as the number of the balls 16 (six in this embodiment) at equal angular intervals in the circumferential direction. The pockets 26 penetrate between the inner circumferential surface and the outer circumferential surface of the cage 18, and are formed in a rectangular shape that extends longitudinally along the circumferential direction of the cage 18 when viewed from the radially outer side. By accommodating the balls 16 in the pockets 26 respectively, each ball 16 is constantly held by the cage 18 at positions that are at equal angular intervals in the circumferential direction.

[0022] FIG. 2 is a cross-sectional view of the constant velocity joint 10 in FIG. 1 cut along a plane passing through the center of the ball 16 and the center line CL. The cross-sectional view shown in FIG. 2 shows a reference state in which the center lines CL of the center line CL1 of the outer race 12 and the center line CL2 of the inner race 14 are located on a straight line, and the joint angle θ is zero degrees [0 deg].

[0023] FIG. 3 schematically shows the state of FIG. 2 viewed from the direction of arrow A. In FIG. 3, the cage 18 is omitted. The outer ball groove 22 formed on the inner circumferential surface 12a of the outer race 12 is composed of a first outer ball groove 22a and a second outer ball groove 22b. The first outer ball groove 22a and the second outer ball groove 22b are alternately arranged at equal angular intervals in the circumferential direction of the outer race 12. In this embodiment, since six outer ball grooves 22 are provided, as shown in FIG. 3, three first outer ball grooves 22a and three second outer ball grooves 22b are alternately arranged at 60-degree intervals. Also, the second outer ball groove 22b is arranged at a position facing the first outer ball groove 22a with the center line CL1 interposed therebetween.

[0024] The inner ball groove 24 formed on the outer peripheral surface 14a of the inner race 14 is composed of a first inner ball groove 24a and a second inner ball groove 24b. The first inner ball groove 24a and the second inner ball groove 24b are alternately arranged at equal angular intervals in the circumferential direction of the inner race 14. In this embodiment, since six inner ball grooves 24 are provided, as shown in FIG. 3, three first inner ball grooves 24a and three second inner ball grooves 24b are alternately arranged at 60-degree intervals. Further, the second inner ball groove 24b is arranged at a position facing the first inner ball groove 24a with the center line CL2 interposed therebetween.

[0025] The first outer ball groove 22a and the first inner ball groove 24a are arranged at the same position in the rotational direction about the center line CL. In other words, when the first outer ball groove 22a and the first inner ball groove 24a are viewed in the radial direction about the center line CL, they are arranged at positions where they overlap each other (i.e., positions where they face each other). A ball 16 for torque transmission is interposed between the first outer ball groove 22a and the first inner ball groove 24a.

[0026] The second outer ball groove 22b and the second inner ball groove 24b are arranged at the same position in the rotational direction about the center line CL. In other words, when the second outer ball groove 22b and the second inner ball groove 24b are viewed in the radial direction about the center line CL, they are arranged at positions where they overlap each other (i.e., positions where they face each other). A ball 16 for torque transmission is interposed between the second outer ball groove 22b and the second inner ball groove 24b.

[0027] The cage 18 is interposed in the annular space formed between the outer race 12 and the inner race 14, and is rotated about the joint center point O shown in FIG. 2 during torque transmission.

[0028] Further, a first groove portion 30 that sandwiches the ball 16 is formed by the first outer ball groove 22a and the first inner ball groove 24a, and a second groove portion 32 that sandwiches the ball 16 is formed by the second outer ball groove 22b and the second inner ball groove 24b. As shown in FIG. 3, these first groove portion 30 and second groove portion 32 are alternately provided in the rotational direction about the center line CL.

[0029] In the first groove portion 30 shown in FIG. 2, in the reference state where the joint angle θ is zero degrees [0 deg], the opening angle α at which the first outer ball groove 22a and the first inner ball groove 24a sandwich the ball 16 is open toward the cup opening side of the outer race 12. The opening angle α is an angle formed by the intersection of the tangent line Lo1 between the first outer ball groove 22a and the ball 16 and the tangent line Li1 between the first inner ball groove 24a and the ball 16. Further, the opening angle α is also an angle formed by the center locus of the ball 16 rolling in the first outer ball groove 22a and the center locus of the ball 16 rolling in the first inner ball groove 24a.

[0030] In the second groove portion 32, in the reference state where the joint angle θ is zero degrees [0 deg], the opening angle β at which the second outer ball groove 22b and the second inner ball groove 24b sandwich the ball 16 is open toward the cup back side (i.e., the cup bottom side) of the outer race 12. The opening angle β is an angle formed by the intersection of the tangent line Lo2 between the second outer ball groove 22b and the ball 16 and the tangent line Li2 between the second inner ball groove 24b and the ball 16. Further, the opening angle β is also an angle formed by the center locus of the ball 16 rolling in the second outer ball groove 22b and the center locus of the ball 16 rolling in the second inner ball groove 24b.

[0031] In this way, since the opening angles α and β open in different directions from each other and the opening angles α and β are alternately arranged, when transmitting torque, the load F1 in the direction of the center line CL acting on the ball 16 intervening in the first groove portion 30 and the load F2 in the direction of the center line CL acting on the ball 16 intervening in the second groove portion 32 act in directions canceling each other out. As a result, the total value of the loads in the direction of the center line CL acting on each ball 16 becomes small. In relation to this, since the force in the direction of the center line CL acting on the cage 18 via each ball 16 is reduced, the sliding resistance generated between the inner peripheral surface 12a of the outer race 12 and the outer peripheral surface of the cage 18 is reduced, and the sliding resistance generated between the outer peripheral surface 14a of the inner race 14 and the inner peripheral surface of the cage 18 is reduced. As a result, the torque transmission efficiency of the constant velocity joint 10 is increased and the fuel consumption (or electricity cost) is improved. Also, during the idling operation of the engine, the vibration of the engine (idle vibration) is likely to be transmitted to the driver, but by reducing the sliding resistance of the constant velocity joint 10, the effect that the vibration of the engine is less likely to be transmitted to the driver can also be obtained. Note that during normal driving, since the torque input to the constant velocity joint 10 is relatively low torque, the effects of the improvement in fuel consumption (electricity cost) and the reduction in idle vibration described above are preferably obtained in the low torque region.

[0032] Incidentally, when the joint angle θ of the constant velocity joint 10 becomes a predetermined angle θ2 or more (see FIG. 4), the opening angle β in the second groove portion 32 is configured to cross zero degrees (0 deg). When the opening angle β becomes zero degrees or near zero degrees, the load F2 acting on the ball 16 arranged in the second groove portion 32 becomes small. As a result, the ball 16 is not pushed out to the center line CL by the second outer ball groove 22b and the second inner ball groove 24b, and the ball 16 locks between the second outer ball groove 22b and the second inner ball groove 24b. At this time, energy is accumulated in the ball 16, and when the ball 16 is released from the locked state, there is a possibility that abnormal noise and vibration may occur due to the ball 16 suddenly starting to move.

[0033] Figure 4 is a diagram showing the relationship between the opening angles α and β with respect to the joint angle θ in the constant velocity joint 10. In Figure 4, the horizontal axis represents the joint angle θ, and the vertical axis represents the maximum values of the changes in the opening angles α and β with reference to the reference opening angles α0 and β0 when the joint angle θ is 0 degrees (0 deg). Note that when the joint angle θ is 0 degrees, regardless of the rotation angle of the constant velocity joint 10, the opening angles α and β are maintained at the reference opening angles α0 and β0, respectively. That is, when the joint angle θ is 0 degrees, the opening angles α and β are constant regardless of the rotation angle of the constant velocity joint 10.

[0034] First, regarding the opening angle α, every time the constant velocity joint 10 makes one rotation, the opening angle α transitions between the reference opening angle α0 when the joint angle θ is 0 degrees and the opening angle α shown by the solid line. As shown in Figure 4, the change amount of the opening angle α from the reference opening angle α0 is small in the range of all joint angles θ used during running. That is, the opening angle α hardly changes even when the constant velocity joint 10 makes one rotation. Also, the opening angle α is greater than 0 degrees in the range of all joint angles θ.

[0035] Next, the opening angle β will be described. The opening angle β changes between the reference opening angle β0 when the joint angle θ is 0 degrees (0 deg) and the opening angle β shown by the dashed line every time the constant velocity joint 10 makes one rotation. For example, at the joint angle θ1, every time the constant velocity joint 10 makes one rotation, the opening angle β transitions between the reference opening angle β0 and the opening angle β1. Therefore, at the joint angle θ1, during the rotation of the constant velocity joint 10, the opening angle β crosses the estimated ball lock range sandwiched by the dash-dotted line. The estimated ball lock range is the range where the opening angle β crosses 0 degrees, and it is the region where the load F2 in the direction of the center line CL acting on the ball 16 becomes zero or substantially zero, and temporary locking of the ball 16 occurs during the rotation of the constant velocity joint 10. Therefore, at the joint angle θ1, locking of the ball 16 occurs at the second groove portion 32 during the rotation of the constant velocity joint 10.

[0036] As shown in FIG. 4, in the constant velocity joint 10, as the joint angle θ increases, the amount of change in the opening angle β during the rotation of the constant velocity joint 10 increases. And when the joint angle θ becomes equal to or greater than a predetermined angle θ2, since it is configured to pass through an estimated ball lock range where the opening angle β crosses zero degrees during the rotation of the constant velocity joint 10, locking of the ball 16 occurs in the second groove portion 32.

[0037] FIG. 5 is a diagram for explaining a mechanism in which abnormal noise and vibration occur due to the ball 16 being locked in the second groove portion 32.

[0038] At A1 shown in FIG. 5, as the opening angle β of the second groove portion 32 approaches the above-described estimated ball lock range, the load F2 for pushing out the ball 16 decreases. At A2, as the opening angle β enters the estimated ball lock range, the load F2 acting on the ball 16 becomes equal to or less than the frictional force acting between the ball 16, the second outer ball groove 22b, and the second inner ball groove 24b. At this time, the ball 16 cannot be pushed out, and the ball 16 is locked between the second outer ball groove 22b and the second inner ball groove 24b. At A3, the energy due to the pressing of the ball 16 is accumulated as the locked ball 16 is pressed by other balls via the cage 18. At A4, other balls 16 attempt to rotate the cage 18. At A5, although the cage 18 attempts to move the ball 16, the cage 18 does not start moving smoothly because the frictional resistance between the spherical surface of the cage 18, the spherical surface of the outer ball groove 22, and the spherical surface of the inner ball groove 24 is high. At A6, the cage 18 starts to move and the ball 16 is released, but since the accumulated energy is suddenly released, the ball 16 and the cage 18 start to move suddenly, resulting in abnormal noise at A7. Or, at A8, as the opening angle β changes with the rotation of the constant velocity joint 10, the ball 16 is released, but also at this time, the ball 16 and the cage 18 start to move suddenly, resulting in abnormal noise and vibration at A7.

[0039] FIG. 6 shows the measurement results of the presence or absence of abnormal noise for each torque input to the constant velocity joint 10. Note that the joint angle θ is fixed at 15 degrees (15 deg) and the rotational speed is fixed at 200 rpm. Also, at 15 degrees of the joint angle θ, the opening angle β crosses zero degrees during the rotation of the constant velocity joint 10. As shown in FIG. 6, no abnormal noise was detected when the input torque was 800 Nm or less, but abnormal noise was detected when the input torque became 1000 Nm or more. Thus, as the torque input to the constant velocity joint 10 increases, the load applied to the ball 16 increases, and the energy accumulated in the ball 16 at the time of locking of the ball 16 increases, resulting in the generation of abnormal noise and vibration.

[0040] FIG. 7 shows the torque transmission path when torque is input to the constant velocity joint 10. When torque is input to an intermediate shaft (not shown) spline-fitted to the inner race 14, this torque is transmitted to the inner race 14. Next, the ball groove clearance Gapi, which is the play formed between the inner ball groove 24 of the inner race 14 and the ball 16, is filled, and the inner race 14 presses the ball 16. Next, the ball groove clearance Gap o, which is the play formed between the ball 16 and the outer ball groove 22 of the outer race 12, is filled, and the ball 16 presses the outer race 12. As a result, torque is transmitted to the outer race 12.

[0041] As described above, when the constant velocity joint 10 transmits torque, the ball groove clearance Gapi between the inner ball groove 24 and the ball 16 and the ball groove clearance Gap between the ball 16 and the outer ball groove 22 are filled. Here, if the ball groove clearance Gapo and the ball groove clearance Gapi (hereinafter, when not distinguishing between them, each ball groove clearance Gap) are made different between the first groove portion 30 and the second groove portion 32, the load applied to the ball 16 during torque transmission can be made different between the ball 16 in the first groove portion 30 and the ball 16 in the second groove portion 32. For example, when the ball groove clearance Gap of a specific ball 16 increases, other balls 16 come into contact with the outer ball groove 22 and the inner ball groove 24 first and receive the load, and the load applied to the specific ball 16 decreases. Therefore, the greater the ball groove clearance Gap, the smaller the load applied to the ball 16. Further, since the abnormal noise and vibration generated when the lock of the ball 16 in the second groove portion 32 is released occur when the load applied to the ball 16 increases, the abnormal noise and vibration can be suppressed by reducing the load applied to the ball 16 in the second groove portion 32.

[0042] In consideration of the above, in the constant velocity joint 10, in the low torque region where the torque input to the constant velocity joint 10 is relatively low, the load applied to the ball 16 in the second groove portion 32 is set to be greater than the load applied to the ball 16 in the first groove portion 30. That is, in the low torque region, each ball groove clearance Gap formed in the second groove portion 32 is set to be smaller than each ball groove clearance Gap formed in the first groove portion 30.

[0043] Furthermore, in the high torque region where the torque input to the constant velocity joint 10 is relatively high, the load applied to the ball 16 in the second groove portion 32 is set to be smaller than the load applied to the ball 16 in the first groove portion 30. That is, in the high torque region, each ball groove clearance Gap in the second groove portion 32 is set to be larger than each ball groove clearance Gap in the first groove portion 30.

[0044] Specifically, when the outer ball groove 22 is cut by a plane perpendicular to the center line CL1 of the outer race 12, the radius of curvature Ro2 of the arc of the second outer ball groove 22b is formed to be larger than the radius of curvature Ro1 of the arc of the first outer ball groove 22a when the first outer ball groove 22a is cut by a plane perpendicular to the center line CL1 of the outer race 12. The radius of curvature Ro1 also corresponds to the radius of the arc when the first outer ball groove 22a is viewed in the direction along the center line CL1 of the outer race 12. The radius of curvature Ro2 also corresponds to the radius of the arc when the second outer ball groove 22b is viewed in the direction along the center line CL1 of the outer race 12.

[0045] Further, when the inner ball groove 24 is cut by a plane perpendicular to the center line CL2 of the inner race 14, the radius of curvature Ri2 of the arc of the second inner ball groove 24b is formed to be larger than the radius of curvature Ri1 of the arc of the first inner ball groove 24a when the first inner ball groove 24a is cut by a plane perpendicular to the center line CL2 of the inner race 14. The radius of curvature Ri1 also corresponds to the radius of the arc when the first inner ball groove 24a is viewed in the direction along the center line CL2 of the inner race 14. The radius of curvature Ri2 also corresponds to the radius of the arc when the second inner ball groove 24b is viewed in the direction along the center line CL2 of the inner race 14.

[0046] Fig. 8 shows the relationship between the radii of curvature R of the outer ball groove 22 of the outer race 12 and the inner ball groove 24 of the inner race 14. As can also be seen from Fig. 8, in the outer race 12, the radius of curvature Ro2 of the second outer ball groove 22b is formed to be larger than the radius of curvature Ro1 of the first outer ball groove 22a. Also, in the inner race 14, the radius of curvature Ri2 of the second inner ball groove 24b is formed to be larger than the radius of curvature Ri1 of the first inner ball groove 24a.

[0047] By being formed as described above, near the groove bottom 34 of the outer ball groove 22, the ball groove clearance Gapo1 of the first outer ball groove 22a becomes larger than the ball groove clearance Gapo2 of the second outer ball groove 22b. On the other hand, at a position away from the groove bottom 34 of the outer ball groove 22, the ball groove clearance Gapo2 of the second outer ball groove 22b becomes larger than the ball groove clearance Gapo1 of the first outer ball groove 22a.

[0048] Therefore, when the ball 16 is near the groove bottom 34 of the outer ball groove 22, the load applied to the ball 16 in the second outer ball groove 22b becomes larger than the load applied to the ball 16 in the first outer ball groove 22a. On the other hand, when the ball 16 is at a position away from the groove bottom 34 of the outer ball groove 22, the load applied to the ball 16 in the first outer ball groove 22a becomes larger than the load applied to the ball 16 in the second outer ball groove 22b.

[0049] Also, near the groove bottom 36 of the inner ball groove 24, the ball groove clearance Gapi1 of the first inner ball groove 24a becomes larger than the ball groove clearance Gapi2 of the second inner ball groove 24b. On the other hand, at a position away from the groove bottom 36 of the inner ball groove 24, the ball groove clearance Gapi2 of the second inner ball groove 24b becomes larger than the ball groove clearance Gapi1 of the first inner ball groove 24a.

[0050] Therefore, when the ball 16 is near the groove bottom 36 of the inner ball groove 24, the load applied to the ball 16 in the second inner ball groove 24b becomes larger than the load applied to the ball 16 in the first inner ball groove 24a. On the other hand, when the ball 16 is at a position away from the groove bottom 36 of the inner ball groove 24, the load applied to the ball 16 in the first inner ball groove 24a becomes larger than the load applied to the ball 16 in the second inner ball groove 24b.

[0051] Here, when the torque applied to the constant velocity joint 10 is large and when it is small, the contact points between the ball 16 and the outer ball groove 22 and the inner ball groove 24 change. FIG. 9 shows the locus of the contact points between the ball 16 and the outer ball groove 22 and the inner ball groove 24 when torque is input to the constant velocity joint 10. In FIG. 9, the upper side of the paper corresponds to the radial direction centered on the center line CL, and the left - right direction of the paper corresponds to the direction of the center line CL. Also, FIG. 9(a) on the left side of the paper shows a state where the joint angle θ is 20 degrees (20 deg) and the torque input to the constant velocity joint 10 is a relatively low torque of 300 Nm. FIG. 9(b) on the right side of the paper shows a state where the joint angle θ is 20 degrees and the torque input to the constant velocity joint 10 is a relatively high torque of 900 Nm.

[0052] Comparing the locus Xout1 of the contact point between the ball 16 and the outer ball groove 22 shown in FIG. 9(a) with the locus Xout2 of the contact point between the ball 16 and the outer ball groove 22 shown in FIG. 9(b), the locus Xout2 is displaced at a position farther from the groove bottom 34 of the outer ball groove 22 than the locus Xout1. Also, comparing the locus Xin1 of the contact point between the ball 16 and the inner ball groove 24 shown in FIG. 9(a) with the locus Xin2 of the contact point between the ball 16 and the inner ball groove 24 shown in FIG. 9(b), the locus Xin2 is displaced at a position farther from the groove bottom 36 of the inner ball groove 24 than the locus Xin1.

[0053] Therefore, in the low - torque region where the torque input to the constant velocity joint 10 is relatively small, the ball 16 contacts near the groove bottom 34 of the outer ball groove 22, and the ball 16 contacts near the groove bottom 36 of the inner ball groove 24. Also, in the high - torque region where the torque input to the constant velocity joint 10 is relatively large, the ball contacts at a position away from the groove bottom 34 of the outer ball groove 22, and the ball 16 contacts at a position away from the groove bottom 36 of the inner ball groove 24.

[0054] As described above, in the low torque region where the torque input to the constant velocity joint 10 is relatively low, the ball 16 contacts near the groove bottom 34 of the outer ball groove 22. At this time, the ball groove clearance Gapo1 between the ball 16 and the first outer ball groove 22a becomes larger than the ball groove clearance Gapo2 between the ball 16 and the second outer ball groove 22b. Therefore, among the total loads applied to each ball 16, the load (shared load) borne by the ball 16 in the second outer ball groove 22b becomes larger than the load (shared load) borne by the ball 16 in the first outer ball groove 22a.

[0055] Also, in the low torque region, the ball 16 contacts near the groove bottom 36 of the inner ball groove 24. At this time, since the ball groove clearance Gapi1 between the ball 16 and the first inner ball groove 24a is larger than the ball groove clearance Gapi2 between the ball 16 and the second inner ball groove 24b, among the total loads applied to each ball 16, the load (shared load) borne by the ball 16 in the second inner ball groove 24b becomes larger than the load (shared load) borne by the ball 16 in the first inner ball groove 24a.

[0056] From the above, in the low torque region where the torque input to the constant velocity joint 10 is relatively low, the shared load of the ball 16 in the second groove portion 32 becomes larger than the shared load of the ball 16 in the first groove portion 30. At this time, the load acting on the ball 16 in the first groove portion 30 and the load acting on the ball 16 in the second groove portion 32 cancel each other out, thereby obtaining the above-described effects of improving the torque transmission efficiency and reducing the idle vibration. Also, since the torque input to the constant velocity joint 10 is relatively low, abnormal noises and vibrations shown in FIG. 6 do not occur.

[0057] Also, in a high torque region where the torque input to the constant velocity joint 10 is relatively high, the balls 16 contact at positions away from the groove bottom 34 of the outer ball groove 22. At this time, the ball groove clearance Gapo2 between the ball 16 and the second outer ball groove 22b becomes larger than the ball groove clearance Gapo1 between the ball 16 and the first outer ball groove 22a. Therefore, among the total loads applied to each ball 16, the load (shared load) borne by the ball 16 in the second outer ball groove 22b becomes smaller than the load (shared load) borne by the ball 16 in the first outer ball groove 22a.

[0058] Also, in the high torque region, the balls 16 contact at positions away from the groove bottom 36 of the inner ball groove 24. At this time, the ball groove clearance Gapi2 between the ball 16 and the second inner ball groove 24b becomes larger than the ball groove clearance Gapi1 between the ball 16 and the first inner ball groove 24a. Therefore, among the total loads applied to each ball 16, the load (shared load) borne by the ball 16 in the second inner ball groove 24b becomes smaller than the load (shared load) borne by the ball 16 in the first inner ball groove 24a.

[0059] From the above, in the high torque region where the torque input to the constant velocity joint 10 is relatively high, the shared load of the balls 16 in the second groove portion 32 becomes smaller than the shared load of the balls 16 in the first groove portion 30. That is, the load applied to the balls 16 sandwiched by the second outer ball groove 22b and the second inner ball groove 24b becomes smaller than the load applied to the balls 16 sandwiched by the first outer ball groove 22a and the first inner ball groove 24a. Therefore, when the opening angle β in the second groove portion 32 approaches zero degrees (0 deg) and the balls 16 are temporarily locked, the energy accumulated in the balls 16 becomes smaller. As a result, abnormal noises and vibrations generated when the lock of the balls 16 in the second groove portion 32 is released are suppressed.

[0060] FIG. 10 is a table summarizing the effects obtained by varying the radii of curvature R of the outer ball groove 22 and the inner ball groove 24 between the first groove portion 30 and the second groove portion 32. As shown in FIG. 10, in the constant velocity joint 10, in the low torque region, the ball groove clearances Gapo1 and Gapi1 in the first groove portion 30 are larger than the ball groove clearances Gapo2 and Gapi2 in the second groove portion 32. Therefore, in the constant velocity joint 10, the shared load of the balls 16 in the second groove portion 32 is larger than the shared load of the balls 16 in the first groove portion 30. In this case, the original effects of the constant velocity joint 10, namely, high efficiency of torque transmission and reduction of idle vibration, can be obtained.

[0061] Also, in the high torque region, the ball groove clearances Gapo2 and Gapi2 in the second groove portion 32 are larger than the ball groove clearances Gapo1 and Gapi1 in the first groove portion 30. Therefore, in the constant velocity joint 10, the shared load of the balls 16 in the first groove portion 30 is larger than the shared load of the second groove portion 32. At this time, since the load applied to the balls 16 in the second groove portion 32 decreases compared to the load applied to the balls 16 in the first groove portion 30, the energy accumulated in the balls 16 when the balls 16 in the second groove portion 32 are locked decreases. As a result, the abnormal noise and vibration (NV) generated when the balls 16 in the second groove portion 32 are released are suppressed.

[0062] As described above, according to this embodiment, when the outer ball groove 22 of the outer race 12 that constitutes the second groove portion 32 is cut by a plane perpendicular to the center line CL1, the radius of curvature Ro2 of the second outer ball groove 22b is formed larger than the radius of curvature Ro1 of the first outer ball groove 22a that constitutes the first groove portion 30. At the same time, when the inner ball groove 24 of the inner race 14 that constitutes the second groove portion 32 is cut by a plane perpendicular to the center line CL2, the radius of curvature Ri2 of the second inner ball groove 24b is formed larger than the radius of curvature Ri1 of the first inner ball groove 24a that constitutes the first groove portion 30. Therefore, under the condition that a high torque is applied to the constant velocity joint 10 and the load on the ball 16 increases, the load on the ball 16 on the second groove portion 32 side can be reduced. As a result, the abnormal noise and vibration generated when the lock of the ball 16 in the second groove portion 32 is released can be suppressed.

[0063] Further, according to this embodiment, when the joint angle θ of the second groove portion 32 becomes a predetermined angle θ2 or more, the opening angle β in the second groove portion 32 crosses zero. Therefore, the ball 16 in the second groove portion 32 locks in the range where the opening angle β includes zero. At this time, even when the torque applied to the constant velocity joint 10 is in a high torque state, by reducing the load on the ball 16 on the second groove portion 32 side, the abnormal noise and vibration generated when the lock of the ball 16 in the second groove portion 32 is released can be suppressed.

[0064] As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is also applicable in other aspects.

[0065] For example, in the foregoing embodiment, the radius of curvature Ro2 of the second outer ball groove 22b of the second groove portion 32 is larger than the radius of curvature Ro1 of the first outer ball groove 22a of the first groove portion 30, and the radius of curvature Ri2 of the second inner ball groove 24b of the second groove portion 32 is larger than the radius of curvature Ri1 of the first inner ball groove 24a of the first groove portion 30. However, the present invention is not necessarily limited to this aspect. Specifically, it is sufficient if either one of the following is satisfied: the radius of curvature Ro2 of the second outer ball groove 22b of the second groove portion 32 is formed to be larger than the radius of curvature Ro1 of the first outer ball groove 22a of the first groove portion 30, and the radius of curvature Ri2 of the second inner ball groove 24b of the second groove portion 32 is formed to be larger than the radius of curvature Ri1 of the first inner ball groove 24a of the first groove portion 30.

[0066] Note that the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0067] 10: Constant velocity joint 12: Outer race 12a: Inner peripheral surface 14: Inner race 14a: Outer peripheral surface 16: Ball 22: Outer ball groove 24: Inner ball groove 30: First groove portion 32: Second groove portion Ri1: Radius of curvature (radius of the arc of the inner ball groove of the first groove portion) Ri2: Radius of curvature (radius of the arc of the inner ball groove of the second groove portion) Ro1: Radius of curvature (radius of the arc of the outer ball groove of the first groove portion) Ro2: Radius of curvature (radius of the arc of the outer ball groove of the second groove portion) θ: Joint angle θ2: Predetermined angle α: Opening angle of the first groove portion β: Opening angle of the second groove portion

Claims

1. A cup-shaped outer race provided with a plurality of outer ball grooves on its inner peripheral surface, an inner race provided with a plurality of inner ball grooves on its outer peripheral surface and disposed inside the outer race, and a plurality of balls interposed between the outer ball grooves and the inner ball grooves for torque transmission. And in a reference state where the joint angle with a joint angle of zero degrees in which the center lines of the outer race and the inner race are located on a straight line, the tangent line between the outer ball groove and the ball and the tangent line between the inner ball groove and the ball intersect. A first groove portion in which the opening angle formed thereby opens toward the cup opening side of the outer race, and a second groove portion in which the opening angle opens toward the cup bottom side of the outer race. When the joint angle formed by the intersection of the center line of the outer race and the center line of the inner race becomes a predetermined angle or more, the opening angle in the second groove portion is configured to straddle zero. A constant velocity joint, The radius of the arc of the outer ball groove of the outer race constituting the second groove portion is formed larger than the radius of the arc of the outer ball groove constituting the first groove portion when the outer ball groove is cut by a plane perpendicular to the center line of the outer race, and, The radius of the arc of the inner ball groove of the inner race constituting the second groove portion is formed larger than the radius of the arc of the inner ball groove constituting the first groove portion when the inner ball groove is cut by a plane perpendicular to the center line of the inner race. At least one of them is satisfied A constant velocity joint characterized by the above.

2. When the outer ball groove of the outer race constituting the second groove portion is cut by a plane perpendicular to the center line of the outer race, the radius of the arc of the outer ball groove is formed larger than the radius of the arc of the outer ball groove constituting the first groove portion, and The radius of the arc of the inner ball groove of the inner race constituting the second groove portion is formed larger than the radius of the arc of the inner ball groove constituting the first groove portion when the inner ball groove is cut by a plane perpendicular to the center line of the inner race The constant velocity joint according to claim 1, characterized by the above.

Images