Tripod constant velocity joint

Abstract

A tripod constant velocity joint is provided with an outer ring, a tripod, and a plurality of roller units (30), each of the plurality of roller units (30) having an outer roller (31), an inner roller, and a cylindrical needle (33) sandwiched between the outer roller (31) and the inner roller, the number (A) of the needle (33), the needle diameter (B), and the circumferential gap (C) being values satisfying the following formula (1): [C / (A * B + C)] * 100 > = 0.678... (1).

Description

Technical Field

[0001] The present disclosure relates to a tripod constant velocity joint. Background Art

[0002] Such a tripod constant velocity joint is disclosed in Patent Document 1 below. The roller unit constituting the tripod constant velocity joint has an outer roller, an inner roller, and a cylindrical rolling element sandwiched between the outer roller and the inner roller. In order to suppress the generation of a forced force caused by a change in the universal joint angle, the tripod constant velocity joint is configured such that the clearance between the inner roller and the restricting portion on the outer roller side is larger than the reciprocating movement force between the trunnion and the inner roller under the common angle of the universal joint and smaller than the convex surface length of the rolling element.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-190250 Summary of the Invention

[0006] The above-described tripod constant velocity joint prevents the inner roller from coming into contact with the restricting portion by optimizing the clearance between the inner roller and the restricting portion on the outer roller side, thereby suppressing the forced force applied from the inner roller. However, there is a need for a technique to further suppress the forced force in order to improve quietness.

[0007] The present disclosure provides a tripod constant velocity joint having excellent quietness.

[0008] One aspect of the present disclosure is a tripod constant velocity joint including: an outer ring having a plurality of raceways extending in the axial direction; a tripod having three shaft portions; and a plurality of roller units formed in a ring shape and rotatably supported on the three shaft portions respectively, and rolling in respective ones of the plurality of raceways, wherein each of the plurality of roller units has an outer roller, an inner roller, and a cylindrical needle roller sandwiched between the outer roller and the inner roller, and the number of needle rollers, the needle diameter, and the circumferential clearance of the needle rollers are values satisfying the following formula (1): [C / (A×B + C)]×100 ≥ 0.678…(1).

[0009] Advantages of the Invention

[0010] The tripod constant velocity joint according to the above-described method can expand the circumferential clearance of the needle rollers by setting the number of needle rollers, the diameter of the needle rollers, and the circumferential clearance to values that satisfy formula (1). Thereby, the force applied from the inner roller during the rotational movement of the tripod constant velocity joint can be suppressed, and the quietness can be improved to a desired level.

[0011] Therefore, according to the above-described method, a tripod constant velocity joint with excellent quietness can be provided.

[0012] It should be noted that the reference numerals in parentheses described in the claims indicate the correspondence with the specific components described in the following embodiments, and do not limit the technical scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above object and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. Regarding the accompanying drawings, Figure 1 is an axial perspective view of a constant velocity joint assembly including the tripod constant velocity joint of Embodiment 1, Figure 2 is a cross-sectional view seen from the opening side of the outer race, Figure 1 of, Figure 3 is a cross-sectional view showing an enlarged view of the peripheral portion of the roller unit located on the torque transmission side in the width direction of the raceway groove in Figure 2 above, Figure 4 is a diagram schematically showing the circumferential clearance of the needle rollers, Figure 5 is a graph showing the relationship between the value on the left side of formula (1) and the applied force, Figure 6 is a graph showing the relationship between the value on the left side of formula (2) and the applied force. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Hereinafter, a tripod constant velocity joint as an embodiment of the above-described method will be described with reference to the accompanying drawings.

[0015] It should be noted that in the present specification and the accompanying drawings, unless otherwise specified, the axial direction of the outer race is defined as the X-axis direction, the axial direction of the needle rollers constituting the roller unit is defined as the Y-axis direction, and the direction in which the needle rollers are arranged, i.e., the circumferential direction of the needle rollers, is defined as the Z-axis direction.

[0016] (Embodiment 1)

[0017] Figure 1The tripod constant velocity joint 101 of the illustrated Embodiment 1 is used, for example, in a power transmission shaft of a vehicle. At this time, the constant velocity joint 101, together with the shaft 102 and the protective cover 103, forms a constant velocity joint assembly 101A. This constant velocity joint assembly 101A is used in a connecting portion between a differential and a wheel (both not shown).

[0018] 1. Structure of the tripod constant velocity joint 101

[0019] As Figure 1 shown, the tripod constant velocity joint (hereinafter simply referred to as "constant velocity joint") 101 includes an outer race 10, a tripod 20, and three roller units 30.

[0020] The outer race 10 is formed in a bottomed cylindrical shape having an opening 10a on one end side in its axial direction X. On the other hand, the outer race 10 may also be formed in a cylindrical shape penetrating in the axial direction X. The outside of the bottom surface of the outer race 10 is connected to the differential. On the inner peripheral surface of the outer race 10, three raceway grooves 11 extending in the axial direction X are formed at equal intervals in the circumferential direction from the opening 10a of the outer race 10 toward the inside ( Figure 1 the left side).

[0021] The tripod 20 is movable along the axial direction X and tiltable relative to the outer race 10. The tripod 20 includes a boss 21 and three shaft portions (also referred to as "tripod shaft portions") 22 extending radially outward from the boss 21. The outer peripheral surface of each shaft portion 22 is formed in a spherical convex shape. That is, the axial cross-sectional shape of the outer peripheral surface of the shaft portion 22 is formed in an arc convex shape.

[0022] The shaft 102 is connected to the boss 21 of the tripod 20. In a state where an angle is given to the shaft 102 and the outer race 10, torque is transmitted between the shaft 102 and the outer race 10 via the tripod 20 and the roller unit 30. At this time, the angle formed by the shaft 102 and the outer race 10 is referred to as the "joint angle" of the constant velocity joint 101.

[0023] The protective cover 103 is formed in a corrugated cylindrical shape that can expand and contract along the axial direction X and can bend. One end portion of the protective cover 103 in the axial direction X is attached to the opening 10a side of the outer peripheral surface of the outer race 10, and the other end portion in the axial direction X is attached to the outer peripheral surface of the shaft 102. In this way, the protective cover 103 closes the opening 10a side of the outer race 10. The protective cover 103 has a function of sealing so that the grease accommodated in the inner region of the outer race 10 does not leak from the opening 10a of the outer race 10.

[0024] 2. Structure of the roller unit 30

[0025] As Figure 2As shown, the roller unit 30 is formed in a ring shape. The roller unit 30 can rotate on the outer peripheral side of each of the three shaft portions 22, can slide in the axial direction of each of the shaft portions 22, and is supported so as to be able to tilt relative to the shaft portions 22 respectively. Further, the three roller units 30 are respectively arranged so as to be able to roll along the three raceway grooves 11. Therefore, the three roller units 30 are configured to roll relative to the three raceway grooves 11 while maintaining their postures.

[0026] The roller unit 30 includes an outer roller 31, an inner roller 32, a needle roller 33, and a snap ring 34. The inner roller 32 is disposed inside the outer roller 31. The inner roller 32 is configured such that its inner peripheral surface 32a contacts the outer peripheral surface of the shaft portion 22. The needle roller 33 is a cylindrical rolling element sandwiched radially between the outer roller 31 and the inner roller 32. The snap ring 34 is fixed to the inner peripheral surface of the outer roller 31. The snap ring 34 is an anti-drop member that prevents the inner roller 32 and the needle roller 33 from dropping off the outer roller 31 in the needle roller axial direction Y. The snap ring 34 is also referred to as a "circlip". In this way, the roller unit 30 having a structure in which two rollers (the outer roller 31 and the inner roller 32) are overlapped and arranged in the radial direction is a roller unit generally referred to as a "double-roller type".

[0027] The outer ring 10 has a bottom portion 12 and groove side surfaces 13 on both sides in the groove width direction ( Figure 2 the left-right direction) of the raceway groove 11 with respect to the bottom portion 12. A transmission surface 13a for transmitting torque by contacting the outer peripheral surface (the outer peripheral surface 31a of the outer roller 31) of the roller unit 30 is formed on the groove side surface 13. The cross-sectional shape of the transmission surface 13a is a concave shape with a specified curvature or a combination of multiple curvatures.

[0028] The roller unit 30 is arranged such that the outer peripheral surface 31a of the outer roller 31 fits on the two transmission surfaces 13a. The roller unit 30 is configured such that when the outer ring 10 rotates, according to the rotation direction, the outer peripheral surface 31a of the outer roller 31 contacts one of the two transmission surfaces 13a of the raceway groove 11, and torque is transmitted between the outer ring 10. That is, by switching the rotation direction of the outer ring 10, the surface that contacts the outer peripheral surface 31a of the outer roller 31 among the two transmission surfaces 13a is switched.

[0029] Here, the side in the groove width direction of the raceway groove 11 where torque is transmitted between the raceway groove 11 and the roller unit 30 when the outer ring 10 rotates is defined as the "torque transmission side". In addition, the side opposite to the torque transmission side, that is, the side opposite to the side where torque is transmitted between the raceway groove 11 and the roller unit 30, is defined as the "reverse torque transmission side".

[0030] A support surface 12a that faces one end surface 31b of the outer roller 31 is provided at a specified position on the bottom 12 of the raceway groove 11. This support surface 12a contacts the roller unit 30 that moves obliquely with the torque transmission of the constant velocity universal joint 101 on the reverse torque transmission side, and functions to support the roller unit 30.

[0031] In the constant velocity universal joint 101 of this embodiment, the roller unit 30 is provided with two clearance expansion structures 30a and 30b for expanding the clearance around the needle roller 33. Hereinafter, with reference to Figures 3 to 6 These two clearance expansion structures 30a and 30b will be described.

[0032] 3. Clearance expansion structure 30a

[0033] As Figure 3 shown, a flange portion 31c that faces the snap ring 34 along the needle roller axis Y is provided on the outer roller 31 of the roller unit 30. The inner roller 32 and the needle roller 33 are both installed in the space between the flange portion 31c of the outer roller 31 and the snap ring 34. Therefore, the flange portion 31c functions as a restricting portion that restricts the movement of the inner roller 32 and the needle roller 33 in the needle roller axis Y direction.

[0034] The clearance expansion structure 30a is a structure in which the dimension Y1 of the clearance in the needle roller axis Y between the needle roller 33 and the snap ring 34 is greater than or equal to the dimension Y2 of the clearance in the needle roller axis Y between the inner roller 32 and the snap ring 34. That is, the value of the dimension Y1 can be a value that is the same as the dimension Y2, or can also be a value that exceeds the dimension Y2.

[0035] Here, the dimension Y1 is defined as the dimension of the clearance formed between the other end surface 33b of the needle roller 33 and the snap ring 34 when one end surface 33a of the needle roller 33 in the needle roller axis Y abuts against the flange portion 31c of the outer roller 31. Similarly, the dimension Y2 is defined as the dimension of the clearance formed between the other end surface 32c of the inner roller 32 and the snap ring 34 when one end surface 32b of the inner roller 32 in the needle roller axis Y abuts against the flange portion 31c of the outer roller 31.

[0036] According to such a clearance expansion structure 30a, the clearance in the needle roller axis Y formed between the needle roller 33 and the snap ring 34 can be expanded. Thereby, the contact frequency of the one end surface 33a of the needle roller 33 contacting the flange portion 31c of the outer roller 31 or the other end surface 33b of the needle roller 33 contacting the snap ring 34 can be reduced. Therefore, the rotational resistance of the needle roller 33 can be reduced.

[0037] 4. Clearance expansion structure 30b

[0038] As Figure 4As shown, when the number of needles of the needle roller 33 is set to A, the diameter of the needle of the needle roller 33 is set to B, and the circumferential clearance C in the circumferential direction Z of the needle of the needle roller 33 is set, the clearance expansion structure 30b is a structure that sets the number of needles A, the needle diameter B, and the circumferential clearance C to values that satisfy the following formula (1).

[0039] In Figure 4 , the pitch circle diameter of the needle roller is set to D1, the inner diameter of the outer roller 31 is set to D2. Additionally, for ease of explanation, the needle roller 33 is schematically shown. It should be noted that the circumferential clearance C of the needle roller 33 is defined as the clearance formed at one place when all the needle rollers 33 are gathered along the circumferential direction Z of the needle roller.

[0040] [C / (A×B + C)]×100 ≥ 0.678…(1)

[0041] Here, formula (1) is derived by the inventor of the present application based on the evaluation results of actually using the constant velocity universal joint 101. On the left side of formula (1), the term equivalent to (A×B + C) is a term that approximately represents the pitch length of the arc of the needle roller pitch circle by simply using the needle diameter B as the straight line length.

[0042] As Figure 5 shown, the inventor of the present application actually measured the forced force N applied from the inner roller 32 when the value of the circumferential clearance C of the needle roller 33 was changed in various ways using a known vibration measuring instrument. At this time, the circumferential clearance C of the needle roller 33 can vary depending on the parameters of the number of needles A, the needle diameter B, and the needle roller pitch circle diameter D1 as shown in the following formula (1a). Therefore, by appropriately changing the combination of the values of these parameters, the value of the circumferential clearance C of the needle roller 33 can be changed.

[0043] C = {[D1×sin(π / A)] - B}×A…(1a)

[0044] It should be noted that when the constant velocity universal joint 101 rotates in a torque load state with a universal joint angle, the vibration forced force caused by the frictional force generated between the three shaft portions 22 of the three ball pins 20 and the roller unit 30 is a vibration forced force that rotates three times based on the situation where vibrations occur three times during one rotation. Therefore, in this method, the vibration forced force that rotates three times is actually measured as the forced force N. This vibration forced force changes with the change of the universal joint angle and is generated by the contact between the inner roller 32 and the flange portion 31c of the outer roller 31.

[0045] The inventors of the present application have found that, based on the above evaluation results, when the force N in the measured value (marked with ○) is lower than the threshold value Nth, that is, when the left side value of formula (1) is 0.678 or more, it has a high effect of suppressing the force N and is effective in reducing the vehicle's quietness to the desired level. If the clearance expansion structure 30b is adopted, the vibration transmitted to the vehicle body via the shaft 102 during the rotational movement of the constant velocity joint 101 is suppressed to a low level, thereby ensuring the quietness of the vehicle.

[0046] It should be noted that in the clearance expansion structure 30b, instead of using the above formula (1), the circumferential clearance C of the needle roller 33 and the needle roller pitch circle diameter D1 can be set to values that satisfy the following formula (2).

[0047] [C / (D1×π)]×100≥0.678…(2)

[0048] Here, similar to formula (1), formula (2) is derived based on the evaluation results of the inventors of the present application actually evaluating the constant velocity joint 101. In the left side of formula (2), the term equivalent to (D1×π) is the arc length. Therefore, compared with the term (A×B + C) equivalent to the left side of formula (1) that uses the needle roller diameter B as the straight line length, the pitch length can be derived more strictly.

[0049] As Figure 6 shown, the measured value (marked with △) is substantially the same as the measured value (marked with ○) in Figure 5 . Therefore, it is confirmed that the measured value of the force N in the measured value (marked with △) in Figure 6 is lower than the measured value of the threshold value Nth, that is, when the left side value of formula (2) is 0.678 or more, similar to the case of Figure 5 , it has a high effect of suppressing the force N and is effective in reducing the vehicle's quietness to the desired level. That is, the left side value of formula (1) is substantially the same as the left side value of formula (2), and in either formula, the lower limit value is set to 0.678.

[0050] It should be noted that the circumferential clearance C of the needle roller 33 will not be a size more than that of one needle roller 33. Therefore, it is preferable to set the value of the needle roller diameter B equivalent to the needle roller 33 as the upper limit value of the circumferential clearance C. Of course, an appropriate value lower than the needle roller diameter B can also be used as the upper limit value.

[0051] 5. Function and effect

[0052] Next, the function and effect of the above Embodiment 1 will be described.

[0053] The roller unit 30 of the constant velocity universal joint 101 of the above-described Embodiment 1 includes two clearance expansion structures 30a and 30b. By adopting these two clearance expansion structures 30a and 30b, it is possible to expand both the clearance in the needle axial direction Y and the clearance in the needle circumferential direction Z of the needle rollers 33. Thereby, it is possible to suppress the force N applied by the inner roller 32 during the rotation of the constant velocity universal joint 101 and improve the quietness to a desired level. These two clearance expansion structures 30a and 30b are highly versatile structures that can be applied regardless of changes in the dimensions of the constant velocity universal joint 101 and the like.

[0054] The present disclosure has been described based on the above-described manner, but the present disclosure is understood not to be limited to this manner and structure. The present disclosure also includes various modifications and modifications within an equivalent range. In addition, various combinations, forms, and other combinations and forms including only one element, more than one element, or less than one element also fall within the scope and the scope of the idea of the present disclosure.

[0055] In the above-described manner, the case where two clearance expansion structures 30a and 30b are provided in the roller unit 30 is illustrated. However, instead, only the clearance expansion structure 30b may be provided in the roller unit 30. The clearance expansion structure 30b is particularly excellent in suppressing the force N applied by the inner roller 32 during the rotation of the constant velocity universal joint 101.

[0056] In the above-described manner, the constant velocity universal joint 101 for a power transmission shaft of a vehicle is illustrated. However, the constant velocity universal joint 101 may be applied to a steering operation shaft (steering gear) of a vehicle.

Claims

1. A tripod constant velocity joint (101) comprising: An outer ring (10) having a plurality of raceways (11) extending in the axial direction (X); A tripod (20) having three shaft portions (22); and A plurality of roller units (30) formed in a ring shape, rotatably supported on the three shaft portions respectively, and rolling in respective ones of the plurality of raceways. Each of the plurality of roller units has an outer roller (31), an inner roller (32), and cylindrical needle rollers (33) sandwiched between the outer roller and the inner roller. The number A of the needle rollers, the diameter B of the needle rollers, and the circumferential clearance C of the needle rollers are values satisfying the following formula (1): [C / (A×B + C)]×100 ≥ 0.678…(1).

2. The tripod constant velocity joint according to claim 1, wherein Each of the plurality of roller units is configured such that a value corresponding to the diameter of the needle roller is the upper limit value of the circumferential clearance.

3. The tripod constant velocity joint according to claim 1 or 2, wherein Each of the plurality of roller units has a snap ring (34) that prevents the inner roller and the needle rollers from coming off in the axial direction (Y) of the needle rollers relative to the outer roller. The dimension (Y1) of the clearance in the axial direction of the needle rollers between the needle rollers and the snap ring is greater than or equal to the dimension (Y2) of the clearance in the axial direction of the needle rollers between the inner roller and the snap ring.

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