Tripod type constant velocity joint
By optimizing the number, diameter, and circumferential gap of needles in the tripod constant velocity joint, the joint achieves reduced noise and vibration through expanded gaps, addressing the suppression of forced forces.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- JTEKT CORP
- Filing Date
- 2023-01-23
- Publication Date
- 2026-06-23
AI Technical Summary
Existing tripod constant velocity joints fail to adequately suppress forced forces during rotational operations, leading to noise and vibration issues.
The tripod constant velocity joint is designed with specific settings for the number of needles, needle diameter, and circumferential gap that satisfy the equation [C/(A×B+C)]×100≧0.678, expanding the gaps around the needles to reduce contact frequency and rotational resistance.
This design effectively suppresses the coercive force applied during rotation, enhancing quietness and reducing noise and vibration in vehicles.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a tripod constant velocity joint.
Background Art
[0002] The following Patent Document 1 discloses this type of tripod constant velocity joint. The roller unit constituting this tripod constant velocity joint has an outer roller, an inner roller, and a columnar rolling element sandwiched between the outer roller and the inner roller. In order to suppress the generation of a forced force due to a change in the joint angle, this tripod constant velocity joint is configured such that the gap between the inner roller and the regulating portion on the outer roller side is larger than the reciprocating movement force between the trunnion and the inner roller at the normal joint angle and smaller than the crowning length of the rolling element.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
[0004] The above-mentioned tripod constant velocity joint attempts to suppress the forced force applied from the inner roller by optimizing the gap between the inner roller and the regulating portion on the outer roller side and preventing the inner roller from contacting the regulating portion. However, in order to improve quietness, a technique for further suppressing the forced force is required.
[0005] The present disclosure aims to provide a tripod constant velocity joint with excellent quietness.
[0006] One aspect of the present disclosure is an outer ring having a plurality of raceways extending in the axial direction, a tripod having three shaft portions, A plurality of roller units formed in an annular shape, rotatably supported on each of the three shaft portions, and each rolling in each of the plurality of raceway grooves, Equipped with, Each of the aforementioned roller units has an outer roller, an inner roller, and a cylindrical needle sandwiched between the outer roller and the inner roller. The number of needles, needle diameter, and circumferential gap of the aforementioned needle are set to values that satisfy the following equation (1), in a tripod-type constant velocity joint, It is located there. [C / (A×B+C)]×100≧0.678···(1) [Effects of the Invention]
[0007] According to the tripod-type constant velocity joint of the above embodiment, the circumferential gap of the needles can be expanded by setting the number of needles, needle diameter, and circumferential gap of the needles to values that satisfy equation (1). This suppresses the coercive force applied from the inner roller during the rotational operation of the tripod-type constant velocity joint, thereby increasing the quietness to a desired level.
[0008] Therefore, according to the above embodiment, a tripod-type constant velocity joint with excellent quietness can be provided.
[0009] The symbols in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of this disclosure. [Brief explanation of the drawing]
[0010] The purposes, other purposes, features, and benefits of this disclosure described above will become clearer from the following detailed description, which is accompanied by the attached drawings. [Figure 1] Figure 1 is an axial perspective view of a constant velocity joint assembly including a tripod-type constant velocity joint according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view of Figure 1, seen from the opening side of the outer ring. [Figure 3] 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. [Figure 4] Figure 4 is a schematic diagram showing the circumferential gap of the needle. [Figure 5] Figure 5 is a graph showing the correlation between the value on the left side of equation (1) and the forcing force. [Figure 6] Figure 6 is a graph showing the correlation between the value on the left side of equation (2) and the forcing force. [Modes for carrying out the invention]
[0011] Below, a tripod-type constant velocity joint, which is one embodiment of the above-described aspect, will be explained with reference to the drawings.
[0012] In this specification and drawings, unless otherwise specified, the axial direction of the outer ring is defined as the X-axis direction, the needle axis direction of the needles constituting the roller unit is defined as the Y-axis direction, and the needle circumferential direction, which is the direction in which the needles are arranged, is defined as the Z-axis direction.
[0013] (Embodiment 1) The tripod-type constant velocity joint 101 of Embodiment 1, shown in Figure 1, is used, for example, in the power transmission shaft of a vehicle. In this case, the constant velocity joint 101, together with the shaft 102 and the boot 103, forms a constant velocity joint assembly 101A. This constant velocity joint assembly 101A is used at the connection points of the differential and the wheels (neither of which are shown).
[0014] 1. Structure of the tripod-type constant velocity joint 101 As shown in Figure 1, the tripod-type constant velocity joint (hereinafter simply referred to as "constant velocity joint") 101 comprises an outer ring 10, a tripod 20, and three roller units 30.
[0015] The outer ring 10 is formed in a bottomed cylindrical shape having an opening 10a at one end side in the axial direction X. On the other hand, the outer ring 10 may be formed in a cylindrical shape penetrating in the axial direction X. The outside of the bottom surface of the outer ring 10 is connected to the differential. On the inner peripheral surface of the outer ring 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 ring 10 toward the back side (the left side in FIG. 1).
[0016] The tripod 20 is movable in the axial direction X and tiltable with respect to the outer ring 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.
[0017] The shaft 102 is connected to the boss 21 of the tripod 20. Torque transmission is performed between the shaft 102 and the outer ring 10 via the tripod 20 and the roller unit 30 in a state where an angle is given to the shaft 102 and the outer ring 10. At this time, the angle formed by the shaft 102 and the outer ring 10 is referred to as the "joint angle" of the constant velocity joint 101.
[0018] The boot 103 is formed in a bellows cylindrical shape that is stretchable and bendable in the axial direction X. One end portion of the boot 103 in the axial direction X is attached to the opening 10a side of the outer peripheral surface of the outer ring 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 boot 103 closes the opening 10a side of the outer ring 10. The boot 103 has a function of sealing so that the grease accommodated in the inner region of the outer ring 10 does not leak from the opening 10a of the outer ring 10.
[0019] 2. Structure of the roller unit 30 As shown in Figure 2, the roller unit 30 is formed in an annular shape. The roller unit 30 is rotatable on the outer circumference of each of the three shaft portions 22, slidable in the axial direction of each of the shaft portions 22, and tiltable relative to each of the shaft portions 22. Furthermore, each of the three roller units 30 is arranged to roll along each of the three raceway grooves 11. Thus, the three roller units 30 are configured to roll while maintaining their orientation relative to the three raceway grooves 11.
[0020] The roller unit 30 includes an outer roller 31, an inner roller 32, a needle 33, and a retaining ring 34. The inner roller 32 is positioned inside the outer roller 31. The inner roller 32 is configured such that its inner circumferential surface 32a contacts the outer circumferential surface of the shaft portion 22. The needle 33 is a cylindrical rolling element sandwiched radially between the outer roller 31 and the inner roller 32. The retaining ring 34 is locked to the inner circumferential surface of the outer roller 31. This retaining ring 34 is a retaining member that prevents the inner roller 32 and the needle 33 from coming off the outer roller 31 in the needle axis direction Y. The retaining ring 34 is also called a "snap ring". A roller unit 30 with a structure in which two rollers (outer roller 31 and inner roller 32) are arranged radially in overlapping positions is generally called a "double roller type" roller unit.
[0021] The outer ring 10 has a bottom portion 12 and groove side surfaces 13 located on both sides of the groove width direction (left-right direction in Figure 2) of the raceway groove 11 relative to the bottom portion 12. A transmission surface 13a is formed on the groove side surfaces 13 that transmits torque by contact with the outer circumferential surface of the roller unit 30 (outer circumferential surface 31a of the outer roller 31). The cross-sectional shape of the transmission surface 13a is concave, which is a predetermined curvature or a combination of multiple curvatures.
[0022] The roller unit 30 is arranged such that the outer circumferential surface 31a of the outer roller 31 is fitted into two transmission surfaces 13a. The roller unit 30 is configured such that when the outer ring 10 rotates, the outer circumferential surface 31a of the outer roller 31 contacts one of the two transmission surfaces 13a of the raceway groove 11 according to the direction of rotation, thereby transmitting torque between the roller unit 30 and the outer ring 10. In other words, when the direction of rotation of the outer ring 10 changes, the surface to which the outer circumferential surface 31a of the outer roller 31 contacts among the two transmission surfaces 13a changes.
[0023] Here, in the groove width direction of the raceway groove 11, the side on which torque is transmitted between the raceway groove 11 and the roller unit 30 when the outer ring 10 rotates is referred to as the "torque transmission side." Conversely, the side opposite to the torque transmission side, and on the opposite side from where torque is transmitted between the raceway groove 11 and the roller unit 30, is referred to as the "anti-torque transmission side."
[0024] A support surface 12a is provided at a predetermined position on the bottom 12 of the raceway groove 11, facing one end face 31b of the outer roller 31. This support surface 12a contacts the roller unit 30, which tilts in conjunction with the torque transmission of the constant velocity joint 101, on the side opposite to the torque transmission, and serves to support the roller unit 30.
[0025] In this embodiment of the constant velocity joint 101, the roller unit 30 is equipped with two gap expansion structures 30a and 30b for expanding the gap around the needle 33. These two gap expansion structures 30a and 30b will be described below with reference to Figures 3 to 6.
[0026] 3. Gap expansion structure 30a As shown in Figure 3, the outer roller 31 of the roller unit 30 is provided with a retaining ring 34 and a flange portion 31c facing the needle axis direction Y. The inner roller 32 and the needle 33 are both interposed in the space between the flange portion 31c of the outer roller 31 and the retaining ring 34. Therefore, the flange portion 31c functions as a restricting part that restricts the movement of the inner roller 32 and the needle 33 in the needle axis direction Y.
[0027] The gap expansion structure 30a is a structure in which the dimension Y1 of the gap in the needle axis direction Y between the needle 33 and the retaining ring 34 is set to be greater than or equal to the dimension Y2 of the gap in the needle axis direction Y between the inner roller 32 and the retaining ring 34. That is, the value of dimension Y1 may be the same as dimension Y2, or it may be a value greater than dimension Y2.
[0028] Here, dimension Y1 is defined as the dimension of the gap formed between the other end face 33b of the needle 33 in the needle axis direction Y and the retaining ring 34 when one end face 33a of the needle 33 in the needle axis direction Y is brought into contact with the flange 31c of the outer roller 31. Similarly, dimension Y2 is defined as the dimension of the gap formed between the other end face 32c of the inner roller 32 in the needle axis direction Y and the retaining ring 34 when one end face 32b of the inner roller 32 in the needle axis direction Y is brought into contact with the flange 31c of the outer roller 31.
[0029] This gap expansion structure 30a allows for the expansion of the gap in the needle axis direction Y formed between the needle 33 and the retaining ring 34. This reduces the frequency of contact between one end face 33a of the needle 33 and the flange 31c of the outer roller 31, or between the other end face 33b of the needle 33 and the retaining ring 34. Therefore, the rotational resistance of the needle 33 can be reduced.
[0030] 4. Gap expansion structure 30b As shown in Figure 4, when the number of needles in needle 33 is A, the needle diameter of needle 33 is B, and the circumferential gap of needle 33 in the needle circumferential direction Z is C, the gap expansion structure 30b is a structure in which the number of needles A, the needle diameter B, and the circumferential gap C are set to values that satisfy the following equation (1).
[0031] In Figure 4, the needle pitch circle diameter is denoted as D1, and the inner diameter of the outer roller 31 is denoted as D2. For the sake of explanation, the needles 33 are shown schematically. The circumferential gap C of the needles 33 is defined as the gap formed at one location when all the needles 33 are gathered in the circumferential direction Z.
[0032] [C / (A×B+C)]×100≧0.678···(1)
[0033] Here, equation (1) was derived based on evaluation results obtained by the inventors through actual use of the constant velocity joint 101. In the left side of equation (1), the term corresponding to (A × B + C) is an approximation of the pitch length, which is the arc length of the needle pitch circle, by conveniently using the needle diameter B, which is the straight length.
[0034] As shown in Figure 5, the inventors measured the force N applied from the inner roller 32 when the value of the circumferential gap C of the needle 33 was varied using a known vibration measuring instrument. At this time, the circumferential gap C of the needle 33 can change depending on the parameters of the number of needles A, the needle diameter B, and the needle pitch circle diameter D1, as shown in equation (1a) below. Therefore, the value of the circumferential gap C of the needle 33 can be changed by appropriately changing the combination of values of these parameters.
[0035] C=[[D1×sin(π / A)]-B]×A...(1a)
[0036] Furthermore, when the constant velocity joint 101 is rotated under a torque load with a joint angle, the vibration forcing force caused by the frictional force generated between the three shaft portions 22 of the tripod 20 and the roller unit 30 is a rotational third-order vibration forcing force, based on the fact that vibration occurs three times during one rotation. Therefore, in this embodiment, the rotational third-order vibration forcing force is measured as the forcing force N. This vibration forcing force is generated when the inner roller 32 comes into contact with the flange portion 31c of the outer roller 31 as the joint angle changes.
[0037] Based on the above evaluation results, the inventors have found that among the measured values (○ plot), those in which the forcing force N is below the threshold Nth, that is, those in which the value on the left side of equation (1) is 0.678 or higher, have a high effect in suppressing the forcing force N and are effective in reducing the vehicle's quietness to a desired level. By adopting the gap expansion structure 30b, the vibration transmitted to the vehicle body via the shaft 102 during the rotational operation of the constant velocity joint 101 is kept low, thereby ensuring the quietness of the vehicle.
[0038] In addition, in the gap expansion structure 30b, instead of using equation (1) above, the circumferential gap C of the needle 33 and the needle pitch circle diameter D1 may be set to values that satisfy equation (2) below.
[0039] [C / (D1×π)]×100≧0.678···(2)
[0040] Here, equation (2), like equation (1), was derived based on evaluation results obtained by the inventors through actual use of the constant velocity joint 101. In the left side of equation (2), the term corresponding to (D1 × π) is the arc length, so the pitch length can be derived more precisely compared to the term corresponding to (A × B + C) on the left side of equation (1), which uses the needle diameter B, which is the straight length.
[0041] As shown in Figure 6, the measured values (△ plots) generally coincide with the measured values (○ plots) in Figure 5. Therefore, among the measured values (△ plots) in Figure 6, those in which the forcing force N is below the threshold Nth, i.e., those in which the value of the left side of equation (2) is 0.678 or higher, were confirmed to have a high effect in suppressing the forcing force N, similar to the case in Figure 5, and were effective in reducing the vehicle's quietness to the desired level. In other words, the value of the left side of equation (1) and the value of the left side of equation (2) generally coincide, and in both equations, the lower limit is set to 0.678.
[0042] Furthermore, the circumferential gap C of the needle 33 will never exceed the size of one needle 33. For this reason, it is preferable to set the upper limit of the circumferential gap C to a value corresponding to the needle diameter B of the needle 33. Of course, any appropriate value less than the needle diameter B may also be set as the upper limit.
[0043] 5. Effects Next, the effects and advantages of the above-described embodiment 1 will be explained.
[0044] The constant velocity joint 101 of the above-described embodiment 1 is equipped with two gap expansion structures 30a and 30b in the roller unit 30. By employing these two gap expansion structures 30a and 30b, both the gap in the needle axis direction Y and the gap in the needle circumferential direction Z of the needle 33 can be expanded. This suppresses the coercive force N applied from the inner roller 32 during the rotational operation of the constant velocity joint 101, thereby increasing quietness to a desired level. These two gap expansion structures 30a and 30b are highly versatile structures that can be applied regardless of changes in the size of the constant velocity joint 101.
[0045] While this disclosure is written in accordance with the form described above, it is understood that this disclosure is not limited to that form or structure. This disclosure also includes various variations and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include one, more, or fewer of those elements, fall within the scope and idea of this disclosure.
[0046] In the above-described embodiment, an example was given in which the roller unit 30 is provided with two gap expansion structures 30a and 30b, but instead, the roller unit 30 may be provided with only the gap expansion structure 30b. The gap expansion structure 30b is particularly excellent at suppressing the coercive force N applied from the inner roller 32 when the constant velocity joint 101 is rotating.
[0047] In the above-described embodiment, a constant velocity joint 101 used in the power transmission shaft of a vehicle was given as an example, but this constant velocity joint 101 may also be applied to the steering shaft of a vehicle.
Claims
1. An outer ring (10) having multiple raceway grooves (11) extending in the axial direction (X), A tripod (20) having three shaft portions (22), A plurality of roller units (30) are formed in an annular shape, rotatably supported on each of the three shaft portions, and each rolls in each of the plurality of raceway grooves, Equipped with, Each of the aforementioned roller units has an outer roller (31), an inner roller (32), and a cylindrical needle (33) sandwiched between the outer roller and the inner roller. A tripod-type constant velocity joint (101) wherein the number of needles (A), needle diameter (B), and circumferential gap (C) of the aforementioned needle are values that satisfy the following equation (1). [C / (A×B+C)]×100≧0.678...(1)
2. The tripod-type constant velocity joint according to claim 1, wherein each of the plurality of roller units is configured to set the upper limit of the circumferential gap to a value corresponding to the needle diameter.
3. Each of the aforementioned roller units has a retaining ring (34) that prevents the inner roller and the needle from coming off in the needle axis direction (Y) relative to the outer roller. A tripod-type constant velocity joint according to claim 1 or 2, wherein the dimension of the gap in the needle axial direction between the needle and the retaining ring (Y1) is configured to be greater than or equal to the dimension of the gap in the needle axial direction between the inner roller and the retaining ring (Y2).