Sliding constant velocity universal joint

Abstract

This reduces the induced thrust of the double-offset constant velocity universal joint during vehicle startup. [Solution] The radial gap between the cylindrical inner surface 6 of the outer joint member 2 of the double offset type constant velocity universal joint 1 and the outer surface of the cage 5 is set to 0.160 to 0.200 mm. This shifts the operating angle at which induced thrust begins to occur to the higher angle side, thereby reducing induced thrust in the low operating angle range.

Description

Technical Field

[0001] The present invention relates to a sliding constant velocity joint.

Background Art

[0002] Constant velocity joints applied to automotive drive shafts and propeller shafts are roughly classified into a sliding type that allows both angular displacement and axial relative movement between two shafts, and a fixed type that allows angular displacement between two shafts but does not allow axial relative movement between the two shafts.

[0003] As sliding constant velocity joints, a double offset type constant velocity joint (DOJ) using balls as rolling elements for transmitting rotational torque and a tripod type constant velocity joint (TJ) using rollers as rolling elements are known. For example, Patent Document 1 below shows a double offset type constant velocity joint that is made lightweight and compact by increasing the number of balls from six to eight. Further, Patent Document 2 below shows a double offset type constant velocity joint in which the maximum operating angle is increased to 30° or more and further weight reduction and compactification are achieved.

[0004] The double offset type constant velocity joint has advantages over the tripod type constant velocity joint in that it has less circumferential play, excellent responsiveness, and low manufacturing costs. On the other hand, it has a disadvantage in that the sliding resistance (slide resistance) is large and vehicle vibrations, particularly engine vibrations during idling, are easily transmitted. Therefore, various countermeasures against idling vibrations have been studied in double offset type constant velocity joints. For example, Patent Document 3 below shows a technique for absorbing idling vibrations by providing a gap between the outer peripheral surface of the inner ring and the inner peripheral surface of the cage.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, as vehicle ride comfort improves, the NVH (Noise, Vibration, Harshness) characteristics required of constant velocity universal joints are also becoming more stringent. Due to its structure, double offset constant velocity universal joints inevitably experience sliding contact between components. Therefore, even with measures such as those shown in Patent Document 3, it is difficult to reduce the sliding resistance to the same level as tripod-type sliding constant velocity universal joints, where components primarily contact each other by rolling. This sliding resistance problem, particularly the idling vibration problem, has become a bottleneck, and in recent years, the application range of double offset constant velocity universal joints has been almost entirely limited to parts that are less susceptible to engine vibration (for example, rear drive shafts).

[0007] Incidentally, in recent years, vehicle electrification has progressed, and the number of electric vehicles (EVs) that run solely on the power of an electric motor, and hybrid vehicles (HEVs) that run on the power of both an electric motor and an engine, is increasing. Because electric motors have superior responsiveness compared to engines, constant velocity universal joints that transmit power from electric motors also require low circumferential play and excellent responsiveness. Furthermore, since EVs do not generate engine vibrations, and in HEVs the engine is basically stopped when the vehicle is stopped (idling), these vehicles do not experience the idling vibration problem, which is the main reason why the application of double offset type constant velocity universal joints is limited. From these perspectives, in EVs and HEVs, the adoption of double offset type sliding constant velocity universal joints with low circumferential play and excellent responsiveness is being considered as a sliding type constant velocity universal joint installed in power transmission systems such as drive shafts and propeller shafts.

[0008] On the other hand, in a sliding constant velocity universal joint, an axial load (induced thrust) is generated due to frictional force between internal parts when the joint rotates at an operating angle. Specifically, as shown in Figure 10, the resultant force of the axial resistance Qx caused by the frictional force at the contact point between the track groove 101a of the outer joint member 101 and the ball 102, and the axial resistance Hx caused by the frictional force at the contact point between the outer spherical surface 103a of the cage 103 and the cylindrical inner circumferential surface 101b of the outer joint member 101 is the induced thrust.

[0009] Figure 11 shows the results of a mechanism analysis of the induced thrust Fx (=Qx+Hx) generated when a double-offset constant velocity universal joint with eight balls rotates at its operating angle. With the constant velocity universal joint at its operating angle, the phase angle at which the balls are positioned on the opening side of the outermost joint member is 0 degrees, and the phase angle at which they are positioned on the inner side of the outermost joint member is 180 degrees. As shown in the figure, the double-offset constant velocity universal joint generates an induced thrust of the same order as the number of balls n (8th order in the illustrated example) due to its structure. This nth-order induced thrust can resonate with the vehicle body, causing various vibration problems such as lateral swaying and booming noise during acceleration. These problems are particularly pronounced in EVs and HEVs, which are known for their quiet operation. Therefore, if the induced thrust during vehicle acceleration can be reduced, the double-offset constant velocity universal joint may be suitable for use in EVs and HEVs.

[0010] Therefore, the present invention aims to reduce the induced thrust of a double-offset constant velocity universal joint during vehicle starting, making it suitable for use in the power transmission system of vehicles (EVs and HEVs) driven by electric motors. [Means for solving the problem]

[0011] The inventors investigated the relationship between the magnitude of the nth-order component of the induced thrust generated in a double-offset constant velocity universal joint and the radial gap between the inner surface of the outer joint member and the outer surface of the cage (hereinafter referred to as the "outer ring-cage radial gap"). Specifically, they analyzed the nth-order component of the induced thrust when the operating angle was changed for both a double-offset constant velocity universal joint (conventional product) with an outer ring-cage radial gap of 0.05 mm and a double-offset constant velocity universal joint (improved product 1) with a larger outer ring-cage radial gap than the conventional product (specifically, 0.16 mm). In both the conventional product and improved product 1, the axial gap between the outer surface of the inner joint member and the inner surface of the cage (hereinafter referred to as the "inner ring-cage axial gap") was 0.15 mm, and the axial gap between the cage pocket and the ball (hereinafter referred to as the "pocket gap") was 0.025 mm. The analysis conditions assume a starting phase where resonance between the nth-order induced thrust and the vehicle body is a problem, with a rotational speed of 150 min⁻¹. -1 The torque was set to 900 Nm.

[0012] Figure 12 shows the analysis results for the conventional product, and Figure 13 shows the analysis results for improved product 1. In both the conventional product and improved product 1, the induced thrust generally increases as the operating angle increases. In the conventional product, induced thrust begins to occur when the operating angle exceeds 2°, and at an operating angle of 5°, the induced thrust exceeds 10N, a level that could be problematic in vehicles. In contrast, in improved product 1, induced thrust hardly occurs until the operating angle is around 5°, and even at an operating angle of 8°, the induced thrust is less than 10N. Thus, in improved product 1, which has a larger radial gap between the outer ring and the cage, the operating angle at which induced thrust begins to occur is shifted to a higher angle compared to the conventional product, and the induced thrust is smaller in the low operating angle range of 8° or less. This is thought to be because increasing the radial gap between the outer ring and the cage increases the operating angle at which contact load between the inner surface of the outer joint member and the outer surface of the cage begins to occur (see Figure 14).

[0013] Based on the above findings, the present invention provides a sliding constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed on its cylindrical inner circumferential surface; an inner joint member having a plurality of linear track grooves formed on its spherical outer circumferential surface; a plurality of balls disposed between the track grooves of the outer joint member and the track grooves of the inner joint member; and a cage having an outer spherical surface portion that slides against the cylindrical inner circumferential surface of the outer joint member and an inner spherical surface portion that slides against the spherical outer circumferential surface of the inner joint member, wherein the center of curvature of the outer spherical surface portion and the center of curvature of the inner spherical surface portion of the cage are offset by an equal distance on the opposite side of the axial direction from the joint center, The present invention provides a sliding constant velocity universal joint in which the radial gap between the cylindrical inner surface of the outer joint member and the outer surface of the cage is 0.160 to 0.200 mm.

[0014] As described above, by increasing the radial clearance between the outer ring and cage compared to conventional products, the operating angle at which the nth-order component of induced thrust begins to occur is shifted to a higher angle, thereby reducing induced thrust in the low operating angle range, which is frequently used (see Figure 13). Therefore, vibrations caused by the induced thrust of the sliding constant velocity universal joint can be suppressed when the vehicle starts.

[0015] In the above-mentioned sliding constant velocity universal joint, the rotational speed is 150 min⁻¹ in the operating angle range of 5° or less. -1 It is preferable to set the radial clearance between the outer ring and the cage such that the induced thrust generated under a torque of 900 Nm is 10 N or less.

[0016] Furthermore, the inventors analyzed the nth-order induced thrust component when the operating angle was changed for improved product 2, which has a larger axial clearance between the inner ring and cage than improved product 1. Specifically, improved product 1 has an axial clearance between the inner ring and cage of 0.15 mm, while improved product 2 has an axial clearance between the inner ring and cage of 1.00 mm. In both improved products 1 and 2, the radial clearance between the outer ring and cage is 0.160 mm, and the pocket clearance is 0.025 mm. The analysis conditions were the same as described above.

[0017] The analysis results of the improved product 2 are shown in Fig. 15. The improved product 2 has a reduced induced thrust in the operating angle range of 8 to 10° compared to the improved product 1 (see Fig. 13). Specifically, for the improved product 1, the induced thrust exceeds 10 N at an operating angle of 10°, while for the improved product 2, the induced thrust is 10 N or less even at an operating angle of 10°. Thus, by making not only the radial clearance between the outer ring and the cage but also the axial clearance between the inner ring and the cage larger than those of the conventional product (for example, 0.6 to 1.5 mm), an effect of reducing the induced thrust in the operating angle range of 8° or more can be expected. This is presumably because by providing the axial clearance between the inner ring and the cage, the inner ring can move axially relative to the cage, and this relative movement absorbs the axial load transmitted from the inner ring to the cage.

[0018] In the above sliding constant velocity joint, at least one of the track grooves of the outer joint member, the cylindrical inner peripheral surface, and the track grooves of the inner joint member can be a forging surface.

[0019] The number of balls in the above sliding constant velocity joint can be, for example, eight.

[0020] The above sliding constant velocity joint can be suitably mounted on a vehicle having an electric motor as a drive source. Specifically, a wheel drive device can be obtained that includes an electric motor, a wheel, and a power transmission system that transmits the driving force of the electric motor to the wheel via the above sliding constant velocity joint.

Effects of the Invention

[0021] As described above, according to the present invention, since the induced thrust of the double offset type constant velocity joint at the start of the vehicle can be reduced, it can be suitably used in the power transmission systems of EVs and HEVs.

Brief Description of the Drawings

[0022] [Figure 1] It is a plan view of an electric vehicle (EV). [Figure 2]Axial sectional view of a sliding constant velocity joint (double offset constant velocity joint) according to an embodiment of the present invention. [Figure 3] Cross-sectional view of the sliding constant velocity joint of FIG. 2 in a direction perpendicular to the axis. [Figure 4] Cross-sectional view of the outer joint member in a direction perpendicular to the axis. [Figure 5] Cross-sectional view of the inner joint member in a direction perpendicular to the axis. [Figure 6] Axial sectional view of the cage. [Figure 7] Front view schematically showing a measuring device for induced thrust. [Figure 8] Cross-sectional view showing an example of the specifications of the fitting portion between the inner joint member and the cage. [Figure 9] Cross-sectional view showing another example of the specifications of the fitting portion between the inner joint member and the cage. [Figure 10] Cross-sectional view showing the portion where an axial load is applied when the double offset constant velocity joint rotates at its operating angle. [Figure 11] Diagram showing the analysis result of the induced thrust of the double offset constant velocity joint. [Figure 12] Diagram showing the analysis result of the induced thrust for each operating angle of the double offset constant velocity joint according to the conventional product. [Figure 13] Diagram showing the analysis result of the induced thrust for each operating angle of the double offset constant velocity joint according to Improved Product 1. [Figure 14] Diagram showing the analysis result of the contact load between the outer joint member and the cage in the conventional product and Improved Product 1. [Figure 15] Diagram showing the analysis result of the induced thrust for each operating angle of the double offset constant velocity joint according to Improved Product 2.

Mode for Carrying Out the Invention

[0023] An embodiment of the sliding constant velocity joint according to the present invention will be described in detail below based on the drawings.

[0024] Figure 1 shows an electric vehicle (EV) that runs solely on the power of an electric motor. This electric vehicle has a front wheel drive system 61 that drives the front wheels 51 and a rear wheel drive system 62 that drives the rear wheels 52. Each wheel drive system 61, 62 has a drive unit 63 including an electric motor and a drive shaft 64 as a power transmission system that transmits the driving force of the electric motor to the front wheels 51 or rear wheels 52. In the illustrated example, the drive unit 63 of the front wheel drive system 61 is connected to the left and right front wheels 51 via the left and right drive shafts 64, and the drive unit 63 of the rear wheel drive system 62 is connected to the left and right rear wheels 52 via the left and right drive shafts 64.

[0025] Each drive shaft 64 has a sliding constant velocity universal joint 1 provided on the inboard side (drive unit 63 side), a fixed constant velocity universal joint 65 provided on the outboard side (wheel 51, 52 side), and an intermediate shaft 66 connecting both constant velocity universal joints 1 and 65. As this sliding constant velocity universal joint 1, a double offset type constant velocity universal joint according to one embodiment of the present invention is applied. The configuration of this sliding constant velocity universal joint 1 will be described in detail below.

[0026] As shown in Figures 2 and 3, the sliding constant velocity universal joint 1 of this embodiment comprises a cup-shaped outer joint member 2 with an open end in the axial direction (the left end in Figure 2), an inner joint member 3 arranged on the inner circumference of the outer joint member 2, a plurality of balls 4, and a cage 5 that holds the plurality of balls 4. The internal components 10, consisting of the inner joint member 3, the balls 4, and the cage 5, are housed on the inner circumference of the outer joint member 2 so as to be axially displaceable. The end of the intermediate shaft 66 (see Figure 1) is connected to the axial hole 11 of the inner joint member 3 by spline fitting. In the following description, in the state with an operating angle of 0° as shown in Figure 2, the axial direction of the outer joint member 2 and the inner joint member 3 is referred to as the "axial direction," the bottom side of the outer joint member 2 (right side in Figure 2) in the axial direction is referred to as the "rear joint side," and the opening side of the outer joint member 2 (left side in Figure 2) is referred to as the "opening joint side."

[0027] The cylindrical inner surface 6 of the outer joint member 2 has linear track grooves 7 extending in the axial direction formed at equal intervals at multiple locations in the circumferential direction. The spherical outer surface 8 of the inner joint member 3 has linear track grooves 9 extending in the axial direction formed at equal intervals at multiple locations in the circumferential direction. One ball 4 is placed between the track grooves 7 of the radially opposing outer joint member 2 and the track grooves 9 of the radially opposing inner joint member 3, and transmits rotational torque between the two joint members 2 and 3.

[0028] The cage 5 is substantially cylindrical, with pockets 12 formed at equal intervals at multiple locations in the circumferential direction. Each pocket 12 holds one ball 4. The outer circumferential surface of the cage 5 has an outer spherical portion 13 that slides against the cylindrical inner circumferential surface 6 of the outer joint member 2, and tapered surfaces 14 provided on both axial sides of the outer spherical portion 13. The inner circumferential surface of the cage 5 has an inner spherical portion 15 that contacts the spherical outer circumferential surface 8 of the inner joint member 3. In this embodiment, the number of track grooves 7, 9, balls 4, and pockets 12 is shown as 8, but it is not limited to this, and for example, these numbers may be 6.

[0029] At least one of the track grooves 7 of the outer joint member 2, the cylindrical inner circumferential surface 6 of the outer joint member 2, and the track groove 9 of the inner joint member 3 is a forged surface. In this embodiment, the track grooves 7 of the outer joint member 2, the cylindrical inner circumferential surface 6, and the track groove 9 of the inner joint member 3 are all forged surfaces. The spherical outer circumferential surface 8 of the inner joint member 3, the outer spherical portion 13 and inner spherical portion 15 of the cage 5, and the inner circumferential surface of the pocket 12 are, for example, ground surfaces.

[0030] The curvature centers O1 of the outer spherical portion 13 and O2 of the inner spherical portion 15 of the cage 5 (i.e., the curvature centers of the spherical outer surface 8 of the inner joint member 3) are offset by an equidistant distance F on the opposite side of the axial direction from the joint center O (the intersection of the plane passing through the centers of all the balls 4 and the axes of both joint members 2 and 3), that is, from the axial center of the pocket 12 (see Figure 2). In the illustrated example, the curvature center O1 of the outer spherical portion 13 of the cage 5 is offset towards the back of the joint relative to the joint center O, and the curvature center O2 of the inner spherical portion 15 of the cage 5 is offset towards the joint opening relative to the joint center O.

[0031] As a result, when an operating angle is applied between the outer joint member 2 and the inner joint member 3, the ball 4 held in the pocket 12 of the cage 5 is always maintained within the plane that bisects the operating angle at any operating angle, thereby ensuring constant velocity between the outer joint member 2 and the inner joint member 3. Furthermore, the internal component 10 is axially movable relative to the outer joint member 2 as the ball 4 held in the cage 5 rolls on the track groove 7 of the outer joint member 2. Alternatively, the center of curvature O1 of the outer spherical portion 13 of the cage 5 may be positioned on the joint opening side, and the center of curvature O2 of the inner spherical portion 15 of the cage 5 may be positioned on the joint back side.

[0032] In this embodiment, the internal gap of the sliding constant velocity universal joint 1 is set as shown in Table 1 below.

[0033] [Table 1]

[0034] Here, "PCD (pitch circle diameter) gap" refers to the difference between the PCD of the ball 4 when it is in contact with the track groove 7 of the outer joint member 2 (outer ring PCD) and the PCD of the ball 4 when it is in contact with the track groove 9 of the inner joint member 3 (inner ring PCD), as shown in Figures 4 and 5. Also, "outer ring-cage radial gap" refers to the difference between the inner diameter of the cylindrical inner circumferential surface 6 of the outer joint member 2 (outer ring inner diameter) and the maximum outer diameter of the outer spherical surface portion 13 of the cage 5 (cage outer diameter), as shown in Figures 4 and 6. "Inner ring-cage radial gap" refers to the difference between the outer diameter of the spherical outer circumferential surface 8 of the inner joint member 3 (inner ring outer diameter) and the maximum inner diameter of the inner spherical surface portion 15 of the cage 5 (cage inner diameter), as shown in Figures 5 and 6. "Inner ring-cage axial clearance" refers to the axial clearance formed between the outer circumferential surface of the inner joint member 3 and the inner circumferential surface of the cage 5. Specifically, as shown in Figure 2, when the spherical outer circumferential surface 8 of the inner joint member 3 and the inner spherical surface portion 15 of the cage 5 are fitted together and arranged coaxially, it refers to the relative allowable axial movement between the inner joint member 3 and the cage 5. Furthermore, "pocket clearance" refers to the difference between the axial width of the pocket 12 of the cage 5 (cage pocket width) and the diameter of the ball 4 (ball diameter), as shown in Figures 4 and 6.

[0035] In a double-offset constant-velocity universal joint, increasing the radial clearance between the outer ring and cage can lead to increased play between the outer joint member 2 and the cage 5, potentially causing noise and vibration problems. Therefore, in conventional double-offset constant-velocity universal joints, the radial clearance between the outer ring and cage was kept below 0.160 mm, as shown in Table 1 above.

[0036] In contrast, in the double offset constant velocity universal joint 1 of this embodiment, as shown in Table 1 above, the radial clearance between the outer ring and cage is made larger than that of conventional products, specifically to 0.160 mm or more. As a result, the operating angle at which induced thrust begins to occur is larger compared to conventional products (see Figure 13), and the induced thrust in the operating angle range of 5° or less is set to 10 N or less, and preferably in the operating angle range of 8° or less is set to 10 N or less. On the other hand, in order to suppress the generation of abnormal noise and vibration, the radial clearance between the outer ring and cage is set to 0.200 mm or less. In this embodiment, the internal clearances other than those mentioned above, namely the PCD clearance, the radial clearance between the inner ring and cage, the axial clearance between the inner ring and cage, and the pocket clearance, are the same as those of conventional products.

[0037] When installed in a vehicle, the operating angle of the sliding constant velocity universal joint 1 is often set to approximately 4-5°. The operating angle of a constant velocity universal joint refers to the operating angle generated in each constant velocity universal joint of the drive shaft when the steering is set to the straight position in a vehicle with one occupant on a horizontal, flat road surface. In this case, when the vehicle starts moving, the sliding constant velocity universal joint 1 is used at an operating angle of 5° or less. Therefore, as described above, by suppressing the induced thrust in the operating angle range of 5° or less to 10N or less, vibrations caused by resonance between the induced thrust of the sliding constant velocity universal joint 1 and the vehicle body are reduced when the vehicle starts moving. For this reason, the sliding constant velocity universal joint 1 described above can be suitably used in electric vehicles (EVs) which have excellent quietness.

[0038] Furthermore, electric vehicles offer greater flexibility in vehicle layout compared to vehicles powered solely by an engine, which may result in the sliding constant velocity universal joint 1 being used at a higher angle, i.e., a larger operating angle. In this case, it is preferable to adjust the size of the radial clearance between the outer ring and cage of the sliding constant velocity universal joint 1 to extend the operating angle range in which the induced thrust is suppressed to 10N or less to 8°. This makes it possible to suppress vibrations during starting even when the operating angle of the sliding constant velocity universal joint 1 is greater than 5°.

[0039] The actual measurement of the induced thrust of the sliding constant velocity universal joint 1 is performed using the apparatus shown in Figure 7. This figure shows a part of the power circulation type testing machine used to measure the induced thrust force and slide resistance force. In this figure, the double offset type constant velocity universal joint of this embodiment is positioned on side A (hereinafter referred to as the "A-side joint"), and a paired fixed type constant velocity universal joint (for example, a Zepper-type constant velocity universal joint) is positioned on side B (hereinafter referred to as the "B-side joint"). The inner joint member of the A-side joint and the inner joint member of the B-side joint are connected via an intermediate shaft, and a predetermined operating angle θ is applied to both joints. In addition, the outer joint member of the A-side joint is connected to a load cell, and the outer joint member of the B-side joint is connected to a hydraulic servo.

[0040] During induced thrust measurement, a load torque at a predetermined rotational speed is applied to the B-side coupling. This load torque is transmitted from the B-side coupling to the A-side coupling via the intermediate shaft, causing the A-side coupling to rotate at a speed equal to the input rotational speed. At this time, induced thrust is generated inside the A-side coupling, and this induced thrust is detected by a load cell via the outer coupling member of the A-side coupling.

[0041] For example, with the above device, the rotation speed is 150 min⁻¹. -1 The load torque is set to 900 N·m, and the device is swept at a constant oscillation speed from 0° to 12° with an operating angle θ. The effective value (mean square rms of the result of Fourier transform of the axial load data) of the nth-order component (the 8th-order component in this embodiment) obtained by frequency analysis of the measured data is acquired as the induced thrust.

[0042] The present invention is not limited to the embodiments described above. Other embodiments of the present invention will be described below, but redundant explanations of points similar to those in the embodiments described above will be omitted.

[0043] For example, as shown in Table 2 below, the axial clearance between the inner ring and cage may be made larger than that of conventional products, and the pocket clearance may be made larger than 0.

[0044] [Table 2]

[0045] By making the pocket gap greater than 0, i.e., a positive value, an axial gap is formed between the inner circumferential surface of the pocket 12 of the cage 5 and the ball 4. In Figures 8 and 9, if the axial width of the pocket 12 of the cage 5 is Lc and the diameter of the ball 4 is Db, then the pocket gap δ1 is expressed as δ1 = Lc - Db. By providing a positive pocket gap δ1, the ball 4 can roll more easily within the pocket 12 of the cage 5. Furthermore, by increasing the axial gap between the inner ring and the cage, relative axial movement between the inner joint member 3 and the cage 5 becomes possible. As a result, axial load is less likely to be transmitted through the path of inner joint member 3 → ball 4 → outer joint member 2, or inner joint member 3 → cage 5 → outer joint member 2, and induced thrust is reduced.

[0046] The specific specifications for providing an axial clearance between the inner ring and the cage are explained using Figure 8. In this specification, the radius of curvature Rc of the inner spherical surface 15 of the cage 5 is greater than the radius of curvature Ri of the spherical outer surface 8 of the inner joint member 3, and the center of curvature of the radius of curvature Rc is radially offset with respect to the axis of the cage 5. The radial clearance between the spherical outer surface 8 of the inner joint member 3 and the inner spherical surface 15 of the cage 5 is smallest at the outermost diameter (axial center) of the inner spherical surface 15 of the cage 5, and gradually increases from there toward both sides in the axial direction. The radial clearance between the outermost diameter of the inner spherical surface 15 of the cage 5 and the spherical outer surface 8 of the inner joint member 3 is substantially zero, but a small radial clearance is provided to allow relative movement between the two. As a result, an axial clearance is provided between the cage 5 and the inner joint member 3 that allows relative axial movement between the two.

[0047] Figure 9 shows another specification for providing an axial clearance between the inner ring and the cage. In this specification, the spherical outer surface 8 of the inner joint member 3 is formed as a single sphere with a radius of curvature Ri, similar to Figure 8. On the other hand, a cylindrical portion 16 parallel to the axis of the cage 5 is formed on the inner surface of the cage 5, and inner spherical portions 15 with a radius of curvature Rc are smoothly connected to both axial ends of the cylindrical portion 16. The radius of curvature Rc of the inner spherical portion 15 of the cage 5 and the radius of curvature Ri of the spherical outer surface 8 of the inner joint member 3 are substantially Rc ≈ Ri, although there is a small spherical gap for sliding guidance. In this specification, the spherical outer surface 8 of the inner joint member 3 is axially guided by the cylindrical portion 16 on the inner surface of the cage 5, allowing the inner joint member 3 to move axially relative to the cage 5 by the axial dimension S of the cylindrical portion 16. That is, the axial dimension S of the cylindrical portion 16 becomes the axial clearance between the inner ring and the cage.

[0048] As a result, the operating angle range in which induced thrust can be suppressed to 10N or less can be extended to 9°, preferably to 10° (see Figure 15). This makes it possible to suppress vibrations during vehicle startup caused by induced thrust, even when the normal operating angle of the sliding constant velocity universal joint 1 is 8° or more or 9° or more.

[0049] Furthermore, while the track groove 7 and cylindrical inner surface 6 of the outer joint member 2, and the track groove 9 of the inner joint member 3 are generally forged to reduce manufacturing costs, they may also be finished by machining or grinding after heat treatment (quenching). Similarly, while the outer and inner surfaces of the cage 5 are generally ground to a finish as described above, they may also be finished by machining or rolling after heat treatment (quenching).

[0050] Furthermore, the double-offset sliding constant velocity universal joint according to the present invention is not limited to electric vehicles (EVs) that use only an electric motor as a power source, but can also be applied to the power transmission systems of hybrid electric vehicles (HEVs) that use both an electric motor and an engine as power sources, and vehicles that use only an engine as a power source. [Explanation of symbols]

[0051] 1. Sliding constant velocity universal joint (double offset type constant velocity universal joint) 2. Outer joint member 3. Inner joint member 4 balls 5 cages 7, 9 Track grooves 10 Internal parts 13 Outer spherical part 15 Inner spherical part O joint center Center of curvature of the outer spherical portion of the O1 cage Center of curvature of the inner spherical surface of the O2 cage

Claims

1. An outer joint member having multiple straight track grooves formed on its cylindrical inner surface, An inner joint member having multiple straight track grooves formed on its spherical outer surface, A plurality of balls are arranged between the track groove of the outer joint member and the track groove of the inner joint member, The device comprises an outer spherical surface portion that slides against the cylindrical inner surface of the outer joint member, and an inner spherical surface portion that slides against the spherical outer surface of the inner joint member, and a cage that holds the plurality of balls, In a sliding constant velocity universal joint in which the curvature centers of the outer spherical portion and the curvature centers of the inner spherical portion of the cage are offset by an equal distance on the opposite side of the joint center in the axial direction, A sliding constant velocity universal joint in which the radial gap between the cylindrical inner surface of the outer joint member and the outer surface of the cage is 0.160 to 0.200 mm.

2. In the operating angle range of 5° or less, rotational speed 150 min －１ The sliding constant velocity universal joint according to claim 1, wherein the induced thrust generated under the condition of a torque of 900 Nm is 10 N or less.

3. The sliding constant velocity universal joint according to claim 1, wherein the axial gap between the spherical outer surface of the inner joint member and the inner surface of the cage is 0.6 to 1.5 mm.

4. The sliding constant velocity universal joint according to claim 1, wherein at least one of the track groove of the outer joint member, the cylindrical inner circumferential surface, and the track groove of the inner joint member is a forged surface.

5. The sliding constant velocity universal joint according to claim 1, wherein the number of balls is eight.

6. A sliding constant velocity universal joint according to claim 1, which is mounted on a vehicle driven by an electric motor.

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