Tripod type constant velocity universal joint

Abstract

To provide a double-roller tripod type constant velocity universal joint capable of preventing deterioration of an NVH performance due to noise or vibration, and effectively preventing early damage.SOLUTION: On an outer peripheral surface of a leg shaft, convex curves are swollen on both sides in a torque transmission direction on vertical and horizontal cross sections. A curvature center of the convex curve on the vertical cross section is offset on a side opposite to the convex curve. The curvature center of the convex curve on the horizontal cross section is offset on the convex curve side. When a curvature radius of the convex curve on the vertical cross section is designated as R and a curvature radius of the convex curve on the horizontal cross section is designated as r, R>r is satisfied. When an offset amount of the curvature center on the vertical cross section is designated as F, a vertical inclination angle between the leg shaft and an inner ring is designated as α, and a clearance between the leg shaft and the inner ring is designated as S, the following relation is satisfied.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tripod-type constant velocity universal joint. [Background technology]

[0002] In driveshafts used in automotive power transmission systems, a sliding-type constant velocity universal joint is often provided on the inboard side (the center side in the vehicle width direction) and a fixed-type constant velocity universal joint is provided on the outboard side (the outside side in the vehicle width direction).The sliding-type constant velocity universal joint here allows both angular displacement and relative axial movement between the two shafts, while the fixed-type constant velocity universal joint allows angular displacement between the two shafts but does not allow relative axial movement between the two shafts.

[0003] A tripod constant velocity universal joint is known as a sliding type constant velocity universal joint. This tripod constant velocity universal joint is available in single roller and double roller types. A single roller type tripod constant velocity universal joint has rollers inserted into track grooves of an outer joint member rotatably attached to the trunnions of the tripod members via a plurality of needle rollers. A double roller type tripod constant velocity universal joint, as shown in FIGS. 9 and 10 , has rollers 111 disposed in track grooves 105 of an outer joint member 102, and an inner ring 112 fitted onto the trunnions 132 of a tripod member 103 to rotatably support the rollers 111 (see, for example, Patent Document 1).

[0004] In a double-roller tripod constant velocity universal joint, the cross section of the trunnion 132 (cross section perpendicular to the axis of the trunnion) is elliptical, as shown in Fig. 11, and the inner circumferential surface of the inner ring 112 has a convex arc cross section, as shown in Fig. 9. This allows the rollers 111 to oscillate relative to the trunnion 132, as shown in Fig. 12, which has the advantage of reducing induced thrust (axial force induced by friction between parts inside the joint) and sliding resistance compared to a single-roller type. Also, as shown in Fig. 11, the trunnion 132 has an elliptical cross section, but in this case, its major axis a is aligned parallel to the torque load direction and its minor axis b is aligned perpendicular to the torque load direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-320563 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-described tripod-type constant velocity universal joint, as shown in Fig. 10, outer peripheral surfaces 115 of rollers 111 are convex curved surfaces having arc-shaped generatrix lines, and roller guideways 106 that come into contact with these have a cross-sectional concave shape (Gothic arch shape) that follows the shape of outer peripheral surfaces 115 of rollers 111, and these form angular contact. Therefore, due to the structure, when the constant velocity universal joint rotates with an operating angle, a phenomenon occurs in which roller unit 104 including rollers 111 and inner ring 112 tilts in the direction of arrow B1 in a cross section perpendicular to the joint axial direction as shown in Fig. 13 (hereinafter referred to as "left-right tilt"), and a phenomenon in which roller unit 104 tilts in the direction of arrow B2 in a cross section parallel to the joint axial direction as shown in Fig. 14 (hereinafter referred to as "front-rear tilt"). When the roller unit 104 tilts left and right or front and rear, the rolling and sliding resistance at the contact points between the rollers 111 and the roller guideways 106 and the rotational resistance of the roller unit 104 relative to the trunnion 32 increase. Furthermore, the needle rollers 117 in the roller unit 104 are unable to roll relative to the roller guideways 106 in the axial direction of the outer joint member 102, increasing the sliding resistance. If these factors become significant, the induced thrust and sliding resistance increase, causing a problem of deterioration in the NVH (Noise, Vibration, Harshness) characteristics of the constant velocity universal joint.

[0007] Furthermore, in the above-described tripod-type constant velocity universal joint, the trunnion 132 has an elliptical cross section and the inner peripheral surface of the inner ring 112 has a convex arc cross section. This results in a substantially point contact between the inner ring 112 and the trunnion 132, thereby suppressing the friction moment that acts to tilt the roller unit 104 as the trunnion 132 moves. Even when the joint is angled, the trunnion 132 contacts the center of the inner ring 112 in the width direction (the axial direction of the trunnion 132), thereby suppressing left-right tilt. However, when the joint is angled, the elliptical cross section of the trunnion 132 generates a force that causes the roller unit 104 to tilt forward and backward (see FIG. 12 ). Furthermore, because the contact area between the trunnion 132 and the inner ring 112 is small, the surface pressure at their contact surfaces increases under high torque loads, such as those caused by extremely harsh vehicle operating conditions, raising concerns about the impact on the durability of the trunnion 132.

[0008] Therefore, the present invention provides a double roller type tripod constant velocity universal joint that can achieve smooth operation without creating a negative clearance between the trunnion and the inner surface of the inner ring even at the maximum operating angle, can prevent deterioration of NVH performance due to the generation of abnormal noise and vibration, and can also effectively prevent early damage. [Means for solving the problem]

[0009] The tripod constant velocity universal joint of the present invention comprises an outer joint member having three track grooves formed on its inner peripheral surface extending in the joint axial direction, each track groove being provided with a pair of roller guide surfaces opposing each other in the joint circumferential direction; a tripod member arranged on the inner peripheral surface of the outer joint member and having three trunnions protruding in the joint radial direction toward the track grooves; and three roller units each consisting of an inner ring arranged on the outer periphery of the trunnions and supported by the trunnions in a rotatable and swingable state, an outer ring arranged in the track grooves and positioned on the outer diameter side of the inner ring, and a plurality of rolling elements arranged between the inner ring and the outer ring to support the inner ring and the outer ring so as to be rotatable relative to each other, wherein the outer peripheral surface of the outer ring is cylindrical, and The guide surface is flat, the inner peripheral surface of the inner ring is cylindrical, the outer peripheral surface of the trunnion is convexly curved in both directions in the torque transmission direction in both vertical and horizontal sections, the center of curvature of the convex curve in the vertical section is offset from the central axis of the trunnion to the side opposite the convex curve, the center of curvature of the convex surface in the horizontal section is offset from the central axis of the trunnion to the side of the convex curve and in the direction of rotation of the tripod members, where R is the radius of curvature of the convex curve in the vertical section and r is the radius of curvature of the convex curve in the horizontal section, R>r, F is the offset of the center of curvature in the vertical section, α is the angle of inclination between the trunnion and the inner ring, and S is the gap between the trunnion and the inner ring in the direction of rotation of the tripod members, the relationship in Equation 1 satisfies, and α is expressed by Equation 2 below. Note that the units of S, F, R, R, etc. in the following equations are mm.

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[0010]

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[0011] In the tripod constant velocity universal joint of the present invention, the rollers have cylindrical outer peripheral surfaces and the roller guideway is flat. In this case, when torque is applied, the flat roller guideway and the cylindrical outer peripheral surface of the roller press against each other via a linear contact portion, thereby suppressing left and right tilt of the roller (see FIG. 11). Furthermore, by providing a pair of guide surfaces on both widthwise sides of the roller guideway that can abut against the roller from both axial sides, left and right tilt of the roller can be more reliably prevented.

[0012] When the trunnion has an offset arc shape and the inner surface of the inner ring is a flat cylinder, the gap between the trunnion and the roller inner diameter (journal clearance) varies depending on the lateral tilt angle between the tripod member and the roller. In particular, when the center of the arc (center of curvature) of the axially convex curve of the trunnion is offset outward from the trunnion central axis, the larger the lateral tilt angle, the smaller the gap. If the journal clearance is too small, the lateral tilt angle increases when the constant velocity universal joint operates at a high operating angle. This causes the gaps between the trunnion and the roller inner diameter to become negative and interfere with each other, resulting in noise and vibration, which can lead to poor NVH performance and early damage. Conversely, if the journal clearance is too large, circumferential backlash increases, degrading NVH performance.

[0013] For this reason, it is necessary to set the journal clearance to an appropriate value. Therefore, in the tripod constant velocity universal joint according to the present invention, by setting the above equations 1 and 2, interference between the trunnion and the inner peripheral surface of the inner ring can be avoided.

[0014] When the minimum value of the gap is Smin, it is preferable that Smin be expressed by the following equation 3.

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[0015] When the maximum value of the gap is max and the minimum value of the gap is Smin, Smax is preferably expressed by the following equation 4.

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[0016] This setting effectively prevents the gap (journal gap) between the trunnion and the inner peripheral surface of the roller (the inner peripheral surface of the inner ring) from becoming excessive, effectively preventing an increase in circumferential backlash and a deterioration in NVH characteristics.

[0017] It can be used in constant velocity universal joints with a maximum working angle of 23 to 28 degrees. That is, in constant velocity universal joints with such maximum working angles, even when the working angle is taken, the gap (journal gap) between the trunnion and the inner peripheral surface of the unit in the roller (inner peripheral surface of the inner ring) does not become negative, preventing the generation of abnormal noise and vibration, suppressing circumferential backlash, and preventing a deterioration in NVH performance. [Effects of the Invention]

[0018] The present invention achieves smooth operation without creating a negative gap between the trunnion and the inner surface of the inner ring, even at the maximum operating angle, and prevents deterioration of NVH performance due to the generation of abnormal noise and vibration, while also effectively preventing early damage. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of a tripod type constant velocity universal joint according to the present invention in the joint axial direction. [Figure 2] FIG. 2 is a cross-sectional view taken along the line KK in FIG. [Figure 3] FIG. 2 is a vertical cross-sectional view of a roller cassette. [Figure 4] FIG. 2 is a cross-sectional view of the roller cassette. [Figure 5] FIG. 4 is a simplified cross-sectional view of a main part showing the left and right tilt angles between the trunnion and the inner ring. [Figure 6]FIG. 2 is a simplified cross-sectional view of a main part showing the outer diameter dimension of the trunnion and the left and right tilt angle between the inner rings. [Figure 7] FIG. 7 is an enlarged cross-sectional view of a main part of FIG. 6. [Figure 8] 1 shows parameters used in the present invention, where (a) is a relationship diagram showing the relationship between the radius of curvature of the convex curved portion in the longitudinal section of the leg shaft, the left-right tilt angle, the swing radius, and PCR, and (b) is a relationship diagram showing the relationship between the right tilt angle, the swing radius, and PCR. [Figure 9] FIG. 1 is a cross-sectional view of a conventional tripod-type constant velocity universal joint taken in the joint axial direction. [Figure 10] FIG. 10 is a partial cross-sectional view taken along line KK in FIG. 9. [Figure 11] FIG. 10 is a cross-sectional view taken along line LL in FIG. 9. [Figure 12] 10 is a cross-sectional view showing a state in which the tripod constant velocity universal joint of FIG. 9 has an operating angle. [Figure 13] 10 is a cross-sectional view of the tripod constant velocity universal joint of FIG. 9, perpendicular to the joint axial direction, showing a state in which a roller unit is tilted left and right. [Figure 14] 10 is a cross-sectional view of the tripod constant velocity universal joint of FIG. 9 in the joint axial direction, showing a state in which a roller unit is tilted forward and backward. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 8. Figs. 1 to 4 show a tripod type constant velocity universal joint 1 according to the present invention, and this tripod type constant velocity universal joint 1 is of a double roller type. In the following description, the axial direction of the tripod type constant velocity universal joint when the operating angle is 0° will be referred to as the "joint axial direction," and the circumferential direction and radial direction centered on the axis at this time will be referred to as the "joint circumferential direction" and the "joint radial direction," respectively.

[0021] As shown in FIGS. 1 and 2, this tripod type constant velocity universal joint 1 includes an outer joint member 2, a tripod member 3 as an inner joint member, and a roller unit 4 as a torque transmission member.

[0022] The outer joint member 2 is cup-shaped with one open end in the joint axial direction and the other closed end (see Fig. 1). Three linear track grooves 5 extending in the joint axial direction are formed on the inner peripheral surface of the outer joint member 2 at equal intervals in the joint circumferential direction (see Fig. 2). Each track groove 5 is formed with a pair of roller guideways 6 arranged opposite each other in the joint circumferential direction. Each roller guideway 6 extends in the joint axial direction. A tripod member 3 and a roller unit 4 are housed inside the outer joint member 2.

[0023] The tripod member 3 integrally comprises a body 31 (trunnion body) having a central hole 30, and three trunnion journals 32 protruding radially from trisecting positions in the joint circumferential direction on the outer peripheral surface of the body 31. A male spline formed on the shaft 8 is fitted into a female spline formed in the central hole 30 of the body 31, and these are fixed in the joint axial direction with a retaining ring or the like, thereby connecting the tripod member 3 and the shaft 8 so as to be able to transmit torque.

[0024] The roller units 4 are provided on the outer periphery of each trunnion 32 of the tripod member 3 and, as shown in FIGS. 3 and 4 , are housed in the track grooves 5 of the outer joint member 2. The roller unit 4 includes an outer ring 11, which is an annular roller centered on the axis of the trunnion 32; an annular inner ring 12, which is disposed on the inner periphery of the outer ring 11 and fitted onto the trunnion 32; and rolling elements 13, which are interposed between the outer ring 11 and the inner ring 12. In this embodiment, a large number of full-complement needle rollers without a cage are used as an example of the rolling elements 13. The needle rollers 13 are disposed so as to roll freely between the cylindrical inner peripheral surface of the outer ring 11 as an outer raceway surface and the cylindrical outer peripheral surface of the inner ring 12 as an inner raceway surface. The roller unit 4, which is made up of the outer ring 11, the inner ring 12, and the needle rollers 13, is held together by a pair of snap rings 14 to prevent spontaneous disassembly.

[0025] Next, we will explain the relationship between the roller guideway 6 and the outer ring 11. In this case, the joint axial direction is indicated as the Z direction, the axial direction of the trunnion 32 is indicated as the Y direction, and the torque transmission direction perpendicular to both the joint axial direction Z and the trunnion axial direction Y is indicated as the X direction.

[0026] The outer peripheral surface 15 of the outer ring 11 is a cylindrical surface centered on the axis of the leg shaft 32. End faces 16 of the outer ring 11 on both sides in the axial direction thereof are flat surfaces perpendicular to the axis thereof (see FIG. 3). The outer peripheral surface 15 and both end faces 16 of the outer ring 11 are connected via chamfers 17. The chamfers 17 are, for example, made up of a tapered surface with a linear cross section and a convex curved surface with a curved cross section (for example, an arc shape) that smoothly connects the tapered surface with the outer peripheral surface 15 and both end faces 16.

[0027] A pair of roller guideways 6 of each track groove 5 of the outer joint member 2 are flat surfaces parallel to each other. A pair of guide surfaces 7 is provided on both sides of each roller guideway 6 in the width direction (Y direction). The guide surfaces 7 rise from both ends of the roller guideway 6 in the width direction toward the side closer to the axis Y of the trunnion 32. The shapes of the roller guideway 6 and the guide surfaces 7 follow the shapes of the outer peripheral surface 15 and chamfer 17 of the outer ring 11. Specifically, in the cross section shown in FIG. 3 , the roller guideway 6 and the outer peripheral surface 15 of the outer ring 11 are parallel, and the distance W between the pair of opposing roller guideways 6 is slightly larger than the diameter of the outer peripheral surface 15 of the outer ring 11. As a result, a small gap in the X direction is formed between the roller guideway 6 and the outer peripheral surface 15 of the outer ring 11. 3, the guide surfaces 7 are substantially parallel to the chamfers 17 of the outer ring 11 and are composed of, for example, an inclined surface with a linear cross section and a concave surface with a curved cross section (for example, an arc-like shape) that smoothly connects the inclined surface and the roller guideway surface 6. The distance in the Y direction between the pair of guide surfaces 7 provided on both sides in the width direction of the roller guideway surface 6 is slightly larger than the distance in the Y direction between the pair of chamfers 17 provided on both sides in the width direction of the outer peripheral surface 15 of the outer ring 11. This forms a small gap in the Y direction between the guide surfaces 7 and the chamfers 17 of the outer ring 11.

[0028] When torque is applied to the outer joint member 2 in the direction of arrow T in FIG. 2, the outer peripheral surface 15 of the outer ring 11 is pressed against the roller guideway 6 on the left side of the figure. In this embodiment, as described above, the roller guideway 6 is a flat surface and the outer peripheral surface 15 of the outer ring 11 is a cylindrical surface, so they press against each other via a linear contact portion. This corrects the posture of the outer ring 11 so that the outer peripheral surface 15 of the outer ring 11 is parallel to the roller guideway 6, thereby suppressing left-right tilt of the outer ring 11 (see FIG. 13). Furthermore, the guide surface 7 abuts against the chamfer 17 of the outer ring 11 from the Y direction, thereby restricting the front-rear tilt of the outer ring 11 (see FIG. 14) and further suppressing left-right tilt of the outer ring 11.

[0029] When torque is applied to the outer joint member 2 in the direction of arrow T in Fig. 2 as described above, the outer peripheral surface 15 of the outer ring 11 is pressed against the roller guideway 6 on the left side in the figure (hereinafter referred to as the "torque-loaded side roller guideway 6"), while gaps are formed between the roller guideway 6 on the right side in the figure (hereinafter referred to as the "non-torque-loaded side roller guideway 6") and the guide surfaces 7 on both sides of it in the width direction, and the outer peripheral surface 15 and chamfers 17 of the outer ring 11. At this time, if the roller unit 4 tilts and the outer peripheral surface 15 and chamfers 17 of the outer ring 11 come into contact with the roller guideway 6 and guide surfaces 7 on the non-torque-loaded side, the rotational resistance of the outer ring 11 increases.

[0030] Therefore, in this embodiment, the initial gap between the outer ring 11 and the roller guideway 6 and the shape of the guide surface 7 are designed so that when torque is applied to the tripod member 3, the outer ring 11 comes into contact with the roller guideway 6 on the torque-loaded side, but does not come into contact with the roller guideway 6 on the non-torque-loaded side and the guide surfaces 7 on both sides of it in the width direction.

[0031] Next, the shapes of the inner peripheral surface 18 of the inner ring 12 and the outer peripheral surface 33 of the trunnion 32 will be described in detail with reference to Figures 3 and 4. The inner peripheral surface 18 of the inner ring 12 is a cylindrical surface parallel to the trunnion axis direction Y.

[0032] In a vertical cross section including the axis of the trunnion 32 itself, the outer peripheral surface 33 of the trunnion 32 has a convex curve that bulges out on both sides in the torque transmission direction X. In the illustrated example, the convex curve in the vertical cross section of the outer peripheral surface of the trunnion 32 is formed by an arc 33a with a curvature radius R. As a result, the apex (end in the X direction) of the arc 33a on the outer peripheral surface of the trunnion 32 closely faces the cylindrical inner peripheral surface 18 of the inner ring 12, and the gap between the outer peripheral surface 33 of the trunnion 32 and the inner peripheral surface 18 of the inner ring 12 gradually increases from the apex of the arc 33a to both sides in the Y direction. In this case, the center of curvature A of the arc 33a of the convex curve in the vertical cross section is offset by a dimension F to the opposite side of the convex curve.

[0033] In a cross section of the trunnion 32 taken in a direction perpendicular to its own axis as shown in Figure 4, the outer circumferential surface of the trunnion 32 has a convex curve that bulges out on both sides in the torque transmission direction X. In the illustrated example, the convex curve in the cross section of the outer circumferential surface of the trunnion 32 is formed by an arc 33b with a curvature radius r. In this case, the center of curvature Ob of the arc 33b of the convex curve in the cross section is offset by a dimension E toward the convex curve side.

[0034] The arc 33b of the outer surface of the leg shaft 32 closely faces the cylindrical inner surface 18 of the inner ring 12 at its top (end in the X direction), and as it goes from the top to both sides in the Z direction, it moves away from the inner surface 18 of the inner ring 12, leaving a gap G between them in the Z direction.

[0035] As described above, the outer peripheral surface 33 of the trunnion 32 has an aspheric shape in which the radius of curvature R of the convex curve (arc 33a) in the longitudinal cross section is different from the radius of curvature r of the convex curve (arc 33b) in the transverse cross section. The radius of curvature R is set to be larger than the radius of curvature r, i.e., R>r. In this case, the radius of curvature R is set to be larger than half the maximum dimension of the trunnion 32 in the torque transmission direction (the maximum diameter DJ of the trunnion 32 when the operating angle is 0°, which will be described later), and the radius of curvature r is set to be smaller than half of DJ. Here, DJ (see FIGS. 3 and 6) is the outer diameter of the trunnion 32 when the operating angle is 0° and can be called the journal diameter.

[0036] When the trunnion 32 has an offset arc shape and the inner peripheral surface of the inner ring 12 has a flat cylindrical shape, the gap between the major axis of the trunnion 32 in its cross section and the inner diameter of the inner ring 12 (D-DJ (journal clearance) in FIG. 3) varies depending on the left-right tilt angle between the tripod member 3 and the inner ring 12. In particular, when the arc center of the axially convex curved surface of the trunnion 32 in its longitudinal section (A, A' (center of curvature) in FIG. 3) is offset from the central axis P of the trunnion 32, the larger the left-right tilt angle of the trunnion 32, the smaller the gap becomes. If the journal clearance is too small, the left-right tilt angle of the trunnion 32 increases when the constant velocity universal joint operates at a high operating angle, causing the gaps between the trunnion 32 and the inner diameter of the inner ring 12 to become negative and interfere with each other, which can lead to noise and vibration, deterioration of NVH performance, and early damage. Conversely, if the journal clearance is too large, circumferential backlash increases and NVH performance deteriorates.

[0037] For this reason, it is necessary to set the journal clearance to an appropriate value. Therefore, in the tripod constant velocity universal joint according to the present invention, interference between the trunnion 32 and the inner peripheral surface 18 of the inner ring 12 can be avoided by setting the above equations 3 and 4. In equation 3, S is called the journal clearance, and when the inner diameter of the inner ring 11 is D and the maximum diameter of the trunnion 32 at a working angle of 0° is DJ, S = D - DJ. Furthermore, F is the offset of the axial radius, which is the offset of the center of curvature A of the convex curved surface in the longitudinal cross section from the trunnion center. α is the left-right tilt angle, which is the angle at which the trunnion center P tilts with respect to a plane that is parallel to the joint axis and passes through the trunnion center P. In equation 4, θ is the working angle of the constant velocity universal joint.

[0038] The minimum value of the journal clearance (Smin) can be set using the following equation 5. The maximum value of the journal clearance (Smax) can be expressed using the following equation 6.

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[0039]

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[0040] Incidentally, α in Equation 5 is the lateral tilt angle when the joint has an operating angle θ, and can be expressed by the following Equation 7. Fig. 7 is an explanatory diagram showing the maximum outer diameter of the trunnion when the trunnion forms a lateral tilt angle of α, and Figs. 8(a) and (b) show the relationship between PCR and the trunnion whirl radius e (see Figs. 5 and 8) when the trunnion forms a lateral tilt angle of α.

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[0041] Here, O is the center of the tripod member 3, P is the intersection of the leg axis 32 and the PCR, and O' is the intersection of the tangent drawn from P to a circle with a whirl radius of e. Therefore, PO in Equation 7 indicates the length of the line segment between the intersection P and the center of the tripod member 3, and OO' indicates the length of the line segment between the center of the tripod member 3 and the intersection O'. Therefore, Equation 7 can be derived from the definition of the inverse trigonometric function. Furthermore, the line segment PO is the PCR, and the line segment OO' has a radius of e, and Equation 7 can be replaced with the following Equation 8.

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[0042] Furthermore, the whirling radius e can be expressed by the following equation 9 using the PCR and the operating angle θ. Therefore, by substituting equation 9 into equation 8, we obtain equation 10, from which equation 11 can be calculated.

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[0043]

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[0044]

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[0045] Next, we will explain how to calculate the maximum outer diameter DJ' (see FIG. 6) of the trunnion 32 when the left-right tilt angle is α shown in FIG. 7. In FIG. 7, if the centers of curvature (central points) of the convex curved portion in the vertical cross section of the trunnion 32 are A and A', and if lines drawn horizontally from the respective central points A and A' intersect with the arc of the convex curved portion at points C and C', the dimension between C and C' is the maximum outer diameter DJ'. In other words, DJ' = CC', and if the intersection point with the perpendicular line dropped from intersection point P to line segment AC is P', then the following relational expression (12) holds.

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[0046] In this case, AC=R, AP=F, and ∠PAP'=α. Therefore, DJ' can be expressed by the following equation 13. Also, AP' can be expressed by equation 14.

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[0047]

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[0048] Incidentally, it is preferable that the minimum journal clearance be such that there is no interference between the trunnion 32 and the inner peripheral surface of the inner ring 12 during maximum operation. In this case, if the inner diameter of the inner ring when the operating angle is 0° is D and the outer diameter of the trunnion when the operating angle is 0° is DJ, then the journal clearance S is D-DJ, and this journal clearance S must be equal to or greater than the value of the formula shown in equation 15.

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[0049] In this case, DJ' can be expressed by the formula shown in formula 13, and DJ can be expressed as 2(RF). By substituting these into formula 15, we get formula 16, and then formula 17 can be obtained.

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[0050]

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[0051] Therefore, the relational expression shown in Equation 1 is the condition for preventing interference between the trunnion 32 and the inner peripheral surface of the inner ring. In this case, the minimum journal clearance (Smin) can be set as shown in Equation 5. Furthermore, the maximum journal clearance (Smax) can be set as shown in Equation 6.

[0052] According to the tripod constant velocity universal joint of the present invention, the rollers 11 have cylindrical outer peripheral surfaces, and the roller guideway 6 is a flat surface. In this case, when a torque load is applied, the flat roller guideway 6 and the cylindrical outer peripheral surfaces of the rollers 11 press against each other via a linear contact portion, thereby suppressing left and right tilt of the rollers 11 (see FIG. 11). Furthermore, by providing a pair of guide surfaces 7, 7 on both sides of the width of the roller guideway 6, which can abut against the rollers 11 from both sides in the axial direction, left and right tilt of the rollers 11 can be more reliably prevented.

[0053] In the tripod constant velocity universal joint, by setting the above formulas 1 and 2, interference between the trunnion 32 and the inner peripheral surface 18 of the inner ring 12 can be avoided as shown in FIG.

[0054] For this reason, in this tripod constant velocity universal joint, even at the maximum operating angle, there is no negative clearance between the trunnion 32 and the inner surface 18 of the inner ring 12, allowing for smooth operation, preventing deterioration of NVH performance due to the generation of abnormal noise and vibration, and also effectively preventing early damage.

[0055] When the minimum value of the clearance is Smin, it is preferable that Smin be expressed by the above-mentioned equation 5. By setting it in this way, interference between the trunnion 32 and the inner peripheral surface of the roller (inner peripheral surface 18 of the inner ring 12) can be effectively prevented even when the constant velocity universal joint has the maximum operating angle.

[0056] When the maximum value of the clearance is max and the minimum value of the clearance is Smin, Smax is preferably expressed by the above-mentioned equation 6. By setting it in this way, it is possible to effectively prevent the clearance (journal clearance) between the trunnion 32 and the inner peripheral surface of the roller (inner peripheral surface 18 of the inner ring 12) from becoming excessive. As a result, it is possible to effectively prevent an increase in circumferential backlash and a deterioration in NVH characteristics.

[0057] Furthermore, by making the radius of curvature R larger than the radius of curvature r, the length of the contact area between the outer surface 33 of the trunnion 32 and the inner surface 18 of the inner ring 12 in the trunnion axis direction (i.e., the minor axis of the contact ellipse) becomes longer, thereby suppressing the increase in surface pressure at these contact areas.

[0058] It can be used in constant velocity universal joints with a maximum working angle of 23 to 28 degrees. That is, in a constant velocity universal joint with such a maximum working angle, even when the working angle is taken, the gap (journal gap) between the trunnion 32 and the inner peripheral surface of the unit in the roller (inner peripheral surface 18 of the inner ring 12) does not become negative, preventing the generation of abnormal noise and vibration, suppressing circumferential backlash, and preventing a deterioration in NVH performance.

[0059] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible, and the center of curvature and radius of curvature of the convexly curved portion in the longitudinal section and the center of curvature and radius of curvature of the convexly curved portion in the transverse section can be changed as desired as long as they satisfy the above-mentioned equations 1 to 17. Furthermore, the tripod-type constant velocity universal joint can be used for a drive shaft equipped in the torque transmission system of an automobile, but the use of constant velocity universal joints is not limited to automobiles and can naturally be used widely in the power transmission systems of automobiles and industrial equipment in general. [Explanation of symbols]

[0060] 2 Outer joint member 3 Tripod member 4 Roller unit 5 Straight track grooves 6 Roller guideway 11 Outering 12 Inner ring 18 Inner surface 32 Leg axis 33 Outer surface 33a Arc 33b Arc

Claims

1. a tripod-type constant velocity universal joint comprising: an outer joint member having three track grooves formed on an inner peripheral surface thereof, the track grooves extending in a joint axial direction, and a pair of roller guideways opposed in a joint circumferential direction, in each track groove; a tripod member arranged on an inner peripheral surface of the outer joint member and having three trunnions protruding in a joint radial direction toward the track grooves; and three roller units each comprising an inner ring arranged on an outer periphery of the trunnions and supported by the trunnions in a state where it can rotate and swing on the trunnions, an outer ring arranged in the track grooves and positioned on the outer diameter side of the inner ring, and a plurality of rolling elements arranged between the inner ring and the outer ring and supporting the inner ring and the outer ring so as to be rotatable relative to each other, the outer peripheral surface of the outer ring is cylindrical and the roller guideway is flat, the inner peripheral surface of the inner ring is cylindrical, the outer peripheral surface of the trunnion has a convex curve bulging out on both sides in the torque transmission direction in a longitudinal section which is a section including the axis of the trunnion itself and a transverse section which is a section perpendicular to the axis of the trunnion itself, the center of curvature of the convex curve in the longitudinal section is offset to the side opposite the convex curve with respect to the central axis of the trunnion, the center of curvature of the convex curved surface in the transverse section is offset to the convex curve side with respect to the central axis of the trunnion and in the rotation direction of the tripod member, when the radius of curvature of the convex curve in the longitudinal section is R and the radius of curvature of the convex curved surface in the transverse section is r, R>r, A tripod-type constant velocity universal joint characterized in that, when F is the offset amount of the center of curvature in the longitudinal section, α is the left-right inclination angle between the trunnion and the inner ring, and S is the clearance in the rotation direction of the tripod member between the trunnion and the inner ring, the relationship of the following equation 1 is satisfied, and α is expressed by the following equation 2. [Equation 1] [Equation 2]

2. 2. The tripod type constant velocity universal joint according to claim 1, wherein when the minimum value of said clearance is Smin, Smin is expressed by the following equation 3. [Equation 3]

3. 2. The tripod type constant velocity universal joint according to claim 1, wherein when the maximum value of said clearance is max and the minimum value of said clearance is Smin, Smax is expressed by the following equation 4: [Equation 4]

4. 2. The tripod type constant velocity universal joint according to claim 1, wherein the maximum operating angle is set to 23 to 28 degrees.

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