JP2007327617A - Tripod type constant velocity joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tripod type constant velocity joint capable of miniaturizing it while reducing a derived thrust force. <P>SOLUTION: An intermediate shaft direction width bx of a tripod shaft part 22 (width of the tripod shaft part 22 viewed from a torque transmission direction) of the tripod type constant velocity joint is formed to get narrow from a root side toward a tip side, in a torque transmission zone. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tripod type constant velocity joint.

  The conventional tripod shaft portion has a cylindrical shape. In this tripod type constant velocity joint, when the rotational force is transmitted when the joint angle is not 0 degrees, the roller rotates around the axis of the tripod shaft part and reciprocates in the axial direction along the guide groove of the outer race. Move back and forth. At this time, since the tripod shaft portion is cylindrical, the roller is always located coaxially with the tripod shaft portion. Therefore, slip occurs between the roller and the guide groove, and as a result, an induced thrust force is generated in the joint axial direction. This induced thrust force causes generation of vibrations and noise of the vehicle body and affects the NVH performance of the vehicle.

  Therefore, in order to reduce the induced thrust force, for example, there are those disclosed in Japanese Patent Laid-Open No. 3-172619 (Patent Document 1) and Japanese Patent Laid-Open No. 2000-320563 (Patent Document 2). In the tripod constant velocity joint disclosed in Patent Document 1, the outer peripheral surface shape of the tripod shaft portion is spherical. Accordingly, the roller can swing with respect to the tripod shaft portion, and no slip occurs between the roller and the guide groove.

In the tripod constant velocity joint disclosed in Patent Document 2, the tripod shaft portion is always an elliptic cylinder having the same axial orthogonal cross-sectional shape. The elliptic cylinder has a shape in which a gap is formed between the tripod shaft and the roller in the intermediate shaft axial direction, and the tripod shaft and the roller are in contact with each other in the torque transmission direction. Therefore, when viewed from the direction of torque transmission, the roller can operate so as to be inclined with respect to the tripod shaft portion. As a result, no slip occurs between the roller and the guide groove.
Japanese Patent Laid-Open No. 3-172619 JP 2000-320563 A

  Here, in the tripod type constant velocity joint disclosed in Patent Document 1, since the root portion of the tripod shaft portion is constricted, the section modulus of the root portion is small. Further, in the tripod type constant velocity joint disclosed in Patent Document 2, the tripod shaft portion is always an elliptic cylinder having the same axis orthogonal cross-sectional shape, so that the section coefficient of the root portion of the tripod shaft portion is small. Therefore, in any of the above cases, it is necessary to increase the cross-sectional shape of the tripod shaft portion in order to ensure the strength of the tripod shaft portion. Therefore, the outer shape of the tripod type constant velocity joint is increased.

  This invention is made | formed in view of such a situation, and it aims at providing the tripod type | mold constant velocity joint which can reduce in size, reducing induced thrust force.

  Therefore, the present inventor has intensively studied to solve this problem, and as a result of trial and error, in order to reduce the induced thrust force, the required swing angle of the roller with respect to the tripod shaft portion is set so that the roller relative to the tripod shaft portion is We came up with the present invention by conceiving different things depending on the position.

  First, the required rocking angle of the roller with respect to the tripod shaft for reducing the induced thrust force will be described. When the joint angle is 0 degree, the relative position of the roller with respect to the tripod shaft is always constant. The position of the roller in this case is the most proximal side in the torque transmission region of the tripod shaft.

  Here, a torque transmission area | region is an axial direction area | region of the tripod shaft part in which the site | part which contributes to torque transmission is included among the outer peripheral surfaces of a tripod shaft part. The portion contributing to torque transmission is a portion of the tripod shaft portion that can contact the roller when torque transmission is performed between the tripod shaft portion and the roller.

  On the other hand, when the joint angle is not 0 degree, the roller reciprocates in the tripod shaft direction with respect to the tripod shaft portion. And when a roller is located in the most base side among tripod shaft parts, in order to reduce an induced thrust force, it is good for the roller rotation axis of a roller and the tripod shaft of a tripod shaft part to correspond. In this case, the position of the roller with respect to the tripod shaft portion coincides with the position of the roller with respect to the tripod shaft portion when the joint angle is 0 degree.

  Further, when the joint angle is not 0 degree and the roller is positioned on the tip side of the tripod shaft portion, in order to reduce the induced thrust force, the roller is inclined with respect to the tripod shaft portion. Good. The inclination angle may be increased as the roller goes to the tip side of the tripod shaft portion.

  In other words, when the roller is located on the root side of the tripod shaft, the tripod shaft portion becomes closer to the tip side of the tripod shaft portion so that the roller rotation shaft of the roller matches the tripod shaft of the tripod shaft portion. It is preferable that the inclination angle of the roller with respect to is increased.

  Therefore, the tripod type constant velocity joint of the present invention is as follows. That is, the tripod constant velocity joint of the present invention includes an outer race, a tripod, and a roller. The outer race has a cup shape, and three guide grooves extending in the direction of the rotation axis (hereinafter referred to as “outer race rotation axis”) are formed on the inner peripheral surface. The tripod includes a cylindrical boss portion and three tripod shaft portions that extend from the boss portion to the outside in the radial direction of the intermediate shaft shaft and are inserted into the respective guide grooves. The roller is formed in a ring shape and is rotatably supported by each tripod shaft portion, and engages with the guide groove so as to be able to roll. In the torque transmission region of the tripod shaft portion, the intermediate shaft axial width of the tripod shaft portion is formed to be smaller from the root side toward the tip side.

  That is, according to the tripod type constant velocity joint of the present invention, in the torque transmission region, the intermediate shaft axial width of the tripod shaft portion is formed smaller as it goes from the root side to the tip side. Here, the inner diameter of the roller is at least equal to or greater than the width in the axial direction of the intermediate shaft at the root of the tripod shaft. If it does so, in the front-end | tip part of a tripod shaft part, when it sees from a torque transmission direction, a clearance gap will be formed between a tripod shaft part and a roller. Therefore, the roller can swing on the tip end side of the tripod shaft portion when viewed from the torque transmission direction. Further, as the roller moves from the base side to the tip side of the tripod shaft portion, the swing angle of the roller with respect to the tripod shaft portion can be increased when viewed from the torque transmission direction. Thereby, the rocking | fluctuation angle of the roller with respect to a tripod shaft part can be changed so that an induced thrust force may be reduced.

  Furthermore, according to the tripod type constant velocity joint of the present invention, the width of the tripod shaft portion in the intermediate shaft axial direction is formed smaller toward the tip side. That is, the intermediate shaft axial width of the base portion of the tripod shaft portion can be increased. For example, in the base part of the tripod shaft part, it is possible to prevent a gap from being generated between the roller and the tripod shaft part. Therefore, the section modulus of the root portion of the tripod shaft portion can be increased. As a result, the strength of the tripod shaft can be increased, so that the outer shape of the tripod constant velocity joint can be reduced.

  For example, it compares with the case of the tripod axial part which consists of an elliptic cylinder described in patent document 2. FIG. For example, the shape of the tip part of the tripod shaft part of the present invention is the elliptical shape of the tripod shaft part described in Patent Document 2. In this case, the torque transmission direction width of the root portion of the tripod shaft portion of the present invention is larger than the small diameter of the ellipse. Therefore, the section modulus of the root portion of the tripod shaft portion of the present invention can be made larger than the section modulus of the root portion of the tripod shaft portion described in Patent Document 2. Therefore, the outer shape of the tripod type constant velocity joint can be reduced as compared with the case of the tripod shaft portion made of an elliptic cylinder.

  Further, when the direction perpendicular to the intermediate shaft axis and the tripod axis is defined as the torque transmission direction, the torque transmission direction width of the tripod shaft portion is formed to be smaller from the root side toward the tip side in the torque transmission region. Good. In this case, the inner diameter of the roller is at least equal to or greater than the width in the torque transmission direction at the root of the tripod shaft. If it does so, in the front-end | tip part of a tripod shaft part, when it sees from an intermediate shaft axial direction, a clearance gap will be formed between a tripod shaft part and a roller. Therefore, the roller can swing on the tip side of the tripod shaft portion when viewed from the axial direction of the intermediate shaft. Furthermore, as the roller goes from the base side to the tip side of the tripod shaft portion, the swing angle of the roller with respect to the tripod shaft portion can be increased when viewed from the intermediate shaft axial direction. As a result, the degree of freedom of rocking of the roller increases toward the tip end side of the tripod shaft portion. As a result, generation of induced thrust force can be further reduced.

  In the torque transmission region, the torque transmission direction width of the tripod shaft portion may be the same from the root side to the tip side. Even in this case, since the necessary swing angle of the roller with respect to the tripod shaft portion is secured, the generation of the induced thrust force can be sufficiently reduced. However, in this case, the induced thrust force may increase because the degree of freedom of oscillation is smaller than in the case where the width in the torque transmission direction is reduced from the base side to the tip side.

  Here, as described above, in order to reduce the induced thrust force and the like, the roller needs to swing with respect to the tripod shaft when viewed from the torque transmission direction. On the other hand, when viewed from the axial direction of the intermediate shaft, the roller does not have to swing so much with respect to the tripod shaft portion. For example, in the tripod type constant velocity joint described in Patent Document 1, the roller can swing greatly with respect to the tripod shaft portion when viewed from either the intermediate shaft axial direction or the torque transmission direction. However, when viewed from the axial direction of the intermediate shaft, the roller may swing with respect to the tripod shaft portion, so that the end surface of the roller may come into contact with the guide groove. This contact causes slippage between the roller and the guide groove, resulting in an induced thrust force.

  Therefore, the intermediate shaft axial width of the tip portion of the tripod shaft portion may be formed smaller than the torque transmission direction width of the tip portion of the tripod shaft portion. As a result, at the tip of the tripod shaft, the angle at which the roller can swing relative to the tripod shaft when viewed from the intermediate shaft axial direction is such that the roller can swing relative to the tripod shaft when viewed from the torque transmission direction. It can be made smaller than an angle. Therefore, in order to reduce the induced thrust force, the required swing angle of the roller with respect to the tripod shaft when viewed from the torque transmission direction is ensured, and the roller swings with respect to the tripod shaft when viewed from the intermediate shaft axial direction. By the movement, it is possible to reduce an increase in the induced thrust force due to the contact between the end face of the roller and the guide groove.

  In the torque transmission region, the ratio of the intermediate shaft axial width of the tip portion of the tripod shaft portion to the intermediate shaft axial width of the root portion of the tripod shaft portion may be 0.25 to 0.8. Preferably, the ratio is 0.45 to 0.65. More preferably, the ratio is 0.55. Thereby, when a roller is located in the front end side of a tripod shaft part, a roller can fully rock | fluctuate with respect to a tripod shaft part. Therefore, the induced thrust force can be reliably reduced.

  In the torque transmission region, the ratio of the torque transmission direction width of the tip portion of the tripod shaft portion to the torque transmission direction width of the root portion of the tripod shaft portion is preferably 0.7 to 1.0. Preferably, the ratio is 0.85 to 0.98. More preferably, the ratio is 0.95. Thereby, the induced thrust force can be reliably reduced.

  In addition, when the tripod shaft section is formed in an elliptical cross-sectional shape, the torque transmission direction width of the tripod shaft section is defined as a, and the intermediate shaft axial width of the tripod shaft section is defined as b. In this case, the ellipticity b / a of the root portion of the tripod shaft portion is 0.70 to 1.30, and the ellipticity b / a of the tip portion of the tripod shaft portion is preferably 0.35 to 0.80. Preferably, the ellipticity b / a of the root portion is 0.95 to 1.05, and the ellipticity b / a of the tip portion is 0.45 to 0.65. Thereby, the induced thrust force can be reliably reduced.

  Also, in the torque transmission region, the intermediate shaft axial width of the tripod shaft portion may be equal to or less than the torque transmission direction width of the tripod shaft portion at the same tripod axial position. As a result, at any position in the tripod axial direction, the angle at which the roller can swing relative to the tripod shaft when viewed from the intermediate shaft axial direction is such that the roller swings relative to the tripod shaft when viewed from the torque transmission direction. It becomes smaller than the movable angle. Therefore, in order to reduce the induced thrust force at any position in the tripod shaft direction, the roller can be swung with respect to the tripod shaft portion when viewed from the torque transmission direction, and viewed from the intermediate shaft axis direction. In this case, it is possible to reduce an increase in the induced thrust force due to the contact between the end face of the roller and the guide groove due to the rocking of the roller with respect to the tripod shaft portion.

  Moreover, it is good for the axis orthogonal cross-sectional shape of the root part of a tripod shaft part to be formed circularly. This makes it possible to increase the section modulus of the root portion of the tripod shaft portion. Therefore, since the strength of the tripod shaft portion can be increased, the outer shape of the tripod constant velocity joint can be further reduced. In particular, when the diameter of the cross-sectional shape perpendicular to the axis is substantially equal to the inner diameter of the roller, the section modulus is maximum.

  According to the tripod type constant velocity joint of the present invention, it is possible to reduce the size while reducing the induced thrust force.

  Next, the present invention will be described in more detail with reference to embodiments. Here, the tripod type constant velocity joint of the present embodiment will be described by taking as an example a case where it is used for coupling a power transmission shaft of a vehicle. Specifically, this is a case where the shaft portion connected to the differential gear is used as a connecting portion between the intermediate shaft.

  This tripod type constant velocity joint will be described with reference to FIGS. FIG. 1 is a sectional view in the axial direction of an intermediate shaft of a tripod constant velocity joint (hereinafter referred to as “intermediate shaft axial view”). FIG. 2 is an axial sectional view (hereinafter referred to as “torque transmission direction view”) of the tripod type constant velocity joint. FIG. 3 is a view of the tripod 20 as viewed from the tip side of the tripod shaft portion 22. That is, FIG. 3 is a view of the tripod 20 as viewed from the upper side of FIG.

  The tripod type constant velocity joint includes an outer race 10 connected to one side shaft (not shown), a tripod 20 connected to the other side shaft (not shown) (intermediate shaft), the outer race 10 and the tripod. 20 and a roller 30 interposed therebetween.

  The outer race 10 is formed in a cup shape (bottomed cylindrical shape), and the outer side of the cup bottom is connected to a shaft on one side. Three guide grooves 11 extending in the outer race rotation axis direction (the front-rear direction in FIG. 1 and the left-right direction in FIG. 2) are formed at equal intervals on the inner peripheral surface of the cup-shaped portion of the outer race 10. 1 and 2, only one guide groove 11 is shown.

  The tripod 20 is disposed inside the cup-shaped portion of the outer race 10. The tripod 20 includes a boss portion 21 and three tripod shaft portions 22. The boss portion 21 has a cylindrical shape, and the inner peripheral side of the boss portion 21 is connected to the end portion of the other side shaft (intermediate shaft).

  Each tripod shaft portion 22 extends outwardly in the radial direction of the intermediate shaft shaft (axial center of the tripod 20) on the outer peripheral side of the boss portion 21 and is equally spaced in the circumferential direction of the boss portion 21. Is formed. The tripod shaft portion 22 has a columnar shape having an elliptical cross-sectional shape (including a circular cross-sectional shape). Specifically, as shown in FIGS. 1 and 3, in the torque transmission region, the torque transmission direction width ax of the tripod shaft portion 22 is formed to be slightly smaller from the root side to the tip side of the tripod shaft portion 22. ing. That is, the torque transmission direction width a <b> 2 of the tip portion of the tripod shaft portion 22 is formed to be smaller than the torque transmission direction width a <b> 1 of the root portion of the tripod shaft portion 22. Although details will be described later, the torque transmission direction width ax of the tripod shaft portion 22 may be all constant.

  As shown in FIGS. 2 and 3, in the torque transmission region, the intermediate shaft axial width bx of the tripod shaft portion 22 is formed so as to decrease from the root side to the tip side of the tripod shaft portion 22. That is, the intermediate shaft axial width b <b> 2 of the tip portion of the tripod shaft portion 22 is formed smaller than the intermediate shaft axial width b <b> 1 of the root portion of the tripod shaft portion 22. The intermediate shaft axial width b2 of the tip portion of the tripod shaft portion 22 is formed to be smaller than the torque transmission direction width a2 of the tip portion.

  Here, the torque transmission region is a region shown in FIG. 2, and is an axial region of the tripod shaft portion 22 including a portion contributing to torque transmission on the outer peripheral surface of the tripod shaft portion 22. The part contributing to torque transmission is a part that can contact the inner roller 31 of the roller 30 in the tripod shaft part 22 when torque transmission is performed between the tripod shaft part 22 and the roller 30. The parts contributing to this torque transmission are the left and right ends of the tripod shaft 22 in FIG. The detailed shape of tripod shaft 22 will be described later.

  The roller 30 has a ring shape. The roller 30 is pivotally supported on the outer peripheral side of the tripod shaft portion 22 so as to be rotatable around the tripod shaft and slidable in the tripod shaft direction. Further, the roller 30 can swing with respect to the tripod shaft portion 22. Further, the roller 30 is disposed in the guide groove 11 so as to be able to roll. The roller 30 includes an inner roller 31, an outer roller 32, a plurality of needles 33, and two snap rings 34 and 34.

  The inner roller 31 has a cylindrical shape, and is pivotally supported by the tip 221 of each tripod shaft 22 so as to be able to rotate, slide and swing. The cylindrical inner surface of the inner roller 31 is in contact with the tripod shaft portion 22. The cylinder length of the inner roller 31 is slightly smaller than the length of the torque transmission region of the tripod shaft portion 22. The inner diameter of the inner roller 31 is slightly larger than the major diameter of the root portion of the tripod shaft portion 22.

  Here, the intermediate shaft axial width bx of the tripod shaft portion 22 is formed so as to decrease from the root side to the tip side. Therefore, when the inner roller 31 is located at the root portion of the tripod shaft portion 22, the roller 30 can hardly swing with respect to the tripod shaft portion 22 in the torque transmission direction view (FIG. 2). On the other hand, when the inner roller 31 is located at the tip of the tripod shaft 22, the roller 30 can swing greatly with respect to the tripod shaft 22 in the torque transmission direction view (FIG. 2). The swing angle increases as the position of the inner roller 31 with respect to the tripod shaft portion 22 moves from the root side to the tip side.

  On the other hand, the torque transmission direction width ax of the tripod shaft portion 22 may be constant from the root side to the tip side. In this case, regardless of the position of the inner roller 31 in the tripod shaft portion 22, the roller 30 hardly swings with respect to the tripod shaft portion 22 as viewed in the axial direction of the intermediate shaft (FIG. 1).

  Moreover, the torque transmission direction width ax of the tripod shaft part 22 may be formed smaller as it goes from the root side to the tip side. In this case, when the inner roller 31 is located at the root portion of the tripod shaft portion 22, the roller 30 hardly swings with respect to the tripod shaft portion 22 as viewed in the axial direction of the intermediate shaft (FIG. 1). On the other hand, when the inner roller 31 is located at the tip of the tripod shaft 22, the roller 30 can swing with respect to the tripod shaft 22 as viewed in the axial direction of the intermediate shaft (FIG. 1). The swing angle increases as the position of the inner roller 31 with respect to the tripod shaft portion 22 moves from the root side to the tip side. Further, the intermediate shaft axial width b2 of the tip portion of the tripod shaft portion 22 is formed to be smaller than the torque transmission direction width a2 of the tip portion. Therefore, when the inner roller 31 is positioned at the tip of the tripod shaft portion 22, the swingable angle of the roller 30 in the intermediate shaft axial direction view (FIG. 1) is the same as that of the roller 30 in the torque transmission direction view (FIG. 2). It becomes smaller than the swingable angle.

  The outer roller 32 has a cylindrical shape. The outer peripheral surface of the outer roller 32 has a shape that follows the guide groove 11. Accordingly, the outer roller 32 is engaged with the guide groove 11 so as to be able to roll about the vertical axis (around the tripod axis) in FIG. Further, on the inner peripheral surface of the outer roller 32, locking grooves 32a are formed on the radially outer side (upper side in FIG. 1) and the radial inner side (lower side in FIG. 1). Each needle 33 has an elongated cylindrical shape, and is interposed between the inner roller 31 and the outer roller 32 so as to be able to roll with respect to the inner roller 31 and the outer roller 32.

  The snap rings 34, 34 are fitted in the locking grooves 32a, respectively, so as to engage with the inner roller 31 and the needle 33 in the roller rotation axis direction (vertical direction in FIG. 1). That is, the snap rings 34 and 34 prevent the inner roller 31 and the needle 33 from separating from the inner side of the outer roller 32 in the upward and downward directions in FIG.

  In the above description, the inner roller 31 of the roller 30 is cylindrical. However, the inner peripheral surface or the outer peripheral surface of the inner roller 31 may be formed in a spherical shape, or the roller rotation shaft radial direction (radially outer side). Or it may have a dent or a bulge in the radially inner side. In the above description, the outer roller 32 is also cylindrical. However, the outer peripheral surface or inner peripheral surface of the outer roller 32 may be formed in a spherical shape, or may be a roller rotation shaft radial direction (radial outer side or radial direction). It may have a dent or bulge inside.

  Next, the operation of the tripod constant velocity joint described above will be described. First, when the joint angle is 0 degree, that is, when the intermediate shaft axis and the outer race rotation axis coincide with each other, the roller 30 is positioned at the root portion of the tripod shaft portion 22. At this time, in order for the roller 30 to roll smoothly along the guide groove 11, the roller rotation shaft of the roller 30 and the tripod shaft of the tripod shaft portion 22 should coincide. When the roller 30 is positioned at the root of the tripod shaft 22, the roller 30 hardly swings with respect to the tripod shaft 22, and the roller rotation shaft of the roller 30 and the tripod shaft of the tripod shaft 22 are almost the same. It will be in a consistent state. Therefore, when the joint angle is 0 degree, the roller 30 can roll smoothly along the guide groove 11.

  On the other hand, when the joint angle is not 0 degrees, that is, when the intermediate shaft shaft and the outer race rotation shaft are inclined, the roller 30 reciprocates between the root portion and the tip portion of the tripod shaft portion 22. . When the joint angle is not 0 degree and the roller 30 is positioned at the root portion of the tripod shaft portion 22, the roller 30 rotates in order to smoothly roll along the guide groove 11. It is preferable that the axis and the tripod axis of the tripod shaft portion 22 coincide with each other. When the roller 30 is positioned at the root of the tripod shaft 22, the roller 30 hardly swings with respect to the tripod shaft 22, and the roller rotation shaft of the roller 30 and the tripod shaft of the tripod shaft 22 are almost the same. It will be in a consistent state.

  Further, in order to smoothly roll the roller 30 along the guide groove 11 when the roller 30 is positioned at the tip of the tripod shaft portion 22 when the joint angle is not 0 degree, two points in FIG. As indicated by a chain line, the roller 30 may be inclined with respect to the tripod shaft 22 in the torque transmission direction view (FIG. 2). When the roller 30 is positioned at the tip of the tripod shaft portion 22, the roller 30 can largely swing with respect to the tripod shaft portion 22, so that the roller 30 extends along the guide groove 11. Swings against. Therefore, even when the joint angle is not 0 degree, the roller 30 can roll smoothly along the guide groove 11.

  Next, an experiment was conducted in which the induced thrust force was measured when the torque transmission direction width ax and the intermediate shaft axial direction width bx of the tripod shaft portion 22 were changed. In this experiment, the outer race 10 was supported on the detection bearing, the tripod 20 was held at a predetermined angle with respect to the outer race 10, and the thrust force generated in the detection bearing was measured. That is, this thrust force corresponds to the induced thrust force generated by the tripod constant velocity joint.

  As a first experiment, an induced thrust force generated when the intermediate shaft axial width bx was changed in a state where the torque transmission direction width ax was fixed was measured. Here, as a condition of the first experiment, the intermediate shaft axial width bx is made smaller from the root to the tip side. Furthermore, the tripod axis orthogonal cross-sectional shape of the tripod shaft portion 22 is an elliptical shape in which the intermediate shaft axial width bx is an ellipse major axis or minor axis.

  The measurement results are shown in FIG. In FIG. 4, the horizontal axis represents the ratio (bx / b1) of the intermediate shaft axial width bx at an arbitrary position to the intermediate shaft axial width b1 of the root portion, and the vertical axis represents the tip portion of the tripod shaft portion 22 from the root portion. Axial position up to In FIG. 4, the range where the induced thrust force is a predetermined value or less is indicated by dark hatching.

  As can be seen from FIG. 4, when the intermediate shaft axial width b1 of the root portion is 1, the induced thrust force is small when the intermediate shaft axial width b2 of the tip portion is 0.25 to 0.8. Further, the induced thrust force is further small when the intermediate shaft axial width b2 of the tip portion is in the range of 0.45 to 0.65. And, the induced thrust force is the smallest when the intermediate shaft axial width b2 of the tip is 0.55.

  Here, the larger the tip portion ratio b2 / b1, the smaller the swing angle of the roller 30 when the roller 30 is positioned at the tip portion of the tripod shaft portion 22. Therefore, it is considered that the roller 30 cannot smoothly roll into the guide groove 11 and the induced thrust force is increased.

  In the dark hatching range shown in FIG. 4, the shape between the root portion and the tip portion of the intermediate shaft axial width bx of the tripod shaft portion 22 is not limited as long as the above condition is satisfied. Good. That is, the path from the root part to the tip part may be a straight line, a curve with a uniform curvature, or a curve with a changing curvature. However, between the root portion and the tip portion of the intermediate shaft axial width bx of the tripod shaft portion 22, the induced thrust force increases as the rate of change of the ratio bx / b1 increases from the root portion to the tip portion. It is getting smaller.

  As a second experiment, an induced thrust force generated when the torque transmission direction width ax was changed in a state where the intermediate shaft axial direction width bx was fixed was measured. Here, as a condition of the second experiment, the torque transmission direction width ax is constant over the entire length from the root portion to the tip portion, or is made smaller as going from the root portion to the tip side. Furthermore, the tripod axis orthogonal cross-sectional shape of the tripod shaft part 22 is an elliptical shape in which the torque transmission direction width ax is an ellipse major axis or minor axis.

  The measurement results are shown in FIG. In FIG. 5, the horizontal axis represents the ratio (ax / a1) of the torque transmission direction width ax at an arbitrary position to the torque transmission direction width a1 of the root portion, and the vertical axis represents the distance from the root portion to the tip portion of the tripod shaft portion 22. Axial position. In FIG. 5, the range where the induced thrust force is equal to or less than a predetermined value is indicated by dark hatching.

  As can be seen from FIG. 5, when the torque transmission direction width a <b> 1 of the root part is 1, the induced thrust force is small when the torque transmission direction width a <b> 2 of the tip part is 0.7 to 1.0. Further, the induced thrust force is further smaller when the torque transmission direction width a2 of the tip portion is in the range of 0.85 to 0.98. And, the induced thrust force is the smallest when the intermediate shaft axial width b2 of the tip is 0.95.

  Here, when the tip portion ratio a2 / a1 is smaller than 0.7, when the roller 30 is positioned at the tip portion of the tripod shaft portion 22, the degree of freedom of rocking of the roller 30 in the axial direction of the intermediate shaft is large. growing. For this reason, the end face of the roller 30 may come into contact with the guide groove 11. This contact is considered to have increased the induced thrust force.

  In addition, as long as it is the range of the deep hatching shown in FIG. 5, any shape may be sufficient between the root part of the torque transmission direction width ax of the tripod shaft part 22 and a front-end | tip part, if the said conditions are satisfy | filled. . That is, the path from the root part to the tip part may be a straight line, a curve with a uniform curvature, or a curve with a changing curvature. However, between the root part and the tip part of the torque transmission direction width ax of the tripod shaft part 22, the induced thrust force becomes smaller as the rate of change of the ratio ax / a 1 increases from the root part to the tip part. It has become.

  As a third experiment, when the tripod axis orthogonal cross-sectional shape of the tripod shaft portion 22 is an elliptical shape in which the intermediate shaft axial width bx or the torque transmission direction width ax has a major axis or a minor axis, and the ellipticity bx / ax is changed The induced thrust force generated in the was measured. Here, as a condition in the third experiment, the intermediate shaft axial width bx is made smaller from the root to the tip side. Further, the torque transmission direction width ax is constant over the entire length from the root portion to the tip portion, or is made smaller as going from the root portion to the tip side. Furthermore, the ellipticity bx / ax is made smaller as it goes from the root part to the tip side.

  The measurement results are shown in FIG. In FIG. 6, the horizontal axis is the ellipticity bx / ax, and the vertical axis is the axial position from the root portion to the tip portion of the tripod shaft portion 22. In FIG. 6, the range where the induced thrust force is a predetermined value or less is indicated by dark hatching.

  As can be seen from FIG. 6, the ellipticity b1 / a1 at the base is 0.70 to 1.30, and the ellipticity b2 / a2 at the tip is in the range of 0.35 to 0.80. The power is small. Further, the ellipticity b1 / a1 of the root portion is 0.95 to 1.05, and the ellipticity b2 / a2 of the tip portion is in the range of 0.45 to 0.65, and the induced thrust force is further small. The induced thrust force is the smallest when the ellipticity b1 / a1 of the root portion is 1.00 and the ellipticity b2 / a2 of the tip portion is 0.55.

  In addition, as long as the above conditions are satisfied, any shape may be used between the root portion and the tip portion of the tripod shaft portion 22 as long as the range is the dark hatching shown in FIG. That is, the path from the root part to the tip part may be a straight line, a curve with a uniform curvature, or a curve with a changing curvature. However, between the root portion and the tip portion of the tripod shaft portion 22, the induced thrust force decreases as the change rate of the ellipticity bx / ax increases from the root portion to the tip portion.

  Here, the tripod shaft part 22 of this embodiment has a larger section modulus at the root part than the tip part. Therefore, the strength of the tripod shaft portion 22 can be increased, and as a result, the tripod constant velocity joint can be downsized. In particular, the tripod axis orthogonal cross-sectional shape of the root portion can be a circle having the maximum section modulus.

An intermediate shaft axial view of a tripod type constant velocity joint is shown. The torque transmission direction view of a tripod type constant velocity joint is shown. It is the figure which looked at the tripod 20 from the front end side of the tripod shaft part 22. FIG. The measurement result of a 1st experiment is shown. The measurement result of 2nd experiment is shown. The measurement result of the third experiment is shown.

Explanation of symbols

10: outer race, 11: guide groove,
20: Tripod, 21: Boss part, 22: Tripod shaft part,
30: Roller, 31: Inner roller, 32: Outer roller, 33: Needle,
34: Snap ring

Claims (9)

An outer race having a cup shape and having three guide grooves formed in the inner peripheral surface extending in the direction of the rotation axis;
A tripod comprising: a cylindrical boss portion; and three tripod shaft portions that extend from the boss portion to the outside in the radial direction of the intermediate shaft shaft and are inserted into the guide grooves.
A roller having a ring shape and rotatably supported by each of the tripod shafts and rotatably engaged with the guide groove;
A tripod type constant velocity joint comprising:
In the torque transmission region of the tripod shaft portion, a tripod type constant velocity joint is characterized in that an intermediate shaft axial width of the tripod shaft portion is formed to decrease from the root side to the tip side. When the direction perpendicular to the intermediate shaft axis and tripod axis is defined as the torque transmission direction,
2. The tripod constant velocity joint according to claim 1, wherein in the torque transmission region, a torque transmission direction width of the tripod shaft portion is formed to decrease from the root side toward the tip side.   The tripod constant velocity joint according to claim 1 or 2, wherein the intermediate shaft axial width of the tip of the tripod shaft is smaller than the torque transmission width of the tip of the tripod shaft.   The ratio of the intermediate shaft axial direction width of the tip of the tripod shaft part to the intermediate shaft axial width of the root part of the tripod shaft part in the torque transmission region is 0.25 to 0.8. The tripod type constant velocity joint as described in any one of 1-3.   The ratio of the torque transmission direction width of the tip portion of the tripod shaft portion to the torque transmission direction width of the root portion of the tripod shaft portion in the torque transmission region is 0.7 to 1.0. The tripod type constant velocity joint as described in any one of 4. The tripod shaft portion has an axial cross-sectional shape that is elliptical,
When the torque transmission direction width of the tripod shaft portion is defined as a and the intermediate shaft axial width of the tripod shaft portion is defined as b,
In the torque transmission region, the ellipticity b / a of the root portion of the tripod shaft portion is 0.70 to 1.30, and the ellipticity b / a of the tip portion of the tripod shaft portion is 0.35 to 0.00. The tripod constant velocity joint according to any one of claims 1 to 5, which is 80.   7. The torque transmission region according to claim 1, wherein an intermediate shaft axial width of the tripod shaft portion is equal to or less than a torque transmission direction width of the tripod shaft portion at the same tripod axial position. Tripod type constant velocity joint.   The tripod type constant velocity joint according to any one of claims 1 to 7, wherein an inner peripheral surface of the roller is cylindrical.   The tripod type constant velocity joint according to any one of claims 1 to 8, wherein an axis orthogonal cross-sectional shape of a root portion of the tripod shaft portion is formed in a circular shape.

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