JP2008089021A - Constant velocity universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant velocity universal joint capable of lengthening the rolling fatigue service life of a tripod member, and capable of enhancing strength against surface starting-point type damage. <P>SOLUTION: This tripod type constant velocity universal joint has an outside joint member 1 forming three track grooves 2 in the axial direction in an inner peripheral part and having respectively an axial directional roller guide surface 3 on both sides of the respective track grooves 2, the tripod member 4 having three leg shafts 5 projected in the radial direction, and a roller 7 rotatably supported via a plurality of needle-like rollers 6 arranged on an outer peripheral surface of the respective leg shafts 5 of the tripod member 4 and inserted into the track grooves 2, and can move this roller 7 in the axial direction of the outside joint member 1 along the roller guide surface 3. A surface layer part formed by high concentration carburizing quenching-tempering, is arranged in the tripod member 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a constant velocity universal joint used for a power transmission device of an automobile or various industrial machines, and more particularly to a tripod type constant velocity universal joint.

  For example, a sliding tripod type constant velocity universal joint is used to transmit rotational power from an automobile engine to wheels at a constant speed. This sliding tripod type constant velocity universal joint connects two shafts on the drive side and the driven side, transmits rotational torque at a constant speed even if the two shafts have an operating angle, and has a relative axial displacement. It has an acceptable structure.

  This sliding tripod type constant velocity universal joint generally has an outer joint member in which three track grooves in the axial direction are formed on the inner peripheral portion, and an axial roller guide surface is provided on each side of each track groove; A tripod member having three leg shafts projecting in the radial direction and a roller externally fitted to the outer peripheral surface of each leg shaft of the tripod member via a plurality of needle rollers are mainly configured. (For example, refer to Patent Document 1).

The sliding tripod constant velocity universal joint having the above configuration operates as follows. That is, when the leg shaft of the tripod member and the roller guide surface of the outer joint member are engaged with each other in the rotational direction via the roller, the rotational torque is transmitted from the drive side to the driven side at a constant speed. Further, each roller rolls on the roller guide surface while rotating with respect to the leg shaft, so that the relative axial displacement and angular displacement between the outer joint member and the tripod member are absorbed. Further, the axial displacement of each leg shaft with respect to the roller guide surface accompanying the change in the rotational direction phase when the outer joint member and the tripod member transmit the rotational torque while taking the operating angle is absorbed.
JP 2000-320563 A

  However, in the tripod type constant velocity universal joint having the above-described configuration, when a rotational force is transmitted between the outer joint member and the tripod member, rolling and slip occur simultaneously between the leg shaft and the needle roller. For this reason, wear is likely to occur at the contact portion between the leg shaft and the needle roller, in particular, peeling or smearing is likely to occur on the surface of the leg shaft, shortening the rolling fatigue life of tripod members, There is a possibility of causing damage.

  Accordingly, an object of the present invention is to provide a constant velocity universal joint capable of extending the rolling fatigue life of the leg shaft of a tripod member and increasing the strength against surface-origin damage.

  In order to solve the above-mentioned problem, the invention of claim 1 includes an outer joint member in which three track grooves in the axial direction are formed on the inner periphery, and each has an axial roller guide surface on each side of each track groove; A tripod member having three leg shafts projecting in the radial direction, and a roller inserted into the track groove in a state of being rotatably attached to each leg shaft of the tripod member via a plurality of needle rollers. A constant velocity universal joint formed such that the roller is movable in the axial direction of the outer joint member along the roller guide surface, and the tripod member is provided with a surface layer portion formed by high-concentration carburizing and quenching and tempering. It is characterized by being.

  According to the present invention, the surface layer portion (high concentration carburized layer) is formed on the tripod member by high concentration carburizing and quenching and tempering. This high-concentration carburized layer has a structure in which carbides are dispersed in a martensite matrix, and has high wear resistance, surface damage resistance, and fatigue strength. Therefore, the tripod member can be given high resistance against rolling fatigue and high strength against cracking.

  In particular, by forming a surface layer portion by high-concentration carburizing quenching and tempering on the leg shaft of the tripod member, peeling and smearing are less likely to occur on the surface of the leg shaft, and resistance to rolling fatigue and strength against cracking, etc. Can increase.

  Further, the torsional fatigue becomes a problem because the torsional stress is concentrated at the base end portion of the leg shaft of the tripod member at the time of torque transmission and is usually left in an unground state. On the other hand, by forming a high-concentration carburized layer on the surface layer portion of the tripod member, the surface hardness increases and the torsional fatigue strength can be improved.

The high-concentration carburizing treatment is a treatment for forming a high-density fine dispersion structure of carbide on the steel surface layer, and is applied to a site where wear resistance, surface damage resistance, and fatigue strength are important.
In high-concentration carburizing treatment, it is necessary to control the carburization distribution and carbide precipitation in steel. In order to control the size and amount of the carbide, the cooling process after the carburizing treatment is repeated several times to repeat the diffusion of C into the steel and the precipitation of the carbide in the carburized layer. It is known that a steel surface on which a large amount of carbide is precipitated is excellent in wear resistance and surface damage resistance. Further, it is known that the fatigue strength of the portion is improved as the carbide is finely dispersed and precipitated.
The high-concentration carburizing treatment here means that the total concentration of carbon in the carbide and martensite is 1.5% or more, and the carbide that is a stress concentration source in the treated portion has an average diameter of 7.5 μm or less, preferably Carburizing treatment of 5 μm or less is designated as high-concentration carburizing treatment.

  The surface layer portion may be formed at least directly below the contact surface with the needle roller of the tripod member. The structure in which the surface layer portion is formed only directly below the contact surface, the surface layer immediately below the contact surface and the surrounding surface. Both the configuration in which the portion is formed and the configuration in which the surface layer portion is formed immediately below the entire surface of the component are included.

  According to another aspect of the invention, in the constant velocity universal joint according to claim 1, the thickness of the surface layer portion of the tripod member is 0.2 mm or more immediately below the contact portion with the needle roller.

  According to the constant velocity universal joint having the above configuration, by making the thickness of the surface layer portion 0.2 mm or more, even if wear due to contact with the needle rollers occurs, the early occurrence of peeling or smearing can be prevented. Occurrence of cracks and the like starting from can be prevented. Therefore, it is possible to effectively improve the resistance to rolling fatigue of the surface layer portion and the strength against surface-origin damage. Moreover, by ensuring a sufficient thickness of the high-concentration carburized layer, the surface hardness can be effectively increased and the torsional fatigue strength can be improved.

  The thickness of the surface layer is preferably 1.6 mm or less from the viewpoint of securing the toughness of the leg shaft and the formation efficiency of the high-concentration carburized layer.

  The invention according to claim 2 is the constant velocity universal joint according to claim 1, characterized in that the tripod member is made of steel having a carbon content of 0.15 to 0.40 wt%.

  According to the constant velocity universal joint of claim 2, the surface layer portion is a highly concentrated carburized layer and has a structure excellent in durability against rolling fatigue, while the core portion has a structure having toughness. Therefore, a tripod member having a long rolling fatigue life and a high cracking strength can be obtained.

  According to the present invention, since the surface layer portion formed by high concentration carburizing and quenching and tempering is provided on the tripod member of the constant velocity universal joint, the rolling fatigue life of the tripod member can be extended. As a result, it is possible to provide a constant velocity universal joint that is more durable and strong while maintaining the current size, and more durable and strong than the current product while maintaining a smaller size. A constant velocity universal joint can be provided.

  Hereinafter, the constant velocity universal joint of the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1A is a cross-sectional view showing a tripod type constant velocity universal joint as an embodiment of the present invention, and FIG. 1B is a vertical cross-section showing the joint in an operating angle θ. 1 (C) is a perspective view showing a roller and a roller guide surface taken out.

  In this tripod type constant velocity universal joint, three cylindrical track grooves 2 extending in the axial direction are formed on the inner peripheral surface of the outer joint member 1. A tripod member 4 is inserted into the outer joint member 1. The tripod member 4 has three leg shafts 5 projecting in the radial direction, and an annular roller 7 rotates on a cylindrical outer peripheral surface of the leg shaft 5 via a plurality of needle rollers 6. It is fitted externally. The roller 7 of the tripod member 4 is inserted into the track groove 2 of the outer joint member 1.

  In each track groove 2, a pair of roller guide surfaces 3 facing in the circumferential direction is formed by a concave curved surface parallel to the axial direction. The outer peripheral surface of each roller 7 of the three leg shafts 5 is formed in a convex curved surface that matches the roller guide surface 3. Each roller 7 is movable along the track groove 2 while engaging with the roller guide surface 3 of the corresponding track groove 2 and rotating around the leg shaft 5. In this tripod type constant velocity universal joint, the drive shaft is connected to the outer joint member 1 and the driven shaft is connected to the tripod member 4.

  This constant velocity universal joint rotates from the driving side to the driven side by engaging the leg shaft 5 of the tripod member 4 and the roller guide surface 3 of the outer joint member 1 via the roller 7 in the biaxial rotation direction. Torque is transmitted at a constant speed. Further, as each roller 7 rolls on the roller guide surface 3 while rotating with respect to the leg shaft 5, relative axial displacement and angular displacement between the outer joint member 1 and the tripod member 4 are absorbed. Is done.

  Here, as shown in FIG. 1B, when the rotational force is transmitted with the joint at the operating angle θ, the roller 7 and the roller guide surface 3 are inclined with respect to each other as shown in FIG. It becomes a relationship to have a relationship. In this case, the roller 7 tries to roll and move in the direction indicated by the arrow t in FIG. 1B, whereas the track groove 2 is a part of a cylindrical surface parallel to the axis of the outer joint member 1. The roller 7 moves while being restrained by the track groove 2. Rolling and slipping occur simultaneously between the leg shaft 5 of the tripod member 4 and the needle roller 6, which causes peeling or smearing on the outer peripheral surface of the shaft leg 5 of the tripod member 4. Further, with torque transmission, the torsional stress concentrates on the base end portion of the leg shaft 5 of the tripod member 4 and causes torsional fatigue.

  On the other hand, the tripod type constant velocity universal joint of the present embodiment is different from the conventional tripod type constant velocity universal joint in that the leg shaft 5 of the tripod member 4 is provided with a surface layer portion formed by high concentration carburizing and quenching and tempering. ing. The surface layer portion is not limited to the leg shaft 5 and may be provided in another portion of the tripod member 4.

  The tripod member 4 is manufactured from a steel material having a carbon content of 0.15 to 0.40 wt% through the main processes of forging, machining, high-concentration carburizing and tempering, and grinding. In the high-concentration carburizing and tempering process, for example, carburizing steel is used, heating and cooling are performed a plurality of times between a predetermined heating temperature and a cooling temperature, and the carbides are refined without being precipitated in a network form at the grain boundaries. To deposit uniformly. The surface layer portion (high-concentration carburized layer) formed in this way has a thickness of 0.2 mm or greater and 1.6 mm or less. Moreover, the surface hardness of the surface layer portion is formed to be HRC58 or higher.

  Thereby, since the surface layer part of high hardness is obtained by the precipitation of the carbide | carbonized_material on the leg shaft 5 of the tripod member 4, the high tolerance with respect to rolling fatigue and the high intensity | strength with respect to a surface origin type | mold damage are obtained. Further, since the surface hardness of the leg shaft 5 is increased by the surface layer portion formed of the high-concentration carburized layer, the torsional fatigue strength necessary for torque transmission can be sufficiently obtained even when left in an unground state. . Furthermore, by setting the thickness of the surface layer portion to 0.2 mm or more, even if wear due to contact with the needle rollers 6 occurs, early occurrence of peeling and smearing is prevented, and cracks and the like starting from these are generated. Can be prevented. Therefore, the resistance against rolling fatigue and the strength against surface-origin damage can be effectively improved with respect to the leg shaft 5 of the tripod member 4. In addition, by sufficiently securing the thickness of the high-concentration carburized layer, the surface hardness of the leg shaft 5 can be effectively increased, and the torsional fatigue strength can be improved.

  For the tripod type constant velocity universal joint shown in FIG. 1, tripod members A and B (comparative example) in which the surface layer portion is formed by carburizing and quenching and tempering, and the tripod member in which the surface layer portion is formed to be 0.1 mm by high concentration carburizing and quenching and tempering A life test conducted on C (comparative example) and tripod members D and E (examples) in which the surface layer portion is formed to be 0.2 mm or more by high-concentration carburizing and quenching and tempering will be described (see Table 1). The tripod member A of the comparative example has a surface layer part thickness of 0.1 mm, and the tripod member B of the comparative example has a surface layer part thickness of 0.2 mm. Further, the tripod member D of the example was provided with a surface layer portion having a thickness of 0.2 mm only on the surface of the leg shaft 5, and the tripod member E of the example was provided with a surface layer portion having a thickness of 0.2 mm on the entire surface. The tripod members A to E were prepared to have the same dimensions by using the same materials except for the heat treatment and thickness of the surface layer portion described above.

  In the life test, the operation is performed with the same rotational torque, operating angle, and rotation speed, and the operation time in which damage (peeling, wear, etc.) of the outer peripheral surface of the leg shaft 5 exceeds a predetermined ratio is defined as the life. In the rolling fatigue life column of Table 1, “◎” is given when the target operation time is sufficiently satisfied, “◯” is given when the target operation time is satisfied, and “△” is shown when the target operation time is not satisfied.

  From Table 1, at least the leg shaft 5 of the tripod member 4 is provided with a surface layer portion formed by high-concentration carburizing quenching and tempering, and the thickness of the surface layer portion is 0.2 mm or more, so that the rolling fatigue life is sufficiently obtained. It can be said that it can be extended. Therefore, a tripod type constant velocity universal joint having higher durability and strength can be obtained while maintaining the conventional size. In addition, a smaller tripod type constant velocity universal joint can be obtained while ensuring durability and strength equal to or higher than those of conventional ones.

It is a figure which shows the constant velocity universal joint of embodiment of this invention, (A) is a cross-sectional view of a joint, (B) is a longitudinal cross-sectional view of the state which took the operating angle of the joint of (A), (C) FIG. 3 is a perspective view showing a roller and a roller guide surface taken out.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer joint member 2 Track groove 3 Roller guide surface 4 Tripod member 5 Leg shaft 6 Needle roller 7 Roller

Claims (4)

Tripod member having three axial track grooves formed on the inner periphery, outer joint members having axial roller guide surfaces on both sides of each track groove, and three leg shafts projecting in the radial direction And a roller inserted into the track groove in a state of being rotatably attached to each leg shaft of the tripod member via a plurality of needle rollers, the roller being an outer joint member along the roller guide surface In the constant velocity universal joint formed to be movable in the axial direction of
A constant velocity universal joint characterized in that a surface layer portion formed by high-concentration carburizing and quenching and tempering is provided on the tripod member.   The constant velocity universal joint according to claim 1, wherein the tripod member is made of steel having a carbon content of 0.15 to 0.40 wt%.   The constant velocity universal joint according to claim 1, wherein the tripod member has a surface hardness of HRC58 or more.   The constant velocity universal joint according to any one of claims 1 to 3, wherein a surface layer portion formed by high-concentration carburizing and tempering of the tripod member has a thickness of 0.2 mm or more immediately below the contact portion with the roller mechanism. .

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