JP2009052656A - Outer coupling member of constant velocity universal joint and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the chance of generating brittle fracture in an outer coupling member when a high load or an impact load is applied to a constant velocity universal joint. <P>SOLUTION: An outer coupling member 2b is mounted on a torque-transmitting constant velocity universal joint with angle displacement allowed via rolling bodies 32 between itself and an internal coupling member 3, and is formed with a truck groove 25 for housing the rolling bodies 32 on an internal diametral surface. The outer coupling member 2b is provided with a hardfacing layer S by applying a carburizing hardening process to the internal diametral surface 22 of the outer coupling member 2, and besides a tempered layer S1 not subjected to the carburizing hardening process is formed by applying an anti-carburizing process to at least part of the outer diametral surface 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an outer joint member of a constant velocity universal joint and a manufacturing method thereof.

  For example, in Patent Document 1, as shown in the cross-sectional view of FIG. 3, an inner joint member 3 (tripod member) having three leg shafts 31 projecting in the outer diameter direction and an inner joint member 3 on the inner periphery are provided. A so-called tripod type constant velocity universal joint including an outer joint member 2 to be accommodated is shown. In this constant velocity universal joint, torque is transmitted between the outer joint member 2 and the inner joint member 3 while allowing angular displacement and axial displacement. A hardened layer S is formed on the outer diameter surface 21 and the inner diameter surface 22 of the outer joint member 2 of the constant velocity universal joint by carburizing and hardening treatment. Thus, by forming the hardened layer S on the surface layer, the strength against the load received from the roller 32 during torque transmission can be increased. On the other hand, since the inside of the outer joint member 2 is not cured, the outer joint member 2 as a whole can exhibit excellent toughness.

JP 2001-193752 A

  However, when carburizing and quenching is performed on the outer joint member 2, the hardness of the surface is increased, while the ductility of the surface is deteriorated and the surface is crack sensitive. For this reason, when the hardened layer S is formed on both the inner diameter surface 22 and the outer diameter surface 21 of the outer joint member 2, the surface is brittle when a high load or an impact load is applied to the outer joint member 2. There is a risk of breakage without plastic deformation and sudden operation failure of the constant velocity universal joint.

  Accordingly, an object of the present invention is to reduce the risk of brittle fracture occurring in the outer joint member when a high load or impact load is applied to the constant velocity universal joint.

  In order to achieve the above object, the present invention is equipped with a constant velocity universal joint that transmits torque while allowing angular displacement between the inner joint member and the inner joint member, and accommodates the rolling element on the inner surface. In the outer joint member in which the track grooves are formed, a hardened layer that has been subjected to carburizing and quenching hardening treatment is provided on the inner diameter surface, and a tempered layer that is not subjected to carburizing and hardening treatment is provided on at least a part of the outer diameter surface. It is characterized by that.

  Here, the carburizing and quenching is a metal hardening process in which carbon is immersed in the surface of the steel and then hardened by hardening (see JIS B 6905-1995). That is, when low carbon steel is heated to a predetermined temperature in a carburizing agent, carbon diffuses and the carbon content of the steel surface layer increases. When this is quenched, the carburized layer hardens and becomes a surface with excellent wear resistance. At this time, since the inside of the base material remains low carbon steel, the product is rich in toughness as a whole and has high surface hardness. Further, tempering refers to a process of heating and holding the quenched steel at a relatively high temperature (450 ° C. to 650 ° C.) for an appropriate time (eg, about 1 to 2 hours) (so-called high temperature tempering, JIS B). 6905-1995). By this tempering treatment, a tempered layer is formed in which supersaturated carbon is precipitated as carbide in α-iron. Carburized and quenched martensite (alpha iron with supersaturated carbon in solid solution) has the property of being extremely hard and poor in ductility, but the tempered layer has a good balance between strength and ductility. It is an organization.

  In the outer joint member of the present invention, since the hardened layer that has been subjected to carburizing and quenching hardening treatment is provided on the inner diameter surface, the inner diameter surface has excellent wear resistance. Accordingly, the wear resistance of the track grooves formed on the inner diameter surface is enhanced, and wear due to contact of rolling elements such as rollers can be suppressed. On the other hand, since carburizing and hardening treatment is not performed on the outer diameter surface that does not require so much wear resistance, problems such as deterioration of ductility or crack sensitivity due to the formation of a hardened layer can be avoided. Furthermore, by providing a tempered layer on this surface, strength and ductility can be imparted to the outer diameter surface in a balanced manner, so that the outer joint member is brittle even when a high load or impact load is applied to the constant velocity universal joint. Can be more effectively prevented from occurring.

  The outer joint member of the constant velocity universal joint is required to have excellent strength and toughness because the track groove receives a drag force from the rolling element during torque transmission. In particular, in the axial region where the rolling element can contact the track groove, it is easily affected by the drag from the rolling element. Therefore, providing the ductility by providing the tempered layer on the outer diameter surface in the axial direction region can more effectively prevent brittle breakage of the outer joint member.

  The surface hardness of the tempered layer is preferably set within a range of Hv250 or more and 450 or less. This is because if it is less than Hv250, the strength required for the outer diameter surface cannot be obtained, and if it exceeds Hv450, ductility is insufficient and brittle damage may occur.

  The prior austenite grain size of the surface layer of the tempered layer is No. It is preferable to set it to 8 or more. Old austenite grain size is No. If it is less than 8, the ductility is insufficient and brittle damage may occur.

  The outer joint member of the constant velocity universal joint as described above is subjected to a tempering treatment on the portion subjected to the carburizing and quenching treatment after performing the carburizing and quenching hardening treatment in a state where the carburizing treatment is performed on at least a part of the outer peripheral surface. It can manufacture by performing. By performing the tempering process only on the necessary parts in this way, the manufacturing time can be shortened and the cost can be reduced. Further, when this tempering treatment is performed by high frequency induction heating, the outer joint member can be locally heated for a short time.

  As described above, according to the present invention, even if a high load or an impact load is applied to the constant velocity universal joint, it is possible to reduce the possibility that brittle fracture occurs in the outer joint member.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a tripod type constant velocity universal joint, and this tripod type constant velocity universal joint includes an outer joint member 2 and a tripod member 3 as an inner joint member housed in the outer joint member 2. In this constant velocity universal joint, torque is transmitted between the outer joint member 2 and the tripod member 3 while allowing angular displacement and axial displacement.

  The outer joint member 2 includes a bottomed cylindrical cup part (mouse part) 23 and a stem part 24 protruding from the mouse part 23. The stem portion 24 is coupled to a first rotating shaft (not shown) by a spline or serration shaft formed at the end portion so that torque can be transmitted. The mouse portion 23 is formed with a track groove 25 extending in the axial direction at a position equally divided into three in the circumferential direction on the inner periphery. The mouse part 23 has a non-cylindrical shape in which a large diameter part 23a and a small diameter part 23b appear alternately in a cross section. That is, the mouse portion 23 is formed with the large-diameter portion 23a and the small-diameter portion 23b, so that the three track grooves 25 extending in the axial direction are formed on the inner peripheral surface thereof. Roller guide surfaces 26 are formed on the side walls of each track groove 25 facing in the circumferential direction.

  The tripod member 3 includes a boss 30 and a leg shaft 31. The boss 30 is formed with a spline or serration hole 33 which is coupled to the second rotating shaft (shaft) so as to be able to transmit torque. The leg shaft 31 protrudes in the radial direction from the circumferentially divided position of the boss 30. A roller 32 is also fitted around each leg shaft 31 of the tripod member 3 so as to be rotatable about an axis (axis) as a torque transmission member. Each roller 32 is accommodated in each track groove 25 of the outer joint member 2. Note that the leg shaft 31 and the roller 32 are not brought into contact with the inner peripheral surface 27 of the large diameter portion 23a. Further, the roller 32 may be a double roller type having an inner roller and an outer roller or only a single roller type.

  A hardened layer S is formed on the inner diameter surface of the outer joint member 2. This hardened layer S can be formed by carburizing and quenching. The carburizing process includes solid carburizing, liquid carburizing, gas carburizing, and vacuum carburizing. Solid carburization is capable of processing large parts, is suitable for small-scale production, and has the advantage of low equipment costs. Liquid carburization is advantageous for the processing of small parts, can form a thin hardened layer, and has the advantage of low equipment costs. Gas carburization can adjust the carbon concentration, is easy to automate, and is suitable for mass production. Vacuum carburization is advantageous in terms of grain boundary oxidation because the working environment is good, the glitter of the treated product is good, and the grain boundary oxidation.

  For this reason, in order to form the hardened layer S on the inner diameter surface of the outer joint member 2, the various carburizing processes can be performed, but constant velocity universal joints are often mass-produced. Gas carburization is preferred. For example, if the constant velocity universal joint is of a size that can be used for a drive shaft of a vehicle, the thickness of the hardened layer S is preferably about 0.5 mm to 2 mm. That is, the thickness of the hardened layer S is preferably 10% or more and 40% or less of the thickness of the mouth portion 23 of the outer joint member 2. This is because if the thickness of the hardened layer S is less than 10%, the required strength cannot be obtained, and if it exceeds 40%, the toughness becomes too small and the strength decreases.

  Further, during the carburizing process of the outer joint member 2, a carburizing process is performed on a predetermined portion of the outer diameter surface 21, that is, the axial region H shown in FIG. 2 in this embodiment. The axial region H corresponds to a region where the roller guide surface 26 of the track groove 25 and the roller 32 can come into contact, that is, a region where the track groove 25 receives a drag force from the roller 32 when torque is transmitted. In this way, by applying a carburizing treatment to a predetermined portion of the outer diameter surface 21, a carburized layer is not formed on the outer diameter surface 21, and problems such as deterioration of ductility or crack sensitivity due to the formation of the carburized layer can be avoided. it can.

  After the carburizing and quenching step, the tempered layer S1 is provided by applying a tempering treatment to the axial region H of the outer diameter surface 21 that has been subjected to the carbonization prevention treatment. Specifically, a tempered layer in which supersaturated carbon is precipitated as carbides in α-iron by heating and holding in a relatively high temperature state (about 450 ° C. to 650 ° C.) for about 1 to 2 hours and then cooling. S1 is formed. Since this tempered layer has a structure with a good balance between strength and ductility, these properties can be imparted to the outer joint member 2.

  For example, if the constant velocity universal joint is of a size that can be used for a drive shaft of a vehicle, the thickness of the tempered layer S1 is preferably about 0.5 mm to 2 mm. That is, the thickness of the hardened layer S is preferably 10% or more and 40% or less of the thickness of the mouth portion 23 of the outer joint member 2. This is because if the thickness of the hardened layer S is less than 10%, the required ductility is not imparted to the outer diameter surface 21, and if it exceeds 40%, the toughness becomes too small and the strength is lowered.

  In the present invention, since the hardened layer S that has been subjected to carburizing and quenching hardening treatment is provided on the inner diameter surface, the wear resistance is excellent on the inner diameter surface side. For this reason, the wear of the guide surface 26 due to the movement of the torque transmitting means (roller 32) in the track groove 25 can be suppressed. In addition, since the tempering treatment S1 that is not carburized and hardened is provided on the outer diameter surface 21, the outer diameter surface 21 is excellent in ductility characteristics, and instantaneously even when a high load or impact load is applied. Brittle fracture can be prevented from occurring.

  In addition, it is possible to perform local tempering treatment only in the longitudinal direction (axial direction) functionally necessary parts (axial direction region H in this embodiment), and is excellent in ductility in weak places (stress concentration parts). The tempered layer S1 is formed. For this reason, it is not necessary to perform the local refining process over the entire outer diameter surface, and the manufacturing time can be shortened and the cost can be reduced.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be variously modified. For example, if there is no particular problem in terms of cost or the like, the tempered layer S1 may be formed over the entire length of the outer joint member. Moreover, in the said embodiment, although the hardened layer S is provided over the perimeter of an internal diameter surface, the area | region which performs a carbon-proof process at the time of a carburizing process is expanded, for example, the part which the roller 32 contacts the hardened layer S, ie, You may provide only in the guide surface 26. FIG.

  In the above embodiment, the torque transmission means is for a tripod type constant velocity universal joint, which is a roller. However, the constant velocity universal joint is another sliding type constant velocity universal joint in which the torque transmission means is a ball. May be. Further, according to the present invention, since the hardened layer S of the inner diameter surface is formed, wear of the roller guide surface 26 on which the roller 32 or the like rolls can be suppressed, so that it is particularly excellent in the sliding type constant velocity universal joint. However, the present invention may be applied to other various fixed type constant velocity universal joints.

  In order to confirm the effect of the present invention, the following tests were conducted.

  First, an outer joint member according to the present invention, that is, a tripod type constant velocity universal joint (Example) having an outer joint member (see FIG. 1) having a tempered layer S1 that has not been subjected to carburizing and quenching, and the entire surface layer A constant velocity universal joint (comparative example) having an outer joint member (see FIG. 3) having a hardened layer formed by carburizing and quenching was prepared. These outer joint members are made of SCr420 as a material, heated to 900 ° C., forged, cold-finished forged, further machined, and heat-treated. This heat treatment is performed by carburizing and quenching. Specifically, after performing carburizing diffusion treatment (8 hours) at 930 ° C., oil quenching is performed from 870 ° C. The outer joint member of the comparative example is subjected to carburizing and quenching on the inner diameter surface and the outer diameter surface, and the outer joint member of the example is subjected to the same carburizing and quenching with the outer diameter surface being subjected to the carburizing treatment, and then only the outer diameter surface. A tempering treatment by induction heating at 30 kHz was performed. In order to prevent softening of the inner surface during this induction heating, the inner surface was cooled with water. As a result, the carburized hardened layer formed on the inner and outer diameter surfaces of the outer joint member of the comparative example and the inner diameter surface of the outer joint member of the example has a surface hardness of Hv 720 and an effective effect depth of 0.7 mm. there were. Moreover, the surface hardness of the tempered layer formed in the outer-diameter surface of the outer joint member of an Example was Hv280.

(1) Single swing torsion fatigue test Using the constant velocity universal joints according to the above examples and comparative examples, a single swing torsion fatigue test was performed under the following conditions using a hydraulic torsion fatigue tester.
Torque: 0-2500Nm
Joint working angle: 0deg
Frequency: 2Hz

  As a result, the outer joint member according to the comparative example was damaged at about 100,000 times, whereas the outer joint member according to the example was damaged at about 230,000 times. That is, the outer joint member according to the example was about 2.3 times stronger than the outer joint member according to the comparative example.

(2) Static torsion strength test Moreover, the static torsion strength test was done on condition of the following using the constant velocity universal joint which concerns on said Example and a comparative example.
Joint working angle: 0deg
Slide out (Loaded at a position 10 mm from the opening side end of the outer joint member)
Twist speed: 25deg / 1min

  As a result, the outer joint member according to the comparative example broke at about 5100 Nm, whereas the outer joint member according to the example broke at about 6630 Nm. That is, the outer joint member according to the example was about 1.3 times stronger than the outer joint member according to the comparative example.

It is a cross-sectional view of the constant velocity universal joint using the outer joint member which shows embodiment of this invention. It is sectional drawing which shows a part of said outer joint member in a cross section. It is a cross-sectional view of a constant velocity universal joint using a conventional outer joint member.

Explanation of symbols

2 outer joint member 21 outer diameter surface 22 inner diameter surface 23 mouse portion 24 stem portion 25 track groove 26 roller guide surface 3 tripod member (inner joint member)
30 Boss 31 Leg shaft 32 Roller 33 Serration hole S Hardened layer S1 Tempered layer

Claims (6)

In an outer joint member that is equipped with a constant velocity universal joint that transmits torque while allowing angular displacement between the inner joint member and the inner joint member, and in which a track groove that accommodates the rolling element is formed on the inner surface,
A constant velocity universal joint characterized in that a hardened layer that has been subjected to carburizing and hardening treatment is provided on the inner diameter surface, and a tempered layer that has not been subjected to carburizing and hardening treatment is provided on at least a part of the outer diameter surface. Outer joint member.   The outer joint member of a constant velocity universal joint according to claim 1, wherein the tempered layer is provided on an outer diameter surface in an axial region where the rolling element can contact the track groove.   The outer joint member of the constant velocity universal joint according to claim 1, wherein a surface layer hardness of the tempered layer is Hv250 or more and 450 or less.   The former austenite grain size of the surface layer of the tempered layer is No. The outer joint member of the constant velocity universal joint according to claim 1, wherein the outer joint member is eight or more. An outer joint member is provided which is mounted on a constant velocity universal joint that transmits torque while allowing angular displacement between the inner joint member and the inner joint member, and in which a track groove for accommodating the rolling element is formed on the inner diameter surface. A method for
A constant velocity universal joint characterized by subjecting at least a part of the outer peripheral surface to a carburizing and hardening treatment after performing a carburizing and hardening treatment on the entire surface and then subjecting the portion subjected to the carburizing treatment to a tempering treatment. The manufacturing method of the outside joint member of.   The manufacturing method of the outer joint member of the constant velocity universal joint of Claim 5 which performed the said tempering process by high frequency induction heating.

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