JP5148384B2 - Constant velocity universal joint shaft and constant velocity universal joint - Google Patents

Description

The present invention relates to a constant velocity universal joint shaft and a constant velocity universal joint.

  A power transmission device that transmits engine power of a vehicle such as an automobile to a wheel transmits power from the engine to the wheel, and also causes radial or axial displacement from the wheel that occurs when the vehicle bounces or turns when traveling on a rough road. , And moment displacement must be allowed. For this reason, for example, as shown in FIG. 3, one end of the drive shaft 1 interposed between the engine side and the wheel side is connected to the differential through the inboard side sliding type constant velocity universal joint 2. The other end is connected to the wheel via a wheel bearing device (not shown) including the fixed type constant velocity universal joint 3 on the outboard side.

  That is, the pair of constant velocity universal joints 2 and 3, the drive shaft 1 connected to these constant velocity universal joints, and the constant velocity universal joint 3 on the outboard side of the pair of constant velocity universal joints 2 and 3 and the wheel A wheel bearing assembly (hereinafter referred to as an axle module) in which the bearing is unitized is configured. The side that is outside the vehicle when assembled in a vehicle such as an automobile is the outboard side (left side of the drawing), and the side that is inside the vehicle when assembled in a vehicle such as an automobile is called the inboard side (right side of the drawing). .

  The constant velocity universal joint 3 includes a plurality of outer rings 5 serving as outer joint members, an inner ring 6 serving as an inner joint member disposed on the inner side of the outer ring 5, and a plurality of torque transmissions interposed between the outer ring 5 and the inner ring 6. The ball 7 and the cage 8 that is interposed between the outer ring 5 and the inner ring 6 and holds the ball 7 are configured as main members. Inner ring 6 hole inner diameter 6a and shaft 1 end 1a are coupled by spline fitting to transmit torque.

  The outer ring 5 is composed of a mouse part 11 and a stem part (shaft part) 12. The mouse part 11 has a bowl shape opened at one end, and a plurality of track grooves 14 extending in the axial direction are circumferentially formed on the inner spherical surface 13 thereof. It is formed at equal intervals in the direction. The track groove 14 extends to the open end of the mouse portion 11. In the inner ring 6, a plurality of track grooves 16 extending in the axial direction are formed on the outer spherical surface 15 at equal intervals in the circumferential direction.

  The opening of the mouse part 11 is covered with a boot 20. The boot 20 includes a large-diameter portion 20a, a small-diameter portion 20b, and a bellows portion 20c that connects the large-diameter portion 20a and the small-diameter portion 20b. The large-diameter portion 20a is externally fitted to the opening of the mouse portion 11, and is fastened by the boot band 21 in this state, and the small-diameter portion 20b is externally fitted to the boot mounting portion 1b of the shaft 1, and in this state, the boot band 21 It is concluded.

  The sliding type constant velocity universal joint on the inboard side includes an outer ring 23 as an outer joint member in which a plurality of linear track grooves 22 are formed in an axial direction on a cylindrical inner surface 23a, and a spherical outer surface 26a. And an inner ring 26 as an inner joint member in which a plurality of linear track grooves 25 are formed in the axial direction, and a ball 27 that is interposed between the track groove 22 of the outer ring 23 and the track groove 25 of the inner ring 26 to transmit torque. And a cage 28 that is interposed between the inner diameter surface of the outer ring 23 and the outer diameter surface of the inner ring 26 and holds the ball 27.

  The outer ring 23 includes a cup portion 29a in which the track groove 22 is formed on the inner diameter surface 23a, and a stem portion 29b protruding from the bottom wall of the cup portion 29a. Inner ring 26 hole inner diameter 26b and shaft 1 end 1c are coupled by spline fitting to transmit torque.

  The opening of the cup portion 29 a is covered with the boot 40. The boot 40 includes a large diameter portion 40a, a small diameter portion 40b, and a bellows portion 40c that connects the large diameter portion 40a and the small diameter portion 40b. The large-diameter portion 40a is externally fitted to the opening of the cup portion 29a, and is fastened by the boot band 41 in this state, and the small-diameter portion 40b is externally fitted to the boot mounting portion 1d of the shaft 1, and in this state, the boot band 41 It is concluded.

  In this way, the opening portion of the constant velocity universal joint on the outboard side (fixed type constant velocity universal joint) or the constant velocity universal joint on the inboard side (sliding type constant velocity universal joint) Is covered with boots 20 and 40. In this case, the boots 20 and 40 are tightened by reducing the diameters of the band 21 and 41 capable of reducing the diameter.

  By the way, in a constant velocity universal joint, if it is light and compact, it contributes to improving the fuel efficiency of the automobile and the freedom of the drive train layout. desirable. For this reason, it is preferable that the shaft (intermediate shaft) in the axle module can be similarly reduced in weight.

  Therefore, there is a conventional technique that can achieve weight reduction and reinforce the decrease in strength (Patent Document 1). The thing of this patent document 1 is the power transmission shaft by which the whole axial direction was heat-processed, Comprising: It heat-processed until the predetermined site | part of an axial direction reaches an axial center part, and processing of the shaft The root part of the accompanying notch is shot peened.

In addition, there is one that can obtain excellent static torsional strength characteristics and excellent torsional fatigue strength characteristics (Patent Document 2). The one described in Patent Document 2 defines the content ratio of C, Si, Mn, S, Mo, B, Al, Ti, N, Cr, and P, and the bainite + martensite structure fraction is 40%. Further, the hardness is set to 250 to 340 HV.
JP 2003-307111 A JP 2006-138007 A

  In the thing of patent document 1, although static strength improves by quenching to an axial center part, fatigue strength falls. For this reason, shot peening is applied to the notch to prevent the fatigue strength from decreasing. Thus, the thing of patent document 1 needed to perform the shot peening process in a shaping | molding process, and while there existed a fault that a shaping time became long while it became high cost. The reason why the fatigue strength is lowered by quenching to the center is that the compressive residual stress normally generated on the surface by the high-frequency heat treatment becomes smaller or becomes the tensile residual stress.

  Moreover, in the thing of patent document 2, in order to raise the hardness of a non-hardening part, the raw material hardness is 250-340HV. However, when the material hardness is increased, the workability is inferior, and in particular, the processing (rolling processing) of male splines or the like becomes difficult.

  In view of the above-mentioned problems, the present invention provides a shaft for a constant velocity universal joint that can improve static torsional strength, prevent a decrease in fatigue strength, and is excellent in workability, and the like. A method for manufacturing a shaft for a speed universal joint, and a constant speed universal joint using such a shaft for a constant speed universal joint are provided.

The shaft for constant velocity universal joints of the present invention is a shaft for constant velocity universal joints that has been subjected to surface hardening treatment by induction hardening, and after being subjected to a tempering treatment with a hardness of 250 HV to 400 HV , a high frequency for surface hardening. Ri Na and surface hardening treatment by quenching is applied, as the shaft material, to generate a high compressive residual stress in induction hardening for the surface hardening, the carbon steel carbon content of 0.3 wt% to 0.5 wt% In addition to limiting, the shaft material hardness before the tempering treatment is set to 150 HV to 230 HV, the hardness of the hardened layer after induction hardening is set to 550 HV to 750 HV, and the tempering treatment is set as the heat tempering. Is performed by induction heat treatment using the induction hardening apparatus for surface hardening .

  According to the constant velocity universal joint shaft of the present invention, the hardness can be set to 250 HV to 400 HV by tempering treatment. Here, the term “tempering” refers to an operation for making the crystal grains of steel finer, homogenizing the material, improving ductility and toughness, and improving the properties. There are thermal tempering that performs quenching, tempering, or annealing, and mechanical tempering that combines mechanical work and annealing. By this refining, the structure of the non-quenched part is changed from a ferrite-pearlite structure or a ferrite-pearlite structure to a troostite structure or a sorbite structure.

  The tempering treatment is a heat tempering for heat treatment of quenching and tempering, and at least one of quenching and tempering can be performed by high-frequency heat treatment. The induction heat treatment is quenching performed by a heating method using an electromagnetic induction phenomenon called “high-frequency induction heating”. When a metal (electrical conductor) is placed in a coil through which a high-frequency current flows, an induction current caused by a high-frequency magnetic flux flows on the surface of the metal due to electromagnetic induction. This current loses energy due to the resistance of the metal and generates heat. Induction heating uses this heat generation phenomenon as a heat source.

  High frequency induction heating has the following advantages. The work environment is good because it can be heated without contact and the work itself generates heat. Because it can be heated in a short time, oxidation is extremely low. Rapid heating is possible and energy efficiency is good. Local heating is possible, and the quenching conditions can be easily adjusted. Less quenching distortion than other quenching methods. It is easy to automate and can be integrated into a machining line.

  The constant velocity universal joint according to the present invention is a constant velocity universal joint including an outer joint member, an inner joint member, and a torque transmission member interposed between the outer joint member and the inner joint member. A shaft for a quick universal joint is connected to the inner joint member.

  In the present invention, the hardness of the non-quenched portion (inside the shaft) is increased by performing the tempering treatment. For this reason, the tensile strength of a non-hardened part is improved and static torsional strength improves. In addition, since the hardness of the non-quenched part is increased by refining, the material may be low in hardness, and the material can be easily turned and rolled, and the workability can be improved. In particular, when the material hardness before the tempering treatment is less than 250 HV, the processing becomes easier.

  The heat treatment after tempering does not need to be induction hardened to the center (axial center), the compressive residual stress after heat treatment is generated in the same way as normal induction hardening, and there is no reduction in fatigue strength. Further, the tempering process has an advantage that it is less expensive than shot peening. When induction hardening is performed on medium carbon steel containing 0.3 wt% to 0.5 wt% of carbon, high compressive residual stress is generated and fatigue strength is improved. For this reason, the fatigue strength can be further improved by making the shaft a medium carbon steel containing 0.3 wt% to 0.5 wt% of carbon.

  In this way, if a shaft that can improve static torsional strength and prevent deterioration of fatigue strength is used, a high-quality constant velocity universal joint with excellent durability can be provided.

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

  FIG. 2 shows an axle module using the constant velocity universal joint shaft according to the present invention. The axle module includes a constant velocity universal joint T1 on the outboard side, a constant velocity universal joint T2 on the inboard side, and a shaft (shaft for constant velocity universal joint) 65 connected to the constant velocity universal joints T1 and T2. Prepare. The side that is outside the vehicle when assembled in a vehicle such as an automobile is the outboard side (left side of the drawing), and the side that is inside the vehicle when assembled in a vehicle such as an automobile is called the inboard side (right side of the drawing). .

  As shown in FIG. 2, the fixed type constant velocity universal joint includes an outer ring 53 as an outer member (outer joint member) in which a plurality of track grooves 52 are formed on an inner spherical surface 51, and a track groove of the outer ring 53 on an outer spherical surface 54. Torque is interposed between the inner ring 56 as an inner member (inner joint member) in which a plurality of track grooves 55 paired with the inner ring 52 are formed, and between the track grooves 52 of the outer ring 53 and the track grooves 55 of the inner ring 56. A ball 57 as a torque transmitting member for transmission and a cage 58 interposed between the inner spherical surface 51 of the outer ring 53 and the outer spherical surface 54 of the inner ring 56 to hold the ball 57 are provided.

  The inner ring 56 has a hole inner diameter 56a and a male spline 65a at one end of the shaft 65 coupled by spline fitting, so that torque transmission with the shaft 65 becomes possible. Further, a retaining ring 60 for retaining is attached to the male spline 65a of the shaft 65.

  The outer ring 53 includes a mouse part 53a and a stem part (shaft part) 53b. The mouse part 53a has a bowl shape opened at one end, and a plurality of track grooves 52 extending in the axial direction are circularly formed on the inner spherical surface 51 thereof. It is formed at equal intervals in the circumferential direction.

  The opening of the mouse part 53 a is covered with a boot 70. The boot 70 includes a large diameter portion 70a, a small diameter portion 70b, and a bellows portion 70c that connects the large diameter portion 70a and the small diameter portion 70b. The large-diameter portion 70a is externally fitted to the opening of the mouse portion 53a, and the band 111 is fastened in this state. The small-diameter portion 70b is externally fitted to the boot mounting portion 65b of the shaft 65, and the band 111 is fastened in this state. Yes.

  The sliding type constant velocity universal joint includes an outer ring 83 as an outer joint member in which a plurality of linear track grooves 82 are formed in an axial direction on a cylindrical inner surface 83a, and a plurality of straight lines on a spherical outer surface 86a. A ball as a torque transmission member that transmits torque by being interposed between an inner ring 86 as an inner joint member in which an axial track groove 85 is formed in the axial direction and a track groove 82 of the outer ring 83 and a track groove 85 of the inner ring 86 87 and a cage 88 that is interposed between the inner diameter surface of the outer ring 83 and the outer diameter surface of the inner ring 86 and holds the ball 87.

  The outer ring 83 includes a cup portion 90 in which the track groove 82 is formed on the inner diameter surface 83 a and a stem portion 91 that protrudes from the bottom wall of the cup portion 90. The inner ring 86 has a hole inner diameter 86b and a male spline 65c at the other end of the shaft 65 coupled by spline fitting so that torque can be transmitted to the shaft 65. A retaining ring 61 for retaining is attached to the male spline 65c of the shaft 65.

  The opening of the cup 90 is covered with the boot 100. The boot 100 includes a large diameter portion 100a, a small diameter portion 100b, and a bellows portion 100c that connects the large diameter portion 100a and the small diameter portion 100b. The large diameter portion 100a is externally fitted to the opening of the cup portion 90, and the band 111 is fastened in this state, and the small diameter portion 100b is externally fitted to the boot mounting portion 65d of the shaft 65, and the band 111 is fastened in this state. Yes.

  The shaft 65 is a solid body and includes a shaft main body 92 and the male splines 65 a and 65 c provided at both ends of the shaft main body 92. The male splines 65a and 65c are formed in the large end portion of the end portion that is connected to the shaft main body 92 through tapered portions 93a and 93c that expand from the main body side toward the end portion side.

  The shaft main body 92 is formed with boot mounting portions 65b and 65d. In this case, a large diameter portion 94b is formed on the male spline 65c side of the shaft main body 92, and a circumferential groove 95b is formed in the large diameter portion 94b. The boot mounting part 65b is comprised by providing. Further, a large diameter portion 94d is formed on the male spline 65c side of the shaft body 92, and a circumferential groove 95d is provided in the large diameter portion 94d, thereby forming a boot mounting portion 65d. In addition, taper 96b, 97b, 96d, 97d is provided in the both ends of large diameter part 94b, 94d. Circumferential grooves 98 and 99 are formed in the male splines 65a and 65c, respectively.

  By the way, as shown in FIG. 1, the shaft 65 has a hardened layer 120 formed over the entire surface thereof. The surface hardened layer 120 is formed by a surface hardening process by induction hardening. The hatching in the example is for showing that the surface hardening layer 120 is formed on the shaft 65, and the actual surface hardening layer 120 is formed on the entire surface of the shaft 65.

  Next, a method for manufacturing the shaft 65 will be described. First, a rod-shaped material made of medium carbon steel containing carbon content of 0.3 wt% to 0.5 wt% is prepared. Next, a tempering process is performed on the material. The tempering treatment is a heat tempering that performs a heat treatment of quenching and tempering. Quenching and tempering can be performed by induction heat treatment. That is, the tempering treatment changes the structure from a ferrite-pearlite structure or a ferrite-pearlite structure to a troostite structure or a sorbite structure. The hardness of the material before tempering (the hardness of the non-quenched portion other than the hardened surface layer 120) is about 150 HV to 230 HV. And it shall be 250HV or more by refining.

  The induction heat treatment is quenching performed by a heating method using an electromagnetic induction phenomenon called “high-frequency induction heating”. When a metal (electrical conductor) is placed in a coil through which a high-frequency current flows, an induction current caused by a high-frequency magnetic flux flows on the surface of the metal due to electromagnetic induction. This current loses energy due to the resistance of the metal and generates heat. Induction heating uses this heat generation phenomenon as a heat source. The high frequency induction heating has the following advantages. The work environment is good because it can be heated without contact and the work itself generates heat. Because it can be heated in a short time, oxidation is extremely low. Rapid heating is possible and energy efficiency is good. Local heating is possible, and the quenching conditions can be easily adjusted. Less quenching distortion than other quenching methods. It is easy to automate and can be integrated into a machining line.

  After that, since machining accuracy is required, a shaft including male splines 65a and 65b and boot mounting portions 65b and 65d (shaft before forming a hardened layer) is formed by turning and rolling. Note that this turning and rolling may be performed before tempering in consideration of ease of processing.

  Next, the surface hardened layer 120 is formed by induction heat treatment (induction hardening) to complete the shaft 65. The hardness of the hardened layer 120 is about 550 to 750 HV. By this induction hardening, it has a high torsional strength. In addition, after induction hardening, you may temper as needed. Here, tempering is a heat treatment performed for the purpose of imparting toughness to steel hardened by quenching, and refers to an operation in which the steel is reheated from the martensite structure, held for a certain time, and then gradually cooled.

  By the way, a compressive stress is generated by high-frequency heat treatment. Therefore, the hardness of the material before the high-frequency heat treatment is 250 HV or higher by refining, but is preferably 400 HV or lower.

  According to the present invention, the tempering treatment increases the hardness of the non-quenched portion (inside the shaft). For this reason, the tensile strength of a non-hardened part is improved and static torsional strength improves. In addition, since the hardness of the non-quenched part is increased by refining, the material may be low in hardness, and the material can be easily turned and rolled, and the workability can be improved. In particular, when the material hardness before the tempering treatment is less than 250 HV, the processing becomes easier.

  The heat treatment after tempering does not need to be induction hardened to the center (axial center), the compressive residual stress after heat treatment is generated in the same way as normal induction hardening, and there is no reduction in fatigue strength. Further, the tempering process has an advantage that it is less expensive than shot peening. When induction hardening is performed on medium carbon steel containing 0.3 wt% to 0.5 wt% of carbon, high compressive residual stress is generated and fatigue strength is improved. For this reason, the fatigue strength can be further improved by making the shaft 65 a medium carbon steel containing a carbon amount of 0.3 wt% to 0.5 wt%.

  As described above, if the shaft 65 that can improve the static torsional strength and prevent the fatigue strength from being lowered is used, a high-quality constant velocity universal joint that is excellent in durability can be provided.

In the method for manufacturing a constant velocity universal joint shaft according to the present invention, it is possible to stably and inexpensively manufacture a shaft that can improve static torsional strength and prevent a decrease in fatigue strength.

  In the embodiment, the quenching and tempering in the tempering process is performed by induction heat treatment, but various other heat treatments such as carburizing and quenching can be employed. Here, the carburizing and quenching is a method in which carbon is infiltrated / diffused from the surface of the low carbon material and then quenched. By performing the tempering treatment by high frequency heat treatment, the high frequency heat treatment apparatus used at the time of forming the hardened layer can be used as it is, and the cost can be reduced. Note that only one of the tempering quenching and tempering may be performed by high-frequency heat treatment, and the other may be performed by other heat treatment means.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment, and various modifications are possible. In the axle module shown in FIG. (Fixed constant velocity universal joint) T1 is a bar field type (BJ) in which the track groove bottom has an arc portion, but the track groove bottom has an arc portion and a straight portion (UJ). ). The constant velocity universal joint (sliding constant velocity universal joint) T2 on the inboard side is a double offset type constant velocity universal joint, but other sliding constant velocity universal joints such as a tripod type constant velocity universal joint. It may be.

It is a side view of the shaft which shows embodiment of this invention. It is sectional drawing of the axle module using the shaft shown in the said FIG. It is sectional drawing of the axle module using the conventional shaft.

Explanation of symbols

65 Shaft 120 Hardened layer T1 Constant velocity universal joint T2 Constant velocity universal joint

Claims (2)

A shaft for a constant velocity universal joint that has been surface hardened by induction hardening,
Hardness Ri Na by surface hardening treatment by induction hardening is decorated after the made refining and 250HV～400HV, as shaft material, to generate a high compressive residual stress in induction hardening for the surface hardening, the carbon content Is limited to 0.3 wt% to 0.5 wt% of medium carbon steel, the shaft material hardness before tempering is set to 150 HV to 230 HV, and the hardness of the hardened layer after induction hardening is set to 550 HV to 750 HV. A shaft for a constant velocity universal joint characterized in that the tempering treatment is a heat tempering and the heat tempering is performed by an induction heat treatment using the surface hardening induction hardening apparatus. The constant velocity universal joint according to claim 1, comprising: an outer joint member; an inner joint member; and a torque transmission member interposed between the outer joint member and the inner joint member. A constant velocity universal joint characterized in that a shaft is connected to the inner joint member .

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