JP2016038048A - Constant velocity joint and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant velocity joint capable of easily and efficiently suppressing abrasion due to torque transmission at low cost, and excellent in durability, and provide a manufacturing method of the constant velocity joint.SOLUTION: A first constant joint 10 includes high hardness layers 30a, 30b comprising ceramic or cermet, on a member surface to be at least one of the inner surface of an outer cup 16 and the outer surface of an inner ring 18. The high hardness layers 30a, 30b may be a multilayer structure whose porosity in a thickness direction varies. The porosity on the central side (sides of second layers 304a, 304) of the thickness direction may be made larger than those on both end sides (sides of first layers 302a, 302b and sides of third layers 306a, 306b).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a constant velocity joint that transmits torque between an outer member and an inner member via a torque transmission member, and a manufacturing method thereof.

  In a power transmission mechanism such as an automobile, a rotational driving force is transmitted from one transmission shaft to the other transmission shaft using a constant velocity joint interposed between the transmission shafts. Generally, a barfield type constant velocity joint is interposed between the drive shaft and the hub (outboard side) of the transmission shaft, and a tripod type is provided between the differential gear and the drive shaft (inboard side). A speed joint is interposed.

  These constant velocity joints are interposed between the outer member connected to one transmission shaft, the inner member positioned and fixed to the tip of the other transmission shaft, and the outer member and the inner member to transmit torque. And a torque transmission member to perform. As a material for the constant velocity joint, steel is usually employed from the viewpoint of manufacturing cost, formability, and the like.

  For example, in a Barfield type constant velocity joint, the outer member has a cup shape in which a bottomed hole into which the inner member is inserted is formed, and the outer wall of the cup-shaped bottom portion is connected to the transmission shaft. A shaft portion is formed to protrude. A plurality of first ball grooves spaced apart from each other at equal intervals are formed on the inner wall of the outer member.

  The inner member has an annular shape in which a plurality of second ball grooves are provided on the outer peripheral wall so as to correspond to the first ball grooves. The torque transmission member is composed of a plurality of balls inserted between the first ball groove and the second ball groove so as to be able to roll, and the balls are composed of an inner surface of the outer member and an outer surface of the inner member. And is held by a retainer interposed between them. That is, when this ball comes into contact with each of the first ball groove and the second ball groove, torque transmission is performed between the outer member and the inner member via the ball (torque transmission member).

  On the other hand, in the tripod type constant velocity joint, the outer member has a cup shape in which the shaft portion protrudes in the same manner as the tripod type, and the inner wall of the outer member has a plurality of tracks spaced apart at equal intervals. Grooves are formed. The inner member is a so-called spider having an annular portion and a plurality of trunnions protruding from the outer peripheral wall of the annular portion. The inner member is inserted into the outer member so that the trunnions are respectively accommodated in the track grooves of the outer member.

  The torque transmission member is a substantially annular roller that is rotatably fitted to each trunnion of the inner member, and is in sliding contact with the inner wall of the track groove. That is, the inner peripheral wall of the roller is in contact with the outer wall of the trunnion, and the outer peripheral wall of the roller is in contact with the inner wall of the track groove, whereby the outer member and the inner member are interposed between the rollers (torque transmission member). Torque is transmitted.

  Therefore, the inner surface of the outer member (in particular, the inner walls of the track groove and the first ball groove) and the outer surface of the inner member (in particular, the side wall of the trunnion and the inner wall of the second ball groove) are connected to the torque transmission member (roller or ball). Wear is likely to occur due to contact. As means for suppressing this wear, it is known to form a hardened layer by applying heat treatment to the inner surface of the outer member and the outer surface of the inner member (hereinafter also collectively referred to as the member surface).

  In this hardened layer, since the maximum value of hardness is mainly determined by the amount of carbon contained in the member surface, there is a limit to the hardness of the member surface that can be raised by forming the hardened layer. Also, the hardness of the hardened layer is likely to vary due to variations in carbon distribution and quenching temperature within the surface of the member. Furthermore, the hardness of the hardened layer decreases as the depth increases, that is, toward the inside of the outer member or the inner member. A). Therefore, even if a hardened layer is formed on the surface of the member, there is a concern that the hardened layer may be peeled off if stress due to torque transmission is continuously applied to a portion below the determination hardness. That is, there is a concern that the above wear cannot be sufficiently suppressed only by forming a hardened layer on the surface of the member.

  Further, when heat treatment is performed to form a hardened layer, thermal deformation and dimensional change occur in the outer member and the inner member. Therefore, in order to obtain an outer member and an inner member having desired shapes, it is necessary to design a die for forging with high precision in consideration of the thermal deformation and dimensional change due to the heat treatment described above. The joint manufacturing process becomes complicated. Further, as the heat treatment, induction hardening is generally performed, but in this case, energy such as electric power consumed to obtain a cured layer is increased.

  Therefore, it has been proposed to form a constant velocity joint from ceramics such as sialon and silicon nitride instead of steel to suppress the above wear. Ceramics are excellent in wear resistance, corrosion resistance, insulation, and the like, and have higher hardness and higher strength at high temperatures than the above hardened layer. Therefore, by adopting ceramics as the material for the constant velocity joint, the surface of the member can be made to have a hardness capable of suppressing the above wear. For example, Patent Document 1 proposes forming a torque transmission member (ball) from a β sialon sintered body as ceramics.

JP 2010-1940 A

  In order to obtain a constant velocity joint from ceramics, it is necessary to form ceramic powder by cold isostatic pressing (CIP), and then perform hot isostatic pressing (HIP) after sintering. . In this case, since the manufacturing process becomes complicated, manufacturing efficiency decreases, mass production becomes difficult, and the shape obtained by molding is limited, so that the degree of freedom of the shape of the constant velocity joint decreases. Is concerned.

  In addition, when ceramics is used as the material for the constant velocity joint, the equipment cost and the manufacturing cost are significantly increased as compared with the case where steel is used. Therefore, it is not realistic to form all the components of the constant velocity joint from ceramics. However, as proposed in Patent Document 1, even if only the torque transmission member is formed of ceramics among the components of the constant velocity joint, it is difficult to sufficiently suppress the wear generated on the member surface. .

  An object of the present invention is to solve this type of problem, and to provide a constant velocity joint that can easily and efficiently suppress wear due to torque transmission at low cost and has excellent durability, and a method for manufacturing the same. To do.

  The present invention is a constant velocity joint comprising: an outer member; an inner member inserted into the outer member; and a torque transmission member interposed between the outer member and the inner member to transmit torque. A member surface that is at least one of the inner surface of the outer member and the outer surface of the inner member is provided with a high hardness layer mainly composed of ceramics or cermet. Here, the main component means that the ratio of ceramics or cermet in the high hardness layer is approximately 80 atm% or more, and the ratio may be 100 atm%.

  The high hardness layer provided on the member surface of the constant velocity joint according to the present invention is superior in wear resistance, corrosion resistance, insulation, and the like, for example, compared to a hardened layer formed by subjecting the member surface to heat treatment, High hardness (surface pressure resistance) and high temperature strength. Therefore, in this constant velocity joint, even if the torque transmission member comes into contact with the surface of the member provided with the high hardness layer, it is possible to effectively suppress the wear and show excellent durability.

  Further, since the high hardness layer can be ground, the dimensions of the inner member and the outer member can be adjusted after the high hardness layer is formed. Therefore, it is not necessary to design a die for forging with high precision in advance in consideration of dimensional changes of the inner member and the outer member, and a constant velocity joint can be obtained easily and efficiently. Furthermore, since it is not necessary to perform heat treatment such as induction hardening, energy such as electric power consumed in the process of obtaining a constant velocity joint can be reduced.

  Moreover, since it is possible to form an outer member and an inner member from steel etc., the manufacturing cost of a constant velocity joint can be reduced compared with the case where all the components are formed from ceramics or cermet. . Furthermore, for example, a constant velocity joint can be obtained without going through a complicated manufacturing process such as molding by CIP or HIP, thereby improving the production efficiency and the degree of freedom of the shape of the constant velocity joint, and the equipment cost. Can be reduced.

  Therefore, wear due to torque transmission can be easily and efficiently suppressed at low cost, and a constant velocity joint excellent in durability can be obtained. That is, this constant velocity joint can have both the advantages of a steel material such as low cost and excellent formability, and the advantages of a ceramic material or cermet material such as high hardness and excellent wear resistance. Further, as described above, sufficient strength can be maintained even if the volume of the inner member or the outer member is reduced by the amount that the hardness of the member surface can be effectively increased by the high hardness layer. For this reason, it becomes possible to reduce the size of the constant velocity joint.

  In the constant velocity joint, the high hardness layer preferably has a multilayer structure. In this case, it is possible to obtain a high hardness layer having various functions in accordance with the material of the constant velocity joint, usage conditions, and the like.

  In the above constant velocity joint, the multilayer structure of the high hardness layer is formed by changing the porosity in the thickness direction, and the porosity on the center side in the thickness direction is larger than the porosity on both end sides. Is preferably large. In this case, of the high hardness layer formed on the member surface, one side close to the member surface and the other side close to the contact surface in contact with the torque transmitting member are formed more densely than the center side. become. Therefore, the hardness on the contact surface side of the high hardness layer can be set to a value that can effectively suppress wear due to torque transmission. Moreover, the adhesiveness (adhesion) between the member surface side of the high hardness layer and the member surface can be improved.

  On the other hand, the center side of the high-hardness layer can hold the lubricant well in the pores due to the high porosity, and can enhance the lubricant-holding ability of the high-hardness layer. This makes it possible to supply a lubricant appropriately between the torque transmission member and the high-hardness layer to form a lubricating film, thereby maintaining good lubrication. That is, wear on the surface of the member provided with the high hardness layer can be more effectively suppressed. In addition, the central side of the high hardness layer has a higher porosity than both end sides, and thus can function as a buffer material. Therefore, for example, it is possible to absorb the contact surface pressure of the torque transmission member with respect to the high hardness layer by causing elastic deformation at the center side of the high hardness layer. For this reason, the durability of the entire constant velocity joint can be enhanced.

  That is, by providing a high-hardness layer having a multilayer structure as described above, it is possible to obtain a constant velocity joint that exhibits even more excellent durability and has an appropriately long life.

  In the constant velocity joint, the porosity on the other side close to the contact surface in contact with the torque transmission member is larger than the porosity on one side close to the member surface among both end sides in the thickness direction. It is preferable. In this case, the adhesion between the member surface and the high hardness layer can be improved, and the lubricant is provided between the contact surface and the central pore in the thickness direction via the other pore close to the contact surface. Becomes easy to move. Therefore, the high hardness layer can be formed more firmly on the surface of the member, and the lubricity between the contact surface and the torque transmission member can be maintained better to improve the wear resistance. As a result, it is possible to obtain a constant velocity joint that is excellent in durability and has a long life.

  In the constant velocity joint, the high hardness layer is preferably formed by thermal spraying. In this case, for example, compared to the case where the high hardness layer is formed by coating, adhesion, or the like, the material can be selected with a high degree of freedom, and the high hardness layer can be obtained efficiently and with high accuracy. Also, for example, by adjusting the conditions during spraying (spraying speed, spraying distance, spraying temperature, etc.) and the particle size and type (component) of the material particles, it is easy to form a multi-layered high hardness layer. Can be formed.

  According to another aspect of the present invention, there is provided a constant velocity joint including an outer member, an inner member inserted into the outer member, and a torque transmission member interposed between the outer member and the inner member to transmit torque. The method comprises a high hardness layer forming step of forming a high hardness layer mainly composed of ceramics or cermet on a member surface which is at least one of an inner surface of the outer member and an outer surface of the inner member. Features.

  In the method of manufacturing the constant velocity joint according to the present invention, even if the torque transmission member comes into contact with the surface of the member provided with the high hardness layer, it is possible to effectively suppress wear, and to have excellent durability. It is possible to obtain a constant velocity joint having a long life. In addition, since it is not necessary to perform heat treatment such as induction hardening, energy such as electric power consumed in the process of obtaining a constant velocity joint can be reduced.

  Furthermore, the manufacturing cost of the constant velocity joint can be reduced as compared with the case where all of the components are formed from ceramics or cermet. Furthermore, since it is not necessary to go through complicated manufacturing processes such as molding by CIP or HIP, for example, the manufacturing efficiency and the degree of freedom of the constant velocity joint can be improved, and the equipment cost can be reduced.

  Therefore, wear due to torque transmission can be easily and efficiently suppressed at low cost, and a constant velocity joint excellent in durability can be obtained. In addition, since the hardness of the member surface can be effectively increased by the high hardness layer, the constant velocity joint can be reduced in size while maintaining sufficient strength of the inner member and the outer member.

  In the constant velocity joint manufacturing method, in the high hardness layer forming step, the high hardness layer is formed by thermal spraying on the member surface, and the thermal spraying condition is changed so that the high hardness layer has a multilayer structure. It is preferable. In this case, it is possible to obtain a high hardness layer having various functions in accordance with the material of the constant velocity joint, usage conditions, and the like. In addition, since the high hardness layer is formed by thermal spraying, for example, compared to the case where the high hardness layer is formed by coating, adhesion, or the like, the degree of freedom of material selection is high, and the high hardness layer is obtained efficiently and accurately It becomes possible. In addition, for example, a high hardness layer having a multilayer structure can be easily formed by adjusting the spraying speed and the particle size and type of the particles used as the material.

  In the manufacturing method of the constant velocity joint, in the high hardness layer forming step, the thermal spraying conditions are changed in the order of the first condition, the second condition, and the third condition, and the first condition is applied to the surface of the member. While the first layer to be deposited is formed and the second condition is satisfied, the second layer is formed so as to be continuous from the first layer and have a higher porosity than the first layer, and While the conditions are satisfied, it is preferable to form the third layer so as to be continuous from the second layer and have a lower porosity than the second layer. In this case, in the high hardness layer, the first layer close to the member surface and the third layer close to the contact surface in contact with the torque transmission member may be formed more densely than the second layer on the center side. it can. Therefore, the adhesiveness between the first layer and the member surface can be improved. Further, the hardness of the third layer can be set to a value that can effectively suppress wear due to torque transmission.

  On the other hand, in the second layer having a large porosity, the lubricant can be well retained in the pores. This makes it possible to supply a lubricant appropriately between the torque transmission member and the third layer to form a lubricating film, so that the mutual lubrication can be maintained well. That is, wear on the surface of the member provided with the high hardness layer can be more effectively suppressed.

  Further, since the porosity of the second layer is larger than that of the first layer and the third layer, the second layer functions as a buffer material. Therefore, since the contact surface pressure of the torque transmission member with respect to the high hardness layer is absorbed by, for example, elastic deformation of the second layer, durability of the entire constant velocity joint can be improved. That is, by forming a high-hardness layer having a multilayer structure as described above, it is possible to obtain a constant velocity joint that exhibits further excellent durability and has an appropriately long life.

  In the method for manufacturing the constant velocity joint, it is preferable that the first condition and the third condition are set so that the porosity of the third layer is larger than that of the first layer. In this case, the adhesion between the member surface and the first layer can be improved. Further, the lubricant can move between the surface (contact surface) of the third layer and the pores of the second layer via the pores of the third layer. Therefore, the high hardness layer can be formed more firmly on the surface of the member, and the lubricity between the contact surface and the torque transmission member can be maintained better to improve the wear resistance. As a result, it is possible to obtain a constant velocity joint that is excellent in durability and has a long life.

  In the method for manufacturing the constant velocity joint, it is preferable to further include a grinding step of grinding a part of the high hardness layer. This grinding makes it possible to adjust the dimensions of the inner member and outer member after forming a high hardness layer, eliminating the need to design a forging die with high precision in advance, making constant velocity joints easy and efficient. Can be obtained.

  According to the present invention, by forming a high hardness layer on the surface of a member, constant velocity joints that can easily and efficiently suppress wear due to torque transmission at low cost, have excellent durability, and can be downsized. Can be obtained.

It is a principal part schematic sectional drawing of a power transmission mechanism provided with the constant velocity joint (1st constant velocity joint and 2nd constant velocity joint) which concerns on this embodiment. 2 is a partially enlarged view of a high hardness layer of the constant velocity joint of FIG. 1 and a graph showing the relationship between the thickness of the high hardness layer, hardness (solid line), and residual compressive stress (dashed line). It is a schematic explanatory drawing explaining the manufacturing method of the 2nd constant velocity joint of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a constant velocity joint according to the present invention will be described in detail with reference to the accompanying drawings by giving preferred embodiments in relation to the manufacturing method thereof.

  The constant velocity joint according to the present invention can be applied even if it is interposed between any transmission shafts on the inboard side and the outboard side of a power transmission device such as an automobile. For this reason, in the present embodiment, as shown in FIG. 1, the first constant velocity joint 10 is a bar field type provided on the outboard side, and the second constant velocity joint 12 is a tripod type provided on the inboard side. An example will be described.

  That is, the first constant velocity joint 10 is interposed between the drive shaft 14 and the hub (not shown), and the second constant velocity joint 12 is interposed between the differential gear (not shown) and the drive shaft 14.

  First, the configuration of the first constant velocity joint 10 will be described. The first constant velocity joint 10 is basically composed of an outer cup (outer member) 16, an inner ring (inner member) 18, and a ball (torque transmission member) 20. Each of these members is, for example, steel. Etc.

  The outer cup 16 has a cup shape with a bottomed hole, and the shaft portion 21 is integrally connected to the hub. For example, six first ball grooves 22 are formed on the inner surface formed of the spherical surface of the outer cup 16 along the axial direction and at equal intervals around the axis.

  The inner ring 18 has an annular shape in which a plurality of second ball grooves 24 are provided on the outer peripheral wall so as to correspond to the first ball groove 22 described above, and is accommodated in the outer cup 16. Further, the inner ring 18 is spline-fitted to one end portion of the drive shaft 14 through a hole formed at the center thereof.

  One ball 20 is disposed between the first ball groove 22 and the second ball groove 24 facing each other so as to be able to roll, and is interposed between the inner surface of the outer cup 16 and the outer surface of the inner ring 18. The retainer 26 is held. The ball 20 comes into contact with each of the first ball groove 22 and the second ball groove 24 to transmit torque between the outer cup 16 and the inner ring 18.

  A rubber or resin joint boot 28 a having a bellows portion is mounted between the outer cup 16 and the drive shaft 14. A grease composition is enclosed as a lubricant in the joint boot 28a.

  In the first constant velocity joint 10, a high hardness layer 30 a is formed on the inner surface of the outer cup 16, and a high hardness layer 30 b is formed on the outer surface of the inner ring 18. Details of the high hardness layers 30a and 30b will be described later.

  Next, the configuration of the second constant velocity joint 12 will be described. The second constant velocity joint 12 basically includes an outer ring member (outer member) 32, a spider (inner member) 34, and a roller (torque transmission member) 36. Each of these members is, for example, steel. Etc.

  The outer ring member 32 has a cup shape with a bottomed hole, and the shaft portion 37 is integrally connected to the differential gear. For example, three track grooves 38 are formed on the inner surface of the outer ring member 32 at equal intervals around the axis.

  The spider 34 includes an annular portion 40 and a plurality of trunnions 42 protruding from the outer peripheral wall of the annular portion 40. The spider 34 is inserted into the outer ring member 32 so that the trunnions 42 are accommodated in the track grooves 38, respectively. The annular portion 40 is serrated to the other end portion of the drive shaft 14 through a hole formed in the center thereof.

  The roller 36 has an annular shape that is rotatably fitted to the trunnion 42 via a plurality of rolling elements 44, and is in sliding contact with the inner wall of the track groove 38. That is, the inner peripheral wall of the roller 36 is in contact with the outer wall of the trunnion 42 and the outer peripheral wall of the roller 36 is in contact with the inner wall of the track groove 38, so that torque is generated between the outer ring member 32 and the spider 34 via the roller 36. Transmission takes place. In addition, the rolling element 44 should just be a rolling bearing containing a needle, a roller, etc., for example.

  Like the joint boot 28a, the joint boot 28b is mounted between the outer ring member 32 and the drive shaft 14 so that the grease composition is enclosed therein.

  In the second constant velocity joint 12, a high hardness layer 30 a is formed on the inner surface of the outer ring member 32, and a high hardness layer 30 b is formed on the outer surface of the spider 34. Hereinafter, the inner surface of the outer cup 16 and the outer surface of the inner ring 18 of the first constant velocity joint 10, the inner surface of the outer ring member 32, and the outer surface of the spider 34 are collectively referred to as a member surface. As shown in FIG. 2, the high hardness layers 30a and 30b formed on the surface of the member have a multilayer structure in which the porosity changes in the thickness direction. The configuration of the high hardness layers 30a and 30b will be specifically described in relation to the method for manufacturing the constant velocity joint according to the present embodiment.

  In this method of manufacturing a constant velocity joint, in order to obtain each component of the first constant velocity joint 10 and the second constant velocity joint 12, the steel material that has been subjected to heat treatment and lubrication treatment is forged, A molded body of each shape is obtained. Of these molded bodies, the high hardness layers 30a and 30b are respectively formed on the inner surface of the outer member (outer cup 16, outer ring member 32) and the member surface which is the outer surface of the inner member (inner ring 18, spider 34). A hardness layer forming step is performed.

  The formation of the high hardness layers 30a, 30b can be performed by applying various methods such as coating and adhesion, but is preferably performed by thermal spraying (plasma spraying, high-speed flame spraying, etc.). By applying thermal spraying, it is possible to increase the degree of freedom of material selection and to obtain the high hardness layers 30a and 30b efficiently and with high accuracy. In addition, for example, by adjusting the conditions (spraying speed, spraying distance, spraying temperature, etc.) during spraying, and the particle size and type (component) of particles used as a material, desired density and porosity can be easily obtained. The high-hardness layers 30a and 30b having a multilayer structure can be formed.

  Therefore, in this embodiment, an example in which the high hardness layers 30a and 30b are formed by thermal spraying will be described. As shown in FIG. 3, in the high hardness layer forming step, a thermal spray gun 46 is used to melt the particles as a material and spray the material onto the surface of the member to form a film. At this time, the outer member and the inner member are cooled so as not to exceed, for example, 100 ° C. by a cooling unit (not shown) in order to prevent the temperature from rising excessively. The cooling means can be performed by a known method using a cooling medium such as cooling water. FIG. 3 illustrates the case where the high hardness layer 30a is formed on the inner surface of the outer ring member 32 as the outer member.

  In the high hardness layer forming step, the thermal spraying conditions are changed so that the high hardness layers 30a and 30b have a multilayer structure in which the porosity changes in the thickness direction. That is, the spraying conditions are in the order of the first condition, the second condition, and the third condition from the member surface side of the high hardness layers 30a and 30b toward the contact surface 48 side with the torque transmission member (ball 20, roller 36). It is changing.

  Of the high hardness layer 30a, a layer formed while the spraying condition is the first condition is referred to as a first layer 302a. Similarly, layers formed while the spraying conditions are the second condition and the third condition are referred to as a second layer 304a and a third layer 306a, respectively. Note that the porosity and components of each of the first layer 302a to the third layer 306a change in an inclined manner. Therefore, although each layer of the high hardness layer 30a is not divided by a clear boundary, for convenience of explanation, a portion of the high hardness layer 30a that is formed under the same thermal spraying condition is defined as one layer.

  Similar to the high-hardness layer 30a, the high-hardness layer 30b is also a multi-layer consisting of a first layer 302b, a second layer 304b, and a third layer 306b that are formed during the first condition, the second condition, and the third condition, respectively. It is a structure.

  That is, each of the high hardness layers 30a and 30b has the first layers 302a and 302b formed on one side close to the member surface of both end sides in the thickness direction, and the third layer 306a on the other side close to the contact surface 48. , 306b are formed. The second layers 304a and 304b are interposed between the first layers 302a and 302b and the third layers 306a and 306b, respectively.

  Here, the high hardness layer 30a and the high hardness layer 30b are formed in the same manner except that the constituent components of the third layers 306a and 306b are different from each other. Specifically, the third layer 306a is made of, for example, mixed particles containing 80 to 90 atm% WC, 5 to 10 atm% Co, and 3 to 8 atm% CrC in order to improve wear resistance particularly well. Formed as. Therefore, in this case, the third layer 306a is composed of cermet. On the other hand, the third layer 306b includes, for example, 70 to 90 atm% WC, 1 to 10 atm% Co, 1 to 5 atm% CrC, and 1 to 5 atm% Ni in order to achieve a balance between toughness and wear resistance. Mixed particles are formed as starting materials. That is, the third layer 306b is also composed of cermet.

  Therefore, hereinafter, the case where the high hardness layer 30a is formed will be described as an example. Since the high hardness layer 30b can be formed in substantially the same manner as the high hardness layer 30a, the description thereof is omitted.

  Specifically, in the high hardness layer forming step, first, the porosity of the first layer 302a is reduced as much as possible in order to improve the adhesion with the member surface particularly effectively. The thermal spraying is performed under the first condition that is possible. That is, the first condition is set so that the upper limit of the porosity of the first layers 302a and 302b is 0.5 to 3%.

  Here, the “porosity” is calculated based on the measurement of the porosity by image processing described in “The Thermal Spraying Engineering Handbook” (page 600, published in January 2010). That is, the sample cross section is mirror-polished and then photographed with an optical microscope. This is a value obtained by binarizing the obtained image and calculating the area of the pore portion (for example, black) in the entire area. Alternatively, the porosity may be measured by a water immersion method.

As the starting material of the first layer 302a, for example, Al ₂ O ₃ , FeMn, Cr ₂ O ₃ is blended so that the adhesion between the first layer 302a and the surface member can be particularly effectively improved. It is configured. The thickness of the first layer 302a is set to 100 μm or less in consideration of adhesion to the member surface and impact resistance.

  Therefore, by setting the porosity, the constituent material, and the thickness of the first layer 302a as described above, it is possible to effectively prevent the high hardness layer 30a from peeling off from the member surface.

  Next, thermal spraying is performed on the first layer 302a deposited on the member surface under the second condition so that the second layer 304a having a higher porosity than the first layer 302a is formed. For example, the second condition is set so that the porosity of the second layer 304a is 2 to 5% and does not exceed the porosity of the first layer 302a. Thus, by setting the porosity to 2% or more, it becomes possible to satisfactorily hold the lubricant such as the above-described grease composition in the pores of the second layer 304a.

  In addition, the second layer 304a can function as a cushioning material between the first layer 302a and the third layer 306a. That is, the contact surface pressure of the torque transmission member with respect to the high hardness layer 30a is absorbed by, for example, elastic deformation of the second layer 304a. Thereby, the durability of the entire unit of the first constant velocity joint 10 and the second constant velocity joint 12 (hereinafter collectively referred to as the constant velocity joints 10 and 12) can be enhanced. Moreover, it can suppress appropriately that the impact resistance of the high hardness layer 30a falls by setting the porosity of the 2nd layer 304a to 5% or less.

The material constituting the second layer 304a preferably includes a component common to both the first layer 302a and the third layer 306a in order to suppress delamination between the high hardness layers 30a. An example of such a component system is WC ₁₀ CrC ₇ Ni. In addition, the thickness of the second layer 304a can be arbitrarily set between, for example, 10 to 50 μm, and more preferably 20 to 30 μm. In this case, it is possible to appropriately balance the impact resistance with the lubricant holding ability of the high hardness layer 30a.

  Next, thermal spraying is performed on the second layer 304a under the third condition so that a third layer 306a having a higher porosity than the first layer 302a and a lower porosity than the second layer 304a is formed. I do. For example, the third condition is set so that the porosity of the third layer 306a is 0.5 to 2%. In this case, the hardness of the third layer 306a can be set to a value that can effectively suppress wear due to torque transmission. Further, the lubricant can be moved between the surface of the third layer 306a (contact surface 48) and the pores of the second layer 304a through the pores of the third layer 306a.

  Therefore, for example, while the operation of the constant velocity joints 10 and 12 is stopped, the lubricant can be effectively retained in the pores of the second layer 304a from the contact surface 48 through the pores of the third layer 306a. it can. On the other hand, during the operation of the constant velocity joints 10 and 12, the lubricant held in the mechanism of the second layer 304a can move to the contact surface 48 through the pores of the third layer 306a. As a result, the lubricity between the contact surface 48 and the torque transmission member can be maintained better and the wear resistance can be improved.

  As described above, the material constituting the third layer 306a is made of a component that can effectively improve wear resistance, toughness, and the like. Moreover, it is preferable that the thickness of the 3rd layer 306a shall be 10-50 micrometers, for example. In this case, it is possible to effectively prevent the third layer 306a from peeling from the second layer 304a while maintaining the hardness of the third layer 306a sufficiently.

High hardness layers 30a and 30b can be formed on the surface of the member by the above-described high hardness layer forming step. At this time, the total thickness of the high hardness layers 30a and 30b is preferably 50 to 200 μm, and more preferably 70 to 100 μm. Moreover, although the maximum value of the spraying speed (particle spraying speed) by the above-mentioned spraying gun 46 depends on the spraying method and the component (specific gravity) of the particles, for example, the high-speed flame spraying is used to remove Al ₂ O ₃ particles. In the case of thermal spraying, it reaches 400 to 1000 m / sec. As the particles collide with each other at such a high speed, work hardening occurs on the member surface, and an influence layer 50 in which a part of the particles is alloyed with the member surface is formed. Further, as shown by the one-dot chain line in FIG. 2, residual compressive stress can be generated inside the high hardness layers 30a and 30b.

  The influence layer 50 and residual compressive stress also effectively improve the hardness of the surface of the member on which the high hardness layers 30a and 30b are formed and effectively peel the high hardness layers 30a and 30b from the surface of the member. It becomes possible to suppress. In addition, the thickness of the influence layer 50 and the magnitude of the residual compressive stress can be appropriately set by adjusting the spraying conditions (particularly, the spraying speed).

  A grinding step of grinding a part of the third layers 306a and 306b in the high hardness layers 30a and 30b is performed. Accordingly, the outer member and the inner member can be obtained by adjusting the dimensions. That is, in the high hardness layer forming step, it is preferable that the third layers 306a and 306b are formed to have a thickness larger than the preferable thickness by a grinding allowance of 20 to 80 μm ground in the grinding step.

  As described above, in the inner member and the outer member, after the high hardness layer 30a is formed, the size can be adjusted by performing a grinding process. Therefore, it becomes unnecessary to design a forging die in advance with high accuracy, and the inner member and the outer member can be obtained easily and efficiently. In addition, it is preferable that the surface roughness of the surface (contact surface 48) of the 3rd layer 306a after grinding is adjusted to 12.5-25S.

  Next, the constant velocity joints 10 and 12 can be obtained by appropriately combining the outer member and the inner member in which the high hardness layers 30a and 30b are formed and the dimensions are adjusted as described above.

  As described above, the high-hardness layers 30a and 30b are superior in wear resistance, corrosion resistance, insulation, and the like, and have hardness (surface pressure resistance), for example, as compared with a hardened layer formed by subjecting a member surface to heat treatment. High strength at high temperatures. Therefore, even if the torque transmission member comes into contact with the surface of the member provided with the high hardness layers 30a and 30b, it is possible to effectively suppress wear.

  Further, since the outer member and the inner member can be formed from steel or the like, the manufacturing cost of the constant velocity joints 10 and 12 is reduced as compared with the case where all of the constituent elements are formed from ceramics or cermet. be able to. Furthermore, for example, the constant velocity joints 10 and 12 can be obtained without going through complicated manufacturing processes such as molding by CIP or HIP, thereby improving the manufacturing efficiency and the degree of freedom of the shape, and reducing the equipment cost. It becomes possible to reduce.

  From the above, it is possible to easily and efficiently suppress wear due to torque transmission at low cost, and to obtain constant velocity joints 10 and 12 excellent in durability. That is, the constant velocity joints 10 and 12 can have the advantages of a steel material such as low cost and excellent formability, and the advantages of a ceramic material or cermet material such as high hardness and excellent wear resistance. Further, as described above, sufficient strength can be maintained even if the volume of the inner member or the outer member is reduced, because the hardness of the member surface can be effectively increased by the high hardness layers 30a and 30b. For this reason, the constant velocity joints 10 and 12 can be reduced in size.

  As described above, the multilayer structure of the high hardness layers 30a and 30b is formed by changing the porosity in the thickness direction. The porosity is larger on the central side in the thickness direction (second layers 304a and 304b side) than on both end sides (first layers 302a and 302b side and third layers 306a and 306b side). is there. In this case, of the high hardness layers 30a and 30b formed on the member surface, one side close to the member surface (the first layer 302a and 302b side) and the other side close to the contact surface 48 in contact with the torque transmission member (the first layer) The three layers 306a and 306b side) are denser than the center side.

  Therefore, as is clear from the relationship between the thickness and hardness of the high hardness layers 30a and 30b indicated by solid lines in FIG. 2, the hardness (denseness) on the contact surface side and member surface side of the high hardness layers 30a and 30b is excellent. Can be raised. As a result, wear due to torque transmission can be effectively suppressed, and adhesion (adhesion) between the high hardness layers 30a and 30b and the member surface can be improved satisfactorily.

  On the other hand, the central side of the high hardness layers 30a and 30b can hold the lubricant well in the pores due to the large porosity, and can enhance the lubricant holding ability of the high hardness layers 30a and 30b. As a result, a lubricant can be appropriately supplied between the torque transmitting member and the high hardness layers 30a and 30b to form a lubricating film, so that mutual lubrication can be maintained well. That is, wear on the surface of the member provided with the high hardness layers 30a and 30b can be more effectively suppressed. Further, the central side of the high hardness layers 30a and 30b has a larger porosity than both end sides, and thus can function as a cushioning material.

  Therefore, for example, it is possible to absorb the contact surface pressure of the torque transmitting member with respect to the high hardness layers 30a and 30b due to elastic deformation occurring at the center side of the high hardness layers 30a and 30b. For this reason, durability of the constant velocity joints 10 and 12 as a whole can be enhanced.

  In other words, by providing the high-hardness layers 30a and 30b having the multilayer structure as described above, it is possible to obtain constant velocity joints 10 and 12 that exhibit further excellent durability and have an appropriately long life. .

  In addition, this invention is not specifically limited to above-described embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.

  For example, in the above embodiment, the high hardness layers 30a and 30b are formed on all of the inner surface of the outer member and the outer surface of the inner member. However, the present invention is not particularly limited to this. The high hardness layers 30a and 30b may be provided only on necessary portions of the inner surface of the outer member and the outer surface of the inner member.

  The high hardness layer 30a and the high hardness layer 30b are formed in the same manner except that the constituent components of the third layers 306a and 306b are different from each other, but are not particularly limited thereto. For example, each of the first layer 302a to the third layer 306a and the first layer 302b to the third layer 306b may be formed in the same manner with various properties such as each other's constituent components, porosity, and thickness, It may be formed to be completely different. That is, the multi-layer structure of the high hardness layer 30a and the high hardness layer 30b is not limited to the above three layers, and has a variety of functions in accordance with the materials and usage conditions of the constant velocity joints 10 and 12. What is necessary is just to adjust suitably. Furthermore, the high hardness layers 30a and 30b may have a single layer structure.

DESCRIPTION OF SYMBOLS 10 ... 1st constant velocity joint 12 ... 2nd constant velocity joint 14 ... Drive shaft 16 ... Outer cup 18 ... Inner ring 20 ... Ball 22 ... 1st ball groove 24 ... 2nd ball groove 26 ... Retainer 28a, 28b ... Boot for joints 30a, 30b ... high hardness layer 32 ... outer ring member 34 ... spider 36 ... roller 38 ... track groove 40 ... annular portion 42 ... trunnion 44 ... rolling element 46 ... thermal spray gun 48 ... contact surface 50 ... influence layer 302a, 302b ... first 1st layer 304a, 304b ... 2nd layer 306a, 306b ... 3rd layer

Claims (10)

A constant velocity joint comprising: an outer member; an inner member inserted into the outer member; and a torque transmitting member interposed between the outer member and the inner member to transmit torque.
A constant velocity joint comprising a high hardness layer mainly composed of ceramics or cermet on a member surface which is at least one of an inner surface of the outer member and an outer surface of the inner member. The constant velocity joint according to claim 1,
The constant velocity joint, wherein the high hardness layer has a multilayer structure. In the constant velocity joint according to claim 2,
The multilayer structure of the high hardness layer is formed by changing the porosity in the thickness direction,
The constant velocity joint according to claim 1, wherein a porosity on a central side in the thickness direction is larger than a porosity on both ends. In the constant velocity joint according to claim 3,
The constant velocity characterized in that the porosity on the other side close to the contact surface in contact with the torque transmitting member is larger than the porosity on one side close to the member surface among both end sides in the thickness direction. Joint. In the constant velocity joint according to any one of claims 1 to 4,
The constant velocity joint, wherein the high hardness layer is formed by thermal spraying. An outer member, an inner member inserted into the outer member, and a torque transmission member that transmits torque by being interposed between the outer member and the inner member,
It has a high hardness layer forming step of forming a high hardness layer mainly composed of ceramics or cermet on a member surface which is at least one of the inner surface of the outer member and the outer surface of the inner member. A method for manufacturing a joint. In the manufacturing method of the constant velocity joint of Claim 6,
In the high hardness layer forming step, the high hardness layer is formed on the surface of the member by thermal spraying, and the thermal spraying conditions are changed so that the high hardness layer has a multilayer structure. Method. In the manufacturing method of the constant velocity joint of Claim 7,
In the high hardness layer forming step, the spraying conditions are changed in the order of the first condition, the second condition, and the third condition,
During the first condition, forming a first layer deposited on the surface of the member,
During the second condition, the second layer is formed so as to be continuous from the first layer and have a higher porosity than the first layer,
A method of manufacturing a constant velocity joint, wherein the third layer is formed so as to be continuous from the second layer and to have a lower porosity than the second layer while the third condition is satisfied. In the manufacturing method of the constant velocity joint of Claim 8,
The method for manufacturing a constant velocity joint, wherein the first condition and the third condition are set so that the porosity of the third layer is larger than that of the first layer. In the manufacturing method of the constant velocity joint of any one of Claims 6-9,
The method of manufacturing a constant velocity joint, further comprising a grinding step of grinding a part of the high hardness layer.

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