JP2006117982A - Method for manufacturing vehicle drive system component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance production efficiency by improving a method for manufacturing vehicle drive system components. <P>SOLUTION: This method for manufacturing drive system components is a method for manufacturing vehicle drive system components. This manufacturing method includes a first process S1 of working a material and forming the drive system components and a second process S2 of applying gas soft-nitriding treatment to the drive system components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a drive system component of a vehicle, and more particularly to a method for manufacturing a drive system component used in a lockup device of a fluid type torque transmission device.

  For example, a torque converter is known as a fluid torque transmission device for a vehicle. The torque converter is a device for transmitting torque from the engine to the transmission side by fluid. The torque converter mainly adjusts the front cover to which torque from the engine is input, the impeller provided in the front cover, the turbine disposed opposite to the impeller, and the flow of fluid from the turbine to the impeller. Therefore, it is composed of a stator. A fluid chamber is formed by the front cover and the impeller, and the fluid chamber is filled with a fluid such as hydraulic oil. The torque converter includes a lockup device disposed between the turbine and the front cover.

  The lock-up device is a device having a clutch function that directly transmits torque by mechanically connecting a front cover and a turbine, and a damper function that absorbs and attenuates torque fluctuations. Usually, the lock-up device has a piston that can be frictionally connected to the front cover, a torsion spring disposed on the inner peripheral side of the piston, and a driven plate that is elastically connected to the piston in the rotational direction by the torsion spring. ing. The driven plate is fixed to the turbine.

The piston divides the space between the front cover and the turbine in the axial direction, and can move in the axial direction due to a hydraulic pressure difference on both sides in the axial direction. Then, when the friction facing that is annularly stretched around the outer periphery of the piston is pressed against the flat friction surface of the front cover, the torque input to the front cover is transmitted to the lockup device. As a result, the front cover and the turbine are mechanically connected, and torque transmission efficiency is improved when the difference in rotational speed between the two is small (see, for example, Patent Document 1).
Japanese Utility Model Publication No. 06-47763

  The drive system components that make up the drive system device such as the torque converter described above generally come into contact with and slide with other members in general, so the surface is hardened as necessary to wear resistance. And increased fatigue resistance. Here, the piston of the lockup device will be described as an example.

  The piston has a substantially cylindrical tubular portion extending in the axial direction on the outer peripheral side. A torsion spring is disposed on the inner peripheral side of the cylindrical portion of the piston. As a method of holding the torsion spring, there are a case where it is directly held by the outer peripheral side cylindrical portion of the piston and a case where a retaining plate is provided between the outer peripheral side cylindrical portion of the piston and the torsion spring in the radial direction. The torsion spring is pressed to the outer peripheral side by centrifugal force and repeatedly expands and contracts at the time of lockup connection and release, so that the peripheral members such as the piston and the retaining plate are required to have wear resistance. Therefore, the piston or the retaining plate is subjected to hardening treatment such as carburizing quenching and tempering (carburizing treatment), carbonitriding quenching and tempering (carbonitriding treatment), or nitriding treatment, in whole or in part. (For example, refer to Patent Document 1 [0004], [0017]).

  In the carburizing treatment, after diffusing C on the surface of the material, the material is hardened and martensitic transformed to increase the hardness of the material. The carburized material generally has a deep hardening depth, and examples of applicable materials include carbon steel and alloy steel having a C content of 0.25% by weight or less. However, the carburizing process requires a processing cost because the quenching temperature is as high as 920 to 950 ° C., and the distortion of the material generated during the processing is large, so that it is not suitable for the curing process of a plate-like material such as a piston.

  In the carbonitriding process, the applicable materials are extremely mild steel and low carbon steel, and the quenching temperature is slightly low at 850 to 860 ° C. compared to the carburizing process. Become. However, a steel material that has been subjected to carbonitriding has the disadvantages that retained austenite is easily generated and the hardened layer is brittle.

  Furthermore, in the nitriding treatment, the applicable material is limited to a nitriding material (a steel material including Al, Cr, etc., for example, SACM (JIS G 4202)). Further, although the processing temperature is lower than that of carburizing or carbonitriding, a very long processing time is required depending on the nitriding depth. For example, in order to secure a nitriding depth of 0.1 mm, a processing time of nearly 10 hours is required.

  The curing processing method described above is widely used as a curing processing method for parts of a vehicle drive system. However, since carburizing and carbonitriding processes are high in processing temperature, residual stress is likely to occur, and processes such as tempering and distortion correction are required. In addition, although the nitriding process has a low processing temperature, the processing time becomes very long. As a result, since the total heat treatment time becomes long in any of the processing methods, the production efficiency is lowered and the production cost is increased.

  An object of the present invention is to improve the production efficiency of drive system parts by devising a curing method for drive system parts of a vehicle.

  The drive system component manufacturing method according to claim 1 is a vehicle drive system component manufacturing method. This manufacturing method includes a first step of processing a material and molding a drive system component, and a second step of subjecting the drive system component to gas soft nitriding.

  The gas soft nitriding treatment refers to a treatment for soft nitriding a material by feeding a mixed gas of a nitriding gas and a carburizing gas into a furnace containing the material and heating it at a high temperature. In the gas soft nitriding treatment, a compound layer is formed on the surface of the material, nitrogen is diffused secondarily, and the hardness near the surface is improved. The heating temperature of the gas soft nitriding treatment is around 570 ° C., and the treatment time is 1 to 5 hours. The target steel types are wide from mild steel to high alloy steel, and the surface hardness after processing varies depending on the steel type. Therefore, various surface hardness can be obtained by selecting the steel type.

  In this manufacturing method, since the gas soft nitriding treatment is performed in the second step, the treatment temperature can be lowered as compared with the conventional carburizing treatment or carbonitriding treatment. Thereby, in this manufacturing method, since distortion of a processed product decreases compared with the conventional carburizing process and carbonitriding process, the distortion correction process, such as a press temper, becomes unnecessary. Moreover, the tempering process required by the conventional carburizing process and carbonitriding process becomes unnecessary. As a result, in this manufacturing method, since the total heat treatment time can be shortened, the production efficiency can be improved.

  The drive system component manufacturing method according to claim 2 is the drive system component manufacturing method according to claim 1, wherein the drive system component has a C content of 0.15 wt% or less and a Cr content of 1.0 to 1.3 wt%. It is steel within the range.

  As described above, conventionally, carbon steel or the like is subjected to a carburizing process to harden drive system components. However, in this manufacturing method, a gas soft nitriding treatment is performed on a steel material in which the contents of C and Cr are 0.15 wt% or less and 1.0 to 1.3 wt%, respectively. As a result, the hardness characteristics of the material are comparable to those of the carburized material. In particular, it has been found that the effective hardening depth of the material surface is maximized when the C and Cr contents are within the above ranges. The gas soft nitriding treatment can shorten the overall heat treatment time compared with the conventional curing treatment. Thereby, in this manufacturing method, the production efficiency can be improved as compared with the carburizing process, the carbonitriding process, or the nitriding process while securing the same hardness characteristics as the carburizing process. Moreover, since the C content of the material is 0.15% by weight or less, the workability in the first step is improved as compared with the conventional case.

  The drive system component manufacturing method according to claim 3 is the drive system component according to claim 1 or 2, wherein the S content in the drive system component is 0.005 wt% or less.

  In this manufacturing method, since the S content of the drive system component is 0.005% by weight or less, bending workability such as press working can be improved, and end face cracking or the like during press working can be prevented. it can.

  According to a fourth aspect of the present invention, there is provided a drive system component manufacturing method according to any one of the first to third aspects, wherein the drive system component is disposed in a space between the front cover of the fluid torque transmission device and the turbine. It is a part which comprises the lockup apparatus for connecting with. The lockup device includes an annular piston that is movable in the axial direction and that can be coupled to the front cover, an annular drive member that is fixed to the piston, and an elastic member that is disposed between the piston and the drive member in the radial direction. And a driven member fixed to the turbine.

  In this manufacturing method, since the gas soft nitriding treatment is applied to the piston of the lockup device, a piston having a high surface hardness can be obtained by selecting a steel type. Thereby, even if it is a structure which makes a piston and an elastic member slide directly, abrasion of a piston can be prevented. In addition, since a structure in which the piston and the elastic member are directly slidable can be adopted, it is not necessary to provide the retaining plate on the outer peripheral side of the elastic member. As a result, in this manufacturing method, the elastic member can be arranged on the outer peripheral side in the lockup device, and a wide twist angle can be realized.

  According to a fifth aspect of the present invention, there is provided a drive system component manufacturing method according to the fourth aspect, wherein the piston has an outer peripheral cylindrical portion having a substantially cylindrical shape extending axially on the outer peripheral side, and the elastic member is the outer peripheral cylindrical portion. It is slidable with the inner peripheral side.

  In this manufacturing method, the elastic member is slidable with the inner peripheral surface of the outer cylindrical portion of the piston subjected to gas soft nitriding treatment, so that the piston is prevented from being worn even if the piston and the elastic member slide. can do.

  In the drive system component manufacturing method according to the present invention, the production efficiency can be improved.

  An embodiment of the present invention will be described with reference to the drawings.

1. Manufacturing Method of Drive System Parts (1) Manufacturing Process FIG. 1 shows a manufacturing process as one embodiment according to the present invention. As shown in FIG. 1, the manufacturing process of the present invention includes a first process and a second process.

  In the first step S1, the material is processed to form a drive system component. Examples of the drive system parts include parts constituting a device such as a torque converter, a clutch, or a transmission. About the pre-processing of these components, since there is no difference from the conventional processing method, description is abbreviate | omitted.

  Next, in the second step S2, gas soft nitriding is performed on the drive system component processed in the first step S1. Here, the gas soft nitriding process will be described in detail.

(2) Gas soft nitriding treatment 1) Gas soft nitriding treatment With gas soft nitriding treatment, a mixed gas of nitriding gas and carburizing gas is fed into a furnace containing the material and heated at a high temperature to soft nitriding the material The process to do. The heating temperature is generally around 570 ° C., and the treatment is performed over 1 to 5 hours. The target steel types are wide from mild steel to high alloy steel, and the surface hardness after processing varies depending on the steel type. Therefore, various surface hardness can be obtained by selecting the steel type.

  When gas soft nitriding is performed, a compound layer is formed on the surface of the material, and nitrogen atoms are secondarily diffused to increase the hardness in the vicinity of the surface. The compound layer is mainly composed of nitride and has an influence on the surface hardness. On the other hand, the occurrence of lattice distortion accompanying the solid solution of nitrogen affects the curing depth. Generally, when Cr etc. contain in steel materials, a compound layer becomes hard and the hardness of a diffused layer also becomes high.

  As a feature of the gas soft nitriding treatment as compared with the conventional carburizing treatment or carbonitriding treatment, first, there is little distortion of the material. This is because the processing temperature is lower than that of carburizing or carbonitriding, and it is not necessary to use phase transformation. Thereby, in the gas soft nitriding process, the distortion correction process performed in the carburizing process or the carbonitriding process becomes unnecessary. In addition, gas soft nitriding has a lower processing temperature than carburizing and carbonitriding, eliminating the need for the tempering process required for carburizing and carbonitriding, and shortening the overall heat treatment time. Can improve production efficiency. Furthermore, in the gas soft nitriding treatment, by selecting an appropriate steel type, it is possible to obtain the same hardness characteristics as the carburizing treatment. Therefore, materials suitable for gas soft nitriding will be described.

2) Material suitable for gas soft nitriding FIG. 2 shows the influence of alloying elements on surface hardness. In FIG. 2, the vertical axis represents hardness (BHV), and the horizontal axis represents alloy element content (% by weight). From FIG. 2, it can be seen that the elements effective for securing the surface hardness in the gas soft nitriding treatment are Cr and Al having a very strong affinity for nitrogen. Accordingly, the present invention describes the case where Cr is contained.

  FIG. 3 shows the influence of the amount of Cr added (content) on the hardening depth. The vertical axis in FIG. 3 shows the effective hardening depth (mm) in the case of Hv420, the horizontal axis shows the amount of Cr added (wt%), and the material is based on a low carbon steel with a C content of 0.20 wt%. Yes. From FIG. 3, it is understood that the Cr addition amount effective for securing the hardening depth in the gas soft nitriding treatment is in the range of 1.0 to 1.3% by weight, and preferably 1.0% by weight. . Furthermore, the figure which compared the hardness characteristic after heat processing of Cr addition steel, SPHC (hot rolled steel plate), and 0.30 weight% C steel in FIG. 4 is shown. The vertical axis in FIG. 4 indicates the surface hardness (Hv 100 g), and the horizontal axis indicates the depth (mm) from the surface layer. In FIG. 4, three types of steel materials subjected to gas soft nitriding treatment and those subjected to conventional carburizing treatment are compared. In this case, the gas soft nitriding treatment conditions are treatment temperature: 570 ° C. and treatment time: 3 hours. From FIG. 4, SPHC subjected to gas soft nitriding and 0.3 wt% C steel subjected to gas soft nitriding have lower surface hardness and hardening depth than SPHC subjected to carburizing. I understand. On the other hand, 1.0 wt% Cr-0.07 wt% C steel subjected to gas soft nitriding treatment has the same surface hardness and hardening depth as SPHC subjected to carburizing treatment. For example, when the surface hardness after gas soft nitriding treatment is compared, SPHC: Hv525, 0.30 wt% C steel: Hv378, whereas 1.0 wt% Cr-0.07 wt% C steel: It is about the same as SPHC that has been carburized to a very high level as Hv711. Further, when comparing the hardness of 0.1 mm depth after gas soft nitriding treatment, it is SPHC: Hv260, 0.30 wt% C steel: Hv328, whereas 1.0 wt% Cr-0.07. Weight% C steel: Hv585, which is very high and comparable to SPHC subjected to carburizing treatment. In addition, although content of C is 0.07 weight%, if it is 0.15 weight% or less (JIS G 3131), the effect equivalent to the above will be acquired.

  From the above results, the steel material capable of effectively improving the surface hardness and the hardening depth by gas soft nitriding is C: 0.15 wt% or less, Cr: 1.0 to 1.3 wt% I understand that there is.

3) Improvement of bending workability The 0.07 wt% C-1.0 wt% Cr steel described above is based on a low carbon steel with a low C content. Therefore, bending workability such as press working is improved. In addition, the S content is lower than that of conventional SPHC. Specifically, the upper limit of the S content of SPHC is 0.05% by weight or less (JIS G 3131), whereas 0.07% by weight C-1.0% by weight Cr steel is 0%. 0.005% by weight or less. In general, a steel material having a high S content improves machinability but lowers bending workability. Therefore, since the bending workability such as press working is improved as compared with the conventional steel material having a large S content such as SPHC, it is possible to prevent the end face from being cracked during the press working. In addition, although content of C is 0.07 weight%, if it is 0.15 weight% or less (JIS G 3131), the effect equivalent to the above will be acquired. Moreover, although content of Cr is 1.0 weight%, if it exists in the range of 1.0-1.3 weight%, the effect equivalent to the above will be acquired.

(3) Operational effects of the present invention The following operational effects can be obtained by applying the gas soft nitriding treatment as described above to a method for manufacturing a drive system component.

  In this manufacturing method, since the gas soft nitriding process is performed on the drive system components in the second step S2, the processing temperature can be lowered as compared with the conventional carburizing process or carbonitriding process. Thereby, compared with the conventional carburizing process and carbonitriding process, since distortion of a processed product decreases, distortion correction processes, such as a press temper, become unnecessary. Moreover, the tempering process required by the conventional carburizing process and carbonitriding process becomes unnecessary. Further, the processing time can be shortened as compared with the conventional nitriding treatment. As a result, this manufacturing method can shorten the overall heat treatment time, and can improve the production efficiency. In addition, when the C and Cr contents of the drive system parts are 0.15 wt% or less and 1.0 to 1.3 wt%, respectively, the surface hardness and the hardening depth are the same as those of the conventional carburizing treatment. You can get it. Moreover, workability | operativity can be improved because content of C of drive-train components shall be 0.15 weight% or less. Further, when the Cr content is in the range of 1.0 to 1.3% by weight, the effective hardening depth of the drive system component after the gas soft nitriding treatment can be maximized. Furthermore, since the S content is 0.005% by weight or less, it is possible to improve the bending workability at the time of press working of the drive system components, and to prevent cracking of the end face at the time of press working.

  As described above, in this manufacturing method, it is possible to improve the production efficiency of the drive system parts while ensuring the same hardness characteristics as the carburizing process.

2. Application of the lock-up device of the present invention to a piston A case where a piston of a lock-up device of a torque converter is manufactured by the manufacturing method according to the present invention will be described.

(1) Structure of torque converter First, the structure of the torque converter will be described. FIG. 5 is a schematic vertical sectional view of the torque converter. OO in FIG. 5 indicates the rotation axis of the torque converter 1. In FIG. 5, the torque converter 1 forms a fluid chamber by a front cover 2 and an impeller shell 9 fixed to the outer peripheral side protruding portion 8 of the front cover 2. The front cover 2 can be attached to each crankshaft (not shown) of the engine by each component, and torque from the engine is input. A plurality of impeller blades 10 are fixed inside the impeller shell 9. The impeller 3 is constituted by the impeller shell 9 and the impeller blade 10. A turbine 4 is disposed at a position facing the impeller 3 in the fluid chamber. The turbine 4 includes a turbine shell 11 and a plurality of turbine blades 12 fixed on the turbine shell 11. An inner peripheral end of the turbine shell 11 is fixed to a flange 15 of the turbine hub 13 via a rivet 14. The turbine hub 13 has a spline groove 20 that engages with a main drive shaft of a transmission (not shown) on an inner peripheral portion. A stator 5 is disposed between the inner periphery of the impeller 3 and the inner periphery of the turbine 4. The stator 5 adjusts the direction of fluid returned from the turbine 4 to the impeller 3, and is supported by a fixed shaft (not shown) via a stator support mechanism 6.

(2) Structure of Lock-up Device The lock-up device 7 is a device that is disposed in the space between the front cover 2 and the turbine 4 and mechanically connects the front cover 2 and the turbine 4. The lock-up device 7 mainly includes a piston 22 and an elastic coupling mechanism 40 for elastically coupling the piston 22 to the turbine 4.

  The piston 22 is a disk-shaped member, and divides the space between the front cover 2 and the turbine shell 11 into a first hydraulic chamber 36 on the front cover 2 side and a second hydraulic chamber 37 on the turbine 4 side. Are arranged as follows. The piston 22 is made of a thin metal plate. The piston 22 has an inner peripheral cylindrical portion 23 extending toward the transmission side on the inner peripheral side. The inner peripheral cylindrical portion 23 is supported on the outer peripheral surface 19 of the cylindrical portion 16 of the flange 15 of the turbine hub 13 so as to be relatively movable in the axial direction and the circumferential direction. That is, the inner peripheral surface 25 of the inner peripheral cylindrical portion 23 is in contact with the outer peripheral surface 19 of the cylindrical portion 16. An annular groove is formed on the outer peripheral surface 19 of the cylindrical portion 16 at an intermediate position in the radial direction. A seal ring 18 is disposed in the annular groove, and the seal ring 18 is in contact with an inner peripheral surface 25 of the inner peripheral cylindrical portion 23. Thus, the seal ring 18 seals the inner peripheral portions of the first hydraulic chamber 36 and the second hydraulic chamber 37.

  An outer peripheral cylindrical portion 24 extending to the transmission side is formed on the outer peripheral portion of the piston 22. An annular friction facing 35 is provided on the engine side of the outer periphery of the piston 22. The friction facing 35 is opposed to an annular flat friction surface 2 a formed on the inner periphery of the front cover 2. Due to the engagement between the friction facing 35 and the friction surface 2 a of the front cover 2, the outer peripheral portions of the first hydraulic chamber 36 and the second hydraulic chamber 37 are sealed.

  The elastic coupling mechanism 40 is disposed between the piston 22 and the turbine 4, more specifically, between the outer peripheral portion of the piston 22 and the outer peripheral portion of the turbine shell 11. The elastic coupling mechanism 40 includes a retaining plate 27 disposed on the inner peripheral side of the outer peripheral cylindrical portion 24 of the piston 22, a driven plate 33 as a driven member, an outer peripheral cylindrical portion 24, and a retaining plate. 27 and a plurality of coil springs 32 arranged in the radial direction. The retaining plate 27 is an annular plate member disposed on the outer peripheral transmission side of the piston 22, that is, on the inner peripheral side of the outer peripheral cylindrical portion 24. The inner peripheral portion of the retaining plate 27 is fixed to the piston 22 by a plurality of rivets (not shown). The retaining plate 27 is a member for holding the coil spring 32 together with the outer cylindrical portion 24. The retaining plate 27 has a holding portion 29 that supports the inner peripheral sides of a plurality of coil springs 32 arranged in the circumferential direction. The holding portion 29 is formed by cutting and raising from a disc-shaped portion of the retaining plate 27. The outer peripheral side cylindrical portion 24 of the piston 22 has engaging portions 30 for supporting both sides of each coil spring 32 in the circumferential direction. The driven plate 33 is an annular plate member fixed to the rear surface of the outer peripheral portion of the turbine shell 11. The driven plate 33 is formed with a plurality of claw portions 34 arranged in the circumferential direction and extending toward the engine side. The claw portions 34 are engaged with both ends of each coil spring 32 in the circumferential direction. Thereby, the torque from the piston 22 is transmitted to the driven plate 33 via the coil spring 32.

  In the lockup device 7 described above, the coil spring 32 is disposed on the inner peripheral side of the outer peripheral side cylindrical portion 24 of the piston 22. Therefore, at the time of lockup connection, the inner peripheral surface of the outer cylindrical portion 24 and the coil spring 32 slide directly. Therefore, the piston 22 must be made of a material considering wear resistance.

(3) Manufacturing process The manufacturing process of the piston 22 described above will be described. FIG. 6 shows an example of the manufacturing process of the piston 22. First, in the punching step S11, an annular and plate-like member, which is the original shape of the piston 22, is punched from the material. In the cutting and raising step S12, a part of the punched member is cut and raised to form the engaging portion 30 and the like. In the bending step S13, the inner peripheral portion and the outer peripheral portion of the punched member are bent in the axial direction over the entire periphery, and the inner peripheral tubular portion 23 and the outer peripheral tubular portion 24 are formed. Then, in the gas soft nitriding step S14, the above-described gas soft nitriding treatment is performed on the entire piston 22 in a state where the processing and molding of each part are completed. Finally, in the finishing step S15, the piston 22 is subjected to shot blasting, rust prevention treatment, and the like.

(4) Effect 1) Effect on Manufacturing Process The effect on the manufacturing process when the piston 22 is manufactured by the manufacturing method according to the present invention will be described. In the conventional carburizing process and carbonitriding process, tempering is performed in the hardening process corresponding to process S14. Further, in order to remove the distortion of the piston 22 after the curing process, the distortion of the press temper or the like is corrected. However, since the gas soft nitriding process is performed in this piston manufacturing process, the tempering process and the distortion correcting process are not required, and the total heat treatment time can be shortened. Specifically, the heat treatment time can be shortened to about ½ to 比 べ as compared with a conventional manufacturing process including carburizing, carbonitriding, or nitriding. Therefore, by adopting gas soft nitriding as a method for curing drive system components, production efficiency can be greatly improved.

2) Effect as a piston The effect which the piston 22 manufactured with the manufacturing method which concerns on this invention has is demonstrated with the operation | movement. When the front cover 2 is rotated by torque from the engine, the impeller 3 is also rotated together with the front cover 2. When the impeller 3 rotates, hydraulic fluid as a fluid flows from the outer periphery side of the impeller 3 to the outer periphery side of the turbine 4 by the impeller blade 10 and centrifugal force. The hydraulic oil that flows to the outer peripheral side of the turbine 4 returns from the inner peripheral side of the turbine 4 to the inner peripheral side of the impeller 3 through a flow path inside the turbine 4 formed by the turbine blades 12. At this time, since the hydraulic oil collides with the turbine blade 12, the turbine 4 rotates in the same direction as the impeller 3. Due to the flow of the hydraulic oil, the torque input to the front cover 2 rotates the turbine 4. Torque is transmitted to the main drive shaft via the turbine 4.

  Further, during operation of the torque converter 1, hydraulic oil is supplied into the first hydraulic chamber 36 from the inner peripheral side. The hydraulic oil flows in the first hydraulic chamber 36 outward in the radial direction, further flows toward the axial transmission side, and finally flows into the fluid working chamber (torus). Therefore, the piston 22 has moved most to the axial turbine 4 side, and the friction facing 35 of the piston 22 is separated from the friction surface 2 a of the front cover 2. At this time, the hydraulic oil in the fluid working chamber is discharged to the outside through the space between the inner peripheral portions of the turbine 4 and the stator 5.

  At the time of lockup connection, the hydraulic circuit is switched, and the hydraulic oil in the first hydraulic chamber 36 is drained from the inner periphery. Therefore, the hydraulic pressure in the first hydraulic chamber 36 is lower than the hydraulic pressure in the second hydraulic chamber 37. As a result, the piston 22 moves to the front cover 2 side, and the friction facing 35 is strongly pressed against the friction surface 2 a of the front cover 2.

  When the friction facing 35 is pressed against the friction surface 2a of the front cover 2, torque is input from the front cover 2 to the piston 22 via the friction surface, and the piston 22 rotates integrally with the front cover 2. When the piston 22 rotates, the coil spring 32 is compressed between the engaging portion 30 and the claw portion 34. When the coil spring 32 is compressed, the claw portion 34 is pushed in the direction of rotation of the piston 22 by the elastic force, and the turbine 4 rotates integrally with the front cover 2. As a result, the front cover 2 and the turbine 4 are mechanically connected by the lockup device 7, and the torque transmission efficiency of the torque converter 1 is improved.

  Since the coil spring 32 is disposed on the inner peripheral side of the outer peripheral cylindrical portion 24 of the piston 22, the coil spring 32 is pressed against the inner peripheral surface of the outer peripheral cylindrical portion 24 by centrifugal force during lockup connection. Further, at the time of lock-up connection and release, the coil spring 32 repeatedly expands and contracts in the rotation direction. Therefore, the inner peripheral surface of the outer peripheral cylindrical portion 24 repeats sliding with the outer peripheral side of the coil spring 32. However, since the piston 22 of the lock-up device 7 according to the present invention is manufactured from the steel material that has been subjected to the above-described gas soft nitriding treatment, the surface hardness and the hardening depth of the entire piston 22 are comparable to those of the carburizing treatment. It is improving. Therefore, even if it slides with the coil spring 32, the hardened layer of the piston 22 is not peeled off, and wear of the piston 22 can be prevented.

  At the time of relative rotation between the piston 22 and the turbine 4, the inner peripheral surface 25 of the inner peripheral side cylindrical portion 23 of the piston 22 slides in the rotational direction with the outer peripheral surface 19 of the cylindrical portion 16 of the turbine hub 13. Further, at the time of lockup connection and release, the piston 22 and the turbine 4 move relative to each other in the axial direction, so that the inner peripheral surface 25 slides with the outer peripheral surface 19 in the axial direction. However, since this piston 22 is made of the material subjected to the above-described gas soft nitriding treatment, the surface hardness and hardening depth of the entire piston 22 are improved to the same extent as the carburizing treatment. Therefore, it is possible to prevent the piston 22 from being worn against sliding with the turbine hub 13. Further, since a structure in which the piston 22 and the coil spring 32 are directly slidable can be employed, it is not necessary to provide the retaining plate 27 on the outer peripheral side of the elastic member. As a result, when the manufacturing method of the present invention is applied to the manufacture of the piston 22 of the lockup device 7, the coil spring 32 can be arranged on the outer peripheral side in the lockup device 7, and a wide torsion angle can be realized.

3. Other Embodiments The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention. Other embodiments will be described below.

(1) Drive system component In the above-described embodiment, the piston 22 of the lockup device 7 has been described as an example of the drive system component. However, the drive system component can also be applied to other drive system components that require wear resistance and the like. It is.

The figure which shows the manufacturing process as one Embodiment which concerns on this invention. The figure which shows the influence of the alloy element which acts on surface hardness. The figure which shows the influence of the Cr addition amount which acts on hardening depth. The figure which compared the hardness characteristic after heat processing of Cr addition steel, SPHC, and 0.30 weight% C steel. 1 is a schematic longitudinal sectional view of a torque converter 1 as one embodiment of the present invention. An example of a manufacturing process of the piston 22.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Torque converter 2 Front cover 3 Impeller 4 Turbine 5 Stator 7 Lock-up device 22 Piston 23 Inner peripheral side cylindrical part 24 Outer peripheral side cylindrical part 25 Inner peripheral surface 27 Retaining plate (support member)
29 holding part 30 engaging part 32 coil spring 33 driven plate (driven member)
34 nail | claw part 40 elastic connection mechanism S1 1st process S2 2nd process

Claims (5)

A method of manufacturing a drive system component for a vehicle,
A first step of processing the material and molding the drive system component;
A second step of performing gas soft nitriding treatment on the drive system component,
Manufacturing method of drive system parts. The drive system parts are:
C content is 0.15 wt% or less,
The Cr content is a steel material in the range of 1.0 to 1.3% by weight,
The method for manufacturing a drive system component according to claim 1. The S content of the drive train component is a steel material of 0.005% by weight or less,
A method for manufacturing a drive system component according to claim 1 or 2. The drive system component is a component that constitutes a lock-up device that is disposed in a space between the front cover of the fluid torque transmission device and the turbine and mechanically connects the two.
The lock-up device is disposed between an annular piston that is axially movable and connectable to the front cover, an annular drive member fixed to the piston, and a radial direction between the piston and the drive member. An elastic member and a driven member fixed to the turbine,
A method for manufacturing a drive train member according to any one of claims 1 to 3. The piston has an outer cylindrical portion having a generally cylindrical shape extending in the axial direction on the outer peripheral side,
The elastic member is slidable with the inner peripheral side of the outer peripheral cylindrical portion.
The manufacturing method of the drive system metal component of Claim 4.

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