JPH11269545A - Quenching of lock-up clutch piston of torque converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flatness of a piston after the press tempering by keeping the posture of the piston in perpendicular in immersing the piston in a quenching oil to minimize the degradation of the flatness of the piston during the quenching. SOLUTION: A piston is immersed in a quenching oil 2 in a final quenching process of a lock-up clutch piston of a torque converter, and quenched. Deep recesses 101 are formed in a jig 1 at equal intervals, and a piston Lc is suspended at these recess 101 parts. The posture of the piston Lc is regulated in the perpendicular condition by the recesses 101. When the piston Lc is immersed in the quenching oil 2 in a perpendicularly held condition, most of the difference in the cooling speed between a face side and a back side of the piston Lc can be eliminated. That is, both the face side L1 and the back side L2 of the piston Lc are simultaneously brought into contact with the quenching oil 2. Thus, no major changes are necessary for the treatment processes or facilities in this quenching treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art Generally, a fluid torque converter (hereinafter simply referred to as a torque converter) is used as a starting element of an automatic transmission for a vehicle. The torque converter transmits power and amplifies torque via a fluid (hydraulic oil), and has both a function as a starting clutch and a function as a continuously variable transmission. FIG. 7 is a longitudinal sectional view of the torque converter. The torque converter TC has an outer shell integrally connecting the front cover F and the pump shell Ps, and the outer shell is filled with a fluid. A number of pump blades Pb are integrally attached to the pump shell Ps to form the pump P. Further, in the torque converter TC, facing the pump P,
A turbine T is arranged. The turbine T includes a turbine shell Ts and a number of turbine blades Tb integrally attached to the turbine shell Ts, and is capable of transmitting power to an input shaft (not shown) of the automatic transmission via a hub Th. Connected. On the other hand, a plurality of set blocks SB are fixed to the front cover F, and a drive plate (not shown) attached to an output shaft of the engine is fixed to the set blocks SB by bolts. Therefore, the power of the engine is “drive plate” → “front cover F” → “pump P” → “fluid”
The power is transmitted through a route of “turbine T” → “hub Th” → “input shaft of the automatic transmission”.

Further, a stator S is disposed between the pump P and the turbine T. The stator S is supported via a one-way clutch on a cylindrical stator support (not shown) formed in a case of the automatic transmission. The stator S has an operation region where the rotational difference between the pump P and the turbine T is large (hereinafter, referred to as a converter phase).
The flow direction of the fluid flowing out of the turbine T is determined by the pump P
A torque amplifying operation is performed by converting the rotation in a direction that promotes the rotation of. On the other hand, in an operation region where the rotation difference between the pump P and the turbine T is small (hereinafter, referred to as a coupling phase),
By the action of the one-way clutch, the stator S idles following the flow of the fluid, and efficient power transmission is performed between the pump P and the turbine T.

In recent years, with the aim of improving the fuel efficiency of automobiles by improving the power transmission efficiency of a torque converter,
Generally, a lock-up clutch mechanism is disposed between the turbine T and the front cover F. The lock-up clutch mechanism includes a piston Lc disposed movably in the axial direction between the turbine T and the front cover F.
The piston Lc is connected to the hub Th so as to be able to transmit a rotational force via a torsional damper Dp that attenuates a rotational torsional vibration caused by a torque fluctuation of the engine. The piston Lc is urged toward the front cover F by hydraulic pressure, so that the piston Lc engages with the front cover F via an annular friction material M attached to the piston Lc so as to be able to transmit power. . That is, the power of the engine is “drive plate” → “front cover F” → “piston Lc” → “torsional damper Dp” → “hub T
h ”→“ the input shaft of the automatic transmission ”, and power is transmitted more efficiently because the fluid does not pass through.

As described above, since the piston Lc is pressed against the front cover F by hydraulic pressure to transmit the power of the engine, high strength is required. Therefore, usually, after the piston Lc is formed by pressing, a heat treatment such as carburizing and quenching is performed to secure a desired strength. Conventionally, the piston Lc has been carburized and quenched by the method described below.

FIG. 3 is a block diagram showing an example of the flow of the carburizing and quenching process. The piston Lc is heated to about 450 degrees Celsius in the first preheating step, and then to about 800 degrees Celsius in the second preheating step. After these preheating steps, the carburizing / diffusion step carries out a carburizing treatment to impregnate carbon into the piston Lc surface while maintaining the temperature. After the carburized piston Lc was gradually cooled to about 750 degrees Celsius in the first quenching step and the second quenching step, the quenching oil heated to about 120 degrees Celsius in the final step was stored. It is immersed in an oil bath and quenched, and a series of carburizing and quenching processes are completed. Then, as shown in FIG. 4, a series of carburizing and quenching processes are performed on the piston Lc in a state where the jig 1 'is inserted into the center hole a and suspended in the air. In the jig 1 ', dents 101' are formed at equal intervals.
The piston Lc is suspended from each of the 01 'portions.
At this time, since the piston Lc is asymmetrical in the left-right direction as viewed in the vertical direction in the figure, the piston Lc balances in a state inclined with respect to the vertical direction as shown in FIG.

[0006]

The piston Lc is required to have good flatness in order to make stable frictional engagement with the front cover F. However, in general, when quenching is performed, there is a problem that the flatness of the piston Lc is deteriorated due to heat treatment distortion. Therefore, press tempering (heat setting) is performed as a post-step of the quenching treatment to correct the heat treatment distortion. It will be good. Then, when the present inventor studied, they obtained an experimental result that when the cooling rate was different between the front side and the back side of the piston, the deterioration of the flatness increased. Based on the experimental results, the present invention minimizes the deterioration of the piston flatness during the quenching process without making any major changes to the conventional quenching process and equipment, thereby enabling the piston flatness after the press tempering process to be performed. It is an object of the present invention to provide a method of hardening a lock-up clutch / piston of a torque converter which can be improved as much as possible.

[0007]

A method for hardening a lock-up clutch / piston of a torque converter according to the present invention is characterized in that at least when the piston is immersed in quenching oil, the attitude of the piston is vertical.

[0008]

Embodiments of the present invention will be described below. The method of quenching the lock-up clutch / piston of the torque converter in the present invention comprises the same steps as the conventional method shown in FIG. In the method of the present invention, as shown in FIGS. 1 and 2, deep jigs 101 are formed in the jig 1 at equal intervals, and the piston Lc is hung on the jig 101. At this time, the attitude of the piston Lc is regulated by the depression 101 to a vertical state. In this way, by immersing the piston Lc in quenching oil while maintaining the posture of the piston Lc vertically, the difference in cooling rate between the front side and the back side of the piston Lc can be almost eliminated.

That is, as shown in FIG. 5, the attitude of the piston Lc is inclined with respect to the vertical direction in the prior art. As shown, the front side L1 is brought into contact with the quenching oil 2 and cooled before the back side L2, so that a difference occurs in the cooling rate. On the other hand, in the present invention, as shown in FIG. 2, since the posture of the piston Lc is held vertically, when compared at the same radial position D, the front side L1 and the back side L2 simultaneously contact the quenching oil 2,
In principle, there is no difference in cooling rate between the front side and the back side of the piston Lc.

[0010]

According to the above-described structure, in the method for quenching the lock-up clutch / piston of the torque converter according to the present invention, when the piston is immersed in quenching oil in the final step and rapidly cooled, the cooling rate between the front and rear sides of the piston is reduced. Since there is almost no difference, it is possible to prevent the flatness from being deteriorated due to the difference in cooling rate. Therefore, it is possible to minimize the deterioration of the piston flatness in the quenching process and to improve the piston flatness after the press tempering process as much as possible without making significant changes to the conventional quenching process and equipment. .

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a mounting state of a piston to a jig in the present invention.

FIG. 2 is an explanatory view showing a final step in the present invention.

FIG. 3 is a block diagram showing an example of a flow of a carburizing and quenching process.

FIG. 4 is an explanatory view showing a state in which a piston is attached to a jig in a conventional method.

FIG. 5 is an explanatory view showing a final step in a conventional method.

FIG. 6 is a partially enlarged view showing a contact state between a piston and quenching oil in a final step in a conventional method.

FIG. 7 is a longitudinal sectional view of the torque converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Jig 101 Depression 2 Quenching oil a Center hole Dp Torsional damper F Front cover Lc Piston M Friction material P Pump S Stator T Turbine TC Torque converter

Claims (1)

[Claims] In a quenching process of a lock-up clutch / piston of a torque converter, the posture of the piston is made vertical when at least the piston is immersed in quenching oil. Quenching method.