JPH09143566A - Diaphragm spring and method for heat treating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of heat treatment processes of a diaphragm spring and the production cost by tempering only annular part after quenching the whole diaphragm spring. SOLUTION: The diaphragm spring 5 comprising an annular elastic part 5a, lever parts 5b, slits 5c, oval holes 5d and a center hole 5e is obtd., by punching out from a steel plate material. After heating the whole diaphragm spring 5 at about 840 deg.C in a heating furnace, the spring is quickly cooled in a water vessel to execute the quenching and the whole body is made to martensitic structure. Successively, high-frequency induction heating is executed only to the annular part 5a by using a round coil to execute the tempering. This first tempering process is to be performed at >=430 deg.C, preperably 450 deg.-550 deg.C for 20-30sec. Further, the second tempering process at low temp., such as at about 200 deg.C is executed to the whole body between the quenching process and the first tempering process, and it is desirable to improve the strength and the impact value of the lever part 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm spring and a heat treatment method thereof, and more particularly to a diaphragm spring used in a clutch cover assembly and a heat treatment method thereof.

[0002]

2. Description of the Related Art A diaphragm spring is a disk-shaped member used in a clutch cover assembly, and is composed of an annular elastic portion and a plurality of lever portions extending radially inward from the annular elastic portion. One of the inner and outer peripheral portions of the annular portion is supported on the clutch cover side and the other urges the pressure plate. A release device such as a bearing is engaged with the tips of the plurality of levers.

In such a diaphragm spring,
It is necessary that the annular portion has a desired elasticity and the lever portion has a certain hardness. In order to impart such characteristics to each part, the heat treatment shown in FIG. 8 is conventionally performed.
First, the diaphragm spring was quenched at 840 ° C, and then low temperature tempered at 200 ° C and 40 ° C.
Temper at 0 ° C. Furthermore, induction hardening is performed on the tip portion of the lever, and finally the entire diaphragm spring is low temperature tempered at 200 ° C. As a result, the hardness of the tip of the lever that engages with the release device is increased, and the annular portion has sufficient elasticity.

[0004]

The heat treatment of the conventional diaphragm spring described above requires a large number of steps, resulting in high manufacturing cost. An object of the present invention is to reduce the number of heat treatment steps for a diaphragm spring.

[0005]

A heat treatment method for a diaphragm spring according to claim 1 is a heat treatment method for a diaphragm spring having an annular portion and a plurality of lever portions extending radially inward from the annular portion. Contains. ◎ Quenching process of quenching the entire diaphragm spring ◎ First tempering process of tempering only the annular part In this method, since only the annular part is tempered in the first tempering process, a plurality of lever parts have high hardness. And the annulus has the desired elasticity. Here, since the number of manufacturing steps is smaller than in the conventional case, the manufacturing cost is reduced.

The heat treatment method for the diaphragm spring according to claim 2 further includes the following steps. ◎ Second tempering step in which the entire diaphragm spring is tempered at a lower temperature than the first tempering step between the quenching step and the first tempering step. In this method, the lever portion is tempered at a low temperature and the impact value is reduced. Get higher As a result, cracking or breaking of the lever portion is less likely to occur.

In the heat treatment method for the diaphragm spring according to the third aspect, high frequency induction heating is performed in the first tempering step. In the heat treatment method for the diaphragm spring according to the fourth aspect, the first tempering step is performed at 430 ° C. or higher. In the heat treatment method for the diaphragm spring according to claim 5, 450 in the first tempering step.
Heat at ~ 550 ° C.

In the heat treatment method for the diaphragm spring according to the sixth aspect, 20 to 3 in the first tempering step.
Heat for 0 seconds. Here, since heating is performed in a relatively short time, heat conduction to the lever portion is reduced. Moreover, since it is such a short time, it is preferable to heat at 450-550 degreeC. A diaphragm spring according to a seventh aspect includes an annular elastic portion and a plurality of lever portions. The plurality of lever portions extend inward in the radial direction from the annular elastic portion and have uniform hardness in the radial direction. Therefore, the strength of the plurality of lever portions is improved.

In the diaphragm spring according to the eighth aspect, the hardness of the plurality of lever portions is HRA79 or higher.
A diaphragm spring according to a ninth aspect includes an annular elastic portion and a plurality of lever portions. The annular elastic portion has a troostite structure. The plurality of lever portions extend inward in the radial direction from the annular elastic portion and have a tempered martensite structure.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A clutch cover assembly 1 shown in FIG. 1 includes a clutch cover 2 whose outer peripheral portion is fixed to a flywheel (not shown), and a pressure plate 3 arranged on the inner peripheral side of the clutch cover 2. Pressure plate 3
Strap plate 4 for connecting the clutch cover 2 with the clutch plate 2
, A diaphragm spring 5, and two wire rings 6 supported by a tab 7 bent from the inner peripheral side of the clutch cover 2 and supporting the diaphragm spring 5.

As is apparent from FIG. 2, the diaphragm spring 5 is composed of an annular elastic portion 5a and a plurality of lever portions 5b extending inward in the radial direction from the annular elastic portion 5a. A slit 5c is formed between each lever portion 5b, and an oval hole 5 is provided on the base side of the slit 5c.
d is formed. The tab 7 of the clutch cover 2 penetrates through several oval holes 5d and is further bent outward in the radial direction. The two wire rings 6 sandwich the inner peripheral portion of the annular elastic portion 5b in the axial direction. Annular elastic part 5a
The outer peripheral portion of is in contact with the pressure plate 3. A release device (not shown) is engaged with the tip of the lever portion 5b of the diaphragm spring 5, that is, around the center hole 5e.

The manufacturing process of the diaphragm spring will be described. First, the inner and outer diameters are punched out from a steel plate material to obtain a disk-shaped plate member. Next, slit 5
Punch out c and the oval hole 5d. Subsequently, planar correction and polishing are performed. Furthermore, coining is performed and the finished inner diameter is punched. Finally, press the plate to adjust the shape of the diaphragm spring.

Next, the heat treatment of the diaphragm spring will be described with reference to the process block diagram of FIG. In the quenching process of the entire diaphragm spring shown in FIG. 4, the diaphragm spring 5 is heated by the heater 10 in the heating furnace at about 840 ° C. as shown in FIG.
And is rapidly cooled in the water tank 12. Through such a treatment, the entire diaphragm spring 5 has a martensite structure. Subsequently, in the low temperature tempering process of the entire diaphragm spring shown in FIG. 4, the diaphragm spring 5 is heated to 200 ° C. by the heater 10 in the heating furnace as shown in FIG. It Through this process, the diaphragm spring 5
The whole has a tempered martensite structure. As a result,
The impact value of the lever portion 5b increases, and the lever portion 5b is less likely to crack or break.

In the induction tempering step of the annular elastic portion 5a shown in FIG. 4, only the annular elastic portion 5a is heated using the high frequency induction heating device 15 shown in FIG. The high frequency induction heating device 15 includes a rotary table 16 and a coil 17. Diaphragm spring 5 is rotary table 1
6. The coil 17 is arranged below the diaphragm spring 5 and has a circular shape corresponding to the annular elastic portion 5a. The coil 17 is connected to a high frequency current source (not shown). When the high frequency current is supplied to the coil 17, the annular elastic portion 5a is generated by the electromagnetic induction current.
The surface of the is heated rapidly. Here, the high frequency heating is performed in the range of 450 to 550 ° C. for 20 to 30 seconds. Since heating is performed in such a short time, heat conduction from the annular elastic portion 5a to the lever portion 5b can be reduced. The heating temperature is 430
Although it is sufficient if the temperature is not lower than 0 ° C, the heating time is relatively short, and therefore it may be preferable to increase the heating time. It should be noted that the rotation of the rotary table 16 reduces the uneven heating of the diaphragm spring 5. As a result of the above,
The annular elastic portion 5a has a troostite structure.

Excellent Effect in Heat Treatment Step In the above-described embodiment, in the induction tempering step of the annular portion, the three steps in the conventional example (high temperature tempering of the entire diaphragm spring, induction hardening of the lever tip and low temperature of the entire diaphragm spring) are performed. This means that the processing equivalent to (tempering) was performed. In this way, the number of heat treatment steps is significantly reduced compared to the conventional case. As a result, the manufacturing cost is significantly reduced. In addition, the reduction in the number of steps facilitates automation.

The obtained diaphragm spring is excellent
Effect FIG. 3 shows a radial hardness distribution of the diaphragm spring. The solid line is the diaphragm spring 5 in the above-described embodiment, and the dotted line is the diaphragm spring described in the related art. In the conventional diaphragm spring, only the tip portion of the lever portion is about HRC55, and the hardness suddenly decreases as it goes to the outside in the radial direction, and then the hardness becomes about HRC45 at the middle portion in the radial direction. The hardness is the same up to the annular elastic part. A portion of the lever portion whose hardness is reduced to HRC45 or less is called a soft band. The soft band is a portion where the temperature did not rise sufficiently and the hardness became low because the tip of the lever portion was partially quenched again at 800 ° C. or higher after quenching and tempering. This soft band increases the bending loss of the lever portion. Further, the hardness HRC is about 45 from the radial middle portion to the radial outer portion of the lever portion 5b, and as a result, the lever portion 5b is formed.
The bending loss of is large.

On the other hand, the annular elastic portion 5a has a hardness of about HRC45 as in the conventional example, but the portion of the lever portion 5b further inside in the radial direction than the oval hole 5d has a substantially uniform hardness of HRC55. There is. The hardness of the lever portion 5b is HRA79 or higher. In this way, the lever portion 5
Since b has substantially the same hardness in the radial direction and the hardness is high, the bending loss of the lever 5a is reduced.

After the heat treatment, the diaphragm spring 5 is shot peened and set to complete.

[0019]

The heat treatment method for a diaphragm spring according to the present invention is a heat treatment method for a diaphragm spring having an annular portion and a plurality of lever portions extending radially inward from the annular portion, and includes the following steps. ◎ Quenching process of quenching the entire diaphragm spring ◎ First tempering process of tempering only the annular part In this method, since only the annular part is tempered in the first tempering process, a plurality of lever parts have high hardness. And the annulus has the desired elasticity. Here, since the number of manufacturing steps is smaller than in the conventional case, the manufacturing cost is reduced.

If the second tempering process for tempering the entire diaphragm spring at a lower temperature than the first tempering process is further included between the quenching process and the first tempering process, the lever portion is tempered at a low temperature. As a result, the shock value increases. As a result, cracking or breaking of the lever portion is less likely to occur.

[Brief description of the drawings]

FIG. 1 is a schematic vertical cross-sectional view of a clutch cover assembly that employs a diaphragm spring as an embodiment of the present invention.

FIG. 2 is a perspective view of a diaphragm spring.

FIG. 3 is a graph showing the radial hardness of the diaphragm spring.

FIG. 4 is a block diagram of a heat treatment process of a diaphragm spring.

FIG. 5 is a schematic diagram showing a quenching process.

FIG. 6 is a schematic diagram showing a low temperature tempering process.

FIG. 7 is a schematic perspective view showing an induction tempering process.

FIG. 8 is a heat treatment process block diagram of the diaphragm spring in the conventional example.

[Explanation of symbols]

 5 Diaphragm spring 5a Lever part 5b Annular elastic part 10 Heater 11 Belt conveyor 12 Water tank 15 High frequency induction heating device 16 Rotary table 17 Coil

Claims (9)

[Claims] 1. A heat treatment method for a diaphragm spring having an annular portion and a plurality of lever portions extending radially inward from the annular portion, the quenching step of quenching the entire diaphragm spring, and the tempering step of only the annular portion. 1. A heat treatment method for a diaphragm spring, including the tempering step. 2. The method according to claim 1, further comprising a second tempering step of tempering the entire diaphragm spring at a temperature lower than that of the first tempering step between the quenching step and the first tempering step. A heat treatment method for the diaphragm spring described. 3. The heat treatment method for a diaphragm spring according to claim 1, wherein high frequency induction heating is performed in the first tempering step. 4. The heat treatment method for a diaphragm spring according to claim 1, wherein the first tempering step is performed at 430 ° C. or higher. 5. In the first tempering step, 450-55.
The heat treatment method for a diaphragm spring according to claim 1, wherein the diaphragm spring is heated at 0 ° C. 6. The heat treatment method for a diaphragm spring according to claim 5, wherein heating is performed for 20 to 30 seconds in the first tempering step. 7. A diaphragm spring comprising: an annular elastic portion; and a plurality of lever portions that extend radially inward from the annular elastic portion and that have a uniform hardness in the radial direction. 8. The diaphragm spring according to claim 7, wherein the hardness of the plurality of lever portions is HRA79 or more. 9. A diaphragm spring comprising: an annular elastic portion having a troostite structure; and a plurality of lever portions extending radially inward from the annular elastic part and having a tempered martensite structure.