JP2001140932A - Piston for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce weight and facilitate the manufacture by a piston made by pressing sheet metal. SOLUTION: A piston body 1 is constituted by mutually combining a pressure receive member 3 as a circular ring which is made of sheet metal and a contact member 4 as a substantially short cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston for an automatic transmission.

[0002]

2. Description of the Related Art An automatic transmission used in an automobile or the like includes a hydraulically operated clutch device in which an annular piston has a cylindrical pressure chamber (space).
The piston is reciprocated by hydraulic pressure, spring, and the like.

That is, as shown in FIGS. 10 and 11, a conventional piston of this type comprises an annular piston main body 31 made by cutting aluminum die cast, and a piston main body 31 shown in FIG.
Seal members 32 and 33 (e.g., rubber D-rings and O-rings) disposed on the inner and outer peripheral sides of the base 31 and are mounted in a cylindrical space (drum housing) 34.

[0004] The piston body 31 has annular-wall-shaped walls 35, 35 corresponding to pressure chambers, an inner peripheral wall 36 protruding from the inner peripheral edge of the pressure chamber corresponding wall 35, and an outer peripheral edge of the pressure chamber corresponding wall 35. And an outer peripheral wall 37 protruding from the outer peripheral wall.
A sealing material 33 is attached to each of the 37.

A fluid supply passage 39 is connected to and connected to the pressure chamber 38. When a fluid is supplied to the pressure chamber 38 through the passage 39, the piston 40 is pressed as shown in FIGS. As a result, the relatively thick outer peripheral wall 37 as the annular contact portion 41 is pressed against the annular plate-like clutch plates 42. That is, the clutch plates 42 are fastened and released by the reciprocating motion of the piston 40 in the axial direction, thereby changing the gear ratio of the automatic transmission. (Note that 43 is piston 40
This is a spring for returning the spring. )

Then, as is apparent from FIGS. 10 and 11,
The thickness center line of the relatively thick annular contact portion 41 substantially coincides with the center C ₁ of the clutch plate 42 so that the annular contact portion 41 presses the center C ₁ of the clutch plate 42. ing.

However, recently, the production cost has been reduced,
In order to make the mounting space compact and omit the rubber seal mounting step, a piston 40 made of a sheet metal press as shown in the sectional view of the main part of the assembly in FIG. 12 and the sectional view of the piston in FIG. 13 has begun to be applied.

That is, as shown in FIGS. 12 and 13, the piston 40 has a piston body 31 made of a sheet metal press, and lip portions 44 and 45 on the inner and outer peripheral sides of the piston body 31 and is attached to the piston body 31. Rubber coating 46 integrally baked and welded
(Note that in FIG. 12, FIG. 10 and FIG.
The same reference numeral as 11 has the same configuration).

Then, as shown in FIG. 12 and FIG.
The integrated sheet metal piston 40 has an annular contact with a U-shaped cross section.
It has a contact portion 41. That is, this is shown in FIGS. 10 and 11.
When making an aluminum die-cast piston from sheet metal,
Minimize the decrease in the contact area with the clutch plate 42,
Clutch pre-load so as not to apply an uneven load to the
Center C of tot 42₁ So that the annular contact portion 41 is pressed,
As shown in FIG. 12 and FIG.
(Lower surface) as flat surface, contact with clutch plate 42
Ensure a sufficient area, and adjust the diameter of the
Rate 42 center C ₁ Set to match the diameter position of
I have.

[0010]

The piston 40 made of sheet metal (press) shown in FIG. 12 and FIG. 13 is used for forming a cold-rolled steel sheet or a hot-rolled steel sheet into a press (plastic ) Fabricated by processing. The sheet metal (press) piston 40 is
For compactness and weight reduction, it is desirable to use a steel with a high yield point (SAPH, SPFH, etc.) and reduce the thickness to a minimum.

However, it is attempted to form a piston body 31 having a complicated and deep drawing portion {U-shaped annular contact portion 41} as shown in FIGS. 12 and 13 from a single steel plate. Then, it was found that a steel sheet having a high yield point as described above had poor elongation and "cracks" occurred during press (plastic) working.

Therefore, if a steel sheet (SPC, SPH material, etc.) which is inferior in material strength (yield point) but has good elongation is used,
Although the above-mentioned problem of "cracking" can be solved, a problem arises in that the plate thickness increases and the piston weight increases.

In recent years, automatic transmissions for automobiles have been improved in performance,
In addition, demands for weight reduction and miniaturization are increasing in consideration of environmental problems. Therefore, it is desired to further reduce the weight of the piston as one mechanical element of the automatic transmission. However, in the above-described sheet metal (press) piston 40 (shown in FIGS. Due to the problem of "cracking" at the time, the plate thickness could not be reduced, and further weight reduction was difficult.

The present inventors have technically analyzed the conventional sheet metal (press) piston 40 shown in FIGS. 12 and 13. The plate thickness of the sheet metal piston body 31 is usually determined from the result of obtaining the maximum stress value acting on the piston body 31 by stress analysis or the like (naturally, it is premised on the selection of the type of steel plate that can be pressed. ). In the case of the shape as shown in FIG. 13, the maximum stress generating position is determined by the innermost end (in the axial direction) where the largest deformation occurs in the axial direction with the fulcrum at the upper end base (point A) of the abutting portion 41 having a U-shaped cross section when the clutch plate is fastened. Near point B)
It was found from stress analysis, functional tests, and the like that the vicinity of the point B was the starting point of cracking.

On the other hand, since the contact portion 41 having a U-shaped cross section has a cylindrical structure, it is sufficient that the contact portion 41 has a thickness sufficient to support an axial load when the clutch plate is fastened. (Material), so that the above B
With the required thickness near the point, the overall thickness had to be determined, and the overall thickness was unnecessarily large.

The present invention has been invented based on such technical analysis, and has as its object to reduce the weight of the entire piston and increase the degree of freedom in designing the piston.

[0017]

In order to achieve the above object, a piston for an automatic transmission according to the present invention comprises an annular pressure receiving member made of sheet metal corresponding to a cylindrical pressure chamber, and a separate component from the pressure receiving member. And an annular abutting member that has a base end secured to the pressure receiving member and has a distal end in contact with the clutch plate in a shape extending toward the clutch plate.

Further, the contact member has a substantially short cylindrical shape having an outer peripheral wall having a substantially I-shaped cross section. Further, the contact member is a substantially cylindrical shape having an outer peripheral wall having a substantially I-shaped cross section and is made of sheet metal, and the base end side of the contact member is press-fitted and fixed to the outer peripheral edge of the pressure receiving member. I have.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 illustrate a piston P for an automatic transmission according to the present invention, which is used as a hydraulically operated piston in an automatic transmission used in an automobile or the like. That is, a clutch device operated by hydraulic pressure is provided inside the automatic transmission, and is used as a clutch piston or a cancel piston.

As shown in FIG. 1, an annular piston main body 1 viewed from a direction parallel to the axis L, and a rubber coating 2 provided integrally with the piston main body 1 by heat welding or the like.
And

The piston body 1 is made of an annular pressure receiving member 3 made of sheet metal corresponding to the cylindrical pressure chamber 8, and is made of a separate component from the pressure receiving member 3 made of sheet metal, and is extended toward the clutch plate 5. An annular contact member 4 whose base end 4a side is fixed to the pressure receiving member 3. The (extended) tip 4b side of the contact member 4 can directly contact the clutch plate 5.

The pressure receiving member 3 made of sheet metal includes an inner peripheral wall 6,
A pressure receiving wall portion 9 (in a direction substantially perpendicular to the axis L) and an outer peripheral wall portion 7 are provided. The lower end of the inner peripheral wall portion 6 is bent in the inner diameter direction, and an inner lip portion 10 is integrally provided. ) 11 inner diameter side outer peripheral surface
Contact slidably with 12. Further, an outer lip portion 13 is integrally provided on the outer peripheral wall portion 7 itself or on a corner portion between the outer peripheral wall portion 7 and the pressure receiving wall portion 9. And slidably contact the outer peripheral side inner peripheral surface 14 of the cylindrical space (drum housing) 11.

By the way, in the embodiment shown in FIGS. 1 and 2, the annular (substantially short cylindrical) contact member 4 has its base end 4a bent in the outer diameter direction to form a pressure receiving wall. Until it comes into contact with the portion 9, the outer peripheral edge of the base end 4a is fixed to the inner peripheral surface of the outer peripheral wall portion 7 by press fitting, or by welding such as spot welding or bonding with an adhesive or the like. The contact member 4 and the pressure receiving member 3 are fixed to each other.

Then, the diameter dimension D ₄ of the contact member 4 is set so that the tip (lower end) 4b of the substantially short cylindrical contact member 4 contacts the center C ₁ of the annular plate-like clutch plates 5. Set.

In the present invention, the clutch plate 5
The center C _{1 of the} annular belt-shaped contact portions of the plurality of clutch plates 5, which are alternately held on the outer diameter side and the inner diameter side and are arranged in a stack, come into contact with each other (in a pressurized and pressed state). Is defined as a position in the radial direction near the center in the width direction.

In FIGS. 1 and 2, the contact member 4 is preferably made of sheet metal (press), and can be easily fixed to the pressure receiving member 3 by press-fitting, welding, bonding or the like. Since the piston body 1 is configured to be mutually fixed as the pressure receiving member 3 and the contact member 4 as separate parts, as apparent from comparison with FIG. 12 of the conventional example, the pressure receiving member 3 is required to have a deep drawing process. Pressing (plasticity) can be performed using a high-strength material (SAPH, SPFH material, etc.) with poor elongation, which reduces the thickness and weight. I can figure it out. On the other hand, the contact member 4 has a single-layer structure, and is thin enough to withstand a compressive force (using a similar high-strength material). Further, the groove of the U-shaped contact portion 41 shown in FIG. Since the filling rubber portion 47 can be omitted, further weight reduction can be realized.

Next, FIGS. 3 to 9 exemplify another embodiment. The piston body 1 is composed of two parts, a pressure receiving member 3 and a contact member 4, and is press-fitted and welded to each other. It can be seen that the degree of freedom in design of the shape and material of the contact member 4 is significantly increased by adopting a configuration in which the contact member 4 is fixed by adhesion or the like.

Hereinafter, each embodiment will be described mainly with reference to FIG.
The difference between FIG. 3 and FIG. 2 is as follows. In FIG. 3, the base end 4a of the short cylindrical (annular) contact member 4 is bent into an inverted U-shape, and the outer peripheral wall of the pressure receiving member 3 is formed. 7 is press-fitted and fixed. There is an advantage that the press-fit fixing strength is increased. Other effects (advantages) are the same as those in FIGS.

In FIG. 4, the tip 4b of the short cylindrical (annular) contact member 4 is bent in the inner diameter direction. In FIG. 5, the tip 4b of the contact member 4 is bent in the outer diameter direction. Thus, it is possible to reduce the contact surface pressure between the clutch plates 5 (see FIG. 1), it becomes easy to make match contact pressing portion to the clutch plate 5 ... center C ₁ of the.

In any of FIGS. 2 to 5 described above, the two parts 3 and 4 constituting the piston body 1 can be made thin by using a high-strength metal material. In addition, as shown in FIGS. 2 to 5, the contact member 4 has an outer peripheral wall having a substantially I-shaped cross section, so that weight reduction is achieved.

Next, in FIG. 6, a different material is used as the contact member 4. For example, a stainless steel plate is bent in a U-shape and fixed to the pressure receiving member 3. In addition,
At this time, the shape of the pressure receiving member 3 is slightly different from FIGS. 1 to 5, and the U-shaped cross section 15 is formed to have a smaller axial dimension (compared with FIG. Contact member 4
Are added to reach the clutch plate 5 (see FIG. 1). In each of the embodiments of FIGS. 1 to 6 described above, in response to a change in the center C ₁ of the clutch plate 5 (see FIG. 1) and a change in the axial distance to the clutch plate 5, There is an advantage that the radial dimension / axial dimension and shape of the contact member 4 can be easily changed freely.

In FIG. 7, a substantially short cylindrical contact member 4 is
A material having a small specific gravity such as aluminum or an alloy thereof, or a synthetic resin is used. In this case, the clutch plate 5
There is an advantage that the radial dimension and axial dimension of the contact member 4 can be freely changed in response to the change of the center C ₁ (see FIG. 1) and the axial dimension up to that point.

FIGS. 8 and 9 show a sheet metal (press) part having a U-shaped part 16 in the cross-sectional shape of the contact member 4. It is fixed (integrated) by bonding or bonding. In this case, even when the clutch plate is changed (increase in the change and must contact area of the center position C ₁ or the like) a readily compatible, and has the advantage of obtaining reducing the weight, moreover, optionally, 1 , Fig. 12
Spring 43 shown in the figure is integrated into the U-shaped part 16 (packed)
Is also possible.

The shape of the pressure receiving member 3 is not limited to FIGS. 1 to 9 as long as the thickness in the axial direction is small.
It is free to be deformed, and the rubber coating 2 is not integrated, but the inner lip and the outer lip may be separated from each other.

[0036]

According to the present invention, the following significant effects can be obtained by the above configuration.

That is, the weight can be reduced without impairing the function of the conventional piston shown in FIG. 12 and the material cost can be reduced and the plastic (press) working can be facilitated.
Further, it is possible to cope with a change in the shape of the cylindrical space (drum housing) of the clutch device to which the piston according to the present invention is applied and a change in the dimensions of the clutch pedal with high design flexibility. For example, for the same pressure receiving member 3,
When the diameter and axial direction of the contact member 4 are different,
Select and fix.

(According to the second and third aspects), the weight can be further reduced, and the production becomes easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a piston for an automatic transmission according to the present invention.

FIG. 2 is a sectional view of a main part showing a first embodiment of the piston.

FIG. 3 is a sectional view of a main part showing a second embodiment of the piston.

FIG. 4 is a sectional view of a main part showing a third embodiment of the piston.

FIG. 5 is a cross-sectional view of a main part showing a fourth embodiment of the piston.

FIG. 6 is a sectional view of a main part showing a fifth embodiment of the piston.

FIG. 7 is a sectional view of a main part showing a sixth embodiment of the piston.

FIG. 8 is a sectional view of a main part showing a seventh embodiment of the piston.

FIG. 9 is a sectional view of a main part showing an eighth embodiment of a piston.

FIG. 10 is a sectional view of a main part showing a conventional example.

FIG. 11 is a sectional view of a main part showing a pressed state of the clutch plate.

FIG. 12 is a cross-sectional view of a main part showing a usage state of a piston using a conventional piston body made of sheet metal.

13 is a sectional view of a main part of the piston shown in FIG. 12.

[Explanation of symbols]

3 Pressure receiving member 4 Contact member 4a Base end 4b Tip 5 Clutch plate 8 Pressure chamber L Center of axis C ₁ Center

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Ohori 663 Minoshima, Arita-shi, Wakayama F-term in Mitsubishi Cable Industries, Ltd. Mishima Works (reference) 3J057 AA04 BB04 CA03 DA18 GA11 HH02 JJ04

Claims (3)

[Claims] An annular pressure receiving member made of a sheet metal corresponding to a cylindrical pressure chamber, and a pressure receiving member made of a separate component from the pressure receiving member and extending toward a clutch plate side, a base end side of which is fixed to the pressure receiving member and a distal end thereof. An annular contact member having a side contacting the clutch plate. 2. The piston for an automatic transmission according to claim 1, wherein the contact member has a substantially short cylindrical shape having an outer peripheral wall having a substantially I-shaped cross section. 3. The contact member has a substantially cylindrical shape having an outer peripheral wall having a substantially I-shaped cross section, and is made of sheet metal. The base end side of the contact member is pressed into the outer peripheral edge of the pressure receiving member. The piston for an automatic transmission according to claim 1, which is fixed.