JPH07269663A - Automatic transmission - Google Patents

Abstract

PURPOSE:To improve the rigidity of return springs by disposing uniformly continuously circumferentially the return spring to smooth the return of a piston by the return springs while forming circumferentially continuously a press part of the piston for pressing a frictional element. CONSTITUTION:A piston 44 is fitted inside the bottom 42a side of a second drum 42 provided with a reverse clutch 20. An annular press part 44a is provided to project from the outer periphery of the side face of the piston 44 opposed to the reverse clutch 20 to make the tip of the press part 44a abut sgainst the reverse clutch 20. A plurality of return springs 46 are disposed at equal intervals on the outer periphery of a reduced diameter part 44c formed of a vertical surface 44b on the outer periphery of the press part 44a. The return springs 46 are contractively provided between the vertical surface 44b and a snap ring 48 engaging the inner periphery of the second drum 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, by switching the power transmission path of a planetary gear mechanism through a plurality of friction elements,
The present invention relates to an automatic transmission that can obtain a plurality of shift speeds.

[0002]

2. Description of the Related Art An automatic transmission of this type is disclosed in, for example, Japanese Utility Model Laid-Open No. 2-58650 (F16H3 / 44). In this automatic transmission, a friction element constituted by a multi-plate clutch is fastened by a piston arranged on one side of the friction element. In this case, a fastening force is generated in the piston by the control hydraulic pressure supplied to the cylinder chamber, and the fastening force is transmitted to the friction element via the pressing portion protruding from the piston.

A return spring is provided on the piston, and the return spring is composed of a plurality of compression coil springs. These return springs are formed by notching the pressing portion at three large circumferential positions. It can be installed in a space.

[0004]

However, in such a conventional automatic transmission, the pressing portion of the piston is largely divided into three in the circumferential direction by the spring arrangement space, and the divided pressing portion serves as a friction element. It is designed to transmit the fastening force. Therefore, the rigidity of the pressing portion is significantly reduced due to the divided portion, and particularly when the piston has a large diameter and the fastening force generated by the control hydraulic pressure is large, the divided pressing portion has an outer diameter direction. There is a risk that it will be expanded and deformed.

Further, as described above, the return spring is mounted in the spring disposition space. The spring disposition space is divided in the circumferential direction with the pressing portion in between, and a plurality of return springs are provided in each spring disposition space. It is supposed to be arranged.
For this reason, the push-back force of the return spring becomes non-uniform in the circumferential direction, and in some cases, when the piston is returned, the sliding surface is twisted, which causes a drag phenomenon of the friction element. .

In view of such conventional problems, therefore, the present invention arranges the return springs continuously and evenly in the circumferential direction to smoothly return the pistons by the return springs while pressing the friction elements. An object of the present invention is to provide an automatic transmission in which the parts are continuously formed in the circumferential direction and the rigidity thereof can be improved.

[0007]

To achieve the above object, the present invention comprises a plurality of friction elements for switching the power transmission paths of the planetary gear mechanism, and a plurality of gear shifts can be obtained by appropriately switching these friction elements. In the automatic transmission configured as described above, a cylindrical drum that constitutes a part of the power transmission path and has one friction element attached to its inner circumference, and the friction element housed inside the cylindrical drum. And a piston for fastening, and forming an annular pressing portion that continuously contacts the friction element in the circumferential direction of the piston, and is arranged on the outer periphery of the pressing portion, with one end on the piston side. It is configured by providing a return spring that is locked and the other end is locked to the cylindrical drum side.

Further, it is desirable to dispose a drum to which another friction element is attached, radially inward of the friction element attached to the cylindrical drum.

[0009]

In the automatic transmission of the present invention having the above-described structure, the fastening force generated in the piston is transmitted to the friction element through the pressing portion formed in the piston to fasten the friction element. When the friction element is released, a pushing-back force acts on the piston via a return spring arranged on the outer circumference of the pressing portion. Therefore, by arranging the return spring on the outer periphery of the pressing portion, it is possible to prevent the return spring and the pressing portion from interfering with each other. Therefore, the pressing portion can be formed as an annular shape that is continuous in the circumferential direction, and the rigidity of the pressing portion is significantly improved, and the pressing portion is easily deformed even when a large fastening force is generated in the piston. It is possible to prevent it. Further, since the return spring can also be arranged in a continuous annular shape along the outer circumference of the pressing portion, the push-back force of the piston can be uniformly applied over the entire circumference of the piston, and the friction element can be released. With this, the piston can be smoothly returned to prevent the drag phenomenon of the friction element.

Further, by disposing a drum having another friction element attached to the inside of the friction element attached to the cylindrical drum in the radial direction, the two friction elements are arranged so as to overlap each other in the axial direction. be able to. Therefore, the axial length of the automatic transmission can be significantly reduced, and the layout in the engine room can be facilitated.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of an automatic transmission 10 according to the present invention, FIG. 1 is a cross-sectional view showing a main part of the automatic transmission 10, and FIG. 2 shows a lower half from a central axis of the automatic transmission 10. It is a schematic block diagram which shows.

That is, as shown in FIG. 1, the automatic transmission 10 of this embodiment is provided with two planetary gear mechanisms, a first planetary gear 12 and a second planetary gear 14, and these first and second planetary gear mechanisms are provided. In each power transmission path of the planetary gears 12, 14, as shown in a simplified manner in FIG. 2, a forward clutch 16, a 3-4 clutch 18, a reverse clutch 20,
Low and reverse brake 22, 2-4 brake 24
And a one-way clutch 26. The engagement and disengagement of each of the friction elements is controlled by a control oil pressure supplied from a control valve (not shown), so that a shift speed corresponding to each operating condition such as vehicle speed and accelerator opening can be obtained. The forward clutch 16, the 3-4 clutch 18, the reverse clutch 20 and the low and reverse brake 22 are each configured as a multi-plate clutch, and the 2-4 brake 24 is configured as a band brake.

An engine (not shown) is arranged on the right side of the automatic transmission 10 in the drawing, and the engine rotation is input to the input shaft 30 of the automatic transmission 10 via the torque converter 28. Is appropriately shifted by the gear train, and then output to the differential gear 36 via the output drive gear 32 and the output driven gear 34.

Further, the automatic transmission 10 of this embodiment provided with the gear train having the above-mentioned structure is provided with a forward clutch 16
(Fwd CL), 3-4 clutch 18 (3-4 CL), reverse clutch 20 (Rev CL) and low and reverse brake 22 (L / R Br), 2-4 brake 24 (2-4 Br) are next. By engaging and disengaging as shown in Table 1, 1st (first forward speed), 2nd (second forward speed), 3rd
(3rd forward speed), 4th (4th forward speed), and Rev (reverse speed) are available. In the table, ◯ indicates a fastened state and x indicates a released state. In addition, the operating state of the one-way clutch (OWC) is also shown in the table, and L
Indicates a locked state and F indicates a free state.

[0015]

[Table 1] By the way, in this embodiment, the first planetary gear 12 is used.
To the front (side where the torque converter 28 is arranged)
Is provided with a 3-4 clutch 18, a reverse clutch 20, and a 2-4 brake 24, a forward clutch 16 is provided behind the second planetary gear 14, and an outer peripheral portion of the second planetary gear 14 is provided. A low and reverse brake 22 is provided.

The 3-4 clutch 18 is the first drum 40.
The reverse clutch 20 is provided between the outer circumference of the first drum 40 and the inner circumference of the second drum 42 as a cylindrical drum. Further, a 2-4 brake 24 is provided on the outer periphery of the second drum 42. The first and second drums 40, 42
Are each formed in a bottomed cylindrical shape, and the first drum 40 is concentrically arranged inside the second drum 42.

The second drum 42 has an annular portion 42b formed by bending a central opening of a bottom portion 42a into a tubular shape, and the annular portion 42b is fitted to the outer periphery of a tubular portion 38a integral with the housing 38. A piston 44 for engaging the reverse clutch 20 is slidably fitted inside the bottom portion 42a of the second drum 42. By the way, in this embodiment, since the first drum 40 is fitted inside the second drum 42, the piston 44 and the reverse clutch 2 are engaged.
It is provided at a predetermined distance from 0. Therefore, a pressing portion 44a is provided in an annular shape so as to project from the outer peripheral portion of the side surface of the piston 44 facing the reverse clutch 20.
The tip of a is brought into contact with the reverse clutch 20.

A vertical surface 44b is provided on the outer periphery of the pressing portion 44a from the base end portion toward the tip portion to form a reduced diameter portion 44c over the entire circumference, and a plurality of return springs 46 are provided on the outer periphery of the reduced diameter portion 44c. They are arranged at equal intervals. The return spring 46 has the vertical surface 44b.
And a snap ring 48 that is engaged with the inner circumference of the second drum 42. And the piston 44
And a bottom portion 42a of the second drum 42, a cylinder chamber 50 is formed, and when a control hydraulic pressure is introduced into the cylinder chamber 50, a fastening force is generated in the piston 44, and the fastening force is applied to the pressing portion 44a. Reverse clutch 2 via
Transmitted to 0.

With the above structure, the automatic transmission 1 of the present embodiment
At 0, the reverse clutch 20 provided on the second drum 42 generates a fastening force on the left side of the drawing in the piston 44 when the control hydraulic pressure is introduced into the cylinder chamber 50, and this fastening force causes the reverse clutch to move. While the control valve 20 is fastened, the control oil pressure is removed from the cylinder chamber 50, whereby the piston 44 is pushed back by the urging force of the return spring 46 and the reverse clutch 20 is opened.

By the way, the fastening force is transmitted to the reverse clutch 20 via the annular pressing portion 44a protruding from the piston 44, and the return spring 46 of the piston 44 is arranged on the outer periphery of the reduced diameter portion 44c and returns. Since the spring 46 and the pressing portion 44a can be prevented from interfering with each other, the pressing portion 44a can be formed in a continuous annular shape along the outer circumference of the piston 44. Therefore, by forming the pressing portion 44a in a continuous annular shape in this manner, the rigidity of the pressing portion 44a is significantly improved, and the pressing portion 44a is prevented from being easily deformed even by a large fastening force. can do.

Further, since the return springs 46 can be arranged in a continuous annular shape along the outer circumference of the pressing portion 44a, by arranging the return springs 46 at equal intervals, the pushing back force of the piston 44 can be reduced. The piston 44 can be made to act evenly in the circumferential direction. Therefore, when the control oil pressure is removed with the opening of the return spring 46, the piston 44 can be smoothly returned without causing any twisting, and the drag phenomenon can be reliably prevented.

By the way, in this embodiment, the first drum 40 having the 3-4 clutch 18, which is another friction element, is disposed radially inward of the reverse clutch 20 provided on the second drum 42. The two friction elements of the reverse clutch 20 and the 3-4 clutch 18 may be axially superposed with each other. Therefore, the axial length of the automatic transmission 10 can be significantly reduced, and the layout in the engine room can be facilitated.

Although the automatic transmission 10 of the above-described embodiment discloses the case where two planetary gear mechanisms of the first planetary gear 12 and the second planetary gear 14 are provided in the gear train, the present invention is not limited to this. Instead, for example, as in the automatic transmission 10a shown in FIGS. 3 and 4, the planetary gear mechanism may be configured by the Ravigneaux type planetary gear 100. The Ravigneaux planetary gear 100 includes a small sun gear 102 and a large sun gear 104 arranged side by side in the axial direction, a short pinion gear 106 meshed with the small sun gear 102, and a large sun gear meshed with the short pinion gear 106. In the present embodiment, the forward clutch 16 is provided inside the front end portion of the first drum 40. The long pinion gear 108 meshed with the 104 and the internal gear 110 meshed with the long pinion gear 108 are provided. The 3-4 clutch 18 is provided on the rear side of the Ravigneaux type planetary gear 100.

[0024]

As described above, in the automatic transmission according to claim 1 of the present invention, the pressing portion for transmitting the fastening force generated in the piston to the friction element is annularly formed in the circumferential direction of the piston. A return spring that forms the push-back force when the friction element is opened and acts on the piston.
Since the return spring and the pressing portion can be prevented from interfering with each other because they are arranged on the outer periphery of the pressing portion, the pressing portion can be formed as an annular shape that is continuous in the circumferential direction, and the return spring can be pressed by the pressing member. They can be arranged in a continuous ring along the outer circumference of the part. Therefore, the rigidity of the pressing portion can be significantly improved,
Even when a large fastening force is applied to the piston, the pressing portion can be prevented from being easily deformed.
Further, the pushing-back force of the piston can be uniformly applied over the entire circumference of the piston, the piston can be smoothly returned along with the release of the friction element, and the dragging phenomenon of the friction element can be reliably prevented. You can

Further, according to the second aspect of the present invention, since the drum having another friction element attached is arranged radially inward of the friction element attached to the cylindrical drum, the two friction elements are provided. Since they can be arranged so as to overlap each other in the axial direction, the axial length of the automatic transmission can be significantly reduced, and various excellent effects can be obtained such that the layout in the engine room can be facilitated.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of an automatic transmission showing an embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of an automatic transmission according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a lower half from a central axis of an automatic transmission showing another embodiment of the present invention.

[Explanation of symbols]

10, 10a automatic transmission 12 first planetary gear (planetary gear mechanism) 14 second planetary gear (planetary gear mechanism) 16 forward clutch (friction element) 18 3-4 clutch (friction element) 20 reverse clutch (friction element) ) 42 second drum 44 piston 44a pressing portion 46 return spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuhiko Iwasaki 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (2)

[Claims] 1. An automatic transmission comprising a plurality of friction elements for switching power transmission paths of a planetary gear mechanism, wherein a plurality of shifts can be obtained by appropriately switching these friction elements. A cylindrical drum, which constitutes a part of the cylindrical drum and has one friction element attached to the inner periphery thereof, and a piston which is housed inside the cylindrical drum to fasten the friction element, are provided. To form a ring-shaped pressing portion that continuously contacts the friction element, is disposed on the outer periphery of the pressing portion, one end is locked to the piston side, and the other end is to the cylindrical drum side. An automatic transmission characterized by having a return spring for locking. 2. The automatic transmission according to claim 1, wherein a drum having another friction element attached is arranged radially inward of the friction element attached to the cylindrical drum.