JPH0447480Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a hydraulic circuit for an automatic transmission.

(Prior Art) Automatic transmissions are equipped with frictional engagement devices such as clutches and brakes, and the power transmission path can be switched by operating the frictional engagement devices as appropriate. Such a friction fastening device is generally operated by hydraulic pressure, and therefore a hydraulic servo device is attached to the friction fastening device. A hydraulic oil passage for supplying and discharging hydraulic oil is connected to the servo chamber of this hydraulic servo device, and a switching valve connected to this hydraulic oil passage allows the servo chamber to be placed on the hydraulic source side or It is designed to be selectively connected to the drain side.

For devices equipped with the above-mentioned hydraulic circuit, it is possible to supply operating pressure to the hydraulic servo device not linearly, but by forming a hydraulic shelf, that is, increasing the hydraulic pressure in stages. This is desired from the viewpoint of preventing gear shifting shock. For this reason,
Conventionally, as shown in Japanese Utility Model Application Publication No. 58-146101, an accumulator has been proposed in which an accumulator is connected to the operating pressure oil passage between the switching valve and the servo chamber. That is, in this accumulator, an accumulator chamber connected to a working pressure oil passage is defined by a movable partition, and the movable partition does not displace until the hydraulic pressure in the working pressure oil passage reaches a predetermined pressure. The hydraulic pressure increases linearly and is supplied to the servo chamber, while when the hydraulic pressure in the working pressure oil passage exceeds a predetermined pressure, the movable bulkhead moves and the accumulator chamber expands, and this expansion action causes the hydraulic pressure to increase. A shelf will be formed. After the accumulator chamber is completely expanded, hydraulic pressure is again supplied to the servo chamber while increasing linearly.

Incidentally, it is desirable that the connection of the frictional fastening device be relatively slow in order to prevent gear shifting shocks, etc., but it is also desirable to disconnect it quickly because the connection of other frictional fastening devices may be started. It is necessary that this be done. For this reason, hydraulic servo devices usually have a mechanism called drift-on-ball, which opens when the hydraulic pressure in the servo chamber decreases.
A hydraulic pressure relief mechanism is often provided to open the servo chamber to the low pressure side.

However, simply releasing the hydraulic pressure from the above-mentioned hydraulic pressure relief mechanism is not sufficient to quickly reduce the pressure in the servo chamber, partly because the volume of the accumulator chamber is quite large, and some countermeasures are desired in this regard. It is rare.

(Purpose of the invention) The present invention was made in consideration of the above circumstances, and its purpose is to reduce the pressure in the servo chamber in a device in which an accumulator is provided between the switching valve and the servo chamber. An object of the present invention is to provide a hydraulic circuit for an automatic transmission that can be opened more quickly.

(Structure of the invention) In order to achieve the above-mentioned purpose, the present invention has the following structure. That is, a hydraulic servo device for operating a friction engagement device for switching a power transmission path of an automatic transmission, a working pressure oil path for supplying and discharging working hydraulic pressure to and from a servo chamber of the hydraulic servo device, and a control pressure. a switching valve that switches the operating pressure oil passage between the hydraulic pressure source side and the drain side; The main body and the piston define an accumulator chamber connected to the operating pressure oil passage, and a return spring is provided to bias the piston toward the accumulator chamber. an accumulator, the piston being displaced against the biasing force of the return spring to expand the accumulator chamber when the pressure in the working pressure oil passage becomes equal to or higher than a predetermined pressure; a relief passageway connected to the port; and a relief passageway connected to the relief passageway and switched between an open position in which the relief passageway and the drain port are connected in response to a control pressure of the switching valve, and a closed position in which connection between the two is prevented. The spool is provided with a switchable spool, and an on-off valve that brings the spool to an open position when the servo chamber is drained.

(Operation of the invention) With the above-described configuration, the hydraulic pressure in the servo chamber is also drained through a separate relief passage, thereby quickly releasing the hydraulic pressure from the servo chamber. In particular, since the on-off valve connected to the relief passage operates in response to the control pressure of the switching valve, the operation of this on-off valve itself is performed promptly in synchronization with the hydraulic pressure release request of the servo chamber.
Hydraulic pressure is released quickly from the servo chamber.

Here, it is preferable to configure a part of the relief passage by an accumulator rear chamber defined on the opposite side from the accumulator chamber, in order to more quickly release the pressure in the servo chamber.
That is, when the pressure in the servo chamber is released, the released hydraulic pressure is also supplied to the back chamber of the accumulator, so that the rate at which the volume of the accumulator chamber is reduced can be further accelerated.

(Embodiments) Examples of the present invention will be described below with reference to the attached drawings.

In FIG. 1, C is a clutch as a friction engagement device of an automatic transmission, and this has a clutch drum 1 and a clutch hub 2 that are arranged so as to be able to rotate relative to each other, and the clutch drum 1 has a drive plate 3. However, the clutch hub 2 also holds a driven plate 4. When the drive plate 3 and the driven plate 4 are separated from each other, the clutch drum 1 and the clutch hub 2 can rotate relative to each other when the clutch is disengaged.On the other hand, when the plates 3 and 4 are in pressure contact with each other,
When the clutch is connected, the clutch drum 1 and the clutch hub 2 rotate integrally with each other. Of course, depending on whether the clutch C is disconnected or connected, the power transmission path of the automatic transmission is switched.

The clutch C is operated on and off by a hydraulic servo device B. To explain this part, a piston 5 is held in the clutch drum 1 so as to be slidable in the axial direction of the clutch drum 1.
A servo chamber 6 is defined by the clutch drum 1 and the clutch drum 1. When operating pressure is supplied into the servo chamber 6 from the oil port 7, the piston 5 is displaced to the left in FIG. When the pressure oil is released, the piston 5 is returned to its original position by the return spring 9, and the clutch is in a disengaged state. The Kurachi drum 1 has a relief passage 10 that communicates the servo chamber 6 with the low pressure side.
A spherical valve body 11 is provided in the relief passage 10, and a hydraulic pressure relief mechanism (drift-on-ball) is formed by the two 10 and 11.

In FIG. 1, reference numeral 21 denotes a switching valve, 31 denotes an accumulator 51 an on-off valve, and these will be described below in order.

The switching valve 21 is in the form of a spub valve, and its main body 22 includes a hydraulic pressure inflow port 23, an outflow port 24, a control pressure inflow port 25, and a drain port 2.
6 is formed. The working hydraulic pressure (line pressure) P _L is introduced into the working hydraulic pressure inflow port 23 after the pressure from an oil pump (not shown) as a hydraulic pressure source is regulated. Also,
The control pressure inflow port 25 is configured to introduce a control pressure Ps for shifting. In such a switching valve 21, when there is no control pressure Ps, the spool 28 is displaced to the right in the figure by the return spring 27, communicating the outflow port 24 with the drain port 26, and when the control pressure Ps is When introduced, the spool 28 is displaced to the left to communicate the outflow port 24 with the hydraulic pressure inflow port 23.

The accumulator 31 has a piston 33 as a movable partition that is slidably inserted into the main body 32.
With this piston 33, an accumulator chamber 34 is formed in the main body 32 at its left end side.
is defined. This piston 33 is arranged at a predetermined interval on the right side in the figure.
It integrally has an auxiliary piston 35 with a diameter smaller than that of piston 3, and the back side of the piston 33, that is, the piston 33
An accumulator rear chamber 36 is defined between the auxiliary piston 35 and the auxiliary piston 35 . The main body 32 includes
Port 3 that is always open to the accumulator chamber 34
7. A port 38 that is always open to the accumulator rear chamber 36; a port 40 that is always open to the working chamber 39 defined on the right side of the auxiliary piston 35;
and a drain port 4 which is normally open to the accumulator rear chamber 36 but is closed when the piston 33 is located near the right stroke end.
1 is formed. And the piston 33
is normally located at the left stroke end in the figure in response to the operating hydraulic pressure P _L from the return spring 42 and the port 40, and when a hydraulic pressure of a predetermined left or more is applied to the port 37, that is, the accumulator chamber 34, It is now displaced to the center right.

The on-off valve 51 is in the form of a spool valve, and its main body 52 has an inflow port 53 and an outflow port 5.
4. A control port 55 is formed. This control port 55 is always open to a control chamber 57 defined on the left end side of the spool 56.
When a control pressure (speed change control pressure Ps in the embodiment as described later) is introduced to 7, the spool 56 is displaced to the right in the figure against the return spring 58, thereby opening the outflow ports 53 and 54. Shut off (close). Conversely, when the above-mentioned shift hydraulic pressure Ps is released,
The spool 56 is displaced to the left in the figure, and the inflow and outflow ports 53 and 54 are communicated with each other (opened).

To explain the connection relationship of each of the above-mentioned elements C, 21, 31, 51, the outflow port 24 of the switching valve 21 and the servo chamber 6 are connected via an operating pressure oil passage 61. A one-way orifice 62 is connected in the middle. This one-way orifice 62 has the functions of a one-way valve 62a and an orifice 62b, and while it slowly transmits the working hydraulic pressure from the outflow port 24 to the servo chamber 6, it also transmits the working pressure from the servo chamber 6 side to the outflow port 24. Pressure transmission is supposed to be done promptly.

Further, two branch oil passages 63 and 64 are branched from the operating pressure oil passage 61 between the one-way orifice 62 and the servo chamber 6, and one branch oil passage 63 is connected to the port 37 of the accumulator chamber 31. The other branch oil passage 64 is connected to the inflow port 53 of the on-off valve 51. The outflow port 54 of the on-off valve 51 is connected to the port 38 (accumulator rear chamber 36) of the accumulator 31 via the communication passage 65, and the other branch passage 6
4 and the communication path 65 constitute a relief path.

Further, a shift hydraulic pressure Ps is introduced into the control port 55 of the on-off valve 51 via a communication path 66.

Next, the operation of the above configuration will be explained. First, the case of connecting the clutch C will be explained. In this case, the shift hydraulic pressure Ps is applied to the port 25 of the switching valve 21 and the port 5 of the on-off valve 51.
5 will be introduced. As a result, the switching valve 21 has its inflow and outflow ports 23 and 24 communicating with each other, while the on-off valve 51 has its outflow and inflow ports 53 and 54 blocked and is closed. As a result, the working oil pressure P _L becomes
The oil will be supplied to the servo chamber 6, but when the oil pressure in the working pressure oil passage 61 increases to a certain predetermined pressure (less than P _L ), the piston 33 of the accumulator 31 is displaced to the right, and its The accumulator chamber 34 is expanded. Then, the rise in oil pressure in the servo chamber 6 is delayed by the amount of expansion of the accumulator chamber 34, and after the accumulator chamber 34 has fully expanded,
The oil pressure in the servo chamber 6 rises again. FIG. 2 shows the state in which the pressure in the servo chamber 6 increases. As can be understood from FIG. 2, the oil pressure in the servo chamber 6 is increased slowly. Note that when the oil pressure in the servo chamber 6 increases, the spherical valve body 11 closes the relief passage 10.

Conversely, when the clutch C is disengaged, that is, the pressure in the servo chamber 6 is released, the shift hydraulic pressure Ps is applied to the port 25 of the switching valve 21 and the port 55 of the on-off valve 51.
will no longer work. Thereby, the outflow port 24 of the switching valve 21 is communicated with the drain port 26, while the inflow/outflow ports 53 and 54 of the on-off valve 51 are communicated with each other. In this state, the pressure in the servo chamber 6 can be released by opening the relief passage 10 of the spherical valve 11 due to the action of centrifugal force, or by switching from the operating pressure oil passage 61. Although this is done via the valve 21, the present invention further includes:
It is also carried out through the back chamber 36 of the accumulator.
To explain this point in detail, the working pressure oil passage 61 and therefore the servo chamber 6 connected thereto are connected to the accumulator 31.
Since the servo chamber 6 is also in communication with the expanded accumulator chamber 34, in order to release the pressure in the servo chamber 6, it is necessary to also release the pressure in the accumulator chamber 34, which has a large volume. However, in the present invention, the servo chamber 6 is also provided in the accumulator rear chamber 36.
In other words, as the volume of the accumulator chamber 34 decreases, the piston 3
3 to the left in FIG. 1, the volume of the accumulator rear chamber 36 also increases by that amount, and the pressure of the servo chamber 6 escapes there as well. In the case of this embodiment, since the accumulator rear chamber 36 itself is drained as the piston 33 is displaced to the left in FIG. 1, the pressure is released more quickly.

In this way, the accumulator rear chamber 36 is in charge of releasing the pressure in the accumulator chamber 34, so that the pressure in the servo chamber 6 is released, that is, the clutch C is disengaged quickly. Incidentally, time t1 in FIG. 2 is the time when the pressure release of the servo chamber 6 is started, and the solid line shows the case of this embodiment, and the broken line shows the conventional case.

(Effects of the invention) As is clear from the above, the invention has the following effects:
Even in the case where hydraulic pressure is supplied to the servo chamber of the frictional fastening device via the accumulator, the pressure in the servo chamber can be quickly released.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing changes in oil pressure in the servo chamber. C...Clutch, B...Hydraulic servo device, 6...
... Servo chamber, 21 ... Switching valve, 23 ... Hydraulic pressure inflow port, 24 ... Outflow port, 26 ... Drain port, 31 ... Accumulator, 33 ... Piston, 34 ... Accumulator chamber, 36 ... Accumulator Rear chamber, 51... Opening/closing valve, 61...
Operating pressure oil passage, 64... Branch passage (relief passage), 6
5...Communication path (relief path).

Claims (1)

[Scope of Claim for Utility Model Registration] A hydraulic servo device for operating a friction engagement device for switching a power transmission path of an automatic transmission, and a working pressure for supplying and discharging working hydraulic pressure to and from a servo chamber of the hydraulic servo device. an oil passage; a switching valve that is switched by the action of control pressure to switch the operating pressure oil passage between a hydraulic pressure source side and a drain side; and a switching valve connected to the operating pressure oil passage between the servo chamber and the switching valve. and includes a piston that is slidably inserted into the main body, the main body and the piston define an accumulator chamber that is connected to the working pressure oil passage, and a return that urges the piston toward the accumulator chamber. an accumulator provided with a spring, and configured such that when the pressure in the working pressure oil passage reaches or exceeds a predetermined pressure, the piston is displaced against the biasing force of the return spring and the accumulator chamber is expanded; a relief passage connecting the operating pressure oil passage to the drain port; an open position connected to the relief passage and connecting the relief passage and the drain port in response to the control pressure of the switching valve; and an open position connecting the relief passage and the drain port, and preventing connection between the two. A hydraulic circuit for an automatic transmission, comprising: a spool that can be switched to a closed position and a closed position, and an on-off valve that brings the spool to an open position when the servo chamber is drained.