KR100448789B1 - pressure control system for automatic transmission - Google Patents

Abstract

The present invention relates to a hydraulic control device of an automatic transmission, and by supplying the operating pressure to the corresponding friction element to be engaged at the time of shifting from the N range to the R range can be made directly from the manual valve, to the fail of the pressure control solenoid valve In addition to preventing the closing end of the shift is not possible, by installing the accumulator that is supplied at the same time as the operating pressure and the signal pressure at the same time on the line through which the line pressure is supplied, so that the friction elements can be smoothly tightened. The purpose is.

In order to achieve the above object, the present invention, the regulator valve 12 for regulating the flow rate discharged from the oil pump 10 in conjunction with the drive of the engine to the line pressure, and the line pressure regulated from the regulator valve 12 Reducing valve 14 for reducing pressure, for supply of operating pressure to a corresponding friction element of each shift stage during shifting; In the hydraulic control apparatus of the automatic transmission including shift control means, pressure control means, switching means, fail safe means and the like, the R range pressure port 16b of the manual valve 16 is connected to the first pipe line L1. Directly connected to the third clutch (C3) via the via, and the line pressure supplied from the R range pressure port (16b) on the first pipe line (L1) to gradually adjust the change in the operating pressure in accordance with the difference in area It is characterized in that the accumulator 34 is installed.

Description

Pressure control system for automatic transmission

The present invention relates to a hydraulic control apparatus of an automatic transmission, and more particularly, to close the directional valve to supply the operating pressure to the friction element that is engaged when shifting from the N range to the R range, and the friction It relates to a hydraulic control device of an automatic transmission in which pressure adjustment at the elements can be made through an accumulator.

In general, the automatic transmission is a device that can change the driving force output from the engine during driving in multiple stages according to the driving state, which is possible by appropriately operating the friction element in the planetary gear system forming the multi-speed stage.

To this end, the automatic transmission is a torque converter that is operated in accordance with the drive of the engine to increase the torque to transmit to the input shaft of the transmission; A plurality of gears such as sun gear, carrier and ring gear are used to form a multi-speed stage by utilizing the driving force input from the torque converter as input elements, reaction force elements and output elements, respectively, through a plurality of friction elements of clutches and brakes. A planetary gear device forming a predetermined gear train by means of; An oil pump operated according to driving of an engine to discharge a rated flow rate required for operation of the torque converter, a plurality of friction elements, and lubrication of various lubrication parts in the transmission; The hydraulic oil supply and release of the hydraulic pressure to the corresponding friction elements of the torque converter and the planetary gear unit are respectively switched for the operation of the selected shift mode during manual shifting or the preset shift pattern for automatic shifting via the hydraulic oil discharged from the oil pump. In addition, the hydraulic control device having a valve body for forming a flow path to the friction element by installing a predetermined direction switching and pressure control valves to improve the feeling of shifting through pressure control during shifting; In order to operate from the selected shift mode to a predetermined shift pattern during shifting, various driving information is input from the engine and the planetary gear unit, and the control signals necessary for the operation of the hydraulic control device, that is, specific valves of the hydraulic control device, respectively. And a shift control device for outputting a corresponding control signal for on / off control or duty control.

Meanwhile, in the automatic transmission that implements the forward 4 speed and the reverse 1 speed as shown in FIG. 1, the hydraulic control device previously applied by the present applicant as patent No. 2000-31289 dated June 8, 2000 is shown in FIG. 1. As shown, the flow rate discharged from the oil pump 10 with the start of the engine is regulated by the regulator valve 12 to a constant pressure (hereinafter referred to as the line pressure), and a part thereof is operated by the damper clutch. A shift control means, a pressure control means, a switching means, a fail safe means, and an NR control means for supplying a pressure to the reducing valve 14, and the other part to selectively supply a working pressure to the friction element operating at each shift stage. It is configured to supply to the hydraulic control unit including.

The shift control means is composed of a manual valve 16 in communication with a plurality of conduits to supply hydraulic pressure through each range conduit while being linked to the driver's select lever operation.

The pressure control means includes first, second and third pressure control solenoid valves S1, S2 and S3 for controlling the control pressure supplied from the reducing valve 14, and the first, second and third pressure control solenoid valves. The first, second, and third pressure control valves 18, 20, and 22 control the oil pressure supplied from the manual valve 16 while being independently controlled by the control pressures supplied from S1, S2, and S3. .

The switching means includes a first switch valve 24 for selectively supplying hydraulic pressure supplied from the first pressure control valve 18 to two flow paths, and a hydraulic pressure and a manual supplied from the third pressure control valve 22. The second switch valve 26 for supplying the hydraulic pressure supplied from the valve 16 to the two friction elements, and the pressure switch supplied from the reducing valve 14 on / off control to the first switch valve 24 And an on / off solenoid valve S4 for changing the flow path of the second switch valve 26.

The fail-safe means includes a first fail-safe valve 28 for supplying hydraulic pressure supplied from the first switch valve 24 and the manual valve 16 to the friction elements operating at low speed and backward, and a second pressure control valve ( And a second fail-safe valve 30 for supplying the hydraulic pressure supplied from 20) to the friction elements operating at the second and fourth speeds.

The N-R control means comprises an N-R control valve 32 for controlling the reverse pressure to supply hydraulic pressure to the clutch that operates only at the shift stage of the R range.

Further, as the friction element, the first clutch C1, the second clutch C2, the third clutch C3, the fourth clutch C4, the first brake B1, the second brake B2, It has two one-way clutches (not shown).

Therefore, in the conventional hydraulic control apparatus configured as described above, the oil pump 10 discharges a predetermined amount of rated flow rate in accordance with the operation of the engine, and the flow rate discharged from the oil pump 10 is the regulator valve. (12) is regulated to line pressure and supplied to the manual valve (16), the second switch valve (26), and the first fail-safe valve (28), respectively, a portion of which is provided by the reducing valve (14). The pressure is reduced to an appropriate level and then supplied to the first pressure control valve 18, the second pressure control valve 20, and the third pressure control valve 22, respectively.

At this time, when the manual valve 16 is switched to the N range, as shown in FIG. 1, the line pressure regulated from the regulator valve 12 is supplied to the first fail-safe valve 28 to perform its operation. The first switch valve through the on / off solenoid valve (S4) which acts as a signal pressure to be promoted, and the depressurized pressure reduced from the reducing valve 14 is turned off under the control of the shift control device (TCU). It is supplied to the 24 and the second switch valve 26 to act as a signal pressure to facilitate its operation, and as a result the switching of the flow path toward the first brake (B1) and the fourth clutch (C4) to be made do.

Thereafter, the line pressure output through the N, P, D, L range pressure port 16a of the manual valve 16 is supplied to the first pressure control valve 18, wherein the first pressure control solenoid The valve S1 passes through the first pressure control valve 18, the first switch valve 24, and the first fail-safe valve 28 according to the duty control of the shift control device TCU. It is possible to smoothly fasten the first brake B1 while appropriately controlling the line pressure supplied thereto.

In addition, the line pressure regulated through the regulator valve 12 is directly supplied to the fourth clutch C4 through the second switch valve 26 to achieve fast fastening.

On the other hand, when the manual valve 16 is switched to the R range, as shown in Fig. 2, the line pressure regulated from the regulator valve 12 is supplied to the first fail-safe valve 28 to stop its operation. Acts as a signal pressure to be promoted, the pressure reducing pressure from the reducing valve 14 passes through the second pressure control solenoid valve (S2) is turned off under the control of the transmission control unit (TCU) through the connecting pipe (L) Supplied to the NR control valve 32 to act as a signal pressure for its operation, and the on / off pressure reduced from the reducing valve 14 is turned off under the control of the shift control unit TCU. The on / off solenoid valve S4 is supplied to the first switch valve 24 and the second switch valve 26 to act as a signal pressure for its operation, and as a result, the first brake B1. And the third clutch C3 and the fourth This switching of the flow path towards the reochi (C4) will be written.

Thereafter, the line pressure output through the R range pressure port 16b of the manual valve 16 is supplied to the third clutch C3 through the NR control valve 32 and at the same time the first fail-safe valve ( The first brake B1 is supplied to the first brake B1 through 28 to engage the third clutch C3 with the first brake B1.

In addition, the line pressure regulated through the regulator valve 12 is directly supplied to the fourth clutch C4 through the second switch valve 26 to achieve fast fastening.

As a result, the reverse shift in accordance with the manual valve 16 switching to the R range is completed, and the vehicle is driven backward.

Accordingly, in the conventional hydraulic control device configured as described above, the second pressure control solenoid valve S2 is used to supply the line pressure to the third clutch C3 during the shift from the N range to the R range and the R range to the N range. ) Was essential.

However, the second pressure control solenoid valve S2 also serves to control the operation of the second brake B2 through the second pressure control valve 20, that is, the second pressure control solenoid valve ( Since S2 serves to dually control the operation of the third clutch C3 and the second brake B2, this causes a deterioration of the control performance, and thus the second pressure control solenoid valve S2. In the case of failing, a shift from the N range to the R range and the R range to the N range is impossible.

Accordingly, the present invention has been made in view of the above, by supplying the operating pressure to the friction element that is fastened at the time of shifting from the N range to the R range can be made directly from the manual valve, the pressure control solenoid valve In addition to preventing the closing of the gear that cannot be shifted due to the fail, by installing an accumulator that simultaneously supplies the line pressure as the operating pressure and the signal pressure on the pipeline where the line pressure is supplied, the friction elements can be smoothly tightened. It is an object of the present invention to provide a hydraulic control device of an automatic transmission.

The present invention for achieving the above object, the regulator valve for regulating the flow rate discharged from the oil pump in conjunction with the drive of the engine to the line pressure, the reducing valve for reducing the line pressure regulated from the regulator valve, shift To supply the working pressure to the corresponding friction element in the visual shift stage; Shift control means composed of a manual valve in communication with a plurality of conduits to supply hydraulic pressure through each range conduit while being linked to a driver's select lever operation; The manual valve is controlled independently by the first, second and third pressure control solenoid valves for controlling the control pressure supplied from the reducing valve, and the control pressure supplied from the first, second and third pressure control solenoid valves. Pressure control means consisting of first, second and third pressure control valves for controlling the hydraulic pressure supplied from the; The first switch valve for selectively supplying the hydraulic pressure supplied from the first pressure control valve to the two flow paths, and the hydraulic pressure supplied from the third pressure control valve and the hydraulic pressure supplied from the manual valve to the two friction elements A switching means comprising a second switch valve and an on / off solenoid valve configured to change a flow path between the first switch valve and the second switch valve by controlling on / off of a reduced pressure supplied from the reducing valve; A first fail-safe valve for supplying the hydraulic pressure supplied from the first switch valve and the manual valve to the friction elements operating at low speed and backward, and a friction for operating the hydraulic pressure supplied from the second pressure control valve at 2 speed and 4 speed. In the hydraulic control device of the automatic transmission comprising a second fail-safe means for supplying to the urea, the R range pressure port of the manual valve is directly connected to the third clutch via the first conduit The accumulator is connected to the first pipe line, and an accumulator is configured to adjust an increase in operating pressure based on a difference in area of the line pressure supplied from the R range pressure port.

1 is a hydraulic circuit diagram showing a state of the N range in the conventional hydraulic control device of the automatic transmission.

Figure 2 is a hydraulic circuit diagram showing a state of the R range in the conventional hydraulic control device of the automatic transmission.

Figure 3 is a hydraulic circuit diagram showing a state of the N range in the hydraulic control apparatus of the automatic transmission according to the present invention.

Figure 4 is a hydraulic circuit diagram showing a state of the R range in the hydraulic control apparatus of the automatic transmission according to the present invention.

Fig. 5 is a schematic diagram showing the configuration of a third clutch and an accumulator, which are main parts of the present invention.

<Description of Symbols for Main Parts of Drawings>

10-Oil Pump 12-Regulator Valve

14-Reducing Valve 16-Manual Valve

18-First Pressure Control Valve 20-Second Pressure Control Valve

22-Third Pressure Control Valve 24-First Switch Valve

26-second switch valve 28-first fail-safe valve

30-second fail safe valve 32-N-R control valve

34-accumulator

C1-first clutch C2-second clutch

C3-3rd Clutch C4-4th Clutch

B1-first brake B2-second brake

S1-first pressure control solenoid valve

S2-second pressure control solenoid valve

S3-Third Pressure Control Solenoid Valve

S4-On / Off Solenoid Valve

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a hydraulic circuit diagram showing a state of the N range in the hydraulic control apparatus of the automatic transmission according to the present invention, Figure 4 is a hydraulic circuit diagram showing a state of the R range in the hydraulic control apparatus of the automatic transmission according to the present invention. 5 is a schematic view showing the configuration of a third clutch and an accumulator, which is a main part of the present invention, in which the same reference numerals are given to the same reference numerals as in FIGS. 1 to 2 showing the hydraulic control apparatus of the conventional automatic transmission. Let's do it.

As shown in FIG. 3, the hydraulic control apparatus of the automatic transmission according to the present invention regulates the flow rate discharged from the oil pump 10 with the line pressure by the regulator valve 12 with the start of the engine, and a part thereof is a damper. Shift control means, pressure control means, switching means, and fail-safe means for supplying the working pressure of the clutch and the reducing valve 14 and the other part to selectively supply the working pressure to the friction elements operating at each shift stage. And to supply a hydraulic control including means.

Here, the shift control means is made of a manual valve (16) in communication with a plurality of pipelines to supply hydraulic pressure through each range pipeline while being linked to the driver's select lever operation, the pressure control means is the reducing valve ( 14, the first, second and third pressure control solenoid valves S1, S2 and S3 for controlling the control pressure supplied from the first and second pressure control solenoid valves S1, S2 and S3. Each of the first, second, and third pressure control valves 18, 20, and 22 controls the hydraulic pressure supplied from the manual valve 16 while being independently controlled by a control pressure.

The switching means includes a first switch valve 24 for selectively supplying the oil pressure supplied from the first pressure control valve 18 to two flow paths, and a hydraulic pressure supplied from the third pressure control valve 22. And the second switch valve 26 for supplying the hydraulic pressure supplied from the manual valve 16 to the two friction elements and the depressurization supplied from the reducing valve 14 to be controlled on / off. 24) and an on / off solenoid valve S4 for switching the flow path through the movement of the spool of the second switch valve 26.

In addition, the fail-safe means includes a first fail-safe valve 28 for supplying the hydraulic pressure supplied from the first switch valve 24 and the manual valve 16 to the friction elements operating at low speed and backward, and the second pressure control. It consists of a second fail-safe valve 30 for supplying the hydraulic pressure supplied from the valve 20 to the friction elements operating at the second and fourth speed.

Meanwhile, the friction element may include a first clutch C1, a second clutch C2, a third clutch C3, a fourth clutch C4, a first brake B1, a second brake B2, It has two one-way clutches (not shown).

Here, the manual valve 16 has N, P, D, L range pressure ports 16a for supplying line pressures in the N, P, D, and L ranges, and R range pressure for supplying line pressure only in the R range. A port 16b, a D and L range pressure port 16c for supplying line pressures respectively in the D and L ranges, and an L range pressure port 16d for supplying line pressure only in the L ranges are provided.

As illustrated in FIG. 5, the accumulator 34 provided in the third clutch C3 is supported by a predetermined shape of the housing 34a and the return spring 34b in the housing 34a. By having a piston 34c, the interior of the housing 34a is divided into a first pressure chamber 34d and a second pressure chamber 34e via the piston 34c, and the first pressure chamber ( The area of 34d) is formed larger than the area of the second pressure chamber 34e.

To this end, a protruding member 34f for forming the second pressure chamber 34e is integrally formed on the rear surface of the piston 34c of the accumulator 34 and between the protruding member 34f and the housing 34a. A sealing material 34g for airtightness is installed in the space 34h, and the first pressure chamber (34h) is formed between the first pressure chamber 34d and the second pressure chamber 34e in the housing 34a. A discharge port EX for returning the hydraulic oil leaking from the 34d) and the second pressure chamber 34e to the oil pan, respectively, is provided.

Further, the first pressure chamber 34d of the housing 34a communicates with the R range pressure port 16b of the manual valve 16 via the first pipe line L1, and the first pressure chamber 34d of the housing 34a is connected to the first pressure chamber 34d. The second pressure chamber 34e communicates with the R range pressure port 16b of the manual valve 16 via the second pipeline L2 branched from the first pipeline L1.

As a result, the piston 34c which is elastically supported in the housing 34a via the return spring 34b has an area A1 of the first pressure chamber 34d and a side of the second pressure chamber 34e. As the area A2 is formed to be different from each other, the same line pressure acts on the first pressure chamber 34d and the second pressure chamber 34e through the first pipe line L1 and the second pipe line L2, respectively. In this case, the piston 34c gradually contracts the return spring 34b by the area difference A1-A2 between the first pressure chamber 34d and the second pressure chamber 34e. By gradually increasing the working pressure acting as the pressure chamber (3) of the third clutch (C3) it is possible to reduce the impact generated during the engagement of the third clutch (C3).

On the other hand, the line pressure output through the N, P, D, L range pressure port 16a of the manual valve 16 is the first pressure control valve 18, the second pressure control valve 20 and the third The first pressure control solenoid valve S1, the second pressure control solenoid valve S2, and the third pressure control solenoid valve S3 are respectively supplied to the pressure control valve 22. According to the duty control of the control panel) through the first pressure control valve 18, the second pressure control valve 20 and the third pressure control valve 22 to appropriately control the line pressure supplied or released to the friction element do.

In addition, the line pressure output through the R range pressure port 16b of the manual valve 16 is supplied to the third clutch C3 through one side of the accumulator 34 through the first conduit L1. In addition, the second conduit L2 branched from the first conduit L1 is supplied to the other side of the accumulator 34.

In addition, in the present invention, the NR control valve 32 allowing the supply of the line pressure to the third clutch C3 at the time of shifting to the conventional R range is deleted, and the second pressure control is performed from the NR control valve 32. The connection line L disposed between the solenoid valves S2 is also deleted.

On the other hand, the first fail-safe valve 28 is connected through a third pipe line (L3) branched from the first pipe line (L1).

In the figure, reference numerals (b) and (c) denote pistons and multi-plate clutches provided in the third clutch C3, respectively.

Therefore, in the hydraulic control apparatus of the present invention configured as described above, first, the oil pump 10 discharges a predetermined amount of rated flow rate in accordance with the operation of the engine, and the flow rate discharged from the oil pump 10 is the regulator. The valve 12 is regulated to line pressure and supplied to the manual valve 16, the second switch valve 26, and the first fail-safe valve 28, respectively, some of which are supplied to the reducing valve 14. The pressure is reduced to an appropriate level and then supplied to the first pressure control valve 18, the second pressure control valve 20, and the third pressure control valve 22, respectively.

At this time, when the manual valve 16 is switched to the N range, as shown in FIG. 3, the line pressure regulated from the regulator valve 12 is supplied to the first fail-safe valve 28 to stop its operation. The first switch valve (I) acts as a signal pressure, and the on / off solenoid valve (S4) is turned off under the control of the shift control unit (TCU) to reduce the pressure reduced from the reducing valve (14). It is supplied to the 24 and the second switch valve 26 to act as a signal pressure to facilitate its operation, and as a result the switching of the flow path toward the first brake (B1) and the fourth clutch (C4) to be made do.

Thereafter, the line pressure output through the N, P, D, and L range pressure ports 16a of the manual valve 16 is controlled by the first pressure control valve 18, the second pressure control valve 20, and the third pressure control valve. The first pressure control solenoid valve S1 is supplied to the pressure control valve 22, wherein the first pressure control solenoid valve S1 is controlled by the first pressure control valve 18 and the first switch valve 24 according to the duty control of the shift control apparatus TCU. ) And smoothly tighten the first brake B1 while appropriately controlling the line pressure supplied to the first brake B1 via the first fail-safe valve 28.

In addition, the line pressure regulated through the regulator valve 12 is directly supplied to the fourth clutch C4 through the second switch valve 26 to achieve fast fastening.

On the other hand, when the manual valve 16 is switched to the R range, as shown in Figure 4, the line pressure regulated from the regulator valve 12 is supplied to the first fail-safe valve 28 to stop the operation thereof. The first switch valve (I) acts as a signal pressure, and the on / off solenoid valve (S4) is turned off under the control of the shift control unit (TCU) to reduce the pressure reduced from the reducing valve (14). It is supplied to the 24 and the second switch valve 26 to act as a signal pressure to facilitate its operation, as a result of which the first brake (B1), the third clutch (C3) and the fourth clutch (C4) Switching of the flow path is made.

Thereafter, the line pressure output through the R range pressure port 16b of the manual valve 16 is supplied to the third clutch C3 through the accumulator 34 through the first pipe line L1 and at the same time. The third clutch C3 is supplied to the first brake B1 through the first fail-safe valve 28 through which the flow path is switched through the third pipeline L3 branched from the first pipeline L1. ) And the first brake B1 can be fastened.

In addition, the line pressure regulated through the regulator valve 12 is directly supplied to the fourth clutch C4 through the second switch valve 26 to achieve fast fastening.

As a result, the reverse shift in accordance with the manual valve 16 switching to the R range is completed, and the vehicle is driven backward.

At this time, the line pressure supplied to the first pipe line L1 through the R range pressure port 16b of the manual valve 16 is first supplied to the first pressure chamber 34d of the accumulator 34 and the It is supplied to the second pressure chamber 34e of the accumulator 34 through the second pipeline L2 branched from the first pipeline L1.

As a result, the line pressure supplied to the pressure chamber (a) of the third clutch C3 is an accumulator according to the area difference between the first pressure chamber 34d and the second pressure chamber 34e of the accumulator 34. Since it can rise gradually through the buffering function of 34, the piston (b) of the said 3rd clutch C3 engages a multi-plate clutch (c) gradually, and the fastening of the said 3rd clutch C3 becomes smooth. It can be done.

That is, as the accumulator 34 is supplied with the line pressure to the first pressure chamber 34d and the second pressure chamber 34e at the same time, the piston by the line pressure acting as the first pressure chamber 34d ( The first pressure is caused by the difference between the pressing force acting on the front surface of 34c, the line pressure acting on the second pressure chamber 34e, and the pressing force acting on the rear surface of the piston 34c by the resistance force of the return spring 34b. 3 By adjusting the increase in the operating pressure acting as the pressure chamber (3) of the clutch (C3) to allow the movement of the piston (B) for fastening the multi-plate clutch (C) to be made gradually, the third clutch (C3) of Fastening is made smoothly.

As described above, according to the hydraulic control apparatus of the automatic transmission according to the present invention, when the manual valve 16 according to the operation of the select lever in the automatic transmission moves from the N range to the R range, the third clutch ( Line pressure for controlling the operating pressure of C3) is directly transmitted from the R range pressure port 16b of the manual valve 16 through the first conduit L1 disposed between the accumulator 34 of the third clutch C3. As such, the configuration of the NR control valve 32 for switching the flow path between the manual valve 16 and the third clutch C3 as in the prior art can be abolished, and the NR control valve 32 ) And the configuration of the connection line (L) between the second pressure control solenoid valve (S2) for supply of the signal pressure for the flow path switching thereof can also be abolished.

In addition, the second pressure control solenoid valve S2 does not play a dual role of controlling the operation of the third clutch C3 and the second brake B2, and controls only the operation of the second brake B2. As it plays a role, the performance of the control can be prevented.

In addition, since the line pressure can be directly transmitted from the manual valve 16 to the third clutch C3 even when the second pressure control solenoid valve S2 is failed in shifting from the N range to the R range, There is an advantage that a smooth shift can be made.

Claims (5)

A regulator valve 12 for regulating the flow rate discharged from the oil pump 10 linked with the driving of the engine to the line pressure, a reducing valve 14 for reducing the line pressure regulated from the regulator valve 12, and a shift To supply the working pressure to the corresponding friction element in the visual shift stage; Shift control means composed of a manual valve 16 in communication with a plurality of conduits so as to be connected to a driver's select lever operation and to supply hydraulic pressure through each range conduit; First, second and third pressure control solenoid valves S1, S2 and S3 for controlling the control pressure supplied from the reducing valve 14, and the first, second and third pressure control solenoid valves S1, S2, Pressure control means composed of first, second and third pressure control valves 18, 20 and 22 for controlling the hydraulic pressure supplied from the manual valve 16 while being independently controlled by the control pressure supplied from S3); The first switch valve 24 for selectively supplying the hydraulic pressure supplied from the first pressure control valve 18 to two flow paths, and the hydraulic pressure and manual valve 16 supplied from the third pressure control valve 22. The second switch valve 26 for supplying the hydraulic pressure supplied from the two friction elements, and the pressure reduction supplied from the reducing valve 14 on / off control to control the first switch valve 24 and the second switch Switching means comprising an on / off solenoid valve S4 for changing a flow path of the valve 26; The first fail-safe valve 28 for supplying the hydraulic pressure supplied from the first switch valve 24 and the manual valve 16 to the friction elements operating at low speed and backward, and the second pressure control valve 20. In the hydraulic control device of an automatic transmission comprising: a fail-safe means consisting of a second fail-safe valve (30) for supplying the hydraulic pressure to be operated at the second and fourth speed. The R range pressure port 16b of the manual valve 16 is directly connected to the third clutch C3 via the first pipeline L1, and the R range pressure port 16b is provided on the first pipeline L1. Accumulator 34 is provided with a piston 34c which is supported by the spring 34b in the housing 34a so as to gradually adjust the change in the working pressure according to the difference in area. ; The accumulator (34) is configured to partition the inside of the housing (34a) into a first pressure chamber (34d) and a second pressure chamber (34e) having different areas. delete The method of claim 1, The area of the first pressure chamber (34d) is larger than the area of the second pressure chamber (34e), the hydraulic control device of the automatic transmission. The method of claim 1, A protruding member 34f for forming the second pressure chamber 34e is formed on the rear surface of the piston 34c, and a sealing material 34g for hermetic sealing is provided between the protruding member 34f and the housing 34a. And a discharge port EX is provided in the space 34h formed between the first pressure chamber 34d and the second pressure chamber 34e in the housing 34a. Control unit. The method of claim 1, The first pressure chamber 34d communicates with the R range pressure port 16b of the manual valve 16 via the first pipe line L1, and the second pressure chamber 34e communicates with the first pipe line ( A hydraulic control device for an automatic transmission, characterized in that the communication with the R range pressure port (16b) of the manual valve (16) via a second pipe (L2) branched from (L1).