JPH0429668A - Control device of automatic transmission - Google Patents

Abstract

PURPOSE:To prevent a speed change shock at the time of speed change so as to perform the speed change in good responsiveness by providing such constitution as controlling a line pressure to be decreased only for a period from the time of detecting the speed change to its completion by a detecting means, at the time of the speed change. CONSTITUTION:In a detecting means 52, timing, in which a speed change mechanism input side rotational speed is started to change toward a rotational speed after a speed change from providing a speed change signal, is detected based on a detection signal of a turbine speed. A line pressure control means 51 controls a line pressure in accordance with an operational condition and also controlling a line pressure regulating means 31 so as to decrease the line pressure by a predetermined amount only for a period from the time of detecting the timing by the detecting means 52 to speed change completion time, at the time of a speed change. Further a control unit 50 is provided with a back pressure control means 53 for controlling a back pressure regulating means 33 so that a back pressure of an accumulator 32 is generated in a value corresponding to transmission torque despite decrease of the line pressure at the time of the speed change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an automatic transmission, and particularly to control of line pressure, etc. of a hydraulic control circuit for friction elements.

[Conventional technology]

In general, an automatic transmission consists of a torque converter, a multi-stage transmission mechanism connected to its output side, various friction elements such as clutches and brakes that are actuated by hydraulic pressure to switch the power transmission path of the multi-stage transmission mechanism, and friction elements such as clutches and brakes. A hydraulic control circuit is provided for supplying and discharging hydraulic pressure to the elements. The supply and discharge of hydraulic pressure is controlled in accordance with the operating conditions, and the Wl friction element is engaged and released, thereby automatically shifting the gears.

In such an automatic transmission, for example,
As shown in Publication No. 8021, a line pressure regulating valve that controls the line pressure supplied to the friction elements is provided in the hydraulic control circuit, and when the gear is not changed, the pressure is adjusted to ensure sufficient engagement force for the friction elements according to the engine load, etc. A control device is known in which the line pressure is controlled so that the same pressure is obtained, and on the other hand, the line pressure is controlled to a lower pressure when changing gears than when not changing gears. According to this device, sudden switching of friction elements during gear shifting is suppressed to prevent torque shock.

In addition, in order to alleviate the shock when the friction element is engaged, an accumulator is connected to the operating pressure supply circuit to the friction element, so that when the hydraulic pressure is supplied to the friction element, the pressure accumulated in the accumulator is reached. It is known that the pressure acting on the friction elements is maintained at a moderate shelf pressure while the hydraulic oil accumulates, and the friction elements are gradually tightened while this shelf pressure is maintained. . In this way, even in a hydraulic control circuit equipped with an accumulator, if the line pressure is lowered during gear shifting, it is possible to secure a sufficient period during which the shelf pressure is maintained even if an accumulator with a relatively small capacity is used. Effective in preventing shift shock.

[Problem to be solved by the invention]

However, when controlling the line pressure to be lower during gear shifting, conventional devices reduce the line pressure for a predetermined period of time from the time the gear shift signal is received, in response to the gear shift signal for shifting gears. Therefore, there was a problem in terms of responsiveness. That is, for example, during a predetermined gear shift in which a specific friction element is switched to the engaged state, the pressure acting on the friction element increases to some extent after the supply of hydraulic pressure to the friction element is started by switching the shift valve in response to the shift signal. By the way, since the friction element starts to engage, there is a certain amount of delay from when the gear shift signal is received until the friction element starts to engage, and in the case where the above-mentioned accumulator is installed, there is a certain delay until the above-mentioned shelf pressure is reached. be. In conventional devices, the flow rate of hydraulic oil supplied to the friction elements is low by lowering the line pressure even from the time the gear shift signal is received until the friction elements begin to engage or until the shelf pressure is reached. As a result, the rate of increase in the operating pressure decreases, and the response delay until the friction element starts to engage increases.

In view of these circumstances, the present invention prevents shift shock by suppressing sudden switching of friction elements during gear shifting, and also improves responsiveness by avoiding an increase in response delay until the friction elements start switching. The purpose is to enable gear shifting. Furthermore, even when equipped with an accumulator, the purpose is to enable responsive gear shifting while effectively preventing shift shock by adjusting the shelf pressure using the accumulator and ensuring a shelf pressure holding period. That is.

[Means to solve the problem]

In order to achieve the above object, the first invention provides a line pressure adjusting means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a line pressure adjustment means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a transmission mechanism input after a transmission signal is received. a detection means for detecting the time when the side rotational speed starts to change toward the rotational speed after the shift; and a detection means for controlling the line pressure according to the operating condition, and for ending the shift from the time detected by the detection means during the shift. and line pressure R11lm means for controlling the line pressure adjusting means so as to reduce the line pressure by the period up to the time.

A second invention also provides a line pressure adjusting means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a back pressure of an accumulator connected to an operating pressure supply circuit to the friction element. a back pressure adjusting means for adjusting the line pressure independently of the line pressure; a detecting means for detecting when the speed change mechanism input side rotation speed begins to change toward the post-shift speed after a speed change signal; line pressure control that controls the line pressure adjusting means to reduce the line pressure by -ta according to the operating state and reducing the line pressure only for a period from the time detected by the detection means at the time of shifting until the end of shifting; and back pressure control means for controlling the back pressure adjusting means so that the back pressure of the accumulator is set to a value corresponding to the transmitted torque regardless of the drop in the line pressure during gear shifting.

[Effect]

According to the configuration of the first invention, during gear shifting, the time when the friction element actually starts switching is detected after the gear shift signal is received, and the line pressure is kept relatively high until this time, resulting in poor responsiveness. From this point on, the line pressure is lowered to slow down the switching of the friction elements.

Further, according to the configuration of the second invention, the operating pressure of the friction element is maintained at an appropriate shelf pressure during gear shifting due to the action of the accumulator, and in this case, the line pressure is lowered to maintain the shelf pressure for a period of time. On the other hand, the back pressure of the accumulator is controlled to a value corresponding to the transmitted torque regardless of the drop in line pressure, so that the back pressure does not fluctuate when the line pressure drops during gear shifting. , above--improper fluctuations in pressure are prevented and the buffering effect of the accumulator is effectively obtained.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the overall configuration of an embodiment of the present invention. In this figure, automatic transmission AT includes a torque converter 2 and a multi-stage transmission mechanism 10 connected to the output side of the torque converter 2.
and a hydraulic control circuit 30. The multi-stage transmission mechanism 10 includes various friction elements (
A hydraulic control circuit 30 controls the engagement and release of various frictional elements (clutches, brakes).

The hydraulic control circuit 30 is provided with hydraulic supply/discharge control elements (not shown in FIG. 1) such as various shift valves that switch between supplying and discharging hydraulic pressure to each friction element, and also operates the friction elements. A line pressure adjusting means 31 is provided to adjust the line pressure. Further, an accumulator 32 connected to the operating pressure supply circuit to the friction element and a back pressure adjusting means 33 for the accumulator 32 are provided, and in this embodiment, the back pressure adjusting means 33 adjusts the back pressure of the accumulator 32 to the line pressure. It can be adjusted independently.

Reference numeral 50 denotes a control unit (ECU) for the hydraulic control circuit 30, which is composed of a microcomputer and the like. A signal from a turbine rotation speed sensor 62 that detects the turbine rotation speed of the torque converter 2 corresponding to the rotation speed on the input side of the transmission, and the like are input.

This control unit 5o controls the speed change by outputting a signal to control the shift valve, etc. according to the operating state determined by the throttle opening, turbine rotation speed, etc., based on a speed change pattern with a shift line determined in advance. The line pressure control means 51 includes a line pressure control means 51 and a detection means 52 related to the control. The detection means 52 detects, for example, an inflection point as described below based on a detection signal of the turbine rotation speed (speed change mechanism input side rotation speed), so that the speed change mechanism input side rotation speed is detected after the speed change signal is received. The line pressure control means 51 controls the line pressure according to the operating condition, and detects the timing when the rotation speed starts to change toward the rotation speed after shifting. The line pressure adjusting means 31 is controlled to reduce the line pressure by a predetermined amount only during the period from the above timing to the end of the shift. Furthermore, the control unit 50
includes back pressure control means 53 for controlling the back pressure adjusting means 33 so that the back pressure of the accumulator 32 is at a value corresponding to the transmitted torque regardless of the decrease in the line pressure during gear shifting.

FIG. 2 shows an example of the structure of the torque converter 2 and multi-stage transmission mechanism 10 of an automatic transmission.

In this figure, the torque converter 2 includes a pump 3 fixedly installed in a case connected to the output shaft 1 of the engine,
A turbine 4 is arranged to face the pump 3 and is driven by the pump 3 via hydraulic oil, and a fixed shaft is interposed between the pump 3 and the turbine 4 and connected via a one-way clutch 6. The stator 5 is supported on the stator 7.

Furthermore, this torque converter 2 is provided with a lock-up clutch 8 that directly connects its input side and output side.

The transmission mechanism 10 includes an oil pump driving solid shaft 12 whose base end is fixed to the output shaft 1 of the engine and whose distal end is connected to the oil pump 11. It has a hollow turbine shaft 13 whose base end is connected to the turbine 4 of the torque converter 2, and on this turbine shaft 13, a Ravigneau-type planetary gear device 14 is provided. This planetary gear device 14 includes a small diameter sun gear 15, a large diameter sun gear 16, a long pinion gear 17,
It has a short pinion gear 18 and a ring gear 19. The above small diameter sun gear 15 and large diameter sun gear 16
are loosely fitted to the turbine shaft 13, and a plurality of short pinion gears 18 mesh with the small diameter sun gear 15,
A long pinion gear 17 meshes with the short pinion gear 18 and the large diameter sun gear 16, a ring gear 19 meshes with the long pinion gear 17, and the long pinion gear 17 and the short pinion gear 18 are rotatably supported by a carrier 28. . The following various friction elements are incorporated into this planetary gear device 14.

A forward clutch 20 and a coast clutch 21 are arranged in parallel between the turbine shaft 13 and the small diameter sun gear 15. The forward clutch 20 is connected to the turbine shaft 1 via a first one-way clutch 22.
3 to the small diameter sun gear 15, and the coast clutch 21
3 and small-diameter sun gear 15, mutual power transmission is interrupted. A 2-4 brake 23 is arranged radially outward of the coast clutch 21, and includes a brake drum 23a connected to the large diameter sun gear 16 and a brake band 23b hooked to the brake drum 23a. When this 2-4 brake 23 is engaged, the large diameter sun gear 16 is fixed. On the side of this 2-4 brake 23, the brake drum 2
A reverse clutch 24 for intrusion driving is disposed to connect and disconnect power transmission between the large-diameter sun gear 16 and the turbine shaft 13 via the gear 3a. Further, a low reverse brake 25 for engaging and disengaging the carrier 28 and the case is arranged between the carrier 28 of the planetary gear device 14 and the case of the transmission mechanism 10. A clutch 26 is arranged.

A 3-4 clutch 27 is disposed between the carrier 28 and the turbine shaft 13 to connect and disconnect power transmission between them. Also, on the side of this 3-4 clutch 27,
An output gear 29 connected to the ring gear 19 is disposed, and this gear 29 is connected to the output shaft 2.
It is attached to 9a.

This transmission mechanism 10 itself has four forward speeds and one reverse speed, and can obtain the desired speed by appropriately operating the clutches 20.21, 24.27 and the brake 23.25. It is possible. Here, Table 1 shows the relationship between each gear stage and the operation of the clutch and brake.

Fig. 3 shows a part of the oil pressure t11110000, and this figure shows the hydraulic supply/discharge system for the apply boat 23c of the 7 actuators of the 2-4 brake 23 and the back pressure adjustment system for the accumulator 32 connected thereto. , and line pressure adjustment system. In addition, above 2
The actuator of the -4 brake 23 is composed of a servo piston having the apply boat 23c and a release port (not shown), and engages the 2-4 brake 23 when hydraulic pressure is supplied only to the apply boat 23C. The 2-4 brake 23 is released at other times. In 1st gear, hydraulic pressure is discharged from both boats, in 2nd gear, hydraulic pressure is supplied to the apply boat 23C, in 3rd gear, hydraulic pressure is also supplied to the release boat, and in 4th gear, hydraulic pressure is supplied to the release port. By supplying and discharging hydraulic pressure to each boat, as shown in Table 1, the 2-4 brake 23 is released in 1st and 3rd gears, and released in 2nd and 4th gears. It is considered to be concluded.

This hydraulic pressure I! l In the control circuit 30, the oil pump 1
The pressure of the hydraulic oil discharged from the main line L1 from the main line L1 is regulated by the pressure regulator valve 34, and this pressure regulator valve 34
Controlled by a duty solenoid valve 35.

That is, the hydraulic pressure of the hydraulic oil, which has been reduced to a predetermined pressure by the reducing valve 36, is duty controlled by the first duty solenoid valve 35, that is, the opening/closing time ratio of the first duty solenoid valve 35 is adjusted and drained. By controlling the amount, the oil pressure is controlled.

By applying this oil pressure as a pilot pressure to the boat 34a on one end side of the pressure regulator valve 34 via the line L2, the line pressure is adjusted in accordance with this pilot pressure. In this way, the line pressure adjusting means 31
is configured, and the first duty solenoid valve 35
is operated by a duty signal from the control unit 50, thereby controlling the line pressure.

The line pressure of the main line L1 is guided to the shift valve 37 through a line L3 when the vehicle is in the forward travel range via a manual valve for range selection (not shown).

A servo apply line L4 serving as an operating pressure supply circuit is provided between the shift valve 37 and the apply boat 23C of the 2-4 brake 23, and a one-way orifice 38 is interposed in this servo apply line L4. .

Pilot boat 37 on one end side of the shift valve 37
A pilot line L5 is connected to a, and a solenoid valve 39 is connected to this pilot line L5. This solenoid valve 39 is connected to the control unit 5
It is turned ON and OFF by a control signal from 0. In 1st gear, the solenoid valve 39 is turned OFF, and a predetermined pilot pressure acts on the pilot boat 37a, so that the spool 37b of the shift valve 37 is located on the left side in the figure, and the servo apply line L4 is connected to the drain boat. It becomes a state where there is no communication. Also, during 1=22 gear shifting (when shifting from 1st to 2nd gear), the solenoid valve 39 is turned OFF.
By switching to N, the pilot pressure is drained, the spool 37b moves to the right side in the figure, the servo apply line L4 is brought into communication with the line L3, and the hydraulic pressure is applied to the apply boat 2 via the one-way orifice 38.
Supplied to 3C.

An accumulator 32 is connected via a one-way orifice 40 to a portion of the servo apply line L4 between the one-way orifice 38 and the apply boat 23c. This accumulator 32 adjusts the increase in servo apply pressure (pressure applied to the apply boat 23C) and provides a buffering effect during a 1-2 shift when hydraulic pressure is supplied to the apply boat 23c and the 2-4 brake 23 is engaged. A piston 32 that expands and contracts the pressure accumulation chamber 32a.
b, and the piston 32b is urged in a direction to reduce the pressure accumulation chamber 32a by the back pressure introduced into the back pressure introduction boat 32c and the spring 32d. In addition, the one-way orifice 4O is configured so that the hydraulic fluid can be quickly discharged from the apply boat 23G during a 2-1 gear shift (when shifting from 2nd gear to 1st gear) when the 2-4 brake 23 is released. In order to do this, the flow of hydraulic oil from the accumulator 32 to the servo apply line L4 is slowed down. is configured to pass through the aperture 40b.

The back pressure of the accumulator 32 is controlled by a back pressure adjusting means 33 composed of an accumulator control valve 41, a second duty solenoid valve 42, and the like. That is, the accumulator control valve 41 has a spool 41a, a boat 41b that communicates with a line L6 through which hydraulic pressure is introduced from a main line, etc., and a boat 41G that communicates with a back pressure introduction boat 32G of the accumulator 32 via a back pressure supply line L7. , a drain boat 41d, a pilot boat 41e connected to the pilot line L8, and the like. By operating the spool 41a in accordance with the pilot pressure introduced into the pilot boat 41e and the pressure on the boat 41c side, pressure corresponding to the pilot pressure is sent to the back pressure supply inlet L7. Hydraulic pressure adjusted to a constant pressure by a reducing valve 43 is sent to this accumulator control valve 41 to a pilot line L8, and a second duty solenoid valve 42 connected to this pilot line L8 controls this line. The pilot pressure guided from L8 to the pilot boat 416 is duty-controlled. In this way, the back pressure of the accumulator 32 is adjusted independently of the line pressure, and the second duty solenoid valve 42 is actuated by the duty signal from the control unit 50, so that the back pressure is adjusted. It's about to be controlled.

Note that the hydraulic control circuit 30 includes a shift valve (1) shown in the figure.
-2 shift valve) 37, a 2-3 shift valve and a 3-4 shift valve each controlled by a solenoid valve are provided, and their operation causes the release boat of the 2-4 brake 23 and the 3-4 clutch to be activated. 27. Hydraulic pressure is also supplied and discharged to and from the coast clutch 21 and the like depending on the operating state and the like. Furthermore, in FIG. 3, the back pressure of the accumulator (1-2 accumulator) 32 connected to the servo apply line L4 is adjusted by the back pressure adjusting means 33, but the The back pressure adjustment of the 2-3 accumulators connected to the working pressure supply circuit may also be performed independently of the line pressure by the back pressure adjustment means 33, and when the back pressure of a plurality of accumulators is adjusted in this way. In this case, the back pressure supply line L7 may be branched and connected to the back pressure introduction boat of each accumulator.

FIG. 4 is a flowchart showing a specific example of the control performed by the control unit 50 as the line pressure control means 51 and the back pressure control means 53.

In this flowchart, first, in step S1, the throttle opening degree and the turbine rotation speed are measured by the sensors 61 and 6, respectively.
2, and in step S2 it is checked whether there is a predetermined shift signal such as a 1-2 shift. The determination in step S2 is N.
o, the normal line pressure III is set in step S3.
After performing the operation ill ii, return. In the process of step S3, in order to obtain the line pressure necessary to secure the friction element engagement force depending on the operating condition, for example, the line pressure according to the throttle opening and the turbine rotation speed is determined from the map, and the corresponding response is determined. Then, the control value (duty rate) of the first duty solenoid valve 35 is calculated.

When the determination in step S2 is YES, the type of shift is determined in step S4, and then in step S5 the control value of the second duty solenoid pulse 42 corresponding to the control value of the back pressure of the accumulator is determined. calculate. This control value is calculated according to the throttle opening, the turbine rotation speed, the type of speed change, etc. so that it becomes a value corresponding to the transmitted torque. For example, the 1-2 accumulator 32 shown in FIG.
When adjusting the back pressure of a 2-3 accumulator (not shown) using the back pressure adjustment means 33, determine whether it is a 1-2 shift or a 2-3 shift, and determine the type of shift and throttle opening. Then, a control value for the second duty solenoid valve 42 is determined from a map or the like in accordance with the turbine rotation speed. This control! l
It is used to control back pressure during gear shifting.

Next, in step S6, it is checked whether the turbine rotational speed has reached an inflection point no shown in FIG. 5, which will be described later. The line pressure is maintained at the normal value until the inflection point is reached, but after the inflection point is reached, a line pressure correction value ΔP is determined according to the operating condition etc. in step S7, and in step S8, The duty rate of the first duty solenoid valve 35 is changed so as to reduce the line pressure by this correction value ΔP. Furthermore, in step S9, the turbine rotation speed n is changed to the inflection point rotation speed nQ.
Then, it is checked whether or not the shift has ended based on whether the shift end rotation speed n1 determined by the shift type (gear ratio) has been reached, and the line pressure is maintained at the value lowered in step S8 until the shift is completed. , returns when the gear shift is completed.

FIG. 5 is a time chart showing changes in line pressure, servo apply pressure, and turbine rotation speed during 12-speed shifting when using the device of this embodiment. Based on this diagram, the operation of the device of this embodiment is shown. Explain.

In this figure, to is 1-2 depending on the change in operating conditions.
Indicates the time point at which a shift signal is applied to start shifting. At this shift start time point to, the solenoid valve 39 is turned ON, and the corresponding shift valve 37 is operated to lead line pressure to the servo apply line L4.
While the servo apply pressure is low due to a delay in the supply of hydraulic oil to the apply boat 23c, the 2-4 brake 23 is in a released state, and at the time t1 when the servo apply pressure rises to a predetermined value, the 2-4 brake 23 is engaged. start.

At this point t1, the turbine rotation speed reaches an inflection point nQ,
From this point in time t1, the turbine rotational speed begins to decrease. Further, from around this point t1, the servo apply pressure is maintained at the shelf pressure by the action of the accumulator 32, that is, from point a when the servo apply pressure reaches the pressure corresponding to the back pressure, the piston 32b of the accumulator 32 is pushed. Ttsu pressure accumulation chamber 3
By introducing hydraulic oil into 2a, piston 32b
The servo apply pressure is maintained at a shelf pressure with a gradual rise until it moves to the terminal end (until the dot in FIG. 5).

During this time, engagement of the 2-4 brake 23 progresses, and the turbine rotational speed gradually decreases to the rotational speed n1 at the end of the shift.

During such a shift, the line pressure is controlled to a lower value by the correction value ΔP from time t1 when the turbine rotational speed reaches an inflection point to time t2 when the shift ends.

As a result, during the period from t1 to t2, the flow rate of the hydraulic oil supplied to the apply port 23c side through the one-way orifice 38 is appropriately reduced, and the 2-4 brake 23
The progress of the conclusion becomes slow.

In particular, in relation to the accumulator 32, the period (a-b) during which the servo apply pressure is maintained at the shelf pressure is made sufficiently long without increasing the capacity of the accumulator 32, and the shelf pressure is maintained until after the completion of fastening. Effective slow motion can be obtained.

Moreover, the line pressure is lowered in this way from time t1 when the turbine rotation speed reaches the inflection point, and even after the shift starts, the line pressure remains the same as before the shift until the turbine rotation speed reaches the inflection point. By keeping the servo alignment pressure at a high value, the responsiveness of the rise in servo alignment pressure at the beginning of gear shifting is improved, and 2-4
Before the rake 23 starts to engage, there is a period (to-tl) not related to the shift shock.

In addition, in the device of this embodiment, the back pressure of the 74 accumulator 32 during gear shifting is controlled independently of the line pressure. It does not cause fluctuations in In other words, in a conventional hydraulic control circuit having one accumulator, the run pressure and the corresponding pressure are applied to the accumulator as J pressure, but in this structure, when the line pressure is reduced during gear shifting as described above, The back pressure of the accumulator 32 fluctuates, and there is a possibility that a shock may occur due to the shelf pressure fluctuation in response to this. However, in the device of this embodiment, the back pressure of the accumulator 32 is independently milled, so during gear shifting. Even if the line pressure decreases, the above shelf pressure will not fluctuate and it will remain appropriate! The side effects will be maintained.

〔Effect of the invention〕

As described above, the invention according to claim 1 controls the line pressure of the hydraulic control circuit according to the operating state, and at the time of gear shifting, after a gear shift signal is received, the speed change mechanism input side rotation speed changes to the rotation speed after the gear shift. The line pressure is kept at 1ilJillL so that the line pressure starts to change from this time to the end of the shift, so the hydraulic pressure at the beginning of the shift until the friction element starts to engage is reduced. This makes it possible to prevent shift shock while improving responsiveness during start-up.

Further, the invention according to claim 2 provides, in addition to the above configuration,
The back pressure of the accumulator connected to the operating pressure supply circuit to the element is adjusted independently of the line pressure, and the back pressure of the accumulator is adjusted to a value corresponding to the transmitted torque regardless of the drop in the line pressure during gear shifting. Since the line pressure is maintained at tilJl[lL, the line pressure control described above improves the responsiveness of the oil pressure rise at the beginning of gear shifting, while ensuring a sufficient shelf pressure retention period due to the action of the accumulator. Even if the line pressure decreases, the above-mentioned shelf pressure does not change, and the tlNjj effect can be effectively produced.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, Fig. 2 is a schematic diagram showing the outline of the structure of an automatic transmission, and Fig. 3 is a hydraulic circuit diagram of the main part of the hydraulic pressure-1111 circuit. ,
FIG. 4 is a flowchart showing an example of controlling line pressure and accumulator back pressure. FIG. 5 is a time chart showing changes in line pressure, servo apply pressure, and turbine rotation speed during 1-2 gear shifting. AT... automatic transmission, 1o... transmission mechanism, 3o...
- Hydraulic control circuit, 31... Line pressure adjustment means, 32.
Reaccumulator, 33... Back pressure adjustment means, 5o...
- Control unit, 51... line pressure means, 52... detection means, 53... back pressure control means.

Claims (1)

[Scope of Claims] 1. A line pressure adjustment means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a line pressure adjustment means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a rotation speed on the input side of the transmission mechanism after a transmission signal is received. detecting means for detecting when the line pressure starts to change toward the speed change; A control device for an automatic transmission, comprising: line pressure control means for controlling the line pressure adjustment means to reduce the line pressure. 2. The line pressure refers to a line pressure adjusting means for adjusting the line pressure of a hydraulic control circuit for a friction element incorporated in a multi-stage transmission mechanism, and a back pressure of an accumulator connected to an operating pressure supply circuit to the friction element. A back pressure adjustment means that adjusts independently, a detection means that detects when the speed change mechanism input side rotation speed starts to change toward the speed change after a speed change signal is received, and a detection means that adjusts the line pressure according to the operating condition. a line pressure control means for controlling the line pressure adjusting means so as to reduce the line pressure by a period from the time detected by the detection means to the end of the shift at the time of a shift; A control device for an automatic transmission, comprising: back pressure control means for controlling the back pressure adjusting means so that the back pressure of the accumulator is set to a value corresponding to the transmitted torque regardless of a decrease in pressure.