JPH1144360A - Oil pressure control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a sense of incompatibility when shift-down is caused by failure in an engine brake attaining condition. SOLUTION: An oil pressure control device has a directional control valve 2 to supply-discharge oil pressure of frictionally engaging elements B-1 and B-3 for an engine brake, a first solenoid valve S3 to output switching signal pressure to it, a second solenoid valve S4 to output switching signal pressure different between a prescribed shift stage and the other shift stage time and a control valve 8 to impress output signal pressure of the second solenoid valve S4 on the directional control valve 2 at shift-down time to the prescribed shift stage under oil pressure supply to the frictionally engaging element B-1 by the directional control valve 2. At shift-down time to the prescribed shift stage from the other shift stage by fail, oil pressure is discharged from the frictionally engaging element B-3 by switching the directional control valve 2, and attainment of an engine brake condition is avoided by releasing it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for an automatic transmission, and more particularly, to a fail-safe technique for a hydraulic circuit for achieving engine braking.

[0002]

2. Description of the Related Art In a conventional automatic transmission, one of different frictional engagement elements is disengaged and the other is disengaged in order to prevent a shift shock due to tie-up of the two frictional engagement elements at the time of a shift for engaging the other. In some cases, a one-way clutch is incorporated in a gear train in order to eliminate the torque supporting state of the friction engagement element on the side of the gear train as the shift progresses. In such a transmission, the torque applied to the reaction force element reverses when the coasting state is established from the engine driving state at the gear position in which the reaction force element of the planetary gear is locked by the one-way clutch. Be free. Therefore, torque from the wheel side is not transmitted to the engine via the gear train, and the engine braking effect cannot be obtained as it is. Therefore, conventionally, generally, a friction engagement element capable of supporting torque in both directions such as a multi-plate brake is provided in parallel with the one-way clutch, and is engaged to achieve engine braking. An example of such a gear train is disclosed in JP-A-61-41.
There is a technique disclosed in Japanese Patent Application Publication No. 063.

[0003] By the way, the engine braking effect is as follows.
It is useful when traveling on a downhill road or the like, but when traveling on a congested road or the like, frequent on / off operations of the accelerator pedal give a jerky feeling, and therefore it is better not to cause this problem for smooth traveling. Therefore, in a conventional normal automatic transmission, at a reduction gear in a "D" (drive) range in which all forward gears can be achieved for normal traveling, the friction engagement element in parallel with the one-way clutch is released. In the low-speed gear in a range position such as the “2” (second) range or the “L” (low) range in which the engine braking effect is not generated and a limited plurality of gears on the low gear side can be achieved, The friction engagement element is engaged so that an engine braking effect is generated. Selection of such a range position is performed by mechanically switching a manual valve provided in a hydraulic control device of the automatic transmission using a shift lever.

[0004] In recent years, there has been proposed an automatic transmission in which an operation like a manual transmission capable of directly selecting a gear position intended by a driver is possible. As an example of such a technique, there is a technique disclosed in JP-A-5-60210. In this technique, a circuit configuration is employed in which a frictional engagement element for achieving engine braking is engaged by controlling a solenoid valve while a manual valve of a hydraulic control device is kept at a "D" range position.

[0005]

In the automatic transmission according to the latter proposal, when the shift solenoid valve fails due to lack of a signal or the like while the vehicle is running at the second speed in a state where engine braking can be achieved. Then, the shift valve operated by the signal pressure is switched to the state of achieving the first speed.
At the time of this switching, the brake for achieving the second speed and the brake for achieving the second speed engine brake are released, and the brake for achieving the first speed engine brake is engaged. The engine brake can be achieved. In particular, when such a downshift due to a failure occurs during a coast, unexpected strong engine braking is applied, and the driver feels great discomfort.

In view of the above, even if a failure occurs in the shift solenoid valve in a state where engine braking can be achieved, the present invention identifies an automatic downshift that occurs as a normal downshift and avoids achieving engine braking. A first object is to provide a hydraulic control device for a transmission.

A second object of the present invention is to mechanically assure the operation of the hydraulic control device for preventing the engine braking effect from occurring at the time of downshifting due to the occurrence of the failure, using only a hydraulic circuit configuration. And

Further, a third object of the present invention is to minimize an increase in the number of components for adopting the above circuit configuration.

A fourth object of the present invention is to maximize the effect of reducing the sense of discomfort given to the driver.

[0010]

SUMMARY OF THE INVENTION In order to achieve the first object, the present invention provides a method for driving a vehicle at a predetermined speed and at other speeds.
An automatic transmission capable of achieving an engine braking state by engaging different friction engagement elements, wherein a hydraulic control device that controls the friction engagement elements controls supply and discharge of hydraulic pressure to and from the friction engagement elements. A switching valve for controlling, and a first solenoid valve for outputting a signal pressure for controlling the hydraulic supply and discharge to the switching valve, a hydraulic control apparatus for an automatic transmission,
A second solenoid valve that outputs a different signal pressure in the predetermined gear and another gear, and an output from the second solenoid valve when shifting to a predetermined gear in a state where hydraulic pressure can be supplied by the switching valve. And a control valve for applying a signal pressure to the switching valve, and at the time of shifting to a predetermined shift speed, discharging the oil pressure by the switching valve to achieve the engine braking state by engagement of the friction engagement element. It is characterized in that it is avoided.

Further, in order to achieve the second object, the control valve is configured to connect the second solenoid valve to a switching valve by a signal pressure applied by shifting to the predetermined gear position. Is done.

In order to achieve the third object, a shift valve that switches between the predetermined shift speed and another shift speed is disposed between the switching valve and the friction engagement element. Configuration.

Then, in order to achieve the fourth object,
The predetermined shift speed is the first speed, and the other shift speeds are higher shift speeds.

[0014]

According to the present invention, in the case of a gear other than the predetermined gear, the second solenoid valve switches the switching valve to a position where the friction engagement element for achieving engine braking is released. To output the signal pressure,
Even if the gear is shifted down to a predetermined gear while the vehicle is running in a state where engine braking can be achieved with other gears due to a shift valve stick or a failure of a shift solenoid valve, when the gear becomes a predetermined gear, As the control valve is switched to supply the signal pressure from the second solenoid valve to the switching valve, the second solenoid valve causes the switching valve to discharge hydraulic pressure to the friction engagement element for achieving engine braking. Therefore, according to the present invention, it is possible to reduce a sense of discomfort due to an unintended downshift by the driver in a state where the engine brake is applied.

Further, according to the second aspect of the present invention, the control valve is opened by the signal pressure applied by the shift to the predetermined shift speed, whereby the second solenoid valve is connected to the switching valve. Since the operation of discharging the hydraulic pressure by the switching valve occurs, the frictional engagement element for achieving the engine brake is released only by mechanical switching of the hydraulic circuit of the hydraulic control device, and the engine brake is operated. The effect of reducing the discomfort caused by the unexpected downshift of the driver can be mechanically guaranteed.

According to the third aspect of the present invention, it is possible to switch the hydraulic pressure supply according to the shift speed between the switching valve and the friction engagement element by the shift valve. Since a plurality of different frictional engagement elements for achieving the engine brake can be controlled in accordance with the gear, the number of valves can be reduced and the cost can be reduced.

According to the configuration of the fourth aspect, the downshift at the time of a failure prevents the engine braking effect from being produced when the first speed state giving the greatest deceleration feeling is obtained. Therefore, even in the event of a failure, it is possible to reduce the sense of discomfort given to the driver.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 2 as a skeleton of the gear train, this transmission uses a torque converter T with a lock-up clutch as a starting device, and combines two planetary gear units U1 and U2 as speed change elements to make three forward gears and one reverse gear. Is a four-speed automatic transmission in which an overdrive mechanism including a planetary gear unit U0 is disposed at the preceding stage.

The planetary gear unit U0 be connected to the torque converter T is connected to the carrier C ₀ to the turbine output shaft, clutch the sun gear S _0, parallel C-
0 and the carrier C ₀ via a one-way clutch F-0, so that the sun gear S ₀ can be locked by a brake B-0. The ring gear _R0, which constitutes the output element of the planetary gear unit U0, is connected to a subsequent transmission mechanism via parallel clutches C-1 and C-2.

[0020] The clutch C-1, the ring gear R ₁ of the planetary gear unit U1 is coupled, the clutch C-2
Include both sun gears S ₁ and S 2 of both gear units U 1 and U 2.
₂ are connected. Then, the carrier C ₁ of the planetary gear unit U1 is connected to the ring gear R ₂ of the planetary gear unit U2, the carriers C ₁ and the ring gear R ₂ is connected to an output shaft as an output element of the automatic transmission. Further, both sun gears S ₁ and S ₂ can be locked by a brake B-1 and can be locked by a one-way clutch F-1 and a brake B-2 in series, and the carrier C of the planetary gear unit U2 can be locked.
₂ is a parallel one-way clutch F-2 and brake B
-3 for locking.

The automatic transmission having the above-described structure can be used as shown in the engagement chart of FIG.
That is, "P" (parking), "R" (reverse),
Each clutch C-0 to C-2 and brakes B-0 to B according to "N" (neutral), "D", "2", and "L"
-3 engagement or disengagement, one-way clutch (OW.
C) Operates by locking or freeing F-0 to F-2. In the figure, a circle indicates engagement for each clutch and brake, a lock for one-way clutch, and a cross indicates release for the clutch and brake, and free for one-way clutch.

As can be seen with reference to FIGS. 2 and 3, in the third speed of the automatic transmission, the clutch C-0 is engaged, the planetary gear unit U0 is directly connected, and the clutch C-1 and the clutch C-1 are engaged. This is achieved by engaging both C-2 and bringing both planetary gear units U1 and U2 into a directly connected state. In the fourth speed, the carrier C that takes a reaction force on the sun gear S ₀ locked by the engagement of the brake B-0.
The rotational speed of the ring gear _R0 is increased by the rotation of the _0- pinion and the planetary gear units U1 and U2 in which the clutch C-1 and the clutch C-2 are both engaged. An overdrive state occurs.

In the second speed in the "D" range manual mode according to the subject of the present invention, unlike the second speed in the "D" range auto mode, the "2" range or the "2" speed is used. By obtaining the same engagement state of the brake B-1 as in the second speed in the L "range, an engine braking effect during coasting can be obtained. At this time, the ring gear R
_With the input to ₁ , the revolution of the pinion due to the reaction force of the engagement of the sun gear S ₁ is output as the rotation of the carrier C ₁ due to the lock of the _one -way clutch F-1 and the engagement of the brake B-2. In contrast, coasting, the input to the carrier C ₁ is taking a reaction force in the locking of the sun gear S ₁ by the engagement of the brake B-1, is output in the reverse route to the ring gear R _1.

Also, a manual (MAN) in the "D" range
In the first speed in the UAL) mode, the engine driving state, the input to the ring gear R _1, in the locking of the carrier C ₂ by the locking of the one-way clutch F-2, the reaction force rotation by reversal of the sun gear S ₁ is the ring gear R Output as ₂ forward rotation. In contrast, coasting is the engagement of the carrier C ₂ input by the engagement of the brake B-3 to the ring gear R _2, outputs reaction force rotation by reversal of the sun gear S ₁ is a forward rotation of the ring gear R ₁ Is done.

Next, the structure of the engine brake control circuit of the hydraulic control device for controlling the clutch and brake of the gear train will be described with reference to FIG. This circuit is
A supply of line pressure (P _L ) in which the discharge pressure of a pump (not shown) is adjusted by the primary regulator valve according to the vehicle running load, and the “D” range pressure (P _D) is selected according to the switching position by operating the shift lever. ), "2" range pressure,
A manual valve 1 is provided for outputting "L" range pressure (P _L ) and "R" range pressure (P _R ) to each oil passage. The figure shows the neutral state of the manual valve 1.

The oil passages L1 and L2 to which the "D" range pressure (P _D ) and the "L" range pressure (P _L ) are supplied from the manual valve 1 have engine brakes at the first speed and the second speed. To achieve this, a coast brake relay valve 2 is interposed as a switching valve. This relay valve 2
"D" range pressure (P _D) and "L" range pressure (P _L) either selective engine braking achieved friction engagement elements, that is, in this embodiment, the brake B-3
And a switching valve that controls the supply to the brake B-1, and more specifically, performs a function of supplying to one side and shutting off and discharging the other side. Therefore, coast brake relay valve 2
Has lands 21 and 22 at both ends and is slidable in the valve hole, a return spring 23 for applying a spring return force to one end of the spool 20, and a displacement force by a signal pressure to the other end. And a plunger 24 slidable within the valve hole.

The oil passage L3 to which the hydraulic pressure is supplied via the coast brake relay valve 2 is branched into two, and the signal pressure output from the shift solenoid valve S1 indicated by an abbreviation in FIG. The hydraulic pressure generated in the oil passage due to the closing of the solenoid valve is switched between the second speed and the third speed in accordance with the solenoid pressure (P _S1 ), and the circuit is connected to the oil passages capable of achieving the respective gears. A 2-3 shift valve 3 for setting a state is connected.

2-3 One output oil passage L4 of shift valve 3
Switches between the first speed and the second speed in accordance with the solenoid pressure (PS ₂ ) output from the shift solenoid valve S2, also indicated by an abbreviation, to form an oil passage capable of achieving the respective gears. It is connected to a 1-2 shift valve 4 to be connected. The corresponding output oil passage L5 of the 1-2 shift valve 4
Is connected to a brake B-3 as a friction engagement element for achieving the first speed engine brake. The valve inserted in the oil passage L4 connecting the 2-3 shift valve 3 and the 1-2 shift valve 4 is a low coast modulator valve 5. The modulator valve 5 in accordance with the first speed of the engine required engagement torque of the brake achieved when the brake B-3, vacuum supplied by "D" range pressure (P _D) over the 2-3 shift valve 3 Then, it is supplied to the 1-2 shift valve 4.

The other output oil passage L6 of the 2-3 shift valve 3
Is directly connected to the 1-2 shift valve 4, and the corresponding output oil passage L7 of the 1-2 shift valve 4 passes through the second coast modulator valve 6 to provide a brake as a friction engagement element for achieving the second speed engine brake. B-1. The second coast modulator valve 6 is also supplied with the "D" range supplied through the 2-3 shift valve 3 and the 1-2 shift valve 4 in accordance with the required engagement torque of the brake B-1 when achieving the second speed engine braking. This is for reducing the pressure (P _D ).

The second coast modulator valve 6
The valve 7 inserted in the oil passage L7 connecting the brake B-1 for achieving the second speed engine brake is a cutoff valve. The cutoff valve 7 switches between a manual mode and an automatic transmission mode to change the speed of supplying hydraulic pressure to the brake B-1 as a friction engagement element for achieving the second speed engine brake. It fulfills the function of improving the brake engagement response.

The hydraulic pressure (P _L ) of the line pressure hydraulic passage is supplied to the outer end of the plunger 24 of the coast brake-release valve 2 through an orifice. A normally-closed type in which a signal is released when turned on or applied when turned off (in this specification, an output includes both release and application of a signal pressure. Therefore, output of a signal pressure does not necessarily mean supply of pressure). The on / off solenoid valve S3 is provided as the first solenoid valve according to the present invention. The signal pressure oil passage LS3 is also connected to the spool end of the cutoff valve 7 so that a signal pressure can be applied.

According to a feature of the present invention, the coast brake relay valve 2 includes a separate plunger 24 abutting on the end of the spool 20, and has a second pressure receiving portion at the end of the spool 20. Therefore, the spool 20 applies the solenoid pressure (P _{S 3} ) to the outer end of the plunger 24 and the solenoid pressure (P _{S 3} ) to the end of the spool 20 described later.
_{S 4} ) The “D” range pressure oil passage L
1 and the drain connection of the oil passages L3 to L7 downstream thereof.

The oil pressure (P _L ) of the line pressure oil passage is supplied to the signal pressure oil passage LS4 for applying the solenoid pressure (P _{S 4} ) to the second pressure receiving portion through an orifice. A normally-closed on-off solenoid valve S4 for releasing when turned on or applying voltage when turned off is provided. A coast brake control valve 8 is interposed in the oil passage LS4. Coast brake control valve 8
A spring-return type spool valve that opens and closes by applying a signal pressure to the spool end. In this embodiment, the signal pressure for detecting the first speed is applied to a frictional clutch engaged to achieve the gear position. Supply pressure to brake B-2 as composite element (P _{B 2} )
It has been. The signal pressure (P _{B 2} ) is always supplied at the second speed or higher, as can be seen with reference to FIG.
Is always kept in the shut-off state except when the first speed is achieved.

FIG. 4 shows the first of the solenoid valves shown in FIG.
The operation charts at the high speed and the second speed are extracted and the solenoid signal patterns are shown. As shown in the figure, the shift solenoid valve S1 is always on (released in the present embodiment) in both the first speed (1st) and the second speed (2nd). Also, the shift solenoid valve S2 is turned on (also released) at the second speed.
It is said. The solenoid valve S3 is turned on (same release) only when the engine brake (E / G) is achieved, whereas the solenoid valve S4 is turned on (same release) only when the first speed engine brake is achieved. Have been. Accordingly, in the second speed, when the signal is turned off due to a lack of a signal of the solenoid valve S2 or the like, and the signal pattern when the normal first speed engine braking is achieved, the solenoid valve S4
Can be identified by the signals on and off being reversed.

The hydraulic circuit having such a configuration operates as follows. First, the first speed auto (AUTO) mode, by turning on the shift solenoid valve S1 of the normally closed, it until 2-3 solenoid pressure that has been applied to the spool end of the shift valve 3 (P _{S 1)} is To be released, the spool switches to the position shown in the right half of the drawing. Further, since the solenoid valve S3 are to be turned off, coast brake relay valve 2 is now applied to the solenoid pressure (P _{S 3)} to the outer end of the plunger 24, the manual valve 1 by the land 22 of the spool 20 Oil passage L1 from
And the oil passages L3 to L5 downstream therefrom are drain-connected via the oil passage L2 and the manual valve 1. Thereby, the brake B-3 for achieving the first speed engine brake is achieved.
Is discharged and engine braking is not achieved.

On the other hand, a manual (MANUA)
L) In the case of the first speed in the mode, the shift solenoid valve S
1 and both solenoid valves S3 and S4 are turned on. As a result, the coast brake relay valve 2 is released from applying the solenoid pressure (P _S3 ) to the end of the plunger 24,
The spool 20 is at the right half position in the figure. Also, 2-3
The shift valve 3 is at the spool position shown in the right half of the drawing for the above-described reason. Moreover, the 1-2 shift valve 4, because of the state of application of the solenoid pressure (P _{S 2),} is in the spool position shown in half rightward. Therefore, in this case, manual "D" range pressure supplied from the valve 1 (P _D) is supplied to the low coast modulator valve 5 via coast brake relay valve 2 and the 2-3 shift valve 3, where it was vacuum The modulator pressure is supplied to the brake B-3 via the 1-2 shift valve 4. This state is shown in the figure by marking the oil passages with ● and ○ marks.

Next, the second speed in the auto (AUTO) mode corresponds to the two-shift solenoid valve S1 and the solenoid valve S2.
Is turned on and the solenoid valve S3 is turned off. At this time, the coast brake relay valve 2 is applied with the solenoid pressure (PS ₃ ) to the outer end of the plunger 24 as in the case of the first speed in the automatic mode. Supply oil passage L1
And the oil passages L3, L5, L6 downstream therefrom are drain-connected via the oil passage L2 and the manual valve 1.
As a result, the hydraulic pressure of the brake B-1 for achieving the second speed engine brake is discharged, and the engine brake is not achieved.

Further, the second speed in the manual mode is achieved by turning on the solenoid valves S1 and S2 for both shifts and the solenoid valve S3. In this case, coast brake relay valve 2 is released to the application of solenoid pressure to the plunger 24 ends (P _{S 3),} the spool position shown right half. Further, the 2-3 shift valve 3 is at the spool position shown in the right half of the figure for the above-described reason. Furthermore,
1-2 shift valve 4 also, because in the released state of the solenoid pressure (P _{S 2),} is in the spool position shown in half leftward.
Therefore, in this case, manual "D" range pressure supplied from the valve 1 (P _D) is supplied to the low coast modulator valve 5 via coast brake relay valve 2 and the 2-3 shift valve 3, where it was vacuum The modulator pressure ( _PDM ) is supplied to the 1-2 shift valve 4, but is shut off by the shift valve 4 and is not supplied to the brake B-3. On the other hand, coast brake relay valves 2 to 2-
3 via the shift valve 3,1-2 shift valve 4 is supplied to the second coast modulator valve 6 in "D" range pressure (P _D) is led to cut-off valve 7 is reduced in pressure by the modulator valve 6, it After that, it is supplied to the brake B-1. Therefore, in this case, the engine brake is achieved by the engagement of the brake B-1.

In this embodiment, at the time of the third speed,
There is a difference between ON and OFF of the solenoid valve S3 between the auto mode and the manual mode. In this case, regardless of the presence or absence of the output of the coast brake relay valve 2, the hydraulic pressure to the engine brake related oil passage is controlled by the 2-3 shift valve 3. No supply is made. In this case, the gear train is directly connected.

Next, at another shift speed according to the subject of the present invention, that is, at the time of achieving the second speed, the shift solenoid valve S
If 2 has failed in an off state in chipping and other emergency signal, the 1-2 shift valve 4 is in the application of the solenoid pressure (P _{S 2),} it is switched first speed (the right half) position, thereby The gear train is shifted down to the first speed achievement state. At this time, if no special measures are taken, the circuit will be in a state in which the first-speed engine braking in the manual mode can be achieved, and a stronger engine braking state than expected by the driver during the coast will occur.

On the other hand, in this embodiment to which the present invention is applied, the second solenoid valve S4 is turned off, so that the first speed engine brake can be prevented from being applied. That is, in this case, the brake B being supplied to the coast brake control valve 8 at the second speed or higher.
The -2 pressure (P _{B 2} ) is released in the shift to the first speed, whereby the coast brake control valve 8 is opened. As a result, the solenoid pressure (P _{S 4),} via the coast brake control valve 8 is applied to the coast brake relay valve 2, depressed De "D" range pressure oil passage L1 of the spool 20 is cut off, at the same time, The oil passages L3 to L5 downstream therefrom are drain-connected via the oil passage L2 and the manual valve 1. As a result, the oil pressure in the oil passage portion indicated by a circle in the figure is discharged in spite of the first speed state in the manual mode, and the engine brake avoidance state can be obtained.

Thus, according to this embodiment, "D"
Addition of control valve and solenoid valve to various failures such as missing solenoid signal, malfunction of solenoid valve, stick of shift valve, etc. in the hydraulic control circuit that enabled first and second speed engine braking in the range By doing so, it is possible to mechanically cope with the situation, and it is possible to avoid an uncomfortable feeling when the downshift to the first speed occurs due to the failure by canceling the engine brake achievement state.

As described above, the present invention has been described based on one embodiment. However, the present invention can be modified by changing the specific structure of various details within the scope of the individual claims. Can be implemented.

[Brief description of the drawings]

FIG. 1 is a partial circuit diagram of a hydraulic control device according to an embodiment to which the present invention is applied.

FIG. 2 is a skeleton diagram showing a gear train of the automatic transmission according to the embodiment.

FIG. 3 is an operation chart of the automatic transmission according to the embodiment.

FIG. 4 is a chart showing a solenoid signal pattern extracted from the operation chart.

[Explanation of symbols]

 B-1 Brake (Friction engagement element) B-3 Brake (Friction engagement element) S3 Solenoid valve (First solenoid valve) S4 Solenoid valve (Second solenoid valve) 2 Coast brake relay valve (Switching valve) 3 2-3 shift valve 4 1-2 shift valve (shift valve) 8 Coast brake control valve (control valve)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhito Yamada 10 Takane, Fujii-machi, Anjo, Aichi Prefecture Inside Aisin AW Co., Ltd. No. 10 Inside Aisin AW Co., Ltd. (72) Inventor Hiroyuki Tsukamoto No. 10 Inside Aisin AW Co., Ltd. (72) Inventor Kazunori Ishikawa Takane Fujiicho, Anjo City, Aichi Prefecture No. 10 Inside Aisin AW Co., Ltd. (72) Inventor Kunihiro Iwazuki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Tohru Matsubara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile (72) Inventor Keihan Fukumura 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Akita Shinji Kasuga 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Koji Taniguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (4)

[Claims] 1. An automatic transmission capable of achieving an engine braking state by engaging different friction engagement elements at a predetermined shift speed and another shift speed, wherein a hydraulic pressure for controlling the friction engagement elements is provided. The control device includes a switching valve that controls supply and discharge of hydraulic pressure to and from the friction engagement element, and a first solenoid valve that outputs a signal pressure for controlling the hydraulic supply and discharge to the switching valve. A hydraulic control device for an automatic transmission, comprising: a second solenoid valve that outputs a different signal pressure at the predetermined shift speed and another shift speed; and shifting to a predetermined shift speed in a state where hydraulic pressure can be supplied by the switching valve. And a control valve for applying a signal pressure output from the second solenoid valve to the switching valve, and when shifting to a predetermined gear, discharging the hydraulic pressure by the switching valve causes the friction engagement element to Engine brake state due to engagement A hydraulic control device for an automatic transmission, characterized by avoiding achievement of the above. 2. The hydraulic control of an automatic transmission according to claim 1, wherein the control valve connects the second solenoid valve to a switching valve by a signal pressure applied by shifting to the predetermined shift speed. apparatus. 3. Between the switching valve and the friction engagement element,
The hydraulic control device for an automatic transmission according to claim 1, wherein a shift valve that switches between the predetermined shift speed and another shift speed is disposed. 4. The hydraulic control for an automatic transmission according to claim 1, wherein the predetermined speed is a first speed, and the other speed is a speed higher than the first speed. apparatus.