JP2717093B2 - Lockup control device for automatic transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for controlling lockup of a torque converter of an automatic transmission.

(Prior Art) In recent years, in a lock-up control device for an automatic transmission having a torque converter, development of slip control of a lock-up clutch has been attempted to improve fuel efficiency.

Such a conventional lockup control device for an automatic transmission is as follows.

For example, the lock-up control device shown in FIG. 4 is a vehicle repair manual ('83 -10, No. 10305) issued by Mitsubishi Motors Corporation.
202), on page 14 wherein the damper clutch (lockup clutch) of the torque converter is switched by switching the damper clutch (lockup clutch) control valve 1 by on / off control of the solenoid valve 2. The lock-up / slip control of No. 3 is performed. The fail safe is performed by computer software.

The lock-up control device shown in Fig. 5 is based on the automobile repair manual ('85 -8, Corona FF, 6109) issued by Toyota Motor Corporation.
The lock-up signal valve 5 is operated by ON / OFF control of the solenoid valve 4 to lock-up the hydraulic signal from the valve 5 via the oil passage L1. The signal is input to a relay valve 6 and the valve 6 is switched to perform lock-up / slip control of a lock-up clutch 7 of the torque converter. A lock-up oil pressure signal to the lock-up clutch 7 is supplied from the 1-2 shift valve 8 through the lock-up signal valve 5 and the lock-up relay valve 6, and the failure of the hydraulic circuit causes a failure. Safe is established.

The lock-up control device shown in Fig. 6 is based on the page C of the automobile repair manual (Atlas, RE4R02A) issued by Nissan Motor Co., Ltd.
33, a shuttle shift valve 11 is connected between the lock-up control valve 9 and the lock-up solenoid 10, and the shuttle shift valve 11 is connected to the shift valve 12 through the oil passage L2. The switching is controlled by a hydraulic pressure signal supplied through the switch. When the lock-up solenoid 10 is stuck in the ON state, the shuttle shift valve 11 operates to turn on the lock-up clutch 14 only at the second, third and fourth speeds, and does not turn on at the first speed and reverse. Thus, fail-safe is established in the configuration of the hydraulic circuit.

(Problems to be Solved by the Invention) However, the lock-up control device in the conventional automatic transmission as described above has the following disadvantages.

That is, in the lock-up control device shown in FIG. 4, the fail-safe is performed only by the computer software, and the fail-safe is not established in the configuration of the hydraulic circuit. If the stick is stuck in the ON state, there is a possibility that the engine may stall when starting the engine at the 1st speed and the reverse.

In the lock-up control device shown in FIG. 5, even if the solenoid valve 4 fails, fail-safe is established due to the hydraulic circuit configuration. However, when the lock-up / slip control of the lock-up clutch is performed by duty control, Since the lock-up signal valve 5 is interposed on the way, there is a disadvantage that the response is poor.

In the lock-up control device shown in FIG. 6, even if the lock-up solenoid 10 fails, the fail-safe is established due to the hydraulic circuit configuration, but the orifice 13 is located between the lock-up solenoid 10 and the shuttle shift valve 11.
And the overall length of the shuttle shift valve 11 is long, so that the configuration of the hydraulic circuit is large and complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems in the lock-up control device for a conventional automatic transmission. That is, the present invention can achieve fail-safe in the configuration of the hydraulic circuit, has excellent responsiveness to a hydraulic signal, has a simple hydraulic circuit configuration, and has a high degree of freedom in design. It is intended to provide a control device.

(Means for Achieving the Object) To achieve the above object, the present invention provides a lock-up control valve connected to a lock-up clutch of a torque converter and a lock-up control solenoid for controlling the switching of the lock-up control valve. A lock-up control solenoid valve, the lock-up control valve is switched to a lock-up clutch engagement side by connecting a spool switching chamber of the lock-up control valve to a drain, and the spool switching chamber and the drain are connected to each other. In the lock-up control device of the automatic transmission, which is switched to the lock-up clutch releasing side by disconnecting the connection of the lock-up clutch, the lock-up control valve has a spool switching chamber and a locker. A lock-up fail valve is connected between the lock-up control solenoid valve and a first port connected to the spool switching chamber and a second port connected to the lock-up control solenoid valve. And a first chamber for urging the spool of the lock-up fail valve to the first position connecting the first port and the second port, and a second position for urging the spool between the first port and the second port. A second chamber, and a spring interposed in the second chamber for urging the spool in the same direction as the hydraulic pressure in the second chamber, wherein a D-range is provided to the first chamber from a shift hydraulic control circuit of the automatic transmission. Pressure is input and the B1 brake pressure is input to the second chamber, and the spool of the lock-up fail valve moves to the D range pressure and the B1 brake pressure. And or when D range pressure key pressure is equivalent
When the B1 brake pressure is no longer input, the switch is switched to the second position, and when the B1 brake pressure is reduced and becomes smaller than the D range pressure, the switch is switched to the first position.

(Operation) Control of engagement / disengagement of the lock-up clutch of the torque converter by the lock-up control device of the automatic transmission is basically performed by on / off control of a lock-up control solenoid valve. The valve switches the lock-up control valve to the lock-up clutch engagement side by connecting the spool switching chamber of the lock-up control valve to the drain, thereby introducing the engagement hydraulic pressure to the lock-up clutch, and the lock-up control solenoid valve. Disconnects the connection between the spool switching chamber and the drain, switches the lock-up control valve to the lock-up clutch releasing side, discharges the engagement hydraulic pressure from the lock-up clutch, and releases the clutch. Release hydraulic pressure to the switch.

A lock-up fail valve connected between the spool switching chamber of the lock-up control valve and the lock-up control solenoid valve reduces the B1 brake pressure input to the second chamber and inputs the B1 brake pressure to the first chamber. When the pressure is lower than the D range pressure (line pressure), that is, on the high speed side of each shift range, the D range pressure in the first chamber is larger than the sum of the B1 brake pressure in the second chamber and the spring force of the spring. When it becomes larger, it is switched to the first position side,
By connecting the first port and the second port, switching control of the lock-up control valve by the lock-up control solenoid valve is permitted.

However, when the B1 brake pressure introduced into the second chamber of the lock-up fail valve becomes the same as the D range pressure, that is, the line pressure, that is, 1 in each shift range.
When the shift solenoid valve of the gear stage or the hydraulic control circuit of the automatic transmission is out of order, or when the D range pressure and B1 brake pressure are no longer input to the lock-up fail valve, that is, when the shift range is reverse, The spool of the lock-up fail-valve is switched to the second position to disconnect the connection between the first port and the second port, so that the lock-up control valve spool switching chamber is independent of the operation of the lock-up control solenoid valve. And drain connection.

Due to the operation of the lock-up fail valve as described above, even if the lock-up control solenoid valve fails, the engagement of the lock-up clutch becomes inconvenient, such as the above-described low speed stage and reverse range of each shift range. In this case, the lock-up control valve is held on the lock-up clutch release side, and fail-safe is established.

(Examples) Hereinafter, the present invention will be described in more detail based on examples shown in the drawings.

FIG. 1 shows a lock-up control circuit portion of a hydraulic control circuit of an automatic transmission, in which reference numeral 20 denotes a lock-up clutch (hereinafter, L / U clutch) of a torque converter, and reference numeral 21 denotes a lock-up control valve (hereinafter, L / U clutch). U control valve), 22 is a primary regulator valve, 23 is a normally closed type lock-up control solenoid valve (hereinafter L / U control solenoid valve), 24 is a torque converter control valve, and 25 is a pressure modifier valve These are the same as the hydraulic control circuit of the conventional automatic transmission.

The lock-up control device for an automatic transmission according to the present invention includes:
A lock-up fail valve 26 is provided between the L / U control valve 21 and the L / U control solenoid valve 23.
(Hereinafter, an L / U fail valve) is newly added, and the operation of the L / U fail valve 26 is controlled by two types of hydraulic pressures, as described later.

Next, before describing the connection and operation of the L / U fail valve 26, the L / U control valve 21 and
The general operation control of the lock-up clutch by the L / U control solenoid valve 23 will be described.

The upper and lower chambers 21B and 21C of the spool 21A of the L / U control valve 21 have ports 21a and 2c respectively.
The control oil pressure is input from the pressure modifier valve 25 via 1b, and when oil pressure is applied to both the upper and lower chambers 21B and 21C,
When the sum of the oil pressure in the lower chamber 21C and the spring force of the spring 21D interposed in the lower chamber 21C becomes larger than the oil pressure in the upper chamber 21B, the spool 21A slides upward. At this time, the oil pressure from the primary regulator valve 22 is
The oil is supplied to the torque converter lock-up release oil passage L11 via the 1c-port 21d, and the lock-up clutch 20 is released.

When the L / U control solenoid valve 23 connected to the lower chamber 21C of the L / U control valve 21 is turned on and the hydraulic pressure in the lower chamber 21C is drained, the L / U
The control valve spool 21A is the upper chamber 21B
It is urged by the internal oil pressure and slid downward (the state shown in FIG. 1). At this time, the torque converter lock-up release oil passage L11 is connected to the drain, and the hydraulic pressure input from the primary regulator valve 22 to the port 21e via the oil passage L12 instead flows from the port 21f to the torque converter lock-up oil passage L13. And the lock-up clutch 20 is engaged.

The L / U fail valve 26 is connected between the lower end chamber 21C of the L / U control valve 21 and the L / U control solenoid valve 23 as described above. Port 26a (first port)
L / U control solenoid valve 23 is connected to port 26b
(The second port), and an oil passage L14 which D range pressure P _D to be described later is supplied oil passage L15 which is also the B1 brake pressure P _B to the port 26c is supplied is connected to the port 26 d. A lower chamber 26C to which the oil passage L15 is connected via the port 26d.
In the (second chamber), the spring 26D has a spool 26A
Is provided so as to urge upwardly.

The hydraulic pressure in the upper chamber 21B (first chamber) connected to the oil passage L14 via the port 26c and the lower chamber 2
According to the relationship between the oil pressure in 1C and the spring force of the spring 26D, the port 26a is connected to the port 26b when the spool 26A is in the raised position as shown in FIG. 1, and when the spool 26A is in the lowered position. Cuts off the connection between the port 26a and the port 26b, and cuts off the connection of the lower end side chamber 21C of the L / U control valve 21 to the drain regardless of the operation of the L / U control solenoid valve 23. .

FIG. 2 shows a hydraulic control circuit of an automatic transmission for third forward speed including the above-mentioned lock-up control device. FIG. 3 shows a gear that is switched by the hydraulic control circuit of FIG. The train is shown. In Fig. 2, 27 is B
-1 control and boost valve, 28 is a 1-2 shift valve, 29 is a 2-3 shift valve, 30 is a normally closed type shift control connected to the B-1 control and boost valve 27 and the 1-2 shift valve 28 Solenoid valve 31 is 2-3 shift valve 29
Shift control solenoid valve connected to, 32
Is a manual valve, 33 is a duty control valve, 34 is a pressure control solenoid valve, 35 is a 2-3-3 / 2 timing valve, 36 is a low coast modulator valve, 37 is a B-1 and accumulator control valve, 38 is a C-1 accumulator.

The operation of each engagement element of the gear train in FIG. 3 at each shift speed is as shown in Table 1 below, and the operation of shift control solenoid valves 30 and 31 in the hydraulic control circuit at this time is as follows. As shown in Table 2.

Port 26c on the upper end side of L / U fail valve 26 described above
The oil passage L14 is connected to the D range pressure output port 32a of the manual valve 32 so that the D range pressure (line pressure) P _D is input, and the lower port 26d is
Oil passage L15 is B-1 control and boost valve 27
So that the the B1 brake pressure P _B is inputted by B1 is connected to the brake pressure output port 27a of the.

Next, the operation of the hydraulic control circuit of FIG. 2 will be described.

(1) Pressure generation Oil pressure is generated by the oil pump by the engine rotation,
The pressure is adjusted to a constant pressure by the regulator valve 22 (hereinafter, this oil pressure is referred to as line pressure). This line pressure is controlled by manual valve 32, L / U control valve 21, pressure modifier valve 25 and duty control valve.
Entered in 33. The line pressure input to the pressure modifier valve 25 is reduced to generate a modifier pressure, and this modifier pressure is applied to the lower end of the L / U control valve 21, the duty control valve 33, and the orifice 41-L / U control valve. Output to port 26a of L / U fail valve 26 via chamber 21C-oil passage L16.

The duty control valve 33 generates a duty control pressure by the line pressure and the modifier pressure and the on / off control of the attached pressure control solenoid valve 34, and the duty control pressure is used as a B-1 and accumulator control valve.
37, L / UACC control valve (port 21g) above L / U control valve 21, backup port 22a for regulator valve 22 and 2-3 / 3-2 timing valve 35
Output to On the other hand, the pressure adjustment port of the regulator valve 22
After the line pressure is input from the port 22c to the torque converter control valve 24 from the port 22c through the bypass orifice 42 and is regulated (hereinafter, the regulated hydraulic pressure is referred to as the converter pressure), the L / U control valve 21 Is output.

(2) N range and P range The line pressure input from the regulator valve 22 to the manual valve 32 is sealed or drained by the manual valve 32, and there is no hydraulic output to the shift valve.

(3) 1st speed D range The line pressure becomes 2 by switching the manual valve 32.
Output from the B-1 control and boost valve 27 via the -3 shift valve 29, the 1-2 shift valve 28 and the orifice 43 to the propulsion chamber and the L / U of the B1 brake servo 44 from the B-1 control and boost valve 27.
Output to the fail valve 26. As a result, the band brake B1 is engaged, and the first speed in the D range is established (see Table 1).

At this time, as shown in Table 2, the solenoid valve 30 is off and the solenoid valve 31 is on, whereby the hydraulic pressure input to the 2-3 shift valve 29 and the 1-2 shift valve 28 is reduced. Sealed.

B-1 and accumulator control valve 37
Adjusts the line pressure by the duty control pressure input from the duty control valve 33,
The secondary pressure is output (hereinafter, this secondary pressure is referred to as an accumulator control pressure). This accumulator control pressure is applied to the back pressure chamber of the C-1 accumulator 38 and the B-
1 Output to control and boost valve 27, but B
The -1 control and boost valve 27 seals the accumulator control pressure.

(4) D range 2nd speed As shown in Table 2, both solenoid valves 30 and 31 are turned on, and 1-2 shift valve 28 and B-1 control and boost valve 27 are switched. As a result, the accumulator control pressure is input to the propulsion chamber of the B1 brake servo 44 instead of the line pressure of the D range first speed.
At the same time, the accumulator control pressure is input to the lower chamber 21C of the L / U fail valve 26. On the other hand, when the solenoid valve 30 is turned on, the 1-2 shift valve 28 is switched, and the line pressure is input to the C1 clutch and the propulsion chamber of the C-1 accumulator 38 via the C1 orifice 45. As a result, as shown in Table 1, the second speed in the D range is established.

(5) D range 3rd speed As shown in Table 2, the solenoid valve 30 remains on, the solenoid valve 31 is turned off, the 2-3 shift valve 29 is switched, and the line from the 2-3 shift valve 29 Orifice 4 depending on the level of duty control pressure
6, 47 is selected and input to the 2-3 / 3-2 timing valve 35, and is input to the back pressure chamber of the B1 brake servo 44 via this valve 35.
It is input to the C2 clutch via the shift valve 29. Thus, the D range 3 speed is established by releasing the band brake B1 and engaging the C2 clutch (see Table 1).

(6) D range 3 → 2nd speed shift down When the solenoid valve 31 is turned on, the 2-3 shift valve 29 is switched upward, and the hydraulic pressure is supplied from the back pressure chamber of the B1 brake servo 44 to the orifice 47 and the check ball, or It is drained from the drain port of the 2-3 shift valve 29 via the 2-3 / 3-2 timing valve 35 and the orifice. Further, the manual valve 32 is drained from the C2 clutch via a 2-3 shift valve 29, a 1-2 shift valve 28 and a low coast modulator valve 36.

(7) D range 2 → 1st shift down When the solenoid valve 30 is turned off, the 1-2 shift valve 28 and the B-1 control and boost valve 27 are switched downward, and the check ball, 1 It is drained from a drain port via a -2 shift valve 28 and a 2-3 shift valve 29. Further, in the engagement chamber of the B1 brake servo 44, only the hydraulic pressure input by the switching of the 1-2 shift valve 28 changes from the accumulator control pressure to the line pressure.

(8) 2nd range 1st, 2nd, 3rd speed The 2nd range 1st, 2nd speed is the same as the D range 1st, 2nd speed, respectively. The downshift of the second range and the third speed is performed by detecting the vehicle speed.

(9) L range 1st speed The line pressure is output from the port 32a of the manual valve 32 in the same manner as in the D range 1st speed.
After the line pressure is output from the port 32b to the port 29a of the 2-3 shift valve 29 to urge the valve 29 not to be switched downward, and after the line pressure from the port 32b is reduced by the low coast modulator valve 36, , 1-2 shift valve 28 and 2-3 shift valve 29 to output to the C2 clutch.

(10) L range second speed 1-2 shift valve by turning on solenoid valve 30
28 switches to the upward direction, port 32b of manual valve 32
Line pressure is sealed by a 1-2 shift valve 28,
The hydraulic pressure from the C2 clutch is 2-3 shift valve 29,1-
It is drained through a two-shift valve 28 and a manual valve 32. By detecting the vehicle speed, L range 2nd speed → 1
The downshift of the speed is performed, and the upshift is not performed.

(11) The line pressure is B- from the port 32c of the reverse manual valve 32.
1 Via the control and boost valve 27 to the backup port 22a of the regulator valve 22,
Reverse is established by outputting to the C2 clutch via the 2-shift valve 28 and 2-3 shift valve 29 and to the B2 brake via the B2 orifice 48. At this time, the hydraulic pressure for establishing the forward range is drained via the manual valve 32. When switching from the reverse range to the neutral range, the hydraulic pressure from all the engagement elements from the B2 brake via the B2 check valve 49 is drained via the manual valve 32 due to the flow reverse to that at the time of supply. .

(12) When the solenoid valves 30 and 31 fail If the solenoid valve 30 and the solenoid valve 31 are both off due to a failure, the vehicle starts in the 3rd speed while in the D range. At this time, the port 32a of the manual valve 32
Is input to the backup port 22a of the regulator valve 22 via the 2-3 shift valve 29 and the B-1 control and boost valve 27, and the line pressure is increased. Further, the line pressure from the manual valve 32 is input to the back pressure chamber of the B1 brake servo 44 via the orifice 46 or 47 and the 2-3-3 / 2 timing valve 35, whereby the band brake B1 is released and 2 It is supplied to the C2 clutch via the -3 shift valve 29, and is further input to the C1 clutch from the 1-2 shift valve 28.

(13) Lock-up and lubrication system The on / off control of the lock-up clutch 20 is performed by the L / U control solenoid valve 23. In each range, L / U is set only when the D range is the second speed, the third speed, and the L range is the second speed. The operation of the control solenoid valve 23 becomes effective. That is, as described with reference to FIG.
When the L / U control solenoid valve 23 is turned on at the 3rd speed, the 3rd speed or the 2nd speed of the L range, the lower chamber 21C of the L / U control valve 21 is drained. The lock-up clutch 20 is engaged by being supplied to the lock-up oil passage L13. The back pressure of the lock-up clutch 20 is
Drained through 21d and drain port. Also, L /
The pressure oil output from the U control valve 21 is supplied as lubricating oil to the gear train via the cooler bypass valve 39 and the cooler 40 via the orifice 50.

When the L / U control solenoid valve 23 is off, the spool 21A of the L / U control valve 21 is held at the raised position by the L / U control solenoid valve 23, so the oil pressure in the lock-up oil passage L13 is supplied from the drain port. Drained, instead line pressure at ports 21c and 21d
Via the torque converter lockup release oil passage L11
And the lock-up clutch 20 is released. On the other hand, the pressure oil that has passed through the torque converter returns to the L / U control valve 21 through the lock-up oil passage L13, and the orifice 50 or the port 21h, the cooler bypass valve 39,
The lubricant is supplied to the gear train via the cooler 40.

Next, operation of the L / U control solenoid valve 23 and establishment of fail-safe by the solenoid valve 23 will be described.

The port 26c of the L / U fail valve 26, as described above, D range pressure from the manual valve 32 is input, also from B1 control and boost valve 27 B1 brake pressure P _B is input to the port 26d And the D range pressure P _D in the upper end chamber 26B of the L / U fail valve 26, the B1 brake pressure P _B and the spring 2 in the lower end chamber 26C.
Spool according to the magnitude relationship with the sum of the spring force of 6D
26A is switched.

The operation of the L / U fail valve 26 in each shift range is as shown in Table 3 below. Note that in Table 3
B1 Hydraulic p columns of the brake pressure P _B shows a state in which the line pressure is smaller than the size P of the reduced pressure has been D-range pressure P _D by B1 and the accumulator control valve 37 (e.g., P Is 5 kg / cm ² and p is 3 kg / c
m ^2). When the B1 brake pressure P _B is reduced (when the pressure is p), the relationship is set so that P> p + spring force. At this time, the spool 26A of the L / U fail valve 26 is set to the D range pressure. Spring 2 energized by P _D
It is switched to the drawing downward against 6D, passed ports 26a and 26b communicate with each other, when the D range pressure P _D and the B1 brake pressure P _B is the same size is switched to the drawing direction the spool 26A is by the spring 26D As a result, communication between the ports 26a and 26b is cut off.

Here, when the L / U control solenoid valve 23 sticks in the ON state, that is, when the solenoid valve 23
Is in the open state, D range 1st gear,
When the shift control solenoid valves 30 and 31 fail, the lock-up clutch 20 is set in each of the D range third speed, the L range first speed, and the reverse shift state.
Are required to be prevented from engaging. Therefore, in each of these shift states, the L / U control valve
The connection between the lower end chamber 21C of 21 and the drain is cut off, the spool 21A is urged to the raised position, and hydraulic pressure is supplied from the primary regulator valve 22 to the torque converter lock-up release oil passage L11 via the ports 21c and 21d. Need to be

Therefore, when such a demand is attempted to be satisfied by the L / U fail valve 26, as shown in Table 4 below, the shift state of each range in which the engagement of the lock-up clutch 20 is required to be prevented is required. In this case, the spool 26A of the L / U fail valve 26 is switched to the raised position, and the connection between the ports 26a and 26b is cut off, thereby irrespective of the operation state of the L / U control solenoid valve 23. It is necessary to cut off the connection between the lower end chamber 21C and the drain. In other shift states,
In order to connect 26a and 26b, the spool 26A needs to be held at the lower position.

The Table 4, the Table 3 above D range pressure P _D and B1
When comparing the position of the spool 26A of the L / U fail valve 26 by the action of the brake pressure P _B, becomes the spool position in each shift state match, thus by L / U fail valve 26 L / U control solenoid valve 23
Fail-safe at the time of failure.

(Effects of the Invention) As described above, according to the present invention, fail-safe at the time of failure of the lock-up control solenoid valve can be easily established on the circuit configuration of the hydraulic control circuit of the automatic transmission. The configuration is very simple, the response at the time of fail-safe is fast, and the lock-up fail valve operation is performed because one valve is added and the operation is performed by two different oil pressures from the shift hydraulic control circuit. Since other hydraulic pressures can be used as the hydraulic pressure, the design can be easily changed, and the present invention can be applied to various gear trains.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a lock-up control device showing one embodiment of the present invention, FIG. 2 is a hydraulic control circuit diagram of an automatic transmission including the lock-up control device of the embodiment, and FIG. Skeleton diagram showing the gear train of the automatic transmission shown in FIG.
FIG. 5 is a hydraulic circuit diagram showing a conventional example, FIG. 5 is a hydraulic circuit diagram showing another conventional example, and FIG. 6 is a hydraulic circuit diagram showing still another conventional example. 20 Lockup clutch 21 Lockup control valve 21A Spool 21C Lower chamber (spool switching chamber) 23 Lockup control solenoid valve 26 Lockup fail valve 26A Spool 26B … Top chamber (first chamber) 26C… Bottom chamber (second chamber) 26D… Spring 26a… port (first port) 26b… port (second port) P _D … D range pressure, P _B …… B1 brake pressure

Claims (1)

(57) [Claims] A lock-up control valve connected to a lock-up clutch of a torque converter and a lock-up control solenoid valve for controlling switching of the lock-up control valve, wherein the lock-up control solenoid valve is a lock-up control valve. The lockup control valve is switched to the lockup clutch engagement side by connecting the spool switching chamber to the drain, and the lockup control valve is switched to the lockup clutch release side by disconnecting the connection between the spool switching chamber and the drain. In a lockup control device for a transmission, a lockup valve is provided between a spool switching chamber of the lockup control valve and a lockup control solenoid valve. The lock-up fail valve has a first port connected to the spool switching chamber, a second port connected to the lock-up control solenoid valve, and a first port connected to the lock-up fail valve spool. A first chamber biased toward a first position connecting the first port and the second port;
A second chamber for biasing the first port and the second port to a second position for blocking the first port and a spring interposed in the second chamber for biasing the spool in the same direction as the hydraulic pressure in the second chamber; The D range pressure is input to the first chamber from the shift hydraulic control circuit of the automatic transmission, and is input to the second chamber.
When the B1 brake pressure is input, the spool of the lock-up fail valve is switched to the second position when the D range pressure and the B1 brake pressure are equal or when both the D range pressure and the B1 brake pressure are not input. When the B1 brake pressure is reduced and becomes smaller than the D range pressure, the first
A lock-up control device for an automatic transmission, which is switched to a position side.