JP7586743B2 - Hydraulic control device for automatic transmission - Google Patents

Description

The present invention relates to a hydraulic control device that controls an automatic transmission installed in a vehicle.

A hydraulic control device for an automatic transmission is known that includes a plurality of normally closed solenoid valves that output engagement pressure in an energized state to each of the hydraulic servos of a plurality of hydraulic friction engagement devices, a normally open solenoid valve that outputs hydraulic pressure in a de-energized state, a manual valve that outputs forward range pressure when the range operation position is in the forward range position and outputs reverse range pressure when the range operation position is in the reverse range position, and a switching valve that switches a spool valve to a fail position when the range operation position is in the forward range position and all solenoid valves are de-energized, supplying forward range pressure to a predetermined hydraulic servo among the plurality of hydraulic servos to form a predetermined forward stage, thereby enabling evacuation driving in the event of an all-off fail in which all solenoid valves are de-energized. This is the hydraulic control device for an automatic transmission described in Patent Document 1.

JP 2007-177933 A

However, when the range operation position is switched from the reverse range position to the neutral range position, during so-called garage operation, in order to adjust the engagement pressure of the hydraulic servo of the hydraulic friction engagement device that forms the reverse gear, if the hydraulic pressure from the above-mentioned normally open solenoid valve is supplied as the source pressure of the normally closed solenoid valve that outputs the engagement pressure to this hydraulic servo, there is a problem that when the range operation position is quickly switched from the neutral range to the forward range, the forward range pressure is supplied from the switching valve to the specified hydraulic servo, causing a shock.

The present invention was made against the background of the above circumstances, and its purpose is to provide a hydraulic control device for an automatic transmission that can suppress shocks that occur when in a garage while allowing evacuation driving when all solenoid valves are de-energized.

The gist of the first invention is (a) a hydraulic control device for an automatic transmission that forms a reverse gear and multiple forward gears depending on the engagement state of multiple hydraulic friction engagement devices, (b) multiple normally closed solenoid valves that output engagement pressure to the hydraulic servos of each of the multiple hydraulic friction engagement devices in an energized state, (c) a normally open solenoid valve that outputs hydraulic pressure in a de-energized state, (d) a manual valve that outputs forward range pressure when the range operation position is set to the forward range position and outputs reverse range pressure when the range operation position is set to the reverse range position, and (e) a spool valve that is biased toward a normal position by hydraulic pressure from a first hydraulic servo of the multiple hydraulic servos and a biasing force of a biasing member and is biased toward a fail position by hydraulic pressure from the normally open solenoid valve, and when the range operation position is in the forward range position and all solenoid valves are de-energized, the spool valve is switched to the fail position, and the multiple hydraulic servos are The hydraulic circuit includes a switching valve that supplies the forward range pressure to a second hydraulic servo of the servos to form a predetermined forward stage, and (f) a control device that controls the energization of the normally open solenoid valve, (g) the hydraulic circuit is configured to be able to supply hydraulic pressure from the normally open solenoid valve as the source pressure of a normally closed solenoid valve that outputs an engagement pressure to a hydraulic servo of a hydraulic friction engagement device that forms the reverse stage when the range operation position is switched from the reverse range position to the neutral range position, and (h) the control device is configured to cut off the energization of the normally open solenoid valve on the condition that when the range operation position is switched from the reverse range position to the neutral range position, the hydraulic pressure of the first hydraulic servo is a predetermined hydraulic pressure that does not switch the spool valve element in the switching valve to the fail position due to the hydraulic pressure from the normally open solenoid valve and is maintained in the normal position.

The gist of the second invention is that in the first invention, the control device is further configured to cut off the current to the normally open solenoid valve when the range operation position is switched from the reverse range position to the neutral range position, provided that the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device that forms the reverse stage is a second predetermined hydraulic pressure at which hydraulic control of the hydraulic servo is required.

According to the first invention, when all solenoid valves are de-energized while the range operation position is in the forward range position, the spool valve of the switching valve is switched to the fail position by the hydraulic pressure from the normally open solenoid valve, and the forward range pressure is supplied from the switching valve to the second hydraulic servo to form a predetermined forward stage. This enables evacuation driving using the predetermined forward stage. In addition, when the range operation position is switched from the reverse range position to the neutral range position, the hydraulic pressure from the normally open solenoid valve is supplied as the source pressure of the normally closed solenoid valve that outputs engagement pressure to the hydraulic servo of the hydraulic friction engagement device that forms the reverse stage, making it possible to hydraulically control the hydraulic servo of the hydraulic friction engagement device that forms the reverse stage, and suppressing shocks that occur during the switching transition period. At this time, the normally open solenoid valve is de-energized under the condition that the hydraulic pressure of the first hydraulic servo is a predetermined hydraulic pressure that does not switch the spool valve of the switching valve to the fail position due to the hydraulic pressure from the normally open solenoid valve and maintains it in the normal position, so that the spool valve of the switching valve is prevented from switching to the fail position during the switching transition period. As a result, even if the range operation position is quickly switched from the reverse range position to the forward range position via the neutral range position, the switching valve is prevented from switching to the fail position and the forward range pressure is prevented from being supplied from the switching valve to the second hydraulic servo, and shock caused by the forward range pressure being supplied to the second hydraulic servo in the forward range can be prevented.

According to the second invention, when the range operation position is switched from the reverse range position to the neutral range position, the normally open solenoid valve is de-energized on the condition that the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device that forms the reverse stage is a second predetermined hydraulic pressure that requires hydraulic control. Therefore, when hydraulic control of the hydraulic servo of the hydraulic friction engagement device that forms the reverse stage using the hydraulic pressure from the normally open solenoid valve as the source pressure is not required, the normally open solenoid valve is maintained energized, thereby eliminating unnecessary de-energization of the normally open solenoid valve.

1 is a functional block diagram illustrating a main part of a control function of a control device, i.e., an electronic control device, mounted on the vehicle, in addition to showing a schematic configuration diagram of a vehicle to which the present invention is applied; 2 is an engagement operation table of hydraulic friction engagement devices when a plurality of forward gears and a plurality of reverse gears are respectively established in the automatic transmission of FIG. 1 . FIG. 2 is a hydraulic circuit diagram showing a part of a hydraulic circuit that controls the operation of an automatic transmission and a torque converter. 4 is a diagram showing energized and non-energized regions of a solenoid valve when switching from an R position to an N position; FIG. 4 is a flowchart illustrating a main part of the control operation of the electronic control device, that is, the control operation when the range operation position is switched from the R position to the N position. 5 is a time chart showing a control state when a range operation position is switched from an R position to an N position. 5 is a flowchart illustrating a main part of the control operation of an electronic control device corresponding to another embodiment of the present invention, that is, the control operation when the range operation position is switched from the R position to the N position.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Figure 1 shows a schematic diagram of a vehicle 10 to which the present invention is applied, and also shows a functional block diagram illustrating the main parts of the control functions of a control device, i.e., an electronic control device 100, mounted on the vehicle 10. The vehicle 10 includes an engine 12, a power transmission device 50, a pair of left and right drive wheels 52L, 52R, a hydraulic circuit 70, and an electronic control device 100. The engine 12 is a driving force source. The power transmission device 50 includes a torque converter 14, a vehicle automatic transmission 20 (hereinafter referred to as the automatic transmission 20), a differential gear device 40, and the like. The engine 12 and the power transmission device 50 form a vehicle drive device 60. In Figure 1, the torque converter 14 and the automatic transmission 20 are shown in a schematic diagram.

The torque converter 14 includes a pump wheel 14p connected to the crankshaft 30 of the engine 12, and a turbine wheel 14t connected to the automatic transmission 20 via an input shaft 32 that corresponds to the output side member of the torque converter 14. A lock-up clutch LU is provided between the pump wheel 14p and the turbine wheel 14t, and the pump wheel 14p and the turbine wheel 14t are rotated integrally by fully engaging the lock-up clutch LU.

The automatic transmission 20 includes a single-pinion first planetary gear set 22 made up of a sun gear S1, a pinion P1, and a carrier CA2, a double-pinion second planetary gear set 24 made up of a sun gear S2, a plurality of pairs of pinions P2 and P1 that mesh with each other, a carrier CA2, and a ring gear R2, a single-pinion third planetary gear set 26 made up of a sun gear S3, a pinion P3, a carrier CA3, and a ring gear R3, and a single-pinion fourth planetary gear set 28 made up of a sun gear S4, a pinion P4, a carrier CA4, and a ring gear R4, and outputs the rotation of the input shaft 32 from the output shaft 34 by changing the speed. The first planetary gear set 22 and the second planetary gear set 24 are partially connected to each other, forming a so-called Ravigneaux type planetary gear train.

The automatic transmission 20 is equipped with a plurality of hydraulic friction engagement devices, namely clutches C1, C2, C3, C4, brakes B1, and B2. The automatic transmission 20 has 10 forward speeds and a reverse speed by switching the engagement states of the plurality of clutches C1-C4 and brakes B1, B2. The hydraulic friction engagement devices are composed of wet multi-plate clutches and brakes that are pressed by hydraulic servos (hydraulic actuators) provided thereon, and band brakes that are tightened by hydraulic servos. The automatic transmission 20 can be placed in a neutral state by cutting off the power transmission between the engine 12 and the drive wheels 52L, 52R by releasing the clutches C1, C2, C3, C4, brakes B1, and B2.

The driving force output from the automatic transmission 20 to the output shaft 34 is transmitted to a pair of left and right drive wheels 52L, 52R via the differential gear device 40 and a pair of left and right axles 36L, 36R.

The hydraulic circuit 70 is configured to control the hydraulic oil sent to the torque converter 14 and the automatic transmission 20 using hydraulic oil sent from the oil pump 18, which is driven by the engine 12.

The vehicle 10 is equipped with an electronic control device 100, which is a control device that controls each part related to the running of the vehicle 10. The electronic control device 100 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input/output interface, etc., and the CPU executes various controls of the vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The hydraulic control device 72 is configured to include this electronic control device 100 and the hydraulic circuit 70.

The electronic control device 100 is supplied with various input signals detected by various sensors provided in the vehicle 10. For example, based on detection signals from the engine speed sensor 80, input shaft speed sensor 82, output shaft speed sensor 84, accelerator opening sensor 86, throttle opening sensor 88, range operation position sensor 90, hydraulic oil temperature sensor 92, brake operation amount sensor 94, etc., the engine speed Ne (rpm), the input shaft speed Nin (rpm) which is the turbine speed Nt (rpm), the output shaft speed Nout (rpm) corresponding to the vehicle speed V (km/h), the accelerator opening θacc (%), the throttle valve opening θth (%), the range operation position POSsh switched by the shift lever 74 provided in the vehicle 10, the hydraulic oil temperature Toil (°C), the brake operation amount θbrk (%) indicating the magnitude of the driver's deceleration operation, etc. are supplied.

The electronic control device 100 also outputs an engine output control signal Se for controlling the output of the engine 12, a hydraulic control command signal Sp for hydraulic control such as shifting of the automatic transmission 20, etc. The hydraulic control command signal Sp is, for example, a signal for controlling the hydraulic pressure of the hydraulic oil supplied to the hydraulic servo of each hydraulic friction engagement device of the automatic transmission 20, a signal for controlling the engagement state of the lock-up clutch LU, etc. The hydraulic control command signal Sp is output to each solenoid valve provided in the hydraulic circuit 70.

The electronic control device 100 functionally comprises an engine output control unit 102 as an engine output control means, an AT shift control unit 104 as an AT shift control means, and a garage control unit 106 as a garage control means.

The engine output control unit 102 calculates the required driving force Fdem by applying driving force related values such as the accelerator opening θacc and the vehicle speed V to a driving force map, which is a relationship that is determined in advance experimentally or by design and stored. The engine output control unit 102 sets a target engine torque Tetgt at which the required driving force Fdem is obtained, and outputs a command to the engine control device 96 to control the engine 12 so that the target engine torque Tetgt is obtained.

The AT shift control unit 104 uses a shift map, which is a relationship that is determined in advance by experiment or design and stored, to determine whether to shift the automatic transmission 20, and when it determines that a shift should be performed, outputs a hydraulic control command signal Sp to the hydraulic circuit 70 to execute shift control of the automatic transmission 20. The shift map is a predetermined relationship having shift lines for determining whether to shift the automatic transmission 20, for example, on a two-dimensional coordinate system with vehicle speed V and required driving force Fdem as variables. The shift lines in the shift map are upshift lines for determining whether to upshift, and downshift lines for determining whether to downshift.

When the range operation position POSsh is switched, for example, from the D position, which is a forward range position, or the R position, which is a reverse range position, to the N position, which is a neutral range position, or when the range operation position POSsh is switched from the N position to the D position or the R position, the garage control unit 106 appropriately controls the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device that is released or engaged during the switching transition period, thereby executing garage control to suppress shocks that occur during the switching transition period. For example, when the range operation position POSsh is switched from the D position or the R position to the N position, the garage control unit 106 controls the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device that is released during the switching transition period so that it is released while suppressing shocks. Also, when the range operation position POSsh is switched from the N position to the D position or the R position, the garage control unit 106 controls the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device that is engaged during the switching transition period so that it is engaged while suppressing shocks.

2 is an engagement operation table showing the engagement states of the hydraulic friction engagement devices when multiple forward and reverse gears are established in the automatic transmission 20 of FIG. 1. In FIG. 2, "POSITION" indicates each range operation position (range operation position) POSsh that can be switched by the driver, "P" indicates the P position for switching to the vehicle stop range (P range), "R" indicates the R position (reverse range position) for switching to the reverse range (R range) for reverse driving, "N" indicates the N position (neutral range position) for switching to the neutral range (N range) in which power transmission is cut off, and "D" indicates the D position (forward range position) for switching to the forward range (D range) for forward driving. "1ST" to "10TH" indicate the 1st forward gear 1ST to the 10th forward gear 10TH in the D range. "R→N" indicates switching the range operation position POSsh from the R position to the N position. In addition, "SOLENOID ALL OFF" indicates the state when an abnormality occurs in which power supply to all solenoid valves is cut off. Note that the range operation position POSsh corresponds to the range operation position of the present invention, the D position corresponds to the forward range position of the present invention, the R position corresponds to the reverse range position of the present invention, and the N position corresponds to the neutral range position of the present invention.

In FIG. 2, SL1 to SL6 and SR (SORENOID) indicate the operating states of the linear solenoid valves SL1 to SL6 and the solenoid valve SR provided in the hydraulic circuit 70. In SL1 to SL6 and SR, "○" indicates an energized state (ON state), "×" indicates a non-energized state, and "△" indicates a control state in which the supply current is controlled. In addition, C1 to C4 (CLUTCH) and B1, B2 (BRAKE) indicate the operating states of the clutches C1 to C4 and the brakes B1, B2. In clutches C1 to C4 and brakes B1, B2, "○" indicates an engaged state, "×" indicates a released state (disengaged state), and "△" indicates a control state in which the torque capacity of the clutch and brake are adjusted, respectively. The electronic control unit 100 switches between multiple forward and reverse gears by controlling the energization of the linear solenoid valves SL1-SL6 and the solenoid valve SR according to the engagement operation table in Figure 2.

In this embodiment, the engagement pressures Pc1 to Pb2 of the hydraulic servos SVc1 to SVc4, SVb1, and SVb2 (see FIG. 3) of the clutches C1 to C4 and the brakes B1 and B2 are controlled by independent linear solenoid valves SL1 to SL6 (see FIG. 3). Specifically, the hydraulic pressure of the hydraulic servo SVc1 of the clutch C1 is controlled by the linear solenoid valve SL1. In other words, the hydraulic pressure regulated by the linear solenoid valve SL1 is supplied to the hydraulic servo SVc1 of the clutch C1 as the engagement pressure Pc1. In addition, the hydraulic pressure (engagement pressure Pc2) of the hydraulic servo SVc2 of clutch C2 is controlled by linear solenoid valve SL2, the hydraulic pressure (engagement pressure Pc3) of the hydraulic servo SVc3 of clutch C3 is controlled by linear solenoid valve SL3, the hydraulic pressure (engagement pressure Pc4) of the hydraulic servo SVc4 of clutch C4 is controlled by linear solenoid valve SL4, the hydraulic pressure (engagement pressure Pb1) of the hydraulic servo SVb1 of brake B1 is controlled by linear solenoid valve SL5, and the hydraulic pressure (engagement pressure Pb2) of the hydraulic servo SVb2 of brake B2 is controlled by linear solenoid valve SL6.

The linear solenoid valves SL1 to SL6 are normally closed solenoid valves that are configured to output hydraulic pressure in an energized state and not output hydraulic pressure in a de-energized state. Therefore, when the linear solenoid valves SL1 to SL6 are energized, hydraulic pressure (engagement pressure) is supplied from the linear solenoid valves SL1 to SL6 to the hydraulic servos SVc1 to SVb2 of the corresponding clutches C1 to C4 and brakes B1 and B2, respectively, to be in an engaged state, and when they are de-energized, hydraulic pressure is not supplied to the corresponding clutches C1 to C4 and brakes B1 and B2, and they are in a released state. For example, in the 5th forward gear 5TH in the D range, the clutches C2, C4, and brake B1 are engaged as shown in FIG. 2, and in relation to this, the linear solenoid valves SL2, SL4, and SL5 are in an energized state "○".
On the other hand, the solenoid valve SR is a normally open solenoid valve that is configured so that no hydraulic pressure is output when it is energized, but hydraulic pressure is output when it is de-energized. The solenoid valve SR corresponds to the normally open solenoid valve of the present invention.

Here, in the fail state ("SORENOID ALL OFF") in which all of the linear solenoid valves SL1 to SL6 and solenoid valve SR shown in the engagement operation table in Figure 2 are de-energized, i.e., in the non-energized state, all of the linear solenoid valves SL1 to SL6 and solenoid valve SR are non-energized as shown in Figure 2. Also, as shown by "R (R position)" in the fail state, when the fail state is switched to while traveling in reverse, clutches C2, C3 and brake B2 are engaged. Also, "1ST-4TH → 4TH" in the fail state indicates that when the fail state is switched to while traveling in any of the forward gears from 1st forward gear 1ST to 4th forward gear 4TH, the gear will switch to 4th forward gear 4TH. Also, "5TH-10TH→8TH" in the failure state indicates that if the failure state occurs while driving in any of the forward gears from 5th forward gear 5TH to 10th forward gear 10TH, the gear will switch to 8th forward gear TH. In this way, even if the failure state occurs while driving forward, a specified forward gear is formed, making it possible to drive to safety. Note that the structure in which a specified gear is formed even if the power supply to all linear solenoid valves SL1-SL6 and solenoid valve SR is cut off will be described later.

Figure 3 is a hydraulic circuit diagram showing a portion of a hydraulic circuit 70 that controls the operation of the automatic transmission 20 and the torque converter 14. Figure 3 shows the linear solenoid valves SL1 to SL6 that control the clutches C1 to C4 and the brakes B1 and B2, respectively, the solenoid valve SR, the manual valve 110, the first check valve 120, the second check valve 130, the third check valve 140, the clutch control valve 150, and the fail-safe valve 160 that constitute the hydraulic circuit 70.

The linear solenoid valve SL1 has a first input port SL1a, an output port SL1c, and a feedback port SL1d. The first input port SL1a is connected to the output port 120c (described later) of the first check valve 120. The output port SL1c is connected to the feedback port SL1d and the hydraulic servo SVc1 of the clutch C1. Therefore, the hydraulic pressure output from the output port SL1c is supplied to the hydraulic servo SVc1 of the clutch C1 as the engagement pressure Pc1. In the energized state, the linear solenoid valve SL1 adjusts the hydraulic pressure input from the first input port SL1a to the hydraulic pressure supplied to the hydraulic servo SVc1 of the clutch C1, and outputs the adjusted hydraulic pressure from the output port SL1c as the engagement pressure Pc1 of the clutch C1.

The linear solenoid valve SL2 has a first input port SL2a, a second input port SL2b, an output port SL2c, and a feedback port SL2d. The first input port SL2a is connected to the output port of a modulator valve (not shown). The second input port SL2b is connected to a third output port 160l (described later) of the fail-safe valve 160. The output port SL2c is connected to the feedback port SL2d and the hydraulic servo SVc2 of the clutch C2. Therefore, the hydraulic pressure output from the output port SL2c is supplied to the hydraulic servo SVc2 of the clutch C2 as the engagement pressure Pc2.

When energized, the linear solenoid valve SL2 adjusts the hydraulic pressure input from the first input port SL2a, i.e., the modulator pressure Pmod output from the modulator valve, to the original pressure to be supplied to the hydraulic servo SVc2 of the clutch C2, and outputs the adjusted hydraulic pressure from the output port SL2c as the engagement pressure Pc2 of the clutch C2. In addition, when energized, the linear solenoid valve SL2 is configured such that communication between the first input port SL2a and the output port SL2c is blocked and communication between the second input port SL2b and the output port SL2c is established.

The linear solenoid valve SL3 has a first input port SL3a, a second input port SL3b, an output port SL3c, and a feedback port SL3d. The first input port SL3a is connected to an output port 130d (described later) of the second check valve 130. The second input port SL3b is connected to a first output port 140c of the third check valve 140. The output port SL3d is connected to the feedback port SL3d and the hydraulic servo SVc3 of the clutch C3. Therefore, the hydraulic pressure output from the output port SL3c is supplied to the hydraulic servo SVc3 of the clutch C3 as the engagement pressure Pc3.

When energized, the linear solenoid valve SL3 adjusts the hydraulic pressure input from the first input port SL3a to the hydraulic pressure supplied to the hydraulic servo SVc3 of the clutch C3, and outputs the adjusted hydraulic pressure from the output port SL3c as the engagement pressure Pc3 of the clutch C3. When energized, the linear solenoid valve SL3 is configured such that communication between the first input port SL3a and the output port SL3c is blocked and communication between the second input port SL3b and the output port SL3c is established.

The linear solenoid valve SL4 has a first input port SL4a, a second input port SL4b, an output port SL4c, and a feedback port SL4d. The first input port SL4a is connected to an output port 120c (described later) of the first check valve 120. The second input port SL4b is connected to a second output port 160k (described later) of the fail-safe valve 160. The output port SL4c is connected to the feedback port SL4d and the hydraulic servo SVc4 of the clutch C4. Therefore, the hydraulic pressure output from the output port SL4c is supplied to the hydraulic servo SVc4 of the clutch C4 as the engagement pressure Pc4.

When energized, the linear solenoid valve SL4 adjusts the hydraulic pressure input from the first input port SL4a to the hydraulic pressure supplied to the hydraulic servo SVc4 of the clutch C4, and outputs the adjusted hydraulic pressure from the output port SL4c as the engagement pressure Pc4 of the clutch C4. When energized, the linear solenoid valve SL4 is configured such that communication between the first input port SL4a and the output port SL4c is blocked and communication between the second input port SL4b and the output port SL4c is established.

The linear solenoid valve SL5 has a first input port SL5a, a second input port SL5b, an output port SL5c, and a feedback port SL5d. The first input port SL5a is connected to the output port 120c of the first check valve 120. The second input port SL5b is connected to a second output port 150g (described later) of the clutch control valve 150. The output port SL5c is connected to the feedback port SL5d and the hydraulic servo SVb1 of the brake B1. Therefore, the hydraulic pressure output from the output port SL5c is supplied to the hydraulic servo SVb1 of the brake B1 as the engagement pressure Pb1.

When energized, the linear solenoid valve SL5 adjusts the hydraulic pressure input from the first input port SL5a to the hydraulic pressure supplied to the hydraulic servo SVb1 of the brake B1, and outputs the adjusted hydraulic pressure from the output port SL5c as the engagement pressure Pb1 of the brake B1. When energized, the linear solenoid valve SL5 is configured such that communication between the first input port SL5a and the output port SL5c is blocked and communication between the second input port SL5b and the output port SL5c is established.

The linear solenoid valve SL6 has a first input port SL6a, a second input port SL6b, an output port SL6c, and a feedback port SL6d. The first input port SL6a is connected to the output port of a modulator valve (not shown). The second input port SL6b is connected to a fifth output port 150j (described later) of the clutch control valve 150. The output port SL6c is connected to the hydraulic servo SVb2 of the brake B2 via the fail-safe valve 160. Therefore, the hydraulic pressure output from the output port SL6c is supplied to the hydraulic servo SVb2 of the brake B2 as the engagement pressure Pb2 via the fail-safe valve 160.

When energized, the linear solenoid valve SL6 adjusts the hydraulic pressure input from the first input port SL6a, i.e., the modulator pressure Pmod output from the modulator valve, to the original pressure to be supplied to the hydraulic servo SVb2 of the brake B2, and outputs the adjusted hydraulic pressure from the output port SL6c as the engagement pressure Pb2 of the brake B2. In addition, when energized, the linear solenoid valve SL6 is configured such that the first input port SL6a and the output port SL6c are cut off from each other, and the second input port SL6b and the output port SL6c are connected.

The solenoid valve SR has an input port SRa and an output port SRb. The input port SRa is connected to the output port of a modulator valve (not shown) and is configured to receive the modulator pressure Pmod adjusted by the modulator valve. The solenoid valve SR uses a normally open solenoid valve that outputs hydraulic pressure (modulator pressure Pmod) from the output port SRb in a non-energized state. The output port SRb is connected to a first input port 130a (described later) of the second check valve 130 and a first oil chamber 160a (described later) of the fail-safe valve 160.

The manual valve 110 is configured to output a forward range pressure PD when the range operation position POSsh is set to the D position, which is the forward range position, and to output a reverse range pressure PR when the range operation position POSsh is set to the R position, which is the reverse range position. The manual valve 110 is equipped with a line pressure input port 110a to which the line pressure PL is input, a forward range pressure output port 110b, a reverse range pressure output port 110c, a drain port EX, and a spool valve element 110s for switching the communication state of each port. In FIG. 3, the ports 110a to 110c and the spool valve element 110s are indicated by the symbols a to c and s, respectively.

The spool valve 110s is switched to a position corresponding to the range operation position POSsh by the driver operating the shift lever 74. FIG. 3 shows the state in which the manual valve 110 is switched to the N position, which is the neutral range position. At this time, the line pressure input port 110a is not connected to any port, and the forward range pressure output port 110b and the reverse range pressure output port 110c are each connected to the drain port EX. Therefore, neither the forward range pressure PD nor the reverse range pressure PR is output. The same state occurs when the manual valve 110 is switched to the P position, which is the vehicle stop range position. The line pressure PL is a hydraulic pressure regulated by a regulator valve (not shown).

When the manual valve 110 is switched to the D position, which is the forward range position, the line pressure input port 110a is connected to the forward range pressure output port 110b, and the reverse range pressure output port 110c is connected to the drain port EX. At this time, the line pressure PL is output from the forward range pressure output port 110b as the forward range pressure PD. Also, when the manual valve 110 is switched to the R position, which is the reverse range position, the line pressure input port 110a is connected to the reverse range pressure output port 110c, and the forward range pressure output port 110b is connected to the drain port EX. At this time, the line pressure PL is output from the reverse range pressure output port 110c as the reverse range pressure PR.

The first check valve 120 has a first input port 120a, a second input port 120b, and an output port 120c, and is configured so that when hydraulic pressure is input from either the first input port 120a or the second input port, the hydraulic pressure is output from the output port 120c. In FIG. 3, the ports 120a to 120c are indicated by the symbols a to c, respectively.

The first input port 120a is connected to the forward range pressure output port 110b of the manual valve 110. When the range operation position POSsh is switched to the D position, the forward range pressure PD is input to the first input port 120a and output from the output port 120c. The second input port 120b is connected to the output port of the linear solenoid valve SLU (not shown). When the control pressure Pslu is output from the linear solenoid valve SLU, the control pressure Pslu is input to the second input port 120b and output from the output port 120c. The output port 120c is connected to the third input port 130c of the second check valve 130 (described later), the first input port SL1a of the linear solenoid valve SL1, the first input port SL4a of the linear solenoid valve SL4, and the first input port SL5a of the linear solenoid valve SL5.

The second check valve 130 has a first input port 130a, a second input port 130b, a third input port 130c, and an output port 130d, and is configured to output hydraulic pressure from the output port 130d when hydraulic pressure is input from any of the first input port 130a, the second input port 130b, and the third input port 130c. In FIG. 3, the ports 130a to 130d are indicated by the letters a to d, respectively.

The first input port 130a is connected to the output port SRb of the solenoid valve SR. When the signal pressure Psr is output from the output port SRb of the solenoid valve SR, the signal pressure Psr is input from the first input port 130a and output from the output port 130d. The second input port 130b is connected to the reverse range pressure output port 110c of the manual valve 110. When the range operation position POSsh is switched to the R position, the reverse range pressure PR is input from the second input port 130b and output from the output port 130d. The third input port 130c is connected to the output port 120c of the first check valve 120. When the oil pressure output from the output port 120c is output, the oil pressure is input to the third input port 130c and output from the output port 130d. The output port 130d is connected to the first input port SL3a of the linear solenoid valve SL3.

The third check valve 140 has a first input port 140a, a second input port 140b, a first output port 140c, a third input port 140d, a fourth input port 140e, and a second output port 140f. In FIG. 3, the ports 140a to 140f are indicated by the letters a to f, respectively. The third check valve 140 is configured such that when hydraulic pressure is input from either the first input port 140a or the second input port 140b, the hydraulic pressure is output from the first output port 140c, and when hydraulic pressure is input from either the third input port 140d or the fourth input port 140e, the hydraulic pressure is output from the second output port 140f.

In the third check valve 140, the first input port 140a is connected to the second output port 150g of the clutch control valve 150, which will be described later, and the second input port 140b is connected to the third output port 160l of the fail-safe valve 160, which will be described later. The first output port 140c is connected to the second input port SL3b of the linear solenoid valve SL3. The third input port 140d is connected to the third output port 150h of the clutch control valve 150, which will be described later, and the fourth input port 140e is connected to the third output port 160l of the fail-safe valve 160, which will be described later. The second output port 140f is connected to the fourth input port 160f of the fail-safe valve 160, which will be described later.

The clutch control valve 150 (hereinafter, control valve 150) includes a first oil chamber 150a, a second oil chamber 150b, a pressure-receiving port 150c, a first input port 150d, a second input port 150e, a first output port 150f, a second output port 150g, a third output port 150h, a fourth output port 150i, a fifth output port 150j, a first communication port 150k, a second communication port 150l, a spring 150sp accommodated in the second oil chamber 150b, a first spool valve element 150s1, and a second spool valve element 150s2. In FIG. 3, the oil chambers 150a, 150b, the ports 150c-150l, the spring 150sp, and the spool valve elements 150s1, 150s2 are indicated by the symbols a-l, sp, and s1-s2, respectively.

The first oil chamber 150a is connected to the hydraulic servo SVc3 of the clutch C3. The second oil chamber 150b is connected to the hydraulic servo SVb2 of the brake B2. The pressure-receiving port 150c is connected to the hydraulic servo SVb1 of the brake B1. The first input port 150d is connected to the second output port 160k of the fail-safe valve 160, which will be described later. The second input port 150e is connected to the forward range pressure output port 110b of the manual valve 110. The first output port 150f is connected to a control valve (not shown). The second output port 150g is connected to the first input port 140a of the third check valve 140 and the second input port SL5b of the linear solenoid valve SL5. The third output port 150h is connected to the third input port 140d of the third check valve 140. The fourth output port 150i is connected to the sixth input port 160h of the fail-safe valve 160, which will be described later. The fifth output port 150j is connected to the second input port SL6b of the linear solenoid valve SL6. The first communication port 150k and the second communication port 150l are connected to each other.

In the control valve 150, the hydraulic pressure (engagement pressure Pc3) of the hydraulic servo SVc3 of the clutch C3 is supplied to the first oil chamber 150a, the hydraulic pressure (engagement pressure Pb2) of the hydraulic servo SVb2 of the brake B2 is supplied to the second oil chamber 150b, and the hydraulic pressure (engagement pressure Pb1) of the hydraulic servo SVb1 of the brake B1 is supplied to the pressure receiving port 150c. When the hydraulic pressure of the hydraulic servo SVc3 of the clutch C3 is supplied to the first oil chamber 150a, the first spool valve element 150s1 is biased downward on the paper (towards the second oil chamber 150b), and when the hydraulic pressure of the hydraulic servo SVb1 of the brake B1 is supplied to the pressure receiving port 150c, the first spool valve element 150s1 is biased downward on the paper. In addition, when the hydraulic pressure of the hydraulic servo SVb2 of the brake B2 is supplied to the second oil chamber 150b, the second spool valve element 150s2 is biased toward the upper side of the paper (the first oil chamber 150a side). The second spool valve element 150s2 is constantly biased toward the upper side of the paper by the spring 150sp.

In the states of 1st forward gear 1ST to 4th forward gear 4TH, P range, N range, and R range, the hydraulic pressure of the hydraulic servo SVb2 supplied to the second oil chamber 150b and the biasing force of the spring 150sp that biases the second spool valve element 150s2 upward on the page becomes greater than the hydraulic pressure of the hydraulic servo SVc3 supplied to the first oil chamber 150a and the biasing force of the hydraulic servo SVb1 supplied to the pressure-receiving port 150c that biases the first spool valve element 150s1 downward on the page. At this time, the control valve 150 is in a state on the left side of the page with respect to the center line CL of the control valve 150 shown in FIG. 3.

On the other hand, in the state of 5th forward gear 5TH to 10th forward gear 10TH, the force that urges the first spool 150 valve element s1 downward on the paper based on the hydraulic pressure of the hydraulic servo SVc3 supplied to the first oil chamber 150a and the hydraulic pressure of the hydraulic servo SVb1 supplied to the pressure receiving port 150c becomes greater than the force that urges the second spool valve element 150s2 upward on the paper based on the hydraulic pressure of the hydraulic servo SVb2 supplied to the second oil chamber 150b and the spring 150sp. Therefore, the first spool valve element 150s1 and the second spool valve element 150s2 move downward on the paper, and at this time, the forward range pressure PD is input to the second communication port 150l via the second input port 150e and the first communication port 150k. When forward range pressure PD is input to second communication port 150l, first spool valve element 150s1 and second spool valve element 150s2 are separated by forward range pressure PD. Therefore, in the state of 5th forward gear 1ST to 10th forward gear 10TH, control valve 150 is in the state on the right side of the center line CL of control valve 150 in FIG. 3.

The fail-safe valve 160 is provided to form a predetermined gear and perform evacuation driving when an abnormality occurs in which the power supply to all solenoid valves is cut off during driving (hereinafter referred to as an all-off fail). The fail-safe valve 160 includes a first oil chamber 160a, a second oil chamber 160b, a first input port 160c, a second input port 160d, a third input port 160e, a fourth input port 160f, a fifth input port 160g, a sixth input port 160h, a seventh input port 160i, a first output port 160j, a second output port 160k, a third output port 160l, a spool valve element 160s, a spring 160sp, and a drain port EX. In FIG. 3, the oil chambers 160a, 160b, the ports 160c-160l, the spring 160sp, and the spool valve element 160s are indicated by the symbols a-l, sp, and s, respectively. The fail-safe valve 160 corresponds to the switching valve of the present invention, and the spring 160sp corresponds to the biasing member of the present invention.

The first oil chamber 160a is connected to the output port SRb of the solenoid valve SR. The second oil chamber 160b is connected to the hydraulic servo SVb2 of the brake B2. The first input port 160c is connected to the output port of the solenoid valve SLT (not shown) and is supplied with the control pressure Pslt output from the solenoid valve SLT. The second input port 160d is connected to the output port SRb of the solenoid valve SR. The third input port 160e is connected to the output port SL6c of the linear solenoid valve SL6. The fourth input port 160f is connected to the second output port 140f of the third check valve 140. The fifth input port 160g is connected to the forward range pressure output port 110b of the manual valve 110. The sixth input port 160h is connected to the fourth output port 150i of the control valve 150. The seventh input port 160i is connected to the reverse range pressure output port 110c of the manual valve 110. The first output port 160j is connected to the hydraulic servo SVb2 of the brake B2. The second output port 160k is connected to the second input port SL4b of the linear solenoid valve SL4 and the first input port 150d of the control valve 150. The third output port 160l is connected to the second input port SL2b of the linear solenoid valve SL2, the second input port 140b of the third check valve 140, and the fourth input port 140e.

In the fail-safe valve 160, the signal pressure Psr of the solenoid valve SR is supplied to the first oil chamber 160a, and the hydraulic pressure of the hydraulic servo SVb2 of the brake B2, i.e., the engagement pressure Pb2, is supplied to the second oil chamber 160b. In addition, the spring 160sp housed in the second oil chamber 160b biases the spool valve element 160s toward the upper side of the paper (the first oil chamber 160a side) in FIG. 3. As a result, the spool valve element 160s of the fail-safe valve 160 is biased toward the first oil chamber 160a side (the upper side of the paper in FIG. 3, the normal position side described later) by the engagement pressure Pb2 of the brake B2 and the spring 160sp, and is biased toward the second oil chamber 160b side (the lower side of the paper in FIG. 3, the fail position side described later) by the signal pressure Psr of the solenoid valve SR. Therefore, when the biasing force that biases the spool valve element 160s toward the second oil chamber 160b based on the signal pressure Psr supplied to the first oil chamber 160a becomes greater than the biasing force that biases the spool valve element 160s toward the first oil chamber 160a based on the engagement pressure Pb2 supplied to the second oil chamber 160b and the spring 160sp, the spool valve element 160s is moved toward the second oil chamber 160b.

When the solenoid valve SR is energized, it does not output the signal pressure Psr, so when it is energized, the spool valve element 160s is moved upward on the paper and to the left of the center line CL of the fail-safe valve 160 shown in FIG. 3. Hereinafter, this state will be referred to as the normal state of the fail-safe valve 160, and the position of the spool valve element 160s in the normal state will be referred to as the normal position. As shown in the engagement operation table in FIG. 2, the solenoid valve SR is energized during normal driving conditions, so the fail-safe valve 160 is basically in the normal state.

On the other hand, if an all-off failure occurs while driving, for example, the signal pressure Psr is output from the solenoid valve SR and supplied to the first oil chamber 160a, causing the spool valve element 160s to move toward the second oil chamber 160b, and to the right of the center line CL of the failsafe valve 160 shown in Figure 3. Hereinafter, this state is referred to as the fail state of the failsafe valve 160, and the position of the spool valve element 160s in the fail state is referred to as the fail position.

The following describes the operation of the hydraulic circuit 70 when an all-off failure occurs, in which all solenoid valves are de-energized while the vehicle is running. First, we will explain the case when an all-off failure occurs while the vehicle is running in 1st forward gear 1ST to 4th forward gear 4TH.

When the vehicle is traveling in 1st forward gear 1ST to 4th forward gear 4TH, the control valve 150 is in the state shown on the left side of the paper with respect to the center line CL in Figure 3. Also, under normal circumstances, the solenoid valve SR is in an energized state and the signal pressure Psr is not output from the solenoid valve SR, so the fail-safe valve 160 is in the normal state shown on the left side of the paper with respect to the center line CL in Figure 3.

When an all-off fail occurs from this state, all solenoid valves are de-energized, resulting in the "SORENOID ALL OFF" state shown in the engagement operation table in FIG. 2. At this time, the linear solenoid valves SL1 to SL6 no longer output hydraulic pressure. On the other hand, the solenoid valve SR outputs the signal pressure Psr because it is a normally open solenoid valve. When the signal pressure Psr is output from the solenoid valve SR, the signal pressure Psr is input to the first oil chamber 160a of the fail-safe valve 160, so that the spool valve element 160s of the fail-safe valve 160 is switched to the fail position shown on the right side of the center line CL in FIG. 3. At this time, the fourth input port 160f and the first output port 160j are connected, and the fifth input port 160g and the second output port 160k are connected.

In addition, since the forward range pressure PD is input to the fifth input port 160g, the forward range pressure PD is output from the second output port 160k. Since the second output port 160k and the second input port SL4b of the linear solenoid valve SL4 are connected, the forward range pressure PD is input to the second input port SL4b. Here, since the second input port SL4b and the output port SL4c of the linear solenoid valve SL4 are connected in a non-energized state, the forward range pressure PD is output from the output port SL4c and supplied to the hydraulic servo SVc4 of the clutch C4. In addition, since the second output port 160k of the fail-safe valve 160 is connected to the first input port 150d of the control valve 150, the forward range pressure PD is input to the first input port 150d. In the state of 1st forward gear 1ST to 4th forward gear 4TH, the first input port 150d and the third output port 150h are communicated with each other, so that the forward range pressure PD is output from the third output port 150h. Furthermore, since the third output port 150h is connected to the third input port 140d of the third check valve 140, the forward range pressure PD is output from the second output port 140f. This forward range pressure PD is input to the fourth input port 160f of the failsafe valve 160 and output from the first output port 160j, so that the forward range pressure PD is supplied to the hydraulic servo SVb2 of the brake B2. As a result, if an all-off failure occurs while traveling in 1st forward gear 1ST to 4th forward gear 4TH, the spool valve element 160s of the failsafe valve 160 is switched to the fail position, and the forward range pressure PD is supplied to the hydraulic servo SVc4 of the clutch C4 and the hydraulic servo SVb2 of the brake B2, forming 4th forward gear 4TH and enabling evacuation traveling. Note that the hydraulic servo SVc4 of the clutch C4 corresponds to the second hydraulic servo of the present invention.

Next, we will explain what happens when an all-off fail occurs while driving in 5th forward gear 5TH to 10th forward gear 10TH. When driving in 5th forward gear 5TH to 10th forward gear 10TH, the control valve 150 is in the state shown on the right side of the page with respect to the center line CL of the control valve 150 in Figure 3. Also, under normal circumstances, the fail-safe valve 160 is in the normal state shown on the left side of the page with respect to the center line CL of the fail-safe valve 160 in Figure 3.

When all solenoid valves are de-energized from this state, no hydraulic pressure is output from the linear solenoid valves SL1 to SL6, while the solenoid valve SR outputs the signal pressure Psr, causing the fail-safe valve 160 to switch to the fail state shown on the right side of the center line CL in Figure 3. At this time, the fourth input port 160f is connected to the first output port 160j, and the fifth input port 160g is connected to the second output port 160k.

In addition, the forward range pressure PD is input to the fifth input port 160g, and the forward range pressure PD is output from the second output port 160k. Since the second output port 160k is connected to the second input port SL4b of the linear solenoid valve SL4, the forward range pressure PD is input to the second input port SL4b and output from the output port SL4c, so that the forward range pressure PD is supplied to the hydraulic servo SVc4 of the clutch C4. In addition, the forward range pressure PD output from the second output port 160k is input to the first input port 150d of the control valve 150. Here, in the state of 5th forward gear 5TH to 10th forward gear 10TH, the first input port 150d and the second output port 150g are connected, so that the forward range pressure PD is output from the second output port 150g. The second output port 150g is connected to the second input port SL5b of the linear solenoid valve SL5, and the second input port SL5b and the output port SL5c are connected to each other when not energized, so that the forward range pressure PD is output from the output port SL5c and supplied to the hydraulic servo SVb1 of the brake B1. Furthermore, the second output port 150g is connected to the first input port 140a of the third check valve 140, so that the forward range pressure PD is output from the first output port 140c. The first output port 140c is connected to the second input port SL3b of the linear solenoid valve SL3, and the second input port SL3b and the output port SL3c are connected to each other when not energized, so that the forward range pressure PD is output from the output port SL3c and supplied to the hydraulic servo SVc3 of the clutch C3. As a result, if an all-off failure occurs while driving in 5th forward gear 5TH to 10th forward gear 10TH, the spool valve 160s of the failsafe valve 160 is switched to the fail position, and the forward range pressure PD is supplied to the hydraulic servos SVc3, SVc4, and SVb1 of the clutches C3 and C4, and the brake B1, respectively, to form 8th forward gear 8TH, enabling evacuation driving.

Next, we will explain what happens when an all-off fail occurs while the vehicle is traveling in reverse, i.e., while the vehicle is traveling in reverse gear. When traveling in reverse, the control valve 150 is in the state shown on the left side of the page with respect to the center line CL of the control valve 150 in Figure 3. Also, under normal circumstances, the fail-safe valve 160 is in the normal state shown on the left side of the page with respect to the center line CL of the fail-safe valve 160 in Figure 3.

When all solenoid valves are de-energized from this state, hydraulic pressure is no longer output from the linear solenoid valves SL1 to SL6, while the solenoid valve SR outputs the signal pressure Psr, causing the spool valve element 160s of the fail-safe valve 160 to switch to the fail position. At this time, the fourth input port 160f and the first output port 160j are connected, the fifth input port 160g and the second output port 160k are connected, and the seventh input port 160i and the third output port 160l are connected.

During reverse driving, the reverse range pressure PR is input to the seventh input port 160i, and this reverse range pressure PR is output from the third output port 160l. Since the third output port 160l is connected to the second input port SL2b of the linear solenoid valve SL2, the reverse range pressure PR is input to the second input port SL2b, and is output from the output port SL2c that communicates with the second input port SL2b when not energized. This supplies the reverse range pressure PR to the hydraulic servo SVc2 of the clutch C2. In addition, since the third output port 160l is connected to the second input port 140b and the fourth input port 140e of the third check valve 140, the reverse range pressure PR is output from the first output port 140c and the second output port 140f. Since the first output port 140c is connected to the second input port SL3b of the linear solenoid valve SL3, the reverse range pressure PR is input to the second input port SL3b, and is output from the output port SL3c that is connected to the second input port SL3b when de-energized. This causes the reverse range pressure PR to be supplied to the hydraulic servo SVc3 of the clutch C3. In addition, since the second output port 140f from which the reverse range pressure PR is output is connected to the fourth input port 160f of the fail-safe valve 160, the reverse range pressure PR is output from the first output port 160j that is connected to the fourth input port 160f in the fail state. This causes the reverse range pressure PR to be supplied to the hydraulic servo SVb2 of the brake B2. As a result, if an all-off failure occurs while driving in reverse gear, the spool valve 160s of the failsafe valve 160 is switched to the fail position, and reverse range pressure PR is supplied to the hydraulic servos SVc2, SVc3, and SVb2 of clutch C2, clutch C3, and brake B2, respectively, forming a reverse gear and enabling evacuation driving.

Next, the operation of the hydraulic circuit 70 when the range operation position POSsh is switched from the R position (reverse range position) to the N position (neutral range position) will be described. When the range operation position POSsh is switched from the R position to the N position, as shown in the engagement operation table of FIG. 2, the solenoid valve SR is switched from an energized state to a de-energized state during the switching transition period ("○→×"). This is to supply the signal pressure Psr of the solenoid valve SR as the source pressure of the linear solenoid valve SL3 in order to execute the release control (drain control) of the clutch C3 that forms the reverse stage when switching from the R position to the N position (also called "garage time"). When the range operation position POSsh is switched from the R position to the N position, the solenoid valve SR is switched to a de-energized state, and the signal pressure Psr is output from the solenoid valve SR. This signal pressure Psr is input to the first input port SL3a of the linear solenoid valve SL3 via the second check valve 130, so that the signal pressure Psr is supplied as the base pressure to the linear solenoid valve SL3, which outputs hydraulic pressure (engagement pressure Pc3) to the hydraulic servo SVc3 of the clutch C3, enabling drain control to adjust the engagement pressure Pc3 during garage operation. In this way, the signal pressure Psr of the solenoid valve SR is supplied as the base pressure to the linear solenoid valve SL3 during the switching transition period, enabling release control (drain control) of the clutch C3, thereby suppressing shocks that occur during the switching transition period.

Since the output port SRb of the solenoid valve SR is connected to the first oil chamber 160a of the fail-safe valve 160, for example, if the range operation position POSsh is quickly switched from the R position via the N position to the D position, the signal pressure Psr is input to the first oil chamber 160a of the fail-safe valve 160, causing the fail-safe valve 160 to switch to a failed state during the transitional period when switching to the D range, and a shock may occur due to the gear stage being transiently formed when an all-off failure occurs.

In response to this, the garage control unit 106 is configured to cut off the power to the solenoid valve SR on the condition that when the range operation position POSsh is switched from the R position to the N position, the engagement pressure Pb2 supplied to the hydraulic servo SVb2 of the brake B2 is a predetermined hydraulic pressure Pb2r at which the spool valve element 160s in the fail-safe valve 160 is not switched to the fail position by the signal pressure Psr from the solenoid valve SR, which is a normally open solenoid valve, and is maintained in the normal position. When the above condition is met, the fail-safe valve 160 is maintained in the normal position even if the power to the solenoid valve SR is cut off during the switching transition period. Therefore, even if the signal pressure Psr is output from the solenoid valve SR during the transition from the R position to the N position, the fail-safe valve 160 will not switch to a failed state, and even if the R position is quickly switched to the D position via the N position, shock caused by the spool valve element 160s of the fail-safe valve 160 switching to the failed position is prevented. Note that the hydraulic servo SVb2 of the brake B2 corresponds to the first hydraulic servo of the present invention, and the predetermined hydraulic pressure Pb2r corresponds to the predetermined hydraulic pressure of the present invention.

The predetermined hydraulic pressure Pb2r at which the above condition is satisfied is a value in a range in which the force biasing the spool valve element 160s of the fail-safe valve 160 to the normal position based on the spring 160sp of the fail-safe valve 160 and the engagement pressure Pb2 of the brake B2 is greater than the force biasing the spool valve element 160s of the fail-safe valve 160 to the fail position based on the signal pressure Psr from the solenoid valve SR. Figure 4 is a diagram showing the energized and non-energized regions of the solenoid valve SR when the range operation position POSsh is switched from the R position to the N position. In Figure 4, the horizontal axis corresponds to the engagement pressure Pc3 [kPa] of the clutch C3, and the vertical axis corresponds to the engagement pressure Pb2 [kPa] of the brake B2. Here, only the engagement pressure Pb2 of the brake B2 will be described.

The regions A and B shown in FIG. 4 correspond to the region (FSV malfunction region) where the spool valve element 160s of the fail-safe valve 160 switches to the fail position when the range operation position POSsh is switched from the R position to the N position because the engagement pressure Pb2 of the brake B2 is low. That is, in the regions A and B, the biasing force F1 that biases the spool valve element 160s to the normal position based on the engagement pressure Pb2 of the brake B2 and the spring 160sp is smaller than the biasing force F2 that biases the spool valve element 160s to the fail position based on the signal pressure Psr, and when the signal pressure Psr of the solenoid valve SR is input to the first oil chamber 160a of the fail-safe valve 160, the spool valve element 160s is moved to the fail position.

On the other hand, areas C and D correspond to areas where the spool valve element 160s is maintained in the normal position even if the signal pressure Psr is output from the solenoid valve SR when the range operation position POSsh is switched from the R position to the N position. In areas C and D, the biasing force F1 that biases the spool valve element 160s to the normal position based on the engagement pressure Pb2 of the brake B2 and the spring 160sp becomes greater than the biasing force F2 that biases the spool valve element 160s to the fail position based on the signal pressure Psr when the signal pressure Psr is output from the solenoid valve SR, and the spool valve element 160s of the failsafe valve 160 is maintained in the normal position even if the signal pressure Psr of the solenoid valve SR is input to the first oil chamber 160a.

Here, the lower limit threshold value α (boundary value) of the engagement pressure Pb2 of the brake B2, at which the spool valve element 160s is maintained in the normal position even when the signal pressure Psr is output from the solenoid valve SR, is a value at which the biasing force F2 toward the fail position based on the signal pressure Psr of the solenoid valve SR is equal or approximately equal to the biasing force F2 toward the normal position based on the engagement pressure Pb2 of the brake B2 and the spring 160sp. Thus, the lower limit threshold value α is calculated based on the pressure receiving area A1 of the first oil chamber 160a to which the solenoid valve SR is input, the signal pressure Psr (i.e., the modulator pressure Pmod) of the solenoid valve SR, the pressure receiving area A2 of the second oil chamber 160b to which the brake B2 is input, and the biasing force Fsp of the spring 160sp. Specifically, the lower limit threshold value α can be calculated based on the following formula (1). The predetermined oil pressure Pb2r corresponds to an oil pressure value higher than the lower limit threshold value α.
Psr×A1=α×A2+Fsp...(1)

When the garage control unit 106 determines that the range operation position POSsh has been switched from the R position to the N position, it determines whether the engagement pressure Pb2 of the brake B2 is the predetermined hydraulic pressure Pb2r, specifically, whether the engagement pressure Pb2 of the brake B2 is higher than the lower threshold value α. The garage control unit 106 cuts off the power to the solenoid valve SR when the engagement pressure Pb2 of the brake B2 is higher than the lower threshold value α, and maintains the solenoid valve SR when the engagement pressure Pb2 is equal to or lower than the lower threshold value α. As a result, when the fail-safe valve 160 is switched to the fail state during the switching transition period, the power to the solenoid valve SR is maintained, and when the fail-safe valve 160 is maintained in the normal state during the switching transition period, the power to the solenoid valve SR is cut off, thereby preventing the spool valve element 160s of the fail-safe valve 160 from being switched to the fail position during the switching transition period.

For example, the engagement pressure Pb2 of the brake B2 is an estimated hydraulic pressure value based on the indicated pressure Pb2* (command pressure) of the brake B2 output from the electronic control device 100 to the hydraulic circuit 70. Alternatively, a hydraulic sensor that detects the hydraulic pressure of the hydraulic servo SVb2 of the brake B2 may be attached, and the engagement pressure Pb2 detected by the hydraulic sensor may be applied. Alternatively, a value obtained by adding a margin value X1 that takes into account the variation of parts, etc. to the lower limit threshold value α may be set as the judgment value, and whether or not to cut off the current to the solenoid valve SR may be determined based on whether or not the engagement pressure Pb2 of the brake B2 is higher than the judgment value.

In addition, to reliably determine that the engagement pressure Pb2 of the brake B2 is higher than the lower threshold value α, the garage control unit 106 can also determine whether or not to cut off the current to the solenoid valve SR based on whether or not a preset predetermined time tk has elapsed during which the engagement pressure Pb2 is higher than the lower threshold value α. The predetermined time tk is determined experimentally or by design, and is set to a value that ensures that the engagement pressure Pb2 is higher than the lower threshold value α. The predetermined time tk may also be changed according to the oil temperature, etc., taking into account the responsiveness of the hydraulic pressure.

In addition, even after the solenoid valve SR is de-energized, the garage control unit 106 continues to determine whether the engagement pressure Pb2 is higher than the lower threshold value α, and when the engagement pressure Pb2 falls below the lower threshold value α during garage control, it stops de-energizing the solenoid valve SR and switches it to a conductive state. This prevents the spool valve element 160s of the fail-safe valve 160 from moving to the fail position during garage control. When the garage control unit 106 determines that garage control has ended because the release of the hydraulic friction engagement device released by garage control has been completed, it switches the solenoid valve SR to a conductive state. In addition, when an abnormality is detected in the linear solenoid valve SL6, the garage control unit 106 switches the solenoid valve SR to a conductive state because the ability of the actual pressure to follow the command pressure Pb2* is not guaranteed.

Figure 5 is a flowchart that explains the main control operations of the electronic control unit 100, i.e., the control operations when the range operation position POSsh is switched from the R position to the N position. This flowchart is executed repeatedly while the vehicle is being driven.

First, in step S10 (hereinafter, step is omitted) corresponding to the control function of the garage control unit 106, it is determined whether garage control is being executed in response to the range operation position POSsh being switched from the R position to the N position. If the range operation position POSsh has not been switched or the garage control has ended, the determination in S10 is negative, and the solenoid valve SR is energized (SR solenoid is turned ON) in S40 corresponding to the control function of the garage control unit 106. If the determination in S10 is positive, it is determined in S20 corresponding to the control function of the garage control unit 106 whether the engagement pressure Pb2 of the brake B2 is higher than the lower limit threshold value α. If the determination in S20 is negative, the solenoid valve SR is energized in S40. On the other hand, if the determination in S20 is positive, the solenoid valve SR is de-energized in S30 corresponding to the control function of the garage control unit 106 (SR solenoid is turned OFF). At this time, because the engagement pressure Pb2 of the brake B2 is higher than the lower limit threshold α, even if the solenoid valve SR is de-energized and the signal pressure Psr is output from the solenoid valve SR, the spool valve element 160s of the fail-safe valve 160 is prevented from switching to the fail position. Therefore, even if the range operation position POSsh is quickly switched from the N position to the D position, the spool valve element 160s of the fail-safe valve 160 is prevented from transiently switching to the fail position in the D range, and shock during the switching transition is prevented.

Figure 6 is a time chart showing the control state when the range operation position POSsh is switched from the R position to the N position. In Figure 6, the time chart on the left corresponds to the time chart based on conventional control, and the time chart on the right corresponds to the time chart in this embodiment. In Figure 6, the horizontal axis corresponds to time t [sec], and the vertical axis corresponds, from the top, to the range operation position POSsh, the energization instruction of the signal pressure Psr of the solenoid valve SR, the instruction pressure Pc3* of the clutch C3, and the instruction pressure Pb2* of the brake B2.

At time t1, when the range operation position POSsh is switched from the R position to the N position, the release control (garage control) of the clutch C3 and the brake B2 is started. For both the clutch C3 and the brake B2, the command pressure is reduced by a predetermined value at time t1, and then the command pressure is temporarily held and then reduced toward zero at a predetermined gradient. Also, at time t1, the solenoid valve SR is de-energized (OFF) to ensure the source pressure for executing the release control of the clutch C3. At time t2, when the command pressure Pb2* of the brake B2 becomes the lower limit threshold value α, in this embodiment, the solenoid valve SR is switched to energized (ON). Therefore, the spool valve element 160s of the fail-safe valve 160 is prevented from switching to the fail position during the garage control. At time t3, the command pressure Pb2* of the brake B2 becomes zero, so that the end of the garage control is determined, and in the conventional control, the solenoid valve SR is switched to energized (ON) at time t3.

As described above, according to this embodiment, when all solenoid valves are de-energized when the range operation position POSsh is in the D position, the spool valve element 160s of the fail-safe valve 160 is switched to the fail position by the signal pressure Psr from the solenoid valve SR, and the forward range pressure PD is supplied from the fail-safe valve 160 to the hydraulic servo SVc4 of the clutch C4 to form a predetermined forward stage. This enables evacuation travel using the predetermined forward stage. In addition, when the range operation position POSsh is switched from the R position to the N position, the signal pressure Psr from the solenoid valve SR is supplied as the source pressure of the linear solenoid valve SL3 that outputs the engagement pressure Pc3 to the hydraulic servo SVc3 of the clutch C3 that forms the reverse stage, making it possible to hydraulically control the hydraulic servo SVc3 of the clutch C3 that forms the reverse stage, and suppressing shocks that occur during the switching transition period. At this time, the hydraulic pressure (engagement pressure Pb2) of the hydraulic servo SVb2 of the brake B2 is a predetermined hydraulic pressure Pb2r that does not switch the spool valve element 160s of the fail-safe valve 160 to the fail position due to the signal pressure Psr from the solenoid valve SR and is maintained in the normal position, so that the solenoid valve SR is de-energized, and the spool valve element 160s of the fail-safe valve 160 is prevented from switching to the fail position during the switching transition period. As a result, even if the range operation position POSsh is quickly switched from the R position to the N position via the D position, the fail-safe valve 160 is prevented from switching to the fail position and the forward range pressure PD is prevented from being supplied from the fail-safe valve 160 to the hydraulic servo SVc4 of the clutch C4, and shock caused by the forward range pressure PD being supplied to the hydraulic servo SVc4 in the D range can be prevented.

Next, another embodiment of the present invention will be described. In the following description, parts common to the previous embodiment will be given the same reference numerals and will not be described.

In the above embodiment, when the range operation position POSsh is switched from the R position to the N position, the solenoid valve SR is deenergized on the condition that the hydraulic pressure (engagement pressure Pb2) of the hydraulic servo SVb2 of the brake B2 is a predetermined hydraulic pressure Pb2r. In this embodiment, the solenoid valve SR is further deenergized on the condition that the hydraulic pressure (engagement pressure Pc3) of the hydraulic servo SVc3 of the clutch C3 forming the reverse gear is a predetermined hydraulic pressure Pc3r at which release control (drain control) of the hydraulic servo SVc3 of the clutch C3 is required. The hydraulic servo SVc3 of the clutch C3 corresponds to the hydraulic servo of the hydraulic friction engagement device forming the reverse gear of the present invention, and the predetermined hydraulic pressure Pc3r corresponds to the second predetermined hydraulic pressure of the present invention.

In the aforementioned FIG. 4, the horizontal axis indicates the engagement pressure Pc3 of the clutch C3. In FIG. 4, regions B and D correspond to regions where it is necessary to secure the source pressure supplied to the linear solenoid valve SL3 when performing the release control (drain control) of the clutch C3 during garage control. In other words, regions B and D correspond to regions where it is necessary to perform the release control of the engagement pressure Pc3 of the clutch C3 by the linear solenoid valve SL3 using the signal pressure Psr as the source pressure. On the other hand, regions A and C correspond to regions where the engagement pressure Pc3 of the clutch C3 is low and it is not necessary to perform the release control of the clutch C3, that is, the signal pressure Psr of the solenoid valve SR is not required as the source pressure.

In garage control, the solenoid valve SR is de-energized in order to ensure the base pressure (signal pressure Psr) required to execute the release control of the clutch C3. If the pressure of the clutch C3 is so low that it has no torque capacity, there is no need to execute the release control and there is no need to ensure the base pressure. In such a case, the solenoid valve SR is not de-energized, so it remains energized.

Here, the lower limit threshold value β, which is the boundary between areas A and C and areas B and D where release control of the clutch C3 is required, is set to, for example, a value obtained by adding a margin value X2 that takes into consideration variations in parts and the like to the pack end pressure Pend, which is the hydraulic pressure immediately before the clutch C3 produces torque capacity. In other words, the lower limit threshold value β is a value calculated by the following formula (2). The predetermined hydraulic pressure Pc3r is a range of hydraulic pressure values at which the clutch C3 has a torque capacity, and corresponds to a hydraulic pressure value higher than the lower limit threshold value β.
β=Pend+X2...(2)

In this embodiment, the garage control unit 106a (the reference number is changed to 106a to distinguish it from the previous embodiment) cuts off the power supply to the solenoid valve SR when the range operation position POSsh is switched from the R position to the N position, on the condition that the engagement pressure Pb2 of the hydraulic servo SVb2 of the brake B2 is a predetermined hydraulic pressure Pb2r and the engagement pressure Pc3 of the hydraulic servo SVc3 of the clutch C3 forming the reverse gear is a predetermined hydraulic pressure Pc3r. That is, when the range operation position POSsh is switched from the R position to the N position, the garage control unit 106a judges whether the engagement pressure Pb2 of the brake B2 is higher than the lower limit threshold α and the engagement pressure Pc3 of the clutch C3 is higher than the lower limit threshold β, and cuts off the power supply to the solenoid valve SR when it is determined that the engagement pressure Pb2 of the brake B2 is higher than the lower limit threshold α and the engagement pressure Pc3 of the clutch C3 is higher than the lower limit threshold β. On the other hand, when the engagement pressure Pb2 of the brake B2 is equal to or lower than the lower threshold value α and/or the engagement pressure Pb2 of the clutch C3 is equal to or lower than the lower threshold value β, the garage control unit 106a maintains the energization of the solenoid valve SR. For example, the engagement pressure Pc3 of the clutch C3 is an oil pressure value estimated based on the command pressure Pc3* of the clutch C3, or an oil pressure value directly detected by an oil pressure sensor. In addition, in order to reliably determine that the engagement pressure Pc3 is higher than the lower threshold value β, it may be possible to determine whether the state in which the engagement pressure Pc3 is higher than the lower threshold value β has elapsed for a predetermined time tl.

In addition, even after the garage control unit 106a cuts off the power supply to the solenoid valve SR, it continues to determine whether the engagement pressure Pb2 of the brake B2 is higher than the lower threshold value α and whether the engagement pressure Pc3 of the clutch C3 is higher than the lower threshold value β, and switches the solenoid valve SR to the powered state when at least one of these conditions is no longer met. In addition, when the garage control unit 106a determines that the garage control has ended, it switches the solenoid valve SR to the powered state.

Figure 7 is a flowchart that explains the main control operations of the electronic control unit 100 in this embodiment, i.e., the control operations when the range operation position POSsh is switched from the R position to the N position. This flowchart is executed repeatedly while the vehicle is being driven.

First, in S10, which corresponds to the control function of the garage control unit 106a, it is determined whether garage control is being performed when the range operation position POSsh is switched from the R position to the N position. If the range operation position POSsh is not being switched or the garage control is terminated, the determination in S10 is negative, and the solenoid valve SR is energized (SR solenoid ON) in S40, which corresponds to the control function of the garage control unit 106a. If the determination in S10 is positive, it is determined in S100, which corresponds to the control function of the garage control unit 106a, whether the engagement pressure Pb2 of the brake B2 is higher than the lower limit threshold α and the engagement pressure Pc3 of the clutch C3 is higher than the lower limit threshold β. If the determination in S100 is negative, the solenoid valve SR is energized in S40, which corresponds to the control function of the garage control unit 106a. On the other hand, if the determination in S100 is positive, in S30, which corresponds to the control function of the garage control unit 106a, the solenoid valve SR is de-energized (SR solenoid OFF), and the base pressure (signal pressure Psr) associated with the drain control of the clutch C3 is secured. In this way, the de-energization of the solenoid valve SR is limited to the region where the base pressure associated with the drain control of the clutch C3 needs to be secured, thereby preventing unnecessary de-energization of the solenoid valve SR.

As described above, this embodiment can achieve the same effects as the previous embodiment. Furthermore, according to this embodiment, when the range operation position POSsh is switched from the R position to the N position, the solenoid valve SR is deenergized on the condition that the hydraulic pressure of the hydraulic servo SVc3 of the clutch C3 that forms the reverse gear is a predetermined hydraulic pressure Pc3r that requires hydraulic control of the clutch C3. Therefore, when hydraulic control of the hydraulic servo SVc3 of the clutch C3 that forms the reverse gear using the signal pressure Psr of the solenoid valve SR as the base pressure is not required, the solenoid valve SR is maintained energized, thereby eliminating unnecessary deenergization of the solenoid valve SR.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

For example, in the above embodiment, the signal pressure Psr of the solenoid valve SR is input to the first oil chamber 160a of the fail-safe valve 160 and is supplied as the base pressure of the linear solenoid valve SL3 that controls the engagement pressure Pc3 of the clutch C3, but this is not necessarily limited to the solenoid valve SR of this embodiment. In other words, any solenoid valve can be used as appropriate as long as it is composed of a normally open solenoid valve that outputs hydraulic pressure in a non-energized state, and the output hydraulic pressure is supplied as the base pressure of a normally closed solenoid valve that outputs engagement pressure to a hydraulic servo of a hydraulic friction engagement device that forms a reverse gear, and is supplied to an oil chamber that biases the spool valve element of the fail-safe valve toward the fail position.

In addition, in the above embodiment, the engagement pressure Pb2 of the brake B2 is supplied to the second oil chamber 160b as the hydraulic pressure for biasing the spool valve element 160s of the fail-safe valve 160 to the normal position, but this is not necessarily limited to the engagement pressure Pb2 of the brake B2. In other words, as long as the hydraulic pressure of the hydraulic servo of the hydraulic friction engagement device is input to bias the spool valve element 160s of the fail-safe valve 160 to the normal position, the hydraulic servo of the hydraulic friction engagement device can be changed as appropriate.

In the above embodiment, if an all-off failure occurs while driving in 1st forward gear 1ST to 4th forward gear 4TH, 4th forward gear 4TH is formed as the predetermined forward gear, and if an all-off failure occurs while driving in 5th forward gear 5TH to 10th forward gear 10TH, 8th forward gear 8TH is formed as the predetermined forward gear. However, the predetermined gear is not necessarily limited to 4th forward gear 4TH or 8th forward gear 8TH, and the predetermined gear can be changed as appropriate. In addition, the control valve 150 is not necessarily required in the hydraulic circuit 70, and it can be omitted. For example, the control valve 150 can be omitted by forming a single predetermined gear when an all-off failure occurs while driving in any of the forward gears from 1st forward gear 1ST to 10th forward gear 10TH.

In the above embodiment, the automatic transmission 20 includes the first planetary gear unit 22 to the fourth planetary gear unit 28, the clutches C1 to C4, and the brakes B1 and B2, and is configured to be switchable between 10 forward speeds and 1 reverse speed; however, the number and structure of the speeds are not limited to the embodiment and may be changed as appropriate. As the structure of the automatic transmission is changed, the combination of the operating states of the clutches and brakes that form the forward speeds and reverse speeds is changed, and accordingly, the engagement pressure of the hydraulic friction engagement device supplied to the second oil chamber 160b of the failsafe valve 160 and the linear solenoid valve to which the signal pressure Psr is supplied as the base pressure are changed as appropriate.

The structure of the fail-safe valve 160 in the above embodiment is not limited to the embodiment and can be modified as appropriate. In short, as long as the fail-safe valve is configured so that the spool valve element is switched to the fail position when the solenoid valve SR is input, it can be modified as appropriate within the scope of no contradiction.

Note that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

20: Automatic transmission 70: Hydraulic circuit 72: Hydraulic control device 100: Electronic control device (control device)
110: Manual valve 160: Fail-safe valve (switching valve)
160s: spool valve element 160sp: spring (biasing member)
B1, B2: Brakes (hydraulic friction engagement devices)
C1 to C4: Clutch (hydraulic friction engagement device)
SL1 to SL6: Linear solenoid valves (normally closed solenoid valves)
SR: Solenoid valve (normally open solenoid valve)
SVc1 to SVb2: Multiple hydraulic servos SVb2: Hydraulic servo (first hydraulic servo)
SVc4: Hydraulic servo (second hydraulic servo)
SVc3: Hydraulic servo (hydraulic servo of a hydraulic friction engagement device forming a reverse gear)
POSsh: Range operation position (range operation position)
PD: forward range pressure PR: reverse range pressure Pb2r: predetermined oil pressure Pc3r: predetermined oil pressure (second predetermined oil pressure)

Claims (2)

A hydraulic control device for an automatic transmission that forms a reverse gear and a plurality of forward gears by the engagement states of a plurality of hydraulic friction engagement devices, comprising:
a plurality of normally closed solenoid valves each outputting an engagement pressure to a hydraulic servo of each of the plurality of hydraulic friction engagement devices when energized;
A normally open solenoid valve that outputs hydraulic pressure when de-energized;
a manual valve that outputs a forward range pressure when a range operation position is set to a forward range position and outputs a reverse range pressure when the range operation position is set to a reverse range position;
a switching valve having a spool valve that is biased toward a normal position by hydraulic pressure from a first hydraulic servo of the plurality of hydraulic servos and a biasing force of a biasing member, and that is biased toward a fail position by hydraulic pressure from the normally open solenoid valve, wherein when the range operation position is in a forward range position and all solenoid valves are in a de-energized state, the spool valve is switched to the fail position and the forward range pressure is supplied to a second hydraulic servo of the plurality of hydraulic servos to form a predetermined forward stage;
A control device that controls energization of the normally open solenoid valve,
the hydraulic circuit is configured to be able to supply hydraulic pressure from the normally open solenoid valve as a source pressure for a normally closed solenoid valve that outputs an engagement pressure to a hydraulic servo of a hydraulic friction engagement device that forms the reverse stage when the range operation position is switched from the reverse range position to a neutral range position,
the control device is configured to cut off current flow to the normally open solenoid valve when the range operation position is switched from the reverse range position to the neutral range position, on the condition that the hydraulic pressure of the first hydraulic servo is a predetermined hydraulic pressure at which the spool valve element of the switching valve is not switched to the fail position by the hydraulic pressure from the normally open solenoid valve and is maintained in the normal position. 2. The hydraulic control device for an automatic transmission according to claim 1, further comprising: a control device configured to cut off current flow to the normally open solenoid valve when the range operation position is switched from the reverse range position to the neutral range position, on the condition that a hydraulic pressure of a hydraulic servo of a hydraulic friction engagement device that forms the reverse stage is a second predetermined hydraulic pressure at which hydraulic control of the hydraulic servo is required.

Images