As the engine turns, the ATF pump starts to operate. Automatic transmission fluid (ATF) is drawn through the ATF strainer (filter) and discharged into the hydraulic circuit. Then, ATF flowing from the ATF pump becomes line pressure that is regulated by the main regulator valve. Torque converter pressure from the main regulator valve is regulated by the torque converter regulator valve and then flows to the torque converter. The torque converter regulator valve prevents torque converter pressure from rising. Line pressure also becomes torque converter clutch pressure that is regulated by the lock-up control valve, and flows to the torque converter clutch. The PCM switches shift solenoid valves ON and OFF, and it controls the shift solenoid pressure to the shift valves. Applying shift solenoid pressure to the shift valves moves the position of the shift valve, and switches the port of hydraulic pressure. The PCM also controls A/T clutch pressure control solenoid valves A, B, C, and D. The A/T clutch pressure control solenoid valves regulate hydraulic pressure, and applies the pressure to the clutch. When shifting between gears, the clutches are engaged by the A/T clutch pressure control solenoid valve pressures. The PCM actuates the shift solenoid valves to move the position of the shift valves. This movement switches the fluid flow to each clutch. Shifting is completed after the clutch is engaged by the A/T clutch pressure control solenoid valve pressures.

Line pressure (1) regulated by the main regulator valve flows to the shift solenoid valves. The PCM switches the shift solenoid valves ON and OFF. The conditions of the shift solenoid valves and the positions of the shift valves are as follows:

Line pressure (1) regulated by the main regulator valve flows to the shift solenoid valves. The PCM switches the shift solenoid valves ON and OFF. The conditions of the shift solenoid valves and the positions of the shift valves are as follows:

When shifting to D or S from N, the condition of shift solenoid valves A and B remains the same as in N, and the manual valve moves to the D position. Line pressure (4) from the manual valve is applied to the shift valve C line pressure port (4) and the A/T clutch pressure control solenoid valves A pressure port (4) and B pressure port (4). As shift solenoid valve A is ON and shift solenoid valve B is OFF, the line pressure (4A) from shift valve A applies to the shift valve C pressure port (4B) through shift valve B (4A, 4B). Shift valve C remains on the left side by the hydraulic pressure (4B) from shift valve B. Immediately after moving the shift lever to D or S from N, A/T clutch pressure control solenoid valve D operates to apply A/T clutch pressure control solenoid valve D pressure (58) to the 1st clutch passed through the lock-up shift valve pressure ports (58, 58’), the shift valve C pressure ports (58’, 3B), the manual valve pressure ports (3B, 5A), and the shift valve C pressure ports (5A, 10). A/T clutch pressure control solenoid valve D applies hydraulic pressure gently to the 1st clutch, and the 1st clutch is engaged smoothly.

The PCM commands shift solenoid valves A and B ON in 1st gear. Shift solenoid valve B is turned ON from OFF to apply shift solenoid valve B pressure (SB) to shift valve B. Shift valve B is moved to the right side by the shift solenoid valve B pressure (SB) to close the line pressure port (4B) leading to shift valve C. As the line pressure (4B) from shift valve B is not applied to shift valve C, shift valve C is moved to the right side by a spring force to connect the line pressure port (4) on shift valve C and the 1st clutch pressure port (10). With this shift valve C movement, line pressure (4) from the manual valve becomes 1st clutch pressure (10) at shift valve C, and flows to the 1st clutch. Then the 1st clutch is engaged by 1st clutch pressure (10).

The condition of shift solenoid valves A and B in 2nd gear remains the same as in 1st gear, the PCM commands shift solenoid valves A and B ON. As the speed of the vehicle reaches the programmed value, the PCM activates A/T clutch pressure control solenoid valve A, and applies CPC pressure (55) to shift valve A. Shift valve A remains on the right side as in the 1st gear. CPC pressure (55) from A/T clutch pressure control solenoid valve A becomes 2nd clutch pressure (20) at shift valve A, and flows to the 2nd clutch. Then the 2nd clutch is engaged by 2nd clutch pressure (20). The 1st clutch is also engaged, but since the rotation speed of the countershaft exceeds that of 1st gear, no power is transmitted because the one-way clutch causes 1st gear to free-wheel.

The PCM commands shift solenoid valve A OFF and shift solenoid valve B ON in 3rd gear. As the speed of the vehicle reaches the programmed value, the PCM activates A/T clutch pressure control solenoid valve B, and applies CPC pressure (56) to the shift valve B pressure port (56). Shift valve B remains on the right side as in the 1st gear. CPC pressure (56) from A/T clutch pressure control solenoid valve B becomes 3rd clutch pressure (30) at shift valve B, and flows to the 3rd clutch. Then the 3rd clutch is engaged by 3rd clutch pressure (30). The 1st clutch is also engaged, but since the rotation speed of the countershaft exceeds that of 1st gear, no power is transmitted because the one-way clutch causes 1st gear to free-wheel.

The PCM commands shift solenoid valves A OFF and shift solenoid valve B ON and OFF (depending on the shift schedule) in 4th gear. As the speed of the vehicle reaches the programmed value, the PCM activates A/T clutch pressure control solenoid valve C, and applies CPC pressure (57) to the shift valve C pressure port (57). As line pressure (4B) from shift valve B is not applied to shift valve C, shift valve C is moved to the right side by a spring force to connect the CPC pressure port (57) on shift valve C and the line pressure port (5B) leading to the reverse inhibitor valve. Since the reverse inhibitor valve also remains on the right side under a line pressure (4), it connects the CPC pressure port (5B) from shift valve C on the reverse inhibitor valve to the pressure port (40) leading to the 4th clutch. With this shift valve C and the reverse inhibitor valve operations, CPC pressure (57) flows from the reverse inhibitor valve pressure port (5B, 40) to the 4th clutch through shift valve C pressure ports (57, 5B). Then the 4th clutch is engaged by 4th clutch pressure (40). The 1st clutch is also engaged, but since the rotation speed of the countershaft exceeds that of 1st gear, no power is transmitted because the one-way clutch causes 1st gear to free-wheel.

The condition of shift solenoid valves A and B in 5th gear remains the same as in 4th gear, the PCM commands shift solenoid valve A OFF and shift solenoid valve B ON and OFF (depending on the shift schedule). As the speed of the vehicle reaches the programmed value, the PCM activates A/T clutch pressure control solenoid valve A, and applies CPC pressure (55) to the shift valve A pressure port (55). As shift solenoid valve A remains OFF, shift valve A is stayed in the left side by a spring force, to connect the CPC pressure port (55) on shift valve A and the 5th clutch pressure port (50). CPC pressure (55) becomes 5th clutch pressure (50) at shift valve A, and flows to the 5th clutch. Then the 5th clutch is engaged by 5th clutch pressure (50). 1st clutch is also engaged, but since the rotation speed of the countershaft exceeds that of 1st gear, no power is transmitted because the one-way clutch causes 1st gear to free-wheel.

The PCM commands shift solenoid valves A and B OFF in 6th gear. As the speed of the vehicle reaches the programmed value, the PCM activates A/T clutch pressure control solenoid valve B, and applies CPC pressure (56) to the shift valve B pressure port (56). As shift solenoid valve B remains OFF, shift valve B is stayed in the left side by a spring force, to connect the CPC pressure port (56) on shift valve B and the 6th clutch pressure port (60). With this shift valve B movement, CPC pressure (56) becomes 6th clutch pressure (60) at shift valve B, and flows to the 6th clutch. Then the 6th clutch is engaged by 6th clutch pressure (60). The 1st clutch is also engaged, but since the rotation speed of the countershaft exceeds that of 1st gear, no power is transmitted because the one-way clutch causes 1st gear to free-wheel.

The vehicle is moved backward by engaging the 4th clutch. When shifting to R from N, shift solenoid valve A turns ON, shift solenoid valve B turns OFF, and shift solenoid valve C turns ON, and the manual valve moves to the R position. Line pressure (3) from the manual valve is applied to the shift valve C line pressure port (3) and the reverse inhibitor valve line pressure port (3). The reverse inhibitor valve is moved to the left side by shift solenoid valve C pressure (SC) to connect the line pressure port (3C) from the shift fork shaft on the reverse inhibitor valve and the 4th clutch pressure port (40) leading to the 4th clutch. As line pressure (1, 4A) flows from shift valve A to the shift valve C line pressure port (4B) through shift valve B (4A, 4B), shift valve C is moved to the left side. Immediately after moving the shift lever to R from N, A/T clutch pressure control solenoid valve D operates to apply A/T clutch pressure control solenoid valve D pressure (58) to the 4th clutch through the lock-up shift valve pressure ports (58, 58'), the shift valve C pressure ports (58', 3B), the manual valve pressure ports (3B, 3A), the shift fork shaft pressure ports (3A, 3C), and the reverse inhibitor valve pressure ports (3C, 40). Then, A/T clutch pressure control solenoid valve D applies hydraulic pressure gently to the 4th clutch, and the 4th clutch is engaged smoothly.

The vehicle is moved backward by engaging the 4th clutch and reversing the mainshaft rotation with the reverse idler gear. Shift solenoid valves A and B remain OFF, and shift solenoid valve C turns ON when the vehicle moving backward. As shift solenoid valves A and B remain OFF, shift valve C is moved to the right side by a spring force to connect the line pressure port (3) on shift valve C and the line pressure port (3B) leading to the reverse inhibitor valve. The reverse inhibitor valve is moved to the left side by shift solenoid valve C pressure (SC) to connect the line pressure port (3C) from the shift fork shaft on the reverse inhibitor valve and the 4th clutch pressure port (40) leading to the 4th clutch. Line pressure (3) from the manual valve is also applied to the shift fork shaft line pressure port (3') through the reverse inhibitor valve line pressure ports (3, 3'), which moves the shift fork shaft to the right side, and connects the port (3A) from the manual valve on the shift fork shaft to the line pressure port (3C) leading to the reverse inhibitor valve. With this shift valve C, the reverse inhibitor valve, and the shift fork shaft movement, line pressure (3C) becomes 4th clutch pressure (40) at the reverse inhibitor valve, and flows to the 4th clutch. Then the 4th clutch is engaged by 4th clutch pressure (40).

When R is selected while the vehicle is moving forward at speeds over 6 mph (10 km/h), the PCM commands shift solenoid valve C to remain OFF so that shift solenoid valve C pressure (SC) is not applied to the reverse inhibitor valve. Line pressure (3) stops at the reverse inhibitor valve, and is not applied to the shift fork shaft. This control does not switch to the hydraulic circuit leading to reverse while the vehicle is moving forward at speeds over 6 mph (10 km/h).