1. Roles of components

The gears are shifted by switching the operation of the clutches and brakes. The shift valves switch the fluid passage that causes the hydraulic pressure to be applied on the brakes and clutches. The shift valves are 1- 2, 2- 3, and 3-4.

2. Operation

Example: 1-2 shift valve

When the hydraulic pressure is applied on the top of shift valve, the transaxle is kept in first gear because the shift valve is at the bottom and fluid passages to the clutches and brakes are cut off. However, when the hydraulic pressure that was applied is cut off by the operation of the solenoid valve, the spring force moves the valve up, so the fluid passage to B2 is opened, B2 operates, and the gear is shifted up to 2nd gear.

Solenoid Valve

The solenoid valve is operated by signals from the Engine & ECT ECU to operate the shift valves and control the hydraulic pressure. There are two types of solenoid valves. A shift solenoid valve opens and closes the fluid passage according to signals from the ECU (opening the fluid passage for an on signal and closing it for an off signal). A linear solenoid valve controls the hydraulic pressure in a linear manner according to the electrical current sent from the ECU. Shift solenoid valves are used for controlling gear shift and linear solenoid valves are used for such functions as controlling hydraulic pressure.

HINT:

There is also a type of shift solenoid valve that raises a spool to open the fluid passage when the signal is off and closes the fluid passage when the signal is on. Also, the shift solenoid valve has No.1 and No.2 while the linear solenoid valve has a SLT that is used instead of the throttle valve and a SLU to control the lock up, etc.

Throttle Valve

The throttle valve produces throttle pressure in response to accelerator pedal angle via throttle cable and throttle cam. Throttle pressure is applied on the primary regulator valve and, accordingly, regulates line pressure in accordance with the throttle valve opening. Some models control the throttle pressure with a linear solenoid valve (SLT) instead of a throttle valve. Such models control the throttle pressure by the Engine & ECT ECU sending signals to the linear solenoid valve according to the signals from the throttle position sensor (accelerator opening angle).

1. Line pressure optimal control

The ECT uses a throttle position sensor to detect the accelerator opening angle (load) and control the line pressure. The line pressure is controlled by using a linear solenoid valve (SLT). Through the use of the linear solenoid valve (SLT), the line pressure is optimally controlled in accordance with the engine torque information, as well as with the internal operating conditions of the torque converter and the transaxle. Accordingly, the line pressure can be controlled minutely in accordance with the engine output, traveling condition, and the ATF temperature, thus realizing smooth shift characteristics and optimizing the workload on the oil pump.

HINT:

For line pressure control, some models use the throttle cable in the same manner as the full hydraulically-controlled automatic transaxle.

SERVICE HINT:

If the solenoid valve (SLT) fails, the inner valve will be fixed at the top (Hi side), so there will be a greater shock during shifting.

2. Clutch pressure optimal control

Linear solenoid valve (SLT) is used for optimal control of clutch pressure. The ECU monitors the signals from various types of sensors such as the input turbine speed sensor, allowing linear solenoid valve (SLT) to minutely control the clutch pressure in accordance with engine output and driving conditions. As a result, smooth shift characteristics have been realized.

3. Clutch to clutch pressure control

When the automatic transaxle shifts, hydraulic pressure is released from one element and used for another. The clutch to clutch pressure control is adopted to make this process smooth. This control that the ECU sends a signal to the linear solenoid valve (SLT) and the hydraulic pressure applying on the back pressure side of the accumulator is optimized.

4. Engine torque control

Engagement of the clutches and brakes of the planetary gear unit in the transaxle is controlled smoothly by momentarily retarding the engine ignition timing when gears are shifting up or down in the transaxle. When the ECU judges a gear shift timing according to signals from various sensors, it activates the shift control solenoid valves to perform gear shifting. When the gear shifting starts, the ECU retards the engine ignition timing to reduce the engine torque. As a result, engagement force of the clutches and brakes of the planetary gear unit is weakened and the gear shift change is performed smoothly.

5. “N” to “D” squat control

When the transaxle is shifted from the “N” range to the “D” range, the squat control system prevents it from shifting directly into 1st gear, by causing it to shift into 2nd or 3rd gear first, and then into 1st gear. It does this in order to reduce shifting shock and squatting of the vehicle. Squat control functions only when all of the following conditions exist simultaneously.

Vehicle halted

Stop light switch ON

Transaxle being shifted from “N” range to “D” range

Coolant warmed-up

6. Shifting control in uphill/downhill driving

In a conventional automatic transaxle, when accelerating/decelerating on a hill, the gears will frequently shift depending on the conditions, which prevents smooth driving. To perform the shifting control in uphill/ downhill driving, the Engine & ECT ECU uses the throttle position sensor and speed sensor signals to select the optimum gear position. When the ECU determines to be climbing, shifting up to the O/D gear is restricted to achieve smooth driving. In addition, when the ECU determines to be descending and brake operation is detected, the transaxle is shifted down to the 3rd gear and engine braking is engaged.

HINT:

Hill climbing and descending is determined by comparing the actual acceleration calculated from the speed sensor signal with the standard acceleration stored in the ECUÅfs memory.

The Engine & ECT ECU has programmed in its memory a lock-up clutch operation pattern for each driving mode. Based on this lock-up pattern, the ECU turns the solenoid valve on or off in accordance with the vehicle speed signals and the throttle opening signals. The ECU will turn on solenoid valve to operate the lockup system if the following three conditions exist simultaneously.

1. The vehicle is traveling in 2nd or 3rd gear or in overdrive (“D” range).

2. The vehicle speed is at or above the specified speed and the throttle opening angle is at or above the specified value.

3. The ECU has received no mandatory lock-up system cancellation signal.

The ECU controls the lock-up timing in order to reduce shock during shifting. If the transaxle shifts up or down while the lock- up system is in operation, the ECU deactivates the lock-up system. This helps to reduce shifting shock. After shifting up or down is completed, the ECU reactivates the lock-up system. However, the ECU forces to cancel the lock-up under the following conditions.

1. The stop light switch comes on (during braking).

2. The IDL points of the throttle position sensor close.

3. The coolant temperature is below a certain temperature.

4. The vehicle speed drops about 10 km/h or more below the set speed while the cruise control system is operating.

Control of Flex Lock-up

The flex lock-up clutch system expands the lock- up operation range by stabilizing and keeping a slight slippage of the lock-up clutch to improve the fuel economy. The Engine & ECT ECU determines the flex lock-up operation range from the throttle opening angle and vehicle speed, and then the ECU sends a signal to the linear solenoid valve (SLU). In addition, the ECU uses the engine speed and transaxle input speed sensor signal to detect the difference between the torque converter pump impeller (engine) and turbine runner (transaxle) speeds. This makes feedback control to optimize the power transmission distribution of the torque converter (fluid power transmission) and lock-up clutch (mechanical power transmission).

The Engine & ECT ECU performs the following controls.

Control of shift timing

Control of lock-up

Control of flex lock-up

Other controls

The ECT vehicle can be driven smoothly and comfortable by the above controls.

Control of Shift Timing

The Engine & ECT ECU has programmed into its memory the optimal shift pattern for each shift lever position and each driving mode. Based on the shift pattern, the ECU turns the solenoid valves on or off in accordance with the vehicle speed signal from the vehicle speed sensor, with the throttle opening angle signal from the throttle position sensor and with various sensor/switch signals. In this manner, the ECU operates each solenoid valve, opening or closing the fluid passages to the clutches and brakes permits shifting up or down of the transaxle.

SERVICE HINT:

When a vehicle is driven, you can judge if the automatic transaxle is faulty or not by how well the shifting points conform to the automatic shift diagram.

The relationship between the vehicle speed and gear varies by the accelerator opening angle even at the same vehicle speed. When driving while normally keeping the accelerator opening constant, the vehicle speed increases and the transaxle shifts up. When the accelerator is released at point A shown in the figure at left and the accelerator opening reaches point B, the transaxle shifts up from 3rd to O/D gear. Conversely, when the accelerator is further depressed at point A and the accelerator opening reaches point C, the transmission shifts down from 3rd to 2nd gear.

HINT:

When the coolant temperature is low, the transaxle does not shift up to O/D gear.

REFERENCE:

The speed at which the transaxle shifts up and the speed at which it shifts down occur with in a certain range, regardless of the gear. This range is called hysteresis. Hysteresis is a characteristic built into every automatic transaxle to prevent the transaxle from shifting up and down too frequently. The shift timing control differs depending on the driving pattern select switch mode. The ECU determines what the current mode is and controls the shift timing.

Example: For the power mode, the gear shift point and lock-up point are set to a higher engine speed than for the normal mode, which allows the driving sportier vehicle as using a higher engine speed.

Shift lever lock systems are adopted to prevent mis-operation of the shift lever. With this mechanism, when the shift lever is in the “P” range, the shift lever cannot move unless the ignition key is in the ON position and the brake pedal is depressed. Also, when the shift lever is not in the “P” range, the ignition key cannot be turned from ON or ACC to LOCK and the ignition key cannot be removed. There is a release button for manually canceling the shift lock mechanism if the battery is dead.

2. Components

The shift lever section includes the shift lock plate, shift lock link, shift lock solenoid, shift lock computer, and shift lock release button. The key cylinder section comprises such parts as the lock pin and cam. The lock pin is connected to the shift lock plate via the parking lock cable.

HINT:

Some models eliminate the parking lock cable and control with a solenoid valve.

3. Operation

(1) Shift lever lock mechanism When the shift lever is in the “P” range, unless the ignition key is in the ON position and the brake pedal is depressed, no current flows to the shift lock solenoid, so the shift lever cannot be moved. When shift lock plate moves to the release side by the shift lock solenoid, the shift lever can be moved when pushing the shift lever knob button, the shift lock pin is pushed down and shift lock link moves downward.

(2) Key interlock mechanism When pushing the shift lever knob button, the shift lock pin is pushed down and the shift lock link moves downward. When the shift lever is moved to the ranges except ÅgPÅh range, the shift lock link is fixed at the lock position. And the key cylinder side lock pin is fixed on the lock side. The effect is that unless the shift lever is moved to the “P” range, the ignition key cannot be turned from ON or ACC to LOCK and the ignition key cannot be removed.

Control of ECT

The Engine & ECT ECU controls gear shift timing and lock-up by controls to the solenoid valves of the hydraulic control unit to maintain the optimal driving condition using the signals from the sensors and switches mounted on the engine and automatic transaxle. In addition, the ECU is provided with diagnosis and fail-safe functions when a sensor, etc., fails.

HINT:

The current ECU is an integration ofthe Engine ECU and ECT ECU, butpreviously it was separated.

The sensors/switches play the role of collecting the types of data used to determine the various controls, and convert them into electrical signals, which are then transmitted to the Engine & ECT ECU. The types of sensors/switches are as follows.

1. Throttle position sensor / Accelerator pedal position sensor

This detects the opening angle of thethrottle valve.

2. Kick down switch

This detects if the accelerator pedalis being depressed to full throttle.

3. Crankshaft position sensor

This detects the engine speed.

4. Transaxle speed sensor

Input turbine speed sensor

This detects the automatic transaxle

input shaft speed.

Counter gear speed sensor

This detects the automatic transaxle

output shaft speed.

5. Water temperature sensor

This detects the coolant temperature.

6. Vehicle speed sensor

This detects the vehicle speed.

7. Transaxle fluid temperature sensor

This detects the ATF (Automatic Transaxle Fluid) temperature in the automatic transaxle.

8. Overdrive main switch

The overdrive main switch is the O/D cancel switch. When the switch is turned OFF, the O/D gear does not shift up even when the shift up speed is reached. If the switch is turned OFF while driving in the O/D gear, the transaxle shifts down to the 3rd gear. In addition, the O/D OFF indicator light is turned on while the overdrive main switch is OFF.

HINT:

The overdrive main switch is sometimes also called the overdrive OFF switch or transaxle (transmission) control switch. With the gate type shift lever, the O/D can be canceled by operating the lever. There is no O/D OFF indicator light because a positioning light can be used to show the shift lever position.

9. Neutral start switch

The neutral start switch transmits the shift lever position to the Engine & ECT ECU. The ECU receives information on the range into which the transaxle has been shifted from the shift position sensor located in the neutral start switch, then determines the appropriate shift pattern.

HINT:

The contacts of this switch are also used to turn on one of the shift lever position indicator light to inform the driver of the current position of the shift lever. In addition, the ECU controls so that the starter can be operated only while the shift lever is in the “P” or “N” ranges, and so that when the shift lever is in the “R” range, a reverse warning buzzer sounds and the backup light turns on. Signals sent to the ECU from the neutral start switch vary by models.

10.Stop light switch

When the brake pedal is being depressed, the Engine & ECT ECU cancels the lock-up. This prevents the engine from being stalled by the lock-up

11.Driving pattern select switch

The driving pattern select switch allows the driver to select the mode of choice. The mode switches that are installed depend on the model and the region.

Power mode: This sets the gear shift timing to the high engine speed range.

Snow mode: This sets the 2nd gear as the start-off gear.

Economy mode: This advances the gear shift timing to lower the fuel consumption while driving.

Manual mode: This makes gear hold possible using the shift lever position.

Each gear condition is explained using the solenoid valves and shift valves.

1. 1st gear

For gear shift from neutral to 1st gear, the fluid passage to C1 is opened by switching the manual valve. Since the No. 1 solenoid valve is on and the No. 2 solenoid valve is off, the fluid passage to C0 is opened. (No.1 solenoid valve is on, and No.2 solenoid valve is off.) The operation of C1 and F2 creates the fluid passage for 1st gear. In the “D” and “2″ ranges, the engine brake is not applied because of the operation of F2. In the “L” range, the passage to B3 is opened and the engine brake is applied.

Hydraulic pressure to the planetary gear unit

C1 from manual valve

C0 from 3-4 shift valve

B3 from 2-3 shift valve

2. 2nd gear

The No. 2 solenoid valve is switched from off to on according to signals from the ECU. (No.1 solenoid valve is on, and No.2 solenoid valve is on.) The hydraulic pressure applied on the top of the 1-2 and 3-4 shift valves is discharged and the 1-2 shift valve is moved up by the force of the spring. Therefore, the fluid passage opens to B2. The operation of C1 and B2 (F1) shifts up to 2nd gear. In the “D” range, the engine brake is not applied because of the operation of F1. In the “2″ range, the fluid passage to B1 is opened and the engine brake is applied.

Hydraulic pressure to the planetary gear unit

C1 from manual valve

C0 from 3-4 shift valve

B2 from 1-2 shift valve

B1 from 1-2 shift valve

3. 3rd gear

The No. 1 solenoid valve is switched from on to off according to signals from the ECU. (No.1 solenoid valve is off, and No.2 solenoid valve is on.) The hydraulic pressure starts to be applied on the top of the 2-3 shift valve, moving down the 2-3 shift valve. Therefore, the fluid passage opens to C2. The operation of C1 and C2 shifts the gear up to 3rd gear.

Hydraulic pressure to the planetary gear unit

C1 from manual valve

C0 from 3-4 shift valve

B2 from 1-2 shift valve

C2 from 2-3 shift valve

4. O/D gear

The No. 2 solenoid valve is switched from on to off according to signals from the ECU. (No.1 solenoid valve is off, and No.2 solenoid valve is off.) The hydraulic pressure starts to be applied on the top of the 1-2 and 3-4 shift valves, moving down the 3-4 shift valve. (The line pressure from the 2-3 shift valve is applied at the bottom of the 1-2 shift valve, so 1-2 shift valve does not move.) Therefore, the fluid passage that had been acting on C0 to B0 is switched and the gear is shifted up to the O/D gear. When the overdrive main switch is OFF, it cannot shift up to the O/D gear. Because the ECU does not send the signal to turn off the No.2 solenoid valve.

Hydraulic pressure to the planetary gear unit

C1 from manual valve

B0 from 3-4 shift valve

B2 from 1-2 shift valve

C2 from 2-3 shift valve

Description

The shift lever corresponds to the gear shift lever of the manual transaxle. The driver can select the driving mode – forward or reverse travel, neutral, and park – by operating this lever. There are the following types of shift levers. The shift lever used depends on the vehicle and grade.

1. Straight type

2. Column type

3. Gate type

4. Straight type with E-shift system

HINT:

The overdrive main switch may also be called the overdrive OFF switch or the transaxle (transmission) control switch. The E-shift type can shift the gear up or down with the transaxle/transmission shift switch.

The valve body consists of an upper valve body, and a lower valve body. The valve body resembles a labyrinth, containing many passages through which the transaxle fluid flows. Many valves are built into these passages, they contained therein control fluid pressure and switch fluid from one passage to another. Normally, the valve body contains the

Primary regulator valve

Manual valve

Shift valves (1-2, 2-3, 3-4)

Solenoid valves (No. 1, No. 2)

Throttle valve

The number of valves depends on the model and some have valves other than those above.

Primary Regulator Valve

1. Roles of components

The primary regulator valve adjusts the hydraulic pressure (line pressure) to each element in conformity with the engine power to prevent pump power loss.

2. Operation

When the hydraulic pressure from the oil pump rises, the valve spring is compressed, the fluid passage to the drain is opened, and the line pressure is kept constant. Also, a throttle pressure operates under the valve and when the accelerator opening angle increases, the line pressure rises to prevent clutch and brake slipping. In the “R” range, the line pressure is raised further to prevent clutch and brake slipping.

Manual Valve

The manual valve is connected with the shift lever and linkage or the cable. Changing the shift lever position switches the fluid passage of manual valve and operates in each shift range.

Shift Level     Planetary

Position         Gear Unit

P         -           B3

R         -           C2,B3

N         -           -

D         -           C1

2          -           C1,B1

L          -           C1,B3

HINT:

In general, cables are used in FF (Front-engine, Front-wheel-drive) vehicles and linkage is used in FR

(Front-engine, Rear-wheel-drive) vehicles.

The oil pump is driven by the torque converter (engine) to supply the hydraulic pressure that is required for the operation of the automatic transaxle.

HINT:

Use the dipstick for fluid level inspection, making sure that the engine is running at an idle and that the ATF (Automatic Transaxle Fluid) is at normal operating temperature.

NOTICE:

When towing an automatic transaxle vehicle, since the oil pump does not operate, the fluid lubrication inside the transaxle can be insufficient and there is a danger of the transaxle being seized. For this reason, the automatic transaxle vehicle should be towed at a low speed (no more than 30 km/h) and no more than 80 km at one time. As a better method, the automatic transaxle vehicle should be towed with its drive wheels lifted clear of the ground, or the drive or propeller shaft should be disconnected.

The clutches and brakes that operate the planetary gear unit are operated by hydraulic pressure. The hydraulic control unit generates and adjusts this hydraulic pressure and switches its passage. The illustration on the left shows the hydraulic circuitry for the A140E model. The hydraulic pressure operates through various hydraulic pressure passages.

HINT:

If the battery is dead, it is possible to start the engine of manual transaxle vehicles by push-starting it, but with automatic transaxle vehicles, this is not possible. During push-starting, since the oil pump is not operating, the operating hydraulic pressure of the planetary gear unit is not generated. In other words, the power from the tires is not transmitted to the engine. The hydraulic control unit has the following three functions.

1. To generate hydraulic pressure

The oil pump has the function of generating the hydraulic pressure. The oil pump generates the hydraulic pressure required for automatic transaxle operation by driving the torque converter case (engine).

2. To adjust hydraulic pressure

The hydraulic pressure compressed by the oil pump is adjusted with the primary regulator valve. Also, the throttle valve produces the hydraulic pressure appropriate to the engine output.

3. To shift gears (to make theclutches and brakes operate)

When the clutch and brake operations of the planetary gear unit are switched, the gears are shifted. The fluid passage is created in accordance with the shift position by the manual valve. When the vehicle speed rises, signals are sent to the solenoid valves from the Engine & ECT ECU (Electronic Control Unit). The solenoid valves operate each shift valve to shifting the gears. The major components of the hydraulic control unit are the following.

Oil pump

Valve body

Primary regulator valve

Manual valve

Shift valve

Solenoid valve

Throttle valve