With CVT Part 3

ELECTRONIC CONTROL SYSTEM








The electronic control system consists of the Powertrain Control Module (PCM), sensors, three linear solenoids, and an inhibitor solenoid. Shifting is electronically controlled under all conditions. The PCM is located below the dashboard, behind the kick panel on the driver's side.
The TCM controls the transmission to reduce engine speed and retain the engine's cooling efficiency when the vehicle is driven with full throttle acceleration.
If the vehicle is continuously driven at full throttle acceleration, the TCM regulates the pulley hydraulic pressure to increase the pulley ratio, which, as the result, reduces the engine speed and retains the designed cooling efficiency. After the vehicle has been driven at a lower engine speed for a while, the PCM increases the pulley ratio to the original ratio.
For smooth starting in the [R] position, the TCM sends a signal to the ECM to cut off the A/C clutch (if the A/C is on) and increases the engine speed to 900 rpm when the transmission is shifted to the [R] position.

The start clutch functions to make smooth starting possible. To let the start clutch function properly, the PCM regulates the start clutch hydraulic pressure based on the engine's negative pressure memorized in the [N] position.


HYDRAULIC CONTROL
The hydraulic control system is controlled by the Automatic Transmission Fluid (ATF) pump, the valves, and the solenoids. The ATF pump is driven by the input shaft. The ATF pump and the input shaft are linked by the ATF pump drive chain and the sprockets. The inhibitor solenoid valve and the linear solenoids, which are located on their valve body, are controlled by the Transmission Control Module (TCM)or Powertrain Control Module (PCM). Fluid from the ATF pump flows through the Pressure High (PH)regulator valve to maintain specified pressure to the drive pulley, the driven pulley, and the manual valve.
The lower valve body assembly includes the main valve body, the PL regulator valve body, the shift valve body, the start clutch control valve body, and the secondary valve body.

Main Valve Body





The main valve body contains the Pressure High (PH) control valve, the lubrication valve, and the Pitot regulator valve.
- Pressure High (PH) Control Valve
The PH control valve supplies PH Control pressure (PHC) in accordance with the PH-PL control pressure (HLC), and supplies PH control pressure to the PH regulator valve, which also regulates PH pressure. At kick-down, it increases PH control pressure which increases the high (PH) pressure. This shortens the shift speed by releasing the Reverse Inhibitor pressure (RI) from the inhibitor solenoid valve.

- Lubrication Valve
The lubrication valve controls the lubrication pressure to each shaft and maintains lubrication pressure. When the pressure is too high, the spring is compressed. This moves the lubrication valve and opens the fluid leak passage.

- Pitot Regulator Valve
The Pitot regulator valve controls the Start Clutch pressure (SC) in accordance with the engine speed, when the electronic control system is faulty.

Secondary Valve Body





The secondary valve body contains the Pressure High (PH) regulator valve, the clutch reducing valve, the start clutch valve accumulator, and the shift inhibitor valve.

- PH Regulator Valve
The PH regulator valve maintains hydraulic pressure supplied from the Automatic Transmission Fluid (ATF) pump, and supplies PH pressure to the hydraulic control circuit and the lubrication circuit. PH pressure is regulated at the PH regulator valve by the Ph Control pressure (PHC) from the PH control valve.

- Clutch Reducing Valve
The clutch reducing valve receives PH pressure from the PH regulator valve and regulates the Clutch Reducing pressure (CR). The clutch reducing valve supplies clutch pressure (CR) to the manual valve and the start clutch control valve, and supplies signal pressure to the PH-PL pressure control valve, the shift control valve, and the inhibitor solenoid valve.

- Start Clutch Valve Accumulator
The start clutch valve accumulator stabilizes the hydraulic pressure that is supplied to the start clutch.

- Shift Inhibitor Valve
The shift inhibitor valve switches the fluid passage to switch the start clutch control from electronic control to hydraulic control when the electronic control system is faulty. It also supplies clutch reducing pressure (CR) to the Pitot regulator valve and the Pitot lubrication pipe.

PL Regulator Valve Body





The Pressure Low (PL) regulator valve body contains the PL regulator valve and the Pressure High (PH)-PL control valve, which is joined with the PH-PL control linear solenoid. The inhibitor solenoid is bolted on the PL regulator valve body.

- PL Regulator Valve
The PL regulator valve supplies low pressure (PL) to the pulley to eliminate steel belt slippage. The PL pressure is controlled by the PH-PL control pressure (HLP).

- PH-PL Control Valve
The PH-PL control valve controls the PL regulator valve according to engine torque. The PH-PL control valve supplies PH-PL control pressure (HLC) to the PH control valve to regulate PH pressure higher than PL pressure. The PH-PL control valve is controlled by the PH-PL control linear solenoid, which is controlled by the TCM or PCM.

- Inhibitor Solenoid
The inhibitor solenoid controls the reverse inhibitor valve by turning on and off. Also, the inhibitor solenoid controls PH control pressure (PHC) by applying Reverse Inhibitor pressure (RI) to the PH control valve. The inhibitor solenoid is con trolled by the Transmission Control Module (TCM) or Powertrain Control Module (PCM).

Start Clutch Control Valve Body
The start clutch control valve body contains the start clutch control valve. Both are joined to the start clutch control linear solenoid.

- Start Clutch Control Valve
The start clutch control valve controls start clutch engagement according to the throttle opening. The start clutch control valve is controlled by the start clutch control linear solenoid, which is controlled by the Transmission Control Module (TCM) or Powertrain Control Module (PCM).

Shift Valve Body





The shift valve body contains the shift valve and the shift control valve. Both are joined to the shift control linear solenoid.

- Shift Valve
The shift valve is controlled by Shift Valve pressure (SV) from the shift control valve. The shift valve distributes PH pressure and PL pressure to drive pulley and the driven pulley, to shift the transmission.

- Shift Control Valve
Valve The shift control valve controls the shift valve in accordance with the throttle opening and vehicle speed. The shift control valve is controlled by the shift control linear solenoid, which is controlled by the Transmission Control Module (TCM) or Powertrain Control Module (PCM). When the electronic control system is faulty, the shift control valve switches the shift inhibitor valve to uncover the port leading the Pitot regulator pressure to the start clutch.

Manual Valve Body





The manual valve body contains the manual valve and the reverse inhibitor valve. The manual valve body is bolted to the intermediate housing.

- Manual Valve
The manual valve mechanically uncovers/covers the fluid passage according to the shift lever position.

- Reverse Inhibitor Valve
The reverse inhibitor valve is controlled by the Reverse Inhibitor pressure (RI). It intercepts the hydraulic circuit to the reverse brake while the vehicle is moving forward at speeds over approximately 6 mph (10 km/h).


HYDRAULIC FLOW





[N] Position





As the engine turns, the Automatic Transmission Fluid (ATF) pump also starts to operate. Fluid from the ATF pump flows to the PH regulator valve and the clutch reducing valve. The Pressure High (PH) regulator valve regulates High Pressure (PH), and send it to the shift valve and the PL regulator valve. The high pressure (PH) flows to the movable face of the driven pulley via the shift valve, and turns into Low Pressure (PL) at the PL regulator valve. The low pressure (PL) flows to the movable face of the drive pulley via the shift valve. At this time, the pulley ratio remains low.
The High Pressure (PH) becomes the Clutch Reducing pressure (CR) at the clutch reducing valve. The clutch reducing pressure (CR) flows to the start clutch control valve, the manual valve, the PH-PL control valve, and the shift control valve, and is intercepted by those valves.
Under this condition, hydraulic pressure is not applied to the clutches and reverse brake.

[D] position, at low speed range





The flow of fluid up to the drive pulley, the driven pulley, and the clutch reducing valve is the same as in [N] position. The pulley ratio is low because the driven pulley receives High Pressure (PH), and the drive pulley receives Low Pressure (PL). The Clutch Reducing pressure (CR) flows through the manual valve to the forward clutch, then forward clutch is engaged. The forward clutch then drives the drive pulley shaft, which drives the driven pulley shaft. Also, clutch reducing pressure (CR) flows to the start clutch control valve, and becomes Clutch Control pressure (CC). Clutch control pressure (CC) becomes Start Clutch pressure (SC) at the shift inhibitor valve. Start clutch pressure (SC) is applied to the start clutch to engage the start clutch.

[D] position, at middle speed range





As the speed of the vehicle reaches the prescribed value, the shift control linear solenoid is activated by the Transmission Control Module (TCM) or Powertrain Control Module (PCM). The shift control linear solenoid controls the shift control valve to activate Shift Valve pressure (SV). Clutch Reducing pressure (CR) from the clutch reducing valve becomes shift valve pressure (SV) at the shift control valve. Shift valve pressure (SV) flows to the left end of the shift valve, the shift valve to the right side and positioning it in the middle of its travel. The shift valve covers the port to stop High Pressure (PH) to the pulleys, and uncovers the port leading Low Pressure (PL) to the pulleys. The drive pulley and the driven pulley receive low pressure (PL). At this time, the pulley ratio is in the middle. Pressure remains to apply the forward clutch and the start clutch.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

[D] position, at high speed range





As the speed of the vehicle reaches the prescribed value, the shift control linear solenoid moves the shift control valve to increase Shift Valve pressure (SV) at the left end of the shift valve. The shift valve moves to the right side compared to its position at the middle pulley ratio. The shift valve uncovers the port leading High Pressure (PH) to the drive pulley and uncovers the port leading Low Pressure (PL) to the driven pulley. The drive pulley receives high pressure (PH) and the driven pulley receives low pressure (PL). The pulley ratio is high. Pressure remains to apply the forward clutch and the start clutch.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

[R] position





The flow of fluid up to the drive pulley, the driven pulley, and the clutch reducing valve is the same as in [N] position. The pulley ratio is low because the driven pulley receives High Pressure (PH) and the drive pulley receives Low Pressure (PL).
The manual valve is shifted into the [R] position, and it uncovers the port that leads Reverse Brake Pressure (RBP) to the reverse inhibitor valve. The inhibitor solenoid turns off by means of the TCM or PCM, and Reverse Inhibitor pressure (RI) is applied to the right end of the reverse inhibitor valve. The reverse inhibitor valve moves to the left side, and uncovers the port that leads reverse brake pressure (RVS) to the reverse brake. Clutch Reducing pressure (CR) becomes reverse brake pressure (RVS) at the manual valve, and flows to the reverse brake. The reverse brake is engaged, and it locks the ring gear.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

[R] position
Reverse Inhibitor Control





If the [R] position is selected while the vehicle is moving forward at speeds over 6 mph (10 km/h), the inhibitor solenoid doesn't turn off by means of the Transmission Control Module (TCM) or Powertrain Control Module (PCM). Reverse Inhibitor pressure (RI) is not applied to the reverse inhibitor valve as the reverse inhibitor solenoid turns on. The reverse inhibitor valve is kept on the right side, and covers the port to stop Reverse Brake Pressure (RVS) to the reverse brake from the manual valve. Reverse brake pressure (RVS) is not applied to the reverse brake, and power is not transmitted to the reverse direction.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

[P] position





The flow of fluid up to the drive pulley, the driven pulley, and the clutch reducing valve is the same as in [N] position. Clutch Reducing Pressure (CR) flows to the start clutch control valve, the manual valve, and the shift control valve, and is intercepted by those valves. Under this condition, hydraulic pressure is not applied to the clutches and reverse brake.

[D] position, when the electronic control system is faulty.





When the electronic control system (linear solenoids and sensors) is faulty, the transmission uses the Pitot Pipe Pressure (PP) to allow the vehicle to drive.
When all linear solenoids and sensors are off because of a faulty electronic control system, Clutch Reducing Pressure (CR) flows to the start clutch control valve, the manual valve, the PH-PL control valve, and the shift control valve. Clutch reducing pressure (CR) becomes Shift Valve Pressure (SV) at the shift control valve, and shift valve pressure (SV) is applied to the left end of the shift valve and the right end of the shift inhibitor valve. The shift valve moves to the right side, and uncovers the port that leads High Pressure (PH) to the drive pulley and uncovers the port that leads Low Pressure (PL) to the driven pulley. At this time, the pulley ratio is high. The shift inhibitor valve moves to the left side, and uncovers the port that leads Shift Inhibitor Pressure (SI) to the Pitot lubrication pipe and the Pitot regulator valve. The Pitot lubrication pipe discharges fluid inside of the Pitot flange, and discharged fluid enters into the Pitot pipe and it is applied to the left end of the Pitot regulator valve. The Pitot regulator valve moves to the right side, and uncovers the port that leads Pitot Regulator Pressure (PR) to the shift inhibitor valve. Pitot regulator pressure (PR) becomes Start Clutch Pressure (SC) at the shift inhibitor valve, and is applied to the start clutch. The start clutch is engaged. The Forward Clutch Pressure (FWD) is applied to the forward clutch, and the forward clutch is engaged. This allows the vehicle to drive.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

[R] position, when the electronic control system is faulty.





The flow of fluid up to the drive pulley, the driven pulley, and the start clutch is the same as in [D] position.
The manual valve is shifted into the [R] position, and it uncovers the port that leads Reverse Brake Pressure (RVS) to the reverse inhibitor valve. Reverse Inhibitor Pressure (RI) is applied to the right end of the reverse inhibitor valve because of a faulty inhibitor solenoid. The reverse inhibitor valve moves to the left side, and uncovers the port that leads reverse brake pressure (RVS) to the reverse brake. Clutch Reducing Pressure (CR) becomes reverse brake pressure (RVS) at the manual valve, and flows to the reverse brake. The reverse brake is engaged and locks the ring gear. This allows the vehicle to drive in reverse.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.


PARK MECHANISM





The park mechanism locks the transmission by engaging the park pawl with the park gear which is integral with the secondary drive gear. The secondary drive gear engages with the secondary driven gear which engages with the final driven gear.
Shifting to [P] position causes the park cone (installed at the end of the park rod) to press the park pawl onto the park gear. Even if the end of the park pawl rides on the top of the park gear teeth, slight movement of the vehicle will cause the park pawl and the park gear to mesh with each other completely because the park cone receives the tension from the park rod spring. The park pawl receives the tension (which acts to separate the park pawl from the park gear) from the park pawl spring.