CVT System Description - Hydraulic Flow

CVT System Description - Hydraulic Flow

Hydraulic Flow

As the engine turns, the CVTF pump starts to operate. Transmission fluid (CVTF) is drawn through the CVTF strainer (filter) and discharged into the hydraulic circuit. Then, CVTF flowing from the CVTF pump flows to the pressure high (PH) regulator valve and becomes pressure high (PH) pressure. PH pressure flows to the pulley control valves and then to the pulleys.

The PCM actuates the solenoid valves to control hydraulic pressure shifting pulley ratio and engaging the start clutch.

Hydraulic Pressure Flow Circuit Diagram










Hydraulic Flow (cont'd)

N Position

Fluid from the CVTF pump is regulated to high pressure at the pressure high (PH) regulator valve, and flows to pulley control valves A and B. The CVT driven pulley pressure control solenoid valve and the CVT drive pulley pressure control solenoid valve control the PH regulator valve which applies pressure to the pulleys. The driven pulley receives pressure higher than the pressure the drive pulley receives. Hydraulic pressure to the forward clutch is blocked by the manual valve, and hydraulic pressure to the start clutch is blocked by the CVT clutch pressure control solenoid valve. Under this condition, hydraulic pressure is not applied to the start clutch and the forward clutch.






D Position, at low speed range

The manual valve is shifted into the D position, and uncovers the forward clutch (FWD) pressure port leading to the forward clutch. Forward clutch (FWD) pressure flows to the forward clutch, the forward clutch is engaged, and drives the input shaft and the drive pulley shaft. The drive pulley receives low pressure, and the driven pulley receives high pressure. The PCM actuates the CVT clutch pressure control solenoid valve to control start clutch pressure. Start clutch control (CC) pressure from the CVT clutch pressure control solenoid valve becomes start clutch (SC) pressure at the shift inhibitor valve, and flows to the start clutch. The start clutch is engaged, and the vehicle moves.






Hydraulic Flow (cont'd)

D Position, at high speed range

As the speed of the vehicle reaches the programmed value, the PCM controls the CVT driven pulley pressure control solenoid valve and the CVT drive pulley pressure control solenoid valve to provide about the same hydraulic pressure to the pulleys. The diameter in contact with the steel belt on the drive pulley and the driven pulley becomes nearly equal, and the pulley ratio is in high. Hydraulic pressure is then applied to the start clutch and the forward clutch.






D Position, at top speed range

Vehicle speed is further increased, the PCM controls the CVT driven pulley pressure control solenoid valve and the CVT drive pulley pressure control solenoid valve to apply hydraulic pressure to the drive pulley and to the driven pulley. The drive pulley receives high pressure and the driven pulley receives low pressure. The drive pulley provides the steel belt a large-diameter contact and the driven pulley provides a small-diameter contact, and the result is a high pulley ratio. Hydraulic pressure remains to apply to the start clutch and the forward clutch.






Hydraulic Flow (cont'd)

R Position

The manual valve is shifted into the R position, uncovers the reverse brake (RVS) pressure port leading to the reverse inhibitor valve. The reverse inhibitor solenoid is turned OFF by the PCM, and reverse inhibitor (RI) pressure is applied to the right end of the reverse inhibitor valve. The reverse inhibitor valve is moved to the left side, and uncovers the reverse brake (RVS') pressure port leading to the reverse brake. Clutch reducing (CR) pressure becomes reverse brake (RVS) pressure, and flows to the reverse brake via the reverse inhibitor valve. The reverse brake is engaged, and it locks the planetary carrier.

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






R Position: Reverse Inhibitor Control

If R is selected while the vehicle is moving forward at speeds over 6 mph (10 km/h), the PCM outputs a signal to turn ON the reverse inhibitor solenoid, and reverse inhibitor (RI) pressure in the right end of the reverse inhibitor valve is released. The reverse inhibitor valve is moved to the right side, and blocks the reverse brake pressure port leading to the reverse brake from the manual valve. Reverse brake (RVS) pressure 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.






Hydraulic Flow (cont'd)

P Position

The manual valve is shifted into the P position, the manual valve blocks hydraulic pressure to the forward clutch. Hydraulic pressure is not applied to the start clutch and the forward clutch, and power is not transmitted to the drive pulley shaft.






D Position, when an electronic control system malfunction occurs.

When an electronic control system malfunction occurs in D, and the CVT clutch pressure control solenoid valve cannot control the start clutch pressure circuit, the transmission creates a temporary circuit for start clutch pressure control to allow the vehicle to be driven.

The CVT clutch pressure control clutch solenoid valve covers the start clutch control (CC) pressure port leading to the shift inhibitor valve, and the shift inhibitor valve is moved to the left side by drive pulley control (DRC) pressure. Clutch reducing (CR) pressure becomes shift inhibitor (SI) pressure at the shift inhibitor valve. Pressure then flows to the left side of the start clutch back-up valve, and becomes start clutch control B (CCB) pressure. Start clutch control B (CCB) pressure becomes start clutch (SC) pressure at the shift inhibitor valve, and flows to the start clutch. Clutch reducing (CR) pressure also flows to the manual valve and becomes forward clutch (FWD) pressure. The start clutch and the forward clutch are engaged, and the vehicle can move.

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






Hydraulic Flow (cont'd)

R Position, when an electronic control system malfunction occurs.

When an electronic control system malfunction occurs in R, and the CVT clutch pressure control solenoid valve cannot control the start clutch pressure circuit, the transmission creates a temporary circuit for start clutch pressure control to allow the vehicle to be driven.
The CVT clutch pressure control solenoid valve covers the start clutch control pressure (CC) port leading to the shift inhibitor valve, and the shift inhibitor valve is moved to the left side by drive pulley control pressure (DRC). Clutch reducing pressure (CR) becomes shift inhibitor pressure (SI) at the shift inhibitor valve. Pressure then flows to the left side of the start clutch back-up valve, and becomes start clutch control B pressure (CCB). Start clutch control B pressure (CCB) becomes start clutch pressure (SC) at the shift inhibitor valve, and flows to the start clutch. Clutch reducing pressure (CR) also flows to the manual valve and becomes reverse brake pressure (RVS). The start clutch and the reverse brake are engaged, and the vehicle can be driven 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 is splined to the final drive shaft, and the final drive gear integrated with the final drive shaft engages the final driven gear.

Shifting to P 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 rod spring puts tension on the park cone. The park pawl receives the tension (which acts to separate the park pawl from the park gear) from the park pawl spring.