CVT System Description Hydraulic Flow (CVT)

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 the 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 at the Port for use in the Hydraulic Circuit:





N Position

Fluid from the CVTF pump is regulated to high pressure at the pressure high (PH) regulator valve, and flows to the pulley control valves. The CVT driven pulley pressure control solenoid valve and the CVT drive pulley pressure control solenoid valve control pulley control valves A and B, which apply 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 pressure (FWD) port leading to the forward clutch. The forward clutch pressure (FWD) 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 the start clutch pressure (SC). The start clutch control pressure (CC) from the CVT clutch pressure control solenoid valve becomes the start clutch pressure (SC) at the shift inhibitor valve, and flows to the start clutch. The start clutch is engaged, and the vehicle moves.






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 remains applied to the start clutch and the forward clutch.


D Position, at top speed range

The 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 applied to the start clutch and the forward clutch.


R Position

The manual valve is shifted into the R position, and uncovers the reverse brake pressure (RVS) port leading to the reverse inhibitor valve. The inhibitor solenoid is turned OFF by the PCM, and the reverse inhibitor pressure (SA) 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 pressure (RVS') port leading to the reverse brake. The clutch reducing pressure (CR) becomes the reverse brake pressure (RVS), 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 inhibitor solenoid, and the reverse inhibitor pressure (SA) in the right end of the reverse inhibitor valve is released. The reverse inhibitor valve is moved to the right side, and uncovers the stop reverse brake pressure (RVS) port leading to the reverse brake from the manual valve. The 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 manual valve is shifted into the P position, and the manual valve blocks hydraulic pressure to the forward clutch. Hydraulic pressure is not applied to the start and forward clutches, 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 the 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 the drive pulley control pressure (DRC). The clutch reducing pressure (CR) becomes the shift inhibitor pressure (SI) at the shift inhibitor valve. The shift inhibitor pressure (SI) then flows to the left side of the start clutch back-up valve, and the becomes start clutch control B pressure (CCB). The start clutch control B pressure (CCB) becomes the start clutch pressure (SC) at the shift inhibitor valve, and flows to the start clutch. The clutch reducing pressure (CR) also flows to the manual valve and becomes the forward clutch pressure (FWD). 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.






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 the 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 the drive pulley control pressure (DRC). The clutch reducing pressure (CR) becomes the shift inhibitor pressure (SI) at the shift inhibitor valve. The shift inhibitor pressure (SI) then flows to the left side of the start clutch back-up valve, and becomes the start clutch control B pressure (CCB). The start clutch control B pressure (CCB) becomes the start clutch pressure (SC) at the shift inhibitor valve, and flows to the start clutch. The clutch reducing pressure (CR) also flows to the manual valve and becomes the reverse brake pressure (RVS). The start clutch and the reverse brake are engaged, and the vehicle can reverse.

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






Operation of the Start Clutch Pressure

The start clutch control pressure (CC) from the CVT clutch pressure control solenoid valve becomes start clutch pressure (SC) at the shift inhibitor valve, and flows to the start clutch. The PCM actuates the CVT clutch pressure control solenoid valve to control start clutch pressure when starting the vehicle. The start clutch is engaged like a torque converter to control smooth starting-off and creeping in D and R.






Operation of the Pulleys Pressure

The pressure high pressure (PH) from the PH regulator valve becomes the driven pulley pressure (DN) and the drive pulley pressure (DR) at pulley control valve A and pulley control valve B, and flows to the driven pulley and the drive pulley. The PCM actuates the CVT pulley pressure control solenoid valve to control the pulley pressure control valve. The pulley control valve controls the hydraulic pressure to the drive pulley and the driven pulley to control the pulley ratio.






When the pulley ratio is low (low vehicle speed), high hydraulic pressure works on the movable face of the driven pulley and increases the effective diameter of the driven pulley, and a lower hydraulic pressure works on the movable face of the drive pulley to decrease the effective diameter of the drive pulley. When the pulley ratio is high (high vehicle speed), high hydraulic pressure works on the movable face of the drive pulley and increases the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to reduce the effective diameter of the driven pulley.