CVT System Description

General Operation


The continuously variable transmission (CVT) is an electrically controlled automatic transmission with drive and driven pulleys, and steel belt. The CVT provides non-stage speeds forward and 1 reverse. The entire unit is positioned in line with the engine.

Transmission

Around the out side of the flywheel is a ring gear which meshes with the starter pinion when the engine is being started. The transmission has four parallel shafts: the input shaft, the drive pulley shaft, the driven pulley shaft, and the final drive shaft. The input shaft is in line with the engine crankshaft. The drive pulley shaft and driven pulley shaft consist of movable and fixed face pulleys. Both pulleys are linked by the steel belt.
The input shaft includes the sun gear and planetary gears with carrier. The drive pulley shaft includes the drive pulley and forward clutch. The driven pulley shaft includes the driven pulley, start clutch, and the secondary driven gear which is integral with the park gear. The final drive shaft is positioned between the secondary drive gear and the final driven gear. The final drive shaft includes the final drive gear and the secondary driven gear which serves to change the rotation direction, because the drive pulley shaft and driven pulley shaft rotate the same direction. When certain conditions of the planetary gears in the transmission are engaged by the forward clutch and the reverse brake, power is transmitted from the drive pulley shaft to the driven pulley shaft to provide [L], [S], [D], and [R] positions.

Electronic Control

The electronic control system consists of the powertrain control module (PCM), sensors, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions. The PCM is located below the dashboard, behind the glove box.

Hydraulic Control

The valve bodies include the main valve body, the ATF pump body, the control valve body, the ATF pass body, and the manual valve body. The ATF pump body is bolted on the main valve body. The main valve body is bolted on the flywheel housing. The control valve body is positioned outside of the transmission housing. The ATF pass body is positioned on the main valve body, and connected hydraulic circuit between the control valve body, main valve body and internal hydraulic circuit. The manual valve body is positioned on the intermediate housing.
The ATF pump is the trochoid type, and the inner rotor is splined with the input shaft. The pulleys and clutches receive fluid from their respective feed pipes, and the reverse brake receives fluid from internal hydraulic circuit.

Shift Control

The PCM controls to shift pulley ratio the solenoids, which receiving input signal from the various sensors and switches located throughout the vehicle. The PCM actuates the CVT speed change control valve and CVT pulley pressure control valve to change pulley control pressure. The drive pulley control pressure is applied to the drive pulley, and the driven pulley control pressure is applied to the driven pulley, and pulley ratio is changed to their effective ratio.

Gear Selection


The shift lever has six positions: [P] PARK, [R] REVERSE, [N] NEUTRAL, [D] DRIVE, [S] SECOND, and [L] LOW.


Position Description 
[P] PARK Front wheels locked; park pawl engaged with park gear on the driven pulley shaft. The start clutch and forward clutch released. 
[R] REVERSE Reverse; reverse brake engaged. 
[N] NEUTRAL Neutral; the start clutch and forward clutch released. 
[D] DRIVE General driving; the transmission automatically adjusts to keep the engine at the best speed for driving under all conditions. 
[2] SECOND For rapid acceleration; the transmission selects a wider range of ratios to give better acceleration. 
[L] LOW For engine braking and power for climbing; the transmission shifts into the lowest range of the ratios. 

Starting is possible only in [P] and [N] positions because of a slide-type neutral-safety switch.

Automatic Transaxle (A/T) Gear Position Indicator

The A/T gear position indicator in the instrument panel shows what position has been selected without looking down at the console.

Clutches/Reverse Brake/Planetary Gear/Pulleys


Clutches/Reverse Brake

The Multi Matic uses the hydraulic-actuated clutches and brake to engage and disengage the transmission gears. When hydraulic pressure is introduced into the clutch drum and the reverse brake piston cavity, the clutch piston and the reverse brake piston move. This presses the friction discs and steel plate together, locking them so they don't slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear, and through engaged ring gear to pinion gears.
Likewise, when the hydraulic pressure is bled from the clutch pack and reverse brake piston cavity, the piston releases the friction discs and the steel plates, and they are free to slid past each other. This allows the gear to spin independently on its shaft, transmitting no power.

Start Clutch

The start clutch engages/disengages the secondary drive gear, and is located at the end of the driven pulley shaft. The start clutch is supplied hydraulic pressure by its ATF feed pipe within the driven pulley shaft.

Forward Clutch

The forward clutch engages/disengages the sun gear, and is located at the end of the drive pulley shaft. The forward clutch is supplied hydraulic pressure by its ATF feed pipe within the drive pulley shaft.

Reverse Brake

The reverse brake locks the planetary carrier in [R] position, and is located inside the intermediate housing around the planetary carrier. The reverse brake discs are mounted to the planetary carrier and the reverse brake plates are mounted on the intermediate housing. The reverse brake is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.

Planetary Gear

The planetary gear consists of the sun gear, planetary pinion gears, and ring gear. The sun gear is connected to the input shaft with splines. The pinion gears are mounted on the planetary carrier. The planetary carrier is located on the end of the input shaft, over the sun gear. The ring gear is located in the planetary carrier, and connected to the forward clutch drum. The sun gear inputs the engine power via the input shaft to the planetary gears, and the carrier outputs the engine power. The planetary gear mechanism is only used for switching the rotation direction of the pulley shafts. In [D], [S], and [L] position (forward range), the pinion gears don't rotate and revolve around the sun gear, so the carrier rotates. In [R] position (reverse range), the reverse brake locks the planetary carrier, and the sun gear drives the pinion gears to rotate. The pinion gears rotate, but don't revolve around the sun gear. The pinion gears drive the ring gear in the opposite direction from the rotation direction of the sun gear.

Pulleys

Each pulley consists of a movable face and a fixed face, and the effective pulley ratio changes with engine speed. The drive pulley and the driven pulley are linked by the steel belt.
To achieve a low pulley ratio, high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage. To achieve a high pulley ratio, high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the driven pulley, and low hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.

Transmission Cutaway View

 

Power Flow


[P] Position


Hydraulic pressure is not applied to the start clutch, forward clutch, and the reverse brake. Power is not transmitted to the secondary drive gear. The secondary drive gear is locked by the park pawl interlocking the park gear.

[N] Position


Engine power transmitted from the flywheel drives the input shaft, but the hydraulic pressure is not applied to the forward clutch and reverse brake. Power is not transmitted to the drive pulley shaft. Also hydraulic pressure is not applied to the start clutch.


 

[D], [S], and [L] Position (Forward Range)




 

Power Flow (cont'd)


[R] Position (Reverse Range)


 

Electronic Control System


Functional Diagram

The electronic control system consists of the powertrain control module (PCM), sensors, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions.

The PCM inputs signals from the sensors, switches, and other control units, perform processing data, and outputs signals for engine control system and CVT control system. The CVT control system includes shift control/pulley pressure control, start clutch pressure control, reverse inhibitor control, and also a grade logic control is stored in the PCM. The PCM actuates the solenoid valves to control shifting transmission pulley ratios.


 

Electronic Control System (cont'd)


Electronic Controls Location

 

 

Shift Control/Pulley Pressure Control

The PCM compares actual driving conditions with memorized driving conditions to control shifting, and instantly determines a ratio of drive pulley and driven pulley by various signals sent from sensors and switches. The drive pulley drives the driven pulley by the steel belt at a ratio between 2.367-0.407 in non-stage in the [D] position. In the [R] position, the ratio is set to 1.326 when pressing the accelerator, and to 2.367 when the accelerator released. When the pulley ratio is low (vehicle speed is low), the driven pulley receives high pulley pressure to hold large diameter, and the drive pulley receives low pressure to hold diameter of proportion to the driven pulley. When the pulley ratio is high (vehicle speed is high), the driven pulley receives low pressure, and drive pulley receives high. The PCM actuates the pulley pressure control valves to regulate optimum pulley pressure to the pulleys for reducing belt slippage and long belt life.

 

Electronic Control System (cont'd)


Start Clutch Pressure Control

Hydraulic-controlled start clutch works smooth starting-off and creeping in [D], [S], [L], and [R] positions like the torque converter. The PCM inputs signals from the sensors and switches, and actuates the start clutch pressure control valve to regulate the start clutch pressure.

 

PCM Electrical Connections

 

Electronic Control System (cont'd)


PCM Inputs and Outputs

 


PCM CONNECTOR A (31P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
A2 YEL/BLK IGP2 Power supply circuit from main relay With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
A3 YEL/BLK IGP1 Power supply circuit from main relay With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
A4 BLK PG2 Ground  
A5 BLK PG1 Ground  
A10 GRN/BLK SG2 Sensor ground  
A11 GRN/WHT SG1 Sensor ground  
A18 BLU/WHT VABS Vehicle speed sensor signal input With ignition switch ON (II): About 5 V
With ignition switch OFF: 0 V 
A20 YEL/GRN VCC2 Power supply circuit for sensors With ignition switch ON (II): About 5 V
With ignition switch OFF: 0 V 
A21 YEL/RED VCC1 Power supply circuit for sensors With ignition switch ON (II): About 5 V
With ignition switch OFF: 0 V 
A23 BRN/BLK LG2 Ground  
A24 BRN/BLK LG1 Ground  


PCM CONNECTOR B (24P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
B7 GRN/WHT DN LS + CVT pulley pressure control valve power supply positive electrode With ignition switch ON (II): Pulsing signal 
B16 YEL SC LS + CVT start clutch pressure control valve power supply positive electrode With ignition switch ON (II): Pulsing signal 
B24 BLU/WHT DR LS + CVT speed change control valve power supply positive electrode With ignition switch ON (II): Pulsing signal 


PCM CONNECTOR C (22P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
C1 PNK/BLK DN LS - CVT pulley pressure control valve power supply negative electrode With ignition switch ON (II): Pulsing signal 
C6 GRN/BLK SOL INH Inhibitor solenoid control With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0V 
C7 RED/BLU NDR CVT drive pulley speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
With engine at idle in [N] position: About 2.5 V 
C8 PNK/BLU SC LS - CVT start clutch pressure control valve power supply negative electrode With ignition switch ON (II): Pulsing signal 
C9 BLU/WHT ATP S Transmission range switch [S] position input In [S] position: 0 V
In other than [S] position: About 10 V 
C10 WHT ATP R Transmission range switch [R] position input In [R] position: 0V
In other than [R] position: About 10 V 
C11 BLU ATP L Transmission range switch [L] position input In [L] position: 0V
In other than [L] position: About 10 V 
C12 LT GRN ATP NP Transmission range switch [P] and [N] position input In [P] and [N] position: 0V
In other than [P] and [N] position: About 5 V 
C15 WHT NDN CVT driven pulley speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
With engine at idle in [N] position: About 2.5 V 
C16 GRN/YEL DR LS - CVT speed change control valve power supply negative electrode With ignition switch ON (II): Pulsing signal 
C20 PNK ATP D Transmission range switch [D] position input IN [D] position: 0V
In other than [D] position: About 8 V 
C22 WHT/RED VEL1 CVT speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
With driving (front wheels rotating): About 2.5 V 


PCM CONNECTOR E (31P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
E11 PNK D IND [D] indicator control When ignition switch is first turned ON (II): About 6 V for 2 seconds
In [D] position: About 6 V 
E22 WHT/BLK BK SW Brake pedal position switch signal input Brake pedal pressed: Battery voltage
Brake pedal released: 0 V 
E29 BRN SCS SCS terminal signal input With ignition switch ON (II)
  • SCS terminals open: About 5 V or battery voltage
  • SCS terminals short-circuited to ground: 0 V
 

Hydraulic Control


The hydraulic control system is controlled by the ATF pump, the valves, and the solenoids. The ATF pump is driven by the input shaft. Fluid from the ATF pump flows through the PH regulator valve to maintain specified pressure to the drive pulley, the driven pulley, and the manual valve.
The valve bodies include the main valve body, the ATF pump body, the control valve body, and the manual valve body. The main valve body is bolted on the flywheel housing. The ATF pump body is bolted on the main valve body. The control valve body located outside of the transmission housing. The manual valve body is bolted on the intermediate housing.

Control Valve Body

The control valve body is located outside of the transmission housing, and contains the CVT speed change control valve, the CVT pulley pressure control valve, the CVT start clutch pressure control valve, the drive pulley control valve, and the driven pulley control valve.


 

Main Valve Body

The main valve body contains the PH regulator valve, the PH control shift valve, the clutch reducing valve, the shift inhibitor valve, the start clutch accumulator valve, the start clutch shift valve, the start clutch back-up valve, and the lubrication valve.


 

Hydraulic Control (cont'd)


ATF Pump Body

The ATF pump body is bolted on the main valve body, and the ATF pump is trochoid type. The inner rotor is splined with the input shaft, and driven by the input shaft. The ATF pump supplies hydraulic pressure to the PH regulator valve.

 

Manual Valve Body

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


 

Hydraulic Flow


As the engine turns, the ATF pump starts to operate. Automatic transmission fluid (ATF) is drawn through the ATF strainer and discharged into the hydraulic circuit. Then, ATF flowing from the ATF pump flows to the PH regulator valve and becomes the PH pressure. The PH pressure flows to the pulley control valves and then to the pulleys. The PCM actuates the solenoids to control hydraulic pressure shifting pulley ratios and engaging the start clutch.

Hydraulic pressure at the port is follows:

Port No. Description of Pressure Port No. Description of Pressure 
CC CLUTCH CONTROL PH PRESSURE HIGH 
CCB CLUTCH CONTROL B PHC PRESSURE HIGH CONTROL 
COL ATF COOLER RCC RECIRCULATION 
CR CLUTCH REDUCING RI REVERSE INHIBITOR 
DN DRIVEN PULLEY RVS REVERSE BRAKE 
DNC DRIVEN PULLEY CONTROL   RVS' REVERSE BRAKE 
DR DRIVE PULLEY SC START CLUTCH 
DRC DRIVE PULLEY CONTROL SI SHIFT INHIBITOR 
FWD FORWARD CLUTCH DRAIN 
LUB LUBRICATION HX HIGH POSITION DRAIN 
  LUB' LUBRICATION AX AIR DRAIN 
  LUB'' LUBRICATION   

 

Hydraulic Flow (cont'd)


[N] Position


Fluid from the ATF pump regulates high pressure at the PH regulator valve, and becomes the pressure high (PH) pressure. The PH pressure becomes the clutch reducing (CR) pressure at the clutch reducing valve, and flows to the CVT speed change control valve and CVT pulley pressure control valve. The CVT speed change control valve change the CR pressure to the drive pulley control (DRC) pressure, and supplies the DRC pressure to the PH control shift valve and drive pulley control valve. Likewise, the CVT pulley pressure control valve supplies the driven pulley control (DNC) pressure to the PH control shift valve and driven pulley control valve. The PCM controls the CVT speed change control valve and CVT pulley pressure control valve to regulate the DNC pressure higher than the DRC pressure. The driven pulley receives the driven pulley (DN) pressure higher than the drive pulley (DR) pressure applied to the drive pulley. At this time, the pulley ratio is low.
The manual valve intercepts the hydraulic pressure to the forward clutch, and the shift inhibitor valve intercepts the hydraulic pressure to the start clutch. Under this condition, hydraulic pressure is not applied to the forward clutch, start clutch, and reverse brake.


 

[D] Position, at low speed range


The fluid flow circuit to the drive pulley and driven pulley is the same as in the [N] position, and the pulley ratio remains low. The manual valve is shifted in [D] position, and uncovers the port leading the forward clutch (FWD) pressure to the forward clutch. The FWD pressure flows to the forward clutch, and the forward clutch is engaged. The forward clutch drives the input shaft and drive pulley shaft. The PCM actuates the CVT start clutch pressure control valve to supply the clutch control (CC) pressure to the shift inhibitor valve. The CC pressure becomes the start clutch (SC) pressure at the shift inhibitor valve, and the SC pressure flows to the start clutch. The start clutch is engaged, and the vehicle moves.



 

Hydraulic Flow (cont'd)


[D] Position, at middle speed range


As the speed of the vehicle reaches the prescribed value, the CVT speed change control valve and CVT pulley pressure control valve are activated by the PCM. The CVT speed change control valve regulates the DRC pressure, and the CVT pulley pressure control valve regulates the DNC pressure to apply the same volume of the hydraulic pressure to the pulleys. The drive pulley and driven pulley received same volume pressure apply the same pulley diameter to the steel belt. At this time, pulley ratio is in the middle. Hydraulic pressure remains to apply the forward clutch and start clutch.




 

[D] Position, at high speed range


Vehicle speed is further increased, the CVT speed change control valve and CVT pulley pressure control valve controls the DR pressure higher than DN pressure to regulate the DRC and DNC pressure. The drive pulley receives higher pressure than driven pulley received pressure. The drive pulley apply the large pulley diameter to the steel belt, and the pulley ratio is in the high. Hydraulic pressure remains to apply to the forward clutch and start clutch.


 

Hydraulic Flow (cont'd)


Reverse Inhibitor Control


If the [R] position is selected while the vehicle is moving forward at speed over 6 mph (10 km/h), the PCM outputs the signal to turn ON the inhibitor solenoid, and the reverse inhibitor (RI) pressure in the right end of the reverse inhibitor valve is released. The reverse inhibitor valve moves to the right side, and covers the port to stop the reverse brake (RVS) pressure to the reverse brake from the manual valve. The 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.



 

[R] Position


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

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


 

Hydraulic Flow (cont'd)


[P] Position


The manual valve is shifted into [P] position, and covers the port leading the hydraulic pressure to the forward clutch and reverse brake. The shift inhibitor valve intercepts the hydraulic pressure to the start clutch. The fluid flow circuit to the drive pulley and driven pulley is the same as in the [N] position, but the hydraulic pressure is not applied to the forward clutch, start clutch, and reverse brake.


 

[D] Position, when an electronic control system breakdown occurs.


When an electronic control system breakdown occurs, the transmission creates temporary fluid flow circuit to allow the vehicle to drive. The drive pulley control (DRC) pressure exceeds a prescribed value at the CVT speed change control valve, the DRC pressure flows to the shift inhibitor valve, and the shift inhibitor valve is moved to the left side. The clutch reducing (CR) pressure from the clutch reducing valve becomes the shift inhibitor (SI) pressure at the shift inhibitor valve. The SI pressure flows to the start clutch shift valve and start clutch back-up valve, and becomes to the clutch control B (CCB) pressure at the start clutch back-up valve. The CCB pressure becomes the start clutch (SC) pressure at the shift inhibitor valve, and the SC pressure flows to the start clutch. The start clutch is 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 breakdown occurs.


When an electronic control system breakdown occurs, the transmission creates temporary fluid circuit to allow the vehicle to drive. The fluid flow circuit to the reverse brake is the same a in the [R] position, and the reverse brake is engaged. The drive pulley control (DRC) pressure exceeds a prescribed value at the CVT speed change control valve, the DRC pressure flows to the shift inhibitor valve, and the shift inhibitor valve is moved to the left side. The clutch reducing (CR) pressure from the clutch reducing valve becomes the shift inhibitor (SI) pressure at the shift inhibitor valve. The SI pressure flows to the start clutch shift valve and start clutch back-up valve, and becomes to the clutch control B (CCB) pressure at the start clutch back-up valve. The CCB pressure becomes the start clutch (SC) pressure at the shift inhibitor valve, and the SC pressure flows to the start clutch. The start clutch is engaged, and the vehicle can move.


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 with the final drive shaft, and the final drive gear which is integral with the final drive shaft engages 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 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.


 

Circuit Diagram