CVT SYSTEM

Pulley Ratio Control

1. The ECM calculates the target primary pulley speed in accordance with the accelerator pedal position signal, vehicle speed signal, and stop light switch signal, in order to attain an optimal pulley ratio and shifting speed. To allow the actual primary pulley speed (acquired from the primary speed sensor) to match the target primary pulley speed, the ECM actuates shift solenoid valves DS1 and DS2 in order to control the inflow and outflow volume of line pressure to and from the primary pulley. As a result, optimal pulley ratio and shifting speed have been achieved.

   

2. When the shift lever is in D, the system effects engine integrated control to optimize fuel economy characteristics and driving performance.

3. The sport mode limits the shift range for the acceleration side and maintains the primary pulley speed at high speeds. This produces a moderate engine braking force and provides an excellent shift response.

   

   

4. When the shift lever is in M, the shift characteristic is as shown below. The system will upshift automatically when the vehicle reaches the set speed during acceleration.

   

5. The system determines the driver's acceleration request based on the vehicle speed and the changes in the accelerator pedal position. When the system determines this request, it will change the shift characteristic into one in which the engine speed and vehicle speed increase linearly. This improves the acceleration feeling.

   

   *1	Engine Speed
   *2	Time
   *3	Vehicle Speed
   *4	Accelerator Pedal Depressed Angle

Neutral Control

1. While the vehicle is stopped with the shift lever in D, by disconnecting the engine and CVT (release the forward clutch halfway), engine load is reduced. This improves fuel economy.

   

Shift Control in Uphill/Downhill Traveling

1. The ECM determines that the vehicle is driving uphill or downhill based on the accelerator pedal position sensor signal and the vehicle speed signal. During uphill driving, it limits upshift to achieve smooth driving. During downhill driving, it downshifts upon detecting brake pedal operation, in order to provide moderate engine braking.

   

2. The actual acceleration calculated from the vehicle speed signal is compared with the reference acceleration (based on level road travel) stored in the ECM to determine uphill or downhill travel.

   

Lock-up Control

1. The lock-up operation range has been expanded from that of the previous automatic transaxle, thus enabling control to start from low speeds.

2. The lock-up operation range during deceleration has been expanded to the low-speed range. This expands the fuel cut range and achieves excellent fuel economy.

   

   *1	Lock-up Off
   *2	Throttle Opening Angle
   *3	Lock-up On
   *4	Vehicle Speed

Flex lock-up Control

• The duty solenoid (SLU) for lock-up engagement pressure control, which allows more precise lock-up clutch control, has been adopted. Therefore, high fuel economy has been realized along with the improved transmission efficiency.

1. Flex start control

   
   

   • By actively operating the lock-up clutch at vehicle start, the transmission efficiency has been improved. Therefore, more effective engine operating range can be used.

   

   

2. Flex lock-up control at deceleration

   
   

   • The fuel-cut range has been expanded by operating the lock-up clutch until low vehicle speeds and maintaining a small speed difference between the engine speed and the turbine speed while decelerating the vehicle.

Oil Pump Motor Assembly Control

• Because the engine stop and start ECU operates the oil pump motor assembly at the time of idle stop, the CVT oil pressure is secured, enabling smooth vehicle start.

  

1. Oil Pump Motor Assembly Operation Control

   
   

   • The oil pump motor assembly is operated according to the engine stop signal.

   • After engine automatic start, operation of the oil pump motor assembly stops either when the engine speed exceeds a set value or when driving force is generated.

     Oil pump motor assembly operation (O: Operating, X: Not operating, -: Idle stop is disabled)

     Shift Position	P	R	N	D	M
     Brake ON (applied)	O	-	O	O	-*2
     Brake OFF (not applied)	X*1	-	X*1	-	-*2

     Tech Tips

     *1: Operates a certain period of time after the vehicle is stopped, and then stops after a while.

     *2: When the vehicle was stopped with the shift lever in the D position, and then the lever was changed to the M position after idle stop was engaged, the idle stop and the oil pump motor assembly continue to operate.

     Oil pump motor assembly operation condition

     	Condition	Remarks
     CVT Oil Temperature	25 -100 [°C]	Detected from the oil temperature sensor in the CVT

2. Optimal Stand-by Pressure Control

   
   

   • This control optimally maintains the oil pressure generated from the oil pump motor assembly during idle stop.

   • This control is intended to ensure reliability. The necessary stand-by pressure is also controlled optimally to secure vehicle responsiveness when starting from the idle stop status, and unnecessary electricity has been reduced to improve fuel economy. In addition, the oil pressure is raised at the time of engine automatic start to secure responsiveness.

3. Stand-by Pressure Learning Control

   
   

   • Performs learning control to optimally control the oil pressure of the oil pump motor assembly at the time of stand-by.

     

4. Continual Operation Prohibition Control

   
   

   • This control prohibits continual and longtime operation of the oil pump motor assembly to ensure reliability.

Shift Lock System

1. A shift lock system consisting of a key interlock device* and a shift lock mechanism is used.

   
   

   • *: Models without entry and start system

2. On the models without the entry and start system, the key interlock device prevents the key from being pulled out after the ignition switch is turned off, unless the shift lever is moved to P. Thus, the driver is urged to park the vehicle with the shift lever in P.

3. The shift lock mechanism prevents the shift lever from being moved to a position other than P, unless the ignition switch (engine switch*) is turned to ON, and brake pedal is depressed. It prevents the vehicle from starting off suddenly.

   
   

   • *: Models with entry and start system

4. A shift lock release button, vehicle manually overrides the shift lock mechanism, is used.

   

Oil Pump Assembly

1. The trochoid gear type oil pump is used.

2. The oil pump assembly is operated by the torque converter. It lubricates the planetary gear units and supplies operating fluid pressure to the hydraulic control.

   

   Text in Illustration

   *1	Oil Pump Assembly	*2	Oil Pump Body
   *3	Front Oil Pump Drive Gear	*4	Front Oil Pump Driven Gear
   *5	Stator Shaft	*6	Pump Cover

Forward/Reverse Switching Unit

1. The forward/reverse switching unit consists of a planetary gear, a forward clutch, and a reverse brake.

2. The forward clutch, which acts during a forward movement, connects the input shaft with the planetary carrier.

3. The reverse brake, which acts during a reverse movement, keeps the ring gear stationary.

   

Pulley and Steel Belt

1. The widths of the grooves of the pulleys are changed through hydraulic control.

2. During acceleration, the action of shift solenoid valve DS1 increases the fluid inflow volume to the primary pulley, thus narrowing the width of the pulley groove.

3. During deceleration, the action of shift solenoid valve DS2 increases the fluid outflow volume to the primary pulley, thus widening the width of the pulley groove.

4. The secondary pulley is hydraulically controlled by the shift solenoid valve SLS. It controls the belt clamping pressure to ensure the proper power transmission efficiency.

   

5. The primary pulley uses a single piston construction.

   

   *1	Chamber
   *2	Pulley Ratio (Low)
   *3	Pulley Ratio (High)

6. The steel belt consists of elements and 2 rows of steel rings. In contrast to the chains and V-belts that transmit power through the use of tensile force, the steel belt uses the compressive action (pushing force) of the elements to transmit power.

   

   Text in Illustration

   *1

   Steel Ring

   *2

   Element

Reduction Gear and Differential

1. The reduction gear reduces the power output from the secondary pulley and transmits it to the differential.

2. A 2 pinion type differential is used.

   

   Text in Illustration

   *1	Reduction Drive Gear	*2	Reduction Driven Gear
   *3	Front Differential	-	-

Parking Lock Mechanism

1. A parking lock mechanism is used on the secondary pulley. The engagement of the parking lock pawl with the parking lock gear integrated with the secondary pulley locks the movement of the vehicle.

   

   Text in Illustration

   *1

   Parking Lock Pawl

   *2

   Parking Lock Gear

Oil Cooler

1. The transmission oil cooler uses engine coolant to warm up the CVT fluid quickly. Consequently, the friction losses of the CVT are quickly reduced, thus improving fuel economy.

2. After warming up the CVT fluid, the engine coolant flows into the transmission oil cooler to cool down the CVT fluid.

   

Oil Pump Motor Assembly

1. The exclusively used oil pump motor assembly has been provided for the vehicles with the stop and start system and is installed on the front of the CVT case. This enables a stable CVT fluid supply at the time of idle stop, and delivers good responsiveness without any uncomfortable feel, and smooth drivability, at the time of vehicle start from the engine stopped status.

2. By integrating the oil pump motor driver into the oil pump motor assembly, a small-sized and weight reduced system has been achieved.

3. The oil pump motor assembly provided for the vehicles with the stop and start system is controlled by the engine stop and start ECU.

4. The configuration and operations of the parts other than the oil pump motor assembly are the same as the vehicles without the stop and start system.

   Tech Tips

   The oil pump motor assembly only operates when the engine is in the idle stop status. While the engine is operating, CVT fluid is supplied from the regular oil pump assembly.

   

   Text in Illustration

   *1

   Oil Pump Motor Assembly

   -

   -

5. The oil pump motor assembly consists of oil pump motor driver section, DC sensorless and brushless motor section, and oil pump section.

6. A cycloid type oil pump has been used for the oil pump section to provide a stable oil supply.

7. The oil pump motor driver controls the oil pump motor assembly operations according to the signals (duty signals) from the engine stop and start ECU.

   

   Text in Illustration

   *1	Radiator Sheet	*2	Radiator Fin
   *3	Oil Pump Motor Driver	*4	Driven Rotor
   *5	Drive Rotor	*6	Shaft
   *7	Magnet	-	-
   *a	Oil Pump Motor Driver Section	*b	DC Sensorless and Brushless Motor Section
   *c	Oil Pump Section	-	-

Transmission Valve Body Assembly

1. The transmission valve body assembly consists of the upper and lower valve bodies and 5 shift solenoid valves.

   

   Text in Illustration

   *1	Rear Upper Valve Body	*2	Upper Valve Body
   *3	Shift Solenoid Valve SLU	*4	Shift Solenoid Valve DS2
   *5	Lower Valve Body	*6	Shift Solenoid Valve DS1
   *7	Shift Solenoid Valve SLT	*8	Shift Solenoid Valve SLS

2. To ensure the proper control of the belt clamping pressure necessary for transmitting torque, the system controls the hydraulic pressure applied to the secondary pulley. The transmission valve body assembly is provided with a dedicated hydraulic pressure circuit for belt clamping pressure control. This circuit optimally controls the hydraulic pressure applied to the secondary pulley, thus achieving superior torque transmission performance.

   

   Text in Illustration

   *1	Oil Pump Assembly	*2	No. 3 Line Pressure Modulator Valve
   *3	Primary Regulator Valve	*4	Clutch Apply Control Valve
   *5	Shift Solenoid Valve SLS	*6	No. 1 Line Pressure Modulator Valve
   *7	Shift Solenoid Valve SLT	*8	Primary Pulley
   *9	Secondary Pulley	-	-

3. Pulley ratio control is effected by controlling the inflow and outflow of the CVT fluid to and from the primary pulley. Separate hydraulic circuits are provided for acceleration (fluid inflow) and deceleration (fluid outflow) in order to provide fine-tuned control and a high level of reliability.

   

   Text in Illustration

   *1	Oil Pump Assembly	*2	Shift Solenoid Valve DS2
   *3	Shift Solenoid Valve DS1	*4	Bypass Valve
   *5	No. 1 Ratio Control Valve (Acceleration Control)	*6	No. 2 Ratio Control Valve (Deceleration Control)
   *7	Primary Pulley	*8	Secondary Pulley

Shift Solenoid Valves DS1, DS2 and SLU

1. Shift solenoid valves DS1, DS2 and SLU use a 3-way solenoid valve.

2. Shift solenoid valve DS1 controls acceleration by increasing the fluid flow volume to the primary pulley.

3. Shift solenoid valve DS2 controls deceleration by increasing the fluid flow volume from the primary pulley.

4. Shift solenoid valve SLU is used for the lock-up clutch pressure control.

   

Shift Solenoid Valves SLS and SLT

1. Shift solenoid valves SLS and SLT use a linear solenoid valve.

2. Shift solenoid valve SLS controls the hydraulic pressure applied to the secondary pulley in order to control the belt clamping pressure necessary for transmitting torque.

3. Shift solenoid valve SLT controls line pressure. A linear solenoid valve is used to enable precise control in accordance with the variation of the pulley ratio.

   

Transmission Revolution Sensors and Oil Pressure Sensor

1. The transmission revolution sensor (NIN) detects the input shaft speed and participates in shift control.

2. The transmission revolution sensor (NOUT) detects the output shaft speed and participates in shift control.

3. The transmission revolution sensor (NT) detects the forward clutch turbine speed and participates in lock-up clutch pressure control and forward clutch pressure control.

4. The oil pressure sensor detects the hydraulic pressure applied to the secondary pulley and participates in belt clamping pressure control, which optimally controls the clamping pressure of the steel belt necessary for transmitting torque.

   

   Text in Illustration

   *1	Transmission Revolution Sensor (NT)	*2	Transmission Revolution Sensor (NOUT)
   *3	Transmission Revolution Sensor (NIN)	*4	Oil Pressure Sensor

CVT Fluid Temperature Sensor

1. Detects the fluid temperature, effects shift control in accordance with the fluid temperature, and participates in lock-up clutch pressure control, forward clutch pressure control, and belt clamping pressure control.

   

   Text in Illustration

   *1

   CVT Fluid Temperature Sensor

   *2

   Transmission Valve Body Assembly

Shift Control Mechanism

1. A gate type shift lever that uses a transmission control cable is used.

2. The shift control mechanism consists of a shift lock control unit assembly and a transmission control cable assembly.

   

   *1	Shift Lock Control Unit Assembly
   *2	Transmission Control Cable Assembly
   *3	Shift Pattern

CVT Power Flow

1. The changing of the pulley ratio is accomplished in a continuously variable manner by varying the widths of the grooves of the primary and secondary pulleys.

   

   Text in Illustration

   *1	Primary Pulley	*2	Secondary Pulley
   *3	Reverse Brake	*4	Forward Clutch
   *5	Input Shaft	*6	Reduction Drive Gear
   *7	Reduction Driven Gear	*8	Differential Ring Gear

2. Shift Lever in D (Pulley Ratio Low)

   

3. Shift Lever in D (Pulley Ratio High)

   

4. Shift Lever in N

   

5. Shift Lever in R

   

Oil Pump Motor Assembly

1. Normal Operation

   
   

   • The oil pump assembly in the CVT, which is powered by the engine, generates oil pressure. At this time, the oil pressure to be applied to the oil pump motor assembly is blocked by the check valve installed in the discharge section of the oil pump motor assembly. The oil pump motor assembly is not operating at this time.

   

2. Idle Stop Operation

   
   

   • During idle stop operation, the oil pump assembly operation is stopped. At this time, the oil pump motor assembly operates according to the signals sent from the oil pump motor driver and generates oil pressure to open the check valve and supply oil pressure to the CVT valve body.

   

3. Engine Automatic Start Operation

   
   

   • During engine automatic start operation, oil pressure generated by both the oil pump motor assembly and the oil pump assembly is applied to the system. When the oil pressure generated from the oil pump assembly exceeds the oil pressure generated from the oil pump motor assembly, the check valve closes and the oil pressure generated from the oil pump motor assembly is no longer applied. The oil pump motor assembly stops according to signals such as engine speed.