K41A - CVT - General Info

CVT SYSTEM > GENERAL OUTLINE

1. A newly developed K41A Continuously Variable Transaxle (CVT) is used for the1KR-FE engine models.

2. The K41A CVT, including a pair of the pulleys and the belt in the shift mechanism, is a transaxle which steplessly shifts from start-up to the maximum speed and this offers a smooth shift feeling and an excellent fuel economy.

3. A gate type shift lever is used for the shift control mechanism. 4. A shift lock system is used to prevent the shift lever from being wrongly operated.

SPECIFICATION

Continuously Variable Transaxle Item Specification

Shift Mechanism Pulley and Belt Forward/Reverse Switching Mechanism Double Pinion Type Planetary Gear

Forward 2.386 to 0.426 Pulley Ratio (Speed Ratio) Reverse (Planetary gear

ratio included) 2.505

Differential Gear Ratio (Reduction gear ratio included) 5.403

Shift Pattern P - R - N - D - S - B Fluid Capacity 6.37 Liters (6.73 US qts, 5.61 Imp. qts) Fluid Type Toyota Genuine CVT Fluid TC Weight (Reference)* 60.9 kg (134.3 lb) HINT:

*: Weight shows the figure with the fluid fully filled.

Gears and Friction Discs Item Specification

Planetary Gear

Sun Gear No. of Teeth 40

No. 1 Pinion Gear

No. of Teeth 18

No. 2 Pinion Gear

No. of Teeth 17

Ring Gear No. of Teeth 82

Forward Clutch No. of Discs 2 Reverse Brake No. of Discs 3

Drive Gear No. of Teeth 27 Reduction

Gear Driven Gear No. of Teeth 40

Drive Pinion No. of Teeth 17

Ring Gear No. of Teeth 62

Differential Gear

No. of Differential Pinion 2

Torque Converter Item Specification

Torque Converter Type 3-element, 1-step, 2-phase Stall Torque Ratio 2.00 MAIN FEATURES

1. The K41A CVT has achieved the following performance through the use of the items listed below.

Item Fuel EconomyPower

Efficiency Driveability Quietness Compact

and Lightweight

Pulley and Belt Type Shift Mechanism

Double Pinion Type

Forward/Reverse Switching Mechanism Torque Converter with Low Speed Lock-up Clutch

High-pressure Oil Pump CVT Fluid Warmer High-pressure Hydraulic Control Circuit (Valve Body Unit)

Speed Ratio Control (Shift Control)

Belt Clamping Force Control

Engine - CVT Integrated Control

Automatic Shift Control

Acceleration Improvement Control

Uphill/Downhill Shift Control

Lock-up Control

Electronic Control System

Neutral Control

CVT SYSTEM > SYSTEM DIAGRAM

CVT SYSTEM > PARTS LOCATION

Text in Illustration

*1 Continuously Variable Transaxle Assembly *2 ECM

*3 Brake Actuator Assembly *4 Throttle Body Assembly

Skid Control ECU Throttle Position Sensor

*5 Crank Position Sensor *6 Engine Coolant Temperature Sensor*7 Accelerator Pedal Sensor *8 Stop Light Switch *9 Air Conditioning Amplifier *10 Shift Lock Control ECU

*11

Shift Lock Control Unit

Transmission Control Switch Shift Lock Solenoid P Detection Switch

*12Key Interlock Solenoid (Models without entry and start system)

*13 DLC3 *14 Combination Meter Assembly *15 Shift Position Indicator *16 Check Engine Warning Light

Text in Illustration *1 Solenoid Valve DS1 *2 Solenoid Valve DS2 *3 Solenoid Valve DSU *4 Solenoid Valve SL *5 Solenoid Valve SLS *6 CVT Fluid Temperature Sensor *7 CVT Fluid Pressure Sensor *8 Transmission Revolution Sensor NIN

*9 Transmission Revolution Sensor NOUT *10 Transmission Revolution Sensor NT

*11 Park/Neutral Position Switch *12 CVT Fluid Warmer (Transmission Oil Cooler)

CVT SYSTEM > DETAILS FUNCTION OF MAIN COMPONENTS

1. The main components of the K41A CVT system are as follows:

Component Function

Pulley and Belt Unit

Continuously varies the pulley ratio from start-up to the maximum speed via the hydraulic control.

Planetary Gear Unit

Switches the forward or reverse movement via the hydraulic control.

Torque Converter

Increases the engine torque and transmits it to the CVT.

Oil Pump Supplies the oil pressure necessary for the hydraulic control. CVT Fluid Warmer Keeps the CVT fluid temperature optimal.

Valve Body Unit Controls the hydraulic pressure using the solenoid valves. Solenoid Valve DS1

Controls the oil inflow to the primary pulley and sets the pulley ratio to high side.

Solenoid Valve DS2

Controls the oil outflow from the primary pulley and sets the pulley ratio to low side.

Solenoid Valve DSU

Controls the engagement oil pressure of the lock-up clutch.

Solenoid Valve SL

Switches the usage of the solenoid valve SLS.

Solenoid Valve SLS

Controls the oil pressure of the secondary pulley and generates the belt clamping force.

Controls the engagement oil pressure of the forward clutch and reverse brake.

CVT Fluid Temperature Sensor

Detects the CVT fluid temperature.

CVT Fluid Pressure Sensor Detects the secondary pulley oil pressure.

Transmission Revolution Sensor NIN

Detects the primary pulley speed.

Transmission Revolution Sensor NOUT

Detects the secondary pulley speed.

Continuously Variable Transaxle Assembly

Transmission Detects the turbine speed of the torque

Revolution Sensor NT

converter.

Park/Neutral Position Switch Detects the shift lever position. Shift Lock Control Unit

Transmission Control Switch Detects the shift lever in S.

Engine Coolant Temperature Sensor Detects the engine coolant temperature. Throttle Position Sensor Detects the throttle valve opening angle. Crank Position Sensor Detects the engine speed. Accelerator Pedal Sensor Detects the accelerator pedal opening angle. Stop Light Switch Detects the brake pedal depressed.

Skid Control ECU

Transmits the vehicle speed and the longitudinal acceleration signal to the ECM.

Transmits the operating states of the ABS and VSC to the ECM.

Air Conditioning Amplifier Transmits the operating state of the air conditioning system to the ECM.

ECM Drives each solenoid valve based on signals from each sensor and switch and optimally controls the CVT.

Shift Position Indicator Indicates the shift lever position. Combination

Meter Assembly Check Engine Warning Light

Illuminates or blinks to inform the driver when the ECM detects a malfunction.

2. The main components of the shift lock system are as follows:

Component Function Shift Lock Solenoid Locks the shift lever in P. Shift Lock Control

Unit P Detection Switch Detects the shift lever in P.

Stop Light Switch Detects the brake pedal depressed.

Key Interlock Solenoid* Disables the key to be pulled out in any position other than in P.

Shift Lock Control ECU Controls the shift lock solenoid and the key interlock solenoid based on signals from

each switch.

1. *: Models without entry and start system

SYSTEM CONTROL

1. Control List

1. The electronic control system of the K41A CVT consists of the controls listed below.

Control Outline Speed Ratio Control (Shift Control)

Shifts the pulley and belt unit to an optimal speed ratio (pulley ratio) by controlling the oil inflow/outflow from the primary pulley.

Belt Clamping Force Control

Generates the belt clamping force necessary to transmit the torque of the pulley and belt unit by controlling the oil pressure of the secondary pulley.

Engine - CVT Integrated Control

Controls the engine and the CVT in an integrated way, based on lockup signals and torque down demands from the CVT and output torque and fuel cut signals from the engine, and offers smooth and powerful driving and excellent fuel economy.

Automatic Shift Control

Changes the shift range of the speed ratio according to the shift position selected by the driver.

Acceleration Improvement Control

Optimizes the shift characteristics of the speed ratio based on the driver's acceleration request determined by the ECM to improve the acceleration feeling.

Uphill/Downhill Shift Control

Controls to restrict the upshift or to provide appropriate engine braking force by using the ECM to determine whether the vehicle is traveling on uphill or downhill.

Lock-up Control Engages the lock-up clutch from low vehicle speeds to improve the fuel economy.

Neutral Control Disengages the transaxle from the engine to improve fuel economy while the vehicle is stopped.

2.

3. Speed Ratio Control (Shift Control)

1. The CVT shift mechanism controls the oil inflow/outflow from the primary pulley in the pulley and belt unit and continuously varies the speed ratio (pulley ratio).

2. The ECM determines the target primary pulley speed at which the optimal speed ratio can be obtained, based on the accelerator pedal opening angle and vehicle speed and brake signals. The ECM activates the solenoid valves DS1 and DS2 to make the target primary pulley speed equal to the actual primary pulley speed detected by the transmission revolution sensor NIN, thus sifting to an optimal speed ratio in accordance with the driving conditions.

3. When the shift mechanism is upshifting, the solenoid valve DS1 controls the oil inflow to the primary pulley through the No. 1 ratio control valve and sets the speed ratio to high.

4. When the shift mechanism is downshifting, the solenoid valve DS2 controls the oil outflow from the primary pulley through the No. 2 ratio control valve and sets the speed ratio to low.

4.

5. Belt Clamping Force Control

1. The pulley and belt unit transmits the torque via the belt between the pulleys. The belt clamping force control generates the belt clamping force necessary to transmit the torque by controlling the oil pressure of the secondary pulley.

2. The ECM controls the secondary pulley oil pressure through the No. 1 line pressure modulator valve by activating the solenoid valve SLS based on the input torque. In addition, the secondary pulley oil pressure is detected by the CVT fluid pressure sensor, thus optimally controlling the belt clamping force.

6.

7. Automatic Shift Control

1. The automatic shift control changes the shift range of the speed ratio in accordance with the shift position selected by the driver.

2. When the shift lever is in D, the ECM controls the speed ratio over the entire control area to improve the fuel economy and drivability.

3. When the shift lever is in S, the ECM controls the speed ratio by restricting the control area on the high ratio side to improve the acceleration response and generate an appropriate engine braking force.

4. When the shift lever is in B, the ECM controls the speed ratio by restricting the control area to the low ratio side to generate a large engine braking force.

8.

9. Acceleration Improvement Control

1. The acceleration improvement control optimizes the shift characteristics of the speed ratio to improve the acceleration feeling.

2. When the driver intends to accelerate the vehicle, the ECM determines the acceleration request from changes in the vehicle speed and the accelerator pedal opening angle and shifts the speed ratio to increase the engine speed and the vehicle speed linearly.

10.

11. Uphill/Downhill Shift Control

1. The uphill/downhill shift control helps shifting to an optimal speed ratio while driving on a winding uphill or downhill road.

2. When the ECM determines uphill travel, the control restricts upshifting, thus offering smooth driving.

3. If a signal indicating that the driver has operated the brake pedal is input while the ECM detects downhill travel, the control downshifts the speed ratio and generates an optimal engine braking force.

4. 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.

12.

13. Lock-up Control

1. The ECM engages or disengages the lock-up clutch by activating the solenoid valve DSU based on the accelerator pedal opening angle and the vehicle speed.

2. The CVT engages the lock-up clutch from low vehicle speeds to improve the fuel economy. Even during deceleration, the lock-up clutch continues to engage to the low vehicle speeds, thus expanding the engine fuel cut area.

14.

15. Neutral Control

1. Neutral control is used to disengage the transaxle from the engine while the vehicle is stopped. This reduces the load on the engine and improves fuel economy.

2. When the shift lever is in D and the vehicle is stopped, the ECM semi-disengages the forward clutch using the solenoid valve SLS. However, when the ECM detects a gradient exceeding the reference value based on longitudinal acceleration signals from the skid control ECU, the ECM stops the neutral control.

FUNCTION

1. Shift Control Mechanism

1. A gate type shift lever is used. 2. The gate type shift lever can be manipulated only by the fore-aft and side-

to-side operation. However, the movement from P to R is restricted by the shift lock system. Under emergency conditions, the restriction can be released by the shift lock override button.

3. The shift pattern includes P, R, N and D shift positions, and furthermore S and B shift positions to select the shift range of the automatic shift control.

2.

3. Shift Lock System

1. In the shift lock system, the shift lock function and the key interlock function* are controlled by the shift lock control ECU.

2. The shift lock function prevents the shift lever from being moved to any position other than P, unless the ignition switch is ON, and the brake pedal is depressed. This function helps to prevent unintentional acceleration.

3. The key interlock function* 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.

4. The shift lock control ECU uses the P detection switch to detect the shift lever position, and receives input signals from the stop light switch and ignition switch. Upon receiving these signals, the shift lock control ECU turns on the shift lock solenoid and the key interlock solenoid* in order to release the shift lock and key interlock*.

1. *: Models without entry and start system

CONSTRUCTION

1. Continuously Variable Transaxle Assembly

1. The continuously variable transaxle (CVT) assembly mainly consists of the following: a pulley and belt unit as a shift mechanism, a planetary gear unit as a forward/reverse switching mechanism, a torque converter, a differential, a CVT fluid warmer to keep the CVT fluid temperature optimal, an oil pump and a valve body unit for hydraulic control.

Text in Illustration *1 Pulley and Belt Unit *2 Planetary Gear Unit *3 Oil Pump *4 Torque Converter

*5 Differential *6 Reduction Drive Gear *7 Reduction Driven Gear *8 Differential Drive Pinion *9 Differential Ring Gear *10 Differential Pinion

2. Pulley and Belt Unit (Shift Mechanism)

1. The pulley and belt unit consists of a primary pulley, a secondary pulley and a metal belt applied to the pulleys.

2. In the primary and secondary pulleys integrated with the piston, the pulley groove width can be changed by each chamber's hydraulic control.

3. The metal belt consists of elements and 2 multi-layered rings which hold the elements in a belt-shaped form.

3.

4. Planetary Gear Unit (Forward/Reverse Switching Mechanism)

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

2. A double pinion type planetary gear is used to adjust the forward and reverse gear ratios to be almost the same, thus improving the maneuverability while in reverse.

3. When the forward clutch is engaged, the input shaft is connected to the planetary carrier.

4. When the reverse brake is engaged, the ring gear is fixed to the transaxle case.

Text in Illustration *1 Sun Gear *2 No. 1 Pinion Gear *3 No. 2 Pinion Gear *4 Ring Gear *5 Planetary Carrier *6 Input Shaft *7 Forward Clutch *8 Reverse Brake *9 Transaxle Case - -

5.

6. Torque Converter

1. A compact and lightweight torque converter equipped with a lock-up function is used.

2. A damper is used for the lock-up clutch to perform the lock-up operation from a low speed range. This improves the fuel economy and offers a smooth shift feeling.

Text in Illustration *1 Pump Impeller *2 Turbine Runner *3 Stator *4 One-way Clutch *5 Lock-up Clutch *6 Damper

7.

8. Oil Pump

1. The oil pump is driven by the torque converter. It supplies operating oil pressure for the hydraulic control.

2. The discharge volume of the oil pump has been optimized, reducing the drive torque while ensuring the oil pressure necessary for the hydraulic control.

Text in Illustration *1 Pump Body *2 Drive Gear *3 Driven Gear *4 Pump Cover *5 Stator Shaft - -

9.

10. CVT Fluid Warmer

1. The CVT fluid warmer 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. The CVT fluid warmer works as a cooler after the CVT fluid has become heated, thus cooling down the CVT fluid.

11.

12. Valve Body Unit

1. The valve body unit consists of the upper valve body, rear upper valve body, lower valve body and 5 solenoid valves.

Text in Illustration *1 Rear Upper Valve Body *2 Upper Valve Body Cover

*3 Upper Valve Body *4 Valve Body Plate *5 Lower Valve Body *6 Manual Valve *7 Solenoid Valve DS1 *8 Solenoid Valve DS2 *9 Solenoid Valve DSU *10 Solenoid Valve SL *11 Solenoid Valve SLS - -

Text in Illustration

*1 Rear Upper Valve Body (Bottom View) *2 Lock-up Control Valve

*3 Upper Valve Body (Bottom View) *4 Shift Valve *5 Clutch Control Valve *6 Secondary Regulator Valve

*7 No. 2 Line Pressure Modulator Valve *8 Solenoid Modulator Valve

*9 Lower Valve Body (Upper View) *10 No. 1 Accumulator

*11 Primary Regulator Valve *12 No. 1 Line Pressure Modulator Valve *13 No. 1 Ratio Control Valve *14 No. 2 Ratio Control Valve

13. Solenoid Valves

1. The functions of each solenoid valve are outlined in the table below.

Solenoid Valve Type Control

Operating State Function

DS1 3-way Duty-cycle

Control

Duty ratio decreases (OFF): Control pressure decreases Duty ratio increases (ON):

Controls the oil inflow to the primary pulley.

Control pressure increases

DS2 3-way Duty-cycle

Control

Duty ratio decreases (OFF): Control pressure decreases Duty ratio increases (ON): Control pressure increases

Controls the oil outflow from the primary pulley.

DSU 3-way Duty-cycle

Control

Duty ratio decreases (OFF): Control pressure decreases Duty ratio increases (ON): Control pressure increases

Controls the lock-up clutch engagement oil pressure.

SL 3-way ON/OFF Control

OFF: Control pressure decreases ON: Control pressure increases

Switches the usage of the solenoid valve SLS.

SLS Linear Current Control

Current decreases: Control pressure increases Current increase: Control pressure decreases

Controls the secondary pulley oil pressure.

Controls the engagement oil pressure of the forward clutch and reverse brake.

14. CVT Fluid Temperature Sensor

1. A thermistor type CVT fluid temperature sensor is used.

2. The CVT fluid temperature sensor is installed in the lower valve body unit for direct detection of the CVT fluid temperature.

15.

16. CVT Fluid Pressure Sensor

1. A piezoresistance type CVT fluid pressure sensor is used.

2. The CVT fluid pressure sensor detects the secondary pulley oil pressure to optimally control the belt clamping force.

NOTICE: After replacing the CVT fluid pressure sensor, the CVT or the ECM, calibration of the CVT fluid pressure is required. For details, refer to the Repair Manual.

17.

18. Transmission Revolution Sensors

1. The functions of each transmission revolution sensor are outlined in the table below.

Transmission Revolution

Sensor Type Output Signal Function

NIN Pick-

up Coil

Analog Signal

Detects the primary pulley speed from the rotation of the timing rotor on the primary pulley.

NOUT Hall High/Low

Digital Signal

Detects the secondary pulley speed from the rotation of the reduction driven gear.

NT Hall High/Low

Digital Signal

Detects the turbine speed from the rotation of the timing rotor on the forward clutch drum connected to the torque converter turbine runner.

2.

3.

4.

5.

6.

7.

19. Park/Neutral Position Switch and Transmission Control Switch

1. The park/neutral position switch sends the P, R, N, D and B position signals to the ECM.

2. The transmission control switch sends the S position signal to the ECM. 3. The ECM controls the CVT system in accordance with the shift lever

position signals.

4. The ECM transmits signals to the combination meter assembly for the shift position indicator (P, R, N, D, S and B) in response to the signals received from the switches.

OPERATION

1. Pulley and Belt Unit (Shift Mechanism)

1. In the pulley and belt unit, the hydraulic control changes the pulley groove width, changing the belt contact radius. Thus, the pulley ratio continuously

varies in a range of 2.386 (low ratio) to 0.426 (high ratio) when the vehicle is moving forward.

2. Planetary Gear Unit (Forward/Reverse Switching Mechanism)

1. In the planetary gear unit, the forward or reverse movement of the vehicle is switched by switching of the hydraulic circuit via the manual valve in the valve body unit.

2. When the vehicle is moving forward, the input shaft is connected to the planetary carrier by the forward clutch being engaged. Thus, the engine rotation which is input to the input shaft is transmitted to the pulley and belt unit through the planetary carrier in the same direction of the engine rotation.

3. When the vehicle is moving reverse, the ring gear is fixed to the transaxle case by the reverse brake being engaged. Thus, the engine rotation which is input to the input shaft rotates the sun gear, No. 1 and No. 2 pinion gears as shown in the illustration. The No. 2 pinion gear moves along the fixed ring gear and this movement is transmitted to the pulley and belt unit through the planetary carrier in the direction opposite to the engine rotation.

3.

4. Transaxle Power Flow

1. The engine rotation is input to the input shaft through the torque converter. In the planetary gear unit, the forward or reverse movement of the vehicle is switched. In the pulley and belt unit, the shifting is performed in accordance with the pulley ratio. The engine rotation is transmitted to the differential gear through the reduction gear.

Text in Illustration *1 Input Shaft *2 Planetary Gear Unit *3 Pulley and Belt Unit *4 Reduction Drive Gear *5 Reduction Driven Gear *6 Differential Drive Pinion *7 Differential Ring Gear - -

FAIL-SAFE

1. If the ECM detects a malfunction in the CVT system, the ECM illuminates or blinks the check engine warning light to inform the driver.

2. The fail-safe function minimizes the loss of operability when an abnormality occurs in a sensor or solenoid valve. For details, refer to the Repair Manual.

DIAGNOSIS

1. When the ECM detects a malfunction in the CVT system, the ECM makes a diagnosis and memorizes the failed section. At the same time, the Diagnostic Trouble Code (DTC) is stored in the ECM memory.

2. The DTC can be read by connecting an intelligent tester II to the DLC3. For details, refer to the Repair Manual.