Continuously Variable Transaxle (Cvt): Overview Suzuki SX4 I рестайлинг

CVT Mechanical Description

Continuously variable transaxle (CVT) can vary the actual gear ratio continuously and stepless from low-speed to high-speed range depending on the driving conditions. The CVT allows an improved driveability with reduced shift-shock in comparison with an existing A/T (Automatic Transaxle).

This transaxle is an electronic control fully automatic transaxle with forward continuously variable and reverse 1-speed.

The torque converter is a 3-element, 1-step and 2-phase type and is equipped with an automatically controlled lock-up mechanism.

The gear change device consists of a ravigneaux type planetary gear unit, multiple disc type clutch, multiple disc type brake, steel belt, primary pulley and secondary pulley.

The hydraulic pressure control device consists of a valve body assembly, line pressure control solenoid valve (linear solenoid), secondary pressure control solenoid valve (linear solenoid), TCC solenoid valve (linear solenoid) and lock-up/select switching solenoid valve. Optimum line pressure complying with engine torque is produced by the pressure control solenoid valves in dependence upon control signal from TCM. This makes it possible to control the line pressure with high accuracy in accordance with the engine power and running conditions to achieve smooth shifting characteristics and high efficiency.

The TCM can change the dimension between the two pulley surfaces. To continuously vary its gear ratio, the TCM simultaneously adjusts the diameter of the primary pulley that transmits torque from engine and the secondary pulley that transfers torque to the wheels. With continuously shifting of gear ratio, the CVT can avoid the shift-shock and deliver smooth driving.

Scheme 2

Operation Table of Mechanical Components

OPERATION TABLE OF MECHANICAL COMPONENTS

CVT Control Description

Gear Ratio Control

In order to achieve the optimum gear ratio for the driving force in accordance with the vehicle operating conditions, TCM detects vehicle conditions based on vehicle speed or input signals such as an accelerator pedal position.

TCM selects the optimum gear ratio and determines the gear change steps based on each input signal. By outputting these command signals to the stepper motor, TCM controls the line pressure to the primary pulley, decides the adjustable pulley position of the primary pulley, and controls the gear ratio.

Lock up control

When the vehicle speed exceeds the specified value, the TCC solenoid valve completely engages the TCC upon control signal from TCM. This control helps to improve the transaxle efficiency.

Slope shift control

TCM distinguishes uphill or downhill according to vehicle speed, accelerator pedal position and/or brake pedal position, and controls gear ratio as follows

1. Uphill: To improve acceleration, gear ratio in the high speed range is limited.
2. Downhill: To obtain effective engine brakes, gear ratio is downshifted.

Garage shift control

If the select lever is shifted from "D" to "R" range while the vehicle is running at a specified speed or higher, TCM controls the transaxle operation and automatically shifts the transaxle to neutral in order to protect CVT inside parts from damage.

Manual mode control

When the select lever is shifted to "M" position, or when the shift paddle switch is operated with the select lever in "D" range, TCM switches the control mode from automatic mode to manual mode, while maintaining the actual gear ratio.

In manual mode, every time the paddle-up switch, paddle-down switch, shift-up switch or shift-down switch is turned on, TCM selects the predetermined gear ratio for 1-speed to 6-speed, and performs shift up or shift down depending on the vehicle speed.

Operation Table of Solenoid Valves and Stepper Motor

OPERATION TABLE OF SOLENOID VALVES AND STEPPER MOTOR

OPERATION TABLE

CVT Diagnosis General Description

This vehicle is equipped with an electronic transaxle control system, which controls the gear ratio control, TCC operation, etc. suitably to vehicle driving conditions.

TCM has an On-Board Diagnosis (OBD) system which detects a malfunction in this system and abnormality of those parts that influence the engine exhaust emission.

When diagnosing a trouble in transaxle including this system, be sure to have full understanding of the outline of On-Board Diagnostic System Description and each item in Precautions in Diagnosing Trouble and execute diagnosis according to CVT SYSTEM CHECK to obtain correct result smoothly.

On-Board Diagnostic System Description

For CVT control system, TCM has following functions.

Scheme 3

1. When the ignition switch is turned ON with the engine at a stop, MIL (1) turns ON to check the MIL and its circuit.
2. When TCM detects a malfunction in CVT control system (and/or a malfunction which gives an adverse effect to vehicle emission) while the engine is running, TCM requires ECM to make the malfunction indicator lamp in the meter cluster of the instrument panel turn ON. TCM stores the malfunction area (DTC according to SAE J2012) in TCM memory. (If it detects that continuously 3 driving cycles are normal after detecting a malfunction, however, it makes MIL turn OFF although DTC stored in its memory will remain.)
3. Malfunctions detected by TCM are stored in its memory as pending DTC, confirmed DTC (current and history) and permanent DTC. The permanent DTC, among others, will be stored in the memory that cannot be manually erased. (For the details, refer to description on «PERMANENT DTC»(ref-514590-S28198817812012112100000) )
4. It is possible to communicate through DLC (3) by using not only SUZUKI scan tool (2) but also CAN communication OBD generic scan tool which are in compliance with SAE J1978. (Diagnostic information can be accessed by using a scan tool.)
5. For information about the following items, refer to «OBD (ON-BOARD DIAGNOSTIC) SYSTEM DESCRIPTION»(ref-514565-S33043738492012112100000) . Warm-up cycle Driving cycle 2 driving cycle detection logic Pending DTC Freeze frame data

CAN Communication System Description

Refer to CAN COMMUNICATION SYSTEM DESCRIPTION for CAN communication System description.

DTC Description/Detecting Condition/Confirmation Procedure

P0641

Refer to DTC P0641 .

P0707

Refer to DTC P0707 .

P0712

Refer to DTC P0712 .

P0713

Refer to DTC P0713 .

P0842

Refer to DTC P0842/P0843 .

P0843

Refer to DTC P0842/P0843 .

P0847

Refer to DTC P0847/P0848 .

P0848

Refer to DTC P0847/P0848 .

P0962

Refer to DTC P0962/P0963 .

P0963

Refer to DTC P0962/P0963 .

P0966

Refer to DTC P0966/P0967 .

P0967

Refer to DTC P0966/P0967 .

P1970

Refer to DTC P1970 .

P2763

Refer to DTC P2763 .

P2764

Refer to DTC P2764 .

Operation

PRIMARY AND SECONDARY PRESSURE SENSOR POWER SUPPLY CIRCUIT MONITOR OPERATION TABLE

TRANSMISSION RANGE SENSOR CIRCUIT MONITOR OPERATION CHART

TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT MONITOR OPERATION CHART

PRIMARY PRESSURE SENSOR CIRCUIT MONITOR OPERATION CHART

SECONDARY PRESSURE SENSOR CIRCUIT MONITOR OPERATION CHART

LINE PRESSURE CONTROL SOLENOID VALVE CIRCUIT MONITOR OPERATION CHART

SECONDARY PRESSURE CONTROL SOLENOID VALVE CIRCUIT MONITOR OPERATION CHART

Enable conditions

SECONDARY PRESSURE CONTROL SOLENOID VALVE CIRCUIT MONITOR ENABLE CONDITIONS CHART

SENSOR GROUND CIRCUIT MONITOR OPERATION CHART

TCC SOLENOID VALVE CIRCUIT MONITOR OPERATION CHART

P062F

Refer to DTC P062F .

P0703

Refer to DTC P0703 .

P0705

Refer to DTC P0705 .

P0711

Refer to DTC P0711 .

P0716

Refer to DTC P0716 .

P0717

Refer to DTC P0717 .

P0721

Refer to DTC P0721 .

P0722

Refer to DTC P0722 .

P0741

Refer to DTC P0741 .

P0776

Refer to DTC P0776/P0777 .

P0777

Refer to DTC P0776/P0777 .

P0871

Refer to DTC P0871 .

P0961

Refer to DTC P0961 .

P1810

Refer to DTC P1810 .

P1816

Refer to DTC P1816 .

P1818

Refer to DTC P1818 .

U0073

Refer to DTC U0073 .

U0100

Refer to DTC U0100 .

TCM INTERNAL CIRCUIT/MEMORY MONITOR OPERATION CHART

BRAKE SWITCH RATIONALITY MONITOR OPERATION CHART

TRANSMISSION RANGE SENSOR RATIONALITY MONITOR OPERATION CHART

TRANSMISSION FLUID TEMPERATURE SENSOR RATIONALITY MONITOR OPERATION CHART

PRIMARY PULLEY SPEED SENSOR RATIONALITY MONITOR OPERATION CHART

SECONDARY PULLEY SPEED SENSOR RATIONALITY MONITOR OPERATION CHART

TCC SOLENOID VALVE RATIONALITY MONITOR OPERATION CHART

SECONDARY PRESSURE CONTROL SOLENOID VALVE RATIONALITY MONITOR OPERATION CHART

PRIMARY PRESSURE SENSOR/SECONDARY PRESSURE SENSOR RATIONALITY MONITOR OPERATION CHART

LINE PRESSURE CONTROL SOLENOID VALVE RATIONALITY MONITOR OPERATION CHART

LOCK-UP/SELECT SOLENOID VALVE RATIONALITY MONITOR OPERATION CHART

STEPPER MOTOR CIRCUIT RATIONALITY MONITOR OPERATION CHART

CAN COMMUNICATION SIGNAL RATIONALITY MONITOR OPERATION CHART