Control System

System Description

• CVT detects the vehicle driving status from switches, sensors and signals, and controls the vehicle so that the optimum shift position and shift timing may always be achieved. It also controls the vehicle to reduce shift and lockup shock, etc.
• Receives input signals from switches and sensors.
• Sends the output signal necessary for operation of solenoid valves, and evaluates the line pressure, shift timing lockup operation, engine brake performance, etc.
• If a malfunction occurs on the electric system, activate the fail-safe mode only to drive the vehicle.

Control Item		Shift Control	Line Pressure Control	Select Control	Lock-up Control	Fail-Safe Function*
Input	Engine Torque Signal (CAN Communication)	X	X	X	X	X
	Engine Speed Signal (CAN Communication)	X	X	X	X	X
	Accelerator Pedal Position Signal (CAN Communication)	X	X	X	X	X
	Throttle Position Signal (CAN Communication)	X	X	-	X	X
	Brake Pedal Position Signal (CAN Communication)	X	X	X	X	-
	Secondary Pressure Sensor	X	X	X	-	X
	CVT Fluid Temperature sensor	X	X	X	X	X
	Primary Speed Sensor	X	X	X	X	X
	Secondary Speed Sensor	X	X	X	X	X
	Output Speed Sensor	X	X	X	X	X
	Transmission Range Switch	X	X	X	X	X
Output	Line Pressure Solenoid valve	X	X	X	-	X
	Primary Pressure Solenoid valve	X	X	-	-	X
	Torque Converter Clutch Solenoid Valve	-	-	-	X	X
	High Clutch and Reverse Brake Solenoid Valve	X	-	X	-	X
	Low Brake Solenoid Valve	X	-	X	-	X
	Shift Position Indicator (CAN Communication)	-	-	X	-	-
* If these input/output signals show errors, TCM activates the fail-safe function.

Control Item		Idling Stop Control	Fail-Safe Function*
Input	Electric Oil Pump Input (STATE)	X	X
Output	Electric Oil Pump Relay	X	-
	Electric Oil Pump Output (SIG)	X	-
* If these input/output signals show errors, TCM activates the fail-safe function.

Fail-Safe 

TCM has a fail-safe mode. The mode functions so that operation can be continued even if the signal circuit of the main electronically controlled input/output parts is damaged.

If the vehicle shows following behaviors including "poor acceleration", a malfunction of the applicable system is detected by TCM and the vehicle may be in a fail-safe mode. At this time, check the DTC code and perform inspection and repair according to the malfunction diagnosis procedures.

Protection Control 

The TCM becomes the protection control status temporarily to protect the safety when the safety of TCM and transmission is lost. It automatically returns to the normal status if the safety is secured. The TCM has the following protection control.

Control	When a wheel spin is detected, the engine output and gear ratio are limited and the line pressure is increased. At 1st gear, the clutch pressure is increased.
Vehicle Behavior in Control	If the accelerator is kept depressing during wheel spin, the engine revolution and vehicle speed are limited to a certain degree. From the 1st gear, up-shift to a certain gear ratio is only allowed.
Normal Return Condition	Wheel spin convergence returns the control to the normal control.

Control	When the CVT fluid temperature is high, the gear shift permission maximum revolution and the maximum torque are reduced than usual to prevent increase of the oil temperature.
Vehicle Behavior in Control	Power performance may be lowered, compared to normal control.
Normal Return Condition	The control returns to the normal control when CVT fluid temperature is lowered.

Control	Engine output is controlled according to a vehicle speed while reversing the vehicle.
Vehicle Behavior in Control	Power performance may be lowered while reversing the vehicle.
Normal Return Condition	Torque returns to normal by positioning the selector lever in a range other than "R" position.

Control	The reverse brake is controlled to avoid becoming engaged when the selector lever is set in "R" position while driving in forward direction at more than the specified speed.
Vehicle Behavior in Control	If the selector lever is put at "R" position when driving with the forward gear, the gear becomes neutral, not reverse.
Normal Return Condition	The control returns to normal control when the vehicle is driven at low speeds. (The reverse brake becomes engaged.)

Line Pressure Control 

Highly accurate line pressure control (secondary pressure control) reduces friction for improvement of fuel economy.

• Normal Oil Pressure Control

  Appropriate line pressure and secondary pressure suitable for driving condition are determined based on the accelerator pedal position, engine speed, primary pulley (input) speed, secondary pulley (output) speed, vehicle speed, input torque, stop lamp switch signal, transmission range switch signal, lock-up signal, power voltage, target shift ratio, oil temperature and oil pressure.

• Secondary Pressure Feedback Control

  In normal oil pressure control and oil pressure control in shifting, highly accurate secondary pressure is determined by detecting the secondary pressure using an oil pressure sensor and by feedback control.

Shift Control 

In order to select the gear ratio which can obtain the driving force in accordance with driver's intention and the vehicle condition, the TCM monitors the driving conditions such as the vehicle speed and the throttle position, and select the optimum gear ratio, and determines the gear change steps to the gear ratio.

The information is output to the primary pressure solenoid valve to control the line pressure input/output to the primary pulley, to determine the primary pulley (movable pulley) position and to control the gear position.

• Drive (D) Position

  Shifting over all the ranges of gear ratios from the lowest to the highest.

• Low (L) Position

  By limiting the shifting range only to the lowest of the gear ratio, a large driving force and engine brake are obtained.

• Hill Climbing and Descending Control

  When downhill is detected with the accelerator pedal released, the engine brake will be strengthened up by downshifting so as not to accelerate the vehicle more than necessary.

• Control in Acceleration

  According to the vehicle speed and a change of accelerator pedal angle, driver's request for acceleration and driving scene are judged. This function assists improvement in acceleration feeling by making the engine speed proportionate to the vehicle speed.

Select Control 

Based on accelerator pedal angle, engine speed, primary pulley speed, and the secondary pulley speed, the optimum operating pressure is set to reduce impact of a selector lever operation while shifting from "N" ("P") to "D" ("R") position.

Lock-up Control 

The torque converter clutch piston located in the converter is engaged to eliminate slip to increase power transmission efficiency. The control valve operation is performed by the torque converter clutch solenoid valve, which is controlled by a signal sent by the TCM. This control valve engages or releases the torque converter clutch piston directly using the pressure provided by the oil pump.

In lock-up released state, the torque converter clutch control valve is set into the unlocked state by the solenoid and the lock-up pressure apply is drained. In this way, the clutch piston is not coupled.

In the lock-up applied state, the torque converter clutch control valve is set into the locked state by the solenoid and lock-up apply pressure is generated. In this way, the clutch piston is pressed and coupled.

Idling Stop Control 

In this system, ECM performs integrated control based on the information from control units, sensors and switches via CAN communication.

TCM switches electric oil pump relay on, when it comes to acceptable vehicle speed.

When CVT is in a condition of idling stop, TCM sends a signal of "ready" for idling stop to ECM.

ECM judges if it can stop engine based on the information from control units, sensors and switches, and sends a signal of engine stop to related control units, and stop the engine.

TCM commands electric oil pump to start/stop by PWM signal (duty %), and status signal of electric oil pump is transmitted through PWM signal (duty %) to TCM.