Suspension Control ( Automatic - Electronic ): Description and Operation
ELECTRONIC MODULATED AIR SUSPENSION DESCRIPTIONAn electronic modulated air suspension contains compressed air that acts as a spring. and the spring rate and vehicle height are controlled automatically according to the driving conditions. The shock absorber damping force is also controlled electronically to suppress vehicle posture changes such as rolling. nose-diving and squatting, thus maintaining outstanding riding comfort and controllability.
SPRING RATE AND DAMPING FORCE CONTROL
VEHICLE HEIGHT CONTROL
This system consists of a Pneumatic Cylinder which has pressured air in an air chamber, an ECU which automatically switches the spring rate and vehicle height between two ranges (normal and high) according to the driving conditions and also two (2) modes (normal and high) which the driver can choose from according to preference.
Also, the damping force of the shock absorber is automatically switched by the ECU between three levels (soft, medium and firm) and the driver can choose one of two (2) modes (normal, sport) according to preference.
Combined control of the spring rate, vehicle height and damping force suppresses changes in the vehicle's attitude such as roll, nose dive and squat to provide outstanding riding comfort and controllability.
1. INPUT SIGNALS
1. Steering Sensor Signal
Rotation angle of the steering wheel are input to TERMINAL SS1 and SS2 of air suspension ECU.
2. Throttle Position Sensor Signal
The throttle valve opening angle is detected and the signal is input to TERMINALS L1, L2 and L3 of the air suspension ECU via the Engine Control Module (engine and Electronic Controlled Transmission ECU).
3. Vehicle Speed Sensor Signal
The vehicle speed is detected by vehicle speed sensor (speed sensor) no.1 and the signal is input to TERMINAL SPD of the air suspension ECU.
4. Stop Light SW Signal
The brake operation signal is detected and a signal is input to TERMINAL STP of air suspension ECU.
5. LRC SW Signal
Whether the LRC switch is in normal or sport mode is detected and the signal is input to TERMINAL TSW of the air suspension ECU.
6. Height SW Signal
Whether the height switch is in normal or high mode is detected and the signal is input to TERMINAL HSW of the air suspension ECU
7. Height Control Sensor Signal
The vehicle height and the different levels of the road surface are detected by the height control sensor and the Signal is input to TERMINALS SHFL, SHFR, SHRL and SHRR of the air suspension ECU.
8. Door Courtesy SW Signal
Whether the door is open or closed is detected and input to the air suspension ECU.
2. AIR SUSPENSION OPERATION
* High Position
Signals from the vehicle speed sensor (speed sensor), height control sensor and so on are input to the air suspension ECU, which operates so that the current flows from the air suspension ECU to height control valve no. and no.2 to open the Pneumatic Cylinder valve.
As a result, the passage is opened as far as the height control dryer. Then, the current flowing to the height control relay flows to the height control compressor. Control of this current by the air suspension ECU causes the compressor to operate and air flows into the Pneumatic Cylinder to raise the vehicle height.
* Low Position
Signals from the vehicle speed sensor (speed sensor), height control sensor and so on are input to the air suspension ECU, which operates so that current flows from the air suspension ECU to height control valve no.1 and no.2 to open the Pneumatic Cylinder valve.
As a result, the passage is opened as far as the height control dryer. Then, the current flows to the height control exhaust valve installed in the height control dryer, control of this current by the air suspension ECU causes the valve to open so that the air inside the Pneumatic Cylinder is expelled and the vehicle height is lowered.
3. BASIC OPERATION OF SUSPENSION CONTROL ACTUATOR (LRC (LEXUS RIDE CONTROL) OPERATION)
1. From Soft or Medium to Firm Position
The current flows from TERMINAL FL+ and RM+ of air suspension ECU --> TERMINAL 1 of each actuator --> TERMINAL 2 --> TERMINAL FL- and RM- of ECU --> GROUND, causing the motor inside the actuator to rotate, and switch the rotary valve control rod of the shock absorber to the FIRM position. At this time, the rotary valve control rod and air valve control rod inside the suspension control actuator are linked by a gear so that the air valve control rod also rotates and the air valve closes, causing the spring rate to change to FIRM position
2. From Soft or Firm to Medium Position
Current flows from TERMINAL FCH and RCH of air suspension ECU --> TERMINAL 3 of each actuator --> TERMINAL 4 --> GROUND, switching the rotary valve control rod of the shock absorber to the MEDIUM position.
The air valve control rod rotates at this time but the spring rate remains in the FIRM position because the air valve is also closed when the rotary valve control rod is in MEDIUM position.
3. From Firm or Medium to Soft Position
The current flows in reverse to (1) above and the current flows from TERMINAL FL- and RM- of air suspension ECU --> TERMINAL 2 of each actuator --> TERMINAL 1 --> TERMINAL FL+ and RM+ of ECU --> GROUND, causing the motor in the actuator to rotate. As a result, the rotary valve control rod of the shock absorber is switched to SOFT position. At this time, the air valve control rod is rotated to open the air valve and the spring rate is set to the SOFT position because the air passage between the main air chamber and sub air chamber in the Pneumatic Cylinder is opened.
Each position inside the actuator is as follows.
Medium : Center
Soft : Left
Firm : Right
To switch to each position, the current flows as described above. Based on the above movement, the air suspension ECU operates and controls the actuator according to the input signals.