Design
Design
Height sensor, suspension
A height sensor is connected to the suspension for each wheel via a link system. The height sensor measures the wheel's vertical position in relation to the body. The sensors are supplied with 5 V by the suspension module (SUM). When the vehicle is stationary, the output signal from the sensor is approximately 2.5 V. When there is vertical movement the signal will oscillate around this value; the greater the movement the greater the deviation. The voltage can oscillate between 0.5-4.5 V.
Note! The values move in different directions on the left and right-hand sides. Upwards body movement results in increased voltage on the left-hand side and a voltage drop on the right-hand side.
Information about the wheel's position and movement is used together with the signals from the acceleration sensors on the body by the control module to calculate damping in each shock absorber.
The height sensors can be diagnosed by the Suspension module (SUM) and must be calibrated after replacement.
Acceleration sensor, body
There are three different acceleration sensors on the car body; two front ones and one rear one.
The front ones are at the front edge of the wheel housings behind each front lamp.
The rear one is on the floor in the luggage compartment in front of the left tail lamp in the S80. In the V70/XC70 it is on the floor in the luggage compartment to the right of the spare wheel well.
The acceleration sensors are supplied with 5 V from the Suspension module (SUM). The output signal from each sensor, when the vehicle is stationary, is 2 V.
During vertical acceleration movements, the signal oscillates around that value; the greater the acceleration, the greater the deviation. Information about the body's acceleration is used together with signals from the wheel's height sensor of the control module to calculate the damping in each shock absorber.
The acceleration sensors are diagnosed by the Suspension module (SUM).
Note! It is important that the acceleration sensors are securely installed with the connector turned in the correct direction. The front sensors must have their connectors turned downwards and the rear sensor connectors upwards. (Note that the sensors are not the same and have different P/Ns.) If an acceleration sensor is loose, the control module may receive incorrect values resulting in poorer vehicle driving characteristics.
the shock absorber
Note! The illustration is of a front shock absorber.
The damping force in the four shock absorbers is altered individually using control valves, which are affected by solenoids. Valves and solenoids are located in the lower end of the shock absorbers.
The suspension module (SUM) controls the current to the solenoids. Lower current gives lower damping forces, high current higher damping forces.
The valves are sprung so that they return to their original position if there is no flow through the solenoids. This results in the shock absorbers functioning as conventional passive shock absorbers if the valves are not affected by the solenoids.
The solenoids are diagnosed by the Suspension module (SUM).
Exploded view of the shock absorber
The shock absorbers are oil hydraulic with gas pressure to prevent deposit build-up. The design is of the 3 tube shock absorber type with three shock absorber tubes instead of two as in traditional shock absorbers. The extra tube creates an oil duct past the piston on the high pressure side so that the oil flow can always travel the same way in the control valve.
Oil flow in the shock absorber
1. Piston's movement
2. Oil flow
The flow always travels in the same direction through the oil duct and control valve (C) due to check valves in the piston (A) and in the bottom of the shock absorber cylinder (B). When the shock absorber is depressed, the oil flows up through the check valve in piston the (A). When the shock absorber is pulled out, the oil flows through the check valve at the bottom (B). In both cases, the oil flows the same direction through the oil duct and through the control valve (C).
Control valve
Damping becomes harder or softer depending on the pressure in the shock absorber and on the ease of oil flow through the shock absorber. This is controlled by the varying opening area in the control valve. The area is determined by the distance between the valve seat (6) and the main cone (5). The main flow of oil (A) travels through this.
A smaller flow (B) travels through the pilot valve at the same time and produces a counter pressure to the main cone (5). The solenoid that is controlled by the Suspension module (SUM) affects the pilot valve (2) and, depending on the solenoid's force, obtains different counter pressures in the valve. In the event of any faults, the control valve shifts to passive position and the fail-safe valve (4) controls the counter pressure with a ball and spring instead, then as the fail-safe flow (C). The valve is installed so that the shock absorber functions safely. This passive position cannot be set using any of the selectable driving modes.
Driving modes switches
The switches for selecting a driving mode are located in front of the gear selector in the center console.
There are three different driving modes:
- COMFORT
- SPORT
- ADVANCED
In the "COMFORT" driving mode, ride comfort is prioritized. In "SPORT" mode driving pleasure is prioritized.
The "ADVANCED" mode sets the shock absorbers to a characteristic optimized for more aggressive driving.
The selected driving mode is confirmed by an LED which lights in the relevant switch.
The switch unit is connected via a cable directly to the suspension module (SUM).
The light intensity of the switch lighting is controlled together with the lighting for the dashboard and the radio.
The switch unit is diagnosed by the Suspension module (SUM).