Damper valve, component description - GF32.31-P-5112SX

MODEL 221 with CODE (489) Airmatic (semi-active air suspension) up to Model Year 8 

Damper valves 

In the vehicle each of four damping valve units is fitted with two solenoid valves. The damping valve units are assigned to one wheel in each case:

• Left front axle damping valve unit (Y51)
• Right front axle damping valve unit (Y52)
• Left rear axle damping valve unit (Y53)
• Right rear axle damping valve unit (Y54)
  Fig 1: Identifying Damper Valve Unit Components

  Courtesy of MERCEDES-BENZ USA

The damping valve units serve to changeover to various damping characteristics in order to adapt the damping to the driving style and road surface condition.

Two solenoid valves with which four damper characteristics can be realized are located in each damping valve unit. The damping valve units can be controlled individually for each wheel.

The AIRmatic with ADS control unit (N51) has two damping valve output stages for the control for each wheel. The damping valve units are actuated in a pulse width modulated manner with approx. 800 Herz via the output stages. The switching frequency of the damping valve units can be up to 5 Herz.

The following actuation logic applies to the 4 damping valve characteristics:

• Rebound and compression hard:
  • Solenoid valve 1 not actuated
  • Solenoid valve 2 not actuated
• Rebound hard/compression soft:

  Solenoid valve 1 actuated

  • Solenoid valve 2 not actuated
• Rebound soft/compression hard:
  • Solenoid valve 1 not actuated
  • Solenoid valve 2 actuated
• Rebound and compression soft:

  Solenoid valve 1 actuated

  • Solenoid valve 2 actuated

Schematic representation, e.g. front suspension strut 

The bypass valves form one unit consisting of ball valve and restrictor.

Four damping force stages can be achieved via the actuation of the AIRmatic with ADS control unit. The damping valve units can be adjusted individually for each wheel.

An open circuit in the line to the individual damping valve units is recognized by the AIRmatic control unit.

Damping force setting 1 

For rolling along comfortably with minor body movements and low longitudinal and lateral acceleration. Solenoid valves 1 and 2 are open in this damping force stage so that the greatest proportion of the oil share flows in parallel with the hard rebound and compression stage of the operating piston via the softer reed valves of the solenoid valves. The comfort  rebound and compression setting is therefore achieved.

Damping force setting 2 

The reed valves at the valve piston generate a somewhat firmer setting.

If the body moves downwards and if solenoid valve 2 is open and solenoid valve 1 is closed, a slightly firmer setting is achieved by the reed valves on the valve piston.

The reed valves (a = hard compression and b = soft rebound) at solenoid valve 1 generate a hard  compression and a soft  rebound.

Damping force setting 3 

The reed valves at the valve piston generate an even firmer setting.

If the body moves upwards and if solenoid valve 1 is open and solenoid valve 2 is closed, a hard rebound stage and a soft compression stage is achieved by the plate valves (c = rebound hard and d = compression soft) on solenoid valve 2

Damping force setting 4 (driving safety setting) 

For increased driving safety during high longitudinal and lateral accelerations of the vehicle.

Solenoid valves 1 and 2 are closed. The reed valves (a = hard compression and c = hard rebound) generate a hard  compression and rebound. All the oil flows via the hard rebound and compression of the operating piston.

These damping force settings are also engaged even if the ADS has any system errors.