Active Seat

Active Seat

The active seat was introduced for the first time in the E38 for model year '99. The active seats in the E65/E66 have been adapted to the E65/E66 electrical system.

The active seats relieve the back muscles and spinal column on longer journeys. The seat cushion of the active seat is moved up and down in stages. For safety reasons, the active seat is paused when the vehicle is cornering.







The following components are required for the active seat function:

- Switch block, auxiliary functions, driver and passenger
- BZM
- Car Access System (CAS)
- Seat module, driver and passenger (SMFA/SMBF)
- 1 active seat unit per seat

The signals for operating the active seat are transmitted over the buses.

Signal path: Switch block, auxiliary functions, active seat 14-pin ribbon cable BZM K-CAN S CAS K-CAN P SMFA or SMBF.

Functional Description

The system is filled with a glycol fluid. This fluid is pumped alternately into the left and right fluid bags (by reversing the direction of pump rotation).

The following components are required for the active-seat function:

- Hydraulic pump: the hydraulic-pump motor is activated with alternating polarity by semi conductors in the seat module.

- Hall sensor: a Hall sensor records the revolutions of the hydraulic-pump motor. The motor function is monitored with this signal.

- Solenoid valve: the solenoid valve is installed between the two fluid bags and opens and closes the delivery to the fluid bags. The valve is activated by semiconductors in the seat module. The solenoid valve is closed when the system is deactivated and in the intervals between the adjustments. In order not to irritate the driver when cornering fast, the operational sequence of the active seat is stopped immediately at high transversal acceleration: the solenoid valve remains closed from a specific transversal vehicle acceleration. The yaw-rate sensor telegrams the transversal-acceleration signal via the bus system.

- Vacuum switch: a vacuum switch is installed in each of the fluid bags. These switches identify the extent to which the fluid bags are drained. In the event of a fault, the system stops or holds in order to avoid further damage.