Seats: Description and Operation
Design and functionGeneral
The power seat is available as a driver's seat and as a passenger seat. The seats have a memory function and an integral diagnosis system. The memory function has three memory buttons for different seat settings.
There is one control for the seat cushion and one for the backrest. The control module, which is located under the seat, controls four motors. Three of these motors are under the seat; one is in the backrest.
The memory-type control module takes seat position information from four position sensors, each in the form of a potentiometer driven by a worm gear unit on the output shaft of the particular motor.
Controls
The seat controls are located on a panel at the side of the seat. The panel has two controls and four buttons. The horizontal control (shaped like a seat cushion) adjusts the height of the front and rear edges of the seat cushion and the for-and-aft position of the seat. The vertical control (shaped like a backrest) adjusts the angle of the backrest. The three memory buttons are used to store and adjust the various settings. To move the seat to a stored setting, press and hold the button until the seat reaches the stored position. If the button is released while the seat is moving, the seat stops immediately. To store a seat position, press the programming button at the same time as one of the memory buttons.
Note: If more than one control button is pressed at the same time, the seat stops immediately.
Components
There are nine relays in the control module, two for each motor and one main on/off relay. There is also a microprocessor. The functions of the four motors are as follows:
motor 1 controls fore-and-aft movement of the seat
motor 2 controls backrest angle
motor 3 controls seat cushion height at the rear
motor 4 controls seat cushion height at the front.
On the output shaft of each motor there is a worm gear unit that drives a potentiometer (5). The resistance of the potentiometer is proportional to the position of the motor output shaft.
Safety functions
Power to the motor relays and electronics is indirectly controlled by the push-buttons. When the user releases a control button, the main on/off relay cuts off the power so that the seat stops moving.
If the user presses more than one button at the same time, the seat stops moving. Only the motors that control seat cushion height can be operated at the same time.
The system detects a broken, short-circuited or grounded sensor wire. The motors can then only be operated without their memory function.
The system detects a broken, short-circuited or grounded motor wire and disables that motor. The other motors can only be operated without their memory function.
If a button is held pressed for more than 30 seconds, a timer circuit cuts off the power supply to the motors by de-energizing the main relay.
The seat positions are held in an EEPROM which retains information indefinitely in the absence of power.