| 摘要 |
Typically, a steering column (4) is immobilised by a bolt (15) driven into a recess by a reversible motor (10). The motor is controlled by two change-over relays (13,13'), switched by transistors (12,12') selectively operated by an elecronic controller (11). Each relay's moving contact, connected to one motor pole, normally completes an earth connection. Depending on the rotation required, one relay is energised to break this connection and connect its motor pole to the supply (Vbat, 17), the other pole remaining earthed. The controller is powered up by a third transistor (14) only when the access control unit (2) accepts the driver's authorisation; the same unit unlocks the doors, permits start-up and, via the controller (11), withdraws the column locking bolt. A blocking relay (5) also energised, prepares the circuit of a change-over relay (3) which is then closed by the bolt's end-of-travel switch (16). This relay deenergises the motor circuit (17) and makes supply available to essential engine auxiliaries (+APC). Following this sequence, neither an electrical control fault nor spurious attempts to lock the steering can degrade safety in normal operation. Equally, the engine cannot be started with the lock bolt incompletely withdrawn. After the driver leaves the fully locked state is regained.
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