Electrical steering lock device and related method

1. An electrical steering lock device comprising:

a lock shaft operative to protrude into and retract from a lock groove, formed on a steering shaft, such that the lock shaft assumes a protruding position to engage with the lock groove for blocking rotation of the steering shaft while assuming a retracting position to disengage from the lock groove for unlocking rotation of the steering shaft;

a drive unit for protruding and retracting the lock shaft; and

a drive member linked with the drive unit in engagement with the lock shaft, which serves as a cam follower, to protrude and retract the lock shaft with respect to the lock groove,

wherein the drive member includes a cam having a cam surface with a contour shape to allow the lock shaft to move at a first speed, at which the lock shaft moves from inside the lock groove, to be slower than a second speed, at which the lock shaft moves outside the lock groove, and

wherein a surface area of a sliding surface between the drive member and the cam follower includes a first surface area associated with the first speed and a second surface area associated with the second speed which is narrower than the first surface area.

2. The electrical steering lock device according to claim 1 ,

wherein the retracting force, occurring when the lock shaft is retracted from the lock groove by the drive unit, is set such that the retracting force, occurring when the lock shaft is moved inside the lock groove, is set to be greater than that occurring when the lock shaft is moved outside the lock groove.

3. The electrical steering lock device according to claim 1 , further comprising:

a steering-lock prevention device cooperating with the lock shaft and operative to restrict unintentional movement of the lock shaft toward the protruding position.

4. The electrical steering lock device according to claim 3 , wherein

the lock shaft includes an engaging portion; and

the steering-lock prevention device includes a lock member selectively engageable with the engaging portion of the lock shaft to block unintentional locking movement of the lock shaft.

5. The electrical steering lock device according to claim 1 , wherein

the cam is formed by overlapping a first plate segment and a second plate segment, which have different contour shapes, and

wherein the first surface area associated with the first speed includes cam surfaces of the first and second plate segments, and

wherein the second surface area associated with the second speed includes a cam surface of the second plate segment.

6. An electrical steering lock device comprising:

lock means operative to protrude into and retract from a lock groove, formed on a steering shaft, such that the lock means assumes a protruding position to engage with the lock groove for locking rotation of the steering shaft while assuming a retracting position to disengage from the lock groove for unlocking rotation of the steering shaft;

drive means for protruding and retracting the lock means; and

a cam means linked with the drive means in engagement with the lock means, which serves as a cam follower, to protrude and retract the lock means with respect to the lock groove,

wherein the cam means includes a cam having a cam surface with a contour shape to allow the lock means to move at a first speed, at which the lock means moves from inside the lock groove, to be slower than a second speed, at which the lock means moves outside the lock groove, and

wherein a surface area of a sliding surface between the cam means and the cam follower includes a first surface area associated with the first speed and a second surface area associated with the second speed which is narrower than the first surface area.