1. Field of the Invention
The present invention relates, generally, to a vehicle body and, more particularly, to an extending and retracting device for a step of the vehicle body.
2. Description of the Related Art
A step under a door of a vehicle is used for a passenger to get on or off the vehicle. In terms of ergonomics, the vehicle step is generally mounted at a level of 15 cm with respect to the ground so that it is convenient for the passenger to get on or off it, but this level does not provide sufficient ground clearance during operation of many vehicles. The level of the vehicle step should be higher than ground clearance of the vehicle. Therefore, it is difficult to meet ground-clearance and convenience requirements simultaneously with a conventional vehicle step.
U.S. Pat. No. 6,830,257 discloses a retractable vehicle step employing a four-link mechanism. When a door of a vehicle is opened, the vehicle step is automatically extended out downwardly from the chassis of the vehicle near the board of the body of the vehicle so that a passenger can step on the extended vehicle step. When the vehicle door is closed, the vehicle step is automatically retracted upwardly to its original position, thus not affecting disadvantageously ground clearance of the vehicle.
The retractable vehicle step disclosed in U.S. Pat. No. 6,830,257 employs one motor to drive a pair of four-link mechanisms used to deploy and retract a step member. Since the pair of four-link mechanisms is driven by one motor, a driving force applied to the retractable vehicle step is not balanced, and rotations of two four-link mechanisms of the retractable vehicle step are not synchronous so that operation of the retractable vehicle step is not reliable. If a conventional four-link retractable vehicle step employs two motors to drive the two four-link mechanisms simultaneously, rotations of the two motors and/or four-link mechanisms may not be synchronous so that the four-link mechanisms may interfere with each other. The retractable vehicle step may be destroyed due to the interference and fail to operate.
Furthermore, in a conventional vehicle step apparatus, a distance between two pivot shafts connecting the four-link mechanism with the step member is short so that stress tends to concentrate on respective positions of the pivot shafts when a passenger steps on an extended step member. Thus, the pivot shafts tend to be destroyed over time due to their lack of mechanical strength. Therefore, reliability is reduced, and cost is increased.
Thus, there is a need in the related art for a vehicle step apparatus that is stable and not subject to these deficiencies and operation of which is reliable. There is also a need in the related art for such a vehicle step apparatus that does not increase cost.