The present invention relates to a motor-contained electric actuator for controlling the posture of the backrest of a chair in a motor vehicle.
An electric actuator generally comprises a DC motor body and a worm reduction mechanism such as a worm wheel. This type of actuator comprises various functional parts that increase the total number of parts. In order to decrease the parts volume of the whole actuator, a small motor is integrally connected to a reduction mechanism. In this case, load resistance by a driver generates load in a thrust direction requiring provision of a bearing structure to support it.
To make an electric actuator smaller, a worm is directly formed on a motor shaft of a small motor to constitute a motor body and a reduction mechanism. Load acts in a radial direction to the motor shaft on which the workpiece is formed depending on load resistance. Thus it is necessary to provide a radial bearing on each side of the worm teeth.
In an electric actuator in which the worm is integrally connected with a reduction mechanism, it is necessary not only to provide a thrust bearing on each end of the motor shaft but also to provide a thrust-radial bearing at an axial end portion of the worm to lead troublesome construction of the electric actuator.
For example, when thrust is supported by a ball bearing at an axial end portion near the worm of the motor shaft, radial force acts on that portion and it thus requires a radial bearing.
A known motor-contained electric actuator makes not only the structure of the axial end portion more complicated but also the bearing structure of the reduction mechanism thus causing motor body assembly to be more complicated as well.