Rotation speed control apparatus of open close body for vehicle and rotation speed control method of the same

1. A rotation speed control apparatus of an open close body rotatably attached to a vehicle body so as to be freely opened and closed, comprising:

an opening and closing means having a motor for opening and closing the open close body;

a detector for detecting a position of the open close body; and

a controller for PWM controlling the motor, increasing a duty ratio of the PWM control according to a given increasing rate just after starting the motor, reducing the duty ratio to a given value by detecting a start of the open close body by means of the detector, and keeping the given value of the duty ratio for a given period.

2. A rotation speed control apparatus of claim 1 , wherein the controller gradually increases the duty ratio applied to the motor from a given value according to a given rate, in the case that the controller discriminates that the rotation speed of the open close body reaches at most a given speed.

3. A rotation speed control apparatus of claim 1 , wherein the open close body is provided with a latch apparatus to which a striker provided in the vehicle body is guided, and

wherein a detector for detecting an engaging state of the latch apparatus is provided within the latch apparatus.

4. A rotation speed control apparatus of claim 3 , wherein the latch apparatus comprises a latch rotatably mounted to the latch apparatus; and a ratchet having a pawl portion being engaged with the latch and rotatably mounted to the latch apparatus, and

wherein the pawl portion of the ratchet and a half latch engagement portion of the latch are engaged in the case that the open close body is in a door ajar state,

and wherein, in the case that the open close body is in a door close state, the striker is engaged with an engagement groove of the latch, and the pawl portion of the ratchet and a full latch engagement portion of the latch are engaged.

5. A rotation speed control apparatus of claim 4 , wherein the detector further comprises a first detecting apparatus for detecting the door ajar state, a second detecting apparatus for detecting the door close state, and a third detecting apparatus for detecting the state of the ratchet.

6. A rotation speed control apparatus of claim 1 , wherein the detector comprises a rotary encoder.

7. A rotation speed control method of an open close body rotatably attached to a vehicle body so as to be freely opened and closed, comprising the steps of:

increasing a voltage applied to a motor driving the open close body step by step from an initial voltage;

detecting a start of rotation of the open close body;

reducing the voltage applied to the motor to a given value and keeping the electric voltage constant until a rotation speed of a rear gate becomes smaller than a given target rotation speed;

increasing the voltage applied to the motor every given time;

keeping the voltage applied to the motor constant until the open close body reaches a given position; and

stopping the motor at a time when the open close body reaches the given position.