DOOR OPENING AND CLOSING ASSISTANCE DEVICE

1 . A door opening and closing assistance device, comprising:

a three-phase DC motor configured to generate power for assisting an operation force of a door that is supported on a vehicle body and allowed to be opened and closed; and

a controller configured to control the three-phase DC motor,

wherein the controller is configured to set and cancel

door balance control in which an output of the three-phase DC motor is controlled to balance a component of a weight of the door in an opening and closing direction of the door such that the door is stationary, and

power assistance control in which the output of the three-phase DC motor is controlled to generate an assistance force in the opening and closing direction of the door, and

when a state that an opening and closing acceleration of the door is equal to or more than a third threshold continues for predetermined time or more in a state that the door balance control is set, the controller switches from the door balance control to the power assistance control.

2 . A door opening and closing assistance device, comprising:

a three-phase DC motor configured to assist an operation force of a door that is supported on a vehicle body and allowed to be opened and closed; and

a controller configured to control the three-phase DC motor,

wherein the controller is configured to set and cancel

pre-power assistance control in which an output of the three-phase DC motor is controlled such that a resultant force with a component of a weight of the door in an opening and closing direction of the door has a predetermined magnitude in a direction opposite to the opening and closing direction due to the weight of the door, to move the door, and

power assistance control in which the output of the three-phase DC motor is controlled to generate an assistance force in the opening and closing direction of the door, and

when a state that an opening and closing acceleration of the door is equal to or more than a third threshold continues for predetermined time or more in a state that the pre-power assistance control is set, the controller switches from the pre-power assistance control to the power assistance control.

3 . The door opening and closing assistance device according to claim 1 ,

wherein the controller is configured to set and cancel door holding control of maintaining a position of the door in which at least two phases of the three-phase DC motor are energized, and set energized phases according to a circumferential position of a rotor relative to a stator of the three-phase DC motor,

the door holding control is set when an opening and closing speed of the door is equal to or less than a first threshold, and

when at least one of the opening and closing acceleration, the opening and closing speed, and a movement distance of the door is equal to or more than a second threshold in a state that the door holding control is set, the controller switches from the door holding control to the door balance control.

4 . The door opening and closing assistance device according to claim 2 ,

wherein the controller is configured to set and cancel door holding control of maintaining a position of the door in which at least two phases of the three-phase DC motor are energized, and set energized phases according to a circumferential position of a rotor relative to a stator of the three-phase DC motor,

the door holding control is started when an opening and closing speed of the door is equal to or less than a first threshold, and

when at least one of the opening and closing acceleration, the opening and closing speed, and a movement distance of the door is equal to or more than a second threshold in a state that the door holding control is set, the controller switches from the door holding control to the pre-power assistance control.

5 . The door opening and closing assistance device according to claim 1 , further comprising:

a sensor attached to the door,

wherein the controller is configured to acquire at least one of the opening and closing acceleration, an opening and closing speed, and a movement distance of the door based on a detection value of the sensor.

6 . The door opening and closing assistance device according to claim 2 , further comprising:

a sensor attached to the door,

wherein the controller is configured to acquire at least one of the opening and closing acceleration, an opening and closing speed, and a movement distance of the door based on a detection value of the sensor.

7 . The door opening and closing assistance device according to claim 5 ,

wherein the door opening and closing assistance device is coupled to the vehicle body via a door hinge provided at a one end portion thereof, and assists an opening and closing operation of a hinged door rotatable about a pivot shaft of the door hinge, and

the sensor is attached to an other end portion of the hinged door opposite to the one end portion.

8 . The door opening and closing assistance device according to claim 6 ,

wherein the door opening and closing assistance device is coupled to the vehicle body via a door hinge provided at a one end portion thereof, and assists an opening and closing operation of a hinged door rotatable about a pivot shaft of the door hinge, and

the sensor is attached to an other end portion of the hinged door opposite to the one end portion.

9 . The door opening and closing assistance device according to claim 7 ,

wherein the sensor is provided inside a door latch device of the hinged door.

10 . The door opening and closing assistance device according to claim 8 ,

wherein the sensor is provided inside a door latch device of the hinged door.