Electric pump device

Abstract

An electric pump device (1) according to the present invention comprises an oil pump (10) that discharges oil; a motor (20) that drives the oil pump (10); and a control unit (30) that controls the value of current supplied to the motor (20) to control rotation of the motor (20), thereby controlling the flow rate of fluid discharged from the oil pump (10). The device is configured such that at startup of the motor (20), until the rotational speed of the motor (20) comes near to a target rotational speed set beforehand, the motor (20) is driven by open loop control that restricts the value of current supplied to the motor (20) to lower than a predetermined upper limit, and that when the rotational speed of the motor (20) has come near to the target rotational speed, the motor (20) is driven by feedback control that keeps the rotational speed at a steady rotational speed.

1 . An electric pump device comprising:
 a fluid pump that discharges fluid;   a motor that drives the fluid pump; and   a control unit that controls the value of current supplied to the motor to control rotation of the motor, thereby controlling the flow rate of fluid discharged from the pump,   wherein at startup of the motor, until the rotational speed of the motor comes near to a target rotational speed set beforehand, the control unit drives the motor by open loop control that restricts the value of current supplied to the motor to lower than a predetermined upper limit, and   wherein when the rotational speed of the motor has come near to the target rotational speed, the control unit drives the motor by feedback control that keeps the rotational speed at a steady rotational speed.   
     
     
         2 . The electric pump device according to  claim 1 , wherein specified rotational frequencies for the motor are set beforehand in the control unit, and
 wherein in the open loop control, the specified rotational speed of the motor is increased stepwise to supply current of a value according to the specified rotational speed to the motor.   
     
     
         3 . The electric pump device according to  claim 1 , comprising a temperature detector that detects a temperature of fluid,
 wherein at startup of the motor, when the temperature of the fluid detected by the temperature detector is lower than a specified temperature, the open loop control is performed for a relatively long time, and when the temperature of the fluid detected by the temperature detector is higher than or equal to the specified temperature, the open loop control is performed for a relatively short time.   
     
     
         4 . The electric pump device according to  claim 2 , comprising a temperature detector that detects a temperature of fluid,
 wherein at startup of the motor, when the temperature of the fluid detected by the temperature detector is lower than a specified temperature, the open loop control is performed for a relatively long time, and when the temperature of the fluid detected by the temperature detector is higher than or equal to the specified temperature, the open loop control is performed for a relatively short time.