Engine cooling device

An engine cooling device comprising:

• a circulation circuit for coolant flowing through a water jacket formed inside an engine;
• a mechanical water pump that operates in response to rotation of the engine and that circulates the coolant through the circulation circuit;
• a flow rate control valve that serves to adjust a flow rate of the coolant flowing through the circulation circuit, that has a valve body driven by an electric actuator operating by being supplied with electric power from an in-vehicle electric power supply, and that allows a flow channel area for the coolant to change depending on an operating position of the valve body;
• and
• a control unit that sets an operating position within a prescribed control range as a target operating position in accordance with an operating situation of the engine, and that performs drive control of the actuator to change the operating position of the valve body to the set target operating position, wherein
• the control unit performs protection control for setting an operating position where a withstanding pressure limit rotational speed is equal to or higher than a current engine rotational speed, as the target operating position, and performs retreat control for reducing the control range to a retreat operation range set in advance, as a range of the operating position including a maximum withstanding pressure operating position, when a supply voltage of the in-vehicle electric power supply has dropped, in a case where the withstanding pressure limit rotational speed is defined as a maximum value of the engine rotational speed at which a hydraulic pressure in any region of the circulation circuit is lower than an upper limit of the hydraulic pressure permissible in the region, and where the maximum withstanding pressure operating position is defined as an operating position where the withstanding pressure limit rotational speed is highest among operating positions within the control range.