Engine cooling apparatus

Abstract

The present invention provides an engine cooling apparatus that is capable of suppressing cavitation in a high rotation region while achieving an increase in a circulation flow rate of cooling water in a low/medium rotation region. The engine cooling apparatus includes: a main cooling water circuit that circulates the cooling water between an engine and a radiator; a branch portion provided between the engine and the radiator; a thermostat; temperature detecting means; a first bypass flow passage; a second bypass flow passage that connects the engine to the branch portion; a control valve; a bypass convergence portion; a water pump; valve opening control means; and engine rotation speed detecting means.

1 . An engine cooling apparatus comprising:
 a main cooling water circuit that circulates cooling water between an engine and a radiator;   a branch portion provided in the main cooling water circuit between the engine and the radiator;   a thermostat provided in the main cooling water circuit between the radiator and the engine on a side where the branch portion is not provided;   temperature detecting means for detecting a temperature of the cooling water in the main cooling water circuit;   a first bypass flow passage provided between the branch portion and the thermostat;   a second bypass flow passage that connects the engine to the branch portion and connects the thermostat to the engine;   a control valve provided in the second bypass flow passage;   a bypass convergence portion between the main cooling water circuit and the second bypass flow passage;   a water pump that is provided between a downstream side of the thermostat and an upstream side of the engine and activated by driving the engine;   valve opening control means for controlling an opening of the control valve; and   engine rotation speed detecting means for detecting a rotation speed of the engine,   wherein, when the temperature of the cooling water is equal to or lower than a predetermined temperature, the first bypass flow passage is set in a circulation state in which the cooling water flows,   when the temperature of the cooling water is equal to or higher than the predetermined temperature, the first bypass flow passage is set in a non-circulation state in which the cooling water does not flow,   when the engine rotation speed detected by the engine rotation speed detecting means is equal to or lower than a predetermined rotation speed, the control valve is controlled to a fully open state by the valve opening control means, and   when the engine rotation speed detected by the engine rotation speed detecting means is equal to or higher than the predetermined rotation speed, the opening of the control valve is controlled by the valve opening control means in a fully closed direction from the fully open state in accordance with an increase in the rotation speed.   
     
     
         2 . The engine cooling apparatus according to  claim 1 , wherein control is performed to reduce the predetermined rotation speed as the temperature of the cooling water detected by the temperature detecting means increases.