Intake-air cooling device for engine and method for cooling engine

Abstract

A first cooling water circuit is configured such that the cooling water that has come out from the engine passes through the first intake-air cooling device and returns to the engine again. A second cooling water circuit is configured such that the cooling water that has come out from the engine passes through the second intake-air cooling device and returns to the engine again. A heat exchanger is configured to perform heat exchange between the cooling water that has come out from the engine and flowing to the first intake-air cooling device and the cooling water that has come out from the second intake-air cooling device and that is flowing to the engine.

1 . An intake-air cooling device for an engine that is provided on the engine including a cooling water circuit through which cooling water for the engine flows and a supercharger that supercharges intake air for the engine, comprising a first intake-air cooling device, a second intake-air cooling device, and a heat exchanger, wherein:
 the cooling water circuit has a first cooling water circuit and a second cooling water circuit;   the first intake-air cooling device is configured such that the intake air is cooled with the cooling water in the first cooling water circuit, and the second intake-air cooling device is configured such that, with the cooling water in the second cooling water circuit, the intake air that has been cooled by the first intake-air cooling device is further cooled;   the first cooling water circuit is configured such that the cooling water that has come out from the engine passes through the first intake-air cooling device and returns to the engine again;   the second cooling water circuit is configured such that the cooling water that has come out from the engine passes through the second intake-air cooling device and returns to the engine again; and   the heat exchanger is configured to perform heat exchange between the cooling water that has come out from the engine and flowing to the first intake-air cooling device and the cooling water that has come out from the second intake-air cooling device and that is flowing to the engine.   
     
     
         2 . The intake-air cooling device for an engine according to  claim 1 , wherein
 the first cooling water circuit includes a first radiator for cooling the cooling water and the second cooling water circuit includes a second radiator for cooling the cooling water flowing through the second cooling water circuit, and   the cooling water that has come out from the engine and that has been cooled by the second radiator flows through the second intake-air cooling device.   
     
     
         3 . The intake-air cooling device for an engine according to  claim 1 , wherein
 the cooling water in the first cooling water circuit that has come out from the first intake-air cooling device and the cooling water in the second cooling water circuit that has come out from the heat exchanger are combined and returned to the engine.   
     
     
         4 . The intake-air cooling device for an engine according to  claim 1 , further comprising:
 a first water temperature detector that detects water temperature of the cooling water in the first cooling water circuit entering the heat exchanger;   a second water temperature detector that detects water temperature of the cooling water in the second cooling water circuit entering the heat exchanger;   a bypass flow path that bypasses the cooling water in the second cooling water circuit such that the cooling water does not flow through the heat exchanger;   a valve that controls whether the cooling water in the second cooling water circuit is allowed to flow through the bypass flow path; and   a control device that is configured to control operation of the valve, wherein   the control device performs:   a control of the valve such that, when the water temperature of the cooling water in the second cooling water circuit is higher than the water temperature of the cooling water in the first cooling water circuit, the cooling water in the second cooling water circuit is allowed to flow through the heat exchanger; and   a control of the valve such that, when the water temperature of the cooling water in the first cooling water circuit is higher than the water temperature of the cooling water in the second cooling water circuit, the cooling water in the second cooling water circuit is allowed to bypass the heat exchanger without flowing therethrough.   
     
     
         5 . A method of cooling intake-air for an engine including a cooling water circuit through which cooling water for the engine flows and a supercharger that supercharges the intake air for the engine, wherein
 the cooling water circuit has a first cooling water circuit and a second cooling water circuit;   a first intake-air cooling device that is configured such that the intake air is cooled with the cooling water in the first cooling water circuit, and a second intake-air cooling device that is configured such that, with the cooling water in the second cooling water circuit, the intake air that has been cooled by the first intake-air cooling device is further cooled are provided;   the first cooling water circuit is configured such that the cooling water that has come out from the engine passes through the first intake-air cooling device and returns to the engine again;   the second cooling water circuit is configured such that the cooling water that has come out from the engine passes through the second intake-air cooling device and returns to the engine again;   a heat exchanger that is configured to perform heat exchange between the cooling water that has come out from the engine and flowing to the first intake-air cooling device and the cooling water that has come out from the second intake-air cooling device and that is flowing to the engine is provided;   a first water temperature detector that detects water temperature of the cooling water in the first cooling water circuit entering the heat exchanger is provided;   a second water temperature detector that detects water temperature of the cooling water in the second cooling water circuit entering the heat exchanger is provided; and   a bypass flow path that bypasses the cooling water in the second cooling water circuit such that the cooling water does not flow through the heat exchanger is provided; and   a valve that controls whether the cooling water in the second cooling water circuit is allowed to flow through the bypass flow path is provided;   the method comprising:   controlling the valve such that, when the water temperature of the cooling water in the second cooling water circuit is higher than the water temperature of the cooling water in the first cooling water circuit, the cooling water in the second cooling water circuit is allowed to flow through the heat exchanger; and   controlling the valve such that, when the water temperature of the cooling water in the first cooling water circuit is higher than the water temperature of the cooling water in the second cooling water circuit, the cooling water in the second cooling water circuit is allowed to bypass the heat exchanger without flowing therethrough.