Cooling system

Abstract

The objective is to provide a cooling system that suppresses the boiling of coolant in turbochargers and oil coolers. [Solution] A cooling system comprising: a first circulation path through which coolant circulates in the engine; a mechanical water pump provided in the first circulation path and driven by the rotation of the engine; a second circulation path communicating with the first circulation path through which coolant circulates between a supercharger and an oil cooler mounted on the engine without passing through the engine; an electric water pump provided in the second circulation path; a switching valve that can switch between a first state in which coolant flows in both the first and second circulation paths, and a second state in which the first circulation path is blocked and coolant flows in the second circulation path; and a control device that controls the system to the second state by the switching valve when the rotation of the engine is stopped, and drives the electric water pump.

Description

Technical Field

[0001] The present invention relates to a cooling system.

Background Art

[0002] There is a cooling system having a circulation path in which cooling water circulates through an engine (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A mechanical water pump driven by the rotation of an engine may be provided in the circulation path. When the rotation of the engine stops, the mechanical water pump also stops, and the cooling water in the circulation path stagnates. When a supercharger or an oil cooler is provided in the circulation path, the cooling water stagnates in the supercharger or the oil cooler. The capacity of the cooling water in the supercharger or the oil cooler is relatively small, and immediately after the engine stops, the supercharger or the oil cooler is still hot. Therefore, there is a risk that the cooling water boils in the supercharger or the oil cooler.

[0005] Therefore, an object of the present invention is to provide a cooling system that suppresses boiling of the cooling water in a supercharger or an oil cooler.

Means for Solving the Problems

[0006] The above objective can be achieved by a cooling system comprising: a first circulation path through which coolant circulates in the engine; a mechanical water pump provided in the first circulation path and driven by the rotation of the engine; a second circulation path communicating with the first circulation path and through which coolant circulates between a supercharger and an oil cooler mounted on the engine without passing through the engine; an electric water pump provided in the second circulation path; a switching valve that can switch between a first state in which coolant flows in both the first and second circulation paths, and a second state in which the first circulation path is blocked and coolant flows in the second circulation path; and a control device that controls the system to the second state by the switching valve when the engine rotation is stopped and drives the electric water pump.

[0007] The first circulation path includes a radiator path from the engine through the radiator to the engine again, and a heater core path from the engine through the heater core to the engine again, and the length of the second circulation path may be shorter than the lengths of the radiator path and the heater core path, respectively.

[0008] The second circulation path may be provided only with the electric water pump, the supercharger, and the oil cooler.

[0009] The control device may stop the electric water pump when the engine is operating at a low load, and control the electric water pump to the first state by the switching valve when the engine is operating at a high load, which is higher than the low load state. [Effects of the Invention]

[0010] According to the present invention, a cooling system can be provided that suppresses the boiling of coolant in the supercharger and oil cooler. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the vehicle's configuration. [Figure 2] This is a schematic diagram of the cooling system installed in the vehicle. [Figure 3] This flowchart illustrates the E-WP drive control performed by the ECU. [Modes for carrying out the invention]

[0012] [Vehicle Outline] Figure 1 is a schematic diagram of the vehicle 100. The vehicle 100 includes an engine 1, an intake passage 3, an exhaust passage 4, a supercharger 5, an intercooler 6, a catalytic converter 7a, a filter 7b, a bypass passage 8, a wastegate valve (hereinafter referred to as WGV) 9, an automatic transmission 21, a differential gear 23, wheels 25, and an ECU (Electronic Control Unit) 30. The engine 1 is a gasoline engine. The driving force of the engine 1 is transmitted to the wheels 25 via the automatic transmission 21 and the differential gear 23. The vehicle 100 is an engine-powered vehicle equipped with the engine 1 as a power source. However, it may also be a hybrid vehicle equipped with an electric motor in addition to the engine 1 as a power source.

[0013] Engine 1 has four cylinders 2, but the number of cylinders is not limited to this. Each cylinder 2 is equipped with a fuel injector 2a and a spark plug 2b. Engine 1 is connected to an intake passage 3 and an exhaust passage 4. A compressor 5b of the supercharger 5 is located in the middle of the intake passage 3. A turbine 5a of the supercharger 5 is located in the middle of the exhaust passage 4. The turbine 5a and the compressor 5b are coaxially connected by a shaft. The supercharger 5 supercharges the intake air into engine 1.

[0014] In the middle of the exhaust passage 4, there is a bypass passage 8 that bypasses the turbine 5a, and a WGV9 that opens and closes the bypass passage 8. The opening degree of the WGV9 is adjusted by an electric actuator 9a that drives the WGV9. The opening degree of the WGV9 is feedback-controlled by the ECU 30 so that the boost pressure becomes a target boost pressure determined according to the operating state of the engine 1. The ECU 30 controls the opening degree of the WGV9 by outputting a command value to the electric actuator 9a. The WGV9 is a normally closed type that is fully closed when the electric actuator 9a is not energized.

[0015] In the intake passage 3, an intercooler 6 for cooling the intake air is located downstream of the compressor 5b. Downstream of the intercooler 6 in the intake passage 3, a throttle valve 3a for adjusting the amount of intake air for the engine 1 is located.

[0016] In the exhaust passage 4, downstream of the turbine 5a, a catalyst 7a for purifying exhaust gases and a filter 7b for collecting exhaust gas particles are provided. The filter 7b is located downstream of the catalyst 7a. The catalyst 7a contains catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has oxygen storage capacity, and purifies NOx, HC, and CO. The filter 7b is a porous ceramic structure.

[0017] The ECU30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The ECU30 controls the engine 1 based on information from sensors and other information stored in the ROM, according to a control program pre-stored in the ROM. The ECU30 is an example of a control device.

[0018] The ECU 30 controls the operating state of the engine 1 based on the detection signals from various sensors such as the crank angle sensor 11, air flow meter 12, air-fuel ratio sensor 13, and accelerator opening sensor 14. The crank angle sensor 11 detects the rotational angle of the crankshaft of the engine 1. The air flow meter 12 detects the amount of intake air inhaled into the intake passage 3. The air-fuel ratio sensor 13 detects the air-fuel ratio of the exhaust gas discharged from the engine 1. The accelerator opening sensor 14 detects the accelerator opening, which is the amount of operation of the accelerator pedal.

[0019] The ECU 30 grasps the engine speed and load of the engine 1 based on the output signals of various sensors. The ECU 30 outputs a command signal to various drive circuits connected to the output ports according to the operating state thus grasped. The controls performed by the ECU 30 in this way include throttle control for adjusting the opening of the throttle valve 3a, fuel injection control for adjusting the injection amount of the fuel injection valve 2a, and ignition timing control for adjusting the ignition timing of the ignition plug

[0020] [Schematic Configuration of Cooling System] Figure 2 is a schematic configuration diagram of the cooling system 200 mounted on the vehicle 100. In the cooling system 200, heat exchange is performed between the engine 1 and the cooling water flowing through the engine 1, and the engine 1 is cooled. The cooling system 200 includes a radiator 51, a reserve tank 52, a heater core , a throttle water jacket 55, a mechanical water pump (hereinafter referred to as M-WP) 57, an exhaust cooling section 58, an inlet 59, an electric water pump (hereinafter referred to as E-WP) 67, an oil cooler 68, and a supercharger 5.

[0021] M-WP57 is a mechanical pump driven by the rotation of engine 1 to convey cooling water. A part of the cooling water flows from M-WP57 through path 43a to the cylinder block 1B, cylinder head 1A, and exhaust cooling section 58 of engine 1. Also, a part of the cooling water flows from M-WP57 through path 43b to the exhaust cooling section 58. The cooling water flows from the exhaust cooling section 58 through path 44 to the multi-functional valve 50. The multi-functional valve 50 is a four-way valve to which paths 41, 45, and 47 are connected. The opening degrees of paths 41, 45, and 47 are changed according to the rotational angular position of the rotor of the multi-functional valve 50 described later. The rotor of the multi-functional valve 50 is controlled by the ECU 30. Details will be described later.

[0022] Path 41 is connected between the multi-functional valve 50 and the inlet 59, and a radiator 51 is provided midway. In the radiator 51, heat exchange is performed between the cooling water and the outside air, promoting the heat dissipation of the cooling water. The cooling water discharged from the radiator 51 flows through path 41 to the inlet 59. A path 42 is provided that branches at a portion of path 41 upstream of the radiator 51 and rejoins path 41 at a portion of path 41 downstream of the radiator 51. A reserve tank 52 is provided midway in path 42.

[0023] Path 45 is connected to the multi-functional valve 50 and the inlet 59, and a throttle water jacket 55 is provided midway. The throttle water jacket 55 is provided inside the throttle valve 3a. In the throttle water jacket 55, heat exchange is performed between the cooling water and the throttle valve 3a to cool the throttle valve 3a.

[0024] Path 46 is connected to a portion of path 45 upstream of the throttle water jacket 55 and the inlet 59. A heater core 56 is provided in path 46. In the heater core 56, heat exchange is performed between the cooling water and the air for vehicle interior heating.

[0025] Route 47 is connected to the multi-function valve 50 and route 44, and has an E-WP 67, an oil cooler 68, and a supercharger 5 along its path. The E-WP 67 is an electric pump that is driven by instructions from the ECU 30 to transport coolant. In the oil cooler 68, heat exchange takes place between the coolant and engine oil to cool the engine oil. In the supercharger 5, heat exchange takes place between the coolant and the supercharger 5 as the coolant passes through the housing of the supercharger 5 to cool the supercharger 5. The upstream end of route 47 is connected to the multi-function valve 50. The downstream end of route 47 is connected to route 44. Thus, the coolant circulating in route 47 does not pass through the engine 1.

[0026] As described above, the coolant that has passed through engine 1, the multi-function valve 50, the radiator 51, the reserve tank 52, the throttle water jacket 55, and the heater core 56 flows to the inlet 59. The coolant supplied to the inlet 59 flows back to engine 1 via the M-WP 57. Routes 41, 42, 43a, 43b, 44, 45, and 46 are examples of the first circulation route. In addition, the coolant that has passed through the oil cooler 68 and the supercharger 5 via route 47 from the multi-function valve 50 flows to route 44. That is, the coolant circulating in route 47 does not pass through engine 1. Route 47 is an example of the second circulation route.

[0027] The length of path 47 is shorter than the length of the radiator path from engine 1 through radiator 51 to engine 1 again. The length of the radiator path is the sum of the lengths of paths 44, 41, and 43a or 43b. Also, the length of path 47 is shorter than the length of the heater core path from engine 1 through heater core 56 to engine 1 again. The length of the heater core path is the sum of the lengths of path 44, the portion of path 45 from the multi-function valve 50 to the branching of path 46, path 46, and path 43a or 43b. Thus, path 47 is shorter than the lengths of both the radiator path and the heater core path.

[0028] One of the factors that allows the length of path 47 to be shortened is that path 47 is equipped only with the E-WP67, oil cooler 68, and supercharger 5. For example, if a throttle water jacket 55 were to be added to path 47, the length of path 47 could become longer than that of the radiator path or heater core path.

[0029] Next, the multi-function valve 50 will be described. The multi-function valve 50 switches the open and closed states of paths 41, 45, and 47. Specifically, the multi-function valve 50 switches between the following states: all paths 41, 45, and 47 are closed; paths 41 and 47 are closed and path 45 is open; path 41 is closed and paths 45 and 47 are open; all paths 41, 45, and 47 are open; paths 41 and 45 are closed and path 47 is open; path 45 is closed and paths 41 and 47 are open; and paths 45 and 47 are closed and path 41 is open.

[0030] Here, the state in which at least one of paths 41 and 45 is opened, and path 47 is opened, is referred to as the first state. In the first state, coolant flows to at least the engine 1, oil cooler 68, and supercharger 5 via the M-WP 57. The system is controlled to the first state while the engine 1 is running. The state in which both paths 41 and 45 are closed and path 47 is opened is referred to as the second state. In the second state, coolant does not flow to the engine 1, radiator 51, throttle water jacket 55, and heater core 56. Also, when the E-WP 67 is driven in the second state, coolant flows to the oil cooler 68 and supercharger 5. In Figure 2, the path through which coolant does not flow is shown with a dotted line, and the path through which coolant flows is shown with a solid line, representing the second state. The multi-function valve 50 is an example of a switching valve.

[0031] [E-WP drive control] Next, the drive control of the E-WP67 performed by the ECU30 will be described. Figure 3 is a flowchart illustrating the drive control of the E-WP67 performed by the ECU30. The ECU30 determines whether or not the rotation of the engine 1 has stopped (step S1). The stopping of the rotation of the engine 1 may be, for example, an intermittent stop due to the idle stop function, or a stop due to turning off the ignition. Furthermore, the stopping of the rotation of the engine 1 does not necessarily mean that the engine 1 has stopped completely, but may also be determined to be stopped when the rotation speed is below a speed at which it can be considered to be almost stopped. The stopping of the rotation of the engine 1 is determined by the ECU30 based on the detected value of the crank angle sensor 11.

[0032] If the answer in step S1 is Yes, the ECU 30 controls the multi-function valve 50 to switch to the second state (step S2) and drives the E-WP 67 (step S3). As a result, the coolant circulates through path 47 to the oil cooler 68 and the supercharger 5, but does not flow to the engine 1, radiator 51, throttle water jacket 55, or heater core 56. This allows the coolant to circulate efficiently to the oil cooler 68 and the supercharger 5, suppressing the boiling of the coolant in the oil cooler 68 and the supercharger 5. Furthermore, as mentioned above, the length of path 47 is shorter than the lengths of the radiator path and the heater core path, respectively. Therefore, pressure loss of the coolant circulating through path 47 is suppressed, and the power consumption of the E-WP 67 is reduced.

[0033] If the answer in step S1 is No, i.e., if engine 1 is running, the ECU 30 determines whether engine 1 is in a high-load operating state (step S4). Here, a high-load operating state is an operating state in which the intake air volume of engine 1 exceeds a predetermined value. The predetermined value is set to the minimum intake air volume at which, with only the M-WP57, engine 1 may become hot and the circulation flow rate of the coolant in the cooling system 200 may become insufficient. The intake air volume is calculated by the ECU 30 based on the value detected by the airflow meter 12.

[0034] If the answer in step S4 is No, that is, if the engine 1 is in a low-load operating state with a load lower than that of a high-load operating state, the ECU 30 maintains the E-WP 67 in a stopped state (step S5). If the answer in step S4 is Yes, the ECU 30 controls the multi-function valve 50 to the first state (step S6) and drives the E-WP 67 (step S3). By controlling the multi-function valve 50 to the first state and driving the E-WP 67 in the high-load operating state in this way, the circulation flow rate of the coolant is increased by the M-WP 57 and the E-WP 67, and the engine 1, oil cooler 68 and turbocharger 5 can be effectively cooled.

[0035] Vehicle 100 may be a hybrid vehicle equipped with an engine 1 and a motor as a power source for driving.

[0036] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0037] 1 Engine 5. Supercharger 6 Intercoolers 30 ECU (Control Unit) Routes 41, 42, 43a, 43b, 44, 45, 46 (First Circular Route) 47 Routes (Second Circulation Route) 50 Multifunctional valve (switching valve) 57 Mechanical water pump 67 Electric water pump 200 Cooling System

Claims

1. The first circulation path through which the coolant circulates in the engine, A mechanical water pump provided in the first circulation path and driven by the rotation of the engine, A second circulation path is connected to the first circulation path, and the cooling water circulates between the supercharger and oil cooler mounted on the engine without passing through the engine, An electric water pump provided in the second circulation path, A switching valve that can switch between a first state in which cooling water flows through both the first and second circulation paths, and a second state in which the first circulation path is blocked and cooling water flows through the second circulation path, A cooling system comprising: a control device that controls the engine to the second state by the switching valve when the engine rotation is stopped, and drives the electric water pump.

2. The first circulation path includes a radiator path from the engine through the radiator to the engine again, and a heater core path from the engine through the heater core to the engine again. The cooling system according to claim 1, wherein the length of the second circulation path is shorter than the lengths of the radiator path and the heater core path, respectively.

3. The cooling system according to claim 2, wherein the second circulation path is provided only with the electric water pump, the supercharger, and the oil cooler.

4. The cooling system according to claim 3, wherein the control device stops the electric water pump when the engine is in a low-load operating state, and controls the engine to the first state by the switching valve to drive the electric water pump when the engine is in a high-load operating state where the load is higher than the low-load operating state.

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