JP2018080608A - Cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system capable of restraining wrong judgement in abnormal judgement of a switch valve.SOLUTION: An ECU 32 does not executes abnormal judgement of a switch valve 30 when a difference between a target rotation number and an actual rotation number of a water pump 10 is no less than a predetermined rotation number, even if a difference of outputs of water temperature sensors 14, 27 while commands for making the switch valve 30 into a valve-opening state to the switch valve 30. According to the cooling system 1, the abnormal judgement of the switch valve 30 is not executed when there is high possibility that air is generated in a water channel, so that possibility that wrong judgement might occur in the abnormal judgement of the switch valve 30 can be reduced.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to cooling systems, and more particularly, to a cooling system configured to cool an internal combustion engine.

  WO 2014/178112 discloses a cooling system configured to cool an internal combustion engine. The cooling system includes a first coolant circuit that passes through the internal combustion engine and a second coolant circuit that does not pass through the internal combustion engine. A valve is provided between the first cooling water circuit and the second cooling water circuit. When the valve is closed, the cooling water in the second cooling water circuit circulates, but the cooling water in the first cooling water circuit hardly circulates. On the other hand, when the valve is open, the cooling water in both the first and second cooling water circuits circulates.

  When the valve is closed, the cooling water in the first cooling water circuit passes through the internal combustion engine, so the temperature of the cooling water in the first cooling water circuit is the same as that in the second cooling water circuit. It is higher than the temperature of the cooling water. On the other hand, when the valve is in the open state, the cooling water circulating through each of the first and second cooling water circuits is mixed, so the temperature difference between the cooling water circulating through each cooling water circuit becomes small. . Therefore, in this cooling system, the temperature difference between the cooling water in each of the first and second cooling water circuits is not less than a predetermined temperature, even though a command for opening the valve is sent to the valve. If it is, it is determined that the valve has a closed failure (see Patent Document 1).

International Publication No. 2014/178112

  In the cooling system disclosed in Patent Document 1, the temperature of the cooling water in the first and second cooling water circuits is detected by a water temperature sensor. When air (bubbles) is present around the water temperature sensor, the detection accuracy of the water temperature sensor may be reduced. Therefore, in the cooling system disclosed in Patent Document 1, when there is air around the water temperature sensor, the valve (switching valve) is in the open state, but the valve is closed. May be misjudged.

  The present disclosure has been made to solve such a problem, and an object thereof is to provide a cooling system capable of suppressing erroneous determination in abnormality determination of a switching valve.

  The cooling system of the present disclosure is configured to cool an internal combustion engine. The cooling system includes first and second water channels, a pump, a switching valve, first and second water temperature sensors, and a control device. The first water channel is configured to circulate cooling water through the internal combustion engine. The second water channel is configured to circulate the cooling water without passing through the inside of the internal combustion engine. The pump is configured to circulate cooling water in the first and second water channels. The switching valve is disposed on the downstream side of the internal combustion engine, and is configured to adjust the amount of cooling water flowing from the first water channel to the second water channel by switching between the valve open state and the valve closed state. ing. The first water temperature sensor is disposed between the internal combustion engine and the switching valve in the first water channel. The second water temperature sensor is disposed on the downstream side of the second water channel with respect to the position where the first water channel merges via the switching valve. The control device determines whether the switching valve is abnormal, and controls the pump so that the actual rotational speed of the pump approaches the target rotational speed. In the state in which the control device sends a command for opening the switching valve to the switching valve, even if the difference between the outputs of the first and second water temperature sensors is equal to or higher than the predetermined temperature, the actual rotation of the pump When the difference between the number and the target rotational speed is equal to or greater than a predetermined number, the abnormality determination is not executed.

  In this cooling system, even when the difference between the outputs of the first and second water temperature sensors is equal to or higher than a predetermined temperature at the time of opening the switching valve, the difference between the actual rotational speed of the pump and the target rotational speed is a predetermined number of times. If this is the case (when there is a high possibility that a large amount of air is contained in the water channel), the abnormality determination of the switching valve is not executed. Therefore, according to this cooling system, it is possible to reduce the possibility of erroneous determination in the abnormality determination of the switching valve due to air in the water channel.

  According to the present disclosure, it is possible to provide a cooling system that can suppress erroneous determination in abnormality determination of the switching valve.

It is a figure which shows schematic structure of the cooling system of the vehicle carrying an engine. It is a figure for demonstrating the path | route which a cooling water flows in each after cold, half warm-up, and after complete warm-up. It is a flowchart which shows the process sequence of abnormality determination of a switching valve.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals and description thereof will not be repeated.

[Configuration of cooling system]
FIG. 1 is a diagram showing a schematic configuration of a cooling system for a vehicle equipped with an engine. In the figure, each arrow indicates a pipe through which cooling water passes. In addition, the arrow shown with a dashed-dotted line shows a sensor output or a control signal output. A water channel through which the cooling water circulates is formed by a plurality of pipes. In the cooling system 1, the cooling water flows through each pipe, whereby the engine 26 (described later) and the like are cooled or warmed up.

  Referring to FIG. 1, a cooling system 1 includes a water pump 10, an EGR (Exhaust Gas Recirculation) cooler 12, an EGR valve 16, a throttle body 18, a heater core 20, an exhaust heat recovery device 22, and an engine 26. A switching valve 30, water temperature sensors 14 and 27, a radiator 28, a thermostat 24, and an ECU (Electronic Control Unit) 32.

  The water pump 10 is configured to circulate cooling water in the water channel by being driven by an electric motor. The water pump 10 discharges cooling water from the thermostat 24 side to the EGR cooler 12 and the engine 26 side. The rotation speed of the water pump 10 is detected by a sensor (not shown). The detection result is output to the ECU 32.

  The EGR cooler 12 is connected to the water pump 10 via a pipe. The EGR cooler 12 is configured to cool the EGR gas with cooling water. The EGR valve 16 is connected to the EGR cooler 12 via a pipe. The EGR valve 16 is cooled by cooling water. The throttle body 18 is connected to the EGR valve 16 through a pipe. The throttle body 18 is warmed up by the cooling water warmed by passing through the EGR cooler 12 and the EGR valve 16. Thereby, freezing of the throttle body 18 is prevented.

  The heater core 20 is connected to the EGR cooler 12 via a pipe. The heater core 20 is configured to warm the air with cooling water warmed by passing through the EGR cooler 12. The air heated by the heater core 20 is blown into the vehicle interior by a blower for heating or defroster, for example. The exhaust heat recovery device 22 is connected to the heater core 20 via a pipe. The exhaust heat recovery unit 22 is configured to warm the cooling water by the heat of the exhaust gas.

  The engine 26 is connected to the water pump 10 via a pipe (not shown). A pipe is provided inside the engine 26, and the engine 26 is cooled by cooling water passing through the pipe.

  The switching valve 30 is connected to the engine 26 via a pipe. The switching valve 30 is configured to be able to switch between a valve opening state and a valve closing state. When the switching valve 30 is in the open state, the cooling water that has passed through the engine 26 is sent to the EGR cooler 12 and the radiator 28. On the other hand, when the switching valve 30 is in a closed state, delivery of the cooling water that has passed through the engine 26 to the EGR cooler 12 is suppressed. The switching valve 30 is composed of, for example, an FSV (Flow Shutting Valve).

  The water temperature sensor 27 is disposed between the engine 26 and the switching valve 30 and is configured to measure the temperature of cooling water (cooling water heated by the engine 26) flowing downstream of the engine 26. The water temperature sensor 14 is disposed on the downstream side of the junction point between the pipe connecting the switching valve 30 and the EGR cooler 12 and the pipe connecting the water pump 10 and the EGR cooler 12. The water temperature sensor 14 is configured to measure the temperature of the cooling water in which the cooling water bypassing the engine 26 and the cooling water heated by the engine 26 are mixed when the switching valve 30 is opened. In addition, the water temperature sensor 14 is configured to measure the temperature of the cooling water that bypasses the engine 26 when the switching valve 30 is closed. That is, when the switching valve 30 is in the open state, the water temperature detected by the water temperature sensor 14 is higher than when the switching valve 30 is in the closed state, and the difference in water temperature detected by each of the water temperature sensors 14 and 27 is different. Get smaller. The detection results of the water temperature sensors 27 and 14 are output to the ECU 32.

  The radiator 28 is connected to the engine 26 via a pipe. The radiator 28 is configured to dissipate heat of the cooling water by exchanging heat between the cooling water heated through the engine 26 and the outside air.

  The thermostat 24 is connected to the throttle body 18, the exhaust heat recovery device 22, and the radiator 28 via piping. The thermostat 24 includes a valve 24a that opens and closes according to the coolant temperature. A pipe provided on the downstream side of the radiator 28 is connected to the valve 24a. For example, the valve 24a opens when the temperature of the cooling water passing through the thermostat 24 is high, and closes when the temperature of the cooling water is low. Therefore, when the temperature of the cooling water flowing from the throttle body 18 and the exhaust heat recovery device 22 becomes high, the valve 24 a is opened, and the cooling water cooled by the radiator 28 passes through the thermostat 24. On the other hand, when the temperature of the cooling water flowing from the throttle body 18 and the exhaust heat recovery device 22 is low, the valve 24a is closed, and the passage of the cooling water thermostat 24 cooled by the radiator 28 is suppressed. The

  The ECU 32 includes a CPU (Central Processing Unit) and a memory (not shown), and controls, for example, the water pump 10 and the switching valve 30 based on information stored in the memory and information from each sensor.

  For example, the ECU 32 is configured to control the water pump 10 so that the actual rotational speed of the water pump 10 approaches the target rotational speed.

  Moreover, ECU32 is comprised so that abnormality determination of the switching valve 30 may be performed, for example. The abnormality determination of the switching valve 30 will be described in detail later.

  The water channel formed by the pipe connecting the water pump 10, the engine 26, the radiator 28, and the thermostat 24 corresponds to the “first water channel”. Further, the water channel formed by the pipe connecting the water pump 10, the EGR cooler 12, the heater core 20, the exhaust heat recovery device 22, and the thermostat 24 corresponds to a “second water channel”. In the second water channel, the cooling water flows from the water pump 10 to the EGR cooler 12 through a pipe that bypasses the engine 26.

[Cooling water circulation path]
FIG. 2 is a diagram for explaining paths through which cooling water flows when the engine 26 is cold, half-warmed, and after fully warmed-up. Referring to FIG. 2, the left side shows the cooling water path in the cold state and the valve states of the thermostat 24 and the switching valve 30, and the center shows the cooling water path and the valves of the thermostat 24 and the switching valve 30 in the half-warm-up state. The right side shows the path of the cooling water and the valve states of the thermostat 24 and the switching valve 30 after complete warm-up.

  Referring to the left side of FIG. 2, in the cold state, the thermostat 24 and the switching valve 30 are closed. This is because it is not necessary to cool the engine 26 in the cold state. In this state, the cooling water that has passed through the engine 26 hardly passes through the switching valve 30, and the cooling water that has passed through the radiator 28 hardly passes through the thermostat 24. That is, while the cooling water circulates in the water channel 42 (second water channel), the cooling water hardly circulates in the water channel 40 (first water channel).

  Referring to the center of FIG. 2, at the time of half warm-up, the thermostat 24 is in the closed state, but the switching valve 30 is switched to the opened state. This is for suppressing overheating of the engine 26. Thereby, the cooling water flowing from the engine 26 circulates by passing through the switching valve 30, so that the engine 26 is cooled. On the other hand, the cooling water that has passed through the radiator 28 hardly passes through the thermostat 24.

  Referring to the right side of FIG. 2, after complete warm-up, the thermostat 24 and the switching valve 30 are opened. This is because the engine 26 is cooled using the cooling water cooled by the radiator 28. Thereby, the cooling water that has passed through the engine 26 and the cooling water that has passed through the radiator 28 pass through the switching valve 30 and the thermostat 24, respectively. As a result, the temperature of the cooling water circulating through the water channels 40 and 42 is lowered by the cooling water that has passed through the radiator 28, and the engine 26 is cooled by the cooling water having the lowered temperature.

[Improved accuracy of switching valve abnormality determination]
In the cooling system 1, the abnormality determination of the switching valve 30 is performed as described above. In particular, a method for detecting an abnormality (closing failure) in which the switching valve 30 does not open although the ECU 32 sends a valve opening command to the switching valve 30 will be described.

  Referring again to FIG. 1, the water temperature sensor 27 measures the temperature of the cooling water on the downstream side of the engine 26. On the other hand, the water temperature sensor 14 measures the temperature of the cooling water downstream of the junction of the cooling water flowing in from the engine 26 when the switching valve 30 is opened and the cooling water flowing in from the water pump 10 bypassing the engine 26. . As described above, since the cooling water on the downstream side of the engine 26 flows into the water temperature sensor 14 when the switching valve 30 is opened, the water temperature detected by the water temperature sensor 14 is higher than when the valve is closed. As a result, the difference in water temperature detected by each of the water temperature sensors 14, 27 is reduced.

  Therefore, in the cooling system 1 according to the present embodiment, the ECU 32 determines whether the switching valve 30 is abnormal by referring to a difference between detection results of the water temperature sensors 14 and 27 after sending a valve opening command to the switching valve 30. (Determining whether or not a closed failure has occurred) is executed. This control is performed when the difference in water temperature detected by each of the water temperature sensors 14 and 27 is equal to or higher than a predetermined temperature even though a valve opening command is sent to the switching valve 30. It is based on the idea that there is a high possibility that is not open. The predetermined temperature is a temperature determined in advance through experiments or the like, for example.

  However, when air (bubbles) is present around at least one of the water temperature sensors 14, 27, the detection accuracy of the water temperature sensors 14, 27 may be reduced. Therefore, if it is determined that the switching valve 30 is always closed when the difference between the water temperatures detected by each of the water temperature sensors 14 and 27 is equal to or higher than the predetermined temperature, the air around the water temperature sensors 14 and 27 If there is, there is a possibility that it is erroneously determined that the switching valve 30 has a closed failure even though the switching valve 30 has not closed.

  When there is a high possibility that air is present around the water temperature sensors 14 and 27, the water pump 10 is also highly likely to be engaged with air. When the water pump 10 is engaged with air, the actual rotational speed of the water pump 10 becomes larger than the target rotational speed. Therefore, when the difference between the actual rotational speed of the water pump 10 and the target rotational speed is equal to or greater than the predetermined rotational speed, it can be said that the water pump 10 is engaged in air and air is generated in the water channel. . The predetermined number of rotations is a temperature determined in advance through experiments or the like, for example.

  Therefore, in the cooling system 1 according to the present embodiment, the ECU 32 has a difference between the outputs of the water temperature sensors 14 and 27 equal to or higher than a predetermined temperature in a state in which a command for opening the switching valve 30 is sent to the switching valve 30. Even when the difference between the target rotational speed of the water pump 10 and the actual rotational speed is equal to or greater than a predetermined number, the abnormality determination of the switching valve 30 is not executed. Therefore, according to this cooling system 1, when there is a high possibility that air is generated in the water channel, the abnormality determination of the switching valve 30 is not executed, so that an erroneous determination in the abnormality determination of the switching valve 30 occurs. The possibility can be reduced.

[Processing procedure for switching valve abnormality determination]
FIG. 3 is a flowchart showing a processing procedure for determining the abnormality of the switching valve. The process shown in this flowchart is performed by the ECU 32 on the switching valve 30 in a state in which a condition that can ensure the accuracy of the process is satisfied, for example, the water temperature detected by the water temperature sensor 14 is equal to or lower than a predetermined temperature. On the other hand, it is executed after a valve opening command is sent.

  Referring to FIG. 3, ECU 32 determines whether or not the difference between the detection results of water temperature sensors 14, 27 is equal to or higher than a predetermined temperature (step S100). If it is determined that the difference between the detection results of the water temperature sensors 14 and 27 is less than the predetermined temperature (NO in step S100), there is a high possibility that the switching valve 30 is open, and the process proceeds to return.

  On the other hand, if it is determined that the difference between the detection results of the water temperature sensors 14 and 27 is equal to or higher than the predetermined temperature (YES in step S100), there is a possibility that the switching valve 30 has a closed failure. It is determined whether or not the difference between the actual rotational speed of 10 and the target rotational speed is a predetermined number or more (step S110). For example, this determination is performed when the target rotational speed of the water pump 10 is in the low rotational speed range.

  If the difference between the actual rotational speed of the water pump 10 and the target rotational speed is equal to or greater than the predetermined rotational speed (YES in step S110), at least one of the water temperature sensors 14, 27 is accurately caused by the air in the water channel. Therefore, the ECU 32 does not execute the abnormality determination of the switching valve 30 (step S120).

  On the other hand, when the difference between the actual rotational speed of water pump 10 and the target rotational speed is less than the predetermined rotational speed (NO in step S110), ECU 32 causes water pump 10 to output the maximum output for a predetermined time (for example, several seconds). The water pump 10 is controlled to drive (step S130). Thereafter, the ECU 32 determines whether or not the water pump 10 is idling based on the rotational speed at the time of maximum output of the water pump 10 (step S140).

  If it is determined that the water pump 10 is idling (YES in step S140), at least one of the water temperature sensors 14, 27 may not be able to accurately detect the water temperature due to air in the water channel. The ECU 32 does not execute the abnormality determination of the switching valve 30 (step S120). On the other hand, when it is determined that water pump 10 is not idling (NO in step S140), ECU 32 determines that switching valve 30 is abnormal (closed failure) (step S150).

  As described above, in cooling system 1 according to the present embodiment, ECU 32 has a difference between the outputs of water temperature sensors 14 and 27 in a state in which a command for opening switching valve 30 is sent to switching valve 30. Even if the temperature is equal to or higher than the predetermined temperature, if the difference between the target rotational speed of the water pump 10 and the actual rotational speed is equal to or higher than the predetermined number, the abnormality determination of the switching valve 30 is not executed. Therefore, according to this cooling system 1, when there is a high possibility that air is generated in the water channel, the abnormality determination of the switching valve 30 is not executed, so that an erroneous determination in the abnormality determination of the switching valve 30 occurs. The possibility can be reduced.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Cooling system, 10 Water pump, 12 EGR cooler, 14, 27 Water temperature sensor, 16 EGR valve, 18 Throttle body, 20 Heater core, 22 Exhaust heat recovery device, 24 Thermostat, 26 Engine, 28 Radiator, 30 Switching valve, 32 ECU 40, 42 Waterway.

Claims (1)

A cooling system configured to cool an internal combustion engine,
A first water channel configured to circulate cooling water through the internal combustion engine;
A second water channel configured to circulate the cooling water without passing through the internal combustion engine;
A pump configured to circulate the cooling water in the first and second water channels;
The cooling water is disposed on the downstream side of the internal combustion engine, and is configured to adjust the amount of cooling water flowing from the first water channel to the second water channel by switching between a valve open state and a valve closed state. Switching valve,
A first water temperature sensor disposed between the internal combustion engine and the switching valve in the first water channel;
In the second water channel, a second water temperature sensor disposed on the downstream side of the position where the first water channel merges via the switching valve;
And a controller for controlling the pump so that the actual rotational speed of the pump approaches a target rotational speed while performing an abnormality determination of the switching valve,
Even if the difference between the outputs of the first and second water temperature sensors is equal to or higher than a predetermined temperature in a state in which the control device sends a command for opening the switching valve to the switching valve. The cooling system in which the abnormality determination is not executed when the difference between the actual rotational speed and the target rotational speed is a predetermined number of times or more.

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