AU2022200864A1 - Cooling system and method for controlling cooling system - Google Patents

Abstract

OF THE DISCLOSURE A cooling system 70 includes a fuel dosing valve 61 provided in an exhaust path of an engine 10, the fuel dosing valve 61 adding fuel for purifying exhaust to the exhaust, an electric pump 73 that causes coolant to circulate through not only an 5 existing system that allows the coolant to circulate throughout a cooling object different from the fuel dosing valve 61 but also an add-on system that allows the coolant to circulate throughout the fuel dosing valve 61, a plurality of sensors (an air flow meter 21, an exhaust temperature sensor 36A, a coolant temperature sensor 71A, a rotation speed sensor 73A) that detect values of a plurality of indicators (an amount of intake 10 air, a temperature of exhaust, a temperature of coolant, a rotation speed of the electric pump 73) different from a temperature of the coolant in the add-on system, and an ECU 50 that controls the electric pump 73. The ECU 50 estimates a temperature related to the dosing valve from the values of the plurality of indicators detected by the plurality of sensors. It is possible to estimate the temperature related to the dosing valve 15 without installing a new sensor that detects a temperature of coolant in a path through which the coolant is circulated to cool the dosing valve. 1/10 cc C4 cn w of v u--

Description

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Cooling System and Method for Controlling Cooling System

This nonprovisional application is based on Japanese Patent Application No. 2021-025211 filed on February 19, 2021 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION Field of the Invention This disclosure relates to a cooling system and a method for controlling the cooling system, and more particularly to a cooling system of an internal combustion engine and a method for controlling the cooling system. Description of the Background Art In order to purify exhaust of internal combustion engines, some internal combustion engines have dosing valves for injecting an additive such as fuel or aqueous urea solution provided in their exhaust paths. Such a dosing valve, however, becomes extremely hot due to exhaust heat, so that internal components of the dosing valve may deteriorate due to the heat. To cope with such a problem, a cooling method for cooling a dosing valve by circulating a cooling fluid with a cooling pump (see, for example, Japanese Patent Laying-Open No. 2018-009456). In the cooling method disclosed in Japanese Patent Laying-Open No. 2018-009456, in order to not only prevent the dosing valve from deteriorating due to heat but also prevent a decrease in amount of electricity stored in a battery after an engine is stopped, a determination is made as to whether it is necessary to drive the cooling pump based on a temperature near the dosing valve after the engine is stopped. Furthermore, the cooling effect of latent heat of vaporization of the cooling fluid is used to shorten a drive period of the cooling pump. SUMMARY OF THE INVENTION In the cooling method disclosed in Japanese Patent Laying-Open No. 2018 009456, the dosing valve is cooled after the engine is stopped, but the dosing valve may become hot even while the engine is in operation, so that it is necessary to drive the cooling pump so as to cool the dosing valve. Taking mountability in an engine room and cost into consideration, it is desirable that an existing cooling pump, if available, be used to cool a plurality of cooling objects. For example, a possible solution is to use a cooling pump for water-cooling an intercooler provided for regulating the temperature of intake air in the intake path of the engine to cool not only the intercooler but also the dosing valve. In such a solution, overcooling of the intake air passing through the intercooler may cause the engine to misfire or deteriorate the exhaust performance. In order to avoid such a situation, it is necessary to shorten the drive period of the cooling pump over which the cooling pump is driven in response to a request to cool the dosing valve. A possible solution is to drive the cooling pump based on a temperature related to the dosing valve. Installing a new sensor that detects the temperature related to the dosing valve, however, deteriorates the mountability in the engine room and increases cost. The present disclosure has been made to solve the above-described problems, and it is therefore an object of the present disclosure to provide a cooling system and a method for controlling the cooling system that allow a temperature related to a dosing valve that adds, to exhaust of an internal combustion engine, an additive to purify the exhaust to be estimated without installing a new sensor that detects a temperature of cooling fluid in a path through which the cooling fluid is circulated to cool the dosing valve. A cooling system of an internal combustion engine according to the present disclosure includes a dosing valve provided in an exhaust path of the internal combustion engine, the dosing valve adding an additive for purifying exhaust to the exhaust, a pump that causes a cooling fluid to circulate through not only a first circulation path that allows the cooling fluid to circulate throughout a cooling object different from the dosing valve but also a second circulation path that allows the cooling fluid to circulate throughout the dosing valve, a plurality of sensors that detect values of a plurality of indicators different from a temperature of the cooling fluid in the second circulation path, and a control device that control the pump. The control device estimates a temperature related to the dosing valve from the values of the plurality of indicators detected by the plurality of sensors. According to the present disclosure, it is possible to provide a cooling system and a method for controlling the cooling system that allow a temperature related to a dosing valve that adds, to exhaust of an internal combustion engine, an additive to purify the exhaust to be estimated without installing a new sensor that detects a temperature of cooling fluid in a path through which the cooling fluid is circulated to cool the dosing valve. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating an outline of a structure of an internal combustion engine system according to the present embodiment. Fig. 2 is a diagram illustrating an outline of a structure of a part including and around a fuel dosing valve according to the present embodiment. Fig. 3 is a flowchart illustrating a flow of electric pump control processing according to the present embodiment. Fig. 4 is a diagram illustrating a correlation between parameters on a map used for obtaining the amount of increase in temperature of coolant in a fuel dosing valve holder according to the present embodiment. Fig. 5 is a diagram illustrating a correlation between a rotation speed and discharge amount of the electric pump according to the present embodiment. Fig. 6 is a diagram for describing a flow rate ratio between an intercooler system and a fuel dosing valve system according to the present embodiment. Fig. 7 is a diagram illustrating a correlation between parameters on a map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder according to the present embodiment. Fig. 8 is a first diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder according to the present embodiment. Fig. 9 is a second diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder according to the present embodiment. Fig. 10 is a third diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder according to the present embodiment. Fig. 11 is a fourth diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder according to the present embodiment. Fig. 12 is a diagram illustrating a correlation between parameters on a map used for obtaining the temperature of coolant in the fuel dosing valve holder according to a second embodiment. Fig. 13 is a diagram illustrating a correlation between the amount of intake air, the temperature of exhaust around the fuel dosing valve, and the energy of exhaust near the fuel dosing valve according to the second embodiment. Fig. 14 is a diagram illustrating a correlation between the rotation speed of the electric pump and the amount of inflow water into the fuel dosing valve holder according to the second embodiment. Fig. 15 is a diagram illustrating an outline of a structure of an internal combustion engine system according to a third embodiment. Fig. 16 is a diagram illustrating an outline of a structure of an internal combustion engine system according to a fourth embodiment. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Names and functions of such components are also the same. Therefore, no redundant detailed description will be given of such components.

[First embodiment] Fig. 1 is a diagram illustrating an outline of a structure of an internal combustion engine system 1 according to the present embodiment. Referring to Fig. 1, the internal combustion engine system 1 is mounted on a vehicle. The internal combustion engine system 1 includes an engine 10, a turbocharger 22, a first oxidation catalyst (hereinafter referred to as a "diesel oxidation catalyst (DOC)") 41, and a particulate filter (hereinafter referred to as a "diesel particulate filter (DPF)) 42, a selective reduction catalyst (hereinafter referred to as a "selective catalytic reduction (SCR)") 43, a second oxidation catalyst 44, a control device (hereinafter referred to as an "electronic control unit (ECU)") 50, and a cooling system 70. The ECU 50 is a well-known ECU including a central processing unit (CPU) 51, a read-only memory (RAM) 52, a random access memory (ROM) 53, a timer 54, and an electrically erasable programmable read-only memory (EEPROM) 55. The ECU 50 controls each component of the vehicle such as the engine 10. TheCPU51 executes various operations in accordance with various programs and maps stored in the ROM 52. The RAM 53 temporarily stores a result of an operation executed by the CPU 51 and data input from each detection device. The EEPROM 55 stores, for example, data that is saved while a main switch of the vehicle is off. The turbocharger 22 is a turbine 22A that is rotationally driven by exhaust flowing from an exhaust inlet to an exhaust outlet, and a compressor 22B that compresses intake air flowing from an intake inlet with driving force from the turbine 22A and discharges the air thus compressed from an intake outlet. An air filter (not illustrated) removes foreign matter such as dust contained in the intake air. An intake pipe 11A has one end connected to the air filter. The compressor 22B has the intake inlet connected to the other end of the intake pipe 11A. An air flow meter 21 is provided in the intake pipe 11A, detects a flow rate of passing intake air, and outputs a detection signal indicating the flow rate thus detected to the ECU 50.

The compressor 22B has the intake outlet connected to one end of an intake pipe1lB. An intake manifold 11C has an intake inlet connected to the other end of the intake pipe 11B. An intercooler 71 is provided in the intake pipe 11B, and cools, with coolant flowing through an internal coolant flow path, the intake air passing through an internal intake flow path of the intercooler 71, the internal intake flow path serving as a part of the intake pipe 11B. An intake temperature sensor 23A is provided in the intake pipe 11B upstream from the intercooler 71, detects a temperature of the intake air before flowing into the intercooler 71, and outputs a detection signal indicating the temperature thus detected to the ECU 50. An intake temperature sensor 23B is provided in the intake pipe 11B downstream from the intercooler 71, detects a temperature of the intake air cooled by the intercooler 71, and outputs a detection signal indicating the temperature thus detected to the ECU 50. The intake manifold 11C distributes the intake air flowing through the intake pipe 11B to each cylinder of the engine 10. The engine 10 is a diesel engine and includes injectors 14A to 14D that inject fuel supplied from a fuel tank (not illustrated) into each cylinder in accordance with a control signal from the ECU 50. The engine 10 compresses the intake air flowing from the intake manifold 1IC, generates rotational driving force by combustion that takes place when fuel is injected into the compressed intake air, and discharges exhaust generated by the combustion from each cylinder to an exhaust manifold 12A. Exhaust from the engine 10 contains carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and nitrogen oxides (NOx). A crank angle sensor 27 is provided in the engine 10, detects a rotation angle of a crankshaft of the engine 10, and outputs a detection signal indicating the rotation angle thus detected to the ECU 50. A cam angle sensor 28 is provided in the engine 10, detects a compression top dead center of a predetermined cylinder of the engine 10, and outputs a detection signal to the ECU 50 in response to the detection. An accelerator opening sensor 25 detects the amount of depression of an accelerator pedal operated by the driver, and outputs a detection signal indicating the amount of depression thus detected to the ECU 50. The ECU 50 calculates the rotation speed of the engine 10 from the rotation angle of the crankshaft indicated by the detection signal output from the crank angle sensor 27, calculates a required load from the rotation speed of the engine 10 thus calculated and the amount of depression of the accelerator pedal indicated by the detection signal output from the accelerator opening sensor 25, and then calculates a fuel injection amount from the required load and the temperature of intake air indicated by the detection signal output from the intake temperature sensor 23B. The ECU 50 calculates a fuel injection timing for each cylinder from the rotation angle of the crankshaft indicated by the detection signal output from the crank angle sensor 27 and the timing of the compression top dead center of the predetermined cylinder indicated by the detection signal output from the cam angle sensor 28 and causes the injectors 14A to 14D to inject fuel by the fuel injection amount thus calculated at the timing thus calculated. The exhaust manifold 12A collects exhaust from each cylinder of the engine 10 into an exhaust pipe 12B. The exhaust manifold 12A has an exhaust outlet connected to one end of the exhaust pipe 12B. The turbine 22A of the turbocharger 22 has an exhaust inlet connected to the other end of the exhaust pipe 12B. The turbine 22A of the turbocharger 22 has an exhaust outlet connected to one end of an exhaust pipe 12C. The DOC 41 has an exhaust inlet connected to the other end of the exhaust pipe 12C. The DOC 41 purifies exhaust by oxidizing carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust. An exhaust temperature sensor 36A is provided in the exhaust pipe 12C, detects a temperature of exhaust before flowing into the DOC 41, and outputs a detection signal indicating the temperature thus detected to the ECU 50. A fuel dosing valve 61 is provided in the exhaust pipe 12C extending between the turbine 22A of the turbocharger 22 and the exhaust temperature sensor 36A, and adds (injects) fuel supplied from a fuel tank (not illustrated) to the exhaust as an additive.

The DPF 42 is provided adjacent to an exhaust outlet of the DOC 41. The DPF 42 collects particulate matter (PM) contained in exhaust. An exhaust temperature sensor 36B is provided between the DOC 41 and the DPF 42, detects a temperature of exhaust flowing out from the DOC 41, and outputs a detection signal indicating the temperature thus detected to the ECU 50. A differential pressure sensor 35 detects differential pressure across the DPF 42, and outputs a detection signal indicating the differential pressure thus detected to the ECU 50. The ECU 50 estimates the accumulation amount of particulate matter (PM) collected by the DPF 42 using the differential pressure indicated by the detection signal output from the differential pressure sensor 35. The ECU 50 controls the fuel dosing valve 61 to add fuel when the accumulation amount exceeds a predetermined threshold. When the fuel is added, the fuel undergoes an oxidation reaction in the DOC 41, and heat generated by the reaction increases the temperature of exhaust flowing into the DPF 42. The ECU 50 regulates the amount of fuel to be added by the fuel dosing valve 61 so as to make the exhaust temperature indicated by the detection signal output from the exhaust temperature sensor 36B equal to a temperature suitable for burning off particulate matter (PM). As a result, the particulate matter (PM) accumulated on the DPF 42 is burned off, and the collection capacity of the DPF 42 is recovered (restored). The DPF 42 has an exhaust outlet connected to one end of an exhaust pipe 12D. The SCR 43 has an exhaust inlet connected to the other end of the exhaust pipe 12D. The SCR 43 reduces and removes nitrogen oxides (NOx) contained in exhaust using ammonia produced, by the heat of the exhaust, from an aqueous urea solution added by an aqueous urea solution dosing valve 62. An exhaust temperature sensor 36C and an NOx sensor 37A are provided in the exhaust pipe 12D extending between the DPF 42 and the SCR 43. The exhaust temperature sensor 36C detects a temperature of exhaust flowing out from the DFP 42, and outputs a detection signal indicating the temperature thus detected to the ECU 50. The NOx sensor 37A detects the concentration of NOx contained in the exhaust flowing out from the DPF 42, and outputs a detection signal indicating the concentration thus detected to the ECU 50. The aqueous urea solution dosing valve 62 is provided in the exhaust pipe 12D extending between the NOx sensor 37A and the SCR 43, and adds (injects) an aqueous urea solution supplied from an aqueous urea solution tank (not illustrated) to exhaust as an additive. The SCR 43 has an exhaust outlet connected to one end of an exhaust pipe 12E. The second oxidation catalyst 44 has an exhaust inlet connected to the other end of the exhaust pipe 12E. An exhaust temperature sensor 36D and an NOx sensor 37B are provided in the exhaust pipe 12E. The exhaust temperature sensor 36D detects a temperature of exhaust flowing out from the SCR 43, and outputs a detection signal indicating the temperature thus detected to the ECU 50. The NOx sensor 37B detects the concentration of NOx contained in the exhaust flowing out from the SCR 43, and outputs a detection signal indicating the concentration thus detected to the ECU 50. The ECU 50 calculates how much NOx has been removed by the SCR 43 from the concentration of NOx indicated by the detection signals output from the NOx sensors 37A, 37B and the temperature of exhaust indicated by the detection signal output from the exhaust temperature sensor 36D, and controls the aqueous urea solution dosing valve 62 to add the aqueous urea solution in a manner that depends on how much NOx has been removed. As a result, NOx contained in the exhaust is reduced and removed by the SCR 43. The second oxidation catalyst 44 oxidizes and removes excess ammonia that has not been used by the SCR 43. Exhaust flowing out from an exhaust outlet of the second oxidation catalyst 44 passes through a muffler (not illustrated) or the like to the atmosphere. The cooling system 70 according to the present embodiment includes a coolant circulation system for an existing intercooler 71 (hereinafter referred to an "existing system") and a coolant circulation system for the fuel dosing valve 61 (hereinafter referred to as an "add-on system") added to the existing system. The cooling system 70 includes the intercooler 71 described above, an intercooler radiator 72, an electric pump 73, the fuel dosing valve 61 described above, a fuel dosing valve holder 74, and a coolant circulation channel 75. The ECU 50 serves as a part of the cooling system 70 by controlling the electric pump 73 of the cooling system 70. The coolant circulation channel 75 includes a radiator outlet pipe 75AA, a pump outlet pipe 75BA, an intercooler inflow pipe 75BB, a fuel dosing valve inflow pipe 75BC, an intercooler outflow pipe 75CA, and a fuel dosing valve outflow pipe 75CB. The electric pump 73 includes a motor driven in response to a control signal from the ECU 50, and uses driving force of the motor to pressure-feed coolant to cause the coolant to circulate through the coolant circulation channel 75. The electric pump 73 includes a rotation speed sensor 73A for the motor. The rotation speed sensor 73A detects a rotation speed of the motor and outputs a detection signal indicating the rotation speed thus detected to the ECU 50. Coolant flows into the electric pump 73 through the radiator outlet pipe 75AA. The coolant pressure-fed from the electric pump 73 flows through the pump outlet pipe 75BA and then is split into the intercooler inflow pipe 75BB and the fuel dosing valve inflow pipe 75BC. Coolant diverted to the intercooler inflow pipe 75BB flows into the intercooler 71. The intercooler 71 has been described above, so that no redundant description of the intercooler 71 will be given below. Coolant flowing through the internal coolant flow path of the intercooler 71 is heated by exchanging heat with intake air passing through the intake flow path connected to the intake pipe 11B. A coolant temperature sensor 71A is provided in the coolant flow path upstream from the intercooler 71, detects a temperature of coolant at an inlet of the intercooler 71, and outputs a detection signal indicating the temperature thus detected to the ECU 50. A coolant temperature sensor 71B is provided in the coolant flow path downstream from the intercooler 71, detects a temperature of coolant at an outlet of the intercooler 71, and outputs a detection signal indicating the temperature thus detected to the ECU 50. The coolant flowing out from the intercooler 71 flows through the intercooler outflow pipe 75CA into the intercooler radiator 72. Coolant diverted to the fuel dosing valve inflow pipe 75BC flows into the fuel dosing valve holder 74. Fig. 2 is a diagram illustrating an outline of a structure of a part including and around the fuel dosing valve 61 according to the present embodiment. Referring to Fig. 2, the fuel dosing valve holder 74 includes a housing 74C that encloses the fuel dosing valve 61. The housing 74C is provided with a coolant inlet 74A and a coolant outlet 74B. A space between the housing 74C and the fuel dosing valve 61 is filled with coolant flowing in from the fuel dosing valve inflow pipe 75BC through the coolant inlet 74A. The coolant that fills the space flows out from the coolant outlet 74B. Since the fuel dosing valve 61 is provided in the exhaust pipe 12C through which high-temperature exhaust gas flows, the fuel dosing valve 61 is heated by the exhaust flowing through the exhaust pipe 12C and the exhaust pipe 12C. Provided inside the fuel dosing valve 61 is a resin material for holding a solenoid in position, the solenoid being provided for injecting fuel. When this resin material deteriorates and erodes due to heat, a void is produced around a coil of the solenoid. This brings the coil into an air-adiabatic condition, so that the coil is burnt out due to the self-heating of the coil. The fuel dosing valve 61 is cooled by the coolant filling the fuel dosing valve holder 74. This can prevent the coil of the fuel dosing valve 61 from being burned out. The coolant flowing out from the coolant outlet 74B of the fuel dosing valve holder 74 flows through the fuel dosing valve outflow pipe 75CB, then joins the intercooler outflow pipe 75CA, and flows into the intercooler radiator 72. The intercooler radiator 72 is provided separately from an engine radiator 15 that cools engine coolant circulating throughout the engine 10 to cool the engine 10. The intercooler radiator 72 cools coolant flowing throughout the intercooler radiator 72 by exchanging heat between the outside air flowing in contact with an outer surface of the intercooler radiator 72 and the coolant. The coolant flowing out from the intercooler radiator 72 flows through the radiator outlet pipe 75AA and then returns to the electric pump 73.

As described above, in the existing system, coolant flows in the order of the radiator outlet pipe 75AA, the electric pump 73, the pump outlet pipe 75BA, the intercooler inflow pipe 75BB, the intercooler 71, the intercooler outflow pipe 75CA, the intercooler radiator 72. In the add-on system, coolant is split in the pump outlet pipe 75BA of the existing system to flow in the order of the fuel dosing valve inflow pipe 75BC, the fuel dosing valve holder 74 (the fuel dosing valve 61), and the fuel dosing valve outflow pipe 75CB and join the intercooler outflow pipe 75CA. The add-on system is parallel to the intercooler inflow pipe 75BB, the intercooler 71, and the intercooler outflow pipe 75CA of the existing system. In the cooling system 70 described above, the electric pump 73 for the water cooling intercooler 71 provided for regulating the temperature of intake air in the intake path of the engine 10 is used to cool not only the intercooler 71 but also the fuel dosing valve61. In this case, overcooling of intake air passing through the intercooler 71 may cause the engine 10 to misfire or deteriorate the exhaust performance. Inorderto avoid such a situation, it is necessary to shorten a drive period of the electric pump 73 over which the electric pump 73 is driven in response to a request to cool the fuel dosing valve 61. A possible solution is to drive the electric pump 73 based on a temperature related to the fuel dosing valve 61. Installing a new sensor that detects the temperature related to the fuel dosing valve 61, however, deteriorates the mountability in the engine room and increases cost. Therefore, the cooling system 70 includes the fuel dosing valve 61 provided in the exhaust path of the engine 10, the fuel dosing valve 61 adding fuel that is an additive for purifying exhaust to the exhaust, the electric pump 73 that circulates coolant through not only the existing system that allows the coolant to circulate throughout the intercooler 71 that is a cooling object difference from the fuel dosing valve 61 but also the add-on system that allows the coolant to circulate throughout the fuel dosing valve 61, the ECU 50 that controls the electric pump 73, and the plurality of sensors (e.g. air flow meter 21, exhaust temperature sensor 36A, coolant temperature sensor 71A, rotation speed sensor 73A) that detect values of a plurality of indicators different from the temperature of coolant in the add-on system, and the ECU 50 estimates the temperature related to the fuel dosing valve 61 based on the values of the plurality of indicators detected by the plurality of sensors. This allows the temperature related to the fuel dosing valve 61 that adds, to exhaust of the engine 10, fuel that is an additive to purify the exhaust to be estimated without installing a new sensor that detects a temperature of coolant in a path through which the coolant is circulated to cool the fuel dosing valve 61. Fig. 3 is a flowchart illustrating a flow of electric pump control processing according to the present embodiment. The electric pump control processing is called and executed by the CPU 51 of the ECU 50 for each predetermined control cycle from higher-level processing. Referring to Fig. 3, first, the CPU 51 of the ECU 50 estimates a coolant temperature Tc at the outlet of the fuel dosing valve holder 74 (step S111). Amethod for estimating temperature Tc will be described later. Next, the CPU 51 determines an intake air temperature Ta at the outlet of the intercooler 71 indicated by the detection signal output from the intake temperature sensor 23B that detects temperature Ta (step S112). The CPU 51 outputs a control signal to the electric pump 73 to determine whether the electric pump 73 is in operation (step S113). When it is determined that the electric pump 73 is not in operation (NO in stepS113), the CPU 51 determines whether coolant temperature Tcestimated in step Sillexceeds a predetermined temperature T1 (Tc > TI) (step S114). Predetermined temperature TI is a reference temperature of coolant at the outlet of the fuel dosing valve holder 74 for determining that thermal deterioration of the resin material of the fuel dosing valve 61 further progresses. When coolant temperature Tc exceeds the predetermined temperature TI, thermal deterioration progresses faster than a predetermined degree that causes concern about the possibility of thermal deterioration. When it is determined that Tc > T1 is not satisfied (NO in step S114), the CPU 51 determines whether intake air temperature Ta at the outlet of the intercooler 71 determined in step S112 exceeds a predetermined temperature T3 (Ta > T3) (step S115). Predetermined temperature T3 is a reference temperature of intake air at the outlet of the intercooler 71 for determining that the efficiency of the engine 10 becomes less than a predetermined value due to the intake air temperature being low. When intake air temperature Ta at the outlet of the intercooler 71 exceeds predetermined temperature T3, the efficiency of the engine 10 becomes less than the predetermined value. When it is determined that Ta> T3 is not satisfied (NO instep S115), the CPU 51 returns the execution control to the higher-level processing that is the caller of this electric pump control processing. On the other hand, when it is determined that Tc > Ti(YES in step S114) or Ta > T3 (YES in step S115), the CPU 51 calculates a required discharge flow rate of the electric pump 73 (step S116). When Tc > TI is satisfied, a required discharge flow rate of the electric pump 73 is calculated from a required flow rate calculation map having cooling efficiency11 of the intercooler 71 and the flow rate of intake air flowing into the intercooler 71 as axes. Cooling efficiency i can be calculated by an equation of i = (temperature of intake air at the inlet of the intercooler - temperature of intake air at the outlet of the intercooler) * 100/(temperature of intake air at the inlet of the intercooler - temperature of water at the inlet of the intercooler). This required flow rate calculation map is set so that the higher cooling efficiency i or the larger the inflow/intake air flow rate, the larger the required flow rate. When Ta > T3 is satisfied, the required flow rate and the drive period are calculated based on a concept of feeding coolant to replace all the coolant filling the volume of the space of the fuel dosing valve holder 74 so as to make the required flow rate * the drive period equal to the volume. When Tc > TI and Ta > T3 are satisfied, the larger of the required flow rate when Tc > T is satisfied and the required flow rate when Ta > T3 is satisfied is selected. Next, the CPU 51 controls the electric pump 73 to discharge coolant at the required flow rate calculated instep S116 (step S117). After step S117, the CPU 51 returns the execution control to the higher-level processing that is the caller of this electric pump control processing. When it is determined that the electric pump 73 is in operation (YES in step S113), the CPU 51 determines whether coolant temperature Tc estimated in step S111 is less than a predetermined temperature T2 (Tc < T2) (step S121). Predetermined temperature T2 is a reference temperature of coolant at the outlet of the fuel dosing valve holder 74 for determining that thermal deterioration of the resin material of the fuel dosing valve 61 does not further progress. When coolant temperature Tc falls below predetermined temperature T2, thermal deterioration progresses faster than the predetermined degree that causes concern about the possibility of thermal deterioration. When it is determined that Tc < T2 is not satisfied (NO in step S121), the CPU 51 transfers the execution control to step S116 described above. When it is determined that Tc < T2 is satisfied (YES in step S121), the CPU 51 determines whether intake air temperature Ta at the outlet of the intercooler 71 determined in step S112 is less than a predetermined temperature T4 (Ta < T4) (step S122). Predetermined temperature T4 is a reference temperature of intake air at the outlet of the intercooler 71 for determining that the engine 10 misfires or the exhaust performance deteriorates due to the intake air temperature being too low. When intake air temperature Ta at the outlet of the intercooler 71 falls below predetermined temperature T4, the engine 10 may misfire or the exhaust performance may become less than a regulatory standard. When it is determined that Ta < T4 is not satisfied (NO in step S122), the CPU 51 transfers the execution control to step S116 described above. When it is determined that Ta < T4 is satisfied (YES in step S122), the CPU 51 controls the electric pump 73 to stop (step S123). After step S123, the CPU 51 returns the execution control to the higher-level processing that is the caller of this electric pump control processing. Next, a description will be given of the method for estimating coolant temperature Tc at the outlet of the fuel dosing valve holder 74 in step S111.

Temperature Tc (°C) can be estimated by an equation of Tc (°C)= Tc (°C) during the previous control cycle + (the amount of increase in temperature of coolant in the fuel dosing valve holder 74 per unit time (°C/sec) - the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 per unit time (°C/sec)) * control cycle (sec). The amount of increase in temperature of coolant in the fuel dosing valve holder 74 per unit time can be calculated based on a state of exhaust around the fuel dosing valve holder 74. Fig. 4 is a diagram illustrating a correlation between parameters on a map used for obtaining the amount of increase in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 4, the larger the flow rate of intake air (the amount of intake air) detected by the air flow meter 21, the larger the amount of increase in temperature of coolant. Further, the higher the temperature of exhaust around the fuel dosing valve 61, the larger the amount of increase in temperature of coolant. The temperature of exhaust around the fuel dosing valve 61 can be regarded as the same as the temperature of exhaust detected by the exhaust temperature sensor 36A. Therefore, the amount of increase in temperature of coolant in the fuel dosing valve holder 74 per unit time is obtained based on the map illustrated in Fig. 4 where a correlation between the amount of intake air, the temperature of exhaust around the fuel dosing valve 61, and the amount of increase in temperature of coolant in the fuel dosing valve holder 74 is set. Fig. 5 is a diagram illustrating a correlation between the rotation speed and discharge amount of the electric pump 73 according to the present embodiment. Referring to Fig. 5, as the rotation speed of the electric pump 73 increases, the discharge amount increases exponentially. The higher the temperature of coolant, the lower the kinematic viscosity of coolant, so that when the kinematic viscosity of coolant is lower, the discharge amount becomes larger even at the same rotation speed. The lower the temperature of coolant, the higher the kinematic viscosity of coolant, so that when the kinematic viscosity of coolant is higher, the discharge amount becomes lower even at the same rotation speed. According to the present embodiment, the ECU 50 calculates the required flow rate of coolant, as illustrated in step S116 of Fig. 3. The ECU 50 obtains the rotation speed of the electric pump 73 for discharging coolant at the required flow rate based on the correlation illustrated in Fig. 5. The ECU 50 controls the motor of the electric pump 73 to rotate the motor at the rotation speed thus obtained in step S117. Fig. 6 is a diagram for describing a flow rate ratio between the system for the intercooler 71 and the system for the fuel dosing valve 61 according to the present embodiment. Referring to Fig. 6, the distribution ratio of the discharge flow rate of the electric pump 73 between the system for the intercooler 71 and the system for the fuel dosing valve 61 is constant regardless of the discharge flow rate of the electric pump 73. Fig. 7 is a diagram illustrating a correlation between parameters on a map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 7, the higher the temperature of coolant at the inlet of the fuel dosing valve holder 74, the larger the amount of decrease in temperature of coolant in the fuel dosing valve holder 74. The temperature of coolant at the inlet of the fuel dosing valve holder 74 is regarded as the same as the temperature of coolant at the inlet of the intercooler 71 detected by the coolant temperature sensor 71A. Therefore, the higher the temperature of coolant at the inlet of the intercooler 71 detected by the coolant temperature sensor 71A, the larger the amount of decrease in temperature of coolant. Further, the higher the rotation speed of the motor of the electric pump 73 obtained in Fig. 5, the larger the amount of decrease in temperature of coolant. The amount of decrease in temperature of coolant per unit time is obtained based on the map where the correlation illustrated in Fig. 7 is set. Fig. 8 is a first diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 8, it is conceivable that with the temperature of coolant in the fuel dosing valve holder 74 equal to 100°C, when coolant having a temperature of 25°C flows in by 20% of the capacity of the fuel dosing valve holder 74, the temperature of coolant in the fuel dosing valve holder 74 will become approximately equal to 85°C. Fig. 9 is a second diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 9, it is conceivable that with the temperature of coolant in the fuel dosing valve holder 74 equal to 100°C, when coolant having a temperature of 25°C that is the same as in Fig. 8 flows in by 80% of the capacity of the fuel dosing valve holder 74 that is different from in Fig. 8, the temperature of coolant in the fuel dosing valve holder 74 will become approximately equal to 40°C. Referring to Figs. 8 and 9, it is conceivable that with the temperature of coolant flowing into the fuel dosing valve holder 74 constant, the larger the flow rate, the larger the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 per unit time. Accordingly, as illustrated in Fig. 7, the correlation where the higher the rotation speed of the motor of the electric pump 73, the larger the amount of decrease in temperature of coolant can be derived. Fig. 10 is a third diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 10, it is conceivable that with the temperature of coolant in the fuel dosing valve holder 74 equal to 100°C, when coolant having a temperature of 25°C flows in by 20% of the capacity of the fuel dosing valve holder 74, the temperature of coolant in the fuel dosing valve holder 74 will become approximately equal to 85°C. Fig. 11 is a fourth diagram for describing a correlation between parameters on the map used for obtaining the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 according to the present embodiment. Referring to Fig. 11, it is conceivable that with the temperature of coolant in the fuel dosing valve holder 74 equal to 100°C, when the coolant having a temperature of 50°C different from in Fig. 10 flows in by 20% of the capacity of the fuel dosing valve holder 74 that is the same as in Fig. 10, the temperature of coolant in the fuel dosing valve holder 74 will become approximately equal to 90°C. Referring to Figs. 10 and 11, it is conceivable that with the flow rate of coolant flowing into the fuel dosing valve holder 74 constant, the lower the temperature of the flowing coolant, the larger the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 per unit time. Accordingly, as illustrated in Fig. 7, the correlation where the higher the temperature of coolant at the inlet of the intercooler 71, the larger the amount of decrease in temperature of coolant can be derived.

[Second embodiment] According to the first embodiment, the amount of increase in temperature of coolant in the fuel dosing valve holder 74 is calculated from the amount of intake air and the temperature of exhaust around the fuel dosing valve 61, the amount of decrease in temperature of coolant in the fuel dosing valve holder 74 is calculated from the temperature of coolant at the inlet of the intercooler 71 and the discharge flow rate of the electric pump (rotation speed of the electric pump 73), and coolant temperature Tc in the fuel dosing valve holder 74 is estimated from the amount of increase and amount of decrease in temperature of coolant in the fuel dosing valve holder 74. According to the second embodiment, coolant temperature Tc in the fuel dosing valve holder 74 is estimated by a method different from the method according to the first embodiment. According to the second embodiment, temperature Tc is estimated by an equation of Tc (°C) during the previous control cycle + the amount of increase in temperature of coolant in the fuel dosing valve holder 74 per unit time (°C/sec) * the control cycle (sec). Note that when the amount of increase exceeds 0, temperature Tc increases. When the amount of increase is less than 0, temperature Tc decreases. Fig. 12 is a diagram illustrating a correlation between parameters on a map used for obtaining the temperature of coolant in the fuel dosing valve holder 74 according to the second embodiment. Referring to Fig. 12, a correlation between the temperature of coolant flowing into the fuel dosing valve holder 74, the temperature of coolant in the fuel dosing valve holder 74, and the amount of increase in temperature of coolant in the fuel dosing valve holder 74 per unit time relative to the energy of exhaust near the fuel dosing valve 61 is predetermined for each amount of inflow water into the fuel dosing valve holder 74 (Vn (n = 1, 2, 3, ...) by simulation or experiment. The temperature of coolant flowing into the fuel dosing valve holder 74 is regarded as the same as the temperature of coolant at the inlet of the intercooler 71 detected by the coolant temperature sensor 71A. Suppose the temperature of coolant in the fuel dosing valve holder 74 is the same as the temperature of coolant in the fuel dosing valve holder 74 during the previous control cycle. The energy of exhaust near the fuel dosing valve 61 is obtained as follows. Fig. 13 is a diagram illustrating a correlation between the amount of intake air, the temperature of exhaust around the fuel dosing valve 61, and the energy of exhaust near the fuel dosing valve 61 (energy of gas near the dosing valve) according to the second embodiment. Referring to Fig. 13, the larger the flow rate of intake air (amount of intake air) detected by the air flow meter 21, the larger the energy of gas near the dosing valve. Further, the higher the temperature of exhaust around the fuel dosing valve 61, the larger the energy of gas near the dosing valve. The temperature of exhaust around the fuel dosing valve 61 can be regarded as the same as the temperature of exhaust detected by the exhaust temperature sensor 36A. Therefore, the energy of gas around the dosing valve illustrated in Fig. 12 is obtained based on the map illustrated in Fig. 13 where a correlation between the amount of intake air, the temperature of exhaust around the fuel dosing valve 61, and the energy of gas near the dosing valve is set. The amount of inflow water into the fuel dosing valve holder 74 Vn is obtained as follows. Fig. 14 is a diagram illustrating a correlation between the rotation speed of the electric pump 73 and the amount of inflow water into the fuel dosing valve holder 74 according to the second embodiment. Referring to Fig. 14, as the rotation speed of the electric pump 73 increases, the amount of inflow water increases exponentially.

The higher the temperature of coolant, the lower the kinematic viscosity of coolant, so that when the kinematic viscosity of coolant is lower, the amount of inflow water becomes larger even at the same rotation speed. The lower the temperature of coolant, the higher the kinematic viscosity of coolant, so that when the kinematic viscosity of coolant is higher, the amount of inflow water becomes smaller even at the same rotation speed. Therefore, referring to Fig. 14, the amount of inflow water into the fuel dosing valve holder 74 Vn can be obtained from the rotation speed of the electric pump 73 and the temperature of coolant flowing into the fuel dosing valve holder 74.

[Third embodiment] According to the first embodiment, the cooling system 70 of the internal combustion engine system 1 cools not only the intercooler 71 but also the fuel dosing valve61. According to the third embodiment, a cooling system 70A of an internal combustion engine system 1A cools not only the intercooler 71 but also the fuel dosing valve 61 and the aqueous urea solution dosing valve 62. Fig. 15 is a diagram illustrating an outline of a structure of the internal combustion engine system 1A according to the third embodiment. ReferringtoFig. 15, the internal combustion engine system 1A according to the third embodiment corresponds to an internal combustion engine system obtained by replacing the cooling system 70 of the internal combustion engine system 1 according to the first embodiment with the cooling system 70A illustrated in Fig. 15. The cooling system 70A according to the third embodiment includes, in addition to the components of the cooling system 70 according to the first embodiment, an aqueous urea solution dosing valve holder 76 and a coolant circulation channel 75A obtained by modifying the coolant circulation channel 75 according to the first embodiment. The coolant circulation channel 75A according to the third embodiment includes, in addition to the coolant circulation channel 75 according to the first embodiment, an aqueous urea solution dosing valve inflow pipe 75BD, and an aqueous urea solution dosing valve outflow pipe 75CC, but does not include the fuel dosing valve outflow pipe 75CB. Coolant flowing out from the coolant outlet 74B of the fuel dosing valve holder 74 flows through the aqueous urea solution dosing valve inflow pipe 75BD into the aqueous urea solution dosing valve holder 76. The aqueous urea solution dosing valve holder 76 is the same in structure as the fuel dosing valve holder 74 described with reference to Fig. 2. Since the aqueous urea solution dosing valve 62 is provided in the exhaust pipe 12D through which high-temperature exhaust gas flows, the aqueous urea solution dosing valve 62 is heated by the exhaust flowing through the exhaust pipe 12D and the exhaust pipe 12D. Provided inside the aqueous urea solution dosing valve 62 is a resin material for holding a solenoid in position, the solenoid being provided for injecting an aqueous urea solution. When this resin material deteriorates and erodes due to heat, a void is produced around a coil of the solenoid. This brings the coil into an air-adiabatic condition, so that the coil is burnt out due to the self-heating of the coil. The aqueous urea solution dosing valve 62 is cooled by the coolant filling the aqueous urea solution dosing valve holder 76. This can prevent the coil of the aqueous urea solution dosing valve 62 from being burned out. Coolant flowing out from the aqueous urea solution dosing valve holder 76 flows through the aqueous urea solution dosing valve outflow pipe 75CC, thenjoins the intercooler outflow pipe 75CA, and flows into the intercooler radiator 72. As described above, in the existing system, coolant flows in the order of the radiator outlet pipe 75AA, the electric pump 73, the pump outlet pipe 75BA, the intercooler inflow pipe 75BB, the intercooler 71, the intercooler outflow pipe 75CA, the intercooler radiator 72. In the add-on system, coolant is split in the pump outlet pipe 75BA of the existing system to flow in the order of the fuel dosing valve inflow pipe 75BC, the fuel dosing valve holder 74 (the fuel dosing valve 61), the aqueous urea solution dosing valve inflow pipe 75BD, the aqueous urea solution dosing valve holder 76 (the aqueous urea solution dosing valve 62), and the aqueous urea solution dosing valve outflow pipe 75CC, and joins the intercooler outflow pipe 75CA. Theadd-on system is parallel to the intercooler inflow pipe 75BB, the intercooler 71, and the intercooler outflow pipe 75CA of the existing system. Such a cooling system 70A can also estimate a temperature related to the aqueous urea solution dosing valve 62 in the same manner as in the first embodiment or the second embodiment.

[Fourth embodiment] According to the third embodiment, the fuel dosing valve holder 74 and the aqueous urea solution dosing valve holder 76 are connected in series in the add-on system. According to the fourth embodiment, the fuel dosing valve holder 74 and the aqueous urea solution dosing valve holder 76 are connected in parallel in the add-on system. Fig. 16 is a diagram illustrating an outline of a structure of an internal combustion engine system 1B according to the fourth embodiment. ReferringtoFig. 16, the internal combustion engine system 1B according to the fourth embodiment corresponds to an internal combustion engine system obtained by replacing the cooling system 70 of the internal combustion engine system 1 according to the first embodiment with a cooling system 70B illustrated in Fig. 16. The cooling system 70B according to the fourth embodiment includes, in addition to the components of the cooling system 70 according to the first embodiment, the aqueous urea solution dosing valve holder 76 and a coolant circulation channel 75B obtained by modifying the coolant circulation channel 75 according to the first embodiment. The coolant circulation channel 75B according to the fourth embodiment includes, in addition to the coolant circulation channel 75 according to the first embodiment, an aqueous urea solution dosing valve inflow pipe 75BE, and an aqueous urea solution dosing valve outflow pipe 75CD. Coolant pressure-fed from the electric pump 73 flows through the pump outlet pipe 75BA and then is split into not only the intercooler inflow pipe 75BB and the fuel dosing valve inflow pipe 75BC according to the first embodiment but also the aqueous urea solution dosing valve inflow pipe 75BE. Coolant diverted to the aqueous urea solution dosing valve inflow pipe 75BE flows into the fuel dosing valve holder 74. The aqueous urea solution dosing valve holder 76 is the same in structure as the fuel dosing valve holder 74 described with reference to Fig. 2, as in Fig. 15 of the third embodiment. Coolant flowing out from the aqueous urea solution dosing valve holder 76 flows through the aqueous urea solution dosing valve outflow pipe 75CD, joins the fuel dosing valve outflow pipe 75CB, joins the intercooler outflow pipe 75CA, and then flows into the intercooler radiator 72. As described above, in the existing system, coolant flows in the order of the radiator outlet pipe 75AA, the electric pump 73, the pump outlet pipe 75BA, the intercooler inflow pipe 75BB, the intercooler 71, the intercooler outflow pipe 75CA, the intercooler radiator 72. In the add-on system, coolant is split in the pump outlet pipe 75BA of the existing system to flow through the first path in the order of the fuel dosing valve inflow pipe 75BC, the fuel dosing valve holder 74 (the fuel dosing valve 61), and the fuel dosing valve outflow pipe 75CB and joins the intercooler outflow pipe 75CA, and to flow through the second path in the order of the aqueous urea solution dosing valve inflow pipe 75BD, the aqueous urea solution dosing valve holder 76 (the aqueous urea solution dosing valve 62), and the aqueous urea solution dosing valve outflow pipe 75CC and joins the fuel dosing valve outflow pipe 75CB. Thetwopaths of the add-on system are parallel to the intercooler inflow pipe 75BB, the intercooler 71, and the intercooler outflow pipe 75CA of the existing system. Such a cooling system 70B can also estimate a temperature related to the aqueous urea solution dosing valve 62 in the same manner as in the first embodiment or the second embodiment.

[Other modifications] (1) According to the above-described embodiments, as illustrated in steps S111 and S113 of Fig. 3, when the temperature at the outlet of the fuel dosing valve holder 74 exceeds predetermined temperature T, it is determined that the fuel dosing valve 61 further deteriorates. The condition, however, is not limited to the above, and as long as the deterioration of the dosing valve such as the fuel dosing valve 61 or the aqueous urea solution dosing valve 62 can be determined, any other temperature related to the dosing valve may be used such as a temperature of a predetermined internal part (for example, the coil or resin material) of the dosing valve 61 or the aqueous urea solution dosing valve 62. (2) Each of the values detected by temperature sensors such as the coolant temperature sensors 71A, 71B, the intake temperature sensors 23A, 23B, and the exhaust temperature sensors 36A, 36C, and the rotation speed sensor 73A of the electric pump 73 according to the above-described embodiments may be a value estimated from a value detected by a different sensor. (3) According to the above-described embodiments, with the coolant outlet temperatures of the fuel dosing valve holder 74 and the aqueous urea solution dosing valve holder 76 each regarded as the temperature related to the dosing valve such as the fuel dosing valve 61 or the aqueous urea solution dosing valve 62, a determination is made of the cooling of the dosing valve. The temperature related to the dosing valve, however, is not limited to the above, and may be a temperature inside the fuel dosing valve holder 74 or the aqueous urea solution dosing valve holder 76, or a temperature of a predetermined part of the fuel dosing valve 61 or the aqueous urea solution dosing valve 62. (4) According to the above-described third and fourth embodiments, in the cooling systems 70A, 70B, both the fuel dosing valve 61 and the aqueous urea solution dosing valve 62 are cooled by the coolant for cooling the intercooler 71. The cooling method, however, is not limited to the above, and only the aqueous urea solution dosing valve 62 may be cooled by the coolant for cooling the intercooler 71. (5) The above-described disclosure may be regarded as follows: the disclosure of the cooling systems 70, 70A, 70B; the disclosure of the control device (for example, the ECU 50) of the cooling systems 70, 70A, 70B, the disclosure of the control method or control program executed by the control device of the control systems 70, 70A, 70B; and the disclosure of the method for estimating the temperature related to the dosing valve (the fuel dosing valve 61, the aqueous urea solution dosing valve 62).

[Summary] (1) As illustrated in Figs. 1, 15, and 16, a cooling system (e.g. cooling system 70, 70A, 70B) of an internal combustion engine (e.g. internal combustion engine system 1, 1A, 1B) includes a dosing valve (e.g. fuel dosing valve 61, aqueous urea solution dosing valve 62) that is provided in an exhaust path of an internal combustion engine (e.g. engine 10), the dosing valve adding, to exhaust, an additive (e.g. fuel, an aqueous urea solution) to purify the exhaust, a pump (e.g. electric pump 73) that causes a cooling fluid (e.g. coolant) to circulate through not only a first circulation path (e.g. an existing system) that allows the cooling liquid to circulate throughput a cooling object different from the dosing valve but also a second circulation path (e.g. an add-on system) that allows the cooling fluid to circulate throughout the dosing valve, and a plurality of sensors (e.g. air flow meter 21, exhaust temperature sensor 36A, coolant temperature sensor 71A, rotation speed sensor 73A) that detect values of a plurality of indicators (e.g. an amount of intake air, a temperature of exhaust, a temperature of coolant, a rotation speed of the electric pump 73) different from a temperature of the cooling fluid in the second circulation path, and a control device (e.g. ECU 50) that control the pump. As illustrated in step S111 of Fig. 3, Figs. 4 to 7 and 12 to 14, the control device estimates, from the values of the plurality of indicators detected by the plurality of sensors, a temperature related to the dosing valve (the temperature may be a temperature of coolant at the outlet of the fuel dosing valve holder 74 or the aqueous urea solution dosing valve holder 76, a temperature of coolant in the fuel dosing valve holder 74 or the aqueous urea solution dosing valve holder 76, or a temperature of a predetermined part of the fuel dosing valve 61 or the aqueous urea solution dosing valve 62). This allows the temperature related to the dosing valve that adds, to exhaust of the engine 10, an additive to purify the exhaust to be estimated without installing a new sensor that detects a temperature of cooling fluid in a path through which the cooling fluid is circulated to cool the dosing valve. (2) As illustrated in Figs. 4 to 7, a plurality of first indicators among the plurality of indicators may be indicators (e.g. the amount of intake air, the temperature of exhaust) related to exhaust serving as a medium that applies heat to the dosing valve, and a plurality of second indicators among the plurality of indicators may be indicators (e.g. the temperature of coolant, the rotation speed of the electric pump 73) related to cooling fluid serving as a medium that takes heat from the dosing valve. As illustrated in step S111 of Fig. 3, and Figs. 4 to 7, the control device may determine, based on values of the plurality of first indicators, a first amount obtained by converting a degree to which the exhaust contributes to an increase in the related temperature into an amount of increase in temperature of the cooling fluid per unit time, determine, based on values of the plurality of second indicators, a second amount obtained by converting a degree to which the cooling fluid contributes to a decrease in the related temperature into an amount of decrease in temperature of the cooling fluid per unit time, and estimate the current related temperature by adding, to the related temperature previously estimated, a value obtained by multiplying a value obtained by subtracting the second amount from the first amount by an amount of time elapsed from last time to current time. (3) As illustrated in Figs. 1, 15, and 16, the plurality of the sensors may include an air flow meter (e.g. air flow meter 21) that detects an amount of intake air flowing into to the internal combustion engine, and an exhaust temperature sensor (e.g. exhaust temperature sensor 36A) that detects a temperature of exhaust from the internal combustion engine. As illustrated in step S111 of Fig. 3 and Fig. 4, the control device may determine the first amount based on the amount of intake air detected by the air flow meter and the temperature of exhaust detected by the exhaust temperature sensor. (4) As illustrated in Figs. 1, 15, and 16, the plurality of sensors may include a fluid temperature sensor (e.g. coolant temperature sensor 71A) that detects a temperature of the cooling fluid in the first circulation path, and a related amount sensor (e.g. rotation speed sensor 73A) that detects an amount related to a flow rate of the cooling fluid. As illustrated instep S111 of Fig. 3 and Figs. 5 to 7, the control device may determine the second amount based on the temperature detected by the fluid temperature sensor and the related amount detected by the related amount sensor. (5) As illustrated in Figs. 1, 2, 15, and 16, a holder that encloses the dosing valve (e.g. fuel dosing valve holder 74, aqueous urea solution dosing valve holder 76) may be further provided, the holder including an inlet (e.g. coolant inlet 74A) and an outlet (e.g. coolant outlet 75B) for the cooling fluid, and the related temperature may be a temperature of the cooling fluid at the outlet. Although the embodiments of the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is set forth by the claims, and the present invention is intended to include the claims, equivalents of the claims, and all modifications within the scope.

Claims (6)

WHAT IS CLAIMED IS:

1. A cooling system of an internal combustion engine, comprising: a dosing valve provided in an exhaust path of the internal combustion engine, the dosing valve adding an additive for purifying exhaust to the exhaust; a pump that causes a cooling fluid to circulate through not only a first circulation path that allows the cooling fluid to circulate throughout a cooling object different from the dosing valve but also a second circulation path that allows the cooling fluid to circulate throughout the dosing valve; a plurality of sensors that detect values of a plurality of indicators different from a temperature of the cooling fluid in the second circulation path; and a control device that control the pump, wherein the control device estimates a temperature related to the dosing valve from the values of the plurality of indicators detected by the plurality of sensors.

2. The cooling system according to claim 1, wherein the plurality of indicators include a plurality of first indicators and a plurality of second indicators, the plurality of first indicators are indicators related to the exhaust serving as a medium that applies heat to the dosing valve, the plurality of second indicators are indicators related to the cooling fluid serving as a medium that takes heat from the dosing valve, and the control device determines, based on values of the plurality of first indicators, a first amount obtained by converting a degree to which the exhaust contributes to an increase in the related temperature into an amount of increase in temperature of the cooling fluid per unit time, determines, based on values of the plurality of second indicators, a second amount obtained by converting a degree to which the cooling fluid contributes to a decrease in the related temperature into an amount of decrease in temperature of the cooling fluid per unit time, and estimates the current related temperature by adding, to the related temperature previously estimated, a value obtained by multiplying a value obtained by subtracting the second amount from the first amount by an amount of time elapsed from last time to current time.

3. The cooling system according to claim 2, wherein the plurality of sensors include an air flow meter that detects an amount of intake air flowing into to the internal combustion engine, and an exhaust temperature sensor that detects a temperature of exhaust from the internal combustion engine, and the control device determines the first amount based on the amount of intake air detected by the air flow meter and the temperature of exhaust detected by the exhaust temperature sensor.

4. The cooling system according to claim 2, wherein the plurality of sensors include a fluid temperature sensor that detects a temperature of the cooling fluid in the first circulation path, and a related amount sensor that detects an amount related to a flow rate of the cooling fluid, and the control device determines the second amount based on the temperature detected by the fluid temperature sensor and the related amount detected by the related amount sensor.

5. The cooling system according to any one of claims 1 to 4, further comprising a holder that encloses the dosing valve, the holder including an inlet and an outlet for the cooling fluid, wherein the related temperature is a temperature of the cooling fluid at the outlet.

6. A method for controlling a cooling system of an internal combustion engine, the cooling system including: a dosing valve provided in an exhaust path of the internal combustion engine, the dosing valve adding an additive for purifying exhaust to the exhaust; a pump that causes a cooling fluid to circulate through not only a first circulation path that allows the cooling fluid to circulate throughout a cooling object different from the dosing valve but also a second circulation path that allows the cooling fluid to circulate throughout the dosing valve; a plurality of sensors that detect values of a plurality of indicators different from a temperature of the cooling fluid in the second circulation path; and a control device that control the pump, the method comprising: causing the control device to estimate a temperature related to the dosing valve from the values of the plurality of indicators detected by the plurality of sensors; and causing the control device to control the pump based on the related temperature estimated.