JP2014009617A - Cooling device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling device of an internal combustion engine capable of preventing cooling water in the internal combustion engine from being boiled during early warming-up while promoting the early warming-up of the internal combustion engine.SOLUTION: An ECU 12 of a cooling device 13 switches a three-way solenoid valve 22 into a second communication position on the condition that a temperature of cooling water flowing through an upstream side main supply pipe 15A and a bypass pipe 20 is less than T1°C at which condensed water is not produced in an EGR cooler 11. Further, the ECU 12 of the cooling device 13 switches the three-way solenoid valve 22 into a first communication position on the condition that a temperature of the cooling water flowing through the upstream side main supply pipe 15A and a main supply pipe 15 is T1°C or more.

Description

  The present invention relates to a cooling device for an internal combustion engine, and more particularly to a cooling device for an internal combustion engine that uses cooling water heated by a heat exchanger that recovers heat of exhaust gas so as to quickly warm up the internal combustion engine. .

  An internal combustion engine having an EGR (Exhaust Gas Recirculation) device for recirculating a part of the exhaust gas to a combustion chamber of the internal combustion engine in order to reduce NOx (nitrogen oxide) contained in the exhaust gas is known. Yes.

  This internal combustion engine is known to have an EGR cooler for cooling the exhaust gas recirculated through the EGR device by exchanging heat with cooling water flowing through the internal combustion engine.

  By the way, at the time of cold start of the internal combustion engine, the temperature difference between the exhaust gas flowing through the EGR cooler and the cooling water becomes very large because the temperature of the cooling water of the internal combustion engine is extremely low. For this reason, the recirculated exhaust gas is rapidly cooled in the EGR cooler, and moisture contained in the exhaust gas may be liquefied in the EGR cooler, and a large amount of condensed water may be generated in the EGR cooler. is there.

  Further, when the internal combustion engine is cold-started, the EGR gas is in a low temperature state, which causes the combustion to become unstable. That is, with low-temperature EGR gas, the fuel is not completely atomized, and the combustion reaction becomes slow due to the mixing of burned gas. Furthermore, since the mixed state also deteriorates, the combustion becomes unstable. As a result, fuel efficiency may be deteriorated during cold start.

  Therefore, by prematurely warming up the EGR gas at the time of cold start of the internal combustion engine, it is possible to suppress the generation of condensed water in the EGR cooler and to suppress the deterioration of the fuel efficiency of the internal combustion engine while It is necessary to reduce NOx contained in the gas.

  For example, a cooling water circuit of an EGR cooler described in Patent Document 1 is known as one that can achieve early warm-up of an internal combustion engine during a cold start. This EGR cooler cooling water circuit is an EGR apparatus that includes an EGR pipe that recirculates a part of exhaust gas by communicating an exhaust side and an intake side of an internal combustion engine, and an EGR cooler provided in the EGR pipe. It is a cooling water circuit of an EGR cooler.

  This cooling water circuit of the EGR cooler branches from the thermostat that opens and closes the outlet side cooling water flow path of the EGR cooler, and the cooling water chamber of the EGR cooler and the thermostat in the outlet side cooling water flow path to the thermostat sensing chamber. It is equipped with a temperature-sensing greenhouse-side branch channel that constantly flows cooling water.

  This thermostat is provided with a valve member that shuts off the outlet side cooling water flow path when the cooling water flowing into the temperature-sensitive room is below a predetermined temperature and communicates the outlet side cooling water flow path when the temperature exceeds a predetermined temperature. Yes.

  In the cooling water circuit of the EGR cooler having such a configuration, when the cooling water is lower than a predetermined temperature, the cooling water flowing into the EGR cooler is cut off by shutting off the outlet side cooling water flow path of the EGR cooler by the valve member in the thermostat. A slight flow rate through the temperature-sensitive greenhouse side branch channel can be achieved.

  For this reason, the amount of cooling water supplied to the internal combustion engine through the EGR cooler can be reduced, and the cooling water can be heated with the EGR gas in the EGR cooler. Therefore, early warm-up of the EGR cooler can be achieved.

JP 2007-92718 A

  In such a conventional EGR cooler cooling water circuit, when the cooling water is below a predetermined temperature, the amount of cooling water supplied to the internal combustion engine through the EGR cooler is reduced so that the EGR cooler can be warmed up early. However, since a small amount of cooling water is supplied to the EGR cooler at the cold start, it is difficult to further promote early warm-up of the EGR cooler.

  In order to promote early warm-up of the internal combustion engine at the time of cold start of the internal combustion engine, it is conceivable to stop supplying cooling water to the internal combustion engine. Sometimes, when the operating state of the internal combustion engine becomes a high load, the cooling water in the internal combustion engine may boil.

  And if the cooling water boils, ethylene glycol, rust preventive agent, etc. contained in the cooling water will deteriorate and deteriorate, or the internal pressure of the piping constituting the cooling water circuit will rise and the piping will be excessive. There is a possibility that a load may act, which is not preferable.

  The present invention has been made to solve the above-described conventional problems, and prevents the cooling water in the internal combustion engine from boiling during the early warm-up while achieving the early warm-up of the internal combustion engine. An object of the present invention is to provide a cooling device for an internal combustion engine that can be used.

  In order to achieve the above object, a cooling apparatus for an internal combustion engine according to the present invention includes (1) one end connected to the exhaust pipe of the internal combustion engine and the other end connected to the intake pipe of the internal combustion engine. An EGR pipe that supplies a part of the exhaust gas from the exhaust pipe to the intake pipe, an EGR cooler that is provided in the EGR pipe and is supplied with cooling water of the internal combustion engine, and is provided in the exhaust pipe, An internal combustion engine cooling apparatus comprising: a heat exchanger that recovers heat of exhaust gas in an exhaust pipe and heats cooling water supplied from the internal combustion engine, the internal combustion engine, the EGR cooler, and the heat exchange A cooling water supply pipe that circulates the cooling water in the order of the heat exchanger, and the cooling water supply pipe that is branched downstream of the heat exchanger, and that is upstream of the cooling water supply pipe and the EGR cooler downstream of the heat exchanger. The cooling water supply pipe on the side A first branch position provided in the cooling water supply pipe on the downstream side of the heat exchanger and connected to the downstream side of the heat exchanger and the internal combustion engine. Switching means for switching the downstream side of the heat exchanger and the upstream side of the EGR cooler to a second communication position communicating with each other via the branch pipe, and boiling detection for detecting boiling of cooling water in the internal combustion engine And a control means for performing switching control of the switching means, the control means, on the condition that the boiling detection means has detected boiling of cooling water at the time of cold start of the internal combustion engine, the switching means The unit is configured to switch the means to the first communication position.

  In the cooling device for the internal combustion engine, the control unit controls the switching unit, so that the coolant is supplied to a first communication position where the downstream side of the heat exchanger communicates with the internal combustion engine, and the heat exchanger The downstream side and the upstream side of the EGR cooler are switched to the second communication position where the downstream side and the EGR cooler communicate with each other via the branch pipe.

  Therefore, at the time of cold start of the internal combustion engine, the control means switches the switching means to the second communication position and circulates between the heat exchanger and the EGR cooler, so that the cooling water warmed by the exhaust gas is EGR. The cooler can be supplied and the EGR cooler can be warmed.

  Therefore, the EGR cooler can be warmed up early, and the EGR gas can be supplied to the EGR pipe at an early stage while suppressing the generation of condensed water in the EGR cooler.

As a result, it is possible to prevent the combustion of the internal combustion engine from becoming unstable due to the EGR gas recirculated to the internal combustion engine, and to prevent the fuel efficiency from deteriorating during a cold start of the internal combustion engine.
Further, when the switching means is switched to the second communication position, the supply of cooling water to the internal combustion engine can be stopped, and the internal combustion engine can be warmed up early.

  Further, since the cooling water supply to the internal combustion engine is stopped when the internal combustion engine is cold started, there is a risk that the cooling water of the internal combustion engine will boil when the internal combustion engine enters a high-load operation state. The control means switches the switching means to the first communication position when the cooling water in the internal combustion engine boils.

  Therefore, the heat exchanger and the internal combustion engine can be communicated with each other via the cooling water supply pipe so that the cooling water can be supplied from the heat exchanger to the internal combustion engine. Can be suppressed from boiling.

  In the cooling apparatus for an internal combustion engine according to (1), (2) the control unit sets the switching unit to the switching unit on the condition that the temperature of the cooling water flowing through the cooling water supply pipe is lower than a predetermined temperature. Switching to the second communication position and switching the switching means to the first communication position on condition that the temperature of the cooling water flowing through the cooling water supply pipe is equal to or higher than the predetermined temperature. .

  In this internal combustion engine cooling apparatus, the control means switches the switching means to the second communication position on the condition that the temperature of the cooling water flowing through the cooling water supply pipe is lower than a predetermined temperature. During start-up, the cooling water is circulated between the heat exchanger and the EGR cooler, and the cooling water heated by the exhaust gas can be supplied to the EGR cooler, so that the EGR cooler can be warmed up early. .

  For this reason, the EGR gas can be supplied to the EGR pipe at an early stage, and the fuel efficiency can be prevented from deteriorating when the internal combustion engine is cold-started.

  Further, since the control means switches the switching means to the first communication position on the condition that the temperature of the cooling water flowing through the cooling water supply pipe is equal to or higher than a predetermined temperature, the control means is warmed up after the EGR cooler is warmed up early. The cooling water can be supplied to the internal combustion engine, so that the internal combustion engine can be warmed up quickly.

  In the internal combustion engine cooling device according to (1) or (2), (3) flow path area varying means for varying the flow area of the EGR pipe is provided, and the control means includes the cooling water supply pipe On the condition that the temperature of the cooling water flowing through is lower than the predetermined temperature, the flow path area variable means is controlled to fully close the EGR pipe.

  In this internal combustion engine cooling apparatus, the control means controls the flow path area variable means to fully close the EGR pipe on condition that the temperature of the cooling water flowing through the cooling water supply pipe is lower than a predetermined temperature. During the warm-up of the EGR cooler, the EGR gas is not rapidly cooled by the low-temperature EGR cooler, and it is possible to reliably prevent the condensed water from being generated in the EGR cooler.

  ADVANTAGE OF THE INVENTION According to this invention, the internal combustion engine cooling device which can prevent that the cooling water in an internal combustion engine boils during early warming up can be provided, aiming at early warming up of an internal combustion engine. .

1 is a diagram illustrating an embodiment of a cooling device for an internal combustion engine according to the present invention, and is a schematic configuration diagram of the internal combustion engine including the cooling device. It is a figure which shows one Embodiment of the cooling device of the internal combustion engine which concerns on this invention, and is a control block diagram of an internal combustion engine. It is a figure which shows one Embodiment of the cooling device of the internal combustion engine which concerns on this invention, and is a flowchart of an engine control program. It is a figure which shows one Embodiment of the cooling device of the internal combustion engine which concerns on this invention, and is a figure which shows the time transition of the temperature of the cooling water in an engine, and the temperature of the cooling water supplied to an EGR cooler. It is a figure which shows one Embodiment of the cooling device of the internal combustion engine which concerns on this invention, and is a figure which shows the fuel consumption efficiency of the internal combustion engine at the time of supply of EGR gas, and the time of non-supply.

Embodiments of a cooling apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings.
1 to 5 are diagrams showing an embodiment of a cooling device for an internal combustion engine according to the present invention.
First, the configuration will be described.
In FIG. 1, an engine 1 as an internal combustion engine is constituted by, for example, a diesel engine or a gasoline engine provided with a supercharger (not shown), and the engine 1 includes a cylinder block 2 and a cylinder head 3.

  The cylinder block 2 is provided with a plurality of cylinders 4, and a piston (not shown) is provided in the cylinder 4 so as to be reciprocally movable in the vertical direction, and the reciprocating movement of the piston is converted into rotational movement of a crankshaft (not shown). It has come to be. In the present embodiment, a four-cylinder engine is taken as an example, but the number of cylinders is not limited to this.

  The cylinder head 3 is provided with a valve operating device such as an intake / exhaust cam (not shown), an intake / exhaust cam shaft, an intake / exhaust valve, a fuel injection valve, etc., and the valve operating device is an intake (not shown) formed in the cylinder head 3. The port and exhaust port are opened and closed.

  An intake pipe 5 is attached to the cylinder head 3 so as to communicate with the intake port. The intake pipe 5 introduces intake air into a combustion chamber defined by the cylinder 4, the cylinder head 3 and the piston. ing.

  An exhaust pipe 6 is attached to the cylinder head 3 so as to communicate with the exhaust port. The exhaust pipe 6 discharges the exhaust gas burned in the combustion chamber to the outside. In FIG. 1, the exhaust pipe 6 is attached to the cylinder block 2, but is actually attached to the cylinder head 3.

  An exhaust heat recovery unit 7 as a heat exchanger is attached to the exhaust pipe 6. The exhaust heat recovery unit 7 exchanges heat between the heat of the exhaust gas flowing through the exhaust pipe 6 and the cooling water. By doing so, the cooling water is heated.

  Further, the engine 1 is provided with an EGR device 8. The EGR device 8 includes an EGR pipe 9 having one end connected to the exhaust pipe 6 and the other end connected to the intake pipe 5, and an intermediate portion of the EGR pipe 9. An EGR valve 10 as a flow path area varying means provided in the EGR, an EGR cooler 11 provided on the downstream side of the EGR valve 10, and an ECU that controls opening and closing of the EGR valve 10 according to the rotational speed and load of the engine 1 (Electronic Control Unit) 12.

  The EGR valve 10 appropriately adjusts the opening degree of the EGR pipe 9 from the fully closed state where the opening degree of the EGR pipe 9 is zero to the fully opened state where the opening degree of the EGR pipe 9 is 100%. The opening / closing control is performed based on the duty value of the opening degree signal output from.

  When the EGR valve 10 is opened, a part of the exhaust gas discharged to the exhaust pipe 6 is recirculated to the combustion chamber of the engine 1 through the EGR pipe 9 and the intake pipe 5. When the EGR gas is recirculated to the engine 1, intake air containing exhaust gas is supplied to the combustion chamber of the engine 1, so that NOx can be reduced.

  The EGR cooler 11 cools the EGR gas by exchanging heat between the heat of the EGR gas and the cooling water. When the EGR gas is cooled, it is recirculated to the combustion chamber of the engine 1. EGR gas charging efficiency can be improved, and the combustion temperature in the combustion chamber can be lowered to further improve the NOx suppression effect.

  The engine 1 is provided with a cooling device 13. The cooling device 13 includes a main supply pipe 15 including a radiator 14, and the main supply pipe 15 is connected to the engine 1. That is, the main supply pipe 15 includes an inlet portion 15 a connected to the cylinder block 2 and an outlet portion 15 b connected to the cylinder head 3.

  The main supply pipe 15 is provided with a water pump 16. The water pump 16 is composed of a trochoid pump, a gear pump, and the like. When the water pump 16 is rotated by the crankshaft of the engine 1, the rotational speed increases in proportion to the rotational speed of the engine. Therefore, when the rotation speed of the water pump 16 increases, the amount of cooling water discharged from the water pump 16 increases in proportion to the rotation speed.

  When the water pump 16 is driven during the operation of the engine 1, the cooling water circulates between the radiator 14 and a water jacket that forms a cooling water passage (not shown) formed in the cylinder block 2 and the cylinder head 3 of the engine 1. To do.

  In FIG. 1, the arrows written on the cylinder block 2 and the cylinder head 3 indicate the flow of cooling water in the engine 1, and the cooling water supplied from the main supply pipe 15 to the cylinder block 2 is After the cylinder 4 and each part of the cylinder block 2 are cooled, each part of the cylinder head 3 is cooled and discharged to the main supply pipe 15.

  When the cooling water circulates between the water jacket and the radiator 14 through the main supply pipe 15, the cooling water which has been heated by removing heat from the cylinder 4 and each part of the engine 1 is introduced into the radiator 14 and cooled by the radiator 14. The cooling water is pumped by the water pump 16 and introduced again into the water jacket of the engine 1.

  An EGR cooler 11 is provided on the main supply pipe 15, and the EGR cooler 11 cools EGR gas flowing through the EGR pipe 9 with cooling water flowing through the main supply pipe 15.

  Further, a bypass pipe 17 is branched and connected to the main supply pipe 15, and the bypass pipe 17 is connected to the main supply pipe 15 on the upstream side and the downstream side of the EGR cooler 11. The bypass pipe 17 is provided with a heater core 18. The heater core 18 exchanges heat between the cooling water and air by introducing the cooling water heated by the combustion heat of the engine 1 through the bypass pipe 17. Is supposed to do. The air warmed by this heat exchange is used for heating the passenger compartment.

  In addition, a three-way solenoid valve 19 is provided at a branch portion between the main supply pipe 15 and the bypass pipe 17, and this three-way solenoid valve 19 is controlled by the ECU 12 so that the coolant supply destination is the EGR cooler 11 or The flow path is switched so as to be either one of the heater cores 18.

  That is, the three-way solenoid valve 19 has a first communication position that communicates the engine 1 and the EGR cooler 11 via the main supply pipe 15, and a second communication position that communicates the engine 1 and the heater core 18 via the bypass pipe 17. It can be switched to the communication position.

  A bypass pipe 20 is branched and connected to the main supply pipe 15 on the downstream side of the EGR cooler 11, and the exhaust heat recovery unit 7 is provided in the bypass pipe 20. The exhaust heat recovery unit 7 heats the cooling water by exchanging heat between the heat of the exhaust gas flowing through the exhaust pipe 6 and the cooling water flowing through the bypass pipe 20. The connection position between the main supply pipe 15 and the bypass pipe 20 constitutes a branch portion 15c.

  Further, the downstream end of the bypass pipe 20 bypasses the radiator 14 and is connected to the main supply pipe 15 on the downstream side of the radiator 14. For this reason, when the cooling water discharged from the engine 1 to the main supply pipe 15 is supplied to the bypass pipe 20, the cooling water is supplied in the order of the EGR cooler 11, the exhaust heat recovery unit 7, and the engine 1.

  That is, the portion of the main supply pipe 15 upstream of the branching portion 15 c (hereinafter referred to as the upstream main supply pipe 15 </ b> A) and the bypass pipe 20 supply cooling water in the order of the engine 1, the EGR cooler 11, and the exhaust heat recovery device 7. It constitutes a circulating cooling water supply pipe.

  A bypass pipe 21 as a branch pipe is branched and connected to the bypass pipe 20 on the downstream side of the exhaust heat recovery unit 7, and the downstream end of the bypass pipe 21 is upstream of the upstream side of the water pump 16. It is connected to the main supply pipe 15A.

  A branch portion between the bypass pipe 20 and the bypass pipe 21 is provided with a three-way electromagnetic valve 22 as a switching means. The three-way electromagnetic valve 22 is controlled by the ECU 12 so that the cooling water supply destination is exhausted. A first communication position that communicates the downstream side of the recovery unit 7 and the engine 1, and a second communication position that communicates the downstream side of the exhaust heat recovery unit 7 and the upstream side of the EGR cooler 11 via the bypass pipe 20. It is supposed to switch to.

The main supply pipe 15 on the downstream side of the radiator 14 is provided with a known wax-type thermostat 23, and this thermostat 23 is used when the cooling water flowing through the main supply pipe 15 is at a warm-up temperature Th ° C. or higher. The main supply pipe 15 is opened to circulate cooling water between the engine 1 and the radiator 14.
In this state, the high-temperature cooling water that cools the cylinder 4 and each part by taking the heat of the cylinder 4 and each part of the engine 1 is cooled by the radiator 14, and the low-temperature cooling water is introduced into the engine 1.

  Further, the thermostat 23 closes the main supply pipe 15 when the cooling water flowing through the main supply pipe 15 is lower than the warm-up temperature Th ° C., and connects the exhaust heat recovery unit 7 through the upstream main supply pipe 15A and the bypass pipe 20. Cooling water is circulated with the engine 1. In this state, since the cooling water is not cooled by the radiator 14, warm-up of the engine 1 is promoted at the time of cold start or the like.

  On the other hand, a water temperature sensor 24 is provided in the main supply pipe 15 on the downstream side of the EGR cooler 11, and this water temperature sensor 24 is configured by a thermistor or the like whose resistance value changes according to the temperature of the cooling water, A voltage that changes according to the change in the resistance value is output to the ECU 12 as a signal representing the temperature of the cooling water (see FIG. 2).

  Further, the engine 1 is provided with a water temperature sensor 25 and a pressure sensor 26. The water temperature sensor 25 is constituted by the same thermistor as the water temperature sensor 24, and detects the temperature of the cooling water flowing through the water jacket of the engine 1 and changes the temperature of the cooling water according to the change in the resistance value. The signal is output to the ECU 12 as a signal (see FIG. 2).

The pressure sensor 26 is provided close to the water temperature sensor 25, detects the pressure in the water jacket of the engine 1, and outputs a signal corresponding to the pressure to the ECU 12 (see FIG. 2).
The engine 1 is provided with a crank angle sensor 27 that detects the rotation speed of the crankshaft. The crank angle sensor 27 detects the rotation speed of the crankshaft and outputs a signal corresponding to the rotation speed to the ECU 12. (See FIG. 2).

  In addition, an ignition switch 28 is connected to the ECU 12, and the ignition switch 28 outputs a start signal for starting the engine 1 to the ECU 12 (see FIG. 2).

  The ECU 12 includes a microcomputer such as a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory).

  The CPU executes various arithmetic processes including an engine control program for controlling the EGR device 8 and cooling the engine 1 stored in the ROM. The RAM is a non-volatile memory that temporarily stores calculation results in the CPU, data input from the above-described water temperature sensors 24 and 25, and the pressure sensor 26, and the like, and also constitutes a part of the work area. .

  The ECU 12 controls the EGR valve 10 based on the detection information of the crank angle sensor 27 and the water temperature sensor 24, thereby adjusting the opening of the EGR pipe 9 according to the rotational speed and load of the engine 1. .

  Further, the ECU 12 sets the three-way solenoid valve 22 on the condition that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is equal to or higher than a predetermined temperature T1 ° C. based on the detection information of the water temperature sensor 24. Is switched to the first communication position, and the three-way solenoid valve 22 is switched to the second communication position on condition that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is less than T1 ° C. It has become.

  Note that T1 ° C. is set to a temperature at which condensed water is not generated in the EGR cooler 11 even when EGR gas is supplied to the EGR cooler 11, and this T1 ° C. is set to a temperature lower than the warm-up temperature Th ° C. ing.

  Further, the ECU 12 detects boiling of the cooling water in the engine 1 based on detection information of the water temperature sensor 25 and the pressure sensor 26. The water temperature sensor 25, the pressure sensor 26, and the ECU 12 provide boiling detection means. It is composed.

  Further, the ECU 12 is configured to forcibly switch the three-way solenoid valve 22 to the first communication position on the condition that the boiling of the cooling water in the engine 1 is detected when the engine 1 is cold started. It constitutes a control means.

  Further, the ECU 12 controls the EGR valve 10 based on the detection information of the water temperature sensor 24 on the condition that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is less than T1 ° C. 9 is controlled to be fully closed.

  Further, the ECU 12 receives a signal from the air conditioning switch 30 (see FIG. 2). When the signal is input from the air conditioning switch 30, the ECU 12 determines that there is a heating request, Switching control of the three-way solenoid valve 22 is performed so that the cooling water supply destination is the heater core 18.

  In addition, a radiator fan 29 is provided at a position facing the radiator 14, and the radiator fan 29 is controlled by the ECU 12. Specifically, the ECU 12 uses a radiator fan to assist cooling of the cooling water based on the detection information of the water temperature sensor 24 when the temperature of the cooling water is a temperature T2 higher than the warm-up temperature Th ° C. 29 is driven. In the cooling device 13 according to the present embodiment, the ECU 12 constitutes a control means.

  The cooling device 13 of the present embodiment includes an ECU 12, a radiator 14, a main supply pipe 15, a water pump 16, a bypass pipe 17, three-way solenoid valves 19 and 22, bypass pipes 20 and 21, and a thermostat 23 for cooling the engine 1. The apparatus 13 is configured.

Next, the operation will be described.
FIG. 3 is a flowchart of the engine control program stored in the ROM of the ECU 12, and this flowchart is executed by the CPU. This flowchart is executed when the engine 1 is cold-started, and ends when the temperature of the cooling water reaches the warm-up temperature.

  In FIG. 3, the ECU 12 determines whether or not a start signal is input from the ignition switch 28 (step S1).

  When the start signal is input from the ignition switch 28, the ECU 12 determines that the engine 1 has been started and determines whether there is a heating request (step S2).

  When no signal is input from the air conditioning switch 30, the ECU 12 determines that there is no heating request and switches the three-way solenoid valve 19 to the first communication position (step S3). Next, the ECU 12 determines whether or not the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is lower than T1 ° C. based on the detection information of the water temperature sensor 24 (step S4).

  When the ECU 12 determines that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is less than T1 ° C., the ECU 12 determines that the engine 1 is cold starting, and the three-way solenoid valve 22 is switched to the second communication position (step S5).

  For this reason, since the cooling water flows in the order of the upstream main supply pipe 15A, the bypass pipe 20 and the bypass pipe 21 by driving the water pump 16, the cooling water is supplied in the order of the EGR cooler 11 and the exhaust heat recovery unit 7. That is, the cooling water is circulated between the EGR cooler 11 and the exhaust heat recovery unit 7.

  For this reason, the heat of the exhaust gas discharged to the exhaust pipe 6 and the cooling water are subjected to heat exchange, whereby the cooling water is heated in the exhaust heat recovery unit 7 and the heated cooling water is supplied to the EGR cooler 11. Then, the EGR cooler 11 is warmed up.

  A part of the cooling water discharged from the EGR cooler 11 is supplied to the radiator 14 through the main supply pipe 15 on the downstream side of the branching portion 15c. However, the cooling water is lower than the warm-up temperature Th ° C. The thermostat 23 downstream of the radiator 14 is fully closed. For this reason, the cooling water is not cooled by the radiator 14 and the cooling water is not supplied to the engine 1.

Next, the ECU 12 fully closes the EGR valve 10 and does not introduce EGR gas into the EGR pipe 9 (step S6). For this reason, generation of condensed water in the EGR cooler 11 by the EGR gas introduced into the EGR pipe 9 is suppressed.
Next, the ECU 12 determines whether or not the cooling water in the engine 1 is boiling based on the detection information of the water temperature sensor 25 and the pressure sensor 26 (step S7).

  If the ECU 12 determines that the cooling water in the engine 1 has not boiled, the ECU 12 proceeds to step S2. If the ECU 12 determines that the cooling water in the engine 1 is boiling, the ECU 12 forcibly switches the three-way solenoid valve 22 to the first communication position (step S8).

  The cooling water in the engine 1 boils in this way because the supply of the cooling water to the engine 1 is stopped and the cooling water stays in the water jacket of the engine 1. This is because the operation state becomes a high load, and the cooling water locally becomes high in the engine 1.

  If the three-way solenoid valve 22 is forcibly switched to the first communication position when the cooling water in the engine 1 has boiled, the cooling water is not supplied to the bypass pipe 21 by driving the water pump 16, and the upstream main Since it flows through the supply pipe 15 </ b> A and the bypass pipe 20, the cooling water is supplied in the order of the engine 1, the EGR cooler 11, and the exhaust heat recovery unit 7.

That is, the cooling water is circulated between the engine 1, the EGR cooler 11, and the exhaust heat recovery unit 7, cooling water having a temperature lower than that of the boiling cooling water is supplied to the engine 1, and the cooling water in the engine 1 is boiled. Is suppressed.
The ECU 12 forcibly switches the three-way solenoid valve 22 to the first communication position and then returns to step S7 to monitor whether or not the boiling of the cooling water in the engine 1 is suppressed.

  If the ECU 12 determines in step S4 that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is equal to or higher than T1 ° C., the ECU 12 switches the three-way solenoid valve 22 to the first communication position. After that (step S10), the opening degree of the EGR valve 10 is set with the opening degree based on the detection information of the crank angle sensor 27 and the water temperature sensor 24, and the EGR valve 10 is opened (step S11).

  When the three-way solenoid valve 22 is switched to the first communication position, the cooling water flows through the upstream main supply pipe 15A and the bypass pipe 20 by driving the water pump 16, so that the cooling water flows into the engine 1, the EGR cooler 11, and the exhaust heat. They are supplied in the order of the collector 7. That is, the cooling water is circulated between the engine 1, the EGR cooler 11 and the exhaust heat recovery unit 7.

Further, a part of the cooling water discharged from the EGR cooler 11 is supplied to the radiator 14 through the main supply pipe 15, but the cooling water is still lower in temperature than the warm-up temperature, and the thermostat 23 downstream of the radiator 14. Is fully closed, the cooling water is not cooled by the radiator 14 and the cooling water is not supplied to the engine 1.
For this reason, the cooling water heated by the exhaust heat recovery device 7 is supplied to the engine 1 and the engine 1 is warmed up early.

  Next, the ECU 12 determines whether or not the temperature T of the cooling water is lower than the warm-up temperature Th ° C. based on the detection information of the water temperature sensor 24 (step S11). When the ECU 12 determines that the temperature T of the cooling water is lower than the warm-up temperature Th ° C., the ECU 12 returns the process to step S10 and determines that the temperature T of the cooling water is equal to or higher than the warm-up temperature Th ° C. In this case, the current process is terminated. Thereafter, the cooling device 13 shifts to normal control.

  When the temperature T of the cooling water becomes equal to or higher than the warm-up temperature Th ° C., the thermostat 23 is fully opened, so that the cooling water circulates between the engine 1 and the radiator 14 to cool the cylinder 4 and each part of the engine 1. it can.

  Further, in the normal control, the thermostat 23 is controlled to open and close based on the temperature of the cooling water to circulate the cooling water between the engine 1 and the radiator 14 or bypass the radiator 14 and the engine 1 and the exhaust heat recovery unit 7. Is a control that circulates between

On the other hand, when a signal is input from the air conditioning switch 30 in step S2, the ECU 12 determines that there is a heating request and switches the three-way solenoid valve 19 to the second communication position (step S9). The process moves to step S4.
When the three-way solenoid valve 19 is switched to the second communication position, the bypass pipe 20 is communicated with the bypass pipe 17.

  If the ECU 12 determines in step S4 that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is less than T1 ° C., the ECU 12 moves the process to step S5 and performs a cold start of the engine 1. It is determined that it is time, and the three-way solenoid valve 22 is switched to the second communication position.

  For this reason, the cooling water is branched from the upstream main supply pipe 15 </ b> A to the bypass pipe 17 by driving the water pump 16, and the cooling water flows in the order of the bypass pipe 17, the bypass pipe 20 and the bypass pipe 21. For this reason, the cooling water is circulated between the heater core 18 and the exhaust heat recovery unit 7, and the air heated by heat exchange with the cooling water flowing in the heater core 18 is used for heating the vehicle interior.

If the ECU 12 determines in step S4 that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is equal to or higher than T1 ° C., the ECU 12 moves the process to step S10 and sets the three-way solenoid valve 22 to Switch to 1 communication position.
When the three-way solenoid valve 22 is switched to the first communication position, the cooling water flows through the bypass pipe 17 and the bypass pipe 20 by driving the water pump 16, so that the cooling water flows through the engine 1, the heater core 18, and the exhaust heat recovery unit 7. They are supplied in order.

That is, the cooling water is circulated between the engine 1, the heater core 18, and the exhaust heat recovery unit 7 and supplied to the heater core 18. For this reason, the air heated by heat exchange with the cooling water flowing in the heater core 18 is used for heating the passenger compartment.
ECU12 will perform the process after step S6 after step S6, if the process of step S6 and S10 is each complete | finished.

  When the cooling water supply destination is selectively switched to the EGR cooler 11 and the heater core 18 by the three-way solenoid valve 19, not only the cooling water supply destination is set to one of the EGR cooler 11 and the heater core 18. The distribution ratio of the cooling water to the EGR cooler 11 and the heater core 18 may be changed. For example, when cooling water is supplied in preference to the EGR cooler 11, the cooling water distribution ratio is set to 80% for the EGR cooler 11 and 20% for the heater core 18.

  As described above, in the cooling device 13 of the present embodiment, the ECU 12 controls the three-way solenoid valve 22, whereby the cooling water supply destination is communicated between the downstream side of the exhaust heat recovery unit 7 and the engine 1. The communication position and the downstream side of the exhaust heat recovery unit 7 and the upstream side of the EGR cooler 11 are switched to the second communication position that communicates via the bypass pipe 17.

  In particular, the ECU 12 of the cooling device 13 according to the present embodiment has a condition that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the bypass pipe 20 is less than the temperature T1 ° C. at which condensed water is not generated in the EGR cooler 11. Since the three-way solenoid valve 22 is switched to the second communication position, the cooling water is circulated between the exhaust heat recovery device 7 and the EGR cooler 11 and warmed by the exhaust gas when the engine 1 is cold started. The cooling water can be supplied to the EGR cooler 11, and the EGR cooler 11 can be warmed up early.

  For this reason, it is possible to prevent the EGR gas flowing through the EGR pipe 9 from being rapidly cooled by the EGR cooler 11, and to supply the EGR gas to the EGR pipe 9 at an early stage. As a result, it is possible to prevent the combustion of the engine 1 from becoming unstable due to the EGR gas recirculated to the engine 1 and to prevent the fuel efficiency from deteriorating when the engine 1 is cold started.

  FIG. 4 is a diagram illustrating a change in the temperature of the cooling water in the engine 1 and a change in the temperature of the cooling water supplied to the EGR cooler 11. As shown in FIG. 4, in the present embodiment, the temperature of the cooling water supplied to the EGR cooler 11 can be warmed up earlier than the temperature of the cooling water in the engine 1, so that the EGR gas is supplied to the EGR pipe. 9 can be supplied early.

  Further, as is clear from FIG. 5, it is clear that when the EGR gas is supplied to the EGR pipe 9 at an early stage, the fuel efficiency is improved as compared with the case where the EGR gas is not supplied. When the EGR pipe 9 is supplied to the EGR pipe 9 at an early stage, the fuel efficiency can be improved as compared with the case where EGR gas is not supplied to the EGR pipe 9 at an early stage.

  In the present embodiment, when the three-way solenoid valve 22 is switched to the second communication position, the supply of cooling water to the engine 1 can be stopped, so that the engine 1 can be warmed up early. be able to.

  Further, the ECU 12 of the cooling device 13 of the present embodiment sets the three-way solenoid valve 22 to the first one on the condition that the temperature of the cooling water flowing through the upstream main supply pipe 15A and the main supply pipe 15 is T1 ° C. or higher. Since the communication position is switched, the coolant that has been warmed up after the EGR cooler 11 is warmed up can be supplied to the engine 1, so that the engine 1 can be warmed up early.

  Further, since the supply of cooling water to the engine 1 is stopped when the engine 1 is cold-started, the cooling water of the engine 1 may boil when the engine 1 enters a high load operation state.

  Since the ECU 12 of the cooling device 13 of the present embodiment is configured to switch the three-way solenoid valve 22 to the first communication position when the cooling water in the engine 1 boils during the cold start of the engine 1, The exhaust heat recovery unit 7 and the engine 1 can be communicated with each other via the upstream main supply pipe 15 </ b> A and the bypass pipe 20, and cooling water can be supplied from the exhaust heat recovery unit 7 to the engine 1. For this reason, boiling of the cooling water in the engine 1 can be suppressed during the early warm-up of the engine 1.

  Since the boiling of the cooling water in the engine 1 can be suppressed in this way, the ethylene glycol, the rust inhibitor, etc. contained in the cooling water are altered and deteriorated, or the main supply pipe 15 constituting the cooling device 13, It is possible to prevent the internal pressure of the bypass pipe 17 and the bypass pipes 20 and 21 from rising and an excessive load from acting on the main supply pipe 15 and the like.

  Further, the ECU 12 of the cooling device 13 of the present embodiment controls the EGR valve 10 and fully closes the EGR pipe 9 on condition that the temperature of the cooling water flowing through the main supply pipe 15 is lower than T1 ° C. During the warm-up of the EGR cooler 11, the EGR gas is not rapidly cooled by the low-temperature EGR cooler 11, and the generation of condensed water in the EGR cooler 11 can be reliably prevented.

  When the thermostat 23 is fully opened, the cooling water circulates between the engine 1 and the radiator 14. At this time, a part of the cooling water flows through the bypass pipe 20. In this case, the cooling performance of the engine 1 may be improved by optimally designing the flow passage area and flow passage resistance of the bypass pipe 20 so that a large amount of cooling water flows through the radiator 14.

  The ECU 12 of the cooling device 13 according to the present embodiment switches the three-way solenoid valve 22 to the first communication position when the cooling water in the engine 1 boils, but the cooling water in the engine 1 boils. If there is a possibility of this, the three-way solenoid valve 22 may be switched to the first communication position.

  In this case, the ECU 12 is based on the detection information of the water temperature sensor 25 and the pressure sensor 26 when the pressure and temperature of the cooling water in the engine 1 become a pressure and temperature close to the pressure and temperature at which the cooling water boils. It may be determined that there is a possibility of boiling.

  As described above, the cooling apparatus for an internal combustion engine according to the present invention can prevent the cooling water in the internal combustion engine from boiling during the early warm-up while achieving the early warm-up of the internal combustion engine. This is useful as a cooling device for an internal combustion engine that has an effect and uses the cooling water heated by the heat exchanger that recovers the heat of the exhaust gas so that the internal combustion engine can be warmed up early.

1 engine (internal combustion engine)
5 Intake pipe 6 Exhaust pipe 7 Waste heat recovery unit (heat exchanger)
9 EGR pipe 10 EGR valve (flow area variable means)
11 EGR cooler 12 ECU (control means, boiling detection means)
13 Cooling device 15A Upstream main supply pipe (cooling water supply pipe)
20 Bypass pipe (cooling water supply pipe)
21 Bypass pipe (branch pipe)
22 Three-way solenoid valve (switching means)
25 Water temperature sensor (boiling detection means)
26 Pressure sensor (boiling detection means)

Claims (3)

An EGR pipe having one end connected to the exhaust pipe of the internal combustion engine and the other end connected to the intake pipe of the internal combustion engine, and supplying a part of the exhaust gas of the internal combustion engine from the exhaust pipe to the intake pipe; EGR cooler provided in the EGR pipe and supplied with cooling water of the internal combustion engine, and cooling water provided in the exhaust pipe and recovering heat of exhaust gas in the exhaust pipe and supplied from the internal combustion engine. A cooling device for an internal combustion engine comprising a heat exchanger for heating,
A cooling water supply pipe for circulating cooling water in the order of the internal combustion engine, the EGR cooler, and the heat exchanger;
A branch pipe branched from the cooling water supply pipe on the downstream side of the heat exchanger, and connecting the cooling water supply pipe on the downstream side of the heat exchanger and the cooling water supply pipe on the upstream side of the EGR cooler; ,
A first communication position that is provided in the cooling water supply pipe on the downstream side of the heat exchanger, and that connects the cooling water to the downstream side of the heat exchanger and the internal combustion engine; and Switching means for switching the downstream side and the upstream side of the EGR cooler to a second communication position that communicates via the branch pipe;
Boiling detection means for detecting boiling of cooling water in the internal combustion engine;
Control means for performing switching control of the switching means,
The control means switches the switching means to the first communication position on condition that the boiling detection means detects boiling of cooling water when the internal combustion engine is cold-started. Cooling system. The control means switches the switching means to the second communication position on the condition that the temperature of the cooling water flowing through the cooling water supply pipe is lower than a predetermined temperature,
2. The internal combustion engine according to claim 1, wherein the switching unit is switched to the first communication position on condition that the temperature of the cooling water flowing through the cooling water supply pipe is equal to or higher than the predetermined temperature. Cooling system. Having flow path area variable means for changing the flow path area of the EGR pipe,
The control means controls the flow path area variable means to fully close the EGR pipe on the condition that the temperature of the cooling water flowing through the cooling water supply pipe is lower than the predetermined temperature. The cooling device for an internal combustion engine according to claim 1 or 2.

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