JP2018119423A - Engine cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively promote a temperature rise of cooling water flowing in an EGR cooler and enable early introduction of EGR gas.SOLUTION: An engine cooling system includes: a pump 33; an engine side flow passage 40 connected to a pump suction port 47 from a pump discharge port 41 at least via an engine E; an EGR cooler side flow passage 48 connected to the pump suction port 47 from the pump discharge port 41 via an EGR cooler 22; a temperature sensor 65 for acquiring a temperature of cooling water; valves 37, 38 capable of opening/closing the engine side flow passage 40; a temperature rise device 50 capable of raising a temperature of the cooling water flowing in the EGR cooler side flow passage 48; and a control section 64 for performing temperature rise control for raising the temperature of the cooling water flowing in the EGR side flow passage 48 by closing the valves 37, 38, causing the cooling water to flow in the EGR side flow passage 48 and operating the temperature rise device 50 when the temperature of the cooling water is less than a predetermined threshold temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine cooling system.

  As this type of engine cooling system, for example, Patent Document 1 provides an engine bypass flow path that bypasses the water jacket in a main cooling water circuit in which an engine water jacket, a low-pressure EGR cooler, a radiator, and the like are interposed. A structure in which an exhaust heat recovery device for heating cooling water is provided in the engine bypass flow path is disclosed.

  According to the structure described in this document, from the start of the engine until the cooling water temperature reaches a predetermined warm air temperature, the circulation of the cooling water in the water jacket is completely stopped to promote engine warm-up, and the engine bypass flow The temperature of the cooling water flowing through the passage is raised to the exhaust dew point by the exhaust heat recovery device, thereby preventing the generation of condensed water in the low pressure EGR device.

JP 2014-9634 A

  By the way, in the technique described in Patent Document 1, the cooling water heated by the exhaust heat recovery unit is supplied from the engine bypass flow path to the low pressure EGR side flow path, the radiator bypass flow path that bypasses the radiator, the water pump inlet flow path, and the like. Is circulated through a main cooling water circuit composed of a plurality of flow paths. For this reason, the amount of heat released from the cooling water to the outside air is increased by the cooling water flowing through the plurality of flow paths until the cooling water temperature reaches the exhaust dew point temperature. It may not be possible. That is, since the temperature rise efficiency of the cooling water is reduced, it takes time from the start of the engine to the start of introduction of the EGR gas, and the exhaust emission performance may not be sufficiently improved.

  An object of the technology of the present disclosure is to improve exhaust emission performance by effectively promoting the temperature rise of the cooling water flowing through the EGR cooler and enabling early introduction of EGR gas.

  The technology of the present disclosure includes a pump that pumps cooling water of an engine, an engine-side flow path that is connected to a suction port of the pump through at least the engine from the discharge port of the pump, and distributes the cooling water, At least one of the EGR cooler-side flow channel that is connected to the pump suction port via the EGR cooler and flows the cooling water from the pump discharge port, and the engine-side flow channel or the EGR cooler-side flow channel Acquired by the temperature sensor for acquiring the temperature of the cooling water flowing through the valve, the valve capable of opening and closing the engine side flow path, the temperature raising device capable of raising the temperature of the cooling water flowing through the EGR cooler side flow path, and the temperature sensor When the temperature of the coolant to be discharged is lower than a predetermined threshold temperature at which condensed water can be generated by cooling the EGR gas, the valve is closed and the engine side flow path is closed. While stopping the flow of the cooling water, the cooling water is made to flow through the EGR side flow path, and the temperature raising device is operated to raise the temperature of the cooling water flowing through the EGR side flow path. And a control unit.

  Further, the temperature sensor is a cooler outlet temperature sensor disposed in the EGR cooler side flow path downstream of the EGR cooler, and the control unit is configured to perform the temperature increase control, thereby performing the temperature increase control. It is preferable that the introduction of EGR gas to the EGR cooler is started when the temperature of the cooling water acquired in step S1 reaches the threshold temperature.

  The temperature sensor further includes an engine outlet temperature sensor disposed in the engine side flow path downstream of the engine, and the control unit acquires the engine outlet temperature sensor from the start of introduction of the EGR gas. It is preferable to continue the temperature increase control until the temperature of the cooling water to be exceeded exceeds the threshold temperature.

  The engine-side flow path includes a radiator that cools cooling water flowing in the engine-side flow path by heat exchange with outside air, and a bypass flow path that branches from between the engine and the radiator and bypasses the radiator Further, at the branch portion between the engine side flow path and the bypass flow path, the cooling water is supplied until the temperature of the cooling water that has passed through the engine reaches a predetermined warm-up temperature that is higher than the threshold temperature. A thermostat that bypasses the radiator and flows through the bypass flow path may be provided.

  The engine-side flow path further includes a heater core-side flow path that is branched from between the engine and the thermostat, and in which a heater core that heats air with heat of cooling water is interposed, and the valve is the bypass You may provide in at least one of a flow path and the said heater core side flow path.

  In addition, a heater core that heats air with heat of cooling water may be interposed in the EGR cooler side flow path downstream of the EGR cooler.

  Moreover, the said temperature rising apparatus may be arrange | positioned at the said EGR cooler side flow path upstream from the said EGR cooler.

  Further, the temperature raising device may be a heater type temperature raising device.

  The temperature raising device may be an exhaust heat type temperature raising device.

  The temperature raising device may be a regenerator type temperature raising device.

  According to the technology of the present disclosure, it is possible to improve the exhaust emission performance by effectively promoting the temperature rise of the cooling water flowing through the EGR cooler and enabling early introduction of EGR gas.

1 is a schematic overall configuration diagram showing an engine system to which an engine cooling system according to a first embodiment of the present invention is applied. It is a typical lineblock diagram showing the heating device of the engine cooling system concerning a first embodiment of the present invention. It is a typical block diagram which shows the modification of the heating apparatus of the engine cooling system which concerns on 1st embodiment of this invention. It is a typical block diagram which shows the modification of the heating apparatus of the engine cooling system which concerns on 1st embodiment of this invention. It is a typical block diagram which shows the modification of the heating apparatus of the engine cooling system which concerns on 1st embodiment of this invention. It is a figure explaining the flow-path switching operation | movement according to the cooling water temperature of the engine cooling system which concerns on 1st this embodiment of this invention. It is a figure explaining the flow-path switching operation | movement according to the cooling water temperature of the engine cooling system which concerns on 1st this embodiment of this invention. It is a figure explaining the flow-path switching operation | movement according to the cooling water temperature of the engine cooling system which concerns on 1st this embodiment of this invention. It is a flowchart figure explaining the temperature rising control system of the engine cooling system which concerns on 1st embodiment of this invention. It is a figure explaining the effect of the temperature rising control of the engine cooling system which concerns on 1st embodiment of this invention. It is a figure explaining the engine cooling system which concerns on 2nd embodiment of this invention.

  Hereinafter, an engine cooling system according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First embodiment]
First, an overall configuration of an engine system 10 to which the engine cooling system according to the present embodiment is applied will be described with reference to FIG. The engine system 10 includes a diesel engine (hereinafter simply referred to as “engine”) E. An intake passage 11 is connected to the intake manifold 10a of the engine E, and an exhaust passage 12 is connected to the exhaust manifold 10b. In the intake passage 11, a turbocharger compressor 13 and an intercooler 14 for cooling the intake air are arranged in this order from the intake upstream side, and in the exhaust passage 12, a supercharger turbine 15 is arranged. Further, the engine system 10 is provided with an exhaust gas recirculation (hereinafter referred to as “EGR device”) 20 that recirculates a part of the exhaust gas from the exhaust passage 12 to the intake passage 11.

  The EGR device 20 is configured by arranging an EGR cooler 22 and an EGR valve 24 in this order in an EGR passage 21 that communicates the upstream side of the exhaust passage 12 with respect to the turbine 15 and the downstream side of the compressor 13 of the intake passage 11. ing. The EGR flow path 21 forms a flow path for supplying recirculated exhaust gas (hereinafter referred to as EGR gas) flowing from the exhaust passage 12 to the EGR flow path 21 to the intake passage 11. The EGR cooler 22 is interposed in an EGR cooler-side cooling water channel 48 described later, and cools the EGR gas by exchanging heat with the cooling water. The EGR valve 24 is provided on the EGR flow path 21 and adjusts the EGR gas flow rate on the EGR flow path 21. The EGR valve 24 is electrically connected to an electronic control unit (hereinafter referred to as ECU) 64, and is controlled by a command from the ECU 64. The EGR device 20 is not limited to the high pressure EGR device that recirculates the EGR gas to the intake passage 11 downstream of the compressor 13, and the low pressure EGR device that recirculates the EGR gas to the intake passage 11 upstream of the compressor 13. It may be.

  Next, the overall configuration of the engine cooling system according to the present embodiment will be described.

  As shown in FIG. 1, the engine cooling system includes an engine side cooling water flow path 40 and an EGR cooler side cooling water flow path 48. An oil cooler 35, a heater core 31, a thermostat 34, and a radiator 32 are provided in the engine side cooling water flow path 40. The EGR cooler 22 is provided in the EGR cooler side cooling water flow path 48. Further, the water pump 33 is provided with a pump discharge port 41 on the outlet side of the water pump 33 and a pump suction port 47 on the inlet side of the water pump 33.

  The engine-side cooling water flow path 40 includes an oil cooler 35, a water jacket 42 formed in a cylinder block of the engine E, a radiator inlet-side flow path 43 connecting the outlet of the water jacket 42 and the radiator 32, and the radiator 32. A radiator outlet-side flow path 44 connecting the outlet and the pump suction port 47, and a branch from the radiator inlet-side flow path 43, and merge with the pump suction port 47 (or the radiator outlet-side flow path 44) to connect the radiator 32. A bypass flow path 45 that bypasses, a heater core inlet-side flow path 46A that connects the upstream side of the branch portion of the bypass flow path 45 and the inlet of the heater core 31, an outlet of the heater core 31 and a pump suction port 47 (or a bypass flow path). 45) is connected to the heater core outlet side flow path 46B.

  The heater core 31 constitutes a part of an air-conditioning heater (not shown) that supplies warm air into the vehicle interior of the vehicle, and dissipates heat from engine cooling water (hereinafter referred to as cooling water) for heating. It is provided as a heat exchanger for use.

  The radiator 32 is provided as a heat exchanger that cools the cooling water by exchanging heat with the cooling air supplied to the surface of the radiator 32 and dissipating the heat of the cooling water.

  The water pump 33 is driven by the power of the engine E and pumps the cooling water. The water pump 33 may be a pump driven by a power other than the power of the engine E.

  The oil cooler 35 is provided as a heat exchanger for exchanging heat between cooling water and engine oil to cool the engine oil.

  The thermostat 34 is provided at a branch portion between the radiator inlet-side channel 43 and the bypass channel 45. When the temperature of the cooling water passing through the thermostat 34 is lower than a predetermined warm-up temperature (for example, about 80 ° C.), the thermostat 34 distributes the cooling water to the bypass flow path 45 that bypasses the radiator 32. On the other hand, when the temperature of the cooling water passing through the thermostat 34 becomes equal to or higher than a predetermined warm-up temperature (for example, about 80 ° C.), the thermostat 34 switches the flow of the cooling water from the bypass flow path 45 to the radiator inlet side flow path 43. It is like that.

  In the present embodiment, the bypass channel 45 is provided with a bypass side opening / closing valve 38 that can block the channel in the bypass channel 45 and stop the flow of the cooling water. In addition, the heater core outlet side channel 46B is provided with a heater core side opening / closing valve 37 that can block the channel in the heater core outlet side channel 46B and stop the flow of cooling water. The opening and closing operations of the valves 37 and 38 are controlled by commands of the electrically connected ECU 64. The heater core side opening / closing valve 37 may be provided in the heater core inlet side flow path 46A.

  The heater core side opening / closing valve 37 may be provided in the heater core inlet side flow path 46A. In addition, the heater core side opening / closing valve 37 and the bypass side opening / closing valve 38 are configured separately. However, in other embodiments, the heater core side opening / closing valve 37 and the bypass side opening / closing valve 38 are integrated, for example. It may be configured as an integral structure by a rotary valve.

  The engine-side cooling water temperature sensor 39 is provided in the radiator inlet-side flow path 43 upstream from the branch portion (or the thermostat 34) with the heater core inlet-side flow path 46A, and from the water jacket 42 to the radiator inlet-side flow path. The temperature of the cooling water flowing into 43 is measured. The EGR cooler side cooling water temperature sensor 65 is provided in the EGR cooler outlet side flow path 46B, and measures the temperature of the cooling water that has passed through the EGR cooler 22. The sensor values of these sensors 39 and 65 are input to the electrically connected ECU 64.

  The EGR cooler-side cooling water flow path 48 branches from the pump discharge port 41 and is connected to the EGR cooler 22 inlet, and the EGR cooler outlet-side flow path 48A connects the EGR cooler 22 outlet and the pump suction port 47. Side flow path 48B. Further, a temperature raising device 50 for raising the temperature of the cooling water flowing into the EGR cooler 22 is interposed in the EGR cooler inlet-side flow path 48A.

  FIG. 2 is a schematic diagram illustrating an example of the temperature raising device 50. The temperature raising device 50 shown in FIG. 2 is configured by a heater type heating device. The heater-type heating device includes, for example, an electric electric heater 51, and the electric heater 51 generates heat by flowing an electric current through a metal wire having a high electric resistance such as a nichrome wire. The electric power generated by the alternator, the generator 52, and / or the electric power stored in the battery is energized to the heating device 50 via the controller 53 controlled by the ECU 64 to cause the heating device 50 to generate heat. The control 53 may be provided integrally with the ECU 64 as a part of the functional element of the ECU 64.

  FIG. 3 is a schematic diagram illustrating another example of the temperature raising device 50. The temperature raising device 50 shown in FIG. 3 is configured by an exhaust heat type heating device. The exhaust heat type heating device 50 is a heating device that heats the cooling water using the amount of heat of the exhaust gas. More specifically, the exhaust heat type heating device 50 includes heat that performs heat exchange between the exhaust heat recovery unit 54 that recovers the exhaust heat of the exhaust gas and the coolant that flows through the EGR cooler-side coolant flow channel 48 and the refrigerant. An exchanger 55, a refrigerant circulation channel 56 for circulating the refrigerant between the exhaust heat recovery unit 54 and the heat exchanger 55, a refrigerant pump 57 provided on the refrigerant circulation channel 56 and controlled by the ECU 64, It has.

  For example, the exhaust heat recovery device 54 is disposed along a pipe on the downstream side of a catalyst (for example, a three-way catalyst or an SCR catalyst) disposed in the exhaust gas passage. At the time of cold start, it is arranged on the downstream side of the catalyst so that the activation of the catalyst is not hindered by the temperature decrease of the exhaust gas. With such a mechanism, the exhaust heat recovery unit 54 recovers the exhaust heat of the exhaust gas, and performs heat exchange with the refrigerant on the refrigerant circulation passage 56. The refrigerant pump 57 circulates the refrigerant in the refrigerant circulation channel 56, and performs heat exchange between the refrigerant and the cooling water flowing through the EGR cooler-side cooling water channel 48 in the heat exchanger 55. Therefore, the cooling water flowing through the EGR cooler-side cooling water channel 48 can be heated by the amount of heat (thermal energy) of the exhaust gas.

  FIG. 4 is a schematic diagram showing another example of the temperature raising device 50. The temperature raising device 50 shown in FIG. 4 is configured by a latent heat accumulator type heating device. When the engine E is in a warm-up state, the regenerator type heating device 50 stores heat in the regenerator such as the latent heat accumulator 58 when the engine E is in a warm-up state. It is possible to provide a heating device that heats the cooling water by radiating heat under the control of the controller 59 connected to the. The control 59 may be provided integrally with the ECU 64 as a part of the functional element of the ECU 64.

  FIG. 5 is a schematic diagram showing another example of the temperature raising device 50. The temperature device 50 shown in FIG. 5 is configured by another heat storage type heating device. The regenerator-type heating device 50 includes a heat accumulator 60 that accumulates the amount of heat that the cooling water or exhaust gas has when the engine E is in a warm-up state, cooling water that flows through the EGR cooler-side cooling water channel 48, and A heat exchanger 61 that performs heat exchange with the refrigerant, a refrigerant circulation passage 62 that circulates the refrigerant between the heat accumulator 60 and the heat exchanger 61, and a refrigerant pump 63 that is provided on the refrigerant circulation passage 62. It is equipped with.

  The heat accumulator 60 is controlled in response to a control command from a controller 66 connected to the ECU 64 to dissipate heat. Therefore, the heat accumulator 60 accumulates the heat quantity of the cooling water or the exhaust gas, and performs heat exchange with the refrigerant on the refrigerant circulation passage 62. The refrigerant pump 63 circulates the refrigerant in the refrigerant circulation passage 62, and performs heat exchange between the refrigerant and the cooling water flowing through the EGR cooler-side cooling water passage 48 in the heat exchanger 61. Therefore, the cooling water flowing through the EGR cooler side cooling water flow path 48 can be heated by the amount of heat stored in the heat accumulator 60. Note that the heat accumulator 60 may be disposed in any location of the exhaust gas flow path or the cooling water circuit, for example, in order to dissipate the amount of heat of the exhaust gas or cooling water accumulated during the past engine operation. Further, the control 66 may be provided integrally with the ECU 64 as a part of the functional element of the ECU 64.

  Next, the flow path switching operation according to the coolant temperature of the engine cooling system according to the present embodiment will be described based on FIGS.

6, at the start of the engine E, the cooling water temperature T _w is a diagram explaining the flow of cooling water is lower than the predetermined EGR introduction threshold temperature T _THV. In this embodiment, EGR introduction threshold temperature _{T THV} is exhaust dew point temperature (e.g., about 50 ° C.), the cooling water temperature _{T w} is less temperature range, the condensed water from the EGR gas in the EGR cooler 22 It is set as a temperature threshold that can be generated.

If the cooling water temperature _{T w} is lower than the EGR introduction threshold temperature _{T THV,} heater core on-off valve 37 and in response to a command from ECU 64 (see FIG. 1), the bypass on-off valve 38 is closed. That is, as indicated by a solid line in FIG. 6, the cooling water pumped by the water pump 33 is supplied from the pump discharge port 41 to the EGR cooler inlet-side flow path 48A → EGR cooler 22 → The EGR cooler outlet-side flow path 46B is circulated in the order of the pump suction port 47. In this state, by heating the cooling water by heating device 50, cooling water temperature T _w it is early increased to EGR introduction threshold temperature T _THV, so that the early introduction of the EGR gas is achieved.

7, the cooling water temperature T _w is EGR introduction threshold temperature T _THV or more, and, the warm-up temperature of the engine E (e.g., about 80 ° C.) is a diagram illustrating the flow of cooling water until reached. When the cooling water temperature _{T w} reaches the EGR introduction threshold temperature _{T THV,} ECU 64 and the heater core on-off valve 37 in response to a command (see Fig. 1), the bypass on-off valve 38 is switched from the closed to the open. Also, until the cooling water temperature T _w reaches the warm-up temperature, the thermostat 34, the cooling water is circulated in the bypass passage 44 that bypasses the radiator 32.

  That is, as shown by a solid line in FIG. 7, the cooling water pumped by the water pump 33 is (1) from the pump discharge port 41, the oil cooler 35 → the water jacket 42 → the radiator inlet side flow path 43 → the thermostat 34 → The flow path flows in the order of the bypass flow path 45 → the pump suction port 47, and (2) flows from the radiator inlet side flow path 43 in the order of the heater core inlet side flow path 46A → heater core 31 → heater core outlet side flow path 46B → pump suction port 47. (3) From the pump discharge port 41, a total of three channels are circulated in the order of EGR cooler inlet side channel 48A → EGR cooler 22 → EGR cooler outlet side channel 46B → pump suction port 47. The

8, the cooling water temperature T _w is the warm-up temperature (e.g., about 80 ° C.) is a diagram illustrating the flow of cooling water in the state has been reached. When the cooling water temperature T _w reaches the warm-up temperature, the flow path of the cooling water is switched from the bypass passage 45 to the radiator inlet-side channel 43 by the thermostat 34. That is, as shown by a solid line in FIG. 8, the cooling water pumped by the water pump 33 is (1) from the pump discharge port 41, the oil cooler 35 → the water jacket 42 → the radiator inlet side flow path 43 → the radiator 32 → Radiator outlet side flow path 44 → flow path flowing in order of pump suction port 47, (2) From radiator inlet side flow path 43, heater core inlet side flow path 46A → heater core 31 → heater core outlet side flow path 46B → pump inlet side flow path 47, and (3) a total of three flows flowing from the pump discharge port 41 in the order of the EGR cooler inlet side flow path 48A → EGR cooler 22 → EGR cooler outlet side flow path 48B → pump suction port 47. Circulated through the road.

  Next, the control flow of the engine cooling system of the present embodiment will be described based on FIG. This control starts simultaneously with the start of the engine E (starting by turning on the key switch of the ignition switch or starting the engine E by releasing the so-called idling stop function).

At step S100, EGR cooler-side cooling water temperature sensor 65 or, whether the cooling water temperature _{T w0} detected by the engine-side cooling water temperature sensor 39 is below the EGR introduction threshold temperature _{T THV} is determined. If the coolant temperature _{T w0} is less than the EGR introduction threshold temperature _{T THV} (Yes), the control proceeds to step S110. On the other hand, if the cooling water temperature _{T w0} is equal to or higher than the EGR introduction threshold temperature _{T THV} (negative), the control ends. In addition, the sensor value used for the said determination is not limited to the sensor value of each water temperature sensor 65,39, You may use the sensor value of the engine oil temperature sensor which is not shown in figure.

  In step S110, the heater core side opening / closing valve 37 and the bypass side opening / closing valve 38 are closed in response to a command from the ECU 64, and “cooling water temperature raising control” is performed to raise the temperature of the cooling water by the temperature raising device 50. Is done.

In step S120, whether or not the cooling water temperature _{T w1} of the EGR cooler 22 the outlet is detected by the EGR cooler-side cooling water temperature sensor 65 has reached the EGR introduction threshold temperature _{T THV} is determined. If the coolant temperature _{T w1} reaches the EGR introduction threshold temperature _{T THV} (Yes), the control proceeds to step S130, by opening the EGR valve 24 in response to a command from the ECU 64, the introduction of EGR gas Be started. On the other hand, when the cooling water temperature _{T w1} does not reach the EGR introduction threshold temperature _{T THV} (negative), the control is returned to step S110, "cooling MizuNoboru temperature control" it is continued.

In step S140, whether or not the cooling water temperature _{T w2} of the water jacket 42 outlet is detected by the engine-side cooling water temperature sensor 39 is above EGR introduction threshold temperature _{T THV} is determined. If the coolant temperature _{T w2} is less than the EGR introduction threshold temperature _{T THV} (negative), the control is returned to step S110, "cooling MizuNoboru temperature control" is continued. That is, after starting the introduction of the EGR gas, the engine side cooling is continued by continuing the “cooling water temperature increase control” until the cooling water temperature T _w2 in the engine side cooling water flow path 40 becomes _{equal to} or higher than the EGR introduction threshold temperature T _thv. It is possible to effectively prevent low-temperature cooling water from flowing from the water flow path 40 to the EGR cooler-side cooling water flow path 48.

In the determination of step S140, when the cooling water temperature _{T w2} is more EGR introduction threshold temperature _{T THV} (Yes), the control proceeds to step S150, the ends "Cooling MizuNoboru temperature control". That is, the heater core side opening / closing valve 37 and the bypass side opening / closing valve 38 are opened, and the temperature rise of the cooling water by the temperature raising device 50 is stopped, and then this control is terminated. If priority is given to the early warm-up of the engine E, the cooling water temperature _Tw2 is set to the warm-up temperature by _{raising the} temperature of the cooling water by the temperature raising device 50 while opening the valves 37 and 38 in step S150. You may continue until you reach it.

As described above in detail, according to the engine cooling system of the present embodiment, when the engine E is started, when the cooling water temperature is _lower than the EGR introduction threshold temperature T _thv that can generate condensed water by cooling the EGR gas, The cooling water in the engine side cooling water flow path 40 is stopped, the cooling water is circulated in the EGR side cooling water flow path 48, and the cooling water circulating in the EGR side cooling water flow path 48 is further heated by the temperature raising device 50. The “cooling water temperature rise control” is performed. As a result, as shown by the characteristic line A in FIG. 10, the time required for raising the cooling water to the EGR introduction threshold temperature T _thv (see t1) is the same as the characteristic line B in which the temperature rise control is not performed. Compared to the time (see t2), the exhaust emission performance can be effectively shortened, and the exhaust gas emission performance can be improved reliably by enabling early introduction of EGR gas.

  In addition, by configuring the EGR side cooling water flow path 48 with a short flow path in which only the temperature raising device 50 and the EGR cooler 22 are interposed, it is possible to suppress the heat radiation amount to the outside air of the cooling water. Compared to the technique described in Patent Document 1 that uses a long flow path at the time of warming, the temperature raising time of the cooling water can be surely shortened even at the time of cold start.

[Second Embodiment]
Next, based on FIG. 11, the engine cooling system which concerns on 2nd embodiment of this invention is demonstrated. In the second embodiment, in the first embodiment, the heater core side cooling waters 46 </ b> A and B are omitted, and the heater core 31 is arranged in the EGR cooler outlet side flow path 48 </ b> B downstream of the EGR cooler 22. With this configuration, the indoor heater can be used at an early stage while increasing the temperature of the cooling water flowing through the EGR cooler 22. Further, by eliminating the heater core side opening / closing valve 37 and using only one bypass side opening / closing valve 38 for the “cooling water temperature rise control”, the entire apparatus can be simplified and the cost can be reduced. it can.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

For example, at least one of the heater core on-off valve 37 and the bypass-side opening and closing valve 38, the cooling water temperature is closed when less than the EGR introduction threshold temperature T _THV, the coolant becomes equal to or higher than the EGR introduction threshold temperature T _THV opening You may comprise by the thermostat to do.

  The engine E is not limited to a diesel engine, and can be widely applied to other engines such as a gasoline engine.

DESCRIPTION OF SYMBOLS 10 Engine system 20 EGR apparatus 21 EGR flow path 22 EGR cooler 24 EGR valve 30 Engine cooling system 31 Heater core 32 Radiator 33 Water pump 34 Thermostat 35 Oil cooler 37 Heater core side opening / closing valve (valve)
38 Bypass side open / close valve (valve)
39 Engine side coolant temperature sensor (temperature sensor)
40 Engine-side cooling water flow path (engine-side flow path)
41 Pump discharge port 42 Water jacket (engine side flow path)
43 Radiator inlet-side flow path (engine-side flow path)
44 Radiator outlet side flow path (engine side flow path)
45 Bypass passage (engine side passage)
46A Heater core inlet side flow path (engine side flow path)
46B Heater core outlet side flow path (engine side flow path)
47 Pump intake port 48 EGR cooler side cooling water flow path (EGR cooler side flow path)
48A EGR cooler inlet side channel (EGR cooler side channel)
48B EGR cooler outlet channel (EGR cooler channel)
50 Temperature raising device 64 ECU (control unit)
65 EGR cooler side coolant temperature sensor (temperature sensor)

Claims (10)

A pump for pumping engine coolant,
An engine-side flow path that is connected to the suction port of the pump through at least the engine from the discharge port of the pump and distributes cooling water;
An EGR cooler-side flow passage that is connected to the suction port of the pump through an EGR cooler and distributes cooling water from the discharge port of the pump;
A temperature sensor for acquiring a temperature of cooling water flowing through at least one of the engine side flow path or the EGR cooler side flow path;
A valve capable of opening and closing the engine side flow path;
A temperature raising device capable of raising the temperature of the cooling water flowing through the EGR cooler side flow path;
When the temperature of the cooling water acquired by the temperature sensor is lower than a predetermined threshold temperature at which condensed water can be generated by cooling the EGR gas, the valve is closed to flow the cooling water in the engine side flow path. And a controller for performing temperature rise control for causing the cooling water to flow through the EGR side flow path and operating the temperature raising device to raise the temperature of the cooling water flowing through the EGR side flow path. An engine cooling system comprising: The temperature sensor is a cooler outlet temperature sensor disposed in the EGR cooler side flow path downstream of the EGR cooler;
The said control part starts introduction | transduction of EGR gas to the said EGR cooler, if the temperature of the cooling water acquired with the said cooler exit temperature sensor by implementation of the said temperature rising control reaches the said threshold temperature. Engine cooling system. As the temperature sensor, further comprising an engine outlet temperature sensor disposed in the engine side flow path downstream of the engine,
The engine cooling system according to claim 2, wherein the control unit continues the temperature increase control until the temperature of the cooling water acquired by the engine outlet temperature sensor from the start of introduction of the EGR gas exceeds the threshold temperature. . The engine side flow path further includes a radiator that cools cooling water flowing through the engine side flow path by heat exchange with outside air, and a bypass flow path that branches from between the engine and the radiator to bypass the radiator. Prepared,
The branch of the engine side flow path and the bypass flow path bypasses the cooling water from the radiator until the temperature of the cooling water that has passed through the engine reaches a predetermined warm-up temperature that is higher than the threshold temperature. A thermostat is provided for circulation to the bypass flow path,
The engine cooling system according to any one of claims 1 to 3, wherein the valve is provided in the bypass flow path. The engine side flow path further includes a heater core side flow path that is branched from between the engine and the thermostat and in which a heater core that heats air with heat of cooling water is interposed,
The engine cooling system according to claim 4, wherein the valve is provided in at least one of the bypass channel and the heater core side channel. The engine cooling system according to any one of claims 1 to 4, wherein a heater core that heats air with heat of cooling water is interposed in the EGR cooler side flow path downstream of the EGR cooler. The engine cooling system according to any one of claims 1 to 6, wherein the temperature raising device is disposed in the EGR cooler side flow path upstream of the EGR cooler. The engine cooling system according to any one of claims 1 to 7, wherein the temperature raising device is a heater type temperature raising device. The engine cooling system according to any one of claims 1 to 7, wherein the temperature raising device is an exhaust heat type temperature raising device. The engine cooling system according to any one of claims 1 to 7, wherein the temperature raising device is a regenerator type temperature raising device.

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