JP2016135997A - Cooling system for internal combustion engine, internal combustion engine and cooling method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system for an internal combustion engine, the internal combustion engine and a cooling method for the internal combustion engine that can shorten warming-up time at start of the engine during a warming-up operation of the engine and can prevent a decline in exhaust gas purification processing capacity by maintaining a temperature of a catalyst supported by an exhaust emission control device at a level equal to or higher than an activation temperature also during a normal operation after warming-up of the engine.SOLUTION: In a cooling system 1 for an internal combustion engine including an intercooler system 16 on the downstream side of a supercharging compressor 15b, the intercooler system 16 is constituted by disposing an air-cooling type intercooler 16a exchanging heat with the atmosphere A1 and a water-cooling type intercooler 16b exchanging heat with engine cooling water W in parallel with each other, and a flow passage switching mechanism 16c is controlled in accordance with an operating state of an internal combustion engine 10.SELECTED DRAWING: Figure 1

Description

  The present invention can shorten the warm-up time when the engine is cold-started, and can maintain the temperature of the catalyst of the exhaust gas purification processing apparatus at or above the activation temperature during normal operation after the engine is warmed-up. The present invention relates to a cooling system for an internal combustion engine, an internal combustion engine, and a cooling method for the internal combustion engine, which can prevent a reduction in exhaust gas purification capacity.

  In an internal combustion engine such as a diesel engine, as shown in FIG. 3, a turbo system with an intercooler that combines a turbo-type supercharging system 15 and an intercooler 16a in order to achieve both high engine output and low exhaust gas level. Has been introduced. In this system, the intake air A introduced into the intake passage 12 from the atmosphere is compressed by the compressor 15b of the turbo-type supercharging system 15 so that the energy is increased and the temperature rises. Therefore, in order to lower the intake air temperature, the compressor 15b Heat is exchanged by the intercooler 16a on the downstream side. In this case, a part of the energy of the intake air A compressed by the compressor 15b is released to the atmosphere A1, and energy loss occurs.

  In relation to this energy loss countermeasure, although it is a power generation system, an engine main body cooling system that cools a required cooling part of the engine main body, and a supply air cooling system that cools pressurized air to be supplied to the engine, In the engine cooling system having the above structure, the charge air cooler arranged in the charge air cooling system is composed of two heat exchanging parts, a low temperature side heat exchanging part and a high temperature side heat exchanging part, and is circulated through the engine main body cooling system An engine cooling system that recovers heat from both a medium and a cooling medium that circulates through a high-temperature side heat exchange section of a charge air cooler has been proposed (see, for example, Patent Document 1).

  However, in such an engine cooling system, a heat exchanger for recovering waste heat for recovering heat from these cooling media and supplying hot water is provided, which is difficult to use for an internal combustion engine mounted on a vehicle. There is a problem.

  On the other hand, in a vehicle-mounted internal combustion engine that frequently starts and stops compared to the internal combustion engine of the power generation system, the intake air is cooled by an air-cooled intercooler regardless of the operating state of the engine in relation to the energy loss in the intake air. If the outside air temperature is low during normal operation after engine warm-up, the problem is that the warm-up time until the engine warms up becomes longer when the engine is cold started. There is a problem that the engine intake temperature is lowered, the exhaust temperature is lowered, and it becomes difficult to secure the activation temperature of the catalyst carried in the exhaust gas purification processing apparatus for exhaust aftertreatment.

  In this connection, two supercharged air coolers are provided, and when the internal combustion engine is cold started, the supercharged air is cooled only when the supercharged air cooler reaches a predetermined temperature by bypassing the supercharged air cooler, Supercharged air of a multi-cylinder internal combustion engine with a turbocharger that uses two supercharged air coolers for high-temperature supercharged air and uses one supercharged air cooler for intermediate-temperature supercharged air A cooling device has been proposed (see, for example, Patent Document 2).

  However, this configuration only changes the cooling capacity of the supercharged air cooler in three stages including the bypass according to the operating state of the internal combustion engine, and can reduce the amount of energy loss. There is a problem that the energy loss cannot be recovered, and the problem of a decrease in exhaust temperature after engine warm-up cannot be solved sufficiently.

JP 2000-186549 A JP-T-2004-511694

  On the other hand, the present inventor needs to warm the engine cooling water when the engine is cold started. Therefore, if a part of the energy of the intake air discharged by the intercooler can be transferred to the engine cooling water, the warming air can be warmed. Focusing on the fact that the engine cooling water temperature is 80 ° C to 90 ° C after the engine is warmed up and that the engine intake water can be warmed with this engine cooling water to increase the intake air temperature. Next, the engine intake air temperature and the exhaust temperature are in a substantially linear relationship (see FIG. 4), and the exhaust air temperature can be raised by raising the intake air temperature. As a result, it has been found that the exhaust temperature can be raised and the activation temperature of the catalyst of the exhaust gas purification device can be maintained.

  The present invention has been made in view of the above, and an object of the present invention is to reduce the warm-up time at the start of the engine during the warm-up operation of the engine and to perform the normal operation after the engine warm-up. Even in such a case, the internal combustion engine cooling system, the internal combustion engine, and the cooling of the internal combustion engine that can maintain the temperature of the catalyst carried by the exhaust gas purification processing apparatus at or above the activation temperature to prevent the exhaust gas purification processing capacity from being lowered. It is to provide a method.

  In order to achieve the above object, the internal combustion engine cooling system of the present invention is an internal combustion engine cooling system including an intercooler system downstream of a supercharging compressor, wherein the intercooler system exchanges heat with the atmosphere. And an air-cooled intercooler that exchanges heat with the engine coolant, and the intake air after passing through the compressor is either the air-cooled intercooler or the water-cooled intercooler. A flow path switching mechanism that switches the flow path of the intake air so as to flow through one side is provided, and a control device that controls the cooling system of the internal combustion engine provides the flow path switching mechanism according to the operating state of the internal combustion engine. Configured to control.

  According to this configuration, heat can be exchanged between the supercharged intake air and the atmosphere or the engine cooling water according to the operating state of the engine. Therefore, according to the outside air temperature and the warm-up state of the engine, the intake air Switch the heat exchange partner to air or engine cooling water, recover a part of the intake air energy compressed and heated by the compressor, and supply the intake air temperature to the cylinder more appropriately Accordingly, the temperature of the exhaust gas flowing into the exhaust gas purification device can be adjusted.

  In the above cooling system for an internal combustion engine, the engine cooling water for heat exchange with the water-cooled intercooler is guided from the outlet of a water pump to the water-cooled intercooler, and after exiting from the water-cooled intercooler, the EGR cooler When the engine is cold-started, the engine cooling water whose temperature has risen through the water-cooled intercooler can be allowed to flow into the EGR cooler at the time of cold start of the engine, so that EGR by the engine cooling water in the EGR cooler The degree of cooling of the gas can be reduced, the temperature of the EGR gas can be suppressed, and the adhesion of HC or the like in the exhaust gas whose temperature has been reduced can be prevented.

  Further, in the cooling system for an internal combustion engine described above, when the first temperature, which is the temperature of the engine cooling water, is less than a preset warm-up completion determination temperature threshold value during cold start of the internal combustion engine, Controls the flow path switching mechanism so as to flow through the water-cooled intercooler, and the flow path switching mechanism so that intake air flows through the air-cooled intercooler when the first temperature is equal to or higher than the warm-up completion determination temperature threshold. When configured to control the following, the following effects can be obtained.

  In other words, prior to the completion of warm-up at the cold start of the engine, in the conventional technology, part of the intake air energy was radiated to the atmosphere by the air-cooled intercooler. However, a part of this intake air energy was transferred to the water-cooled intercooler. By exchanging heat in the engine, it is possible to move to the engine cooling water and raise the temperature of the engine cooling water. Therefore, it is possible to shorten the warm-up time of the engine and realize early warm-up of the engine. In addition, after the warm-up is completed, the intake air can be cooled by the air-cooled intercooler as in the prior art.

  In the internal combustion engine cooling system, the temperature of the exhaust gas flowing into the exhaust gas purification device provided in the exhaust passage of the internal combustion engine during the normal operation after the warm-up operation of the internal combustion engine is completed. When the second temperature is equal to or higher than a preset purification process determination temperature threshold, the flow path switching mechanism is controlled so that the intake air flows through the air-cooled intercooler, and the second temperature is the purification process. When the temperature is less than the determination temperature threshold and the supercharging pressure is greater than or equal to a preset water-cooling switching determination pressure threshold, the flow path switching mechanism is controlled so that the intake air flows through the air-cooled intercooler, and the second When the temperature is less than the purification process determination temperature threshold and the supercharging pressure is less than the water cooling switching determination pressure threshold, the flow path is configured so that intake air flows through the water cooled intercooler. Configured to control the exchange mechanism. The term “normal operation” as used herein means that special engine operation is not included in PM regeneration operation, sulfur purge operation, NOx regeneration operation, etc. for the exhaust gas purification device.

  That is, when the second temperature is equal to or higher than the purification process determination temperature threshold value, the temperature of the exhaust gas flowing into the exhaust gas purification device is high, and there is no possibility that the temperature of the catalyst carried on the exhaust gas purification device becomes lower than the activation temperature. Cool the intake air with an air-cooled intercooler.

  However, the temperature of the exhaust gas flowing into the exhaust gas purification device is low because the second temperature is less than the purification processing determination temperature threshold, for example, the temperature of the catalyst is activated at 180 ° C. or less at the inlet of the exhaust gas purification device. When there is a possibility that the temperature is lower than the temperature, heat is exchanged with the intake air using engine cooling water whose water temperature is circulated at 80 to 90 ° C. with a water-cooled intercooler, and heat with the air at a temperature lower than this water temperature. By not performing replacement, the amount of temperature drop of the intake air can be reduced, the intake air temperature can be maintained at a relatively high temperature, the exhaust gas temperature can be maintained at a relatively high temperature, and the catalyst temperature can be maintained above the activation temperature. Like that.

  However, in an engine operating state where the supercharging pressure is equal to or higher than the water cooling switching determination pressure threshold and the supercharging pressure is high and the compressor outlet temperature is high, for example, 160 ° C. or higher, this high temperature intake air If it flows through the intercooler, the temperature of the engine cooling water becomes high, and when it exceeds 100 ° C, it may boil and bubbles may be generated. Therefore, the air flow type intercooler is controlled by controlling the flow path switching mechanism. To avoid bubbles in the engine coolant.

  Therefore, according to this configuration, during the normal operation after the engine warm-up operation is completed, the amount of decrease in the intake air temperature is adjusted while avoiding the generation of bubbles in the engine cooling water, and the exhaust temperature due to the decrease in the intake air temperature is adjusted. It is possible to suppress the decrease, maintain the activation temperature of the catalyst of the exhaust gas purification processing device, and prevent the exhaust gas purification performance from deteriorating during low load operation of the engine.

  When the control device is configured to perform control over a preset control time to switch the flow of intake air to the air-cooled intercooler and the water-cooled intercooler by the flow path switching mechanism, the flow path switching Therefore, it is possible to avoid a sudden change in the operating state of the engine.

  In order to achieve the above object, an internal combustion engine of the present invention includes the above cooling system for an internal combustion engine, and can achieve the same effects as the above cooling system for an internal combustion engine.

  In addition, the internal combustion engine cooling method of the present invention for achieving the above-described object includes an air-cooled intercooler that exchanges heat with the atmosphere downstream of a supercharging compressor, and a water-cooled type that exchanges heat with engine cooling water. An intercooler is provided in parallel, and a flow path switching mechanism is provided for switching the flow path of the intake air so that the intake air after passing through the compressor flows through either the air-cooled intercooler or the water-cooled intercooler. In the internal combustion engine cooling system in the internal combustion engine cooling system, the flow path switching mechanism is configured to be controlled in accordance with an operating state of the internal combustion engine.

  Further, in the internal combustion engine cooling method, when the internal combustion engine is cold started, if the first temperature, which is the temperature of the engine coolant, is less than a preset warm-up completion determination temperature threshold, The flow path switching mechanism is controlled to flow through a cooler, and the flow path switching mechanism is controlled so that intake air flows through the air-cooled intercooler when the first temperature is equal to or higher than the warm-up completion determination temperature threshold.

  Furthermore, in the cooling method for an internal combustion engine, a second temperature that is a temperature of exhaust gas flowing into an exhaust gas purification device provided in an exhaust passage of the internal combustion engine during normal operation after completion of warm-up operation of the internal combustion engine. Is equal to or higher than a preset purification process determination temperature threshold, the flow path switching mechanism is controlled so that intake air flows through the air-cooled intercooler, and the second temperature is less than the purification process determination temperature threshold. When the supercharging pressure is equal to or higher than a preset water-cooling switching determination pressure threshold, the flow path switching mechanism is controlled so that intake air flows through the air-cooled intercooler, and the second temperature is When the processing determination temperature threshold value is less than and the supercharging pressure is less than the water cooling switching determination pressure threshold value, the flow path switching mechanism is controlled so that intake air flows through the water cooling type intercooler.

  According to these methods, the same operational effects as those of the cooling system for the internal combustion engine can be obtained.

  According to the internal combustion engine cooling system, internal combustion engine, and internal combustion engine cooling method of the present invention, heat exchange can be performed between the supercharged intake air and the atmosphere or engine cooling water in accordance with the operating state of the engine. Therefore, according to the outside air temperature and the warm-up state of the engine, the heat exchange partner of the intake air is switched to the atmosphere or the engine cooling water, and the intake air is recovered while collecting a part of the intake air energy compressed and heated by the compressor. Accordingly, the temperature of the exhaust gas can be supplied into the cylinder, and accordingly, the temperature of the exhaust gas flowing into the exhaust gas purification device can also be adjusted.

It is a figure showing typically composition of a cooling system of an internal-combustion engine of an embodiment concerning the present invention. It is an example of the control flow of the cooling method of the internal combustion engine of embodiment which concerns on this invention, and is a figure which shows the time of engine warm-up operation. It is a figure which shows typically the structure of the cooling system of the internal combustion engine of a prior art. It is a figure for demonstrating the relationship between the intake air temperature with respect to an engine, and exhaust temperature.

  Hereinafter, an internal combustion engine cooling system, an internal combustion engine, and an internal combustion engine cooling method according to embodiments of the present invention will be described with reference to the drawings. The internal combustion engine of the embodiment according to the present invention is configured to include the cooling system 1 of the internal combustion engine of the embodiment according to the present invention, and has the same functions and effects as the cooling system 1 of the internal combustion engine described later. There is an effect. In this embodiment, a turbo-type supercharging system compressor is described as an example. However, a mechanical compressor may be used as long as the compressor can be supercharged. Further, it may be supercharged in a single stage or in multiple stages.

  As shown in FIG. 1, an engine (internal combustion engine) 10 including an internal combustion engine cooling system 1 according to an embodiment of the present invention includes an engine main body 11, an intake passage 12, and an exhaust passage 13. It has a turbo-charging system and an EGR system.

  The intake passage 12 is connected to the intake manifold 11a, and in order from the upstream side, an air flow rate (MAF) sensor (not shown), a compressor 15b of the turbocharger 15, an intercooler system 16, and an intake throttle valve 17 are provided. The exhaust passage 13 is connected to the exhaust manifold 11b and is provided with a turbine 15a of the turbocharger 15 and an exhaust gas purification processing device (not shown) in order from the upstream side. The EGR passage 14 is provided by connecting the exhaust manifold 11b and the intake manifold 11a, and an EGR cooler 14a and an EGR valve 14b are provided in this order from the upstream side.

  Then, the fresh air A introduced from the atmosphere is sent to the combustion chamber in the cylinder (cylinder) together with the EGR gas Ge flowing into the intake manifold 11a from the EGR passage 14 as necessary. The fuel is burned by being mixed with the fuel injected from the fuel injection device, thereby generating power in the engine 10. Then, the exhaust gas G generated by combustion in the engine 10 flows out to the exhaust manifold 11b, part of which flows as EGR gas Ge into the EGR passage 14, and the remaining exhaust gas Ga (= G-Ge) is exhausted. After flowing out into the passage 13 and being purified by the exhaust gas purifying apparatus via the turbine 15a, it is discharged to the atmosphere via a muffler (not shown).

  In the present invention, in the cooling system 1 for an internal combustion engine of the present invention, which includes a turbo-type supercharging system and includes an intercooler system 16 on the downstream side of the compressor 15b for supercharging, the intercooler system 16 Two intercoolers, an air-cooled intercooler 16a in which A exchanges heat with the atmosphere A1, and a water-cooled intercooler 16b in which intake air A exchanges heat with the engine coolant W, are arranged in parallel. Is done.

  In addition, a three-way valve (flow path switching mechanism) 16c that switches the flow path of the intake air A so that the intake air A after passing through the compressor 15b flows through either the air-cooled intercooler 16a or the water-cooled intercooler 16b, The passage 12 is provided at a portion branched from the compressor 15b to the flow paths of the two intercoolers 16a and 16b. In other words, the three-way valve 16c is provided at a branch point for switching the flow of the intake air A after passing through the compressor 15b to either the air-cooled intercooler 16a or the water-cooled intercooler 16b. Instead of the three-way valve 16c, an open / close valve may be provided on the upstream side of each of the air-cooled intercooler 16a and the water-cooled intercooler 16b.

  The flow path of the engine cooling water W for cooling the water-cooled intercooler 16b will be described. The engine cooling water W branches from the radiator 21, the water pump 22, the engine body 11, and the radiator 21 in this order to the turbine 15 a after branching from the downstream of the engine body 11 in the first passage 20 a. The second flow path 20b returning to the water pump 22 is used for circulation.

  In addition, when the thermostat 23 is arrange | positioned in the upstream of the radiator 21, and the temperature of the engine cooling water W becomes below the setting temperature of the thermostat 23, a part of 1st flow path 20a will be automatically made into the 4th flow path 20d ( It is configured to switch to the dotted line) and bypass the radiator 21 and enter the water pump 22.

  Further, a third flow of the engine cooling water W is branched from the downstream of the water pump 22 of the first flow path 20a to the water-cooled intercooler 16b, and merges upstream of the water pump 22 via the EGR cooler 14a. A path 20c is provided so that the engine cooling water W is repeatedly circulated in the order of the water pump 22, the water-cooled intercooler 16b, and the EGR cooler 14a.

  As a result, when the engine 10 is cold started, the engine cooling water W that has passed through the water-cooled intercooler 16b and has risen in temperature can be caused to flow into the EGR cooler 14a. Therefore, the engine cooling water W in the EGR cooler 14a The cooling degree of the EGR gas Ge can be reduced. Therefore, the temperature reduction of the EGR gas Ge can be suppressed, and the HC in the exhaust gas Ge whose temperature has been reduced can be prevented from adhering to the internal piping of the EGR cooler 14a.

  The intake manifold 11a is provided with a supercharging pressure sensor (MAP sensor) 30 for detecting the supercharging pressure P of the intake air A after being compressed and heated through the compressor 15b. An exhaust gas temperature sensor 31 for detecting the temperature Tg of the gas Ga is provided, and a water temperature sensor 32 for detecting the temperature Tw of the engine cooling water W is provided in the flow path 20a of the engine cooling water W, respectively.

  The supercharging pressure sensor 30 may be provided at any position in the intake passage 12 or the intake manifold 11a on the downstream side of the compressor 15b, and the exhaust temperature sensor 31 in the turbine 15a may be provided in the exhaust passage 13. Although it may be provided on either the upstream side or the downstream side, since the temperature of the exhaust gas Ga flowing into the exhaust gas purification device (not shown) is important, it is preferably provided on the immediate upstream side of the exhaust gas purification device. Further, the water temperature sensor 32 may be any one of the first to third flow paths 20a, 20b, and 20c of the engine cooling water W, and the arrangement position thereof is not limited, but determines the warm-up state of the engine 10. For this reason, it is preferably provided on the immediate downstream side of the engine body 11.

  Moreover, as shown in FIG. 1, the control apparatus 50 which controls the cooling system 1 of the internal combustion engine of this invention is provided. The control device 50 is normally incorporated in an engine control unit (ECU) that controls the overall operation state of the engine 10, but may be provided independently.

  And in the cooling system 1 of the internal combustion engine of this invention, this control apparatus 50 is comprised so that the three-way valve 16c may be controlled according to the driving | running state of the engine 10. FIG. Accordingly, heat exchange can be selectively performed between the supercharged intake air A and the atmosphere A1 or the engine cooling water W according to the operating state of the engine 10, so that the outside air temperature or the warm-up state of the engine 10 Accordingly, the heat exchange partner of the intake air A is switched to the atmosphere A1 or the engine cooling water W, and the temperature of the intake air A is increased while recovering a part of the energy of the intake air A compressed and heated by the compressor 15b. By supplying an appropriate temperature into the cylinder, the temperature of the exhaust gas Ga flowing into the exhaust gas purification device is adjusted.

  More specifically, when the first temperature Tw, which is the temperature of the engine coolant W, is less than the preset warm-up completion determination temperature threshold value Twc when the engine 10 is cold started, the intake air A is water-cooled. The three-way valve 16c is controlled so as to flow through the intercooler 16b. Further, when the first temperature Tw is equal to or higher than the warm-up completion determination temperature threshold value Twc, the three-way valve 16c is controlled so that the intake air A flows through the air-cooled intercooler 16a.

  Thus, prior to the completion of warm-up at the time of cold start of the engine 10, in the prior art, a part of the energy of the intake air A is radiated to the atmosphere A1 by the air-cooled intercooler 16a. Is moved to the engine cooling water W by heat exchange in the water-cooled intercooler 16b, and the engine cooling water W is heated. Therefore, the warm-up time of the engine 10 can be shortened and the early warm-up of the engine 10 can be realized. In addition, after the warm-up is completed, the intake air A is cooled by the air-cooled intercooler 16a as in the prior art.

  Further, the control device 50 is configured to perform the following control. During normal operation after completion of the warm-up operation of the engine 10, the second temperature Tg, which is the temperature of the exhaust gas Ga flowing into the exhaust gas purification device provided in the exhaust passage 13 of the engine 10, is a preset purification process determination temperature threshold value. When it is equal to or higher than Tgc, the three-way valve 16c is controlled so that the intake air A flows through the air-cooled intercooler 16a. The term “normal operation” as used herein means that special engine operation is not included in PM regeneration operation, sulfur purge operation, NOx regeneration operation, etc. for the exhaust gas purification device. Further, the purification process determination temperature threshold value Tgc is a temperature set based on a temperature necessary for ensuring the activation temperature of the exhaust gas purification process apparatus, and is calculated in advance through experiments or the like and stored in the control apparatus 50. Keep it.

  As a result, the temperature of the exhaust gas Ga flowing into the exhaust gas purification device is high when the second temperature Tg is equal to or higher than the purification treatment determination temperature threshold Tgc, and the temperature of the catalyst carried on the exhaust gas purification device may be lower than the activation temperature. When there is no air, the intake air A is cooled by the air-cooled intercooler 16a.

  Further, when the second temperature Tg is less than the purification process determination temperature threshold Tgc and the supercharging pressure Pg is equal to or higher than the preset water cooling switching determination pressure threshold Pgc, the intake air A flows through the air-cooled intercooler 16a. Thus, the three-way valve 16c is controlled.

  When the temperature of the intake air A rises due to supercharging and the intake air A is circulated through the water-cooled intercooler 16b, the water-cooling switching determination pressure threshold value Pgc increases the temperature Tw of the passage for passage of the engine cooling water W. For example, the pressure is 100 ° C. or higher, and the pressure at which bubbles are likely to be generated in the engine cooling water W. The pressure is calculated in advance through experiments or the like and stored in the control device 50.

  When the second temperature Tg is less than the purification process determination temperature threshold Tgc and the supercharging pressure Pg is less than the water cooling switching determination pressure threshold Pgc, the intake air A flows through the water cooling intercooler 16b in three directions. The valve 16c is controlled.

  As a result, the second temperature Tg is less than the purification process determination temperature threshold Tgc, and the temperature of the exhaust gas Ga flowing into the exhaust gas purification device is low, for example, 180 ° C. or less at the inlet of the exhaust gas purification device. When there is a possibility that the temperature becomes lower than the activation temperature, heat exchange with the intake air A is performed using the engine cooling water W circulating at a water temperature of 80 ° C. to 90 ° C. in the water cooling type intercooler 16b. That is, heat exchange with the atmosphere A1 having a temperature lower than the water temperature of the engine cooling water W is not performed. Accordingly, the amount of intake air temperature can be reduced, the intake air temperature can be maintained at a relatively high temperature, the exhaust gas temperature can be maintained at a relatively high temperature, and the catalyst temperature can be maintained at the activation temperature or higher.

  However, when the supercharging pressure Pg is equal to or higher than the water cooling switching determination pressure threshold Pgc, the supercharging pressure Pg is high and the outlet temperature of the compressor 15b is high, for example, 160 ° C. or higher. When the high-temperature intake air A is passed through the water-cooled intercooler 16b, the temperature of the engine cooling water W becomes high, and when it reaches 100 ° C. or more, it may boil and generate bubbles. In order to avoid this, the three-way valve 16c is controlled to cause the intake air A to flow through the air-cooled intercooler 16a to avoid the generation of bubbles in the engine coolant W.

  As a result, during normal operation after completion of the warm-up operation of the engine 10, the temperature decrease amount of the intake air temperature is adjusted while avoiding the generation of bubbles in the engine cooling water W, thereby suppressing the exhaust gas temperature decrease due to the intake air temperature decrease. Then, the activation temperature of the catalyst of the exhaust gas purification processing apparatus is maintained. As a result, it is possible to prevent the exhaust gas purification performance from being lowered during the low load operation of the engine 10.

  In addition, the control apparatus 50 is comprised so that the switching of the flow of the intake air A to the air cooling type intercooler 16a and the water cooling type intercooler 16b by the three-way valve 16c may be performed over a preset control time. As a result, a sudden change in the intake air temperature associated with the flow path switching is avoided, and a sudden change in the operating state of the engine 10 is avoided.

  In the internal combustion engine cooling system 1, as described above, during the warm-up operation of the engine 10, depending on whether or not the temperature Tw of the engine coolant W is less than a preset warm-up completion determination temperature threshold Twc, Further, during normal operation after the warm-up operation of the engine 10 is completed, whether or not the temperature Tg of the exhaust gas Ga is less than the purification process determination temperature threshold Tgc, and the supercharging pressure Pg of the compressor 15b is less than the water cooling switching determination pressure threshold Pgc. The three-way valve 16c is controlled according to both whether or not. The flow of the intake air A after passing through the compressor 15b is switched to either the air-cooled intercooler 16a or the water-cooled intercooler 16b by controlling the three-way valve 16c.

  Next, an internal combustion engine cooling method according to an embodiment of the present invention using the internal combustion engine cooling system 1 will be described with reference to the control flow of FIG.

  The control flow of FIG. 2 is a control flow during warm-up operation of the engine 10, and is a control flow that is called from an advanced control flow and starts when warming up when the engine 10 is cold-started. This is shown as a control flow that is repeatedly called and executed until the operation of the engine 10 is completed.

  When the control flow of FIG. 2 starts, it is determined in step S11 whether or not the first temperature Tw, which is the temperature of the engine coolant W, is equal to or higher than a preset warm-up completion determination temperature threshold Twc. When the first temperature Tw is lower than the warm-up completion determination temperature threshold value Twc in step S11 (NO), the process proceeds to step S15, the three-way valve 16c is controlled, and the intake air A is supplied to the water-cooled intercooler 16b. After the control of the three-way valve 16c is completed, the process returns and the present control flow is finished.

  On the other hand, when the temperature Tw of the engine coolant W is equal to or higher than the warm-up completion determination temperature threshold Twc in step S11 (YES), the process proceeds to step S12, and the purification process determination temperature at which the temperature Tg of the exhaust gas Ga is set in advance. It is determined whether or not it is equal to or greater than a threshold value Tgc.

  In step S12, when the temperature Tg of the exhaust gas Ga is equal to or higher than the purification process determination temperature threshold Tgc (YES), the process proceeds to step S14, and the three-way valve 16c is controlled to flow the intake air A to the air-cooled intercooler 16a. Then, after the control of the three-way valve 16c is completed, the process returns to end this control flow.

  On the other hand, when the temperature Tg of the exhaust gas Ga is less than the purification process determination temperature threshold value Tgc in step S12 (NO), the process proceeds to step S13, and in step S13, the supercharging pressure Pg of the compressor 15b is set in advance. It is determined whether or not the water-cooling switching determination pressure threshold Pgc is set.

  When the supercharging pressure Pg of the compressor 15b is equal to or higher than the water cooling switching determination pressure threshold value Pgc in step S13 (YES), the process proceeds to step S14, the three-way valve 16c is controlled, and the intake air A is supplied to the air cooling intercooler 16a. After the control of the three-way valve 16c is completed, the process returns and the present control flow ends.

  On the other hand, when the supercharging pressure Pg of the compressor 15b is less than the water cooling switching determination pressure threshold value Pgc in step S13 (NO), the process proceeds to step S15, and the three-way valve 16c is controlled to take in the water cooling type intercooler 16b. A is flown, and after the control of the three-way valve 16c is completed, the process returns and the present control flow is ended.

  In the middle of the control based on the control flow of FIG. 2, when the engine 10 is stopped, etc., an interrupt is generated and the return is made to return to the advanced control flow. To do.

  With these controls, in the internal combustion engine cooling method in the internal combustion engine cooling system 1 described above, the three-way valve 16c can be controlled in accordance with the operating state of the engine 10, and the temperature of the engine coolant W can be determined when the engine 10 is cold started. When the first temperature Tw is less than a preset warm-up completion determination temperature threshold Twc, the three-way valve 16c is controlled so that the intake air flows through the water-cooled intercooler 16b, and the first temperature Tw is the warm-up completion determination temperature. Above the threshold Twc, the three-way valve 16c can be controlled so that the intake air A flows through the air-cooled intercooler 16a.

  Further, the second temperature Tg, which is the temperature of the exhaust gas Ga flowing into the exhaust gas purification device provided in the exhaust passage 13 of the engine 10 during normal operation after completion of the warm-up operation of the engine 10, is a predetermined purification process determination. When the temperature is equal to or higher than the temperature threshold Tgc, the three-way valve 16c is controlled so that the intake air A flows through the air-cooled intercooler 16a, the second temperature Tg is less than the purification process determination temperature threshold Tgc, and the supercharging pressure Pg Is equal to or higher than the preset water cooling switching determination pressure threshold value Pgc, the three-way valve 16c is controlled so that the intake air A flows through the air cooling type intercooler 16a, and the second temperature Tg is less than the purification processing determination temperature threshold value Tgc. When the supercharging pressure Pg is less than the water cooling switching determination threshold value Pgc, the three-way valve 16c is controlled so that the intake air A flows through the water cooling type intercooler 16b. Door can be.

  According to the internal combustion engine cooling system 1, the internal combustion engine, and the internal combustion engine cooling method configured as described above, between the supercharged intake air A and the atmosphere A <b> 1 or the engine coolant W depending on the operating state of the engine 10. Since heat exchange can be performed, the heat exchange partner of the intake air A is switched to the atmosphere A1 or the engine cooling water W according to the outside air temperature or the warm-up state of the engine 10, and the intake air compressed and heated by the compressor 15b. While recovering a part of the energy of A, the temperature of the intake air A can be supplied to the cylinder at a more appropriate temperature, and accordingly, the temperature of the exhaust gas Ga flowing into the exhaust gas purifying device is also increased. You can adjust it.

1, 1X internal combustion engine cooling system 10, 10X engine (internal combustion engine)
11 Engine body 11a Intake manifold 11b Exhaust manifold 12 Intake passage 13 Exhaust passage 14 EGR passage 14a EGR cooler 14b EGR valve 15 Turbocharger (turbo supercharger)
15a Turbine 15b Compressor 16 Intercooler system 16a Air-cooled intercooler 16b Water-cooled intercooler 16c Three-way valve (flow path switching mechanism)
17 Intake throttle valves 20a, 20b, 20c, 20d, 20X Engine cooling water flow path 21 Radiator 22 Water pump 23 Thermostat 30 Supercharging pressure sensor (MAP sensor)
31 Exhaust temperature sensor 32 Water temperature sensor 50 Control device A Intake (fresh air)
A1 Atmosphere Ga Exhaust gas Ge EGR gas W Engine cooling water

Claims (7)

In a cooling system for an internal combustion engine provided with an intercooler system downstream of a supercharging compressor,
The intercooler system is configured by arranging in parallel an air-cooled intercooler that exchanges heat with the atmosphere and a water-cooled intercooler that exchanges heat with engine cooling water,
A flow path switching mechanism that switches the flow path of the intake air so that the intake air after passing through the compressor flows through either the air-cooled intercooler or the water-cooled intercooler;
A cooling system for an internal combustion engine, wherein a control device for controlling the cooling system for the internal combustion engine is configured to control the flow path switching mechanism in accordance with an operating state of the internal combustion engine. The control device is
During a cold start of the internal combustion engine,
When the first temperature, which is the temperature of the engine cooling water, is less than a preset warm-up completion determination temperature threshold, the flow path switching mechanism is controlled so that intake air flows through the water-cooled intercooler, and the first temperature is 2. The internal combustion engine cooling system according to claim 1, wherein the flow path switching mechanism is controlled so that intake air flows through the air-cooled intercooler at a warm-up completion determination temperature threshold value or more. The control device is
During normal operation after completion of warm-up operation of the internal combustion engine,
When the second temperature, which is the temperature of the exhaust gas flowing into the exhaust gas purification device provided in the exhaust passage of the internal combustion engine, is equal to or higher than a preset purification processing determination temperature threshold, the intake air flows through the air-cooled intercooler. Controlling the flow path switching mechanism as follows:
When the second temperature is lower than the purification treatment determination temperature threshold and the supercharging pressure is equal to or higher than a preset water-cooling switching determination pressure threshold, the flow path is configured so that intake air flows through the air-cooled intercooler. Control the switching mechanism,
When the second temperature is less than the purification treatment determination temperature threshold and the supercharging pressure is less than the water cooling switching determination pressure threshold, the flow path switching is performed so that intake air flows through the water cooling intercooler. The cooling system for an internal combustion engine according to claim 1 or 2, configured to control the mechanism.   The internal combustion engine provided with the cooling system of the internal combustion engine of any one of Claims 1-3.   An air-cooled intercooler that exchanges heat with the atmosphere and a water-cooled intercooler that exchanges heat with the engine coolant are arranged in parallel on the downstream side of the supercharging compressor, and the intake air after passing through the compressor is cooled by the air-cooling. An internal combustion engine cooling method in an internal combustion engine cooling system provided with a flow path switching mechanism that switches a flow path of intake air so as to flow through either the water-cooled intercooler or the water-cooled intercooler. A cooling method for an internal combustion engine, wherein the internal combustion engine is controlled in accordance with an operating state of the internal combustion engine.   When the internal combustion engine is cold started, if the first temperature, which is the temperature of the engine coolant, is less than a preset warm-up completion determination temperature threshold, the flow path switching mechanism is set so that intake air flows through the water-cooled intercooler. 6. The cooling method for an internal combustion engine according to claim 5, wherein the flow path switching mechanism is controlled so that intake air flows through the air-cooled intercooler when the first temperature is equal to or higher than the warm-up completion determination temperature threshold. During normal operation after completion of warm-up operation of the internal combustion engine,
When the second temperature, which is the temperature of the exhaust gas flowing into the exhaust gas purification device provided in the exhaust passage of the internal combustion engine, is equal to or higher than a preset purification processing determination temperature threshold, the intake air flows through the air-cooled intercooler. Controlling the flow path switching mechanism as follows:
When the second temperature is lower than the purification treatment determination temperature threshold and the supercharging pressure is equal to or higher than a preset water-cooling switching determination pressure threshold, the flow path is configured so that intake air flows through the air-cooled intercooler. Control the switching mechanism,
When the second temperature is less than the purification treatment determination temperature threshold and the supercharging pressure is less than the water cooling switching determination pressure threshold, the flow path switching is performed so that intake air flows through the water cooling intercooler. The method for cooling an internal combustion engine according to claim 5 or 6, wherein the mechanism is controlled.

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