JP2011058437A - Internal combustion engine equipped with egr system and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine equipped with an EGR system provided with an air-cooled EGR cooler in an intake manifold and executing EGR at appropriate EGR gas temperature while regulating formation of condensed water of EGR gas. <P>SOLUTION: The EGR cooler for cooling EGR gas A is formed out of the air-cooled EGR cooler 20 including an EGR gas cooling pipe 20a provided in the intake manifold 11, includes a first bypass passage 16 bypassing an intercooler 15 for cooling intake air A, and is provided with a first bypass valve 17 in the first bypass passage 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine equipped with an EGR system and a control method therefor, and more specifically, an air-cooled EGR cooler is provided in an intake manifold, and the temperature of EGR gas can be controlled to generate condensed water of EGR gas. The present invention relates to an internal combustion engine equipped with an EGR system capable of adjusting the temperature of EGR gas to an appropriate temperature while suppressing the above, and a control method thereof.

  In internal combustion engines such as diesel engines, it is known that NOx can be effectively reduced by mounting an EGR cooler in the EGR passage and performing EGR at a high EGR rate. In recent years, in order to further reduce NOx, since it is desired to improve the cooling performance of the EGR cooler, a water-cooled EGR cooler with high cooling efficiency has been used for the EGR cooler.

  FIG. 8 shows an internal combustion engine 1X equipped with an EGR system using the water-cooled EGR cooler 20X. In this example, a bypass passage 22 for bypassing the water-cooled EGR cooler 20X and a bypass valve 23 for operating whether or not to bypass are provided.

  However, when this water-cooled EGR cooler is used and the internal combustion engine is cold, the EGR gas is supercooled by the water-cooled EGR cooler, so that the combustion temperature in the cylinder decreases, and HC, CO In addition to the problem that the amount of exhaust gas increases, there is a problem that the temperature of the EGR gas falls below the dew point in the EGR cooler and the water in the EGR gas is condensed (liquefied) to generate condensed water. When this condensed water is generated, soot is accumulated in a lacquer shape, and the EGR cooler is blocked.

  For this reason, in some internal combustion engines, in order to perform not only EGR (COOL-EGR) due to cold air but also EGR (HOT-EGR) due to warm air, a bypass passage that bypasses the EGR cooler is provided, and a gas inlet of the EGR cooler is provided. A water-cooled EGR cooler with a bypass valve that can bypass the EGR gas without passing through the EGR cooler and perform EGR by warm air has been put into practical use.

  However, in this water-cooled EGR cooler with a bypass valve, when the internal combustion engine is cold, the bypass valve of the EGR cooler is opened to bypass the EGR gas, but the cooling performance (temperature efficiency) of the EGR cooler There is a problem that condensate is more likely to be generated as the temperature is improved. In addition, in order to avoid this problem, there is a problem that the EGR gas cannot be sufficiently cooled when EGR by warm air is performed in a wide operation region of the internal combustion engine.

  In this connection, a water-cooled EGR cooler and an air-cooled EGR cooler are provided in the EGR passage to cool the EGR gas using the engine cooling water with the water-cooled EGR cooler and the intake air with the air-cooled EGR cooler. An EGR system for an internal combustion engine that is used and cooled has been proposed (see, for example, Patent Document 1).

  In this EGR system, a bypass passage is provided in the intake passage on the upstream side of the compressor of the turbocharger, an air-cooled EGR cooler is disposed in the bypass passage, and the air temperature on the downstream side of the compressor is set to a predetermined temperature. When it exceeds the limit, the amount of intake air is reduced by the flow adjustment valve provided in the bypass passage, preventing the temperature of the intake air entering the compressor from becoming high and preventing the compressor from being damaged by high-temperature intake air. .

JP 2006-207467 A

  The present invention has been made in view of the above-described situation, and an object of the present invention is to provide an air-cooled EGR cooler in the intake manifold and suppress the generation of condensate of EGR gas while maintaining an appropriate EGR gas temperature. An internal combustion engine having an EGR system that can perform EGR and a control method thereof.

  In order to achieve the above object, an internal combustion engine having an EGR system of the present invention is an EGR gas cooling pipe provided with an EGR cooler for cooling EGR gas in an intake manifold in the internal combustion engine having an EGR system. The air-cooled EGR cooler is provided with a first bypass passage that bypasses the intercooler for cooling the intake air, and the first bypass valve is provided in the first bypass passage.

  According to this configuration, since the EGR cooler is formed of an air-cooled EGR cooler, condensation of moisture in the EGR gas due to the overcooling of the EGR gas can be suppressed. Further, when the engine is cold, the first bypass valve is opened, and the intake air (fresh air) is not cooled by the intercooler, but is sent to the air-cooled EGR, and the EGR gas is cooled by the warm intake air. Cooling can be suppressed. In addition, when the engine is warm, the EGR gas can be cooled with the intake air cooled by the intercooler by closing the first bypass valve, and the intake efficiency of the cylinder can be increased.

  In the internal combustion engine provided with the EGR system described above, if a second bypass passage for bypassing the air-cooled EGR cooler is provided, and a second bypass valve is provided in the second bypass passage, the EGR gas is supplied by the air-cooled EGR cooler. Since it can avoid cooling, it can avoid that EGR gas is overcooled and the condensation of the water | moisture content in EGR gas can be prevented.

  In the internal combustion engine equipped with the EGR system described above, if the cooling air volume adjusting means for adjusting the amount of intake air or the mixed gas of intake air and EGR gas hitting the EGR gas cooling pipe is provided, The following effects can be obtained.

  That is, when the engine is cold, in the low-speed operation region of the internal combustion engine, the amount of intake air or mixed gas that hits the EGR gas cooling pipe is reduced by the cooling air volume adjusting means, and the amount of heat released from the EGR gas cooling pipe is reduced. In addition, when the engine is warm, in the high-speed operation region of the internal combustion engine, the amount of intake air or mixed gas that hits the EGR gas cooling pipe is increased by the cooling air volume adjusting means, and the amount from the EGR gas cooling pipe is increased. The amount of heat radiation can be increased. Therefore, EGR can be performed at the temperature of the EGR gas suitable for the operating conditions of the internal combustion engine while suppressing the condensation of moisture in the EGR gas.

  This cooling air volume adjusting means can be formed by, for example, a rectifying valve (rectifying fin) provided at the inlet portion of the intake manifold and upstream of the EGR gas cooling pipe.

  The first bypass valve, the second bypass valve and the cooling air flow rate adjusting means are opened according to the operating conditions (engine speed, intake air temperature, exhaust gas temperature, coolant temperature, load, fuel injection amount) of the internal combustion engine. The temperature and the cooling air volume are controlled. Moreover, it is preferable to enhance the heat dissipation effect of the EGR gas cooling pipe by providing fins in the EGR gas cooling pipe. In addition, it is preferable that the high temperature side of the EGR gas cooling pipe is arranged on the inlet side of the mixed gas of the intake manifold so that the cooling effect is further increased.

  In the internal combustion engine equipped with the EGR system, when the engine is cold, the first bypass valve is opened, and in other cases, the first bypass valve is closed. By controlling the valve, when the engine is cold, the first bypass valve is opened, the intake air (fresh air) is not cooled by the intercooler, but sent to the air-cooled EGR cooler, and the EGR gas is cooled by the warm intake air The overcooling of the EGR gas can be suppressed. In addition, when the engine is warm, the EGR gas can be cooled with the intake air cooled by the intercooler by closing the first bypass valve, and the intake efficiency of the cylinder can be increased.

  In the internal combustion engine equipped with the EGR system, the first bypass valve and the second bypass valve are opened when the engine is cold, and the first bypass valve and the second bypass valve are opened in other cases. 2 When the bypass valve is controlled to be closed, the first and second bypass valves are opened by the control of the first and second bypass valves so that the intake air (fresh air) is cooled by the intercooler when the engine is cold. In addition, the EGR gas can be supplied to the intake manifold without being cooled by bypassing the air-cooled EGR cooler while being sent to the air-cooled EGR cooler, thereby suppressing overcooling of the EGR gas. Further, when the engine is warm, the EGR gas can be cooled by the intake air cooled by the intercooler by closing the first bypass valve, and the EGR gas can be cooled by the air-cooled EGR cooler by closing the second bypass valve. The intake efficiency in the cylinder can be increased.

  Further, in the internal combustion engine equipped with the EGR system described above, in the low speed operation region of the internal combustion engine when the engine is cold, the air volume adjusting means reduces the amount of intake air or mixed gas that hits the EGR gas cooling pipe, Control is made to reduce the amount of heat released from the EGR gas cooling pipe, and in the high-speed operation region of the internal combustion engine when the engine is warm, the amount of intake air or mixed gas that hits the EGR gas cooling pipe is increased, and EGR When controlling to increase the amount of heat released from the gas cooling pipe, by controlling the cooling air volume adjusting means, while suppressing the condensation of moisture in the EGR gas, at the temperature of the EGR gas suitable for the operating conditions of the internal combustion engine, EGR can be performed.

  According to the internal combustion engine provided with the EGR system and the control method thereof according to the present invention, by providing the cooler portion of the air-cooled EGR cooler in the intake manifold and controlling the temperature of the EGR gas in combination with the bypassed intercooler, EGR can be performed at the temperature of the EGR gas suitable for the operating conditions of the internal combustion engine while suppressing the generation of condensed water of the EGR gas.

It is the figure which showed the structure of the internal combustion engine provided with the EGR system of embodiment which concerns on this invention. It is the figure which showed the structure of the air-cooling type EGR cooler of the internal combustion engine provided with the EGR system of embodiment which concerns on this invention. It is a top view of the rectifying valve of the air volume adjusting means. FIG. 4 is a side view of FIG. 3. It is the figure which showed the case where the air quantity adjustment means was made to the direction which reduces the quantity of the intake air which hits an EGR gas cooling pipe, or mixed gas. It is the figure which showed the case where the air volume adjustment means was made to increase the quantity of the intake air or mixed gas which hits an EGR gas cooling pipe. It is the figure which showed the relationship between the operating state of an internal combustion engine, and the opening-and-closing state of each valve | bulb of an EGR valve, the 2nd bypass valve of an EGR cooler, an intake manifold rectification valve, and the 1st bypass valve of an intercooler. It is the figure which showed the structure of the internal combustion engine provided with the EGR system equipped with the water-cooled EGR cooler of the prior art.

  Hereinafter, an internal combustion engine provided with an EGR system according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, an internal combustion engine 1 equipped with an EGR system according to an embodiment of the present invention is provided with an intake manifold 11 and an exhaust manifold 12 in an engine body 10. An intake passage 13 through which intake air A and EGR gas Ge flows is connected. An exhaust passage 18 through which exhaust gas G flows is connected to the exhaust manifold 12.

  The intake passage 13 is provided with an air cleaner (not shown), an intake air amount sensor (not shown), an intake throttle valve (not shown), a compressor 14a of the turbocharger 14, an intercooler 15 and the like from the upstream side. The exhaust passage 18 is provided with a turbine 14b of the turbocharger 14, an exhaust gas processing device (not shown), a silencer (not shown) and the like from the upstream side. Further, an EGR passage 19 that connects the exhaust manifold 12 and the intake passage 13 between the intercooler 15 and the intake manifold 11 is provided. The turbine 14b is provided with a waste gate valve 14bc.

  In the present invention, in the intake passage 13, a first bypass passage 16 that flows intake air (fresh air) A by bypassing the intercooler 15 is provided, and a first bypass valve 17 is provided in the first bypass passage 16. Since the amount of intake air A passing through the intercooler 15 can be adjusted by opening and closing the first bypass valve 17 and adjusting the valve opening, the amount of cooling of the intake air A and the temperature of the intake air A are adjusted. it can.

  At the same time, as shown in FIG. 2, the EGR cooler provided in the EGR passage 19 is formed by an air-cooled EGR cooler 20 provided with an EGR gas cooling pipe 20 a provided in the intake manifold 11. In addition, a second bypass passage 22 is provided in which the EGR gas Ge flows around the air-cooled EGR cooler 20, and a second bypass valve 23 is provided in the second bypass passage 22.

  The air-cooled EGR cooler 20 includes an EGR gas cooling pipe 20a, fins 20b connected to the EGR gas cooling pipe 20a and disposed around the EGR gas cooling pipe 20a, and cooling air volume adjusting means. Since the cooling effect can be further increased by disposing the high temperature side of the EGR gas cooling pipe on the inlet side of the mixed gas of the intake manifold, it is preferable to configure in this way.

  This cooling air volume adjusting means is a rectifying valve (rectifying fin) provided at the inlet of the intake manifold 11 and upstream of the intake air A or mixed gas (intake air A and EGR gas Ge) A + Ge of the EGR gas cooling pipe 20a. ) 20c.

  The intake air A or the mixed gas A + Ge whose flow is controlled by the rectifying valve (rectifying fin) 20c hits the EGR gas cooling pipe 20a and the fin 20b, whereby the heat of the EGR gas Ge flowing inside the EGR gas cooling pipe 20a is increased. It is transmitted to the intake air A or the mixed gas A + Ge. In other words, the heat of the EGR gas Ge is radiated from the EGR gas cooling pipe 20a to the intake air A or the mixed gas A + Ge.

  As shown in FIGS. 3 and 4, the rectifying valve 20 c is formed to have a flat plate-like valve body 20 cc that rotates around a rotary shaft 20 cb connected to an actuator 20 ca such as an electric motor. As shown in FIG. 5, when the valve body 20cc of the air volume adjusting means is rotated in the closing direction, the amount of intake air A or mixed gas A + Ge impinging on the EGR gas cooling pipe 20a is reduced. When 20 cc is rotated in the opening direction (the direction opposite to the closing direction), the amount of intake air A or mixed gas A + Ge impinging on the EGR gas cooling pipe 20a is increased.

  With this configuration, by controlling the rotation of the actuator 20ca, the amount of the intake air A or the mixed gas A + Ge that strikes the EGR gas cooling pipe 20a can be increased or decreased, and the temperature of the EGR gas Ge can be adjusted. The intake air A or the mixed gas A + Ge passes through the outside of the EGR gas cooling pipe 20a and then enters the intake passage provided in the cylinder head 10a.

  Next, a control method in the internal combustion engine 1 will be described. As shown in FIGS. 1 and 2, in the EGR system of the internal combustion engine 1, the EGR valve 21, the second bypass valve 23 of the EGR cooler 20, the rectifying valve 20 c in the intake manifold 11, and the first bypass valve of the intercooler 15. 17 is controlled to open and close. In this control, as shown in FIG. 7, depending on the operating state of the internal combustion engine, that is, the low, medium and high speeds of the engine when the engine is cold, and the low and medium speeds of the engine when the engine is warm. Depending on the high-speed driving state, the open / closed state is properly used.

  That is, when the internal combustion engine 1 is cold, the EGR valve 21 is opened to perform EGR, and the second bypass valve 23 of the EGR cooler 20 is opened to avoid cooling of the EGR gas Ge. Further, the first bypass valve 17 of the intercooler 15 is opened, and the intake air A that is not cooled is caused to flow into the intake manifold 11. This prevents overcooling of the EGR gas Ge and prevents moisture in the EGR gas Ge from condensing.

  In the low-speed operation region when the engine is cold, the rectifying valve 20c in the intake manifold 11 is closed to reduce the amount of intake air A or mixed gas A + Ge that hits the EGR gas cooling pipe 20a. Thereby, the cooling amount of the EGR gas Ge is reduced. Next, in the medium speed operation region, the amount of intake air A or mixed gas A + Ge that strikes the EGR gas cooling pipe 20a is adjusted by adjusting the valve opening of the rectifying valve 20c. As a result, the cooling amount of the EGR gas Ge is adjusted to obtain an appropriate EGR gas temperature. Further, in the high-speed operation region, the rectifying valve 20c is opened to increase the amount of intake air A or mixed gas A + Ge that hits the EGR gas cooling pipe 20a. As a result, the cooling amount of the EGR gas Ge is increased, and an appropriate EGR gas temperature is obtained.

  Further, when the internal combustion engine 1 is warm, the EGR valve 21 is opened to perform EGR, and the second bypass valve 23 of the EGR cooler 20 is closed so that the EGR gas Ge is cooled by the air-cooled EGR cooler 20. Cool with. Further, the first bypass valve 17 of the intercooler 15 is closed, and the cooled intake air A is caused to flow into the intake manifold 11 to increase the cooling capacity of the air-cooled EGR cooler 20. Thereby, the temperature of the EGR gas Ge is lowered to an appropriate EGR gas temperature.

  Further, in the low-speed operation region when the engine is warm, the rectifying valve 20c in the intake manifold 11 is closed to reduce the amount of intake air A or mixed gas A + Ge that hits the EGR gas cooling pipe 20a. Thereby, the cooling amount of the EGR gas Ge is reduced. Next, in the medium speed operation region, the amount of intake air A or mixed gas A + Ge that strikes the EGR gas cooling pipe 20a is adjusted by adjusting the valve opening of the rectifying valve 20c. As a result, the cooling amount of the EGR gas Ge is adjusted to obtain an appropriate EGR gas temperature. Further, in the high-speed operation region, the rectifying valve 20c is opened to increase the amount of intake air A or mixed gas A + Ge that hits the EGR gas cooling pipe 20a. As a result, the cooling amount of the EGR gas Ge is increased, and an appropriate EGR gas temperature is obtained.

  By controlling the valves 17, 20 c, 21, and 23 described above, the temperature of the EGR gas Ge can be effectively controlled both when the internal combustion engine 1 is cold and warm.

  Therefore, according to the internal combustion engine including the EGR system having the above-described configuration and its control method, the EGR gas cooling pipe 20a that is the cooler of the air-cooled EGR cooler 20 is provided in the intake manifold 11 and includes the first bypass passage 16. By controlling the temperature of the EGR gas Ge in combination with the intercooler 15, the EGR is performed at the temperature of the EGR gas Ge suitable for the operating conditions of the internal combustion engine 1 while suppressing the generation of condensed water of the EGR gas Ge. Can do.

  According to the internal combustion engine equipped with the EGR system of the present invention and the control method therefor, an EGR gas cooling pipe of an air-cooled EGR cooler is provided in the intake manifold, and the temperature of the EGR gas is controlled in combination with an intercooler with a bypass passage. Thus, EGR can be performed at the temperature of the EGR gas suitable for the operating conditions of the internal combustion engine while suppressing the generation of condensed water of the EGR gas, and therefore, it can be used for an internal combustion engine mounted on an automobile or the like.

1 Internal combustion engine
11 intake manifold 13 intake passage 15 intercooler 16 first bypass passage 17 first bypass valve 18 exhaust passage 19 EGR passage 20 air-cooled EGR cooler 20a EGR gas cooling pipe 20b fin 20c rectifying valve 21 EGR valve 22 second bypass passage 23 second 2 Bypass valve A Intake air A + Ge mixed gas G Exhaust gas Ge EGR gas

Claims (6)

  In an internal combustion engine equipped with an EGR system, an EGR cooler for cooling EGR gas is formed by an air-cooled EGR cooler provided with an EGR gas cooling pipe provided in an intake manifold, and an intercooler for cooling intake air An internal combustion engine equipped with an EGR system, wherein a first bypass passage for bypassing the first bypass passage is provided, and a first bypass valve is provided in the first bypass passage.   2. An internal combustion engine having an EGR system according to claim 1, wherein a second bypass passage that bypasses the air-cooled EGR cooler is provided, and a second bypass valve is provided in the second bypass passage.   3. The EGR system according to claim 1, further comprising a cooling air amount adjusting unit that adjusts an amount of intake air that hits the EGR gas cooling pipe or an amount of mixed gas of intake air and EGR gas. 4. Internal combustion engine equipped with.   An internal combustion engine comprising the EGR system according to any one of claims 1 to 3, wherein the first bypass valve is opened when the engine is cold, and the first bypass valve is otherwise. A method for controlling an internal combustion engine equipped with an EGR system characterized in that   The internal combustion engine having the EGR system according to any one of claims 2 and 3, wherein when the engine is cold, the first bypass valve and the second bypass valve are opened, and in other cases Closes the first bypass valve and the second bypass valve, and controls the internal combustion engine with an EGR system.   4. An internal combustion engine equipped with the EGR system according to claim 3, wherein in the low speed operation region of the internal combustion engine when the engine is cold, the air volume adjusting means reduces the amount of intake air or mixed gas that hits the EGR gas cooling pipe. In addition, control is performed so as to reduce the amount of heat released from the EGR gas cooling pipe, and in the high-speed operation region of the internal combustion engine when the engine is warm, the amount of intake air or mixed gas that hits the EGR gas cooling pipe is increased. A control method for an internal combustion engine equipped with an EGR system, wherein control is performed so as to increase the amount of heat released from the EGR gas cooling pipe.

Images