Exhaust gas recirculation system for internal combustion engines

Abstract

To introduce EGR gas to an intake passage while generation of condensation water is suppressed even when a temperature of cooling water is low.SOLUTION: An internal combustion engine 1 includes an exhaust gas recirculation device 200. The exhaust gas recirculation device 200 includes: an EGR passage 10 for introducing part of exhaust gas to an intake passage 4 as EGR gas; an EGR cooler 12 provided in the EGR passage 10 to exchange heat between cooling water of the internal combustion engine 1 and the EGR gas; and an EGR valve 230 provided in the EGR passage 10 between the intake passage 4 and the EGR cooler 12. The EGR valve 230 includes: a temperature sensitive part with which the EGR gas comes into contact; and a valve element that opens when a temperature of the EGR gas coming into contact with the temperature sensitive part is higher than a prescribed temperature to allow a flow of the EGR gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

Background Art

[0002] As described in Patent Document 1, an exhaust gas recirculation device having an EGR passage for introducing a part of the exhaust gas of an internal combustion engine into the intake passage as EGR gas is known. This exhaust gas recirculation device includes an EGR cooler provided in the EGR passage for performing heat exchange between the cooling water of the internal combustion engine and the EGR gas. Further, this exhaust gas recirculation device includes an EGR valve for opening and closing the EGR passage. This EGR valve has a valve actuator that is deformed according to the temperature of the cooling water and a valve body. When the temperature of the cooling water becomes a predetermined value or more, the valve actuator is deformed and the valve body is opened, so that EGR gas is introduced into the intake passage. When EGR gas is introduced into the intake passage by such an exhaust gas recirculation device, the combustion temperature of the air-fuel mixture decreases, so that the amount of NOx generated in the internal combustion engine decreases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the temperature of the EGR gas passing through the EGR cooler becomes lower than the dew point temperature, condensed water is generated in the EGR gas. Therefore, when the temperature of the EGR gas is lower than the dew point temperature, usually, the EGR valve is closed.

[0005] Incidentally, the higher the EGR gas flow rate in the EGR passage, the lower the cooling efficiency of the EGR cooler. As a result, the temperature of the EGR gas does not decrease easily as it passes through the EGR cooler, and the temperature of the EGR gas may exceed the dew point temperature. In this state where the temperature of the EGR gas is high, condensation is less likely to occur, making it possible to introduce EGR gas. However, with the conventional technology described above, the EGR valve does not open when the cooling water temperature of the internal combustion engine is low, so even if conditions are such that condensation is less likely to occur, it is not possible to introduce EGR gas. [Means for solving the problem]

[0006] An exhaust gas recirculation device for an internal combustion engine that solves the above problems comprises: an EGR passage for introducing a portion of the exhaust gas from the internal combustion engine as EGR gas into the intake passage; an EGR cooler provided in the EGR passage for performing heat exchange between the cooling water of the internal combustion engine and the EGR gas; and an EGR valve provided in the EGR passage between the intake passage and the EGR cooler. The EGR valve has a temperature-sensing part that comes into contact with the EGR gas, and a valve body that opens when the temperature of the EGR gas in contact with the temperature-sensing part is higher than a predetermined temperature, thereby allowing the flow of the EGR gas. [Effects of the Invention]

[0007] This internal combustion engine's exhaust gas recirculation system can introduce EGR gas into the intake passage while suppressing condensation, even when the coolant temperature is low. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the configuration of an exhaust gas recirculation device for an internal combustion engine according to one embodiment. [Figure 2] This is a cross-sectional view of the EGR valve of the same embodiment. [Figure 3] This is a timing chart to explain the operation of the embodiment. Figure 3(A) shows the changes in EGR gas temperature and EGR cooler water temperature. Figure 3(B) shows the changes in pressure loss in the EGR passage. [Figure 4] This flowchart shows the procedure for processing performed by the control device in a modified example of the same embodiment. [Figure 5] This is a cross-sectional view of the EGR valve in a modified example of the same embodiment. [Modes for carrying out the invention]

[0009] Below, one embodiment of an exhaust gas recirculation device for an internal combustion engine will be described with reference to Figures 1 to 3. <Configuration of an internal combustion engine> Figure 1 shows an internal combustion engine 1 equipped with an exhaust gas recirculation device according to this embodiment. The internal combustion engine 1 is an internal combustion engine that uses hydrogen gas as fuel.

[0010] The internal combustion engine 1 is equipped with a fuel injection valve 5 that supplies hydrogen gas, which is the engine fuel, to the combustion chamber. An intake passage 4 is connected to the internal combustion engine 1. A surge tank 2 is provided in the middle of the intake passage 4. A throttle valve 3 for regulating the amount of intake air is also provided in the intake passage 4, upstream of the surge tank 2.

[0011] An exhaust passage 6 is connected to the internal combustion engine 1. A supercharger 13 is provided in the middle of this exhaust passage 6, which uses exhaust pressure to supercharge the intake air. The supercharger 13 is a well-known variable displacement supercharger, and the boost pressure can be adjusted.

[0012] The supercharger 13 comprises a compressor housing 13a that houses a compressor wheel 13c and a turbine housing 13b that houses a turbine wheel 13t. The turbine housing 13b is located in the middle of the exhaust passage 6. A catalyst 7 for purifying exhaust gas is provided in the exhaust passage 6 downstream of the turbine housing 13b.

[0013] The compressor housing 13a is located in the middle of the intake passage 4. An intercooler 14 is provided in the intake passage 4 between the compressor housing 13a and the throttle valve 3. The intake air, whose temperature has risen due to supercharging, is cooled by the intercooler 14.

[0014] The internal combustion engine 1 is equipped with an exhaust gas recirculation device (hereinafter referred to as the EGR device) that introduces a portion of the exhaust gas into the intake passage 4 as EGR gas. The EGR device 200 has an EGR passage 10 for introducing EGR gas into the intake passage 4.

[0015] The EGR passage 10 is a passage that branches off from the exhaust passage 6 downstream of the turbine housing 13b and is connected to the intake passage 4 upstream of the compressor housing 13a. An EGR cooler 12 is provided in the middle of the EGR passage 10 to perform heat exchange between the cooling water of the internal combustion engine 1 and the EGR gas. The EGR cooler 12 is connected to a cooling water circuit 300 through which the cooling water of the internal combustion engine 1 circulates.

[0016] An EGR valve 230 is provided in the EGR passage 10 between the intake passage 4 and the EGR cooler 12 to open and close the EGR passage 10. The structure of the EGR valve 230 will be described later. When the EGR valve 230 opens, a portion of the exhaust gas passing through the exhaust passage 6 flows into the EGR passage 10 as EGR gas. The EGR gas that flows into the EGR passage 10 undergoes heat exchange in the EGR cooler 12 and is then introduced into the intake passage 4 and, together with fresh air, is reintroduced into the combustion chamber of the internal combustion engine 1. When EGR gas is introduced into the combustion chamber, the combustion temperature of the air-fuel mixture decreases, thereby suppressing the generation of NOx in the internal combustion engine 1.

[0017] The operating state of the internal combustion engine 1 and the like are detected by various sensors. For example, the crank angle sensor 60 detects the crank angle which is the rotation angle of the crankshaft of the internal combustion engine 1. Also, the air flow meter 61 detects the intake air amount GA which is the amount of air inhaled into the internal combustion engine 1. Further, the water temperature sensor 64 detects the water temperature THW which is the temperature of the cooling water of the internal combustion engine 1. Also, the air-fuel ratio sensor 65 is provided in the exhaust passage 6 upstream of the catalyst 7 and detects the air-fuel ratio AF. Also, the accelerator sensor 67 detects the accelerator operation amount ACCP which is the depression amount of the accelerator pedal. Also, the throttle sensor 68 detects the throttle opening TA which is the opening degree of the throttle valve 3.

[0018] The control device 100 controls the internal combustion engine 1. And the control device 100 operates various operation target devices such as the throttle valve 3, the fuel injection valve 5, the ignition plug of the internal combustion engine 1, and the supercharger 13.

[0019] The control device 100 includes a CPU 110 that performs arithmetic processing, a memory 120 in which control programs and data are stored, and the like. And the control device 100 executes processes related to various controls by the CPU 110 executing the programs stored in the memory 120.

[0020] Detection signals of the various sensors described above are input to the control device 100. Hydrogen gas which is the engine fuel has a wider range of combustible mixtures compared to gasoline and can burn even with a lean mixture. Therefore, the control device 100 adjusts the output of the internal combustion engine 1 through combustion control as follows.

[0021] That is, the control device 100 calculates a required output Pe, which is a required value of the engine output of the internal combustion engine 1, based on the accelerator operation amount ACCP or the like. The control device 100 sets a required injection amount Qd based on the required output Pe. The required injection amount Qd is the target value of the fuel injected from the fuel injection valve 5. The control device 100 calculates a required air amount GAd, which is the target value of the intake air amount required to obtain the target air-fuel ratio AFt, based on the target air-fuel ratio AFt and the required injection amount Qd. The target air-fuel ratio AFt in the present embodiment is a lean air-fuel ratio such as an air excess ratio λ = 2.5 to 3.0. Then, the control device 100 controls the fuel injection valve 5 so that the required injection amount Qd is obtained. Further, the control device 100 controls the opening degree of the throttle valve 3 and the boost pressure of the supercharger 13 so that the required air amount GAd is obtained. In this way, in the internal combustion engine 1, the output is adjusted by changing the air-fuel ratio of the air-fuel mixture through the adjustment of the fuel injection amount and the intake air amount.

[0022] <Structure of EGR valve> FIG. 2 shows the cross-sectional structure of the EGR valve 230. As shown in the figure, the EGR valve 230 includes a housing 220 that forms a part of the EGR passage 10. The housing 220 is formed, for example, in a tubular shape, one end of which is an inlet 221 through which the EGR gas that has passed through the EGR cooler 12 flows in, and the other end is an outlet 222 through which the EGR gas flows out toward the EGR passage 10 connected to the intake passage 4.

[0023] A displaceable valve body 223 is installed inside the housing 220. The valve body 223 is provided with a through hole 229. This through hole 229 is provided to allow a small amount of EGR gas to pass through the valve body 223, so that even when the valve body 223 is closed, the EGR gas that has passed through the EGR cooler 12 comes into contact with the temperature sensing element 227, which will be described later. The diameter of the through hole 229 is set, for example, as follows. That is, even if the EGR gas passing through the through hole 229 when the valve body 223 is closed contains condensed water, the diameter of the through hole 229 is set so that the amount of condensed water contained is less than the minimum amount of condensed water that would adversely affect the internal combustion engine 1. Examples of condensed water adversely affecting the internal combustion engine 1 include corrosion of parts, misfires, and erosion of the compressor wheel 13c.

[0024] A valve seat 224 is provided on the inner wall of the housing 220, to which the valve body 223 can abut. When the valve body 223 is in contact with the valve seat 224, it is in a closed state, blocking the flow of EGR gas from the inlet 221 to the outlet 222. When the valve body 223 is in a position away from the valve seat 224, it is in an open state, allowing the flow of EGR gas from the inlet 221 to the outlet 222.

[0025] A spring seat 225 is installed inside the housing 220 in the portion of the housing 220 that is closer to the outlet 222 than the valve body 223. Multiple holes pass through the spring seat 225. The presence of these holes allows the flow of EGR gas from upstream to downstream of the spring seat 225 in the housing 220. Alternatively, a gap may be provided between the spring seat 225 and the inside of the housing 220 to allow the flow of EGR gas from upstream to downstream of the spring seat 225 in the housing 220.

[0026] A spring 226 is interposed between the valve body 223 and the spring seat 225 to bias the valve body 223 toward the valve seat 224. A temperature-sensing element 227 is installed in the portion of the housing 220 between the valve body 223 and the spring seat 225. The temperature-sensing element 227 is fixed to the valve body 223 in a position downstream of the valve body 223 in the direction of EGR gas flow, and is inserted into the spring seat 225 so as to be movable relative to the spring seat 225.

[0027] A temperature-sensing material, wax, is sealed inside the temperature-sensing element 227. A guide bar 228, fixed to the housing 220, is inserted into the temperature-sensing element 227. The wax sealed inside the temperature-sensing element 227 solidifies and shrinks when the temperature of the EGR gas in contact with the temperature-sensing element 227 is low, and melts and expands when the temperature is high.

[0028] When the volume change of the wax alters the insertion depth of the guide bar 228 into the temperature sensing element 227, the temperature sensing element 227 is displaced together with the valve body 223. This displacement of the valve body 223 causes the valve body 223 in the EGR valve 230 to open or close. More specifically, when the temperature of the EGR gas reaches a predetermined opening temperature Tref, the wax melts and expands, causing the valve body 223 to open. The opening temperature Tref is, for example, the lowest temperature of the EGR gas at which the generation of condensed water can be suppressed.

[0029] Thus, the valve body 223 is configured to open when the temperature of the EGR gas in contact with the temperature sensing element 227 is higher than a predetermined opening temperature Tref, thereby allowing the flow of EGR gas.

[0030] <Operation of this embodiment> Figure 3 shows the changes in each value after engine startup. Hereafter, a state in which the EGR gas flow rate in the EGR passage 10 is high will be referred to as high flow rate, and a state in which the EGR gas flow rate in the EGR passage 10 is low compared to this high flow rate will be referred to as low flow rate. A state in which the EGR gas flow rate is high is a state in which the exhaust gas flow rate is high. A state in which the exhaust gas flow rate is high is, for example, when the internal combustion engine 1 is operating at high rotation speed or under high load.

[0031] Line L1 in Figure 3(A) shows the change in the water temperature of the cooling water supplied to the EGR cooler 12. Line L2 in Figure 3(A) shows the change in the gas temperature of the EGR gas that has passed through the EGR cooler 12 at high flow rates. Line L3 in Figure 3(A) shows the change in the gas temperature of the EGR gas that has passed through the EGR cooler 12 at low flow rates. Line L4 in Figure 3(B) shows the change in the pressure loss in the EGR passage 10 at high flow rates. Line L5 in Figure 3(B) shows the change in the pressure loss in the EGR passage 10 at low flow rates.

[0032] As shown in Figure 3, when engine starting begins at time t0, the temperature of the coolant in the internal combustion engine 1 rises, and consequently, the water temperature of the EGR cooler 12, indicated by line L1, also rises. Then, when the rise in the coolant temperature subsides, the rise in the water temperature of the EGR cooler 12 also subsides.

[0033] As the water temperature of the EGR cooler 12 rises, the gas temperature of the EGR gas also rises. At low flow rates, the cooling efficiency of the EGR cooler is high, so the difference between the water temperature of the EGR cooler 12 and the gas temperature of the EGR gas is small, as shown by lines L1 and L3. Then, at time t2, when the gas temperature reaches the valve opening temperature Tref, the EGR valve 230 begins to open. As a result, as shown by line L5, the pressure loss in the EGR passage 10 begins to decrease and the introduction of EGR gas begins. After that, when the EGR valve 230 is fully open, the decrease in the pressure loss in the EGR passage 10 stabilizes and becomes a constant value. At low flow rates, the difference between the water temperature of the EGR cooler 12 and the gas temperature of the EGR gas is small. Therefore, the opening timing of the EGR valve 230 is the same as that of an EGR valve in which cooling water, rather than EGR gas, comes into contact with the temperature sensing element 227.

[0034] On the other hand, at high flow rates, the cooling efficiency of the EGR cooler decreases, so the difference between the water temperature of the EGR cooler 12 and the gas temperature of the EGR gas increases, as shown by lines L1 and L2, and the temperature of the EGR gas does not decrease easily as it passes through the EGR cooler 12. As a result, the temperature of the EGR gas exceeds the dew point temperature. In this state where the temperature of the EGR gas is high, condensation is less likely to occur, making it possible to introduce the EGR gas. At high flow rates, the gas temperature of the EGR gas is higher than at low flow rates, so the gas temperature reaches the valve opening temperature Tref at time t1, which is earlier than time t2. When the gas temperature reaches the valve opening temperature Tref, the EGR valve 230 starts to open. As a result, as shown by line L4, the pressure loss in the EGR passage 10 begins to decrease and the introduction of EGR gas begins. This timing of EGR gas introduction at high flow rates is earlier than the timing of EGR gas introduction at low flow rates. When the EGR valve 230 is fully open, the decrease in pressure loss in the EGR passage 10 stabilizes and becomes constant.

[0035] <Effects of this embodiment> (1) When the temperature of the EGR gas in contact with the temperature sensing element is higher than a predetermined temperature, the valve body of the EGR valve opens. Therefore, even when the temperature of the cooling water is low, the EGR gas can be introduced into the intake passage while suppressing the generation of condensate.

[0036] (2) When the EGR gas flow rate in the EGR passage 10 is high, the timing of introducing the EGR gas into the intake passage 4 becomes earlier compared to when the EGR gas flow rate is low. Therefore, a large amount of EGR gas can be introduced into the intake passage 4 earlier.

[0037] (3) The valve body 223 is a valve body having a through hole 229. Therefore, even when the valve body 223 is closed, the EGR gas flows through the through hole 229, so that a flow of EGR gas is generated inside the EGR valve 230. Consequently, even when the valve body 223 is closed, the EGR gas comes into contact with the temperature sensing element 227, so that the valve body 223 can be opened and closed according to the temperature of the EGR gas.

[0038] (4) The EGR valve 230 is opened and closed by the temperature sensing element 227. Therefore, it is less expensive than EGR valves in which the opening and closing of the valve body is controlled using solenoid valves or the like, but it is inferior in terms of controllability of the amount of gas introduced when introducing EGR gas.

[0039] In this respect, the internal combustion engine 1 is an internal combustion engine that uses hydrogen gas as fuel. Compared to an internal combustion engine that uses gasoline as fuel, the hydrogen gas-fueled internal combustion engine 1 has a wider range of combustible air-fuel mixtures and higher resistance to misfires. Therefore, precise control of the gas amount is not required when introducing EGR gas. Accordingly, in this embodiment, the EGR device 200 of the hydrogen gas-fueled internal combustion engine 1 is equipped with an EGR valve 230 having the temperature-sensing section 227 described above. Thus, an inexpensive EGR valve can be used while suppressing the occurrence of misfires.

[0040] (5) When an EGR valve is used in which the opening and closing of the valve body is controlled using a solenoid valve or the like, the development time required for the program that controls the solenoid valve, the time required to determine the appropriate values ​​during control, and the drive circuit that drives the solenoid valve are required, which increases costs. In this respect, the EGR valve 230 of this embodiment has the valve body 223 opened and closed by the temperature sensing unit 227, so such an increase in costs can be suppressed.

[0041] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0042] The internal combustion engine 1 may perform combustion with a fuel-air mixture with an excess air ratio of 1 or less when the EGR valve 230 is open. Figure 4 shows the procedure of the process that the control device 100 executes to implement this modification example. The process shown in Figure 2 is realized by the CPU 110 executing a program stored in the memory 120 of the control device 100 at predetermined intervals. In the following, the step number of each process is represented by a number preceded by "S".

[0043] In the series of processes shown in Figure 4, the control device 100 determines whether or not the EGR valve 230 is open (S100). In process S100, the method for determining whether or not the EGR valve 230 is open can be appropriately adopted. For example, when EGR gas is introduced into the intake passage 4 by opening the EGR valve 230, the air-fuel ratio AF detected by the air-fuel ratio sensor 65 changes. Therefore, the control device 100 determines that the EGR valve 230 is open when it determines that such a change in the air-fuel ratio AF has been detected.

[0044] If the EGR valve 230 is determined to be open during the S100 process (S100: YES), the control device 100 performs stoichiometric combustion (S110). Stoichiometric combustion is an example of combustion using a fuel-air mixture with an excess air ratio of 1 or less. The control device 100 performs stoichiometric combustion by adjusting the opening of the throttle valve 3 and the amount of fuel injected from the fuel injector 5. Alternatively, as the S110 process, rich combustion, which is an example of combustion using a fuel-air mixture with an excess air ratio of 1 or less, may be performed.

[0045] On the other hand, if it is not determined that the EGR valve 230 is open during the S100 process (S100: NO), the control device 100 performs lean combustion (S120). Lean combustion is combustion of a fuel-air mixture with an excess air ratio greater than 1. In this embodiment, lean combustion, which is combustion of a fuel-air mixture with an excess air ratio significantly greater than 1, is performed as lean combustion by the S120 process. The control device 100 performs lean combustion by adjusting the opening of the throttle valve 3 and the amount of fuel injected from the fuel injector 5.

[0046] Then, once the control device 100 has executed the process in S110 or S120, it terminates this process. According to this modification example, when the EGR valve 230 is open, combustion is performed with a fuel-air mixture with an excess air ratio of 1 or less. In other words, stoichiometric combustion or rich combustion is performed. Compared to lean combustion, which is combustion with a fuel-air mixture with an excess air ratio significantly greater than 1, stoichiometric and rich combustion tend to increase engine output but also increase NOx emissions. In this modification example, when the EGR valve 230 is open and EGR gas is being introduced, combustion is performed with a fuel-air mixture with an excess air ratio of 1 or less. Therefore, it is possible to increase engine output while suppressing NOx emissions.

[0047] In the above embodiment, a through hole 229 is provided in the valve body 223. Alternatively, the EGR valve 230 may have a bypass passage through which EGR gas flows, bypassing the valve body 223. Figure 5 shows the cross-sectional structure of the EGR valve 230 in this modified example. As shown in Figure 5, the valve body 223 of the EGR valve 230 in this modified example does not have the through hole 229. A bypass passage 240 is integrally molded into the housing 220 of the EGR valve 230. The bypass passage 240 is a passage through which the EGR gas flowing in from the inlet 221 bypasses the valve body 223 and flows to the outlet 222. It is desirable to set the direction of formation of the bypass passage 240 so that the EGR gas flowing out of the bypass passage 240 is directed toward the temperature sensing element 227. Alternatively, the bypass passage 240 may be provided as a separate component rather than being integrally molded into the housing 220 of the EGR valve 230.

[0048] In this modified example, even when the valve body 223 is closed, the EGR gas flows through the bypass passage 240 and into the EGR valve 230, creating a flow of EGR gas inside the EGR valve 230. Therefore, even when the valve body 223 is closed, the EGR gas comes into contact with the temperature sensing element 227, allowing the valve body 223 to be opened and closed according to the temperature of the EGR gas.

[0049] The EGR valve 230 may have both a valve body 223 having the through hole 229 and a bypass passage 240. • Although internal combustion engine 1 was an internal combustion engine that used hydrogen gas as fuel, it may also be an internal combustion engine that uses other fuels. In this case as well, effects other than those described in (4) above can be obtained.

[0050] The temperature-sensing material of the temperature-sensing section 227 was wax, but other temperature-sensing materials may be used. Examples of other temperature-sensing materials include shape memory alloys and bimetals. The EGR system 200 was a low-pressure exhaust gas recirculation system in which an EGR passage 10 branched from the exhaust passage 6 downstream of the turbine housing 13b was connected to the intake passage 4 upstream of the compressor housing 13a. Alternatively, the EGR system 200 may be a high-pressure exhaust gas recirculation system in which an EGR passage 10 branched from the exhaust passage 6 upstream of the turbine housing 13b was connected to the intake passage 4 or surge tank 2 downstream of the throttle valve 3.

[0051] The control device 100 includes a CPU 110 and a memory 120, and executes software processing. However, this is merely an example. The control device 100 may include, for example, a dedicated hardware circuit (e.g., an ASIC) that processes at least a portion of the software processing performed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c): (a) A processing unit that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) A processing unit and a program storage device that execute a portion of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software circuits with processing units and program storage devices, and multiple dedicated hardware circuits. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software circuits and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0052] <Additional Notes> The technical concepts that can be understood from the above embodiments and modified examples are described below. [Note 1] An exhaust gas recirculation device for an internal combustion engine, comprising: an EGR passage for introducing a portion of the exhaust gas from the internal combustion engine as EGR gas into an intake passage; an EGR cooler provided in the EGR passage for performing heat exchange between the cooling water of the internal combustion engine and the EGR gas; and an EGR valve provided in the EGR passage between the intake passage and the EGR cooler, wherein the EGR valve has a temperature-sensing part in contact with the EGR gas, and a valve body that opens when the temperature of the EGR gas in contact with the temperature-sensing part is higher than a predetermined temperature, thereby allowing the flow of the EGR gas.

[0053] [Note 2] The exhaust gas recirculation device for an internal combustion engine as described in Note 1, wherein the temperature sensing element is located downstream of the valve body in the flow direction of the EGR gas, and the valve body is a valve body having a through hole.

[0054] [Note 3] The temperature sensing element is located downstream of the valve body in the flow direction of the EGR gas, and the EGR valve has a bypass passage through which the EGR gas flows, bypassing the valve body, in the exhaust gas recirculation device for an internal combustion engine as described in Note 1 or Note 2.

[0055] [Note 4] The internal combustion engine is an internal combustion engine that uses hydrogen gas as fuel. Exhaust gas recirculation device for an internal combustion engine as described in any of Notes 1 to 3. [Note 5] The exhaust gas recirculation device for the internal combustion engine described in any of Notes 1 to 4, which performs combustion with a mixture having an excess air ratio of 1 or less when the EGR valve is open. [Explanation of symbols]

[0056] 1…Internal combustion engine 4…Intake passage 6... Exhaust passage 7…Catalyst 10...EGR passage 12…EGR cooler 13…Supercharger 100...Control device 110...CPU 120...memory 200... Exhaust gas recirculation system (EGR system) 220... Housing 221...Inlet 222... Outlet 223... Valve body 224... Valve seat 225... Spring seat 226... Spring 227...Temperature sensing part 228... Guide bar 229... Through hole 230…EGR valve 240... Bypass passage 300…Cooling water circuit

Claims

1. An exhaust gas recirculation device for an internal combustion engine, An EGR passage for introducing a portion of the exhaust gas from the internal combustion engine into the intake passage as EGR gas, An EGR cooler is provided in the EGR passage and performs heat exchange between the cooling water of the internal combustion engine and the EGR gas. The system includes an EGR valve provided in the EGR passage between the intake passage and the EGR cooler, The aforementioned EGR valve is The temperature-sensing part that comes into contact with the EGR gas, The valve body opens when the temperature of the EGR gas in contact with the temperature sensing element is higher than a predetermined temperature, thereby allowing the flow of the EGR gas. The temperature sensing element is positioned downstream of the valve body in the flow direction of the EGR gas. The valve body is a valve body having a through hole. An exhaust gas recirculation device for internal combustion engines.

2. An exhaust gas recirculation device for an internal combustion engine, An EGR passage for introducing a portion of the exhaust gas from the internal combustion engine into the intake passage as EGR gas, An EGR cooler is provided in the EGR passage and performs heat exchange between the cooling water of the internal combustion engine and the EGR gas. The system includes an EGR valve provided in the EGR passage between the intake passage and the EGR cooler, The aforementioned EGR valve is The temperature-sensing part that comes into contact with the EGR gas, The valve body opens when the temperature of the EGR gas in contact with the temperature sensing element is higher than a predetermined temperature, thereby allowing the flow of the EGR gas. The temperature sensing element is positioned downstream of the valve body in the flow direction of the EGR gas. The EGR valve has a bypass passage through which the EGR gas flows, bypassing the valve body. An exhaust gas recirculation device for internal combustion engines.

3. The aforementioned internal combustion engine is an internal combustion engine that uses hydrogen gas as fuel. Exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2.

4. The internal combustion engine performs combustion with a fuel-air mixture with an excess air ratio of 1 or less when the EGR valve is open. Exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2.

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