JP5845619B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

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

  Conventionally, in order to reduce fuel consumption of an internal combustion engine, an exhaust gas recirculation device that recirculates gas burned in a combustion chamber as EGR gas to an intake passage has been proposed (for example, see Patent Document 1).

  The exhaust gas recirculation device disclosed in Patent Document 1 adjusts the flow rate of an EGR passage that recirculates part of the exhaust gas flowing through the exhaust passage to the intake passage and the EGR gas that is provided in the EGR passage and recirculates to the intake passage. It has an EGR valve and an EGR cooler that is provided on the exhaust passage side from the EGR valve and cools the EGR gas to be recirculated by heat exchange with the engine cooling water. A part of the engine cooling water discharged from the water pump is supplied to the EGR cooler, and the EGR gas is cooled by heat exchange between the EGR gas flowing inside the EGR cooler and the engine cooling water.

  Further, in the internal combustion engine equipped with the exhaust gas recirculation device disclosed in Patent Document 1, the EGR gas is caused to flow into the EGR cooler even though the EGR valve is fully closed due to exhaust pulsation in the exhaust passage. Inflowing, condensed water is generated in the EGR passage and the like, and this condensed water causes corrosion of each member.

  Therefore, in addition to the exhaust gas recirculation device disclosed in Patent Document 1, the exhaust gas is further provided with a switching valve that is provided on the exhaust passage side of the EGR cooler and shuts off the EGR gas supplied from the exhaust passage to the EGR passage. A reflux apparatus has been proposed (see, for example, Patent Document 2).

  The exhaust gas recirculation device disclosed in Patent Document 2 connects an intake passage and an exhaust passage to recirculate part of the exhaust from the internal combustion engine to the intake passage, and cools EGR gas in the middle of the EGR passage. An EGR cooler, determination means for determining whether or not condensed water generated by cooling the EGR gas in the EGR cooler stays in the EGR cooler, and the determination means determines that the condensed water stays in the EGR cooler; And a switching valve that suppresses the inflow of the EGR gas to the EGR cooler when the EGR gas is not recirculated to the intake passage.

  In the exhaust gas recirculation device disclosed in Patent Document 2, since the switching valve is closed when the EGR valve is fully closed, the EGR gas is prevented from flowing into the EGR cooler, and the inside of the EGR cooler It is possible to suppress the retention of condensed water in

JP 2009-228530 A JP 2007-303381 A

  However, in the conventional exhaust gas recirculation device described above, the EGR valve and the switching valve are opened simultaneously when the start condition of EGR control for recirculating exhaust gas is satisfied. Therefore, when the EGR valve shifts to the open state in order to start the EGR control, the exhaust gas does not flow into the EGR passage, and there is a possibility that the introduction delay of the EGR gas into the intake passage may occur.

  Further, when the EGR control end condition is satisfied, the EGR valve and the switching valve are closed simultaneously. For this reason, when the EGR valve approaches the closed state, the switching valve also approaches the closed state, so that there is a possibility that the flow rate of EGR gas to the intake passage that is originally required cannot be secured.

  Therefore, in any case, since the opening / closing timing of the switching valve is not optimized, there is a situation in which the EGR gas does not reach the desired flow rate, and as a result, the desired combustion characteristics cannot be obtained in the engine and the fuel consumption characteristics are reduced. There was a possibility.

  The present invention has been made to solve such a problem, and provides an exhaust gas recirculation device for an internal combustion engine that can prevent the generation of condensed water in the EGR device and can make the EGR gas have a desired flow rate. With the goal.

  An exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is an exhaust gas recirculation apparatus for an internal combustion engine that recirculates a part of the exhaust gas discharged from the internal combustion engine to the exhaust passage as EGR gas to the intake passage to achieve the above-described object, An EGR cooler that is provided in an EGR passage that connects the exhaust passage and the intake passage and cools the EGR gas, and is provided closer to the exhaust passage than the EGR cooler, and is driven between an open state and a closed state. And a first valve that blocks the EGR gas from flowing into the EGR passage in the closed state, and is provided closer to the intake passage than the EGR cooler, and the EGR gas is introduced into the intake passage. A second valve that adjusts the amount of inflow, and the first valve transitions from the closed state to the open state before the condition for the second valve to transition from the closed state to the open state is satisfied. Conditions are met And wherein the Rukoto.

  With this configuration, when the second valve shifts from the closed state to the open state, since the first valve starts shifting from the closed state to the open state, the introduction delay of the EGR gas into the intake passage is prevented. Can be prevented. Therefore, at the start of the exhaust gas recirculation control by the second valve, the EGR gas can be reliably supplied to the internal combustion engine, so that the fuel consumption can be improved.

  In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the first valve changes from the open state to the closed state on condition that a condition for the second valve to transition from the open state to the closed state is satisfied. The transition condition is established.

  With this configuration, the first valve can be prevented from shifting to the closed state earlier than the second valve, so that a desired EGR gas flow rate can be ensured and fuel efficiency can be improved.

  Moreover, the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is characterized in that the first valve is constituted by a temperature sensitive valve whose opening degree changes according to the temperature of the cooling water of the internal combustion engine.

  With this configuration, the first valve can take an opening degree corresponding to the operating condition of the internal combustion engine. Therefore, for example, when the first valve is configured to be closed when the cooling water temperature is lower than the dew point temperature of the EGR gas, the first valve is closed during warm-up of the internal combustion engine. In the situation where the EGR pipe and the EGR cooler forming the EGR passage are lower than the dew point temperature and condensed water is generated when exhaust gas is introduced, it is possible to prevent the exhaust gas from being introduced into the EGR passage. it can. On the other hand, since the engine is opened after the warm-up of the internal combustion engine is completed, it is possible to prevent a delay in introducing the EGR gas into the intake passage.

  In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the first valve has a condition for transition from the closed state to the open state that the temperature of the cooling water is equal to or higher than the dew point temperature of the EGR gas. It is characterized by that.

  With this configuration, since the first valve is closed when the cooling water temperature is low, it is possible to suppress the exhaust gas from entering the EGR passage by the exhaust pulsation and generating condensed water in the EGR device. In addition, when the cooling water temperature is high and the possibility that condensed water is generated is reduced, the first valve shifts to the open state, thereby preventing the exhaust gas recirculation control by the second valve from being affected. it can.

  Further, in the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the first valve is a temperature at which the temperature of the cooling water starts to adjust the amount of the EGR gas flowing into the intake passage by the second valve. It is characterized by shifting to the fully open state before reaching.

  With this configuration, since the first valve can be shifted to the fully open state before the execution of the exhaust gas recirculation control is started, a desired exhaust gas recirculation amount can be realized when the exhaust gas recirculation control is started. Become.

  Further, in the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the first valve is installed in the valve body installed in the EGR passage, the cooling water passage for flowing in the cooling water of the internal combustion engine, and the cooling water passage. A heat-sensitive deformable member that deforms according to the temperature of the cooling water, and a connecting member that connects the valve body and the heat-sensitive deformable member, wherein the valve body includes the heat-sensitive deformable member. It shifts between a closed state and an open state by being driven according to the deformation | transformation of this, It is characterized by the above-mentioned.

  With this configuration, since the first valve includes any of the valve body, the heat-sensitive deformation member, and the connecting member, the exhaust gas recirculation device can be reduced in size.

  An exhaust gas recirculation device for an internal combustion engine according to the present invention includes an actuator having a cooling water passage through which cooling water flows into the internal combustion engine, and the first valve includes a valve body installed in the EGR passage. The actuator is provided with a heat-sensitive deformation member that is installed in the cooling water channel and deforms according to the temperature of the cooling water, and a connecting member that connects the valve body and the heat-sensitive deformation member. The valve moves between a closed state and an open state when the valve body is driven according to the deformation of the heat-sensitive deformation member.

  With this configuration, since the actuator is isolated from the first valve, the actuator and the cooling water passing through the actuator are overheated even when the first valve is disposed at a position exposed to the high-temperature exhaust gas. Can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas recirculation apparatus of the internal combustion engine which can make EGR gas the desired flow volume while preventing generation | occurrence | production of condensed water in an EGR apparatus can be provided.

1 is a schematic configuration diagram illustrating an exhaust gas recirculation device for an internal combustion engine according to a first embodiment of the present invention. 1 is a schematic block diagram showing the configuration of an exhaust gas recirculation apparatus according to a first embodiment of the present invention and its surroundings. It is a schematic block diagram which shows the structure of the cooling water circuit which concerns on the 1st Embodiment of this invention. It is a top view of the bimetal periphery of the switching valve which concerns on the 1st Embodiment of this invention. It is sectional drawing of the bimetal periphery of the switching valve which concerns on the 1st Embodiment of this invention. It is a top view of the valve body periphery of the switching valve which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the exhaust gas recirculation apparatus which concerns on the 1st Embodiment of this invention. It is a schematic block diagram which shows the exhaust gas recirculation apparatus of the internal combustion engine which concerns on the 2nd Embodiment of this invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In this embodiment, the case where the exhaust gas recirculation apparatus according to the present invention is applied to a vehicle equipped with a four-cylinder gasoline engine will be described.

  First, the configuration will be described.

  As shown in FIG. 1, the engine 1 includes a cylinder head 10 and a cylinder block (not shown). The cylinder head 10 and the cylinder block form four cylinders 5. In these cylinders 5, combustion chambers 7 are respectively defined by pistons. The cylinder head 10 is formed with an intake port for introducing outside air into the cylinder 5 and an exhaust port for discharging exhaust gas from the cylinder 5.

  Each intake port is provided with an injector for injecting fuel, and the injected fuel is mixed with air and introduced into the combustion chamber 7 as an air-fuel mixture. The cylinder head 10 is provided with an ignition plug 15 for igniting the air-fuel mixture introduced into each combustion chamber 7. The ignition plug 15 is controlled in ignition timing by an ECU (Electronic Control Unit) 80 described later. It is like that.

  The injector is configured by an electromagnetically driven on / off valve. When a predetermined voltage is applied by the ECU 80, the injector is opened and fuel is injected into the intake port of each cylinder 5.

  The engine 1 further has an intake manifold 11 a connected to the cylinder head 10, and the intake manifold 11 a constitutes a part of the intake passage 11. The intake passage 11 is provided with an air cleaner and an air flow meter 22 (not shown) in order from the upstream side. The intake passage 11 is further provided with a throttle valve 18 for adjusting the intake air amount on the upstream side of the intake manifold 11a.

  The throttle valve 18 is constituted by an electronically controlled on-off valve whose opening degree can be adjusted steplessly. The flow area of the intake air is reduced under a predetermined condition, and the supply amount of the intake air is reduced. To be adjusted. The ECU 80 controls the throttle motor installed in the throttle valve 18 to adjust the opening degree of the throttle valve 18.

  The engine 1 further has an exhaust manifold 12 a connected to the cylinder head 10, and the exhaust manifold 12 a constitutes a part of the exhaust passage 12. In the exhaust passage 12, a catalyst device 13 made of, for example, a three-way catalyst is disposed.

  The engine 1 further includes an exhaust gas recirculation device (hereinafter referred to as an EGR device) 30. The EGR device 30 recirculates a part of the exhaust gas flowing through the exhaust passage 12 to the intake passage 11 and supplies it to the combustion chamber 7 of each cylinder 5 as EGR gas. Thereby, a pumping loss is reduced and fuel consumption is improved.

  The EGR device 30 includes an EGR pipe 33 that connects the intake manifold 11a and the exhaust pipe 16 and has an EGR passage 34 formed therein. The EGR pipe 33 is provided with an EGR cooler 31 and an EGR valve 32 for cooling the EGR gas flowing through the EGR passage 34 in order from the upstream side of the EGR gas flow.

  The EGR valve 32 is provided with a linear solenoid 32a provided therein and a base end portion inserted through the linear solenoid 32a, and a valve body 32b for opening and closing the EGR passage 34 is provided at the tip portion thereof. And a shaft 32c. By controlling energization of the linear solenoid 32a, the shaft 32c is reciprocated in the axial direction by the electromagnetic force and the biasing force of a spring (not shown), and the EGR passage 34 is opened and closed by the valve body 32b.

  The EGR valve 32 in the present embodiment is a normally closed type valve that is opened when the linear solenoid 32a is energized and closed when the linear solenoid 32a is not energized. Here, the EGR valve 32 according to the present embodiment constitutes a second valve according to the present invention.

  The ECU 80 adjusts the opening degree of the EGR valve 32 so as to connect the exhaust passage 12 and the intake passage 11 to adjust the amount of EGR gas introduced into the intake manifold 11a from the exhaust manifold 12a, that is, the exhaust gas recirculation amount. It has become.

  The EGR cooler 31 has a configuration in which a cooling water pipe is stretched around the outer periphery of the EGR gas passage in the housing. The EGR gas supplied from the EGR pipe 33 is cooled by heat exchange with the cooling water flowing through the cooling water pipe when passing through the EGR gas passage, and is guided downstream.

  The EGR device 30 according to the present embodiment includes a switching valve 35 on the upstream side of the EGR cooler 31. As will be described later, the switching valve 35 opens and closes according to the coolant temperature of the engine 1. Here, the switching valve 35 according to the present embodiment constitutes a first valve according to the present invention.

  As shown in FIGS. 1 and 2, a vehicle equipped with the engine 1 according to the present embodiment includes a cooling water temperature sensor 21, an air flow meter 22, an intake air temperature sensor 23, a pressure sensor 24, an A / F sensor 25, an exhaust temperature. A sensor 26, a throttle opening sensor 27, an accelerator opening sensor 29, a valve opening sensor 36, an engine speed sensor 37, a vehicle speed sensor 38, and a switching valve opening sensor 39 are provided. Each of these sensors outputs a signal representing a detection result to the ECU 80.

  The coolant temperature sensor 21 is disposed in a water jacket formed in the cylinder block of the engine 1, and outputs a detection signal corresponding to the coolant temperature THW of the engine 1 to the ECU 80. The air flow meter 22 is arranged upstream of the throttle valve 18 in the intake passage 11 and outputs a detection signal corresponding to the intake air amount to the ECU 80.

  The intake air temperature sensor 23 is disposed in the intake manifold 11a, and outputs a detection signal corresponding to the intake air temperature to the ECU 80. The pressure sensor 24 is disposed in the intake manifold 11a, and outputs a detection signal corresponding to the intake pressure to the ECU 80.

  The A / F sensor 25 is disposed in the exhaust passage 12 on the upstream side of the catalyst device 13, and outputs a detection signal corresponding to the oxygen concentration (exhaust A / F) in the exhaust gas to the ECU 80. The exhaust temperature sensor 26 is disposed in the exhaust passage 12 on the downstream side of the catalyst device 13, and outputs a detection signal corresponding to the exhaust temperature to the ECU 80.

  The throttle opening sensor 27 outputs a detection signal corresponding to the opening of the throttle valve 18 to the ECU 80. The accelerator opening sensor 29 outputs a detection signal corresponding to the depression amount of the accelerator pedal to the ECU 80.

  The engine rotation speed sensor 37 detects the rotation speed of the crankshaft of the engine 1 and outputs it to the ECU 80 as the engine rotation speed. The vehicle speed sensor 38 detects the rotational speed of the wheel and outputs it to the ECU 80 as a signal representing the vehicle speed.

  The valve opening sensor 36 has a resistor that is DC-driven and a brush that slides on the surface of the resistor. The brush is configured to operate integrally with the shaft 32c of the EGR valve 32. A voltage signal corresponding to the lift position of the shaft 32c, that is, the opening degree of the EGR valve 32 appears on the brush. Therefore, the ECU 80 can detect the opening degree of the EGR valve 32 by acquiring a signal appearing on the brush of the valve opening degree sensor 36. The switching valve opening sensor 39 outputs a signal corresponding to the opening of the switching valve 35 to the ECU 80.

  As shown in FIG. 2, the ECU 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a backup memory 84, and the like.

  The ROM 82 includes various control programs including a program for performing the exhaust gas recirculation amount control and a control program for controlling the fuel injection amount for the cylinder 5, and a map referred to when executing these various control programs. It is remembered. The CPU 81 executes various arithmetic processes based on various control programs and maps stored in the ROM 82. In addition, the RAM 83 temporarily stores calculation results by the CPU 81, data input from the above-described sensors, and the like. The backup memory 84 is configured by a non-volatile memory, and stores, for example, data to be saved when the engine 1 is stopped.

  The CPU 81, ROM 82, RAM 83, and backup memory 84 are connected to each other via a bus 87 and are connected to an input interface 85 and an output interface 86.

  The input interface 85 includes a cooling water temperature sensor 21, an air flow meter 22, an intake air temperature sensor 23, a pressure sensor 24, an A / F sensor 25, an exhaust temperature sensor 26, a throttle opening sensor 27, an accelerator opening sensor 29, a valve opening. A sensor 36, an engine speed sensor 37, a vehicle speed sensor 38, and a switching valve opening sensor 39 are connected. The vehicle may be mounted with an ECU other than the ECU 80, and signals output from at least some of these sensors may be input to the ECU 80 via the other ECU.

  The output interface 86 is connected to the spark plug 15, the throttle valve 18, the EGR valve 32, the injector, and the like.

  The ECU 80 performs various controls of the engine 1 including exhaust gas recirculation amount control, fuel injection amount control, and the like based on the outputs of the various sensors described above.

  FIG. 3 is a schematic diagram showing a cooling water circuit 40 that supplies cooling water to the EGR device 30 according to the present embodiment. The cooling water circuit 40 supplies the cooling water discharged from the water pump 44 in the order of the engine 1, the heater core 45, the switching valve 35, the EGR cooler 31, the EGR valve 32, and the throttle valve 18, and returns to the water pump 44. 47 and a thermostat (not shown) installed downstream of the cylinder head 10 constituting the engine 1, a part of the cooling water branched from the first path 47 and flowing out from the engine 1 is supplied to the radiator 46, and the water pump 44 And a second path 48 to return to.

  When the cooling water flowing back through the first path 47 is heated by heat exchange with the cylinder block and the cylinder head 10 constituting the engine 1, it is cooled by heat exchange with the heater core 45 and then supplied to the EGR cooler 31. .

  On the other hand, when the cooling water returning through the second path 48 is branched from the first path 47 by a thermostat installed downstream of the cylinder head 10, it is supplied to the radiator 46 and cooled by heat exchange with the outside air. Further, the thermostat blocks the second path 48 when the cooling water temperature THW of the engine 1 is lower than the cooling water temperature during normal driving due to warm-up or traveling in a cold region. It is like that. Further, the thermostat gradually opens the second path 48 as the cooling water temperature THW increases, so that the ratio of the cooling water amount returning to the second path 48 to the cooling water amount returning to the first path 47 increases. It has become.

  Hereinafter, a more characteristic configuration of the EGR device 30 according to the embodiment of the present invention will be described.

  In the switching valve 35, a cooling water pipe 41 constituting a part of the first path 47 of the cooling water circuit 40 is disposed inside. A bimetal 52 is installed in the cooling water pipe 41 and is deformed according to the cooling water temperature THW of the engine 1. Here, the cooling water pipe 41 and the bimetal 52 according to the present embodiment constitute the cooling water channel and the heat-sensitive deformation member according to the present invention, respectively.

  The switching valve 35 includes a valve body 51 installed in the EGR passage 34, and a connecting member 53 that connects the bimetal 52 and the valve body 51. The valve body 51 rotates between a blocking position where the exhaust gas flows into the EGR passage 34 and an open position where the exhaust gas can flow into the EGR passage 34 according to the deformation of the bimetal 52. It comes to move.

  That is, the switching valve 35 is closed when the valve body 51 is moved to the shut-off position, and the switching valve 35 is opened when the valve body 51 is moved to the open position.

  In the present embodiment, the switching valve 35 is closed when the cooling water temperature THW is equal to or lower than the predetermined value X1, while the switching valve 35 is opened according to the cooling water temperature THW when the cooling water temperature THW exceeds the predetermined value X1. It has come to take a degree.

  The predetermined value X1 is set so that the switching valve 35 is closed if the dew point temperature is equal to or lower than the dew point temperature even when the dew point temperature is highest in the assumed outside air temperature and humidity ranges. In the present embodiment, the predetermined value X1 is set to 60 ° C. As a result, the switching valve 35 is closed during the warm-up of the engine 1 in which the EGR pipe 33, the EGR cooler 31, and the like are at or below the dew point temperature.

  That is, the switching valve 35 prevents the exhaust gas from flowing into the EGR device 30 due to exhaust pulsation during the warm-up of the engine 1 and being cooled below the dew point temperature by the EGR pipe 33 or the EGR cooler 31 to generate condensed water. It is like that.

  The switching valve 35 is configured to be fully opened when the coolant temperature THW further rises and reaches a predetermined temperature higher than the predetermined value X1 and lower than the predetermined value X2. The predetermined value X2 represents a temperature at which the ECU 80 shifts the EGR valve 32 from the closed state to the open state and starts the exhaust gas recirculation amount control. In the present embodiment, the predetermined value X2 is set to 70 ° C. Yes.

  If the exhaust gas recirculation amount is adjusted at the downstream side of the EGR device 30, that is, at a position as close as possible to the intake passage 11, the accuracy of the flow rate control is improved. Therefore, the exhaust gas recirculation amount is adjusted by the EGR valve 32, while the switching valve 35 may be in two states, a fully closed state and a fully open state. Accordingly, it is preferable that the switching valve 35 is configured with a bimetal 52 or the like so that when the transition from the closed state to the open state is started due to an increase in the coolant temperature THW, the transition valve 35 is shifted to the fully open state at a temperature as low as possible.

  Next, the mechanism of the switching valve 35 will be described with reference to FIGS.

  As shown in FIG. 4, the bimetal 52 is formed in a spiral shape, and the material of the metal disposed outside the spiral is lower than the thermal expansion coefficient of the metal disposed inside the spiral. Has been. Therefore, as the cooling water temperature THW passing through the bimetal 52 increases, the spiral of the bimetal 52 is deformed so as to spread.

  A base end portion 52 b of the bimetal 52 is fixed to the inner wall 42 of the cooling water pipe 41. Further, the bimetal 52 is disposed such that a side surface orthogonal to the central axis of the spiral is along the flow direction of the cooling water. The bimetal 52 expands and contracts in the direction of the central axis of the spiral with the base end portion 52b as a fixed end. Specifically, as shown in FIG. 4, the bimetal 52 has a greater amount of deformation in the direction of the arrow X as the cooling water temperature THW of the cooling water flowing through the cooling water pipe 41 becomes higher. The amount of entrainment at the center (involvement amount) is reduced.

  On the other hand, an output rotation shaft 54 that rotates in accordance with the expansion / contraction of the bimetal 52, that is, the change in the amount of winding at the center of the spiral, is connected to the distal end portion 52a of the bimetal 52 along the central axis direction of the spiral. . As shown in FIG. 5, the output rotation shaft 54 passes through a through hole 51 </ b> A formed in the wall portion of the cooling water pipe 41. Then, one end of a bimetal side connecting member 53 a that rotates in synchronization with the rotation of the output rotation shaft 54 is connected to the tip of the output rotation shaft 54 that protrudes from the cooling water pipe 41. . The bimetal side connecting member 53a constitutes a part of the connecting member 53 described later. A through-hole 51A formed in the wall portion of the cooling water pipe 41 is provided with a seal (not shown) that suppresses leakage of the cooling water.

  On the outer periphery of the cooling water pipe 41, two limiting members (not shown) protruding in a direction substantially parallel to the output rotation shaft 54 are formed so as to limit the movement of the bimetal side connecting member 53a. When the cooling water temperature THW is equal to or lower than the predetermined value X1, the bimetal side connecting member 53a is restricted from moving by contacting one of the limiting members at a position indicated by a two-dot chain line in FIG. 4, and the cooling water temperature THW increases. As a result, it moves in the direction of arrow A. When the coolant temperature THW further rises, the coolant temperature THW is restricted to the position indicated by the solid line in FIG. 4 by coming into contact with the other restricting member.

  The connecting member 53 includes a bimetal side connecting member 53a, a valve body side connecting member 53b connected to the valve body 51 (see FIG. 6), and a connecting portion 53c that connects the bimetal side connecting member 53a and the valve body side connecting member 53b. Has been. Therefore, when the output rotation shaft 54 rotates as the bimetal 52 expands and contracts, the bimetal side connecting member 53a also rotates according to the amount of rotation. Then, the rotation of the bimetal side connecting member 53a is transmitted to the valve body side connecting member 53b via the connecting portion 53c, whereby the valve body side connecting member 53b is also rotated, and the rotation of the valve body side connecting member 53b is the valve. It is transmitted to the body 51.

  As shown in FIG. 6, the valve body 51 is disposed in the EGR passage 34 formed in the switching valve 35, and the outer diameter thereof is substantially the same as the inner diameter of the EGR passage 34 and is thermally expanded. However, the inner wall of the EGR pipe 33 is determined so that the rotation is not limited. Further, the valve body 51 is formed in a substantially disc shape, and an input rotation shaft 55 and a fixed shaft are respectively provided on the peripheral portion of the valve body 51 at positions symmetrical to each other with respect to the center of the valve body 51. It is extended. The fixed shaft is supported so as to be rotatable with respect to the wall portion of the EGR passage 34.

  The input rotation shaft 55 passes through a through hole formed in the wall portion of the EGR pipe 33, and the end of the valve body side connecting member 53 b is connected to the tip protruding from the EGR pipe 33. . The input rotation shaft 55 rotates in synchronization with the rotation of the valve body side connecting member 53b. As a result, the valve body 51 rotates about an axis along the input rotation shaft 55 and the fixed shaft, and the circulation area of the EGR passage 34 is adjusted by the rotation of the valve body 51. A seal (not shown) is provided in the through hole formed in the EGR pipe 33.

  In addition, when the bimetal side connecting member 53a is in the position of the two-dot chain line in FIG. 4, that is, when the coolant temperature THW is equal to or lower than the predetermined value X1, the valve body 51 is in the position indicated by the two-dot chain line in FIG. The switching valve 35 is fully closed. When the coolant temperature THW rises and the bimetal side connecting member 53a moves in the direction of the arrow A shown in FIG. 4, the valve body 51 moves in the direction of the arrow B shown in FIG. Then, before the coolant temperature THW reaches the predetermined value X2, the valve body 51 moves to the position shown by the solid line in FIG. 6, and the switching valve 35 is fully opened.

  On the other hand, when the engine 1 is stopped and the coolant temperature THW is lowered to the predetermined value X1 or less, the switching valve 35 is fully closed. However, in this state, the ECU 80 has already finished the exhaust gas recirculation amount control. That is, when the ECU 80 shifts the EGR valve 32 to the closed state in order to end the exhaust gas recirculation amount control, the switching valve 35 is kept open. Until the EGR valve 32 shifts to the fully closed state, the exhaust gas continues to flow into the EGR device 30 and the adjustment of the exhaust gas recirculation amount by the EGR valve 32 is continued.

  In addition, when the cooling water temperature is equal to or lower than X1, since the switching valve 35 has shifted to the closed state, when the engine 1 is started again, the exhaust gas flows into the EGR device 30 due to exhaust pulsation. Is to prevent.

  Next, the operation of the EGR device 30 according to the present embodiment will be described with reference to FIG. The ECU 80 always obtains a signal representing the cooling water temperature THW from the cooling water temperature sensor 21.

  First, when the engine 1 is started and the warm-up operation is started, the coolant temperature THW starts to rise. At this time, if the coolant temperature THW is equal to or lower than the predetermined value X1, the connecting member 53 is in the position indicated by the two-dot chain line in FIG. 4, and thus the valve body 51 is also in the position indicated by the two-dot chain line in FIG. The switching valve 35 is closed. Therefore, in a situation where the cooling water temperature THW is equal to or lower than the dew point temperature and there is a possibility that condensed water may be generated when the exhaust gas is cooled by the EGR pipe 33 or the EGR cooler 31, the switching valve 35 is closed and the exhaust pulsation occurs. Since the exhaust gas is prevented from flowing into the EGR passage 34 due to the above, it is possible to suppress the generation of condensed water in the EGR pipe 33 and the EGR cooler 31.

  When the coolant temperature THW exceeds the predetermined value X1 (YES in step S11), the switching valve 35 starts to shift from the closed state to the open state. As described above, the switching valve 35 is fully opened before the coolant temperature THW reaches the predetermined value X2 (step S12).

  On the other hand, if the cooling water temperature THW remains below the predetermined value X1 (NO in step S11), the switching valve 35 remains closed (step S13) and continues to suppress the inflow of exhaust gas to the EGR device 30. . In this case, since the coolant temperature THW is naturally equal to or lower than the predetermined value X2, the EGR valve 32 is also kept closed (step S16).

  Next, when the ECU 80 determines that the coolant temperature THW continues to rise and the signal input from the coolant temperature sensor 21 indicates that the coolant temperature THW exceeds the predetermined value X2 (in step S14). YES), the exhaust gas recirculation amount control by the ECU 80 is started (step S15). At this time, since the switching valve 35 is already fully opened, the ECU 80 can realize an appropriate exhaust gas recirculation amount by controlling the opening degree of the EGR valve 32.

  On the other hand, when the ECU 80 determines that the coolant temperature THW is equal to or lower than the predetermined value X2 (NO in step S14), the exhaust gas recirculation amount control by the ECU 80 is not executed and the EGR valve 32 is maintained in the closed state (step). S16).

  As described above, in the EGR device 30 according to the first embodiment of the present invention, when the EGR valve 32 shifts from the closed state to the open state, the switching valve 35 starts shifting from the closed state to the open state. Therefore, it is possible to prevent a delay in introducing EGR gas into the intake passage 11. Therefore, at the start of exhaust gas recirculation control by the EGR valve 32, the EGR gas can be reliably supplied to the engine 1, so that the fuel consumption can be improved.

  Further, since the switching valve 35 can be prevented from shifting to the closed state earlier than the EGR valve 32, a desired EGR gas flow rate can be secured, and fuel consumption can be improved.

  Further, the switching valve 35 can take an opening degree corresponding to the operating state of the engine 1. Specifically, the switching valve 35 is configured to be closed when the coolant temperature THW is lower than the dew point temperature of the EGR gas, and is closed when the engine 1 is warmed up. Therefore, the exhaust gas is introduced into the EGR passage 34 in a situation where the EGR pipe 33 and the EGR cooler 31 forming the EGR passage 34 are lower than the dew point temperature and condensed water is generated when the exhaust gas is introduced. Can be prevented. On the other hand, after the warm-up of the engine 1 in which the cooling water temperature THW is high and the possibility of generating condensed water is reduced, the switching valve 35 shifts to an open state, so that the introduction of EGR gas into the intake passage 11 is delayed. Can be prevented.

  Further, since the switching valve 35 can be shifted to the fully opened state before the execution of the exhaust gas recirculation amount control is started, a desired exhaust gas recirculation amount can be realized when the exhaust gas recirculation amount control is started.

  Further, since the switching valve 35 includes any of the valve body 32b, the bimetal 52, and the connecting member 53, the EGR device 30 can be reduced in size.

  In the above description, the case where the switching valve 35 shifts between the open state and the closed state according to the deformation of the bimetal 52 has been described. However, the switching valve 35 only needs to be a temperature-sensitive valve whose opening degree changes depending on the cooling water temperature THW. For example, the opening degree changes using a deformation of wax used for a thermostat or the like instead of the bimetal 52. It may be. In this case, during warming up, the shaft-like member held by the spring is moved by the wax expanded in accordance with the rise in the cooling water temperature, so that the valve body 51 disposed in the EGR passage 34 is rotated. Is preferable.

  Moreover, in the above description, the case where the cooling water of the engine 1 was supplied to the EGR cooler 31 via the switching valve 35 was demonstrated. However, the cooling water circuit 40 is not limited to that shown in FIG. 4. For example, the cooling water may be supplied to the switching valve 35 via the EGR cooler 31.

  In the above description, the switching valve 35 starts to shift to the open state when the predetermined value X1 reaches 60 ° C. near the dew point temperature of the exhaust gas, and is lower than 70 ° C. at which EGR control is started. Although the case where the temperature is shifted to the fully open state has been described, the present invention is not limited to this. What is necessary is just to be comprised so that it may transfer.

  Moreover, in the above description, the case where the switching valve 35 has any of the valve body 51, the bimetal 52, and the connection member 53 was demonstrated. However, as will be described below as the second embodiment of the present invention, the bimetal 52 and the connecting member 53 may be installed as separate components from the switching valve 35.

  Hereinafter, an exhaust gas recirculation apparatus according to a second embodiment of the present invention will be described with reference to FIG.

  In the exhaust gas recirculation apparatus according to the second embodiment, the same components as those in the exhaust gas recirculation apparatus according to the first embodiment described above will be described using the same reference numerals as those in the first embodiment. In particular, only the differences will be described in detail.

  The EGR device 30 according to the present embodiment includes a switching valve 61 that is installed in the EGR pipe 33 and takes at least two states of a fully open state and a fully closed state. The EGR device 30 includes an actuator 62 that is driven according to the coolant temperature THW of the engine 1, and the actuator 62 is configured separately from the switching valve 61.

  The switching valve 61 has a valve body 51 configured in the same manner as in the first embodiment. A cooling water pipe 41 that constitutes a part of the first path 47 of the cooling water circuit 40 is disposed inside the actuator 62. The actuator 62 includes a bimetal 52 installed in the cooling water pipe 41 and a connecting member 53 for transmitting expansion and contraction of the bimetal 52 to the valve body 51.

  As in the first embodiment, the connecting member 53 includes a valve body side connecting member, a bimetal side connecting member, and a connecting portion. The switching valve 61 and the actuator 62 are connected via a bimetal side connecting member, a bimetal side connecting member, and a connecting portion. Thereby, the switching valve 61 according to the present embodiment is in a closed state when the cooling water temperature THW is equal to or lower than the predetermined value X1 and the cooling water temperature THW is the same as the switching valve 35 according to the first embodiment. If it continues to rise, it shifts to the fully open state before reaching the predetermined value X2.

  With such a configuration, the cooling water pipe 41 in which the bimetal 52 is installed is installed not in the casing that constitutes the switching valve 61 but in the casing that constitutes the actuator 62. Therefore, the actuator 62 is moved away from the exhaust manifold 12a. As a result, the temperature rise of the cooling water due to the heat of the exhaust gas can be prevented.

  In the above description, the case where the actuator 62 has the bimetal 52 has been described. However, the present invention is not limited to this, and similarly to the switching valve 35 according to the first embodiment, other temperature sensitive members such as wax are provided. You may do it.

  As described above, since the actuator 62 is isolated from the switching valve 61, the EGR device 30 according to the second embodiment of the present invention is disposed at a position where the switching valve 61 is exposed to high-temperature exhaust gas. Even in this case, it is possible to prevent the actuator 62 and the cooling water passing through the actuator 62 from being overheated.

  In the above description, the case where the switching valves 35 and 61 are configured by a water temperature driving actuator that is driven according to the water temperature, such as bimetal or wax, has been described. Thereby, since the opening degree of the switching valves 35 and 61 is adjusted according to the coolant temperature THW, the EGR device 30 can prevent the exhaust gas from flowing into the EGR device 30 during warm-up. In addition, since it is not necessary to install an actuator such as a solenoid for driving the valve, a small and low-cost EGR device 30 can be realized. However, the switching valves 35 and 61 may be configured by valves such as solenoid valves whose opening degree is controlled by the ECU 80.

  In this case, the ECU 80 controls the opening degree of the switching valves 35 and 61 according to the signal input from the coolant temperature sensor 21. Specifically, the ECU 80 maintains the switching valves 35 and 61 in the fully closed state when the cooling water temperature THW is equal to or lower than the predetermined value X1, and when the cooling water temperature THW exceeds the predetermined value X1, The switching valves 35 and 61 are shifted from the fully closed state to the fully opened state. The predetermined value X1 may be set to a value higher than the dew point temperature of the exhaust gas and lower than the cooling water temperature at which the exhaust gas recirculation amount control is started.

  In the above description, the case where the EGR device 30 is applied to the engine 1 that does not include the turbo unit has been described. However, the present invention is not limited thereto, and the EGR device 30 may be applied to the engine 1 that includes the turbo unit. Good.

  In this case, the EGR device 30 may constitute a so-called HPL (High-Pressure Loop) that acquires exhaust gas from the upstream side of the turbine wheel and recirculates it as EGR gas to the downstream side of the compressor wheel. Further, the EGR device 30 may constitute an LPL (Low-Pressure Loop) that acquires exhaust gas from the downstream side of the turbine wheel and recirculates it as EGR gas to the upstream side of the compressor wheel.

  Moreover, although the EGR apparatus 30 demonstrated the case where it applied to the vehicle carrying the engine 1 comprised by the gasoline engine, it is not limited to this, The EGR apparatus 30 mounts well-known internal combustion engines, such as a diesel engine. It may be applied to the vehicle.

  In the above description, the case where the EGR device 30 is applied to a port injection engine in which fuel is injected into the intake port has been described. However, the present invention is not limited to this, and fuel is directly injected into each combustion chamber 7. The EGR device 30 may be applied to an in-cylinder injection engine. Further, the EGR device 30 may be applied to an engine in which both in-cylinder injection and port injection are performed.

  Further, the EGR device 30 may be applied not only to a vehicle that uses only the engine 1 as a power source, but also to a hybrid vehicle that uses an engine and a rotating electrical machine as power sources. In this case, compared to a vehicle using only the engine 1 as a power source, the engine 1 is frequently started and stopped repeatedly. Therefore, by providing an actuator that is driven according to the coolant temperature THW of the engine 1, The switching valves 35 and 61 can be reliably opened and closed according to the cooling water temperature THW. Therefore, it is possible to reliably prevent the generation of condensed water when the temperatures of the EGR valve 32 and the EGR pipe 33 are lowered, and when the execution of the control is started, the switching valves 35 and 61 are surely shifted to the open state. Therefore, it is possible to prevent the delay in introducing the EGR gas to the engine 1 and improve the fuel consumption.

  As described above, the exhaust gas recirculation apparatus according to the present invention has an effect of preventing generation of condensed water in the EGR apparatus and making the EGR gas at a desired flow rate. Useful for.

1 Engine 5 Cylinder 7 Combustion Chamber 11 Intake Passage 11a Intake Manifold 12 Exhaust Passage 12a Exhaust Manifold 18 Throttle Valve 21 Cooling Water Temperature Sensor 22 Air Flow Meter 23 Intake Air Temperature Sensor 27 Throttle Opening Sensor 29 Accelerator Opening Sensor 30 EGR Device (Exhaust Recirculation Device) )
31 EGR cooler 32 EGR valve (second valve)
33 EGR pipe 34 EGR passage 35 Switching valve (first valve)
36 Valve opening sensor 37 Engine speed sensor 39 Switching valve opening sensor 40 Cooling water circuit 41 Cooling water piping (cooling water channel)
42 inner wall 47 first path 51 valve body 52 bimetal (heat-sensitive deformation member)
53 connecting member 53a bimetal side connecting member 53b valve body side connecting member 53c connecting portion 54 rotating shaft for output 55 rotating shaft for input 61 switching valve 62 actuator 80 ECU

Claims (7)

An exhaust gas recirculation device for an internal combustion engine that recirculates a part of exhaust gas discharged from an internal combustion engine to an exhaust passage as EGR gas to an intake passage,
An EGR cooler that is provided in an EGR passage that communicates the exhaust passage and the intake passage, and cools the EGR gas;
The EGR cooler is provided on the exhaust passage side and is driven between an open state and a closed state, and blocks the EGR gas from flowing into the EGR passage in the closed state. A valve,
A second valve that is provided closer to the intake passage than the EGR cooler and adjusts the amount of the EGR gas flowing into the intake passage;
Before conditions the second valve moves from the closed state to the open state is established, the exhaust gas recirculation system for an internal combustion engine in which the first valve, characterized in that the condition is satisfied for transition from a closed state to an open state . On the condition that the condition where the second valve is shifted from the open state to the closed state is satisfied, to claim 1 where the conditions in which the first valve is shifted from the open state to the closed state, characterized in that the established An exhaust gas recirculation device for an internal combustion engine as described.   3. The exhaust gas recirculation of the internal combustion engine according to claim 1, wherein the first valve is configured by a temperature sensitive valve whose opening degree changes according to a temperature of cooling water of the internal combustion engine. apparatus.   4. The exhaust gas recirculation device according to claim 3, wherein the first valve has a condition that the temperature of the cooling water is equal to or higher than a dew point temperature of the EGR gas as a transition condition from the closed state to the open state. .   The first valve shifts to a fully open state before the temperature of the cooling water reaches a temperature at which adjustment of the amount of the EGR gas flowing into the intake passage by the second valve starts. The exhaust gas recirculation device for an internal combustion engine according to claim 3 or 4, wherein: The first valve includes a valve body installed in the EGR passage,
A cooling water passage for flowing in the cooling water of the internal combustion engine;
A heat-sensitive deformation member installed in the cooling water passage and deformed according to the temperature of the cooling water;
A connecting member for connecting the valve body and the heat-sensitive deformation member,
6. The first valve according to claim 1, wherein the first valve shifts between a closed state and an open state by driving the valve body in accordance with deformation of the heat-sensitive deformation member. An exhaust gas recirculation device for an internal combustion engine according to claim 1. An actuator which cooling water channel is formed in which the cooling water of the internal combustion engine flows,
The first valve includes a valve body installed in the EGR passage,
The actuator is a heat-sensitive deformation member that is installed in the cooling water channel and deforms according to the temperature of the cooling water;
A connecting member for connecting the valve body and the heat-sensitive deformation member,
6. The first valve according to claim 1, wherein the first valve shifts between a closed state and an open state by driving the valve body in accordance with deformation of the heat-sensitive deformation member. An exhaust gas recirculation device for an internal combustion engine according to claim 1.

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