JP2009091918A - Egr cooler bypass structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR cooler bypass structure having a small and simple structure for shutting off an EGR passage having a bypass line bypassing an EGR cooler, on the upstream side of the EGR cooler. <P>SOLUTION: The EGR cooler bypass structure comprises a flow-in port 77, a flow-out port 78, the EGR cooler 42, an upstream chamber 79 communicated with both the flow-in port 77 and a cooler inlet 71, a downstream chamber 80 communicated with both the flow-out port 78 and a cooler outlet 72, a bypass opening 81 for communicating the upstream chamber 79 with the downstream chamber 80, and a swing valve 82 rockable around a rotating shaft 83 located on the opposite side to the EGR cooler 42 via the bypass opening 81. The swing valve 82 is displaceable to a shut-off position for shutting off the flow-in port 77, a cooler position of shutting off the bypass opening 81, and a bypass position for allowing distribution from the flow-in port 77 through the bypass opening 81 to the flow-out port 78. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an EGR cooler bypass structure.

  FIG. 5 and the like of Japanese Patent Application Laid-Open No. 2007-100236 disclose an EGR cooler in which EGR gas flows in a U-shape and an EGR cooler bypass valve. The EGR cooler bypass valve includes a bypass passage for bypassing the EGR cooler and allowing EGR gas to pass therethrough, and a swing valve (swing arm type valve element). The swing valve is rotatable to a position where the EGR gas flows to the EGR cooler and a position where the EGR gas flows to the bypass flow path. When the engine is cold, if the EGR gas is passed through the EGR cooler, the EGR gas is supercooled, and combustion may be worsened. According to the EGR cooler bypass structure of the above publication, overcooling of the EGR gas can be prevented by flowing the EGR gas through the bypass flow path in such a case. Furthermore, since the bypass passage is formed in the housing of the EGR cooler bypass valve, it is not necessary to provide the bypass passage as a separate pipe, and the size and simplification can be achieved.

Japanese Patent Laid-Open No. 2007-100522 Japanese Patent Laid-Open No. 11-324821

  By the way, in an internal combustion engine, by controlling the valley of the exhaust manifold pressure pulsation to coincide with the valve overlap period in which the exhaust valve opening period and the intake valve opening period overlap, the charging efficiency (in-cylinder A technique for improving the air amount is known. In other words, in the internal combustion engine, the exhaust valves are pulsated by sequentially opening the exhaust valves of the respective cylinders and releasing the exhaust gas into the exhaust manifold. On the other hand, the intake manifold pressure is substantially constant. The exhaust manifold pressure at the valley of the pulsation is lower than the intake manifold pressure depending on operating conditions. Accordingly, by matching the timing of the pulsation valley of the exhaust manifold pressure with the valve overlap period, the exhaust manifold pressure can be made lower than the intake manifold pressure during the valve overlap period. Accordingly, fresh air easily flows into the cylinder from the intake valve, and burned gas in the cylinder can be surely expelled to the exhaust valve by the fresh air flowing from the intake valve. That is, the scavenging effect can be exhibited. As a result, the amount of residual gas is reduced, and the amount of fresh air sucked into the cylinder can be improved. That is, the filling efficiency can be improved.

  However, according to the knowledge of the present inventors, in an internal combustion engine having an EGR path such as an EGR passage or an EGR cooler, the effect of the charging efficiency improvement control using the pulsation of the exhaust manifold pressure as described above is exhibited. There is a problem that it is difficult. The reason is considered as follows.

  When the internal volume of the exhaust manifold is large, the pulsation of the exhaust manifold pressure is weakened and the amplitude thereof is reduced. In an internal combustion engine having an EGR path, the EGR passage and the EGR cooler communicate with the exhaust manifold, so that the volume of the exhaust manifold is substantially enlarged by the volume of the EGR passage and the EGR cooler. As a result, the amplitude of the pulsation of the exhaust manifold pressure becomes smaller, and the pulsation valley becomes shallower. For this reason, the differential pressure between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley is reduced. Therefore, the scavenging effect is not sufficiently exhibited, and the filling efficiency is hardly improved.

  Therefore, when performing the charging efficiency improvement control, it is desirable to block the EGR passage upstream of the EGR cooler in order to increase the amplitude of the pulsation of the exhaust manifold pressure. However, when a valve for blocking the EGR passage is provided, there is a problem that the EGR device is increased in size and the manufacturing cost is increased.

  The present invention has been made in view of the above points, and is an EGR path that includes a bypass passage that bypasses the EGR cooler, and has an EGR path that can be blocked on the upstream side of the EGR cooler with a small and simple structure. It aims at providing a cooler bypass structure.

In order to achieve the above object, a first invention is an EGR cooler bypass structure,
An inlet through which EGR gas flows,
An outlet through which EGR gas flows out;
An EGR cooler having a cooler inlet and a cooler outlet adjacent to the cooler inlet and having an EGR gas outflow direction opposite to the EGR gas inflow direction to the cooler inlet;
An upstream chamber communicating with both the inlet and the cooler inlet;
A downstream chamber communicating with both the outlet and the cooler outlet;
A bypass opening for communicating the upstream chamber and the downstream chamber;
A swing valve swingable about a rotating shaft located on the opposite side of the EGR cooler through the bypass opening;
With
The swing valve includes a blocking position for blocking the inlet, a cooler position for introducing the EGR gas in the upstream chamber into the cooler inlet by blocking the bypass opening, and the inlet from the inlet through the bypass opening. It is possible to displace to a bypass position that allows flow to the outlet.

The second invention is the first invention, wherein
The blocking position is between the cooler position and the bypass position.

The third invention is the first invention, wherein
The shut-off position is outside the cooler position and the bypass position.

  According to the first aspect of the present invention, there is no need to provide a bypass flow path for bypassing the EGR cooler as a separate pipe, and the size and simplification can be achieved. Further, when the swing valve is in the shut-off position, the EGR cooler and the EGR passage can be shut off from the exhaust manifold, and the exhaust system volume can be reduced. By reducing the exhaust system volume, the amplitude of the exhaust manifold pressure pulsation can be increased, so that the effect of the charging efficiency improvement control using the exhaust manifold pressure pulsation can be increased. Furthermore, since one swing valve can be displaced to the cooler position, the bypass position, and the shut-off position, it is not necessary to provide a separate valve for shutting off the EGR passage. For this reason, the EGR device can be simplified and miniaturized.

  According to the second invention, since the shut-off position is between the cooler position and the bypass position, the swing valve can quickly move to the shut-off position from the cooler position or the bypass position. it can. For this reason, the effect of the filling efficiency improvement control can be quickly increased at the start of acceleration. Therefore, the engine torque can be increased quickly and an excellent acceleration response can be obtained.

  According to the third invention, since the shut-off position is outside the cooler position and the bypass position, the flow of the EGR gas is momentarily switched between the state in which the EGR gas is passed through the EGR cooler and the state in which the EGR cooler is bypassed. There will be no breaks. For this reason, smooth switching can be performed.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an example of a system including an EGR cooler bypass structure according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes a diesel engine 10. It is assumed that the diesel engine 10 is mounted on a vehicle and used as a power source. Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. In the common rail 14, high-pressure fuel pressurized by the supply pump 16 is stored. Then, fuel is supplied from the common rail 14 to the injectors 12 of each cylinder. The exhaust gas discharged from each cylinder is collected by the exhaust manifold 20 and flows into the exhaust passage 18.

  The diesel engine 10 includes a turbocharger 24. The turbocharger 24 includes a turbine 24a that is operated by a flow of exhaust gas, and a compressor 24b that is driven by the turbine 24a and compresses intake air. The turbine 24 a of the turbocharger 24 is disposed in the middle of the exhaust passage 18. A DPF 26 for capturing PM (Particulate Matter) in the exhaust gas is installed in the exhaust passage 18 on the downstream side of the turbine 24a.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air sucked through the air cleaner 30 is compressed by the compressor 24 b of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by the intake manifold 34 and flows into each cylinder.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of an EGR passage 40 is connected to the intake passage 28 in the vicinity of the intake manifold 34. The other end of the EGR passage 40 is connected to the exhaust manifold 20 of the exhaust passage 18. In this system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed.

  In the middle of the EGR passage 40, an EGR cooler unit in which the EGR cooler 42 and the flow path switching valve 76 are integrated is provided. An EGR valve 44 is provided in the EGR passage 40 on the downstream side of the EGR cooler unit. By changing the opening degree of the EGR valve 44, the amount of exhaust gas passing through the EGR passage 40, that is, the amount of external EGR can be adjusted. The EGR cooler unit will be described in detail later.

  The system according to the present embodiment further includes an accelerator opening sensor 66 that detects the amount of depression of the accelerator pedal (accelerator opening) of the vehicle on which the diesel engine 10 is mounted, and an ECU (Electronic Control Unit) 50. Yes. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 controls the operating state of the diesel engine 10 by operating each actuator according to a predetermined program based on the output of each sensor.

  Although not shown, the diesel engine 10 of the present embodiment includes an intake variable valve operating apparatus that varies the valve opening characteristics of the intake valve, and an exhaust variable valve operating apparatus that varies the valve opening characteristics of the exhaust valve. With these variable valve gears, the length of the valve overlap period (hereinafter simply referred to as “valve overlap period”) in which the valve opening period of the exhaust valve and the valve opening period of the intake valve overlap is changed. It is comprised so that it can be made to.

  FIG. 2 is a cross-sectional view showing the structure of the EGR cooler unit (EGR cooler 42 and flow path switching valve 76) in the first embodiment of the present invention. As shown in FIG. 2, the EGR cooler 42 has a cooler inlet 71 and a cooler outlet 72 adjacent to the cooler inlet 71. The EGR gas flowing in from the cooler inlet 71 flows so as to make a U-turn in the EGR cooler 42 and flows out from the cooler outlet 72. That is, the EGR gas inflow direction to the cooler inlet 71 and the EGR gas outflow direction from the cooler outlet 72 are opposite to each other. The outward path that continues from the cooler inlet 71 and the return path that continues to the cooler outlet 72 are separated by a partition wall 73. Heat exchangers 74 and 75 are installed on the forward path and the return path, respectively. Engine cooling water flows through the heat exchangers 74 and 75, and the EGR gas is cooled by the cooling water.

  The flow path switching valve 76 includes an inlet 77 through which EGR gas flows from the upstream EGR passage 40, an outlet 78 through which EGR gas flows into the downstream EGR passage 40, and both the inlet 77 and the cooler inlet 71. An upstream chamber 79 that communicates, a downstream chamber 80 that communicates with both the outlet 78 and the cooler outlet 72, a bypass opening 81 that communicates the upstream chamber 79 and the downstream chamber 80, and a swing valve 82 are provided.

  The swing valve 82 is installed to be swingable about a rotation shaft 83 located on the opposite side of the EGR cooler 42 via the bypass opening 81. The swing valve 82 includes a cooler position for passing EGR gas through the EGR cooler 42, a bypass position for passing EGR gas through the bypass opening 81 without passing through the EGR cooler 42, and an upstream side of the EGR cooler 42. Thus, the EGR passage 40 can be displaced to a blocking position where the EGR passage 40 is blocked. The swing valve 82 is driven by an actuator (not shown) such as a negative pressure actuator or an electric motor, and is displaced to the above three positions.

  FIG. 2 shows a state where the swing valve 82 is in the cooler position (a state via the cooler). In this state, the tip of the swing valve 82 faces the end surface of the partition wall 73 through a minute clearance. As a result, the bypass opening 81 is blocked by the swing valve 82. For this reason, the EGR gas that has flowed into the upstream chamber 79 from the inlet 77 is introduced into the cooler inlet 71, and sequentially passes through the heat exchangers 74 and 75, the cooler outlet 72, and the downstream chamber 80, and then passes through the EGR from the outlet 78. It flows out downstream of the passage 40.

  FIG. 3 shows a state where the swing valve 82 is in the blocking position (blocking state). The shut-off position is a position where the swing valve 82 has rotated about 45 ° clockwise in the figure from the cooler position. In this state, the tip of the swing valve 82 and the inner wall surface 85 of the upstream chamber 79 face each other with a minute clearance. As a result, the inflow port 77 is blocked by the swing valve 82.

  FIG. 4 shows a state where the swing valve 82 is in the bypass position (bypass state). The bypass position is a position where the swing valve 82 is further rotated about 45 ° clockwise in the figure from the shut-off position. In this state, the bypass opening 81 is opened. Therefore, the EGR gas that has flowed into the upstream chamber 79 from the inflow port 77 passes through the bypass opening 81 as it is to the downstream chamber 80 and flows out from the outflow port 78 to the downstream side of the EGR passage 40.

  When external EGR is performed, when the EGR gas is cooled by the EGR cooler 42 at the time of light load, the in-cylinder temperature becomes too low, and the combustion deteriorates and the HC emission amount tends to increase. Therefore, when the load is light, the EGR can be performed without passing through the EGR cooler 42 by setting the swing valve 82 to the bypass position. For this reason, the deterioration of combustion due to the in-cylinder temperature becoming too low can be avoided, and the HC emission amount can be reduced.

As described above, the system of the present embodiment is configured to increase the charging efficiency η _v (in-cylinder air amount) of the diesel engine 10 using the pulsation of the exhaust manifold pressure in a predetermined operation region (for example, a low rotation high load region). It is possible to execute control for improving the filling efficiency. FIG. 5 is a diagram showing the relationship between the intake manifold pressure and the exhaust manifold pressure and the crank angle during the execution of the charging efficiency improvement control.

  As shown in FIG. 5, in the charging efficiency improvement control, the intake variable valve operating device and the exhaust variable valve operating device are controlled so that the valve overlap period is sufficiently long. Further, as shown in FIG. 5, the intake manifold pressure is substantially constant regardless of the crank angle. On the other hand, the exhaust manifold pressure pulsates (periodically varies) as the exhaust gas is intermittently discharged from the exhaust valve of each cylinder.

As the opening timing of the exhaust valve is later, the timing at which the exhaust gas is discharged into the exhaust manifold 20 is delayed, so the waveform of the exhaust manifold pressure pulsation shifts to the right in FIG. That is, the waveform of the exhaust manifold pressure pulsation moves to the left and right in FIG. 5 by changing the opening timing of the exhaust valve. Therefore, by setting the opening timing of the exhaust valve to an appropriate timing, as shown in FIG. 5, the valley portion of the exhaust manifold pressure pulsation can be matched with the valve overlap period. In the charging efficiency improvement control, the exhaust variable valve operating device is controlled so that such an opening timing of the exhaust valve is realized, so that the valley portion of the exhaust manifold pressure pulsation coincides with the valve overlap period. As a result, the exhaust manifold pressure can be made lower than the intake manifold pressure during the valve overlap period. This makes it easy for fresh air to flow into the cylinder, and provides a scavenging effect that quickly expels burnt gas in the cylinder to the exhaust port. By executing the charging efficiency improvement control in this way, the amount of residual gas can be sufficiently reduced, and the amount of fresh air filled in the cylinder can be increased accordingly. That is, the filling efficiency η _v can be increased. As a result, the torque of the diesel engine 10 can be improved.

  By the way, the exhaust manifold pressure indicated by the dotted line in FIG. 5 is a waveform when the swing valve 82 is in the cooler position, that is, when the EGR gas is allowed to flow to the EGR cooler 42. On the other hand, the exhaust manifold pressure indicated by the solid line in FIG. 5 is a waveform when the swing valve 82 is in the cutoff position.

  The pulsation of the exhaust manifold pressure becomes weaker as the volume of the exhaust manifold 20 and the volume of the space communicating with the exhaust manifold 20 (hereinafter collectively referred to as “exhaust system volume”) are increased. This is because even if the same amount of exhaust gas is discharged from the exhaust valve, the exhaust manifold pressure is less likely to increase as the exhaust system volume increases.

  When the swing valve 82 is in the cooler position, the EGR passage 40 and the EGR cooler 42 communicate with the exhaust manifold 20, so that the exhaust system volume is increased by the amount of the EGR passage 40 and the EGR cooler 42. For this reason, as shown by the dotted line in FIG. 5, the exhaust manifold pressure pulsation tends to be weakened, and the amplitude thereof tends to be small. As a result, since the differential pressure (A in FIG. 5) between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley tends to be small, the scavenging effect is not sufficiently exhibited, and the effect of the charging efficiency improvement control is small. Easy to be. That is, it is difficult to sufficiently improve the engine torque.

  Further, when the swing valve 82 is in the bypass position, the volume of the EGR passage 40 is added to the exhaust system volume, so that the effect of the charging efficiency improvement control is likely to be reduced as described above.

  On the other hand, when the swing valve 82 is set to the shut-off position, the EGR cooler 42 and the EGR passage 40 downstream from the flow path switching valve 76 are disconnected from the exhaust manifold 20 to prevent their volume from being added to the exhaust system volume. Therefore, the exhaust system volume can be reduced. For this reason, as shown by the solid line in FIG. 5, the exhaust manifold pressure at the early stage of the exhaust stroke is increased by the exhaust gas discharged from the exhaust valve, and the exhaust manifold pressure at the later stage of the exhaust stroke can be lowered as a reaction. . That is, the pulsation of the exhaust manifold pressure can be increased and the amplitude thereof can be increased. Therefore, the differential pressure (B in FIG. 5) between the intake manifold pressure and the exhaust manifold pressure at the pulsation valley can be increased, and the scavenging effect can be sufficiently exhibited. As a result, the effect of the charging efficiency improvement control is greatly exerted, and the engine torque can be sufficiently improved.

  As described above, according to the present embodiment, when the charging efficiency improvement control is executed, the swing valve 82 is switched to the shut-off position, thereby reducing the exhaust system volume and thereby increasing the amplitude of the exhaust manifold pressure pulsation. Therefore, the effect of the charging efficiency improvement control can be sufficiently exerted, and the in-cylinder air amount (engine torque) can be sufficiently increased.

  By the way, as a configuration for shutting off the EGR cooler 42 from the exhaust manifold 20, an EGR valve for controlling the EGR amount is arranged on the upstream side of the EGR cooler 42, and the EGR valve is closed to shut off the EGR path. Configuration is also conceivable. However, when the EGR valve is arranged on the upstream side of the EGR cooler 42, the distance from the intake passage 28 to the EGR valve becomes longer, so the EGR gas inflow into the intake passage 28 after changing the opening of the EGR valve. There will be a delay before the quantity actually changes. As a result, it becomes difficult to accurately control the EGR amount. On the other hand, in this embodiment, as shown in FIG. 1, since the EGR valve 44 is on the downstream side of the EGR cooler 42, the control delay of the EGR amount can be suppressed, and highly accurate EGR control is performed. Can do.

  Further, according to the present embodiment, the single swing valve 82 can realize switching to the cutoff state in addition to switching between the state via the cooler and the bypass state. That is, it is not necessary to newly install a valve for shutting off the EGR passage 40 on the upstream side of the EGR cooler 42. For this reason, the EGR device can be simplified and miniaturized.

  Moreover, according to this embodiment, regarding the position of the swing valve 82, the cutoff position (FIG. 3) is between the cooler position (FIG. 2) and the bypass position (FIG. 4). For this reason, both the rotation angle of the swing valve 82 from the cooler position to the shut-off position and the rotation angle of the swing valve 82 from the bypass position to the shut-off position can be reduced (both are about 45 °). Therefore, the swing valve 82 can be quickly moved to the shut-off position from either the cooler position or the bypass position. That is, it is possible to quickly switch to the shut-off state from either the state via the cooler or the bypass state.

  During normal operation of the diesel engine 10, EGR is normally executed, so the swing valve 82 is in either the cooler position or the bypass position. On the other hand, at the time of acceleration (at the time of high load), charging efficiency improvement control is executed, and the swing valve 82 moves to the cutoff position in order to enhance the effect of this charging efficiency improvement control. At this time, if the time required for the swing valve 82 to move from the cooler position or the bypass position to the shut-off position is long, the timing at which the effect of the charging efficiency improvement control is enhanced, that is, the timing at which the engine torque is sufficiently increased is delayed. Therefore, it becomes difficult to obtain a good acceleration response. On the other hand, in this embodiment, since the swing valve 82 can be quickly moved from the cooler position to the shut-off position at the start of acceleration, the effect of the charging efficiency improvement control can be quickly increased. That is, the engine torque can be increased quickly. Therefore, an excellent acceleration response can be obtained.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 6 to FIG. 8. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit. This embodiment is the same as the first embodiment described above except that the structure of the flow path switching valve is different.

  FIG. 6 is a cross-sectional view showing the structure of the EGR cooler unit (EGR cooler 42 and flow path switching valve 76 ′) according to Embodiment 2 of the present invention. As shown in FIG. 6, the EGR cooler 42 in the present embodiment is the same as that in the first embodiment. On the other hand, the flow path switching valve 76 ′ in this embodiment is different from the first embodiment described above in the arrangement of the bypass position of the swing valve 82. In the flow path switching valve 76 ′, an abutment surface 84 with which the tip of the swing valve 82 abuts when the swing valve 82 is in the blocking position is formed on the inner wall of the upstream chamber 79. Thereby, the swing valve 82 is configured not to rotate clockwise relative to the contact surface 84 in the drawing. FIG. 6 shows a state in which the swing valve 82 is at the cooler position, and this state is the same as in the second embodiment described above.

  FIG. 7 shows a state where the swing valve 82 is in the bypass position. In the present embodiment, when the swing valve 82 rotates counterclockwise in the drawing from the cooler position, the bypass position is set. In such a bypass state, since the bypass opening 81 is opened, the EGR gas flows downstream of the EGR passage 40 without passing through the EGR cooler 42.

  FIG. 8 shows a state where the swing valve 82 is in the cutoff position. In such blocking, the inlet 77 is blocked by the tip of the swing valve 82 coming into contact with the contact surface 84. By setting such a shut-off state, it is possible to prevent the volume of the EGR cooler 42 and the EGR passage 40 downstream from the flow path switching valve 76 ′ from being added to the exhaust system volume, as in the first embodiment. The exhaust system volume can be reduced. For this reason, the pulsation of the exhaust manifold pressure becomes strong, and the effect of the filling efficiency improvement control can be exerted greatly.

  As described above, in the present embodiment, with respect to the position of the swing valve 82, there is a blocking position shown in FIG. 7 outside the cooler position shown in FIG. 6 and the bypass position shown in FIG. For this reason, when switching between the state via the cooler and the bypass state during execution of the external EGR, the flow of the EGR gas is not interrupted even for a moment, and smooth switching can be performed.

  Since this embodiment is the same as Embodiment 1 except for the points described above, further description is omitted.

It is a figure which shows an example of the system provided with the EGR cooler bypass structure of Embodiment 1 of this invention. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 1 of this invention. It is a figure which shows the relationship between the intake manifold pressure and exhaust manifold pressure in execution of filling efficiency improvement control, and a crank angle. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the EGR cooler unit (EGR cooler and flow-path switching valve) in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 20 Exhaust manifold 24 Turbocharger 24a Turbine 24b Compressor 26 DPF
28 Intake passage 34 Intake manifold 36 Intake throttle valve 38 Air flow meter 40 EGR passage 42 EGR cooler 44 EGR valve 50 ECU
71 Cooler inlet 72 Cooler outlet 73 Bulkhead 74, 75 Heat exchanger 76, 76 'Channel switching valve 77 Inlet 78 Outlet 79 Upstream chamber 80 Downstream chamber 81 Bypass opening 82 Swing valve 83 Rotating shaft 84 Abutting surface 85 Inner wall surface

Claims (3)

An inlet through which EGR gas flows,
An outlet through which EGR gas flows out;
An EGR cooler having a cooler inlet and a cooler outlet adjacent to the cooler inlet and having an EGR gas outflow direction opposite to the EGR gas inflow direction to the cooler inlet;
An upstream chamber communicating with both the inlet and the cooler inlet;
A downstream chamber communicating with both the outlet and the cooler outlet;
A bypass opening for communicating the upstream chamber and the downstream chamber;
A swing valve swingable about a rotating shaft located on the opposite side of the EGR cooler through the bypass opening;
With
The swing valve includes a blocking position for blocking the inlet, a cooler position for introducing the EGR gas in the upstream chamber into the cooler inlet by blocking the bypass opening, and the inlet from the inlet through the bypass opening. An EGR cooler bypass structure, wherein the EGR cooler bypass structure is displaceable to a bypass position that allows flow to the outlet.   The EGR cooler bypass structure according to claim 1, wherein the blocking position is between the cooler position and the bypass position.   The EGR cooler bypass structure according to claim 1, wherein the blocking position is outside the cooler position and the bypass position.

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