JP4858150B2 - Exhaust gas circulation device and exhaust gas circulation method for turbo engine - Google Patents

Description

  The present invention relates to an exhaust gas circulation device and an exhaust gas circulation method for a turbocharged engine used for recirculation of exhaust gas of an internal combustion engine or the like.

  An engine mounted on a vehicle employs an exhaust gas recirculation system (EGR system) that recirculates a part of exhaust gas to the intake side in order to reduce NOx. As shown in FIG. 10, in the EGR system 1X, an exhaust gas circulation passage (EGR passage) 7 that connects the exhaust system passage 3 and the intake system passage 5 of the engine E is provided, and an EGR gas is provided in the EGR passage 7. An exhaust gas circulation valve (EGR valve) 8 for adjusting the amount and an EGR cooler 9 for cooling the EGR gas Ge are provided. An intercooler 51 is provided in the intake passage 5, and a turbocharger 11 having a turbine in the exhaust passage 4 and a compressor in the intake passage 5 is provided.

  However, in the case of an engine equipped with a turbocharger, as shown in FIG. 11, in the supercharged state where the load (torque) shifts to a high load, the intake side pressure (intake pressure) Pin is exhausted. Since the pressure (exhaust pressure) Pex becomes higher, EGR can be performed while the load (torque) is low, but EGR cannot be performed when the load (torque) is high.

  However, as shown in FIG. 12, even if the intake pressure Pin is larger than the exhaust pressure Pex, that is, even if the differential pressure (ΔP = Pex−Pin) is negative (−), it is viewed on a temporal basis. The pulsating exhaust pressure Pex and the pulsating intake pressure Pin are temporarily reversed, and the differential pressure (ΔP = Pex−Pin) becomes positive (+). EGR can be performed by flowing exhaust gas from the intake side to the intake side.

  In order to utilize this phenomenon, a reed valve (reed valve) that allows only the flow from the exhaust side to the intake side is provided in the EGR passage to widen the operating range of the engine capable of EGR and to perform EGR reliably. There has been proposed an EGR system with a one-way type reed valve (see, for example, Patent Document 1).

  In this one-way type EGR system with a reed valve, for example, a reed valve 10 having a structure as shown in FIG. 13 is provided. When the exhaust pressure Pex is larger than the intake pressure Pin as shown in FIG. As shown in FIG. 15, when the exhaust pressure Pex is smaller than the intake pressure Pin, the EGR gas Ge is not allowed to pass therethrough. The arrangement of the reed valve in the EGR passage is an effective means for high supercharging and high EGR of the engine.

  However, in this EGR system, at the time of acceleration, the intake side (inlet side) is in a state where both the air amount and the pressure (pressure ratio) are large due to the supercharging of the compressor. However, as shown in FIG. When decelerating from point A in the load state and transitioning to point B in the low load state, the compressor continues to rotate due to the inertia of the turbocharger even if the air amount and pressure (pressure ratio) on the intake side are reduced. The pressure ratio does not drop suddenly. As a result, since the pressure (pressure ratio) remains high despite the small amount of air, there is a problem in that it moves from point A to point B as shown in FIG. is there.

  In other words, when the boost pressure (intake-side supercharging pressure) becomes large when the engine is shifted from the acceleration state to the deceleration state and enters the surge region of the turbocharger (supercharger), the turbocharger surge noise is generated. appear. More specifically, when entering the surge region, the air flow from the compressor blades repeatedly peels off and reattaches to return to a normal state. In addition, it is repeatedly pushed back to the upstream air cleaner side, and a surge phenomenon occurs, and the intake pressure also pulsates between the air cleaner and the intake manifold, and sound is generated due to fluctuations in this pressure.

  As a countermeasure against this surge, in EGR systems without reed valves such as small engines, the EGR valve is opened during deceleration to release pressure from the intake system to the exhaust system. An EGR system with a reed valve is used so that EGR can be performed even during feeding. In the case of this EGR system with a reed valve, there is a problem that the pressure cannot be released because the EGR passage is closed by the reed valve.

As a countermeasure against this surge, in a gasoline engine or the like, a method has been proposed in which a relief valve (blow-off valve) is provided in the intake manifold to release the increased pressure into the atmosphere. However, with this method, the problem of surge noise can be solved by releasing the pressure from the surge region, but instead, high-pressure air is discharged directly into the atmosphere. It becomes. Further, although it is conceivable that the pressure relief destination is on the supercharger inlet side or outside the intake pipe, there is a problem that piping is complicated.
Japanese Utility Model Publication No. 06-40343

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a turbocharger equipped with a reed valve for preventing a backflow from the intake side to the exhaust side provided in the exhaust gas circulation passage. An object of the present invention is to provide an exhaust gas circulation device and an exhaust gas circulation method for an engine with a turbo that can reduce the occurrence of a surge noise of a turbocharger even when the engine is decelerated from acceleration.

In order to achieve the above object, an exhaust gas circulation device for a turbocharged engine includes an exhaust gas circulation passage communicating an engine exhaust passage and an intake passage, and an exhaust gas circulation valve provided in the exhaust gas circulation passage. And an exhaust gas circulation device for a turbocharged engine provided with a reed valve for preventing a backflow from the intake side to the exhaust side provided in the exhaust gas circulation passage, the gas from the intake side to the exhaust side of the reed valve A relief valve is provided to release the exhaust gas, and the exhaust gas circulation valve is controlled to open before the turbocharger enters the surge region, and the relief valve is provided with a difference between the intake pressure and the exhaust pressure in the surge region. When the pressure becomes higher than a predetermined set pressure of the relief valve, the valve is set to open . In other words, a surge valve is reduced by mounting a relief valve (pressure adjusting valve) and releasing pressure (boost) from the intake side to the exhaust side (exhaust side). The predetermined set pressure is set in advance by experiments or the like and stored in an engine control device or the like.
In the above exhaust gas circulation device for a turbocharged engine, the relief valve is provided in the reed valve (check valve) or a bypass passage that bypasses the reed valve.

  An exhaust gas circulation method for a turbocharged engine for achieving the above-described object includes an exhaust gas circulation passage that connects an exhaust passage and an intake passage of the engine, and an exhaust gas provided in the exhaust gas circulation passage. A reed valve for preventing a back flow from the intake side to the exhaust side provided in the exhaust gas circulation passage and a relief valve for releasing gas from the intake side to the exhaust side of the reed valve are provided. In an exhaust gas circulation device for a turbocharged engine, the exhaust gas circulation valve is controlled to open before the turbocharger enters the surge region, so that the differential pressure between the intake pressure and the exhaust pressure in the surge region is the relief. When the pressure becomes higher than a predetermined set pressure of the valve, the relief valve opens and gas is released from the intake side to the exhaust side.

  This set pressure is set based on data such as experimental results so that the relief valve opens when the turbocharger enters the surge region and the differential pressure between the intake pressure and the exhaust pressure becomes higher than the specified set pressure. . Since this set pressure varies depending on the engine, it is preferable to provide an adjustment portion (adjuster) in the relief valve so that the set pressure of the relief valve can be easily changed.

  According to the exhaust gas circulation device and the exhaust gas circulation method for a turbocharged engine according to the present invention, when the relief valve is provided and the engine is shifted from acceleration to deceleration, the exhaust gas circulation valve (EGR valve) is opened to When the differential pressure between the exhaust pressure and the exhaust pressure exceeds the set pressure of the relief valve, the relief valve opens so that the pressure can be released from the intake system to the exhaust system. Therefore, the noise generated in the surge region of the turbocharger can be reduced while utilizing the characteristics of the reed valve. In addition, by providing the relief valve on the reed valve, surge noise that occurs during deceleration from acceleration can be prevented, and noise during blow-off can be reduced by releasing pressure to the exhaust side.

  Hereinafter, an exhaust gas circulation device and an exhaust gas circulation method for a turbocharged engine according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an exhaust gas circulation device 1 for a turbocharged engine according to a first embodiment of the present invention includes a part of exhaust gas (EGR gas) from an exhaust manifold 3 of an engine body 2 to an intake manifold 6. An exhaust gas circulation passage (EGR passage) 7 for recirculating Ge is provided by connecting the exhaust manifold 3 (or the exhaust pipe 4) and the intake pipe 5 (or the intake manifold 6). The EGR passage 7 is provided with an exhaust gas circulation valve (EGR valve) 8 that adjusts the flow rate of the EGR gas Ge, and an EGR cooler 9 that cools the EGR gas Ge. Further, gas is supplied from the exhaust side to the intake side. A reed valve (check valve) 10 is provided that allows the gas to pass but does not allow gas to pass from the intake side to the exhaust side.

  The exhaust gas circulation valve 8 is connected by an air tank 12 and air pipes 13 and 14, and is controlled to be opened and closed by operating on / off valves (solenoid valves) 15 and 16 provided in the air pipes 13 and 14. The The on-off valves 15 and 16 are controlled by an engine control unit (ECU) 19 that receives signals from the rotation sensor 17 and the accelerator opening sensor 18 and the like.

  A turbine 11 a of the turbocharger 11 is disposed in the exhaust pipe 4 and is driven by the exhaust gas G. By driving the turbine 11 a, a compressor (not shown) of the turbocharger 11 is operated, and the fresh air A is compressed and supplied to the intake manifold 6 via the intake pipe 5.

  In the first embodiment of the present invention, as shown in FIG. 2, the reed valve 10 has a difference between the intake side pressure (intake pressure) Pin and the exhaust side pressure (exhaust pressure) Pex with respect to the reed valve 10. When the pressure (ΔP = Pin−Pex) becomes larger than the set pressure Pset, a relief valve (blow-off valve) 20 is provided to release gas from the intake side to the exhaust side. The predetermined set pressure Pset is set in advance by experiments or the like.

  An example of a detailed configuration of the relief valve 20 is shown in FIG. In the relief valve configuration of FIG. 3, when the differential pressure between the intake pressure Pin and the exhaust pressure Pex is not equal to or higher than a predetermined set pressure Pset, the force receiving plate 21 is moved by the spring 22 that urges the force receiving plate 21. Is connected to a valve seat 24 provided on the wall surface of the reed valve 10 to stop the flow of gas, but the differential pressure between the intake pressure Pin and the exhaust pressure Pex is a predetermined set pressure Pset. In this case, the force Fp for pulling the valve element 23 away from the valve seat 24 becomes larger than the urging force Fs of the spring 22, and the force receiving plate 21 and the valve element 23 move to the exhaust side, so that the valve element 23 Is separated from the valve seat 24 to allow gas flow. That is, the intake pressure (boost pressure) is released to the exhaust side.

  The predetermined set pressure Pset of the relief valve 20 can be adjusted by the magnitude of the biasing force Fs of the spring 22. Therefore, a male screw is formed on the connecting rod 25 that connects the force receiving plate 21 and the valve body 23, and the distance between the force receiving plate 21 and the valve body 23 is changed by the tightening amount of the nut 26, and the spring 22. The magnitude of the urging force Fs can be adjusted. The connecting rod 25 and the nut 26 serve as an adjustment unit. Since this predetermined set pressure Pset differs depending on the engine, it is obtained experimentally for each engine.

  FIG. 4 shows the relationship between the operation of the reed valve 10 and the relief valve 20 and the gas flow rate. During the EGR, as shown in FIG. 5, the exhaust gas circulation valve 8 is open, so the exhaust pressure Pex is larger than the intake pressure Pin, and the differential pressure ΔP1 = Pex−Pin is positive (+ ), The reed valve 10 is opened, and the EGR gas Ge flows from the exhaust side to the intake side.

  When the differential pressure ΔP1 = Pex−Pin decreases, the reed valve 10 closes. However, even if the differential pressure ΔP1 = Pex−Pin becomes negative (−), as shown in FIG. Since there is a portion (shaded portion) that becomes +), the exhaust gas circulation valve 8 can be opened to perform EGR (EGR use range).

  Further, when the differential pressure ΔP1 = Pex−Pin becomes small, there is no portion that becomes positive (+) temporarily. Therefore, the exhaust gas circulation valve 8 is closed and EGR is not performed. Further, the exhaust gas circulation valve 8 is opened before the turbocharger 11 enters the surge region. As a result, when the differential pressure ΔP1 = Pex−Pin becomes smaller than a predetermined set pressure (−Pset), in other words, when the differential pressure ΔP2 = Pin−Pex becomes larger than the predetermined set pressure Pset, as shown in FIG. Since the relief valve 20 is opened, gas flows from the intake side to the exhaust side, and the boost pressure can be released to the exhaust side. Even in the high supercharging EGR state, the differential pressure ΔP1 = Pex−Pin is negative (−) and the differential pressure ΔP2 = Pin−Pex is positive (+), but the absolute value is small. Therefore, as shown in FIG. 4, by setting the predetermined set pressure Pset for opening the relief valve 20 to a large value, the relief valve 20 is not opened in the EGR use region, but the relief valve 20 is opened only in the surge region. can do.

  In addition, when only the reed valve 10 of the prior art as shown in FIG. 7 and the relief valve 20 is not provided, the same operation as in FIG. 5 can be performed, but the exhaust side of the boost pressure as shown in FIG. You can't escape.

  Then, in the exhaust gas circulation device 1 of the turbo engine, control is performed so that the exhaust gas circulation valve 8 is opened before the turbocharger 11 enters the surge region. The control in this surge region can set the engine speed and load (accelerator opening) of the engine that opens the exhaust gas circulation valve 8 based on data such as experimental results. It can be easily implemented by adding to the preset map data for conventional EGR control.

  Next, a second embodiment will be described. As shown in FIGS. 8 and 9, in the exhaust gas circulation device 1 </ b> A for the turbocharged engine according to the second embodiment of the present invention, the relief valve 20 is not provided in the reed valve 10, but is lead to the EGR passage 7. It is provided in a bypass passage 30 that bypasses the valve 10. Other configurations, operations of the relief valve 20 and the operation and effects thereof are the same as those of the first embodiment.

  Therefore, according to the exhaust gas circulation device and the exhaust gas circulation method of the turbocharged engine of the present invention, as shown in FIG. 16, the acceleration (point A) is shifted to the deceleration (point B), and the low load is reduced from the high load state. Since the boost pressure can be released to the exhaust side even when entering the surge region of the turbocharger 11 as shown in FIG. 17 when shifting to the load state, taking advantage of the characteristics of the reed valve 10, one-way in acceleration While high supercharging EGR is possible by this method, it is possible to reduce the sound generated in the surge region of the turbocharger 11.

  In addition, by providing the relief valve 20 in the reed valve 10, gas can be released into the exhaust gas circulation passage 7, so that the surge noise generated from acceleration to deceleration can be prevented by releasing pressure to the exhaust side, The sound at the time of blow-off of the relief valve 20 can also be reduced. Further, it is possible to avoid the occurrence of blow-off noise when a blow-off valve is provided externally.

It is a figure which shows the structure of the exhaust-gas circulation apparatus of the engine with a turbo of 1st Embodiment which concerns on this invention. It is a figure which shows the structure of the reed valve provided with the relief valve. It is a fragmentary sectional view which shows the structure of a relief valve. It is a schematic diagram which shows the action | operation area | region of a reed valve and a relief valve. It is a schematic diagram showing a gas flow when the EGR valve is open and the reed valve is open. It is a schematic diagram showing a gas flow when the EGR valve is open and the relief valve is open. It is a schematic diagram showing a gas flow when the EGR valve is open and the reed valve is open when there is no relief valve. It is a figure which shows the structure of the exhaust-gas circulation apparatus of the engine with a turbo of 2nd Embodiment which concerns on this invention. It is the elements on larger scale which show the structure of the bypass channel | path part which provided the relief valve of FIG. It is a figure which shows typically the EGR system of a prior art. It is a figure which shows typically the area | region where EGR is possible, and the area where EGR is impossible. It is a figure which shows typically the part which can be EGR by a reed valve. It is a perspective view of a reed valve. It is typical sectional drawing which shows the valve opening state of a reed valve. It is typical sectional drawing which shows the valve closing state of a reed valve. It is typical explanatory drawing which shows the state which transfers to acceleration from deceleration. It is a schematic diagram which shows the surge area | region of a turbocharger.

Explanation of symbols

1, 1A Exhaust gas circulation device for turbo engine 3 Exhaust manifold 4 Exhaust pipe 5 Intake pipe 6 Intake manifold 7 Exhaust gas circulation path (EGR path)
8 Exhaust gas circulation valve (EGR valve)
9 EGR cooler 10 Reed valve (check valve)
11 Turbocharger 19 Engine control unit (ECU)
20 Relief valve 30 Bypass passage A Fresh air G Exhaust gas Ge Part of exhaust gas (EGR gas)
Pin Intake side pressure (Intake pressure)
Pex Exhaust pressure (exhaust pressure)
Pset Predetermined set pressure

Claims (3)

An exhaust gas circulation passage communicating the exhaust passage and the intake passage of the engine, an exhaust gas circulation valve provided in the exhaust gas circulation passage, and a reverse flow from the intake side to the exhaust side provided in the exhaust gas circulation passage. In an exhaust gas circulation device for a turbocharged engine having a reed valve for preventing, a relief valve for releasing gas from the intake side to the exhaust side of the reed valve is provided, and the exhaust gas circulation valve is provided in a surge region of the turbocharger. And the relief valve is set to open when the differential pressure between the intake pressure and the exhaust pressure in the surge region is higher than a predetermined set pressure of the relief valve. An exhaust gas circulation device for a turbocharged engine.   The exhaust gas circulation device for a turbocharged engine according to claim 1, wherein the relief valve is provided in the reed valve or a bypass passage that bypasses the reed valve. An exhaust gas circulation passage communicating the exhaust passage and the intake passage of the engine, an exhaust gas circulation valve provided in the exhaust gas circulation passage, and a reverse flow from the intake side to the exhaust side provided in the exhaust gas circulation passage. In an exhaust gas circulation device for a turbocharged engine having a reed valve for preventing and providing a relief valve for releasing gas from the intake side to the exhaust side of the reed valve, the exhaust gas before the turbocharger enters the surge region When the pressure difference between the intake pressure and the exhaust pressure in the surge region becomes higher than a predetermined set pressure of the relief valve by controlling to open the circulation valve, the relief valve opens and the intake side to the exhaust side An exhaust gas circulation method for a turbocharged engine characterized by allowing gas to escape.

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