JP2016109072A - Egr system of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR system of an engine capable of achieving a large number of EGR flow passages with a small number of components, and capable of recirculating a target EGR gas amount required in each in a wide range of a driving condition of an engine.SOLUTION: An EGR system of an engine includes: a shared EGR passage 6 for connecting an exhaust passage 42 on a downstream side of a turbine 5T of a supercharger and an air supply passage on an upstream side of a compressor 5C; a first branch part 61, and a second branch part 62 which is closer to the exhaust passage side than the first branch part, in the shared EGR passage; a compressor bypass passage 36 branched from an air supply passage 32 on the downstream side of the compressor, and connected to the shared EGR passage in the first branch part; a turbine bypass passage 46 branched from an exhaust passage 41 on the upstream side of the turbine and connected to the shared EGR passage in the second branch part; an air supply side valve device for controlling a fluid passing through the first branch part; and an exhaust side valve device for controlling a fluid passing through the second branch part.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an engine EGR system.

  Conventionally, an EGR system for an engine has been known. For example, in a diesel engine, it is used as a means for reducing NOx when the engine is out in exhaust gas regulations that are becoming more severe. Further, in a gasoline / gas engine, an EGR system is used as a means for reducing NOx and suppressing knocking.

  In this EGR system, the exhaust passage and the supply passage are connected by the EGR passage so that a part of the exhaust gas from the engine is recirculated from the exhaust passage connected to the engine to the supply passage. The EGR system can be classified according to the connection mode of the passages. That is, HPL-EGR that is recirculated from the turbine inlet of the turbocharger to the compressor outlet, LPL-EGR that enters from the turbine outlet to the compressor inlet, HPtoLP-EGR that enters from the turbine inlet to the compressor inlet, and the like. There is also a Dual-EGR system using both HPL-EGR and LPL-EGR.

  In Patent Document 1, in view of the advantages and disadvantages of each EGR system, there is a system that switches the flow path through which EGR gas is recirculated according to the operating conditions in order to ensure a high EGR rate in the operating conditions of the engine. Proposed. Specifically, in Patent Document 1, switching between LPL-EGR and HPtoLP-EGR is performed in accordance with engine operating conditions.

JP 2011-69226 A

  However, the EGR system disclosed in Patent Document 1 cannot realize an advantageous HPL-EGR with low load and low rotation. Moreover, there is no disclosure about the response to the surging of the compressor performed as the EGR system or the turbine rotation speed control.

  In view of the above circumstances, at least one embodiment of the present invention can realize a large number of EGR flow paths with a small number of parts, and recirculate a target EGR gas amount required in each of a wide range of engine operating conditions. It is an object of the present invention to provide an engine EGR system that can reduce NOx emissions and reduce fuel consumption.

(1) An engine EGR system according to at least one embodiment of the present invention includes:
An engine EGR system comprising a turbocharger comprising a turbine provided in an exhaust passage through which exhaust gas flows and a compressor provided in an air supply passage through which supply air flows,
A shared EGR passage connecting the exhaust passage downstream of the turbine and the air supply passage upstream of the compressor;
A first branch portion that becomes a branch path in the shared EGR passage and a second branch portion that is closer to the exhaust passage than the first branch portion;
An EGR cooler provided in the shared EGR passage between the first branch part and the second branch part;
A compressor bypass passage branched from the air supply passage on the downstream side of the compressor and connected to the shared EGR passage in the first branch portion;
A turbine bypass passage branched from the exhaust passage on the upstream side of the turbine and connected to the shared EGR passage in the second branch portion;
An air supply side valve device configured to control a flow direction of fluid passing through the first branch part;
An exhaust side valve device configured to control a flow direction of fluid passing through the second branch part;
A valve control device configured to include a control execution unit that controls the exhaust-side valve device and the supply-side valve device;

  According to the configuration of (1) above, for exhaust gas including a flow path that passes only through the shared EGR passage, or a flow path that passes through the shared EGR passage and at least one of the compressor bypass passage and the turbine bypass passage. A plurality of flow paths are formed by controlling the exhaust side valve device and the supply side valve device. The EGR cooler is disposed between the first branch portion and the second branch portion of the shared EGR passage, which is a portion through which exhaust gas (EGR gas) always passes when recirculating from the exhaust passage to the supply passage. The For this reason, many EGR flow paths can be realized with a small number of parts, and the flow paths for exhaust gas according to engine operating conditions and load fluctuations can be set appropriately. Therefore, the target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine, and reduction of NOx emission and fuel consumption can be realized. If a flow path that does not pass through all of the shared EGR passage, the compressor bypass passage, and the turbine bypass passage (a flow path that includes only the supply passage and the exhaust passage) is included, a plurality of passages including this one flow passage are included. One flow path is selected from the flow paths.

(2) In some embodiments, in the configuration of (1) above,
The valve control device
A compressor operating state confirmation unit for confirming the operating state of the compressor,
When it is determined by the compressor operation state confirmation unit that the operation state of the compressor enters the surge region, the control execution unit is configured to have at least a part of the supply air flowing through the supply passage on the downstream side of the compressor. The air supply side valve device is controlled so as to be able to flow from the compressor bypass passage through the common EGR passage to the air supply passage on the upstream side of the compressor.
According to the configuration of (2) above, when the operating state of the compressor enters the surge region, the supply air can flow while bypassing the compressor from the downstream side to the upstream side of the compressor in the supply passage. The compressor bypass flow path is formed by controlling the supply side valve device. For this reason, it is possible to recirculate the target EGR gas amount required in each of a wide range of operating conditions of the engine to the engine while preventing the compressor from being operated in the surge region.

(3) In some embodiments, in the configuration of (1) above,
The valve control device
A turbo rotational speed confirmation unit for confirming a turbo rotational speed that is the rotational speed of the supercharger;
When it is determined by the turbo rotational speed confirmation unit that the turbo rotational speed is greater than the target rotational speed, the control execution unit is configured so that at least a part of the exhaust gas flowing through the exhaust passage on the upstream side of the turbine is The exhaust-side valve device is controlled so as to be able to flow from the turbine bypass passage to the exhaust passage on the downstream side of the turbine through the shared EGR passage.
According to the configuration of (3) above, when it is determined that the turbo rotation speed is higher than the target rotation speed, the exhaust gas can flow while bypassing the turbine from the upstream side of the turbine to the downstream side in the exhaust passage. The turbine bypass flow path is formed by controlling the exhaust side valve device. Thus, since the exhaust side valve device performs the same function as the wastegate valve, the turbo rotational speed can be achieved without providing a separate means for controlling the rotation of the supercharger such as the wastegate valve and the variable nozzle mechanism. The target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine while controlling the engine.

(4) In some embodiments, in the configuration of (1) above,
The valve control device
An EGR determination unit that determines whether the exhaust gas needs to be recirculated from the exhaust passage to the supply passage;
An EGR flow path determining unit that determines an EGR flow path that is a flow path from the exhaust path to the air supply path for recirculating the exhaust gas based on an operation map that includes an engine speed and an engine torque. In addition,
When it is determined by the EGR determination unit that the exhaust gas needs to be recirculated, the control execution unit is configured to form the EGR flow path determined by the EGR flow path determination unit. The apparatus and the supply side valve device are configured to be controlled.
In the engine EGR system described in (1) above, the flow from the exhaust passage for recirculating the exhaust gas to the supply passage is controlled by controlling the exhaust side valve device and the supply side valve device, respectively. A plurality of patterns of EGR flow paths that are paths are formed.
According to the configuration of (4) above, when exhaust gas recirculation from the exhaust passage to the air supply passage is necessary, an EGR passage suitable for the engine operating condition is determined from among a plurality of patterns of EGR passages. Is done. As a result, an appropriate EGR flow path is formed in accordance with engine operating conditions and fluctuations thereof, so that the target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine. .

(5) In some embodiments, in the configuration of (1) above,
The valve control device
A compressor operation state confirmation unit for confirming the operation state of the compressor;
A turbo rotational speed confirmation unit for confirming a turbo rotational speed that is the rotational speed of the supercharger;
An EGR determination unit that determines whether the exhaust gas needs to be recirculated from the exhaust passage to the supply passage;
An EGR flow path determining unit that determines an EGR flow path, which is a flow path from the exhaust path for recirculating the exhaust gas to the air supply path, based on an operation map including an engine speed and an engine torque; In addition,
The control execution unit
When it is determined by the compressor operation state confirmation unit that the operation state of the compressor enters the surge region, at least a part of the supply air flowing through the supply air passage on the downstream side of the compressor is removed from the compressor bypass passage. Configured to control the air supply side valve device so as to be able to flow through the common EGR passage and flow into the air supply passage on the upstream side of the compressor; and
When the turbo rotational speed confirmation unit determines that the turbo rotational speed is greater than the target rotational speed, at least a part of the exhaust gas flowing through the exhaust passage on the upstream side of the turbine is removed from the turbine bypass passage. The exhaust-side valve device is controlled so as to be able to flow through the common EGR passage and flow into the exhaust passage on the downstream side of the turbine, and the exhaust gas recirculation is performed by the EGR determination unit. Is determined to be necessary, the exhaust side valve device and the supply side valve device are controlled so as to form the EGR flow path determined by the EGR flow path determination unit.
According to the configuration of (5) above, the exhaust side valve device and the air supply side valve device are controlled after confirmation of the operating state of the compressor, confirmation of the turbo rotation speed, and determination of the EGR flow path. That is, considering whether the operating state of the compressor enters the surge region, whether the turbo rotational speed is larger than the target rotational speed, whether EGR is necessary, and the EGR flow path suitable for the engine operating state One channel is selected from the plurality of channels. For this reason, by forming an appropriate flow path according to the engine operating conditions and load fluctuations, the target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine. .

(6) In some embodiments, in the above configurations (1) to (5),
The exhaust side valve device is
A first exhaust valve provided in the turbine bypass passage;
The shared EGR passage comprises a second exhaust side valve provided between the second branch portion and the exhaust passage,
The air supply side valve device comprises:
A first air supply side valve provided in the compressor bypass passage;
The common EGR passage includes a second air supply side valve provided between the first branch portion and the air supply passage.
According to the configuration (6), the flow rate can be controlled together with the flow direction of the exhaust gas by controlling each of the two valves provided on the exhaust side and the supply side. Accordingly, since an appropriate flow path is set and the flow rate of the exhaust gas is controlled, the target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine.

  According to at least one embodiment of the present invention, a large number of EGR flow paths can be realized with a small number of parts, and a target EGR gas amount required in each of a wide range of operating conditions of the engine can be recirculated. An engine EGR system capable of realizing NOx emission reduction and fuel consumption reduction is provided.

It is a figure showing typically composition of an engine EGR system concerning one embodiment of the present invention. It is a figure explaining the 1st flow path (HPL-EGR) realizable by the engine EGR system shown by FIG. It is a figure explaining the 2nd flow path (LPL-EGR) realizable by the EGR system of the engine shown by FIG. It is a figure explaining the 3rd flow path (HPtoLP-EGR) realizable by the engine EGR system shown in FIG. It is a figure explaining the 4th flow path (compressor bypass + HPL-EGR) realizable by the engine EGR system shown by FIG. It is a figure explaining the 5th flow path (compressor bypass + LPL-EGR) realizable by the engine EGR system shown by FIG. It is a figure explaining the 6th flow path (compressor bypass + HPtoLP-EGR) realizable by the engine EGR system shown in FIG. It is a figure explaining the 7th flow path (turbine bypass + HPL-EGR) realizable by the engine EGR system shown in FIG. It is a figure explaining the 8th flow path (turbine bypass + LPL-EGR) realizable by the engine EGR system shown by FIG. It is a figure explaining the 9th flow path (turbine bypass + HPtoLP-EGR) realizable by the engine EGR system shown in FIG. It is a figure which shows the functional block of the valve control apparatus which concerns on one Embodiment of this invention. It is a figure explaining an example of the operation map of the engine concerning one embodiment of the present invention. It is a figure explaining an example of the operating state map of the compressor concerning one embodiment of the present invention. It is a figure explaining the flow-path determination flow of the flow path through which the exhaust gas by the valve control apparatus which concerns on one Embodiment of this invention passes. It is a figure explaining the flow-path determination flow of the flow path containing a compressor bypass among the flow paths through which the exhaust gas by the valve control apparatus which concerns on one Embodiment of this invention passes. It is a figure explaining the flow-path determination flow of the flow path containing a turbine bypass among the flow paths through which the exhaust gas by the valve control apparatus which concerns on one Embodiment of this invention passes. It is a figure explaining the channel setting according to the operating condition of the engine of the engine EGR system concerning one embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  FIG. 1 is a diagram schematically showing the configuration of an engine EGR system 1 (hereinafter, EGR system 1) according to an embodiment of the present invention. As shown in FIG. 1, the EGR system 1 includes an engine 2, an air supply passage 3, an exhaust passage 4, a supercharger 5 (exhaust turbine supercharger) including a compressor 5C and a turbine 5T, a first A shared EGR passage 6 having a branch portion 61 and a second branch portion 62, an air supply side valve device 34, an exhaust side valve device 44, and a valve control device 8 are provided.

  The engine 2 is, for example, a diesel engine or a gasoline / gas engine. An air supply passage 3 and an exhaust passage 4 are connected to the engine 2, and intake air (supply air Fi) including fresh air Fs from the outside of the EGR system 1 is supplied to the engine 2 through the air supply passage 3. Inhale into each cylinder inside. Further, the fuel is burned together with the supply air Fi (oxygen) in the combustion chamber of the engine 2, and the combustion gas generated by the combustion is discharged to the outside of the EGR system 1 through the exhaust passage 4. In addition, in the illustration of FIG. 1, the multi-cylinder engine 2 of 6 cylinders is illustrated, but it is not limited to this, The number of cylinders is arbitrary.

  The supply passage 3 is a passage through which the supply air Fi flows, and is configured by an intake manifold, an intake pipe, and the like for distributing the supply air Fi to each cylinder of the engine 2. 1, the compressor 5C of the supercharger 5 for compressing the supply air Fi from the upstream side is connected to the supply passage 3. Further, an intercooler 37 is provided downstream of the compressor 5C in the air supply passage 3, and air supply is performed in order to avoid a decrease in air density caused by the supply air Fi compressed by the compressor 5C trying to expand. It is configured to cool Fi. A common EGR passage 6 and a compressor bypass passage 36, which will be described later, are connected to the air supply passage 3, but the throttle valve (not shown) is located more than the position of the air supply passage 3 to which the common EGR passage 6 is connected. It may be provided on the upstream side.

  The exhaust passage 4 is a passage through which the exhaust gas Fe flows, and is configured by an exhaust manifold, an exhaust pipe, or the like that bundles exhaust from each cylinder of the engine 2. The exhaust passage 4 is connected to a turbine 5T of the supercharger 5. A common EGR passage 6 and a turbine bypass passage 46, which will be described later, are connected to the exhaust passage 4, but the catalyst for purifying the exhaust gas Fe is from the position of the exhaust passage 4 to which the common EGR passage 6 is connected. May also be provided downstream.

  As described above, the supercharger 5 includes the turbine 5T provided in the exhaust passage 4 and the compressor 5C provided in the air supply passage 3. The compressor 5 </ b> C and the turbine 5 </ b> T are respectively connected to both ends of one rotating shaft 52. Then, the exhaust gas Fe from the engine 2 flows into the turbine 5T from the upstream side (turbine inlet passage 41) in the exhaust passage 4 and is rotationally driven by energy generated by the flow of the exhaust gas Fe. When the turbine 5T is driven to rotate, the compressor 5C connected to the other end of the rotating shaft 52 is also driven to rotate. When the compressor 5C is driven to rotate, the supply air Fi flowing into the compressor 5C from the upstream side (compressor inlet passage 31) of the compressor 5C is compressed and sent to the downstream side (compressor outlet passage 32) of the compressor 5C. The exhaust gas Fe flows out downstream of the turbine 5T (turbine outlet passage 42) in the exhaust passage 4 after the turbine 5T is rotationally driven.

The shared EGR passage 6 connects the air supply passage 3 and the exhaust passage 4 so that fluid such as the exhaust gas Fe and the air supply Fi can pass through the engine 2 away from the supercharger 5. That is, the shared EGR passage 6 connects the exhaust passage 4 on the downstream side of the turbine 5T and the air supply passage 3 on the upstream side of the compressor 5C.
The shared EGR passage 6 includes a first branch portion 61 that is a branch path in the shared EGR passage 6 and a second branch portion 62 that is closer to the exhaust passage 4 than the first branch portion. have. An EGR cooler 64 is provided in the shared EGR passage 6 between the first branch portion 61 and the second branch portion 62. The EGR cooler 64 is for lowering the temperature of the high-temperature exhaust gas Fe, and is used for increasing the density of the exhaust gas Fe by cooling the exhaust gas Fe. In addition, as long as it is provided between the 1st branch part 61 and the 2nd branch part 62 of the shared EGR channel | path 6, it may be physically one and may be comprised from several EGR cooler 64. FIG. .
A compressor bypass passage 36 and a turbine bypass passage 46 are connected to the first branch portion 61 and the second branch portion 62, respectively.

  In the compressor bypass passage 36, the supply air Fi compressed by the compressor 5C is returned to the upstream side again while bypassing the compressor 5C, or the exhaust gas Fe bypasses the compressor 5C and passes from the common EGR passage 6 to the downstream of the compressor 5C. And is branched from the air supply passage 3 on the downstream side of the compressor 5 </ b> C, and is connected to the shared EGR passage 6 in the first branch portion 61. In other words, the compressor bypass passage 36 connects the compressor outlet passage 32 and the first branch portion 61. Further, the connection position of the compressor bypass passage 36 in the compressor outlet passage 32 is on the upstream side of the intercooler 37 in the illustration of FIG. Thus, by taking the line (compressor bypass passage 36) from the upstream side of the intercooler 37, it is possible to release the pressure immediately after the compressor 5C, and the responsiveness to lower the pressure ratio when entering the surge region is improved. ing.

  The turbine bypass passage 46 is a passage for the exhaust gas Fe from the engine 2 to flow around the turbine 5T, and is branched from the exhaust passage 4 on the upstream side of the turbine 5T. The shared EGR passage 6 is connected. In other words, the turbine bypass passage 46 connects the turbine inlet passage 41 and the second branch portion 62 of the shared EGR passage 6.

  The supply side valve device 34 and the exhaust side valve device 44 control the flow direction of fluid (exhaust gas Fe, supply air Fi, etc.) in each of the compressor bypass passage 36, the turbine bypass passage 46, and the shared EGR passage 6. To do. Further, the supply side valve device 34 and the exhaust side valve device 44 are controlled in accordance with a command from the valve control device 8 (control execution unit 81).

  The valve control device 8 may be an ECU (electronic control unit). Furthermore, it may be provided in a well-known ECU such as an engine control ECU that controls the engine 2, or may be provided separately as a new ECU.

  In the example of FIG. 1, the air supply side valve device 34 is provided between the first air supply side valve 34 a provided in the compressor bypass passage 36 and the first branch portion 61 and the air supply passage 3 in the shared EGR passage 6. The second air supply side valve 34b. The exhaust side valve device 44 includes a first exhaust side valve 44 a provided in the turbine bypass passage 46 and a second exhaust side valve 44 b provided between the second branch portion 62 and the exhaust passage 4 in the shared EGR passage 6. Become. In some other embodiments, the supply side valve device 34 and the exhaust side valve device 44 may be three-way valves provided in the first branch portion 61 and the second branch portion 62, respectively. Further, the supply side valve device 34 (first supply side valve 34a, second supply side valve 34b) and the exhaust side valve device 44 (first exhaust side valve 44a, second exhaust side valve 44b) pass through the passage. A gate valve configured to be fully closed or fully open may be used. Moreover, the flow control valve which can control the flow volume of the exhaust gas which flows through a channel | path by using by intermediate opening degree may be sufficient. According to such a configuration, the flow rate can be controlled together with the flow direction of the exhaust gas Fe by controlling the two valves respectively provided on the exhaust side and the supply side.

  According to the above configuration, the exhaust gas Fe passes through at least one of the compressor bypass passage 36, the turbine bypass passage 46, and the shared EGR passage 6 by controlling the supply side valve device 34 and the exhaust side valve device 44. It becomes possible. That is, the EGR system 1 can realize a plurality of exhaust gas Fe flow paths by controlling the air supply side valve device 34 and the exhaust side valve device 44, respectively. For example, the EGR system 1 has nine flow paths as illustrated in FIGS. 2A to 4C.

  2A to 4C are views for explaining a plurality of (9) exhaust gas Fe flow paths formed by the EGR system 1 in some embodiments.

In the illustration of FIG. 2A, the EGR system 1 is formed with an HPL-EGR type flow path. That is, on the exhaust side, the first exhaust side valve 44a is opened. Therefore, the exhaust gas Fe can be diverted from the turbine inlet passage 41 to the turbine bypass passage 46, and can flow to the second branch portion 62 via the turbine bypass passage 46. Further, the second exhaust side valve 44b is closed, and the flow of the exhaust gas Fe between the second branch portion 62 and the turbine outlet passage 42 via the shared EGR passage 6 is prohibited.
On the other hand, on the supply side, the first supply side valve 34a is opened, and the exhaust gas Fe can flow from the shared EGR passage 6 to the compressor outlet passage 32 via the turbine bypass passage 46. Yes. Further, the second supply side valve 34b is closed, and the flow of the exhaust gas Fe between the first branch portion 61 and the compressor inlet passage 31 via the shared EGR passage 6 is prohibited.

  According to this HPL-EGR system, the high-pressure exhaust gas Fe before passing through the turbine 5T is recirculated from the turbine inlet passage 41 to the compressor outlet passage 32. That is, the high-pressure exhaust gas Fe from the exhaust passage 4 is recirculated to the high-pressure side air supply passage 3 downstream of the compressor 5C, and then merged with the air supply Fi compressed by the compressor 5C. Into the engine 2. Therefore, an EGR line based on the HPL-EGR system even in the operation condition of the engine 2 having a relatively low load (in this case, a flow path including a flow path that passes through the turbine bypass path 46, the shared EGR path 6, and the compressor bypass path 36) Since the differential pressure before and after can be ensured, a large amount of EGR gas can be recirculated. For this reason, in some embodiments, it is used under the operating conditions of the engine 2 in the low speed and low load region.

In the illustration of FIG. 2B, the EGR system 1 of the engine 2 is formed with an LPL-EGR type flow path. That is, on the exhaust side, the first exhaust side valve 44a is closed, and the flow of the exhaust gas Fe from the turbine inlet passage 41 to the turbine bypass passage 46 is prohibited. Further, the second exhaust side valve 44b is opened, and the flow of the exhaust gas Fe between the second branch portion 62 and the turbine outlet passage 42 via the shared EGR passage 6 is permitted.
On the other hand, on the supply side, the first supply side valve 34a is closed, and the flow between the shared EGR passage 6 and the compressor outlet passage 32 via the compressor bypass passage 36 is prohibited. Further, the second air supply side valve 34b is opened, and the exhaust gas Fe is set to be able to flow from the first branch portion 61 to the compressor inlet passage 31 of the air supply passage 3 via the shared EGR passage 6. Has been.

  According to this LPL-EGR system, the low-pressure exhaust gas Fe after passing through the turbine 5T is recirculated from the turbine outlet passage 42 to the compressor inlet passage 31. That is, the low-pressure exhaust gas Fe from the exhaust passage 4 is recirculated to the low-pressure side air supply passage 3 upstream of the compressor 5C, and then merged with the fresh air Fs and flows into the compressor 5C as the supply air Fi. For this reason, the temperature of EGR gas can be suppressed lower than the HPL-EGR method and HPtoLP-EGR described later, and the combustion temperature can be further lowered. Further, since the exhaust gas Fe after the energy is recovered by the turbine 5T is recirculated, the work amount of the turbine 5T is not reduced. However, since the differential pressure before and after the EGR line (in this case, the flow path consisting of the flow path passing through the entire length of the shared EGR path 6) cannot be increased, the flow path is switched to the EGR line by the LPL-EGR method. The delay time until the flow rate becomes stable becomes longer than that of the HPL-EGR method or HPtoLP-EG. For this reason, in some embodiments, the engine 2 is used under the operating condition of the engine 2 from the middle load region to the high load region, which can take a large differential pressure before and after the EGR line.

In the example of FIG. 2C, the EGR system 1 is formed with an HPtoLP-EGR type flow path. That is, on the exhaust side, the first exhaust side valve 44a is opened. Therefore, the exhaust gas Fe can be diverted from the turbine inlet passage 41 to the turbine bypass passage 46, and can flow to the second branch portion 62 via the turbine bypass passage 46. Further, the second exhaust side valve 44b is closed, and the flow of the exhaust gas Fe between the second branch portion 62 and the turbine outlet passage 42 via the shared EGR passage 6 is prohibited.
On the other hand, on the supply side, the first supply side valve 34a is closed, and the exhaust gas Fe is prohibited from flowing from the shared EGR passage 6 to the compressor outlet passage 32 via the compressor bypass passage 36. Yes. Further, the second air supply side valve 34 b is opened, and the exhaust gas Fe can flow from the first branch portion 61 to the compressor inlet passage 31 via the shared EGR passage 6.

  According to the HPtoLP-EGR method, the high-pressure exhaust gas Fe before passing through the turbine 5T is recirculated from the turbine inlet passage 41 to the compressor inlet passage 31. That is, the high-pressure exhaust gas Fe from the exhaust passage 4 is returned to the low-pressure side air supply passage 3 upstream of the compressor 5C, and then merged with the fresh air Fs and flows into the compressor 5C as the supply air Fi. For this reason, the differential pressure before and after the EGR line (in this case, the flow path consisting of the flow path passing through the turbine bypass passage 46 and the shared EGR path 6) can be made larger than the HPL-EGR method and the LPL-EGR method. A large amount of EGR gas can be refluxed. However, since at least a part of the exhaust gas Fe flows by bypassing the turbine 5T, the work amount of the supercharger 5 is reduced, so that it is not suitable for a high load where a high supercharging pressure is required. For this reason, in some embodiments, the amount of supplied air is relatively small, and the engine 2 is used in a medium / low / medium / low load region, which is an operating condition of the engine 2 that requires a high EGR rate.

  In the following examples of FIGS. 3A to 3C, an EGR flow path including a compressor bypass is set in the EGR system 1. 3A, the exhaust gas Fe passes through the compressor bypass passage 32 from the compressor outlet passage 32 without passing through the compressor 5C, passes through the common EGR passage 6, and passes through the compressor inlet passage. The flow path can return to 31.

In the illustration of FIG. 3A, the above-described EGR system 1 is formed with a compressor bypass system that is a flow path including only a compressor bypass. That is, on the exhaust side, the first exhaust side valve 44a is closed, and the flow of the exhaust gas Fe that diverts from the turbine inlet passage 41 to the turbine bypass passage 46 is prohibited. The second exhaust side valve 44b is also closed, and the flow of the exhaust gas Fe between the second branch portion 62 of the shared EGR passage 6 and the exhaust passage 4 (turbine outlet passage 42) is also prohibited. That is, the exhaust gas Fe passes through the turbine 5T from the turbine inlet passage 41 to the turbine outlet passage 42 without being diverted in the middle.
On the other hand, on the air supply side, the first air supply side valve 34a is opened. That is, the supply air Fi can be diverted from the compressor outlet passage 32 to the compressor bypass passage 36 and can flow to the first branch portion 61 via the compressor bypass passage 36. Further, the second air supply side valve 34 b is also opened, and the air supply Fi can flow from the first branch portion 61 to the compressor inlet passage 31 via the shared EGR passage 6.

  According to this turbine bypass system, the pressure ratio of the compressor 5C can be lowered while maintaining the passage flow rate of the supply air Fi passing through the compressor 5C and the rotational speed of the turbine 5T, and therefore the surging of the compressor 5C can be prevented. Can do. For this reason, in some embodiments, when the load of the engine 2 is increased from idling, the compressor 5C is prevented from entering the surge region due to excessive increase of the supercharging pressure by the supercharger 5. Used for.

  In the illustration of FIG. 3B, the EGR system 1 has a HPtoLP-EGR type flow path (compressor bypass + HPtoLP-EGR type) together with the compressor bypass type. That is, on the exhaust side, the first exhaust side valve 44a is in an open state, and conversely, the second exhaust side valve 44b is in a closed state. On the air supply side, the first air supply side valve 34a and the second air supply side valve 34b are both open. As a result, the exhaust gas Fe can flow from the turbine inlet passage 41 to the second branch portion 62 via the turbine bypass passage 46. Further, the supply air Fi including the EGR gas that has been circulated in the supply passage 3 can flow from the compressor outlet passage 32 to the second branch portion 62 via the compressor bypass passage 36. The EGR gas and the supply air Fi from the two directions can further pass through the first branch portion 61 and flow into the compressor inlet passage 31.

  According to this compressor bypass + HPtoLP-EGR method, the pressure ratio of the compressor 5C can be lowered while maintaining the flow rate of the supply air Fi and the rotational speed of the turbine 5T, as in the compressor bypass method. For this reason, the surging of the compressor 5C can be prevented, and the EGR gas can be recirculated. In some embodiments, the compressor bypass + HPtoLP-EGR system, when the load of the engine 2 is increased from the idling operation, the compressor 5C enters the surge region due to excessive increase of the supercharging pressure by the supercharger 5. This is used when it is desired to recirculate the EGR gas while preventing this.

  In the illustration of FIG. 3C, the EGR system 1 includes a LPL-EGR type flow path as well as a compressor bypass type (compressor bypass + LPL-EGR type). That is, on the exhaust side, the first exhaust side valve 44a is in a closed state, and conversely, the second exhaust side valve 44b is in an open state. On the air supply side, the first air supply side valve 34a and the second air supply side valve 34b are both open. As a result, the exhaust gas Fe is prohibited from being diverted from the turbine inlet passage 41 to the turbine bypass passage 46, while the first branch portion passes through the second branch portion 62 of the shared EGR passage 6 from the turbine outlet passage 42. It is possible to flow to 61. The supply air Fi can flow from the compressor outlet passage 32 to the second branch portion 62 via the compressor bypass passage 36. The EGR gas and the supply air Fi from the two directions can further flow into the compressor inlet passage 31 via the first branch portion 61.

  According to this compressor bypass + LPL-EGR method, similarly to the compressor bypass method, the pressure ratio of the compressor 5C can be lowered while maintaining the flow rate of the supply air Fi and the rotational speed of the turbine 5T, and the compressor 5C can be surging. While preventing, EGR gas can be recirculated. Further, unlike the compressor bypass + HPtoLP-EGR method, the exhaust gas Fe after the energy is recovered by the turbine 5T is recirculated, so that the work amount of the turbine 5T is not reduced. For this reason, in some embodiments, when the load of the engine 2 is increased from idling, the compressor 5C is prevented from operating in the surge region due to excessive increase of the supercharging pressure by the supercharger 5. Used when EGR gas is to be introduced.

  In the following examples of FIGS. 4A to 4C, an EGR flow path including a turbine bypass is set in the EGR system 1. 4A, the exhaust gas Fe passes through the turbine bypass passage 46 from the turbine inlet passage 41 without passing through the turbine 5T, passes through the shared EGR passage 6, and passes through the turbine outlet passage 42. It is a flow path which can return to.

In the illustration of FIG. 4A, the above-described EGR system 1 is formed with a turbine bypass system that is a flow path including only a turbine bypass. That is, on the exhaust side, the first exhaust side valve 44a is opened. Therefore, the exhaust gas Fe can be diverted from the exhaust passage 4 (turbine inlet passage 41) to the turbine bypass passage 46, and can flow to the second branch portion 62 via the turbine bypass passage 46. . Further, the second exhaust side valve 44 b is also opened, and the exhaust gas Fe can flow from the second branch portion 62 to the turbine outlet passage 42 via the shared EGR passage 6.
On the other hand, on the supply side, the first supply side valve 34a is closed, and the exhaust gas Fe is prohibited from flowing from the shared EGR passage 6 to the compressor outlet passage 32 via the compressor bypass passage 36. Yes. The second supply side valve 34b is also closed, and the flow of exhaust gas Fe between the first branch portion 61 and the compressor inlet passage 31 via the shared EGR passage 6 is also prohibited.

  According to the turbine bypass system, at least a part of the exhaust gas Fe is diverted to the turbine bypass passage 46, so that the energy flowing into the turbine 5T can be reduced, and the same effect as the wastegate (WG) valve is realized. can do. For this reason, in some embodiments, when the load of the engine 2 is reduced, unnecessary rotation of the turbine 5T exceeding the target rotational speed is avoided, or the excess of the turbine 5T due to an increase in the air supply amount at low temperatures. Used to prevent rotation. Further, the WG valve can be dispensed with.

  In the illustration of FIG. 4B, the EGR system 1 includes a HPL-EGR system flow path as well as a turbine bypass system (turbine bypass + HPL-EGR system). That is, on the exhaust side, the first exhaust side valve 44a and the second exhaust side valve 44b are both open. On the supply side, the first supply side valve 34a is open, and conversely, the second supply side valve 34b is closed. As a result, the exhaust gas Fe can flow from the turbine inlet passage 41 to the second branch portion 62 via the turbine bypass passage 46. Further, from the second branch portion 62, a flow path that passes through the shared EGR passage 6 toward the turbine outlet passage 42, and a compressor outlet passage from the first branch portion 61 of the shared EGR passage 6 via the compressor bypass passage 36. The exhaust gas Fe can flow in two directions of the flow path toward 32.

  According to the turbine bypass + HPL-EGR method, the energy flowing into the turbine 5T can be reduced as in the turbine bypass method, and the high-pressure exhaust gas Fe in the turbine inlet passage 41 can be returned to the compressor outlet passage 32. For this reason, in some embodiments, it is used when it is necessary to introduce EGR gas while preventing unnecessary turbine work when the load of the engine 2 is reduced.

  In the example of FIG. 4C, the EGR system 1 includes a flow path of the HPtoLP-EGR system together with the turbine bypass system (turbine bypass + HPtoLP-EGR system). That is, on the exhaust side, the first exhaust side valve 44a and the second exhaust side valve 44b are both open. On the supply side, the first supply side valve 34a is closed, and conversely, the second supply side valve 34b is opened. As a result, the exhaust gas Fe can flow from the turbine inlet passage 41 to the second branch portion 62 via the turbine bypass passage 46. Further, from the second branch portion 62, a flow path that passes through the shared EGR passage 6 to the turbine outlet passage 42, and a compressor inlet from the second branch portion 62 of the shared EGR passage 6 via the first branch portion 61. The exhaust gas Fe can flow in two directions of the flow path toward the passage 31.

  According to the turbine bypass + HPtoLP-EGR method, the energy flowing into the turbine 5T can be reduced and the EGR gas can be recirculated to the compressor inlet passage 31 as in the turbine bypass method. Moreover, since the differential pressure before and after the EGR line (in this case, the flow path passing through the turbine bypass passage 46 and the common EGR passage 6) is more likely to be generated, EGR gas can be recirculated in a large amount as compared with the turbine bypass + HPL-EGR method. For this reason, in some embodiments, it is used when the load of the engine 2 is sharply reduced.

  The EGR system 1 includes a flow path when the first exhaust side valve 44a, the second exhaust side valve 44b, the first supply side valve 34a, and the second supply side valve 34b are all closed. Can also be set. That is, in this case, the flow of the exhaust gas Fe to all the passages of the compressor bypass passage 36, the turbine bypass passage 46, and the shared EGR passage 6 is prohibited, so that the supply air Fi is not divided in the middle. All of the exhaust gas Fe flows through the air supply passage 3 to the engine 2 and is exhausted to the outside of the EGR system 1 via the exhaust passage 4 without being divided in the middle.

  According to the above configuration, the plurality of flow paths for the exhaust gas Fe passing through at least one of the shared EGR passage 6, the compressor bypass passage 36, or the turbine bypass passage 46 include the exhaust side valve device 44 and the supply side. It is formed by the control of the valve device 34. Further, the EGR cooler 64 includes a first branch portion 61 and a second branch portion of the shared EGR passage 6 that are portions through which the exhaust gas Fe (EGR gas) always passes when recirculating from the exhaust passage 4 to the supply passage 3. 62. For this reason, the flow path for the exhaust gas Fe according to the engine operating conditions and load fluctuations can be appropriately set. Therefore, the target EGR gas amount required in each of a wide range of operating conditions of the engine 2 can be recirculated to the engine 2, and reduction of NOx emission amount and fuel consumption can be realized. Including a flow path that does not pass through all of the shared EGR passage 6, the compressor bypass passage 36, and the turbine bypass passage 46 (a flow path including only the supply passage 3 and the exhaust passage 4). One channel is selected from among a plurality of channels including.

In the embodiment shown in FIG. 1, the valve control device 8 includes a control execution unit 81 that controls the exhaust side valve device 44 and the air supply side valve device 34.
In some other embodiments, as shown in FIG. 5, the valve control device 8 further includes a compressor operation state confirmation unit 82 for confirming the operation state of the compressor 5C. When the compressor operation state confirmation unit 82 determines that the operation state of the compressor 5C enters the surge region, the valve control device 8 determines at least the supply air Fi flowing through the supply passage 3 on the downstream side of the compressor 5C. The supply side valve device 34 is configured to be controlled so that a part can pass from the compressor bypass passage 36 through the shared EGR passage 6 to the supply passage 3 upstream of the compressor 5C.

  As described above, the compressor operation state confirmation unit 82 is configured to determine whether or not the compressor bypass system is necessary by determining whether or not the operation state of the compressor 5C enters the surge region. At the same time, the compressor operation state confirmation unit 82 is configured to input the determination result to the control execution unit 81. Therefore, as illustrated in FIG. 5, the operating state of the compressor 5 </ b> C is input to the compressor operating state confirmation unit 82.

  The operating state of the compressor 5C may be, for example, a pressure ratio that is a ratio between a fresh air amount that is a flow rate of the fresh air Fs and an atmospheric pressure and a pressure at the outlet of the compressor 5C. In this case, the new air amount may be detected by a flow rate detection means 38 such as an air amount sensor, and the pressure ratio is detected by a pressure ratio detection means 39 such as a pressure sensor. May be. That is, the detection values from the flow rate detection means 38 and the pressure ratio detection means 39 may be input to the compressor operation state confirmation unit 82 as information regarding the operation state of the compressor 5C.

  In some embodiments, the operation state of the compressor 5C may be confirmed by the compressor operation state confirmation unit 82 by comparing the input operation state of the compressor 5C with the operation state map 87. A well-known map can be used as the operating state map 87. For example, when a new air amount and the above pressure ratio are input, the operating state map 87 is a new air amount, the above pressure ratio, and an operating state map. By comparing these, it is possible to determine whether or not the surge region has entered. In determining whether or not the surge region has entered, not only when the operating state of the compressor 5C is in the surge region, but also when the possibility of entering the surge region is predicted to be high, the determination of entering the surge region is affirmed. Then, it may be determined.

  FIG. 6 shows an example of the operating state map 87. The fresh air amount is indicated on the horizontal axis, the pressure ratio is indicated on the vertical axis, and the surge region is the region on the left side of the surge line SL. The supply air Fi compressed by the compressor 5C is recirculated from the compressor outlet passage 32 to the compressor inlet passage 31 by the compressor bypass passage, thereby increasing the amount of air supply passing through the compressor inlet passage 31 or the above pressure. By reducing the ratio, the operating state of the compressor 5C can be changed away from the surge region. In addition, the broken line in FIG. 6 shows the equal rotation speed curve EL. Further, in some other embodiments, for example, the load to the surge region is changed according to the fluctuation state of the load state of the engine 2 such as a load increase from a low load state or a change from a high load state to a low load state. Intrusion determination may be performed. Further, the new air amount may be an air supply amount (a flow rate of the supply air Fi).

  In addition, the control execution unit 81 receives an input of the determination result of the intrusion determination to the surge region by the compressor operation state confirmation unit 82, and sets the flow path according to the determination result. That is, when it is determined that the operating state of the compressor 5C enters the surge region, the flow path formed in the EGR system 1 includes the compressor bypass channel, and when it is determined that the compressor 5C does not enter the surge region. The compressor bypass flow path will not be included. More specifically, when it is determined that the EGR system 1 enters the surge region, any of the flow paths including the compressor bypass system and the compressor bypass system (see, for example, FIGS. 3A to 3C) is formed. On the contrary, when it is determined not to enter the surge region, any of the flow paths not including the compressor bypass system (for example, see FIGS. 2A to 2C and FIGS. 4A to 4C) is formed.

  According to the above configuration, when the operating state of the compressor 5C enters the surge region, the exhaust gas Fe can flow while bypassing the compressor 5C from the downstream side to the upstream side of the compressor 5C in the air supply passage 3. The compressor bypass flow path is formed by controlling the supply side valve device 34. For this reason, it is possible to recirculate the target EGR gas amount required in each of a wide range of operating conditions of the engine 2 to the engine while preventing the compressor 5C from being operated in the surge region.

  Further, in some other forms, as shown in FIG. 5, the valve control device 8 further includes a turbo rotational speed confirmation unit 83 that confirms the turbo rotational speed that is the rotational speed of the supercharger 5. When the turbo rotation speed confirmation unit 83 determines that the turbo rotation speed is larger than the target rotation speed, the control execution unit 81 at least part of the exhaust gas Fe flowing through the exhaust passage 4 on the upstream side of the turbine 5T. Is configured to control the exhaust-side valve device 44 so as to be able to flow from the turbine bypass passage 46 through the shared EGR passage 6 to the exhaust passage 4 on the downstream side of the turbine 5T.

  As described above, the turbo rotational speed confirmation unit 83 is configured to compare the turbo rotational speed with the target rotational speed and determine whether or not the turbine bypass system is necessary according to the determination result by this comparison. That is, when it is determined that the turbo speed is higher than the target speed, it is determined that a turbine bypass system is necessary to avoid an increase in the supercharging pressure, and conversely, the turbo speed is equal to or lower than the target speed. In this case, it is judged that the turbine bypass method is unnecessary. At the same time, the turbo rotational speed confirmation unit 83 is configured to input the determination result to the control execution unit 81. Therefore, as shown in FIG. 5, the turbo rotation speed confirmation unit 83 includes the turbo rotation speed information that is information about the turbo rotation speed and the target rotation speed that is information about the target rotation speed. Information is entered.

The turbo rotational speed information is information necessary for estimating (calculating) the turbo rotational speed or the turbo rotational speed. In some embodiments, the turbo rotational speed is input to the turbo rotational speed confirmation unit 83 as turbo rotational speed information. In this case, the turbo rotational speed may be directly detected by a rotational speed detecting means capable of detecting the rotational speed of the supercharger 5 and input as turbo rotational speed information.
In some other embodiments, information for calculating the turbo rotational speed is input to the turbo rotational speed confirmation unit 83 as turbo rotational speed information, and the turbo rotational speed confirmation unit 83 receives the turbo rotational speed from the input information. Calculate the number.

  The turbo rotational speed can be calculated from, for example, a new air amount, a pressure ratio that is a ratio of atmospheric pressure (pressure at the inlet of the compressor 5C) and pressure at the outlet of the compressor 5C. For this reason, the turbo rotational speed calculation by the turbo rotational speed confirmation unit 83 is performed by using the detected values from the flow rate detection means 38 and the pressure ratio detection means 39 (39a, 39b) as turbo rotational speed information as illustrated in FIG. The turbo rotational speed may be calculated based on the input. In general, in the engine 2 having the external EGR and the supercharger 5, the fuel injection amount instruction value of the engine ECU, the atmospheric pressure sensor, the engine speed Ne, the flow rate of the fresh air Fs, and the pressure of the supply manifold In many cases, temperature is measured and used for control. For this reason, if the turbo rotational speed is calculated in this way, the turbo rotational speed can be calculated without providing a new sensor for the EGR system 1.

  On the other hand, the target rotational speed information is information necessary for calculating the target rotational speed or the target rotational speed. The target rotational speed is a rotational speed required to obtain a supercharging pressure corresponding to the output required for the engine 2, for example, depending on the operation amount of the accelerator pedal that determines the opening of the throttle valve. The target rotational speed may be determined. In addition to this, the target rotation speed may be determined within a range of the rotation speed that avoids over-rotation of the turbine 5T that may cause damage to the turbine 5T. In some embodiments, the target rotational speed is input to the turbo rotational speed confirmation unit 83. In some other embodiments, information for calculating the target rotational speed is input to the turbo rotational speed confirmation unit 83, and the turbo rotational speed confirmation unit 83 calculates the target rotational speed from this input information.

  Further, the control execution unit 81 receives an input of the turbo rotation speed determination result from the turbo rotation speed confirmation unit 83, and sets the flow path setting according to the determination result. That is, when it is determined that the rotation speed of the turbine 5T (supercharger 5) is larger than the target rotation speed, the flow path formed in the EGR system 1 includes a turbine bypass flow path, and the turbine 5T rotation When it is determined that the number is equal to or less than the target rotational speed, the turbine bypass passage is not included. More specifically, in the EGR system 1, when it is determined that the rotational speed of the turbine 5T is larger than the target rotational speed, in order to avoid further increase in the rotational speed of the supercharger 5, the turbine bypass Any of the flow paths including the system (for example, see FIGS. 4A to 4C) is formed, and conversely, when the turbo rotation speed is equal to or lower than the target rotation speed, the flow path not including the turbine bypass system (for example, FIG. 2A). To 3C) is formed.

  According to the above configuration, when it is determined that the turbo rotational speed is higher than the target rotational speed, the exhaust gas Fe flows while bypassing the turbine 5T from the upstream side to the downstream side of the turbine 5T in the exhaust passage 4 A possible turbine bypass flow path is formed by controlling the exhaust side valve device 44. Thus, since the exhaust side valve device 44 performs the same function as the wastegate valve, the turbocharger 5 is not provided with a separate means for controlling the rotation of the supercharger 5 such as a wastegate valve or a variable nozzle mechanism. The target EGR gas amount required in each of a wide range of operating conditions of the engine 2 can be recirculated to the engine while controlling the rotational speed.

The number and installation positions of the flow rate detection means 38 for detecting the fresh air amount and the pressure ratio detection means 39 for detecting the pressure ratio between the inlet and outlet of the compressor are arbitrary.
For example, in the illustration of FIG. 1, the flow rate detection means 38 is provided in the air supply passage 3 on the upstream side of the connection point between the shared EGR passage 6 and the air supply passage 3.
On the other hand, in the illustration of FIG. 1, the pressure ratio detection means 39 is a pressure detection means 39 a for detecting the atmospheric pressure provided in the compressor inlet passage on the upstream side of the connection location between the shared EGR passage 6 and the air supply passage 3. The pressure detection means 39b is configured to detect the pressure at the outlet of the compressor 5C provided in the compressor outlet passage 32. Further, as illustrated in FIG. 1, the pressure detection means 39 b for detecting the pressure at the outlet of the compressor 5 </ b> C may be provided in the compressor outlet passage 32 on the downstream side of the intercooler 37. You may calculate using the pressure loss calculated from the downstream pressure and the amount of fresh air.

  In some other embodiments, the valve control device 8 includes an EGR determination unit 84 that determines whether or not the exhaust gas Fe needs to be recirculated from the exhaust passage 4 to the air supply passage 3, and the exhaust gas Fe is recycled. An EGR flow path determining unit 85 that determines an EGR flow path that is a flow path from the exhaust passage 4 to the air supply path 3 for circulation on the basis of an operation map 86 including the engine speed Ne and the engine torque T. Including. When the EGR determination unit 84 determines that recirculation of the exhaust gas Fe is necessary, the control execution unit 81 forms the EGR flow path determined by the EGR flow path determination unit 85 so as to form the EGR flow path. The device 44 and the supply side valve device 34 are configured to be controlled.

  That is, recirculation necessity determination information for determining the necessity of recirculation of the exhaust gas Fe from the exhaust passage 4 to the air supply passage 3 is input to the EGR determination unit 84. The recirculation necessity determination information may be, for example, the detected value of the temperature of the exhaust gas Fe, a knock sensor, a NOx sensor, or the like. In addition, the operating condition of the engine 2 is input to the EGR flow path determination unit 85, and the operation map 86 can be referred to. Then, referring to the operation map 86 using the operating conditions of the engine 2, one flow path can be selected from a plurality of EGR flow paths.

  The operation map 86 is configured such that an EGR flow path to be selected according to the operating condition of the engine 2 is obtained. For example, the operating condition of the engine 2 may be the engine speed Ne and the engine torque T, and the operation map 86 in this case is as illustrated in FIG. That is, in the operation map 86 illustrated in FIG. 7, the horizontal axis indicates the engine speed Ne, and the vertical axis indicates the engine torque T. The HPL-EGR flow path is selected in the low load area (area where both Ne and T are small), and the LPL-EGR flow path and medium load area (area where both Ne and T are large) are selected. (Ne and T are larger than the low load region and smaller than the high load region), the HPtoLP-EGR flow path is selected. In other words, the intersection point when the operating conditions (engine speed Ne and engine torque T) input to the EGR flow path determining unit 85 are plotted in FIG. 7 corresponds to any of the regions divided by the above three methods. Thus, an EGR channel to be selected is obtained. The engine rotational speed Ne may be detected by the rotational speed detection means 22 that can detect the engine rotational speed. Further, the engine torque T may be detected by a torque sensor, or may be calculated based on the fuel injection amount.

  According to the above configuration, when the exhaust gas Fe needs to be recirculated from the exhaust passage 4 to the air supply passage 3, the flow from the exhaust passage 4 to the air supply passage 3 for recirculating the exhaust gas Fe is performed. An EGR flow path suitable for the operating condition of the engine 2 is determined from a plurality of EGR flow paths that are roads. As a result, an appropriate flow path is formed according to the operating conditions of the engine 2 and fluctuations thereof, so that the target EGR gas amount required in each of a wide range of operating conditions of the engine 2 can be recirculated to the engine. it can.

  In some other embodiments, as shown in FIG. 5, the control execution unit 81 receives outputs from the compressor operation state confirmation unit 82, the turbo rotation number confirmation unit 83, and the EGR flow path determination unit 85. It may be configured to be input. As a result, the control execution unit 81 receives three pieces of information, that is, whether the EGR flow path, the necessity of the compressor bypass flow path, and the necessity of the turbine bypass flow path, and are exemplified in FIGS. 8A to 8C. Thus, based on these input information, one flow path most suitable for the operating condition of the engine 2 can be selected from a plurality of flow paths for the exhaust gas Fe. And the control execution part 81 forms the selected flow path in the EGR system 1 by controlling the air supply side valve device 34 and the exhaust side valve device 44.

  FIG. 8A to FIG. 8C are diagrams illustrating a flow path determination flow of a flow path to be realized by the EGR system 1 in some embodiments. FIG. 8A is a diagram for explaining the entire flow path determination flow. 8B illustrates details of the flow path determination including the compressor bypass (step S820) in FIG. 8A, and FIG. 8C illustrates details of the flow path determination including the turbine bypass in FIG. 8A (step S830). It is. 8A to 8C are described using the operation map 86 illustrated in FIG.

  In step S81 of FIG. 8A, it is determined whether the operating state of the compressor 5C enters the surge region. If it is determined in step S81 that the surge region is not entered, it is determined in subsequent step S82 whether the turbo speed is greater than the target speed. If the turbo rotational speed is equal to or lower than the target rotational speed in step S82, it is determined in step S83 whether EGR is necessary (whether exhaust gas Fe is recirculated). If it is determined in step S83 that EGR is necessary, the operating condition of the engine 2 is confirmed in step S84.

In step S85 to step S89, in order to determine the EGR flow path to be set, it is determined in which region of the operation map 86 the detected operating condition (engine speed Ne, engine torque T) of the engine 2 is present. Is done. That is, first, in step S85, it is determined whether the operating condition of the engine 2 is a region where LPL-EGR is used. If it is determined that the region uses LPL-EGR, the LPL-EGR method (see FIG. 2B) is selected in step S89.
Conversely, if it is determined in step S85 that the operating condition of the engine 2 is not in the region using LPL-EGR, in step S86, is the operating condition of the engine 2 in the region using HPtoLP-EGR? To be judged. If it is determined in step S86 that the region is not in the area where HPtoLP-EGR is used, the HPL-EGR method (see FIG. 2A) is selected in step S87. On the other hand, if it is determined in step S86 that the region is in the area where HPtoLP-EGR is used, the HPtoLP-EGR flow path (see FIG. 2C) is selected in step S88.

On the other hand, if it is determined in step S81 that the operating state of the compressor 5C enters the surge region, a flow path including a compressor bypass system is set. Specifically, in step S820, as illustrated in FIG. 8B, one flow path is selected from the flow paths including the compressor bypass (for example, see FIGS. 3A to 3C).
If it is determined in step S82 that the turbo speed is greater than the target speed, a flow path including a turbine bypass system is set. Specifically, in step S830, as illustrated in FIG. 8C, one flow path is selected from the flow paths including the turbine bypass (for example, see FIGS. 4A to 4C).

  If it is determined in step S83 that EGR is unnecessary, it is determined that the compressor bypass method and the turbine bypass method are also unnecessary. Therefore, the supply side valve device 34 and the exhaust side valve device 44 are controlled so that the exhaust gas Fe image does not pass through any of the compressor bypass passage 36, the turbine bypass passage 46, and the shared EGR passage 6. A passage (default passage) is selected.

  FIG. 8B is a diagram illustrating details of step S820 of FIG. 8A in some embodiments. That is, if it is determined in step S81 of FIG. 8A that the operating state of the compressor 5C enters the surge region, whether or not EGR is necessary is determined in step S821 of FIG. 8B. If it is determined in step S821 that EGR is unnecessary, the compressor bypass method is selected in step S826.

Conversely, if it is determined in step S821 that EGR is necessary, the operating conditions of the engine 2 are confirmed in step S822, as in step S84 described above. In step S823, it is determined whether the operating condition of the engine 2 is in the region using LPL-EGR. If it is determined that the operating condition is in the region using LPL-EGR, the compressor bypass + LPL-EGR method (FIG. 3C). Browse) is selected.
On the other hand, if it is determined in step S823 that the region is not in the region using LPL-EGR, the compressor bypass + HPtoLP-EGR method (see FIG. 3B) is selected in step S825.

FIG. 8C is a diagram illustrating details of step S830 of FIG. 8A in some embodiments.
is there. That is, if it is determined in step S82 in FIG. 8A that the turbo rotation speed is greater than the target rotation speed, whether or not EGR is necessary is determined in step S831 in FIG. 8C. If it is determined in step S831 that EGR is unnecessary, a turbine bypass system (see FIG. 4A) is selected in step S836.

Conversely, if it is determined in step S831 that EGR is necessary, the operating condition of the engine 2 is confirmed in step S832, as in step S84 described above. In step S833, it is determined whether or not the operating condition of the engine 2 is in a region where HPtoLP-EGR is used. ) Is selected.
On the other hand, if it is determined in step S833 that there is no HPtoLP-EGR region, the turbine bypass + HPL-EGR method (see FIG. 4B) is selected in step S835.

  According to the configuration for performing the flow path determination flow as described above, after confirming the operating state of the compressor 5C, confirming the turbo rotation speed, and determining the EGR flow path, the exhaust side valve device 44 and the supply side valve Device 34 is controlled. That is, whether the operating state of the compressor 5C enters the surge region, whether the turbo rotation speed is larger than the target rotation speed, the necessity of EGR, and the EGR flow path suitable for the operating state of the engine 2 are considered. Above, one channel is selected from among a plurality of channels. For this reason, the target EGR gas amount required in each of a wide range of the operating conditions of the engine 2 can be recirculated to the engine by setting an appropriate flow path according to the operating conditions of the engine and its fluctuations. it can.

  FIG. 9 is a diagram illustrating the switching of the flow path for the exhaust gas Fe according to the load state (region) of the EGR system 1 in some embodiments. In FIG. 9, the horizontal axis indicates time t, and the vertical axis indicates engine load P, showing how the engine load P changes as time t elapses.

In FIG. 9, the engine 2 is idling at time t0. During idle operation, the engine 2 is in a low rotation (low speed) and low load state. In this case, it is preferable to use an HPL-EGR system that can recirculate a lot of EGR gas.
Then, during time t0 to t1, the load gradually increases from the idle operation. As described above, when the load is increased from the idling operation, the supercharging pressure by the supercharger 5 is increased by increasing the fuel injection amount, but the flow rate of the fresh air Fs is insufficient and the operating state of the compressor 5C is in the surge region. Easy to rush. Therefore, a flow path including a compressor bypass is preferable only during a load increase. Further, in the compressor bypass + HPtoLP-EGR method, the exhaust gas Fe is recirculated from the turbine inlet passage 41, so that the energy of the exhaust gas Fe by the turbine 5T is not sufficiently recovered. For this reason, it is preferable to use a compressor bypass method (see FIG. 3A) or a compressor bypass + LPL-EGR method (see FIG. 3C), and to prevent the operation state of the compressor 5C from entering the surge region while maintaining the turbo rotational speed. be able to.

  Between times t1 and t2, the engine 2 is operating in a medium load state. During such medium load operation, the HPtoLP-EGR method is preferable. That is, under such operating conditions, the fresh air amount of the fresh air Fs is sufficient, but since the target EGR gas amount is large, the EGR gas amount is insufficient in both the HPL-EGR method and the LPL-EGR method. It's easy to do. Therefore, a large amount of EGR gas can be introduced by adopting the HPtoLP-EGR system in which the differential pressure before and after the piping is most likely to stand.

  Between times t2 and t3, the engine 2 is rising from the middle load state to the high load state. When rising from such a medium load state to a high load state, the HPtoLP-EGR system can take a large differential pressure before and after the EGR line until a differential pressure is established between the supply passage 3 and the exhaust passage 4. Is preferably continued. After that, when the flow rate of the EGR gas increases, it is preferable to switch to the LPL-EGR system that can take a large differential pressure before and after the EGR line in the middle load state to the high load state.

  Between the times t3 and t4, the engine 2 is in a high load state. In such a high load state, an LPL-EGR system that can take a large differential pressure before and after the EGR line in a medium load state to a high load state is preferable. Further, in the LPL-EGR method, the temperature of the EGR gas can be lowered as compared with the case where the HPL-EGR method is used, and therefore the reduction of NOx emission can be expected due to a decrease in the combustion temperature. Further, in the case of a spark ignition engine, the temperature in the combustion chamber before the start of the compression process of the engine 2 is reduced, so that knocking is suppressed as compared with the HPL-EGR method, and the ignition timing can be further advanced, thereby reducing fuel consumption. Improvement can be expected.

  Between times t4 and t5, the engine 2 is gradually lowered from the high load state to the medium load state. When such an engine 2 is lowered from a high load state to a medium load state, a flow path including a turbine bypass is preferable. Moreover, since the load of the engine 2 is gradually reduced, it is preferable to switch from the LPL-EGR method to the turbine bypass + HPL-EGR method. Thereby, since at least a part of the exhaust gas Fe bypasses the turbine 5T due to the formation of the turbine bypass flow path, unnecessary rotation of the turbine 5T exceeding the target rotational speed can be avoided. Further, when the temperature or flow rate of the exhaust gas Fe at the turbine inlet is lowered, it is preferable to switch to the HPtoLP-EGR system that can increase the differential pressure before and after the EGR line.

From time t5 to t6, the engine 2 is operating in a medium load state, and thus the same as the above-described t1 to t2.
Further, the load on the engine 2 decreases during the time t6 to t7, and the idling operation is performed at the time t7. When the load is reduced in this way, it is preferable to switch to the turbine bypass + HPL-EGR method from time t4 to time t5. Further, when the gas temperature / flow rate at the inlet of the turbine 5T decreases, it is preferable to switch to the HPL-EGR method.

  In this way, by appropriately switching the flow path according to the engine operating conditions and fluctuations thereof, the target EGR gas amount required in each of a wide range of engine operating conditions can be recirculated to the engine, Reduction of NOx emissions and reduction of fuel consumption are realized.

The present invention is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.
Further, the present invention can be applied to general internal combustion engines such as diesel engines, and can be applied to, for example, vehicles, ships, power generation engines, and the like.

DESCRIPTION OF SYMBOLS 1 Engine EGR system 2 Engine 22 Rotation speed detection means 3 Supply air passage 31 Compressor inlet passage 32 Compressor outlet passage 33 Temperature detection means 34 Supply side valve device 34a First supply side valve 34b Second supply side valve 36 Compressor Detour passage 37 Intercooler 38 Flow detection means 39 Pressure ratio detection means 39a Pressure detection means 39b Pressure detection means 4 Exhaust passage 41 Turbine inlet passage 42 Turbine outlet passage 44 Exhaust side valve device 44a First exhaust side valve device 44b Second exhaust side Valve device 46 Turbine bypass passage 5 Turbocharger 52 Shaft 5C Compressor 5T Turbine 6 Shared EGR passage 61 First branch portion 62 Second branch portion 64 EGR cooler 8 Valve controller 81 Control execution portion 82 Compressor operation state confirmation portion 83 Turbo speed Confirmation part 8 EGR determination unit 85 EGR flow path determining section 86 working map

Fe Exhaust gas Fi Supply air Fs Fresh air Ne Engine speed T Engine torque SL Surge line EL Constant speed curve P Engine load t Time (time)
S step

Claims (6)

An engine EGR system comprising a turbocharger comprising a turbine provided in an exhaust passage through which exhaust gas flows and a compressor provided in an air supply passage through which supply air flows,
A shared EGR passage connecting the exhaust passage downstream of the turbine and the air supply passage upstream of the compressor;
A first branch portion that becomes a branch path in the shared EGR passage and a second branch portion that is closer to the exhaust passage than the first branch portion;
An EGR cooler provided in the shared EGR passage between the first branch part and the second branch part;
A compressor bypass passage branched from the air supply passage on the downstream side of the compressor and connected to the shared EGR passage in the first branch portion;
A turbine bypass passage branched from the exhaust passage on the upstream side of the turbine and connected to the shared EGR passage in the second branch portion;
An air supply side valve device configured to control a flow direction of fluid passing through the first branch part;
An exhaust side valve device configured to control a flow direction of fluid passing through the second branch part;
An engine EGR system comprising a valve control device configured to include a control execution unit that controls the exhaust side valve device and the air supply side valve device. The valve control device
A compressor operating state confirmation unit for confirming the operating state of the compressor,
When it is determined by the compressor operation state confirmation unit that the operation state of the compressor enters the surge region, the control execution unit may at least part of the supply air flowing through the supply passage on the downstream side of the compressor Is configured to control the air supply side valve device so as to be able to flow from the compressor bypass passage through the common EGR passage to the air supply passage upstream of the compressor. The engine EGR system according to claim 1. The valve control device
A turbo rotational speed confirmation unit for confirming a turbo rotational speed that is the rotational speed of the supercharger;
When it is determined by the turbo rotational speed confirmation unit that the turbo rotational speed is greater than the target rotational speed, the control execution unit is configured so that at least a part of the exhaust gas flowing through the exhaust passage on the upstream side of the turbine is The exhaust-side valve device is configured to be controlled so as to be able to flow from the turbine bypass passage to the exhaust passage on the downstream side of the turbine through the shared EGR passage. The engine EGR system according to claim 1. The valve control device
An EGR determination unit that determines whether the exhaust gas needs to be recirculated from the exhaust passage to the supply passage;
An EGR flow path determining unit that determines an EGR flow path that is a flow path from the exhaust path to the air supply path for recirculating the exhaust gas based on an operation map that includes an engine speed and an engine torque. In addition,
When it is determined by the EGR determination unit that the exhaust gas needs to be recirculated, the control execution unit is configured to form the EGR flow path determined by the EGR flow path determination unit. The engine EGR system according to claim 1, wherein the engine EGR system is configured to control a device and the air supply side valve device. The valve control device
A compressor operation state confirmation unit for confirming the operation state of the compressor;
A turbo rotational speed confirmation unit for confirming a turbo rotational speed that is the rotational speed of the supercharger;
An EGR determination unit that determines whether the exhaust gas needs to be recirculated from the exhaust passage to the supply passage;
An EGR flow path determining unit that determines an EGR flow path, which is a flow path from the exhaust path for recirculating the exhaust gas to the air supply path, based on an operation map including an engine speed and an engine torque; In addition,
The control execution unit
When it is determined by the compressor operation state confirmation unit that the operation state of the compressor enters the surge region, at least a part of the supply air flowing through the supply air passage on the downstream side of the compressor is removed from the compressor bypass passage. Configured to control the air supply side valve device so as to be able to flow through the common EGR passage and flow into the air supply passage on the upstream side of the compressor; and
When the turbo rotational speed confirmation unit determines that the turbo rotational speed is greater than the target rotational speed, at least a part of the exhaust gas flowing through the exhaust passage on the upstream side of the turbine is removed from the turbine bypass passage. Configured to control the exhaust valve device such that it can flow through the shared EGR passage and flow into the exhaust passage downstream of the turbine; and
When it is determined by the EGR determination unit that the exhaust gas needs to be recirculated, the exhaust side valve device and the air supply side are formed so as to form the EGR channel determined by the EGR channel determination unit. The engine EGR system of claim 1, wherein the engine EGR system is configured to control the valve device. The exhaust side valve device is
A first exhaust valve provided in the turbine bypass passage;
The shared EGR passage comprises a second exhaust side valve provided between the second branch portion and the exhaust passage,
The air supply side valve device comprises:
A first air supply side valve provided in the compressor bypass passage;
The engine EGR according to any one of claims 1 to 5, further comprising a second air supply side valve provided between the first branch portion and the air supply passage in the shared EGR passage. system.

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