JPH04287859A - Exhaust gas recirculation system for engine with supercharger - Google Patents

Abstract

PURPOSE:To surely perform exhaust gas recirculation(EGR) even in a supercharging region with excellent operating reliability. CONSTITUTION:In an engine 1 provided with superchargers 10, 11, an EGR passage 82 is provided with an EGR valve 84, and there are provided a negative pressure passage 89 for taking out intake negative pressure around a throttle valve 4 so as to lead it as operating pressure into the diaphragm chamber 84a of the EGR valve 84, and a pressure passage for taking out intake normal pressure around the throttle valve 4 so as to lead it as operating pressure into the diaphragm lower chamber 84f of the EGR valve 84. The respective passages 89, 98 are provided with VSVs 90, 99. When the intake state is judged to be in a nonsupercharging region where supercharging pressure is not generated on the basis of the detection result of an intake pressure sensor 62, an ECU 71, opens only one VSV 90, and when the intake state is judged to be in a supercharging region, the ECU 71 opens only the other VSV 99. Accordingly, even in the supercharging region difficult to obtain the intake negative pressure as the operating pressure, the EGR valve 84 is operated to perform EGR.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a supercharged engine that is equipped with a supercharger in an intake system and an exhaust system, and operates the supercharger according to operating conditions, and more particularly relates to a supercharged engine that is equipped with a supercharger in an intake system and an exhaust system. It is related to the device.

0002

[Prior Art] Conventionally, a technology for a supercharged engine has been provided in which a supercharger is installed in the intake system and exhaust system of an engine, and the supercharger is operated according to the operating state of the engine. Various proposals have been made. In addition, in order to reduce NOx from engine exhaust gas, exhaust gas recirculation, or EGR, is used to extract a portion of the exhaust gas from the exhaust system and recirculate it to the intake system by controlling appropriate temperature, timing, or flow rate. The technology is also generally known, and application to supercharged engines as described above is also being considered.

An example of applying EGR technology to a supercharged engine is disclosed in, for example, Japanese Patent Laid-Open No. 61-43262 (first conventional example). In this first conventional technique, a supercharger is provided in an intake pipe and an exhaust pipe of an engine. Then, when the exhaust energy acts on the turbocharger turbine at a predetermined engine speed or higher,
The compressor of the supercharger is driven to supercharge the intake pipe. In addition, as for EGR technology, communication between the exhaust take-off passage branched from the exhaust pipe and the exhaust introduction passage connected to the intake pipe is established using a two-stage diaphragm type exhaust recirculation valve (
It is opened and closed by the EGR valve. EG
The R valve includes first and second pressure chambers, and a diaphragm provided in each pressure chamber is connected to a valve body that opens and closes communication between the exhaust outlet passage and the exhaust introduction passage.

[0004] In a region where negative intake pressure is generated in the intake passage of the carburetor, the intake negative pressure is
The valve body is opened by the diaphragm in the same chamber. Thereby, the exhaust gas take-out passage and the exhaust gas introduction passage are communicated with each other, and a portion of the exhaust gas flowing through the exhaust pipe is recirculated to the intake pipe. On the other hand, in the region where supercharging pressure is generated in the intake pipe by the turbocharger (supercharging region),
A negative pressure passage communicating with the second pressure chamber is opened by a switching valve operated by each sensor that detects the operating state of the engine and a computer. This negative pressure passage is a passage that introduces the negative pressure of the intake passage into the second pressure chamber, and a negative pressure tank is provided in the middle thereof to temporarily store the negative pressure of the intake passage. Then, the negative pressure stored in the negative pressure tank is introduced into the second pressure chamber via the switching valve, which acts on the diaphragm in the same chamber to open the valve body and recirculate a portion of the exhaust gas to the intake pipe. It looks like this. In other words, EGR is possible even in the supercharging range.

[0005] Similarly, a technique that enables EGR in the supercharging region is disclosed in Japanese Patent Laid-Open No. 60-93166 (second prior art example). In the technology of this second conventional example, an exhaust gas recirculation control valve (EGR valve) is provided in the middle of a recirculation passage that recirculates exhaust gas from the exhaust gas pipe to the intake pipe.
It is configured to be driven to open and close by a step motor. As a result, even in the supercharging region where intake negative pressure as the operating pressure cannot be obtained, the EGR valve can be opened and closed as appropriate to
I try to do R.

[0006]

[Problems to be Solved by the Invention] However, in the technique of the first conventional example, each pressure chamber in the EGR valve is provided with a spring for returning the diaphragm. was getting bigger. Further, when the supercharging pressure is high, it is difficult to obtain a negative pressure corresponding to the high supercharging pressure, and there is a problem that a sufficient amount of EGR cannot be secured in the supercharging region. Furthermore, in order to enable EGR even in the supercharging region, the EGR valve is opened by controlling the negative pressure stored in the negative pressure tank using a switching valve. Therefore, when the engine is operated continuously in a high load range, the negative pressure stored in the negative pressure tank disappears, making it difficult to operate the EGR valve, which may make it impossible to adjust the EGR amount.

Furthermore, in the technique of the second conventional example, since the step motor that drives the EGR valve to open and close lacks high-temperature reliability, there is a problem in installing it in an exhaust system that gets hot, and it is not practical. There wasn't. This invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an exhaust gas for a supercharged engine that has excellent operational reliability and is capable of reliably performing EGR even in the supercharging range. The purpose of the present invention is to provide a reflux device.

[0008]

[Means for Solving the Problems] In order to achieve the above object, in this invention, an intake system M2 of an engine M1 is provided.
and a supercharger M4 provided in the exhaust system M3, and an exhaust system M3.
and an exhaust gas recirculation passage M5 provided between the exhaust gas recirculation passage M5 and the intake system M2 to take out a part of the exhaust gas from the exhaust system M3 and recirculate it to the intake system M2, and for opening and closing the exhaust gas recirculation passage M5. A recirculation passage opening/closing means M6 is provided and is operated to open in proportion to the intake negative pressure introduced from the intake system M2.
, a negative pressure passage M8 that extracts the intake negative pressure near the throttle valve M7 in the intake system M2 and introduces it as operating pressure into the recirculation passage opening/closing means M6; Negative pressure passage opening/closing means M whose drive is controlled to adjust the operating pressure introduced into the passage opening/closing means M6
In the exhaust gas recirculation system for a supercharged engine comprising:
0 and is provided for opening and closing its pressure passage M10,
A pressure passage opening/closing means M11 that is drive-controlled to adjust the operating pressure introduced into the recirculation passage opening/closing means M6, and an intake system M
Intake state detection means M12 for detecting the intake state in No. 2
Based on the detection result of the intake state detection means M12,
A supercharging region determining means M13 that determines whether the intake state is in a supercharging region where supercharging pressure is generated, and a supercharging region determining means M1 thereof.
If the determination result of step 3 is in the non-supercharging region, drive control is performed to open only the negative pressure passage opening/closing means M9, and if the determination result of the supercharging region determination means M13 is in the supercharging region, The pressure passage opening/closing means M14 is provided to drive and control the pressure passage opening/closing means M11 so as to open only the pressure passage opening/closing means M11.

[0009]

[Operation] According to the above structure, when the engine M1 is in operation, the intake state detection means M12 detects the intake state in the intake system M2. Based on the detection result, the supercharging region determining means M13 determines whether the intake state is in a supercharging region where supercharging pressure is generated.

When the determination result of the supercharging region determining means M13 is in the non-supercharging region, the opening/closing control means M14 is driven to close the pressure passage opening/closing means M11 and open only the negative pressure passage opening/closing means M9. Control. As a result, the intake negative pressure in the vicinity of the throttle valve M7 is introduced into the recirculation passage opening/closing means M6 as an operating pressure through the negative pressure passage M8. Therefore, the recirculation passage opening/closing means M6 is opened in proportion to the intake negative pressure, and part of the exhaust gas is recirculated from the exhaust system M3 to the intake system M2 through the exhaust gas recirculation passage M5.

On the other hand, the supercharger M4 is activated and the intake system M2
is in a state where supercharging pressure is generated, so that the judgment result of the supercharging region determining means M13 becomes the supercharging region, and the opening/closing control means M
14 controls the drive so that the negative pressure passage opening/closing means M9 is closed and only the pressure passage opening/closing means M11 is opened. As a result, the positive intake pressure in the intake system M2 is introduced into the recirculation passage opening/closing means M6 as an operating pressure through the pressure passage M10. Therefore, the recirculation passage opening/closing means M6 is operated to open, and a portion of the exhaust gas is recirculated from the exhaust system M3 to the intake system M2 through the exhaust gas recirculation passage M5.

0012

Embodiments (First Embodiment) Hereinafter, a first embodiment of the exhaust gas recirculation system for a supercharged engine according to the present invention will be described in detail with reference to FIGS. 2 to 7. 2, 5, and 6 are schematic configuration diagrams illustrating an in-line six-cylinder supercharged gasoline engine system mounted on a vehicle in this embodiment. The intake system of the engine 1 is provided with a surge tank 2 for preventing intake pulsation or intake interference. Also, on the upstream side of the surge tank 2, a throttle body 3 is installed.
is provided. A throttle valve 4 is provided inside the throttle body 3 and is opened and closed in conjunction with the operation of an accelerator pedal (not shown). By opening and closing the throttle valve 4, the intake air amount Q to the surge tank 2 is adjusted. Furthermore, the downstream side of the surge tank 2 is connected to each cylinder #1, #2, #3, #4 of the engine 1.
, #5, and #6. The intake manifold 5 is provided with fuel injection valves (injectors) 6A, 6B, 6C, 6D, 6E, and 6F for injecting and supplying fuel to each cylinder #1 to #6 of the engine 1, respectively. Each of the injectors 6A to 6F is supplied with fuel at a predetermined pressure from a fuel tank by the operation of a fuel pump (not shown). Furthermore,
Spark plugs 7A, 7B, 7C, 7D, 7E, and 7F are provided corresponding to each cylinder #1 to #6 of the engine 1, respectively.

On the other hand, in the exhaust system of the engine 1, each cylinder #
An exhaust manifold 8 is provided to lead out exhaust gas from #1 to #6. This exhaust manifold 8 is assembled into two groups: cylinder groups #1 to #3 that do not cause exhaust interference with each other, and cylinder groups #4 to #6 that also do not cause exhaust interference with each other. That is, the exhaust manifold 8 includes a main exhaust collecting section 8a and a sub-exhaust collecting section 8b, and both the exhaust collecting parts 8a and 8b are communicated with each other through a communication passage 9. The exhaust gases from the cylinder groups #1 to #3 are collected in the main exhaust collecting section 8a, and the exhaust gases from the cylinder groups #4 to #6 are collected in the sub-exhaust collecting part 8b.

In the intake system and exhaust system of the engine 1, a main turbocharger 10 and a sub-turbocharger 11, each serving as a supercharger, are provided in parallel. That is, the turbine 10a constituting the main turbocharger 10 has its upstream side connected to the main exhaust collecting portion 8a of the exhaust manifold 8. Further, the turbine 11a constituting the sub-turbocharger 11 has an upstream side connected to the exhaust manifold 8.
It is connected to the sub-exhaust gas collecting section 8b. In other words, cylinder groups #1 to #1 of the engine 1 correspond to the main turbocharger 10.
#3 is in communication with the cylinder group #4 to #6 of the engine 1 corresponding to the sub-turbocharger 11. Furthermore,
The downstream side of each turbine 10a, 11a is communicated with separate main and sub exhaust passages 12, 13. The main and auxiliary exhaust passages 12 and 13 merge on the downstream side thereof and are communicated with the outside via a catalytic converter 14 having a built-in three-way catalyst.

On the other hand, the main and sub turbochargers 10,
The upstream sides of the compressors 10b and 11b constituting the compressor 11 are communicated with separate main and sub intake passages 15 and 16, respectively. The upstream sides of each of the main and auxiliary intake passages 15 and 16 merge into one common intake passage 17 and communicate with the outside via an air cleaner 18. Moreover, each compressor 10b, 11
The downstream side of b is connected to separate main and sub intake passages 19 and 20. The downstream sides of each of the main and auxiliary intake passages 19 and 20 merge into and communicate with one common intake passage 21, which communicates with the surge tank 2 via an intercooler 22 for intake air cooling, and further through the throttle body 3. ing.

In this embodiment, the main turbocharger 10 is operated from a low intake air amount region to a high intake air amount region of the engine 1, and the auxiliary turbocharger 11 is stopped in the low intake air amount region and is operated in the high intake air amount region. It operates only in the intake air amount range, and both the main and auxiliary turbochargers 10,
11 constitutes a so-called "two-stage twin-turbo system."

[0017] In order to enable activation and deactivation of both the main and sub turbochargers 10 and 11, the sub turbocharger 1
An exhaust switching valve 23 is provided in the middle of the auxiliary exhaust passage 13 communicating with the first turbine 11a. Further, an intake switching valve 24 is provided in the middle of the auxiliary intake passage 20 that communicates with the compressor 11b of the auxiliary turbocharger 11. These exhaust switching valves 23 and intake switching valves 24 are driven by diaphragm actuators 27 that are driven by opening and closing switching of three types of first and second vacuum switching valves (hereinafter simply referred to as "VSV") 25 and 26, respectively.
, 28, respectively. Atmospheric air is introduced into the atmospheric ports of the first and second VSVs 25 and 26 via an air filter 29, and required high-pressure air is introduced from the pressure tank 30 into the pressure ports.

[0018] Therefore, the first and second VSVs 25, 26
The introduction of air pressure into the diaphragm chambers 27a, 28a of each actuator 27, 28 is adjusted by switching the opening/closing of , thereby operating each actuator 27, 28, and opening/closing the exhaust switching valve 23 and the intake switching valve 24, respectively. . That is, when the first VSV 25 is turned on, it operates the actuator 27 to fully open the exhaust switching valve 23, and when it is turned off, it operates the actuator 27 to fully close the exhaust switching valve 23. let When the second VSV 26 is turned on, it operates the actuator 28 to fully open the intake switching valve 24, and when it is turned off, it operates the actuator 28 to fully close the intake switching valve 24. let and,
When both the exhaust switching valve 23 and the intake switching valve 24 are fully open, a "double supercharging stage" occurs in which both the main and auxiliary turbochargers 10, 11 operate, and both the switching valves 23, 24
When both are fully closed, a "single supercharging stage" is established in which only the main turbocharger 10 operates.

Turbine 11a of sub-turbocharger 11
An exhaust bypass passage 31 that bypasses the exhaust switching valve 23 and communicates with the main exhaust passage 12 is provided in the auxiliary exhaust passage 13 that communicates with the main exhaust passage 12 . Moreover, in this exhaust bypass passage 31,
An exhaust bypass valve 32 is provided to open and close the passage 31. This exhaust bypass valve 32 is opened and closed by a diaphragm type actuator 33. The diaphragm chamber 33a of this actuator 33 is
It communicates with the auxiliary intake passage 20 on the downstream side of the intake switching valve 24, and also communicates with the auxiliary intake passage 16 on the upstream side of the compressor 11b via a dual-type third VSV 34. By opening and closing this third VSV34,
By adjusting the introduction of supercharging pressure by the compressor 10b into the diaphragm chamber 33a, the actuator 33
is operated to open and close the exhaust bypass valve 32. That is, the third VSV 34 is duty controlled to adjust the amount of supercharging pressure bleed into the atmosphere by the compressor 10b of the main turbocharger 10,
The opening degree (opening amount) of the exhaust bypass valve 32 is made variable by adjusting the operating pressure of the actuator 33 to the diaphragm chamber 33a.

Furthermore, both passages 20 and 16 are communicated between the auxiliary intake passage 20 upstream of the intake switching valve 24 and the main intake passage 15 upstream of the compressor 10b of the main turbocharger 10. A first intake bypass passage 35 is provided. Further, a first intake bypass valve 37 is provided at one end of the first intake bypass passage 35 and is driven by a diaphragm type actuator 36 in order to open and close the passage 35 . This actuator 36 is driven by opening/closing switching of the fourth VSV 38 of three types. Atmospheric air is introduced into the atmospheric port of this fourth VSV 38 via an air filter 29, and required high pressure air is introduced from the pressure tank 30 into the pressure port.

Accordingly, based on the opening/closing switching of the fourth VSV 38, the introduction of air pressure into the diaphragm chamber 36a of the actuator 36 is adjusted, thereby operating the actuator 36 and opening/closing the first intake bypass valve 37. . That is, when the fourth VSV 38 is turned on, it operates the actuator 36 to fully close the first intake bypass valve 37, and when it is turned off, it operates the actuator 36 to fully open the first intake bypass valve 37. Actuator 3
Activate 6. This first intake bypass passage 35 is a passage opened to smoothly switch from the operation of only the main turbocharger 10 to the operation of both the main and auxiliary turbochargers 10 and 11.

Note that the pressure port of the pressure tank 30 is connected to the common intake passage 21 upstream of the intercooler 22.
The main turbocharger 10 supplies supercharging pressure to the pressure tank 30. Also, a bypass passage 39 that communicates the upstream side and the downstream side of the intake switching valve 24 in the auxiliary intake passage 20 is provided.
A reed valve 40 is provided. When the outlet pressure of the compressor 11b of the sub-turbocharger 11 becomes higher than that of the main turbocharger 10,
Air is bypassed from the upstream side to the downstream side of the intake switching valve 24 via the bypass passage 39 and the reed valve 40.

On the other hand, in the main turbocharger 10,
A wastegate passage 41 is provided between the upstream side and the downstream side of the turbine 10a. Further, this wastegate passage 41 is provided with a wastegate valve 42 that opens and closes the passage 41. In order to prevent the supercharging pressure by the main turbocharger 10 from exceeding a preset pressure, the wastegate valve 42 bypasses exhaust gas flowing into the turbine 10a to the outlet side of the turbine 10a. This is for adjusting the output of the main turbocharger 10a and controlling the supercharging pressure by the main turbocharger 10. The wastegate valve 42 is opened and closed by a diaphragm type actuator 43. The diaphragm chamber 43a of this actuator 43 is communicated with the main intake passage 19 downstream of the compressor 10b, and the fifth V
It communicates with the main intake passage 15 on the upstream side of the compressor 10b via the SV44. And that fifth V
The introduction of supercharging pressure by the compressor 10b into the diaphragm chamber 43a is adjusted by opening and closing the SV 44, thereby operating the actuator 43 and opening and closing the wastegate valve 42. That is, the fifth VSV 44 is duty-controlled to adjust the amount of supercharging pressure bleed into the atmosphere, and to control the diaphragm chamber 43a of the actuator 43.
The opening degree of the wastegate valve 42 (
opening amount) is variable.

[0024] Also, related to the main turbocharger 10, there is a main intake passage 15 on the upstream side of the compressor 10b, and a common intake passage 21 on the downstream side of the compressor 10b.
A second intake bypass passage 45 is provided between the two. On one end side of this second intake bypass passage 45,
A second intake bypass valve 47 is provided to open and close the passage 45, which is driven by a diaphragm actuator 46. A diaphragm chamber 46a of this actuator 46 is communicated with the surge tank 2. Therefore, the actuator 46 is operated so that the second intake bypass valve 47 is opened only when the inside of the surge tank 2 becomes negative pressure, and the actuator 46 is operated so that the second intake bypass valve 47 is closed at other times. 46 is activated.

The engine 1 receives outside air introduced through the air cleaner 18 through the common intake passage 17, the main and auxiliary intake passages 15 and 16, and the main and auxiliary turbochargers 1.
The air is taken in through compressors 10b and 11b, intercooler 22, surge tank 2, intake manifold 5, etc. Further, at the same time as taking in the outside air, the engine 1 takes in fuel injected from each of the injectors 6A to 6F. Furthermore, the engine 1 explodes and burns the mixture of the taken in fuel and outside air in the combustion chambers of each cylinder #1 to #6 to obtain driving force, and then sends the exhaust gas to the exhaust manifold 8, the main The gas is discharged to the outside via the turbines 10a and 11a of the auxiliary turbochargers 10 and 11, the main and auxiliary exhaust passages 12 and 13, and the catalytic converter 14.

Each sensor for detecting the operating state of the engine 1 includes a throttle valve 4 in the throttle body 3.
A throttle opening sensor 61 is provided to detect the opening (throttle opening) ACCP. The surge tank 2 is provided with an intake pressure sensor 62 that detects the intake pressure PM within the surge tank 2 . In this embodiment, the throttle opening sensor 61 and the intake pressure sensor 62 constitute intake state detection means for detecting the intake state in the intake system. On the downstream side of the air cleaner 18,
A well-known movable vane air flow meter 63 for measuring the amount of intake air Q passing through the common intake passage 17 is provided. Further, the engine 1 is provided with a water temperature sensor 64 that detects the temperature of the cooling water (cooling water temperature) THW. Furthermore, an oxygen sensor 65 is provided near the confluence of the main and auxiliary exhaust passages 12 and 13 to detect the oxygen concentration in the exhaust gas, that is, to detect the exhaust air-fuel ratio. This oxygen sensor 65 is arranged at a position offset from the main exhaust passage 12.

An ignition signal distributed by a distributor 48 is applied to each of the spark plugs 7A to 7F provided in each cylinder #1 to #6 of the engine 1. The distributor 48 synchronizes the high voltage output from the igniter 49 with the crank angle of the engine 1 to each spark plug 7A~
This is for distribution to the 7th floor. The ignition timing of each spark plug 7A to 7F is determined by the high voltage output timing from the igniter 49.

The distributor 48 has a built-in rotor (not shown) that rotates in conjunction with the rotation of the engine 1. This distributor 48 is provided with a rotation speed sensor 66 that detects the engine rotation speed NE from the rotation of the rotor. Similarly, cylinder discrimination sensors 67 are respectively attached to the distributors 48 to detect changes in the crank angle of the engine 1 at a predetermined rate according to the rotation of the rotor. In this embodiment, assuming that the engine 1 rotates twice per stroke, the cylinder discrimination sensor 67 detects the crank angle at a rate of 360° CA. Further, a transmission (not shown) drivingly connected to the engine 1 is provided with a vehicle speed sensor 68 for detecting vehicle speed.

Furthermore, the starter (not shown) that is driven to start the engine 1 includes a starter that outputs a starter signal ST that is turned on and off as the starter is driven and stopped, and instructs during and after starting. A switch 69 is provided. In addition, the engine 1 of this embodiment is equipped with an exhaust gas recirculation device (hereinafter simply "EG") as shown in FIGS.
81 (referred to as "R device") is provided. This EGR device 81 includes an exhaust gas recirculation passage (EGR passage) 82 provided between an exhaust system and an intake system. This EG
The R passage 82 is for taking out a part of the exhaust gas from the exhaust system and recirculating it to the intake system, and as shown in FIG. It is arranged in the exhaust passage 83 of cylinder #6 leading to cylinder #6. On the other hand, the intake port 82 which is the other end side of the EGR passage 82
b is placed in the surge tank 2 as shown in FIG. A part of the exhaust gas taken out through the exhaust passage 83 of cylinder #6 is recirculated to the surge tank 2 through the EGR passage 82.

An EGR valve 84 is provided in the middle of the EGR passage 82 as a recirculation passage opening/closing means for opening and closing the passage 82. This EGR valve 84 is opened in proportion to the intake negative pressure introduced from the intake system. Figure 3
As shown in FIG. 2, the EGR valve 84 includes a diaphragm chamber 84a containing a diaphragm 86 urged by a spring 85, and a main body casing 84b communicating with the EGR passage 82. In addition, the diaphragm 86 has
The proximal end of a valve rod 87a having a valve body 87 fixed to the distal end thereof is fixed, and the distal end side of the valve rod 87a is arranged so as to be reciprocating inside the main body casing 84b. The diaphragm 86 and the valve rod 87a are connected to the spring 8
5 and is pressed downward. On the other hand, the inside of the main body casing 84b is divided into an upper chamber 84c and a lower chamber 84d by a partition wall, and a valve hole 84e that is opened and closed by a valve body 87 is formed in the partition wall. And upper chamber 8
4c is connected to the surge tank 2 through the EGR passage 82, and the lower chamber 84d is connected to the cylinder # through the EGR passage 82.
It communicates with the exhaust passage 83 of No. 6. Further, below the diaphragm 86, a diaphragm lower chamber 84f is formed. An introduction port 84g communicating with the outside is formed in this diaphragm lower chamber 84f. In addition, lower chamber 84
In the middle of the EGR passage 82 between d and the exhaust passage 83,
An EGR cooler 88 is provided. This EGR cooler 88 is formed integrally with the engine block, and is for cooling the exhaust gas by exchanging heat with the outside air while passing it through.

In order to introduce the intake negative pressure of the intake system into the diaphragm chamber 84a of the EGR valve 84 as an operating pressure, a negative pressure passage 89 is provided which communicates the diaphragm chamber 84a with the throttle body 3. The introduction port 89a, which is one end of the negative pressure passage 89, communicates with the upstream side of the throttle valve 4 when the throttle valve 4 is in a fully closed state. and,
By opening the throttle valve 4, the introduction port 89
a is located on the downstream side of the throttle valve 4, and the intake negative pressure generated there is introduced into the negative pressure passage 89.

In the middle of this negative pressure passage 89, there is a diaphragm chamber 8 of the EGR valve 84 that opens and closes the negative pressure passage 89.
Sixth VSV90 of three types as a negative pressure passage opening/closing means whose opening/closing is controlled to adjust the operating pressure introduced into 4a.
is provided. One pressure port of this sixth VSV 90 is communicated with the throttle body 3 via a negative pressure passage 89. Further, an air filter 92 is connected to the atmospheric port of the VSV 90 via an atmospheric passage 91, so that atmospheric air is introduced.

Similarly, an EGR valve modulator 93 is provided in the middle of the negative pressure passage 89 and communicates with the other pressure port of the sixth VSV 90. This EGR valve modulator 93 controls the exhaust pressure (
This is to increase and adjust the intake negative pressure applied to the diaphragm chamber 84a in proportion to the exhaust pressure). That is, E.G.
The R valve modulator 93 includes an upper passage 93a communicating with the negative pressure passage 89, and a main body casing 93b containing a diaphragm 94. Further, the main body casing 93b is divided into an atmospheric chamber 93c and an exhaust pressure chamber 93d with a diaphragm 94 as a boundary. A communication port 93e is formed between the atmospheric chamber 93c and the upper passage 93a, and an atmospheric port 93f is formed in the side wall of the atmospheric chamber 93c. By introducing atmospheric pressure into the atmospheric chamber 93c through the atmospheric port 93f, the atmospheric pressure acts on the negative pressure passage 89 from the communication port 93e through the upper passage 93a.

[0034] Also, the exhaust pressure chamber 9 of the EGR valve modulator 93
3d and the lower chamber 84d of the EGR valve 84 are communicated via an exhaust pressure passage 95, so that the exhaust pressure applied to the lower chamber 84d acts on the exhaust pressure chamber 93d. Also, the exhaust pressure chamber 9
In order to restrict the introduction of atmospheric pressure into the upper passage 93a in proportion to the exhaust pressure acting on the diaphragm 94, a
A valve body 96 is provided for adjusting the opening degree of the communication port 93e. The atmospheric chamber 93c includes a spring 97 that biases the diaphragm 94 against exhaust pressure. The diaphragm 94 is upwardly displaced against the biasing force of the spring 97 in proportion to the exhaust pressure acting on the exhaust pressure chamber 93d, and the communication port 9
The opening degree of 3e is adjusted by the valve body 96. Furthermore, when exhaust pressure equal to or higher than a predetermined value is applied to the exhaust pressure chamber 93d, the upward displacement of the diaphragm 94 causes the communication port 93e to close to the valve body 96.
completely closed by. In other words, the EGR valve modulator 93 restricts the introduction of atmospheric pressure into the upper passage 93a in proportion to the exhaust pressure applied to the EGR valve 84, thereby allowing the diaphragm chamber 84a of the EGR valve 84 to flow through the negative pressure passage 89. The operating pressure is adjusted to increase.

Therefore, the introduction port 89a of the negative pressure passage 89
In other words, the engine 1 is in a state where the intake negative pressure is acting on the
When operating in a medium load range, the sixth VSV 90 is turned on and both pressure ports communicate with each other, so that the intake negative pressure acting on the negative pressure passage 89 is transferred to the EGR valve modulator 93.
acts on the diaphragm chamber 84a of the EGR valve 84 through the upper passage 93a, and the valve body 87 moves upward to open the valve hole 84e.
will be held. That is, by turning on the sixth VSV 90, the EGR passage 82 is opened by the EGR valve 84, and the recirculation of exhaust gas from the exhaust passage 83 of cylinder #6 to the surge tank 2, that is, EGR is permitted. At this time, EG
When the exhaust pressure acting on the R valve 84 does not exceed a predetermined value, the intake negative pressure applied to the EGR valve modulator 93 is appropriately attenuated by the atmospheric pressure introduced through the atmospheric port 93f. As a result, the intake negative pressure to the diaphragm chamber 84a is moderately suppressed, the opening degree of the EGR valve 84 is suppressed, and the recirculation amount of exhaust gas in the EGR passage 82, that is, the EGR valve 84 is suppressed.
The amount of GR is suppressed.

On the other hand, when the exhaust pressure acting on the EGR valve 84 exceeds a predetermined value, the communication port 93e of the EGR valve modulator 93 is closed, the introduction of atmospheric pressure from the atmospheric port 93f is cut off, and the EGR valve modulator 93 is All of the acting negative intake pressure acts on the diaphragm chamber 84a of the EGR valve 84 without being attenuated. As a result, the intake negative pressure to the diaphragm chamber 84a is increased, and the EGR valve 8
4, the EGR passage 82 is wide open and the amount of EGR is increased.

Also, by turning off the sixth VSV 90 and communicating one pressure port with the atmospheric port, the EGR
Atmospheric pressure acts on the diaphragm chamber 84a of the EGR valve 84 through the upper passage 93a of the valve modulator 93, and the valve element 87 returns downward, closing the valve hole 84e. That is, by turning off the sixth VSV 90, the EGR passage 82 is closed by the EGR valve 84, and EGR is blocked.

As described above, the EGR device 81 of this embodiment
Now, when the engine 1 is operating in a low/medium load range, the intake negative pressure introduced from the vicinity of the throttle valve 4 into the diaphragm chamber 84a of the EGR valve 84 as a working pressure is adjusted in order to control the EGR amount.・A configuration for controlling is made. In addition, in the EGR device 81 of this embodiment, a configuration is added to ensure the amount of EGR even in the supercharging region where the vicinity of the throttle valve 4 becomes positive pressure due to the supercharging operation of each turbocharger 10, 11. There is.

That is, as shown in FIGS. 2 and 3, the EGR valve 8
A pressure passage 98 is provided between 4 and the negative pressure passage 89, which communicates both 84 and 89. An outlet 98a, which is one end of the pressure passage 98, is communicated between the introduction port 89a and the sixth VSV 90 through a negative pressure passage 89. As a result, the negative pressure passage 8 in the throttle body 3
The introduction port 89a of the pressure passage 98 also serves as an introduction port of the pressure passage 98. Then, due to the supercharging operation of each turbocharger 10, 11, the introduction port 89
When the vicinity of a becomes positive pressure, the positive pressure is applied to the outlet 98a.
It is adapted to be taken out from the pressure passage 98. The other end of the pressure passage 98 is communicated with an introduction port 84g that opens into the diaphragm lower chamber 84f of the EGR valve 84. Then, the positive pressure taken out at the outlet 98a is used as the operating pressure of the EGR valve 84 in the diaphragm lower chamber 8.
It is being introduced in 4F.

Further, in the middle of this pressure passage 98, a pressure passage opening/closing means is provided which is controlled to open and close in order to open and close the passage 98 and to adjust the operating pressure introduced into the diaphragm lower chamber 84f of the EGR valve 84. 7th VSV9 of three methods
9 is provided. Both pressure ports of this VSV 99 are communicated with pressure passages 98, respectively. Also, the same V
An air filter 92 is connected to the atmospheric port of the SV 90 via an atmospheric passage 91, so that atmospheric air is introduced.

Therefore, the introduction port 89a of the negative pressure passage 89
When positive intake pressure is acting on the pressure passage 98, that is, when the engine 1 is operating in the supercharging region, the seventh VSV 99 is turned on and both pressure ports communicate with each other. The pressure is in the diaphragm lower chamber 8 of the EGR valve 84.
4f, the valve body 87 is pushed up, and the valve hole 8
4e is fully opened. In other words, the seventh VSV9
9 is turned on, the EGR valve 84 starts EGR.
Passage 82 is opened to allow EGR. At this time, E
Since the GR valve 84 is fully open, the EG
The amount of R is not particularly controlled, and a large amount of EGR is allowed. That is, in this embodiment, the diaphragm chamber 8 of the EGR valve 84 is generated near the throttle valve 4.
In addition to the negative intake pressure introduced into the EGR valve 4a, the positive intake pressure that acts near the throttle valve 4 and is introduced into the diaphragm lower chamber 84f acts as the operating pressure of the EGR valve 84. In this way, the introduction port 89a of the negative pressure passage 89
The reason why the pressure passage 98 is used is because the pressure near the throttle valve 4 is negative in the low/medium load range where the opening of the throttle valve 4 is small, and the pressure is positive in the supercharging range where the opening is large. .

Among the constituent members described above, each of the injectors 6A to 6F, the igniter 49, and the first to seventh VSVs 25, 26, 34, 38, 44, 90, 99
is electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 71 that constitutes a supercharging range determining means and an opening/closing control means, and their drive timings are controlled by the operation of the ECU 71. .

Next, the configuration of the ECU 71 will be explained with reference to the block diagram shown in FIG. The ECU 71 includes a central processing unit (CPU) 72, a read-only memory (ROM) 73 that stores predetermined control programs, etc., and a random access memory (RA) that temporarily stores calculation results of the CPU 72.
M) 74, a backup RAM 75 for storing pre-stored data, etc., and each of these parts and an external input circuit 76, an external output circuit 77, etc. are connected by a bus 78 to form a logic operation circuit.

The external input circuit 76 includes the aforementioned throttle opening sensor 61, intake pressure sensor 62, air flow meter 63, water temperature sensor 64, oxygen sensor 65, rotational speed sensor 66, cylinder discrimination sensor 67, vehicle speed sensor 68, and starter sensor. Switches 69 and the like are connected respectively. Then, the CPU 72 reads output signals from the air flow meter 63, each of the sensors 61, 62, 64 to 68, and the starter switch 69 as input values via the external input circuit 76.

Furthermore, the CPU 72 controls each injector 6 connected to the external output circuit 77 based on these input values.
A to 6F, igniter 49 and 1st to 7th VSV25
, 26, 34, 38, 44, 90, 99, etc. are suitably controlled. In this example, fuel injection is performed in each cylinder #1.
- Independent injection for each #6, each injector 6A
~6F are individually driven and controlled when the injection timing for each cylinder #1~#6 arrives. In the engine 1 of this embodiment, fuel injection in each cylinder #1 to #6 is performed in the order of cylinder #1, cylinder #5, cylinder #3, cylinder #6, cylinder #2, and cylinder #4. It has become.

In the supercharged gasoline engine system configured as described above, the ECU 71 determines the current operating state based on input values from the air flow meter 63, the sensors 61, 62, 64-68, and the starter switch 69. The operation of the main turbocharger 10 and the sub-turbocharger 11 is controlled as follows depending on the operating state.

First, when the operating state of the engine 1 is in a low speed range,
When the load is in a high load range, the ECU 71 closes both the exhaust switching valve 23 and the intake switching valve 24, and closes the first and second V
Controls switching between SV25 and 26. This results in a "single supercharging stage" in which only the main turbocharger 10 is operated. In this "single supercharging stage", exhaust gas from the engine 1 flows only through the main turbocharger 10, as shown by the arrow in FIG. 5, and rotationally drives the turbine 10a. Furthermore, the exhaust gas that has passed through the turbine 10a passes through the main exhaust passage 12, reaches the confluence of both the main and auxiliary exhaust passages 12 and 13, as shown by the arrow in FIG. It passes through and is discharged to the outside. In this way, the reason why a "single supercharging stage" is used in the low intake air amount region is that in the low intake air amount region, the supercharging characteristics by only the main turbocharger 10 are better.
This is because the supercharging characteristics are superior to those provided by the auxiliary turbochargers 10 and 11. By using such a "single supercharging stage", the torque of the engine 1 increases quickly, and the response in the low speed range can be significantly improved.

Furthermore, in this embodiment, the oxygen sensor 65
The installation position is the turbine 1 of the main turbocharger 10.
Since it is offset from the main exhaust passage 12 communicating with the main turbocharger 10, the exhaust gas flow from the main turbocharger 10 efficiently hits the oxygen sensor 65 and its oxygen concentration is detected. Therefore, the oxygen sensor 65 is rapidly warmed by the exhaust gas flow, and can quickly reach a stable output temperature characteristic range for air-fuel ratio control. In this "single supercharging stage", the entire amount of the exhaust gas flow always hits the oxygen sensor 65, and even in the "double supercharging stage", which will be explained later, the main turbocharger 10 is always operated.
Since the exhaust gas flow from the exhaust gas always hits the oxygen sensor 65, the oxygen concentration of the exhaust gas can be detected with high accuracy by the oxygen sensor 65. Therefore, oxygen sensor 6
By feeding back the detection signal in 5,
It becomes possible to always perform accurate air-fuel ratio control. Furthermore,
When the operating state of the engine 1 is in a low speed range and a low load range, the ECU 71 controls the first and second VSVs 25 and 26 so that the exhaust switching valve 23 remains closed and only the intake switching valve 24 is opened. Switch control. As a result, both the main and auxiliary intake passages remain in the "single supercharging stage".
5 and 16 are both opened, and an increase in intake resistance due to the operation of only the main turbocharger 10 can be suppressed. By doing so, it is possible to improve the boost pressure rise characteristics and operational response at the beginning of acceleration from a low load range.

Furthermore, when the operating state of the engine 1 shifts from a low intake air amount region to a high intake air amount region, that is, when switching from a "single supercharging stage" to a "double supercharging stage," the ECU 71 controls the exhaust gas flow. The first and second VSV2 are opened so that both the switching valve 23 and the intake switching valve 24 are opened.
5 and 26 are switched and controlled. At this time, the exhaust bypass valve 32 is opened when the exhaust switching valve 23 is closed.
The ECU 71 switches and controls the third VSV 34. That is,
By flowing part of the exhaust gas to the sub-turbocharger 11, the approach rotation speed of the sub-turbocharger 11 is increased,
Stage switching can be performed more smoothly. At the same time, the EC is opened so as to open the first intake bypass valve 37.
By U71 switching and controlling the fourth VSV38,
Stage switching can be performed even more smoothly.

On the other hand, when the operating state of the engine 1 is in a high intake air amount region, the ECU 71 operates so that both the exhaust switching valve 23 and the intake switching valve 24 remain open and the exhaust bypass valve 32 is closed. 1st to 3rd VSV25, 26
, 34 are switched and controlled. As a result, a "double supercharging stage" state in which supercharging is performed by both the main and sub turbochargers 10 and 11 is maintained. In this "double supercharging stage," the exhaust gas from the engine 1 is transferred to both the main and auxiliary turbochargers 1, as shown by the arrows in Figure 6.
0 and 11 to rotate the respective turbines 10a and 11a. Furthermore, the exhaust gas that has passed through each of the turbines 10a and 11a passes through both the main and auxiliary exhaust passages 12 and 13 to reach their confluence, as shown by the arrows in FIG. 6, and further passes through the catalytic converter 14 downstream. and flows to the outside. In this way, by using the "double supercharging stage", the main
Both compressors 1 of both secondary turbochargers 10 and 11
Sufficient supercharging pressure is obtained by 0b and 11b, and the output of the engine 1 in the high speed range is improved. Then, the E
The CU 71 drives and controls the fifth VSV 44 (duty control).

Next, the EGR control processing operation executed by the ECU 71 in the exhaust gas recirculation system for the supercharged engine configured as described above will be explained with reference to the flowchart shown in FIG. This EGR control routine is executed by regular interrupts at predetermined time intervals. When the process moves to this routine, first in step 201,
Based on the detected values of the intake pressure sensor 62, water temperature sensor 64, and starter switch 69, the intake pressure PM and cooling water temperature THW are determined.
and the starter signal ST.

Subsequently, in step 202, it is determined whether or not the engine 1 has been started based on the starter signal ST read earlier. Here, if it is not after the start, it is assumed that EGR is not performed, and step 203
In order to close the negative pressure passage 89, the sixth VSV 9
Turn off 0. Further, in step 204, the seventh VSV 99 is turned off in order to close the pressure passage 98 as well. That is, the EGR valve 84 is closed to cut off the recirculation of exhaust gas to the surge tank 2. Then, the subsequent processing is temporarily terminated.

On the other hand, if it is determined in step 202 that the engine 1 has been started, then in step 205,
It is determined whether the previously read cooling water temperature THW is "40° C." or higher. In other words, it is determined whether the engine 1 has reached a temperature suitable for performing EGR. If the cooling water temperature THW is not a temperature suitable for performing EGR, it is assumed that EGR will not be performed, and step 203;
The process in step 204 is executed, and the subsequent process is temporarily terminated.

[0054] Also, in step 205, the cooling water temperature T
If the HW is at a temperature suitable for EGR, the EGR
To perform R, in step 206, it is determined whether or not the inside of the surge tank 2 is at negative pressure based on the previously read intake pressure PM. That is, it is determined whether or not the surge tank 2 is in a low/medium load range where the pressure inside the surge tank 2 is negative. Then, in step 206, if the pressure is in the low/medium load range where the pressure is negative, in step 207, first, the seventh VSV 99 is turned off in order to close the pressure passage 98. Next, in step 208, the sixth VSV 90 is turned on to open the negative pressure passage 89, and the subsequent processing is temporarily terminated. That is, in the low/medium load range, only the negative pressure passage 89 is opened to utilize the intake negative pressure generated near the throttle valve 4, and the diaphragm chamber 84 of the EGR valve 84 is opened.
Intake negative pressure is introduced into a as working pressure. This results in
The valve body 87 of the EGR valve 84 moves upward to open the EGR valve 84, and the EGR passage 82 is opened to perform EGR.

On the other hand, in step 206, if the pressure inside the surge tank 2 is positive rather than negative, it is assumed that the turbocharger 10, 11 is in the supercharging region, and in step 209, the The sixth VSV 90 is turned off to close the pressure passage 89. Next, in step 210, the seventh VS
Turn on the V99 and temporarily end the subsequent processing. That is, in the supercharging region, only the pressure passage 98 is opened to utilize the positive intake pressure generated near the throttle valve 4.
Intake positive pressure is introduced into the diaphragm lower chamber 84f of the EGR valve 84 as an operating pressure. As a result, the valve body 87 of the EGR valve 84 is pushed up, the EGR valve 84 is opened, and the EGR valve 84 is opened.
Passage 82 is opened and EGR is performed. In this way, EGR control that is effective in reducing NOx is performed.

As explained above, the EGR of this embodiment
According to the device 81, in the low/medium load range of the engine 1 where the inside of the surge tank 2 becomes negative pressure, only the negative pressure passage 89 is opened and the intake negative pressure is introduced into the diaphragm chamber 84a of the EGR valve 84 as operating pressure. The EGR valve 84 is opened securely and the EGR valve 84 is opened.
GR will be held. On the other hand, in the supercharging region of the engine 1 where the pressure inside the surge tank 2 is positive, only the pressure passage 98 is opened and positive intake pressure is introduced into the diaphragm lower chamber 84f of the EGR valve 84 as operating pressure, and the EGR valve 84 is Definitely open E
GR will be held.

Therefore, according to the EGR device 81 of this embodiment, EGR can be performed not only in the low/medium load range of the engine 1 but also in the supercharging range where it is difficult to obtain intake negative pressure as the operating pressure.
EGR can be performed by reliably applying operating pressure to the valve 84. In addition, in order to perform EGR in the supercharging region, the diaphragm lower chamber 8 is
It acts on 4f. Therefore, unlike the case where intake negative pressure is used as the operating pressure, the operating pressure to the EGR valve 84 does not become insufficient or disappears, and a large amount of EGR that meets the demands of the supercharging region can be secured. Can be done. As a result, the temperature of the exhaust gas from the engine 1 is lowered, the air-fuel ratio in the supercharging region can be made leaner, and fuel efficiency can be significantly improved.

Moreover, according to the EGR device 81 of this embodiment, when negative intake pressure acts on the diaphragm chamber 84a of the EGR valve 84 and when positive intake pressure acts on the diaphragm lower chamber 84f, the diaphragm The direction of displacement of the diaphragm 86 is not reversed, and no unreasonable force is applied to the diaphragm 86, thereby improving its reliability. Further, since the EGR valve 84 is only provided with one spring 85 for returning the diaphragm 86, the first EGR valve equipped with a two-stage diaphragm type EGR valve is
Unlike the conventional example, the operating pressure can be set low. Further, since the EGR valve 84 is simply a single-stage diaphragm mechanical valve, reliability at high temperatures can be ensured, unlike the second conventional technique in which the EGR valve 84 is driven by a step motor. Therefore, the operational reliability of the EGR device 81 can be improved. In addition, in the EGR device 81 of this embodiment, the negative pressure passage 89 and the EGR
A pressure passage 98 is connected to the valve 84, and a seventh
Since only the VSV99 is provided, there is no need to use an expensive step motor, and an increase in manufacturing costs can be suppressed.

(Second Embodiment) Next, a second embodiment of the exhaust gas recirculation system for a supercharged engine according to the present invention will be described with reference to FIGS. 8 to 10. In this embodiment, the same members as those in the first embodiment are as follows:
The same reference numerals are used to omit the explanation, and only the different points will be explained.

FIG. 7 is a schematic diagram illustrating the supercharged gasoline engine system in this embodiment. As is clear from this figure, in this embodiment, the EGR device 1
The outlet 98a of the pressure passage 98 of 00 is connected to the intercooler 2.
The second embodiment is disposed in communication with the common intake passage 21 on the upstream side of the second embodiment, and is different from the first embodiment in this point. In other words, the EGR device 100 of this embodiment has a configuration for adjusting and controlling the intake negative pressure introduced into the diaphragm chamber 84a of the EGR valve 84 in order to control the EGR amount in the low and medium load range of the engine 1. In addition, a configuration is added to ensure EGR in the high load range of the engine 1 (including from near atmospheric pressure to the supercharging range). In the schematic configuration diagram of FIG. 7, only the EGR control control system executed by the ECU 71 is illustrated, and illustration of other control systems is omitted.

Next, the processing operation of EGR control executed by the ECU 71 in the exhaust gas recirculation system for the supercharged engine configured as described above will be explained with reference to the flowchart shown in FIG. This EGR control routine is executed by regular interrupts at predetermined time intervals. When the process moves to this routine, first in step 301,
Based on the detected values of the throttle opening sensor 61, intake pressure sensor 62, water temperature sensor 64, and starter switch 69, the slot opening ACCP, intake pressure PM, cooling water temperature THW, and starter signal ST are respectively read.

Subsequently, in step 302, it is determined whether the engine 1 has been started or not based on the starter signal ST read earlier. Here, if it is not after the start, it is assumed that EGR is not performed, and step 303
In order to close the negative pressure passage 89, the sixth VSV 9
Turn off 0. Further, in step 304, the seventh VSV 99 is turned off to close the pressure passage 98 as well. That is, the EGR valve 84 is closed to cut off the recirculation of exhaust gas to the surge tank 2. Then, the subsequent processing is temporarily terminated.

On the other hand, if it is determined in step 302 that the engine 1 has been started, then in step 305,
It is determined whether the previously read cooling water temperature THW is "40° C." or higher. In other words, it is determined whether the engine 1 has reached a temperature suitable for performing EGR. If the cooling water temperature THW is not a temperature suitable for performing EGR, it is assumed that EGR will not be performed and step 303;
The process in step 304 is executed, and the subsequent process is temporarily terminated.

[0064] Also, in step 305, the cooling water temperature T
If the HW is at a temperature suitable for EGR, the EGR
To perform R, in step 306, the previously read intake pressure PM is set to ``-100mmHg''.
” is less than or equal to the value. That is, it is determined whether or not the inside of the surge tank 2 is in a low/medium load range where the pressure is more negative than "-100 mmHg".

Then, in step 306, if the inside of the surge tank 2 is below the value of "-100 mmHg", in step 307, the seventh VSV 99 is turned off in order to close the pressure passage 98. Next, step 3
At 08, the sixth VSV is opened to open the negative pressure passage 89.
90 is turned on, and the subsequent processing is temporarily terminated. In other words,
In order to utilize the intake negative pressure generated near the throttle valve 4, only the negative pressure passage 89 is opened, and the intake negative pressure is introduced into the diaphragm chamber 84a of the EGR valve 84 as an operating pressure. As a result, the valve body 87 of the EGR valve 84 moves upward to open the EGR valve 84, and the EGR passage 82 is opened.
R is performed.

On the other hand, in step 306, if the inside of the surge tank 2 is larger than the value of "-100 mmHg", in step 309, the throttle valve 4 is opened based on the throttle opening degree ACCP read earlier. In other words, it is determined whether the engine 1 is in a non-idle state. Here, if the throttle valve 4 is in an idling state where it is not opened, the processing in steps 303 and 304 is executed assuming that EGR is not performed, and the subsequent processing is temporarily terminated.

On the other hand, in step 309, if the throttle valve 4 is in a non-idling state in which it is open, it is assumed that the high load region is in the supercharging region due to the supercharging operation of each turbocharger 10, 11, and step 309 is performed. At 310,
First, the sixth VSV 90 is turned off to close the negative pressure passage 89. Next, in step 311, the pressure passage 98
The seventh VSV 99 is turned on to open the file, and the subsequent processing is temporarily terminated. That is, in order to utilize the positive intake pressure generated near the throttle valve 4, only the pressure passage 98 is opened, and the positive intake pressure is introduced into the diaphragm lower chamber 84f of the EGR valve 84 as an operating pressure. As a result, EGR
The valve body 87 of the valve 84 is pushed up, the EGR valve 84 is opened, the EGR passage 82 is opened, and EGR is permitted. In this way, EGR control that is effective in reducing NOx is performed.

As explained above, the EGR of this embodiment
According to the device 100, the inside of the surge tank 2 is “-100m
In the low/medium load range of the engine 1 where the value is below the value of ``mHg'', only the negative pressure passage 89 is opened and the intake negative pressure is transferred to the EGR valve 84.
The operating pressure is introduced into the diaphragm chamber 84a of the EG
The R valve 84 is reliably opened and EGR is performed. On the other hand, it is in a non-idling state and the inside of the surge tank 2 is "-100m".
In the high load range of the engine 1, where the value exceeds the value of ``mHg'', only the pressure passage 98 is opened and the positive intake pressure is applied to the EGR valve 8.
Introduced as working pressure into the lower diaphragm chamber 84f of No. 4,
EGR valve 84 is reliably opened to perform EGR.

Therefore, according to the EGR device 100 of this embodiment, the EGR system can be used not only in the low/medium load range of the engine 1 but also in the high load range where it is difficult to obtain intake negative pressure as the operating pressure.
EGR can be performed by reliably applying operating pressure to the R valve 84. Also, in order to perform EGR in the high load range,
The positive intake pressure generated in the high load region is used to act on the diaphragm lower chamber 84f. For this reason, the EGR valve 84
There is no shortage or loss of working pressure to the
It is possible to secure a large amount of EGR that meets the demands of the high load range. As a result, the temperature of the exhaust gas from the engine 1 is lowered, the air-fuel ratio can be made leaner in the high load range, and fuel efficiency can be significantly improved.

Moreover, in the EGR device 100 of this embodiment, the outlet 98a of the pressure passage 98 is connected to the intercooler 22.
Since it is located in the common intake passage 21 on the upstream side of the
The operating pressure of the EGR valve 84 in a high load range can be increased. That is, on the upstream side of the intercooler 22, the positive intake pressure increases by the amount excluding the pressure loss of the intercooler 22 (in this case, about 150 mmHg),
The operating pressure acting on the diaphragm lower chamber 84f of the EGR valve 84 through the pressure passage 98 also increases accordingly. Therefore, even if the inside of the surge tank 2 is at atmospheric pressure, the EGR valve 8
An operating pressure corresponding to the pressure loss of the intercooler 22 can be applied to the lower diaphragm chamber 84f of No. 4. As a result, the area where EGR is possible can be expanded.

FIG. 10 is a graph illustrating a region in which EGR is impossible in the relationship between engine speed NE and engine load. Here, if the minimum required operating pressure to open the EGR valve 84 is "approximately 100 mmHg", since it is the same in both the negative pressure region and the positive pressure region, it is "approximately ±100 mmHg" with respect to atmospheric pressure. The range becomes a region in which the EGR valve 84 does not open, that is, a region in which EGR is impossible. In FIG. 10, the region between the curve shown by the broken line and the curve shown by the two-dot chain line is the region where EGR is impossible, and corresponds to the region where EGR is impossible in the EGR device 81 of the first embodiment. . On the other hand, in the EGR device 100 of this embodiment,
Since the area where EGR is possible can be expanded by the pressure loss of the intercooler 22, the area where EGR is not possible is between the curve shown by the broken line and the curve shown by the solid line in FIG.

According to the EGR device 100 of this embodiment, the diaphragm 84a of the EGR valve 84 is affected by negative intake pressure and when positive intake pressure is applied to the diaphragm lower chamber 84f. The direction of displacement of the diaphragm 86 is not reversed, and no unreasonable force is applied to the diaphragm 86, thereby improving its reliability. Furthermore, since the EGR valve 84 is only provided with one spring 85 for returning the diaphragm 86, the first EGR valve equipped with a two-stage diaphragm type EGR valve is
Unlike the conventional example, the operating pressure can be set low. Further, since the EGR valve 84 is a single-stage diaphragm type mechanical valve, reliability at high temperatures can be ensured, unlike the technique of the second conventional example in which the EGR valve 84 is driven by a step motor. Therefore, the operational reliability of the EGR device 100 can be improved. In addition, in the EGR device 100 of this embodiment, the negative pressure passage 89 and the EGR
Since the pressure passage 98 is connected to the R valve 84 and the seventh VSV 99 is simply provided in the middle, an increase in manufacturing costs can be suppressed without using an expensive step motor.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but may be implemented as follows by appropriately changing a part of the structure without departing from the spirit of the invention. (1) In each of the embodiments described above, each EGR device 81, 100 is provided with an EGR valve modulator 93, but the EGR device may be configured by omitting the EGR valve modulator 93.

(2) In each of the above embodiments, an in-line 6-cylinder supercharged gasoline engine system is used, but the system may also be applied to a V-type engine instead of an in-line engine. Instead of a cylinder engine, it can also be embodied in a 4-cylinder, 8-cylinder, etc. engine.

[0075]

As described in detail above, according to the present invention, a recirculation passage opening/closing means for opening and closing the exhaust gas recirculation passage is provided, and intake negative pressure near the throttle valve is taken out and supplied to the recirculation passage opening/closing means. A negative pressure passage is provided for introducing the working pressure, and a pressure passage is provided for taking out the intake positive pressure in the intake system and introducing it as the working pressure to the recirculation passage opening/closing means. Negative pressure passage opening/closing means and pressure passage opening/closing means are provided, and when the intake condition is in a non-supercharging region where boost pressure does not occur, only the negative pressure passage opening/closing means is opened, and when the intake condition is in an overcharging region where boost pressure is generated. Since only the pressure passage opening/closing means is opened in the supply region, operational reliability can be improved, and exhaust gas recirculation is ensured not only in the non-supercharged region but also in the supercharged region. It has an excellent effect of being able to do the following.

[Brief explanation of the drawing]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a supercharged gasoline engine system in a first embodiment embodying the present invention.

FIG. 3 is a diagram illustrating an EGR device in the first embodiment.

FIG. 4 is a block diagram showing the configuration of an ECU in the first embodiment.

FIG. 5 is a schematic configuration diagram illustrating the supercharging operation in the "single supercharging stage" of the turbocharged gasoline engine system in the first embodiment.

FIG. 6 is a schematic configuration diagram illustrating the supercharging operation in the "double supercharging stage" of the turbocharged gasoline engine system in the first embodiment.

[Fig. 7] E executed by the ECU in the first embodiment
3 is a flowchart illustrating a GR control processing routine.

FIG. 8 is a schematic configuration diagram illustrating a supercharged gasoline engine system according to a second embodiment of the present invention.

[Fig. 9] E executed by the ECU in the second embodiment
3 is a flowchart illustrating a GR control processing routine.

FIG. 10 is a graph illustrating areas where EGR is impossible in the second embodiment.

[Explanation of symbols]

1...Engine 2...Surge tank 4 that makes up the intake system...Throttle valve 8...Exhaust manifold 10 that makes up the exhaust system...Main turbocharger 11 that makes up the supercharger...Sub-turbocharger 61 that makes up the supercharger...Intake Throttle opening sensor 62 constituting the state detection means...Intake pressure sensor 71 constituting the intake state detection means...
ECU 81 constituting supercharging area determination means and opening/closing control means...EGR device 82...EGR passage 84 as exhaust gas recirculation passage...EGR valve 89 as recirculation passage opening/closing means...Negative pressure passage 90...Negative pressure passage opening/closing Sixth VSV98 as a means...pressure passage

Claims (1)

[Claims] 1. A supercharger provided in an intake system and an exhaust system of an engine, and a supercharger provided between the exhaust system and the intake system, the supercharger being provided to take out a part of exhaust gas from the exhaust system and an exhaust gas recirculation passage for recirculating the exhaust gas to the exhaust gas recirculation passage, and a recirculation passage opening/closing means provided for opening and closing the exhaust gas recirculation passage, the recirculation passage opening/closing means being operated to open in proportion to the intake negative pressure introduced from the intake system; a negative pressure passage for extracting intake negative pressure near the throttle valve in the intake system and introducing it as working pressure to the recirculation passage opening/closing means; In an exhaust gas recirculation device for a supercharged engine, the exhaust gas recirculation device includes a negative pressure passage opening/closing means that is drive-controlled to adjust the introduced working pressure, and the recirculation passage opening/closing means extracts intake air positive pressure in the intake system. a pressure passage introduced as a working pressure into the recirculation passage opening/closing means, a pressure passage opening/closing means provided for opening and closing the pressure passage and driven and controlled to adjust the working pressure introduced into the recirculation passage opening/closing means, and the intake system. an intake state detection means for detecting an intake state at the intake state; and a supercharging region determining means for determining whether or not the intake state is in a supercharging region where supercharging pressure is generated based on a detection result of the intake state detecting means. , when the determination result of the supercharging region determining means is in the non-supercharging region, drive control is performed to open only the negative pressure passage opening/closing means;
and opening/closing control means for driving and controlling the pressure passage opening/closing means so as to open only the pressure passage opening/closing means when the judgment result of the supercharging region determining means is in the supercharging region. Exhaust gas recirculation device.