JPS62218650A - Exhaust gas recirculation device for internal combustion engine with supercharger - Google Patents

Abstract

PURPOSE:To enable the secure recirculation of exhaust gases in that which the exhaust gases are recirculated on the downstream side of a supercharger, by providing a throttle valve controlling the exhaust gas pressure on the down stream side of an exhaust gas intake part so as to control the throttle valve in response to the operating conditions. CONSTITUTION:On the downstream side of a supercharger 4 and a throttle valve 5, an exhaust gas recirculation passage 7 is connected, and a negative pressure is introduced into an EGR valve 9 provided in this recirculation passage via a solenoid valve 11 which is controlled by a control unit 10 so as to enable the recirculation of exhaust gases. On the downstream side of the exhaust gas intake part in the exhaust gas recirculation passage 7, an exhaust gas throttle valve 12 which controls the exhaust gas pressure is provided, and the exhaust gas throttle valve 12 is open/close controlled by an actuator 14. The control unit 10 controls the introduction of negative pressure into the actuator 13 via a solenoid valve 15 so that the recirculation of exhaust gases can be carried out in conformity with operating conditions, and controls the opening of the exhaust gas throttle valve 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an exhaust gas recirculation device for an internal combustion engine with a supercharger, and more particularly to an exhaust gas recirculation device that ensures that recirculated exhaust gas flows into an intake passage. Relating to equipment.

(Prior art) A part of the exhaust gas is returned to the intake passage (intake pipe) when the internal combustion engine is in a partial load operating state to purify the exhaust gas emitted from the internal combustion engine, particularly to reduce nitrogen oxides. Exhaust gas recirculation (hereinafter referred to as EGR)
) is publicly known. Furthermore, in an internal combustion engine equipped with a supercharger for improving intake air filling efficiency and increasing engine output, it is also known to perform EGR in the intake pipe downstream of the supercharger.

(Problems to be Solved by the Invention) However, in the conventional EGR device for an internal combustion engine with a supercharger, depending on the operating condition of the engine, the pressure inside the intake pipe becomes higher than the pressure of the recirculated exhaust gas, and the recirculated exhaust gas flows backward. Therefore, there may be a problem that the required EGP cannot be performed.

The present invention prevents the backflow of recirculated exhaust gas that occurs in conventional EGR devices attached to supercharged internal combustion engines and becomes an obstacle when performing EGR. An object of the present invention is to provide an EGR device that can reliably recirculate gas to an intake pipe and perform required BGR.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the EGR device for an internal combustion engine with a supercharger according to the present invention provides Passage and exhaust i! In an exhaust gas recirculation device, the exhaust gas recirculation device is provided in the middle of an exhaust gas recirculation passage that communicates with the air intake passage, and includes a recirculation amount control means that controls the amount of exhaust gas recirculated from the exhaust passage to the intake passage according to the operating state of the engine. , a throttle valve means provided in the exhaust passage downstream of the exhaust passage side end of the exhaust gas recirculation passage for controlling the exhaust gas pressure; and the throttle valve means for controlling the exhaust gas pressure so as to increase the exhaust gas pressure during a predetermined operating state of the engine. and pressure control means for controlling opening and closing of the means.

(Function) The throttle valve means is controlled in the direction of increasing exhaust gas pressure during a predetermined operating state by the pressure control means. As a result, the pressure of the recirculated exhaust gas in the exhaust gas recirculation passage increases and exceeds the internal pressure of the intake passage, and the recirculated exhaust gas, which is controlled to the required amount according to the engine operating condition, flows into the intake pipe via the recirculation passage. do.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an EGR system for an internal combustion engine with a supercharger according to a first embodiment of the present invention, in which an air cleaner 3, e.g. A mechanical supercharger 4 that is mechanically connected to the output shaft and directly driven by the engine 1, and an intake throttle valve 5 are sequentially provided, and a throttle opening sensor 6 is connected to the throttle valve 5. There is.

One end of an exhaust gas recirculation passage 7 communicates with the downstream side of the throttle valve 5 of the intake pipe 2, and the other end of the recirculation passage 7 communicates with an exhaust passage (exhaust pipe) 8 of the engine 1, so that part of the exhaust gas The air can be refluxed to the intake pipe 2 via the reflux passage 7. For example, a diaphragm type EGR valve 9 is disposed in the middle of the exhaust gas recirculation passage 7 to control on/off the recirculation of exhaust gas, and the diaphragm 9 of the BGR valve 9
A first solenoid valve 11 which is controlled on and off by a control unit 10 and can selectively communicate with the atmosphere and the intake pipe 2 is provided in the first chamber 9b facing one side of e.
Atmospheric pressure or negative pressure is supplied depending on whether the diaphragm 9e is turned on or off, and the second chamber 9c facing the other side of the diaphragm 9e communicates with the atmosphere. The valve body 9a connected to the diaphragm 9e is connected to the differential pressure between the first chamber 9b and the second chamber 9c, and the first chamber 9b.
A spring 9d is housed in the spring 9d and presses the diaphragm 9e.
The valve 9 is seated or lifted depending on the resultant force of the spring force.
provided to turn off or on the recirculation of exhaust gases through the

An exhaust throttle valve 12 is rotatably arranged in the exhaust pipe 8 of the engine 1 downstream from the exhaust pipe side end of the exhaust gas recirculation passage 7.
The throttle valve 12 has a lever 13 that is rotatable integrally with its rotation shaft.
The operating shaft 1 of the diaphragm actuator 14 is
4e. The throttle valve 12 controls the amount of exhaust gas recirculated together with the EGR valve 9 and the like. The first chamber 14 faces one side of the diaphragm 14d of the seven cutuators 14.
A communicates with the atmosphere, and a second solenoid valve 15 that is controlled on and off by the control unit IO and can selectively communicate with the atmosphere and the inside of the intake pipe 2 is connected to the second chamber 14b facing the other side. The corresponding negative pressure is supplied,
The operating shaft 14e of the actuator I4 is accommodated in the differential pressure between the first chamber 14a and the second chamber 14b and the second chamber 14b,
The control unit IO has a slider that takes an operating position according to the resultant force of the spring force of the spring 14C that presses the diaphragm 14d, and the operating position, that is, the opening degree of the exhaust throttle valve 12, is linked to the operating shaft 14e. It is detected by a potentiometer 16 connected to.

In addition to the aforementioned throttle opening sensor 6 and potentiometer 16, the control unit 10 is connected to an engine water temperature sensor 17 for detecting engine cooling water temperature, an engine rotation speed sensor 18, and the like. This control unit 1O is composed of, for example, a microprocessor with memory, an A/D converter, an input/output device, etc. As shown in FIG. A predetermined value of the exhaust throttle valve opening is stored, and various predetermined values described below are also stored.

Hereinafter, the operation of the EGR device configured as described above will be explained with reference to a control program (FIG. 3) that is executed at predetermined intervals by the control unit IO.

First, the control unit IO controls the throttle opening detected by the throttle opening sensor 6, the engine water temperature sensor 17, and the engine rotation speed sensor 18, respectively.
The detected values of the engine water temperature and engine speed are read (step 101), and then, in steps 102 and 103, it is determined whether the engine is in an operating state in which EGR should be prohibited. That is, in step 102, it is determined whether or not the throttle opening is in a high-load operating state (the operating region indicated by diagonal lines in FIG. 4) with a predetermined value or more.
In step 3, it is determined whether or not the engine is in a cold state where the engine water temperature is below a predetermined value (for example, 60° C.). When the engine 1 is operating under high load, that is, when the detected throttle opening is larger than the predetermined value (the determination result in step 102 is affirmative (Y
ES), or during cold engine operation, that is, when the detected engine water temperature is lower than the predetermined value (60°C) (if the determination result in step 103 is affirmative (YES))
, the solenoid valve 11 is communicated with the atmosphere side, and the EGRGeO
2 open state (Step 104), then the solenoid valve 15 is communicated with the intake pipe 2 side until the detected exhaust throttle valve opening degree from the potentiometer 16 reaches a value representing a fully open state, and the exhaust throttle valve 12 is fully opened ( Step 105). Since EGR is not performed during high-load operation or cold engine operation, there is no need to increase the recirculated exhaust gas pressure (
, the exhaust throttle valve 12 is fully opened, that is, deactivated.

On the other hand, if it is not during high load operation or cold operation (both determination results in steps 102 and 103 are negative).
)), the solenoid valve 11 is communicated with the intake pipe side to open the EGRGeO2 state (Step 106), and the detected exhaust throttle valve opening is adjusted according to the engine speed and throttle opening shown in FIG. The exhaust throttle valve 12 controls the duty ratio of the solenoid valve 15 so as to match the opening value.
is maintained at a predetermined opening degree (step 107), as a result,
The exhaust passage is throttled by the exhaust throttle valve 12 with a predetermined opening degree, and back pressure is applied to the exhaust gas in the exhaust gas recirculation passage 7. The recirculated exhaust gas pressure exceeds the intake pipe internal pressure, and the recirculated exhaust gas flows into the intake pipe 2. flows into.

Furthermore, the amount of recirculation depends on the engine speed and throttle opening.

Next, an EGR device according to a second embodiment of the present invention will be explained.

The second embodiment is different from the first embodiment in which the exhaust gas recirculation amount is also controlled by the exhaust throttle valve 12, and the exhaust gas recirculation amount is controlled by opening and closing the exhaust throttle valve 12 on and off. This is controlled by controlling the amount of EGRGeO2 lift. For this purpose, a solenoid valve 11 communicating with the EGRGeO2 first chamber 9b is provided so that the on-off duty ratio can be controlled by the control unit 10, and the negative pressure supplied to the first chamber 9b is applied to the EGRGeO2 body according to the on-off duty ratio of the valve 11. The lift a of 9a is variably controlled. Note that the other configurations are the same as those of the first embodiment, so explanations will be omitted.

The operation of the second embodiment ρBGR device will be explained below.

The operation during high-load operation and cold operation is the same as that of the first embodiment described above, and EGRGeO2 is opened and EGR is not performed. Since there is no need to increase the recirculated exhaust gas pressure, the exhaust throttle valve 12 is fully opened. do.

On the other hand, if the detected exhaust throttle valve opening is neither high load operation nor cold engine operation, the detected exhaust throttle valve opening is set to a predetermined value of the exhaust throttle valve opening, for example 50.
The solenoid valve 15 is selectively communicated with the atmosphere side and the intake pipe 2 side so that the exhaust throttle valve 12 is maintained at this predetermined opening degree.

As a result, the exhaust passage is throttled by the exhaust throttle valve 12 having a predetermined opening degree, the pressure of the recirculated exhaust gas exceeds the internal pressure of the intake pipe, and the recirculated exhaust gas can flow into the intake pipe 2. Then, the control unit 10 controls the on-off duty ratio of the solenoid valve 11 to a predetermined on-off duty ratio that has been set and stored in advance according to the engine speed E& and the throttle opening, thereby adjusting the EGRGeO2 lift amount to a predetermined value. Then, an amount of exhaust gas corresponding to the engine speed and the throttle opening is recirculated into the intake pipe 2.

In both of the above embodiments, the present invention was applied to a gasoline engine, but it may also be applied to a diesel engine.

Further, although the engine load is detected from the throttle opening degree, the engine load may also be detected from the intake pipe internal pressure detected by a pressure sensor communicating with the intake pipe, or, for example, by a Karman vortex type air flow sensor. Value A/N found from airflow iA and engine speed N
It may also be detected from.

Furthermore, the exhaust throttle valve 12 in the first embodiment and the EGRGeO2 solenoid valve in the second embodiment! 5
and 11, and supplied atmospheric pressure or negative pressure to the second chamber 14b of the actuator 14 and the EGRGeO 21 chamber 9b to control each lift amount. The exhaust throttle valve 12 in the first embodiment and the EGRGeO2 lift amount in the second embodiment may be controlled.

Furthermore, a turbocharger may be used as the supercharger.

(Effects of the Invention) As described in detail above, the present invention enables the throttle valve means provided in the exhaust passage downstream of the exhaust passage side end of the exhaust gas recirculation passage to exhaust gas by the pressure control means during a predetermined operating state of the engine. The pressure of the recirculated exhaust gas is increased by controlling in the direction of increasing gas pressure, and the recirculated exhaust gas, which is controlled to a required amount according to the operating state of the internal combustion engine by the recirculation amount control means, flows into the intake passage via the recirculation passage. This makes it possible to prevent the backflow of recirculated exhaust gas which becomes an obstacle when performing EGR, and even in an internal combustion engine with a supercharger, the required amount of exhaust gas can be reliably recirculated to the intake passage, and the required EGR can be performed.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an example of an EGR system for an internal combustion engine with a supercharger according to the present invention, and Fig. 2 shows the throttle opening-engine speed-exhaust throttle valve opening characteristic set and stored in the control unit. Graph shown, 3rd
The figure is a flowchart of the control program executed by the control unit, and FIG. 4 is a graph showing the operating range of the internal combustion engine that performs EGR. 1...Gasoline engine, 2...Intake pipe, 5...
Throttle valve, 6... Throttle opening sensor, 7...
・IJl gas recirculation passage, 8-1... Exhaust pipe, 9...
EGR valve, 1°...Control unit, 11.1
5...Solenoid valve, 12...Exhaust throttle valve, 14.
...Actuator, 16...Potentiometer, 1
7... Engine water temperature sensor, 18... Engine rotation speed sensor. Applicant: Mitsubishi Motors Corporation Representative: Patent Attorney: Kanji Nagato

Claims (1)

[Claims] The supercharger is disposed in the middle of the intake passage of an internal combustion engine, and is disposed in the middle of the exhaust gas recirculation passage that communicates the intake passage and the exhaust passage downstream of the supercharger. In an exhaust gas recirculation device equipped with a recirculation amount control means for controlling according to operating conditions, a throttle valve means for controlling exhaust gas pressure is provided in the exhaust passage downstream of the exhaust passage side end of the exhaust gas recirculation passage. and pressure control means for controlling the opening and closing of the throttle valve means so that exhaust gas pressure increases during predetermined operating conditions of the engine. Device.