JP3426417B2 - Exhaust gas recirculation system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation (hereinafter referred to as EGR) device for an automobile engine equipped with a supercharger.

[0002]

2. Description of the Related Art A conventional EGR device for a supercharged engine is constructed as shown in FIG.
The exhaust passage 2 on the upstream side a and the intake passage 3 on the downstream side of the compressor 1b of the supercharger 1 are communicated with each other by the EGR passage 4.
An EGR valve 5 is installed in the passage 4. In the figure, 6 is an intercooler.

[0003]

However, in the above engine with a supercharger, as shown in FIG. 6, it is impossible to perform EGR in the middle and high load regions of the engine, and
While by R, NO _X reduction of high load has been difficult.

This is because, unlike a non-supercharged engine, in a supercharged engine, the intake pressure pb at the engine inlet becomes higher than the exhaust pressure pit at the engine outlet in the middle and high load regions, as shown in FIG. .

In this supercharged engine, a throttle valve is provided on the exhaust side in order to make the exhaust pressure higher than the intake pressure.
Bypass intake boost (reject intake to turbine exit). When the VG turbo is adopted, the nozzle is closed up to the turbine nozzle opening to secure the necessary exhaust pressure and reduce performance deterioration such as fuel consumption. However, none of these methods can be adopted because they cause deterioration in engine performance such as fuel consumption due to increase in exhaust pressure.

In Japanese Utility Model Publication No. 3-11401, a normally closed valve for engine braking provided separately from an intake valve and an exhaust valve is used to recirculate a part of exhaust gas into a combustion chamber. It is disclosed that the combustion conditions are improved.

According to this, the normally closed valve is opened from immediately after the exhaust valve is opened to immediately after the intake valve is opened in the next stroke, and a part of the exhaust gas is returned to the combustion chamber through the normally closed valve. There is no problem when applying to a non-supercharged engine, but when applying to a supercharged engine, if the intake valve is opened while the normally closed valve is open, exhaust gas does not recirculate to the combustion chamber. There is a problem that the inhaled intake air flows back into the exhaust passage, so it cannot be used at all.

Therefore, an object of the present invention is to provide an exhaust gas recirculation system capable of ensuring a required EGR rate in a wide operating range of a supercharged engine.

[0009]

In an exhaust gas recirculation system according to the present invention, in an engine with a supercharger, an intake port is installed in a predetermined period including at least a timing near the start of exhaust valve lift or a time during which the exhaust valve lift is rising. Opening / closing means and intake
A pressure sensor for detecting the maximum pressure,
When the pressure detected by the service is high, the exhaust valve lift starts
Open the intake port near the time and detect it with the pressure sensor.
When the pressure released is low and the lift of the exhaust valve is rising
Characterized by opening the intake port .

It is preferable in terms of simplification of the opening / closing drive mechanism if the opening / closing means is composed of a third valve provided separately from the intake valve for intake to the combustion chamber in the intake stroke.

[0011]

The opening / closing means is an intake valve for intake air into the combustion chamber in the intake stroke, and is driven by a second drive means provided separately from the first drive means for opening / closing the intake valve in the intake stroke. When it is driven to open and close, it is preferable in terms of sharing members and reliability of the opening and closing drive mechanism.

[0013]

[0014]

[0015]

[0016]

According to the above construction, the opening / closing means is opened when the pressure in the cylinder is higher than the intake boost pressure, and the exhaust gas (burnt gas) in the cylinder is temporarily returned to the intake port. EGR in the supercharged engine is achieved by sucking this exhaust gas into the cylinder again in the intake stroke.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an exhaust gas recirculation system according to the present invention will be described below in detail with reference to the accompanying drawings. Figure 1
Is a schematic configuration diagram of the first embodiment of the exhaust gas recirculation device, and FIG.
It is an exhaust valve lift curve.

In FIG. 1, reference numeral 10 denotes an engine body composed of a cylinder block 11 and a cylinder head 12. A combustion chamber 14 is defined by a piston 13 in the cylinder block 11, and the cylinder head 12 communicates with an intake manifold 15. An intake port 16 to be connected and an exhaust port (not shown) connected to communicate with an exhaust manifold (not shown) are formed.

The intake port 16 is an auxiliary intake port 17
The auxiliary intake port 17 is opened / closed by a third valve 21 driven by a valve mechanism 20 other than the rocker arm mechanism 19 for driving the intake valve 18 for opening / closing the intake port 16.

The valve mechanism 20 is provided with an oil pump 22 for pressurizing engine oil, an oil passage 24 for guiding the pressurized oil to a drive portion 23 of the third valve 21, and an oil passage 24. The three-way solenoid valve 26, which is switch-controlled by a signal from the control unit 25, and the spring 27, which always biases the third valve 21 in the drive section 23 in the valve closing direction, can be switched by the three-way solenoid valve 26. When the pressurized oil acts on the drive unit 23, the third valve 21 opens against the biasing force of the spring 27. Reference numeral 29 in the figure is a pressure sensor, which detects the intake boost pressure of the intake manifold 15 and inputs a signal to the control unit 25. Further, reference numeral 28 in the drawing is a pressure regulating valve.

Then, the control unit 25
Controls the three-way solenoid valve 26 so that the third valve 21 opens and closes with a lift curve as shown in FIG. That is,
The third valve 21 is opened for a predetermined period including the vicinity of the bottom dead center at which the exhaust valve starts to open, which is the time when the pressure in the cylinder (combustion chamber 14) is higher than the intake boost pressure in any operating range.

The EGR amount is map-controlled by the control unit 25 according to the timing and lift amount as determined in accordance with the engine operating condition.

With this structure, the exhaust stroke starts
Boost pressure using the expansion force of the gas in the nearby combustion chamber 14
Required for high-power intake port 16 (auxiliary intake port 17)
A certain amount of exhaust gas (burnt gas) is made to flow backward,
The rocker arm mechanism 19 injects the exhaust gas thus generated into the intake valve 1
In the intake stroke in which 8 is opened, the air is sucked into the combustion chamber 14 again.
Allows EGR to be performed in all operating areas of the supercharged engine.
No, the target NO _XReduction can be achieved.

On the other hand, when the intake boost pressure detected by the pressure sensor 29 is high and a large amount of EGR is required because the intake boost pressure changes depending on the engine operating condition, the solid line in FIG. Lift as shown. When the intake boost pressure is low, the lift is performed as indicated by the one-dot chain line in FIG. Further, when the intake boost pressure is low and a large amount of EGR is not required, a control signal is output from the control unit 25 to the three-way solenoid valve 26 to lift as shown by the chain double-dashed line in FIG.

Further, in the multi-cylinder engine, the provision of the third valve 21 for each cylinder also has an advantage of suppressing the variation in the EGR rate between the cylinders.

Further, since EGR can be performed without increasing the exhaust pressure (engine outlet pressure),
EG without degrading engine performance such as deterioration of fuel efficiency
NO _X reduction by R can be realized.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the present invention. This is an example in which the rocker arm mechanism 19 is partially used to open and close one intake valve 18 of the multi-valve system with the lift curve shown in FIG.

That is, the drive unit 23A of the intake valve 18 is provided with an EG
Only when the valve for R is opened, the slave piston 30 which is separated from the rocker arm mechanism 19 and can be operated independently is incorporated, and the same control hydraulic pressure as in the first embodiment is applied to this slave piston 30.

On the other hand, when the valve for EGR is closed, the intake valve 18 is the valve spring 19a of the rocker arm mechanism 19.
As a result, the valve is closed in the same manner as the normal intake stroke. In addition, 3 in the figure
Reference numeral 1 is a return spring of the slave piston 30.

According to this embodiment as well, by opening and closing the intake valve 18 with the lift curve shown in FIG. 2, the same operation and effect as in the first embodiment can be obtained.

In each of the above embodiments, the third valve 21
It goes without saying that a drive mechanism other than the hydraulic valve mechanism shown in the drawing may be adopted as the open / close drive mechanism for the intake valve 18.

[0033]

As described above, according to the present invention, in the engine with a supercharger, the intake port is opened / closed during a predetermined period including at least the timing near the start of the lift of the exhaust valve or the time during which the lift of the exhaust valve is rising. Since the means is provided, it is possible to secure the required EGR rate in a wide operating range without deteriorating the engine performance, and it is possible to achieve the target NO _X reduction.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an exhaust gas recirculation device according to the present invention.

FIG. 2 is a lift curve of intake and exhaust valves.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the exhaust gas recirculation device according to the present invention.

FIG. 4 is a schematic configuration diagram of an EGR device in a conventional supercharged engine.

FIG. 5 is a comparative explanatory diagram showing a relationship between a 13-mode exhaust gas test point and a suction / exhaust pressure difference.

FIG. 6 is an explanatory diagram showing a relationship between an EGR-impossible region and a 13-mode exhaust gas test point.

[Explanation of symbols]

10 engine body 14 Combustion chamber 16 intake ports 17 Auxiliary intake port 18 intake valve 19 Rocker arm mechanism 20 Valve mechanism 21 Third valve 22 Oil pump 23,23A drive unit 24 oil passage 25 control unit 26 three-way solenoid valve 29 Pressure sensor

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-4-284149 (JP, A) JP-A-5-195879 (JP, A) JP-A-2-140454 (JP, A) JP-A-4- 262035 (JP, A) JP-A-54-33915 (JP, A) Actually opened 60-116066 (JP, U) Actually opened 54-54732 (JP, U) Actually opened 56-2005 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 25/07 510 F02M 25/07 550 F02M 25/07 570 F02B 37/00 302 F02D 13/02

Claims (3)

(57) [Claims] 1. An opening / closing means for opening an intake port in a supercharged engine in a predetermined period including at least a timing near a start of a lift of an exhaust valve or a timing during a lift of an exhaust valve.
And a pressure sensor for detecting the intake boost pressure,
When the pressure detected by the pressure sensor is high, the exhaust valve
Open the intake port near the lift start time,
Exhaust valve lift rises when the pressure detected by the service is low
An exhaust gas recirculation device that opens the intake port during the middle period . 2. The exhaust gas recirculation system according to claim 1, wherein the opening / closing means is a third valve provided separately from an intake valve that intakes air into the combustion chamber during an intake stroke. 3. The opening / closing means is an intake valve for performing intake air into a combustion chamber in an intake stroke, and a second drive provided separately from a first drive means for opening / closing driving the intake valve in the intake stroke. The exhaust gas recirculation device according to claim 1, which is driven to open and close by means.