JPH0447153A - Internal exhaust gas recirculation type engine - Google Patents

Abstract

PURPOSE:To enable lean combustion and enlarge output by constructing a device for recirculating a part of exhaust gas to a combustion chamber in such a way as to communicate a pressure accumulating chamber with the combustion chamber through a pressure accumulating valve and to open/close this pressure accumulating valve temporarily at the specified time. CONSTITUTION:A pressure accumulating valve 12 is closably provided at the entrance of a pressure accumulating chamber 11 communicated with a combustion chamber 4. This pressure accumulating valve 12 is switched by a control device 13 such as cam mechanism. A by-pass passage 14 is provided between the pressure accumulating chamber 11 and an exhaust port, and a pressure reducing valve 15 energized in the valve closing direction by a spring 16 is provided at the by-pass passage 14. The pressure accumulating valve 12 is opened in the latter stage of an expansion stroke (an intake valve 8 and an exhaust valve 9 are closed at this time) to let combustion gas flow into the pressure accumulating chamber 11. Afterwards, the pressure accumulating valve 12 is closed, and then opened again in the first stage of a compression stroke to let the combustion gas in the pressure accumulating chamber 11 flow into fresh air sucked into a cylinder 2. Stratified charge with fresh air converging on a position close to a spark plug 10 can be thereby performed to obtain desirable ignitability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vehicle or general-purpose engine that uses exhaust gas recirculation (EGR) to improve thermal efficiency and reduce NOx emissions.

(Prior art) A conventional exhaust recirculation engine is disclosed in Japanese Patent Application Laid-Open No. 63-10927.
6, a part of the exhaust gas that has first flowed out into the exhaust pipe is made to flow into the fresh air in the intake pipe through the exhaust gas recirculation valve, and is sucked into the combustion chamber together with the fresh air. Generally, the opening and closing of the valve is controlled according to the operating condition of the vehicle.

(Problems to be Solved by the Invention) In the above-mentioned conventional technology, the fresh air is diluted by the mixing of the reflux gas, which tends to cause misfires, and this tendency is particularly noticeable at partial loads where the intake amount is small. Therefore, it is difficult to improve the thermal efficiency by increasing the amount of reflux gas to increase the pressure and increase the actual compression. The present invention aims to solve these problems of the prior art.

(Means for Solving the Problems) A first means for solving the problems in the present invention is that, in an engine that recirculates a portion of exhaust gas to a combustion chamber, a pressure accumulating chamber communicating with the combustion chamber, and a pressure accumulating chamber communicating with the combustion chamber; and a pressure accumulation valve that opens and closes between the pressure accumulation chamber and the pressure accumulation chamber, and a pressure accumulation valve control device that temporarily opens and closes the pressure accumulation valve so that the exhaust valve effectively opens during the expansion stroke (before and during the first half of the compression stroke σ). The second
The means is characterized in that, in the first means, a pressure reducing valve is provided between the front 81 pressure accumulating chamber and the exhaust passage for discharging the exhaust gas to the outside to control the pressure in the pressure accumulating chamber. .

(Function) According to the first means, part of the combustion gas in the combustion chamber flows into the accumulator chamber by closing the accumulator valve at the latter stage of the engine's explosion and expansion stroke and before opening the exhaust valve. be trapped. Then, during the first half of the compression stroke when the pressure is low,
The pressure accumulation valve is opened to release the trapped combustion gas into the combustion chamber, the pressure accumulation valve is closed to perform so-called EGR, and then the reflux gas is compressed together with fresh air in the combustion chamber to perform an explosion stroke.

The reflux gas flowing into the fresh air has a short contact time and distance with the fresh air, so it is difficult to mix, and stratified air supply is performed, resulting in good ignition and combustion. Moreover, since the amount of intake air increases by the amount of inflow of the recirculated gas, actual compression increases, thermal efficiency improves, and NOx generation is suppressed by lowering the combustion temperature.

Furthermore, according to the second means, it is possible to adjust the amount of gas trapped in the pressure accumulation chamber, and therefore it is possible to recirculate combustion gas suitable for the operating conditions.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In Fig. 4, reference numeral 1 is a four-cycle engine, which has a cylinder 2, a piston 3, and a combustion chamber 4 as usual, and a cylinder head 5 that covers these has an intake port 6, an exhaust lower, an intake valve 8, and an exhaust valve. 9 and a spark plug 10 are provided.

In addition to this, the present invention provides a pressure accumulation chamber 11 communicating with the combustion chamber 4.
is provided, and a pressure accumulation valve 12 is provided at the inlet so as to be openable and closable. I3 is a control device for opening and closing the pressure accumulation valve 12, which may be a cam mechanism like the intake valve 8 and exhaust valve 9, or may be electrically controlled. Moreover, a bypass 14 is provided between the pressure accumulation chamber 11 and the exhaust port,
In addition, the pressure reducing valve 15 is pressurized by a spring 16 in the valve closing direction.

Figures 5 and 6 show examples of the arrangement of answers on a plan view.
The figure shows a case where there is one intake valve 8 and one exhaust valve 9, and Fig. 6 shows two each.
However, the arrangement of the answers can be changed as appropriate. In addition, the bypass 14 and pressure reducing valve 1 shown in FIG.
5 can be omitted.

In this engine 1, the intake valve 8 and the exhaust valve 9 are closed in the latter half of the expansion stroke in FIG. 1, but the pressure accumulation valve 12 is opened and combustion gas flows into the pressure accumulation chamber 11. It operates as shown. The answer valve lift is as shown in Fig. 7, and in the intake stroke I, compression stroke ■, expansion stroke ■, and exhaust stroke ■, the intake valve 8 operates normally as shown by curve A, and the exhaust valve 9 operates normally as shown by curve B. Accumulator valve I2 is curved C,,C2
It operates as shown.

First, in the expansion stroke shown in FIG. 1, the pressure accumulation valve 12 opens as shown by curve c2 in FIG. When the pressure in the same chamber is excessive, the pressure reducing valve is opened against the force of the spring 16 to release the pressure to the exhaust lower and adjust the pressure to a constant level.

Next, in the exhaust stroke of FIG. 2 and the intake stroke of FIG. 3, that is, in the ■ and 1 of FIG.
In the first half of the compression stroke (2), the accumulator valve 12 opens again as shown by curve C4, allows the combustion gas in the accumulator chamber 11 to flow into the fresh air sucked into the cylinder 2, and then closes.

The combustion gas flows into the cylinder 2 as shown by arrow E, but by giving it directionality along the cylinder wall, it flows at a position far from the ignition plug 1o, and fresh air flows at a position close to the ignition plug 1o. Stratified air supply with concentrated air is performed.

FIG. 8 is an acupressure diagram, where curve P is the present invention, P is the normal type, P3 is motoring acupressure, and the curve P of the present invention is:
During the intake stroke, the inflow of combustion gas creates a pressure difference from the normal type curve P at point a, and in the expansion stroke ■, due to an increase in actual compression, a pressure difference greater than the pressure difference in the intake stroke occurs, increasing the output. let However, after the pressure accumulation valve 12 is opened at point a2, the pressure difference reverses, but the pressure difference is relatively small, and the resulting decrease in output is small compared to the increase.

Although the four-stroke ignition engine has been described above, the present invention can also be applied to two-cycle engines, diesel engines, and the like.

(Effects of the Invention) As described above, according to the present invention, exhaust gas is recirculated inside the engine without passing through the exhaust pipe and the intake pipe, so that the recirculated gas is mixed with fresh air in the intake pipe. Since the fresh air is injected into the cylinder without any oxidation, it is easy to form a layer of reflux gas on the circumferential surface and the bottom surface and to perform stratified air supply that concentrates fresh air near the ignition plug. This makes it possible to increase the amount of gas recirculation to increase actual compression and to perform lean combustion, which has the effect of making it easier to increase output. Moreover, since the exhaust gas is recirculated inside the engine body, the recirculation mechanism is compact and the entire engine can be made smaller.

Further, the second means has the effect of regulating the upper limit of the amount of reflux gas and avoiding ignition errors due to excessive reflux.

[Brief explanation of the drawing]

1 to 4 show longitudinal sectional views of an embodiment of the present invention, in which FIG. 1 shows the expansion and pressure accumulation stroke, FIG. 2 shows the exhaust stroke, and FIG.
The figure shows the intake stroke, FIG. 4 shows the compression and exhaust recirculation process, FIGS. 5 and 6 show the valve arrangement, FIG. 7 shows the valve lift diagram, and FIG. 8 shows the acupressure diagram. 4... Combustion chamber 6... Intake
Lower...Exhaust port 8...Suction
Air valve 9... Exhaust valve 11...
Accumulation chamber 12...Pressure accumulation valve 1
5... Pressure reducing valve Fig. 1 Fig. 3

Claims (2)

[Claims] (1) In an engine that recirculates part of the exhaust gas to the combustion chamber, there is a pressure accumulation chamber that communicates with the combustion chamber, a pressure accumulation valve that opens and closes between the combustion chamber and the pressure accumulation chamber, and a pressure accumulation chamber before the exhaust valve effectively opens during the expansion stroke. and a pressure accumulation valve control device that temporarily opens and closes the pressure accumulation valve during the first half of the compression stroke. (2) Internal exhaust gas recirculation according to claim (1), further comprising a pressure reducing valve for controlling the pressure of the pressure accumulation chamber, which is interposed between the pressure accumulation chamber and an exhaust passage for discharging exhaust gas to the outside. formula engine.