JPH0642410A - Internal combustion engine provided with exhaust gas reflux device - Google Patents

Abstract

PURPOSE:To suppress generation of heat loss in reflux exhaust gas, and also prevent combustion product material from piling in an intake valve. CONSTITUTION:When a valve body (EGR valve) 4 is opened by one side cam nose 22a of a cam shaft 22 in its expansion stroke, a part of combustion (exhaust) gas is accumulated in an exhaust gas reserving tank 10 through a reflux port 9. When the valve body 4 is opened again by the other side cam nose 22b in the intake stroke, accumulated combustion gas is circulated into a cylinder directly, and it is mixed with new air. A reflux amount is controlled in such a way that pressure in the reserving tank 10 is regulated by a pressure regulating valve 25 provided in a communicating pipe 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine equipped with an exhaust gas recirculation device for reducing NOx (nitrogen oxide) which is one kind of harmful exhaust gas.

[0002]

2. Description of the Related Art An exhaust gas recirculation system, in which a part of exhaust gas is recirculated to an intake system to lower the combustion temperature in a cylinder, is the most effective method for reducing NOx emissions. Is used.

In the conventional exhaust gas recirculation system, the downstream side (or the exhaust pipe) of the exhaust manifold and the intake manifold are connected by a bypass pipe, and the opening degree of an EGR valve provided in the middle of the exhaust gas recirculation system is used to determine the engine load and rotational speed. Generally, the amount of exhaust gas recirculated to the engine is controlled by adjusting the amount of exhaust gas.

[0004]

In the conventional exhaust gas recirculation system described above, NOx production can be effectively reduced according to the exhaust gas recirculation amount, but on the other hand, ignitability is impaired and CO, HC, carbon, etc. Air pollutants and components that adversely affect the engine itself will increase.

Further, when the exhaust gas is recirculated using the bypass pipe as described above, the recirculated exhaust gas is cooled by heat dissipation while passing through the bypass pipe, and the thermal efficiency is lowered to adversely affect the engine performance.

Further, combustion products such as carbon contained in the exhaust gas are deposited on the umbrella portion of the intake valve, which deteriorates the durability of the intake valve, increases the intake resistance, and causes swirl disturbance. I may let you.

The present invention has been made to solve the above problems, and effectively recovers the residual energy of the recirculated exhaust gas to reduce the heat loss, pumping loss, CO, HC, carbon, etc. of the engine. An internal combustion engine equipped with an exhaust gas recirculation device that suppresses an increase in combustion products and prevents carbon and the like from depositing on the intake valve, thereby improving engine performance and durability of the intake valve. The purpose is to provide an institution.

[0008]

To achieve the above object, according to the present invention, a recirculation port communicating with a combustion chamber is formed at a proper position of a cylinder head, and an exhaust gas storage tank is connected to an outlet end of the recirculation port. At the same time, a valve body for opening and closing the reflux port is provided at a key portion of the reflux port, and the valve body is opened and closed at a predetermined timing in an expansion stroke and an intake stroke by an appropriate valve drive means. .

[0009]

When the valve driving means opens the valve body in the expansion stroke,
Part of the combustion (exhaust) gas is accumulated in the exhaust gas storage tank through the recirculation port. Then, when the valve element is opened again by the valve drive means in the intake stroke, the accumulated combustion gas directly flows back into the cylinder and mixes with the fresh air to lower the combustion temperature and suppress the generation amount of NOx.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a DOHC 4-cycle 4-cylinder gasoline engine, in which each cylinder (1) is
2 intake valves (2), 1 exhaust valve (3), 1
EGR valves (4) are provided.

Reference numeral (5) is an intake port formed in a cylinder head (13) (not shown in FIG. 1) corresponding to each intake valve (2). Each intake port (5) is connected to an intake manifold (6). )
Is in communication with.

Similarly, (7) is an exhaust port, and each exhaust port
(7) communicates with the exhaust manifold (8). EGR valve
Each recirculation port (9) corresponding to (4) communicates with an exhaust (combustion) gas storage tank (hereinafter abbreviated as a storage tank) (10).

The return port (9) and the storage tank (10)
It is advisable to consider the heat insulation by covering the inner and outer peripheral surfaces thereof with a heat insulating material such as ceramics, or by manufacturing the material with a low thermal conductivity.

Next, with reference to FIGS. 2 to 4, the valve operating mechanism and the exhaust gas recirculation mechanism of each valve will be described in detail. (11)
Is a cylinder block, (12) is a piston that moves up and down in the cylinder (1) formed in the cylinder block (11), and (13) is a cylinder head.

The cylinder head (13) has a V-shaped intake valve (2) on one side, and an exhaust valve (3) and an EGR valve (4) on the other side, and the cylinder head (13). It is slidably provided by opening and closing the open ends of the ports (5), (7) and (9) corresponding to the valves formed in 13).

The diameter of the cap portion of the exhaust valve (3) depends on the intake valve.
The diameter is larger than that of (2), and the diameter of the cap portion of the EGR valve (4) is small. (14) (15) (16) are the above valves (2)
(3) A tappet loosely fitted to the shaft ends of (4) from above and slidably fitted to the cylinder head (13).

(17), (18) and (19) are the cylinder head (13) and
A valve spring compressed between each spring retainer (not shown) locked to the shaft end of each valve (2) (3) (4),
These springs (17) (18) (19) make each valve (2) (3)
(4) is always biased upward.

Above the tappet (14) are two intake valves.
A camshaft (20) having two rotating cams (20a) of the same phase for independently driving (2) is arranged in a direction orthogonal to the axis of the intake valve (2).

Above the tappets (15) and (16), as shown in detail in FIG. 4, a rotary cam (21) for driving the exhaust valve (3).
And a camshaft (23) including a rotary cam (22) for driving the EGR valve (4) are arranged in parallel with the camshaft (20).

The rotary cams (20a) and (21) for driving the intake valve (2) and the exhaust valve (3) have appropriate profiles so that the same valve timing and lift amount as those of a normal DOHC engine can be obtained. Is set to.

The rotary cam (22) for driving the EGR valve (4) is provided with two cam noses (22a) and (22b) which are equal to each other and have different required angular phases in the circumferential direction. For example, as shown in FIG. The profile is set so that it opens and closes at various valve timings.

That is, the EGR valve (4) is designed to open twice during the intake stroke and during the expansion stroke. Specifically, the profile of the rotary cam (22) is set so that the valve opens twice in the middle of the suction stroke and in the latter half of the expansion stroke. The lift amount when the valve is open is small.

The storage tank (10) and the exhaust manifold (8) are communicated with each other by a communication pipe (24), and a pressure adjusting valve (25) is provided in the middle thereof. The pressure adjusting valve (25) is an actuator (illustrated in the figure) that operates based on signals output from various sensors and control units (neither shown) that detect the engine operating conditions such as engine load, rotational speed, air-fuel ratio, etc. It is composed of, for example, a solenoid valve or a butterfly valve whose opening degree is controlled by (omitted) and adjusts the pressure in the storage tank (10) according to the operating state of the engine.

Thus, the camshaft (23) is rotated by the operation of the engine, and the rotating cam (22) for driving the EGR valve (4).
One cam nose (22a) of each cylinder (1) E
When the GR valve (4) is opened in the latter half of the expansion stroke, part of the high-temperature, positive-pressure combustion gas flows into the storage tank (10) through the reflux port (4).

At the end of the expansion stroke, EG
When the R valve (4) is closed, high temperature and high pressure combustion (exhaust gas) is accumulated in the storage tank (10). Then, after the exhaust stroke,
When the EGR valve (4) is opened again in the middle of the intake stroke, the combustion gas is accumulated in the storage tank (10) and the combustion gas is compressed by the negative pressure in the cylinder and its own pressure into the cylinder (1).
It flows in vigorously and mixes with fresh air.

As a result, the combustion temperature is lowered in the expansion stroke, and the NOx emission amount is reduced. At this time, as described above, the recirculation amount of the combustion gas sent into the cylinder (1) is controlled by controlling the pressure control valve (25) according to the operating state of the engine, and the pressure of the combustion gas in the storage tank (10) is The engine performance and the target NO
It is controlled to a preferable range compatible with the x level.

As described above, in the above embodiment, a part of the combustion gas is stored in the storage tank (10) during the expansion stroke.
Since the pressure is stored in the inside of the cylinder and is directly recirculated into the cylinder in the next intake stroke, the temperature of the exhaust gas flowing into the cylinder is very high. Therefore, unlike the conventional EGR system in which exhaust gas is returned to the intake system through the bypass pipe, heat loss does not occur and the thermal efficiency of the engine does not decrease, and the engine performance is not adversely affected.

Further, since the exhaust gas is directly recirculated into the cylinder, it is possible to prevent the combustion products such as carbon from being deposited on the head portion of the intake valve (2) and the durability of the intake valve (2). The intake resistance is not increased and the swirl is not disturbed as well.

Further, an activating component remains in the combustion gas flowing into the recirculation port (9) during the expansion stroke, and this gas is recirculated into the cylinder to promote the next ignition and combustion. However, NOx can be effectively reduced while realizing efficient combustion while suppressing the production of CO, HC, and carbon.

Since the recirculated exhaust gas is introduced at a positive pressure during the intake stroke, the pumping loss that occurs during the intake stroke is reduced, and engine performance can be improved especially under partial load.

Since the EGR valve (4) is arranged in parallel on the exhaust valve (3) side and is driven by the normal exhaust valve (3) driving camshaft (23), the EGR valve (4) ) It is not necessary to provide a special drive means for exclusive use, and the structure of the entire engine is simplified.

The present invention is not limited to the above embodiment, but can take various forms. For example, in the embodiment, the two cam noses (2) of the cam (22) for driving the EGR valve (4) are used.
2a) and (22b) have the same profile,
You may make them different.

The EGR valve (4) is independently driven without using the camshaft (23) as in the embodiment, by using an actuator utilizing compressed air or vacuum pressure, or linking with a step motor or the like. However, if you do this, EGR
The opening / closing timing of the valve (4) and the lift amount can be controlled more finely according to the operating state of the engine.

Further, the EGR valve (4) is driven by a camshaft which is independent of the exhaust valve, and a known variable valve timing control device or lift control device used for a valve operating system is used in combination to exhaust the exhaust gas. It is possible to finely control the gas recirculation amount.

It is also possible to improve engine performance by appropriately setting the shape of the return port (9) so as to give a swirl to the sucked mixture. Needless to say, the disposition position of the EGR valve (4) is not limited to the above embodiment.

The present invention can be applied not only to the engine equipped with the DOHC direct drive type valve operating mechanism, but also to a rocker arm type or push rod type engine.
It can also be applied to 2-stroke engines and diesel engines.

[0037]

The present invention has the following effects. (a) Since no heat loss occurs in the recirculated exhaust gas, the thermal efficiency of the engine is improved.

(B) The activation component contained in the recirculated exhaust gas improves ignition and combustion, and can reduce NOx while suppressing generation of CO, HC and the like.

(C) Since the recirculated exhaust gas is sucked at a positive pressure, pumping loss is reduced and engine performance is improved.

(D) Since exhaust gas is directly recirculated into the cylinder, combustion products are not accumulated on the intake valve,
The durability of the intake valve is improved.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional front view of a main part taken along the line AA of FIG.

FIG. 3 is an enlarged vertical cross-sectional front view of the main part, which is also taken along the line BB.

FIG. 4 is a perspective view of a main part showing a valve operating mechanism of an exhaust valve and an EGR valve.

FIG. 5 is an explanatory diagram showing valve timings of intake and exhaust valves and an EGR valve.

[Explanation of symbols]

(1) Cylinder (2) Intake valve (3) Exhaust valve (4) EGR valve
(Valve) (5) Intake port (6) Intake manifold (7) Exhaust port (8) Exhaust manifold (9) Recirculation port (10) Exhaust gas storage tank (11) Cylinder block (12) Piston (13) Cylinder head (14) (15) (16) Tappet (17) (18) (19) Valve spring (20) Camshaft (20a) Rotating cam (21) (22) Rotating cam (22a) (22b) Cam nose (23) Cam Shaft (24) Communication pipe (25) Pressure regulating valve
(Pressure adjusting means)

Claims (3)

[Claims] 1. A valve for forming a recirculation port communicating with a combustion chamber at an appropriate position of a cylinder head, connecting an exhaust gas storage tank to an outlet end of the recirculation port, and opening / closing the recirculation port at a key part of the recirculation port. An internal combustion engine equipped with an exhaust gas recirculation device, characterized in that a body is provided and the valve body is opened and closed at a predetermined timing in an expansion stroke and an intake stroke by an appropriate valve drive means. 2. The internal combustion engine provided with the exhaust gas recirculation device according to claim 1, wherein the exhaust gas storage tank is connected to the exhaust pipe via a pressure adjusting means. 3. The internal combustion engine provided with the exhaust gas recirculation device according to claim 1, wherein the valve driving means is a camshaft for driving an exhaust valve having two cam noses.