JP2612683B2 - Engine intake control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in an engine mainly used for a passenger car, and relates to a device for reducing nitrogen oxides emitted from the engine as much as possible.

[Conventional technology]

Nitrogen oxides emitted from engines are known as air pollutants, and automobile engines are provided with various types of nitrogen oxide emission control means. That is, for example, it is an electronic fuel injection device in which the fuel supply amount is reduced or excessively supplied in an operation state in which nitrogen oxides are easily generated, or a feedback carburetor which functions similarly. I do. In some cases, the catalytic reduction device is provided in an exhaust passage.

On the other hand, as a method of reducing nitrogen oxides without using such complicated and expensive means, during the overlap of the intake and exhaust valves, a large amount of burned gas in the combustion chamber is caused to flow back to the intake passage, so-called internal EGR. Are known. However, in this method, during a low load operation including an idling operation of the engine, the burned gas excessively flows back into the intake passage due to an excessive intake negative pressure generated in the intake passage, and returns to the combustion chamber again in a subsequent intake stroke. Therefore, the stability of combustion is impaired.

[Summary of the Invention]

The present invention focuses on the fact that the amount of burned gas flowing backward from the combustion chamber to the intake passage changes depending on the volume of the intake passage downstream of the throttle valve, and a manual operation for controlling the intake air amount of the engine to the intake passage near the intake valve. A throttle valve is provided to reduce the volume of the intake passage downstream of the throttle valve, and a resistance valve is provided upstream of the throttle valve for controlling the passage resistance of the intake passage in relation to the load of the engine. A resistance valve with a large opening when the throttle valve opening is a small opening, a small opening when the throttle valve opening is a medium opening, and a large opening when the throttle valve opening is a large opening It is.

〔Example〕

Hereinafter, the present invention will be described with reference to the illustrated embodiments. In FIG. 1, reference numeral 1 denotes a four-stroke engine, which has a combustion chamber 5 formed by a cylinder 2, a cylinder head 3 and a piston 4. The interior of the combustion chamber 5 communicates with an intake passage 7 via an intake valve 6 and an exhaust passage 9 via an exhaust valve 8. Reference numeral 11 denotes a valve operating mechanism, which has a valve operating cam shaft 12 and a swing arm 13. The intake passage 7 includes the cylinder head 3 and the intake pipe 14.
, The upstream end of which is open to the atmosphere.

A manual throttle valve 15 is provided in the intake passage 7 near the intake valve 6.
Is provided. The installation position of the throttle valve 5 is set so that the volume of the intake passage 7 downstream of the throttle valve 15 is smaller than 1/2 of the stroke volume of the combustion chamber. Accordingly, even if a large negative pressure in the combustion chamber 5 acts during the intake stroke of the engine in the intake passage downstream of the throttle valve 15, even if the piston moves through the compression stroke and the explosion stroke to the next intake stroke, the throttle is restricted. The intake air passing through the valve 15 returns to approximately the atmospheric pressure. Therefore, at the beginning of the intake stroke in which the intake valve 6 opens again, the burned gas flowing back to the intake passage 7 decreases. Therefore, the amount of burned gas mixed during the subsequent intake stroke is reduced, and the efficiency of charging fresh air is improved, so that a misfire tendency that tends to occur during low-load operation is reduced.

If the volume of the intake passage 7 downstream of the throttle valve 15 becomes larger than this, the intake negative pressure during the intake stroke remains until the start of the next intake stroke, and the efficiency of charging the fresh air is reduced. Instability and, in extreme cases, a misfire. The operation arm 16 connected to the throttle valve 15 is connected to an accelerator pedal or other throttle valve operator, and is opened and closed by manual operation. Reference numeral 17 denotes a fuel injection nozzle provided downstream of the throttle valve 15.

Reference numeral 18 denotes a sub intake passage provided in the intake passage 7. When the throttle valve 15 is in the closed position, its upstream end, that is, the auxiliary intake port, is open to the outer edge and close to the downstream side in the opening direction of the throttle valve 15. The downstream end of the sub intake passage 18 is located near the intake valve 6 and opens directly in the combustion chamber 5 during opening of the intake valve 6. The configuration of the auxiliary intake passage 18 is not limited to this embodiment. For example, a small-diameter through-hole may be formed in the throttle valve 15, and the throttle valve 15 may be formed in parallel with the axis of the cylinder 2. The same effect can be expected by using a so-called vertical axis. In addition, such an auxiliary intake passage 18
Is preferably provided, the downstream side of the throttle valve 15 of the intake passage 7 of each cylinder is formed independently without communication with a balance pipe or the like. That is, this allows the minimum opening of the throttle valve 15 to be set relatively large, thereby preventing the carbon component contained in the burned gas blown back from the combustion chamber 5 from accumulating on the downstream surface of the throttle valve 15. You can do it.

Reference numeral 19 denotes a butterfly-shaped resistance valve, which is provided on the upstream side separated from the throttle valve 15, and is configured to increase the airflow resistance of the intake passage 7 when the engine is under a heavy load. Resistance valve
The installation position of 19 is set such that the intake passage volume between the throttle valve 15 and the resistance valve 19 is twice or more the intake passage volume 9 downstream of the throttle valve 15. That is, the amount of burned gas that is blown back to the intake passage 7 during medium / high load operation of the engine in which the throttle valve 15 opens relatively widely is defined. That is, if there is such a volume downstream of the resistance valve 19, the burned gas necessary to reduce nitrogen oxides in the subsequent combustion stroke is mixed into fresh air until the next intake stroke. I can do it. If the volume is excessively large, the efficiency of charging fresh air is reduced, and a sufficient output cannot be obtained. On the other hand, when the amount is excessively small, the amount of burned gas mixed into the fresh air decreases, and it becomes impossible to reduce the emission amount of nitrogen oxides to a desired small amount.

Reference numeral 21 denotes a negative pressure responsive means for adjusting the ventilation area of the butterfly-shaped resistance valve 19 to be large or small, that is, a diaphragm. Diaphragm
The inside of the outer box 22 is divided into two chambers by a disc-shaped elastic film 23 made of phosphor bronze, one side of which is an air chamber 24 which always communicates with the atmosphere, and the other side is an air intake passage through a conduit 25. 7 is a negative pressure chamber 26. The other end of the conduit 25 communicates with the wall surface of the intake passage 7 in close proximity to the throttle valve 15 and on the upstream side in the opening direction,
When the throttle valve 15 is at a low opening including the idling opening,
Atmospheric pressure acts on the negative pressure chamber 26 from the intake passage 7. 27 is a rod connecting the elastic film 23 and the operating arm of the resistance valve 19.

Thus, when the throttle valve 15 is at a low opening including the idling opening, the atmosphere acts on the atmosphere chamber 24, and the resistance valve 19 reaches the maximum opening by the elasticity of the elastic film 23, and the air flows through the intake passage 7. Minimize resistance.

At this time, since both ends of the sub intake passage 18 are on the downstream side of the throttle valve 15, no airflow is generated.

FIG. 2 shows another embodiment, in which the fuel supply means is replaced with the fuel injection nozzle 17 in the embodiment of FIG.
Only the point using 31 is different. In this case, the carburetor 31 is preferably provided on the upstream side of the resistance valve 19, but since a low-speed fuel system including the low-speed fuel nozzle 32 cannot be provided near the throttle valve 15, a negative valve having a variable venturi member 34 is provided. A low-speed fuel is supplied from the main fuel nozzle 33 using a pressure-responsive variable venturi carburetor, a so-called SU carburetor. SU
Type carburetors usually do not have a choke valve for cold start,
In this example, a choke valve 35 is provided.

The present invention can be applied not only to the single cylinder engine described above but also to a multi-cylinder engine as shown in FIG. Third
The drawing is different in that the intake pipe 14 interposed between the cylinder head 3 and the carburetor 31 is a branch pipe 14a.
In this case, the resistance valve 19 is provided in the collecting part 36, and the throttle valve 15 is provided in each branch part 37.

Next, the operation of this embodiment will be described. First, when the engine is started and operated at low load, that is, the throttle valve
When the valve 15 is at the low opening, the intake air flow is small and the throttle valve 15
The intake negative pressure that spreads downstream of is relatively high (the intake pressure is low). However, since the volume of the intake passage 7 downstream of the throttle valve 15 is considerably small, the air-fuel mixture flows through the outer peripheral gap of the throttle valve 15 and the negative pressure disappears (stroke pressure) while the stroke proceeds through compression, explosion, and exhaust. Is higher). Therefore, even if the intake valve 6 is opened in the next intake stroke, burned gas hardly flows back to the intake passage 7. Therefore, even when the intake and exhaust valves are both opened, that is, when the overlap is large, the combustion is not unstable during the explosion stroke. At this time, as shown in FIG. 5, the resistance valve 19 is opened relatively large, and there is no problem in operation. It is well known that the generation of nitrogen oxides during such a low-load operation is small.

Next, when the opening of the throttle valve 15 is increased in order to increase the engine output, the inlet of the auxiliary intake passage 18 and the opening of the conduit 25 located near the outer periphery of the throttle valve 15 are on the opposite side of the throttle valve 15 from the above. Will open. Then, an intake negative pressure acts on the diaphragm 21 to reduce the opening of the resistance valve 19 against the elasticity of the elastic film 23 and increase the ventilation resistance of the intake passage 7. Therefore, a relatively large volume is formed in the intake passage 7 downstream of the resistance valve 19, and the intake negative pressure once applied during the intake stroke is reduced to near atmospheric pressure even by the air flowing through the resistance valve 19. Therefore, a large amount of burned gas flows back into the intake passage 7 in the next intake stroke. Therefore, since a relatively large amount of burned gas flows into the combustion chamber 5 together with fresh air, the proportion of burned gas in the intake air increases,
Since the high-speed combustion of the flame in the explosion stroke is inhibited, the generation of nitrogen oxides is reduced.

On the other hand, the pressure at the inlet of the sub intake passage 18 increases to near atmospheric pressure, and the pressure at the outlet opening near the intake valve 6 is kept relatively low. After passing through the intake passage 18 at high speed, a thin and fast air flow is generated from the injection port in the intake passage 7 and injected into the combustion chamber 5 to vigorously agitate the air-fuel mixture in the combustion chamber to generate a turbulent flow, thereby increasing the air-fuel mixture speed. In addition, stable combustion is performed, and combustion instability due to recirculation of burned gas is eliminated.

When the opening of the throttle valve 15 is fully opened, the engine generates the maximum output at the current engine speed. In this case, the intake air flow rate increases with an increase in the engine speed, and when it approaches the maximum output, the negative pressure in the intake pipe increases due to the ventilation resistance (the pressure decreases).
The elasticity of the 23 increases the opening of the resistance valve 19 and contributes to ensuring the maximum flow rate. On the other hand, in this state, the pressure difference between the inlet and the outlet of the sub-intake passage 18 disappears, and the sub-intake hardly flows. However, as the intake air flow increases, the swirl and turbulence of the intake air generated in the combustion chamber 5 increase, and Since it is stabilized, there is no particular problem.

Although the above description has been given of the engine having one intake passage in one cylinder, it is needless to say that the present invention can be applied to a multi-cylinder engine using an intake branch pipe as shown in FIG. As shown in FIG. 2, the present invention is applicable to an engine using a carburetor. Further, in the above embodiment, the diaphragm 21 is configured to operate by the intake negative pressure near the throttle valve 15, but the operation itself of the resistance valve may be experimentally determined so as to open and close according to the load. The control may depend on both the downstream suction negative pressure and the engine speed.

〔The invention's effect〕

As described above, the present invention provides a manual throttle valve for controlling the intake air amount of the engine in the intake passage near the intake valve, reduces the volume of the intake passage downstream of the throttle valve, and separates the intake passage from the throttle valve. A resistance valve is provided on the upstream side to control the passage resistance of the intake passage in relation to the load of the engine. This resistance valve is set to a large opening when the throttle valve opening is small, and the throttle valve opening is medium opening. When the engine is at a low load, the volume on the downstream side of the throttle valve decreases, and the intake air from the combustion chamber is reduced. Since the amount of burned gas flowing back to the passage is reduced, combustion instability does not occur even in a high-output engine in which the intake and exhaust valves overlap greatly. Also, when the engine is operated in a medium / high load state in which the opening of the throttle valve increases, the opening of the resistance valve decreases, and the burned gas flows back to a relatively large volume downstream of the resistance valve. The proportion of burned gas mixed into the air increases, the maximum combustion temperature in the combustion stroke is suppressed, and the generation of nitrogen oxides decreases. Further, according to the present invention, as in the case of using a catalyst to reduce the emission of nitrogen oxides into the atmosphere, the present invention can be implemented in countries where fuel containing an anti-knock material such as tetraethyl lead is not available, for example, in European countries. Has the effect that can be. In addition, even in the configuration of the device, according to the conventional engine output,
There is an effect that a highly precise device such as a fuel injection device or a feedback type carburetor in which the mixing ratio of air and fuel is adjusted is not required.

The present invention is not limited to the gasoline engine shown in the above embodiment, but can be applied to a diesel engine. Further, as in the embodiment, the resistance valve is controlled by the negative pressure responsive means, and when the throttle valve is at the minimum opening position, the negative pressure responsive means is opened to the open side of the outer periphery or to the ゝ upstream side. When communicating with the mouth, the opening and closing mechanism of the resistance valve is simplified, and quick response is obtained.

[Brief description of the drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of an engine, and FIG. 2 is a first embodiment showing another embodiment.
FIG. 3 is a sectional view corresponding to the drawing, FIG. 3 is a partially cutaway plan view showing still another embodiment, FIG. 4 is a diagram showing valve overlap, and FIG. 5 is a characteristic diagram of the resistance valve 19. 5 combustion chamber, 6 intake valve, 7 intake passage, 8
Exhaust valve, 9 ... Exhaust passage, 14 ... Intake pipe, 15 ... Throttle valve, 16 ... Operation arm, 17 ... Fuel injection nozzle, 18 ... Sub intake passage, 19 ... Resistance valve, 21 ... Negative pressure response means.

Claims (10)

(57) [Claims] 1. A manual throttle valve for controlling the amount of intake air of an engine is provided in an intake passage near an intake valve to reduce the volume of the intake passage downstream of the throttle valve, and to be provided upstream on the upstream side of the throttle valve. A resistance valve that controls the passage resistance of the intake passage in relation to the load of the engine is provided. This resistance valve is set to a large opening when the throttle opening is small, and is set to a medium opening when the throttle opening is medium. An intake control device for an engine, wherein the throttle opening is large when the throttle valve opening is large. 2. The resistance valve is controlled by negative pressure responsive means,
2. The engine according to claim 1, wherein said negative pressure responsive means communicates with a negative pressure outlet opening at an open side of said outer periphery or at an upstream side when said manual throttle valve is at a minimum opening position. Intake control device. 3. The engine is of a spark ignition type and has an intake passage having a low-speed fuel injection port opened near a manual throttle valve and a main fuel injection port opened upstream of an auxiliary throttle valve. 2. The intake control device for an engine according to claim 1, further comprising a heater. 4. The intake system according to claim 1, wherein the intake passage of the engine includes an electromagnetic opening / closing type fuel injection nozzle connected to a discharge port of a fuel injection pump near a manual throttle valve. Control device. 5. The intake control system for an engine according to claim 1, wherein the engine is a diesel type having a fuel injection nozzle in a combustion chamber. 6. An intake control system for an engine according to claim 1, wherein the operating means for operating the resistance valve includes a diaphragm which is operated by a negative intake air pressure. 7. The intake control of an engine according to claim 1, wherein the actuating means for operating the resistance valve includes a valve means which uses an intake negative pressure as a pressure source and opens and closes in accordance with the intake negative pressure and the engine speed. apparatus. 8. The intake control system for an engine according to claim 1, wherein the operating means for operating the resistance valve includes a diaphragm operated by exhaust pressure. 9. The intake control of an engine according to claim 1, wherein the installation position of the throttle valve is set such that the volume of the intake passage downstream of the throttle valve is smaller than 1/2 of the stroke volume of the combustion chamber. apparatus. 10. The throttle valve and the resistance valve are installed at a position where the intake passage volume downstream of the throttle valve is smaller than 1/2 of the stroke volume of the combustion chamber. 2. The intake control device for an engine according to claim 1, wherein the intake passage volume between the two is set to be at least twice the intake passage volume downstream of the throttle valve.