JPS6027781Y2 - Internal combustion engine air supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air supply system for an internal combustion engine, and its purpose is to reduce the rate of fluctuation in combustion pressure and to enable stable operation with a lean air-fuel mixture.

Generally, it is already known that preheating the intake air significantly improves the ignition combustibility in the combustion chamber and reduces the combustion pressure fluctuation rate. Measures are taken to heat and preheat the mixture that is drawn into the combustion chamber.

However, in the conventional structure as described above, the heating of the air-fuel mixture considerably reduces the fuel filling efficiency, and especially when a lean air-fuel mixture is used, the effect of the reduction in the filling efficiency is large, which is undesirable.

This invention attempts to address the above-mentioned conventional problems.
Embodiments will be described below with reference to the accompanying drawings.

Figures 1 and 2 show an embodiment of the present invention.
An example of applying the present invention to a side valve type engine is shown.

In the figure, 1 is a carburetor, 2 is a suction pipe, the suction pipe 2 branches into 2a and 2b in the middle, and only one suction pipe 2b has a double pipe structure, and a passage 2b' for exhaust gas or engine cooling water, etc. and an exhaust pipe 7 is installed in the passage 2b' as shown in the figure.
Part of the exhaust gas inside the engine or engine cooling water can be introduced to heat the engine.

On the other hand, on the engine side, a first intake valve 3 and a second intake valve 4 are respectively provided at appropriately spaced positions such as on both sides of an exhaust valve 6 in one cylinder part. The unheated suction pipe 2a is connected to the second intake valve 4, and the heated suction pipe 2b is connected to the second intake valve 4, respectively.

The shape of the volume portion 5a of the cylinder head 5 through which the air-fuel mixture taken in from both the first and second intake valves flows is as follows:
As shown in the figure, the intake air-fuel mixture flows almost directly into the upper part of the piston 8 from the first intake valve 3, but the air-fuel mixture that flows in from the second intake valve 4 is introduced toward the upper part of the piston 8 while changing the flow direction. It is configured to have a shaped portion 5a' that provides some resistance to the flow.

The ignition plug 9 is disposed near the second intake valve 4 and on the way of the air-fuel mixture flowing from the second intake valve 4 toward the piston 8 .

10 indicates a muffler.

In the above, the respective valve timings of the two intake valves 3 and 4 are, for example, as shown in FIG. The second intake valve 4 is set to open around BBDC 90' and close around ABDC 55°, so that the second intake valve 4 opens and closes much later than the first intake valve 3 so that there is a time difference between the two.

In the above configuration, first, when the first intake valve 3 opens, the carburetor 1
The air-fuel mixture is sucked in an unheated state through one suction pipe 2a, and flows into the upper part of the piston as shown by arrow A.

Before the intake air from the first intake valve 3 ends, the second intake valve 4 opens, and a portion of the air-fuel mixture from the carburetor 1 is also sucked through the intake pipe 2b through the second intake valve 4 section.

During that time, the first intake valve 3 is closed, and after that, the second intake valve 4 is closed.
It can only be inhaled from the body.

The air-fuel mixture taken in through the second intake valve 4 is heated by exhaust gas, engine cooling water, etc. while passing through the intake pipe 2b.

As mentioned above, the air-fuel mixture that is drawn in separately from the two intake valves 3 and 4 with a time difference is that the normal air-fuel mixture that is not preheated is near the top of the piston, and the preheated air-fuel mixture is near the section 5a' of the cylinder head volume section 5a. Since the spark plug 9 mainly contains heated air-fuel mixture, ignition combustion by the spark plug 9 can be carried out extremely effectively, and the combustion flame of this preheated air-fuel mixture fills the entire combustion chamber. Combustion of the mixture takes place.

Since the preheated air-fuel mixture near the spark plug 9 is completely vaporized and homogenized, the initial combustion time (primary flame propagation time) is not very long and a stable flame is formed, which spreads extremely throughout the entire combustion chamber. Flame spreads smoothly.

As described above, according to the present invention, two intake valves are provided in the same cylinder, and the intake pipe is configured to branch into two so that the air-fuel mixture is supplied to each of the two intake valves from the same carburetor. In addition, by providing a heating mechanism for the passing air-fuel mixture only in one intake pipe, it is possible to solve the problem of reduced fuel filling efficiency due to heating of the intake air. The stratified air supply of the normal air-fuel mixture and the preheated air-fuel mixture, which is not preheated, is carried out by using differential valve timing, etc., and by providing a spark plug in the preheated air-fuel mixture layer, ignition combustion and the propagation of the flame are stabilized. Compared to conventional device b, which does not have an air-fuel mixture preheating device, and conventional device C, which uses a complete air-fuel mixture preheating system, the device a of the present invention has considerably higher combustion pressure, resulting in an increase in effective work and, at the same time, Like〈
Compared to the conventional method (b), the method (a) of the present invention lowers the combustion pressure fluctuation rate, and in particular allows the use of a lean mixture, making it possible to expand the flammable limit air-fuel ratio, etc.
Coupled with the fact that the present invention can be applied to a simple mechanism with two carburetors and one camshaft, the industrial value is extremely great.

Although the present invention is structurally extremely easy to apply to a side valve type engine as shown in the illustrated embodiment, it goes without saying that the present invention is applicable not only to side valve type engines but also to all types of engines. do not have.

[Brief explanation of the drawing]

Fig. 1 is an explanatory plan view schematically showing an embodiment of the present invention, Fig. 2 is a sectional view along the line X-X of Fig. 1, and Fig. 3 shows an example of the valve timing of the intake valve in the present invention. It is an explanatory diagram. Figures 4 and 5 are diagrams comparing the functions of the present invention with conventional devices, and Figure 4 shows when the throttle is fully open (A/F =
16 to 18), and FIG. 5 is a diagram showing the combustion pressure fluctuation rate. 1... Carburizer, 2, 2a, 2b... Suction pipe, 3... First intake valve, 4... Second intake valve, 5. ...Cylinder head, 5a...
... Volume part, 6 ... Exhaust valve, 7 ... Exhaust pipe, 9 ... Spark plug.

Claims (1)

[Scope of utility model registration request] In an internal combustion engine, first and second intake valves are provided at appropriate distances from each other in one cylinder part, and an intake pipe is branched from the carburetor and connected to both the first and second intake valves, respectively. , a preheating mechanism for the intake air-fuel mixture is provided only in the intake pipe connected to the second intake valve, and the shape of the volume of the cylinder head through which the air-fuel mixture sucked from both the first and second intake valves flows is changed to the second intake valve. The non-preheated air-fuel mixture taken in from the second intake valve flows almost directly into the upper part of the piston, but the preheated air-fuel mixture taken in from the second intake valve changes its flow direction and flows toward the upper part of the piston while being subjected to flow resistance. The valve timing of the second intake valve is set to be significantly delayed so that it starts opening in the latter half of the opening period of the first intake valve and closes after a predetermined time delay after the first intake valve closes. An air supply system for an internal combustion engine, characterized in that an ignition plug is disposed at a position midway through the inflow of the preheated air-fuel mixture toward the piston from the second intake valve.