JPS6229657Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a means for preventing air pulsation caused by the internal combustion engine of a small tiller.

(Prior technology) In working machines and light vehicles equipped with an internal combustion engine, such as small tillers such as Taylor and cultivators, mowers, furrow cutters, and paddy weeders, the internal combustion engine is located near the height of the plowing hoe, and the In such cases, internal combustion engines tend to inhale air mixed with dust. Although an air cleaner has been installed to prevent dust from being sucked in, the air cleaner is severely damaged. Therefore, as a means of solving these problems, it has been considered to provide the air intake at a high position and at a distance, and it is common practice to provide the air intake in the vicinity of the hand push handle. This way, the air intake is located close to where people stand, so the amount of dust is relatively reduced, but the long air intake pipe causes severe pulsation, which may cause a drop in output in the operating rotation range. Harmful effects will occur.

1 and 2 show a conventional example. In FIG. 1, 1 is a carburetor, 2 is an air cleaner, and 3 is an air intake pipe connecting the carburetor 1 and the air cleaner 2. The air cleaner 2 shall be installed with a stay 4 in a place with little dust. If this is done, pulsations will occur in the air intake pipe 3 as the engine is driven, making the supply of air unstable, resulting in a significant drop in horsepower. As a countermeasure, conventionally,
As shown in the figure, a control plate 6 is provided at the attachment point of the air intake pipe 3 to the carburetor 1 with a case 5 interposed therebetween. This control board 6 is an orifice and the air suction pipe 3
The opening is about 20mmφ compared to the inner diameter of 31mmφ.

The air cleaner 2 shown in Fig. 2 is attached directly to the carburetor 1, and air is taken in through the air intake pipe 3. A large surge tank 7 is installed in the middle of the air intake pipe 3 to prevent pulsation. It is designed to reduce the

8 is an element and is housed in case 5,
11 is an element holder.

What is shown in Figure 3 is its horsepower curve, and there is no air intake pipe and the air cleaner 2 is directly connected to the carburetor 1.
The horsepower curve for the case where only the 1 m long surge tank 7 is installed in the middle of the air suction pipe 3 is the curve a, and the horsepower curve for the case where the large capacity surge tank 7 is installed in the middle of the air suction pipe 3 (see Figure 2) is the curve b. An elbow 9 with a 15 mm diameter hole is used for the air intake at the tip. The b-curve shows a considerable decrease in horsepower compared to the a-curve.

(Problems to be solved by the invention) As shown in Fig. 3 above, in the model shown in Fig. 2, there is a considerable decrease in horsepower, and the surge tank does not subside properly, resulting in large air pulsations and a large drop in performance. .

In addition, in the one shown in FIG.
Attempts have been made to eliminate pulsation by using an orifice to control the amount of air passing through, but the problem remains that it is still not sufficiently effective.

(Means for Solving Problems) The present invention is a small internal combustion engine in which air is taken into the carburetor through a long air intake pipe, and the air exhaust port of the air intake pipe is located close to the carburetor. A control plate is interposed at the attachment point between the carburetor and the air intake pipe, and the control plate is made of a mesh such as metal lath, wire mesh, punched metal, etc., and the air passage area is adjusted to This air pulsation prevention device is characterized in that the area is set to 40 to 60% of the air pulsation prevention device, and that the air intake pipe has a constriction that narrows the area to 10 to 30%.

In addition, the mounting portion may have an air cleaner or may not have an air cleaner, and if there is an air cleaner, the control plate may be located on the air intake pipe side of the air cleaner element, and the air cleaner may not be located at the mounting portion. In some cases, an air cleaner may be provided at the other end of the air intake pipe.

(Function) The air passage taken into the internal combustion engine from the carburetor is intermittently opened and closed by the piston of the internal combustion engine, so air compression waves are generated in the air intake pipe, and air pulsation reflected pressure waves are generated. This occurs between the air intake part of the air intake pipe and the connection part on the carburetor side, and the amount of air intake decreases in a certain operating speed range of the internal combustion engine, reducing the output. By setting the air passage range to 40 to 60%, the propagation of pulsation is dispersed and blocked. Due to mutual interference with the control board, the negative effects of long pipes can be completely eliminated.

(Example) An example of the present invention will be described with reference to FIGS. 4a and 4b and FIG. 5. FIGS. 4a and 4b are compared with the conventional example shown in FIG. , and there is a restriction at the air intake port of the air intake pipe line 3. In FIG. 4a, 12 is a diaphragm, and other than that, FIG. 1 and FIG. 4a are the same. Further, when comparing FIG. 2 with FIG. 5 of the present invention, it is the same as FIG. 2 except that the control plate 6 is located in the vicinity of the carburetor 1 in FIG. 5 and there is no surge tank.

The control board 6 of the present invention is installed near the carburetor 1 at the attachment point of the air suction pipe 3, and is made of a mesh 10, and may be made of metal lath or wire mesh with an air flow rate of 40 to 60%. By stacking multiple sheets or by using punched metal, the incoming air is squeezed and dispersed.

In addition, the aperture 12 on the air intake side, which is the other end of the air intake pipe 3, has a diameter of 15 mm at the air intake port at the tip, whereas the inner diameter of the air intake pipe 3 is 31 mmφ in Fig. 5.
An elbow 9 with a hole of mmφ is used. Providing the throttle 12 in such an air intake port is similar to the conventional example (FIG. 2).

Experiment Next, FIG. 6 shows a comparison of horsepower curves obtained by inserting throttles (control board 6 and throttle 12) at both ends of the air intake pipe 3.

Curve a...When there is no air intake pipe line Curve c...The horsepower for the rotational speed of the present invention is suppressed, and fuel consumption decreases as the horsepower decreases Curve d...The control plate 6 in Fig. 5 is connected to the orifice 17mmφ
The opening of the air intake pipe is 1m, and the throttle (the tip of the air intake pipe) has a diameter of 15mm.The pulsation is severe, and horsepower is not produced particularly at low rotation speeds.

Curve e...Condition shown in Figure 1, control plate orifice 20mm
φ Horsepower is the same as in the present invention, but there is pulsation and fuel consumption is slightly higher.

f curve... without a control board.

The pulsation is severe and the horsepower is low and not good.

Although the invention (curve c) of the present invention is not as good as the curve a without an air intake pipe, it is superior to the conventional one.

Experiment Next, the experimental results regarding the aperture 12 are shown in FIG. This is a diagram when the diameter of the aperture at the tip of the elbow is kept constant at 15 mmφ and the amount of aperture through which the control board (air cleaner hole) passes through is varied. Aperture amount approximately 30%
In this case, the output drop is large at high speed rotation, and although the output drop is small at 67% aperture, rotational fluctuations due to pulsation occur throughout the rotation range, making it difficult to put it to practical use. On the chart, the output is the best at any rotation speed when the aperture is approximately 56%.

Experiment We used a metal lath for the control board and kept the passage area of the air cleaner hole constant at approximately 56%.
It is a chart showing changes in the amount of restriction at the tip of the elbow with respect to the air suction pipe passage area.

Even if you narrow it down to about 13%, there is little output drop, but about
When throttled to 38% and 4000 RPM, the output drop will be very large due to pulsation, and there is a danger that the air-fuel ratio will become too low. It seems best for the elbow air intake to be around 15mmφ for each rotation speed.

(Effects of the invention) This invention was devised to disperse the occurrence of pulsation and obtain a smooth air flow rate even if an air intake pipe exists. When air is taken in through a long air intake pipe, the air passage area of the tip air intake and air cleaner hole is narrowed down, creating a function that disperses and blocks pulsations.

This technical idea is based on the case where the air cleaner is separated from the carburetor and an air intake pipe is provided in the middle (the fourth
This works effectively both in Figure a) and when the air cleaner is installed near the carburetor (Figure 5), which is the same as when air suction pipes are installed but pulsation is not installed. It is possible to create a smooth air intake condition like this. By doing this, there is no need to install a surge tank near the handle, and the elbow can be secured to the air intake with a nylon band, so that the direction of the elbow opening can be changed depending on the direction of the wind or in the case of rain. You can also do things like

[Brief explanation of the drawing]

Figures 1 and 2 are side sectional views showing the state of air introduction into the carburetor to explain the conventional example, and Figure 3
The figure shows the horsepower curve of the conventional example.
4b is a partial illustration of the control board, FIG. 5 is a side sectional view of the present invention corresponding to FIG. 2, and FIG. 6 is a side sectional view of the present invention corresponding to FIG. Figures 7 and 8, which compare the horsepower curves with the conventional example, are charts showing the results of comparative experiments on the effects of the present invention. 1... Carburetor, 2... Air cleaner, 3
... Air intake pipe, 5 ... Case, 6 ... Control board, 7 ... Surge tank, 8 ... Element, 9
...Elbow, 10...Net body, 11...Element presser, 12...Aperture.

Claims (1)

[Scope of utility model registration request] In a small internal combustion engine that takes air into the carburetor through a long air intake pipe,
The long air suction pipe has a constriction at the air intake port, and a control plate at the air discharge port of the air suction pipe.
%, and the control board controls the air flow rate.
An air pulsation prevention device characterized in that it is constituted by a net having a ratio of 40 to 60%.