JPH0372815B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to an exhaust device that utilizes exhaust gas.

Conventional Technology The cylinder and muffler of an internal combustion engine are sometimes housed inside a cover to block out the noise generated by them and to improve their appearance, but since the cylinder and muffler also generate high heat,
A device is required that introduces external air into the cover as cooling air and blows it to these high-temperature areas to cool them down.
As one type of this device, a cooling fan driven by an internal combustion engine is provided, and a diff user is placed close to the exhaust gas outlet of the muffler, and a jet of exhaust gas ejected from the exhaust gas outlet of the muffler to the diff user causes the inside of the cover to be heated. There is a known device that sucks air into the diffuser and blows it against the high-temperature parts of the cylinder or muffler to cool the high-temperature parts and actively exhausts the air that tends to stay inside the cover to the outside. There is. However, in conventional exhaust gas exhaust devices, the exhaust gas outlet of the muffler is formed as a relatively large circular or oval single hole, so the jet velocity of the exhaust gas is also relatively slow and the diffuser is not connected to the exhaust gas outlet of the muffler. Because of this, the overall shape of the device is large, and the shape and dimensions of the muffler and differential user are restricted, making it difficult to design them freely, making it difficult to make the device smaller and lighter. However, it has disadvantages such as being unsuitable as an air exhaust device for an internal combustion engine of a portable working machine.

Problems to be Solved by the Invention Therefore, the present invention has been made to eliminate the drawbacks of such conventional techniques, and has a small and lightweight structure, a high degree of freedom in shape design, and high efficiency. The purpose is to provide an exhaust device that utilizes exhaust gas.

Means for Solving the Problem That is, according to the present invention, an air exhaust device that uses exhaust gas to exhaust air in a cover surrounding a muffler of an internal combustion engine has a plurality of openings each having a relatively small opening size in the muffler. A plurality of exhaust gas outlets are arranged to form an exhaust gas outlet area, a diff user is disposed close to the exhaust gas outlet area, and an exhaust port for discharging air in the cover is provided between the exhaust gas outlet area and the diff user. and a configuration configured to define.

Function: Therefore, the air inside the cover is efficiently sucked into the diffuser from the exhaust port by the exhaust gas flow, and is discharged to the outside together with the exhaust gas, and the distance between the muffler and the diffuser is shortened to improve the exhaust system. By shortening the length, the entire structure can be made compact.

Embodiments Next, the present invention will be described based on embodiments shown in the drawings.

The embodiment shown in FIG. 1 is an example in which the present invention is applied to an exhaust gas exhaust system of an internal combustion engine for driving a brush cutter. The engine 1 is installed horizontally inside and a cover 2 surrounding the internal combustion engine 1 is provided, and the cover 2
is adapted to be attached at its front end 3 to the rear end of the operating rod. The internal combustion engine 1 includes a cylinder 4, a crankcase 5 disposed continuously with the cylinder 4, a crankshaft 6 rotatably supported by the crankcase 5, and a crankshaft 6 attached to the tip of the crankshaft 6. a cooling fan 7 and a centrifugal clutch 8; a carburetor 9 and an air cleaner 10 disposed above the cylinder 4; and a muffler 11 disposed below the cylinder 4. It is disposed within the cover 2. Further, a recoil type starter 1 for starting the internal combustion engine 1 is provided at the rear end of the crankshaft 6.
2 are arranged.

The muffler 11 muffles the exhaust gas discharged from the cylinder 4 while exhausting the exhaust gas to the outside through a plurality of relatively small diameter exhaust gas outlets 13 that are collectively arranged at appropriate locations. The number and individual sizes of the exhaust gas outlets 13 are such that the total opening area thereof corresponds to the opening area of a conventional single exhaust gas outlet, which is necessary to efficiently discharge exhaust gas from the muffler 11. To be elected. A diff user 14 is disposed adjacent to the exhaust gas outlet 13 so as to match the jet direction of the exhaust gas from the exhaust gas outlet 13, and in this embodiment, the diff user 14 is formed integrally with the cover 2. has been done. An annular exhaust port 15 is defined between the exhaust gas outlet 13 of the muffler 11 and the differential user 14 for discharging the air inside the cover 2 into the differential user 14. , the diffuser 14 and the air exhaust port 15 constitute an air exhaust device 16 that actively exhausts air that tends to stay inside the cover 2 as will be described later.

The structure and operation of this ventilation device 16 will be explained in more detail with reference to FIG. 2. As shown in FIG. 2, the exhaust gas ejected from each of the exhaust gas outlets 13 of the muffler 11 is discharged into the diffuser 14 with almost the same diffusion angle θ as from a conventional single exhaust gas outlet. In the space between the exhaust gas outlets 13 and the diffuser 14, the exhaust gas ejected from all the exhaust gas outlets 13 is limited to the inner space of the outermost diffusion surface A of the exhaust gas flow, and the exhaust gas is The outward diffusion surface A prevents inconvenient exhaust gas backflow and contamination.
It is preferable to define a continuous diffusion space B that widens toward the end together with the diffusion inner circumferential surface 17 of the diff user 14 . This configuration is determined by suitably selecting the shape and arrangement of the exhaust gas outlet 13 and the spacing L between the exhaust gas outlet 13 and the throat 18 of the diffuser 14. The interval L is such that the smaller the diameter of each exhaust gas outlet 13 is, the higher the jet velocity from each outlet 13 can be, and the larger the outer diameter of the area of the exhaust gas outlet 13 as a whole becomes.
8 can be placed closer to the inside, so that it can be shortened, thereby shortening the overall length of the exhaust device 16. Furthermore, as the diameter of the exhaust gas outlet 13 is made smaller, the position where the air flow noise due to the exhaust gas is ejected becomes closer to the exhaust gas outlet 13.
4 itself also acts as a sound insulating cover for airflow noise.
Further, if necessary, as shown in FIG. 1, a sound absorbing material 19 can be attached to the inner surface of the cover 2 for further sound insulation, and a sound absorbing material can also be attached to the inner surface of the diff user 14 for sound absorption. Also,
The exhaust gas outlet 13 can be formed by a radial, parallel or spiral slit in addition to a circular small hole.

With the above-described configuration, the internal combustion engine 1 is connected to the starter 12.
When started and operated by the cooling fan 7
is rotated and sucks outside air into the cover 2 through the suction port 20 formed on the front side of the cover 2, and this sucked air is used as cooling air to hit the high-temperature parts of the internal combustion engine 1, particularly the cylinder 4 and the muffler 11. At the same time, part of the cooling air flows through the cover 2.
The vaporizer 9 is cooled through a hole 22 formed in a partition wall 21 inside, and is discharged to the outside from an outlet 23 formed at the rear end of the cover 2. Exhaust gas generated in the cylinder 4 by the operation of the internal combustion engine 1 is discharged into a muffler 11, and the muffler 11 injects the exhaust gas from its exhaust gas outlet 13 into a differential user 14, and further discharges the exhaust gas through the differential user 14 to the outside. On the other hand, the cooling air that tends to stay around the internal combustion engine 1 inside the cover 2 is sucked into the diff user 14 from the exhaust port 15 by the exhaust gas flow jetted from the exhaust gas outlet 13 of the muffler 11 to the diff user 14, and the exhaust gas is released to the outside together with the Therefore, the cooling air is efficiently discharged to the outside without remaining inside the cover 2, so that the internal combustion engine 1 can be effectively cooled even if the cooling fan 7 has a smaller blowing capacity than before. This makes it possible to reduce noise from the cooling fan 7 and reduce output loss.

Next, a comparative experiment was conducted between the device of the present invention and two conventional devices regarding the relationship between the distance L between the exhaust gas outlet 13 of the muffler 11 and the throat 18 of the diffuser 14 and the amount of air discharged from inside the cover 2. Explain. The device of the present invention used in this experiment has the dimensions and shape shown in FIG.
12 pieces form an exhaust gas outlet area with a diameter D ₁ of 20 mm,
The total opening area is ^38mm2 , and the conventional device 1 is formed with a single hole with a diameter of 6.9mm as the exhaust gas outlet 13,
The opening area was 38 mm ² , and in the conventional device 2, the exhaust gas outlet 13 was formed by a single hole with a diameter of 10 mm, and the opening area was 79 mm ² . Note that the diameter D ₂ of the throat portion 18 of the differential user 14 was 20 mm. The results of this experiment are shown diagrammatically in FIG. In FIG. 4, solid lines, chain lines, and dotted lines indicate the device of the present invention, conventional device 1, and conventional device 2, respectively. From this result, it will be understood that the device of the present invention can significantly shorten the length of the air exhaust device 16 compared to the conventional device, and has extremely high air exhaust efficiency.

Next, in another embodiment of the present invention shown in FIGS. 5 and 6, exhaust gas outlets 26 consisting of a plurality of small holes or slits are arranged in a straight line on one side 25 of the muffler 24. The side surface 25 of this muffler 24 is covered with a cover 27 which also serves as an air exhaust guide, and an air exhaust port 28 and a diffuser 29 are formed therebetween. The exhaust gas outlet 26 can determine the exhaust gas ejection angle by bending the side surface 25 of the muffler 24 to an appropriate angle α, and the diff user 29 can be adjusted by appropriately narrowing the side surface 25 of the muffler 24 as shown by the dotted line in FIG. It is possible to form a throat even when it is tied.

Furthermore, in still another embodiment of the present invention shown in FIG. 7, a step 32 is formed on the side surface 31 of the muffler 30, and a plurality of exhaust gas outlets 33 are formed in this step 32 by arranging them in a straight line. The other parts are formed similarly to the parts of the embodiment shown in FIGS. 5 and 6.

Effects of the Invention With the configuration of the present invention explained above, the present invention has the following effects:
Since multiple exhaust gas outlets with relatively small opening sizes are provided, the jet velocity from each exhaust gas outlet can be increased, and the outer diameter of the exhaust gas outlet area as a whole can be increased. It is possible to shorten the overall length of the exhaust device by bringing the diffuser closer to the outlet, and it is also possible to bring the generation position of airflow noise due to exhaust gas jetting closer to the exhaust gas outlet, so that the diff user itself can act as a sound insulating cover for airflow noise. Furthermore, in conjunction with the configuration of the differential user, the cooling air that tends to stagnate inside the cover is efficiently discharged to the outside, increasing the cooling effect, allowing a considerable degree of freedom in design, and making it widely applicable to various types of engines. The structure is small and compact, and the engine noise can be effectively insulated.

In the illustrated embodiment, the cooling air from the cooling fan 7 is guided into the space between the cover 2 and the muffler 11, but it is also possible to surround the muffler part with an independent cover or the like and provide an outside air intake port at an appropriate position. Alternatively, the exhaust device of the present invention may be configured to draw in outside air.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the exhaust gas exhaust device according to the present invention, and FIG. 2 is a cutaway view of the main part of FIG. 1, showing the structure and operation of the exhaust gas device of the present invention. FIG. 3 is a diagram explaining the structure of the device used in the comparative experiment between the device of the present invention and the conventional device, and FIG. 4 is a diagram showing the results of the experiment using the device of FIG. 3.
FIG. 5 is a schematic perspective view of a muffler according to another embodiment of the present invention, FIG. 6 is a cutaway view of a main part of the embodiment of FIG. 5, and FIG. 7 is a muffler according to still another embodiment of the present invention. It is a schematic perspective view. 1... Internal combustion engine, 2, 27... Cover, 11,
24, 30...muffler, 13, 26, 33...
Exhaust gas outlet, 14, 29...Diff user, 1
5, 28...exhaust port, 16...exhaust device.

Claims (1)

[Claims] 1. In the exhaust device 16 that uses exhaust gas to exhaust air in the covers 2, 27 surrounding the mufflers 11, 24, 30 of the internal combustion engine 1, the muffler has a plurality of holes each having a relatively small opening size. The exhaust gas outlets 13, 26, 33 are arranged to form an exhaust gas outlet area, and the diffuser users 14, 29 are disposed adjacent to the exhaust gas outlet area, and the air in the cover is disposed between the exhaust gas outlet area and the diffuser user. A ventilation device using exhaust gas, characterized in that it is configured to define exhaust ports 15 and 28 for discharging the gas.