JP2604659B2 - General-purpose internal combustion engine with secondary air supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a general-purpose internal combustion engine including a secondary air supply device for supplying secondary air to an exhaust system, and a muffler having an exhaust gas purifying function for reacting the secondary air supplied by the secondary air supply device with exhaust gas. Things.

[0002]

2. Description of the Related Art From the viewpoint of environmental protection, not only internal combustion engines mounted on automobiles but also small-sized general-purpose internal combustion engines include HC, CO, and HC in exhaust gas discharged from the internal combustion engines. There is an increasing demand for removing harmful gases such as NOx.

In order to remove these harmful gases, in a general-purpose internal combustion engine having a muffler equipped with an exhaust gas purifying function, the muffler is brought as close as possible to an exhaust port, and a secondary gas is mixed with the exhaust gas. It is necessary to cause an oxidation-reduction reaction in the mixed gas before the temperature of the gas does not decrease.

[0004] Further, in a secondary air supply device for supplying secondary air to an exhaust system by utilizing exhaust pulsation, it is necessary to improve the efficiency of secondary air supply by effectively operating the exhaust pulsation operation.
In the case of a low-speed engine such as a general-purpose internal combustion engine, the longer the exhaust passage length from the exhaust port to the atmosphere opening, the better.

However, in general-purpose internal combustion engines, the general-purpose internal combustion engines have to be transported to various installation locations in a wide variety of fields of use. It was difficult to obtain a general-purpose internal combustion engine.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an improvement of a general-purpose internal combustion engine with a secondary air supply device which overcomes such difficulties, and relates to a method for removing a gas from the atmosphere through a reed valve by utilizing exhaust pulsation. In a general-purpose internal combustion engine having a secondary air supply device for supplying secondary air to an exhaust system, an exhaust pipe connected from an exhaust port to a muffler having an exhaust gas purifying function is shortened, and the length of the exhaust pipe is shorter than the length of the exhaust pipe. The length of a tail pipe that opens from the silencer to the atmosphere is set to be long, and the tail pipe is disposed downstream of the cooling air passage of the internal combustion engine.

According to the present invention, as described above, in a general-purpose internal combustion engine provided with a secondary air supply device that supplies secondary air from the atmosphere to the exhaust system through the reed valve using exhaust pulsation, the exhaust gas is supplied from the exhaust port to the exhaust gas. Since the exhaust pipe connected to the silencer having a purifying function is shortened, the temperature of the mixed gas of the secondary air and the exhaust gas supplied from the secondary air supply device does not decrease, and the mixed gas is removed from the silencer. And the redox reaction can be reliably caused in the silencer, and harmful gases such as HC, CO and NOx can be sufficiently removed.

In the present invention, since the length of the tail pipe opening from the muffler to the atmosphere is set longer than the length of the exhaust pipe, the length of the exhaust passage from the exhaust port to the atmosphere opening may be increased. This makes it possible to effectively use the exhaust pulse operation to increase the supply efficiency of the secondary air and sufficiently improve the exhaust gas purification rate.

Further, in the present invention, since the tail pipe is disposed downstream of the cooling air passage of the internal combustion engine, the mixed gas of the secondary air and the exhaust gas causes an oxidation reaction in the muffler having the exhaust gas purifying function. However, even if the tail pipe is heated to a high temperature due to the temperature rise of the reaction gas, the tail pipe can be cooled by the cooling air after cooling the internal combustion engine, thereby avoiding damage to the tail pipe. In addition to this, it is possible to prevent the heating of the auxiliary equipment of the internal combustion engine near the tail pipe.

Further, since the internal combustion engine to which the present invention is applied is a general-purpose internal combustion engine that is operated at a predetermined rated speed, the exhaust passage length at which the pulsation effect can be maximized at the rated speed is set. By appropriately selecting the length of the tail pipe so as to fit, the length of the exhaust passage from the exhaust port to the open end of the tail pipe through the exhaust pipe, the muffler, and the tail pipe can be appropriately set. By exhibiting a very high pulsation effect, the secondary air can be sufficiently supplied into the exhaust gas.

Further, in the present invention, the tail pipe can be made to fit into the space in the rectangular parallelepiped space passing through the outermost portion of the general-purpose internal combustion engine, so that the general-purpose internal combustion engine can be made compact.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention shown in the drawings will be described below. In the general-purpose internal combustion engine 1, the cylinder 2
The fuel tank 5 is disposed above a crankcase 4 that supports the crankshaft 3.

A silencer 6 is disposed above the cylinder 2, and the silencer 6 is connected to an exhaust port 27 of the general-purpose internal combustion engine 1 by a short exhaust pipe 7 that rises upward from the side of the front side of the cylinder 2. ing.

Further, a carburetor 9 is disposed on the far side of the cylinder 2 opposite to the exhaust pipe 7 with the cylinder 2 interposed therebetween.
Above it, an air purifier 10 is arranged.

The muffler 6 in this embodiment is a thermal reactor capable of oxidizing unburned gas such as HC and CO remaining in exhaust gas, and includes a muffler upper casing 11 and a muffler. The lower casing 12 is made of a thin steel plate, and the upper partition plate 13 and the lower partition plate 14 made of a thin steel plate whose central portions are bulged upward and downward, respectively, are formed in the middle by superimposing back to back, The edges of the upper partition plate 13 and the lower partition plate 14 are arranged so that the middle first chamber 15 is located substantially at the center of the space in the silencer 6. The silencer 6 is constituted by being sandwiched between the edges of the upper case 11 and the end of the upper case 11 being bent downward in a U-shape and crimped.

A communication hole 16 is formed in the central bulge of the upper partition plate 13.
Are opened, and the upper partition plate 13 and the lower partition plate
Communication holes 17, 18 are also provided in the middle part between the central bulge and the edge of 14
Is opened, and the muffler 6 has a muffler upper casing.
A second chamber 19 is defined by 11 and the upper partition plate 13, and a third chamber 20 is defined by the muffler lower casing 12 and the lower partition plate 14, and the exhaust pipe 7 is connected to the muffler lower casing 12 and The exhaust port 27 communicates with the first chamber 15 through the exhaust pipe 7 through the lower partition plate 14.

Further, in the tail pipe 21 which penetrates the lower partition plate 14 and whose upper end is open to the third chamber 20,
The exhaust passage length longer than the exhaust pipe 7 and opening from the exhaust port 8 to the atmosphere through the exhaust pipe 7, the silencer 6, and the tail pipe 21 is the most pulsating at the rated rotation speed of the general-purpose internal combustion engine 1. The length of the tail pipe 21 is set so as to match the length that can bring out the effect.

Further, a cooling fan 8 that rotates integrally with the crankshaft 3 of the general-purpose internal combustion engine 1 is provided in a cooling fan shroud 22 of the general-purpose internal combustion engine 1, and a part of the cooling air generated by the cooling fan 8 is provided. Impinges on the carburetor 9 and the cylinder 2 so that the carburetor 9 and the cylinder 2 are cooled, and the rest of the cooling air is cooled by cooling air passages 23a and 23b (see hatched in FIG. After passing through the cooling air passages 23a and 23b, the tail pipe 21 comes into contact with the tail pipe 21 from the openings thereof, and the tail pipe 21 is cooled by the cooling air.

The cylinder head 24 at the top of the cylinder 2
A combustion chamber 25 and an intake port 26 and an exhaust port 27 communicating therewith are formed, and an intake valve 28 and an exhaust valve 29 that open and close the intake port 26 and the exhaust port 27 with respect to the combustion chamber 25 are provided. The intake valve 28 and the exhaust valve 29 are fitted to the cylinder head 24, and are opened once each time the crankshaft 3 rotates twice by a normal valve operating mechanism.

Further, as shown in FIG. 4 and FIG.
And a lower bulging portion 31 is protruded, and a partition wall 32 is erected on the upper bulging portion 30 and the lower bulging portion 31, and the cylinder head 24
The cooling air passage 23a is formed by the lower side surface, the upper swelling portion 30, the lower swelling portion 31, and the partition wall 32.

Further, a concave portion 33 is formed on the outer surface of the partition wall 32, and a secondary air pipe 34 penetrating the partition wall 32 and the cylinder 2 and communicating the exhaust port 27 and the concave portion 33 is fitted. A reed valve 36 is fitted to 33 via a rubber sealing material 35, its outer opening is closed by a cooling air introduction plate 37, and the cooling air introduction plate 37 is fixed to the cylinder 2 with bolts 38. The concave valve 33 and the cooling air introduction plate 37 form a reed valve chamber 39, and the cylinder head 24 and the cooling air introduction plate 37 form a cooling air passage 23b.

In addition, a bulging portion 40 is formed on the cooling air introducing plate 37, and a tube receiving tube 41 projects from the bulging portion 40. The lower end of the joint tube 42 is fitted into the tube receiving tube 41, and The upper end of the tube 42 is connected to the air purifier 10, and the secondary air pipe 34, the reed valve 36, the reed valve chamber 39, and the tube receiving tube 41 constitute a secondary air supply device 43.

Since the illustrated embodiment is configured as described above, when the general-purpose internal combustion engine 1 is operated, the exhaust valve
A negative pressure lower than the atmospheric pressure is generated intermittently due to the pulsation of the exhaust gas accompanying the opening and closing of the valve 29, and the reed valve 36 is opened by the negative pressure, and the joint tube 42 and the secondary air pipe 34 After the secondary air is supplied to the exhaust port 27 through the outlet port and mixed with the exhaust gas, the secondary air flows into the first chamber 15 in the muffler 6 through the exhaust pipe 7 to cause an oxidation reaction, Exhaust gas is purified.

In this case, the length of the exhaust passage of the exhaust port 27, the exhaust pipe 7, the silencer 6, and the tail pipe 21 is such that the pulsation effect can be obtained most at the rated rotation speed of the general-purpose internal combustion engine 1. Therefore, since the supply amount of the secondary air is large, and the secondary air is heated to a high temperature by the heat of the cylinder 2 while passing through the inside of the secondary air pipe 34, the exhaust gas purification efficiency is high.

After a part of the cooling air passes through the cooling air passage 23 to cool the sealing material 35 of the reed valve 36 and hits the tail pipe 21, the tail air is oxidized by the unburned gas in the exhaust gas. Even if the pipe 21 is heated to a high temperature, the pipe 21 is cooled, and damage to the tail pipe 21 and accessories near it can be prevented.

In the above-described embodiment, the silencer 6 is a thermal reactor. However, the catalyst may be supported on the upper partition plate 13 and the lower partition plate 14 so that the exhaust gas undergoes oxidation and reduction reactions. Good.

[Brief description of the drawings]

FIG. 1 is a front view illustrating an embodiment of a general-purpose internal combustion engine with a secondary air supply device according to the present invention.

FIG. 2 is a side view thereof.

FIG. 3 is a plan view thereof.

FIG. 4 is an enlarged vertical sectional front view of a main part of FIG. 1;

FIG. 5 is an enlarged cutaway side view of a main part of FIG. 2;

FIG. 6 is a vertical sectional front view of the silencer according to the embodiment.

[Description of the drawings]

DESCRIPTION OF SYMBOLS 1 ... General-purpose internal combustion engine, 2 ... cylinder, 3 ... crankshaft, 4 ... crankcase, 5 ... fuel tank, 6 ... silencer, 7 ... exhaust pipe, 8 ... cooling fan, 9 ... carburetor, 10
… Air purifier, 11… Muffler upper casing, 12… Muffler lower casing, 13… Upper divider, 14… Lower divider, 15
... first chamber, 16, 17, 18 ... communicating hole, 19 ... second chamber, 20 ... third chamber, 21 ... tail pipe, 22 ...
Cooling fan shroud, 23 cooling air passage, 24 cylinder head, 25 combustion chamber, 26 intake port, 27 exhaust port, 28 intake valve, 29 exhaust valve, 30 bulge, 31 lower part Swelling part, 32 ... Partition wall, 33 ... Recess, 34 ... Secondary air pipe, 35 ... Seal material, 36 ... Reed valve, 37 ... Cooling air introduction plate, 38 ... Bolt, 39 ... Reed valve chamber, 40 ... Swelling Ide, 41
... tube receiving tube, 42 ... joint tube, 43 ... secondary air supply device.

Claims (1)

(57) [Claims] 1. A muffler having a function of purifying exhaust gas from an exhaust port in a general-purpose internal combustion engine having a secondary air supply device for supplying secondary air from the atmosphere to the exhaust system through a reed valve using exhaust pulsation. The length of the tail pipe that opens from the muffler to the atmosphere is set longer than the length of the exhaust pipe connected to the exhaust pipe, and the tail pipe is disposed downstream of the cooling air passage of the internal combustion engine. A general-purpose internal combustion engine with a secondary air supply device.