JPS5853655A - Valve shaft sealing device of carburetor for internal- combustion engine with supercharger - Google Patents

Abstract

PURPOSE:To perform good sealing of a valve shaft in a well slidable state with bearing parts of a carburetor main unit supporting the valve shaft, by providing annular grooves in the periphery of the valve shaft and supplying pressurized air in the delivery side of a supercharger to said annular grooves. CONSTITUTION:Annular grooves 54A, 54B, at a face-to-face position to internally peripheral surfaces of bearing parts 48 in the inside of sealing members 52, are formed to a valve shaft 46 in a carburetor main unit 42. Though a pressurized mixture in an intake passage 44 tends to leak out to the atmosphere from between the peripheral surface of the valve shaft 46 and the internally peripheral surface of the bearing parts 48, the annular grooves 54 are provided and pressurized air is fed from a surge tank (not shown in the drawing), and internal pressure in the annular grooves 54 is higher than internal pressure of the intake passage 44. Accordingly, the pressurized mixture between the valve shaft 46 and the bearing parts 48 is pressed back into the intake passage 44 never to leak out to the outside. Further the pressurized air in the annular grooves 54 flows through the sealing members 52, even if slightly leaked out to the atmosphere, a bad influence is almost not caused, and the necessity for firmly pressing the sealing members 52 to the valve shaft 46 is eliminated, then slide resistance can be also decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a carburetor for use in a supercharged internal combustion engine, in which a throttle valve is fixed to a valve shaft and a bearing portion of a carburetor body that supports the valve shaft. This relates to a sealing device for sealing.

There is an internal combustion engine in which a carburetor is provided in the middle of an intake passage that guides pressurized air discharged by a supercharger to the intake side of the internal combustion engine, and the carburetor mixes fuel into the pressurized air. In this case, the sealing between the valve stem to which the linear throttle valve is fixed and the bearing part of the carburetor body that rotatably supports this valve stem is improved to prevent leakage of the pressurized mixture, and It is also necessary to improve the slidability of the shaft. For this reason, the same applicant has proposed forming a labyrinth groove in the bearing portion and configuring the labyrinth groove to communicate with the discharge side of the supercharger (Utility Model Publication No. 19710/1983).

However, in this conventional sealing device, an annular labyrinth groove is formed on the inner circumferential surface of the bearing portion, which has the disadvantage of poor workability and reduced productivity.

This invention was made in view of the above circumstances, and it not only improves the sealing performance and slidability between the valve stem and the bearing part of the carburetor body that supports this valve stem, but also has excellent workability and productivity. An object of the present invention is to provide a valve shaft sealing device for a carburetor for an internal combustion engine equipped with a supercharger, which can significantly improve performance.

In order to achieve such an object, the present invention provides a carburetor for an internal combustion engine with a supercharger, in which a valve shaft to which a throttle valve is fixed is rotatably supported on a bearing portion of a carburetor main body. forms an annular groove facing the inner circumferential surface of the bearing portion, while
The carburetor main body is configured to form an air passage opening into the annular groove, and supply pressurized air from the discharge side of the supercharger to the air passage. The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a side view of an internal combustion engine to which an embodiment of the present invention is applied, FIG. 2 is a partially sectional side view of its carburetor, and FIG. 3 is a sectional view taken along line 11 in FIG. In FIG. 1, reference numeral 10 is a main body of a parallel multi-cylinder internal combustion engine, 12 is an air cleaner, and 14 is an exhaust turbine supercharger (turbo supercharger). The supercharger 14 includes a turbine that is rotatably driven by exhaust gas led through an exhaust pipe 16 and a compressor that is directly connected to the turbine.
8 is compressed by this compressor, and this compressed air is supplied to a surge tank 22 via an intake pipe 20. 24 is an exhaust pipe that guides exhaust gas from the supercharger 14 to the atmosphere.

26 is a carburetor interposed between the surge tank 22 and the intake port of the engine body lo, one carburetor 26 is connected to each cylinder, and each carburetor 26 is connected to a connecting member 27.
28, but only one is shown in the figure. The carburetor 26 includes a known negative pressure responsive piston type throttle valve 29 and a butterfly valve type throttle valve 3o located downstream thereof.
(FIG. 2), the piston-type throttle valve 29 is moved up and down by the negative pressure generated in its venturi portion 32 in accordance with the intake flow velocity, thereby changing the intake passage area. A jet needle 34 is suspended from the piston-type throttle valve 29, and the jet needle 34 moves forward and backward into the needle jet 36 as the throttle valve 28 moves up and down, automatically controlling the amount of fuel supplied. . Furthermore, the pressure of the pressurized air discharged from the supercharger 14 is guided to the float chamber 38 located below the dollar jet 36 through a pipe 40 (FIG. 1).
Fluctuations in the air-fuel ratio due to pressure fluctuations of this pressurized air are suppressed.

The butterfly valve type throttle valve 30 is connected to the intake passage 4 in the carburetor main body 42.
4 (FIG. 3). The valve shaft 46 is connected to the bearing portion 48 (48A, 48B) of the main body 42.
), and bearing portions 48 are provided at both ends of the valve shafts.
A retaining ring 50 (50A, 50B) is attached to the end face of the valve shaft 46 to restrict movement of the valve shaft 46 in the axial direction.

Note that between this retaining ring 50 and the bearing portion 48, there is a seal member 52 (52A, 52B) that comes into sliding contact with the outer peripheral surface of the valve shaft 46.
is being held.

An annular groove 54 (54A, 54B) is formed in the valve shaft 46 and faces the inner peripheral surface of the bearing portion 48 inside the seal member 52. Furthermore, air passages 56 (56A, 56B) opening to each of these annular grooves 54 are formed in the main body 42,
Each of these air passages 56 communicates with an air passage 58 that traverses the interior of the main body 42 substantially horizontally.

One end of this substantially horizontal air passage 58 is connected to the surge tank 22 through a vibro 0 (see FIG. 1), and the other end of this air passage 58 is connected to another adjacent vaporizer (not shown) through a connecting pipe 62. ) is connected to a similar air passageway formed within the body of the.

Note that the valve shaft 46 is rotated by a throttle operating mechanism via a throttle wire (not shown). ! The valve shafts of adjacent carburetors are rotated in substantially the same phase by the respective interlocking mechanisms.

Next, the operation of this embodiment will be explained. While the engine is operating, the exhaust gas drives the turbine of the supercharger 14. The compressor driven by this turbine is connected to the air purifier 12. compressing the air taken in through the intake pipe 18;
Pressurized air is fed to the surge tank 22 via the intake pipe 20. The pressurized air in the surge tank 22 flows into the intake passage 44 in accordance with the opening degree of the throttle valve 30, and at this time, the negative pressure generated in the venturi section 32 causes the piston-type throttle valve 29 to move up and down, thereby reducing the intake air. Change the aisle area.

This vertical movement of the throttle valve 29 changes the opening area of the main nozzle at the upper end of the needle jet 36, and the float chamber 38
The flow rate of fuel drawn into the intake passage 44 is controlled. At this time, the throttle effect of the venturi section 32 acts on the intake air flowing through the intake passage 44, and the throttle valve 29
The pressure downstream of is lower than the pressure upstream of it, but
The pressure is higher than atmospheric pressure. Therefore, the intake passage 44
The pressurized air-fuel mixture inside tends to leak into the atmosphere from between the outer circumferential surface of the valve shaft 46 and the inner circumferential surface of the bearing portion 48 . However, an annular groove 54 is formed in this valve stem 46, and a vibro 0° air passage 58.56 is connected from the surge tank 12 to the annular groove 54.
Since pressurized air is supplied through the annular groove 5,
4 is higher than the internal pressure of the intake passage 44 downstream of the throttle valve 29. Therefore, the pressurized air-fuel mixture between the valve shaft 46 and the bearing portion 48 is pushed back into the intake passage 44 by the pressurized air in the annular groove 54 . Therefore, the air-fuel mixture does not leak to the outside of the carburetor 26. Note that even if the pressurized air in the annular groove 54 leaks slightly to the atmosphere through the seal member 52,
Since there is almost no inconvenience, the sealing member 52 is attached to the valve shaft 46.
In addition, there is no need to apply excessively strong pressure, and sliding resistance can be reduced.

Further, since the annular groove 54 is provided on the outer periphery of the valve shaft 46, the annular groove can be formed extremely easily by lathe processing or the like.

In this embodiment, the pressurized air is guided from the surge tank 12 to the annular groove 54, but the present invention allows the annular groove 54 to
It is clear that leakage of the air-fuel mixture can be prevented by communicating with the air-fuel mixture.

In this embodiment, one annular groove 54 is provided at each end of the valve stem 46 as shown in FIG. 3, but a plurality of adjacent annular grooves may be formed at each end of the valve stem.

As described above, in this invention, an annular groove is formed on the outer periphery of the valve stem, and pressurized air from the discharge side of the aging machine is supplied to this annular groove, so that the pressure in the annular groove is reduced to the pressure near the valve stem. The pressure becomes higher than the internal pressure of the intake passage, and the air-fuel mixture does not leak from between the valve stem and the bearing.

In addition, there is almost no problem even if the pressurized air in the annular groove leaks to the atmosphere from between the valve stem and the bearing, so there is no need to use a stain seal member with large contact pressure and contact area, and the sliding of the valve stem Resistance can be reduced. On the other hand, since the block groove is formed on the outer periphery of the valve stem, it can be processed extremely easily using a lathe or the like, and productivity is significantly improved compared to the case where an annular groove is formed on the inner circumferential surface of the bearing part.

[Brief explanation of the drawing]

FIG. 1 is a side view of an internal combustion engine to which an embodiment of the present invention is applied, FIG. 2 is a partially sectional side view of its carburetor, and FIG. 3 is a sectional view taken along line 11 in FIG. 14...Supercharger, 26...Carburizer, 30...throttle valve, 42...main body, 46...valve shaft, 48...
Bearing part. 54... Annular groove, 56.58... Air passage. Patent Applicant Yamaha Motor Co., Ltd. Agent Patent Attorney Yama 1) Written by: rIA1”-.Qヂ′

Claims (1)

[Claims] In a carburetor for an internal combustion engine with a supercharger, in which a valve shaft to which a throttle valve is fixed is rotatably supported on a bearing part of a carburetor body,
The valve shaft is formed with an annular groove that faces the inner circumferential surface of the bearing part, while the carburetor body is formed with an air passage that opens into the annular groove, and the air passage is pressurized on the discharge side of the supercharger. A valve shaft sealing device for a carburetor for an internal combustion engine with a supercharger, which supplies air.