JPH10306878A - Construction of check valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealing performance at valve closing and stablely and lightly opening the valve by penetrating a bar member through a tapered part which is formed on one end of a cylindrical valve body made of rubber and becomes gradually thin to the extreme end side in wall thickness. SOLUTION: In a valve body 56 forming the lower end part taper and made of rubber, the upper end part is locked with a linear projection 52a, and the tapered part is fitted from the outside to a bar member 44 downward projecting from the axis of a cover 41. By such constitution, when negative pressure in a fuel tank feeding fuel to an engine through a carburetor is increased, air passes the gap between a screw shaft part 39 and a screw hole 42, and enters the interior of the valve body 56 through the grooves 45a, 45b of a passage member 45, the groove 43a of a cylinder part 43, and the gap between the cylinder part 43 and an inner cylinder part 52. In this case, since atmospheric pressure inside the valve body 56 is higher than atmospheric pressure outside the valve body 56, the tapered part of the valve body 56 fitted to the bar member 44 from the outside is pushed open and the air is introduced into the fuel tank. Hereby, the fuel tank can be prevented from deforming due to excessive low inner pressure of the fuel tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a check valve for a fuel pump of a membrane carburetor of an internal combustion engine mounted on a portable working machine or the like.
The present invention relates to a check valve suitable for a check valve of a primer pump, an exhalation valve of a fuel tank, and the like.

[0002]

2. Description of the Related Art As disclosed in Japanese Utility Model Laid-Open Publication No. 4-95650, in a mushroom-shaped composite check valve having an intake valve and a discharge valve of a fuel pump integrally, an umbrella portion is formed as a suction valve, and a shaft portion is formed. Is generally a discharge valve. However, in the above-described structure, the composite check valve has a shaft portion formed of rubber with a rectangular cross section, and then the shaft portion is cut with a blade. However, the closing force of the closing of the discharge valve is largely due to the elasticity of the rubber itself, and if dust enters the discharge valve, the closing will be poor.
The closing performance (the sealing property at the time of closing the valve) is not always good. Since the discharge valve has a cut in the rubber molded body with a blade, the discharge valve is apt to be torn from the cut portion and has poor durability. When not used for a long time, the cut rubber may stick together. It is difficult to increase the passage area of the discharge valve, and it is difficult to enhance the pump performance because the passage resistance is large.

In the above-described composite check valve, the suction valve uses the outer edge portion of the umbrella portion, that is, a portion having a large outer diameter, and thus operates with sufficiently weak fluid pressure. However, the discharge valve is provided at the shaft center portion. Therefore, the stroke or expansion of the valve element is small, and the operating pressure of the discharge valve increases.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a check valve structure which is easy to process, has excellent sealing properties when the valve is closed, and has a stable and light operation when the valve is opened. Is to provide.

[0005]

Means for Solving the Problems To solve the above-mentioned problems, the present invention has a structure in which one end of a cylindrical valve body made of rubber is provided.
A tapered portion with a gradually decreasing thickness is formed at the tip, and a rod member is penetrated into the tapered portion.

[0006]

According to the present invention, the check valve is formed of a rubber molded body having a cylindrical cross section, and is tapered such that the thickness of the tip becomes gradually thinner. A rod member is inserted into the tapered portion of the valve body to close the passage of the valve body. At this time, the check valve is brought into close contact with the rod member by the elastic restoring force of the valve body itself and the fluid pressure acting on the outer peripheral surface on the outlet side. When the fluid pressure on the inlet side becomes higher than the fluid pressure on the outlet side, the distal end side of the valve body is expanded and separated from the rod member, thereby allowing the fluid to pass from the inlet to the outlet.

[0007]

FIG. 1 shows a fuel tank provided with a check valve according to the present invention;
FIG. 2 is a side sectional view showing a schematic configuration of a fuel tank that stores fuel supplied to an internal combustion engine. The fuel tank 30 is integrally provided with a fuel injection pipe 38 closed by a lid 41.
1 is provided with a check valve A according to the invention. Also,
A fuel supply pipe 34 having a filter 35, a pipe 33 and a pipe 32 are drawn out from the upper wall of the fuel tank 30 via a grommet 36, and a check valve B according to the present invention is provided at the upper end of the pipe 32.
Is connected. However, it is sufficient that one of the check valve A and the check valve B is attached to the fuel tank 30.

FIG. 2 is a side sectional view of a check valve A as an exhalation valve integrally formed with the lid 41. Lid 41 is screw hole 4
2 is screwed into the screw shaft 39 of the fuel injection pipe 38. A gap for guiding the atmosphere into the fuel injection pipe 38 or releasing the internal pressure of the fuel injection pipe 38 to the outside is formed in the screw portion of the screw hole 42 of the lid 41 and the screw shaft 39 of the fuel injection pipe 38. Be provided. A passage member 45 formed of an annular plate having a radial passage groove 45a and an axial passage groove 45b in a top wall portion of the lid 41.
And a gasket 46 made of an annular plate are overlapped, and when the lid 41 is fastened to the fuel injection pipe 38, the gasket 46
Is strongly in contact with the end of the fuel injection pipe 38. A cylindrical portion 43 protruding downward is formed integrally with the center of the lid 41, and an axial passage groove 43 a is formed on the outer peripheral wall of the cylindrical portion 43. The cylindrical portion 43 is fitted into the annular groove 54 of the valve housing 51. Although the valve housing 51 is cylindrical as a whole, an outer cylinder 53 and an inner cylinder 52 are defined in an upper half by an annular groove 54, and the gasket 46 is fitted to the outer cylinder 53. An annular ridge 5 is formed on the inner peripheral wall of the intermediate portion of the inner cylindrical portion 52.
2a is formed integrally.

The valve body 56 made of rubber has a ridge 52 at the upper end.
The lower end is tapered, and the tapered portion is externally fitted to a rod member 44 projecting downward from the axis of the lid 41. A cup 57 having a through hole 58 is press-fitted into the lower half of the valve housing 51 to prevent foreign matter and the like from adhering to the valve body 56 when the lid 41 is removed.

According to the above-described check valve A, as the fuel inside the fuel tank 30 is supplied from the fuel supply pipe 34 to the engine through the carburetor, the negative pressure inside the fuel tank 30 increases, Passes through the gap between the screw shaft portion 39 and the screw hole 42, passes through the grooves 45 a and 45 b of the passage member 45, the groove 43 a of the cylindrical portion 43, and the gap between the cylindrical portion 43 and the inner cylindrical portion 52, and passes through the valve body 56. Go inside the. The atmospheric pressure inside the valve body 56 is
6 is higher than the air pressure on the outside of the fuel tank 30, the tapered portion of the valve body 56 fitted to the rod member 44 is pushed open.
Is introduced inside. In this way, the internal pressure of the fuel tank 30 is excessively reduced, and the deformation of the fuel tank 30 is prevented.

In the embodiment shown in FIG. 3, when the internal pressure of the fuel tank 30 becomes low, the atmosphere is introduced into the fuel tank 30, and conversely, the fuel in the high temperature fuel tank 30 in summer is vaporized. FIG. 6 is a side sectional view of a composite check valve B that releases the internal pressure of the fuel tank 30 to the outside when the internal pressure increases. The composite check valve B comprises a cylindrical container 66, a lid 61 for closing the upper end of the container 66, and a valve body 64 made of rubber.
Has a passage 68 connecting tube 32 (FIG. 1). A filter 67 is accommodated at the bottom of the container 66, an annular ridge 66 a is formed on an intermediate inner peripheral wall so as to protrude radially inward, and an annular groove provided on an outer peripheral wall of a cylindrical valve body 64 made of rubber or the like. 64c is locked to the ridge 66a. The inner space of the upper end portion 64a of the valve body 64 is formed in a conical shape so that the wall thickness is gradually reduced upward, and is elastically closely contacted with the inner peripheral surface of the container 66. The lower end portion 64b of the valve body 64 is tapered as a whole, and its thickness is gradually reduced downward, and is externally fitted to a rod member 65 protruding downward from the lid 61. A gap is provided between the outer peripheral surface of the valve body 64 and the inner peripheral surface of the container 66, except for the upper end 64a. A filter 62 is accommodated at the upper end of the container 66 and a lid 61 is provided.
A gap 63 that connects the inside of the container 66 to the outside via the filter 62 is provided between the container 66 and the container 66.

When the inside of the fuel tank 30 becomes lower than the atmospheric pressure, the air passes through the gap 63 and the filter 62 and the valve 6
4 flows inside. The atmospheric pressure inside the valve body 64 is
6, the lower end 64b of the valve body 64 is expanded, and the air flows into the fuel tank 30 through the filter 67 and the passage 68 to reduce the internal pressure of the fuel tank 30. It works to prevent the fuel tank 30 from being deformed due to abnormal lowering.
Conversely, when the internal pressure of the fuel tank 30 becomes higher than the atmospheric pressure due to the vaporization of the fuel at a high temperature in the summer, the mixture of the air inside the fuel tank 30 and the vaporized fuel passes through the passage 68 and the filter 67. It flows out to the lower half of the container 66, and furthermore, the upper end 64 a is pressed radially inward from the gap between the inner peripheral surface of the container 66 and the outer peripheral surface of the valve body 64 and flows out to the upper half of the container 66. Then, it flows out through the filter 62 and the gap 63 to the outside. Thus, an abnormal increase in the internal pressure of the fuel tank 30 is suppressed.

FIG. 4 is a front sectional view of a mushroom-type composite check valve according to the present invention provided on a manual primer pump attached to the bottom of a membrane type vaporizer. In the carburetor, a substantially cylindrical throttle valve having a throttle hole is rotatably and vertically movably supported by a carburetor body 21 having an intake passage 26. A throttle valve lever 24 is coupled to a throttle valve shaft 25 projecting upward from the carburetor body 21, and a follower 23 projecting downward from the throttle valve lever 24 is provided with a cam of a lid 22 fixed to the upper wall of the carburetor body 21. The surface 22a is slid by a spring (not shown). A needle valve 27 integral with the shaft 25 is fitted into a fuel supply pipe 28 projecting from the bottom of the carburetor body 21 into the intake passage 26, and the injection hole of the fuel supply pipe 28 is moved as the needle valve 27 moves up and down. The opening degree of 28a is adjusted.

At the bottom of the carburetor body 21, a membrane fuel pump driven by the pulsating pressure of the crank chamber of the engine and a constant pressure fuel chamber defined by the membrane 8a are provided, and the fuel in the fuel tank is not shown. It is supplied to the constant pressure fuel chamber via the hose, the connecting pipe 20, the fuel pump, and the inflow valve. The fuel in the constant pressure fuel chamber is sucked from the fuel supply pipe 28 into the intake passage 26 through the injection hole 28a.

The primer pump includes a wall plate 8 as a pump main body connected to the bottom of the vaporizer main body 21, a hemispherical elastic pressing body (spoid) 18 connected to the wall plate 8 and defining a pump chamber 17. It comprises a mushroom-type composite check valve C integrally provided with a suction valve and a discharge valve. The wall plate 8 is superimposed on the bottom surface of the vaporizer main body 21 via the membrane 8a, and is joined by bolts (not shown). A depression 14 is formed in the center of the upper wall surface of the wall plate 8, and constitutes an atmosphere chamber for applying the atmospheric pressure of the fuel tank 30 to the membrane 8 a defining the constant pressure fuel chamber. A through hole 7 which forms a part of an outlet passage is provided at the center of the wall plate 8, and the upper end of the through hole 7 is closed by a stopper 13. At the lower end of the through hole 7, that is, at a portion close to the lower wall surface 8b, a constricted portion 7a formed of an annular ridge is formed. The end flange of the elastic pressing body 18 is overlapped on the lower wall surface 8b, and is fixed by the annular pressing plate 16.

The wall plate 8 is provided with an inlet passage 12 and an outlet passage 15 along the plate surface. The outer end of the inlet passage 12 is closed by a ball 9 and communicates with a constant pressure fuel chamber (not shown) of a carburetor body 21 via a passage 10 perpendicular to the plate surface. The inner end of the entrance passage 12 bends downward and opens to the lower wall surface 8b.
The outlet passage 15 has an inner end communicating with the through hole 7, and a connection pipe 19 for connecting a hose to the outer end.

The mushroom-type composite check valve C allows the flow of fuel from the inlet passage 12 to the pump chamber 17 and the flow of fuel vapor from the pump chamber 17 to the outlet passage 15 through the holes 5 and the through holes 7. A discharge valve is provided integrally. A mushroom-type composite check valve C molded from rubber or a soft synthetic resin has an umbrella portion 3 integrally provided at the lower end of a hollow shaft portion 4. An annular ridge is provided on the outer peripheral surface of the shaft portion 4. The upper end of the shaft portion 4 is tapered to form a sheet portion which is fitted to a rod member 13a projecting downward from the plug 13, and the hole 5 is elastically closed. The umbrella portion 3 elastically closely contacts the lower wall surface 8b of the wall plate 8, and the entrance passage 1
2 is closed. When the mushroom-type composite check valve C is pushed into the through-hole 7 from the lower wall surface 8b, the above-mentioned ridge is deflated and passes through the constricted portion 7a of the through-hole 7, and is fitted into the large-diameter portion of the through-hole 7, and The peripheral edge of the portion 3 is elastically closely contacted with the lower wall surface 8b.

Now, when the elastic pressing body 18 is crushed by hand,
The fuel vapor or air in the pump chamber 17 pushes the seat portion through the hole 5 to flow out to the through hole 7 and is discharged from the outlet passage 15 to a fuel tank (not shown). When the force applied to the elastic pressing member 18 is released, the pump chamber 17 expands to a negative pressure, so that the fuel vapor or air in the constant pressure fuel chamber pushes the umbrella section 3 from the inlet passage 12 and flows into the pump chamber 17. . As described above, by repeatedly crushing the elastic pressing body 18, fuel vapor or air in the constant-pressure fuel chamber is released to the fuel tank, and new fuel in the fuel tank (not shown) is connected to the connection pipe 20 and the carburetor body 21. The fuel is supplied to the constant-pressure fuel chamber via the fuel pump and the inflow valve.

The check valve according to the present invention can be applied not only to a discharge valve but also to a suction valve, similarly to the conventional one.

[0020]

According to the present invention, as described above, the check valve is constituted by inserting the rod member into the tapered portion of the cylindrical valve body made of rubber, and has the following features.

If a hard synthetic resin material different from rubber is used for the rod member, sticking between the rubbers does not occur unlike the conventional check valve. It is even better if the material of the rod member is a low friction fluorine resin.

Since the rubber of the discharge valve of the composite check valve can be formed thin, the tapered portion of the valve body is brought into close contact with the rod member by the surrounding fluid pressure, so that the closing performance is good and the valve opening pressure can be reduced. .

Unlike the conventional check valve, post-processing such as cutting off the tip of the check valve becomes unnecessary, and the valve body does not tear during long-term use.

A mold for molding a discharge valve from rubber is
Since the cross section can be made circular, manufacture is easy.

The valve opening pressure of the check valve can be changed by changing the size of the rod member. That is, the valve opening pressure can be increased by making the rod member thicker, and the valve opening pressure can be lowered by making the rod member thinner.

Since the fluid resistance of the discharge valve is small, the pressure loss of the fluid is small.

Since the discharge valve opens at a low valve opening pressure and has a large stroke or spread, even if dust is caught, the discharge valve immediately flows out, and there is little chance that the discharge valve will cause defective sealing or malfunction of the discharge valve.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a fuel tank provided with a check valve according to the present invention.

FIG. 2 is a side sectional view of the check valve according to the first embodiment of the present invention.

FIG. 3 is a side sectional view of a check valve according to a second embodiment of the present invention.

FIG. 4 is a side sectional view of a check valve according to a third embodiment of the present invention.

[Explanation of symbols]

A: check valve B: check valve C: compound check valve 3: umbrella
4: Shaft portion 5: Hole 7: Through hole 7a: Constricted portion 8: Wall plate 8a: Membrane 8b: Lower wall surface 12: Inlet passage 13: Plug 13a: Bar member 14: Recess 15: Outlet passage 17: Pump chamber 18: Elastic pressing body 21: vaporizer main body 22: lid 22
a: Cam surface 23: Follower 24: Throttle valve lever 2
5: shaft 26: intake path 27: needle valve 28: fuel supply pipe 28a: injection hole 30: fuel tank 34: fuel supply pipe 3
5: Filter 38: Fuel injection tube 39: Screw shaft 4
1: lid 42: screw hole 43: cylindrical portion 43a: groove 4
4: Rod member 45: Passage member 45a: Groove 45b: Groove 46: Gasket 51: Valve housing 52: Inner cylinder portion 52a: Ridge 53: Outer cylinder portion 54: Annular groove 56: Valve body 61: Lid 62: Filter 63 : Gap 64: valve element 64 a: upper end 64 b:
Lower end 65: rod member 64c: annular groove 66: container
66a: Ridge 67: Filter

Claims (5)

[Claims] 1. A check valve according to claim 1, wherein a tapered portion having a gradually decreasing thickness is formed at one end of a cylindrical valve body made of rubber, and a rod member is passed through said tapered portion. Construction. 2. A rod member penetrating the valve body has a circular cross section.
The check valve structure according to claim 1. 3. The check valve structure according to claim 1, wherein a component member of the fuel pump and a rod member are integrally formed. 4. The check valve structure according to claim 1, wherein the fuel tank and the rod member are integrally formed in the exhalation valve of the fuel tank of the portable work machine. 5. A composite check valve in the form of a mushroom made of rubber used for a fuel pump, wherein an umbrella portion forms a suction valve and a hollow shaft portion of a shaft forms a discharge valve. A check valve structure characterized in that a rod member is passed through a shaft portion of the check valve.