JP4427892B2 - Pressure control valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure control valve that controls the pressure of a controlled fluid, and is used, for example, in an evaporative fuel processing system of a car.
[0002]
[Prior art]
As a conventional pressure control valve, the entire diaphragm made of only a rubber material such as hydrin, fluorosilicone, NBR (nitrile-butadiene rubber) is made of rubber.
[0003]
[Problems to be solved by the invention]
However, when this type of pressure control valve is used in an evaporative fuel processing system, the first chamber side may be filled with fuel vapor. For this reason, the rubber diaphragm 20 is exposed to fuel vapor, which may shorten the durable life of the diaphragm.
[0004]
In addition, since the diaphragm is made of rubber such as hydrin, fluorosilicone, NBR (nitrile-butadiene rubber), the diaphragm itself permeates the fuel vapor, and the fuel vapor leaks from the first chamber to the second chamber side. Furthermore, it sometimes leaked into the atmosphere.
[0005]
This leakage of fuel vapor has not been a problem because the regulation value has been relatively gradual in the past, but it is not only necessary to cope with the regulation value that will become increasingly stringent in the future, but it is also necessary to consider the environment further. It is desired.
[0006]
An object of the present invention is to provide a pressure control valve capable of improving the durability of a diaphragm against fuel vapor and reliably preventing the fuel vapor from leaking from the first chamber to the second chamber side in view of the above points. And
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention employs technical means described in claims 1 to 3 .
[0008]
According to the invention of claim 1, since the diaphragm has a composite layer in which a gas blocking layer that blocks the passage of gas and a resin layer are laminated on the side facing the first chamber, the composite layer is provided on one side of the diaphragm. It becomes a joined structure, the film thickness of the diaphragm is not so thick, the fuel vapor can be effectively prevented from leaking, and the manufacturing cost can be reduced.
[0009]
According to the invention of claim 1 , since the diaphragm is formed by joining the rubber layer provided on the side facing the second chamber and the composite layer, the composite layer is formed on one side of the rubber layer of the diaphragm. The bonded structure does not increase the thickness of the diaphragm so much that it suppresses swelling of the diaphragm itself due to fuel vapor, effectively preventing leakage of fuel vapor while maintaining durability, and the flexibility of the diaphragm membrane The manufacturing cost can be reduced while maintaining the above.
[0010]
According to the invention of claim 1 , since the gas barrier layer is a layer coated with an ethylene-vinyl alcohol copolymer, and the resin layer is a layer coated with a polyamide-based resin such as nylon, Swelling of the diaphragm itself due to fuel vapor is suppressed, leakage of fuel vapor is effectively prevented while maintaining durability, and the flexibility of the membrane of the diaphragm can be maintained.
[0011]
According to the first aspect of the present invention, since the fluorine rubber layer made of a fluorine-based rubber material is further disposed on the surface of the composite layer, the gas barrier layer or the member sandwiching the diaphragm and the composite layer or The portion that rubs with the resin layer is covered and protected by the fluororubber layer, and is prevented from being peeled off or torn.
[0012]
Further, it is possible to further prevent the fuel vapor from permeating from the first chamber to the second chamber.
[0013]
According to the first aspect of the present invention, the fluoro rubber layer is provided along the outer peripheral portion of the diaphragm by bending the fluoro rubber layer substantially at a right angle so that the fluoro rubber layer is displaced along with the operation of the diaphragm. This is effective in preventing the fluororubber layer from coming off.
[0014]
According to the second aspect of the present invention, since the annular protrusion is provided on the contact portion of the housing that contacts the peripheral portion of the diaphragm and presses the peripheral portion, the contact between the peripheral portion of the diaphragm and the housing The amount of fuel vapor leakage from the contact portion can be further reduced.
[0015]
According to the invention of claim 3, since the fluororubber layer is disposed between the diaphragm upper surface and the member in contact with the diaphragm, it is possible to prevent the fluororubber from being hardened and the diaphragm from moving in an extremely low temperature environment. Smooth operation of the diaphragm can be ensured.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
(First Reference Example )
1 to relate the first reference example of FIG. 3 is the invention, FIG. 1 is a cross sectional view taken along the central axis of the pressure control valve 27, A-part enlarged cross section of FIG. 2 is a diaphragm 20 in FIG. 1 FIG. 3 is an enlarged cross-sectional view of a main part in FIG. Pressure control valve 27 of the present invention
Is used, for example, in an evaporative fuel processing system of an automobile, and particularly as a negative pressure control valve in a fuel tank.
[0018]
1 to 3, a hole into which a bearing 2 is press-fitted is opened at the center of an aluminum die-cast holder 1, and a shaft 3 is slidably fitted into a hole formed inside the bearing 2. Yes.
[0019]
The shaft 3 is disposed on substantially the same axis as the valve plate 4 and has a round hole as the second hooking portion 5 at the shaft tip portion 15. The shaft 3 is made of a metal material such as stainless steel, and the valve plate 4 is made of a resin material or a metal material.
[0020]
One end of the valve plate 4 has an abutting portion 9 that abuts on a valve seat 7 formed on a housing 6 that forms part of a casing made of aluminum die casting to open and close the port 8.
[0021]
The first fluid passage 43 and the second fluid passage 44 are connected to a second control chamber 42 that constitutes a second chamber of the control chamber, and the first fluid passage 43 is further connected to a fuel tank (not shown). The passage 44 is connected to a canister (not shown) or the atmosphere.
[0022]
The second control chamber 42 is also communicated with the lower surface of the diaphragm 20 through the communication hole 47.
[0023]
Further, a first hooking portion 10 extending in the axial direction is provided on the other end side of the valve plate 4. The 1st hook part 10 consists of a hook part, and is fitted in the round hole as the 2nd hook part 5 with the loose fitting part 12 which is a clearance gap. The gap of the loosely fitting portion 12 is set (predetermined gap) in consideration of a biasing force of a first biasing spring 14 to be described later so as to give a predetermined valve opening delay and start opening at a predetermined pressure. ing.
[0024]
Further, a spring holder 13 is fitted in the middle portion of the valve plate 4, and the first urging spring 14 is fitted in a compressed state between the valve plate 4 and the holder 1 via the spring holder 13. In addition, it is sandwiched between the holder 1 and the housing 6 and is screwed together by a plurality of screws 16.
[0025]
On the other hand, the shaft 3 is gripped at the upper part in FIG. 1 and is driven in the vertical direction in FIG. The upper portion of the shaft 3 is sealed at the center portion where the hole of the diaphragm 20 is formed, and is pressed and held downward by a ring 45 in FIG.
[0026]
2 and 3, the diaphragm 20 has a gas blocking layer 20b for blocking the permeation of gas such as fuel vapor on the surface of the diaphragm 20 facing the first control chamber 41 forming the first chamber. And the resin layer 20c are overlapped and bonded together, the rubber layer 20a is provided on the surface of the diaphragm 20 facing the second control chamber 42 forming the second chamber, and the rubber layer 20a and the composite layer 200 Are formed by joining. The gas barrier layer 20b is coated with an ethylene-vinyl alcohol copolymer, the resin layer 20c is coated with a polyamide-based resin such as nylon, and the rubber layer 20a is hydrin, fluorosilicone, nitrile-butadiene rubber. The rubber material such as was used.
[0027]
The surface of the diaphragm 20 facing the second control chamber 42 side may be a rubber layer because the first fluid passage 43 communicating from the second control chamber 42 to the fuel tank is normally blocked by the valve plate 4. The reason why the plate 4 is opened and the second control chamber 42 communicates with the fuel tank is when the fuel tank is at a high negative pressure, and fuel vapor does not accumulate in the second control chamber 42 at that time. Therefore, the composite layer 200 is not necessary on the second control chamber 42 side.
[0028]
The diaphragm 20 is sandwiched between the second plate 22 and the third plate 23 made of sheet metal, and is locked to the upper portion of the shaft 3.
[0029]
As shown in FIG. 1, a second urging spring 24 is sandwiched between the second plate 22 and the first plate 21 in a compressed state, and the amount of compression is a female screw fixed to the upper part of the cover 28. The fine adjustment screw 26 screwed into 25 can be adjusted by the screwing amount. The potting 29 prevents the fine adjustment screw from loosening and maintains airtightness. The inner peripheral surface of the cover 28 that forms a part of the housing forms a first control chamber 41 that forms a part of the control chamber, and the first control chamber 41 is connected to a fuel tank (not shown) by a pipe 31.
[0030]
The cover 28 supports the female screw 25 and also fixes the peripheral portion of the diaphragm 20 to the holder 1 with a seal. A clearance 30 is provided between the stopper 46 on the inner peripheral surface of the cover 28 and the upper surface of the second plate 22, and the range in the vertical direction of the clearance 30 is the range in which the diaphragm 20 can move in the vertical direction.
[0031]
The cover 28 seals the inside of the cover 28 together with the diaphragm 20, and includes a pipe 31 for adjusting the vertical movement of the shaft 3 by adjusting the pressure inside the cover 28.
[0032]
Next, the operation of the pressure control valve 27 will be described.
[0033]
In FIG. 1, when the pressure in the fuel tank (not shown) is a positive pressure or a negative pressure smaller than the first predetermined value, the force by which the second urging spring 24 pushes down the diaphragm 20 pushes up the diaphragm 20. Since it is larger than the force, the pressure control valve 27 is in the state shown in FIG. 1 or FIG.
[0034]
That is, the diaphragm 20 is pressed against the upper surface of the holder 1 by the second urging spring 24, and the shaft 3 is at the lowest position of the movable range of the shaft 3. Therefore, the valve plate 4 constituting the movable valve body is pushed down by the first urging spring 14, and the contact portion 9 is pressed against the valve seat 7 to be in a closed state, and the first hook portion 10 and the second hook portion. The loose fitting part 12 which is a gap between the two is the largest.
[0035]
The negative pressure in the fuel tank is larger than the first predetermined value, and the first hooking portion 10 and the second hooking portion 5 are in contact with each other, that is, the negative pressure is smaller than the second predetermined value at which the gap between the loose fitting portions 12 is eliminated. In some cases, the force by which the second urging spring 24 pushes down the diaphragm 20 is smaller than the force by which the diaphragm 20 is pushed up by the negative pressure of the first control chamber 41, so that the diaphragm 20 is pushed upward in FIG. Accordingly, the shaft 3 is pulled up, and the clearance of the loose fitting portion 12 becomes smaller as the negative pressure in the fuel tank increases, and finally the clearance becomes zero at the second predetermined negative pressure.
[0036]
In this way, until the clearance of the loosely fitting portion 12 forming the coupling mechanism becomes zero from the maximum value, the second locking portion formed at the tip of the shaft 3 coupled to the diaphragm 20 serving as the driving means is formed. Since the second hooking portion 5 does not engage with the first hooking portion 10 that forms the first locking portion formed on the top of the valve plate 4 that forms the movable valve body, the second hooking portion of the shaft 3 together with the diaphragm 20 Even if 5 moves upward in FIG. 1, the first hook 10 does not move. For this reason, the valve plate 4 is not opened, and the valve plate 4 is opened after the second hooking portion 5 is further moved upward. Therefore, the loose fitting portion 12 that forms the coupling mechanism becomes a valve opening delay mechanism.
[0037]
When the negative pressure in the fuel tank is a negative pressure larger than the second predetermined value, the second urging spring 24 pulls up the valve plate 4 via the second hook 5 and the first urging spring. 14 is a balance between the force that pushes down the valve plate 4 via the spring holder 13 and the force due to the pressure difference between the upper and lower surfaces of the valve plate 4.
[0038]
The second biasing spring 24 is compressed to the maximum until the second plate 22 hits the stopper 46 of the cover 28 and the clearance 30 becomes zero, and the shaft 3 is further pulled up accordingly, and the valve plate 4 constituting the movable valve body is opened. Accordingly, the first urging spring 14 is also compressed to a predetermined value.
[0039]
When the valve plate 4 is opened, fuel vapor or air flows from a canister (not shown) or the atmosphere to the negative pressure fuel tank, and when the inside of the fuel tank reaches the negative pressure of the second predetermined value, the valve plate 4 is closed and flows. Stops.
[0040]
According to the present embodiment, when the diaphragm 20, the shaft 3, and the valve plate 4 are operated in accordance with the pressure difference between the pressure in the fuel tank and the pressure on the canister or the atmosphere side, By setting the urging force of the one urging spring 14 or the like, the valve plate 4 can be started from a pressure state as close as possible to the predetermined pressure to be opened without operating the valve plate 4 linearly according to the pressure difference. As a result, the pressure difference from the starting pressure at which valve opening starts to the predetermined pressure at which a predetermined opening is obtained can be set small. That is, the responsiveness of valve opening / closing can be improved and the flow rate control accuracy can be improved.
[0041]
In addition, a composite layer 200 is provided in which the gas barrier layer 20b and the resin layer 20c are overlapped and joined to the surface of the diaphragm 20 facing the first control chamber 41, which is the first chamber that may be filled with fuel vapor. Since the rubber layer 20a is provided on the surface of the diaphragm 20 facing the second control chamber 42, which is the second chamber, and the rubber layer 20a and the composite layer 200 are joined to form the diaphragm 20, the rubber layer of the diaphragm 20 is formed. The composite layer 200 is joined to one side of 20a, and the film thickness of the diaphragm 20 does not increase so much. Swelling of the diaphragm 20 itself by fuel vapor is suppressed, and effective leakage of fuel vapor is maintained while maintaining durability. Thus, the manufacturing cost can be reduced while maintaining the flexibility of the membrane of the diaphragm 20.
[0042]
Furthermore, the gas barrier layer 20b is coated with an ethylene-vinyl alcohol copolymer, the resin layer 20c is coated with a polyamide-based resin such as nylon, and the rubber layer 20a is hydrin, fluorosilicone, nitrile-butadiene rubber. Since the rubber material such as the above is used, swelling of the diaphragm 20 itself due to fuel vapor is suppressed, leakage of the fuel vapor is effectively prevented while maintaining durability, and the flexibility of the diaphragm film can be maintained.
[0043]
(Second reference example )
FIG. 4 relates to a second reference example of the present invention, and is an enlarged cross-sectional view of a main part of a portion corresponding to FIG. The difference from the first reference example is that a fluorine rubber layer 20d made of a fluorine-based rubber material is further arranged on the side of the composite layer 200 opposite to the rubber layer 20a, that is, the side facing the first control chamber 41. That is. As a result, the portions of the composite layer 200 where the gas barrier layer 20b or the resin layer 20c of the composite layer 200 rubs against each other are sandwiched and protected by the fluororubber layer 20d to be peeled off or torn. Is prevented.
[0044]
(First Embodiment)
FIG. 5 relates to the first embodiment of the present invention, and is an enlarged cross-sectional view of a main part corresponding to FIG. The difference from the second reference example is that an annular convex portion B is provided at the contact portion between the peripheral portion of the diaphragm 20 and the cover 28 that forms a part of the housing, and the pressing force of the contact portion against the diaphragm 20 is increased. It is a point that was strengthened. Thereby, the leakage amount of the fuel vapor from the contact portion between the peripheral edge portion of the diaphragm 20 and the cover 28 forming a part of the housing can be further reduced.
[0045]
( Second Embodiment)
FIG. 6 relates to the second embodiment of the present invention, and is an enlarged cross-sectional view of a main part corresponding to FIG. The difference from the second reference example is that a removal preventing portion 20e is provided along the outer peripheral portion of the diaphragm 20 by bending and extending the fluororubber layer 20d substantially at a right angle. Thereby, it is possible to prevent the fluororubber layer 20d from being displaced with the operation of the diaphragm 20, and to prevent the fluororubber layer 20d from coming off.
[0046]
( Third embodiment)
FIG. 7 relates to the third embodiment of the present invention, and is an enlarged cross-sectional view of the main part of the portion corresponding to FIG. The difference from the second reference example is that the fluororubber layer 20d is disposed only in a portion of the diaphragm 20 that is substantially sandwiched between the second plate 22 and the third plate 23, and the cover 28 and the holder 1. It is. Thereby, it is possible to prevent the fluororubber layer 20d from being hardened and the diaphragm 20 from moving in an extremely low temperature environment, and to ensure a smooth operation of the diaphragm 20.
[Brief description of the drawings]
FIG. 1 relates to a first reference example of the present invention, and is a cross-sectional view along a central axis of a pressure control valve 27 of the present invention.
FIG. 2 relates to a first reference example of the present invention, and is an enlarged cross-sectional view of a portion A of a diaphragm 20 in FIG.
FIG. 3 relates to a first reference example of the present invention and is an enlarged cross-sectional view of a main part in FIG.
FIG. 4 relates to a second reference example of the present invention, and is an enlarged cross-sectional view of a main part of a portion corresponding to FIG. 3;
FIG. 5 relates to the first embodiment of the present invention, and is an enlarged cross-sectional view of a main part of a portion corresponding to FIG. 4;
FIG. 6 relates to a second embodiment of the present invention, and is an enlarged cross-sectional view of a main part of a portion corresponding to FIG.
FIG. 7 relates to a third embodiment of the present invention and is an enlarged cross-sectional view of a main part of a portion corresponding to FIG.

Claims (3)

A housing having a control room composed of a first chamber and a second chamber;
In the pressure control valve having a structure that guides a pressure medium containing fuel vapor to the first chamber, having a diaphragm that drives the shaft in an axial direction while separating and sealing the first chamber and the second chamber,
The diaphragm has, on the side facing the first chamber, a composite layer in which a gas blocking layer and a resin layer that block the passage of gas are laminated, and a rubber layer provided on the side facing the second chamber; Formed by joining the composite layer,
The gas barrier layer is a layer coated with an ethylene-vinyl alcohol copolymer, and the resin layer is a layer coated with a polyamide-based resin such as nylon,
On the surface of the composite layer, a fluorine rubber layer made of a fluorine rubber material is further disposed.
A pressure control valve characterized by comprising a slip-off preventing portion that extends by bending the fluororubber layer substantially perpendicularly along the outer peripheral portion of the diaphragm . 2. The pressure control valve according to claim 1 , wherein an annular convex portion is provided at an abutting portion of the casing that abuts on a peripheral edge portion of the diaphragm to press the peripheral edge portion . The pressure control valve according to claim 1, characterized in that arranged the fluorine rubber layer between the diaphragm top surface abutting member.

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