JP2006035872A - Sealing structure of opening part of fuel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish compatibility of reduction of leakage of fuel vapor due to its permeation through a gasket 30 and maintenance of durability of the gasket 30. <P>SOLUTION: The gasket 30 made of a rubber type elastic material is interposed between a head end 12b of a cylindrical projected part 12 to surround an opening part 10a of a fuel tank 10 and a mounting member 20 arranged to block the opening part 10a, and this gasket 30 is made of a relatively inside thick part 31 in the gas permeating direction and a relatively outside thin part 32 and is closely connected to the cylindrical projected part 12 and the mounting member 20 in a state where a squeeze margin of the thick part 31 is relatively large and a squeeze margin of the thin part 32 is relatively small. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sealing structure that seals between an opening of a fuel tank and a mounting member attached to the opening.

In a fuel tank mounted on an automobile or the like, a gap between a cylindrical opening formed on the upper part and an attachment member attached to close the cylindrical opening is sealed with a gasket made of a rubber-like elastic material. As a typical prior art, for example, the one described in Patent Document 1 below is known.
JP2002-114046

  The gasket described in Patent Document 1 is compressed between the tip of a cylindrical portion that forms the opening of the fuel tank and an attachment member that is fastened and fixed to the nut by a nut. It fulfills the function of sealing against fuel.

Here, in recent years, in addition to a direct sealing function for blocking the leakage of fuel, which is a liquid, an improvement in sealing performance against permeation of fuel vapor generated by fuel volatilization has been demanded. FIG. 6 is an explanatory diagram showing a simplified mounting state of the gasket. As shown in FIG. 6, when the gap between the two members 101 and 102 is sealed with a gasket 103 made of a rubber-like elastic material, The thickness of the gasket 103 between 101 and 102 is t, the fuel vapor permeation distance is L, the cross-sectional area in the circumferential direction (t × circumference length) is A, and the inherent gas of the rubber-like elastic material forming the gasket 103 When the permeation coefficient is α, the pressure of the fuel vapor to be sealed is P ₁ , the pressure of the external atmosphere is P ₂ , and the time is T, the fuel vapor permeation amount V is expressed by the following equation (1).
V = α · (P ₁ −P ₂ ) · A · T / L (1)

  That is, from the above equation (1), it is effective to reduce the cross-sectional area A, in other words, the wall thickness t and increase the permeation distance L, in order to reduce the fuel vapor permeation amount in the same material. Recognize. However, when the thickness t in the compression direction is reduced, the amount of crushing is also reduced, the sealing performance against fuel as a liquid is likely to be reduced, and an overcompressed state is likely to occur, and the distortion rate due to compression set (sag) increases. There is a problem that durability is lowered. Therefore, in the conventional gasket as described in Patent Document 1, it is difficult to achieve both low gas permeability and durability maintenance.

  The present invention has been made in view of the above points, and its technical problem is that in a sealing structure of an opening of a fuel tank, a reduction in leakage due to fuel vapor passing through the gasket, and a gasket The goal is to maintain both durability and durability.

  As a means for effectively solving the technical problem described above, a fuel tank opening sealing structure according to the invention of claim 1 includes a tip of a cylindrical protrusion surrounding the fuel tank opening, and the opening. A gasket made of a rubber-like elastic material is interposed between the mounting member and the mounting member arranged so as to close the portion. The thick-walled portion and the thin-walled portion are brought into close contact with the cylindrical projecting portion and the mounting member with a required crushing margin.

  In this configuration, the thick-walled portion of the gasket is relatively on the inside, and a sufficient crushing allowance is provided to ensure sealing against liquid fuel. The relatively thin-walled portion on the outside is The fuel vapor permeation area is reduced to effectively reduce the gas permeation amount. Further, since the thick part and the thin part are formed in series with respect to the fuel vapor permeation direction, the permeation distance becomes long, which also effectively acts on the reduction of the gas permeation amount.

  A fuel tank opening sealing structure according to a second aspect of the present invention is the configuration according to the first aspect, wherein the fuel tank opening portion is continuous in the circumferential direction with the cylindrical protrusion or the attachment member in the thick or thin portion. A seal protrusion is formed, and this seal protrusion is completely crushed in the mounted state. For this reason, a crushing rate can be partially raised in a seal protrusion.

  The fuel tank opening sealing structure according to the invention of claim 3 is the structure of claim 1, wherein the crushing allowance of the thick part is relatively large and the crushing allowance of the thin part is relatively small. is there. For this reason, a relatively large crushing margin is ensured in the thick-walled portion to ensure the required sealing performance against the liquid fuel, while the outer thin-walled portion is decompressed by passing through the thick-walled portion. Because the fuel vapor is sealed, even with a small crushing allowance, it is possible to sufficiently reduce the leakage of liquid fuel and fuel vapor leakage due to permeation, and the crushing allowance is small, so the compression set is also small and durable. Sex is maintained.

  According to the sealing structure of the opening portion of the fuel tank according to the first aspect of the invention, the liquid fuel is shut off at the thick portion of the gasket, and the permeation area of the fuel vapor is reduced at the relatively thin portion at the outer side. At the same time, by increasing the permeation distance, leakage due to permeation of fuel vapor can be reduced.

  According to the sealing structure of the opening portion of the fuel tank according to the invention of claim 2, since the maximum portion of the crushing rate is formed by the seal protrusion, the sealing performance against liquid fuel and fuel vapor can be improved.

  According to the sealing structure of the fuel tank opening according to the invention of claim 3, the required sealing performance against the liquid fuel is secured in the thick part of the gasket, and the crushing margin of the thin part is relatively reduced. Therefore, the required durability can be ensured.

  Hereinafter, a preferred embodiment of a fuel tank opening sealing structure according to the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a partial sectional view showing the first embodiment cut along a plane passing through the axis of the gasket, and FIG. 2 is a partial sectional view showing the gasket in FIG. 1 cut along a plane passing through the axis. It is.

  In FIG. 1, reference numeral 10 indicates a part of a synthetic resin fuel tank mounted on an automobile, and a cylindrical projecting portion projecting outward (upward) is formed on an upper wall portion 11 of the fuel tank 10. 12 is formed. The cylindrical protrusion 12 forms an opening 10a of the fuel tank 10 on the inner periphery thereof, in other words, is formed so as to surround the opening 10a, and has a male screw portion 12a on the outer peripheral surface. Is formed.

  A mounting member 20 is arranged on the outer side (upper side) of the cylindrical protrusion 12 so as to close the opening 10a on the inner periphery thereof. The attachment member 20 is, for example, a bracket of a fuel pump, and the outer peripheral flange portion 22 extends from the inner surface (lower surface) of the disk portion 21 supported at the tip of the cylindrical protruding portion 12 and is inserted into the opening portion 10a. The cylindrical portion 23 is formed.

  A gasket 30 is interposed between the tip (upper end) 12 b of the cylindrical projecting portion 12 in the fuel tank 10 and the outer peripheral flange portion 22 of the mounting member 20. The gasket 30 is formed of a rubber-like elastic material. As shown in FIG. 2 as a single unit, the gasket 30 is relatively inward of the thick portion 31 on the inner side (in this embodiment, on the inner peripheral side). The outer thin portion 32 (in this embodiment, the outer peripheral side) and the annular protrusion 33 projecting in the axial direction are formed on the inner peripheral portion of the thick portion 31.

  The rubber-like elastic material of the gasket 30 is preferably NBR (nitrile rubber) or FKM (fluororubber) such as NBR (nitrile rubber) or FKM (fluorine rubber), which has a small compression set, excellent oil resistance and low temperature resistance, and low gas permeability. FKM is superior to NBR in terms of compression set, gas permeability and oil resistance (swelling resistance).

Specifically, the axial thickness t ₁ of the thick portion 31 in the gasket 30 is secured to a size that allows a sufficient crushing margin, and the axial thickness t ₂ of the thin portion 32 is the above-described thickness. It is sufficiently thinner than the thickness t _1. As a specific example, the thickness _{t 1} is approximately 3 mm, the wall thickness _{t 2} is approximately 1 mm. Further, the contact surface 30a with the mounting member 20 is formed flat, and the contact surface with the tip 12b of the cylindrical projecting portion 12 in the fuel tank 10 is formed with an inner peripheral plane 31a corresponding to the thick portion 31 and a thin wall. A flat surface 32a on the outer peripheral side corresponding to the portion 32 is formed with a predetermined axial step Δt (= t ₁ −t ₂ ) via the annular step portion 30b.

  On the other hand, the close contact surface with the gasket 30 at the tip 12b of the cylindrical protrusion 12 of the fuel tank 10 also has a step shape corresponding to the gasket 30, and the axial step St is a thick portion 31 in the gasket 30. And is formed slightly smaller than the axial step Δt of the thin portion 32. And by forming in this way, in the mounting | wearing state shown by FIG. 1, it is about 30% in the thick part 31 between the outer periphery collar part 22 of the attachment member 20, and the front-end | tip 12b of the cylindrical protrusion part 12. FIG. When the axial compression is applied at the crushing rate, the thin portion 32 is subjected to the axial compression at a crushing rate of substantially the same rate or less.

  In FIG. 1, reference numeral 40 is an annular fastening member for fastening the mounting member 20 together with the gasket 30 to the distal end 12 b of the cylindrical projecting portion 12 of the fuel tank 10. The binding member 40 includes an outer cylindrical portion 41 having an inner peripheral surface formed with a female screw portion 41a that is screwed with the male screw portion 12a of the cylindrical projecting portion 12 of the fuel tank 10, and one axial end (upper end) thereof. The presser bar part 42 extends to the inner peripheral side and can come into contact with the outer peripheral hook part 22 of the mounting member 20. Further, on the outer peripheral surface of the outer cylinder portion 41, there are formed irregularities 41b for preventing slipping when the binding member 40 is rotated in the binding or relaxation direction with fingers.

Incidentally, the axial height of the flange portion 12c formed on the outer periphery of the distal end 12b of the tubular projection 12 is formed slightly smaller than the axial thickness t ₂ of the thin portion 32 of the gasket 30 When the fastening member 40 is tightened, an appropriate crushing allowance is set. In other words, when the thin-walled portion 32 of the gasket 30 is in close contact between the tubular projecting portion 12 and the outer peripheral flange portion 22 of the mounting member 20 with a crushing ratio of 0, the projecting edge portion 12c and the outer peripheral portion The gap G with the flange portion 22 is set so as to correspond to the maximum value of the crushing allowance allowed for the thin-walled portion 32, so that the gasket 30 is prevented from being over-compressed and an appropriate crushing allowance is given. Yes. Even when it is difficult to set the gap G due to the production of the cylindrical projecting portion 12 in the fuel tank 10, by managing the torque at the time of tightening by the fastening member 40, it is possible to manage an appropriate crushing allowance (crushing rate). Is possible.

  The fuel tank opening sealing structure according to the first embodiment having the above-described configuration is such that the outer peripheral flange portion 22 of the attachment member 20 for attaching a fuel pump or the like is attached to the tip 12b of the cylindrical protrusion 12 in the fuel tank 10 as a gasket. 30, and by screwing the female screw part 41 a of the outer cylinder part 41 of the fastening member 40 into the male screw part 12 a of the cylindrical projecting part 12 from above, The part 22 is fastened between the presser bar part 42 of the fastening member 40 and the gasket 30 supported by the tip 12b of the cylindrical projecting part 12, and the fuel 30 is compressed by the gasket 30 compressed along with this. The fuel in 10 is sealed.

  The gasket 30 applies axial compression to the thick portion 31 on the inner peripheral side with a sufficient crushing ratio of about 30%, for example, so that liquid fuel in the fuel tank 10 and fuel vapor generated by its volatilization are generated. The sealing performance against is secured. On the other hand, the thin-walled portion 32 on the outer peripheral side mainly uses the fuel decompressed by the thick-walled portion 31 as a sealing target, and therefore exhibits a sufficient sealing property against liquid fuel and fuel vapor even with a small crushing allowance. be able to.

  The thin portion 32 in the gasket 30 has a small thickness between the close contact surfaces of the tip 12b of the cylindrical projecting portion 12 of the fuel tank 10 and the outer peripheral flange portion 22 of the mounting member 20, and therefore in the equation (1) described above. Since the cross-sectional area A is reduced, and the thick portion 31 and the thin portion 32 are continuous in series with respect to the direction of fuel vapor transmission, the permeation distance L in equation (1) is increased, and thus the gas permeation amount is increased. V can be effectively reduced. Further, by selecting a rubber-like elastic material such as NBR or FKM having a low gas permeability as the material of the gasket 30, the gas transmission coefficient α in the equation (1) becomes small. Effective for reducing V.

  In FIG. 1, the inner peripheral surface of the gasket 30 (the inner peripheral surfaces of the thick portion 32 and the annular protrusion 33) is shown in a non-contact state with the mounting member 20. When contacting the outer peripheral surface of the cylindrical portion 23 with an appropriate surface pressure, the annular protrusion 33 also forms a sealing surface, and the permeation distance L of the fuel vapor becomes longer, so that even better sealing performance is exhibited.

  Next, FIG. 3 is a second embodiment of the fuel tank opening sealing structure according to the present invention, FIG. 4 is a third embodiment, and FIG. 5 is a fourth embodiment. It is a fragmentary sectional view cut and shown by a plane.

First, in the form shown in FIGS. 3 and 4, the annular step portion that increases the axial thickness t ₁ of the thick portion 31 also on the close contact surface side with the outer peripheral flange portion 22 (see FIG. 1) of the mounting member 20. 30c is formed. For this reason, a large crushing allowance can be given to the thick part 31 of the gasket 30 in the state mounted between the cylindrical protruding part 12 and the attachment member 20 shown in FIG.

  And the gasket 30 of the 3rd form shown by FIG. 4 among these is the seal | sticker protrusion 34 which continued to the circumferential direction on the both surfaces of the axial direction in the thick part 31, and the single side | surface (both sides may be sufficient) of the thin part 32, respectively. 35 is formed. Since the seal ridges 34 and 35 are completely crushed in the mounted state, the thick wall portion 31 and the thin wall portion 32 have a locally crushed ratio in the seal ridges 34 and 35, so that the sealing ridges 34 and 35 are sealed. It is possible to further improve the properties.

  Further, the gasket 30 of the fourth form shown in FIG. 5 has a circular cross-sectional shape (the cross-sectional shape shown in the drawing) in which the thick portion 31 on the inner peripheral side is cut in a plane that passes through the axial center. The protruding portion 36 is formed at the outer peripheral end of the thin portion 32. The protruding portion 36 has an O-ring shape having a smaller wire diameter (cross-sectional area) than the thick-walled portion 31, that is, the illustrated cross-sectional shape is circular.

  In this case, as indicated by the alternate long and short dash line in the figure, the opposing surfaces of the cylindrical projecting portion 12 of the fuel tank 10 that clamps the gasket 30 from both sides in the axial direction and the outer peripheral flange portion 22 of the mounting member 20 are The gasket 30 has a shape having peripheral grooves 12d and 22a having a rectangular cross section such as an O-ring mounting groove in a portion corresponding to the thick portion 31. By doing this, when the axial compression is applied to the thick portion 31 between the circumferential grooves 12d and 22a at a crushing rate of about 30%, the thin portion 32 has a crushing rate of substantially the same or less. Be subject to axial compression.

  When the thin-walled portion 32 of the gasket 30 is in close contact between the cylindrical projecting portion 12 of the fuel tank 10 and the outer peripheral flange portion 22 of the mounting member 20 with a crushing ratio of 0, the shoulder of the circumferential groove 12d A gap G between 12e (or a groove shoulder 12g of a circumferential groove 12f described later) and the outer peripheral flange portion 22 is set to correspond to the maximum value of the crushing allowance allowed for the thin portion 32. For this reason, the overcompression with respect to the gasket 30 is prevented, and an appropriate crushing allowance is given.

  Therefore, the thick portion 31 has excellent sealing performance similar to that of the O-ring, and the sealing performance against the fuel in the fuel tank 10 and the fuel vapor generated by its volatilization is ensured. And, the thin-walled portion 32 on the outer peripheral side is formed in a thin plate-like shape as in the first embodiment described above, and mainly the fuel decompressed by the thick-walled portion 31 is to be sealed. Even with a small crushing allowance, a sufficient sealing performance against liquid fuel and fuel vapor can be exhibited. By reducing the crushing allowance, the compression set of the thin portion 32 is also reduced, and its durability is maintained. .

  In FIG. 5, the protrusion 36 on the outer periphery of the thin portion 32 is not disposed in the circumferential grooves 12 f and 22 b formed in the cylindrical protrusion 12 of the fuel tank 10 and the outer peripheral flange 22 of the mounting member 20. Although shown as being accommodated by contact, the circumferential grooves 12f and 22b may be closely contacted with an appropriate crushing allowance.

It is a fragmentary sectional view which cut | disconnects and shows the 1st form in the sealing structure of the opening part of the fuel tank which concerns on this invention by the plane which passes along the axial center of a gasket. It is a fragmentary sectional view which cut | disconnects and shows the gasket in FIG. 1 by the plane which passes along the axial center. It is a fragmentary sectional view which cuts and shows a gasket by the plane which passes along the axial center as a 2nd form in the sealing structure of the opening part of the fuel tank which concerns on this invention. It is a fragmentary sectional view which cuts and shows a gasket by the plane which passes along the axial center as a 3rd form in the sealing structure of the opening part of the fuel tank which concerns on this invention. It is a fragmentary sectional view which cuts and shows a gasket by the plane which passes along the axial center as a 4th form in the sealing structure of the opening part of the fuel tank which concerns on this invention. It is explanatory drawing which simplifies and shows the mounting state of a gasket.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 10a Opening part 11 Upper wall part 12 Cylindrical protrusion part 12a Male screw part 12b Tip 12c Projection edge part 12d, 12f, 22a, 22b Circumferential groove 20 Mounting member 21 Disc part 22 Outer peripheral flange part 23 Cylindrical part 30 Gasket 30b 30c Annular step 31 Thick part 32 Thin part 33 Annular protrusions 34, 35 Seal protrusion 36 Projection part 40 Tightening member 41 Outer cylinder part 41a Female thread part 42 Presser foot part

Claims (3)

  Between the tip of the cylindrical projection (12) surrounding the opening (10a) of the fuel tank (10) and the mounting member (20) arranged so as to close the opening (10a), rubber A gasket (30) made of an elastic material is interposed, and the gasket (30) is composed of a relatively thick inner portion (31) and a relatively thin outer portion (32) relative to the gas permeation direction. The thick-walled portion (31) and the thin-walled portion (32) are in close contact with the cylindrical projecting portion (12) and the mounting member (20) with a required crushing margin. Sealing structure.   In the thick wall portion (31) or the thin wall portion (32), a seal protrusion (34, 35) continuous in the circumferential direction is formed in a close contact portion with the cylindrical protrusion (12) or the mounting member (20). 2. The fuel tank opening sealing structure according to claim 1, wherein the protrusions (34, 35) are completely crushed in the mounted state. 2. The fuel tank opening sealing structure according to claim 1, wherein a crushing margin of the thick portion (31) is relatively large and a crushing margin of the thin portion (32) is relatively small.

Images