JP4559724B2 - Seal ring - Google Patents

Description

  The present invention relates to a seal ring having an electrical insulating property, which is useful, for example, as a dust seal means in a fuel cell.

  In a fuel cell vehicle equipped with a fuel cell, the electrical insulation of the fuel cell unit is a very important issue in terms of safety. FIG. 5 is an explanatory diagram showing a schematic configuration of the in-vehicle fuel cell unit 100, where reference numeral 101 is a fuel cell body, 102 is a reformer comprising a reformer, a CO purifier, and the like that reform raw gas into hydrogen gas. And is housed in a box 103 provided with an insulating sheet 104. Further, the fuel cell main body 101 and the reformer 102 are supported via a mount 105 having electrical insulation.

As is well known, the fuel cell main body 101 generates electricity by reacting hydrogen and oxygen to generate water. An external fuel supply pipe, an oxidizing gas supply pipe, and cooling water supply are provided. A plurality of pipes 106 such as pipes are connected, and these pipes 106 are disposed through the box 103. The penetration part of the pipe 106 in the box 103 is sealed by a seal ring (grommet) 107 made of a rubber-like elastic material as described in, for example, Patent Document 1 below, and thereby the box 103 from the outside is sealed. Prevents intrusion of dust and water droplets. As the seal ring 107, a well-known oil seal-like shape made of a rubber-like elastic material as shown in Patent Document 1 is employed.
JP 2000-291522 A

  By the way, the fuel cell main body 101 and the pipe 106 connected to the fuel cell main body 101 are at a high potential. On the other hand, the box 103 containing the fuel cell main body 101 is made of metal. It is necessary to ensure electrical insulation with 106. However, the seal ring 107 provided on the outer periphery of the pipe 106 is formed of a rubber-like elastic material having electrical insulation, but the rubber-like elastic material has a slight conductivity. Therefore, when the fuel cell main body 101 becomes a high potential due to power generation, there is a risk of leakage from the pipe 106 to the box 103 via the seal ring 107, and the occurrence of leakage may cause a very dangerous situation. .

  The present invention has been made in view of the above problems, and a technical problem thereof is to provide a seal ring that can improve electrical insulation and effectively prevent leakage through a seal portion. .

As means for effectively solving the above-mentioned conventional technical problems, the seal ring according to the invention of claim 1 is a seal ring formed of a rubber-like elastic material, and is closely fixed to the opening of one member. A grommet portion, a seal lip in close contact with the outer peripheral surface of the other member penetrating the inner periphery of the opening, and a membrane portion continuously formed between the grommet portion and the seal lip, S is a circumferential sectional area of the portion, L is a length of the film portion between the grommet portion and the seal lip, R _A is a target insulation resistance value between the one member and the other member, and the rubber shape When the volume resistivity of the elastic material is R _B , the following equation (1):
L / S> R _A / R _B (1)
By satisfying the above, electrical insulation is ensured , the seal lip is formed in a cylindrical shape thicker than the film portion, and a projecting piece is formed on the outer periphery .

  According to the seal ring of the first aspect of the invention, the insulation of the seal ring is achieved by sufficiently increasing the length L of the film part and sufficiently reducing the cross-sectional area S so as to satisfy the expression (1). Since the resistance value is larger than the target insulation resistance value, excellent electrical insulation can be ensured even if the potential difference between one member to which the seal ring is attached and the other member is large.

  Hereinafter, preferred embodiments of a seal ring according to the present invention will be described with reference to the drawings. 1 is a cross-sectional view showing a first embodiment of a seal ring 6 according to the present invention together with a part of an in-vehicle fuel cell unit, FIG. 2 is a cross-sectional view showing a main part of FIG. 1, and FIG. 4 is a half sectional view showing a part of the seal ring 6. FIG.

  First, in FIG. 1, reference numeral 1 indicates a top plate portion (hereinafter simply referred to as a box) of a box of an in-vehicle fuel cell unit. The box 1 corresponds to one member described in claim 1 and is made of a metal plate. The box 1 houses a fuel cell main body (fuel cell stack) 2 in which a large number of unit cells made of a fuel electrode, an electrolyte, an air electrode, and a separator are stacked.

  The fuel cell main body 2 is connected to pipes 3 such as a fuel (hydrogen) supply pipe, an oxidizing gas (for example, air) supply pipe, a cooling water supply pipe, and the like. The joint portion 31 has 32 and 33. The joint portion 31 corresponds to the other member described in claim 1, and the connection ports 32 and 33 are connected to rubber hoses 4 and 5 extending from a fuel supply portion or the like (not shown). ing.

  The joint portion 31 in the pipe 3 is located on the inner periphery of the pipe insertion hole 1 a opened in the box 1. The pipe insertion hole 1a corresponds to an opening of one member described in claim 1, and a seal ring 6 is interposed as a dust seal between the pipe insertion hole 1a and the joint part 31. ing.

  The seal ring 6 is formed of a rubber-like elastic material, and as shown in FIGS. 2 and 3, a grommet portion 61 having an annular groove 61a extending radially in the outer peripheral portion, and an inner peripheral side thereof. A seal lip 62 and a film part 63 formed continuously between the grommet part 61 and the seal lip 62 are provided. The film part 63 is sufficiently thin as compared with the grommet part 61, has a uniform thickness t, and is formed in a bellows shape having a cross-sectional shape meandering in a substantially S shape repeatedly in the axial direction. . Further, the seal lip 62 is formed in a cylindrical shape that is appropriately thicker than the film portion 63 in order to give an appropriate tightening force to the pipe 3 (joint portion 31).

  That is, as shown in FIG. 2, the seal ring 6 includes a grommet portion 61 that is closely attached to the opening edge of the pipe insertion hole 1 a of the box 1 in the annular groove 61 a and a seal lip 62. However, dust or water splashes are prevented from entering the box 1 by being brought into close contact with the outer peripheral surface of the joint portion 31 penetrating the inner periphery of the pipe insertion hole 1a with an appropriate pressing force. It is. Moreover, since the bellows-shaped film | membrane part 63 can be deform | transformed flexibly, it can absorb and install the eccentricity of the piping penetration hole 1a and the coupling part 31 of the piping 3. FIG.

  The pipe 3 shown in FIG. 1 is electrically connected to the fuel cell main body 2 through water generated by the reaction of hydrogen and oxygen, cooling water, and the like, and thus has a high potential. In the meantime, it is necessary to ensure electrical insulation. For this reason, the insulation resistance value of the seal ring 6 is extremely high (for example, more than 200 MΩ) so that slight leakage from the joint portion 31 of the pipe 3 to the box 1 does not occur via the seal ring 6. There is a need to.

In the seal ring 6 of the present invention, for the purpose of improving the insulation resistance value, the circumferential cross-sectional area when the film part 63 is cut in the circumferential direction is S, and the film part 63 along the cross section of FIGS. If the length L, a box 1 and a target insulation resistance between the joint portion 31 R _a, the volume resistivity of the rubber-like elastic material and R _B, the following equation (1);
_{L / S> R A / R} B ... (1)
In other words, the material of the seal ring 6 and the shape and dimensions of the film portion 63 are defined.

  That is, the seal ring 6 has as small a cross-sectional area S as possible, that is, a thin film thickness t and a conduction length L of the film part 63 between the grommet part 61 and the seal lip 62 as much as possible. Therefore, the insulation resistance value of the seal ring 6 is improved. Since the film portion 63 has a cross-sectional shape meandering in the axial direction, a length L for securing a required insulation resistance value can be obtained with a small mounting space in the radial direction or the axial direction.

Here, the above equation (1) will be described. The cross-sectional area S of the film part 63 differs depending on the radius of the cutting circumference (smaller as it is cut on the inner peripheral side), but the film part 63 is shown in FIGS. When divided along the cross-section, the cross-sectional area S can be considered to be approximately equal when the division interval is significantly reduced. Therefore, when the film part 63 is divided into n along the cross section, the left side of the equation (1) can be expressed as ΔL ₁ / ΔS ₁ + ΔL ₂ / ΔS ₂ +... + ΔL _n / ΔS _n . That is, the cross-sectional area S at the left side of the equation (1) can be said to be the average value of the cross-sectional area ΔS ₁ ~ΔS _n of the outer circumferential edge from the inner circumferential edge of the membrane portion 63.

On the other hand, the electrical resistance value of an object is influenced by the shape of the object, that is, proportional to the energization length and inversely proportional to the cross-sectional area. The volume resistivity R _B except such a shape element, which represents the magnitude of the resistance possessed by the material itself, i.e. the resistance value of the object volume resistivity × length ÷ cross-sectional area Therefore, the electrical resistance value R of the membrane part 63 in the illustrated seal ring 6 is expressed by the following equation (2):
R = R _B · L / S (2)
Is required.

Therefore, by satisfying the expression (1), the cross-sectional area S of the film part 63 is reduced, and the length L along the cross-section shown in the figure is increased, whereby the electric resistance value R of the film part 63 is obtained as a box. The target insulation resistance value between 1 and the joint portion 31 can be made larger than _RA . Further, from equation (1), the rubber-like elastic material used for the sealing ring 6, of course the better high volume resistivity R _B is specifically, 10 ¹² ~10 ¹³ Ω · cm approximately EPDM having a high volume resistivity _{R B} (ethylene propylene rubber) or NR (natural rubber) is most preferred.

  Further, by reducing the thickness t of the film part 63, the insulation resistance value due to the reduction of the cross-sectional area S is increased, and the contact of the film part 63 due to the eccentricity between the pipe insertion hole 1a and the joint part 31 of the pipe 3 and Accordingly, it is possible to effectively prevent a decrease in resistance value and an electrical short circuit considered in the worst case.

  Next, FIG. 4 is sectional drawing which shows the 2nd form of the seal ring 6 which concerns on this invention. The seal ring 6 according to this embodiment is different from the first embodiment described above in that a plurality of projecting pieces 64 are formed on the outer periphery of the seal lip 62 at equal intervals in the circumferential direction for easy mounting. It is. The configuration of the other parts is the same as in FIGS.

  In addition, this invention is not limited to the form of illustration, For example, the film | membrane part 63 can also be made into the shape meandered repeatedly in the radial direction.

It is sectional drawing which shows the seal ring 6 which concerns on this invention with a part of vehicle-mounted fuel cell unit. (First form) It is sectional drawing which shows the principal part of FIG. FIG. 3 is a half sectional view showing a part of the seal ring 6 of FIG. 2. It is sectional drawing which shows the seal ring 6 which concerns on this invention. (Second form) 2 is an explanatory diagram showing a schematic configuration of an in-vehicle fuel cell unit 100. FIG.

Explanation of symbols

1 box (one member)
1a Pipe insertion hole (opening)
2 Fuel cell body 3 Piping 31 Joint part (other member)
32, 33 Connection port 4, 5 Rubber hose 6 Seal ring 61 Grommet portion 61a Annular groove 62 Seal lip 63 Film portion 64 Projection piece

Claims (1)

A seal ring (6) formed of a rubber-like elastic body, the grommet portion (61) being closely fixed to the opening (1a) of one member (1), and the inner periphery of the opening (1a) A seal lip (62) that is in close contact with the outer peripheral surface of the other member (31) that passes through the film, and a film part (63) that is continuously formed between the grommet part (61) and the seal lip (62). The circumferential cross-sectional area of the film part (63) is S, the length of the film part (63) between the grommet part (61) and the seal lip (62) is L, and the one member (1) When the target insulation resistance value between the first member and the other member (31) is R _A , and the volume specific resistance value of the rubber-like elastic material is R _B , the following equation (1):
L / S> R _A / R _B (1)
The electrical insulation is ensured by satisfying the above, and the sealing lip (62) is formed in a cylindrical shape thicker than the film part (63), and the projecting piece (64) is formed on the outer periphery. Seal ring.

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