JPH09152033A - Seal ring, its manufacture, and seal-ring structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily reduce the cost of a product through the enhancement of yields by reducing frictional resistance to ensure a smooth sliding movement. SOLUTION: The sliding parts of a piston 11 and a cylinder 12 comprise an O-ring 15 made from rubber, fitted into a circular groove 14 formed in the outer peripheral surface 13 of the piston 11, and a seal ring 17 pressed into contact with the outer periphery of the O-ring 15 and freely slidably fitted in between the outer periphery of the O-ring 15 and the inner peripheral surface 16 of the cylinder 12. The seal ring 17 is thin-walled and cylindrical, has a circumferential wall part 18 curved and deformed in the direction of an axis by being expanded toward its outside diameter, and presses against the O-ring 15 in such a way as to hold the ring from outside. Since the circumferential wall part 18 of the seal ring 17 forms a cylindrical surface curved in such a way as to project in the direction of the axis, it comes close to making linear contact with the inner peripheral surface 16 which is the surface in sliding contact with the cylinder 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal ring, a method of manufacturing the same, and a seal ring structure, which is used for a sliding portion of a fluid pressure device, for example, a vacuum pump for a brake booster of an automobile, and a sliding portion of a piston. The present invention relates to a seal ring to be assembled, a manufacturing method thereof, and a seal ring structure.

[0002]

2. Description of the Related Art For example, when driving an automobile,
For a vacuum pump for a brake booster that uses a negative pressure of an engine suction or a negative pressure of a vacuum pump to reduce the operating force at the time of braking, a seal structure as shown in Fig. 8 is adopted in a sliding portion between a cylinder and a piston. Has been done.

As shown in FIG. 1, this sealing structure is made of a rubber O-ring 4 fitted in an annular groove 3 formed in the outer peripheral surface 2 of the piston 1, and is pressed against the outer periphery of the O-ring 4. It is composed of a seal ring 7 called a slipper seal that is slidably fitted between the inner peripheral surface 6 of the cylinder 5.
The seal ring 7 prevents the O-ring 4 from coming into direct contact with the sliding portion to prevent the O-ring 4 from being worn or damaged, and has excellent wear resistance. Teflon (trade name) is commonly used.

The seal ring 7 is made of a pipe-shaped ring material 8 as shown in FIG. The ring material 8 has an inner diameter smaller than the seal ring 7 as a product and an outer diameter larger than the seal ring 7. Then, as shown by a broken line in the figure, the inner diameter surface and the outer diameter surface of the ring material 8 are cut so that the outer diameter and the inner diameter have predetermined dimensions, and the ring material 8 is cut by a predetermined length in the axial direction. As shown in (1), a cylindrical seal ring 7 having an outer diameter and an inner diameter of predetermined dimensions is obtained.

[0005]

By the way, in the above-mentioned conventional seal ring 7, since the outer diameter surface thereof forms a straight cylindrical surface along the axial direction, almost the entire outer diameter surface is the cylinder 5. It comes into surface contact with the inner peripheral surface 6. As a result, the sliding resistance of the piston 1 with respect to the cylinder 5 is large, and there is a high possibility that smooth sliding of the piston 1 will be obstructed.

Further, since the seal ring 7 is manufactured by cutting the inner and outer diameter surfaces of the pipe-shaped ring material 8 (see FIG. 9), much material is wasted, which is troublesome and the yield is poor. There was a problem that this would increase the cost of the product.

Therefore, the present invention has been proposed in view of the above problems, and an object of the present invention is to ensure smooth sliding in a sliding portion and improve the yield to reduce the cost of the product. It is to realize it easily.

[0008]

As a technical means for achieving the above object, the seal ring of the present invention has a thin wall and a tubular shape, and is bulged toward the outer diameter side to be bent and deformed in the axial direction. It is characterized by having a peripheral wall part.

In the method for manufacturing a seal ring of the present invention, a doughnut-shaped thin ring member is cut out from a pipe-shaped ring material by slicing, and the thin ring member has one surface on the outer diameter side and the other surface. Is deformed into a cylindrical shape so that it is on the inner diameter side, and is bulged toward the outer diameter side of the cylinder to be bent and deformed in the axial direction.

Further, the seal ring structure of the present invention has a thin and tubular shape, and a seal ring having a peripheral wall portion which is bulged toward the outer diameter side and bent and deformed in the axial direction, and the peripheral wall of the seal ring. It is characterized in that it is configured with an O-ring fitted inside the part.

Further, the seal ring structure of the present invention relatively slides a seal ring having a thin wall and a tubular shape, and having a peripheral wall portion which is bulged toward the outer diameter side and bent and deformed in the axial direction. To contact the sliding surface of one of the two members,
The O-ring fitted inside the peripheral wall portion of the seal ring is fitted into the concave groove formed in the sliding surface of the other member,
The seal ring and the O-ring are interposed between the two members.

[0012] It is desirable that the seal ring structure be used as a vacuum pump for a brake booster.

[0013]

1 to 7 show an embodiment of the present invention.
Will be described. This embodiment is applied to a vacuum pump for a brake booster that uses a suction negative pressure of an engine or a negative pressure of a vacuum pump to reduce an operating force at the time of braking when driving an automobile or the like.

FIG. 1 shows a sliding portion between a piston 11 and a cylinder 12 in a vacuum pump for a brake booster, which is made of rubber and is fitted in an annular groove 14 formed in an outer peripheral surface 13 of the piston 11, which is one member. O-ring 1
5 and the O-ring 15 on the outer periphery of the cylinder 12 by pressure contact.
And a seal ring 17 called a slipper seal that is slidably fitted between the inner peripheral surface 16 and the inner peripheral surface 16.

The seal ring 17 of the present invention has a thin and cylindrical shape, and has a peripheral wall portion 18 which is bulged outward and curved and deformed in the axial direction. The O-ring 15 is held from the outside. Press to hold it. On the other hand, since the peripheral wall portion 18 of the seal ring 17 forms a cylindrical surface that is curved in a protruding shape along the axial direction thereof, the inner peripheral surface 16 that is a sliding surface with the cylinder 12 is in a state close to line contact. Become.

The curved peripheral wall portion 18 of the seal ring 17 has a smaller radius of curvature than the O-ring 15 located inside thereof, and, for example, has a seal radius larger than the outer peripheral radius of curvature of the cross-sectional shape of the O-ring 15. The inner peripheral radius of curvature of the cross-sectional shape of the ring 17 is about 3 to 30%, preferably about 5 to 2
5%, O-ring 15 and seal ring 17
It is desirable that the and are integrated. If this radius of curvature ratio is less than about 3%, it is unsuitable because the seal ring 17 may be disengaged from the O-ring 15 during piston operation. It is not suitable because it becomes difficult to integrate the ring 17 with the ring 17. The curvature described above may be a radius of curvature in which the curvature continuously changes.

The O-ring 15 and the seal ring 17 which are thus integrated are as shown in FIG.
If both ends of the cross-sectional shape of the O-ring 1 are set so as to fit in the concave groove 14 of the piston 11, the seal ring 17
There is no departure from 5.

The crushing margin of the O-ring 15 is about 8 to 30% of the cross-sectional diameter of the O-ring 15, preferably about 8 to 30%.
If it is about 24% and is about 0.1 to 1.1 mm, preferably about 0.1 to 0.6 mm, good sealing properties can be expected. If the crushing margin is too small, reliability such as sealing property cannot be expected, and conversely, if it is too large, sliding resistance increases and assembly becomes difficult.

The seal ring 17 is made of fluorine resin,
It is preferable to use an ultra-high molecular weight polyethylene resin or an aromatic polyester resin, the surface of which is oriented in a certain direction by, for example, the production method of the present invention. Among the fluororesins, perfluoro fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) are Since the circumference of the molecular skeleton is entirely fluorine, it has excellent sliding properties such as friction characteristics.

It is to be noted that the resin is not limited to the above-mentioned resin, and may be a resin having a band structure, the surface of which has a molecular direction oriented in a fixed direction. As the resin having a band structure, for example, a resin having a crystallinity of about 20 to 80% or more may be used, and tetrafluoroethylene resin which is a kind of fluorine resin can be used. In the case of a fluorine-based resin such as a tetrafluoroethylene resin, if the crystallinity is about 50 to 80% or more or a value exceeding these, it is considered that the band structure portion is large and preferable. The tetrafluoroethylene resin may be blended with various fillers.

Fluorine type resins, ultra high molecular weight type polyethylene resins and aromatic type polyester resins are plastics showing low friction at low speed sliding and are widely used as sliding materials. Regarding these resins, when the generally used molecular orientation is not oriented, a large peak resistance value is shown at startup, and then the molecular orientation is aligned in a certain direction by sliding, so the resistance value is It decreases and stabilizes at an almost constant value. Therefore, if the seal ring 17 in which the molecular direction is orientated in advance to a fixed direction, that is, the sliding direction is used, the peak value of the starting resistance is reduced, the frictional resistance is stabilized from the time of starting, and a preferable sliding action is obtained.

Examples of the aromatic polyester resin include polymers made of paraoxybenzoic acid, aromatic dicarboxylic acids, aromatic diols, etc., and homopolymers made of paraoxybenzoic acid and the above three types of copolymers. There are things that consist of. These are wholly aromatic polyester resins, and homopolymers of paraoxybenzoic acid are excellent in heat resistance, and the above three kinds of copolymers are excellent in creep resistance, moldability and the like. A polymer having such a molecular structure has a property that orientation is strongly exhibited.

The band structure is a structure in which slippage is likely to occur as a structure of a molecular texture, and the friction coefficient is further reduced by orienting the molecular direction in a fixed direction. The band structure is a structure peculiar as a molecular assembly of plastics, and a tetrafluoroethylene resin is typical as a resin having this structure. The friction coefficient of the tetrafluoroethylene resin when the filler is blended is greatly reduced as compared with the case where the filler is not blended. It is considered that this is because the filler prevents the band structure from being broken. As the filler, any one of glass-based fiber, carbon-based fiber, graphite-based powder, and polyimide-based resin powder or 2
It is preferable to use one or more species. The same applies when a filler is added to the ultra high molecular weight polyethylene.

Particularly, as the material of the seal ring 17, for example, a composition in which the above-mentioned PTFE resin which is a fluorine resin is used as a continuous phase and a polyimide resin is dispersed therein is most suitable. By mixing both the PTFE resin as the dispersion medium and the polyimide resin as the dispersoid as described above, a composition having excellent wear resistance and a low coefficient of friction and optimal as a slipper seal can be obtained.

Specifically, the above-mentioned PTFE is prepared by polymerizing tetrafluoroethylene under pressure using a known method, for example, a free radical catalyst such as peroxide or persulfate. Obtainable. A typical production method of PTFE resin is US Pat.
No. 93967.

Further, the polyimide can be generally obtained by reacting a primary diamine with an aromatic tetracarboxylic acid, an anhydride or an ester to form a linear polyamic acid and heating it to convert it into a polyimide. For methods of making various polyimide and polyamic acid resins, see US Pat. Nos. 3,190,856, 310577.
5, No. 3179635, No. 2421024, No. 3
No. 037966, No. 2710853, No. 317963
4, No. 2,731,447 and No. 2,712,543.

As a method for producing a mixture of PTFE resin and polyimide resin, for example, the polyimide resin is finely pulverized into particles having a size of about 10 to 80 μm, particularly 70 to 80 μm by a pulverizer or directly during the manufacturing process. Then, there is a method of mixing this with a PTFE resin crushed to a size of about 5 to 50 μm, particularly 25 to 40 μm.
As another mixing method, a polyimide resin is used as PTF.
E Add to suspension of resin, stir to evenly disperse it, then add non-aqueous solvent like acetone to precipitate solids, filter, wash and dry to get homogeneous mixture Is the way. Incidentally, contrary to the above, the polyimide resin may be dispersed and the granular PTFE resin may be added thereto.

In order to ensure that the mixture of the PTFE resin and the polyimide resin has a continuous phase or matrix of the PTFE resin, the amount of the polyimide resin contained in the mixture should be 50% by weight or less. In other words,
It is preferable that the mixture contains 50% by weight or more of the PTFE resin. Actually, 80-90% by weight of PTFE resin
When mixed with 20 to 10% by weight of polyimide resin, a mixture having properties suitable for molding the seal ring 17 was obtained. As the filler added to the mixture of the PTFE resin and the polyimide resin, graphite, glass fiber, metal oxides such as copper oxide, lead oxide, iron oxide, mica, talc, bronze, copper, aluminum, silver ,
There are molybdenum, fiber flux (trade name), etc.,
It is believed that the amount added should generally not exceed about 20%, preferably about 15% by weight of the mixture.

Other materials for the seal ring 17 include 50 to 80% PTFE, a silicate selected from the group consisting of glass, talc, mica and aluminum silicate, aluminum, molybdenum and silver. A homogenous mixture with a third composition selected from the group consisting of copper, lead, lead oxide, iron oxide and copper oxide, wherein the silicate is present in an amount equal to or twice that of the third composition. Those are preferable.

The average particle size of these fillers may be about 0.1 to 100 μm, for example,
An average particle size of about 0.1 to 3 μm, preferably about 0.1 to 1 μm with the metal-based filler or the like is preferable because it is less likely to damage a counterpart member such as a cylinder and maintain slidability. it is conceivable that.

The surface roughness on the outer peripheral surface of the seal ring 17 or the inner peripheral surface 16 of the cylinder 12 which slides with each other is Rmax. , Ra, Rz, etc., is about 3 to 25 μm or less, preferably about 8 or less by the evaluation method defined in JIS.
It is less than or equal to μm, more preferably less than or equal to about 3.2 μm. This is because when the surface roughness exceeds the predetermined range, the sliding surface is often scratched, which is considered to cause friction. The lower limit of the surface roughness may be about 0.1 μm or more in consideration of efficiency during processing.

However, since it takes a long time to perform a surface finishing process on the outer peripheral surface of the seal ring 17 or the inner peripheral surface 16 of the cylinder 12, it is not efficient and is affected by the formation of a transfer film of the resin material. Therefore, it is estimated that the range may be about 3 to 8 μm or less as long as the specifications and conditions are not affected by wear.

The O-ring 15 located inside the above-mentioned seal ring 17 is made of rubber having appropriate elasticity, for example, natural rubber, styrene-butadiene rubber,
Butyl rubber, ethylene propylene rubber, chloroprene rubber, nitrile rubber, urethane rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber and fluorine rubber are suitable, especially heat resistance and oil resistance. Acrylic rubber is considered to be preferable from the viewpoint of properties. Further, the elasticity of rubber is preferably about 60 to 100, and preferably about 70 to 90 in terms of rubber hardness (Hs), since a suitable elastic force can be obtained.

The seal ring 17 described above is manufactured in the following manner. First, as shown in FIG. 2, a pipe-shaped ring material 19 is prepared, and the ring material 19 is sliced into thin-walled portions as indicated by broken lines in the figure to form a donut-shaped thin-walled ring member as shown in FIG. Cut out 20. Then, while deforming the thin ring member 20 into a tubular shape such that one surface thereof is on the outer diameter side and the other surface is on the inner diameter side, the thin ring member 20 is bulged to the tubular outer diameter side to be bent and deformed. Thereby, as shown in FIG. 4, a seal ring 17 having a peripheral wall portion 18 in which a substantially cylindrical central portion bulges toward the outer diameter side and is bent and deformed in the axial direction is obtained.

As a method of deforming the thin-walled ring member 20 into a cylindrical shape, the thin-walled ring member 20 is appropriately heated, for example, at a temperature not lower than the heat deformation temperature and not higher than the melting point, depending on the material, but specifically about 60 to About 260 ° C, preferably about 8
The thin ring member 20 is preheated to about 0 to 200 ° C. to soften the thin ring member 20 to improve moldability. After this heating, the thin ring member 20 is held by a gripping means such as a vacuum chuck, and as shown in FIG. 5, the upper end is tapered and expands downward, and the outer peripheral surface 21 extends from the upper end to the lower end. The thin ring member 20 is inserted and attached to the taper jig 22 on which the protruding curved surface is formed.

Further, as shown in FIG. 6, a press-fitting jig 24 made of a plate-like body such as the rubber described above or the elastic plastic described above having a circular hole 23 in the center.
The thin ring member 2 inserted into the taper jig 22 by
Press 0 downwards. At this time, as the press-fitting jig 24 descends, the hole 23 of the press-fitting jig 24 is moved to the outer peripheral surface 2 of the taper jig 22.
1, the thin-walled ring member 20 is pressed against the outer peripheral surface 21 of the taper jig 22 by the lower surface of the press-fitting jig 24, the inner diameter is expanded while sliding along the outer peripheral surface 21, and gradually becomes a tubular shape. Molded. In this way, the thin ring member 20 is deformed along the protruding curved surface of the taper jig 21.

The thin ring member 20 deformed by the taper jig 22 and the press-fitting jig 24 is asymmetric with respect to the axial direction in which one opening has a large diameter and the other opening has a small diameter, as shown in FIG. It becomes a cylindrical seal ring 17 '. Therefore, after removing the seal ring 17 ′ from the taper jig 22 by an appropriate means, the side where the opening has a large diameter is pressed from the outside toward the axial center by a correction jig (not shown) in the radial direction. Then, one of the opening sides is reduced in diameter to finally form a cylindrical seal ring 17 that is substantially symmetrical with respect to the axial direction (see FIG. 4). By thus forming the seal ring 17 in a substantially symmetrical shape with respect to the axial direction, it is possible to prevent the seal ring 17 from being displaced in the sliding direction when sliding in the reciprocating direction. Will be easier.

The above-described method of deforming the thin-walled ring member 20 into a tubular shape is merely an example, and is a cylindrical seal ring that is substantially symmetrical with respect to the axial direction in which the thin ring member 20 bulges outward and is bent and deformed in a protruding shape. Various other methods are conceivable as the transformation method of 17. The radius of curvature ratio with respect to the O-ring 15 that changes the curved state of the seal ring 17 between large and small is set when the thin ring member 20 is deformed as described above.

The seal ring 17 thus obtained
The O-ring 15 is fitted on the inner diameter side of the above, and the integral body including the seal ring 17 and the O-ring 15 is attached to the sliding portion between the piston 11 and the cylinder 12 in the vacuum pump for the brake booster in a press-fitted state. That is, the O-ring 15 is fitted into the annular groove 14 on the outer peripheral surface 13 of the piston 11, and the seal ring 1 on the outer periphery of the O-ring 15 is fitted.
7 is interposed between the inner peripheral surfaces 16 of the cylinder 12 (see FIG. 1). When used as a seal structure for a vacuum pump for a brake booster in this way, reliable and reliable sliding characteristics, such as a stable friction coefficient even after long-term use, stick-slip, and reusability after long-term suspension Since the low friction coefficient and the like can be improved and the sealing property is excellent, the boost pressure and the like are relatively stable, and a highly reliable vacuum pump for a brake booster can be provided.

The mating members such as the piston 11 and the cylinder 12 are cast steel, cast iron, aluminum alloys, stainless steel alloys, rolled steels for general structures, carbon steels for machine structures, and other special extremely mild steels, extremely mild steels, mild steels, Examples include semi-mild steel, semi-hard steel, hard steel, and hardest steel, but are not particularly limited, but mild steel rolled steel that is relatively excellent in press workability such as bending and punching, and
It is considered that the cast metal is preferable because it is suitable in rigidity, efficient in manufacturing, and good in price.

[0041]

According to the present invention, since the seal ring has a thin wall and a tubular shape, and has a peripheral wall portion which is bulged outwardly and is bent and deformed in the axial direction, the outside of the peripheral wall portion is prevented. The radial surface can be in a state close to line contact with the sliding surface. As a result, the sliding resistance can be reduced and smooth sliding can be realized.

Further, since the seal ring of the present invention is manufactured by cutting a pipe-shaped ring material by slicing, there is no waste of material, no labor is required, the yield is significantly improved, and the product cost is increased. It is easy to go down.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view showing a seal ring structure in which a seal ring of the present invention is combined with an O ring and incorporated in a sliding portion between a piston and a cylinder.

FIG. 2 is a sectional view showing a ring material from which a thin ring member for producing a seal ring is cut out.

3 is a sectional view showing a thin ring member cut out from the ring material of FIG.

FIG. 4 is a cross-sectional view showing a seal ring manufactured by deforming the thin ring member of FIG.

FIG. 5 is a cross-sectional view showing a taper jig for manufacturing a seal ring from a thin ring member.

FIG. 6 is a sectional view showing a taper jig and a press-fitting jig for manufacturing a seal ring from a thin ring member.

7 is a sectional view showing a seal ring obtained by the taper jig and the press-fitting jig of FIG.

FIG. 8 is a partially enlarged cross-sectional view showing a seal ring structure in which a conventional seal ring is combined with an O ring and incorporated in a sliding portion between a piston and a cylinder.

FIG. 9 is a sectional view showing a ring material from which a conventional seal ring is cut out.

FIG. 10 is a cross-sectional view showing a seal ring cut out from the ring material of FIG.

[Explanation of symbols]

 11 one member (piston) 12 the other member (cylinder) 15 O-ring 17 seal ring 18 peripheral wall 19 ring material 20 thin ring member

Claims (5)

[Claims] 1. A seal ring, which is thin and has a tubular shape, and which has a peripheral wall portion that is bulged outwardly and is bent and deformed in the axial direction. 2. A donut-shaped thin-walled ring member is sliced from a pipe-shaped ring material, and the thin-walled ring member is formed into a tubular shape with one surface on the outer diameter side and the other surface on the inner diameter side. A method for manufacturing a seal ring, which is characterized in that, while deforming, it bulges toward the outer diameter side of the cylinder and is bent and deformed in the axial direction. 3. A seal ring having a thin wall, a cylindrical shape, and a peripheral wall portion that is bulged toward the outer diameter side and is bent and deformed in the axial direction, and an O that is fitted inside the peripheral wall portion of the seal ring.
A seal ring structure characterized by being configured with a ring. 4. One of two members that relatively slide a seal ring that is thin and has a tubular shape, and has a peripheral wall portion that is bulged toward the outer diameter side and is bent and deformed in the axial direction. The O-ring, which is brought into pressure contact with the sliding surface of the member and is fitted inside the peripheral wall portion of the seal ring, is fitted into the concave groove formed in the sliding surface of the other member, and the seal ring and the O-ring are formed into two members. A seal ring structure characterized by being interposed between them. 5. The seal ring structure according to claim 3, wherein the seal ring is used in a vacuum pump for a brake booster.