JP3918415B2 - Elastic gasket - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an elastic gasket that seals between a substantially rigid main body member having an annular gasket receiving seat and a substantially flexible lid member having a gasket holding groove corresponding to the gasket receiving seat. Here, a cylinder head cover gasket (also known as a rocker cover gasket, hereinafter referred to as “cover gasket”), which is an automobile part, will be described as an example of an elastic gasket, but is not limited thereto. For example, the present invention can be applied to a timing belt cover gasket or the like.
[0002]
In the present specification, the compressive strain rate is a percentage of the compressive strain (ε = Δh / H in FIG. 2).
[0003]
[Prior art]
Normally, when sealing between the lid member and the main body member using a gasket, the height of the gasket is compressed at a predetermined compression rate (adding a predetermined compressive strain) to ensure the surface pressure required for sealing. Sealing is performed by the reaction force (surface pressure) from the gasket.
[0004]
For example, the seal between the cylinder head (main body member) 12 and the head cover (lid member) 14, both of which are both made of metal (for example, aluminum casting) and are substantially rigid, is usually performed as follows (FIGS. 1 and 2). reference).
[0005]
The cylinder head 12 has an annular seal receiving seat 13 at the upper end surface of the peripheral wall, and the head cover 14 corresponds to the seal receiving seat 13 by forming a gasket holding wall 16 having an inverted L-shaped cross section on the peripheral wall at the lower end side. A gasket holding groove 18 is provided.
[0006]
As a gasket, a gasket base portion 20 having a substantially circular cross section that abuts on the gasket receiving seat 13, and a cross-sectional bullet-shaped groove fitting portion 22 that protrudes upward from the gasket base portion 20 and fits into the gasket holding groove 18. The thing 24 of the cross-sectional substantially dull shape provided with these is prepared. Here, the bottom surface side of the gasket base portion 20 is provided with an inverted trapezoidal bottom seal lip (one in the illustrated example) 26 that presses against the gasket seat 13 to form a seal surface when a predetermined compressive strain rate is loaded. The bottom seal lip 26 is provided with bottom auxiliary seal ridges 27 and 27 from the viewpoint of facilitating securing a seal surface pressure (minimum set surface pressure). The two bottom auxiliary seal protrusions 27 and 27 are from the standpoint of seating stability. Similarly, the top side of the groove fitting portion 22 is a top seal lip 28 that presses against the bottom of the gasket holding groove 18 to form a seal surface when a predetermined compressive strain rate is applied. The top auxiliary seal protrusions 29 are provided in the central portion from the viewpoint of facilitating securing the surface pressure (minimum set surface pressure).
[0007]
The gasket 24 is usually manufactured by injection molding or the like using a synthetic rubber (for example, acrylic rubber) material having a hardness of H _S (JIS A) and excellent heat resistance of 60 to 70.
[0008]
First, the groove fitting portion 22 of the gasket 24 is inserted into the gasket holding groove 16 of the head cover 14 to hold the gasket 24 on the head cover 14. Subsequently, the head cover 14 holding the gasket 24 is set (arranged) on the cylinder head 12. Then, projectingly formed bolt head seats 12a and screw seats 14a formed at predetermined intervals (usually 80 to 150 mm) on the upper surface side of the cylinder head 12 and the lower surface side of the head cover 14 respectively. The gasket 24 is fastened by a bolt (with a wrench hole in the illustrated example), and the gasket 24 is compressed in the vertical direction so as to have a predetermined compressive strain rate (for example, 8 to 30% in order to ensure a predetermined seal surface pressure). In the illustrated example, the cylinder head 12 is positioned at the broken line portion.
[0009]
The bottom seal lip 26 of the gasket base portion 20 is pressed against the gasket receiving seat (seal seat) 13 of the cylinder head 12, and the top seal lip 28 of the groove fitting portion 22 is the top of the gasket holding groove 18 of the head cover 14. And a predetermined sealing surface pressure (for example, 0.5 MPa or more) was secured.
[0010]
[Problems to be solved by the invention]
However, in recent years, for the purpose of weight reduction and cost reduction, the use of plastic (heat-resistant reinforced plastic) that is easy to process from metal as the material of the head cover has started. For example, with respect to the head cover, from the viewpoint of heat resistance, oil resistance, noise suppression, etc., a material in which a filler, a reinforcing agent, or the like is appropriately added to polyamide such as nylon 66 or nylon 6 is employed.
[0011]
As described above, it has been found that when the head cover is made of plastic (resinized) and the gasket holding wall portion has a substantially non-rigid structure, it is difficult to ensure the same seal surface pressure as that of the conventional case.
[0012]
When the head cover is tightened with screws to obtain a predetermined seal surface pressure, the screw tightening part directly receives the fastening force, so it is easy to ensure a predetermined compressive strain rate (seal surface pressure). In the intermediate position, the fastening force of the head screw fastening portion does not sufficiently act, and it is difficult to secure a predetermined compressive strain rate (seal surface pressure).
[0013]
In order to ensure a predetermined seal surface pressure even at an intermediate position of the screw fastening portion, if the set compressive strain rate at the fastening portion is increased, this causes a lift at the intermediate portion of the fastening portion due to the compression reaction force of the gasket. . In particular, this tendency becomes more noticeable when the engine head temperature becomes high during summer and the like, and the plastic head cover thermally expands and the rigidity factor (also decreases).
[0014]
In view of the above, the present invention provides a lid member having a gasket holding groove such as a head cover made of plastic or thinned aluminum material so that it is substantially non-rigid. It is an object of the present invention to provide an elastic gasket that can easily secure a predetermined sealing pressure.
[0015]
SUMMARY OF THE INVENTION
In order to solve the above-described problems, the present inventors have made extensive efforts to develop them, and as a result, have arrived at an elastic gasket having the following configuration.
[0016]
An elastic gasket that seals between a main body member having a gasket receiving seat having an annular shape and a substantially rigid structure and a lid member having a gasket holding wall having a substantially non-rigid structure that forms a gasket holding groove corresponding to the gasket receiving seat. ,
A gasket holding groove having one or more bottom seal lips that are in pressure contact with the gasket receiving seat, and a top seal lip that protrudes upward from the gasket base and presses against the groove bottom of the gasket holding groove. A groove fitting portion to be fitted to,
A seating stabilization lip whose tip abuts against the gasket seat is provided on both sides of the bottom seal lip forming portion.
[0017]
By setting it as the said structure, while the width | variety of the bottom part seal lip for ensuring a sealing surface pressure can be made relatively small, the height of a gasket can be made relatively high. This is because when the gasket is compressed, the ease of escape to one side by narrowing the width of the bottom seal lip and the occurrence of waist break in the vicinity of the bottom by increasing the gasket can be prevented.
[0018]
Therefore, the compression reaction force of the top seal lip with respect to the gasket holding wall can be reduced by reducing the width of the portion forming the bottom seal lip, which is accompanied by the gasket compression reaction force at the intermediate position of the fastening portion in the gasket holding wall having a substantially non-rigid structure. Lifting deformation can be reduced. In addition, the variation of the compression strain rate due to the rise in deformation (warp deformation) of the gasket holding wall and the relative compression amount variation (absolute amount) of the gasket due to the compression set of the gasket itself also increases the gasket height. It can be made relatively small.
[0019]
Therefore, even if the lid member having a gasket holding groove such as a head cover is made of plastic and made substantially non-rigid, it is easy to ensure a predetermined sealing pressure with the gasket receiving seat of the substantially rigid body member.
[0020]
In the above configuration, the width of the portion forming the base seal surface (hereinafter referred to as “the base seal surface forming portion”) / the thickness (height) of the gasket = 1/3 to 1/5. It becomes easier to secure the effect.
[0021]
If the shoulder of the seating stabilization lip is chamfered to form a slope, the flange formed by chamfering the shoulder of the seating stabilization lip is compressed by the side surfaces on the lower end of the gasket holding groove of the lid member when the elastic gasket is compressed. It is not compressed, that is, as shown in FIG. 5, there is a gap between both sides of the lower end of the gasket holding groove. Therefore, an unnecessary reaction force against the elastic gasket can be suppressed.
[0022]
Furthermore, the elastic gasket made of acrylic rubber is excellent in oil resistance and heat resistance. When cylinder head cover gaskets are applied, the set compression strain rate (set compression amount) is taken into consideration (incorporated). The ratio of (compression set amount) can be made relatively small, and the effect of the present invention can be made more reliable.
[0023]
And the sealing structure in the case of sealing between a cover member and a main-body member with the said elastic gasket is set as the following structure, when applying to a gasket cover etc., for example.
[0024]
The gasket holding groove of the lid member has a depth of 50% or more of the total height of the elastic gasket, and the elastic gasket is sealed in the gasket holding groove with a compression strain rate of 12 to 35%. In this case, it is possible to ensure the minimum required seal surface pressure.
[0025]
In addition, it is possible to form a warping reinforcing rib located in the middle of the fastening part between the upper side of the gasket holding wall having an inverted L-shaped cross section forming the gasket holding groove and the peripheral wall of the cover member. It is desirable that the deformation due to lifting due to the gasket compression reaction force can be reduced.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a cover gasket (elastic gasket) which is an embodiment of the present invention will be described in detail mainly based on FIGS. In this embodiment, the figure symbols are three digits, and for the parts corresponding to the above-mentioned examples, “1” is added to the hundreds of the same figure symbols, and all or part of the explanation is omitted. There is.
[0027]
In this embodiment, the cylinder head 112 which is a main body member is made of aluminum or cast iron, and has an annular and rigid structure gasket receiving seat 113 as described above.
[0028]
The head cover 114 as a lid member is made of plastic (reinforcing agent filling type: for example, glass fiber 35% filling 66 nylon) and has a substantially non-rigid structure that forms a gasket holding groove 118 corresponding to the gasket receiving seat 113. A gasket holding wall 116 is provided. Here, examples of the “reinforcing agent filling type” include glass fiber 35% filled 66 nylon, glass fiber 25% / inorganic powder 15% filled 66 nylon, and glass fiber 45% filled 6 nylon.
[0029]
Here, “substantially non-rigid body structure” is a term for “substantially rigid body structure”, and not only a material having a low “rigidity” is used as in the present embodiment, but also a thin-walled section modulus is rigid. This includes cases where the structure is low.
[0030]
The cover gasket 124 includes a gasket base 120 having a bottom seal lip 126 that abuts the gasket receiving seat 113, and protrudes upward from the gasket base 120 to fit into the gasket holding groove 118, and a groove bottom 118 a of the gasket holding groove 118. And a groove fitting portion 122 having a top seal lip 128 that is pressed against the groove lip 128.
[0031]
And in this embodiment, in order to solve the above-mentioned subject of the present invention, bottom seal surface formation width B (width of bottom seal lip 126) B of gasket 124 is made relatively small, and total height H of gasket 124 is set. Has been raised. That, B (bottom seal surface formation width) / H (gasket height) = 1 / 3-1 / 5, preferably is 1 / 3.5 to 1 / 4.5. If the B / H value is too large , the bottom seal surface becomes relatively large , and the push-up force (compression reaction force) of the gasket holding wall 116, that is, the groove bottom portion ( nadir portion ) 118a of the gasket holding groove 118 becomes large. On the other hand, if the B / H value is too small, the seating stability of the gasket during compression will be lacking. For example, when the width B of the seal lip 126 is 2.5 to 5 mm as described later, the gasket height is 7.5 to 25 mm.
[0032]
Here, when the width of the gasket receiving seat 113 is 10 mm, the width “b” of the gasket base portion 120 is 5 to 8 mm including the seating stable lip pairs 136 and 136 described later. If the width is too narrow, there will be a problem with the seating stability of the gasket 124. If the width is too wide, there is a risk of sticking out of the side edge of the gasket receiving seat 113 due to variations in assembly of the gasket 124. Problems occur. Further, the height h1 of the gasket base 120 is set to 2 to 4 mm. If the height is too low, it is difficult to absorb gap variations (manufacturing / assembling) between the lower end side surfaces 119 , 119 of the gasket holding groove 118 and the gasket receiving seat 113. On the other hand, if the height is too high, the seating stability of the gasket 124 is insufficient, and the gasket 124 is likely to be bent at the connecting portion between the gasket base portion 120 and the groove fitting portion 122 during fastening. Reference numeral 122a denotes a drop-off preventing rib, which is appropriately provided at a predetermined interval.
[0033]
Here, the bottom seal lip 126 has an inverted trapezoidal cross section, and is provided with a variation absorbing groove 126a at the center, which is an alternative to forming the above-mentioned bottom holding seal protrusions 27 and 27. Naturally, instead of the variation absorbing groove portion 126a or together with the groove portion 126a, as described above, the bottom portion holding seal protrusion may be formed. Furthermore, although the seating stability is inferior, the bottom seal lip 126 may be divided into a plurality of pieces.
[0034]
For example, when the width of the general-purpose gasket receiving seat 113 is 10 mm, the bottom seal lip 126 has a height h2 = 1 to 2 mm and a width B = 2.5 to 5 mm. The width of the variation absorbing groove 126a is about 1 mm and the depth is about 0.3 mm.
[0035]
If the height of the seal lip 126 is too high or too narrow, when the head cover 114 is bolted, the seal lip 126 will bend in the width direction (disengage at the tip), and the compression load will be applied to the gasket seat. It does not act in a direction orthogonal to 113, and it becomes difficult to ensure a predetermined seal surface pressure. Conversely, if the bottom seal lip 126 is too low or too wide, the load for securing a predetermined seal surface pressure is likely to increase relatively, that is, the compression reaction force against the gasket holding wall 116 also increases. Therefore, it becomes difficult to prevent the head cover 114 from being deformed.
[0036]
In the present embodiment, the seating lip pairs 136 and 136 are provided on both sides of the seal lip 126 so that the tip lip is not easily generated even if the width of the bottom seal lip 126 is relatively small. The seating stabilization lip pair 136, 136 has an inner opening angle α = 60 to 120 °, and has a tapered end section with both outer walls substantially upright. If the opening angle is too small or too large, it is difficult to achieve the seating stabilizing effect of the bottom seal lip 126.
[0037]
The seating stability lip pairs 136 and 136 are not for securing the seal surface pressure but for regulating the clearance of the tip of the seal lip 126. That is, as shown in FIG. 5, when the pair of taper ends are subjected to shear resistance on both sides of the seating surface as shown in FIG. It has a sticky action (pseudo truss structure) that supports it from the direction. The tip does not have to be tapered, but a reaction force upward from the seating stabilization lip pair 136, 136 is generated due to the compressive load, and the reaction force received by the groove bottom 118a of the gasket holding groove 118 of the head cover 114 increases. The tips of the seating stabilization lip pairs 136 and 136 are preferably tapered. The outward projecting direction of the seating stability lip pairs 136 and 136 may be horizontal as shown by a two-dot chain line, but a cross-sectional shape with a chamfered shoulder 136a is desirable as shown in the figure. Similarly, when the gasket is compressed, interference between the lower side surfaces 119 and 119 of the holding groove 118 of the head cover 114 and the shoulder 136a causes the same problem as described above. Here, the chamfering angle β of the shoulder 136a is set to 30 to 60 °. When the chamfering angle β is too small, the lower end side surfaces 119 and 119 of the holding groove 118 of the head cover 114 and the shoulder 136a easily interfere with each other. On the other hand, if the chamfer angle β is too large, it is difficult to obtain the tensioning action (supporting action) of the seating stability lip pairs 136 and 136, and it is difficult to achieve the seating stability action.
[0038]
In addition, the groove fitting portion 122 protruding upward from the gasket base portion 120 has a flat end and a tapered shape (a tower-like trapezoid) in the illustrated example. This is because it is easy to insert into the gasket holding groove 118 and retains its shape against falling. Here, the taper is usually set to 1/8 to 1/12. If the taper is too large or too small, the insertion workability into the gasket holding groove is adversely affected. The height of the groove fitting portion 122 is obtained by subtracting the gasket base portion height h from the above-described gasket height H, and is usually 5 to 20 mm. A top auxiliary seal projection 129 is formed on the top of the top seal lip 128 of the groove fitting portion 122 in the same manner as described above. The top auxiliary seal projection 129 is trapezoidal in the example shown in the figure, but may be semicircular, and usually has a base width of 0.5 to 1 mm, a height of 0.2 to 1 mm.
[0039]
The gasket is usually integrally formed by injection molding, transfer molding or the like using a rubber material such as acrylic rubber and nitrile rubber having excellent heat resistance and oil resistance.
[0040]
Next, how the gasket 124 is used will be described.
[0041]
Here, the gasket holding groove 118 of the head cover 114 has a taper opening at a groove bottom side portion 118a of 2 to 4 ° (3 ° in the illustrated example) and taper from an opening side portion (about ¼ from the opening side) 118b. The taper opening has an angle of 30 to 50 ° (40 ° in the illustrated example). This is to facilitate the insertion of the gasket and to improve the shape retention against falling. Further, the depth of the gasket holding groove 118 is 50% or more of the gasket height, preferably 55% or more (about 61.5% in the figure). If the depth is too shallow, a problem is likely to occur in the gasket holding performance of the gasket holding groove 118, and buckling is likely to occur in the groove fitting portion of the gasket.
[0042]
Further, in the present embodiment, the warp preventing rib 138 is provided between the upper side of the gasket holding wall 116 and the peripheral wall of the head cover (lid member) 114 at an intermediate position between the fastening portions 114a and 114a (see FIG. 1) of the gasket holding wall 116. Is formed. This is to reduce the floating deformation of the gasket holding wall 116 due to the gasket compression reaction force at the intermediate position of the fastening part. The thickness of the warp preventing rib 138 is 5 to 15 mm when the above-described glass fiber reinforced nylon 66 is used.
[0043]
In the same manner as described above, the groove fitting portion 122 of the gasket 124 is inserted and held in the gasket holding groove 118 of the inverted head cover 114, and then the head cover 114 is faced down and overlapped with the cylinder head 112, and bolts Fasten with 132. At this time, if the seating stability lip pair 136, 136 abuts against the gasket receiving seat 113 of the cylinder head 112 and the gasket has an assembly inclination during the period from the overlap to the initial fastening, the inclination is compensated. Works. In addition, after the middle stage of the bolt fastening, the seating stabilization lip pairs 136 and 136 effectively convert the compression load into the seal surface pressure by acting as a stick to the central pillar portion of the gasket having a vertically long cross section. To do.
[0044]
Further, since the width of the bottom seal lip is relatively small, the reaction force between the fastening parts (bolts 132) is also small, and as a result, the floating (warp deformation) of the gasket holding wall 116 between the fastening parts is small. . Further, since the overall height of the gasket is relatively high, even if the gasket holding wall 116 is lifted or a gasket compression set is generated, the compression amount variation (absolute amount) is absorbed to change the compression strain rate. Can be reduced. That is, it becomes easy to ensure a predetermined sealing pressure between the gasket receiving seat 113 of the substantially rigid cylinder head 112 and the substantially non-rigid head cover 114.
[Brief description of the drawings]
FIG. 1 is an overall exploded perspective view showing an example of a cylinder head (main body member) / head cover (lid member) pair to which the present invention is applied and a cover gasket (elastic gasket) assembled between them.
FIG. 2 is a partial cross-sectional view when a conventional gasket is fitted and held on a head cover and then placed on a cylinder head and assembled and fastened.
FIG. 3 is an exploded partial cross-sectional view of a cover gasket and a head cover for assembling the cover gasket according to an embodiment of the present invention.
FIG. 4 is a partial cross-sectional view showing a state where the gasket is similarly held in the gasket holding groove of the head cover.
FIG. 5 is a partial cross-sectional view when the gasket is similarly fitted and held on the head cover and then mounted on the cylinder head and assembled and fastened.
[Explanation of symbols]
12, 112: Cylinder head (main body member)
13, 113: Gasket receptacles 14, 114: Head cover (lid member)
16, 116: Gasket holding wall 18, 118: Gasket holding groove 20, 120: Gasket base portion 22, 122: Groove fitting portion 24, 124: Cover gasket 26, 126: Bottom seal lip 28, 128: Top seal lip 136 : Seating stability lip 138: Warpage prevention rib

Claims (6)

An elastomer is sealed between a body member having an annular and substantially rigid structure gasket receiving seat and a lid member having a substantially non-rigid structure gasket retaining wall corresponding to the gasket receiving seat. In an elastic gasket formed from a material,
A gasket base portion having one or a plurality of bottom seal lips pressed against the gasket seat, a top seal lip protruding upward from the gasket base portion and pressed against the groove bottom portion of the gasket holding groove, and the gasket A groove fitting portion that fits into the holding groove, and
A seating stabilization lip whose tip abuts against the gasket receiving seat is provided on both sides of the bottom seal lip forming portion,
Elastic shoulder of the seating stabilizing lip, is chamfered at 30 to 60 °, when the elastic gasket compression, characterized in that it is to have a gap between the lower end sides of the gasket retention groove gasket.   2. The elastic gasket according to claim 1, wherein the width of the portion forming the bottom seal lip (the seal lip forming portion) / the thickness of the gasket (height) = 1/3 to 1/5.   The elastic gasket according to claim 1 or 2, wherein the elastic gasket is formed of an elastomer material having a hardness Hs (JIS A) of 50 to 70.   4. The elastic gasket according to claim 1, wherein the elastic gasket is a cylinder head cover gasket.   In the structure in which the gap between the lid member and the main body member is sealed with the elastic gasket according to claim 1, the depth of the gasket holding groove of the lid member has 50% or more of the gasket height, A sealing structure between a lid member and a main body member, wherein the elastic gasket is capable of ensuring a minimum required sealing surface pressure when loaded with a predetermined compressive strain rate of 12 to 35%.   6. A warping prevention rib is formed between a fastening portion between an upper side of an inverted L-shaped gasket holding wall forming the gasket holding groove and a peripheral wall of the lid member. The sealing structure between the lid member / main body member as described.

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