Sealing structure

Abstract

In this sealing structure, the width (W2) of a recessed part (54) is larger than the width (W1) between both side surfaces (51) of a base part (51), and a central part (Q) in the width direction of the recessed part (54) is positioned closer to the base part (51) side than a tip (apex P) of a pair of protruding parts (531) (532), and thus the rigidity of the recessed part (54) is relatively small. As a result, the volume (amount) of a liquid gasket (6) extruded from the recessed part (54) can be reduced.

Description

Seal Structure

[0001] The present invention relates to a seal structure for sealing between joining surfaces of three members.

[0002] For example, in a conventional sealing structure, as described in Patent Document 1 below, a resin gasket is provided between the joint surfaces of a head cover, a chain cover, and a cylinder head in an internal combustion engine to seal the joint surfaces, and a liquid gasket is provided between the joint surfaces of the chain cover and the cylinder head to seal the joint surfaces.

[0003] The gasket has a base portion that is accommodated in a groove formed in the joining surface of the head cover, a sealing portion that is sandwiched between the joining surfaces of the head cover, the chain cover, and the cylinder head, and a recess that stores a liquid gasket that is sandwiched between the joining surfaces of the chain cover and the cylinder head.

[0004] However, in the conventional seal structure, the width of the recess is narrower than the width of the base, which increases the strength of the recess. As a result, when the head cover is joined to the chain cover and cylinder head, the base is compressed within the groove. When the recess protrudes toward the chain cover and cylinder head, the force pushing out the liquid gasket that accumulates in the recess becomes strong. This causes the liquid gasket in the recess to be forcefully pushed out toward both ends of the recess, which can reduce the volume (amount) of the liquid gasket retained in the recess. This leaves room for improvement.

[0005] Japanese Patent Application Laid-Open No. 2007-024210

[0006] In one aspect, the present invention provides a seal structure in which a first member is joined across joining surfaces of a second member and a third member that overlap each other, and in which the first member, the second member, and the third member are joined together, the seal structure sealing the joining surfaces of the first member, the second member, and the third member, the seal structure comprising: a gasket sealing the joining surfaces of the first member, the second member, and the third member; and a liquid gasket sealing the joining surfaces of the second member and the third member, the gasket comprising a base portion that opens into the joining surface of the first member and is held in an elastic state in a groove formed along the circumferential direction of the joining surface; and both sides of an outer end portion of the base that face outward from the opening of the groove. a sealing portion extending from the edge in a width direction perpendicular to the circumferential direction and sandwiched between the joining surfaces of the first member and the second and third members; a pair of protrusions provided on both ends in the width direction at the bottom of the sealing portion facing the second and third members and protruding from the bottom toward the second and third members; and a recess provided between the pair of protrusions in the width direction and recessing the bottom toward the base to hold the liquid gasket, wherein the width of the recess in the width direction is set larger than the width between both side surfaces of the base, and the center of the recess in the width direction is located closer to the base than the tips of the protrusions.

[0007] In this way, the width of the recess is greater than the width between the two side surfaces of the base, and the widthwise center of the recess is positioned closer to the base than the tips of the protrusions, which makes the recess relatively less rigid. Therefore, when the first member is joined to the second member and the third member, the base is compressed within the groove, and when the recess protrudes toward the second member and the third member, the force pushing out the liquid gasket that accumulates in the recess can be reduced. This reduces the volume (amount) of the liquid gasket that is pushed out of the recess.

[0008] FIG. 6 is an exploded perspective view of three members of an internal combustion engine to which the present invention is applied. FIG. 7 is a side view of the internal combustion engine shown in FIG. 1. FIG. 8 is a perspective view of a resin gasket according to a first embodiment of the present invention. FIG. 9 is a cross-sectional view taken along line A-A in FIG. 3. FIG. 10 is a transverse cross-sectional view of a resin gasket showing the results of a simulation of the flow behavior of a liquid gasket accompanying compressive deformation of the resin gasket shown in FIG. 4. FIG. 11 is a perspective view of a resin gasket according to a second embodiment of the present invention. FIG. 12 is a cross-sectional view taken along line B-B in FIG.

[0009] Each embodiment of the sealing structure according to the present invention will be described in detail below with reference to the drawings. In each of the following embodiments, the sealing structure according to the present invention will be described in terms of its application to an internal combustion engine for an automobile, as in the conventional case. Note that the present invention is not limited to the internal combustion engine for an automobile exemplified in each of the following embodiments, and can also be applied to configurations other than the above-described internal combustion engine, as long as it spans the joining surfaces of three members.

[0010] First Embodiment FIGS. 1 to 5 show a first embodiment of a seal structure according to the present invention.

[0011] (Configuration of Internal Combustion Engine) FIG. 1 shows a perspective view of an internal combustion engine EG to which a seal structure according to the present invention is applied, and FIG. 2 shows a side view of the internal combustion engine EG shown in FIG.

[0012] 1 and 2, an internal combustion engine EG to which the seal structure according to the present invention is applied mainly comprises a cylinder block 1, which corresponds to the second member according to the present invention, a cylinder head 2, which corresponds to the third member according to the present invention, and a front cover 3, which corresponds to the first member according to the present invention. Both the cylinder block 1 and the cylinder head 2 are formed by casting or the like from a metal material such as an aluminum alloy. The cylinder head 2 is disposed on top of the cylinder block 1. The front cover 3 covers the front ends of the cylinder block 1 and the cylinder head 2.

[0013] A metal gasket 4, for example, made of metal, is interposed between the joint surfaces of the cylinder block 1 and the cylinder head 2, i.e., between the upper end surface 11 of the cylinder block 1 and the lower end surface 21 of the cylinder head 2, which overlap each other. Furthermore, a resin gasket 5, for example, made of a heat-resistant rubber or resin material, is provided between the joint surfaces of the three members, i.e., between the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2 and the inner surface 31 of the front cover 3. A liquid gasket 6 is provided between the metal gasket 4 and the resin gasket 5 to fill gaps formed between the metal gasket 4 and the resin gasket 5 at the joint surfaces of the three members, thereby sealing the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2 and the inner surface 31 of the front cover 3.

[0014] (Sealing Structure) Fig. 3 shows an enlarged perspective view of the essential parts of the resin gasket 5, viewed from below. Fig. 4 shows a widthwise cross-sectional view (transverse cross-sectional view) of the resin gasket 5, taken along line A-A in Fig. 3. The imaginary lines shown in Fig. 4 indicate the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2 and the groove 32 of the front cover 3, and the center line Z indicates the widthwise center of the transverse cross section of the resin gasket 5, with the resin gasket 5 being formed symmetrically across the center line Z in the widthwise direction.

[0015] 3 and 4, the resin gasket 5 is made of a resin material and formed in a generally rectangular ring shape along the peripheral edge of the front cover 3, and integrally includes a base 51, a sealing portion 52, and a pair of protrusions 531, 532, which are formed symmetrically with respect to the center line Z. In addition, a recess 54 recessed toward the base 51 is formed between the pair of protrusions 531, 532 in the width direction.

[0016] The base 51 extends along the depth direction of a series of grooves 32 formed as recesses along the circumferential direction on the inner surface 31 of the front cover 3, and is held in an elastic state within the grooves 32. That is, when the front cover 3 is attached, the front cover 3 is pressed against the cylinder block 1 and the cylinder head 2, causing the base 51 to compress and deform in the height direction of the resin gasket 5 (the vertical direction in FIG. 4 ).

[0017] Furthermore, a pair of protrusions 55 are formed on both side surfaces 510 in the width direction of the base 51, so as to be symmetrical with respect to the center line Z. The protrusions 55 elastically contact the inner surface 322 of the groove 32 and function to prevent the base 51 from slipping out of the groove 32. The pair of protrusions 55 may be provided intermittently in the circumferential direction on both side surfaces 510 of the base 51, or may be provided continuously along the circumferential direction.

[0018] The seal portions 52 extend from both side edges of the outer end of the base portion 51, which faces outward through the opening 320 of the groove portion 32, in a width direction (left-right direction in FIG. 4 ) perpendicular to the circumferential direction, to the outside beyond both side surfaces 510 of the base portion 51. The seal portions 52 have a first seal surface 521 parallel to the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, and a second seal surface 522 parallel to the inner surface 31 of the front cover 3. That is, the seal portions 52 are sandwiched between the joining surfaces of the cylinder block 1 and the cylinder head 2 and the front cover 3, and the first seal surface 521 comes into close contact with the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, and the second seal surface 522 comes into close contact with the inner surface 31 of the front cover 3, thereby providing a liquid-tight seal between the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2 and the inner surface 31 of the front cover 3.

[0019] The pair of protrusions 531, 532 protrude toward the opposite side of the base 51 of the seal portion 52 (toward the bottom 520), and extend generally parallel to the circumferential direction of the resin gasket 5 so as to face both widthwise ends of the seal portion 52. When the front cover 3 is pressed against the cylinder block 1 and the cylinder head 2, the resin gasket 5 is compressed and deformed in the height direction (the up-and-down direction in FIG. 4 ), so that the pair of protrusions 531, 532 elastically contact the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, thereby providing a liquid-tight seal between the cylinder block 1 and the outer surfaces 12, 22 of the cylinder head 2.

[0020] Furthermore, in the region spanning the joining surfaces of the cylinder block 1 and the cylinder head 2 and filled with the liquid gasket 6, the pair of protrusions 531, 532 are provided such that the apex P of each of the protrusions 531, 532 is located outside the both side surfaces 510 of the base 51 in the width direction. In other words, the pair of protrusions 531, 532 are provided such that the width W2 of the recess 54 in the width direction is larger than the width W1 between the both side surfaces 510 of the base 51. As a result, the recess 54 is provided so as to extend over a width direction region that is relatively larger than the width direction region between the both side surfaces 510 of the base 51.

[0021] Furthermore, in the region spanning the joining surfaces of the cylinder block 1 and the cylinder head 2 and filled with the liquid gasket 6, a pair of end wall constituent portions 533, 534 are provided at both circumferential ends, connecting the pair of protrusions 531, 532. The pair of end wall constituent portions 533, 534 cooperate with the pair of protrusions 531, 532 to form a generally oval annular protrusion 53 that surrounds the joining surfaces of the cylinder block 1 and the cylinder head 2 and defines a closed space between the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2 (see FIG. 3 ).

[0022] The tip portions of the pair of protrusions 531, 532 have curved surfaces that are arc-shaped in the widthwise cross section shown in FIG. 4. In this embodiment, the tip portions of the pair of protrusions 531, 532 have asymmetric shapes in which the first curved surfaces 531a, 532a located on the inner side in the widthwise direction (toward the recess 54) and the second curved surfaces 531b, 532b located on the outer side in the widthwise direction (toward the seal portion 52) have different curvatures. Specifically, the tip portions of the pair of protrusions 531, 532 are formed so that the radius of curvature R1 of the first curved surfaces 531a, 532a is larger than the radius of curvature R2 of the second curved surfaces 531b, 532b. As a result, the inner surface of the recess 54 is formed to be approximately arc-shaped in the widthwise cross section shown in FIG. 4.

[0023] 4, the recess 54 is formed such that, in the height direction of the resin gasket 5 (the up-and-down direction in FIG. 4), at least the center Q of the bottom 540 of the recess 54 is located closer to the base 51 than the tips (vertices P) of the pair of protrusions 531, 532. As a result, the pair of protrusions 531, 532 abut against the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, respectively, and thereby define a concave seal retaining space S between the recess 54 and the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, capable of retaining the liquid gasket 6.

[0024] (Flow Behavior of Liquid Gasket) FIG. 5 shows the results of a simulation of the flow behavior of the liquid gasket 6 accompanying compressive deformation of the resin gasket 5 that occurs when the front cover 3 is placed over the cylinder block 1 and the cylinder head 2 .

[0025] That is, as the front cover 3 is attached to the liquid gasket 6 in an unpressurized state as shown in Figure 5(a), the resin gasket 5 is pressed toward the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2. Then, as shown in Figure 5(b), the liquid gasket 6 first has difficulty entering the relatively narrow space between the joining surfaces of the cylinder block 1 and the cylinder head 2, and expands in the width direction. Here, because the pair of protrusions 531, 532 are formed wide, a pressing force acts on the liquid gasket 6 in the recess 54, mainly toward the cylinder block 1 and the cylinder head 2, as shown by the arrows in Figure 5(b), and the outward flow of the liquid gasket 6 is suppressed.

[0026] Next, the resin gasket 5 is pressed further toward the cylinder block 1 and cylinder head 2 until the leading end of the resin gasket 5 abuts against the outer surfaces 12, 22 of the cylinder block 1 and cylinder head 2, respectively. As shown in Figure 5(c), the liquid gasket 6 is pressed by the recess 54 and forced into the seal groove G between the joining surfaces of the cylinder block 1 and the cylinder head 2. At this time, because the pair of protrusions 531, 532 are formed wide, the liquid gasket 6 is forced into the seal groove G while being held by the wide recess 54 with a wide pushing width.

[0027] Thereafter, the resin gasket 5 is further pressed toward the cylinder block 1 and cylinder head 2, and the leading end of the resin gasket 5 is compressively deformed, causing the liquid gasket 6 to begin to escape outward in the width direction within the seal groove G, as shown in Figure 5(d).The resin gasket 5 is then further pressed from this state, and is pushed in to a depth position where the center Q of the bottom 540 of the recess 54 is flush with the outer surfaces 12, 22 of the cylinder block 1 and cylinder head 2.The liquid gasket 6 within the recess 54 is then completely filled within the seal groove G, as shown in Figure 5(e), and is held within the seal groove G.

[0028] (Effects of the Present Embodiment) From the above configuration, in the seal structure according to the present embodiment, the width W2 of the recess 54 is larger than the width W1 between the both side surfaces 510 of the base 51, and the center Q of the recess 54 is formed to be located closer to the base 51 than the tips (vertices P) of the protrusions 531, 532. This results in a relatively low rigidity of the recess 54. Therefore, when the cylinder block 1 and the cylinder head 2 are joined to the front cover 3, the base 51 is compressed within the groove 32, causing the recess 54 to protrude toward the cylinder block 1 and the cylinder head 2. This reduces the force that pushes out the liquid gasket 6 that accumulates in the recess 54. This reduces the volume (amount) of the liquid gasket 6 that is pushed out of the recess 54.

[0029] In addition, in this embodiment, the tip portions of the pair of protrusions 531, 532 have asymmetric shapes in which the first curved surfaces 531a, 532a located on the inner side in the width direction (toward the recess 54) and the second curved surfaces 531b, 532b located on the outer side in the width direction (toward the seal portion 52) have different curvatures. Specifically, the tip portions of the pair of protrusions 531, 532 according to this embodiment are formed so that the radius of curvature R1 of the first curved surfaces 531a, 532a is larger than the radius of curvature R2 of the second curved surfaces 531b, 532b. This makes it possible to suppress stress concentration on the first curved surfaces 531a, 532a that come into pressure contact with the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2, respectively.

[0030] In this embodiment, a pair of protrusions 55 that can elastically contact the inner surface 322 of the groove 32 is formed on both side surfaces 510 in the width direction of the base 51. As a result, the protrusions 55 elastically contact the inner surface 322 of the groove 32, which effectively prevents the base 51 from coming off the groove 32 and ensures appropriate sealing properties of the resin gasket 5.

[0031] (Modifications) In the first embodiment, as one example of configuring the tip ends of the pair of protrusions 531, 532 to have an asymmetrical shape, the radius of curvature R1 of the first curved surfaces 531a, 532a is larger than the radius of curvature R2 of the second curved surfaces 531b, 532b. However, the radius of curvature R1 of the first curved surfaces 531a, 532a and the radius of curvature R2 of the second curved surfaces 531b, 532b may have an inverse relationship. In this way, when the radius of curvature R2 of the second curved surfaces 531b, 532b is formed larger than the radius of curvature R1 of the first curved surfaces 531a, 532a, it is possible to ensure a larger volume of the recess 54. This allows a larger amount of liquid gasket 6 to be held in the recess 54, allowing a larger amount of liquid gasket 6 to remain in the recess 54 within the seal groove G.

[0032] 6 and 7 show a second embodiment of the seal structure according to the present invention, in which the configurations of the pair of protrusions 531, 532 and the recess 54 are modified. Note that the basic configuration other than these modifications is the same as that of the first embodiment, and therefore the same components as those of the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0033] Fig. 5 shows an enlarged perspective view of the resin gasket 5 according to this embodiment, in which the essential parts of the resin gasket 5 are enlarged and displayed from below. Fig. 7 shows a cross-sectional view of the resin gasket 5 taken along line B-B in Fig. 6.

[0034] 7, in the seal structure according to this embodiment, a pair of protrusions 531, 532 are formed symmetrically with respect to an apex P, and the radius of curvature R1 of the first curved surfaces 531 a, 532 a and the radius of curvature R2 of the second curved surfaces 531 b, 532 b at the tips of the protrusions 531, 532 are formed to be approximately equal. Furthermore, in this embodiment, the recess 54 is formed so that the bottom 540 is flat and horizontal, as shown in FIGS.

[0035] As described above, in this embodiment, the radius of curvature R1 of the first curved surfaces 531 a, 532 a and the radius of curvature R2 of the second curved surfaces 531 b, 532 b are substantially equal at the tip ends of the pair of protrusions 531, 532. This prevents stress from concentrating on either the first curved surfaces 531 a, 532 a or the second curved surfaces 531 b, 532 b when the resin gasket 5 is pressed against the outer surfaces 12, 22 of the cylinder block 1 and the cylinder head 2.

[0036] The present invention is not limited to the configurations exemplified in the above-described embodiments, but can be freely modified depending on the specifications of the joining surfaces of the three components to which the present invention is applied, such as the specific shapes of the base 51, the seal portion 52, and the pair of protrusions 531, 532, and the presence or absence of the convex portion 55.

Claims

1. A seal structure in which a first member is joined across the joining surfaces of a second member and a third member that overlap each other, and which seals between the joining surfaces of the first member, the second member, and the third member at the joining portions of the first member, the second member, and the third member, comprising: a gasket that seals between the joining surfaces of the first member, the second member, and the third member; and a liquid gasket that seals between the joining surfaces of the second member and the third member, wherein the gasket has: a base that opens into the joining surface of the first member and is held in an elastic state in a groove that is formed along the circumferential direction of the joining surface; a seal portion that extends in a width direction perpendicular to the circumferential direction from both side edges of the outer end of the base that faces outward from the opening of the groove, and is sandwiched between the joining surfaces of the first member, and the second member and the third member; and a pair of protrusions that are provided on both ends in the width direction at the bottom of the seal portion that faces the second member and the third member, and that protrude from the bottom toward the second member and the third member. a recess provided between the pair of protrusions in the width direction, the bottom of which is recessed toward the base to hold the liquid gasket, wherein the width of the recess in the width direction is set to be larger than the width between both side surfaces of the base, and the center of the recess in the width direction is located closer to the base than the tips of the protrusions.

2. A seal structure as claimed in claim 1, wherein the tip ends of the pair of protrusions have curved surfaces whose cross sections in the width direction are arc-shaped, and the curved surfaces are formed in an asymmetric shape with different curvatures on the inside and outside in the width direction, with the radius of curvature on the inside being larger than that on the outside.

3. A seal structure as claimed in claim 1, wherein the tip ends of the pair of protrusions have curved surfaces whose cross sections in the width direction are arc-shaped, and the curved surfaces are formed symmetrically so that the radii of curvature are equal on the inside and outside in the width direction.

4. A seal structure according to any one of claims 1 to 3, wherein the base has a pair of protrusions on both sides in the width direction that are capable of elastically contacting the inner surfaces of the groove.

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