JP3309513B2 - Cylinder head gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head gasket interposed between a cylinder head and a top deck of a cylinder block in an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, this kind of cylinder head gasket has a bore hole for communicating a cylinder bore and a combustion chamber, and is interposed between a top deck portion of a cylinder block and a cylinder head when used. And these three are fastened by a head bolt.

[0003] The cylinder head gasket is required to have a function of sealing high-temperature and high-pressure combustion gas generated in the combustion chamber. Therefore, it is important to increase the contact pressure (surface pressure) generated between the periphery of the cylinder bore in the top deck portion and the periphery of the bore hole in the cylinder head gasket when fastening with the head bolt. Similarly, it is important to increase the contact pressure (surface pressure) generated between the periphery of the combustion chamber in the cylinder head and the periphery of the bore hole in the cylinder head gasket.

Therefore, a cylinder head gasket having a hard shim having a constant thickness arranged around the bore hole has been put to practical use. In addition, instead of using shims, those using grommets or wiring or forming beads are also known.

When the cylinder head is fastened to the cylinder block with the cylinder head gasket interposed therebetween,
The cylinder bore may be distorted and the roundness may be reduced.
8, the top deck portion 53 of the cylinder block 52 is lifted toward the cylinder head 54 by tightening the head bolt 51, as indicated by the solid line in FIG.
At this time, as compared with the periphery of the cylinder bore 56 where the shim 55 is disposed, the head bolt hole 57 without the shim 55 is lifted more. As a result, the top deck 53
As the distance from the cylinder bore 56 increases, the cylinder head 54 is inclined closer to the cylinder head 54. Along with this, the bore wall 58 having the cylinder bore 56 is deformed outward (in the direction indicated by the arrow), and the roundness of the cylinder bore 56 is reduced. This problem also occurs when a grommet, wiring, a bead, or the like is used instead of the shim 55.

As a technique for addressing the above-mentioned problem, for example, there is a technique disclosed in Japanese Utility Model Laid-Open Publication No. 1-1070. In this technique, as shown in FIG. 9, a shim 61 is provided near an insertion hole 59 for a head bolt 51 and outside of a bore hole 60 from the center of the insertion hole 59.
Such a configuration is devised such that the distortion of the cylinder bore 56 is caused only by the tightening force of the head bolt 51.

[0007]

However, the occurrence of distortion of the cylinder bore 56 depends not only on the tightening force of the head bolt 51 but also on the rigidity of the top deck portion 53.
For example, in recent years, in order to reduce the weight of an engine, it has been required to reduce its overall length (length in the cylinder arrangement direction). In order to meet this demand, it has been considered to provide a bolt hole 63 in the cylinder block 52 into which the bolt 62 for mounting the engine mount is screwed, as shown by a two-dot chain line in FIG.

In this case, the boss 6 having the bolt holes 63
4, when the top deck 53 and the bore wall 58 are connected, the boss 6
The rigidity of the portion corresponding to No. 4 is higher than the other portions.
Then, the tightening force of the head bolt 51 on the top deck portion 53 is transmitted to the bore wall 58 via the boss portion 64, and the bore wall 58 is pulled. Therefore, the bore wall 58 is further deformed by the amount of the tension, and the cylinder bore 5 is deformed.
6 is greatly distorted.

Therefore, the above-mentioned publication technique in which the rigidity of the top deck portion 53 is not taken into consideration cannot completely cope with the deformation of the bore wall 58 caused by the boss portion 64, and the cylinder bore 5
6 cannot be sufficiently reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to open a cylinder block corresponding to a part having high rigidity even in a part of a top deck portion of the cylinder block. An object of the present invention is to provide a cylinder head gasket capable of suppressing a part of a peripheral part of a hole from being deformed more than other parts and making the amount of distortion of the opening uniform.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a cylinder block which is interposed between a top deck portion of a cylinder block and a cylinder head which are fastened to each other by a fastening member. An annular surface for adjusting the contact pressure with the top deck and the cylinder head around the holes provided corresponding to the cylinder bores of the cylinder block, while pressing against the deck and the cylinder head to seal between them. a cylinder head gasket having a pressure adjusting means, before
Around the cylinder bore, a part of its circumference is
A fastening portion where the binding member is fastened and a wall surface of the cylinder bore;
The thickness of the top deck part between is more local than other parts
Area is formed, and the cylinder bore circumference
In the part where the thickness of the top deck part is locally large
The surface pressure adjusting force of the surface pressure adjusting member of
It is set smaller than other parts of the surface pressure adjusting member .

[0012]

[Action] A cylinder head gasket is interposed between the top deck of the cylinder block and the cylinder head,
In a state where these are fastened to each other by the fastening member, the top deck portion is lifted toward the cylinder head. At this time, the top deck portion, than the surrounding apertures or the cylinder head aperture of arranged cylinder block of the surface pressure adjusting members, is lifted so high as near the fastening member without the member. As a result, the top deck portion is inclined so as to be closer to the cylinder head as the distance from the opening increases. Along with this, the periphery of the opening in the cylinder block is deformed outward. The amount of deformation at this time differs depending on the rigidity of the top deck portion. In other words, in places where the rigidity is high, the tightening force of the fastening member extends to the peripheral portion of the opening, and the portion is strongly pulled toward the fastening member.

On the other hand, in the present invention, the cylinder bore
The thickness of the top deck is locally large in the circumferential direction
Area, that is, the rigidity of the top deck
The surface pressure of the surface pressure adjustment member in the part located at the raised part
Adjustment force is located at the lower rigidity of the top deck
It is set smaller than other parts of the same surface pressure adjusting member . For this reason, in the top deck portion, the lift amount near the fastening member at the high rigidity portion is smaller than the lift amount near the fastening member at the low rigidity portion. Then, the peripheral portion of the opening is strongly pulled at the high rigidity portion by the tightening force of the fastening member, but the amount of deformation of the peripheral portion of the opening due to the pull is offset by a decrease in the lifting amount in the top deck portion. as a result,
Irrespective of the degree of rigidity of the top deck, the amount of distortion of the opening becomes almost uniform in any part.

[0014]

FIG. 1 shows an embodiment in which the present invention is embodied in a cylinder head gasket applied to a multi-cylinder engine.
4 will be described with reference to FIG.

As shown in FIG. 2, a plurality of substantially cylindrical bore walls 2 having open upper and lower ends are arranged in a cylinder block 1 of the engine. Inside each bore wall 2 is a cylinder bore 3 as an opening of the cylinder block 1, in which a piston is housed so as to be able to reciprocate. A water jacket 4 is formed around the bore wall 2. The water jacket 4 is a passage through which cooling water for cooling the bore wall 2 and the combustion chamber passes. A plurality of head bolt holes 6 are drilled around each bore wall 2 in the top deck portion 5 constituting the upper portion of the cylinder block 1.

In order to shorten the overall length of the engine (the length in the arrangement direction of the bore walls 2), a plurality of bolt holes 7 are formed in one side (the left side in FIG. 2) of the cylinder block 1. . When the engine mount is mounted on the cylinder block 1, these bolt holes 7 are used for mounting bolts 8.
Is a hole to be screwed. More specifically, as shown in FIGS. 1 and 2, a boss portion 9 having a bolt hole 7 extending in the arrangement direction of the bore walls 2 is provided in the cylinder block 1. The boss portion 9 connects the top deck portion 5 and the bore wall 2. Therefore, the top deck 5
In this case, the rigidity of the portion corresponding to the boss portion 9 (the portion surrounded by a dashed line in FIG. 2) is higher than other portions where the boss portion 9 is not provided.

As shown in FIG. 1, the top deck 5
, A cylinder head 12 is stacked with a cylinder head gasket (hereinafter simply referred to as a gasket) 11 interposed therebetween. These three members 5, 11 and 12 are fastened and fixed by a plurality of head bolts 13 as fastening members. In the cylinder head 12, a combustion chamber 15 is formed at a location corresponding to the cylinder bore 3.

The gasket 11 has a substrate 16 having elasticity. The substrate 16 is formed of a metal plate having a constant thickness at any position. In the substrate 16, a bore hole 17 is formed at a position corresponding to the cylinder bore 3 and the combustion chamber 15 to allow the two 3 and 15 to communicate with each other. Further, the head bolt 13 is provided on the substrate 16.
Insertion hole 18 is formed. An annular bead 21 is formed around each of the bore holes 17 of the substrate 16.
Each bead 21 projects downward (toward the top deck 5),
It has a circular cross section. These beads 21 hold the cylinder head 1 when the head bolt 13 is tightened.
2 and the upper surface of the top deck portion 5 are elastically pressed against each other.

On the lower surface of the substrate 16, an annular shim 22 having a predetermined thickness is fixed between the bead 21 and the peripheral edge of each bore hole 17. The shim 22 is a surface pressure adjusting unit for adjusting the contact pressure (surface pressure) of the gasket 11 with respect to the top deck 5 and the cylinder head 12.
Make up the material . More specifically, the gasket 11 is required to have a function of sealing high-temperature and high-pressure combustion gas generated in the combustion chamber 15 during operation of the engine. For this reason, the surface pressure generated between the periphery of the cylinder bore 3 in the top deck portion 5 and the periphery of the bore hole 17 of the gasket 11 is increased by the shim 22. Similarly, the periphery of the combustion chamber 15 in the cylinder head 12 and the gasket 1
The surface pressure generated between the periphery of one of the bore holes 17 is increased by the shim 22.

In this embodiment, as shown in FIGS. 3 and 4,
The thickness of the shim 22 in the high-rigidity portion (the portion surrounded by the dashed line in FIG. 3) of the top deck portion 5, that is, the portion where the boss portion 9 is provided is larger than the thickness of the other low-rigidity portions. Is also set small. In other words, in the portion of the gasket 11 having the shim 22, the intervals between the portions that come into contact with the top deck portion 5 and the cylinder head 12 are t1 and t2. The interval t1 is an interval at a location where the top deck portion 5 has high rigidity (the left side in FIG. 4). The interval t2 is an interval at a location where the rigidity of the top deck portion 5 is low (the right side in FIG. 4). In this embodiment, t1 <
The intervals t1 and t2 are set so as to be t2. With this setting, the top deck portion 5 having high rigidity of the shim 22 is formed.
Are smaller than the surface pressure adjusting force of the shim 22 corresponding to the low-top deck portion 5 having low rigidity.

As described above, as a method of changing the thickness of the shim 22 only partially, a method of pressing only a predetermined portion of an annular shim material having a constant thickness to reduce the thickness, and a method of reducing the thickness of the C shape are used. Any method may be used in which a separate thin shim material is joined to the rest of the shim material.

Next, the operation and effect of the embodiment constructed as described above will be described. As shown in FIG. 1, a gasket 11 is interposed between the top deck portion 5 and the cylinder head 12, and these gaskets 11 are connected to a plurality of head bolts 13.
The top deck portion 5 is lifted toward the cylinder head 12 in a state where they are fastened to each other. At this time, the top deck 5 is provided with the cylinder bore 3 in which the shim 22 is arranged.
Is lifted higher near the head bolt hole 6 where the shim 22 is not provided than in the surrounding area. As a result, the top deck 5
The cylinder head 12 becomes farther away from the cylinder bore 3.
Incline to approach. Accordingly, the bore wall 2 is deformed outward (in the direction indicated by the arrow).

The amount of deformation at this time depends on the rigidity of the top deck 5. That is, at the location where the boss 9 is provided, the boss 9 connects the top deck portion 5 and the bore wall 2 to increase the rigidity of the top deck portion 5. Therefore, when the top deck portion 5 is lifted, the tightening force of the head bolt 13 at that time is transmitted to the bore wall 2 via the boss portion 9, and the bore wall 2 is further pulled outward. Therefore, assuming that the thickness of the shim 22 is uniform at any portion, the high-rigidity portion having the boss 9 is further deformed as shown by a two-dot chain line in FIG.

However, in this embodiment, the thickness of the shim is set in consideration of the rigidity of the top deck 5, and
Interval t at a high rigidity point than interval t2 at a low rigidity point
1 is smaller. That is, the surface pressure adjusting force of the portion of the shim 22 corresponding to the top deck portion 5 having high rigidity is smaller than the surface pressure adjusting force of the portion of the shim 22 corresponding to the top deck portion 5 having low rigidity. For this reason, the head bolt 1 is higher in the high rigidity area than in the low rigidity area.
The lifting amount in the vicinity of 3 is reduced. Then, the boss 9
Although the bore wall 2 is strongly pulled by
The amount of deformation of the bore wall 2 due to the tension is offset by the decrease in the amount of lifting. As a result, the amount of distortion of the bore wall 2 can be made substantially uniform regardless of the level of rigidity.

Further, according to this embodiment, the gasket 1
(1) The gas sealing property is improved. This is because, at the high rigidity portion of the top deck 5, the tightening force of the head bolt 13 directly acts on the peripheral portion of the cylinder bore of the top deck 5 via the boss 9, so that the shim 22 and the top deck 5
The surface pressure between them becomes higher than the surface pressure in portions other than the high rigidity. At this time, assuming that the thickness of the shim 22 is constant, the surface pressure between the shim 22 and the top deck portion 5 at a position slightly away from the boss portion 9 increases at the high rigidity portion. Drops by the amount Therefore, there is a possibility that the combustion gas leaks from the portion where the surface pressure is reduced.

On the other hand, in the present embodiment, since the thickness of the shim 22 corresponding to the high-rigidity portion of the top deck portion 5 is reduced, the surface pressure at the same portion is correspondingly reduced.
Due to this decrease in surface pressure, the surface pressure becomes almost constant at any part of the shim 22. For this reason, gas sealing performance can be improved and gas leakage can be eliminated.

The present invention is not limited to the configuration of the above-described embodiment, and may be arbitrarily changed without departing from the gist of the present invention, for example, as follows. (1) As the surface pressure adjusting member , the shim 22 in the above embodiment is used.
Instead, a wiring 23 and a grommet 24 as shown in FIG. 5 may be used. The wiring 23 is fitted on the inner peripheral edge of the bore 17 of the graphite substrate 16 and is locked by a grommet 24 formed in a U-shaped cross section. In this case, the interval between the upper surface and the lower surface of the grommet 24 corresponds to the intervals t1 and t2 in the embodiment. The left side portion in FIG. 5 corresponds to a portion of the top deck portion 5 with high rigidity, and the wiring 23 is crushed in advance.
Further, the right side portion in FIG. 5 corresponds to a portion of the top deck portion 5 where the rigidity is low. The intervals t1 and t2 are set so that t1 <t2 is satisfied.

(2) As the surface pressure adjusting member , a bead 25 as shown in FIG. FIG. 3A shows an example in which one bead 25 is formed on the substrate 16. (B) shows an example in which another substrates 26 and 27 are laminated on both sides of the substrate 16 and beads 25 are formed on them. In the case of (a), the height of the bead 25 (the distance between the upper surface of the substrate 16 and the lower end surface of the bead 25) corresponds to the distances t1 and t2 in the embodiment. In the case of (b), the interval between the upper end surface of the upper bead 25 and the lower end surface of the lower bead 25 corresponds to the intervals t1 and t2 in the embodiment.

(3) In FIG. 7A, the surface pressure adjusting force is changed by adjusting the height (interval t1, t2) of the bead 25. However, as shown in FIG.
May be the same (interval t1), and the surface pressure adjusting force may be changed by adjusting the bead widths w1 and w2. The left part of FIG. 6 corresponds to a portion of the top deck portion 5 where the rigidity is high, and the right portion corresponds to a portion of the top deck portion 5 where the rigidity is low. Each bead width is set to w1 such that the surface pressure adjusting force of the portion corresponding to the top deck portion 5 having high rigidity of the bead 25 is smaller than the surface pressure adjusting force of the portion corresponding to top deck portion 5 having low rigidity. > W2.

[0030]

[0031]

According to the present invention as described in detail above, shea
The thickness of the top deck is limited in the circumferential direction of the
The part that is locally enlarged, that is, the rigidity of the top deck
Surface pressure adjustment of the part located at the site where the property is locally increased
The surface pressure adjusting force of the adjusting member and the rigidity of the top deck are lower
Other parts of the same surface pressure adjustment member
Because it is set to be smaller than that, even if there is a part with high rigidity in the top deck part, part of the surrounding area of the opening of the cylinder block corresponding to that part is deformed more than other parts And an excellent effect that the amount of distortion of the opening can be made uniform.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a state in which a cylinder head is fastened to a cylinder block with a cylinder head gasket interposed therebetween in one embodiment of the present invention.

FIG. 2 is a partial plan view of a cylinder block in one embodiment.

FIG. 3 is a plan view of a cylinder head gasket of one embodiment.

FIG. 4 is a partially enlarged cross-sectional view taken along a line AA in FIG. 3;

FIG. 5 is a partial cross-sectional view of a cylinder head gasket showing another example using a wiring and a grommet instead of a shim.

FIG. 6 is a partial cross-sectional view of a cylinder head gasket showing another example in which beads are formed instead of shims.

FIGS. 7A and 7B are partial cross-sectional views of a cylinder head gasket showing another example in which beads are formed instead of shims.

FIG. 8 is a partial sectional view showing a state where a cylinder head is fastened to a cylinder block with a conventional cylinder head gasket interposed therebetween.

FIG. 9 is a bottom view of a conventional cylinder head gasket.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 3 ... Cylinder bore as opening of cylinder block, 5 ... Top deck part, 11 ... Cylinder head gasket, 12 ... Cylinder head, 13 ...
Head bolts as fastening members, 17 ... bore holes, 22 ...
Shim as surface pressure adjusting member , 23: wiring as surface pressure adjusting member , 24: grommet as surface pressure adjusting member , 25: bead as surface pressure adjusting member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-100249 (JP, A) JP-A 2-81969 (JP, U) JP-A 2-16859 (JP, U) JP-A 63-249 40565 (JP, U) JP-A 2-67161 (JP, U) JP-A 4-36164 (JP, U) JP-A 62-77367 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F16J 15/08 F16J 15/12

Claims (1)

(57) [Claims] 1. A cylinder block is interposed between a top deck portion of a cylinder block and a cylinder head which are fastened to each other by a fastening member. The fastening member fastens the top deck portion and the cylinder head to seal the space therebetween. A cylinder head gasket having an annular surface pressure adjusting member for adjusting a contact pressure with respect to the top deck portion and the cylinder head around a hole provided corresponding to the cylinder bore of the cylinder block , Around the part of its circumference
A fastening portion to which a fastening member is fastened and a wall surface of the cylinder bore
The thickness of the top deck section between the
A locally large portion is formed, and the thickness of the top deck around the cylinder bore is locally reduced.
The surface pressure adjusting member in a portion located at a large portion locally
Surface pressure adjusting force compared to the rest of the surface pressure adjusting member.
A cylinder head gasket characterized by being set small.