JP2001221102A - Gasket seal structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket seal structure for an internal combustion engine narrowing a space between cylinder shafts, preventing shear stress from acting on a gasket, minimizing wedge action, and having excellent crack resistance. SOLUTION: In an internal combustion engine wherein a gasket having a bead portion form so as to surround a cylinder bore is laid between a cylinder block and a cylinder head, the bead portions 1b around the cylinder bore have a trapezoidal cross section, and the bead portion B2 between cylinder shafts is formed by merging the trapezoidal bead portions 1b around the cylinder bore and has a trapezoidal cross section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a seal structure using a gasket interposed between a cylinder block and a cylinder head of an internal combustion engine.

[0002]

2. Description of the Related Art A gasket interposed between a cylinder block and a cylinder head has a bead portion surrounding a cylinder bore. When the cylinder block and the cylinder head are fastened with a head bolt, the bead portion is compressed. To tightly seal the combustion chamber.

[0003] Generally, a cylinder sleeve made of a high-strength material is press-fitted or cast into a cylinder block body made of an aluminum alloy or the like to form a cylinder bore. Therefore, a gasket due to a difference in thermal expansion coefficient between the cylinder block body and the cylinder sleeve. Japanese Patent Application Laid-Open No. 11-182341 discloses a conventional technique that takes into consideration the effect on the sealing performance of the apparatus.

FIG. 8 shows an example described in the publication. FIG.
Is a cross-sectional view showing the seal structure of the internal combustion engine 01, in which the mating surfaces of the cylinder block 02 and the cylinder head 04 correspond to each other, and a gasket 05 in which three thin plates are overlapped between the mating surfaces. Interposed.

[0005] The cylinder block 02 is made of a high-strength material cylinder sleeve 03 on a cylinder block body 02a made of aluminum alloy.
(Even if it is an aluminum alloy sleeve, the strength is higher in each step than the cylinder block body.) The aluminum alloy cylinder head 04 corresponds to the recess forming the combustion chamber in the cylinder bore of the cylinder sleeve 03 Then, the gasket 05 is sandwiched and overlapped, and both are firmly fastened by the head bolt.

[0006] The gasket 05 has a concentric bore bead portion 05a having a larger diameter than the cylinder sleeve 03 and a peripheral bead portion 05b along the periphery of the mating surface so as to surround the cylinder sleeve 03. The bore bead portion 05a is a so-called full bead having a substantially triangular cross section. And bore bead part 05a
Are arranged so as to abut only the cylinder block main body 02a without passing over the cylinder sleeve 03.

That is, there is a possibility that a step in the cylinder axis direction may occur between the mating surface of the cylinder block main body 02a and the mating surface of the cylinder sleeve 03 due to the difference in the coefficient of thermal expansion during the hot operation of the internal combustion engine. The bore bead part 05a is the cylinder block body 02a and the cylinder sleeve
Since it does not extend to both of them, no shear stress acts on the bore bead portion 05a to lower the sealing performance.

[0008]

However, the bore bead portion 05
Aluminum alloy cylinder block body 02a that clamps a
, The load sharing ratio to the bore bead portion 05a may be reduced, and sealing performance may be reduced.

When the bore bead between the cylinder shafts is a single bead having a substantially triangular cross section, as shown in FIG. 9, the bead portions b1 and b1 on both sides other than between the cylinder shafts merge between the cylinder shafts. When forming one bead portion B2 by
Confluence b3, b where the ridge lines of both bead portions b1, b1 intersect
No. 3 has an acute projection shape, and crack resistance is reduced due to squeezing pressure in the structure, so that it is easily broken. Therefore, if two beads are provided between the cylinder shafts, the crack resistance is improved, but the distance between the cylinder shafts cannot be shortened (the shaft is narrowed) to reduce the size of the internal combustion engine.

Further, as described in the above publication, the gasket 05
The bore bead portion 05a of the cylinder block main body 02a only makes contact with the cylinder block main body 02a, so that a larger space is required than in the past in order to ensure the seal, and the downsizing of the internal combustion engine due to the narrow shaft, which is a recent need, has been required. I can not plan.

Further, since the bore bead portion 05a is located at a certain distance from the end edge 05c of the gasket 05 so as to abut only on the cylinder block main body 02a, a wedge action (wedge effect) due to the combustion finger pressure is easily exerted, and the sealing is performed. Reduce the nature.

Conventionally, as shown in FIG.
There is an example in which a stopper 011 such as a turn is interposed at the opening end corresponding to the cylinder bore of 0, and this stopper is used to prevent the bend portion from fully bending and reduce the wedge action.

However, the presence of the stopper is disadvantageous for narrowing the axis between the cylinder shafts, and an eccentric load acts on the gasket to deteriorate durability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to narrow the axis between the cylinder shafts, to exert no shear stress on the gasket, to minimize wedge action, and to prevent cracking. The present invention provides a gasket seal structure for an internal combustion engine which is excellent in performance.

[0015]

In order to achieve the above object, according to the first aspect of the present invention, a gasket having a bead portion formed so as to surround a cylinder bore is provided between a cylinder block and a cylinder head. In the internal combustion engine interposed, the cross section of the bead around the cylinder bore has a trapezoidal shape, and the cross section of the bead between the cylinder axes has a trapezoidal cross section when the trapezoidal bead section around the cylinder bore merges. A gasket seal structure for an internal combustion engine in which one bead portion is formed.

The bead portions having a trapezoidal cross section merge from both sides between the cylinder shafts to form a single bead portion having a trapezoidal cross section. Therefore, the half bead combination other than between the cylinder shafts improves crack resistance. In addition, no sharp projections are formed at the junction where the beads on both sides meet,
Crack resistance is significantly improved.

Since the cross section of the bead portion has a trapezoidal shape corresponding to a combination of half bead shapes, the bead portion itself has excellent crack resistance against pinching pressure. Furthermore, since there is a single bead structure between cylinder axes,
The axis between the cylinder shafts can be narrowed, and the size of the internal combustion engine can be reduced.

According to a second aspect of the present invention, the cylinder bore of the high-strength portion is provided between a cylinder block having a high-strength portion formed on the cylinder bore side of a cylinder block body made of a light metal material and a cylinder head made of a light metal material. In an internal combustion engine in which a gasket having a bead portion formed so as to surround is interposed, the bead portion between cylinder axes is arranged so as to straddle the mating surface of the cylinder block main body and contact only the high strength portion. 1 is a gasket seal structure of an installed internal combustion engine.

When the load is applied, the seal portion where the surface pressure of the bead portion becomes the highest is only in the high-strength portion having the same thermal expansion coefficient, so that there is no drop in the high-strength portion and there is no step in the seal portion. Shear stress does not act to lower the sealing performance, and since the sealing portion is located at the end of the gasket applied to the high-strength portion on the cylinder bore side, wedge action due to combustion finger pressure is minimized and high sealing performance is secured. be able to.

Since the bead portion between the cylinder shafts straddles the mating surface of the cylinder block main body and abuts only on the high strength portion, the mating surface of the cylinder block main body is narrowed so that the axis between the cylinder shafts can be narrowed. The downsizing of the internal combustion engine can be achieved.

According to a third aspect of the present invention, in the gasket seal structure for an internal combustion engine according to the second aspect, the bead portion of the gasket has a trapezoidal cross section.

A bead portion having a trapezoidal cross section corresponds to a combination of half bead shapes, and prevents crack cracks, which are characteristics of a half bead, and improves the durability of the gasket.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to FIGS. The gasket 1 according to the present embodiment has a structure in which three thin plates 2, 3, and 4 made of stainless steel are stacked.

As shown in FIG. 1, the gasket 1 is interposed between an aluminum alloy cylinder block 20 and an aluminum alloy cylinder head 30, and is pressed by steel bolts.
The internal combustion engine is an in-line four-cylinder engine, in which four cylinder sleeves 21 made of cast iron are cast into an aluminum alloy cylinder block body 20a of a cylinder block 20, and four cylinder bores 21a are formed side by side.

A water jacket 20b is formed around the four cylinder sleeves 21. The space between the cylinder shafts is narrow, the space between adjacent cylinder sleeves 21 is small, and no water jacket is formed between the cylinder shafts.

When the gasket 1 is viewed from above, four cylinder openings 1a having a diameter equal to the inner diameter of the cylinder sleeve 21 are formed side by side as shown in FIG. 2, and a bead portion 1b is formed around each cylinder opening 1a. Formed to enclose,
A cooling water opening 1c is formed along the outer periphery of the bead portion 1b. Other gasket 1 has bolt insertion opening 1d
And an oil return opening 1e.

The bead portion 1b surrounding the periphery of each cylinder opening 1a has a trapezoidal cross section, and as shown in FIG.
1 and B1 merge from both sides to form one bead portion B2.

At the junctions B3 and B3 where the flat bottoms of the bead sections B1 and B1 having trapezoidal cross sections on both sides intersect, the bottom sides on both sides become one bottom without forming an acute projection. Thus, a bead portion B2 having a trapezoidal cross section is formed (see FIG. 4). Therefore, it is excellent in crack resistance against pinching pressure of the bead portion B2 where the bead portions B1 and B1 join between the cylinder shafts.

FIGS. 4 and 5 show a gasket seal structure between cylinder shafts. One trapezoidal bead portion 1b (B2) is formed on the gasket 1 between the cylinder shafts. That is, the lower thin plate 2 has a trapezoidal bead portion 2b swelling upward, the middle thin plate 3 has a trapezoidal bead portion 3b swelling downward, and the upper thin plate 3 has a trapezoidal bead portion 3b swelling upward. Are laminated and interposed between the cylinder block 20 and the cylinder head 30.

As schematically shown in FIG. 5, a cylinder block body 20a is sandwiched between adjacent cylinder sleeves 21 between the cylinder shafts.
The mating surfaces of the cylinder blocks 21 and 21 and the cylinder block body 20a form the same surface.

On the other hand, the lower thin plate 2 of the gasket 1 has a trapezoidal bead portion 2b bulging upward at the center, and hem portions 2c, 2c on both sides across the cylinder block body 20a.
Abuts only on the mating surfaces of the cylinder sleeves 21 and 21.

In this manner, the gasket 1 composed of the three thin plates 2, 3, and 4 is provided with the cylinder block 20 and the cylinder head 30.
The bead portion 2b in the lower thin plate 2
The left and right bent portions 2d, 2d are seal portions having the highest surface pressure. The bent portions 2d, 2d and the skirt portions 2c, 2c serving as the seal portions abut only on the mating surfaces of the cylinder sleeves 21, 21.

The aluminum alloy cylinder block body 20a and the cast iron cylinder sleeve 21 of the cylinder block 20
Due to the difference in the coefficient of thermal expansion, a step may be formed on the mating surface of the cylinder block body 20a and the cylinder sleeve 21 in a hot operation state.

Even when the cylinder block is sleeveless, the cylinder bore side portion is configured to have higher strength than the others, and even if a periodic load due to a pressure change that presses the gasket is applied to the cylinder block in the same manner. Steps may occur due to differences in strength.

However, even if a step is generated, the bent portions 2d, 2d and the skirt portions 2c, 2c serving as the seal portions of the gasket 1 abut only on the mating surfaces of the cylinder sleeves 21, 21 as described above. No shear stress acts on the part due to the step, and the sealing performance does not deteriorate.

The bent portions 2d, 2d, which are the seal portions having the highest surface pressure, are located at the bases of the skirt portions 2c, 2c at the left and right ends of the thin plate 2 of the gasket 1 on the cylinder sleeve 21, so that the combustion finger pressure is applied. The wedge action (wedge effect), that is, the effect of turning up the end of the thin plate 2 is minimized, and high sealing performance is ensured.

The gasket 1 comprises a cylinder block body 20
a, a single bead structure is provided between the cylinder sleeves 21 and 21 on both sides, so that the center cylinder block body 20a can be narrowed, and the axis between the cylinder shafts can be narrowed. Miniaturization can be realized.

As shown in FIGS. 6 and 7, the gasket 1 has a bead portion 1b (B1) around a cylinder bore 21a.
Is formed, and a half bead portion 1f is formed at the end. The portion corresponding to the water jacket 20b is closed by the gasket 1 except for the portion having the cooling water opening 1c.

Since the gasket 1 has a trapezoidal bead portion 1b, it corresponds to a combination of half beads, and can be easily deformed in the cylinder axis direction as compared with a triangular bead, and cracks and the like are prevented. Durability is improved.

The gasket 1 is a stopperless having no stopper at the end, and can promote the narrowing of the axis between the cylinder shafts. In addition, the uneven load of the stopper against the thin plates 2, 3, and 4 of the gasket 1 can be reduced. Since there is no, the durability is further improved.

In addition, since the gasket 1 is a single bead between the cylinder shafts and is stopperless, the unbalanced load can be suppressed and bore deformation, distortion of the valve seat, deformation of the crank journal and cam journal, and the like can be prevented. .

In the above embodiment, the cylinder block 20
Has a cast iron cylinder sleeve 21 cast into the cylinder block body 20a.However, even if a cylinder sleeve made of an aluminum alloy is press-fitted or sleeveless, the cylinder bore side part has a particularly high strength. The present invention is applicable to the present invention and has the same effects as described above.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a cylinder block, a gasket, and a cylinder head according to an embodiment of the present invention.

FIG. 2 is a plan view of a gasket.

FIG. 3 is an enlarged view of a portion between cylinder axes of the gasket.

FIG. 4 is a partial view showing a structure of a gasket between cylinder shafts.

FIG. 5 is a diagram schematically showing a cross section of a main part between cylinder axes.

FIG. 6 is a partial view showing the structure of the gasket and the cylinder block other than between the cylinder shafts.

FIG. 7 is a diagram schematically showing a cross section of a main part other than between cylinder axes.

FIG. 8 is a sectional view of a main part showing a conventional gasket seal structure.

FIG. 9 is a plan view showing a space between cylinder axes of a conventional gasket.

FIG. 10 is a sectional view showing an example of a gasket provided with a stopper.

[Explanation of symbols]

1 ... gasket, 2, 3, 4 ... thin plate, 20 ... cylinder block, 21 ... cylinder sleeve, 30 ... cylinder head.

Claims (3)

[Claims] 1. An internal combustion engine in which a gasket having a bead formed to surround a cylinder bore is interposed between a cylinder block and a cylinder head, wherein the bead around the cylinder bore has a trapezoidal cross section. A gasket seal structure for an internal combustion engine, wherein a trapezoidal bead around the cylinder bore joins the bead between cylinder axes to form a single bead having a trapezoidal cross section. 2. A cylinder block comprising a light metal material, a cylinder block having a high strength portion formed on a cylinder bore side of a cylinder block body, and a cylinder head made of a light metal material.
In the internal combustion engine provided with a gasket having a bead portion formed so as to surround the cylinder bore of the high-strength portion, the bead portion between the cylinder shafts extends over the mating surface of the cylinder block main body to form the high-strength portion. A gasket seal structure for an internal combustion engine, wherein the gasket seal structure is provided so as to abut only on the gasket seal. 3. The gasket seal structure for an internal combustion engine according to claim 2, wherein a cross section of the bead portion of the gasket has a trapezoidal shape.