JP4488574B2 - Gasket seal structure for internal combustion engines - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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]
[Prior art]
The gasket interposed between the cylinder block and the cylinder head is formed with a bead portion so as to surround the cylinder bore. When the cylinder block and the cylinder head are fastened with a head bolt, the bead portion is compressed and the combustion chamber is compressed. Seal tightly.
[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, the sealing performance of the gasket due to the difference in thermal expansion coefficient between the cylinder block body and the cylinder sleeve Japanese Patent Laid-Open No. 11-182341 discloses a conventional technique that takes into account the influence on the above.
[0004]
An example described in the publication is shown in FIG.
FIG. 8 is a cross-sectional view showing the seal structure of the internal combustion engine 01, showing the mating surfaces of the cylinder block 02 and the cylinder head 04 in correspondence with each other, and a gasket in which three thin plates are overlapped between the mating surfaces. 05 is inserted.
[0005]
The cylinder block 02 is made of a cylinder block body 02a made of an aluminum alloy and a cylinder sleeve 03 made of high-strength material (even if it is an aluminum alloy sleeve, it is stronger in each stage than the cylinder block body). The cylinder head 04 made of the cylinder is overlapped with the cylinder bore of the cylinder sleeve 03 so as to correspond to the concave portion constituting the combustion chamber with the gasket 05 interposed therebetween, and both are firmly fastened by the head bolt.
[0006]
The gasket 05 is formed with a concentric bore bead part 05a having a larger diameter than the cylinder sleeve 03 and a peripheral bead part 05b along the peripheral edge 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.
The bore bead portion 05a is disposed so as to contact only the cylinder block body 02a without passing over the cylinder sleeve 03.
[0007]
That is, a step in the cylinder axial direction may occur between the mating surface of the cylinder block body 02a and the mating surface of the cylinder sleeve 03 due to the difference in thermal expansion coefficient in the hot operation state of the internal combustion engine, but the bore bead portion 05a of the gasket 05 However, since it does not extend over both the cylinder block main body 02a and the cylinder sleeve 03, a shearing stress does not act on the bore bead portion 05a to reduce the sealing performance.
[0008]
[Problems to be solved by the invention]
However, the drop of the aluminum alloy cylinder block main body 02a sandwiching the bore bead portion 05a may reduce the load sharing ratio to the bore bead portion 05a, thereby reducing the sealing performance.
[0009]
If the bore bead portion between the cylinder shafts is a single bead having a substantially triangular cross section, the bead portions b1 and b1 on both sides other than between the cylinder shafts merge between the cylinder shafts as shown in FIG. When forming the bead portion B2, the joining portions b3 and b3 where the ridge lines of both bead portions b1 and b1 intersect each other have an acute protrusion shape, and the structure is easily cracked due to the reduced crack resistance against the pinching force. .
Therefore, if two beads are provided between the cylinder shafts, the size of the internal combustion engine cannot be reduced by shortening (narrowing the shaft) between the cylinder shafts instead of improving crack resistance.
[0010]
Further, since the bore bead portion 05a of the gasket 05 is brought into contact only with the cylinder block main body 02a as in the example of the above publication, a large space is required as compared with the prior art in order to secure the seal. The internal combustion engine cannot be downsized by reducing the shaft.
[0011]
Furthermore, since the bore bead portion 05a is located at a certain distance from the edge 05c of the gasket 05 so as to contact only the cylinder block body 02a, the wedge action (wedge effect) due to the combustion finger pressure is likely to work greatly and the sealing performance is lowered. Let
[0012]
In addition, as shown in FIG. 10, there is an example in which a stopper 011 such as a fold is interposed at the opening end corresponding to the cylinder bore of the gasket 010, and the stopper prevents the bead part from being bent completely and tries to reduce the wedge action. To do.
[0013]
However, the presence of the stopper is disadvantageous for narrowing the distance between the cylinder shafts, and an offset load is applied to the gasket to deteriorate the durability.
[0014]
The present invention has been made in view of the above points, and the purpose of the invention is to narrow the shaft between the cylinder shafts, so that the shear stress does not act on the gasket and the wedge action is minimized, and the crack resistance is excellent. It is in the point which provides the gasket seal structure of an internal combustion engine.
[0015]
[Means for solving the problems and effects]
In order to achieve the above object, an invention according to claim 1 is directed to an internal combustion engine in which a gasket having a bead portion formed so as to surround a cylinder bore is interposed between a cylinder block and a cylinder head. the bead portion is cross section along the entire circumference, flat annular and bottom of the bent outer inclined continuing in the annular outer inner inclined side and the annular bottom continuous bent in annular inner of the same annular base of A trapezoidal shape by forming a side and an inner hem parallel to the bottom side that is bent and connected to the inner inclined side and an outer hem portion parallel to the bottom and bent to the outer inclined side. No, the bead portion between the cylinder axis, the both bead portions of the trapezoid is joined around the cylinder bore, the two base is merged to become a single base from each other, both outer inclined side and both the outer skirt is cylindrical Absent between the shaft, the two inner inclined edges that are formed so as independently to surround the cylinder bore cross-section are formed one bead portion of the trapezoidal shape with a flat bottom, said gasket, Three thin plates are stacked one on top of the other. The lower layer has a trapezoidal bead portion that bulges upward, the middle layer has a trapezoidal bead portion that bulges downward, and the upper thin plate has a trapezoidal shape. 3 parts in which the bottom bulge and the middle thin plate are overlapped with each other at the bottom, and the middle thin plate and the upper thin plate are overlapped with each other at the bottom. A gasket seal structure for an internal combustion engine in which the bead portions of the thin plate overlap each other in the vertical position .
[0016]
Between the cylinder shafts, the trapezoidal bead sections merge from both sides to form a single bead section having a trapezoidal cross section, so the crack resistance is improved because of the combination of half beads other than between the cylinder axes, A sharp protrusion shape is not formed at the junction where the bead portions on both sides meet, and the crack resistance is remarkably improved.
[0017]
Moreover, since the cross-sectional shape of the bead portion has a trapezoidal shape corresponding to a combination of half-bead shapes, the shape of the bead portion itself is excellent in crack resistance against pinching pressure.
Further, since the single bead configuration is used between the cylinder shafts, it is possible to narrow the shafts between the cylinder shafts and to reduce the size of the internal combustion engine.
[0018]
According to a second aspect of the present invention, the cylinder bore of the high-strength portion is surrounded between a cylinder block in which a high-strength portion is formed on the cylinder bore side of the cylinder block body made of light metal material and a cylinder head made of light metal material. is gasket interposed having the formed bead portion, according to claim 1, wherein the bead portion of the portion between the cylinder axis is disposed so as to abut only on the high-strength portion across the mating surface of the cylinder block body This is a gasket seal structure of the internal combustion engine.
[0019]
Since the seal part where the surface pressure of the bead part becomes the highest when the load is applied is only in the high-strength part having the same thermal expansion coefficient, there is no drop in the high-strength part, and there is no step in the seal part and shear stress is generated. It does not deteriorate the sealing performance by acting, and further, since the sealing portion is at the gasket end portion applied to the high strength portion on the cylinder bore side, the wedge action due to the combustion finger pressure is minimized, and the high sealing performance can be secured. .
[0020]
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 can be narrowed to reduce the axis between the cylinder shafts. Miniaturization can be achieved.
[0022]
The bead portion having a trapezoidal cross section corresponds to a combination of half bead shapes, and prevents cracks and the like, which are the characteristics of the half bead, and improves the durability of the gasket.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an 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 overlapped.
[0024]
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 clamped by steel bolts.
The internal combustion engine is an in-line four-cylinder engine, and four cylinder sleeves 21 made of cast iron are cast into an aluminum alloy cylinder block body 20a of the cylinder block 20 to form four cylinder bores 21a side by side.
[0025]
A water jacket 20 b is formed around the four cylinder sleeves 21.
The space between the cylinder shafts is a narrow shaft, the distance between the adjacent cylinder sleeves 21, 21 is narrow, and no water jacket is formed between the cylinder shafts.
[0026]
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 the bead portion 1b surrounds each cylinder opening 1a. A cooling water opening 1c is formed along the outer periphery of the bead portion 1b.
In addition, the gasket 1 is formed with a bolt insertion opening 1d, an oil return opening 1e, and the like.
[0027]
The bead portion 1b surrounding each cylinder opening 1a has a trapezoidal cross section. As shown in FIG. 3, bead portions B1 and B1 other than between the cylinder shafts join together from both sides between the cylinder shafts. A bead portion B2 of the book is formed.
[0028]
The bases on both sides become one base without forming sharp projections at the junctions B3 and B3 where the flat bases of the bead parts B1 and B1 having a trapezoidal cross section on both sides meet, and one is directly between the cylinder shafts. A bead portion B2 having a trapezoidal cross section is formed (see FIG. 4).
Therefore, the crack resistance with respect to the pinching pressure of the bead portion B2 where the bead portions B1 and B1 between the cylinder shafts merge is excellent.
[0029]
The gasket seal structure between the cylinder shafts is shown in FIGS.
One trapezoidal bead portion 1b (B2) is formed in the gasket 1 between the cylinder shafts.
That is, the lower-layer thin plate 2 has a trapezoidal bead portion 2b bulging upward, the middle-layer thin plate 3 has a trapezoidal bead portion 3b bulging downward, and the upper-layer thin plate 3 has a trapezoidal bead portion 3b bulging upward. The three thin plates 2, 3, 4 are overlapped and interposed between the cylinder block 20 and the cylinder head 30.
[0030]
As schematically shown in FIG. 5, the cylinder block body 20a is sandwiched between the cylinder sleeves 21 and 21 adjacent to each other between the cylinder shafts, and the mating surfaces of the cylinder sleeves 21 and 21 and the cylinder block body 20a. Form the same plane.
[0031]
On the other hand, the thin plate 2 under the gasket 1 is formed with a trapezoidal bead portion 2b bulging upward in the center, and the hem portions 2c and 2c on both sides straddling the cylinder block body 20a are the mating surfaces of the cylinder sleeves 21 and 21. It touches only to.
[0032]
Thus, when the gasket 1 composed of three layers of thin plates 2, 3 and 4 is sandwiched between the cylinder block 20 and the cylinder head 30, the left and right bent portions 2d and 2d of the bead portion 2b are the most surface in the lower layer thin plate 2. It becomes a seal part where the pressure increases.
The bent portions 2d and 2d and the skirt portions 2c and 2c serving as seal portions abut only on the mating surfaces of the cylinder sleeves 21 and 21, respectively.
[0033]
The aluminum alloy cylinder block main body 20a of the cylinder block 20 and the cast iron cylinder sleeve 21 may cause a step on the mating surface between the cylinder block main body 20a and the cylinder sleeve 21 in a hot operation state due to the difference in thermal expansion coefficient. .
[0034]
Even when the cylinder block is sleeveless, the cylinder bore side part is constructed with higher strength than the others, and even if a cyclic load due to pressure changes that sandwich the gasket is applied to the cylinder block in the same way, the difference in strength May cause a step.
[0035]
However, even if a step is generated, the bent portions 2d and 2d and the skirt portions 2c and 2c, which are the seal portions of the gasket 1, as described above, abut only on the mating surfaces of the cylinder sleeves 21 and 21. No shear stress is exerted, and the sealing performance is not deteriorated.
[0036]
Further, since the bent portions 2d and 2d, which are the seal portions with the highest surface pressure, are located at the bases of the bottom portions 2c and 2c of the left and right end portions of the thin plate 2 of the gasket 1 on the cylinder sleeve 21, the wedge action ( The wedge effect), that is, the effect of turning up the end of the thin plate 2 is minimized, and high sealing performance is ensured.
[0037]
Since the gasket 1 has a single bead structure extending between the cylinder sleeves 21 and 21 on both sides across the cylinder block main body 20a, the central cylinder block main body 20a can be narrowed, and the narrow axis between the cylinder axes can be reduced. Therefore, the internal combustion engine can be downsized.
[0038]
As shown in FIGS. 6 and 7, the gasket seal structure at the portion not between the cylinder shafts has a bead portion 1b (B1) formed around the cylinder bore 21a and a half bead portion 1f formed at the end portion. Yes.
The portion corresponding to the water jacket 20b is closed by the gasket 1 except for the portion having the cooling water opening 1c.
[0039]
Since the bead portion 1b has a trapezoidal shape, the gasket 1 corresponds to a combination of half beads, and is easier to deform in the cylinder axial direction than a triangular bead, and prevents cracking and the like and has durability. It has improved.
[0040]
This gasket 1 is stopperless without a stopper at the end, can promote the narrowing of the shaft between the cylinder shafts, and there is no offset load on the thin plates 2, 3, 4 of the gasket 1 of the stopper, Durability is further improved.
[0041]
Further, since the gasket 1 is made of a single bead between the cylinder shafts and is stopperless, it is possible to suppress uneven load and prevent deformation of the bore, distortion of the valve seat, deformation of the crank journal and the cam journal, and the like.
[0042]
In the above embodiment, the cylinder block 20 is a cast iron cylinder sleeve 21 cast into the cylinder block body 20a. However, even if the cylinder sleeve made of aluminum alloy is press-fitted or sleeveless, The cylinder bore side portion is configured with particularly high strength, and is applicable to the present invention, and can provide 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 the gasket.
FIG. 3 is an enlarged view of a portion between the cylinder shafts 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 shafts.
FIG. 6 is a partial view showing the structure of a gasket and a cylinder block other than between the cylinder shafts.
FIG. 7 is a diagram schematically showing a cross-section of the main part other than between the cylinder shafts.
FIG. 8 is a cross-sectional view of a main part showing a conventional gasket seal structure.
FIG. 9 is a plan view showing between cylinder axes of a conventional gasket.
FIG. 10 is a cross-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 (2)

In an internal combustion engine in which a gasket having a bead portion formed so as to surround a cylinder bore is interposed between a cylinder block and a cylinder head,
The bead portion around the cylinder bore cross-section over the entire circumference, the bottom of the flat annular, continuous bent annularly outside the inner inclined side and the annular bottom continuous bent in annular inner of the same annular base A base is formed by forming an outer inclined side, an inner hem parallel to the base bent and connected to the inner inclined side, and an outer hem parallel to the base bent and connected to the outer inclined side. No shape,
The bead portion between the cylinder shafts is
Both bead portions trapezoidal around the cylinder bores merge,
Both bases merge together into a single base,
The outer slopes and the outer hems do not exist between the cylinder shafts,
Both inner inclined sides are independently formed to surround the cylinder bore,
One trapezoidal bead portion having a flat bottom surface is formed,
The gasket is
Three thin plates are stacked one above the other,
The trapezoidal bead portion bulges upward in the lower layer thin plate, the trapezoidal bead portion bulges down in the middle thin plate, and the trapezoidal bead portion bulges up in the upper thin plate,
The bottom thin plate and the middle thin plate are overlapped with each other at the bottom, and the middle thin plate and the upper thin plate are overlapped with each other at the bottom.
A gasket seal structure for an internal combustion engine , wherein the bead portions of the three thin plates overlap each other in the vertical position . A gasket having a bead portion formed so as to surround the cylinder bore of the high-strength portion between a cylinder block having a high-strength portion formed on the cylinder bore side of the cylinder block body made of light metal material and a cylinder head made of light metal material. Is intervened,
2. The gasket seal structure for an internal combustion engine according to claim 1, wherein the bead portion between the cylinder shaft portions is disposed so as to contact only the high-strength portion across the mating surface of the cylinder block body.

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