JP4640342B2 - Seal structure and gasket for internal combustion engine - Google Patents

Description

  The present invention relates to a seal structure for an internal combustion engine in which a gasket is disposed between a cylinder head and a cylinder block, and the gasket.

  As a gasket provided between a cylinder head and a cylinder block, a multilayer structure composed of a plurality of metal plates is known. As such a gasket, for example, Patent Document 1 includes a cylinder head side metal plate, a cylinder block side metal plate, and a metal plate disposed between the head side gasket and the block side gasket. A three-layer structure is disclosed.

A coating layer is formed on the metal plate on the cylinder head side and the metal plate on the cylinder block side by attaching a softer material (for example, rubber material) than the metal plate to the surface. By forming such a coating layer, the degree of adhesion between the internal combustion engine (cylinder block and cylinder head) and the gasket is increased, and the leakage of combustion gas and cooling water from between the cylinder block and the cylinder head is suitably suppressed. .
Japanese Examined Patent Publication No. 8-16510

  Here, in addition to the function of sealing the leakage of combustion gas and cooling water from between the cylinder block and the cylinder head, the gasket has a short cycle accompanying the combustion of the fuel in order to suppress a decrease in the reliability of the cylinder block. A function for suppressing deformation of the cylinder block (specifically, its cylinder bore) is required. In order to sufficiently exhibit such a function (function to suppress deformation of the cylinder block), it is necessary to form the coating layer with a material that is hard to some extent. However, if a very hard material is used as a material for forming the coating layer, the degree of adhesion between the internal combustion engine and the gasket may be excessively reduced, and in this case, sufficient sealing performance by the gasket cannot be obtained. .

  In the seal structure of an internal combustion engine, the restriction on the characteristics of the coating layer formed on the gasket is one factor that hinders improvement in seal performance and suppression of deformation of the cylinder block.

  This situation is not limited to a seal structure in which a multilayer gasket is used, but also in a seal structure in which a single-layer gasket made of a single metal plate with a coating layer formed on the surface is used. ing.

  The present invention has been made in view of the above circumstances, and the object thereof is suitable for use in a seal structure of an internal combustion engine that can suitably suppress deformation of a cylinder block while maintaining seal performance, and the seal structure. Is to provide a simple gasket.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 is an internal combustion engine in which a gasket having a metal plate and a coating layer made of a material softer than the metal plate formed on the surface of the metal plate is disposed between the cylinder block and the cylinder head. In the sealing structure, the gist is that the coating layer on the cylinder head side surface of the gasket is formed of a material having a smaller transverse elastic modulus than the coating layer on the cylinder block side surface of the gasket. To do.

According to the above configuration, since the coating layer on the cylinder head side surface of the gasket is formed of a material having a relatively low transverse elastic modulus, the coating layer is greatly deformed so as to follow the thermal expansion of the cylinder head. Can do. Therefore, the degree of adhesion between the cylinder head and the gasket can be increased to maintain high sealing performance with the gasket. In addition, since the coating layer on the cylinder block side surface of the gasket is formed of a material having a large transverse elastic modulus, the deformation amount of the coating layer (specifically, the deformation amount with respect to the shearing force acting on the coating layer) is kept small. Therefore, deformation of the cylinder block accompanying the generation of combustion pressure in a short cycle can be suitably suppressed.

As the soft material for forming the coating layer, for example, a rubber material such as fluorine rubber, nitrile rubber, or silicone rubber can be employed.
According to a second aspect of the present invention, in the internal combustion engine seal structure according to the first aspect, the gasket includes a first metal plate facing the cylinder head and a second metal plate facing the cylinder block. And a third metal plate disposed between the first metal plate and the second metal plate, and surfaces of the first metal plate and the second metal plate. The gist is that each of the coating layers is formed.

  According to the above configuration, in a seal structure of an internal combustion engine in which a multi-layered gasket that has been frequently used in recent years is employed, deformation of the cylinder block can be suitably suppressed while maintaining the seal performance.

According to a third aspect of the present invention, in the seal structure for an internal combustion engine according to the first or second aspect,
The gist of the cylinder block is that it is of an open deck type in which a water jacket having a shape surrounding the cylinder bore is opened in the cylinder head side surface.

  An internal combustion engine using an open deck type cylinder block as compared to an internal combustion engine using a closed deck type cylinder block in which the opening area of the water jacket on the cylinder head side surface is very small or “0” Since the amount of deformation required for deformation of the cylinder block in a short period accompanying intermittent generation of the combustion pressure tends to be large, it is difficult to set the characteristics of the coating layer.

  According to the above configuration, in the internal combustion engine in which such an open deck type cylinder block is employed, the characteristics of the coating layers can be easily set by forming the coating layers with different materials.

The invention according to claim 4 is a gasket in which a coating layer made of a material softer than the metal plate is formed on the surface of the metal plate, and disposed between the cylinder block and the cylinder head of the internal combustion engine. The gist of the invention is that the coating layer on the cylinder head side surface is made of a material having a smaller transverse elastic modulus than the coating layer on the cylinder block side surface.

According to the above configuration, since the coating layer on the cylinder head side surface is formed of a material having a relatively small transverse elastic modulus, the coating layer can be greatly deformed so as to follow the thermal expansion of the cylinder head. . Therefore, the close contact degree between the cylinder head and the gasket can be increased, and the sealing performance can be maintained high. In addition, since the coating layer on the cylinder block side surface is formed of a material having a large transverse elastic modulus, the deformation amount of the coating layer (specifically, the deformation amount with respect to the shearing force acting on the coating layer) can be kept small. And deformation of the cylinder block accompanying the generation of combustion pressure in a short cycle can be suitably suppressed.

  The invention according to claim 5 is the gasket according to claim 4, wherein the first metal plate facing the cylinder head, the second metal plate facing the cylinder block, and the first metal plate. And a third metal plate disposed between the second metal plates, and the coating layers are formed on the surfaces of the first metal plate and the second metal plate, respectively. It is the gist of what has been done.

  According to the above configuration, the deformation of the cylinder block can be suitably suppressed while maintaining the sealing performance by the multilayer gasket.

Hereinafter, an embodiment in which a seal structure and a gasket according to the present invention are embodied will be described.
FIG. 1 shows a configuration of an internal combustion engine to which the present embodiment is applied.

  As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 11 and a cylinder head 12. A gasket 20 is disposed between the cylinder block 11 and the cylinder head 12.

FIG. 2 shows an exploded perspective structure of the internal combustion engine 10.
As shown in FIG. 2, a plurality (four in the present embodiment) of cylinder bores 13 are formed inside the cylinder block 11. Further, a water jacket 14 having a shape surrounding the circumference of each cylinder bore 13 is formed inside the cylinder block 11. Further, the cylinder block 11 is provided with an introduction port 15 for introducing cooling water from the outside into the water jacket 14. In the present embodiment, the cylinder block 11 is an open deck type in which the water jacket 14 opens on the surface of the cylinder head 12 side.

  On the surface of the cylinder block 11 on the cylinder head 12 side, a plurality of (in the present embodiment, ten) fastening holes 16 each having a female screw formed therein are provided. Further, bolt holes (not shown) are formed at positions corresponding to the respective fastening holes 16 in the cylinder head 12. Further, bolt holes 21 are formed at positions corresponding to the respective fastening holes 16 in the gasket 20.

  In the internal combustion engine 10, a bolt (not shown) is screwed into the fastening hole 16 of the cylinder block 11 while being inserted into the bolt hole of the cylinder head 12 and the bolt hole 21 of the gasket 20. Thus, the gasket 20 is disposed between the cylinder block 11 and the cylinder head 12 so that high surface pressure is generated between the cylinder block 11 and the gasket 20 and between the cylinder head 12 and the gasket 20. In this state, the cylinder block 11 and the cylinder head 12 are fastened and fixed.

  In the present embodiment, by disposing the gasket 20 in this way, the gap between the cylinder block 11 and the cylinder head 12 is sealed, and leakage of combustion gas from the inside of the cylinder bore 13 to the outside through the gap and water Cooling water leakage from the inside of the jacket 14 to the outside is prevented.

  Incidentally, the surface of the cylinder block 11 on the cylinder head 12 side, the surface of the cylinder head 12 on the cylinder block 11 side, and the gasket 20 are respectively located at positions corresponding to each other between the inside of the cylinder block 11 and the inside of the cylinder head 12. Gas holes for circulating blow-by gas between them, oil holes for circulating lubricating oil (both not shown), and the like are also provided.

Hereinafter, the structure of the gasket 20 will be described in detail.
FIG. 3 shows an end face structure of the gasket 20 in a cross section taken along the line AA of FIG.
As shown in FIG. 3, the gasket 20 of the present embodiment has a five-layer structure in which five metal plates (22a, 22b, 22c, 22d, 22e) are stacked in order from the cylinder head 12 side. Is adopted. These metal plates 22a to 22e are all formed of a stainless steel plate.

  Of these five metal plates, two metal plates 22a, 22b on the cylinder head 12 side and metal plate 22e on the cylinder block 11 side are provided with inner peripheral bead portions 23a, 23b, 23e and outer peripheral bead portions 24a, 24b. , 24e are formed. These inner peripheral bead portions 23a, 23b, 23e and outer peripheral bead portions 24a, 24b, 24e are all formed by projecting a part of the metal plates 22a, 22b, 22e.

  In the portions where the inner peripheral bead portions 23a, 23b, 23e and the outer peripheral bead portions 24a, 24b, 24e are provided, the gasket 20 and the internal combustion engine 10 (specifically, the cylinder block 11) are compared with the other portions. Further, the surface pressure generated between the surfaces facing the cylinder head 12) or the surface pressure generated between the metal plates is increased, and the sealing function is increased.

  The inner peripheral bead portions 23a, 23b, and 23e extend in a shape that surrounds the cylinder bore 13 in a portion between the cylinder bore 13 and the water jacket 14 (refer to FIG. 2). By providing such inner peripheral bead portions 23a, 23b, and 23e, leakage of combustion gas from the inside of the cylinder bore 13 is suitably prevented.

  The outer peripheral bead portions 24 a, 24 b, and 24 e are extended in a shape surrounding the water jacket 14. By providing the outer peripheral bead portions 24a, 24b, and 24e, leakage of cooling water from the water jacket 14 to the outside of the internal combustion engine 10 is suitably prevented.

  Of the five metal plates, the two metal plates 22a, 22b on the cylinder head 12 side and the metal plate 22e on the cylinder block 11 side have coating layers 25a, 25b, 25e formed on the surfaces thereof. . The coating layers 25a, 25b, and 25e are formed in a substantially uniform thickness using a softer material (specifically, fluororubber) than the metal plates 22a, 22b, and 22e.

  On the other hand, of the five metal plates, the metal plates 22c and 22d excluding the two metal plates 22a and 22b on the cylinder head 12 side and the metal plate 22e on the cylinder block 11 side, that is, the metal plates 22a and 22b and the metal plate. The inner peripheral bead portion, the outer peripheral bead portion, and the coating layer are not formed on the metal plates 22c and 22d disposed between 22e.

  In FIG. 3, in order to facilitate understanding, the thicknesses of the metal plates 22a to 22e and the thicknesses of the coating layers 25a, 25b, and 25e are shown thicker than actual. In the present embodiment, the metal plate 22a functions as a first metal plate facing the cylinder head, the metal plate 22e functions as a second metal plate facing the cylinder block, and the metal plates 22b, 22c, 22d functions as a third metal plate disposed between the first metal plate and the second metal plate.

In the present embodiment, the coating layers 25a, 25b, and 25e of the metal plates 22a, 22b, and 22e are formed using materials having different transverse elastic coefficients. Specifically, the coating layers 25a and 25b of the two metal plates 22a and 22b on the cylinder head 12 side are made of a material having a smaller transverse elastic modulus than the coating layer 25e of the metal plate 22e on the cylinder block 11 side. It is formed.

  FIG. 4 shows the characteristics of the respective forming materials (specifically, the relationship between the acting shear load and the deformation amount). In FIG. 4, a line L1 indicates the characteristics of the material for forming the coating layers 25a and 25b of the metal plates 22a and 22b on the cylinder head 12 side, and a line L2 indicates the coating layer 25e of the metal plate 22e on the cylinder block 11 side. The characteristics of the forming material are shown.

  As is apparent from FIG. 4, when the same shear load is applied, the amount of deformation of the forming material of the coating layers 25a and 25b is larger than the amount of deformation of the forming material of the coating layer 25e. A material for forming the layers 25a, 25b, and 25e is selected. By the way, when a rubber material such as fluoro rubber is used as the coating layer forming material as in the present embodiment, the transverse elastic modulus is changed by changing the amount of filler or additive contained therein. be able to.

Hereinafter, the operation by providing the gasket 20 (FIG. 3) described above will be described.
During operation of the internal combustion engine 10, the cylinder block 11, the cylinder head 12, and the gasket 20 move relative to each other due to a difference in thermal expansion amount.

  Among them, the relative movement between the cylinder head 12 and the gasket 20 is mainly caused by the difference in the amount of thermal expansion accompanying the temperature rise of the internal combustion engine 10. Therefore, the relative movement proceeds at a relatively slow speed.

In view of this point, in the present embodiment, the coating layers 25a and 25b of the two metal plates 22a and 22b on the cylinder head 12 side among the five metal plates constituting the gasket 20 are compared in the lateral elastic modulus. It is made of a small material. Therefore, the coating layers 25a and 25b can be greatly deformed so as to follow the deformation of the cylinder head 12, thereby maintaining a state in which the degree of adhesion between the cylinder head 12 and the gasket 20 is large. The sealing performance by 20 can be maintained high.

  On the other hand, the relative movement between the cylinder block 11 and the gasket 20 is caused by the periodic deformation of the cylinder block 11 accompanying the intermittent generation of the combustion pressure inside the cylinder bore 13 (see FIG. 2). Therefore, the cylinder block 11 and the gasket 20 relatively move with a very short period.

In the present embodiment, the coating layer 25e of the metal plate 22e on the cylinder block 11 side among the five metal plates constituting the gasket 20 is formed of a material having a large transverse elastic coefficient, and the coating layer 25e The amount of deformation can be kept small. Therefore, the amount of relative movement between the cylinder block 11 and the gasket 20 can be suppressed to a small amount, and as a result, the deformation of the cylinder block 11 in the short cycle described above can be preferably suppressed.

  In addition, as a structure for making the deformation amount of each coating layer different, while forming these coating layers with the same material, compared with the coating layer of the metal plate on the cylinder head side, the metal plate on the cylinder block side It is also conceivable to form a thin coating layer.

  However, in such a configuration, the coating layer of the metal plate on the cylinder block side tends to be thin, and the degree of close contact between the cylinder block and the gasket tends to be small, so that sufficient sealing performance may not be obtained. Further, since the coating layer of the metal plate on the cylinder head side tends to be thick, when the coating layer is deteriorated, the bolt fastening force is likely to be excessively reduced.

  In this regard, in the present embodiment, the deformation amounts of the coating layers 25a, 25b, and 25e are made different by forming the coating layers 25a, 25b, and 25e using forming materials having different characteristics. The coating layers 25a, 25b, and 25e can be set to appropriate thicknesses. Therefore, it is possible to reduce the possibility of causing the above-described lack of sealing performance and excessive reduction in bolt tightening force.

  Further, the internal combustion engine 10 of the present embodiment employs an open deck type cylinder block 11, and therefore, a closed deck type cylinder in which the opening area of the water jacket on the cylinder head side surface is very small or “0”. Compared to an internal combustion engine that employs a block, the amount of deformation of the cylinder block 11 that accompanies the generation of combustion pressure tends to increase. Therefore, when each coating layer is formed of the same material, it can be said that it is difficult to set characteristics of the same material. In this regard, according to the present embodiment, by forming the coating layers 25a, 25b, and 25e with different materials, it is possible to relatively easily set the characteristics of the forming materials of the coating layers 25a, 25b, and 25e. it can.

As described above, according to the present embodiment, the effects described below can be obtained.
(1) The coating layers 25a and 25b of the metal plates 22a and 22b on the cylinder head 12 side are made of a material having a smaller transverse elastic modulus than the coating layer 25e of the metal plate 22e on the cylinder block 11 side. . Therefore, it is possible to maintain a high degree of adhesion between the cylinder head 12 and the gasket 20 and maintain high sealing performance by the gasket 20. In addition, the amount of deformation of the coating layer 25e of the metal plate 22e on the cylinder block 11 side can be suppressed to be small, and the deformation of the cylinder block 11 accompanying the generation of combustion pressure in a short cycle can be suitably suppressed.

  (2) Characteristics of forming materials of the coating layers 25a, 25b, and 25e in the internal combustion engine in which the open deck type cylinder block 11 is easily set. Can be set easily.

The above embodiment may be modified as follows.
-The formation aspect of each inner periphery bead part 23a, 23b, 23e and each outer periphery bead part 24a, 24b, 24e can be changed arbitrarily.

A part or all of the inner peripheral bead portions 23a, 23b, 23e and the outer peripheral bead portions 24a, 24b, 24e can be omitted.
As the material for forming each coating layer 25a, 25b, 25e, a rubber material other than fluoro rubber, such as nitrile rubber or silicone rubber, can be employed. Moreover, you may make it form each coating layer 25a, 25b, 25e using various elastomers other than a rubber material. Furthermore, as a material for forming each coating layer, it is possible to use different types of materials such as, for example, fluorine rubber and nitrile rubber, or rubber material and elastomer.

-You may make it use the thing in which the coating layer 25b is not formed as a metal plate 22b.
・ As long as the gasket has a coating layer on the metal plate arranged closest to the cylinder block and the metal plate arranged closest to the cylinder head, the gasket has two to four layers or more than six layers. The present invention can also be applied to a gasket having a multilayer structure and a seal structure of an internal combustion engine in which such a gasket is used.

  In the present invention, coating layers are respectively formed on the surface of the metal plate disposed closest to the cylinder block side and the surface of the metal plate disposed closest to the cylinder head side. The present invention can be applied to any other gasket and a seal structure of an internal combustion engine in which the gasket is used.

The present invention can also be applied to a gasket having a single layer structure and a seal structure of an internal combustion engine in which the gasket is used. In this case, the coating layer on the cylinder head side surface of the gasket may be formed of a material having a smaller transverse elastic modulus than the coating layer on the cylinder block side surface of the gasket.

  The present invention can be applied to an internal combustion engine having 1 to 3 cylinders and an internal combustion engine having 5 or more cylinders.

1 is a perspective view showing a perspective structure of an internal combustion engine to which a seal structure and a gasket according to an embodiment embodying the present invention are applied. The disassembled perspective view which shows the disassembled perspective structure of the same internal combustion engine. FIG. 3 is an end view showing an enlarged end face structure of a gasket in a cross section taken along line AA in FIG. 2. The graph which shows the characteristic of the forming material of each coating layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder block, 12 ... Cylinder head, 13 ... Cylinder bore, 14 ... Water jacket, 15 ... Introduction port, 16 ... Fastening hole, 20 ... Gasket, 21 ... Bolt hole, 22a, 22b, 22c, 22d , 22e ... metal plate, 23a, 23b, 23e ... inner peripheral bead portion, 24a, 24b, 24e ... outer peripheral bead portion, 25a, 25b, 25e ... coating layer.

Claims (5)

In a seal structure for an internal combustion engine, in which a gasket having a metal plate and a coating layer made of a material softer than the metal plate formed on the metal plate is disposed between the cylinder block and the cylinder head,
The internal combustion engine seal characterized in that the coating layer on the cylinder head side surface of the gasket is made of a material having a smaller transverse elastic modulus than the coating layer on the cylinder block side surface of the gasket. Construction. The seal structure for an internal combustion engine according to claim 1,
The gasket is disposed between the first metal plate facing the cylinder head, the second metal plate facing the cylinder block, and the first metal plate and the second metal plate. An internal combustion engine seal structure, wherein the coating layer is formed on the surface of each of the first metal plate and the second metal plate. The seal structure for an internal combustion engine according to claim 1 or 2,
The cylinder block is of an open deck type in which a water jacket having a shape surrounding a cylinder bore is opened on a surface on the cylinder head side. In the gasket disposed between the cylinder block and the cylinder head of the internal combustion engine, a coating layer made of a material softer than the metal plate is formed on the surface of the metal plate.
The gasket characterized in that the coating layer on the cylinder head side surface is made of a material having a smaller transverse elastic coefficient than the coating layer on the cylinder block side surface. A first metal plate facing the cylinder head; a second metal plate facing the cylinder block; a third metal plate disposed between the first metal plate and the second metal plate; The gasket according to claim 4, wherein the coating layer is formed on the surfaces of the first metal plate and the second metal plate, respectively.

Images