JPH1182156A - Lower face structure of cylinder head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sealability of a contact face at a cylinder bore partition wall part without deforming the sliding contact parts of a cylinder head or a cylinder block with other parts by uniforming the surface pressure of the whole contact face to heighten the surface pressure of the contact face at the cylinder bore partition wall part without increasing the axial tension of a head bolt to heighten the surface pressure of the whole contact part regarding the contact face between the cylinder head and the cylinder block. SOLUTION: In a cylinder head 1 connected to the upper face of a cylinder block by a head bolt through a gasket, the lower face of the cylinder head 1 opposed to the upper face of the cylinder block is formed in a face inclined obliquely upward from a center part toward an end part in the cross direction of the cylinder head 1 at least on one side, with the cross direction center part as a boundary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head connected to an upper surface of a cylinder block via a gasket by a head bolt in an engine body, and more particularly to a lower structure of such a cylinder head.

[0002]

2. Description of the Related Art In an engine body such as a vehicle engine,
The cylinder head and the cylinder block are integrally connected by a head bolt via a gasket. In this case, the cylinder block is located on both outer sides of the row of cylinder bores along the cylinder arrangement direction with respect to the cylinder block side. A bolt hole for screwing a head bolt is formed between both ends of each cylinder and each cylinder, and corresponding to the bolt hole,
On the side of the cylinder head, a bolt through hole for penetrating the head bolt is formed, and each head bolt is screwed into the bolt hole of the cylinder block through the bolt through hole of the cylinder head, thereby tightening the head bolt. The surface pressure of the mating surface between the cylinder head and the cylinder block connected via the gasket is maintained.

[0003] On the other hand, in the engine body in which the cylinder head and the cylinder block are connected as described above, an aluminum alloy cylinder block is provided with an iron-based cylinder bore in order to enhance wear resistance of the inner peripheral surface of the cylinder bore. The one with the sleeve fitted has been used in general, and the chrome plating with high wear resistance is applied to the inner peripheral surface of the cylinder bore without providing such an iron-based sleeve to reduce the weight. A so-called sleeveless cylinder block to which the above has been applied is also generally used.

[0004]

By the way, in the conventional engine as described above, the surface pressure distribution on the mating surface between the cylinder head and the cylinder block due to the tightening of the head bolt is inevitably increased around the head bolt.
Since the surface pressure is reduced in the cylinder bore partition (the thin wall portion between the cylinder bores of each cylinder) away from the head bolt, particularly in the cylinder bore partition where the beads around each cylinder bore are adjacent to each other with a gasket. In addition, the sealing property of the mating surface between the cylinder head and the cylinder block is deteriorated, and there is a possibility that gas leaks from one cylinder bore to the other cylinder bore at the corresponding portion.

Therefore, by increasing the axial force of the head bolt (increasing the tightening force by the head bolt) and increasing the surface pressure of the entire mating surface between the cylinder head and the cylinder block,
If the surface pressure of the mating surface at the cylinder bore partition is to be increased, the coaxiality of the cam shaft and the roundness of the lift turbo are deteriorated on the cylinder head side, and the cylinder block side, especially the cylinder bore In the case of a sleeveless cylinder block without an iron-based sleeve, the cylinder bore may be deformed, and such deformation of each part may adversely affect friction, lubrication, oil consumption, and the like. Becomes

The present invention solves the above-mentioned problem by increasing the axial force of the head bolt on the mating surface of the cylinder head and the cylinder block without increasing the surface pressure of the entire mating surface. By increasing the surface pressure of the mating surface at the cylinder bore partition by making the surface pressure of the entire surface uniform, the cylinder bore partition can be deformed without deforming the sliding contact with other parts of the cylinder head or cylinder block. It is an object of the present invention to improve the sealing performance of a mating surface in a part.

[0007]

According to the present invention, in order to solve the above-mentioned problems, the head bolt is connected to the upper surface of the cylinder block via a gasket by a head bolt. In the cylinder head, the lower surface of the cylinder head opposed to the upper surface of the cylinder block has a boundary near the center in the width direction, and at least one of the sides, from the vicinity of the center to the end in the width direction of the cylinder head. It is characterized in that it is formed as a surface inclined obliquely upward.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cylinder head according to an embodiment of the present invention;

FIGS. 1 and 2 show a cylinder head of a four-cylinder engine according to an embodiment of a cylinder head having a lower surface structure of the present invention. FIG. 1 shows a front surface of the cylinder head, and FIG. Shows the lower surface of the cylinder head. 3 and 4 show a connection state of a cylinder head and a cylinder block in an engine body. FIG. 3 shows a longitudinal section passing through a cylinder bore at a position along the line AA in FIG. , FIG. 4 shows B in FIG.
FIG. 4 shows a vertical cross section passing through a partition wall between cylinder bores at a position along line -B.

FIGS. 1 and 3 show the cylinder head 1.
As shown in FIG. 4, lower half portions 16 and 17 of each bearing for supporting each of the intake and exhaust cam shafts are provided on the upper surface side thereof.
As shown in FIG. 2, the combustion chamber top plates 11 of the four cylinders are formed on the lower end of the cylinder head 1 at both ends in the longitudinal direction of the cylinder head 1 and at appropriate places therebetween. Each is recessed in a state of being arranged in a line along the longitudinal direction.

The cylinder head is connected to the cylinder block 1 between both ends of the cylinder head and each cylinder on both sides of the row of the combustion chamber top plates 11 along the direction in which the cylinders are arranged. A plurality of bolt through holes 12 for penetrating the head bolts respectively are formed so as to penetrate the cylinder head 1 in the up-down direction and open the lower ends to the lower surfaces of the cylinder heads.

On the lower surface of the cylinder head 1, in addition to the bolt through holes 12, a water jacket 13 formed in the cylinder head communicates with the cylinder block side, and is formed above the cylinder head. The communication portion of the oil return passage 14 from the cam chamber to the cylinder block side is opened.

As shown in FIG. 3, such a cylinder head 1 has a gasket on the upper surface side of the cylinder block 2 such that each combustion chamber top plate 11 covers the upper end opening of each cylinder bore 21 of the cylinder block 2. 4, the head bolts 4 penetrating through the bolt through holes 12 of the cylinder head 1 are screwed into bolt holes 22 formed in the cylinder block 2, respectively, as shown in FIG. When the gasket 3 is interposed between the cylinder block 2 and the cylinder block 2, the gasket 3 is interposed therebetween.

Each cylinder bore 21 of the cylinder block 2
Are so-called sleeveless, in which the inner peripheral surface is plated with high wear resistance and is not provided with an iron-based sleeve, and each bolt hole 22 for screwing a head bolt is On both sides of the row of the cylinder bores 2, at both ends in the longitudinal direction (cylinder arrangement direction) of the cylinder block 1 and at positions corresponding to the partition walls of the cylinder bores 21, the cylinder bores 2 are formed so as to surround the cylinder bores 4 from four sides. .

In the present embodiment, the cylinder block 2 is a cylinder block made of a sleeveless aluminum alloy without an iron-based sleeve.
The invention is not limited thereto, and an aluminum alloy cylinder block provided with an iron-based sleeve or a cast iron cylinder block may be used.

In the cylinder head 1 connected to the upper surface of the cylinder block 2 by the head bolts 4 as described above, in the present embodiment, the lower surface of the cylinder head 1 facing the upper surface of the cylinder block 2 via the gasket 3 As shown in FIG. 5 (A), on both sides of the vicinity of the center in the width direction (the line where the plane X passing through the center axis of the cylinder bore 21 of each cylinder intersects the lower surface of the cylinder head 1), In each case, the lower surface of the cylinder head 1 is downwardly inclined with the line extending in the longitudinal direction at the center in the width direction as the apex. It is formed so as to be convex (the cross section is inverted mountain shape).

Although the degree of downward protrusion of the lower surface of the cylinder head 1 is extremely shown in FIGS. 1 and 5A, it is actually very small.
For example, the inclination angle θ obliquely upward on both sides of a line where the plane X passing through the center axis of the cylinder bore 21 of each cylinder intersects the lower surface of the cylinder head 1 is about 9/1000 °, and the cylinder head The projecting distance d of the center part below the center part with respect to both ends in the width direction is about 10 μm.

According to the cylinder head 1 of the present embodiment having the above-described lower surface structure, the cylinder head 1 (the cylinder head 1
The entire lower surface of the cylinder block is the same plane parallel to the upper surface of the cylinder block), the surface pressure distribution on the mating surface between the cylinder head 1 and the cylinder block 2 due to the tightening of the head bolt 4 increases around the head bolt, and the head bolt 4 (closer to the center in the width direction), while the lower surface of the cylinder head 1 is convex downward (reverse mountain shape in cross section), so that the surface pressure distribution of the mating surface is reduced. It will be uniform.

Therefore, without increasing the axial force of the head bolt 4 (increasing the tightening force), the surface pressure of the cylinder bore partition wall apart from the head bolt 4 can be increased, and the cylinder head 1 in the cylinder bore partition wall can be increased. The sealing performance of the mating surface of the cylinder block 2 can be improved, and as a result, gas leakage at the relevant portion can be avoided, and the coaxiality of the camshaft by increasing the axial force of the head bolt and the like. It is possible to prevent the roundness of the lift turbocharger from deteriorating, and in particular, when the cylinder block is sleeveless, it is possible to prevent the deformation of the cylinder bore and to reduce the friction due to the deformation of those parts.
Adverse effects on lubrication, oil consumption, etc. can be avoided.

While the embodiment of the lower surface structure of the cylinder head of the present invention has been described above, the present invention is not limited to the specific structure shown in the above embodiment, that is, FIG.
As shown in FIG. 5A, both sides of the central portion (plane X) of the cylinder head 1 are not limited to those that are inclined obliquely upward (the cross section is inverted chevron). As shown in (B), the present invention can also be implemented by a structure in which only one side of the central part (plane X) of the cylinder head 1 is inclined obliquely upward toward the end.

[0021]

According to the lower surface structure of the cylinder head of the present invention as described above, the axial force of the head bolt is increased at the mating surface of the cylinder head and the cylinder block to increase the surface pressure of the entire mating surface. Without increasing the surface pressure of the mating surface at the cylinder bore partition by increasing the surface pressure of the entire mating surface, the sealing performance of the mating surface at the cylinder bore partition can be improved. Besides, it is possible to avoid adverse effects on friction, lubrication, oil consumption, and the like due to deformation of the cylinder head and the cylinder block.

[Brief description of the drawings]

FIG. 1 is a front view showing a cylinder head according to an embodiment of a lower surface structure of a cylinder head of the present invention.

FIG. 2 is a bottom view of the cylinder head shown in FIG.

FIG. 3 is a longitudinal sectional view showing a connection state of a cylinder head and a cylinder block in the engine body and passing through a cylinder bore at a position along a line AA in FIG. 2;

FIG. 4 is a vertical cross-sectional view showing a connection state of a cylinder head and a cylinder block in the engine body and passing through a partition wall between cylinder bores at a position along a line BB in FIG. 2;

5A and 5B are explanatory views of (A) the embodiment shown in FIG. 1 and (B) another embodiment of the lower surface structure of the cylinder head of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cylinder block 3 Gasket 4 Head bolt

Claims (1)

[Claims] In a cylinder head connected to an upper surface of a cylinder block via a gasket by a head bolt, a lower surface of the cylinder head opposed to an upper surface of the cylinder block has at least a lower surface with a boundary near a center portion in the width direction. A lower surface structure of the cylinder head, characterized in that one of the sides is formed as a surface that is inclined obliquely upward from near the center to the end in the width direction of the cylinder head.