JPH0443641Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a cylinder head gasket interposed between a cylinder block and a cylinder head of an engine.

(Prior Art) Conventionally, a cylinder head gasket for an engine in which a reinforcing wire ring is provided around the cylinder bore is known, as seen in Japanese Utility Model Application Publication No. 61-99655.

Furthermore, in the above-mentioned prior art example, the hardness of the wiring in the front and rear parts of the engine is lower than that in other parts.

(Problems to be Solved by the Invention) However, in the cylinder head gasket of the preceding example as described above, only the sealing performance of the front and rear ends of the engine is considered.
The actual "sag" of the wiring, that is, the amount of change in thickness, cannot be ensured by simply dividing the front and rear ends of the engine from other parts to ensure approximately uniform sealing performance (thickness) in the circumferential direction of the cylinder bore. It is something that cannot be done.

The settling of the cylinder head gasket, that is, the change in thickness, occurs due to thermal stress due to temperature changes associated with engine operation and explosion stress due to an explosion within the combustion chamber. The cylinder head is repeatedly displaced in the vertical direction, and the wire ring, which initially has a circular cross section, is crushed by the action of vertical force, causing sag where the cross section is deformed into an elliptical shape, which causes a reduction in gas sealing performance. It is something.

The vertical movement of the cylinder head due to the above-mentioned thermal stress and explosive stress is regulated by the head bolt that fastens the cylinder head to the cylinder block, and the amount of displacement differs greatly between the area near the head bolt and the area between the head bolts. , the sag in the vicinity of the head bolt is smaller than in other parts, and in particular, large thermal stress occurs between adjacent bores, so a large sag occurs in this area (see Figure 4 below). reference). Therefore,
With long-term use, the bore may become uneven in its circumferential direction, leading to a decrease in the sealing performance of the combustion chamber.

There is also a structure that increases the surface pressure by forming shims on the gasket in areas of the cylinder head where vertical displacement is large, but with this type the initial thickness of the gasket becomes uneven in the circumferential direction of the bore, and the It is difficult to ensure uniform sealing performance.

Therefore, in view of the above-mentioned circumstances, the purpose of the present invention is to provide an engine cylinder head gasket that has a uniform initial thickness and a uniform sealing performance in the circumferential direction of the bore portion even after long-term use. That is.

(Means for Solving the Problems) In order to achieve the above object, the cylinder head gasket of the present invention has an initial thickness of the gasket set to be approximately constant in the circumferential direction of the bore portion, and the wiring is partially hardened, etc. Accordingly, the resistance to settling in the circumferential direction of the bore portion is increased in the portion between the bores near the head bolt.

(Function) In the cylinder head gasket as described above,
The sagging resistance of the seal reinforcing wire ring in the bore part is increased by partially hardening the area between the bores from the vicinity of the head bolt in the circumferential direction, changing the material, etc., and making the initial thickness almost constant. In addition to achieving uniform sealing performance in the circumferential direction of the bore section when tightened at the initial stage of use, even after long-term use, the settling caused by vertical movement of the cylinder head in the bore section due to thermal stress, explosive stress, etc. is uniform in the circumferential direction. This ensures good sealing performance.

(Example) Hereinafter, an example of the present invention will be described along with the drawings. FIG. 1 is a plan view of a cylinder head gasket for an in-line four-cylinder engine.

This cylinder head gasket 1 is a metal gasket, and has first to fourth bore portions 2 opened corresponding to each cylinder bore of an engine (not shown), and has a cylinder head and a cylinder block on the outside thereof. A bolt hole 3 is formed into which a head bolt to be fastened is inserted. This bolt hole 3
are provided on both sides of the bore gap 4 between each bore part 2 and on both sides of both ends, and each bore part 2 has four bolt holes 3 arranged on its outer circumferential side,
This part is tightened.

The circumferential portion (grommet portion) of each bore portion 2 is provided with:
A seal reinforcing wire ring 5 is provided inside.
That is, as shown in FIG. 2, which shows the cross-sectional structure of the portion 4 between the bores, the top plate 6 constituting the upper surface is located at the opening periphery of the bore portion 2 and is located inside the annular wire ring 5 that follows the shape of the bore portion 2. It is bent downward at the circumference. Furthermore, bead plates 8 and 9 having uneven shapes are interposed between the wire rings 5 and 5 of the adjacent bore portions 2 and 2 above and below a base plate 7 that constitutes the core material of the gasket 1.

Also, cylinder head gasket 1 of this example
is for an engine with a pre-chamber,
A substantially semicircular bead 10 is formed in the gasket 1 corresponding to the installation position of this subchamber (below the bore portion 2 in the figure).

FIG. 3 shows the cross-sectional structure of the gasket 1 in the sub-chamber installation part, from the inner peripheral part of the bore part 2 formed by the top plate 6 and the wiring 5 to the bottom surface of the top plate 5 on the upper surface side. carbon graphite 11,
Base plate 7, lower bead plate 9, back plate 1
2 are laminated in order, and at the end of the subchamber, the carbon graphite 11 is followed by the upper bead plate 8.
The bead 10 is formed by forming substantially semicircular projections 8a and 9a on the upper bead plate 8 and the lower bead plate 9.

In the cylinder head gasket 1 having the above structure, the wire ring 5 is partially hardened except for the area near the bolt hole 3, so that the resistance to settling varies in the circumferential direction of the bore portion 2. The formed one is used. That is, in FIG. 1, the wire ring 5 installed in the inner circumferential portion of each bore portion 2 has low fatigue resistance in the non-hardened area A in the portion near the bolt hole 3 for inserting the head bolt; The part between 4, the lower part of the sub-chamber, the front and rear ends, and the upper side are the hardened area B, and this hardening increases the hardness and increases the resistance to settling.

The gasket 1 with the above structure has an initial thickness of the bore part 2.
The surface pressure is approximately constant in the circumferential direction of the bore portion 2, and in the initial tightened state of the cylinder block and cylinder head with this gasket 1 interposed therebetween, the surface pressure is approximately constant in the circumferential direction of the bore portion 2.
It is uniform in the circumferential direction, and the sealing performance is also uniform.

Due to the effects of thermal stress and explosive stress associated with engine operation, the load when the cylinder head is repeatedly displaced in the vertical direction acts on the gasket 1, causing the wiring 5 to sag, but the portion near the head bolt The sag is small compared to other parts, and in particular, the thermal stress is large in the inter-bore space 4 where the bore portions 2 are adjacent and in the subchamber, so a large sag occurs in these parts.
The wire ring 5 in this part is hardened and has high resistance to fatigue, and after long-term use, the dimensions change approximately evenly in the circumferential direction of the bore part 2, resulting in a uniform gasket thickness that is good and uniform. It is possible to ensure good sealing performance.

Fig. 4 shows a cylinder head gasket 1 having the same structure as shown in Fig. 1, but constructed with wiring that has not been partially hardened, and the cylinder head gasket 1 is installed in an engine and operated for a predetermined period of time. Later, it shows the results of measuring the thickness of the wiring at each position around the circumference of the bore 2 of each cylinder, and the measured values increase from the center to the outer circumference, and the smaller the thickness of the wiring, the smaller the thickness of the wiring. This can be considered to be a large amount. As a result, the thickness is reduced and a large sag occurs in the area between the bores 4 where the bore portion 2 adjoins and in the area where the auxiliary chamber is installed. It was found that the sagging amount was smaller at the top and upper sides, and based on this, partial hardening was performed on the middle part other than the vicinity of the head bolt to improve the sagging resistance and uniformly. It was designed to make the

In addition, in the above embodiment, the wiring 5
Excluding the area near the head bolt, four locations in the middle, including the area between the bores, are partially hardened, but in the case of an engine without a pre-chamber, the corresponding area is hardened. The amount is small, and the thermal stress in the portions other than between the bores is smaller than that between the bores 4, so depending on the engine to which it is applied, only the between the bores 4 may be partially hardened.

Moreover, in addition to hardening, partial improvement in the resistance to settling may be achieved by partially changing the material, or by performing other surface treatments.

(Effects of the invention) According to the invention as described above, the resistance to fatigue of the wiring is made larger between the bores in the circumferential direction of the bore than near the head bolt, and the initial thickness is made substantially constant. At the same time as achieving uniform gas sealing performance in the circumferential direction of the bore in the tightened state at the beginning of use, even after long-term use, the bore circle is prevented from sagging due to vertical movement of the cylinder head around the cylinder bore due to thermal stress, explosion stress, etc. The pressure can be changed uniformly in the circumferential direction, and good sealing performance can be maintained by equalizing the surface pressure in the circumferential direction of the bore.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a cylinder head gasket in an embodiment of the present invention, and Fig. 2 is a -
FIG. 3 is an enlarged cross-sectional view taken along the same line, and FIG. 4 is an explanatory view showing the results of measuring the state of fatigue after use in a wire ring that has not been hardened. 1... Cylinder head gasket, 2... Bore section, 3... Head bolt hole, 4... Between bores, 5...
...Wiring, A...Unhardened range, B...Hardened range.

Claims (1)

[Scope of utility model registration request] In an engine cylinder head gasket in which a seal reinforcing wire ring is provided around the circumference of a bore section opened corresponding to each cylinder bore of the engine, the initial thickness of the gasket is approximately constant in the circumferential direction of the bore section. The engine is characterized in that the wiring is provided by partial quenching or the like so that the resistance to settling in the circumferential direction of the bore portion is greater in the portion between the bores than in the portion near the head bolt. cylinder head gasket.