JPH0428951B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a cylinder head gasket that is installed between the top surface of an engine cylinder block and the bottom surface of a cylinder head to maintain airtightness and liquidtightness between both surfaces. At the inner peripheral edge of the bore hole formed in the sheet of
This invention relates to an improvement in the method of attaching an annular grommet made of thin metal plate.

(Prior Art) As shown in Fig. 1, the cylinder head gasket 1 has bore holes 2, 2 formed in a circular shape to match the opening shape of the top of the cylinder, and a cylinder head gasket 1 for fixing the cylinder head to the cylinder block. Small circular holes 3, 3 for inserting bolts, or through holes 4, 4 for passing cooling water and lubricating oil are bored.

Among the holes drilled in the cylinder head gasket 1 in this way, the inner peripheral edge of the bore hole 2 is made of a thin metal plate in order to prevent the high pressure combustion gas generated within the cylinder from leaking to the outside. Grommet 5 is installed. This grommet 5 is made of a thin metal plate with excellent corrosion resistance such as stainless steel, which is made into an annular shape to match the inner diameter of the bore hole 2, and then folded back into a U-shaped cross section as shown in Fig. 2. Accordingly, it is attached to the inner peripheral edge of the bore hole 2.

Incidentally, such a grommet 5 is made by forming a layer of compound on both the front and back surfaces of a metal plate-shaped core material 10 such as an iron plate with a hook, and is formed by forming a layer of compound on both sides of the core material 10 made of metal such as an iron plate with a hook. Conventionally, this was done in the following manner.

That is, as shown in FIG. 3, an annular grommet material 5 with an L-shaped cross section is inserted into a bore hole 2 formed in a sheet 6.
a, and press-fit an inverted conical upper mold 7 into the cylindrical portion of the chromet material 5a protruding from the upper surface of the sheet 6, and then push the cylindrical portion outward as shown by the chain line in the same figure. After crimping and spreading it toward
A is press-fitted to the inner circumferential edge of a bore hole 2 formed in a sheet 6 constituting the cylinder head gasket 1.

(Problems to be Solved by the Invention) However, when attaching the grommet 5 to the gasket 1 by the conventional method as described above, the following (a) to (d)
This will cause the following inconvenience.

(a) After caulking the grommet material 5a, when the grommet material 5a is further crimped to the inner peripheral edge of the bore hole 2, the grommet material 5a is pressed between the flat upper and lower molds, but the grommet material 5a is thin. Since it is a metal plate and the surface of the sheet 6 is covered with a relatively soft compound, the pressing surfaces of the upper and lower molds also come into contact with the surface of the sheet 6 where no grommet is provided, and the grommet material 5a is attached to the sheet 6. The force to press toward the object becomes weaker.

If the force pressing the grommet material 5a becomes weak in this way, the grommet material 5a will not sink sufficiently into the sheet 6, and the thickness T (Fig. 2) of the grommet-attached portion will be the same as that of the sheet where the grommet 5 is not provided. 6 (FIG. 2), and the step difference (Tt) between the two parts becomes too large.

If a large step is created in the grommet mounting area like this, when the cylinder head gasket 1 is installed between the top surface of the cylinder block and the bottom surface of the cylinder head and is pressed strongly between both surfaces, the pressing force of the grommet mounting area is required. As a result, during operation of the internal combustion engine, this mounting portion becomes sagging, and the thickness T of the mounting portion gradually decreases.

If the thickness T of this part decreases due to the grommet attachment part becoming flat in this way, the sealing performance of the grommet attachment part will deteriorate, and the high pressure gas generated inside the cylinder due to combustion will leak to the outside, causing the engine to deteriorate. This results in a decrease in output.

(b) When crimping the grommet 5 to the periphery of the bore hole 2, first fit the grommet 5 to the inner periphery of the bore hole 2 while the seat 6 is not recessed, as shown in FIG. 4A. Furthermore, this grommet 5 is pressed between the upper and lower dies to press the grommet 5 to the sheet 6 while recessing the sheet 6.

However, when the grommet 5 is crimped in this manner, the gap 8 formed between the inner peripheral edge of the bore hole 2 and the inner surface of the grommet 5 becomes wider.

This is because when the grommet 5 is attached to the inner peripheral edge of the bore hole 2, the cross-sectional shape of the grommet 5 is close to a semicircular arc when the seat 6 is not yet recessed as shown in FIG. 4A. , = The width w of space 8 is not very large, but after that grommet 5
When the sheet 6 is depressed by pressing, the cross-sectional shape of the grommet 5 is deformed into an ellipse, and the width W of the gap 8 becomes wider than before the pressing (W>w).

When the width of the gap 8 between the inner circumferential edge of the bore hole 2 and the inner circumferential surface of the grommet 5 increases in this way, the strength of the grommet 5 decreases, and the grommet 5 cracks during operation of the internal combustion engine, causing damage inside the cylinder. Pressure leaks to the outside, which is likely to cause so-called blow-through.

In particular, if the cross-sectional shape of the grommet 5 becomes uneven in the circumferential direction, the grommet 5
becomes easy to break.

(c) Even when an attempt is made to strongly clamp the grommet 5 between the upper and lower dies, a considerable portion of the pressing force of the upper and lower dies comes into direct contact with both the front and back sides of the sheet 6, and is wasted in pressing the sheet 6. Therefore, unless the output (pressing force) of the press device is considerably increased, the time required to attach the grommet 5 to the peripheral edge of the bore hole 2 becomes long, and the productivity of the cylinder head gasket 1 is poor. Become.

(d) When the grommet 5 is attached to the peripheral edge of the bore hole 2, the sheet 6 at the peripheral edge of the bore hole 2 is crushed and the thickness of the part becomes smaller. The amount of crushing applied tends to be uneven.

That is, when crushing the peripheral edge, a portion of the sheet 6 that constitutes the peripheral edge escapes (flows) in the inner diameter direction, but the amount of escape tends to be uneven in the circumferential direction; In this case, the contact pressure between the grommet 5 and the lower surface of the cylinder head or the upper surface of the cylinder block becomes uneven in the circumferential direction, and the airtightness of the peripheral edge of the bore hole 2 tends to be insufficiently maintained.

The present invention eliminates the above-mentioned disadvantages, and provides a grommet installation method for a cylinder head gasket that does not create a large step in the grommet installation area, and also does not create a large gap between the inner peripheral edge of the bore hole and the grommet. The purpose is to provide a method.

(Means for Solving the Problems) The grommet mounting method of the cylinder head gasket of the present invention involves strongly pressing a sheet formed with a compound layer on both the front and back sides of a core material between upper and lower dies. By recessing a part of the sheet,
After forming a recess on both the front and back sides of this sheet with a diameter that is slightly larger than the bore hole and corresponding to the size of the grommet attachment part, the center part of this recess is punched out to form a bore hole. A grommet having an outer diameter large enough to fit inside the recess is attached to the inner peripheral edge of the recess.

(Example) Next, the present invention will be explained in more detail by explaining the illustrated embodiment.

FIG. 5 shows the gasket sheet 6 before punching out the bore holes. This sheet 6 is made by forming a compound layer on both the front and back sides of a metal core material 10 (see Figs. 6 to 8), such as an iron plate with a hook, and is provided with holes corresponding to the number of bore holes to be punched later. hand,
Circular recesses 9, 9 are formed.

This recess 9 is formed by forming a flat sheet 6 in advance.
By strongly pressing the sheet 6 between the upper and lower molds and recessing a part of the sheet 6, the sheet 6 is formed as shown in FIG.
It is formed on both the front and back sides of the borehole, and has a depth that is the same as or slightly smaller than the thickness of a grommet that will be later attached to the inner peripheral edge of the bore hole.

In the illustrated embodiment, since an integrated grommet 5 as shown in FIG. 1 is installed, adjacent circular recesses 9, 9 have a continuous shape. Furthermore, when pressing the front and back surfaces of the flat sheet 6 to form the recesses 9, the compound constituting the sheet 6 is pressed between the upper and lower dies and flows slightly.
The circumference of the recess 9 may swell, but in order to prevent this, before forming the recess 9, a punched hole with a diameter sufficiently smaller than the bore hole to be punched out later is formed in the center of the recess 9. You can leave it there.
If such a punched hole is formed, the compound pressed between the upper and lower molds will flow inside the punched hole, so that the periphery of the recess 9 will not swell.

In the sheet 6 in which the recesses 9, 9 have been formed on both the front and back surfaces, bore holes 2, 2 are then punched concentrically with the recesses 9, 9, as shown by the chain lines in FIG. 5 and in FIG. Form.

Once the bore holes 2 have been punched out, a grommet 5 is attached to each bore hole 2, 2, and the outer diameter of the grommet 5 is either the same as the diameter of the recess 9 or larger than the diameter of the recess 9. The grommet 5 should be made slightly smaller so that it fits inside the recess 9. In other words, the outer peripheral edge of the grommet 5 is prevented from protruding outside the recess 9.

After punching out the bore hole 2, the procedure for attaching the grommet 5 is the same as in the conventional case, and the grommet material 5a is caulked to the inner peripheral edge of the bore hole 2 using the upper die 7 as shown in FIG. After attaching it, it is crimped between another upper and lower mold. During this crimping work, if the upper and lower molds are flat, pressing the sheet 6 other than the grommet-attached part is the same as in the past, but the grommet-attached part of the sheet 6 is pressed in advance to form the recess 9. Therefore, there is no need to crush the portion covered by the grommet 5 with a portion of the sheet 6. For this reason, there is no need to particularly increase the force that presses the upper and lower dies together.
The time required to crush the grommet 5 into a predetermined shape is short, and no large step is created between the grommet 5 and the sheet 6. Therefore, the work of installing the grommet 5 can be completed in a short time, and there is no possibility that the installed portion will buckle during operation of the internal combustion engine, resulting in poor airtightness of the cylinder.
Further, the cross-sectional shape of the grommet 5 is close to an arc shape as shown in FIG. 8, and the width of the gap 8 can be small.

(Effects of the Invention) Since the grommet mounting method of the cylinder head gasket of the present invention is configured as described above, excellent effects as shown in the following (A) to (D) can be obtained.

(A) Since the peripheral edge of the bore hole 2 where the grommet 5 is to be installed is crushed in advance in a part of the sheet 6, the pressing force of the upper and lower molds for holding the grommet 5 presses the sheet 6. In addition to the fact that the recess 9 is formed in advance, the grommet 5 can be sufficiently sunk into the sheet 6, and there is no space between the surface of the grommet 5 and the sheet 6. There are no steps.

As a result, as the cylinder head gasket is used, the pressing force on the grommet 5 mounting portion does not gradually decrease, and the sealing performance of the grommet 5 mounting portion is ensured sufficiently over a long period of time.

(B) Since the recess 9 is formed in advance by crushing the sheet 6 in the grommet 5 mounting area, when the grommet 5 is mounted on the peripheral edge of the bore hole 2,
There is no need to further crush the grommet 5 after the both ends of the grommet 5 come into contact with both the front and back surfaces of the sheet 6, and the cross-sectional shape of the grommet 5 can be easily controlled to a semicircular arc shape over the entire circumference. becomes.

As a result, sufficient strength of the grommet 5 can be ensured, and the grommet 5 can be maintained even under severe usage conditions.
cracks are less likely to occur.

(C) Since a recess 9 is pre-formed in the grommet 5 attachment part, when the grommet 5 is held between the upper and lower molds, a part of the sheet 6
There is no need to crush the portion covered by the grommet 5, and most of the pressing force of the upper and lower dies can be used to crush the grommet 5. This allows the grommet to be crushed at the periphery of the bore hole 2 without increasing the output of the press device. It is possible to improve the productivity of the cylinder head gasket by shortening the time required to install the cylinder head gasket.

(D) The part of the sheet 6 where the grommet 5 is attached is crushed uniformly in advance, so when installing the grommet 5 around the periphery of the bore hole 2, the sheet around the periphery of the bore hole 2 6 is not crushed, and the thickness and density of the grommet 5 mounting portion are uniform in the circumferential direction.

As a result, the contact pressure between the grommet 5 and the lower surface of the cylinder head or the upper surface of the cylinder block in the circumferential direction becomes uniform, and the airtightness of the peripheral edge of the bore hole is sufficiently ensured.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an example of a cylinder head gasket with a grommet attached, Fig. 2 is an enlarged sectional view taken along line A-A in Fig. 1, and Fig. 3 shows a state in which the grommet is caulked to the inner peripheral edge of the bore hole. A vertical cross-sectional view showing
Figures 4A and 4B show the grommet being crimped by the conventional method; Figure A is in the middle of crimping, Figure B is a sectional view similar to Figure 2, showing the completed crimping, and Figure 5 is a sectional view similar to Figure 2. A plan view of a cylinder head gasket sheet to which a grommet is attached according to the present invention, FIG. 6 is an enlarged BB sectional view of FIG. 5, and FIG. 7 is a cross section similar to FIG. 6 showing the state after punching the bore hole. FIG. 8 is a cross-sectional view similar to FIG. 2 showing a grommet installed by the method of the present invention. 1: Cylinder head gasket, 2: Bore hole,
3: Small circular hole, 4: Through hole, 5: Grommet, 5a:
Grommet material, 6: sheet, 7: upper mold, 8:〓
Between, 9: recess, 10: core material.

Claims (1)

[Claims] 1 The sheet 6, which consists of a compound layer formed on both the front and back sides of the core material and which constitutes the cylinder head gasket, is strongly pressed between the upper and lower dies to partially dent the sheet 6. A recess on both the front and back surfaces of the sheet 6, which has a diameter larger than the bore hole 2 in which the grommet 5 is to be installed, and a depth that is equal to or slightly smaller than the thickness of the thin metal plate constituting the grommet 5. 9 is formed, a bore hole 2 is bored inside the recess 9, and then a grommet 5 having an outer diameter large enough to fit inside the recess 9 is attached to the inner peripheral edge of the bore hole 2. , How to install cylinder head gasket grommets.