JP3026073B2 - Head gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a head gasket having a unitary structure bead used for a head gasket or the like of an internal combustion engine and having enhanced gas sealing performance.

[0002]

2. Description of the Related Art A head gasket 10 for sealing an internal combustion engine between a cylinder block 11 as shown in FIG. 4 and a cylinder head (not shown) has a planar shape as shown in FIG. 5 and has a combustion chamber (cylinder bore). ) In order to seal the combustion gas generated in 21, the lubricating oil circulating in the oil gallery, the cooling water in the water jacket, etc.
It is necessary to generate sufficient sealing surface pressure. In particular, since it is necessary to seal high-temperature and high-pressure combustion gas at the peripheral portion of the combustion chamber 21, a metal gasket excellent in mechanical strength and durability has been used conventionally.

A single metal gasket made of a single metal plate, which is one type of such a head gasket, has a cross-sectional structure shown in FIG. A loop-shaped bead 3 is formed by expanding the substrate 1 to one side, and a high sealing surface pressure is generated by the bead 3. Further, when the bolt is inserted between the cylinder block 11 and the cylinder head 12 and tightened with a bolt, the bolt hole 7 through which the head bolt penetrates is formed.
In addition, a lubricating oil hole 2b, a cooling water hole 2a, and the like are formed, and a seal ring 5 is provided on a peripheral portion thereof.

When the head gasket 10 is sandwiched between the cylinder block 11 and the cylinder head 12, the sealing surface pressure generated by the fastening force of the head bolts can provide sufficient sealing performance for a long period of time. Care is taken to be within a range suitable for holding over, and these head bolts are tightened with a torque wrench to a predetermined tightening torque according to a predetermined order, so that the tightening torque is uniform. It is assembled as follows.

[0005] This is because if the sealing surface pressure generated by the bolt fastening force is too weak, the function of sealing the combustion gas or the like cannot be sufficiently achieved. This is because this may cause breakage or sagging of the part, making it impossible to maintain the sealing performance for a long period of time.

[0006]

However, in the case of the conventional head gasket 20 shown in FIG. 6, it is necessary for the bead 3 to be vibrated due to a change in internal pressure during operation of the engine and a change in heat load due to a change in temperature. When the above pressing force F is applied, this pressing force F acts locally, so that the bead 3 portion is flattened, and it becomes difficult to maintain proper elasticity due to fatigue in a short time. Further, there is a problem that the set may be broken due to settling, the sealing performance may be reduced, and the combustion gas or the liquid may leak.

Therefore, as shown in FIG. 7, a structure was studied in which a grommet 41 was attached to the inside of the bead 3 to prevent the bead 3 from being flattened. The inner portion of the head gasket substrate 1 has an inner portion 1c on the side of the combustion chamber hole 2 of the bead 3 although the inner portion of the grommet 41 has three layers and an effect of protecting the bead 3 can be obtained.
Will face each other.

Therefore, the load caused by the pressing force F acting on the head gasket 30 via the cylinder block 11 and the cylinder head 12 acts intensively on the portion 1c where the both ends 41a and 41b abut, and the head gasket substrate 1 Since a large stress is generated in this portion 1c and a portion where the stress rapidly changes is formed, a crack is easily generated.
c, the damage is enlarged, the sealing performance of the head gasket 30 is deteriorated, and there is a problem that the high temperature and high pressure combustion gas cannot be reliably sealed.

Particularly, in the case of a single head gasket, since the substrate 1 and the grommet 41 are formed thicker than the metal plate constituting the metal plate laminated gasket, the three-layer portion provided with the grommet 41 is provided. From this, the step of the portion that becomes one layer of only the substrate 1 becomes large, the load tends to act intensively with it, and the load is not dispersed like the metal plate laminated gasket, Since a load acts directly on both side surfaces of the substrate 1, there is a problem that the portion 1c is easily damaged.

In view of the above problems, the present invention can maintain the sealing performance by maintaining the elasticity of the bead around the combustion chamber hole for a long period of time while having a single-piece structure, and can maintain the stress around the bead. It is an object of the present invention to provide a head gasket capable of preventing concentration and improving durability.

[0011]

According to the present invention, there is provided a head gasket comprising a single-piece head gasket for use in an internal combustion engine, which is provided at the periphery of each combustion chamber hole. A grommet is attached to a portion surrounding the combustion chamber hole, and the grommet is formed to have a short edge and a long edge, and the short edge is formed by projecting the bead. A long edge portion covers the bead on the concave side of the bead, and extends so as to have an end portion near the outside of the bead, and extends outside the bead. A step is formed in the vicinity .

Alternatively, a bead is formed around the periphery of each combustion chamber hole of a head gasket having a single structure used in an internal combustion engine so as to surround these combustion chamber holes, and a bead is formed around the combustion chamber hole. A grommet is attached, the grommet has a short edge and a long edge, and the short edge is provided inside the bead on the projecting side of the bead, and the long edge is on the concave side of the bead. Covering the bead, and extending so as to have an end near the outside of the bead, forming a step near the outside of the bead, and further, annularly forming a step groove near the outside of the recess of the bead. To accommodate a part of the thickness of the long edge portion.

Further, the head gasket is provided with a coating layer on a contact surface between the cylinder block and the cylinder head. Since the head gasket of the present invention has the above configuration, even if the bead is pressed,
Since it is not completely flattened and the concentration of stress around the bead can be prevented, high durability can be obtained.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a head gasket 10 according to the present invention is a single-piece head gasket 10 used for an internal combustion engine, and the periphery of each combustion chamber hole 2 surrounds the combustion chamber hole 2. An annular bead 3 formed by the head gasket 10 is provided at a peripheral edge located at both ends of the head gasket 10.
An auxiliary bead (seal ring) 5 is formed for sealing water or oil holes.

A grommet 4 is attached to a portion surrounding the combustion chamber hole 2, and the grommet 4 is folded back 4c.
Is formed by providing a short edge portion 4a and a long edge portion 4b on both sides.
A short edge 4a of the grommet 4 is provided on the projecting side of the bead 3 and is disposed inside the bead 3 on the side of the combustion chamber hole 2;
The long edge 4b is provided on the concave side of the bead 3, and this bead 3
Is provided so as to extend to the outside of the bead 3 so as to cover the concave portion.

That is, the short edge 4a of the grommet 4 is formed up to just before the projecting bead 3, and the long edge 4b is formed so as to straddle the recess 3b of the bead 3, and the end portion C is formed outside the bead 3. and extended to have, outside of the bead 3 near
A step is formed beside . The substrate 1 of the head gasket 10 is formed of, for example, a stainless spring steel plate, an iron plate, a copper plate, an aluminum plate, or the like with a thickness of, for example, 0.1 to 0.4 mm. The grommet 4 is formed of, for example, a stainless steel annealed plate, copper, or a mild steel plate. For example, the thickness t1 is set to, for example, 0.08 to 0.12 mm.

As a second embodiment, as shown in FIG. 2, a step groove 1b is provided outside the concave portion of the bead 3 to accommodate a part t3 of the thickness t2 of the long edge 4b of the grommet 4. It is constituted so that. Head gasket 1 at this time
As an example, the grommet 4 is formed so that the thickness t2 of the grommet 4 is about 0.08 to 0.2 mm and the depth t3 of the step groove 1b is about 0.05 to 0.1 mm. Is formed such that the protruding amount t2-t3 of the long edge portion 4b from the substrate 1 is about 0.03 to 0.1 mm.

The head gasket 10 having the stepped groove portion 1b is formed by thinning the portion of the substrate 1 from the stepped groove portion 1b toward the combustion chamber hole 2 by coining or cutting.
The bead 3 is formed by pressing. Alternatively, when pressing the beads 3 on the substrate 1 having the same thickness,
b is also formed and formed at the same time.

Further, as a third embodiment, a coating layer 6 is formed on the head gasket 10 shown in FIGS. As shown in FIGS. 3 and 4, this coating layer 6 is made of silicon rubber, fluorine rubber, molybdenum disulfide (MoS2
), Etc., formed on the contact surface with the cylinder head or cylinder, thereby improving the metal gasket with a single structure that originally had poor adaptability to the machining trace of the tightening surface, and improved the adaptability to the tightening surface Thermal expansion of the tightening surface,
This prevents the grommet 4 from dragging due to contraction. In addition,
The coating layer 6 is not provided on the inner portion of the grommet 4 or the concave portion of the bead 3.

The shape of the bead 3, the thickness of the grommet 4, the thickness of the coating layer 6, and the like are designed in accordance with factors such as the pressure of the combustion gas to be sealed and the bore pitch (the distance between mutually adjacent cylinders). Change and adjust to obtain appropriate sealing surface pressure and durability.

The head gasket 10 constructed as described above
Is pressed between the cylinder block 11 and the cylinder head 12 by a fastener such as a head bolt, and the bead 3 is crushed to form a seal portion. And
When the pressing force F further increases, the portion of the grommet 4 inside the bead 3 that overlaps the three layers is the cylinder block 11.
Abuts on the upper surface of the cylinder head 12 and the lower surface of the cylinder head 12 to protect the bead 3 and secure the seal.

That is, according to the head gasket 10, the combustion chamber hole 2 side of the bead 3 is in contact with the bead 3 and the grommet 4.
Is thickest when three short edges 4a and long edges 4b are overlapped with each other, so that a sufficient surface pressure for sealing the combustion gas can be secured at this portion, and a good sealing portion is formed. Can be. Further, with the three-layer structure, the surface pressure of the inner portion of the bead 3 can be easily adjusted by changing the thickness of the grommet 4.

Further, since the concave portion of the bead 3 is disposed on the long edge portion 4b of the grommet 4 having elasticity, that is, on the sealing member also serving as a cushion, the relatively soft cylinder block 11 made of aluminum alloy or the like can be used. This long edge 4
Since the beads 3 come into contact with each other evenly through the b, the corners of the concave portions of the beads 3 do not directly hit, and even if the substrate 1 expands or contracts due to thermal expansion or the like, the beads 3 are smooth inside the grommet 4. , The damage to the cylinder block 11 does not occur and leakage of the seal can be prevented.

In addition, the contact portions can be dispersed at three positions, namely, the end portion A of the short edge portion 4a of the grommet 4, the portion B of the bead 3, and the end portion C of the long edge portion 4b of the grommet 4, so that each portion has a sealing effect. Can be achieved, and the seal can be made more reliable. Also, the short edge 4 of the grommet 4
By stopping a at the inside of the bead 3, the inside of the bead 3 becomes three layers while the inside of the bead 3 becomes two layers, and when the pressing force F is applied to the bead 3, the short side adjacent to the inside becomes short. By preventing the bead 3 from being completely crushed and flattened by the thickness of the edge portion 4a, the bead 3 can be compensated. Therefore, the bead 3 is prevented from being set, the elasticity is maintained in a pressed state, and the sealing force is maintained. Can be planned.

Further, the ends of the short edge 4a and the long edge 4b of the grommet 4 are arranged on both sides of the bead 3, and the ends of the grommet 4 abut on both side surfaces of the same portion of the head gasket substrate 1. Is avoided, and the discontinuous portions A and C of the stress are dispersed on both the inner and outer sides of the bead 3, so that the durability of the head gasket substrate 1 can be improved.

Further, a step groove 1b is provided in the head gasket substrate 1 so that the bead recess side of the grommet 4 and the head gasket substrate 1 are relatively smoothly connected.
A large load can be prevented from being applied to the portion C where the end of the long edge portion 4b of the grommet 4 is located, and the durability of the head gasket 10 can be increased. In addition, the long edge portion 4b
Can be set irrespective of the plate thickness t1 of the grommet 4, so that the sealing surface pressure of each part can be configured more effectively.

In addition, since the coating layer 6 is formed on the contact surface with the cylinder block 11 and the cylinder head 12, the conformability to the tightening surface is improved, and the grommet due to the thermal expansion and shrinkage of the tightening surface is provided. 4 can be prevented from dragging.

[0028]

According to the head gasket of the first aspect of the present invention, since the grommet is mounted on the hole portion of the gasket substrate and formed in three layers, by adjusting the plate thickness, the inner portion of the bead can be formed. The surface pressure can be easily adjusted, and a sufficient surface pressure for sealing the combustion gas can be secured. As a result, the sealing performance can be improved.

Further, the long edge of the grommet is extended so as to have an end portion near the outside of the bead recess, and a step is formed near the outside of the bead, so that the bead recess side has an elastic grommet. Since it is arranged on the long edge, that is, a kind of cushioning material, the bead uniformly presses the cylinder block through this long edge, and the corner of the concave portion of the bead does not directly contact, The seal block can be prevented from leaking without causing damage to the cylinder block due to beads.

Further, by providing the short edge portion of the grommet inside the bead, when the pressing force is applied to the bead portion, the bead is protected by the thickness of the short edge portion, and the bead is abnormally flattened. Can be prevented. In addition, by displacing the portion where the end of the grommet abuts on the substrate of the head gasket on both sides of the bead, the pressing load can be prevented from being concentrated, and the stress is dispersed on the sealing surface of the cylinder block. At the same time, the durability of the substrate can be improved.

According to the head gasket of the second aspect of the present invention, the substrate is further provided with a stepped groove so as to accommodate a part of the thickness of the long edge of the grommet on the side of the bead recess. The pressing load concentrated on the end of the long edge of the grommet can be reduced, and the durability of the head gasket can be further increased. In addition, claim 3
According to the head gasket of the present invention, since the coating layer is provided on the contact surface with the cylinder or the cylinder head, it is possible to improve the conformability to the tightening surface of the metal gasket having a single-layer structure having relatively poor conformability. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a head gasket according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part of a head gasket according to a second embodiment of the present invention.

3A and 3B are longitudinal sectional views of a main part of a head gasket provided with a coating layer. FIG. 3A is a diagram in which a coating layer is provided on the head gasket of FIG. 1, and FIG. It is provided with a layer.

FIG. 4 is a perspective view showing an example of a cylinder block.

FIG. 5 is a plan view showing an example of a head gasket.

FIG. 6 is a longitudinal sectional view of a main part of a conventional head gasket.

FIG. 7 is a longitudinal sectional view of a main part of a prior art head gasket.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 1b ... Step groove part 2 ... Combustion chamber hole 3 ... Bead 3c ... Foot part 4 ... Grommet 4a ... Short edge part 4b ... Long edge part 4c ... Folding part 5 ... Secondary bead 6 ... Coating layer 7 ... Bolt hole 10, 20, 30 ... head gasket 11 ... cylinder block 12 ... cylinder head 21 ... combustion chamber 23 ... bolt hole

Claims (3)

(57) [Claims] 1. A head gasket having a unitary structure used in an internal combustion engine, a bead is formed on the periphery of each combustion chamber hole so as to surround the combustion chamber hole, and a bead is formed around the combustion chamber hole. A grommet is mounted, the grommet is formed having a short edge and a long edge, and the short edge is disposed inside the bead at a projecting side of the bead, and the long edge is formed by the bead. A head gasket which is formed by covering the bead on the side of the concave portion and extending so as to have an end near the outside of the bead, and forming a step near the outside of the bead. 2. A head gasket having a unitary structure used in an internal combustion engine, a bead is formed on a peripheral portion of each combustion chamber hole so as to surround the combustion chamber hole, and a bead is formed around the combustion chamber hole. A grommet is attached, the grommet has a short edge and a long edge, and the short edge is provided inside the bead on the projecting side of the bead, and the long edge is on the concave side of the bead. Cover the bead, and
Extending so as to have an end portion near the outside of the bead,
A head gasket comprising a step formed near the outside of the bead, and a stepped groove formed annularly near the outside of the recess of the bead so as to accommodate a part of the thickness of the long edge. 3. The head gasket according to claim 1, wherein a coating layer is provided on a contact surface between the cylinder block and the cylinder head of the head gasket.