Cylinder head gasket and engine

The thickness of an intermediate plate portion (31b) is smaller than the thickness of a stopper portion (31a). The thickness of a portion of a cylinder head gasket (20) having the stopper portion (31a) is set to be greater than the thickness of other portions of the cylinder head gasket (20). Before the cylinder head gasket (20) is provided between contact surfaces (12a, 13a), a space (S) is formed between the stopper portion (31a) and an adjustment stopper portion (32a), and the intermediate plate portion (31b) partially contacts the adjustment plate portion, and a bead (33a) contacts the adjustment plate portion (32b).

FIELD OF THE INVENTION

The present invention relates to a cylinder head gasket that is provided between contact surfaces of a cylinder head and a cylinder block.

BACKGROUND OF THE INVENTION

Patent Document 1 discloses a cylinder head gasket80that is shown inFIG. 7of the present application. The cylinder head gasket80is a metal gasket having a laminated structure. The cylinder head gasket80has an intermediate plate81and an adjustment plate82that are laminated on each other, and bead plates83,84that sandwich the intermediate plate81and the adjustment plate82. The intermediate plate81and the cylinder head sandwich the bead plate83and the adjustment plate82and the cylinder block sandwich the bead plate84.

The cylinder head gasket80has a plurality of combustion chamber openings80aeach of which corresponds to one of the cylinder bores formed in the cylinder block. The bead plates83,84have beads83a,84aeach of which surrounds the combustion chamber opening80a. If the cylinder head is fixed to the cylinder block by a bolt in a state where the cylinder head gasket80is provided between contact surfaces of the cylinder head and the cylinder block, the bead83aseals a space between the cylinder head and the intermediate plate81, and the bead84aseals a space between the cylinder block and the adjustment plate82.

The intermediate plate81has a stopper portion81athat is provided around the combustion chamber opening80a. The stopper portion81areceives axial fastening force of the bolt to inhibit the beads83a,84afrom fully collapsing. That is, the stopper portion81acompensates for the space between the contact surfaces of the cylinder head and the cylinder block that is formed by deformation of the cylinder head gasket80due to the fastening force of the bolt. The adjustment plate82adjusts the thickness of the cylinder head gasket80such that the thickness of the cylinder head gasket80becomes equal to the space between the contact surfaces of the cylinder head and the cylinder block. The adjustment plate82has a recess82ato which the stopper portion81ais fitted. In the above publication, the intermediate plate81is referred to as a “compensation plate”, and the stopper portion81ais referred to as a “folded portion”.

The thickness of the stopper portion81ais greater than the thickness of other portions of the intermediate plate81. The stopper portion81aprotrudes along its thickness toward the adjustment plate82. A step81bis formed between the stopper portion81aand the other portions of the intermediate plate81. The measurement along the thickness between the intermediate plate81and the stopper portion81ais referred to as a stopper height H1, and the measurement along the thickness of the recess82ais referred to as an adjustment step height H2. The stopper height H1is greater than the adjustment step height H2.

Therefore, when the cylinder head is fastened to the cylinder block with the bolt, the stopper portion81aclosely contacts the adjustment plate82. However, a space T is formed between the intermediate plate81and the adjustment plate82in the vicinity of the step81b. If the cylinder head gasket80receives pressure fluctuation in the cylinder bore or the repetition of cooling and heating in a state where the space T is formed, the adjustment plate82may flap.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a cylinder head gasket that inhibits flapping of an adjustment plate.

According to one aspect of the present invention, cylinder head gasket that is provided between a contact surface of a cylinder head and a contact surface of a cylinder block, which are connected to each other, is provided. The cylinder block has a cylinder bore. A combustion chamber opening is formed in the cylinder head gasket so as to correspond to the cylinder bore. The cylinder head gasket has an intermediate plate having a stopper portion that is positioned around the combustion chamber opening. The intermediate plate has an intermediate plate portion that is positioned at the outer side of the stopper portion with respect to the combustion chamber opening. The thickness of the intermediate plate portion is smaller than the thickness of the stopper portion. An intermediate step is formed, as a step portion, at the boundary between the stopper portion and the intermediate plate portion. An adjustment plate is provided closer to the cylinder head or to the cylinder block with respect to the intermediate plate. The adjustment plate has an adjustment stopper portion facing the stopper portion and an adjustment plate portion facing the intermediate plate portion. An adjustment step is formed, as a step facing the intermediate step, at the boundary between the adjustment stopper portion and the adjustment plate portion. A bead plate is provided between the adjustment plate and the cylinder head or between the adjustment plate and the cylinder block. The bead plate has a bead that surrounds the combustion chamber opening at the outer side of the stopper portion with respect to the combustion chamber opening. The intermediate plate, the adjustment plate, and the bead plate are laminated to each other. The thickness of a portion of the cylinder head gasket that has the stopper portion is set to be greater than the thickness of other portions of the cylinder head gasket. Before the cylinder head gasket is provided between the contact surfaces, a space is formed between the stopper portion and the adjustment stopper portion, and the intermediate plate portion at least partially contacts the adjustment plate portion, and the bead contacts the adjustment plate portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 3show a cylinder head gasket20according to one embodiment of the present invention.

FIG. 1shows an engine11to which the cylinder head gasket20is attached. The engine11has a cylinder block13and a cylinder head12that is joined to the cylinder block13. A head contact surface12a, which is a contact surface of the cylinder head12, faces a block contact surface13a, which is a contact surface of the cylinder block13. The cylinder block13has a plurality of cylinder bores14, and each cylinder bore14accommodates a piston15so as to reciprocate therein. A peripheral surface of each cylinder bore14, an upper surface of the piston15, and a lower surface of the cylinder head12defines a combustion chamber16.

The cylinder head gasket20is formed in a rectangular plate shape that is arranged between the head contact surface12aand the block contact surface13a.

As shown inFIG. 2, the cylinder head gasket20has a plurality of combustion chamber openings21, coolant passage openings22, oil passage openings23, and bolt insertion openings24. The combustion chamber openings21and the bolt insertion openings24are circular. When the cylinder head gasket20is arranged between the head contact surface12aand the block contact surface13a, each combustion chamber opening21corresponds to one of the cylinder bores14.

As shown inFIG. 3, the cylinder head gasket20has a laminated structure having an intermediate plate31, an adjustment plate32, a head bead plate33, and a block bead plate34that are laminated on each other. The block bead plate34, the intermediate plate31, the adjustment plate32, and the head bead plate33are laminated on each other in this order. That is, the cylinder block13, the block contact surface13a, the block bead plate34, the intermediate plate31, the adjustment plate32, the head bead plate33, the head contact surface12a, and the cylinder head12are arranged in this order. The intermediate plate31, the adjustment plate32, the head bead plate33and the block bead plate34are formed in a rectangular plate and each have an edge31e,32e,33e,34eas an outline. Each of the combustion chamber openings21extends through the block bead plate34, the intermediate plate31, the adjustment plate32, and the head bead plate33.

The intermediate plate31shown inFIG. 3is made of metal and is formed by an iron plate or a stainless steel plate. The intermediate plate31has a stopper portion31aand an intermediate plate portion31b. The stopper portion31ais positioned around the combustion chamber openings21. The intermediate plate portion31bis positioned between the stopper portion31aand a side edge31eof the intermediate plate31. A direction away from the combustion chamber opening21is referred to as outward. It can be said that the intermediate plate portion31bis positioned outside the stopper portion31a.

As shown inFIG. 3, the measurement of the cylinder head gasket20along its normal line is referred to as a thickness. In other words, the lamination direction of the intermediate plate31, the adjustment plate32, the head bead plate33, and the block bead plate34is the thickness direction of the cylinder head gasket20. The thickness of the stopper portion31ais greater than the thickness of the intermediate plate portion31b. In other words, the thickness of the intermediate plate31in the stopper portion31ais different from that in the intermediate plate portion31b. The thickness of the intermediate plate portion31bis within an area between two surfaces of the stopper portion31ain its thickness direction. The cylinder head gasket20has an intermediate step31cthat is a step positioned at a boundary between the stopper portion31aand the intermediate plate portion31b. The height of the intermediate step31cis referred to as a stopper height h1. The stopper height h1represents the measurement along the thickness between a surface of the stopper portion31afacing the adjustment plate32and a surface of the intermediate plate portion31bfacing the adjustment plate32.

In the present embodiment, the thickness of one plate changes at a certain portion so as to form the stopper portion31aand the intermediate plate portion31bhaving different thicknesses. Accordingly, the intermediate step31chas two inclined tapered surfaces so as to increase the width between the surfaces from the intermediate plate portion31btoward the stopper portion31a. The intermediate plate portion31bis positioned between the intermediate step31cand the side edge31eof the intermediate plate31. The intermediate plate portion31bis positioned closer to the side edge31eof the intermediate plate31than the intermediate step31c. The intermediate plate portion31bis a portion of the intermediate plate31other than the stopper portion31aand the intermediate step31c.

The intermediate plate portion31bhas an intermediate bead31dthat is curved to be convex toward the block bead plate34.

The adjustment plate32shown inFIG. 3is made of metal and is an iron plate or a stainless steel plate. The adjustment plate32has an adjustment stopper portion32aand an adjustment plate portion32b. The adjustment stopper portion32ais a first facing portion facing the stopper portion31aand positioned around the combustion chamber opening21. The adjustment plate portion32bis a second facing portion facing the intermediate plate portion31b. The adjustment plate portion32bis positioned between the adjustment stopper portion32aand a side edge32eof the adjustment plate32. The adjustment plate portion32bis positioned at the outer side of the adjustment stopper portion32a.

As shown inFIG. 3, the adjustment plate32is bent at a portion between the adjustment stopper portion32aand the adjustment plate portion32b. The measurement along the thickness between the adjustment stopper portion32aand the intermediate plate portion31bis greater than the measurement along the thickness between the adjustment plate portion32band the intermediate plate portion31b. The thickness of the adjustment stopper portion32ais equal to the thickness of the adjustment plate portion32b. The adjustment step32cis inclined from the adjustment stopper portion32atoward the adjustment plate portion32b. A bent portion of the adjustment plate32between the adjustment stopper portion32aand the adjustment plate portion32bis referred to as an adjustment step32c. The adjustment step32cfaces the intermediate step31c.

The height of the adjustment step32cis referred to as an adjustment step height h2. The adjustment step height h2represents the measurement along the thickness between a surface of the adjustment stopper portion32afacing the intermediate plate31and a surface of the adjustment plate portion32bfacing the intermediate plate31. The stopper height h1is set to be smaller than the adjustment step height h2.

The adjustment plate portion32bis positioned between the adjustment step32cand the side edge32eof the adjustment plate32. In other words, the adjustment plate portion32bis positioned closer to the side edge32eof the adjustment plate32than the adjustment step32c. The adjustment plate portion32bis a portion of the adjustment plate32other than the adjustment stopper portion32aand the adjustment step32c.

The head bead plate33and the block bead plate34are formed of a metal plate such as a stainless steel plate so as to have elasticity. The head bead plate33has a head bead33aand the block bead plate34has a block bead34a. The head bead33aand the block bead34asurround the combustion chamber openings21at the outer side of the stopper portion31a. The head bead33ais positioned between the combustion chamber openings21and the side edge33eof the head bead plate33, and the block bead34ais positioned between the combustion chamber openings21and the side edge34eof the block bead plate34. The head bead33aand the block bead34aare bent so as to be closer to each other and sandwich the intermediate plate portion31band the adjustment plate portion32b. In other words, the head bead33ais bent to be convex toward the adjustment plate portion32band the block bead34ais bent to be convex toward the intermediate plate portion31b.

When the cylinder head gasket20is manufactured, the intermediate plate31, the adjustment plate32, the head bead plate33and the block bead plate34are integrally installed. Before the cylinder head gasket20is provided between the head contact surface12aand the block contact surface13a, the intermediate plate portion31band the head bead33asandwich the adjustment plate portion32bas shown inFIG. 3. That is, a portion of the intermediate plate portion31bother than the intermediate bead31dcontacts the adjustment plate portion32band the head bead33acontacts the adjustment plate portion32b.

Since the stopper height h1is smaller than the adjustment step height h2, a small space S is formed between the stopper portion31aand the adjustment stopper portion32ain a state where the intermediate plate portion31bcontacts the adjustment plate portion32b. The measurement along the thickness of the space S is considered to be the difference between the adjustment step height h2and the stopper height h1.

The stopper thickness S1, which is the total of the thickness of the stopper portion31a, the adjustment stopper portion32a, the head bead plate33, and the block bead plate34, is set to be greater than the bead thickness S2, which is the total of the thickness of the intermediate plate portion31b, the adjustment plate portion32b, the head bead plate33, and the block bead plate34(S1>S2). The stopper thickness S1represents the thickness of a portion of the cylinder head gasket20having the stopper portion31a. The bead thickness S2represents a portion of the cylinder head gasket20having the intermediate bead31d, the head bead33a, and the block bead34a. The stopper thickness S1is greater than the thickness of a portion of the cylinder head gasket20other than the portion of the cylinder head gasket20having the stopper portion31a.

By fastening the cylinder head12to the cylinder block13with bolts in a state where the cylinder head gasket20is arranged between the head contact surface12aand the block contact surface13a, the cylinder head gasket20is mounted to a space between the head contact surface12aand the block contact surface13a. The stopper portion31areceives the axial fastening force due to the fastening of the bolt. This prevents the head bead plate33and the block bead plate34from fully collapsing.

Due to the fastening of the bolt, the head bead33ais pressed against the adjustment plate portion32band the head contact surface12a, and the block bead34ais pressed against the intermediate bead31dand the block contact surface13a. Therefore, the intermediate bead31d, the head bead33a, and the block bead34aseal a space between the head contact surface12aand the block contact surface13awith high linear pressure. Accordingly, high pressure gas in the combustion chambers16is sealed.

While the engine11is running, a space may be formed between the head contact surface12aand the block contact surface13a, and the space may be increased or reduced. However, in the present embodiment, since the stopper thickness S1is greater than the bead thickness S2, the intermediate bead31d, the head bead33aand the block bead34afollow the increasing or reducing of the space that may be formed between the head contact surface12aand the block contact surface13a. Accordingly, the cylinder head gasket20maintains high sealing linear pressure between the cylinder head12and the cylinder block13.

Before the cylinder head gasket20is mounted to a space between the head contact surface12aand the block contact surface13a, portions of the facing surfaces of the intermediate plate portion31band the adjustment plate portion32bcontact each other, and a space S is formed between the facing surfaces of the stopper portion31aand the adjustment stopper portion32a. When the cylinder head12is fixed to the cylinder block13by bolts, the portion closer to the stopper portion31ais compressed by the axial fastening force of the bolts, and the stopper portion31aand the adjustment stopper portion32aclosely contact each other. This eliminates the space S. At this time, since the facing surfaces of the intermediate plate portion31band the adjustment plate portion32bhave contacted each other before the fastening of the bolt, the facing surfaces contact each other after the fastening of the bolt. Therefore, even if the cylinder head gasket20receives the pressure fluctuation in the cylinder bore14or the repetition of cooling and heating, the adjustment plate portion32bcontacts the intermediate plate portion31and the head bead33a. This inhibits the adjustment plate portion32bfrom violently flapping.

The present embodiment has following advantages.

(1) Before the cylinder head gasket20is mounted between the head contact surface12aand the block contact surface13a, the intermediate plate portion31bis formed to have a portion that contacts the adjustment plate portion32band to cause the head bead33ato contact the adjustment plate portion32b. Therefore, in a state where the cylinder head gasket20is mounted to a space between the head contact surface12aand the block contact surface13a, the cylinder head gasket20maintains a state where the intermediate plate portion31bcontacts the adjustment plate portion32band the adjustment plate portion32bcontacts the head bead33a. Therefore, even if the pressure fluctuation in the cylinder bore14or the repetition of cooling and heating of the engine11may be caused, the flapping of the adjustment plate32is inhibited, and especially the flapping of the adjustment plate portion32bis inhibited.

(2) Therefore, for example, the adjustment step portion32cis prevented from repeatedly hitting the head bead plate33, and the head bead plate33is prevented from being damaged. Also, for example, the adjustment stopper portion32ais prevented from flapping and from being hit by the stopper portion31a. The adjustment stopper portion32ais thus inhibited from being depressed.

(3) The intermediate step31cis formed by making the thickness of the intermediate plate31different between the stopper portion31aand the intermediate plate portion31b. When the adjustment stopper portion32ais apart from the stopper portion31ain a state where the adjustment plate32is placed on the intermediate plate31, the adjustment plate portion32beasily contacts the intermediate plate portion31b. In the present embodiment, the adjustment plate portion32breliably contacts the intermediate plate portion31bby setting the stopper height h1to be smaller than the adjustment step height h2.

(4) To cause the intermediate plate portion31bto contact the adjustment plate portion32b, it is ideal that the stopper height h1is equal to the adjustment step height h2. However, it is not realistic to set the stopper height h1to be equal to the adjustment step height h2due to the manufacturing error or the manufacturing cost. In the present embodiment, since the stopper height h1is set to be smaller than the adjustment step height h2, the space S may be formed between a space between the stopper portion31aand the adjustment stopper portion32abefore the cylinder head gasket20is mounted to the space between the head contact surface12aand the block contact surface13a. However, the space S can be eliminated by the fastening of the bolt. Therefore, according to the present embodiment, the manufacturing cost is prevented from increasing, and the intermediate plate portion31breliably contacts the adjustment plate portion32b.

(5) The intermediate plate31has the intermediate bead31d, which protrudes toward the block bead plate34. Therefore, the intermediate plate portion31breliably contacts the adjustment plate portion32b.

(6) The cylinder head gasket20has the head bead plate33and the block bead plate34. Therefore, the space between the head contact surface12aand the cylinder head gasket20is easily sealed, and the space between the block contact surface13aand the cylinder head gasket20is easily sealed. This improves the sealing property of the combustion chamber openings21.

The present embodiment may be modified in the following forms.

The method of forming the stopper portion31aand the intermediate plate portion31bis not limited to partially increasing the thickness of one metal plate forming the intermediate plate31.

FIG. 4shows a stopper portion31athat is formed by folding one plate. In other words, the stopper portion31ais formed by folding a portion of the metal plate forming the intermediate plate31that is closer to the combustion chamber opening21. When the folded portion faces the adjustment plate32, the stopper height h1represents the measurement along the thickness between the folded portion and the intermediate plate portion31b.

FIG. 5shows a stopper portion31athat is formed by joining two plates. That is, another metal plate35is welded to a portion of the metal plate forming the intermediate plate31that is closer to the combustion chamber openings21. When the metal plate35faces the adjustment plate32, the stopper height h1represents the measurement along the thickness between the adjustment plate32and the intermediate plate portion31b.

FIG. 6shows a stopper portion31athat is formed by repeatedly bending one plate so as to have a corrugated form.

For example, the bent portion is formed by bending a portion of the metal plate forming the intermediate plate31that is closer to the combustion chamber opening21so as to have a corrugated form and to increase the height corrugation toward the combustion chamber opening21.

The cylinder head gasket20do not necessarily need to have the block bead plate34, the intermediate plate31, the adjustment plate32, and the head bead plate33arranged in this order from the cylinder block13to the cylinder head12. The order of the intermediate plate31and the adjustment plate32may be opposite. In this case, the intermediate bead31dprotrudes toward the cylinder head12.

The head bead plate33may be omitted. That is, the cylinder head gasket20may have a three-layer structure having the block bead plate34, the intermediate plate31and the adjustment plate32arranged in this order from the cylinder block13to the cylinder head12. In this case, the stopper thickness S1of the cylinder head gasket20is the total of the thicknesses of the stopper portion31a, the adjustment stopper portion32aand the block bead plate34. The bead thickness S2is the total of the thicknesses of the intermediate plate portion31b, the adjustment plate portion32band the block bead plate34.

The block bead plate34may be omitted. That is, the cylinder head gasket20may have a three-layer structure having the intermediate plate31, the adjustment plate32, and the head bead plate33arranged in this order from the cylinder block13to the cylinder head12.

The cylinder head gasket20may further have a third bead plate in addition to the head bead plate33and the block bead plate34.

The head bead33ais not necessarily formed by protruding toward the cylinder block13but formed by protruding toward the cylinder head12.

The intermediate bead31dmay be omitted. In this case, if the intermediate plate portion31bis a flat plate, the whole surface of the intermediate plate portion31bcan contact the adjustment plate portion32bbefore the mounting of the cylinder head gasket20.