JP2009068435A - Head gasket of engine and engine provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the amount of fuel consumption by end gas cooling while preventing a deterioration in emission caused by the extension of a top land part of a piston. <P>SOLUTION: The amount of fuel consumption is reduced by extending and placing the top land part 21a of the piston 21 and by projecting the piston 21 from the top surface 11f of a cylinder block 11 at the time of compression. The head gasket 101 is provided with a gasket body 101a and a lip part 101b which is arranged continuous to it. Then the lip part 101b is bent in the direction where the top land part 21a passes when it compresses a bore B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine head gasket and an engine including the same, and more specifically, in an engine that achieves an end gas cooling effect by projecting a piston from an upper surface of a cylinder block during compression, thereby reducing fuel consumption. The present invention relates to a technique for achieving both reduction of fuel consumption by end gas cooling and suppression of emission.

As is well known, there is a need for significant improvements in fuel consumption and emissions.
As a technique for reducing the fuel consumption, the following end gas cooling is known. By causing the piston to protrude from the upper surface of the cylinder block during compression, the effect of end gas cooling is obtained, abnormal combustion is suppressed, and fuel consumption is reduced. However, although this technique is effective in reducing fuel consumption, the top land portion of the piston is extended in order to obtain the effect of end gas cooling. Since the gap between the land portion and the cylinder block (or liner) and the cylinder head is enlarged, there is a problem that the emission of HC and the like is deteriorated.

Although not related to an end-gas-cooled engine with an extended top land portion, the following technologies exist to suppress the deterioration of emissions due to the existence of a gap (dead volume) between a piston and a cylinder block, etc. . In the head gasket sandwiched between the cylinder head and the cylinder block, the diameter of the bore provided in the head gasket is smaller than the cylinder bore (the bore of the cylinder block) and the outer diameter of the piston (outer diameter of the top land portion) (Patent document 1).
Japanese Utility Model Publication No. 07-020466 (paragraph numbers 0013, 0021)

  In the technique described in the above-mentioned Patent Document 1, a gap around the top land portion of the piston (gap between the top land portion and the cylinder head) is obtained by extending the inner end of the head gasket forming the bore from the inner surface of the cylinder block. This prevents the combustion gas from flowing in and suppresses the generation of unburned gas such as HC in this gap.

  However, this technique does not relate to an end gas cooling engine in which the top land portion protrudes from the upper surface of the cylinder block, and cannot solve the deterioration of the emission in such an end gas cooling engine. Further, in an end gas cooling type engine, even if the inner end of the head gasket protrudes from the inner surface of the cylinder block by the technique described in Patent Document 1, the effect of the gap formed in the engine is eliminated. Is not sufficient, and generation of HC or the like cannot be satisfactorily suppressed.

  In the present invention, in consideration of the above problems, in the engine configured to protrude the piston from the upper surface of the cylinder block at the time of compression, the clearance formed around the top land portion is expanded by the extension of the top land portion. The objective is to reduce fuel consumption by end gas cooling while suppressing deterioration of emissions.

The present invention provides an engine head gasket and an engine including the same.
The head gasket of the engine according to the present invention is provided in an engine in which the top land portion of the piston is inserted into the space in the cylinder head serving as a combustion chamber over the upper surface of the cylinder block during compression. A gasket main body sandwiched between the cylinder head and the cylinder block and a lip portion connected to the gasket main body forming a bore through which the top land portion of the piston passes are configured. In the present invention, the lip portion of the head gasket is provided such that the top land portion is curved in a direction to pass through the bore during compression.

  The engine according to the present invention includes a cylinder block, a piston reciprocally inserted into the cylinder block, a head gasket, and a cylinder head installed with the head gasket sandwiched together with the cylinder block. The top land portion of the piston is configured to be able to move over the upper surface of the cylinder block to the space in the cylinder head serving as a combustion chamber when compressed. In the present invention, the head gasket includes a gasket main body sandwiched between the cylinder head and the cylinder block, and a lip portion continuous with the gasket main body that forms a bore for passing the top land portion of the piston. The lip portion extends from one end near the gasket body to the gap between the top land portion and the cylinder head in the space inside the cylinder head, beyond the block alignment surface of the cylinder head. Established.

  According to the present invention, when the top land portion of the piston is inserted into the space in the cylinder head beyond the upper surface of the cylinder block (the mating surface of the cylinder block with respect to the cylinder head) during compression, the effect of end gas cooling is achieved. The fuel consumption can be reduced. Here, according to the present invention, the head gasket includes a gasket body and a lip portion connected to the gasket main body. The lip portion forms a bore of the head gasket, and the lip portion is formed on the top land. By curving the bore in the direction of passing through the bore during compression, the inflow of combustion gas into the gap formed around the top land portion can be prevented, and emission can be suppressed. Therefore, according to the present invention, it is possible to reduce fuel consumption by end gas cooling while suppressing deterioration of emissions due to the extension of the top land portion.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of an engine 1 according to an embodiment of the present invention by a cross section parallel to a cylinder center line l.

  The engine 1 includes a cylinder block 11, a piston 21 inserted in the cylinder block 11 so as to reciprocate up and down, and a cylinder head disposed on the cylinder block 11 and fastened to the cylinder block 11 by a head bolt (not shown). 31. A liner 12 is fitted into the cylinder block 11, and an inner surface on which the piston 21 slides is formed by the liner 12. The cylinder block 11 and the cylinder head 31 are fastened with a head gasket 101 sandwiched between them, and the head gasket 101 keeps the distance between the cylinder block 11 and the cylinder head 31 constant. During the operation, gas leakage from the combustion chamber C is prevented. The combustion chamber C of the engine 1 is formed as a space sandwiched between the crown surface of the piston 21 and the lower surface of the cylinder head 31.

  The piston 21 has a top land portion 21a extending from a normal piston so that the height ht of the top land portion 21a is increased. When the piston 21 is compressed, the top land portion 21a exceeds the upper surface 11f of the cylinder block 11 and It is comprised so that it may insert even in the space in the cylinder head 31 which becomes. The top land portion 21a of the piston 21 is the one closest to the combustion chamber C (the compression ring 22) among the plurality of piston rings (in this embodiment, the compression rings 22, 23 and the oil ring 24) provided on the piston 21. ) Is a portion of the piston 21 on the combustion chamber C side. By inserting the top land portion 21a into the space in the cylinder head 31, an end gas cooling effect can be obtained during combustion, and fuel consumption can be reduced. In the present embodiment, the head gasket 101 has the same function as that of a normal head gasket, such as ensuring sealing performance against combustion gas, and also has the function of suppressing the deterioration of emissions associated with the extension of the top land portion 21a. Is.

  Air sucked into the engine 1 flows into the combustion chamber C from the intake port 31a together with fuel injected by a fuel injection valve (not shown) installed in the cylinder head 31, and is uniformly mixed in the combustion chamber C. Form a mind. The cylinder head 31 is provided with a spark plug 32 on the cylinder center line l, and the air-fuel mixture formed in the combustion chamber C is ignited by the spark plug 32. Exhaust gas generated by the combustion is discharged through the exhaust port 31b. The intake port 31a is opened and closed by the intake valve 33, and the exhaust port 31b is opened and closed by the exhaust valve 34, respectively.

Next, the configuration of the head gasket 101 according to the present embodiment will be described in more detail.
FIG. 2 shows the configuration of the head gasket 101 by (a) a plane and (b) by a cross section taken along the line AA in FIG. 2 (a).

The head gasket 101 includes a gasket main body 101a and a lip portion 101b.
The gasket main body 101a is sandwiched between the cylinder block 11 and the cylinder head 31 in the same manner as a normal head gasket, and keeps the distance between them constant and ensures sealing performance against combustion gas. The gasket body 101a is provided with a plurality of head bolt holes h through which head bolts are inserted when the cylinder head 31 is assembled.

  On the other hand, the lip portion 101b is for suppressing the deterioration of the emission accompanying the extension of the top land portion 21a of the piston 21, and the lip portion 101b allows the top land portion 21a to pass through during compression. B is formed. In this embodiment, the lip portion 101b is provided integrally with the gasket body 101a, and is provided from one end portion close to the gasket body 101a (hereinafter referred to as the “outer end” of the lip portion 101b). It is curved toward the inner end with a predetermined curvature. The degree of curvature (curvature, R size) is set so that low rigidity can be provided within a range in which the posture of the piston 21 can be maintained with respect to the thrust load acting on the piston 21 due to combustion. . The direction in which the lip portion 101b is curved matches the direction in which the top land portion 21a passes through the bore B during compression.

In the present embodiment, the inner diameter φgsk of the lip portion 101b is set to a value substantially equal to the outer diameter of the piston 21 (the outer diameter of the top land portion 21a) φpst (FIG. 3).
Hereinafter, an operation obtained by the engine 1 and the head gasket 101 according to the present embodiment will be described.

FIG. 3 shows a configuration around the lip portion 101b of the head gasket 101 of the engine 1 by a cross section similar to FIG.
In the engine 1, the head gasket 101 is provided in a state where the gasket main body 101 a is sandwiched between the cylinder block 11 and the cylinder head 31. The lip portion 101b is curved in one direction (direction in which the top land portion 21a of the piston 21 passes during compression) from the outer end toward the inner end, and exceeds the block mating surface 31f of the cylinder head 31 from the outer end. The top land portion 21 a in the space in the cylinder head 31 and the gap g between the cylinder head 31 are extended. In addition, in FIG. 3, the piston 21 has shown the state which exists in a compression top dead center.

  At the time of compression, the top land portion 21a of the piston 21 passes through the bore B of the head gasket 101 just before top dead center, passes over the upper surface 11f (FIG. 1) of the cylinder block 11, and reaches the space in the cylinder head 31. Inserted. Since the lip portion 101b is curved in the direction in which the top land portion 21a passes and its rigidity is kept low, an increase in resistance to the movement of the piston 21 is suppressed.

  When ignition is performed by the spark plug 32 during combustion, a combustion gas flow f is generated toward the gap around the top land portion 21a (the gap between the top land portion 21a and the cylinder head 31) g. In the engine 1 according to the present embodiment, the top land portion 21a is extended for cooling the end gas. Therefore, the gap g is enlarged as compared with a normal engine, and the lip portion 101b of the head gasket 101 is provided. If there is no combustion gas, the combustion gas flows into the gap g and the flow is stagnated therein. Therefore, combustion is not completed well, and unburned gas such as HC is generated. In the present embodiment, the lip portion 101b is provided in the head gasket 101, and the lip portion 101b is curved and extended to the gap g, thereby preventing the inflow of combustion gas into the gap g and generating unburned gas. Is suppressed.

  In the present embodiment, the inner diameter φgsk of the head gasket 101 (lip portion 101b) is set to a value substantially equal to the outer diameter φpst of the piston 21 (top land portion 21a), and moderate rigidity is provided to the lip portion 101b. Therefore, the posture of the piston 21 is maintained by the lip portion 101b with respect to a lateral load (thrust load) caused by combustion, and the positions of the piston rings 22 to 24 with respect to the piston 21 are concentric during combustion. Retained.

According to this embodiment, the following effects can be obtained.
In the present embodiment, the top land portion 21 a of the piston 21 is extended, and the top land portion 21 a is inserted into the space in the cylinder head 31 beyond the upper surface 11 f of the cylinder block 11 during compression. . Thereby, the effect of end gas cooling can be acquired at the time of combustion, and fuel consumption can be reduced.

  In the present embodiment, the head gasket 101 is provided with a lip portion 101 b, the bore B of the head gasket 101 is formed by the lip portion 101 b, and the lip portion 101 b is curved so that the top in the space in the cylinder head 31 is formed. The land portion 21 a and the cylinder head 31 are extended to the gap g. Thereby, inflow of the combustion gas to the clearance gap g can be prevented, generation | occurrence | production of unburned gas, such as HC, can be suppressed, and the deterioration of the emission accompanying extension of the top land part 21a can be suppressed.

  Further, in the present embodiment, since the posture of the piston 21 can be held by the lip portion 101b against the thrust load resulting from combustion, the piston ring with respect to the piston 21 (particularly, the compression ring 22 closest to the combustion chamber C). Can be suppressed, the sealing performance of the piston ring can be improved, and the life of the piston ring can be extended.

  Furthermore, since the eccentricity of the piston ring (particularly the compression ring 22) with respect to the piston 21 is suppressed, the tension of the piston ring can be reduced, and the friction accompanying the movement of the piston 21 can be reduced. Along with this, since the friction at the time of starting is also reduced, it is possible to adopt a smaller starting motor (starter) of the engine 1 and to reduce the cost.

  In the present embodiment, the head gasket is an integrated head gasket in which the gasket main body 101a and the lip portion 101b are formed of a single member. However, the head gasket is not limited to this, for example, the gasket main body 101a portion is constituted by a plurality of laminated members, and at least one of the laminated members has a lip portion 101b. It can also consist of a plurality of members.

Sectional drawing of the engine which concerns on one Embodiment of this invention (A) top view and (b) AA line sectional view of a head gasket according to the same embodiment. Enlarged sectional view around the lip portion of the head gasket of the engine according to the same embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 11 ... Cylinder block, 11f ... Upper surface of cylinder block, 21 ... Piston, 21a ... Top land part, 22-24 ... Piston ring, 31 ... Cylinder head, 31a ... Intake port, 31b ... Exhaust port, 32 ... Spark plug, 33 ... intake valve, 34 ... exhaust valve, 101 ... head gasket, 101a ... gasket body, 101b ... lip, B ... head gasket bore, C ... combustion chamber.

Claims (4)

A head gasket provided in an engine that is inserted into a space in a cylinder head that becomes a combustion chamber when the top land portion of the piston exceeds the upper surface of the cylinder block during compression,
A gasket body sandwiched between the cylinder head and the cylinder block;
Forming a bore through which the top land portion passes, and including a lip portion connected to the gasket body,
The lip portion is a head gasket for an engine provided such that the top land portion is curved in a direction to pass through the bore during compression. A cylinder block;
A piston reciprocally inserted into the cylinder block;
A head gasket according to claim 1;
A cylinder head installed in a state of sandwiching the gasket main body of the head gasket together with the cylinder block, and
An engine configured such that a top land portion of the piston can move over a top surface of the cylinder block to a space in the cylinder head serving as a combustion chamber when compressed. A cylinder block;
A piston reciprocally inserted into the cylinder block;
A head gasket comprising a gasket body and a lip portion connected to the gasket body to form a bore for passing the top land portion of the piston;
A cylinder head installed in a state of sandwiching the gasket main body of the head gasket together with the cylinder block, and
The engine is configured such that the top land portion of the piston can move to the space in the cylinder head that becomes a combustion chamber over the upper surface of the cylinder block during compression,
The lip portion of the head gasket extends from one end close to the gasket body to the gap between the top land portion in the space in the cylinder head and the cylinder head, beyond the block mating surface of the cylinder head. Engine extended to   The engine according to claim 2 or 3, wherein an inner diameter of the lip portion of the head gasket is substantially equal to an outer diameter of the top land portion.

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