JP2006177345A - Combustion chamber cooling structure of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of knocking by reducing temperature of unburned gas in an end gas region. <P>SOLUTION: A high heat conduction member 11 having high thermal conductivity is nipped from above and below by sealing members 8 to 10 provided between a cylinder head 2 and a cylinder block 3 to prevent leakage of gas in a combustion chamber 1. A sealing member storage part 12 is provided in the cylinder head 2 in such a way that the sealing members 8, 10 on an upper side are not exposed to the combustion chamber 1 and the high heat conduction member partitions a part of the combustion chamber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a combustion chamber cooling structure for an engine.

  In the vicinity of the top dead center of the piston, the vicinity of the inner wall surface of the cylinder of the combustion chamber (hereinafter referred to as “end gas region”) is away from the spark plug, so that flame propagation due to combustion is difficult to reach and unburned gas tends to stay. Further, since the temperature rapidly increases due to a decrease in the volume of the end gas region in the vicinity of the top dead center, the unburned gas is self-ignited and knocking is likely to occur.

Therefore, Patent Document 1 describes a technique for suppressing the occurrence of knocking by providing cooling means on the cylinder head and the cylinder block facing the end gas region to cool the unburned gas.
Japanese Patent Laid-Open No. 5-222931

  However, in the above prior art, a part of the portion facing the end gas region of the combustion chamber near the top dead center of the piston is defined by a seal having a low thermal conductivity, so that the combustion chamber temperature can be efficiently cooled. I can't.

  Moreover, since the member in which the cooling water passage is provided is used as the cooling means, the structure becomes complicated.

  The present invention has been made by paying attention to such a conventional problem, and it is possible to reduce the temperature of unburned gas in the end gas region by a simple structure and to suppress the occurrence of knocking in an engine combustion chamber. Its purpose is to provide a structure.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is interposed between a combustion chamber (1) defined by a cylinder head (2), a cylinder block (3) and a piston (4), and between the cylinder head (2) and the cylinder block (3). The sealing member (8-10), the cylinder head (2), the cylinder block (3), and the piston (pinch) that are sandwiched from above and below by the sealing member (8-10) that prevents gas leakage in the combustion chamber (1). 4) A high thermal conductivity member (11) having a higher thermal conductivity and an upper seal member (8) provided on the lower surface of the cylinder head (2) and sandwiching the high thermal conductivity member (11) are provided in the combustion chamber (1). And a high heat conduction member (11) including a seal member accommodating portion (12) for accommodating the upper seal member (8) so as to define a part of the combustion chamber (1). And

  According to the present invention, the upper and lower sealing members sandwiching the high thermal conductivity member do not define a combustion chamber near the top dead center of the piston, and only the high thermal conductivity member is the outer peripheral surface of the combustion chamber. Therefore, the unburned gas in the combustion chamber can be efficiently cooled while maintaining the sealing performance of the combustion chamber.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is an overall configuration diagram of an engine in the present embodiment. FIG. 2 is an enlarged view of a range A in FIG. The combustion chamber 1 is defined by a cylinder head 2 on the upper surface, a cylinder block 3 on the outer peripheral surface, and a piston 4 on the lower surface.

  An intake passage 5 and an exhaust passage 6 are formed in the cylinder head 2, and a spark plug 7 is provided so that the front end faces the inside of the combustion chamber 1. The intake passage 5 supplies an air-fuel mixture containing fuel to the combustion chamber 1, and the exhaust passage 6 discharges the burned gas to the outside. The spark plug 7 ignites the air-fuel mixture in the combustion chamber at a predetermined timing in synchronization with the rotation of the engine.

  The cylinder block 3 is disposed so that the upper surface thereof faces the lower surface of the cylinder head 2. Gasket rings (seal members) 8 and 9 are provided between the cylinder block 3 and the cylinder head 2 to prevent the gas in the combustion chamber from leaking to the outside over the entire circumference. A seal portion (seal member) 10 that further improves the sealing performance is provided on the inner peripheral side of the gasket rings 8 and 9. Further, the ring-shaped high heat conductive member 11 having high heat conductivity is sandwiched from above and below by the gasket rings 8 and 9.

  Further, an annular recess (seal member accommodating portion) 12 for accommodating the upper gasket ring 8 that holds the high heat conductive member 11 is provided on the lower surface of the cylinder head 2. The recess 12 is formed in a portion of the lower surface of the cylinder head 2 facing the cylinder block 3 so as to surround the combustion chamber 1, and the depth thereof is equal to or greater than the thickness of the upper gasket ring 8 to be accommodated. That is, the upper gasket ring 8 does not define the combustion chamber 1 when the upper gasket ring 8 is housed in the recess 12.

  Further, the thickness of the high heat conductive member 11 and the cylinder are set so that the lower gasket ring 9 holding the high heat conductive member 11 is positioned below the outer peripheral end 15 of the piston crown surface 13 near the top dead center of the piston 4. The depth of the recess 12 of the head 2 is set. That is, the lower gasket ring 9 has a structure that does not define the combustion chamber 1 near the top dead center of the piston.

  The piston 4 increases and decreases the volume of the combustion chamber 1 while sliding up and down along the inner wall surface 3a of the cylinder block 3, and repeats intake, compression, expansion, and exhaust strokes.

  Hereinafter, the operation of the engine in the present embodiment will be described. When the air-fuel mixture flowing in from the intake passage 5 is ignited by the spark plug 7, a flame propagates to the surroundings and the air-fuel mixture burns. At this time, the end gas region 14 in the vicinity of the cylinder inner wall surface of the combustion chamber 1 at the top dead center of the piston is located away from the spark plug 7, so that the propagation of the flame is difficult to reach. As a result, the unburned gas in which the fuel in the air-fuel mixture remains unburned stays in the end gas region 14.

  Further, since the volume of the end gas region 14 decreases rapidly in the vicinity of the top dead center while the piston is rising, the ambient temperature of the end gas region 14 increases. As a result, the temperature of the unburned gas staying in the end gas region 14 rises, and self-ignition occurs and knocking easily occurs.

  However, since the combustion chamber 1 in the vicinity of the end gas region 14 is defined by the high heat conductive member 11 having a high thermal conductivity over the entire circumference, heat exchange is efficiently performed between the high heat conductive member 11 and the end gas region 14. The temperature of the end gas region 14 decreases rapidly. As a result, the temperature of the unburned gas also decreases, and knocking due to self-ignition of the unburned gas can be prevented.

  Further, the upper gasket ring 8 sandwiching the high heat conductive member 11 is accommodated in the recess 12 of the cylinder head 2 so as not to define the combustion chamber 1, and the lower gasket ring 9 is disposed near the piston top dead center in the combustion chamber 1. Is set so as to be positioned below the outer peripheral end 15 of the piston crown surface 13. Thus, when the temperature of the end gas region 14 is likely to rise near the top dead center of the piston 4, the upper and lower gasket rings 8, 9 do not define the combustion chamber 1, and only the high heat conduction member 11 is in the combustion chamber. 1 is defined, the temperature of the end gas region 14 can be efficiently cooled while ensuring the airtightness of the combustion chamber 1.

  As described above, in the present embodiment, the combustion chamber 1 is defined by the high heat conductive member 11 having high thermal conductivity over the entire circumference in the vicinity of the top dead center of the piston 4. The temperature of 14 can be reduced efficiently. Therefore, the self-ignition of the unburned gas staying in the vicinity of the end gas can be prevented and the occurrence of knocking can be prevented.

  Further, the high heat conductive member 11 is sandwiched by gasket rings 8 and 9 from above and below, and the upper gasket ring 8 is accommodated in the recess 12 of the cylinder head 2 so as not to define the combustion chamber 1, and the lower gasket ring 9 is Since it is located below the outer peripheral end 15 of the piston crown 13 near the top dead center of the piston 4, the combustion chamber 1 is not defined. Thereby, in the vicinity of the top dead center of the piston 4, the outer peripheral surface of the combustion chamber 1 is defined only by the high heat conductive member 11. Therefore, the end gas region 14 can be efficiently cooled and knocking can be prevented while sufficiently securing the airtightness of the combustion chamber 1 by the upper and lower gasket rings 8 and 9.

  Further, since the end gas region 14 is cooled by sandwiching a member having high thermal conductivity by the gasket rings 8 and 9, knocking can be prevented with a simple structure.

(Second Embodiment)
In this embodiment, the structure of the engine is substantially the same as that of the first embodiment, and a part of the combustion chamber cooling structure is different. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

  FIG. 3 is a block diagram showing the engine in the present embodiment. FIG. 4 is an enlarged view of a range B in FIG. In the present embodiment, the heat insulating film 20 having a lower thermal conductivity than the high heat conductive member 11 is formed on the inner peripheral side (combustion chamber side) of the high heat conductive member 11. The heat insulating film 20 is thinly formed, for example, by spraying so as not to interfere with the piston 4 in the vicinity of the top dead center. As shown in FIG. 5, the heat insulating film 20 is formed only on the exhaust side of the inner peripheral surface of the high thermal conductive member 11.

  Here, since normal knocking is likely to occur on the intake side of the end gas region 14 and hardly on the exhaust side, it is not necessary to reduce the temperature of the combustion gas on the exhaust side in order to prevent knocking. Further, since the heat generated in the combustion chamber 1 is used to increase the pressure in the combustion chamber 1, that is, to push down the piston 4, the output torque per unit fuel flow rate decreases when the amount of heat radiation is large. For the above reason, the heat insulating film 20 is formed only on the exhaust side.

  The operation of the engine combustion chamber cooling structure of the present embodiment will be described with reference to FIG. FIG. 6 is an explanatory diagram showing the relationship between ignition timing and torque for the prior art, the first embodiment, and the present embodiment.

  In the prior art, when the ignition timing is advanced, the limit point where knocking does not occur (hereinafter referred to as “knock limit point”) is the point a, whereas in the first embodiment, the point b is the occurrence of knocking. This can be prevented and the engine output torque at the knock limit point increases. Further, in this embodiment, the knock limit point is point c, and the ignition timing at the knock limit point is the same as in the first embodiment, but the heat dissipation amount is suppressed by the heat insulating film 20, so the engine output torque further increases. To do.

  As described above, in the present embodiment, since the heat insulating film 20 having a lower thermal conductivity than the high heat conductive member 11 is formed on the exhaust side on the inner peripheral side of the high heat conductive member 11, the temperature of the end gas region 14 on the exhaust side is reduced. The decrease can be suppressed. Accordingly, it is possible to suppress the cooling loss due to the temperature drop of the combustion gas on the exhaust side where knocking is difficult to occur while reliably preventing knocking on the intake side where knocking is likely to occur. Therefore, it is possible to prevent a decrease in torque per unit fuel flow rate by increasing the proportion of heat generated in the combustion chamber that can be used for increasing the pressure in the combustion chamber 1.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  For example, in the second embodiment, the heat insulating film 20 is formed on the exhaust side of the high thermal conductive member 11, but the range in which the heat insulating film 20 is formed may be smaller or larger than the range shown in FIG.

It is a block diagram which shows the engine in 1st Embodiment. It is an enlarged view of the range A of FIG. It is a block diagram which shows the engine in 2nd Embodiment. FIG. 4 is an enlarged view of a range B in FIG. 3. It is a block diagram which shows arrangement | positioning of the heat insulation film | membrane at the time of seeing an engine from the perpendicular | vertical upper direction. It is explanatory drawing which showed the relationship between ignition timing and torque about a prior art, 1st Embodiment, and this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Cylinder head 3 Cylinder block 3a Inner wall surface of cylinder block 4 Piston 5 Intake passage 6 Exhaust passage 7 Spark plug 8 Upper gasket ring 9 Lower gasket ring 10 Sealing part 11 High heat conduction member 12 Recess 13 Piston crown surface 14 End gas Region 15 Outer peripheral edge 20 of piston crown surface

Claims (4)

A combustion chamber defined by a cylinder head, a cylinder block and a piston;
From the seal member, the cylinder head, the cylinder block, and the piston interposed between the cylinder head and the cylinder block and sandwiched from above and below by a seal member that prevents leakage of gas in the combustion chamber A high thermal conductivity member with high thermal conductivity;
The upper seal member provided on the lower surface of the cylinder head and sandwiching the high heat conductive member is not exposed to the combustion chamber, and the high heat conductive member defines a part of the combustion chamber. A seal member accommodating portion for accommodating the upper seal member;
An engine combustion chamber cooling structure comprising:   The seal member accommodating portion is provided so as to surround the combustion chamber in a portion facing the cylinder block on the lower surface of the cylinder head, and is equal to or greater than the thickness in the vertical direction of the upper seal member sandwiching the high heat conductive member. The combustion chamber cooling structure for an engine according to claim 1, wherein the structure is an annular recess having a depth of 2 mm.   The lower sealing member for sandwiching the high heat conducting member is disposed below the outer peripheral end of the piston crown surface when the piston is near top dead center. 3. A combustion chamber cooling structure for an engine according to 1 or 2.   The heat insulating film having a lower thermal conductivity than the high heat conductive member, further formed on an exhaust side surface of the surface facing the combustion chamber of the high heat conductive member, further comprising: The engine combustion chamber cooling structure according to any one of the preceding claims.

Images