JP2011256757A - Combustion chamber structure of compression ignition internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure which can reduce a cooling loss while preventing the lowering of filling efficiency, in a compression ignition internal combustion engine.SOLUTION: In the combustion chamber structure of the compression ignition internal combustion engine, an insulating layer which has lower thermal conductivity than other positions is provided on at least one of a sidewall of a cavity provided on a top surface of a piston and a wall surface of a cylinder head commanding a squish area.

Description

  The present invention relates to a structure of a combustion chamber of a compression ignition type internal combustion engine.

  As a combustion chamber structure of a compression ignition type internal combustion engine, a configuration in which a heat insulating layer is provided on the entire wall surface surrounding the combustion chamber is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 04-191413 JP 2006-169987 A

  By the way, according to the conventional combustion chamber structure described above, although the heat generated in the combustion chamber is difficult to be dissipated through the wall surface of the combustion chamber, there is a possibility that the atmospheric temperature in the combustion chamber is difficult to decrease. If the atmospheric temperature in the combustion chamber is difficult to decrease, the amount of air (filling efficiency) charged into the cylinder may be reduced.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to reduce cooling loss while suppressing a decrease in charging efficiency of air charged into a cylinder in a combustion chamber structure of a compression ignition type internal combustion engine. There is to do.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention provides a cavity surrounded by a side wall extending in the cylinder axial direction and a bottom surface extending in the cylinder radial direction provided on a part of the piston top surface, and a portion where no cavity is provided on the piston top surface. And a squish area surrounded by the wall surface of the cylinder head, in a combustion chamber structure of a compression ignition type internal combustion engine, at least one of the side wall of the cavity and the wall surface of the cylinder head desired in the squish area from other parts A heat insulating layer having a low thermal conductivity was provided.

  As a result of diligent experimentation and verification by the present inventor, most of the heat transferred from the combustion chamber to the piston is transferred from the side wall of the cavity toward the piston ring, and then radiated to the cylinder bore wall surface through the piston ring. I found out that It has also been found that most of the heat transferred from the combustion chamber to the cylinder head wall surface is transferred from the site desired in the squish area to the cooling water passage in the cylinder head. That is, most of the heat dissipated from the combustion chamber is dissipated through the cylinder head wall surface desired in the cavity side wall and the squish area.

  Therefore, according to the combustion chamber structure of the compression ignition internal combustion engine of the present invention, the amount of heat radiated from the combustion chamber can be suitably reduced. Furthermore, according to the combustion chamber structure of the compression ignition type internal combustion engine of the present invention, since the heat radiation from the portion excluding the cylinder head wall surface and the cavity side wall desired in the squish area is allowed, the atmospheric temperature in the combustion chamber becomes excessively high. The situation is avoided. As a result, it is possible to reduce the cooling loss while suppressing a decrease in charging efficiency of the air sucked into the cylinder.

  According to the combustion chamber structure of the compression ignition type internal combustion engine according to the present invention, it is possible to reduce the cooling loss while suppressing the decrease in the charging efficiency.

It is a figure which shows schematic structure of the combustion chamber of the internal combustion engine to which this invention is applied. It is an enlarged view of a combustion chamber.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of a combustion chamber of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) provided with a fuel injection valve for injecting fuel into a cylinder.

  In FIG. 1, an internal combustion engine 1 includes a cylinder block 10 having a cylinder 2 and a cylinder head 11 to which a fuel injection valve 4, an intake port 5, an exhaust port 6, and a valve train are attached. I have.

  The cylinder block 10 is provided with a block-side cooling water passage 100 surrounding the cylinder 2. A head side cooling water passage 110 is formed below the intake port 5 and the exhaust port 6 in the cylinder head 11.

  A piston 3 is inserted into the cylinder 2 of the cylinder block 10 so as to be slidable in the cylinder axial direction. The piston 3 is connected to a crankshaft (not shown) via a connecting rod 7. A cavity 30 composed of a substantially cylindrical depression is formed in the central portion of the top surface of the piston 3, and the fuel injected from the fuel injection valve 4 is combusted inside the cavity 30.

  In the internal combustion engine 1 configured as described above, when the piston 3 is located at the top dead center (TDC), a space surrounded by the inner wall surface of the cavity 30 and the wall surface of the cylinder head 11 facing the cavity 30 is formed. A combustion chamber is formed. Further, a squish area is defined by a space surrounded by the peripheral portion of the top surface of the piston 3 (the portion where the cavity 30 is not provided) and the inner wall surface and the cylinder bore wall surface of the cylinder head 11 facing the peripheral portion.

  When the fuel is combusted in the combustion chamber, a part of the heat generated by the combustion of the fuel is radiated through the wall surface that forms the combustion chamber and the squish area, and a cooling loss occurs. On the other hand, the method of providing a heat insulation layer in the wall surface which forms a combustion chamber can be considered. According to this method, although it is possible to reduce the cooling loss, the atmospheric temperature in the cylinder 2 is unlikely to decrease during high-load operation of the internal combustion engine 1, and the charging efficiency of the air sucked into the cylinder 2 is reduced. May be reduced.

  Therefore, the combustion chamber structure of the compression ignition type internal combustion engine of the present embodiment has other parts only on the side wall 30a of the cavity 30 in the piston 3 and the wall surface 11a desired in the squish area in the cylinder head 11, as shown in FIG. A heat insulating layer having a lower thermal conductivity than that of is provided.

Here, as a result of the inventor's earnest experiment and verification, most of the heat transferred from the combustion chamber to the piston 3 is transferred from the side wall 30a of the cavity 30 toward the piston ring, and then the piston ring. It has been found that heat is radiated to the cylinder bore wall surface and the block-side cooling water passage 100 via. It has also been found that most of the heat transferred from the combustion chamber to the wall surface of the cylinder head 11 is transferred from the portion 11a desired in the squish area to the head-side cooling water passage 110. That is, most of the heat radiated from the combustion chamber is radiated through the cavity side wall 30a and the cylinder head wall surface 11a desired in the squish area.

  Therefore, by providing the heat insulating layer on the side wall 30a of the cavity 30 in the piston 3 and the wall surface 11a desired for the squish area in the cylinder head 11, most of the heat radiation can be blocked. Further, since a small amount of heat radiation is allowed from the bottom of the cavity 30 in the piston 3, the portion excluding the wall surface 11 a in the cylinder head 11, and the cylinder bore wall surface, the ambient temperature in the cylinder 2 such as during high load operation of the internal combustion engine 1 is increased. It is also possible to avoid situations where it is difficult to descend.

  Therefore, according to the combustion chamber structure of the compression ignition type internal combustion engine of the present embodiment, it is possible to reduce the cooling loss while suppressing a decrease in the charging efficiency of the air sucked into the cylinder 2.

  In the example shown in FIG. 2 described above, the heat insulating layer is provided on both the side wall 30a of the cavity 30 and the wall surface 11a of the cylinder head 11, but may be provided on only one of them. In that case, although the reduction effect of cooling loss falls, it becomes possible to suppress the fall of the filling efficiency by providing a heat insulation layer more.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Piston 4 Fuel injection valve 5 Intake port 6 Exhaust port 10 Cylinder block 11 Cylinder head 11a Heat insulation layer 30 Cavity 30a Heat insulation layer 100 Block side cooling water path 110 Head side cooling water path

Claims (1)

A cavity provided on a part of the piston top surface and surrounded by a side wall extending in the cylinder axial direction and a bottom surface extending in the cylinder radial direction;
In the combustion chamber structure of a compression ignition type internal combustion engine, including a portion where no cavity is provided on the piston top surface and a squish area surrounded by the wall surface of the cylinder head,
A combustion chamber structure of a compression ignition type internal combustion engine, wherein a heat insulating layer having a lower thermal conductivity than other portions is provided on at least one of a side wall of the cavity and a wall surface of a cylinder head desired in the squish area.

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