JPS63302124A - Heat-insulated engine structure - Google Patents

Abstract

PURPOSE:To obtain a high degree of heat-insulation by providing a cylinder head liner which forms a combustion chamber that lowers the center part of an engine cylinder but heightens the outer peripheral section thereof so as to form a square- cylindrical shape part in the upper section of the combustion chamber, and by disposing intake and exhaust valves in an inclined part in the lower surface of the cylinder head liner. CONSTITUTION:A ceramic thin plate 5 adapted to form a flat surface in a piston head section 1 of a piston 20 on the combustion chamber side, is disposed in the piston head section 1 through the intermediary of a heat-insulating material 3. A cylinder liner 30 is formed so as to form a combustion chamber 15 having such a shape that the center part of the cylinder is low but the outer peripheral section thereof is high so as to cope with the flat surface formed by the ceramic thin plate 5 in the cylinder head section 1. The combustion chamber has a square cross-sectional shape part or a square-cylindrical shape part in the upper section thereof so as to enhance the efficiency of mixture between fuel and air. Further, intake and exhaust valves 21, 27 are disposed in an inclined surface in a lower surface part 22 in the cylinder head liner 30, which is inclined and extended from the cylinder center part to the cylinder outer peripheral section.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an adiabatic engine.

(Prior Art) Conventionally, an adiabatic engine using a ceramic material as a heat insulating material or a heat-resistant material is disclosed in, for example, Japanese Patent Laid-Open No. 122765/1983.
Explain with reference to. In this adiabatic engine 40, a ceramic liner head 41 having a cylinder center portion 42 is fitted inside a cylinder center portion 43 made of cast metal. The liner head 41 is formed by integrally forming the inner wall portion of the cylinder head and the upper part of the cylinder liner, which are exposed to the highest temperature and high pressure gas during one cycle of the engine and from which the greatest amount of heat escapes. The piston head 44 is made of silicon nitride, has a concave central portion, and has a stepped portion 46 formed on the outer periphery of the lower end to prevent positioning and movement when attached to the piston body 47. A hole is provided for the insertion of a bolt for connecting the piston body. A stepped portion 4 into which the lower end outer periphery of the piston head 44 is fitted into the upper end outer periphery of the piston body 47
8, and the center of the upper surface is made to protrude upward to form a protruding part 49.
The upper surface is brought into contact with the lower surface of the piston head 44, and the piston head 44 and the piston body 47 are connected with bolts 50.

Furthermore, the valve 51 has a cylinder liner 4 on the lower surface 52 of the head.
2 in the axial direction. In this configuration, the exhaust turbine is driven by high-temperature exhaust gas from the engine, and the output generated by the exhaust turbine is used to rotate the intake compressor, supercharging the engine, and at the same time rotating the generator. This power is used to rotate an electric motor via a controller, and the output is applied to the engine's crankshaft via a gear.

[Problem that the invention seeks to solve]

However, it is extremely difficult to obtain sufficient heat-insulating properties in heat-insulating engine members such as pistons that use ceramic materials as described above as heat-insulating or heat-resistant materials. The ceramic material is exposed to high temperatures on the combustion chamber side, and therefore receives a heat cylinder, which poses problems in terms of the strength of the ceramic material. In addition, if the thickness of the ceramic material on the wall is increased for insulation purposes, the heat capacity will increase, and during the intake process, the intake air will receive more heat from the combustion chamber and become hotter.
On the other hand, there is a problem in that the suction efficiency is reduced and no air is taken in, but on the other hand, it is necessary to improve the heat insulation properties in the expansion process.

In addition, in a diesel engine, fuel is sprayed from the fuel injection nozzle, and it is desirable that the sprayed fuel quickly mix with the intake air in the combustion chamber and mix uniformly by the swirl generated in the combustion chamber. At present, nothing has been disclosed that satisfies these points.

By the way, in the adiabatic engine 40 disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 59-122765, a recess 45 is formed in the ceramic piston head 44, and the recess 45 must be formed extremely thick for strength. This structure contradicts the idea of minimizing heat capacity. Further, the valve 51 is installed in the axial direction of the cylinder liner 42 according to the structure of the piston head 44, and the valve 51 is installed on the lower surface of the head 51.
No. 2 is formed flat, so the intake air is atomized outward in the radial direction, and it is easy to receive heat from the cylinder liner and the lower surface of the head. Moreover, it is not structured so as to cause the stirring action of swirl. , has the same problems as above.

The purpose of this invention is to solve the above-mentioned problems, and to obtain a high degree of heat insulation and to minimize the heat capacity of the surface of the piston head, which is exposed to combustion gas and becomes hot. The combustion chamber is formed on the radial liner side of the cylinder accordingly, and the shape of the combustion chamber is formed along the fuel spray locus, and the agitation action of swirl is generated within the combustion chamber. It quickly and uniformly mixes the atomized fuel with the intake air, further improving the intake efficiency and cycle efficiency, and does not cause strength problems even when subjected to thermal shock, and has excellent heat resistance and deformation resistance. To provide a structure of an adiabatic engine having improved corrosion resistance, etc., which can obtain a stable mounting condition, and furthermore, can receive and stop pressure acting on a piston head in a preferable state at the time of an explosion. That's true.

The cylinder liner mentioned here is a combination of the upper part of the cylinder liner and the lower part of the head, and has a structure for insulating heat only during the heat generation period when combustion is active.

c. Means for Solving the Problems] In order to solve the above problems and achieve the above objects, the present invention is configured as follows.

That is, the present invention provides a piston head having a flat surface on the combustion chamber side, a radial liner for a cylinder constituting a combustion chamber in which the cylinder center part is low and the outer peripheral part is high and the upper part is formed into a square cylinder; and a valve installed on a sloped surface of the lower surface of the head that slopes from the center to the outer circumference. The valve is installed in an inverted V shape or parallel to the cylinder axis, and the cylinder liner is made of a ceramic material, and the upper part of the cylinder liner and the lower surface of the head are integrally formed, and the valve is installed in an inverted V shape or parallel to the cylinder axis. A ceramic thin plate is disposed on the side of the combustion chamber, and a fuel injection nozzle is further installed in the center of the cylinder, and the combustion chamber is formed in a shape corresponding to a spray locus, that is, a spray pattern of the fuel injection nozzle. The present invention relates to a structure of an adiabatic engine characterized by:

[Effect]

The structure of the adiabatic engine according to the present invention is constructed as described above, and operates as follows. That is, the present invention provides a piston head in which the combustion chamber side is formed as a flat surface;
A radial liner is installed in the cylinder constituting a combustion chamber in which the cylinder center part is low and the outer peripheral part is high and the upper part is formed into a rectangular cylinder, and on the inclined surface of the lower surface of the head which is inclined from the center part to the outer peripheral part. Since it is constructed from a bulb, the thickness of the ceramic thin plate can be made as thin as possible, and its heat capacity can be made as small as possible. Moreover, since the combustion chamber is formed into a rectangular cylinder, the swirl generated within the combustion chamber is broken by the sides of the rectangular cylinder, creating an agitation effect in the swirl, and the atomized fuel and intake air are quickly mixed. In other words, the mixture is uniformly instantaneously near the top dead center, and combustion is performed satisfactorily. Furthermore, if the cylinder head liner is insulated with a heat insulating layer, the thickness of the rad liner to the cylinder can be made thin, and the heat capacity of the rad liner to the cylinder can also be made small. In other words, the rad liner to the cylinder can be made thin. The thinner the ceramic of the piston head is, the better the ability to follow the gas temperature in the combustion chamber, and the wall temperature amplitude between high and low temperatures in the combustion chamber is greater than when the thickness is thicker. and grew bigger,
As a result, the temperature difference between the combustion gas and the ceramic wall of the combustion chamber becomes smaller, and the amount of heat transfer decreases, thereby reducing the amount of heat received by the intake air.

〔Example〕

Hereinafter, embodiments of the structure of an adiabatic engine according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, the structure of an adiabatic engine, which is an embodiment of the present invention, is indicated generally by the numeral 10. The structure lO of the adiabatic engine mainly includes a piston 2 consisting of a piston head part l and a metal piston skirt part 2.
0, a cylinder rad liner 30 made of ceramic such as silicon nitride fitted inside a cylinder head (not shown) made of cast metal, a fuel injection nozzle 25 installed in the center of the cylinder rad liner 30, and a cylinder head liner 3
It consists of an intake valve 21 and an exhaust valve 27 installed on the lower surface 22 of the head. A ceramic thin plate 5 having a flat surface on the combustion chamber side of the piston head portion l of the piston 20 is placed on the piston head portion l via a heat insulating material 3. In addition, in correspondence with the fact that the ceramic thin plate 5 in the piston head portion 1 constitutes a flat surface, the rad liner 30 is configured to form a combustion chamber 15 having a shape that is low at the center of the cylinder and high at the outer circumference of the cylinder. do. That is, the Radliner 30 to the cylinder
The cylinder liner upper part 23 and the head lower surface part 22 are integrated into one body, and the structure is designed to cut off heat only during the heat generation period when combustion is active. The combustion chamber 15 formed by the cylinder liner 30 having such a shape and the ceramic thin plate 5 of the flat piston head portion 1 is configured in a shallow dish shape, which is most suitable as a combustion chamber for an adiabatic engine. be able to.

Furthermore, although FIG. 2 is a cross-sectional view taken along the line ``T'' in FIG. 1, the shape of the combustion chamber 15 is such that, as shown in FIG. The lower part is formed into a round cross section, that is, a cylindrical body 28. Further, it is preferable for the corners of the rectangular cylinder 26 to be formed into curved surfaces, for example, curved surfaces with a radius of approximately 172 to 273 degrees. The swirl generated in the square cylinder 26
The vortices are broken by the edges of the vortex, and a stirring action occurs, and the atomized fuel and intake air are mixed extremely quickly, i.e. near the top dead center, uniformly in an instant, resulting in good combustion. . Further, the outer peripheral surface of the cylinder liner 30 is covered with a heat insulating gasket 29 and a heat insulating layer 2 made of potassium titanate or the like.
4, the cylinder headliner 30 itself can be made thinner, and its heat capacity can be reduced. Furthermore, as shown in FIG. 2, the intake valve 21 and the exhaust valve 27 are installed on the inclined surface of the head lower surface portion 22 of the cylinder liner 30 which is inclined from the cylinder center to the cylinder outer circumference.

As shown in FIG. 1, the head lower surface portion 22 is an inclined surface that rises outward, so an intake valve seat and an exhaust valve seat are respectively formed on the inclined surface, and an intake valve 21 and an exhaust valve seat are formed on each valve seat. If the valve 27 is installed, the intake valve 21 will be installed in an inverted V shape with the exhaust valve 27 (in some cases, it can be installed parallel to the cylinder axis). Therefore, considering the shape of the intake port (not shown) that extends from the radially outer side to the head lower surface portion 22, the flow of intake air during the intake stroke is directed vertically to the engine and toward the center of the combustion chamber 15. The main flow is formed. Therefore, the intake air is less likely to come into contact with the inner wall surface of the Radliner 30 into the cylinder, which is at a high temperature, and the amount of heat received through heat transfer is reduced, so the thermal expansion of the inflowing intake air is reduced and the intake efficiency is reduced. In this case, the ceramic thin plate 5 of the piston head 1
That is, even if the amount of intake air in contact with the top surface increases, the piston 20 is configured to have a small heat capacity as described below, so the intake efficiency will not decrease.On the other hand, the intake valve 21 Since the exhaust valve 27 and the exhaust valve 27 are housed in the combustion chamber 15, the piston 20 may be accidentally
At DC (top dead center), intake valve 21 and exhaust valve 2
7 is fully opened, without interfering with the piston 20,
Safety is always maintained.

Furthermore, the fuel injection nozzle 25 is connected to the rad liner 3 to the cylinder.
In other words, it is installed at the lowest part of the combustion chamber 15.

Moreover, the injection hole of the fuel injection nozzle 25 is formed parallel to the ceramic thin plate 5 of the piston head portion l and facing outward in the radial direction.

Therefore, the combustion chamber 15 is formed corresponding to the spray locus of the fuel injection nozzle 25 (the spray pattern shown in the direction of arrow B in the figure).

Next, regarding the piston 20, the piston head portion l has a mounting boss portion 4 at the center, and is made of a material having a coefficient of thermal expansion approximately equal to that of a ceramic material, high strength, and a relatively high Young's modulus, for example. It is made of materials such as cermet and metal. A combustion chamber is not formed in the piston head portion 1 itself, and the combustion chamber side of the piston head portion 1 is configured to have a flat shape. A central hole 12 is formed in the center of the piston skirt portion 2, into which the mounting boss portion 4 of the piston head portion 1 is fitted. The mounting boss portion 4 of the piston head portion l is located in the center hole 1 of the piston skirt portion.
2, the metal ring 11 is fitted across the fitting groove 14 formed in the mounting boss part 4 and the fitting groove 13 formed in the center hole 12 of the piston skirt part 2, and the metal ring 11 is fitted into the piston. The head portion 1 is locked to the piston skirt portion 2 in a pressed state. Furthermore, a cushioning material 8, which is a heat insulating gasket, is interposed in a pressed state at the central abutment area between the piston head portion 1 and the piston skirt portion 2, and this cushioning material 8 also has a heat insulating function. Further, a heat insulating air layer 9 is formed between the piston head portion 1 and the piston head portion 2. Regarding this piston 20, the ceramic thin plate 5 is arranged on the piston head portion l with a heat insulating material 3 interposed therebetween so as to face the combustion chamber 15. The ceramic thin plate 5 is made of ceramic such as silicon nitride,
A ceramic ring 6 made of a similar material is fitted to the outer periphery of this ceramic thin plate 5, which is manufactured to a thickness of about 1 m or less, or less than lllll11, and the ceramic thin plate 5 and the ceramic ring 6 and are joined, for example, by CvD (i.e. chemical vapor deposition) at the contact point 18.

A stepped portion 16 is formed on the inner circumferential surface of the ceramic ring 6, and the ceramic ring 6 is formed so that the outer circumferential portion 17 of the piston head portion l comes into contact with the stepped portion 16 of the ceramic ring 6.
is fitted. A heat insulating material 3 is enclosed in a space formed by the ceramic thin plate 5, the ceramic ring 6, and the piston head portion l. The heat insulating material 3 is made of materials such as potassium titanate whiskers and zirconia fibers, and serves as a heat insulator and also serves as a structural member for absorbing the pressure acting on the ceramic thin plate 5 during an explosion. By attaching the piston head portion 1 to the piston skirt portion 2 in a pressed state, the outer peripheral portion 17 of the piston head portion l is pressed against the stepped portion 16 of the ceramic ring 6, and the ceramic ring 6 is attached to the piston skirt portion 2.
is pressed by the surrounding area. In this case, a carbon seal 7, which is a gasket, is interposed to seal the ceramic ring 6 and the piston skirt portion 2.

The seal axial force on the carbon seal 7 is exerted by the piston head portion 1 being attached to the piston skirt portion 2 in a pressed state. Regarding the structure of this piston 20, it is necessary that the compressive force caused by the explosion is evenly received by the heat insulating material 3 such as potassium titanate, and for this purpose, the combustion chamber side surface of the piston head 1 and the ceramic thin plate 5 are flat. It has a flat shape.

〔Effect of the invention〕

Since the structure of the adiabatic engine according to the present invention is configured as described above, it has the following unique effects. That is, the present invention provides a piston head having a flat surface on the combustion chamber side, a cylinder head liner constituting a combustion chamber in which the cylinder center part is low and the outer circumferential part is high and the upper part is formed into a square cylinder; and a valve installed on the sloped surface of the lower surface of the head that slopes from the center to the outer periphery, so that a combustion chamber is formed in the radial liner of the cylinder, which is exposed to combustion gas and becomes hot, and is also exposed to combustion gas. The surface of the piston head, which is exposed to high temperatures, can be made flat and made of a thin ceramic plate. Therefore, the thickness of the ceramic thin plate can be made as thin as possible, its heat capacity can be made as small as possible, a high degree of heat insulation can be obtained, and suction efficiency and cycle efficiency can be improved. Moreover, since the combustion chamber is formed into a rectangular cylinder, the swirl generated within the combustion chamber is broken by the sides of the rectangular cylinder, and an agitating action is generated in the swirl, and the atomized fuel and intake air are They are mixed very quickly, ie, instantaneously near top dead center, and are uniformly mixed, resulting in good combustion. Moreover, if the rad liner to the cylinder is insulated with a heat insulating layer, the thickness of the rad liner to the cylinder can be made thin, and the heat capacity of the rad liner to the cylinder can also be made small. That is, the thinner the ceramics of the Radliner and the piston head of the cylinder, the better the ability to follow the gas temperature in the combustion chamber, and the wall temperature amplitude between high and low temperatures in the combustion chamber becomes thinner. As a result, the temperature difference between the combustion gas and the ceramic wall of the combustion chamber becomes smaller, and the amount of heat transfer decreases, thereby reducing the heat received by the intake air. Moreover, the main flow of intake air can flow vertically into the combustion chamber and toward the small flame from a portion located near the center of the valve and valve seat, and therefore, the intake air can flow into the cylinder where the temperature is high. Since there is less contact with the inner wall surface of the herad liner and the amount of heat received through heat transfer is reduced, the thermal expansion of the inflowing intake air is reduced and no reduction in intake efficiency occurs.In this case, the piston head portion Even if the amount of intake air that comes into contact with the ceramic thin plate, that is, the top surface, increases, the piston head is configured to have a small heat capacity, so the intake efficiency will not decrease, and the intake efficiency and cycle efficiency will be improved. can be improved. Furthermore, since the fuel injection nozzle is installed in the center of the cylinder and the combustion chamber is formed in a shape corresponding to the spray locus or spray pattern of the fuel injection nozzle,
Since the amount of heat received by the intake air is small, the thermal expansion of the intake air can be kept small, and the fuel spray can be mixed well with the intake air, resulting in good combustion.

In addition, there will be no strength problems even if subjected to thermal shock, the heat resistance will be improved, a stable mounting condition can be obtained, and the pressure acting on the ceramic thin plate at the time of an explosion can be received in a favorable condition. can be stopped. Furthermore, since the ceramic thin plate and the piston head portion made of cermet or the like have approximately the same coefficient of thermal expansion, there is no problem in the bonding state between the two.
The piston head made of cermet or the like has high rigidity and is not easily deformed even when high pressure is applied, and the connection between the piston head and the piston skirt is stable, and the gas seal at the boundary is maintained. can be achieved stably. Moreover, the heat insulating material is made of, for example, potassium titanate whiskers, zirconia fibers, etc., or a mixture of these and glass fibers, and performs a high-performance heat insulating function for the combustion chamber of the engine. There is no escape of thermal energy from the chamber through the piston, and thermal energy can be confined in the combustion chamber. Therefore, thermal energy can be effectively recovered by an energy recovery device installed downstream of the exhaust gas flow.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the structure of an adiabatic engine according to the present invention, Fig. 2 is a sectional view taken along line ■-■ in Fig. 1, and Fig. 3 is a sectional view showing an example of a conventional adiabatic engine. It is a diagram. l・-・・・Piston head part, 2・・・・・Piston skirt part, 3・・・・・・・Insulation material, 4・・・・・
-Mounting boss part, 5-... Ceramic thin plate, 6...
・-・・−Ceramic ring, 7・・・−Carbon seal, 8・−・−・Buffer material, 9・−1−−・Insulating air layer, IO・・・−・−Insulating engine structure, 11
−−−−・Metal ring, 12・・・・−・−Central hole,
13.14--... Fitting groove, 15...-- Combustion chamber, 16-------- Step portion, 17-- Outer periphery of piston head portion, 20・・・・・・− Piston,
21...--Intake valve, 22---Head lower surface, 23---Cylinder liner upper part, 24--
- Heat insulation layer, 25... Fuel injection nozzle, 26-...
−・−・Square cylinder, 27・−・−・Exhaust valve, 2
8--Cylindrical body, 29--Insulating gasket, 30--Cylinder Radliner, B--
...spray pattern. Patent Applicant Isuri Motors Co., Ltd. Agent Patent Attorney O Naka - Family Disciple 3 Figure 41 4

Claims (6)

[Claims] (1) A piston head with a flat surface on the combustion chamber side, a cylinder head liner that constitutes a combustion chamber with a lower cylinder center and a higher outer periphery, with the upper part formed into a square cylinder, and the center A structure of an adiabatic engine characterized by comprising a valve installed on an inclined surface of a lower surface of the head which is inclined from the outer circumferential portion to the outer circumferential portion. (2) The structure of the adiabatic engine according to claim 1, wherein the outer peripheral surface of the cylinder headliner is insulated by a heat insulating layer. (3) The structure of the adiabatic engine according to claim 1, wherein the valve is installed in an inverted V shape. (4) The structure of the adiabatic engine according to claim 1, wherein the cylinder head liner is made of a ceramic material, and the upper part of the cylinder liner and the lower surface of the head are integrally formed. (5) The structure of the adiabatic engine according to claim 1, wherein a ceramic thin plate is disposed on the combustion chamber side of the piston head. (6) installing a fuel injection nozzle in the center of the cylinder;
2. The adiabatic engine structure according to claim 1, wherein the combustion chamber is formed in correspondence with the spray pattern of the fuel injection nozzle.