JPH066891B2 - Insulation engine structure - Google Patents

Description

The present invention relates to the structure of an adiabatic engine.

[Conventional technology]

Conventionally, a heat insulating engine using a ceramic material as a heat insulating material or a heat resistant material is disclosed in, for example, JP-A-59-122765. The adiabatic engine will be described with reference to FIG.

In the heat insulating engine 40, a ceramic liner head 41 having a cylinder liner portion 42 is fitted inside a cylinder head 43 made of cast metal. Liner head 41
Is a cylinder head inner wall portion, which is the portion exposed to the highest temperature / high pressure gas during one cycle of the engine and in which most heat escapes, and the cylinder liner upper portion are integrally formed.

Further, the piston head 44 is made of silicon nitride, the central portion of which is recessed, and a step portion 46 is formed on the outer periphery of the lower end to prevent positioning and movement at the time of attachment to the piston body 47. A hole for inserting a bolt for connecting the piston body is provided in this. Piston body 4
A step portion 48 into which the lower end outer circumference of the piston head 44 is fitted is formed on the outer periphery of the upper end of 7, and the center of the upper surface is projected upward so that the upper surface of the protruding portion 49 abuts the lower surface of the piston head 44. The piston body 47 is connected with a bolt 50. Further, the valve 51 is arranged on the lower surface 52 of the head in the axial direction of the cylinder liner 42.

The adiabatic engine 40 is configured as described above, and drives the exhaust turbine by the high-temperature exhaust gas from the engine, and rotates the intake compressor by the output obtained from the exhaust turbine by the drive to supercharge the engine. At the same time, the generator is driven to generate electricity. The generated electric power can rotate the electric motor in response to a command from the controller and supply the output of the electric motor to the crankshaft of the engine via the gear.

[Problems to be solved by the invention]

However, it is extremely difficult to obtain sufficient heat insulation characteristics for a piston or the like of a heat insulation engine that uses the ceramic material as a heat insulation material or a heat resistance material. The ceramic material is in a state of being exposed to the high temperature on the combustion chamber side, which causes a heat shock, which causes a problem in strength of the ceramic material.

Further, if the thickness of the ceramic material on the wall surface is increased for heat insulation, the heat capacity of the wall of the combustion chamber increases, and during the intake stroke, the intake air receives much heat from the combustion chamber and reaches a high temperature, and the intake air expands. As a result, it becomes impossible to supply more air to the combustion chamber, resulting in a decrease in suction efficiency, but there is a problem in that the adiabaticity must be improved in the expansion stroke.

Further, in the diesel engine, the fuel is sprayed from the fuel injection nozzle, but it is desirable that the sprayed fuel be quickly mixed with the intake air in the combustion chamber and uniformly mixed by the swirl generated in the combustion chamber. The current situation is that nothing satisfactory is also disclosed.

By the way, in the heat insulating engine 40 disclosed in the above-mentioned Japanese Patent Laid-Open No. 59-122765, a recess 45 is formed in the piston head portion 44 made of ceramic, and the thickness thereof must be formed to be extremely thick in view of strength. Has a structure that contradicts making as small as possible.

In addition, 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 head lower surface 52 is formed flat, so that the intake air is sprayed outward in the radial direction, and the cylinder liner and the head lower surface portion. Therefore, the structure is not so constructed that heat is easily received and the swirl stirring action occurs. Therefore, it has the same problems as described above.

Therefore, an object of the present invention is to solve the above problems, to obtain a high degree of heat insulation, and to make the heat capacity of the surface portion of the piston head which is exposed to combustion gas and becomes high temperature as small as possible. In order to do this, make it thin and have a flat surface,
Since the combustion chamber cannot be formed in the piston head by forming the piston head flat accordingly, the combustion chamber is formed on the cylinder head liner side and the shape of the combustion chamber is formed along the fuel spray trajectory from the fuel injection nozzle. Then, a swirl stirring action is generated in the combustion chamber, and the intake air and the atomized fuel are rapidly and uniformly mixed in the combustion chamber,
Furthermore, the suction efficiency and the cycle efficiency are improved, and there is no problem in strength even if it receives a heat shock, heat resistance,
Provide a structure of an adiabatic engine configured to improve deformation resistance, corrosion resistance, etc., and to obtain a stable mounting state, and further to receive the pressure acting on the piston head in an explosive state in a preferable state. It is to be.

The cylinder head liner referred to here has a structure in which the upper portion of the cylinder liner and the lower surface of the head are integrally formed, and has a structure for shutting off heat only during a heat generation period during which combustion is active.

[Means for solving problems]

The present invention is configured as follows to achieve the above object. That is, the present invention is a piston in which a ceramic thin plate formed with a flat surface on the combustion chamber side is arranged in the piston head through a heat insulating material, the cylinder center is formed low and the outer periphery is formed high, and the upper part is a square tube body. A cylinder head liner that forms a combustion chamber whose lower part is formed into a cylindrical body,
A heat insulating layer disposed between the cylinder head line and the cylinder head, a fuel injection nozzle for injecting fuel into the combustion chamber substantially horizontally from the cylinder center, and the cylinder head line inclined from the cylinder center to the outer periphery. The present invention relates to the structure of an adiabatic engine composed of bubbles installed on the inclined surface of the lower surface of the head.

Further, in the structure of this adiabatic engine, the valves are installed in an inverted V shape with respect to each other.

Further, in the structure of this adiabatic engine, the cylinder head liner is made of a ceramic material, and the head lower surface portion having the inclined surface in which the valve is arranged, the upper portion to the square tubular body, and the lower portion to the cylindrical body. The upper part of the formed cylinder liner is integrally structured.

[Action]

The structure of the heat insulation engine according to the present invention is configured as described above, and operates as follows. That is, the structure of this adiabatic engine is composed of a piston head formed with a flat surface on the combustion chamber side, a cylinder forming a combustion chamber with a cylinder center portion low and an outer peripheral portion high and an upper portion partially formed into a square tubular body. Since it is composed of the headliner and the valve installed on the inclined surface of the lower surface of the head inclined from the central portion to the outer peripheral portion, the thickness of the ceramic thin plate can be formed as thin as possible and its heat capacity can be reduced as much as possible. Can be made very small.

Moreover, since the upper part of the combustion chamber is formed into a square tubular body,
The swirl generated in the combustion chamber is broken by the sides of the rectangular cylinder to generate a stirring action in the swirl, and the sprayed fuel and the intake air are mixed very quickly, that is, evenly near the top dead center during a moment. The combustion is performed well.

Further, if the cylinder head line is thermally insulated by the heat insulating layer, the thickness of the cylinder head liner can be made thin, and the heat capacity of the cylinder head liner can be made small.

Further, the thinner the ceramic thickness of the cylinder head liner and the piston head is made, the better the followability to the gas temperature in the combustion chamber becomes, and the wall temperature amplitude between the high temperature and the low temperature in the combustion chamber becomes thicker. The thickness of the intake air is larger than that of the case where the thickness is large, and as a result, the temperature difference between the combustion gas and the ceramics on the wall surface of the combustion chamber is small, and the amount of heat transfer is reduced.

〔Example〕

Hereinafter, embodiments of the structure of the heat insulation 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 10 of the adiabatic engine is mainly composed of a piston 20 composed of a piston head portion 1 and a metal piston skirt portion 2, and a cylinder head made of ceramics such as silicon nitride fitted inside a cylinder head (not shown) made of casting. The liner 30 includes a fuel injection nozzle 25 installed in the center of the cylinder head liner 30, and an intake valve 21 and an exhaust valve 27 installed in the head lower surface part 22 of the cylinder head liner 30.

A ceramic thin plate 5 in which the combustion chamber side of the piston head portion 1 of the piston 20 is formed into a flat surface, that is, a flat surface.
Are arranged on the piston head portion 1 with the heat insulating material 3 interposed therebetween.
Further, since the combustion chamber cannot be formed in the piston head portion 1 in response to the ceramic thin plate 5 in the piston head portion 1 forming a flat surface, the cylinder head liner 30 has a low cylinder center portion and a cylinder outer peripheral portion. The combustion chamber 15 having a high shape is formed. That is,
The cylinder head liner 30 has a cylinder liner upper portion 23.
The head lower surface portion 22 and the head lower surface portion 22 are combined into an integrated structure, which is a structure for cutting off heat only during a period of intense heat generation of combustion.

The combustion chamber 15 formed by the cylinder head liner 30 having the above-described shape and the ceramic thin plate 5 of the piston head portion 1 having the flat shape is configured in a shallow dish shape most suitable as the combustion chamber of the adiabatic engine. can do.

Further, FIG. 2 is a sectional view taken along the line II-II in FIG. 1. Regarding the shape of the combustion chamber 15, as shown in FIG. Further, the lower portion is formed into a circular body 28 having a round cross section. Further, in terms of fluid flow, it is preferable that the square tubular body 26 has a corner portion formed into a curved surface, for example, a curved surface having a radius of about 1/2 to 2/3 of the radius. With such a shape, the swirl generated in the combustion chamber 15 is broken by the sides of the rectangular cylindrical body 26, that is, the swirl is broken to generate a stirring action,
The atomized fuel and the intake air are mixed very rapidly, that is, near the top dead center and evenly during the moment, and the combustion is satisfactorily performed.

Further, since the outer peripheral surface of the cylinder head liner 30 is shielded by the heat insulating gasket 29 such as potassium titanate and the heat insulating layer 24, the thickness of the cylinder head liner 30 itself can be configured to reduce the heat capacity. be able to.

Further, as shown in FIG. 2, the intake valve 21 and the exhaust valve 27 have a head lower surface portion 2 inclined from the cylinder center portion of the cylinder head liner 30 to the cylinder outer peripheral portion.
It is installed on two inclined planes. As shown in FIG. 1, the head lower surface portion 22 is an inclined surface that rises outward, so that an intake valve seat and an exhaust valve seat are formed on the inclined surface, and the intake valve 21 is formed in each valve seat.
If the exhaust valve 27 is installed, the intake valve 21 is installed in an inverted V shape with the exhaust valve 27 (in some cases, the intake valve 21 can be installed substantially parallel to the cylinder axis).

Due to the inclination of the intake valve 21, the intake air flow in the intake stroke is in the vertical direction of the engine and in the combustion direction in consideration of the shape of the intake port (not shown) extending from the outer side in the radial direction to the head lower surface portion 22. A main flow is formed towards the center of the chamber 15.

Therefore, the intake air is less likely to come into contact with the inner wall surface of the cylinder head liner 30 that is at a high temperature, and the amount of heat received by heat transfer is reduced, so that the thermal expansion of the intake air that flows in is reduced and the intake efficiency is improved. No decrease occurs. In this case, even if the amount of intake air coming into contact with the ceramic thin plate 5 of the piston head portion 1, that is, the top surface increases, the piston 2
Since 0 is configured to have a small heat capacity as described later, the suction efficiency does not decrease.

On the other hand, the intake valve 21 and the exhaust valve 27 are connected to the combustion chamber 15
Since it is housed inside, the piston 20 is
At (top dead center), safety is always maintained without interfering with the piston 20 even when the intake valve 21 and the exhaust valve 27 are fully opened.

Further, the fuel injection nozzle 25 is connected to the cylinder head liner 3
It is installed at the center portion of the cylinder of the head lower surface portion 22 at 0, in other words, at the lowest portion of the combustion chamber 15.
Moreover, the multiple injection holes of the fuel injection nozzle 25 are formed parallel to the ceramic thin plate 5 of the piston head portion 1 and outward in the radial direction. Therefore, the combustion chamber 15 is formed in correspondence with the spray trajectory of the fuel injection nozzle 25 (spray pattern shown by arrow B in the figure).

Next, regarding the piston 20, the piston head portion 1
It has a mounting boss portion 4 at the center, is made of a material having a coefficient of thermal expansion substantially equal to that of a ceramic material, high strength, and a relatively high Young's modulus, for example, a material such as cermet or metal. No combustion chamber is formed in the piston head portion 1 itself, and the combustion chamber side of the piston head portion 1 is formed in a flat shape.

The piston skirt 2 has a piston head 1 at the center.
A central hole 12 into which the mounting boss 4 is fitted is formed. The mounting boss portion 4 of the piston head portion 1 is fitted into the central hole 12 of the piston skirt portion 2, and the fitting groove 14 formed in the mounting boss portion 4 and the central hole 1 of the piston skirt portion 2.
The metal ring 1 straddling the fitting groove 13 formed in
1 is inserted, and the piston head portion 1 is locked to the piston skirt portion 2 in a pressed state.

Further, a cushioning material 8 which is a heat insulating gasket is interposed in a pressed state at a contact portion at a central portion between the piston head portion 1 and the piston skirt portion 2, and the cushioning material 8 also has a heat insulating function. A heat insulating air layer 9 is formed between the piston head portion 1 and the piston skirt portion 2.

For the piston 20, the ceramic thin plate 5 is the combustion chamber 15
Is disposed on the piston head portion 1 via the heat insulating material 3 so as to face. The ceramic thin plate 5 is made of ceramics such as silicon nitride and has a thickness of about 1 mm or less than 1 mm. A ceramic ring 6 made of a similar material is fitted to the outer peripheral portion of the ceramic thin plate 5, and the ceramic thin plate 5 and the ceramic ring 6 are
For example, they are joined by CVD (that is, chemical vapor deposition) at a contact portion indicated by reference numeral 18.

A step portion 16 is formed on the inner peripheral surface of the ceramic ring 6, and the outer peripheral portion 17 of the piston head portion 1 abuts on the step portion 16 of the ceramic ring 6.
Is fitted to. 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 1. The heat insulating material 3 is made of a material such as potassium titanate whiskers and zirconia fiber, and has a heat insulating function and also functions as a structural material that receives the pressure acting on the ceramic thin plate 5 at the time of explosion.

By mounting the piston head portion 1 on the piston skirt portion 2 in a pressed state, the outer peripheral portion 17 of the piston head portion 1 is pressed against the step portion 16 of the ceramic ring 6, and the ceramic ring 6 is attached to the peripheral portion of the piston skirt portion 2. Pressed. 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 acts by the piston head portion 1 being attached to the piston skirt portion 2 in a pressed state.

With respect to the structure of the piston 20, it is necessary to uniformly receive the compressive force due to the explosion by the heat insulating material 3 such as potassium titanate. For this reason, the surface of the piston head portion 1 on the combustion chamber side and the ceramic thin plate 5 are flat. It has a flat shape.

〔The invention's effect〕

Since the structure of the heat insulation engine according to the present invention is configured as described above, it has the following unique effects. That is, the structure of this adiabatic engine is composed of a piston head formed with a flat surface on the combustion chamber side, a cylinder forming a combustion chamber with a cylinder center portion low and an outer peripheral portion high and an upper portion partially formed into a square tubular body. Since it is composed of a headliner and a valve installed on the inclined surface of the lower surface of the head inclined from the central portion to the outer peripheral portion, a combustion chamber is formed in the cylinder headliner that is exposed to combustion gas and becomes high in temperature. The surface of the piston head, which is exposed to combustion gas and becomes hot, can be made flat by using a ceramic thin plate. Therefore, the thickness of the ceramic thin plate can be formed as thin as possible, the heat capacity thereof can be made as small as possible, the followability to the gas temperature can be made good, and a high degree of heat insulating property can be obtained. Improve cycle efficiency.

Moreover, in the cylinder head liner that constitutes the combustion chamber, since the upper portion is formed into a square tubular body and the lower portion is formed into a cylindrical body, the swirl generated in the combustion chamber is broken by the side of the square tubular body and swirled. A stirring action occurs, and the atomized fuel and the intake air are mixed very quickly, that is, evenly in the vicinity of the top dead center during the instant, and the combustion is favorably performed.

Further, if the cylinder head liner is thermally insulated by the heat insulating layer, the thickness of the cylinder head liner can be made thin and the heat capacity of the cylinder head liner can be made small. That is, the thinner the ceramic thickness of the cylinder head liner and the piston head is, the better the followability to the gas temperature in the combustion chamber is, and the wall temperature amplitude at high temperature and low temperature in the combustion chamber becomes thicker. Is thicker than the thicker one, resulting in a smaller temperature difference between the combustion gas and the ceramics on the wall of the combustion chamber.
Since the amount of heat transfer is reduced, the heat reception of the intake air is reduced.

Moreover, the main flow of the intake air can flow into the combustion chamber vertically and toward the center from the portion located near the center of the valve and the valve seat, and therefore the intake air has a high temperature. Since the contact with the inner wall surface of the liner is reduced and the amount of heat received by heat transfer is reduced, the thermal expansion of the inhaled intake air is reduced and the inhalation efficiency is not reduced.

In this case, even if the amount of intake air in contact with the ceramic thin plate, that is, the top surface of the piston head portion increases,
Since the piston head is configured to have a small heat capacity, suction efficiency does not decrease,
Inhalation efficiency and cycle efficiency can be improved.

Further, 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 trajectory of the fuel injection nozzle, that is, the spray pattern, the amount of heat received by the intake air is reduced and the intake air is reduced. The thermal expansion of can be suppressed to a low level, the fuel spray can be mixed well with the intake air, and good combustion can be obtained.

Moreover, even if the piston head portion receives a heat shock, no problem in strength occurs, and heat resistance is improved,
Moreover, a stable mounting state can be obtained, and the pressure acting on the ceramic thin plate at the time of explosion can be received in a preferable state. Moreover, since the ceramic thin plate and the piston head portion such as the cermet have substantially the same thermal expansion coefficient, no problem occurs in the combined state of the two.

Further, the piston head portion such as cermet has a high rigidity and is hard to be deformed even when a high pressure is applied, the coupling state between the piston head portion and the piston skirt portion is stable, and the gas at the boundary portion is stable. The seal can be stably achieved.

Moreover, the heat insulating material is composed of, for example, potassium titanate whiskers, zirconia fibers or the like, or a mixed material of these and glass fibers, and performs a high-performance heat insulating function with respect to the combustion chamber of the engine. There is no outflow of thermal energy from the chamber through the piston and the thermal energy can be trapped in the combustion chamber. Therefore, the thermal energy can be effectively recovered by the energy recovery device installed downstream of the exhaust gas flow.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the structure of the heat insulation engine according to the present invention, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 is a cross section showing an example of a conventional heat insulation engine. It is a figure. 1 ... Piston head part, 3 ... Insulation material, 5 ... Ceramic thin plate, 9 ... Adiabatic air layer, 10 ... Insulation engine structure, 15 ... Combustion chamber, 17 ... Piston head outer peripheral part, 20 ... Piston, 21 ... Intake valve, 22 ...
... Head bottom surface, 23 ... Cylinder liner upper part, 24 ...
… Insulating layer, 25 …… Fuel injection nozzle, 26 …… Square cylinder, 27 …… Exhaust valve, 28 …… Cylinder, 29 …… Insulation gasket, 30 …… Cylinder headliner, B ……
Spray pattern.

Claims (3)

[Claims] 1. A piston in which a ceramic thin plate having a flat surface on the combustion chamber side is disposed in a piston head through a heat insulating material, a cylinder central part is formed low and an outer peripheral part is formed high, and an upper part is a quadrangular cylinder and a lower part is formed. A cylinder head liner forming a combustion chamber formed in a cylindrical body, a heat insulating layer arranged between the cylinder head liner and the cylinder head, a fuel injection nozzle for injecting fuel into the combustion chamber substantially horizontally from the center of the cylinder, And a valve installed on the inclined surface of the lower surface of the head of the cylinder head liner inclined from the center of the cylinder to the outer circumference. 2. The structure of an adiabatic engine according to claim 1, wherein the valves are installed in an inverted V shape. 3. A cylinder liner made of a ceramic material, the lower surface of the head having the inclined surface on which the valve is arranged, the upper part of the cylinder liner and the lower part of the cylinder liner. The structure of the adiabatic engine according to claim 1, wherein the upper part and the upper part are configured as an integrated structure.