JPH066892B2 - 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 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 rotated to generate electricity. The generated electric power can rotate the electric motor according to a command from the controller, and the output thereof can be supplied to the crankshaft of the engine via the gear.

[Problems to be solved by the invention]

However, in an engine member such as a piston that uses the ceramic material as a heat insulating material or a heat resistant material, it is extremely difficult to obtain sufficient heat insulating properties. 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. In addition, if the thickness of the ceramic material on the wall surface is increased for heat insulation, the heat capacity becomes large, and the intake air receives a large amount of heat from the combustion chamber during the intake stroke to reach a high temperature, which reduces intake efficiency and prevents intake of air. However, there is a problem that the adiabaticity must be improved in the expansion process.

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. It becomes easy to receive heat from. Therefore, it has the same problems as described above.

Therefore, an object of the present invention is to solve the above-mentioned problems, and to obtain a high degree of heat insulation and to make the heat capacity of the surface portion of the piston head that is exposed to combustion gas and becomes high temperature as small as possible. Therefore, the combustion chamber cannot be formed on the piston head by forming it on a flat surface and forming the piston head on a flat surface.Therefore, configure the combustion chamber on the cylinder head liner side accordingly and change the shape of the combustion chamber to fuel. It is formed along the spray trajectory, and the intake air inflow part is configured to flow in a large amount in the vicinity of the center, thereby improving the intake efficiency and cycle efficiency, and further, there is a problem in strength even if it receives a heat shock. Without increasing the heat resistance, you can obtain a stable mounting state,
Another object of the present invention is to provide a structure of an adiabatic engine having a structure capable of receiving the pressure acting on the piston head at the time of explosion in a preferable state.

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 constitutes a piston in which a ceramic thin plate having a flat surface on the combustion chamber side is arranged in the piston head through a heat insulating material, and a combustion chamber in which the cylinder center is low and the outer circumference is high. A cylinder head liner disposed in the head, a fuel injection nozzle that injects fuel into the combustion chamber substantially horizontally from the center of the cylinder, and an inclined surface of the lower surface of the head of the cylinder head liner inclined from the center of the cylinder to the outer periphery. The present invention relates to the structure of an adiabatic engine composed of a valve installed in the.

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 and the cylinder liner upper portion are integrally formed.

[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 includes a ceramic piston head having a flat surface on the combustion chamber side, a ceramic cylinder head liner having a low cylinder center portion and a high cylinder outer peripheral portion, and Since it is composed of each valve installed on the inclined surface of the lower surface of the head inclined from the center of the cylinder to the outer peripheral portion of the cylinder, a combustion chamber is formed in the cylinder head liner which is exposed to the combustion gas and becomes high in temperature. The surface of the piston head, which is exposed to heat and is heated to a high temperature, can be flattened and made of a ceramic thin plate. Therefore, the thickness of the ceramic thin plate can be made as thin as possible, the heat capacity thereof 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, 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 of the cylinder head liner in the high temperature state. Since the contact with the inner wall surface is reduced and the amount of heat received by heat transfer is reduced, the thermal expansion of the inflowing intake air is reduced and the suction 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 is increased, the piston head is configured to have a small heat capacity, so that the suction efficiency is lowered. There is no.

Further, since the fuel injection nozzle is installed at the center of the cylinder and the combustion chamber is formed so as to correspond to the spray pattern of the fuel injection nozzle, the swirl is weakly formed and the heat received by the intake air is suppressed to a small level. That is, the thinner the ceramic thin plate of the piston head is, the better the followability to the gas temperature is, and the wall temperature amplitude at high temperature and low temperature in the combustion chamber is higher than that when the thickness is thick. As a result, the temperature difference between the combustion gas and the ceramic on the wall surface of the combustion chamber becomes smaller, and the heat transfer amount decreases, so that the heat reception of the intake air is decreased.

〔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. FIG. 1 is a sectional view showing an embodiment of the structure of the heat insulation engine according to the present invention. The structure 10 of this adiabatic engine has a piston 2 mainly composed of a piston head portion 1 and a metal piston skirt portion 2.
0, a cylinder head liner 30 made of ceramic such as silicon nitride fitted inside a cylinder head (not shown) made of casting, a fuel injection nozzle 25 installed in the center of the cylinder head liner 30, and a cylinder head liner 3.
It is composed of a valve (only the intake valve 21 is shown in the figure) installed on the head lower surface portion 22 of No. 0.

Further, a ceramic thin plate 5 having a flat shape, that is, a flat surface on the combustion chamber side of the piston head portion 1 of the piston 20 is arranged. Further, the cylinder head liner 30 is configured to form the combustion chamber 15 having a shape in which the cylinder center portion is low and the cylinder outer peripheral portion is high, corresponding to the flat ceramic thin plate 5 of the piston head portion 1. To do.

The cylinder head liner 30 has a cylinder liner upper portion 23.
And the lower surface 22 of the head are combined into an integrated structure, which is a structure for cutting off heat only during a period of heat generation during which combustion is active. Cylinder head liner 30 having such a shape
The combustion chamber 15 formed by the flat ceramic thin plate 5 of the piston head 1 is a shallow dish type most suitable as a combustion chamber of an adiabatic engine and can be configured to have a shape in which the volume increases toward the outer periphery. .

Further, the valve 21 is installed on the inclined surface of the head lower surface portion 22 which is inclined from the cylinder center portion to the cylinder outer peripheral portion of the cylinder head liner 30. Head bottom part 2
As shown in the figure, 2 is an inclined surface that rises outward in the radial direction. Therefore, the intake valve seat and the exhaust valve seat are formed on the inclined surface, and the intake valve 21 is installed on each valve seat. Then, the intake valve 21 and the exhaust valve (not shown) are installed in an inverted V shape.

Due to the inclination of the intake valve 21, the flow of the intake air in the intake stroke is as shown in FIG. 2 in consideration of the shape of the intake port 29 extending from the outer side in the radial direction to the lower surface portion 22 of the head. As shown by the arrow A in the figure, the main flow is formed in the vertical direction of the engine and toward the center of the combustion 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 in contact with the ceramic thin plate 5 of the piston head portion 1, that is, the top surface is increased, the piston 20 is configured to have a small heat capacity, so that the suction efficiency is reduced. There is no.

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 injection hole of the fuel injection nozzle 25, that is, the injection port is formed parallel to the ceramic thin plate 5 of the piston head portion 1 and outward in the radial direction. In other words, the combustion chamber 15 is formed so as to correspond to the spray pattern of the fuel injection nozzle 25 (spray locus shown by arrow B in the figure).

Next, regarding the piston 20, the piston head portion 1
It has a mounting boss portion 4 in the center and is made of a material having a thermal expansion coefficient substantially equal to that of the 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. A central mounting hole 12 into which the mounting boss portion 4 of the piston head portion 1 is fitted is formed at the center of the piston skirt portion 2. The mounting boss portion 4 of the piston head portion 1 is fitted in the central mounting hole 12 of the piston skirt portion 2, and is formed in the fitting groove 14 formed in the mounting boss portion 4 and the central mounting hole 12 of the piston skirt portion 2. Mating groove 13
The metal ring 11 is accommodated in a deformed manner straddling the and, and the piston head portion 1 is locked to the piston skirt portion 2 in a pressed state.

Further, a cushioning material 8 made of a heat insulating gasket is provided at the contact portion of the central portion between the piston head portion 1 and the piston skirt portion 2.
Are interposed in a pressed state, 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. Regarding the piston 20, the ceramic thin plate 5 is arranged in the piston head portion 1 via the heat insulating material 3 so as to face the combustion chamber 15. 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, CVD (chemical vapor deposition) at a contact portion indicated by reference numeral 18. Are joined by.
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 or zirconia fiber, and has a heat insulating function.
It 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 against the carbon seal 7 is
The piston head portion 1 works by 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〕

The structure of the heat insulation engine according to the present invention is configured as described above, and has the following effects. That is, the structure of this adiabatic engine is a piston provided with a piston head part having a ceramic thin plate shielded by a heat insulating material by forming the combustion chamber side into a flat surface, the cylinder central part is low and the cylinder outer peripheral part is high. Since it is composed of a ceramic-made cylinder head liner formed in a shape and each valve installed on the inclined surface of the lower surface of the head that is inclined from the center of the cylinder to the outer circumference of the cylinder, it is exposed to combustion gas and exposed to high temperatures. A combustion chamber that extends radially outward is formed in the cylinder head liner, and the surface of the piston head that is exposed to combustion gas and becomes high in temperature is flattened to be a thin 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, and a high degree of heat insulation can be obtained.

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 is increased, the piston head is configured to have a small heat capacity, so that the suction efficiency is lowered. Therefore, the suction efficiency and the cycle efficiency can be improved.

Further, since the fuel injection nozzle is installed in the center of the cylinder and the spray locus of the fuel injection nozzle, in other words, the combustion chamber is formed so as to correspond to the spray pattern,
The formation of swirls becomes weaker, the amount of heat received by the intake air is reduced, and the thermal expansion of the intake air can be suppressed to a small level.The fuel spray is mixed well with the intake air together with the intake air inflow state, and it is compressed more than usual. The ratio can be lowered and good combustion can be obtained.

Regarding the piston head, the thinner the ceramic thin plate of the piston head is configured, the better the followability to the gas temperature is, and the wall temperature amplitude between the high temperature and the low temperature in the combustion chamber is thick. As compared with the case, the temperature difference between the combustion gas and the ceramics on the wall surface of the combustion chamber becomes small as a result, and the heat transfer amount decreases, so that the heat reception of the intake air is decreased.

Moreover, even if it receives a heat shock, there is no problem in strength, heat resistance is improved, and a stable mounting state can be obtained. Furthermore, the pressure acting on the ceramic thin plate at the time of explosion is received in a preferable state. be able to. 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 joint state of the two.

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

The heat insulating material is composed of potassium titanate whiskers, zirconia fibers, etc., or a mixed material of these and glass fibers, which performs a high-performance heat insulating function for the combustion chamber of the engine, and through the piston from the combustion chamber. There is no outflow of heat energy in the above, and heat energy can be confined in the combustion chamber. Therefore, thermal energy can be effectively recovered by the energy recovery device installed downstream in the exhaust gas flow direction.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of the heat insulation engine according to the present invention, FIG. 2 is a sectional view showing the structure of the heat insulation engine showing an example of the cycle process of FIG. 1, and FIG. It is sectional drawing which shows an example of a heat insulation engine. 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 lower surface part, 25 ... fuel injection nozzle, 30 ... cylinder head liner, A ... intake air flow direction, B ...
... Fuel spray trajectory (spray pattern).

Claims (3)

[Claims] 1. A piston in which a ceramic thin plate having a flat surface on the combustion chamber side is arranged in a piston head portion with a heat insulating material interposed between the piston and a combustion chamber in which the cylinder center portion is low and the outer peripheral portion is high. A cylinder head liner disposed inside, a fuel injection nozzle for injecting fuel into the combustion chamber substantially horizontally from the center of the cylinder, and an inclined surface of the head lower surface of the cylinder head liner inclined from the center of the cylinder to the outer periphery. The structure of an adiabatic engine composed of installed valves. 2. The structure of an adiabatic engine according to claim 1, wherein the valves are installed in an inverted V shape. 3. The structure of an adiabatic engine according to claim 1, wherein the cylinder head liner is made of a ceramic material, and the lower surface of the head and the upper portion of the cylinder liner are integrally structured.