JPS6234924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automobile engine, and more particularly to an automobile engine in which portions exposed to high temperatures, such as the inner wall surface of a combustion chamber cylinder, are formed of ceramic material. The automobile engine according to the present invention can be applied to both a spark ignition engine and a compression ignition engine.

[Conventional technology]

Many attempts have been made to use oxide-based, carbide-based, and nitride-based ceramics in high-temperature parts of engines. This is to reduce engine heat loss and improve efficiency by utilizing the heat resistance and low thermal conductivity of ceramic materials. In other words, in general, ceramics not only have excellent heat resistance, but also have thermal conductivity that is comparable to that of aluminum.
177kcal/mh℃, compared to 50-9kcal/mh℃ of copper.
It is small at less than 1kcal/mh℃. Therefore, it is attempted to reduce the heat loss of the engine by utilizing the heat insulating properties of this ceramic material.

[Problem that the invention seeks to solve]

However, if the cylinder is made of ceramic and the insulation is improved, the wall temperature of the cylinder will increase excessively. Reducing engine heat loss has the drawback of increasing combustion gas temperature and increasing nitrogen oxide (NOx) emissions. Moreover, the heat transfer from the combustion gases to the combustion chamber wall increases as the pressure, temperature, and average speed of the piston increase, so if the amount of heat dissipated is not controlled according to changes in these parameters, the combustion chamber wall temperature There is a risk that the temperature will rise excessively and burn out the ceramic.

SUMMARY OF THE INVENTION The present invention aims to eliminate the drawbacks of the prior art described above, and to provide an automobile engine using ceramic that can reduce heat loss of the engine without causing burnout of the ceramic and improve the efficiency of the engine. purpose.

[Means for solving problems]

In order to achieve the above object, the present invention provides an automobile engine having a cylinder in which a piston reciprocates, and an engine cooling means for cooling this cylinder. at least a part of the head of the cylinder is made of ceramic, and temperature detection means detects the temperature of the inner wall surface of the cylinder;
speed detection means for detecting the rotational speed of the engine;
The engine cooling means is actuated based on a detection signal from at least one of the temperature detecting means and the speed detecting means, and the temperature of the inner wall surface of the ceramic wall portion of the cylinder is set to be higher than the temperature of the inner wall surface of the metal wall portion by a predetermined temperature. , and a control means for controlling the temperature of each inner wall surface within a predetermined temperature range.

[Effect]

In the present invention configured as described above, since the combustion chamber on the top dead center side is made of ceramic with excellent heat insulation, the engine can be maintained at a substantially high temperature without causing thermal damage to the metal parts of the cylinder. , the heat loss of the combustion gas during the expansion process is small, the combustion gas temperature can be maintained at a high temperature, and the efficiency of the engine can be improved. Furthermore, the control means controls the inner wall surface of the cylinder to a predetermined temperature based on at least one of the temperature of the inner wall surface of the cylinder and the engine rotational speed, thereby making it possible to prevent burnout of the ceramic.

〔Example〕

Hereinafter, preferred embodiments of the automobile engine according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of an automobile engine according to the present invention.

In FIG. 1, the cylinder 1 has a ceramic wall 8 made of oxide, carbide, or nitride ceramic on the top dead center side, and a metal wall 29 similar to the conventional one on the bottom dead center side. It's summery. A temperature sensor 2 as temperature detection means is attached near the inner wall surface of the cylinder 1 to detect the inner wall surface temperature Tw. The output signal of the temperature sensor 2 is input to a control device 3 which is a control means, and the output of the control device 3 drives a fan motor 5 to operate a cooling fan 4 which is an engine cooling means. The cooling fan 4 controls the heat transfer coefficient _α0 between the outer wall surface and the outside air by flowing a refrigerant (air) along the outer wall surface of the cylinder 1, thereby reducing the temperature of the inner wall surface.
This is to prevent excessive rise in Tw.
Note that the temperature sensor 2 may be provided on both the ceramic wall portion 8 and the metal wall portion 29, or may be provided on only one of them.

A piston 12 is fitted into the inner surface of the cylinder 1, and a combustion chamber is formed in the space above the piston. An intake system having an intake valve 10 and a fuel injection valve 6 is provided on the upper wall of the combustion chamber. Further, an exhaust system having an exhaust valve 11 and an exhaust pipe 15 is provided on the upper wall of the combustion chamber.

A turbine 14 made of ceramic and resistant to high temperature gas is connected to the exhaust pipe 15, and this turbine drives a compressor (not shown) for supercharging air. The exhaust gas exiting the turbine 14 is guided to the catalytic converter 16 along with the exhaust gas that is recirculated from the upstream side of the turbine 14 to the exhaust pipe 15 through the bypass 17.

Ceramic wall portion 8 that constitutes the cylinder 1
generally lacks mechanical strength, so its periphery is reinforced by a support 7. Further, a ceramic wall 2 is provided on the surface of the head of the piston 12.
6 is formed. And the ceramic wall part 8
It is preferable that a cavity 9 is provided between the support body 7 and the support body 7, as shown in FIG. 4, to improve the heat insulation properties of this part.

In addition, when cooling the cylinder 1, a crank angle sensor 32 as a speed detection means provided on the crankshaft and a pick-up 3 opposite to this sensor 32 are used.
3, the engine speed is detected and the signal is input to the control device 3, and the control device 3 controls the piston 1.
Calculate the average speed of 2 and based on the calculated signal,
The motor fan 5 may be driven.

In the embodiment configured as described above, the efficiency of the engine can be improved by forming the ceramic wall portion 8 on the piston top dead center side of the cylinder 1 using ceramic. In other words, ceramic has a very low heat transfer coefficient compared to metal.
Due to its excellent heat resistance, its wall temperature can be raised to 1000 degrees Celsius or more. Therefore,
If the top dead center side of the cylinder 1 is made of ceramic wall 8, there will be less heat transfer from the combustion gas to the wall during the expansion stroke, which has a large effect on engine efficiency.
The heat loss (cooling loss) of the combustion gas is reduced, and the engine can be maintained at a high temperature without causing thermal damage to the metal parts of the cylinder, and the temperature of the combustion gas can be maintained at a high temperature, improving the efficiency of the engine. becomes possible.

If the temperature of the combustion gas is Tg and the temperature of the inner wall surface is Tw, then α(Tg−Tw)=Q...(1) Here, α is the heat transfer coefficient from the gas to the wall, and Q is the amount of heat passing through the wall. show. Now, if the inner wall temperature Tw of the ceramic wall portion 8 is 1000℃ and Tg is 3000℃,
Tg−Tw=2000℃. In conventional metal engines, the Tg value was the same, but the Tw was around 100°C. Therefore, when using ceramic
Tg - Tw = 2000℃, which is about 2/3 of Tg - Tw = 2900℃ in the case of conventional metal, and the amount of heat (heat loss) Q passing through the wall can be reduced to about 2/3. .

Since the heat transfer coefficient α from the combustion gas to the inner wall surface is mainly determined by the flow state of the gas in the combustion chamber, the smaller the flow velocity in the combustion chamber, the smaller its value becomes. However, as the gas flow velocity within the combustion chamber decreases, there is a tendency that the combustion velocity decreases and the thermal efficiency of the engine decreases. Therefore, the inner wall surface temperature Tw needs to be maintained at a value that provides an appropriate combustion rate.
The amount of heat Q transmitted within the ceramic wall 8 is λ(Tw-Ta)/δ=Q (2). Here, λ is the thermal conductivity of ceramic, δ
is the thickness of the ceramic (wall thickness), and Ta is the temperature of the outer wall surface of the ceramic wall portion 8. The amount of heat transferred from the outer wall surface to the outside air can be expressed as α ₀ (Ta−To)=Q (3). Here, α ₀ represents the heat transfer coefficient between the outer wall surface and the outside air, and To represents the temperature of the outside air.

The following two relational expressions can be obtained by using the above relationships of Equation (1), Equation (2), and Equation (3).

Tg−To=(1/α+1/α ₀ +δ/λ)Q ……(4) Tw−To=(δ/λ+1/α ₀ )Q ……(5) That is, The following relational expression is obtained. Therefore, by controlling the heat transfer coefficient α ₀ between the outer wall surface and the outside air (increasing α ₀ ), an excessive increase in the inner wall surface temperature Tw can be prevented,
The inner wall surface can be maintained at a temperature at which a proper combustion rate can be obtained. In this case, it is preferable to locally control the amount of heat radiation so that the temperature of the metal wall 29 in the combustion chamber is 100 to 400°C, and the temperature of the ceramic wall 8 is 600 to 1500°C. Note that when λ/δ is small, Ta (outer wall surface temperature) becomes small, so that the ceramic wall portion 8 can be cooled by water cooling.

On the other hand, as can be seen from the above equation (6), when 1/αc=δ/λ+1/α ₀ (7), Tw-Tc/Tg-Tc=α/αc (8) holds true.

This αc corresponds to the transmission heat transfer coefficient of the ceramic material, and in the case of ceramic, the term δ/λ cannot be ignored. In the case of metals, this term δ/λ can be ignored, and α/αc≈α/α ₀ holds true.

From this equation, it can be seen that if αc is increased in accordance with the increase in the heat transfer coefficient α from the combustion gas to the inner wall surface, an increase in the inner wall surface temperature Tw can be prevented. Note that αc is a coefficient corresponding to the heat transfer coefficient from the inner wall surface facing the combustion chamber to the outside air. Therefore, by controlling αc by the cooling method, the inner wall surface temperature
Tw can be maintained at a predetermined value.

In general, the heat transfer coefficient α from the combustion gas to the inner wall surface
increases as the piston speed increases, as shown in FIG. On the other hand, in a conventional engine where the refrigerant flows in accordance with the rotational speed of the engine, the rate of increase in αc increases as the piston speed increases, and the temperature of the wall surface of the ceramic portion increases, as shown in FIG. have a tendency to be easily Such an increasing tendency causes excessive heating of the ceramic wall in areas where the rotational speed is high, so it is necessary to prevent this. For this purpose, it is necessary to increase the amount of refrigerant in the region where the rotational speed is high. That is, even if metal can be sufficiently cooled by an engine-driven fan, ceramic material has a small αc as shown in FIG. 14, so cooling is insufficient only with a refrigerant flow rate proportional to the engine rotation speed. Therefore, when using ceramic materials, it is necessary to locally control the refrigerant flow rate. Another method for preventing heating is to use a special ceramic material with high thermal conductivity to prevent heating. Furthermore, there is also a method of cooling the ceramic wall using the heat of vaporization of the fuel.

In a conventional engine, the thermal conductivity λ is large because the entire engine is composed of metal parts, and the above-mentioned αc increases in the same way as the heat transfer coefficient α from the combustion gas to the inner wall surface. On the other hand, in engines using ceramic, the thermal conductivity λ of the ceramic portion is generally very small, so that it is easily heated due to thermal resistance when the piston speed increases. In order to prevent this, in the case of a compression ignition engine, etc., as will be described later, it is preferable that the portion where the fuel injection from the injection valve collides is constructed of a wall made of ceramic material.

Further, in the case of the spark ignition engine shown in FIG. 1, it is preferable that the fuel injected from the fuel injection valve 6 enters the combustion chamber in a partially unvaporized state to cool the combustion chamber wall. The reason for this is that although the flow rate of the refrigerant increases in proportion to the engine speed, this increase in flow rate results in insufficient heat dissipation from the ceramic portion during high speed rotation and high load. FIG. 15 is a graph illustrating a tendency for the flow rate and pressure of the cooling fan 4 or the cooling pump to increase in proportion to the rotational speed, resulting in an increase in the flow rate.

In view of this tendency, it is necessary to force the metal part and the ceramic part to have different amounts of heat radiation. For example, metal parts are preferably cooled with conventional cooling systems, and ceramic parts are preferably cooled with additional cooling systems that operate at higher speeds. Furthermore, it is preferable to increase the rotational speed of the cooling fan 4 at high speeds.

It is very difficult to attach a temperature sensor directly to the piston 12, such as the sensor 2 attached to the combustion chamber wall in FIG. Therefore, in order to prevent the ceramic attached to the piston (ceramic wall 26 in FIG. 1, etc.) from heating, it is necessary to reliably cool the piston surface by oil cooling, water cooling, or the like. In this case as well, the surface of the metal part is generally easy to cool, but the ceramic part has low thermal conductivity and is difficult to cool. Therefore, as in the case described above, the ceramic material of the piston head is likely to be heated during high-speed operation. To prevent this heating, it is necessary to substantially increase the cooling rate of the ceramic parts relative to the metal parts as the engine speed increases.

In an engine having a ceramic wall part 8, if the conventional cooling method for an engine using only metal is applied, the temperature of the metal part can be maintained uniformly, but the temperature is higher than that of the metal part.
In the ceramic wall portion 8, which has a poor heat transfer coefficient, the temperature rises as the number of revolutions increases, and there is a risk of heating up in a high speed region and causing thermal burnout. That is, since the metal wall portion 29 and the ceramic wall portion 8 generally have different thermal conductivities, when cooling the ceramic wall portion 8, the pressure and temperature inside the combustion chamber, and the piston 12
It is necessary to increase the amount of heat dissipation in accordance with an increase in the average velocity of the metal wall portion 29, and perform cooling different from that of the metal wall portion 29.

As shown in FIG. 3, the inner wall surface temperature Tw of the ceramic wall portion 8 increases over time after the engine is started. Therefore, the heat loss immediately after startup is the same even when ceramic is used as in a conventional aluminum water-cooled engine. However, in the case of ceramic, the heat transfer coefficient α ₀ from the outer wall surface to the outside air is very small, and if it is not cooled, the inner wall surface temperature Tw will be almost equal to the combustion gas temperature Tg. 4 to suppress an excessive rise in Tw.

In a state where the temperature of the ceramic wall portion 8 has increased, α (heat transfer coefficient from combustion gas to the inner wall surface) = α
₀ (heat transfer coefficient from the outer wall surface to the outside air), and δ
When (wall thickness) = 0, as shown in Figure 2,
The temperature Tw of the inner wall surface and the temperature Ta of the outer wall surface are approximately equal to approximately 1500°C. Also, the wall thickness δ
When is not 0, Tw becomes larger than Ta, as shown by the broken line in Fig. 2, and the value of Tw becomes
The temperature will be considerably higher than 1500℃. The temperature of Ta is much lower than 1500°C.
When Ta becomes small in this way, there is no need to use a heat-resistant material for the support 7, so it is preferable that the thickness δ of the wall of the ceramic material be a certain value (1 mm or more).

On the other hand, as the thickness of the ceramic increases, the heat capacity increases, which tends to increase the temperature of the intake air and reduce the charging efficiency of the engine. There is also a tendency for the concentration of nitrogen oxides (NOx) to increase. In order to prevent such problems, it is preferable to supply fuel with a large latent heat of vaporization, such as methanol, from the fuel injection valve 6 to prevent negative effects such as a decrease in filling efficiency and an increase in nitrogen oxides.

On the other hand, the heat dissipation state, that is, the temperature distribution state, of the ceramic wall portion 8 also differs depending on the thermal conductivity of the ceramic material. An example is shown in FIG. 11th
In the figure, the solid line shows the temperature distribution when the ceramic wall 8 has a relatively high thermal conductivity and the combustion chamber side wall 27 and the cooling side wall 28 have the same heat transfer coefficient, and the dotted line shows the temperature distribution when the ceramic wall 8 has a relatively high thermal conductivity. This is the temperature distribution when the thermal conductivity of No. 8 is low.

In Fig. 11, Tg indicates the combustion gas temperature (for example, 3000℃), Tw indicates the temperature of the combustion chamber side wall (inner wall) (1500℃ in the case of the solid line), and Ta indicates the cooling side wall (outer wall). ) temperature (approximately 1500 for the solid line)
℃ or slightly lower), and To indicates the outside temperature (for example, 0℃).

As can be seen from FIG. 11, the heat dissipation characteristics can also be controlled by varying the thermal conductivity of the combustion chamber ceramic wall 8 itself. However, the metal wall portion 29 is
Since it cannot withstand a temperature of 1500°C, in order to increase the heat transfer coefficient of the wall 28 on the cooling side of this part,
It is necessary to cool this part using water or oil cooling to lower its temperature. On the other hand, since the ceramic material part can withstand high temperatures, the heat transfer coefficient between the cooling side wall 28 and the outside air can be made relatively small, and cooling by air cooling, for example, is sufficient. For example, if a sintered body made by adding beryllium oxide or boron nitride to highly sintered silicon carbide is used as a ceramic material, the specific resistance of the ceramic material made of such a sintered body is 10 ¹² Ωcm. , its thermal conductivity is 0.7 cal/°C, and since this ceramic has a thermal conductivity close to that of metal, air cooling is also possible, making it easy to control the amount of heat dissipation.

The cylinder 1 has a ceramic wall portion 8 and a metal wall portion 29.
When the piston 12 reciprocates up and down within the cylinder 1, a difference occurs in the temperature distribution passing through the wall surface of the cylinder at the piston stroke position. An example is shown in FIG. 13th
In the figure, the temperature distribution at the top dead center of the piston is shown by a solid line, and the temperature distribution at the bottom dead center of the piston is shown by a dashed line.

When the piston 12 is located near the top dead center, both pressure and temperature are high and the heat transfer coefficient is high. Therefore, the temperature distribution becomes as shown by the solid line in FIG. 13. As the piston approaches the bottom dead center, the temperature decreases, resulting in a temperature distribution as shown by the dashed line in FIG.

As mentioned above, if the top dead center side of the cylinder 1 is made of ceramic wall 8 in order to improve the efficiency of the engine, the temperature inside the combustion chamber wall increases, and the intake valve 10 and exhaust valve exposed inside the combustion chamber increase. 11, the piston 12, the spark plug 13, etc., are easily overheated, and special care must be taken to prevent the exhaust valve 11 from burning out. Therefore, it is necessary to cool the inside of the exhaust valve 11 or the vicinity thereof with a refrigerant (cooling air, water, oil).

In addition, the spark plug 13 also needs to be cooled appropriately to prevent its abnormal ignition, and for this purpose, the combustion chamber wall near the spark plug 13 is covered with a metal support 7, as shown in FIG. It is preferable to increase the cooling effect. In the example shown in FIG. 5, the spark plug 13 is attached to the metal support 7 by screw fastening. Further, a ceramic wall portion 8 is attached to the metal support body 7. In addition, in the case of a diesel engine (compression ignition engine), its injection valve is installed in a similar manner. On the other hand, the intake valve 10 is cooled by intake air, so there is no problem of overheating.

In FIG. 1, since the gas discharged through the exhaust valve 11 has a very high temperature, it is preferable that the inner surface of the exhaust pipe 15 is also made of ceramic material.
Note that the temperature of exhaust gas can be lowered by increasing the compression ratio and achieving rapid combustion.
As means for achieving this rapid combustion, methods such as providing appropriate turbulence to the air-fuel mixture and combustion using two spark plugs are used. Along with this, knock control and feedback control using an oxygen sensor are added to prevent engine knock and reduce nitrogen oxides. In addition, a method of reducing nitrogen oxides by performing appropriate exhaust gas recirculation (EGR) is also being used.

In compression ignition engines, there are two methods: one uses wall steam to form an air-fuel mixture, and the other uses a pre-combustion chamber that communicates with a combustion chamber through a nozzle hole.

FIG. 6 is a diagram showing the latter example, that is, an example in which air-fuel mixture is formed in a pre-combustion chamber, and in such a compression ignition engine, heat radiation loss and throttling loss tend to increase. Further, there are problems in that the ignitability at the time of starting is poor and that the nozzle holes 19 (FIG. 6) are easily corroded by high-temperature gas. In the compression ignition engine shown in FIG. 6, the ceramic wall 8 and the nozzle hole 19 or its vicinity (the wall surface of the auxiliary combustion chamber) are formed of ceramic material,
In addition to solving the problem of ignitability, the nozzle hole 19
shots are prevented. In addition, in Figure 6,
The sub-combustion chamber 20, the fuel injection valve 18 and the piston 12 attached to the sub-combustion chamber are shown.

FIG. 7 is a diagram showing another example of the structure of the pre-combustion chamber, in which the inner wall surface of the pre-combustion chamber 20 is composed of a wall 21 made of ceramic material. A fuel injection valve 18 is attached to one side of the pre-combustion chamber 20, and a nozzle hole 19 is formed at the tip exposed to the combustion chamber.

In order to improve the startability of a compression ignition engine, it is effective to use a voltage heating plug to increase the compression temperature. For this purpose, in the pre-combustion chamber shown in FIG. 7, the ceramic wall 21 and the electric heating plug are constructed in one piece. With such a configuration, it is possible to achieve heat insulation and increase the compression temperature, and also to reduce heat radiation loss. Thus, significant advantages can be obtained by constructing the pre-combustion chamber 20 from ceramic material.

FIG. 8 is a diagram showing another example of the structure of the pre-combustion chamber, in which the wall 21 of the pre-combustion chamber 20 is made of ceramic,
Moreover, an electric heating plug 22 is attached to a part thereof. The other structures are substantially the same as those shown in FIG. Even with the configuration shown in FIG. 8, it is possible to increase the compression temperature and improve the ignitability.

FIG. 9 is a diagram showing still another structural example of the pre-combustion chamber. In this case, a heating resistor is attached to a part of the ceramic wall 21 forming the inner wall surface of the pre-combustion chamber 20.
4 is attached to the heating resistor 24, and an electrode 2 is attached to the heating resistor 24.
3 is embedded. This heating resistor 24 is
Generally, PTC (Positive Temperature)
It is made of a ceramic heating element with a coefficient of A general characteristic of this PTC ceramic is that when the temperature becomes abnormally high and exceeds a certain temperature, no current will flow.

Also in the structure shown in FIG. 9, when a current is passed through the heating resistor 24 through the electrode, the resistor 24 is heated, and as in the case of other structural examples, the compression temperature can be increased and the ignitability can be improved. be able to.

FIG. 10 is a diagram showing an example of the structure of a piston of a compression ignition engine.
A ceramic wall 26 is formed in a part of 5. The entire area of the surface 25 is covered with a ceramic wall 26.
However, the extent of the ceramic wall 26 can be determined for each individual engine.

In FIG. 10, fuel injected from the fuel injection valve 18 adheres to the surface 25 in the form of a film. The thickness of the film is about 14 μm. Also, the surface temperature is about 340°C. Therefore, the film is quickly vaporized due to this surface temperature. Thus, at the end of the compression process, the squish expels the fuel near the surface 25 and forms an air-fuel mixture.

According to the structure shown in FIG. 10, at least a part of the surface 25 of the head of the piston 12 is made of a ceramic wall 26,
This makes it possible to prevent heat dissipation into the engine, thereby improving the ignitability and startability of the compression ignition engine.

FIG. 12 shows another embodiment of the automobile engine according to the present invention, in which at least a portion of the head surface (crown portion) 30 of the piston 12 is similar to the embodiment shown in FIG. It is constructed with a wall 31 made of ceramic material with low thermal conductivity, and is intended to maintain the temperature of the wall surface of the upper surface 30 of the crown portion high and to maintain the temperature inside the piston low, while reducing the amount of heat dissipated as a whole. A refrigerant passage 33 is provided around the entire circumference of the cylinder 1, and cooling air or cooling water is circulated by a fan 4 or a pump shown in the figure.

In this embodiment, the outside of the ceramic wall 8 and the outside of the metal wall 29 at the bottom of the cylinder can be cooled with the same refrigerant (air, water, or oil). However, the flow rate of the refrigerant needs to be adjusted depending on the operating conditions. The flow rate of the coolant is controlled, for example, by changing the rotational speed of the fan 4 or the cooling pump depending on the rotational speed of the engine. Further, the rotational speed of the cooling fan 4 can be adjusted depending on the amount of fuel supplied to the engine, that is, the amount of heat generated.

〔Effect of the invention〕

As described above, according to the present invention, by forming the ceramic wall portion on the piston top dead center side of the cylinder, the combustion gas temperature during the expansion stroke can be maintained at a high temperature, and the efficiency of the engine can be improved. Further, by controlling the metal wall portion and the ceramic wall portion of the cylinder within a predetermined temperature range using at least one of the cylinder inner wall surface temperature and the engine rotational speed, engine burnout can be prevented.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the overall configuration of an embodiment of an automobile engine according to the present invention, Fig. 2 is an explanatory diagram showing the temperature distribution passing through the ceramic wall, and Fig. 3 is an explanatory diagram showing the temperature distribution passing through the ceramic wall portion. A graph illustrating changes in temperature on the inner wall surface of the wall, FIG. 4 is a partial sectional view illustrating the structure of the joint between the ceramic wall in FIG. 1 and its support, and FIG. 5 is a graph showing the ignition in FIG. FIG. 6 is a schematic explanatory view showing an embodiment of a compression ignition engine using ceramic material according to the present invention; FIG. 7 is a partial sectional view illustrating the state of attachment of the plug; FIG. 7 is a pre-combustion chamber of the compression ignition engine according to the present invention. 8 is a schematic diagram showing another example of the structure of the pre-combustion chamber of the compression ignition engine of the present invention, and FIG. 9 is a schematic diagram showing another example of the structure of the pre-combustion chamber of the compression ignition engine of the present invention. FIG. 10 is an explanatory diagram illustrating the structure of the piston head of the compression ignition engine of the present invention. FIG. 11 is an explanatory diagram illustrating the temperature distribution of the ceramic wall. FIG. 12 is an explanatory diagram illustrating another structure. 13 is an explanatory diagram illustrating the main parts of a modified embodiment of an automobile engine according to the present invention, FIG. 13 is an explanatory diagram illustrating the temperature distribution of the combustion chamber wall at the top dead center and bottom dead center of the piston, and FIG. A graph illustrating changes in the heat transfer coefficient from the combustion gas to the inner wall surface and the permeation heat transfer coefficient from the inner wall surface of the ceramic wall to the outside air as the speed (engine rotational speed) increases. It is a graph illustrating the relationship between the refrigerant flow rate and refrigerant pressure of a pump, etc., and the engine rotation speed that drives them. DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Temperature sensor, 3... Control device, 4... Cooling fan, 5... Motor fan, 6... Fuel injection valve, 7... Metal support, 8... Ceramic wall, 10... Intake valve, 11... Exhaust valve, 12... Piston, 13... Spark plug, 15... Exhaust pipe, 18... Fuel injection valve, 19... Nozzle hole, 20... Pre-combustion chamber, 21...
Ceramic wall, 22... Electric heating plug, 23... Electrode, 24... Heating resistor, 25... Piston head surface, 26... Ceramic wall, 27... Combustion chamber side wall, 28... Cooling side wall. , 29...metal wall part, 32...
Crank angle sensor, 33...Pick up.

Claims (1)

[Claims] 1. A cylinder in which a piston reciprocates;
An engine cooling means for cooling the cylinder, wherein the piston top dead center side of the cylinder and at least a part of the head of the piston are made of ceramic, and the inner wall surface temperature of the cylinder is controlled. The engine cooling means is actuated based on a detection signal from at least one of the temperature detection means for detecting the temperature detection means, the speed detection means for detecting the rotational speed of the engine, and the temperature detection means and the speed detection means for detecting the rotational speed of the engine. 1. A motor vehicle engine, comprising control means for setting the temperature of the inner wall surface of the ceramic wall portion to a predetermined temperature higher than the temperature of the inner wall surface of the metal wall portion, and controlling the temperature of each of these inner wall surfaces within a predetermined temperature range. 2. In the automobile engine according to claim 1, the predetermined temperature range of the inner wall temperature of the metal wall of the cylinder is 100 to 400°C, and the predetermined temperature range of the inner wall temperature of the ceramic wall is 600 to 1500°C.
An automobile engine characterized by: 3. The automobile engine according to claim 1 or 2, wherein the control means increases the amount of refrigerant delivered from the engine cooling means as the engine rotational speed increases. .