JPS63275892A - Heat insulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat insulator suitable for use in a mechanical element that undergoes repeated temperature changes between high and low temperatures in short periods of time.

[Prior Art] Among the various mechanical elements used in various devices and structures, there are some that undergo repeated temperature changes from high to low temperatures in a short period of time.A typical example is a diesel internal combustion engine. One example is the engine service line. Various heat insulating structures have been adopted for the screw head of the piston and the inner wall surface of the combustion chamber formed in the piston head from the viewpoint of improving thermal efficiency (Japanese Patent Application Laid-Open No. 143328/1984, etc.). The following is known as a typical example of a conventional heat insulating structure.

■ A void is simply formed inside the heat-receiving surface of the machine element, and this serves as an insulating air layer. ■ A solid (monolith) ceramic material is used as the insulating material, and the ceramic material and the air layer are A combination of layers is attached to the heat-receiving surface of a mechanical element to take advantage of the high-temperature properties of ceramic material and the low thermal conductivity of air. In some cases, a porous ceramic material is pasted to form an air layer in the porous portion inside the ceramic material.

For example, as shown in FIG. 12, these are employed as a heat insulating structure on the piston head b of the piston a and the surfaces a and f of the inner wall d of the combustion chamber C.

[Problems to be Solved by the Invention] By the way, from the viewpoint of mechanical strength, etc., the above-mentioned heat-insulating structure (■) has a heat-receiving surface layer of the mechanical element where the heat-insulating air layer is formed by thick and large holes (■). The heat capacity of that part is large, and as a result, the temperature of the heat-receiving part of the mechanical element is maintained at a high temperature.For example, take the piston head b and combustion chamber C of a diesel internal combustion engine. , as shown in Fig. 9, the wall surface temperature of these pistons is maintained at 11 temperatures over V cycles compared to a normal piston without a heat insulating structure (D in the figure is poly).This means that during the combustion stroke However, on the other hand, it heats the intake air during the intake stroke to promote its expansion, and the first
As shown in Fig. 0, the volumetric efficiency (filling efficiency) of intake air was reduced, resulting in a deterioration of combustion efficiency and fuel efficiency as shown in Fig. 11 (indicated by A in the figure). ).

In addition, in the insulation structure (■), the material cost of the monolithic ceramic material is 10 to 100 times that of general metal materials.
There was a problem in that it led to an increase in costs. Furthermore, since ceramic materials have low tensile strength, their durability and reliability against thermal stress and the like are questionable. Furthermore, although it is used in combination with an air layer, the heat transfer to the mechanical element is quite large at the joint between the ceramic material and the mechanical element and the sealing area for sealing the air layer, making it difficult to obtain sufficient heat insulation. There wasn't.

On the other hand, since the insulation structure of Q is porous, there are concerns about its reliability in terms of strength. In addition, when such heat insulation fa''lIi is used in the above-mentioned combustion chamber, etc., high temperature and high pressure gas will enter the porous part, resulting in a lack of reliability and durability and insufficient heat insulation performance. The problem was that I couldn't do it.

Furthermore, with these insulation structures (■) and (■), while it is possible to suppress the wall surface temperature of the combustion chamber etc. to a low level and increase the volumetric efficiency of intake air, the combustion efficiency decreases due to the low wall surface temperature. This has led to problems such as deterioration of fuel efficiency and deterioration of exhaust gas such as unburned emissions (Figures 9 to 1).
(Indicated by E in Figure 1).

[Means for Solving the Problems] The present invention provides a thin film-like skin that covers the surface of a mechanical element subject to temperature changes to form a heat-receiving surface, and a thin film-like skin that is seated on the surface of the mechanical element to support the skin. A thin film-like structural material defining a heat insulating space therebetween is integrally formed, and a pressurized gas supporting external pressure is filled in the heat insulating space.

[Function] Describing the function of the present invention, by forming the entire film in the form of a thin film, the heat receiving portion has a low heat capacity and the temperature changes by following the thermal cycle, and the heat insulating space surrounded by this low heat capacity AV film to ensure necessary and sufficient insulation effect for mechanical elements. In addition, by making the film thinner, it secures a throttling effect on heat flow, restricts heat transfer to mechanical elements through the skin and structural materials, and obtains a heat insulating effect. Then, such a thin film structure is constructed with highly efficient structural strength by the structure of the skin and the structural material. In particular, by filling the adiabatic space with pressurized gas, the external pressure applied to the skin that partitions this adiabatic space can be reduced.
It is designed to be supported by the internal pressure of the adiabatic space created by pressurized gas, and to reduce the applied external pressure.

[Examples] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In this example, the mechanical element was heated to 200°C to 8°C during an extremely short period of one cycle of several 1/100 seconds.
This will be explained by taking as an example the piston of a Dieville internal combustion engine, which is subject to a very rapid temperature change of 00°C.

As shown in FIGS. 2 and 4, on the surface 2 of the piston head, etc., which is the heat receiving side of the mechanical element 1, which undergoes repeated temperature changes from high to low temperatures over a short period of time, there is a A thin film-like skin 3 that covers the surface to form a heat-receiving surface, and a thin film-like skin 3 that hangs down from this to the surface 2 side on the back side of this skin 3 and sits on the surface 2 and supports the -C skin 3.
A heat insulating body 6 is provided which is integrally formed with a membrane-like structural member 5 that defines a heat insulating space 4 between the surface 2 of the mechanical cable 1 and the surface 2 of the mechanical cable 1. The heat insulating body 6 consisting of the skin 3 and the structural material 5 is made of a general heat insulating material such as a metal material or a ceramic material, and the heat insulating body 6 is made of a general heat insulating material such as a metal material or a ceramic material. It functions as a heat receiving part of the mechanical element 1 that covers the surface 2 and exhibits heat insulation properties that suppress the effects of thermal cycles.

More specifically, in the heat insulating body 6, the structural material 5 is composed of a thin film-like wall material 7 forming a honeycomb structure along the surface 2 of the mechanical element 1, and the skin 3 has a honeycomb structure. It is constituted by a collection of thin film-like arches 8 that are stretched between thin film-like wall materials 7 forming a structure, and each of these arches 8 is formed integrally with each wall material 7. The wall materials 7 are respectively erected on the surface 2 of the mechanical element 1, and their side edges are connected to each other to form a honeycomb shape, and each arch 8 has its peripheral edges connected to each other, and its connecting portion 9 is connected to the wall. It is connected to the L edge of the material 7. The heat insulating spaces 4 are partitioned by wall materials 7 on the sides and arches 8 on the top, and are arranged in a plurality of honeycomb shapes on the surface 2 of the machine element 1.

In particular, in this heat insulating space 4, as shown in FIG.
Pressurized gas is sealed to support external pressure. The pressurized gas is sealed in the heat insulating space 4 by a step of attaching the heat insulating body 6 formed in one piece to the surface 2 of the machine element 1 by brazing, gluing, etc. in a pressurized container. This is achieved by

Next, the features in terms of heat countermeasures in a configuration like the one above will be explained.

(2) The arch surface 8 (skin 3) and the wall material 7 (structural material 5) are formed into thin film shapes and have a low heat capacity. A heat insulating space 4 is formed by partitioning this low heat capacity structure. This makes it possible to configure a heat-receiving part whose temperature changes according to the heat cycle, and simply increases the heat capacity of the heat-receiving surface layer to prevent thermal effects on the mechanical element 1 regardless of the heat cycle. Compared to the structure, it is possible to exhibit an accurate and necessary and sufficient heat insulation effect. That is, the thermal cycle
3, when the temperature is high, heat is instantaneously received by the skin 3 etc. with low heat capacity, and while the entire body reaches high temperature, the heat insulating space 4 is closed to the mechanical element 1.
On the other hand, when the temperature is low, the received heat is instantly dissipated from the skin 3 etc. with low heat capacity, and the whole body moves to a low temperature, while providing the necessary insulation effect in the insulation space 4 for the mechanical element 1. demonstrate.

Taking as an example the case where the main heating element 6 is installed on the piston head or the vehicle surface of the combustion chamber of a diesel internal combustion engine, -)
As shown in Fig. 9, the temperature of these upper surfaces during a 1 J cycle of heat from the intake to exhaust stroke of the engine is as shown in Figure 9. On the other hand, during the period when the temperature inside the cylinder decreases from the expansion process due to combustion to the exhaust air and intake air, the heat insulator 6 efficiently releases heat and is lowered. As a result, as shown in Figs. 10 and 11, it is possible to lower the humidity on the walls of the combustion chamber, etc. during the intake stroke and increase the volumetric efficiency of the intake air, and also increase the wall surface temperature during the combustion stroke, thereby increasing the combustion efficiency. This makes it possible to improve fuel efficiency and solve the problems in the conventional example described above (indicated by C in the figure). In this way, the humidity of the heat-receiving surface such as the skin 3 is changed in accordance with the heat cycle to improve the environment inside the cylinder, while the heat-insulating space 4 exerts a heat-insulating effect on the piston as the mechanical element 1, thereby preventing adverse thermal effects. It is designed to prevent

■ Also, since the wall material 7 is formed in an ii shape, the fifth
As shown in the figure, it is possible to exert the effect of restricting the heat flow against the transfer (heat transfer) of the heat received by the skin 3 to the mechanical element 1, and from this aspect as well, the heat insulation properties can be improved. .

■Furthermore, by forming the wall material 7 thinner on the machine element 1 side than on the skin 3 side, the wall material 7 is thinner on the machine element 1 side than on the skin 3 side.
c further restricting the transfer of heat to the mechanical element 1 by the throttling effect,
The heat insulation effect can be further enhanced.

σ) Furthermore, since the radius of curvature of the arched surface 8 is increased and it is formed close to a flat surface, the heat receiving surface area can be reduced, and the volume can be suppressed to reduce the heat capacity.

■ The material has a thermal conductivity of 20 kcal/m, h
, 'C or less and has heat resistance of 850°C or more.

Next, the features of structural reinforcement for achieving the above-mentioned thinning will be explained.

■ Basically, this structure eliminates as much as possible the parts that receive tensile stress, creates a structure that receives compressive stress to the advantage of ensuring structural strength, and makes the film thinner)! We are making it possible for you to do so. As the material, a heat insulating material such as a ceramic material or a metal material with high compressive strength is used. The skin 3 is composed of a shell structure of an arched surface 8 that exhibits highly efficient strength. Particularly in the cylinder of an internal combustion engine, high internal cylinder pressure due to combustion acts on the wall surface, and the skin 3 that receives this pressure is formed by a collection of upwardly convex arched surfaces 8, and the individual nozzle surfaces 8
As shown in FIG. 5, the bifurcated wall material 7 is designed to be subjected to compressive stress, and the compressive stress is applied from above. Further, even when the arch surface 8 expands during thermal cycles, the expansion of the arch surface 8 is suppressed by the adjacent portions, so that compressive thermal stress is applied.

■ As the heat insulator 6 is made thinner and the skin 3 etc. are made thinner as described above, the skin 3 sinks downward due to external pressure such as the combustion pressure inside the cylinder, as shown by the broken line in Figure 6. It will become crowded and dented. The external pressure is 70 to 90 kg/cm2 for a typical non-supercharged direct injection diesel engine.
, 100-150'+9z"C1112 with supercharged engine
reach. Is this concave deformation caused by fluctuations in the cylinder internal pressure of the internal combustion engine (see G in Figure 8)? 7) If it is repeated in an extremely short period, it is not preferable from the viewpoint of ensuring structural strength and reliability of the structure.

Here, if the thickness of the epidermis 3 is increased to suppress Jtil#, the heat capacity will increase, and as shown in Figure 8,
As shown in Figure 1, the temperature of the epidermis 3 could not fully follow the thermal recycling, and the above-mentioned thermal improvement (indicated by C in the figure)
) will not be able to be achieved.

Therefore, in the present invention, in order to ensure structural soundness while forming the skin 3 etc. thin, pressurized gas that supports external pressure is sealed in the heat insulating space 4 as shown in FIG. ing. With this configuration, the external pressure can be considerably offset by the pressurized gas, and the apparent pressure acting on the skin 3's can be reduced, making it possible to ensure structural strength while achieving a thin film structure. can.

In addition, since the pressurized gas sealed in the heat insulating space 4 acts on the concave arch surface 11, it may be applied to the back side of the skin 3. Since it tends to generate a tensile stress of i T, it is preferable that the pressure of the pressurized gas is set to be lower than the working external pressure and not to exceed the tensile strength of the material of the heat insulator 6. For example, 10 to 50 kg/am2 is considered appropriate for the above-mentioned external pressure of 70 to 150 ko/cm2.

■ Structure Moon 5 as a whole constitutes a honeycomb-like isotropic shell structure, which is highly strong as a whole. Therefore, the wall material 7 and the arch surface 8 can be made into a membrane.

Furthermore, the connecting portions 9 between the arches 8 and the connecting portions 10 between the connecting portions 9 and the wall material 7 are rounded and smoothly formed to alleviate stress, as shown in Fig. 2. .

Then, as shown in FIG. 7, the heat insulator 6 thus obtained is attached to the piston head 20 of the piston 19 and the combustion chamber 21 by brazing, gluing, or the like.

By the way, the above-mentioned heat insulating body 6 is designed in consideration of the relationship between the thin film thickness for low heat capacity and the required strength. As a result of analyzing the iron-based materials such as stainless steel selected by the present inventor as the material with the minimum required strength, it has been concluded that it is preferable to design with the following specifications (see Figure 2).

Distance between centers of wall material 7 L: 0,03<L≦0.5 (mm) Maximum height of arch surface 8 1-4: (1,03<H≦ i, o (mm) Thickness of wall material 7 Thickness B: 0.002< B≦0.25 ←I) Thickness at the center of arch surface 8 t: 0,001<t≦0.35 (mm)
Radius of curvature R1 of the arch surface 8 on the heat receiving side: R1'a 2L (am) Radius of curvature R2 of the opposite surface of the arch surface 8 on the heat receiving side: R2≦R
1 Arch surface 8 and wall material 7 Connection part 10 Radius of curvature r”1:B
/2≦ r1≦L/2 (ml゛) 7-ch 8-phase n connection 9 radius of curvature r2: r1≦ r2
≦R2 (ml) Furthermore, according to the analysis by the present inventor, zirconium oxide (ZrO2) having the following specifications has a
It was possible to obtain the wall humidity amplitude (difference between the maximum temperature and the (y-low temperature) in degrees Celsius) and achieve a fuel efficiency improvement of 2.5 to 3%.

Furthermore, with silicon nitride (SitN4), a temperature amplitude of approximately 120° C. could be secured, and fuel efficiency could be improved by approximately 1%.

Note H = 1.0mm, L -1.2mm, B-
0.2mm, t = 0.25n+m,
Rt = 4mm, rt = 0.5mm
, r2-0.8mm A modified example is shown in FIG. 2, and as shown in the figure, the arch surface 8 may be formed so that the thickness increases gradually from the center toward the wall material 7 side. good. In this way, it is possible to further reduce the heat capacity of the heat receiving portion. Furthermore, the connecting portion 10 between the wall material 7 and the arch surface 8 has a thick wall, thereby increasing the structural strength.

Note that the honeycomb structure is not limited to a hexagonal shape, and may be square, pentagonal, hexagonal, or the like.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

A thin film-like skin that covers the surface of a mechanical element that is subject to temperature changes to form a heat-receiving surface, and a thin film-like skin that sits on the surface of the mechanical element to support the skin and define a heat-insulating space between them. Since the structure is formed integrally with the structural material of It is possible to secure the necessary and sufficient insulation effect for the mechanical elements in the insulation space surrounded by a thermal membrane with a high heat capacity.Also, by making the membrane thinner, it can ensure the throttling effect on the heat flow.
Heat insulation can be obtained by regulating heat transfer to mechanical elements through the skin and structural materials. Such a thin-film cross-channel can be constructed with high efficiency and structural strength, depending on the composition of the skin and structural materials.

In particular, the external pressure acting on the heat insulator can be reduced by filling the heat insulating space with pressurized gas that supports the external pressure.
By supplementing the necessary strength, it is possible to make the heat insulator thinner.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of the main part showing the pressure state in a preferred embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part showing the structure of a preferred embodiment of the present invention, and FIG. FIG. 4 is a partially cutaway perspective view showing the entire structure, FIG. 5 is a diagram illustrating the action of pressure and the flow of heat,
Figure 6 is an enlarged sectional view of the main part showing the state of the skin due to the action of pressure, Figure 7 is a side view showing the installation state of the piston l\ of a deep-pil type internal combustion engine as a mechanical element, and Figure 8 is a diesel type internal combustion engine. A graph showing the relationship between the internal combustion engine cycle, wall temperature, and cylinder pressure. Figure 9 is a graph showing the relationship between the cycle and wall temperature of a diesel internal combustion engine. Figure 10 is the gas temperature and volumetric efficiency at the end of the intake stroke. Tono r! A
Fig. 11 is a graph showing the relationship between various heat insulating structures and fuel efficiency, and Fig. 12 is a side sectional view, without showing the piston, of a Deville internal combustion engine to which a conventional heat insulating structure is applied. In the figure, 1 is a mechanical element, 2 is its surface, 3 is a skin, 4 is a heat insulating space, 5 is a structural material, 7 is a wall material, and 8 is an arch surface. Patent Applicant Itzu Jidosha Co., Ltd. Representative Patent Attorney Nobuo Kinutani Fig. 2 Fig. 3 Fig. 6 Fig. 7 Wen Zhanwei kc℃) 1st
Figure 1

Claims (5)

[Claims] (1) A thin film-like skin that covers the surface of a mechanical element that is subject to temperature changes to form a heat-receiving surface, and a thin film-like skin that sits on the surface of the mechanical element to support the skin and define a heat-insulating space between them. What is claimed is: 1. A heat insulating body, characterized in that the heat insulating body is integrally formed with a thin film-like structural material, and the heat insulating space is filled with pressurized gas that supports external pressure. (2) The heat insulator according to claim 1, wherein the thin film skin and the structural material are made of a heat insulating material with high compressive strength. (3) Claim 1 or 2, wherein the structural material is formed thinner on the machine element side than on the skin side in order to restrict the transfer of heat received by the skin to the mechanical element.
The heat insulator described in any of the paragraphs. (4) The structure according to any one of claims 1 to 3, wherein the structural material is a thin film wall material forming a honeycomb structure along the surface of the mechanical element. Thermal insulation. (5) The above-mentioned claim, wherein the skin is constituted by a collection of thin film-like arch surfaces that are stretched between the thin film-like wall materials forming a honeycomb structure, and is formed integrally with these wall materials. The heat insulator according to item 4.