JPH09263300A - High temperature structural body tightening structure for space shuttle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a fastener from being stuck and loosened because of high temperature and permit recycling by fitting the first and second protrusion parts respectively at both ends of a shaft part, and inserting a heat-resisting alloy collar between the first protrusion part of a shaft inserted into a hole at a high temperature structure body formed out of short fiber reinforced ceramic complex material and the high temperature structure body. SOLUTION: A shaft 1 formed out of a short fiber reinforced ceramic complex material is provided with a comical head part 4, a shaft part 3, and a protrusion part 3 at the top of it. The whole surface of the shaft 1 is coated with silicon carbide or aluminum oxide to prevent it from being stuck because of high temperature. At a high temperature structure body 5 where the shaft 1 is inserted, a tapered hole 7 and a hole 8 brought into contact with the head part 4 are formed, whose sectional shapes have a little large width which is a similar figure to the cross section of the first protrusion part 3. The high temperature structure bodies 5, 6 are made of carbon fiber reinforced complex material, and a C collar 9 of niobium alloy which is coated with aluminum diffusion is bedded between the high temperature structure body 6 and the first protrusion part 3. Therefore, by selecting the total length of the C collar 9 and the high temperature structure bodies 5, 6 with thermal expansion coefficient considered, it is possible to attain high tightening force.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fastening structure for a high temperature structure of a space shuttle and its fastener.

[0002]

2. Description of the Related Art Space shuttles that reciprocate between space and the earth are
When entering the atmosphere, the surface of the fuselage is exposed to high temperatures of several thousand and several hundred degrees due to friction with air. In order for the space shuttle to safely return to the ground even at this high temperature, many ceramic composites and carbon fiber reinforced carbon composites with excellent heat resistance are used for the aircraft, and heat resistance is used for fastening these high temperature structures. Bolts and nuts made of highly resistant Fe-based special steel MA956 are used.

In addition, Japanese Patent Laid-Open No. 7-10094 discloses a fastener that does not loosen the high temperature structure of a space shuttle.
As shown in Fig. 5, a heat insulating material is sandwiched between the main structural material of the airframe and the heat resistant panel, and the main structural material and the heat resistant cover are connected at both ends with a metal rod having a thread cut at one end on the heat resistant cover side. Mounting structure that reduces the effect of thermal expansion of the metal rod on the heat-resistant cover tightening by placing two plate-shaped metal nuts facing each other for a short distance and tightening the heat-resistant cover and heat-resistant washer together between the plate metal nuts. Is disclosed.

[0004]

Fe-based special steel MA95
Even with special heat-resistant steels such as No. 6 and the like, when the temperature exceeds 1200 ° C, the breaking strength sharply decreases. Therefore, when a fastener made of a heat-resistant metal material is used at a temperature of 1200 ° C. or higher, a fastener having a large shaft diameter must be used to secure the tightening force, but as a result, the body weight increases. In addition, in the case of a combination of heat resistant steel bolts and nuts and carbon fiber reinforced carbon composite material structure, under the high temperature of a thousand and several hundred degrees when entering the atmosphere, in addition to melting and oxidation of the screw, heat resistant steel and carbon fiber reinforced Seizure occurs due to the diffusion reaction at the part where the carbon material is in contact, and the fastener cannot be reused. As a countermeasure against seizure, a ceramic screw with high heat resistance can be considered, but since ceramic has low toughness, the screw part will be damaged by tightening.

The method disclosed in Japanese Patent Laid-Open No. 7-10094 also uses a metal rod and nut, and therefore, when exposed to a high temperature, seizure, melting, or oxidation of the screw portion is likely to occur. Even if it is not seized, the variation in the properties of the screw surface becomes large due to oxidation, and if the tightening force cannot be guaranteed, there is a high possibility that it cannot be reused.

Once the fastener is seized, the fastener or structure must be destroyed when removing the hot structure during inspection work. Also, the replacement of a large number of fasteners made from special heat-resistant materials with each flight is another issue that must be improved in terms of cost when considering commercial use of space vehicles. Therefore, an object of the present invention is to provide a fastening structure for a high temperature structure of a space shuttle that can be reused without burning, melting, or oxidizing, and does not sag, and a fastener used therefor.

[0007]

In order to achieve this object, the invention described in claim 1 is a fastening structure of a high temperature structure of a space shuttle, which is provided with a shaft portion and one end of the shaft portion. A short fiber reinforced ceramic composite including a first protrusion that is orthogonal to the axis of the shaft that is formed and a second protrusion that is larger than the first protrusion and that is extended to the other end of the shaft. A shaft made of material, a hole provided in the high temperature structure with a size for inserting a portion other than the second locking portion of the shaft, a first protrusion of the shaft inserted in the hole, and And a collar made of heat-resistant alloy steel that is inserted between the body and the machine body.

Regarding the coefficient of thermal expansion of each component in this fastening structure, the collar made of heat-resistant alloy has the largest, the axis made of short fiber reinforced ceramic composite material has the second largest, and the high temperature structural material is carbon fiber reinforced carbon. When a composite material is used, its coefficient of thermal expansion is the smallest. In this case, by selecting the length of the collar so that the thermal expansion length of the tightened portion consisting of the high temperature structure and the collar exceeds the thermal expansion length of the shaft,
There is an effect that the fastening force of the fastener increases and becomes stable as the temperature rises. Moreover, since the screw portion is abolished, there is no fear of seizure or oxidation of the screw.

According to a second aspect of the present invention, in the first aspect, the shaft portion has a circular cross section, and the first locking portion has a flat cross section.

According to a third aspect of the invention, the shaft portion of the second aspect has a flat cross section smaller than the first protrusion portion from the first protrusion portion toward the second protrusion portion. The first portion of the protrusion, the second portion having a circular cross section with a diameter equal to or smaller than the width of the first portion and longer than the hole provided in the high temperature structure, and the same shape as the first protrusion portion. Is a third section having a cross section with a different direction and a length shorter than the hole.
And a portion.

When a high temperature structure is fastened using a shaft having this shaft portion, the shaft is rotated when the shaft is passed to the second portion of the shaft portion, and the shape of the third portion and the hole is formed. And then pass the shaft through the hole. After passing through the shaft, the collar is inserted between the high temperature structure and the first protrusion. If the C color is used as the collar, the diameter of the internal space is made equal to the length of the first portion of the shaft portion in the protruding direction, and the inserted C color is rotated, the C color can be positioned and prevented from coming off.

According to a fifth aspect of the present invention, the head and the shaft of the bolt made of a heat-resistant alloy are covered with a short fiber reinforced ceramic composite material, and the short fiber reinforced at the end opposite to the threaded portion of the bolt. -Type ceramics composite material having a projection, a hole provided in a high temperature structure of a space shuttle having a size other than the above-mentioned projection of the shaft, and a high temperature for the shaft passed through the hole. A first collar made of a short fiber reinforced ceramic composite that is inserted adjacent to the structure, and made of a heat-resistant alloy that is placed in phosphorus contact with the first collar and has a coefficient of thermal expansion higher than that of the bolt that is inserted into the shaft. It is characterized by having a second collar and a nut made of a heat-resistant alloy screwed into the screw of the bolt. In the above-mentioned constituent parts, the length of the shaft and the length of the second collar are appropriately set in consideration of their coefficients of thermal expansion and lengths, so that the thermal expansion length of the second collar is more Can be long. Thus, in this fastening structure, the thermal expansion length is determined by the high temperature structure, the first collar, and the second collar.
The sum of the collars is larger than the axis and the fastening force increases with increasing temperature. In addition, the high temperature anti-sticking process is applied to the shaft and nut to strengthen the anti-sticking.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description, an outline of the aluminum diffusion film treatment used in the present invention will be described. This method is disclosed by the applicant in Japanese Patent Application Laid-Open No. 5-125519, and a niobium alloy is added to a mixed powder of aluminum powder as a coating agent, yttrium halide powder as an activator, and aluminum oxide powder as a sintering inhibitor. Embedded, 900-1200 ° C in inert gas at atmospheric pressure
And heating for 3 to 15 hours. Then, a niobium-aluminum intermetallic compound containing yttrium is formed on the surface of the niobium alloy. When exposed to high temperature in the atmosphere in this state, an aluminum oxide layer is formed on the surface of the niobium alloy, but at the same time, a double oxide or yttrium oxide of aluminum and yttrium is formed at the interface between the aluminum oxide layer and the niobium alloy. Is generated. By these, the aluminum oxide layer is brought into close contact with the surface of the niobium alloy and becomes stable. Although niobium alloy has a high melting point of about 2500 ° C. and excellent heat resistance, it has been limited to use in a vacuum or an inert gas because of its fast rate of progress of oxidation at high temperatures. However, the aluminum diffusion coating method described above has made it possible to use even in a high temperature atmosphere.

An embodiment of the present invention will be described with reference to the drawings. 1A and 1B show the tightening of the embodiment according to claim 1, FIG. 1A is a sectional view of the tightening, and FIG. 1B is a view of FIG. It is a thing. Shaft 1 is made of short fiber reinforced ceramic composite and has a conical head 4
The head portion 4 is provided with a shaft portion 2 extending from the middle of the cone in a circular cross-section by a predetermined length, and a protrusion portion 3 connected to the tip of the shaft portion 2 in a direction orthogonal to the shaft portion 2. The width of the protrusion 3 in the direction orthogonal to the axis of the protrusion is smaller than the diameter of the shaft 2, and the surface 3a facing the head 4 is perpendicular to the shaft 2. The bottom surface of the cone of the head portion 4 is larger than that of the locking portion 3. This axis 1
The entire surface of silicon carbide (SiC)
Alternatively, aluminum oxide (Al2 O3) is subjected to a film treatment by a chemical vapor deposition method.

The high temperature structure 5 to which the shaft 1 is passed and fastened is provided with a conical hole 7 with which the conical surface of the head portion 4 abuts, and a hole 8 having a uniform cross section continuous with the conical hole 7. The hole 8 communicates with the high temperature structure 6, and its cross-sectional shape is similar to the cross section of the first protrusion 3 and has a width slightly larger than that of the first protrusion 3 and the shaft 2. The high temperature structures 5 and 6 are made of a carbon fiber reinforced composite material, and a space between the high temperature structure 6 and the first protrusion 3 of the shaft 1 is made of a niobium alloy that has been treated with an aluminum diffusion coating. C color 9 is fitted.

The shaft 1 is inserted into the holes 7 and 8 from the first protrusion 3. At the time of insertion, the shape of the first protrusion 3 and the shape of the hole 7 or the hole 8 are made to match, and the conical surface 4a of the head 4 is passed until it contacts the conical surface 7a of the conical hole 7. Then, a C collar 9 having a predetermined length is sandwiched in a gap formed between the high temperature structure 6 and the protrusion 3 so as to avoid a concave portion due to the hole 8. The C collar 9 may be sandwiched by cold fitting using liquid nitrogen or the like.

Next, the reason why the fastener of the present invention does not sag, and is not damaged or stuck at a high temperature generated by friction with the atmosphere when the space shuttle enters the atmosphere will be described.

The temperature of the high-temperature structure 5 and the high-temperature structure 5 near the surface, the fastener shaft 2, the high-temperature structure 6, and the C collar 9 which are heated to a few thousand degrees C. by aerodynamic friction with the atmosphere are also lower than the surface of the machine. However, it becomes a high temperature of one thousand and several hundred degrees C. The value of the coefficient of thermal expansion increases in the order of the metal material, the ceramic fiber reinforced composite material, and the carbon fiber reinforced carbon composite material. When applied to the components of the present invention, the C color 9, the shaft 1 and the high temperature structure 5 are shown. The total is 6 and the order is larger. If the total length of the C collar 9 and the high temperature structures 5 and 6 is appropriately selected in consideration of the coefficient of thermal expansion, an elongation larger than the elongation of the shaft 1 can be obtained at high temperature, so that the higher the tightening is, the higher the tightening becomes. It is possible to obtain urging force.

The short fiber reinforced ceramic composite material treated with silicon carbide or aluminum oxide has improved heat resistance of the short fiber reinforced ceramic composite material while improving its oxidation resistance. It has been confirmed that it does not melt even at the temperature of, and that neither diffusion reaction nor oxidation occurs. Accordingly, the shaft 1 made of the silicon carbide or aluminum oxide film-treated short fiber reinforced ceramic composite material is
Even at a high temperature of 00 ° C, there is no melting loss due to heat, and neither diffusion reaction nor oxidation occurs. Further, a niobium alloy treated with an aluminum diffusion coating is used for the C color 9, and the diffusion reaction, the melting and the oxidation with the high temperature structure 6 made of the carbon fiber reinforced carbon composite material do not occur even at a high temperature of 1300 ° C. It has been confirmed.

FIG. 2 shows a shaft portion 2b of the shaft 1 of FIG. 1 in which the shaft portion 2 is connected to the head 4 and has a length which does not project to the inside of the machine body and which has the same sectional shape as the locking portion 3. Is provided so that the displacement of the shaft 1 due to the rotation of the shaft 1 does not occur.

FIG. 3 shows the shaft portion 2 excluding the shaft portion 2b in FIG.
Is a first portion 12 having a protrusion that overlaps the first protrusion 3 at the end connected to the first protrusion 3, and a circular cross section longer than the thickness of the high temperature structures 5 and 6 at the portion connected to the first portion 12. And the second portion 13 of. The height of the protrusion of the first portion 12 of the shaft portion 2 is smaller than that of the protrusion portion 3, and the illustrated width is equal to the width of the first protrusion portion 3. The diameter of the circular cross section of the second portion 13 is made equal to the width of the first protrusion 3 in the figure. If the inner diameter of the C collar 9 is made equal to the length of the first portion 12 in the height direction of the protrusion, the slit of the C collar 9 is rotated in the width direction of the shaft portion 12 as shown in FIG. The collar 9 can be positioned and prevented from coming off.

FIG. 4 shows an embodiment according to a fifth aspect of the present invention, in which the surface of the niobium alloy bolt 15 having a thin shaft portion 16 is treated with an aluminum diffusion coating, and the shaft portion 16 and the head portion 17 are made of silicon carbide or aluminum oxide. The shaft 14 of the fastener is formed by covering the above with a short fiber-reinforced ceramic composite material subjected to a film treatment. Axis 1
The head portion 18 of No. 4 has a conical shape that tapers toward the shaft portion 19. The high temperature structure 22 includes a head portion 18 of the shaft 14.
A conical hole 24 conforming to the conical shape is provided, and a hole 25 through which the screw portion 20 and the shaft portion 19 of the shaft 14 can be inserted is provided so as to communicate therewith, and the hole 25 communicates with the high temperature structure 23.
The shaft 14 is passed through the hole 25 from the screw portion 20, and the first collar 2
1a and the second collar 21b are inserted into the shaft 14 and fastened with a nut 26 made of a niobium alloy which has been treated with an aluminum diffusion coating. The first collar 21a is made of a short fiber reinforced ceramics composite material or the like and its thickness is not specified, but its surface is coated with silicon carbide or aluminum oxide to improve oxidation resistance, and the second collar 21b is a bolt. A metal with a higher coefficient of thermal expansion than the niobium alloy that is the material of
For example, if it is made of Fe-based special alloy MA956,
The length of the collar 1b is set to be about half or more of the shaft 14.
In order to manufacture the shaft 14, first, a shaft member 19 made of a short fiber reinforced ceramics composite material that covers the head portion 17 and the shaft portion 16 of the bolt 15 is divided into two parts at the center cross section of the shaft, and a ceramic is formed into a predetermined mold. Powder and short-fiber silicon carbide are mixed and put together, then baked and solidified, two metal bolts are sandwiched between them, and the shaft member 1 is made of a ceramic adhesive having approximately the same coefficient of thermal expansion.
Glue 9.

The fastening structure becomes hot due to the heat generated by the friction between the air and the airframe, and the thermal expansion length of the high temperature structures 22, 23, the first collar 21a and the second collar 21b is the thermal expansion length of the shaft 14. Since it is longer than the length, the fastening force increases as the temperature rises, and slack does not occur. Further, since the shaft 14 and the nut 23 are made of a niobium alloy whose surface is treated with an aluminum diffusion coating, they do not melt or oxidize and are prevented from sticking. In addition, between the heat-resistant alloy second collar 21b and the high temperature structure 23, the second collar 21 made of a short fiber reinforced ceramic composite material is provided.
Since there is a, sticking due to the diffusion reaction does not occur.

[0024]

As described above, in the fastening structure of the high temperature structure of the space shuttle, the shaft is made of the short fiber reinforced ceramics composite material, and the locking portion and the main body of the body protruding at the end of the shaft. By inserting a color made of heat resistant alloy between and,
It is possible to prevent the fastener from sticking and loosening due to high heat when entering the atmosphere, facilitating removal of the high-temperature structure and enabling reuse of the fastener. Also, a shaft made by covering the head portion and the shaft portion of a heat-resistant alloy bolt with a thinned shaft portion with a short fiber reinforced ceramic composite material, a high temperature structure and a collar made of the short fiber reinforced ceramic composite material, and the bolt. By inserting a heat-resistant alloy collar with a larger coefficient of thermal expansion and tightening it with a heat-resistant alloy nut, the fastening structure is prevented from sticking and slackening when exposed to high temperatures, facilitating removal of the high-temperature structure, and fasteners. Can be reused. The fastener of the present invention is not limited to the space shuttle, but can be applied to fastening members in other high temperature places.

[Brief description of drawings]

FIG. 1 is a view showing a first embodiment of a fastening structure for a high temperature structure according to the present invention, (a) is a sectional view of the attachment, and (b) is a view of (a) viewed from the A side. .

FIG. 2 is an embodiment of the shaft of the fastener of the present invention, (a) is a side view of the shaft, (b) is (a) B-
It is a figure seen from B.

FIG. 3A is a sectional view of a mounting structure according to a second embodiment of the present invention, and FIG. 3B is a perspective view of a shaft of a fastener.

FIG. 4 is a sectional view of another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing an example of a conventional fastening structure, in which (a) is an overall view and (b) is an enlarged view of a portion indicated by C in (a).

[Explanation of symbols]

 2 Shaft part 3 Protrusion part 4 Head part 5 High temperature structure 6 High temperature structure 9 C collar 15 Bolt 20 Screw part 21a 1st collar 21b 2nd collar 26 Nut

Claims (7)

[Claims] 1. In a fastening structure for a high temperature structure of a space shuttle, a shaft portion, a first protrusion extending at one end of the shaft portion and orthogonal to the shaft portion, and extending at the other end of the shaft portion. A shaft made of a short fiber reinforced ceramic composite material, which is provided with a second protrusion having a larger cross section than the first protrusion provided, and the second protrusion larger than the shaft and the first protrusion. A hole provided in the high-temperature structure with a cross-sectional shape smaller than that of the portion, and a collar made of a heat-resistant alloy inserted between the first protrusion of the shaft inserted into the hole and the high-temperature structure. And a fastening structure for a high temperature structure of a space vehicle. 2. The fastening structure for a high temperature structure of a space shuttle according to claim 1, wherein the shaft portion has a circular cross section and the first protrusion has a flat cross section. 3. A first portion, wherein the shaft portion has a protrusion smaller than the first protrusion portion from the first protrusion portion toward the second protrusion portion, and a width of the first portion. A second portion longer than the hole provided in the structure with a circular cross-section equal to or smaller than, and a cross-section having the same shape as the first protrusion and a different inclination from the first protrusion, 3. The fastening structure for a high temperature structure of a space shuttle according to claim 2, further comprising a third portion having a short length. 4. The fastening structure for a high temperature structure of a space shuttle according to claim 1, wherein the color heat-resistant alloy is a niobium alloy treated with an aluminum diffusion film. 5. In a fastening structure for a high temperature structure of a space shuttle, a bolt made of a heat-resistant alloy, a head and a shaft portion of the bolt are covered, and a projection thicker than the screw portion is provided at an end on the head side of the bolt. A shaft provided with a shaft member of a short fiber reinforced ceramic composite material forming a portion, a hole provided in the high temperature structure having a size other than the projection of the shaft, and the hole inserted into the hole. A first collar made of a short fiber reinforced ceramics composite material inserted into a shaft adjacent to the high temperature structure, a second collar inserted into the shaft adjacent to the first collar, and a screw of the bolt A structure for fastening a high-temperature structure of a space shuttle, comprising: a nut made of a heat-resistant alloy that is screwed into the portion. 6. The bolt and nut are made of a niobium alloy treated with an aluminum diffusion coating, and the second collar is F.
The fastening structure for a high temperature structure of a space shuttle according to claim 5, which is made of an e-based special steel. 7. A fastener for fastening a high temperature structure of a space shuttle, wherein a bolt made of a niobium alloy treated with an aluminum diffusion coating and a shaft end and a head of the bolt are covered, and a head side end of the bolt. And a shaft member of a short fiber reinforced ceramic composite material having a protrusion thicker than the screw portion, and a fastener for fastening a high temperature structure of a space shuttle. [0001]