JPS63103204A - Apparatus for connecting two objects of different thermal expansion coefficient - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for joining two bodies having different coefficients of thermal expansion in a manner that minimizes forcing due to thermally induced stresses, and to such a method. It relates to a method for defining fixed points in a device.

Prior Art Previously known devices for fixing two bodies with different coefficients of thermal expansion, in which it is desired to minimize the stresses generated by heat, are mostly based on radii that ensure a rigid connection. ℃ using a directionally flexible coupling member. EP-81
As described in the radioscope in document 0063063, in this case one connection point is held rigid, whereas the other fixed points are each adapted to allow variations in the radial direction. In this case, a radially flexible fastening member with the action of a leaf spring is used. In addition, the minutes of SP■E (vol. 250, pages 24 to 26 in 1980, and pages 3 to 38 in volume 450 in 1983) state that glass smelting with a relatively small coefficient of thermal expansion is disclosed to be fixed to a metal holding structure via a radially flexible member. Further DE-
A type of fastening by means of an elastic adhesive bond is known from C2-3119299. It is also generally known to use flange connections instead of adhesive connections.

However, all types of fastening known up to now have the disadvantage that forces are transmitted from the structure of the holder to the component due to displacement of the fastening points during temperature changes, or that the rigidity of the connection is very low. Even if the force is relatively small, unacceptable deformations can occur in the object to be fixed, which can eliminate or at least severely limit its use. Particularly when the object to be fixed is an optical component, such as a telescope mirror, which has extremely high demands on the surface shape, i.e. in the nanometer range.
Even a small force application causes a visible deformation of the surface, and such deformation significantly reduces the usability of the optical component.

In some cases, such as for example for space exploration, additionally high demands are made on stiffness and strength. However, known fastening methods cannot satisfactorily meet these demands.

Therefore, the object of the present invention is to connect two objects with different coefficients of thermal expansion, applying as little force as possible to the objects to be fixed, despite having sufficient rigidity. The purpose is to provide equipment.

Means for Solving the Problem In order to solve this problem, in the configuration of the present invention, the object to be fixed is indirectly fixed to the holder via a deformable intermediate body.

OPERATION AND EFFECT OF THE INVENTION The requirement for a thermal compensation system is to keep to a minimum the forcing forces due to different coefficients of thermal expansion at the joints. The invention is based on the recognition that deformable (for example hollow cylindrical) objects have points whose position does not change at all or only very slightly during the deformation. This results in the following: two objects with very different coefficients of thermal expansion (e.g. 11-16.10 61
/' steel or 20-24.10 6170 aluminum and 0.1.10 6 110 zero joules)
A material with a third coefficient of thermal expansion different from other materials (
For example, it has become possible to bond using an intermediate made of Imphal or chemical fiber reinforced plastic (2.8-2.4° 10-61/').

By fixing the deformable intermediate body to the component holder at point N, a forcing force is generated which deforms the intermediate body into a wave shape during thermal loading. The corrugated object intersects the original shape, for example a hollow cylinder, which is not subjected to heat load, at 2N points. In other words, N points are created in the intermediate body whose positions do not change with respect to each other.

It is therefore possible to match the expansion properties of the intermediate body and the component to each other. The type of fixation can be freely chosen independently of this (eg gluing in the case of a mirror), and likewise the intermediate body does not have to have a circular shape. In this case, the selection of the material of the intermediate body must be made in conjunction with the material of the component holder, so that a "zero position", ie, a location where no positional changes due to thermal influences occur, is achieved.

Fixation types are particularly problematic in optical components, such as telescope mirrors. This is because in this case even modest forcing causes an undesirable deformation of the optically active surface. In this very application, it is often desirable to hold the object to be fixed in the central hole or at its edges.

The device according to the invention can be used both for fixation in the central hole and for fixation on the outside. The universal usability for both fixed forms is aided by the particularly simple and compact structural form of the system. The number of axes in the intermediate body can be chosen freely, the number of fixing points available at the same time after fixing the deformable body in the holding body corresponding to the number of axes. However, if, on the contrary, we also want to transfer forces from one body to another by the influence of heat, this solution with an intermediate provides ideal conditions. This is because the transmitted force can freely choose its direction. The intermediate body does not have to be circular (although it can be optimally adapted to the particular task by giving it a special shape.

Among the advantages of the fixed form according to the invention are the following. In other words, the system according to the present invention is a simple and compact system in which the number of axes and thus the number of bonding points can be freely selected, and it is also extremely effective in terms of material fatigue at fixed points (for example, creeping at bonded points). Due to their long-term properties and the fact that the fixing points are free from forcing even under temperature loads, such systems are particularly suitable for fixing mirrors with low thermal expansion.

Before fixing the object to be held on its holder, fixing points for it must be defined in the intermediate body. This can be done by division or optical methods. In the calculations, primarily the geometry of the intermediate, material properties such as coefficient of thermal expansion, elasticity, homogeneity, etc., as well as the influence of position, have to be taken into account. Add to this the properties of the bond between the object and the intermediate as well as the properties of the material typical object, so that for the optimal angle ψ between the fixed points there are many (
factors are important.

However, the computational possibilities are limited in accuracy by complexity and material tolerances. The most accurate results are obtained, for example, by optical deformation measurements of mirrors. For this purpose, the position of the fixed point is first roughly determined by calculation. Using an interferometer, the object to be fixed is then measured at two different temperatures throughout the system. Measurements are taken at three points due to the offset of the fixed point, thereby drawing a parabola, with the optimal position of the fixed point being located near the parabola apex. Further optimization is carried out by measuring the assembly temperature and the object to be fixed at higher or lower temperatures. A prerequisite for carrying out this iterative process is a movement-adjustable and ready-dissociable bond between carrier and intermediate.

Example The invention will now be described in detail with reference to the drawings.

FIG. 1 shows the state of an intermediate body 1 fixed to a holder at four points 3 during cooling (FIG. 1a) and during heating (FIG. 1b). In the unheated state, the intermediate body 1 has a circular shape symbolized by the line laK. During cooling of the holding body which has a higher coefficient of thermal expansion than the intermediate body 1 and which fixes the intermediate body 1, the intermediate body 1 is subjected to a forcing force 5 at the fixing point 3, with the fixing point 3 being centered The region 2 between the two nodules moves toward point 6 (a-+ b), and is pushed outward compared to the state 1a where no heat load is applied. As a result of this, since the given interest of the intermediate is sufficient for the diameter produced by the forcing force 5, a displacement occurs, which gives rise to the deformed shape indicated by the reference numeral 1b. The intermediate body 1 reduces its diameter in the unforced state, but only to a very small extent. This is because the coefficient of thermal expansion of the intermediate body 1 is smaller than that of the carrier.

In this case, due to this diameter, excess material has to be pushed away, forming an antinode of the wave. The deformed intermediate body now has a waveform of wavelength λ-1 with the intermediate diameter d and the number of fixed points N, ie a stationary wave is formed in the intermediate body 1.

The intermediate body 1b transformed into a wave intersects the intermediate body in the original shape 1a at the 2N node. This means that there are at most 2XN possible fixing points in the intermediate body 1 for the object to be fixed, for example the mirror of an astronomical telescope, these fixing points being centrally located independently of the coefficient of thermal expansion of the carrier and the intermediate body. It has a constant distance from point 6. All other points in the intermediate body change their distances to the center point 6 to larger or smaller values on cooling. For an object which is fixed at a fixing point 3 on the intermediate body 1 to the intermediate body 1, it and the intermediate body l will no longer be added to the equivalent body at the fixing point during cooling or heating. In other words, the joint is not affected by force.

The situation during heating shown in FIG. 1b corresponds to the situation shown in FIG. 1a, except that in this case the forces and directions of movement have opposite symbols. The fixation point 3a, at which the intermediate body 1a is fixed to the holder, is pulled outwards (position 3c) by a thermal forcing force 8, and the area in the middle between the two nodules is pulled by the cuff to the center point 6. be moved towards. However, the movement of the fixing point between the two nodules (3a-+3C) results in another compensating shape of the intermediate ring IC being deformed as shown in FIG. 1a upon cooling.

Figures 2a and 2b detail other factors that must be considered for position definition.

In this case, unlike FIGS. 1a and 1b, there are only three fixing points 12 on which force 11 acts. That is, by deformation, the thermally optimal point 1 is fixed as a fixed point.
5 some degree of rotation occurs. Intermediate body 9 to be deformed
The six nodes 15 between b and the intermediate body 9a which are not subjected to heat load are respectively connected to the holding body and the intermediate body 9 when the deformation increases.
and move toward the next fixed point 12 between. Although this movement is certainly small, it can cause problems if ignored in objects where the fixed point must be angularly accurate.

By applying the force 11 of the holding body to the intermediate body 9, the intermediate body 9 reaches the deformed state 9b. Fixed point 12
is away from the circle center point 13 in this case. This transformation moves the optimal node from position 15a to position 15b. The distance between the fixed point 12a and the node 15a of the intermediate body 9 of the holding body before deformation, and the fixed point 12 after deformation
The distance between b and node 15b is of virtually equal length, node 15b, however, after deformation having a different distance 18 with respect to the previous fixed point 128. This movement in the original intermediate body 9a can be captured by the angle χ, which corresponds to a constant arc length 16 for the undeformed intermediate body 9a. The defined axial rotation 14 is therefore temperature dependent. Since this movement is carried out by each node 15 between the two fixing points 12, no forcing forces occur if suitable nodes 15 are used; however, the material of the holder and the intermediate body is If such an unfavorable choice is made, very large deformations will occur, and small rotations will have to be accepted.

On the other hand, if materials matched to each other are used for the holder and the intermediate body 9, a situation such as that shown in FIG. 2b results. In this case, the nodes 15 for the parts to be fixed on the intermediate body 9 remain at the same location. Intermediate 9 produced in intermediate 9a by forcing force 11
The deformation of b does not result in a rotational movement of the node 15 if the deformation is just such that the two possible nodes 15 between the two fixed points 12 coincide exactly with each other. . This can be achieved by selecting a suitable material for intermediate 9.

Knowing the given coefficient of thermal expansion and the geometry of the intermediate and the required grade of fixation point positional accuracy, it is possible to define the ideal fixation point computationally and/or optically. can. In this case, during deformation, the deformation in the circular plane is not the only concern, but also in the direction perpendicular to the intermediate plane, influenced by the stiffness of the intermediate material in relation to the geometry of the intermediate. It must be taken into consideration that this may also be a problem.

The resulting changes in the position of the possible fixation points 22 on the intermediate body 20 are shown in FIGS. 3a and 3b, as shown in FIGS. 3a and 3b. is a combination of movement in a circular plane (FIGS. 1a and 1b) and movement in a direction perpendicular to the circular plane. In this case, only the positions of the mutually associated fixing points on the intermediate body 20 remain constant. In principle, there are only at most two point combinations of N points 22 at a distance of 1 from each other, and the position of the N points in the intermediate body 20 is not influenced at any time by thermal changes. The range marked with 2 in FIG. 3b shows the calculated displacements of the fixation points (angular changes Δγ, χ) of different strengths for an intermediate body 20 with a completely defined given geometry. Indicates the area of The degree of movement in the intermediate body 20 depends on the position of the fixing point 21 and on the implementation.

FIG. 4 shows, as an example of use, that an object is attached to the frame 27 via the intermediate body 26 stretched using spacers 24 in order to create an intermediate chamber 29 for an unobstructed configuration of the deformation axis in the intermediate body 26. An external fixation type of fixation 28 is shown.

The fastening part 23 between the frame 27 and the intermediate body 26 is in this case configured as a recess. This fixing type guarantees that the deformation will take place by performing a certain amount of predeformation in a state where no heat load is applied. The connection 25 between the object 28 and the spacer 2 is designed in this embodiment as a bond.

FIG. 5 shows another type of fastening for the mirror 37 on the holder 36. The intermediate body 33 in this embodiment also has a cover 35 for fixing a mirror 37 to a fixing point 34 of the intermediate body 33. This cover 35 in the intermediate body 33 is necessary in order to create an intermediate chamber 32 for establishing the deformation between the intermediate body 33 and the mirror 37. Fixed point 3 at the intersection of intermediate body 33 and line 31
After selecting the number of zeros and the intermediate material, the angle ψ between the fixing points 3o and 34 is determined based on the material properties of the components used. Since the force of the holding body 36 for fixing the intermediate body 33 is transmitted to the intermediate body 33, correspondingly loadable connections must be used for the fixing. The forces acting at the fixation point 34 of the mirror 37 remain extremely constant, so that ideal conditions for all types of fixation (for example adhesive bonding) are obtained in this case.

FIGS. 6a and 6b show a type of fastening in which the mirror 38 of an astronomical telescope is fastened to a holder 40 by means of an intermediate body 39, in which case the inner bore of the arm is not used for the fastening. Since the intermediate body 39 is fixed at point 43 via the screw 41 to the holding body ○, the mirror 38 can be A knot of the shaft is created at point 42, which is an ideal fixation point for. The fixing points +3 of the intermediate body 39 are each located offset by an angle α. The angle ψ between the fixing point (junction between holder and intermediate body) 43 and the fixing point (junction between intermediate body and component) 42 is created by the necessary temperature compensation. Taking into account possible deformations of the intermediate body 39 in the axial direction of the mirror 38, a cover 56 may be provided between the mirror 38 and the intermediate body 39.

7a and 7b show an optimal fixing point 55 of the intermediate body 53 on the holding body 49, with the aim of avoiding thermally induced forcing forces at the fixing point 47 of the mirror 46 on the intermediate body 53. A method of optical position definition is shown.

For this purpose, it is first determined by calculation how many fixing points 47 (here three) are required for the selected fixing type (here adhesive).

The intermediate body 53 used allows a movable fixation in a certain range 44, for example by milling slots 52, which, in the illustrated three-point fixation, are located at fixation points 55.
Allows stepless movement within an angular range of β at each time. This angular range of ±β originates from the uncertainty of the calculation method for defining the position of the fixed point 55.

After the intermediate body 53 has been firmly glued to the mirror 46 and possibly to the pre-assembled holder (central body 49), the holder 4
9, the mirror 46 is measured at assembly temperature and at elevated or depressed temperature. This can be done optically, for example using an interferometer. After evaluation of the observed deformations, the fixing points 55 of the holding body 49 on the intermediate body 53 are moved.

The adjustment is now optimized in an iterative manner, resulting in an optimal angle ψ between the fixed points 55 and 47.
can be adjusted. Tightening with screws 51 and nuts 54 ensures movable fixation. The space for creating the deformation 45 must be guaranteed depending on the specific use case. In the illustrated embodiment, this means that the holder 4
9 and the intermediate body 53 and a spacer 48 between the intermediate body 53 and the mirror 46.

[Brief explanation of the drawing]

FIG. 1a is a diagram schematically showing the deformation of an intermediate fixed at a point of discontinuity upon heating, and FIG. 1b is a diagram schematically showing the deformation in the cooling diagram of the intermediate shown in FIG. 1a. , FIGS. 2a and 2b are schematic diagrams for explaining optimization of material selection for the intermediate, FIG. 3a is a perspective view showing changes in position of fixing points on the outer peripheral surface of the intermediate due to temperature, and FIG. Figure 3b is a partially enlarged view showing the positional change due to temperature of the fixing point shown in Figure 3a, Figure 4 is a sectional view showing the external fixation type of the optical member, and Figure 5 is a partial enlarged view showing the position change due to temperature of the fixing point shown in Figure 3a. Fig. 6a is a sectional view showing the fixing form of the mirror with a central hole, and Fig. 6b is a cross-sectional view of the mirror shown in Fig. 6a. Rear view, No. 7
FIG. 7a shows an adjustment device for optimizing the fixation point under optical monitoring, and FIG. 7b shows an enlarged view of a part of the adjustment device shown in FIG. 7a. 1.9, 20.26.33, 39.53... intermediate,
3, 12, 21.23, 30.43.55...fixed point, cow, 15,22,24,34.42.47...fixed point,
27.36.40.49... Holder, 28.37.3
8.46...Object to be fixed (mirror) Fig, 3a

Claims (1)

[Claims] 1. A device for joining two objects having different coefficients of thermal expansion in order to minimize the forcing force based on stress caused by heat, wherein the object to be fixed (28, 37, 38,
46) is deformable intermediate (1, 9, 20, 26, 33
, 39, 53) indirectly through the holder (27, 36,
40, 49) A device for joining two objects having different coefficients of thermal expansion. 2. The device according to claim 1, wherein the deformable intermediate body has a coefficient of thermal expansion between the coefficient of thermal expansion of the holding body and the coefficient of thermal expansion of the object to be fixed. 3. Fixed points (4, 15, 22, 24, 34, 42, 47
) is the fixed point (3, 1
2, 21, 23, 30, 43, 55). 4. Objects to be fixed (28, 37, 46) and intermediate body (2
6, 33, 53) and the holder (27, 36, 49) are arranged coaxially with respect to each other. 5. Device according to claim 1, characterized in that the object (38) to be fixed, the intermediate body (39) and the holding body (40) are arranged one after the other. 6. The device according to claim 1, wherein the intermediate body (20, 26, 33, 39, 53) is circular. 7. The device according to any one of claims 1 to 4, wherein the object to be fixed is an optical member such as a mirror (28, 37, 38, 46). 8. A method for defining a fixed point in a device for joining two objects having different coefficients of thermal expansion to minimize a forcing force based on stress caused by heat, the method comprising:
A fixed point (55) in the intermediate (59) that binds the
) is optically defined. 9. The method according to claim 8, wherein the position of the fixed point (47) is optimized using an interferometer.