A method for assembling a high lightweight mirror supported by a central shaft

Abstract

The application belongs to the field of mirror assembly, and particularly relates to a center shaft supporting high-lightweight mirror assembly method. The method comprises the following steps: step 1, marking a phase; step 2, initially assembling the center shaft into the inner hole of the primary mirror; step 3, selecting one phase of the center shaft and one phase of the primary mirror seat for paired assembly, then rotating the primary mirror, and selecting one phase of the primary mirror for paired assembly; step 4, turning over the primary mirror, and sequentially installing relevant components to the reflecting surface of the primary mirror; step 5, installing the primary mirror components to the rotary detection frame, building a detection light path, and detecting the surface shape of the primary mirror; step 6, if the surface shape meets the requirements, step 7 is executed, otherwise, the primary mirror pressing ring is loosened, the primary mirror is rotated, the next phase is selected for paired assembly, and step 5 is returned; step 7, installing the primary mirror pressing plate, and completing the assembly of the mirror. The application can reduce the influence of the primary mirror pressing ring on the surface shape in the mirror assembly, and solve the influence of the ground assembly gravity on the detection result.

Description

TECHNICAL FIELD

[0001] The application relates to an assembling method, in particular to an assembling method of a center shaft supporting a high-lightweight reflector. BACKGROUND

[0002] As a key component of a large-aperture optical system, a reflector plays a decisive role in the imaging quality of the system. With the development of space remote sensing technology, space optical systems gradually develop in the direction of long focal length and large aperture. However, with the continuous increase of the aperture of an optical remote sensor, the weight of the reflector increases, and the self-weight and thermal deformation have an impact on the surface shape precision of the reflector mirror. In order to solve these problems, new materials are usually applied or the support structure is improved, and the reflector with a lightweight structure is the most practical and effective method. However, in a certain sense, the lightweight is at the cost of sacrificing the absolute rigidity of the reflector. For a certain support structure form, when the lightweight reaches a certain degree, the reflector is very sensitive to assembly stress, and the deformation problem of the reflector caused thereby is particularly prominent. At this time, how to realize the micro stress assembly of the reflector becomes a decisive factor for the success or failure of the system assembly.

[0003] As shown in Figure 1 and Figure 2 , the existing reflector generally comprises a main mirror 1, a center shaft 2, a main mirror seat 3, a main mirror pressing plate 4, the center shaft 2 is installed in the center hole of the main mirror 1, and a main mirror rubber pad 7, a main mirror steel pad 6 and a main mirror pressing ring 5 are arranged at the shaft hole matching position of the center shaft 2 and the main mirror 1, and the main mirror pressing plate 4 is arranged at the connecting position of the reflecting surface of the main mirror seat 3 and the main mirror 1; wherein the center shaft 2 and the center hole of the main mirror 1 are matched with a small gap, and the center shaft 2 bears the whole weight of the main mirror 1. Since the center shaft 2 has a simple support structure, it is mostly used for main mirrors with an aperture < 600 mm.

[0004] For the main mirror supported by the center shaft, when the lightweight rate of the main mirror reaches 60%, the following problems will be caused due to insufficient rigidity:

[0005] 1. Since the center shaft and the center hole of the main mirror do not match in shape and position tolerance, astigmatism is generated when the main mirror pressing ring is pressed; 2. The adhesive stress generated in the curing process of the adhesive will cause the surface shape of the main mirror to be poor; 3. It is difficult to ensure that the main mirror assembled in the gravity environment has good surface shape in the space state. SUMMARY

[0006] The purpose of the present application is to solve the technical problems that the existing center shaft supported main mirror, when its lightweight rate reaches 60%, due to insufficient rigidity, the center shaft and the center hole of the main mirror do not match in shape and position tolerance, which causes astigmatism when the main mirror pressing ring is pressed and it is difficult to ensure that the main mirror assembled in the gravity environment has good surface shape in the space state, and to provide a center shaft supporting high-lightweight reflector assembling method.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0008] A center shaft supports high lightweight mirror assembly method, which is characterized by comprising the following steps:

[0009] Step 1, mark a plurality of phases for assembly on the outer circumferential surface of the center shaft, the back surface of the primary mirror and the back surface of the primary mirror seat respectively;

[0010] Step 2, place the primary mirror with the reflecting surface downward on the support disc, and then preliminarily assemble the center shaft into the inner hole of the primary mirror;

[0011] Step 3, select one phase of the center shaft and one corresponding phase of the primary mirror seat as the initial phase for paired assembly, and then rotate the primary mirror and select one corresponding phase of the primary mirror as the initial phase for paired assembly;

[0012] Step 4, turn over the primary mirror to make the reflecting surface face upward, and then sequentially install the primary mirror rubber pad, the primary mirror steel pad and the primary mirror compression ring to the reflecting surface of the primary mirror, and pre-tighten the primary mirror compression ring to complete the assembly of the primary mirror component;

[0013] Step 5, install the primary mirror component on the rotary detection frame, build a detection light path, detect the surface shape of the primary mirror at the initial phase, if the surface shape meets the preset requirement, then sequentially detect the surface shapes of the remaining phases, if the surface shapes of the remaining phases cannot all meet the preset requirement, adjust the rotation degree of the primary mirror compression ring at the phase with the worst surface shape to make the surface shape of the phase meet the preset requirement, and then detect the surface shapes of the remaining phases again, if all the surface shapes meet the preset requirement, the matching phase is the best shaft hole matching phase, then execute step 7, if all the surface shapes cannot meet the preset requirement, then execute step 5;

[0014] Step 6, loosen the primary mirror compression ring, rotate the primary mirror, select the next phase for paired assembly, pre-tighten the primary mirror compression ring, and return to step 5;

[0015] Step 7, install the primary mirror compression plate to complete the assembly of the reflecting mirror.

[0016] Further, step 7 is specifically as follows:

[0017] Step 7.1, inject glue into the glue injection hole of the center shaft, determine the rotation frequency and time of the center shaft rotation curing according to the characteristics of the glue, and detect the surface shape accuracy of the center shaft after the glue is dry to ensure that the technical index requirement is met;

[0018] Step 7.2, inject glue into the glue injection hole of the primary mirror seat, and check the surface shape accuracy of the primary mirror seat after the glue is dry to ensure that the micro-stress assembly requirement is met;

[0019] Step 7.3, install the primary mirror compression plate, and inject glue into the glue injection hole of the primary mirror compression plate;

[0020] Step 7.4, apply anti-loosening glue to the primary mirror pressing ring, and complete the assembly of the mirror.

[0021] Further, step 7.3 is specifically:

[0022] Install the primary mirror pressing plate, and pad two layers of polyamide films at the contact position of the primary mirror pressing plate and the primary mirror, inject glue into the glue injection hole of the primary mirror pressing plate, and after the glue layer is cured, remove one layer of polyamide film to ensure that the glue layer does not contact the primary mirror.

[0023] Further, in step 1, the plurality of phases are four, which are 0°, 90°, 180° and 270°, respectively;

[0024] In step 3, the 0° phase of the central shaft and the 0° phase of the primary mirror seat are selected as the initial phase for paired assembly, and the 0° phase of the primary mirror is selected as the initial phase for paired assembly.

[0025] Further, in step 1, the plurality of phases are three, which are 0°, 120° and 360°, respectively;

[0026] In step 3, the 0° phase of the central shaft and the 0° phase of the primary mirror seat are selected as the initial phase for paired assembly, and the 0° phase of the primary mirror is selected as the initial phase for paired assembly.

[0027] Further, step 1 is specifically:

[0028] First, clean the central shaft, the primary mirror, the primary mirror seat and the primary mirror pressing plate, and then mark a plurality of phases that can be used for installation on the outer circumferential surface of the central shaft, the back surface of the primary mirror and the back surface of the primary mirror seat.

[0029] Further, in step 1:

[0030] A marker is used to mark a plurality of phases that can be used for installation on the outer circumferential surface of the central shaft, the back surface of the primary mirror and the back surface of the primary mirror seat.

[0031] Further, in step 2, the central shaft is installed into the inner hole of the primary mirror through the guide sleeve.

[0032] The beneficial effects of the present application are:

[0033] 1. By performing multi-phase optimal shaft hole matching phase optimization on the primary mirror, the central shaft and the primary mirror seat, the influence of the primary mirror pressing ring on the surface shape in the mirror assembly is reduced, and the stability of the surface shape index in the assembly process is improved; and the surface shape is detected at multiple phases, thereby solving the influence of ground adjustment gravity on the detection result, avoiding large changes in the surface shape of the mirror in the space microgravity state, and thereby affecting the imaging quality.

[0034] 2. According to the characteristics of the glue, the rotation frequency and time of the central axis rotation curing are determined, so that the mirror deformation problem caused by the uneven distribution of the adhesive and the large local shrinkage stress is solved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a structural schematic diagram of a reflecting mirror;

[0036] Figure 2 is a schematic diagram of the cooperation and installation of the primary mirror and the central axis;

[0037] Figure 3 is a flowchart of the embodiment of the application;

[0038] Figure 4 is a schematic diagram of the cooperation of the primary mirror and the central axis hole, a is a schematic diagram of the cooperation of the positive cone and the positive cone, b is a schematic diagram of the cooperation of the positive cone and the inverted cone, c is a schematic diagram of the cooperation of the inverted cone and the positive cone, and d is a schematic diagram of the cooperation of the inverted cone and the inverted cone;

[0039] Figure 5 is a schematic diagram of the principle of the optimal axis hole cooperation phase optimization strategy in the embodiment of the application;

[0040] Figure 6 is a state diagram of the thickness of the glue layer before and after the adoption of the rotation curing process in the embodiment of the application, a is a schematic diagram of the state of the thickness of the glue layer before the adoption of the rotation curing process, and b is a schematic diagram of the state of the thickness of the glue layer after the adoption of the rotation curing process.

[0041] In the figure: 1-primary mirror, 2-central axis, 3-primary mirror seat, 4-primary mirror pressing plate, 5-primary mirror pressing ring, 6-primary mirror steel pad, and 7-primary mirror glue pad. DETAILED DESCRIPTION

[0042] In order to make the purpose, advantages and characteristics of the application clearer, the following will make a further detailed description of the center axis supporting high lightweight reflecting mirror assembly method provided by the application in combination with the drawings and specific embodiments. The advantages and characteristics of the application will be clearer according to the following specific embodiments. It should be noted that: the drawings all adopt a very simplified form and all use non-precise proportions, only to facilitate and clearly assist the purpose of explaining the embodiment of the application; secondly, the structure shown in the drawings is often a part of the actual structure.

[0043] Referring to Figure 3 , the center axis supporting high lightweight reflecting mirror assembly method of the embodiment specifically includes the following steps:

[0044] Step 1, clean the related optical and mechanical parts, i.e. the central axis 2, the primary mirror 1, the primary mirror seat 3 and the primary mirror pressing plate 4, etc., to avoid the existence of impurities on the surface of the optical and mechanical parts affecting the assembly; and mark a plurality of phases that can be used for installation on the outer circumferential surface of the central axis 2, the back surface of the primary mirror 1 and the back surface of the primary mirror seat 3, respectively.

[0045] Since the space camera works in the space micro-gravity environment, the assembly environment is in the gravity state. Therefore, how to perform the surface shape inspection during the ground assembly to ensure that the surface shape of the space state mirror meets the index requirements becomes a difficulty in the space camera assembly. In the embodiment, in order to ensure the assembly quality of the main mirror assembly, the mirror surface shape multi-phase detection method is adopted, that is, the surface shape of the mirror assembly is detected at several symmetric phases to ensure that the surface shape is good and symmetric at each phase, so as to ensure the surface shape quality in the space environment. The method is suitable for the surface shape detection of the axisymmetric optical assembly, and the commonly used way is the four-phase surface shape detection strategy or the three-phase surface shape detection strategy in the space camera-gravity environment, that is, the surface shape is detected at 0°, 90°, 180°, 270° or 0°, 120°, 360° phases to ensure that the surface shape data at each phase is symmetric and good in the gravity environment.

[0046] The process method can solve the influence of the ground assembly gravity on the detection result, and is an effective method for predicting the change of the mirror surface shape in the space micro-gravity state.

[0047] In the embodiment, four phases that can be used for installation are marked on the outer peripheral surface of the central shaft 2, the back surface of the main mirror 1 and the back surface of the main mirror seat 3, that is, 0°, 90°, 180° and 270° phases.

[0048] Step 2, place the main mirror 1 upside down on the support disc, that is, place the reflecting surface of the main mirror 1 downward on the support disc, and then assemble the central shaft 2 into the inner hole of the main mirror 1 through the guide sleeve.

[0049] Step 3, assemble the main mirror seat 3 and the central shaft 2, and select the 0° phase of the central shaft 2 and the 0° phase of the main mirror seat 3 as the initial phases for pairing assembly, and then rotate the main mirror 1 to select the 0° phase of the main mirror 1 as the initial phase for pairing assembly.

[0050] Step 4, turn over the main mirror 1 to make the reflecting surface upward, and sequentially install the main mirror rubber pad 7, the main mirror steel pad 6 and the main mirror compression ring 5 to the reflecting surface of the main mirror 1, and appropriately pre-tighten the main mirror compression ring 5, so that the assembly of the main mirror part is completed.

[0051] Step 5, install the main mirror part to the rotary detection frame, build the detection light path, detect the surface shape of the main mirror 1 at the initial phase, if the surface shape meets the preset requirements, sequentially detect the surface shape at the remaining phases, if the surface shapes at the remaining phases cannot all meet the preset requirements, adjust the rotation degree of the main mirror compression ring 5 at the phase with the worst surface shape, so that the surface shape at the phase meets the preset requirements, and then detect the surface shape at the remaining three phases again, if all the surface shapes meet the preset requirements, the matching phase is taken as the best shaft hole matching phase, and then step 7 is performed, if all the surface shapes cannot meet the preset requirements, step 6 is performed.

[0052] Step 6, loosen the primary mirror pressing ring 5, rotate the primary mirror 1, determine the next phase for matching assembly according to the optimal axial hole matching phase optimization strategy, pre-tighten the primary mirror pressing ring 5, and then detect the surface shape of each phase in the manner of step 5. If all the surface shapes meet the preset requirements, the matching phase is the optimal axial hole matching phase. If the preset requirements cannot be met, the next matching phase is determined according to the optimal axial hole matching phase optimization strategy, and the matching assembly is performed again until the optimal axial hole matching phase is found.

[0053] Since the primary mirror 1 is generally rotationally symmetric, a plurality of axial hole matching phases can be determined according to the lightweight structure of the back of the primary mirror 1. In the assembly of the lightweight primary mirror, the center shaft 2 and the primary mirror center hole are usually matched with a small gap. Because of the machining error of the axial hole, such as Figure 4 As shown in the figure, the actual matching of the axial hole is generally divided into the following four types, i.e. positive taper vs. positive taper, positive taper vs. inverted taper, inverted taper vs. positive taper, and inverted taper vs. inverted taper. According to simulation and assembly practice, the optimal matching state is small taper matching of positive taper vs. positive taper. Therefore, in general processing, it is required to be processed as cylindrical matching or small taper matching of positive taper. Before assembly, the size and shape tolerance of the axial hole need to be accurately measured to master the actual matching state. However, due to the high lightweight of the primary mirror 1, the mirror is very sensitive, and under the action of the pre-tightening force of the pressing ring, the surface shape will still be affected.

[0054] In order to find the optimal center shaft 2 and primary mirror 1 center hole matching phase, effectively press the pressing ring, and ensure the stable state of the primary mirror 1, the optimal axial hole matching phase optimization method is adopted in this embodiment, i.e. a plurality of axial hole matching phases are determined according to the structure characteristics of the mirror assembly, and the optimal axial hole matching phase is found by trial assembly and adjustment in the determined axial hole phase to ensure the optimal surface shape of the mirror after the assembly of the mirror assembly. As shown in the figure, the primary mirror 1 and the center shaft 2 can be assembled at 0°, 60°, 120°…360° phase. Figure 5

[0055] The optimal axial hole matching phase optimization strategy when the center shaft 2 is 0° is shown in Table 1 below. Assuming that after trial assembly, the optimal surface shape is A3, it can be determined that the center shaft 20° and the center hole 120° are the optimal axial hole matching phase.

[0056] Table 1 Optimal axial hole matching phase optimization strategy when the center shaft is 0°

[0057] Serial number Center axis Center hole Surface shape Note 1 0° 0° A1 2 0° 60° A2 3 0° 120° A3 Optimal axis-hole fit phase 4 0° 180° A4 5 0° 240° A5 6 0° 300° A6

[0058] This process method can reduce the influence of the tight pressing ring on the surface shape in the assembly of the mirror, and at the same time improve the stability of the surface shape index in the assembly process of the assembly.

[0059] Step 7, install the primary mirror pressing plate 4, and complete the assembly of the primary mirror assembly. ​

[0060] Step 7.1, glue injection into the glue injection hole of the central shaft 2, determine the rotation frequency and time of the rotation curing of the central shaft 2 according to the characteristics of the glue, detect and correct the surface shape accuracy of the central shaft 2 after the glue is dry, and ensure that the technical index requirements are met.

[0061] The actual state of the primary mirror 1 after glue injection in the optical axis horizontal state is shown in Figure 6 The shrinkage stress caused by the glue spot due to the thickness difference between the upper and lower glue layers is not balanced, which finally makes the surface shape of the primary mirror 1 asymmetric and even unable to meet the index requirements. For this, the rotation curing method is adopted in this embodiment, that is, the appropriate rotation curing process is determined according to the viscosity and curing time of the adhesive. For the adhesive with short curing time, continuous or short interval high frequency rotation curing process is suitable, otherwise, low frequency long interval rotation curing process can be used. At the same time, the viscosity of the adhesive is considered, and the viscosity of the adhesive with high viscosity and poor flowability is appropriately increased. Finally, the glue layer thickness is uniform, and the surface shape is good. This process method can solve the mirror deformation problem caused by the large local shrinkage stress due to uneven distribution of adhesive.

[0062] Step 7.2, glue injection into the glue injection hole of the primary mirror holder 3, check and correct the surface shape accuracy of the primary mirror holder 3 after the glue is dry, and ensure that the micro stress assembly requirements are met.

[0063] Step 7.3, install the primary mirror pressing plate 4, and pad two layers of polyamide film at the glue injection position, inject glue into the back glue injection hole of the primary mirror pressing plate 4, and after the glue layer is cured, one layer is removed to ensure that the glue layer does not contact the optical part, so as to ensure the micro stress assembly of the reflecting mirror.

[0064] Step 7.4, point anti-looseness glue injection into the primary mirror pressing ring 5, and complete the assembly of the primary mirror assembly.

Claims

1. A method of supporting a high lightweight mirror assembly by a central shaft, characterized by, The method comprises the following steps: Step 1, marking a plurality of phases for assembly on the outer circumferential surface of the central shaft (2), the back surface of the primary mirror (1) and the back surface of the primary mirror seat (3) respectively; Step 2, placing the primary mirror (1) on the support disc with the reflecting surface facing downwards, and then preliminarily assembling the central shaft (2) into the inner hole of the primary mirror (1); Step 3, selecting one phase of the central shaft (2) and one phase of the primary mirror seat (3) as the initial phase for paired assembly, and then rotating the primary mirror (1) to select one phase of the primary mirror (1) as the initial phase for paired assembly; Step 4, turning over the primary mirror (1) to make the reflecting surface face upwards, sequentially mounting the primary mirror rubber pad (7), the primary mirror steel pad (6) and the primary mirror compression ring (5) on the reflecting surface of the primary mirror (1), and pre-tightening the primary mirror compression ring (5) to complete the assembly of the primary mirror component; Step 5, mounting the primary mirror component on the rotary detection frame, building a detection light path, detecting the surface shape of the primary mirror (1) at the initial phase, and if the surface shape meets the preset requirement, sequentially detecting the surface shape of the remaining phases; if the surface shapes of the remaining phases cannot all meet the preset requirement, adjusting the rotation degree of the primary mirror compression ring (5) at the phase with the worst surface shape to make the surface shape of the phase meet the preset requirement, and then detecting the surface shapes of the remaining phases again; if all the surface shapes meet the preset requirement, the matching phase is taken as the best shaft-hole matching phase, and then step 7 is performed; if all the surface shapes cannot meet the preset requirement, step 6 is performed; Step 6, loosening the primary mirror compression ring (5), rotating the primary mirror (1), selecting the next phase for paired assembly, pre-tightening the primary mirror compression ring (5), and returning to step 5; Step 7, mounting the primary mirror compression plate (4) to complete the assembly of the reflecting mirror.

2. The method of claim 1, wherein Step 7 specifically comprises: Step 7.1, injecting glue into the glue injection hole of the central shaft (2), determining the rotation frequency and time of the rotation of the central shaft (2) according to the characteristics of the glue, detecting the surface shape precision of the central shaft (2) after the glue is dry to ensure that the technical index requirement is met; Step 7.2, injecting glue into the glue injection hole of the primary mirror seat (3), checking the surface shape precision of the primary mirror seat (3) after the glue is dry to ensure that the micro-stress assembly requirement is met; Step 7.3, mounting the primary mirror compression plate (4) and injecting glue into the glue injection hole of the primary mirror compression plate (4); Step 7.4, applying anti-loosening glue to the primary mirror compression ring (5) to complete the assembly of the reflecting mirror.

3. The method of claim 2, wherein the method further comprises: Step 7.3 specifically comprises: Mounting the primary mirror compression plate (4) and placing two layers of polyamide films at the contact position of the primary mirror compression plate (4) and the primary mirror (1), injecting glue into the glue injection hole of the primary mirror compression plate (4), and after the glue layer is cured, removing one layer of the polyamide film to ensure that the glue layer does not contact the primary mirror (1).

4. The central shaft supporting high-lightweight reflecting mirror assembly method according to any one of claims 1-3, characterized in that: In step 1, the plurality of phases are four, which are 0°, 90°, 180° and 270° respectively; In step 3, the 0° phase of the central shaft (2) and the 0° phase of the primary mirror seat (3) are selected as the initial phase for paired assembly, and the 0° phase of the primary mirror (1) is selected as the initial phase for paired assembly.

5. The central shaft supporting high-lightweight reflecting mirror assembly method according to any one of claims 1-3, characterized in that, In step 1, the multiple phases are three, which are 0°, 120° and 360° respectively; In step 3, the 0° phase of the central shaft (2) and the 0° phase of the primary mirror holder (3) are selected as the initial phases for pairing assembly, and the 0° phase of the primary mirror (1) is selected as the initial phase for pairing assembly.

6. The method of claim 1-3, wherein Step 1 is specifically: First, clean the central shaft (2), the primary mirror (1), the primary mirror holder (3) and the primary mirror pressing plate (4), and then mark the multiple phases available for installation on the outer circumferential surface of the central shaft (2), the back surface of the primary mirror (1) and the back surface of the primary mirror holder (3) respectively.

7. The method of claim 6, wherein the method further comprises: In step 1: Use a marker to mark the multiple phases available for installation on the outer circumferential surface of the central shaft (2), the back surface of the primary mirror (1) and the back surface of the primary mirror holder (3) respectively.

8. The method according to claim 1, wherein: In step 2, the central shaft (2) is installed into the inner hole of the primary mirror (1) through the guide sleeve.

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