阅读说明：本技术 基于间隙测量和反馈调节的微牛级冷气推力器装配方法 (micro-Newton cold air thruster assembling method based on gap measurement and feedback adjustment ) 是由 高晨光 汪旭东 王平 刘旭辉 臧孝华 李永 付新菊 宋新河 谢继香 张汝俊 于 2021-06-04 设计创作，主要内容包括：基于间隙测量和反馈调节的微牛级冷气推力器装配方法,其步骤为：组装压电驱动器组件,测量压电驱动器电压—位移特性；测量焊接变形方向,设置推力器阀杆—阀芯间隙预偏置量；装配推力器,调节预紧力,粗调推力器阀杆—阀芯间隙；测量阀杆总行程；测量阀芯开启行程；按照行程测试结果,精调阀杆—阀芯间隙；对推力器进行主动温度控制,标定工作温度范围内阀杆—阀芯间隙的准确值；焊接阀杆和驱动器组件,复测阀杆总行程,开启行程；配置螺接顺序和拧紧力矩大小,微调装配间隙。本发明可以实现微牛级冷气推力器微米级装配精度,满足推力精度要求并保证推力器可靠密封和开启。(The assembling method of the micro-Newton cold air thruster based on clearance measurement and feedback adjustment comprises the following steps: assembling a piezoelectric driver assembly, and measuring the voltage-displacement characteristic of the piezoelectric driver; measuring the welding deformation direction, and setting a valve rod-valve core gap pre-offset of the thruster; assembling a thruster, adjusting pretightening force, and roughly adjusting a gap between a valve rod and a valve core of the thruster; measuring the total stroke of the valve rod; measuring the opening stroke of the valve core; according to the stroke test result, the clearance between the valve rod and the valve core is finely adjusted; performing active temperature control on the thruster, and calibrating the accurate value of the clearance between the valve rod and the valve core within the working temperature range; welding the valve rod and the driver assembly, retesting the total stroke of the valve rod, and opening the stroke; and (4) configuring a screwing sequence and the magnitude of a screwing torque, and finely adjusting the assembly clearance. The invention can realize micron-scale assembly precision of the micro-Newton cold air thruster, meet the requirement of thrust precision and ensure reliable sealing and opening of the thruster.)

1. The assembling method of the micro-Newton cold air thruster based on clearance measurement and feedback adjustment is characterized by comprising the following steps of:

1) assembling a piezoelectric driver assembly;

2) obtaining a measured pre-bias C of the piezoelectric driver assembly;

3) assembling a thruster, and roughly adjusting the axial clearance between a valve rod and a valve core of the thruster;

4) connecting a valve rod to a piezoelectric driver assembly through a thread pair, and measuring the total stroke A of the valve rod of the thruster;

5) measuring the opening stroke B of the valve core of the thruster under the action of the required voltage;

6) according to the total stroke A of the valve rod of the thruster in the step 4) and the opening stroke B of the valve core of the thruster in the step 5), the axial clearance between the valve rod and the valve core is finely adjusted, so that the axial clearance meets the index requirement;

7) the method comprises the following steps of carrying out temperature control on a thruster, calibrating an actual measurement value of an axial clearance between a valve rod and a valve core of the thruster within a working temperature range, and enabling the actual measurement value to meet index requirements within the working temperature range of the thruster by adjusting an adjusting nut arranged on the valve rod;

8) and welding the valve rod of the thruster and the driver assembly to finish assembly.

2. The assembling method of a micro-Newtonian cold air thruster based on gap measurement and feedback regulation of claim 1, wherein the step 2) measures a pre-offset C, specifically:

deformation is generated between the valve rod of the thruster and the piezoelectric actuator assembly due to welding, and the deformation amount in the deformation direction is used as a pre-offset C.

3. The assembling method of a micro-Newton cold air thruster based on clearance measurement and feedback regulation of claim 1, wherein step 3) is to roughly adjust the axial clearance between the valve rod and the valve core of the thruster so that the axial clearance between the valve rod and the valve core of the thruster is not more than 50 μm.

4. The assembling method of a micro-Newtonian cold air thruster based on clearance measurement and feedback regulation of claim 1, wherein the step 4) of measuring the total stroke A of the valve rod of the thruster is specifically as follows:

the valve rod is driven to move in a stretching mode under the action of the piezoelectric driver assembly, and the total stroke A of the valve rod under the action of required voltage is measured.

5. The assembling method of a micro-Newtonian cold air thruster based on clearance measurement and feedback regulation according to any one of claims 1 to 4, wherein the index requirements of step 6) and step 7) are equal to (X + C) ± 30%, where X is the theoretical value of the axial clearance between the valve rod and the valve core.

6. The assembling method of a micro-Newtonian cold air thruster based on gap measurement and feedback regulation of claim 5, wherein the working temperature range in the step 7) is 25-50 ℃.

7. The assembling method of a micro-Newtonian cold air thruster based on clearance measurement and feedback regulation of claim 5, wherein the step 6) is a method for finely adjusting the axial clearance between the valve rod and the valve core, and specifically comprises the following steps:

obtaining an actual measurement value of an assembly clearance according to a difference value between the total stroke A of the valve rod of the thruster in the step 4) and the opening stroke B of the valve core of the thruster in the step 5), wherein the actual measurement value of the assembly clearance is equal to a difference (A-B) between the total stroke of the valve rod and the stroke of the valve core;

according to the measured value of the assembly clearance, the axial clearance between the valve rod and the valve core is adjusted through an adjusting nut arranged on the valve rod, and the axial clearance value is equal to the index requirement.

8. The assembling method of micro-Newtonian cold gas thruster based on gap measurement and feedback regulation of claim 7, wherein after the step 8), further comprising:

9) retesting a total stroke A 'of a valve rod of the thruster and an opening stroke B' of a valve core of the thruster to obtain an axial gap between the retested valve rod of the thruster and the valve core, and judging whether an axial gap value (A '-B') meets a design requirement value X +/-30%; if the requirements are met, the assembly is finished, otherwise, if the requirements are not met, the step 10) is carried out;

10) the assembling method is characterized in that a piezoelectric driver, a screwing sequence and a screwing torque among a valve rod and a shell are configured, the assembling clearance is finely adjusted by configuring different screwing sequences and torque sizes, the axial clearance between the valve rod and a valve core of the thruster meets the design requirement value X +/-30%, and the assembling is completed.

Technical Field

The invention relates to a method for measuring assembly clearance of a cold air thruster and adjusting feedback, in particular to the field of assembly of a micro-thrust space thruster and a flow controller.

Background

The micro-Newton thrust cold air thruster adopts a piezoelectric driver as a driving mechanism, can realize the mu N-level thrust control precision and high thrust stability, and meets the requirement of the non-dragging control of the spacecraft. The internal compact structure of driver subassembly, case subassembly etc. is contained to it, drives the opening of valve core through piezoelectric actuator drive valve rod drive case, realizes different spray tube throttle areas, can realize thrust control and adjustment in very little scope. In the whole working range, the working stroke of the valve core is only 10-20 μm, and the position precision of the valve core needs to reach the level of μm, so that the thrust precision of the thruster can be met, and the thruster can be reliably sealed and opened. Therefore, controlling the position accuracy and clearance size of the piezoelectric actuator, valve stem and valve element is a key factor in achieving high-accuracy thrust control. In order to achieve the assembling precision, the requirements cannot be met by depending on the machining precision of parts and the traditional sequential assembling means, and the final assembling precision and the structural stability need to depend on high-precision measurement and feedback adjusting means.

Disclosure of Invention

The technical problem of the invention is solved: the method overcomes the defects of the prior art, provides a method for measuring, feeding back and compensating the assembly clearance of the high-precision thruster, reduces the dependence on the machining precision of parts, and effectively realizes the clearance measurement and control of the mu m level, thereby realizing the thrust control of the mu N level.

The technical solution of the invention is as follows:

the assembling method of the micro-Newton cold air thruster based on clearance measurement and feedback adjustment comprises the following steps:

1) assembling a piezoelectric driver assembly;

2) obtaining a measured pre-bias C of the piezoelectric driver assembly;

3) assembling a thruster, and roughly adjusting the axial clearance between a valve rod and a valve core of the thruster;

4) connecting a valve rod to a piezoelectric driver assembly through a thread pair, and measuring the total stroke A of the valve rod of the thruster;

5) measuring the opening stroke B of the valve core of the thruster under the action of the required voltage;

6) according to the total stroke A of the valve rod of the thruster in the step 4) and the opening stroke B of the valve core of the thruster in the step 5), the axial clearance between the valve rod and the valve core is finely adjusted, so that the axial clearance meets the index requirement;

7) the method comprises the following steps of carrying out temperature control on a thruster, calibrating an actual measurement value of an axial clearance between a valve rod and a valve core of the thruster within a working temperature range, and enabling the actual measurement value to meet index requirements within the working temperature range of the thruster by adjusting an adjusting nut arranged on the valve rod;

8) and welding the valve rod of the thruster and the driver assembly to finish assembly.

Step 2) the pre-offset C is measured, specifically:

deformation is generated between the valve rod of the thruster and the piezoelectric actuator assembly due to welding, and the deformation amount in the deformation direction is used as a pre-offset C.

And 3) roughly adjusting the axial clearance between the valve rod and the valve core of the thruster so that the axial clearance between the valve rod and the valve core of the thruster is not more than 50 mu m.

Step 4) the method for measuring the total stroke A of the valve rod of the thruster comprises the following specific steps:

the valve rod is driven to move in a stretching mode under the action of the piezoelectric driver assembly, and the total stroke A of the valve rod under the action of required voltage is measured.

And 6) and 7), wherein the index requirement is equal to (X + C) + -30%, wherein X is a theoretical value of an axial clearance between the valve rod and the valve core.

The working temperature range in the step 7) is 25-50 ℃.

Step 6) the method for finely adjusting the axial clearance between the valve rod and the valve core specifically comprises the following steps:

obtaining an actual measurement value of an assembly clearance according to a difference value between the total stroke A of the valve rod of the thruster in the step 4) and the opening stroke B of the valve core of the thruster in the step 5), wherein the actual measurement value of the assembly clearance is equal to a difference (A-B) between the total stroke of the valve rod and the stroke of the valve core;

according to the measured value of the assembly clearance, the axial clearance between the valve rod and the valve core is adjusted through an adjusting nut arranged on the valve rod, and the axial clearance value is equal to the index requirement.

Further, after the step 8), the method further comprises the following steps:

9) retesting a total stroke A 'of a valve rod of the thruster and an opening stroke B' of a valve core of the thruster to obtain an axial gap between the retested valve rod of the thruster and the valve core, and judging whether an axial gap value (A '-B') meets a design requirement value X +/-30%; if the requirements are met, the assembly is finished, otherwise, if the requirements are not met, the operation enters step 10).

10) The assembling method is characterized in that a piezoelectric driver, a screwing sequence and a screwing torque among a valve rod and a shell are configured, the assembling clearance is finely adjusted by configuring different screwing sequences and torque sizes, the axial clearance between the valve rod and a valve core of the thruster meets the design requirement value X +/-30%, and the assembling is completed.

Compared with the prior art, the invention has the advantages that:

(1) the invention meets the assembly precision of the cold air thruster and reduces the requirement on the processing precision of parts

The feedback adjusting method provided by steps 3) to 6) of the invention is adopted in the assembly process of the cold air thruster, so that the accumulated error caused by the dimensional tolerance of the part can be measured and adjusted. In the whole working range, the working stroke of the valve core is only 10-20 μm, the position precision of the valve core needs to reach the level of μm, the valve core is assembled by a plurality of parts, the dimensional precision of the parts is completely ensured by depending on the dimensional precision of the parts, and the dimensional precision of the parts needs to reach more than submicron level.

(2) In steps 3) -6), the stroke of the valve core and the valve rod is measured by adopting a high-precision sensor in the measuring process, the measuring precision can reach 10nm, and the measuring error caused by a conventional measuring mode is avoided; the flow sensor is adopted to indirectly measure the opening stroke of the valve core, so that direct flow data are obtained, the damage in the thruster is avoided, and redundant materials are introduced, so that the clearance between the driving rod and the valve core can be measured in the whole life cycle, and process data are provided for the successful assembly of products.

(3) In the step 7) of the invention, active temperature control is carried out on the thruster in the assembling process so as to calibrate the accurate value of the influence of the temperature on the assembling clearance. The temperature control precision is +/-0.2 ℃, so that the influence of temperature change on the clearance is quantized, the product margin is increased, and the space application reliability is ensured.

(4) In the step 2), a pre-biased control strategy is adopted for welding deformation, the relative direction of deformation is explored, and the gap is pre-adjusted to be 10-20 mu m according to the total change trend so that the final gap is controlled within a required range; the influence of welding deformation is effectively reduced, and the qualification rate of the product assembly process is improved.

(5) Step 9) of the invention analyzes and controls the screwing sequence and the torque, analyzes the influence trend of screw assembly on relative clearance, correctly configures the assembling sequence and the torque, further finely adjusts the clearance value, enables the screwing deformation to be offset positively and negatively, reduces the influence, and finally enables the relative position change caused by assembling the screw to be reduced from 10 mu m to below 2 mu m.

Drawings

FIG. 1 is a flow chart of the steps of the present invention;

FIG. 2 is a schematic illustration of valve stem spool clearance;

FIG. 3 is a schematic diagram of a valve core structure of a valve rod of the micro-Newton cold air thruster;

FIG. 4 is a schematic diagram of the present invention using high precision capacitive sensors to measure the stroke of the valve core and the valve stem and to perform feedback adjustment.

Detailed Description

As shown in fig. 1, the method for assembling a micro-Newton cold air thruster based on clearance measurement and feedback regulation of the invention comprises the following steps:

1) assembling a piezoelectric driver assembly, and measuring the voltage-displacement characteristic of the piezoelectric driver;

2) performing a background test to obtain a measurement pre-offset C;

deformation is generated between the valve rod of the thruster and the piezoelectric actuator assembly due to welding, and the deformation quantity in the deformation direction is used as a pre-bias quantity C;

3) assembling a thruster, adjusting the pretightening force of a piezoelectric driver component, roughly adjusting the axial clearance between a valve rod and a valve core of the thruster, and enabling the axial clearance between the valve rod and the valve core of the thruster to be not more than 50 mu m as shown in figure 2;

4) connecting a valve rod to a piezoelectric driver component through a thread pair (nut), and measuring the total stroke A of the valve rod of the thruster;

driving the valve rod to move in a stretching way under the action of the piezoelectric driver component, and measuring the total stroke A of the valve rod under the action of required voltage;

5) measuring the opening stroke B of the valve core of the thruster:

measuring the opening stroke B of the valve core of the thruster under the action of the required voltage;

6) synchronously and finely adjusting the clearance between the valve rod and the valve core according to the total stroke A of the valve rod of the thruster in the step 4) and the opening stroke B of the valve core of the thruster in the step 5); the method specifically comprises the following steps:

the valve rod and the valve core have an assembly clearance axially, the measured value of the assembly clearance is equal to the difference (A-B) between the total stroke of the valve rod and the stroke of the valve core, and the axial clearance value of the valve rod and the valve core is enabled to be equal to (X + C) ± 30% by finely adjusting the axial clearance of the valve rod and the valve core through an adjusting nut arranged on the valve rod, wherein X is the theoretical value of the clearance of the valve rod and the valve core, and C is the pre-offset.

7) The active temperature control is carried out on the micro-Newton thruster, and the accurate value of the clearance between a valve rod and a valve core in the working temperature range is calibrated, which specifically comprises the following steps: the temperature control and the temperature test are carried out on the micro-cow thruster by adopting the scheme of a heating plate and a thermistor (temperature measuring optical fiber), and the temperature of the thruster is controlled to be 25-50 ℃ (the temperature measuring precision is +/-0.2 ℃). Calibrating the measured value of the valve rod-valve core assembly clearance in the working temperature range, and finely adjusting an adjusting nut arranged on the valve rod to ensure that the axial clearance of the valve rod-valve core can meet the requirement when the thruster is in the working temperature range, namely the axial clearance of the valve rod-valve core is equal to (X + C) + -30%;

8) welding a valve rod and a driver assembly of the thruster, retesting a total stroke A 'of the valve rod, and a valve core opening stroke B' to obtain a retested valve rod-valve core gap, and judging whether a gap value (A '-B') meets a design requirement value X +/-30%; if the requirements are met, the assembly is finished, otherwise, if the requirements are not met, the operation enters step 9).

9) The configuration spiro union order and the tightening torque size, finely tune the fit-up gap: the piezoelectric actuator, the valve rod and the shell are respectively connected by screws, and the assembly clearance is finely adjusted by configuring different bolt connection sequences and torque sizes, so that the valve core-valve rod clearance meets the design requirement X +/-30%.

And 3) roughly adjusting the clearance between the valve rod and the valve core in the step 3), wherein the sum of the dimensional tolerance of parts and the structural deformation caused by pretightening force needs to be calculated.

In the step 5), a high-precision sensor direct measurement method and a flow indirect measurement method are adopted for measuring the opening stroke of the valve core.

In the step 7), the high-precision temperature field test is carried out on the micro-Newton thruster, and the temperature control precision is better than +/-0.2 ℃.

Examples

The specific implementation process of the present invention is described by taking an assembly process of a certain model number 1-50 μ N cold air thrust module as an example, and as shown in fig. 1, the specific implementation flow of the present invention is as follows:

(1) assembling a piezoelectric driver assembly, and measuring the voltage-displacement characteristic of the piezoelectric driver by adopting a high-precision capacitance sensor;

(2) measuring the welding deformation direction and setting a gap pre-offset amount; the relative direction of the deformation of the pre-welding probe adopts a pre-bias assembly strategy, and different forces are applied to the driving rod in advance to control the direction (increasing or decreasing) of the change of the relative position after welding; the gap is adjusted to 10-20 μm in advance according to the total variation trend. So that the final gap is in the range of 20-30 μm.

(3) Assembling a thruster, calculating the error amount caused by the accumulated dimensional tolerance of parts, calculating the sum of structural deformation amount caused by pretightening force, and roughly adjusting the clearance between a valve rod and a valve core by using a gasket with the specification of 0.05 mm-0.2 mm;

(4) introducing a capacitance displacement sensor to measure the displacement change of the valve core (the measurement precision reaches 10 nm); measuring the strokes of a valve rod and a valve core, wherein the valve rod moves under the action of a piezoelectric driver, the given voltage is 20V-100V, and the stroke range of the valve rod under the action of the required voltage is measured; measuring the stroke range of the valve core under the action of 20V-100V voltage.

(5) When the opening stroke of the valve core does not meet the requirement, as shown in fig. 3, the adjusting nut is rotated, the position of the valve rod is finely adjusted, and the valve core stroke under the given voltage is measured until the gap measurement requirement is met under the given voltage;

(6) and carrying out active temperature control on the micro-Newton thruster, and calibrating the accurate value of the clearance between the valve rod and the valve core within the working temperature range. And the temperature control and the temperature test are carried out on the micro-Newton thruster by adopting a scheme of a heating plate and a thermistor (temperature measuring optical fiber). The temperature of the thruster is controlled at 25-50 ℃ (the temperature measurement precision is +/-0.2 ℃), and corresponding clearance values are measured at different temperatures. The adjusting nut shown in fig. 3 is fine-tuned, so that the thruster can meet the requirements within the working temperature range.

(7) And (4) configuring a screwing sequence and the magnitude of a screwing torque, and finely adjusting the assembly clearance.

The micro-deformation caused by the screw connection to the product assembly is in the order of 10 μm and cannot be ignored. Analyzing the influence trend of the force on the relative clearance, performing a test, and accumulating original data; setting the assembling sequence and the tightening torque of each screw according to the summarized deformation trend; according to the influence trend of each screw, the assembly sequence is correctly configured, the clearance value is further finely adjusted, the positive and negative deformation are offset, and the influence is reduced; so that the relative position change caused by assembling the screws is reduced from 10 μm to below 2 μm.

The invention adopts a high-precision capacitance sensor to measure the stroke of the valve core and the valve rod and feed back and adjust the schematic diagram, as shown in figure 4.

In the assembly process, the position and the gap size of the valve core are measured in real time, a feedback adjustment assembly strategy is adopted, and the assembly precision is ensured to meet the requirement by controlling and compensating temperature fields, welding deformation and screw connection stress factors which influence the position and the gap size of the valve core.

The size of a valve core-valve rod gap is a key factor influencing the reliable opening and sealing of the micro-Newton thruster, the size precision of the micro-Newton thruster needs to reach the level of mum, the sequential assembly means based on the size precision of parts cannot meet the assembly requirement, and the deformation caused by welding and environmental temperature change is also a factor which cannot be ignored. Through feedback adjustment based on the displacement sensor, the gap value out-of-tolerance caused by accumulated dimension errors of parts in the assembly process is avoided; by pre-estimating and pre-offsetting welding deformation, the stability of the gap value in the welding process is ensured; and the gap value is ensured to meet the requirement in the full working temperature range through high-precision temperature field-voltage-displacement characteristic measurement and calibration.

The method can meet the requirement of controlling the assembly precision of the micro-Newton cold air thruster, realizes the adjustability, the measurability and the controllability of the whole life cycle of a 10-micron product gap, and successfully completes the development and the delivery after passing an environmental test.

Those skilled in the art will appreciate that the details of the invention not described in detail in the specification are within the skill of those skilled in the art.