阅读说明：本技术 一种电容式薄膜真空计的感应膜片焊后张紧力控制方法 (Method for controlling tension of induction diaphragm of capacitance type thin film vacuum gauge after welding ) 是由 侯少毅 胡强 卫红 胡琅 刘乔 于 2021-11-01 设计创作，主要内容包括：本申请属于机械加工技术领域,公开了一种电容式薄膜真空计的感应膜片焊后张紧力控制方法,包括以下步骤：把感应膜片焊接在电容式薄膜真空计的圆筒状的腔体的下端；腔体的材料的屈服强度比感应膜片的材料的屈服强度低；在腔体的内壁施加压力后卸载压力,使施加压力时腔体的腔壁的内侧部分、腔体的腔壁的外侧部分和感应膜片分别处于塑性变形状态、弹性变形状态和弹性张紧状态,从而使卸载压力后的感应膜片上具有所需的张紧力；该电容式薄膜真空计的感应膜片焊后张紧力控制方法有利于实现对感应膜片焊接后的张紧力的精准控制。(The application belongs to the technical field of machining and discloses a method for controlling tension force of an induction diaphragm of a capacitive film vacuum gauge after welding, which comprises the following steps: welding an induction diaphragm at the lower end of a cylindrical cavity of the capacitance type film vacuum gauge; the yield strength of the material of the cavity is lower than that of the material of the sensing diaphragm; after pressure is applied to the inner wall of the cavity, unloading the pressure, and enabling the inner side part of the cavity wall of the cavity, the outer side part of the cavity wall of the cavity and the sensing diaphragm to be in a plastic deformation state, an elastic deformation state and an elastic tensioning state respectively when the pressure is applied, so that the sensing diaphragm after pressure unloading has required tensioning force; the method for controlling the tension of the welded induction diaphragm of the capacitance type film vacuum gauge is beneficial to realizing the accurate control of the tension of the welded induction diaphragm.)

1. A method for controlling tension of an induction diaphragm of a capacitance type film vacuum gauge after welding is characterized by comprising the following steps:

welding an induction diaphragm at the lower end of a cylindrical cavity of the capacitance type film vacuum gauge; the yield strength of the material of the cavity is lower than that of the material of the sensing diaphragm;

and unloading the pressure after applying the pressure on the inner wall of the cavity, so that the inner part of the cavity wall of the cavity, the outer part of the cavity wall of the cavity and the sensing diaphragm are respectively in a plastic deformation state, an elastic deformation state and an elastic tensioning state when applying the pressure, and the sensing diaphragm after unloading the pressure has a required tensioning force.

2. The method for controlling post-weld tension of an induction diaphragm of a capacitive thin-film vacuum gauge according to claim 1, wherein the material of the cavity is PG 3600 or inconel X600; the material of the sensing diaphragm is inconel X750.

3. The method of claim 1, wherein the ratio of the outer diameter to the inner diameter of the chamber is 1.2 to 1.4.

4. The method of claim 3, wherein the ratio of the outer diameter to the inner diameter of the chamber is 1.3.

5. The method for controlling tension of an induction diaphragm of a capacitive thin film gauge after welding according to claim 1, wherein the step of welding the induction diaphragm to the lower end of the cylindrical cavity of the capacitive thin film gauge comprises:

tensioning the induction diaphragm to enable the induction diaphragm to be in a straight state;

and welding the induction membrane in a straight state at the lower end of the cavity.

6. The method for controlling post-weld tension of a sensing diaphragm of a capacitive diaphragm gauge according to claim 1, wherein the step of unloading the pressure after applying the pressure on the inner wall of the chamber so that the inner portion of the chamber wall of the chamber, the outer portion of the chamber wall of the chamber and the sensing diaphragm are in a plastic deformation state, an elastic deformation state and an elastic tension state respectively when applying the pressure, so that the sensing diaphragm after unloading the pressure has a required tension comprises:

and applying pressure on the inner wall of the cavity by using a hydrostatic pressure application mode.

7. The method as claimed in claim 6, wherein the step of applying pressure to the inner wall of the chamber by hydrostatic pressure comprises:

an upper sealing cover and a lower sealing cover are respectively covered and connected at the upper end and the lower end of the cavity, so that the cavity, the sensing diaphragm and the upper sealing cover enclose an upper cavity, and the sensing diaphragm and the lower sealing cover enclose a lower cavity; the upper sealing cover is provided with an upper liquid inlet communicated with the upper cavity, and the lower sealing cover is provided with a lower liquid inlet communicated with the lower cavity;

and respectively introducing liquid with the same pressure into the upper cavity and the lower cavity through the upper liquid inlet and the lower liquid inlet, and adjusting the pressure of the liquid, so that the required pressure is applied to the inner wall of the cavity.

8. The method for controlling post-weld tension of a sensing diaphragm of a capacitive diaphragm gauge according to claim 1, wherein the step of unloading the pressure after applying the pressure on the inner wall of the chamber so that the inner portion of the chamber wall of the chamber, the outer portion of the chamber wall of the chamber and the sensing diaphragm are in a plastic deformation state, an elastic deformation state and an elastic tension state respectively when applying the pressure, so that the sensing diaphragm after unloading the pressure has a required tension comprises:

and applying pressure on the inner wall of the cavity by using a mechanical pressing mode.

9. The method as claimed in claim 8, wherein the step of applying pressure to the inner wall of the chamber by using a mechanical pressing method comprises:

pressing an interference mandrel into the cavity from the upper end of the cavity to apply a desired pressure against the inner wall of the cavity.

Technical Field

The application relates to the technical field of machining, in particular to a method for controlling tension of an induction diaphragm of a capacitive film vacuum gauge after welding.

Background

The cavity of the capacitance type film vacuum gauge is internally provided with a metal induction diaphragm and a fixed electrode plate, and when the capacitance type film vacuum gauge works, the metal induction diaphragm can be correspondingly deformed by different vacuum degrees of a measured object, so that the capacitance between the metal induction diaphragm and the fixed electrode plate is correspondingly changed, and the vacuum degree of the measured object is measured according to the change condition of the capacitance.

The tension on the metal induction diaphragm is directly related to the deformation characteristic of the diaphragm, and further important influences are generated on key indexes such as measurement accuracy and repeatability of the capacitance type thin film vacuum gauge. The metal sensing diaphragm is generally connected with the cavity in a welding mode, and how to generate or maintain the required tension after welding is a key difficulty in the whole manufacturing process of the capacitance type thin film vacuum gauge. The method generally adopted at present is to tension the metal sensing diaphragm before welding to generate a certain pre-tension force, then welding is carried out, and the appropriate welding process method and welding process parameters are determined through repeated tests so that the metal sensing diaphragm has the required tension force after welding.

By the mode, welding process parameters need to be adjusted for multiple times to perform multiple welding tests, the determination process of the welding process parameters is complex, the trial and error cost is high, the appropriate tension of the diaphragm is still difficult to control effectively, the randomness of the tension of the diaphragm is high, and the product percent of pass is low.

Disclosure of Invention

An object of the application is to provide a tensile force control method after welding of an induction diaphragm of a capacitance type film vacuum gauge, which is beneficial to realizing accurate control of the tensile force after welding of the induction diaphragm, and is further beneficial to improving the product percent of pass.

The application provides a method for controlling tension force of an induction diaphragm of a capacitance type film vacuum gauge after welding, which comprises the following steps:

welding an induction diaphragm at the lower end of a cylindrical cavity of the capacitance type film vacuum gauge; the yield strength of the material of the cavity is lower than that of the material of the sensing diaphragm;

and unloading the pressure after applying the pressure on the inner wall of the cavity, so that the inner part of the cavity wall of the cavity, the outer part of the cavity wall of the cavity and the sensing diaphragm are respectively in a plastic deformation state, an elastic deformation state and an elastic tensioning state when applying the pressure, and the sensing diaphragm after unloading the pressure has a required tensioning force.

According to the tension control method for the induction diaphragm of the capacitive film vacuum gauge after welding, the induction diaphragm is welded at the lower end of the cavity, pressure is applied to the inner wall of the cavity, the inner portion of the cavity wall of the cavity is enabled to yield so as to generate plastic deformation, the outer portion of the cavity wall and the induction diaphragm are both in an elastic deformation state and cannot generate plastic deformation, the inner portion of the cavity generates plastic deformation, the induction diaphragm can keep a required tension due to the constraint of the plastic deformation after pressure unloading, and the whole structure is still in a stable and reliable state and cannot fail. The tension force required by the sensing diaphragm can be accurately controlled and obtained by adjusting the applied pressure, and the whole process is controllable, reliable and stable.

Preferably, the material of the cavity is PG 3600 or inconel X600; the material of the sensing diaphragm is inconel X750.

The material is selected, so that the yield strength of the sensing diaphragm is higher than that of the cavity, plastic deformation of the sensing diaphragm cannot occur, and meanwhile, due to the fact that the thermal expansion properties of the materials are close, the phenomenon that the tensile force in the sensing diaphragm is changed too much due to too large size change deviation of the cavity and the sensing diaphragm when the cavity expands with heat and contracts with cold can be avoided, and the measurement accuracy of the capacitive film vacuum gauge is guaranteed.

Preferably, the ratio of the outer diameter to the inner diameter of the cavity is 1.2-1.4.

Within the range, when the inner wall of the cavity is pressed, the stress difference between the inner wall and the outer wall of the cavity is large enough, so that the effects that the inner part of the cavity is buckled and the outer part of the cavity is in an elastic deformation state are easily realized; meanwhile, the wall thickness of the cavity cannot be too large due to the fact that the ratio of the outer diameter to the inner diameter is too large, and the weight of the capacitance type film vacuum gauge is prevented from being too large.

Preferably, the ratio of the outer diameter to the inner diameter of the cavity is 1.3.

Preferably, the step of welding the sensing diaphragm to the lower end of the cylindrical cavity of the capacitance thin film vacuum gauge comprises:

tensioning the induction diaphragm to enable the induction diaphragm to be in a straight state;

and welding the induction membrane in a straight state at the lower end of the cavity.

In some embodiments, the step of unloading the pressure after applying the pressure on the inner wall of the cavity so that the inner portion of the cavity wall of the cavity, the outer portion of the cavity wall of the cavity, and the sensing diaphragm are in a plastic deformation state, an elastic deformation state, and an elastic tension state, respectively, when applying the pressure, so that the sensing diaphragm has a desired tension after unloading the pressure comprises:

and applying pressure on the inner wall of the cavity by using a hydrostatic pressure application mode.

Preferably, the step of applying pressure to the inner wall of the cavity by using hydrostatic pressure comprises:

an upper sealing cover and a lower sealing cover are respectively covered and connected at the upper end and the lower end of the cavity, so that the cavity, the sensing diaphragm and the upper sealing cover enclose an upper cavity, and the sensing diaphragm and the lower sealing cover enclose a lower cavity; the upper sealing cover is provided with an upper liquid inlet communicated with the upper cavity, and the lower sealing cover is provided with a lower liquid inlet communicated with the lower cavity;

and respectively introducing liquid with the same pressure into the upper cavity and the lower cavity through the upper liquid inlet and the lower liquid inlet, and adjusting the pressure of the liquid, so that the required pressure is applied to the inner wall of the cavity.

In other embodiments, the step of unloading the pressure after applying the pressure on the inner wall of the cavity to make the inner portion of the cavity wall of the cavity, the outer portion of the cavity wall of the cavity, and the sensing diaphragm respectively in a plastic deformation state, an elastic deformation state, and an elastic tension state when applying the pressure, so that the sensing diaphragm after unloading the pressure has a required tension force comprises:

and applying pressure on the inner wall of the cavity by using a mechanical pressing mode.

Preferably, the step of applying pressure to the inner wall of the cavity by using a mechanical pressing manner comprises:

pressing an interference mandrel into the cavity from the upper end of the cavity to apply a desired pressure against the inner wall of the cavity.

Has the advantages that:

the application provides a capacitive film vacuum gauge's response diaphragm welds back tensile force control method, weld the response diaphragm at the cavity lower extreme earlier, exert pressure to the inner wall of cavity again, thereby make the inboard part of the chamber wall of cavity surrender and produce plastic deformation, and the outside part of chamber wall and response diaphragm all are in the elastic deformation state and can not produce plastic deformation, because the inboard part of cavity produces plastic deformation, because plastic deformation's restraint after the pressure uninstallation, the response diaphragm can keep required tensile force, whole structure still is in reliable and stable state this moment, can not become invalid. The tension force required by the sensing diaphragm can be accurately controlled and obtained by adjusting the applied pressure, and the whole process is controllable, reliable and stable. The method for controlling the post-welding tension of the induction diaphragm of the capacitive film vacuum gauge is beneficial to realizing the accurate control of the post-welding tension of the induction diaphragm, thereby being beneficial to improving the product percent of pass.

Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application.

Drawings

Fig. 1 is a flowchart of a method for controlling a post-weld tension of a sensing diaphragm of a capacitive thin film gauge according to an embodiment of the present disclosure.

Fig. 2 is a schematic diagram of stress distribution in the thickness direction when the inside of the cavity is compressed.

Fig. 3 is a diagram of the connection structure between the cavity and the sensing diaphragm.

Fig. 4 shows the stress distribution of the cavity and the sensing diaphragm after pressure relief simulated by the finite element method.

Fig. 5 is an enlarged view of a portion S in fig. 4.

FIG. 6 is a schematic diagram of an exemplary application of hydrostatic pressure to the inner walls of the chamber.

FIG. 7 is a schematic diagram of an exemplary method of applying pressure to the inner walls of a chamber using mechanical compression.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.

Referring to fig. 1, fig. 1 is a method for controlling post-weld tension of an inductive diaphragm of a capacitive thin film gauge according to some embodiments of the present disclosure, including the following steps:

A1. welding an induction diaphragm at the lower end of a cylindrical cavity of the capacitance type film vacuum gauge; the yield strength of the material of the cavity is lower than that of the material of the sensing diaphragm;

A2. and after pressure is applied to the inner wall of the cavity, unloading the pressure, so that the inner part of the cavity wall of the cavity, the outer part of the cavity wall of the cavity and the sensing diaphragm are respectively in a plastic deformation state, an elastic deformation state and an elastic tensioning state when the pressure is applied, and the sensing diaphragm after pressure unloading has required tensioning force.

In practical application, referring to fig. 2, when the inner side of the thick-walled cylinder is subjected to pressure, the stress on the cylinder wall is gradually reduced from inside to outside, wherein the innermost stressMaximum, outermost stressAnd minimum. When the pressure on the inner side of the thick-wall cylinder is large enough to enable the stress on the inner side part of the thick-wall cylinder to reach the yield strength, and the stress on the outer side part of the thick-wall cylinder does not reach the yield strength, the inner side of the thick-wall cylinder generates plastic deformation, the outer side of the thick-wall cylinder is still in an elastic deformation state, and after the pressure is removed, the plastic deformation on the inner side of the thick-wall cylinder cannot recover. By utilizing the principle, in the method for controlling the post-welding tension of the sensing diaphragm of the capacitive film vacuum gauge, the sensing diaphragm is welded at the lower end of a cavity (the cavity belongs to a thick-walled cylinder), pressure is applied to the inner wall of the cavity, so that the inner part of the cavity wall of the cavity is yielded to generate plastic deformation, the outer part of the cavity wall and the sensing diaphragm are both in an elastic deformation state and cannot generate plastic deformation, the inner part of the cavity generates plastic deformation, and after pressure is unloaded, the sensing diaphragm can keep the required tension due to the constraint of the plastic deformation, and at the moment, the whole structure is still in a stable and reliable state and cannot fail. The tension force required by the sensing diaphragm can be accurately controlled and obtained by adjusting the applied pressure, and the whole process is controllable, reliable and stable. The method for controlling the post-welding tension of the induction diaphragm of the capacitive film vacuum gauge is beneficial to realizing the accurate control of the post-welding tension of the induction diaphragm, thereby being beneficial to improving the product percent of pass.

It should be noted that the "lower end" referred to herein is based on the placement shown in fig. 3, and in practical applications, the lower end may be any end of the cavity.

The connection structure between the cavity and the sensing diaphragm after the step a1 is shown in fig. 3, where a part numbered 2 is the cavity and a part numbered 1 is the sensing diaphragm. The detection cavity of the capacitance type thin film vacuum gauge comprises a cylindrical side wall, an upper wall plate and a lower wall plate which are respectively arranged at the upper end and the lower end of the side wall, a cavity used in the method for controlling the tension of the induction diaphragm of the capacitance type thin film vacuum gauge after welding is a part of the side wall, after the step of the method for controlling the tension of the induction diaphragm of the capacitance type thin film vacuum gauge after welding is completed, the other part of the side wall is required to be connected (connected by welding or other connection modes) at the lower end of the cavity to form an integral side wall, and the upper wall plate and the lower wall plate are arranged at the upper end and the lower end of the side wall by welding or other connection modes.

The materials of the cavity and the sensing diaphragm can be selected according to actual needs, and in fact, the yield strength of the sensing diaphragm is higher than that of the cavity, so that the more the sensing diaphragm is beneficial to ensuring that the sensing diaphragm cannot generate plastic deformation.

Preferably, the material of the cavity is PG 3600 or inconel X600; the material of the sensing diaphragm is inconel X750. The material is selected, so that the yield strength of the sensing diaphragm is higher than that of the cavity, plastic deformation of the sensing diaphragm cannot occur, and meanwhile, due to the fact that the thermal expansion properties of the materials are close, the phenomenon that the tensile force in the sensing diaphragm is changed too much due to too large size change deviation of the cavity and the sensing diaphragm when the cavity expands with heat and contracts with cold can be avoided, and the measurement accuracy of the capacitive film vacuum gauge is guaranteed.

In practical application, for a cylindrical cavity, when the inner side of the cylindrical cavity is subjected to pressure, the stress of the innermost side of the cavity wallAnd outermost stressThe following formula can be used for estimation:

；

；

where P is the pressure experienced inside the chamber (pressure referred to herein in the physical sense) and K is the ratio of the outside diameter to the inside diameter of the chamber. From this formula, it can be seen that the greater K, the stress on the innermost side of the cavity wall of the cavityAnd outermost stressThe larger the deviation is, the easier the effect that the inner part of the cavity is yielding and the outer part is in an elastic deformation state is to implement when the method for controlling the tension of the sensing diaphragm of the capacitance type thin film vacuum gauge after welding is implemented, but the larger the wall thickness of the cavity is, the larger the weight of the capacitance type thin film vacuum gauge finally obtained is.

In some preferred embodiments, the ratio of the outer diameter to the inner diameter of the cavity is 1.2 to 1.4. Within the range, when the inner wall of the cavity is pressed, the stress difference between the inner wall and the outer wall of the cavity is large enough, so that the effects that the inner part of the cavity is buckled and the outer part of the cavity is in an elastic deformation state are easily realized; meanwhile, the wall thickness of the cavity cannot be too large due to the fact that the ratio of the outer diameter to the inner diameter is too large, and the weight of the capacitance type film vacuum gauge is prevented from being too large. More preferably, the ratio of the outer diameter to the inner diameter of the cavity is 1.3, the innermost stressAnd outermost stressThe deviation between them can reach 35%.

It should be noted that, although the effect of generating the required tension on the sensing diaphragm can be achieved by applying pressure to make the inner and outer sides of the cavity both generate plastic deformation when the cavity wall of the cavity is thin, the external dimension error of the cavity is increased, and the generation of unqualified products is also caused, which is not beneficial to the improvement of the product yield.

Preferably, the step of welding the sensing diaphragm to the lower end of the cylindrical cavity of the capacitance thin film vacuum gauge comprises:

tensioning the sensing diaphragm to enable the sensing diaphragm to be in a straight state;

and welding the sensing diaphragm in a straight state at the lower end of the cavity.

By enabling the sensing diaphragm to be in a straight state, the situation that the tension of the sensing diaphragm in each direction in the finally obtained capacitance type film vacuum gauge is uneven due to the fact that the sensing diaphragm after welding has wrinkles can be avoided, and therefore the measurement accuracy of the capacitance type film vacuum gauge is guaranteed. When the induction membrane is tensioned, the pre-tensioning force is only required to be the size which can be obtained by straightening the induction membrane to remove wrinkles through tests in advance.

There are many ways of applying pressure to the inner wall of the chamber, and the particular way of applying pressure is not limited herein.

For example, in some embodiments, step a2 includes:

and applying pressure on the inner wall of the cavity by using a hydrostatic pressure application mode.

In some embodiments, the step of applying pressure to the inner wall of the cavity using hydrostatic pressure application comprises:

the upper end and the lower end of the cavity are respectively covered with an upper sealing cover and a lower sealing cover, so that the cavity, the sensing diaphragm and the upper sealing cover enclose an upper cavity, and the sensing diaphragm and the lower sealing cover enclose a lower cavity; the upper sealing cover is provided with an upper liquid inlet communicated with the upper cavity, and the lower sealing cover is provided with a lower liquid inlet communicated with the lower cavity;

and respectively introducing liquid with the same pressure into the upper cavity and the lower cavity through the upper liquid inlet and the lower liquid inlet, and adjusting the pressure of the liquid so as to apply required pressure on the inner wall of the cavity.

As shown in fig. 6, an upper sealing cover 3 and a lower sealing cover 4 are respectively covered and connected at the upper end and the lower end of a cavity 2, sealing rings 5 are respectively arranged between the upper sealing cover 3 and the cavity 2 and between the lower sealing cover 4 and the cavity 2, wherein the upper sealing cover 3 and the lower sealing cover 4 are connected through a plurality of connecting screws 6, so as to clamp the cavity 2 (actually, the upper sealing cover 3 and the lower sealing cover 4 can also be directly pressed to clamp the cavity 1); then, the liquid can be respectively input from the upper liquid inlet 301 and the lower liquid inlet 401, and the effect of applying pressure on the inner wall of the cavity can be achieved by adjusting the liquid pressure of the liquid, wherein the pressure data to be applied can be determined in advance through calculation and/or experiments, so that the liquid pressure can be adjusted according to the pressure data. The pressure is applied by the mode, the pressure adjustment is convenient, when the pressure condition (namely the pressure to be applied) is changed, the structure of the jig (namely the structure of the upper sealing cover 3, the lower sealing cover 4 and the connecting screw rod 6) is not required to be changed, and the process adjustment cost is low.

In practical applications, the hydraulic pressure application method is not limited to this, for example, the upper end of the cavity may be covered with a sealing cover, the lower end of the cavity is placed on the supporting platform, then the liquid is introduced through the upper liquid inlet of the upper sealing cover, and the hydraulic pressure of the liquid is adjusted, so as to apply the required pressure on the inner wall of the cavity. However, compared with the above method, since the supporting platform needs to be in direct contact with the sensing diaphragm to provide a supporting function, the sensing diaphragm is easily scratched, and thus the measurement accuracy of the capacitance type thin film vacuum gauge is affected.

Wherein, the pressure needed to be exerted can be determined by the following ways:

s1, calculating a first limit load according to the following formula:

；

wherein the content of the first and second substances,in order to be the first limit load,the yield strength of the material of the cavity,is the inner diameter of the cavity body,the outer diameter of the cavity;

s2, calculating a second limit load according to the following formula:

；

wherein the content of the first and second substances,is a second limit load;

s3, when the load is greater than the first limit loadAnd is less than the second limit loadSelecting a plurality of pressure values according to a preset step length in the pressure range, and calculating the residual tension on the sensing diaphragm after applying corresponding pressure in the cavity and unloading the pressure by a finite element analysis method;

and S4, calculating to obtain the pressure to be applied according to the required tension, the pressure values and the corresponding residual tension. For example, the pressure to be applied can be calculated by interpolation; and fitting a calculation formula for calculating the pressure value according to the residual tension according to the pressure values and the corresponding residual tension, and substituting the required tension into the calculation formula to calculate the pressure to be applied.

For another example, in other embodiments, step a2 includes:

and applying pressure on the inner wall of the cavity by using a mechanical pressing mode.

In some embodiments, the step of applying pressure to the inner wall of the cavity using mechanical compression comprises:

the interference mandrel is pressed into the cavity from the upper end of the cavity, thereby applying the required pressure on the inner wall of the cavity.

As shown in fig. 7, the interference mandrel 7 is inserted into the cavity 2 from the opening of the upper end of the cavity 2, so that the inner wall of the cavity 2 is squeezed, and the effect of applying pressure is achieved, wherein the interference of the mandrel 7 (i.e. the deviation of the diameter of the mandrel 7 exceeding the inner diameter of the cavity 2) can be determined in advance according to calculation and/or experiments, so that the pressure applied to the inner wall of the cavity 2 is the required pressure. Wherein, in order to facilitate the insertion of the mandrel 7 into the cavity 2, the lower end of the mandrel 7 is provided with a truncated cone shaped guide portion. The mode is used for pressing, the operation is convenient, and the efficiency is higher.

In practical applications, the mechanical pressing manner is not limited to this, for example, two semicircular arc-shaped plates may be inserted into the cavity, so that the two semicircular arc-shaped plates are attached to the inner wall of the cavity, and then the radial pressing force is applied to the two semicircular arc-shaped plates, so as to apply the required pressure to the inner wall of the cavity.

Wherein the pressing is performed in such a way that the pressure applied to the inner wall of the cavity is related to the interference of the mandrel. The required interference of the mandrel can be determined by:

B1. acquiring a plurality of preset interference magnitude data, and calculating residual tension on the induction diaphragm after inserting a mandrel with corresponding interference magnitude into the cavity and extracting the mandrel by a finite element analysis method;

B2. and calculating the required interference of the mandrel according to the required tension, the plurality of preset interference data and the corresponding residual tension. For example, the required interference of the mandrel can be calculated in an interpolation calculation mode; and fitting a calculation formula for calculating the interference according to the residual tension according to the plurality of preset interference data and the corresponding residual tension, and substituting the required tension into the calculation formula to calculate the required interference of the mandrel.

After the required interference of the mandrel is determined, the mandrel with the required interference is pressed into the cavity from the upper end of the cavity, so that the required pressure is applied to the inner wall of the cavity.

The technical process of the tension control method of the capacitive film vacuum gauge after welding is simulated by adopting a finite element method, wherein the material of the cavity is inconel X600 (solid solution state), the material of the sensing diaphragm is inconel X750, and the target tension is 299 MPa; stress distribution conditions of the cavity and the sensing diaphragm after the pressure is applied and relieved are adjusted and are shown in fig. 4 and 5, stress distribution conditions of the cavity in the radial direction are shown in a rectangular part on the right side in fig. 4, an enlarged view of a part S in fig. 4 is shown in fig. 5, at this time, the inner side of the cavity is subjected to plastic deformation, the outer side of the cavity is in an elastic state, and a tension of 299MPa is kept in the sensing diaphragm, so that the effectiveness of the tension control method of the sensing diaphragm of the capacitance type thin film vacuum gauge after welding can be proved.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.