Adjustable vacuum diaphragm group for automatic starter and its manufacturing method

Abstract

The application discloses an adjustable vacuum diaphragm pump group for automatic starter and a manufacturing method thereof, and relates to the field of fuel systems. The vacuum diaphragm pump group comprises a plurality of identical vacuum diaphragm pumps. Each vacuum diaphragm pump comprises two fixedly connected diaphragms which are identical in structure and are respectively an upper diaphragm and a lower diaphragm. The surface of the upper diaphragm is provided with a stepped disc, and the surface of the lower diaphragm is provided with a flat disc. The stepped disc comprises an upper step and a lower step. The upper step is located on the surface of the lower step, and the lower step is located on the surface of the upper diaphragm. The diameter of the upper step is smaller than that of the lower step. The flat disc is a concentric ring structure. The inner hole diameter of the flat disc is the same as the diameter of the upper step of the stepped disc. The vacuum diaphragm pumps are self-positioned through the flat disc and the stepped disc. The application utilizes material characteristics, gas compensation in the cavity and profile structure design to obtain higher sensing sensitivity, temperature resistance, adjustment stability under a large temperature difference and economy, and improves the reliability of the vacuum diaphragm pump group for automatic starter.

Description

Technical Field

[0001] This invention relates to the field of fuel systems, and more particularly to an adjustable vacuum diaphragm assembly for an automatic starter and its manufacturing method. Background Technology

[0002] As one of the most critical operating systems of an aircraft engine, the proper functioning of the fuel system directly determines the engine's performance and reliability. The fuel regulator, a core accessory of the fuel system, not only has the basic function of directly regulating the fuel flow to the combustion chamber, but more importantly, it controls the minimum fuel supply required for engine start-up by adjusting the valve opening. This ensures that the engine receives sufficient fuel to complete the start-up process at different temperatures, altitudes, and even in the air. Therefore, the minimum starting fuel supply is a safety parameter, and compared to the economy and performance of metered flow regulation, the minimum starting fuel supply is more important.

[0003] Traditional aero engines employ mechanical-hydraulic control systems that regulate the engine's starting fuel supply solely based on the compressor outlet pressure. While this system functions well on the ground, controlling the starting process is relatively difficult, primarily due to lower air pressure at high altitudes and a reduced required starting fuel supply. This results in a rich fuel supply during high-altitude starts, leading to a narrow starting envelope, combustion chamber temperatures exceeding upper limits, and long intervals between engine shutdown and restart. Therefore, new aero engines incorporate an automatic starter device in their fuel regulator designs. This device uses a high-altitude air pressure correction diaphragm assembly as a sensitive element. By sensing the air pressure at the engine's altitude, it adaptively adjusts the axial dimensions of the diaphragm assembly to compensate for altitude changes. When altitude increases and ambient pressure decreases, the diaphragm assembly expands, generating strain. This strain then applies tension to the nozzle baffle assembly via a lever principle, increasing valve opening, increasing fuel return, and decreasing fuel supply, thus eliminating the rich fuel condition and improving fuel delivery.

[0004] The working principle of the diaphragm assembly is to sense external atmospheric pressure and temperature, and adjust the height H of the diaphragm itself to control the opening of the valve through levers and springs. Therefore, the diaphragm assembly has extremely high requirements for temperature resistance, pressure sensitivity, and temperature compensation. In addition to considering the basic pressure-displacement characteristic curve relationship of the vacuum diaphragm assembly, the development of this type of vacuum diaphragm assembly also requires that its structure adapt to the high-temperature and high-vibration environment of the engine. Furthermore, the vacuum diaphragm assembly needs to maintain a relatively consistent basic height and characteristic curve under high-temperature, room-temperature, and low-temperature environments. Therefore, the development of this type of vacuum diaphragm assembly is extremely complex.

[0005] Traditional vacuum diaphragm boxes typically use high-elasticity metal materials such as QBe1.9 and 3J53 to make diaphragms as elastic sensitive elements. Their main drawback is that the elastic performance stability of such materials can only be maintained at relatively low temperatures, generally -55℃ to 120℃, which cannot adapt to the harsh high-temperature environment of 180℃ to 215℃ in aero engines.

[0006] In the production of traditional vacuum diaphragm units, the vacuum level of the inner cavity is generally 0 Pa or close to 0 Pa. Under low or high temperature environments, the initial height and pressure-displacement characteristic curves of the diaphragm unit will deviate due to the influence of the temperature coefficient of elastic modulus of the raw materials, resulting in a decrease in its adjustment accuracy under large temperature differences.

[0007] Traditional vacuum diaphragm assembly typically uses a welded structure, with the diaphragm being a one-piece, non-repairable component. When the diaphragm assembly ages after long-term use, it directly affects the diaphragm's pressure-displacement characteristics. When the characteristic curve exceeds the engine envelope, the diaphragm assembly cannot be adjusted and must be scrapped, increasing economic costs.

[0008] Traditional vacuum diaphragm boxes are generally made of 2 or 4 corrugated diaphragms welded together. Their working displacement stroke is generally about 2.5 mm, corresponding to a pressure range of 1400 mmHg to 1900 mmHg. They have low sensitivity to ambient air pressure and low adjustment accuracy. Summary of the Invention

[0009] To address the aforementioned shortcomings in the prior art, this invention provides an adjustable vacuum diaphragm assembly for an automatic starter and its manufacturing method, which solves the problems of existing diaphragm assemblies being unable to adjust the diaphragm components, unable to adapt to the high-temperature working environment of aero engines, high cost, and low adjustment accuracy.

[0010] To achieve the aforementioned objectives, the present invention employs the following technical solution: an adjustable vacuum diaphragm box assembly for an automatic starter, comprising multiple identical vacuum diaphragm boxes. Each vacuum diaphragm box includes two structurally identical diaphragms fixedly connected, namely an upper diaphragm and a lower diaphragm. The surface of the upper diaphragm is provided with a stepped circular plate, and the surface of the lower diaphragm is provided with a flat circular plate. The stepped circular plate includes an upper step and a lower step, with the upper step located on the surface of the lower step and the lower step located on the surface of the upper diaphragm. The diameter of the upper step is smaller than the diameter of the lower step. The flat circular plate has a concentric ring structure, and the inner diameter of the flat circular plate is the same as the diameter of the upper step of the stepped circular plate. The vacuum diaphragm boxes are self-positioned through the flat circular plate and the stepped circular plate.

[0011] The present invention also provides a method for manufacturing an adjustable vacuum diaphragm assembly for an automatic starter, comprising:

[0012] High-temperature resistant metals are selected as the raw materials for the diaphragm based on the operating temperature of the vacuum diaphragm assembly.

[0013] Determine the outer diameter and total height of the vacuum diaphragm assembly, as well as the number of individual vacuum diaphragms, based on the installation interface of the vacuum diaphragm assembly.

[0014] Calculate the dimensions of the diaphragm, flat disc, and stepped disc;

[0015] The corresponding sizes of films, flat circular films, and stepped circular films are processed using molding dies;

[0016] The amount of compensation gas is calculated based on the ambient temperature of the vacuum diaphragm assembly and the raw materials of the diaphragm.

[0017] Weld the vacuum diaphragm according to the compensation gas volume and vacuum diaphragm structure;

[0018] The vacuum membrane box is assembled and welded to obtain a vacuum membrane box assembly.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. By using high-temperature resistant materials as diaphragms, it can adapt to the harsh high-temperature environment of aero engines. At the same time, by evaluating the compensation gas content in the vacuum diaphragm cavity, the output stability of the vacuum diaphragm at different temperatures is improved, the full-temperature error of the vacuum diaphragm is reduced, and the full-temperature accuracy of the vacuum diaphragm assembly is improved.

[0021] 2. By using multiple vacuum diaphragm boxes of the same specifications to form a self-positioning structure and stacking them to form a vacuum diaphragm box assembly, the number of vacuum diaphragm boxes can be adjusted to adapt to the actual installation requirements of the system, improve displacement output, enhance the adjustability of the vacuum diaphragm box assembly, flexibly adjust the height and characteristic indicators of the entire vacuum diaphragm box assembly, improve the sensitivity of the vacuum diaphragm box assembly product, and facilitate the serialization design of the vacuum diaphragm box assembly; at the same time, any vacuum diaphragm box can be replaced to ensure the characteristics of the vacuum diaphragm box assembly, achieve the purpose of rapid repair, and significantly reduce the maintenance and repair costs of the diaphragm box assembly. Attached Figure Description

[0022] Figure 1 A schematic diagram of the diaphragm structure provided for the embodiment;

[0023] Figure 2 A schematic diagram of the flat circular plate structure provided in the embodiment;

[0024] Figure 3 A schematic diagram of the stepped circular plate structure provided in the embodiment;

[0025] Figure 4 A schematic diagram of a single vacuum diaphragm box structure provided for an embodiment;

[0026] Figure 5 This is a schematic diagram of the vacuum membrane box assembly structure provided for an embodiment. Detailed Implementation

[0027] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0028] In one embodiment of the present invention, the automatic starter vacuum diaphragm assembly required for a certain engine is applied in ground and high-altitude environments. The working environment is subject to atmospheric pressure, the installation temperature range is -60℃ to 215℃, the maximum altitude tolerance is -500 to 30000m, the long-term working environment is -400m to 15000m, the working displacement is 5±0.5mm, and the outer diameter of the vacuum diaphragm assembly is... The membrane assembly height is φ51mm. The diameter of the vacuum membrane box must be greater than or equal to φ30mm, and the height must be less than or equal to 24mm. The diameter is 20mm ± 1mm.

[0029] The diaphragm material in the automatic starter diaphragm assembly must possess good elasticity within an ambient and medium temperature range of -55℃ to +215℃. Therefore, this embodiment selects 3J1 as the diaphragm material (materials such as 3J1, 3J21, 3J32, 30Cr13, 05Cr17Ni4Cu5Nb, 0Cr15Ni5Cu2Ti, and 07Cr15Ni7Mo2Al can be selected according to specific requirements). The long-term working environment of this required vacuum diaphragm assembly is -400m to 15000m, which translates to a pressure range of 13.33kPa to 106.6kPa (absolute pressure). The corresponding working pressure difference range is P: P = 106.6 - 13.33 = 93.31kPa.

[0030] Based on four individual diaphragm cells, the mating end face height of a single vacuum diaphragm cell (the mating end face height is the value obtained by subtracting the height of the upper step of the stepped disc from the total height of the diaphragm cell) is: ;

[0031] Select thickness Calculate the outer diameter of the diaphragm based on the C-ring. :

[0032] ;

[0033] Calculate the working diameter of the diaphragm : ;

[0034] The requirements are met.

[0035] Calculate the height of the outer corrugation of the diaphragm. :

[0036] Rounded down to 1.6 mm .

[0037] The thickness of the diaphragm is calculated based on the pressure-displacement characteristics required by the diaphragm capsule. The expression for the pressure-displacement characteristic relationship required by the diaphragm is:

[0038]

[0039] in, This represents the uniformly distributed force borne by a single diaphragm. Indicates the elastic modulus of the diaphragm material. Indicates the pressure of a single diaphragm Displacement value below, , All are constant coefficients;

[0040] The membrane thickness was calculated to be 0.165. mm The overall displacement of the membrane assembly is 5 ± 0.5. mm Take the median value of 5 mm The displacement requirement for a single membrane cell is 1.25. mm Displacement value of a single diaphragm W The requirement is 0.625. mm .

[0041] Based on the above parameters, a film of the corresponding size is processed using a molding die, such as... Figure 1 As shown.

[0042] Calculate the thickness of the flat circular plate :

[0043] When the coefficient is 0.4, ;

[0044] Calculate the outer diameter of the flat circular plate :

[0045] Rounded down to 16 mm The diameter of the central plane of the diaphragm Take 18 mm ;

[0046] Calculate the inner hole size of the flat circular plate : .

[0047] Based on the above parameters, a flat circular piece of the corresponding size is processed using a molding die, such as... Figure 2 As shown.

[0048] Calculate the dimensions of the stepped disc and the height of the lower step. The diameter of the lower step of the stepped disc is The diameter of the upper step of the stepped disc is ; Calculate the height of the upper step of the stepped disc: .

[0049] Based on the above parameters, a stepped circular piece of the corresponding size is processed using a molding die, such as... Figure 3 As shown.

[0050] A certain amount of gas can be sealed inside the vacuum diaphragm box during the welding process. The amount of compensation gas is calculated based on the ambient temperature of the vacuum diaphragm box assembly and the raw materials of the diaphragm. The calculation formula is as follows:

[0051]

[0052] Substituting the relevant parameters into the above formula, the amount of gas to be sealed is calculated to be: n≈4.194×10 -5 mol.

[0053] The obtained membrane, flat circular plate, and stepped circular plate are welded together to obtain a single vacuum membrane box, as shown below. Figure 4 As shown.

[0054] Four vacuum membrane boxes were manufactured according to requirements and assembled to obtain a vacuum membrane box assembly consisting of four vacuum membrane boxes, such as... Figure 5 As shown, the vacuum diaphragm box includes two identical diaphragms fixedly connected, namely an upper diaphragm and a lower diaphragm. The upper and lower diaphragms are connected by electron beam welding or laser welding. To protect the weld seam and improve product safety, a C-ring is provided at the connection between the upper and lower diaphragms. The diaphragm has a concentric corrugated structure with a symmetrical cross-section, consisting of a flat edge, an outer arc corrugation, two or three sinusoidal corrugations, and a central plane from the outside to the inside. A stepped circular piece and a flat circular piece are located at the central plane. The length of the flat edge is 15% of the entire diaphragm. The surface of the upper diaphragm has a stepped circular piece, and the surface of the lower diaphragm has a flat circular piece. The stepped circular piece includes an upper step and a lower step, with the upper step located on the surface of the lower step and the lower step located on the surface of the upper diaphragm. The diameter of the upper step is smaller than the diameter of the lower step. The diaphragm is connected to the flat circular piece and to the stepped circular piece using resistance spot welding technology. The flat circular plate has a concentric ring structure, and the inner diameter of the flat circular plate is the same as the upper step diameter of the stepped circular plate; the vacuum membrane boxes are self-positioned through the flat circular plate and the stepped circular plate.

[0055] Measurements showed that the total height of the vacuum membrane box assembly produced in this embodiment was... =20.13mm. Membrane assembly outer diameter. =φ51.3mm. The overall performance of the diaphragm assembly (at room temperature) is: under a pressure difference of p=93.3kPa, the diaphragm displacement value W=4.86mm; the temperature compensation of the diaphragm assembly at high temperatures is... =-0.23mm, accounting for 4.75% of the total displacement of the membrane box, which is consistent with the 5% compensation required for high temperature expansion, and meets the design requirements.

[0056] If any vacuum diaphragm box in the vacuum diaphragm box assembly shows signs of aging, damage, or other malfunctions after prolonged use, it can be removed from the assembly for adjustment or replacement, preventing more serious equipment failures and reducing maintenance costs and downtime. Furthermore, after removing the faulty diaphragm box, the vacuum diaphragm box assembly can be adjusted according to actual needs, such as adding new diaphragm boxes or reconfiguring the assembly layout. This modular design makes future system expansion or upgrades more convenient, allowing for flexible addition of new diaphragm boxes or components, extending equipment lifespan, reducing maintenance costs, and enhancing system flexibility and scalability.

[0057] In summary, the novel structure of this invention enables adjustable characteristics of the diaphragm assembly, significantly improving the pressure sensing sensitivity of the diaphragm assembly and achieving a displacement output of over 5mm per unit standard atmospheric pressure. The use of a circular arc outer corrugation + sinusoidal corrugation surface design ensures the stability of the diaphragm itself while further reducing the nonlinearity error of the diaphragm, thus improving the testing accuracy of the diaphragm pressure p-displacement w across the entire pressure range. The temperature compensation calculation formula accurately assesses the gas compensation amount of the vacuum diaphragm, reducing the full-temperature testing error caused by the temperature coefficient of elastic modulus of the diaphragm material, and improving the full-temperature testing accuracy of the vacuum diaphragm.

Claims

1. An adjustable vacuum bellows pack for an automatic starter comprising a plurality of identical vacuum bellows, characterized in that, The vacuum membrane box comprises two fixedly connected membrane sheets of the same structure, namely an upper membrane sheet and a lower membrane sheet; the surface of the upper membrane sheet is provided with a stepped disc, and the surface of the lower membrane sheet is provided with a flat disc; the stepped disc comprises an upper step and a lower step, the upper step is located on the surface of the lower step, and the lower step is located on the surface of the upper membrane sheet; the diameter of the upper step is smaller than that of the lower step; the flat disc is a concentric circular ring structure, and the inner hole diameter of the flat disc is the same as the diameter of the upper step of the stepped disc; the flat disc and the stepped disc are self-positioned between the vacuum membrane boxes.

2. An adjustable vacuum diaphragm group for an automatic starter according to claim 1, characterized in that, The upper membrane sheet and the lower membrane sheet of the vacuum membrane box are connected by electron beam welding or laser welding.

3. An adjustable vacuum diaphragm group for an automatic starter according to claim 1, characterized in that, A C-shaped ring is arranged at the connection between the upper membrane sheet and the lower membrane sheet in the vacuum membrane box.

4. An adjustable vacuum diaphragm group for an automatic starter according to claim 1, characterized in that, The membrane sheet is a concentric circular corrugated structure, which is a left-right symmetrical structure, and comprises, from outside to inside, a flat edge, a circular arc outer corrugation, two or three sine corrugations and a central plane; the stepped disc and the flat disc are located at the central plane; the length of the flat edge is 15% of the entire membrane sheet; the outer diameter of the flat disc is 90% of the diameter of the central plane; and the inner hole diameter of the flat disc is half of the outer diameter of the flat disc.

5. An adjustable vacuum diaphragm group for an automatic starter according to claim 1, characterized in that, The outer diameter of the vacuum membrane box is greater than or equal to φ30 mm, and the height is less than or equal to 24 mm.

6. An adjustable vacuum diaphragm group for an automatic starter according to claim 1, characterized in that, The membrane sheet and the flat disc, and the membrane sheet and the stepped disc are connected by resistance spot welding technology.

7. A method of making an adjustable vacuum envelope group for an automatic starter according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: According to the use environment temperature of the vacuum membrane box group, a high-temperature-resistant metal is selected as the raw material of the membrane sheet; According to the mounting interface of the vacuum membrane box group, the outer diameter and total height of the vacuum membrane box group and the number of single vacuum membrane boxes are determined; The sizes of the membrane sheet, the flat disc and the stepped disc are calculated; The membrane sheet, the flat disc and the stepped disc of corresponding sizes are processed by using a forming die; According to the use environment temperature of the vacuum membrane box group and the raw material of the membrane sheet, the amount of compensation gas is calculated; The vacuum membrane box is welded according to the amount of compensation gas and the structure of the vacuum membrane box; The vacuum membrane box group is obtained by assembling the welded vacuum membrane box.

8. The method of claim 7, wherein, The calculation of the size of the membrane sheet is specifically as follows: Calculating the mating end face height of a single vacuum bellows whose expression is wherein, is the total height of the vacuum membrane cassette set, is the number of individual vacuum membrane cassettes; Computing the outer diameter dimension of a diaphragm whose expression is: wherein is the vacuum bell outside diameter dimension, is the C-ring thickness; Calculating the working diameter of a diaphragm whose expression is: ； The working diameter of the diaphragm needs to meet: ; Computing the outer arcuate corrugation height of a diaphragm whose expression is: ； The thickness of the diaphragm is calculated according to the pressure-displacement characteristic relationship of the capsule The expression of the pressure-displacement characteristic relationship of the capsule is wherein, represents the uniform force on the individual diaphragm, represents the modulus of elasticity of the diaphragm material, represents the displacement value of the individual diaphragm under pressure , , are constant coefficients; The total height of the vacuum membrane box group, the number of single vacuum membrane boxes, the outer diameter of the vacuum membrane box and the thickness of the C-shaped ring are set by the user according to requirements.

9. The method of claim 8, wherein, The calculation of the sizes of the flat disc and the stepped disc is specifically as follows: Calculating the thickness of a flat round tablet whose expression is: ； Computing the outer diameter dimension of a flat round tablet whose expression is: wherein represents the diameter of the diaphragm center plane; Computing the inner hole size of a flat round tablet whose expression is: ； Computing the upper step height of a stepped wafer whose expression is: wherein is the lower step height of the stepped wafer, ; The height of the lower step of the stepped disc is equal to the thickness of the flat disc; and the height of the upper step of the stepped disc is 95% of the height of the lower step of the stepped disc; The diameter of the central plane of the membrane sheet is set by the user according to requirements.

10. The method of claim 7, wherein, The calculation formula of the amount of compensation gas is as follows: wherein, represents the number of moles of compensation gas, is the pressure change amount under the temperature difference, is the inner cavity volume of a single vacuum film cartridge, is the ideal gas parameter, is the reference temperature, is the working temperature.

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