Pneumatic electromagnetic valve spool press fitting tool and test method

Abstract

The application discloses a kind of pneumatic electromagnetic valve spool press-fit tool and test method, belong to aerospace pneumatic electromagnetic valve assembly technical field.Working tool includes threaded plug, liquid path spring, press cover, pressure lever, protective sleeve, pressure pad, pressure block.Press cover is H-shaped rotary body, its upper inner hole is equipped with protective sleeve and is guided to valve core assembly radially;Pressure lever in the middle stepped hole is tightly pressed to the lower end surface of framework under the action of liquid path spring, to prevent framework from falling out during press-fit;Pressure block lower end surface is provided with recess to avoid baffle sealing surface, and pressure pad is used to press to the upper end ring surface of valve core.The spring pre-tightening force is preset by adjusting the screwing depth of threaded plug, the press-fit force is quantitatively controlled on-line using pressure sensor, and the closing stroke and depth are accurately controlled by pressure pad and adjusting gasket.Reverse load test and helium mass spectroscopy leak detection are carried out after press-fit, to ensure that the closing is tight and air-tight.The application effectively solves the problems that sealing surface is easily damaged and framework is easily dropped out during press-fit, and significantly improves the product assembly quality and sealing reliability.

Description

Technical Field

[0001] This invention relates to the field of aerospace pneumatic solenoid valve assembly and testing technology, specifically to a press-fitting fixture for a pneumatic solenoid valve core assembly and a press-fitting test method based on the fixture. Background Technology

[0002] Pneumatic solenoid valves are critical switching actuators in the fluid control systems of liquid rocket engines, used to control the flow of fluid and enable repeated engine starts and pulse operation. Their opening and closing dynamics and pulse characteristics directly affect engine performance. The sealing quality of the valve core assembly is closely related to core parameters such as the opening pressure and response time of the pneumatic solenoid valve. After sealing, the valve core assembly must meet stringent airtightness requirements. Many factors affect airtightness, primarily including the uniformity of the valve core skeleton's coverage of the valve core after sealing and the surface quality of the valve core sealing surface.

[0003] Currently, press-fit fixtures are commonly used to ensure the sealing performance of valve core assemblies after sealing. However, most existing press-fit fixtures are direct-pressure structures, with the force-applying end of the fixture directly contacting the sealing surface of the valve core. During the press-fitting process, indentations or micro-damage can easily occur on the valve core surface, thereby compromising the integrity of the sealing surface and directly affecting the product's sealing performance. Therefore, there is an urgent need for a dedicated press-fitting fixture and corresponding press-fitting testing method that can avoid damaging the valve core sealing surface while ensuring the quality and fit of the sealing. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a tooling and testing method for pressing a pneumatic solenoid valve core. This tooling does not cause contact damage to the valve core sealing surface during the pressing and closing process, and prevents the frame from being squeezed out, ensuring a tight fit between the valve core and the frame, thereby improving the product's airtightness and pressing pass rate.

[0005] The technical solution adopted in this invention is: a pneumatic solenoid valve core press-fitting fixture, used for press-fitting a valve core assembly including a valve core, a frame, and a baffle, characterized in that: it includes a threaded plug, a hydraulic spring, a pressure sleeve, an adjusting shim, a pressure rod, a protective sleeve, a pressure pad, and a pressure block; the pressure sleeve is a rotating body, with an internal threaded hole at its lower part that mates with the threaded plug, an internal hole at its upper part for accommodating the protective sleeve, and a stepped circular hole in the middle that is smaller at the top and larger at the bottom, the upper sidewall of the stepped circular hole having a conical surface for valve core closing; the pressure rod is slidably placed in the stepped circular hole, its upper end face... The hydraulic spring is installed inside the pressure sleeve, with its upper and lower ends elastically abutting between the pressure rod and the threaded plug, respectively. The protective sleeve is embedded in the inner hole of the upper part of the pressure sleeve, and the inner hole of the protective sleeve is clearance-fitted with the outer circle of the valve core assembly. The pressure block is a stepped columnar shape, consisting of a first large cylinder and a second small cylinder that can extend into the inner hole of the protective sleeve from top to bottom. The lower end face of the second small cylinder has a groove at its center to avoid the upper end of the baffle. The annular area of ​​the lower end face of the second small cylinder is in contact with the upper end face of the valve core to apply pressure to the valve core assembly. The pressure pad is fitted on the second small cylinder of the pressure block.

[0006] Preferably, it also includes an adjusting shim, which is sleeved on the outer periphery of the second small cylinder of the pressure block and is limited between the top surface of the pressure sleeve and the stepped surface of the pressure block, in order to limit the downward stroke of the pressure block.

[0007] Preferably, the conical surface on the pressure sleeve is a 45° conical surface.

[0008] Preferably, the pressure block and the pressure sleeve are made of 1Cr18Ni9Ti stainless steel.

[0009] Preferably, the pressure sleeve is a cylinder with an H-shaped cross-section.

[0010] A method for press-fitting a pneumatic solenoid valve spool using a pneumatic solenoid valve spool press-fitting fixture includes the following steps: S1. Pre-press fitting measurement: Measure the outer diameter and coaxiality of the valve core to confirm compliance with tolerances.

[0011] S2. Assembly and Adjustment: Install the baffle and skeleton into the valve core to form the valve core assembly, and place the assembly into the protective sleeve of the tooling. Adjust the screw-in distance x of the threaded plug, calculate the spring preload according to the formula f=kx, and make the pressure rod press against the lower end face of the skeleton with the preset force.

[0012] S3. Quantitative Press-Fitting: Place the valve core assembly with the tooling under the press, aligning the pressure block, tooling, and press center. Use a pressure sensor to detect the pressure online. Gradually apply pressure to the pressure block through the press. The pressure block transmits the force to the upper end face of the valve core through the pressure pad, pushing the valve core assembly downward along the inner hole of the protective sleeve. This allows the lower end of the valve core to be closed and wrapped at the conical surface of the pressure sleeve. By selecting pressure pads and adjusting shims of different thicknesses, the closing depth and press-fitting stroke can be precisely controlled.

[0013] S4. Check the sealing function: Apply a safety pressure in the reverse direction according to the operating pressure of the valve core assembly, and check whether the skeleton has come out.

[0014] S5. Sealing test: Assemble the valve core assembly, which has been finished and precision machined, into the pilot valve of the pneumatic solenoid valve, introduce helium gas at the specified pressure, and use a helium mass spectrometer leak detector to test the airtightness to ensure that the leakage rate meets the requirements.

[0015] Preferably, in step S2, the preload force f is calculated according to the formula f=kx, where k is the stiffness coefficient of the hydraulic spring, x is the screw-in distance of the threaded plug, and the value of k ranges from 1000 to 3000 N / m.

[0016] Preferably, the final pressing force F in step S3 is calculated based on the elastic modulus, yield strength, contact area and closing stroke of the valve core material, and is gradually calibrated from the initial pressure F0 to F through trial pressing.

[0017] The beneficial effects of this invention are: 1. By using the groove design on the end face of the pressure block to avoid the sealing surface of the baffle, and by using the pressure pad to transmit force, the pressing force is directly applied to the upper ring surface of the valve core, which completely avoids contact damage to the non-metallic sealing surface during the closing process and ensures the quality of the product sealing surface.

[0018] 2. A bottom hydraulic spring and pressure rod are used to apply a continuously adjustable pre-tightening force to the skeleton, which keeps the skeleton and the baffle tightly closed during the closing process. This effectively prevents the skeleton from shifting or coming off due to uneven force, ensuring the uniformity and fit of the wrapping.

[0019] 3. The protective sleeve provides radial constraint and guidance for the clearance fit of the outer circle of the valve core assembly, while increasing the force-bearing area, so that the lower end of the valve core is evenly compressed, ensuring the coaxiality of the closing and the geometric tolerance.

[0020] 4. By combining the pressure pad thickness with the adjusting shim, precise control of the dual force stroke and the closing depth can be achieved, which can ensure that the closing position completely covers the skeleton and prevent the valve core from being radially deformed due to overpressure.

[0021] 5. The test method incorporates online detection and quantification of pressing parameters using pressure sensors, realizing the transformation from experience-based operation to data-driven process, which significantly improves the pressing qualification rate and product performance consistency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the pneumatic solenoid valve core press-fit fixture of the present invention. In the figure: 1-threaded plug, 2-hydraulic spring, 3-pressure sleeve, 4-adjusting shim, 5-pressure rod, 6-valve core assembly, 7-protective sleeve, 8-pressure pad, 9-pressure block. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] like Figure 1 As shown, a pneumatic solenoid valve core pressing fixture mainly consists of a support part and a pressing guide part.

[0025] The support structure consists of a threaded plug 1, a hydraulic spring 2, and a pressure rod 5. The threaded plug 1 is screwed into the internal threaded hole on the bottom surface of the pressure sleeve 3, and its top has a spring mounting groove. The lower end of the hydraulic spring 2 rests in this groove, and its upper end abuts against the lower end face of the pressure rod 5. The pressure rod 5 slides in the stepped circular hole in the middle of the pressure sleeve 3, and its upper end face directly contacts the lower end face of the skeleton in the valve core assembly 6. By rotating the threaded plug 1, the hydraulic spring 2 can be compressed, applying an adjustable upward preload to the pressure rod 5 to ensure that the skeleton of the valve core assembly 6 is always tightly held in place and not pushed downward during the subsequent press-fitting and closing process.

[0026] The press-fit guiding section includes a pressure sleeve 3, a protective sleeve 7, a pressure pad 8, a pressure block 9, and an adjusting shim 4. The pressure sleeve 3 is a cylindrical shape with an H-shaped cross-section; its upper inner hole holds the protective sleeve 7, and its lower part is a threaded hole. The inner hole of the protective sleeve 7 has a precise clearance fit with the outer circle of the valve core assembly 6 to be closed, providing circumferential constraint and vertical guidance for the assembly. The valve core assembly 6 consists of a valve core, a skeleton, and a baffle. The skeleton is located below the baffle, and the valve core is annular, fitted around the baffle and the outer circumference of the skeleton. The upper surface of the baffle is a non-metallic sealing surface. The purpose of closing the opening is to retract the lower end of the valve core inward, tightly covering the skeleton.

[0027] The pressure block 9 is a stepped column, with its upper large-diameter cylinder connected to the press and its lower small-diameter cylinder extending into the protective sleeve 7. A groove is provided in the center of the end face of the small-diameter cylinder to accommodate and completely avoid the upper surface of the baffle, i.e., the sealing surface. An annular pressure pad 8 is fitted onto the small-diameter cylinder of the pressure block 9. The pressing force is evenly transmitted to the upper end of the valve core through the pressure block 9 and pressure pad 8, thus avoiding the sealing surface. An adjusting shim 4 is fitted onto the small-diameter cylinder of the pressure block 9 and sandwiched between the pressure pad 8 and the stepped surface of the pressure block 9. By replacing shims 4 of different thicknesses or numbers, the downward pressing endpoint of the pressure block 9 can be precisely limited to prevent overpressure. The side wall at the upper end of the stepped hole in the middle of the pressure sleeve 3 is machined with a 45° conical surface. When the valve core is pushed downwards, the lower end of the valve core is forced inward at this conical surface, completing the wrapping of the skeleton.

[0028] In the press-fitting fixture, key load-bearing components such as the pressure block 9 and the pressure sleeve 3 are all made of 1Cr18Ni9Ti stainless steel, which ensures the reliability of mechanical transmission and the service life of the fixture.

[0029] The specific flow of the press-fitting test method for the spool of the pneumatic solenoid valve of the present invention is as follows: Measurement before press-fitting: a digital display micrometer is used to measure the outer circles of the inlet spool and the outlet spool. Two diagonal directions are selected on each spool, and measurements are taken at the upper, middle and lower positions of each diagonal, with a total of six outer diameter data recorded. The maximum difference between the three data on the same diagonal is calculated, and the coaxiality shall meet the design requirements.

[0030] Assembly and press-fitting: put the baffle into the spool, then insert the framework into the spool, and assemble into a spool assembly 6. Place the spool assembly 6 into the protective sleeve 7 of the tooling, and place the whole on the platform of the press. Adjust the screwing distance x of the threaded plug 1, calculate and set the required spring pre-tightening force according to the spring stiffness coefficient k by f=kx, so as to ensure that the framework fits. For spool assemblies with different leakage rate requirements, the liquid path spring 2 with different stiffness coefficients can be replaced, and generally the value range of k is 1000~3000 N / m.

[0031] Trial press-fitting: reset the pressure sensor to zero, set a small initial press-fitting force F0, and operate the press to slowly apply pressure through the pressing block 9. Discharge the part to check the appearance and diameter, and use a standard valve seat to check the radial deformation and movement flexibility of the spool assembly. According to parameters such as the elastic modulus, yield strength, contact area and closing stroke of the spool material, the final quantitative press-fitting parameter F for this batch of spool assemblies 6 is adjusted and determined step by step. During formal press-fitting, the on-line pressure sensor feeds back the pressure value in real time to ensure that the closing force of each product conforms to the value F. The closing depth is locked by reasonably configuring the thickness of the pressure pad 8 and adjusting the gasket 4.

[0032] Inspection of closing functionality: calculate the bearing force N=P×S according to the working pressure P of the part and the pressure-bearing area S, take a safety factor n, and apply a pressure test to the press-fitted assembly with a reverse force N'=nN. Visual inspection confirms that the metal framework does not fall out at all, which proves that the closing is firm and reliable.

[0033] After the quantitative press-fitting indexes are completed, all formal parts are press-fitted according to the determined parameter F. After press-fitting, the parts are discharged for inspection: the appearance is free of damage, the change of outer diameter measured by the micrometer is within 0.002mm, the flexibility checked with the valve seat is intact, and the closing position and wrapping degree meet the standards by visual inspection.

[0034] Sealing test: after press-fitting, the non-metallic sealing surface of the spool assembly needs to be turned and ground. After meeting the requirements of flatness and roughness, it is returned to the test workshop. Match the inlet spool assembly with the outlet spool assembly and install them into the pilot valve part of the pneumatic solenoid valve. Blow off before connecting the pipeline to ensure no excess substances. Helium with pressure P is introduced into the inlet of the air path channel of the pneumatic valve, and detection is carried out at the exhaust port with a helium mass spectrometer leak detector. It is required that the measured leakage rate is not greater than Q Pa·m³ / s, and the air tightness is determined to be qualified.

[0035] Through the above-mentioned tooling and methods, the present invention systematically solves the problems of easy damage to the sealing surface, easy dislodgement of the skeleton, and poor dimensional consistency in valve core press-fitting, providing a guarantee for the high-reliability assembly of pneumatic solenoid valves for liquid rocket engines.

[0036] The above describes specific embodiments of the present invention and the technical principles employed. Any modifications or equivalent transformations based on the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A pneumatic solenoid valve core press-fitting fixture, used for press-fitting a valve core assembly including a valve core, a frame, and a baffle, characterized in that: The system includes a threaded plug, a hydraulic spring, a pressure sleeve, an adjusting shim, a pressure rod, a protective sleeve, a pressure pad, and a pressure block. The pressure sleeve is a rotating body with an internal threaded hole at its lower part that mates with the threaded plug, an internal hole at its upper part for accommodating the protective sleeve, and a stepped circular hole in its middle part (smaller at the top and larger at the bottom). The upper sidewall of the stepped circular hole has a conical surface for the valve core to close. The pressure rod is slidably placed within the stepped circular hole, and its upper end face abuts against the lower end face of the frame. The hydraulic spring is installed inside the pressure sleeve, and its upper and lower ends... The ends are elastically held between the pressure rod and the threaded plug respectively; the protective sleeve is embedded in the inner hole of the upper part of the pressure sleeve, and the inner hole of the protective sleeve is clearance-fitted with the outer circle of the valve core assembly; the pressure block is stepped columnar, consisting of a first large cylinder and a second small cylinder that can extend into the inner hole of the protective sleeve from top to bottom. The lower end face of the second small cylinder is provided with a groove at the center to avoid the upper end of the baffle. The annular area of ​​the lower end face of the second small cylinder is in contact with the upper end face of the valve core to apply pressure to the valve core assembly; the pressure pad is fitted on the second small cylinder of the pressure block.

2. The pneumatic solenoid valve core press-fitting fixture according to claim 1, characterized in that: It also includes an adjusting shim, which is sleeved on the outer periphery of the second small cylinder of the pressure block and is limited between the top surface of the pressure sleeve and the stepped surface of the pressure block, in order to limit the downward stroke of the pressure block.

3. The pneumatic solenoid valve core press-fitting fixture according to claim 1, characterized in that: The conical surface on the pressure sleeve is a 45° conical surface.

4. The pneumatic solenoid valve core press-fitting fixture according to claim 1, characterized in that: The pressure block and pressure sleeve are made of 1Cr18Ni9Ti stainless steel.

5. The pneumatic solenoid valve core press-fitting fixture according to claim 1, characterized in that: The pressure sleeve is a cylinder with an H-shaped cross-section.

6. A method for press-fitting a pneumatic solenoid valve core based on the tooling described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Install the baffle and skeleton into the valve core to form the valve core assembly, and measure the outer diameter and coaxiality of the valve core; S2. Place the valve core assembly into the protective sleeve of the tooling, adjust the screwing distance of the threaded plug, and apply a preset preload to the lower end face of the skeleton through the hydraulic spring and pressure rod to tighten the skeleton; S3. After the press and tooling are aligned, use the press to apply downward pressure to the upper end face of the valve core through the pressure block and pressure pad, push the valve core down along the inner hole of the protective sleeve, and complete the closing and wrapping of the valve core to the skeleton at the conical surface of the pressure sleeve; During the pressing process, the pressing force is detected and controlled by the online pressure sensor, and the closing depth and pressing stroke are controlled by selecting and configuring the thickness of the pressure pad and adjusting the shims; S4. After press-fitting, remove the valve core assembly, check its appearance, dimensions and movement flexibility, and perform a reverse load test to check whether the skeleton has come off; S5. Assemble the precision-machined valve core assembly into the pneumatic solenoid valve, introduce helium gas at the specified pressure, and use a helium mass spectrometer leak detector to test the sealing leakage rate to determine whether it is qualified.

7. The method for press-fitting the valve core of a pneumatic solenoid valve according to claim 6, characterized in that: In step S2, the preload force f is calculated according to the formula f=kx, where k is the stiffness coefficient of the hydraulic spring, x is the screw-in distance of the threaded plug, and the value of k ranges from 1000 to 3000 N / m.

8. The method for press-fitting the valve core of a pneumatic solenoid valve according to claim 6, characterized in that: In step S3, the final pressing force F is calculated based on the elastic modulus, yield strength, contact area, and closing stroke of the valve core material, and is gradually calibrated from the initial pressure F0 to F through trial pressing.

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