Gas filling and recovery device and filling and recovery method for air tightness detection

Abstract

The present invention relates to a gas filling and recovery device and a filling and recovery method for air tightness testing. The gas filling and recovery device includes a pre-vacuum unit, a filling unit, a gas recovery unit, an exhaust gas treatment unit and a main control circuit. The gas outlet of the workpiece to be tested is connected to the air inlet of the pre-vacuum unit. The gas outlet of the pre-vacuum unit is connected to the air inlet of the workpiece to be tested via the gas recovery unit, the filling unit, and the gas recovery unit. The pre-vacuum unit, the filling unit, and the gas recovery unit are each connected to the exhaust gas treatment unit. The filling and recovery method is as follows: pre-vacuum the workpiece, the filling unit fills the gas in the tracer gas cylinder into the workpiece, and the workpiece is tested for air tightness. The pre-vacuum unit extracts the gas from the workpiece and sends it to the gas recovery unit for recycling and storage. The recovered gas that has been treated to meet the requirements is filled into the next workpiece through the filling unit for air tightness testing. The present invention can recycle and reuse the exhaust gas, reduce costs, reduce pollution, and improve safety.

Description

Technical Field

[0001] The present invention relates to the technical field of air tightness detection, and in particular to a gas filling and recovery device and a filling and recovery method for air tightness detection. Background Art

[0002] With the advancement of technology, the airtightness requirements of some products, devices, and equipment are becoming increasingly stringent. Therefore, airtightness testing has gradually shifted from traditional water and pressure testing to gas tracer testing. Gas tracer testing not only accurately locates leaks in devices but also quantitatively analyzes their size, particularly for leaks less than 1mm. Gas tracer testing generally uses helium or a nitrogen-hydrogen mixture as the tracer gas. Helium has limited storage capacity and is relatively expensive. A nitrogen-hydrogen mixture, typically consisting of 5% hydrogen and 95% nitrogen, offers lower cost and higher accuracy. Therefore, nitrogen-hydrogen mixtures are currently the primary tracer gas used for industrial airtightness testing. During gas tracer testing, tracer gas is injected into the device under test and maintained at a certain pressure based on the required accuracy. After testing is complete, the gas inside the workpiece must be exhausted, resulting in exhaust pollution. In particular, hydrogen concentrations reaching a certain level can easily cause fires and explosions. When the number of workpieces to be inspected is large or the workpieces are large in size, a larger volume of filling gas is required, and the volume of exhaust gas discharged also increases, which not only causes a large amount of tracer gas to be lost in vain, resulting in waste, but also greatly increases safety hazards. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a gas filling and recovery device and a filling and recovery method for air tightness testing, which can automatically complete the filling and pressure maintenance of the workpiece to be inspected, and can also recycle and reuse the exhaust gas discharged after the workpiece completes the air tightness testing. It not only reduces the cost of air tightness testing of the workpiece and reduces waste, but also reduces exhaust gas pollution and improves the safety of on-site testing.

[0004] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions: The gas filling and recovery device for air tightness detection of the present invention includes a pre-vacuum unit, a filling unit, a gas recovery unit and a tail gas treatment unit and a main control circuit that controls the operation of the pre-vacuum unit, the filling unit and the gas recovery unit respectively. The air outlet of the workpiece to be detected is connected to the air inlet of the pre-vacuum unit, the air outlet of the pre-vacuum unit is connected to the air inlet of the tail gas treatment unit on one path, and is connected to the air inlet of the gas recovery unit on the other path. The air outlet of the gas recovery unit is connected to the air inlet of the tail gas treatment unit on one path, and is connected to the air inlet of the filling unit on the other path. The air outlet of the filling unit is connected to the air inlet of the workpiece to be detected on one path, and is connected to the air inlet of the tail gas treatment unit on the other path. The pre-vacuum unit evacuates the workpiece to be inspected. The extracted gas is purified by the tail gas treatment unit and discharged into the air. The filling unit fills the workpiece with a tracer gas (a nitrogen-hydrogen mixture with a hydrogen concentration of 5%) at a certain pressure and maintains the pressure according to the command of the main control circuit. During the pressure maintenance process, the workpiece is scanned by an airtightness leak detector for airtightness testing to find the leak point. After the airtightness test is completed, the pre-vacuum unit extracts the gas in the workpiece to the gas recovery unit for recovery and storage. When the next workpiece is next, the pre-vacuum unit evacuates the workpiece again. The gas recovery unit processes the recovered gas so that its hydrogen concentration meets the requirements of the airtightness test. The gas is then input into the workpiece through the filling unit for airtightness testing. This cycle is repeated to complete gas filling, airtightness testing, and gas recovery for multiple workpieces. The entire process of the present invention is completed automatically. The main control circuit controls the process according to the set number of workpieces to be inspected, the workpiece volume, the workpiece filling pressure and the workpiece pressure holding time, as well as the operating parameters measured in real time, to achieve gas filling and gas recovery. The present invention can not only automatically complete the filling and pressure maintenance of the workpiece to be inspected, but also recycle and reuse the tail gas discharged after the workpiece completes the air tightness inspection, which not only reduces the cost of the workpiece air tightness inspection and reduces waste, but also reduces tail gas pollution and improves the safety of on-site inspection.

[0005] Preferably, the pre-vacuum unit includes a first air valve, a first pressure gauge, a first vacuum pump, and a first three-way solenoid valve. The inlet of the first air valve is connected to the air outlet of the workpiece to be inspected, the outlet of the first air valve is connected to the inlet of the first vacuum pump via the first pressure gauge, the outlet of the first vacuum pump is connected to the common port of the first three-way solenoid valve, the first port and the second port of the first three-way solenoid valve are respectively connected to the air inlet of the gas recovery unit and the air inlet of the exhaust gas treatment unit, and the first air valve, the first pressure gauge, the first vacuum pump, and the first three-way solenoid valve are respectively electrically connected to the main control circuit. The air pressure value measured by the first pressure gauge is transmitted to the main control circuit, and the main control circuit controls the start and stop of the first vacuum pump and the connection direction of the first three-way solenoid valve. The pre-vacuum unit works, the first air valve opens, the first vacuum pump starts, and the gas in the workpiece is extracted. When it is not recycled, it is sent to the tail gas treatment unit. When it is recycled, it is sent to the gas recovery unit. The indication of the first pressure gauge is the air pressure in the workpiece. Until the indication of the first pressure gauge reaches -0.5MPa, the vacuuming is completed, the first air valve is closed, and the first vacuum pump stops working.

[0006] Preferably, the filling unit includes a pressure reducing valve, a first flow controller, a first hydrogen concentration detector, a second gas valve, a second pressure gauge, a second three-way solenoid valve, and a third three-way solenoid valve. The inlet of the pressure reducing valve is connected to the tracer gas cylinder, the outlet of the pressure reducing valve is connected to the first port of the second three-way solenoid valve, the second port of the second three-way solenoid valve is connected to the gas recovery unit, the common port of the second three-way solenoid valve is connected to the inlet of the first hydrogen concentration detector via the first flow controller, the outlet of the first hydrogen concentration detector is connected to the common port of the third three-way solenoid valve, the first port of the third three-way solenoid valve is connected to the inlet of the second gas valve, the outlet of the second gas valve is connected to the air inlet of the workpiece to be detected via the second pressure gauge, the second port of the third three-way solenoid valve is connected to the exhaust gas treatment unit, the first flow controller, the first hydrogen concentration detector, the second gas valve, the second pressure gauge, the second three-way solenoid valve and the third three-way solenoid valve are electrically connected to the main control circuit respectively. The air pressure measured by the second pressure gauge is transmitted to the main control circuit, and the hydrogen concentration measured by the first hydrogen concentration detector is also transmitted to the main control circuit. The main control circuit controls the first flow controller, the start and stop of the second gas valve, and the connection direction of the second and third three-way solenoid valves. The tracer gas cylinder contains a nitrogen-hydrogen mixture with a hydrogen concentration of 5%. The first flow controller controls the amount of tracer gas injected and the filling pressure of the workpiece. The first hydrogen concentration detector detects the hydrogen concentration in the flowing gas. If the measured hydrogen concentration reaches 5%, the workpiece is filled; otherwise, the workpiece is not filled and the gas flows to the exhaust gas treatment unit. The reading on the second pressure gauge is the filling pressure of the workpiece. When the filling pressure reaches the airtightness test requirement, the second gas valve closes, stopping the filling of the workpiece. The workpiece can then be scanned with a leak detector to begin the airtightness test.

[0007] Preferably, the gas filling and recovery device for airtightness testing includes a three-pronged tube, and the exhaust gas treatment unit includes a separation tube and a purification tube. The three inlets of the three-pronged tube are respectively connected to the gas outlets of the pre-vacuum unit, the filling unit, and the gas recovery unit. One outlet of the three-pronged tube is connected to the inlet of the separation tube in the exhaust gas treatment unit, and the outlet of the separation tube is connected to the inlet of the purification tube. The three-pronged tube is a three-input and one-outlet device that receives the exhaust gas sent from the pre-vacuum unit, the filling unit, and the gas recovery unit and delivers it to the exhaust gas treatment unit for treatment. Inside the separation tube is a bundle of capillaries coated with a composite palladium film. When hydrogen in the gas passes through the capillaries, due to the pressure difference between the inside and outside of the capillaries, the hydrogen is separated from the gas and permeates into the capillaries, and the remaining gas enters the purification tube. The purification tube contains active oxides. The hydrogen in the residual gas is oxidized by the active oxides to produce water, thereby greatly reducing the hydrogen concentration of the gas finally discharged into the air, effectively reducing environmental pollution.

[0008] Preferably, the gas recovery unit includes a filter, a first buffer tank, a second hydrogen concentration detector, a mixing tank, a second vacuum pump, a second flow controller, a gas supply bottle, and a fourth three-way solenoid valve and a sixth three-way solenoid valve. The inlet of the filter is connected to the gas outlet of the pre-vacuum unit, the outlet of the filter is connected to the common port of the fourth three-way solenoid valve via the first buffer tank, the first port of the fourth three-way solenoid valve is connected to the first inlet of the mixing tank via the second hydrogen concentration detector, the outlet of the mixing tank is connected to the common port of the sixth three-way solenoid valve via the second vacuum pump, the first port and second port of the sixth three-way solenoid valve are respectively connected to the gas inlet of the exhaust gas treatment unit and the gas inlet of the charging unit, the second inlet of the mixing tank is connected to the gas supply bottle via the second flow controller, the second hydrogen concentration detector, the second vacuum pump, the second flow controller, the fourth three-way solenoid valve, and the sixth three-way solenoid valve are respectively electrically connected to the main control circuit. This technical solution is a normal pressure gas recovery circuit. The hydrogen concentration measured by the second hydrogen concentration detector is transmitted to the main control circuit, which controls the start and stop of the second vacuum pump and the second flow controller, as well as the flow direction of the fourth and sixth three-way solenoid valves. The first and second hydrogen concentration detectors have a fast response speed and a wide measuring range. The filter is used to purify the gas, filtering out oxygen, carbon dioxide, oily substances, water vapor, and other substances. The filter's adsorption elements include activated carbon, calcium hydroxide, color-changing silica gel, and anhydrous copper sulfate. The first buffer tank is used to eliminate gas pulsation after the first vacuum pump, reduce dead zones in the gas pipeline, and minimize gas loss. The mixing tank is a pressure-resistant gas storage tank capable of withstanding pressures up to 0.8 MPa. It has two inlets and one outlet and is used to store recycled gas. The second hydrogen concentration detector measures the hydrogen concentration in the recycled gas. If the measured hydrogen concentration does not reach 5%, the second flow controller is activated, and a nitrogen-hydrogen mixture with a higher hydrogen concentration from the replenishment cylinder is delivered to the mixing tank. The replenishment cylinder replenishes the hydrogen concentration in the mixing tank so that the gas concentration output to the filling unit meets the requirements for airtightness testing.

[0009] Preferably, the gas recovery unit includes a compression pump, a second buffer tank and a fifth three-way solenoid valve. The first port and the second port of the fourth three-way solenoid valve are respectively connected to the first port of the fifth three-way solenoid valve and the inlet of the compression pump. The outlet of the compression pump is connected to the second port of the fifth three-way solenoid valve via the second buffer tank. The common port of the fifth three-way solenoid valve is connected to the first inlet of the mixing tank via the second concentration detector. The compression pump and the fifth three-way solenoid valve are electrically connected to the main control circuit respectively. The main control circuit controls the start and stop of the compression pump and the connection direction of the fifth three-way solenoid valve. The second buffer tank is used to eliminate gas pulsation after the compression pump, reduce dead zones in the gas pipeline, and reduce gas loss. This technical solution is a high-pressure recovery gas circuit. The compression pump compresses the recovered gas to a pressure greater than 5 bar, and then delivers it to the mixing tank through the second buffer tank. When the volume of the recovered gas is larger than the mixing tank, high-pressure recovery is required.

[0010] Preferably, the tracer gas cylinder contains a nitrogen-hydrogen mixture with a hydrogen concentration of 5%, and the replenishing gas cylinder contains a nitrogen-hydrogen mixture with a hydrogen concentration of 20%. The nitrogen-hydrogen mixture with a higher hydrogen concentration can quickly replenish the hydrogen concentration in the mixing tank, making it easier to recover gas to meet tracer gas requirements.

[0011] The filling and recovery method of the gas filling and recovery device for air tightness testing of the present invention is as follows: the main control circuit performs process control based on the set number of workpieces to be tested, the workpiece volume, the workpiece filling pressure and the workpiece pressure holding time, as well as the real-time measured operating parameters, and controls the start and stop of the pre-vacuum unit, the filling unit, and the gas recovery unit respectively to achieve gas filling and gas recovery. The filling and recovery method includes the following steps:

[0012] ① Pre-vacuum process: Under the control of the main control circuit, the pre-vacuum unit starts to work, and the pre-vacuum unit vacuums the workpiece to be inspected. The extracted gas is sent to the exhaust gas treatment unit for treatment and then discharged into the air;

[0013] ②Filling process: Under the control of the main control circuit, the filling unit works to fill the tracer gas into the workpiece to be tested for air tightness testing;

[0014] ③ Recovery process: After the air tightness test is completed, under the control of the main control circuit, the pre-vacuum unit extracts the gas from the workpiece to be tested and sends it to the gas recovery unit for recovery and storage;

[0015] ④ Recycled gas reuse process: For the next workpiece to be tested, first perform pre-vacuum treatment on the next workpiece to be tested according to step ①. Then, under the control of the main control circuit, the gas recovery unit processes the recovered gas to make it meet the requirements of air tightness testing. Finally, it is filled into the workpiece to be tested through the filling unit for air tightness testing;

[0016] ⑤ Repeat the recovery process and the recovered gas reuse process until the air tightness test of all workpieces is completed.

[0017] The present invention can not only automatically complete the filling and pressure maintenance of the workpiece to be inspected, but also recycle and reuse the tail gas discharged after the workpiece completes the air tightness inspection, which not only reduces the cost of the workpiece air tightness inspection and reduces waste, but also reduces tail gas pollution and improves the safety of on-site inspection.

[0018] Preferably, the gas recovery unit includes a filter, a first buffer tank, a second hydrogen concentration detector, a mixing tank, a second vacuum pump, a second flow controller, a gas filling bottle and a fourth three-way solenoid valve and a sixth three-way solenoid valve. The inlet of the filter is connected to the gas outlet of the pre-vacuum unit, and the outlet of the filter is connected to the common port of the fourth three-way solenoid valve via the first buffer tank. The first port of the fourth three-way solenoid valve is connected to the first inlet of the mixing tank via the second hydrogen concentration detector. The outlet of the mixing tank is connected to the common port of the sixth three-way solenoid valve via the second vacuum pump. The first port and the second port of the sixth three-way solenoid valve are respectively connected to the air inlet of the tail gas treatment unit and the air inlet of the filling unit. The second inlet of the mixing tank is connected to the gas filling bottle via the second flow controller. The second hydrogen concentration detector, the second vacuum pump, the second flow controller, the fourth three-way solenoid valve and the sixth three-way solenoid valve are respectively electrically connected to the main control circuit.

[0019] The recovery process is as follows: the fourth three-way solenoid valve is opened, the pre-vacuum unit extracts the gas from the workpiece to be inspected and sends it to the filter. After being filtered by the filter, the gas flows through the first buffer tank, the fourth three-way solenoid valve and the second hydrogen concentration detector in sequence, and finally flows into the mixing tank for storage, thereby realizing normal pressure recovery; the second hydrogen concentration detector detects the concentration of hydrogen in the recovered gas and transmits the hydrogen concentration signal to the main control circuit for processing and judgment. If the hydrogen concentration is lower than 5%, the main control circuit calculates the amount of nitrogen-hydrogen mixed gas that needs to be output from the gas replenishment bottle based on the measured hydrogen concentration, the hydrogen concentration in the gas replenishment bottle and the volume of the mixing tank, controls the second flow controller to open, and the gas replenishment bottle transmits the nitrogen-hydrogen mixed gas to the mixing tank.

[0020] The invention can not only recover tail gas from the workpiece, but also detect the hydrogen concentration in the tail gas, and can also make the hydrogen concentration in the mixing tank meet the requirement by replenishing gas.

[0021] Preferably, the gas recovery unit includes a compression pump, a second buffer tank and a fifth three-way solenoid valve, the first port and the second port of the fourth three-way solenoid valve are respectively connected to the first port of the fifth three-way solenoid valve and the inlet of the compression pump, the outlet of the compression pump is connected to the second port of the fifth three-way solenoid valve via the second buffer tank, the common port of the fifth three-way solenoid valve is connected to the first inlet of the mixing tank via the second concentration detector, and the compression pump and the fifth three-way solenoid valve are respectively electrically connected to the main control circuit;

[0022] The recovery process includes: when the volume of the recovered gas is greater than the volume of the mixing tank, the fourth three-way solenoid valve connects the first buffer tank and the compression pump, the fifth three-way solenoid valve connects the second buffer tank and the second hydrogen concentration detector, the pre-vacuum unit extracts the gas from the workpiece to be detected and sends it to the filter, which is filtered and then flows through the first buffer tank, the compression pump, the second buffer tank and the second hydrogen concentration detector in sequence, and finally flows into the mixing tank for storage, thereby realizing high-pressure recovery.

[0023] The beneficial effects of the present invention are as follows: the tracer gas in the workpiece that has completed the air tightness test is recovered and introduced into a mixing tank for storage. When it is necessary to continue testing the next workpiece, the gas in the mixing tank is used to fill the next workpiece, so that the recovered gas can be reused, which greatly reduces the amount of tracer gas used. This not only reduces the cost of air tightness testing of the workpiece and reduces waste, but also reduces tail gas emission pollution and improves the safety of on-site testing. Through precise pressure and concentration control, the testing conditions of multiple workpieces are consistent, ensuring the consistency and accuracy of air tightness testing. The present invention automatically controls the filling and recovery process through the main control circuit, without the need for manual control, which not only saves time and effort, but also avoids errors caused by human control operations and improves the accuracy of control. At the same time, it can communicate with other devices to complete the continuous automatic detection process of multiple workpieces. It has an automated and intelligent workflow and meets the needs of fast and large-scale testing in industrial automation production lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural block diagram of a gas path connection according to the present invention.

[0025] Figure 2 It is a schematic diagram of a gas path connection structure of the present invention.

[0026] In the figure, 1. pre-vacuum unit, 2. charging unit, 3. gas recovery unit, 4. tail gas treatment unit, 5. workpiece air outlet, 6. workpiece air inlet, 7. three-claw tube, 11. first air valve, 12. first pressure gauge, 13. first vacuum pump, 14. first three-way solenoid valve, 21. pressure reducing valve, 22. first flow controller, 23. first hydrogen concentration detector, 24. second air valve, 25. second pressure gauge, 26. second three-way solenoid valve, 27. third three-way solenoid valve, 28. tracer gas cylinder, 31. filter, 32. first buffer tank, 33. second hydrogen concentration detector, 34. mixing tank, 35. second vacuum pump, 36. second flow controller, 37. gas supply cylinder, 38. compression pump, 39. second buffer tank, 310. fourth three-way solenoid valve, 311. fifth three-way solenoid valve, 312. sixth three-way solenoid valve, 41. separation tube, 42. purification tube. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0028] Example: The gas filling and recovery device for air tightness detection of this embodiment is as follows: Figure 1 As shown, it includes a pre-vacuum unit 1, a filling unit 2, a gas recovery unit 3 and an exhaust gas treatment unit 4 and a main control circuit that controls the operation of the pre-vacuum unit, the filling unit and the gas recovery unit respectively. The gas outlet 5 of the workpiece to be inspected is connected to the gas inlet of the pre-vacuum unit. The gas outlet of the pre-vacuum unit is connected to the gas inlet of the exhaust gas treatment unit on one path and to the gas inlet of the gas recovery unit on the other path. The gas outlet of the gas recovery unit is connected to the gas inlet of the exhaust gas treatment unit on one path and to the gas inlet of the filling unit on the other path. The gas outlet of the filling unit is connected to the gas inlet 6 of the workpiece to be inspected on one path and to the gas inlet of the exhaust gas treatment unit on the other path. This embodiment also includes a three-claw pipe 7 for connecting the pre-vacuum unit, the filling unit, the gas recovery unit and the exhaust gas treatment unit. The three inlets of the three-claw pipe are connected to the gas outlets of the pre-vacuum unit, the filling unit and the gas recovery unit respectively, and the outlet of the three-claw pipe is connected to the gas inlet of the exhaust gas treatment unit.

[0029] like Figure 2 As shown, the pre-vacuum unit includes a first gas valve 11, a first pressure gauge 12, a first vacuum pump 13 and a first three-way solenoid valve 14; the gas recovery unit includes a filter 31, a first buffer tank 32, a second hydrogen concentration detector 33, a mixing tank 34, a second vacuum pump 35, a second flow controller 36, a gas replenishment bottle 37, a compression pump 38, a second buffer tank 39 and a fourth three-way solenoid valve 310, a fifth three-way solenoid valve 311, and a sixth three-way solenoid valve 312; the charging unit includes a pressure reducing valve 21, a first flow controller 22, a first hydrogen concentration detector 23, a second gas valve 24, a second pressure gauge 25, a second three-way solenoid valve 26, and a third three-way solenoid valve 27; the exhaust gas treatment unit includes a separation pipe 41 and a purification pipe 42.

[0030] In the pre-vacuum unit, the inlet of the first air valve is connected to the air outlet of the workpiece to be inspected, the outlet of the first air valve is connected to the inlet of the first vacuum pump via the first pressure gauge, the outlet of the first vacuum pump is connected to the common port of the first three-way solenoid valve, and the first port and the second port of the first three-way solenoid valve are connected to the inlet of the filter and one inlet of the three-claw tube respectively. When the pre-vacuum unit is working, the first air valve is opened and the first vacuum pump is started to extract the gas in the workpiece. If it is not recycled, it is sent to the exhaust gas treatment unit, and if it is recycled, it is sent to the gas recovery unit. The reading of the first pressure gauge is the air pressure in the workpiece, until the reading of the first pressure gauge reaches -0.5MPa, the first air valve is closed, and the first vacuum pump stops working. The vacuum pump can withstand 10 -2 The gas pressure of the level is 1L / s and the pumping speed is not less than 1L / s.

[0031] In the filling unit, the inlet of the pressure reducing valve is connected to the tracer gas cylinder 28, which contains a nitrogen-hydrogen mixed gas with a hydrogen concentration of 5%. The outlet of the pressure reducing valve is connected to the first port of the second three-way solenoid valve, the second port of the second three-way solenoid valve is connected to the second port of the sixth three-way solenoid valve in the gas recovery unit, the common port of the second three-way solenoid valve is connected to the inlet of the first hydrogen concentration detector via the first flow controller, the outlet of the first hydrogen concentration detector is connected to the common port of the third three-way solenoid valve, the first port of the third three-way solenoid valve is connected to the inlet of the second gas valve, the outlet of the second gas valve is connected to the gas inlet of the workpiece to be detected via the second pressure gauge, and the second port of the third three-way solenoid valve is connected to the other inlet of the three-claw tube. The first flow controller is used to control the amount of tracer gas injected and the injection pressure of the workpiece. The indication of the second pressure gauge is the injection pressure of the workpiece. The first hydrogen concentration detector detects the hydrogen concentration in the flowing gas. If the measured hydrogen concentration reaches 5%, the workpiece is injected. Otherwise, the workpiece is not injected and the gas flows to the exhaust gas treatment unit or is replenished in the gas recovery unit before injection.

[0032] In the gas recovery unit, the filter outlet is connected to the common port of the fourth three-way solenoid valve via the first buffer tank. The first port of the fourth three-way solenoid valve is connected to the first port of the fifth three-way solenoid valve. The second port of the fourth three-way solenoid valve is connected to the inlet of the compression pump. The compression pump outlet is connected to the second port of the fifth three-way solenoid valve via the second buffer tank. The common port of the fifth three-way solenoid valve is connected to the first inlet of the mixing tank via the second concentration detector. The second inlet of the mixing tank is connected to the gas replenishment cylinder via the second flow controller. The gas replenishment cylinder contains a nitrogen-hydrogen mixture with a hydrogen concentration of 20%. The outlet of the mixing tank is connected to the common port of the sixth three-way solenoid valve via the second vacuum pump. The first port of the sixth three-way solenoid valve is connected to another inlet of the three-claw pipe. The filter is used to purify the gas, filtering out oxygen, carbon dioxide, oily substances, water vapor, and other substances. The filter's adsorption elements include activated carbon, calcium hydroxide, color-changing silica gel, and anhydrous copper sulfate. The first and second buffer tanks are used to eliminate gas pulsation, reduce dead zones in the gas pipeline, and minimize gas loss. The buffer tank is a cylindrical tank. The air inlet pipe of the buffer tank extends into the center of the tank. The part of the air inlet pipe extending into the tank is covered with micro-holes distributed at equal intervals to release the gas impact. The mixing tank is a pressure-resistant gas storage tank that can withstand a pressure of 0.8MPa. It has two inlets and one outlet. The mixing tank stores normal-pressure gas filtered by the filter and pressurized gas compressed by the compression pump. The compression pump compresses the gas to a pressure greater than 5bar. The second hydrogen concentration detector detects the hydrogen concentration in the recovered gas. If the measured hydrogen concentration does not reach 5%, the second flow controller is turned on, and the nitrogen-hydrogen mixed gas in the gas replenishment bottle is delivered to the mixing tank. The gas replenishment bottle is used to supplement the hydrogen concentration in the mixing tank so that the gas concentration output to the filling unit meets the requirements of the air tightness test.

[0033] In the exhaust gas treatment unit, the inlet of the separation tube is connected to the outlet of the three-prong tube, which in turn is connected to the inlet of the purification tube. The gas flowing out of the purification tube outlet is discharged directly into the atmosphere. The separation tube contains a bundle of capillaries coated with a composite palladium membrane. As hydrogen in the gas passes through the capillaries, the pressure differential between the inside and outside of the capillaries causes the hydrogen to separate from the gas and permeate into the capillaries, while the remaining gas enters the purification tube. The purification tube contains active oxides, which oxidize the hydrogen in the residual gas to form water, significantly reducing the hydrogen concentration in the final exhaust gas.

[0034] The first gas valve, first pressure gauge, first vacuum pump, first flow controller, first hydrogen concentration detector, second gas valve, second pressure gauge, second hydrogen concentration detector, compression pump, second vacuum pump, second flow controller, and the first through sixth three-way solenoid valves are connected to the main control circuit via connecting wires. The main control circuit receives operating parameters from the hydrogen concentration detector and pressure gauge and outputs control signals based on these operating parameters to control the start and stop of the gas valve, flow controller, vacuum pump, and compression pump, as well as the connection direction of the three-way solenoid valves, thereby controlling the workflow.

[0035] The main control circuit typically includes a single-chip microcomputer, buttons, a communication module, a signal processing module, and a driver module. It is responsible for receiving, processing, and controlling the output of collected signals. The main control circuit uses conventional circuitry, so it will not be described in detail here. The main control circuit communicates with other devices through the communication module, completing the continuous automatic inspection process for multiple workpieces. This automated and intelligent workflow meets the rapid, high-volume inspection requirements of industrial automation production lines.

[0036] The filling and recovery method of the gas filling and recovery device for air tightness detection is as follows:

[0037] The main control circuit performs process control based on the number of workpieces to be inspected, the workpiece volume, the workpiece filling pressure, and the workpiece pressure holding time set by the buttons, as well as the real-time measured operating parameters (gas pressure and hydrogen concentration), and controls the start and stop of the pre-vacuum unit, the filling unit, and the gas recovery unit, as well as the opening and closing of each gas path, to achieve gas filling and gas recovery. The filling and recovery method includes the following steps:

[0038] ① Pre-vacuum process: The workpiece to be inspected is vacuumed. Under the control of the main control circuit, the first air valve is opened, the common port of the first three-way solenoid valve is connected to the second port, and the first vacuum pump starts to work, extracting the gas in the workpiece to be inspected and sending it to the exhaust gas treatment unit for treatment before being discharged into the air. When the first pressure gauge reaches -0.5MPa, the first air valve is closed and the first vacuum pump stops working.

[0039] ② Filling process: Fill the workpiece to be inspected with tracer gas. Under the control of the main control circuit, the common port of the second three-way solenoid valve is connected to the first port, the first flow controller is turned on, and the nitrogen-hydrogen mixed gas in the tracer gas cylinder flows through the first hydrogen concentration detector. The first hydrogen concentration detector detects the hydrogen concentration in the gas: If the hydrogen concentration does not reach 5%, the common port and the second port of the third three-way solenoid valve are connected, and the gas flows to the exhaust gas treatment unit and finally discharged into the air. If the hydrogen concentration reaches 5%, the common port and the first port of the third three-way solenoid valve are connected, the second gas valve is opened, and the tracer gas is filled into the workpiece to be inspected. When the air pressure value measured by the second pressure gauge reaches the set filling pressure, the second gas valve is closed, the first flow controller stops working, and the workpiece is tested for air tightness. The air tightness leak detector is used to scan the surface of the workpiece to find the leak point.

[0040] ③ Recovery process: After the air tightness test is completed, under the control of the main control circuit, the common end of the first three-way solenoid valve and the first port are connected, the first gas valve is opened, the first vacuum pump starts working, and the gas extracted from the workpiece is delivered to the filter: if the volume of the workpiece is smaller than the volume of the mixing tank, the fourth three-way solenoid valve and the fifth three-way solenoid valve are connected, and the gas flows through the filter, the first buffer tank, the fourth three-way solenoid valve, the fifth three-way solenoid valve and the second hydrogen concentration detector in turn, and finally flows into the mixing tank to achieve normal pressure recovery; if the volume of the workpiece is larger than the volume of the mixing tank, the fourth three-way solenoid valve and the compression pump are connected, the fifth three-way solenoid valve and the second buffer tank are connected, the compression pump is started, and the gas flows through the filter, the first buffer tank, the fourth three-way solenoid valve, the compression pump, the second buffer tank, the fifth three-way solenoid valve and the second hydrogen concentration detector in turn, and finally the gas compressed by the compression pump flows into the mixing tank to achieve high-pressure recovery. When the first pressure gauge reaches -0.5MPa, the first gas valve is closed, the first vacuum pump stops working, and the recovery ends. During this process, the second hydrogen concentration detector detects the concentration of hydrogen in the recovered gas. If the hydrogen concentration is lower than 5%, the main control circuit calculates the amount of hydrogen to be replenished based on the hydrogen concentration measured by the second hydrogen concentration detector, the hydrogen concentration in the gas replenishment bottle, and the volume of the mixing tank, and outputs a signal to the second flow controller. The second flow controller delivers the nitrogen-hydrogen mixed gas in the gas replenishment bottle to the mixing tank according to the command. The gas replenishment volume formula is as follows:

[0041]

[0042] Where: V1 is the volume of the mixing tank, V2 is the volume of gas delivered by the second flow controller, C2 is the hydrogen concentration measured by the second hydrogen concentration detector, and C3 is the hydrogen concentration of the nitrogen-hydrogen mixed gas in the gas replenishment bottle.

[0043] ④ Gas recycling process: For the next workpiece to be inspected, first perform pre-vacuum treatment on the next workpiece to be inspected according to step ①, then under the control of the main control circuit, the sixth three-way solenoid valve and the second three-way solenoid valve are connected, the second vacuum pump is started, the mixing tank outputs gas to the filling unit, the gas flows to the first hydrogen concentration detector through the first flow controller, and the first hydrogen concentration detector detects the hydrogen concentration in the gas: if the hydrogen concentration reaches 5%, the common port of the third three-way solenoid valve is connected to the first port, the second gas valve is opened, and the gas output from the mixing tank is filled into the workpiece to be inspected. When measuring the workpiece, when the air pressure value measured by the second pressure gauge reaches the set filling pressure, the second air valve closes, the first flow controller stops working, and the workpiece is tested for air tightness. The air tightness leak detector is used to scan the workpiece surface to find the leak point. If the hydrogen concentration does not reach 5%, the main control circuit calculates the amount of nitrogen-hydrogen mixed gas that needs to be output by the gas replenishment bottle based on the hydrogen concentration measured by the first hydrogen concentration detector, the hydrogen concentration in the gas replenishment bottle, and the volume of the mixing tank. The second flow controller is controlled to open, and the gas replenishment bottle delivers the nitrogen-hydrogen mixed gas to the mixing tank. The formula for the gas replenishment volume is as follows:

[0044]

[0045] Where: V1 is the volume of the mixing tank, V2 is the volume of gas delivered by the second flow controller, C1 is the hydrogen concentration measured by the first hydrogen concentration detector, and C3 is the hydrogen concentration of the nitrogen-hydrogen mixed gas in the gas replenishment bottle.

[0046] ⑤ Repeat the recovery process and the recovered gas reuse process until the air tightness test of all workpieces is completed.

[0047] After the workpiece inspection is completed, the first three-way solenoid valve, the third three-way solenoid valve and the sixth three-way solenoid valve are connected to the three-claw tube, and the excess gas is separated and purified by the exhaust gas treatment unit and then discharged into the air, reducing environmental pollution and reducing interference with the inspection environment.

Claims

1. A gas filling and recovery device for air tightness detection, characterized in that It includes a pre-vacuum unit, a filling unit, a gas recovery unit and an exhaust gas treatment unit and a main control circuit that controls the operation of the pre-vacuum unit, the filling unit and the gas recovery unit respectively. The gas outlet of the workpiece to be inspected is connected to the gas inlet of the pre-vacuum unit. The gas outlet of the pre-vacuum unit is connected to the gas inlet of the exhaust gas treatment unit on one path and the gas inlet of the gas recovery unit on the other path. The gas outlet of the gas recovery unit is connected to the gas inlet of the exhaust gas treatment unit on one path and the gas inlet of the filling unit on the other path. The gas outlet of the filling unit is connected to the gas inlet of the workpiece to be inspected on one path and the gas inlet of the exhaust gas treatment unit on the other path. The gas recovery unit includes a filter, a first buffer tank, a second hydrogen concentration detector, a mixing tank, a second vacuum pump, a second flow controller, a gas replenishing bottle and a fourth three-way solenoid valve and a sixth three-way solenoid valve. The inlet of the filter is connected to the gas outlet of the pre-vacuum unit, the outlet of the filter is connected to the common port of the fourth three-way solenoid valve via the first buffer tank, the first port of the fourth three-way solenoid valve is connected to the first inlet of the mixing tank via the second hydrogen concentration detector, the outlet of the mixing tank is connected to the common port of the sixth three-way solenoid valve via the second vacuum pump, the first port and the second port of the sixth three-way solenoid valve are respectively connected to the gas inlet of the tail gas treatment unit and the gas inlet of the filling unit, the second inlet of the mixing tank is connected to the gas replenishing bottle via the second flow controller, the second hydrogen concentration detector, the second vacuum pump, the second flow controller, the fourth three-way solenoid valve and the sixth three-way solenoid valve are respectively electrically connected to the main control circuit; wherein the first buffer tank is a cylindrical tank body, the air inlet pipe of the first buffer tank extends into the center position of the tank body, and the air inlet pipe portion extending into the tank body is covered with micropores distributed at equal intervals; The gas recovery unit includes a compression pump, a second buffer tank and a fifth three-way solenoid valve. The first port and the second port of the fourth three-way solenoid valve are respectively connected to the first port of the fifth three-way solenoid valve and the inlet of the compression pump. The outlet of the compression pump is connected to the second port of the fifth three-way solenoid valve via the second buffer tank. The common port of the fifth three-way solenoid valve is connected to the first inlet of the mixing tank via the second concentration detector. The compression pump and the fifth three-way solenoid valve are respectively electrically connected to the main control circuit. It also includes a three-claw type tube, and the exhaust gas treatment unit includes a separation tube and a purification tube. The three inlets of the three-claw type tube are respectively connected to the gas outlets of the pre-vacuum unit, the filling unit, and the gas recovery unit. The outlet of the three-claw type tube is connected to the inlet of the separation tube in the exhaust gas treatment unit, and the outlet of the separation tube is connected to the inlet of the purification tube.

2. The gas filling and recovery device for air tightness detection according to claim 1 is characterized in that The pre-vacuum unit includes a first air valve, a first pressure gauge, a first vacuum pump and a first three-way solenoid valve. The inlet of the first air valve is connected to the air outlet of the workpiece to be inspected, and the outlet of the first air valve is connected to the inlet of the first vacuum pump via the first pressure gauge. The outlet of the first vacuum pump is connected to the common port of the first three-way solenoid valve. The first port and the second port of the first three-way solenoid valve are respectively connected to the air inlet of the gas recovery unit and the air inlet of the exhaust gas treatment unit. The first air valve, the first pressure gauge, the first vacuum pump and the first three-way solenoid valve are respectively electrically connected to the main control circuit.

3. The gas filling and recovery device for air tightness detection according to claim 1 is characterized in that The filling unit includes a pressure reducing valve, a first flow controller, a first hydrogen concentration detector, a second gas valve, a second pressure gauge, a second three-way solenoid valve, and a third three-way solenoid valve. The inlet of the pressure reducing valve is connected to the tracer gas cylinder, the outlet of the pressure reducing valve is connected to the first port of the second three-way solenoid valve, the second port of the second three-way solenoid valve is connected to the gas recovery unit, the common port of the second three-way solenoid valve is connected to the inlet of the first hydrogen concentration detector via the first flow controller, the outlet of the first hydrogen concentration detector is connected to the common port of the third three-way solenoid valve, the first port of the third three-way solenoid valve is connected to the inlet of the second gas valve, the outlet of the second gas valve is connected to the air inlet of the workpiece to be detected via the second pressure gauge, the second port of the third three-way solenoid valve is connected to the exhaust gas treatment unit, the first flow controller, the first hydrogen concentration detector, the second gas valve, the second pressure gauge, the second three-way solenoid valve and the third three-way solenoid valve are electrically connected to the main control circuit respectively.

4. The gas filling and recovery device for air tightness detection according to claim 3 is characterized in that The tracer gas cylinder is filled with a nitrogen-hydrogen mixed gas with a hydrogen concentration of 5%, and the replenishing gas cylinder is filled with a nitrogen-hydrogen mixed gas with a hydrogen concentration of 20%.

5. A filling and recovery method for a gas filling and recovery device for air tightness testing according to claim 1, characterized in that The main control circuit performs process control based on the set number of workpieces to be inspected, the workpiece volume, the workpiece filling pressure and the workpiece pressure holding time, as well as the real-time measured operating parameters, and controls the start and stop of the pre-vacuum unit, the filling unit and the gas recovery unit respectively to achieve gas filling and gas recovery. The filling and gas recovery method includes the following steps: ① Pre-vacuum process: Under the control of the main control circuit, the pre-vacuum unit starts to work, and the pre-vacuum unit vacuums the workpiece to be inspected. The extracted gas is sent to the exhaust gas treatment unit for treatment and then discharged into the air; ②Filling process: Under the control of the main control circuit, the filling unit works to fill the tracer gas into the workpiece to be tested for air tightness testing; ③ Recovery process: After the air tightness test is completed, under the control of the main control circuit, the pre-vacuum unit extracts the gas from the workpiece to be tested and sends it to the gas recovery unit for recovery and storage; ④ Recycled gas reuse process: For the next workpiece to be tested, first perform pre-vacuum treatment on the next workpiece to be tested according to step ①. Then, under the control of the main control circuit, the gas recovery unit processes the recovered gas to make it meet the requirements of air tightness testing. Finally, it is filled into the workpiece to be tested through the filling unit for air tightness testing; ⑤ Repeat the recovery process and the recovered gas reuse process until the air tightness test of all workpieces is completed.

6. The filling and recovery method of the gas filling and recovery device for air tightness detection according to claim 5, characterized in that The gas recovery unit includes a filter, a first buffer tank, a second hydrogen concentration detector, a mixing tank, a second vacuum pump, a second flow controller, a gas filling bottle, and a fourth three-way solenoid valve and a sixth three-way solenoid valve. The inlet of the filter is connected to the gas outlet of the pre-vacuum unit, the outlet of the filter is connected to the common port of the fourth three-way solenoid valve via the first buffer tank, the first port of the fourth three-way solenoid valve is connected to the first inlet of the mixing tank via the second hydrogen concentration detector, the outlet of the mixing tank is connected to the common port of the sixth three-way solenoid valve via the second vacuum pump, the first port and the second port of the sixth three-way solenoid valve are respectively connected to the air inlet of the tail gas treatment unit and the air inlet of the charging unit, the second inlet of the mixing tank is connected to the gas filling bottle via the second flow controller, the second hydrogen concentration detector, the second vacuum pump, the second flow controller, the fourth three-way solenoid valve and the sixth three-way solenoid valve are respectively electrically connected to the main control circuit; The recovery process is as follows: the fourth three-way solenoid valve is opened, the pre-vacuum unit extracts the gas from the workpiece to be inspected and sends it to the filter. After being filtered by the filter, the gas flows through the first buffer tank, the fourth three-way solenoid valve and the second hydrogen concentration detector in sequence, and finally flows into the mixing tank for storage, thereby realizing normal pressure recovery; the second hydrogen concentration detector detects the concentration of hydrogen in the recovered gas and transmits the hydrogen concentration signal to the main control circuit for processing and judgment. If the hydrogen concentration is lower than 5%, the main control circuit calculates the amount of nitrogen-hydrogen mixed gas that needs to be output from the gas replenishment bottle based on the measured hydrogen concentration, the hydrogen concentration in the gas replenishment bottle and the volume of the mixing tank, controls the second flow controller to open, and the gas replenishment bottle transmits the nitrogen-hydrogen mixed gas to the mixing tank.

7. The filling and recovery method of the gas filling and recovery device for air tightness detection according to claim 6, characterized in that The gas recovery unit includes a compression pump, a second buffer tank and a fifth three-way solenoid valve. The first port and the second port of the fourth three-way solenoid valve are respectively connected to the first port of the fifth three-way solenoid valve and the inlet of the compression pump. The outlet of the compression pump is connected to the second port of the fifth three-way solenoid valve via the second buffer tank. The common port of the fifth three-way solenoid valve is connected to the first inlet of the mixing tank via the second concentration detector. The compression pump and the fifth three-way solenoid valve are respectively electrically connected to the main control circuit. The recovery process includes: when the volume of the recovered gas is greater than the volume of the mixing tank, the fourth three-way solenoid valve connects the first buffer tank and the compression pump, the fifth three-way solenoid valve connects the second buffer tank and the second hydrogen concentration detector, the pre-vacuum unit extracts the gas from the workpiece to be detected and sends it to the filter, which is filtered and then flows through the first buffer tank, the compression pump, the second buffer tank and the second hydrogen concentration detector in sequence, and finally flows into the mixing tank for storage, thereby realizing high-pressure recovery.

Images