Microwave oven shell projection welding pressure control device and method and application

Abstract

The invention belongs to the technical field of welding, and discloses a microwave oven shell projection welding pressure control device and method and application. According to the device, an air source is divided into three paths through the air distribution block, the pressure of the upper air chamber and the pressure of the lower air chamber of the air cylinder are controlled respectively, the pressure switch is used for monitoring the pressure of the lower air chamber in real time and triggering an electric signal, double-pressure accurate control of the pre-pressing stage (machine head self-weight pressurization) and the welding stage (dynamic pressure regulation) is achieved, and convex point crushing or incomplete fusion is avoided. In the pre-pressing stage, the upper air chamber is inflated to enable the air cylinder to slowly press down under the dead weight, and the bump is prevented from being impacted; in the welding stage, the air chamber exhausts air and detects the pressure in real time, when the pressure drops to a set threshold value, discharging is triggered, it is ensured that the pressure is matched with the height and diameter of the protruding point during welding, and splashing or deformation is prevented. Therefore, the device can strictly control the welding pressure, and reliable microwave oven projection welding spots can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of welding technology, and in particular to a projection welding pressure control device, method and application of a microwave oven shell. Background Art

[0002] The shell of a microwave oven is usually made of galvanized steel or stainless steel with a shell thickness of 0.5-1.2mm. During the manufacturing process, the shell of a microwave oven needs to meet a series of strict technical requirements to ensure welding strength, sealing and appearance quality. At present, the two mainstream technologies for welding microwave oven shells are energy storage projection welding and medium frequency inverter resistance projection welding to meet the requirements of high precision and high efficiency welding. Since the material of the microwave oven shell is very thin, the connection position requires projection welding bumps 23 (its structure is as follows) Figure 4 The height of the bump (as shown) is only 0.3-0.5mm, and the bump diameter is 1-1.5mm. Due to the small bump diameter, pressure control during projection welding becomes very important. Before welding, the electrode needs to be pressed down to press the upper and lower workpieces tightly. Excessive pressure will cause the bump to be crushed, and subsequent projection welding cannot be performed. Too little pressure makes it difficult to ensure the movement of the cylinder. During the welding process, if the pressure is too low, the contact resistance is large, and spatter and burn-through defects are easily generated. If the pressure is too high, the bump will be crushed prematurely, the weld will not be fused, and the plate will be severely deformed. At the same time, a large forging pressure is required after the welding is completed to ensure that the microwave oven shell and the cover are tightly fitted after the weld is fused. Therefore, the welding pressure must be strictly controlled throughout the welding process to obtain reliable microwave oven projection welds.

[0003] Based on the above existing problems, the present invention proposes a device and method for controlling projection welding pressure of a microwave oven shell, which can accurately control the electrode pressure during the welding electrode pressing stage, the discharge welding stage and after the discharge is completed, thereby obtaining projection welding points with reliable quality. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a device, method and application for controlling projection welding pressure of a microwave oven shell.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A microwave oven shell projection welding pressure control device, capable of performing projection welding on the microwave oven shell through welding convex points, comprising a gas source, a first one-way valve, a gas storage tank, a first pressure switch, a pneumatic triplex, a first gas distributor, a first solenoid valve, a first speed regulating valve, a second speed regulating valve, a second solenoid valve, a third speed regulating valve, a second gas distributor, a second pressure switch, a gas cylinder, a second one-way valve, welding electrodes, and a stored energy welder;

[0007] The gas source is connected to the input end of the first one-way valve, the output end of the first one-way valve is connected to the gas tank, the gas tank is connected to a first pressure switch, the gas tank, the pneumatic triplex and the first gas distributor are connected in sequence, the gas tank is connected to the pneumatic triplex via a switch, the gas source can input gas into the gas tank through the first one-way valve, the gas source can provide gas for the device, the first one-way valve can protect the safety of the device, the gas tank can store gas, the first pressure switch can detect whether the gas source pressure meets the use requirements, the pneumatic triplex can reduce the pressure on the gas, and the first gas distributor can divide the gas into a plurality of gas paths;

[0008] The first solenoid valve, the first speed regulating valve and the second speed regulating valve are connected in sequence and arranged to form a first gas circuit. The input end of the first gas circuit is connected to the first gas distributor block, and the output end of the first gas circuit is connected to the upper gas chamber of the cylinder. The first solenoid valve can control the release and storage of gas in the first gas circuit.

[0009] The second solenoid valve, the third speed regulating valve and the second gas distribution block are connected in sequence and arranged to form a second gas circuit. The air pressure of the second gas circuit is lower than the air pressure of the first gas circuit. The input end of the second gas circuit is connected to the first gas distribution block, and the output end of the second gas circuit is connected to the lower air chamber of the cylinder. The second solenoid valve can control the release and storage of gas in the second gas circuit. The second gas distribution block is connected to a second pressure switch.

[0010] The input port of the second one-way valve is connected to the second gas distribution block, and the output port of the second one-way valve is connected to the first gas distribution block;

[0011] The welding electrode includes an upper electrode and a lower electrode arranged in parallel in the vertical direction. The upper electrode is arranged above the lower electrode. The microwave oven shell to be welded can be detachably fitted on the lower electrode. The working end surface of the cylinder is connected to the upper electrode. The cylinder can drive the upper electrode to move back and forth in the vertical direction. The upper electrode can perform a welding operation on the microwave oven shell under the drive of the cylinder. The welding electrode is connected to the energy storage welder. The energy storage welder is connected to the second pressure switch via a signal. The energy storage welder can provide the energy required for the welding electrode. The arrangement of the energy storage electrode can protect the device from having sufficient voltage for production and processing.

[0012] The first speed regulating valve is connected to the cylinder and can adjust the intake speed of the upper air chamber of the cylinder. The second speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the upper air chamber of the cylinder. The third speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the lower air chamber of the cylinder.

[0013] Furthermore, the device also includes a muffler, which is connected to the first solenoid valve and the second solenoid valve. The muffler can eliminate noise generated by the first solenoid valve and the second solenoid valve when deflation occurs.

[0014] Furthermore, the device also includes a pressure alarm device, and the first pressure switch and the second pressure switch are both connected to set the pressure alarm device. When the pressure value detected by the first pressure switch and the second pressure switch is lower than the set threshold, the pressure alarm device will alarm.

[0015] Furthermore, the device also includes a residual pressure release valve, which is connected to the cylinder and can release the pressure in the lower air chamber of the cylinder.

[0016] A method for controlling projection welding pressure of a microwave oven housing in stages using the above-mentioned device comprises the following steps:

[0017] Pre-compression stage: The upper air chamber of the cylinder is inflated so that the cylinder is slowly pressed down under its own weight to avoid impact on convex points;

[0018] Welding stage: The lower air chamber of the cylinder is exhausted and the pressure is detected in real time. When the pressure drops to the set threshold, discharge is triggered to ensure that the pressure during welding matches the bump height of 0.3-0.5mm and the diameter of 1-1.5mm to prevent spatter or deformation.

[0019] The more specific steps are as follows:

[0020] (1) Place the projection welding portion of the microwave oven shell on the lower electrode, open the first one-way valve, and allow the gas in the gas source to flow into the gas tank. The pressure switch in the gas tank detects the pressure in the gas tank. If the pressure is insufficient (an alarm prompt may be used), the welding is interrupted to prevent explosion points or welding defects caused by pressure loss. If the pressure is normal, open the switch to allow the gas to flow into the pneumatic triplex. The gas is decompressed in the pneumatic triplex and then flows into the first gas distribution block after decompression.

[0021] (2) When the energy storage welder is not started, there is no gas in the upper air chamber of the cylinder, and the lower air chamber of the cylinder is always ventilated and has the same gas pressure as the gas pressure after the pneumatic triplex is decompressed. After the energy storage welder gives a start signal, the first solenoid valve is turned on and the upper air chamber of the cylinder is ventilated. At this time, the gas pressures of the upper and lower air chambers of the cylinder are equal, but due to the effect of the cylinder's own weight and the fact that the force area of ​​the lower air chamber of the cylinder is smaller than the force area of ​​the piston of the upper air chamber, the cylinder will naturally fall, causing the upper electrode to exert a weak downward pressure on the microwave oven shell, causing the device to enter the pre-pressing stage. This pressure will not impact the convex point, thus avoiding the convex point from being crushed during the pre-pressing stage.

[0022] (3) After the cylinder is pressed down until both the upper and lower electrodes are in contact with the microwave oven shell workpiece, the lower air chamber solenoid valve is energized, and the second solenoid valve is energized to release the gas in the second air path, and the gas in the lower air chamber of the cylinder is discharged. Since the gas pressure in the upper air chamber of the cylinder is greater than the gas pressure in the lower air chamber, the welding electrode begins to pressurize the projection welding workpiece. When the second pressure switch detects that the gas pressure in the lower air chamber is reduced to the required pressure, the pressure switch will send a discharge signal to the energy storage welder, and the energy storage welder will discharge at a welding pressure of 3000N-5000N to complete the projection welding of the microwave oven shell. After the welding is completed, the gas in the lower air chamber of the cylinder will be completely exhausted. At this time, the pressure of the electrode on the workpiece reaches the maximum, and further downward pressure is applied to make the microwave oven shell and the shell cover fit tightly after the welding is completed, ensuring that the shell has a better sealing performance.

[0023] (4) After the welding is completed, the first solenoid valve and the second solenoid valve are both powered off, the lower air chamber of the cylinder is ventilated, and the upper air chamber of the cylinder is exhausted, so that the cylinder returns to the raised position, and the upper electrode rises under the push of the cylinder, and the welded microwave oven shell is taken out, completing the whole process.

[0024] The application of the projection welding pressure control device for microwave oven shells as described above in projection welding of microwave oven shells.

[0025] The microwave oven shell projection welding pressure control device as described above is applied in the projection welding of microwave oven shells with a projection height of 0.3-0.5 mm and a diameter of 1-1.5 mm.

[0026] The advantages and positive effects achieved by the present invention are:

[0027] 1. The device of the present invention divides the gas source into three paths through the gas dividing block, which respectively controls the pressure of the upper and lower air chambers of the cylinder. The pressure switch is used to monitor the pressure of the lower air chamber in real time and trigger the discharge signal, realizing the dual pressure precise control in the pre-pressing stage (pressurization by the deadweight of the machine head) and the welding stage (dynamic pressure regulation), and avoiding the bumps from being crushed or not fused. In the pre-pressing stage, the upper air chamber is inflated so that the cylinder is slowly pressed down under its own weight to avoid impacting the bumps; in the welding stage, the lower air chamber is exhausted and the pressure is detected in real time. When the pressure drops to the set threshold, the discharge is triggered to ensure that the pressure during welding matches the bump height (0.3-0.5mm) and diameter (1-1.5mm) to prevent splashing or deformation. Therefore, the device can strictly control the welding pressure and obtain reliable microwave projection welding points.

[0028] 2. The synchronous welding process of the single row of bumps on the microwave oven shell by the device of the present invention realizes the synchronous welding of all bumps under uniform pressure parameters through the gas path device and method. At the same time, after the welding is completed, a greater forging pressure is provided to make the microwave oven shell and the cover plate fit tightly, ensuring the uniform strength of each weld point and no deformation in appearance, thus meeting the requirements of the shell sealing and structural strength.

[0029] 3. The device of this invention incorporates a pressure alarm system, a gas circuit safety mechanism that protects the linked alarm system between the gas tank and the pressure switch. When the gas source pressure is insufficient, an alarm is triggered and welding is interrupted, preventing hot spots or weld defects caused by pressure loss and ensuring a stable welding process. The pressure switch precisely controls the discharge timing of the energy storage welding equipment and also precisely controls the welding pressure.

[0030] 4. The device of the present invention controls the pressure of the upper and lower air chambers of the cylinder, uses a pressure switch to monitor the pressure of the lower air chamber in real time and triggers a discharge signal, thereby achieving precise control of triple pressure in the pre-pressurization stage (pressurization by the weight of the head), the welding stage (dynamic pressure regulation) and the post-weld pressure maintenance stage, avoiding the collapse or unfusion of the convex points and ensuring the close fit between the microwave oven shell and the cover after welding.

[0031] 5. This device can realize synchronous welding of all the convex points of the microwave oven shell (such as 19 evenly distributed convex points in a single row of the microwave oven shell) under uniform pressure parameters, ensuring that the strength of each welding point is consistent and the appearance is not deformed, meeting the shell sealing and structural strength requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structural connection of the device of the present invention and a schematic diagram of the projection welding principle of the microwave oven shell;

[0033] Figure 2 This is a schematic diagram of a control gas circuit connection of the device of the present invention;

[0034] Figure 3 A schematic diagram of the use and structural connection of the welding electrode and the microwave oven housing in the device of the present invention during welding operation;

[0035] Figure 4 A schematic diagram of a structural connection of welding bumps of a microwave oven housing in the prior art;

[0036] Figure 5 A photo of a microwave oven housing to be welded being projection welded using the device of the present invention;

[0037] Figure 6 for Figure 5 A photo of the short side of the projection weld on a microwave oven housing.

[0038] Figure 7 for Figure 5 A real photo of the long side of the projection weld on the microwave oven shell;

[0039] Figure 8 This is a photo of the internal gap of the microwave oven shell after welding using the device of the present invention;

[0040] Figure 9The figure is a photo of the finished projection-welded part of the microwave oven housing after being welded using the device of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the following examples. The following examples are descriptive rather than restrictive, and the scope of protection of the present invention cannot be limited by the following examples.

[0042] The various experimental operations involved in the specific embodiments are all routine techniques in the field. For parts not specifically annotated in this document, ordinary technicians in this field can refer to various commonly used reference books, scientific literature or related instructions, manuals, etc. before the filing date of this invention to implement them.

[0043] Example 1

[0044] A microwave oven shell projection welding pressure control device, the device can be used to perform projection welding on the microwave oven shell 22 through welding convex points, such as Figures 1 to 3 As shown, the device includes an air source 1, a first one-way valve 2, an air storage tank 3, a first pressure switch 4, a pneumatic triplex 5, a first air distributor 6, a first solenoid valve 7, a first speed regulating valve 8, a second speed regulating valve 9, a second solenoid valve 10, a third speed regulating valve 11, a second air distributor 12, a second pressure switch 13, an air cylinder 15, a second one-way valve 16, a welding electrode 17, and a stored energy welder 18;

[0045] The gas supply is connected to the input end of the first one-way valve, and the output end of the first one-way valve is connected to the gas tank. The gas tank is provided with a first pressure switch, the gas tank, the pneumatic triplet and the first gas dividing block are connected in sequence. The gas tank is connected to the pneumatic triplet through a switch (not numbered in the figure) and is provided with the pneumatic triplet. The gas source can input gas into the gas tank through the first one-way valve to provide gas for the device. The first one-way valve can protect the safety of the device, the gas tank can store gas, the first pressure switch can detect whether the gas source pressure meets the use requirements, the pneumatic triplet can reduce the pressure of the gas, and the first gas dividing block can divide the gas into several gas paths; the setting of the first one-way valve ensures that when the gas source fails to send, the gas will not flow back and cause damage to the device, thereby protecting the safety of the device. The gas tank provides a buffering effect for the device, and the pneumatic triplet reduces the pressure, further protecting the device from being in a safe working pressure range; the pressure switch can accurately control the discharge moment of the energy storage welding equipment, and can also accurately control the welding pressure, thereby preventing explosion points or welding defects caused by pressure loss, and ensuring the stability of the welding process;

[0046] The first solenoid valve, the first speed regulating valve and the second speed regulating valve are connected in sequence and arranged to form a first gas circuit. The input end of the first gas circuit is connected to the first gas distributor block, and the output end of the first gas circuit is connected to the upper gas chamber of the cylinder. The first solenoid valve can control the release and storage of gas in the first gas circuit.

[0047] The second solenoid valve, the third speed regulating valve and the second gas distribution block are connected in sequence and arranged as a second gas circuit. The air pressure of the second gas circuit is lower than the air pressure of the first gas circuit. The input end of the second gas circuit is connected to the first gas distribution block, and the output end of the second gas circuit is connected to the lower air chamber of the cylinder. The second solenoid valve can control the release and storage of gas in the second gas circuit. The second gas distribution block is connected to a second pressure switch. The pressure switch can accurately control the discharge moment of the energy storage welding equipment and can also accurately control the welding pressure to prevent explosion points or welding defects caused by pressure loss, thereby ensuring the stability of the welding process.

[0048] The input port of the second one-way valve is connected to the second gas distribution block, and the output port of the second one-way valve is connected to the first gas distribution block; the setting of the second one-way valve ensures that the air pressure of the second gas circuit is lower than the air pressure of the first gas circuit, ensuring the normal operation of the device.

[0049] The welding electrode includes an upper electrode 20 and a lower electrode 21 arranged in parallel in the vertical direction. The upper electrode is arranged above the lower electrode. The microwave oven shell to be welded can be detachably attached to the lower electrode. The working end face of the cylinder is connected to the upper electrode. The cylinder can drive the upper electrode to move back and forth in the vertical direction. The upper electrode can perform a welding operation on the microwave oven shell under the drive of the cylinder; the welding electrode is connected to the energy storage welder, and the energy storage welder is connected to the second pressure switch via a signal. The energy storage welder can provide the energy required for the welding electrode; the provision of the energy storage electrode can ensure that the device has sufficient voltage for production and processing;

[0050] The first speed regulating valve is connected to the cylinder and can adjust the air intake speed of the upper air chamber of the cylinder. The second speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the upper air chamber of the cylinder. The third speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the lower air chamber of the cylinder, so that the operator can adjust the upper and lower pressures and the downward pressure time of the cylinder according to needs, so that the device can meet the production needs of workpieces with different processes and different shapes.

[0051] When the device is in use, a storage energy welder is used to perform projection welding on the microwave oven shell. Before welding begins, the storage energy welder is connected to the gas source and industrial electricity. The position of the microwave oven shell to be projected is placed on the lower electrode. Then, the welding parameters are adjusted, mainly including pre-compression pressure, welding pressure, welding voltage, discharge time and other parameters. After the welding equipment is started, the upper electrode will press the microwave oven projection welding position and the lower electrode under the push of the cylinder. When the welding pressure is reached, the storage energy welder releases the energy stored in the capacitor, and the projection welding position of the microwave oven shell generates Joule heat to complete the welding. After the current is released, the upper electrode rises under the push of the cylinder, and the welding workpiece is taken out to complete the projection welding process of the microwave oven shell.

[0052] Figure 2 This is a schematic diagram showing the convex welding position of the microwave oven shell placed between the upper and lower electrodes. A single row of microwave ovens has 19 convex welding points. A single welding operation needs to ensure that each convex point is connected reliably. Figure 4 This is a schematic diagram of welding bumps. The bumps are evenly distributed in a single row at the welding position. The bump height is 0.3-0.5mm and the bump diameter is 1-1.5mm. Therefore, the cylinder downward pressure must be strictly controlled when the cylinder is pressed down to prevent the weld from being crushed before the energy storage welding equipment discharges. There are two processes of welding pressure that need to be controlled. One is that after the welding equipment is started, the cylinder is pressed down to press the upper and lower electrodes and the workpiece. At this time, only a small force is required to ensure that the cylinder is pressed down quickly, and at the same time, there is basically no impact on the bumps. The pre-pressing stage basically relies on the weight of the machine head to apply pressure. After the upper and lower electrodes contact the workpiece, welding pressure is applied. When the pressure reaches the pressure required for the weld, the energy storage welder discharges to complete the projection welding process.

[0053] The gas path control principle diagram of the entire welding process is as follows Figure 3As shown, the gas source gas enters the gas tank through a one-way valve. The gas tank is equipped with a pressure switch to detect whether the gas source pressure of the equipment meets the use requirements. If it does not meet the requirements, the equipment will have an insufficient pressure alarm to prevent the occurrence of welding pressure loss explosion points. The gas tank is then connected to a set of three-way fittings to reduce the gas pressure for the first time, and then a gas distributor is used to divide one gas into three. One of the ways passes through the solenoid valve, and the speed regulating valve is connected to the upper air chamber of the cylinder. There is no gas in the upper air chamber of the cylinder when the solenoid valve is not energized. One of the other two ways passes through the one-way valve, and the other way passes through the solenoid valve and the speed regulating valve and then converges together to connect a pressure switch and then connected to the lower air chamber of the cylinder. In the initial state, the air pressure in the lower air chamber of the cylinder is equal to the pressure after the three-way fitting is reduced in pressure. In the initial stage, since there is no air pressure in the upper air chamber of the cylinder and there is air pressure in the lower air chamber of the cylinder, the cylinder remains in the raised position. During the welding process, after the energy storage welding receives the start signal, the upper air chamber solenoid valve is energized and gas enters the upper air chamber. At this time, the gas pressures of the upper and lower cylinders are equal, but due to the weight of the machine head, the pressure of the upper air chamber plus the weight of the machine head will be greater than the pressure of the lower air chamber. At this time, the machine head will fall under the action of gravity. The fall of the cylinder will basically not have an impact on the convex point, avoiding the crushing of the convex point in the pre-pressing stage. After the cylinder is pressed down until the upper and lower electrodes are in contact with the workpiece, the lower air chamber solenoid valve is energized to discharge the gas in the lower air chamber. Since the gas pressure in the upper air chamber is greater than the gas pressure in the lower air chamber, the electrode begins to pressurize the workpiece for projection welding. There is a pressure detection switch in the lower air chamber. When the gas pressure in the lower air chamber is reduced to the required pressure, the pressure switch will send a discharge signal to the energy storage welder. At this time, the energy storage welder releases the energy stored in the capacitor to complete the projection welding of the microwave oven shell. At this time, the pressure switch can accurately control the discharge moment of the energy storage welding equipment and can also accurately control the welding pressure. After welding is completed, the upper and lower solenoid valves of the cylinder are de-energized, the lower air chamber of the cylinder is ventilated, the upper air chamber of the cylinder is exhausted, and the cylinder returns to the raised position, completing the entire process.

[0054] In this embodiment, the device further includes a muffler 19 , which is connected to the first solenoid valve and the second solenoid valve. The muffler can eliminate the noise generated by the first solenoid valve and the second solenoid valve when deflation occurs.

[0055] In this embodiment, the device also includes a pressure alarm device. The first pressure switch and the second pressure switch are both connected to set the pressure alarm device. When the pressure value detected by the first pressure switch and the second pressure switch is lower than the set threshold, the pressure alarm device will alarm, so that the operator can understand the corresponding working conditions in time and facilitate the smooth operation.

[0056] In this embodiment, the device also includes a residual pressure release valve 14, which is connected to the cylinder and can release the pressure in the lower air chamber of the cylinder. When the residual pressure release valve is opened, the gas in the lower air chamber of the cylinder is directly discharged, causing the cylinder piston to drop completely. The residual pressure release valve is closed, the lower air chamber of the cylinder is ventilated, and the cylinder rises to its normal position. By opening the residual pressure release valve, all the gas is discharged, making it convenient for the staff to carry out maintenance.

[0057] A method for controlling the projection welding pressure of a microwave oven shell by stages using the device as described above, Figures 1 to 3 As shown, the following steps are included:

[0058] Pre-compression stage: The upper air chamber of the cylinder is inflated so that the cylinder is slowly pressed down under its own weight to avoid impact on convex points;

[0059] Welding stage: The lower air chamber of the cylinder is exhausted and the pressure is detected in real time. When the pressure drops to the set threshold, discharge is triggered to ensure that the pressure during welding matches the bump height of 0.3-0.5mm and the diameter of 1-1.5mm to prevent spatter or deformation.

[0060] The more specific steps are as follows:

[0061] (1) Place the projection welding portion of the microwave oven shell on the lower electrode, open the first one-way valve, and allow the gas in the gas source to flow into the gas tank. The pressure switch in the gas tank detects the pressure in the gas tank. If the pressure is insufficient (an alarm prompt may be used), the welding is interrupted to prevent explosion points or welding defects caused by pressure loss. If the pressure is normal, open the switch to allow the gas to flow into the pneumatic triplex. The gas is decompressed in the pneumatic triplex and then flows into the first gas distribution block after decompression.

[0062] (2) When the energy storage welder is not started, there is no gas in the upper air chamber of the cylinder, and the lower air chamber of the cylinder is always ventilated and has the same gas pressure as the gas pressure after the pneumatic triplex is decompressed. After the energy storage welder gives a start signal, the first solenoid valve is turned on and the upper air chamber of the cylinder is ventilated. At this time, the gas pressures of the upper and lower air chambers of the cylinder are equal, but due to the effect of the cylinder's own weight and the fact that the force area of ​​the lower air chamber of the cylinder is smaller than the force area of ​​the piston of the upper air chamber, the cylinder will naturally fall, causing the upper electrode to exert a weak downward pressure on the microwave oven shell, causing the device to enter the pre-pressing stage. This pressure will not impact the convex point, thus avoiding the convex point from being crushed during the pre-pressing stage.

[0063] (3) After the cylinder is pressed down until both the upper and lower electrodes are in contact with the microwave oven shell workpiece, the lower air chamber solenoid valve is energized, and the second solenoid valve is energized to release the gas in the second air path, and the gas in the lower air chamber of the cylinder is discharged. Since the gas pressure in the upper air chamber of the cylinder is greater than the gas pressure in the lower air chamber, the welding electrode begins to pressurize the projection welding workpiece. When the second pressure switch detects that the gas pressure in the lower air chamber is reduced to the required pressure, the pressure switch will send a discharge signal to the energy storage welder, and the energy storage welder will discharge at a welding pressure of 3000N-5000N to complete the projection welding of the microwave oven shell. After the welding is completed, the gas in the lower air chamber of the cylinder will be completely exhausted. At this time, the pressure of the electrode on the workpiece reaches the maximum, and further downward pressure is applied to make the microwave oven shell and the shell cover fit tightly after the welding is completed, ensuring that the shell has a better sealing performance.

[0064] (4) After the welding is completed, the first solenoid valve and the second solenoid valve are both powered off, the lower air chamber of the cylinder is ventilated, and the upper air chamber of the cylinder is exhausted, so that the cylinder returns to the raised position, and the upper electrode rises under the push of the cylinder, and the welded microwave oven shell is taken out, completing the whole process.

[0065] The application of the projection welding pressure control device for microwave oven shells as described above in projection welding of microwave oven shells.

[0066] The microwave oven shell projection welding pressure control device as described above is applied in the projection welding of microwave oven shells with a projection height of 0.3-0.5 mm and a diameter of 1-1.5 mm.

[0067] Example 2

[0068] Projection welding of a microwave oven shell with dimensions of 440 mm x 338 mm x 200 mm, a shell wall thickness of 0.7 mm, a bump height of 0.3 mm, a bump diameter of 1 mm, and 19 bumps in a single row, is performed using the energy storage welding equipment of the above device, including the following steps:

[0069] (1) Open the first one-way valve, and the gas in the gas source flows into the gas tank. The pressure switch in the gas tank detects whether the pressure in the gas tank is overpressure. If it is overpressure, an alarm is issued. If it is not overpressure, the switch is opened to allow the gas to flow into the pneumatic triplex. The gas is decompressed in the pneumatic triplex to a pressure of 0.3 MPa. After decompression, the gas flows into the first gas block;

[0070] (2) Start the welding machine, connect the upper air chamber solenoid valve, and ventilate the upper air chamber of the cylinder. Due to the different force areas of the upper and lower air chambers and the weight of the equipment, the cylinder will naturally fall, so that the device exerts a weak downward pressure on the shell, causing the device to enter the pre-pressing stage. This pressure will not impact the convex point, thus avoiding the convex point from being crushed during the pre-pressing stage. The overall pre-pressing time is 200ms.

[0071] (3) After the cylinder is pressed down until the upper and lower electrodes of the welding electrode are in contact with the workpiece, the lower air chamber solenoid valve is energized to release the gas in the second air path, so that the gas in the lower air chamber is exhausted. Since the gas pressure in the upper air chamber is greater than that in the lower air chamber, the electrode begins to pressurize the workpiece for projection welding. When the second pressure switch detects that the gas pressure in the lower air chamber has decreased to 0.15MPa, the pressure switch sends a discharge signal to the energy storage welder, so that the energy storage welder releases the energy stored in the capacitor to complete the projection welding of the microwave oven shell. The pressurization time is 200ms, the welding voltage is 350V, and the welding time is 5ms. The welding is completed, and the gas in the lower air chamber of the cylinder has been completely exhausted. At this time, the 3000N pressure of the cylinder is fully applied to the workpiece, ensuring that the microwave oven shell and the shell cover are tightly fitted after welding.

[0072] (4) After welding is completed, the first solenoid valve and the second solenoid valve of the cylinder are both powered off, the lower air chamber of the cylinder is ventilated, and the air chamber on the cylinder is exhausted, so that the cylinder returns to the raised position, completing the entire process.

[0073] like Figures 5 to 9 As shown in the figure, after welding, the surface of the solder joint is flat, the gap inside the microwave oven is good, and the quality of the solder joint meets the use requirements.

[0074] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A projection welding pressure control device for a microwave oven housing, characterized in that: The device can perform projection welding on a microwave oven shell through welding convex points, and comprises a gas source, a first one-way valve, a gas storage tank, a first pressure switch, a pneumatic triplex, a first gas distribution block, a first solenoid valve, a first speed regulating valve, a second speed regulating valve, a second solenoid valve, a third speed regulating valve, a second gas distribution block, a second pressure switch, a gas cylinder, a second one-way valve, a welding electrode, and a stored energy welder; The gas source is connected to the input end of the first one-way valve, the output end of the first one-way valve is connected to the gas tank, the gas tank is connected to a first pressure switch, the gas tank, the pneumatic triplet and the first gas distributor are connected in sequence, the gas tank is connected to the pneumatic triplet through the switch, the gas source can input gas into the gas tank through the first one-way valve, the gas source can provide gas for the device, the first one-way valve can protect the safety of the device, the gas tank can store gas, the first pressure switch can detect whether the gas source pressure meets the use requirements, the pneumatic triplet can reduce the pressure on the gas, and the first gas distributor can divide the gas into several gas paths; The first solenoid valve, the first speed regulating valve and the second speed regulating valve are connected in sequence and arranged to form a first gas circuit. The input end of the first gas circuit is connected to the first gas distributor block, and the output end of the first gas circuit is connected to the upper gas chamber of the cylinder. The first solenoid valve can control the release and storage of gas in the first gas circuit. The second solenoid valve, the third speed regulating valve and the second gas distribution block are connected in sequence and arranged to form a second gas circuit. The air pressure of the second gas circuit is lower than the air pressure of the first gas circuit. The input end of the second gas circuit is connected to the first gas distribution block, and the output end of the second gas circuit is connected to the lower air chamber of the cylinder. The second solenoid valve can control the release and storage of gas in the second gas circuit. The second gas distribution block is connected to a second pressure switch. The input port of the second one-way valve is connected to the second gas distribution block, and the output port of the second one-way valve is connected to the first gas distribution block; The welding electrode includes an upper electrode and a lower electrode arranged in parallel in the vertical direction. The upper electrode is arranged above the lower electrode. The microwave oven shell to be welded can be detachably fitted on the lower electrode. The working end surface of the cylinder is connected to the upper electrode. The cylinder can drive the upper electrode to move back and forth in the vertical direction. The upper electrode can perform a welding operation on the microwave oven shell under the drive of the cylinder. The welding electrode is connected to the energy storage welder. The energy storage welder is connected to the second pressure switch via a signal. The energy storage welder can provide the energy required for the welding electrode. The arrangement of the energy storage electrode can protect the device from having sufficient voltage for production and processing. The first speed regulating valve is connected to the cylinder and can adjust the intake speed of the upper air chamber of the cylinder. The second speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the upper air chamber of the cylinder. The third speed regulating valve is connected to the cylinder and can adjust the exhaust speed of the lower air chamber of the cylinder.

2. The device according to claim 1, characterized in that: The device further comprises a muffler, which is connected to the first solenoid valve and the second solenoid valve. The muffler can eliminate the noise generated by the first solenoid valve and the second solenoid valve when deflation occurs.

3. The device according to claim 1, characterized in that: The device also includes a pressure alarm device. The first pressure switch and the second pressure switch are both connected to set the pressure alarm device. When the pressure value detected by the first pressure switch and the second pressure switch is lower than the set threshold, the pressure alarm device will alarm.

4. The device according to any one of claims 1 to 3, characterized in that: The device further comprises a residual pressure release valve which is connected to the cylinder and can release the pressure in the lower air chamber of the cylinder.

5. The method for controlling projection welding pressure of a microwave oven shell according to any one of claims 1 to 4, characterized in that: The following steps are involved: Pre-compression stage: The upper air chamber of the cylinder is inflated so that the cylinder is slowly pressed down under its own weight to avoid impact on convex points; Welding stage: The lower air chamber of the cylinder is exhausted and the pressure is detected in real time. When the pressure drops to the set threshold, discharge is triggered to ensure that the pressure during welding matches the bump height of 0.3-0.5mm and the diameter of 1-1.5mm to prevent spatter or deformation.

6. The method according to claim 5, characterized in that: Here are the steps: (1) Place the projection welding portion of the microwave oven shell on the lower electrode, open the first one-way valve, and allow the gas in the gas source to flow into the gas tank. The pressure switch in the gas tank detects the pressure in the gas tank. If the pressure is insufficient (an alarm prompt may be used), the welding is interrupted to prevent explosion points or welding defects caused by pressure loss. If the pressure is normal, open the switch to allow the gas to flow into the pneumatic triplex. The gas is decompressed in the pneumatic triplex and then flows into the first gas distribution block after decompression. (2) When the energy storage welder is not started, there is no gas in the upper air chamber of the cylinder, and the lower air chamber of the cylinder is always ventilated and has the same gas pressure as the gas pressure after the pneumatic triplex is decompressed. After the energy storage welder gives a start signal, the first solenoid valve is turned on and the upper air chamber of the cylinder is ventilated. At this time, the gas pressures of the upper and lower air chambers of the cylinder are equal, but due to the effect of the cylinder's own weight and the fact that the force area of ​​the lower air chamber of the cylinder is smaller than the force area of ​​the piston of the upper air chamber, the cylinder will naturally fall, causing the upper electrode to exert a weak downward pressure on the microwave oven shell, causing the device to enter the pre-pressing stage. This pressure will not impact the convex point, thus avoiding the convex point from being crushed during the pre-pressing stage. (3) After the cylinder is pressed down until both the upper and lower electrodes are in contact with the microwave oven shell workpiece, the lower air chamber solenoid valve is energized, and the second solenoid valve is energized to release the gas in the second air path, and the gas in the lower air chamber of the cylinder is discharged. Since the gas pressure in the upper air chamber of the cylinder is greater than the gas pressure in the lower air chamber, the welding electrode begins to pressurize the projection welding workpiece. When the second pressure switch detects that the gas pressure in the lower air chamber is reduced to the required pressure, the pressure switch sends a discharge signal to the energy storage welder, and the energy storage welder discharges at a welding pressure of 3000N-5000N to complete the projection welding of the microwave oven shell. After the welding is completed, the gas in the lower air chamber of the cylinder will be completely exhausted. At this time, the pressure of the electrode on the workpiece reaches the maximum, and further downward pressure is applied to ensure that the microwave oven shell and the shell cover are tightly fitted after the welding is completed, ensuring that the shell has a better sealing performance; (4) After the welding is completed, the first solenoid valve and the second solenoid valve are both powered off, the lower air chamber of the cylinder is ventilated, and the upper air chamber of the cylinder is exhausted, so that the cylinder returns to the raised position, and the upper electrode rises under the push of the cylinder, and the welded microwave oven shell is taken out, completing the whole process.

7. Use of the projection welding pressure control device for a microwave oven shell according to any one of claims 1 to 4 in projection welding of a microwave oven shell.

8. Use of the projection welding pressure control device for microwave oven shells according to any one of claims 1 to 4 in projection welding of microwave oven shells with a bump height of 0.3-0.5 mm and a diameter of 1-1.5 mm.

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