A production and processing control system and control method for an air conditioner silencer

Abstract

The present invention relates to the technical field of muffler processing, and particularly to a production and processing control system and a control method for an air conditioner muffler, including obtaining the equivalent gap of the joint area, and determining whether the joint gap of the welding area is within the standard range; when the joint gap is within the standard range, predicting the critical stress of the joint area according to the joint gap of the welding area and the linear expansion coefficient of the assembly material, and determining the risk level of the copper tube in the joint area during high-frequency brazing; when the copper tube in the joint area is at the first risk level, determining the welding mode of high-frequency brazing according to the critical stress; after determining the welding mode of brazing, determining the welding stage of the weld according to the heating rate, and adopting the corresponding brazing strategy; detecting the current fluctuation of the induction coil during the high-frequency brazing process, and calling back the initial current frequency according to the fluctuation duration. The present invention reduces the welding defect rate of dissimilar metals by adjusting the welding mode and brazing strategy of high-frequency brazing.

Description

Technical Field

[0001] The present invention relates to the technical field of silencer processing, and particularly to a production and processing control system and control method for an air conditioner silencer. Background Art

[0002] An air conditioner silencer is a key component for reducing the airflow noise of an air conditioner system and is widely used in household, commercial, and industrial air conditioning equipment. It mainly attenuates the airflow noise through acoustic structure design (such as expansion chambers, resonance cavities, porous sound-absorbing materials, etc.). However, the processing accuracy, material properties, and structural integrity of the silencer directly affect its noise reduction effect and long-term reliability.

[0003] Chinese Patent Application Publication No.: CN117124022A discloses a manufacturing method for an air conditioner silencer, which uses an induction heating coil to heat the end of a seamless metal tube to 500°C - 1000°C; the rotational speed of the machine tool spindle is increased to 800 r / min - 1000 r / min, so that the spinning wheel moves along the side wall of the seamless metal tube multiple times in a predetermined trajectory, and the moving speed is 1 mm / s - 4 mm / s; the rotational speed of the machine tool spindle is increased to 1100 r / min - 1300 r / min, so that the spinning wheel moves closely along the surfaces of the transition part and the constriction part, and the moving speed is 1 mm / s - 4 mm / s. By using a seamless metal tube to manufacture the air conditioner silencer, the integrity of the air conditioner silencer is ensured, and during the processing, the plasticity of the seamless metal tube is increased by heating to avoid cracks in the seamless metal tube during the processing, thereby further improving the integrity of the air conditioner silencer, and using a machine tool for processing without the need to regularly replace the machine tool equipment, thus reducing the manufacturing cost.

[0004] The following problems exist in the processing and manufacturing process of the existing air conditioner silencers:

[0005] Copper is one of the commonly used materials in the manufacture of air conditioner silencers and is mainly applied to components such as pipelines and heat exchangers. The copper material consumes a relatively high amount of resources;

[0006] The welding defect rate of dissimilar metals is high. During the manufacturing process of air conditioner silencers, welding of dissimilar metals (such as copper, aluminum, steel, etc.) is often involved, and there are significant differences in their chemical compositions, physical properties, and metallographic structures;

[0007] During the manufacturing process of the air conditioner silencer, after welding, the welded part needs to be cleaned to remove welding residues. Summary of the Invention

[0008] Therefore, the present invention provides a production and processing control system and control method for an air conditioner silencer to overcome the problem of high welding defect rate of dissimilar metals in the prior art.

[0009] To achieve the above object, the present invention provides a production and processing control method for an air conditioner silencer, including:

[0010] Add a welding ring to the top of the joint area between the copper tube and the stainless steel housing, and use high-frequency brazing to weld several said joint areas;

[0011] Scan the copper tube-stainless steel housing joint surface to obtain the equivalent gap of the joint area, and determine whether the joint gap in the welding area is within the standard range according to the equivalent gap;

[0012] When the joint gap is within the standard range, estimate the critical stress of the joint area according to the joint gap in the welding area and the linear expansion coefficient of the assembly material, and conduct critical stress determination to determine the risk level of the copper tube in the joint area during high-frequency brazing;

[0013] When the copper tube in the joint area is at the first risk level, adjust the heating rate of the welding area according to the critical stress to determine the welding mode of high-frequency brazing;

[0014] After determining the welding mode of brazing, determine the welding stage of the weld according to the heating rate in combination with the temperature change rate and the ultrasonic amplitude, and adopt corresponding brazing strategies;

[0015] Adopt a preheating brazing strategy in the preheating stage, detect and calculate the copper temperature increase rate and the steel temperature increase rate of the copper tube and the stainless steel housing, and adjust the initial frequency welding power of high-frequency brazing;

[0016] Adopt a melting brazing strategy in the melting stage, and determine the preset welding duration in the melting stage according to the wettability of the solder;

[0017] During high-frequency brazing, detect the current fluctuation of the induction coil, and callback the initial current frequency of high-frequency brazing according to the fluctuation duration of the current fluctuation.

[0018] Further, the process of determining whether the joint gap in the welding area is within the standard range includes,

[0019] When the equivalent gap is less than the first standard value or greater than or equal to the second standard value, it is determined that the joint gap in the workpiece welding area is not within the standard range, and the copper tube and the stainless steel housing are polished or reprocessed;

[0020] When the equivalent gap is greater than or equal to the first standard value and less than the second standard value, it is determined that the joint gap in the workpiece welding area is within the standard range, and the welding mode of high-frequency brazing is determined according to the stress in the joint area.

[0021] Further, when the joint gap is within the standard range, estimate the critical stress of the joint area according to the joint gap and the linear expansion coefficient, and conduct critical stress determination,

[0022] When the critical stress is greater than the yield strength of copper, it is determined that the copper tube in the joint area during high-frequency brazing is in the second risk level;

[0023] When the critical stress is less than or equal to the yield strength of copper, it is determined that the copper tube in the joint area during high-frequency brazing is in the first risk level.

[0024] Furthermore, when the copper tube in the joint area is in the first risk level, the heating rate is controlled by adjusting the heating parameters;

[0025] When the critical stress is less than 0.5 times the yield strength, the induced current of the induction coil is increased to increase the heating rate in the welding area for rapid heating;

[0026] When the critical stress is greater than or equal to 0.5 times the yield strength and less than 0.8 times the yield strength, the induced current of the induction coil is adjusted for medium-speed heating;

[0027] When the critical stress is greater than or equal to 0.8 times the yield strength, the induced current of the induction coil is adjusted for slow heating.

[0028] Furthermore, the process of determining the welding stage of the weld includes,

[0029] The weld temperature and ultrasonic amplitude in the welding area are monitored in real time, and the temperature change curve is plotted based on the weld temperature to calculate the temperature change rate;

[0030] When the actual ratio of the temperature change rate to the heating rate is greater than the ratio evaluation value, or the ultrasonic amplitude is less than the standard amplitude, it is determined that the weld is in the preheating stage, and the corresponding preheating brazing strategy is adopted;

[0031] When the actual ratio of the temperature change rate to the heating rate is less than or equal to the ratio evaluation value, and the ultrasonic amplitude is greater than or equal to the standard amplitude, it is determined that the weld is in the melting stage, and the corresponding melting brazing strategy is adopted;

[0032] After the high-frequency brazing is stopped when the melting duration of the weld in the melting stage reaches the preset welding duration, it is determined that the weld is in the solidification stage.

[0033] Furthermore, in the preheating stage, the corresponding preheating brazing strategy is adopted, the copper-side temperature and the steel-side temperature of the copper tube and the stainless-steel shell are detected, and the copper temperature increase rate and the steel temperature increase rate are calculated based on the copper-side temperature and the steel-side temperature.

[0034] Furthermore, when the copper temperature increase rate is less than or equal to the product of the critical ratio and the steel temperature increase rate, it is determined that the dissimilar metal temperature difference is within an appropriate range; when the copper temperature increase rate is greater than the product of the critical ratio and the steel temperature increase rate, it is determined that there is an excessive risk of dissimilar metal temperature difference, and the initial brazing power of the high-frequency brazing is reduced.

[0035] Further, in the melting stage, a corresponding melting brazing strategy is adopted to obtain the wetting angle, judge the wettability of the solder, and determine the preset welding duration in the melting stage;

[0036] When the wetting angle is greater than the standard angle, it is judged that the filler metal has not spread sufficiently and is not completely wetted, and the welding area is continuously heated in the melting stage;

[0037] When the wetting angle is less than or equal to the standard angle, it is judged that the filler metal has spread sufficiently and is completely wetted, and the melting stage ends and enters the solidification stage. The stage duration of the melting stage is recorded as the preset welding duration.

[0038] Further, brazing is performed on a plurality of the welding areas in sequence to determine the current fluctuation of the induction coil;

[0039] When the fluctuation duration of the current fluctuation exceeding the fluctuation amplitude is greater than the critical duration, it is determined that the arc is abnormal and the initial current frequency is reduced.

[0040] A production and processing control system for an air conditioner silencer, comprising:

[0041] A data acquisition module, which is used to collect the three-dimensional gap distribution of the copper tube-stainless steel shell joint surface, real-time monitor the weld temperature and ultrasonic amplitude in the welding area, detect the copper side temperature and steel side temperature of the copper tube and the stainless steel shell, extract the filler metal edge contour, and detect the induced current of the induction coil;

[0042] A standard evaluation module, which is connected to the data acquisition module and is used to determine whether the joint gap in the welding area is within the standard range according to the equivalent gap;

[0043] A stress determination module, which is connected to the standard evaluation module and is used to estimate the critical stress in the joint area according to the joint gap in the welding area and the linear expansion coefficient of the assembly material, and perform critical stress determination to determine the risk level of the copper tube in the joint area during high-frequency brazing;

[0044] A mode adjustment module, which is connected to the stress determination module and is used to adjust the heating rate of the welding area according to the critical stress and determine the welding mode of high-frequency brazing;

[0045] A stage determination module, which is connected to the mode adjustment module and is used to determine the welding stage of the weld according to the heating rate in combination with the temperature change rate and the ultrasonic amplitude, and adopt a corresponding brazing strategy;

[0046] A feedback adjustment module, which is connected to the data acquisition module and is used to callback the initial current frequency of high-frequency brazing according to the fluctuation duration of the current fluctuation.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: when the joint gap between the copper pipe and the stainless steel shell of the air conditioner muffler at the assembly position is too large, an increase in the thickness of the solder layer will cause a decrease in the shear strength of the joint. During the actual welding process of high-frequency brazing, if the joint gap at the assembly position is too small, there is a risk of blockage of the solder formed by the solder ring. The present invention detects the joint gap between the copper pipe and the stainless steel shell of the air conditioner muffler at the assembly position before high-frequency brazing, determines the assembly condition of the assembly material, avoids some situations that may lead to the workpiece performance not meeting the requirements and risks that may occur during the subsequent welding process, increases the yield rate of the workpiece prepared after the production and processing control of the air conditioner muffler, and improves the preparation efficiency of the air conditioner muffler.

[0048] Furthermore, although the difference in the expansion coefficients of copper and stainless steel is small, in large-sized workpieces or precision joints, thermal stress concentration caused by joint gaps and local temperature gradients may still cause cracks in the copper pipe within the joint area. Traditional brazing uses a fixed heating curve and cannot adapt to variable gap conditions. Compared with traditional brazing, this method estimates the stress magnitude existing in the joint area based on the joint gap in the welding area and the linear expansion coefficient of the assembly material, performs critical stress determination to determine the risk state of the copper pipe within the joint area during high-frequency brazing, and determines the welding mode of brazing according to the relative magnitude relationship between the critical stress and the yield strength of copper. By adjusting the induced current of the induction coil, the heating rate of high-frequency brazing is controlled, thereby reducing the thermal stress fluctuation generated in the joint area during high-frequency brazing, reducing the crack incidence rate of the copper pipe, and saving energy through variable-speed heating, increasing the adaptability and flexibility of high-frequency brazing production and processing control for air conditioner mufflers.

[0049] Furthermore, when the temperature change rate decreases, this method indicates that the solder begins to absorb heat and melt, and reflects the mechanical vibration caused by the internal interface flow of the liquid solder in the joint area according to the amplitude jump. Compared with the traditional method that only relies on temperature thresholds to judge whether high-frequency brazing enters the melting stage, this method adopts multi-modal collaborative determination with strong anti-interference ability. Through the transient characteristics capture of the temperature change rate and ultrasonic vibration, high-precision and anti-interference detection during the welding stage is achieved, especially suitable for high-reliability welding of dissimilar metals. And combined with the determined heating rate to judge the transition from preheating to the melting stage, further improving the adaptability and flexibility of high-frequency brazing production and processing control for air conditioner mufflers.

[0050] Furthermore, in the preheating stage, the method adopts a preheating brazing strategy. Due to the large difference in thermal conductivity between copper and stainless steel, when the temperature increase rate on the copper side is faster than that on the stainless steel side, the power density in this area is reduced to prevent the copper from overheating and softening, avoiding oxidation or deformation caused by local overheating. At the same time, since the initial frequency welding power is changed in the preheating stage, after the brazing heating temperature decreases, the possibility of solder loss and grain growth is reduced. However, due to reasons such as the increase in the surface tension of the solder, the wettability of the solder to the base metal will be reduced. Therefore, in the melting stage, a melting brazing strategy is adopted to measure the spreading ability of the molten solder in the contact gap between the copper tube and the stainless steel shell in the contact area, ensuring that the solder spreads fully and avoiding incomplete fusion or porosity.

[0051] Furthermore, traditional high-frequency brazing relies on single current or temperature monitoring, making it difficult to cope with the instantaneous thermal deformation differences and interface metallurgical reaction uncertainties in the welding of dissimilar metals such as copper and stainless steel, resulting in a relatively high defect rate such as false soldering and cracks. This method conducts all-round multi-modal control and adjustment of the production process through the weld temperature, ultrasonic amplitude, and current fluctuations involved in high-frequency brazing, and ensures the strength consistency of the air-conditioning muffler in the four welding areas by calling back the initial welding parameters, reducing the defect rate of the workpiece and increasing the accuracy of controlling the production and processing of the air-conditioning muffler.

[0052] Furthermore, high-frequency brazing has the following significant advantages. High-frequency induction heating can heat the solder to the melting point in an extremely short time, greatly improving production efficiency; induction heating only acts on the weld area, with a small heat-affected zone and little impact on the properties of the base metal; the high-frequency heating method can ensure uniform temperature in the weld area and improve welding quality; compared with traditional flame heating, high-frequency brazing reduces fumes, dust, and oxidation, and the workshop environment is cleaner. By introducing an automated control system, welding parameters can be monitored in real time to ensure that each welding ring can perform at its best. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a flowchart of the production and processing control method for the air-conditioning muffler in the embodiment of the present invention;

[0054] Figure 2 is a cross-sectional structure diagram of high-frequency brazing in the embodiment of the present invention;

[0055] Figure 3 is a schematic structural diagram of the air-conditioning muffler in the embodiment of the present invention;

[0056] Figure 4 is a module connection diagram of the production and processing control system for the air-conditioning muffler in the embodiment of the present invention.

[0057] In the figure: 1 - copper tube, 2 - stainless steel shell, 3 - welding ring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] To make the objectives and advantages of the present invention more clear and understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and do not limit the protection scope of the present invention.

[0060] It should be noted that in the description of the present invention, the terms indicating the direction or positional relationship such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0061] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0062] Please refer to Figures 1-4 as shown in Figure 1 the flowchart of the production and processing control method for an air conditioner muffler in an embodiment of the present invention; Figure 2 the cross-sectional structure diagram of high-frequency brazing in an embodiment of the present invention; Figure 3 the structural schematic diagram of an air conditioner muffler in an embodiment of the present invention; Figure 4 the module connection diagram of the production and processing control system for an air conditioner muffler in an embodiment of the present invention.

[0063] The present invention provides a production and processing control method for an air conditioner muffler, including:

[0064] Step S1: Add a welding ring to the top of the joint area between the copper tube and the stainless steel shell, and perform welding on several said joint areas by high-frequency brazing;

[0065] Step S2: Scan the copper tube-stainless steel shell joint surface to obtain the equivalent gap of the joint area, and determine whether the joint gap in the welding area is within the standard range according to the equivalent gap;

[0066] Step S3: When the joint gap is within the standard range, estimate the critical stress in the joint area based on the joint gap in the welding area and the linear expansion coefficient of the assembly material, and determine the risk level of the copper tube in the joint area during high-frequency brazing through critical stress determination;

[0067] Step S4: When the copper tube in the joint area is at the first risk level, adjust the heating rate of the welding area according to the critical stress to determine the welding mode of high-frequency brazing;

[0068] Step S5: After determining the welding mode of brazing, determine the welding stage of the weld seam according to the heating rate in combination with the temperature change rate and the ultrasonic amplitude, and adopt corresponding brazing strategies;

[0069] Step S6: Adopt a preheating brazing strategy in the preheating stage, detect and calculate the copper temperature increase rate and the steel temperature increase rate of the copper tube and the stainless steel shell, and adjust the initial frequency welding power of high-frequency brazing;

[0070] Step S7: Adopt a melting brazing strategy in the melting stage, and determine the preset welding duration in the melting stage according to the wettability of the solder;

[0071] Step S8: During high-frequency brazing, detect the current fluctuation of the induction coil, and callback the initial current frequency of high-frequency brazing according to the fluctuation duration of the current fluctuation.

[0072] The working principle of high-frequency brazing is as follows:

[0073] Induction heating: Place the workpiece to be welded in the induction coil and fill it with a brazing filler metal with a melting point lower than that of the workpiece.

[0074] High-frequency current: Generate a strong alternating magnetic field through the induction coil, and the magnetic field induces eddy currents in the workpiece, thereby quickly heating the weld area.

[0075] Melting of the brazing filler metal: When the temperature of the weld area reaches the melting point of the brazing filler metal, the brazing filler metal melts and fills the workpiece gap through capillary action.

[0076] Diffusion and solidification: The liquid brazing filler metal diffuses and dissolves with the workpiece metal, and a firm weld seam is formed after cooling.

[0077] During implementation, the preparatory work before high-frequency brazing includes,

[0078] Prepare the assembly materials for the air-conditioning silencer. The assembly materials include copper tube 1, solder ring 3 and stainless steel shell 2, and ensure that the sizes of copper tube 1, solder ring 3 and stainless steel shell 2 match each other;

[0079] Assemble the copper tube into the stainless steel shell and fix it relatively. Position the fixed workpiece to ensure that the relative position of the workpiece and the induction coil remains unchanged, and add the solder ring annularly to the welding area;

[0080] In this embodiment, the copper tube is a red copper tube, and the welding ring is composed of a copper-based solder. After the welding ring melts, it forms a filler metal for high-frequency brazing.

[0081] High-frequency brazing is used to weld the joint area between the assembled copper tube and the stainless steel housing. The joint area corresponding to the induction coil of the high-frequency brazing is the welding area of the high-frequency brazing;

[0082] Detect the joint gap between the outer diameter of the assembled copper tube and the inner diameter of the housing in the welding area. Scan the copper tube - stainless steel housing joint surface with a line laser sensor to obtain the three-dimensional gap distribution of the joint surface;

[0083] Calculate the equivalent gap de according to the three-dimensional gap distribution, and take the geometric mean of the maximum gap dm and the minimum gap di. The equivalent gap ;

[0084] If the equivalent gap is less than the first standard value or greater than or equal to the second standard value, it is determined that the joint gap in the welding area of the workpiece is not in the standard range, and the copper tube and the stainless steel housing are polished or reprocessed;

[0085] Specifically, when the equivalent gap is less than the first standard value, the copper tube and the stainless steel housing are polished, and when the equivalent gap is greater than or equal to the second standard value, the assembly materials are reprocessed;

[0086] If the equivalent gap is greater than or equal to the first standard value and less than the second standard value, it is determined that the joint gap in the welding area of the workpiece is in the standard range, and the welding mode of the high-frequency brazing is determined according to the stress in the joint area;

[0087] Among them, the first standard value is 0.2 mm, the second standard value is 0.35 mm, and the equivalent gap is denoted as the joint gap.

[0088] Determine the initial welding parameters of the high-frequency brazing. The initial welding parameters include the initial current frequency and the initial frequency welding power of the induction coil;

[0089] Specifically, the initial current frequency of the induction coil is determined according to the wall thickness of the stainless steel housing. High frequency is used for thin-walled parts and low frequency for thick-walled parts. The initial current frequency is positively correlated with the wall thickness of the stainless steel housing; the initial frequency welding power is determined according to the length of the joint area, and the initial frequency welding power is positively correlated with the length of the joint area.

[0090] Specifically, when the joint gap between the copper pipe and the stainless steel shell of the air conditioner silencer at the assembly position is too large, an increase in the thickness of the brazing layer will cause a decrease in the shear strength of the joint. During the actual welding process of high-frequency brazing, if the joint gap at the assembly position is too small, there is a risk of blockage of the brazing material formed by the welding ring. The present invention detects the joint gap between the copper pipe and the stainless steel shell of the air conditioner silencer at the assembly position before high-frequency brazing, determines the assembly condition of the assembly material, avoids some situations that may lead to the workpiece performance not meeting the requirements and possible risks during the subsequent welding process, increases the yield rate of the workpiece prepared after the production and processing control of the air conditioner silencer, and improves the preparation efficiency of the air conditioner silencer.

[0091] When the joint gap is within the standard range, estimate the stress magnitude in the joint area based on the joint gap in the welding area and the linear expansion coefficient of the assembly material, determine the welding mode of brazing, and adjust the heating rate of brazing;

[0092] Estimate the critical stress σ in the joint area according to the joint gap and the linear expansion coefficient;

[0093] σ = E·Δα·ΔT·(1 + de / δ)

[0094] In the formula, E is the elastic modulus of copper, Δα is the difference in expansion coefficients, ΔT is the temperature difference between the current temperature and the melting point of the brazing material, and δ is the thickness of the brazing layer;

[0095] In implementation, E = 120 GPa, Δα = |α1 - α2|, ΔT = Tm - Tc, δ = 0.1 mm, where α1 and α2 are the preset linear expansion coefficients of the copper pipe and the stainless steel shell, α1 = 17×10 -6 / °C, α2 = 16.5×10 -6 / °C, Tm is the current temperature of the detected joint area, Tc is the preset melting point of the brazing material, and Tc = 780°C;

[0096] Conduct a critical stress determination to determine the risk level of the copper pipe in the joint area during high-frequency brazing,

[0097] If the critical stress is greater than the yield strength of copper, it is determined that the copper pipe in the joint area during high-frequency brazing is in the second risk level;

[0098] If the critical stress is less than or equal to the yield strength of copper, it is determined that the copper pipe in the joint area during high-frequency brazing is in the first risk level;

[0099] Among them, the yield strength is the yield strength of copper, which is equal to 70 MPa.

[0100] When the copper pipe in the joint area is in the first risk level, control the brazing temperature and heating rate by adjusting the heating parameters, and the heating parameters include the induction current of the induction coil and the heating time;

[0101] If the critical stress is less than 0.5 times the yield strength, adjust the induced current of the induction coil to rapidly increase the temperature, and increase the heating rate of the welding area by increasing the induced current.

[0102] If the critical stress is greater than or equal to 0.5 times the yield strength and less than 0.8 times the yield strength, adjust the induced current of the induction coil to moderately increase the temperature.

[0103] If the critical stress is greater than or equal to 0.8 times the yield strength, adjust the induced current of the induction coil to slowly increase the temperature.

[0104] In implementation, provide the reference values of this embodiment. The heating rate for rapidly increasing the temperature by adjusting the induced current of the induction coil is 10 °C / s, the heating rate for moderately increasing the temperature is 5 °C / s, and the heating rate for slowly increasing the temperature is 2 °C / s.

[0105] Specifically, although the difference in the expansion coefficients between copper and stainless steel is small, in large-sized workpieces or precision joints, the thermal stress concentration caused by joint gaps and local temperature gradients may still cause cracks in the copper tubes in the joint area. Traditional brazing uses a fixed heating curve and cannot adapt to variable gap conditions. Compared with traditional brazing, this method estimates the stress magnitude in the joint area based on the joint gap in the welding area and the linear expansion coefficient of the assembled materials, determines the risk state of the copper tubes in the joint area during high-frequency brazing through critical stress determination, and determines the welding mode of brazing according to the relative magnitude relationship between the critical stress and the yield strength of copper. By adjusting the induced current of the induction coil, the heating rate of high-frequency brazing is controlled, thereby reducing the thermal stress fluctuation generated in the joint area during high-frequency brazing, reducing the crack incidence rate of copper tubes, and saving energy through variable-speed heating, increasing the adaptability and flexibility for the production and processing control of high-frequency brazing of air-conditioning mufflers.

[0106] After determining the welding mode of brazing, use an infrared thermal imager and an ultrasonic sensor to monitor the weld temperature and ultrasonic amplitude in the welding area in real time, draw a temperature change curve based on the weld temperature, determine the stage where the weld is located, and dynamically adjust the welding parameters.

[0107] Calculate the temperature change rate based on the temperature change curve. The temperature change rate is equal to dT / dt. Determine the welding stage where the weld is located according to the temperature change rate, the determined heating rate, and the ultrasonic amplitude jump.

[0108] If the actual ratio of the temperature change rate to the heating rate is greater than the ratio evaluation value, or the ultrasonic amplitude is less than the standard amplitude, it is determined that the weld is in the preheating stage, and the corresponding preheating brazing strategy is adopted.

[0109] If the actual ratio of the temperature change rate to the heating rate is less than or equal to the ratio evaluation value, and the ultrasonic amplitude is greater than or equal to the standard amplitude, it is determined that the weld is in the melting stage, and the corresponding melting brazing strategy is adopted;

[0110] After the high-frequency brazing is stopped when the melting duration of the weld in the melting stage reaches the preset welding duration, it is determined that the weld is in the solidification stage;

[0111] Among them, the ratio evaluation value is 70%, and the standard amplitude is 5 μm.

[0112] Specifically, when the temperature change rate decreases in this method, it indicates that the filler metal begins to absorb heat and melt, and the mechanical vibration caused by the internal interface flow of the liquid filler metal in the joint area is reflected according to the amplitude jump. Compared with the traditional method that only relies on the temperature threshold to judge whether the high-frequency brazing enters the melting stage, this method adopts multi-modal collaborative determination with strong anti-interference ability. Through the transient characteristics capture of the temperature change rate and ultrasonic vibration, high-precision and anti-interference detection in the welding stage is achieved, which is especially suitable for the high-reliability welding of dissimilar metals. And by combining the determined heating rate to judge the transition from the preheating to the melting stage, the adaptability and flexibility of the high-frequency brazing production and processing control for air-conditioning mufflers are further improved.

[0113] In implementation, the corresponding preheating brazing strategy is adopted in the preheating stage, the copper-side temperature and the steel-side temperature of the copper tube and the stainless steel shell are detected, and the copper temperature increase rate and the steel temperature increase rate are calculated according to the copper-side temperature and the steel-side temperature.

[0114] If the copper temperature increase rate is less than or equal to the product of the critical ratio and the steel temperature increase rate, it is determined that the dissimilar metal temperature difference is within an appropriate range;

[0115] If the copper temperature increase rate is greater than the product of the critical ratio and the steel temperature increase rate, it is determined that there is a risk of excessive dissimilar metal temperature difference, and the initial frequency brazing power is reduced to prevent the copper tube from overheating and softening;

[0116] Specifically, when there is a risk of excessive dissimilar metal temperature difference, the initial frequency brazing power is reduced according to the ratio of the steel temperature increase rate to the copper temperature increase rate;

[0117] Among them, the critical ratio is 115%.

[0118] In the melting stage, the corresponding melting brazing strategy is adopted, and the preset welding duration in the melting stage is determined according to the wettability of the solder;

[0119] In the melting stage, the edge of the filler metal is photographed with a high-speed camera, image processing is performed to extract the liquid-solid interface contour, and the tangent is fitted to calculate the wetting angle.

[0120] If the wetting angle is greater than the standard angle, it is determined that the filler metal is not fully spread and is not completely wetted, and the welding area is continuously heated in the melting stage;

[0121] If the wetting angle is less than or equal to the standard angle, it is determined that the filler metal is fully spread and completely wetted, and the melting stage ends and enters the solidification stage. The stage duration of the melting stage is recorded as the preset welding duration.

[0122] Among them, the standard angle is 20°.

[0123] Specifically, in the preheating stage, a preheating brazing strategy is adopted in this method. Due to the large difference in heat conduction between copper and stainless steel, when the temperature increase rate on the copper side is faster than that on the stainless steel side, the power density in this area is reduced to prevent the copper from overheating and softening and avoid oxidation or deformation caused by local overheating. At the same time, since the initial frequency welding power is changed in the preheating stage, after the brazing heating temperature is reduced, the possibility of filler metal loss and grain growth is reduced. However, due to reasons such as the increase in the surface tension of the filler metal, the wettability of the filler metal to the base metal will be reduced. Therefore, in the melting stage, a melting brazing strategy is adopted to measure the spreading ability of the molten filler metal in the contact gap between the copper tube and the stainless steel shell in the contact area to ensure that the filler metal is fully spread and avoid incomplete fusion or porosity.

[0124] In this embodiment, there are four welding areas in the air conditioner silencer. The four welding areas are brazed in sequence, and the induction coil is detected by a high-frequency current sensor to determine the current fluctuation of the induction coil.

[0125] If the fluctuation duration during which the current fluctuation exceeds the fluctuation amplitude is greater than the critical duration, it is determined that the arc is abnormal, and the initial current frequency is called back.

[0126] Specifically, when the arc is abnormal, the initial current frequency is reduced according to the ratio of the critical duration to the fluctuation duration.

[0127] Among them, the fluctuation amplitude is 5%, and the critical duration is 10 ms.

[0128] Specifically, traditional high-frequency brazing relies on single current or temperature monitoring and is difficult to cope with the instantaneous thermal deformation difference and interface metallurgical reaction uncertainty in the welding of copper-stainless steel dissimilar metals, resulting in a relatively high defect rate such as false soldering and cracks. This method comprehensively controls and adjusts the production and processing process through the weld temperature, ultrasonic amplitude, and current fluctuation involved in high-frequency brazing, and ensures the strength consistency of the air conditioner silencer in the four welding areas by calling back the initial welding parameters, reducing the defect rate of the workpiece and increasing the accuracy of controlling the production and processing of the air conditioner silencer.

[0129] The control system of the embodiment of the present invention applies the above production and processing control method for the air conditioner silencer, including:

[0130] A data acquisition module, which is used to collect the three-dimensional gap distribution of the copper tube-stainless steel shell joint surface, monitor the weld temperature and ultrasonic amplitude in the welding area in real time, detect the copper-side temperature and steel-side temperature of the copper tube and the stainless steel shell, extract the edge contour of the solder, and detect the induced current of the induction coil;

[0131] A standard evaluation module, which is connected to the data acquisition module and is used to determine whether the joint gap in the welding area is within the standard range according to the equivalent gap;

[0132] A stress determination module, which is connected to the standard evaluation module and is used to estimate the critical stress in the joint area according to the joint gap in the welding area and the linear expansion coefficient of the assembly material, and perform critical stress determination to determine the risk level of the copper tube in the joint area during high-frequency brazing;

[0133] A mode adjustment module, which is connected to the stress determination module and is used to adjust the heating rate in the welding area according to the critical stress and determine the welding mode of high-frequency brazing;

[0134] A stage determination module, which is connected to the mode adjustment module and is used to determine the welding stage of the weld according to the heating rate in combination with the temperature change rate and the ultrasonic amplitude, and adopt corresponding brazing strategies;

[0135] A feedback adjustment module, which is connected to the data acquisition module and is used to callback the initial current frequency of high-frequency brazing according to the fluctuation duration of the current fluctuation.

[0136] Specifically, high-frequency brazing has the following significant advantages. High-frequency induction heating can heat the solder to the melting point in an extremely short time, greatly improving production efficiency; induction heating only acts on the weld area, with a small heat-affected zone and little impact on the properties of the base material; the high-frequency heating method can ensure uniform temperature in the weld area and improve the welding quality; compared with traditional flame heating, high-frequency brazing reduces fumes, dust and oxidation, and the workshop environment is cleaner. By introducing an automated control system, welding parameters can be monitored in real time to ensure that each welding ring can perform at its best.

[0137] So far, the technical solutions of the present invention have been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A production and processing control method for an air conditioner silencer, characterized in that a welding ring is added to the top of the joint area between the copper tube and the stainless steel shell, and high-frequency brazing is used to weld a plurality of said joint areas; the joint surface of the copper tube-stainless steel shell is scanned to obtain the equivalent gap of the joint area, and it is determined whether the joint gap in the welding area is within the standard range according to the equivalent gap; when the joint gap is within the standard range, the critical stress of the joint area is estimated according to the joint gap in the welding area and the linear expansion coefficient of the assembly material, and critical stress determination is carried out to determine the risk level of the copper tube in the joint area during high-frequency brazing; when the copper tube in the joint area is at the first risk level, the heating rate of the welding area is adjusted according to the critical stress to determine the welding mode of high-frequency brazing; after determining the welding mode of brazing, the welding stage of the weld seam is determined according to the heating rate in combination with the temperature change rate and the ultrasonic amplitude, and corresponding brazing strategies are adopted; during the preheating stage, a preheating brazing strategy is adopted, the copper temperature increase rate and the steel temperature increase rate of the copper tube and the stainless steel shell are detected and calculated, and the initial frequency welding power of high-frequency brazing is adjusted; during the melting stage, a melting brazing strategy is adopted, and the preset welding duration of the melting stage is determined according to the wettability of the solder; during the high-frequency brazing process, the current fluctuation of the induction coil is detected, and the initial current frequency of high-frequency brazing is called back according to the fluctuation duration of the current fluctuation; the process of determining whether the joint gap in the welding area is within the standard range includes: when the equivalent gap is less than the first standard value or greater than or equal to the second standard value, it is judged that the joint gap in the workpiece welding area is not within the standard range, and the copper tube and the stainless steel shell are polished or reprocessed; when the equivalent gap is greater than or equal to the first standard value and less than the second standard value, it is judged that the joint gap in the workpiece welding area is within the standard range, and the welding mode of high-frequency brazing is determined according to the stress in the joint area; when the joint gap is within the standard range, the critical stress of the joint area is estimated according to the joint gap and the linear expansion coefficient, and critical stress determination is carried out; when the critical stress is greater than the yield strength of copper, it is judged that the copper tube in the joint area during high-frequency brazing is at the second risk level; when the critical stress is less than or equal to the yield strength of copper, it is judged that the copper tube in the joint area during high-frequency brazing is at the first risk level; when the copper tube in the joint area is at the first risk level, the heating rate is controlled by adjusting the heating parameters; when the critical stress is less than 0.5 times the yield strength, the induced current of the induction coil is increased to increase the heating rate of the welding area for rapid heating; when the critical stress is greater than or equal to 0.5 times the yield strength and less than 0.8 times the yield strength, the induced current of the induction coil is adjusted for medium-speed heating; when the critical stress is greater than or equal to 0.8 times the yield strength, the induced current of the induction coil is adjusted for slow heating.

2. The production and processing control method for the air conditioner silencer according to claim 1, characterized in that, the process of determining the welding stage of the weld seam includes: the weld temperature and ultrasonic amplitude of the welding area are monitored in real time, and the temperature change curve is drawn according to the weld temperature to calculate the temperature change rate; When the actual ratio of the temperature change rate to the heating rate is greater than the ratio evaluation value, or the ultrasonic amplitude is less than the standard amplitude, it is determined that the weld is in the preheating stage, and the corresponding preheating brazing strategy is adopted; When the actual ratio of the temperature change rate to the heating rate is less than or equal to the ratio evaluation value, and the ultrasonic amplitude is greater than or equal to the standard amplitude, it is determined that the weld is in the melting stage, and the corresponding melting brazing strategy is adopted; After the high-frequency brazing is stopped when the melting duration of the weld in the melting stage reaches the preset welding duration, it is determined that the weld is in the solidification stage.

3. The production and processing control method for an air conditioner silencer according to claim 2, wherein In the preheating stage, the corresponding preheating brazing strategy is adopted, the copper-side temperature and the steel-side temperature of the copper tube and the stainless steel shell are detected, the copper temperature increase rate and the steel temperature increase rate are calculated according to the copper-side temperature and the steel-side temperature, and the dissimilar metal temperature difference risk is judged.

4. The production and processing control method for the air conditioner silencer according to claim 3, wherein When the copper temperature increase rate is less than or equal to the product of the critical ratio and the steel temperature increase rate, it is judged that the dissimilar metal temperature difference is in an appropriate range; when the copper temperature increase rate is greater than the product of the critical ratio and the steel temperature increase rate, it is judged that there is a risk of dissimilar metal temperature difference, and the initial frequency welding power of the high-frequency brazing is reduced.

5. The production and processing control method for an air conditioner silencer according to claim 2, characterized in that, In the melting stage, the corresponding melting brazing strategy is adopted, the wetting angle is obtained to judge the wettability of the solder, and the preset welding duration in the melting stage is determined; When the wetting angle is greater than the standard angle, it is judged that the solder is not fully spread and is not completely wetted, and the welding area is continuously heated in the melting stage; When the wetting angle is less than or equal to the standard angle, it is judged that the solder is fully spread and completely wetted, the melting stage ends and enters the solidification stage, and the stage duration of the melting stage is recorded as the preset welding duration.

6. The production and processing control method for an air conditioner silencer according to claim 1, wherein, Brazing is carried out on several of the welding areas in sequence, and the current fluctuation of the induction coil is determined; When the fluctuation duration of the current fluctuation exceeding the fluctuation amplitude is greater than the critical duration, it is determined that the arc is abnormal, and the initial current frequency is reduced.

7. A control system using the production and processing control method for an air conditioner muffler according to any one of claims 1-6, characterized in that, Including: A data acquisition module for collecting the three-dimensional gap distribution of the copper tube-stainless steel shell joint surface, real-time monitoring the weld temperature and ultrasonic amplitude of the welding area, detecting the copper-side temperature and the steel-side temperature of the copper tube and the stainless steel shell, extracting the solder edge contour, and detecting the induced current of the induction coil; A standard evaluation module connected to the data acquisition module for determining whether the joint gap of the welding area is in the standard interval according to the equivalent gap; A stress determination module connected to the standard evaluation module for predicting the critical stress of the joint area according to the joint gap of the welding area and the linear expansion coefficient of the assembly material, and performing critical stress determination to determine the risk level of the copper tube in the joint area during high-frequency brazing; A mode adjustment module connected to the stress determination module for adjusting the heating rate of the welding area according to the critical stress and determining the welding mode of the high-frequency brazing; A stage determination module connected to the mode adjustment module for determining the welding stage of the weld according to the heating rate combined with the temperature change rate and the ultrasonic amplitude, and adopting the corresponding brazing strategy; A feedback adjustment module connected to the data acquisition module for callback the initial current frequency of the high-frequency brazing according to the fluctuation duration of the current fluctuation.

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