Ultrasonic atomization pulse type cold air jet cooling and lubricating device and operation process thereof

Abstract

The invention relates to an ultrasonic atomization pulse type cold air jet cooling and lubricating device and an operation process thereof. The device comprises an air compressor, a cold air generator, a gas storage tank, a pulse control valve and an ultrasonic atomization nozzle module which are sequentially connected through a gas pipeline. The ultrasonic atomizing nozzle module comprises an ultrasonic transducer, a stepped amplitude-variable rod, a waterproof cover, a sealing cover and a focusing nozzle. In the working process, the stepped amplitude-variable rod amplifies the high-frequency mechanical vibration amplitude of the ultrasonic transducer, and cutting fluid is efficiently atomized into micron-sized liquid drops through the cavitation effect and the capillary wave effect; meanwhile, the cold air generator converts high-pressure air provided by the air compressor into low-temperature gas and temporarily stores the low-temperature gas in the gas storage tank, and the low-temperature gas is released in a pulse mode through the precise pulse control valve according to the set frequency and duty ratio. The pulse low-temperature gas enters the sealing cover to be fully mixed with the atomized liquid drops, uniform gas-liquid two-phase jet flow is formed, finally, the jet flow is accelerated by the focusing nozzle to form high-speed convergent jet flow, the high-speed convergent jet flow acts on a cutting area accurately, and pulse type efficient cooling and lubricating cutting machining is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and particularly to an ultrasonic atomization pulsed cold air jet cooling and lubrication device for cutting and its operation process. Technical Background

[0002] During the machining process, the cooling and lubrication in the cutting area have an important impact on the machining quality, tool life, and machining efficiency. The cutting heat generated during the cutting process can cause the temperatures of the tool and the workpiece to rise sharply, which in turn leads to problems such as tool wear, workpiece deformation, and deterioration of the surface quality. Effective cooling and lubrication can not only reduce the cutting temperature and tool wear but also improve the machining surface quality and machining efficiency. Therefore, the cooling and lubrication technology has always been a research hotspot in the field of machining.

[0003] Traditional cooling and lubrication methods, such as flood cooling, achieve cooling and lubrication through the continuous pouring of a large amount of cutting fluid. Although this method can reduce the cutting temperature to a certain extent, it has many defects: First, the large amount of cutting fluid used leads to waste of resources and increased costs; second, the chemical components in the cutting fluid may pose hazards to the environment and the health of operators; in addition, the cooling effect of flood cooling is uneven, and it is difficult to precisely control the temperature and lubrication state in the cutting area, especially in high-speed and high-efficiency machining.

[0004] In recent years, new cooling and lubrication technologies such as minimum quantity lubrication (MQL) and cryogenic cooling have gradually been applied. Minimum quantity lubrication atomizes a small amount of cutting fluid and transports it to the cutting area, significantly reducing the amount of cutting fluid used and reducing environmental pollution. However, the cooling capacity of minimum quantity lubrication is limited and it is difficult to handle machining scenarios with high heat generation, such as high-speed cutting or machining of difficult-to-machine materials. Cryogenic cooling technology uses low-temperature gases or liquids (such as liquid nitrogen) to cool the cutting area, which can effectively reduce the cutting temperature, but its lubrication effect is insufficient, and the equipment is complex and the cost is high.

[0005] In summary, in view of the deficiencies of traditional cooling and lubrication methods and the limitations of the existing technologies, there is an urgent need for a new type of cooling and lubrication device that can achieve efficient cooling and lubrication while reducing the amount of cutting fluid used, and has good controllability and adaptability to meet the requirements of modern machining for high efficiency, environmental protection, and precision machining. The present invention is proposed under this background, aiming to solve the defects in the existing technologies through innovative design and promote the further development of machining technology. Summary of the Invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides an ultrasonic atomization pulsed cold air jet cooling and lubrication device and its operating process. Through the synergistic effect of high-frequency acoustic atomization and pulsed cold air, the permeability and heat transfer efficiency of the cooling medium are significantly improved, and it can be applied to high-efficiency precision machining occasions.

[0007] In order to achieve the above invention purpose, the technical solution adopted by the present invention is:

[0008] An ultrasonic atomization pulsed cold air jet cooling and lubrication device includes an air compressor, a cold air generator, a gas storage tank, a pulse control valve, and an ultrasonic atomization nozzle module. The ultrasonic atomization nozzle module is mainly composed of key components such as an ultrasonic transducer, a stepped horn, a waterproof cover, a sealing cover, and a focusing nozzle.

[0009] The air compressor, the cold air generator, the gas storage tank, the pulse control valve, and the ultrasonic atomization nozzle module are sequentially connected through a gas pipeline. The output end of the ultrasonic transducer and the input end of the stepped horn are connected by bolts. The waterproof cover and the sealing cover are distributed on both sides of the flange of the stepped horn and clamp the flange of the stepped horn through bolts, thereby encapsulating the ultrasonic transducer and the stepped horn in its internal cavity. The focusing nozzle is fixed to the outlet side of the tail end of the sealing cover through bolts.

[0010] The cold air generator can reduce the temperature of the high-pressure gas generated by the air compressor to the range of -50 to 0 °C, and the temperature can be precisely adjusted with an adjustment accuracy of not more than 2 °C. The generated low-temperature gas is stored in the gas storage tank.

[0011] The pulse control valve can adjust the low-temperature gas in the gas storage tank to be released in a pulsed form, with a release frequency of 0 - 100 Hz, and the flow rate of the low-temperature gas can be precisely controlled within the range of 10 - 50 L / min.

[0012] The resonance frequency f and resonance length l of the stepped horn respectively satisfy the following conditions:

[0013]

[0014] Wherein, σ is the surface tension of the cutting fluid, ρ is the density of the cutting fluid, d is the droplet diameter, and C is the wave velocity of the metal material used for the stepped horn.

[0015] The magnification coefficient M of the stepped horn is:

[0016]

[0017] Wherein, D1 and D2 are respectively the diameters of the input end and the output end of the stepped horn.

[0018] The stepped horn includes two cylinders with different diameters. The diameter of the output end is smaller than that of the input end, and a circular cross-section flow channel in the shape of the letter "L" is provided inside the output end, which is symmetrically distributed along the central axis. The inlet of the flow channel is located at a position where the length from the input end of the stepped horn is 2l / 3, and the outlet of the flow channel is located at the output end of the stepped horn. The diameter range of the circular cross-section flow channel is 0.5 - 3 mm.

[0019] After the size of the stepped horn is calculated by formulas (1) and (2), the vibration mode needs to be adjusted and the frequency needs to be corrected by ANSYS finite element software. The error between the corrected resonant frequency f0 and the theoretical resonant frequency f does not exceed 5%.

[0020] The ultrasonic transducer uses PZT8 piezoelectric ceramic chips, and the number is 4. The diameter of its output end is equal to the diameter of the input end of the stepped horn.

[0021] On both sides of the tail of the sealing cover, an air inlet and an air outlet are respectively provided. The central axes of the two coincide, and this central axis is perpendicular to the central axis of the stepped horn, parallel to the end face of the output end and maintaining a predetermined distance; the air inlet is connected to a pulse control valve through a gas pipeline, and the moving direction of the pulsed gas in the sealing cover is perpendicular to the acting direction of the ultrasonic vibration.

[0022] An operating process of an ultrasonic atomization pulsed cold air jet cooling and lubrication device is as follows:

[0023] (1) Fix the ultrasonic atomization nozzle module on the machine tool spindle box, and adjust the outlet direction of the focusing nozzle to be the same as the tool rotation direction;

[0024] (2) Turn on the ultrasonic power supply, and adjust the output frequency to f. Under the driving action of the ultrasonic power supply, an ultrasonic vibration with an amplitude of A1 is generated at the output end of the ultrasonic transducer. The stepped horn amplifies the amplitude and generates an ultrasonic vibration with an amplitude of A2 = MA1;

[0025] (3) Turn on the cutting fluid supply system, so that the cutting fluid reaches the output end through the internal flow channel of the stepped horn. The stepped horn amplifies the amplitude of the high-frequency mechanical vibration generated by the ultrasonic transducer, and efficiently atomizes the cutting fluid into micron-sized (diameter 10 - 50 microns) droplets through the cavitation effect and capillary wave effect;

[0026] (4) Turn on the air compressor, so that the high-pressure air is converted into low-temperature gas by the cold air generator and stored in the gas storage tank. The pulsed valve controls the release of the low-temperature gas at a predetermined pulse frequency and duty cycle. The pulsed gas enters the sealing cover and is fully mixed with the atomized droplets to form a uniform gas-liquid two-phase fluid, which is accelerated by the focusing nozzle and reaches the cutting area to achieve pulsed cooling and lubrication cutting processing.

[0027] Beneficial effects:

[0028] (1) The present invention atomizes the cutting fluid into micron-sized droplets through ultrasonic atomization technology, and combines with the pulse injection mode to precisely match the machining rhythm, significantly improving the heat exchange efficiency, achieving comprehensive and uniform cooling and lubrication of complex workpieces, and reducing tool wear.

[0029] (2) The low-temperature jet adopted by the present invention directly hits the heat source area, quickly dissipates the cutting heat, reduces material thermal deformation, residual stress and surface burn, and is especially suitable for difficult-to-machine materials such as superalloys, ensuring machining accuracy and surface integrity.

[0030] (3) The present invention can significantly reduce the consumption of cutting fluid, greatly reduce the waste liquid treatment cost, improve the machining environment, extend the equipment life, and has both environmental protection and economy, meeting the trend of sustainable manufacturing. Description of the Drawings

[0031] Figure 1 is the overall structural schematic diagram of the ultrasonic atomization pulsed cold air jet cooling and lubrication device of the present invention;

[0032] Figure 2 is Figure 1 the structural schematic diagram of the stepped horn;

[0033] Figure 3 is the finite element simulation nephogram of the resonant modes of the ultrasonic transducer and the stepped horn;

[0034] Figure 4 is Figure 1 the structural schematic diagram of the sealing cover in

[0035] Figure 5 is the measurement amplitude curve result diagram of the stepped horn;

[0036] Figure 6 is the droplet size diagram generated by ultrasonic atomization;

[0037] Figure 7 is the effect diagram of the ultrasonic atomization pulsed cold air jet.

[0038] Description of the main reference numerals: air compressor - 1, cold air generator - 2, gas storage tank - 3, pulse control valve - 4, ultrasonic atomization nozzle module - 5, ultrasonic transducer - 5 - 1, stepped horn - 5 - 2, waterproof cover - 5 - 3, sealing cover - 5 - 4, focusing nozzle - 5 - 5, input end of the stepped horn - 6, flange - 7, flow channel - 8, output end of the stepped horn - 9. Detailed Embodiments

[0039] The technical solution of the present invention will be specifically described below in combination with the embodiments and the drawings.

[0040] Embodiment 1

[0041] Figure 1 is the overall structural schematic diagram of the ultrasonic atomization pulsed cold air jet cooling and lubrication device of the present invention; as Figure 1 shown, an ultrasonic atomization pulsed cold air jet cooling and lubrication device includes an air compressor 1, a cold air generator 2, a gas storage tank 3, a pulse control valve 4, and an ultrasonic atomization nozzle module 5; wherein the ultrasonic atomization nozzle module 5 includes: an ultrasonic transducer 5-1, a stepped horn 5-2, a waterproof cover 5-3, a sealing cover 5-4, and a focusing nozzle 5-5.

[0042] The air compressor 1, the cold air generator 2, the gas storage tank 3, the pulse control valve 4, and the ultrasonic atomization nozzle module 5 are sequentially connected through a gas pipeline; the output end of the ultrasonic transducer 5-1 and the input end 6 of the stepped horn 5-2 are connected by bolts, and the waterproof cover 5-3 and the sealing cover 5-4 are respectively arranged on both sides of the flange 7 of the horn 5-3 and clamp the flange 7 of the stepped horn 5-3 through bolts, thereby encapsulating the ultrasonic transducer 5-1 and the stepped horn 5-2 in its internal cavity, and the focusing nozzle 5-5 is fixed to the tail end air outlet side of the sealing cover 5-4 through bolts.

[0043] The cold air generator 2 can reduce the temperature of the high-pressure gas generated by the air compressor 1 to -20°C, and the temperature error range is not greater than 2°C. The generated low-temperature gas is stored in the gas storage tank 3.

[0044] The pulse control valve 4 can adjust the low-temperature gas in the gas storage tank 3 to be released in a pulsed form, the release frequency is 50 Hz, the waveform of the pulse is a square wave, and the flow rate of the low-temperature gas is 25 L / min.

[0045] Figure 2 is the structural schematic diagram of the stepped horn. The resonance frequency f and the resonance length l of the stepped horn respectively satisfy the following conditions:

[0046]

[0047] wherein, σ is the surface tension of the cutting fluid, ρ is the density of the cutting fluid, d is the droplet diameter, and C is the wave velocity of the metal material used for the stepped horn.

[0048] The magnification factor M of the stepped horn is:

[0049]

[0050] wherein, D1 and D2 are respectively the diameters of the input end and the output end of the stepped horn.

[0051] The parameters adopted in the design of this embodiment are as follows: The stepped horn 5-2 is made of TC4 titanium alloy, and the wave velocity is 6100 m / s. The cutting fluid used is Castrol 9954 water-based cutting fluid with a concentration of 8%, the density of the cutting fluid is 996 kg / m 3 , the surface tension is 0.032 N / m, the average diameter of the liquid droplets is 24 μm, the input end diameter is 38 mm, and the output end diameter is 22 mm. The resonant frequency f of the stepped horn 5-2 is calculated to be 50 kHz, the resonant length is 91.5 mm, and the magnification factor is 2.98.

[0052] The input end 6 of the stepped horn 5-2 is provided with a flange 7. Inside the output end 9 of the stepped horn 5-2, there are circular cross-section channels 8 distributed symmetrically in the shape of the letter L. The inlet of the channel 8 is located at a position 61 mm away from the input end of the stepped horn 5-2 in terms of length, and the outlet of the channel 8 is located at the end face of the output end 9 of the stepped horn 5-2. The channel diameter is 1 mm.

[0053] The ultrasonic transducer 5-1 uses PZT8 piezoelectric ceramic sheets, and the number is 4. Its output end diameter is 38 mm. Through the ANSYS finite element software for mode shape adjustment and frequency correction, the modal simulation results of the ultrasonic transducer and the stepped horn are as Figure 3 shown. The corrected resonant frequency is 50.4 kHz, and the error from the theoretical resonant frequency is only 0.8%, meeting the design requirements.

[0054] Figure 4 is a schematic structural diagram of the sealing cover. On both sides of the tail of the sealing cover 5-4, there are an air inlet 10 and an air outlet 11 respectively. The central axes of the two coincide, and this central axis is perpendicular to the central axis of the stepped horn 5-2 and parallel to the end face of the output end 9 and maintains a predetermined distance.

[0055] An operating process of an ultrasonic atomization pulsed cold air jet cooling and lubrication device is as follows:

[0056] (1). Fix the ultrasonic atomization nozzle module 5 on the machine tool spindle box, and adjust the outlet direction of the focusing nozzle 5-5 to be the same as the tool rotation direction;

[0057] (2). Turn on the ultrasonic power supply, adjust the output frequency to 50.4 kHz. Under the driving action of the ultrasonic power supply, the output end of the ultrasonic transducer generates ultrasonic vibration with an amplitude of 1.6 μm. The stepped horn amplifies the amplitude, and its output end generates ultrasonic vibration with an amplitude of 5 μm. The amplitude change curve is as Figure 5 shown;

[0058] (3) Turn on the cutting fluid supply system. The cutting fluid flows through the internal flow channel 8 of the stepped horn and reaches the output end 9. Under the action of ultrasonic vibration, the Castrol 9954 water-based cutting fluid is atomized into small droplets. As Figure 6 shown, the average diameter of the droplets is 24 microns, meeting the usage requirements;

[0059] (4) Turn on the air compressor 1, so that the high-pressure air is converted into low-temperature gas by the cold gas generator 2 and stored in the gas storage tank 3. The pulse control valve 4 is used to control the release of the low-temperature gas at a predetermined pulse frequency of 50 Hz. The pulsed gas enters the sealing cover 5-4 and is fully mixed with the atomized droplets to form a gas-liquid two-phase jet. The profile of the jet is as Figure 7 shown. The gas-liquid two-phase fluid is accelerated by the focusing nozzle 5-5 and then reaches the cutting area, realizing pulsed cooling and lubrication cutting machining.

[0060] This embodiment does not impose any formal restrictions on the shape, material, structure, etc. of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the technical solution of the present invention.

Claims

1. An ultrasonic atomization pulsed cold air jet cooling and lubricating device, characterized in that, It includes an air compressor, a cold gas generator, a gas storage tank, a pulse control valve, and an ultrasonic atomization nozzle module; the air compressor, the cold gas generator, the gas storage tank, the pulse control valve, and the ultrasonic atomization nozzle module are sequentially connected through a gas pipeline; The ultrasonic atomization nozzle module mainly consists of an ultrasonic transducer, a stepped horn, a waterproof cover, a sealing cover, and a focusing nozzle; the output end of the ultrasonic transducer and the input end of the stepped horn are connected by bolts, the waterproof cover and the sealing cover are respectively arranged on both sides of the flange of the stepped horn, and the flange of the stepped horn is clamped by bolts to encapsulate the ultrasonic transducer and the stepped horn in its internal cavity, and the focusing nozzle is fixed to the tail end air outlet side of the sealing cover by bolts.

2. The ultrasonic atomization pulsed cold air jet cooling and lubricating device according to claim 1, wherein The cold gas generator reduces the temperature of the high-pressure gas generated by the air compressor to the range of -50 to 0 °C, and the temperature can be precisely adjusted with an adjustment accuracy of not more than 2 °C, and the generated low-temperature gas is stored in the gas storage tank.

3. The ultrasonic atomization pulsed cold air jet cooling and lubricating device according to claim 1, characterized in that, The pulse control valve adjusts the low-temperature gas in the gas storage tank to be released in a pulsed form, the release frequency is 0 - 100 Hz, and the flow rate of the low-temperature gas can be precisely controlled in the range of 10 - 50 L / min.

4. The ultrasonic atomization pulsed cold air jet cooling and lubricating device according to claim 1, wherein The resonant frequency f and the resonant length l of the stepped horn respectively satisfy the following conditions: Wherein, σ is the surface tension of the cutting fluid, ρ is the density of the cutting fluid, d is the droplet diameter, and C is the wave velocity of the metal material used for the stepped horn; The magnification coefficient M of the stepped horn is: Wherein, D1 and D2 are respectively the diameters of the input end and the output end of the stepped horn; The stepped horn includes two cylinders with different diameters, the diameter of the output end is smaller than that of the input end, and a circular cross-section flow channel in the shape of an L letter is arranged symmetrically along the central axis inside the output end, the flow channel inlet is located at a position where the length from the input end of the stepped horn is 2l / 3, the flow channel outlet is located at the output end of the stepped horn, and the diameter range of the circular cross-section flow channel is 0.5 - 3 mm; After the size of the stepped horn is calculated by formulas (1) and (2), the vibration mode needs to be adjusted and the frequency needs to be corrected by ANSYS finite element software, and the error between the corrected resonant frequency f0 and the resonant frequency f does not exceed 5%.

5. The ultrasonic atomization pulsed cold air jet cooling and lubricating device according to claim 1, characterized in that, The tail part of the sealing cover is respectively provided with an air inlet and an air outlet, the central axes of the two coincide, and this central axis is perpendicular to the central axis of the stepped horn, and is parallel to the end face of the output end and maintains a predetermined distance; the air inlet is connected to the pulse control valve through a gas pipeline, and the movement direction of the pulsed gas in the sealing cover is perpendicular to the action direction of the ultrasonic vibration.

6. The operating process of an ultrasonic atomization pulsed cold air jet cooling and lubricating device according to claim 1, characterized in that, The steps are as follows: (1). Fix the ultrasonic atomization nozzle module on the machine tool spindle box, and adjust the outlet direction of the focusing nozzle to be the same as the tool rotation direction; (2). Turn on the ultrasonic power supply, adjust the output frequency to f, under the driving action of the ultrasonic power supply, the output end of the ultrasonic transducer generates ultrasonic vibration with an amplitude of A1, and the stepped horn amplifies the amplitude to generate ultrasonic vibration with an amplitude of A2 = MA1; (3). Turn on the cutting fluid supply system so that the cutting fluid flows through the internal flow path of the stepped horn and reaches the output end. Under the action of ultrasonic vibration, the cutting fluid is atomized into liquid droplets with a diameter of 10 - 50 microns; (4). Turn on the air compressor so that the high-pressure air is converted into low-temperature gas by the cold gas generator and stored in the gas storage tank. The low-temperature gas is controlled by the pulse control valve to be released at a predetermined pulse frequency. The pulsed gas enters the sealing cover and is fully mixed with the atomized liquid droplets to form a gas-liquid two-phase fluid, which is accelerated by the focusing nozzle and reaches the cutting area to achieve pulsed cooling and lubrication cutting processing.

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