AU2022201195A1

AU2022201195A1 - Multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device

Info

Publication number: AU2022201195A1
Application number: AU2022201195A
Authority: AU
Inventors: Teng GAO; Changhe LI; Hao MA; Shubham Sharma; Xiaoming Wang; Xifeng Wu; Min Yang; Yuying YANG; Zongming Zhou
Original assignee: Qingdao University of Technology; IK Gujral Punjab Technical University
Current assignee: Qingdao University of Technology; IK Gujral Punjab Technical University
Priority date: 2021-11-24
Filing date: 2022-02-22
Publication date: 2023-06-08
Anticipated expiration: 2042-02-22
Also published as: AU2022201195B2; CN114012498A; CN114012498B

Abstract

Disclosed is a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device, belonging to the technical field of machining equipment and including a Minimal Quantity Lubrication (MQL) device, an auxiliary charging device, an electrostatic drive and control device. The MQL device includes a micro-pump and the auxiliary charging device communicated with the micro-pump. The micro-pump is also connected to a frequency generator. The electrostatic drive and control device includes a high-voltage electrostatic generator. Output ends of the high-voltage electrostatic generator are respectively connected to the auxiliary charging device and a nozzle. The auxiliary charging device includes a housing. A charger is arranged in the housing. An oil delivery pipe is arranged at an upper part of the housing. A gas-liquid delivery pipe and a gas inlet pipeline are arranged at a lower part of the housing. The gas-liquid delivery pipe is connected to the nozzle to deliver cooling lubricating oil and compressed gas to the nozzle. 1/8 III 1I-2 II 1 -6 II -1 11 -3 II -4 II -5 FIG-2 I1 - FIG. 1

Description

1/8

III 1I-2 II 1 -6 II -1 11 -3 II -4 II -5

FIG-2

I1 -

FIG. 1

MULTI-ENERGY FIELD DRIVEN ELECTROSTATICALLY ATOMIZED MINIMAL QUANTITY LUBRICANT CONVEYING DEVICE TECHNICAL FIELD

The present invention relates to the technical field of machining equipment, and in particular to, a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device.

BACKGROUND

Descriptions herein only provide background techniques related to the present invention, and do not necessarily constitute the related art. In the field of mechanical processing, a Minimal Quantity Lubrication (MQL) technology is better adaptive to the concept of green manufacturing and sustainable development than traditional cast-type external cooling lubrication and the like. MQL is a technology to spray a minimal quantity of lubricating liquid, water and gas with a certain pressure onto a cutting area to play cooling and lubricating roles. This technology uses a minimal amount of grinding fluid (about several thousandths of the amount used in a traditional cast-type lubrication) while ensuring effective lubrication and cooling effects, so as to reduce costs and environmental pollution as well as the damage to human bodies. At present, MQL cutting fluid is carried by high-pressure gas, and will be spread into a surrounding environment during jetting. When the fluid is sprayed onto the surface of a workpiece, a part of the cutting fluid bounces and is spread into the air, which pollutes, on the one hand, the environment, and reduces, on the other hand, the cooling and lubricating effects of the MQL cutting fluid. The health effects of lubricating liquid and cooling liquid on operators during MQL processing are highly focused now. For example, operators suffer from various respiratory diseases, including occupational asthma, hypersensitivity pneumonitis, loss of lung function, and skin diseases such as allergies, oil acne and skin cancer. An industrial focus on MQL is a potential health hazard to operators from air-powered droplets. For MQL, in the compressed air-powered spraying, sprayed droplets are no longer constrained and move uncontrollably, which will cause a series of problems such as diffusion and drift. The presence of these problems, however, causes the diffusion of small droplets of particles into a working environment, which not only causes great pollution to the environment but also causes great health hazards to staff. When the droplet size is less than 4 um, various occupational diseases can be even caused. It is actually reported that even a short exposure to such an environment may impair lung function. For this reason, the American Institute for Occupational Safety and Health recommends an exposure limit concentration of 0.5 mg/m3 of mineral oil droplets. In order to ensure the health of staff, it is necessary to control small droplets in the MQL process to reduce the amount of spreading. Some researchers have thought of using a high-voltage electric field to control jet, i.e., using a grounded workpiece as a positive electrode and an atomizing nozzle connected to high-voltage electricity as a negative electrode according to an electrostatic attraction principle, electrifying the nozzle to generate a high-voltage electrostatic field between the workpiece and the nozzle, negatively charging oil spray which is sprayed from the nozzle in a manner of contact charging or corona charging, and efficiently and uniformly spraying the oil spray to a cutting area of the workpiece along the direction of an electric field line under the action of the electrostatic field. Through an existing system for an internal cooling process of nano-fluid MQL electrostatic atomization controllable jet, the controllable distribution of MQL cutting fluid droplets in the spraying can be realized by means of an electrostatic atomization principle, the uniformity of a droplet spectrum, the deposition efficiency and the effective utilization of liquid can be improved, and the movement law of droplets can be effectively controlled, thereby reducing the pollution to the environment, and providing better health security for staff. The system includes an adjustable high-voltage direct current power supply, an internal cooling tool converter, a high-voltage electricity conversion device, and an integrated nozzle. The MQL system supplies MQL cutting fluid to an internal cooling drill bit through the internal cooling tool converter. The adjustable high-voltage direct current power supply transmits positive power to an electrode needle of the integrated nozzle through the high-voltage electricity conversion device, grounds negative power and transmits the negative power to a workpiece through an electromagnetic connector, so that an area from the electrode needle to the workpiece forms a corona charging field to perform corona charging on the MQL cutting fluid, thereby realizing electrostatic atomization. Some scholars have proposed a grinding fluid supply device in machining, characterized in that a grinding system thereof is provided with a corona charging nozzle, a nozzle body of the corona charging nozzle is connected to a liquid supply system and a gas supply system, a high-voltage direct current electrostatic generator at a lower part of the nozzle body is connected to a negative electrode of an adjustable high-voltage direct current power supply, a positive electrode of the adjustable high-voltage direct current power supply is connected to a workpiece power-on device, and the workpiece power-on device is attached to an unprocessed surface of a workpiece. Nano-fluid grinding fluid is sent to the corona charging nozzle through the liquid supply system, and meanwhile, compressed air is sent to the corona charging nozzle by the gas supply system. The nano-fluid grinding fluid is driven by the compressed air to be sprayed and atomized from an outlet of the nozzle body while being charged as a controllable jet by the high-voltage direct current electrostatic generator, and is controllably distributed to a grinding area of the workpiece to be processed under the action of an electric field force and an aerodynamic force. Some other scholars have proposed an electrostatic MQL device, including an electrostatic generation device, a liquid supply device, a gas-liquid electric converging device, a gas-liquid electric delivery pipe, a charging device, and a nozzle. The electrostatic generation device includes an electrostatic generator and a transmission wire, and is powered by a power supply. High-voltage electricity is delivered to the gas-liquid electric converging device through a transmission wire. The liquid supply device is composed of a liquid storage tank, a first liquid pipe and a liquid supply pump, and output lubricating liquid is delivered to the gas-liquid electric converging device through the first liquid pipe. An external gas source delivers high-pressure gas to the gas-liquid electric converging device through the first gas pipe. The lubricating liquid is charged by the gas-liquid electric converging device and the charging device, and charging gas spray is sprayed. The inventors have found that an electrostatic atomization technology has made outstanding contributions to the jet control and droplet size control of MQL cutting fluid. The organic combination of high-speed mixed jet and high-voltage electric field achieves a good processing effect. However, there are still some deficiencies in the application process: an electrostatic drive circuit of an electrostatic atomization device is prone to frequency drift and large amplitude change, which makes the high-voltage end voltage unstable and causes non-uniform droplet size, and cannot timely react to the changes of various parameters at the nozzle to form a closed-loop adjustment. When the nano-fluid is used as a lubricant, the nano-particles are easy to deposit and the heat exchange capacity of the lubricant cannot be improved effectively due to the lack of a stirring process. Different types of lubricating oil are used in different working conditions or an oil supply mode is changed, and the conductivities of various types of oil are different. The charging efficiency and the uniformity of charge distribution of the charged oil cannot be guaranteed when the oil is charged only by means of the nozzle. When the atomization voltage is high, the charges will flow back along an oil delivery pipeline, so that a housing of the equipment is charged, thereby reducing the charging efficiency and even causing electric shock accidents.

SUMMARY

In view of the deficiencies of the prior art, an object of the present invention is to provide a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device. Oil is stirred by means of pneumatic turbulent flow to avoid nano-particle accumulation. An auxiliary charging device is arranged by using a skin effect of charges to increase the contact area between a charged surface and the oil and to improve the charging efficiency and the distribution uniformity of charge. The oil flow state in an oil transportation path is changed to block a charge backflow path, thus solving the problems of non-uniform droplet size, non-uniform charge distribution and easy occurrence of electric shock accidents in the existing electrostatically atomized minimal quantity lubricant conveying device. In order to achieve the above objective, the present invention is implemented through the following technical solution: In a first aspect, the present invention proposes a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device, including an MQL device, an auxiliary charging device, an electrostatic drive and control device. The MQL device includes a micro-pump and the auxiliary charging device communicated with the micro-pump. The micro-pump is also connected to a frequency generator. The electrostatic drive and control device includes a high-voltage electrostatic generator. Output ends of the high-voltage electrostatic generator are respectively connected to the auxiliary charging device and a nozzle. The auxiliary charging device includes a housing. A charger is arranged in the housing. An oil delivery pipe is arranged at an upper part of the housing. A gas-liquid delivery pipe and a gas inlet pipeline are arranged at a lower part of the housing. The gas-liquid delivery pipe is connected to the nozzle to deliver cooling lubricating oil and compressed gas to the nozzle. Oil at the nozzle is atomized under the action of the compressed gas and a high-voltage electrostatic field and sprayed to a workpiece processing area for cooling and lubricating. As a further technical solution, the charger includes a plurality of cylinders arranged in parallel, bottoms of the cylinders are connected to a bottom plate, and the bottom plate is connected to the high-voltage electrostatic generator. As a further technical solution, the oil delivery pipe is horizontally arranged and extends into the housing by a set distance, an end of the oil delivery pipe is provided with an upward opening perpendicular to an axis of the oil delivery pipe, and the oil delivery pipe is also connected to the micro-pump. As a further technical solution, the gas-liquid delivery pipe includes a gas pipe and an oil pipe arranged coaxially, the oil pipe is communicated with the housing, the gas pipe sheathes the oil pipe and communicated with the gas inlet pipeline; and a throttle valve is arranged at the gas inlet pipeline and is connected to a first power device, and the first power device is connected to a control board. As a further technical solution, the micro-pump includes a pump body, the pump body has a cavity in which a plunger is arranged, an input end of the cavity is communicated with a first gas inlet, an output end of the cavity is communicated with a first output port which is communicated with an oil inlet and a second gas inlet, and a stopper is arranged outside the plunger to adjust a stroke of the plunger, and is connected to a second power device. As a further technical solution, the first gas inlet and the second gas inlet are both connected to the frequency generator, the oil inlet is communicated with an oil cup, and a part of pulse gas flow emitted by the frequency generator drives the plunger to move while a part of the pulse gas flow enters the oil cup to generate disturbance stirring on oil therein. As a further technical solution, the high-voltage electrostatic generator is provided with a drive circuit which is communicated with a boost rectifier circuit. As a further technical solution, the drive circuit is provided with an oscillator, a voltage stabilizing switching circuit and a switching amplification circuit, the oscillator generates a high-frequency signal with an oscillation frequency, the voltage stabilizing switching circuit converts the high-frequency signal into a stable periodic high-frequency low-amplitude voltage, and the switching amplification circuit amplifies the high-frequency low-amplitude voltage and inputs the high-frequency low-amplitude voltage to the boost rectifier circuit, so as to generate a stable adjustable high-frequency signal. As a further technical solution, the boost rectifier circuit includes a high-voltage coil and a voltage doubling rectifier circuit, the high-voltage coil converts the high-frequency low-amplitude voltage from the drive circuit into a high-voltage high-frequency alternating current of 0-6 kV, and the voltage doubling rectifier circuit rectifies the high-voltage high-frequency alternating current to obtain a high-voltage direct current of 0-60 kV. As a further technical solution, a main control board is further included, which is provided with a control center, a voltage regulation circuit, a current acquisition circuit, a voltage acquisition circuit, and a bus, and the bus communicates the control center with the voltage regulation circuit, the current acquisition circuit and the voltage acquisition circuit. Beneficial effects of the present invention are as follows. According to the present invention, an auxiliary charging device is arranged between a micro-pump and a nozzle, the contact area between a charged surface and oil is increased through a metal electrode in the device using a skin effect of charge, and the charging efficiency and the charging uniformity are improved. According to the present invention, an oil delivery pipe has an upward opening, when entering the auxiliary charging device, the oil will go through a process of ascending and descending, and the oil will change from a continuous liquid beam to large dispersed droplets in this process, so that the direct contact between the uncharged oil and the charged oil is avoided, the backflow of charges is prevented, and the working safety of equipment is improved. According to the present invention, a gas inlet hole connected to the bottom of an oil cup is provided on an oil pump, a part of square wave pulse gas flow driving the oil pump enters the oil cup through the gas inlet hole, and disturbance bubbles will be generated in the oil cup. When nano-particles are added into the oil, the disturbance bubbles can form a stirring effect, thereby avoiding the deposition of the nano-particles, and effectively improving the heat exchange capacity of a lubricant. According to the present invention, a constant-frequency voltage stabilizing oscillating circuit based on an electromagnetic induction law in a high-voltage electrostatic generator, so that a boost end stably outputs adjustable high-voltage static electricity of 0-60 kV. Moreover, by arranging a microcontroller in a control center of a main control board, on the one hand, a voltage closed-loop control is realized, and on the other hand, information interaction between equipment and a machine tool or a computer is realized by using a serial communication function thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings of the specification forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and descriptions thereof are used to explain the present invention but do not constitute an improper limitation on the present invention.

FIG. 1 is a schematic diagram of an overall structure of a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device according to one or more embodiments of the present invention. FIG. 2 is a schematic diagram of an overall structure of a micro-pump according to one or more embodiments of the present invention. FIG. 3 is a schematic diagram of an overall structure of an auxiliary charging device according to one or more embodiments of the present invention. FIG. 4 is a schematic diagram of a pneumatic circuit of an MQL device according to one or more embodiments of the present invention. FIG. 5 is a schematic circuit diagram of an electrostatic generator according to one or more embodiments of the present invention. FIG. 6 is a schematic structure diagram of a main control board according to one or more embodiments of the present invention. FIG. 7 is a schematic circuit diagram of a main control board according to one or more embodiments of the present invention. FIG. 8 is a schematic diagram of a system control relationship according to one or more embodiments of the present invention. FIG. 9 is a schematic diagram of an electrostatic atomization principle according to one or more embodiments of the present invention. FIG. 10 is a schematic diagram of a comparison relationship of actual atomization effects according to one or more embodiments of the present invention. In the figures: the mutual spacing or size is magnified to display the positions of various parts, and the schematic diagrams are used for illustration only, where 1, air compressor; 2, gas storage tank; 3, pressure gage; 4, pressure regulating valve; 5, second throttle valve; 6, overflow valve; and 7, nozzle; box body I, MQL device II, and electrostatic drive and control device III; housing I-1, partition plate I-I-1, and box cover1-2; micro-pump 11-1, oil inlet 11-1-1, gas inlet 11-1-2, output port 11-1-3, pump body11-1-4, plunger 11-1-5, spring 11-1-6, stopper 11-1-7, and gas inlet11-1-8; auxiliary charging device 11-2, cylinder 11-2-1, bottom plate 11-2-2, cavity 11-2-3, housing 11-2-4, end cover 11-2-5, high-voltage cable 11-2-6, oil delivery pipe11-2-7, output port11-2-8, gas-liquid delivery pipe 11-2-9, gas inlet11-2-10, and throttle valve11-2-11; frequency generator 11-3, electromagnetic valve 11-4, electromagnetic valve 11-5, oil cup 11-6, and filter 11-7; high-voltage electrostatic generator 111-1, main control board 111-2, transformer 111-3, main control switch111-4, fuse111-5, and touch screen111-6; drive circuit 111-1-1, and boost rectifier circuit111-1-2; and control center 111-2-1, voltage regulation circuit 111-2-2, current acquisition circuit 111-2-3, voltage acquisition circuit 111-2-4, A/D conversion circuit111-2-5, and bus111-2-6.

DETAILED DESCRIPTION

It should be pointed out that the following detailed descriptions are all illustrative and are intended to provide further descriptions of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those usually understood by a person of ordinary skill in the art to which the present invention belongs. As described in the Background, the conventional electrostatically atomized minimal quantity lubricant conveying device has problems of non-uniform droplet size, non-uniform charge distribution and easy occurrence of electric shock accidents. In order to solve the above technical problems, the present invention proposes a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device. Example 1 In one exemplary embodiment of the present invention, as shown in FIGS. 1-10, a multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device is proposed that includes a box body I, an MQL device II, and an electrostatic drive and control device III. The MQL device II and the electrostatic drive and control device III are integrated in the box body I for delivering cooling lubricating oil and compressed gas to a nozzle under high-voltage static electricity, and oil at the nozzle is atomized and sprayed to a workpiece processing area under the action of the compressed gas and a high-voltage electrostatic field for cooling and lubricating. The MQL device II is used to control the gas-liquid output and perform oil liquid stirring and pre-charging treatment. The electrostatic drive and control device III may generate and output high-voltage static electricity on the one hand, and may control the operation of the whole machine on the other hand. The box body I is responsible for bearing the MQL device II and the electrostatic drive and control device III, and includes a housing I- Iand a box cover 1-2. A partition plate I-I-I inside the housing I-1 divides the housing I-1 into upper and lower layers, an upper space is a mounting area of the MQL device II, and a lower space is a mounting area of the electrostatic drive and control device III. The back of the housing I-1 may be provided with a magnet or a hook, etc. and in practical applications, the equipment may be adsorbed or hung on a machine tool shell and other facilities at any time, so as to facilitate the movement and fixation of the equipment. A front flat area of the box cover 1-2 is used to mount a touch screen111-6 for man-machine interaction. The MQL device II mounted in the upper space of the housing I-1 includes a micro-pump 11-1, an auxiliary charging device 11-2, a frequency generator 11-3, an electromagnetic valve 11-4 (i.e. a first electromagnetic valve), an electromagnetic valve 11-5 (i.e. a second electromagnetic valve), an oil cup 11-6, and a filter11-7. The micro-pump11-1 may supply a minimal quantity of oil, so that the oil enters the auxiliary charging device11-2 for pre-charging treatment, and the auxiliary charging device 11-2 simultaneously enables the convergence of the oil and the compressed gas to be delivered to the nozzle through a pipeline. The micro-pump II-1 and the auxiliary charging device 11-2 are arranged in parallel. The micro-pump 11-1 uses a pneumatic plunger pump and is connected to the frequency generator 11-3. The frequency generator 11-3 changes a gas flow state to drive the operation of the micro-pump 11-1. The electromagnetic valve 11-4 is connected to the frequency generator11-3. The electromagnetic valve 11-5 is connected to the auxiliary charging device 11-2. The electromagnetic valve 11-4 and the electromagnetic valve 11-5 are both used for controlling the on-off of a gas path. The oil cup11-6 is mounted on the micro-pump11-1. The compressed gas is connected to the MQL device II through the filter11-7. It will be appreciated that the arrangement positions of the frequency generator 11-3, the electromagnetic valve 11-4 and the electromagnetic valve 11-5 are determined according to actual mounting spaces without excessive limitation here. In this example, the micro-pump 11-1 is modified on the basis of an existing plunger pump, and the structure and working process of the micro-pump 11-1 are further described in conjunction with FIG. 2. As shown in the figure, the micro-pump 11-1 includes an oil inlet 11-1-1, a gas inlet 11-1-2 (i.e. a first gas inlet), an output port 11-1-3 (i.e. a first output port), a pump body II-1-4, a plunger II-1-5, a spring II-1-6, a stopper II-1-7, and a gas inlet II-1-8 (i.e. a second gas inlet). The first gas inlet is provided at an input end of a cavity, and the first output port is provided at an output end of the cavity. The input end and the output end here are determined according to an output direction of the micro-pump. The oil inlet 11-1-1 and the gas inlet 11-1-2 are respectively provided on two sides of the pump body 11-1-4. A cavity is provided inside the pump body11-1-4. The plunger 11-1-5, the spring 11-1-6 and the stopper 11-1-7 are arranged in the cavity. An end of the plunger11-1-5 is the stopper 11-1-7. The stopper 11-1-7 may adjust a stroke of the plunger 11-1-5. The spring 11-1-6 sheathes the plunger 11-1-5, one end is in contact with the plunger 11-1-5, and the other end is in contact with a wall of the cavity. The stopper11-1-7 is movably arranged in the pump body 11-1-4. A step motor is arranged at one end of the stopper11-1-7 protruding out of the pump body 11-1-4. A microcontroller may control the step motor to drive the stopper 11-1-7 to rotate so as to automatically adjust the amount of oil pumped. One end of the cavity is provided with the output port 11-1-3. A head end of the plunger 11-1-5 is arranged in the output port 11-1-3. The output port11-1-3 is communicated with the oil inlet 11-1-1. Oil is pumped out through the plunger 11-1-5. The oil inlet 11-1-1 is also communicated with the gas inlet 11-1-8 for disturbing the oil in the oil cup 11-6. The gas inlet 11-1-2 is communicated with the cavity and is provided between the plunger 11-1-5 and the stopper 11-1-7 for adjusting the stroke of the plunger11-1-5. The specific working process is: Compressed gas entering from the gas inlet 11-1-2 drives the plunger 11-1-5 to perform a reciprocating motion, oil flowing into the oil inlet 11-1-1 is pumped out, and before the compressed gas enters the micro-pump 11-1, the flow state is changed from a direct current form to a square wave pulse form via the frequency generator 11-3. In a square wave period, the compressed gas enters the pump body 11-1-4 via the gas inlet 11-1-2 at the beginning of operation to push the plunger 11-1-5 to pump out the oil. After the operation is completed, there is no compressed gas input, and the plunger 11-1-5 is reset under the action of the spring 11-1-6. By means of periodic reciprocating motions of the frequency generator 11-3 and the plunger 11-1-5, the oil is continuously pumped out, the stopper 11-1-7 may be rotated to adjust the stroke of the plunger 11-1-5, and thus the amount of oil pumped may be adjusted. Since the oil in the oil cup11-6 is often added with nano-particles to enhance the heat exchange capacity of the oil, the nano-particles are easily deposited in the oil cup and are not easily pumped out, and the gas inlet 11-1-2 and the gas inlet11-1-8 are connected together to the frequency generator 11-3. With the above-described arrangement, while the plunger 11-1-5 pushes out the oil, a part of square wave pulse gas flow emitted from the frequency generator 11-3 enters the oil cup 11-6 from the oil outlet at the bottom of the oil cup 11-6 via the gas inlet 11-1-8 and the oil inlet

11-1-1 in sequence, so as to disturb the oil in the oil cup11-6, and gas entering the oil cup11-6 in each square wave period will form a bubble which may disturb the oil in the oil cup 11-6, thereby achieving the function of stirring the oil and avoiding the deposition of the nano-particles. The auxiliary charging device is mainly used to perform pre-charging treatment before the oil is delivered to the nozzle and perform gas-liquid convergence, and the structure thereof is as shown in FIG. 3. The auxiliary charging device11-2 includes a cylinder11-2-1, a bottom plate 11-2-2, a cavity 11-2-3, a housing 11-2-4, an end cover 11-2-5, a high-voltage cable 11-2-6, an oil delivery pipe 11-2-7, an output port 11-2-8 (i.e. a second output port), a gas-liquid delivery pipe 11-2-9, a gas inlet 11-2-10 (i.e. a third gas inlet), and a throttle valve11-2-11 (i.e. a first throttle valve). The cylinder 11-2-1 and the bottom plate 11-2-2 are made of metal materials and constitute a charger. The cylinder 11-2-1 and the bottom plate 11-2-2 are integrally arranged and are mounted at the bottom of the cavity 11-2-3 via a thread at the bottom of the cylinder 11-2-1. The high-voltage cable 11-2-6 is connected to the bottom plate 11-2-2. The high-voltage cable 11-2-6 is connected to a high-voltage electrostatic generator of the electrostatic drive and control device. High-voltage electricity is introduced and transmitted to each cylinder. The cylinders 11-2-1 are provided in multiple groups and are uniformly distributed on the bottom plate 11-2-2 so as to increase the contact area with the oil, the cavity 11-2-3 is sealed by the end cover 11-2-5, and a rubber sealing rubber pad may be arranged between the cavity 11-2-3 and the end cover 11-2-5 in order to ensure the sealing effect. The oil delivery pipe 11-2-7 is horizontally mounted into the cavity 11-2-3 and is located at the upper part of the cylinder 11-2-1. One end of the oil delivery pipe11-2-7 is connected to the output port 11-1-3 of the micro-pump 11-1 for delivering the oil into the cavity 11-2-3, and the other end of the oil delivery pipe11-2-7 is provided with an opening perpendicular to an axis of the pipeline. The oil delivery pipe has an upward opening, when entering, the oil will go through a process of ascending and descending, and the oil will change from a liquid beam to dispersed droplets in this process, so that the direct contact between the uncharged oil and the charged oil is avoided, and the backflow of charges is prevented. The oil is output from the output port 11-2-8 after being in contact with the charger in the cavity 11-2-3 for pre-charging treatment. The output port 11-2-8 is also used for gas-liquid convergence, and is connected to the gas-liquid delivery pipe 11-2-9. The gas-liquid delivery pipe 11-2-9 is coaxial delivery pipes including a thick pipe and a thin pipe, the gas pipe sheathes the oil pipe, and the compressed gas for oil atomization enters the housing11-2-4 through the gas inlet 11-2-10, and converges with the oil at the output port11-2-8 and enters the gas pipe and the liquid pipe respectively. The gas flow rate is adjusted through the throttle valve 11-2-11, a mounting hole is provided at a position of the housing 11-2-4 close to the output port11-2-8, the mounting hole is respectively communicated with the output port 11-2-8 and the gas inlet port11-2-10, the throttle valve 11-2-11 is arranged in the mounting hole, an upper end of a valve core of the throttle valve 11-2-11 is a conical surface, and a gas inlet gap may be adjusted by rotating the valve core so as to achieve the purpose of adjusting the gas flow rate. A step motor is arranged at a lower end of the throttle valve11-2-11, and the micro-controller may control the step motor to drive the valve core of the throttle valve 11-2-11 to rotate so as to realize automatic adjustment of the gas flow rate. It will be appreciated that the housing 11-2-4, the end cover 11-2-5, the gas pipe and the liquid pipe in the device are made of insulating plastic, rubber, resin, etc. in order to avoid electric shock and prevent the influence on droplet charge. The auxiliary charging device 11-2 may be used in combination with various types of electrostatic atomization nozzles to improve the charging efficiency of different types of lubricating oil. In a practical application process, it is necessary to use different types of nozzles and different types of lubricating oil. The charging modes of various nozzles are different, and the conductivities of various oil are also different. The plurality of cylinders 11-2-1 in the cavity 11-2-3 increase the area of a charged surface and improve the charging efficiency. According to the skin effect of charge, when the charged surface pre-contacts the oil, the charging efficiency will be higher as the contact area increases, thus improving the applicability of the device. The auxiliary charging device 11-2 is applicable to different oil supply modes, such as continuous oil supply and pulse oil supply. Under different working conditions, the oil supply modes are different, and the change of the oil supply modes tends to make droplets charged non-uniformly. For example, when pulse oil supply is used, the oil tends to accumulate at the outlet of the nozzle, resulting in the unstable charging amount of the droplets, which reduces the cooling and lubricating effects. The cavity 11-2-3 may store a certain amount of oil, and the oil entering from the oil delivery pipe 11-2-7 may stay for a relatively long time to ensure sufficient charging and improve the charging uniformity. The auxiliary charging device 11-2 may avoid charge backflow under high-voltage conditions. When the voltage is too high, the charges will flow back to the box body along an oil pipeline, so that the box body is electrified to cause charge loss and electric shock. The oil delivery pipe 11-2-7 in the auxiliary charging device 11-2 has an upward opening at an input end, when entering, the oil will go through a process of ascending and descending, and the oil will change from a liquid beam to dispersed droplets in this process, so that the direct contact between the uncharged oil and the charged oil is avoided, and the backflow of the charges is prevented. In this example, the MQL device II is driven pneumatically, and a pneumatic circuit relationship thereof is as shown in FIG. 4. The compressed gas enters the MQL device II through the filter 11-7, and is then divided into two paths: a path in which compressed gas for pumping oil is controlled by the electromagnetic valve 11-4, and a path in which compressed gas for atomizing is controlled by the electromagnetic valve11-5. The electromagnetic valve 11-4 and the electromagnetic valve 11-5 are both two-position two-way electromagnetic valves. After the two electromagnetic valves are electrified to make pneumatic circuits communicated, compressed gas for pumping oil passes through the frequency generator 11-3 to change from a direct current state to a pulse square wave state. A part of the compressed gas drives the micro-pump 11-1 to pump the oil into the auxiliary charging device 11-2 for pre-charging treatment, and a part of the compressed gas enters the oil cup 11-6 for stirring the oil. The compressed gas for atomizing enters the auxiliary charging device 11-2 and converges with the oil, and finally gas-liquid is delivered to the nozzle 7 through a pipeline. The compressed gas is provided by an external gas source, which is composed of an air compressor 1, a gas storage tank 2, a pressure gage 3, a pressure regulating valve 4, a second throttle valve 5, and an overflow valve 6. One end of the gas storage tank 2 is connected to the air compressor 1, and the gas storage tank 2 is provided with the pressure gage 3 for monitoring a pressure value of the discharged compressed gas. The other end of the gas storage tank 2 is connected to the regulating valve 4 and the second throttle valve 5 in sequence. The overflow valve 6 is arranged between the regulating valve 4 and the second throttle valve 5 for controlling the discharge speed and pressure of the compressed gas. The electrostatic drive and control device III includes a high-voltage electrostatic generator 111-1, a main control board 111-2, a transformer 111-3, a main control switch111-4, a fuse 111-5, and a touch screen 111-6. As shown in FIG. 1, a main body part of the electrostatic drive and control device III is mounted in the lower space of the housing I-1. The high-voltage electrostatic generator 111-1 may generate high-voltage direct current static electricity, and is divided into two parts, i.e. a drive circuit111-1-1 and a boost rectifier circuit 111-1-2. For the convenience of wiring and electrostatic output, the boost rectifier circuit 111-1-2 is arranged in the upper space of the housing I-1. The main control board 111-2 is used for controlling the operation of the whole machine. The transformer 111-3 is a direct current transformer, a rectifier bridge is integrated therein, and alternating current voltage of 220 v is converted into direct currents of 12 v and 24 v by transformation and rectification. The direct current of 12 v is used for the power supply of the main control board 111-2, and the direct current of 24 v is used for the power supply of the high-voltage electrostatic generator 111-1. The main control switch 111-4 and the fuse111-5 are arranged on one side of the outside of the housing I-1, the touch screen111-6 is mounted outside the box cover 1-2, and the touch screen 111-6 can not only be manually input, but also can be in wireless communication with the touch screen 111-6 so as to realize man-machine interaction. FIG. 5 is a circuit diagram of a high-voltage electrostatic generator. As shown in the figure, the drive circuit 111-1-1 is substantially an oscillating circuit, a direct current connected to an input end is changed into a low-voltage high-frequency alternating current. A timer 555 and R 1, R 2 and C 2 constitute a multivibrator and may generate a 1.44 high-frequency signal of an oscillation frequency (R+2R)C 2 , and the oscillation frequency of the signal is a fixed value and is not affected by external factors. A transformer T 1, a triode VT1 , a voltage-stabilizing tube DI, etc. constitute a voltage stabilizing switching circuit, and the generated high-frequency signal is converted into a stable periodic high-frequency low-amplitude voltage. The triodes VT 1 and VT 2 constitute a switching amplification circuit, which amplifies the high-frequency low-amplitude voltage output by the transformer Ti and inputs the voltage into the boost rectifier circuit, and a variable resistor R 3 may adjust the amplitude of the high-frequency low-amplitude voltage by changing the resistance value, and then the output voltage of the boost rectifier circuit may be adjusted. The boost rectifier circuit 111-1-2 includes two parts: a high-voltage coil and a voltage doubling rectifier circuit. The high-voltage coil converts a high-frequency low-amplitude voltage from the drive circuit 111-1-1 into a high-voltage high-frequency alternating current of -6 kV, and then a 10-stage voltage doubling rectifier circuit rectifies the current to obtain a high-voltage direct current power of 0-60 kV. A positive electrode of the voltage doubling rectifier circuit is grounded, and a negative electrode may output negative high-voltage static electricity. The negative electrode is connected to a high-voltage cable and is divided into two paths to respectively deliver the negative high-voltage static electricity to the nozzle and the auxiliary charging device 11-2. A capacitor with a lower capacity is used in the voltage doubling rectifier circuit, so that the output current is kept within a lower level namely a few hundred pA, typically no more than 1 mA. It will be appreciated that, in order to ensure the insulation property of the entire boost rectifier circuit 111-1-2, the boost rectifier circuit 111-1-2 is entirely packaged by resin. The main control board 111-2, as a control center of equipment, is provided with various types of control chips and information acquisition and control circuits. As shown in FIGS. 6 and 7, the main control board is integrated by a control center111-2-1, a voltage regulation circuit 111-2-2, a current acquisition circuit 111-2-3, a voltage acquisition circuit111-2-4, an A/D conversion circuit 111-2-5, and a bus111-2-6. The control center 111-2-1 is composed of a microcontroller and a peripheral circuit, and is used for signal processing to control the operation of the whole machine. The voltage regulation circuit 111-2-2 uses a digital potentiometer, which may change a resistance value according to a signal sent by the control center111-2-1, and a control end thereof is connected to a variable resistor R 3 in the drive circuit111-1-1 through the bus111-2-6 to realize digital voltage regulation. The current acquisition circuit 111-2-3 is composed of a Hall sensor and an inverter. The Hall sensor detects that an input end is connected to an ammeter in the drive circuit 111-1-1 through the bus 111-2-6, uses a Hall induction principle to detect the magnitude of an output current of the drive circuit 111-1-1, converts the current into a voltage analog quantity to be transmitted to the A/D converter 111-2-5, and converts the current into a digital quantity to be transmitted to the control center111-2-1. The voltage acquisition circuit 111-2-4 is composed of a rectifier circuit and an inverter, an input end thereof is connected to a voltmeter in the drive circuit111-1-1 through the bus 111-2-6, and the rectifier circuit converts the voltage output by the drive circuit into a corresponding direct current voltage to be transmitted to the A/D converter 111-2-5, and converts the voltage into a digital quantity to be transmitted to the control center111-2-1. The control center 111-2-1 may obtain a high-voltage value according to a boost ratio of the boost rectifier circuit 111-1-2, and determine whether the electrostatic generator 111-1 is overloaded according to the measured magnitudes of voltage and current. The main control board 111-2 may be connected to the touch screen and the step motor through the bus 111-2-6 to achieve man-computer interaction and gas-liquid flow control, and may also achieve serial communication with a machine tool or a computer to acquire processing parameters of a workpiece in real time. It will be appreciated that only a core functional module is disclosed in this example, in other examples, the main control board 111-2 may perform functional expansion, and a corresponding functional module is added according to actual needs without excessive limitation here. A constant-frequency voltage stabilizing oscillating circuit is designed in the device based on an electromagnetic induction law, so that a boost end stably outputs adjustable high-voltage static electricity of 0-60 kV, the voltage at a high-voltage end is stable and the uniformity of droplet is ensured. By arranging the microcontroller, the voltage closed-loop control is realized to make the equipment devices effectively linked, and the serial communication function is used to realize the information interaction between the equipment and a machine tool or a computer, which improves the adaptability of the device, so that the device can cope with the situation where different types of lubricating oil are used in different working conditions or oil supply modes are changed. FIG. 8 is an overall control relationship diagram of a system. As shown in the figure, the touch screen is connected to the main control board through the bus, and bidirectional information transmission may be performed. On the one hand, the touch screen may display various operating parameters of the equipment, and on the other hand, the touch screen may input control instructions as an operating panel. The main control board sends a control signal, controls the step motor to perform fine adjustment on the gas flow rate and the liquid flow rate, controls the drive circuit and the boost rectifier circuit to output high-voltage static electricity, and acquires current and voltage information about the electrostatic generator to form a closed-loop control. The main control board may also communicate with the machine tool or computer through the bus to acquire processing parameters of the workpiece in real time. As shown in FIG. 9, taking a contact-type charging electrostatic atomization nozzle as an example, in the atomization process, an annular liquid film at an outlet of the nozzle is mainly affected by a gas drag force, an electrostatic field force and a surface tension. The gas drag force and the electrostatic field force accelerate the liquid film to move downstream of the nozzle, and the surface tension hinders the liquid film to move downstream, so as to obtain: mia =F+F-F, (1) m, isthe quality of a liquidfilmat anoutletof anozzle, F§ is agas drag force, F is an electrostatic field force, and F is a surface tension.

1 2 According to the fluid dynamics, the gas drag force is: F = 2 CDpVS (2)

CD is a drag coefficient, Pg is gas density, V, is a relative gas-liquid velocity at the

outlet of the nozzle, and Si is the windward area of an annular liquid film. After an electrostatic field is introduced, the nozzle and the workpiece receiving surface may be regarded as a capacitor, and the charging amount of the nozzle to the liquid film is: QiC' =(3) d

Qzis a charged amount of the liquid film at the outlet of the nozzle, 6, is a relative

dielectric constant of air, so is a vacuum dielectric constant, S, is an opposing area

between two electrodes, U is the voltage of the nozzle, and d is an interelectrode distance. The charging amount of the auxiliary charging device to the oil is: Q2 = it (4) i is current flowing to the auxiliary charging device, and t is the charging time of the oil in the auxiliary charging device. The total charging amount of the liquid film is: Qz = Qi+Q 2 (5) An electrostatic force to which the liquid film is subjected is obtained as:

F,=EdQz= oSU 2 + (6) d d Ed is an interelectrode electric field strength. It can be seen that the electrostatic field

force to which the liquid film is subjected is proportional to the square of the voltage applied on the nozzle. A resultant force of the surface tension on the liquid film at the outlet of the nozzle is:

F, = 2rc(ro +rg /a* (7)

g is the radius of gas core, ro is the radius of the outlet of the nozzle, and a* is the

effective surface tension of liquid after being charged. After the liquid at the outlet of the nozzle is charged, charges are mainly distributed on the surface of the liquid due to the skin effect, and charges of the same kind repel each other, so that the effective surface tension is smaller than the surface effective tension before charging, i.e. a* < a. Assuming that the gas pressure applied on the nozzle is constant, i.e. the gas drag force remains constant, the annular liquid film is more and more prone to tear into small droplets as the voltage increases. The droplets then move under the gas drag force and the electrostatic field force and are constrained by the electrostatic field force. When the liquid film breaks into small droplets moving downstream of the nozzle, the droplets tend to shrink into small spheres with radius R under the action of surface tension and generate static pressure inside the spheres, ignoring the influence of gravity. Moreover, like charges distributed on the droplet surface subjects the droplets as a whole to an electrostatic expansion force opposite to the static pressure. When the static pressure generated by the surface tension is completely counteracted by the electrostatic expansion force, the droplets are further deformed and broken. In an actual test, soybean oil is used as a test object, an air pressure at the outlet of the nozzle is kept at 0.3 MPa. By changing the applied voltage, the atomization of cutting fluid at the outlet of the nozzle is observed. On the one hand, a movement track of droplets basically coincides with an electric field line. On the other hand, through a comparison relationship of atomization effects shown in FIG. 10, it can be seen that after applying high voltage on the nozzle, the atomization effect is better in the voltage range of 20-30 kV. The average volume particle size of droplets is reduced by about 30% compared with the case of only relying on gas atomization. With the increase of voltage, the effect of an electric field on an annular liquid film at the outlet of the nozzle is enhanced. The larger droplets are carried out and constrained by the electric field during the conveying process, and some droplets are aggregated again, which slightly increases the average droplet size. In conclusion, after integrating MQL equipment with a high-voltage direct current power supply, the expected effect can be achieved through the linkage work of the microcontroller. The operation process of the multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device described in this example is as follows: Various operating parameters of current equipment are displayed through the touch screen, control instructions are determined according to the various parameters, and the control instructions are input through the touch screen. The main control board sends a control signal, controls the step motor to perform fine adjustment on the gas flow rate and the liquid flow rate, controls the drive circuit and the boost rectifier circuit to output high-voltage static electricity, and acquires current and voltage information about the electrostatic generator to form a closed-loop control. During this period, the main control board communicates with the machine tool or computer through the bus to acquire processing parameters of the workpiece in real time. After the electromagnetic valve 11-4 and the electromagnetic valve 11-5 are electrified to make pneumatic circuits communicated, compressed gas for pumping oil passes through the frequency generator 11-3 to change from a direct current state to a pulse square wave state. A part of the compressed gas drives the micro-pump 11-1 to pump the oil into the auxiliary charging device 11-2 for pre-charging treatment, and a part of the compressed gas enters the oil cup 11-6 for stirring the oil. The compressed gas for atomizing enters the auxiliary charging device 11-2 and converges with the oil, and finally gas-liquid is delivered to the nozzle 7 through a pipeline. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. A person skilled in the art may make various alterations and variations to the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

CLAIMS What is claimed is:

1. A multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device, comprising a Minimal Quantity Lubrication (MQL) device, an auxiliary charging device, an electrostatic drive and control device; wherein the MQL device comprises a micro-pump and the auxiliary charging device communicated with the micro-pump, and the micro-pump is also connected to a frequency generator; the electrostatic drive and control device comprises a high-voltage electrostatic generator, and output ends of the high-voltage electrostatic generator are respectively connected to the auxiliary charging device and a nozzle; and the auxiliary charging device comprises a housing, a charger is arranged in the housing, an oil delivery pipe is arranged at an upper part of the housing, a gas-liquid delivery pipe and a gas inlet pipeline are arranged at a lower part of the housing, and the gas-liquid delivery pipe is connected to the nozzle to deliver cooling lubricating oil and compressed gas to the nozzle.

2. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 1, wherein the charger comprises a plurality of cylinders arranged in parallel, bottoms of the cylinders are connected to a bottom plate, and the bottom plate is connected to the high-voltage electrostatic generator.

3. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 2, wherein the oil delivery pipe is horizontally arranged and extends into the housing by a set distance, an end of the oil delivery pipe is provided with an upward opening perpendicular to an axis of the oil delivery pipe, and the oil delivery pipe is also connected to the micro-pump.

4. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 1, wherein the gas-liquid delivery pipe comprises a gas pipe and an oil pipe arranged coaxially, the oil pipe is communicated with the housing, the gas pipe sheathes the oil pipe and communicated with the gas inlet pipeline; and a throttle valve is arranged at the gas inlet pipeline and is connected to a first power device, and the first power device is connected to a control board.

5. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 1, wherein the micro-pump comprises a pump body, the pump body has a cavity in which a plunger is arranged, an input end of the cavity is communicated with a first gas inlet, an output end of the cavity is communicated with a first output port, the first output port is communicated with an oil inlet and a second gas inlet, and a stopper is arranged outside the plunger to adjust a stroke of the plunger, and is connected to a second power device.

6. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 5, wherein the first gas inlet and the second gas inlet are both connected to the frequency generator, the oil inlet is communicated with an oil cup, and a part of pulse gas flow emitted by the frequency generator drives the plunger to move while a part of the pulse gas flow enters the oil cup to generate disturbance stirring on oil therein.

7. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 1, wherein the high-voltage electrostatic generator is provided with a drive circuit which is communicated with a boost rectifier circuit.

8. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 7, wherein the drive circuit is provided with an oscillator, a voltage stabilizing switching circuit and a switching amplification circuit, the oscillator generates a high-frequency signal with an oscillation frequency, the voltage stabilizing switching circuit converts the high-frequency signal into a stable periodic high-frequency low-amplitude voltage, and the switching amplification circuit amplifies the high-frequency low-amplitude voltage and inputs the high-frequency low-amplitude voltage to the boost rectifier circuit.

9. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 8, wherein the boost rectifier circuit comprises a high-voltage coil and a voltage doubling rectifier circuit, the high-voltage coil converts the high-frequency low-amplitude voltage from the drive circuit into a high-voltage high-frequency alternating current of 0-6 kV, and the voltage doubling rectifier circuit rectifies the high-voltage high-frequency alternating current to obtain a high-voltage direct current of 0-60 kV.

10. The multi-energy field driven electrostatically atomized minimal quantity lubricant conveying device of claim 1, further comprising a main control board, wherein the main control board is provided with a control center, a voltage regulation circuit, a current acquisition circuit, a voltage acquisition circuit, and a bus, and the bus communicates the control center with the voltage regulation circuit, the current acquisition circuit and the voltage acquisition circuit.