Load-bearing vacuum high-voltage electrode

Abstract

The present application relates to a kind of load-bearing vacuum high-voltage electrode, belong to material surface treatment process equipment technical field.The electrode is composed of combined electrode column, electrode sealing module and electrode support module.Combined electrode column includes upper section outer screw and lower section encapsulated electrode connected by inner sleeve connection, and the lower end of insulating sleeve is inserted in flange sleeve tube;Electrode sealing module includes knife-edge flange fixedly connected with flange sleeve tube;The upper end flange of flange sleeve tube has the middle recess of embedded sealing ring, and the boss with circumferential edge is formed in the ring groove of knife-edge flange;Electrode support module includes at least one level transition support column on lower support column;The opposite end surface of adjacent support column has the dimple of embedded support washer, and the Z-shaped gap is formed by the outward circumferential surface of support washer;Z-shaped gap is less than glow thickness.The present application has good load-bearing performance, high reliability, can prevent vacuum leakage and short circuit between cathode and anode, and basically realizes maintenance-free.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-voltage electric input electrode applicable to a thermal treatment or surface treatment equipment of a plasma field, in particular to a load-bearing vacuum high-voltage electrode, and belongs to the technical field of material surface treatment process equipment. BACKGROUND

[0002] As known from the basic theory of ionization discharge, the electrons and positive ions after ionization of source gas under the action of high-frequency or direct-current electric field will move towards the anode and cathode respectively and gather in the vicinity of the two poles to form a space charge region. The positive ion space charge region has much higher charge density than the electron space charge region because the positive ions have much smaller drift speed than the electrons, so that the entire inter-electrode voltage is almost entirely concentrated in a narrow region near the cathode. Once the space charge reaches the threshold value, a glow discharge phenomenon will occur. The light emission distribution from the cathode to the anode is shown in the attached figure, which is divided into several regions with different glow brightness and voltage drop, including Aston dark region A, cathode glow region B, cathode dark region C, negative glow region D, Faraday dark region E, positive column region F, anode dark region G, and anode glow region H. The Aston dark region, cathode glow region, and cathode dark region are referred to as the cathode drop region, which is the characteristic region of glow discharge, and the thickness of the cathode drop region is referred to as dk. Figure 1

[0003] The vacuum high-voltage lead-in electrode is a key component of thermal plasma treatment equipment, which is used to deliver high-voltage electricity to the workpiece to be processed through the furnace base with opposite polarity to the workpiece. It is required to have the functions of electricity transmission, insulation, sealing, arc discharge prevention, and certain load-bearing capacity, and needs to work for a long time in a heated state. The design reliability of the electrode is very important to ensure the stable operation of the surface modification process. The electrode structure of the prior art is shown in the attached figure. Figure 2 (Combining Figure 4 , the figure shows that the electrode column 6' delivers electricity to the workpiece on the tray through the electricity transmission plate 14' by passing through the insulation assembly composed of the ceramic tube 5', ceramic gasket 10', and ceramic sleeve 12'. The insulation assembly electrically isolates the electrode column 6' from the drag seat 7' and the base 8', so that the workpiece is in an electrically suspended state.

[0004] ​In practical application, the above prior art reflects the following disadvantages: 1) due to sputtering of the thermal plasma, the exposed ceramic tube 5' needs to be regularly ground on the outer surface to remove the metal film deposited due to sputtering, so as to avoid the surface of the ceramic tube 5' from being conductive due to the accumulation of the metal film, and the cleaning and maintenance are complicated; 2) the electrode column 6' not only supplies power to the tray, but also bears the weight of all workpieces, and the thermal shock process under the long-term bearing state is prone to unbalanced load, and in severe cases, the ceramic tube 5' close to the electrode column 6' can be broken to cause short circuit between the cathode and the anode; 3) the O-shaped rubber sealing ring 9' can be aged and heated to cause vacuum leakage in the long-term power transmission process, and thus needs to be regularly replaced, which is inconvenient; 4) the arc is extinguished only by adjusting the gap between the outer sleeve 3' and the gap adjusting inner sleeve 4', and once the gap is deformed due to external factors such as foreign matter falling, the arc extinguishing gap will fail, and arc discharge phenomenon will occur at the position; 5) damage of any component in the insulation assembly can cause electric isolation failure and cause short circuit between the cathode and the anode. SUMMARY

[0005] The present application aims at the above-mentioned disadvantages of the prior art, and provides a load-bearing vacuum high-voltage electrode with strong bearing capacity, which can effectively prevent short circuit failure and significantly prolong the maintenance period.

[0006] In order to achieve the above-mentioned purposes, the basic technical scheme of the load-bearing vacuum high-voltage electrode of the present application is as follows: composed of a combined electrode column, an electrode sealing module and an electrode support module.

[0007] The combined electrode column comprises an upper segment outer screw rod and a lower segment encapsulated electrode in an insulating sleeve, the lower end of the outer screw rod and the upper end of the encapsulated electrode are connected through an inner sleeve, the lower end of the insulating sleeve is inserted into a flange sleeve, the lower end of the encapsulated electrode extends out of the insulating sleeve and the flange sleeve through a threaded head, and the insulating sleeve and the flange sleeve are encapsulated by a ceramic encapsulated head adjacent to the lower end of the encapsulated electrode;

[0008] The electrode sealing module comprises a knife-edge flange fixedly connected to the upper end flange of the flange sleeve through fasteners, and a metal tube extending upward from the knife-edge flange, the upper end of the metal tube is fixedly connected to the furnace bottom; the upper end flange of the flange sleeve has a middle recess in which a sealing ring is embedded, the abutting end surface of the knife-edge flange and the upper end flange of the flange sleeve has a ring groove with a diameter larger than that of the middle recess, and a boss with a circumferential edge is formed in the ring groove; during assembly, the circumferential edge contacts the end surface of the sealing ring and causes plastic deformation of the sealing ring;

[0009] The electrode support module comprises a lower support column fixedly connected with the bottom of the furnace, at least one level of transition support column on the lower support column, and a top support column buckled on the uppermost level of transition support column by connecting with the upper end of the outer screw rod; the opposite end faces of adjacent support columns have respectively a sunken recess with a support washer embedded, and the periphery has respectively a convex and concave relief with a Z-shaped gap formed by the circumferential surface of the support washer outward; the two transverse gaps of the Z-shaped gap and the longitudinal gap between the two transverse gaps are smaller than the glow thickness.

[0010] The above-mentioned combined modular structure design of the present application can conveniently adjust the height of the electrode and the support module according to actual needs; the sealing of the electrode is realized through the road flange and the sealing ring, the load bearing and the high temperature resistance are good and the aging problem does not occur, so the sealing ring does not need to be replaced regularly; the insulation sleeve and the support washer are built-in and do not deposit metal film, so regular maintenance is not needed; the isolation of the electrode and the base is realized through the electrode support module, the multi-layer isolation measures can eliminate the cathode and anode short circuit problem caused by the breakage of a support washer under normal use conditions; the transverse and longitudinal gaps between the support columns can effectively prevent the glow from entering and avoid abnormal conditions such as arc discharge caused by the temperature being too high in the gap.

[0011] Further improvement of the present application is that the lower end of the ceramic packaging head has a reduced diameter port tightly fitted with the packaging electrode, and the reduced diameter port extends upward to a cladding section cladded outside the flange sleeve.

[0012] Further improvement of the present application is that the reduced diameter port is tightly fitted with the ring groove corresponding to the reduced diameter port of the packaging electrode.

[0013] Further improvement of the present application is that the electrode transition support column comprises an intermediate support column on the lower support column and an upper support column on the intermediate support column.

[0014] Further improvement of the present application is that the opposite end faces of adjacent lower support columns and upper support columns have respectively a sunken recess with an intermediate support washer embedded; the upper end periphery of the lower support column has a convex boss formed by the upward extension of the middle part of the reduced diameter step, and the lower end of the upper support column has a convex ring formed by the downward extension of the middle part of the recess.

[0015] Further improvement of the present application is that the outer circle of the intermediate support washer outwardly forms a Z-shaped gap after the assembly of the lower support column and the upper support column.

[0016] Further improvement of the present application is that the outer screw rod and the sealing rings are made of red copper; and the insulation sleeve and the support washers are made of alumina ceramic.

[0017] In summary, the present application has good load bearing performance, high reliability, can eliminate vacuum leakage and short circuit between the cathode and the anode, and basically realizes maintenance-free. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the glow discharge emission distribution.

[0019] Figure 2 This is a schematic diagram of the existing vacuum high-voltage input electrode structure.

[0020] Figure 3 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0021] Figure 4 for Figure 2 Enlarged structural diagram at point A in the middle.

[0022] Figure 5 for Figure 3 Enlarged structural diagram at point B in the embodiment.

[0023] Figure 6 for Figure 3 Enlarged structural diagram at point C in the embodiment. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] This embodiment is a load-bearing vacuum high-voltage electrode installed at the bottom of a vacuum heat treatment furnace, and its structure is as follows: Figure 3 As shown, it consists of a combined electrode post 1, an electrode sealing module 2, and an electrode support module 3.

[0026] The combined electrode post 1 includes an upper external screw 1-3 and a lower encapsulated electrode 1-1 located within an insulating sleeve 1-4. The lower end of the external screw 1-3 and the upper end of the encapsulated electrode 1-1 are connected by an internal screw sleeve 1-2. The insulating sleeve 1-4 is made of alumina, and its lower end is inserted into a flange sleeve 1-5. The threaded end of the encapsulated electrode 1-1 extends out of the insulating sleeve 1-4 and the flange sleeve 1-5, and is electrically connected to the input cable E. The insulating sleeve 1-4 and the flange sleeve 1-5 are encapsulated by a ceramic encapsulation head 1-1' adjacent to the lower end of the encapsulated electrode 1-1. The lower end of the ceramic encapsulation head 1-1' has a reduced diameter opening that fits tightly with the encapsulated electrode 1-1, and a covering section extends upward from this reduced diameter opening to cover the flange sleeve 1-5. The encapsulated electrode 1-1 is tightly fitted with the reduced diameter opening through two annular grooves at the corresponding location. In this way, the combined electrode post can be easily adjusted in overall height as needed through the internal threaded sleeve connection structure to adapt to the support height of the electrode support module.

[0027] The electrode sealing module 2 comprises a knife-edge flange 2-1 fixedly connected with the upper end flange of the flange sleeve 1-5 by a set of hexagonal bolt connection pairs 2-3, and a stainless steel pipe 2-4 extending upwards from the knife-edge flange 2-1 by sealing welding. The upper end of the stainless steel pipe 2-4 is sealingly welded with the lower surface of the furnace bottom D. See Figure 5 The upper end flange of the flange sleeve 1-5 has a middle recess embedded with a sealing ring 2-2 made of soft red copper; the knife-edge flange 2-1 has a ring groove 2-1' with a diameter larger than the middle recess on the abutting end face of the upper end flange of the flange sleeve 1-5, and a convex boss with a circumferential edge 2-1" is formed in the ring groove 2-1'. During assembly, the pressure of the hexagonal bolt connection pairs 2-3 will make the circumferential edge 2-1" contact the end face of the sealing ring 2-2 and plastically deform it to achieve the desired vacuum sealing effect, which can always ensure that the vacuum environment in the furnace is in communication with the internal space of the load-bearing vacuum high-voltage electrode in this embodiment. Although the electrode will significantly heat up due to its own resistance during the transmission of high-voltage and large current, the copper sealing ring not only has good high-temperature resistance and does not require additional cooling measures, but also has high strength and good load-bearing performance and will not age, so compared with traditional rubber sealing rings, the maintenance cycle can be greatly prolonged.

[0028] The electrode support module 3 comprises a lower support column 3-1 sealingly and fixedly connected with the upper surface of the furnace bottom D, an intermediate support column 3-3 located on the lower support column 3-1, an upper support column 3-5 located on the intermediate support column 3-3, and a top support column 3-7 buckled on the upper support column 3-5 by screwing with the upper end of the outer screw rod 1-3. The top support column 3-7 supports the tray P. The middle part of the opposite end faces of adjacent support columns respectively has a sunken recess embedded with a support washer, and the circumferences respectively have convex and concave undulations with Z-shaped gaps formed outward from the circumferential surface of the support washer. See Figure 6 The middle part of the opposite end faces of the intermediate support column 3-3 and the upper support column 3-5 respectively has a sunken recess embedded with an intermediate support washer 3-4, the upper end circumferential edge of the intermediate support column 3-3 has a convex boss formed by the middle part of the reduced diameter step extending upwards, and the lower end of the upper support column 3-5 has a convex ring formed by the middle recess extending downwards around the periphery, and after assembly, a Z-shaped gap is formed outward from the outer circular surface of the intermediate support washer 3-4. The middle part of the opposite end faces of the lower support column 3-1 and the intermediate support column 3-3 respectively has a sunken recess embedded with a lower support washer 3-2, the upper end circumferential edge of the lower support column 3-1 has a convex boss formed by the middle part of the reduced diameter step extending upwards, and the lower end of the intermediate support column 3-3 has a convex ring formed by the middle recess extending downwards around the periphery, and after assembly, a Z-shaped gap is formed outward from the circumferential surface of the lower support washer 3-2. The installation of the upper support washer 3-6 on the upper support column 3-5 and the top support column 3-7 is similar.

[0029] The two lateral gaps d1 of the zigzag gap and the longitudinal gap d2 between the two lateral gaps are equal and smaller than the glow thickness dk, i.e. d1 = d2 < dk. Since the characteristic of the glow discharge is that the glow is self-extinguished when dk is smaller than the threshold value, and the glow thickness dk of the thermal plasma processing is usually greater than 2 mm, d1 = d2 = 0.7-1.0 mm is selected.

[0030] In the embodiment, the top pillar 3-7 is electrically connected to the input electrode, and its surface is covered by the glow G when energized. However, since d1 = d2 < dk, the surface glow is extinguished at the gap (see Fig. 2), thereby avoiding the arc discharge phenomenon. On the contrary, if d1 = d2 ≥ dk, the glow enters the gap, the ions strike the surface inside the gap violently and generate active atoms, which repeatedly bounce inside the gap, and the number of ions and active atoms increases rapidly. The temperature of the region continues to rise, and when the temperature rises to a certain extent, thermal electron emission occurs in the region, which causes the collision ionization and the secondary electron emission of the input electrode to increase sharply, resulting in the inter-electrode gas conduction and the formation of the arc discharge phenomenon, and the electric isolation fails. Figure 6

[0031] Considering that the support pads need to bear the entire weight of the workpiece on the tray and may be subjected to certain thermal shock during the process, each support pad is made of zirconia ceramic. The embodiment adopts a multi-stage pillar and segmented insulation structure, so that even if a support pad is accidentally broken and short-circuited, the electric isolation function of the other support pads can still be ensured. Since the zirconia ceramic has good mechanical properties and high-temperature resistance, the breakage of the support pads can be effectively avoided, and the probability of accidental damage of the support pads is extremely low, so the short circuit of the cathode and anode is objectively eliminated.

[0032] During the chemical heat treatment by means of the embodiment, the workpiece is usually connected to the cathode, and the furnace shell and the like are connected to the anode. The vacuum pump is used to input the process gas (for example, ammonia or a mixture of nitrogen and hydrogen is input into the furnace to form nitrogen-containing positive ions after ionization for ion nitriding, and methane is input into the furnace to obtain carbon ions after ionization for ion carburizing), and the glow discharge of the gas in the furnace is generated under a voltage of 400-800 V to generate plasma. A large number of positive ions strike the workpiece, convert the kinetic energy of the positive ions into heat energy, and increase the temperature of the workpiece, and diffuse into the workpiece surface and form a diffusion layer.

[0033] In addition to the above embodiments, the present application can also have other embodiments. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present application.​

Claims

1. A load-bearing vacuum high-voltage electrode, which is composed of a combined electrode column (1), an electrode sealing module (2) and an electrode support module (3); characterized in that: the combined electrode column comprises an upper section outer screw (1-3) and a lower section encapsulated electrode (1-1) in an insulating sleeve (1-4), the lower end of the outer screw and the upper end of the encapsulated electrode are connected by an inner screw sleeve (1-2); the lower end of the insulating sleeve (1-4) is inserted into a flange sleeve (1-5), the lower end of the encapsulated electrode (1-1) extends out of the insulating sleeve (1-4) and the flange sleeve (1-5) through a threaded head; the insulating sleeve (1-4) and the flange sleeve (1-5) are encapsulated by a ceramic encapsulation head (1-1') adjacent to the lower end of the encapsulated electrode (1-1); the electrode sealing module comprises a knife-edge flange (2-1) fixed to the upper end flange of the flange sleeve by means of fasteners (2-3), and a metal pipe (2-4) extending upward from the knife-edge flange, the upper end of the metal pipe is fixedly connected with the furnace bottom (D); the upper end flange of the flange sleeve has a middle recess embedded with a sealing ring (2-2), the knife-edge flange has a ring groove (2-1') with a diameter larger than the middle recess on the opposite end surface of the upper end flange of the flange sleeve, and a boss with a circumferential edge (2-1") is formed in the ring groove; during assembly, the circumferential edge contacts the end surface of the sealing ring and causes plastic deformation of the sealing ring; the electrode support module comprises a lower support column (3-1) fixedly connected with the furnace bottom, at least one level of transition support columns on the lower support column (3-1), and a top support column (3-7) connected with the upper end of the outer screw (1-3) and buckled on the uppermost level of transition support columns; the opposite end surfaces of adjacent support columns have recesses embedded with support washers in the middle part, and the circumferences have convex-concave undulations with Z-shaped gaps formed outward from the circumferential surfaces of the support washers; the two transverse gaps (d1) of the Z-shaped gaps and the longitudinal gap (d2) between the two transverse gaps are smaller than the glow thickness (dk); each support washer is made of alumina ceramic. The lower end of the ceramic encapsulation head has a reduced diameter port that tightly fits the encapsulated electrode, and the reduced diameter port extends upward out of the cladding section wrapped around the flange sleeve.

2. The self-supporting vacuum high- voltage electrode according to claim 1, characterized in that: The encapsulated electrode corresponds to the reduced diameter port and is tightly fitted with the reduced diameter port through a ring groove.

3. The self-supporting vacuum high- voltage electrode according to claim 2, characterized in that: The electrode transition support column comprises an intermediate support column on the lower support column and an upper support column on the intermediate support column.

4. The self-supporting vacuum high- voltage electrode according to claim 3, characterized in that: The opposite end surfaces of adjacent lower support columns and upper support columns have recesses embedded with intermediate support washers in the middle part; the upper end circumferences of the lower support columns have bosses formed by the middle part of the reduced diameter step extending upward, and the lower end circumferences of the upper support columns have convex rings formed by the middle recess extending downward.

5. The self-supporting vacuum high- voltage electrode according to claim 4, characterized in that: The outer circumferences of the intermediate support washers form Z-shaped gaps outward after the assembly of the lower support columns and the upper support columns.

6. The self-supporting vacuum high- voltage electrode according to claim 5, characterized in that: The outer screw and each sealing ring are made of red copper; the insulating sleeve is made of alumina ceramic.

7. The self-supporting vacuum high- voltage electrode according to claim 6, characterized in that: The two transverse gaps and the longitudinal gap of the Z-shaped gaps are equal and smaller than the glow thickness.

8. The self-supporting vacuum high-voltage electrode according to any of claims 1 to 7, characterized in that: ​

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