A heating element and a vacuum furnace with multi-zone temperature control

Abstract

The present invention relates to a heating element and a vacuum furnace with multi-zone temperature control. In this heating element, the first ends of multiple first heating sheets in the first heating unit are connected in parallel to a first connection sheet, and the second ends are connected in parallel to a first corner connection sheet; the first ends of multiple second heating sheets in the second heating unit are connected in parallel to the first corner connection sheet, and the second ends are connected in parallel to a second corner connection sheet; the first ends of multiple third heating sheets in the third heating unit are connected in parallel to the second corner connection sheet, and the second ends are connected in parallel to a second connection sheet; a first electrode bar is fixed on the first connection sheet, and the first electrode bar is used to connect to the first terminal of a single-phase transformer; a second electrode bar is fixed on the second connection sheet, and the second electrode bar is used to connect to the second terminal of the single-phase transformer; the radial cross-section of the heating element is U-shaped, and the first connection sheet and the second connection sheet are not coplanar. The present invention can reduce the difficulty of temperature regulation of the vacuum furnace and improve the temperature uniformity of the vacuum furnace.

Description

Technical Field

[0001] The present invention relates to the field of temperature control, and particularly to a heating element and a vacuum furnace with multi-zone temperature control. Background Art

[0002] Temperature distribution uniformity is a very important indicator for detecting the performance of a vacuum sintering furnace. The smaller the temperature deviation in each area such as inside the furnace, front, middle, back, top, and bottom, the better the control of the size and performance of the processed object after sintering, the higher the yield rate of the furnace output, and the lower the production cost. The factors affecting temperature distribution uniformity usually include the following: (1) related to design. For example, the size of the furnace body volume, the larger the volume, the worse the uniformity. The position of the upper connection port of the furnace body, such as the large heat dissipation at the pump port; or the large heat dissipation of a cooler at a certain place, etc. (2) The difference in the self-insulation uniformity of the thermal insulation material. The imported one has much better uniformity than the domestic one, and the domestic one is generally not used in furnace types with high dimensional requirements such as the MIM industry. (3) Heating uniformity. There are also differences in the uniformity of the resistance of the heating element itself. Graphite parts of the same material do not necessarily have the same resistivity. (4) The influence of air flow in different areas. For example, hot air flows upward, and generally the temperature in the upper part is higher than that in the lower part.

[0003] Most of the existing vacuum furnaces have single-zone heating. When the temperature difference between the front and back or the top and bottom is large, the resistance value is adjusted by adjusting the size of the heating element, and then heat insulation is carried out by using imported thermal insulation materials to reduce the temperature difference in each area of the vacuum furnace. Therefore, the temperature control method of the existing vacuum furnace is not easy to adjust. Especially in the case of large furnace types, pressurized atmosphere convection and other occasions where the temperature is difficult to control and the deviation is large, the temperature is even more difficult to adjust, resulting in poor temperature uniformity of the vacuum furnace. Summary of the Invention

[0004] The purpose of the present invention is to provide a heating element and a vacuum furnace with multi-zone temperature control to reduce the difficulty of temperature adjustment of the vacuum furnace and improve the temperature uniformity of the vacuum furnace.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] A heating element, comprising: a first connecting piece, a first heating unit, a first corner connecting piece, a second heating unit, a second corner connecting piece, a third heating unit, a second connecting piece, a first electrode bar and a second electrode bar;

[0007] The first heating unit includes a plurality of first heating sheets. The first ends of the plurality of first heating sheets are connected in parallel to the first connecting piece, and the second ends of the plurality of first heating sheets are connected in parallel to the first corner connecting piece;

[0008] The second heating unit includes a plurality of second heating sheets. The first ends of the plurality of second heating sheets are connected in parallel to the first corner connecting sheet, and the second ends of the plurality of second heating sheets are connected in parallel to the second corner connecting sheet;

[0009] The third heating unit includes a plurality of third heating sheets. The first ends of the plurality of third heating sheets are connected in parallel to the second corner connecting sheet, and the second ends of the plurality of third heating sheets are connected in parallel to the second connecting sheet;

[0010] The first electrode rod is fixed on the first connecting sheet and is used for connecting to the first terminal of the single-phase transformer; the second electrode rod is fixed on the second connecting sheet and is used for connecting to the second terminal of the single-phase transformer; the radial cross-section of the heating body is U-shaped, and the first connecting sheet and the second connecting sheet are located on different side walls of the U-shape.

[0011] Optionally, the first heating sheet is a straight-strip heating sheet, a plate heating sheet or a frame heating sheet.

[0012] Optionally, the second heating sheet is a straight-strip heating sheet, a plate heating sheet or a frame heating sheet.

[0013] Optionally, the third heating sheet is a straight-strip heating sheet, a plate heating sheet or a frame heating sheet.

[0014] Optionally, the first ends of the plurality of first heating sheets are connected to the first connecting sheet by bolts and nuts, and the second ends of the plurality of first heating sheets are connected to the first corner connecting sheet by bolts and nuts; the first ends of the plurality of second heating sheets are connected to the first corner connecting sheet by bolts and nuts, and the second ends of the plurality of second heating sheets are connected to the second corner connecting sheet by bolts and nuts; the first ends of the plurality of third heating sheets are connected to the second corner connecting sheet by bolts and nuts, and the second ends of the plurality of third heating sheets are connected to the second connecting sheet by bolts and nuts;

[0015] The first electrode rod is fixed on the first connecting sheet by a nut; the second electrode rod is fixed on the second connecting sheet by a nut.

[0016] The present invention also provides a vacuum furnace with multi-zone temperature control. The vacuum furnace with multi-zone temperature control uses the above-mentioned heating body, and the vacuum furnace with multi-zone temperature control includes: a sealed box, a heating device and a heat insulation cylinder. The heating device is coated on the outside of the sealed box, and the heat insulation cylinder is coated on the outside of the heating device;

[0017] The heating device includes a plurality of heating element groups, and the plurality of heating element groups are uniformly distributed outside the sealed box along the axial direction of the sealed box; each heating element group includes a plurality of heating elements, and the plurality of heating elements are uniformly arranged around the outside of the sealed box;

[0018] Each of the heating elements corresponds to a power controller respectively, and the output power of the single-phase transformer corresponding to the heating element is adjusted through the power controller, so as to adjust the heating temperature of the area of the sealed box corresponding to the heating element.

[0019] Optionally, the number of heating elements in each heating element group is 2 or 4.

[0020] Optionally, the heating device is cylindrical or prismatic;

[0021] When the heating device is cylindrical, the radial cross-sections of the first corner connecting piece, the second corner connecting piece, the first heating piece, the second heating piece and the third heating piece of the heating element are all arc-shaped;

[0022] When the heating device is prismatic, the first corner connecting piece and the second corner connecting piece of the heating element are both located on the side edges of the sealed box; the first heating piece, the second heating piece and the third heating piece are all located on the side surface of the sealed box.

[0023] Optionally, it further includes: a plurality of thermocouples and a plurality of PID controllers; the plurality of thermocouples, the plurality of PID controllers and the plurality of power controllers all correspond to the plurality of heating elements one by one; for the kth heating element, the thermocouple is connected to the PV input end of the PID controller, and is used to transmit the temperature measurement value of the area of the sealed box corresponding to the kth heating element to the PID controller; the control output end of the PID controller is connected to the control input end of the power controller, and the output end of the power controller is connected to the input end of the single-phase transformer corresponding to the kth heating element, and is used to adjust the output power of the single-phase transformer, so as to adjust the temperature heated by the kth heating element.

[0024] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0025] The multi-zone temperature control method of the vacuum furnace of the present invention makes up for the defect of the temperature deviation of the heat preservation material itself and reduces the requirements for the heat preservation material. Moreover, the temperature adjustment method is simple and easy to adjust, and the temperature uniformity can be achieved for furnace types with larger volumes; for furnaces with the same volume, the temperature difference between different zones is also greatly reduced. In addition, the heating rate of the vacuum furnace is increased, the heating process time is shortened, and the cost is saved. The full-furnace yield is also increased, the cost is reduced, and the problems that the product size, appearance and density do not meet the standards due to temperature deviation in some areas of the previous vacuum furnace are solved. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0027] Figure 1 Structural schematic diagram of the heating element of the present invention;

[0028] Figure 2 Flat layout schematic diagram of the heating element of the present invention;

[0029] Figure 3 Cross-sectional view of the vacuum furnace of the present invention;

[0030] Figure 4 First side view of the heating device in the vacuum furnace of the present invention;

[0031] Figure 5 Second side view of the heating device in the vacuum furnace of the present invention;

[0032] Figure 6 Circuit schematic diagram of the heating device in the vacuum furnace of the present invention;

[0033] Figure 7 Comparison diagram of equivalent circuits of the electrode rods of the heating element at different positions;

[0034] Figure 8 Schematic diagram of the heating device in the specific embodiment 1 of the present invention;

[0035] Figure 9 Schematic diagram of the heating element in the heating device in the specific embodiment 1 of the present invention;

[0036] Figure 10 Expansion diagram of the heating element in the heating device in the specific embodiment 1 of the present invention;

[0037] Figure 11 Schematic diagram of the heating device in the specific embodiment 2 of the present invention;

[0038] Figure 12 Schematic diagram of the heating element in the heating device in the specific embodiment 2 of the present invention;

[0039] Figure 13 Expansion diagram of the heating element in the heating device in the specific embodiment 2 of the present invention;

[0040] Figure 14 Schematic diagram of the heating device in the specific embodiment 3 of the present invention;

[0041] Figure 15 Schematic diagram of the heating element in the heating device according to Specific Embodiment 3 of the present invention;

[0042] Figure 16 Exploded view of the heating element in the heating device according to Specific Embodiment 3 of the present invention;

[0043] Figure 17 Schematic diagram of the heating device according to Specific Embodiment 4 of the present invention;

[0044] Figure 18 Schematic diagram of the heating element in the heating device according to Specific Embodiment 4 of the present invention;

[0045] Figure 19 Exploded view of the heating element in the heating device according to Specific Embodiment 4 of the present invention;

[0046] Figure 20 Schematic diagram of the heating device according to Specific Embodiment 5 of the present invention;

[0047] Figure 21 Schematic diagram of the heating element in the heating device according to Specific Embodiment 5 of the present invention;

[0048] Figure 22 Exploded view of the heating element in the heating device according to Specific Embodiment 5 of the present invention;

[0049] Figure 23 First schematic diagram of the heating area at the cross-section of the heating device of the present invention;

[0050] Figure 24 Second schematic diagram of the heating area at the cross-section of the heating device of the present invention. Detailed Description of the Invention

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0052] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Figure 1 Structural schematic diagram of the heating element of the present invention. As Figure 1 shown, the heating element of the present invention includes the following structures: a first connecting piece 1, a first heating unit, a first corner connecting piece 3, a second heating unit, a second corner connecting piece 5, a third heating unit, a second connecting piece 7, a first electrode rod 8, and a second electrode rod 9;

[0054] The first heating unit includes a plurality of first heating sheets (2-1 and 2-2 in the figure are two first heating sheets). The first ends of the plurality of first heating sheets are connected in parallel to the first connecting sheet 1, and the second ends of the plurality of first heating sheets are connected in parallel to the first corner connecting sheet 3.

[0055] The second heating unit includes a plurality of second heating sheets (4-1 and 4-2 in the figure are two second heating sheets). The first ends of the plurality of second heating sheets are connected in parallel to the first corner connecting sheet 3, and the second ends of the plurality of second heating sheets are connected in parallel to the second corner connecting sheet 5;

[0056] The third heating unit includes a plurality of third heating sheets (6-1 and 6-2 in the figure are two third heating sheets). The first ends of the plurality of third heating sheets are connected in parallel to the second corner connecting sheet 5, and the second ends of the plurality of third heating sheets are connected in parallel to the second connecting sheet 7;

[0057] The first electrode bar 8 is fixed on the first connecting sheet 1, and the first electrode bar 8 is used to connect to the first terminal of the single-phase transformer; the second electrode bar 9 is fixed on the second connecting sheet 7, and the second electrode bar 9 is used to connect to the second terminal of the single-phase transformer. The radial cross-section of the heating body is U-shaped, and the first connecting sheet 1 and the second connecting sheet 7 are not coplanar. The U-shape in the present invention refers to a shape with a concave area such as an arc, a semicircle, a figure composed of half a polygon, etc.

[0058] In the present invention, the first heating sheet, the second heating sheet, and the third heating sheet can all be straight-strip heating sheets, plate-shaped heating sheets, or frame-shaped heating sheets. A straight-strip heating sheet means that the heating sheet is in the shape of a straight strip. At this time, the two ends of the straight strip are the two connecting ends of the heating sheet, which are connected to the connecting sheet or the corner connecting sheet. A plate-shaped heating sheet means that the shape of the heating sheet is plate-shaped, such as a flat shape or an arc-shaped plate. At this time, the two parallel straight edges of the plate are the two connecting ends of the heating sheet. A frame-shaped heating sheet means that the shape of the heating sheet is a hollow frame. At this time, the two parallel straight edges of the frame are the two connecting ends of the heating sheet, and the frame edges between the two straight edges can be straight-strip, S-shaped, or other shapes.

[0059] In the above heating element of the present invention, the first end of each first heating sheet is connected to the first connecting sheet 1 by bolts and nuts, and the second end of each first heating sheet is connected to the first corner connecting sheet 3 by bolts and nuts; the first end of each second heating sheet is connected to the first corner connecting sheet 3 by bolts and nuts, and the second ends of multiple second heating sheets are connected to the second corner connecting sheet 5 by bolts and nuts; the first ends of multiple third heating sheets are connected to the second corner connecting sheet 5 by bolts and nuts 11, and the second ends of multiple third heating sheets are connected to the second connecting sheet 7 by bolts and nuts. The first electrode bar 8 is fixed to the first connecting sheet 1 by corresponding nuts 10; the second electrode bar 9 is fixed to the second connecting sheet 7 by corresponding nuts (not marked in the figure).

[0060] Figure 2 is a plan view of the heating element of the present invention laid flat. As Figure 2 shown, in the heating element of the present invention, the first electrode bar and the second electrode bar are respectively connected to two connection terminals of the transformer, thus forming a single-phase circuit. The current enters from the A1 end, flows through the first electrode bar, the first heating sheet 2-1, the first heating sheet 2-2, the first corner connecting sheet 3, the second heating sheet 4-1, the second heating sheet 4-2, the second corner connecting sheet 5, the third heating sheet 6-1, the third heating sheet 6-2, and the second electrode bar 9, and then returns to the B1 end. The entire heating element is equivalent to being in series among three heating units (the first heating unit, the second heating unit, and the third heating unit), and each heating unit is composed of multiple resistors in parallel. Taking the first heating unit including two first heating sheets as an example, the first heating unit is composed of two resistors, namely the first heating sheet 2-1 and the first heating sheet 2-2, in parallel, or can be composed of more than two first heating sheets in parallel.

[0061] Each heating element of the present invention corresponds to a heating area. By adjusting the output power of the transformer corresponding to the heating element, the heating temperature corresponding to the heating element can be further adjusted.

[0062] Based on the above heating element, the present invention also provides a vacuum furnace with multi-zone temperature control, Figure 3 is a cross-sectional view of the vacuum furnace of the present invention. As Figure 3 shown, the vacuum furnace of the present invention includes: a sealed box 31, a heating device 32, a heat insulation cylinder 33, and a sealed box guide rail 35. The heating device 32 is coated on the outside of the sealed box 31, and the heat insulation cylinder 33 is coated on the outside of the heating device 32. The vacuum furnace of the present invention also includes: multiple thermocouples 34 and multiple PID controllers.

[0063] Figure 4 is the first side view of the heating device in the vacuum furnace of the present invention, Figure 5 is the second side view of the heating device in the vacuum furnace of the present invention. Combining Figure 4 andFigure 5 As shown, the heating device 32 of the present invention includes a plurality of heating element groups, which are uniformly distributed along the axis of the sealed box 31 outside the sealed box 31. There are 3 heating element groups shown in the figure. Each heating element group includes a plurality of Figure 1 heating elements as shown. A plurality of heating elements are evenly surrounded outside the sealed box 31 to form a circumferential covering of the sealed box 31. In the figure, the first heating element group includes two heating elements. The two electrode rods of the first heating element are A1 and B1 respectively, and the two electrode rods of the second heating element are A4 and B4 respectively; the second heating element group includes two heating elements. The two electrode rods of the first heating element are A2 and B2 respectively, and the two electrode rods of the second heating element are A5 and B5 respectively; the third heating element group includes two heating elements. The two electrode rods of the first heating element are A3 and B3 respectively, and the two electrode rods of the second heating element are A6 and B6 respectively. Each of the heating elements corresponds to a power controller, and the output power of the single-phase transformer corresponding to the heating element is adjusted through the power controller, and then the heating temperature of the sealed box area corresponding to the heating element is adjusted.

[0064] In the vacuum furnace of the present invention, a plurality of thermocouples, a plurality of PID controllers and a plurality of power controllers all correspond to a plurality of heating elements one by one. Figure 6 It is a circuit schematic diagram of the heating device in the vacuum furnace of the present invention. As Figure 6 shown, for the kth heating element, the thermocouple is connected to the PV input end of the PID controller, and is used to transmit the temperature measurement value of the sealed box area corresponding to the kth heating element to the PID controller; the control output end of the PID controller is connected to the control input end of the power controller, and the output end of the power controller is connected to the input end of the single-phase transformer corresponding to the kth heating element, and is used to adjust the output power of the single-phase transformer, and then adjust the temperature of the kth heating element.

[0065] The heating device 32 in the present invention is cylindrical or prismatic. When the heating device 32 is cylindrical, the radial cross-sections of the first corner connecting piece, the second corner connecting piece, the first heating piece, the second heating piece and the third heating piece of the heating element are all arc-shaped; when the heating device 32 is prismatic, the first corner connecting piece and the second corner connecting piece of the heating element are both located on the side edges of the sealed box; the first heating piece, the second heating piece and the third heating piece are all located on the side surface of the sealed box.

[0066] In the heating element of the present invention, the first electrode rod and the second electrode rod are located on different side walls of the U shape, that is, on different sides. Compared with the heating element with the first electrode rod and the second electrode rod on the same side, the heating element of the present invention has greater advantages. The heating element with the electrode rods on the same side has the following defects:

[0067] Cooling water flows through the metal electrode bar connected to the electrode bar. During the heating process of the heating element, the temperature at the electrode bar is relatively low. The heat on the side connected to the electrode bar will quickly transfer to the electrode bar, resulting in faster heat dissipation on the water-passing side. This will cause the temperature difference between the side connected to the electrode bar and the side not connected to the electrode bar, leading to size deviation of the products on both sides. To solve this problem, it is necessary to adjust the resistance distribution of the heating element so that the resistance of the heating element on the electrode bar side is greater than that on the other side. However, the specific value needs to be obtained through continuous experiments, and the process is extremely complex and cumbersome. Moreover, during the heating-up and heat-preservation processes of the heating element, the heat dissipated to the electrode bar side is different. This results in that although the resistance values on both sides of the heating element are adjusted so that the temperatures on both sides can reach a relatively uniform state during heat preservation, during heating-up, the temperature deviation on both sides is relatively large, and thus the product sizes on both sides will also show relatively large deviations.

[0068] The electrode bar has the following advantages in the heating element structures on both sides:

[0069] Since the electrode bar is on both sides, when the heating element dissipates heat, it will conduct heat to both sides simultaneously. In this way, the temperatures on both sides are relatively uniform, and it is only necessary to keep the resistance values of the heating elements on both sides consistent, which is very easy to achieve. Moreover, the heating element structure with the electrode bar on both sides saves more materials and is more cost-effective.

[0070] Figure 7 Figure for comparing the equivalent circuits of the electrode bar of the heating element at different positions. Combining Figure 7 , assume that for the heating elements with the electrode bar on both sides and the electrode bar on the same side, the resistance value of each heating sheet of each heating element structure is the same. Figure 7 Part (a) in shows the equivalent circuit of the heating element with the electrode bar on both sides, Figure 7 Part (b) in shows the equivalent circuit of the heating element with the electrode bar on the same side. Assume Figure 7 that the resistance value of half a heating sheet in part (b) is 20Ω, then the resistance value of one heating sheet is 10Ω, and the total resistance value of the heating element in a single region is 10×6 = 60Ω.

[0071] Figure 7 For the heating element shown in part (a) in , that is, the heating element of the present invention, to make the total resistance value in a single region also 60Ω, assume the resistance value of half a heating element is R, then the resistance value of one heating sheet is R / 2. Then the total resistance value in a single region = R / 2÷2×3 = 60, and we get R = 80Ω, that is, the resistance value of half a heating sheet is 80Ω, and the resistance value of one heating sheet is 40Ω.

[0072] It can be concluded that under the condition of ensuring the same resistance value in a single region, the resistance value of a single heating sheet in the heating body structure with the electrode rod on both sides is larger. When the heating sheets of the two structures are made of the same material and have the same shape, according to R = ρL / S, the S value of each heating sheet in the heating body structure with the electrode rod on both sides is smaller, where S is the cross-sectional area of the heating sheet, indicating that the heating sheet in the heating body structure with the electrode rod on both sides is thinner than that in the heating body structure with the electrode rod on the same side, that is, it saves more materials.

[0073] The following provides several specific embodiments to further illustrate the solution of the present invention. Specific Embodiment 1

[0075] Figure 8 is a schematic diagram of the heating device according to Specific Embodiment 1 of the present invention. Figure 9 is a schematic diagram of a single heating body in the heating device according to Specific Embodiment 1 of the present invention. Figure 10 is an unfolded view of a single heating body in the heating device according to Specific Embodiment 1 of the present invention. As shown in combination with Figures 8 - 10 In this embodiment, the heating sheet of the heating body is in a straight strip shape. Each of the first heating unit, the second heating unit, and the third heating unit includes 4 straight strip-shaped heating sheets. In this embodiment, the heating temperature control of 6 regions can be achieved. Specific Embodiment 2

[0077] Figure 11 is a schematic diagram of the heating device according to Specific Embodiment 2 of the present invention. Figure 12 is a schematic diagram of a single heating body in the heating device according to Specific Embodiment 2 of the present invention. Figure 13 is an unfolded view of a single heating body in the heating device according to Specific Embodiment 2 of the present invention. As shown in combination with Figures 11 - 13 In this embodiment, the heating sheet of the heating body is in a plate shape. Each of the first heating unit, the second heating unit, and the third heating unit includes 2 plate-shaped heating sheets. In this embodiment, the heating temperature control of 6 regions can be achieved. Specific Embodiment 3

[0079] Figure 14 is a schematic diagram of the heating device according to Specific Embodiment 3 of the present invention. Figure 15 is a schematic diagram of a single heating body in the heating device according to Specific Embodiment 3 of the present invention. Figure 16 is an unfolded view of a single heating body in the heating device according to Specific Embodiment 3 of the present invention. As shown in combination with Figures 14 - 16 In this embodiment, the heating sheet of the heating body is in a frame shape. Each of the first heating unit, the second heating unit, and the third heating unit includes 2 frame-shaped heating sheets. In this embodiment, the heating temperature control of 6 regions can be achieved. Specific Embodiment 4

[0081] Figure 17 Schematic diagram of the heating device according to Specific Embodiment 4 of the present invention Figure 18 Schematic diagram of a single heating element in the heating device according to Specific Embodiment 4 of the present invention Figure 19 Developed view of a single heating element in the heating device according to Specific Embodiment 4 of the present invention. In this embodiment, the heating sheet of the heating element is frame-shaped, and each of the first heating unit, the second heating unit, and the third heating unit includes 2 frame-shaped heating sheets. Each frame-shaped heating sheet is a frame-shaped structure formed by combining three rectangles. In this embodiment, the heating temperature control of 6 regions can be achieved. Compared with the frame shape in Specific Embodiment 3, the heating effect of the heating device in this embodiment is more uniform. Specific Embodiment 5

[0083] Figure 20 Schematic diagram of the heating device according to Specific Embodiment 5 of the present invention Figure 21 Schematic diagram of a single heating element in the heating device according to Specific Embodiment 5 of the present invention Figure 22 Developed view of a single heating element in the heating device according to Specific Embodiment 5 of the present invention. As shown in combination with Figures 20 - 22 In this embodiment, the entire heating device is arranged in a cylindrical shape. In this embodiment, the heating sheet of the heating element is frame-shaped. Different from other embodiments, the electrode rods in this embodiment are located on the same side. In the axial direction of the sealed box, there are 3 groups of heating element groups. In the circumferential direction of the sealed box, each heating element group surrounds and covers the sealed box through four heating elements. In this embodiment, the area controlled by each heating element is relatively small, and the entire heating device realizes the heating temperature control of 12 regions. According to actual needs, the heating device can also be arranged in other shapes, such as a prismatic shape. The structure of the heating device shown in this embodiment has a better temperature control heating effect for a furnace type with a larger diameter.

[0084] Figure 23 The first schematic diagram of the heating area at the cross-section of the heating device according to the present invention. As shown in Figure 23 For a furnace type with a relatively large diameter and a requirement for more uniform temperature, the temperature control area on the cross-section of the sealed box can be designed into the structure shown in Figure 23 By controlling the temperature through six regions: upper left, middle left, lower left, upper right, middle right, and lower right, the heating regions are extended to multiples of 6, 12, 18, 24... in the length direction.

[0085] Figure 24 The second schematic diagram of the heating area at the cross-section of the heating device according to the present invention. As shown in Figure 24 For a furnace type with an even larger diameter and a requirement for more uniform temperature, the temperature control area on the cross-section can be designed into the structure shown in Figure 24The shown structure controls the temperature through eight regions: left 1, left 2, left 3, left 4, right 1, right 2, right 3, and right 4, and extends in the length direction to heating regions that are multiples of 8, such as 8, 16, 24, 32...

[0086] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0087] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A vacuum furnace with multi-zone temperature control, characterized in that, The vacuum furnace with multi-zone temperature control includes: a sealed box, a heating device, and a heat insulation cylinder. The heating device is wrapped outside the sealed box, and the heat insulation cylinder is wrapped outside the heating device. The heating device includes multiple heating element groups, and the multiple heating element groups are evenly distributed along the axial direction of the sealed box outside the sealed box. Each heating element group includes multiple heating elements, and the multiple heating elements are evenly surrounded outside the sealed box. Each heating element corresponds to a power controller respectively. The output power of the single-phase transformer corresponding to the heating element is adjusted through the power controller, and then the heating temperature of the sealed box area corresponding to the heating element is adjusted. The heating element includes: a first connecting piece, a first heating unit, a first corner connecting piece, a second heating unit, a second corner connecting piece, a third heating unit, a second connecting piece, a first electrode rod, and a second electrode rod. The first heating unit includes multiple first heating sheets. The first ends of the multiple first heating sheets are connected in parallel to the first connecting piece, and the second ends of the multiple first heating sheets are connected in parallel to the first corner connecting piece. The second heating unit includes multiple second heating sheets. The first ends of the multiple second heating sheets are connected in parallel to the first corner connecting piece, and the second ends of the multiple second heating sheets are connected in parallel to the second corner connecting piece. The third heating unit includes multiple third heating sheets. The first ends of the multiple third heating sheets are connected in parallel to the second corner connecting piece, and the second ends of the multiple third heating sheets are connected in parallel to the second connecting piece. The first electrode rod is fixed on the first connecting piece, and the first electrode rod is used to connect to the first terminal of the single-phase transformer. The second electrode rod is fixed on the second connecting piece, and the second electrode rod is used to connect to the second terminal of the single-phase transformer. The radial cross-section of the heating element is U-shaped, the first connecting piece and the second connecting piece are not coplanar, and the first connecting piece and the second connecting piece are located on different side walls of the U-shape. In the heating element, the first electrode rod and the second electrode rod are located on different side walls of the U-shape, that is, on different sides. In the heating element, the first electrode rod and the second electrode rod are respectively connected to the two terminals of the transformer, thus forming a single-phase circuit. The current flows through the first electrode rod, multiple first heating sheets, the first corner connecting piece, multiple second heating sheets, the second corner connecting piece, multiple third heating sheets, and the second electrode rod. The whole heating element is equivalent to three heating units, that is, the first heating unit, the second heating unit, and the third heating unit are connected in series, and each heating unit is composed of multiple resistors, that is, multiple heating sheets connected in parallel.

2. The vacuum furnace with multi-zone temperature control according to claim 1, characterized in that, The number of heating elements in each heating element group is 2 or 4.

3. The vacuum furnace with multi-zone temperature control according to claim 1, characterized in that, The heating device is cylindrical or prismatic. When the heating device is cylindrical, the radial cross-sections of the first corner connecting piece, the second corner connecting piece, the first heating sheet, the second heating sheet, and the third heating sheet of the heating element are all arc-shaped. When the heating device is prismatic, the first angle connecting piece and the second angle connecting piece of the heating body are both located on the side edges of the sealed box; the first heating sheet, the second heating sheet and the third heating sheet are all located on the side surface of the sealed box.

4. The vacuum furnace with multi-zone temperature control according to claim 1, characterized in that, It further includes: Multiple thermocouples and multiple PID controllers; multiple thermocouples, multiple PID controllers and multiple power controllers are in one-to-one correspondence with multiple heating bodies; for the k-th heating body, the thermocouple is connected to the PV input end of the PID controller, and is used to transmit the temperature measurement value of the area of the sealed box corresponding to the k-th heating body to the PID controller; the control output end of the PID controller is connected to the control input end of the power controller, and the output end of the power controller is connected to the input end of the single-phase transformer corresponding to the k-th heating body, and is used to adjust the output power of the single-phase transformer, and further adjust the temperature heated by the k-th heating body.

5. The vacuum furnace with multi-zone temperature control according to claim 1, wherein, The first heating sheet is a straight-strip heating sheet, a plate-type heating sheet or a frame-type heating sheet.

6. The vacuum furnace with multi-zone temperature control according to claim 1, characterized in that, The second heating sheet is a straight-strip heating sheet, a plate-type heating sheet or a frame-type heating sheet.

7. The vacuum furnace with multi-zone temperature control according to claim 1, characterized in that, The third heating sheet is a straight-strip heating sheet, a plate-type heating sheet or a frame-type heating sheet.

8. The vacuum furnace with multi-zone temperature control according to claim 1, wherein, The first ends of multiple first heating sheets are connected to the first connecting piece through bolts and nuts, and the second ends of multiple first heating sheets are connected to the first angle connecting piece through bolts and nuts; the first ends of multiple second heating sheets are connected to the first angle connecting piece through bolts and nuts, and the second ends of multiple second heating sheets are connected to the second angle connecting piece through bolts and nuts; the first ends of multiple third heating sheets are connected to the second angle connecting piece through bolts and nuts, and the second ends of multiple third heating sheets are connected to the second connecting piece through bolts and nuts; The first electrode rod is fixed on the first connecting piece through a nut; The second electrode rod is fixed on the second connecting piece through a nut.

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