Single crystal furnace

Abstract

The utility model provides a single crystal furnace which comprises a furnace body and a feeding pipe, the feeding pipe comprises an upper feeding pipe and a lower feeding pipe, the lower feeding pipe comprises a flaring section, a tightening section and a conveying section which are sequentially connected, the diameter of the flaring section is larger than that of the tightening section, and the diameter of the tightening section is larger than that of the conveying section. The discharging end of the upper feeding pipe penetrates through the flaring section and extends into the tightening section, the lower feeding pipe is fixedly arranged in the furnace body, and the discharging end of the conveying section communicates with an inner cavity of the furnace body. According to the utility model, the feed end of the lower feed pipe is provided with the flaring section of which the diameter is greater than that of the tightening section, and the discharge end of the upper feed pipe penetrates through the flaring section and extends into the tightening section, so that even if crushed aggregates are splashed from a gap between the discharge end of the upper feed pipe and the tightening section, the splashed crushed aggregates can enter the flaring section; and the crushed materials fall into the tightening section again from the flaring section under the action of gravity, so that the crushed materials are prevented from polluting a furnace platform or a silicon material, and the quality of a crystal bar produced by a crystal pulling process is ensured.

Description

Technical Field

[0001] The utility model relates to the photovoltaic field, in particular to a single crystal furnace. Background Art

[0002] Traditional single crystal furnaces for pulling single crystals generally use the recharged Czocharlski (RCZ) technique, which involves charging and melting a quartz crucible before pulling the single crystal. After pulling a single ingot, recharging, melting, and pulling the crystal are repeated, repeating the cycle. The recharged Czocharlski (RCZ) technique typically requires 5 to 7 repetitions to pull a furnace, and crystal pulling cannot be performed during the charging and melting process. Each furnace charging and melting process takes 10 to 12 hours, severely impacting crystal pulling efficiency. Continuous Czocharlski (CCZ) is a new crystal pulling process technology that enables simultaneous charging, melting, and pulling, saving time waiting for charging and melting. The theoretical production efficiency of continuous crystal pulling technology can reach over 1.4 times that of recharged crystal pulling technology, while reducing unit power consumption by over 20% and production costs by 10%.

[0003] Continuous crystal pulling requires adding materials while pulling the crystal, and the added silicon material is crushed material with a particle size of less than 5mm. In order to prevent the silicon material from splashing outside the single crystal furnace during the adding process, a feeding tube is usually used to guide the crushed material. One end of the feeding tube is connected to the material barrel, and the other end extends into the crucible inside the single crystal furnace to directly add the crushed material in the material barrel into the crucible.

[0004] like Figure 1 As shown, in the related art, the feeding tube is divided into an upper feeding tube 41 for connecting the material barrel 30 and a lower feeding tube 42 for connecting the furnace body 10. One end of the upper feeding tube 41 is used to connect the material barrel 30, and the other end is connected to the lower feeding tube 42. The lower feeding tube 42 is arranged in the furnace body 10. During the crystal pulling process, the upper feeding tube 41 is inserted into the lower feeding tube 42. While feeding from the material barrel 30 to the crucible 11, the feeding tube is prevented from being damaged due to the position offset of the material barrel 30 and the furnace body 10, thereby improving the safety of the single crystal furnace operation.

[0005] However, because the connection between quartz tubes requires a certain margin, and the operation of other equipment in the single crystal furnace also causes relative vibration between the tubes (for example, the barrel 30 unloads the material through its own vibration, and the equipment used for vacuuming under the furnace body 10 also vibrates), a large gap must be reserved between the outer wall of the discharge end of the upper feeding tube 41 and the inner wall of the feed end of the lower feeding tube 42. Due to the existence of this gap, during the feeding process, due to the vibration of the barrel 30 or the influence of the air pressure changes in the furnace, some broken materials will splash out from the connection between the upper feeding tube 41 and the lower feeding tube 42 onto the external structure of the single crystal furnace, causing contamination of the silicon material and the furnace table.

[0006] How to prevent splashing and ensure the quality of crystal pulling has become a technical problem that needs to be solved urgently in this field. Utility Model Content

[0007] The present invention aims to solve one of the technical problems in the related art to a certain extent. To this end, the present invention provides a single crystal furnace that can prevent debris from splashing out and contaminating the furnace table or silicon material, thereby ensuring the quality of the crystal ingots produced by the crystal pulling process.

[0008] To achieve the above-mentioned purpose, the utility model provides a single crystal furnace, which includes a furnace body and a feeding pipe, the feeding pipe includes an upper feeding pipe and a lower feeding pipe, the lower feeding pipe includes a flaring section, a tightening section and a conveying section connected in sequence, the diameter of the flaring section is larger than the diameter of the tightening section, the diameter of the tightening section is larger than the diameter of the conveying section, the discharge end of the upper feeding pipe passes through the flaring section and extends to be located in the tightening section, the lower feeding pipe is fixedly arranged in the furnace body, and the discharge end of the conveying section is connected to the inner cavity of the furnace body.

[0009] Optionally, a splash guard is provided on the outer side of the upper feeding tube, and the splash guard closes the opening between the flared section and the upper feeding tube.

[0010] Optionally, the splash guard includes a baffle and a limiting cylinder, the upper feeding tube passes through the baffle and is fixedly connected to the baffle, the limiting cylinder is arranged around the lower feeding tube, and the end of the limiting cylinder facing away from the discharge end of the upper feeding tube is fixedly connected to the baffle.

[0011] Optionally, a high-temperature resistant elastic pad is provided on one side surface of the baffle facing the discharge end of the upper feeding tube, the shape of the elastic pad corresponds to the shape of the flared section, and the elastic pad contacts the opening edge of the flared section.

[0012] Optionally, the elastic pad is made of high-temperature resistant rubber.

[0013] Optionally, the elastic pad is made of at least one of polytetrafluoroethylene, silicone, and fluororubber.

[0014] Optionally, the length of the flared section is 5 cm to 10 cm.

[0015] Optionally, the diameter of the expansion section is 1.5 to 3 times the diameter of the contraction section, and the diameter of the contraction section is 1.5 to 3 times the diameter of the conveying section.

[0016] Optionally, the tightening section further includes a docking transition section, which is connected between the tightening section and the conveying section, and the diameter of the docking transition section gradually decreases along the feeding direction of the lower feeding pipe.

[0017] Optionally, the angle between the side wall of the docking transition section and the axis of the docking transition section first increases and then decreases along the direction from the tightening section to the conveying section.

[0018] Optionally, the lower feeding pipe further includes a flaring transition section, which is connected between the flaring section and the tightening section, and the diameter of the flaring transition section gradually decreases along the feeding direction of the lower feeding pipe.

[0019] Optionally, the angle between the side wall of the flared transition section and the axis of the flared transition section first increases and then decreases along the direction from the flared section to the contraction section.

[0020] Optionally, the conveying section includes a first conveying pipe, a second conveying pipe and a third conveying pipe connected in sequence, the first conveying pipe is connected to the tightening section and is coaxially arranged with the expanding section, there is an angle between the axis of the second conveying pipe and the axis of the first conveying pipe, the third conveying pipe is arranged in the same direction as the first conveying pipe, the first conveying pipe and the second conveying pipe pass through the side wall of the furnace body and enter the furnace body, the inner wall of the furnace body has an inner flange, and the discharge end of the third conveying pipe passes through the inner flange.

[0021] Optionally, the material of the feeding tube includes at least one of silicon carbide and silicon nitride.

[0022] Optionally, the single crystal furnace further includes a material barrel, and the feed end of the upper feeding tube is connected to the material barrel.

[0023] In the single crystal furnace provided by the present invention, the feed end of the lower feeding tube is provided with a flaring section with a diameter larger than the tightening section, and the discharge end of the upper feeding tube passes through the flaring section and extends to the tightening section. Therefore, even under the influence of factors such as vibration of the barrel or changes in the air pressure in the furnace, there is debris splashing out from the gap between the discharge end of the upper feeding tube and the tightening section, the splashed debris will also enter the flaring section and fall back into the tightening section from the flaring section under the action of gravity, thereby avoiding the debris from contaminating the furnace table or silicon material and ensuring the quality of the crystal rods produced by the crystal pulling process.

[0024] Furthermore, a splash guard is provided on the upper feeding tube. When the discharge end of the upper feeding tube is docked with the feed end of the lower feeding tube, the splash guard seals the feed end of the lower feeding tube, thereby further preventing broken materials from splashing out of the flared section and contaminating the furnace table or silicon material, ensuring the cleanliness of the crystal pulling operation environment, and improving the purity of the silicon material at the growth surface of the crystal rod, thereby ensuring the growth quality of the crystal rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings:

[0026] Figure 1 It is a structural schematic diagram of a single crystal furnace in the related art;

[0027] Figure 2 This is a schematic structural diagram of a single crystal furnace provided by an embodiment of the present utility model;

[0028] Figure 3 This is a schematic structural diagram of a feeding pipe in a single crystal furnace provided by an embodiment of the present utility model;

[0029] Figure 4 This is a schematic structural diagram of the lower feeding pipe in the single crystal furnace provided by an embodiment of the present utility model;

[0030] Figure 5 It is a structural schematic diagram of an upper feeding tube in a single crystal furnace provided by an embodiment of the present utility model.

[0031] Description of Reference Numerals

[0032] 10. Furnace body; 11. Crucible; 20. Feeding pipe; 30. Feed barrel; 100. Upper feeding pipe; 110. Splash shield; 111. Baffle; 112. Limiting cylinder; 120. Elastic pad; 200. Lower feeding pipe; 210. Expanding section; 211. Expanding transition section; 220. Contracting section; 221. Docking transition section; 230. Conveying section; 231. First conveying pipe; 232. Second conveying pipe; 233. Third conveying pipe; 300. Positioning block; 41. Upper feeding pipe; 42. Lower feeding pipe. DETAILED DESCRIPTION

[0033] The following describes in detail embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described in the embodiments are intended to explain the present invention and are not to be construed as limiting the present invention.

[0034] References in this specification to "one embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment itself can be included in at least one embodiment disclosed herein. The appearance of the phrase "in one embodiment" in various places in the specification does not necessarily refer to the same embodiment.

[0035] In order to solve the above technical problems, as one aspect of the present invention, a single crystal furnace is provided. Figure 2 As shown, the single crystal furnace includes a furnace body 10 and a feeding pipe 20. Figure 3As shown, the feeding pipe 20 includes an upper feeding pipe 100 and a lower feeding pipe 200. The lower feeding pipe 200 includes an expanding section 210, a constricting section 220 and a conveying section 230 connected in sequence. The diameter of the expanding section 210 is larger than the diameter of the constricting section 220. The diameter of the constricting section 220 is larger than the diameter of the conveying section 230. The discharge end of the upper feeding pipe 100 ( Figures 3 to 5 The upper feeding pipe 100 and the lower feeding pipe 200 are both placed in a normal usage state (the top end of the pipe body in the figure is the feeding end, and the bottom end is the discharging end) pass through the expansion section 210 and extend to the tightening section 220. The lower feeding pipe 200 is fixedly arranged in the furnace body 10, and the discharging end of the conveying section 230 is connected to the inner cavity of the furnace body 10.

[0036] In the single crystal furnace provided by the present invention, the feed end of the lower feeding tube 200 is provided with a flaring section 210 whose diameter is larger than the tightening section 220, and the discharge end of the upper feeding tube 100 passes through the flaring section 210 and extends to the tightening section 220. Therefore, even under the influence of factors such as vibration of the barrel or changes in the air pressure in the furnace, there are fragments splashing out from the gap between the discharge end of the upper feeding tube 100 and the tightening section 220. The splashed fragments will also enter the flaring section 210 and fall back into the tightening section 220 from the flaring section 210 under the action of gravity, thereby avoiding the fragments from contaminating the furnace table or silicon material and ensuring the quality of the crystal rods produced by the crystal pulling process.

[0037] It is understood that the length of the flared section 210 should not be too long or too short. If the flared section 210 is too short, the spilled debris will have difficulty in decelerating under gravity and falling as it rises through the flared section 210, and may easily spill out of the flared section 210. If the flared section 210 is too long, it will increase the difficulty of manufacturing the lower feeding tube 200 and cause unnecessary material waste. For example, as an optional embodiment of the present invention, the length of the flared section 210 can be 5 cm to 10 cm.

[0038] In order to further prevent the splashing of broken materials and ensure the cleanliness of the crystal pulling operation environment, as a preferred embodiment of the present invention, Figure 3 、 Figure 5 As shown, a splash shield 110 is provided on the outer side of the upper feeding tube 100 , and the splash shield 110 closes the opening between the flared section 210 and the upper feeding tube 100 .

[0039] In an embodiment of the present invention, a splash guard 110 is further provided on the upper feeding tube 100. When the discharge end of the upper feeding tube 100 is docked with the feed end of the lower feeding tube 200, the splash guard 110 correspondingly closes the feed end pipe opening of the lower feeding tube 200, thereby further preventing broken materials from splashing out of the flared section 210 and contaminating the furnace table or silicon material, ensuring the cleanliness of the crystal pulling operation environment, and improving the purity of the silicon material at the growth surface of the crystal rod, thereby ensuring the growth quality of the crystal rod.

[0040] As a preferred embodiment of the present invention, Figure 5 As shown, the splash guard 110 includes a baffle 111 and a limiting cylinder 112 . The upper feeding tube 100 passes through the baffle 111 . The limiting cylinder 112 is arranged around the lower feeding tube 200 , and the end of the limiting cylinder 112 facing away from the discharge end of the upper feeding tube 100 is fixedly connected to the baffle 111 .

[0041] In the embodiment of the present invention, the splash shield 110 includes a baffle 111 and a limiting cylinder 112. The baffle 111 is used to cover the feed end of the lower feeding pipe 200. The limiting cylinder 112 is arranged around the outer edge of the baffle 111 and extends downward, thereby forming a limiting structure that can surround the outside of the flared section 210. Figure 3 As shown, when the discharge end of the upper feeding tube 100 passes through the flaring section 210 and enters the tightening section 220, the baffle 111 closes the opening of the flaring section 210, and the limiting cylinder 112 surrounds the outside of the flaring section 210 to form a radial limit, thereby ensuring the alignment accuracy between the discharge end of the upper feeding tube 100 and the feed end of the lower feeding tube 200.

[0042] In some embodiments of the present invention, the upper feeding tube 100 can be fixedly connected to the baffle 111, for example, by gluing the two together, or the two can be integrally formed. Alternatively, the baffle 111 can be movably mounted on the upper feeding tube 100, with the baffle's own gravity maintaining its relative position to the upper feeding tube 100 and the flared section 210.

[0043] In order to further ensure the cleanliness of the crystal pulling operation environment and improve the production safety of the crystal pulling process, as an optional embodiment of the present invention, a high-temperature resistant elastic pad 120 is provided on the side surface of the baffle 111 facing the discharge end of the upper feeding tube 100. The shape of the elastic pad 120 corresponds to the shape of the flared section 210, and the elastic pad 120 is in contact with the opening edge of the flared section 210.

[0044] In the embodiment of the present invention, a high temperature resistant elastic pad 120 is provided on one side of the bottom of the baffle 111. The shape of the elastic pad 120 corresponds to the opening shape of the flared section 210. When the discharge end of the upper feeding tube 100 passes through the flared section 210 and enters the tightening section 220, the elastic pad 120 at the bottom of the baffle 111 abuts against the opening edge of the flared section 210, thereby utilizing the elastic pad 120 to buffer the gap between the splash guard 110 of the upper feeding tube 100 and the feeding end of the lower feeding tube 200. The mechanical force of the upper feeding tube 100 and the contraction section 220 of the lower feeding tube 200 is not only prevented from colliding with each other due to factors such as machine vibration, causing wear or breakage, but also the friction between the elastic pad 120 and the opening edge of the flared section 210 is used to prevent radial slippage between the flared section 210 and the splash guard 110, thereby improving the stability of the relative position between the discharge end of the upper feeding tube 100 and the contraction section 220 of the lower feeding tube 200, and ensuring the alignment accuracy between the upper feeding tube 100 and the lower feeding tube 200.

[0045] As a preferred embodiment of the present invention, the material of the elastic pad 120 is selected to be high-temperature resistant rubber to ensure the service life of the elastic pad 120, reduce the maintenance time required to replace elastic consumables, and further improve the crystal pulling efficiency.

[0046] As an optional embodiment of the present invention, the elastic pad 120 may also be made of polytetrafluoroethylene (PTFE), silicone, or fluororubber.

[0047] As an optional embodiment of the present invention, Figure 3 、 Figure 4 As shown, the diameter of the conveying section 230 corresponds to the diameter of the upper feeding tube 100 .

[0048] In the embodiment of the present invention, the diameter of the conveying section 230 is consistent with that of the upper feeding pipe 100, so that the flow rate of the crushed material when passing through the upper feeding pipe 100 is consistent with the flow rate when passing through the conveying section 230, thereby facilitating the control of the amount of crushed material added and avoiding blockage of the crushed material in the downstream pipeline.

[0049] As an optional embodiment of the present invention, the diameter of the expansion section 210 is 1.5 to 3 times the diameter of the contraction section 220 , and the diameter of the contraction section 220 is 1.5 to 3 times the diameter of the conveying section 230 .

[0050] In order to improve the structural strength of the lower feeding pipe 200, as a preferred embodiment of the present invention, Figure 4As shown, the lower feeding tube 200 also includes a docking transition section 221, which is connected between the tightening section 220 and the conveying section 230. The diameter of the docking transition section 221 gradually decreases along the feeding direction of the lower feeding tube 200 (i.e., from the feed port of the lower feeding tube 200 to the discharge port of the lower feeding tube 200).

[0051] In an embodiment of the present invention, a docking transition section 221 is connected between the tightening section 220 and the conveying section 230. The docking transition section 221 is a variable diameter structure. The diameter of the top end of the docking transition section 221 corresponds to the diameter of the tightening section 220, and the diameter of the bottom end of the docking transition section 221 corresponds to the diameter of the conveying section 230, thereby avoiding the step structure caused by the direct connection between the docking transition section 221 and the conveying section 230, reducing the stress concentration points on the lower feeding pipe 200, and at the same time enabling the crushed materials entering the tightening section 220 to automatically flow to the conveying section 230 under the action of gravity, thereby ensuring the smoothness of the flow of crushed materials in the lower feeding pipe 200.

[0052] As a preferred embodiment of the present invention, Figure 4 As shown, the angle between the side wall of the docking transition section 221 and the axis of the docking transition section 221 first increases and then decreases along the direction from the tightening section 220 to the conveying section 230.

[0053] In an embodiment of the present invention, the angle between the side wall of the docking transition section 221 and its own axis first increases and then decreases, so that the angles of the side walls at both ends of the docking transition section 221 correspond to the side walls of the tightening section 220 and the conveying section 230, respectively, thereby achieving a smooth transition connection with the tightening section 220 and the conveying section 230, further reducing the stress concentration points on the lower feeding pipe 200.

[0054] As a preferred embodiment of the present invention, the angle between the side wall of the docking transition section 221 and the axis of the docking transition section 221 is greater than or equal to 0° and less than or equal to 60°, thereby ensuring that the angle of the side wall of the docking transition section 221 is steep enough to allow the crushed materials to slide smoothly down along the docking transition section 221.

[0055] As a preferred embodiment of the present invention, Figure 4 As shown, the lower feeding pipe 200 further includes a flared transition section 211 , which is connected between the flared section 210 and the tightening section 220 . The diameter of the flared transition section 211 gradually decreases along the feeding direction of the lower feeding pipe 200 .

[0056] In an embodiment of the present invention, a flaring transition section 211 is connected between the flaring section 210 and the tightening section 220. The flaring transition section 211 is a variable diameter structure, the diameter of the top end of which corresponds to the diameter of the flaring section 210, and the diameter of the bottom end corresponds to the diameter of the tightening section 220, thereby avoiding the step structure generated by the direct connection between the flaring section 210 and the tightening section 220, reducing the stress concentration points on the lower feeding pipe 200, and at the same time enabling the crushed materials entering the flaring section 210 to automatically flow into the tightening section 220 under the action of gravity, thereby ensuring the smoothness of the flow of crushed materials in the lower feeding pipe 200.

[0057] As a preferred embodiment of the present invention, Figure 4 As shown, the angle between the side wall of the flared transition section 211 and the axis of the flared transition section 211 first increases and then decreases along the direction from the flared section 210 to the constricted section 220 .

[0058] In an embodiment of the present invention, the angle between the side wall of the flared transition section 211 and the axis first increases and then decreases, so that the angles of the side walls at both ends of the flared transition section 211 correspond to the side walls of the flared section 210 and the tightening section 220, respectively, thereby achieving a smooth transition connection with the flared section 210 and the tightening section 220, further reducing the stress concentration points on the lower feeding tube 200.

[0059] As a preferred embodiment of the present invention, the angle between the side wall of the flared transition section 211 and the axis of the flared transition section 211 is greater than or equal to 0° and less than or equal to 60°, thereby ensuring that the angle of the side wall of the flared transition section 211 is steep enough to allow the crushed materials to slide smoothly down the flared transition section 211.

[0060] As an optional embodiment of the present invention, Figure 2 、 Figure 4 As shown, the conveying section 230 includes a first conveying pipe 231, a second conveying pipe 232, and a third conveying pipe 233, which are connected in sequence. The first conveying pipe 231 is connected to the constricting section 220 and is coaxially arranged with the flaring section 210. The axis of the second conveying pipe 232 is at an angle to the axis of the first conveying pipe 231. The third conveying pipe 233 is arranged in the same direction as the first conveying pipe 231. The first conveying pipe 231 and the second conveying pipe 232 pass through the side wall of the furnace body 10 and enter the furnace body 10. The inner wall of the furnace body 10 has an inner flange 12, and the discharge end of the third conveying pipe 233 passes through the inner flange 12.

[0061] In the embodiment of the present invention, the conveying section 230 is a bent structure. Figure 1 、 Figure 4As shown, the first conveying tube 231 and the third conveying tube 233 are arranged vertically, and the second conveying tube 232 is connected obliquely between the first conveying tube 231 and the third conveying tube 233. Therefore, when the third conveying tube 233 is aligned with the crucible 11 in the furnace chamber, the first conveying tube 231 can be biased toward the side wall of the furnace body, so that the expanding section 210 and the upper feeding tube 100 are both arranged on one side of the furnace body. While avoiding the hot field, more operating space is left above the single crystal furnace to facilitate crystal pulling operations.

[0062] As a preferred embodiment of the present invention, Figure 2 As shown, the inner flange 12 has an avoidance hole, and the discharge end of the third conveying pipe 233 passes through the avoidance hole on the inner flange 12 to convey the crushed materials to the crucible 11. The inner flange 12 can reduce the heat loss rate and ensure the temperature in the furnace.

[0063] As a preferred embodiment of the present invention, Figure 3 As shown, a positioning block 300 is provided on the outer wall of the third delivery pipe 233 , and the positioning block 300 is used to contact the hole wall of the avoidance hole to stabilize the position of the lower feeding pipe 200 when the third delivery pipe 233 is inserted into the avoidance hole on the inner flange 12 .

[0064] Alternatively, as Figure 2 As shown, a graphite felt 13 is provided on the hole wall of the avoidance hole, and the graphite felt 13 is sandwiched between the positioning block 300 and the hole wall of the avoidance hole.

[0065] As an optional embodiment of the present invention, the material of the feeding tube 20 can be quartz material. The feeding tube 20 made of quartz material has high structural strength and can adapt to the high temperature environment of the crystal pulling process.

[0066] Alternatively, the material of the feeding tube 20 may also be other materials with high hardness and high temperature resistance, such as ceramic materials such as silicon carbide and silicon nitride.

[0067] As an optional embodiment of the present invention, Figure 2 As shown, the single crystal furnace further includes a material barrel 30 , and the feeding end of the upper feeding pipe 100 is connected to the material barrel 30 .

[0068] As an optional embodiment of the present invention, Figure 3 As shown, a crucible 11 is provided in the inner cavity of the furnace body 10 , and the discharge end of the lower feeding pipe 200 is used to transport silicon material (crushed material) into the crucible 11 .

[0069] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modifications that do not deviate from the functional and structural principles of the present invention are included within the scope of the claims.

Claims

1. A single crystal furnace, comprising a furnace body and a feeding pipe, characterized in that: The feeding pipe includes an upper feeding pipe and a lower feeding pipe, and the lower feeding pipe includes a flaring section, a tightening section and a conveying section connected in sequence, the diameter of the flaring section is larger than the diameter of the tightening section, and the diameter of the tightening section is larger than the diameter of the conveying section; the discharge end of the upper feeding pipe passes through the flaring section and extends to be located in the tightening section, the lower feeding pipe is fixedly arranged in the furnace body, and the discharge end of the conveying section is connected to the inner cavity of the furnace body.

2. The single crystal furnace according to claim 1, characterized in that: A splash guard is provided on the outer side of the upper feeding pipe, and the splash guard closes the opening between the flared section and the upper feeding pipe.

3. The single crystal furnace according to claim 2, characterized in that: The splash shield includes a baffle and a limiting cylinder. The upper feeding pipe passes through the baffle. The limiting cylinder is arranged around the lower feeding pipe, and one end of the limiting cylinder away from the discharge end of the upper feeding pipe is fixedly connected to the baffle.

4. The single crystal furnace according to claim 3, characterized in that A high-temperature resistant elastic pad is provided on one side surface of the baffle facing the discharge end of the upper feeding pipe. The shape of the elastic pad corresponds to the shape of the flared section, and the elastic pad contacts the opening edge of the flared section.

5. The single crystal furnace according to claim 1, characterized in that: The length of the expanded section is 5 cm to 10 cm.

6. The single crystal furnace according to any one of claims 1 to 5, characterized in that: The diameter of the expansion section is 1.5 to 3 times the diameter of the contraction section, and the diameter of the contraction section is 1.5 to 3 times the diameter of the conveying section.

7. The single crystal furnace according to any one of claims 1 to 5, characterized in that: The conveying section includes a first conveying pipe, a second conveying pipe and a third conveying pipe connected in sequence. The first conveying pipe is connected to the tightening section and is coaxially arranged with the expanding section. There is an angle between the axis of the second conveying pipe and the axis of the first conveying pipe. The third conveying pipe is arranged in the same direction as the first conveying pipe. The first conveying pipe and the second conveying pipe pass through the side wall of the furnace body and enter the furnace body. The inner wall of the furnace body has an inner flange, and the discharge end of the third conveying pipe passes through the inner flange.

8. The single crystal furnace according to any one of claims 1 to 5, characterized in that: The lower feeding pipe further includes a butt-joint transition section and a flared transition section, wherein the butt-joint transition section is connected between the tightening section and the conveying section, and the diameter of the butt-joint transition section gradually decreases along the feeding direction of the lower feeding pipe; The flaring transition section is connected between the flaring section and the contraction section, and the diameter of the flaring transition section gradually decreases along the feeding direction of the lower feeding pipe.

9. The single crystal furnace according to claim 8, characterized in that: The angle between the side wall of the butt-joint transition section and the axis of the butt-joint transition section is greater than or equal to 0° and less than or equal to 60°; The angle between the side wall of the flared transition section and the axis of the flared transition section is greater than or equal to 0° and less than or equal to 60°.

10. The single crystal furnace according to any one of claims 1 to 5, characterized in that: The material of the feeding tube is quartz material or ceramic material.

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