Centrifugal fan structure for a flour mill

Abstract

The utility model belongs to the technical field of fan for grinding machine, especially relates to a centrifugal fan structure for grinding machine. A centrifugal fan structure for grinding machine, including drive motor and centrifugal fan, drive motor includes main shaft, the fixed end bearing of sleeve setting on main shaft is angular contact ball bearing, the movable end bearing of sleeve setting on main shaft is cylindrical roller bearing, the flange plate is fixedly connected on the front end cover of drive motor, the flange plate is fixedly connected in the volute rear end cover of centrifugal fan through fastening bolt to fix drive motor on centrifugal fan, the main shaft is coaxially fixedly connected with the fan impeller of centrifugal fan. The utility model can be applicable to grinding machine industry and the direct drive centrifugal fan for medium and large grinding machine with power 100-315kW.

Description

Technical Field

[0001] This utility model belongs to the technical field of fans for grinding mills, and particularly relates to a centrifugal fan structure for grinding mills. Background Technology

[0002] In closed-loop grinding systems used in industries such as ore, building materials, food, and pharmaceuticals, centrifugal fans are responsible for forcibly extracting the ground fine powder from the grinding chamber and conveying it to the classification / dust collection device. The fan's airflow, air pressure, and reliability directly determine the system's capacity and stability. Medium and large-sized grinding mills typically use fans with power ranging from 100-315kW, operating under high-speed and high-load conditions, thus placing higher demands on the transmission efficiency and reliability of the drive system.

[0003] Currently, the grinding mill industry generally adopts the traditional structure of "motor + coupling / pulley + transmission assembly + fan impeller", with a typical arrangement: motor shaft extension → coupling / pulley → bearing housing → fan main shaft → impeller. This structure transmits the motor speed / power to the required fan speed through multi-stage transmission.

[0004] The existing fan structure used in the grinding mill industry has the following drawbacks: a) Complex structure: It requires bearing housings, couplings / pulleys, has a large number of parts, and is difficult to assemble; b) Low transmission efficiency: The pulley relies on belt friction to drive the motor speed and power, with a transmission efficiency of about 92% and the coupling about 95%, both of which have transmission losses; c) High failure rate: frequent belt wear and coupling misalignment failures; d) High vibration and noise: The fan has high vibration and noise due to belt tension and coaxiality error of the double support bearing housing; e) Dust leakage: Traditional shaft extension seals are contact-type felt rings, which can leak dust after wear; f) Gap in medium and large direct drive technology: Existing direct drive solutions for centrifugal fans driven by motors are only applicable to small fans ≤100kW, such as the invention patent with authorization announcement number CN114810637B, entitled "An Integrated High-Speed ​​Direct Drive Fan," which has a flow range of 10-50m³ / min, i.e., 600-3000m³ / h, and a power of basically less than 100kW. However, the air volume of grinding mill fans is 30000-60000 m³ / h, so it is not suitable for the grinding mill industry. When direct drive is used for medium and large fans of 100-315kW in the grinding mill industry, the low critical speed of the rotor and the inability of standard motor bearings to simultaneously bear radial / axial loads lead to resonance and premature bearing failure.

[0005] To address the aforementioned shortcomings, this invention aims to provide a direct-drive centrifugal fan for medium and large-sized grinding mills with a power of 100-315kW, suitable for the grinding mill industry. Utility Model Content

[0006] To address at least one technical problem existing in the prior art, this application provides a centrifugal fan structure for a grinding mill, which is applicable to the grinding mill industry and is a direct-drive centrifugal fan for medium and large-sized grinding mills with a power of 100-315kW.

[0007] To achieve the above objectives, this utility model provides the following technical solution: A centrifugal fan structure for a grinding mill includes a drive motor and a centrifugal fan. The drive motor includes a main shaft, a fixed end bearing sleeved on the main shaft is an angular contact ball bearing, and a floating end bearing sleeved on the main shaft is a cylindrical roller bearing. A flange is fixedly connected to the front end cover of the drive motor, and the flange is fixedly connected to the rear end cover of the centrifugal fan casing by fastening bolts to fix the drive motor to the centrifugal fan. The main shaft is coaxially fixedly connected to the impeller of the centrifugal fan.

[0008] Preferably, a raised ring is formed by extending the inner end face of the flange to its outer side, and an elastic sealing ring is fitted on the raised ring. The raised ring is inserted into the rear end cover of the volute, and the two end faces of the sealing ring abut against the flange and the rear end cover of the volute, respectively.

[0009] Preferably, the front end cover of the drive motor is integrally cast with the flange.

[0010] Preferably, the drive motor is fixedly connected to the motor bracket, the motor bracket includes a rear plate, two side plates fixedly connected to both sides of the rear plate, and a top plate fixedly connected to the upper surface of the rear plate and the two side plates, and two reinforcing steel plates matching the drive motor are fixedly connected to the top plate.

[0011] Preferably, a waist-shaped mounting through hole is provided on the reinforcing steel plate along its length direction, and the mounting through hole extends downward and penetrates the top plate.

[0012] Preferably, a cross-shaped reinforcing rib is fixedly connected to the lower end face of the top plate, the transverse ribs of the reinforcing rib are fixedly connected to the two side plates, the longitudinal ribs of the reinforcing rib are fixedly connected to the top plate and the rear plate respectively, and the transverse ribs and longitudinal ribs of the reinforcing rib are fixedly connected.

[0013] Preferably, it also includes a fan base, the fan base including a base plate, a base frame formed by channel steel enclosing the base plate, a partition plate fixedly connected inside the base frame, and the motor bracket and the volute outlet shell of the centrifugal fan fixedly connected to the fan base.

[0014] Preferably, reinforcing plates are fixedly connected to the rear end cover of the volute in a crisscross pattern.

[0015] Preferably, a reinforcing plate is fixedly connected to the front end cover of the centrifugal fan that is opposite to the rear end cover of the volute.

[0016] Preferably, lifting lugs are fixedly connected to the front end cover and the rear end cover of the volute respectively.

[0017] Compared with the prior art, the beneficial effects of this utility model are: 1. This utility model eliminates the coupling / pulley and transmission assembly in the prior art, and achieves direct drive of the centrifugal fan by setting a high-strength alloy tempered main shaft, angular contact ball bearings at the fixed end, and cylindrical roller bearings at the floating end. This solves the problem of fan resonance and premature bearing failure caused by the low critical rotor speed of medium and large fans operating at 100-315kW, where the standard motor shaft and bearings cannot simultaneously bear the radial load. This enables the application of centrifugal fans in power conditions of 100-315kW, and achieves a critical speed of more than 1.3 times the maximum operating speed of the centrifugal fan steel shaft.

[0018] 2. By setting up flanges and sealing rings, the connection between the centrifugal fan and the flange is sealed, preventing the escape of fine powder materials inside the centrifugal fan, achieving zero leakage of the centrifugal fan, and meeting the environmental protection requirements of environmental friendliness.

[0019] 3. By setting up a specially structured motor bracket and fan base, the overall structural stability of the centrifugal fan is effectively improved, and the fan vibration is reduced, so that the average value of the centrifugal fan vibration is less than 1 mm / s. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of Embodiment 1 of the present utility model.

[0021] Figure 2 This is a front view structural diagram of Embodiment 1 of this utility model.

[0022] Figure 3 for Figure 2 A schematic diagram of the AA cross-section.

[0023] Figure 4 for Figure 3 A magnified structural diagram at point A.

[0024] Figure 5 This is a schematic diagram of the drive motor in an embodiment of the present invention.

[0025] Figure 6 This is a first-view structural schematic diagram of the centrifugal fan according to an embodiment of the present invention.

[0026] Figure 7This is a structural schematic diagram of the centrifugal fan from a second perspective in an embodiment of this utility model.

[0027] Figure 8 This is a schematic diagram of the motor bracket of Embodiment 1 of this utility model.

[0028] Figure 9 This is a schematic diagram of the structure of the fan base according to an embodiment of the present utility model.

[0029] Figure 10 This is a schematic diagram of the structure of Embodiment 2 of this utility model.

[0030] In the diagram: 1. Drive motor; 11. Motor housing; 12. Main shaft; 13. Fixed end bearing; 14. Floating end bearing; 15. Front end cover; 16. Flange; 161. Connecting hole; 162. convex ring; 17. Fastening bolt; 171. Fastening nut; 18. Sealing ring; 19. Mounting base. 2. Centrifugal fan; 21. Rear end cover of volute; 211. Through hole of rear end cover of volute; 212. Center hole of rear end cover of volute; 213. Reinforcing plate; 2131. Reinforcing channel steel; 2132. Reinforcing horizontal plate; 2133. Reinforcing vertical plate; 22. Fan impeller; 23. Volute housing; 24. Retaining ring; 25. Screw; 26. Volute outlet housing; 27. Front end cover of volute; 271. Reinforcing plate; 2711. Reinforcing horizontal plate; 2712. Reinforcing vertical plate; 2713. Reinforcing inclined plate; 28. Lifting lug. 3. Motor bracket; 31. Rear plate; 32. Side plate; 33. Top plate; 34. Reinforcing steel plate; 341. Mounting through hole; 35. Reinforcing rib. 4. Fan base, 41. Base plate, 42. Base frame, 43. Divider plate. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0032] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Example 1

[0033] See appendix Figure 1 , 2 As shown in Figures 1 and 3, a centrifugal fan structure for a grinding mill includes a drive motor 1, a centrifugal fan 2, a motor bracket 3, and a fan base 4.

[0034] The drive motor 1 includes a motor housing 11 and a main shaft 12 disposed within the motor housing 11 along its length. Furthermore, a fixed-end bearing 13, sleeved on the main shaft 12 and fixedly embedded within the motor housing 11, is an angular contact ball bearing, and a floating-end bearing 14, sleeved on the main shaft 12, is a cylindrical roller bearing. The main shaft 12 is a high-strength alloy tempered main shaft made of 40Cr material, using a tempering heat treatment process. Its yield strength is 785 MPa, tensile strength is 980 MPa, allowable safety factor is 10.6, and fracture safety factor is 33.2. By using a high-strength alloy tempered main shaft 12, a floating-end bearing 14 with a cylindrical roller bearing structure, and a fixed-end bearing 13 with an angular contact ball bearing, the problem of fan resonance and premature bearing failure in medium and large centrifugal fans operating at 100-315kW is solved because the rotor's critical speed is low, and the standard motor shaft and bearings cannot simultaneously bear radial loads.

[0035] See Figure 5 As shown, a flange 16 is fixedly connected to the front end cover 15 on the motor housing 11 of the drive motor 1. In order to improve the connection strength between the flange 16 and the front end cover 15 and to avoid connection failure due to vibration, in this embodiment, the front end cover 15 and the flange 16 of the drive motor 1 are integrally cast, that is, an annular flange 16 is formed by extending outward from the edge of the outer end face of the front end cover 15, and eight connection holes 161 are evenly distributed on the flange 16.

[0036] It should be noted that this application modifies the structure of the fixed end bearing 13, the floating end bearing 14 and the front end cover 15 based on the existing drive motor. Other structures, such as the lubrication structure and coil assembly, are existing technologies, and their working principles are also existing technologies. For example, in order to prevent the material in the inner cavity of the centrifugal fan 2 from entering the housing 11 of the drive motor 1, an existing sealing structure is provided between the main shaft 12 and the front end cover 15.

[0037] See Figure 3 , 4 As shown, the drive motor 1 can be directly fixed to the rear end cover 21 of the volute of the centrifugal fan 2 via the flange 16, and the end of the main shaft 12 extending out of the motor housing 11 is coaxially and fixedly connected to the fan impeller 22 of the centrifugal fan 2.

[0038] Specifically, eight through holes 211 are evenly distributed on the volute rear end cover 21, corresponding one-to-one with the connection holes 161 on the flange 16. A central hole 212 is provided in the middle of the volute rear end cover 21. The end of the main shaft 12 extending out of the motor housing 11 is rotatably inserted into the central hole 212 on the volute rear end cover 21 and extends into the inner cavity of the volute housing 23 of the centrifugal fan 2. The connection between the fan impeller 22 and the main shaft 12 is the existing technology, that is, the fan impeller 22 is fixedly sleeved on the main shaft 12 by a key connection. A retaining ring 24 is sleeved on the main shaft 12 outside the fan impeller 22. A screw 25 is threadedly connected to the end of the main shaft 12, and the nut of the screw 25 abuts against the outer end face of the retaining ring 24.

[0039] Fastening bolts 17 are inserted into each connecting hole 161 and into the through hole of the rear end cover of the volute. Fastening nuts 171 are threaded onto the fastening bolts 17 inside the volute housing 23. Thus, the flange 16 is fixedly connected to the rear end cover 21 of the volute of the centrifugal fan 2 by the fastening bolts 17 and the fastening nuts 171, thereby fixing the drive motor 1 to the centrifugal fan 2 and directly connecting the main shaft 12 of the drive motor 1 to the fan impeller 22, thereby realizing the direct drive of the centrifugal fan 2 by the drive motor 1. Compared with the prior art, this utility model adopts the overall structure of a direct-drive centrifugal fan, and the main shaft 12 of the drive motor 1 is directly and rigidly connected to the fan impeller 22, eliminating the intermediate transmission components in the prior art.

[0040] Furthermore, to prevent fine powder material inside the volute housing 23 from escaping through the gap at the connection between the flange 16 and the volute rear end cover 21, thus causing environmental pollution, in this embodiment, a raised ring 162 extends outward from the inner end face of the flange 16. An elastic sealing ring 18 is fitted on the raised ring 162, and the sealing ring 18 is disposed inside each fastening bolt 17. In this embodiment, the end face of the raised ring 162 abuts against the outer end face of the volute rear end cover 21, and the two end faces of the sealing ring 18 respectively abut against the outer end face of the volute rear end cover 21 and the outer end face of the flange 16. That is, a rubber elastic sealing element 18 is press-fitted between the flange 16 and the volute rear end cover 21. By setting the sealing ring 18, the flange 16 and the inside of the volute housing 23 are sealed, preventing the fine powder material inside the volute housing 23 from escaping. Of course, in other embodiments, the protruding ring 162 can also be inserted into the center hole 212 of the rear end cover of the volute, and the two end faces of the sealing ring 18 still abut against the outer end face of the rear end cover 21 of the volute and the outer end face of the flange 16, respectively.

[0041] See Figure 1 , 8 As shown, in order to support the drive motor 1, in this embodiment, the drive motor 1 is fixedly connected to the motor bracket 3.

[0042] This embodiment uses finite element analysis to determine the optimal structure of the motor bracket 3. The motor bracket 3 includes a rear plate 31, two side plates 32 welded to both sides of the rear plate 31, and a top plate 33 welded to the upper surfaces of the rear plate 31 and the side plates 32. Two reinforcing steel plates 34, matching the drive motor 1, are welded to the top plate 33. The rear plate 31 is welded to the side of the side plates 32 furthest from the rear end cover 21 of the volute. The rear plate 31 and the side plates 32 are inclined inwards, while the top plate 33 is horizontal. The two reinforcing steel plates 34 are parallel and perpendicular to the direction of the rear end cover 21 of the volute. By setting the motor bracket 3, sufficient support is provided for the drive motor 1, effectively reducing the vibration of the centrifugal fan 2 and improving structural stability.

[0043] Two oblong mounting through holes 341 are formed along the length of the reinforcing steel plate 34. The mounting through holes 341 extend downward and penetrate the top plate 33, that is, oblong through holes opposite to the mounting through holes 341 are formed on the top plate 33. Two existing sets of motor mounting seats 19 are welded to the lower end of the motor housing 11 of the drive motor 1. When the drive motor 1 is fixedly mounted on the motor bracket 3, the bolts pass through the oblong through holes of the top plate 33 from below and continue to pass through the mounting through holes 341 and the mounting seats 19 and extend to the top of the mounting seats 19. Nuts are threaded onto the bolts above the mounting seats 19.

[0044] Furthermore, a cross-shaped reinforcing rib 35 is welded to the lower end face of the top plate 33. The transverse ribs of the reinforcing rib 35 are welded to the inner sides of the two side plates 32, and the longitudinal ribs of the reinforcing rib 35 are welded to the inner sides of the top plate 33 and the rear plate 31. The transverse and longitudinal ribs of the reinforcing rib 35 are welded to each other.

[0045] See Figure 9 As shown, to further improve the connection strength between the drive motor 1, the centrifugal fan 2, and the motor bracket 3, and to reduce the vibration amplitude, this utility model also includes a fan base 4. The fan base 4 includes a horizontally arranged base plate 41, a rectangular base frame 42 formed by welding channel steel around the base plate 41, and a partition plate 43 welded inside the base frame 42. The rear plate 31 and side plates 32 of the motor bracket 3 are welded to the fan base 4, and the volute outlet shell 26 of the centrifugal fan 2 is welded to the fan base 4. By welding channel steel in a specific manner to form the fan base 4, the overall structural stability of the centrifugal fan 2 is effectively improved, and the vibration of the centrifugal fan 2 is reduced.

[0046] See Figure 6As shown, reinforcing plates 213 are welded in a crisscross pattern to the rear end cover 21 of the volute. In this embodiment, after finite element analysis, the optimal reinforcement positions for the volute shell 23 were determined. Specifically, the reinforcing plates 213 include two vertically arranged reinforcing channel steels 2131 welded to the rear end cover 21 of the volute; multiple reinforcing transverse plates 2132 welded laterally to the two reinforcing channel steels 2131 and the rear end cover 21 of the volute; and reinforcing longitudinal plates 2133 welded longitudinally to each reinforcing transverse plate 2132 and the rear end cover 21 of the volute. This structure improves the overall structural stability of the centrifugal fan 2 and effectively reduces fan vibration.

[0047] See Figure 7 As shown, a reinforcing plate 271 is welded to the front end cover 27 of the centrifugal fan 2, which is opposite to the rear end cover 21 of the volute. The reinforcing plate 271 includes a reinforcing horizontal plate 2711 horizontally welded to the upper and lower parts of the front end cover 27 of the volute, a reinforcing vertical plate 2712 welded to the front end cover 27 of the volute on one side of the reinforcing horizontal plate 2711, and a reinforcing inclined plate 2713 welded to the reinforcing horizontal plate 2711, the reinforcing vertical plate 2712 and the front end cover 27 of the volute.

[0048] To facilitate the transfer and installation of the centrifugal fan 2, lifting lugs 28 are welded onto the front cover 27 and the rear cover 21 of the volute casing, respectively.

[0049] It should be noted that all content not described in this specification is prior art and will not be elaborated here.

[0050] The working principle and process of this embodiment are as follows: Install all components as described above, and turn on the drive motor 1 to directly drive the fan impeller 22 to rotate via the main shaft 12. With this structure, the centrifugal fan can be used in medium to large-sized grinding mills with power ratings of 100-315kW. In this embodiment, the weight of the drive motor 1 is borne by the motor bracket 3, and the flange 16 only cooperates with the sealing ring 18 for sealing.

[0051] According to GB13275-1911, the critical speed of the fan's steel shaft should be at least 1.3 times the maximum operating speed. In actual testing, the critical speed of the integral fan impeller 22 of the centrifugal fan 2 was calculated to be 2200 r / min, and the operating speed of the centrifugal fan 2 was 1489 r / min, with a ratio of 1.478. This meets the requirements of GB13275-1911.

[0052] The vibration test results of the centrifugal fan over two consecutive days are as follows:

[0053] It can be seen that the maximum measured average vibration of the fan is 0.975 mm / s, and the average vibration of the fan is less than 1 mm / s. Example 2

[0054] See Figure 10 As shown, the only difference between this embodiment and Embodiment 1 is that the motor bracket 3 is not provided; instead, the flange 16 is fixedly connected to the rear end cover 21 of the volute casing only by fastening bolts 17 and fastening nuts 171. The volute outlet housing 26 of the centrifugal fan 2 can be welded to the fan base 4. The fan base 4 can have the same structure as the fan base 4 in Embodiment 1, or the partition plate 43 can be omitted. The base plate 41 and the base frame 42 can be adapted according to the size of the volute outlet housing 26. Of course, in other embodiments, the fan base 4 can also be omitted. With the above structure, this centrifugal fan structure can also be used in medium and large-sized grinding mills with a power range of 100-315kW. In this embodiment, the weight of the drive motor 1 is borne by the rear end cover 21 of the volute casing connected to the flange 16 of the drive motor 1. In addition to transmitting the weight of the drive motor 1, the flange 16 also cooperates with the sealing ring 18 to perform a sealing function.

[0055] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A centrifugal fan structure for a grinding mill, comprising a drive motor and a centrifugal fan, characterized in that: The drive motor includes a main shaft, a fixed end bearing sleeved on the main shaft is an angular contact ball bearing, and a floating end bearing sleeved on the main shaft is a cylindrical roller bearing; a flange is fixedly connected to the front end cover of the drive motor, and the flange is fixedly connected to the rear end cover of the centrifugal fan casing by fastening bolts to fix the drive motor to the centrifugal fan; the main shaft is coaxially fixedly connected to the impeller of the centrifugal fan.

2. The centrifugal fan structure for a grinding mill according to claim 1, characterized in that: A raised ring is formed by extending the inner end face of the flange to its outer side. An elastic sealing ring is fitted on the raised ring. The raised ring is inserted into the rear end cover of the volute. The two end faces of the sealing ring abut against the flange and the rear end cover of the volute, respectively.

3. The centrifugal fan structure for a grinding mill according to claim 1, characterized in that: The front cover of the drive motor is integrally cast with the flange.

4. The centrifugal fan structure for a grinding mill according to claim 1, characterized in that: The drive motor is fixedly connected to the motor bracket. The motor bracket includes a rear plate, two side plates fixedly connected to both sides of the rear plate, and a top plate fixedly connected to the upper surface of the rear plate and the two side plates. Two reinforcing steel plates matching the drive motor are fixedly connected to the top plate.

5. The centrifugal fan structure for a grinding mill according to claim 4, characterized in that: An oblong mounting through hole is provided along the length of the reinforcing steel plate, and the mounting through hole extends downward and penetrates the top plate.

6. The centrifugal fan structure for a grinding mill according to claim 5, characterized in that: A cross-shaped reinforcing rib is fixedly connected to the lower end face of the top plate. The transverse ribs of the reinforcing rib are fixedly connected to the two side plates, and the longitudinal ribs of the reinforcing rib are fixedly connected to the top plate and the rear plate respectively. The transverse and longitudinal ribs of the reinforcing rib are fixedly connected.

7. The centrifugal fan structure for a grinding mill according to claim 4, characterized in that: It also includes a fan base, which includes a base plate, a base frame formed by channel steel enclosing the base plate, and a partition plate fixedly connected inside the base frame. The motor bracket and the volute outlet shell of the centrifugal fan are fixedly connected to the fan base.

8. The centrifugal fan structure for a grinding mill according to claim 4, characterized in that: Reinforcing plates are fixedly connected to the rear end cover of the volute in a crisscross pattern.

9. The centrifugal fan structure for a grinding mill according to claim 8, characterized in that: A reinforcing plate is fixedly connected to the front cover of the centrifugal fan, which is opposite to the rear cover of the volute.

10. The centrifugal fan structure for a grinding mill according to claim 9, characterized in that: Lifting lugs are fixedly connected to the front end cover and the rear end cover of the volute respectively.

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