A bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor

Abstract

This invention discloses a direct drive device for a bucket wheel of a bucket wheel excavator based on an axial flux motor, comprising: a multi-disc stacked axial flux permanent magnet synchronous motor; the axial flux permanent magnet synchronous motor uses dual rotors and a single stator as basic units, with at least two basic units, each including a stator disk movably sleeved outside the motor shaft, with flat copper wire windings embedded on both end faces of the stator disk, and a liquid cooling channel inside the stator disk; two rotor disks fixed on the motor shaft, distributed on both sides of the stator disk, with fan-shaped neodymium iron boron permanent magnets attached to the end face of the rotor disk facing the stator disk, the neodymium iron boron permanent magnets being a Halbach array; the motor shaft is rotatably connected to the motor housing, and both ends of the motor shaft are mounted on the front end of the bucket wheel excavator cantilever via bearing seats; the outermost rotor disk has a connecting flange on its outer edge, and the connecting flange is coaxially and fixedly connected to the bucket wheel ring; a liquid cooling circulation system provides coolant to the liquid cooling channel. It has the advantage of eliminating the reducer, requiring only one stage of transmission from the motor rotor to the bucket wheel ring.

Description

Technical Field

[0001] This invention relates to the field of bulk material handling machinery drive technology, and more specifically, to a bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor. Background Technology

[0002] Bucket wheel stacker-reclaimers (abbreviated as bucket wheel reclaimers) are core loading and unloading equipment in bulk material storage yards such as ports, power plants, and mines. Their bucket wheel drive system is one of the most important transmission devices of the whole machine.

[0003] There are two main existing bucket wheel drive schemes. The first is the electric motor-reducer scheme: a three-phase asynchronous motor is used to drive the bucket wheel shaft through a high-ratio planetary reducer (typically 200 to 300) to reduce speed and increase torque, with an output torque exceeding 100 kN·m. The drawbacks of this scheme are: complex reducer structure, high maintenance requirements for the lubrication system, and a long transmission chain resulting in an overall system efficiency of only about 85%. Reducer failure is the main cause of bucket wheel machine downtime. The second is the hydraulic motor scheme: a hydraulic pump station drives a hydraulic motor to rotate the bucket wheel, achieving stepless speed regulation. However, the hydraulic system has a high risk of leakage, is difficult to start at low temperatures, and has an even lower overall efficiency (about 70%).

[0004] In recent years, permanent magnet direct drive technology has been applied in the field of electric drum motors for belt conveyors, employing a radial flux external rotor permanent magnet synchronous motor built into the drum. However, when using radial flux motors for bucket wheel direct drive, the motor's axial length is too large (usually exceeding 500mm), making installation difficult within the limited space at the front end of the bucket wheel cantilever, and the large length-to-diameter ratio of the radial flux motor leads to increased cantilever bending moment. Axial flux motors (also known as disc motors) have the characteristics of a flat structure, short axial dimension, and high torque density; their torque is proportional to the cube of the rotor diameter, and their torque gain at large diameters is far superior to that of radial flux motors. However, there are currently no engineering application cases of using axial flux motors for direct drive of bucket wheel excavators. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of high maintenance requirements for reducers, low transmission chain efficiency, and limited axial installation space in existing bucket wheel excavator drive systems. The invention proposes a transmission device based on a multi-disc stacked axial flux permanent magnet synchronous motor to directly drive the rotation of the bucket wheel.

[0006] To achieve the above objectives, a bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor includes:

[0007] Multi-disc stacked axial flux permanent magnet synchronous motor and liquid cooling circulation system;

[0008] The axial flux permanent magnet synchronous motor uses dual rotors and a single stator as basic units, and stacks at least two basic units in series along the axial direction to form a multi-disc structure with at least four effective air gap surfaces.

[0009] Each basic unit includes:

[0010] A stator disc is movably fitted around the motor shaft, with flat copper wire windings embedded on both end faces of the stator disc. The stator disc has liquid cooling channels inside and is fixed inside the motor housing.

[0011] Two rotor discs, fixedly sleeved on the outside of the motor shaft, are arranged on both sides of the stator disc. A fan-shaped neodymium iron boron permanent magnet is attached to the end face of the rotor disc facing the stator disc. The neodymium iron boron permanent magnets are arranged in alternating N and N polarities to form a Halbach array.

[0012] The motor shaft passes through the center hole of all stator and rotor discs. The motor shaft is rotatably connected to the motor housing. Both ends of the motor shaft are mounted on the front end of the bucket wheel excavator cantilever via bearing seats.

[0013] The outermost rotor disc has a connecting flange on its outer edge, which is fixedly connected to the bucket wheel ring coaxially by bolts;

[0014] The liquid cooling circulation system provides coolant to the liquid cooling channels.

[0015] Furthermore, the liquid cooling channels inside the stator disk are spirally distributed around the axial direction, and the inlet and outlet of the coolant are respectively located on the outer edge of the stator disk. The inlet and outlet are connected to the external liquid cooling circulation pump and radiator via connector pipes.

[0016] Furthermore, the coolant is selected from ethylene glycol aqueous solution or transformer oil.

[0017] Furthermore, the number N of the basic units is determined according to the maximum output torque required by the bucket wheel using the following formula:

[0018] ;

[0019] in, This is the maximum output torque required for the bucket wheel shaft. This refers to the rated output torque of a single basic unit.

[0020] Furthermore, it also includes: a controller, a torque module for acquiring motor shaft torque, and multiple winding temperature sensors for measuring the temperature of flat copper wire windings;

[0021] The winding temperature sensor is embedded inside the stator disk and is close to or embedded in the flat copper wire winding. Each stator disk has 2 to 3 winding temperature sensors. The highest value of all winding temperature sensors is taken as the temperature of the flat copper wire winding.

[0022] When the controller first determines that the motor shaft torque is greater than the warning threshold, the motor shaft speed is reduced. When the controller determines that the motor shaft torque is less than or equal to the warning threshold, the controller then determines that the temperature of the flat copper wire winding is greater than 140 degrees Celsius but not more than 155 degrees Celsius, and the liquid cooling circulation system increases the cooling flow of the coolant. When the controller determines that the temperature of the flat copper wire winding is greater than 155 degrees Celsius, the controller immediately stops the axial flux permanent magnet synchronous motor from working.

[0023] Furthermore, the torque module includes a torque sensor, which is installed at the connecting bolt of the connecting flange.

[0024] The beneficial effects of this invention are as follows:

[0025] By utilizing the physical property that the torque of an axial flux motor is proportional to the cube of its diameter and the linear superposition capability of torque from multiple stacked discs, ultra-large output torque can be achieved within a compact axial space, completely eliminating the reducer, simplifying the transmission chain, and improving system efficiency and reliability.

[0026] Improved transmission efficiency: After eliminating the reducer, there is only one stage of transmission from the motor rotor to the bucket wheel ring, and the overall system efficiency is increased from about 85% in the traditional solution to over 93% (motor efficiency is about 96%, direct drive has no gear loss).

[0027] Reduced maintenance workload: The reducer lubrication system (which requires changing the lubricating oil every 2,000 hours and regularly checking gear wear) is eliminated and replaced with a sealed liquid cooling circulation system (coolant replacement cycle exceeds 20,000 hours), thus reducing maintenance costs.

[0028] Compact axial space: For example, the total axial thickness of the four basic units stacked is about 350mm (including the rotor discs on both sides), and the motor outer diameter of 1800mm can directly utilize the inner diameter space of the bucket wheel ring. The overall axial dimension of the machine is shortened compared to the traditional radial flux direct drive solution.

[0029] Simplified torque transmission path: Compared with the traditional scheme of driving the bucket wheel shaft through a reducer, the motor shaft no longer undertakes the function of outputting all the torque to the bucket wheel, but only transmits the torque between each rotor disc. The torque required by the bucket wheel is directly output to the bucket wheel ring from the outermost rotor disc through the flange, eliminating weak links such as the coupling and shaft shoulder at the output end of the reducer.

[0030] Wide speed range: With low carrier ratio frequency conversion control, it can achieve stepless speed regulation in a wide range from 0.35 to 6.81 r / min. The lower limit of traditional solutions is limited by the motor heat dissipation, which is usually not less than 30% of the rated speed (about 2 r / min).

[0031] Fault-tolerant operation capability: In the multi-disc stacked structure, when a single stator disk or rotor disk fails, it can be electrically isolated, and the remaining basic units can operate at reduced power to avoid a complete shutdown of the bucket wheel excavator. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a cross-sectional view of the overall structure of the axial flux motor direct drive bucket wheel device in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the topology of a multi-disc stacked axial flux motor in an embodiment of the present invention;

[0035] Figure 3 This is the flow chart of the bucket wheel direct drive adaptive control system in this embodiment of the invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] It should be noted that similar reference numerals or letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] A bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor, comprising:

[0039] Multi-disc stacked axial flux permanent magnet synchronous motor and liquid cooling circulation system;

[0040] The axial flux permanent magnet synchronous motor uses dual rotors and a single stator as basic units, and stacks at least two basic units in series along the axial direction to form a multi-disc structure with at least four effective air gap surfaces.

[0041] Each basic unit includes:

[0042] A stator disc is movably fitted around the motor shaft, with flat copper wire windings embedded on both end faces of the stator disc. The stator disc has liquid cooling channels inside and is fixed inside the motor housing.

[0043] Two rotor discs, fixedly sleeved on the outside of the motor shaft, are arranged on both sides of the stator disc. A fan-shaped neodymium iron boron permanent magnet is attached to the end face of the rotor disc facing the stator disc. The neodymium iron boron permanent magnets are arranged in alternating N and N polarities to form a Halbach array.

[0044] The motor shaft passes through the center hole of all stator and rotor discs. The motor shaft is rotatably connected to the motor housing. Both ends of the motor shaft are mounted on the front end of the bucket wheel excavator cantilever via bearing seats.

[0045] The outermost rotor disc has a connecting flange on its outer edge, which is fixedly connected to the bucket wheel ring coaxially by bolts;

[0046] The liquid cooling circulation system provides coolant to the liquid cooling channels.

[0047] Specifically, the multi-disc stacked axial flux permanent magnet synchronous motor uses a dual-rotor-single-stator as the basic unit, with a YASA topology. The motor shaft passes through the center holes of all stator and rotor discs, and both ends of the shaft are fixed to the front end of the bucket wheel boom via bearing seats. The motor bearings are subjected to radial bending moment loads caused by the weight of the bucket wheel and the resistance of digging operations, and transmit torque between the rotor discs, but do not bear the function of outputting all torque to the bucket wheel. All rotor discs are axially locked to the motor shaft as an integral rotating assembly, for example, by means of splines or expansion sleeves to lock in a circumferential lock with the motor shaft, and the two maintain synchronous rotation. This locking connection is used to keep the rotor discs and the motor shaft rotating synchronously. The electromagnetic torque generated by each rotor disc is converged and superimposed through the motor shaft, and is directly output to the bucket wheel ring through the flange on the outermost rotor disc. The motor shaft passes through the center holes of all stator and rotor discs, and the stator discs are coaxially mounted on the motor shaft. The stator discs are fixed to the motor housing by key connections or locating pins, and the stator as a whole is fixed and stationary. The motor shaft is rotatably connected to the motor housing at both ends via bearings. The motor housing contains the basic unit. The motor shaft passes through the motor housing. The connecting flange is located at the output end of the entire motor, and the flange is fixed together with the bucket wheel ring.

[0048] For example, such as Figure 1 As shown, from left to right, are the bucket wheel ring, connecting flange, outer rotor disk 1, permanent magnet layer (Halbach array), air gap 1, stator disk (including flat copper wire winding and liquid cooling channel), air gap 2, permanent magnet layer, and outer rotor disk 2.

[0049] The bucket wheel adopts a multi-disc stacked axial flux permanent magnet synchronous motor for direct drive, which can completely eliminate the reducer. The transmission chain is simplified from four stages of motor-coupling-reducer-bucket wheel shaft to one stage of motor rotor-bucket wheel ring. The multi-disc stacked structure can flexibly match the torque requirements of different bucket wheel machine models by increasing or decreasing the number of basic units.

[0050] The rotor disc is directly coaxially fixed to the bucket wheel ring via a connecting flange. The torque required by the bucket wheel is directly output to the bucket wheel ring from the rotor disc. This eliminates the weak links such as the coupling and shaft shoulder at the output end of the reducer in the traditional solution, reducing the risk of fatigue fracture caused by stress concentration due to the superposition of bending and torsional loads on the bucket wheel shaft.

[0051] The stator disk integrates liquid cooling channels, which utilize the advantages of symmetrical heat dissipation surfaces on both sides of the stator to form a uniform temperature field and control the winding temperature rise within the allowable range of Class F insulation (e.g., less than 155°C).

[0052] The preferred embodiment of the liquid cooling circulation system is that the liquid cooling circulation system includes a liquid cooling circulation pump and a radiator. The liquid cooling channels inside the stator disk are distributed in a spiral shape around the axial direction. The inlet and outlet of the coolant are respectively located on the outer edge of the stator disk. The inlet and outlet are connected to the external liquid cooling circulation pump and radiator through connector pipes.

[0053] More preferably, the coolant is an aqueous solution of ethylene glycol or transformer oil.

[0054] The number of basic units N is determined by the following formula based on the maximum output torque required by the bucket wheel:

[0055] ;

[0056] in, This is the maximum output torque required for the bucket wheel shaft. This refers to the rated output torque of a single basic unit.

[0057] For example, for a working condition requiring 124.1 kN·m, a YASA basic unit with an outer diameter of 1800 mm (rated torque of approximately 31 kN·m, shear stress reference of 40 kPa) is selected, and four basic units are stacked (N=8 air gap surfaces), and the total output torque can reach 124 kN·m.

[0058] In a preferred embodiment, it further includes: a controller, a torque module for acquiring motor shaft torque, and multiple winding temperature sensors for measuring the temperature of flat copper wire windings;

[0059] The winding temperature sensor is embedded inside the stator disk and is close to or embedded in the flat copper wire winding. Each stator disk has 2 to 3 winding temperature sensors. The highest value of all winding temperature sensors is taken as the temperature of the flat copper wire winding.

[0060] When the controller first determines that the motor shaft torque is greater than the warning threshold, the motor shaft speed is reduced. When the controller determines that the motor shaft torque is less than or equal to the warning threshold, the controller then determines that the temperature of the flat copper wire winding is greater than 140 degrees Celsius but not more than 155 degrees Celsius, and the liquid cooling circulation system increases the cooling flow of the coolant. When the controller determines that the temperature of the flat copper wire winding is greater than 155 degrees Celsius, the controller immediately stops the axial flux permanent magnet synchronous motor from working.

[0061] When the temperature is less than or equal to 140 degrees Celsius, the motor shaft operates normally at the set speed.

[0062] There are two options for the torque module: one is to include a torque sensor, which is installed at the connecting bolts of the connecting flange. The other is to use the motor's frequency converter to calculate the motor shaft torque.

[0063] Optionally, a speed sensor for measuring the motor shaft speed can be included, which measures the speed non-contactly on the outer ring of the rotor or the bucket wheel ring. A toothed disc or pulse disc is provided on the outer edge of the rotor (or the outer ring flange bolts can be used directly as pulse markers), and a Hall / magnetoelectric / eddy current proximity switch is installed on the stationary motor housing to output pulses to measure the speed.

[0064] The following are three application examples:

[0065] Example 1 (Basic Example - 4-cell stack):

[0066] A power plant's DQL1650 / 1650·38 bucket wheel stacker-reclaimer originally used a YFBBP250M-4 55kW asynchronous motor (1485r / min) paired with a SEW P2HF 052+X2KP130 planetary reducer (speed ratio 226.841, rated output torque 124.1kN·m) to drive the bucket wheel, with a speed range of 1.7 to 6.81r / min.

[0067] The design was modified to a direct-drive axial flux motor: four dual-rotor-single-stator (YASA) basic units were stacked in series along the axial direction. The motor has an outer diameter of 1820mm, a total axial thickness of 348mm, and a total mass of approximately 3840kg. Each basic unit has a stator disk thickness of 42mm (including an 8mm liquid-cooled channel layer), double-sided flat copper wire windings, and 36 slots on each side; the rotor disk thickness is 28mm (6mm structural steel backplate, 4mm magnet layer, and 18mm yoke). NdFeB N48H grade magnets are used, arranged in a Halbach array, with 4 segments of sector magnets per pole, 48 pole pairs, and a designed air gap of 1.8mm. The stator liquid-cooled channel is filled with a 50% concentration ethylene glycol aqueous solution, with a designed circulation flow rate of 15L / min and a heat dissipation power of 4.2kW. The motor's rated output torque is 128kN·m (continuous from 0 to 7rpm), and the peak torque is 192kN·m (1.5 times overload, sustainable for 30s).

[0068] The frequency converter uses a 380V DC bus power supply and low carrier ratio synchronous modulation (carrier ratio 9 to 15) to achieve stepless speed regulation from 0.35 to 7.0 r / min. Actual data after 12 months of continuous operation in the field shows: total system efficiency of 93.7% (an improvement of 8.7 percentage points compared to the original asynchronous motor and reducer solution); maximum winding temperature of 118℃ (F-class insulation limit of 155℃, margin of 37℃); effective vibration velocity of 3.2 mm / s (ISO 10816-3 standard, Zone A); and fatigue life analysis of the bucket wheel shaft shows an expected lifespan extended to 2.4 times the original, resulting in a cumulative saving of approximately 246 hours of reducer maintenance time.

[0069] Example 2 (Optimized Example – 3-Unit Scheme):

[0070] A DQL1200 / 1200·30 bucket wheel stacker-reclaimer at a port requires a bucket wheel torque of approximately 82 kN·m. Three YASA basic units are stacked, with a motor outer diameter of 1520 mm, a total axial thickness of 268 mm, and a total mass of approximately 2280 kg. The rated output torque is 86 kN·m. Due to the smaller outer diameter and reduced heat dissipation area, an oil cooling scheme using direct spraying of transformer oil onto the stator winding ends is adopted instead of water cooling. This reduces the winding temperature rise by approximately 12°C compared to Example 1.

[0071] Example 3 (Comparative Example – Compared with Radial Flux Direct Drive Scheme):

[0072] A comparative test under the same working conditions was conducted with a bucket wheel excavator of the same model (with the same 124kN·m level) modified with a radial flux external rotor permanent magnet direct drive motor: The axial flux scheme of this invention has an axial thickness of 348mm, which is 33% less than the 520mm of the radial flux scheme, and the calculated value of the overturning moment at the front end of the cantilever is reduced by about 28%; the maximum force on the flange connection bolts between the rotor disc and the bucket wheel ring is reduced by about 35%, and the number of bolts is reduced from 32 to 20; the total mass of the effective materials of the motor (copper plus magnets plus silicon steel sheets) is reduced by about 18%.

[0073] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0074] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A bucket wheel direct drive device of a bucket wheel machine based on an axial flux motor, characterized in that, include: Multi-disc stacked axial flux permanent magnet synchronous motor and liquid cooling circulation system; The axial flux permanent magnet synchronous motor uses dual rotors and a single stator as basic units, and stacks at least two basic units in series along the axial direction to form a multi-disc structure with at least four effective air gap surfaces. Each basic unit includes: A stator disc is movably fitted around the motor shaft, with flat copper wire windings embedded on both end faces of the stator disc. The stator disc has liquid cooling channels inside and is fixed inside the motor housing. Two rotor discs, fixedly sleeved on the outside of the motor shaft, are arranged on both sides of the stator disc. A fan-shaped neodymium iron boron permanent magnet is attached to the end face of the rotor disc facing the stator disc. The neodymium iron boron permanent magnets are arranged in alternating N and N polarities to form a Halbach array. The motor shaft passes through the center hole of all stator and rotor discs. The motor shaft is rotatably connected to the motor housing. Both ends of the motor shaft are mounted on the front end of the bucket wheel excavator cantilever via bearing seats. The outermost rotor disc has a connecting flange on its outer edge, which is fixedly connected to the bucket wheel ring coaxially by bolts; The liquid cooling circulation system provides coolant to the liquid cooling channels.

2. The axial flux machine based bucket wheel excavator bucket wheel direct drive apparatus according to claim 1, characterized in that The liquid cooling channels inside the stator disk are spirally distributed around the axial direction. The inlet and outlet of the coolant are respectively located on the outer edge of the stator disk. The inlet and outlet are connected to the external liquid cooling circulation pump and radiator via connector pipes.

3. The axial flux machine based bucket wheel excavator bucket wheel direct drive apparatus according to claim 1, characterized in that The coolant is either an aqueous solution of ethylene glycol or transformer oil.

4. The axial flux machine based bucket wheel excavator bucket wheel direct drive apparatus according to claim 1, characterized in that The number N of the basic units is determined according to the maximum output torque required by the bucket wheel using the following formula: ； in, This is the maximum output torque required for the bucket wheel shaft. This refers to the rated output torque of a single basic unit.

5. A bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor according to claim 1, characterized in that, Also includes: The system includes a controller, a torque module for acquiring motor shaft torque, and multiple winding temperature sensors for measuring the temperature of flat copper wire windings. The winding temperature sensor is embedded inside the stator disk and is close to or embedded in the flat copper wire winding. Each stator disk has 2 to 3 winding temperature sensors. The highest value of all winding temperature sensors is taken as the temperature of the flat copper wire winding. When the controller first determines that the motor shaft torque is greater than the warning threshold, the motor shaft speed is reduced. When the controller determines that the motor shaft torque is less than or equal to the warning threshold, the controller then determines that the temperature of the flat copper wire winding is greater than 140 degrees Celsius but not more than 155 degrees Celsius, and the liquid cooling circulation system increases the cooling flow of the coolant. When the controller determines that the temperature of the flat copper wire winding is greater than 155 degrees Celsius, the controller immediately stops the axial flux permanent magnet synchronous motor from working.

6. A bucket wheel direct drive device for a bucket wheel excavator based on an axial flux motor according to claim 5, characterized in that, The torque module includes a torque sensor, which is installed at the connecting bolt of the connecting flange.

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