A multi-shaft parallel motor set structure with coaxial rigid coupling of multiple motors

Abstract

The application discloses a multi-motor coaxial rigid coupling multi-shaft parallel motor set structure and belongs to the technical field of high-power motor coupling transmission. The structure comprises at least two groups of coaxial motor unit groups, each group adopting a coaxial rigid coupling structure and comprising one common main shaft and at least two motor units; the motor units in the same group are rigidly connected with the common main shaft; the common main shaftes of the groups are in parallel connection, the number of the motor units in each group is not more than the critical number of single-shaft performance, and the length-diameter ratio of the common main shaft is in a high-rigidity design interval. The application deduces a general rule of the performance critical point of the number of single-shaft motors, breaks through the single-shaft power limit through the multi-shaft parallel architecture, retains the core advantages of the multi-motor coaxial rigid coupling, greatly improves the core performance of the shaft system compared with the long single-shaft scheme of the same power, and reduces the weight of the unit power of the whole machine by more than 70% compared with the traditional single high-power motor, and is suitable for high-power scenes such as wind power, hydroelectric power, ship propulsion and industrial driving.

Description

[0001] manual Technical Field

[0002] This invention belongs to the field of high-power motor coupling transmission technology, specifically relating to a multi-axis parallel motor unit structure with multiple coaxial rigid coupling, which can be bidirectionally adapted to power generation and drive scenarios, including high-power and high-reliability application scenarios such as wind power generation, hydropower generation, all-electric propulsion of ships, and large-scale industrial drive. Background Technology

[0003] In the field of high-power motors, replacing a single ultra-high-power motor with multiple standardized motor units coaxially rigidly coupled is a core technological direction for reducing system size, weight, and cost. Existing coaxial rigid coupling structures include various implementation forms such as through-shaft type and segmented coupling docking type, which can achieve synchronous operation of multiple motors within a certain power range. Compared with traditional gear merging schemes, transmission losses are reduced by 3% to 5%, and coaxiality accuracy is improved by an order of magnitude.

[0004] However, engineering practice shows that there is a physical performance critical point for the number of series motors on a single spindle: as the total power demand increases and the number of series motors increases, the length of a single shaft increases accordingly, and the length-to-diameter ratio (total shaft length / shaft diameter of mating section) continuously increases. When the length-to-diameter ratio exceeds a reasonable threshold, the shaft system will exhibit a significant long-shaft effect: the total torsional angle under rated torque increases linearly with the shaft length, the first-order bending critical speed decreases rapidly with the square of the shaft length, the increased deflection deformation in the middle section of the shaft leads to a decrease in coaxiality accuracy, the torsional vibration natural frequency shifts downward, the risk of resonance increases, and ultimately the overall system performance drops precipitously.

[0005] Simply increasing the shaft diameter to compensate for stiffness will lead to three engineering pain points: First, the inner diameter of the motor rotor is limited, and the shaft diameter cannot be increased indefinitely; second, the shaft weight increases exponentially, which greatly offsets the lightweight advantage of modular motors; and third, the difficulty of machining, heat treatment, and flaw detection of large-diameter shafts increases exponentially, and manufacturing costs soar.

[0006] Existing high-power capacity expansion routes are mainly divided into two categories: one is to return to the traditional architecture of multi-motor gearbox confluence, which has poor mechanical synchronization accuracy, high transmission loss and complex control; the other is to forcibly adopt an ultra-long single-shaft structure, which sacrifices shaft stiffness, critical speed and reliability, resulting in a high risk of failure in long-term operation.

[0007] In summary, the industry lacks a technical solution that can both break through the power expansion limit of a single spindle and fully retain the advantages of high coaxiality, high rigidity, high reliability, and easy maintenance of a coaxial rigid coupling structure. Summary of the Invention

[0008] I. General Derivation of the Critical Point of Uniaxial Performance

[0009] Combining engineering mechanics design principles and the dimensional characteristics of motors in the same series, the general derivation logic of the single-axis performance critical point is as follows:

[0010] 1. Core Criterion: The optimal design range for high-rigidity rotary shaft systems is a length-to-diameter ratio (L / D ratio) of no more than 20:1, where L / D ratio refers to the ratio of the total length of the mating section of the common spindle to the diameter of the mating section shaft. Within this range, the shaft system's torsional stiffness, bending stiffness, critical speed, and coaxiality accuracy are all at their optimal levels. When the L / D ratio exceeds 20:1 and continues to increase, all performance indicators enter a period of rapid decline.

[0011] 2. Relationship between shaft length and number: For coaxial rigidly coupled motor sets, the total length of the common main shaft mating section is composed of two parts: first, the sum of the axial lengths of all motor rotor cores, which equals the number of motors connected in series on a single shaft multiplied by the axial length of a single motor rotor core; second, the sum of the axial clearances of the positioning sleeves between adjacent motors, which equals the number of motors minus one multiplied by the axial clearance of a single positioning sleeve. Therefore, the more motors connected in series on a single shaft, the longer the total length of the shaft mating section.

[0012] 3. Relationship between shaft diameter and power: The shaft diameter is determined by the rated transmitted torque. According to the design criteria for the torsional strength of round shafts, the torsional load-bearing capacity of a round shaft is proportional to the cube of the shaft diameter. Therefore, the minimum shaft diameter required to meet the rated torque requirement is proportional to the cube root of the transmitted torque. Under the premise of constant rated speed, the power transmitted by the shaft is proportional to the torque. Therefore, the shaft diameter corresponding to the rated power is proportional to the cube root of the rated power.

[0013] 4. Relationship between motor axial length and power: For axial flux motors of the same series and design standard, under the design principle of constant electromagnetic load, the effective electromagnetic volume of the motor is proportional to the output power; and motors of the same series follow the geometric similarity design law, with the motor diameter and axial thickness being enlarged synchronously in the same proportion. Therefore, the axial length of a single motor rotor is also proportional to the cube root of the motor's rated power.

[0014] 5. Universality of the Critical Quantity: By combining the relationships between shaft length and number of motors, shaft diameter and power, and motor axial length and power, we can deduce that the length-to-diameter ratio of the shaft system is approximately independent of the power rating of a single motor, and is mainly determined by the number of motors connected in series on a single shaft. This is because when the power of a single motor increases, the proportion of increase in the motor's axial length is basically consistent with the proportion of increase in the shaft diameter. The effects of the two on the length-to-diameter ratio cancel each other out, and ultimately the length-to-diameter ratio only increases linearly with the increase in the number of motors connected in series. Therefore, the critical quantity for single-shaft performance is a relatively stable engineering threshold, not a special case for a specific power, and has universality across the entire power range within the normal power range.

[0015] Considering factors such as positioning clearance and shaft end installation allowance, the critical number of axial flux motors in the 0.5MW~2MW conventional power range is approximately 10 units, corresponding to an optimal threshold with a length-to-diameter ratio close to 20:1. The critical parameters for different power levels are verified as follows:

[0016] Axial length of single motor rotor 210mm 260mm 330mm Common spindle mating section shaft diameter d 105mm 130mm 165mm The total length L of the single-axis tandem 10 units is [missing information]. 2190mm 2690mm 3390mm Corresponding aspect ratio λ 20.9:1 20.7:1 20.5:1 Is it in the high stiffness range? Yes (the critical upper limit) Yes (the critical upper limit) Yes (the critical upper limit)

[0017] When the number of units connected in series on a single axis exceeds 10 and the length-to-diameter ratio exceeds 20:1:

[0018] • Torsional stiffness decreases by more than 35%, and the total torsional angle under rated torque exceeds the allowable value;

[0019] • The first-order bending critical speed decreases with the square of the shaft length, approaching 1.5 times the safe critical value of the operating speed, which significantly increases the risk of resonance;

[0020] • The deflection deformation in the middle section of the shaft increases rapidly, the radial runout rises to over 0.02 mm / m, and the coaxiality accuracy decreases by more than 60%;

[0021] • The natural frequency of torsional vibration shifts downward, making it easier to couple and resonate with the gear meshing frequency and torque pulsation frequency.

[0022] Once this critical point is exceeded, the power gains from forcibly increasing the number of single-axis motors are far from sufficient to offset the performance degradation and reliability risks. The overall cost-effectiveness of adopting a multi-axis parallel solution is higher.

[0023] II. Technical Solution

[0024] To achieve the above objectives, the present invention adopts the following technical solution: a multi-axis parallel motor unit structure with multiple coaxial rigid coupling, comprising at least two sets of coaxial motor unit groups, each set of coaxial motor unit groups adopting a coaxial rigid coupling structure; each set includes a common main shaft and at least two independently operable motor units, each motor unit being a complete motor unit with a single housing, independent stator assembly, independent rotor assembly, and independent winding system; each motor unit within the same set is rigidly connected to the common main shaft, all rotor assemblies maintain synchronous rotation with the common main shaft without relative rotation, and there are no intermediate transmission mechanisms such as gearboxes or clutches between the motor units.

[0025] The common spindles of each coaxial motor unit group are connected in parallel to form a multi-axis joint output / input architecture. Parallel connection can be achieved through various mechanical connection methods such as gear splitting, synchronous coupling groups, and rigid connection transmission to realize power convergence or splitting. The number of motors in each coaxial motor unit group does not exceed the single-axis performance critical number, so that the length-to-diameter ratio of a single common spindle is always within the high-rigidity design range of 20:1.

[0026] As a preferred parallel connection method, each group of common spindles is connected by a gear merging device. A high-precision helical gear transmission mechanism is used in conjunction with a backlash adjustment structure to control the instantaneous speed difference between shafts to a very small range. Compared with the traditional multi-motor independent gear merging scheme, each group in this structure is absolutely rigidly synchronized, with only a small gear backlash between groups, and the synchronization accuracy is still improved by more than an order of magnitude.

[0027] Furthermore, within each coaxial motor unit group, axial positioning sleeves are provided between adjacent motor units, and a locking mechanism is provided at the end of the common spindle to achieve axial pre-tightening positioning of all motor units and eliminate axial movement gaps.

[0028] Furthermore, the number of shaft groups can be flexibly configured according to the total power requirements, and the number of motors in each group can be adjusted within a critical range to achieve modular linear expansion of power.

[0029] As a preferred solution for standardized mass production, each coaxial motor unit group has the same number of motor units, and all motor units have the same rated power, dimensions, and electrical parameters, enabling universal interchangeability across the entire series and further reducing production, maintenance, and spare parts costs.

[0030] III. Comparison of Core Performance with Long Single-Axis Solutions

[0031] Taking a power generation scenario with a total power of 20MW and a single motor of 1MW as an example, the core performance of the shaft system is compared between the "single-shaft 20-unit long single-shaft scheme" and the "dual-shaft 10-unit parallel scheme" (with the performance of a single dual-shaft unit as the benchmark):

[0032] uniaxial length-to-diameter ratio 20.7:1 (Upper limit of the optimal design interval) 41.4:1 (significantly exceeds the threshold) — Torsional stiffness per unit length of shaft system Baseline value 100% Approximately 50% 100% improvement First-order bending critical speed 4500rpm Approximately 1100 rpm 309% increase Radial runout of the entire axis ≤0.008mm / m ≤0.022mm / m Accuracy improved by 175% Rated torque total torsion angle ≤0.31° ≤0.62° Reduce by 50% First-order torsional natural frequency 185Hz Approximately 92Hz Move up 101% Self-weight of a single common spindle Approximately 280kg Approximately 560kg Lose 50%

[0033] IV. Beneficial Effects

[0034] 1. Breaking through the power limit of a single axis while retaining the core advantages of coaxial coupling, the total power can be linearly expanded with the number of shaft groups through a multi-axis parallel architecture, completely breaking the length limit of a single common main shaft, and realizing high-power modular motor units of tens of megawatts; at the same time, it fully retains the core advantages of coaxial rigid coupling structure with no intermediate transmission links, high coaxiality, and low transmission loss. Compared with the traditional multi-motor gear confluence scheme, the transmission loss is reduced by 3% to 5%.

[0035] 2. The stability of the shaft system is comprehensively improved, eliminating the risk of long shaft effect. Each single shaft is controlled within the high stiffness design range with a length-to-diameter ratio of less than 20:1. Compared with the same power long single shaft solution, the torsional stiffness per unit length of the shaft system is increased by 1 times, the first-order bending critical speed is increased by more than 3 times, the coaxiality accuracy of the entire shaft is improved by 1.7 times, and the torsional vibration natural frequency is shifted by 1 time. The resonance, flexural deformation, and accuracy attenuation caused by long shaft effect are eliminated from the structural root, and the long-term operational reliability of the system is greatly improved.

[0036] 3. Significant weight reduction effect, breaking the exponential growth law of weight. The standardized motor unit is modularly expanded, and the total weight of the whole machine increases linearly with power. Taking the power generation mode as an example, the weight per unit power is controlled within 0.6kg / kW; compared with the traditional single high-power motor body of the same power, the weight is reduced by more than 70%, completely getting rid of the industry problem of "the larger the motor, the heavier it is, and the higher the cost per unit power".

[0037] 4. Excellent modularity and maintainability: Each shaft system is an independent module that can be assembled, tested, and transported separately; in case of a single failure, it can be isolated for maintenance while the other can be derated, reducing downtime by more than 90% compared to the overall long shaft solution; at the same time, the length of a single shaft is shortened, making on-site maintenance and motor replacement more convenient, and reducing the total life cycle maintenance cost by more than 40%.

[0038] 5. High degree of standardization, suitable for mass production with the preferred number and parameters of motor units, strong versatility and interchangeability, suitable for mass production, reducing spare parts categories by more than 50%; critical quantity has universality across the entire power range, which can flexibly adapt to the project needs of different power levels, further reducing the total life cycle cost. Attached Figure Description

[0039] Figure 1 is a schematic diagram of the overall structure of the dual-shaft parallel motor unit according to Embodiment 1 of the present invention. Reference numerals: 1 - Coaxial motor unit group; 2 - Common main shaft; 3 - Motor unit; 4 - Gear shunt device. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and three preferred embodiments. All structural parameters and mechanical indicators have been verified by engineering mechanics calculations. As shown in Figure 1, the figure illustrates the 10MW dual-shaft drive motor unit scheme described in Embodiment 1, which is equipped with a total of 10 motor units (3), divided into 2 groups of coaxial motor units (1), with 5 units in each group; each group of coaxial motor units is equipped with a common main shaft (2), and the two groups of coaxial motor units are connected in parallel through a one-to-two gear splitter (4). The technical solution will be described in detail below through three embodiments with different power levels and application scenarios.

[0041] Example 1: 10MW Dual-Shaft Drive Motor Set

[0042] This embodiment is a 10MW high-power drive motor unit, which adopts a dual-axis parallel architecture, with 5 1MW axial flux motors in each group, suitable for low-speed, high-torque drive scenarios such as all-electric propulsion of ships and large mining rolling mills.

[0043] 1. System Configuration

[0044] • Number of shaft groups: 2 sets of coaxial motor units, which are connected in parallel through a one-to-two high-precision gear splitter and combiner device;

[0045] • Single unit configuration: Each unit consists of 5 1MW permanent magnet synchronous axial flux motors with coaxial rigid coupling; each motor has a rotor diameter of 1000mm, an axial thickness of 250mm, a weight of 300kg, a rated speed of 300rpm, and a rated line voltage of 690V.

[0046] • Common spindle: The length of the mating section of a single spindle is approximately 1.34m, the diameter of the mating section is φ130mm, and the length-to-diameter ratio is approximately 10.3:1, which is far better than the critical threshold of 20:1; the material is 42CrMo high-strength alloy structural steel, and the tensile strength after quenching and tempering is ≥1080MPa;

[0047] • Gear splitter / merger device: High-precision helical gear splitter mechanism with a transmission ratio of 1:1, a precision grade not lower than grade 5 as specified in GB / T10095, backlash ≤0.03mm, and rated transmission torque of 35kN・m; the total input power is connected from the input end of the gearbox, and after splitting, it is delivered to the output of the two common main shafts;

[0048] 2. Core performance parameters

[0049] • Single-set shaft torsional stiffness: ≥5.2×10 6 N·m / rad;

[0050] • First-order bending critical speed: ≥1100rpm, which is 3.7 times the maximum operating speed, with no risk of resonance;

[0051] • Radial runout of the entire shaft section: ≤0.006mm / m, meeting high precision requirements;

[0052] • Steady-state speed deviation between groups: ≤0.1%, instantaneous speed difference: ≤0.8%;

[0053] • The total weight of the mechanical structure of the whole machine is about 5.3 tons, with a unit power weight of 0.53 kg / kW, which is more than 70% lighter than the traditional single high-power drive motor of the same power.

[0054] Example 2: 20MW Dual-Shaft Generator Unit

[0055] This embodiment is a 20MW high-power generator set, which adopts a dual-axis parallel architecture, with 10 1MW axial flux motors in each group, suitable for medium and high-speed power generation scenarios such as wind power generation and hydropower generation.

[0056] 1. System Configuration

[0057] • Number of shaft groups: 2 sets of coaxial motor units, which are connected in parallel through a one-to-two high-precision gear splitter and combiner device;

[0058] • Single-unit configuration: Each unit consists of 10 1MW permanent magnet synchronous axial flux motors with coaxial rigid coupling; each motor has a rotor diameter of 1000mm, an overall axial thickness of 300mm, a weight of 360kg, a rated speed of 1500rpm, and a rated line voltage of 1kV.

[0059] • Common spindle: The length of the mating section of a single spindle is approximately 2.69m, the diameter of the mating section is φ130mm, and the length-to-diameter ratio is approximately 20.7:1, which is just at the critical point of single-spindle performance; the material is 42CrMo high-strength alloy structural steel, and the tensile strength after quenching and tempering is ≥1080MPa;

[0060] • Gear splitter / merger device: High-precision helical gear splitter / merger mechanism, transmission ratio 1:1, accuracy grade not lower than grade 5 specified in GB / T10095, backlash ≤0.03mm, rated transmission torque 25kN・m; mechanical power is input to the two common main shafts respectively, and output from the total output end of the gearbox after merging;

[0061] 2. Critical point verification

[0062] Each group has 10 motors, which is exactly the critical number for single-axis performance, and all indicators of the shaft system are at the inflection point between optimal performance and degradation:

[0063] • Radial runout of the entire shaft section ≤ 0.008 mm / m, meeting high precision requirements;

[0064] • The total torsion angle under rated torque is ≤0.31°, which is within the allowable range;

[0065] • The critical speed for first-order bending is ≥4500rpm, which is 3 times the operating speed, providing ample safety margin.

[0066] • First-order torsional vibration natural frequency 185Hz, avoiding all operating excitation frequencies.

[0067] If a single-axis scheme with 20 units is adopted, the total length of the shaft mating section is about 5.38m, and the length-to-diameter ratio is 41.4:1. All performance indicators deteriorate precipitously, making the project extremely infeasible. However, this dual-axis scheme maintains the optimal performance at the critical point of the single axis even with the total power doubled.

[0068] 3. Core performance parameters

[0069] • Total rated power: 20MW;

[0070] • Single-set shaft torsional stiffness: ≥1.9×10 6 N·m / rad;

[0071] • Inter-axial bus power imbalance: ≤1%;

[0072] • Total weight of the mechanical structure: approximately 11.5 tons, with a unit power weight of 0.57 kg / kW, which is more than 70% lighter than the traditional single high-power generator body of the same power.

[0073] • Design lifespan: 20 years, more than 60% longer than traditional solutions.

[0074] Example 3: 40MW quad-shaft generator set

[0075] This embodiment is a 40MW ultra-high power generator set, which adopts a four-axis parallel architecture, with 10 1MW axial flux motors in each group, suitable for large-scale onshore / offshore wind power generation, medium-sized hydropower and other high-power power generation scenarios.

[0076] 1. System Configuration

[0077] • Number of shaft groups: 4 sets of coaxial motor units, which are connected in parallel through a one-to-four high-precision gear splitter and combiner device;

[0078] • Single-unit configuration: Each unit consists of 10 1MW permanent magnet synchronous axial flux motors, rigidly coupled coaxially; the parameters of a single motor are the same as in Example 2: rotor diameter 1000mm, axial thickness of the whole machine 300mm, weight of a single machine 360kg, rated speed 1500rpm, rated line voltage 1kV;

[0079] • Common spindle: The length of the mating section of a single spindle is approximately 2.69m, the diameter of the mating section is φ130mm, and the length-to-diameter ratio is approximately 20.7:1, which is at the critical point of single-spindle performance; the material is 42CrMo high-strength alloy structural steel, and the tensile strength after quenching and tempering is ≥1080MPa;

[0080] • Gear power distribution and merging device: High-precision helical gear one-to-four mechanism, transmission ratio 1:1:1:1, accuracy grade not lower than grade 5 specified in GB / T 10095, backlash ≤0.04mm, rated total transmitted torque 50kN・m; mechanical power is input to the four common spindles respectively, and after merging, it is output uniformly from the total output end of the gearbox;

[0081] 2. Comparison and Verification of Schemes

[0082] If a single-axis 40-unit long single-axis scheme is adopted, the total length of the shaft mating section is about 10.77m, with a length-to-diameter ratio of 82.8:1. The first-order bending critical speed drops to 560rpm, which is lower than the working speed of 1500rpm, and resonance failure will occur, making it completely impractical in engineering. In contrast, each group of this four-axis scheme is in the high-rigidity design range, and while the total power is expanded to 40MW, the core performance of the shaft system is completely consistent with the single-group 10-unit scheme.

[0083] 3. Core performance parameters

[0084] • Total rated power: 40MW;

[0085] • Single-set shaft torsional stiffness: ≥1.9×10 6 N·m / rad;

[0086] • Inter-axial bus power imbalance: ≤1.5%;

[0087] • Total weight of the mechanical structure: approximately 22.4 tons, with a unit power weight of 0.56 kg / kW, which is more than 70% lighter than the traditional single high-power generator body of the same power.

[0088] • Design life: 20 years, suitable for long-term continuous operation scenarios of large power plants.

[0089] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the invention. The number of shaft groups, the number of motors in each group, the parallel connection method, and the motor power rating can all be flexibly adjusted according to the actual application scenario. Any modifications, equivalent substitutions, or improvements made within the core concept and principles of the present invention fall within the protection scope of the present invention.

Claims

1. A multi-axis parallel motor unit structure with multiple coaxial rigid couplings, characterized in that: It includes at least two sets of coaxial motor unit groups, each set of coaxial motor unit groups adopts a coaxial rigid coupling structure, each set contains a common spindle and at least two motor units that can operate independently; each motor unit in the same set is rigidly connected to the common spindle, and all motor units rotate synchronously with the common spindle; the common spindles of each set of coaxial motor unit groups are connected in parallel; the number of motors in each set of coaxial motor unit groups does not exceed the single-axis performance critical number.

2. The multi-axis parallel motor unit structure with multi-machine coaxial rigid coupling according to claim 1, characterized in that: The common spindles of each coaxial motor unit group are connected in parallel through a gear shunt device; in the power generation mode, the mechanical power input to each spindle is combined by the gear shunt device and then output as a total; in the drive mode, the total input power is distributed to each spindle output after being divided by the gear shunt device.

3. The multi-axis parallel motor unit structure with multi-machine coaxial rigid coupling according to claim 1, characterized in that: The single-axis performance critical parameters must meet the following requirements: the length-to-diameter ratio of the common spindle is ≤20:1, the first-order bending critical speed is more than 1.5 times higher than the highest operating speed, and the radial runout of the entire shaft section is ≤0.01mm / m.

4. The multi-axis parallel motor unit structure with multi-machine coaxial rigid coupling according to claim 1, characterized in that: Within each coaxial motor unit group, axial positioning sleeves are provided between adjacent motor units, and a locking mechanism is provided at the end of the common spindle to achieve axial pre-tightening positioning of all motor units.

5. The multi-axis parallel motor unit structure with multi-machine coaxial rigid coupling according to claim 1, characterized in that: Each coaxial motor unit group has the same number of motor units, and all motor units have the same rated power, dimensions, and electrical parameters.

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