Self-starting variable leakage magnetic permanent magnet cutting motor for coal mine tunneling robot

Abstract

The application belongs to the technical field of driving motor of special robot in underground coal mine, and discloses a self-starting variable leakage magnetic permanent magnet cutting motor for coal mine tunneling robot. The motor is self-started without relying on a frequency converter by setting a squirrel cage conductor. On this basis, the motor adds a cross-axis magnetic barrier between adjacent groups of magnetic poles, the cross-axis magnetic barrier adopts a double-layer magnetic barrier group structure, and a double-layer controllable leakage magnetic branch is actively constructed by forming a magnetic pole-to-pole magnetic bridge, so that the leakage magnetic is variable. The application can automatically change the saturation degree of the magnetic flux branch according to the load change, that is, change the magnetic resistance of the leakage magnetic branch to control the amount of leakage magnetic, realize the self-regulation of the leakage magnetic flux, and maintain excellent efficiency under different load conditions.

Description

Technical Field

[0001] This invention belongs to the field of drive motor technology for special robots in coal mines, and specifically relates to a self-starting variable leakage magnet permanent magnet cutting motor for coal mine tunneling robots, which is suitable for application needs in variable load scenarios such as coal mine tunneling. Background Technology

[0002] Coal is the cornerstone of my country's energy security, and its safe, efficient, and intelligent mining is the core direction of the industry's development. As the core equipment of intelligent tunneling faces, the driving performance of the cutting section of a coal mine tunneling robot directly determines the overall tunneling efficiency, reliability, and energy consumption level. The cutting motor, as the "heart" of the cutting drive system of a coal mine tunneling robot, has long faced the severe challenges of harsh working conditions. Currently, the cutting sections of mainstream coal mine tunneling robots both domestically and internationally generally adopt asynchronous motor drives. This technology is mature, robust in structure, relatively low in cost, and can be started directly from a power frequency supply, effectively avoiding the heat dissipation, size, and reliability problems caused by using high-power frequency converters within explosion-proof housings.

[0003] However, the inherent low efficiency, low power factor, and low power density of asynchronous motors have become bottlenecks for improving the energy efficiency of cutting drive systems. Therefore, introducing high-efficiency, high-power-density permanent magnet synchronous motors into cutting drive systems is considered an ideal technical path to overcome these bottlenecks. Permanent magnet motors do not require excitation current and have significantly higher efficiency than asynchronous motors of the same power at rated points and heavy-load areas. They also have a clear advantage in power density, which helps to achieve miniaturization and weight reduction of the cutting section.

[0004] However, if traditional permanent magnet synchronous motors are directly applied to coal mine tunneling scenarios, they will face two fundamental obstacles: First, their constant permanent magnet magnetic field cannot be directly asynchronously started under power frequency power. They must rely on frequency converters to start from zero speed to power frequency, which not only significantly increases system cost, complexity, and potential failure points, but more importantly, the huge heat generated by high-power frequency converters in explosion-proof enclosures is difficult to dissipate effectively, seriously threatening equipment safety and lifespan. Second, even if the starting problem is solved by frequency converters, traditional permanent magnet motors will still generate high iron losses in the stator core under light load or no-load conditions (such as during the cutting interval), resulting in the loss of efficiency advantages under these conditions and the inability to achieve high-efficiency operation across the entire load range.

[0005] In summary, the current cutting drive system for coal mine tunneling robots faces a pressing technical dilemma: while hoping to adopt the high efficiency and high power density advantages of permanent magnet motors to replace existing asynchronous motors, it is also necessary to abandon complex frequency converters to ensure the reliability, safety, and simplicity of underground applications; at the same time, it is required that the motor maintain excellent efficiency throughout the entire working range, including no-load, light-load, rated load, and even short-term overload, in order to truly adapt to the actual working conditions of tunneling operations with drastic load fluctuations. Summary of the Invention

[0006] The purpose of this invention is to propose a self-starting variable leakage flux permanent magnet cutting motor for coal mine tunneling robots. Through the proposed squirrel cage guide bar, the motor can achieve self-starting function without relying on a frequency converter. On this basis, a cross-axis magnetic barrier is added between two adjacent magnetic poles. The cross-axis magnetic barrier adopts a double-layer magnetic barrier group structure, and actively constructs a double-layer controllable leakage flux branch by forming a magnetic bridge between magnetic poles, so as to realize the autonomous adjustment of leakage flux, which is conducive to achieving efficient operation under full load conditions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A self-starting variable leakage magnet permanent magnet cutting motor for a coal mine tunneling robot includes a rotor and a stator; the stator is located outside the rotor; an air gap is left between the stator and the rotor;

[0009] Several sets of magnetic poles are provided on the rotor along its circumferential direction. The magnetic poles are U-shaped and the openings face outwards radially.

[0010] A set of squirrel cage bars is provided at the outer edge of the rotor corresponding to each set of magnetic poles;

[0011] Each group of cage guide bars has the same structure and includes several cage guide bars evenly arranged along the circumference of the rotor.

[0012] A set of cross-axis magnetic barriers for magnetic flux adjustment is set between each pair of adjacent magnetic poles; each set of cross-axis magnetic barriers includes a set of air gap side magnetic barriers and a set of permanent magnet side magnetic barriers in the radial direction of the rotor, forming a double-layer magnetic barrier set.

[0013] The air gap side magnetic barrier assembly includes a first airfoil magnetic barrier unit and a first rectangular magnetic barrier unit symmetrically distributed on both sides of the cross axis;

[0014] The first airfoil magnetic barrier unit is an airfoil groove structure composed of an outer arc edge, a straight edge, and an inner arc edge connected in sequence; wherein the outer arc edge is closer to the air gap side than the inner arc edge.

[0015] The convex surfaces of both the outer and inner arc-shaped edges face the air gap side; the curvature of the outer arc-shaped edge is greater than that of the inner arc-shaped edge, which helps to guide the direction of leakage magnetic flux and makes the air gap magnetic flux density more uniform; the straight edge is parallel to the cross axis.

[0016] The first magnetic bridge is formed by the outer edge of the air gap side magnetic barrier group and the rotor core region between the air gap;

[0017] The permanent magnet side magnetic barrier group includes a second airfoil magnetic barrier unit and a second rectangular magnetic barrier unit symmetrically distributed on both sides of the cross axis; the shape of the second airfoil magnetic barrier unit is the same as that of the first airfoil magnetic barrier unit, but its size is smaller than that of the first airfoil magnetic barrier unit;

[0018] The core region between the inner edge of the air gap side magnetic barrier group and the outer edge of the permanent magnet side magnetic barrier group forms a second magnetic bridge that is "narrow in the middle and expands at both ends". The width of the second magnetic bridge is greater than the width of the first magnetic bridge.

[0019] The present invention has the following advantages:

[0020] As described above, this invention relates to a self-starting variable leakage magnetic permanent magnet cutting motor for a coal mine tunneling robot employing airfoil magnetic barriers. This invention, by setting multiple sets of magnetic poles and squirrel-cage bars on the rotor, allows the motor to start automatically via the raised squirrel-cage bars. After starting, the generated pull torque enables the motor to enter synchronous drive operation. During synchronous drive, the squirrel-cage bars no longer participate in electromechanical energy conversion, thus eliminating rotor losses and resulting in high motor efficiency and large torque. It does not require inverter starting, making the motor more reliable, more stable, and lower in cost. Furthermore, each set of magnetic poles is U-shaped and surrounds the corresponding squirrel-cage bars, fully utilizing the rotor's internal space while providing more space for the quadrature-axis magnetic barriers, ensuring the rationality of the quadrature-axis magnetic barrier setting. Quadrature-axis magnetic barriers are set between adjacent magnetic poles of the rotor, employing a double-layer magnetic barrier structure composed of an air gap-side magnetic barrier group and a permanent magnet-side magnetic barrier group. The air gap-side magnetic barrier group comprises a first airfoil magnetic barrier unit and a first rectangular magnetic barrier unit symmetrically distributed on both sides of the cross-axis. The permanent magnet-side magnetic barrier group comprises a second airfoil magnetic barrier unit and a second rectangular magnetic barrier unit symmetrically distributed on both sides of the cross-axis. Both the first and second airfoil magnetic barrier units employ an airfoil slot structure. The rotor core region between the outer edge of the air gap-side magnetic barrier group and the air gap forms the first magnetic guiding bridge. The core region between the inner edge of the air gap-side magnetic barrier group and the outer edge of the permanent magnet-side magnetic barrier group forms a second magnetic guiding bridge that is "narrow in the middle and expanded at both ends," with a width greater than that of the first magnetic guiding bridge. The magnetic flux generated by the magnetic poles, guided by the rotor airfoil magnetic barrier unit and the rectangular magnetic barrier unit, results in a smoother transition of the air gap magnetic field between the rotor poles, thereby improving the sinusoidal nature of the motor's back EMF and facilitating motor control. Furthermore, the unique airfoil magnetic barrier edge design adopted by the first and second airfoil magnetic barrier units allows for smoother and more controllable guidance of the magnetic flux flow to the corresponding magnetic bridge. This invention utilizes a special magnetic bridge and magnetic barrier structure on the rotor side to facilitate the construction of a controllable leakage flux path. The magnetic saturation of the leakage flux path can be adjusted using the load current, especially the q-axis current, thereby achieving flexible and autonomous control of the leakage flux: Under light load, the leakage flux path is not saturated, resulting in a larger leakage flux, which effectively weakens the air gap magnetic field and reduces iron losses; under medium load, as armature reaction intensifies, the leakage flux path begins to saturate, the leakage flux gradient decreases, and the main air gap flux is steadily increased, avoiding torque pulsation and ensuring smooth operation; under heavy load, the leakage flux path is deeply saturated, and the leakage flux is significantly suppressed, ensuring sufficient air gap flux density and torque output capability. This achieves a better balance between flux adjustment range and torque output capability. Furthermore, by reducing leakage flux under medium and heavy loads, additional copper losses are avoided. Through this innovative design of variable leakage flux, this invention effectively achieves efficient operation under all load conditions. Attached Figure Description

[0021] Figure 1This is a cross-sectional view of the self-starting variable leakage magnetic permanent magnet cutting motor used in the coal mine tunneling robot in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram showing the arrangement of a set of magnetic poles and the cage bars in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of a set of cross-axis magnetic barriers in an embodiment of the present invention;

[0024] Figure 4 This is a speed curve of the starting process of the self-starting variable leakage magnetic permanent magnet cutting motor for the coal mine tunneling robot in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the multi-condition operation magnetic circuit of the self-starting variable leakage magnetic permanent magnet cutting motor for the coal mine tunneling robot in an embodiment of the present invention; Figure 5 (a) represents a light load condition; (b) represents a medium load condition; and (c) represents a heavy load condition.

[0026] Figure 6 This is a magnetic field distribution diagram of the self-starting variable leakage magnetic permanent magnet cutting motor used in the coal mine tunneling robot in this embodiment of the invention; Figure 6 (a) is the unloaded state; (b) is the medium-loaded state; (c) is the heavy-loaded state.

[0027] Figure 7 This is a comparison diagram of the air gap magnetic flux density of the motor of the present invention under no-load conditions and the motor after removing the cross-axis magnetic barrier;

[0028] Figure 8 A comparison of iron losses between the motor of the present invention and the motor after removing the quadrature-axis magnetic barrier under different currents;

[0029] Among them, 1-stator, 2-rotor, 3-armature winding, 4-magnetic pole, 5-edge permanent magnet, 6-middle permanent magnet, 7-q-axis magnetic bridge, 8-squirrel cage conductor; 9-first airfoil magnetic barrier unit, 10-first rectangular magnetic barrier unit;

[0030] 11-Second rectangular magnetic barrier unit, 12-Second airfoil magnetic barrier unit, 13-Magnetic barrier between permanent magnets, 14-First magnetic bridge, 15-Second magnetic bridge, 16-Reinforcing rib; 91-Outer arc edge, 92-Straight edge, 93-Inner arc edge. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0032] Example 1

[0033] This invention addresses the problems of traditional permanent magnet synchronous motors, which rely on frequency converters for starting and suffer from rotor losses during operation, resulting in limited efficiency and torque. By incorporating squirrel-cage bars 8 in the rotor 2, during the starting phase, the armature winding 3 generates a rotating magnetic field that cuts the squirrel-cage bars 8, producing asynchronous torque and driving the motor to start automatically without the need for an external frequency converter. After starting, the motor is pulled to synchronous operation, at which point the squirrel-cage bars 8 no longer participate in electromechanical energy conversion, avoiding rotor losses. This invention achieves self-starting without a frequency converter, has no rotor losses during operation, high efficiency, and large torque, while also being structurally stable, reliable, and lower in cost. Furthermore, this invention addresses the problem of traditional permanent magnet motors having non-adjustable air gap magnetic fields, leading to additional losses and reduced efficiency under light loads. By incorporating quadrature-axis magnetic barriers in the rotor 2, a controllable leakage magnetic branch is constructed, enabling the motor to achieve variable leakage magnetic flux. The invention automatically adjusts the magnetic saturation of the leakage flux bridge based on the load current. Under light load, the load current is small, resulting in low magnetic saturation of the leakage flux bridge, increased leakage flux, weakened air gap magnetic field, and reduced iron losses. Under medium load, the leakage flux gradually decreases with increasing load, while the main air gap flux increases smoothly, avoiding torque pulsation and ensuring stable motor operation. Under heavy load, the load current increases, the magnetic saturation of the leakage flux bridge rises, and the leakage flux decreases to maintain the air gap flux density. This invention allows for flexible control of the leakage flux. Under light load, it reduces iron losses by increasing leakage flux; under medium load, the leakage flux gradually changes for a smooth transition; and under heavy load, it reduces leakage flux, enabling the motor to maintain high torque output capacity while avoiding additional copper losses (if leakage flux is not reduced under heavy load, the armature current needs to be increased to achieve the same torque, resulting in additional copper losses and reduced operating efficiency). In summary, this invention can automatically change the saturation level of the magnetic flux branch according to load changes, that is, change the magnetic reluctance of the leakage flux branch to control the amount of leakage flux, thereby realizing autonomous adjustment of leakage flux and maintaining excellent efficiency under different load conditions.

[0034] like Figure 1 As shown, the self-starting variable leakage magnet permanent magnet cutting motor for the coal mine tunneling robot described in this embodiment specifically includes a stator 1, a rotor 2, and an armature winding 3.

[0035] The stator 1 is located outside the rotor 2; an air gap is left between the stator 1 and the rotor 2. The length of the air gap is related to the power rating of the motor, the permanent magnet material selected, and the processing and assembly technology of the stator 1 and the rotor 2.

[0036] In this embodiment, both the stator 1 and rotor 2 cores are made of laminated silicon steel sheets. The stator 1 has a semi-open slot structure, with the armature winding 3 embedded in the slot. In this embodiment, the armature winding 3 adopts a distributed winding.

[0037] Several sets of magnetic poles 4 are provided on the rotor 2 along its circumferential direction, for example Figure 1The four groups of magnetic poles 4 shown in the figure have the same results for each group of magnetic poles, and each group of magnetic poles is U-shaped as a whole, with the opening of the U-shaped structure facing outward radially.

[0038] To facilitate the installation of magnetic poles, the rotor 2 is equipped with a "U"-shaped permanent magnet mounting slot corresponding to the position of each set of magnetic poles.

[0039] Each set of magnetic poles includes a central permanent magnet 6 and two identical side permanent magnets 5; the central permanent magnet 6 is located at the bottom of the "U"-shaped structure, and each side permanent magnet 5 is located at one side of the "U"-shaped structure.

[0040] The three permanent magnets are arranged in a U-shape, with the U-shaped opening facing outwards, i.e. towards the air gap.

[0041] The two edge permanent magnets 5 are axially symmetrical about the center line of the middle permanent magnet 6; a magnetic barrier 13 between the permanent magnets is provided at the connection between the middle permanent magnet 8 and the edge permanent magnet 5 in each set of magnetic poles to reduce the self-leakage magnetic field at the connection between the two permanent magnets.

[0042] In this embodiment, both the edge permanent magnet 5 and the middle permanent magnet 6 are rectangular permanent magnets.

[0043] Each rectangular permanent magnet has a rectangular cross-section, and the magnetization direction of each permanent magnet is parallel to the length of its shorter side, thus creating a magnetic focusing effect. This effectively improves the salient pole magnetic focusing effect of the motor, as shown in the following example. Figure 1 As shown.

[0044] In addition, this U-shaped permanent magnet structure can also make the motor have better pull torque and step loss torque, reduce rotor resistance, and ultimately enable the motor to obtain better self-starting permanent magnet synchronous drive performance.

[0045] In this embodiment, the permanent magnets of each set of magnetic poles are installed in segments, which can effectively reduce eddy current losses. At the same time, the "U"-shaped structure formed by each set of magnetic poles can maximize the use of rotor space and reduce conflicts with the position of the squirrel cage guide bars.

[0046] A set of squirrel cage guide bars is provided at the outer edge of rotor 2 corresponding to each set of magnetic poles, such as Figure 1 As shown, since there are four sets of magnetic poles, in this embodiment, the number of cage bars can also be designed to be four sets.

[0047] like Figure 2 As shown, each group of magnetic poles tends to surround the corresponding squirrel cage bars. Each group of squirrel cage bars is identical and includes several squirrel cage bars 8 evenly arranged along the circumference of the rotor 2, for example... Figure 2 The seven shown in the image.

[0048] The arrangement of the conductor bars in each group of squirrel cages is matched with the shape of the permanent magnets of the corresponding magnetic poles. This arrangement is reasonable without increasing the volume of the rotor core or the amount of material used. This arrangement method has the following advantages:

[0049] It makes full use of the internal space of the rotor, brings the permanent magnet close to the air gap, reduces magnetic leakage, improves the utilization rate of permanent magnet materials, increases the power density of the motor, ensures output torque and motor efficiency, and improves the motor's load starting performance.

[0050] This invention, by embedding squirrel-cage guide bars inside the rotor 2, retains the high-efficiency steady-state performance of a permanent magnet synchronous motor while also achieving self-starting capability through the squirrel-cage guide bars. It allows for direct grid connection and starts, realizing an integrated working mode of "asynchronous start + synchronous operation." The complete starting process can be divided into three stages:

[0051] After being connected to the power frequency power supply, it first enters the asynchronous start-up stage. The rotating magnetic field of stator 1 cuts the squirrel cage conductor bar 8 to induce current and generate asynchronous torque, which drives the rotor to accelerate. During this asynchronous start-up stage, there is also a permanent magnet braking torque that weakens the starting performance.

[0052] When the rotor speed approaches the synchronous speed, the motor enters the synchronous stage. The permanent magnet torque has a much greater impact on the synchronous pull capability than the reluctance torque. Furthermore, the smaller the resistance of the squirrel cage bars and the greater the slot depth, the stronger the synchronous pull capability. Only after successfully entering synchronous mode can the motor operate stably at the synchronous speed.

[0053] After entering the synchronous operation stage, the rotor 2 runs at synchronous speed, and the squirrel cage bars 8 no longer participate in electromechanical energy conversion. At this time, the motor runs as a permanent magnet synchronous motor. The permanent magnet magnetic field generated by the intermediate permanent magnet 6 and the side permanent magnet 5 embedded in the rotor is coupled with the armature magnetic field of the stator 1 to achieve synchronous drive, thus having the characteristics of high efficiency and high torque density.

[0054] In this embodiment, the number of squirrel cage guide bars 8, the number of stator slots 1, and the number of magnetic pole groups are optimally matched. By selecting the optimal slot-pole match, combined with the size design of the squirrel cage guide bars 8 and the overall optimized design of the motor, the starting torque and pull-in torque of the motor are improved under the premise of strictly controlling the starting voltage, thereby improving the motor's ability to start and pull into synchronous speed.

[0055] The numbers of magnetic poles, squirrel cage bars, and stator slots listed above are merely examples, and the above combination represents the optimal combination. Of course, the numbers of magnetic poles, squirrel cage bars, and stator slots in this embodiment can also be reasonably set as needed.

[0056] Figure 4 The transient speed change graph during motor startup shows the change in rotational speed over time of the self-starting variable leakage magnet permanent magnet motor used in the designed coal mine tunneling robot when voltage is applied. Figure 4It fully demonstrates the three stages of motor startup, and is pulled into synchronization in about 0.1s, with the speed stabilizing at the synchronous speed, and runs as a permanent magnet synchronous motor.

[0057] This invention enables a three-phase self-starting permanent magnet synchronous motor to possess the advantages of both a three-phase asynchronous induction motor and a permanent magnet synchronous motor. While achieving self-starting, due to the excitation effect of the permanent magnet, there is no rotor copper loss, the air gap magnetic flux density is higher, and there is no need to absorb reactive power from the power frequency power supply to establish a magnetic field. Therefore, compared with a three-phase asynchronous induction motor, under the same conditions, the speed of this invention is a constant synchronous speed, unaffected by the load, and the torque density, power factor and efficiency are significantly improved.

[0058] Furthermore, traditional permanent magnet motors suffer from problems such as a surge in copper and iron losses and a significant decrease in efficiency due to the non-adjustable air gap magnetic field generated by the permanent magnets. To address this issue, a cross-axis magnetic barrier is installed between every two adjacent sets of magnetic poles to achieve magnetic flux adjustment. Since there are four sets of magnetic poles in this embodiment, there are also four sets of cross-axis magnetic barriers, such as... Figure 1 As shown.

[0059] Figure 3 The diagram shows the structure of a set of cross-axis magnetic barriers. Each set of cross-axis magnetic barriers includes, from the outside to the inside, a set of air gap side magnetic barriers and a set of permanent magnet side magnetic barriers along the radial direction of rotor 2, and the two together form a double-layer magnetic barrier set.

[0060] The air gap side magnetic barrier group serves as the first layer of magnetic barriers, while the permanent magnet side magnetic barrier group serves as the second layer. The first and second layers of magnetic barriers are separated by a core region (interlayer magnetic bridge), such as... Figure 1 As shown.

[0061] The "from the outside to the inside" here specifically refers to the direction from the air gap side to the rotor shaft center side.

[0062] The air gap side magnetic barrier group includes a first airfoil magnetic barrier unit 9 and a first rectangular magnetic barrier unit 10 symmetrically distributed on both sides of the cross axis.

[0063] Specifically, there are two of each of the first airfoil magnetic barrier unit 9 and the first rectangular magnetic barrier unit 10, and the first rectangular magnetic barrier unit 10, which is located on the same side of the cross axis, is closer to the cross axis (i.e., the q axis) than the first airfoil magnetic barrier unit 9.

[0064] Taking one of the first airfoil magnetic barrier units 9 as an example, the first airfoil magnetic barrier unit 9 is an airfoil groove structure composed of an outer arc edge 91, a straight edge 92 and an inner arc edge 93 connected in sequence.

[0065] The outer arc-shaped edge 91 is closer to the air gap side than the inner arc-shaped edge 93, such as Figure 1 As shown.

[0066] The convex surfaces of both the outer arc edge 91 and the inner arc edge 93 face the air gap side; the curvature of the outer arc edge 91 is greater than that of the inner arc edge 93, which helps to guide the direction of leakage magnetic flux and make the air gap magnetic flux density more uniform.

[0067] The first rectangular magnetic barrier unit 10 is a narrow and long rectangular slot, with its long side arranged radially, that is, the length direction of the first rectangular magnetic barrier unit 10 is parallel to the cross axis direction; the short side of the first rectangular magnetic barrier unit 10 is arranged circumferentially.

[0068] A reinforcing rib 16 is provided between the first airfoil magnetic barrier unit 9 and the first rectangular magnetic barrier unit 10, that is, a gap of 0.5-0.8mm is left between the first rectangular magnetic barrier unit 10 and the first airfoil magnetic barrier unit 9.

[0069] The addition of reinforcing rib 16 can effectively improve the mechanical strength of the rotor and form a q-axis magnetic flux path.

[0070] A q-axis magnetic bridge 7 is formed between two first rectangular magnetic barrier units 10 in the same air gap side magnetic barrier group. The q-axis magnetic bridge 7 is used to provide a magnetic flux path. The setting of the q-axis magnetic bridge 7 can reduce the q-axis magnetic reluctance and improve the sensitivity of leakage flux to armature current.

[0071] The first magnetic bridge 14 is formed by the outer edge of the air gap side magnetic barrier group and the rotor core region between the air gap. The first magnetic bridge 14 is mainly used to guide the armature reaction flux and to provide constraint on the leakage flux of the permanent magnet.

[0072] It should be noted that in this embodiment, the first magnetic bridge 14 exhibits a trend of being "narrow in the middle and expanding at both ends".

[0073] The phrase "narrow in the middle and expanding at both ends" here specifically refers to the fact that the area of ​​the first magnetic bridge 14 near the cross axis is narrower, while the two ends far from the cross axis gradually expand as they move further away from the cross axis.

[0074] In this embodiment, the thickness of the first magnetic bridge 14 ranges from 0.8 to 1.2 mm.

[0075] The first airfoil magnetic barrier unit 9 and the first rectangular magnetic barrier unit 10 can reduce the leakage magnetic flux generated by the magnetic poles inside the rotor 2, increase the air gap magnetic flux density and thus increase the torque. At the same time, the first magnetic bridge 14, due to its easily saturated thickness, can prevent excessive magnetic flux leakage by the magnetic poles, and its saturation degree can be changed with the change of current, thereby forming a controllable leakage magnetic flux path.

[0076] like Figure 1 As shown, in this embodiment, the permanent magnet side magnetic barrier group, i.e. the second layer magnetic barrier group, includes a second airfoil magnetic barrier unit 12 and a second rectangular magnetic barrier unit 11 symmetrically distributed on both sides of the cross axis.

[0077] Specifically, there are two of each of the second airfoil magnetic barrier unit 12 and the second rectangular magnetic barrier unit 11, and the second rectangular magnetic barrier unit 11, which is located on the same side of the cross axis, is closer to the cross axis than the second airfoil magnetic barrier unit 12.

[0078] The second airfoil magnetic barrier unit 12 has the same shape as the first airfoil magnetic barrier unit 9. It is also an airfoil groove structure composed of an outer arc-shaped edge, a straight edge, and an inner arc-shaped edge connected in sequence, such as... Figure 3 As shown.

[0079] In this embodiment, the size of the second airfoil magnetic barrier unit 12 is smaller than that of the first airfoil magnetic barrier unit 9. The inner edge of the second airfoil magnetic barrier unit 12 is adjacent to the end of the corresponding magnetic pole (or permanent magnet mounting slot).

[0080] The end of the magnetic pole or permanent magnet mounting slot here refers to the open end of each "U"-shaped structure, such as... Figure 1 As shown. In practice, the size of the second airfoil magnetic barrier unit 12 is constrained by the size of the permanent magnet mounting slot.

[0081] The special structural arrangement of the permanent magnet side magnetic barrier group and the air gap side magnetic barrier group facilitates the formation of a leakage magnetic path, and can automatically adjust the amount of leakage magnetic field according to the change of load current, thereby achieving the purpose of flexibly adjusting the magnetic flux.

[0082] Meanwhile, since the second airfoil magnetic barrier unit 12 is located near the end of the magnetic pole or permanent magnet mounting slot, the second airfoil magnetic barrier unit 12 can also reduce the self-leakage magnetism of each edge permanent magnet 5, thereby increasing the torque.

[0083] By properly setting the shape of the magnetic barrier, a larger range of magnetic flux adjustment can be obtained, thereby improving the mechanical strength of the rotor and reducing processing costs.

[0084] The core region between the inner edge of the air gap side magnetic barrier group and the outer edge of the permanent magnet side magnetic barrier group forms a second magnetic bridge 15 that is "narrow in the middle and expanded at both ends". This second magnetic bridge 15 provides a leakage magnetic path for the permanent magnet.

[0085] In this embodiment, the width of the second magnetic bridge 15 is greater than the width of the first magnetic bridge 14. In practice, the width of the second magnetic bridge 15 is designed to be, for example, 3-5 mm, which is significantly larger than the size of the first magnetic bridge 14.

[0086] The width of the second magnetic bridge 15 is determined by the magnetic conductivity of the rotor core and the leakage flux control requirements.

[0087] The phrase "narrow in the middle and expanding at both ends" here also refers to the fact that the area of ​​the second magnetic bridge 15 near the cross axis is narrower, while the two ends far from the cross axis gradually expand as they move further away from the cross axis.

[0088] Two second rectangular magnetic barrier units 11 are located symmetrically on both sides of the center of the intersection axis (q-axis), and each second rectangular magnetic barrier unit 11 is parallel to the side of the permanent magnet mounting slot on the corresponding side, such as... Figure 1 As shown.

[0089] For example Figure 1 The cross-axis magnetic barrier is located between the upper left and upper right magnetic poles. The second rectangular magnetic barrier unit 11, which is located slightly to the left in the cross-axis magnetic barrier, is parallel to the side of the left magnetic pole (permanent magnet mounting slot).

[0090] Similarly, the second rectangular magnetic barrier unit 11, located slightly to the right, is parallel to the side of the right magnetic pole (permanent magnet mounting slot).

[0091] The distance between the second rectangular magnetic barrier unit 11 and the corresponding permanent magnet mounting slot is, for example, 0.5-0.8 mm.

[0092] In this embodiment, the interlayer arrangement and airfoil structure of the cross-axis magnetic barrier achieve variable leakage magnetic flux across the entire load range through "graded magnetic saturation + magnetic circuit coupling control". The core mechanism consists of three operating phases:

[0093] I. No-load / light-load conditions: Increase leakage flux, reduce losses.

[0094] With weak armature reaction and negligible demagnetization component, most of the magnetic flux of the permanent magnet flows along the leakage magnetic path formed by the first and second magnetic bridges. The main magnetic flux in the air gap is weakened, and the hysteresis loss and eddy current loss of the iron core are reduced, so as to achieve high efficiency under light load.

[0095] II. Medium load condition: Leakage flux gradually changes, with a smooth transition.

[0096] The armature reaction is enhanced, and the demagnetizing component causes the first magnetic bridge to saturate first, the magnetic reluctance of the magnetic bridge increases sharply, and the leakage flux bypass is blocked; the second magnetic bridge is still not saturated, and the leakage flux path is reduced; the leakage flux gradually decreases with the increase of load, the main magnetic flux in the air gap increases steadily, avoids torque pulsation, and ensures the smooth operation of the motor.

[0097] III. Heavy load conditions: less leakage flux, increased torque.

[0098] The demagnetizing component of the armature reaction current reaches its peak, the first and second magnetic bridges are fully saturated, the magnetic reluctance of the magnetic bridges approaches infinity, and the leakage flux bypass is completely blocked; the magnetic flux of the permanent magnet enters the main magnetic circuit of the stator through the air gap, the air gap magnetic flux density is maximized, the motor output torque is significantly improved, and the power demand of heavy-load conditions is met.

[0099] This invention employs a double-layer magnetic barrier arrangement, with each airfoil magnetic barrier unit in each layer featuring an airfoil edge design. This allows for smoother and more controllable guidance of magnetic flux to the corresponding magnetic bridge. By adjusting the curvature of each airfoil magnetic barrier unit and the geometric dimensions (width, angle) of the corresponding magnetic bridge, this invention can precisely set the load point at which magnetic saturation begins, thereby optimizing the efficiency curve across the entire load range. Furthermore, the radial offset and complementary shape design of adjacent magnetic barrier layers ensures that the saturation process of the magnetic circuit is "step-like" rather than abrupt, avoiding local spikes in magnetic flux density and making leakage flux adjustment smoother. This helps reduce additional iron losses and electromagnetic noise, while also reducing cogging torque and load torque pulsation, resulting in smoother operation.

[0100] Here, radial offset between adjacent magnetic barriers refers to the misalignment, or offset, of the first and second magnetic barrier groups in the radial direction. Complementary shapes mean that the curvature and magnetic bridge dimensions of the two magnetic barriers are complementary in design. The dimensions of the airfoils and rectangles of the two magnetic barriers need to be designed to make the leakage magnetic path, i.e., the magnetic bridge section, smoother, without areas of magnetic concentration.

[0101] Meanwhile, the curved shape of the airfoil used in each airfoil magnetic barrier unit in this embodiment effectively avoids stress concentration, effectively improves the mechanical strength of the rotor structure, and well ensures the structural reliability of the rotor.

[0102] This invention addresses the problem of traditional permanent magnet synchronous motors where magnetic flux is determined by the inherent characteristics of the permanent magnet and cannot be flexibly adjusted in practical applications. It proposes a self-starting, variable leakage flux permanent magnet cutting motor for coal mine tunneling robots to adapt to the switching needs of different working conditions in practical applications. Unlike the traditional motor design logic of "suppressing leakage flux as much as possible to improve magnetic flux utilization," this invention's motor uses a special quadrature-axis magnetic barrier on the rotor side to form a variable leakage flux path. The amount of leakage flux is adjusted by changing the load current, fully leveraging the advantages of adjustable magnetic field, high motor efficiency, and fast dynamic response brought by the variable leakage flux characteristic. This precisely solves the problem of fixed magnetic flux in traditional permanent magnet synchronous motors.

[0103] This invention actively constructs a double-layer controllable leakage flux branch by forming a first magnetic bridge 14 and a second magnetic bridge 15, thereby achieving variable leakage flux. The operating principle of the motor under different working conditions is as follows:

[0104] When operating under no-load or light-load conditions, the input load current is relatively small. At this time, due to the low magnetic reluctance of the first and second magnetic bridges, a large amount of permanent magnet flux passes through the two layers of magnetic bridges, forming leakage flux between adjacent magnetic poles. Therefore, the motor rotor exhibits significant inter-pole leakage flux. For example... Figure 5As shown in (a), a large amount of magnetic flux forms a loop inside the rotor in the form of leakage flux, and the main magnetic flux in the air gap is reduced accordingly. This process not only reduces iron loss under light load conditions, but also improves operating efficiency and stability.

[0105] During medium-load operation, the load current increases, the armature reaction intensifies, and the demagnetizing current component causes the first magnetic bridge to saturate first, resulting in a sharp increase in the bridge's magnetic reluctance and blocking the leakage flux bypass; the second magnetic bridge remains unsaturated and leakage flux persists. For example... Figure 5 As shown in (b), the leakage flux of the magnetic bridge is reduced, the air gap magnetic flux density is steadily increased, the output torque is increased, and the torque pulsation is reduced, thus ensuring the smooth operation of the motor.

[0106] Under heavy load operation, the load current increases significantly, and both the first and second magnetic bridges enter magnetic saturation, resulting in a sharp increase in magnetic reluctance and a substantial decrease in leakage flux. For example... Figure 5 As shown in (c), at this time, almost all of the magnetic flux generated by the permanent magnet enters the air gap and links with the armature winding in 3 turns. The magnetic density of the air gap is strengthened, thereby generating a larger output torque to meet the power performance requirements of heavy-load conditions.

[0107] Additionally, it should be noted that by reducing leakage flux during medium and heavy loads, additional copper losses are avoided, ensuring efficient motor operation under these conditions.

[0108] In summary, this invention effectively achieves high-efficiency operation under full load conditions through the innovative design of a variable leakage magnetic branch.

[0109] Figure 6 (a) shows the distribution of magnetic field lines in the motor of the present invention under no-load conditions. Figure 6 As shown in (a), under no-load conditions, a large number of magnetic lines of force pass through the designed leakage magnetic path, namely the first magnetic bridge 14 and the second magnetic bridge 15, meaning that a large amount of leakage magnetic flux in the motor does not enter the stator side. This indicates that the motor has more leakage magnetic flux under no-load or light-load conditions, thereby reducing the iron loss of the motor and improving the motor efficiency.

[0110] Figure 6 (b) in the diagram shows the distribution of the motor's magnetic field lines under medium load conditions. Figure 6 As shown in (b), there is almost no magnetic leakage in the first magnetic bridge 14, while the second magnetic bridge 15 still has magnetic leakage. This is because the load current saturates the first magnetic bridge 14, while the second magnetic bridge 15 is not saturated and still has magnetic leakage. At this time, the air gap magnetic flux density increases steadily, and the torque output capability of the motor is enhanced.

[0111] Figure 6 (c) in the diagram shows the distribution of the motor's magnetic field lines under heavy load conditions. Figure 6As shown in (c), there is almost no leakage flux in the first magnetic bridge 14 and the second magnetic bridge 15. This is because the load current saturates the magnetic bridge, resulting in high magnetic reluctance and very little leakage flux passing through. That is, the vast majority of the permanent magnet flux in the motor enters the stator side, increasing the air gap magnetic flux density, which greatly increases the motor's torque output capability.

[0112] From the above Figure 6 As can be seen from (a) to (c) in the present invention, the motor of the present invention has different excellent performance under different load conditions, thus achieving a good balance between motor efficiency and torque.

[0113] In addition, to verify the effectiveness of the quadrature-axis magnetic barrier used in the motor of the present invention, a self-starting permanent magnet synchronous motor with the quadrature-axis magnetic barrier removed was compared with the motor of the present invention. Without the quadrature-axis magnetic barrier, the magnetic flux of the motor is fixed and difficult to change.

[0114] Figure 7 A comparison diagram of the air gap magnetic flux density of the two types of motors under no-load conditions is shown. Figure 7 It can be seen that after the addition of cross-axis magnetic barriers to the motor of the present invention, the leakage magnetic flux is effectively reduced, the air gap magnetic flux density amplitude is increased, and the torque density of the motor is improved.

[0115] Figure 8 This is a comparison diagram of the iron losses of the motor of the present invention and the motor after removing the quadrature-axis magnetic barrier. Figure 8 It is easy to see that the motor of the present invention can effectively reduce the iron loss of the motor in the range of 0 to 12A (rated current), thereby improving the efficiency of the motor under light load.

[0116] In summary, this invention can flexibly adjust the leakage flux according to the load conditions. Under light loads, it effectively reduces iron losses by increasing the leakage flux; under medium loads, the leakage flux gradually changes for a smooth transition; and under heavy loads, it reduces the leakage flux, allowing the motor to maintain high torque output capacity while avoiding additional copper losses. The motor of this invention can automatically adjust the magnetic reluctance of the leakage flux path according to the load current, simplifying the motor structure and improving operational reliability. Compared to traditional permanent magnet motors and other variable flux motors that rely on special permanent magnet materials or complex excitation structures, this invention, through its innovative design of actively constructing a variable leakage flux branch, achieves excellent efficiency under different load conditions. Its characteristics are highly suitable for scenarios such as coal mine tunneling robots where load conditions frequently change, providing an innovative solution that combines performance advantages with economic efficiency.

[0117] Example 2

[0118] This embodiment 2 describes a cutting drive system for a coal mine tunneling robot. The cutting drive system adopts a self-starting variable leakage magnet permanent magnet cutting motor for a coal mine tunneling robot as described in embodiment 1 above.

[0119] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A self-starting variable leakage magnetic permanent magnet cutting motor for a coal mine tunneling robot, comprising a rotor and a stator; the stator is located outside the rotor; an air gap is provided between the stator and the rotor; characterized in that, Several sets of magnetic poles are provided on the rotor along its circumferential direction. The magnetic poles are U-shaped and the openings face outwards radially. A set of squirrel cage guide bars is provided at the outer edge of the rotor corresponding to each set of magnetic poles; each set of squirrel cage guide bars has the same structure and includes several squirrel cage guide bars evenly arranged along the circumference of the rotor. A set of cross-axis magnetic barriers is set between each pair of adjacent magnetic poles; each set of cross-axis magnetic barriers includes a set of air gap side magnetic barriers and a set of permanent magnet side magnetic barriers in the radial direction of the rotor, forming a double-layer magnetic barrier set; The air gap side magnetic barrier assembly includes a first airfoil magnetic barrier unit and a first rectangular magnetic barrier unit symmetrically distributed on both sides of the cross axis; The first airfoil magnetic barrier unit is an airfoil groove structure composed of an outer arc edge, a straight edge, and an inner arc edge connected in sequence; wherein the outer arc edge is closer to the air gap side than the inner arc edge. The convex surfaces of both the outer and inner arc-shaped edges face the air gap side; the curvature of the outer arc-shaped edge is greater than that of the inner arc-shaped edge to guide the direction of leakage magnetic flux and make the air gap magnetic flux density more uniform; the straight edge is parallel to the cross axis. The first magnetic bridge is formed by the outer edge of the air gap side magnetic barrier group and the rotor core region between the air gap; The permanent magnet side magnetic barrier group includes a second airfoil magnetic barrier unit and a second rectangular magnetic barrier unit symmetrically distributed on both sides of the cross axis; the shape of the second airfoil magnetic barrier unit is the same as that of the first airfoil magnetic barrier unit, but its size is smaller than that of the first airfoil magnetic barrier unit; The core region between the inner edge of the air gap side magnetic barrier group and the outer edge of the permanent magnet side magnetic barrier group forms a second magnetic bridge that is "narrow in the middle and expanded at both ends". The width of the second magnetic bridge is greater than the width of the first magnetic bridge. In the air gap side magnetic barrier group, there are two first airfoil magnetic barrier units and two first rectangular magnetic barrier units, and the first rectangular magnetic barrier units located on the same side of the cross axis are closer to the cross axis than the first airfoil magnetic barrier units. In the permanent magnet side magnetic barrier group, there are two second airfoil magnetic barrier units and two second rectangular magnetic barrier units, and the second rectangular magnetic barrier units located on the same side of the cross axis are closer to the cross axis than the second airfoil magnetic barrier units; The length direction of the first rectangular magnetic barrier unit is parallel to the cross axis direction; A q-axis magnetic bridge is formed between two first rectangular magnetic barrier units in the same air gap side magnetic barrier group to provide a magnetic flux path; The rotor is provided with a "U"-shaped permanent magnet mounting slot corresponding to the position of each set of magnetic poles; The two second rectangular magnetic barrier units are located on either side of the center of the intersection axis and are placed symmetrically. Each of the second rectangular magnetic barrier units is parallel to the side position of the permanent magnet mounting slot on the corresponding side.

2. The self-starting variable leakage magnetic permanent magnet cutting motor for coal mine tunneling robots according to claim 1, characterized in that, The inner edge of the second airfoil magnetic barrier unit is adjacent to the end of the corresponding magnetic pole.

3. The self-starting variable leakage magnet permanent magnet cutting motor for coal mine tunneling robots according to claim 1, characterized in that, Each set of magnetic poles includes a central permanent magnet and two identical edge permanent magnets; the central permanent magnet is located at the bottom of the "U"-shaped structure, while each edge permanent magnet is located at one side of the "U"-shaped structure. The two edge permanent magnets are axially symmetrical about the center line of the middle permanent magnet; magnetic barriers between permanent magnets are provided at the connection between the middle permanent magnet and the edge permanent magnet in each set of magnetic poles to reduce the self-leakage magnetic field at the connection between the two permanent magnets.

4. The self-starting variable leakage magnetic permanent magnet cutting motor for a coal mine tunneling robot according to claim 3, characterized in that, Both the central permanent magnet and the edge permanent magnets are rectangular permanent magnets; The magnetization direction of each intermediate / edge permanent magnet is parallel to the width direction of that intermediate / edge permanent magnet.

5. The self-starting variable leakage magnet permanent magnet cutting motor for a coal mine tunneling robot according to claim 1, characterized in that, A reinforcing rib is provided between the first airfoil magnetic barrier unit and the first rectangular magnetic barrier unit.

6. The self-starting variable leakage magnet permanent magnet cutting motor for a coal mine tunneling robot according to claim 1, characterized in that, The first magnetic bridge also exhibits a trend of being "narrow in the middle and expanding at both ends".

7. The self-starting variable leakage magnet permanent magnet cutting motor for a coal mine tunneling robot according to claim 1, characterized in that, The cross-axis magnetic barrier achieves variable leakage flux across the entire load range, divided into the following three operating stages: I. No-load / light-load operating conditions; With weak armature reaction and neglecting the demagnetizing component, the magnetic flux of the permanent magnet will flow along the leakage magnetic path formed by the first and second magnetic bridges. The main magnetic flux of the air gap is weakened, and the hysteresis loss and eddy current loss of the iron core are reduced to achieve high efficiency under light load. II. Medium-load operating conditions; The armature reaction is enhanced, and the demagnetizing component causes the first magnetic bridge to saturate first, the magnetic reluctance of the magnetic bridge increases sharply, and the leakage magnetic bypass is blocked; the second magnetic bridge is still not saturated, and the leakage magnetic path is reduced; the leakage magnetic flux gradually decreases with the increase of load, and the air gap main magnetic flux increases steadily. III. Heavy-duty operating conditions; The demagnetizing component of the armature reaction current reaches its peak, the first and second magnetic bridges are completely saturated, the magnetic reluctance of the magnetic bridges approaches infinity, and the leakage magnetic bypass is completely blocked; the magnetic flux of the permanent magnet enters the main magnetic circuit of the stator through the air gap.

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