Position-sensorless permanent magnet synchronous motor and method for aircraft cooling

Abstract

The invention discloses a sensorless permanent magnet synchronous motor for aircraft cooling and a method. The sensorless permanent magnet synchronous motor comprises a shell, a rotor assembly, a stator assembly, a rear end cover, a rear bearing, a front bearing, a conductive sealing ring, a first socket and a second socket, a combination body of the front bearing and the rotor assembly is arranged in an inner cavity of the casing, so that a metal dustproof cover of the front bearing is attached to the end face of a bearing chamber of the casing; the stator assembly is installed in an inner cavity of the machine shell, and the end face of the stator assembly is attached to a blocking shoulder of the inner cavity of the machine shell. The rear bearing is mounted at the rear end of a rotating shaft of the rotor assembly; a conductive sealing ring is installed on a sealing ring groove of the rear end cover, and the rear end cover is installed at the rear end of the machine shell, so that the rotor assembly, the stator assembly, the front bearing and the rear bearing are fixedly supported in the machine shell. And the first socket and the second socket are respectively arranged on the rear end cover through cylindrical head screws with fuse holes at the heads. On the basis that the lightweight design principle is met, design optimization is achieved through the reinforcing ribs and the high-temperature-resistant conductive lubricating grease.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a sensorless permanent magnet synchronous motor and method for aircraft cooling. Background Technology

[0002] Rapid cooling of the brake heat exchanger can shorten aircraft turnaround time, improve aircraft operational responsiveness, and meet operational requirements. The motor is the core component for achieving rapid cooling. AC motors can be classified into asynchronous motors and synchronous motors based on the relationship between operating speed and power frequency. Permanent magnet synchronous motors can be further classified into brushed and brushless motors based on the number of brushes. Currently, brushless motors are commonly used in aircraft. Brushless motors can be further classified into permanent magnet motors with and without position sensors, and into DC and AC motors based on the drive method.

[0003] Currently, most aircraft motors used for rapid cooling of landing gear wheels are brushless DC motors and asynchronous motors. Asynchronous motors are heavy, cause significant power losses to the aircraft's electrical grid, and are prone to momentary spikes in voltage. Brushless DC motors contain Hall effect sensors for position detection, making them susceptible to signal interference. Furthermore, the presence of the position sensor increases the need for commutation poles, Hall effect circuit boards, and mounting structures, hindering lightweight design. Devices for rapid cooling of landing gear wheels must be installed within the landing gear axles. The landing gear is a high-vibration, high-temperature area on the aircraft, and is prone to signal interference, placing stringent requirements on the motor. Compact, interference-resistant sensorless permanent magnet synchronous motors are suitable for the landing gear area.

[0004] In the utility model with announcement number CN 222301610U, a permanent magnet synchronous motor with high permanent magnet utilization rate is proposed. The permanent magnet synchronous motor includes a frame body, a rotor, a transmission shaft and a stator. A through slot is set at the outer end of the rotor to install permanent magnets, and a magnetic guide slot is set on the inner wall of the stator to install magnetic guide plates. The magnetic guide plates enhance the magnetic field. However, the permanent magnet synchronous motor has a short output shaft, small output torque, poor end face sealing and weak waterproofing, which cannot meet the high temperature and high vibration requirements of aircraft.

[0005] A utility model patent with publication number CN 222301509U proposes a high-efficiency, low-noise permanent magnet synchronous motor, including a stator and a rotor. The stator of this motor is fixed within the rotor core ring, and the stator windings form a gradually changing air gap through magnetic tiles and a winding frame. The proposed permanent magnet synchronous motor exhibits low harmonic content in the air gap magnetic field, excellent noise performance, and low torque ripple. However, the rotor-stator structure of this motor is unsuitable for use in aircraft landing gear areas due to its poor vibration resistance and insufficient strength to meet operational requirements.

[0006] In the invention with publication number CN110601448B, a liquid-cooled high power density PMSM motor with no position control was proposed. The motor has a circulating coolant channel structure inside, which realizes the self-cooling of the sensorless motor. However, its structure is an open structure, which cannot meet the IP67 and electromagnetic requirements proposed by aviation equipment.

[0007] According to the search, the existing patented permanent magnet synchronous motors are difficult to use for rapid cooling of aircraft landing gear wheels because their operating conditions are far superior to those of motors used in aircraft landing gear, and there are currently no positionless permanent magnet synchronous motors for cooling aircraft wheels. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a sensorless permanent magnet synchronous motor and method for aircraft cooling, comprising a housing, a rotor assembly, a stator assembly, a rear end cover, a rear bearing, a front bearing, a conductive sealing ring, a first socket, and a second socket. The assembly of the front bearing and rotor assembly is installed within the housing cavity, with the metal dust cover of the front bearing fitting against the bearing chamber end face of the housing. The stator assembly is installed within the housing cavity, with its end face fitting against the inner cavity shoulder of the housing. The rear bearing is installed at the rear end of the rotor assembly's shaft. A conductive sealing ring is installed in the sealing ring groove of the rear end cover, and the rear end cover is installed at the rear end of the housing, thus fixing and supporting the rotor assembly, stator assembly, front bearing, and rear bearing inside the housing. The first socket and the second socket are respectively installed on the rear end cover using cylindrical head screws with fuse holes in their heads. This invention achieves design optimization by using reinforcing ribs and high-temperature conductive grease while meeting lightweight design principles.

[0009] The technical solution adopted by this invention to solve its technical problem is as follows:

[0010] A sensorless permanent magnet synchronous motor for aircraft cooling includes a housing, a rotor assembly, a stator assembly, a rear end cover, a rear bearing, a front bearing, a conductive sealing ring, a first socket, and a second socket.

[0011] The front bearing is mounted on the front shoulder of the rotor assembly shaft;

[0012] The assembly of the front bearing and rotor assembly is installed in the inner cavity of the housing, such that the metal dust cover of the front bearing is in contact with the bearing chamber end face of the housing.

[0013] The stator assembly is installed in the inner cavity of the housing, and the end face of the stator assembly is in contact with the inner cavity shoulder of the housing;

[0014] The rear bearing is mounted at the rear end of the rotor assembly's shaft;

[0015] A conductive sealing ring is installed on the sealing ring groove of the rear end cover. The rear end cover is installed at the rear end of the housing, so that the rotor assembly, stator assembly, front bearing, and rear bearing are fixedly supported inside the housing.

[0016] The first socket and the second socket are respectively mounted on the rear cover by cylindrical head screws with fuse holes in the head.

[0017] Preferably, the housing is a thin-walled structure made of high-strength aluminum alloy, with stepped holes of different diameters inside. The diameters of the stepped holes inside are sequentially the maximum outer diameters of the front bearing, stator assembly, and rear end cover. That is, the functions of the stepped holes inside the housing are, in sequence, to assemble and fix the front bearing, the stator assembly, and the rear end cover. The housing contains a sensor signal transmission channel, which is a rectangular groove of 8mm × 4mm and 58mm deep. The upper end face of the housing has an 8mm long mounting flange structure, which includes 6 screw mounting platforms of 12mm width and 6 M5 threaded holes of 8mm depth, for fixing and connecting with the sensor. The exterior of the housing includes 4 reinforcing ribs of 10mm width and 77mm length. The reinforcing ribs are divided into two sections: one section is 23mm long, and the second section is 10mm wide and spaced 44mm apart. The outer circle of the rear end of the housing has 8 through holes of 2.7mm diameter, which are evenly distributed for mounting and fixing with the rear end cover.

[0018] Preferably, the rotor assembly includes a shaft, a front de-weighting block, a rotor core, magnets, and a rear de-weighting block; the shaft is a hollow long shaft made of titanium alloy with a length of 190mm; the shaft is provided with an M18 thread of 21mm length and a keyway of 5mm width and 24mm length from left to right; the outer diameter of the shaft is 21mm from 21mm from the shaft end, and the length is 118mm; the shaft is provided with a mounting shoulder from 139mm from the shaft end, and the outer diameter of the shoulder is 25mm. The length is 6mm; the rear end of the shoulder is 33.5mm long, and the shaft diameter within the structure is 21mm. Its surface is provided with straight knurling m0.5 to increase friction and facilitate the installation of the rotor core; the rear end of this section of the shaft is the installation position of the rear bearing, with an outer diameter of 17.2mm and a length of 16.2mm; the end face of the front end of the shaft has a hole diameter of 10mm and a hole depth of 100mm, and the end face of the rear end of the shaft has a hole diameter of 10mm and a hole depth of 60mm;

[0019] The front-end weight-removing block is an annular structure with an inner diameter of 25mm, an outer diameter of 37mm, and a thickness of 4mm, and has 8 through holes with a diameter of 3mm evenly distributed inside; the rear-end weight-removing block is an annular structure with an inner diameter of 20mm, an outer diameter of 37mm, and a thickness of 4mm, and has 8 through holes with a diameter of 6mm evenly distributed inside.

[0020] The rotor core is a ring structure made of 10# steel, with an inner diameter of 21mm, an outer diameter of 35mm, and an axial length of 22mm. The rotor core is decorated with straight knurling m0.5 on the outside to increase friction and facilitate installation with the magnet structure.

[0021] The magnet is a structure consisting of 6 magnetic tiles and a stainless steel sheath. The 6 magnetic tiles are uniformly cut from magnetic rings with an outer diameter of 39mm, an inner diameter of 35mm, and a length of 20mm. The stainless steel sheath is a ring structure with an inner diameter of 39mm, an outer diameter of 41mm, and a length of 20mm. The magnetic tiles and the stainless steel sheath in the magnet are bonded together with an adhesive that can withstand 250℃.

[0022] Preferably, the stator assembly comprises slot insulation, insulating end plates, a stator core, enameled wire, and phase insulation. The stator core is made of 35W300 laminated steel, with a 9-slot pear-shaped slot structure. The inner diameter of the stator core is 41mm, the outer diameter is 73.5mm, the spacing between each pear-shaped slot is 8.5mm, and the thickness of the stator core is 20mm. The slot insulation and insulating end plate structures are the same as the stator core structure, only differing in thickness. The thickness of the slot insulation, insulating end plates, and phase insulation is 0.1mm. The material used for the slot insulation is 6650 NHN composite material, the material used for the insulating end plates is modified bismaleimide laminated glass cloth, and the material used for the phase insulation is polyimide film. The enameled wire is QP-2 / 220 enameled round copper wire with an outer diameter of 0.54mm. The enameled wire is wound in a single layer in the stator core.

[0023] Preferably, the rear end cover shown is made of high-strength aluminum alloy and is a cylindrical structure containing an inner hole and two mounting bosses. The left end of the rear end cover includes two inner holes, from top to bottom: a housing mounting hole with a diameter of 70mm and a depth of 12mm; and a rear bearing mounting hole with a diameter of 40mm and a depth of 12.2mm. The right end of the rear end cover includes two mounting bosses, each containing an inner hole with a diameter of 17mm and a depth of 20mm. Four sockets and socket screw mounting holes are evenly distributed on each of the two mounting bosses. The socket screw mounting holes are M3 with a depth of 12mm. The two mounting bosses are 27mm × 27mm directional bosses with an axial length of 21mm.

[0024] Preferably, the socket and receptacle adopt the standard J599 / 21MTAB43PN.

[0025] Preferably, the conductive sealing ring is an HB 7515-1.8×71 O-type rubber sealing ring, and the material is conductive.

[0026] Preferably, both the front and rear bearings are ceramic ball bearings; the rear bearing is a standard structure bearing with an inner diameter of 17mm, an outer diameter of 40mm, and a width of 12mm; and the front bearing is a standard structure bearing with an inner diameter of 20mm, an outer diameter of 47mm, and a width of 12mm.

[0027] A design method for a sensorless permanent magnet synchronous motor for aircraft cooling, comprising the following steps:

[0028] Step 1: Determine the structural dimensions of the permanent magnet synchronous motor;

[0029] A sensor and cooling fan are mounted at the front end of the motor, and a signal transmission channel is required for the sensor. A sensor signal transmission slot is provided in the motor housing. The rotor shaft of the motor is provided with a mounting thread for the cooling fan. The motor shaft is designed as an extra-long structure with a length of 190mm. A mounting flange is provided on the front face of the motor housing. Reinforcing ribs are provided on the outside of the motor housing. The reinforcing ribs enable the motor to contact and support the landing gear wheel axle, thereby reducing weight. Magnets with stainless steel sheaths are used. A permanent magnet synchronous motor without a position sensor is adopted. This motor does not contain a position sensor or commutating poles, which reduces the axial length of the motor body by 1 / 3 and the weight by 1 / 4.

[0030] Step 2: Optimize the electromagnetic protection structure of the permanent magnet synchronous motor;

[0031] The motor bearings were modified from standard parts and replaced with ceramic ball bearings;

[0032] In permanent magnet synchronous motors, conductive grease is applied to the outside of the metal dust cover of the bearing to form a conductive path;

[0033] The sealing ring at the joint of the motor housing was replaced with an O-ring rubber seal made of conductive material;

[0034] Step 3: Optimize bearing selection for permanent magnet synchronous motor lifespan;

[0035] The bearings are ceramic ball bearings, which meet the life requirement of 5,000 take-offs and landings for airborne equipment, and the grease filling amount does not exceed 3%.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. The rotor assembly used in this invention includes an extended 190mm shaft for mechanical transmission of the motor load and high-speed rotation of the rotating magnetic field at 7000r / min. Existing motor shafts are relatively short, while the shaft length of this rotor assembly is a first. The shaft has a stepped, hollow structure with an exposed outer diameter of 20mm. It is made of high-strength TC4 material, which meets the functional requirements of the drive load fan blades for rapid aircraft cooling technology, and also satisfies the structural strength and lightweight design requirements of the high-vibration zone of the landing gear.

[0038] 2. The housing used in this invention is a thin-walled structure with reinforcing ribs, and based on the miniaturized integrated design of aircraft accessories, a sensor signal transmission channel is built into the housing. The housing reduces the use of mounting screws through dimensional clearance settings, and is assembled with other components via clearance fit. The material used is high-strength aluminum alloy, which meets the structural strength, lightweight design, and integration requirements of the high-vibration zone of the landing gear.

[0039] 3. The bearing used in this invention is a high-strength ceramic ball bearing, which is different from the ordinary steel bearings used in the prior art. The inner ring material of this bearing is ceramic, which makes the bearing strong, wear-resistant, and long-lasting, while also having a small shaft current.

[0040] 4. The sensorless permanent magnet synchronous motor for aircraft cooling proposed in this invention is the first time that a sensorless permanent magnet synchronous motor has been used in the aircraft landing gear area. The motor has been optimized for electromagnetic radiation and structural strength. While meeting the principle of lightweight design, the design optimization is achieved through reinforcing ribs and high-temperature conductive grease. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the external shape of the present invention.

[0042] Figure 2 This is a schematic diagram of the structure of the present invention.

[0043] Figure 3 This is the main sectional view of the casing.

[0044] Figure 4 This is a top view of the casing.

[0045] Figure 5 This is a front sectional view of the rotor assembly.

[0046] Figure 6 This is the main sectional view of the stator assembly.

[0047] Figure 7 This is a top view of the stator core.

[0048] Figure 8 This is the main sectional view of the rear cover.

[0049] Figure 9 This is a top view of the rear cover.

[0050] Reference numerals in the attached diagram: 1. Housing; 2. Rotor assembly; 3. Stator assembly; 4. Rear end cover; 5. Rear bearing; 6. Front bearing; 7. Conductive sealing ring; 8. Socket; 9. Socket; 2-1. Shaft; 2-2. Front end weight removal block; 2-3. Rotor core; 2-4. Magnet; 2-5. Rear end weight removal block; 3-1. Slot insulation; 3-2. Insulating end plate; 3-3. Stator core; 3-4. Enamelled wire; 3-5. Phase insulation. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] To address the issues of poor vibration resistance, susceptibility to interference, and heavy weight in existing sensorless permanent magnet synchronous motors, this paper proposes a sensorless permanent magnet synchronous motor for aircraft cooling and its optimization method, taking into account the operating environment and structural layout of aircraft landing gear.

[0053] The motor is an improvement on an existing patented structure, allowing it to be installed within the aircraft landing gear axle and meeting the requirements for high load, high speed, and interference resistance. It comprises a housing, rotor assembly, stator assembly, rear end cover, front bearing, rear bearing, socket, and sealing rings. The housing and rear end cover are made of high-strength 7050 aluminum alloy. The front bearing, rotor assembly, stator assembly, and rear bearing are sequentially installed within the housing cavity. The front and rear bearings are respectively mounted at the front and rear ends of the rotor assembly shaft. The three-phase leads of the stator assembly are led out through openings in the rear end cover and crimped to the socket pins. The sealing rings are installed in the sealing ring grooves of the rear end cover, and the rear end cover is fixed to the housing with eight evenly distributed screws. The socket is fixed to the rear end cover with mounting screws.

[0054] Example:

[0055] like Figure 1 As shown, this embodiment is a sensorless permanent magnet synchronous motor for aircraft cooling, including a housing 1, a rotor assembly 2, a stator assembly 3, a rear end cover 4, a rear bearing 5, a front bearing 6, a conductive sealing ring 7, a socket 8, and a socket 9.

[0056] like Figure 2 As shown, the motor's installation relationship from the inside out is as follows: the front bearing 6 is installed at the front shoulder of the rotor assembly 2's shaft, and the assembly of the front bearing 6 and rotor assembly 2 is installed in the inner cavity of the housing 1, so that the metal dust cover of the front bearing 6 is in contact with the bearing chamber end face of the housing 1; the stator assembly 3 is installed in the inner cavity of the housing 1, so that the end face of the stator assembly 3 is in contact with the inner cavity shoulder of the housing 1; the rear bearing 5 is installed at the rear end of the rotor assembly 2's shaft; a conductive sealing ring 7 is installed on the sealing ring groove of the rear end cover 4, and is installed at the rear end of the housing 1 by eight HB 1-206F-M2.5×5 Phillips head countersunk screws, so that the rotor assembly 2, stator assembly 3, front bearing 6, and rear bearing 5 are fixedly supported inside the housing 1. Sockets 8 and 9 are respectively installed on the rear end cover 4 by four HB 1-203G-M2.5×5 cylindrical head screws with fuse holes in the head.

[0057] The housing 1 is a thin-walled structure made of high-strength aluminum alloy, with stepped holes of different diameters inside, the center line of which is perpendicular to the ground. The diameters of the stepped holes inside are, in order, the maximum outer diameters of the front bearing 6, the stator assembly 3, and the rear end cover 4. That is, the functions of the stepped holes inside the housing 1 are, in order, to assemble and fix the front bearing 6, the stator assembly 3, and the rear end cover 4. The housing 1 contains a sensor signal transmission channel, which is a rectangular groove of 8mm×4mm and 58mm deep. The upper end face of the housing 1 has an 8mm long mounting flange structure, which includes 6 screw mounting platforms of 12mm wide and 6 evenly distributed M5 threaded holes of 8mm deep for fixing and connecting with the sensor. The exterior of the housing 1 includes 4 reinforcing ribs of 10mm wide and 77mm long. These reinforcing ribs are divided into two sections: one section is 23mm long, and the second section is 10mm wide and spaced 44mm apart. The outer circle of the rear end of the housing 1 has 8 evenly distributed through holes of 2.7mm diameter for mounting and fixing with the rear end cover 4.

[0058] like Figure 5 As shown, rotor assembly 2 includes a shaft 2-1, a front de-weight block 2-2, a rotor core 2-3, a magnet 2-4, and a rear de-weight block 2-5. The shaft 2-1 is a hollow long shaft made of titanium alloy, with a length of 190mm, significantly exceeding the length of existing motor shafts. From left to right, the shaft is provided with a 21mm long M18 thread and a 5mm wide, 24mm long keyway for connection with other equipment. Starting 21mm from the shaft end, the outer diameter of the shaft is 21mm, and its length is 118mm. Starting 139mm from the shaft end, the shaft is provided with a mounting shoulder, which has an outer diameter of 25mm and a length of 6mm. The shoulder rear end section has a length of 33.5mm and a shaft diameter of 21mm. Its surface is provided with straight knurling m0.5 to increase friction and facilitate the installation of rotor core 2-3. The rear end of this section is the installation position of the rear bearing 5, with an outer diameter of 17.2mm and a length of 16.2mm. The end face of the front end of the shaft 2-1 has a hole diameter of 10mm and a hole depth of 100mm, and the end face of the rear end of the shaft 2-1 has a hole diameter of 10mm and a hole depth of 60mm.

[0059] The front-end weight-reducing block 2-2 is an annular structure with an inner diameter of 25mm, an outer diameter of 37mm, and a thickness of 4mm. It has eight 3mm diameter through holes evenly distributed inside. The rear-end weight-reducing block 2-5 is an annular structure with an inner diameter of 20mm, an outer diameter of 37mm, and a thickness of 4mm. It also has eight 6mm diameter through holes evenly distributed inside. The weight-reducing blocks are mainly used to reduce weight and balance the rotor assembly 2, preventing swaying and abnormal wear of the permanent magnet synchronous motor during high-speed rotation.

[0060] The rotor core 2-3 is a ring structure made of 10# steel, with an inner diameter of 21mm, an outer diameter of 35mm, and an axial length of 22mm. The rotor core 2-3 is decorated with straight knurled m0.5 on the outside to increase friction and facilitate installation with the magnet structure.

[0061] Magnet 2-4 is a structure consisting of 6 magnetic tiles and a stainless steel sheath. The 6 magnetic tiles are uniformly cut from magnetic rings with an outer diameter of 39mm, an inner diameter of 35mm, and a length of 20mm. The stainless steel sheath is a ring structure with an inner diameter of 39mm, an outer diameter of 41mm, and a length of 20mm. The magnetic tiles and the stainless steel sheath in Magnet 2-4 are bonded together with an adhesive that can withstand 250℃.

[0062] like Figure 6 As shown, the stator assembly 3 comprises slot insulation 3-1, insulating end plate 3-2, stator core 3-3, enameled wire 3-4, and phase insulation 3-5.

[0063] like Figure 7 As shown, the main component of stator assembly 3 is stator core 3-3, which is made of 35W300 laminated silicon steel sheets. The silicon steel sheet uses a common 9-slot pear-shaped slot structure. The inner diameter of the stator core is 41mm, the outer diameter is 73.5mm, the spacing between the pear-shaped slots is 8.5mm, and the thickness of the stator core is 20mm. The slot insulation 3-1 and insulating end plate 3-2 have the same structure as the stator core, only differing in thickness. The thickness of slot insulation 3-1, insulating end plate 3-2, and phase insulation 3-5 is all 0.1mm. Slot insulation 3-1 uses 6650 NHN composite material, insulating end plate 3-2 uses modified bismaleimide laminated glass cloth, and phase insulation 3-5 uses polyimide film. Enamelled wire 3-4 is commonly used QP-2 / 220 enamelled round copper wire with an outer diameter of 0.54mm. The enameled wire 3-4 is wound in a single layer in the stator core 3-3.

[0064] like Figure 8 As shown, the rear end cover 4 is made of high-strength aluminum alloy and is a cylindrical structure with an inner hole and two mounting bosses. The left end of the rear end cover 4 contains two inner holes: from top to bottom, one is a mounting hole for the housing with a diameter of 70mm and a depth of 12mm; the other is a mounting hole for the rear bearing 5 with a diameter of 40mm and a depth of 12.2mm.

[0065] like Figure 9As shown, the right end of the rear cover 4 includes two mounting bosses. Each mounting boss has an inner hole with a diameter of 17mm and a depth of 20mm. Four screw mounting holes for sockets 8 and 9 are evenly distributed on each mounting boss. The screw mounting holes for the sockets are M3 with a depth of 12mm. The two mounting bosses are 27mm × 27mm in size, with an axial length of 21mm. The spacing between the socket screw mounting holes on the mounting bosses can be determined according to the recommended opening dimensions in the connector selection manual for sockets 8 and 9. Sockets 8 and 9 are selected with appropriate connectors based on the number of signals. In this embodiment, sockets 8 and 9 are selected using the standard J599 / 21MTAB43PN connector.

[0066] The conductive sealing ring 7 is an HB 7515-1.8×71 O-type rubber sealing ring, made of conductive material.

[0067] Both the front bearing 6 and the rear bearing 5 are modified standard ceramic ball bearings. Unlike ordinary bearings in existing technology, these bearings are selected based on the landing gear installation environment, featuring low shaft current, long service life, and corrosion resistance. Furthermore, to meet the electromagnetic compatibility requirements of the airborne equipment, the grease in the ceramic ball bearings has been replaced with a high-temperature resistant conductive grease, and the grease filling amount is controlled to not exceed 3%. The rear bearing 5 is a standard structure bearing with an inner diameter of 17mm, an outer diameter of 40mm, and a width of 12mm; the front bearing is a standard structure bearing with an inner diameter of 20mm, an outer diameter of 47mm, and a width of 12mm.

[0068] This invention also proposes a design method for a sensorless permanent magnet synchronous motor for aircraft cooling, the specific steps of which are as follows:

[0069] Step 1: Determine the structural dimensions of the permanent magnet synchronous motor;

[0070] The structural dimensions of the permanent magnet synchronous motor are optimized and determined based on the installation and usage space and the on-machine interconnection relationship.

[0071] In this embodiment, a sensor and a cooling fan need to be installed at the front end of the motor, and a signal transmission channel needs to be provided for the sensor. To meet the integrated design requirements of the airborne equipment, a sensor signal transmission slot is provided in the motor housing, and the rotor shaft of the motor assembly is provided with a cooling fan mounting thread. The motor shaft is designed as an extra-long structure with a length of 190mm, ensuring that the shaft circumference meets the installation space requirements of the motor body structure while also accommodating the sensor installation. To facilitate motor installation on the aircraft, a mounting flange is provided on the front end face of the motor housing. Furthermore, to meet the weight requirements of the motor, reinforcing ribs are provided on the exterior of the motor housing. These ribs provide contact support between the motor and the landing gear wheel axle, achieving weight reduction. This embodiment uses magnets with stainless steel sheaths to prevent magnet breakage in high-vibration environments, thus improving motor strength and lifespan.

[0072] In this implementation, under the strict requirements of structural size and weight, a permanent magnet synchronous motor without a position sensor is selected. This motor does not contain a position sensor or commutating magnetic poles, which reduces the axial length of the motor body by 1 / 3 and the weight by 1 / 4.

[0073] Step 2: Optimize the electromagnetic protection structure of the permanent magnet synchronous motor;

[0074] The electromagnetic protection structure of the permanent magnet synchronous motor is designed to address the problem that existing motors cannot meet the RE10210kHz~18GHz electric field radiation emission requirements of airborne equipment. Due to the principle and structural characteristics of permanent magnet synchronous motors, the motor shafts of existing airborne equipment radiate high-frequency currents from within the motor in the form of an antenna effect, causing excessive external radiation. In this implementation, the motor bearings are modified from standard parts into special bearings. These bearings, using ceramic ball bearings, have a lower electrostatic discharge current, reducing energy and high-frequency common-mode noise, thus solving the problem of excessive electromagnetic radiation caused by stray currents and noise from the bearings in existing technologies.

[0075] In permanent magnet synchronous motors, conductive grease is applied to the outside of the metal dust cover of the bearing to form a conductive path.

[0076] The sealing rings at the motor housing joints have been replaced with O-rings made of conductive rubber, optimizing the motor's electromagnetic seal, eliminating the "slot antenna" effect, and suppressing electromagnetic radiation. They also provide dust and water protection, enabling the airborne equipment to achieve an IP67 sealing protection rating.

[0077] Through experimental verification, it has been shown that after electromagnetic protection optimization, the permanent magnet synchronous motor can pass the RE102 test.

[0078] Step 3: Optimize bearing selection to extend the lifespan of the permanent magnet synchronous motor;

[0079] In existing technologies, many airborne equipment motors suffer from bearing breakage due to improper bearing selection, resulting in the motor failing to rotate. Optimizing the lifespan of permanent magnet synchronous motors aims to solve the problems of easy bearing damage and short lifespan in existing motors. Therefore, a bearing selection method for airborne motors is proposed.

[0080] The permanent magnet synchronous motor of this invention is installed inside the landing gear wheel axle of an aircraft, which is located in the high vibration zone of the aircraft and the mechanical environment is relatively harsh. The selection of bearings must meet the radial load, that is, meet the impact of the peak acceleration of 40g at the moment of landing of the aircraft, and at the same time meet the combined load generated when the motor rotates at high speed.

[0081] Replace ordinary bearing grease with high-temperature conductive grease with a filling amount not exceeding 3%;

[0082] Because the bearings are made of specially designed ceramic ball bearings, they have low shaft current and long service life, which can meet the service life requirement of 5,000 takeoffs and landings required by airborne equipment. Furthermore, the requirement of no more than 3% grease filling avoids motor wear and improves efficiency.

[0083] This completes the optimization of a sensorless permanent magnet synchronous motor for aircraft cooling.

Claims

1. A sensorless permanent magnet synchronous motor for aircraft cooling, characterized in that, Includes housing, rotor assembly, stator assembly, rear end cover, rear bearing, front bearing, conductive sealing ring, first socket and second socket; The front bearing is mounted on the front shoulder of the rotor assembly shaft; The assembly of the front bearing and rotor assembly is installed in the inner cavity of the housing, such that the metal dust cover of the front bearing is in contact with the bearing chamber end face of the housing. The stator assembly is installed in the inner cavity of the housing, and the end face of the stator assembly is in contact with the inner cavity shoulder of the housing; The rear bearing is mounted at the rear end of the rotor assembly's shaft; A conductive sealing ring is installed on the sealing ring groove of the rear end cover. The rear end cover is installed at the rear end of the housing, so that the rotor assembly, stator assembly, front bearing, and rear bearing are fixedly supported inside the housing. The first socket and the second socket are respectively mounted on the rear cover by cylindrical head screws with fuse holes in the head.

2. The sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The casing is a thin-walled structure made of high-strength aluminum alloy, with stepped holes of different diameters inside. The internal stepped holes have diameters corresponding to the maximum outer diameters of the front bearing, stator assembly, and rear end cover, respectively. In other words, the functions of the stepped holes inside the housing are, in sequence, to assemble and fix the front bearing, the stator assembly, and the rear end cover. The housing contains a sensor signal transmission channel, which is an 8mm × 4mm rectangular groove with a depth of 58mm. The upper surface of the housing has an 8mm long mounting flange structure, which includes six 12mm wide screw mounting platforms and six evenly distributed M5 threaded holes with a depth of 8mm for fixing the sensor. The exterior of the housing includes four 10mm wide and 77mm long reinforcing ribs, divided into two sections: one section is 23mm long, and the second section, spaced 44mm apart, is 10mm wide. The outer circumference of the rear end of the housing has eight evenly distributed 2.7mm diameter through holes for mounting and fixing the rear end cover.

3. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The rotor assembly includes a shaft, a front de-weighting block, a rotor core, magnets, and a rear de-weighting block. The shaft is a hollow, long shaft made of titanium alloy, with a length of 190mm. From left to right, the shaft is provided with a 21mm long M18 thread and a 5mm wide, 24mm long keyway. Starting 21mm from the shaft end, the outer diameter of the shaft is 21mm, and its length is 118mm. Starting 139mm from the shaft end, the shaft is provided with a mounting shoulder, with an outer diameter of 25mm and a length... The diameter of the shaft within the structure is 21mm, and the rear end of the shoulder is 33.5mm long. Its surface is knurled with a straight groove (m0.5) to increase friction and facilitate rotor core installation. The rear end of this section of the shaft is the mounting location for the rear bearing, with an outer diameter of 17.2mm and a length of 16.2mm. The end face of the front end of the shaft has a 10mm diameter hole and a depth of 100mm, and the end face of the rear end of the shaft has a 10mm diameter hole and a depth of 60mm. The front-end weight-removing block is an annular structure with an inner diameter of 25mm, an outer diameter of 37mm, and a thickness of 4mm, and has 8 through holes with a diameter of 3mm evenly distributed inside; the rear-end weight-removing block is an annular structure with an inner diameter of 20mm, an outer diameter of 37mm, and a thickness of 4mm, and has 8 through holes with a diameter of 6mm evenly distributed inside. The rotor core is a ring structure made of 10# steel, with an inner diameter of 21mm, an outer diameter of 35mm, and an axial length of 22mm. The rotor core is decorated with straight knurling m0.5 on the outside to increase friction and facilitate installation with the magnet structure. The magnet is a structure consisting of 6 magnetic tiles and a stainless steel sheath. The 6 magnetic tiles are uniformly cut from magnetic rings with an outer diameter of 39mm, an inner diameter of 35mm, and a length of 20mm. The stainless steel sheath is a ring structure with an inner diameter of 39mm, an outer diameter of 41mm, and a length of 20mm. The magnetic tiles and the stainless steel sheath in the magnet are bonded together with an adhesive that can withstand 250℃.

4. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The stator assembly comprises slot insulation, insulating end plates, a stator core, enameled wire, and phase insulation. The stator core is made of 35W300 laminated silicon steel sheets with a 9-slot pear-shaped slot structure. The inner diameter of the stator core is 41mm, the outer diameter is 73.5mm, the spacing between each pear-shaped slot is 8.5mm, and the thickness of the stator core is 20mm. The slot insulation and insulating end plate structures are the same as the stator core structure, only differing in thickness. The thickness of the slot insulation, insulating end plates, and phase insulation is 0.1mm. The material used for the slot insulation is 6650NHN composite material, the material used for the insulating end plates is modified bismaleimide laminated glass cloth, and the material used for the phase insulation is polyimide film. The enameled wire is QP-2 / 220 enameled round copper wire with an outer diameter of 0.54mm. The enameled wire is wound in a single layer in the stator core.

5. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The rear end cover shown is made of high-strength aluminum alloy and is a cylindrical structure with an inner hole and two mounting bosses. The left end of the rear end cover includes two inner holes: from top to bottom, one is a housing mounting hole with a diameter of 70mm and a depth of 12mm; the other is a rear bearing mounting hole with a diameter of 40mm and a depth of 12.2mm. The right end of the rear end cover includes two mounting bosses, each with an inner hole with a diameter of 17mm and a depth of 20mm. Each mounting boss has four sockets and socket screw mounting holes evenly distributed on it. The socket screw mounting holes are M3 and 12mm deep. The two mounting bosses are 27mm × 27mm directional bosses with an axial length of 21mm.

6. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The sockets and outlets are of standard J599 / 21MTAB43PN.

7. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, The conductive sealing ring is an HB 7515-1.8×71 O-type rubber sealing ring, and the material is conductive.

8. A sensorless permanent magnet synchronous motor for aircraft cooling according to claim 1, characterized in that, Both the front and rear bearings are ceramic ball bearings; the rear bearing is a standard structure bearing with an inner diameter of 17mm, an outer diameter of 40mm, and a width of 12mm; the front bearing is a standard structure bearing with an inner diameter of 20mm, an outer diameter of 47mm, and a width of 12mm.

9. A design method for a sensorless permanent magnet synchronous motor as described in claim 1, characterized in that, The specific steps are as follows: Step 1: Determine the structural dimensions of the permanent magnet synchronous motor; A sensor and cooling fan are mounted at the front end of the motor, and a signal transmission channel is required for the sensor. A sensor signal transmission slot is provided in the motor housing. The rotor shaft of the motor is provided with a mounting thread for the cooling fan. The motor shaft is designed as an extra-long structure with a length of 190mm. A mounting flange is provided on the front face of the motor housing. Reinforcing ribs are provided on the outside of the motor housing. The reinforcing ribs enable the motor to contact and support the landing gear wheel axle, thereby reducing weight. Magnets with stainless steel sheaths are used. A permanent magnet synchronous motor without a position sensor is adopted. This motor does not contain a position sensor or commutating poles, which reduces the axial length of the motor body by 1 / 3 and the weight by 1 / 4. Step 2: Optimize the electromagnetic protection structure of the permanent magnet synchronous motor; The motor bearings were modified from standard parts and replaced with ceramic ball bearings; In permanent magnet synchronous motors, conductive grease is applied to the outside of the metal dust cover of the bearing to form a conductive path; The sealing ring at the joint of the motor housing was replaced with an O-ring rubber seal made of conductive material; Step 3: Optimize bearing selection for permanent magnet synchronous motor lifespan; The bearings are ceramic ball bearings, which meet the life requirement of 5,000 take-offs and landings for airborne equipment, and the grease filling amount does not exceed 3%.

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