A direct-drive outer rotor despin motor applied to a rocket projectile

Abstract

The application relates to a direct-drive outer rotor despinning motor applied to a rocket projectile, and solves the technical problems of the existing outer rotor motor, such as complex structure, high machining and assembling requirement, large vibration and noise and low precision. The application comprises a stator seat and a motor shaft; the top of the stator seat is provided with a second ring table and a first ring table; the lower portion of the stator seat is provided with a driver; the motor shaft is connected with the driver through the central holes of the first ring table and the second ring table and the inner hole of the stator seat; the upper end of the motor shaft is provided with a stator top cover; the motor shaft sleeve is provided with a rotor, the side wall of the rotor is provided with an annular cavity with an opening downward; the inner wall of the annular cavity is provided with a rotor iron core; the rotor iron core is provided with a magnetic steel; the first ring table is provided with a stator support; the upper end of the stator support is provided with a stator iron core, the stator iron core is provided with a stator winding, and the stator winding is electrically connected with the driver; a position sensor is arranged between the first ring table and the motor shaft, and the position sensor is electrically connected with the driver.

Description

Technical Field

[0001] This invention relates to external rotor motors, and more specifically to a direct-drive external rotor despinning motor for use in rockets. Background Technology

[0002] After ignition and launch, a rocket typically rotates at high speed around its longitudinal axis to ensure flight stability. However, this can cause motion coupling effects on the seeker and fin attitude. To avoid this effect, an external rotor despinning motor can be used. By rotating in the opposite direction to the rocket body, the coupling effect of the rocket body's motion on the seeker and fins is isolated, thus maintaining the seeker's stability in inertial space. Furthermore, the differential rotation speed of the motor adjusts the fin phase to achieve trajectory correction, ultimately ensuring the rocket's accuracy.

[0003] The rotational speed of a rocket typically increases rapidly from zero to several thousand revolutions per minute at launch, then gradually decreases during flight, eventually dropping to between a few and four hundred revolutions per minute. Therefore, the external rotor despinning motor, a crucial servo component in a rocket, must be able to start quickly and achieve precise speed control over a wide operating speed range.

[0004] The current structure of the external rotor despinning motor is a servo motor with a reducer. That is, a common brushless DC motor is used inside the servo mechanism, and then the reducer reduces the output speed of the motor according to a certain speed ratio, while increasing the output torque to the required level. The external rotor is then driven to rotate through a set of gears and bearings. For example... Figure 1 The diagram shows a despinning motor used in rockets, comprising an inner housing 006, a brushless DC motor 01 embedded within the inner housing 006, and a reduction gear set 02 connected to the output end of the motor shaft of the brushless DC motor 01. The reduction gear set 02 is sleeved on the bottom end of the inner housing 006, and an outer rotor 001 is sleeved on the outside of the inner housing 006 via an outer rotor bearing 012. The reduction gear set 02 and the outer rotor 001 are connected. A driver 008 is provided at the top of the brushless DC motor 01 and connected thereto. The disadvantages of this structure are as follows:

[0005] (i) The structure of the servo mechanism is relatively complex, the processing and assembly process is relatively cumbersome, and because the principle is to embed a motor and drive it, the entire mechanism has many potential failure points.

[0006] (ii) The reduction gear set uses a lot of gears, which requires high machining and assembly precision, and also leads to greater vibration and noise generated by the servo mechanism during operation.

[0007] (iii) Servo control is only performed on the speed of the motor body (i.e. the internal brushless DC motor), and the speed of the outer rotor is indirectly controlled by the reduction ratio normalization calculation. The influence of the deviation of gear set machining and assembly on the speed of the outer rotor is not considered.

[0008] (iv) The drive control of brushless DC motors generally adopts PWM square wave drive mode, which has low speed control accuracy. The speed accuracy error is usually around ten revolutions per minute, which does not meet the high precision requirements of servo systems in some cases (such as when the speed accuracy error requirement is less than 1 revolution per minute). Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of existing external rotor motors, such as complex structure, high processing and assembly requirements, large vibration and noise, and low precision, and to provide a direct-drive external rotor despinning motor for use in rockets.

[0010] The concept of this invention is to provide a direct-drive external rotor motor to overcome the above-mentioned defects. By adopting the direct drive form of the external rotor motor, the reduction gear set can be eliminated, which greatly reduces the complexity of the entire mechanism and simplifies its assembly process, reduces the vibration and noise of the mechanism during operation, and the driver can use a high-precision position sensor to directly collect the speed signal of the external rotor for control, so the speed control accuracy is effectively guaranteed. At the same time, the driver adopts the FOC vector control mode, which greatly improves the speed control accuracy.

[0011] To achieve the above objectives and realize the above concepts, the technical solution provided by the present invention is as follows:

[0012] A direct-drive external rotor despinning motor for use in rockets is unique in that:

[0013] Including the stator housing and motor shaft;

[0014] The stator base has a second ring platform at its top, and a first ring platform at its top. The center of the second ring platform has an inner hole in the stator base that communicates with the center holes of the second ring platform and the first ring platform. The driver is located below the stator base.

[0015] The lower end of the motor shaft passes through the center hole of the first ring platform, the center hole of the second ring platform, and the inner hole of the stator seat in sequence to connect with the driver; the upper end of the motor shaft is provided with a stator top cover;

[0016] A rotor is mounted on the outer side of the middle part of the motor shaft via a bearing. An annular cavity with an opening facing downwards is provided on the side wall of the rotor. A rotor core is provided on the inner wall of the annular cavity. Magnets are provided on the rotor core.

[0017] The first ring platform is fitted with a stator support; the lower end of the stator support abuts against the top surface of the second ring platform, the upper end of the stator support is located in the annular cavity, and the upper end is fitted with a stator core corresponding to the position of the rotor core. The stator core is equipped with stator windings, and the stator windings are electrically connected to the driver.

[0018] A position sensor is installed between the first ring platform and the motor shaft. The position sensor is mounted on the first ring platform and electrically connected to the driver.

[0019] Furthermore, a top cover cavity is provided inside the upper end of the rotor, and the stator top cover is located inside the top cover cavity; a gap is provided between the bottom of the top cover cavity and the lower surface of the stator top cover, and shielding plates are provided on both the bottom of the top cover cavity and the lower surface of the stator top cover.

[0020] Furthermore, the bearing is an angular contact ball bearing.

[0021] Furthermore, there are two bearings, including a first bearing located at the top and a second bearing located at the bottom. The first and second bearings are mounted back-to-back on the outside of the motor shaft.

[0022] The upper end of the first bearing is fixed between the rotor and the motor shaft by an upper pressure cap and a loading nut; the lower end of the second bearing is fixed between the rotor and the motor shaft by a lower pressure cap.

[0023] The rotor core is fixed in the annular cavity by a rotor pressure ring.

[0024] Furthermore, the motor shaft is provided with four steps, forming a first step surface, a second step surface, and a third step surface arranged sequentially from bottom to top;

[0025] The first bearing and the second bearing are sleeved between the first step surface and the second step surface, and the lower end of the second bearing abuts against the first step surface.

[0026] The loading nut is set on the second step surface, and the lower end face of the loading nut abuts against the upper end face of the first bearing and the second step surface respectively;

[0027] The stator top cover is sleeved on the outside of the motor shaft, and the lower end face of the stator top cover abuts against the third step surface and the upper end face of the loading nut respectively.

[0028] The inner wall of the rotor is provided with a limiting boss that abuts against the first bearing and the second bearing;

[0029] An annular upper pressure cover is embedded in the center of the bottom of the top cover cavity, and the lower end of the upper pressure cover is pressed onto the upper end face of the first bearing.

[0030] Furthermore, the stator base is provided with an annular base boss on its outer periphery;

[0031] The outer diameter of the rotor gradually increases from the top to the bottom.

[0032] The lower end of the rotor is fitted onto the outside of the second ring platform and is clearance-fitted with the base boss.

[0033] Furthermore, the stator support has a three-section structure, with the first and third sections parallel to the axis of the motor shaft, and the second section perpendicular to the axis of the motor shaft;

[0034] The first segment is fitted around the outer periphery of the first ring platform, and the lower end face of the first segment abuts against the top surface of the second ring platform.

[0035] The second section is located between the stator core and the position sensor, and is perpendicularly connected to the first and third sections respectively.

[0036] The inner wall of the third section is fitted with the inner wall of the annular cavity with a clearance, and the outer wall of the third section is provided with an annular notch; the stator core is fitted into the annular notch.

[0037] Furthermore, the outer diameter of the rotor is less than 68 mm;

[0038] The driver uses FOC vector control mode;

[0039] The lower end of the stator base is provided with a driver cavity, and the driver is located inside the driver cavity.

[0040] Furthermore, a mounting boss is provided near the bottom of the motor shaft. The outer circle of the mounting boss contacts the inner wall of the second ring platform, and its lower end face abuts against the upper surface of the stator base.

[0041] Furthermore, the rotor core is a ring structure with grooves on the inner wall, and the magnets are multi-pole sector structures with 16 to 24 poles. The magnets are bonded and fixed in the grooves of the rotor core.

[0042] The stator core has an external toothed groove structure with 18 to 27 grooves.

[0043] The stator winding adopts a fractional slot concentrated winding;

[0044] The shielding sheet is made of 1J50 or 1J79 iron-nickel soft magnetic alloy sheet;

[0045] The position sensor uses a 16-bit or 17-bit absolute magnetic encoder.

[0046] The advantages of this invention compared to the prior art are:

[0047] 1. The present invention provides a direct-drive external rotor despinning motor for rockets, which adopts the form of direct drive of the external rotor motor. The external rotor motor is redesigned and has the advantages of simple structure, light weight, high speed control accuracy, high efficiency and high reliability. It is suitable for guidance and control components of medium and high precision rockets and can realize the despinning of the guidance component and control the movement of the rudder ring according to the control command.

[0048] 2. The present invention provides a direct-drive external rotor despinning motor for use in rockets. Based on the principle of external rotor motors and combined with the requirements of despinning motors, the design is redesigned. The overall structure is relatively simple, the processing and assembly process is convenient, the number of transmission parts is small, and the working reliability is high.

[0049] 3. The present invention provides a direct-drive external rotor despinning motor for use in rockets, which eliminates the original servo motor acceleration and reduction gear set structure, greatly reduces the complexity of the entire mechanism and the precision requirements for component processing and assembly, simplifies the assembly process, and reduces the vibration and noise of the mechanism during operation.

[0050] 4. The present invention provides a direct-drive external rotor despinning motor for use in rockets. The driver can use a high-precision position sensor (16-bit magnetic encoder) to directly acquire the rotational speed signal of the external rotor for control, thereby effectively ensuring the speed control accuracy.

[0051] 5. The present invention provides a direct-drive external rotor despinning motor for use in rockets. The driver can adopt FOC vector control mode, so that the speed accuracy error is less than 1 r / min, and the control accuracy is greatly improved.

[0052] 6. The present invention provides a direct-drive external rotor despinning motor for use in rockets, which adopts a multi-pole fractional slot concentrated winding, with small winding end size, simple production and assembly process, and can realize automated production; the use of multi-pole near-pole slots to match the stator and rotor results in low cogging torque and low operating vibration and noise. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of an existing external rotor despinning motor used in rockets.

[0054] The reference numerals in the attached diagram are explained as follows: 01-Brushless DC motor; 02-Reduction gear set; 001-Outer rotor; 006-Inner housing; 008-Driver; 012-Outer rotor bearing.

[0055] Figure 2 This is a schematic diagram of an embodiment of a direct-drive external rotor despinning motor applied to rockets according to the present invention;

[0056] Figure 3 This is a schematic diagram of the stator core structure in an embodiment of the present invention;

[0057] Figure 4 This is a schematic diagram of the rotor core and magnets in an embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of the stator base in an embodiment of the present invention;

[0059] Figure 6 This is a schematic diagram of the motor shaft structure in an embodiment of the present invention;

[0060] Figure 7 This is a schematic diagram of the stator support structure in an embodiment of the present invention.

[0061] The symbols in the attached image are explained as follows:

[0062] 1-Rotor; 2-Shielding plate; 3-Stator core; 4-Rotor core; 5-Magnet; 6-Stator bracket; 7-Magnetic encoder; 8-Driver; 9-Motor shaft; 10-Loading nut; 11-Upper cover; 12-Angular contact ball bearing; 13-Stator winding; 14-Rotor pressure ring; 15-Lower cover; 16-Stator base; 17-Stator top cover;

[0063] 18-First ring platform, 19-Second ring platform, 20-Base boss;

[0064] 21-First step surface, 22-Second step surface, 23-Third step surface, 24-Mounting boss;

[0065] 25 - First paragraph, 26 - Second paragraph, 27 - Third paragraph. Detailed Implementation

[0066] The specific technical solutions in the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0067] This invention mainly comprises, from the outside in, an outer rotor, a stator, a support shaft (corresponding to the motor shaft), a position sensor, and a driver. As a medium-to-high precision guidance and control component for rockets, this invention is used to despin the guidance assembly and control the movement of the rudder rings according to control commands.

[0068] Figures 1-2 A two-pair pole magnet and one-pair carbon brush motor for short-time working mode provided in an embodiment of the present invention includes a stator housing 16 and a motor shaft 9.

[0069] The stator base 16 has a second ring platform 19 on its top, and a first ring platform 18 on its top. The center of the second ring platform 19 has a stator base inner hole that communicates with the center holes of the second ring platform 19 and the first ring platform 18. The stator base 16 has a driver 8 below it. The lower end of the stator base 16 has a driver cavity, and the driver 8 is located in the driver cavity, forming an integrated structure with the motor body.

[0070] The lower end of the motor shaft 9 passes sequentially through the central hole of the first annular platform 18, the central hole of the second annular platform 19, and the inner hole of the stator seat to connect with the driver 8; a stator top cover 17 is provided at the upper end of the motor shaft 9; a rotor 1 is sleeved on the outer side of the middle part of the motor shaft 9 through a bearing 12, and an annular cavity with an opening facing downward is provided on the side wall of the rotor 1; a rotor core 4 is provided on the inner wall of the annular cavity; a magnet 5 is provided on the rotor core 4. A top cover cavity is provided inside the upper end of the rotor 1, and the stator top cover 17 is located inside the top cover cavity; a gap is provided between the bottom of the top cover cavity and the lower surface of the stator top cover 17, and a shielding plate 2 is provided on both the bottom of the top cover cavity and the lower surface of the stator top cover 17.

[0071] The first ring platform 18 is fitted with a stator support 6. The lower end of the stator support 6 abuts against the top surface of the second ring platform 19. The upper end of the stator support 6 is located in the annular cavity. The upper end is fitted with a stator core 3 corresponding to the position of the rotor core 4. The stator core 3 is equipped with a stator winding 13, which is electrically connected to the driver 8. A position sensor 7 is provided between the first ring platform 18 and the motor shaft 9. The position sensor 7 is mounted on the first ring platform 18 and electrically connected to the driver 8.

[0072] Bearing 12 is an angular contact ball bearing. There are two bearings 12, including a first bearing located at the top and a second bearing located at the bottom. The first and second bearings are mounted back-to-back on the outside of the motor shaft 9 and can withstand an axial overload of not less than 200g. The upper end of the first bearing is fixed between the rotor 1 and the motor shaft 9 by the upper pressure cover 11 and the loading nut 10. The lower end of the second bearing is fixed between the rotor 1 and the motor shaft 9 by the lower pressure cover 15. The rotor core 4 is fixed in the annular cavity by the rotor pressure ring 14.

[0073] The motor shaft 9 has four steps, forming a first step surface 21, a second step surface 22, and a third step surface 23 arranged sequentially from bottom to top; a first bearing and a second bearing are sleeved between the first step surface 21 and the second step surface 22, with the lower end of the second bearing abutting against the first step surface 21; a loading nut 10 is set on the second step surface 22, with the lower end face of the loading nut 10 abutting against the upper end face of the first bearing and the second step surface 22 respectively; a stator top cover 17 is sleeved on the motor shaft 9, with the lower end face of the stator top cover 17 abutting against the third step surface 23 and the upper end face of the loading nut 10 respectively; a limiting boss is provided on the inner wall of the rotor 1, abutting against the first bearing and the second bearing; an annular upper pressure cover 11 is embedded in the center of the bottom of the top cover cavity, with the lower end of the upper pressure cover 11 pressed against the upper end face of the first bearing.

[0074] The stator base 16 has an annular base boss 20 on its outer periphery; the outer diameter of the rotor 1 gradually increases from the upper end to the lower end; the lower end of the rotor 1 is fitted onto the outer side of the second annular platform 19 and is clearance-fitted with the base boss 20.

[0075] The stator support 6 has a three-section structure. The first section 25 and the third section 27 are parallel to the axis of the motor shaft 9, and the second section 26 is perpendicular to the axis of the motor shaft 9. The first section 25 is sleeved on the outer periphery of the first ring platform 18, and the lower end face of the first section 25 abuts against the top surface of the second ring platform 19. The second section 26 is located between the stator core 3 and the position sensor 7, and is perpendicularly connected to the first section 25 and the third section 27 respectively. The inner wall of the third section 27 is clearance-fitted with the inner wall of the annular cavity, and the outer wall of the third section 27 is provided with an annular notch. The stator core 3 is sleeved in the annular notch.

[0076] A mounting boss 24 is provided near the bottom of the motor shaft 9. The outer circle of the mounting boss 24 contacts the inner wall of the second ring platform 19, and its lower end face abuts against the upper surface of the stator seat 16.

[0077] In this embodiment of the invention, the outer diameter of rotor 1 is 64mm; the driver 8 adopts FOC vector control mode. Rotor core 4 is a ring structure with grooves on the inner wall, magnet 5 is a multi-pole sector structure with 20 poles, and magnet 5 is bonded and fixed in the grooves of rotor core 4; stator core 3 is an external toothed structure with 21 slots; stator winding 13 adopts a fractional-slot concentrated winding; shielding sheet 2 is made of 1J50 iron-nickel soft magnetic alloy lamination; position sensor 7 is a hollow shaft structure and adopts a 17-bit absolute magnetic encoder.

[0078] The above description is merely one embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent structural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A direct-drive external rotor despinning motor for use in rockets, characterized in that: Includes stator housing (16) and motor shaft (9); The stator base (16) has a second ring platform (19) at its top, and a first ring platform (18) at its top. The center of the second ring platform (19) has a stator base inner hole that communicates with the center holes of the second ring platform (19) and the first ring platform (18). The stator base (16) has a driver (8) at its bottom. The lower end of the motor shaft (9) passes through the center hole of the first ring platform (18), the center hole of the second ring platform (19) and the inner hole of the stator seat in sequence and is connected to the driver (8); the upper end of the motor shaft (9) is provided with a stator top cover (17); The rotor (1) is sleeved on the outer side of the middle part of the motor shaft (9) through the bearing (12). The rotor (1) has an annular cavity with an opening facing downward on its side wall. The rotor core (4) is provided on the inner wall of the annular cavity. The rotor core (4) is provided with a magnet (5). The first ring platform (18) is fitted with a stator support (6); the lower end of the stator support (6) abuts against the top surface of the second ring platform (19), the upper end of the stator support (6) is located in the annular cavity, and the upper end is fitted with a stator core (3) corresponding to the position of the rotor core (4), and a stator winding (13) is provided on the stator core (3), and the stator winding (13) is electrically connected to the driver (8); A position sensor (7) is provided between the first ring platform (18) and the motor shaft (9). The position sensor (7) is installed on the first ring platform (18) and electrically connected to the driver (8).

2. The direct-drive external rotor despinning motor for use in rockets according to claim 1, characterized in that: The upper end of the rotor (1) is provided with a top cover cavity, and the stator top cover (17) is located in the top cover cavity; there is a gap between the bottom of the top cover cavity and the lower surface of the stator top cover (17), and shielding plates (2) are provided on both the bottom of the top cover cavity and the lower surface of the stator top cover (17).

3. A direct-drive external rotor despinning motor for use in rockets according to claim 1 or 2, characterized in that: The bearing (12) is an angular contact ball bearing.

4. A direct-drive external rotor despinning motor for use in rockets according to claim 3, characterized in that: There are two bearings (12), including a first bearing located above and a second bearing located below. The first bearing and the second bearing are mounted back-to-back on the outside of the motor shaft (9). The upper end of the first bearing is fixed between the rotor (1) and the motor shaft (9) by an upper pressure cover (11) and a loading nut (10); the lower end of the second bearing is fixed between the rotor (1) and the motor shaft (9) by a lower pressure cover (15). The rotor core (4) is fixed in the annular cavity by a rotor pressure ring (14).

5. A direct-drive external rotor despinning motor for use in rockets according to claim 4, characterized in that: The motor shaft (9) is provided with four steps, forming a first step surface (21), a second step surface (22) and a third step surface (23) arranged from bottom to top; The first bearing and the second bearing are sleeved between the first step surface (21) and the second step surface (22), and the lower end of the second bearing abuts against the first step surface (21); The loading nut (10) is disposed on the second step surface (22), and the lower end face of the loading nut (10) abuts against the upper end face of the first bearing and the second step surface (22) respectively; The stator top cover (17) is sleeved on the outside of the motor shaft (9), and the lower end face of the stator top cover (17) abuts against the third step surface (23) and the upper end face of the loading nut (10); The inner wall of the rotor (1) is provided with a limiting boss that abuts against the first bearing and the second bearing; An annular upper pressure cover (11) is embedded in the center of the bottom of the cavity of the top cover, and the lower end of the upper pressure cover (11) is pressed onto the upper end surface of the first bearing.

6. A direct-drive external rotor despinning motor for use in rockets according to claim 1, characterized in that: The stator base (16) is provided with an annular base boss (20) on its outer periphery; The outer diameter of the rotor (1) gradually increases from the upper end to the lower end; The lower end of the rotor (1) is fitted onto the outside of the second ring platform (19) and is clearance-fitted with the base boss (20).

7. A direct-drive external rotor despinning motor for use in rockets according to claim 6, characterized in that: The stator support (6) has a three-section structure, with the first section (25) and the third section (27) parallel to the axis of the motor shaft (9), and the second section (26) perpendicular to the axis of the motor shaft (9). The first segment (25) is fitted around the outer periphery of the first ring platform (18), and the lower end face of the first segment (25) abuts against the top surface of the second ring platform (19); The second segment (26) is located between the stator core (3) and the position sensor (7), and is perpendicularly connected to the first segment (25) and the third segment (27) respectively; The inner wall of the third section (27) is clearance-fitted with the inner wall of the annular cavity, and the outer wall of the third section (27) is provided with an annular notch; the stator core (3) is fitted into the annular notch.

8. A direct-drive external rotor despinning motor for use in rockets according to claim 1, characterized in that: The outer diameter of the rotor (1) is less than 68 mm; The driver (8) adopts FOC vector control mode; The lower end of the stator base (16) is provided with a driver cavity, and the driver (8) is located in the driver cavity.

9. A direct-drive external rotor despinning motor for use in rockets according to claim 8, characterized in that: The motor shaft (9) has a mounting boss (24) near its bottom end. The outer circle of the mounting boss (24) contacts the inner wall of the second ring platform (19), and its lower end face abuts against the upper surface of the stator seat (16).

10. A direct-drive external rotor despinning motor for use in rockets according to claim 1, characterized in that: The rotor core (4) is a circular ring structure with grooves on the inner wall, and the magnet (5) is a multi-pole fan-shaped structure with 16 to 24 poles. The magnet (5) is bonded and fixed in the groove of the rotor core (4). The stator core (3) has an external toothed groove structure with 18 to 27 grooves; The stator winding (13) adopts a fractional slot concentrated winding; The shielding sheet (2) is made of 1J50 or 1J79 iron-nickel soft magnetic alloy sheet; The position sensor (7) uses a 16-bit or 17-bit absolute magnetic encoder.

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