JP5887808B2 - Electric power steering motor and electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering motor and an electric power steering device.

  There is an electric power steering (EPS) that assists a steering force necessary for steering an automobile with a motor in addition to a human operating force. In an electric power steering device, it is required to reduce noise that enters the ears of the steering wheel and vibrations transmitted through the hand.

  In addition, since electric power steering motors can improve durability and high output, brushless motors are becoming mainstream instead of brushed motors. If the brushless motor has a structure in which the excitation coil is a concentrated winding instead of a structure in which the excitation coil is a distributed winding, the cost can be reduced and the brushless motor can be made compact.

  In general, a structure in which the exciting coil is a concentrated winding is more likely to generate vibration than a structure in which the exciting coil is a distributed winding. Further, in the structure in which the flat magnet is embedded in the rotor yoke, there is a risk that vibration will further increase. This is because torque ripple (fluctuation in output torque) occurs because of a sudden fluctuation in magnetic flux density between a pair of adjacent flat magnets (magnetic pole switching part), which is thought to cause vibration and noise. ing.

  For example, as a technique for suppressing torque ripple in a permanent magnet embedded rotary electric machine in which flat plate-shaped permanent magnets are arranged in a rotationally symmetrical manner, Patent Document 1 discloses an outer periphery of a rotor corresponding to a pair of adjacent magnetic pole ends. A permanent magnet-embedded rotary electric machine formed in a concave part and a convex part is described.

JP 2011-062059 A

  The technique described in Patent Document 1 has a complicated structure and a high manufacturing cost because the outer periphery of the rotor is formed into a concave portion and a convex portion. In the technique disclosed in Patent Document 1, the electrical angle θ1 at the end of the convex portion is in the range of 70 ° to 80 ° with the radial straight line closest to the end passing through the magnetic pole center of the permanent magnet. The electrical angle θ2 of the deepest portion of the concave portion centered on the rotation axis of the rotor is greatly restricted, such as being in the range of (θ1-10 °) to θ1 with a radial straight line as a base point.

  The present invention has been made in view of the above, and an object thereof is to provide an electric power steering motor and an electric power steering device that can suppress torque ripple and suppress an increase in manufacturing cost.

  In order to solve the above-described problems and achieve the object, an electric power steering motor includes a rotor yoke having an arcuate outer periphery, a stator core disposed in an annular shape with a predetermined interval outside the rotor yoke, An excitation coil that generates a magnetic field for exciting the stator core, and a flat magnet embedded in the rotor yoke, and the center of gravity of the flat magnet has a rotor yoke radius of 1 when the rotor yoke has a radius of 1 It is in the position of 0.70 or more and 0.87 or less from the center of rotation.

  With the above configuration, torque ripple can be suppressed. Further, the rotor yoke can be a simple arc-shaped rotor yoke. For this reason, the increase in manufacturing cost can be suppressed.

  As a desirable mode of the present invention, it is preferable that the barycentric position of the flat magnet is in a position of 0.75 or more and 0.87 or less from the rotation center of the rotor yoke when the radius of the rotor yoke is 1.

  With the above configuration, torque ripple can be suppressed and a decrease in average torque can be suppressed.

  As a desirable mode of the present invention, it is preferable that the center of gravity of the flat magnet is in a position of 0.79 or more and 0.86 or less from the rotation center of the rotor yoke when the radius of the rotor yoke is 1.

  With the above configuration, torque ripple can be suppressed and a decrease in average torque can be suppressed.

  As a desirable mode of the present invention, it is preferable that the center of gravity of the flat magnet is in a position of 0.83 or more and 0.85 or less from the rotation center of the rotor yoke when the radius of the rotor yoke is 1.

  With the above configuration, it is possible to suppress the decrease in average torque and to significantly suppress torque ripple.

  As a desirable mode of the present invention, it is preferable that the rotor yoke is provided with a flux barrier at both ends of the flat magnet.

  With the above configuration, a magnetic short circuit between the S pole and the N pole of the flat magnet can be suppressed.

  As a desirable mode of the present invention, it is preferable that the exciting coil is wound around the stator core by concentrated winding.

  With the above configuration, torque ripple is suppressed, so that vibration caused by concentrated winding excitation coils can be suppressed. If the structure is such that the exciting coil is concentrated winding, the cost can be reduced and the brushless motor can be made compact.

  As a desirable mode of the present invention, it is preferable that the electric power steering apparatus obtains an auxiliary steering torque by the electric power steering motor.

  With the above configuration, since the torque ripple is suppressed, even when the auxiliary steering torque is transmitted to the steering wheel, it is possible to operate in a state in which a sense of incongruity is suppressed.

  According to the present invention, it is possible to provide an electric power steering motor and an electric power steering device that can suppress torque ripple and suppress an increase in manufacturing cost.

FIG. 1 is a configuration diagram of an electric power steering apparatus including a brushless motor according to the present embodiment. FIG. 2 is a front view for explaining an example of a speed reducer included in the electric power steering apparatus of the present embodiment. FIG. 3 is a cross-sectional view schematically showing the configuration of the motor of this embodiment on a virtual plane including the central axis. FIG. 4 is a cross-sectional view schematically showing the configuration of the motor of the present embodiment, cut along a virtual plane orthogonal to the central axis. FIG. 5 is an explanatory view schematically showing the rotor of the present embodiment. FIG. 6 is an explanatory diagram illustrating torque ripple in an evaluation example of the present embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

  FIG. 1 is a configuration diagram of an electric power steering apparatus including a brushless motor according to the present embodiment. First, an outline of an electric power steering apparatus 80 including the brushless motor according to the present embodiment will be described with reference to FIG.

  The electric power steering device 80 includes a steering wheel 81, a steering shaft 82, a steering force assist mechanism 83, a universal joint 84, a lower shaft 85, a universal joint 86, in the order in which the force applied from the steering wheel is transmitted. A pinion shaft 87, a steering gear 88, and a tie rod 89 are provided. The electric power steering device 80 includes an ECU (Electronic Control Unit) 90, a torque sensor 91a, and a vehicle speed sensor 91b.

  The steering shaft 82 includes an input shaft 82a and an output shaft 82b. The input shaft 82a has one end connected to the steering wheel 81 and the other end connected to the steering force assist mechanism 83 via the torque sensor 91a. The output shaft 82 b has one end connected to the steering force assist mechanism 83 and the other end connected to the universal joint 84. In the present embodiment, the input shaft 82a and the output shaft 82b are made of a magnetic material such as iron.

  The lower shaft 85 has one end connected to the universal joint 84 and the other end connected to the universal joint 86. The pinion shaft 87 has one end connected to the universal joint 86 and the other end connected to the steering gear 88.

  Steering gear 88 includes a pinion 88a and a rack 88b. The pinion 88a is connected to the pinion shaft 87. The rack 88b meshes with the pinion 88a. The steering gear 88 is configured as a rack and pinion type. The steering gear 88 converts the rotational motion transmitted to the pinion 88a into a linear motion by the rack 88b. The tie rod 89 is connected to the rack 88b.

  The steering force assist mechanism 83 includes a speed reducer 92 and the brushless motor 10. The reduction gear 92 is connected to the output shaft 82b. The brushless motor 10 is an electric motor that is connected to the reduction gear 92 and generates auxiliary steering torque. In the electric power steering device 80, a steering column is constituted by the steering shaft 82, the torque sensor 91a, and the speed reducer 92. The brushless motor 10 gives auxiliary steering torque to the output shaft 82b of the steering column. That is, the electric power steering apparatus 80 of this embodiment is a column assist system.

  In the column-assist type electric power steering apparatus 80, the distance between the operator and the brushless motor 10 is relatively short, and the noise of the brushless motor 10, vibrations transmitted through the hand, or torque changes may affect the operator. For this reason, the electric power steering device 80 is required to reduce noise entering the ears of the steering wheel and vibration or torque change transmitted through the hand.

  FIG. 2 is a front view for explaining an example of a speed reducer included in the electric power steering apparatus of the present embodiment. FIG. 2 shows a part in cross section. The speed reducer 92 is a worm speed reducer. The reduction gear 92 includes a reduction gear housing 93, a worm 94, a ball bearing 95 a, a ball bearing 95 b, a worm wheel 96, and a holder 97.

  The worm 94 is coupled to the shaft 21 of the brushless motor 10 by a spline or an elastic coupling. The worm 94 is held in the speed reducer housing 93 so as to be rotatable by a ball bearing 95 a and a ball bearing 95 b held by the holder 97. The worm wheel 96 is rotatably held by the speed reducer housing 93. The worm teeth 94 a formed on a part of the worm 94 mesh with the worm wheel teeth 96 a formed on the worm wheel 96.

  The rotational force of the brushless motor 10 is transmitted to the worm wheel 96 through the worm 94 to rotate the worm wheel 96. The reduction gear 92 increases the torque of the brushless motor 10 by the worm 94 and the worm wheel 96. Then, the reduction gear 92 gives an auxiliary steering torque to the output shaft 82b of the steering column shown in FIG.

  The torque sensor 91a shown in FIG. 1 detects the driver's steering force transmitted to the input shaft 82a via the steering wheel 81 as a steering torque. The vehicle speed sensor 91b detects the traveling speed of the vehicle on which the electric power steering device 80 is mounted. The ECU 90 is electrically connected to the brushless motor 10, the torque sensor 91a, and the vehicle speed sensor 91b.

  The ECU 90 controls the operation of the brushless motor 10. Moreover, ECU90 acquires a signal from each of the torque sensor 91a and the vehicle speed sensor 91b. That is, the ECU 90 acquires the steering torque T from the torque sensor 91a, and acquires the traveling speed V of the vehicle from the vehicle speed sensor 91b. The ECU 90 is supplied with electric power from a power supply device (for example, a vehicle-mounted battery) 99 with the ignition switch 98 turned on. The ECU 90 calculates an assist steering command value of the assist command based on the steering torque T and the traveling speed V. Then, the ECU 90 adjusts the power value X supplied to the brushless motor 10 based on the calculated auxiliary steering command value. The ECU 90 acquires the information on the induced voltage from the brushless motor 10 or the information on the rotation of the rotor from the resolver described later as the operation information Y.

  The steering force of the driver (driver) input to the steering wheel 81 is transmitted to the speed reduction device 92 of the steering force assist mechanism 83 via the input shaft 82a. At this time, the ECU 90 acquires the steering torque T input to the input shaft 82a from the torque sensor 91a, and acquires the traveling speed V from the vehicle speed sensor 91b. The ECU 90 controls the operation of the brushless motor 10. The auxiliary steering torque created by the brushless motor 10 is transmitted to the speed reducer 92.

  The steering torque (including auxiliary steering torque) output via the output shaft 82 b is transmitted to the lower shaft 85 via the universal joint 84 and further transmitted to the pinion shaft 87 via the universal joint 86. The steering force transmitted to the pinion shaft 87 is transmitted to the tie rod 89 via the steering gear 88 to steer the steered wheels. Next, the brushless motor 10 will be described.

  FIG. 3 is a cross-sectional view schematically showing the configuration of the motor of this embodiment on a virtual plane including the central axis. FIG. 4 is a cross-sectional view schematically showing the configuration of the motor of the present embodiment, cut along a virtual plane orthogonal to the central axis. As shown in FIG. 3, the brushless motor 10 includes a housing 11, a bearing 12, a bearing 13, a resolver 14, a rotor 20, and a stator 30 as a brushless motor stator.

  The housing 11 includes a cylindrical housing 11a and a front bracket 11b. The front bracket 11b is formed in a substantially disc shape and is attached to the cylindrical housing 11a so as to close one open end of the cylindrical housing 11a. The cylindrical housing 11a is formed with a bottom 11c at the end opposite to the front bracket 11b so as to close the end. The bottom part 11c is formed integrally with the cylindrical housing 11a, for example. As a magnetic material forming the cylindrical housing 11a, for example, a general steel material such as SPCC (Steel Plate Cold Commercial), electromagnetic soft iron, or the like can be applied. The front bracket 11b serves as a flange when the brushless motor 10 is attached to a desired device.

  The bearing 12 is provided inside the cylindrical housing 11a and at a substantially central portion of the front bracket 11b. The bearing 13 is provided inside the cylindrical housing 11a and at a substantially central portion of the bottom portion 11c. The bearing 12 rotatably supports one end of a shaft 21 that is a part of the rotor 20 disposed inside the cylindrical housing 11a. The bearing 13 rotatably supports the other end of the shaft 21. Thereby, the shaft 21 rotates around the central axis Zr.

  The resolver 14 is supported by a terminal block 15 provided on the front bracket 11b side of the shaft 21. The resolver 14 detects the rotational position of the rotor 20 (shaft 21). The resolver 14 includes a resolver rotor 14a and a resolver stator 14b. The resolver rotor 14a is attached to the circumferential surface of the shaft 21 by press fitting or the like. The resolver stator 14b is disposed to face the resolver rotor 14a with a predetermined gap.

  The stator 30 is provided in a cylindrical shape so as to surround the rotor 20 inside the cylindrical housing 11a. The stator 30 is attached, for example, by being fitted to the inner peripheral surface 11d of the cylindrical housing 11a. The central axis of the stator 30 coincides with the central axis Zr of the rotor 20. The stator 30 includes a cylindrical stator core 31 and an excitation coil 37. In the stator 30, an exciting coil 37 is wound around the stator core 31.

  As shown in FIG. 4, the stator core 31 includes a plurality of divided cores 32. The plurality of split cores 32 are arranged at equal intervals in the circumferential direction around the central axis Zr (the direction along the inner peripheral surface 11d of the cylindrical housing 11a shown in FIG. 3). Hereinafter, the circumferential direction around the central axis Zr is simply referred to as the circumferential direction. The stator core 31 is configured by combining a plurality of divided cores 32. The stator core 31 is press-fitted into the cylindrical housing 11a, so that the stator 30 is provided in the cylindrical housing 11a in an annular state. The stator core 31 and the cylindrical housing 11a may be fixed by adhesion, shrink fitting, welding or the like in addition to press-fitting.

  The split core 32 is formed by stacking and bundling a plurality of core pieces formed in substantially the same shape in the central axis Zr direction. The split core 32 is formed of a magnetic material such as an electromagnetic steel plate. The split core 32 has a back yoke 33 and teeth 34. The back yoke 33 includes an arc-shaped portion. The back yoke 33 forms an annular shape when the plurality of divided cores 32 are combined. The teeth 34 are portions extending from the inner peripheral surface of the back yoke 33 toward the rotor 20.

  The exciting coil 37 shown in FIG. 4 is a linear electric wire. The exciting coil 37 is concentratedly wound around the outer periphery of the tooth 34 of the split core 32 via an insulator 37a. The insulator 37a is a member for insulating the exciting coil 37 and the split core 32, and is formed of a heat resistant member. By combining a plurality of stator cores 31 thus configured as shown in FIG. 4, the stator 30 has a shape that can surround the rotor 20.

  The rotor 20 is provided inside the cylindrical housing 11a so as to be rotatable about the central axis Zr with respect to the cylindrical housing 11a. The rotor 20 includes a shaft 21, a rotor yoke 22, and a magnet 23. The shaft 21 is formed in a cylindrical shape. The rotor yoke 22 is formed in a cylindrical shape. Note that the rotor yoke 22 has an arcuate outer periphery, and the number of processing steps can be reduced.

  The rotor yoke 22 is manufactured by laminating thin plates such as electromagnetic steel plates and cold-rolled steel plates by means of adhesion, boss, caulking or the like. The rotor yoke 22 is sequentially stacked in the mold and discharged from the mold. The rotor yoke 22 is fixed to the shaft 21 by press-fitting the shaft 21 into, for example, a hollow portion thereof. The shaft 21 and the rotor yoke 22 may be integrally formed.

  A plurality of magnets 23 are provided on the outer periphery of the rotor yoke 22. The magnet 23 is a permanent magnet, and S poles and N poles are alternately arranged at equal intervals in the circumferential direction of the rotor yoke 22. As a result, the number of poles of the rotor 20 shown in FIG. 4 is 14 poles in which N poles and S poles are alternately arranged on the outer circumferential side of the rotor yoke 22 in the circumferential direction of the rotor yoke 22.

  The magnet accommodation hole 24 is a through hole formed in the rotor yoke 22. A plurality of magnet housing holes 24 are provided on the outer peripheral portion and arranged at equal intervals. The magnet 23 is accommodated in the magnet accommodation hole 24 of the rotor yoke 22 and attached by, for example, a magnetic force. In the present embodiment, the magnet 23 has a divided shape (segment structure). FIG. 5 is an explanatory view schematically showing the rotor of the present embodiment.

  As shown in FIG. 5, the magnet 23 in which the N pole is magnetized on the outer peripheral side of the rotor yoke 22 and the magnet 23 in which the S pole is magnetized on the outer peripheral side of the rotor yoke 22 are arranged in the circumferential direction of the rotor yoke 22. They are alternately arranged at equal intervals.

  In FIG. 5, the length in the long side direction of the flat and rectangular magnet 23 is Wm, and the length in the short side direction is tm. Further, the center of gravity of the flat magnet 23 is M. The radius from the central axis Zr to the outer periphery of the rotor yoke 22 is Rr, and the distance from the central axis Zr to M, which is the center of gravity of the magnet 23 described above, is Lm.

  The flux barrier 25 is a through hole provided in the rotor yoke 22 in order to prevent a magnetic flux short circuit between the S pole and the N pole of the magnet 23. The flux barrier 25 only needs to be capable of suppressing or blocking the passage of magnetic flux, and may be a gap or a non-magnetic insulating material.

  By providing the flux barrier 25 on the rotor yoke 22, a difference in magnetic resistance occurs on the outer periphery of the rotor yoke 22. For example, a portion near the outer periphery of the rotor yoke 22 in contact with the long side of the magnet 23 becomes a magnetic concave portion 27, and the vicinity of the flux barrier 25 becomes a magnetic convex portion called a bridge portion 26.

  For this reason, on the outer periphery of the rotor yoke 22, magnetic concave portions 27 and bridge portions 26 that are magnetic convex portions are alternately arranged, and the magnetic concave portions 27 have the q axis and the bridge portions 26 that are magnetic convex portions. Each is called the d-axis. Further, the magnet 23 is embedded in the rotor yoke 22 so as to include a bridge portion 26 that is a magnetic convex portion, and constitutes a closed magnetic circuit. And in the magnetic recessed part 27, the magnetic flux density is lower than the bridge part 26 which is a magnetic convex part.

  When the magnet 23 is embedded in the rotor yoke 22 to form a closed magnetic circuit, reluctance torque due to magnetic unevenness generated on the outer periphery of the rotor yoke 22 is generated in addition to the magnet torque of the magnet 23. As a result, the total torque generated in the rotor 20 is improved even if the magnetic flux interlinking from the rotor yoke 22 to the stator core 31 is reduced.

  In FIG. 5, the flux barriers 25 on both sides of the plate-like magnet 23 are such that the distance between the bridge portions 26 arranged with the magnet 23 interposed therebetween is greater than Wm, which is the length in the long side direction of the plate-like magnet 23. In addition, an angle θm of the d axis is set. Let Wq be the distance between adjacent flux barriers 26, and let Wb be the distance from the flux barrier 26, which is the magnetic path width of the bridge portion 26, to the outer periphery of the rotor yoke 22. Note that when Wb and Wq are reduced, the magnetic resistance increases.

  As shown in FIG. 5, the excitation coil 37 of FIG. 4 includes excitation coils 37U, 37V, and 37W for three-phase excitation. The exciting coil 37U is wound around the teeth 34U. The exciting coil 37V is wound around the teeth 34V. The exciting coil 37W is wound around the teeth 34W. The exciting coils 37U, 37V, and 37W of the present embodiment are so-called Y connections. The exciting coils 37U, 37V, and 37W may be delta-connected.

(Evaluation example)
FIG. 6 is an explanatory diagram illustrating torque ripple in an evaluation example of the present embodiment. Rr, which is the outer diameter of the rotor yoke 22 of the brushless motor 10 of the above-described embodiment, is fixed to 22.7 mm, and Lm, which is the distance from the central axis Zr to the center of gravity M of the magnet 23, is changed. The change of torque ripple was evaluated. In FIG. 6, Tav indicates the average torque, and Trp indicates the torque ripple. In FIG. 6, the evaluation example evaluates the case where Lm is 16 mm, 17 mm, 18 mm, 19 mm and 20 mm. In the evaluation example, six magnets 23 are embedded in the rotor yoke 22, and Wm is 9.76 mm and tm is 2.90 mm. The magnet 23 is a magnet having a saturation magnetic flux density of 1.32 T or more and 1.37 T or less and a coercive force of 994 kA / m or more. In the evaluation example, Wb is 0.5 mm, Wq is 1.5 mm, and θm is 40 °. The interval (gap length) between the stator core 31 and the rotor yoke 22 is 0.6 mm. The number of teeth is nine. The evaluation example is a 6 pole 9 slot brushless motor.

  In FIG. 6, the horizontal axis indicates σ = Lm / Rr, which is the ratio of Lm, which is the distance from the central axis Zr to the center of gravity M of the magnet 23, to the above-mentioned Rr. The vertical axis represents average torque and torque ripple. Here, σ is the distance from the center axis Zr, which is the rotation center of the rotor yoke 22, to the outer periphery, that is, when the radius is 1, the ratio of the distance from the center axis Zr indicating the center of gravity of the magnet 23 toward the outer periphery to the radius. It is.

  As shown in FIG. 6, σ is preferably 0.70 or more and 0.87 or less. That is, M, which is the gravity center position of the magnet 23, is preferably in the range of 0.70 to 0.87 from the rotation center of the rotor yoke 22 when the radius of the rotor yoke 22 is 1. Thereby, a torque ripple can be 0.3 Nm or less. σ is more preferably 0.75 or more and 0.87 or less. Thereby, while suppressing a torque ripple to 0.30 Nm or less, an average torque shall be 2.65 Nm or more, and the fall of an average torque can be suppressed.

  As shown in FIG. 6, σ is more preferably 0.79 or more and 0.86 or less. Thereby, while suppressing a torque ripple to 0.26 Nm or less, an average torque can be made into 2.65 Nm or more, and the fall of an average torque can be suppressed. Further, σ is more preferably 0.83 or more and 0.85 or less. Thereby, while suppressing a torque ripple to 0.20 Nm or less, an average torque shall be 2.65 Nm or more, and the fall of an average torque can be suppressed.

  It is thought that torque ripple (variation in output torque) occurs because the magnetic flux density fluctuates between adjacent magnets 23 (magnetic pole switching portion), which causes vibration and noise. The brushless motor 10 of the present embodiment described above has a rotor yoke 22 whose outer periphery is arcuate, a stator core 31 arranged in an annular shape with a predetermined interval outside the rotor yoke 22, and a magnetic field for exciting the stator core 31. When the distance between the excitation coil 37 to be generated and the central axis Zr (rotation center) of the rotor yoke 22 to the outer periphery is 1, the ratio of the rotor yoke 22 having a ratio of 0.70 to 0.87 from the rotation center toward the outer periphery. And a flat plate-like magnet 23 in which the center of gravity is embedded at the position.

  With the above configuration, the brushless motor 10 according to the present embodiment suppresses a decrease in average torque, suppresses fluctuations in magnetic flux density between adjacent magnets 23 (magnetic pole switching portion), and generates vibration and noise of the rotor 20. Suppressed. Further, the rotor yoke 22 can be formed in a simple arc shape. For this reason, the brushless motor 10 can suppress an increase in manufacturing cost.

  The exciting coil 37 is preferably wound around the stator core 22 by concentrated winding. With this configuration, since the torque ripple is suppressed, vibration caused by the concentrated winding exciting coil 37 can be suppressed. If the excitation coil 37 has a concentrated winding structure, the cost can be reduced and the brushless motor 10 can be made compact.

  The electric power steering device 80 obtains auxiliary steering torque by the brushless motor 10 described above. Since the brushless motor 10 suppresses torque ripple, the electric power steering device 80 can operate in a state in which a sense of discomfort is suppressed even when the auxiliary steering torque is transmitted to the steering person. For this reason, even if the electric power steering apparatus 80 is a column assist system, it can make a low vibration.

  As described above, the electric power steering apparatus of the present embodiment has been described by taking the column assist method as an example, but it can also be applied to a pinion assist method and a rack assist method.

DESCRIPTION OF SYMBOLS 10 Brushless motor 11 Housing 11a Tubular housing 11b Front bracket 11c Bottom part 11d Inner peripheral surface 12, 13 Bearing 14 Resolver 14a Resolver rotor 14b Resolver stator 15 Terminal block 20 Rotor 21 Shaft 22 Rotor yoke 23 Magnet 30 Stator 31 Stator core 32 Divided core 33 Yoke 34 Teeth 37 Exciting coil 37a Insulator 80 Electric power steering device 81 Steering wheel 82 Steering shaft 82a Input shaft 82b Output shaft 83 Steering force assist mechanism 84, 86 Universal joint 85 Lower shaft 87 Pinion shaft 88 Steering gear 88a Pinion 88b Rack 89 Tie rod 90 ECU
91a Torque sensor 91b Vehicle speed sensor 92 Deceleration device 93 Deceleration device housing 94 Worm 94a Worm tooth 95a, 95b Ball bearing 96 Worm wheel 96a Worm wheel tooth 97 Holder 98 Ignition switch 99 Power supply Zr Central shaft

Claims (4)

A rotor yoke having an arcuate outer periphery;
A stator core disposed annularly with a predetermined interval outside the rotor yoke;
An exciting coil for generating a magnetic field for exciting the stator core;
A flat magnet embedded in the rotor yoke;
A flux barrier on both sides of the short side of the flat magnet in a virtual plane orthogonal to the central axis, and capable of suppressing or blocking the passage of magnetic flux by a through-hole penetrating the rotor yoke ,
The rotor yoke is laminated with a thin plate having no through hole in the outer peripheral portion and the inner peripheral portion of the rotor yoke that are in contact with the long side of the flat magnet in a virtual plane orthogonal to the central axis,
Arranged so that the through holes are in contact with both ends of the flat magnet,
The position of the center of gravity of the flat magnet in a virtual plane orthogonal to the central axis is 0.83 or more and 0.85 or less from the rotation center of the rotor yoke when the radius of the rotor yoke is 1. For motors. The through hole is disposed so as to contact a bridge portion between the flux barrier and the outer periphery of the rotor yoke, and a short side of the flat magnet in a virtual plane orthogonal to the central axis,
The minimum distance from the flux barrier, which is the magnetic path width of the bridge portion, to the outer periphery of the rotor yoke is equal to or greater than the thickness of the thin plate, and the long side of the flat magnet in a virtual plane perpendicular to the central axis An electric power steering motor smaller than a portion near the outer periphery of the rotor yoke in contact with the rotor yoke . The exciting coil, an electric power steering motor according to claim 1 or claim 2 are wound around the stator core by concentrated winding. An electric power steering apparatus that obtains an auxiliary steering torque by the electric power steering motor according to any one of claims 1 to 3 .

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