JP2013085407A - Brushless motor control method and brushless motor control apparatus, brushless motor, and electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor having a difference between inductance in a d-axis direction and inductance in a q-axis direction which prevents torque reduction in a high load side, and achieves improvement of the torque of the motor and reduction in the size.SOLUTION: A brushless motor 3 includes a rotor core having a polygonal cross section, and a segment magnet mounted in each side portion of the outer periphery of the rotor core, and inductance in a d-axis direction and inductance in a q-axis direction are different from each other. A control apparatus 50 of the brushless motor 3 has a current sensor 61, and a current command section 51 for calculating a winding current value according to a load state. The current command section 51 has a supply current amount calculating section 52 for performing advance angle control in a high load region in which an output torque is reduced with respect to a theoretical torque due to an influence of armature reaction, and adding a d-axis current Id' to a supply current with respect to an armature wire, and an advance angle control map 63 indicating a relationship between a phase current and an advance angle value.

Description

  The present invention relates to a torque improving technique in a brushless motor, and more particularly to a technique effective when applied to a brushless motor used as a drive source of an electric power steering apparatus (EPS).

  Generally, a brushless motor of the SPM (Surface Permanent Magnet) type with a magnet attached to the rotor surface has a d-axis (direction of magnetic flux generated by the magnetic pole (the central axis direction of the permanent magnet)) and q-axis (electrical and magnetic with the d-axis). It is considered that there is no difference in the inductance in the direction perpendicular to the axis (the axis between the permanent magnets), and the reluctance torque generated by the inductance difference between the d and q axes cannot be used. In particular, when a ring magnet is used, since the outer periphery of the rotor is covered with a uniform-width magnet, there is no difference in magnetoresistance between the d and q axes (the salient pole ratio = 1), and there is an inductance on the d and q axes. There is no difference and no reluctance torque is generated.

The total torque Tt of the brushless motor is
Tt = Magnet torque Tm + Reluctance torque Tr
= P · φa · Iq + p · (Lq−Ld) · Id · Iq
(P: number of pole pairs, φa: armature flux linkage by permanent magnet, Lq: q-axis inductance, Ld: d-axis inductance, Id: d-axis current, Iq: q-axis current)
In the SPM type motor that is expressed as follows and has no difference between the inductances Ld and Lq, the second term of the above equation is zero. Therefore, even if the d-axis current Id is applied to such a motor, the torque is not reflected at all, and a torque increase due to the reluctance torque cannot be expected.

JP 2009-72056 A

  On the other hand, in order to increase the torque of the motor, it is conceivable to increase the rotor magnetic flux by using a magnet having a high magnetic flux density such as a neodymium magnet. However, magnets using rare earths are very expensive and have problems in supplying resources, so it is desirable to suppress the amount used. For this reason, in order to increase torque without increasing the number of magnets, conventionally, measures have been taken to increase the number of turns of the winding, such as increasing the number of turns of the winding by reducing the rotor diameter, etc. Various methods for increasing the motor torque by changing the loading ratio from magnetic loading to electric loading have been proposed.

  However, when the number of winding turns is increased to obtain torque, the inductance of the coil increases accordingly. As the inductance increases, the effect of the armature reaction increases on the high load side (high current region), and as shown in FIG. 11, a so-called torque droop occurs, and the actual torque (flux × current) is actually increased. The resulting torque will be low. If the torque droop occurs, the motor efficiency decreases, and it is necessary to supply more phase current in order to obtain the same torque as the theoretical torque. For example, in order to obtain a torque of 4.0 Nm in the motor shown in FIG. 11, a current of nearly 100 A is actually required due to the torque, although theoretically just over 80 A is sufficient.

  Therefore, if the axial length is increased to compensate for the torque droop and the magnetic flux is increased, the motor becomes larger, and when an expensive magnet such as a neodymium magnet is used, the amount of magnet increases and the cost increases. In order to make it less susceptible to the effects of armature reaction, the inductance can be reduced. To reduce the inductance while maintaining the torque, the number of turns can be reduced, the shaft length can be increased, and the stator magnetic flux density can be reduced. It is necessary to increase the teeth width, which is also not preferable because the motor size increases.

  SUMMARY OF THE INVENTION An object of the present invention is to prevent torque droop on the high load side in a motor having a difference in inductance between the d-axis direction and the q-axis direction, and to improve the motor torque and reduce the size.

  A brushless motor control method according to the present invention includes a stator having a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator, and is formed by the permanent magnet. A method for controlling a brushless motor having a difference between an inductance in the d-axis direction and an inductance in the q-axis direction of a magnetic path, in which the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction And a lead angle control for adding a d-axis current Id to the supply current to the armature winding, and in the high load region, the magnet torque due to the magnetic attractive force of the permanent magnet and the inductance difference of the magnetic path The rotor is rotated by a reluctance torque based on the above.

  In the present invention, the advance angle control is performed in a high load region for a brushless motor having different inductances in the d-axis direction and the q-axis direction, and the rotor is rotated by the magnet torque and the reluctance torque. As a result, torque is increased in the torque droop region, and the torque performance of the brushless motor is improved. Further, as the motor torque is improved, the same torque can be obtained with a motor having a smaller physique, and the motor can be reduced in size and weight.

  In the brushless motor control method, the rotor includes a rotor core having a polygonal cross section, and a segment magnet attached to each side portion of the outer periphery of the rotor core, and a d-axis along the central axis direction of the segment magnet You may use what has a difference between the direction inductance and the q-axis inductance passing through the rotor core apex portion between the segment magnets. Further, the advance angle control may be performed only in the high load region and may not be performed in the low load region where the influence of the armature reaction is small and the output torque does not decrease much with respect to the theoretical torque. Furthermore, the brushless motor may be a motor used as a drive source of the electric power steering apparatus.

  A brushless motor control device according to the present invention includes a stator including a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator, and is formed by the permanent magnet. A control device for controlling the driving of a brushless motor having a difference between an inductance in the d-axis direction and an inductance in the q-axis direction of a magnetic path, wherein the current sensor detects a phase current of the armature winding; A current command unit that calculates a winding current value supplied to the brushless motor according to a load state of the brushless motor, and the current command unit is based on a phase current value detected by the current sensor. Then, advance angle control is performed in a high load region where the output torque decreases with respect to the theoretical torque due to the effect of the armature reaction, and the d-axis current Id is added to the supply current to the armature winding Characterized in that it has a supply current calculation section for.

  In the present invention, the advance angle control is performed in the high load region by the supply current calculation unit for the brushless motor in which the inductance in the d-axis direction and the inductance in the q-axis direction are different, and the rotor is generated by magnet torque and reluctance torque Rotate. As a result, torque is increased in the torque droop region, and the torque performance of the brushless motor is improved. Further, as the motor torque is improved, the same torque can be obtained with a motor having a smaller physique, and the motor can be reduced in size and weight.

  In the brushless motor control device, an advance angle control map showing a relationship between the phase current and an advance value β in the advance angle control may be arranged in the current command unit. The rotor includes a rotor core having a polygonal cross section, and a segment magnet attached to each side portion of the outer periphery of the rotor core, and an inductance in the d-axis direction along the central axis direction of the segment magnet; You may use what has a difference with the q-axis inductance which passes along the said rotor core apex angle part between the said segment magnets. Furthermore, the brushless motor may be a motor used as a drive source of the electric power steering apparatus.

  A brushless motor of the present invention is a brushless motor having a stator having armature windings of a plurality of phases, and a rotor in which permanent magnets are arranged and rotatably arranged inside the stator. A rotor core having a polygonal cross section, and a segment magnet attached to each side portion of the outer periphery of the rotor core, and an inductance in the d-axis direction along the central axis direction of the segment magnet, Supply to the armature winding in a high load region in which there is a difference between the q-axis inductance passing through the rotor core apex angle portion and the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction Lead angle control is performed to add the d-axis current Id to the current, and the magnetic attraction force of the permanent magnet is increased in the high load region. A magnet torque that said rotor by the reluctance torque based on the inductance difference of the magnetic path is characterized by rotating.

  The brushless motor of the present invention includes a rotor core having a polygonal cross section and segment magnets attached to each side portion of the outer periphery of the rotor core, and the advance angle control is performed in a high load region, and the magnet The rotor rotates with torque and reluctance torque. As a result, torque can be increased in the torque droop region, and the motor torque can be increased without increasing the phase current, without increasing the shaft length, or increasing the tooth width. Further, as the motor torque is improved, the same torque as before can be obtained with a smaller physique, and the motor can be reduced in size and weight.

  On the other hand, an electric power steering apparatus according to the present invention includes a stator having a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator. An electric power steering apparatus using, as a drive source, a brushless motor having a difference between an inductance in a d-axis direction and an inductance in a q-axis direction of a magnetic path to be formed, wherein the brushless motor is influenced by an armature reaction In the high load region where the output torque decreases with respect to the theoretical torque, the advance angle control is performed to add the d-axis current Id to the supply current to the armature winding, and in the high load region, the permanent torque The rotor is rotated by the magnet torque generated by the magnetic attraction force of the magnet and the reluctance torque based on the inductance difference of the magnetic path. And butterflies.

  In the electric power steering apparatus of the present invention, in the electric power steering apparatus, a brushless motor having a different inductance in the d-axis direction and an inductance in the q-axis direction is used as a drive source, and advance angle control is performed in a high load region. Thus, the rotor is rotated by the magnet torque and the reluctance torque. As a result, torque is increased in the torque droop region, and the burden on the driver at the time of stationary is reduced, and the EPS motor is reduced in size and weight.

  According to the brushless motor control method and the control device of the present invention, a lead angle control is performed in a high load region for a brushless motor having a different d-axis inductance and q-axis inductance, and a magnet torque and a reluctance torque are obtained. Therefore, the torque is increased in the torque droop region, and the torque performance of the brushless motor can be improved. Further, as the motor torque is improved, the same torque can be obtained with a motor having a smaller physique, and the motor can be reduced in size and weight.

  According to the brushless motor of the present invention, the rotor core having a polygonal cross section and the segment magnets attached to the respective sides of the outer periphery of the rotor core, the advance angle control is performed in the high load region, and the magnet Since the rotor is rotated by the torque and the reluctance torque, the torque can be increased in the torque droop region, and the torque performance of the motor can be improved. Further, as the motor torque is improved, the same torque can be obtained with a smaller physique, and the motor can be reduced in size and weight.

  According to the electric power steering apparatus of the present invention, a brushless motor having a d-axis direction inductance and a q-axis direction inductance different from each other is used as a drive source, and the advance angle is increased in a high load region during the drive control of the brushless motor. Since the rotor is rotated by the magnet torque and the reluctance torque, the torque is increased in the torque droop area, reducing the burden on the driver during stationary operation, and reducing the EPS motor size and weight. Is possible.

It is explanatory drawing which shows the structure of EPS using a brushless motor. It is sectional drawing which shows the structure of the brushless motor used by EPS of FIG. It is explanatory drawing which shows the structure of a stator core and a rotor. It is explanatory drawing which shows the structure of the d-axis direction and the q-axis direction in the brushless motor of FIG. It is a block diagram which shows the structure of the control apparatus in EPS of FIG. (A) is explanatory drawing which shows the relationship between d-axis current Id, q-axis current Iq, and advance angle value (beta), (b) is explanatory drawing which shows an example of an advance angle control map. It is the graph which compared the torque value when not performing with advance angle control. It is a graph which shows the change of the torque ripple when Id is made to make Iq at the time of high load constant. It is the graph which showed the change of the number of rotations when not carrying out advance angle control. It is explanatory drawing which shows the modification of a stator core. It is explanatory drawing which shows the modification of a stator core.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of an EPS using a brushless motor, and a control process according to the present invention is performed. An electric power steering device (EPS) 1 shown in FIG. 1 has a column assist type structure that applies an operation assisting force to a steering shaft 2, and a brushless motor 3 (hereinafter abbreviated as a motor 3) serves as a power source. It is used.

  A steering wheel 4 is attached to the steering shaft 2, and the steering force of the steering wheel 4 is transmitted to the tie rod 6 via a pinion and a rack shaft (not shown) disposed in the steering gear box 5. Wheels 7 are connected to both ends of the tie rod 6, and the tie rod 6 is operated in accordance with the operation of the steering wheel 4, and the wheels 7 are steered left and right via a knuckle arm or the like (not shown).

  In the EPS 1, an assist motor unit 8 that is a steering force assist mechanism is provided on the steering shaft 2. The assist motor unit 8 includes a motor 3 and a speed reduction mechanism unit 9 and a torque sensor 11. A worm and a worm wheel (not shown) are arranged in the speed reduction mechanism section 9, and the rotation of the motor 3 is decelerated and transmitted to the steering shaft 2 by the speed reduction mechanism section 9. The motor 3 and the torque sensor 11 are connected to a control device (ECU) 12.

  When the steering wheel 4 is operated and the steering shaft 2 rotates, the torque sensor 11 is activated. The ECU 12 appropriately supplies electric power to the motor 3 based on the torque detected by the torque sensor 11. When the motor 3 is actuated, the rotation is transmitted to the steering shaft 2 via the speed reduction mechanism unit 9 and a steering assist force is applied. The steering shaft 2 is rotated by the steering assist force and the manual steering force, and this rotational motion is converted into a linear motion of the rack shaft by rack-and-pinion coupling in the steering gear box 5, and the steering operation of the wheels 7 is performed. Is done.

  FIG. 2 is a cross-sectional view showing the configuration of the motor 3. As shown in FIG. 2, the motor 3 is an inner rotor type brushless motor having a stator 21 on the outside and a rotor 22 on the inside. The stator 21 includes a housing 23, a stator core 24 fixed to the inner peripheral side of the housing 23, and a winding 25 wound around the stator core 24. The housing 23 is formed of iron or the like into a bottomed cylindrical shape, and a synthetic resin bracket 30 is attached to the opening. The stator core 24 has a structure in which a large number of steel plates are laminated, and a plurality of teeth protrude from the inner peripheral side of the stator core 24. The stator core 24 is skewed so that the induced voltage waveform of the winding 25 is a sine wave. The skew may be formed on the rotor 22 side.

  FIG. 3 is an explanatory diagram showing the configuration of the stator core 24 and the rotor 22. The stator core 24 is formed of a ring-shaped yoke portion 26 and teeth 27 that are formed so as to protrude inward from the yoke portion 26. Nine teeth 27 are provided, slots 28 (9) are formed between the teeth 27, and the motor 3 has a nine-slot configuration. A winding 25 is wound around each tooth 27 by concentrated winding, and the winding 25 is accommodated in each slot 28. Each winding 25 is star-connected in three phases of U, V, and W, and is connected to a battery (not shown) via a power supply wiring 29. The winding 25 is supplied with trapezoidal phase currents (U, V, W) including harmonic components.

  The rotor 22 is disposed inside the stator 21 and has a configuration in which a rotating shaft 31, a rotor core 32, and a magnet 33 are arranged coaxially. A rotor core 32 in which many steel plates are laminated is attached to the outer periphery of the rotating shaft 31. The rotor core 32 is formed in a hexagonal cross section, and a segment type magnet 33 is arranged on each side portion 32a on the outer periphery thereof. The magnets 33 are attached to a magnet holder 34 fixed to the rotating shaft 31, and six magnets 33 are arranged along the circumferential direction. That is, the motor 3 has a 6-pole 9-slot configuration.

  One end of the rotating shaft 31 is rotatably supported by a bearing 35 press-fitted into the bottom of the housing 23. The other end of the rotating shaft 31 is rotatably supported by a bearing 36 attached to the bracket 30. A spline portion 37 is formed at an end portion (left end portion in FIG. 2) of the rotating shaft 31, and is connected to the worm shaft of the speed reduction mechanism portion 9 by a joint member (not shown). A worm is formed on the worm shaft and meshes with a worm wheel fixed to the steering shaft 2 by the speed reduction mechanism unit 9.

  The bracket 30 accommodates a bearing 36 and a resolver (angle sensor) 41 that detects the rotational position of the rotor 22. The resolver 41 includes a resolver stator 42 fixed to the bracket 30 side and a resolver rotor 43 fixed to the rotor 22 side. A coil 44 is wound around the resolver stator 42, and an excitation coil and a detection coil are provided. A resolver rotor 43 is disposed inside the resolver stator 42. The resolver rotor 43 has a structure in which metal plates are laminated, and has convex portions in three directions.

  When the rotating shaft 31 rotates, the resolver rotor 43 also rotates in the resolver stator 42. A high frequency signal is applied to the exciting coil of the resolver stator 42, and the phase of the signal output from the detection coil changes due to the proximity of the convex portion. The rotational position of the rotor 22 is detected by comparing the detection signal with the reference signal. Then, based on the rotational position of the rotor 22, the current to the winding 25 is appropriately switched, and the rotor 22 is rotationally driven.

  In such EPS1, when the steering wheel 4 is operated and the steering shaft 2 is rotated, the rack shaft is moved in a direction corresponding to the rotation, and a steering operation is performed. By this operation, the torque sensor 11 is activated, and electric power is supplied from the battery (not shown) to the winding 25 via the power supply wiring 29 according to the detected torque. When electric power is supplied to the winding 25, the motor 3 operates and the rotating shaft 31 and the worm shaft rotate. The rotation of the worm shaft is transmitted to the steering shaft 2 via the worm wheel to assist the steering force.

Here, the total torque Tt of the motor 3 is as described above.
Tt = Tm + Tr
= P · φa · Iq + p · (Lq−Ld) · Id · Iq
Conventionally, in an SPM motor such as the motor 3, there is no difference in inductances Ld and Lq, and the second term in the above equation is 0, so it has been considered that reluctance torque cannot be used. In contrast, in the SPM motor in which the segment magnet is arranged on the outer peripheral surface of the rotor core having a polygonal cross section, the present inventors have an inductance difference between the d-axis direction and the q-axis direction, unlike a motor using a ring magnet. I thought about this, and examined whether it could be used to increase torque.

  As shown in FIG. 4, in the motor 3, between the teeth 27 in the d-axis direction (the central axis direction of the magnet 33) and the q-axis direction (the direction connecting the rotor center and the apex portion 32 b of the rotor core 32). The sizes of the gaps 20 formed in (1) are different (radial length S1: d-axis direction, S2: q-axis direction). Since the magnetic permeability of the magnet 33 is equivalent to that of air, in the motor 3, the magnetoresistance in the q-axis direction where the rotor core 32 (using a silicon steel plate) is large is smaller than that in the d-axis direction. That is, the q-axis inductance Lq is larger than the d-axis inductance Ld (Lq> Ld), and there is a difference in the d · q-axis inductance. Therefore, the motor 3 can increase the torque by taking the positive value of the second term of the above equation, performing the advance angle control, and applying Id.

  FIG. 5 is a block diagram showing the configuration of the control device 50 of the EPS 1, and the advance angle control according to the present invention is executed by the control device 50. The control device 50 is provided with a current command unit 51, and EPS 1 is a value detected from the torque sensor 11 input to the current command unit 51, rotational position information of the rotor 22 detected by the resolver 41, current Drive control is performed based on phase current value information from the sensor 61.

  As shown in FIG. 5, the motor load (torque value) accompanying the operation of the steering wheel 4 is input from the torque sensor 11 to the control device 50 as motor load information. Further, the rotor rotational position information is input to the current command unit 51 from the resolver 41 provided in the motor 3. The rotor rotational position information from the resolver 41 is also input to the rotor rotational speed calculation unit 62 provided in the previous stage of the current command unit 51, and the rotor rotational speed calculation unit 62 is based on the rotor rotational position information. The rotational speed of 22 is calculated, and the value is input to the current command unit 51 as rotor rotational speed information. Further, the motor 3 is provided with a current sensor 61 that monitors the supply current of each phase, and the phase command value of the motor 3 is input from the current sensor 61 to the current command unit 51.

  The current command unit 51 is provided with a supply current amount calculation unit 52 that performs arithmetic processing based on these detection values and calculates the amount of current supplied to the motor 3. The supply current amount calculation unit 52 calculates the current command values Id ′ and Iq ′ for the d-axis and the q-axis from the rotor rotation position information, the rotor rotation number information, and the motor load information from the resolver 41, and the vector control unit 53 Output. Further, the phase current value of the motor 3 is fed back from the current sensor 61 to the supply current amount calculation unit 52, and the supply current amount calculation unit 52 applies to the motor 3 based on the detected current value (phase current). Advance angle control is performed and the current command value Id ′ is set. The relationship between the phase current value and the advance value β is stored in the advance angle control map 63, and the supply current amount calculation unit 52 refers to the advance angle control map 63 to determine the current command value Id ′. .

  FIG. 6A is an explanatory diagram showing the relationship between the d-axis current Id, the q-axis current Iq and the advance value β, and FIG. 6B is an explanatory diagram showing an example of the advance control map 63. As shown in the dq axis vector diagram of FIG. 6A, the advance value β varies depending on the values of Iq and Id. The combined vector of Iq and Id is Ia, and if the effective value of the phase current (U phase) is Iu, there is a relationship of Ia = √3 × Iu between Ia and Iu. In the motor 3, the advance value β is set as shown in FIG. 6B so that Id is added in the high current region. It should be noted that setting may be made such that Id is added in the entire current range, but since no torque drift occurs in the low current range, in this embodiment, as much Id as necessary within the required range is provided to reduce the control load. The advance value β is set in such a way as to add.

  The vector control unit 53 includes d-axis and q-axis PI (proportional / integral) control units 54d and 54q, and a coordinate axis conversion unit (dq / UVW) 55, and current command values Id 'and Iq' are , Input to the PI control units 54d and 54q, respectively. The PI control units 54d and 54q have detection current values I (d) and I (I () obtained by dq-axis conversion of three-phase (U, V, W) motor current values via a coordinate axis conversion unit (UVW / dq) 56. q) has been entered. The PI control units 54d and 54q perform PI calculation processing based on the current command values Id ′ and Iq ′ and the detected current values I (d) and I (q), and voltage command values Vd and Vq for the d and q axes. Is calculated. The voltage command values Vd, Vq are input to the coordinate axis converter 55, converted into three-phase (U, V, W) voltage command values Vu, Vv, Vw and output. The voltage command values Vu, Vv, Vw output from the coordinate axis conversion unit 55 are applied to the motor 3 via the inverter 57.

  In such a motor 3, the salient pole ratio ≠ 1 due to the configuration in which the segment magnet is arranged on the rotor 22 having a polygonal cross section, and the reluctance that has not been used in the conventional SPM motor by using the inductance difference between Ld and Lq. Use torque to increase torque. In particular, by performing advance angle control in a high load region (high current region) where torque sagging occurs and applying Id, the torque reduction due to torque sagging can be reduced by reluctance torque without increasing the control load in the normal load region. To compensate. FIG. 7 is a graph comparing the torque values when the advance angle control is performed and when the advance angle control is not performed. The experiment is performed such that the torque at Max 85 Arms is approximately equal to the theoretical torque in FIG. Results are shown.

  As shown in FIG. 7, in the case of no advance angle control, torque drooping starts around the phase current 50 Arms. On the other hand, in the control according to the present invention, the advance value is gradually increased from the time when 30 Arms has passed, and the change amount is maximized around 50 Arms to increase Id. As a result, in the case of the advance angle control, the reluctance torque compensates for the torque droop from around the phase current of 50 Arms, and with the increase of the phase current, the torque increases to almost the same as the theoretical torque, eliminating the problem of drooping torque. We were able to.

  As described above, in the control processing according to the present invention, the lead angle control is introduced in a high load region in which the so-called torque droop in which the actual output torque decreases with respect to the theoretical torque due to the armature reaction, and the supply current to the winding 25 is Is added with d-axis current Id. As a result, reluctance torque is added to magnet torque in the torque droop region, and torque is increased. At this time, in the present invention, since the value of the phase current is adjusted only by the advance angle control, the motor torque can be increased without increasing the phase current. Further, if the same torque is obtained as the motor torque is improved, a motor having a smaller physique is sufficient, and the motor can be reduced in size and weight. Further, since it is not necessary to increase the shaft length or widen the teeth width when increasing the torque, the motor size is not increased. In particular, when the present invention is applied to an EPS motor, the maximum torque of the motor is increased, so that it is possible to reduce the burden on the driver at the time of stationary. In addition, the EPS motor can be reduced in size and weight, which contributes to a reduction in vehicle weight and fuel consumption.

On the other hand, if Id is increased, the reluctance torque is increased by that amount. However, if Id is excessively increased, a torque ripple is increased. FIG. 8 is a graph showing a change in torque ripple when Id is applied with a constant Iq at a high load, and how the torque ripple is increased when Id is increased by changing the advance angle β. The result of verifying whether it has changed to is shown. As shown in FIG. 8, when Iq = 147A is constant, the torque ripple increases when Id exceeds 30A. This means that the torque ripple increases when the advance angle β = 11.5 degrees (tan ⁻¹ β = 30/147). That is, torque ripple tends to increase as Id increases with respect to the ratio of Iq, and it can be seen from the results of FIG. 8 that the advance angle is preferably suppressed to about 10 °.

  Further, in the control mode in which the advance angle control is performed in the high load region as in this embodiment, there is almost no change in the rotational speed. FIG. 9 is a graph showing changes in the rotational speed when the advance angle control is performed and when it is not performed. In FIG. 9, the advance angle control is started in the vicinity of the phase current 40 Arms, but the subsequent motor rotation speed is almost the same as the case without the advance angle control. Therefore, in the control mode according to the present invention, it is easy to manage the torque and the rotational speed. For example, if the control is applied to the pump drive motor, the maximum discharge amount can be increased while maintaining the rotational speed, and the operation efficiency of the pump is increased. There is an advantage that it is possible to improve. Note that if the advance angle control is performed in the low load region, the rotational speed tends to be too high, and only in the high load region where the actual output torque decreases with respect to the theoretical torque due to the armature reaction, including the viewpoint of reducing the control load. It is desirable to perform the advance angle control.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example in which the present invention is applied to an SPM type brushless motor has been described. However, the present invention can be applied to any brushless motor that can use a reluctance torque based on an inductance difference between magnetic paths. Of course, the present invention can also be applied to an ordinary IPM (Interior Permanent Magnet) type motor. Further, the shape of the rotor core is not limited to that having a regular polygonal cross section as shown in FIG. 3 as long as an inductance difference occurs between the d-axis direction and the q-axis direction. For example, as shown in FIG. 10, the present invention can also be applied to a core-shaped motor having protrusions between magnets.

  Furthermore, in the above-described embodiment, the example in which the present invention is applied to the EPS has been shown. However, the application target is not limited to the EPS, and various industries such as electric vehicles, hybrid vehicles, home appliances such as air conditioners, and pumps. The present invention can also be applied to a motor used in a machine or the like.

1 Electric power steering system (EPS)
2 Steering shaft 3 Brushless motor 4 Steering wheel 5 Steering gear box 6 Tie rod 7 Wheel 8 Assist motor unit 9 Deceleration mechanism unit 11 Torque sensor 12 Control device (ECU)
20 Air gap 21 Stator 22 Rotor 23 Housing 24 Stator core 25 Winding 26 Joint portion 27 Teeth 28 Slot 29 Power supply wiring 30 Bracket 31 Rotating shaft 32 Rotor core 32a Each side portion 32b Vertical corner portion 33 Magnet 34 Magnet holder 35 Bearing 36 Bearing 37 Spline Unit 41 Resolver 42 Resolver stator 43 Resolver rotor 44 Coil 50 Control device 51 Current command unit 52 Supply current amount calculation unit 53 Vector control unit 54d, 54q PI control unit 55 Coordinate axis conversion unit (dq / UVW)
56 Coordinate axis converter (UVW / dq)
57 Inverter 61 Current sensor 62 Speed calculator 63 Lead angle control map Id d-axis current Iq q-axis current Id ′, Iq ′ current command value Ld d-axis inductance Lq q-axis inductance S1 radial length S2 of the gap in the d-axis direction q-axis radial gap length Tt Total torque Tm Magnet torque Tr Reluctance torque β Lead angle

Claims (10)

A stator having a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator, and an inductance in a d-axis direction of a magnetic path formed by the permanent magnet And a method of controlling a brushless motor having a difference between the inductance in the q-axis direction,
In the high load region where the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction, advance angle control is performed to add the d-axis current Id to the supply current to the armature winding, and in the high load region A control method for a brushless motor, wherein the rotor is rotated by a magnet torque generated by a magnetic attraction force of the permanent magnet and a reluctance torque based on an inductance difference of a magnetic path. The brushless motor control method according to claim 1, wherein the rotor includes a rotor core having a polygonal cross section, and segment magnets attached to respective side portions of the outer periphery of the rotor core,
Control of a brushless motor, wherein there is a difference between an inductance in a d-axis direction along a central axis direction of the segment magnet and a q-axis inductance passing through the rotor core apex angle portion between the segment magnets Method.   3. The brushless motor control method according to claim 1, wherein the advance angle control is performed only in the high load region.   4. The brushless motor control method according to claim 1, wherein the brushless motor is used as a drive source of an electric power steering apparatus. 5. A stator having a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator, and an inductance in a d-axis direction of a magnetic path formed by the permanent magnet And a control device that performs drive control of a brushless motor having a difference between the inductance in the q-axis direction,
A current sensor for detecting a phase current of the armature winding;
A current command unit that calculates a winding current value supplied to the brushless motor according to a load state of the brushless motor;
The current command unit performs advance angle control in a high load region where the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction based on the phase current value detected by the current sensor, and the armature A brushless motor control device comprising a supply current calculation unit for adding a d-axis current Id to a supply current for a winding.   6. The brushless motor control apparatus according to claim 5, wherein the current command unit includes an advance angle control map showing a relationship between the phase current and an advance value β in the advance angle control. Control device. The brushless motor control device according to claim 5 or 6, wherein the rotor includes a rotor core having a polygonal cross section, and a segment magnet attached to each side portion of the outer periphery of the rotor core,
Control of a brushless motor, wherein there is a difference between an inductance in a d-axis direction along a central axis direction of the segment magnet and a q-axis inductance passing through the rotor core apex angle portion between the segment magnets apparatus.   8. The brushless motor control device according to claim 6, wherein the brushless motor is used as a drive source of an electric power steering device. A brushless motor having a stator provided with a multi-phase armature winding, and a rotor in which a permanent magnet is arranged and rotatably arranged inside the stator,
The rotor includes a rotor core having a polygonal cross section, and a segment magnet attached to each side portion of the outer periphery of the rotor core, the inductance in the d-axis direction along the central axis direction of the segment magnet, There is a difference between q-axis inductance passing through the rotor core apex portion between the segment magnets,
In the high load region where the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction, the advance angle control is performed to add the d-axis current Id to the supply current to the armature winding, and the high load region A brushless motor in which the rotor is rotated by a magnet torque generated by a magnetic attraction force of the permanent magnet and a reluctance torque based on an inductance difference between magnetic paths. A stator having a plurality of phases of armature windings, and a rotor in which a permanent magnet is disposed and rotatably disposed inside the stator, and an inductance in a d-axis direction of a magnetic path formed by the permanent magnet And an electric power steering device using a brushless motor having a difference between the inductance in the q-axis direction as a drive source,
The brushless motor is subjected to advance angle control in which a d-axis current Id is added to the supply current to the armature winding in a high load region where the output torque decreases with respect to the theoretical torque due to the influence of the armature reaction. In the high load region, the electric power steering device is characterized in that the rotor is rotated by a magnet torque due to a magnetic attractive force of the permanent magnet and a reluctance torque based on an inductance difference between magnetic paths.

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