JP2006050709A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize an electric power steering device which is small and has a high output torque and can realize lower cogging torque. <P>SOLUTION: This electric power steering device rotates an output shaft with a motor, based on the torque detected by a torque detection means interposed between an input shaft coupled with a handle and an output shaft coupled with a steering mechanism. The motor 5 comprises a stator 6, where coils 9 and 10 are wound on each of two or more salient poles 13 and 14 provided in the stator core 8 and a rotor 7, where more permanent magnets 18 than the above salient poles 13 and 14 are arranged to a rotor core 17 at equal intervals in the circumferential direction. Also, the salient poles 13 constitute one or more salient pole groups 11 which have, by the amount of two or more phases, groups I, II, and III, each consisting of two or more salient poles 13 where the coils 9 of application of the same phase of voltage are wound and the winding directions of the coils 9 on adjacent salient poles 13 are of reverse direction to each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus that achieves a small size, high output torque, and low cogging torque.

  2. Description of the Related Art Conventionally, an electric power steering apparatus configured to assist a steering force by a steering wheel with a driving force of a motor is known, and has started to be widely used in light cars, and is being applied to small cars. In addition, since ordinary vehicles (medium / large vehicles) with a large body weight require a large steering force, hydraulic power steering devices are widely used at present. However, in recent years, energy saving and weight reduction due to environmental problems, vehicles From the standpoint of improving the layout performance, etc., there is a demand for the development of an electric power steering device that is highly efficient, can be miniaturized, and does not complicate the layout due to piping or the like.

  However, in the electric power steering device for a light vehicle, a commutator motor that does not require an inverter is used in terms of cost. However, since the commutator motor has a winding on the rotor, the mass increases and the handle There is a problem that the feeling of operation is not good, and the efficiency is 60%, which is inferior to the brushless motor of 90%, so it is difficult to apply to ordinary cars. In addition, a normal vehicle requires a large steering force as described above, and the output torque required for the motor is large. Therefore, in a normal 12V or 24V power supply specification, the current becomes large, and the capacity of the control switching element becomes large. There is a problem that it becomes large and expensive.

  For this reason, a motor for an electric power steering apparatus that can be applied to an ordinary vehicle needs a small size, large torque, high efficiency, and low current driving technology. As a motor miniaturization technique, there are IPM (Interior Permanent Magnet) equipped with a permanent magnet embedded rotor, brushless, and concentrated winding. However, the concentrated winding IPM is difficult to apply to the electric power steering apparatus because the cogging torque becomes large.

  Therefore, in a conventional electric power steering apparatus, a multi-pole SPM (Surface Permanent Magnet) brushless motor in which a large number of permanent magnets are arranged on the surface of a rotor core is applied in order to achieve a low cogging torque.

Further, in an electric power steering apparatus that detects a steering torque with a torque sensor and controls the driving force of the motor based on the detected steering torque, an IPM brushless motor is used as the motor, and the rotation speed reaches a predetermined range. In such a case, it is known that field-weakening control is performed to prevent a sudden decrease in output torque in a high-speed rotation range corresponding to high-speed steering (see, for example, Patent Document 1).
JP 2002-345281 A

  However, in the configuration in which the multipole SPM motor is applied, there is a problem that the stator winding space is reduced due to the increase in the number of poles, and the physique is increased in order to secure the torque in order to reduce the torque. Moreover, since the demagnetization tolerance of the permanent magnet arranged on the rotor surface is small, there is a problem that the field weakening cannot be applied to a large extent and the torque cannot be reduced in the high speed range. In addition, since the SPM motor has a structure in which a permanent magnet is bonded to the rotor surface, the reliability of bonding becomes an issue, and as a countermeasure against magnet peeling or cracking, a pipe (can) made of a thin plate such as SUS on the outer surface of the rotor. ) Is shrink-fitted, or a glass cloth or other reinforced structure is used to reduce the efficiency due to the eddy current flowing in the can, the motor efficiency decreases due to the wide air gap, the size increases, There are also problems such as increased costs due to complexity and an increase in the number of parts.

  In addition, the electric power steering apparatus using the IPM brushless motor disclosed in Patent Document 1 is applicable to ordinary vehicles that require a high-class feeling because the cogging torque is large as described above and the steering wheel feels poor. In addition, if distributed winding is used instead of concentrated winding in order to reduce the cogging torque, there is a problem that the size cannot be reduced and the cogging torque and the size cannot be reduced.

  In view of the above-described conventional problems, an object of the present invention is to provide an electric power steering apparatus that is small in size, has a high output torque, can achieve a low cogging torque, and can improve controllability.

  The electric power steering apparatus according to the present invention is an electric power steering apparatus in which a steering force is increased or decreased by a motor. The motor includes a stator in which a winding is wound around each of a plurality of salient poles provided on the stator core, and the protrusion on the rotor core. It is composed of a rotor in which a larger number of permanent magnets are arranged at equal intervals in the circumferential direction than the number of poles, and the salient poles are wound around windings to which in-phase voltage is applied and adjacent to each other. One or a plurality of salient pole groups having a plurality of phases corresponding to groups of a plurality of salient poles whose winding directions are opposite to each other are formed.

  According to this configuration, the concentrated winding stator can secure a high output torque with a compact configuration, and since the number of rotor poles is larger than the number of salient poles, the cogging torque can be reduced and controllability is improved. A small size, high output torque, low cogging torque and improved controllability can be realized, and characteristics required for an electric power steering device can be satisfied.

  In addition, the salient pole is a group of a plurality of salient poles in which windings to which in-phase voltage is applied are wound and winding directions of adjacent salient pole windings are opposite to each other. It consists of a first salient pole group having several minutes and one or more salient poles located between mutually different phase salient pole groups in the first salient pole group, and adjacent when there are a plurality of salient poles. One or a plurality of second salient pole groups each having a plurality of salient poles whose winding directions of the windings of the salient poles are opposite to each other are formed, and the first salient pole group Also, a separate drive circuit may be provided for the second salient pole group.

  According to this configuration, the rotor has a large number of poles, and can be configured to effectively use the space generated between the salient poles. In addition to the above effects, the volume efficiency is further increased and the cogging torque is further reduced. Can do.

  In addition, if the configuration has a plurality of salient pole groups and a separate drive circuit is provided for each salient pole group, the function of the electric power steering device is completely achieved even if one of the drive circuits fails. There is no fear of losing it, and its reliability can be improved.

  In addition, if the current applied to the windings of the salient pole group is weakened and the field control is performed according to the detected torque or speed requirement of steering, a high output torque can be obtained with a small current by increasing the number of turns of the winding, and a small capacity. An inverter using an inexpensive switching element can be adopted, and the cost can be reduced.

  In addition, if the permanent magnet of the rotor is embedded in the rotor core, reluctance torque can be used and high output torque can be obtained, the demagnetization resistance is large, and field weakening control can be greatly applied. In addition, an inverter using an inexpensive switching element can be employed, and the cost can be reduced, and a required torque can be secured even in a high-speed rotation range.

  In addition, the number of phases is set to three phases of U, V, and W, and the number of winding groups in which three groups around which the windings are wound is one, and the number of salient poles of one group of salient pole groups. Or, the sum of the number of salient poles of one group in the first and second salient pole groups is n, k is a positive integer, the total number T of salient poles is T = 3 × s × n, and the pole number of the rotor is P If P is 2 × (s (± 1 + 3k)) and P is the smallest P larger than T, the volumetric efficiency can be increased and the cogging torque can be minimized, which is particularly effective for the electric power steering apparatus.

  Further, when energization control is performed on the windings wound around the salient poles of the first salient pole group using the output signal from the windings wound around the salient poles of the second salient pole group, the encoder and the like are expensive. High accuracy by detecting the rotational phase accurately and without performing any error due to mounting, which would be a problem when using a detection device such as an encoder. Controllability can be ensured.

  Further, the control signal is corrected by correcting the output signal from the winding wound around one of the second salient pole groups based on the magnetic coupling coefficient with the winding wound around the other salient pole. When the energization control is performed on the windings that are generated and wound around the salient poles of the first salient pole group based on this control signal, the rotational phase can be accurately detected without providing an expensive device such as an encoder. Based on this, sinusoidal control of the applied current to the winding can be performed, and high efficiency and controllability can be ensured.

  In addition, when a plurality of salient pole groups are provided and groups of salient salient poles in the same phase are arranged at an electrical angle of 360 °, a radial balance of forces acting on the rotor in a motor provided with a plurality of winding groups can be obtained. Smooth rotation can be obtained easily and stably.

  In addition, if the spacing between the salient poles in each group of salient poles is set to be approximately the same as the spacing between the permanent magnets of the rotor, the phases of the salient poles and the permanent magnets match, so there is no phase shift and high torque. And good controllability up to high speed can be obtained.

  In addition, the interval between the salient poles in each group of salient pole groups is set to be approximately the same as the arrangement interval of the permanent magnets of the rotor and the interval given by (360 ° / total salient pole number). The cogging torque can be reduced and controllability at high speed can be ensured in a well-balanced manner.

  In addition, when a plurality of salient pole groups are provided, the windings of the salient poles of the same group in each salient pole group are connected in series, and the windings of the same phase group are connected in parallel between the salient pole groups, the in-phase windings The return current between the wires can be prevented, and the winding diameter with respect to the necessary winding impedance can be reduced by parallel connection between the salient pole groups, and the winding work can be facilitated.

  In addition, since the power steering device of the present invention is low cogging, there is no sense of incongruity even when the motor is not controlled, and the motor and the output shaft can be coupled without a clutch, and the configuration is This simplifies the cost reduction.

  According to the electric power steering device of the present invention, the concentrated winding stator can ensure a high output torque with a compact configuration and can reduce the cogging torque because the number of rotor poles is larger than the number of salient poles. Improved controllability, small size, high output torque, low cogging torque, improved controllability, and improved reliability through IPM, satisfying the characteristics required for electric power steering devices it can.

  Hereinafter, each embodiment of the electric power steering apparatus of the present invention will be described with reference to FIGS.

(First embodiment)
First, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes an output shaft having one end connected to a steering mechanism (not shown) and the other end connected to a handle (steering wheel) (not shown) via a torsion bar 2. (Not shown). Further, a torque sensor (not shown) for detecting torque acting between the output shaft 1 and the input shaft based on the relative rotational displacement amount is disposed between the output shaft 1 and the input shaft. A worm wheel gear 3 is fixed to the output shaft 1, and a worm gear 4 meshed with the worm wheel gear 3 is connected to the output shaft of the motor 5. The motor 5 is driven and controlled based on torque detected by the torque sensor (not shown). Thus, the output shaft 1 is rotationally driven by the motor 5 based on the detected torque, and the operating force of the steering mechanism (not shown) is reduced.

  As shown in FIG. 2, the motor 5 includes a stator 6 in which windings 9 and 10 are provided on a stator core 8 and a rotor 7 in which a permanent magnet 18 is embedded in a rotor core 17. The stator core 8 of the stator 6 is configured by laminating electromagnetic steel plates, and a plurality of salient poles 13 constituting the first salient pole group 11 and a plurality of salient poles 14 constituting the second salient pole group 12 on the inner periphery thereof. (The hatched lines are distinguished from the salient poles 13), the windings 9 constituting the first winding group 15 are wound around the salient poles 13 and the second poles are wound around the salient poles 14. Winding 10 constituting the wire group 16 is wound. The rotor core 17 of the rotor 7 is also configured by laminating electromagnetic steel plates, and a plurality (even number) of permanent magnets 18 are arranged at equal intervals and adjacent to each other in different magnetic field directions.

  The permanent magnet 18 may be embedded in the rotor core 17 or disposed on the surface of the rotor core 17. However, if the configuration is embedded as illustrated, the portion of the rotor 7 facing the stator 6 has a low magnetic resistance and a low magnetic flux. Is formed by the permanent magnet 18 and the portion where the magnetic resistance is high and the magnetic flux is relatively difficult to pass, so that a difference can be made between the inductance in the q-axis direction and the inductance in the d-axis direction. As shown in FIG. 3, it is preferable that the generated motor torque can be increased by both the magnet torque and the reluctance torque. Moreover, since the permanent magnet 18 is not exposed to the outer periphery of the rotor 7, it is preferable that there is no risk of damage due to peeling or chipping. Furthermore, since the demagnetization tolerance is increased, the field weakening control described later can be greatly applied.

There are a total of six salient poles 13 of the first salient pole group 11 around which the winding 9 of the first winding group 15 is wound. (U ₁ ) salient pole group I to which phase voltage is applied, salient pole group II to which voltage of V (V ₁ ) phase is applied, salient pole group III to which voltage of W (W ₁ ) phase is applied Two salient poles 13 are arranged in each salient pole group. Each salient pole group I, II, III is arranged with a phase difference of 120 ° in electrical angle, and the first winding group 15 constitutes a three-phase winding of U phase, V phase, and W phase. . In each salient pole group I, II, III, the winding directions of the windings 9 of the salient poles 13 adjacent to each other are opposite to each other, and the polarities of the adjacent salient poles 13 are reversed. Yes. Thus, the magnetic field can be deviated and the iron loss can be reduced.

Between the salient pole groups I, II, and III, one salient pole 14 of the second salient pole group 12 around which the winding 10 of the second winding group 16 is wound is disposed. A voltage of U (U ₂ ) phase, V (V ₂ ) phase, and W (W ₂ ) phase is applied to 10. When there are a plurality of salient poles 14 arranged between the salient pole groups I, II, III, the winding directions of the windings 10 of the salient poles 14 adjacent to each other are opposite to each other. The polarities of the poles 14 are reversed from each other.

As described above, in the present embodiment, each of the first salient pole groups 11 includes two salient poles 13 (that is, the first salient pole group 11 includes two forks). The U ₁ phase, the V ₁ phase, and the W ₁ phase winding set as one set includes one winding set number, and is composed of six salient poles 13. In addition, the second salient pole group 12 includes one salient pole 14 between each salient pole group I, II, III (that is, the second salient pole group 12 is one fork), and the U ₂ phase, A set of windings of the V ₂ phase and the W ₂ phase is set as one set, and the number of winding sets is one, and three salient poles 14 are provided. The stator 6 has nine salient poles including six salient poles 13 of the first salient pole group 11 and three salient poles 14 of the second salient pole group 12.

Here, the total number of salient poles, which is the sum of the number of salient poles 13 of the first salient pole group 11 and the salient poles 14 of the second salient pole group 12, is T, and the first salient pole group 11 and the second salient pole group 11 The total number T of salient poles, where n is the sum of the number of salient poles of the salient pole group 12, s is the number of winding pairs, and k is a positive integer,
T = 3 × s × n (1)
Given in. The number of poles P of the permanent magnet 18 of the rotor 7 is
P = 2 × (s (± 1 + 3k)) (2)
And a value larger than T is set.

The above equation (2) is defined by the condition of smoothly rotating when a current is passed through the first winding group 15 sequentially in the U phase, V phase, and W phase. That is, if the number of pole pairs of the magnet is P / 2, the induced voltage function Be of the magnet is
Be = sin (P / 2 × θ) (3)
It can be expressed as. Here, since it is a three-phase motor, U, V, and W are shifted by 120 ° in electrical angle. Therefore, when the respective phase windings are energized while being shifted by 120 ° in terms of electrical angle, the rotor only has to be rotated in the same direction at the same angle. Therefore, the following formula sin (P / 2 × (θ + 120 / s))
= Sin (P / 2 × θ ± 120 + 360k) (4)
It will be sufficient if is established.

When the induced voltage function (rotor) is at a position shifted by 120 ° in electrical angle from Be = 0 at a certain time (the expression of the formula is a mechanical angle), the equation (4) is 120 ° on another axis on the stator side. (Shift of U, V, W) If the position is the same as the shifted position, the rotor position (induced voltage function Be) is always electrical even if energized sequentially at a position shifted 120 ° from U to V and V to W. The same value can be taken, and it can be smoothly rotated once. When formula (4) is arranged, the number of pole pairs P / 2 is
P / 2 = s (± 1 + 3k) (5)
Thus, the number P of poles is a function of the number s of winding sets as in the above equation (2).

  Specific examples of the combinations of the number of poles P and the total number of salient poles T thus obtained include those shown in Table 1.

表１において、永久磁石１８の極数Ｐは、Ｔより大きい種々の値をとることができるが、Ｔより大きい値の中で最小のものを採用すると、体積効率が最も高くなるとともにコギングトルクを最小にすることができて好適である。本実施形態では叉数ｎが３で、総突極数Ｔが９であるため、永久磁石１８の極数は１０に設定している。

In Table 1, the number of poles P of the permanent magnet 18 can take various values larger than T. However, if the smallest value among the values larger than T is adopted, the volume efficiency becomes the highest and the cogging torque is increased. It can be minimized and is preferable. In this embodiment, the fork number n is 3 and the total salient pole number T is 9, so the number of poles of the permanent magnet 18 is set to 10.

  Further, in the present embodiment, the arrangement pitch of the salient poles 13 of the first salient pole group 11 is made equal to the arrangement pitch of the permanent magnets 18, that is, 360 / P (= 36 °), and the second salient pole group 12. In this example, the salient poles 14 are arranged at intervals of 120 °, and the interval between the salient poles 14 is set to 42 °. As described above, when the arrangement pitch of the salient poles 13 of the first salient pole group 11 is substantially equal to the arrangement pitch of the permanent magnets 18, the phases of the salient poles 13 and the permanent magnets 18 coincide with each other. Sex is obtained. On the other hand, since the arrangement pitch of the salient poles 13 of the first salient pole group 11 and the salient poles 14 of the second salient pole group 12 becomes unequal when viewed all around the stator 6, the cogging torque is not uniform. It becomes uniform. Therefore, the arrangement pitch of the salient poles 13 of the first salient pole group 11 is 360 / P (= 36 °) equal to the arrangement pitch of the permanent magnets 18, and 360 / T in which the salient poles 13 and 14 are arranged at equal intervals. (= 40 °) can be selected according to which of controllability and cogging torque is prioritized.

Further, since P> T as described above, the arrangement pitch of the permanent magnets 18 is smaller than the average arrangement pitch of the salient poles 13 and 14, so that the effective width in the circumferential direction of the permanent magnets 18 is shown in FIG. D ₁ and the circumferential width of the tip of salient poles 13 and 14 being d ₂ , d ₁ ≦ d ₂ can be set, so that the entire permanent magnet 18 always has the tip of salient poles 13 and 14. Therefore, the induced voltage waveform becomes a sine wave, and the waveform distortion of the induced voltage can be prevented, and controllability can be improved and cogging torque can be reduced.

  In the above configuration, U-phase, V-phase, and W-phase voltages are sequentially applied to the windings 9 and 10 of the first winding group 15 and the second winding group 16 by an inverter (not shown). At the same time, the energization control is performed on the windings 9 and 10 according to the detected torque from the torque sensor, so that the motor 5 is rotationally driven with the driving force corresponding to the operating force of the steering wheel, thereby reducing the operating force of the steering mechanism. can do.

  In addition, the motor 5 has a large number of turns of the windings 9 and 10 so that the required output torque can be secured even at a low current in order to reduce the cost of the switching element of the inverter to be energized. is doing. As a result, as indicated by a broken line in FIG. 4, when the rotational speed of the motor 5 exceeds a certain value, the output torque rapidly decreases. Therefore, as indicated by a solid line in FIG. 4, the phase of the current flowing through the windings 9 and 10 is 0 ° to 90 ° according to the output torque value and the rotational speed required for the output shaft 1 (0 ° to 60 in FIG. 4). Although the characteristics in the range of ° are shown in the drawing, the necessary rotational speed and output torque are ensured by performing field-weakening control that is appropriately advanced in the range of phase control up to 90 °). Even if the number of turns of the windings 9 and 10 is set to be large, since the value of the flowing current is small, the wire diameter of the windings 9 and 10 can be reduced, and the physique of the motor 5 is not increased. The steering operation force is the heaviest when the vehicle is stopped, and decreases rapidly once the vehicle starts to move. Therefore, in this configuration, the number of turns of the winding is set to a large value, and when the steering speed (motor speed) is close to stopping, it is set so that a large torque is generated with a small current. Proceed appropriately (for example, from 0 to around 30 degrees in FIG. 3), and since a large torque is not required at higher speeds, the phase can be advanced from 40 degrees to 60 degrees or more so that it can respond to higher speeds. This is a very effective configuration for achieving both performance costs.

  According to the three-fold concentrated winding embedded magnet motor 5 of the present embodiment as described above, as shown in Table 2, as compared with the conventional distributed winding embedded magnet motor and concentrated winding embedded magnet motor of the same size. Significant and remarkable characteristics can be achieved.

表２において、分布巻埋込磁石モータでは、ステータスロットを２７と多くして分布巻きしているのでコギングトルクが小さく、無通電発電波形は正弦波となるが、コイルエンドが大きくなってしまうという問題があり、集中巻埋込磁石モータでは最大トルクが１０〜２０％程度向上し、８極、１２スロットで、コイルエンドは小さくなるが、コギングトルクは５〜１０倍にも大きくなり、無通電発電波形が歪み波となってしまうという問題があるのに対して、本実施形態の３叉集中巻埋込磁石モータでは１０極、９スロットで、無通電発電波形は正弦波となるとともにコイルエンドは小さくなり、かつ最大トルクが分布巻埋込磁石モータに対して３０〜４０％程度向上するとともにコギングトルクも分布巻埋込磁石モータと同等であり、体格が小さくかつ高出力トルクが得られ、制御性が良くかつコギングトルクが小さいという電動パワーステアリング装置に要求される機能を効果的に奏するモータを得ることができる。

In Table 2, the distributed winding embedded magnet motor has distributed winding with the status lot increased to 27, so the cogging torque is small and the non-energized power generation waveform is a sine wave, but the coil end is large. There is a problem, and the concentrated torque embedded magnet motor improves the maximum torque by about 10 to 20%. With 8 poles and 12 slots, the coil end is reduced, but the cogging torque is increased 5 to 10 times, and no current is applied. In contrast to the problem that the power generation waveform becomes a distorted wave, the three-forged concentrated winding embedded magnet motor of this embodiment has 10 poles and 9 slots. And the maximum torque is improved by about 30 to 40% compared to the distributed winding embedded magnet motor, and the cogging torque is equivalent to the distributed winding embedded magnet motor. It is and high output torque can be obtained small, it is possible to obtain a motor to achieve the required function effectively in the electric power steering apparatus that good controllability and cogging torque is small.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In the following description of the embodiment, the same components as those in the preceding embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences that are the characteristics of this embodiment will be mainly described.

  In the present embodiment, the number of salient poles 13 in each of the U-phase, V-phase, and W-phase salient pole groups I, II, and III in the first salient pole group 11 is three, and the U-phase The nine salient poles 13 are provided by arranging one set of the windings of a set of windings of the V phase and the W phase, and the second salient pole group 12 is not provided. Further, a 10-pole, 9-slot three-for-one concentrated winding embedded magnet motor is constructed. In addition, the arrangement pitch of the salient poles 13 of the first salient pole group 11 is equal to the arrangement pitch of the permanent magnets 18 of the rotor 7, that is, 360 / P (= 36 °). The arrangement pitch of the salient poles 13 of the first salient pole group 11 is 360 / P (= 36 °) equal to the arrangement pitch of the permanent magnets 18 and 360 / T (= 40 °) may be selected.

  Even in the configuration of the present embodiment, the configuration in which the two motors are substantially integrated in common with the rotor 7 in the first embodiment is different from the configuration of a single motor. However, the same operation and effect can be obtained by the multi-fork motor.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. As shown in FIG. 6A, the motor 5 in this embodiment includes a three-pronged first salient pole group 11 and a three-pronged second salient pole group 12, and the total number T of salient poles is T. 18, the number of poles P of the rotor 7 is set to 20, and as shown in FIG. 6B, the first winding 9 is wound around the salient poles 13 of the first salient pole group 11. A first winding 21 comprising a winding 10 in which U ₁ phase, V ₁ phase, and W ₁ phase currents are wound around the salient poles 14 of the second salient pole group 12 from the first inverter 21 to the winding group 15. The second inverter 22 supplies the U ₂ phase, V ₂ phase, and W ₂ phase currents to the two winding groups 16 separately. Both inverters 21 and 22 are respectively supplied with power from an external power source 19. Note that C ₁ and C ₂ in FIG. 6A are neutral connection points of the first winding group 15 and the second winding group 16.

  According to the present embodiment, since two motors of equivalent output are integrated with the rotor 7 in common and the inverters 21 and 22 for driving each motor are individually provided, either one of the motors Even if the inverters 21 and 22 break down, there is no risk of losing the function of the electric power steering device. It is no longer that the steering force changes and leads to an accident, and the reliability can be improved. Also, by providing a plurality of inverters, the capacity of one inverter can be reduced with respect to a single inverter configuration, and a small switching element can be used, which is advantageous in terms of cost. For example, if the control target value of the inverter is determined by a control method such as PDI so as to minimize the so-called error amount obtained by subtracting the control target steering force from the difference between the steering load force and the steering force, one inverter Since the control target of the remaining inverters increases instantaneously when there is a failure, if the inverter and motor capacity are sufficient, the steering force can be changed from before the failure, and even if there is no capacity margin, the steering force It is possible to minimize the change of. Furthermore, if the maximum current value of the inverter and the maximum torque of the motor are sufficient, but there is not enough room for heat capacity when energized for a long time, the current value is increased for a short time when one side of the inverter fails, and the steering force changes. Then, the inverter current can be gradually reduced to eliminate the risk of an accident due to a sudden change in steering force.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. As shown in FIG. 7A, the motor 5 in this embodiment is provided with a five-forked first salient pole group 11 and a two-forked second salient pole group 12, and the total number T of salient poles is T. 21, the number of poles P of the rotor 7 is set to 22, and as shown in FIG. 7B, the U ₂ phase from the winding wound around the salient poles 14 of the second salient pole group 12, The waveform of the V ₂ phase and W ₂ phase output signals (a), (b), and (c) is shaped by the waveform shaping circuit 23 so that the phases of the U phase, V phase, and W phase are shifted by 120 °. A wave control signal 24 is obtained, the inverter is controlled by the rectangular wave control signal 24, and U ₁ for the first winding group consisting of the windings wound around the salient poles 13 of the first salient pole group 11 is obtained. Phase control of the phase, V ₁ phase, and W ₁ phase is performed.

  According to the present embodiment, the rotational phase of the motor 5 can be accurately detected without providing an expensive device such as an encoder, and high controllability can be secured by performing current phase control based on the rotational phase.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG. As shown in FIG. 8A, the motor 5 in this embodiment includes a five-forked first salient pole group 11 and a two-forked second salient pole group 12 as in the fourth embodiment. The total number T of salient poles is set to 21 and the number of poles P of the rotor 7 is set to 22. Then, as shown in FIG. 8B, the sine wave control is performed by appropriately correcting the output signal of the U ₂ phase from the winding wound around the salient pole 14 of the second salient pole group 12. The signal v _U2 is obtained. That is, the U ₂ phase output signal V _U2 is input to the adder 25, and the V ₂ phase output signal V _V2 is added to the magnetic coupling coefficient M ₁₂ of the U ₂ phase and V ₂ phase windings by a predetermined coefficient K. _One corrected by a correction coefficient (K ₁ M ₁₂ ) multiplied by ₁ , similarly V _W2 corrected by (K ₁ M ₁₃ ), V _U1 corrected by (K ₂ M ₂₁ ), By subtracting and inputting V _V1 corrected by (K ₂ M ₂₂ ) and V _W1 corrected by (K ₂ M ₂₃ ), a sine wave control signal v _U2 is obtained. The sine wave control signals v _V2 and v _W2 can be similarly obtained for the V ₂ phase and the W ₂ phase. The inverter is controlled by these sine wave control signals v _U2 , v _V2 , and v _W2 , and the U ₁ phase for the first winding group consisting of the windings wound around the salient poles 13 of the first salient pole group 11. , V ₁ phase, W ₁ phase current phase control is performed.

  According to the present embodiment, the rotational phase of the motor 5 can be accurately detected without providing an expensive device such as an encoder, and without being affected by an installation error of the encoder, etc. Sine wave control of the applied current can be performed, and high efficiency and controllability can be ensured.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG. As shown in FIG. 9, the motor 5 in the present embodiment is provided with a five-forked first salient pole group 11 and a two-forked second salient pole group 12 as in the fourth embodiment. The total salient pole number T is set to 21 and the pole number P of the rotor 7 is set to 22. The arrangement pitches θ ₁ , θ ₂ , θ ₃ , and θ ₄ of the salient poles 13 of the first salient pole group 11 are substantially matched with the arrangement pitch of the permanent magnets 18 of the rotor 7. That is, θ ₁ = θ ₂ = θ ₃ = θ = 360 ° / P is set. Further, the arrangement pitch θ ₁ , θ ₂ , θ ₃ , θ ₄ of the salient poles 13 of the first salient pole group 11 is determined by the total number of salient poles T (T = 21), θ ₁ = θ ₂ = θ ₃ = By setting θ = 360 ° / T, the cogging torque can be further reduced.

  According to this embodiment, since the arrangement pitch of the salient poles 13 of the first salient pole group 11 is substantially equal to the arrangement pitch of the permanent magnets 18, the phases of the salient poles 13 and the permanent magnets 18 coincide with each other. There is no deviation, high controllability is obtained, and since the number of poles P of the rotor 7 is as large as 22, the unevenness of the cogging torque can be suppressed.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 10, the motor 5 in this embodiment is provided with a plurality of sets (two sets in the illustrated example) of three trident first salient pole groups 11 each including three in-phase salient poles 13. The number of winding sets s is a motor of 2, and the U ₁ phase and U ₂ phase, the V ₁ phase and V ₂ phase, and the W ₁ phase and W ₂ phase of the same phase are arranged every 360 ° in electrical angle. . In addition, as shown in FIG. 11, in the winding group 15 of the same phase, for example, the U phase, the three windings 9 in each of the U ₁ phase and the U ₂ phase are connected in series, and the U ₁ phase and the U phase _{The two} phases are connected in parallel.

  According to the present embodiment, the in-phase salient pole group and the winding group are arranged at an electrical angle of 360 °, so that the radial balance of the force acting on the rotor in the motor provided with the plurality of winding groups. And smooth rotation can be obtained easily and stably. In addition, since the windings 9 are connected in series in the same winding set, the return current can be prevented and the winding sets are connected in parallel, so even if the wire diameter is reduced, each phase Resistance can be reduced, copper loss can be reduced, and reduction in efficiency at high output can be suppressed.

  In the above description of the embodiment, the examples of the permanent magnet embedded in the rotor are V-shaped and flat-plate types. However, other shapes such as a U-shape can be arbitrarily set. Although an example of one layer in the radial direction is shown, it is also possible to provide a gap between permanent magnets of the same polarity as a multilayer structure of two or more layers. It is also possible to increase the magnetoresistance ratio between the d-axis and the q-axis by providing a groove in the silicon steel plate portion substantially parallel to the permanent magnet at the radial back surface position of the permanent magnet.

  Further, as described above, when the number of salient poles of the first motor and the second motor is T, the salient pole group is arranged so that the arrangement pitch θ is approximately θ = 360 / T. Although this is preferable in terms of torque, when θ is the number of rotor poles, θ is an angle approximately equal to θ = 360 / 3M defined by M, where 2P = 3 × M + α (α is a positive integer of 2 or less), In the example of 9, the arrangement may be such that θ1 = θ2 = θ3 = θ4 = θ. In the example of FIG. 9, each phase of the first motor is configured with 5 salient poles, and each phase of the second motor is configured with 2 salient poles, but the configuration in which 1 to 3 salient poles are deleted from each phase or specific phase. It is good.

  In addition, the present invention provides a so-called column type electric power steering system in which a motor is placed on a steering shaft, a rack and pinion type electric power steering system in which a motor is placed in a rack and pinion section, and a rack shaft type electric motor in which a motor is coaxially mounted on a rack shaft. Needless to say, it can be applied to any system such as a power steering system.

  In addition, although all the above explanations have been given taking an example of a steering force assist type power steering system, the steering force is not necessarily reduced, but can be controlled to become heavier, for example, at high speeds. This can increase the stability during high-speed driving.

  In addition, all of the above explanations have been given taking an example of a power steering system that reduces (increases) steering force with a motor, but the so-called steer-by-wire type in which the steering wheel and wheels are mechanically separated. It goes without saying that the configuration of the present invention can also be applied to this steering system.

  The electric power steering device of the present invention can achieve a small size, high output torque, low cogging torque and improved controllability, satisfy characteristics required for the electric power steering device, and various vehicles, particularly This is useful for electric power steering devices for ordinary and large vehicles.

1 is a partial cross-sectional configuration diagram of a main part in a first embodiment of an electric power steering apparatus of the present invention. It is sectional drawing which shows schematic structure of the motor of the embodiment. It is a characteristic view which shows the relationship between the current phase angle and torque of the same embodiment. FIG. 6 is a characteristic diagram showing the relationship between the rotational speed and torque with the current phase advance angle as a parameter in field weakening control of the same embodiment. It is sectional drawing which shows schematic structure of the motor in the 2nd Embodiment of this invention. The motor in the 3rd Embodiment of this invention is shown, (a) is sectional drawing which shows schematic structure of a motor, (b) is a block diagram of a drive circuit. The motor in the 4th Embodiment of this invention is shown, (a) is sectional drawing which shows schematic structure of a motor, (b) is explanatory drawing of the formation circuit of a rectangular wave control signal. The motor in the 5th Embodiment of this invention is shown, (a) is sectional drawing which shows schematic structure of a motor, (b) is explanatory drawing of the formation circuit of a sine wave control signal. It is sectional drawing which shows schematic structure of the motor in the 6th Embodiment of this invention. It is sectional drawing which shows schematic structure of the motor in the 7th Embodiment of this invention. It is a connection circuit diagram of the winding in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Output shaft 5 Motor 6 Stator 7 Rotor 8 Stator core 9, 10 Winding 11 1st salient pole group 12 2nd salient pole group 13, 14 Salient pole 15 1st winding group 16 2nd winding group 17 Rotor core 18 Permanent magnet 21, 22 Inverter

Claims (13)

  In an electric power steering apparatus that increases or decreases a steering force by a motor, the motor includes a stator in which a winding is wound around each of a plurality of salient poles provided on the stator core, and a number of permanent magnets on the rotor core than the number of salient poles. The salient poles are composed of rotors arranged at equal intervals in the circumferential direction, and the salient poles are wound with windings to which in-phase voltage is applied and the winding directions of adjacent salient pole windings are opposite to each other. One or a plurality of salient pole groups having a plurality of salient pole groups each having a number of phases as a direction are configured.   In an electric power steering apparatus that increases or decreases a steering force by a motor, the motor includes a stator in which a winding is wound around each of a plurality of salient poles provided on the stator core, and a number of permanent magnets on the rotor core than the number of salient poles. The salient poles are composed of rotors arranged at equal intervals in the circumferential direction, and the salient poles are wound with windings to which in-phase voltage is applied and the winding directions of adjacent salient pole windings are opposite to each other. A first salient pole group having a plurality of phases corresponding to a number of phases, and one or a plurality of salient pole groups located between mutually different phase salient pole groups in the first salient pole group When there are a plurality of salient poles and there are a plurality of salient poles, a second salient pole group having a plurality of salient poles corresponding to a plurality of phases, the winding directions of windings of adjacent salient poles being opposite to each other. An electric power steering device comprising one or a plurality of components   3. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus has a plurality of salient pole groups, and an individual drive circuit is provided for each salient pole group.   The electric power steering apparatus according to any one of claims 1 to 3, wherein field conduction control is performed by weakening energization of the windings of the salient pole group in accordance with a detected torque or speed request for steering.   The electric power steering apparatus according to claim 4, wherein a permanent magnet of the rotor is embedded in the rotor core. S is the number of winding sets in which three groups of three windings of U, V, and W are wound, and the number of salient poles of one group of salient pole groups or the first and second salient poles The total number T of salient poles, where n is the sum of the number of salient poles in one group and k is a positive integer,
T = 3 × s × n
The number of rotor poles is P,
P = 2 × (s (± 1 + 3k))
The electric power steering apparatus according to any one of claims 1 to 5, wherein the minimum P is greater than T and the minimum P is satisfied.   The current control for the winding wound around the salient pole of the first salient pole group is performed using an output signal from the winding wound around the salient pole of the second salient pole group. The electric power steering device described in 1.   A control signal is generated by correcting an output signal from a winding wound around one of the second salient pole groups based on a magnetic coupling coefficient with a winding wound around another salient pole. The electric power steering apparatus according to claim 2, wherein energization control is performed on the winding wound around the salient poles of the first salient pole group based on the control signal.   The electric power steering apparatus according to any one of claims 1 to 8, wherein a plurality of salient pole groups are provided and in-phase salient pole groups are arranged at an electrical angle interval of 360 °.   The electric power steering apparatus according to any one of claims 1 to 9, wherein the interval between the salient poles in each group of salient pole groups is arranged at substantially the same interval as the arrangement interval of the permanent magnets of the rotor.   The interval between the salient poles in each group of salient pole groups is set to be approximately the same as the arrangement interval of the permanent magnets of the rotor and the interval given by (360 ° / total number of salient poles). The electric power steering device according to any one of claims 1 to 9.   A plurality of salient pole groups are provided, windings of salient poles of the same group in each salient pole group are connected in series, and in-phase group windings are connected in parallel between the salient pole groups. Item 12. The electric power steering device according to any one of Items 1 to 11.   The electric power steering apparatus according to any one of claims 1 to 12, wherein the motor and the output shaft are coupled without a clutch.

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