JP4713335B2 - Motor and electric power steering device - Google Patents

Description

  The present invention relates to a motor and an electric power steering apparatus, and more particularly to a motor technology suitable for a system controlled using torque.

  For example, an electric power steering device is used as a device for controlling a motor using a torque sensor. An electric power steering device detects the steering force of a driver and assists the force of steering a tire with a motor in accordance with the size and direction of the electric power steering device. It is starting to be used. FIG. 10 shows an example of a system configuration diagram of the electric power steering apparatus. The electric power steering apparatus includes a steering wheel 1, a steering shaft 2 that is rotated by operation of the steering wheel 1, tires 3a and 3b that are steered by the steering shaft 2, a three-phase motor 5 that generates assist torque that assists steering, A torque sensor 4 that detects the steering torque of the steering shaft 2, a controller 6 that calculates the assist torque using the detected steering torque as an input, and controls the three-phase motor 5 based on the calculated torque, and a battery 7. The

When the driver operates the steering wheel 1, the tires 3 a and 3 b are steered via the steering shaft 2. At that time, the steering torque τ of the driver is detected by a torque sensor 4 attached to the steering shaft 2. When this steering torque τ is input to the controller 6, the controller 6 calculates an assist torque command value τ _MR to be generated by the three-phase magnet motor 5. Next, the controller 6 performs a control calculation so that the torque generated by the three-phase motor 5 is in accordance with the assist torque command τ _MR , converts the DC power of the battery 7 into AC power, and converts the three-phase voltage into the three-phase voltage. Applied to the motor 5.

  A motor mainly applied to the electric power steering apparatus includes a stator 61 and a rotor 64 as shown in FIGS. A coil is wound around the rotor 64 in the direction of the rotation axis. For this reason, the coil ends 62 and 63 become useless spaces that do not contribute to the motor torque. For this reason, there has been a problem in miniaturizing the motor.

On the other hand, as one form of a motor / generator, a motor having a claw-type magnetic pole capable of generating a magnetic flux by a current flowing through a coil has been proposed (for example, see Patent Document 1). Thereby, the useless space of a coil end can be eliminated and the proposal which achieves size reduction is made. Furthermore, a motor with less loss and noise has been developed by integrally molding a stator having a claw-shaped magnetic pole with a dust core.
JP 2001-161054 A

  The electric power steering is a vehicle-mounted device that makes a steering wheel operation comfortable by detecting a torque change in the steering wheel operation of the driver and controlling the assist torque of the motor. In order to detect the torque change in the above-mentioned driver's steering operation, it is known to use a sensor called a normal torque sensor. Various types of torque sensors have been proposed. Generally, a motor and a torque sensor are often attached separately.

  If the motor and the torque sensor are installed close to each other, a change in the rotating magnetic field occurs when the motor is driven, and the change in the magnetic flux may affect the torque sensor and cause a problem. Also, the effect of changes in current can be problematic. Therefore, when the torque sensor and the motor are integrated, there is a problem in that the detection signal of the torque sensor is affected by these electromagnetic noises.

  An object of the present invention is to solve the conventional problems, and to provide a motor and an electric power steering apparatus in which a torque sensor and a motor are integrated without being affected by electromagnetic noise.

In order to solve the above-mentioned problems, the present invention intends to cope with the following.
In a three-phase motor in which a current flows through a three-phase coil of a stator to generate a rotating magnetic field and the rotor drives a rotating shaft, a hollow portion is provided inside the rotor. The hollow portion of the rotor is configured to shield the magnetic field so as not to be affected by the rotating magnetic field due to the current of the three-phase coil, and a torque sensor for detecting the torque of the rotating shaft is built in the hollow portion. By adopting such a configuration, the torque sensor can be integrated in a compact manner without being affected by noise.

  A claw-type magnetic pole motor using a dust core has been proposed as a motor for reducing loss. This claw-type magnetic pole motor can be easily designed and manufactured with a structure having eight or more poles, and can be said to be a motor suitable for multipolarization.

  By the way, when the number of poles is designed to be 8 or more, the rotating magnetic flux mainly passes through the outer peripheral surface of the rotor and the shallow portion below the surface, and almost no magnetic flux is present at the center of the rotor. No state. For this reason, a multi-pole motor having eight or more poles does not affect the motor characteristics even if the center portion of the rotor is a hollow portion. In addition, since the tendency becomes so large that there are many poles of a motor, a hollow part can be enlarged.

  Based on these facts, the present invention that solves the above problems will be described. First, a claw-type magnetic pole having a pole number of 8 poles or more is integrally formed using a dust core. Next, a stator for one phase is configured by sandwiching a coil wound concentrically with respect to the rotating shaft and sandwiching two molded claw-shaped magnetic poles as a pair. A plurality of concentric circles of the one-phase stators are used to form an n-phase stator (n is an integer of 2 or more). Providing a motor with a smaller and more compact torque sensor that generates less heat by incorporating a hollow structure in the rotor of this motor and incorporating a torque sensor that detects the torque of the rotating shaft inside the rotor. Can do. Furthermore, by arranging the magnetic flux shield inside the rotor, it is possible to make the structure less affected by the rotating magnetic field.

  As another solution, the rotor is integrally molded using a bond magnet and a magnetic powder material. In this molding, the magnetic permeability is lowered as the torque sensor is approached in the radial direction of the rotor so as not to affect the torque sensor provided inside. Due to such characteristics, when the rotor is molded, it is possible for the rotor to have a function of magnetic shielding, and it is possible to improve by reducing the magnetic influence on the torque sensor provided inside.

  Further, the detection signal of the torque sensor is drawn from a position as far as possible from the position of the inlet of the power line for supplying driving power to the stator of the motor to the motor. When there is a power supply line for operating the torque sensor, the power supply line is also drawn out from the position of the power line as far as possible from the position of the inlet of the power line to the motor.

  According to the present invention, it is possible to provide a motor with a built-in torque sensor and an electric power steering device that are smaller and have improved reliability compared to the conventional method.

The best mode for carrying out the present invention will be described.
Hereinafter, embodiments of a motor and an electric power steering apparatus according to the present invention will be described with reference to the drawings.

  Examples will be described. FIG. 1 is a configuration diagram of a three-phase motor of this embodiment. FIG. 2 is a system configuration diagram showing an example of an electric power steering apparatus using the three-phase motor 5 of this embodiment. 2 has a structure in which a three-phase motor 5 having a built-in torque sensor is attached to the rotating shaft of the steering shaft 2 as compared with the conventional system configuration shown in FIG. For this reason, the whole apparatus can be put together compactly.

  First, the three-phase motor 5 in FIG. 1 will be described. The stator is composed of stator cores 11 to 16 and stator coils 17 to 19. The stator coil 17 is sandwiched with the same-shaped stator cores 11 and 12 facing each other to form a stator for one phase. FIG. 3 shows an exploded view thereof. The stator cores 11 and 12 each have claw-type magnetic poles on the inner circumference. As shown in FIG. 3, in this embodiment, the number of poles is 24, and as described above, since the magnetic flux mainly passes near the peripheral surface of the rotor 22, the rotor 22 is made hollow. Can do. Since the magnetic flux passes near the peripheral surface of the rotor 22 when the number of poles is large, the number of poles is preferably eight or more, and the 24-pole motor is more effective than the case of eight poles.

  Similarly, a combination of the stator coil 18 and the stator cores 13 and 14 and a combination of the stator coil 19 and the stator cores 15 and 16 form a stator for one phase. A three-phase stator can be formed by applying a three-phase voltage to the stator coils 17 to 19. The end of the stator coil 17 is a u-phase power lead wire 20. In FIG. 1, position sensors 71 to 73 are arranged on the three-phase stators to detect the position of the rotor 22. The position sensors 71 to 73 are fixed to spacers 74 to 76 inserted between the phase stator cores. The spacers 74 to 76 are used so that the magnetic flux generated in each phase does not affect the other phases, whereby the three-phase induced voltage can be kept uniform. Further, by arranging the position sensors 71 to 73 in the spacers 74 to 76, a space for separately providing the position sensors is not necessary. Therefore, the position of the rotor 22 can be detected without significantly increasing the volume of the three-phase motor 5, and the size of the position sensor motor can be reduced.

  Next, the rotor 22 and its interior will be described. 6A and 6B are a cross-sectional view of the rotor 22 and a side view seen from the axial direction. The rotor 22 includes a rotor magnetic member 23 and a rotor structural member 28. In the case of FIG. 6, the rotor magnetic member 23 is a magnet. The magnetic flux passes through the rotor structural member 28 but does not affect the interior of the rotor structural member 28. By generating a rotating magnetic field by the stator coils 17 to 19, the output shaft 25 on the steering shaft is rotated.

Further, as shown in FIG. 1, a torque sensor 26 is accommodated in the rotor 22. The torque sensor 26 is disposed between the input shaft 24 and the output shaft 25 on the steering shaft. The fixed portion of the torque sensor 26 is fixed to the stator side of the motor 5 by a torque sensor fixing member 27, and the rotating portion of the torque sensor 26 is attached to the input shaft 24 and the output shaft 25. Accordingly, when the driver steers the steering wheel, a steering torque τ is generated on the input shaft 24, and the steering torque τ can be detected by the torque sensor 26. As described above, the rotor 22 of the three-phase motor 5 outputs the assist torque τ _M according to the assist torque command value τ _MR calculated by the steering torque τ. The rotor 22 is attached to the output shaft 25, the output shaft, the torque is generated by adding the steering torque tau and the assist torque tau _M. Accordingly, the tires 3a and 3b can be steered with a small steering torque τ.

  Now, details of the torque sensor 26 will be described. FIG. 4 shows only the torque sensor 26 taken out in FIG. An exploded view of the torque sensor 26 is shown in FIG. The rotating portion of the torque sensor 26 is attached to the input shaft 24 by the input shaft attachment member 31 and to the output shaft 25 by the output shaft attachment member 32, respectively, and a torsion bar 33 is disposed therebetween. The torsion bar 33 has a structure that generates a torsion angle θ substantially in proportion to the steering torque τ. Further, the sensor rotating part magnetic member 34 is attached to the input shaft attaching member 31, and the sensor rotating part magnetic members 35 to 37 and the spacer 42 are attached to the output shaft attaching member 32. Each of the sensor rotating portion magnetic members 34 and 35 to 37 is a magnetic body that allows easy passage of magnetic flux, and has tooth-shaped uneven portions. On the other hand, on the torque sensor fixing member 27, sensor fixing portion magnetic members 38 and 39, sensor coils 40 and 41, and a spacer 43 are arranged. When a current is passed through the sensor coil 40, a magnetic flux is generated in a closed loop using the fixed portion magnetic member 38 and the sensor rotating portion magnetic members 34 and 35 as magnetic paths. Similarly, when a current is passed through the sensor coil 41, a magnetic flux is generated in a closed loop using the fixed portion magnetic member 39 and the sensor rotating portion magnetic members 36 and 37 as magnetic paths.

  The detection principle of the torque sensor 26 will be described. When the steering torque τ is generated, the torsion bar 33 generates a twist angle θ accordingly. Due to the torsion of the torsion bar 33, the sensor rotating part magnetic member 34 and the sensor rotating part magnetic member 35 are relatively displaced. As a result, the relative positional relationship changes between both tooth-shaped concavo-convex portions. Therefore, the magnetic flux generated by the current of the sensor coil 40 changes. That is, the inductance L1 for the sensor coil 40 changes. Therefore, the inductance L1 can be measured by detecting a change in the current of the sensor coil 40. On the other hand, the sensor coil 41 can detect the inductance L <b> 2 using the fixed portion magnetic member 39 and the sensor rotating portion magnetic members 36 and 37 as magnetic paths. Here, since the sensor rotating portion magnetic members 36 and 37 are fixed to the output shaft mounting member 32, the magnetic circuit is constant. Therefore, if the inductance L1 is detected with the inductance L2 as a reference, an inductance change due to temperature or the like can be taken into consideration. As described above, since the sensor output corresponding to the torsion angle θ can be obtained, the steering torque τ can be detected with high accuracy. In addition, the inductance detected by the sensor coils 40 and 41 has a feature that the magnetic path is closed inside the torque sensor 26, so that the inductance is hardly affected by the magnetic flux from the rotor 22. Therefore, by using such a torque sensor, even if a torque sensor is built in the three-phase motor 5, the torque can be detected with high accuracy.

FIG. 7 is a side view of the rotor magnetic member 23 as viewed from the axial direction. The rotor magnetic member 23 includes a bond magnet 53, a high permeability magnetic member 51 formed of a magnetic powder material, and a low permeability magnetic member 52, and is produced by integral molding. Thereby, a rotor with uniform performance and high dimensional accuracy can be provided at low cost. By adopting this structure, since the magnetic flux mainly passes through the high permeability magnetic member 51, the magnetic flux passing through the low permeability magnetic member 52 disposed inside thereof is less, including that the magnetic path becomes longer. Become. Furthermore, by using the rotor structural member 28 as a magnetic flux shield, it is possible to further prevent the magnetic flux of the rotor from affecting the torque sensor 26.

  FIG. 8 is a side view of the motor outer shape showing the drawing method of the power lead wires 20a to 20f and the torque sensor lead wires 21a and 21b of the three-phase motor 5 in the three-phase motor 5 as seen from the axial direction. The power lead lines 20a to 20f are drawn from the upper part of FIG. 8, and the torque sensor lead lines 21a and 21b are drawn from the lower part. By setting the signal line of the torque sensor to be approximately 180 ° different from the power line, the influence of electromagnetic noise due to the power line received by the signal line of the torque sensor can be minimized. The torque sensor lead wire 21 may not always be 180 ° due to the relationship between the three-phase motor and the external device, but it is desirable to pull it out from a direction at least 90 ° apart from the mechanical angle. .

FIG. 9 is a configuration diagram suitable for an electric power steering apparatus in another embodiment different from FIG. 1 in which a three-phase motor and a planetary gear mechanism are combined. 1 is attached to the output shaft 25, the rotor 22 is attached to the sun gear 54 in FIG. As a result, the output torque from the three-phase motor 5 is output to the sun gear 54, and is decelerated and transmitted to the output shaft mounting member 57 via the planetary gear 55 and the ring gear 57. Since the output shaft attaching member 57 is attached to the output shaft 25, the ratio of the reduction ratio (1 / N) (where N> 1) is set to the speed of the three-phase motor 5 by these gears. To slow down. Conversely, since the torque at the output shaft 25 is increased N times with respect to the torque of the three-phase motor 5, if the required assist torque τ _M at the output shaft 25 is constant, the maximum rating of the motor torque Can be reduced to (1 / N). By adopting this embodiment, an electric power steering device using a more compact motor with a torque sensor can be realized.

  The above is the embodiment applied to the electric power steering apparatus, but it goes without saying that it can be applied to a product using a torque sensor. Moreover, although the case where the torsion bar was used as a torque sensor was demonstrated, you may use the torque sensor which has another detection principle.

The block diagram of the three-phase motor of an Example. The system block diagram which shows an example of the electric power steering apparatus using the three-phase motor of an Example. The exploded view which decomposed | disassembled the stator of the three-phase motor of an Example. The assembly figure of the torque sensor incorporated in the three-phase motor of an Example. The exploded view of the torque sensor built in the three-phase motor of an Example. Sectional drawing of the rotor structural member of the three-phase motor of an Example, and the side view seen from the axial direction. The side view which looked at the rotor magnetic member of the three-phase motor of an Example from the axial direction. The side view which looked at the motor external shape which shows the drawing-out method of the electric power leader line and torque sensor leader line of the three-phase motor of an Example from the axial direction. The block diagram which shows the 2nd example suitable for the electric power steering apparatus which combined the three-phase motor and planetary gear mechanism of the Example. The system block diagram which shows the structural example of the conventional electric power steering apparatus. Sectional drawing of the conventional motor.

Explanation of symbols

1: Handle 2: Steering shaft 3a, 3b: Tire 4: Torque sensor 5: Three-phase motor 6: Controller 7: Battery 11-16: Stator core 17-19: Stator coil 20: Power lead wire 21: Torque sensor Lead wire 22: rotor 23: rotor magnetic member 24: input shaft 25: output shaft 26: torque sensor 27: torque sensor fixing member 28: rotor structure member 31: input shaft fixing member 32: output shaft fixing member 33: Torsion bars 34 to 37: sensor rotating portion magnetic member 38, 39: sensor fixing portion magnetic member 40, 41: sensor coil 42, 43: spacer 51: high permeability magnetic member 52: low permeability magnetic member 53: bond magnet 54 : Sun gear 55: Planetary gear 56: Ring gear 57: Output shaft mounting member 61: Stator 62, 63: Coil end 64: Time Child 65: End bracket

Claims (7)

And n-phase stator having a plurality of one phase of the stator comprised in the claw-type magnetic pole and the claw-type magnetic poles of a pair of integrally molded magnetic powder material and a coil for generating a magnetic flux, rotated by the magnetic flux A rotor for generating torque on the shaft, the rotor being composed of a magnetic member and a structural member , the inside being a hollow structure, and the magnetic permeability of the inner side of the magnetic member of the rotor being the rotor The motor has a lower magnetic permeability than the outer part of the magnetic member, and a torque sensor for detecting the torque of the rotating shaft is built in the inner hollow structure portion. The motor according to claim 1,
The rotor has a magnetic flux shield disposed between an inner surface and a built-in torque sensor. An n-phase stator having a plurality of one-phase stators composed of a pair of claw-shaped magnetic poles integrally formed with magnetic powder material and a coil that generates magnetic flux in the claw-shaped magnetic poles, and a rotating shaft by the magnetic flux The rotor is composed of a magnetic member and a structural member, and the inside has a hollow structure, and the structural member of the rotor is a magnetic flux shield, A motor characterized in that a torque sensor for detecting torque is incorporated in the inner hollow structure portion . In the motor according to claims 1 to 3 ,
The coil is characterized in that the lead wire is concentrated at a position within a mechanical angle of 90 degrees in the circumferential direction of the motor, and the lead wire of the torque sensor is drawn from a location separated from all the lead lines by a mechanical angle of 90 degrees or more. Motor. In the electric power steering device for controlling the assist torque assisted by the motor by the steering torque,
5. The electric power steering apparatus according to claim 1, wherein the motor is a motor according to claim 1, and a built-in torque sensor detects the steering torque. In a motor including a stator that generates a rotating magnetic field by a three-phase current that flows through a coil, and a rotor that generates torque on a rotating shaft by the rotating magnetic field,
The rotor is composed of a magnetic member and a structural member, and the inside has a hollow structure, and the magnetic permeability of the inner side of the magnetic member of the rotor is lower than the permeability of the outer side of the magnetic member of the rotor, A torque sensor for detecting the torque of the rotating shaft is built in the inner hollow structure portion, and a shielding structure is provided for preventing the rotating magnetic field generated by the coil from affecting the signal of the torque sensor. Motor. The motor according to claim 1,
The motor is characterized in that a magnetic shielding member is disposed between the stator and another stator, and a position sensor for detecting the position of the rotor is disposed on the magnetic shielding member.

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