JP4366823B2 - Brushless motor control device for power steering - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a brushless motor that is optimal for an electric power steering device that reduces the steering force of an automobile.Control unitIn particular, there are no motor shorts or locks, and the brushless motor can be easily wound and reduced in size and cost.Control unitAbout. In addition, the present invention provides a brushless with improved inductance characteristics in a brushless motor by improving the winding method of the coil.For motor control devicesRelated.
[0002]
[Prior art]
Conventionally, a motor with a brush is generally used as an assist drive source for an electric power steering apparatus. Further, a brushless motor is used for reducing inertia in steering and improving durability of the motor. Yes.
[0003]
As a winding method of the motor coil, there are lap winding and wave winding. For motors with coils wound in lap winding, 1) winding is easy to manufacture and inserts into the stator core, 2) easy to miniaturize, 3) simple winding structure and difficult to break the coil, It has the characteristic that the reliability with respect to insulation is also high. For this reason, a lap winding is generally used in a brushless motor as an assist drive source of an electric power steering apparatus.
[0004]
On the other hand, a coil-wound motor is not looped, so the inductance is smaller than that of a lap motor, the motor output is more responsive to changes in drive current, and current fluctuations There are advantages such as being small.
[0005]
As a method of winding a coil in a conventional motor, there is a method described in JP-A-7-163074. The wave winding method disclosed in this publication is a stator winding method for a multi-phase motor in which coils of each phase are inserted into the slots of the stator core by wave winding, and the conductors constituting the coils of each phase are respectively connected. Divided coils are formed in a plurality of pieces, and these bundled coils are sequentially inserted into slots in parallel with each phase to form stator windings.
[0006]
By the way, as a power source of the conventional electric power steering apparatus, for example, a brushless motor as disclosed in JP-A-9-149616 is used. FIG. 19 is a radial sectional view of the brushless motor. The stator core 201 is disposed on the outer peripheral side of the rotor 200, and the coil 202 is wound around a slot opened from the inner peripheral side of the stator core 201. Is a motor housing 203. That is, the stator core 201 of this brushless motor has a slot opening on the inner peripheral side (rotor side), and the coil 202 is wound around the slot through this opening.
[0007]
On the other hand, if the motor used in the electric power steering device is short-circuited or locked, it becomes impossible to steer. Therefore, it is highly reliable to attach a cover to prevent scattering of the magnet and coat the coil with an insulating agent. I try to have sex. Also, in order to prevent the influence on the vehicle even if the motor is short-circuited or locked, a relay is provided at the midpoint of the motor coil as shown in JP-A-10-243687, or utility model registration No. 2585705. As shown in FIG. 1, there is a motor provided with a clutch on the output shaft. That is, in Japanese Patent Application Laid-Open No. 10-243687, the drive circuit unit of the brushless motor includes a bridge circuit composed of a plurality of switching elements, a power source is connected to the input terminal of the bridge circuit, and the brushless motor is connected to the output terminal of the bridge circuit. And a switch means for opening a closed loop is connected to the neutral point of the brushless motor.
[0008]
Although not a motor for an electric power steering device, a brushless motor using a split core is also disclosed in, for example, Japanese Patent Application Laid-Open No. 11-234928.
[0009]
[Problems to be solved by the invention]
However, if the slot opening is on the inner peripheral side (rotor side) as in the conventional brushless motor described above, the coil is pushed in from the rotor side using a jig or the like when the coil is inserted (wound). As a result, the coil is easily damaged when the coil is inserted. Coil damage can cause a motor short circuit.
[0010]
In addition, the motor short-circuit of the electric power steering apparatus must be absolutely impossible because the power generation braking of the motor occurs at the time of steering and the steering becomes heavy, and in the worst case, the steering becomes impossible. For this reason, the reliability of the motor with respect to a short circuit is improved by inserting insulating paper between coils or coating a coil with an insulating agent to enhance insulation. Therefore, an accompanying work process has occurred in manufacturing the motor, which has been a problem in terms of cost reduction. Further, when a short circuit occurs, the relay is turned off or the clutch is turned off to prevent the dynamic braking from working. Even in this case, relays, clutches and other devices are required, which is a problem in terms of cost reduction.
[0011]
In addition, since irregularities are formed on the inner circumference of the stator due to the slot opening, if foreign matter enters the motor due to inadequate maintenance, the foreign matter is caught in the concave portion of the stator and further caught in the gap between the rotor. As a result, the motor may become unable to rotate.
[0012]
On the other hand, in the conventional electric power steering device, if there is a torque ripple in the motor used as the assist drive source of the electric power steering device, the ripple becomes a fluctuation of the assist torque, which impairs the smoothness of steering. There was a problem that made it feel uncomfortable.
[0013]
The motor of the assist drive source of the electric power steering device is used from a state where it hardly moves (a state where the steering wheel is held) to a state where it rotates at a high speed (during a sudden steering) according to the steering speed of the steering that the driver steers. Is done. Torque ripple is small in the entire speed range, and a stable output (the number of rotations following the steering and the torque commensurate with the steering force) is required.
[0014]
In addition, in an electric power steering apparatus that controls a brushless motor by rectangular wave drive, the motor is multiphase or multipolar in order to obtain a small, efficient and stable output. When a multi-phase or multi-pole motor is rotated at a high speed, the time from commutation (switching the excitation phase) to the next commutation is extremely short. For motors with large inductance, the electrical constant is large and the current rises. Therefore, there is a problem that the next commutation time comes before the current rises sufficiently, and the motor does not flow as intended, so that the motor output is insufficient and unstable. Since the torque is proportional to the current, there is a problem that if the current does not flow, the torque decreases accordingly.
[0015]
This problem will be specifically described with reference to the drawings. FIG. 10 shows a typical example of winding development of a brushless motor for a conventional electric power steering apparatus. FIG. 11 is a representative example of the winding development of a brushless motor for another conventional electric power steering apparatus. These are both examples of three-phase, six-pole lap windings. An excitation coil 76 is formed in a loop for each phase, and is wound several times. Such a conventional brushless motor includes a rotatable rotor having a permanent magnet fixed on the outer peripheral surface, a multi-phase excitation coil 76 surrounding the outer peripheral surface of the rotor, and an excitation coil on the inner peripheral surface of a cylindrical yoke portion. And a stator core formed with a plurality of teeth 70 for holding 76.
[0016]
The motor used for the assist power source of the electric power steering apparatus needs a large output that secures both the torque and the rotational speed necessary for steering. In order to obtain this output in an automobile using a 12V battery as a power source, naturally a large current is required.
[0017]
In addition, even if the motor has a large output, the number of coil conductors, that is, the number of turns of the coil is relatively small if the motor is a high rotation type motor with a small torque constant. However, in the case of an electric power steering device, the reduction gear ratio is increased. If the torque is to be secured, there is a problem that the space of the speed reduction portion is increased and the steering steering feeling is deteriorated due to the motor inertia, and the speed reduction ratio cannot be remarkably increased. That is, the motor of the electric power steering apparatus has a large torque constant and is used with a large current.
[0018]
For this reason, the motor of the electric power steering apparatus has a configuration in which the number of conductors of the coil, that is, the number of turns of the coil is large and the resistance is small.
[0019]
Specifically, the number of coil conductors per pole is 20 turns or more, and in order to reduce resistance, a thick wire is wound or several bundled coils are wound.
[0020]
The inductance L of one phase in such a motor is approximately proportional to the square of the number N of turns of the exciting coil 76. A brushless motor for an electric power steering apparatus has a large inductance, and thus has a large inductance. Inductance includes self-inductance and mutual inductance, but this brushless motor is dominant in self-inductance and has the same configuration as a solenoid when viewed from a single-phase exciting coil. Therefore, inductance L is expressed by the following general formula (1 ).
[0021]
L = μ ・ S ・ N²/ I (1)
Here, S is the cross-sectional area of the teeth 70, I is the length of the teeth 70, and μ is the magnetic permeability of the teeth 70.
[0022]
The electrical time constant τ is
τ = L / R (2)
Indicated by Here, R is the resistance value of the exciting coil 76.
[0023]
This brushless motor has an inductance equivalent to 1, for example, 300 μH, a coil resistance of about 0.05 ohms, and an electrical time constant τ of about 6 milliseconds. In addition, since the brushless motor of this example has 3 phases and 6 poles, there are 18 commutations per rotation (3 phases × 6 poles = 18), and when this motor is rotated at 1000 rpm, it is 1 in 3.3 milliseconds. Rotating flow (1 / {(1000/60) * 18} = 0.0033).
[0024]
That is, the commutation time (about 3 milliseconds) is shorter than the electrical time constant τ (about 6 milliseconds) of the brushless motor. Since the electrical time constant τ is 63% of the final value of the current, if the current is commutated in a shorter time than the value of the electrical time constant τ, the current will flow slightly against the original final value. become.
[0025]
Furthermore, in an electric power steering device that controls a brushless motor by rectangular wave drive, if the phase currents of the excitation phase (ON phase) that rises during commutation and the excitation phase (OFF phase) that falls are not matched, Since the flowing all-phase current fluctuates, it causes torque ripple. On the other hand, torque ripple can be significantly suppressed by controlling the current change rate of the phase current during commutation. However, a brushless motor with a large inductance has a slow rise in current, and when rotating at high speed, There was a problem that the flow time was too short to control. FIG. 12 is a waveform diagram showing a state at the time of commutation of excitation current of a conventional brushless motor for an electric power steering apparatus. A solid line is an actual current value of each phase, and a dotted line is a current value of each phase that should flow. As shown in this figure, in the conventional brushless motor, the current flows only slightly with respect to the final flow value, and the excitation phase that rises at the time of commutation (ON phase) and the excitation phase that falls (OFF phase) ) Phase currents do not match.
[0026]
Furthermore, in the method of winding a coil in the motor disclosed in the above publication, one phase is wound with a predetermined number of turns, and when one phase finishes winding, the next phase is wound. A coil is wound. When the coil is wound for each phase in this way, the shape of the coil end, which is a transfer portion between one coil and the other coil, is the status of the coil 375a of the first wound phase as shown in FIG. The coil 375c of the last wound phase is located in the slot opening 372a (inner peripheral side of the stator core 374) in the back of the lot 372 (outer peripheral side of the stator core 374). The coil 375b is a coil wound second.
[0027]
Thus, since the radial position of the coil 375 in each phase status lot 372 is different, the length of the coil end 371 varies depending on each phase, and the magnetic flux can be easily passed depending on the position in the status lot 372. Because of the variation, the inductance varies depending on the position of the coil 375. That is, since the position of the coil 375 (375a, 375b, 375c...) In the status lot 372 is biased, the inductance is unbalanced between the phases.
[0028]
Due to this imbalance, the conventional coil winding method in a motor has a problem that current fluctuation and torque ripple become large. A motor wound with a coil by wave winding inherently has a small inductance. Therefore, if there is an imbalance in inductance between phases, there is a drawback that it greatly affects current fluctuation and torque ripple.
[0029]
  The present invention has been made for the above-described circumstances, and a first object of the present invention is to provide a low-speed brushless motor in an electric power steering apparatus that controls a brushless motor serving as an assist driving force source by rectangular wave driving. A stable desired output torque can be obtained regardless of whether the rotation is high speed or high speed, and even when the brushless motor is rotated at a high speed, torque ripple can be greatly suppressed and smooth. Ideal for electric power steering devices that can provide a steering feelBrushless motor control deviceIs to provide.
[0030]
  A second object of the present invention is to provide a brushless motor that is optimal for an electric power steering apparatus that is free from motor short-circuiting or locking, can be easily wound, and is reduced in size and cost.Control unitIs to provide. Furthermore, the third object of the present invention is to equalize the inductance of each phase in a motor in which the coils of each phase are wound in a wave, and to reduce current fluctuation and torque ripple.Brushless motor control deviceIs to provide.
[0031]
  The present inventionA rotatable rotor having a permanent magnet fixed on the outer peripheral surface, a multi-phase excitation coil surrounding the outer peripheral surface of the rotor, a cylindrical yoke portion, and the excitation coil held on the inner peripheral surface of the yoke portion And a stator core formed by forming a plurality of teeth, and a control device for a brushless motor for power steering, wherein the exciting coil is wound around the stator core in a wave winding that does not form a loop for each coil corresponding to a pole.In relation to the above of the present inventioneachMy goal is,Drive means for generating a rectangular wave excitation signal to be supplied to each excitation phase of the brushless motor for power steering, and control means for determining the direction of the excitation signal and switching on / off for each excitation phase The control means includes a drive circuit for generating an excitation current to be supplied to the excitation coil as the excitation signal, and switching between the excitation phase in which the excitation current rises and the excitation phase in which the excitation current falls when the excitation current is switched by rectangular wave control. The teeth of the brushless motor for power steering are achieved by supplying a drive signal that matches or has the same rate of current change to the drive circuit. In addition, the inner peripheral surface is substantially circular with no irregularities, and the rotor rotates inside the teeth. Or one end of the coil end drawing position of each excitation coil is arranged on the inner peripheral side of the stator core with respect to each adjacent other phase coil end, and each excitation coil This is achieved more effectively by arranging the other end of the coil end lead-out position on the outer peripheral side of the stator core with respect to each adjacent coil end of the other phase.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
In the brushless motor serving as the assist drive source of the electric power steering apparatus of the present invention, the multi-phase excitation coil is wound with a wave winding that does not form a loop for each pole, so the inductance of the brushless motor can be reduced, Regardless of whether the brushless motor is rotating at low speed or high speed, a stable desired output torque can be obtained, and torque ripple can be greatly suppressed even when the brushless motor is rotated at high speed. In addition, electromagnetic noise, magnetostrictive noise and operating noise can be reduced, and a smooth steering feeling can be obtained.
[0039]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electric power steering apparatus (column type) according to an embodiment of the present invention. The steering force applied to the steering wheel 1 is transmitted to the steering shaft 2 composed of the input shaft 2a and the output shaft 2b. One end of the input shaft 2 a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2 b via the torque sensor 3. The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force is further transmitted to the tie rod 9 via the steering gear 8 to steer the steered wheels. The steering gear 8 is configured in a rack and pinion type having a pinion 8a and a rack 8b, and the rotational motion transmitted to the pinion 8a is converted into a straight motion by the rack 8b.
[0040]
A reduction gear 10 for transmitting an auxiliary steering force (assist force) to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The brushless motor 12 that generates the auxiliary steering force is connected to the reduction gear 10. The output shaft is connected. The torque sensor 3 is disposed on the steering wheel 1 and detects the steering torque transmitted to the input shaft 2a. For example, the torsion bar twisting the steering torque interposed between the input shaft 2a and the output shaft 2b. Torque detection comprising an analog voltage corresponding to the magnitude and direction of torsion occurring in the steering shaft 2 when the driver steers the steering wheel 1 is converted to angular displacement and detected by a potentiometer. The signal TV is output. For example, when the steering wheel 1 is in a neutral state, the torque sensor 3 outputs a predetermined neutral voltage V0 as a torque detection signal TV. When the steering wheel 1 is turned to the right, the torque sensor 3 responds to the steering torque at that time. When the voltage increasing from the neutral voltage V0 is turned to the left, a voltage decreasing from the neutral voltage V0 is output according to the steering torque at that time.
[0041]
The controller 13 is a controller that controls the drive of the brushless motor 12 and controls the steering assist force to the steering system, and is operated by being supplied with power from a vehicle-mounted battery 16. The negative electrode of the battery 16 is grounded, and the positive electrode is connected to the controller 13 via the ignition switch 14 and the fuse 15a for starting the engine, and is directly connected to the controller 13 via the fuse 15b. For example, the power supplied through the memory is used for memory backup. Then, the controller 13 drives and controls the brushless motor 12 based on the torque detection signal TV from the torque sensor 3 and the vehicle speed detection signal VP from the vehicle speed sensor 17 disposed on the output shaft of the transmission, for example.
[0042]
FIG. 2 is a cross-sectional view showing the configuration (column type) of the motor of the electric power steering apparatus according to the embodiment of the present invention. The brushless motor 12 includes a cylindrical housing 22, a permanent magnet 25 which is disposed along the axis of the housing 22, and is fixed to a rotatable rotating shaft 24 by bearings 23 a and 23 b, and the permanent magnet 25. The rotor is fixed to the inner peripheral surface of the housing 22 so as to surround it, and is composed of a stator 26 around which three-phase exciting coils 26a, 26b, and 26c are wound. The rotor is rotatable by a rotating shaft 24 and a permanent magnet 25. 27 is formed.
[0043]
On the other hand, the permanent magnet 25 constituting the rotor 27 has, for example, three S poles and three N poles, and a total of six poles magnetized at equal intervals in the circumferential direction. Here, in this case, the permanent magnet 25 magnetized to 6 poles, 3 poles each of S and N poles, is applied, but the S poles and N poles are alternately arranged at equal intervals in the circumferential direction. As long as it is magnetized, it may be two poles, S pole and N pole, or a plurality of poles.
[0044]
FIG. 3 is a cross-sectional view showing another configuration (rack coaxial type) of the electric power steering apparatus according to the embodiment of the present invention.
[0045]
In this electric power steering apparatus, the steering gear box 54 has a rack shaft 55 extending in the vehicle width direction extending through the left and right sides, and the pinion of the lower steering shaft 53C and the rack of the rack shaft 55 are engaged with each other. Further, tie rods 57A and 57B are connected to both ends of the rack shaft 55 extending left and right via ball joints 56A and 56B, and an unillustrated outer end side of the tie rods 57A and 57B can rotate a steered wheel (not shown). It is connected to the supporting knuckle so that the steering force can be transmitted. In addition, dust boots 55A and 55B are externally fitted between both ends of the rack shaft 55 and the tie rods 57A and 57B, respectively, so that dust or the like enters the steering gear box 54 or the housing 59. Is preventing.
[0046]
The rack shaft 55 is inserted through a cylindrical housing 59 fixed to a vehicle body (not shown) via brackets 58A and 58B. Specifically, the housing 59 is caulked from the side close to the steering gear box 54 to the connecting portion 59A coupled to the steering gear box 54, the relatively thick cylindrical portion 59B, and the outer peripheral surface of the cylindrical portion 59B. A relatively thin cylindrical portion 59C that is stopped, and a preload member 59D that is screwed into and fixed to the end of the cylindrical portion 59C, each of the connecting portion 59A and the preload member 59D are brackets 58A, It is fixed to the vehicle body via 58B.
[0047]
Among these, the relatively thin cylindrical portion 59C includes a large-diameter portion 59a that is fixed to the cylindrical portion 59B and relatively long and extends in the axial direction, a small-diameter portion 59b into which the preload member 59D is screwed, and a large-diameter portion 59a. And a tapered portion 59c that connects the small diameter portions 59b. A cylindrical rotation shaft 60A is disposed inside the housing 59 so as to surround the rack shaft 55 in a non-contact and coaxial manner, and a cylindrical permanent magnet 60B is disposed on the outer peripheral surface of the rotation shaft 60A. It is fixed. The permanent magnet 60B is a magnet in which S and N poles are alternately magnetized in the circumferential direction at equal intervals, and a rotatable rotor 60 is constituted by the rotating shaft 60A and the permanent magnet 60B.
[0048]
FIG. 4 is a block diagram showing the configuration of the controller 13. The controller 13 includes, for example, a control circuit 61, an FET gate drive circuit 62, a motor drive circuit 64, a current detection circuit 66, and a rotor position detection circuit 68. .
[0049]
The control circuit 61 is composed of, for example, a microcomputer and includes at least an interface unit that performs input / output processing with an externally connected device, and a storage unit such as a ROM and a RAM. Then, the torque generation direction is detected for the torque detection signal TV comprising the analog voltage from the torque sensor 3 depending on whether it is higher than a predetermined neutral voltage V0, and a predetermined process is performed to obtain a torque detection value T. The vehicle speed detection value V is calculated by integrating the number of pulses per unit time based on the vehicle speed detection signal VP comprising a pulse signal corresponding to the rotation of the output shaft from the vehicle speed sensor 17. Based on these detection values T and VP, a motor drive signal SM to be supplied to the brushless motor 12 is calculated by, for example, PID control (proportional / integral / differential), and PWM (Pulse Width Modulation) is calculated based on the motor drive signal SM. ) Signal is formed, and a pulse width modulation signal PWM is formed based on this PWM signal and output to the FET gate drive circuit 62.
[0050]
The FET gate drive circuit 62 is configured by, for example, a multiplexer or the like, and includes a pulse width modulation signal PWM and a direction signal from the control circuit 61, and upper stage gate signals Ga1 to Gc1 and lower stage side gate signals Ga2 to Ga2 from the rotor position detection circuit 68. When Gc2 is input and the direction signal is forward rotation, a predetermined value is applied to the gate terminal of the corresponding transistor of the motor drive circuit 64 specified by the gate signals Ga1 to Gc2 while the pulse width modulation signal PWM is “HIGH”. When a voltage is supplied and the direction signal is reversely rotated, the upper gate signals Ga1 to Gc1 are processed as lower gate signals, and the lower gate signals Ga2 to Gc2 are processed as upper gate signals, respectively. A predetermined voltage is supplied to the terminal while the pulse width modulation signal PWM is “HIGH”.
[0051]
The current detection circuit 66 has, for example, a current detection resistor, amplifies the voltage generated at both ends of the current detection resistor, removes noise, and outputs the amplified current to the control circuit 61 as a motor current detection signal I. In the current detection circuit 66, it is assumed that sufficient filtering is performed on each signal so that the effective value of the motor current detection signal I can be obtained. The motor driving circuit 64 includes six field effect transistors (FETs) Ta1, Tb1, Tc1, Ta2, Tb2, and Tc2. In these FETs Ta1 to Tc2, a pair of corresponding FETs such as Ta1 and Ta2, Tb1 and Tb2 are connected in series, and each of the series circuits connected in series is arranged in parallel between both terminals of the power supply. At the same time, the connecting portion of the FETs in series relation is electrically connected to the outer ends of the respective excitation coils 26a to 26c (the side opposite to the center side of the star connection).
[0052]
The gate voltages of the FETs Ta1 to Tc2 are controlled by the FET gate drive circuit 62 based on the output of the phase detection element 31 described above. The direction and magnitude of the excitation current to each excitation coil 26a to 26c in the motor drive circuit 64 is specifically as shown in FIG. Here, in FIG. 5, the U phase corresponds to the excitation coil 26a, the V phase corresponds to the excitation coil 26b, and so on, each phase corresponds to each excitation coil, and the W phase corresponds to the excitation coil 26e. .
[0053]
As a result, in the winding development view of the present invention shown in FIGS. 6 and 7, an upward current (positive phase in FIG. 5) and a downward current (negative phase in FIG. 5) flow. A pole and an S pole are generated. Therefore, the rotor 27 is rotated by the magnetic attractive force and the repulsive force between the N or S pole of the permanent magnet of the rotor 27 and the N or S pole generated in the exciting coil 26.
[0054]
6 to 8 show development views according to embodiments of the windings of the brushless motor, which is an assist drive source of the electric power steering apparatus according to the present embodiment. FIG. 6 is an exploded view of the winding of the brushless motor according to the first embodiment of the present invention. FIG. 7 is a developed winding view of a brushless motor according to a second embodiment of the present invention. FIG. 8 is an exploded view of the winding of the brushless motor according to the third embodiment of the present invention.
[0055]
6 and 7 are examples of windings of a brushless motor having three phases and six poles, respectively. The winding of one exciting coil 26 (U phase) passes through the winding groove a, passes through the winding groove b separated by the number of phases, and then reciprocates the teeth 70, and then the next winding at the same pitch. Winding is performed so as to pass through the wire groove c, and the stator 26 is wound around once so as to return to the original winding groove a. Next, the same path is followed, and the stator 26 is similarly turned around and the line of the exciting coil 26 is returned to the original winding groove a. Such winding is repeated so that the number of conductors of the exciting coil 26 is set to a predetermined number.
[0056]
The exciting coil 26 may be a single wire wound or a bundle of several wires. In this brushless motor, since the exciting coil 26 is not formed in a loop as shown in FIGS. 6 to 8, the number of turns of the exciting coil that affects the inductance of the motor is 0, and the self-inductance of the brushless motor is Is extremely small. Moreover, in this brushless motor, since the number of conductors is the same as that of the conventional lap winding as shown in FIG. 10 or FIG. 11, the electric resistance of the exciting coil is almost the same as that of the lap winding, and only the inductance is reduced. .
[0057]
For example, as shown in FIGS. 6 and 7, since the inductance corresponding to 1 of the wound brushless motor is 80 μH or less and the resistance is about 0.05 ohm, the electrical time constant τ is τ = L / R = 80 μH / 0.05 ohm = 1.6 milliseconds or less.
[0058]
Since this brushless motor has 3 phases and 6 poles, there are 18 commutations per rotation (3 phases × 6 poles = 18), and if this motor is rotated at 1000 rpm, it will flow once per 3.3 milliseconds. (1 / {(1000/60) * 18} = 0.0033).
[0059]
As a result, even when the brushless motor is rotating at high speed, the electrical time constant τ (1.6 milliseconds) is smaller than the commutation period (about 3 milliseconds), and the excitation current is sufficiently stable. It can flow.
[0060]
Next, an electric power steering apparatus according to another embodiment will be described below. In the drive control of the brushless motor that is the assist drive source, by controlling the current change rate of the phase current at the time of commutation, by matching the current change rate of the rising phase and falling phase of the exciting current when switching the exciting current The torque ripple of the brushless motor can be greatly suppressed.
[0061]
A specific example will be described with reference to the controller 13 shown in FIG. The FET gate drive circuit 62 generates excitation signals to be supplied to the excitation phases a to c of the brushless motor 35. The control circuit 61 supplies the FET gate drive circuit 62 with a drive signal that makes the current change rates of the rising phase and falling phase of the exciting current coincide with each other or the same when switching the exciting current.
[0062]
  This is because when the brushless motor 35 rotates, a counter electromotive force is generated in the motor coil, current becomes difficult to flow, the current stops early in the OFF phase, and the rise of the current is delayed in the ON phase. It is to correct in a controlled manner. In reality, the brushless motor 35Applied voltageTherefore, the ON phase current cannot rise quickly. The phase currents are matched by delaying the fall of the OFF-phase current.
[0063]
Here, when the inductance of the brushless motor 35 is large, the rise of the ON-phase current is delayed, and the OFF-phase is energized during that time. If current continues to flow indefinitely, the next commutation time will be reached, which is not preferable because it deviates significantly from the original excitation interval.
[0064]
In this brushless motor, since the inductance is smaller than that of the conventional brushless motor, the phase currents of the ON phase and the OFF phase can be matched even at high speed rotation, and torque ripple can be suppressed.
[0065]
In the above-described embodiment, a three-phase six-pole brushless motor has been described. However, the brushless motor according to the present invention is not limited to three phases, and the number of poles is not limited to six. As shown in the winding development view of FIG. 8, a five-phase four-pole brushless motor has the same operations and effects as the above-described embodiment. The electric power steering apparatus according to the present invention is not limited to the B / S rack type brushless motor as shown in FIG. 3 but also the column type brushless motor as shown in FIG. There are actions and effects.
[0066]
Further, the brushless motor for an electric power steering apparatus has the following structural features, and a wave winding in which a coil is not formed in a loop shape is easy to manufacture and there is no problem in reliability.
[0067]
1. The outer diameter of the motor (inner diameter of the stator core) is large (particularly B / S rack type), and the winding is easy to mold.
[0068]
2. The number of turns of the winding is large, and the lap winding stator core can be used, and the degree of freedom of design is large, and it is easy to miniaturize like lap winding.
[0069]
3. The brushless motor for an electric power steering apparatus is provided with sufficient protection and fail-safe because the steering operation becomes impossible when the motor is locked. The excitation coil is also reinforced with mechanical strength and electrical insulation, such as being hardened with resin, and has a structure that does not deteriorate reliability even when wave winding.
[0070]
In the above, the embodiment of the electric power steering device by the rectangular wave drive has been described. However, the brushless motor for the electric power steering device may be controlled by the sine wave drive. If the inductance of the brushless motor is large even in sine wave drive, the rise of the excitation current is delayed, and the current balance of each phase is lost, causing torque ripple. Therefore, even if the above-described embodiment is applied to a sine wave drive electric power steering apparatus, the same operations and effects as the above-described embodiment are obtained.
[0071]
In the brushless motor of the present invention, since the coil is wound from the outer peripheral side of the stator core, the coil can be wound without being pushed into the slot, so that the coil is not damaged and the motor is short-circuited. Absent. Further, since there is no unevenness due to the slot opening on the inner peripheral surface of the stator, the gap between the stator and the rotor is the same over the entire circumference. Therefore, even if a foreign object enters the motor, the foreign object is not sandwiched between the stator and the rotor, and the motor is not locked. Thus, the reliability of the motor is remarkably improved with a simple configuration, and there is an advantage that sufficient safety can be secured even without a relay or clutch.
[0072]
The present invention can be applied not only to a brushless motor of a column type and pinion type electric power steering apparatus, but also to a brushless motor of a rack assist type electric power steering apparatus.
[0073]
Embodiments of the present invention will be described below with reference to the drawings.
[0074]
The brushless motor 120 of the present invention is applied in place of the brushless motor 12 as a power source in the electric power steering apparatus shown in FIG. The driver's steering force applied to the steering wheel 1 is transmitted to the steering shaft 2 composed of the input shaft 2a and the output shaft 2b. One end of the input shaft 2 a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2 b via the torque sensor 3. Then, the steering force transmitted to the output shaft 2 b is transmitted to the pinion shaft 7 via the universal joints 4 and 6. The steering force is further transmitted to the tie rod 9 via the steering gear 8 to steer the steered wheels. The steering gear 8 is configured as a rack and pinion type having a pinion 8a and a rack 8b, and the rotational motion transmitted to the pinion 8a is converted into a straight motion by the rack 8b.
[0075]
A reduction gear 10 that transmits an auxiliary steering force (assist force) to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2, and a brushless motor 120 that generates the auxiliary steering force is connected to the reduction gear 10. ing. The torque sensor 3 detects the steering torque transmitted to the input shaft 2a. For example, the torque sensor 3 converts the steering torque into a torsion angle displacement of a torsion bar inserted between the input shaft 2a and the output shaft 2b. The displacement is detected by a potentiometer, and when the driver steers the steering wheel 1, a torque detection signal TV having an analog voltage corresponding to the magnitude and direction of the twist generated in the steering shaft 2 is output. For example, when the steering wheel 1 is in a neutral state, the torque sensor 3 outputs a predetermined neutral voltage V0 as a torque detection signal TV. When the steering wheel 1 is turned to the right from this position, the torque sensor 3 responds to the steering torque. When the voltage increasing from the neutral voltage V0 is turned to the left, a voltage decreasing from the neutral voltage V0 according to the steering torque is output.
[0076]
A controller 13 composed of a CPU or the like is a unit that controls the driving of the brushless motor 120 and controls the steering assist force to the steering system, and operates when power is supplied from the in-vehicle battery 16. The negative electrode of the battery 16 is grounded, and its positive electrode is connected to the controller 13 via the ignition switch 14 and the fuse 15a for starting the engine, and is directly connected to the controller 13 via the fuse 15b, and via the fuse 15b. The power supplied is used for memory backup, for example. Then, the controller 13 drives and controls the brushless motor 120 based on the torque detection signal TV from the torque sensor 3 and the vehicle speed detection signal VP from the vehicle speed sensor 17 disposed on the output shaft of the transmission, for example.
[0077]
Next, a fourth embodiment of the brushless motor 120 according to the present invention will be described with reference to FIG. That is, FIG. 13 shows a cross-sectional structure of the stator core of the brushless motor 120. The stator core includes an annular yoke portion 121 and a teeth portion 122 formed of a radial partition wall having a large number of winding recesses (slots). The teeth portion 122 has an integral structure in which adjacent teeth are coupled to each other at a coupling portion 122a on the inner peripheral side. That is, the slot opening of the tooth portion 122 is formed on the outer peripheral side. Further, the yoke part 121 and the tooth part 122 are detachable (fitted), and the tooth part 122 is structured to be fitted to the inner periphery of the yoke part 121.
[0078]
FIG. 14 shows an example of assembly as a brushless motor 120 using the stator core of FIG. 13 corresponding to FIG. First, a large number of stator cores composed of teeth portions 122 are laminated to form a cylindrical laminate, and coils 124 are wound around the slots 123 of the teeth portions 122 of the laminate from the outer periphery, and windings are wound around the teeth portions 122. After that, the tooth portion 122 is fitted and fixed to a cylindrical yoke portion 121 (core) in which a large number of sheets are stacked. At that time, the surface of the slot 123 is insulated by the powder coating 125. This insulation may be another insulation method such as insulating paper. The outer periphery of the yoke portion 121 is a motor housing 126, and a rotor 128 in which a magnet 127 is layered is disposed at the center of the tooth portion 122. The magnet 127 uses a ring magnet, and the outer periphery of the rotor 128 is almost a perfect circle.
[0079]
As described above, in the brushless motor 120 of the present invention, the coil 124 is directly wound around the slot 123 from the outer diameter side of the tooth portion 122, so there is no need to push the coil 124 into the slot 123. For this reason, an excessive force or a local force is not applied to the coil, and the coil 124 is not damaged. Further, the inner peripheral surface 122b of the tooth portion 122 having an integral structure has no irregularities and is almost a perfect circle. The rotor 128 rotates inside the integrally structured tooth portion 122, but the outer periphery (magnet 127) of the rotor 128 has a substantially perfect circle. The gap is almost equal over the entire circumference. Therefore, even if a foreign object enters the motor, there is no place to be caught between the stator and the rotor, so the foreign object is not caught and the motor cannot be rotated. Even if a reinforcing cover is attached to the magnet surface of the rotor 128, the same effect is obtained.
[0080]
The magnetic circuit of the brushless motor 120 includes a main magnetic path that passes from the magnetic pole of the magnet 127 through the tooth portion 122 → the yoke portion 121 → the tooth portion 122 through the gap and returns to the counter magnetic pole of the magnet 127 through the gap again. In addition, a short-circuit magnetic path passing through the coupling portion 122a having the inner diameter of the tooth portion 122 is formed. However, in the motor for the electric power steering apparatus, the performance deterioration due to the short-circuit magnetic path is 2% or less, and there is almost no influence. Since the coil is wound from the wide outer periphery side of the slot opening, the winding space factor of the slot is increased, and the performance can be improved by 10% or more.
[0081]
Next, a fifth embodiment of the brushless motor according to the present invention is shown in FIG. 15 corresponding to FIG. 13, but in this embodiment, the slot opening provided on the outer diameter side of the tooth portion 122 is arranged in the circumferential direction. A flange 122c protruding in both directions is provided. The flange portion 122 c makes it difficult for the coil wire to be broken when the coil 124 is wound, and also prevents the coil 124 from coming into contact when the tooth portion 122 is fitted to the yoke portion 121. Furthermore, by increasing the contact surface between the tooth portion 122 and the yoke portion 121, it is effective to stabilize the fitting operation and secure a magnetic path. A radial sectional view of a brushless motor 120A using the stator core of FIG. 15 is shown in FIG. 16 corresponding to FIG.
[0082]
Furthermore, FIG. 17 shows a sixth embodiment of the brushless motor according to the present invention. In this example, the coil portion 124 is wound around the tooth portion 122 of the fifth embodiment, but the yoke portion is not a laminated core, but a press-molded yoke 121a constitutes the outer box (housing) of the motor. . A tooth portion 122 around which a coil 124 is wound is fitted into a cylindrical yoke 121a, and a rotor 128 is incorporated to constitute a brushless motor. In this case, magnetic considerations such as making the yoke 121a thicker than the outer box of the conventional motor are necessary, but since a member dedicated to the yoke is not necessary, the motor can be reduced in size and cost.
[0083]
Similarly, FIG. 18 shows a seventh embodiment in which the yoke portion is not a laminated core but the housing 121b of the electric power steering apparatus is a yoke. In this example, the shaft of the rotor is a hollow shaft 140, and a rack 141 is coaxially disposed inside the hollow shaft 140. In this example, the housing of the rack 141 also serves as the motor housing, and also functions as a yoke portion.
[0084]
In the motor of the present invention, one end of the coil end drawing position in each coil is arranged on the inner peripheral side of the stator with respect to the adjacent coil end of the other phase, and the other end of the coil end drawing position is adjacent. It is arranged on the outer peripheral side of the stator with respect to the coil ends of the other phases, and the inclination of all the exciting coils is uniform, and the length when viewed from the coil end side can be arranged to be the same. Can be made uniform, and current fluctuation and torque ripple can be reduced.
[0085]
Therefore, by using the motor of the present invention as an assist drive source for the electric power steering apparatus, an electric power steering apparatus that can obtain a smoother steering feeling than the conventional one can be realized.
[0086]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 20 is a sectional structural view of the three-phase brushless motor according to the eighth embodiment of the present invention as seen from the axial direction, and FIG. That is, FIG. 20 is a diagram when the stator is viewed from the axial direction, and shows the routing of the coil end 301 that is a transfer portion between one excitation coil and another excitation coil.
[0087]
At both ends A and B, which are the drawing positions of one coil end 301, the other end B is adjacent to the outer peripheral side O of the slot 302 with respect to the coil end 301a of the other phase to which one end A is adjacent. An exciting coil is wound so as to be on the inner peripheral side I with respect to the coil end 301b of the other phase. As a whole, all the coil ends 301 are arranged so as to be wound obliquely from the outer peripheral side O to the inner peripheral side I of the slot 302. That is, in this brushless motor, a multiphase exciting coil is wound in a slot 302 of the stator core 304 in a wave winding, and one end (end A) of the coil end 301 in each exciting coil is adjacent to another phase. The other end (end B) of the coil end 301 is positioned on the outer peripheral side O of the stator core 304 with respect to the coil end 301a of the stator. Is arranged.
[0088]
On the other hand, the winding method of the exciting coil is as shown in the winding development diagram shown in FIG. 2. One winding (U phase) of the exciting coil 326 passes through the slot 302 a and passes through the coil end 311 to the number of phases. After reciprocating the teeth 303 through the slots 302b separated by the groove pitch, the coils are sequentially wound so as to pass through the next slots 302c at the same pitch via the coil end 312, and the stator is rotated once to return to the original slots. It is rolled back to 302a. Next, the same path is followed, and the stator is made one turn and the line of the exciting coil 326 is returned to the original slot 302a. Such winding is repeated to make the number of conductors of the exciting coil 326 a predetermined number of turns.
[0089]
By winding in this way, the excitation coils 326 of the respective phases are arranged so as to partially overlap each other on the outer peripheral side O and the inner peripheral side I in the slot 302. Since the excitation coils 326 of all phases have the same inclination and the lengths of the coil ends 301 are equally arranged, even if there is a variation according to the magnetic flux in the slot 302, the variation cancels out in the phase. The inductance between the phases becomes equal.
[0090]
The exciting coil 326 may be one wound with a single wire or may be a bundle of several wires. In this brushless motor, since the exciting coil 326 is not formed in a loop as shown in FIG. 21, the number of turns of the exciting coil that affects the inductance of the motor is 0, and the self-inductance of the brushless motor is extremely small. . In addition, since the brushless motor has the same number of conductors as that of the conventional lap winding, the electric resistance of the exciting coil is substantially the same as that of the lap winding, and only the inductance can be reduced.
[0091]
FIG. 22 is a cross-sectional view showing a configuration of a brushless motor 320 according to an eighth embodiment of the present invention. The brushless motor 320 is disposed along a cylindrical housing 322 and an axis of the housing 322. A permanent magnet 325 fixed to a rotatable rotating shaft 324 by bearings 323a and 323b, and fixed to the inner peripheral surface of the housing 322 so as to surround the permanent magnet 325, and three-phase exciting coils 326a, 326b and 326c The rotor 327 is formed by the rotating shaft 324 and the permanent magnet 325.
[0092]
On the other hand, the permanent magnet 325 constituting the rotor 327 has, for example, three S poles and three N poles, and a total of six poles magnetized at equal intervals in the circumferential direction. Here, in this case, a permanent magnet 325 magnetized with a total of 6 poles, 3 poles each of S and N poles, is applied, but the S poles and N poles are alternately arranged at equal intervals in the circumferential direction. As long as it is magnetized, it may be two poles, S pole and N pole, or a plurality of poles.
[0093]
For example, as shown in FIG. 20 and FIG. 21, the equivalent of 1 of the wound brushless motor has an inductance of 80 μH or less and a resistance of about 0.05 ohm, so the electrical time constant τ is τ = L / R = 80 μH / 0.05 ohm = 1.6 milliseconds or less.
[0094]
Since this brushless motor has 3 phases and 6 poles, there are 18 commutations per rotation (3 phases × 6 poles = 18), and if this motor is rotated at 1000 rpm, it will flow once per 3.3 milliseconds. (1 / {(1000/60) * 18} = 0.0033). As a result, even when the brushless motor is rotating at high speed, the electrical time constant τ (1.6 milliseconds) is smaller than the commutation period (about 3 milliseconds), and the excitation current is sufficiently stable. It can flow.
[0095]
In the above-described embodiment, a three-phase six-pole brushless motor has been described. However, the motor according to the present invention is not limited to three phases, and the number of poles is not limited to six. The five-phase four-pole brushless motor as shown in the winding development view of FIG. 23 has the same operations and effects as the above-described embodiment.
[0096]
As described above, as a method for winding the coil around the stator, for example, the exciting coils 326 of all phases are formed in a wave-like shape without being wound directly around the stator core 304, and the formed exciting coil 326 is then attached to the stator core 304. A method of inserting into the slot 302 is used. Here, the exciting coil 326 of each phase is wound around the jig on the winding machine side in a wave shape by a predetermined number of turns, and the exciting coil 326 is temporarily formed. The temporarily formed coils are inserted into the slots 302 of the stator 304 sequentially or simultaneously to be formed.
[0097]
The exciting coil 326 may be a coil in which a plurality of magnet wires are bundled and formed, or a coil in which one magnet wire is formed. In FIG. 20, the coil end 301 is shown as a model so that the arrangement can be easily understood.
[0098]
A motor in which an exciting coil is wound in a wave winding has a smaller inductance than a lap winding motor. Therefore, if the inductance is unbalanced between the phases, the imbalance acts greatly, resulting in a large current fluctuation and a large amount. There is an adverse effect that torque ripple occurs. However, in the brushless motor of this embodiment, as shown in FIG. 20, the drawing positions of the coil ends 301 of the respective exciting coils are arranged equally in all phases, so that the magnetic flux in the slot 302 is as follows. Even if there is a variation, they cancel each other out within the phase and equalize the inductance between the phases.
[0099]
Thereby, according to the brushless motor of the present embodiment, the inductance between phases can be made extremely balanced as compared with the conventional wave winding brushless motor, and the current fluctuation and torque ripple are greatly reduced. be able to.
[0100]
FIG. 24 is a sectional structural view showing a ninth embodiment regarding the arrangement of the excitation coils of the respective phases of the brushless motor according to the present invention.
[0101]
In the brushless motor of this embodiment, the slot opening 352a is provided not on the stator inner peripheral side I but on the outer peripheral side O (stator yoke portion 356 side). That is, the motor has a structure in which the stator is divided into a tooth portion (core) 353 and a yoke portion (core) 356. According to this configuration, the exciting coil can be inserted and wound from the outer peripheral side of the slot 352. Then, after the winding of the exciting coil is completed, the tooth portion 353 and the yoke portion 356 are fitted. Reference numeral 351 denotes a coil end, which is wound so that one end A is positioned on the outer peripheral side O and the other end B is positioned on the inner peripheral side I.
[0102]
FIG. 25 is a sectional structural view showing a tenth embodiment of the arrangement of the excitation coils for each phase of the brushless motor according to the present invention.
[0103]
The brushless motor of the present embodiment is an example of a five-phase four-pole motor shown in the winding development view of FIG. Also in this embodiment, as in the brushless motor shown in FIGS. 20 and 24, the end portions A and B (the radial positions in the slots 362) that are the drawing positions of the coil ends 361 are the same as the end portions A. Each excitation coil 326 is wound such that the other phase coil end 361a is on the outer peripheral side O of the slot 362 and the other end B is on the inner peripheral side I with respect to the other phase coil end 361b. .
[0104]
Since each of the exciting coils of the brushless motor shown in FIG. 24 and FIG. 25 is arranged so that the coil ends are uniformly lengthed and inclined as in the case of FIG. 20, the brushless shown in FIG. Similar to the motor, even if there is a variation in the magnetic flux in the slot, the variation is canceled out in the phase, and the inductance between the phases is made equal. Thereby, compared with the conventional wave winding brushless motor, the inductance between phases can be made into a very well-balanced thing, and an electric current fluctuation and a torque ripple can be reduced significantly.
[0105]
In the above-described embodiment, a three-phase motor and a five-phase motor are described as an embodiment. However, the motor according to the present invention is not limited to this, and may be applied to a motor having any other number of phases. Can do. In the above-described embodiments, the brushless motor is described as an embodiment. However, the motor according to the present invention is not limited to this, and can be applied to other types of motors other than the brushless motor.
[0106]
  As a result, the current fluctuation and torque ripple of the motor of the present invention are greatly reduced. Therefore, the motor of the present invention can be used as an assist drive source for an electric power steering apparatus.UseThus, it is possible to realize an electric power steering apparatus that can obtain a steering feeling that is smoother than the conventional one.
[0107]
The eleventh embodiment is a brushless motor in which a multiphase coil is wound in a wave winding as shown in FIG. 6 referred to in the first embodiment described above in the stator core slot. 13 and 14 referred to in FIG. 14, the stator core has a tooth portion 122 that is coupled with adjacent teeth on the inner peripheral side of the teeth and has an opening on the outer peripheral side, and a magnetic core on the outer peripheral side of the tooth portion 122. The brush portion motor is configured with a yoke portion 121 that forms a path, and has a configuration in which the yoke portion 121 is fixed after winding from the outer peripheral side of the tooth portion 122.
[0108]
That is, in the brushless motor of the eleventh embodiment, the coil is formed by wave winding as shown in the first embodiment, and the stator core is the inner circumference of the teeth as shown in the fourth embodiment. This is a brushless motor having a tooth portion 122 (hereinafter referred to as a “divided core”) that is joined by teeth adjacent to each other and has an opening on the outer peripheral side.
[0109]
As a result, the brushless motor of the eleventh embodiment has a coiled wave winding, so that the inductance of the brushless motor can be reduced and stable regardless of whether the brushless motor is rotating at low speed or high speed. A desired output torque can be obtained, and even when the brushless motor is rotated at a high speed, torque ripple can be greatly suppressed, and electromagnetic noise, magnetostrictive noise and operating noise can be reduced, and smooth It is possible to provide an electric power steering device that can obtain a good steering feeling.
[0110]
Further, in the brushless motor of the eleventh embodiment, since the stator core is a “divided core”, the coil is not damaged when the coil is wound, and the gap between the tooth portion 122 and the rotor 128 is uniform. Reliability for short circuit and lock is remarkably improved. Further, since the winding is wound from the outside, the winding can be simplified, the productivity is improved, the space factor is improved, and a complicated winding such as a wave winding can be simplified. Since there is no unevenness on the inner periphery of the tooth portion 122, the cogging torque is small, and when used in an electric power steering apparatus, a smoother steering feeling can be obtained. Furthermore, by using the yoke portion 121 as a motor or an outer box (motor housing 126) of an electric power steering apparatus including the motor, the motor can be reduced in size and cost can be reduced.
[0111]
In the twelfth embodiment, in the brushless motor of the eleventh embodiment, as shown in FIG. 20, one end of the drawing position of the coil end 301 of each coil is connected to the adjacent coil end 301b of the other phase. On the other hand, the other end of the drawing position of the coil end 301 of each coil is arranged on the outer peripheral side O of the stator core with respect to the adjacent coil end 301a of the other phase. (Hereinafter, referred to as “aligned winding”).
[0112]
In other words, the brushless motor of the twelfth embodiment is a combination of the eleventh embodiment and the eighth embodiment. The coil is formed by wave winding and “aligned winding”, and the stator core is This is a “split core”.
[0113]
As a result, the brushless motor of the twelfth embodiment has the effects provided by the brushless motor of the twelfth embodiment, can equalize the inductance of each phase of the coil, and can reduce current fluctuation and torque ripple. Further reductions can be made.
[0114]
In the thirteenth embodiment, the brushless motor of the eleventh embodiment or the brushless motor of the twelfth embodiment is used as an assist drive source in a power steering device that reduces the steering force of an automobile.
[0115]
As a result, the brushless motor of the thirteenth embodiment can obtain a smoother steering feeling even when the steering wheel is rotated at a low speed or at a high speed. An electric power steering device that can reduce noise, reduce the size, and reduce the cost can be realized.
[0116]
【The invention's effect】
As described above, according to the present invention, in the brushless motor serving as the assist drive source, the multi-phase excitation coil is wound in a wave winding that does not form a loop for each pole, so that the inductance of the brushless motor can be reduced. A stable desired output torque can be obtained regardless of whether the brushless motor rotates at a low speed or a high speed, and torque ripple is greatly suppressed even when the brushless motor is rotated at a high speed. Therefore, it is possible to provide an electric power steering device that can reduce electromagnetic noise, magnetostrictive noise, and operation noise, and can obtain a smooth steering feeling.
[0117]
Further, according to the brushless motor of the present invention, the coil is not damaged when the coil is wound, the gap between the tooth portion and the rotor is uniform, and the reliability with respect to the motor short circuit and the lock is remarkably improved. Further, since the winding is wound from the outside, the winding can be simplified, the productivity is improved, the space factor is improved, and a complicated winding such as a wave winding can be simplified. Since there is no unevenness on the inner periphery of the tooth portion, the cogging torque is small, and when used in an electric power steering device, a smooth steering feeling can be obtained. Furthermore, by making the yoke part an outer case of a motor or an electric power steering apparatus including the motor, the motor can be reduced in size and cost can be reduced.
[0118]
Further, according to the present invention, one end of the coil end drawing position in each coil is disposed on the inner peripheral side of the stator with respect to the adjacent coil end of the other phase, and the other end of the coil end drawing position is Since it is arranged on the outer peripheral side of the stator with respect to the coil ends of the adjacent other phases, the inclination of all the excitation coils becomes uniform, and the length when viewed from the coil end side can be arranged the same. The inductance of each phase can be made uniform, and a brushless motor with small current fluctuation and torque ripple can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an electric power steering apparatus (column type) according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration (column type) of a brushless motor of the electric power steering apparatus according to the embodiment of the present invention.
FIG. 3 is a cross-sectional view showing another configuration (rack coaxial type) of the electric power steering apparatus according to the embodiment of the present invention.
4 is a block diagram showing a configuration of a controller in FIG. 1. FIG.
FIG. 5 is a waveform diagram of excitation current.
FIG. 6 is a winding development view of the brushless motor for the electric power steering apparatus according to the first embodiment of the present invention.
FIG. 7 is a developed winding view of a brushless motor for an electric power steering apparatus according to a second embodiment of the present invention.
FIG. 8 is a developed winding view of a brushless motor for an electric power steering apparatus according to a third embodiment of the present invention.
FIG. 9 is a waveform diagram showing a state at the time of commutation of excitation current of the brushless motor for an electric power steering apparatus according to the embodiment of the present invention.
FIG. 10 is a winding development view of a brushless motor for a conventional electric power steering apparatus.
FIG. 11 is a winding development view of a brushless motor for another conventional electric power steering apparatus.
FIG. 12 is a waveform diagram showing a state of a conventional brushless motor for an electric power steering device when an exciting current is commutated.
FIG. 13 is a structural diagram of a stator core showing a fourth embodiment of a brushless motor according to the present invention.
FIG. 14 is a radial sectional view showing a fourth embodiment of the brushless motor according to the present invention.
FIG. 15 is a structural diagram of a stator core showing a fifth embodiment of the brushless motor according to the present invention.
FIG. 16 is a radial sectional view showing a fifth embodiment of the brushless motor according to the present invention.
FIG. 17 is an axial sectional view showing a sixth embodiment of a brushless motor according to the present invention.
FIG. 18 is an axial sectional view showing a seventh embodiment of the brushless motor according to the present invention.
FIG. 19 is a structural diagram of a stator core of a conventional brushless motor.
FIG. 20 is a sectional structural view showing an eighth embodiment regarding the arrangement of excitation coils for each phase of the brushless motor according to the present invention.
FIG. 21 is a developed winding view of a three-phase brushless motor according to an eighth embodiment of the present invention.
FIG. 22 is a cross-sectional view showing a configuration of a brushless motor according to an embodiment of the present invention.
FIG. 23 is a developed winding view of a five-phase brushless motor according to an embodiment of the present invention.
FIG. 24 is a sectional structural view showing a ninth embodiment of the arrangement of the excitation coils for the respective phases of the brushless motor according to the present invention.
FIG. 25 is a sectional structural view showing a tenth embodiment of the arrangement of the excitation coils for each phase of the brushless motor according to the present invention.
FIG. 26 is a cross-sectional structure diagram showing an example of the arrangement of excitation coils for each phase of a conventional brushless motor.
[Explanation of symbols]
1 Steering wheel
2 Steering shaft
3 Torque sensor
4 Universal joint
5 Lower shaft
6 Universal joint
7 Pinion shaft
8 Steering gear
9 Tie Rod
10 Reduction gear
12 Brushless motor
13 Controller
14 Ignition switch
15 fuse
16 battery
17 Vehicle speed sensor
22 Housing
23 Bearing
24 Rotating shaft
25 Permanent magnet
26 Excitation coil
27 Rotor
70 teeth
120 brushless motor
121 Yoke part
122 Teeth
123 slots
124 coils
125 powder coating
126 motor housing
127 magnet
128 rotor
301 Coil end
302 slots
302a Slot opening
303 Teeth
304 Stator core
320 brushless motor
321 stator
322 housing
323 Bearing
324 axis of rotation
325 Permanent magnet
326 Excitation coil
327 rotor
351 Coil end
352 slots
352a Slot opening
353 teeth
356 Yoke part
361 Coil end
362 slots

Claims (3)

A rotatable rotor having a permanent magnet fixed on the outer peripheral surface, a multi-phase excitation coil surrounding the outer peripheral surface of the rotor, a cylindrical yoke portion, and the excitation coil held on the inner peripheral surface of the yoke portion A control core of a brushless motor for power steering, wherein the excitation coil is wound around the stator core in a wave winding that does not form a loop for each coil corresponding to a pole, and a stator core formed with a plurality of teeth. Drive means for generating a rectangular wave excitation signal to be supplied to each excitation phase of the brushless motor for power steering, and control means for determining the direction of the excitation signal and switching on / off for each excitation phase The control means includes a drive circuit that generates an excitation current to be supplied to the excitation coil as the excitation signal, and controls the excitation current by rectangular wave control. For power steering, the drive circuit is configured to supply a drive signal that makes the current change rate of the excitation phase where the excitation current rises and the fall of the excitation phase coincide with each other or the same level when switching. Brushless motor control device. The teeth of the brushless motor for power steering have an integral structure in which the inner peripheral sides are joined together by adjacent teeth, and the inner peripheral surface is substantially round with no irregularities, and the inner side of the teeth is the rotor. The control device for a brushless motor for power steering according to claim 1, wherein One end of the coil end extraction position of each excitation coil is disposed on the inner peripheral side of the stator core with respect to each adjacent other phase coil end, and the other end of the coil end extraction position of each excitation coil is 3. The control device for a brushless motor for power steering according to claim 1, wherein the controller is disposed on an outer peripheral side of the stator core with respect to each adjacent coil end of another phase.

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