JPH03190585A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To suppress torque ripple easily by providing a stator in which a plurality of coils having effective pitch of 180 deg. electric angle, and a rotor arranged, on the circumference thereof, with a plurality of permanent magnets having trapezoidal flat part magnetized at 60 deg.. CONSTITUTION:A plurality (eight, in the drawing) of permanent magnets 3, alternately magnetized with multi-poles, are arranged on the circumference of a disc 2' thus forming a rotor 2. The permanent magnet 3 is magnetized such that the flux distribution at the flat part will be trapezoidal at electrical angle of 60 deg.. A plurality (six, in the drawing) of air-core coils X1, X2-Z1, Z2, interlinking with the permanent magnets, are arranged thus forming a stator 4. Effective pitch of each coil is set at 180 deg. electric angle, and the coils X1, X2-Z1, Z2 are connected in series or parallel into three-phase coils. Power is fed sequentially from a drive circuit (not shown) to the three-phase coils based on output signals from position detecting elements A-C, arranged in the centers of the coils X1-Z1, thus rotating the rotor 2 around a shaft 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless DC motor in which power supply to three-phase coils is sequentially electronically switched using transistors or the like in accordance with the position of a movable part (rotor) of the motor.

Brushless DC motors are used in a variety of audio and video equipment because they do not generate sparks or noise due to brushes and have a long lifespan. Japanese Patent Publication No. 55-6938 describes a method of passing current in one direction (half-wave drive) to three-phase coils connected in a star shape and a method of passing current in both directions (full-wave drive) in such a brushless DC motor. (driving) method is shown. Brushless DC motors using three-phase coils have the advantage of simple motor structure and drive circuit, and have been put into practical use more widely than ever.

However, conventional brushless DC motors using three-phase coils have the disadvantage that the generated torque (electromagnetic force due to magnets and current) varies depending on the rotational position, resulting in large torque ripple.

In order to eliminate such drawbacks, the applicant has filed a patent application filed in 1973.
No. 2-67671 proposes a brushless DC motor that reduces such torque ripple (in this example, half-wave drive is used in which current flows in one direction through the coil), but the method described above is proposed. In order to reduce torque ripple, the width of the flat part of the magnetic flux density generated by the magnet (magnetic flux acting on the coil) must be made wider than 120' in electrical angle (one magnetic pole pitch is 180°). First, it is difficult to magnetize and form such wide N and S poles adjacent to each other on a single magnet, making it impossible to sufficiently reduce ripple torque.

In addition, motors with an air-core coil placed between a cylindrical magnet and a cylindrical smooth iron core, and motors with an air-core coil placed between a disc-shaped magnet and a disc-shaped iron plate, etc. For slotless type brushless DC motors (magnet rotates and the coil, iron core and iron plate are fixed to the stator) and coreless type brushless DC motors (magnet and iron plate and iron core rotate as one and the coil is fixed to the stator), Because the gap between the magnet surface and the iron core/iron plate is wide, the magnetic flux density (
It is difficult to make the angle of the flat part (strongest part of N pole or S pole) of the component perpendicular to the coil sufficiently wide, and in normal motors it is around 601 to 90 inches (electrical angle).
As a result, in such a brushless DC motor, the ripple in the generated torque is extremely large when using the current supply method (half-wave drive and full-wave drive) as shown in Japanese Patent Publication No. 55-6938. Thick (thick) significantly impedes the rotational performance of the motor, posing a major problem in practice.

The present invention takes these points into consideration and aims to provide a brushless DC motor that has extremely little torque ripple even though it uses three-phase coils.

The present invention will be explained below based on illustrated embodiments.

An embodiment of the present invention is shown in FIGS. 1 to 4. FIG. 1 is a vertical sectional view showing the structure of the motor. A multi-pole magnetized annular magnet 3 is fixed to the stator, and a zero-rotation shaft 1 that rotates integrally is supported by a journal bearing 6 and a thrust bearing 7 of the stator. An air-core coil 5 is fixed to the surface of the iron plate 4 of the stator, and is rotated in a predetermined direction by the interaction between the axial magnetic flux density of the magnetic field formed between the magnet 3 and the iron plate 4 and the current flowing through the coil. It's getting torque.

FIG. 2(a) shows an example of the magnetic pole arrangement of the magnet 3.

The magnet 3 has an equal angular pitch (mechanical angle 45゜me c
It is magnetized to have 8 N poles and 8 S poles alternately arranged at an electrical angle of 180' or approximately equal angular pitch.

Figure 3 shows the distribution of the magnetic flux density B (φ) in the axial direction of the magnetic field generated by the magnet 3 over 360''e1 (the same applies to the other magnetic poles). is shown as 180'el in electrical angle.The distribution is
The width of the flat part of the N pole and S pole where the magnetic flux density is the strongest is 6
It has a trapezoidal wave or approximately trapezoidal wave shape with 0' el (1/3 of the lift pole pitch).

FIG. 2(B) shows the arrangement of the coils and Hall elements for position detection in the stator example. In this example, six concentrated winding coils X, Y, Z, X2, . Y2゜Z2 are arranged at an equal angular pitch (60' mech = 240@ej or approximately equal angular pitch.The center pitch of the effective coil sides involved in torque generation extending in the radial direction of each coil (
This is called the effective pitch) is made equal to or approximately equal to one magnetic pole pitch (180"effi) of the magnet 3 (generally, it is an odd multiple of the 1M one pole pitch). As a result, the coils X1 and x2 are They have the same phase and are connected in series or parallel to form the first phase coil group X, the coils Y and Y2 form the second phase coil group Y, and the coils Z1 and 22 form the third phase coil group Z. is forming.

Hall elements A, B, and C for position detection are arranged at the center of the coils χI, YI, and Zl, and detect the magnetic flux density of the magnet 3, and based on the output, the three-phase coil groups x, y
, z is switched and controlled. This will be discussed later.

FIG. 4 shows a circuit connection diagram of the drive circuit in this embodiment. In the same figure, x, y, z are circular connections (delta connections)
3-phase coil group A, B.

C is a Hall element for position detection (Fig. 2), 24°25.
26 is a first output transistor group, 27°28.29 is a second output transistor group, and 20 is a resistor for detecting the combined current supplied to the coils X, Y, and Z. The first output transistor 24°25.26 is one end (emitter side)
are commonly connected and connected to the ○ side power supply terminal via the resistor 20, each output terminal (collector terminal) is connected to each junction of coils x, y, and z connected in a ring, and the control terminal (base terminal ) Activation/inactivation is controlled by the current flowing to the cell.

The second output transistors 27, 28, and 29 have one end (emitter side) commonly connected to the ■ side power supply terminal, and each output terminal (collector terminal) is connected to the first transistor 24,
It is connected to each output terminal of 25 and 26, and activation/deactivation is controlled by the current to the control terminal (base terminal). In addition, a portion 21 surrounded by a broken line is a position detector constituted by Hall elements A, B, and C, and 22 is a Hall element A,
B.

A first output transistor group 24 responsive to multiple outputs of C.
25. A first distribution controller that distributes and controls the energization of 26;
Reference numeral 3 denotes a second distribution controller that distributes and controls the energization of the second output transistor group 27, 28, 29 responsive to each output of the Hall elements A, B, and C.

Further, 30 is a speed detector (various known configurations can be used) that detects the rotational speed of the rotor 2 and converts it into a command voltage signal 84 corresponding to the speed; 31 and 45 are voltage/current converters; 32 is a current mirror circuit.

Next, its operation will be explained. Power supply voltage ■.

When 20V is applied to the speed detector 30, the command signal 8
The voltage values of DC power supply 4 and DC power supply 33 are compared in voltage/current converter 31, and a current corresponding to the difference between the two is absorbed.

FIG. 5 shows an example of the configuration of the voltage/current converter 31.

In the figure, a signal 84 and a power supply 33 are applied to the base terminals of differential transistors 102 and 103, respectively, and the current value of a constant current source 106 is distributed to each collector side according to the voltage difference. Its collector current is the transistor 108
．． It is compared and inverted by a current mirror circuit 109, and is output (
current sink).

The output of the voltage/current converter 31 is connected to the current mirror circuit 3
2, the output of the transistor 36 is supplied to the first distribution controller 22, and converted into a voltage signal V by a diode 43 and a resistor 44. Further, the output of the transistor 37 is supplied to the second distribution controller 23,
Voltage signal ■2 by diode 52゜53 and resistor 51
is converted to

The voltage signal ■ and the voltage drop across the resistor 20 are compared in the voltage/current converter 45, and a current corresponding to the difference between the two is output (
(current sink) and is supplied as a common emitter current of the transistors 48, 49, and 50 forming the first differential circuit 81.

FIG. 6 shows an example of the configuration of the voltage/current converter 45.

In the same figure, a voltage signal (2) is applied to the base side of the transistor 1200, a voltage drop signal of the resistor 20 is applied to the emitter side, and a collector current flows according to the difference between the two, and is caused by the current mirror formed by the transistors 122 and 123. The current is inverted and supplied to the first differential circuit 81.

The output voltages of the Hall elements A and BC are respectively applied to the base terminals of the transistors 48, 49.50 of the differential circuit 81, and the common emitter current is distributed to each collector current according to the difference in base voltage. The collector current of the transistor with the lowest voltage is the largest, and the collector currents of the other transistors are zero or approximately zero.

The collector currents of transistors 4B and 49.50 are the first
The current becomes the base current of each of the output transistor groups 24, 25, and 26, and the current is amplified to the coil X.

Supplied to Y and Z.

The current supplied to the coils X, Y, and Z is detected as a voltage drop across the resistor 20, and is input to the voltage/current converter 45.

As a result, the voltage/current converter 45. First differential circuit 8
1. A first feedback loop (current feedback loop) is formed by the first output transistor group 24.25° 26 and the resistor 20.
is composed of coils x, y.

The current supplied to Z is ensured to have a current value corresponding to the voltage signal v (therefore, the output command signal 84 of the speed detector 30). As a result, the output transistors 24, 25, 26
The influence of variations in hrt, etc. is significantly reduced.

In addition, as the magnet rotates 30 times, the Hall elements A, B,
As the output voltage of C changes, the energization of the first output transistors 24, 25, and 26 is controlled and smoothly switched so that current is supplied to the corresponding coil. Note that the capacitor 46 is connected to the feedback loop described above. It is used for phase compensation (oscillation prevention).

Next, the operation of the second distribution controller and the second output transistor will be explained. The second distribution controller 23 includes a detection/comparator 82 that compares the operating voltage of the transistor in the energized state of the first output transistor group 24.2526 with a reference voltage signal v2, and a second differential circuit 83. It is made up of.

The output of the current mirror circuit 32 is input to the detection/comparator 82, and the resistor 51. The first by diode 52.53
The common connection terminal of the output transistors 24, 25, and 26 (
A reference voltage signal (2) of a predetermined voltage value is generated from the emitter side).

The emitter side of each of the detection transistors 54, 55, and 56 is connected to the reference potential point (signal ■2 point) as an input terminal in a DC manner (
(directly or via a resistor, diode, etc.), and each base side is connected to the first output transistor 24 as a detection terminal.
, 25 and 26 in a direct current manner.

As a result, the emitter-base forward voltage (VB!=i0.7V) is lower than the operating voltage (absolute value of VCE) of the first output transistors 24, 25, and 26 in the energized state and the reference voltage signal 2. ), the corresponding detection transistor becomes conductive and outputs a current to the collector side.

FIG. 7 shows the current path when output transistors 27 and 25 are activated. The current path is the O side power supply terminal →
Second output transistor 27 → coils X, Y, Z → first
output transistor 25 → resistor 20 → ○ side power supply terminal, and the operating voltage (Vc) of the first output transistor 25 in the energized state becomes smaller than the voltage (v4) of the other output transistors 24 and 26. As a result, , the operating voltage of the output transistor 25 and the reference voltage signal v2 are compared by the detection transistor 55, and a collector current corresponding to the difference is output.The output currents of each detection transistor 54, 55, and 56 are combined (the collector side is common connection), is inverted and amplified by a current mirror of a transistor 59, a diode 57, and resistors 58 and 60, and is inverted and amplified by a second differential circuit 83.
is attracted as a common emitter current.

The outputs of the Hall elements A, B, and C are applied to each base terminal of the transistors 63, 64, and 65 of the differential circuit 83, and the common emitter current is distributed to the collector side according to the base voltage. The collector currents of the transistors 63, 64, and 65 become the base currents of the second output transistors 27, 28, and 29, and switch and control the energization of the coils X, Y, and Z.

Therefore, the detector/comparator 82. Second differential circuit 83, second
output transistors 27, 28, 29 and coils X, Y,
Z constitutes a second feedback loop, which operates to match the operating voltage (VC) of the energized transistor of the first output transistor 24, 25, 26 to a predetermined small voltage value in the active region. To illustrate this, a decrease in the operating voltage of the first output transistor is detected and compared by the detection and comparator 82 to increase its sink current and increase the base current of the second output transistor.
Therefore, the collector current is increased and the coils X, Y
, increase the current supplied to Z. Since the output current (sinking current) of the first output transistor is kept constant by the operation of the first feedback loop described above, when the output current of the second output transistor increases, the coils x, y,
The voltage drop across z is increased and the operating voltage of the first output transistor is increased. As a result, the energization of the second output transistor is controlled so that the operating voltage of the first output transistor is constant or substantially constant.

If such a second feedback loop is provided, the second differential circuit 83. and second output transistors 27, 28 .
29 is stabilized, and switching of the energizing transistors responsive to the output of the position detector 21 is performed reliably and smoothly.

In addition, the value of the reference voltage signal v2 can be set sufficiently smaller than the power supply voltage 3=20V, and the operating voltage when the first output transistor is energized is controlled to a small value within the active region. x, y.

The maximum value of the voltage supplied to Z can be made sufficiently large.

Note that the capacitor 61 is used for phase compensation (
oscillation prevention), and the second output transistor 27, 2
Capacitor 66.68.70 connected in parallel with 8.29
The series circuit of resistors 67, 69, and 71 reduces the spike-like voltage caused by switching the current path.

Next, regarding the energizing operation and generated torque of the embodiment shown in FIGS. 1 to 4, FIG. 8 (relationship diagram between magnet and coil), FIG. This will be explained with reference to the route switching diagram).

FIG. 8 is a diagram showing the relationship between the magnet 3 and the coil X1. In general, the generated torque is proportional to the product of current and magnetic flux density (Fleming's law). Considering the case where current i is passed through coil X in Fig. 8, the effective coil sides at both ends of coil Since the direction of the current is reversed in the extended part), the generated torque τ is -1 (B(θ) - B (θ+α))...
(1), where k is a proportionality constant, θ is the rotation angle (electrical angle) between one point R of the magnet 3 and one point Q of the stator when viewed from the rotation center 0, and α is the effective angle of the coil X1. Pitch (center pitch of effective coil sides expressed in electrical angle).

As shown in Fig. 2, the coils X and X2 are placed in the same phase, and the coils X and X2 are connected in series or in parallel to form the first phase coil group X. Coil X,
, the effective pitch α of X2 is defined as the 1 magnetic pole pitch 1 of magnet 3
The coil group Y of the second phase is arranged with an electrical phase difference of 120° e! from the coil group X of the first phase. The third phase coil group Z is connected to the second phase coil group Y and 120@
They are arranged with a phase difference of el. Furthermore, the magnetic flux density B(φ) generated by the N and S poles of the magnet 3 is the third
60°e as shown in the figure 1. Therefore, the coils x, y of each phase have a trapezoidal distribution with a flat part.
, the current I in z! , [Y, ■ Torque due to the coils x, y, z of each phase when supplying 2 τ8. τ9. τ2 is 1 °Ix (B(θ)-B(θ+180"ei...(2) r, =, Iy ・ (B(θ+120'ef
fi)-8(θ+300@e jri) ・=43
) rz = KI - tz ・ (B(θ+240"
ejri-B(θ+420" ejri l
--(4), and the resultant generated torque T is T-τ8+τ7+τ2......(
5).

(2), (3>, (4) From formulas, each phase coil x, y
, z is found to be proportional to the difference in magnetic flux density between the effective coil sides at both ends of the effective pitch of the coil. Figure 9(a) shows the change in the magnetic flux density difference with respect to the rotation angle.The effective pitch of each of the six coils is 180°e! (
(odd multiple of ), the waveform is similar or substantially similar to the magnetic flux density distribution of the magnet 3, and is a trapezoidal wave or approximately trapezoidal waveform with a flat portion of 60"el. Also, the coil X, 120'eff for Y and Z each
It has a phase difference of i.

Hall elements A, B, and C are each coil Xl.

It is placed at the center of Y, Z, (Fig. 2) and outputs a Hall voltage proportional to the magnetic flux density at each position. Therefore, as shown in FIG. 9(b), a three-phase trapezoidal voltage waveform similar to the distribution of magnetic flux density B(φ) is output.

Based on the three-phase Hall voltage shown in FIG. 9(c), the coil X is driven by the drive circuit shown in FIG.

When the current paths to Y and Z are switched, the current paths are switched as shown in FIG.

That is, if UA, (JB and UC are the output voltages of Hall elements A, B, and C, respectively, then ■ UA, tJ, , U
o area CmEO&lQ■) First output transistor 2
6 and the second output transistor 28 are activated.
Since the resistances of the coils x and yz of each phase are equal (or nearly equal), the composite supply current to the coils is NY-21,/3 for coil Y, and 1. for coils X and Z. -12-
1t/3 (ignoring the back electromotive force), where Ix, I, , I2 have the (basic) direction in FIG. 10 as the positive direction.

■ U8. [Area of IA and Uo (Fig. 1O)) The first output transistor 26 and the second output transistor 27 are activated.

(2) Regions U, UC, and UA (Fig. 1O) The first output transistor 25 and the second output transistor 27 are activated.

(2) Region uo, LJ, UA (Figure 1O (2)) The first output transistor 25 and the second output transistor 29 are activated.

(2) Regions Uo, UA, and UB (Fig. 10 (2)) The first output transistor 24 and the second output transistor 29 are activated.

(2) Areas of UA, Uo, and UB (Fig. 10 (2)) The first output transistor 24 and the second output transistor 28 are activated.

Next, start with ■ and repeat this step by step.

As a result, as the magnet 3 rotates, the coil x of each phase
, y, z current 1. , I, , I2 are shown in Fig. 9 (
It changes as shown in C), (d), and (e) (
(if the effect of back electromotive force is ignored).

Now, if we consider the generated torque in the state ■, (2).

From equations (3) and (4), τ work, τ7. τ2 is shown in Figure 9 (f
), and the resultant generated torque T is completely constant.

The other states U (■, ■, ■, ■, ■) are similarly constant.

Motor torque ripple is the supply current! When , is set as - constant, the generated torque varies locally (according to the rotation angle), but in the brushless DC motor of the present invention, the generated torque is uniform (Fig. 9 (f)), and the torque ripple is is zero.

Next, the influence of the back electromotive force induced in the coils X, Y, and Z as the rotor rotates will be explained.

The back electromotive force generated in the motor coil is proportional to the product of the rotational speed N of the rotor and the magnetic flux density on the effective coil side (Fleming's law). Therefore, in the configuration of this embodiment, the The induced back electromotive force ex, eY,
ez is 2 ・N・ (B (θ) −B(θ+180° e j! ) )...
−(6)eY=2 =N−(B (θ+120”e
jri−B(θ+300° e l ) ) −=
−(1) eZ − to 2 ・N・ (B (θ+240
″el)-B(θ+420°el)) ・Old...(
8), and if the speed N is constant (K2 is a proportionality constant)
, is proportional to the difference in magnetic flux density between the effective pitches of the coils x, y, and z of each phase. That is, the three-phase back electromotive force eX of FIG. 9 (waveform compatible with the waveform of the magnetic flux density difference of al (trapezoidal wave or trapezoidal waveform with a flat part of 60"el),
eY and e2 are generated.

Now, taking as an example the state of ■ in FIGS. 9 and 10, the composite current ■ as shown in FIG. 11.

is divided into 11 and 12. Here, if the coil resistance of each phase is ``, then the voltage/current relational expression % formula %) (9) holds true.

Since the back electromotive force ex, eY, e2 changes as shown in Fig. 9(a), eX+eY+e at any position on the rotor.
2=0 --00. That is, the loop voltage due to the back electromotive force ex, eY, e2 generated in the three-phase coils X, Y, and Z connected in a ring is always zero, and no ring current flows.

Therefore, from equation (9), Qω, (I+), 1l=21
．． /3 ・・・・・・021i
2 = I t / 3 ・
...It becomes 0 hot water. Similarly, ■, ■, ■ in Figure 10
Also in , ■, and ■, (because Equation 10 holds true and there is no effect of back electromotive force, the currents 1x, IY to the coils X, Y, and Z of each phase when the rotor is rotating at high speed.

■□ becomes as shown in FIG. 9 (C), (d), and (e), and the generated torque T becomes uniform.

As described above, the brushless DC motor of the present invention generates uniform torque (zero torque ripple) at any rotational speed, and has little torque fluctuation or vibration. This is the coils X and Y for each phase.

The waveform of the back electromotive force generated at Z is 60aeI! By creating a trapezoidal waveform or a trapezoidal waveform with a flat part of The current path is switched every 60"el, and a large current (21t/3) is shunted to the coil of the phase where the back electromotive force is flat, and the coil of the other two phases is This is achieved by dividing a small current (It/3) in series.In such a motor, the effective pitch of the effective coil side of each phase coil is set to 1 of the magnet.
By making it an odd number multiple of the magnetic pole pitch (180°el) and by making it into a trapezoidal wave or trapezoidal wave-like waveform with a pitch of 60°C2 in the flat part where the N pole and S pole are strong due to the distribution of magnetic flux density generated by the magnet. It can be easily achieved. If we do this, the flat part of the N-pole and S-pole of the magnet where the generated magnetic flux density is strongest will be 60°el and one magnetic pole pitch (
It only requires one-third of 180''effi), can be easily magnetized into a single disc-shaped magnet (or annular magnet), and can be magnetized even when the gap between the magnet and the iron plate (or iron core) is wide. It can be easily achieved.

That is, it is suitable for slotless type or coreless type brushless DC motors. However, the present invention is not limited to such a case, and can also be configured with a brushless DC motor with a core and slot (this will be described later).

Furthermore, in the above embodiment, the operating voltage of the first output transistor when it is energized is detected, and the second output transistor is controlled (second feedback loop) so that the voltage becomes a predetermined value. For stable.

Allows for reliable and smooth current switching. moreover,
Since the current flowing through the first output transistors 24, 25, and 26 is detected and a current corresponding to the voltage signal vI is caused to flow (first feedback loop), the current switching of the first output transistor is difficult. It becomes stable, reliable, and smooth, and the detection of its operating voltage becomes easy and reliable.

In addition, a PNP type detection transistor whose input terminal side is DC connected to the potential point of the reference voltage signal v2, and each detection terminal side is connected DC to each output terminal of the first output transistor 24, 25, 26. 54.55.56, the elements required to detect the operating voltage of the first output transistors 24, 25.26 are transistors 54.55.56.
55°5659, diodes 52, 53, 57, resistor 5
1.58.60, and can be integrated into an integrated circuit (IC) on a single silicon chip. As a result, when the drive circuit part shown in Fig. 4 is constructed using a chip integrated circuit, the number of external parts is reduced, making manufacturing extremely easy, and the detection characteristics also have less variation in correlation, making it possible to The current is also small.

Furthermore, in the embodiment described above, the first output transistor 24
．． 25. The reference voltage signal v2 to be compared with the operating voltage of 26 is changed in response to the command voltage signal 84, and the coils X, Y
, When the current supplied to Z (that is, the current flowing through the first output transistor) is large, the signal ■2 is increased,
When the supplied current is small, the signal v2 is made small.

This causes the first output transistors 24, 25, 26
The operating voltage of the transistor in the energized state (VC) is
Regardless of the magnitude of the current, it is ensured that (
the second output transistor 2 so that the voltage value is small)
7.28.29 energizing current is controlled. In other words, the saturation region (saturation voltage) of the transistor increases as the conducting current increases.
The second output transistor is detected and compared before it reaches the saturation region, and the second output transistor is controlled. This stabilizes the operation of the second feedback loop.

FIG. 12 shows another configuration example of the drive circuit used in the brushless DC motor of the present invention. In the same figure, parts having the same functions as those explained in the drive circuit of FIG. 4 are the same. The symbol is attached. In Figure 12,
21 is a position detector, 22 is a first distribution controller, 23 is a second distribution controller, 24, 25.26 is a first output transistor, 27.28.2'9 is a second output transistor, 30 is a speed detector, 31.45 is a voltage/current converter,
32 is a current mirror circuit, 81 is a first differential circuit, 8
3 is a second differential circuit.

first output transistors 24, 25, 26, resistor 20,
A first feedback loop (current feedback loop) is configured by the voltage/current converter 45 and the first differential circuit 81, and a current corresponding to the command voltage signal 84 is transmitted to the Hall element A of the position detector 21.
, B, and C to the coils x, y, and z via selected output transistors.

The detection/comparator 90 of the second distribution controller 23 compares the operating voltage of the second output transistors 27, 28, and 29 in the energized state with the diodes 132, 133, and the resistor 13.
The transistor 136 detects the reference voltage signal v3 generated at
, 138 and 140, and the output signal is further compared with a reference voltage signal by the differential circuit of transistors 145 and 146, and is output from the collector side of the transistor 146, and is outputted from the collector side of the transistor 146. It is supplied as a common emitter current. The transistors 63, 64.65 of the second differential circuit 83 are switched between active and inactive in response to the outputs of the Hall elements A, B, and C of the position detector 21, and the second output transistors 27.2B, 29 is controlled. That is, a second feedback loop is formed by the detection/comparator 90, the second differential circuit 83, and the second output transistor 27, 28, 29, and the operating voltage of the second output transistor in the energized state is Detect and
The current flowing through the second output transistor is controlled so that the voltage is a small value within the active region.

Even with such a configuration, the above-mentioned FIG. 9(C).

The currents shown in (d) and (e) are supplied, and the generated torque becomes uniform.

FIG. 13 shows another example of a drive circuit used in the brushless DC motor of the present invention. This drive circuit significantly reduces the collector loss of the output transistor by supplying power to the motor coil through a switching voltage conversion method that obtains a variable output DC voltage from a DC power source.

In the figure, 200 is a DC power supply, and a portion 201 surrounded by a broken line is the DC power supply 200 and coil X.

A switching type voltage converter is inserted between Y and Z, 202 is a position detector constituted by Hall elements A, B, and C, and 203 is a coil x, y, This is a distributor that controls the current path to z. Moreover, the first switch transistors 204, 205,
206 has one end connected to the negative output terminal of the voltage converter 201 (
The emitter side) are commonly connected, and each output terminal (collector side) is connected to a plurality of points of the three-phase coil x, y, z connected in a ring, and the current to the control terminal (base side) is connected to the distributor 203. It is controlled by the on/off operation.

The second switch transistors 207, 208 and 209 have one end (collector side) commonly connected to the work type side output terminal of the voltage converter 201, and each output terminal (emitter side)
It is connected to each output terminal of the switch transistors 204, 205, and 206, and the current flowing to its control terminal (base side) is controlled by the distributor 203 to perform on/off operation.

Next, its operation will be explained. Magnet 3 (first
The rotation speed of the motor (see figure) is detected by the speed detector 210, and the voltage signal (■) corresponds to the rotation speed.

Output. According to the output voltage vd of the speed detector 210, the switching controller 222 of the voltage converter 201 turns on and off the switching transistor 221, and controls the on-time ratio (on-time/on-off cycle time). . The switching controller 222 is composed of, for example, a triangular wave generator and a comparator (a variety of known configurations can be used), and generates a pulse signal with a duty ratio corresponding to the input voltage to control the switching transistor 221 on and off. do. The output pulse voltage from the switching transistor 221 is passed through the diode 223.
Inductance element 224. The output voltage of the voltage converter 201 is smoothed by the capacitor 225. is a value corresponding to the on-time ratio of the switching transistor 221, that is, a value corresponding to the output voltage V of the speed detector 210.

Output voltage of voltage converter 201■. is applied to the three-phase coils x, y, and z via the first switch transistors 204, 205, 206 and the second switch transistors 207, 208, and 209, and the rotational position of the magnet 3 is detected by the position detector 202. The 0 divider 203 which detects the voltage signal and inputs the voltage signal according to the position to the divider 203 has a current supply device 211, a first differential circuit 212, a second differential circuit 213, and a current mirror circuit 2.
14.215216, the first and second
The transistors 238 and 23 of the differential circuits 212 and 213 of
The output voltage of the position detector 202 is applied to each base terminal of 9°240.241, 242, and 243, respectively.

Current supply 211 connects first and second differential circuits 212 .
A common emitter current is supplied to 213. In the first differential circuit 212, one transistor is activated in response to the base voltage of the transistors 238, 239, and 240 (output of the position detector 202), and the common emitter current is distributed to the collector side.

Each collector current of the transistors 238, 239, 240 is
6 base currents, and one first switch transistor corresponding to the output of the position detector 202 is always turned on.

Further, the second differential circuit 213 has a transistor 241.2.
42,243 base voltage (output of position detector 202)
In response to this, one transistor becomes active and distributes the common emitter current to the collector side. transistor 241,
The respective collector currents of 242 and 243 become base currents of the second switch transistors 207, 208, and 209+7) through current mirror circuits 214, 215, and 216, respectively, and the second switch transistors according to the output of the position detector 202 One transistor is always on.

That is, in response to the output of the position detector 202, the distributor 2
03 is the first switch transistor 204, 205,
206 and second switch transistors 207, 208,
209 is turned on and off, and as the rotor 2 (see Figure 1) rotates, the current path to the three-phase coils x, y, and z is switched to the first
They are switched sequentially as shown in Figure 0.

If the first switch transistor 206 and the second switch transistor 207 are currently on (the first
(corresponding to 1), a current flows as shown in Fig. 14. Therefore, V, = V 2 ・Vct (sat)
・・・・・・041=r −i, 10ex
...0!9-2 r -i2- (ey
+e2) --(16)11=il+i□
...07), where " is the resistance of the coil. From the above explanation (Fig. 9), in the brushless DC motor of the present invention, eX + eY + eZ - 0 always holds. OI) formula], the result is i, -21,
/3 ・・・・・・0DDi2=
1. /3...0! +
t= (3/2・1/r) ・ [Vo-2°VCt+mouth t+ex)・・・・・・(
).

Here, the generated torque fluctuation when the output voltage vc of the voltage converter 201 is constant becomes the torque ripple.・vCl
isatl is the saturation voltage of the switch transistor,
It can be considered constant.

Therefore, the current supplied to the coil from equation (a)! , becomes related to the back electromotive force ex of the coil ) as shown in the solid line 60″
changes into a trapezoidal waveform with a flat part of el [i.e.
Each waveform in FIG. 9(a) represents each back electromotive force ex, e, , e2
], and since the state shown in FIG. 14 corresponds to the state (■) in FIGS. 9 and 10, eX is constant during this period.

Therefore, from equation (to), the composite current 1t becomes constant, and αm
A constant current i, , +2 corresponding to the O'J equation is shunted to the coils of each phase. The same applies to other states, and as the rotor 2 rotates, the coils X of each phase.

Currents ■8°rY, i□ as shown in FIGS. 9(c), (d), and (e) are supplied to Y and Z. As a result, the combined generated torque T=τwork+τ7+τ2 becomes uniform (torque ripple is zero) as shown in FIG. 9(f).

In this drive circuit, a switching type voltage converter 201 is used to convert the voltage of the DC power supply 200 to
The first and second switch transistors 204, 205, 206, 2 operate on and off by obtaining a desired DC voltage x (corresponding to the output signal of the speed detector 210) from V.
07.208209 is supplied to three-phase coils X, Y, and Z.

As a result, the collector losses in the first and second switch transistors and the conversion losses caused by the voltage converter 201 are considerably reduced, and the first and second output transistors operating in analog form as shown in FIGS. This is significantly smaller than the collector loss consumed at 24, 25°, 26.27.28.29. Particularly, the effect is large when the coil voltage (2) (FIG. 14) is small, and the power loss of this drive circuit is significantly reduced.

Furthermore, in the drive circuit of FIG.
01 output voltage V. By detecting this and making the base currents of the first and second switch transistors small when vo is small and large when vo is large, base current loss is also reduced.

To explain this, the current supply 2 of the distributor 203
11 is the output voltage ■ of the voltage converter 201.

is detected by the resistor 227, and its voltage value V. When becomes larger, the common emitter current of the first and second differential circuits 212, 213 is increased, and the first and second switch transistors 204, 205, 206, 207, 208, .
Increase the base current to 209. Conversely, when the output voltage VC of the voltage converter 201 becomes smaller, the current supplyer 211
This reduces the output current of the first and second switch transistors, thereby reducing the base currents of the first and second switch transistors (sufficient base current is always supplied so that the switch transistors operate on and off).

As a result, sufficient base current is supplied to the first and second switch transistors even during large current operation during startup and acceleration (when V increases and the current supplied to the coil increases), and at a constant speed. During small current operation during rotation (when vo is small and the current supplied to the coil is also small), the base current is small (to a point slightly higher than the minimum required value).
are doing.

As a result, the base current loss when a small current is passed through the first and second switch transistors is significantly reduced.

In the above embodiment, the three-phase coils X,,X2゜y,,y
2. Although an example is shown in which z, , and z2 are arranged so that they do not overlap in a plane (see Figure 2 (c)), the present invention is not limited to such a case, but can also be applied to a case where three-phase coils are arranged so as not to overlap each other in a two-dimensional manner. 15 and 16.
This will be explained with reference to the figures.

FIG. 15 shows a wave-wound coil 400 for one phase. Opposing the 8-pole magnetized magnet 3 [see Figure 2 (a)], the magnet 3 is shifted in phase by 120° el.
The phase coils 400 are superimposed to form a three-phase coil x,
y and z are formed.

The coil 400 of each phase has an effective coil side pitch of 180''
effi (odd multiple of) to reduce fluctuations in generated torque.

Figure 16 shows eight concentratedly wound coils 411°412.
413, 414, 415, 416, 417°, 418 are connected in series to form a coil group for l phase.

Further, in the above-mentioned embodiments, a slotless type brushless DC motor was explained as an example (FIG. 1), but the present invention is not limited to such a case, and a brushless DC motor with a core and a front can also be configured.

FIG. 17 shows an example of a motor with a core and slot proposed by the present applicant in Japanese Patent Application No. 52-67671. In the figure, a magnet 502 attached to a rotor 501
Four magnetic poles are magnetized and formed at equal angles (90 degrees mech) or approximately equal angles. As shown in FIG. 3, the distribution of magnetic flux density generated by the magnet 502 is 60@ej!
It has a trapezoidal or trapezoidal waveform with a flat portion.

A stator core 503 is arranged opposite to the magnetic poles of the magnet 502, and the stator core 503 is connected to the main salient pole 50.
4 and three auxiliary salient poles 505 are provided. 3
Each main salient pole is 240°ei! (or 120°
The winding groove 506 is arranged with a phase difference of el).
3-phase coils X and Y.

2 is wrapped.

The pitch of the grooves at both ends of each main salient pole is set to 96'mech (192
°el), the pitch of the grooves at both ends of each auxiliary salient pole is 24°me
ch (48°el). Each coil x,
The effective pitch of y and z (pitch that collects magnetic flux) is
is equal to the pitch of the grooves at both ends of the main salient pole (190" el), and is equal to the pitch of one magnetic pole of the magnet 502 (180" el).
It is done almost equally to ejri.

Therefore, such a motor is driven by a drive circuit as shown in FIGS. 4, 12, or 13 in FIGS. 9(c) and (d).
), (e), the generated torque will be uniform (torque ripple is small).

Note that an auxiliary groove 507 is provided at the tip of each main salient pole 504 at a 24° angle.
Three winding grooves 506 and auxiliary grooves 507 are provided for each mech, and the winding grooves 506 and the auxiliary grooves 507 are arranged at an equal angular pitch (24 degrees mech) or a substantially equal angular pitch, so that the coggin torque is also reduced.

In each of the above-described embodiments of the present invention, the position detector is constructed using a Hall element, but the present invention is not limited to such a case.
Needless to say, a high frequency coupling method, a supersaturated inductor method, etc.) may be used.

As is clear from the above description, the brushless DC motor of the present invention generates uniform torque (small torque ripple) and has significantly small torque fluctuations. Therefore, if a brushless DC motor for, for example, audio/visual equipment is constructed based on the present invention, a high-performance equipment can be realized.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of a motor according to an embodiment of the present invention, and FIGS. 2(a) and (b) are diagrams showing the arrangement of the magnetic poles of the magnet and the arrangement of the coil and Hall element in the same embodiment. 3 is a distribution diagram of the magnetic flux density generated by the magnet, FIG. 4 is a drive circuit diagram in an embodiment of the present invention, and FIGS. 5 and 6 are specific configuration examples of voltage/current converters, respectively. 7 is a circuit diagram for explaining the operation of FIG. 4, FIG. 8 is a diagram showing the relationship between the magnet, coil, and Hall element in the same embodiment, and FIG. 9(a)
. (b), (c), (d), (e), (f) are waveform diagrams for explaining the operation of the embodiment shown in Figs. 1 to 4, and Fig. 10 is a coil diagram in the same embodiment. 11 is a diagram for explaining the current flowing to the coil, and FIGS. 12 and 13 each show other examples of drive circuits that can be used in the present invention. Wiring diagram, 1st
Figure 4 is a diagram for explaining the current to the coil in the same embodiment, Figures 15 and 16 are diagrams showing other configuration diagrams (for one phase) of the coil used in the present invention, and Figure 17 is a diagram for explaining the current to the coil in the same embodiment. FIG. 7 is a configuration cross-sectional view showing another motor structure that can be used in the present invention. 1...Rotating shaft, 2...Rotor, 3...
...Magnet, 4...Stator, 5...
...Coil, XI~Z2゜X, Y, Z...
Coil, A, B, C...Hall element, 2I...
...Position detector, 22.23...First and second distribution controller, 24,25.26...First output transistor, 27.28.29. ...Second
Output transistor, 30...Speed detector, 3
1゜45...Voltage/current converter, 32...
...Current mirror circuit, 81.83...1st
and second differential circuit, 82.90...detector/comparator, 200...DC power supply, 201...
Voltage converter, 202...Position detector, 203.
...Distributor, 204, 205, 206...
・First switch transistor, 207, 208° 20
9...Second switch transistor, 210.
...Speed detector, 211...Current supply device, 212°213...First and second differential circuit,
214,215゜216... Current mirror circuit, 222 Old... Switching controller, 400,41
1-418 Old... Coil, 501... Rotor, 502... Magnet, 503...
Stator core, 504...Main salient pole, 505...
...Auxiliary salient pole.

Claims (2)

[Claims] (1) Multiple permanent magnetic poles of N pole and S pole are magnetized alternately,
The flat part of the distribution of magnetic flux density on the circumference is electrical angle 60
A rotor having a magnet having a trapezoidal wave shape of approximately 180° is disposed at a position interlinking with the magnetic flux of the magnet, and the effective pitch of each coil is approximately 180° electrical angle, and the effective pitch of each coil is The distribution of the magnetic flux density difference generated by the magnet is made into a trapezoidal wave shape with a flat part having an electrical angle of about 60 degrees with respect to the rotation angle of the rotor, and a three-phase coil group formed by connecting a plurality of the coils in a ring; position detection means for detecting the rotational position of the rotor;
a first output transistor group consisting of three transistors forming a current path between the three nodes of the three-phase coil group connected in a ring and one end of the DC power supply; a second output transistor group consisting of three transistors forming a current path between the other ends of the DC power supply;
In response to a command signal instructing current supply to the coil group and in response to an output signal of the position detection means,
controlling distribution of energization of the first output transistor group so as to supply current to one node of the coil group of the phase in which the distribution of the generated magnetic flux density difference is flat among the coil groups of the phase; 1 distribution control means, and the second output so as to form a current path of the DC power source with the other node of the coil group of the phase located in the flat portion in response to the output signal of the position detection means. a second distribution control means for distributing and controlling energization of the transistor group; , controlling the conduction current of the second output transistor group in response to an output signal of the operation detecting means that detects the operating voltage of the second output transistor group, and controlling the conduction current of the second output transistor group in the energized state. A brushless direct current motor that includes a control means that increases the applied current when the operating voltage increases and decreases the applied current when the operating voltage decreases. (2) Multi-pole magnetization with alternating N and S permanent magnetic poles,
The flat part of the distribution of magnetic flux density on the circumference is electrical angle 60
A rotor having a magnet having a trapezoidal wave shape of approximately 180° is disposed at a position interlinking with the magnetic flux of the magnet, and the effective pitch of each coil is approximately 180° electrical angle, and the effective pitch of each coil is The distribution of the magnetic flux density difference generated by the magnet is made into a trapezoidal wave shape with a flat part having an electrical angle of about 60 degrees with respect to the rotation angle of the rotor, and a three-phase coil group formed by connecting a plurality of the coils in a ring; position detection means for detecting the rotational position of the rotor;
a first output transistor group consisting of three transistors forming a current path between the three nodes of the three-phase coil group connected in a ring and one end of the DC power supply; a second output transistor group consisting of three transistors forming a current path between the other ends of the DC power supply;
In response to a command signal instructing current supply to the coil group and in response to an output signal of the position detection means,
controlling distribution of energization of the first output transistor group so as to supply current to one node of the coil group of the phase in which the distribution of the generated magnetic flux density difference is flat among the coil groups of the phase; 1 distribution control means, and the second output so as to form a current path of the DC power source with the other node of the coil group of the phase located in the flat portion in response to the output signal of the position detection means. a second distribution control means for distributing and controlling energization of a group of transistors, the second distribution control means comprising a reference voltage generation means for obtaining a reference voltage signal that changes a voltage value in response to the command signal; Comparing means for comparing the operating voltage of transistors in the energized state of the second output transistor group with the reference voltage signal; and responding to an output signal of the comparing means comparing the operating voltage of the second output transistor group. control means for controlling the conduction current of the second output transistor group, increasing the conduction current when the operating voltage of the second output transistor in the energized state increases, and decreasing the conduction current when the operation voltage decreases; A brushless DC motor consisting of: