JPH0634615B2 - Brushless DC motor - Google Patents

Description

The present invention relates to a brushless DC motor which sequentially and electronically switches power supply to coils of three phases in accordance with the position of a motor movable portion (rotor) using a transistor or the like.

Brushless DC motors are used in various audio and video equipment because they do not generate sparks or noise due to brushes and have a long life. Japanese Examined Patent Publication No. 55-6938 discloses a brushless DC motor in which a star-connected three-phase coil is supplied with a current in one direction (half-wave drive) and a current in both directions (full-wave). Drive) is shown. Brushless DC motors that use three-phase coils have the advantage that the motor structure and drive circuit are simple, and have been widely put into practical use.

However, a conventional brushless DC motor using a three-phase coil has a drawback in that generated torque (electromagnetic force generated by a magnet and an electric current) varies depending on a rotational position, resulting in a large torque ripple. In order to eliminate such a drawback, the applicant of the present invention has proposed a brushless DC motor in which the torque ripple is reduced in Japanese Patent Application No. 52-67671 (in the embodiment, a coil is unidirectional). Half-wave drive to flow current). However, in order to reduce the torque ripple by the above method, the width of the flat portion of the generated magnetic flux density (magnetic flux acting on the coil) of the magnet should be 120 ° or more in electrical angle (one magnetic flux pitch is 180 °). It must be widened, and it is difficult to magnetize and form such wide N and S poles adjacent to a single magnet, and the ripple torque cannot be sufficiently reduced. In addition, a so-called motor such as a motor that arranges an air-core coil between a cylindrical magnet and a cylindrical smooth iron core or a motor that arranges an air-core coil between a disk-shaped magnet and a disk-shaped iron plate, For slotless type (magnet rotates and coil and iron core / iron plate is fixed to stator) brushless DC motor and coreless type (magnet and iron plate / iron core rotates integrally and coil is fixed to stator) brushless DC motor Since the gap between the magnet surface and the iron core / iron plate is wide, the angle width of the flat portion (the strongest portion of the N pole or S pole) of the magnetic flux density (component orthogonal to the coil) in the coil portion can be made sufficiently wide. It is difficult, and the angle is about 60 ° to 90 ° (electrical angle) in a normal motor. As a result, in such a brushless DC motor, the ripple of the generated torque is very large by the current energization method (half-wave drive and full-wave drive) as shown in Japanese Patent Publication No. 55-6938, and the rotation of the motor is very large. It significantly impaired the performance and became a big problem in practical use.

In consideration of such a point, the present invention is to provide a brushless DC motor having extremely small torque ripple while using a three-phase coil.

Hereinafter, the present invention will be described based on illustrated embodiments.

1 to 4 show one embodiment of the present invention. FIG. 1 is a vertical cross-sectional view showing the motor structure, in which a rotor 2 made of a magnetic material having a rotating shaft 1 attached thereto is fixed with an annular magnet 3 magnetized in multiple poles in the thickness direction. To rotate. The rotary shaft 1 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 magnetic flux density in the axial direction of the magnetic field formed between the magnet 3 and the iron plate 4 and the current flowing through the coil. Getting torque.

FIG. 2A shows an example of the magnetic pole arrangement of the magnet 3. The magnet 3 has an N pole at an equal angular pitch (mechanical angle 45 ° mech = electrical angle 180 ° el) or a substantially equal angle pitch.
It is magnetized to have eight poles alternately.

FIG. 3 shows the distribution of the magnetic flux density B (φ) in the axial direction of the magnetic field generated by the magnet 3 for 360 ° el (same for other magnetic poles). Here, one magnetic pole pitch of the magnet 3 is shown as an electrical angle of 180 ° el. The distribution is N
The width of the flat part where the magnetic flux density of the pole and the south pole is the strongest is 60
It has a trapezoidal wave or a substantially trapezoidal wave shape with an angle of el (1/3 of one magnetic pole pitch).

FIG. 2 (b) shows the arrangement of the coils on the stator side and the Hall elements for position detection. In this example, the six concentrated winding coils X ₁ , Y ₁ , Z ₁ , X ₂ , Y ₂ , Z ₂ are arranged at an equiangular pitch (60 ° mech = 240 ° el) or a substantially equiangular pitch. ing. The center pitch of effective coil sides (referred to as an effective pitch), which is involved in the generation of torque extending in the radial direction of each coil, is equal to or substantially equal to one magnetic pole pitch (180 ° el) of the magnet 3. Is an odd multiple of one magnetic pole pitch). As a result, the coils X ₁ and X ₂ have the same phase and are connected in series or in parallel to form the first-phase coil group X, the coils Y ₁ and Y ₂ form the second-phase coil group Y, and the coil Z 1. ₁ and Z ₂
Form a third-phase coil group Z.

Hall elements A, B and C for position detection are arranged in the central portions of the coils X ₁ , Y ₁ and Z ₁ , and the magnetic flux density of the magnet 3 is detected, and the three-phase coil group X,
The current to Y and Z is switched and controlled. This will be described later.

FIG. 4 shows a circuit connection diagram of the drive circuit in this embodiment. In the figure, X, Y and Z are three-phase coil groups which are annularly connected (delta connection), A, B and C are hall elements for position detection (FIG. 2), and 24, 25 and 26 are first Output transistor group, 27, 28 and 29 are second output transistor groups, and 20 is a resistor for detecting a combined supply current to the coils X, Y and Z. First output transistor 2
4, 25 and 26 have one ends (emitter side) commonly connected and connected to the side power supply terminal via the resistor 20, and each output terminal (collector terminal) is a coil X, Y,
The active / inactive state is controlled by a current to a control terminal (base terminal) connected to each Z contact.

The second output transistors 27, 28, 29 have one end (emitter side) commonly connected and connected to the side power supply terminal, and each output terminal (collector terminal) has a first transistor 24,
The output terminals 25 and 26 are connected to each other, and activation / inactivation is controlled by a current to a control terminal (base terminal). Further, a portion 21 surrounded by a broken line is a position detector composed of Hall elements A, B and C, and 22 is a Hall element A,
First output transistor group 2 that responds to multiple outputs of B and C
A first distribution controller 23 for distributing and controlling the energization of 4, 25, 26, and 23 for distributing and controlling the energization of the second output transistor groups 27, 28, 29 in response to the respective outputs of the Hall elements A, B, C. It is a second distribution controller.

Further, 30 is a speed detector (various well-known configurations are available) that detects the rotation 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, the operation will be described. 20 for power supply voltage V _s
When V is applied, the command signal 84 of the speed detector 30 and the voltage value of the DC power supply 33 are compared in the voltage / current converter 31, and the current corresponding to the difference between them is absorbed.

FIG. 5 shows a configuration example of the voltage / current converter 31. In the figure, the signal 84 and the power supply 33 are the differential transistor 10
2, 103 are respectively applied to the base terminals, and the current value of the constant current source 106 is distributed to each collector side according to the voltage difference. The collector current of the transistors 108, 1
It is compared and inverted by the current mirror circuit 09, and is output (current is absorbed) through the transistor 111 whose base is grounded.

The output of the voltage / current converter 31 is the current mirror circuit 3
The current is inverted by 2, and the output of the transistor 36 is supplied to the first distribution controller 22 and converted into the voltage signal V ₁ by the diode 43 and the resistor 44. The output of the transistor 37 is supplied to the second distribution controller 23,
The voltage signal V _{2 is} generated by the diodes 52 and 53 and the resistor 51.
Is converted to.

The voltage signal V ₁ and the voltage drop of the through hole 20 are compared by the voltage / current converter 45, and the current corresponding to the difference between them is output (current absorption), and the transistor forming the first differential circuit 81. It is supplied as a common emitter current of 48, 49, 50.

FIG. 6 shows a configuration example of the voltage / current converter 45. In the figure, the voltage signal V ₁ is applied to the base side of the transistor 120.
Is applied, a voltage drop signal of the resistor 20 is applied to the emitter side, a collector current according to the difference between the two flows, the current is inverted by the current mirror of the transistors 122 and 123, and the current is supplied to the first differential circuit 81. To be done.

The output voltages of the Hall elements A, B, C are applied to the base terminals of the transistors 48, 49, 50 of the differential circuit 81, respectively, and the common emitter current is distributed to the collector currents according to the difference in the base voltages. , The collector current of the transistor having the lowest base voltage becomes the largest, and the collector currents of the other transistors become zero or substantially zero.

The collector currents of the transistors 48, 49 and 50 are the first
The base currents of the output transistor groups 24, 25, and 26 are amplified and current-amplified and supplied to the coils X, Y, and Z.

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

As a result, the voltage / current converter 45, the first differential circuit 8
1, the first feedback loop (current feedback loop) by the first output transistor group 24, 25, 26 and the resistor 20
And the supply current to the coils X, Y, Z is surely the voltage signal V ₁ (therefore, the output command signal 8 of the speed detector 30).
The current value corresponds to 4). As a result, the influence of variations in h _FE of the output transistors 24, 25, 26 is significantly reduced.

Further, as the magnet 3 rotates, the Hall elements A, B,
The output voltage of C changes, and the energization of the first output transistors 24, 25, 26 is controlled so that the current is supplied to the corresponding coil, and the switching is smoothly performed. The capacitor 46 is provided for phase compensation (oscillation prevention) of the feedback loop described above.

Next, operations of the second distribution controller and the second output transistor will be described. The second distribution controller 23 includes a detection / comparator 82 for comparing the operating voltage of the transistors in the first output transistor groups 24, 25, 26 in the energized state with the reference voltage signal V ₂ , and a second difference. It is composed of a dynamic circuit 83.

The output of the current mirror circuit 32 is input to the detection / comparator 82, and the resistor 51 and the diodes 52 and 53 make the first output.
The reference voltage signal V ₂ having a predetermined voltage value is generated from the common connection terminal (emitter side) of the output transistors 24, 25 and 26.

Each emitter side of the detection transistors 54, 55, 56 is connected as an input terminal to a reference potential point (point of the signal V ₂ ) in direct current (directly or via a resistor, a diode, etc.),
Each base side has a first output transistor 2 as a detection terminal.
The output terminals of 4, 25, and 26 are connected in a direct current manner. As a result, the first output transistors 24, 25, 2
When the operating voltage (absolute value of V _CE ) of the transistor in the energized state of 6 and the reference voltage signal V _{2 become} smaller than the forward voltage between the emitter and the base (V _BE ≈0.7 V), the corresponding detection transistor becomes conductive. , Output current to the collector side.

FIG. 7 shows the current path when the output transistors 27 and 25 are active. The current path is the side power supply terminal →
The second output transistor 27 → coil X, Y, Z → first output transistor 25 → resistor 20 → side power supply terminal, and the operating voltage (V _CE ) of the first output transistor 25 in the energized state is the other output transistor. It becomes smaller than the voltage (V _CE ) of 24 and 26. As a result, the operating voltage of the output transistor 25 and the reference voltage signal V ₂ are compared by the detection transistor 55, and the collector current corresponding to the difference is output. The output currents of the detection transistors 54, 55, 56 are combined (collector side is commonly connected), inverted and amplified by the current mirror of the transistor 59, the diode 57, and the resistors 58, 60, and the second differential circuit 83.
Is drawn as a common emitter current of.

The outputs of the Hall elements A, B, C are applied to the base terminals of the transistors 63, 64, 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 the energization of the coils X, Y and Z is controlled to be switched.

Therefore, the detection / comparator 82, the second differential circuit 83, the second
Output transistors 27, 28, 29 and coils X, Y,
A second feedback loop is formed by Z and operates so that the operating voltage (V _CE ) of the first output transistors 24, 25 and 26 in the conducting state matches the predetermined small voltage value in the active region. To do. To explain this, the decrease in the operating voltage of the first output transistor is detected and compared by the detection / comparator 82 to increase its sink current, and the base current of the second output transistor,
Therefore, the collector current is not increased and the coil X,
Increase the current supplied to Y and Z. Since the output current (suction current) of the first output transistor is made 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, Z
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 becomes constant or substantially constant.

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

Further, the value of the reference voltage signal V ₂ can be set sufficiently smaller than the power supply voltage V _s = 20V, and the operating voltage of the first output transistor when energized is controlled to a small value within the active region. The maximum value of the voltage supplied to the coils X, Y, Z can be made sufficiently large.

The capacitor 61 is for phase compensation (oscillation prevention) of the second feedback loop, and the second output transistor 27,
28, 29 capacitors 66, 68, 7 connected in parallel
A series circuit of 0 and resistors 67, 69, 71 reduces spike-like voltage due to switching of the current path.

Next, regarding the energizing operation and the generated torque of the embodiment shown in FIGS. 1 to 4, FIG. 8 (relationship diagram between the magnet and the coil), FIG. 9 (operation explanatory waveform diagram) and FIG. 10 (current) This will be described with reference to a road switching diagram).

FIG. 8 is a diagram showing the relationship between the magnet 3 and the coil X ₁ . Generally, the generated torque is proportional to the product of current and magnetic flux density (Fleming's law). Considering the case where the current i is passed through the coil X ₁ in FIG. 8, the direction of the current is reversed at the effective coil sides (portions extending in the radial direction) at both ends of the coil X ₁ , so that the generated torque τ is τ = k · i {B (θ) −B (θ + α)} (1) Here, k is a proportional constant, θ is a rotation angle (electrical angle) when one point R of the magnet 3 and one point Q of the stator are viewed from the rotation center O, and α is an effective pitch of the coil X ₁ (effective coil side). (Electrical angle of the center pitch of)
Is.

As shown in FIG. 2, the coils X ₁ and X ₂ are electrically in phase, and the coils X ₁ and X ₂ are connected in series or in parallel to form a first-phase coil group X. Coil X ₁ , X
₂ effective pitch α is 1 magnetic pole pitch 180 of magnet 3
Equal to (or an odd multiple of) el. Also, the second-phase coil group Y is arranged so as to have an electrical phase difference of 120 ° el with the first-phase coil group X, and
The phase coil group Z is arranged to have a phase difference of 120 ° el with the second phase coil group Y. In addition, magnet 3
As shown in FIG. 3, the magnetic flux density B (φ) generated by the N and S poles has a trapezoidal wave-like distribution having a flat portion of 60 ° el. Therefore, when the currents I _X , I _Y , and I _Z are supplied to the coils X, Y, and Z of the respective phases, the coils X of the respective phases,
The torques τ _X , τ _Y , and τ _{Z due to Y} and _Z are respectively τ _X = K ₁ · I _X · {B (θ) −B (θ + 180 ° el} ... (2) τ _Y = K ₁ · I _Y · {B (θ + 120 ° el) −B (θ + 300 ° el)} …… (3) τ _Z = K ₁ · I _Z・ {B (θ + 240 ° el) −B (θ + 420 ° el)} …… (4) , The resultant torque T is T = τ _X + τ _Y + τ _Z (5).

From equations (2), (3), and (4), it is understood that the torque generated by the coils X, Y, and Z of each phase is proportional to the difference in magnetic flux density at the effective coil sides at both ends of the effective pitch of the coil. Fig. 9
The change in the magnetic flux density difference with respect to the rotation angle is shown in (a).
Since the effective pitch of each coil is set to 180 ° el (an odd multiple of 180 ° el), a waveform similar to or substantially similar to the magnetic flux density distribution of the magnet 3 is formed, and a trapezoidal wave or a substantially trapezoidal wave having a flat portion of 60 ° el is formed. Becomes the waveform of. Further, the coils X, Y, and Z each have a phase difference of 120 ° el.

The Hall elements A, B, and C respectively include coils X ₁ , Y ₁ , and
It is placed at the center of Z ₁ (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 the magnetic flux density B (φ) is output.

When the current path to the coils X, Y, Z is switched by the drive circuit of FIG. 4 based on the three-phase Hall voltage as shown in FIG. 9 (b), the current path is accompanied by the rotor circuit. Then, switching is performed as shown in FIG. That is, v
_{When A} , v _B , and v _C are output voltages of the Hall elements A, B, and C, respectively, the regions of U _A , U _B , and U _C (FIG. 10) are the first output transistor 26 and the second output transistor 28. Becomes active. At this time, coils of each phase X, Y, Z
Resistors are equal (or substantially equal), the composed supply current _{I t} to the coil is _I Y = _-2I t / 3 in the coil Y, shunts and _{I X = I Z = I t} / 3 in the coil X and Z (When the back electromotive force is ignored). Where I _X , I _Y , and I _Z are the tenth
The (basic) direction in the figure is the forward direction.

Regions of U _B , U _A , and U _C (FIG. 10) The first output transistor 26 and the second output transistor 27 are activated.

Regions of U _B , U _C , and U _A (FIG. 10) The first output transistor 25 and the second output transistor 27 are activated.

Regions of U _C , U _B , and U _A (FIG. 10) The first output transistor 25 and the second output transistor 29 are activated.

Regions of U _C , U _A , and U _B (FIG. 10) The first output transistor 24 and the second output transistor 29 are activated.

Regions of U _A , U _B , and U _C (FIG. 10) The first output transistor 24 and the second output transistor 28 are activated.

Then go back and repeat this step by step. As a result, as the magnet 3 rotates, the coils X, Y, and
Currents I _X , I _Y , and I _{Z to Z} are shown in FIGS. 9 (c), (d), and (e).
It changes as shown in (when the effect of back electromotive force is ignored).

Considering the torque generated in the state of (2), (3),
From equation (4), τ _X , τ _Y , and τ _Z are as shown in FIG. 9 (f), and the resultant torque T is completely constant. Other states (,
,,,) is also constant.

Torque ripple of the motor is supplied but the current (corresponding to the rotation angle) locational torque generated when the a I _t constant is change, the generated torque is uniform (Fig. 9 is a brushless DC motor of the present invention (f)) and the torque ripple is zero.

Next, the influence of the back electromotive force induced in the coils X, Y, Z with the rotation of the rotor will be described. The inverse dielectric pressure 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 coil X,
The counter electromotive voltages e _X , e _Y , and e _Z induced in _Y and _Z are e _X = K ₂ · N · {B (θ) −B (θ + 180 ° el)} (6) e _Y = K ₂・ N ・ {B (θ + 120 ° el) −B (θ + 300 ° el)} …… (7) e _Z = K ₂・ N ・ {B (θ + 240 ° el) −B (θ + 420 ° el)} …… ( 8), and if the speed N is constant (K ₂ is a proportional constant), it is proportional to the magnetic flux density difference between the effective pitch ends of the coils X, Y, and Z of each phase. That is, the three-phase back electromotive force e _X , e _{Y of} a waveform similar to the waveform of the magnetic flux density difference of FIG. 9 (a) (trapezoidal wave having a flat portion of 60 ° el or trapezoidal wave),
e _Z occurs.

Now, considering taking the state of the Figure 9 and Figure 10 as an example, the composite current I _t as shown in FIG. 11 i ₁ and i ₂
Divert to. Here, the coil resistance of each phase is r. The voltage-current relationship _{r · i 1 + e X =} 2r · i 2 - (e Y + e Z) ...... (9) i 1 + i 2 = I t ...... (10) is satisfied.

Since the back electromotive forces e _X , e _Y , and e _Z change as shown in FIG. 9 (a), e _X + e _Y + e _Z = 0 (11) at any position of the rotor. That is, a three-phase coil X, which is annularly connected,
The loop voltage due to the counter electromotive voltages e _X , e _Y , and e _Z generated in Y and Z is always zero, and no annular current flows.

Therefore, from (9), (10) and (11), i ₁ = 2I _t / 3 (12) i ₂ = I _t / 3 (13). Similarly, in equation (11) in FIG. 10 as well, since the effect of the back electromotive force does not occur, the coils X, Y, and Currents I _X , I _Y , and I _{Z to Z} are 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 has a uniform generated torque (torque ripple is zero) at any rotation speed, and has little torque fluctuation or vibration. This phase coils X, Y, by forming the trapezoidal wave or trapezoidal waveform having a flat portion of the waveform 60 ° el of the back electromotive voltage generated in Z, the three-phase counter electromotive voltages e _X, e _Y ,
The sum of e _Z is always zero, and the sum voltage (e _X + e _Y + e
Flowing a point that none with the annular current zero based on _Z), a large current (2I t / ₃₎ to the phase of the coil comprising a flat portion of the counter electromotive voltage by switching a current path every 60 ° el min, It is obtained by connecting another two-phase coil in series and shunting a small current (It / 3). In such a motor, the effective pitch of the effective coil side of each phase coil is an odd multiple of one magnetic pole pitch (180 ° el) of the magnet, and the distribution of the magnetic flux density generated by the magnet has N pole and S pole. It can be easily realized by forming a trapezoidal wave or a trapezoidal wave having a pitch of the strong flat portion of 60 ° el. If this is done, the N pole of the magnet,
The flat part of the part where the magnetic flux density of the S pole is the strongest is 60 ° el and 1/3 of one magnetic pole pitch (180 ° el), which is easy for a single disc magnet (or annular magnet). It can be magnetized and easily realized even when the gap between the magnet and the iron plate (or iron core) is wide.

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

Further, in the above-described embodiment, the operating voltage when the first output transistor is energized is detected, and the second output transistor is controlled so that the voltage becomes a predetermined value (second feedback loop). Therefore, stable, reliable, and smooth current switching can be performed. Further, the first output transistor 2
Since the currents of 4, 25 and 26 are detected and the current corresponding to the voltage signal V ₁ is made to flow (first feedback loop), the switching of the current of the first output transistor is stable, reliable and It becomes smooth, and the detection of its operating voltage becomes easy and reliable.

Further, a PNP-type detection in which the input terminal side is DC-connected to the potential point of the reference voltage signal V ₂ and each detection terminal side is DC-connected to each output terminal of the first output transistors 24, 25, 26 Since the transistors 54, 55, 56 are used, the elements required for detecting the operating voltage of the first output transistors 24, 25, 26 are the transistors 54, 55, 56.
55, 56, 59, diodes 52, 53, 57 and resistors 51, 58, 60, which can be integrated into a single silicon chip (IC). As a result, when the drive circuit portion shown in FIG. 4 is configured by a one-chip integrated circuit, the number of external parts is reduced, the manufacturing is significantly facilitated, and the variation in the correlation of the detection characteristics is reduced, which is necessary for the detection. Current is small.

In addition, in the above-described embodiment, the first output transistor 2
Reference voltage signal V ₂ to be compared with operating voltages of 4, 25 and 26
In response to the command voltage signal 84, the coil X,
The signal V ₂ is increased when the supply current to the Y and Z (that is, the conduction current of the first output transistor) is large, and the signal V ₂ is decreased when the supply current is small. This ensures that the operating voltage (V _CE ) of the transistors in the energized state of the first output transistors 24, 25, 26 will be a (small) voltage value in the active region regardless of the magnitude of the energized current. To the second output transistor 2
The energizing currents 7, 28 and 29 are controlled. That is, the saturation region (saturation voltage) of the transistor increases with an increase in the energizing current, but the reference voltage signal V ₂ is interlockedly changed to increase to the same level or more, so that the first
The output transistor is detected and compared before reaching 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 figure, parts having the same functions as those described in the drive circuit of FIG. 4 are designated by the same reference numerals. In FIG.
21 is a position detector, 22 is a first distribution controller, 23 is a second distribution controller, 24, 25 and 26 are first output transistors, 27, 28 and 29 are second output transistors,
30 is a speed detector, 31 and 45 are voltage / current converters, 3
2 is a current mirror circuit, 81 is a first differential circuit, and 83
Is a second differential circuit.

The first output transistor 24, 25, 26, the resistor 20,
The voltage / current converter 45 and the first differential circuit 81 constitute a first feedback loop (current feedback loop), and the current corresponding to the command voltage signal 84 is applied to the hall elements A, B, and B of the position detector 21. It is supplied to the coils X, Y, Z via the output transistor selected by C.

The detection / comparator 90 of the second distribution controller 23 is configured so that the second output transistors 27, 28 and 29 have operating voltages of the transistors in the energized state, the diodes 132 and 133, and the resistor 13
The reference voltage signal V ₃ generated at the detection transistor 13
6, 138, 140 to compare and detect the output signal, the differential circuit of the transistors 145, 146 further compares the output signal with the reference voltage signal, and outputs the output signal from the collector side of the transistor 146. Is supplied as a common emitter current of. 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, C of the position detector 21, and the second output transistors 27, 28, It controls the energization of 29. That is, the detection / comparator 90, the second differential circuit 83, and the second output transistors 27, 28, 29.
Constitutes a second feedback loop, detects the operating voltage of the transistor in the conducting state of the second output transistor, and controls the second voltage so that the voltage becomes a small value in the active region.
The current flowing through the output transistor of is controlled.

Even with such a configuration, the above-mentioned FIG. 9 (c), (d),
The current shown in (e) is supplied, and the generated torque becomes uniform.

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

In the figure, 200 is a DC power source, a portion 201 surrounded by a broken line is a switching type voltage converter inserted between the DC power source 200 and the coils X, Y and Z, and 202 is Hall elements A, B and C. A position detector constituted by 203
Are coils X, Y, Z in response to the output of the position detector 202.
Is a distributor that controls the current path to the. The first switch transistors 204, 205, 206 are three-phase coils in which one end (emitter side) is commonly connected to the negative output terminal of the voltage converter 201 and each output terminal (collector side) is annularly connected. It is connected to the X, Y, Z connecting contacts, and the current to its control terminal (base side) is controlled by the distributor 203 to perform on / off operation.

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

Next, the operation will be described. Magnet 3 (first
The rotation speed (see the drawing) is detected by the speed detector 210, and the voltage signal V _d corresponding to the rotation speed is output. The switching controller 222 of the voltage converter 201 turns on / off the switching transistor 221 according to the output voltage V _d of the speed detector 210, and controls the on time ratio (on time / on / off cycle time). There is. The switching controller 222 is configured by, for example, a triangular wave generator and a comparator (various known configurations can be used), generates a pulse signal having a duty ratio corresponding to the input voltage, and turns on the switching transistor 221.
Turn off. The output pulse voltage of the switching transistor 221 is smoothed by the diode 223, the inductance element 224, and the capacitor 225, and the output voltage V _C of the voltage converter 201 is the switching transistor 22.
The value corresponds to the ON time ratio of 1, that is, the value corresponding to the output voltage V _d of the speed detector 210.

The output voltage V _C of the voltage converter 201 is applied to the three-phase coils X, Y, Z via the first switch transistors 204, 205, 206 and the second switch transistors 207, 208, 209.

The rotational position of the magnet 3 is detected by the position detector 202, and a voltage signal corresponding to the position is input to the distributor 203. The distributor 203 includes a current supplier 211, a first differential circuit 212, a second differential circuit 213, and current mirror circuits 214, 215, 216, and the first and second differential circuits 212, 213. Transistor 238,
The output voltage of the position detector 202 is applied to the base terminals of 239, 240, 241, 242, and 243, respectively.

The current supplier 211 includes the 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, 240 (output of the position detector 202) and distributes the common emitter current to the collector side. Transistors 238, 239, 240
Each collector current of the first switch transistor 20
The base currents of 4, 205, and 206 are generated, and one first switch transistor corresponding to the output of the position detector 202 is always turned on.

In addition, the second differential circuit 213 includes transistors 241,
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 collector currents of 242 and 243 become the base currents of the second switch transistors 207, 208 and 209 via the current mirror circuits 214, 215 and 216, respectively, and the second switch according to the output of the position detector 202. One transistor is always on.

That is, the distributor 2 responds to the output of the position detector 202.
03 is the first switch transistor 204, 205,
206 and the second switch transistors 207, 208,
209 is controlled to be turned on and off, and the current path to the three-phase coils X, Y, and Z is set to the first as the rotor 2 (see FIG. 1) rotates.
Switching is performed sequentially as shown in FIGS.

Now, when the first switch transistor 206 and the second switch transistor 207 are turned on (first switch transistor
(Corresponding to FIG. 0), a current flows as shown in FIG. _{Therefore, V M = V C -2 ·} V CE (sat) ...... (14) = r · i 1 + e X ...... (15) = 2r · i 2 - (e Y + e Z) ...... (16) I _i = i ₁ + i ₂ (17) Here, r is the resistance of the coil. From the above description (FIG. 9), in the brushless DC motor of the present invention, e _X + e _Y + e _Z = 0 is always satisfied (see the equation (11)). As a _{result, i 1 = 2I t / 3} ...... (18) i 2 = I t / 3 ...... (19) I t = (3/2 · 1 / r) · _[V C -2 · _{V CE (sat )} -E _X ] ... (20)

Here, the generated torque fluctuation when the output voltage V _C of the voltage converter 201 is constant becomes the torque ripple. V
_{CE (sat)} is the saturation voltage of the switch transistor and can be considered constant.

Therefore, (20) although the current I _t to be supplied to the coils will be related to the counter electromotive voltage e _X coil X from equation counter electromotive voltage e _X is if the rotational speed N is constant, (6) According to the formula, it is proportional to the difference in magnetic flux density and changes into a trapezoidal wave shape with a flat portion of 60 ° el as shown by the solid line in Fig. 9 (a) [ie, Fig. 9
Each waveform is KakugyakuOkoshi voltage _e X of _(a), e _Y, may be considered that the waveform of _{e Z].} The state shown in FIG. 14 corresponds to the states shown in FIGS. 9 and 10, so that e _X is constant during this period.

Therefore, (20) the resultant current I _t is constant from the equation (18),
The constant currents i ₁ and i ₂ corresponding to the equation (19) are shunted to the coils of each phase. The same applies to other states, and the rotor 2
Fig. 9 shows the coils X, Y, and Z of each phase as they rotate.
Currents I _X , I _Y , and I _{Z as in} (c), (d), and (e) are supplied. As a result, the synthetic generated torque T = τ _X + τ _Y + τ
_Z is uniform (torque ripple is zero) as shown in FIG.

In this driving circuit, using a voltage converter 201 of the switching type, voltage _V s = 20V of the DC power supply 200
A desired DC voltage V _X (corresponding to the output signal of the speed detector 210) is obtained from the first and second switch transistors 204, 205, 206, 20 which are turned on and off.
7, 208, 209 supply to three-phase coils X, Y, Z.

As a result, the collector loss in the first and second switch transistors and the conversion loss due to the voltage converter 201 become considerably small, and the first and second output transistors operating in analog as shown in FIGS. It is significantly smaller than the collector loss consumed at 24, 25, 26, 27, 28 and 29. In particular, the effect is large when the coil voltage V _M (FIG. 14) is small, and the power loss of this drive circuit is extremely small.

Further, in the drive circuit of FIG. 13, the voltage converter 2
By detecting the output voltage V _{C of} 01 and making the base currents of the first and second switch transistors small when V _C is small and large when V _C is large, the base current loss is also reduced.

To explain this, the current supplier 2 of the distributor 203
Reference numeral 11 detects the output voltage V _C of the voltage converter 201 by the resistor 227, and when the voltage value V _C increases, the common emitter current of the first and second differential circuits 212 and 213 increases, and the first and the second differential circuits 212 and 213 increase. 2 switch transistors 20
The base current to 4,205,206,207,208,209 is increased. On the contrary, when the output voltage V _C of the voltage converter 201 becomes small, the output current of the current supplier 211 becomes small, and the base currents of the first and second switch transistors are made small (the switch transistors are turned on / off). Enough base current is always supplied so that).

As a result, a sufficient base current is supplied to the first and second switch transistors even at the time of large current operation during startup / acceleration (when V _C becomes large and the supply current to the coil becomes large), and at the same time the constant speed is maintained. At the time of low current operation during rotation (when V _C becomes small and the supply current to the coil also becomes small), the base current is made small to a level slightly larger than the necessary minimum value. As a result, the base current loss of the first and second switch transistors when a small current is applied is significantly reduced.

In the above-mentioned embodiment, the three-phase coils X ₁ , X ₂ , Y ₁ , Y
An example has been shown in which ₂ , Z ₁ and Z ₂ are arranged so as not to overlap in a plane [see FIG. 2 (b)], but the present invention is not limited to such a case, and three-phase coils are stacked. You may arrange so that it may match. This will be described with reference to FIGS. 15 and 16.

FIG. 15 shows a coil 400 for one phase wound in a wave. A three-phase coil X, Y, Z is formed by stacking three-phase coils 400 facing each other with magnets 8 magnetized [see FIG. 2 (a)] and having phases shifted by 120 ° el.
To form.

The coil 400 of each phase has an effective coil side pitch of 180 ° el (an odd multiple of 180 ° el) to reduce the fluctuation of the generated torque.

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

Furthermore, in the above-described embodiment, the slotless type brushless DC motor has been described as an example (FIG. 1), but the present invention is not limited to such a case, and a brushless DC motor with a core slot can also be configured.

FIG. 17 shows an example of a motor with a core slot proposed by the present applicant in Japanese Patent Application No. 52-67671. In the figure, a magnet 502 attached to a rotor 501
Has magnetic poles of four poles formed at equal angles (90 ° mech) or substantially equal angles. The distribution of the magnetic flux density generated by the magnet 502 is, as shown in FIG. 3, a trapezoidal wave having a flat portion of 60 ° el or a trapezoidal waveform. A stator iron core (core) 503 is arranged so as to face the magnetic poles of the magnet 502, and the stator iron core 503 is provided with three main salient poles 504 and three auxiliary salient poles 505. Each of the three main salient poles is 240 ° el (or 12
The groove 50 for winding is arranged with a phase difference of 0 ° el).
Three-phase coils X, Y and Z are wound around the coil 6.

The pitch of the grooves on both ends of each main salient pole is 96 ° mech (192
° el), the pitch of the grooves on both ends of each auxiliary salient pole is 24 ° me
It is said to be about ch (48 ° el). Each coil X,
The effective pitch of Y and Z (pitch for collecting magnetic flux) is almost equal to the pitch of the grooves at both ends of the main salient pole (190 ° el), and the pitch of one magnetic pole of the magnet 502 (180 ° el).
Is almost equal to.

Therefore, the driving circuit shown in FIG. 4, FIG. 12 or FIG. 13 is used to drive such a motor as shown in FIG. 9 (c), (d), (e).
If such a current is supplied, the generated torque becomes uniform (the torque ripple is small).

In addition, three auxiliary grooves 507 are provided at the tip of each main salient pole 504 at every 24 ° mech, and the winding grooves 506 and the auxiliary grooves 507 have an equal angular pitch (24 ° mech) or a substantially equal angular pitch. It is arranged so that the cogging torque is also small.

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

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

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a motor structure of one embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are views showing the arrangement of magnetic poles of a magnet and the arrangement of coils and Hall elements in the same embodiment. FIG. 3 is a distribution diagram of the magnetic flux density generated by the magnet, FIG. 4 is a drive circuit diagram in the embodiment of the present invention, and FIGS. 5 and 6 are specific configuration examples of the voltage / current converter. 7 is a circuit diagram for explaining the operation of FIG. 4, FIG. 8 is a diagram showing the relationship between the magnet, the coil and the Hall element in the same embodiment, and FIGS. 9 (a) and 9 (b). ，
(c), (d), (e) and (f) are waveform charts for explaining the operation of the embodiment shown in FIGS. 1 to 4, and FIG. 10 is a current path to the coil in the embodiment. Showing switching of the coil, FIG. 11 is a diagram for explaining a current to the coil, and FIGS. 12 and 13 are wiring diagrams showing other examples of the drive circuit which can be used in the present invention. FIG. 14 is a diagram for explaining a current to a coil in the same embodiment, FIGS. 15 and 16 are diagrams showing another configuration diagram (for one phase) of the coil used in the present invention, and FIG. 17 is a diagram. FIG. 7 is a configuration cross-sectional view showing another motor structure that can be used in the present invention. 1 ... Rotary axis, 2 ... Rotor, 3 ... Magnet, 4 ...
... stator, 5 ...... _{coils, X 1 ~Z 2, X,} Y, Z ...
... Coil, A, B, C ... Hall element, 21 ... Position detector, 22, 23 ... First and second distribution controller, 24,
25, 26 ... First output transistor, 27, 28,
29 ... Second output transistor, 30 ... Speed detector, 31, 45 ... Voltage / current converter, 32 ... Current mirror circuit, 81, 83 ... First and second differential circuit,
82, 90 ... Detection / comparator, 200 ... DC power supply, 2
01 ... voltage converter, 202 ... position detector, 203 ...
... Distributor, 204, 205, 206 ... first switch transistor, 207, 208, 209 ... second switch transistor, 210 ... speed detector, 211 ...
Current supply device 212, 213 ... First and second differential circuit, 214, 215, 216 ... Current mirror circuit,
222 ... Switching controller, 400, 411-41
8 ... Coil, 501 ... Rotor, 502 ... Magnet, 503 ... Stator core, 504 ... Main salient pole, 50
5 ... Auxiliary salient pole.

Claims (2)

[Claims] 1. A rotor having a magnet in which a plurality of N-pole and S-pole permanent magnetic poles are alternately magnetized, and a magnetic flux density distribution on the circumference is a trapezoidal wave whose flat portion has an electrical angle of about 60 °. The magnets are arranged at positions intersecting with the magnetic flux, the effective pitch of each coil is set to an electrical angle of about 180 °, and the distribution of the magnetic flux density difference generated by the magnets at both ends of the effective pitch of each coil is rotated. Regarding the angle, the flat part has a trapezoidal wave shape with an electrical angle of about 60 °,
A three-phase coil group formed by annularly connecting the plurality of coils, position detecting means for detecting a rotational position of the rotor, and three nodes of the three-phase coil group annularly connected. A first output transistor group consisting of three transistors forming a current path between one end of the DC power supply, and three output transistors forming a current path between the three nodes and the other end of the DC power supply. A second output transistor group consisting of transistors and a command signal for commanding current supply to the coil group, and in response to an output signal of the position detecting means, the three phase coil groups First distribution control means for distribution-controlling the energization of the first output transistor group so as to supply a current to one node of the coil group of a phase in which the distribution of the generated magnetic flux density difference is in a flat portion, Output signal of position detection means And a second distribution control means for distributing and controlling the energization of the second output transistor group so as to form a current path of the DC power supply with the other node of the coil group of the phase in the flat portion. The second distribution control means includes an operation detecting means for detecting an operating voltage of a transistor in a conductive state of the first output transistor group, and an operation detecting means for detecting an operating voltage of the first output transistor group. The energization current of the second output transistor group is controlled in response to the output signal of the operation detection means, and the second output transistor is energized when the operating voltage of the energized first output transistor increases. The energized current is reduced, and when the operating voltage of the first output transistor in the energized state decreases, the second energized state in the second output transistor decreases.
Brushless DC motor including control means for increasing the energizing current of the output transistor of the above. 2. A rotor having a magnet in which a plurality of N-pole and S-pole permanent magnetic poles are alternately magnetized, and a magnetic flux density distribution on the circumference is trapezoidal with a flat portion having an electrical angle of about 60 °. The magnets are arranged at positions intersecting with the magnetic flux, the effective pitch of each coil is set to an electrical angle of about 180 °, and the distribution of the magnetic flux density difference generated by the magnets at both ends of the effective pitch of each coil is rotated. Regarding the angle, the flat part has a trapezoidal wave shape with an electrical angle of about 60 °,
A three-phase coil group formed by annularly connecting the plurality of coils, position detecting means for detecting a rotational position of the rotor, and three nodes of the three-phase coil group annularly connected. A first output transistor group consisting of three transistors forming a current path between one end of the DC power supply, and three output transistors forming a current path between the three nodes and the other end of the DC power supply. A second output transistor group consisting of transistors and a command signal for commanding current supply to the coil group, and in response to an output signal of the position detecting means, the three phase coil groups First distribution control means for distribution-controlling the energization of the first output transistor group so as to supply a current to one node of the coil group of a phase in which the distribution of the generated magnetic flux density difference is in a flat portion, Output signal of position detection means And a second distribution control means for distributing and controlling the energization of the second output transistor group so as to form a current path of the DC power supply with the other node of the coil group of the phase in the flat portion. The second distribution control means includes a reference voltage generation means for obtaining a reference voltage signal that changes a voltage value in response to the command signal, and the first distribution control means.
Comparing means for comparing the operating voltage of the transistor in the energized state of the output transistor group with the reference voltage signal, and the output signal of the comparing means for comparing the operating voltage of the first output transistor group in response to the output signal of the comparing means. And controlling the energization current of the second output transistor group to decrease the energization current of the second output transistor which is in the energized state when the operating voltage of the first output transistor which is in the energized state is increased, and which is in the energized state. A brushless DC motor configured to include control means for increasing a conduction current of the second output transistor which is in a conduction state when the operating voltage of the first output transistor decreases.