JPS6359785A - Brushless motor - Google Patents

Abstract

PURPOSE:To enable coils to be excited without a position detector, by adding the voltage induced to coils of each phase at a definite ratio to compare with reference voltage by a comparator, and by adding the output of the comparator to switching transistors through diodes. CONSTITUTION:Voltage is induced to coils 1-3 by the rotation of a rotor. The voltage thus induced is applied to negative input terminals of comparators 7-9 at a definite ratio and is compared with the reference voltage. Diodes 22-24 are connected so as to supply the outputs of comparators 7-9 in an identical orientation. By controlling switching transistors 4-6 through diodes 22-24 with the outputs of comparators 7-9, coils 1-3 of each phase is excited in sequence to rotate the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a brushless motor used in tape recorders, video tape recorders, and the like.

(b) Prior Art Recently, brushless motors have been widely used in tape recorders, video tape recorders, etc. because they do not generate noise and have a long life. For example, as described in Japanese Utility Model Application Publication No. 59-53696, the brushless motor uses a position detector to detect the position of the rotor in order to cause current to flow through the coils of each phase sequentially, and thereby to sequentially switch the switching elements. Need to turn it on and off.

(c) Problems to be solved by the invention As mentioned above, conventional brushless motors require a position detector such as a Hall element to turn the switching elements on and off sequentially, but brushless motors have recently become smaller in size. As devices have become smaller and thinner, there is no longer enough space to install the position detector.

Therefore, the present invention provides a brushless motor that can detect the rotational position of the rotor without using a position detector, turn on and off the switching elements sequentially, and sequentially flow current through the coils of each phase. (2) Means for Solving Problems As described above, the brushless motor of the present invention includes a plurality of coils forming each phase, switching transistors connected to these coils, and a switching transistor corresponding to each phase. A comparator is provided for applying the voltage induced in each phase at a fixed ratio to one input terminal and comparing the voltages applied to the other input terminal, and the outputs of these comparators are oriented in the same direction. In addition, it is constructed by a diode that can be connected as shown in FIG.

(f) Function Since the brushless motor of the present invention has the above-described configuration, a voltage is induced in each coil when the rotor is rotated. The induced voltage is superimposed on one input terminal of each comparator at a constant ratio and compared with the reference voltage applied to the other input terminal, making the output of the - comparator a negative voltage and the output of the other comparator positive. Since it is a voltage, one diode is energized, the switching transistor connected to the diode is turned on, and one coil is energized and excited. When the rotor finishes rotating, the voltage induced in each coil changes, and the output of the comparator, which was a negative voltage, becomes a positive voltage and the output of the other comparators becomes a negative voltage. Turn on electricity and excite other coils. In this way, the coils of each phase are sequentially excited to rotate the rotor.

(F) Embodiment An embodiment of the brushless motor of the present invention will be described with reference to the drawings.

In Fig. 1, (1), (2), and (3) the first phase, which becomes the V and W phases. The second and third coils have one end commonly connected and connected to a power source, and the other end grounded via switching transistors (6), (5), and (4), respectively. (8)<7) (9) is the first. second and third comparators, one end of which is connected to the first comparator through resistors (11), (12), and (10), respectively; Second. Connected to one end of the third coil (1) (2) < 3) and resistor (14) (15) < 13
) and diode (1B) (19) (20) (21) (
16) Through (17), the first. Second. It is also connected to one end of the third coil (1) (2) < 3), and is also connected to one end of the first coil. The other ends of the second and third comparators (8), (7), and (9) are connected to the first and third comparators (8), (7), and (9). Second. It is read directly to the commonly connected neutral point of the third coils (1), (2), and (3). Furthermore, the first. The output sides of the second and third comparators (8), (7), and (9) are sequentially coupled through diodes (22), (23), and (24) connected in one direction. The current flowing through the diode (23) is applied to the switching transistor (4), the current flowing through the diode (23) is applied to the switching transistor (6), and the current flowing through the diode (24) is applied to the switching transistor (5). The resistance values of the resistors (10, 11, and 12) are set to be one times the resistance value of the resistors (13, 14, and 15).

Next, the operation of the brushless motor of the present invention will be explained. A rotor that moves magnets that are magnetized to a sine wave (
(not shown) rotates in the forward direction, the first coil (1) of the U phase and the second coil (2) of the V phase rotate as shown in FIG.
) and the W-phase third coil (3), the induced voltages u, v of sinusoidal waves differing in phase by 120 degrees.

produces W. Considering the energization timing of each phase, for example, the third coil (3) of the W phase has the to
It passes during period t+. The relationship between the induced voltages during this period to-t is as shown in equation (1).

2 Ew+ (Eu or Ev) < VN ・=
”(1) Here Eo... 1st coil (1)
Induced voltage Ev induced in the second coil (2) Induced voltage EV induced in the second coil (2) Induced voltage E induced in the second coil (2)・Induced voltage VN induced in the third coil (3)...First. 2nd and 3rd coil (1)
It is the potential of the neutral point combining (2) and (3).

At point F in FIG. 1, only the larger of the induced voltage EU or the induced voltage Ey is superimposed on the induced voltage Ew by the diodes (16) and (17). Therefore, the voltage applied to the positive input terminal point C of the third comparator (9) is 2Ew+(E,,orE
v)・・・・・・・・・・・・(2) (Figure 5 (d)).

Therefore, turning on the W-phase third film (3) is as follows:
This is the period during which the voltage in equation 2) becomes negative compared to the neutral point potential (19). That is, in the period of io t+ mentioned above, the third
The voltage induced in the coil (3) and generated in the resistor (10) is -
k (where E is the maximum voltage induced in each coil and generated in the resistor (10)), and the voltage induced in the first coil (1) or the second coil (2) and generated in the resistor (13) is E. . Since the voltage applied to the positive terminal of the third comparator (9) shown in equation (2) is always more negative than the voltage applied to the negative terminal (8), the output of the third comparator (9) is negative.

On the other hand, the voltage applied to the positive input terminal B of the first comparator (8) is 2 Eu+ (Ew or Ev) """・"(3
), and the voltage ■ applied to the negative input terminal is always larger, so the output of the second comparator (8) becomes positive. Therefore, the diode (22) becomes conductive and applies a forward bias voltage to the switching transistor (4) to turn on the switching transistor (4).
Voltage from LR is supplied.

As the rotation of the rotor advances and reaches the period 11-11, the voltage expressed by the equation (3) applied to the positive terminal B of the second comparator (8) becomes more negative than the potential V8 at the neutral point (the fifth Figure c), 2nd
The voltage applied to the positive terminal A point of the comparator (7) is 2 Ev+ (Eo or Ew) ...=.
・”・” (4) Since it becomes more positive than the neutral point potential VN (
2), the output of the second comparator (7) becomes a positive voltage, the diode (23) becomes conductive, and a forward bias voltage is applied to the switching transistor (6), turning on the switching transistor (6). Apply current from the power supply to Koinoden 1).

When the rotor rotates further and reaches the period tz to, the second
The voltage applied to the positive terminal point A of the comparator (7) becomes more negative than the potential vN of the neutral point (Fig. 5), the output of the second comparator (7) becomes negative, and the output of the third comparator ( Since the output of 9) becomes positive, the diode (24) turns on, applies forward bias voltage to the switching transistor (5), turns on the switching transistor 5), and causes current from the power supply to flow through the second coil (2). .

When the rotor is rotated from the period to to, T again,
-T, the switching transistor (4) is made conductive as described above, and current from the power source is passed through the third coil (3) to excite the third coil (3). In this way, switching transistors (4), (6), and (5> become conductive one after another.

FIG. 2 is a block diagram showing another embodiment of the present invention, in which when the interlocking changeover switches (26, 27, and 28) are switched to the opposite side to that shown, the connection is similar to that described above, and rotation occurs in the forward direction. And selector switch (26) (27) (28
) as shown, the diode (22a) (2
3g) (24a) are diodes (22) (23) (24
) is in the opposite direction, so it is the first one. Second and third comparators (8
)(7) The direction in which the current flows through the output diode in (9) is reversed, causing the rotor to rotate in the opposite direction. That is, when the rotor is reversely rotated, the first. 2nd and 3rd coil <1) (2) (3
), the induced voltages u, v, w as shown in Fig. 6(a) are generated, and in the period to-t+, the voltage shown by equation (4) applied to the positive terminal of the second comparator (7) becomes negative. The voltage becomes negative with respect to the potential vN applied to the terminal, producing a negative voltage at the output terminal, but the positive terminal of the first comparator (8) becomes positive with respect to the potential VN, producing a positive voltage at the output terminal. ), apply a forward bias voltage to the switching transistor,
The switching transistor (5) is turned on and voltage from the power source is supplied to the second coil (2) to excite it.

When the rotor rotates, the first comparator (8
) produces a negative output voltage, and since a positive voltage is produced at the output terminal of the third comparator (9), the diode <23a) is made conductive, which also turns on the switching transistor (6) and excites the first coil (1). be done. In this way, as the rotor rotates, the switching transistor (5), the switching transistor (6), and the switching transistor (4)
> The second coil (2) and the first coil (1) are electrically connected in this order.
and the third coil (3) are sequentially excited to rotate the rotor counterclockwise.

Fig. 3 shows the actual circuit of the brushless morph of the present invention, and Fig. 1. Second and third comparators (8) (7) (9)
are composed of transistors (40) to (45), respectively, and the bases of the transistors (40), (42), and (44) correspond to the positive terminals in FIG. The induced voltages of the first, second, and third coils (1), (2), and <3) are applied through 〉 to (21), and the bases of the transistors (41), (43, and 45) are connected in common. A sex point potential V.C is applied, and the transistors (46) (47>(48)
0) (42) (44). The transistors (49) to (54) are selectively turned on and off by a changeover switch (55) to change the direction of rotation of the motor.

If the contact of the changeover switch (55) is now switched to the state shown, the transistors (52), (53), and (54) are turned on. In the period of jo il in FIG. 5, the base voltage of the transistor (40) is the same as that of the transistor (41).
Since it becomes negative than the base voltage VCC of the transistor (
40) is turned off and the transistor (46>) is also turned off.

Therefore, the diode-connected transistor (22) is turned on, and Mm flows through the transistor (22) and the transistors (57) (58) (59) are connected by the current mirror circuit.
A current flows through the third coil (3), turning on the transistor (4), and causing current to flow through the third coil (3) to excite it. At this time, the base voltage of the transistors (42) and (44) is
Since the base voltage of 43)(45) is more positive, transistor (42)<44) is turned on and transistor<47)(
4B), the transistors (5) and (6) are turned off and no current flows through the first and second coils (1) and (2).

When the rotor rotates and the period tL-it begins, the base voltage of the transistor (42) becomes negative compared to the base voltage of the transistor (43), so the transistor (42) is turned off, and the transistor (47) is also turned off. The off-state transistor (23) is turned on. On the other hand, since the voltage at point A becomes positive, the transistor (44) is turned on and the transistor (48) is also turned on, and the current from the power supply passes through the transistor (48) and the transistor (54) to the diode-connected transistor (23). flows. Therefore, current flows through the transistors (61), (60), and (62) by the current mirror circuit, turning on the transistor (5) and exciting the first coil (1). During the period when the rotor is in the tz to state, the transistor (6) turns on and current flows through the coil (2) to excite it. Therefore, the coils (3) (1) < 2) are sequentially energized as shown in FIG. 5, causing the rotor to rotate in the forward direction.

Next, when the contact piece of the changeover switch (55) is switched to the CCW side opposite to that shown in the diagram, the transistors (49) (50) (5
1) is turned on and the transistor (52) <53) (54
) can be turned off. In FIG. 6, during the to-t+ period, the transistor (48) is turned off and the transistor (2
4) is turned on, current from the power supply flows to the transistor (24) through the transistors (47) and (50) which are turned on. Therefore, current also flows through transistors (63), (64), and (65) due to the current mirror.
The transistor <6) is turned on and the second coil (2> is excited. In the period t+Lt in Fig. 2, the transistor (47) is turned off and the transistor (23) is turned on, so the transistor (61) ( A current flows through 60)<62), turning on the transistor (5) and exciting the first coil (1). Furthermore, in the period tff1-t3, the transistor (4) is turned on and the third coil (3) is excited. When the selector switch (55) is switched to the opposite side from the one shown in the figure, the first switch is set as shown in FIG. 6(E). Third. Second
Coils (1), (3), and (2) are excited in this order to rotate the rotor in the opposite direction.

Next, the starting circuit will be explained.

When the rotor is not rotating at all even after the power is turned on,
The rotor cannot rotate as it is and needs to be started. Figure 4 shows the starting circuit, (71) (72
)(70) is the first. each first in the second and third switch circuits.
．． Second and third switch circuits (71) <72) <70
) are connected to the collectors of the first, second and third comparators (8) (7) (9) in FIG.
) to which the voltages at each point B, A, and C of the positive terminal are applied <77) (78) (76), the transistor (7
7) (78)<76) and transistors (83) (84) (85) whose bases and emitters are commonly coupled, respectively.
...and the transistors (83) (84) (
A transistor <105> is connected to the emitter of 85). <87)<86) (8B) are auxiliary switching transistors that are turned on and off in synchronization with the switching transistors (4), (5), and (6), respectively, and control the transistors (91), (96), and (89), respectively. (
92) (93) (94) are the transistors (79)
The transistors (80), (81), etc. control the transistors (98), (99), and (100).

Next, the operation of this starting circuit will be explained. Assume that when the power switch (not shown) is turned on, the first coil (1) of the U phase remains energized. 1st coil (1)
is energized because the positive terminal of the first comparator 8), that is, the point B, is at a negative voltage, so the collector of the transistor (77) of the first switch circuit (71) is at a negative voltage with respect to the neutral point. , the remaining voltages at point A and point 0 are positive voltages, and current flows from the second comparator (7) to the first comparator (8). Therefore, the auxiliary switching transistor (88) is turned on in synchronization with the switching transistor (6). When the auxiliary switching transistor (88) is turned on, the transistor <89) is turned on and the transistor (89) is turned on.
82), the third switch circuit (70) is forcibly turned off. In this state, when the starting circuit (not shown) is operated and a starting pulse is applied to the terminal (101), the second and third switch circuits (70) are turned off. The three-switch circuits (71, 72) respond to the activation pulse, and the transistors (77, 78) turn on, lowering the potentials at points B and A, but the potential at point 0 remains the same, so the transistors (77, 78)... In Figure 1, the output of the third comparator (9) is a positive voltage, and the outputs of the first and second comparators 8) (7) are negative voltages, so the output voltage of the third comparator (9) is The current flows through the diode (24) to the output terminal of the second comparator (7), and in order to turn on the switching transistor (5), the second coil (2), which is in the V phase, is energized. As mentioned above, when the activation pulse is applied, the transistor <84) (
85) (102) (103) are also turned on, and transistors (92) and (93) are turned on, respectively.

When the transistor <92> (93) is turned on, the transistor (98>) is also turned on, turning off the transistor (82).

As mentioned above, when the starting pulse is applied, the first coil (1
) to the second coil (2). When the switching transistor (5) is turned on, the auxiliary switching transistor (86) is turned on in synchronization with it, the transistor (90) is also turned on, and the transistor (10) is turned on.
5) is turned off, but since the transistor (106) is already turned on, the first switch circuit (71) is still able to receive the activation pulse. However, when the activation pulse becomes low level, the transistors (76) (7
7) (78) is turned off.

At this time, since the transistor (86) is on, the transistor (90) is turned on and the transistor (105) is turned off, making the second switch circuit (71) unable to receive the activation pulse.

Therefore, when the next activation pulse is applied, the transistor (7
6) (78) turns on and makes the 0 point and A point negative voltage, but B
Since the voltage at the point remains positive, current flows from the first comparator (8) through the diode (22) to the third comparator (<9), turning on the transistor (4) and turning on the W-phase third coil ( 3)
is energized. In this way, each time a starting pulse is applied, a starting pulse is applied to the first coil (1), second coil (2), and third coil (3) in this order to rotate the rotor.

(G) Effects of the Invention As described above, the brushless morph of the present invention applies the voltage induced in the multiphase coil to one input terminal of the comparator at a constant ratio, and applies the reference voltage applied to the other input terminal. The outputs are applied in one direction using diodes, and the voltage difference between the outputs turns on one diode, and turns on the switching transistor (-) provided corresponding to the diode. Since the coils are energized in sequence, it is possible to eliminate the need for holes, etc. for rotation detection, which were conventionally required.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the brushless morph of the present invention, FIG. 2 is a block diagram showing another embodiment of the brushless motor of the present invention, and FIG. 3 is a circuit diagram of the brushless motor of the present invention. FIG. 4 is a circuit diagram used in the brushless motor of the present invention, and FIGS. 5 and 6 are signal waveform diagrams of various parts of the brushless motor of the present invention. (1) (2) (3)... 1st. 2nd and 3rd Koinotsu (4) (5) (6)... Switching transistor, (7) (8) (9)... 1st. Second and third comparators. Applicant Sanyo Electric Co., Ltd. and one other agent Patent attorney Takuji Nishino and one other person No. 1rA Figure 2 Figure 16

Claims (2)

[Claims] (1) The voltages induced in the coils constituting the plurality of phases are added to a comparator provided for each phase and compared with a reference voltage, and the outputs of these comparators are directed and added to each one by a diode,
A brushless motor characterized in that when the output of the comparator energizes the - diode, the coil of the phase corresponding to this diode is energized. (2) In claim 1, first, second and third switching transistors are connected to the first, second and third coils, respectively, and the − input terminal of the comparator is connected to each corresponding coil. The reference voltage is connected through one resistor and connected to another coil through a second resistor and a diode, and the induced voltage generated in each phase is superimposed at a fixed ratio on the above-mentioned input terminal and applied to other input terminals. The outputs of the first, second, and third comparators are connected in a ring shape with diodes oriented in the same direction, and the - of the first, second, or third comparators is compared with the voltage. The voltage difference between the output and the other output turns on one of the diodes, turns on the first, second or third switching transistor provided corresponding to the diode, and turns on the first, second or third switching transistor. A brushless motor characterized by exciting one of three coils.