JPH0681544B2 - Brushless motor - Google Patents

Description

The present invention relates to a brushless motor used in a tape recorder or a video tape recorder.

(B) Prior Art Recently, in tape recorders, video tape recorders, and the like, brushless motors are often used because they do not generate noise or have a long life. Such a brushless motor, for example, as described in Japanese Utility Model Application Laid-Open No. 59-53696, detects the position of the rotor by a position detector in order to sequentially pass a current through the coils of each phase, thereby switching the switching element. It is necessary to turn them on and off sequentially.

(C) Problems to be Solved by the Invention As described above, the conventional brushless motor requires a position detector such as a hall element to sequentially turn on and off the switching elements, but the brushless motor is small and thin. As a result, the space for mounting the position detector has run out. Therefore, it is necessary to compare the induced voltage generated in the coil of each phase and the reference voltage with a comparator, turn on the diode by the output obtained from each comparator, and thereby turn on the switching element. Invented and applied for a patent (Japanese Patent Application No. 61-2)
No. 02449). However, since the energization voltage and the induced voltage generated in the coil of each phase at the time of light load or no load are the same, it is sometimes difficult to detect the induced voltage with the comparator, and in particular, it is impossible to invert the rotor. Become.

The present invention provides a brushless motor that eliminates such drawbacks.

(D) Means for Solving the Problems In the brushless motor of the present invention, first, second and third switching in which first, second and third coils constituting a plurality of phases are connected as loads respectively The transistor and the first input terminal are connected to the corresponding first, second and third coils through a first resistor and a second resistor and a diode, respectively, and to another coil. The first, second and third comparators in which the induced voltages generated in the coils of the respective phases are superimposed and input at a constant ratio, and the reference voltage is input to the second input terminal, and the first, second and third comparators are also provided. 2 and 3
First, second and third positive feedback transistors connected to a first input terminal of a comparator and turned on and off in synchronization with the first, second and third switching transistors, and the first and second And a diode connected between the output terminals of the third comparator so as to have the same conduction direction in a ring shape.

(E) Action In the present invention, the first, second and third switching transistors are turned on by the ON operation of the diode due to the voltage difference between the output terminals of the first, second and third comparators. Thus, any one of the first, second, and third coils is excited, and the first, second, and third positive feedback transistors are turned on to activate the first, second, and third comparators. The induced voltage applied to one input terminal is reduced.

(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) are first, second, and third coils that are U, V, and W phases, one end of which is commonly connected and connected to a power source, and the other end of which is switching respectively. It is grounded through the transistors (4), (5) and (6).
(7), (8) and (9) are the first, second and third comparators, which are the first
Is connected to one end of each of the first, second, and third coils (1), (2), (3) via resistors (10), (11), (12), and resistors (13) ( 14) (15) and diodes (16) (17) (18) (19) (20) (21) through one end of the different first, second, third coils (1) (2) (3) Is also connected to the first, second and third comparators (7)
The second input terminals of (8) and (9) are connected to the commonly connected neutral points of the first, second, and third coils (1), (2), and (3). Furthermore, first, second and third comparators (7) (8)
The output side of (9) is sequentially coupled by the diodes (22), (23) and (24) connected in one direction, and the current flowing in the diode (22) is applied to the switching transistor (4). The current flowing through the diode (23) is applied to the switching transistor (5), and the current flowing through the diode (24) is applied to the switching transistor (6). The resistors (10) (11) (1
The resistance value of 2) is set to be 1/2 times the resistance value of the resistors (13) (14) (15). (25) (26) (27) are the first,
A positive feedback transistor connected between the first input terminals of the second and third comparators (7), (8) and (9) and ground, and turned on and off in synchronization with the switching transistors (4), (5) and (6). To be done.

Next, the operation of the brushless motor of the present invention will be described. When a rotor (not shown) having a magnet magnetized into a sine wave rotates in the positive direction, the U-phase first coil (1) and the V-phase second coil (1) as shown in FIG. The coil (2) and the W-phase third coil (3) generate sinusoidal induced voltages u, v, w having a phase difference of 120 degrees in this order. Considering the energization timing of each phase, for example, the W-phase third coil (3) is energized during the period of t ₀ -t ₁ shown in FIG. The relationship of the induced voltage in the period of t ₀ -t _{1 is} as shown in equation (1).

2E _W + (E _U or E _V ) <V _N ……… (1) Where E _U …… Induced voltage induced in the first coil (1) E _V …… Induced in the second coil (2) Induced voltage E _W: Induced voltage induced in the third coil (3) V _N : Potential of the neutral point connecting the first, second and third coils (1) (2) (3) .

At point F in FIG. 1, only the larger one of the induced voltage E _U or the induced voltage E _V is superimposed on the induced voltage E _W in the diodes (21) and (20). Therefore, the voltage applied to the first input terminal point C, which is the positive input terminal of the third comparator (9), is 2E _W + (E _U orE _V ) ... (2) (Fig. 3 (d)) .

Therefore, the W-phase third coil (3) is turned on during the period when the voltage of the equation (2) becomes negative as compared with the neutral point potential V _N. That is, during the period of t ₀ -t ₁ described above, the voltage induced in the third coil (3) and generated in the resistance (12) is −E _O / 2 (where E _O is the maximum voltage generated in the resistance (10) induced in each coil). Voltage) or less, and the voltage generated in the resistance (15) induced in the first coil (1) or the second coil (2) does not become larger than E _O. Therefore, the third comparator shown in the formula (2) above. Since the voltage applied to the first input terminal, which is the positive input terminal of (9), is always more negative than V _N applied to the second input terminal, which is the negative input terminal, the output of the third comparator (9) is negative. .

While the voltage applied to the first input terminal point A is a positive input terminal of the first comparator (7) is _{2E U + (E W orE V} ) .................. (3) , and the always negative input terminal Since it is higher than the voltage V _N applied to the second input terminal, the output of the second comparator (8) becomes positive. Therefore, the diode (24) is turned on and a forward bias voltage is applied to the switching transistor (6) to turn on the switching transistor (6), so that the voltage from the power supply is supplied to the third coil (3).

When the rotation of the rotor progresses and becomes a period of t ₁ -t ₂ , the voltage of the formula (3) applied to the first input terminal point A, which is the positive input terminal of the first comparator (7), changes to the neutral point. than the potential V _N becomes negative (third map segments), the voltage applied to the first input terminal point B is a positive input terminal of the second comparator (8) _{2E V + (E U orE W} ) ............ ...... (4) becomes more positive than the neutral point potential V _N (Fig. 3D), so the output of the second comparator (8) becomes a positive voltage and the diode (22)
Are turned on, a forward bias voltage is applied to the switching transistor (4), the switching transistor (4) is turned on, and a current from the power supply is passed through the first coil (1).

When the rotor further rotates and enters the period of t ₂ -t ₀ , the voltage applied to the first input terminal point B which is the positive input terminal of the second comparator (8) becomes negative from the neutral point potential V _N ( Fig. 3b), the second
Since the output of the comparator (8) becomes negative and the output of the third comparator (9) becomes positive, the diode (23) is turned on and a forward bias voltage is applied to the switching transistor (5). ) Is turned on and the second coil (2)
The current from the power supply is applied to.

When the rotor is rotated from the period of t ₂ -t _0, the period of t ₀ -t ₁ starts again, the switching transistor (6) is turned on as described above, and the current from the power source is supplied to the third coil (3). The third coil (3) is excited. In this way, the switching transistors (4), (5) and (6) are turned on one after the other, and the first, second and third coils (1), (2) and (3) are sequentially excited, so that FIG. As shown, torque is generated to rotate the rotor.

By the way, the positive feedback transistors (25), (26) and (27) are turned on at the same time as the switching transistors (4), (5) and (6). That is, when the induced voltage of the third coil (3) decreases at t ₀ in FIG. 3 and the output of the third comparator (9) becomes negative, the diode (24) becomes conductive, and this output causes the switching transistor The positive feedback transistor (27) is turned on together with (6). When the positive feedback transistor (27) is turned on, the voltage at the first input terminal point C, which is the positive input terminal of the third comparator (9), further decreases, as shown in FIG. 6, and the third comparator (9 ) Is further stabilized. Similarly, at t ₁ in FIG. 3, the induced voltage of the first coil (1) is lowered and the switching transistor (4) and the positive feedback transistor (25) are turned on. When the positive feedback transistor (25) is turned on, the detection voltage at point A drops and the first
The negative of the comparator (7) is further stabilized. In this way, the positive feedback transistors (25), (26) and (27) are turned on each time the energized phase is switched, and the potentials at the first input terminal points A, B and C are lowered to stabilize the first, second An electric current is applied to the third coils (1), (2) and (3).

FIG. 2 is a block diagram showing another embodiment of the present invention. By changing over the changeover switches (31), (32) and (33), the rotor can be rotated in either forward or reverse direction. However, when the changeover switches (31), (32), and (33) are changed over to the opposite side of the drawing, the connection is the same as that described above, and the forward rotation is performed. And the changeover switches (31) (32) (33)
, The diodes (28) (29) (3
Since 0) is in the opposite direction to the diodes (22) (23) (24), the direction of conduction of the diodes of the outputs of the first, second and third comparators (7) (8) (9) is opposite. , Rotate the rotor in the opposite direction. That is, when the rotor is rotated in the reverse direction, induced voltages u, w, v shown in FIG. 4 (a) are generated in the first, second and third coils (1), (2) and (3), and t ₀ During the period of -t _1, the voltage given by the equation (4) applied to the first input terminal of the second comparator (8) becomes negative with respect to the potential V _N applied to the second input terminal and a negative voltage is applied to the output terminal. Although it occurs (Fig. 4B), the first input terminal of the first comparator (7) becomes positive with respect to the potential V _N, so that a positive voltage is generated at the output terminal (Fig. 4C), and the diode (29) is applied. When turned on, a forward bias voltage is applied to the switching transistor, the switching transistor (5) is turned on, and a voltage from the power supply is supplied to the second coil (2) for excitation.

During the period of t ₁ -t _{2 when} the rotor rotates, a negative output voltage is generated from the first comparator (7) (Fig. 4C), and a positive voltage is generated at the output terminal of the third comparator (9). (28) becomes conductive, whereby the switching transistor (4) is also turned on and the first coil (1) is excited. As described above, as the rotor rotates, the switching transistor (5), the switching transistor (4), and the switching transistor (6) are electrically connected in this order to the second coil (2), the first coil (1), and the third coil (3). ) Are sequentially excited to rotate the rotor counterclockwise. The torque at that time is shown in FIG.

By the way, when the rotor is rotated as described above, the voltages induced in the first, second and third coils (1), (2) and (3) are as shown in FIG. Since the motor current is small, the terminal voltage when energized is the same as the induced voltage waveform. If now switching the changeover switch for reversing the rotation of the rotor at t ₀ in FIG. 5 (31) (32) (33) opposite to the illustrated second comparator output (8) is positive (the (Fig. 5B), 1st
When the output of the comparator (7) is negative (Fig. 5C), the diode (22) is on, but the output of the third comparator (9) is positive (Fig. 5D), and the first comparison Since the output of the device (7) is negative, the diode (28) is turned on and a current continuously flows through the first coil (1). However, when there is no load, the terminal voltages of the coils (1), (2) and (3) become equal to the induced voltage, and at time t ₁ , the output of the first comparator (7) is positive and the second comparator (8) ) Output becomes negative, the diode (29) is turned on, the second coil (5) is energized, and the current continues to flow in the order of the first, second and third coils (1) (2) (3). The rotor is not reversed. However, in the present invention, since the positive feedback transistors (25), (26) and (27) are connected, the positive feedback transistor (25) is turned on at the time of t ₁ in FIG. 5 and the first comparator (7) Since the voltage at the first input terminal point A, which is the positive input terminal, is lowered, the output of the first comparator (7) becomes negative until time t ₂ (Fig. 5C), and the current flows through the first coil (1). Flows. The output of the point of time of t ₂ when the third comparator (9) is negative (Fifth Zuro), energization of the ends until it turned once was diode (28) the first coil is turned off (1) However, the terminal voltage of the first coil (1) is due to the induced voltage, and the output of the first comparator (7) changes from negative to positive,
Further, since the output of the second comparator (8) becomes negative (Fig. 5D), the diode (29) is turned on and a current flows through the second coil (2). Similarly, as shown in FIG. 5 (e), the first, second and third coils (1), (2) and (3) are energized in this order. (1) (2)
A period occurs in which the current flowing in (3) and the induced voltage are in the same direction, and as shown in (Fig. 5), a partial reversal torque is generated and the rotor is rapidly stopped, and then the rotor is stopped. Rotate in the opposite direction. When the rotor is rotated, as described above, the third,
The second and first coils (3), (2) and (1) are energized in this order to keep the rotor rotating in the opposite direction.

(G) Effect of the Invention According to the present invention, the voltage induced in the coil of each phase is applied to the first input terminal of the comparator while being superimposed on the first input terminal at a constant ratio, and with the reference voltage applied to the second input terminal. The output signals obtained by the comparison operation are obtained, and these output signals are configured to be added to the diodes that are connected between the output terminals of each comparator so that the conduction directions are the same in a ring shape. In a brushless motor configured so that one diode is turned on and a switching transistor provided corresponding to the diode is turned on to sequentially energize a coil to drive rotation, the brushless motor is synchronized with the switching transistor. A positive feedback transistor that turns on and off is provided and is applied to the first input terminal of each comparator when the positive feedback transistor is in the on state. Since the induced voltage generated is reduced, it is possible to accurately switch the energized phases under light load and no load. Therefore, according to the present invention, when the rotation direction of the rotor is switched by switching the switch, there is feedback in which the current flowing in the coil and the induced voltage are in the same direction, so that the reversal torque can be generated and the rotor can be generated. Can be rapidly stopped and reversed, and the reverse rotation operation can be reliably performed under no load.

[Brief description of drawings]

1 is a circuit diagram of a brushless motor of the present invention, FIG. 2 is a circuit diagram of another embodiment of the brushless motor of the present invention,
FIG. 3, FIG. 4, FIG. 5 and FIG. 6 are signal waveform diagrams of each part of the brushless motor of the present invention. (1) (2) (3) ... first, second and third coils,
(4) (5) (6) ... Switching transistor,
(7) (8) (9) ... First, second and third comparators, (2
5) (26) (27) …… Positive feedback transistor.

Claims (1)

[Claims] 1. A first, second and third switching transistor having a plurality of phases and first, second and third coils respectively connected to the first, second and third coils as a load. And a first input terminal is connected to the corresponding first, second and third coils via a first resistor and a second resistor and a diode to another coil, respectively. First, second, and third comparators in which the induced voltages generated in the phase coils are superimposed and input at a fixed ratio, and the reference voltage is input to the second input terminal;
First, second and third positive feedback transistors connected to first input terminals of second and third comparators and turned on and off in synchronization with the first, second and third switching transistors; A diode connected between the output terminals of the first, second and third comparators so as to have the same conduction direction in a ring shape, and between the output terminals of the first, second and third comparators. The first, second, and third switching transistors are turned on by the ON operation of the diode due to the voltage difference between the first, second, and third coils, thereby exciting any one of the first, second, and third coils and the first coil. The brushless mode is characterized in that the induced voltage applied to the first input terminals of the first, second and third comparators is reduced by turning on the second and third positive feedback transistors. .