JPS5996859A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce the cost, size, power consumption and low speed rotating irregularity by winding a detecting coil exclusively for a stator core to form a rotating position detecting mechanism, thereby eliminating a special position detector and a speed detector. CONSTITUTION:Induced voltages generated at detecting coils 19-11 which are wound on a stator core are respectively applied to transistors 21-23 through amplifiers 12-14 and waveform shapers 14-17, and drive currents are respectively flowed to 3-phase stator coils 24-26. The output of a waveform shaper 15 is applied as a set input of an R-S flip-flop 36 through a differentiator 35. A clock pulse from a crystal vibrator 32 is applied as a reset input of the flip- flop 36 through a frequency divider 33 and a differentiator 34. This flip-flop 36 outputs a rectangular wave in response to the rotating speed, and which is applied to a control transistor 40 through an integrator 37.

Description

[Detailed description of the invention] The present invention relates to a planless motor.

Conventional brushless motors use Hall elements to determine the rotational position.
Most of them were detected by using position detection elements such as photoelectric elements. FIG. 1 shows a conventional example using a Hall element as a position detection element. A rotor magnet 2 is fixed to the inner periphery of a rotor yoke 1, and a rotating shaft 3 is fixed to the rotor yoke 1, thereby forming a rotating body. A coil 5 is wound around the stator core 4,
The stator core 4 is fixed to a bearing holder 7 to which a bearing 6 is fixed. Hall element 10 is fixed to printed circuit board 9. 8 is a mounting plate, and 11 is a case. In the brushless motor with the structure shown in Figure 1, the Hall element detects the leakage magnetic flux of the rotor magnet on the outside or below the stator coil due to the structure, so if there is a shape restriction, it is not possible to install the Hall element. There were times when it was impossible. Further, when installing the position detection element, the position accuracy of the position detection element is directly affected by the detection error, worsening uneven rotation, and, if necessary, requiring position adjustment, which also leads to an increase in the number of assembly steps.

Furthermore, when using a Hall element, current is periodically passed through the Hall element, which is unsuitable for the power consumption ratio. In addition, if an abnormal load is applied to the motor and, in the worst case, the motor is restrained, an abnormal current will flow through the drive coil.
There was a possibility that the fill would burn out, so it was necessary to add a protection circuit to the control circuit.

In addition, when performing precise speed control in a brushless motor, it is necessary to use a speed detector such as a tough generator in addition to the normal position detection element 1, which poses problems in terms of miniaturization and cost reduction. .

The present invention eliminates the drawbacks of the prior art, and eliminates the need for special position detection elements and speed detectors by detecting the induced voltage of the detection coil wound around the multi-pole stator, either overlappingly with the drive coil or alone. The cost of brushless motors is lower due to the use of .

The aim is to achieve miniaturization, power consumption ratio, and low rotation unevenness.

The present invention will be described in detail below based on examples.

FIG. 2 shows a schematic cross-sectional view of the brushless motor of the present invention.
Showing a phase brushless motor. In this embodiment, one of the multipolar stator coils for each phase is used as a detection filter. 1 is a stator coil for 1-phase detection, 2 is a stator coil for 2-phase detection, 3 is a stator coil for 3-phase detection, 1-1 to 1-8 are stator coils for 1-phase drive, 2-
1 to 2-8 are two-phase drive stator coils, 6-1 to 3
-8 is a stator coil for six-phase drive, 4 is a rotor magnet magnetized to 36 poles, 5 is a rotor yoke, 6 is a stator core, 7 is a ball bearing, and 8 is a rotating shaft connected to the rotor yoke. rotor magnet 4
is fixed to the rotor yoke 8 and rotates around the rotating shaft 8. Stator coil 1 for 1-phase detection, stator coil 2, 3 for 2-phase detection by rotation of rotor magnet 4
An induced voltage is generated in the stator coil 3 for phase detection, an induced voltage is generated in the stator coil 1 for 1-phase detection, and the induced voltage in the stator coil 1 for 1-phase detection is used as a position detection signal to excite the stator coil for 1-phase drive. Then, the two-phase drive stator coil is excited using the induced voltage of the two-phase detection stator coil 2 as a position detection signal, and the six-phase drive stator coil is excited using the induced voltage of the six-phase detection stator coil as a position detection signal. Depending on the situation, the rotor magnet 4 may be moved in a predetermined direction.
is driven to rotate.

FIG. 6 shows a specific example of a drive circuit for a brushless motor according to the present invention. 9 is a 1-phase detection coil, 10 is a 2-phase detection coil, 11 is a 3-phase detection coil, 12, 13.1
4 is an inverting amplifier, 15.1<S, 17 is a waveform shaping circuit,
18, 19.20 are base resistors, 21, 22.23 are drive transistors, 24 is a stator coil for one-phase drive,
25 is a stator coil for two-phase drive, 26 is a stator coil for three-phase drive, and 27 is a power source. Further, operating waveforms for one phase are shown in FIG. The induced voltage waveforms 28 generated in the position detection stator coils 9, 10, and 11 due to the rotation of the rotor magnet are extracted as amplified signals 29 by the inverting amplifiers 12, 13, and 14, respectively. After converting each amplified signal into a square wave 30 by passing it through a waveform shaping circuit 15, 16, 17, driving transistors 21, 22, 23 are driven via base resistors 189, 9, 20,
Drive currents are sequentially applied to the three-phase stator coils 24, 25, and 26 with a phase difference of 120 electrical degrees. The drive coil current waveform looks like 31. As a result, the rotor magnet is rotationally driven in a predetermined direction.

FIG. 5 shows an example of a drive circuit including speed control when using a PLL control method, and shows a case where an R-S flip-flop is used as a phase comparator. 32 is a crystal oscillator, 33 is a frequency divider, 34°35 is a differential circuit, 36 is R-S
Flip-flop, 67 is an integrator, 38 is a base resistor,
39 is a voltage dividing resistor, 40 is a control transistor, and 41 is a power supply. A waveform whose frequency is divided by the crystal oscillator 32 and the frequency divider 33 as much as possible to have the same period as the arbitrarily set rotational speed is converted into a trigger waveform by passing it through a differentiating circuit 64. On the other hand, due to the rotation of the rotor magnet, the amplifier 1
2. The signal converted into a square wave by the waveform shaping circuit 15 is converted into a trigger waveform by the differentiating circuit 35.

Hereinafter, the speed control operation will be explained using FIG. 6.

As described above with reference to FIGS. 2 and 3, the induced voltage generated in the detection coils 9, 10, and 11 is inverted and amplified through the inverting amplifiers 12, 13', and 14, and the waveform shaping circuit 15 , 16, and 17, it is converted into a square wave by passing through the resistors 18, 19, and 20, and drives the transistors 21, 22, and 26, and the three-phase stator coil 2
4, 25° and 26, and any one of the 6-phase detection coils is used as a speed detection signal.
The induced voltage waveform 42 of the phase detection coil is also used as a speed detection signal. Induced voltage waveform 4 of one-phase detection coil 9
2 is passed through an inverting amplifier 12 to produce an inverted amplified waveform 43, and the converted square wave 4 is passed through a waveform shaping circuit 15.
4 is converted into a trigger waveform (hereinafter referred to as rotation pulse 44) through a differentiating circuit 35. Further, a clock pulse 46 generated by the crystal oscillator 32 is converted into a frequency-divided waveform 47 by a frequency divider 63, and converted into a trigger waveform (hereinafter referred to as reference pulse 48) through a differentiating circuit 64.

The R-87 lip 70 knob 36 is set by the rotation pulse and the output becomes a high level, and the reference pulse is reset and the output becomes a low level. By repeating this alternately, a square wave corresponding to the rotation speed of 49 is created. By passing the square wave through an integrator 67, a DC voltage of 50
, and controls the control transistor 40 whose ON region is set to an appropriate value by the voltage dividing ratio of the base resistor 38'' and the voltage dividing resistor 39 through the base resistor 38'' and the voltage dividing resistor 39. At 51, the reference pulse 48
Since the periods of the rotation pulses 45 are equal and the high level width of the output waveform 38 of the R-87 lip-flop is wide and the DC voltage value is high as shown in the output waveform 50 of the integrator 37, the collector current of the control transistor 40 is small. When a disturbance is added and the rotation speed slows down, the period of the rotation pulse becomes wider as shown in the rotation section 52, so the high level width of the output waveform 49 of the R-S flip-flop becomes narrower, and the output waveform 50 of the integrator 67 becomes narrower.
As shown in the figure, the DC voltage value decreases and the collector current of the control transistor 40 increases, which tends to increase the driving force. Therefore, the rotational speed becomes like the specified rotational speed section 56 again.

As described above, in the present invention, there is no need to use a position detection element such as a Hall element to wind the detection coil around the stator in the same way as the drive coil, and there is no need to provide a space for the element. In addition, when using the position detection element, extremely accurate positioning is required for its installation, and the positional accuracy itself causes a detection error, deteriorating the rotation speed, and in some cases, position adjustment may be required, so it is difficult to assemble. Although this may lead to an increase in the number of man-hours, according to the present invention, since the detection coil is wound around the stator, extremely accurate detection is performed, and of course there is no need for position adjustment. Furthermore, there is no need to constantly supply a current to a position detection element such as a Hall element. In addition, when an abnormal load is expected on the motor, especially when a situation where it is restrained occurs, as a protection measure, it is necessary to encapsulate a heat sensitive element such as a temperature heater in the motor itself, or add a protection circuit within the motor control circuit. There is a need to. However, according to the present invention, the induced voltage generated by the rotation of the rotor magnet is used to detect the rotational position and rotational speed, so if an abnormal condition such as a motor lock-up occurs and the motor stops rotating, Since no induced voltage is generated, there is no need to take any special protective measures. That is, not only can the brushless motor itself be made smaller, lower in price, and lower in rotational speed, but also the circuit can be made smaller, lower in price, and lower in power consumption.

Furthermore, although a six-phase brushless motor has been described, the present invention can also be applied to brushless motors having a number of phases other than six, such as a two-phase brushless motor and a four-phase brushless motor.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional brushless motor, ie, a radial gap type motor, Fig. 2 is a schematic sectional view showing an embodiment of the present invention, Fig. 3 is a drive circuit diagram of the present invention, and Fig. 4 is a radial gap type motor.
FIG. 5 is a signal waveform diagram illustrating the operation of the drive circuit shown in the figure, FIG. 5 is a drive circuit diagram including the speed control of the present invention, and FIG. 6 is a signal waveform diagram illustrating the speed control operation of the present invention. 1.9 is a stator coil for 1-phase detection, 2 and 10 are stator coils for 2-phase detection, 3 and 11 are stator coils for 6-phase detection 1-1 to 1-8.24 are stator coils for 1-phase drive, 2 -1. ~2-8.25 is a stator coil for 2-phase drive, 2-1 ~ 2-8.26 is a stator coil for 6-phase drive,
4 is a rotor magnet, 5 is a yoke, 6 is a stator,
7 is a ball bearing, 8 is a rotating shaft, 12, 13.14
is an amplifier, 15, 16, 17 are waveform shaping circuits, 18゜1
9. 20, 33 are pace resistors, 21, 22, 26 are driving transistors, 32 are crystal oscillators, 33 are frequency dividers, 3
4.35 is a differentiation circuit, 36 is an R-S flip-flop,
37 is an integrator, 68 is a base resistor, 69 is a voltage dividing resistor, 4
0 is a control transistor, and 27.41 is a power supply. Above Figure 1-Figure 2 [Figures ゛-3M
Qv:3/ffρ-CLθl-o. Figure 4

Claims (2)

[Claims] (1) In a planless motor equipped with a rotor magnet magnetized into multiple poles, a multiphase stator coil for applying rotational force to the rotor magnet, and a rotational position detection mechanism for the rotor magnet, A brushless motor that features a dedicated detection coil wound around the stator core as a rotational position detection mechanism. (2) A brushless motor characterized in that the detection coil is used to detect the rotational speed of the rotor magnet.