JPH0720386B2 - Brushless motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor that can perform a positioning operation and can rotate at high speed.

2. Description of the Related Art The development of semiconductor technology and digital technology in recent years has promoted the digitization of all industrial devices and promoted the adoption of microcomputers. A motor capable of digital positioning operation is suitable as a drive source for these devices, and conventionally, a stepping motor or a servo motor has been used.

Hereinafter, a conventional stepping motor will be described with reference to the drawings. FIG. 17 shows a principle diagram of a conventional permanent magnet (PM) type stepping motor.
Reference numeral 171 is a stator, 172 is a rotor made of a magnet, and 173 is a coil. If the coils are excited in order from the outside, the rotor will change position and step by step depending on the state of energization of the coils. First
FIG. 18 shows the torque distribution of the stepping motor shown in FIG. 17, and it can be seen that it has a position holding characteristic and obtains a rotation speed synchronized with an external signal. However, the stepping motor is not suitable for high speed rotation because the rise of the current is delayed at high speed due to the influence of the time constant of the coil and the iron loss, and the torque is not generated in good timing. Especially when the magnetic pole pitch is made fine in order to improve the position resolution, 1
Since the switching frequency per rotation is increased, the effect was significant.

In addition, in order to compensate the above-mentioned drawbacks of the stepping motor, a method may be adopted in which an encoder is attached to the outside and the switching of the energized phase is speeded up in time according to the speed of the motor to cover the rise delay of the current. In the method, there is a drawback that the size is large because the encoder is mounted outside the motor and the encoder is expensive.

Furthermore, the stepping motor has a
As shown in Fig. 19, there is generally a phenomenon that vibrationally stops around a stop point, and there is a drawback that it takes time to determine the position. In order to reduce this vibration and shorten the time to determine the position, it is necessary to give mechanical viscous resistance (mechanical damping) to the rotor, and in this case there is a drawback that the structure becomes complicated. . Also, the torque distribution waveform of the stepping motor is determined by the core shape, coil current, winding specifications, etc., and the torque-angle ratio near the stop point, which is important for position accuracy, cannot be changed significantly. There was a limit to.

Next, a conventional servo motor will be described. FIG. 20 shows a positioning control system of a servomotor, 201 is a motor, 202 is an encoder, 203 is a control circuit including a deviation counter, and 204 is a drive circuit.

The positioning servo system configured as described above can operate at high speed in accordance with the digital position command and can obtain positioning characteristics. Also, electrical damping can be added, and stopping is not oscillatory. However, it has the drawbacks that the encoder is expensive and that the circuit scale of the control system is large and expensive.

Problems to be Solved by the Invention As described above, the stepping motor has a drawback that it cannot rotate at a high speed, the time until position determination is long, and the torque distribution cannot be widely changed. However, it has a drawback that the size is large and the encoder is expensive. Further, the servo motor has a drawback that the control system and the encoder are expensive.

In view of the above problems, the present invention provides a brushless motor having a highly accurate positioning function and a high-speed rotatability, which has a shape similar to that of a conventional stepping motor and has a relatively simple circuit configuration.

Means for Solving the Problems In order to solve the above problems, a brushless motor according to the present invention comprises: (1) a rotor made of a magnetic material or a magnet; and (2) a stator facing the rotor via a gap. A stator having at least a core and a plurality of coils; (3) a bearing device that rotatably supports the rotor; and (4) a stator mounted on the stator, which detects changes in the rotor position and outputs this as an electrical signal. And a non-contact sensor that outputs substantially sinusoidal position signals whose phases are different from each other, (5) Speed detecting means for converting a change in the position signal into a speed signal, (6) Step command from the outside An electronic switch means for receiving the signals and selecting the above polyphase position signals in order according to the number of step command signals; (7) a differentiating means for outputting the amount of change of the selected position signal; (8) the selected position After signal amplification Limiting processing means, or processing means composed of a widening circuit including an integrating circuit, (9) Addition value of speed signal and selected position signal, change amount of position signal, and command amount from the outside And (10) a sine wave type drive circuit for energizing a plurality of coils according to the advanced position signal.

According to the present invention, with the above configuration, the position signal obtained by the non-contact sensor built in the motor is advanced by the position signal for phase excitation by the position signal itself selected by the electronic switch means, and the phase is advanced. A brushless motor having a stepping function and a positioning function is obtained by energizing a coil by a position signal. Furthermore, by adding to the speed signal and the amount of advance command, the amount of advance of the position signal is increased as a whole according to the speed to cover the rising delay of the current and high-speed operation can be performed. Further, by adding the amount of change in the phase command position signal as a damping signal to the amount of phase advance, vibration at stop is suppressed and the time until the position is determined is shortened. Then, by adding the signal from the outside to the phase advance amount, the stop position can be moved according to the external signal. Further, the positional accuracy and reproducibility can be improved by changing the torque distribution waveform.

Embodiment Hereinafter, a brushless motor according to an embodiment of the present invention will be described with reference to the drawings.

1A and 1B show a mechanical portion of a brushless motor according to a first embodiment of the present invention. FIG. 1A is a vertical sectional view and FIG. 1B is a lateral sectional view.

In FIG. 1, 1 is a rotor core having magnetic pole teeth on the circumferential surface, 2 is a stator core having magnetic pole teeth on the surface facing the rotor, 3 is a magnet laminated on the rotor core, Reference numeral 4 is a three-phase twelve coil, and 5 is a non-contact sensor that outputs a substantially sinusoidal signal whose phase is shifted by 120 °.

FIG. 2 is a block diagram of an electric circuit portion of the brushless motor of the first embodiment. In FIG. 2, 20 is the mechanical part of the above-mentioned motor, 21 is a rotor, 22a, 22b, 22c are three-phase coils, and 23 is a non-contact sensor composed of a magnetoresistive element. twenty four
Reference numerals a, 24b, 24c are position signal amplifiers for amplifying the three-phase position signal outputs of the non-contact sensor. 25 is a phase advancing circuit for advancing or retarding the phase of the 3-phase position signal according to the phase advancing command amount, 26 is a 3-phase motor in which a current proportional to the advanced position signal is passed through the coil of the 3-phase motor. It is a sine wave drive circuit. 27a, 27b, and 27c are amplifiers that invert three-phase position signals. Reference numeral 28 is an electronic switch circuit that receives a step command signal from the outside and selects and outputs one from a total of six signals of the position signal and the inverted position signal.

Reference numeral 29 is a differentiator that takes out the change of the selected position advance command position signal and widens it. Reference numeral 30 is a processing circuit for increasing the selected position signal and performing processing for limiting the amplitude. Reference numeral 31 is a frequency-voltage conversion (FV conversion) circuit that converts a change in the position signal from the non-contact sensor into a speed signal, and 32 is an adder, the output of which is a phase advance command signal of the phase advancer 25.

The operation of the brushless motor configured as above will be described below.

In the reluctant type motor that utilizes the force generated by the stator and rotor magnetic pole teeth like the motor of this embodiment, the magnetic flux in the air gap between the stator and the rotor is improved by devising the shape of the magnetic pole teeth. The distribution can be approximated to a sine wave.

When a constant current is applied to each coil phase in this way, the torque due to each phase of the coil, A, B, and C, is as shown in FIG. 3, with respect to the rotor electrical angle θ and the tooth pitch τ (electrical angle 2π ) Can be expressed as a sine wave with a period. In the case of this embodiment, since the motor is a three-phase motor, each torque distribution is out of phase by 120 °.

A non-contact sensor consisting of a magnetoresistive element has 3 in 1 chip.
The phase sensor elements are configured to detect the positions of the magnetic pole teeth of the rotor. FIG. 4 shows the sensor arrangement and output. In FIG. 4, 41 is a rotor magnetic pole tooth, and 42 is a non-contact sensor. When the rotor moves in the θ direction, three-phase sensor outputs are obtained due to changes in the relative positions of the center a, b, c of each sensor element and the rotor magnetic pole teeth. As for the sensor output, a sinusoidal output can be obtained by adjusting the mounting position of the magnetoresistive element and the strength of the bias magnet 43.

The non-contact sensor is basically attached as shown in FIG. In FIG. 5, reference numeral 51 is a stator one-phase magnetic pole tooth, 52 is a rotor magnetic pole tooth, and 53 is a one-phase sensor corresponding to the stator magnetic pole tooth phase. No torque is generated when the rotor and stator pole teeth face each other as shown in FIG. 5 (a).

In the case of the positional relationship of (b), a torque in the θ direction acts due to the attraction force between the magnetic pole teeth. In the case of (c), a torque in the θ direction is generated by the repulsive force. Sensors (a), (b), (c)
As shown in FIG. 5, when the stator magnetic pole teeth are arranged, the relationship between the torque distribution of each phase and the sensor output is shown in FIG.
As shown in (e), the relationship is 90 ° out of phase. However, the excitation sensor signal is advanced by an arbitrary angle by the phase advancer 25.

When the sinusoidal drive circuit is used as in the present invention, the coil current of each phase changes according to the sinusoidal position signal.

Therefore, the torque of each phase is A phase K ₁ · I _A · sin θ B phase Phase C K ₁ : Constant I _A , I _B , I _C : Each phase current.

Since the current of each phase is proportional to the sensor signal, K _2: constants alpha: becomes fast angle sensor signal, the entire torque distribution Becomes

Ordinary brushless motors Is equivalent to And generate continuous torque.

In the brushless motor of the present invention, the phase advance amount α is changed according to the sensor signal itself to provide the positioning characteristic.

The phase advancing circuit 25 in FIG. 2 is a circuit for advancing the phase of the above-mentioned sinusoidal excitation sensor signal in accordance with the advancing command voltage, and changes the sinusoidal value depending on the vector addition method of the sensor signals or the instruction amount. The reference signal and the sensor signal are obtained by the occupant method. The sensor signal is a phase advance circuit for phase excitation.
At the same time as being led to 25, it is also used for advance command.
As shown in FIG. 2, the three-phase sensor signals are inverted, and a total of six signals are input to the electronic switch circuit 28.

As shown in FIG. 6, the electronic switch circuit 28 is composed of a hexadecimal reversible counter 61 and a decoder 62 which selects one of the six signals by the counter output. With this configuration, six signals can be selected in order for the phase advance commands in both directions.

The FV conversion circuit 31 is a circuit that generates a voltage according to the speed from a change in the sensor signal, and is configured by a circuit centering on a differentiator.

Now, the operation of the brushless motor of the present invention in the case where the interval between pulse commands from the outside is long and the speed voltage can be almost ignored will be described.

FIG. 7 shows a distribution diagram of six signals for phase advance. The sensor signals are inverted and a sinusoidal signal with a phase difference of 60 ° is produced.

They are Can be expressed as

It is now assumed that a is selected as the phase advance signal by the electronic switch circuit. Further, if the coefficient of the advance command voltage of the phase advancer 31-the advance angle is β and the amplification rate of the processing circuit 30 is γ, (1)
From the formula, the torque distribution is Becomes

The shape of this torque distribution changes according to the values of β, γ, and K ₃ as shown in Fig. 8. It is shown that the point has the position retention characteristic. Also β
By changing the value of γ · K ₃ , the inclination of the torque distribution near the positioning point, which is important for the positioning characteristics (T-θ characteristic)
It also shows that can be changed. That is, in a normal stepping motor, the torque distribution is However, the inclination in the vicinity of the position holding point at this time is almost equal to that in the case of βγK ₃ = 1 in FIG.

However, in the case of the brushless motor of the present invention, By setting the degree to about, the T-θ characteristic near the position holding point can be approximately doubled. Further, the amplification factor γ of the processing circuit 30 is given a non-linear characteristic as shown in FIG. 9 (a) so that the values of β, γ and K ₃ are If the swing range is restricted so that it does not exceed the value shown in Fig. 8 (c),
It is possible to increase the inclination of the torque-angle near the position holding point without having to worry about the dent of the torque as in (d). At this time, the torque distribution becomes as shown in FIG. 9 (b), and the positioning error with respect to the disturbance can be reduced.

Now, in the same way as the torque distribution for the advance signal a Fig. 10 shows the torque distribution when the advance signals a, b, c, and are selected. As you can see from this figure,
It can be seen that an uneven torque distribution having six position holding points within one pitch of the magnetic pole teeth can be obtained.

If the electronic switch circuit is set to reversibly select the phase-advancing sensor signal in the order of abc by the external clock, and if the signal a is currently selected,
The rotor stably holds its position at the point shown in Fig. 10 according to the torque distribution determined by Ta. Next, when the phase advance command in the positive direction is applied from the outside, the sensor signal is selected by the electronic switch circuit. As a result, the positive torque at the point on FIG. 9T moves to the working point on the rotor and holds the position. In this way, the rotor steps in accordance with the number of external pulses. When a step command in the negative direction is input when the point is stable, the sensor signal a for phase advance is selected, the negative torque of the point acts on the rotor, and the rotor moves in the opposite direction and stabilizes at the point. However, it can be seen that there is a reversible movement according to the external pulse.

If the T-θ characteristic near the position holding point is linearized as shown in FIG. 11A, it can be considered that a feedback system (b) based on the sensor signal is formed.

(In FIG. 11, J is the rotor inertia, S is the Laplace operator, and K ₄ and K ₅ are constants.) In the case of such a secondary servo system, the position is as shown in FIG. 11 (c). Differential term of K ₅ S
By putting in the feedback loop, the settling property during positioning can be changed.

Normally, when there is no differential term as in (b), the rotor stops vibrationally, but if you set the value of K ₅ to an appropriate value as in (c), you can suppress the vibration and settle. You can shorten the time until. Also, the adjustment of the value of K ₅ can be done electrically, as in the case of stepping motors,
There is no need to do it mechanically.

Now, the positioning characteristic is determined by the torque distribution of the equation (1), but when an arbitrary bias voltage K ₆ is applied to this phase advance amount α from the position fine adjustment input terminal of FIG. 33, the sensor signal a is selected. If so, the amount of phase advance is And the torque distribution is Therefore, the distribution is out of phase by βK ₆ from the distribution of equation (2). Therefore, the stable point of the torque θ, that is, the stop position of the rotor can be arbitrarily and continuously changed according to the value of the position fine adjustment input.

Next, when the interval of the external step command is shortened and the speed of the rotor is increased accordingly, the output voltage of the FV converter 31 is increased, and this speed voltage is added to the phase advance position voltage by the adder 32. As a result, the phase excitation sensor has a larger amount of phase advance than when the speed is slow. By appropriately adjusting the level of the FV conversion output, the rising delay of the coil current due to the increase of the switching frequency can be covered by the phase advance of the excitation position signal to enable high-speed operation.

As described above, according to the present embodiment, a rotor made of a magnetic material having magnetic pole teeth having a constant pitch on the circumference, a stator core having magnetic pole tooth groups, a magnet, and a multiphase coil. A non-contact sensor that detects irregularities of the magnetic poles of the rotor and outputs a substantially sinusoidal position signal;
By providing the electronic switch means, the differentiating means, the amplitude increasing circuit with the amplitude limit, the position fine adjustment input terminal, the phase advancing means, and the sine wave type driving circuit, the stepping function and the settling property are well positioned. It is possible to obtain a small and inexpensive brushless motor which has a positioning function capable of fine adjustment and rotates at high speed.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 12 is a block diagram of an electric circuit portion of the brushless motor according to the second embodiment of the present invention.

In the figure, 120 is a mechanical part of the motor, this part is the same as that of the first embodiment, 121 is a rotor, 122a, 122b, 1
22c is a three-phase coil, and 123 is a non-contact sensor. Again 12
4a, 124b, 124c are position signal amplification circuits, 125 is a phase advance circuit, 126
Is a three-phase sinusoidal drive circuit, 127a, 127b, 127c are inverting amplifiers, 128 is an electronic switch circuit, 129 is a differentiator, 131 is an FV conversion circuit, and the above electric circuit has the configuration shown in FIG. It is similar. The difference from the configuration of FIG. 2 is that a widening device including an integrating circuit is used for 130, and the position fine adjustment input signal is added by an adder 133.

In the first embodiment, in order to improve the T-.theta. Characteristic of the torque distribution, the advance position signal is widened and the amplitude is limited to obtain a torque distribution with a large T-.theta. .

However, with this method, depending on the motor, there is a case where the amplification factor cannot be increased so much due to the influence of the mechanical resonance frequency of the rotor. Therefore, the present embodiment incorporates the concept of integral compensation in which only the gain in the low frequency band is increased, as is the case with a normal positioning servo system.

The amplification circuit 130 including the integrator is composed of the circuits shown in FIGS. 13 (a) and 13 (b). When such an amplifier is used, the amplification factor in the high frequency range is Or However, the amplification rate when stopped is the maximum amplification rate of the operational amplifier in (a), and in (b). The T-θ characteristic can be greatly improved. In the case of such a configuration, the sensitivity of the position fine adjustment input is deteriorated, so that the addition point is changed from the case of the first embodiment and the addition is performed in the preceding stage of the amplifier 130.

As described above, in the second embodiment of the present invention, the widening circuit including the integrator is used as the position signal widening circuit in the first embodiment. The torque inclination can be increased even for a motor whose characteristics cannot be improved, and the positioning function can be improved.

In the first and second embodiments described above, all conventional brushless motors can be applied to the mechanical portion of the motor. That is, as shown in FIG.
1, the rotor core 142 and the stator core 143 both have magnetic pole teeth, a brushless motor having a rotor with multi-pole magnetized magnets as shown in FIG.
As shown in the figure, a brushless motor having a rotor composed of magnets magnetized in multiple poles on a disk surface may be used. Moreover, in the embodiment, the magnetoresistive element is used as the non-contact sensor, but this may also be a hall element or an optical sensor. 3 more
The third phase of the phase position signal may be obtained by combining the first and second phase signals. Further, in the embodiment, the brushless motor having a three-phase coil is used, but the same effect can be obtained by using another brushless motor having two or more phases. In FIG. 14, 144 is a coil, 145 is a non-contact sensor, and 146 is a yoke. In FIG. 15, 151 is a stator core, 152 is a magnet, 153 is a coil, and 154 is a non-contact sensor. further,
In FIG. 16, 161 is a rotor magnet, 162 is a stator yoke,
Reference numeral 163 is a coil, and 164 is a non-contact sensor.

EFFECTS OF THE INVENTION As described above, the present invention provides a rotor made of a magnetic material or a magnet, a stator having at least a stator core and a plurality of coils, a bearing device, and a non-contact for detecting the position of the rotor. By providing a sensor, speed detecting means, electronic switch means for receiving an external pulse, phase advancing means, differentiating circuit, position signal processing circuit, and sine wave type drive circuit, the settling property is good and the position fine adjustment is performed from the outside. It is possible to obtain a small, inexpensive brushless motor which has a highly accurate positioning function capable of performing high-speed rotation and rotates at high speed in synchronization with an external step pulse.

[Brief description of drawings]

1A is a vertical sectional view of a brushless motor according to a first embodiment of the present invention, FIG. 1B is a horizontal sectional view thereof, and FIG. 2 is a block diagram of an electric circuit according to the first embodiment of the present invention. Third
The figure shows the torque distribution of each phase of the first embodiment, FIG. 4 (a) shows the arrangement of the non-contact sensor, (b) shows its output waveform, and FIG. 5 (a)-(). e) is a diagram showing a sensor arrangement and torque and sensor output distribution, FIG. 6 is a configuration diagram of the electronic switch means of the first embodiment, FIG. 7 is a diagram showing a waveform of a phase advance position signal, and FIG. Figures (a) to (d) and Figure 9 (b)
Is a diagram showing a torque distribution of the first embodiment, FIG. 9 (a) is a diagram showing a phase advance command signal of the first embodiment, and FIG. 10 is a diagram explaining a torque distribution and an operation of stepping, Figure 11 (a),
(B) and (c) are diagrams for explaining electrical damping at the time of stop, FIG. 12 is a block diagram of an electric circuit according to a second embodiment of the present invention, and FIGS. 13 (a) and (b) are integral diagrams. Figure showing an example of the circuit,
14 (a) and 14 (b) are perspective views and cross-sectional views of a main part showing another embodiment of the present invention, and FIGS. 15 (a), (b), 16 (a) and (b) are FIG. 17 is a longitudinal sectional view and a lateral sectional view showing a motor main mechanism portion of still another embodiment of the present invention, FIG. 17 is a principle diagram of a conventional stepping motor, and FIG. 18 is a diagram showing a torque distribution of the motor of FIG. FIG. 19 is a diagram showing the settling property of a stepping motor, and FIG. 20 is a diagram showing a control system of a conventional servo motor. 1,142 …… Rotor, 2,143,151 …… Stator core, 3,146,15
2,161 ... Magnet, 4,144,153,163 ... Coil, 5,23,145,1
54,164 …… Non-contact sensor, 20,120 …… Motor part, 25,125
...... Phase advance circuit, 26,126 …… Sine wave drive circuit, 28,128 ・ ・ ・
… Electronic switch circuit, 29,129 …… Differentiator, 31,131 …… FV
Transducers, 41, 52 ... Rotor pole teeth, 51 ... Stator pole teeth.

Claims (8)

[Claims] 1. A rotor, a stator including a stator core that faces the rotor with a gap therebetween, a bearing device that rotatably supports the rotor, and a rotor device that is attached to the stator to rotate the rotor. A plurality of non-contact sensors that detect a change in position of the child and convert it into an electric signal, and output substantially sinusoidal position signals having different phases, and a speed that converts the change in the position signal into a speed signal. A detection means, an electronic switch means for receiving a step command signal from the outside and selecting the plurality of position signals in order according to the number of pre-step command signals, and a differentiating means for outputting a change amount of the selected position signal, Means for processing the selected position signal, the speed signal, the selected and processed position signal, the change amount of the position signal and the added value of the command amount from the outside, as the amount of phase advance, the phase of the position signal To advance A brushless motor comprising: phase means; and a sinusoidal drive circuit that energizes the plurality of coils according to the advanced position signal, wherein the rotor is a magnet and a magnetic body in which the magnets are laminated from both sides. And a stator core having magnetic pole teeth formed on the circumference of the magnetic body, the stator comprising a magnetic pole tooth group on the rotor facing surface and a plurality of coils wound around the stator core. The non-contact sensor detects irregularities of magnetic pole teeth of the rotor and converts the irregularities into an electric signal. 2. A rotor, a stator provided with a stator core facing the rotor with a gap therebetween, a bearing device for rotatably supporting the rotor, and a rotor mounted on the stator for rotating the rotor. A plurality of non-contact sensors that detect changes in the position of the child and convert this to an electric signal, and output position signals in a substantially sinusoidal wave form with different phases, and a speed that converts the change in the position signal into a speed signal. A detecting means, an electronic switch means for receiving a step command signal from the outside and selecting the above-mentioned many position signals in order according to the number of step command signals; and a differentiating means for outputting a variation amount of the selected position signal, A means for processing the selected position signal, a phase signal of the position signal, the sum of the speed signal, the selected and processed position signal, the change amount of the position signal, and the command amount from the outside as a phase advance amount. To advance Means and a sine wave type drive circuit for energizing the plurality of coils by the advanced position signal, wherein the rotor is a magnetic pole having a constant pitch on the circumference. The stator is made of a magnetic material, and the stator is wound around the stator core, the stator core having magnetic pole teeth on the surface facing the rotor, the magnet mounted on the stator core, and the stator core. A brushless motor comprising a plurality of coils, wherein the non-contact sensor detects irregularities of magnetic pole teeth of the rotor and converts the irregularities into an electric signal. 3. The brushless motor according to claim 1, wherein a magnetoresistive element is used for the non-contact sensor. 4. The brushless motor according to claim 2, wherein a magnetoresistive element is used for the non-contact sensor. 5. The brushless motor according to claim 1, wherein the processing means for the selected position signal comprises a widening circuit and a swing limiting circuit. 6. The brushless motor according to claim 2, wherein the processing means for the selected position signal comprises a widening circuit and a swing limiting circuit. 7. The brushless motor according to claim 1, wherein the processing means for the selected position signal comprises a widening circuit including an integrating circuit. 8. The brushless motor according to claim 2, wherein the means for processing the selected position signal comprises a widening circuit including an integrating circuit.