JPH0667259B2 - 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.

A conventional stepping motor will be described below with reference to the drawings.

FIG. 20 shows a principle diagram of a conventional permanent magnet (PM) type stepping motor. 201 is a stator, 202 is a rotor made of a magnet, and 203 is a coil.

If the above coils are sequentially excited from the outside, the rotor will change position depending on the energized state of the coils and will advance. FIG. 21 shows the torque distribution of the stepping motor shown in FIG. 20, and it can be seen that it has position holding characteristics and can obtain 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 a timely manner. In particular, when the magnetic pole pitch is made fine in order to increase the position resolution, the switching frequency per one rotation increases, which has a large effect.

In order to avoid the above-mentioned drawbacks of stepping motors, a method may be adopted in which an encoder is attached to the outside to speed up the switching of the energized phases in time according to the speed of the motor to cover the rising 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.

Next, a conventional servo motor will be described. Figure 22 shows
A servomotor positioning control system is shown, in which 221 is a motor, 222 is an encoder, 223 is a control circuit including a deviation counter, and 224 is a drive circuit.

The positioning servo system configured as described above can operate at high speed in accordance with a digital position command and can obtain positioning characteristics. However, it has the drawbacks that the encoder is expensive and 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 be operated at high speed, and the stepping motor provided with an encoder has a drawback that the shape 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 positioning function and 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 core that faces the rotor via a gap. And a stator having at least a plurality of coils, (3) a bearing device that rotatably supports the rotor, and (4) a rotor mounted on the stator, which detects the position of the rotor and converts it into an electrical signal. A non-contact sensor that outputs position signals having mutually different phases, (5) a processing unit that generates a plurality of first phase advance command signals from the position signals, and (6) a step command signal that receives an external step command signal. An electronic switch means for selecting a plurality of first phase advance commands in order according to the number of advance command signals; and (7) a speed for producing at least one second phase advance command signal according to the frequency of the position signal or the step command signal. Detection means, ( ) A phase advancing means for advancing the phase of the position signal in response to the first and second phase advancing command signals, and (9) a drive circuit for energizing a plurality of coils by the advanced position signal. It is a thing.

With the above-described structure, the present invention advances the position signal obtained by the non-contact sensor built in the motor by the first advance command signal selected by the electronic switch means,
A coil is energized by the advanced phase signal to obtain a brushless motor having a stepping function and a positioning function. Further, the position signal is further advanced by the second advance command obtained according to the speed to increase the overall amount of advance when the speed increases, thereby covering the rising delay of the current and increasing the speed. You can drive.

Embodiment A brushless motor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1, FIG. 2 and FIG. 3 show the mechanical portion of the brushless motor of the first embodiment of the present invention. In these figures, 1 is a rotor composed of magnets magnetized in multiple poles on the circumferential surface, 2a, 2b, 2c and 2d are stator cores having a plurality of magnetic poles on the inner circumference, and 3a and 3b are 2 It is a coil with two phases and is wound on the winding frames 4a and 4c and housed in the stator core.

Reference numerals 5a and 5b are non-contact sensors composed of Hall elements that detect the leakage magnetic flux of the rotor and output two-phase signals that are 90 degrees out of phase in electrical angle.

FIG. 4 is a block diagram of an electric circuit portion of the brushless motor of the first embodiment. In FIG. 4, 40 is the mechanical part of the above-mentioned motor, 41 is a rotor, 42a and 42b are two-phase coils, 4
3a and 43b are non-contact sensors. Reference numerals 44a and 44b are shaping circuits that convert the signals of the non-contact sensor into rectangular waves. 45
Is a phase advancing circuit for advancing the phase of the position signal in accordance with the two kinds of phase advancing command signals, and 46 is a drive circuit for supplying a current according to the change in the polarity of the position signal advanced in the coil of the two-phase motor. . Reference numeral 47 is a processing circuit which produces four first advance command signals from the two-phase position signals. An electronic switch circuit 48 receives a step command signal from the outside and selects and outputs one of the four first phase command signals. 49 is the position signal,
Or the second according to the speed from the frequency of the step command from the outside
Is a speed detection circuit that outputs a phase advance command signal, and 50 is a flip-flop circuit that determines the direction of stepping and switches between a phase advance and a phase delay.

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

FIG. 5 is a diagram showing the principle of the brushless motor of this embodiment and the torque distribution of the motor. FIG. 5 (a) is a principle diagram of the present brushless motor and shows the two-phase coils A and B and the magnet rotor. The torque distribution when a constant current is applied to each phase is shown in (b).

Since the current flows in the forward and reverse directions in the coil, the torque distribution is A, B,
, And these have a substantially sinusoidal distribution at an angle of 0. In a normal brushless motor, the position of the non-contact sensor that detects the position of the rotor is adjusted to the fifth position.
Although the continuous torque as shown in FIG. 5C is obtained, the position of the non-contact sensor is adjusted so that the torque distribution shown in FIG. 5D is obtained in the brushless motor of the present invention. When such energization is performed, the rotor does not rotate and is held at a position determined by the energized phase and has positioning characteristics.

First, the basic relationship between the sensor signal for one phase, the rotor and the torque distribution will be described with reference to FIG. When a Hall element is used for the non-contact sensor 61, the sensor output changes in a substantially sinusoidal shape as shown in FIG. 6 (a) according to the change in the rotor magnetic flux.

The mounting position of the Hall element is not the circumferential facing surface but the facing surface of the end surface of the rotor, but since there is the leakage magnetic flux of the rotor magnet, an output signal proportional to the main magnetic flux can be obtained. Then, the sensor signal is shaped into the signal shown in (b).

When the positional relationship between the stator magnetic pole 62 and the rotor magnetic pole 63 is as shown in FIG. 6 (c), the torque is 0 at the stable point when the attractive force is working. (D) is an unstable point when the repulsive force is working, and the torque is also 0 in this point. As for the relationship between the stator magnetic poles and the rotor poles at the maximum torque, torque acts in the respective directions by the attractive force and the repulsive force in FIG.

When the direction of the coil current is changed depending on the polarity of the sensor signal and continuous torque is generated as in a normal brushless motor [Fig. 5 (c)], it is indicated by A in Fig. 6 (f). Further, the sensor may be arranged so that the center of the sensor element is displaced from the center of the stator magnetic pole by 1/4 pitch.

In the brushless motor of the present invention, in order to obtain positioning characteristics, the center of the sensor element and the center of the stator magnetic pole are arranged so as to coincide with each other as shown in (f) B.

The processing circuit 47 for producing the first phase advance command signal produces four phase advance command signals corresponding to the four energization states from the rectangular wave digital position signals a and b. FIG. 7 (a) shows the circuit configuration. The input signals a, b are processed to obtain the advance command signals a, ab, b, as shown in FIG. 7 (b).

As shown in FIG. 8, the electronic switch circuit 48 includes four kinds of up / down counters 81 for receiving an external step command and a decoder 82 for selecting one of the four first phase advance commands according to the counter output. It consists of With this configuration, four advance commands can be reversibly selected in order with respect to the step commands in both directions.

The speed detection circuit 49 that produces the second advance command signal is a circuit that outputs a signal according to the speed of the rotor, and needs to have a function of determining the cycle of the frequency of the sensor signal or the external step pulse. In this embodiment, the method of counting the period of the external stepping pulse with the reference clock and comparing it with the set value is adopted. FIG. 9 shows the configuration. A mono-multivibrator 93 is used to generate a latch pulse and a reset pulse from external pulses input from the step command input 99, and the pulse from the reference oscillator 91 is counted by an 8-bit counter 92. The counter output is four comparators 94a, 94b, 94c, 94
It is input to d and compared with the set values N1, N2, N3, N4.
The set value determines the cycle, that is, the speed, and in the present embodiment, there are four set values, so that the speed determination signal of five stages can be output. Since the output of the comparator is held by the latch pulse immediately before the reset pulse, the latch 95 holds the speed determination value according to the cycle of the external step pulse. The latched output is the unlatched comparator 94a,
The outputs of 94b, 94c and 94d are compared by the comparator 96. The output signal of the comparator 96 is used as the control signal of the selector 97 which selects the two signals. The selector 97 selects the latch output when the latch output is smaller than the outputs of the comparators 94a, 94b, 94c and 94d, and selects the comparator output when the latch output becomes larger than the comparator output. That is, the smaller value is selected. Since the output of the comparators 94a, 94b, 94c, 94d is given a digit so that it becomes larger as a 4-bit value when the speed is faster (when the cycle is shorter), the slower speed signal is given priority. Will be there. This is because when the external stepping pulse suddenly disappears or a slow speed command is given, the old speed information remains in the latch 95 until the next latch pulse (stepping pulse) enters. This is because the value of is increased as the reference clock is continuously counted and the comparator output is decreased, so that the speed information is updated with this new slower speed signal. When this operation is shown in FIG. 10, when the cycle of the external stepping pulse is short and the comparator outputs are all in the H state and the external pulse suddenly disappears, the outputs of the latch 95 are all H,
As the value of the counter increases, the speed signal becomes slower one after another, and finally the speed signal becomes the lowest level. The ninth
Reference numeral 98 in the figure is a converter for converting the selector output into a binary number and outputting it.

The flip-flop circuit 50 determines the direction of the step command pulse (CW or
The CC flip-flop is used to determine whether CCW) or not, and as shown in FIG. 11, it is composed of an RS flip-flop, and its output indicates the rotation direction of the rotor.

Next, the structure of the phase advance circuit 45 is shown in FIG. The phase advancing circuit digitally produces a phase advancing signal at a certain phase angle from the sensor signal, and selects and outputs it by the combined value of the first and second phase advancing command signals. I am taking it. In this embodiment, since the step width of the phase advance amount is set to 22.5 ° (electrical angle), 16 kinds of signals including sensor signals are prepared and selected as shown in the excitation signal vector diagram of FIG. 13 (a). Good. First, the phase advance signal generation circuit section will be described. The input two-phase sensor signals are exclusive-ORed and then inverted, so that two signals shown in FIG. 13 (b) are obtained. The logical product of this signal and the reference clock from the oscillating circuit 121 is taken to obtain dispersed clock pulses as shown in FIG. 13 (c). This clock pulse counter 123
Count with a, 123b. The counter is reset by a reset pulse generated by the mono multivibrator 122 from the signal shown in FIG. 13 (b). As a result, the count values of the counters 123a and 123b change with time as shown in FIG. 13 (d). From the output of this counter, the arithmetic circuit 124
a, 124b, 124c, 125a, 125b, 125c 1 / 4,1 / 2,3 / respectively
Get the value of 4. The operations of 1/4 and 1/2 are obtained by 2-bit shift and 1-bit shift of the counter output, respectively.
The calculation of / 4 can be obtained by the sum of 1/2 and 1/4.
The digital comparators 126a, 126b, 126c, 127 compare the calculation result obtained from one counter and the rising value of the other counter.
By comparing with a, 127b, and 127c, it is possible to obtain a rectangular wave having a rising edge whose phase is different from that of the sensor signal. This is shown in FIG. These waveforms are processed by the processing circuit 128 to obtain 12 rectangular waves each having a duty of about 50% and having different phases. These waveforms are shown in Fig. 13 (a) with the sensor signal and its four inverted signals.
It consists of 16 signal groups with different phases. The 16 signals are input to selectors 133 and 134, and one of each is selected.

The selection command signals of the selectors 133 and 134 are synthesized from the first and second phase advance command signals. The second advance command signal advances the phase corresponding to the signal number in FIG. 13 (a). That is, when the number indicated by the command increases by 1, it works to advance the phase by 22.5 °, and advances the phase according to the speed. The first advance command signal is different from this, and when it is at the H level, the phase is set in four steps.
Advances, and when L level, does not advance the phase.
Since the phase advance level is determined by these combined values, the output of the processing circuit 131 that generates the number 0 or 4 from the first phase advance command and the second phase advance command value are added by the adder 132. . In this case, the direction of the advancement phase differs depending on the rotation direction of the rotor, and when it goes in the opposite direction, it is necessary to delay the phase advancement. You have selected. The command to this selector is given by the forward / reverse signal obtained from FIG. The outputs of the selectors 133 and 134 are always adjusted so that they are out of phase with each other by 90 °.
It becomes the excitation signal of the phase coil. As shown in FIG. 13 (a), signals "0" and "4" are output when there is no advance command signal, and "1" and "5" depending on the level when there is a advance command signal.
Two-phase signals with advanced phases such as "2" and "6" are output.

Now, the operation of the brushless motor of the present invention when the interval between pulse commands from the outside is long and the second phase advance command is 0
It will be explained with reference to FIG. FIG. 15 (a) shows the torque distribution when a constant current is applied to the two-phase coils A and B. (B) shows two-phase sensor output signals. Unlike a normal brushless motor, the torque distribution and the sensor signal have a relationship of being displaced by 1/4 pitch. FIG. 15 (c) shows the torque distribution in each excitation mode in the case of two-phase full-wave drive, which is the combined value of the two phases of torque shown in (a).

At the stable point in FIG. 15 (c), when excited so that the torque AB is generated, the electronic switch circuit 48
Make sure that ab of the first advance command in FIG. 15 (d) is selected. If there is no step command from outside in this state, AC
The rotor keeps the same position according to the torque curve. If the electronic switch selects the first phase advance command signals ab → b and → a → ab one after another as the positive step pulse is input one by one, when the above ab is selected and stable. When one pulse of the forward direction command is input to, the first advance command signal is switched to b, and the output level of the electronic switch 48 is L.
To H. The phase advance circuit 45 receives the H level signal and advances the sensor signal by 90 ° to change the excitation mode and torque distribution to. Since the rotor is held in the state of, when the torque distribution is switched to B, the torque in the positive direction acts on the rotor and the rotor rotates in the positive direction as shown by the dotted line in Fig. 15 (c). . When the rotor comes to a point, the first phase advance command b changes to L level and no phase advance occurs.
Since the A-phase sensor signal also changes to the L level, the excitation mode remains B without changing to the next mode and is stable at the point of FIG. 15 (c) according to this torque distribution. In this state, if the next positive-direction pulse is one pulse, the first advance command signal is selected and similarly moves to the next stable point.

When one backward command pulse is input in the state of FIG. 15 (c), the quaternary counter output in the electronic switch 48 returns to the previous state and the first phase advance command signal ab is selected. At the same time, the output of the flip-flop circuit 50 is inverted by the reverse pulse, and the phase advance circuit 45 is in the phase delay mode. When the rotor is at the point, the first phase advance command ab is at H level, so the sensor signal is delayed by 90 ° and the excitation mode and torque curve are selected as AB, and when the direction is forward and AB is selected as the torque curve. The rotor is point-stable as in the directional case.

As described above, it can be seen that the stepwise rotation is performed step by step in accordance with the external step pulse. Next, when the interval of the external step command is shortened and the speed of the rotor is increased accordingly, the value of the second phase advance command signal is increased and is added by the first phase advance command signal and the adder 132, The excitation signal has a larger amount of phase advance than when the speed is slow. By adjusting the relationship between the speed and the second phase advance command, it is possible to generate a continuous torque close to the peak point of the torque distribution of FIG. 5 (c), which is the same as in a normal brushless motor. The coil excitation can be switched early to cover the rising delay of the coil current due to the increase of the switching frequency, and high-speed operation can be performed.

As described above, according to the present embodiment, the rotor composed of magnets magnetized on the circumferential surface in multiple poles, the stator core having a plurality of magnetic poles on the inner circumference, and the stator composed of two-phase coils are provided. A non-contact sensor that detects the magnetic poles of the rotor and outputs two-phase signals having mutually different phases; processing means that outputs a first phase advance command signal from the position signal; electronic switch means; By providing the speed detecting means for generating the phase advance command signal and the drive circuit, it is possible to obtain a small and inexpensive brushless motor which has a stepping function and a positioning function and rotates at a high speed.

In the above embodiments, all the conventional brushless motors can be applied to the mechanical portion of the motor.

That is, as shown in FIG. 16, a rotor composed of a magnet 162 magnetized in multiple poles on the inner surface of the cylinder and a magnetic pole on the rotor facing surface, and a stator 161 provided with a multi-phase coil 163 and a rotor. A brushless motor provided with a non-contact sensor 164 for detecting a magnetic pole and converting it into an electric signal, and a rotor made of a magnetic material having magnetic pole teeth with a constant pitch on the circumference as shown in FIG. 172 and a stator core 1 having magnetic pole teeth on the rotor facing surface 1
71, the magnet 174 attached to the stator core 171, and the stator core
A brushless motor equipped with a multi-phase coil 173 wound around 171 and a non-contact sensor 175 that detects the unevenness of the rotor magnetic pole teeth and converts it into an electric signal, and as shown in FIG. A magnetic body to be laminated from, a rotor 182 provided with magnetic pole teeth cut on the circumference of the magnetic body, a stator core 181 provided with magnetic pole tooth groups on the rotor facing surface, and a multiphase coil 183, A brushless motor equipped with a non-contact sensor 184 for detecting the unevenness of the magnetic pole teeth of the rotor and converting it into an electric signal, or a rotor composed of magnets magnetized in multiple poles on a disk plane as shown in FIG.
A brushless motor may be provided with 192, a stator composed of a coil 193 and a yoke 191 arranged on the disk-opposing surface, and a non-contact sensor 194 that detects a magnetic pole of the rotor and converts it into an electric signal.

Further, in the embodiment, the two-phase brushless motor is used, but the same effect can be obtained by using other three-phase or more brushless motors.

Further, the speed detection method in the embodiment also uses the method of counting the reference clock, but the method of counting the external stepping pulse or the sensor signal within a unit time, the method of using them together, or the differentiation of the sensor original signal Alternatively, a method of operating a mono-multivibrator by using a sensor signal or an external step pulse as a trigger to obtain an analog speed signal and comparing it with a reference voltage may be used. Further, although the step of advancing the phase is also set to 22.5 ° (electrical angle) in this embodiment, the same effect can be obtained even if the angle is set to another angle.

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-position detecting device for detecting the position of the rotor. A contact sensor, a processing means for producing a first advance command signal from the position signal, and a step command signal from the outside,
Electronic switch means for selecting the first phase advance command signal in order, speed detection means for generating a second phase advance command signal according to the frequency of the position signal or the command signal, first, second
By providing a phase advancing means for advancing the phase of the position signal according to the phase advancing command signal and a drive circuit for energizing the coil, it has a positioning function and rotates at high speed in synchronization with an external step pulse. A small brushless motor can be obtained.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a motor according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the same, FIG. 3 is a sectional view of the same, and FIG. 4 is an electric circuit of an embodiment of the present invention. Block diagram, fifth
FIGS. 6 (a) to 6 (d) are diagrams showing a coil connection diagram and torque distribution of the embodiment of the present invention, FIGS. 6 (a) to 6 (f) are diagrams for explaining sensor positions of the embodiment, and FIG. FIGS. 8A and 8B are circuit diagrams of the first phase advance command signal generating circuit of the embodiment of the present invention and output waveform diagrams of respective parts, FIG. 8 is a block diagram of an electronic switch, and FIGS. b) is a block diagram of the second phase advancing command signal generating circuit and a pulse waveform diagram, FIG. 10 is an operation explanatory diagram of the block diagram of FIG. 9, and FIGS. 11 (a) and 11 (b) are of a flip-flop circuit. Circuit diagram and waveform diagram of each part, FIG. 12 is a block diagram of a phase advancing circuit, FIGS. 13 (a) to (d), 14
The figure is a diagram for explaining the operation of the phase advancing circuit, and FIGS. 15 (a) to 15 (d) are diagrams for explaining the operation of the embodiment. FIGS. 16 to 19 are views showing a motor portion of another embodiment of the present invention. FIGS. 16 (a) and 16 (b) are a longitudinal sectional view and a transverse sectional view of a magnet rotary type motor, and FIG. Figures (a) and (b) are a perspective view and a sectional view showing the main structure of a motor in which the rotor is made of a magnetic material having magnetic pole teeth, and Figures 18 (a) and (b) show the rotor having magnetic pole teeth. Longitudinal and transverse cross section of a motor with a core and a magnet,
19 (a) and 19 (b) are a sectional view and a top view of a motor whose rotor is a disk-shaped magnet, FIG. 20 is a principle diagram of a conventional PM type stepping motor, and FIG. 21 is its torque distribution. FIG. 22 is a block diagram of a positioning control system using a conventional servomotor. 1,162,192 …… Rotor magnets, 2a, 2b, 2c, 2d, 161,171,181…
… Stator core, 172,182 …… Rotor core, 3a, 3b, 42a, 42
b, 163,173,183,193 …… coil, 45 …… phase advancing circuit, 46…
… Driving circuit, 48 …… Electronic switch circuit, 47 …… Processing circuit that creates the first phase advance command, 49 …… Speed detection circuit, 50 ……
Flip-flop circuit, 94a, 94b, 94c, 94d, 96 ... Comparator.

Claims (2)

[Claims] 1. A rotor, a stator provided with a stator core that faces the rotor with a gap, a bearing device attached to the stator to rotatably support the rotor, and the stator. A plurality of non-contact sensors that are attached and that detect the position of the rotor and convert it into an electric signal and output position signals having different phases, and a plurality of first advance command signals from the position signals. A processing means for generating a signal, an electronic switch means for receiving a step command signal from the outside, and selecting the plurality of first phase advance command signals in order according to the number of step command signals, and a frequency of the position signal or the step command signal. Speed detection means for producing at least one second phase advancing command signal in accordance with the above, phase advancing means for advancing the phase of the position signal in response to the first and second phase advancing command signals, and the position signal The plurality of carp A brushless motor having a drive circuit for urging a rotor, wherein the rotor is a magnet having multi-pole magnetized on a cylindrical outer surface, and the stator has a pole on an opposite surface of the rotor circumference. And a plurality of coils, the non-contact sensor detects a magnetic pole of the rotor and converts the magnetic pole into an electric signal. 2. The brushless motor according to claim 1, wherein a hall element is used for the non-contact sensor.