JP2515095B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention simplifies the contents of rotation control to realize high-speed control,
The present invention relates to a brushless motor that enables precise control.

[Conventional technology]

Generally, in a brushless motor in which a permanent magnet is provided in a rotor and an exciting coil is provided in a stator, rotation control of the motor is performed by rotating magnetic field control. In order to perform the rotating magnetic field control, it is necessary to detect the rotational position of the rotor and control the phase of the current flowing through the exciting coil in synchronization with the rotational position.

[Problems to be solved by the invention]

However, phase control is complicated, there is a limit to high-speed control and precision control, and there is a problem that the cost is high.

Therefore, an object of the present invention is to simplify the control contents of the brushless motor and enable high-speed control and precision control.

[Means for solving problems]

Therefore, the present invention is characterized in that the current control of the exciting coil in the brushless motor as described above is achieved by reversing the energizing direction of the exciting coil facing the permanent magnet.

Specifically, the brushless motor of the present invention is one in which a permanent magnet is provided in a rotor and an exciting coil is provided in a stator, and the energizing direction that reverses the energizing direction of the exciting coil between the power supply and the exciting coil. Connect the switching means.

In addition, a plurality of exciting coils connected in series with each other are used as the same phase, and the detecting coil is wound around at least one exciting coil in each phase, and the magnetic flux of the permanent magnet accompanying the rotation of the rotor is wound around these detecting coils. The electromotive force is sequentially generated by the change of.

Then, in response to the electromotive force from the detection coil, it is detected that the permanent magnet is at a position facing the exciting coil, and the switching actuating means for actuating the energizing direction switching means is operated so as to reverse the energizing direction of the exciting coil. Prepare

[Action]

As a result, when one permanent magnet reaches a position facing one exciting coil as the rotor rotates, it is detected by the detecting coil and the switching operation means, and the energizing direction of the exciting coil is reversed. Due to the reversal of the energizing direction, torque in the rotating direction is continuously applied to the permanent magnet that has passed over the exciting coil. Next, when another permanent magnet reaches a position facing the exciting coil, the energizing direction of the exciting coil is similarly reversed again. In this way, the rotating torque is continuously applied to the permanent magnets to rotate the rotor. By reversing the energizing direction to the exciting coil as described above, the permanent magnet is always attracted and repelled in the rotating direction, and thus the rotating torque is increased.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

2 to 4 show an embodiment of the present invention, FIG. 2 is a partial sectional front view, and FIG. 3 is a sectional view showing the IIIA-IIIA line sectional view and the IIIB-IIIB line sectional section of FIG. 2 at the same time. 4 and 5 are bottom views of the stator case.

In each figure, 10 is a rotor, 20 is a stator, 11 is a permanent magnet, and 21 is an exciting coil. A plurality of permanent magnets 11,
In this case, 16 pieces are arranged in an annular shape around the rotary shaft 12, and the permanent magnets 11 are arranged so that their magnetic pole directions are parallel to each other. Of course, the magnetic poles of each permanent magnet 11 are
Adjacent permanent magnets 11 are arranged in opposite directions.

A plurality of pairs of permanent magnets 11 arranged in this manner are set, and in this case, three pairs are fixed around the rotary shaft 12 to form the rotor 10, and the permanent magnet pairs arranged in an annular shape are , Is fixed on the rotating shaft 12 by a fixing bracket 14. At this time, the rotary shaft 12 and each fixing member 14 are spline-fitted 13, and the fixing member 14 and the permanent magnet 11 are fixed to each other with an adhesive.

A plurality of, in this case, 12 exciting coils 21 are arranged in an annular shape on the side of the permanent magnets 11 arranged in an annular shape, and each exciting coil 21 has a magnetic flux and a chain of each permanent magnet 11. It is arranged to intersect. In this way, the exciting coil set disposed on the side of the permanent magnet 11 may be disposed on only one side of the permanent magnet 11, but may be disposed on both sides.
In the case of this embodiment, as is clear from FIG. 2, of the three annular permanent magnet sets, the middle one is provided with exciting coil sets on both sides thereof.

An iron core 22 is provided at the center of each exciting coil 21, and as is clear from FIG.
Is extended to the opposite side of the permanent magnet 11 through the outer peripheral side of the permanent magnets 11 arranged in an annular shape. However, in the case of this embodiment, each exciting coil 21 of the four exciting coil groups is
The iron cores 22 are arranged in a line in the direction of the rotating shaft 12, and their cores 22 are integrated with each other. The iron core 22 is made of a laminated iron plate, and one end of the iron core 22 is fitted into a groove 23 formed on the bottom surface of the case 24 of the stator 20 as shown in FIG.
The other end is pressed by the cover 25 via the spacer 29. Further, as is apparent from FIG. 3, spacers 26 are interposed between the iron cores 22, and some of the spacers 26 are fixed to the case 24 by pins 27.
That is, a rotation stopper is provided in the rotation direction of the rotating shaft 12. In FIG. 2, reference numeral 15 denotes a bearing, which rotatably supports the rotary shaft 12 with respect to the case 24. Further, 16 is a seal to prevent water, dust, etc. from entering the motor.

The excitation coils 21 arranged in an annular shape have three adjacent sets as one set, and there are four sets around the entire circumference. The excitation coils 21 at corresponding positions between the sets, that is, in-phase positions are all in series. The coils are in-phase, which are connected to each other and electrically controlled to be the same. Furthermore, an integrated iron core
The exciting coil 21 wound around 22 is also connected in series. Therefore, the exciting coils 21 are 4 × 4 and 16 pieces are connected in series.

As described above, the number of the exciting coils 21 is three in one set, whereas the number of the permanent magnets 11 is four in the corresponding range. That is, the number of permanent magnets 11 is one more than the number of exciting coils 21 in one set.

6 to 8 show one iron core 22 and the exciting coil 21 wound around it in an enlarged manner. Further, FIG. 5 shows a state of magnetization of the iron core 22 when the exciting coil 21 is energized. Since the permanent magnet 11 is sandwiched in the magnetic path formed by the iron core 22 as described above, when the permanent magnet 11 is located at the position shown in FIG. , A reluctance torque is generated between the exciting coil 21 and the permanent magnet 11 as indicated by an arrow F, as indicated by the alternate long and short dash line in FIG.

FIG. 9 shows three exciting coils A to C forming a set.
The positional relationship between 21 and the permanent magnet 11 of the rotor 10 is shown on a plane, and the energization direction of the exciting coil 21, that is, the manner in which the polarity is switched with the rotation of the rotor 10, is shown over time.

First, at the timing of t ₀ shown in (a), the exciting coil
21A to 21C, the magnetic poles on the permanent magnet 11 side are sequentially N, N, and S as shown in (B), while the permanent magnet 11 of the rotor 10 is positioned as shown in the figure. Therefore, torque is generated in the rotor 10 in the downward direction of the figure as indicated by the arrow. Next, at the timing of t ₁ , the energizing direction of the B exciting coil 21 is reversed to switch the polarity, and the permanent magnet 11 side is sequentially set to N, S, S. That is, when the exciting coil 21 and the permanent magnet 11 are in a one-to-one opposite position, the polarity of the exciting coil 21 is switched. In this way, when the exciting coil 21 and the permanent magnet 11 are opposed to each other, no torque is generated between the exciting coil 21 and the permanent magnet 11, but as described above, the number of the exciting coils 21 is different from that of the exciting coil 21. Since the number of permanent magnets 11 is increased, even if one set of exciting coils 21 and permanent magnets 11 face each other, other exciting coils 21 and permanent magnets 11 do not face each other and torque is generated. ing.

In FIG. 9, (c) shows the energizing direction of the exciting coil 21, and the energizing direction of the B exciting coil 21 is reversed at the timing of t ₁ . After that, similarly t ₃ , t ₅ , t ₇ , t ₉ , t
_{When the} exciting coil 21 and the permanent magnet 11 face each other at the timing of ₁₁ , the polarity of the exciting coil 21 is reversed. Then, at the timing of t ₁₃ , the exciting coil 21 of B is again turned on.
The polarity is switched to complete one cycle of operation, and thereafter, this operation is repeated and the rotor 10 is rotated.

In this way, the exciting coil 21 switches the polarity when facing one permanent magnet 11 in a one-to-one relationship.
In order to detect the state in which the exciting coil 21 faces one permanent magnet 11 in a one-to-one manner, the detecting coil 28 is wound around the exciting coil 21 as shown in FIGS. ing. However, since the positional relationship between the exciting coil 21 and the permanent magnet 11 is the same in each set, the detection coil 28 is provided only in the exciting coil 21 of one set. In addition, the exciting coil 21 wound around one iron core 22
Even if there are plural excitation coils, it is sufficient to provide the detection coil 28 only for one excitation coil 21 for the same reason, but in the case of FIG. 7, detection is made for all excitation coils 21 wound on one iron core 22. A coil 28 is provided, and these detection coils 28 are all connected in series.

The detection coil 28 is affected by the magnetic field of the permanent magnet 11,
An electromotive force is generated, and the signal waveform thereof is as shown in FIG. That is, an alternating current signal that switches the direction of the electromotive force is generated at a position where the exciting coil 21 and the permanent magnet 11 face each other one-on-one. The signal from the detection coil 28 is shaped into a rectangular wave by waveform shaping, and only the change of the signal is extracted by the differentiating circuit. This differential signal is shown in FIG. 9 (e), and the polarity of the exciting coil 21 is switched using this differential signal as a trigger.

In the above, the case where the number of the exciting coils 21 in one set is three has been described, but the number of the exciting coils 21 can be an arbitrary number of 2 or more, and FIGS. Are shown in comparison with each other when the number of exciting coils 21 is 2 to N. As is apparent from FIGS. 10 (a) to 10 (d), the number of permanent magnets 11 is N + 1 with respect to the number N of exciting coils 21 in one set, so that the rotor rotates during the rotation of the rotor 10. Exciting coil 21 regardless of angle
A torque can be generated between the magnet and the permanent magnet 11. Further, the switching of the energizing direction for switching the polarity of the exciting coil 21 is (1 / 2N) × (2 / N + 1) × (2π / m)
[However, N is the number of poles of the exciting coil 21 and m is the number of sets].

FIG. 1 shows a circuit for controlling the energization of the exciting coil 21, and the electromotive force from each detecting coil 28 is a waveform processing circuit.
In 56, the waveform is shaped and differentiated, and the differentiated signal is sent to the predrive circuit 30 and the microcomputer 51. The pre-drive circuit 30 receives the differentiated signal and forms a signal for operating the drive circuit 40.
40 controls the energization of each exciting coil 21. Further, the microcomputer 51 detects the rotation speed and the rotation position of the rotor 10 based on the differential signal from the waveform processing circuit 56.
On the other hand, the microcomputer 51 also receives the speed command 52, the position command 53, and the torque command 54, and the speed command 52 determines that the speed detected by the differential signal matches the speed according to the speed command 52. Rotor in the open position
A signal is sent to the pre-drive circuit 30 so that the rotation of 10 is stopped. Here, the drive circuit 40 corresponds to the energization direction switching means in the present invention, and the pre-drive circuit 3
The 0, the microcomputer 51 and the waveform processing circuit 56 constitute the switching operation means 70 in the present invention.

FIG. 11 shows the details of the pre-drive circuit 30,
As is clear from this figure, the pre-drive circuit 30 receives the differential signal from the waveform processing circuit 56 and inverts the T-type flip-flops 31 to 33 each time, and the outputs of the flip-flops 31 to 33 are used to perform It consists of six AND gates 34 to 39 which select signals from the computer 51 and send them to the drive circuit 40. For example, when the T terminal of the flip-flop 31 receives a differential signal from the waveform processing circuit 56, the flip-flop 31 is inverted and switches the opened AND gate from 34 to 35 or from 35 to 34.

FIG. 12 shows details of the drive circuit 40,
The drive circuit 40 has a plurality of transistors that conduct,
The non-conducting combination controls the energization of the exciting coil 21 having three circuits. That is, when the AND gate 34 is opened and the AND gate 35 is closed, the duty ratio signal from the microcomputer 51 is applied to the bases of the transistors 41 and 42 of the drive circuit 40, and the transistor is used at the duty ratio of the duty ratio signal.
When 41 and 42 are conducted, the exciting coil 21 of A is energized, and when the AND gate 34 is closed and the AND gate 35 is opened, the duty ratio signal from the microcomputer 51 is applied to the transistors 43 and 44. When applied to the base, the transistors 43 and 44 are turned on at the duty ratio of the duty ratio signal, and the exciting coil 21 of A is energized in the opposite direction. In other words, the flip-flop 31 is inverted so that the AND gates 34 and 35 are opened and closed, whereby the energizing direction of the exciting coil 21 of A is reversed and the polarity of the exciting coil 21 is switched. Similarly, the energizing directions of the B exciting coil 21 and the C exciting coil 21 are switched by reversing the flip-flops 32 and 33 to switch the polarity.

13 and 14 are flowcharts showing the main parts of the program for operating the microcomputer 51. The program of FIG. 13 controls the duty ratio of the energizing current of the exciting coil 21,
This is a time interrupt processing routine that is activated every 100 milliseconds.

First, in step 101, the duty ratio DUTY of the energizing current of the exciting coil 21 is obtained according to the torque command 54.
This may be obtained by calculation or may be obtained by reading the data stored in the memory in advance, but is obtained as shown in FIG. 15 with respect to the command torque Tc by the torque command 54.

Next, at step 102, the command speed N by the speed command 52
The difference ΔN between c and the current speed N is determined. The current speed N is set by the waveform processing circuit by a program (not shown).
It is determined by measuring the interval at which the differential signal from 56 is generated. FIG. 17 shows an example of how the speed N changes with respect to the commanded speed Nc. In the next step 103, the duty ratio correction amount ΔDUTY is calculated based on the speed difference ΔN.
Is required. This correction amount ΔDUTY is also calculated in step 10 above.
As in the case of 1, it may be obtained by calculation or may be obtained by reading the data stored in the memory in advance, but it is obtained as shown in FIG. 16 for the speed difference ΔN. In step 104, the duty ratio calculated in step 101
The final duty ratio DUTY is obtained by adding the DUTY and the correction amount ΔDUTY obtained in step 103. In this way, in the program of FIG. 13, the duty ratio DUTY of the current supplied to the exciting coil 21 is controlled so as to maintain the speed Nc according to the speed command 52.

Since the program in FIG. 13 is started every 100 milliseconds, the duty ratio DUTY calculated in step 104
Value is preset to a presettable down counter (not shown) and this down counter is down-counted by a clock signal of 1 millisecond, so that the down counter immediately outputs a pulse of duty ratio DUTY obtained in step 104. You can get a signal. This pulse signal is sent to the a terminal of the predrive circuit 30.

The program of FIG. 14 is a part of a main processing routine program (not shown), and is a program for controlling the stop position of the rotor 10, that is, the motor.

When this program is started, in step 105, the position Pc commanded by the position command 53 and the current rotational position P
And the difference ΔP from The current rotational position P is measured by counting the differential signal from the waveform processing circuit 56 by a counter (not shown).

In step 106, it is determined whether the position difference ΔP is “0”. Until the current rotational position P reaches the command position Pc, a negative decision is made in step 106, and step 1
At 09, it is determined whether the difference ΔP is positive. At this time, the difference ΔP is positive, so the routine proceeds to step 110, where it is judged if a flag F, which will be described later, is set to “1”. At this time, since the flag F has not been set, a negative determination is made in step 110, and the above processing is repeated until the current rotational position P reaches the command position Pc.

When the current rotational position P eventually reaches the command position Pc, an affirmative decision is made in step 106, the duty ratio DUTY is set to "0" in step 107, and the energization of the exciting coil 21 is stopped. Then, in step 108, the flag F is set to "1", and it is stored that the current rotational position P has reached the command position Pc.

As shown in FIG. 18, the current rotational position P is the command position Pc.
Even if it reaches, the rotor 10 does not stop at the command position Pc due to inertia, and overruns. When an overrun occurs in this way, negative determination is made in both steps 106 and 109, and
At 113, it is determined whether the flag F is set to "1". Now, since the flag F is set, an affirmative decision is made in step 113, and a reverse pulse is generated in step 111. This reverse rotation pulse is sent to the b to d terminals of the predrive circuit 30 via the backflow prevention diode 55 in FIG. 1 and causes the three flip-flops 31 to 33 of the predrive circuit 30 to perform a reverse operation all together. When the flip-flops 31 to 33 are inverted, as described above, the energizing direction of the exciting coil 21 is reversed and the polarity of the exciting coil 21 is reversed, so that it is clear from (b) of FIG. Torque is generated in each permanent magnet 11 in the direction opposite to that shown by the arrow. Therefore, when the reverse rotation pulse is generated in step 111, the rotor 10
The rotation direction of is reversed. Then, in step 112,
The flag F is reset to "0".

Even if the torque applied to the rotor 10 is rotated, the rotor 10 does not immediately rotate in the reverse direction due to inertia, but the direction of rotation is changed, and the rotational position P reaches the command position Pc again as shown in FIG. At this time, step 106 is again affirmatively determined to set the duty ratio DUTY to zero, and step 106
At 108, the flag F is set to "1".

Even if the current rotational position P reaches the command position Pc, the rotor 10
Overruns again and step 109 is affirmatively determined. Then, in step 110, since the flag F is set at this time, an affirmative judgment is made, a reverse rotation pulse is generated in step 111, and the rotation direction of the rotor 10 is reversed again.

By repeating the operation by the stop position control routine program of FIG. 14 as described above, as shown in FIG.
10 is stopped at the command position Pc.

〔The invention's effect〕

As described above, according to the present invention, since the current control of the exciting coil in the brushless motor is achieved by reversing the energizing direction of the exciting coil facing the permanent magnet, the content of the rotation control of the brushless motor is simplified. ,
High-speed control, precision control can be enabled.
The cost can be reduced, the reliability can be improved, the motor can be downsized, and the energizing direction of the exciting coil can be reversed, so that the rotor receives a force in both directions of attraction and repulsion. Since it always works, it has a remarkable effect such as increasing the rotating torque.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram showing a control circuit of an embodiment of the present invention, FIGS. 2 to 4 show a mechanical structure of the above embodiment, and FIG. Partial sectional front view, FIG. 3 is IIIA- in FIG.
FIG. 4 is a bottom view of the stator case, showing a cross section taken along line IIIA and a cross section taken along line IIIB-IIIB at the same time. FIG. 5 is a diagram for explaining the operation of the above embodiment. Sixth
FIG. 8 to FIG. 8 are enlarged views of one iron core in the above embodiment, FIG. 6 is a perspective view, FIG. 7 is a front view of a state in which an exciting coil is wound, and FIG. It is a VIII-VIII sectional view taken on the line. Further, FIG. 9 is a diagram for explaining the operation of the above embodiment, FIG. 10 is an explanatory diagram similar to FIG. 9 when the number of exciting coils and permanent magnets are changed, and FIG. Detailed circuit diagram of the pre-drive circuit of FIG. 1, FIG.
FIG. 13 and FIG. 14 are detailed circuit diagrams of the drive circuit shown in the figure, and FIG. 15 to FIG. 18 are flowcharts showing the main program of the microcomputer of FIG. It is a figure for demonstrating operation. 10 …… Rotor 11 …… Permanent magnet 20 …… Stator 21 …… Excitation coil 22 …… Iron core 28 …… Detection coil 40 …… Drive circuit (energization direction switching means) 70 …… Switching operation means

Claims (1)

(57) [Claims] 1. A brushless motor in which a plurality of permanent magnets are arranged in a rotor and a plurality of exciting coils are arranged in a stator, and the brushless motor is connected between a power source and an exciting coil to reverse the energizing direction of the exciting coil. The energization direction switching means and a plurality of exciting coils connected in series with each other have the same phase, and are wound around at least one exciting coil in each phase, and are caused by a change in the magnetic flux of the permanent magnet due to the rotation of the rotor. A detecting coil that generates electric power, and an electromotive direction from which the exciting coil is energized when the permanent magnet is detected to be in a position facing the exciting coil by receiving an electromotive force from the detecting coil. A brushless motor comprising: a switching actuating means for actuating the switching means.