JPH05292782A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To provide a DC brushless motor in which the motor can be downsized and made thin by obviating the necessity of position detecting element such as a Hall element. CONSTITUTION:Rotational direction and rotational moving amount are detected, respectively, through a direction detecting means 3 and a counting means 4 based on two-phase frequency signals outputted from a frequency generator 1 as a permanent magnet rotor 20 rotates. A phase regulating means 5 produces an address signal from count values of the counting means 4 depending on a rotational direction commond 14 and a waveform generating means 6 produces a three-phase position signal based on the address signal in reference to a function table. A power supply means 7 feeds stator windings 11, 12, 13 with driving currents corresponding to the three-phase position signal thus rotating a rotor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor which does not require a position detecting element for detecting the rotational position of a permanent magnet rotor.

[0002]

2. Description of the Related Art A brushless DC motor has a long life because it has no mechanical contacts as compared to a DC motor with a brush, and at the same time has less electrical noise. -Widely applied to audio equipment.

Conventionally, this type of brushless DC motor has been
A position detecting element (for example, a hall element) corresponding to a brush is used for switching the energizing phase of the stator winding. However, the position detection element itself is not inexpensive at all, and the cost of the brushless DC motor is significantly higher than that of the brush DC motor due to the complexity of adjusting the mounting position of the element and the increase in the number of wires. Further, since the position detecting element has to be mounted inside the motor, there are often restrictions on the structure of the motor. In recent years, with the miniaturization of equipment, motors used have also become smaller and thinner, and there is no more room for mounting position detection elements such as Hall elements.

Therefore, some brushless DC motors having no position detecting element such as a hall element have been proposed.

As a brushless DC motor of this type having no position detecting element, there is one that utilizes an output pulse of a frequency generator attached to the motor. The counter counts the output pulses of a frequency generator that generates pulses according to the rotation of the rotor, and the drive current having a preset current pattern corresponding to the count value is used as the three-phase stator winding. In order to rotate the permanent magnet rotor (for example, Japanese Patent Laid-Open No. 63-262088).

[0006]

However, in the above configuration, since the initial position of the rotor is not known when the power is turned on, the brushless DC motor shown in the above-mentioned prior art is provided with a special reset signal generating circuit. When the power is turned on, the counter is reset by using a reset signal, and a predetermined reset current is supplied to the stator winding so that the rotor and the stator winding have a predetermined positional relationship in advance.

However, when a predetermined reset current is supplied to the stator winding in order to determine the initial position, the rotor starts to move, and the position of the rotor is oscillatory around the initial position, and it is difficult to reach the initial position. Do not stand still. Therefore, from the reset mode in which a predetermined reset current is supplied to the stator winding when the power is turned on and the rotor is stopped at a predetermined position, the output pulse of the frequency generator is counted according to the rotation of the rotor. However, there is a problem in that it is difficult to shift to the position detection mode, and the startup time becomes long.

Therefore, it cannot be used for applications in which rotation and stop are frequently repeated and a short starting time is required.

Moreover, in the brushless DC motor shown in the above-mentioned prior art, in order to detect the initial position of the rotor when the power is turned on, a predetermined reset current is supplied to the stator winding to rotate the rotor and the stator. Even if the coil and the winding are configured to have a predetermined positional relationship, the positional relationship between the rotor and the stator winding varies greatly depending on the load when the motor is under a load. .. Therefore, the rotor cannot be fixed at a predetermined position in the reset mode.

Therefore, in the brushless DC motor shown in the above-mentioned prior art, the reset mode is shifted to the regular position detection mode in which the output pulses of the frequency generator are counted according to the rotation of the rotor. However, since the phase of the current supplied to the stator winding deviates significantly from the regular phase, highly efficient driving cannot be realized.

Therefore, the brushless DC motor shown in the prior art has a problem that it can be applied only to applications where the motor is in a no-load state when the power is turned on.

In view of the above problems, the present invention can detect the positional relationship between the rotor and the stator winding when the power is turned on in a short time, and the output of the frequency generator from the phase matching mode when the power is turned on. An object of the present invention is to provide a brushless DC motor that can quickly switch to a normal position detection mode that counts pulses.

Further, according to the present invention, the initial position can be detected extremely accurately regardless of the magnitude of the load even when the motor is already loaded when the power is turned on. Therefore, it is possible to provide a brushless DC motor that does not require a position detection element, can be driven with high efficiency, and can be applied to a wide range of purposes.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, a brushless DC motor of the present invention comprises a frequency generator that generates frequency signals of a plurality of phases proportional to the rotation speed of a permanent magnet rotor, and Direction detecting means for detecting the rotation direction of the permanent magnet rotor from the phase frequency signal and outputting the direction signal, and the number of pulses of at least one frequency signal of the frequency generator is up-counted or down-counted according to the direction signal. Counting means, waveform generating means for generating waveform signals of a plurality of phases according to the count value of the counting means, and electric power is supplied to the stator windings according to the waveform signals of the plurality of phases to generate a rotating magnetic field. Power supply means, initial position detection means for detecting the initial position of the magnetic poles of the permanent magnet rotor by rotating the rotating magnetic field in the forward and reverse directions, and rotating in response to the rotation direction command. Phase adjusting means for shifting the phase of the magnetic field from the initial position in the forward direction or the reverse direction by a predetermined value, and rotating the rotating magnetic field generated by the stator in the forward and reverse directions at the time of turning on the power source to initialize the permanent magnet rotor. It is equipped with a configuration for matching the phases.

[0015]

According to the present invention, with the above configuration, the counter counts the output pulse of the frequency generator generated according to the rotation of the rotor. Since the position signal is created based on the count value, the position detection element required for the conventional brushless DC motor is not required, so the complexity of adjusting the mounting position of the element and the number of wires are reduced. The cost of the motor is reduced. Further, since it is not necessary to mount the position detection element inside the motor, the motor is not restricted in structure and can be made extremely small and thin.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A brushless DC motor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of a brushless DC motor according to an embodiment of the present invention. In FIG. 1, 20 is a permanent magnet rotor and 11, 12, 13 are three-phase stator windings. Reference numeral 1 denotes a frequency generator, which generates two-phase frequency signals m1 and m2 having different phases proportional to the rotation of the permanent magnet rotor 20. The two-phase frequency signals m1 and m2 are input to the waveform shaping circuit 2 and converted into rectangular wave signals s1 and s2, and then input to the direction detection circuit 3. The direction detection circuit 3 outputs a direction signal d according to the forward and reverse rotation directions of the permanent magnet rotor 20. Reference numeral 4 denotes a counter, which receives the rectangular wave signal s1 and the direction signal d output from the direction detection circuit 3 and determines the number of pulses of the rectangular wave signal s1 generated according to the rotation of the permanent magnet rotor 20 according to the rotation direction. Count up or count down. An initial position detection circuit 8 receives the count value c of the counter 4, rotates the rotating magnetic field of the stator in the forward and reverse directions during phase matching, calculates the initial position of the permanent magnet rotor, and counts the initial value q. Output to 4. The initial position detection circuit 8 not only outputs the initial value q to the counter 4, but also outputs the address command b to the selection circuit 9 during phase matching. Reference numeral 5 denotes a phase adjustment circuit, which adds or subtracts a predetermined value from the count value c of the counter 4 according to the direction command r input to the input terminal 14, and outputs the address signal a. Selection circuit 9
Selects either the address signal a or the address command b in accordance with the phase adjustment command t input to the terminal 15 and outputs the address f to the waveform generation circuit 6. The waveform generation circuit 6 outputs three-phase position signals p1, p2, p3 according to the address f output from the selection circuit 9. A power supply circuit 7 receives the three-phase position signals p1, p2, p3. The position signals p1, p2, p3 of the three phases are amplified by the driving amplifiers 71, 72, 73, respectively, and the position signals p1, p2, p3
Currents i1, i2, i3 proportional to the magnitudes of p2, p3 are supplied to the stator windings 11, 12, 13.

The operation of the brushless DC motor of the present invention will be described in detail with reference to the embodiment constructed as described above.

First, the case where the permanent magnet rotor 20 is rotating in a normal state will be described. 2 is a circuit configuration diagram of an embodiment of the direction detection circuit 3, and FIG. 3 shows a signal waveform diagram of each part thereof.

In FIG. 2, reference numeral 21 is a data input type flip-flop circuit to which the two-phase rectangular wave signals s1 and s2 output from the waveform shaping circuit 2 are input. The rectangular wave signal s1 is input to the data input terminal D of the flip-flop circuit 21, and the rectangular wave signal s2 is input to the clock input terminal CK.

FIG. 3A shows the waveforms of the rectangular wave signals s1 and s2 when the permanent magnet rotor 20 rotates in the positive direction, and FIG. 3B shows the permanent magnet rotor 20 rotating in the opposite direction. The waveforms of the rectangular wave signals s1 and s2 at this time are shown. Since the data input type flip-flop circuit 21 holds the state of the data input terminal D at each rising edge of the signal input to the clock input terminal CK and outputs the state from the output terminal Q, as shown in FIG. 3A. When the permanent magnet rotor 20 is rotating in the positive direction, the output Q of the data input type flip-flop circuit 21 is always in the high potential state (hereinafter, "
On the other hand, when the permanent magnet rotor 20 is rotating in the opposite direction, the phase of the rectangular wave signal s1 is delayed by 90 degrees from the rectangular wave signal s2 as shown in FIG. Is always in a low potential state (hereinafter referred to as “L” state) As is clear from the above, the direction of the permanent magnet rotor 20 can be detected by the direction detection circuit 3 of FIG. The direction signal d output from the direction detection circuit 3 is in the "H" state when the permanent magnet rotor 20 is rotating in the forward direction, and is in the "L" state when rotating in the reverse direction. Since the rectangular wave signal s1 output from the waveform shaping circuit 2 and the direction signal d from the direction detection circuit 3 are input to the counter 4, the counter 4 outputs the direction signal d.
The rectangular wave signal s1 is up-counted or down-counted according to That is, since the number of pulses of the rectangular wave signal s1 generated according to the rotation of the permanent magnet rotor 20 is up-counted or down-counted according to the rotation direction, the permanent magnet rotor 2 is calculated from the count value of the counter 4.
A rotational movement amount of 0 can be obtained. However, the counter 4 is indefinite in the initial state when the power is turned on, and a method of giving the initial value will be described in detail in the phase matching operation described in FIGS. 8, 9 and 10.

First, the operation of the brushless DC motor of the present invention when rotating in a steady state will be described.

FIG. 4 is a signal waveform diagram of each part during steady rotation of the brushless DC motor of the present invention. In FIG. 4, e
1, e2, e3 are generated voltage waveforms induced in the stator windings 11, 12, 13, respectively. p1, p2, p3 are three-phase position signals generated by the waveform generating circuit 6, and the generated voltage waveform e is generated in accordance with the rotational position of the permanent magnet rotor 20.
1, e2, and e3 have the same phase relationship. This is a sinusoidal signal waveform, and the power supply circuit 7 uses the three-phase position signal p
1, p2, p3 are each amplified by power, and a sine wave
The phase drive currents i1, i2, i3 are applied to the stator windings 11, 12,
Supply to each of the 13 phases. As a result, the three-phase drive current i1,
A rotating magnetic field is generated in the stator windings 11, 12, and 13 by i2 and i3, and the rotating magnetic field interacts with the magnetic poles of the permanent magnet rotor 20 and the rotating magnetic field generated by the stator windings 11, 12, and 13. As a result, the permanent magnet rotor 20 receives a rotational force and starts rotating.

FIG. 5 is a vector diagram showing the phase relationship between the magnetic poles of the permanent magnet rotor 20 and the rotating magnetic fields generated by the stator windings 11, 12, and 13. In FIG. 5, Φ is a magnetic pole vector indicating the magnetic pole of the permanent magnet rotor 20, and I is a magnetomotive force vector indicating the rotating magnetic field generated by the stator windings 11, 12, and 13.

FIG. 5A is a vector diagram showing that the motor is rotating in the forward direction (clockwise direction), and FIG. 5B is a vector diagram showing that the motor is rotating in the reverse direction (counterclockwise direction). The magnetic force vector I and the magnetic pole vector Φ respectively rotate in the directions shown. As is apparent from the figure, in order to rotate the permanent magnet rotor 20 continuously, the phase of the magnetomotive force vector I generated in the stator windings 11, 12, 13 is determined by the magnetic pole vector of the permanent magnet rotor 20. It suffices to always advance the rotation direction by 90 degrees from the phase of Φ. That is, in order to rotate in the positive direction, the magnetomotive force vector I is set to 9 clockwise.
In order to advance it by 0 degree and rotate it in the opposite direction, it is sufficient to advance the magnetomotive force vector I by 90 degrees counterclockwise.

The operation of each part of the embodiment of the present invention that performs such signal processing will be described in detail.

FIG. 6 is a block diagram showing an embodiment of the position adjusting circuit 5, the waveform generating circuit 6, the initial position detecting circuit 8 and the selecting circuit 9 which constitute the brushless DC motor of the present invention.

In this embodiment, the position adjusting circuit 5, the waveform generating circuit 6, the initial position detecting circuit 8 and the selecting circuit 9 are the arithmetic unit 6
1, memory 62, and digital-analog converters 63 and 6
4, 65. The arithmetic unit 61 operates according to a predetermined built-in program, which will be described later, stored in a ROM (Read Only Memory) area of the memory 62, and a direction command r input to the terminal 14 and a phase adjustment command t input to the terminal 15. And the count value c of the counter 4 are fetched into a RAM (random access memory) area, and a predetermined calculation is performed to obtain an address f. Next, the arithmetic unit 61 stores 1 in advance in the ROM area of the memory 62 according to the address f.
By referring to the function table of the sine wave for the period, the three-phase digital position signals dp1, d corresponding to the address f
p2 and dp3 are obtained and output to the digital-analog converters 63, 64 and 65, respectively. The digital-analog converters 63, 64, 65 convert the three-phase digital position signals dp1, dp2, dp3 into analog values, and output three-phase position signals p1, p2, p3.

Next, a built-in program stored in the ROM area of the memory 62 will be described.

First, the normal mode in which processing is performed during normal rotation will be described with reference to the basic flow chart shown in FIG.

In process 71, an interrupt is awaited when the count value c of the counter 4 changes. When an interrupt occurs, the process proceeds to process 72.

In process 72, the count value c of the counter 4 and the direction command r input to the terminal 14 are fetched and stored in the RAM area.

In process 73, it is determined whether the direction command r is a forward direction command or a reverse direction command. When the direction command r is a forward direction command, in step 74, a predetermined value (corresponding to 90 degrees in terms of phase) is added to the count value c of the counter 4 to calculate the address f. When the direction command r is a reverse direction command, a predetermined value (corresponding to 90 degrees in terms of phase) is subtracted from the count value c of the counter 4 to calculate the address f. Processes 71, 72, 73, 74, and 75 are arithmetic processes performed by the phase adjustment circuit 5.

The processing 76 is based on the address f obtained in the processing 74 or the processing 75, and the 3 required for the next processing 77.
The phase addresses f1, f2, f3 are determined.

That is, since the phases of the position signals p1, p2 and p3 are shifted by 120 degrees (FIG. 4), f1 = f (1) f2 = f + (120) (2) f3 = f- (120) From (3), the address values of the three phases f1, f2, and f3 are calculated. Note that (120) is an address count value equivalent to 120 degrees when converted into a phase.

In the process 77, the RO in the memory 62 is calculated based on the three-phase address values f1, f2 and f3 obtained in the process 76.
Referring to the sine wave function table stored in the M area, the three-phase digital position signals dp1, dp2, dp3
Ask for.

In process 78, the three-phase digital position signals dp1, dp2, dp3 obtained in process 77 are output to the digital-analog converters 63, 64, 65 shown in FIG. Digital-analog converter 63, 64, 65
Converts the digital position signals dp1, dp2, and dp3 into analog values, and outputs the position signal p as shown in FIG.
1, p2, p3 are output. Processes 76, 77 and 78 are arithmetic processes performed by the waveform generation circuit 6. After this process,
The process moves to the process 71, and the above processes are repeated.

By performing the above processing in the phase adjusting circuit 5 and the waveform generating circuit 6, the position signals p1, p2 and p3 are output to the power supply circuit 7 in accordance with the rotation of the permanent magnet rotor 20.

The power supply circuit 7 includes stator windings 1, 12,
A sinusoidal drive current i1, i2, i3 is supplied to 13. That is, the amount of rotation of the permanent magnet rotor 20 is detected,
The magnetic field generated by the stator windings 11, 12 and 13 is rotated by that amount of rotation. As a result, the stator windings generate a rotating magnetic field, and the magnetomotive force vector I of the rotating magnetic field is formed so as to always be out of phase with the magnetic pole vector Φ of the permanent magnet rotor 20 by 90 degrees as shown in FIG. To be done. Then, due to the interaction between the magnetic pole vector I and the magnetic pole vector Φ, the permanent magnet rotor 20 receives the rotational force and continues to rotate.

However, in the initial state when the power is turned on, the count value of the counter 4 is indefinite, and the initial count value cs
Need to give.

Next, the phase matching operation for giving the initial value to the counter 4 in the brushless DC motor of the present invention will be described in detail.

The initial position detection circuit 8 of FIG. 1 forcibly rotates the rotating magnetic field generated by the stator windings 11, 12, and 13 in the forward and reverse directions when the power is turned on, and the permanent magnet rotor 2 is rotated.
The phase relationship between the zero magnetic pole and the rotating magnetic field generated by the stator windings 11, 12, and 13 is detected.

FIG. 8 shows the relationship between the magnetic pole vector Φ generated by the permanent magnet rotor 20 and the magnetomotive force vector I generated by the stator windings 11, 12, 13 for explaining the phase matching operation of the present invention. It is a vector diagram represented by a vector.

At the time of phase matching, a phase matching command is input to the terminal 15 of the selecting circuit 9, and the selecting circuit 9 inputs the address command b of the initial position detecting circuit 8 to the waveform generating circuit 6. Therefore, at the time of phase matching, the address f input to the waveform generating circuit 6 is forcibly changed irrespective of the rotation of the permanent magnet rotor 20, and accordingly, the direction of the magnetomotive force vector Φ of the stator winding is correspondingly changed. Is changed. Then, due to the interaction between the magnetic pole vector I and the magnetic pole vector Φ, the permanent magnet rotor 20 receives a rotational force and starts moving accordingly. Now, assuming that the motor is in an unloaded state, the magnetomotive force vector I and the magnetic pole vector Φ completely match (at that time, the torque generated by the motor is zero). This is shown in FIG. 8A. However, when the motor is in a loaded state, the magnetomotive force vector I and the magnetic pole vector Φ do not match,
A certain phase angle θ is maintained according to the magnitude of the load. Moreover, the direction of the phase shift is such that when the motor is rotated in the forward direction (clockwise direction), the magnetic pole vector Φ shifts from the magnetomotive force vector I in the counterclockwise direction by an angle θ, and the motor moves in the reverse direction. When rotated in the (counterclockwise) direction, the magnetic pole vector Φ shifts clockwise from the magnetomotive force vector I by the angle θ as shown in FIG. 8C. However, counter 4
Since the rectangular wave signal s1 is up-counted or down-counted according to the direction signal d, the rotational movement amount of the permanent magnet rotor 20 is always detected.
Now, assuming that the initial value of the counter 4 is cs and the magnetomotive force vector I of the stator winding is rotated in the positive direction by Δf, the count value of the counter 4 is c1 = cs + Δf−h (4). However, h is a count value corresponding to the phase angle θ in FIG. 8 when converted into a phase.

If the magnetomotive force vector I of the stator winding is rotated in the opposite direction by Δf, the count value of the counter 4 becomes c2 = cs-Δf + h (5).

Therefore, from the expressions (4) and (5), the initial value of the counter 4 can be calculated by cs = (c1 + c2) / 2 (6).

The operation of one embodiment of the present invention for performing such phase matching processing will be described in more detail.

The phase matching mode in which the phase matching process is performed will be described with reference to the flow chart shown in FIG.

In FIG. 9, in process 91, the address f input to the waveform generating circuit 6 is incremented by 1, and process 9 is performed.
Move to 2. The initial value of the address f at the time of phase matching is zero.

In process 92, it is determined whether the address f exceeds Δf. When the address f is within Δf, the process proceeds to the processing 91 again, and the address f is further incremented by 1. When the address f exceeds Δf, the process 93
Move to.

In the process 93, the count value c of the counter 4 is fetched and stored in the RAM area as the first count value c1, and then the process 94 is executed.

In process 94, the address f input to the waveform generating circuit 6 is decremented by 1 this time, and the process shifts to process 95.

In process 95, it is determined whether the address f exceeds -Δf. When the address f is within -Δf, the processing shifts to the processing 94 again, and the address f is further decreased by 1. Then, when the address f exceeds -Δf, the processing shifts to processing 96.

In process 96, the count value c of the counter 4 is fetched and stored in the RAM area as the second count value c2, and then the process 97 is entered.

In process 97, the first count value c1 and the second count value c2 obtained in process 93 and process 96, respectively.
The calculation of the equation (6) is performed based on the
Find s. After the calculation process of process 97 is completed, the process proceeds to process 98.

In process 98, c obtained by the calculation of process 97
The value s is transferred to the counter 4 as an initial value.

The above processings 91 to 98 are caused by the magnetic pole vector Φ of the permanent magnet rotor 20 and the stator windings 11, 12 and 13 in the phase matching mode operation in the initial state such as power-on. The phase alignment of the magnetic force vector I is completed (FIG. 8A).

In the above example, the rotating magnetic field was rotated once in the forward direction and once in the reverse direction in the phase matching mode operation, but after performing the same operation a plurality of times, the average value is calculated. May be. After the phase matching is completed, the mode is shifted to the normal mode described in FIG. 7 and the permanent magnet rotor 20 is rotated.

Another embodiment of the phase matching process will be described. FIG. 10 is a flowchart of another embodiment of the phase matching mode in which the phase matching process is performed. Hereinafter, description will be given along the flowchart shown in FIG.

In FIG. 10, in process 101, the address value f input to the waveform generating means 6 is increased by 1,
The process moves to the process 102. The initial value of the address value f at the time of phase matching is zero.

In process 102, it is determined whether the address value f exceeds Δf. When the address value is within Δf, the address f is further increased by 1 in process 101. When the address f exceeds Δf, the process shifts to the process 103.

In process 103, the address f input to the waveform generator 6 is decremented by 1, and the process proceeds to process 104.

In process 104, it is determined whether the address f exceeds -Δf. When the address value is within -Δf, the address f is further reduced by 1 in step 103. Then, when the address f exceeds -Δf, the processing shifts to the processing 105.

In step 105, the elapsed time in the phase adjustment mode is counted and it is determined whether the predetermined time has been exceeded. If the predetermined time is not exceeded, the process moves to the process 101 again, and the processes from 101 to 105 are repeated. When the phase matching mode has passed the predetermined time, the process 106 is entered.

In process 106, the count value of the counter 4 is reset to zero. The above processing 101 to processing 106 is the operation of the phase matching mode in the initial state such as power-on.

By performing the processing shown in the flowchart of FIG. 10, it is possible to confirm that the phase of the magnetic pole vector Φ of the permanent magnet rotor 20 matches the phase of the magnetomotive force vector I generated by the stator windings 11, 12, and 13. It shows in FIG.

In FIG. 11, reference numeral 111 denotes the stator winding 1.
It shows the behavior of the magnetomotive force vector I generated by 1, 12, and 13. The magnetomotive force vector I oscillates in the forward and reverse directions by the processing shown in the flowchart of FIG. 10, and stops after a predetermined time elapses. Reference numeral 112 shows the behavior of the magnetic pole vector Φ of the permanent magnet rotor 20.

As shown in FIG. 11, the stator windings 11, 1
Since the magnetomotive force vector I generated by 2 and 13 vibrates violently in the forward and reverse directions, the magnetic pole vector Φ of the permanent magnet rotor 20 vibrates in the forward and reverse directions due to electromagnetic interaction with the magnetomotive force vector I. Receive. However, since the inertia of the permanent magnet rotor 20 is sufficiently large, the magnetomotive force vector I
, And the permanent magnet rotor 20 starts to rotate by receiving its average rotational force. Then, when the phase of the magnetic pole vector Φ of the permanent magnet rotor 20 matches the phase of the magnetomotive force vector I generated by the stator windings 11, 12, 13 (FIG. 8A), the permanent magnet rotor 2
0 is stationary.

Therefore, at this time, the count value of the counter 4 may be reset to zero. In the embodiment of phase matching shown in FIG. 9, the first count value c1 of the counter 4 and the second count value c1
Although a memory (RAM) for storing the count value c2 of the above is required, such a memory is not required in the embodiment of FIG. 10, and it is not necessary to perform the calculation shown in the equation (6). Therefore, there is an advantage that the processing program can be simplified.

In the embodiment of FIG. 10, the stator winding 1
The magnetomotive force vector I generated by 1, 12, and 13 is configured to vibrate in the forward and reverse directions with a constant amplitude for a predetermined time as shown in FIG. 11, but as shown by 121 in FIG. The amplitude of the vibration of the vector I may be configured to decay with time. The amplitude of vibration of the magnetomotive force vector I is set to a constant amplitude as indicated by 111 in FIG. 11, and only the magnitude of the magnetomotive force vector I is calculated as shown in FIG.
As shown in B, it may be configured to decay with time.

In the embodiment for phase matching shown in FIG. 11, since the magnetomotive force vector I is oscillated in the forward and reverse directions for a predetermined time with a constant amplitude, the vibration at the time of phase adjustment is transmitted to the outside of the motor for a predetermined time. In the embodiment shown in FIG. 12A, since the amplitude of the vibration of the magnetomotive force vector I is attenuated with time, there is an advantage that the vibration transmitted to the outside of the motor is not a concern because the vibration during phase matching is attenuated with time. Further, in the embodiment shown in FIG. 12B, since the magnitude of the magnetomotive force vector I is attenuated with time, there is an advantage that the power required for phase matching can be reduced as compared with the embodiment shown in FIG. ..

After the phase matching is completed, the normal mode described with reference to FIG. 7 is entered to rotate the permanent magnet rotor 20.

As described above, since the brushless DC motor of the present invention creates the three-phase position signals based on the two-phase frequency signals having different phases output from the frequency generator, the position detecting element such as the Hall element is used. Need not be provided.

In the waveform generating circuit 6 according to the present invention, the function table of the sine wave of only one cycle is stored in the memory, and the address value is changed by the amount corresponding to the difference in the phase to refer to the function table. Figure 6 shows the phase position signals.
Three digital-analog converters 63,
It outputs to 64 and 65, but after sequentially converting into an analog value using one digital-analog converter, the obtained analog value is held by three sample hold circuits (not shown). It goes without saying that it is also possible to output as a three-phase position signal. Further, not only the function table of the sine wave of only one cycle is stored in the memory, but also the sine waves of the three phases are stored in the function tables respectively, and the digital signals corresponding to the position signals of the three phases are directly stored. The value is converted into three digital-analog converters 63, 64,
It goes without saying that it is also possible to output to 65.

Further, although the embodiment of the present invention is limited to a three-phase motor, it goes without saying that the number of phases is not limited to three and any number of phases may be used.

[0076]

As described above, according to the present invention, since the position detecting element unlike the conventional brushless DC motor is unnecessary, the complexity of adjusting the mounting position of the element and the number of wires are reduced, and the cost is greatly reduced. ..

Furthermore, since it is not necessary to mount the position detecting element inside the motor, the motor can be made ultra-small and ultra-thin without being restricted by the structure.

Further, the brushless DC motor of the present invention is
With the above configuration, there is no particular need for a no-load state during the phase matching operation, and the positional relationship between the permanent magnet rotor and the stator winding can be accurately detected even when the motor is under a load.

Further, after the power is turned on, the frequency generator detects the rotation of the permanent magnet rotor even when the motor is not driven. Therefore, even if the permanent magnet rotor is rotated from the outside for some reason, it is always possible. Since the magnetic pole position is known, the phase matching operation need only be performed when the power is turned on. Therefore, after the completion of the phase matching operation, the start and stop operations do not change at all compared to the conventional brushless DC motor with position detection element, and the same start-up as the conventional brushless DC motor with position detection element. It is possible to construct a brushless DC motor that has characteristics and can be applied to a wide range of purposes.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a brushless DC motor of the present invention.

FIG. 2 is a circuit configuration diagram showing an embodiment of a direction detection circuit according to the present invention.

FIG. 3 is a signal waveform diagram of each part of the direction detection circuit shown in FIG.

FIG. 4 is a signal waveform diagram of each part during steady rotation of the brushless DC motor of the present invention.

FIG. 5 is a vector diagram showing the relationship between the magnetic pole vector Φ of the permanent magnet rotor and the magnetomotive force vector I generated by the stator winding during steady rotation of the brushless DC motor of the present invention.

FIG. 6 is a block diagram showing a configuration of a position adjusting unit, a waveform generating unit, an initial position detecting unit, and a selecting unit which constitute the brushless DC motor of the present invention.

FIG. 7 is a flow chart diagram for explaining processing in a normal mode during normal rotation.

FIG. 8 is a magnetic pole vector Φ of the permanent magnet rotor and a magnetomotive force vector I generated by the stator winding during the phase matching operation.
Vector diagram showing the relationship with

FIG. 9 is a flowchart of one embodiment for performing a phase matching operation.

FIG. 10 is a flowchart of another embodiment for performing a phase matching operation.

11 is a time response waveform diagram showing how the magnetic pole vector Φ of the permanent magnet rotor and the magnetomotive force vector I generated by the stator winding are phase-matched in the embodiment of FIG.

FIG. 12 is a time response waveform diagram showing how the magnetic pole vector Φ of the permanent magnet rotor and the magnetomotive force vector I generated by the stator winding are aligned in another embodiment.

[Explanation of symbols]

 1 frequency generator 2 waveform shaping means 3 direction detecting means 4 counting means 5 phase adjusting means 6 waveform generating means 7 power supply means 8 initial position detecting means 11, 12, 13 stator winding 20 permanent magnet rotor

Claims (13)

[Claims] 1. A rotor having a plurality of magnetic poles, a plurality of phases of stator windings disposed in the rotor with a predetermined gap, and a plurality of phases proportional to the number of rotations of the rotor. A frequency generator for generating a frequency signal, a direction detecting means for detecting a rotation direction of the rotor from the frequency signals of the plurality of phases and outputting a direction signal, and at least one of the frequency generators according to the direction signal. Counting means for up-counting or down-counting the pulses of one frequency signal; initial position detecting means for calculating an initial value of the rotor from the count value of the counting means and outputting the initial value to the counting means; Phase adjustment means for adding or subtracting the count value of the counting means by a predetermined value according to the above, waveform generation means for generating waveform signals of a plurality of phases according to the output of the phase adjustment means, A brushless DC motor comprising a power supply means for supplying power to a stator winding in accordance with waveform signals of a plurality of phases. 2. The initial position detecting means detects a first count value of the counting means when it is rotated in the forward direction and a second count value of the counting means when it is rotated in the opposite direction, The brushless DC motor according to claim 1, wherein an average value of the count value of 1 and the second count value is configured to be an initial value of the counting means. 3. A rotor having a plurality of magnetic poles, a plurality of phases of stator windings arranged in the rotor with a predetermined gap, and a plurality of phases proportional to the number of rotations of the rotor. A frequency generator for generating a frequency signal, a direction detecting means for detecting a rotation direction of the rotor from the frequency signals of the plurality of phases and outputting a direction signal, and at least one of the frequency generators according to the direction signal. Counting means for up-counting or down-counting pulses of one frequency signal, phase adjusting means for adding or subtracting a predetermined value to or from the count value of the counting means according to a rotation direction command, and output according to the output of the phase adjusting means. Waveform generating means for generating waveform signals of a plurality of phases, power supply means for supplying electric power to the stator windings according to the waveform signals of the plurality of phases, and rotating magnetic field generated by the stator windings. Brushless DC motor, characterized in that the initial value of the rotor defining the initial positions of the magnetic poles of the permanent magnet rotor is constructed from the initial position detecting means for outputting to said counting means by vibrating in forward and reverse directions. 4. The initial position detecting means is characterized in that the frequency for vibrating the rotating magnetic field generated by the stator winding in the forward and reverse directions is made sufficiently larger than the time constant determined by the inertia of the rotor and the generated torque. The brushless DC motor according to claim 3. 5. The brushless according to claim 3, wherein the initial position detecting means attenuates the amplitude of the vibration that vibrates the rotating magnetic field generated by the stator winding in the forward and reverse directions with time. DC motor. 6. The brushless DC motor according to claim 3, wherein the initial position detecting means attenuates the magnitude of the rotating magnetic field generated by the stator winding with time. 7. The phase adjusting means adds or subtracts the count value of the counting means in accordance with the rotation direction command to determine the phase of the rotating magnetic field generated by the stator winding in electrical angle from the phase of the magnetic pole of the permanent magnet rotor. The brushless DC motor according to claim 1 or 3, wherein the brushless DC motor is configured to rotate by 90 degrees. 8. The waveform generating means comprises memory means for storing a sinusoidal signal in advance and a digital-analog converter for converting a digital value read from the memory means into an analog value. Claim 1
Alternatively, the brushless DC motor according to claim 3. 9. The brushless DC motor according to claim 8, wherein the waveform generating means stores in advance a sinusoidal signal having only one cycle. 10. The waveform generating means has a half cycle or one cycle.
9. The brushless DC motor according to claim 8, wherein a sinusoidal signal having only / 4 cycle is stored in advance. 11. The brushless DC motor according to claim 1 or 3, wherein the initial position detection means is configured to operate only when the power is turned on. 12. The frequency generating means is configured to be readable even when the rotor is stationary.
Alternatively, the brushless DC motor according to claim 3. 13. A counting means, a phase adjusting means, a waveform generating means and an initial position detecting means are composed of a memory means for storing program data according to processing contents, and an arithmetic processing unit for executing processing according to the program data. The brushless DC motor according to claim 1 or 3, wherein the brushless DC motor is configured.