JPH04340391A - Motor control system - Google Patents

Abstract

PURPOSE:To reduce noise of a DC motor by providing both ends with drive signals instead of bringing drive pulses to the middle of the interior of one phase and by adding micropulses upon a change of drive pulse signal from off to on or from on to off. CONSTITUTION:The control part 2 of a MPU 5 generates drive signals for twice controls on and off of coil current in each coil switch phase. That is, a usual fundamental frequency of 1740Hz can be changed double to 3480Hz, so that noise is reduced with the fundamental frequency kept away from an audible range. The control part 2 of the MPU 5 adds micropulses of slight time width to zones inside each phase where a pulse waveform changes from on to off and from off to on every coil switch phase. Then, a current waveform becomes smooth by synthesization with the result that noise components due to a steep rise and fall decreases. This process can reduce noise of a DC motor 1 due to a fundamental frequency present in an audible band.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control method for a DC motor used as a spindle motor of a magnetic disk drive. The spindle motor of a magnetic disk drive uses a DC motor with a brushless structure, and if the fundamental frequency of the drive pulse signal determined by the rotation speed is in the audible frequency range, a resonant frequency in the audible range will be generated and the noise will increase. There is a problem with this, and improvement in this point is desired.

0002

2. Description of the Related Art Conventionally, in magnetic disk devices, it is necessary to suppress the noise level during operation to below a value determined by standards. The main noise generated by magnetic disk drives is the spindle motor that rotates the magnetic disk. A DC motor with a brushless structure is normally used as this spindle motor, and the coils are switched in a number of phases determined by the product of the number of coil phases and the number of magnetic poles of the rotor every rotation. A constant rotation speed is obtained by duty-controlling the on-time of the drive pulse signal that causes current to flow.

FIGS. 19(a), 19(b), and 19(c) show driving pulse signals of the conventional method. If the time of one phase is T1, and the duty ratio of the power to be supplied is Duty, then T2= The drive waveform is such that current flows through the coil over T1×Duty.

FIGS. 19(a), (b), and (c) show T through which current flows.
The timing of the two hours is different from the center, beginning, and end, but what they have in common is that there is one on-time and one off-time in one phase, so the fundamental frequency of the drive pulse signal is 1. It is determined by the number of phases per rotation.

[0005]

[Problem to be Solved by the Invention] However, with the increase in the recording capacity of magnetic disk devices in recent years, the number of disk rotations by the spindle motor has increased.
When using a brushless DC motor with 8 phase poles,
Since the disc rotation speed is around 4300 rpm,
24 phases of coil switching are performed per rotation, as shown in Figure 19.
The fundamental frequency of the drive pulse signal that performs duty control shown in is 1740Hz (=4300rpm/60sec
×24 phases).

[0006] The fundamental frequency of this drive pulse is 1740Hz.
is the audible frequency that is most easily perceived as noise, and driving the motor using this drive pulse generates a resonant frequency in the audible range, causing the problem that the noise is amplified more than expected. In order to solve this problem, it is possible to reduce the fundamental frequency component by setting a slicing level to the current flowing through the coil, but this creates another problem in that sufficient torque cannot be generated due to current slicing.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a motor control method that can easily reduce noise by devising the motor drive waveform. .

[0008]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. First, as shown in FIG. 1(a), the present invention
The DC motor 1 has phase M poles, for example, 3 phases and 8 poles, and one rotation of the DC motor 1 is divided into N×M (=3×8=24 phases) coil switching phases, and the direction of the current flowing through the stator coil is set to a predetermined direction. A control unit that generates a rotating magnetic field by repeatedly switching the coil phases according to the order in units of 2×N phases, for example, in units of 6 phases, and drives the DC motor 1 by duty-controlling the coil energization period using drive pulse signals of each phase. The target is a motor control system with 2.

Regarding such a motor control system, in the first invention of the present application, the control unit 2 generates a drive pulse signal as shown in FIG. 1(b) that turns the coil current on and off twice in each coil switching phase. The invention is characterized in that it has a means for doing so. Further, in the second invention of the present application, the control unit 2 is provided with a minute pulse having a small time width added to the portion where the pulse waveform switches from on to off and from off to on within each phase for each coil switching phase.
) is characterized in that it is provided with means for generating the drive pulse signal shown in FIG.

Furthermore, in the third invention of the present application, the control section 2 includes:
As shown in Fig. 1(d), the duty ratio is cumulatively added for each coil switching phase that constitutes one rotation, and the drive pulse signal of the coil switching phase in which the integer part of this cumulative addition value has changed is set as an on-pulse. The duty is controlled by the number of on-pulses and the number of off-pulses among the (N x M) coil switching phases that make up one rotation of the motor. It is characterized by

Furthermore, the fourth invention of the present application provides that the control section 2:
As shown in Fig. 1(e), a random number is set for each coil switching phase that constitutes one rotation, and this random number is compared with the duty ratio. If the random number is smaller than the duty ratio, the drive pulse signal is turned on pulse, and the random number is is equal to or greater than the duty ratio, means is provided to turn the drive pulse signal into an off-pulse, and similarly to the fourth invention, the number of on-pulse phases and the off-pulse among the (N×M) coil switching phases constituting one rotation of the motor are provided. It is characterized by duty control based on the number of phases.

On the other hand, the fifth invention of the present application is a combination of the first invention and the second invention. That is, as a fifth invention, the control unit 2 includes a first means for generating a drive pulse signal that turns the coil current on and off twice in the coil switching phase, and a drive pulse signal that switches from on to off and from off to on. A second means for generating a drive pulse signal with a minute pulse of a small time width added to the switching portion, and a switching means for alternately outputting the drive pulse signals of the first means and the second means for each coil switching phase are provided. It is characterized by:

A sixth invention of the present application is characterized in that the first invention and the second invention are alternately switched using the random numbers of the fourth invention. That is, the sixth invention includes a first means for generating a drive pulse signal that turns the coil current on and off twice for each coil switching phase in the control unit 2, and a first means for generating a drive pulse signal that turns the coil current on and off twice for each coil switching phase, and a drive pulse signal that turns the coil current from on to off and from off to on. A second means generates a drive pulse signal with a minute pulse of a small time width added to the switching part, and a random number is set for each coil switching phase that makes up one rotation, and the random number is determined by comparing the random number and the duty ratio. The present invention is characterized in that a switching means is provided which outputs the drive pulse signal of the first means if the random number is smaller than the duty ratio, and outputs the drive pulse signal of the second means if the random number is greater than or equal to the duty ratio.

Furthermore, the seventh invention of the present application is characterized in that the second invention and the third invention are combined. That is, the seventh invention causes the control unit 2 to generate a drive pulse in which minute pulses with a short time width are added to the portions where the pulse waveform switches from on to off and from off to on within each phase for each coil switching phase. means to cumulatively add the duty ratio for each coil switching phase that constitutes one rotation, output a drive pulse signal with a minute pulse added at the coil switching phase where the integer part of the cumulative addition value has changed, and detect the change in the integer part. and means for stopping the output of the drive pulse signal in the coil switching phase when the coil is not switched.

Finally, the eighth invention of the present application is characterized in that the second invention and the fourth invention are combined. That is, the eighth invention includes a minute pulse adding means for adding a minute pulse with a small time width to the portion where the drive pulse signal switches from on to off and from off to on in each coil switching phase in the control unit 2. Then, set a random number for each coil switching phase that makes up one rotation,
Means is provided to compare the random number and the duty ratio, and if the random number is smaller than the duty ratio, output a drive pulse signal with minute pulses added thereto, and to stop outputting the drive pulse signal if the random number is greater than or equal to the duty ratio. It is characterized by

[0016]

[Operations] According to the motor control system of the present invention having such a configuration, the following effects can be obtained. In the first invention, the drive pulses are not brought to the center of one phase, but to both ends, thereby doubling the number of on and off times within one phase and doubling the number of switching times. The conventional fundamental frequency of 1740 Hz can be doubled to 3480 Hz, and noise can be reduced by moving the fundamental frequency away from the center of the audible band.

Furthermore, in the second invention, two effects can be expected by adding a minute pulse when the drive pulse signal changes from OFF to ON or from ON to OFF. One is that by adding minute pulses, the switching frequency becomes higher and goes out of the audible range, making it possible to reduce noise. The second reason is that the current in the motor coil does not follow minute pulses due to inductance, so the current waveform becomes smooth and noise components are reduced.

In the fourth invention, instead of changing the duty within one phase, one phase is turned only on or only off, and the duty is controlled during the coil switching phase of one rotation. That is, a duty ratio, which is a decimal number greater than or equal to 0 and less than 1, is added to each coil switching phase during one rotation, and the phase when the integer part changes is turned on, and the phase when it is not changed is turned off. Such control reduces the periodicity of on and off, making it difficult to generate noise.

[0019] In the fifth invention, which controls the duty during the coil switching phase of one rotation in the same way as the fourth invention, a random number is set for each coil switching phase and compared with the duty ratio, and (random number) < (
The phase with (duty ratio) is turned on, and the phase with (random number) ≧ (duty ratio) is turned off. In this case, since the coil phase turns on and off during one rotation is done randomly without any periodicity, noise with a specific frequency is not generated, and the noise is reduced to near white noise with a low noise level. .

Of course, the fifth to eighth inventions are a combination of the first to fourth inventions.
Regarding the invention, results can also be obtained by combining the noise reduction effects of each invention.

[0021]

Embodiment FIG. 2 is a block diagram showing an embodiment of the present invention. In FIG. 2, reference numeral 1 denotes a DC motor with a brushless structure, and a three-phase eight-pole motor is taken as an example. That is, the DC motor 1 has star-connected stator coils L1 and L2.
, L3 are provided. Further, the rotor 3 has eight magnetic poles in which north poles and south poles are alternately provided.

Further, Hall elements 4-1, 4-2, 4-3 are provided corresponding to the stator coils L1, L2, L3, respectively, and rotation detection signals H1, H synchronized with the rotation of the rotor 3 are provided.
2, H3 is detected and the microprocessor (hereinafter referred to as “MPU”) is detected.
'') 5 to the input registers 6, etc. MPU
5, a control section 2 that generates a drive pulse signal for controlling the DC motor 1 is realized by program control. The control unit 2 receives rotation detection signals H1 from the Hall elements 4-1 to 4-3.
-H3, drive pulse signals S1 to S6 are output from the output register 7.

Since the output signal of the output register 7 is at TTL level, the level conversion circuit 8 converts it into a driving signal for the switching FET of the switching circuit 9. The drive circuit 9 is provided with six switching FETs Q1 to Q6.
Coil terminal A is connected between Q2 and Q4, coil terminal B is connected between Q2 and Q5, and coil terminal C is connected between Q3 and Q6.

S1 to switching circuit 9 from MPU 5
The S6 signal has patterns shown in the decoding table of FIG. 3 set in advance for states 1 to 6 determined by the rotation detection signals H1 to H3 from the Hall elements 4-1 to 4-3. Furthermore, the switching of the stator coils L1 to L3 of the DC motor 1 by the switching circuit 9 and the direction of the current for states 1 to 6 are as shown in FIG.

Furthermore, states 1 to 6 in FIGS. 3 and 4 are similar to those in FIG.
Rotation detection signals H from Hall elements 4-1 to 4-3 shown in
It is determined by the combination of 1 to H3. Furthermore, regarding duty control, D is input to the input register 10 of the MPU 5 in FIG.
An index pulse obtained every revolution of the disk rotated by the C motor 1 and a reference clock pulse from a reference oscillator are given, and in the control section 2, the index pulse is controlled according to the leading or lagging phase of the index pulse with respect to the reference clock pulse. The duty ratio is determined for each rotation, and the ON time of the S1 to S6 signals from the output register 7 within one phase T1 is determined.

That is, if the index pulse lags behind the reference clock pulse, the duty ratio is increased, and if the index pulse lags behind the reference clock pulse, the duty ratio is decreased, and feedback is performed by duty control such that the phase difference is always kept at zero. . [Embodiment of the first invention] Regarding the embodiment of FIG. 2, in the first invention of the present application, the control unit 2 of the MPU 5 is configured to turn on and off the coil current twice in each coil switching phase. It is characterized in that it generates a drive pulse signal.

For example, as in the S1 signal of FIG. 6(a), 1
The signal waveform is such that the S1 signal is repeatedly turned on and off twice within the T1 period constituting one phase. In other words, this means that the S1 signal pulse is not brought to the center of the phase switching as in the conventional case shown in FIG. 19, but is brought to both ends of the phase switching. By adopting the waveform shown in Fig. 6(a), the number of switching times of the current flowing through the stator coil within one phase can be reduced to two, and the conventional fundamental frequency of 1740 Hz is doubled to 3480 Hz. Noise can be reduced by moving it away from the audible range.

FIG. 7 shows the waveforms of the S1 to S6 signals according to the first invention together with the rotation detection signals H1 to H3 from the Hall element for states 1 to 6. Since one rotation has 24 phases, the waveforms of the S1 to S6 signals are shown for states 1 to 6. 6 corresponds to 1/4 rotation. Furthermore, Figure 5
shows extracted state 6 and state 1 portions of the S1 signal. As is clear from FIG. 7, the waveform that turns on and off twice in one phase shown in FIG.
These are the S1 to S3 signals among the six signals, and the basic pattern shown in FIG. 3 is used as is for the S4 to S6 signals.

Next, assuming that the first on time of the one-phase pulse waveform shown in FIG. 7 is Tc, and the next off time is T3, steps S1 to S3 in FIG.
The signal generation process will be explained as follows. (F1) Detect the initial state and set it in the state counter n. For example, when state 1 in FIG. 6 is first detected from the Hall element rotation detection signals H1 to H3, the state counter n is set to n=1.

(F2) Next, the Sn signal is set to H and the internal timer is started from 0. Here state counter n=1
Therefore, the S1 signal is set to H and an internal timer is started. Note that the internal timer may be external to the MPU 5. (F3) Wait until the internal timer reaches time Tc in FIG. 6. (F4) Set the S1 signal to L and start the internal timer from 0.

(F5) Wait until the internal timer reaches T3. (F6) Set the Sn signal, that is, the S1 signal, to H. (F7) Wait until the state of the Hall element becomes the next state 2. (F8) Set the Sn signal, that is, the S1 signal, to L. (F9) Increment the status counter n by 1 and n=
Let n+1=2.

(F10) Determine whether the status counter n has reached n=7. At this time, since n=2, the process returns to F2 and starts processing the S3 signal in state 2. On the other hand, when the processing of state 6 is completed, since n=7, the process advances to F11. (F11) Initialize the state counter n to n=1, and
Return to step 2 and repeat the process from state 1. Note that the signals S1 to S1 to be processed based on the value of the state counter n
S3 is specified with reference to the decoding table shown in FIG.

That is, (1) the S1 signal is specified for state counters n=1, 6, (2) the S2 signal is specified for state counters n=4, 5, and (3) the S2 signal is specified for state counters n=2, 3.
Now specify the S3 signal. [Embodiment of the second invention] Next, in the second invention of the present application,
The control unit 2 of the MPU 5 shown in FIG. 2 generates a drive pulse in which minute pulses with a short time width are added to the parts where the pulse waveform switches from on to off and from off to on within each phase for each coil switching phase. It is characterized by being made to do.

FIG. 9(a) shows an S according to an embodiment of the second invention.
The signal waveform of one signal is shown for states 1 and 6.
Minute pulses with short time widths are added before and after the pulse waveform brought to the center within one phase T1. Due to the addition of this minute pulse, the current waveform flowing through the stator coil in Figure 9(b) is such that the current does not follow the current due to the inductance of the stator coil due to the minute pulse, and the current waveform is smooth due to the combination with the current flowing due to the original pulse waveform. Become.

If the current waveform can be made smooth in this way,
Noise components caused by sudden rises and falls of the current waveform can be reduced. FIG. 9(c) shows the case where the original pulse waveform is brought to the beginning of one phase T1, and FIG. 9(d) shows the case where the original pulse waveform is brought to the end of one phase T1. Micropulses are added before and after the pulse waveform.

FIGS. 10 and 11 are flowcharts showing the process of generating S1 to S3 signals to which minute pulses are added according to the second invention. Note that the times Td, Ton, and Toff for specifying the waveforms used in the processing in FIGS. 10 and 11 are defined as shown in FIG. 12. The processing in FIGS. 10 and 11 is as follows. (F1) Detect the initial state and set it in the state counter n. For example, when state 1 in FIG. 6 is first detected from the Hall element rotation detection signals H1 to H3, the state counter n is set to n=1.

(F2) Start the internal timer from 0. (F3) Wait until the internal timer reaches Td. (F4) Since the state counter n=1, the Sn signal,
For example, the S1 signal is set to H and the internal timer is started from 0. (F5) Wait until the internal timer reaches Ton.

(F6) Set the Sn signal, for example the S1 signal, to L and start the internal timer from 0. (F7) Wait until the internal timer reaches Toff. (F8) Set the Sn signal, for example, the S1 signal, to H and wait until the internal timer reaches T4.

(F9) Set the Sn signal, for example the S1 signal, to L and start the internal timer from 0. (F10) Wait until the internal timer reaches Ton. (F11) Set the Sn signal, for example, the S1 signal, to H and start the internal timer from 0.

(F12) Wait until the internal timer becomes Toff. (F13) Set the Sn signal, for example, the S1 signal, to L and wait until the next state 2 is reached. (F14) Increment the status counter n by 1 and
=n+1=2. (F15) Determine whether the state counter n has reached n=7. At this time, since n=2, the process returns to F2 and starts processing the S3 signal in state 2. On the other hand, when the processing of state 6 is completed, since n=7, the process advances to F11.

(F16) Initialize the state counter n to n=1, return to F2, and repeat the process from state 1 again. Note that the signals S1 to S1 to be processed based on the value of the state counter n
S3 is specified with reference to the decoding table shown in FIG.

That is, (1) the S1 signal is specified for state counters n=1, 6, (2) the S2 signal is specified for state counters n=4, 5, and (3) the S2 signal is specified for state counters n=2, 3.
Now specify the S3 signal. [Embodiment of the third invention] In the third invention of the present application, FIG.
The control unit 2 of the MPU 5 shown in Figure 2 does not control the duty of the drive pulse signal for each phase, but rather controls the number of on-pulse phases and the number of off-pulse phases among the 24 coil switching phases that make up one rotation of the motor. Specifically, the duty ratio (duty) is cumulatively added for each of the 24 coil switching phases constituting one rotation to obtain a cumulative value (sum), and this cumulative value is (su
The phase in which the integer part of m) changes is turned on, and the phase in which the integer part does not change is turned off.

To explain specifically, the duty ratio (
duty)=0.5, when the duty ratio (duty) is added for each phase, the cumulative addition value (sum) increases as shown in the sum in FIG. Note that the number of times indicates the number of phases, and the number of times 1 to 24 is repeated in one rotation. For the cumulative addition value (sum) of this duty ratio, the phase whose integer part does not change with respect to the previous phase is turned off,
The phase whose integer part has changed is turned on. Of course, the value of the duty ratio (duty) is determined for each rotation.

Further, when the duty ratio (duty) is 0.8, the result is as shown in FIG. 14. By switching the coil on and off for each phase based on the cumulative addition of the duty ratio for each phase, the periodicity of the drive pulse signal can be relaxed, making it difficult to generate noise.

FIG. 15 is a flowchart showing the process of the third invention for controlling on/off of each phase shown in FIGS. 13 and 14, and is performed as follows. (F1) Detect the initial state and set it in the state counter n. For example, when state 1 in FIG. 6 is first detected from the rotation detection signals H1 to H3 of the Hall element, the state counter n is set to n=1, for example.

(F2) Set cumulative addition value sum=0. (F3) Calculate sum=sum+duty using the currently set duty ratio duty. (F4) Determine 1≦sum. F5 if 1 or more
Proceed to. If it is less than 1, proceed to F6.

(F5) Since the value is 1 or more, the Sn signal, for example, the S1 signal, is turned on, and sum is returned to a small number by setting sum=sum-1. (F6) Since the value is 1 or less, the Sn signal, for example, the S1 signal, is turned off. (F7) Wait until the state of the Hall element changes. (F8) Increment the status counter n by 1 and n=
Let n+1=2.

(F9) Determine whether the status counter n has reached n=7. At this time, since n=2, the process returns to F3 and begins processing the S3 signal in state 2. On the other hand, state 6
When processing is completed, since n=7, the process advances to F10. (F10) Initialize the state counter n to n=1, and
Return to step 2 and repeat the process from state 1. Note that the signal Sn that turns on or off at F5 and F6 is determined according to the decoding table shown in FIG. 3 based on the value of the state counter n.

That is, S for state counter n=1 to 6
The processing of the 1 to S6 signals is as follows. State 1; S1, S5 State 2; S3, S5 State 3; S3, S4 State 4; S2, S4 State 5; S2, S6 State 6; S1, S6 [Embodiment of the fourth invention] In the fourth invention of the present application Yes, Figure 2
The control unit 2 of the MPU 5 shown in FIG. 1 sets a random number (rnd) of 0 or more and less than 1 for each coil switching phase that constitutes one rotation, and compares this random number (rnd) with a duty ratio (duty). Then, if (rnd)<(duty), the phase is turned on, and if (rnd)≧(duty), the phase is turned off.

Similar to the third invention, the fourth invention also controls the duty based on the number of on-pulse phases and the number of off-pulse phases among the 24 coil switching phases. For example, when the duty ratio (duty) is 0.8, the on/off state of each phase is as shown in FIG. 16. Looking at the on and off states shown by the switch in Figure 16, out of 10 times, it is off three times and on seven times, and the duty ratio is 0.7.
However, since phase switching occurs 24 times in one rotation, the error with duty=0.8 becomes even smaller.

Furthermore, even if there is a shift in the duty ratio over several rotations, this does not pose a problem because it is corrected by controlling the duty ratio based on the phase comparison between the index pulse and the reference clock pulse. Figure 17 is Figure 16
The waveforms of the actual S1 to S6 signals obtained by on/off control based on the comparison of the duty ratios of random numbers are shown together with the rotation detection signals H1 to H3 obtained from the Hall elements.

[0052] Conditions 1 to 6 in Fig. 17 result in 1/4 rotation,
By repeating these states 1 to 6 four times, the motor rotates once. As is clear from the drive waveform in FIG. 17, the S1 to S6 signals that drive the DC motor 1 are turned on and off randomly without any periodicity, so no noise with a specific period is generated. The noise can be reduced by approaching white noise, which has a low noise level.

FIG. 18 is a flow chart showing the processing for generating waveforms S1 to S6 in FIG. 17, which is performed as follows. (F1) Detect the initial state and set it in the state counter n. For example, when state 1 in FIG. 6 is first detected from the Hall element rotation detection signals H1 to H3, the state counter n is set to n=1.

(F2) Generate a random number greater than or equal to 0 and less than 1, and r
nd. (F3) Compare the random number rnd and the currently set duty ratio duty as rnd<duty. (F4) If rnd is smaller than duty, Sn signal,
For example, turn on the S1 signal.

(F5) If rnd is greater than duty,
Turn off the Sn signal, for example, the S1 signal. (F6) Wait until the state of the Hall element changes. (F7) Increment the status counter n by 1 and n=
Let n+1=2. (F8) Determine whether the status counter n has reached n=7. At this time, since n=2, the process returns to F2 and starts processing the S3 signal in state 2. On the other hand, when the processing of state 6 is completed, since n=7, the process advances to F9.

(F9) Initialize the state counter n to n=1, return to F2, and repeat the process from state 1 again. Incidentally, the Sn signal to be turned on or off at F4 and F5 is determined according to the decode table shown in FIG. 3 based on the value of the state counter n.

That is, S for state counter n=1 to 6
The processing of the 1 to S6 signals is as follows. State 1; S1, S5 State 2; S3, S5 State 3; S3, S4 State 4; S2, S4 State 5; S2, S6 State 6; S1, S6 [Embodiment of the fifth invention] The fifth invention of the present application is , is a combination of the first invention and the second invention.

That is, in the fifth invention, the control unit 2 of the MPU 5 shown in FIG. 2 generates signals S1 to S6 that turn the coil current on and off twice within the coil switching phase, as shown in FIGS. As shown in FIG. 9, the S1 to S6 signals are provided with a function to generate a signal in which minute pulses with a small time width are added to the parts where the S1 to S6 signals switch from on to off and from off to on. Two types of S1 to S6 signals are switched to be output alternately for each phase. [Embodiment of the sixth invention] The sixth invention of the present application is characterized in that the first invention and the second invention are alternately switched using the random number of the fourth invention.

That is, in the sixth invention, the control unit 2 of the MPU 5 shown in FIG. 2 generates signals S1 to S6 that turn the coil current on and off twice within the coil switching phase, as shown in FIGS. 6 and 7. As shown in FIG. 9, there is provided a function to generate a signal in which minute pulses with a small time width are added to the parts where the S1 to S6 signals switch from on to off and from off to on.

Then, in the same manner as shown in the flowchart of FIG. 18, a random number (rnd) is set for each phase change and compared with the duty ratio (duty). If the random number (rnd) is smaller than the duty ratio (duty), the phase It is characterized in that it generates S1 to S6 that are turned on and off twice within the range, and outputs S1 to S6 signals with minute pulses added before and after if the random number (rnd) is greater than or equal to the duty ratio (duty). [Embodiment of the seventh invention] The seventh invention of the present application is characterized in that the second invention and the third invention are combined.

That is, in the seventh invention, the control unit 2 of the MPU 5 shown in FIG. S1 to S6 with a minute pulse of a time width added
It has a function to generate a signal, and as shown in the flowchart of FIG. 15, the duty ratio (dut
y), and output S1 to S6 signals with minute pulses added in the coil switching phase where the integer part of this cumulative addition value (sum) changes, and the integer part does not change. It is characterized in that the outputs of S1 to S6 are stopped in the coil switching phase. [Embodiment of the eighth invention] Finally, the eighth invention of the present application is the second embodiment of the eighth invention.
It is characterized by a combination of the invention and the fourth invention.

That is, in the eighth invention, the control section 2 of the MPU 5 shown in FIG. Furthermore, as shown in the time chart of Fig. 18, a random number (rnd) is set for each coil switching phase that constitutes one rotation, and the random number (rnd) and duty are If the random number is smaller than the duty ratio, it outputs the S1 to S6 signals with minute pulses added, and if the random number is greater than or equal to the duty ratio, it stops outputting the S1 to S6 signals. do.

[0063]

As explained above, according to the present invention, the noise caused by the fundamental frequency of 1740Hz in the audible band, which is easily perceived as noise when driving a 3-phase 8-pole DC motor, can be eliminated by driving pulses. It can be sufficiently reduced by processing the waveform.

[Brief explanation of drawings]

[Fig. 1] Diagram explaining the principle of the present invention

[Figure 2] Configuration diagram of an embodiment of the present invention

FIG. 3 is an explanatory diagram of a decoder table for obtaining signals S1 to S6 from states 1 to 6 determined by the rotation detection signal used in the embodiment of FIG. 2.

FIG. 4 is an explanatory diagram showing coil energization corresponding to S1 to S6 signals of states 1 to 6 in FIG. 3;

FIG. 5 is an explanatory diagram of the pattern of the rotation detection signal from the Hall element that gives states 1 to 6 in FIGS. 3 and 4.

[Fig. 6] Drive waveform explanatory diagram of the first invention

[Fig. 7] Waveform explanatory diagram showing S1 to S6 signals according to the first invention

FIG. 8 is a flowchart showing waveform generation processing according to the first invention.

[Fig. 9] Drive waveform explanatory diagram of the second invention

FIG. 10 is an explanatory diagram showing waveform generation processing according to the second invention.

FIG. 11 is an explanatory diagram showing waveform generation processing according to the second invention (continued)

FIG. 12 is an explanatory diagram showing the time of each part of the waveform performed in the processing of FIGS. 10 and 11.

FIG. 13 is an explanatory diagram showing the on/off pattern of each phase when the duty ratio is 0.5 according to the third invention.

FIG. 14 is an explanatory diagram showing the on/off pattern of each phase when the duty ratio is 0.8 according to the third invention.

FIG. 15 is a flowchart showing signal processing of the third invention.

[Fig. 16] An explanatory diagram showing on-off patterns of each phase determined by comparison of random numbers and duty ratios of the fourth invention

[Fig. 17] S1~ generated in the fourth invention
Waveform explanatory diagram of S6 signal

FIG. 18 is a flowchart showing signal processing of the fourth invention.

[Fig. 19] Explanatory diagram showing conventional drive waveforms

[Explanation of symbols]

1: DC motor 2: Control section 3: Rotor 4-1 to 4-3: Hall element 5: Microprocessor (MPU) 6, 10: Input register 7: Output register 8: Level conversion circuit 9: Switching circuit

Claims (9)

[Claims] Claim 1: An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and controls the duty of the coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2), wherein the control section (2) includes means for generating a drive pulse signal that turns the coil current on and off twice in each coil switching phase. Motor control method. Claim 2: An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and controls the duty of the coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2) In the motor control system comprising A motor control method characterized by comprising means for generating a drive pulse to which minute pulses are added. 3. An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2), the control unit (2) cumulatively adds a duty ratio for each coil switching phase that constitutes one rotation, and controls the coil switching in which the integer part of the cumulative addition value has changed. The motor 1 is provided with means for setting the drive pulse signal of the phase to an on-pulse and the drive pulse signal of the coil switching phase whose integer part does not change to an off-pulse.
A motor control method characterized by duty control based on the number of on-pulse phases and the number of off-pulse phases among the (N×M) coil switching phases that constitute rotation. 4. An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2) In the motor control system comprising If the random number is smaller than the duty ratio, the drive pulse signal is set as an on-pulse, and if the random number is equal to or greater than the duty ratio, the drive pulse signal is set as an off-pulse. A motor control method characterized by duty control based on the number of phases and the number of off-pulse phases. 5. An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2), the control unit (2) includes a first means for generating a drive pulse signal that turns the coil current on and off twice within the coil switching phase; a second means for generating a drive pulse signal in which minute pulses with a short time width are added to the parts where the coil switches from on to off and from off to on; and a drive pulse signal of the first means and the second means for each coil switching phase. A motor control system characterized by comprising a switching means for alternately outputting the following. 6. An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2), the control unit (2) includes a first means for generating a drive pulse signal that turns the coil current on and off twice for each coil switching phase; and a drive pulse signal. a second means for generating a drive pulse signal in which minute pulses with a short time width are added to the parts where the coil switches from on to off and from off to on; and a duty ratio, and if the random number is smaller than the duty ratio, the switching means outputs the driving pulse signal of the first means, and if the random number is equal to or higher than the duty ratio, the switching means outputs the driving pulse signal of the second means. A motor control method characterized by: [Claim 7] An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2) In the motor control system comprising A means for generating a drive pulse to which minute pulses are added, cumulatively adding a duty ratio for each coil switching phase constituting one rotation, and adding the minute pulses at a coil switching phase where the integer part of the cumulative addition value changes. A motor control method comprising means for outputting a drive pulse signal and stopping output of the drive pulse signal at a coil switching phase in which the integer part does not change. 8. An N-phase M-pole DC motor (1), one rotation of the DC motor (1) is divided into (N×M) coil switching phases, and the direction of current flowing through the stator coil is determined in a predetermined order. A control unit (1) that repeatedly switches coil phases in units of (2×N) phases to generate a rotating magnetic field, and duty-controls a coil energization period using a drive pulse signal in each phase to drive the DC motor (1). 2), the control unit (2) controls a small time width in the portion where the drive pulse signal switches from on to off and from off to on within each phase for each coil switching phase. a micropulse adding means for adding a micropulse, and a random number is set for each coil switching phase constituting one rotation, the random number is compared with a duty ratio, and if the random number is smaller than the duty ratio, the micropulse is added. A motor control system comprising means for outputting a drive pulse signal and stopping output of the drive pulse signal if the random number is equal to or greater than a duty ratio. 9. The motor control method according to claim 1, wherein a three-phase eight-pole DC motor is used as the DC motor (1).