JPH04364394A - Brushless motor - Google Patents

Abstract

PURPOSE:To realize a quiet motor by reducing noise vibration generated at the time of operating a brushless DC motor. CONSTITUTION:1) Noise of a motor is previously measured, a current waveform in which noise of a frequency synchronized with a rotation is reduced, is obtained, the waveform is stored in a PROM 600, this information is called at the time of operating, a current corresponding to a load is applied to driving coils 51, 52 53 thereby to reduce the noise. 2) Noise measuring means made of a microphone 620, etc., is provided in an apparatus, noise at the time of operating is measured, and a current waveform is always so set that the noise of the frequency synchronized with the rotation becomes a predetermined value or less. 3) Noise measuring means made of a microphone 622, etc., is provided in an apparatus, noise of an initial state of an operation is measured, and a current waveform is so set that the noise of the frequency synchronized with the rotation at that time becomes a predetermined value or less. This information is stored in a RAM 605, and then it is operated with the waveform as a reference.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor used in various electronic devices such as video tape recorders (hereinafter abbreviated as VTR).

0002

[Prior Art] In recent years, VTRs have been required to be smaller and thinner, as well as to have lower noise. To this end, motors, which are the core components of VTRs, have also been made smaller, thinner, and more compact.
There is a growing demand for lower noise.

FIG. 1 shows a cross-sectional view of a motor section of a rotary head device of a VTR in a conventional example and in the present invention. In the figure, a rotor magnet 1 magnetized into a plurality of poles in the direction of the rotation axis is fixed to a back yoke 2 made of a magnetic material by adhesive or the like. Further, a rotating yoke 3 made of a magnetic material is arranged to face the rotor magnet 1 and rotates integrally with the shaft 80. This shaft 80 is rotatably supported by a fixed drum 90 via a bearing 200. Further, in the gap formed by the rotor yoke 3 and the rotor magnet 1, the armature 5 is fixed to the fixed drum 90 with screws 85. The armature 5 is composed of drive coils 51, 52, and 53 formed by etching or plating, arranged at equal pitches on both sides of an insulating substrate 4 made of heat-resistant resin, as shown in FIG. Here, the drive coils 51, 52, and 53 have three phases, and twelve drive coils are arranged on each surface of the insulating substrate 4. Note that through holes 6 are provided to electrically connect both surfaces of the insulating substrate 4.

Further, on the armature 5, on the side opposite to the rotating yoke 3, there is provided a 3.
Hall elements 31, 32, and 33 are arranged. As a drive circuit for driving the motor, as shown in FIG.
2, 43, 44, 45, and 46. Transistors 41, 42, and 43 are connected to a power source 800, and transistors 44, 45, and 46 are grounded via a detection resistor 48. Further, the outputs of the Hall elements 31, 32, and 33 are input to the current control circuit 500.

The operation of a rotary head device equipped with a conventional motor configured as described above will be described below. As shown in FIG. 3, from the rotor magnet 1, an axial leakage magnetic flux 60 and a fringing magnetic flux 61 are generated as leakage magnetic flux. The Hall elements 31 , 32 , and 33 detect leakage magnetic flux 60 in the axial direction of the rotor magnet 1 and input an output signal with an amplitude proportional to this leakage magnetic flux 60 to the current control circuit 500 . The current control circuit 500 includes three Hall elements 31 and 32.
, 33, the first phase drive coil 51, the second phase drive coil 52, and the third phase drive coil 53 are sequentially switched on and off. Hall elements 31 and 32 at this time
, 33 and the energization waveforms 201, 202, 203 for each phase are shown in FIG. 10(A). As shown in the figure, the energization waveforms I201, 202, and 203 are rectangular waves with an electrical angle of 120°.

[0006] Here, the energization waveforms I201 and 20 shown in the same figure
2, 203 is applied to the drive coils 51, 52, 53, the rotor magnet 1 receives rotational biasing force from the armature 5 and continues to rotate in a predetermined direction. Note that when the rotor magnet 1 is rotationally driven, the drive coils 51, 52, and 53 are
), the back electromotive force voltages 301, 302, 303
occurs.

[0007]

However, the above configuration has the following problems.

When a current is applied to the drive coils 51, 52, 53, a rotational urging force is generated because the drive coils 51, 52, 53
This is because the current applied to follows Fleming's left-hand rule.

However, from the rotor magnet 1, a fringing magnetic flux 6 is generated as a leakage magnetic flux other than the axial component 60.
1 is also generated at the same time, and this fringing magnetic flux 61 and the current create an excitation force that attracts and repels each other in the axial direction between the drive coils 51, 52, 53 and the rotor magnet 1 according to Fleming's left-hand rule. occurs. The principle of generation of this attractive and repulsive force can be explained from another perspective as follows. When a unit DC current is applied to one of the three-phase drive coils to forcibly rotate the rotor magnet 1,
When the polarity of the magnetic poles of the rotor magnet 1 and the polarity of the drive coil are opposite to each other, attraction occurs, and when the polarity is the same, repulsion is generated. At this time, the excitation force per unit DC current of each phase is Kz491
,492,493. Then Kz491,492,
493, when the number of magnetized poles of the rotor magnet is 2P poles (P is an integer), as shown in FIG. 10(A), an alternating force is generated P times while the rotor magnet 1 rotates once.

However, in order to perform rotational drive in an actual motor, the energization waveforms I201, 202, 203 applied to the drive coils 51, 52, 53 are changed to 1 in accordance with the rotational phase of the rotor magnet 1 as shown in the figure. Since the polarity is switched P times during rotation, the excitation force Fz when the motor is running
401, 402, 403 are energizing waveforms I201, 20 to excitation force Kz491, 492, 493 per unit DC current.
2,203, resulting in an alternating force of 2P times during one rotation, as shown in the figure. This can be expressed numerically as follows. When first considering the first phase excitation force Fz401, it becomes as shown in (Equation 1).

[0011]

[Math 1]

Here, in (Equation 1), the excitation force Kz per unit DC current and the energization waveform I are respectively,

[0013]

[Math 2]

[0014]

[Math 3]

[0015] Therefore, by substituting (Math. 2) and (Math. 3) into (Math. 1), we get

[0016]

[Math 4]

[0017] The excitation forces of the second phase and the third phase can be calculated in the same way, so their description is omitted here.

For example, here, both the excitation force Kz per unit DC current and the drive current I have a first-order component as a fundamental wave (j=1
, k=1). At this time, the excitation force Fz401 is

[0019]

[Math 5]

[0020] Therefore, the excitation force Fz401 has only a single component. However, as shown in the figure, the actual energization waveforms I201, 202, and 203 generally have a rectangular waveform with an electrical angle of approximately 120 degrees, and thus have harmonic components. By the way, amplitude 1 is 12
The Fourier series of a rectangular wave current at 0° has the following values.

[0021] Primary: 1.108, Tertiary: 0.011,
5th: 0.215, 7th: 0.163, 9th: 0
．． 011 11th: 0.094, 13th: 0.090, 15th: 0
．． 011, 17th: 0.059, 19th: 0.063 (
(The following is omitted) Therefore, even if the excitation force Kz per unit DC current has only a first-order component as a fundamental wave, the excitation force Fz401 generated in the drive coil of each phase,
402 and 403 have 2nd, 4th, 6th, 8th, . . . (even-order) frequency components. Here, a frequency analysis diagram of a composite excitation force 400 obtained by adding the three-phase excitation forces FZ401, 402, and 403 is shown in FIG. 12(A). In this example, the number of magnetized poles of the rotor magnet 1 is 16 (that is, P
= 8), and the rotational speed is 45 revolutions per second. Therefore, in the same figure, 2.16KHz, which has the highest level, is 6
Corresponds to the harmonic component. As shown in the figure, 6, 12,
18...The three-dimensional components have the same generated phase, so they emphasize each other. Note that the other components cancel each other out topologically, and their levels are suppressed.

When such an excitation force is generated, the armature 5
will vibrate and generate noise. This excitation force or noise is proportional to the load torque applied to the motor, that is, to the current value. Generally speaking, as the rotation speed increases, harmonic components become more audible to the human ear (several K).
Hz) noise. Particularly in camera-integrated VTRs, this motor noise enters the microphone and is recorded as noise in the audio signal, or is perceived as harsh noise by the photographer, significantly reducing the sound quality and quality of the device. There was a problem.

[0023] In order to reduce this noise, conventionally adopted methods include energizing waveforms 221, 222, 2
23 into a sinusoidal waveform as shown in FIG. As shown in FIG. 11, the excitation force Kz491 per current generally includes not only a first-order component but also harmonic components, so even in this case, the excitation force Fz421, 42
2,423 is the 2nd, 4th, 6th, 8th...order component (even order)
will have the following. Note that the excitation force K per unit DC current
The frequency analysis results of z492 and 493 are the same as the excitation force Kz491 per unit DC current. Here, a frequency analysis diagram of the composite excitation force 420 obtained by adding the three-phase excitation forces FZ421, 422, and 423 is shown in FIG. 12(B). In this case, by making the energization waveforms 221, 222, and 223 sinusoidal, the harmonic components of the composite excitation force 420 are
), but the 2.16 KHz component is still large.

Furthermore, if there are factors such as variations in motor assembly, the noise level between individual motors will also vary greatly.

[0025]

[Means for Solving the Problems] The technical means of the first invention to solve the above problems is to apply a certain load to the motor in advance and measure the noise at a frequency synchronized with the rotation of the motor. At that time, find a current waveform that reduces this noise, store this basic waveform in a storage means such as PROM, and when actually using it, call up the basic current waveform information in this PROM and calculate the load and rotation. By applying current to the coil that corresponds to the phase.

Further, the technical means of the second invention is to provide a noise measuring means in the equipment, measure the noise generated during operation in synchronization with the rotation of the motor, and keep the noise below a predetermined value. By constantly setting the current waveform.

[0027] Further, the technical means of the third invention is to provide a noise measuring means in the equipment, measure the noise of a frequency synchronized with the motor generated in the initial state of operation, and adjust the noise so that the noise is below a predetermined value. Set the basic current waveform. This basic current waveform information is stored in the RAM, and subsequent operations are performed based on this basic current waveform information.

[0028]

[Operation] The operation of the technical means of the first invention is as follows. In other words, as mentioned above, apply a certain load to the motor in advance, measure the noise at a frequency synchronized with the rotation of the motor, find the current waveform that will reduce this noise, and store this basic waveform in the PROM. When the motor is assembled, the basic current waveform information in this PROM is recalled and a current corresponding to the load and rotational phase is applied to the coil, thereby eliminating dimensional variations when the motor is assembled. Even if such problems occur, it becomes possible to set the optimum current waveform for each individual motor, and it becomes possible to achieve quietness.

Further, the effects of the technical means of the second invention are as follows. In other words, by installing a noise measuring means in the equipment as described above, and measuring the noise synchronized with the rotation of the motor that occurs during operation, the current waveform is constantly set so that this noise is below a predetermined value. ,
To set the optimum current waveform for each individual motor and the current operating condition, even if there are changes in operating conditions such as temperature/humidity environment, load applied to the motor, rotation speed, etc., as well as variations in motor assembly. This makes it possible to reduce noise in, for example, a stationary VTR.

Further, the effects of the technical means of the third invention are as follows. That is, as described above, the equipment is equipped with a noise measuring means to measure the noise at a frequency synchronized with the motor generated in the initial state of operation, and the basic current waveform is set so that this noise is below a predetermined value. By storing this basic current waveform information in RAM and operating based on this basic current waveform information in subsequent operations,
To set the optimum current waveform for each individual motor and the current operating condition, even if there are changes in operating conditions such as temperature/humidity environment, load applied to the motor, rotation speed, etc., as well as variations in motor assembly. This makes it possible to reduce noise in, for example, a camera-integrated VTR.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of the motor section of the rotary head device of a VTR in this embodiment. In the figure, a rotor magnet 1 magnetized into a plurality of poles in the direction of the rotation axis is fixed to a back yoke 2 made of a magnetic material by adhesive or the like. Further, a rotating yoke 3 made of a magnetic material is arranged to face the rotor magnet 1 and rotates integrally with the shaft 80. This shaft 80
is rotatably supported by a fixed drum 90 via a bearing 200. Further, an armature 5 is mounted on a fixed drum 9 in a gap formed between the rotor yoke 3 and the rotor magnet 1.
0 with screws 85. This armature 5 is composed of drive coils 51, 52, and 53 formed by etching or plating, arranged at equal pitches on both sides of an insulating substrate 4 made of heat-resistant resin, as shown in FIG. 2(A). There is. Here, the drive coils 51, 52, and 53 have three phases, and twelve drive coils are arranged on each surface of the insulating substrate 4. Note that through holes 6 are provided to electrically connect both surfaces of the insulating substrate 4. Furthermore, on the armature 5, on the side facing the rotating yoke 3, three Hall elements 31, 32,
33 are arranged.

As a drive circuit for driving the motor,
As shown in FIG. 4, drive coils 51, 52, and 53 are connected in a star configuration, and their respective input terminals are connected to transistors 41, 42, 43, 44, 45, and 46. Transistors 41, 42, 43 are powered by a power source 800
The transistors 44, 45, and 46 are grounded via a detection resistor 48. Also, Hall element 3
The outputs of 1, 32, and 33 are input to the current control circuit 501.

The PROM 600 also stores basic energization waveform information for the drive coils 51, 52, and 53 in accordance with the rotational phase of the rotor magnet 1. This basic energization waveform information is
When the motor is assembled at the factory, the noise component synchronized with the rotation of the motor is measured with a predetermined load torque applied to the motor, and the current waveform is set so that this noise component is below a predetermined level. The current waveform of

FIG. 4 shows PRO on the motor assembly line.
The process up to writing basic energization waveform information to M600 is shown by a broken line. A microphone 625 for noise measurement is provided on the motor assembly line. Here, the output of the microphone 625 is passed through the amplifier 630 to
It is input to a digital filter 640. With a predetermined load torque applied to the operating motor, motor noise is input to the digital filter 640 from the microphone 625. With this digital filter 640,
A noise component with a frequency proportional to the motor's rotational frequency is extracted and its level is measured. The output of this digital filter 640 is input to a current waveform setting circuit 650. The current waveform setting circuit 650 sets the energization waveforms 211, 212, 213 applied to the drive coils 51, 52, 53 so that the noise component with a frequency proportional to the rotational frequency of the motor is smaller than a predetermined level. Energization waveforms 211 and 212 set by the current waveform setting circuit 650
, 213 are PR
Stored in OM600. The above is the process up to writing the basic energization waveform information into the PROM 600. Here, the energization waveform information calling means 610 for calling the basic energization waveform information stored in this PROM 600 is connected to the VTR main body 9.
It is connected to PROM600 of 00. The energization waveform information called here is input to the current control circuit 501 and compared with the outputs of the Hall elements 31, 32, and 33.
The drive current waveform to be applied to the drive coils 51, 52, 53 is controlled.

The operation and function of the rotary head device equipped with the motor of this embodiment constructed as described above will be explained below. As shown in FIG. 3, from the rotor magnet 1, an axial leakage magnetic flux 60 and a fringing magnetic flux 61 are generated as leakage magnetic flux. The Hall elements 31 , 32 , 33 detect leakage magnetic flux 60 in the axial direction of the rotor magnet 1 and input an output signal with an amplitude proportional to this leakage magnetic flux 60 to the current control circuit 501 . The current control circuit 501 includes three Hall elements 3
Based on the output signals of 1, 32, and 33 and the energization waveform information called from the PROM 600 by the energization waveform information calling means 610, the first phase drive coil 51, the second phase drive coil 52, and the third phase drive coil The energization is sequentially switched to 53 and 53. The output signals 101, 102, 103 of the Hall elements 31, 32, 33 at this time and the energization waveforms 211, 212, 213 for each phase are shown in FIG.

Here, the current shown in the figure is applied to the drive coil 51,
52 and 53, the rotor magnet 1 receives a rotational biasing force from the armature 5 and continues to rotate in a predetermined direction. Note that when the rotor magnet 1 is rotationally driven, the drive coils 51 and 52
, 53 have a back electromotive force voltage 301, as shown in FIG.
302 and 303 occur. Drive coils 51, 52, 5
When a current is applied to the drive coil 5, a rotational urging force is generated due to the axial leakage flux 60 shown in FIG.
This is because the currents applied to 1, 52, and 53 follow Fleming's left-hand rule. Here, a fringing magnetic flux 61 is simultaneously generated from the rotor magnet 1 as leakage magnetic flux other than the axial leakage magnetic flux 60, and this fringing magnetic flux 61 and current are driven according to Fleming's left-hand rule. Exciting forces are generated between the coils 51, 52, 53 and the rotor magnet 1 that attract and repel each other in the axial direction. This excitation force causes the armature 5 of the motor to vibrate in the axial direction, thereby generating noise and vibration.

In this embodiment, PROM600
a drive coil 51 corresponding to the rotational phase of the rotor magnet 1;
The basic energization waveform information for the drive coils 52 and 53 is stored, and is called by the energization waveform information calling means 610, and this energization waveform information is input to the current control circuit 501 to energize the drive coils 51, 52, and 53. Waveforms 211, 212, 21
It controls 3. This basic energization waveform information is obtained by measuring the noise component synchronized with the rotation of the motor with a predetermined load torque applied to the motor when the motor is assembled at the factory.
A current waveform is used when the current waveform is set so that this noise component is below a predetermined level. For example, the rotation speed is 45 revolutions per second, and the number of magnetized poles of rotor magnet 1 is 1.
When there are 6 poles (i.e. P=8), the problematic noise frequency f
teeth,

[0039]

[Math 6]

[0040] In order to reduce this frequency component, (j+k) or (j-
It is sufficient to apply a j-order current component such that k) is 6 to the energization waveform. Here, the excitation force per unit current Kz49
When 1 is expanded into a Fourier series, k=1 as shown in Figure 11.
The next component is the largest. Therefore, the frequency order of the current increment to be applied may be j=5 or 7.

Here, when the energization waveform is set to a value as shown in the following (Equation 7), the excitation force Fz411, 412,
413 and the combined excitation force 410 are shown in FIG.

[0042]

[Math. 7]

In (Equation 7), the current increment of the seventh order component is:
This is only 1% of the first order component of the fundamental wave. Therefore, the energization waveform 211 in FIG. 7 and the energization waveform 2 in FIG. 10(B)
There is apparently not much difference with 21. Therefore, there is no significant decrease in efficiency or increase in torque ripple regarding torque generation. However, when the combined excitation forces 400 and 420 are compared with each other, the difference in level is obvious.

A frequency analysis diagram of the combined excitation force 410 is shown in FIG. Comparing this with the frequency analysis diagram of the combined excitation force in FIG. 12(B) when the energization waveform is sinusoidal in the conventional example, it can be seen that the 2.16 KHz component is reduced by about 16 dB. To actually set the current waveform, apply a current increment with a frequency component proportional to the rotational frequency of the motor to the initial value of the current waveform, and adjust the phase so that the noise level of each frequency is reduced. Adjust the level. If the target level is still not reached when a current increment of a certain frequency component is applied, the frequency of the current increment may be changed again and the phase and level may be adjusted so as to reduce the noise level. Note that the load torque applied when measuring noise in a factory may be the load applied when the equipment is used. To apply a load, a magnetic field is applied to the conductive material portion of the motor rotor, and the eddy current loss generated at this time makes it possible to apply a non-contact load.

[0045] The drive current is set in this way, and the PR
By storing the information in the OM 600, it is possible to reduce the noise level during operation of the motor compared to a conventional motor. Furthermore, individual variations in motors can be absorbed, and assembly accuracy can be relaxed. Furthermore, since noise and vibration can be reduced, the chassis, exterior, etc. of the VTR can be made thinner and lighter, resulting in cost and weight reductions. Furthermore, especially in a camera-integrated VTR, it is possible to move the microphone 622 closer to the VTR mechanism, thereby making it possible to reduce the size and weight of the deck itself.

As described above, according to this embodiment, it is possible to reduce the noise and vibration of the motor, although the configuration is simple.

Next, an embodiment of the second invention will be described with reference to the drawings. Note that points that overlap with the first invention will be omitted here.

As a drive circuit for driving the motor,
As shown in FIG. 5, drive coils 51, 52, and 53 are connected in a star configuration, and their respective input terminals are further connected to transistors 41, 42, 43, 44, 45, and 46. Transistors 41, 42, 43 are powered by a power source 800
The transistors 44, 45, and 46 are grounded via a detection resistor 48. Also, Hall element 3
The outputs of 1, 32, and 33 are input to the current control circuit 502.

A microphone 620 for detecting equipment noise is also provided in the VTR main body 900, and detects noise when the motor is operating. The output of this microphone 620 is input to a digital filter 640 via an amplifier 630. Here, the digital filter 640 extracts a noise component with a frequency proportional to the rotational frequency of the motor, and its level is measured. The output of this digital filter 640 is input to a current waveform setting circuit 650. The current waveform setting circuit 650 sets the drive current waveform so that the noise component at a frequency proportional to the rotational frequency of the motor is smaller than a predetermined level.

Furthermore, the energization waveform information set by the current waveform setting circuit 650 is input to the current control circuit 502, where it is compared with the outputs of the Hall elements 31, 32, and 33, and is determined to be applied to the drive coils 51, 52, and 53. Controls the drive current waveform.

The operation and function of the rotary head device equipped with the motor of this embodiment constructed as described above will be explained below. As shown in FIG. 3, from the rotor magnet 1, an axial leakage magnetic flux 60 and a fringing magnetic flux 61 are generated as leakage magnetic flux. The Hall elements 31 , 32 , 33 detect leakage magnetic flux 60 in the axial direction of the rotor magnet 1 and input an output signal with an amplitude proportional to this leakage magnetic flux 60 to the current control circuit 502 . The current control circuit 502 includes three Hall elements 3
1, 32, 33 output signals and current waveform setting circuit 650
Based on the energization waveform information set in , the first phase drive coil 5
1, a second phase drive coil 52, and a third phase drive coil 53
The power is switched on sequentially. Hall element 3 at this time
1, 32, 33 output signals 101, 102, 103,
FIG. 7 shows energization waveforms 211, 212, and 213 for each phase.

Here, the current shown in the figure is applied to the drive coil 51,
52 and 53, the rotor magnet 1 receives a rotational biasing force from the armature 5 and continues to rotate in a predetermined direction.

When a current is applied to the drive coils 51, 52, 53, a rotational urging force is generated in the drive coils 51, 52, 53, with respect to the axial leakage flux 60 shown in FIG.
This is because the current applied to follows Fleming's left-hand rule. Here, from the rotor magnet 1, a fringing magnetic flux 61 is generated as a leakage magnetic flux other than the axial leakage magnetic flux 60.
The fringing magnetic flux 61 and the current also generate an excitation force that attracts and repels each other in the axial direction between the drive coils 51, 52, 53 and the rotor magnet 1, according to Fleming's left-hand rule. Occur. This excitation force causes the armature 5 of the motor to vibrate in the axial direction, thereby generating noise and vibration.

In this embodiment, the generated noise is detected by the microphone 620, and the current waveform setting circuit 650 is set so that the detected noise is below a predetermined value.
The drive current is always set at . Therefore, the excitation forces 411, 412, 413 and the combined excitation force 410 are as shown in FIG.

To set the current waveform, apply a current increment with a frequency component proportional to the rotational frequency of the motor to the initial value of the current waveform, and at this time, set the current waveform so that the noise level at each frequency is reduced. Adjust phase and level. If the target level is not reached when a current increment of a certain frequency component is applied, the frequency of the current increment may be changed again and the phase and level may be adjusted so that the noise level is reduced.

[0056] In this way, by constantly monitoring the noise of the equipment and setting the energization waveform so that the noise is below a predetermined level, it is possible to reduce the noise level during motor operation compared to conventional motors. It becomes possible. Furthermore, individual variations in motors can be absorbed, and assembly accuracy can be relaxed. Furthermore, since noise and vibration can be reduced, the chassis and exterior of the VTR can be made thinner and lighter, resulting in lower costs and lighter weight.

As described above, according to this embodiment, it is possible to reduce the noise and vibration of the motor, although the configuration is simple.

Next, an embodiment of the third invention will be described with reference to the drawings. Note that points that overlap with the first invention will be omitted here.

As a drive circuit for driving the motor,
As shown in FIG. 6, the drive coils 51, 52, and 53 are connected in a star configuration, and their respective input terminals are connected to transistors 41, 42, 43, 44, 45, and 46. Transistors 41, 42, 43 are powered by a power source 800
The transistors 44, 45, and 46 are grounded via a detection resistor 48. Also, Hall element 3
The outputs of 1, 32, and 33 are input to the current control circuit 502.

The VTR main body 900 is also provided with an imaging device such as a CCD (not shown) for photographing an image, and a microphone 622 for recording.
It consists of Here, the output of the microphone 622 is
Through the amplifier 630, the changeover switches 635, 63
6, the signal is selectively input to the digital filter 640 and the audio processing circuit 700. During shooting, audio information detected by the microphone 622 is input to the audio processing circuit 700 and recorded on a tape (not shown) by the audio recording circuit (not shown) and audio head (not shown) of the VTR. Ru.

On the other hand, when the tape is loaded onto the rotating drum and the motor of the rotating drum is rotating and the digital filter 640 is in standby mode, the microphone 6
22, the noise of the VTR mechanism is input. This digital filter 640 extracts a noise component with a frequency proportional to the rotational frequency of the motor and measures its level. The output of this digital filter 640 is input to a current waveform setting circuit 650. The current waveform setting circuit 650 sets the energization waveforms 211, 212 to be applied to the drive coils 51, 52, 53 so that the noise component at a frequency proportional to the rotational frequency of the motor is smaller than a predetermined level.
, 213 are set. The energization waveforms 211, 212, and 213 set by the current waveform setting circuit 650 are stored in the RAM 605 by the energization waveform information writing means 615.

Here, energization waveform information calling means 610 for calling the energization waveforms 211, 212, and 213 stored in this RAM 605 is connected to the RAM 605. The energization waveform information called here is the current control circuit 50.
3 and is compared with the outputs of the Hall elements 31, 32, 33 to control the drive current waveforms to be applied to the drive coils 51, 52, 53.

The operation and function of the rotary head device equipped with the motor of this embodiment constructed as described above will be explained below. As shown in FIG. 3, from the rotor magnet 1, an axial leakage magnetic flux 60 and a fringing magnetic flux 61 are generated as leakage magnetic flux. The Hall elements 31, 32, and 33 detect leakage magnetic flux 60 in the axial direction of the rotor magnet 1, and input an output signal with an amplitude proportional to this leakage magnetic flux 60 to the current control circuit 503. The current control circuit 503 includes three Hall elements 3
Based on the output signals of 1, 32, and 33 and the energization waveform information called out from the RAM 605 by the energization waveform information calling means 610, the first phase drive coil 51, the second phase drive coil 52, and the third phase drive coil The energization is sequentially switched to 53 and 53. At this time, the output signals 101, 102, 103 of the Hall elements 31, 32, 33 and the energization waveform 2 to each phase
11, 212, and 213 are shown in FIG.

Here, the current shown in the figure is applied to the drive coil 51,
52 and 53, the rotor magnet 1 receives a rotational biasing force from the armature 5 and continues to rotate in a predetermined direction. The reason why a rotational urging force is generated when a current is applied to the drive coils 51, 52, 53 is that the current applied to the drive coils 51, 52, 53 is Fleming's By following the left hand rule. here,
From the rotor magnet 1, a fringing magnetic flux 61 is simultaneously generated as a leakage flux other than the axial leakage flux 60, and this fringing magnetic flux 61 and current are also generated in the drive coil 51, according to Fleming's left-hand rule. 52, 53
An excitation force is generated between the rotor magnet 1 and the rotor magnet 1 to attract and repel each other in the axial direction. This excitation force causes the armature 5 of the motor to vibrate in the axial direction, thereby generating noise and vibration. In this embodiment, the noise generated during the shooting standby state is detected by the microphone 622, and the current waveform setting circuit 650 sets the energization waveforms 211, 212 so that the detected noise is below a predetermined value. , 213 are set. Therefore, the excitation forces 411, 412, 413 and the combined excitation force 41
0 is as shown in FIG.

To set the current waveform here, apply a current increment with a frequency component proportional to the rotational frequency of the motor to the initial value of the current waveform, and at this time, set the current waveform so that the noise level at each frequency is reduced. , adjust phase and level. If the target level is not reached when a current increment of a certain frequency component is applied, the frequency of the current increment may be changed again and the phase and level may be adjusted so that the noise level is reduced.

In this way, the noise of the equipment is monitored in the shooting standby state, and the energization waveforms 211, 212, and 213 are set so that the noise is below a predetermined level.
05 and called up and controlled during actual photographing, it is possible to reduce the noise level during motor operation compared to conventional motors. Furthermore, individual variations in motors can be absorbed, and assembly accuracy can be relaxed. Furthermore, since noise and vibration can be reduced, the chassis and exterior of the VTR can be made thinner and lighter, resulting in lower costs and lighter weight. In particular, in a camera-integrated VTR, the microphone 622 is
Since it is possible to get closer to the TR mechanism,
It becomes possible to reduce the size and weight of the deck itself.

As described above, according to this embodiment, it is possible to reduce the noise and vibration of the motor despite the simple configuration.

In this embodiment, the energization waveforms for three phases are stored, but if the variation in coil shape etc. is small, only the energization waveform for one phase may be stored as a representative. Further, in this embodiment, the noise is monitored in the photographing standby state, but it may also be periodically monitored during photographing or when the load on the motor changes significantly.

Note that in each of the embodiments of the first, second, and third inventions, the output signals of the Hall elements 31, 32, and 33 were used to detect the rotational phase of the rotor magnet 1; The invention is not limited to this, for example, the back electromotive force voltages 301, 302,
A so-called sensorless drive method may be adopted in which the phase is detected by detecting the 0 cross point of 303. Or a frequency generator that detects the rotational speed of the motor.
The phase may be detected using a Generator (not shown) and a Pulse Generator (not shown) that generates a signal once per revolution of the motor and detects the absolute position of the rotor.

Furthermore, although the present embodiment has been described as a motor for a rotating drum device for a VTR, the present invention is not limited thereto, and can be applied to any type of brushless motor for any purpose. It is clear that it is possible.

[0071]

Effects of the Invention As described above, according to the brushless motor according to the first invention, a certain load is applied to the motor in advance and noise at a frequency synchronized with the rotation of the motor is measured. Find a current waveform that reduces By applying the current to the coil, even if dimensional variations occur when the motor is assembled, it becomes possible to set the optimum current waveform for each individual motor, and it becomes possible to achieve quietness.

On the other hand, according to the brushless motor according to the second aspect of the invention, the device is provided with a noise measuring means, and while the noise generated during operation is measured in synchronization with the rotation of the motor, this noise is adjusted to a predetermined value. By constantly setting the current waveform as shown below, even if there are changes in operating conditions such as temperature/humidity environment, load applied to the motor, rotation speed, etc., as well as variations in motor assembly, each individual motor can be Moreover, it becomes possible to set the optimum current waveform for the current operating situation, and it becomes possible to achieve quietness in, for example, a stationary VTR.

Furthermore, according to the brushless motor according to the third aspect of the present invention, the device is provided with a noise measuring means to measure the noise of a frequency synchronized with the motor generated in the initial state of operation, and the noise becomes below a predetermined value. Set the basic current waveform as follows. This basic current waveform information is stored in RAM,
In subsequent operations, by operating based on this basic current waveform information, the motor will remain stable even if there are changes in operating conditions such as temperature/humidity environment, load applied to the motor, rotation speed, etc., as well as variations in motor assembly. It is now possible to set the optimal current waveform for each individual and the operating situation at that time.
For example, it becomes possible to achieve quietness in a camera-integrated VTR or the like.

[Brief explanation of drawings]

[Fig. 1] Side sectional view of a rotating drum device equipped with a brushless motor according to the present invention and a conventional example.

[Fig. 2] Plan view of armature in the present invention and conventional example

[Figure 3] Schematic diagram of magnetic flux flow in a magnetic circuit

[Figure 4] First
Drive circuit diagram in one embodiment of the invention of

[Fig. 5] Drive circuit diagram in an embodiment of the second invention

[Fig. 6] Drive circuit diagram in an embodiment of the third invention

[Figure 7] First, second, third
Phase relationship diagram of various signals in the invention of

[Figure 8] Frequency analysis diagram of composite excitation force in the first, second, and third inventions

[Figure 9] Drive circuit diagram in conventional example

FIG. 10 (a) is a phase relationship diagram of various signals in a conventional example; (b) is a phase relationship diagram of various signals in another conventional example;

[Figure 11] Frequency analysis diagram of excitation force Kz per unit current

[Figure 1
2] (a) is a frequency analysis diagram of the composite excitation force in a conventional example (b) is a frequency analysis diagram of the composite excitation force in another conventional example

[Explanation of symbols]

1 Rotor magnet 5 Armature 31, 32, 33 Hall element 51, 52, 53 Drive coil 500, 501, 502, 503 Current control circuit 60
0 PROM 605 RAM 610 Energization waveform information calling means 615 Energization waveform information writing means 620, 622, 625 Microphone 630 Amplifier 640 Digital filter 650 Current waveform setting circuit

Claims (3)

[Claims] 1. An energization waveform storage means in which basic energization waveform information for the coil according to the rotational phase of the rotor is stored in advance, and an energization device for calling up information on the basic energization waveform stored in the energization waveform storage means. a waveform information calling means, a rotational phase detection means for detecting the rotational phase of the rotor, and the basic energization waveform is amplified according to the rotational phase of the rotor and the load torque of the motor detected by the rotational phase detection means. and an energizing means for applying a current to the coil, and measures a noise component synchronized with the rotation of the rotor with a predetermined load torque applied to the motor, and measures the noise component to keep the noise below a predetermined level. A brushless motor whose energization waveform information is a current waveform when the current waveform is set to . 2. Noise detection means for detecting equipment noise; noise component extraction means for extracting a noise component proportional to the rotational frequency of the rotor of the motor from among the noise measured by the noise detection means; a rotational phase detection means for detecting the rotational phase of the child; an energization waveform setting means for setting a current waveform to be applied to the coil so that the noise component is below a predetermined level; and a current set by the energization waveform setting means. A brushless motor comprising an energizing means for applying a waveform to a coil. 3. A noise detection means for detecting the noise of the equipment in a predetermined operation mode of the equipment, and extracting a noise component proportional to the rotational frequency of the motor rotor from the noise measured by the noise detection means. Noise component extraction means;
rotational phase detection means for detecting the rotational phase of the rotor;
energization waveform setting means for setting a current waveform applied to the coil so that the noise component is below a predetermined level; energization waveform storage means for storing current waveform information set by the energization waveform setting means; energization waveform information calling means for calling information on the energization waveform stored in the energization waveform storage means; and energization waveform information calling means in accordance with the rotational phase of the rotor and the load torque of the motor detected by the rotational phase detection means. 1. A brushless motor comprising: energizing means for applying to a coil a current obtained by amplifying the energizing waveform called by the brushless motor.