JP3299435B2 - Device for detecting rotor position of brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor position detecting device for a brushless motor, and more particularly to a floppy disk using a change in magnetic field of a magnetic pole of a rotor of a brushless motor used as a spindle motor of a floppy disk driving device. The present invention relates to a rotor position detecting device suitable for generating an index signal for drive control and the like.

[0002]

2. Description of the Related Art A floppy disk drive device is provided with an index signal output device for detecting the rotation of a motor and generating and outputting an index signal in order to know the start position of a data track on the floppy disk. In recent years, a floppy disk drive index signal output device for driving a 3.5-inch floppy disk, which is increasing in demand, employs either an electromagnetic generation method or a photoelectric generation method.

An index signal output device adopting an electromagnetic generation method includes an index magnet provided on the outer periphery of a rotor of a spindle motor for rotating a disk, and a magnetic element such as a Hall element and a Hall IC for detecting the magnetic force of the index magnet. A detector for generating an index signal. The index signal output device adopting the photoelectric generation method includes an index reflector provided on the outer periphery of the rotor of the spindle motor, and a light detector such as an optical transistor for receiving light emission of a light signal and a reflected light signal. And generates an index signal.

Each of the magnetic detector and the photodetector is fixed to a board (circuit board) on which a spindle motor is mounted. This type of index signal output device is provided with a movable adjustment mechanism that can move a fixed position of a magnetic detector or a photodetector for the purpose of making the index signal coincide with a predetermined track start position.

Further, instead of the above-mentioned system having mechanical parts such as the index magnet and the magnetic detector, the index reflector and the photodetector, an index signal output device for electrically generating an index signal has been developed. (For example, JP-A-2-10569). In this index signal output device, as shown in FIG. 6 (operation timing chart), first, a substantially sinusoidal output peak (A) of a Hall element generated by rotation of a rotor magnet mounted on a rotor of a spindle motor.
Point), and charge the capacitor with the held voltage as the reference voltage. The reference voltage charged in the capacitor decays with time. Then, the attenuated reference voltage is compared with the detected voltage at the peak (point B) of the substantially sine wave in the cycle of the next stage of the output of the Hall element, and when the detected voltage is lower than the reference voltage, the index is determined. Generate and output signals.

[0006]

However, in the conventional index signal output device, the index magnet and the magnetic detector, the index reflection plate and the photodetector are used in both the electromagnetic generation system and the photoelectric generation system. The number of external mechanical parts such as mechanical parts and mechanical parts of the movable adjustment mechanism increases. For this reason, there is a problem that the man-hour for assembling the index signal output device increases, and as a result, the man-hour for assembling the spindle motor increases.

[0007] Further, the increase in the number of external mechanical parts and the increase in the number of assembling steps increase the product price of the spindle motor. A great deal of labor is also required for maintenance.

The index signal output device for electrically generating an index signal can reduce the number of mechanical parts as much as possible, and can solve the above-mentioned problem as a so-called sensorless device. However, as shown in FIG. 6, when the amplitude of the output waveform of the Hall element fluctuates as at point C, if a reference voltage is generated at the peak when the amplitude changes, the reference voltage and the next In accordance with the result of comparison with the voltage of the peak (point D) of the sine wave of the cycle of the stage, an index signal that should not be output is output, and a malfunction occurs. Therefore, in order to clearly distinguish the reference voltage from the sine waveform of the Hall element output, the rotor magnetic pole was magnetized stronger than the magnetic force of the magnetic pole so that a larger amplitude waveform was generated at the peak portion of the sine waveform. It is conceivable to improve the accuracy by providing a portion and comparing the detection waveform of the strong magnetization portion with a reference voltage.

However, recently, in order to improve the driving force of the brushless motor, the magnetic pole of the rotor magnet is often subjected to saturation magnetization. The problem in this case is
When the magnetic pole is in a saturated state, it is practically impossible to perform stronger magnetization. Therefore, when a strong magnetized portion having a magnetic force stronger than the magnetic force of the magnetic pole of the rotor magnet is provided, the magnetic pole of the rotor magnet cannot be saturated and magnetized, and as a result, the efficiency of the motor decreases. .

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the number of mechanical parts in the apparatus configuration and to generate an accurate index signal without reducing the efficiency of a brushless motor even when the magnetic poles of a rotor magnet are saturated. An object of the present invention is to provide a device for detecting a rotor position of a brushless motor.

[0011]

In order to solve the above-mentioned problems, the present invention provides a rotor magnet mounted on a rotor and having a plurality of driving magnetic poles, and a rotor magnet disposed in a region facing the rotor magnet. A plurality of magnetic detecting means for detecting a magnetic field passing by rotation of the magnet and outputting a rotational position signal having a substantially sinusoidal waveform of a plurality of phases; and a predetermined electrical angle from a magnetic center of at least one driving magnetic pole of the rotor magnet. A position detection magnetic pole formed at a position where the angular phase is advanced, and generating a magnetic field weaker than the driving magnetic pole, and a positive / negative in each cycle of an arbitrary phase of the rotation position signal output from the magnetic detection means. A reference voltage generation unit that samples and holds a value at a predetermined point before any one of the peaks and outputs a reference voltage; By comparing the reference voltage output from the force it has been rotated position signal and the reference voltage generating means, and the index signal combining means for outputting the index signal,
It is comprised including.

In the position detecting device according to the present invention, the position detecting magnetic pole is magnetized with a magnetic force weaker than the magnetic force of the magnetic pole provided with the position detecting magnetic pole. In the output waveform of the rotational position signal output from the controller, a concave deformed portion occurs at a stage before the peak of each cycle. On the other hand, the voltage at a predetermined point before the peak of each cycle in the output waveform of the rotation position signal is sampled and held as a reference voltage by the reference voltage generation means, and the reference voltage is converted to the voltage of the rotation position signal by the index signal synthesis means. Is compared to And in this case,
The vicinity of the peak of the rotational position signal immediately after the deformed portion has a value higher than the reference voltage, and as a result, an index signal is generated from the index signal combining means.

That is, according to the present invention, even if the magnetic poles of the rotor magnet are made to be in the saturation magnetization, the position detecting magnetic poles may have a magnetic force weaker than the peripheral magnetic force. It is possible to improve the accuracy of the index signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2A and 2B show the configuration of an embodiment of a brushless motor according to the present invention. FIG. 1 is a side view having a partial vertical cross section of the brushless motor, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a horizontal cross sectional view. The brushless motor is a spindle motor for a floppy disk drive.

As shown in FIGS. 1 and 2, the brushless motor 1 is, for example, a circumferentially opposed three-phase brushless motor. This brushless motor 1 includes a board (circuit board)
2, a shaft 3, a rotor (rotor case) 4, a rotor magnet 5, a coil 6, a laminated core 7, and a bearing 8.

A circuit element such as a drive control LSI (not shown) for controlling the drive of the brushless motor 1, a resistance element, a capacitance element and the like is mounted on the substrate 2. A bearing 8 is fixed on the substrate 2, and a laminated core 7 around which a coil 6 is wound is attached to the bearing 8. The bearing 8 rotatably supports the shaft 3 erected at the center of the substantially cup-shaped rotor 4. An annular rotor magnet 5 is mounted on the inner peripheral surface of the peripheral wall of the rotor 4, and the rotor magnet 5 faces the laminated core 7 at an appropriate interval.

The rotor 4 has a chucking pin 4 on its upper surface.
B and a chucking magnet 4A. That is,
The brushless motor 1 of this embodiment drives a 3.5-inch floppy disk to rotate. When a predetermined current is applied to the coil, the rotor 4 of the brushless motor 1 rotates about the shaft 3 by the electromagnetic action of the rotor magnet 5 and the laminated core 7, and the rotor 4 is rotated by the chucking pin 4B and the chucking magnet. The floppy disk is rotated via 4A.

The rotor magnet 5 is shown in FIGS.
As shown in (a development view schematically showing the magnetic poles of the rotor magnet), a plurality of magnetic poles of N and S poles are arranged along the circumference of the rotor 4. In the present embodiment,
The rotor magnet 5 is magnetized in a total of eight sets, that is, 16 poles, with one set of the N pole and the S pole. Since the circumference of the rotor 4 is 360 degrees in mechanical angle, the N pole and the S pole are sequentially arranged every 22.5 degrees in mechanical angle.

The laminated core 7 has a plurality of salient poles projecting radially. As shown in FIG.
In the present embodiment, a total of 12 salient poles of the laminated core 7 are arranged every 30 degrees in mechanical angle. A three-phase coil 6 is wound around each salient pole.

Of the twelve laminated cores 7, a hall element 18 as a magnetic detecting means is provided on the surface of the substrate 1 between four predetermined continuous salient poles and a total of three.
Are placed. That is, as shown in FIGS. 2 and 3, the Hall elements 18U, 18V and 18W are arranged on the surface of the substrate 1.

The magnetic detecting means 18 detects the magnetic fields of a plurality of magnetic poles as the rotor magnet 5 mounted on the rotor 4 rotates, and generates a rotational position signal (sine wave electromotive force, current or voltage) having a substantially sinusoidal waveform. Is output. Hall element 18U is 3
The U-phase (first phase) of the phase rotation position signal is output. Hall element 18V outputs the V phase (second phase) of the three-phase rotation position signals. In addition, Hall element 18W
Outputs the W phase (third phase) of the three-phase rotation position signals.

Each of the Hall elements 18U, 18V, and 18W maintains a mechanical angle of 15 degrees from the center of the salient poles of two adjacent laminated cores 7 and has a mechanical angle of 30 degrees from each other. It is arranged at. This Hall element 18
Each of U, 18V, and 18W is not newly provided to generate an index signal, but a Hall element, which is a conventional magnetic detection unit for driving a brushless motor, is used as it is.

A plurality of magnetic poles of the rotor magnet 4;
Laminated core 7, Hall elements 18U, 18V and 18W
As shown in FIG. 3, each time one set of magnetic poles (N, S) passes in the vicinity of the Hall element 18, the brushless motor 1 outputs one cycle of a substantially sinusoidal waveform. Can output the rotational position signal. The waveform in FIG. 3 shows a U-phase output waveform as a rotational position signal detected and output by the Hall element 18U. One cycle of one phase waveform is 360 degrees in electrical angle (θe). Since the brushless motor 1 of this embodiment has eight sets of magnetic poles, when the brushless motor 1 makes one rotation, a substantially sinusoidal waveform having eight periods is output. Hall element 18U, 18
As shown in FIG. 5, the output waveforms of the U-phase, V-phase, and W-phase output from V and 18W respectively have 12
It has a phase difference of 0 degrees.

The brushless motor 1 constructed as described above
As shown in FIGS. 1, 2 and 3, a plurality of magnetic poles (N-pole and S-pole) of a rotor magnet 5 mounted on the rotor 4 are shown in FIG.
Among the poles (a total of 16 poles), a position detecting magnetic pole 5M is provided at a predetermined position of one magnetic pole (N pole in this embodiment). In the present embodiment, the position detecting magnetic pole 5M is a portion where the magnetic force is locally weaker than the magnetic force of the N pole itself of the rotor magnet 5, and is formed by, for example, the following method.

That is, as a first method, a predetermined portion of the magnetizing head for magnetizing the rotor magnet 5 is cut in advance, and the magnetizing head is magnetized by bringing the magnetizing head close to the rotor magnet 5. There is. When magnetization is performed with such a magnetization head, the predetermined portion is farther away from the rotor magnet 5 than other portions, so that only the portion is weakly magnetized.

As a second method, after a driving magnetic pole is magnetized on the entire circumference of the rotor magnet 5, a specific magnetic pole (for example, one of N poles) has a reverse polarity (S
Pole) is partially magnetized.

Further, as a third method, in contrast to the second method, a partial magnetic pole (S-pole) is applied in advance before the driving magnetic pole is magnetized on the rotor magnet 5, and thereafter, There is a method of magnetizing such that a reverse pole (N pole) overlaps a partial magnetic pole.

Further, as a fourth method, a portion where the magnetic force is locally weak can be formed by cutting a predetermined portion of the rotor magnet 5 having the driving magnetic poles magnetized all around.

Further, as a fifth technique, the shape of the magnetizing head is devised, for example, a part of the magnetizing head is completely removed, and the magnetizing head is used to perform magnetizing. A non-magnetized portion may be formed.

The position detecting magnetic pole 5M thus formed is formed at a position advanced by a predetermined angle phase in electrical angle from the magnetic center of the driving magnetic pole. That is, in detail, it is formed 30 degrees in electrical angle from the magnetic center of the N pole of the driving magnetic pole. By forming the position detecting magnetic pole 5M, an output waveform of eight periods as a rotation position signal output from each of the Hall elements 18U, 18V, 18W for each rotation of the rotor 4 of the brushless motor 1 Of these, a dent-shaped irregular portion is generated in front of any one positive peak. The irregular portion is formed at an electrical angle of about 60 degrees from the boundary between the S pole and the N pole within a half cycle of an arbitrary cycle of the output waveform of the rotational position signal.

Of the Hall elements 18, the Hall elements 18U and 18V are connected to the main part of the rotor position detecting device shown in FIG. 4 (block circuit diagram). The rotor position detecting device mainly includes a rotor magnet 5, a magnetic detecting unit 18, a reference voltage generating unit 19, and an index signal synthesizing unit 20.

The reference voltage generating means 19 includes a Hall element 18
An amplifier 10 connected to the output terminal of U, a first comparator 16 also connected to the output terminal of the Hall element 18U,
Offset circuit 17 connected to the output terminal of amplifier 10
A second comparator 16 connected to the output terminal of the Hall element 18V; a sample hold circuit 12 connected to the first comparator 16, the offset circuit 17 and the second comparator 11; A sample and hold capacitor 13 connected between the potentials.

The index signal synthesizing means 20 compares a reference voltage, which is an output signal of the sample-and-hold circuit 12, with an output signal of the amplifier 10.
And a waveform shaping circuit 1 connected to each output terminal of the third comparator 14 and the first comparator 16 to output an index signal
5 is provided.

The above configuration is specifically described as follows. That is, the amplifier 10 amplifies the U-phase (first phase) output signal as the rotational position signal output from the Hall element 18U. Then, the amplifier 10 outputs the output signal to each of the offset circuit 17 and the third comparator 14.

The second comparator 11 inputs a V-phase (second phase) output signal as a rotational position signal output from the Hall element 18V, and starts a voltage hold in a sample-and-hold circuit 12 described later. (Hold command)
Is generated and output to the sample and hold circuit 12.

The sample hold circuit 12 is connected to the first comparator 16, the offset circuit 17 and the second comparator 11. Based on the hold command from the second comparator 11, the sample hold circuit 12 is provided for each cycle of the U-phase output waveform. A predetermined point before the peak (30 degrees before the peak in electrical angle) is sampled and held, and the sample and hold capacitor 13 is charged and held as a reference voltage. The potential of the U-phase output signal sampled and held is boosted by the offset circuit 17 in advance. Further, the reference voltage charged in the sample and hold capacitor 13 is forcibly discharged according to the timing control signal from the first comparator 16.

The third comparator 14 compares the reference voltage sampled and held in the sample and hold circuit 12 and charged in the sample and hold capacitor 13 with the U-phase rotational position signal output from the amplifier 10. . Among the eight phases of the U-phase output waveform generated by one rotation of the rotor 4, the position detection magnetic pole 5 locally formed on the rotor magnet 5 is provided in front of one waveform peak.
M creates a dented profile. This deformed portion has a voltage value lower than that of a normal substantially sinusoidal voltage. On the other hand, the offset voltage value is set so that the reference voltage sampled and held in the vicinity of the deformed portion does not exceed the peak voltage in the same half cycle. Below the voltage. Therefore, when the peak voltage immediately after the deformed portion exceeds (when exceeds) the reference voltage, the third comparator 14 outputs a pulse signal as shown in FIG.
Note that the offset voltage is set so that the reference voltage at the preceding stage exceeds the peak voltage with respect to the U-phase output waveform having no deformed portion. Since the voltage has already been exceeded, no pulse signal is output.

The timing of charging and discharging the reference voltage to the sample and hold capacitor 13 is controlled by a timing control signal of the first comparator 16.

The waveform shaping circuit 15 normalizes the signal output from the third comparator 14 in accordance with the timing control signal of the first comparator 16, shapes the waveform into a pulse-like stable index signal, and detects the rotor position. An index signal is output to the outside of the device.

Next, the operation of the rotor position detecting device according to the present invention will be described with reference to FIGS.

The rotation of the rotor 4 and the rotor magnet 5 of the brushless motor 1 shown in FIGS.
From each of the Hall elements 18U, 18V and 18W, a substantially sinusoidal waveform of three phases of U phase, V phase and W phase shown in FIG. 5 is detected as a rotational position signal. In FIG. 5, these three-phase output waveforms respectively show the output waveforms of the Hall amplifier. The amount of charge stored in the capacitor is a reference voltage stored in the sample-and-hold capacitor 13, and a is a third comparator 14
And b indicates the respective output waveforms of the waveform shaping circuit 15.

First, as shown in FIG.
The output signal of U is input to the first comparator 16. The first comparator 16 provides a sample-and-hold capacitor at a zero-cross point (0-degree point in the U-phase waveform) at which the output waveform of the U-phase (first phase) as the rotational position signal switches from the negative side to the positive side. 13 outputs a timing signal to start charging the reference voltage. In charging the sample-and-hold capacitor 13 with the reference voltage, the voltage boosted by the offset circuit 17 is charged. This offset circuit 1
The boosted voltage 7 is set to an offset voltage value such that the reference voltage sampled and held near the deformed portion does not exceed the peak voltage in the same half cycle as described above.

Next, based on the output of the Hall element 18V, the second comparator 11 samples and holds the hold command at the zero crossing point where the V-phase (second phase) output waveform switches from the positive side to the negative side. Output to the circuit 12. Based on this hold command, the charging of the sample-and-hold capacitor 13 with the reference voltage ends. That is, hold is started. This sample hold capacitor 1
3 is completed at the point before the peak (U) in each cycle of the U-phase output waveform as the rotational position signal.
Approximately 60 electrical degrees from the zero crossing point in the phase output waveform
Degree point).

The forced discharge of the reference voltage charged in the sample and hold capacitor 13 shown in FIG. 5 is controlled by a timing control signal output from the first comparator 16 as in the start of charging. That is, the forced discharge of the reference voltage charged in the sample-and-hold capacitor 13 is performed at the zero-cross point (180-degree point of the U-phase output waveform) at which the output waveform of the U-phase switches from the positive side to the negative side.

On the other hand, the rotational position signal of the Hall element 18U amplified by the amplifier 10 is sent to the third comparator 14. The third comparator 14 outputs the output waveform of the U-phase (first phase) and the reference voltage charged in the sample-and-hold capacitor 13 so as to be sampled at an offset and 30 ° before the peak of the U-phase. Compare the held voltage waveform.

As shown in FIG. 5, the output waveform of each of the Hall elements 18U, 18V, 18W
A local concave deformed portion is formed by the position detecting magnetic pole 5M provided at the N pole. When the rotor 4 (or the rotor magnet 5) makes one rotation, the sine waveform of each phase becomes 8
A cycle portion is generated, but a deformed portion is generated only in one of the eight periods, and only in the preceding stage of the positive half period of the one period.

In the U-phase (first phase) output waveform of the rotational position signal, the reference voltage sampled and held within the same half cycle as the positive half cycle having the deformed part is the same as the U-phase waveform peak preceding stage. Since it is held near the deformed part,
The output waveform of the phase exceeds the reference voltage near the peak after the deformed portion. At this time, the third comparator 14 outputs a pulse signal as shown in FIG. 5A. The pulse signal is input to the waveform shaping circuit 15, which shapes the waveform based on the timing control signal from the first comparator 16 and outputs an index signal. This index signal is output outside the index signal output device.

The third comparator 14 operates in the U phase (first phase).
Also in the next cycle after the cycle having the deformed portion in the output waveform of the above (1), the offset is applied and the reference voltage sampled and held before the peak and the output waveform of the U phase are compared. However, since the U-phase output waveform after the second cycle does not have a deformed portion, that is, a dent on the waveform, the reference voltage is boosted by the above-described offset voltage value before the peak of the U-phase. At the hold timing, the reference voltage has already exceeded the peak value. Therefore, no pulse signal is output after the second cycle.

That is, as shown in FIG. 5, in the case of a U-phase waveform having a period in which no deformed portion is generated, the reference voltage of the sample-and-hold circuit 12 takes the amplitude value of a normal U-phase output waveform. 7, the reference voltage becomes higher than the peak value of the U-phase waveform, and the third comparator 14 does not generate an output.

The above can be summarized as follows. The position detecting magnetic pole 5M is magnetized with a magnetic force that is weaker than the magnetic force (for example, saturation magnetization) of the magnetic pole on which the position detecting magnetic pole 5M is provided. Therefore, the output waveform of the U-phase is as shown in FIG. Then, a concave deformed portion is generated at a point near the phase angle of 60 degrees. The sample and hold circuit 12 starts charging from the zero-cross point of the U-phase voltage, and applies a predetermined offset voltage to the voltage at the phase angle of the U-phase voltage of 60 degrees (the zero-cross point of the V-phase voltage) by the offset circuit 7. Hold the voltage. This hold voltage is used as a reference voltage in the third comparator 1
At 4, the voltage is compared with the U-phase voltage output from the amplifier 10. In this case, the vicinity of the peak of the U-phase waveform immediately after the deformed portion has a value higher than the reference voltage, and the third comparator 1
4 will produce an output.

As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and can be variously modified without departing from the gist thereof. Needless to say.
For example, in the above embodiment, the reference voltage generation means
The reference voltage is output by sampling and holding the value at a predetermined point before the peak on the positive side in each cycle of the U phase in the rotational position signal output from the magnetic detection means.
The configuration may be such that the reference voltage is output based on not only the phase but also the V-phase or W-phase rotational position signal.

In the above embodiment, the position detecting magnetic pole 5M is formed at a position advanced by a predetermined angle phase in electrical angle from the magnetic center of the N pole of the driving magnetic pole. Thus, the position detecting magnetic pole 5M may be formed at a position advanced by a predetermined angle phase. The position detecting magnetic pole 5M is formed, for example, by locally magnetizing the N pole at a predetermined position of the S pole of the driving magnetic pole. In this case, the reference voltage generating means is configured to sample and hold a value at a predetermined point before the negative peak in each cycle of an arbitrary phase in the rotational position signal and output a reference voltage. Further, in the above embodiment, as shown in FIG. 3, the offset circuit 17 is provided to generate the reference voltage. However, instead of this, the output voltage of the amplifier 10 is directly amplified by a predetermined amplification using an amplification circuit. It is also possible to adopt a configuration in which the voltage is boosted by linearly amplifying the temperature.

Further, in the above-described embodiment, an example is shown in which the position detecting magnetic pole 5M is formed at a position advanced by 30 degrees in electrical angle from the magnetic center of one driving magnetic pole. Similar effects can be obtained even with a corner (for example, 45 degrees). Furthermore, the present invention is naturally applicable to brushless motors other than the floppy disk drive motor.

[0054]

As described above, according to the present invention,
Since the so-called sensorless rotor position detecting device that electrically generates the index signal is configured, the number of mechanical parts can be reduced.

Further, according to the present invention, in the brushless motor, the position detecting magnetic pole is formed on the magnetic pole of the rotor magnet and a locally deformed portion is generated in the output waveform of the magnetic detecting means. Waveform comparison can be reliably performed only within a half cycle, and output of an incorrect index signal can be prevented.

Furthermore, according to the present invention, even if the magnetic poles of the rotor are saturated, the position detecting magnetic poles for generating the deformed portion need only have a magnetic force weaker than the surrounding magnetic force, and the magnetic force of the magnetic poles themselves is enhanced. And the accuracy of the index signal can be improved.

[Brief description of the drawings]

FIG. 1 is a partially sectional side view showing a configuration of a brushless motor according to an embodiment of the present invention.

FIG. 2A is a plan view of a main part of the brushless motor, and FIG. 2B is a cross-sectional view thereof.

FIG. 3 is a development view showing a positional relationship between a rotor magnet and a magnetic detector of the brushless motor.

FIG. 4 is a block circuit diagram of the rotor position detecting device of the brushless motor.

FIG. 5 is a timing chart showing an operation of the rotor position detecting device.

FIG. 6 is a timing chart showing the operation of a conventional index output device.

[Explanation of symbols]

 Reference Signs List 1 spindle motor 2 substrate 4 rotor 5 rotor magnet 5M rotation inspection unit 6 coil 7 laminated iron core 10 amplifier circuit 11, 14, 16 voltage comparison circuit 12 sample and hold circuit 13 sample and hold capacitor 15 waveform shaping circuit 17 offset circuit 18 Hall element

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H02K 29/08 H02K 11/00 C (56) References JP-A-6-311782 (JP, A) JP-A-7-131965 (JP, A JP-A-2-84094 (JP, A) JP-A-61-218384 (JP, A) JP-A-61-202213 (JP, A) JP-A-61-128759 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02P 6/00-6/24

Claims (9)

(57) [Claims] 1. A rotor magnet mounted on a rotor and having a plurality of driving magnetic poles, a rotor magnet disposed in a region facing the rotor magnet, and detecting a magnetic field passing by rotation of the rotor magnet to detect a plurality of phases of substantially sinusoidal. A plurality of magnetic detecting means for outputting a rotational position signal having a waveform, formed at a position advanced by a predetermined angle phase in electrical angle from a magnetic center of at least one driving magnetic pole of the rotor magnet; A magnetic pole for position detection that generates a weak magnetic field, and a value of a predetermined point before any one of the positive and negative peaks in each cycle of an arbitrary phase among the rotational position signals output from the magnetic detecting means. A reference voltage generating means for holding and outputting a reference voltage; and a rotational position signal output from the magnetic detecting means and the reference voltage generating means. By comparing the power reference voltage,
A rotor position detecting device for a brushless motor, comprising: an index signal synthesizing unit that outputs an index signal. 2. The brushless motor rotor position detecting device according to claim 1, wherein the reference voltage generating means includes an offset circuit for increasing a potential of the rotational position signal. 3. The magnetic detecting means according to claim 1, wherein said magnetic detecting means comprises three magnetic detectors, and these magnetic detectors output three-phase rotational position signals having a phase difference of 120 ° from each other. A rotor position detector for brushless motors. 4. The reference voltage generating means receives a first phase and a second phase rotation position signals among the three phase rotation position signals, and samples and holds based on the first phase rotation position signals. A first comparator for controlling the timing of the second phase, a second comparator for controlling the timing at which the reference voltage is held based on the rotational position signal of the second phase, and each of the first comparator and the second comparator. A sample-and-hold circuit that samples and holds a voltage value at a predetermined point before the waveform peak of the first phase in accordance with the output signal, and a capacitor that charges the voltage sampled and held by the sample-and-hold circuit. The rotor position detecting device for a brushless motor according to claim 1. 5. The reference voltage generating means includes an amplifier for amplifying the rotational position signal of the first phase, and the index signal synthesizing means includes a reference voltage which is an output signal of the amplifier and an output signal of the sample and hold circuit. 5. The apparatus according to claim 4, further comprising a third comparator that compares the first and second signals with each other, and forming an index signal from an output signal of the third comparator. 6. A third comparator for comparing a rotation position signal output from the magnetic detector with a reference voltage output from the reference voltage generator, and an output signal of the third comparator. 2. A rotor position detecting device for a brushless motor according to claim 1, further comprising: a waveform shaping circuit for shaping the waveform of the signal to form an index signal. 7. The brushless motor rotor position detecting device according to claim 1, wherein the position detecting magnetic pole is formed at a position advanced by 30 degrees in electrical angle from the magnetic center of the driving magnetic pole. . 8. The magnetic pole for position detection is formed at a position advanced by a predetermined angle phase in electrical angle from the magnetic center of at least one N pole of the driving magnetic pole, and the rotational position signal output from the magnetic detection means is 2. The rotor position detecting device for a brushless motor according to claim 1, wherein a deformed portion is formed before the at least one positive peak. 9. The position detecting magnetic pole is formed at a position advanced by a predetermined angle phase in electrical angle from the magnetic center of at least one S pole of the driving magnetic pole, and the rotational position signal output from the magnetic detecting means is 2. The rotor position detecting device for a brushless motor according to claim 1, wherein a deformed portion is formed before the at least one negative peak.