JPH09149675A - Rotation position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a stable operation against the fluctuation of a load by a method wherein a means by which an offset signal is generated in accordance with an exciting current detection signal supplied from a motor is provided in a rotation position detector. SOLUTION: A rotation position detector 1 generates an index signal (h) in accordance with a rotor position detection signal (b) which is supplied from a rotor position detecting means 7 and an exciting current detection signal Vnf which is supplied from a driver 9. An offset correcting means (OF) 10 generates an offset signal Iof in accordance with the exciting current detection signal Vnf and supplies the signal Iof to a differential amplifying means 11. Further, the OF 10 converts the exciting current detection signal Vnf corresponding to the exciting current value of an armature coil 6 into the offset signal Iof which is a constant current signal and supplies the signal Iof to the input stage resistor Rof of the differential amplifying means 11. That is, the rotor position detection signal (b) which is distorted by the influence of a magnetic field generated by the armature coil 6 can be corrected by the offset signal Iof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational position detecting device for driving a recording medium such as a magnetic head drum driven by a brushless motor or the like at a constant rotational speed in a predetermined rotational phase.

[0002]

2. Description of the Related Art Generally, in a motor for rotationally driving a rotary magnetic head device or the like, an object to be rotated such as a magnetic head drum is rotationally driven at a constant speed in a predetermined rotational phase, so that it corresponds to a rotation reference position of a rotor. With accurate and stable timing,
There is a need for a rotational position detector that produces a so-called index signal of one pulse per revolution.

Regarding a conventional rotary position detecting device, a rotary position detecting device incorporated in a four-phase brushless motor is taken as an example.
Description will be given based on the attached drawings. FIG. 6 is a schematic front view of a four-phase brushless motor, and FIG. 7 is a side view of a four-phase brushless motor.

In FIGS. 6 and 7, a four-phase brushless motor 100 has a permanent magnet 103 of 14 poles fixedly attached to the outer peripheral portion of a rotor 102, and a non-magnetized portion 108 provided on one of the permanent magnets 103. 12 stator cores 105
To each of the armature coils 106 (L1, L2, L3,
L4) is wound and each of them is connected in a delta form to form a four-phase stator 104, and rotor position detecting means 107 having two Hall elements for detecting the rotational position of the rotor 102.
Are arranged on the motor board 111 to form main mechanical elements.

(L1 and L2) and (L3 and L4) of the armature coil 106 are approximately {(π / 2) + nπ} in electrical angle.
Has a phase difference of radian (n = 0, ± 1, ± 2, ...),
(L1 and L3) and (L2 and L) of the armature coil 106
4) is an electrical angle of approximately (π + nπ) radians (n = 0, ±
, ± 2, ...).

In the Hall elements (HG1, HG2) forming the rotor position detecting means 107, the phase difference between the rotor position detection signals (a, b), which is the output signal, is {(π / 2) + nπ in terms of electrical angle. } Radian (n = 0, ± 1, ± 2,
Are arranged so as to have a phase difference of.

Further, the brushless motor 100 has the armature coil 106 based on the rotor position detection signals (a, b) corresponding to the rotational position detected by the rotor position detecting means 107.
A drive device 109 for generating an exciting current and a rotor position detection signal b detected by the rotor position detection means 107 (HG2)
Based on the index signal h corresponding to the non-magnetized portion 108
The rotational position detection device 110 for generating
11 is built in and is comprised.

FIG. 3 is a block diagram of a conventional rotational position detecting device, and FIG. 4 is a timing diagram of the conventional rotational position detecting device. 3 and 4, the rotor position detection signals (a, b) generated by the two Hall elements (HG1, HG2) according to the 14-pole permanent magnet 103 formed on the rotor 102 are supplied to the drive device 109. At the same time, the rotor position detection signal b is also supplied to the rotational position detection device 110.

The driving device 109 sequentially supplies an exciting current to the four-phase armature coils 106 based on the rotor position detection signals (a, b) to rotate the rotor 102. The rotational position detection device 110 generates the index signal h based on the rotor position detection signal b.

A rotor position detection signal (a, which is provided by the rotor position detection means 107 in accordance with the rotational position of the rotor 102).
b) is generated when the non-magnetized portion 108 provided in one of the permanent magnets 103 arranged in the rotor 102 faces the Hall elements (HG1, HG2) once per one rotation of the rotor 102. It contains a waveform with a small amplitude.

The Hall elements (HG1, HG2) are influenced by the magnetic field generated according to the current direction and the amount of the armature coil 106 exciting current, and the rotor position detection signals (a, b) are influenced by the magnetic field. Minute error voltage is superimposed. In FIG. 4, waveforms (a) and (b) drawn together with the rotor position detection signals (a and b) are signal voltage components (a ′, b ′) and error (a ″, b ″). It is a voltage component.

The rotational position detecting device 110 comprises a differential amplifying means 110a, a peak hold means 110b, a reference voltage generating means 110c, a voltage comparing means 110d, a discriminating means 110e, and a waveform shaping means 110f.

The differential amplifying means 110a comprises a differential amplifying circuit and an output amplifying circuit, amplifies the rotor position detection signal b provided by the Hall element HG2 to generate an index position signal c, and the peak hold means 110b and the voltage. In addition to being supplied to the comparison means 110d and the waveform shaping means 110f, a balanced reference signal Vref that has become a balanced DC potential by adding unbalanced output signals of opposite phases to each other is supplied to the reference voltage generation means 110c.

The peak hold means 110b generates a peak hold signal d based on the index position signal c and supplies it to the reference voltage generation means 110c. In order to detect and hold the maximum value of the index position signal c, and prevent malfunction due to AM fluctuations included in the rotor position detection signal b due to uneven magnetization of the permanent magnet 103, FIG.
As shown by the waveform (c) in FIG.

The reference voltage generation means 110c generates a comparison reference signal Vsh based on the peak hold signal d and the balanced reference signal Vref and supplies it to the voltage comparison means 110d. The voltage level of the comparison reference voltage Vsh is about 8 which is the potential difference between the peak hold signal d and the balanced reference signal Vref.
The voltage is divided by resistance division so as to be 5%, and as shown in the waveform (c), the peak and peak hold signal d of the waveform when the permanent magnet 103 provided with the non-magnetized portion 108 faces the Hall element HG2. Set to an intermediate level to the voltage level of.

The voltage comparison means 110d generates a peak comparison signal e based on the index position signal c and the comparison reference signal Vsh and supplies it to the discrimination means 110e. As shown in the waveform (e), the peak comparison signal e is the Hall element H.
When the G2 and the permanent magnet 103 having no non-magnetized portion face each other, the low level is generated, and in other cases, the high level is generated.

The discriminating means 110e comprises an RS type flip-flop and a D type flip-flop, and based on the peak comparison signal e and the index position signal f, the waveforms (e, f, g, h) shown in FIG. 4 are obtained. And the index signal h is generated.

The waveform shaping means 110f shapes the index position signal c, generates a rectangular wave index shaping signal f as shown in the waveform (f), and supplies it to the discrimination means 110e.

With these configurations, the permanent magnet 1 provided with the non-magnetized portion 108 is based on the rotor position detection signal b supplied from the Hall element HG2 of the rotor position detecting means 107.
There is known a rotational position detection device configured to obtain accurate timing when 03 faces the Hall element HG2.

[0020]

In the conventional rotary position detecting device 110, the rotor position detecting signals (a, b) supplied from the Hall elements (HG1, HG2) of the rotor position detecting means 107 are shown in FIG. As shown in waveforms (a) and (b), in addition to the signal voltage component corresponding to the magnetic flux of the permanent magnet 103, the error voltage component corresponding to the magnetic flux generated according to the excitation current of the armature coil 106 is superimposed. There is.

The waveforms (a ', b') in the waveforms (a) and (b) shown in FIG. 4 are signal voltage components, and the rectangular waveforms (a ", b") having small amplitudes are error voltage components. is there.

When the load applied to the rotor 102 is increased, the exciting current of the armature coil 106 is increased to cope with the increase of the load. Therefore, the magnetic flux generated by the armature coil 106 is also increased and the Hall elements (HG1, HG2). The influence of the magnetic field on the object increases, and the waveforms (a ″, b ″) that are error voltage components
Becomes larger.

The peak value of the waveform included in the rotor position detection signal b supplied to the rotational position detection device 110 at the timing when the Hall element HG2 faces the permanent magnet 103 provided with the non-magnetized portion 108 has an increased error. There is a problem that the index signal h is not generated because the voltage exceeds the comparison reference voltage Vsh due to the voltage component (b ″).

Further, in the conventional rotational position detecting device 110, the Hall elements (HG1, HG2) and the permanent magnet 103 are used.
Has a temperature characteristic that cannot be ignored. For example, for Hall elements, InSb with low cost and high magnetic sensitivity characteristics
The output amplitude temperature characteristic when using the Hall element is 25
The output amplitude value at ° C is about 1.7 times at -10 ° C and about 1/3 at 60 ° C.

FIG. 5 is an enlarged view of the timing of the conventional rotational position detecting device, and is an enlarged view of the waveform (c) shown in FIG. In FIG. 4, the index position signal c (waveform c)
Oscillates around the balanced reference signal Vref, which is the midpoint potential of the index position signal c. Hall element HG2
Is the peak value of the waveform c and the balanced reference signal Vr at the timing facing the permanent magnet 103 provided with the non-magnetized portion 108.
The potential difference with ef is V2, the potential difference between the peak value one cycle before and the balanced reference signal Vref is V1,
Here, the peak hold signal d (waveform d) changes from the potential of V1 to Ed in one cycle of the rotor position detection signal (T seconds).
If the potential becomes

[0026]

## EQU1 ## Ed = (V1 + Vref) * exp (-T / R
* C) -Vref

However, R and C are peak hold means 11
0b is the capacitance value of the peak hold capacitor C and the discharge resistance value R is the resistance value. Further, the value Vt of the comparison reference voltage Vsh after T seconds is 85% of the potential of Ed,

[0028]

(2) Vt = 0.85 * Ed

Further, in order to obtain the index signal h, it is essential that the potential of Vt exceeds the potential of V2.

[0030]

[Formula 3] V2 <Vt

From the equations 1 to 3, (Vref / V1) = V
Then, (V2 / V1) is given by the following equation.

[0032]

[Formula 3] V2 / V1 <0.85 {(1 + V) * exp
(-T / R * C) -V}

For example, T = 5 ms, C = 0.1 μF, R
= 10 MΩ, Vref = 4.3 V, and V1 at (25 ° C.) is (V1 = 0.3 V), V2 / V1 (25 ° C.) is as follows.

[0034]

[Equation 5] V2 / V1 (25 ° C) <0.785

Since the output amplitude value at 60 ° C. is 1/3 of the output amplitude value at 25 ° C., (V1 = 0.1
V), V2 / V1 (60 ° C) becomes V2 / V1
(60 ° C) <0.66.

In the manufacturing process of the non-magnetized portion 108, (V2 / V
The product whose 1) became 0.785 to 0.66 is 25 ° C.
In case of normal operation, malfunction occurs at 60 ° C, and in order to guarantee operation up to 60 ° C, (V2 /
The manufacturing process must be controlled so that V1) <0.66.

Further, in the case of a VTR drum brushless motor, the (V2 / V1) is inspected with the installation dimension at the design center of the rotor 102 alone, but the standard value considers the variation of the installation dimension during set mounting. Must.

When the gap (tg) between the permanent magnet 103 and the motor substrate 111 is widened due to the variation in the mounting dimensions in the set mounting process, the output amplitude value of the Hall element becomes about 0.6 times the design value, so 60 °. V1 in C is
V1 = 0.1 * 0.65 = 0.065V and V2 /
V1 (60 ° C) is given by the following equation.

[0039]

[Equation 6] V2 / V1 (60 ° C) <0.565

Therefore, (V2 / V1) is (V2 / V1)
It is necessary to manage the variation so that <0.565), but if the value of (V2 / V1) is made small, the torque ripple of the rotor 102 increases because it affects the current distribution ratio of the armature coil 106 exciting current. , From this constraint (V2 /
When V1> 0.5), the range of (V2 / V1) is as follows.

[0041]

(7) 0.5 <(V2 / V1) <0.565

There is a problem that it is very difficult to manage the variation in the manufacturing process so that it falls within the range of (V2 / V1) shown in Formula 7.

Also, considering the condition of equation 5, (V2 / V
If the range of 1) is the following equation,

[0044]

[Equation 8] 0.5 <(V2 / V1) <0.785

If the variation in the manufacturing process is controlled under the condition of the equation (8), the productivity of the brushless motor will be greatly improved, but it is necessary to narrow the operating temperature range and further reduce the variation in the mounting dimension. However, there is a problem that it is necessary to use parts that are good and costly.

The present invention has been made in order to solve such a problem, and an object thereof is to detect a non-magnetized portion provided in one of permanent magnets arranged in a rotor by using an exciting current as a hall element. It is an object of the present invention to provide a rotational position detecting device that operates stably even when affected by a magnetic field that is generated, and also with respect to load fluctuations applied to a rotor, has a wide stable operating temperature range, and has high production efficiency.

[0047]

In order to solve the above-mentioned problems, a rotational position detecting device according to the present invention comprises an offset correcting means for generating an offset signal based on an exciting current detection signal supplied from a brushless motor. It is characterized by

Since the rotational position detecting device is provided with the offset correcting means for generating the offset signal according to the armature coil exciting current and providing it to the differential amplifying means, the differential amplifying means uses the offset signal for the armature. It is possible to correct the rotor position detection signal which is distorted by the influence of the magnetic field generated by the coil.

Further, the rotational position detecting device according to the present invention is characterized in that the balanced reference signal provided by the differential amplifying means is supplied to the reference potential side of the peak hold capacitor provided in the peak hold means.

Since the reference potential of the peak hold capacitor provided in the peak hold means for detecting and holding the maximum value of the index position signal is the potential of the balanced reference signal, it does not depend on the amplitude variation of the index position signal. It can operate stably.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a rotational position detecting device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a rotational position detecting device according to the present invention, and FIG. 2 is a timing diagram of the rotational position detecting device according to the present invention. Since the four-phase brushless motor described above is used for the configuration of the mechanical elements such as the rotor and the stator of the brushless motor and the arrangement of the hall elements, reference is made here to FIGS. 6 and 7. The description is omitted.

1 and 2, the rotor position detecting means 7 includes two Hall elements HG1 and HG2 for detecting the rotational position of the rotor 2, and the permanent magnets arranged on the rotor 2 by the rotational movement of the rotor 2. Each time 3 passes through the rotor position detection means 7, a rotor position detection signal (a, b) is generated and provided to the drive device 9 and the rotational position detection device 1 is also provided.
To provide.

The Hall elements (HG1, HG2) have a phase difference between the output signals of the Hall elements (HG1, HG2) and the rotor position detection signals (a, b) in terms of electrical angle {(π / 2) + nπ} radians (n = 0). , ± 1, ± 2, ...).

The rotor position detection signals (a, b) are generated with a phase difference of π / 2 from each other as shown in FIG. 2 every time the permanent magnet 3 of the rotor 2 passes through the Hall elements HG1 and HG2. To be done.

The rotor position detection signal (a, b) is
The non-magnetized portion 8 provided on one of the permanent magnets 3 arranged on the rotor 2 is arranged once for each rotation of the rotor 2 and the hall element (HG
1 and HG2) includes a waveform with a small amplitude generated at the time of facing the HG2).

The Hall elements (HG1, HG2) are influenced by the magnetic field generated according to the current direction and the amount of the armature coil 6 exciting current, and the rotor position detection signals (a, b) are generated.
The error voltage component of the influence of this magnetic field is superposed on. In FIG. 2, waveforms (a) and (b) drawn together with the rotor position detection signals (a, b) are signal voltage components (a ′, b ′), and (a ″, b ″) are errors. It is a voltage component.

The drive device 9 is provided with two sets (not shown) corresponding to the hall elements (HG1, HG2) of the control means composed of a differential amplifier and the drive means composed of a power amplifier composed of power transistors, and a rotor. Position detection signal (a,
Based on b), exciting currents are sequentially supplied to the four-phase armature coils 6 to rotationally drive the rotor 2.

The control means uses the rotor position detection signals (a, b)
On the basis of the timing signal supplied from the control means, the drive means sequentially drives the power transistors based on the timing signal supplied from the control means. Excitation current is sequentially supplied to the armature coils 6 of the phases to rotate the rotor 2.

The driving means is provided with two sets of power amplifiers each having a pair of a power supply transistor on the sink side and a source side, and each of the terminals on the sink side and the source side is a connection point of four delta-connected armature coils 6. , And the pair of power transistors on the sink side and the source side are driven by the timing signal pair to supply an exciting current to the armature coil 6.

Both the emitter terminals of the power transistors on the sink side are connected to the ground, and the collector terminals of the power transistors on the source side are both connected to the constant voltage power supply Vcc via a feedback resistor.
Armature coil 6 detected by a feedback resistor while being connected to
An exciting current detection signal Vnf corresponding to the exciting current is generated.
The exciting current detection signal Vnf is provided from the collector terminal to the offset correcting means 10 provided in the rotational position detecting device 1.

The rotational position detecting device 1 comprises an offset correction means 10, a differential amplification means 11, and a peak hold means 1.
2, reference voltage generating means 13, voltage comparing means 14,
A rotor position detection signal b supplied from the rotor position detection means 7 and provided with a waveform shaping means 15 and a discrimination means 16;
The index signal h is generated based on the exciting current detection signal Vnf supplied from the drive device 9.

The offset correction means 10 is provided with a constant current output amplifier, and generates an offset signal Iof based on the exciting current detection signal Vnf supplied from the drive device 9 and provides it to the differential amplification means 11.

Further, the offset correction means 10 converts the exciting current detection signal Vnf corresponding to the exciting current value of the armature coil 6 into the offset signal Iof which is a constant current signal, and the preamplification provided in the differential amplifying means 11. Input stage resistance Rof of the circuit
To provide.

The waveform (k) shown in FIG. 2 represents the input offset voltage Vof generated from the offset signal Iof and the input stage resistance Rof. The offset signal Iof is the error voltage of the waveform (b) of the input offset voltage Vof. Ingredient b ″
It is set to be equal to the error voltage amplitude Vb.

In the constant current amplifier, for example, a current mirror circuit is composed of two transistors whose bases are connected to each other. One transistor is connected to the collector and the base, and is connected to a constant voltage power source through a resistor, and an emitter. Is an input terminal of the exciting current detection signal Vnf supplied from the driving device 9.

The emitter of the other transistor is grounded through a resistor, the collector is connected to a constant current source, and the output terminal of the offset signal Iof is used.

The differential amplification means 11 produces the index position signal c based on the rotor position detection signal b supplied from the Hall element HG2 of the rotor position detection means 7 and the offset signal Iof supplied from the offset correction means 10. Generated, peak hold means 12 and voltage comparison means 14
And the waveform shaping means 15, and the unbalanced output signals having opposite phases are added to each other, and the balanced reference signal Vref which becomes a balanced DC potential is supplied to the peak hold means 12, the reference voltage generating means 13, and the waveform. And shaping means 15.

The differential amplifying means 11 comprises a differential amplifying circuit and an output amplifying circuit, and as shown in the waveform (b) of FIG. 2, the rotor position detection signal is distorted under the influence of the magnetic field of the armature coil. b (waveform b) is amplified, and the error voltage component (b ″) of the rotor position detection signal b that is generated by distortion is corrected by the offset signal Iof to generate a signal voltage component (waveform b ′).

Further, the differential amplifying means 11 synthesizes the balanced output signals having opposite phases to each other to generate a balanced reference signal Vref which is a constant voltage signal which is balanced and stable with respect to both output signals.

The differential amplifier circuit comprises a main differential amplifier circuit with a preamplifier circuit. The preamplifier circuit connects the emitters of the two transistors to their respective current sources connected to a constant voltage power supply via their respective emitter resistors, and the collectors thereof are both grounded. The input signal to the preamplifier circuit connects the rotor position detection signal b, which is the positive and negative balanced output of the Hall element HG2, to the base of each transistor.

The output signal of the preamplifier circuit is obtained from the connection point between the emitter resistor and the current source, and is connected to the bases of the transistors of the main differential amplifier circuit to obtain the balanced input signal of the main differential amplifier circuit. To be configured.

The offset signal I supplied from the offset correction means 10 is applied to the output point of one of the preamplifier circuits.
of is connected to the main differential amplifier circuit to be an input signal.

In the main differential amplifier circuit, for example, the output of each preamplifier circuit is connected to the bases of two transistors,
The emitters are connected via resistors and are grounded via their respective current sources. On the other hand, the collector is configured to be connected to a constant voltage power source via each load resistance and also connected to the base of each transistor of the output amplifier circuit as an output terminal of the main differential amplifier circuit.

The output amplifier circuit is provided with an emitter follower circuit in which the emitter is grounded through a constant current source and the collector is connected to a constant voltage power source, and the base of each transistor is supplied from the collector of the main differential amplifier circuit. The unbalanced output signals of are connected, and the index position signal c with the reduced output resistance is obtained from one of the emitters.

Further, the respective emitters are connected via the resistors connected in series, and the balanced reference signal Vref is output from the connection point of the resistors. The balanced reference signal Vref is a balanced DC potential obtained by adding signals of opposite phases, which appear in each emitter.

Since the index position signal c always oscillates around the potential of the balanced reference signal Vref, the peak potential of the index position signal c and the balanced reference signal Vref.
Index position signal peak potential Vc which is the potential difference between
Is balanced and stable against the DC fluctuation of the index position signal c and is not affected by the fluctuation.

2 is a signal voltage component of the rotor position detection signal b, and a waveform b ″ is an error voltage component. The waveform (k) is supplied from the offset correction means 10. The input offset voltage Vof generated from the offset signal Iof and the input stage resistance Rof is shown.

The input offset voltage Vof has a waveform (b)
The value of the offset signal Iof is set to be equal to the error voltage amplitude Vb of the error voltage component b ″ of the offset correction means 1.
It is set to 0.

As shown in the waveform c of the waveform (l), the index position signal peak potential Vc becomes equal to the peak potential (dotted line in the figure) when only the waveform b ′ of the signal voltage component is amplified, and the Even if the applied load changes, the stable index position signal c is output.

As described above, since the rotational position detecting device according to the present invention includes the offset correcting means 10 for generating the offset signal Iof based on the exciting current detection signal Vnf supplied from the brushless motor, the differential amplifying means is provided. 1
1 can correct the rotor position detection signal b which is distorted by the influence of the magnetic field generated by the armature coil 6 by the offset signal Iof.

The peak hold means 12 generates a peak hold signal d based on the index position signal c supplied from the differential amplifier means 11 to generate a reference voltage generation means 13.
To provide.

The peak hold means 12 includes, for example, an operational amplifier, a diode and a capacitor, the anode terminal of the diode is connected to the output terminal of the operational amplifier, and the cathode terminal is directly connected to the inverting input terminal of the operational amplifier. With the circuit configuration, the index position signal c is connected to the non-inverting input terminal, and the peak hold signal d is obtained from the cathode terminal.

Further, a peak holding capacitor C in which a discharging resistor R is connected in parallel to the cathode terminal of the diode
Is connected to one end and the other end is connected to the balanced reference signal Vref supplied from the differential amplifying means 11.

The peak hold means 12 detects the maximum value of the index position signal c (waveform c) as shown by the waveform d of the waveform (1) shown in FIG.
In order to prevent the malfunction due to the AM fluctuation included in the rotor position detection signal b due to the uneven magnetization of the permanent magnet 3, the discharge is performed for a relatively long time through the discharge resistor R.

Since the reference voltage of the peak hold capacitor C is set to the potential of the balanced reference signal Vref, the balanced reference signal Vref fluctuates in phase with the index position signal c even if the index position signal c fluctuates, resulting in the waveform (l). The index position signal peak potential Vc and the peak hold signal d shown are obtained at stable potentials.

The reference voltage generation means 13 generates the comparison reference signal Vsh based on the peak hold signal d supplied from the peak hold means 12 and the balanced reference signal Vref supplied from the differential amplification means 11, and the voltage is generated. Comparison means 1
4

The reference voltage generating means 13 includes, for example, a voltage follower circuit composed of an operational amplifier and a resistance dividing circuit,
The respective signals are impedance-converted by a voltage follower circuit, the outputs of the respective signals are connected via two resistors, and the comparison reference signal vsh is obtained from the connection point of the resistors.

The voltage level of the comparison reference voltage Vsh is divided by the resistance dividing circuit so that the voltage level becomes about 85% of the potential difference between the peak hold signal d and the balanced reference signal Vref. The permanent magnet 3 provided with the magnetic portion 8 is set to an intermediate level between the peak value of the waveform and the voltage level of the peak hold signal d when the permanent magnet 3 faces the Hall element HG2.

The voltage comparison means 14 generates a peak comparison signal e based on the index position signal c supplied from the differential amplification means 11 and the comparison reference signal Vsh supplied from the reference voltage generation means 13 to discriminate the peak position comparison signal e. The means 16 are provided.

The voltage comparison means 14 is provided with, for example, a voltage comparison circuit composed of a hysteresis feedback circuit composed of an operational amplifier and a threshold setting circuit, and supplies the comparison reference signal Vsh to the setting terminal of the threshold setting circuit to compare the voltages. The index position signal c is supplied to the comparison signal input terminal of the voltage comparison circuit as a reference signal of the circuit.

As shown in the waveforms (l) and (e), when the potential of the index position signal c exceeds the potential of the comparison reference signal Vsh, a low level rectangular wave is generated, and when it is lower than the comparison reference signal Vsh, a high level rectangular wave is generated. c is shaped and a peak comparison signal e is generated. The peak comparison signal e is
The Hall element HG2 and the permanent magnet 3 without the non-magnetized portion 8 are generated so as to be at a low level at the timing when they face each other.

As described above, the rotational position detecting device according to the present invention supplies the balanced reference signal Vref provided by the differential amplifying means 11 to the reference potential side of the peak holding capacitor C provided in the peak holding means 12. Therefore, the stable operation can be performed without depending on the variation in the amplitude of the index position signal c.

The peak hold capacitor C provided in the peak hold means and the discharge resistor R are connected to the balanced reference signal V.
By connecting to ref, the discharge potential Ed after T seconds of the peak hold signal d shown in FIG.

[0094]

[Equation 9] Ed = V1 * exp (-T / R * C)

V1 is the peak potential of the index position signal at the magnetized portion magnetic pole detection timing. The discharge potential Vt of the comparison reference signal Vsh after T seconds is calculated from the equation 2 (Vt =
0.85 * Ed), and the peak potential V2 of the index position signal at the non-magnetized portion magnetic pole detection timing is from (3) to (V2 <Vt), so (V2 / V1) is given by the following equation.

[0096]

## EQU10 ## (V2 / V1) <0.85 {exp (-T / R * C)}

As shown in Equation 10, (V2 / V1) is
The term that depends on the index position signal c is eliminated, and as shown in the prior art, stable in a wide temperature range without depending on the temperature characteristics of the Hall element HG2 appearing in the rotor position detection signal b and the variations in the manufacturing / assembly process. Since the index signal h can be obtained and the manufacturing standard of (V2 / V1) does not need to take the high temperature time into consideration, 0.5 <(V2 / V1) <0.785 shown in Expression 8 is obtained. It should be managed within the range of.

The waveform shaping means 15 includes the index position signal c supplied from the differential amplification means 11 and the balanced reference signal V.
The index shaping signal f is generated based on ref and is provided to the discrimination means 16.

The waveform shaping means 15 is provided with, for example, a voltage feedback circuit composed of a hysteresis feedback circuit composed of an operational amplifier and a threshold setting circuit, and the balanced reference signal Vref is supplied to the setting terminal of the threshold setting circuit to compare the voltages. The index position signal c is supplied to the comparison signal input terminal of the voltage comparison circuit as a reference signal of the circuit.

As shown in waveforms (l) and (f), the index position signal c is a high level when the potential of the index position signal c exceeds the potential of the balanced reference signal Vref, and a low level rectangular wave when it is lower than the potential of the balanced reference signal Vref. c is shaped and an index shaping signal f is generated.

The discrimination means 16 comprises an RS type flip-flop and a D type flip-flop, and based on the peak comparison signal e supplied from the voltage comparison means 14 and the index shaping signal f supplied from the waveform shaping means 15. The index signal h is generated.

Further, the discrimination means 16 uses the peak comparison signal e
An RS flip-flop that is set at a low level of and is reset at a low level of the index shaping signal f,
The output signal g from the RS flip-flop is supplied to the D input terminal, the index shaping signal f is supplied to the CK input terminal, and D triggered by the falling edge of this signal is supplied.
Type flip-flop.

As shown in FIG. 2, the waveform (g) is output from the output terminal of the RS flip-flop, and the index signal h shown in the waveform (h) is output from the NQ output terminal of the D-type flip-flop.

[0104]

As described above, the rotational position detecting device according to the present invention comprises the offset correcting means for generating the offset signal based on the exciting current detection signal supplied from the brushless motor, and the differential amplifying means , Because the offset signal can correct the rotor position detection signal that is distorted by the influence of the magnetic field generated by the armature coil,
Even if the load applied to the rotor fluctuates, the rotor operates stably and the index signal can be reliably obtained.

Further, in the rotational position detecting device according to the present invention, since the balanced reference signal provided by the differential amplifying means is supplied to the reference potential side of the peak hold capacitor provided in the peak hold means, the index position signal Since the potential relationship of (Vsh> V2) does not change even if there is a variation in amplitude, the index does not depend on variations in the index position signal due to the temperature characteristics of the Hall element, variations in the mounting process, etc. You can get a signal.

Therefore, in the rotational position detecting device according to the present invention, even if the Hall element for detecting the non-magnetized portion provided in one of the permanent magnets arranged in the rotor is affected by the magnetic field generated by the exciting current, In addition, it is possible to provide a rotational position detection device that operates stably with respect to load fluctuations applied to the rotor, has a wide stable operating temperature range, and has high production efficiency.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a rotational position detecting device according to the present invention.

FIG. 2 is a timing chart of the rotational position detecting device according to the present invention.

FIG. 3 is a block configuration diagram of a conventional rotational position detecting device.

FIG. 4 is a timing chart of a conventional rotational position detecting device.

FIG. 5 is an enlarged timing diagram of a conventional rotational position detecting device.

FIG. 6 is a schematic front view of a four-phase brushless motor.

FIG. 7 is a schematic side view of a four-phase brushless motor.

[Explanation of symbols]

1 ... Rotational position detection device, 2 ... Rotor, 3 ... Permanent magnet, 4
... Stator, 6 ... Armature coil, 7 ... Rotor position detection means, 8 ... Non-magnetized part, 9 ... Drive device, 10 ... Offset correction means, 11 ... Differential amplification means, 12 ... Peak hold means, 13 ... Reference Voltage generating means, 14 ... Voltage comparing means, 1
5 ... Waveform shaping means, 16 ... Discrimination means, C ... Peak hold capacitors, HG1, HG2 ... Hall element, R ... Discharge resistance, Rof ... Input stage resistance, a, b ... Rotor position detection signal, a ', b ′ ... Signal voltage component of rotor position detection signal, a ″, b ″ ... Error voltage component of rotor position detection signal,
c ... Index position signal, d ... Peak hold signal,
e ... Peak comparison signal, f ... Index shaping signal, h ...
Index signal, tg ... Gap between permanent magnet and motor board, Ed ... Discharge potential after T seconds of peak hold signal, I
of ... Offset signal, T ... Cycle of rotor position detection signal, Vb ... Error voltage amplitude, Vc ... Index position signal peak potential, Vnf ... Excitation current detection signal, Vof ... Input offset voltage, Vref ... Balance reference signal, Vsh ... Comparison Reference signal, Vt ... Discharge potential T seconds after the comparison reference signal,
V1 ... Peak potential of the index position signal at the magnetized portion magnetic pole detection timing, V2 ... Peak potential of the index position signal at the non-magnetized portion magnetic pole detection timing.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hideki Maedo 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Inventor Masao Mizumoto Keihan Hondori, Moriguchi City, Osaka Prefecture 2-5-5 Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A differential amplification means for generating an index position signal and a balanced reference signal based on a rotor position detection signal supplied from a brushless motor, and a peak hold means for detecting and holding a maximum value of the index position signal. In the rotational position detection device that generates an index signal based on the rotor position detection signal supplied from the brushless motor, the rotational position detection device, based on the excitation current detection signal supplied from the brushless motor A rotational position detecting device comprising an offset correction means for generating an offset signal. 2. The rotational position detecting device according to claim 1, wherein a balanced reference signal provided by the differential amplifying means is supplied to a reference potential side of a peak hold capacitor provided in the peak hold means. .