JP2005051855A - Rotational position detecting circuit of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotational position detecting circuit of a motor which does not use a Hall element for a lower manufacturing cost. <P>SOLUTION: The rotational position detecting circuit of a motor comprises a stator part 30 in which a plurality of magnetic pole members are spaced around a rotational axis with a stator coil 36 wound, and a rotor part 32 whose entire circumference is evenly divided and alternately magnetized in S poles and N poles. One magnetic pole member in the stator part is wound with an index detecting coil 37 instead of the stator coil 36, and one section among a plurality of magnetized sections of the rotor part 32 is reduced in magnetization relative to other magnetized sections to constitute a demagnetized part 38. The demagnetized part 38 of the rotating rotor part 32 is detected by the index detecting coil 37. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotational position detection circuit for a motor, and more particularly to a rotational position detection circuit for a motor that detects the rotational position of a spindle motor.
[0002]
[Prior art]
FIG. 4 is a plan view showing an example of a spindle motor in a flexible disk device provided with a rotational position detection circuit of a conventional motor. In the figure, the spindle motor includes a stator portion 10 and a ring-shaped rotor portion 12 that surrounds the outer periphery of the stator portion 10 and rotates around a rotation shaft 14.
[0003]
The stator portion 10 is configured by fixing an iron core member 15 having 18 pole pieces 15a arranged at equal intervals around a rotating shaft 14, and winding a stator coil 16 around each of the pole pieces 15a. The stator coil 16 is provided with six sets of three phases of U phase, V phase, and W phase.
[0004]
The rotor part 12 is magnetized alternately in S poles and N poles by dividing the entire circumference into 20 parts, for example. An index detecting magnet 18 is fixed at one place on the outer periphery of the rotor portion 12. The Hall element 22 is fixed to the circuit board 20 at a position facing the rotor portion 12.
[0005]
FIG. 5 shows a block diagram of an example of a conventional rotational position detection circuit of a motor. In the figure, an index detection circuit 24 as a rotational position detection circuit is provided on the circuit board 20, and two voltage output terminals of the Hall element 22 are connected to terminals 25a and 25b. A bias application terminal of the Hall element 22 is connected to the terminal 25c, and a reference voltage (bias voltage) is applied from a reference voltage source 26 in the index detection circuit 24.
[0006]
The terminals 25a and 25b are connected to the inverting input terminal and the non-inverting input terminal of the comparator 27a via resistors R1 and R2. The non-inverting input terminal of the comparator 27a is connected to one end of the constant current source 27b, and the other end of the constant current source 27b is grounded via the switch 27c. The switch 27c is turned on only when the output of the comparator 27a is low level, connects the constant current source 27b to the non-inverting input terminal of the comparator 27a, and the comparator 27a has hysteresis only on the high level side. That is, the comparator 27a, the constant current source 27b, and the switch 27c constitute a hysteresis comparator.
[0007]
Here, when the start signal (S / S) shown in FIG. 6 (A) becomes a low level and the rotor section 12 rotates, the index between the terminals 25a and 25b is as shown by the solid and broken lines in FIG. 6 (B). A sine wave detection signal is obtained every time the detection magnet 18 passes the position facing the hall element 22, and the comparator 27a compares this with the threshold value Vhys, and compares the pulse signal (Z signal) shown in FIG. ) Is output.
[0008]
The Z signal is supplied to the delay circuit 28, which generates the I signal shown in FIG. 6D that rises with a delay of time T1 from the fall timing of the Z signal and falls with a delay of time T2. Is supplied to the output circuit 29, and the output circuit 29 outputs the index signal (ID signal) shown in FIG. 6E obtained by inverting the I signal from the terminal 25e.
[0009]
Examples of generating an index signal using a Hall element as described above include those described in Patent Document 1 or Patent Document 2. Further, Patent Document 3 discloses a technique in which a part of the magnetic flux of the rotor magnet is leaked to the outside from a window provided in the rotor yoke, and this leakage magnetic flux is detected by a coil.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-339889
[Patent Document 2]
Japanese Patent Application Laid-Open No. 10-127087
[Patent Document 3]
JP 2000-44891A [0013]
[Problems to be solved by the invention]
A circuit that generates an index signal using a conventional Hall element has a problem that the cost increases because an expensive Hall element is required. Further, the conventional circuit for detecting the leakage magnetic flux by the coil has a problem that the man-hour is increased because the window portion is provided in the rotor yoke, which takes time and increases the manufacturing cost.
[0014]
The present invention has been made in view of the above points, and an object thereof is to provide a rotational position detection circuit for a motor that can reduce the manufacturing cost without using a Hall element.
[0015]
[Means for Solving the Problems]
According to the first aspect of the present invention, a stator portion (30) in which a plurality of magnetic pole pieces are arranged at equal intervals around a rotating shaft and a stator coil (36) is wound, and the entire circumference is equally divided into S poles, A rotational position detection circuit of a motor having rotor portions (32) alternately magnetized to N poles,
An index detecting coil (37) is wound around one magnetic pole piece of the stator portion instead of the stator coil (36),
Demagnetizing one portion of the plurality of magnetized portions of the rotor portion (32) with respect to the other magnetized portions to constitute a demagnetized portion (38),
By detecting the demagnetization part (38) of the rotating rotor part (32) with the index detection coil (37), the rotational position can be detected without using a Hall element, and a window part is provided in the rotor yoke. Therefore, the manufacturing cost can be kept low.
[0016]
The invention according to claim 2 comprises a hysteresis comparator (48) for rectangularizing the detection signal output by the index detection coil (37),
By having a logic circuit (50) that generates a pulse-shaped index signal at a pulse missing portion corresponding to the demagnetization section (38) from the output signal of the hysteresis comparator (48), a pulse-shaped rotational position detection signal is obtained. An index signal can be output.
[0017]
In the invention according to claim 3, the logic circuit includes an inverter (52) for inverting the output signal of the hysteresis comparator (48), and
A delay circuit (54) for delaying the output signal of the hysteresis comparator (48) for a predetermined time;
An AND circuit (56) that performs an AND operation on the output signal of the inverter (52) and the output signal of the delay circuit (54);
The invention according to claim 2 can be realized by having an adjustment circuit (58, 60) that performs waveform shaping and timing adjustment of the output signal of the AND circuit (56) and outputs the result.
[0018]
In the invention according to claim 4, the adjustment circuit includes a second delay circuit (58) that outputs a signal having a predetermined pulse width that rises after a predetermined time from the rise of the output signal of the AND circuit (56);
The invention according to claim 3 can be realized by having an output circuit (60) for inverting the output signal of the second delay circuit (58).
[0019]
Note that the reference numerals in the parentheses are given for ease of understanding, are merely examples, and are not limited to the illustrated modes.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a plan structural view of an embodiment of a spindle motor in a flexible disk device provided with a motor rotational position detection circuit of the present invention. In the figure, the spindle motor includes a stator portion 30 and a ring-shaped rotor portion 32 that surrounds the outer periphery of the stator portion 30 and rotates around a rotation shaft 34.
[0021]
The stator portion 30 is configured by fixing an iron core member 35 having 18 pole pieces 35a arranged at equal intervals around a rotating shaft 34, and winding a stator coil 36 around 17 pole pieces 35a out of 18 poles. Has been. The stator coil 36 is provided with 6 sets of U and V phases and 5 sets of W phases for the three phases U phase, V phase and W phase. An index detection coil 37 is wound around the remaining magnetic pole piece 35b for one W-phase.
[0022]
The rotor portion 32 is magnetized alternately into S poles and N poles by dividing the entire circumference into 20 parts, for example. One of the 20 magnetized portions is demagnetized with respect to the other magnetized portion to constitute a demagnetized portion 38.
[0023]
The circuit board 40 has terminals 36a, 36b, 36c of the stator coil 36 and terminals 37a, 37b of the index detection coil 37 drawn out.
[0024]
FIG. 2 shows a block diagram of an embodiment of the rotational position detection circuit of the motor of the present invention.
In the figure, an index detection circuit 44 as a rotational position detection circuit is provided on a circuit board 40, and both ends of an index detection coil 37 are connected to terminals 45a and 45b. One end of an index detection coil 37 is connected to the terminal 45c, and a reference voltage (bias voltage) is applied from a reference voltage source 46 in the index detection circuit 44.
[0025]
The terminals 45a and 45b are connected to the inverting input terminal and the non-inverting input terminal of the hysteresis comparator 48 through resistors R11 and R12. A resistor R13 is connected between the output terminal of the hysteresis comparator 48 and the inverting input terminal.
[0026]
Here, when the start signal (S / S) shown in FIG. 3A becomes a low level, the rotor portion 32 rotates. As shown by a solid line and a broken line in FIG. 3B, between the terminals 45a and 45b, a sine wave detection signal (the amplitude of which decreases every time the demagnetizer 38 passes through a position facing the index detection coil 37). Coil signal) is obtained.
[0027]
The hysteresis comparator 48 includes a first threshold value VhysH corresponding to, for example, 90% of the maximum value of the sine wave waveform of the coil signal shown in FIG. 3B and a second threshold value corresponding to, for example, 10% of the minimum value of the sine wave waveform. VhysL, and outputs a signal that becomes high level when the coil signal exceeds the first threshold value VhysH and becomes low level when the coil signal falls below the second threshold value VhysL.
[0028]
That is, the hysteresis comparator 48 rectangularizes the coil signal and outputs a pulse signal (Z signal) shown in FIG. Here, in the portion where the amplitude of the coil signal corresponding to the demagnetizing unit 38 is reduced, the first threshold value and the second threshold value of the hysteresis comparator 48 are not reached, and the Z signal is lost by one pulse.
[0029]
This Z signal is supplied to an inverter 52 and a delay circuit 54 in the delay circuit 50. The inverter 52 inverts the Z signal to generate the Z1 signal shown in FIG. The delay circuit 54 generates the Z2 signal shown in FIG. 3E that rises with a delay of time T0 from the falling timing of the Z signal, and supplies the Z2 signal to the AND circuit 56.
[0030]
The delay time T0 is set to be about one cycle of the coil signal when the rotational speed of the rotor section 32 is approximately 300 rpm or approximately 360 rpm. As a result, the AND circuit 56 outputs only one pulse of the Z3 signal shown in FIG. 3F during the high level period of the Z1 signal corresponding to the one-pulse missing portion of the Z signal.
[0031]
The Z3 signal is supplied to the delay circuit 58, and the delay circuit 58 rises with a delay of time T1 from the rising timing of the Z3 signal, and falls with a delay of time T2 from the rising timing of the Z3 signal, as shown in FIG. The I signal is generated and supplied to the output circuit 60, and the output circuit 60 outputs the index signal (ID signal) shown in FIG. The delay circuit 58 and the output circuit 60 perform waveform shaping and timing adjustment.
[0032]
As described above, in this embodiment, the rotational position of the motor can be detected using an inexpensive coil instead of an expensive Hall element, and it is not necessary to provide a window portion in the rotor yoke, and manufacturing is performed while suppressing an increase in man-hours. Cost can be kept low.
[0033]
【The invention's effect】
As described above, according to the first aspect of the present invention, an index detection coil is wound around one magnetic pole piece of the stator portion instead of the stator coil, and one of the plurality of magnetized portions of the rotor portion is wound. The demagnetizing part is demagnetized with respect to other magnetized parts to form a demagnetizing part, and the demagnetizing part of the rotating rotor part is detected by the index detection coil, thereby detecting the rotational position without using the Hall element. Thus, there is no increase in man-hours such as providing a window on the rotor yoke as in the prior art, and the manufacturing cost can be kept low.
[0034]
According to a second aspect of the present invention, a hysteresis comparator that rectangularizes a detection signal output from the index detection coil, and a pulse-shaped index signal is generated from the output signal of the hysteresis comparator at a missing pulse portion corresponding to the demagnetization unit. By having a logic circuit, a pulsed index signal can be output as a rotational position detection signal.
[0035]
In the invention according to claim 3, the logic circuit includes an inverter that inverts the output signal of the hysteresis comparator, a delay circuit that delays the output signal of the hysteresis comparator for a predetermined time, an output signal of the inverter, and an output signal of the delay circuit. The invention according to claim 2 can be realized by including an AND circuit that performs AND operation and an adjustment circuit that performs waveform shaping and timing adjustment of an output signal of the AND circuit.
[0036]
According to a fourth aspect of the present invention, the adjustment circuit includes a second delay circuit that outputs a signal having a predetermined pulse width that rises a predetermined time after the rising of the output signal of the AND circuit, and an output that inverts the output signal of the second delay circuit. By having the circuit, the invention of claim 3 can be realized.
[Brief description of the drawings]
FIG. 1 is a plan structural view of an embodiment of a spindle motor in a flexible disk device equipped with a motor rotational position detection circuit of the present invention.
FIG. 2 is a block diagram of an embodiment of a motor rotational position detection circuit according to the present invention.
3 is a signal waveform diagram of each part of the circuit in FIG. 2;
FIG. 4 is a plan structural view of an example of a spindle motor in a flexible disk device provided with a conventional motor rotational position detection circuit.
FIG. 5 is a block diagram of an example of a conventional rotational position detection circuit of a motor.
6 is a signal waveform diagram of each part of the circuit in FIG. 5;
[Explanation of symbols]
30 Stator part 32 Rotor part 34 Rotating shaft 35 Iron core member 35a Magnetic pole piece 35b Magnetic pole piece 36 Stator coil 37 Index detection coil 38 Demagnetizing part 40 Circuit board 46 Reference voltage source 48 Hysteresis comparator 52 Inverter 54, 58 Delay circuit 60 Output circuit

Claims (4)

A motor having a stator part in which a plurality of magnetic pole pieces are arranged at equal intervals around a rotating shaft and wound with a stator coil, and a rotor part that is equally divided into S and N poles by equally dividing the entire circumference. A rotational position detection circuit,
An index detection coil is wound around one magnetic pole piece of the stator portion instead of the stator coil,
Demagnetizing one portion of the plurality of magnetized portions of the rotor portion with respect to other magnetized portions to constitute a demagnetized portion,
A rotation position detection circuit for a motor, wherein the demagnetization portion of the rotating rotor portion is detected by the index detection coil. In the rotation position detection circuit of the motor according to claim 1,
A hysteresis comparator that rectangularizes the detection signal output by the index detection coil;
A rotation position detection circuit for a motor, comprising: a logic circuit that generates a pulsed index signal at a pulse missing portion corresponding to the demagnetization unit from an output signal of the hysteresis comparator. In the rotational position detection circuit of the motor according to claim 2,
The logic circuit includes an inverter that inverts an output signal of the hysteresis comparator;
A delay circuit for delaying the output signal of the hysteresis comparator for a predetermined time;
An AND circuit that performs an AND operation on the output signal of the inverter and the output signal of the delay circuit;
A motor rotational position detection circuit comprising an adjustment circuit that performs waveform shaping and timing adjustment of an output signal of the AND circuit and outputs the result. In the rotation position detection circuit of the motor according to claim 3,
The adjustment circuit includes a second delay circuit that rises after a predetermined time from the rise of the output signal of the AND circuit and outputs a signal having a predetermined pulse width;
A rotation position detection circuit for a motor, comprising an output circuit for inverting the output signal of the second delay circuit.

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