JPS5886609A - Generator for rotation position signal - Google Patents

Abstract

PURPOSE:To obtain a high-precision rotation position signal usable as a magnetic disk index signal at low cost, and to incorporate all parts in a motor, by equipping a magnetic sensor with a Hall element and high-gain amplifier. CONSTITUTION:A rotor 1 is fitted with an index magnet 5, and an iron core 3 is fitted with a bias magnet 6 facing said index magnet 5 and a magnetic sensor 7 positioned on the front surface of said magnet 6. For the sensor 7, an OP amplifier, etc., is combined with a sensor element for an analog output. The magnet 6 has the opposite polarity to the index magnet to inverting the polarity of a magnetic field operating on the Hall element of the magnetic sensor 7 when facing the index magnet 5, and therefore a magnetic field by a rotating magnet 2 and armature winding 5 is produced in the motor; and the magnet 6 has enough strength to stabilize the output polarity of the Hall element 10 against those magnetic fields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational position signal generator, and more particularly to a small, inexpensive, and highly accurate position i signal generator.

For example, in a magnetic disk storage device, in order to determine the □' position of the start of writing in one track, one
Although a rotational position signal (I9. index signal) is required at the rate of rotation, the signal does not change even if there are changes in the environment such as temperature and humidity or changes in the power supply voltage. must be extremely small, for example, the angle *
Accuracy of 0.2° or less is required.

In order to generate such highly accurate rotational position signals, conventionally, iron pieces were attached to the rotor of the magnetic disk drive motor, or recesses were provided in the iron rotor, and changes in magnetic resistance caused by these factors were detected using a proximity switch. The detection method was used. Although this method has a simple structure, it has the disadvantage that the proximity switch is very expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a small rotational position signal generating device which can obtain a highly accurate position signal at low cost without using the above-mentioned proximity switch, and which can house the entire device in a motor.

The implementation of the present invention will be described below with reference to all the drawings.

Figure tIi41 shows a rotating magnet type motor to which the present invention is applied.
1 is a rotor, 2 is a rotating magnet fixed to this, 3#i armature core, 4 is an armature winding, an index magnet 5 is attached to the rotor 1, and the index magnet 5 faces the iron core 3. A bias magnet 6 and a magnetic sensor 7 located in front of the magnet '6 are attached to the magnetic center t7, which has an analog output sensor element such as a Hall element, a KOP amplifier, or a high gain amplifier such as a voltage comparator. A Hall IC (
Hall switch) may be used.

Bias magnet 6Fi has a polarity opposite to that of the index magnet 5 so as to reverse the polarity of the magnetic field acting on the Hall element of the air sensor 7 when it faces the index magnet 5. A simple ferrite magnet is used, and a rare/earth (Baja) magnet with a 5K index coercive force is used. Inside the motor, there are magnetic fields generated by the rotating magnet 2 and magnetic fields generated by the electronic winding 4, so the bias magnet 6 must be strong enough to stabilize the output polarity of the Hall element against these magnetic fields. It is determined that there will be.

Figure 2 shows a circuit diagram of the magnetic sensor 7 that uses a Hall element. 8 is a DC power supply terminal, 9 is an index signal output terminal, 10 is a Hall element, 11 is an OF assist, and 12 is a feedback resistance for preventing chattering. When the motor is operated, a signal containing a pulse signal p corresponding to the rotation period To of the motor is applied to the output terminals a and b of the hole element 10, as shown in FIG. In the same figure, the m part is the bias magnet 6
%'' is the output due to the magnetic field whose polarity has been reversed by the index magnet 4. The latter output is waveform-shaped by the op amplifier 11 to become a rectangular wave pulse p1, and Ht is the The zero line of the combined magnetic field of both magnets 5 and 6 is shown.

The width of the pulse signal p1 changes depending on the waveform of the pulse signal p and the strength of the combined magnetic field of both the magnets 5.6. The pulse width of the signal p decreases almost linearly as the temperature increases, while the width of the two magnets 5.6 of 4! ! Since 1W magnetism has a negative temperature coefficient and is the magnet 6, the zero line t2 at -temperature is lower than the zero line jlK at low temperature. Therefore, the rising time T1 and falling time T2 of the pulse signal p1 are mt
As the temperature rises, 1 becomes tl.
It advances by te2tit2 and lags behind by te2tit2. According to experiments, t
lFi, the magnetic disk rotation speed was 3.9μ8 (at 56oo rpm).In other words, using a Hall element, a high-precision rotational position signal that fully satisfies the required accuracy of 4 angle IILtf 1 degree 0.2 degrees was obtained. In the Jokii experiment, the magnetic sensor 7 was attached to the part between the poles for measurement.

and a high gain amplifier 9.
In addition, it is possible to obtain a high-precision rotational position signal that can be used as an index signal for a magnetic disk at a low cost, and all the parts of the nine magazines produced in that year can be directly incorporated into the motor. Therefore, there are four things that make it easier to design the device.

[Brief explanation of drawings]

The drawing is a partial elevational view of one embodiment of the present invention, and Figure 2 is a circuit diagram of a magnetic sensor. FIGS. 3a and 3b are a Hall element output waveform diagram and a magnetic sensor output waveform diagram, respectively, and FIG. 4 is a physical property variation due to temperature at the time of the rise of the magnetic sensor output pulse. 1-...Motor rotor, S, 4...Motor stator, 5
... Index magnet, 6... Bias magnet,
7... Magnetic sensor °, 10... Hall element, 11.
...High gain amplifier. Representative patent attorney Tsuyoshi Yukawa - 1 other person

Claims (3)

[Claims] (1) An indexing magnet with a large holding force, a Hall element that rotates relative to the magnet and passes through the magnetic field of the magnet, and a high gain amplifier that increases the output of the Hall element in a t-bottom shape. a magnetic sensor; and a magnetic sensor magnet that moves integrally with the magnetic sensor and reverses the polarity of the magnetic field within the magnetic sensor upon passage of the magnetic sensor. (2) The 11-position pulse generator according to claim 1, wherein the index magnet is attached to the motor rotor, and the magnetic sensor and bias magnet are attached to the motor stator. (3) The rotational position signal generating device 0 according to claim 1 or 2, wherein the index magnet is a rare earth magnet, and the bias magnet is a ferrite magnet.