JPH03250450A - Device for driving disk - Google Patents

Abstract

PURPOSE:To stably obtain an index signal by forming a bias magnet for impressing a magnetic bias to a magnetic flux detecting element. CONSTITUTION:The bias magnet 9 for impressing the magnetic bias is formed on the back of the magnetic flux detecting element 8. On the other hand, S and N poles are fixed to both the ends of the magnet 9 and the magnetic poles are arranged so that the same polarity as that of a driving magnet 6 to which an index magnet 7 is fixed is turned to the magnet 7 in order to include index pulse width within a regulated value. Since the magnet 9 is arranged, the same state as the retreat of the magnetic force generating area of both the magnets 6, 7 from the element 8 is generated and the magnetic force of the magnet 6 having the same polarity as that turned to the magnet 7 side is weakened against the magnetic flux detecting element. Thereby, the element 8 is driven only by the magnet without being driven by the magnet 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disk drive device for rotationally driving a disk medium based on an index signal.

[Prior Art] FIGS. 5 and 6 are a plan view and a front sectional view showing a conventional disk drive device.

The disk drive device shown here is mainly composed of a drive mechanism belonging to a brushless motor, and is roughly divided into a rotor and a stator.

The stator includes a printed circuit board l on which a circuit pattern is formed on the surface and a bearing 2 held in the center, and a bearing 2.
It is composed of a plurality of coils 3 arranged radially at equal intervals (with respect to the circumferential direction) around the periphery of the coil 3 and energized by a predetermined mote.

On the other hand, the rotor has a rotating shaft 4 which is supported by a bearing 2, and a disk-shaped rotor yoke 5 which is rotatably fixed to the upper part of the rotating shaft 4. On the lower surface of the rotor yoke 5, driving machinets 6 are provided, each of which has an S pole and an N pole arranged in close contact with each other in the circumferential direction.

In addition to the drive mechanism having such a configuration, an index pulse detection mechanism is also provided. This index pulse detection mechanism includes an index magnet 7 that acts on the center of the outer periphery of one of the drive magnets 6 provided on the rotor yoke to strengthen the magnetic force of the polarity, and a fixed arrangement opposite to this index magnet 7. It is composed of a magnetic flux sensing element 8. The magnetic flux sensing element 8 is, for example,
A Hall IC including a Hall element is required.

In the above configuration, the rotor can be rotated by applying a pulse current to the coil 3 from a drive circuit (not shown) that performs pulse width modulation to generate a rotating magnetic field. A rotational force is generated in the rotor yoke 5 due to the counterforce that is sequentially generated between the rotating magnet y and the driving magnet 6, and the rotor yoke 5 rotates.

Along with this rotation, an index pulse is generated every time the index magnet 7 passes directly in front of the magnetic flux sensing element 8. Using this index pulse, the drive circuit controls the timing of energization of each coil 3 and operates to maintain a desired speed.

[Problem to be solved by the invention] However, in the above-mentioned conventional disk drive device,
The seventh
As shown in the figure (in the figure, the shaded area indicates the range of variation in the on-point of the magnetic flux sensing element 8), even though it is desired to detect only the index magnet, the driving magnet may be detected. there were. For this reason,
This resulted in a decrease in yield and reliability.

The object of the present invention has been made in view of the above-mentioned state of the prior art, and provides a disk drive device that prevents magnetic flux detection by a drive magnet and allows index pulses to be within the standard. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a rotor in which driving magnets are arranged in a disk shape such that different polarities are adjacent to each other, and a driving magnet for this rotor. a stator disposed to face the stator; an index magnet attached to the outer peripheral edge of any one of the drive magnets; In a disk drive device equipped with a magnetic flux sensing element that generates an index signal each time the magnetic flux sensing element passes, a bias magnet that applies a magnetic bias to the magnetic flux sensing element is provided.

[Operation] According to the above means, the bias magnet forms a state in which the magnetic force generation lines of the driving magnet and the index magnet for the magnetic flux sensing element are alternated, and the driving magnet and the index magnet are placed in the detection sensitivity region of the magnetic flux sensing element. It acts so that the magnetic force does not reach it. Therefore, the magnetic flux detection element operates only by the index magnet, and can stably obtain an index signal without picking up leakage magnetic flux from the drive magnet. Furthermore, it becomes possible to keep the index signal within the standard.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a plan view and a front sectional view showing a disk drive device of the present invention. In addition.

In FIGS. 1 and 2, the same reference numerals are used for the same parts as used in the conventional example described above. Therefore, redundant explanation will be omitted below.

As shown in FIGS. 1 and 2, this embodiment is characterized by a structure in which a bias magnet 9 for applying a magnetic bias is provided at the rear of the magnetic flux sensing element 8.

This bias magnet 9 has a structure in which an S pole and an N pole are provided at both ends. In order to keep the index pulse width shown in FIG. Deploy. In FIG. 1, since the driving magnet 6 on which the index magnet 7 is provided has an S pole, the bias magnet 9 has its S pole side facing the driving magnet 6 side.

By providing the bias magnet 9, a state similar to that in which the magnetic force generating areas of the driving magnet 6 and the index magnet 7 are retreated from the magnetic flux sensing element 8 occurs,
The driving magnet 6 having the same polarity as the index magnet 7 side has a weakened magnetic force with respect to the magnetic flux sensing element 8 .

As a result, the driving magnet 6 causes the magnetic flux sensing element 8 to
However, as shown in FIG. 4, only the index magnet 7 causes the magnetic flux sensing element 8 to operate.

[Effects of the Invention] As is clear from the above, according to the present invention, there is provided a rotor in which drive muckets are arranged in a disc shape so as to have different polarities or are adjacent to each other, and a rotor that faces the drive mucknets of this rotor. an index magnet attached to the outer periphery of any one of the drive magnets; and a stator fixedly installed opposite to the index magnet, with the index magnet passing through the opposing position. In a disk drive device equipped with a magnetic flux sensing element that generates an index signal every time an index signal is generated, a bias magnet that applies a magnetic bias to the magnetic flux sensing element is provided, so that magnetic flux leakage from the driving magnet is not picked up. , it is possible to obtain the index signal stably. Furthermore, it becomes possible to keep the index signal within the standard.

[Brief explanation of drawings]

FIG. 1 is a plan view of a disk drive device according to the present invention, FIG. 2 is a front sectional view of the configuration shown in FIG. 1, and FIG. 3 is an explanatory diagram showing the standard of index pulse width. FIG. 4 is an explanatory diagram showing the magnetic flux detection operation according to the present invention, FIG. 5 is a plan view of a drive device of a conventional disk drive device, and FIG. 6 is a front sectional view of the configuration of FIG. 5. FIG. 7 is an explanatory diagram showing the magnetic flux detection operation of a conventional disk drive device. In the figure, l Buwant board 2: Bearing 3: Coil 4, Rotation axis 5° Rotor yoke 6: Drive magnet 7: Index magnet 8, Magnetic flux sensing element 9: Bias magnet

Claims (1)

[Claims] a rotor in which drive magnets are arranged in a disk shape so that different polarities are adjacent to each other; a stator disposed to face the drive magnets of the rotor; and an outside of any one of the drive magnets. In the disk drive device, the disk drive device includes an index magnet attached to the periphery, and a magnetic flux sensing element that is fixedly installed opposite to the index magnet and generates an index signal every time the index magnet passes the opposing position. A disk drive device characterized by being provided with a bias magnet that applies a magnetic bias to a magnetic flux sensing element.