JPH04371015A - Pulse generator - Google Patents

Abstract

PURPOSE:To use an index magnet having a low magnetic characteristic advantageous with respect to cost by selecting the arrangement of the index magnet in consideration of the leakage magnetic flux from a driving magnet and obtaining a stable pulse width to suppress the influence due to the leakage in the index magnet part upon peripheral equipments. CONSTITUTION:The motor built in a pulse generating device consists of a rotor yoke 4, a driving magnet 5 constituting the yoke, a motor shaft 6, a printed circuit board 7, a coil 8, a stator 9, a housing 10, and bearings 11 and 12. In this constitution, an index magnet 1 arranged with the S pole face outside, a magnetic flux detecting element 2 which is close to the yoke 4 and consists of a Hall IC to sense the S pole magnetic flux, and a printed circuit board 3 are provided in the neutral zone of magnetization of the magnet 5, and the overall quantity of the magnetic flux is suppressed to obtain a fixed magnetic flux, consequently, a stable pulse width. Thus, elements affected by magnetism are not present around the detecting element 2.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a pulse generator that generates pulse signals for position detection and rotation detection, and in particular, the present invention relates to a pulse generator that generates pulse signals for position detection and rotation detection. The present invention relates to a pulse generator that is incorporated in a motor configured as shown in FIG.

0002

[Prior Art] Conventionally, a pulse generator incorporated in a motor as described above for detecting the position and rotation of a motor shaft uses an index magnet on the outer peripheral surface of a motor rotor formed from a drive magnet. It was fixed in any position (regardless of the magnetic pole of the driving magnet).

0003

However, the above-mentioned conventional example has the following drawbacks because it does not take into account the leakage magnetic flux of the drive magnet that constitutes the rotor of the motor. That is, since the leakage magnetic flux of the drive magnet and the magnetic flux of the index magnet overlap arbitrarily, there is a large variation in the total amount of magnetic flux received by a magnetic flux sensing element, such as a Hall IC (Hall IC). There was a drawback that the variation in pulse width became large.

[0004] Furthermore, when a magnetic detection mechanism such as a magnetic head is disposed around the motor, and the above-mentioned total magnetic flux is large, the total magnetic flux affects the recording and reproducing waveforms of the magnetic head. There were also drawbacks such as mechanical parts malfunctioning.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pulse generator configured to take into account the leakage magnetic flux of the drive magnet so that there is no variation in the total amount of magnetic flux.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a pulse generator provided in a motor in which drive magnets are arranged around a motor shaft so that their polarities alternate. , an index magnet arranged on the outer peripheral surface of the drive magnet, and a magnetic flux arranged at a distance from the index magnet so as to detect the magnetic flux of the index magnet, and which generates an index pulse signal when the index magnet passes an opposing position. The present invention employs a pulse generator characterized in that the position of the index magnet with respect to the drive magnet is in a fixed relationship with the position of the drive magnet.

[0007] Furthermore, in the pulse generator, if it is desired to suppress the total amount of magnetic flux, it is desirable to arrange the index magnet at a position opposite to the neutral zone of the magnetization of the drive magnet, and to increase the total amount of magnetic flux. In some cases, the index magnet is arranged so as to be centrally opposed to the poles of the drive magnet.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side sectional view of a motor and a pulse generator of a first embodiment incorporated in the motor, FIG. 2 is a plan view of FIG. 1, and FIG. 3 shows a magnetic flux generated when the motor rotates. It is a graph showing the total amount of magnetic flux detected by a detection element.

In FIGS. 1 and 2, the motor consists of a rotor yoke 4, a drive magnet 5 (a drive magnet arranged such that its north and south poles are arranged alternately around the motor shaft) constituting the rotor, and a shaft. It consists of a (motor shaft) 6, a motor PCB (printed circuit board) 7, a coil 8, a stator 9, a housing 10, and bearings 11 and 12. A pulse generator is built into this motor, and the pulse generator is connected to the index magnet 1 which is arranged so that the S pole surface is facing outward in the neutral zone of the magnetization of the drive magnet 5, and the index magnet 1 which is spaced apart from the drive magnet 4. A magnetic flux sensing element 2 such as a Hall IC that senses the S-pole magnetic flux placed close to each other across the
It consists of a PCB (printed circuit board) 3.

When the motor is driven, the total amount of magnetic flux detected by the Hall IC 2 is the sum of the zero value of the sine wave of the leakage magnetic flux and the amount of magnetic flux of the index magnet 1, as shown in FIG. is above the ON level of the Hall IC, but below the amount of magnetic flux that would have an adverse effect. Therefore, by arranging the index magnet 1 in the neutral zone of the magnetization of the drive magnet as described above, it is possible to suppress the total amount of magnetic flux, obtain a constant magnetic flux, and obtain a stable pulse width. It will be done.

Next, a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. Similar to FIG. 1, FIG. 4 shows the index magnet 1 placed around the rotor.
In this embodiment, the index magnet 1 is arranged at the center of the S pole of the drive magnet 5. For this reason,
As shown in Figure 5, the total amount of magnetic flux detected by the Hall IC is
Index magnet 1 is placed at the peak of the sine wave of leakage magnetic flux.
The value is obtained by adding the amount of magnetic flux of , and a large value that considerably exceeds the on level of the Hall IC is obtained. Therefore, this embodiment is suitable when there are no elements around the magnetic flux sensing element that are affected by magnetism. Furthermore, since the total amount of magnetic flux to be detected only needs to slightly exceed the on-level of the Hall IC, the index magnet can be made of a material with low magnetic properties, which is advantageous in terms of cost.

0012

[Effects of the Invention] As explained above in detail, in the present invention, the arrangement of the index magnet is selected in consideration of leakage magnetic flux from the drive magnet, so a stable pulse width can be obtained, and The influence of peripheral devices can be suppressed, and index magnets with low magnetic properties can be used, which is advantageous in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view of a motor and a first embodiment of a pulse generator incorporated in the motor.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a graph showing the total amount of magnetic flux detected by a magnetic flux detection element when the motor rotates.

FIG. 4 is a plan view of the second embodiment.

FIG. 5 is a graph showing the total amount of magnetic flux in the second example.

[Explanation of symbols]

1 Index magnet 2 Magnetic flux sensing element 3 Hall ICPCB 4 Rotor yoke 5 Driving magnet 6 Shaft (motor shaft) 7 Motor PCB 8 Coil

Claims (3)

[Claims] Claim 1: A pulse generator provided in a motor in which drive magnets are arranged around a motor shaft so that their polarities alternate, an index magnet arranged on the outer peripheral surface of the drive magnet, and a magnetic flux of the index magnet. It has a magnetic flux sensing element that is arranged at a distance from the index magnet to detect the index magnet and generates an index pulse signal when the index magnet passes the opposing position, and drives the arrangement position of the index magnet with respect to the drive magnet. A pulse generator characterized by having a constant relationship with the arrangement position of a magnet. 2. The pulse generator according to claim 1, wherein each of the index magnets is arranged at a position opposite to a neutral zone of magnetization of the drive magnet to suppress the total amount of magnetic flux detected by the magnetic flux detection element. A pulse generator characterized by: 3. The pulse generator according to claim 1, wherein each of the index magnets is arranged to face the center of the pole of the drive magnet to increase the total amount of magnetic flux detected by the magnetic flux detection element. A pulse generator characterized by: