JPH08204254A - Motor - Google Patents

Abstract

PURPOSE: To obtain a motor in which a bias magnet can be set easily when it is required. CONSTITUTION: The motor comprises a rotor 10 carrying a multipolar magnet 13, a stator 20 having a magnetic permeable stator board 20 and holding the rotor 10 rotatably, a magnetoresistive element 22 mounted on the surface of the stator board 21 in order to detect variation in the flux of the magnet 13 carried on the rotor 10, and a section 40 in the stator board 21 for housing a bias magnet 30 which applies a magnetic bias depending on the magnetoresistive element 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor, and more particularly to improvement of a motor having a magnetoresistive element for detecting a change in magnetic flux of a rotor magnet.

[0002]

2. Description of the Related Art FIG. 10 shows a flat capstan motor provided in a VTR device or the like. The capstan motor includes a rotor 1 and a stator 2, and the rotor 1 is rotatable with respect to the stator 2. The rotor yoke 3 of the rotor 1 includes a main magnet 4 and a magnet 5.
It has. The stator 2 includes an iron substrate 6, a magnetic resistance element 7 and a coil 8. The magnetized surface 9 of the magnet 5 is magnetized so that S poles and N poles are alternately magnetized in the circumferential direction. The magnetoresistive element 7 is also called an MR sensor, and detects the change in the magnetic flux of the magnetized surface 9 of the magnet 5 which is magnetized in multiple poles, so that the rotational speed or the rotational speed of the rotor 1 can be detected. Has become.

[0003]

As shown in FIGS. 11 and 12, in the conventional capstan motor, the magnetoresistive element 7 is fixed to the iron substrate 6 via the holder 7a. The iron substrate 6 is a substrate forming a part of a magnetic circuit for passing a magnetic flux generated by energizing the coil 8. The magnetoresistive element 7 is arranged so as to face the magnetized surface 9 of the rotor 1 in the circumferential direction with a slight gap. In this way, the magnetoresistive element 7 is
Since the holder 7a of the magnetoresistive element 7 on the iron substrate 6 is used in a very large area, it can be said that the iron substrate 6 can be used effectively. If the iron substrate 6 is used in a large area, the rotation driving force of the rotor 1 cannot be sufficiently exerted. Therefore, a method is conceivable in which the magnetoresistive element 7 is made into a small chip and directly mounted on the iron substrate 6 so that the magnetoresistive element 7 faces the lower surface of the magnetized surface 9. By thus forming the magnetoresistive element 7 into a chip, the used area of the iron substrate 6 becomes 1/4 or less.

By the way, when a change in the magnetic flux in the multi-pole magnetized portion of the magnetized surface 9 is detected by using such a magnetoresistive element 7, a sine curve detection signal is obtained. There is a type that uses a bias magnet in the vicinity of the magnetoresistive element 7 in order to halve the signal period. This bias magnet applies a bias magnetic field to the magnetoresistive element 7 in addition to the magnetic field of the magnetized surface 9 to shift the output characteristic of the magnetoresistive element 7 to double the cycle of the detection signal. However, as described above, the magnetoresistive element 7
When surface mounting is performed on the iron substrate 6, it is not easy to dispose the bias magnet.

Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide a motor in which a bias magnet can be easily set even when a bias magnet is required.

[0006]

In order to achieve the above object, according to the invention of claim 1, a rotor provided with a magnet having multi-pole magnetization and a stator substrate made of a magnetically permeable material are provided.
A stator that rotatably holds the rotor, a magnetoresistive element that is disposed on the surface of the stator substrate and that detects a change in the magnetic flux of the magnet of the rotor, and a magnetic resistance element that corresponds to the magnetoresistive element. This is achieved by a motor having a housing for housing a bias magnet in the stator substrate for applying a bias. In the invention of claim 2, preferably, the accommodating portion of the bias magnet is a concave portion formed in the stator substrate corresponding to the magnetoresistive element. In the invention of claim 3, preferably, the accommodating portion of the bias magnet is a hole formed in the stator substrate corresponding to the magnetoresistive element. In the invention of claim 4, preferably, the rotor is integrated with a capstan shaft for feeding the tape-shaped recording medium.

[0007]

According to the above structure, in the invention of claim 1, it is only necessary to dispose the bias magnet in the accommodating portion of the stator substrate, and the bias magnet is separately provided in addition to the magnetic field of the magnet magnetized in multiple poles. The bias magnetic field is applied to the magnetoresistive element. In the invention of claim 2, the bias magnet is attached to the recess of the stator substrate, and in the invention of claim 3, the bias magnet is attached to the hole of the stator substrate.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

FIG. 1 shows a capstan motor which is a preferred embodiment of the motor of the present invention. The capstan motor includes a rotor 10, a stator 20 and a pulley 10.
a. The rotor 10 is the main magnet 1
1, a rotor yoke 12, a magnet 13 for detecting rotation,
A capstan shaft 14 and the like are provided. The pulley 10a is
The pulley 10a is fixed to a rotor boss (not shown) integrated with the rotor yoke 12 by, for example, caulking, so that the pulley 10a can transmit the rotation of the motor as a driving force of another mechanism. ing.

The stator 20 has an iron substrate 21, a magnetic resistance element 22, a coil 23, a housing 24, and a bearing 26. The main magnet 11 of the rotor 10 is, for example, a donut-shaped rotor rotation driving magnet in which N and S poles are alternately magnetized. The rotation speed detecting magnet 13 is, for example, a ring-shaped magnet in which N poles and S poles are alternately magnetized to have more poles than the driving main magnet 11. The rotation detecting magnet 13 is fixed to the peripheral surface of the rotor yoke 12. The magnet 13 includes the magnetized surface 25 in which the N poles and the S poles are alternately magnetized as described above. Capstan shaft 1
4 is rotatably supported by the bearing 26 of the housing 24 and the like.

The plurality of coils 23 of the stator 20 are fixed to one surface of the iron substrate 21 so as to face the main magnet 11. When the coil 23 is energized, the magnetic flux generated by the coil 23 is interrelated with the magnetic flux from the main magnet 11 via the magnetic path formed of the iron substrate 21, and the rotor 10
Are rotatable with respect to the stator 20. With this rotation, the capstan shaft 14 and a capstan roller (not shown) convey a magnetic tape such as a VTR tape in a predetermined direction by friction.

FIG. 2 shows a rotation detecting magnet 1 of FIG.
3 and the vicinity of the magnetoresistive element 22 are shown. FIG. 3 shows FIG. 2 in a larger scale. FIG. 3 shows the magnetized surface 25 of the magnet 13 for rotation detection, the magnetoresistive element 22, the bias magnet 30, the iron substrate 21, and the like. The magnetoresistive element 22 is a chip-shaped element, detects a change in magnetic flux of the N pole and the S pole on the magnetized surface 25 of the magnet 13, and controls a change in current in a sine curve shape by the change in magnetic flux. It can be sent to a target site such as a department. The iron substrate 21 is a magnetically permeable substrate, and the iron substrate 21 has a recess 40 formed therein. The recess 40 is formed so as to correspond to the lower surface of the chip-shaped magnetoresistive element 22, and the recess 40 is a housing portion for housing the bias magnet 30.

The magnetoresistive element 22 shown in FIGS. 3 and 4 is fixed to one surface 21a of the iron substrate 21. The magnetized surface 25 of the rotation detecting magnet 13 which is magnetized in multiple poles is arranged so as to face the magnetoresistive element 22. The bias magnet 30 is attached to the bottom surface of the magnetoresistive element 22 so as to fit into the recess 40 serving as a housing portion. By adopting the recess 40 in this way, that is, by partially making the iron substrate 21 half-blanked, the bias magnet 30 is recessed into the recess 4.
It can be fixed to 0 by inserting, press-fitting, or adhering with an adhesive, or a combination thereof. Even when the magnetic resistance element 22 is fixed to the one surface 21a of the iron substrate 21 by fixing the bias magnet 30 in the half-pulled state, the rotor 1 is
The bias magnet 30 can be arranged on the zero magnetized surface 25 without any space problem.

The bias magnet 30 of this type is arranged with respect to the magnetoresistive element 22 for the following reason. 6 and 7 show the output characteristics of the magnetoresistive element in the comparative example of the implementation exception of the present invention. In FIG. 6, the bias magnet 30 is not arranged in the recess 40, and the magnetoresistive element 22 is formed on the one surface 21 a of the iron substrate 21.
An example of the output characteristics of the magnetoresistive element 22 in the case where it is only fixed to is shown. The horizontal axis H represents the magnetic field and the vertical axis represents the resistance value, and the resistance value is highest when the magnetic field is zero. The resistance value decreases as the magnetic field progresses in the positive or negative direction.

FIG. 7 shows a waveform W1 of a change in the magnetic field of the magnetized surface 25 of the rotor 10 of FIG. 3 and an output waveform W2 of the magnetoresistive element.
Shows the correspondence of the waveforms of. As is apparent from FIG. 7, the waveform W1 of the change in the magnetic field of the magnetized surface 25 has a sine wave shape, and the output waveform W2 of the magnetoresistive element is also a sine waveform. Point P of the waveform W1 of the change in the magnetic field on the magnetically magnetized surface
Output waveform W of the magnetoresistive element corresponding to 1 to P10
The waveforms of points Q1 to Q10 in 2 correspond. That is, the waveform W1 indicated by the points P1 to P6
The output waveform W2 of the magnetoresistive element corresponds to points Q1 to Q6 corresponding to one cycle of. That is, one cycle of the waveform W1 of the magnetic field change corresponds to two cycles of the output waveform W2 of the magnetoresistive element.

8 and 9 show the output characteristics of the magnetoresistive element in the embodiment shown in FIG. 3 of the present invention, as compared with the comparative example of the implementation exception shown in FIGS. 6 and 7. That is, the characteristic is shown when the bias magnet 30 is set for the recess 40 of FIG. By setting the bias magnet 30 in this way, the peak PK of the resistance value of the magnetoresistive element moves to the minus magnetic field (-) side, as indicated by the arrow Y in FIG. That is, the resistance value peak PK is magnetically shifted, and the output characteristic of the magnetoresistive element 22 as shown in FIG. 8 is obtained. FIG. 9 shows the case of the output characteristic of the magnetoresistive element 22 of FIG. 8, and shows the correspondence between the waveform W3 of the change in the magnetic field due to the magnetizing surface 25 and the output waveform W4 of the magnetoresistive element. Points F1 to F7 in the waveform W3 of the change in the magnetic field correspond to G1 to G7 in the output W4 of the magnetoresistive element. That is, one cycle indicated by points G1 to G6 corresponds to the output waveform W4 of the magnetoresistive element in correspondence with one cycle corresponding to points F1 to F6 in the waveform W3 of the magnetic field change. Therefore, by arranging the bias magnet 30 in the magnetoresistive element 22, the output waveform of the magnetoresistive element is compared between FIG. 9 and FIG. 7 as shown in comparison with FIG. 6 to FIG. 9, for example. , Can be half the period (frequency).

Another Embodiment In the embodiment of FIG. 3, the bias magnet 30 is the iron substrate 2
It is fixed to the concave portion 40 of No. 1 by press fitting or adhesion with an adhesive. On the other hand, in the embodiment shown in FIG. 5, a hole 21b is formed in the iron substrate 21. This hole 21b
The bias magnet 30 is fixed to the base plate by press-fitting, bonding with an adhesive, or a combination thereof. A chip-shaped magnetoresistive element 22 is fixed to the upper surface 21 a of the iron substrate 21 so as to correspond to the bias magnet 30. The magnetized surface 25 of the magnet 13 for detecting the rotation of the rotor 10 faces the magnetic resistance element 22. The bias magnet 30 has, for example, a circular shape, a square shape, or a rectangular shape.

As described in the above embodiments, in the flat capstan motor, the chip-shaped magnetoresistive element 22 is used.
Is surface-mounted on the iron substrate 21, and the bias magnet 30 is arranged on the lower side corresponding to the surface-mounted magnetic resistance element 22. By arranging the bias magnet 30 so as to be embedded in the iron substrate 21 as described above, a model requiring such a bias magnet 30 for the magnetoresistive element 22 or a bias magnet 30 for the magnetoresistive element 22. It is possible to support both models that do not require.

When the magnetoresistive element 22 is surface-mounted on the iron substrate 21, a concave portion is a housing portion for disposing the bias magnet 30 at a position where the chip-shaped magnetoresistive element 22 is surface-mounted. 40 (see FIG. 3) and hole 21b
(See FIG. 5), the structure is simple because it is sufficient to set. By the way, by adopting the structure of the embodiment of the present invention, the used area on the iron substrate is reduced by about 25% as compared with the conventional case where the magnetoresistive element is fixed to the iron substrate using the holder. be able to. Therefore, the used area of the iron substrate is reduced, and the iron substrate can be downsized.

The present invention is not limited to the above embodiment. Although the iron substrate is used as the magnetically permeable material in the above-described embodiments, the present invention is not limited to this, and it is also possible to employ another type of magnetically permeable substrate. Although the capstan motor is described as an example of the motor in the above-described embodiments, the motor of the present invention can be applied to not only this but also motors in other fields.

[0021]

As described above, according to the present invention, the bias magnet can be easily set even when the bias magnet is required.

[Brief description of drawings]

FIG. 1 is a side view showing a capstan motor which is a preferred embodiment of a motor of the present invention.

FIG. 2 is a diagram showing a magnetized surface of a rotor of a capstan motor, a magnetoresistive element, and an iron substrate.

FIG. 3 is an enlarged view showing a portion of FIG.

FIG. 4 is a plan view showing a rotor, a magnetoresistive element, and an iron substrate.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing an output characteristic of a magnetoresistive element when there is no bias magnet.

FIG. 7 is a diagram showing the relationship between the waveform of the change in the magnetic field on the magnetized surface and the output waveform of the magnetoresistive element when there is no bias magnet.

FIG. 8 is a diagram showing output characteristics of a magnetoresistive element when a bias magnet is provided.

9 is a diagram showing the relationship between the waveform of the change in the magnetic field on the magnetized surface and the output waveform of the magnetoresistive element in the case of FIG.

FIG. 10 is a diagram showing a conventional capstan motor.

11 is an enlarged view showing the vicinity of a magnetic resistance element and a rotor of the conventional capstan motor of FIG.

12 is a plan view showing the rotor of FIG. 11, a magnetoresistive element, and an iron substrate.

[Explanation of symbols]

 10 rotor 13 multi-pole magnetized magnet 14 capstan shaft 20 stator 21 iron substrate (substrate made of magnetically permeable material) 21b hole (accommodation part) 22 magnetoresistive element 25 multi-pole magnetized surface 40 recess ( (Accommodation section)

Claims (4)

[Claims] 1. A rotor provided with a magnet that is magnetized in multiple poles, a stator provided with a stator substrate made of a magnetically permeable material, and a stator for rotatably holding the rotor, and a stator disposed on a surface of the stator substrate. A magnetoresistive element for detecting a change in magnetic flux of the magnet of the rotor; and an accommodating portion for accommodating a bias magnet in the stator substrate to apply a magnetic bias corresponding to the magnetoresistive element, A motor comprising: 2. The motor according to claim 1, wherein the accommodating portion of the bias magnet is a concave portion formed in the stator substrate so as to correspond to the magnetoresistive element. 3. The motor according to claim 1, wherein the accommodating portion of the bias magnet is a hole formed in the stator substrate corresponding to the magnetoresistive element. 4. The motor according to claim 2, wherein the rotor is integrated with a capstan shaft for feeding a tape-shaped recording medium.