JPH03215153A - Motor - Google Patents

Abstract

PURPOSE:To prevent the magnetic flux of a permanent magnet from leaking to outside by completely covering the periphery of the permanent magnet and a stator with a back yolke and a yoke. CONSTITUTION:For a motor 18, the rotor 20 is constituted of a circular permanent magnet 5, which is magnetized in the specified number of poles, and a back yoke 19 made of magnetic material, which is so brought into contact as to wrap this. A stator 41 is constitute of plural sets of stator windings 21a and stator plates 22 made of nonmagnetic material, which are arranged in opposition with the permanent magnet 5. Furthermore, a motor shaft 24, which rotates in a body with the back yoke 19, is borne for free rotation by a bearing member 23. And the yoke 25 made of magnetic material, which is arranged opposite to the rotor 20 across the stator 41, is joined at the periphery end face 25a to the yoke 19 so that it may wrap the stator 20, thus it is so constituted as to be driven integrally with the rotor 20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a motor used in audiovisual equipment such as video tape recorders, audio cassette tape recorders, and record players.

BACKGROUND OF THE INVENTION A side sectional view of a conventional motor is shown in FIG. In FIG. 4, in this conventional motor 1, a first plane part 2 is magnetized with a predetermined number of poles, and a back yoke 4 made of a magnetic material is in contact with and fixed to a second plane part 3. By arranging the first flat part 2 of the annular permanent magnet 5 and the annular or disc-shaped yoke 6 made of a magnetic material that rotates integrally with the permanent magnet 5 to face each other, the rotor can be rotated. 7. In addition, a stator flat plate 10 made of a non-magnetic material has an electrical wiring section in which stator windings 9 of multiple phases are arranged in a magnetic space formed between the opposing surfaces of the permanent magnet 5 and the yoke 6. Equipped with A motor shaft 11 that is fixed to a back yoke 4 made of a magnetic material on the second flat part 3 of the permanent magnet 5 and rotates integrally with the back yoke 4 is attached to a motor board 1.
The bearing member 13 is fitted into the bearings 13a and 13b of the bearing member 13 attached to the bearing member 2, and is rotatably supported.

Further, the end surface of the motor shaft 11 is thrust-supported by coming into contact with the thrust receiving material 14 . An annular magnet 15 fixed to the outer circumferential surface of the back yoke 4 and magnetized with multiple poles on the outer circumferential surface has a magnetic detection element 1 disposed near the outer circumferential surface of the annular magnet 15.
6 constitutes a rotational frequency detection means 17.

Problems to be Solved by the Invention The conventional motor 1 configured as described above has a permanent magnet 5.
Since there is no magnetic shield in the radial direction of the magnetic space constituted by the yoke 6 and the yoke 6, the magnetic flux from the permanent magnet 5 leaks in the radial direction of the motor 1 and flows into the equipment equipped with the motor 1, causing magnetic flux in the equipment. There was a problem in that it caused external disturbances and deteriorated the performance of the equipment. Further, there is a problem in that switching noise generated when switching the energization of the stator winding 9 also enters the equipment and adversely affects the performance of the equipment.

In addition, there is also the problem that foreign objects are likely to enter between the opposing surfaces of the permanent magnet 5 and the stator winding 9 and between the opposing surfaces of the stator flat plate 10 and the yoke 6, causing malfunction of the motor 1.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a motor that prevents magnetic leakage and switching noise from entering equipment and has excellent dustproof effects.

Means for Solving the Problems In order to solve the above problems, the motor of the present invention includes a motor shaft, which rotates integrally with the motor shaft, and has a first plane portion magnetized with a predetermined number of poles. a rotor comprising an annular permanent magnet; and a back yoke made of a magnetic material and arranged on the second plane side of the permanent magnet and configured to wrap around the outer periphery of the permanent magnet; The stator includes a stator including a stator winding arranged opposite to the rotor, and a yoke made of a magnetic material and arranged opposite to the rotor with the stator in between, and the back yoke and The yoke is joined to the stator so as to wrap around the stator on the outer peripheral side of the stator, and the yoke is configured to be rotationally driven integrally with the rotor.

Function The present invention has the above-described configuration, so that the outer peripheral portions of the permanent magnet 5 and the stator 41 are connected to the back yoke 19 and the yoke 2.
5, even if the magnetic flux from the permanent magnet 5 leaks in the radial direction of the motor 1, the leaked magnetic flux will flow into the back yoke 19 or the yoke 25, so that it will not leak to the outside of the motor 18. There isn't.

Example A first embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a side sectional view of a first embodiment of the invention. 1st
In the figure, the motor 18 includes a circular permanent magnet 5 magnetized with a predetermined number of poles on a first plane part 2, and a back yoke 19 made of a magnetic material on a second plane part 3. A rotor 20 is constituted by a back yoke 19 which is fixed in contact with the rotor so as to wrap around the rotor. In addition, a plurality of phase stator windings 21 are arranged opposite to the first plane portion 2 of the permanent magnet 5.
The stator 41 is also constituted by a stator flat plate 22 made of a non-magnetic material and having an electric wiring portion to which the stator winding 21 is fixed. The motor shaft 24, which rotates integrally with the back yoke 19, is fitted into the bearings 23a and 23b of the bearing member 23 attached to the stator flat plate 22, and is rotatably supported. Further, the end surface of the motor shaft 24 is thrust-supported by contacting a thrust bearing 23c provided in the bearing member 23. On the outer periphery of the bearing member 23, a soldering portion 22 of the stator winding 21 provided on the stator flat plate 22 is provided.
a, and an electric circuit section (not shown) for driving the motor.
An electrical connection section 40 is provided for electrically connecting the two.

On the other hand, a yoke 25 made of a magnetic material, which is disposed opposite to the rotor 20 with the stator 41 in between, is joined to the back yoke 19 at an outer peripheral end surface 25a so as to wrap around the stator 20 on the outer peripheral side of the stator 20, and is rotated. It is configured to be rotationally driven integrally with the child 20.

This joint may be made by bonding the back yoke 19 and the yoke 25, or by providing a step on either the back yoke 19 or the yoke 25 as in the second embodiment shown in FIG. The yoke 25 is fitted to the back yoke 19 by using the attractive force due to the magnetic force of the permanent magnet 5,
Suction and bonding may also be used.

In the first embodiment of the motor of the present invention constructed as described above, the outer circumferential portions of the permanent magnet 5 and the stator 41 are completely covered by the back yoke 19 and the yoke 25, so that there is no light from the permanent magnet 5. Even if the magnetic flux leaks in the radial direction of the motor 1, the leaked magnetic flux flows into the back yoke 19 or the yoke 25, and therefore does not leak to the outside of the motor 18. Therefore, since no magnetic disturbance is applied to the equipment equipped with the motor 18, it is possible to obtain the effect that the performance of the equipment is not deteriorated. Further, switching noise generated when switching the current supply to the stator winding 21 is also shielded by the back yoke 19 or the yoke 25, so that it is possible to eliminate the effect on the equipment. Further, it is possible to obtain the effect that foreign objects and the like can be prevented from entering the motor 18 from outside. Furthermore, the effect of being able to shield motor noise caused by vibrations of the stator winding 21 due to the magnetic flux in the circumferential direction of the permanent magnet 5, vibrations of the stator flat plate 22 generated when switching the current supply to the stator winding 21, etc. can also be obtained. be able to.

The purpose of the second embodiment of the motor of the present invention is to prevent magnetic leakage caused by the motor's permanent magnets and switching noise caused by the motor's stator windings from entering the rotational frequency detection means, and to achieve high accuracy. The object of the present invention is to provide a motor with high rotational accuracy from which a rotational frequency detection signal can be obtained.

The rotational speed of the VTR's capstan motor and cylinder motor must be kept constant with extremely high precision, but if noise is superimposed on the rotational frequency detection signal and the S/N ratio of the signal worsens, the motor will rotate unevenly. As a result, the rotation accuracy of the motor deteriorates, making it difficult to obtain desired characteristics. In the conventional motor 1 shown in FIG. 4, a part of the leakage magnetic flux of the permanent magnet 5 reaches the back yoke 4 made of magnetic material, passes through the back yoke 4, and converges on the permanent magnet 5 again. . However, since there is no magnetic shield in the radial direction of the magnetic space constituted by the permanent magnet 5 and the yoke 6, a part of the leakage magnetic flux from the permanent magnet 5 also leaks in the radial direction of the motor 1, and the magnetic sensing element 16 It converges. Therefore, the magnetic detection element 16 is connected to the annular magnet 1.
Not only the leakage magnetic flux of the permanent magnet 5 but also the leakage magnetic flux of the permanent magnet 5 is detected, and noise with a frequency proportional to the number of magnetized poles of the permanent magnet 5 is superimposed on the output signal of the magnetic detection element 16, which impairs the rotation accuracy of the motor 1. There was a problem that it deteriorated.

A second embodiment of the present invention will be described below based on the drawings.

FIG. 2 is a side sectional view of a second embodiment of the invention. Components that are the same as those explained in FIG. 1 are denoted by the same reference numerals, and their explanation will be omitted. In FIG. 2, an annular cane magnet 29 is fixed on the outer peripheral surface of the back yoke 27 of the motor 26, the outer peripheral surface of which is magnetized with a plurality of poles and rotates integrally with the rotor 32. The annular magnet 29 and at least one magnetic detection element 30 provided near the periphery of the annular magnet 29 constitute a rotational frequency detection means 31. Further, a yoke 28 made of a magnetic material and arranged to face the rotor 32 is joined together with the back yoke 27 on the outer peripheral side of the stator 41 so as to wrap around the stator 41.

When the stator winding 21 of the motor 26 is energized, the rotor 32 rotates around the motor shaft 24 according to Fleming's law. As the rotor 32 rotates, the annular magnet 2
9 also rotates, the leakage magnetic flux from the annular magnet 2θ intersects with the magnetic detection element 30, and a signal with a frequency proportional to the rotation frequency of the rotor 32 is output, and the rotation frequency detection means 3
1 detects the rotation frequency of the rotor 32. And a control circuit (not shown) so that the period of the frequency signal is constant.
Controlled by The leakage magnetic flux of the permanent magnet 5 leaks to the vicinity of the magnetic detection element 30, but a back yoke 27 made of a magnetic material and a yoke 28 made of a magnetic material are interposed between the magnetic detection element 30 and the leakage magnetic flux to shield the leakage magnetic flux. do. Therefore, the leakage magnetic flux is caused by the back yoke 27 or the yoke 28.
After reaching , all back yoke 27 or yoke 2
8 and returns to the permanent magnet 5 again. Furthermore, if the thickness of the outer circumferential surfaces of the back yoke 27 and yoke 28 is made larger than the thickness of other parts, and is made thick enough to prevent magnetic saturation, the magnetic detection element 3 of the leakage magnetic flux
0 can be more completely prevented.

The second embodiment of the motor of the present invention configured as described above can shield leakage magnetic flux from the permanent magnet 5 to the magnetic detection element 30, and the magnetic detection element 30 can block only the leakage magnetic flux from the annular magnet 29. Therefore, noise components are not superimposed on the frequency signal of the rotor 32 detected by the rotational frequency detection means 31. Therefore, a motor with high rotational accuracy can be realized.

The purpose of the third embodiment of the motor of the present invention is to provide a motor that prevents the motor shaft from running out and also prevents the rotor of the motor from detaching when a severe impact is applied to the motor.

In order to reduce costs in the conventional motor 1 shown in FIG. 4, an inexpensive oil-impregnated sintered alloy is often used for the bearing that supports the motor shaft 11 instead of using an expensive ball bearing. However, bearing 13a. Due to the difference in temperature expansion coefficient between the bearing 13b and the motor shaft 11, the bearing 13
Since a proper clearance is essential between a, 13b and the motor shaft 11, motors in which the motor shaft 11 is always pressed in one direction in the radial direction (so-called lateral pressure is always applied) are excluded. Therefore, axial vibration of the motor shaft 11 within the clearance between the motor shaft 11 and the ldl receiver 1 3 al 1 3 b is unavoidable. Therefore, over time, the motor shaft 11 and bearings 1 3 a, 1 3
When the clearance between the two parts increases due to wear, etc., the phase of the center of rotation of the motor shaft 11 changes unspecified, resulting in aperiodic shaft runout, or periodic overall shaft runout that occurs constantly in the clearance. There was a problem in that it was easy for this to occur. If such a motor that is prone to shaft runout is used, there are problems in that it degrades the performance of the equipment and also causes bearing noise. In addition, in order to prevent shaft vibration in the radial direction of the motor shaft 11, a permanent magnet for attracting the motor shaft 11 is separately provided near the motor shaft 11, and the motor shaft 11 is moved in one direction by the attractive force of the permanent magnet. A configuration has been proposed in which this bias is applied, but since a permanent magnet for attraction must be provided separately, there are problems in that the number of parts and assembly man-hours increases, the structure is complicated, and costs are increased. Ta.

A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a side sectional view of a third embodiment of the invention. Components that are the same as those explained in FIG. 1 are denoted by the same reference numerals, and their explanation will be omitted. In FIG. 3, an annular magnet 35 is fixed on the outer peripheral surface of a back yoke 33 of a motor 32, the outer peripheral surface of which is magnetized with a plurality of poles and rotates integrally with a rotor 39. The rotational frequency detection means 38 is constituted by the annular magnet 35 and at least one magnetoresistive element 37 made of a ferromagnetic thin film having a magnetoresistive effect and provided near the periphery of the annular magnet 35. There is. The magnetoresistive element 37 is held by a holding member 36 made of a magnetic material and having protrusions 36a facing each other at a predetermined interval on the axial end face of the rotor 39, and the holding member 36 is a substrate on which the motor 32 is attached. (not shown). Further, a yoke 34 made of a magnetic material and arranged to face the rotor 39 is joined together with the back yoke 33 on the outer peripheral side of the stator 41 so as to wrap around the stator 41.

In the third embodiment of the motor of the present invention configured as described above, the rotor 39 is radially attached to the holding member 36 made of a magnetic material holding the magnetoresistive element 37 due to the magnetic force of the annular magnet 35. Since it is constantly attracted, the motor shaft 24 is always pressed in one direction in the radial direction of the bearings 23a and 23b.

Therefore, when the motor 32 rotates, side pressure is applied to the motor shaft 24 in the direction of the arrow A in FIG. 3, so that the motor shaft rotates without causing any vibration. In other words, motor shaft runout caused by the clearance between the motor shaft 24 and the bearings 23a, 23b can be reliably prevented. Furthermore, bearing noise caused by motor shaft runout can also be reduced. Therefore, there is no need to separately provide a permanent magnet for attraction to bias the motor shaft as in the conventional case, and a motor with a simple structure and low cost can be realized. Furthermore, since the holding member 36 is provided with protrusions 36a that are arranged opposite to each other at a predetermined interval on the end face of the rotor 39 in the axial direction, even when severe vibrations or shocks are applied to the motor, the motor cannot be reactivated. The motor 3 of the rotor 39 can be
It is also possible to obtain the effect of being able to prevent separation from 2.

Effects of the Invention As described above, the motor of the present invention includes a motor shaft, an annular permanent magnet that rotates integrally with the motor shaft, and has a first plane portion magnetized with a predetermined number of poles. , the second of its permanent magnets
a rotor including a back yoke made of a magnetic material arranged on the flat side of the permanent magnet and configured to wrap around the outer periphery of the permanent magnet; and a stator winding arranged opposite to the rotor. The stator is composed of a stator including wires, and a yoke made of a magnetic material and placed opposite to the rotor with the stator in between, and the bathok yoke and the yoke wrap around the stator on the outer circumferential side of the stator. Since the yoke is connected to the rotor and rotated integrally with the rotor, the outer periphery of the permanent magnet and stator is completely covered by the back yoke and the yoke, so there is no interference from the permanent magnet. Even if magnetic flux leaks in the radial direction of the motor, the leaked magnetic flux flows into the back yoke or yoke and does not leak to the outside of the motor. Therefore, since no magnetic disturbance is applied to equipment equipped with a motor, it is possible to obtain the effect that the performance of the equipment is not deteriorated. Also, the switching noise that occurs when switching the stator winding current,
Since it is shielded by the back yoke or yoke, the influence on the equipment can be eliminated. Further, it is possible to obtain the effect of being able to prevent foreign matter from entering the motor from outside. Furthermore, it is possible to obtain the effect of shielding motor noise caused by vibrations of the stator windings caused by the magnetic flux in the circumferential direction of the permanent magnets, vibrations of the stator flat plates that occur when switching the energization of the stator windings, and the like.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a first embodiment of the motor of the present invention, FIG. 2 is a side sectional view of the second embodiment of the motor of the present invention, and FIG.
The figure is a side sectional view of a third embodiment of the motor of the present invention, and FIG. 4 is a side sectional view of a conventional motor. 5... Permanent magnet, 19.27... Back yoke, 20, 32.39... Rotor, 21... Stator winding, 23... Bearing, 24... Motor shaft,
25.28... Yoke, 29.35... Annular magnet, 30... Magnetic detection element, 31.38
... rotational frequency detection means, 36 ... holding member,
37-... Magnetoresistive element, 41... Stator.

Claims (3)

[Claims] (1) A motor shaft, an annular permanent magnet that rotates integrally with the motor shaft and whose first plane part is magnetized with a predetermined number of poles, and a second plane part of the permanent magnet. A rotor including a back yoke made of a magnetic material arranged on the side and configured to wrap around the outer periphery of the permanent magnet, and a stator winding arranged opposite to the rotor. and a yoke made of a magnetic material and arranged opposite to the rotor with the stator in between, and the back yoke and the yoke are arranged so as to wrap around the stator on the outer circumferential side of the stator. A motor characterized in that the yoke is connected to the rotor and rotated integrally with the rotor. (2) A motor shaft, an annular permanent magnet that rotates integrally with the motor shaft and whose first plane part is magnetized with a predetermined number of poles, and a second plane part of the permanent magnet. A rotor including a back yoke made of a magnetic material arranged on the side and configured to wrap around the outer periphery of the permanent magnet, and a stator winding arranged opposite to the rotor. a stator made of a magnetic material; a yoke made of a magnetic material disposed opposite to the rotor with the stator in between; The back yoke and the yoke are fixed on the outer circumferential side of the stator. 1. A motor characterized in that the annular magnet is bonded so as to wrap around the child, and the annular magnet is disposed on a back yoke or an outer circumferential surface of the yoke. (3) A motor shaft, a bearing that rotatably supports the motor shaft, a rotor that is fixed to the motor shaft and rotates integrally with the motor shaft, and a stator winding that is arranged opposite to the rotor. a stator including a wire; an annular magnet having a plurality of poles magnetized on its outer peripheral surface and rotating integrally with the rotor; A magnetoresistance consisting of at least one ferromagnetic thin film having a magnetoresistance effect, which is held by a holding member made of a magnetic material and has protrusions arranged opposite to each other, and which is provided facing the vicinity of the outer peripheral surface of the annular magnet. What is claimed is: 1. A motor characterized in that it is equipped with rotational frequency detection means including a rotational frequency detection element.