JPH0712833A - Rotation detector - Google Patents

Abstract

PURPOSE:To eliminate fluctuation in the output of index signals by forming a magnetic circuit by providing a magnetic rotating signal generating section in a rotor and incorporating a magnetic detector in the circuit. CONSTITUTION:A flange section 5 is formed on the outer peripheral surface of a rotor yoke 2 and an index magnet 3 is buried in the hole section 5A of the section 5. When the yoke 2 is rotated, the magnet 3 comes to exist between a magnetism sensitive element 4 and the front end section 7c of an index yoke 7 at the rate of one time per one rotation. The clearance between the front end section 7c and magnet 3 is small and a closed magnetic circuit is formed from the magnet 3 to the magnet 3 through the front end section 7c and a substrate 8. Since the element 4 is positioned in the magnetic circuit, the element 4 can output index signals having less fluctuation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detecting device used for a rotating body such as a motor.

[0002]

2. Description of the Related Art A rotation detecting device adapted to detect magnetic flux by a magnetic sensitive element is often attached to various rotary driving devices such as a motor. 13 and 14 show a conventional example of a floppy disk drive device to which such a rotation detecting device is applied. 13 and 14, a hole is formed in the substrate 68, and a thrust bearing 78 is attached to the hole. A cylindrical bearing holder 75 is attached so as to surround the outer periphery of the thrust bearing 78 on the upper surface of the substrate 68. The bearing holder 75 has a collar portion 75a formed on the lower outer peripheral surface thereof.
A stator core 73 is mounted on the upper end surface of the. The stator core 73 is formed by stacking a plurality of core elements. A plurality of salient poles are formed on the outer circumference of the stator core 73, and a coil 74 is wound around each salient pole. A spacer 77 is interposed between the stator core 73 and the substrate 68, and the stator core 73 and the spacer 77 are fixed to the substrate 68 with a screw 76 screwed into the substrate 68 from the stator core 73 side.

A cylindrical bearing 72 is attached to the inner surface of the peripheral wall of the bearing holder 75. A rotary shaft 79 is inserted through a hole in the center of the bearing 72, and the rotary shaft 79 is rotatable with respect to the stator core 73 and the fixed member of the substrate 68. The lower end of the rotary shaft 79 is in contact with the thrust bearing 78, so that the rotary shaft 79 is supported by the thrust bearing 78 in the thrust direction. Also, the rotating shaft 79
Are supported by bearings 72 in the radial direction.

A hub base 71, on which a floppy disk or the like is mounted, is attached to the upper end of the rotary shaft 79. A cup-shaped rotor yoke 62 is attached to the hub base 71. A drive pin 69 that engages with a floppy disk or the like mounted on the hub base 71 is attached to the outer side of the hub base 71 of the rotor yoke 62. The drive magnet 61 is attached to the inner surface of the peripheral wall of the rotor yoke 62. The inner peripheral surface of the drive magnet 61 opposes the salient poles of the stator core 73 with a gap therebetween. Therefore, by energizing the coil 74 wound around the salient poles of the stator core 73, the drive magnet 61 and the rotor yoke 62 are controlled. Is urged, and the rotary shaft 79 is rotationally driven.

On the other hand, an index magnet 63 is embedded in a specific portion of the outer surface of the peripheral wall of the rotor yoke 62. A magnetic sensitive element 67 is mounted on the substrate 68 at a position outside the rotor yoke 62. When the rotor yoke 62 is rotated, the index magnet 63 faces the magnetic sensitive element 67 at a rate of once per rotation. When the index magnet 63 faces the magnetic sensitive element 67, the magnetic sensitive element 67 detects the magnetic flux of the index magnet 63 and outputs the index pulse signal once per rotation. In this way, the index magnet 63 and the magnetically sensitive element 67 constitute a rotation detecting device.

The floppy disk drive device is not limited to the one in which the components are mounted on only one side of the substrate as described above, but the components can be mounted on both sides of the substrate as shown in FIG. Some are organized. In FIG. 15, a bearing holder 35 is attached to the hole of the substrate 28. The bearing holder 35 includes a central cylindrical portion 35a and a collar portion 35b formed on the upper end of the cylindrical portion 35a. Further, the outer edge portion of the lower end surface of the collar portion 35b is in contact with the substrate 28.

The stator core 3 is provided at the lower end of the cylindrical portion 35a.
3 is attached. A plurality of salient poles are formed on the outer circumference of the stator core 33, and a coil 34 is wound around each salient pole. A spacer 37 is interposed between the stator core 33 and the collar portion 35.
A screw 36 penetrates the spacer 3, the spacer 37, and the substrate 28. The screw 36 is screwed into the thickened portion of the collar portion 35b, and by the screw 36, the stator core 33,
The spacer 37 is fixed.

A bearing 32 is press-fitted and fixed to the inner peripheral surface of the cylindrical portion 35a of the bearing holder 35. A rotary shaft 39 is inserted in the inner peripheral surface of the bearing 32. A hub base 31 on which a floppy disk or the like is mounted is attached above the substrate 28 at the upper end of the rotary shaft 39. Hub stand 3
A drive pin 39 that engages with the floppy disk is attached to the position 1 near the outer circumference. On the other hand, the rotating shaft 3
A cup-shaped rotor yoke 22 is attached to the lower end of the substrate 9 below the substrate 28. The drive magnet 21 is attached to the inner surface of the peripheral wall of the rotor yoke 22,
The inner peripheral surface of the drive magnet 21 faces the salient poles of the stator core 33 with a gap. Therefore, by energizing the coil 34, the drive magnet 21 and the rotor yoke 22 are urged to rotate the rotary shaft 39.

An index magnet 83 is embedded in the outer surface of the peripheral wall of the rotor yoke 22. Also, the substrate 2
A magnetic sensitive element 87 is attached to a position on the lower surface side of 8 outside the rotor yoke 22. Rotor yoke 22
When is rotated, the index magnet 83 faces the magnetic sensitive element 87 at a rate of once per rotation, and the magnetic sensitive element 87 detects the magnetic flux of the index magnet 83 and outputs an index pulse. In this way, the index magnet 83 and the magnetically sensitive element 87 constitute a rotation detecting device.

[0010]

All of the conventional rotation detecting devices described above are magnetically sensitive elements and receive the magnetic flux from the index magnet to output an index signal. The index signal is the outer diameter of the rotor yoke or the magnetically sensitive element. It is easily affected by the mounting position of the element, which causes a large variation in the output of the index signal.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a rotation detecting device in which variations in index signal output are eliminated.

[0012]

In order to achieve the above object, the present invention provides a magnetic circuit including a magnetic rotation signal generator provided in a rotor and forming a closed loop,
A magnetic detector provided in the stator portion and arranged in the magnetic circuit.

[0013]

The magnetic rotation signal generator is formed on the rotor to form a magnetic circuit, and the magnetic detector is mounted in the magnetic circuit. Since the magnetic detector exists in the magnetic circuit, it can receive a signal of sufficient output.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a magnetic detection device according to the present invention will be described below with reference to the drawings. 1 to 3
In the above, a hole is formed in the substrate 8 made of a magnetic material, and a thrust bearing 18 is attached to the hole. A cylindrical bearing holder 15 is provided on the upper surface of the substrate 8 so as to surround the thrust bearing 18 on the outer periphery of the thrust bearing 18.
Is attached. The bearing holder 15 has a flange portion 15a formed on the lower outer peripheral surface, and the inner edge portion of the stator core 13 is placed on the upper end surface of the flange portion 15a.
The stator core 13 has a plurality of salient poles on the outer circumference, and a coil 14 is wound around each salient pole. A spacer 17 is interposed between the stator core 13 and the substrate 8, and the stator core 13 and the spacer 17 are fixed to the substrate 8 by a screw 16 that penetrates the stator core 13 and the spacer 17 and is screwed into the substrate 8.

A cylindrical bearing 12 is mounted on the inner surface of the peripheral wall of the bearing holder 15. A rotary shaft 19 is inserted through the center hole of the bearing 12, and the rotary shaft 19 is rotatable with respect to a fixed member such as the stator core 13 and the substrate 8. The lower end of the rotary shaft 19 is in contact with the thrust bearing 18, so that the rotary shaft 19 is supported by the thrust bearing 18 in the thrust direction. The rotating shaft 19 is supported by the bearing 12 in the radial direction.

A hub base 11 on which a floppy disk or the like is placed is attached to the upper end of the rotary shaft 19.
A cup-shaped rotor yoke 2 is attached to the hub base 11. A drive pin 9 for engaging with a floppy disk or the like placed on the hub base 11 is attached to the rotor yoke 2. The drive magnet 1 is attached to the inner surface of the peripheral wall of the rotor yoke 2. The inner peripheral surface of the drive magnet 1 faces the salient poles of the stator core 13 with a gap therebetween, and therefore the coil 14 wound around the salient poles is formed.
The drive magnet 1 and the rotor yoke 2 are biased by controlling the energization of the rotating shaft 19 to rotate the rotating shaft 19.

On the other hand, a flange portion 5 is formed on the outer surface of the peripheral wall of the rotor yoke 2, a hole portion 5a as shown in FIG. 3 is formed in the flange portion 5a, and the index magnet 3 is formed in the hole portion 5a. Is buried. Further, in FIG. 2, a magnetically sensitive element 4 is mounted on the substrate 8 at a position facing the lower end surface of the flange portion 5 of the rotor yoke 2 with a gap. On the other hand, an index yoke 7 is attached to the rear of the magnetic sensitive element 4 on the substrate 8 with a screw 10. The index yoke 7 is in the form of a step and is fixed to the substrate 8 and fixed by the screw 10. The fixed portion 7a is perpendicular to the substrate 8, and the upright portion 7b is parallel to the substrate 8.
and c. The tip portion 7c of the index yoke 7 formed so as to be parallel to the substrate 8 has a brim portion 5
It is opposed to the upper end surface with a gap. The index magnet 3, the magnetically sensitive element 4, and the index yoke 7 constitute a rotation detecting device.

When the rotor yoke 2 is rotated, the index magnet 3 is present between the magnetic sensitive element 4 and the tip portion 7a of the index yoke 7 at a rate of once per rotation. In this way, the magnetic sensitive element 4 and the index yoke 7 are
When the index magnet 3 exists between the tip end portions 7c of the index magnets 3, the gap between the tip end portions 7c and the index magnets 3 is small, and the index magnets 3 pass through the tip end portion 7c of the index yoke 7 and the substrate 8. A closed magnetic circuit returning to the magnet 3 is formed. Since the magnetic sensitive element 4 is arranged in such a closed magnetic circuit, it is possible to output a stable index signal with little variation.

Further, in the rotation detecting device having the above structure, even if the dimensional accuracy of various parts is varied and the height of the flange portion 5 in which the index magnet 3 is embedded from the substrate 8 is increased, the index yoke 7 is provided. Tip 7
On the contrary, since the distance from c is small, the output of the index signal at the magnetic sensitive element 4 does not change. Therefore, a stable signal output can be obtained. Further, since the tip end portion 7c of the index yoke 7 exists at a position facing the flange portion 5 of the rotor yoke 2 and plays a role of retaining, the rotor including the rotary shaft 19 and the rotor yoke 2 is taken out when the floppy disk or the like is taken out. It is possible to prevent such a problem that the is pulled out in the radial direction.

Although the index magnet 3 is embedded in the hole 5a formed in the flange portion 5 of the rotor yoke 2, a cutout 6 is formed in the flange portion 5 as shown in FIG. The index magnet 3 may be attached to the notch 6. The effect is the same.

The rotation detecting device as described above can be applied to a floppy disk drive device in which components are arranged on both sides of a substrate as shown in FIG. Since the basic configuration of the floppy disk drive device shown in FIG. 5 is substantially the same as that of the conventional example shown in FIG. 16, common parts are denoted by the same reference numerals. Also, since the basic configuration has already been described in the conventional art, only the different parts, that is, the configuration of the rotation detecting device and the part to which such a rotation detecting device is attached will be described. Figure 5
At the opening side of the peripheral wall of the rotor yoke 22, a collar portion 25 is formed, and the collar portion 25 has a hole portion 25.
a is formed. An index magnet 23 is embedded in the hole 25a. A magnetic sensitive element 24 is attached to the lower surface of the substrate 28 at a position facing the upper end surface of the collar portion 25 with a gap.

On the other hand, an index yoke 27 is attached by a screw 30 to the rear side of the magnetic sensitive element 24 on the lower end surface side of the substrate 28. Index yoke 27
Is a fixing portion 27 fixed to the substrate 28 with a screw 30.
a, an upright portion 27 formed so as to be perpendicular to the substrate 28 from the fixed portion 27a, and a tip portion 27c bent from the upright portion 27 so as to be parallel to the substrate 28. The tip portion 27c faces the lower end surface of the collar portion 25 with a gap. When the rotor yoke 22 rotates, the index magnet 23 exists between the magnetic sensitive element 24 and the tip portion 27c at a rate of once per one rotation. When the index magnet 23 exists between the magnetic sensitive element 24 and the tip portion 27c, the tip portion 2
Since a slight gap is formed between the index magnet 7c and the index magnet 23, the index magnet 23 reaches the index magnet 23 again via the tip portion 27a of the index yoke 27 and the substrate 28 as in the above-described embodiment. , A closed magnetic circuit is formed. Since the magnetically sensitive element 24 is arranged in the closed magnetic circuit, it is possible to output a stable index signal without variations, as in the above-described embodiment.

As another example of the rotation detecting device, a magnetic sensitive element 4 mounted on the upper surface of the substrate 8 at a position facing the lower end surface of the flange portion 5 of the rotor yoke 2 is provided with an index signal as shown in FIG. Instead of the detection coil pattern 40, the index signal detection coil pattern 40
You may make it output an index signal by. The index signal detecting coil pattern 40 is separate from the FG signal detecting coil pattern as shown in FIG. 7, but as shown by reference numeral 40 ′ in FIG. You may make it a structure combined.

Next, another example of the rotation detecting device will be described. In FIG. 9, a notch 6 is formed in the collar portion 5 of the rotor yoke 2. The index signal detecting coil pattern 40 as described above is formed on the upper surface of the substrate 8 at a position facing the lower end surface of the flange portion 5. On the other hand, a fixed magnet 41 is attached by a screw 10 to the rear of the index signal detection coil pattern 40 on the substrate 8. The upper portion of the fixed magnet 41 is a protruding portion 41a extending toward the rotor yoke 2, and the lower end surface of the protruding portion 41a faces the upper end surface of the collar portion 5 with a gap.

In the rotation detecting device having the above-described structure, when the floppy disk drive device is driven to rotate, the rotor magnet 2 which is the rotor is attracted by the fixed magnet 41, and as a result, the rotary shaft 19 receives the bearing 12.
It is rotationally driven in a state of being biased to one place inside. Therefore, even if a sintered oil-impregnated bearing is used for the bearing 12 and a clearance is generated between the rotary shaft 19 and the bearing 12, the rotary shaft 19 can be rotationally driven without rattling.

Further, the rotor yoke 2 rotates and the notch 6
Is located between the index detecting coil pattern 40 and the protrusion 41a of the fixed magnet 41, the protrusion 41
a and the index detecting coil pattern 40 are directly opposed to each other, and the index detecting coil pattern 40 has the protrusion 4
It receives the magnetic flux from 1a. Further, when the collar portion 5 other than the notch 6 is located between the index detecting coil pattern 40 and the protruding portion 41 a of the fixed magnet 41,
Since the flange portion 5 blocks the protrusion 41a and the index detecting coil pattern 40 from directly facing each other, the magnetic flux from the protrusion 41a does not reach the index detecting coil pattern 40. In this way, the position of the notch 6 changes as the rotor yoke 2 rotates, and the magnetic flux reaching the index detecting coil pattern 40 changes, so that the index signal is output. Even with such a configuration, since the index detection pattern 40 exists in the magnetic circuit, it is possible to output a stable index signal without variations as in the above-described embodiment.
The notch 6 formed in the collar portion 5 may have any shape, for example, a circular hole. Further, the fixed magnet 41 may be attached by using an adhesive instead of using the screw 10.

As a modification of FIG. 9, the protrusion 41a of the fixed magnet 41 may be replaced with an index yoke 43 as shown in FIG. 10 to form a rotation detecting device. Alternatively, as shown in FIG. 10, the index detecting pattern 40 may be replaced with the magnetically sensitive element 4 to form a rotation detecting device. The same effect as the embodiment shown in FIG. 9 is obtained.

Next, still another example of the rotation detecting device will be shown. In FIG. 11, the magnetic sensitive element 4 is arranged on the substrate 8 outside the flange portion 5 of the rotor yoke 2,
An index yoke portion including a yoke holder 46 and an index yoke 45 is arranged on the substrate 8 further outside the magnetically sensitive element 4. As shown in FIG. 12, a groove 46a is formed in the rectangular parallelepiped-shaped yoke holder 46, and a bent portion of the index yoke 45 is fitted in the groove 46a. Therefore, the index yoke 45 can be slid with the groove 46a as a guide. A long hole 45a is formed on the upper surface of the index yoke 45.
Is formed, and the screw 10 is inserted into the long hole 45a. The screw 10 penetrates the yoke holder 46 and is screwed into the substrate 8 as shown in FIG. 11, and restricts the index yoke 45 from sliding. The portion of the index yoke 45 that is not in contact with the yoke holder 46 is the magnetic sensing element 4 attached to the substrate 8.
12, the portion of the index yoke 45 closest to the rotor yoke 2 becomes a protruding portion 45b and faces the upper end surface of the collar portion 5 with a gap, as shown in FIG. Has become.

Also in the rotation detecting device having the above-mentioned structure, the magnetic sensitive element 4 is located in the closed magnetic circuit from the index magnet 3 to the index yoke 45 and the substrate 8 to the index magnet 3. Therefore, it is possible to obtain a sufficient output index signal. Further, since the magnetic sensitive element 4 is arranged outside the rotor yoke 2 on the substrate 8, there is no influence on the dimension in the thickness direction of the floppy disk device to which the rotation detecting device is attached in this case.

[0030]

According to the present invention, a magnetic circuit that includes a magnetic rotation signal generator provided in a rotor to form a closed loop, and a magnetic detector provided in the stator and arranged in the magnetic circuit. Therefore, a sufficient index signal output can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a rotation detecting device according to the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a perspective view showing an example of a rotor yoke to which an index magnet of the same rotation detecting device is attached.

FIG. 4 is a perspective view showing another example of a rotor yoke to which an index magnet of the above rotation detection device is attached.

FIG. 5 is a sectional view showing another application example of the above rotation detection device.

FIG. 6 is a sectional view showing another embodiment of the rotation detecting device according to the present invention.

FIG. 7 is a perspective view showing an example of an index detection pattern applied to the above rotation detection device.

FIG. 8 is a perspective view showing another example of the index detection pattern of the same.

FIG. 9 is a cross-sectional view showing still another embodiment of the rotation detecting device according to the present invention.

FIG. 10 is a cross-sectional view showing still another embodiment of the rotation detecting device according to the present invention.

FIG. 11 is a cross-sectional view showing still another embodiment of the rotation detecting device according to the present invention.

FIG. 12 is a perspective view showing an example of an index detection unit applied to the above rotation detection device.

FIG. 13 is a perspective view showing an example of a conventional rotation detection device.

FIG. 14 is a sectional view of the same.

FIG. 15 is a cross-sectional view showing another application example of the conventional rotation detection device.

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[Procedure amendment]

[Submission date] November 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art A rotation detecting device adapted to detect magnetic flux by a magnetic sensitive element is often attached to various rotary driving devices such as a motor. 13 and 14 show a floppy disk drive to which such a rotation detecting device is applied.
A conventional example of a spindle motor for a rotary device is shown. 13,
In FIG. 14, holes are formed in the substrate 68,
A thrust bearing 78 is attached to the hole. A cylindrical bearing holder 75 is attached so as to surround the outer periphery of the thrust bearing 78 on the upper surface of the substrate 68. The bearing holder 75 has a flange portion 75a formed on the lower outer peripheral surface thereof, and the stator core 73 is placed on the upper end surface of the flange portion 75a. The stator core 73 is formed by stacking a plurality of core elements. A plurality of salient poles are formed on the outer circumference of the stator core 73, and a coil 74 is wound around each salient pole. Stator core 73
A spacer 77 is interposed between the stator core 73 and the spacer 68 between the stator core 73 and the spacer 68.
It is fixed to.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

The stator core 3 is provided at the lower end of the cylindrical portion 35a.
3 is attached. A plurality of salient poles are formed on the outer circumference of the stator core 33, and a coil 34 is wound around each salient pole. Between the stator core 33 and the flange portion 35b and the spacer 37 is interposed, these stator core 3
A screw 36 penetrates the spacer 3, the spacer 37, and the substrate 28. The screw 36 is screwed into the thickened portion of the collar portion 35b, and by the screw 36, the stator core 33,
The spacer 37 is fixed.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

A bearing 32 is press-fitted and fixed to the inner peripheral surface of the cylindrical portion 35a of the bearing holder 35. A rotary shaft 39 is inserted in the inner peripheral surface of the bearing 32. A hub base 31 on which a floppy disk or the like is mounted is attached above the substrate 28 at the upper end of the rotary shaft 39. Hub stand 3
A drive pin 29 engaging with the floppy disk is attached to the position 1 near the outer circumference. On the other hand, the rotating shaft 3
A cup-shaped rotor yoke 22 is attached to the lower end of the substrate 9 below the substrate 28. The drive magnet 21 is attached to the inner surface of the peripheral wall of the rotor yoke 22,
The inner peripheral surface of the drive magnet 21 faces the salient poles of the stator core 33 with a gap. Therefore, by energizing the coil 34, the drive magnet 21 and the rotor yoke 22 are urged to rotate the rotary shaft 39.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

On the other hand, a flange portion 5 is formed on the outer surface of the peripheral wall of the rotor yoke 2, and a hole portion 5a as shown in FIG. 3 is formed in the flange portion 5 , and the index magnet 3 is formed in the hole portion 5a. Is buried. Further, in FIG. 2, a magnetically sensitive element 4 is mounted on the substrate 8 at a position facing the lower end surface of the flange portion 5 of the rotor yoke 2 with a gap. On the other hand, an index yoke 7 is attached to the rear of the magnetic sensitive element 4 on the substrate 8 with a screw 10. The index yoke 7 is in the form of a step and is fixed to the substrate 8 and fixed by the screw 10. The fixed portion 7a is perpendicular to the substrate 8, and the upright portion 7b is parallel to the substrate 8.
and c. The tip portion 7c of the index yoke 7 formed so as to be parallel to the substrate 8 has a brim portion 5
It is opposed to the upper end surface with a gap. The index magnet 3, the magnetically sensitive element 4, and the index yoke 7 constitute a rotation detecting device.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

When the rotor yoke 2 is rotated, the index magnet 3 is present between the magnetic sensitive element 4 and the tip portion 7c of the index yoke 7 at a rate of once per rotation. In this way, the magnetic sensitive element 4 and the index yoke 7 are
If the index magnet 3 exists between the tip portion 7c, the distal end portion 7c, the gap between the index magnet 3 is small, the index magnet 3, in
A closed magnetic circuit returning to the index magnet 3 via the dex yoke 7 and the substrate 8 is formed. Since the magnetic sensitive element 4 is arranged in such a closed magnetic circuit, it is possible to output a stable index signal with little variation.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Further, in the rotation detecting device having the above structure, even if the dimensional accuracy of various parts is varied and the height of the flange portion 5 in which the index magnet 3 is embedded from the substrate 8 is increased, the index yoke 7 is provided. Tip 7
On the contrary, since the distance from c is small, the output of the index signal at the magnetic sensitive element 4 does not change. Therefore, a stable signal output can be obtained. Further, since the tip end portion 7c of the index yoke 7 exists at a position facing the flange portion 5 of the rotor yoke 2 and plays a role of retaining, the rotor including the rotary shaft 19 and the rotor yoke 2 is taken out when the floppy disk or the like is taken out. It is possible to prevent problems such as the slip-out due to the radial bearing .

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

The rotation detecting device as described above has a floppy disk in which components are arranged on both sides of a substrate as shown in FIG.
It is also applicable to spindle motors for quad drive devices . The floppy disk drive device shown in FIG.
The basic structure of the spindle motor for use in the present invention is substantially the same as that of the conventional example shown in FIG. Also, since the basic configuration has already been described in the conventional art, only the different parts, that is, the configuration of the rotation detecting device and the part to which such a rotation detecting device is attached will be described. In FIG. 5, a collar portion 25 is provided on the opening side of the peripheral wall of the rotor yoke 22.
And a hole 25a is formed in the collar 25. An index magnet 23 is embedded in the hole 25a. On the lower surface of the substrate 28, the brim 2
A magnetically sensitive element 24 is attached at a position facing the upper end surface of 5 with a gap.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

On the other hand, an index yoke 27 is attached by a screw 30 to the rear side of the magnetic sensitive element 24 on the lower end surface side of the substrate 28. Index yoke 27
Is a fixing portion 27 fixed to the substrate 28 with a screw 30.
a, an upright portion 27b formed so as to be perpendicular to the substrate 28 from the fixed portion 27a , and an upright portion 27b to the substrate 28.
And a front end portion 27c that is bent so as to be parallel to. The tip portion 27c faces the lower end surface of the collar portion 25 with a gap. When the rotor yoke 22 rotates, the index magnet 23 exists between the magnetic sensitive element 24 and the tip portion 27c at a rate of once per one rotation. When the index magnet 23 is present between the magnetically sensitive element 24 and the tip portion 27c, a slight gap is formed between the tip portion 27c and the index magnet 23. From the magnet 23 to the index yoke 27,
A closed magnetic circuit is formed from the substrate 28 to the index magnet 23 again. Magnetic sensitive element 24
Are arranged in a closed magnetic circuit, it is possible to output a stable index signal without variations, as in the above-described embodiment.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

The rotation detecting device having the above-mentioned configuration is a flow detecting device.
When the spindle motor for the ppy disk drive device is driven to rotate, the fixed magnet 41 pulls the rotor yoke 2 which is the rotor.
The rotating shaft 19 is rotationally driven in a state of being biased to one place in the bearing 12. Therefore, even if a sintered oil-impregnated bearing is used for the bearing 12 and a clearance is generated between the rotary shaft 19 and the bearing 12, the rotary shaft 19 can be rotationally driven without rattling.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

The rotation detecting device having the above construction also includes the index magnet 3, the index yoke 45, and the base.
The magnetically sensitive element 4 is located in a closed magnetic circuit that extends from the plate 8 to the index magnet 3. Therefore, it is possible to obtain a sufficient output index signal. Further, since the magnetically sensitive element 4 is arranged on the substrate 8 outside the rotor yoke 2, a magnetic disk drive for the floppy disk drive device to which the rotation detecting device in this case is attached .
It does not affect the dimension of the pindle motor in the thickness direction.

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 11

[Correction method] Change

[Correction content]

FIG. 11

[Procedure Amendment 13]

[Document name to be corrected] Drawing

[Correction target item name] Figure 15

[Correction method] Change

[Correction content]

FIG. 15

Claims (1)

[Claims] 1. A magnetic circuit that includes a magnetic rotation signal generator provided in a rotor to form a closed loop, and a magnetic detector provided in the stator and arranged in the magnetic circuit. Rotation detection device.