JPH06261523A - Rotation detector - Google Patents

Abstract

PURPOSE:To improve the detection accuracy of a rotation detector even when a large number of magnetism sensitive elements are used and, at the same time, to reduce the outside diameter of an FG magnet without deteriorating the detection accuracy. CONSTITUTION:A sensor section 30 has eight magnetism sensitive elements 31A-31H and the elements are divided into a first and second layers 41 and 43 in groups of four elements, with two layers stacked in the radial direction of an FG magnet 13. Since the overall width of the elements 31A-31H is reduced in the sensor section 30 as compared with the conventional 13 the gaps 1 between each element 31A-31H and the magnet 13 becomes almost equal to another and, at the same time, the influences of leakage magnetic fluxes from rotor magnets also become almost equal to each other, the output levels of rotation detecting signals P1 and P2 become the same in prescribed phases. Therefore, the rotating station detection accuracy of this rotation detector can be improved.

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 suitable for application to a capstan motor of a VTR or tape recorder.

[0002]

2. Description of the Related Art In a VTR (video tape recorder) and a tape recorder, a capstan motor 1 as shown in FIG. 8 is used for carrying a magnetic tape.
The capstan motor 1 is a face-to-face type motor, and includes a rotor portion 10, a stator portion 20, and a sensor portion 30.

As shown in FIG. 9, in the rotor section 10, a disc-shaped rotor magnet 11 is provided with a cover 12 for enclosing the outer peripheral side and the upper side thereof, and the outer peripheral side further has an FG for rotation detection ( Frequency Generator) Magnet 13 is attached. A rotating shaft 14 is attached to the center of the rotor portion 10, and the rotating shaft 1 is attached by a bearing portion 22 fixed to a stator substrate 21 of the stator portion 20.
4 is rotatably supported. As a result, the rotor unit 10 rotates smoothly. The rotor magnet 11 and the FG magnet 13 are magnetized with a plurality of magnetic poles having the same width over the entire circumference.

In the stator section 20, FIG. 8 and FIG.
As shown in FIG. 3, a plurality of drive coils 23 arranged to face the lower surface of the rotor magnet 11 are fixed to the stator substrate 21. A magnetic field is generated by sequentially supplying an exciting current to the drive coil 23, and the magnetic field rotates the rotor magnet 11, that is, the rotor unit 10.

In the sensor section 30, as shown in FIG. 10, eight magnetic sensitive elements 31A to 31H are provided at predetermined intervals so as to face the outer peripheral surface of the FG magnet 13 of the rotor section 10.
In this example, the FG magnets 13 are arranged at an interval of ½ of the magnetic pole width λ. The magnetic sensitive elements 31A to 31H are F
It detects a change in the magnetic field caused by the rotation of the G magnet 13, and is formed by a conductive material having a magnetoresistive effect in an elongated U-shape on a substrate 32 formed of an insulating material such as a glass plate or a ceramic plate. There is. As a result, a slot-shaped thin film resistance element is formed, and the resistance value changes according to the change in the magnetic field.

The magnetic sensitive elements 31A to 31H are connected in series to form a sensor 38. The sensor 38 is shown in FIG.
It is equivalent to a bridge circuit as shown in. The power supply VCC and the ground GND are connected to two terminals 34 and 35 on one diagonal of the bridge circuit, and two rotation detection signals P1 and P2 having different phases are output from the two terminals 36 and 37 on the other diagonal. It Here, one side of the bridge circuit is formed by two resistance elements in order to increase the output levels of the rotation detection signals P1 and P2.

The resistance values of the magnetic sensitive elements 31A to 31H change as the magnetic field changes, as described above. Therefore, F
When the G magnet 13 rotates, the resistance value of the bridge circuit changes, which causes the output terminals 36 and 37 to output rotation detection signals P1 and P2 having a substantially sine wave whose phase is shifted by about 180 degrees as shown in FIG. . This rotation detection signal P1,
By counting the zero cross points of P2 or the difference signal P3 thereof, it becomes possible to detect the rotational state such as the rotational speed of the FG magnet 13, that is, the rotor unit 10. The use of the differential signal P3 improves the S / N ratio.

In FIG. 9, magnetic sensitive elements 31A to 31H are provided.
The substrate 32 holding the is attached to a predetermined position of the stator substrate 21 by the support portion 33. As a result, the distance between the magnetic sensitive elements 31A to 31H and the FG magnet 13 becomes a predetermined dimension, and it becomes possible for the magnetic sensitive elements 31A to 31H to detect changes in the magnetic field of the FG magnet 13.

[0009]

In the capstan motor 1 described above, the magnetic sensitive elements 31A to 31 are used.
Since the interval of H is wide, as shown in FIG. 13, the magnetic sensitive elements 31A, 31H at both ends and the magnetic sensitive elements 31D, 31E and FG in which the gap δ2 between the FG magnet 13 is at the center.
It is considerably larger than the gap δ1 of the magnet 13. Therefore, the output level of one rotation detection signal P1 using the magnetic sensitive elements 31A and 31H at both ends as resistance elements becomes lower than the output level of the other rotation detection signal P2.

Further, since the widths of the magnetic sensitive elements 31A to 31H are large, the magnetic flux leakage of the rotor magnet 11 which is received by the magnetic sensitive elements 31D and 31E at the center and the magnetic sensitive elements 31A and 31H at both ends is affected. different. For this reason, it is difficult for the conventional capstan motor 1 to accurately detect the rotation state of the rotor unit 10.

Further, in order to downsize a VTR or a tape recorder using the capstan motor 1 described above, it is necessary to downsize the capstan motor 1. For that purpose, the outer diameter of the rotor portion 10 must be made small, but if this is done, the outer diameter of the FG magnet 13 becomes small, and the following problems occur.

That is, when the outer diameter of the FG magnet 13 is reduced, the magnetic pole width λ is set when the number of magnetic poles is the same as the conventional one.
Becomes smaller. This makes it difficult to magnetize the magnetic poles, and the outputs of the rotation detection signals P1 and P2 become small, resulting in poor detection accuracy.

In order to avoid such a problem, if the outer diameter of the FG magnet 13 is reduced by reducing the number of magnetic poles by keeping the magnetic pole width λ the same, the rotation detection signals P1 and P2.
Since the frequency of is decreased and the zero cross point is decreased, the detection accuracy of the rotation state is deteriorated especially at low speed rotation, and the rotation control becomes difficult.

Therefore, the present invention has solved the above-mentioned problems, and can accurately detect the rotating state even when a large number of magnetic sensitive elements are used, and further reduce the outer diameter of the FG magnet. Even so, it proposes a rotation detecting device capable of preventing the detection accuracy of the rotation state from being lowered.

[0015]

In order to solve the above-mentioned problems, according to the present invention, a plurality of magnetic poles mounted on the outer peripheral side of a rotor magnet of a face-to-face motor and magnetized with the same width along the circumferential direction. A rotation detecting FG magnet, and a plurality of magnetic sensitive elements for detecting a change in a magnetic field generated by the rotation of the FG magnet, and a plurality of magnetic sensitive elements output according to a change in resistance value of the magnetic sensitive element. In a rotation detection device configured to detect a rotation state of a rotor magnet by detecting a rotation detection signal, a magnetic sensitive element for outputting each rotation detection signal is laminated in a radial direction of an FG magnet. It is what

[0016]

In FIG. 1, the sensor section 30 has eight magnetic sensitive elements 31A to 31H, each of which has four magnetic sensitive elements 31A to 31H.
The first and second layers 43 are divided and laminated in the radial direction of the FG magnet 13. Magnetosensitive element 3 of each layer 41, 43
1A to 31F and 31G to 31D are completely overlapped as shown in FIG. As a result, each sensor 38
Two rotation detection signals P1 and P2 (FIG. 12) having a phase difference of 180 degrees are output from A and 38B. Then, by counting the zero-cross points of the rotation detection signals P1 and P2, the rotation state of the rotor unit 10 (FIG. 8) can be detected.

In this sensor unit 30, eight magnetic sensitive elements 31A to 31H are used, but the conventional sensor unit 30 is used.
Since the entire width can be made narrower than that of FIG. 13, the gaps δ1 between the magnetic sensitive elements 31A to 31H and the FG magnet 13 are substantially the same, and the influence of the leakage magnetic flux of the rotor magnet 11 is large. Also becomes substantially uniform, the output levels of the rotation detection signals P1 and P2 are the same and have a predetermined phase. Therefore, it becomes possible to accurately detect the rotation state.

Further, as shown in FIG. 3, three sensors 38 are provided.
By arranging A to 38C so as to be shifted by ⅙ of the magnetic pole width λ, it becomes possible to output three rotation detection signals P1, P2, P3 whose phases are shifted by 60 degrees as shown in FIG. . In this case, the rotation detection signals P1, P2,
Since the number of zero cross points of P3 increases, it becomes possible to improve the detection accuracy of the rotation state.

Further, as shown in FIG.
By arranging 38C by shifting by 1/3 of the magnetic pole width λ, it becomes possible to output the rotation detection signals P1 to P3 whose phases are shifted by 120 degrees as shown in FIG. in this case,
Since both the cross points and the zero cross points of the rotation detection signals P1 to P3 can be used for detecting the rotation state, the rotation accuracy can be further improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment in which the rotation detecting device according to the present invention is applied to a capstan motor will be described in detail with reference to the drawings. The same parts as those of the capstan motor 1 described above are designated by the same reference numerals and detailed description thereof is omitted.

FIG. 1 shows a sensor unit 30 of a capstan motor 1 to which a rotation detecting device according to the present invention is applied. The structure of the capstan motor 1 is the same as that shown in FIG. In this sensor unit 30, four magnetic sensitive elements 31G, 31B, 31
E and 31D are arranged on the same plane of the substrate 32 to form the second layer 43. An insulating layer 42 is provided on the surface side of the second layer.
Is provided, and four magnetic sensitive elements 31A, 31H, 31C, 31F are arranged on the same plane on the surface side to form the first layer 41.

The first layer of the magnetic sensitive elements 31A to 31F and the second layer
The magnetic sensitive elements 31G to 31D of the layer are F
The G magnets 13 are arranged at intervals of ½ of the magnetic pole width λ. The patterns of the magnetic sensitive elements 31A to 31F of the first layer and the magnetic sensitive elements 31G to 31D of the second layer are symmetrical to each other, and the magnetic sensitive elements 31A to 31 of the layers 41 and 43 are formed.
H, 31G to 31D are laminated so as to completely overlap each other in the radial direction of the FG magnet 13.

The magnetic sensitive elements 31A to 31 of the respective layers 41 and 43
F and 31G-31D are connected in series, and thereby two sensors 38A and 38B are formed.
Further, the magnetic sensitive elements 31A to 31F of the first layer 41 and the magnetic sensitive elements 31G to 31D of the second layer 43 are connected in series. Then, the power supply VCC is connected to the connection midpoint between the magnetic sensitive element 31A at the left end of the first layer 41 and the second magnetic sensitive element 31B of the second layer 43, and the second magnetic sensitive element 31H of the first layer 41 is connected. A ground GND is connected to the middle point of connection between the magnetic sensitive element 31G at the left end of the second layer 43 and the second layer 43.

Further, the third magnetic sensitive element 3 of the first layer 41
An output terminal 36 for the rotation detection signal P1 is connected to the midpoint of connection between 1C and the fourth magnetic sensitive element 31F. Furthermore,
An output terminal 37 for the rotation detection signal P2 is connected to the midpoint of connection between the third magnetic sensitive element 31E and the fourth magnetic sensitive element 31D of the second layer 43. The sensors 38A and 38B formed in this way are equivalent to the bridge circuit shown in FIG. Therefore, the rotation detection signals P1 and P2 output from the sensor unit 30 are substantially sine waves as in FIG. 12, and the phase difference between them is approximately 180 degrees. Rotation detection signal P
By counting the zero cross points of 1 and P2,
It becomes possible to detect the rotation state of the rotor unit 10.

In this sensor section 30, like the conventional sensor section 30 (FIG. 10), eight magnetic sensitive elements 31A to 31A are provided.
31H is used, but there are 2 sensors 3 4 each
It is divided into 8A and 38B, and these are FG magnet 13
Since they are stacked in the radial direction of the
The width of the entire 1H sensor 38A, 3B can be reduced to 1/2 of the conventional width.

Therefore, even if the magnetic pole surface of the FG magnet 13 is arcuate, the gaps between the magnetic sensitive elements 31A to 31H and the magnetic pole surface have almost the same size .delta.1, and therefore the output levels of the rotation detection signals P1 and P2. Is large, and both have the same waveform. In addition, each of the magnetic sensitive elements 31A to 31
Since the influence of the magnetic flux leaked from the rotor magnet 11 on the H is also substantially uniform, it is possible to accurately detect the rotating state of the rotor unit 10.

In the above-described embodiment, the magnetic sensitive elements 31A to 31H of the first layer 41 and the magnetic sensitive elements 31G to 3 of the second layer 43.
Although the case where 1D is completely overlapped and laminated has been described, the magnetic sensitive elements of each layer can be shifted and laminated as described below.

For example, as shown in FIG. 3, three sensors 3
8A, 38B and 38C are the magnetic pole width λ of the FG magnet 13
It is possible to arrange them by ⅙ of each other, and to laminate them into three layers 41, 43 and 45 as shown in FIG. Each layer 4
Insulating layers 42 and 44 are provided between 1, 43 and 45.

These sensors 38A to 38C output three rotation detection signals P1, P2 and P3 whose phases are shifted by 60 degrees as shown in FIG. Each signal P1, P
By counting the zero cross points of 2 and P3, it becomes possible to detect the rotation state of the rotor unit 10. In this case, since there are many zero-cross points, it becomes possible to detect the rotation state more accurately, and rotation control becomes easy even at low speed rotation.

Further, in this case, 12 magnetic sensitive elements 31
Even if A to 31L are used, since the width is the same as that when four magnetic sensitive elements are used, the output level of each rotation detection signal P1, P2, P3 is uniform and the rotor magnet 13 has the same output level as described above. The influence of the leakage magnetic flux becomes uniform. Therefore,
It is possible to accurately detect the rotation state of the rotor unit 10.

FIG. 6 shows three sensors 38A-38C as F
The case where the G magnets 13 are arranged so as to be offset by 1/3 of the magnetic pole width λ is shown. Also in this case, the sensors 38A to 38C
Are laminated in the radial direction of the FG magnet 13 as in FIG. Then, from each of the sensors 38A to 38C, as shown in FIG. 7, the rotation detection signals P1 whose phase difference is shifted by 120 degrees.
P2 and P3 are output.

In this case, since the intervals of the cross points of the rotation detection signals P1 to P3 are the same, the rotation state is detected by counting these cross points and the zero cross points of the rotation detection signals P1 to P3. Will be possible. Here, since a total of 12 cross points can be used, it is possible to improve the detection accuracy of the rotation state.

Further, the width of the entire sensors 38A to 38C can be made narrower than in the conventional case, whereby the output levels of the respective rotation detection signals P1 to P3 become the same as described above, and the leakage magnetic flux of the rotor magnet 11 is made. Since the influence of is also substantially uniform, it becomes possible to accurately detect the rotation state.

In the above-mentioned embodiment, the case where the magnetic sensitive element is laminated in two layers or three layers has been described, but it is possible to laminate in N layers. In this case, the rotation detection signals output from the respective layers may be output with a shift of (360 / N) degrees.

[0035]

As described above, the present invention has a plurality of magnetic sensitive elements, and a plurality of sensors for outputting a rotation detection signal according to the rotation of the FG magnet are laminated in the radial direction of the FG magnet. There is something.

Therefore, according to the present invention, even if there are a large number of magnetic sensitive elements, they can be accommodated in a relatively narrow width, so that the outer peripheral surface of the disc-shaped FG magnet and each magnetic sensitive element can be accommodated. It becomes possible to make the intervals of substantially the same. Further, since the influence of the magnetic flux leaked from the rotor magnet becomes substantially uniform, each rotation detection signal has a predetermined phase at the same output level, which makes it possible to improve the detection accuracy of the rotation state of the rotor portion.

If the magnetic sensitive elements are laminated so that the phase difference of each rotation detection signal is shifted by 60 degrees and output,
The number of zero-cross points of each rotation detection signal increases, and it becomes possible to improve the detection accuracy of the rotation state. If the phase difference of each rotation detection signal is set to 120 degrees, the intervals of the cross points of each rotation detection signal become the same, so this cross point can be used for detecting the rotation state, and it can be used together with the zero cross point. By using it, it is possible to further improve the detection accuracy of the rotation state.

[Brief description of drawings]

FIG. 1 is a sectional view of a sensor unit 30 of a capstan motor 1 to which a rotation detection device according to the present invention is applied.

FIG. 2 is a plan development view of magnetic sensitive elements 31A to 31H.

FIG. 3 shows three sensors 38A to 38C each having a magnetic pole width of 1 /
Magnetic sensitive elements 31A to 31 when they are arranged by shifting by 6
It is a plane development view of L.

4 is a cross-sectional view of the sensors 38A-38H of FIG.

5 is a waveform diagram of rotation detection signals P1 to P3 output from the sensors 38A to 38C of FIG.

FIG. 6 shows three sensors 38A to 38C each having a magnetic pole width of 1 /
Magnetosensitive elements 31A to 31 when they are arranged by shifting by 3
It is a plane development view of L.

7 is a waveform diagram of rotation detection signals P1 to P3 output from the sensors 38A to 38C of FIG.

FIG. 8 is a configuration diagram of a general capstan motor 1.

9 is a sectional view of the capstan motor 1. FIG.

FIG. 10 shows a magnetic sensing element 31 in a conventional sensor section 30.
It is a figure explaining arrangement of A-31H.

11 is a diagram illustrating an equivalent circuit of the sensor 38. FIG.

FIG. 12 is a rotation detection signal P output from a sensor 38.
It is a waveform diagram of 1, P2.

FIG. 13 is a diagram showing each magnetic sensing element 3 in the conventional sensor unit 30.
It is a figure explaining the gap between 1A-31H and FG magnet 13.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capstan motor 10 Rotor part 11 Rotor magnet 13 FG magnet 14 Rotating shaft 20 Stator part 21 Stator substrate 23 Drive coil 30 Sensor part 31A-31L Magnetic sensitive element 32 Substrate 33 Support part 38, 38A-38C Sensor 41 First layer 42 , 44 Insulating layer 43 Second layer 45 Third layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H02K 11/00 B 8525-5H

Claims (6)

[Claims] 1. An FG magnet for rotation detection, which is mounted on the outer peripheral side of a rotor magnet of a face-to-face motor and has a plurality of magnetic poles magnetized in the same width along the circumferential direction, and generated by rotation of the FG magnet. A plurality of magnetic sensitive elements for detecting a change in the magnetic field to detect the rotation state of the rotor magnet by detecting a plurality of rotation detection signals output according to changes in the resistance value of the magnetic sensitive element. In the rotation detecting device for detecting, a magnetic sensing element for outputting each of the rotation detecting signals is laminated in a radial direction of the FG magnet. 2. The magnetic sensitive element is laminated in a first layer and a second layer, and the magnetic sensitive element of the second layer is arranged with a predetermined gap from the magnetic sensitive element of the first layer. The rotation detection device according to claim 1, wherein the rotation detection device is provided. 3. The predetermined interval is set so that the rotation detection signal output from the magnetic sensing element of the first layer and the rotation detection signal output from the magnetic sensing element of the second layer have opposite phases. The rotation detection device according to claim 2, wherein the rotation detection device is provided. 4. The predetermined value is set so that the phase difference between the rotation detection signal output from the magnetic sensing element of the first layer and the rotation detection signal output from the magnetic sensing element of the second layer becomes 60 degrees. The rotation detecting device according to claim 2, wherein the interval is set. 5. The predetermined value is set so that the phase difference between the rotation detection signal output from the magnetic sensing element of the first layer and the rotation detection signal output from the magnetic sensing element of the second layer becomes 120 degrees. The rotation detecting device according to claim 2, wherein the interval is set. 6. The magnetic sensitive element is laminated in N layers,
2. The rotation detecting device according to claim 1, wherein the magnetic sensitive element is arranged so that a phase difference between rotation detecting signals output from the layers adjacent to each other is (360 / N) degrees.