JPH07303361A - Rotation detector - Google Patents

Abstract

PURPOSE:To enable a rotation detector to detect the rotation of a rotor without receiving any influence from rotor magnets. CONSTITUTION:A rotation detector is provided with magnetized sections 11 arranged on the outer periphery of a rotor section and a sensor section 10 composed of a plurality of magnetism sensitive elements 13 arranged in a stator section so that the elements 13 can face to the magnetized sections 11 and the sensor section 10 is provided with a plurality of element patterns 13-A and 13-B constituting a bridge so that the center positions PC of the patterns 13-A and 13-B can coincide with each other in the direction L nearly perpendicular to the magnetized sections 11.

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 in, for example, a VTR capstan motor.

[0002]

2. Description of the Related Art Conventionally, for example, a VTR capstan motor is constructed as shown in FIGS. In FIG. 7, a capstan motor 1 is used for carrying a magnetic tape, and is configured as a surface facing motor including a rotor portion 2, a stator portion 3 and a sensor portion 4.

The rotor section 2 has a disk-shaped rotor magnet 2a, a cover 2b surrounding the outer peripheral side and the upper side of the rotor magnet 2a, and an FG (for detecting rotation) attached to the outer peripheral side of the cover 2b. frequency generat
or) a magnet 2c.

As shown in FIG. 8, a rotating shaft 2d is attached to the center of the rotor portion 2. The rotating shaft 2d is rotatably supported by a bearing portion 3b fixed to a stator substrate 3a of the stator portion 3.
In addition, as shown in FIG.
The a and FG magnets 2c have a plurality of magnetic poles magnetized over the entire circumference. Furthermore, this FG magnet 2
c is magnetized so that the magnetic pole widths λ are substantially the same on the circumference.

The stator portion 3 has a plurality of drive coils 3c fixed to the stator substrate 3a so as to face the lower surface of the rotor magnet 2a. As a result, a magnetic field is generated by sequentially supplying an exciting current to the drive coil 3c. Therefore, this magnetic field causes the rotor magnet 2a and the rotor portion 2 to rotate around the rotation axis 2d.

Further, the sensor portion 4 has a plurality of magnetic sensitive elements 4a arranged at a predetermined interval so as to face the outer peripheral surface of the FG magnet 2c of the rotor portion 2. The magnetic sensitive element 4a is for detecting a magnetic field generated by the rotation of the FG magnet 2c. The magnetic sensitive element 4a is formed of a conductive material having a magnetoresistive effect in the shape of an elongated comb tooth on a substrate 4b made of an insulating material such as a glass plate or a ceramic plate, for example. As a result, a slot-shaped thin film resistance element is formed, and the resistance value changes due to the change in the magnetic field.

As shown in FIG. 10, the magnetic sensitive element 4a includes magnetic sensitive elements 4a-1, 4a-2, 4a in order from the left side.
Four -3, 4a-4 are arranged so that the intervals are ⅙, ⅓, and ⅙ of the pair of magnetic pole widths λ of S and N, respectively.

The magnetic sensitive elements 4a are connected in series with each other to form a sensor 4c composed of a bridge circuit as shown in the equivalent circuit of FIG. The power supply VCC and the ground GND are respectively connected to the two diagonal terminals 4d and 4e of the bridge circuit. Further, output terminals 4f and 4g for outputting two rotation detection signals P1 and P2 having different phases are connected to the other two terminals of the other diagonal line.

According to such a configuration, the magnetic sensitive element 4a
As described above, the resistance value changes with the change in the magnetic field, respectively, and as a result, the rotation detection signals P1 and P of the sine wave as shown by the solid lines in FIG. 12 are output from the output terminals 4f and 4g.
2 is output. The rotation detection signals P1 and P2 are
They are 60 degrees out of phase with each other.

Thus, as shown in FIG. 9, the phase difference 6 is obtained by taking the difference signal P3 between the output signals P1 and P2.
Rotation detection of 0 degree is performed. Therefore, the number of rotations of the FG magnet 2c and the rotor portion 2 is detected by counting the zero-cross points of the difference signal P3. At that time, the S / N ratio is improved by using the differential signal P3.

[0011]

By the way, as shown in FIG. 13, the magnetically sensitive element (magnetoresistive element) constituting such a sensor portion is near the boundary of magnetization, that is, a region having a strong magnetic field. There is a characteristic that causes an extreme change in resistance when facing the. The rotation detection as described above is performed by utilizing such a property. That is, F as shown in FIG.
Each magnetosensitive element undergoes a resistance value change as shown in FIG. 13 in response to the action of the magnetic flux from the G magnet 2c, so that a rotation detection signal having a sine wave as shown in FIG. 12 is obtained.

However, in such a capstan motor 1 as shown in FIG. 9, since the FG magnets 2c are concentrically provided around the rotor magnet 2a, as shown in FIG. The leakage magnetic flux from the rotor magnet 2a may act on each magnetic sensitive element.

That is, in the magnetic sensitive element 4a shown in FIG.
First element pattern 4a-A and second element pattern 4a
-B and B are arranged along the moving direction F of the FG magnet 2c. In this case, the element patterns 4a-A and 4a-B have different positions along the moving direction F, that is, the center positions PC of the respective element patterns are laterally displaced in the drawing. Therefore, the rotor magnet 2
When a is in a specific position, this rotor magnet 2
When affected by the leakage magnetic flux from a as shown in FIG. 15, there is a difference in the amount of leakage magnetic flux sensed between the element patterns 4a-A and 4a-B.

As a result, when the rotation detection signal P3 is taken when the rotation detection signal P3 is obtained, the sine waveform is distorted due to the resistance value change due to the magnetic field of the FG magnet 2c of each element pattern 4a-A and 4a-B shown in FIG. There is a problem in that the position and interval of the zero cross points are displaced, and the accuracy of rotation detection is reduced.

In view of the above points, the present invention improves the accuracy of rotation detection by not being influenced by the leakage magnetic flux of the rotor magnet when the rotation is detected by using the magnetic sensitive element. Another object of the present invention is to provide a rotation detection device.

[0016]

According to the present invention, the above object is to provide a rotatably supported rotor portion, a stator portion fixedly disposed facing the rotor portion, and an outer circumference of the rotor portion. And a sensor section composed of a plurality of magnetic sensitive elements arranged in the stator section facing the magnetized section. The sensor section forms a bridge. This is achieved by a rotation detecting device that is provided with a plurality of element patterns, and is configured such that the center positions of the element patterns that form each pair forming a bridge are aligned in the direction substantially orthogonal to the magnetized portion.

Preferably, the element pattern is formed on a substrate.

[0018]

According to the above structure, the centers of the element patterns forming each pair of the sensor parts are aligned with each other in the direction substantially orthogonal to the magnetized part on the rotor side. Therefore, the strength of the magnetic field from the magnetized portion and the strength of the magnetic field from the rotor magnet on the inner peripheral side of the magnetized portion match in each pair of patterns.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the examples described below are suitable specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows the structure of the main part of a sensor section in an embodiment of the rotation detecting device according to the present invention, and the other structure of the present rotation detecting device is shown in FIGS. Since the configuration is the same as that of the rotation detection device, duplicate description will be omitted and differences will be mainly described.

In FIG. 1A, the sensor unit 10 of the rotation detecting device has a plurality of element patterns 13 formed on the substrate so as to face the outer peripheral surface of the FG magnet 11 of the rotor unit. There is. In this embodiment, the element pattern 13 made of a magnetic sensitive element is a pair of element patterns 13-A.
And 13-B. Here, the element patterns 13-A and 13-B are configured by collectively arranging a predetermined number of patterns, and the required number is collected according to the purpose. Therefore, in an extreme case, only one pattern may be arranged at equal intervals, or a larger number of patterns than those shown in the drawing may be aggregated to form individual pattern groups forming a pair of patterns. Good.

Each element pattern 13-A, 13-B has a pattern (pattern group) at equal intervals, in this case λ /
The element patterns 13 are arranged at equal intervals of four.
The center PCs of −A and 13-B are arranged so as to be aligned with the virtual line L orthogonal to the FG magnet 11. Here, the FG magnet 11 is magnetized to the outer peripheral surface at multi-poles at equal intervals, and the magnetic pole width λ forming each pair on the circumference.
However, they are magnetized so that they are almost the same.

Each of these magnetic sensitive elements, 13-A and 13-B
Are connected in series as shown in the equivalent circuit of FIG. 1B, and the power supply VCC and the ground G are respectively connected to the terminals at both ends.
An ND is connected and an output P is taken out from a terminal provided between the magnetic sensitive elements 13-A and 13-B.

Therefore, the rotation of the capstan motor or the like is detected by processing the sine wave as shown in FIG. 5 generated based on the output from the output terminal P.
Here, in the present embodiment, the rotor magnet 2a
From (see FIG. 9), the leakage magnetic flux as shown in FIG. 15 may act on each of the element patterns 13-A and 13-B. However, the center PCs of the element patterns 13-A and 13-B are aligned with the virtual line L of FIG. Therefore, the leakage magnetic field from the rotor magnet 2a always acts equally on the element patterns 13-A and 13-B, and the amount of magnetic flux applied to each element pattern is the same.

As a result, even if the magnetic flux leaks from the rotor magnet 2a acts on the sensor portion 10, they do not cancel each other out and the sine wave based on the output from the output terminal P is not distorted. Therefore, it is possible to always detect the correct rotation of the capstan motor or the like.

FIG. 2 shows the structure of a sensor unit 20 according to the second embodiment of the present invention, and the FG magnet is omitted because it is the same as that in FIG. In this embodiment, the magnetic sensitive elements are arranged in a phase difference pattern of 180 degrees. That is, the element patterns are arranged at equal intervals of λ / 4, and the element patterns 23-A and 23
-C is a paired pattern, and the element pattern 23-
B and the element pattern 23-D are a pair of patterns.

The element patterns 23-A, 23-
B, 23-C, and 23-D are connected in series, respectively, and the first output terminal P1 is provided between the element pattern 23-B and the element pattern 23-D, and the element pattern 23-A and the element pattern 23-C. A second output terminal P2 is provided between them. In addition, the element pattern 23-A and the element pattern 23
A power supply VCC is connected between -B, and a ground GND is connected between the element patterns 23-C and 23-D.

Further, in the present embodiment, the element pattern 23-A and the element pattern 23- which are the element patterns to be paired with each other.
The center PC of C is a virtual line L1 orthogonal to the FG magnet.
23- which is another pair of element patterns aligned above.
B and the center PC of the element pattern 23-D are aligned and arranged on another virtual line L2 orthogonal to the FG magnet.

As a result, even in the present embodiment, even if the leakage magnetic flux from the rotor magnet acts on the element patterns as the pair of magnetically sensitive elements, the amount of magnetic flux affecting each element pattern is equal. The effect of such a leakage magnetic flux is canceled between the paired patterns. Therefore, the correct sine wave is generated from the first output terminal P1 and the second output terminal P2, and thus the rotation detection signal is
It will be output as a sine wave without distortion. Thus, when the rotation detection signal P3, which is a differential signal, is obtained by the method shown in FIG. 12, the position and interval of the zero-cross points are not displaced, and the rotation detection accuracy is improved. Becomes

By the way, when the connection as shown in FIG. 2 is made in the element pattern as in the second embodiment, the first output terminal P1 and the second output terminal P2 are as shown in the figure. Since they are separated from each other in the left and right positions, a slight phase difference occurs between the respective detection signals based on the positional relationship with the FG magnet 11. Therefore, the accuracy of the rotation detection of the capstan motor or the like is slightly lowered.

Therefore, by constructing the sensor portion as shown in FIG. 3, such a defect can be eliminated. A sensor unit 3 according to a third embodiment of the present invention shown in FIG.
0, the element patterns 33-A, 33- of the magnetic sensitive element
The arrangement of B, 33-C, and 33-D is the same as that of the embodiment of FIG. 2, and the element patterns forming a pair are the element pattern 33-A and the element pattern 33-C.
The element pattern 33-B and the element pattern 33-D are the same in that they are a pair.

Then, the center PC of the element pattern 33-A and the element pattern 33-C which are paired element patterns.
Are aligned on an imaginary line L1 orthogonal to the FG magnet, and the center PCs of the element patterns 33-B and the element pattern 33-D which are the other pair are on another imaginary line L2 orthogonal to the FG magnet. It is aligned and arranged.

The present embodiment differs from the embodiment of FIG. 2 in that the output terminals P1 and P2, the power supply VCC, and the ground GN.
D connection. FIG. 4 shows an equivalent circuit of the sensor unit 30 of the present embodiment, and each magnetic sensitive element 33-A, 33-.
B, 33-C, and 33-D are connected in series with each other to form a sensor including a bridge circuit. In this bridge circuit, a first output terminal P1 is provided between the element pattern 33-C and the element pattern 33-D, and a second output terminal P1 is provided between the element pattern 33-A and the element pattern 33-B. P2 is provided. In addition, the element pattern 33-
A power supply VCC is connected between B and the element pattern 33-D, and a ground GND is connected between the element pattern 33-A and the element pattern 33-C.

As a result, in the third embodiment, similarly to the second embodiment, the leakage magnetic flux from the rotor magnet can be canceled and the rotation can be accurately detected. Further, the output terminals P1 and P2 are close to each other as shown in FIG. 3, and the distances from the FG magnet 11 are almost the same. As a result, each output terminal P1
Since there is almost no phase difference between the output signals from P2 and P2, rotation detection can be performed with higher accuracy as compared with the sensor unit 20 of the second embodiment.

FIG. 6 shows still another embodiment of the present invention. The sensor unit 40 shown in this figure has a pair of element patterns 4 as element patterns of the magnetic sensitive element.
3-A, 43-C and 43-B, 43-D are respectively arranged, and the individual element patterns constituting these are λ / 4.
They are arranged with a space between each.

However, inside the pair of patterns, a space of λ / 4 is left, and this constitutes the sensor section 40 having a 90 ° phase difference pattern. The other structure is the same as that of the third embodiment. Therefore, as in this embodiment, the present invention can be used to easily configure a sensor unit having a desired phase difference. Also in this case, if the centers of the paired element patterns are made to coincide with each other, it is possible to effectively cancel the leakage flux of the rotor magnet and perform highly accurate rotation detection.

[0037]

As described above, according to the present invention, when the rotation is detected by using the magnetic sensitive element, the influence of the leakage magnetic flux of the rotor magnet is not exerted and the accuracy of the rotation detection is improved. It is possible to provide a rotation detection device configured as described above.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a rotation detection device according to the present invention, (a) a schematic diagram showing the configuration of a sensor unit,
(B) It is a figure which shows the equivalent circuit of a sensor part.

FIG. 2 is a schematic diagram showing a configuration of a sensor unit according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an equivalent circuit of the sensor unit of FIG.

FIG. 4 is a schematic diagram showing a configuration of a sensor unit according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a waveform of an output signal from an output terminal P of the sensor unit according to the first embodiment.

FIG. 6 is a schematic diagram showing a configuration of a sensor unit according to still another embodiment of the present invention.

FIG. 7 is a plan view showing an example of a conventional VTR capstan motor.

8 is a schematic cross-sectional view showing the configuration of a rotation detection device in the capstan motor of FIG.

9 (a) is a plan view showing a magnetizing configuration of a rotor magnet in the capstan motor of FIG. 7, and FIG. 9 (b) is an enlarged plan view showing a magnetizing configuration of an FG magnet.

10 is a schematic diagram showing a configuration of a sensor unit in the rotation detection device of FIG.

11 is an equivalent circuit diagram showing a connection state of each magnetic sensitive element in the sensor unit of FIG.

12 is a diagram showing a relationship between rotation detection signals output from the sensor unit of FIG.

13 is a diagram showing how the resistance value changes when a magnetic field acts on the magnetic sensing element in the sensor section of FIG.

14 is a diagram showing magnetic flux from an FG magnet in the sensor section of FIG.

15 is a diagram showing a state of leakage magnetic flux of a rotor magnet acting on the sensor unit of FIG.

FIG. 16 is a diagram illustrating a configuration example of a sensor unit of a rotation detection device.

FIG. 17 is a diagram illustrating another configuration example of the sensor unit of the rotation detection device.

[Explanation of symbols]

 10 Sensor part 11 FG magnet of rotor part 13,23,33,43 Element pattern L1, L2 Virtual line PC Center position of magnetic sensitive part pattern

Claims (2)

[Claims] 1. A rotor part rotatably supported, a stator part fixedly arranged facing the rotor part, a magnetizing part arranged on the outer periphery of the rotor part, and a magnetizing part. And a sensor section composed of a plurality of magnetically sensitive elements arranged facing each other in the stator section, wherein the sensor section is provided with a plurality of element patterns forming a bridge, and forming the bridge. A rotation detecting device, characterized in that the center positions of the element patterns forming each pair coincide with each other in a direction substantially orthogonal to the magnetized portion. 2. The rotation detecting device according to claim 1, wherein the element pattern is formed on a substrate.