JP3336661B2 - Rotation detection device - Google Patents

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 use in a capstan motor of a VTR, a tape recorder or the like.

[0002]

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

As shown in FIG. 3, a cover 12 for covering the outer peripheral side and the upper side of a rotor magnet 11 is attached to a rotor section 10, and an FG (for detecting rotation) is further provided on the outer peripheral side. Frequency Generator) Magnet 13 is attached. A rotating shaft 14 is attached to the center of the rotor unit 10, and a rotating unit 1 is fixed to a bearing unit 22 fixed to a stator substrate 21 of the stator unit 20.
4 is rotatably supported. As a result, the rotor unit 10 rotates smoothly. The rotor magnet 11 and the FG magnet 13 have the same width over the entire circumference, and a plurality of magnetic poles are magnetized.

In the stator section 20, FIGS. 2 and 3
As shown in FIG. 2, a plurality of drive coils 23 arranged opposite to 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. 4, twelve magnetic sensitive elements 31A to 31L are arranged at predetermined intervals so as to face the outer peripheral surface of the FG magnet 13 of the rotor section 10. In this example, three rotation detection signals P1,
In order to output P2 and P3, each of the magnetic sensitive elements 31A to 31A
Three sensors 39A to 39C are formed by using four Ls.

The left magnetic sensing element 31A and the second magnetic sensing element 31D in the sensor 39A for the rotation detection signal P1.
And the distance between the third magnetic element 31I and the fourth magnetic element 31L are determined by the magnetic pole width λ of the FG magnet 13.
Is set the same as Also, the second magnetic sensitive element 3
The interval between 1D and the third magnetic sensitive element 31I is set to 1.5 times the magnetic pole width λ.

[0007] The magnetic sensitive elements 31B to 31 in the sensors 39B and 39C for the other two rotation detection signals P2 and P3.
J, 31K to 31C are also the second magnetic sensitive elements 31
Sensor 39A except that the distance between E, 31H and the third magnetic sensitive element 31G, 31F is set to の of the magnetic pole width λ.
Is set to the same interval as. Furthermore, each sensor 39A ~
39C are shifted by １ ／ of the magnetic pole width λ.

The magnetic sensitive elements 31A to 31L detect a change in a magnetic field caused by rotation of the FG magnet 13, and have a magnetoresistive effect on a substrate 32 formed of an insulating material such as a glass plate or a ceramic plate. It is formed in an elongated U-shape with a conductive material. As a result, a slot-shaped thin film resistance element is formed, and the resistance value changes due to a change in the magnetic field.

The sensors 39A to 39C are connected in parallel and are equivalent to the circuit shown in FIG. In this circuit, a power supply VCC and a ground GND are connected to terminals 34 and 35 at both ends of a resistor element group for outputting the rotation detection signals P1 to P3.
Are connected, and the terminals 36, 37,
38, three rotation detection signals P1, P2,
P3 is output. Here, the power supply VCC and the ground G
Two resistance elements are connected between the ND and the output terminals 36, 37, 38 because the rotation detection signals P1, P2, P3
This is to increase the output level of.

As described above, the resistance values of the magnetic sensitive elements 31A to 31L change with the change of the magnetic field. Therefore, F
When the G magnet 13 rotates, the resistance value of the bridge circuit changes, and as a result, substantially sinusoidal rotation detection signals P1, P2, whose phases are shifted from the output terminals 36, 37, 38 by approximately 120 degrees as shown in FIG. P3 is output. By counting the zero cross points of the rotation detection signals P1, P2, and P3 and the cross points of the rotation detection signals P1 to P3, it is possible to detect the rotation state such as the rotation speed of the FG magnet 13, that is, the rotor unit 10. Become.

In FIG. 3, the magnetic sensitive elements 31A to 31L
Is attached to a predetermined position of the stator substrate 21 by the support portion 33. Thus, the distance between the magnetic sensitive elements 31A to 31L and the FG magnet 13 has a predetermined size, and the change in the magnetic field of the FG magnet 13 can be detected by the magnetic sensitive elements 31A to 31L.

[0012]

By the way, in the above-mentioned capstan motor 1, the magnetically sensitive elements 31A to 31A are provided.
Since the number of L is large, the overall width is widened. As shown in FIG. 7, the gap .delta.2 between the magnetic sensitive elements 31A and 31C at both ends and the FG magnet 13 is located at the center.
The gap δ1 between the I, 31J and the FG magnet 13 is considerably larger.

Therefore, the magnetic sensing elements 31A,
31C and the magnetic sensing elements 31I and 31J at the center are FG
Since the magnetic fields received from the magnets 13 are different, there arises a problem that the output level of each of the rotation detection signals P1 to P3 becomes small or the rotation detection signals P1 to P3 are output with a phase shift.

Further, since the distance between each of the magnetic sensitive elements 31A to 31L and the rotor magnet 11 is different, the influence of the leakage magnetic flux of the rotor magnet 11 received by each of the magnetic sensitive elements 31A to 31L is also different. For this reason, the conventional capstan motor 1 has a large number of magnetically sensitive elements 31A to 31A.
When 31L is used, there is a problem that the detection accuracy of the rotation state of the rotor unit 10 decreases.

Further, in order to reduce the size of a VTR or a tape recorder using the above-described capstan motor 1, it is necessary to reduce the size of the capstan motor 1. For this purpose, the outer diameter of the rotor section 10 must be reduced, but if this is done, the outer diameter of the FG magnet 13 will be reduced, and the gap between the magnetic sensitive elements 31A, 31C and the FG magnet 13 at both ends will increase. Since it spreads, there arises a problem that the detection accuracy of the rotation state is further reduced.

Accordingly, the present invention has been made to solve the above-mentioned problem, and it is possible to improve the detection accuracy of the rotational state even when a large number of magnetically sensitive elements are used, and to further reduce the outer diameter of the FG magnet. This also proposes a rotation detecting device capable of preventing the detection accuracy of the rotation state from lowering.

[0017]

In order to solve the above-mentioned problems, according to the present invention, there are provided a plurality of magnetic poles attached to the outer peripheral side of a rotor magnet of a surface-facing motor and magnetized at the same width along the circumferential direction. And a plurality of magnetic sensitive elements for detecting a change in a magnetic field generated by rotation of the FG magnet, and a plurality of magnetic sensitive elements output according to a change in the resistance value of the magnetic sensitive element. In a rotation detecting device that detects the rotation state of a rotor magnet by detecting a rotation detection signal, a magnetic sensitive element for outputting each rotation detection signal has a predetermined output phase.
The FG magnets are arranged so as to be displaced at predetermined intervals to obtain a difference and to overlap along the center axis direction of the FG magnet.

[0018]

In FIG. 1, the sensor section 30 has twelve magnetic sensitive elements 31A to 31L.
Sensors 39A to 39C for outputting three rotation detection signals by using four of each of A to 31L are formed. The magnetic sensitive elements 31B to 31J of the sensor 39B are arranged so as to be sandwiched between the magnetic sensitive elements 31A to 31L of the sensor 39A, and the total height of both the sensors 39A and 39B is substantially magnetic sensitive. This is the height of one element.

The sensor 39C is disposed so as to overlap the sensors 39A and 39B along the center axis direction of the FG magnet 13, and the total height T2 of the sensors 39A to 39C is substantially equal to two magnetic elements. Equivalent to height, this is F
The height is set to be equal to or less than the height T1 of the G magnet 13.

The resistance of each of the magnetic sensitive elements 31A to 31L changes with the rotation of the FG magnet 13, whereby three rotation detection signals P1 to P3 are output from the output terminals 36 to 38. The rotation detection signals P1 to P3 are out of phase by 120 degrees, and the rotation state of the rotor unit 10 is detected by counting the zero cross point of each signal P1 to P3 and the cross point of each signal P1 to P3. Becomes possible.

In this sensor unit 30, it is possible to fit the length of eight magnetic sensitive elements 31A to 31L in spite of using twelve magnetic sensitive elements 31A to 31L. Therefore, it is possible to equalize the distance between each of the magnetic sensitive elements 31A to 31L and the FG magnet 13, so that the output levels of the rotation detection signals P1 to P3 are the same and have a predetermined phase. This makes it possible to increase the accuracy of detecting the rotation state of the rotor unit 10.

[0022]

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 above-mentioned capstan motor 1 are denoted by the same reference numerals, and detailed description 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 configuration of the capstan motor 1 is the same as that of FIG. In the sensor section 30, twelve magnetic sensitive elements 31A to 31L are used to output three rotation detection signals P1 to P3. These magnetic sensitive elements 31A to 31L have three sensors 39A for detecting the respective rotation detection signals P1 to P3.
Four are used for each of ~ 39C.

The left magnetic sensing element 31A and the second magnetic sensing element 31D in the sensor 39A for the rotation detection signal P1.
And the distance between the third magnetic element 31I and the fourth magnetic element 31J is set to be the same as the magnetic pole width λ of the FG magnet 13, and the distance between the second magnetic element 31D and the third magnetic element 31D
The interval between the second magnetic sensitive elements 31I is set to 1.5 times the magnetic pole width λ.

The leftmost magnetic sensitive element 31B and the second magnetic sensitive element 31E in the sensor 39B for the rotation detection signal P2.
And the distance between the third magnetic element 31G and the fourth magnetic element 31J is the same as the magnetic pole width λ, and the distance between the second magnetic element 31E and the third magnetic element 31G is the magnetic pole. It is の of the width λ.

The magnetic sensitive elements 31B to 31J of the sensor 39B
Are arranged within the interval between the magnetically sensitive elements 31A to 31L of the sensor 39A, and the total height of the two sensors 39A and 39B is substantially the same as the height of one magnetically sensitive element. The magnetic sensitive elements 31B to 31J of the sensor 39B are
FG magnet 1 for the magnetic sensitive elements 31A to 31L
3 are shifted by 磁 of the magnetic pole width λ.

The magnetic sensitive elements 31C to 31K of the sensor 39C for the rotation detection signal P3 are set at the same intervals as the magnetic sensitive elements 31B to 31J of the sensor 39B.
A and 39B are arranged so as to overlap along the central axis direction of the FG magnet 13. In FIG. 1, a sensor 39C is arranged above the sensors 39A and 39B. Further, the magnetic sensitive elements 31C to 31K of the sensor 39C are arranged shifted from the magnetic sensitive elements 31A to 31L of the sensor 39A by ／ of the magnetic pole width λ.

The magnetic sensitive element 31 of each of the sensors 39A to 39C
A to 31L are all the same height,
A to 31L are contained within a dimension T2 which is the same as or smaller than the thickness T1 of the FG magnet 13. Thereby, all the magnetic sensitive elements 31A to 31L effectively receive the magnetic field of the FG magnet 13.

A power supply VCC is connected to a terminal 34 connected to the leftmost magnetic sensitive elements 31A, 31B and 31C of the sensors 39A to 39C, and rightmost magnetic sensitive elements 31L and 31C.
A ground GND is connected to a terminal 35 connected to J and 31K.

The second magnetically sensitive element 31D of the sensor 39A
The output terminal 36 of the rotation detection signal P1 is connected to the middle point of connection between the second magnetic sensor element 31E and the third magnetic sensor element 31G of the sensor 39B. The output terminal 37 of the rotation detection signal P2 is connected. The second magnetic sensitive elements 31F and 3 of the sensor 39C
The rotation detection signal P
The third output terminal 38 is connected.

The sensors 39A-39 formed in this way
C is equivalent to the circuit shown in FIG. Therefore, the rotation detection signals P1 to P3 output from the sensor unit 30
Becomes a substantially sine wave similarly to FIG.
It becomes degree. By counting the zero cross points of the rotation detection signals P1 to P3 and the cross points of the rotation detection signals P1 to P3, the rotation state of the rotor unit 10 can be detected.

In this sensor unit 30, twelve magnetically sensitive elements 31A to 31A to 31A to 31C are provided, similarly to the conventional sensor unit 30 (FIG. 4).
Although 31L is used, since the entire width is accommodated in eight magnetic sensitive elements, the magnetic sensitive elements 31A and 31A at both ends are used.
The difference between the gap δ2 between 31L and the FG magnet 13 and the gap δ1 between the magnetic sensing elements 31E and 31F at the center and the FG magnet 13 are reduced.

Therefore, the magnetic field of the FG magnet 13 is applied substantially uniformly to each of the magnetic sensitive elements 31A to 31L, and the effect of the leakage magnetic flux of the rotor magnet 11 is also uniform, so that each of the rotation detection signals P1 to P3 Have the same output level and a predetermined phase. As a result, it is possible to increase the accuracy of detecting the rotation state of the rotor unit 10 as compared with the related art.

Further, even if the outer diameter of the FG magnet 13 becomes small, the distance between each of the magnetically sensitive elements 31A to 31L and the FG magnet 13 can be kept relatively equal. Even if the size is reduced, it is possible to prevent the detection accuracy of the rotation state from lowering.

Although the above embodiment has been described with reference to the case where three rotation detection signals P1 to P3 having a phase difference of 120 degrees are output, two rotation detection signals may be output. In this case, it is possible to displace the magnetic sensitive elements so that the two rotation detection signals have opposite phases, or to displace the magnetic sensitive elements so that the phase difference is 60 degrees or 120 degrees. It is. Further, the present invention can be applied to a case where N rotation detection signals are output. In this case, the phase difference between the rotation detection signals is (3
It is possible to arrange the magnetic sensitive element so as to be 60 / N) degrees.

[0036]

As described above, according to the present invention, the magnetic sensing element for outputting a plurality of rotation detection signals by the rotation of the FG magnet has a predetermined interval for obtaining a predetermined output phase difference.
, And are arranged so as to overlap along the central axis direction of the FG magnet.

Therefore, according to the present invention, even when there are a large number of magnetic sensitive elements, they can be accommodated in a relatively short length. Can be made substantially the same. Furthermore, since the influence of the leakage magnetic flux of the rotor magnet is also substantially uniform, each rotation detection signal has a predetermined phase at the same output level, thereby enabling the detection accuracy of the rotation state of the rotor unit to be improved more than before. Become. Also, FG
Even when the outer diameter of the magnet is reduced, the distance between the magnetically sensitive element and the FG magnet can be kept substantially the same, so that the capstan motor can be downsized without lowering the rotation state detection accuracy. There are effects such as being possible.

[Brief description of the drawings]

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

FIG. 3 is a cross-sectional view of the capstan motor 1.

FIG. 4 shows a magnetic sensing element 31A in a conventional sensor unit 30.
It is a figure explaining arrangement of -31L.

FIG. 5 is a diagram illustrating an equivalent circuit of sensors 39A to 39C.

FIG. 6 is a waveform diagram of rotation detection signals P1 to P3 output from sensors 39A to 39C.

FIG. 7 shows each magnetic sensitive element 31 in a conventional sensor unit 30;
It is a figure explaining the gap of A-31L and FG magnet 13.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capstan motor 10 Rotor part 11 Rotor magnet 13 FG magnet 14 Rotation axis 20 Stator part 21 Stator substrate 23 Drive coil 30 Sensor part 31A-31L Magnetic element 32 Substrate 33 Support part 39A-39C Sensor

Continuation of front page (56) References JP-A-2-119555 (JP, A) JP-A-4-37063 (JP, A) JP-A-4-233411 (JP, A) JP-A-62-116212 (JP) , A) Fully open sho 64-50315 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02K 29/08 H02K 21/00 G01B 7/30 101 G01D 5/245 G01P 3 / 487 H02K 11/00

Claims (4)

(57) [Claims] 1. An FG magnet for rotation detection having a plurality of magnetic poles attached to the outer peripheral side of a rotor magnet of a surface-facing motor and having the same width along the circumferential direction, and generated by rotation of the FG magnet. A plurality of magnetically sensitive elements for detecting a change in the magnetic field, and detecting a plurality of rotation detection signals output in response to a change in the resistance value of the magnetically sensitive element, thereby detecting the rotation state of the rotor magnet. In the rotation detecting device configured to detect the rotation, a magnetic-sensitive element for outputting each of the rotation detection signals is provided .
A rotation detection device, wherein the rotation detection device is arranged so as to shift its position at a predetermined interval to obtain a constant output phase difference and to overlap along the central axis direction of the FG magnet. Wherein said rotation detection signal is two outputs, the
In order for the two rotation detection signals to be out of phase with each other,
The rotation detecting device according to claim 1, wherein a fixed interval is set . 3. The apparatus according to claim 2, wherein the two rotation detection signals are output , and the predetermined interval is set so that the phase difference between the two rotation detection signals is 60 degrees.
2. The rotation detecting device according to 1 . 4. Two rotation detection signals are output, and a phase difference between the two rotation detection signals is 120 degrees.
Rotation detecting device according to claim 1, wherein said predetermined interval is set.