JPH0642774B2 - Rotating device - Google Patents

Description

The present invention relates to a rotating device including a frequency generator (hereinafter, abbreviated as FG) that generates a signal having a frequency according to the number of rotations of a rotating body.

As is well known, the role of the FG is to take out a frequency signal according to the number of rotations of the rotating body and to control the speed or phase of the rotating body. The frequency signal holding means having the above is arranged on the rotating side, and the signal detecting means for detecting and extracting the signal information is arranged on the fixed side. A number of such methods have been proposed in the past, and representative methods include a method of forming a magnetic circuit and inducing and detecting a change in magnetic flux with a coil, and a method of detecting transmission or reflection of light by a light receiving portion. Further, as described above, the rotation of the rotating body is controlled by receiving the FG signal, so that the FG signal is required to have high precision and high resolution. For that purpose, it is necessary that the FG signal output has a predetermined value in any state of the rotating device without load and with load. That is, if the signal output decreases, the S / N ratio cannot be sufficiently obtained, and as a result, the resolution as the rotation detection signal deteriorates, making it impossible to perform rotation control with high rotation accuracy.

In general, a bearing that rotatably supports a rotating shaft usually has a small radial clearance from the rotating shaft. Therefore, a member (for example, a pinch roller) that rotates with a pressing force in the radial direction on the rotating shaft. When the pressing force of () is applied, the rotary shaft is tilted by the above-mentioned radial clearance. Therefore, the gap between the rotation side and the fixed side of the FG portion may change, which leads to deterioration of the SN ratio.

Conventionally, as one of the measures to solve this problem, the rotation side and the fixed side of the FG section are opposed to each other over the entire circumference, and even if radial movement on the rotation side occurs, the signals are averaged over the entire circumference to obtain the signal. Has been done. However, the method of taking out the entire circumference has drawbacks that result in an increase in size, cost, and weight of the device. For this reason, it is conceivable that the rotation side of the FG section holds frequency signal information over the entire circumference, but the fixed side detects one point or two points divided by 180 ° for the purpose of averaging. There is.

The present invention provides a rotating device having the above-mentioned configuration, which can obtain a stable FG signal output regardless of the load state of the rotating device.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to a direct drive type capstan device used for running and driving a magnetic tape such as an audio tape recorder or a video tape recorder. That is, the capstan shaft 1 also used as a motor shaft is driven to rotate by the built-in brushless motor 10.
2 is a rotating device that presses the pinch roller 14 and the idler 36 to rotate them, holds the magnetic tape 16 between them to drive them at a constant speed, and transmits rotational power to other rotating members. The capstan shaft 12 is rotatably supported by a bearing 20 mounted on a substrate 18 of the device body with a predetermined gap. The brushless motor 10 is
A back yoke 21 made of a magnetic material that rotates integrally with the capstan shaft 12, a rotor 22 made of a ring-shaped permanent magnet 23 fixed to the back yoke 21, and a magnetized surface of the rotor 22 (a lower surface in the figure) are planarly opposed to each other. The stator 24 is provided with a predetermined winding. The stator 24 is the substrate 18
It is fixed via a support rod 26. The capstan shaft 12 is supported in the thrust direction at the center of the stator 24. The Hall element 28 provided near the winding of the stator 24 detects the rotational position of the rotor 22 to switch the current flowing through the stator winding of each phase.

The FG unit 30 that extracts the rotation signal information according to the rotation of the rotor 22 is located on the outer circumference of the rotor 22. That is, the rotor 22
The outer periphery of the back yoke 21, more specifically, the outer periphery of the back yoke 21 is fixed with an annular magnet 32 magnetized to have a plurality of N-poles and S-poles alternately on the peripheral surface so as to rotate integrally with the rotor 22. And a point near the outer circumference of the annular magnet 32 or 180
A detection head (or Hall element) 34 for detecting the frequency signal magnetic flux from the annular magnet 32 at two positions of the ° division.
Is arranged.

Generally, for the purpose of highly accurate rotation control, it is preferable that the signal frequency is high, and therefore, the number of magnetized magnetic poles of the ring magnet 32 is high, and therefore the magnetized width per pole is narrow.
The magnetic flux interlinking to the detection head 34 attached to the stator 24 is reduced while maintaining a predetermined gap G in non-contact with the annular magnet 32, and the management of the gap G is important for obtaining a constant signal output. Become. However, as described above, when the capstan device is used in the capstan device, it receives lateral pressure in a certain direction due to the pressing force of the pinch roller 14 and the idler 36. Therefore, only a slight radial gap between the capstan shaft 12 and the bearing 20 is applied. Will tilt and rotate. Therefore, the annular magnet 32 attached to the roller 22 also tilts, and the center of rotation moves on the pressing direction line. Although this state is a simplified diagram, the state of movement of the ring-shaped magnet 32 seen in a plan view is exaggeratedly shown by a dotted line in FIG. That is, the capstan shaft 12 inclines in the direction 15 of the combined force of the two vectors due to the pressing direction and the pressing force of the pinch roller 14 and the idler 36 acting on the capstain shaft 12, so that the annular magnet 32 moves as shown by the dotted line. To do.
At this time, as described above, the gap G between the annular magnet 32 and the detection head 34 needs to be invariable, so that the detection head 34 is located on the line YY 'substantially perpendicular to the resultant force 15.
Is effective. If it is arranged on this line, the change in the gap G can be ignored even if the rotation center of the annular magnet 32 moves as shown by the dotted line. Although FIG. 2 shows an example in which one detection head is provided, there is no problem even if two detection heads are provided on this line.

Although the configuration of the annular magnet and the detection head is shown as the FG system in the above-described embodiments, the effectiveness of the present invention is not lost in any combination of the light transmission system and the reflection system.

As described above, according to the present invention, a stable FG signal output can be obtained without being affected by the pressing rotation member regardless of whether the FG signal detecting means is a one-point or two-point system. For downsizing, weight saving, and high performance,
It brings a great effect.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a schematic plan view of an essential part for explaining the function and effect. 12 ... Capstan shaft, 14 ... Pinch roller, 15
…… Synthetic force, 20 …… Bearing, 30 …… FG part, 32 ……
Ring magnet, 34 ... Detection head, 36 ... Idler.

Claims (1)

[Claims] 1. A rotating shaft rotatably supported in a bearing with a predetermined clearance, and a ring-shaped member which rotates integrally with the rotating shaft and has signal information of a predetermined frequency on the entire peripheral surface portion. The frequency signal holding means and one or one in the circumferential direction with a constant gap in the radial direction from the peripheral surface portion of the frequency signal holding means.
It is provided at two locations divided by 80 ° and comprises signal detection means for detecting signal information from the frequency signal holding means, and the rotating shaft can rotate with a predetermined pressing force in the radial direction. A plurality of predesigned rotating members are pressed, and the signal detecting means is arranged so as to be positioned on a line substantially perpendicular to the vector combining direction determined by the pressing direction and the pressing force of the plurality of rotating members. A rotating device characterized by being installed.