JPS6245782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating device equipped with a frequency generator (hereinafter abbreviated as FG) that generates a signal with a frequency corresponding to the rotational speed of a rotating body.

As is well known, the role of the FG is to extract a frequency signal corresponding to the rotation speed of a rotating body and to control the speed or phase of the rotating body. A frequency signal holding means having a frequency signal is provided on the rotating side, and a signal detecting means for detecting and extracting the signal information is provided on the stationary side. A number of methods have been proposed in the past, and representative methods include a method in which a magnetic circuit is configured and changes in magnetic flux are detected by induction using a coil, and a method in which transmission or reflection of light is detected by a light receiving section. Furthermore, as mentioned above, since the rotation of the rotating body is controlled in response to the FG signal, the FG signal is required to have high precision and high resolution performance. For this purpose, it is necessary that the FG signal output has a predetermined value regardless of whether the rotating device is under no load or under load. That is, if the signal output decreases, a sufficient signal-to-noise ratio cannot be obtained, and as a result, the resolution of the rotation detection signal deteriorates, making it impossible to control rotation with high rotational accuracy.

In general, bearings that rotatably support a rotating shaft usually have a small radial gap with the rotating shaft, so members that rotate with a radial pressing force on the rotating shaft (for example, pinch rollers) ), the rotating shaft tilts by the amount of the above diameter gap. Therefore, the gap between the rotating side and fixed side of the FG section may also change, and the above-mentioned SN
This leads to a worsening of the ratio.

Traditionally, one way to solve this problem is to
The rotating side and the stationary side of the FG section are made to face each other around the entire circumference, and even if radial movement occurs on the rotating side, it is averaged over the entire circumference to extract the signal. However, the method of extracting the entire circumference has the disadvantage that it results in an increase in size, cost, and weight of the device. For this reason, a method has been proposed in which the rotating side of the FG section retains frequency signal information over the entire circumference, but the fixed side is detected at one point or at two points divided by 180 degrees for the purpose of averaging. There is.

The present invention provides a rotating device having the above-described configuration, which is capable of obtaining a stable FG signal output regardless of the load condition of the rotating device.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to a direct drive type capstan device used for driving a magnetic tape in an audio tape recorder or a video tape recorder. That is, it is a rotating device that presses a pinch roller 14 against a capstan shaft 12 which also serves as a motor shaft, which is rotationally driven by a built-in brushless motor 10, to rotate it, and pinches a magnetic tape 16 between the pinch rollers and drives the magnetic tape 16 at a constant speed. be. The above capstan shaft 12 is the board 1 of the main body of the device.
It is rotatably supported by a bearing 20 attached to a shaft 8 with a predetermined gap therebetween. The brushless motor 10 includes a back yoke 21 made of a magnetic material that rotates together with a capstan shaft 12, and a rotor 22 made of a ring-shaped permanent magnet 23 fixed to the back yoke 21.
and a stator 2 provided with a predetermined winding that faces the magnetized surface (lower surface in the figure) of the rotor 22 in a plane.
Consists of 4. The stator 24 is fixed to the substrate 18 via a support rod 26. The capstan shaft 12 is supported in the thrust direction at the center of the stator 24. In addition, the rotor 22 is connected to a Hall element 28 provided near the windings of the stator 24.
The rotational position of the stator is detected and the current flowing through the stator windings of each phase is switched.

An FG unit 30 that extracts rotation signal information corresponding to the rotation of the rotor 22 is located on the outer periphery of the rotor 22. That is, on the outer periphery of the rotor 22, more specifically, on the outer periphery of the back yoke 21, there are N poles and S poles on the entire circumferential surface.
An annular magnet 32 having a plurality of alternately magnetized poles is fixed to rotate integrally with the rotor 22, and a magnet from the annular magnet 32 is placed at one point near the outer circumference of the annular magnet 32 or at two points separated by 180 degrees. Detection head (or Hall element) that detects the frequency signal magnetic flux
34 are arranged.

Generally, when aiming at high-precision rotation control, it is preferable to have a high signal frequency, so the annular magnet 3
Since the number of multi-pole magnetized poles in No. 2 is high, and the magnetization width per pole is narrow, the magnet is connected to the detection head 34 attached to the stator 24 while maintaining a predetermined gap G without contacting the annular magnet 32. Interlinking magnetic flux is also reduced, and management of the gap G is also important in order to obtain a constant signal output. However, as mentioned above, when used in a capstan device, it receives lateral pressure in a certain direction due to the pressure of the pinch roller 14, so the capstan shaft 12 rotates with an inclination due to the slight radial gap between the capstan shaft 12 and the bearing 20. It turns out. Therefore, the annular magnet 32 attached to the roller 22
The rotation center will also be tilted, and the rotation center will move along the pressing direction line. Although this is a simplified diagram, the movement of the annular magnet 32 in a plan view is shown in exaggerated dotted lines in FIG. 2. At this time,
As mentioned above, since the gap G between the annular magnet 32 and the detection head 34 needs to remain unchanged, in the present invention, the detection head 34 is connected to the pinch roller 1.
A detection head 34 is disposed on a line X-X' substantially perpendicular to the pressing direction of 4. If arranged on this line, even if the rotation center of the annular magnet 32 moves as shown by the dotted line, the change in the gap G can be ignored. Second
The figure shows an example with one detection head, but
Providing two detection heads on this line will not cause any problems.

FIG. 3 shows an example in which there are two pressing rotating members in the capstan device shown in FIG. 1.
That is, for example, in order to transmit rotational power from the capstan shaft to other rotating members, the idler 36 is often pressed against the capstan shaft as shown in FIG. 1. In such cases, capstan shaft 1
It is clear that the inclination direction of 2 is the composite direction of the vector directions of the two points. Therefore, at this time, the detection head 34 is placed on the line Y-Y' which is approximately perpendicular to the direction of synthesis.
Place.

In the above embodiments, the FG method was shown using a configuration of an annular magnet and a detection head, but the effectiveness of the present invention is not lost in any combination of light transmission methods, reflection methods, etc.

As described above, according to the present invention, regardless of whether the FG signal detection means is a one-point or two-point method, a stable FG signal output can be obtained without being affected by the pressing rotating member, and the equipment can be This has great effects in achieving smaller size, lighter weight, and higher performance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a schematic plan view of the main part for explaining the function and effect of the same embodiment, and FIG. 3 is a diagram illustrating the function and effect of another embodiment of the present invention. FIG. 2 is a schematic plan view of main parts for explanation. 12... Capstan shaft, 14... Pinch roller, 20... Bearing, 30... FG section, 32... Annular magnet, 34... Detection head.

Claims (1)

[Scope of Claims] 1. A rotating shaft rotatably supported by a bearing;
A ring-shaped frequency signal holding means that rotates integrally with the rotating shaft and has signal information of a predetermined frequency on its entire circumferential surface, and a ring-shaped frequency signal holding means that has a certain gap in the radial direction from the circumferential surface of the frequency signal holding means. The rotary shaft is provided with a signal detecting means disposed at one location in the circumferential direction or at two locations separated by 180 degrees and detecting signal information from the frequency signal holding means, and a predetermined pressing force is applied to the rotating shaft in the radial direction. The signal detecting means is arranged so as to be located on a direction line substantially perpendicular to the pressing direction of the rotating member with respect to the rotating shaft. Features a rotating device. 2. When there are a plurality of arbitrary rotating members that rotate with a predetermined pressing force in the radial direction with respect to the rotating shaft, the signal is detected so as to be located on a direction line that is approximately perpendicular to the vector composite direction of the plurality of rotating members. The rotating device according to claim 1, further comprising means.