JPS59183328A - Detector for rotation - Google Patents

Abstract

PURPOSE:To enable the sure detection of the phase of a rotating body by a construction wherein magnetic substances provided on the rotating body oppositely to a magnetism-sensitive element disposed on a fixed member are made to pass over the element and an output signal varying sharply is taken out of the magnetism-sensitive element. CONSTITUTION:Magnets 6 and 7 having reverse polarities to each other are provided in the periphery on the lower side of a rotating body 5, while a Hall element 9 is set at a position on a fixed member 8 opposite to said magnets. Based on rapid changes in the magnetic fields of the magnets 6 and 7 which are rotated, an output signal varying sharply can be taken out of the Hall element 9, and thereby the phase of rotation of video heads 3 and 4 of a rotary drum 2 can be detected without fail. Accordingly, coils or the like become unnecessary, and this enables the improvement in the reliability of a detecting section, favorable spacing, easy assembling and the reduction of the cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotation detection device suitable for use, for example, in detecting the head position of a drum of a VTR.

BACKGROUND TECHNOLOGY AND PROBLEMS For example, in VTRs, etc., the so-called pulse generator (PG) uses a vertical synchronization signal separated from the input video signal during recording and a control signal recorded on the tape during playback as the reference signal for the drum servo. The output signal is used.

This pulse generator generally consists of a single magnet placed on the rotating side and a detection coil placed on the stationary side. When the magnet passes through the detection coil, the coil changes as shown in FIG. A sinusoidal signal (hereinafter referred to as a zero cross signal) that changes to the positive or negative side with respect to the zero level as shown is detected, and in synchronization with the zero cross point of this signal, a pulse signal as shown in FIG. 2 BIC is detected. is formed and used as a comparison signal for servo.

However, when a coil is used for pulse generator detection, there are disadvantages such as winding a thin wire many times (because of this, there are many defects due to disconnection, and the large number of components, resulting in high cost and complexity). was there.

Therefore, it is possible to use a so-called Hall element instead of a coil for detection, but in a configuration that simply combines this Hall element and a conventional single magnet, the waveform of the signal obtained at the output side of the Hall element will be , the waveform does not have a zero cross like the one obtained with the coil method described above, but a broad waveform that rises in one direction with the zero level as a reference, as shown in Figure 2, and is accurate enough to be used as a position reference. The points were advantageous ((・There was a drawback car.

OBJECTS OF THE INVENTION The present invention takes the above points into consideration and provides a rotation detection device that can reliably detect the phase, etc. of a rotating body with a simple configuration.

Summary of the Invention The present invention includes a magneto-sensitive element disposed on a fixed part, and a magnetic body disposed on a rotating body that rotates with respect to the fixed part so as to face the magneto-sensitive element. This rotation detection device is characterized by extracting an output signal that changes sharply from the magnetic sensing element when a magnetic substance passes through the magnetic sensing element, and the number of parts is reduced and the shape is small. , and the cost is also low.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4, taking as an example the case where it is applied to detecting the head position of a drum for a VTR.

Figure 3 shows the overall configuration of this embodiment. In the figure, (1) is a rotating shaft that is driven by a drum motor (not shown), and (2) is attached to this rotating shaft (1). The rotated drum (131, t4) is connected to the rotary drum (3
), the video heads (31, (
In order to detect the position of the rotary shaft (11), for example, a disk-shaped rotating body (5) is attached to the rotating shaft (11) apart from the rotating drum (2). For example, as shown in Fig. 4, cylindrical magnets (6) and (7), for example, are installed in a parallel relationship so that the polarities are opposite to each other, that is, the north and south poles are continuous. This combination can generate a sudden change in the magnetic field.The fixed part corresponding to the rotating body f5J is equipped with magnets (6) and (7) so as to face them when they rotate. is provided with a Hall element (9), and lead wires (101 and (I) are connected from the output side of this Hall element (9)
Output signals are taken out to output terminals α2 and (131) via ll.

When the magnet (attached to the rotating body (5)) [61, (71) passes over this Hall element (9), the polarity of the magnetic field passing through the Hall element (9) changes, and accordingly. Since the output signal of the Hall element (9) is also inverted, an output signal that crosses zero, similar to the signal shown in FIG. 1A, is output to the output terminal (12+ and a3). A Norculus signal is generated in synchronization with the 27th point, and this signal is compared with a reference signal as a comparison signal to trap the rotating drum (2) so as to overshadow the phase servo.

In this way, in this embodiment, a pair of magnets are arranged in parallel to the Hall element (9) so that their polarities are opposite to each other, and a sudden change in the magnetic field is generated. An output signal that changes sharply, such as a zero cross signal, can be extracted from the element, and the rotational phase of the head can thereby be detected reliably.

Application Example In the above-mentioned embodiment, the present invention is applied to detecting the position of the head of a VT), but the present invention is not limited to this, and the present invention is also applicable to detecting the phase, etc. of other rotating bodies. The same applies to cases where

Effects of the Invention As described above, according to the present invention, a magnetic body is provided on a rotary body that rotates with respect to a fixed part on which a magnetically sensitive element is disposed so as to face the magnetically sensitive element, and this magnetic body is attached to the magnetically sensitive element. The phase of the rotating body can be reliably detected based on this output signal, and the phase of the rotating body can be reliably detected based on this output signal. As there is no need to use a coil or the like, the reliability of the pulse generator part is improved, space is more efficient, assembly is easier, and costs are lower.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the conventional example,
FIG. 3 is a block diagram showing one embodiment of the present invention, and FIG. 4 is a diagram showing the other country for providing a detailed explanation of the invention. (1) is the rotating shaft, (2) is the rotating drum, [31, (41
is the video head, (5) is the rotating body, +61, (71
is a magnet, (8) is a fixed part, and (9) is a Hall element. @Figure 1 Figure 3 Figure 2

Claims (1)

[Scope of Claims] 1. A magnetic sensing element disposed on a fixed part, and a magnetic body disposed on a rotating body that rotates with respect to the fixed part so as to face the magnetic sensing element, A rotation detecting device characterized in that when a magnetic body passes through a portion of the magnetically sensitive element, an output signal that changes sharply is extracted from the magnetically sensitive element. 2. The rotation detecting device according to claim 1, wherein the magnetic body comprises a plurality of magnets combined in parallel so that their polarities are opposite to each other.