JPS6218642A - Cylinder device - Google Patents

Abstract

PURPOSE:To make a device small in size and easy to handle by providing a rotating-side rotary transformer of a VTR with an oscillating member of a switching and rotation phase detecting PG of a magnetic head and providing a detecting member of the PG on a fixed cylinder in such position that the detecting member can face the oscillating member. CONSTITUTION:A PG magnet 4 buried in a rotary transformer 11 rotated as one body together with a rotating cylinder 2 passes on an iron core 13 to change the magnetic field, and this change is taken out as an electric pulse signal by a PG coil 7 to switch the magnetic head and to detect the rotation phase. The PG magnet 4 is buried in the rotary transformer 11, and the PG iron core and the PG coil are buried in a rotary transformer 12 and a thick part 1a of a fixed cylinder 1. As the whole of the cylinder device, the capacity is not increased at all by providing the PG. Since the precision of the gap between the iron core 13 and the PG magnet 4 is as high as that between rotary transformers 11 and 12, the variance of the output value of the PG is reduced very much.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cylinder device for a helical scan type video tape recorder (hereinafter referred to as VTR).

[Technical background of the invention]

Cylinder devices used in helical scan type VTRs are roughly classified into two types of structures as described below. One of them is one in which a rotating disk on which a plurality of magnetic heads are mounted is provided between fixed upper and lower cylinders. The other type is one in which a rotating cylinder is arranged opposite to a fixed cylinder, and a plurality of magnetic heads are mounted on this rotating cylinder. In any of the above cylinder devices, when recording and reproducing images, the magnetic tape is run obliquely to the axial direction of the fixed cylinder and the rotating cylinder along the outer peripheral surfaces of these cylinders. As a result, information is recorded or reproduced by performing a so-called helical scan in which a rotating magnetic head traces diagonally with respect to the width direction of the magnetic tape.

The above-mentioned cylinder device includes a pulse generator (for switching the plurality of magnetic heads and detecting the magnetic head rotation phase).
(hereinafter referred to as PG) is provided. This PG is composed of a PG magnet as an oscillating member, a PG coil as a detecting member, a PG head, a Hall element, etc.

FIG. 5 is a partially sectional front view showing a conventional mounting structure in which the front MαG is mounted to a cylinder device having a structure in which the rotary cylinder and the fixed cylinder are arranged facing each other. A rotating cylinder 2 on which a magnetic head 2a is coaxially mounted is rotatably provided on the fixed cylinder 1, and is configured to be rotationally driven by a cylinder motor 3. A PG magnet 4 is fixedly installed near the inner peripheral surface of the rotating cylinder 2, and this PG magnet 4 rotates together with the rotating cylinder 2. A connector 5 is installed on the outer peripheral surface of the fixed cylinder 1.
is fixed substantially parallel to the axial direction, and this connector 5
A PG coil 7 is fixedly attached to the upper end of the coil via a bracket 6. This PG coil 7 is provided at a position facing the pG magnet 4, and when the PG magnet 4 rotates and passes under the PG coil 7, a change in the magnetic field occurs. The structure is such that the change in the magnetic field is extracted as an electrical pulse signal by the PG coil 7.

FIG. 6 is a partially sectional front view showing a conventional example in which the PG magnet 4 is fixed to the rotor 8 of the cylinder motor 3. In this case, instead of the PG coil 7, a KPG head 9 is fixed on the stator board 10 of the cylinder motor 3, and has exactly the same effect as the conventional example described above.

[Problems with background technology]

In the above-mentioned five conventional cylinder devices, the PG coil 7 or PG hept 9, which is a PG detection section, is provided on the top of the rotary cylinder 2 or on the side of the cylinder motor 3, respectively. For this reason, there was a problem in that the space occupied by the cylinder device became large, which went against the demand for miniaturization. Particularly, the conventional example shown in FIG. 5 has the drawback that accidents such as coil breakage are likely to occur due to contact with hands or the like when handling the cylinder device. Furthermore, there is a problem that the gap between the PG magnet 4 and the I'G coil or the PG hepto 9 varies, and the output value of I)G varies.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a cylinder device that is small in size, easy to handle, and highly accurate.

[Summary of the invention]

The present invention provides a rotary transformer button on the rotating side of a VTR, a PG oscillating member for switching the magnetic head, and detecting the rotational phase, and also providing a PG detecting member on a fixed cylinder at a position where it can face the oscillating member. In this way, the intended purpose was achieved.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cylinder device according to the present invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.

In these figures, parts that are the same as or equivalent to those shown in FIG. 5 are designated by the same reference numerals, and their explanations will be omitted. FIG. 1 is a cross-sectional view showing a rotating side rotary transformer according to this embodiment. A PG magnet 4 is embedded near the outer periphery of a substantially disk-shaped rotary transformer 11 formed of a ferrite core or the like. Both end surfaces of this PG magnet 4 are finished so as to be substantially flush with both surfaces of the rotary transformer 110.

FIG. 2 is a sectional view showing a main part of a cylinder device in which the rotary transformer 11 shown in FIG. 1 is fixedly attached to the rotary cylinder 2. As shown in FIG. The rotary transformer 11 is fixed to the surface of the rotating cylinder 2 on the fixed cylinder 1 side. Fixed cylinder 1
A fixed rotary transformer 12 is fixedly installed on the surface facing the zero rotary transformer 11. The rotary transformer 11
An iron core 13 is provided on the same radius as the PG magnet 4 embedded in the center of rotation. This iron core 13
A PG coil 7 is embedded in the thick portion 1a of the fixed cylinder 1, with the PG coil 7 at the center. The iron core l3 passes through the fixed rotary transformer 12, and its end face is connected to the rotary transformer 12.
The rotary side opening is finished so as to be flush with the surface facing the Tali transformer 11.

The operation of this embodiment configured as described above will be explained below. A PG magnet 4 embedded in a rotary transformer 11 that rotates together with the rotating cylinder 2.
However, by passing over the iron core 13, a change in the magnetic field occurs as in the conventional example.

Changes in this magnetic field are extracted as electrical pulse signals by the PG coil 7 to perform switching of the magnetic head (not shown) and detection of the rotational phase. At this time, the PG magnet 4 is embedded in the rotary transformer 11, and the I'G iron core and PG magnet 4 are embedded in the rotary transformer 11.
The coil is embedded in the rotary transformer 12 and the thick wall portion 1aK of the fixed cylinder 1. Therefore, for the cylinder device as a whole, there is no increase in appearance due to the provision of PG.Also, the accuracy of the gap between the iron core 13 and the PG magnet 4 is
Since the accuracy is as high as the accuracy of the gap between the rotary transformers 11 and 12, variations in the output value of the PG can be made extremely small.

FIG. 3 is a cross-sectional view showing a rotating side rotary transformer according to another embodiment of the present invention, and FIG. 4 is a cross-sectional view showing a main part of a rotating cylinder device in which the rotary transformer shown in FIG. It is a diagram.

In this embodiment, the PG magnet 4 is embedded radially from the outer circumferential side of the rotating side rotary transformer 11, and the PG coil 7
is embedded in the thick wall portion 1b of the side surface of the fixed side rotary transformer 1. The PG magnet 4, the PG coil, and the iron core 13 of It/7 are provided at the same position in the direction of the rotation axis, and have the same operation and effect as the above-mentioned embodiment. In the embodiment, the case where the PG magnet 4 was embedded in the rotary transformer 11 was explained, but instead of embedding the PG magnet 4, the rotary transformer 11 formed of a ferrite core in that part was magnetized. You may.

〔Effect of the invention〕

As mentioned above, according to the present invention, a PG magnet is formed in a part of the rotating side rotary transformer of a cylinder device of a VTR, and a PG coil is embedded in a thick part of a stationary cylinder.
Since the G is configured, it is possible to provide a compact and highly accurate cylinder device.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a rotating side rotary transformer according to an embodiment of the cylinder device according to the present invention, FIG. 3 is a cross-sectional view showing a rotating side rotary transformer according to another embodiment of the present invention, FIG. FIG. 6 is a partially sectional front view showing a conventional cylinder device. 1-...Fixed cylinder 2...Rotating cylinder 2a...
・Magnetic head 4...PG magnet

[Oscillating member] 7
...PG coil (detection member) 11...Rotary side rotary transformer. Agent Patent Attorney Nori Ken Chika Yudo Hiroshi Uji Figure 1 Figure 2 1111 Mon Mushiichi Figure 3 41Q

Claims (3)

[Claims] (1) In a cylinder device for a video tape recorder comprising a fixed cylinder and a rotating cylinder placed opposite to the fixed cylinder and mounted with a magnetic head, oscillation of a pulse oscillator for switching the magnetic head and detecting the rotational phase. A cylinder device characterized in that a member is provided on a rotating side rotary transformer, and a detection member of the pulse oscillator is provided at a position where it can face the oscillation member of the fixed cylinder. (2) The cylinder device according to claim 1, wherein the oscillating member is formed by magnetizing a part of the rotary transformer. (3) The cylinder device according to claim 1, wherein the oscillating member is a magnet embedded in a part of the rotary transformer.