JPH0152807B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention has a wide track width (tape width).
This invention relates to a DC magnetic field reversal erasing head that is used in VHS video tape recorders and the like to erase tape in a pseudo-AC manner.

[Prior Art and Background of the Invention] By the way, an erasing head for performing pseudo-AC erasing for audio has already been disclosed in Utility Model Publication No. 53-7698,
It has been proposed as in Publication No. 53-37612.
In this case, since the tape is used for audio, the width of the tape is narrow (≒3.81 m/m), and the width of the core part around which the coil is wound can be made equal to or greater than the width of the tape sliding contact area, so it is possible to There is no variation in leakage magnetic flux in the tape width direction.

However, when trying to use the above audio head as an erasing head for a VHS video tape recorder with a wide tape width (≒12.65 m/m), the volume of the erasing head becomes extremely large if the same structure is used because the tape width is wide. It's boring and not practical. In order to solve this problem, a head that performs pseudo-AC erasure as shown in Figure 7 was considered, but since it is a system that forms one magnetic path b, the tape is in sliding contact as shown in Figure 6 A. The leakage magnetic flux at the magnetic pole portion of the erase head varied greatly in the tape width direction, and the distortion rate was also 4%, making it difficult to use as an erase head for a VTR.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a DC magnetic field reversal type erasing head that has almost no variation in leakage magnetic flux in the width direction of the tape and has a distortion rate of 2%. .

[Means for Solving the Problems] In order to achieve the above object, the present invention has a configuration in which a first core plate having a side frame shape and a second core plate having a substantially T-shaped side face are arranged perpendicularly to the second core plate. Each core has a side exposed between opposite sides of the first core plate, and a horizontal side of the second core plate overlaps a horizontal side closing between the opposite sides of the first core plate. The plates are overlapped alternately so as to form a gap between the plates, and the depth of the core plate is increased as the horizontal side of the first core plate that comes into sliding contact with the tape goes from the center in the tape width direction to both ends. The horizontal side of the second core plate on the side that comes into sliding contact with the tape is made shorter in depth as it goes from the center in the tape width direction to both ends, and the superposed first or The gist of this invention is a direct current magnetic field reversal type erasing head characterized by coils being symmetrically wound around the second core plate so that the core has two magnetic paths.

[Example] The details of the embodiment will be explained below with reference to the drawings.

As shown in Figure 1A, the first frame has a rectangular frame shape on its side.
The core plate 1 and the second core plate 2 having a generally T-shaped side surface shown in FIG. The horizontal side 2b of the second core plate 2 overlaps the horizontal side 1b of the first core plate 1 that closes the space between the opposite sides 1a, and the horizontal side 2b of the second core plate 2 overlaps the horizontal side 1b of the first core plate 1 that closes the space between the opposing sides 1a. Polymerization is carried out alternately so that gap 3 is formed. Further, the rear end of the vertical side 2a of the second core plate 2 is brought into overlapping contact with the other horizontal side 1c of the first core plate 1.

Further, the horizontal side 1b of the first core plate 1 on the side that comes into sliding contact with the tape is formed so that the depth dimension of the core plate becomes longer as it goes from the center in the tape width direction to both ends, while the second core plate The horizontal side 2b on the side that comes into sliding contact with the tape 2 is formed so that the depth dimension of the core plate becomes shorter as it goes from the center in the tape width direction to both ends.

Due to the above polymerization, the opposite side 1a of the first core plate 1
A coil 4 is wound symmetrically around the vertical sides 2a of the second core plate 2 exposed between them, so that the second core plate 2 becomes an excitation core and the first core plate 1 becomes an induction core.

[Function] Therefore, the magnetic field forms two loops that are distributed vertically in the figure with the vertical side 2a as a boundary, as shown by the arrows in FIG. In other words, it can be seen from this figure that if a leakage magnetic flux of 2/1l is guaranteed for the gap height l, the entire gap height, in other words, the entire tape width can be effectively guaranteed.

Further, the distribution of the magnetic field strength of the loops distributed vertically is made uniform due to the change in the depth dimension of the horizontal sides 1b and 2b, so that the unerased portions at both ends are improved, and the occurrence of distortion due to the unerased portions can be suppressed.

FIG. 6 shows a characteristic diagram of the change in distortion rate in the tape width direction between the conventional example and the present invention. It can be stabilized.

Figure 3 shows a modified example, in which the first
The core plate 1 is formed into a side U-shaped frame shape, and the T-shaped second core plate 2 is further provided with a connecting side 2c on its vertical side 2a, and the first and second core plates 1 and 2 are connected to each other. When polymerized as shown in FIG. 4, the connecting side 2c is the first
The opening end of the core plate 1 is closed by polymerization, and its function is the same as in the previous example.

FIG. 5 shows an example in which the winding portion of the coil 4 is changed from the example shown in FIG. In this case, the first core plate 1 serves as an excitation core, and the second core plate 2 serves as an induction core.

[Effects of the Invention] As described above, according to the present invention, two loops are generated vertically from the center in the width direction of the tape, and can be used in a pseudo-AC manner as a wide erasing head for VHS type video tape recorders and the like. It can be used as an erasing head for erasing data, saving power and effectively performing the erasing function without increasing the volume of the head. Furthermore, in the present invention, a first side frame-shaped first part of the erasing head is provided.
The horizontal side of the core plate on the tape sliding surface side is formed to have a longer depth from the center to both ends, and
The depth of the horizontal side of the second core plate on the tape sliding surface side is made shorter from the center to both ends, resulting in a more uniform distribution of magnetic field strength, which significantly improves the amount of unerased material at both ends. This makes it possible to reduce the distortion rate to an extremely low level, which has a great advantage.

[Brief explanation of drawings]

Figure 1 A and B are slope views of the first core plate and second core plate, Figure 2 is a slope view of the same superposition state, Figure 3 A,
B is a perspective view of the first core plate and the second core of the second embodiment; FIG. 4 is a perspective view of the same superposed state; FIG. 5 is a perspective view showing a modification of the winding position of the coil in FIG. 4;
FIG. 6 is a characteristic diagram showing the change in distortion rate between the present invention and the conventional example, and FIG. 7 is a perspective view of the audio erasing head. 1...First core plate, 2...Second core plate, 3...Gap, 4...Coil.

Claims (1)

[Claims] 1 A first core plate with a frame-like side surface and a second core plate with a substantially T-shaped side surface.
A core plate is arranged such that the vertical side of the second core plate is exposed and interposed between the opposite sides of the first core plate, and the horizontal side of the second core plate is located between the opposite sides of the first core plate. The core plates are overlapped alternately so as to form a gap between each core plate by overlapping the horizontal sides that close the
The horizontal side of the first core plate on the side that comes into sliding contact with the tape is formed so that the depth of the core plate becomes longer as it goes from the center in the tape width direction to both ends, and the horizontal side of the second core plate on the side that comes into sliding contact with the tape The depth of the core plate is shortened as the horizontal side goes from the center to both ends in the tape width direction, and the superposed first or second
A DC magnetic field reversal type erasing head characterized in that coils are wound symmetrically around core plates so that the core has two magnetic paths.