JPH0469801A - External magnetic field applying device - Google Patents

Abstract

PURPOSE:To efficiently secure a uniform magnetic field by costituting a magnetic pole of a winding coil insertion part and a magnetic field applying part whose length corresponds to the recording and reproducing face of a recording medium and providing a hole or a notch correspondingly to the center of this magnetic field applying part. CONSTITUTION:A magnetic pole 1 arranged correspondingly to a recording medium consists of the winding coil insertion part and the magnetic field applying part which has the length corresponding to the recording and reproducing face of the recording medium, and a notch 7 is formed in the center of this magnetic field applying part 1A of the magnetic pole 1. The magnetic pole 1 is provided with a taper part 1B to more effectively uniformize the intensity of the magnetic field. When the notch having 2mm width is provided in the center and tapers having 0.3/4 gradient are formed in both ends of the magnetic field 1, the difference of the intensity of the magnetic fiels is suppressed to 8 to 12 gausses in actual measurement. Thus, the intensity of the perpendicular magnetic field is uniformized to perform stable recording without increasing the cost, and the magnetic field inversion time is shortened to increase the recording speed because the inductance of this magnetic circuit is reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an information recording/reproducing device that records, reproduces, or erases information on an information recording medium using light and magnetism, and the magnetism is controlled externally. The present invention relates to an external magnetic field applying device that applies an external magnetic field.

(Conventional technology) Conventional 5], Historical information = Self-recording and reproducing devices are used because it is necessary to apply a bias magnetic field whose polarity can be reversed in order to repeatedly record and erase information. There are two types of external magnetic field applying devices: one that mechanically reverses a permanent magnet, and the other that uses an electromagnet to switch the magnetic field generation current. Because of this, it is rarely adopted,
Rather, the latter is used, but in this case the strength of the magnetic field in the radial direction of the recording medium (in the longitudinal direction of the magnetic poles)
Looking at the distribution of , as shown in Figure 5, there is a distribution of several 1. There is a peak at the center, and the gap between the recording surface of the disk-shaped recording medium and the magnetic pole is 1. In this case, the difference from the center is as much as 40 Gauss, and stable recording cannot be expected when considering the surface runout of the recording medium and the mechanical installation error of the external magnetic field applying device.

Therefore, it has been proposed to form tabers at both ends of the electromagnet. That is, as shown in FIG.
The length is approximately IO,, from both ends of, approximately 0.3. , a magnetic field strength distribution as shown in FIG. 6 is obtained. Here, the tube 2 is fitted into the wire-wound coil insertion portion IA of the magnetic pole 1, and the air-core coil 5 is attached to the outside thereof. In this case, the tube 2 has a wall thickness of 0.2. It is preferably made of a cylindrical body of a fluorine-based resin of about 100 mL, heated with a heater or the like to soften it, and then tightly attached to the magnetic pole l. The coil 5 is inserted into a yoke 6 having a C-shaped cross section, and is located between its upper side 6A and its bottom 6B, with heat dissipation sheets 4 made of insulating material above and below. The heat dissipation plate 3 is attached to the upper side 6A with an adhesive, and is provided with a beat 3A for preventing removal, and the beat 3A is in elastic contact with the upper side 6A. has been done. Then, pass the caulking foot LC of the magnetic pole through a slit (not shown) provided in the yoke 6,
It is caulked on the back side. In this case, it is preferable to use a heat dissipation sheet made from silicone rubber with a fine ceramic compound added, which has a thermal conductivity five times that of conventional silicone rubber.

(Problem to be Solved by the Invention) However, in the conventional example described above, the variation in the magnetic field strength at the center of the magnetic pole l is about 20 Gauss, which is an improvement compared to the above-mentioned example. Due to the miniaturization and thinning of devices, when the gap between the magnetic pole l and the recording surface of the recording medium is 1 m+++ or less, the margin decreases due to surface runout of the recording medium and mechanical installation errors of the external magnetic field applying device. is a concern. In addition, when the radius of the recording medium becomes larger and the length of the magnetic field application part by the magnetic pole 1 becomes longer, in addition to the difference in magnetic field strength between the central part and both ends of the magnetic pole 1, the difference between the tapered part IB and the magnetic pole A drop in the magnetic field strength appears between the central part of 1 and the objective cannot be achieved sufficiently.

(Objective of the Invention) The present invention has been made based on the above-mentioned circumstances, and provides an external magnetic field applying device that can ensure a sufficiently efficient and uniform magnetic field in an effective vertical magnetic field generation region. This is what I am trying to do.

(Means for Solving the Problems) Therefore, the present invention provides an information recording and reproducing apparatus that records, reproduces, or erases information on an information recording medium using light and magnetism, and in which a perpendicular magnetic field to the recording medium is applied to the recording medium from an external source. In an external magnetic field applying device that applies control, a magnetic pole arranged corresponding to a recording medium is connected to an insertion portion of a wire-wound coil and a magnetic field applying portion having a length corresponding to the recording/reproducing surface of the recording medium. The magnetic pole is provided with a hole or a notch corresponding to the center of the magnetic field application section.

(Function) By providing a hole or notch located in the center of the magnetic field application part of the magnetic pole within the range of the effective vertical magnetic field covered by the magnetic pole, the magnetic field strength can be made uniform, without increasing costs. Stable recording and erasing can be performed, the inductance of the magnetic circuit can be reduced, the magnetic field reversal time can be shortened, and the speed of the information recording and reproducing apparatus can be increased.

(Example) An example of the present invention will be specifically described below with reference to the drawings. In the figure, descriptions of members similar to those used in the magnetic head shown in FIG. 3 will be omitted. In particular, in this embodiment, a notch 7 is formed in the magnetic pole at the center of the magnetic field application section IA, as shown in FIGS. 1 and 2. As a result, the following experiment resulted in the distribution of magnetic field strength as shown in Figure 7.

That is, the above-mentioned external magnetic field application device is attached to a jig that can be moved in parallel on a stage in one direction, and a gap corresponding to the gap between the recording surface of the recording medium and the above-mentioned magnetic pole is placed above the magnetic pole l. , set the Gauss meta probe. In this state, stage 1. When the magnetic field strength at each part of the magnetic pole is measured, the magnetic field strength at each part is made uniform as shown in FIG. In the above embodiment, the magnetic pole I is provided with a tapered portion IB, which effectively equalizes the magnetic field strength. "7 bars with a gradient of 0.3/M are installed at both ends of the J-ta 2 magnetic pole 1 in the notch with a width of 2 □".
1, the magnetic field strength i is suppressed to ε(to 12 Gauss).

Another embodiment of the invention is shown in FIG.
C' is a scale at the center of the magnetic field application part] 7, and the magnetic pole l
Hole 8 of the round liver is drilled)
It is possible to achieve the same uniformity of magnetic field strength as with the above cutout. 14. As is well known, a punching process such as fine punching is required, and considering the shape of the punch and the deformation after machining, the above-mentioned circular shape is preferable. There is a new shape-C.

(Effects of the Invention) The present invention is as described in detail below, and the magnetic poles arranged corresponding to the recording medium are connected to the insertion portion of the wire-wound coil and
-! 1.1 Since the recording magnetic pole is provided with a hole or notch corresponding to the center of the magnetic field application section of the recording medium, The magnetic field application part is perpendicular to that 6! i W +7) Strong uniformity
I can pay the tithe. Now, without giving up the strike, the inductance of this magnetic circuit becomes smaller. The magnetic field reversal time can be shortened, and high-speed recording can be achieved.3

[Brief explanation of drawings]

Figure 1 is an iE blood diagram of a small "4" magnetic core which is an embodiment of the present invention. Figure 2 is an exploded perspective view of 1111. Figure 3 is an exploded perspective view of a conventional example. Figure 4 is an exploded perspective view of the present invention. 15 to 7 are graphs showing the distribution of the magnetic field strength at the magnetic field application part of the magnetic pole. l. 1 Δ. l B. 2 , 3. 4. 5. 7. Magnetic pole 1. Magnetic field application section Taper section Tube Heat sink Heat dissipation sheet Coil 641. Core l;/7r) Notch 801. Hole Fig. 1 Fig. 2 fjlJ Fig.

Claims (1)

[Claims] An information recording/reproducing device that records, reproduces, or erases information on an information recording medium using light and magnetism, and an external magnetic field applying device that applies a perpendicular magnetic field to the recording medium under external control. The correspondingly arranged magnetic poles consist of an insertion part of the wire-wound coil and a magnetic field application part having a length corresponding to the recording/reproducing surface of the recording medium, and the magnetic poles have a magnetic field application part having a length corresponding to the recording/reproducing surface of the recording medium. An external magnetic field applying device characterized in that a hole or a notch is provided in the external magnetic field applying device.