JP4203924B2 - Magnetic head - Google Patents

Description

  The present invention relates to a magnetic head, and more particularly to a magnetic head capable of reducing a spacing loss when reading magnetic information from a magnetic recording medium, simplifying an output waveform, and easily performing magnetic information detection processing based on the output waveform. About.

  Magnetic heads are widely used for reading magnetic information recorded on magnetic stripes of magnetic recording media. A magnetic head 1 illustrated in FIG. 6 is used for authenticating a bill as a magnetic recording medium, and is disposed at a yoke 3 having a gap g formed at a front end portion and a rear end portion of the yoke 3. The magnet 4 and the coils 5 and 5 ′ wound around the yoke 3 are accommodated in the case 2, and the case 2 is filled with resin. The magnet 4 is disposed in such a direction that its magnetic axis is along the outer surface of the front end of the yoke 3 (reading surface on which the bill 30 can be slidably contacted, that is, the inspection surface) 3a. When the bill 30 moves in the direction of the arrow on the inspection surface 3a of the magnetic head 1 and the magnetic stripe 31 provided as magnetic information on the bill 30 crosses the gap g, the leakage flux in the gap g and thus the flux passing through the yoke 3 is increased. The authenticity of the banknote 30 is identified based on the induced current generated in the coils 5, 5 ′ along with the magnetic flux change. Here, the change (detection sensitivity) of the leakage magnetic flux when the magnetic stripe 31 passes in the vicinity of the gap g increases as the width of the gap g decreases. However, the leakage magnetic flux reaches the inspection surface 3a as the gap width decreases. The distance decreases and the spacing loss increases. Therefore, in the banknote identification device, the banknote 30 is pressed against the inspection surface 3a by a roller or a pad so as to reduce the distance between the inspection surface and the banknote and hence the spacing loss. Problem arises.

In order to solve this problem, the present applicant, as shown in FIG. 7, the yoke 13 around which the coils 15 and 15 ′ are wound, and the direction in which the magnetic axis crosses the inspection surface 13 a in the gap of the yoke 13. Proposed a magnetic head 11 including a magnet 14 arranged in such a direction as to extend in the direction (see Patent Document 1). The magnetic head 11 has a magnet 14 disposed so that the magnetic axis extends in a direction crossing the inspection surface 13a, and increases the reach of the magnetic fluxes Φ1 and Φ2 (see FIGS. 8 to 11). The pacing loss is reduced.
JP 2002-312909 A

  For reading magnetic information from the magnetic recording medium, the magnetic head 11 shown in FIG. 7 is used together with a magnetic information detection circuit shown in FIG. 13, for example. The magnetic information recorded on the magnetic recording medium 30 such as a banknote corresponds to the magnetization direction of the magnetic material constituting the magnetic stripe 31, and the magnetic recording medium 30 is moved along the reading surface (inspection surface) 13 a of the magnetic head 11. The output voltage (corresponding to the induced current generated in the coils 15 and 15 ′) output from the magnetic head 11 when sliding, and the output of the differential amplifier 32 ′ in FIG. 13 peaks at the position where the magnetization direction is reversed. Take. The peak detection circuit 33 'connected to the differential amplifier 32' outputs a peak pulse signal when the amplifier output takes a peak. Then, magnetic information is detected based on the peak pulse signal output from the peak detection circuit 33 '.

  The magnet 14 of the magnetic head 11 in FIG. 7 is disposed vertically in the gap at the tip of the yoke, and the magnetic flux from the N pole to the S pole of the magnet 14 is on the entry side as viewed in the moving direction of the magnetic recording medium 30. It is comprised from magnetic flux (PHI) 1 and magnetic flux (PHI) 2 by the side of separation (refer FIGS. 8-11). As shown in FIG. 8, when the magnetic recording medium 30 enters the magnetic head 11 along the reading surface 13a of the yoke 13 and approaches the magnetic flux [Phi] 1, the magnetic flux [Phi] 1 passing through the approaching yoke changes in the increasing direction and the separation side. The magnetic flux Φ2 passing through the yoke changes in a decreasing direction to generate induced currents flowing in the coils 15 and 15 ′, and voltage is applied from the coils 15 and 15 ′ to the negative input terminal and the positive input terminal of the differential amplifier 32 ′. In this case, the output of the differential amplifier 32 'becomes negative as shown in FIG. Next, as shown in FIG. 9, when the magnetic recording medium 30 approaches the magnetic flux Φ2, the magnetic recording medium 30 becomes magnetic flux Φ1 due to a change in the decreasing direction of the magnetic flux Φ1 passing through the yoke 13 and a change in the increasing direction of the magnetic flux Φ2. An induced current in the direction opposite to the induced current generated when the voltage approaches is generated in the coils 15 and 15 ', and the amplifier output becomes positive. Also, as shown in FIG. 10, when the magnetic recording medium 30 exits the magnetic flux Φ1, induced current is generated in the coils 15 and 15 ′ due to the change in the magnetic flux Φ1 passing through the yoke 13 in the decreasing direction and the change in the increasing direction of the magnetic flux Φ2. Occurs and the amplifier output becomes positive. Then, as shown in FIG. 11, when the magnetic recording medium 30 passes through the magnetic flux Φ2, an induced current is generated in the coils 15, 15 ′ due to a change in the magnetic flux Φ1 passing through the yoke 13 in the increasing direction and a change in the decreasing direction of the magnetic flux Φ2. Occurs and the output of the differential amplifier 32 'becomes negative.

As described above, the magnetic head 11 in FIG. 7 outputs two peak voltages, positive and negative, for each reversal position of the magnetization direction of the magnetic material in the magnetic stripe 31, and each magnetization direction for detecting magnetic information. The inversion position is determined based on two peak pulse signals (amplifier outputs) corresponding to two peak voltages, as illustrated in FIG.
An object of the present invention is to provide a magnetic head that can reduce the spacing loss when reading magnetic information from a magnetic recording medium, and that can simplify the output waveform and perform the magnetic information detection process more easily. .

According to a first aspect of the present invention, there is provided a magnetic head comprising: a yoke; a coil wound around the yoke; and a magnet disposed near the tip of the yoke so that the magnetic axis extends along the reading surface. It is characterized by providing.
The magnetic head according to the present invention forms a magnetic flux by arranging a magnet near the front end of the yoke, so that a magnetic flux leaked in the gap at the front end of the yoke is generated by a magnet arranged at the rear end of the yoke. The reach of the magnetic flux is increased and the spacing loss is reduced. For this reason, reading of magnetic information from the magnetic recording medium is performed with high accuracy without pressing the magnetic recording medium against the reading surface typically formed by the tip of the yoke. Further, in the magnetic head of the present invention, since the magnet is arranged so that the magnetic axis extends along the reading surface, compared with the conventional magnetic head having the magnetic axis extending in the direction crossing the reading surface. The output waveform of the magnetic head generated along with the relative movement between the magnetic head and the magnetic recording medium is simplified, and the magnetic information detection process is simplified.

  That is, as shown in FIG. 3, when the magnetic recording medium 30 approaches the magnetic flux Φ of the magnetic head 21, the magnetic flux Φ changes in the increasing direction on the magnetic recording medium 30 side, and the magnetic flux Φ passing through the yokes 23 and 23 ′ decreases. Since the direction changes, an induced current is generated in the coils 25 and 25 '. In this example, the generation of the induced current reduces the output voltage of the magnetic head 21 and makes the output of the amplifier 32 shown in FIG. 2 negative. Thereafter, as shown in FIG. 4, when the magnetic recording medium 30 moves away from the magnetic flux Φ of the magnetic head 21, the magnetic flux Φ changes in the decreasing direction on the magnetic recording medium 30 side and passes through the yokes 23, 23 ′. Changes in an increasing direction. For this reason, an induced current in the opposite direction to the induced current generated when the magnetic recording medium 30 approaches the magnetic flux Φ is generated in the coils 25 and 25 ′, the output voltage of the magnetic head 21 is increased, and the output of the amplifier 32 is increased. Become positive. That is, as illustrated in FIG. 5, one peak output is generated for each inversion position of the magnetization direction of the magnetic material in the magnetic stripe 31.

  The output waveform of the magnetic head of the present invention is simple, and the magnetic information detection process based on the magnetic head output is simplified accordingly.

  In the magnetic head of the present invention, a magnet is arranged at the tip of the yoke to form a magnetic flux, so that the reach of the magnetic flux is increased and the spacing loss can be reduced. In addition, since the magnetic head of the present invention is arranged so that the magnetic axis extends along the reading surface, the output waveform of the magnetic head can be simplified, and magnetic information detection processing based on the output waveform can be performed. It can be made easy.

Hereinafter, a magnetic head according to an embodiment of the present invention will be described with reference to FIG.
The magnetic head 21 of this embodiment is used as an identification sensor mounted on, for example, a banknote identification device (not shown), and generates an output representing magnetic information included in the magnetic stripe 31 of the banknote 30 as a magnetic recording medium. It has become.
The magnetic head 21 includes a yoke 23, a magnet 24, detection coils 25 and 25 ′, and support bases 26 and 29 that are housed in a case 22 together with inner ends of connection terminals 27 and 27 ′ and molded with a resin 28. It is. The outer end portions of the connection terminals 27 and 27 ′ are connected to an identification circuit portion (not shown) of the banknote recognition device via, for example, a magnetic information detection circuit illustrated in FIG.

The yoke 23 is fixed to the upper surface of the support base 26 and extends in the width direction of the magnetic head 23c, leg portions 23b, 23b 'extending from both ends of the center portion 23c in the magnetic head height direction, both leg portions 23b, The front end portions 23a and 23a 'extend in the height direction of the magnetic head from the upper end of 23b', respectively, and are formed in a U-shape as viewed from the front.
A gap into which the rod-shaped magnet 24 is fitted is formed between the tip portions 23 a and 23 a ′ of the yoke 23. The gap forming surfaces (inner side surfaces) of the yoke tip portions 23a and 23a ′ are formed as stepped surfaces, and the outer surfaces of the yoke tip portions 23a and 23a ′ are used for reading magnetic information from the magnetic stripe 31 of the banknote 30. For this purpose, a reading surface (inspection surface) 23d is formed.

  The magnet 24 is arranged in the gap between the yoke tip portions 23a and 23a ′ so that its magnetic axis (line connecting the N pole and the S pole) extends along the inspection surface 23d. It is supported by a support base 29. The upper surface of the magnet 24 slightly protrudes from the inspection surface 23 d and the upper surface of the case 22. Further, both end surfaces of the magnet 24 are in contact with the stepped surfaces of the yoke tip portions 23a and 23a '. That is, the length of the magnet 24 is larger than the separation distance between the opposing surfaces of the yoke tip portions 23a and 23a ′, and the magnet 24 is lengthened without increasing the width direction dimension of the magnetic head 21, thereby generating a strong magnetic force. Trying to get.

  The yoke 23 of the magnetic head 21 has tip portions 23a and 23a 'extending from the leg portions 23b and 23b' in the height direction of the magnetic head, and the yoke tip portions 23a and 23a 'and the yoke leg portions. 23 b and 23 b ′ are close to the magnet 24. For this reason, the magnetic flux change in the yoke accompanying the passage of the magnetic stripe 31 is increased, and the detection sensitivity is increased. Further, since the shape of the yoke 23 is extremely simple, the assembling property can be improved and the cost can be reduced.

Coils 25 and 25 ′ are wound around the leg portions 23b and 23b ′ of the yoke 23, respectively. The coils 25 and 25 ′ are connected in series with each other. 'And a magnetic information detection circuit are connected to the recognition circuit unit of the bill recognition device.
In the example shown in FIG. 2, one end of the coil series connection body including the coils 25 and 25 ′ is connected to the input end of the amplifier 32 of the magnetic information detection circuit, and the other end of the coil series connection body is grounded. The magnetic information detection circuit of FIG. 2 amplifies the output of the magnetic head 21 (the induced voltage in the coils 25 and 25 ′) that changes with the relative movement of the magnetic head 21 and the bill 30 by the amplifier 32. The peak output is detected by the peak detection circuit 33, and the magnetic information recorded on the magnetic stripe 31 of the banknote 30 is detected based on the detected peak output. The detected magnetic information is used for authenticating the bill.

Hereinafter, the operation of the magnetic head 21 configured as described above will be described.
The magnet 24 is arranged in such a direction that its magnetic axis extends in a direction crossing the inspection surface 23d, and as shown in FIGS. 3 and 4, the magnetic flux Φ from the N pole to the S pole of the magnet 24 Is generated around the magnet 24. Compared to the leakage magnetic flux in the conventional magnetic head 1 (FIG. 6), the reach distance of the magnetic flux Φ of the magnetic head 21 is very large, so the allowable maximum distance of the bill 30 from the inspection surface 23d becomes very large. For this reason, under the condition that the spacing loss is the same, the distance between the bill 30 and the inspection surface 23d can be increased, and the bill can be identified without pressing the bill 30 against the inspection surface 23d. Therefore, in the inspection using the magnetic head 21, the bill 30 is moved along the inspection surface 23d in a state where the bill 30 is lightly contacted with the inspection surface 23d of the magnetic head 21 or in a non-contact state with the inspection surface 23d. Is preferred.

When the magnetic stripe 31 of the banknote 30 passes through the magnet 24, most of the magnetic flux Φ that is uniformly distributed outside the magnetic head 21 passes through the magnetic stripe 31, so that the magnetic flux passing through the yoke 23 changes greatly. A large electromotive voltage is generated in the coils 25 and 25 ′ along with the change in the magnetic flux.
That is, as shown in FIG. 3, when the bill 30 as the magnetic recording medium approaches the magnetic flux Φ of the magnetic head 21, the magnetic flux Φ changes in the increasing direction on the bill 30 side, and the magnetic flux Φ passing through the yokes 23 and 23 ′ is changed. Since it changes in the decreasing direction, an induced voltage is generated in the coils 25 and 25 ', the output voltage of the magnetic head 21 decreases, for example, and the output of the amplifier 32 shown in FIG. 2 becomes negative. Thereafter, as shown in FIG. 4, when the bill 30 moves away from the magnetic flux Φ of the magnetic head 21, the magnetic flux Φ changes in the decreasing direction on the bill 30 side, and the magnetic flux Φ passing through the yokes 23, 23 ′ increases. Therefore, an induced voltage in the opposite direction to that when the banknote 30 approaches the magnetic flux Φ is generated in the coils 25 and 25 ′, the output voltage of the magnetic head 21 increases, and the output of the amplifier 32 becomes positive. That is, as shown in FIG. 5, one peak output is generated for each reversal position of the magnetization direction of the magnetic material in the magnetic stripe 31.

In the case of the magnetic head 11 of FIG. 7, it is necessary to detect the magnetic information by determining the magnetization direction reversal position based on the two peak outputs. In this respect, the magnetic head 21 of this embodiment has each magnetization direction reversal. Since one peak voltage is generated at the position and the output waveform is simple, magnetic information detection processing based on the magnetic head output is simplified accordingly.
As described above, according to the magnetic head 21 of the present embodiment, since the inspection can be performed with high accuracy without pressing the banknote 30 against the inspection surface 23d, the wear of the inspection surface 23d can be greatly reduced, and the magnetic head 21 can be reduced. Since the output waveform is simple, the magnetic information detection process for banknote identification based on the output waveform can be easily performed.

The magnetic head of the present invention is not limited to the above-described embodiment, and can be variously modified.
For example, in the embodiment, a magnetic head that functions as a banknote identification sensor that detects a magnetic stripe provided on a banknote has been described, but the present invention includes other magnetic ink detection sensors, MICR (Magnetic Ink Character Reader) reading sensors, It can be applied to proximity sensors, magnetic identification sensors, and the like.

  In the above embodiment, in order to reduce the width dimension of the magnetic head and improve the detection sensitivity, the coils 25 and 25 'are wound around the yoke legs 23b and 23b', and the magnet legs 23b and 23b 'are magnetized. Both ends of the magnet 24 are fitted to the stepped gap forming surfaces of the yoke tip portions 23a and 23a ′ extending in the head height direction, but the gap forming surface of the yoke tip portion is formed on the stepped surface. This is not essential, and as shown in FIG. 14, the end face of the magnet 24 may simply be brought into contact with the gap forming face formed by the straight inner side faces of the yoke tip portions 23a and 23a ′. Further, an air gap or a non-magnetic material may be interposed between the gap forming surface and the magnet end surface.

Further, the yoke tip portions 23a and 23a ′ are not extended from the yoke leg portions 23b and 23b ′ in the magnetic head height direction, and the yoke tip portions 23a and 23a are the same as the conventional ones shown in FIGS. 'May be extended in the magnetic head width direction. Further, instead of the yoke leg coils 25 and 25 ', one coil may be wound around the yoke central portion 23c.
Further, it is not essential to slightly protrude the upper surface of the magnet 24 from the inspection surface 23d, and the magnet 24 may be disposed so that the upper surface of the magnet is flush with the inspection surface 23d as shown in FIG. Alternatively, as shown in FIG. 15, the magnet 24 may be arranged so that the entire magnet 24 is disposed outside the gap between the yoke tip portions 23a and 23a ′. In this case, the reading surface (inspection surface) of the magnetic head can be formed by the yoke tip surface (inner surface of the magnet 24) or the outer surface of the magnet 24.

  The length of the magnet 24 may be the same or substantially the same as the gap width between the yoke tip portions 23a and 23a ′ as shown in FIGS. 14 and 15, and may be shorter than the gap width as shown in FIG. Further, as shown in FIG. 17, it may be longer than the gap width. Even when the magnet 24 is disposed in the gap between the yoke tip portions 23a and 23a ', the length of the magnet 24 can be appropriately set. Then, by changing the length of the magnet 24 in this way, the reading resolution of the magnetic stripe by the magnetic head can be adjusted. That is, when a fine resolution is desired, the length of the magnet 24 is shortened, and when a large resolution is desired, the length of the magnet 24 is increased.

  The magnetic information detection circuit shown in FIG. 2 is an example, and the circuit configuration is not limited to that shown in FIG. Other points can be variously modified.

1 is a cross-sectional view of a magnetic head according to an embodiment of the present invention. FIG. 2 is a schematic block diagram showing an example of a magnetic information detection circuit that detects magnetic information from the output of the magnetic head shown in FIG. 1. FIG. 2 is a schematic partial view showing a state in which a bill as a magnetic recording medium moves in a direction approaching a magnetic flux Φ formed by the magnetic head of FIG. 1. FIG. 2 is a schematic partial view showing a state in which a bill moves in a direction away from a magnetic flux Φ formed by the magnetic head of FIG. 1. It is a figure which shows the change of the output of the amplifier shown in FIG. 2 with the movement of the banknote in which the magnetic stripe was formed. It is sectional drawing of a conventionally well-known magnetic head. FIG. 7 is a cross-sectional view of a magnetic head created to reduce the spacing loss in the magnetic head shown in FIG. 6. FIG. 8 is a schematic partial view showing a state when a bill approaches the magnetic flux Φ <b> 1 on the entry side formed by the magnetic head of FIG. 7. FIG. 8 is a schematic partial view showing a state when a bill approaches the magnetic flux Φ <b> 2 on the separation side formed by the magnetic head of FIG. 7. It is a schematic fragmentary figure which shows a mode when a banknote detaches | leaves from magnetic flux (PHI) 1. It is a schematic fragmentary figure which shows a mode when a banknote detaches | leaves from magnetic flux (PHI) 2. It is a figure which shows the change of the amplifier output accompanying the movement of the banknote in which the magnetic stripe was formed. It is a schematic block diagram which shows an example of the magnetic information detection circuit used with the magnetic head of FIG. FIG. 6 is a schematic partial view of a magnetic head according to a modification of the present invention in which an end surface of a magnet is brought into contact with an inner side surface of a yoke tip. FIG. 10 is a schematic partial view of a magnetic head according to another modified example in which the entire magnet is arranged outside the gap between the yoke tip portions. FIG. 10 is a schematic partial view of a magnetic head according to another modification in which the length of the magnet is shorter than the gap width. FIG. 10 is a schematic partial view of a magnetic head according to still another modification in which the length of the magnet is longer than the gap width.

Explanation of symbols

21 Magnetic head 23 Yoke 23a, 23a 'Yoke tip 23b, 23b' Yoke leg 23c Yoke center 23d Reading surface (inspection surface)
24 magnet 25, 25 'detection coil 30 banknote (magnetic recording medium)
31 Magnetic stripe

Claims (3)

York,
A coil wound around the yoke;
And a magnet disposed near the tip of the yoke in such a direction that the magnetic axis extends along the reading surface.   The yoke has a central portion extending in the magnetic head width direction, leg portions extending from both ends of the central portion in the magnetic head height direction, and tip portions extending from the upper ends of the both leg portions, The magnetic head according to claim 1, wherein a tip portion constitutes the reading surface.   The magnetic head according to claim 2, wherein the magnet is disposed so that the magnet is disposed between or just above the tip portions of the yoke.

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