JP2005259242A - Head drum device and magnetic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a head drum device which can prevent the electrostatic destruction of an MR head. <P>SOLUTION: The head drum device 3 is provided with; a rotary drum 10; a fixed drum 11 which is kept at ground electrical potential; and a reproducing head 15 which reads a signal from a magnetic tape by means of a head element comprising an MR element (magneto-resistive effect type). The rotary drum 10 is turnably supported by an integrally fixed conductive shaft 13 and a conductive bearing 14 on the fixed drum 11 side. Consequently, the rotary drum 10 is at the ground electrical potential through the fixed drum 11, and the electrostatic destruction of the MR element can stably be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a helical scan type head drum device for writing and reading signals to and from a magnetic tape, and a magnetic recording / reproducing device having the same, and more particularly, a head using an MR head as a magnetic head for signal reading. The present invention relates to a drum apparatus and a magnetic recording / reproducing apparatus including the drum apparatus.

  2. Description of the Related Art In recent years, in a magnetic recording / reproducing apparatus that records and reproduces signals using a magnetic tape, further improvement in recording density is desired as the amount of information handled increases. By adopting MR (Magneto Resistive) heads and GMR (Giant Magneto Resistive) heads, which have higher sensitivity, instead of conventional inductive heads as magnetic heads for reading signals on magnetic tape, The recording density of the tape can be improved.

  The MR head is a magnetic head that reads a signal recorded on a magnetic recording medium such as a magnetic tape by utilizing the magnetoresistive effect of the MR element, and has a high signal detection sensitivity and can obtain a large reproduction output. Therefore, a magnetic recording / reproducing apparatus equipped with an MR head can easily reduce the recording track width on the magnetic tape and increase the recording density in the linear direction, thereby enabling high-density data recording and reproduction. Become.

  Incidentally, the MR head has a property that it is weak against static electricity and heat as compared with a conventional inductive head. That is, the MR element inside the MR head is formed by a thin film having a nanometer size, but it is known that an electrostatic breakdown phenomenon easily occurs in this element portion and the thin film is destroyed. Further, the MR head requires a sense current for reading a signal, and for this purpose, power is supplied from an external circuit to the rotary head. Therefore, stray charges are accumulated in the rotary head, and the electrostatic breakdown of the MR head is likely to occur.

  In the process leading to the electrostatic breakdown, when the MR element receives a certain amount of electrostatic energy, first, a part of the thin film is damaged to change the magnetic characteristics, and output degradation of the MR head occurs. Thereafter, the stress of electrostatic energy continues to be accumulated in the MR element, whereby the entire thin film is destroyed and the MR head does not output at all.

  With respect to such electrostatic breakdown, conventionally, in a helical scan type magnetic recording / reproducing apparatus using a magnetic tape as a recording medium, a rotating shaft is grounded by bringing a conductive shaft grounding member into contact with the shaft of the rotating drum. Thus, the increase in the surface potential of the magnetic head is suppressed to prevent it (for example, see Patent Document 1).

As a conventional technique for releasing static electricity from a rotating body, a rolling bearing provided with conductive grease has been proposed (see, for example, Patent Document 2).
JP 2003-22507 (paragraph numbers [0023] to [0031], FIG. 2) JP 2002-364653 A (paragraph numbers [0016] to [0019], FIG. 1)

  However, since the conventional shaft ground rotates while being in mechanical contact with the rotating shaft of the rotary head, the contact portion of the shaft ground is worn away by friction due to long-term use, and the contact state changes. . When the contact state changes, the resistance value between the rotating shaft and the ground changes, so that the potential of the rotating drum becomes unstable.

  As a result, in the conventional head drum device, even with a magnetic head that has no problem immediately after its start of use, the contact surface becomes rusted with the passage of time, and the surface potential of the rotating drum rises instantaneously. Therefore, there has been a problem that electrostatic breakdown cannot be effectively prevented.

The present invention has been made in view of such problems, and an object of the present invention is to provide a head drum device capable of more stably preventing the occurrence of electrostatic breakdown of an MR head.
Another object of the present invention is to more stably prevent the occurrence of electrostatic breakdown of the MR head in a magnetic recording / reproducing apparatus including the MR head.

  In the present invention, in order to solve the above problems, in a head drum device for writing and reading signals on a magnetic tape helically wound on the outer peripheral surface, it is fixed integrally with a fixed drum held at a ground potential. A rotating drum rotatably supported with respect to the fixed drum by a conductive shaft, and a magnetoresistive element as a head element for reading a signal from the magnetic tape, the signal reading surface being the rotating drum A reading head portion fixed to the rotating drum so as to be in sliding contact with the magnetic tape on an outer peripheral surface of the rotating drum, and the conductive shaft of the rotating drum so that the rotating drum is at a ground potential through the fixed drum. There is provided a head drum device having a conductive bearing portion that is supported on the fixed drum side.

  In such a head drum device, the rotating drum and the fixed drum are electrically connected via the conductive shaft and the conductive bearing portion, and the fixed drum is held at the ground potential. Is maintained at the ground potential for a long time even when it rotates. Accordingly, it is possible to more reliably prevent the occurrence of electrostatic breakdown of the MR head.

  Further, according to the present invention, in a magnetic recording / reproducing apparatus that records and reproduces signals using a magnetic tape, a fixed drum held at a ground potential and a conductive shaft fixed integrally with the fixed drum rotate around the fixed drum. A rotary drum that is movably supported, and a magnetoresistive element as a head element for reading a signal from the magnetic tape, the signal reading surface being in sliding contact with the magnetic tape at the outer peripheral surface of the rotary drum A reading head portion fixed to the rotating drum; and a conductive bearing portion that supports the conductive shaft of the rotating drum on the fixed drum side so that the rotating drum is at ground potential via the fixed drum. A magnetic recording / reproducing apparatus is provided.

  In such a magnetic recording / reproducing device, in the head drum device, the rotating drum and the fixed drum are electrically connected via the conductive shaft and the conductive bearing portion, and the fixed drum is held at the ground potential. Therefore, the rotating drum is held at the ground potential for a long time even when it rotates. Accordingly, it is possible to more reliably prevent the occurrence of electrostatic breakdown of the MR head.

  According to the present invention, since the rotating drum to which the MR head is fixed is held at the ground potential for a longer time than in the case where the conventional shaft ground is used, the electrostatic breakdown of the MR head is prevented. Occurrence can be prevented more stably.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an outline of a magnetic tape traveling system in a magnetic recording / reproducing apparatus including a head drum apparatus to which the present invention is applied.

  A magnetic recording / reproducing apparatus 1 shown in FIG. 2 is an apparatus for recording and reproducing signals using a magnetic tape 2 as a recording medium. For example, a data storage device of a computer device, a recording device of a video signal or an audio signal, etc. Used as As shown in FIG. 2, a magnetic recording / reproducing apparatus 1 includes a head drum device 3 that writes and reads signals to and from a magnetic tape 2, a capstan 4 that moves the magnetic tape 2 at a predetermined speed, and a pinch roller 5. The plurality of tape guides (TG) 6a, 6b, 6c, 6d and 6e for assisting the traveling of the magnetic tape 2 are configured. The cassette case 7 inserted into the magnetic recording / reproducing apparatus 1 is made of a low-resistance synthetic resin material and includes a take-up reel 7a and a supply reel 7b for the magnetic tape 2.

  The head drum device 3 has a cylindrical shape having a smooth outer peripheral surface as a whole, and as shown in FIG. 1 to be described later, a rotating drum 10 having a conductive shaft 13 and a fixed drum 11 that rotatably supports the rotating drum 10. It is divided into and. Reproducing and recording magnetic heads are provided on the outer peripheral surface of the head drum device 3, and each magnetic head rotates on the outer peripheral surface as the rotating drum 10 rotates. .

  In the magnetic recording / reproducing apparatus 1, when recording and reproduction of the magnetic tape 2 are performed, the cassette case 7 is inserted from the lower side to the upper side in FIG. Then, as the rotating drum of the head drum device 3 rotates, the pinch roller 5 and the TGs 6a to 6e move upward in the figure to perform the loading operation, and the magnetic tape 2 is a part of the outer peripheral surface of the head drum device 3. Wrapped around. At the same time, the magnetic tape 2 travels as the capstan 4 and the take-up reel 7a rotate, and the magnetic head on the rotary drum scans the surface of the magnetic tape 2 to start writing and reading signals.

FIG. 1 is a longitudinal sectional view showing a head drum device to which the present invention is applied.
The head drum device 3 has a cylindrical shape having a smooth outer peripheral surface as a whole, and includes an upper rotary drum 10 and a lower fixed drum 11 provided coaxially. A motor 12 for rotating the rotary drum 10 is provided below the fixed drum 11.

  A shaft 13 made of a conductive material is integrally fixed to the central portion of the rotary drum 10, and the shaft 13 and the fixed drum 11 are conductive bearings composed of a ball bearing 14a containing conductive grease. 14 is connected. The motor 12 includes a stator 12 a and a rotor 12 b, the stator 12 a is fixed to the fixed drum 11, and the rotor 12 b is fixed to the shaft 13 integrally. With such a structure, the rotating drum 10 rotates with respect to the fixed drum 11 as the rotor 12 b of the motor 12 rotates.

  The rotating drum 10, the fixed drum 11, and the shaft 13 are all made of a conductive material such as aluminum, and the rotating drum 10 is electrically connected to the fixed drum 11 via the shaft 13 and the bearing 14 as will be described later. Connected. The fixed drum 11 is electrically connected to a chassis (not shown) which is the ground of the magnetic recording / reproducing apparatus 1 and is held at a ground potential.

  Further, the rotary drum 10 is provided with a reproducing head unit 15 so that the reading unit protrudes from the outer peripheral surface. In the reproducing head unit 15, an MR element is used as a head element. Two reproducing head portions 15 are provided on the outer peripheral portion, and these are provided at positions facing the rotary drum 10 at 180 °. The rotary drum 10 is further provided with two recording head portions (not shown) at positions 90 ° apart from the respective reproduction head portions 15 on the rotary drum 10. In addition, for example, four recording head units and four reproducing head units 15 may be provided on the outer periphery.

  Further, a current supply circuit 16 for supplying a sense current to the head element of the reproducing head unit 15 is provided on the upper portion of the rotary drum 10. In addition, a rotary transformer 17 is provided inside the fixed drum 11, and is provided between a recording head unit and a reproducing head unit 15 provided on the rotary drum 10 and a control circuit provided outside the head drum device 3. It is possible to exchange signals.

  For example, a signal to be recorded on the magnetic tape 2 is supplied to the recording head unit via the rotary transformer 17. Further, a sense current for the head element of the reproducing head unit 15 is supplied from an external circuit to the current supply circuit 16 via the rotary transformer 17, and a voltage change in the head element is detected via the rotary transformer 17 in the external circuit. Thus, the recording signal of the magnetic tape 2 can be read.

  Next, the reproducing head device will be described with reference to FIGS. FIG. 3 is a plan view showing the configuration of the reproducing head device, and FIG. 4 is a side view showing the configuration of the reproducing head device. 3 shows a configuration including a mounting portion of the reproducing head unit 15 as viewed from below the head drum device 3 shown in FIG. 1, and FIG. 4 shows a reproducing head device 18 shown in FIG. The tape running surface is shown.

  The reproducing head device 18 has a structure in which an MR element 18c and a pair of shield films 18d and 18e made of a soft magnetic material are disposed between a conductive head substrate 18a and a protective substrate 18b. Insulating films 18f and 18g are formed between the head substrate 18a and the protective substrate 18b and the shield films 18d and 18e, and the MR films are interposed between the shield films 18d and 18e via the insulating films 18h and 18i. The element 18c is formed to form a magnetic head for reproduction. Such a reproducing head device 18 is connected to the terminals 20a and 20b by conducting wires 19a and 19b and the like, and thereby power is supplied to the reproducing head device 18.

  Further, as shown in FIG. 4, the reproducing head device 18 is fixed to a conductive base metal 21 with an adhesive 22, and the base metal 21 is fixed to the rotary drum 10 with a set screw 23 made of a conductor. ing. In FIGS. 3 and 4, the MR element 18c is shown large for easy understanding of the structure, but actually, the MR element 18c is much finer than the head substrate 18a and the protective substrate 18b. .

In the reproducing head device 18, the shield films 18d and 18e constitute a pair of magnetic shield members, and the MR element 18c is disposed in the shield gap between the pair of magnetic shield members. As a result, the frequency characteristics and the resolution are improved. The shield films 18d and 18e are made of, for example, a permalloy plating film, and the insulating films 18f to 18i are made of, for example, Ai ₂ O ₃ , which are formed into a thin film on the head substrate 18a and bonded to the protective substrate 18b. Thus, the reproducing head device 18 is formed. Further, in the reproducing head device 18, the end surface facing outward (downward in FIG. 3) from the outer peripheral surface of the rotary drum 10 is polished, and this end surface is used as the sliding surface of the magnetic tape 2.

Further, as described above, the head substrate 18a and the protective substrate 18b are formed of a conductive material. Specifically, Al ₂ O ₃ —TiC, MnZn ferrite, or the like having an electric resistance value of 10 ¹⁰ Ω or less that is not charged with static electricity is used. Further, the head substrate 18a and the protective substrate 18b are electrically connected to the base metal 21 by, for example, a conductive paste 24 or the like, apart from adhesion by an adhesive 22 such as an epoxy type. As the conductive paste 24, for example, a silver paste is used. The base metal 21 is made of brass, for example, and is fixed to the rotating drum 10 and electrically connected thereto by a conductive metal set screw 23. Furthermore, the rotating drum 10 has conductivity, and is electrically connected to the fixed drum 11 so as to have a ground potential. Therefore, the head substrate 18a and the protective substrate 18b are electrically connected to the rotary drum 10 having the ground potential via the base metal 21.

  By the way, as described above, the cassette case 7 in which the magnetic tape 2 is wound and stored is usually formed of a low-resistance synthetic resin material. Such a cassette case 7 is rubbed with, for example, an artificial fiber packing material or gloves in the process of handling by the user, or rubbed with a component when loading the magnetic recording / reproducing apparatus 1. Static electricity is easily charged. When the magnetic tape 2 housed in the cassette case 7 charged with static electricity in this way comes into contact with the reproducing head device 18, a flow of electric charges from the magnetic tape 2 through the MR element 18c to the ground of the device occurs. This causes electrostatic breakdown of the MR element 18c.

In this manner, when electrostatic discharge occurs, in the reproducing head device 18 configured as described above, a large amount of discharge current from the magnetic tape 2 flows to the head substrate 18a and the protective substrate 18b that are set to the ground potential. As a result, the amount of current flowing through the MR element 18c is reduced, and electrostatic breakdown is prevented. In the reproducing head device 18 of the above embodiment, both the head substrate 18a and the protective substrate 18b are made conductive, but either of them may be made of a material having conductivity, that is, an electric resistance value of 10 ¹⁰ Ω or less. Good.

  However, in order to prevent such electrostatic breakdown of the MR head, it is ideal that no static electricity is generated. In the head drum device 3 to which the present invention is applied, a countermeasure for suppressing the generation of static electricity in the operator or the manufacturing process by stabilizing the charging potential in the magnetic recording / reproducing apparatus 1 to be equal to or lower than the electrostatic breakdown voltage of the MR element 18c. It alone makes up for the insufficiency. That is, instead of the conventional shaft grounding, the shaft 13 is supported by the conductive bearing 14, so that the rotary drum 10 is reliably held at the ground potential, and even when used for a long time, it is mechanical like the shaft grounding. The increase in potential of the rotating drum due to the change is not caused. Accordingly, it is possible to prevent electrostatic breakdown of the MR head without requiring antistatic treatment of each component and ground connection of the metal part.

  In the present embodiment, specifically, the conductive bearing 14 includes the conductive powder (carbon) in the lubricant (grease) of the ball bearing so that the shaft does not lose its smoothness of rotation. 13 is secured. Here, carbon is used as the conductive powder of the lubricant, but the present invention is not limited to this, and it is also possible to impart conductivity to the grease using other metal powders. .

Next, a magnetic recording / reproducing apparatus using a conductive bearing 14 will be manufactured, and the effects of the present invention will be described in comparison with a conventional apparatus using a shaft ground.
As a comparative example, the effect of preventing electrostatic breakdown was compared using a magnetic recording / reproducing apparatus in which a shaft ground is attached and the shaft of the rotating drum is supported by a conventional non-conductive bearing. Each of the magnetic recording / reproducing apparatuses of Examples and Comparative Examples was equipped with two reproducing MR heads and measured after continuously rotating the rotating drum at 6000 rpm. Further, a commercially available ME (Metal Evaporated) tape was used as a storage medium, and recording and reproduction were repeated in a constant temperature and humidity environment, and a new cassette was exchanged every 100 hours.

  FIG. 5 is a diagram showing the change over time of the MR head output (Vp-p [mV]). Here, the output voltage value of the MR head before the assembly of the rotating drum, and the head output voltage value after 500 hours have elapsed after repeating the recording and reproducing operations and after 1000 hours have elapsed are shown.

  In the MR head of the example, there is no change in the head output after 500 hours and 1000 hours of use. On the other hand, the MR head of the comparative example did not change after 500 hours, but it can be seen that the output of the head has deteriorated to almost half after 1000 hours of use.

  FIG. 6 is a diagram showing a change with time of the MR head wear amount. The amount of wear of the reproducing head was the same for both the example and the comparative example, and the amount of wear generated when the head sliding surface was in contact with the magnetic tape was the same, even after 500 hours and 1000 hours. It shows that. Therefore, it can be seen that the deterioration of the head output in the comparative example shown in FIG. 5 is not caused by an abnormal change in the head shape.

  FIG. 7 is a diagram showing a change with time of the electric potential in the rotating drum rotating shaft. Here, the resistance value between the shaft and the ground after 500 hours and 1000 hours is measured for the potential at the rotating shaft.

In the embodiment, even after 1000 hours of use, the resistance value between the shaft and the ground does not change. On the other hand, in the comparative example, it can be seen that with the passage of time, the effect of the shaft ground is reduced, and the resistance value between the shaft and the ground is significantly increased. Usually, in order to prevent electrostatic breakdown of the MR head, it is preferable that the electric resistance value between the rotating drum 10 and the fixed drum 11 is 10 ³ Ω or less. It can be seen that electrostatic breakdown can be reliably prevented for a longer time.

  FIG. 8 is a diagram showing the change over time of the surface potential in the electric circuit on the rotating drum. Here, the surface potential of the current supply circuit was measured after 500 hours and 1000 hours by a surface potential meter or the like.

  In the rotating drum of the example, the potential on the circuit board is stable at almost a constant value after 500 hours or 1000 hours, but in the comparative example, the potential is proportional to the passage of time. It is rising.

  Further, after 1000 hours of use, no damage was observed on the surface portion of the MR head of the example. However, in the MR head of the comparative example, traces dissolved by heat at the time of electrostatic breakdown were observed in a part of the MR element.

  As described above, as apparent from the comparison of the electrostatic breakdown prevention effect based on the actual measurement results, the magnetic recording / reproducing apparatus of the present invention suppresses the increase in the potential of the rotating drum over a long period of time, There is a remarkable effect that electrostatic breakdown can be surely prevented.

  Therefore, in the head drum apparatus to which the present invention is applied and the magnetic recording / reproducing apparatus including the head drum apparatus, electrostatic breakdown of the MR head can be more stably prevented. For example, a large-capacity tape streamer or a high-performance VTR can be used. Etc. can be improved. Further, by eliminating the conventional shaft grounding part and integrating the functions with existing bearing parts, the magnetic recording / reproducing apparatus can be downsized.

  In the above description, the example in which the head drum device of the present invention is provided in a magnetic recording / reproducing apparatus using a magnetic tape has been described. However, the present invention can also be applied to a magnetic reproducing apparatus capable of only reproducing a magnetic tape. Is possible.

It is a longitudinal section showing a head drum device to which the present invention is applied. It is a figure which shows the example of schematic structure of the magnetic recording / reproducing apparatus using the head drum apparatus with which this invention is applied. It is a top view which shows the structure of the reproducing head apparatus. It is a side view which shows the structure of the reproducing head apparatus. It is a graph explaining the electrostatic breakdown prevention effect in this invention compared with the conventional apparatus, Comprising: It is a figure which shows the time-dependent change of MR head output. Similarly, it is a figure which shows the time-dependent change of MR head wear amount. Similarly, it is a figure which shows the time-dependent change of the electric potential in a rotating drum rotating shaft. Similarly, it is a figure which shows the time-dependent change of the surface potential in the electric circuit on a rotating drum.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnetic recording / reproducing apparatus, 2 ... Magnetic tape, 3 ... Head drum apparatus, 4 ... Capstan, 5 ... Pinch roller, 6a-6e ... Tape guide, 7 ... Cassette case, 7a ... Take-up reel, 7b ... supply reel, 10 ... rotary drum, 11 ... fixed drum, 13 ... shaft, 14 ... bearing, 14a ... ball bearing, 15 ... reproducing head, 16 ... current supply Circuit: 17 ... Rotary transformer, 18 ... Reproducing head device, 18a ... Head substrate, 18b ... Protection substrate, 18c ... MR element, 18d, 18e ... Shield film, 18f-18i ... Insulating film, 19a, 19b ... Conductor, 20a, 20b ... Terminal, 21 ... Base metal, 22 ... Adhesive, 23 ... Set screw, 24 ... Conductive paste

Claims (8)

In a head drum device for writing and reading signals on a magnetic tape wound helically around an outer peripheral surface,
A fixed drum held at ground potential;
A rotating drum rotatably supported with respect to the fixed drum by a conductive shaft fixed integrally;
A read head unit that includes a magnetoresistive element as a head element for reading a signal from the magnetic tape, and is fixed to the rotating drum so that a signal reading surface is in sliding contact with the magnetic tape at an outer peripheral surface of the rotating drum; ,
A conductive bearing for bearing the conductive shaft of the rotating drum on the fixed drum side so that the rotating drum is at ground potential via the fixed drum;
A head drum device comprising:   The head drum device according to claim 1, wherein the bearing portion includes a ball bearing containing conductive grease.   The head drum device according to claim 2, wherein the conductive grease contains carbon.   In the read head unit, conductive head substrates and protective substrates electrically connected to the rotary drum are respectively disposed on both sides of the head element via insulating films. The head drum device according to claim 1.   2. The head drum device according to claim 1, wherein a rotary transformer for transmitting and receiving an electric signal between the head element and an external circuit is provided between the rotating drum and the fixed drum. .   6. The head drum device according to claim 5, wherein the rotary drum is equipped with an electric circuit for supplying a sense current for signal reading supplied through the rotary transformer to the head element. The head drum device according to claim 1, wherein a resistance value between the rotating drum and the fixed drum is 10 ³ Ω or less. In a magnetic recording / reproducing apparatus for recording and reproducing signals using a magnetic tape,
A fixed drum held at ground potential;
A rotating drum rotatably supported with respect to the fixed drum by a conductive shaft fixed integrally;
A read head unit that includes a magnetoresistive element as a head element for reading a signal from the magnetic tape, and is fixed to the rotating drum so that a signal reading surface is in sliding contact with the magnetic tape at an outer peripheral surface of the rotating drum; ,
A conductive bearing for bearing the conductive shaft of the rotating drum on the fixed drum side so that the rotating drum is at ground potential via the fixed drum;
A magnetic recording / reproducing apparatus comprising: a head drum device having:

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