JPH11213338A - Magnetic head assembly and magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic head assembly and a magnetic disk device, capable of preventing electric discharging between a head and a disk by a potential induced by the electrode of an induction magnetic head and preventing the damaging of the magnetic head and the magnetic disk and securing data reliability. SOLUTION: This magnetic head assembly is provided with an induction thin film magnetic head element having a coil 6 wound between a magneto- resistance effect magnetic head element 7 having a magneto-resistance effect element and lower cores 4a and 4b, and an ABS film 10 formed on a surface facing a magnetic disk. In this case, by grounding the upper and lower cores 4a and 4b via a connecting part 9 and setting the potentials of the upper and lower cores 4a and 4b lower than the withstand voltage of an insulated protective film, electric discharge with the magnetic disk is prevented, and breaking and noises in the magnetic disk and the head are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head assembly and a magnetic disk drive on which a magneto-resistance effect type magnetic head element and an inductive type thin film magnetic head element are mounted, and more particularly, to preventing a discharge between write magnetic poles. A magnetic head assembly and a magnetic disk drive that prevent the reliability of data reproduction.

[0002]

2. Description of the Related Art In recent years, a magnetic head assembly in a magnetic disk drive is provided with a magnetoresistive effect type magnetic head element utilizing a magnetoresistive effect for data reproduction and a recording induction for the purpose of increasing recording density and data transfer speed. A composite type magnetic head assembly equipped with a thin film type magnetic head element is employed. A magnetic recording method adopted in recent magnetic disk devices is a conventional RLL (Run L / L).
PRML (Partial Response M) suitable for high-density recording from the "length limited" method
maximum likelihood) system. Therefore, in recent magnetic disk devices, high recording density and high-speed data transfer are performed by a combination of a magnetoresistance effect type magnetic head element and PRML type magnetic recording.

In a magnetic disk drive, it is necessary to increase the data write frequency in order to transfer data at a high speed. In the PRML system, the write frequency is further increased to perform 8/9 conversion. Tend to be, for example, RL
In the 1-7 conversion of the L system, the maximum frequency was 36 MHz, but in the PRML system, the maximum frequency was 54 MHz, and the writing frequency was about 1.5.
The writing circuit for high-frequency writing is required.

A data write circuit for a magnetic induction type magnetic core according to the prior art, as shown in FIG.
A voltage source 20 for supplying a voltage in accordance with an instruction from a receiver, a receiver 22 for receiving data to be written by a magnetic head from a higher level, and a collector connected to a voltage from the voltage source 20 via a resistor 23, and the receiver 22 (Tr) 24 and 25 whose write data is input as bases, and the voltage from the voltage source 20 is connected to the base via the resistor 23 and the voltage from the voltage source 20 is connected to the collector via the resistor 23. Transistors 26 and 27;
Transistors 28 and 29 receiving the emitter outputs of the transistors 26 and 27 as collectors and inputting the output from the transceiver 22 through a resistor 35, respectively.
A current source 33 connected to the emitters of the transistors 24 and 25, a current source 32 connected to the emitters of the transistors 28 and 29, and the voltage from the voltage source 20 and the emitter output of the transistor 27. And a write magnetic head element 31 connected to the other end of which the voltage from the pressure source 20 and the emitter output of the transistor 26 are connected.

This data writing circuit includes a write gate W /
By closing the switch 34 in response to the instruction from G, the current from the current sources 32 and 33 is supplied to the transistors 24 and 25 and the transistors 26 to 29. At this time, when the write data P and N are inputted. Driving the receiver 22 in accordance with the polarity thereof, inverting the transistors 24 and 25 connected to the receiver 22, and alternately turning on / off the pair of the transistors 27 and 28 and the transistors 26 and 29 by the inversion. Thus, the operation is performed such that the direction of the write current supplied to the magnetic head element 31 is alternately reversed to perform the data write. As a document describing a data writing circuit for these magnetic disk devices, for example, JP-A-7-169005 is cited.

[0006]

In the data writing circuit according to the prior art described above, the magnetic head element has an inductance L of an arbitrary value proportional to the number of turns of the writing coil.
When writing data, the inductance L and the write current dI / dt
A flyback voltage proportional to the product of the rising speed of the head element 31 is generated at both ends of the head element 31, and a large flyback voltage as shown in FIG. In particular, in the write circuit having the configuration shown in the figure, the voltage Vx of the voltage source had to be set higher than the flyback voltage, and the voltage Vx had to be set higher to perform the above-described high-speed writing. . Also, in this circuit, the voltage Vx of the voltage source via the resistor 30 is applied to both ends of the head element 31 to turn off the current sources 32 and 33 even during non-writing.

Therefore, a potential which is divided by the capacitance between the coil and the magnetic pole and the capacitance between the magnetic pole and the magnetoresistive element is generated in the upper and lower cores of the magnetic head element connected to the data writing circuit according to the prior art. When this potential exceeds the withstand voltage of the protective film for insulating the magnetic head slider, or when the distance between the magnetic disk element and the magnetic disk becomes shorter due to the protrusion on the magnetic disk, a discharge is generated between the magnetic head element and the magnetic disk. In addition to the defect that the magnetic disk surface and the magnetic head may be damaged, the discharge noise is applied as pulse noise to the data read by the magnetoresistive head element even when the damage does not occur, There is also a problem that the reliability of data reading is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art, and to prevent discharge between a head and a disk due to a potential induced at an electrode of an inductive magnetic head element. It is an object of the present invention to provide a magnetic head assembly and a magnetic disk drive capable of preventing data breakage and ensuring data reliability.

[0009]

According to the present invention, there is provided a magnetic head element having a magnetoresistive element whose resistance value is converted by a magnetic field from a magnetic disk, and a coil disposed between an upper core and a lower core. A magnetic head assembly having an inductive thin-film magnetic head element wound thereon and having an insulating protective film on a surface facing the magnetic disk, wherein the potential of the upper and lower cores is set to a withstand voltage of the insulating protective film or less. The first feature is that the potential of the upper and lower cores is set to be equal to or lower than the withstand voltage of the insulating protective film by grounding the upper and lower cores.

The present invention also provides a magnetoresistive head element having a magnetoresistive element whose resistance value is converted by a magnetic field from a magnetic disk, and an inductive thin film magnetic head element having a coil wound between an upper core and a lower core. A magnetic head assembly comprising: a magnetic head assembly having an insulating protective film on a surface facing the magnetic disk; and a write circuit for writing data using the inductive thin film magnetic head element. A third feature is that the embedded circuit is configured such that the electric potential of the upper and lower cores is lower than the withstand voltage of the insulating protective film during a time other than when data is written by inductive thin film magnetic head element data.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a magnetic head assembly according to the present invention and a magnetic disk drive provided with the magnetic head assembly will be described in detail with reference to the accompanying drawings. I do.

Each core of the induction type magnetic head element of the above-mentioned composite type thin film magnetic head is electrically conductive and is usually insulated from other parts and is disposed between the core and the magnetoresistive effect type head element. Induced to an intermediate level between the voltage of the thin-film magnetic head element and the voltage of the magnetoresistive head element, damage to the element and the magnetic disk as described in the above-mentioned problem section and other injuries have occurred. . The inventors focused on the cause of the breakage, and in order to reduce the voltage induced between the upper and lower cores, a magnetic head assembly in which the magnetic poles were grounded via terminals and a voltage induced in the core A magnetic disk device including a data writing circuit for controlling the voltage to be equal to or lower than the discharge voltage of the magnetic disk.

An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view for explaining an embodiment of a magnetic head assembly according to the present invention, and FIG. 2 is a view showing a schematic configuration of a magnetic disk drive to which the present invention is applied.

First, as shown in FIG. 2, a magnetic disk drive to which the present invention is applied includes a spindle 15 for supporting the magnetic disk 1, a spindle motor 20 for driving the spindle 15 to rotate, and a gimbal 12 on the magnetic disk 1. And a voice coil motor (VCM: VCM) for driving the head arm 17 to position the magnetic head assembly 2 at a desired position on the magnetic disk 1.
(Not shown), a recording / reproducing circuit (R / WIC) 16 for recording / reproducing data on / from a magnetic disk using the magnetic head assembly 2, and a control unit 19 for controlling the mechanisms and circuits. The control unit 19 drives the voice coil motor in accordance with a drive signal to position the magnetic head assembly 2 on a predetermined track on the magnetic disk 1. The recording / reproducing circuit 16 causes the magnetic head assembly 2 to transfer data to the magnetic disk 1. It operates so as to perform the recording and reproduction of the information.

As shown in FIG. 1, the magnetic head assembly 2 according to the present embodiment
And a slider unit 3 that is held through the slider and generates a levitation force due to the viscous flow of air to the surface of the magnetic disk.
The head unit 100 is arranged at the rear end of the disk unit and records and reproduces data on and from the magnetic disk. An insulating ABS film (insulating protective film) is formed on the slider unit 3 and the head unit 100 facing the magnetic disk. ) Is covered. The head unit 100 is a composite type comprising a write head unit 102 corresponding to an inductive thin film magnetic head element for data recording and a read head unit 101 corresponding to a magnetoresistive magnetic head element for data reproduction. A magnetic head assembly is mounted on the lower rear end portion of the head to record and reproduce data on the magnetic disk.

As shown in FIGS. 5 and 6, the detailed structure of the head portion 100 is such that a coil 6 is wound between a lower core 4a and an upper core 4b corresponding to magnetic poles, respectively, and the leading end portion on the magnetic disk side is narrowed. An inductive thin film magnetic head element portion (corresponding to the write head portion 102 in FIG. 1) for generating a magnetic field in the gap portion 20 and writing data to be applied to the electrode portion 30, and between the lower core 4b and the shield 5 Placed in
A magnetoresistive effect type magnetic head element portion (corresponding to the read head portion 101 in FIG. 1) including an MR element 7 and an electrode 8 whose resistance values change in accordance with a change in the magnetic field from the magnetic disk is laminated and an insulator is formed. It is configured to be sealed by 11. The MR element 7 applies a bias current to one end via the electrode 8 and grounds the other end, and detects a change in the bias current value based on a change in the resistance value due to a magnetic field from the magnetic disk. It is for regenerating.

The magnetic head assembly according to the present embodiment electrically connects a part of the upper core 4a and the lower core 4b of the inductive type thin-film magnetic head element to the lower core 4b.
b and the rear end (the upper side in FIG. 5) of the shield 5 are connected by a connecting portion 9, and the connecting portion 9 is electrically connected to the grounded sliding member 3 via a spring 13 and a gimbal 12, so that the upper part And the lower cores 4a and 4b and the shield 5 are grounded. Incidentally, the upper core 4a and the like are magnetic materials of high permeability rate such permalloy (N _i F _e), the coil 6 made winding between the core 4a and 4b are electrically conductive material such as copper, insulator 11 is an insulating material such as silicon dioxide (S _i O _2), the electrode 8 MR element 7
Is a conductive material that is electrically connected to the outside.

The data write circuit for driving the inductive thin film magnetic head element of the magnetic head assembly has the same basic configuration as the circuit described with reference to FIG. The switch 34 is turned on in response to a write gate signal W / G, which is a write command from the control unit 19 shown in FIG. A pair of transistors 26 and 29 and a pair of transistors 2
7 and 28 alternately turn on / off,
The data is recorded on the magnetic disk by inverting the write current applied to the write head 31.

In the write circuit thus configured, when the data transfer rate is 16 MB / sec, the minimum data inversion interval of the write current is as fast as about 8 ns, and the direction of the write current is within 8 ns. It is necessary to satisfy the characteristic of reversing the value. When such high-speed writing is performed, a flyback voltage _VFB expressed by the following equation is generated at both ends of the head 31.

[0020]

V _FB = L × di / dt where L: write head inductance di / dt: write current change gradient Here, write head inductance L is 250 nH, d
When i is 80 mApp and dt = 4 ns in consideration of the overshoot of the write current, the flyback voltage _VFB is 5 V
Therefore, the values of the voltages Vcc and Vx of the voltage source 20 need to be higher than the flyback voltage V _FB (5 V).

Here, in the magneto-resistive magnetic head element for data reproduction, since one end of the MR element 7 is grounded as described above, the voltage of the terminal on the ground side is at the ground level, and the bias current is The voltage of the application side terminal is 200 to 30
The value is as low as 0 mV level.

Therefore, an equivalent circuit between the coil 6 of the write head element 31, the upper and lower cores 4a / 4b, and the MR element 7, as shown in FIG.
(C _A ), upper and lower cores 4a / 4b, capacity 39
(C _B ) and a series circuit of a virtual resistor 36 included in the circuit from the power supply Vcc, a virtual switching element 50 included in the circuit, and a resistor 38 corresponding to the internal resistance of the MR element 7. Are connected via a terminal 41. Further, the cores 4a / 4b are grounded via the connection section 9 shown in FIG.

Therefore, the data write circuit according to the present embodiment is structured by connecting the connection portion 9 shown in FIG. 5 and grounding the upper and lower cores 4a / 4b shown in FIG.
It is possible to prevent the electrodes of the upper and lower cores 4a / 4b from being charged with excessive voltage, thereby preventing discharge between the magnetic disk and the magnetic head. Thus, the data writing circuit according to the present embodiment can prevent the discharge, prevent the magnetic disk surface and the magnetic head from being damaged, suppress the discharge noise, and improve the reliability of data data reading.

In the above embodiment, an example has been described in which the upper and lower cores are grounded via the connection portion 9 to prevent the generation of a large flyback voltage applied to the magnetic head. It is not limited,
For example, discharge noise during reproduction can be suppressed by the above-described writing circuit.

In the data write circuit according to the present embodiment, the voltage source 20 lowers the voltage Vx to the ground level (substantially 0 V) at a time other than the data write timing by the write gate W / G as shown in FIG. By controlling the voltage to be sufficiently lower than the withstand voltage (for example, several V to several tens of V) of the ABS film of the magnetic head slider, the discharge between the magnetic disks can be prevented, and the surface of the magnetic disk can be prevented. In addition, it is possible to prevent damage to the magnetic head and improve the reliability of data reading.

Particularly, in recent magnetic disk devices, due to the demand for large capacity, the ABS film thickness tends to be thin and the withstand voltage may be low, and the flying height of the head tends to further decrease. In the disk device, the magnetic head assembly according to each of the above embodiments and the device including the magnetic head assembly can suppress discharge noise and further improve the reliability of data reading.

[0027]

As described above, in the magnetic head assembly according to the present invention, the electric potential of the upper and lower cores of the inductive type thin-film magnetic head element is set to be lower than the withstand voltage of the insulating protective film. To prevent discharge noise during data reproduction, prevent damage to the magnetic head and magnetic disk, and further ensure data reliability. Further, the magnetic head assembly according to the present invention has the same effect as described above by grounding the upper and lower cores and by setting the potential to be equal to or lower than the withstand voltage of the insulating protective film. Can be obtained.

Further, in the magnetic disk drive according to the present invention, the data write circuit adjusts the electric potential of the upper and lower cores during the time other than the time of data writing by the data of the inductive thin film magnetic head element. With the configuration below the voltage, it is possible to suppress the charged voltage of the upper and lower cores in a circuit without modifying the magnetic head assembly and obtain the same effect as described above.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a magnetic head assembly according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a magnetic disk drive to which the magnetic head assembly according to one embodiment of the present invention is applied;

FIG. 3 is a diagram for explaining a writing circuit that drives an inductive thin film magnetic head element to write data.

FIG. 4 is a diagram for explaining a relationship between voltages according to a write gate signal by the write circuit.

FIG. 5 is a view for explaining a detailed structure of a magnetic head assembly according to one embodiment of the present invention.

FIG. 6 is a perspective view schematically showing the magnetic head assembly shown in FIG. 5;

FIG. 7 is a diagram showing an equivalent circuit in a circuit configuration including a write head element and upper and lower cores;

[Explanation of symbols]

1: magnetic disk, 2: magnetic head assembly, 3: magnetic head assembly
Slider part, 4a: upper core, 4b: lower core, 5 shield :, 6: coil, 7: MR element, 8: electrode, 9: connecting part, 10: ABS film, 11: insulator, 12: gimbal, 13 : Spring, 15: spindle, 16: recording / reproducing circuit, 17: head arm, 18: actuator, 1
9: control unit, 20: spindle motor, 100: head unit, 101: read head unit, 102: write head unit.

Claims (3)

[Claims] 1. A magnetoresistive head element having a magnetoresistive element whose resistance value is converted by a magnetic field from a magnetic disk, and an inductive thin film magnetic head element having a coil wound between an upper core and a lower core. A magnetic head assembly having an insulating protective film on a surface facing a magnetic disk, wherein the electric potential of the upper and lower cores is set to be lower than the withstand voltage of the insulating protective film. 2. The magnetic head assembly according to claim 1, wherein the upper and lower cores are grounded so that the potential of the upper and lower cores is lower than the withstand voltage of the insulating protective film. 3. A magnetoresistive effect type magnetic head element having a magnetoresistive effect element whose resistance value is converted by a magnetic field from a magnetic disk, and an inductive type thin film magnetic head element having a coil wound between an upper core and a lower core. A magnetic head assembly having an insulating protective film on a surface facing a magnetic disk; and a write circuit for writing data using the inductive thin film magnetic head element, wherein the write circuit is A magnetic disk device wherein the potential of the upper and lower cores is set to be equal to or lower than the withstand voltage of an insulating protective film during a time other than when data is written by inductive thin film magnetic head element data.