JP4177910B2 - Magnetic head assembly and magnetic disk drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic head assembly and a magnetic disk apparatus equipped with a magnetoresistive effect type magnetic head element and an inductive type thin film magnetic head element, and in particular, discharge between write magnetic poles is prevented to improve data reproduction reliability. The present invention relates to a magnetic head assembly and a magnetic disk apparatus that are prevented.
[0002]
[Prior art]
Magnetic head assemblies in recent magnetic disk devices have a magnetoresistive effect magnetic head element using a magnetoresistive effect for data reproduction and an inductive thin film magnetic head element for recording in order to increase recording density and data transfer speed. A composite magnetic head assembly equipped with is used. Further, the magnetic recording system employed in recent magnetic disk devices is shifting from the conventional RLL (Run Length Limited) system to the PRML (Partial Response Maximum Likely Hood) system suitable for high recording density. Therefore, in recent magnetic disk devices, high recording density and high-speed data transfer are performed by a combination of a magnetoresistive head element and PRML magnetic recording.
[0003]
In the magnetic disk device, it is necessary to increase the data writing frequency in order to transfer data at high speed, and the PRML method tends to further increase the writing frequency because of 8/9 conversion. For example, in the RLL method 1-7 conversion, the highest frequency was 36 MHz, but the PRML method has a write frequency of about 1.5 times 54 MHz, and this high frequency writing circuit is required.
[0004]
As shown in FIG. 3, a data writing circuit for a magnetic induction type magnetic core according to the prior art includes a voltage source 20 that supplies a voltage in response to an instruction from a write gate W / G, and data that is written by a magnetic head from above. From the voltage source 20, transistors (Tr) 24 and 25 that connect the voltage from the voltage source 20 through a resistor 23 and write data from the receiver 22 as a base input, Are connected to the base via the resistor 23 and collector connected to the voltage from the voltage source 20 via the resistor 23, and the emitter outputs of the transistors 26 and 27 are input to the collector and from the transceiver 22 Of the transistors 28 and 29, and the transistors 24 and 2 respectively. The current source 33 connected to the emitter of the transistor 28, the current source 32 connected to the emitters of the transistors 28 and 29, the voltage from the voltage source 20 and the emitter output of the transistor 27 are connected to one side. And a magnetic head element 31 for writing to which the emitter output of the transistor 26 is connected to the other.
[0005]
This data writing circuit supplies the current from the current sources 32 and 33 to the transistors 24 and 25 and the transistors 26 to 29 by closing the switch 34 in accordance with an instruction from the write gate W / G. When the write data P and N are input, the receiver 22 is driven according to the polarity thereof, and the transistors 24 and 25 connected to the receiver 22 are inverted, whereby the transistors 27 and 28 and transistors 26 and 29 are inverted. By alternately turning on / off these pairs, the direction of the write current supplied to the magnetic head element 31 is alternately reversed to perform data writing.
As a document describing the data writing circuit for the magnetic disk device, for example, JP-A-7-169005 is cited.
[0006]
[Problems to be solved by the invention]
In the above-described prior art data write circuit, the magnetic head element has an inductance L having an arbitrary value proportional to the number of turns of the write coil, and the rising speed of the inductance L and the write current dI / dt during data writing. A flyback voltage proportional to the product of the two is generated at both ends of the head element 31, and a large flyback voltage as shown in FIG. In particular, in the writing circuit having the configuration shown in the figure, the voltage Vx of the voltage source needs to be set higher than the flyback voltage, and the voltage Vx needs to be set higher in order to perform the above-described high-speed writing. . Further, in this circuit, the voltage source voltage Vx via the resistor 30 is applied to both ends of the head element 31 in order to turn off the current sources 32 and 33 even during non-writing.
[0007]
Therefore, the upper and lower cores of the magnetic head element connected to the data writing circuit according to the prior art generate a capacitance between the coil and the magnetic pole and a capacitance between the magnetic pole and the magnetoresistive element and a capacitance divided potential. Exceeds the withstand voltage of the protective film for insulating the magnetic head slider, or the distance between the magnetic disk surface and the magnetic disk surface due to the protrusion on the magnetic disk causes discharge between the magnetic head element and the magnetic disk. In addition, there is a problem that there is a possibility that the magnetic head may be damaged, and even when the magnetic head is not damaged, discharge noise is applied as pulse noise to data read by the magnetoresistive effect type magnetic head element. There was also a problem that reliability was lowered.
[0008]
An object of the present invention is to eliminate the disadvantages of the prior art described above, and to prevent discharge between the head and the disk due to the potential induced in the electrodes of the induction type magnetic head element, and to damage the magnetic head and the magnetic disk. It is an object of the present invention to provide a magnetic head assembly and a magnetic disk device capable of preventing and ensuring data reliability.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a magnetoresistive effect magnetic head element having a magnetoresistive effect element whose resistance value is converted by a magnetic field from a magnetic disk, and an inductive thin film magnetic head in which a coil is wound between upper and lower cores. In a magnetic head assembly including an element and having an insulating protective film on the surface facing the magnetic disk, the first feature is that the potential of the upper and lower cores is configured to be equal to or lower than the withstand voltage of the insulating protective film. A second feature is that the potentials of the upper and lower cores are configured to be equal to or lower than the withstand voltage of the insulating protective film by grounding the upper and lower cores.
[0010]
The present invention also includes a magnetoresistive effect magnetic head element having a magnetoresistive effect element whose resistance value is converted by a magnetic field from a magnetic disk, and an inductive thin film magnetic head element in which a coil is wound between upper and lower cores. A magnetic disk drive comprising: a magnetic head assembly having an insulating protective film on a surface facing the magnetic disk; and a writing circuit for writing data using the inductive thin film magnetic head element. A third feature is that the potentials of the upper and lower cores are configured to be equal to or lower than the withstand voltage of the insulating protective film except when data is written by inductive thin film magnetic head element data.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic head assembly and a magnetic disk apparatus having the magnetic head assembly according to the present invention will be described in detail below with reference to the drawings. First, the principle will be described.
[0012]
Each core of the inductive magnetic head element of the composite thin film magnetic head described above is electrically conductive, usually insulated from other parts, and sandwiched between the magnetoresistive head element, so that the thin film magnetic By being induced at an intermediate level between the voltage of the head element and the voltage of the magnetoresistive head element, damage to the element and the magnetic disk, such as those described in the above-mentioned column, occur. The inventors pay attention to the cause of the breakage, and in order to reduce the voltage induced between the upper and lower cores, the magnetic head assembly in which the magnetic pole is grounded via a terminal and the voltage induced in the core. The present invention invents 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.
[0013]
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining one embodiment of a magnetic head assembly according to the present invention, and FIG. 2 is a diagram showing a schematic configuration of a magnetic disk apparatus to which the present invention is applied.
[0014]
First, as shown in FIG. 2, a magnetic disk apparatus to which the present invention is applied includes a spindle 15 that supports the magnetic disk 1, a spindle motor 20 that rotationally drives the spindle 15, and a gimbal 12 on the magnetic disk 1. A head arm 17 that elastically supports the magnetic head assembly 2, and a voice coil motor (VCM: not shown) that drives the head arm 17 to position the magnetic head assembly 2 at a desired position on the magnetic disk 1. Actuator 18, 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 mechanism and circuit, the control unit 19 drives the voice coil motor by a drive signal to move the magnetic head assembly 2 to the magnetic disk. The recording and reproducing circuit 16 while being positioned on a predetermined track on the first magnetic head assembly 2 is intended to operate so as to perform recording and reproduction of data on the magnetic disk 1.
[0015]
As shown in FIG. 1, the magnetic head assembly 2 according to the present embodiment is held by a gimbal 12 via a spring 13 and generates a levitation force by an air viscous flow with the magnetic disk surface, and the slider. The head part 100 is arranged roughly at the rear end of the part 3 and records and reproduces data on the magnetic disk. An insulating ABS film (insulating material) is formed on the slider part 3 and the surface of the head part 100 facing the magnetic disk. It is covered with a protective film. The head unit 100 is a composite type composed of 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 effect magnetic head element for data reproduction. A magnetic head assembly is mounted on the lower rear end to record and reproduce data on the magnetic disk.
[0016]
As shown in FIGS. 5 and 6, the detailed structure of the head portion 100 is a gap portion in which a coil 6 is wound between a lower core 4a and an upper core 4b corresponding to magnetic poles and the tip 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) that generates a magnetic field at 20 and writes data applied to the electrode portion 30 is disposed between the lower core 4b and the shield 5. A magnetoresistive effect type magnetic head element portion (corresponding to the read head portion 101 in FIG. 1) including the MR element 7 and the electrode 8 whose resistance value changes in accordance with the change of the magnetic field from the magnetic disk is laminated and insulated. The body 11 is configured to be sealed. 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 by a resistance value change due to a magnetic field from the magnetic disk. Reproduction is performed.
[0017]
The magnetic head assembly according to the present embodiment is electrically connected to a part of the upper core 4a and the lower core 4b of the inductive thin film magnetic head element, and the rear end portions of the lower core 4b and the shield 5 (in FIG. The upper and lower cores 4a and 4b and the shield 5 are grounded by connecting the connecting portion 9 on the upper side) and connecting the connecting portion 9 to the grounded sledder portion 3 via the spring 13 and the gimbal 12. It is configured. The upper core 4a and the like are a magnetic material having a high magnetic permeability such as permalloy (N _i F _e ), and the coil 6 wound between the cores 4a and 4b is a conductive material such as copper. The insulator 11 is an insulating material such as silicon dioxide (S _i O ₂ ), and the electrode 8 is a conductive material that is connected to the MR element 7 and is electrically connected to the outside.
[0018]
The data write circuit for driving the inductive thin film magnetic head element of this magnetic head assembly has the same basic configuration as the circuit described with reference to FIG. 3, and this circuit is shown in FIG. While the switch 34 is turned on in response to the write gate signal W / G which is a write command from the control unit 19 and the current from the current sources 33 and 32 is being supplied, the magnetic pole by the input of the write data P and N from the upper level A pair of transistors 26 and 29 and a pair of transistors 27 and 28 are alternately turned on / off for each inversion, thereby reversing the write current applied to the write head 31 and recording data on the magnetic disk. It is.
[0019]
In the writing circuit configured in this way, when the data transfer rate is 16 MB / sec, the minimum data inversion interval of the write current becomes as fast as about 8 ns, and the direction of the write current is inverted within 8 ns. It is necessary to satisfy the characteristics. When such high-speed writing is performed, a flyback voltage V _FB represented by the following equation is generated at both ends of the head 31.
[0020]
[Expression 1]
V _FB = L × di / dt
L: write head inductance di / dt: change gradient of write current Here, the write head inductance L is 250 nH, di is 80 mApp, and dt = 4 ns in consideration of overshoot of the write current. In this case, the flyback voltage V _FB becomes 5 V. Therefore, the voltages Vcc and Vx of the voltage source 20 need to be larger than the flyback voltage V _FB (5 V).
[0021]
Here, in the magnetoresistive effect type magnetic head element for data reproduction, since one end of the MR element 7 is grounded as described above, the voltage of the ground side terminal is at the ground level, and the bias current application side terminal Is a low value of 200 to 300 mV.
[0022]
Accordingly, an equivalent circuit between the coil 6, the upper and lower cores 4a / 4b and the MR element 7 of the write head element 31 is shown in FIG. 7, with the coil 6, the capacitor 40 (C _A ), the upper and lower cores 4a. / 4b, a series circuit via the capacitor 39 (C _B ), a virtual resistor 36 included in the circuit from the power source Vcc, a virtual switching element 50 included in the circuit, and an internal resistance of the MR element 7. This corresponds to a circuit configuration in which a series circuit of resistors 38 is connected via a terminal 41. The core 4a / 4b is grounded via the connection portion 9 shown in FIG.
[0023]
Therefore, the data write circuit according to the present embodiment is structurally connected to the upper and lower cores 4a / 4 by grounding the connection portion 9 shown in FIG. 5 and equivalently the ground of the upper and lower cores 4a / 4b shown in FIG. It is possible to prevent the electrode 4b from being charged with an excessive voltage, and thus to prevent discharge between the magnetic disk and the magnetic head. As a result, 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.
[0024]
In the embodiment, the example in which the generation of a large flyback voltage applied to the magnetic head is prevented by grounding the upper and lower cores via the connecting portion 9 is described, but the present invention is limited to this. Instead, for example, the above-described writing circuit can suppress discharge noise during reproduction.
[0025]
In the data write circuit according to the present embodiment, the voltage source 20 reduces the voltage Vx to the ground level (substantially 0 V) when the voltage source 20 is not at the data write timing by the write gate W / G as shown in FIG. By controlling to a value sufficiently lower than the withstand voltage (for example, several V to several tens of volts) of the ABS film of the magnetic head slider, the discharge between the magnetic disks can be prevented and the magnetic disk surface and the magnetic head can be prevented. Damage prevention and data read reliability can be improved.
[0026]
Particularly in recent magnetic disk devices, due to the demand for larger capacity, it is considered that the ABS film thickness tends to be thin and the withstand voltage is lowered, and the head flying height tends to further decrease. In these magnetic disk devices, The magnetic head assembly and the apparatus including the magnetic head assembly according to each of the embodiments can further improve the reliability of data data reading by suppressing discharge noise.
[0027]
【The invention's effect】
As described above, in the magnetic head assembly according to the present invention, the potential of the upper and lower cores of the inductive thin film magnetic head element is configured to be equal to or lower than the withstand voltage of the insulating protective film, so It is possible to prevent discharge noise during reproduction, prevent damage to the magnetic head and magnetic disk, and further ensure data reliability. Furthermore, the magnetic head assembly according to the present invention is configured such that the upper and lower cores are grounded and the potential thereof is set to be equal to or lower than the withstand voltage of the insulating protective film, thereby easily suppressing the voltage of the upper and lower cores. Can be obtained.
[0028]
Furthermore, in the magnetic disk apparatus according to the present invention, the potential of the upper and lower cores is made lower than the withstand voltage of the insulating protective film while the data writing circuit is not writing data by the data of the inductive thin film magnetic head element. With this configuration, it is possible to obtain the same effect as described above by suppressing the voltage of the upper and lower cores in a circuit manner without modifying the magnetic head assembly.
[Brief description of the drawings]
FIG. 1 is a view 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 device to which a magnetic head assembly according to an embodiment of the present invention is applied.
FIG. 3 is a diagram for explaining a writing circuit for writing data by driving an inductive thin film magnetic head element;
FIG. 4 is a view for explaining a voltage relationship according to a write gate signal by the writing circuit.
FIG. 5 is a view for explaining a detailed structure of a magnetic head assembly according to an embodiment of the present invention.
6 is a perspective view schematically showing the magnetic head assembly shown in FIG.
FIG. 7 is a diagram showing an equivalent circuit in a circuit configuration such as a write head element and upper and lower cores.
[Explanation of symbols]
1: magnetic disk, 2: magnetic head assembly, 3: slider portion, 4a: upper core, 4b: lower core, 5 shield :, 6: coil, 7: MR element, 8: electrode, 9: connection portion, 10: ABS film, 11: insulator, 12: gimbal, 13: spring, 15: spindle, 16: recording / reproducing circuit, 17: head arm, 18: actuator, 19: control unit, 20: spindle motor, 100: head unit, 101: read head portion, 102: write head portion.

Claims (1)

A magnetoresistive effect magnetic head element having a magnetoresistive effect element whose resistance value is converted by a magnetic field from the magnetic disk and an inductive thin film magnetic head element in which a coil is wound between the upper and lower cores are mounted and face each other. In a magnetic disk drive comprising a magnetic head assembly having an insulating protective film on a surface and a writing circuit for writing data using the inductive thin film magnetic head element,
Capacitances between the upper and lower cores and the coil connected to the data writing circuit, and the upper and lower cores and the magnetoresistors connected to the data writing circuit, except when data is written by the inductive thin film magnetic head element The potential generated in the upper core and the lower core in a state where the capacitance is divided into the capacitance between the effect elements is configured to be equal to or lower than the withstand voltage of the insulating protective film by grounding the upper and lower cores ,
A magnetic disk drive characterized in that the potential Vx of the voltage source is set to a value lower than the withstand voltage of the protective film by the write gate during a time other than when data is written by the inductive thin film magnetic head element .

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