Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
1999-04-05
2001-12-25
Neal, Regina Y. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S046000
Reexamination Certificate
active
06333828
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetic disk unit including magnetic disks, slider suspension assemblies each of which has a slider with at least one thin-film magnetic head element and a resilient suspension for supporting the slider, and head IC chips.
DESCRIPTION OF THE RELATED ART
In such magnetic disk unit, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic hard disks are in general formed on the sliders flying in operation above surfaces of the respective magnetic disks. Each slider is supported by a suspension made of a resilient thin metal plate extended from one end of a movable arm in the magnetic disk unit.
Head IC chips are used for amplifying write current to the magnetic head elements, for amplifying read current from the magnetic head elements and for controlling the write and read operations of the magnetic head elements. Each head IC chip had been mounted on the movable arm located in a rearward position of the suspension or on a flexible printed cable (FPC) also located at a rearward position of the suspension. However, if the head IC chip is mounted on the movable arm or on the FPC, lead lines for electrically connecting the magnetic head element with the IC chip become long causing noises to be easily generated. Also, the long lead lines provide some delay in rising and falling times of pulse signals due to parasitic capacitance and inductance of these lead lines causing the high rate transfer of data to make difficult.
In order to suppress the generation of noises from the lead lines, Japanese patent unexamined publications nos. 53(1978)-69623 and 3(1991)-108120 propose head suspension assemblies wherein the length of the lead lines is shortened by mounting the head IC chips on the sliders or on the suspensions.
However, if the IC chip is mounted on the slider or on the suspension, the IC chip itself is heated to a high temperature due to the write current flowing through the IC chip during recording operation. This generated heat from the head IC chip will exert an influence upon the magnetic head element. That is, when the head IC chip is mounted on the movable arm as in the conventional art, the temperature of the IC chip can be maintained at a low value because the movable arm has sufficient heat capacity and heat dissipation area. Furthermore, the magnetic head element will not receive the influence of the generated heat because the IC chip locates far from the magnetic head element. Whereas, when the IC chip is mounted on the slider or on the suspension, sufficient surface area for dissipating heat generated from the IC chip cannot be obtained and also the reduction of heat during heat conduction cannot be expected. Thus, the temperature of the IC chip itself increases causing a degree of reliability of the IC chip to lower and the magnetic head element will receive the influence of the generated heat.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic disk unit with slider suspension assemblies and head IC chips, whereby increase in temperature of head IC chips can be effectively suppressed.
According to the present invention, a magnetic disk unit includes slider suspension assemblies, each of the assemblies having a slider with at least one magnetic head element and a suspension with one end portion and one surface, the slider being mounted on the one surface of the suspension at the one end portion, magnetic disks, each of the disks having at least one surface which opposes to the slider of the assembly, head IC chips electrically connected to the magnetic head elements, and a control circuit electrically connected with the head IC chips. The control circuit controls operations of each of the magnetic head elements so that the write current is applied to the magnetic head element for a first predetermined period of time and then the application of the write current to the magnetic head element is stopped for a second predetermined period of time which is equal to or longer than the first predetermined period.
The write current Is applied to the magnetic head element for a first predetermined period of time (predetermined write period) for example 3 msec to 1 sec, and just after the period, the application of the write current to the magnetic head element is forcibly stopped for a second predetermined period of time (predetermined write halt period) which is equal to or longer than the write period. The write current heats the head IC chip during the write period. However, during the write halt period which is not shorter than the write period, the write current is stopped from flowing even when there is data to be written to cool the head IC chip. Thus, temperature increasing of the head IC chip can be suppressed to a smaller extent.
It is preferred that the control circuit controls operations of the magnetic head element so that read operations of the magnetic head element is executed during the write halt period.
It is also preferred that the write period is determined by using a unit of time which substantially corresponds to one rotation of the magnetic disks.
Preferably, the control circuit controls the write and write halt periods with respect to the write current applied to the same magnetic head element.
Also preferably, the control circuit controls the write and write halt periods with respect to the write current applied to a plurality of the magnetic head elements. In this case, more preferably, the control circuit controls the write current applied to the magnetic head elements so that the write current is sequentially applied to each of the magnetic head elements for the write period.
It is preferred that the head IC chips are mounted at positions where air flow produced by rotation of the magnetic disks are always provided during operation. For example, the head IC chips may be mounted at positions within peripheral edges of the magnetic disks so as to oppose to surfaces of the magnetic disks, respectively. Alternately, the head IC chips may be mounted on connection line members such as FPCs for connecting the head IC chips with external circuits, respectively. Since airflow due to rotation of the magnetic disks pass near the head IC chips, the head IC chips are always cooled while the magnetic head elements seek above the surfaces of the magnetic disks. Thus, in addition to the aforementioned write halt control, the head IC chips can be effectively cooled to extremely reduce its temperature increasing.
In case that the head IC chips are mounted at positions within peripheral edges of the magnetic disks so as to oppose to surfaces of the magnetic disks, it is preferred that a distance between each of the head IC chips and each of the opposing surfaces of the magnetic disks is equal to or shorter than 1,000 &mgr;m. As a result, the airflow cooling due to disk rotation becomes very effective.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
REFERENCES:
patent: 5910861 (1999-06-01), Ahn
patent: 5920447 (1999-07-01), Sakata et al.
patent: 6014289 (2000-01-01), Goss
patent: 6025988 (2000-02-01), Yan
patent: 6084746 (2000-07-01), Shiraishi et al.
patent: 6118602 (2000-09-01), De La Soujeole
patent: 53-69623 (1978-06-01), None
patent: 6-70848 (1994-09-01), None
Morita Haruyuki
Sakai Masanori
Takano Ken-ichi
Arent Fox Kintner & Plotkin & Kahn, PLLC
Neal Regina Y.
TDK Corporation
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