Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-04-05
2002-04-09
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06369973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk device in which a recording head is moved while a disk as a recording medium is rotated so that information is recorded on and/or reproduced from the disk. More particularly, the present invention relates to a disk device having a temperature control mechanism for suppressing a temperature rise.
2. Description of the Related Art
In a disk device of the above type, an operation called a seek, which involves moving a recording head to a predetermined position at high speed, is frequently repeated in some cases. Such a seek consumes an extremely large amount of power when compared with a normal recording and/or reproduction operation which does not include high-speed movement of the head. Accordingly, if seeks are continuously performed for an extended period of time, the temperature inside the disk device becomes high. In the case where the disk is under control by constant angular velocity (CAV), such heating during the seek mainly arises from a motor driving system for moving the head. In the case where the disk is under control by constant linear velocity (CLV), the heating during the seek mainly arises from a motor driving system for driving the disk, in addition to the motor driving system for moving the head.
Due to such a temperature rise caused by the heating of the driving system during the seek, the temperatures of the disk and components of the disk device exceed their respective allowable temperature levels.
Some measures for overcoming the above problem of temperature rise have been proposed. For example, U.S. Pat. No. 5,566,077 discloses a construction in which a temperature sensor is provided inside an optical disk devise for detecting the temperature of the device so as to limit the operation of the device when the temperature of the device exceeds a predetermined temperature level thereby preventing an excessive temperature rise.
A technique has also been proposed in which the temperature at a desired position is predicted by an arithmetic operation. According to this technique, the cost and the number of assembling steps can be reduced since installation of a temperature sensor is not required. Also, the temperature of a position at which direct installation of a temperature sensor is difficult can be obtained. For example, Japanese Laid-Open Publication No. 7-153208 discloses a construction in which temperature rise of a voice coil motor (VCM) for moving a head is predicted by an arithmetic operation based on a current instruction value for the VCM.
FIG. 5
shows an example of a conventional disk device which predicts a temperature rise by an arithmetic operation.
Referring to
FIG. 5
, a conventional magnetic disk device
101
includes a disk enclosure (DE)
102
. The DE
102
includes a disk motor
103
, a spindle
104
, a voice coil motor (VCM)
106
, and a magnetic head
107
. A magnetic disk
105
is loaded in the DE
102
. The VCM
106
moves the magnetic head
107
in a direction of the radius of the magnetic disk
105
for positioning the magnetic head
107
. The magnetic disk device
101
further includes a servo controller
118
, which includes a VCM control section
135
. The VCM control section
135
includes a temperature detection sub-section
114
for predicting the temperature of the VCM
106
, a positioning control sub-section
115
, and RAM
122
.
The RAM
122
stores data, such as a VCM current instruction value I
v
, the quantity of heat corresponding to a temperature rise &Dgr;Q
v1
, the quantity of heat corresponding to spontaneous heat emission &Dgr;Q
v2
, the quantity of heat of an object to be measured Q
v
, and the temperature of the object to be measured T
v
, renewably. The RAM
122
is provided with a soft timer. In addition, ROM (not shown) prey stores data such as a constant K, a constant indicating heat resistance &thgr;, the heat capacity of the object to be measured C
v
, the environmental temperature T
a
, the sampling time t
s
, a constant a, and a constant b.
In the magnetic disk device
101
with the above configuration, the temperature detection sub-section
114
performs a prediction operation of the temperature of the VCM in the following procedure.
The VCM control section
135
interrupts normal seek control every sampling time t
s
of 66 &mgr;sec, to detect the position of the magnetic head
107
and renew the VCM current instruction value I
v
. Then, the temperature detection sub-section
114
multiplies the second power of the VCM current instruction value I
v
by the coefficients K and t
s
to obtain the quantity of heat corresponding to temperature rise of the object to be measured &Dgr;Q
v1
(=I
v
2
×K·t
s
). A value obtained by subtracting the quantity of heat corresponding to the spontaneous heat emission of the object to be measured &Dgr;Q
v2
from the quantity of heat corresponding to temperature rise &Dgr;Q
v1
is then integrated (Q
v
←Q
v
+&Dgr;Q
v1
−&Dgr;Q
v2
), so as to obtain the quantity of heat of the object to be measured Q
v
and thus detect the temperature of the object to be measured T
v
(T
v
=Q
v
/C
v
).
The above processing is performed every sampling time t
s
and the detected temperature T
v
is stored in the RAM
122
. During a seek, the temperature T
v
is read from the RAM
122
to perform seek control based on the temperature T
v
.
In the seek control, if the detected temperature T
v
is larger than a reference value, the start of the seek is delayed depending on the temperature T
v
, so that temperature rise is suppressed.
A delay amount D by which the start of the seek is delayed is set as a primary function of the temperature T
v
at D=aT
v
−b (wherein a and b are constants stored in the ROM). The delay amount D is set depending on the temperature T
v
in the following manner: When the reference value for the temperature T
v
is T
1
, the delay amount D is set at 0 if T
v
≦T
1
and set at aT
v
−b if T
v
>T
1
.
Accordingly, the seek is started upon receipt of a seek instruction if the temperature T
v
is less than the reference value T
1
, or the seek is started only after a delay by the delay amount D which is proportional to the temperature T
v
if the temperature T
v
exceeds the reference value T
1
. This suppresses the temperature rise of the VCM and thus prevents an occurrence of overheating and breaking of the VCM.
The above conventional disk device has the following problems.
The first problem is that the amount of the arithmetic operation required for the temperature prediction is large. Accordingly, the control section must bear a large burden. More specifically, for the temperature prediction operation, the control section must perform interruption at a very frequent sampling period of 66 &mgr;sec. For each interruption, the control section retrieves the current instruction value I
v
and performs calculations for obtaining the quantity of heat &Dgr;Q
v1
, the quantity of heat radiation &Dgr;Q
v2
, and the temperature T
v
. This interruption is required all the time irrespective of whether the device is under the recording operation or the seek operation. Such frequent interruption significantly increases the burden on the control section of the disk device, lowering the processing capability of the control section.
The second problem is as follows. While the temperature of the VCM is controlled so as not to exceed its allowable temperatures, it has been found that the difference between the temperature of the center of the disk and the ambient temperature, not the temperature of the disk itself, is important in specific cases. Such a specific case includes the case in which a disk is warped when the disk motor is heated. When the disk motor is heated, the inner circumference of the disk which is closer to the disk motor is heated more than the outer circumference of the disk causing a temperature gradient over the inner and outer circumferences of the disk. If the entire disk is heated uniformly, the disk will have little
Mushika Yoshihiro
Nishihara Yasuo
Takauchi Kenji
Hudspeth David
Matsushita Electric Industrial Co. Ltd
Renner , Otto, Boisselle & Sklar, LLP
Wong K.
LandOfFree
Disk device with temperature calculation section for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disk device with temperature calculation section for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disk device with temperature calculation section for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2887090