Electricity: motor control systems – Closed loop speed control system for dc motor with commutator
Reexamination Certificate
2001-07-24
2003-08-26
Nappi, Robert E. (Department: 2837)
Electricity: motor control systems
Closed loop speed control system for dc motor with commutator
C318S132000, C318S254100, C318S432000, C318S434000, C318S434000, C318S696000, C360S075000, C360S078060
Reexamination Certificate
active
06611658
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a drive for a disk (a recording medium in a disk shape) such as a CD-ROM, and more particularly to decelerating and stopping control of a motor which rotates the disk.
BACKGROUND ART
In a disk device
20
such as a CO-ROM drive having components shown in
FIG. 2
, when a disk motor driver
23
receives a command to decelerate or stop rotation of a disk
22
from a controlling means (CPU)
21
of the disk device
20
, a reverse-direction voltage is applied from a disk motor driver
23
to disk motor
24
to exert a forced braking force for rapid deceleration. In the case where rotation of the disk motor
24
is decelerated by applying the reverse-direction voltage to the disk motor
24
to put on a brake as described above, that is, rotation of the disk motor
24
is decelerated in a so-called normal mode, current consumption is considerably high and the disk device
20
used in a portable computer, which-is required to save power, is affected significantly. Reference numeral
25
in
FIG. 2
denotes a signal processing system provided in the disk device
20
and reference numeral
26
denotes a host computer for managing the disk device
20
.
Added to the conventional disk device
20
are power saving functions such as a low-rotation mode and standby mode in light of enhancing the power saving effect. These are the functions of suppressing the power consumption by lowering a rotational speed of the disk motor
24
or bringing the disk motor
24
to a stop condition in compliance with decision by the CPU
21
when no access command such as a read command or seek command is issued by the host computer
26
for a predetermined time. In the portable computer, therefore, a shift to the low rotation mode or sleep mode is often produced and the fact that the high current is consumed by the deceleration of the disk motor
24
for each movement causes trouble.
Japanese Patent Laid-Open No. 11-96649 discloses a disk drive device of a configuration such that in the disk drive device for applying the reverse-direction voltage to a disk motor which rotates a disk to be forcedly stopped, the application of the reverse-direction voltage is suppressed in a power saving mode to inertially rotate the disk motor to be stopped. It also discloses a method of enhancing power saving effect without consuming high current for each shift to the sleep mode by inertially rotating the disk motor in a sleep mode also in a disk drive which shifts from a normal mode to the sleep mode to bring the disk motor to a stop condition when there is no access to the disk for a predetermined time.
As a method of rapidly decelerating and stopping the disk in lower power consumption, Japanese Patent Laid-Open No. 9-285174 discloses a method of decelerating the rotational speed of the disk by bringing a coil of a motor driver IC to a short-circuit condition during the deceleration and utilizing a reverse electromotive force of the motor and a method of compensating for reduction of the braking force at a portion where the reverse electromotive force at the time of a low rotation is reduced in combination with a reverse brake during the stop of the rotation.
However, in the disk drive device disclosed in Japanese Patent Laid-Open No. 11-96649 mentioned above, the power is saved by the inertial rotation during the stop of the disk in the power saving mode, and in addition to this, the drive also applies the reverse voltage to the motor for forced deceleration in such as shifting to the low rotation mode, which consumes extra power.
When applying the reverse voltage to the motor for stop, sometimes the disk is not completely stopped or is rotated in a reverse direction unless the reverse voltage is applied at an appropriate time and voltage corresponding to the current rotational speed and the disk weight. Namely, in the disk drive device disclosed in Japanese Patent Laid-Open No. 11-96649, the inertial rotation is carried out during the stop of the disk in the power saving mode, however, a signal for detecting the number of rotation of the disk is generally such that output from a hall element of the disk motor called FG is converted to pulses and its resolving power is six pulses per rotation of the disk in a three-phase motor which is common in the disk device so that it is difficult to detect the accurate rotational speed immediately before the stop of the rotation. If an ejecting command is issued at this time, the disk cannot be sometimes stopped rapidly and reliably for the reason described above. If the disk is ejected without being reliably stopped, its recording surface is likely to be scratched since existing CD-ROM and DVD-ROM devices are generally of the tray type, and the method of stopping the rotation of the disk more reliably and rapidly and further in the lower power consumption is required.
Moreover, as the method of rapidly decelerating and stopping the disk in the lower power consumption, in the method of decelerating the rotational speed of the disk by bringing the coil of the motor driver IC to the short-circuit condition during the deceleration and utilizing the reverse electromotive force of the motor and the method of compensating for the reduction of the braking force at the portion where the reverse electromotive force at the time of the low rotation is reduced in combination with the reverse brake during the stop of the rotation as disclosed in Japanese Patent Laid-Open No. 9-285174, there is a problem that the reverse electromotive force of the motor is consumed in the driver IC to thereby cause heat generation of the driver IC though not as much as in the method of applying the reverse voltage to the motor for the forced deceleration, and a problem arises that simply using this method is not perfect when the heat generation is desired to be suppressed as much as possible in compact equipment or the like.
DISCLOSURE OF INVENTION
The present invention solves the above problems and has its object to provide a disk device and a disk decelerating and stopping method of the disk device which permits selecting the decelerating method with low power consumption when rapid deceleration is not required and permits stopping the disk rapidly and reliably even if need arises for stopping the disk during the deceleration of the disk by the method with the low power consumption.
In order to solve the above problems, the present invention is a disk device having a function of decelerating or stopping a rotating disk wherein a disk motor which rotates the disk selectively carries out a forced decelerating and stopping operation by applying a reverse-direction voltage in order to forcedly decelerate or stop the disk, or a power saving decelerating and stopping operation with lower power consumption than that for the forced decelerating and stopping operation, depending upon the kind of a command at the time of the deceleration or stop. It is also characterized in that when the disk is to be stopped by the power saving decelerating and stopping operation, a reverse-direction voltage is applied for a certain time to reliably stop the disk after a rotational speed of the disk reaches a certain number of rotation. This permits selecting the power saving decelerating and stopping method with low power consumption when the rapid deceleration is not required and permits stopping the disk promptly and reliably even when a need arises for stopping the disk during the deceleration of the disk by the method with low power consumption.
Further, by selectively switching, according as required, between a short-circuit brake which is capable of deceleration at a higher speed, and an inertial rotation which requires longer time for deceleration but generates less heat in motor driving means, as the power saving decelerating and stopping operation, an appropriate decelerating method can be selected in correspondence to each requirement for suppressing heat generation or operating a rapid deceleration.
The invention according to claim
1
is a disk device having a function of dec
Nappi Robert E.
Parkhurst & Wendel L.L.P.
Smith Tyrone
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