JP2008192184A - Head control device and disk device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable head controller for performing a stable loading/unloading operation or seeking operation even at a low temperature by reducing the viscous resistance of the pivot bearing of an actuator in a low temperature environment, and a disk drive including the same. <P>SOLUTION: The head controller is configured so that a control driving current I output based on a speed difference which is a difference between the target speed of a head 2 and a current head speed is supplied to an actuator 5 to move the actuator 5 to a target position, and a vibration application unit 11 to vibrate the actuator 5 is set, so that high-frequency vibration is applied to the vibration application unit 11 based on an output from a viscosity control unit 10 according an operational environment temperature estimated by an environment detection unit 9. The disk drive including the head controller is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disk device such as a magnetic disk device, and more particularly to a head control device having a function of adjusting a positioning control system in accordance with an environmental temperature and a disk device including the head control device.

As a control method in a conventional magnetic disk apparatus, there is a method of switching between positioning control and speed control in order to move the head to a target track at high speed (seek operation) and follow the target track (following operation) (for example, , See Patent Document 1). In this control method, the acceleration mode is switched to the deceleration mode when the remaining distance reaches a certain value formulated or tabulated with respect to the total movement distance in the seek operation. The acceleration command value for the voice coil motor (hereinafter referred to as VCM) outputs an acceleration command value that is larger than the maximum acceleration that can be generated in the acceleration mode. In the deceleration mode, the acceleration command value is obtained up to the target track obtained at each sampling period. Using the remaining distance x and the actual speed v, a deceleration command value i = Cv ^{2 /} x (C: 0.5 to 1.0) is output to perform seek control. In other words, in a magnetic disk device equipped with such a control method, the current to the VCM is allowed to saturate during seeking, and the seek speed is increased by utilizing the limit of the seek capability.

  As another conventional magnetic disk device, there is an example in which the occurrence of off-track is suppressed by removing the bias of the bearing grease on the actuator shaft in order to perform high-speed seek and high-precision track following even in a low temperature environment ( For example, see Patent Document 2). In the magnetic disk device having such a configuration, after the power is turned on, a motor start command is issued, the spindle motor is started, and steady rotation of the spindle motor is realized. Next, the head is positioned on the zero cylinder and the longest distance seek is performed. Further, a 1/3 stroke seek is performed to position the head on the original zero cylinder. In this way, the bias of the grease is adjusted by performing the seek operation. Then, a pseudo seek operation is performed for a predetermined time or a predetermined number of times before supplying a ready signal indicating that the read / write operation can be started.

As another conventional magnetic disk device, the temperature dependence of the characteristics of the components such as the spindle motor and voice coil motor inside the device is detected, and temperature control is performed to suppress drive performance degradation such as high-precision positioning. (For example, refer to Patent Document 3). In such a magnetic disk device, a temperature adjustment unit for adjusting the temperature of the magnetic disk device main body by adjusting the temperature of the magnetic disk device main body by heating or cooling is provided, and position information included in servo information reproduced from the head, or Based on the current value of the spindle motor, the temperature-dependent characteristics of at least the rotating mechanism including the spindle motor and the VCM are detected, and the detected characteristics are compared with a preset specified value. When it is determined that the heater is in the temperature control section, the heater, the electric fan, or the like is operated so as to suppress the deterioration of the characteristics.
JP-A-9-219074 Japanese Patent Laid-Open No. 5-274772 JP 2003-323790 A

  However, in the conventional head control method in the magnetic disk apparatus, the viscosity characteristic of the VCM pivot bearing grease changes in a low temperature environment, particularly in an environment below freezing point, and the viscosity resistance of the grease increases. As a result, when the head actuator including VCM is operated at high speed, such as seek operation and load / unload operation, the drive current becomes very large, and current for acceleration / deceleration and constant speed control as designed cannot be applied. . As a result, there is a problem that head positioning control cannot be performed at high speed and with high accuracy.

  In addition, there is the following problem even when a long seek operation such as a full stroke or a 1/3 stroke seek is performed in a low temperature environment to remove the bias of the bearing grease on the actuator shaft and reduce the resistance. That is, the friction term in the positioning control system can eliminate the influence of friction, but no improvement is made regarding the viscosity term proportional to the speed. Further, since the improvement is due to the long seek operation, it cannot be used for load control for moving the head onto the disk. Therefore, although head positioning following is effective, when driving at high speed control such as seek operation and load / unload operation, the drive current increases and current for acceleration / deceleration and constant speed control as designed is applied. Can not. As a result, there is a problem that head positioning control cannot be performed at high speed and with high accuracy.

  In addition, in the method of controlling the temperature of the magnetic disk device by the temperature control unit, it is possible to improve the bearing grease viscosity resistance of the actuator shaft by applying heat in a low temperature environment, but it requires heat transfer time. , Waiting time will occur. Alternatively, heat is always applied when the temperature is low, and power consumption increases. There is also a problem that an additional heat source is required.

  The present invention solves the above-mentioned problems, and in the speed control of seek operation and load / unload, the viscous resistance is temporarily reduced by applying minute amplitude vibration to the actuator against the change of the viscous resistance of the actuator pivot bearing grease due to low temperature. It is an object of the present invention to provide a head control device and a disk device using the head control device, which can be made smaller, increase reliability, and perform high-speed seek and stable load / unload.

  In order to achieve this object, a head controller of the present invention comprises a spindle motor that rotates a disk, actuator means that moves the head to a target position on the disk, vibration applying means that vibrates the actuator means, and actuator means. A drive unit that outputs a control drive current for driving; a speed determination unit that determines a target moving speed of the head; and an environment detection unit that detects or estimates an operating environment temperature, and according to the output of the environment detection unit And a viscosity control means for controlling and driving a vibration applying means for applying vibration to the actuator means.

  In the above configuration, the environment detection unit may be configured to estimate the operating environment temperature based on the control amount output from the speed control unit or the spindle control amount for controlling the spindle motor to rotate at a constant speed.

  In the above configuration, the vibration applying means may be a piezoelectric element or an electromagnetic drive element. Furthermore, the frequency of the vibration generated by the vibration applying means is a frequency different from the servo frequency, and in particular, it may be configured to be ultrasonic vibration.

  In the above configuration, the environment detection unit may be configured to estimate the operating environment temperature based on the control amount that is the output of the speed control unit. Further, when the operating environment temperature estimated by the environment detecting means is −5 ° C. or lower, or the control drive current is more than three times the current value at the operating environment temperature 20 ° C., the viscosity control means applies vibration to the actuator means. You may make it have the function to command to a vibration application means.

  This configuration prevents saturation of the control drive current during high-speed seek due to increased viscosity of the pivot bearing of the head actuator, especially at low temperatures, and lower speed, and unstable operation due to saturation of the control drive current during load / unload. can do. As a result, stable head speed control enables high-speed seek and stable load / unload of the head, improving the load / unload reliability and reducing the access time by high-speed seek. Can be realized.

  In the above configuration, the viscosity control means has a control operation monitoring means for judging normal completion of the operation when performing load control for moving the head onto the disk or unload control for moving the head from the disk to the retracted position. However, when normal completion is not possible, a configuration may be adopted in which a command for applying vibration to the actuator means is output to the vibration applying means.

  In the above configuration, the environment detection unit may output a signal corresponding to the output from the temperature sensor provided for detecting the operating environment temperature to the viscosity control unit.

  With this configuration, when performing high-speed seek control for moving the head to the target position and load / unload control for moving the head onto the disk, each operation can be performed reliably without failure. In particular, even in a low temperature environment, it is possible to distinguish between a failure of a load operation, an unload operation or a seek operation caused by an increase in the viscosity of the pivot bearing of the head actuator and a failure due to a defect of the head or other device. As a result, the operation can be surely completed. Therefore, unstable operation during loading, unloading or seeking can be prevented, and the reliability of loading / unloading can be improved, and a head control device and a disk device capable of high-speed seek operation can be realized. .

  According to the head control device and the disk device of the present invention, the saturation of the VCM control drive current at the time of high-speed seek due to the increase in the viscosity of the actuator pivot bearing at a low temperature, the reduction in speed, and the VCM control drive current at the time of load / unload Unstable operation due to the saturation of the data can be prevented, the reliability of loading / unloading can be improved, and high-speed data transfer by high-speed seek can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same element, the same code | symbol is attached | subjected and description may be abbreviate | omitted.

(First embodiment)
1 to 10 are diagrams for explaining a head control device and a disk device including the head control device according to the first embodiment of the present invention.

  FIG. 1 is a block diagram showing the configuration of the head control device. FIG. 2 is a plan view of an actuator having a vibration applying unit for exciting the actuator pivot bearing. FIG. 3 is a schematic cross-sectional view for explaining the configuration of the vibration applying unit.

  FIG. 4 is a block diagram showing a speed control unit in the head control device. FIG. 5 is a block diagram showing a state estimator in the speed control unit. FIG. 6 is a block diagram showing a speed determining unit in the head control device. FIG. 7 is a diagram showing temperature characteristics with respect to the control drive current of the VCM during speed control (seek control).

  FIG. 8 is a diagram for explaining the state of grease in the pivot bearing when ultrasonic vibration is applied. FIG. 8A is a conceptual diagram for explaining a change in the viscosity of grease due to ultrasonic vibration. FIG. 4 is a schematic diagram showing decomposition of a polymer component in grease by ultrasonic vibration.

  Further, FIG. 9 is a graph showing the time response of the head speed, the control drive current of the VCM, and the bias force at the time of seek operation. FIG. 9A shows the case where the environmental temperature is −10 ° C. (C) is a figure in case environmental temperature is +10 degreeC.

  FIG. 10 is a diagram showing time responses of the head speed, the VCM control drive current, and the bias force (estimated value) when seeking at an ambient temperature of −10 ° C. when the viscous resistance is small.

  In FIG. 1, a head 2 is mounted on a head slider 1, and an actuator 5 has the head slider 1 at the tip. The actuator 5 has a function of positioning the head 2 mounted on the head slider 1 to a target position, moving the head 2 onto a disk (not shown), or retracting the head 2 on the disk.

  As shown in FIG. 2, the actuator 5 has a vibration applying unit 11 on the side surface of the actuator 5. The vibration applying unit 11 has a configuration in which, for example, a thin film piezoelectric element is attached as a vibration applying means so that the pivot bearing 53 can be vibrated. When the environmental temperature is low, vibration can be applied to the pivot bearing 53 of the actuator 5 to reduce the viscous resistance of the grease of the pivot bearing 53.

  As shown in FIG. 1, the head control device is constituted by the actuator 5 provided with the vibration applying unit 11 and the speed control system 100 surrounded by a broken line. The position detector 3 in the speed control system 100 detects the current head position X from the servo signal P in the head signal output from the head 2. The position error detector 41 inputs the target position R of the head and the current head position X, and outputs a head position error PE that is the difference between them. The speed error detector 42 receives the target speed Vref and the current head speed V as inputs, and outputs a speed error VE that is the difference between them. The speed determination unit 8 is a speed determination unit that determines a target movement (seek) speed from three signals of the head position X, the head position error PE, and the target position R. The speed control unit 62 included in the control unit 6 is speed control means for deriving the control amount U based on the speed error VE.

  The drive unit 7 is a drive unit that receives the control amount U and outputs a control drive current I to the VCM 52 in order to drive the actuator 5.

  The environment detection unit 9 is an environment detection unit that outputs an environmental temperature with the control amount U as an input. The vibration applying unit 11 is a vibration applying unit that applies vibration to the pivot bearing 53 of the actuator 5. The viscosity control unit 10 is a viscosity control means for controlling the vibration application unit 11 based on an output signal from the environment detection unit 9.

  Here, the vibration application unit 11 as the vibration application unit and the speed control unit 62 as the speed control unit will be described with reference to FIGS. 3 and 4, respectively.

  In FIG. 3, the piezoelectric element that is the vibration applying unit 11 has a structure in which both sides of the piezoelectric thin film 112 are sandwiched between electrodes 111 and 113, and is configured to be affixed to a side surface of a pivot bearing 53 (not shown). . Here, the piezoelectric thin film 112 used is, for example, a PZT thin film, and the thickness thereof is about 5 μm. In addition, when the rectangular wave signal from the viscosity control unit 10 is applied to the electrodes 111 and 113 sandwiching both sides of the piezoelectric thin film 112, the piezoelectric thin film 112 vibrates. For example, Pt is used as the material of the electrodes 111 and 113. The piezoelectric element composed of the electrodes 111 and 113 and the piezoelectric thin film 112 is further coated with a resin. Further, an adhesive is used for sticking to the pivot bearing 53.

  In FIG. 4, the speed control unit 62 receives the speed error signal VE and inputs an integral control gain to a signal obtained by multiplying the speed error signal VE by the speed control gain Kv and an integral value of the speed error VE output from the integrator 624. The signal obtained by multiplying Ki and the signal obtained by multiplying the estimated bias force Fe value, which is the output of the state estimator 63, by the bias force control gain Kd are added by the adder 62A to output the control amount U.

  The state estimator 63 uses the control amount U and the difference Pee between the current position X and the estimated position Xe of the head as input signals, and the estimated position Xe of the head, the estimated speed Ve of the head, and the estimated bias force Fe applied to the actuator 5. Are estimated and output.

  The integrator 624 includes an adder 622A and a delay unit 625, and sequentially integrates the speed error signal VE that is an input signal for each control sampling time, and outputs an integrated value.

  In FIG. 4, the position signal selection unit 43 outputs the estimated position Xe of the head 2 to the position error detection unit 41 when seeking the head at high speed or when the current head position X cannot be detected.

  The state estimator 63 included in the speed control unit 62 will be described with reference to FIG.

  In FIG. 5, a block A, a block B, and a block C represent a state variable matrix 63A, an input variable matrix 63B, and an output variable matrix 63C, respectively, when the actuator 5 and the drive unit 7 are modeled. The gain ke is the gain of the VCM state estimation gain 63g. The block B which is the input variable matrix 63B is a variable of the control amount U. The block A which is the state variable matrix 63A has three variables of the head position Xe, the estimated speed Ve, and the bias force Fe. Further, a signal of a difference Pee between the current position X of the head 2 and the estimated position Xe is an input signal to the VCM state estimation gain 63g.

  Next, the speed determination unit 8 in the speed control system 100 will be described with reference to FIG. In FIG. 6, the speed determination unit 8. The target speed Vref is output using the target position R, the current position X of the head 2 and the head position error PE as input signals. Further, the target speed calculation unit 81 calculates a temporary target speed Vref0 according to (Equation 1) using the head position error PE as an input signal.

(Vref0) ² = 2 · a · PE (Formula 1)
Here, a is the acceleration during seek, and PE is the head position error.

  The movement direction detection unit 83 detects the target position R, the current head position X, and the movement direction. Here, in consideration of the vertical torque characteristics at the time of seek control, a correction signal is output at block 84, and this correction signal and the provisional target speed Vref0 that is the output of the target speed calculation unit 81 are input as input by block 85. The true target speed Vref is determined.

  Next, a method for suppressing the change in the viscosity resistance of the grease in the pivot bearing 53 of the actuator 5 with the temperature, particularly an increase in the viscosity resistance at a low temperature will be described.

  First, it is necessary to detect the environmental temperature. For this temperature detection, a temperature characteristic table of seek current as shown in FIG. 7 is previously stored in the memory, current at a constant speed during seek or peak current during acceleration / deceleration is detected, and the current value More current environmental temperature can be estimated. FIG. 7 shows four cases of the VCM control drive current I with respect to the environmental temperature from the target speed of 100 mm / sec to 400 mm / sec.

  In the present embodiment, as shown in FIG. 1, instead of directly measuring the control drive current I of the VCM, the control drive current I of the VCM is estimated by conversion from the control amount U, and the environment detection unit 9 Is used to estimate the ambient temperature.

  Another example of the method for detecting the operating environment temperature will be briefly described. A temperature characteristic table of at least one of the spindle starting current and driving current of the spindle motor that rotates the disk is previously stored in the memory, and the environment detecting unit 9 as temperature detecting means detects the spindle motor starting current or driving current. The current ambient temperature can be estimated from the current value. Instead of directly measuring the starting current or the driving current, the starting current or the driving current may be estimated by converting from a spindle control amount for controlling the spindle motor to rotate at a constant speed.

  In the environment detection unit 9 to which the control amount U is input, the environment temperature is estimated based on the control drive current I of the VCM estimated from the control amount U, and the seek current stored in advance when the environment temperature is −5 ° C. or lower. When the control drive current I is 3 times or more than the control drive current I corresponding to 20 ° C. in the temperature characteristic table, the viscosity control unit 10 that is the viscosity control unit uses the vibration application unit 11 that is the vibration application unit. A high frequency alternating signal is applied to the piezoelectric element, and vibration is applied to the pivot bearing 53. Here, since the control band is 500 Hz, it is necessary to apply vibration having a frequency sufficiently higher than the control frequency in the control band, for example, ultrasonic vibration, as the vibration application frequency for excitation.

  In FIG. 7 of the present embodiment, the control drive current I corresponding to −5 ° C. is about three times as large as the control drive current I corresponding to 20 ° C. Moreover, the voltage is 3V drive, and since it is a piezoelectric element, almost no current flows and power consumption is hardly affected.

  FIG. 8 is a diagram schematically illustrating a state of grease in the pivot bearing 53 when ultrasonic vibration is applied to the piezoelectric element of the vibration applying unit 11. As shown in FIG. 8A, vortex (cavitation) is temporarily generated in the grease at a low temperature due to ultrasonic vibration by the piezoelectric element. This vortex has the property of diluting the organic material, which reduces the viscosity of the grease. By performing the seek operation in this reduced viscosity state, it is possible to perform a seek operation with a low current even at a low temperature.

  Further, as shown in FIG. 8B, the polymer component in the grease is decomposed by ultrasonic vibration, and this decomposition reduces the molecular structure and reduces the viscous friction. Also, heat is generated by vibration. This heat raises the grease temperature, and the temperature characteristics improve so that the viscous friction is reduced. However, vibration is applied before seeking. Furthermore, when the vibration application is stopped, the vortex disappears. Therefore, vibration application is stopped even at low temperatures during track following that requires high-accuracy positioning.

  Next, as a head control device, the head control in the case where the environment detection unit 9, the viscosity control unit 10 and the vibration application unit 11 in FIG. 1 are not provided, that is, the pivot bearing 53 of the actuator 5 is a bearing having a viscous resistance due to grease. For the apparatus, the head speed V during the seek operation, the VCM control drive current I, and the time response of the estimated bias force Fe value are obtained, and these data are provided in the environment detection unit 9, the viscosity control unit 10 and the vibration application unit 11. Compare with the data of each case.

  FIG. 9 shows the time response of the head speed V, the control drive current I of the VCM, and the estimated bias force Fe value during the seek operation of the head control device without the environment detection unit 9, the viscosity control unit 10, and the vibration application unit 11. It explains using.

  9A, 9B, and 9C, the upper stage shows the head speed V, the middle stage shows the control drive current I of the VCM, and the lower stage shows the estimated bias force Fe. The horizontal axis is time. In this measurement, the head speed V is a target value of 400 mm / sec. A speed profile with acceleration of 72G and deceleration of -18G is the design value. The limit of the applied current is 200 mA.

  9 (a), 9 (b) and 9 (c), in addition to the current during acceleration and deceleration, the current value (estimated bias force Fe value) until reaching a constant speed decreases in temperature. It has increased along with it. Further, when the temperature is low, the time until the constant speed is reached becomes long. When the temperature is −10 ° C., the head speed V does not reach the target value of 400 mm / sec. This is a phenomenon that occurs when the viscosity resistance of the grease in the pivot bearing 53 of the actuator 5 varies with temperature. That is, the viscosity of the grease increases as the temperature decreases, and the VCM control drive current I with respect to the viscous resistance increases in proportion to the speed, resulting in saturation. When the control drive current I of the VCM increases, the power consumption increases, and the usable time is shortened in mobile applications.

  On the other hand, when the environment detection unit 9, the viscosity control unit 10, and the vibration application unit 11 are provided, the viscous resistance is reduced even when the environmental temperature is −10 ° C. as shown in FIG. Head speed V and VCM control drive current I and bias force (estimated) at the time of seeking corresponding to an environmental temperature of −10 ° C. with respect to a head control device that does not include the environment detection unit 9, the viscosity control unit 10, and the vibration application unit 11. The control drive current I of the bias force (estimated value) Fe and VCM is improved by about half with respect to the value (Fe). The head speed V has also reached the target speed of 400 mm / sec, and it has become clear that the seek operation or the load / unload operation can be performed at high speed. Therefore, the operation time can be shortened, and the stability and reliability of the seek operation or load / unload operation can be improved.

  Accordingly, by providing the control amount U as an input, the environment detection unit 9 and the viscosity control unit 10 are provided, and the vibration applying unit 11 using a piezoelectric element is provided in the pivot bearing 53 of the actuator 5, thereby enabling a bias force (estimated value) even at a low temperature. ) The control drive current I of Fe and VCM does not increase, and a seek operation or load / unload operation can be performed at high speed.

  As described above, according to the present embodiment, saturation of the VCM control drive current during high-speed seek due to increase in the viscous resistance of the actuator pivot bearing at low temperatures, resulting in low-speed seek operation, load unloading Unstable operation due to saturation of the control drive current of the VCM during the load operation can be prevented. As a result, the reliability of the load / unload operation can be improved, and a head control device and a disk device capable of high-speed data transfer by high-speed seek can be realized.

(Second Embodiment)
FIGS. 11-15 is a figure for demonstrating the head control apparatus concerning the 2nd Embodiment of this invention. FIG. 11 is a block diagram illustrating a configuration of the head control device. FIG. 12 is a circuit diagram showing a configuration of the counter electromotive voltage detection unit. FIG. 13 is a block diagram showing the configuration of the speed control unit. FIG. 14 is a block diagram illustrating a configuration of the load estimator. FIGS. 15A and 15B show the time response of the head speed (back electromotive voltage) and the VCM control drive current during the load operation. FIG. 15A shows the case where the environmental temperature is 20 ° C., and FIG. It is a figure in the case of 10 degreeC.

  11 is different from the head control device according to the first embodiment shown in FIG. 1 in that it has a back electromotive voltage detection unit 12 that derives the head speed from the back electromotive voltage of the VCM 52 of the actuator 5. And the configuration of the speed control unit 66 that calculates the control amount U using the output signal is different. The other basic configuration of the head control device is the same as that of the head control device according to the first embodiment. Therefore, the basic description will be omitted below, and differences from the head control device according to the first embodiment will be mainly described.

  When the head 2 is moved from the retracted position onto a disk (not shown), that is, a load operation is taken as an example, the operation of the head control device of the present embodiment will be described. In this case, there is no output signal from the head 2, and the head position cannot be detected by the output signal of the head 2. Therefore, there is no output from the position detector 3. Further, when the head position signal is not detected, the speed determination unit 8 outputs the load / unload speed of the head 2 as the target speed Vref. Note that the unload operation is the same as the load operation, and a description thereof is omitted here.

  In FIG. 11, since the head speed signal cannot be detected from the head signal, the head speed Vvcm is detected from the back electromotive voltage of the VCM 52. Here, the counter electromotive voltage detection unit 12 for detecting the head speed Vvcm will be described with reference to FIG.

  In FIG. 12, a detection resistor 522 is provided in series with the coil 521 of the VCM 52, and the driver LSI of the drive unit 7 applies a voltage to both ends thereof so that a control drive current proportional to the control signal flows at both ends. The differential detection units 524 and 527 detect the back electromotive voltage signal Vbemf proportional to the head moving speed by the VCM, and multiply the signal by the speed conversion gain Kb in the block 528 to output the head moving speed Vvcm by the VCM. Is configured to do.

  Next, as shown in FIG. 13, the speed control unit 66 calculates the control amount U using the speed error signal VE, which is an output from the comparator 66S that receives the head speed Vvcm and the target speed Vref, as input signals. ,Output. That is, the target speed Vref and the head speed Vvcm are input to the comparator 66S, and the difference is output as the speed error VE. A signal obtained by adding the signal obtained by multiplying the speed error VE by the gain Kv and the signal obtained by multiplying the load estimation signal Fb, which is the output of the load estimator 65, by the gain Kd, by the adder 64A is output as the control amount U. Here, the load estimator 65 uses the control amount U and the head speed Vvcm signal as input signals.

  Here, the load estimator 65 will be described with reference to FIG. The load estimator 65 includes an actuator model 651 and a low-pass filter (LPF) 652. The actuator model 651 is obtained by modeling a transfer function related to head movement by the actuator 5 with the same transfer function by an electric circuit. That is, the actuator model 651 performs a simulation operation of the positioning control system including the drive unit 7 and outputs an acceleration estimation signal Acce obtained by estimating the head acceleration by the actuator 5.

The load estimator 65 calculates the acceleration estimation signal Acce from the head speed signal Vvcm and calculates the acceleration signal Acc from the control signal U. That is, the acceleration obtained by multiplying the acceleration signal Acc obtained by multiplying the head speed signal Vvcm by the gain Kt · k _da of the block 655 and the control signal U for controlling the actuator 5 by the gain J / L · k _ad of the actuator model 651. The estimated signal Acce is compared by the comparator 653, and the difference is estimated as a disturbance component. The estimated disturbance component passes through the stabilization compensator (low-pass filter LPF) 652 and is output to the disturbance controller 654 as the load estimation signal Fb. The disturbance controller 654 changes the load estimation signal Fb to the dimension of the control signal, and outputs the disturbance compensation signal Uf to the adder 64A in FIG.

  The adder 64 </ b> A in FIG. 13 adds the disturbance compensation signal Uf generated by estimating the load disturbance and the control signal Uv, and outputs the control amount signal U to the drive unit 7.

  Therefore, the head detected by the counter electromotive voltage detection unit 12 from the counter electromotive voltage of the VCM 52 even during a load operation or an unload operation in which there is no head output signal from the head 2 and the head position cannot be detected by the output signal of the head 2. A control amount signal U calculated from the speed and the target speed Vref that is the load / unload speed of the head 2 output from the speed determination unit 8 when the head position signal is not detected is output to the drive unit 7. For this reason, the load / unload operation can be executed at high speed.

  For comparison with the head control device having the speed control system 110 (see FIG. 11) as described above, the head loading operation of the head control device using the actuator 5 in which the vibration applying unit 11 is not provided in the pivot bearing 53 is described. explain. FIG. 15 shows respective time response characteristics with respect to such a head control device with respect to the control drive current and the head speed of the VCM during the load operation at the environmental temperatures of 20 ° C. and −10 ° C. The horizontal axis is time. Further, FIG. 15 shows the control drive current of the VCM and the data corresponding to the VCM speed, that is, the head load speed, as Current and BEMF × 15, respectively. Current indicates data obtained by detecting the control drive current of the VCM as a voltage signal by the current probe, and BEMF × 15 indicates a signal obtained by detecting the voltage across the detection resistor 522 illustrated in FIG. .

  Comparing FIG. 15A and FIG. 15B, when the temperature is low (−10 ° C.), the control drive current of the VCM increases and the load speed becomes slower, and the time for the load operation becomes longer. It has become. This is a phenomenon that occurs when the viscosity resistance of the grease in the pivot bearing 53 of the actuator 5 varies with temperature. That is, the viscosity of the grease increases with a decrease in temperature, and the drive current for the viscous resistance increases in proportion to the speed. Further, FIG. 15C shows data when vibration is applied at a low temperature (−10 ° C.). It can be seen that it is improved by applying vibration.

  When the control drive current of the VCM increases, the power consumption increases, so that the usable time is shortened in mobile applications.

  On the other hand, as shown in FIG. 2 of the first embodiment, the vibration applying section 11 having a thin film piezoelectric element attached to the side surface of the actuator 5 is provided to apply vibration to the pivot bearing 53 of the actuator. When the speed control system 110 includes the environment detection unit 9 and the viscosity control unit 10, the following effects can be obtained. That is, when the environmental detection unit 9 detects that the environmental temperature is equal to or lower than a predetermined temperature, that is, a low temperature, the vibration that is the vibration applying unit is performed by the viscosity control unit 10 that is the viscosity control unit as in the first embodiment. A high frequency alternating signal is applied to the piezoelectric element of the applying unit 11 to vibrate the pivot bearing 53. Thereby, the viscosity of the grease of the pivot bearing 53 can be reduced. As a result, even when the temperature is low, the environmental resistance can be a viscous resistance similar to the viscous resistance in a normal temperature state (for example, 20 ° C.). Therefore, the respective time response characteristics with respect to the control drive current and the head speed of the VCM at the time of speed control (load control) have the same behavior as shown in FIG. 15A, for example.

  As described in the first embodiment, the operating environment temperature is estimated from the control drive current I of the VCM estimated from the control amount U, or is estimated from the spindle control amount for controlling the spindle motor to rotate at a constant speed. The operating environment temperature is estimated from the current. When the estimated operating environment temperature is 0 ° C. or less, the viscosity control unit 10 as the viscosity control unit applies a high-frequency alternating signal to the piezoelectric element of the vibration application unit 11 that is the vibration application unit, and vibrates the pivot bearing 53. Add. Here, it is necessary to apply vibration having a frequency sufficiently higher than the control frequency in the control band, for example, ultrasonic vibration, as the vibration application frequency for excitation. The voltage is 3V drive, and since it is a piezoelectric element, current hardly flows and power consumption is hardly affected. The control band is, for example, 500 Hz.

  Therefore, similarly to the first embodiment, even at a low temperature, by applying a high-frequency alternating signal to the piezoelectric element of the vibration applying unit 11 that is a vibration applying unit and applying vibration to the pivot bearing 53, the actuator 5 A decrease in viscosity due to vortices generated in the grease of the pivot bearing 53 and a decrease in viscous friction due to decomposition of polymer components and generation of heat occur. As a result, even at low temperatures, a load operation or an unload operation can be performed with a low current, power consumption can be kept small, and a load / unload operation can be performed at a high speed.

(Third embodiment)
16 and 17 are diagrams for explaining a head control device according to a third embodiment of the present invention.

  FIG. 16 is a block diagram illustrating a configuration of the head control device. FIG. 17 shows the time response of the head speed and the control drive current of the VCM in the load control in which the head is moved from the lamp position onto the disk when the environmental temperature is −10 ° C., (a) is a normal operation. In the case of time, (b) is a diagram in the case of malfunction.

  FIG. 16 is different from FIG. 11 for explaining the head control device according to the second embodiment in that it has a temperature sensor 21 and the viscosity control unit 10 performs load / unload operations and seek operations to a target position. The control operation monitoring unit 20 is a control operation monitoring unit that determines whether or not the operation is normally completed.

  The other basic configuration of the head control device is the same as that shown in FIG. Hereinafter, differences from the head control apparatus according to the second embodiment will be described.

  When the head 2 is moved from the retracted position onto the disk, that is, a load operation is taken as an example, the operation of the head control device of the present embodiment will be described. In this case, as in the second embodiment, there is no output signal from the head 2, and position detection cannot be performed by the output signal from the head 2, and therefore there is no output from the position detection unit 3. Further, when the head position signal is not detected, the speed determining unit 8 outputs the load / unload speed of the head 2 as the target speed. Since the unload operation is the same as the load operation, the description is omitted.

  In FIG. 16, the temperature sensor 21 directly measures the environmental temperature and inputs the output to the environment detection unit 9. Further, when a signal corresponding to the environmental temperature is output to the viscosity control unit 10 and it is determined that the environmental temperature is low, as in the first embodiment and the second embodiment, the viscosity control means is used. The viscosity control unit 10 applies a high-frequency alternating signal to the piezoelectric element of the vibration applying unit 11 serving as a vibration applying unit to apply vibration to the pivot bearing 53.

  Further, the control operation monitoring unit 20 has a speed profile at the time of loading, unloading and seeking in a memory in advance. Further, the head speed Vvcm output from the back electromotive voltage detection unit 12, the control drive current I of VCM output from the drive unit 7 and the output signal from the head 2 are input to the control operation monitoring unit 20 to load, unload. The head speed during loading or seeking is monitored.

  During the load operation or unload operation, the head speed signal cannot be detected from the output signal from the head 2. For this reason, the head speed V is detected from the counter electromotive voltage of the VCM 52 by the counter electromotive voltage detection unit 12 shown in FIG. 12 of the second embodiment, or the head speed V due to the counter electromotive voltage is not output, or The viscosity control unit 10 determines whether or not the load operation (or unload operation) is incomplete based on information such as a waveform that is different from the velocity profile stored in advance or the head position signal is not detected. Notify

  The viscosity control unit 10 that has received such an incomplete notification of the loading operation (or unloading operation) again applies vibration to the pivot bearing 53 by the vibration applying unit 11 to lower the viscous resistance of the grease, and then again. Performs load control operation. Note that even if the head is damaged, the head position signal is not detected, but the speed profile is detected and the difference is seen, so that the load operation failure due to low temperature is distinguished from the load operation failure due to head failure. It is possible.

  A head in load control in which the head 2 is moved from the ramp position (retracted position) onto the disk for each of cases where the load operation is normal operation and operation failure at an environmental temperature of −10 ° C. The respective time response characteristics of the control drive current I at the speed V and the VCM are shown in FIG. The horizontal axis is time. In FIG. 17, the control drive current of the VCM and the data corresponding to the speed of the VCM, that is, the load speed of the head are shown as Current and BEMF × 15, respectively. Current indicates data obtained by detecting the control drive current of the VCM as a voltage signal by the current probe, and BEMF × 15 indicates a signal obtained by detecting the voltage across the detection resistor 522 illustrated in FIG. .

  As shown in FIG. 17B, in the case of a malfunction in the load operation, since the head 2 has not moved up to the disk, a state in which the large VCM control drive current I still flows continues. Thus, since the time response characteristic waveforms are different for both the head drive speed V and the control drive current I for the VCM, it is possible to distinguish between normal and defective load operations.

  Accordingly, the control operation monitoring unit 20 detects the difference between at least one of the time response characteristics and the speed profile of the head current V and the control current I of the VCM, and determines the presence or absence of the head output signal. The load operation, the unload operation and the seek operation are surely performed. In particular, the load operation or unload operation at a low temperature can be reliably completed.

  In the first to third embodiments, the vibration applying unit 11 as the vibration applying unit is a piezoelectric element. However, a high-frequency signal is applied to the VCM to cause the actuator to swing with a small amplitude. You may add the high frequency vibration (for example, ultrasonic vibration) to produce. The high-frequency vibration is, for example, ultrasonic vibration, but may not be the same as the control band, and may be a frequency higher than the control band, for example, vibration of 5 kHz.

  In the present embodiment, the same effect can be obtained with respect to the torque characteristics of the actuator even when the force is generated in the direction perpendicular to the disk.

  In the first embodiment to the third embodiment, the vibration applying unit 11 is configured to have a piezoelectric element attached to the swing shaft of the actuator. However, the present invention is not limited to this. Other configurations may be used as long as the pivot bearing 53 of the actuator 5 can be vibrated. Moreover, it is not restricted to a piezoelectric element, For example, you may use an electromagnetic drive element.

  In the first embodiment, the piezoelectric thin film is a thin film PZT having a thickness of 5 μm. However, the present invention is not limited to this, and other thicknesses and other piezoelectric materials may be used.

  In the first and third embodiments, the head movement (seek control) when the head 2 is on the disk and the load control for moving the head 2 onto the disk have been mainly described. In the case of unload control in which the head 2 on the disk is moved to the ramp position (retracted position), the same effect can be obtained.

  The head control device and the disk device according to the present invention saturate the control drive current of the VCM during high-speed seek by increasing the viscosity of the pivot bearing of the head actuator at a low temperature, thereby reducing the speed and controlling the VCM during load / unload. Unstable operation due to saturation of drive current can be prevented, load / unload reliability can be improved and high-speed data transfer by high-speed seek is possible, which is useful as a magnetic disk device etc. It can also be used for applications.

1 is a block diagram showing the configuration of a head control device according to a first embodiment of the invention. The top view of the actuator which has a vibration application part for vibrating an actuator pivot bearing in the head control apparatus concerning the embodiment Schematic cross-sectional view for explaining the configuration of a vibration applying unit in the head control device according to the same embodiment The block diagram which shows the speed control part in the head control apparatus concerning the embodiment The block diagram which shows the state estimator in a speed control part in the head control apparatus concerning the embodiment The block diagram which shows the speed determination part in the head control apparatus concerning the embodiment The figure which shows the temperature characteristic with respect to the control drive current of VCM at the time of speed control (seek control) in the head control apparatus concerning the embodiment. The figure explaining the state of the grease in a pivot bearing when ultrasonic vibration is applied in the head control device according to the same embodiment The head control apparatus concerning the embodiment WHEREIN: The figure which shows the head speed at the time of a seek operation | movement, the control drive current of VCM, and the time response of bias force In the head control device according to the embodiment, when the viscous resistance becomes small, the head speed at the time of seeking at the ambient temperature of −10 ° C., the control drive current of the VCM, and the time response of the bias force (estimated value) are shown. Illustration FIG. 3 is a block diagram showing a configuration of a head control device according to a second embodiment of the present invention. The circuit diagram which shows the structure of the back electromotive force detection part in the head control apparatus concerning the embodiment The block diagram which shows the structure of a speed control part in the head control apparatus concerning the embodiment The block diagram which shows the structure of a load estimator in the head control apparatus concerning the embodiment In the head control device according to the same embodiment, a diagram showing the time response of the head speed (back electromotive voltage) during load operation and the control drive current of the VCM. The block diagram which shows the structure of the head control apparatus concerning the 3rd Embodiment of this invention. In the head control apparatus according to the embodiment, when the environmental temperature is −10 ° C., the head speed and the time response of the control drive current of the VCM in the load control for moving the head from the lamp position onto the disk are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head slider 2 Head 3 Position detection part 5 Actuator 6 Control part 7 Drive part 8 Speed determination part 9 Environment detection part 10 Viscosity control part 11 Vibration application part 12 Back electromotive voltage detection part 20 Control action monitoring part 21 Temperature sensor 41 Position error Detection unit 42 Speed error detection unit 43 Position signal selection means 52 Voice coil motor (VCM)
53 Pivot bearing 62, 66 Speed control unit 62A, 64A, 622A Adder 63 State estimator 63A State variable matrix 63B Input variable matrix 63C Output variable matrix 63g VCM state estimation gain 65 Load estimator 66S, 653 Comparator 81 Target speed calculation Unit 83 Movement direction detection unit 84, 85, 528, 655, A, B, C Block 100, 110 Speed control system 111, 113 Electrode 112 Piezoelectric thin film 521 Coil 522 Detection resistance 524, 527 Differential detection unit 624 Integrator 625 Delay 651 Actuator model 652 Low-pass filter LPF (stabilization compensator)
654 Disturbance controller Acc acceleration signal Acce acceleration estimation signal a acceleration Fb load estimation signal Fe bias force (estimated value) (estimated bias force)
I Control drive current Kb, Kd, ke, Ki, Kv Gain P Servo signal PE Head position error Pee difference R Target position U Control amount (control signal, control amount signal)
Uf Disturbance compensation signal Uv control signal V, Vvcm Head speed (signal)
Vbemf Back electromotive force signal VE Speed error (signal)
Ve Estimated speed Vref Target speed Vref0 Temporary target speed X Head position (current position)
Xe estimated position

Claims (12)

A spindle motor that rotates the disk;
An actuator for moving the head to a target position on the disk;
Vibration applying means for vibrating the actuator;
Driving means for outputting a control driving current of a voice coil motor for driving the actuator;
Speed determining means for determining a target moving speed of the head;
Environmental detection means for detecting or estimating the operating environmental temperature,
A head control device comprising: a viscosity control means for controlling and driving the vibration applying means for applying vibration to the actuator means in accordance with an output of the environment detecting means. When the operating environment temperature estimated by the environment detection means is −5 ° C. or lower, or the control drive current is more than three times the current value at the operating environment temperature 20 ° C., the viscosity control means vibrates the actuator means. The head control device according to claim 1, wherein the head control device has a function of commanding application to the vibration applying unit. The head control apparatus according to claim 1, wherein the environment detection unit estimates the operating environment temperature based on a control amount that is an output of the speed control unit. The head control device according to claim 1, wherein the environment detection unit estimates the operating environment temperature based on a spindle control amount for controlling the spindle motor to rotate at a constant speed. The viscosity control means has a control operation monitoring means for judging normal completion of operation in load control for moving the head onto the disk or unload control for moving the head from the disk to a retracted position, 2. The head control apparatus according to claim 1, wherein a command for applying vibration to the actuator means is output to the vibration applying means when normal completion is not possible. The head control apparatus according to claim 5, wherein the environment detection unit outputs a signal corresponding to an output from a temperature sensor provided to detect an operating environment temperature to the viscosity control unit. The control operation monitoring means has a memory for speed profiles during loading, unloading and seeking, and the time response characteristics of the control drive current of the voice coil motor and the load, unload and seek stored in the memory. 7. The head control device according to claim 5, wherein whether the operation is normal or abnormal is determined based on a comparison with time speed profile data and presence / absence of head signal detection. The head control apparatus according to claim 1, wherein a frequency of vibration generated by the vibration applying unit is a frequency different from a servo frequency. The head control apparatus according to claim 8, wherein the vibration generated by the vibration applying unit is ultrasonic vibration. The head control apparatus according to claim 1, wherein the vibration applying unit is a piezoelectric element. The head control device according to claim 1, wherein the vibration applying unit is an electromagnetic drive element. A disk device comprising the head control device according to any one of claims 1 to 12.

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