JP3461218B2 - Magnetic disk drive and head control method applied to the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device having a magnetic head that floats above a magnetic recording medium by an air bearing, and a head control method applied to the device.

[0002]

2. Description of the Related Art Generally, a magnetic head of a magnetic disk device floats with a minute gap maintained by a relative speed with a magnetic recording medium. If this minute gap (flying height) is too small, it may cause trouble such as head crash. Therefore, it is important to properly set the flying height of the head in the magnetic disk device.

Conventionally, when setting the flying height of a head in a magnetic disk device, first, the flying height (hereinafter referred to as the static flying height) is measured while the head is stationary (stopped). This is because the read / write operation is performed while the head is stationary (stopped). And
The levitation amount of the apparatus is set by giving a certain margin to the measured static levitation amount.

If this margin is large, a sufficient flying height (static flying height) can be secured even if there is some variation. However, in order to increase the recording density, the flying height must be minimized, and therefore the margin cannot be made sufficiently large.

However, in the so-called TF (TaperFlat) head which is applied to the conventional magnetic disk drive,
As shown in FIG. 7, since the flying height (static flying height) differs depending on the head position, the above problem was remarkable.

Therefore, in recent years, a so-called TPC (Transversal Pressurizing Contour) head has been adopted, which is capable of making the static flying height almost constant without being influenced by the head position, as disclosed in, for example, USP 4,673,996 and USP 4,870,519. is there. The static flying height characteristics of this TPC head are shown in FIG.

[0007]

As described above, conventionally, in order to set the flying height of the head, the static flying height (the flying height during the read / write operation in which the head is stationary) is set.
Was measured, and the measured static levitation amount had a certain margin.

However, the head is flying not only during the read / write operation but also during the seek operation, for example. Therefore, the present inventors measured the flying height of the head (hereinafter referred to as the dynamic flying height) during seek operation (at the time of full track seek). For example, in the case of a TF head, FIG.
In the case of the TPC head, the dynamic flying height characteristics shown in FIG. 10 were obtained. Here, FIG.
FIGS. 10A and 10A show a flying height characteristic when full track seek is performed on a 2.5-inch magnetic recording medium (disk) from an inner circumference (ID) to an outer circumference (OD). 9 (b) and FIG. 10 (b) show the flying height characteristics when a full track seek is performed from the outer circumference (OD) to the inner circumference (ID). In FIG. 9 and FIG. 10, the static flying height characteristics are shown by broken lines for comparison.

In the conventional magnetic disk device, the head is moved at the same speed in any of seeks in the inner circumference → outer circumference (ID → OD) and outer circumference → inner circumference (OD → ID) directions. . Therefore, even in the full track seek when obtaining the above dynamic flying height characteristic, as shown in FIG. 11, inner circumference → outer circumference (ID → OD) and outer circumference → inner circumference (OD →
The same seek speed (pattern) similar to the conventional one is applied to each of the IDs. Further, regarding the seek acceleration (pattern thereof), as shown in FIG. 12, the same absolute value (acceleration direction, that is, acceleration) in inner circumference → outer circumference (ID → OD) and outer circumference → inner circumference (OD → ID). Only the relationship of deceleration is reversed). Although two types of seek acceleration patterns are shown in FIG. 12, since the absolute values are the same, only one of the patterns needs to be prepared.

As is apparent from FIGS. 9 and 10, the TF
In both the head and the TPC head, the dynamic flying height of the head has a larger variation due to the head position than the static flying height. Further, the dynamic flying height decreases when moving from the inner circumference to the outer circumference. Further, the fluctuation amount of the dynamic flying height is large on the outer peripheral side and the inner peripheral side, that is, during acceleration (acceleration region) and deceleration (deceleration region).

The present inventors have analyzed the factors of the fluctuation and reduction of the dynamic levitation amount as described above, which will be described below.

First, the head of the magnetic disk device floats at a relative speed with respect to the magnetic recording medium as described above. The flying height is the magnetic recording medium (disk) with respect to the longitudinal centerline of the slider part of the head (centerline of the head).
It changes depending on the traveling speed and the traveling direction of.

When the head is stationary at a certain radial position on the medium, the rotational speed of the medium times the peripheral speed of the radius becomes the running speed of the head (the slider portion thereof), and the center line of the slider portion and the medium The angle formed by the tangential direction of is the traveling direction (yaw angle).

However, when the head moves in the radial direction by the seek operation, the traveling direction of the head with respect to the medium is the direction in which the vector of the velocity in the tangential direction of the medium and the vector of the seek velocity are combined.

FIG. 13 shows how the velocity vectors are combined. First, when the head (here, the TPC head) stands still at a certain radial position of the medium and is flying, the traveling speed of the head (of the slider portion) with respect to the medium is the peripheral velocity a in the figure, and the yaw angle is Is θ y. However, when a seek operation is performed, a seek speed b (when seeking from the inner circumference to the outer circumference) or b ′ (when seeking from the outer circumference to the inner circumference) is added, so that the yaw angle is increased. Changes from θy to θy ′ (inner circumference → outer circumference) or θy ″ (outer circumference → inner circumference). Obviously, when the head seeks from the inner circumference to the outer circumference, On the contrary, when the head seeks from the outer circumference to the inner circumference, the yaw angle changes in the smaller direction.

The present inventors have shown in FIGS. 9 and 10 how the yaw angle changes due to the seek direction (inner circumference → outer circumference or outer circumference → inner circumference) and seek speed (target speed during seek). It was assumed that this was related to the fluctuation of the head flying height (dynamic flying height), and the seek direction and seek speed were changed for each of the TF head and the TPC head, and the yaw angle dependence of the head flying height was obtained.

The yaw angle dependence of the flying height of the head is calculated by TF
The head is shown in FIG. 14 and the TPC head is shown in FIG.

As is clear from FIGS. 14 and 15, the head flying height strongly depends on the yaw angle. When the head flies on the inner circumference side (here, the radial position is 18.65 mm) on the medium, the peripheral speed is smaller than the outer circumference.
As shown in FIG. 4 (a) and FIG. 15 (a), the yaw angle is used in a state close to 0 °. When seeking toward the outer circumference from here, when the yaw angle increases as described with reference to FIG. 13 and the same seek speed (or target speed) as in the related art as shown in FIG. 11 is applied. In Fig. 14 (a)
And as shown in FIG. 15 (a), it becomes about 6 °, and the flying height also decreases. The decrease amount is larger in the TPC head.

On the other hand, on the outer peripheral side (here, the radial position is 27.48 m).
Since the peripheral speed increases at m), the head is
As shown in (b) and FIG. 15 (b), it is used with a yaw angle (here, about 10 °), and the flying height is suppressed. When seeking from here to the inner circumference,
As described with reference to FIG. 3, the yaw angle is reduced, and the same seek speed (or target speed) as the conventional one as shown in FIG. 11 is obtained.
When the above is applied, it becomes about 6 ° as shown in FIGS. 14B and 15B, and the flying height increases.

In this way, when the seek speed toward the outer circumference and the seek speed toward the inner circumference are the same as shown in FIG. 11, the yaw angle increases by the same speed vector when moving to the outer circumference. , The amount of levitation at that time (dynamic levitation amount) decreases and increases, respectively. Therefore, as a whole, the dynamic flying height characteristics shown in FIG. 9 (for the TF head) and FIG. 10 (for the TPC head) are given.

As described above, it became clear that the dynamic flying height of the head depends on the yaw angle. In particular,
The yaw angle dependence of the TPC head shown in FIG. 5 has a larger yaw angle dependence near zero yaw angle than the yaw angle dependence of the TF head shown in FIG. ing. This indicates that in the TPC head, the flying height is greatly reduced when the head moves from the inner circumference to the outer circumference during seek. Note that the TFC head is similar in that the flying height is lower when the head moves from the inner circumference to the outer circumference than when the head moves in the opposite direction.

As described above, the fluctuation of the dynamic flying height is particularly large on the outer peripheral side and the inner peripheral side, that is, during acceleration and deceleration (see FIGS. 9 and 10). The present inventors have also analyzed this factor and will describe it.

First, during acceleration / deceleration, as shown in FIG. 16, a roll moment M resulting from a deviation L between the center of gravity G of the head (slider portion) and the support position P is applied to the head (slider portion). Therefore, the roll posture increases,
The flying height fluctuates greatly. In particular, at the time of acceleration from the inner circumference to the outer circumference, since the outer circumference side of (the slider part of) the head where the electromagnetic transducer (transducer) T exists rolls downward, the minimum flying height decreases, which is the worst case.

The problems and their factors in the conventional magnetic disk device described above can be summarized as follows. First, in the conventional magnetic disk device, by adopting the TPC head instead of the TF head, the flying height of the head can be made constant without being influenced by the head position in a static state where the head does not move (a state where no seek is performed). It's starting to happen. However, when the head flying height was measured in a dynamic state in which the head moved (seek operation state), TF
Whether using a head or TPC head,
As shown in FIGS. 9 and 10, the flying height fluctuated and was not constant. In particular, when seeking from the inner circumference to the outer circumference, the flying height decreases, which causes factors such as head crashes and lowers the reliability of the device, as well as the high recording density required in recent years. It also hinders the realization of low levitation required for realization.

The present inventors have found that the reason why the flying height (dynamic flying height) fluctuates in a dynamic state is that the yaw angle changes by a velocity vector determined by the seek direction and seek speed, and When seeking from the circumference to the circumference, we have come to recognize that the dynamic flying height decreases due to an increase in the yaw angle.

Further, the inventors of the present invention, due to the roll moment applied during acceleration / deceleration of the head, particularly when accelerating from the inner circumference to the outer circumference, the outer peripheral side of the head (slider part) where the electromagnetic conversion portion (transducer) is present is lowered. It has also been recognized that since the roll rolls in the direction, the flying height is further reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic disk device capable of controlling the flying height of a head and a head control method applied to the same.

Another object of the present invention is to apply to a magnetic disk device and the same device which can prevent the dynamic flying height of the head from decreasing by controlling the movement of the head so that the yaw angle does not increase as much as possible during seek operation. It is to provide a head movement control method at the time of seeking.

Another object of the present invention is to provide a magnetic disk device and the same device which can prevent the dynamic flying height of the head from being lowered by controlling the movement of the head so that the roll moment applied during the seek operation can be minimized. An object of the present invention is to provide a head movement control method during seek that is applied.

[0030]

According to the first configuration of the present invention, in the magnetic disk device, the factors that cause the head flying height (dynamic flying height) to fluctuate when the head seeks are the seek direction and the seek speed. The yaw angle changes by the amount of the velocity vector determined by the (target velocity), and the dynamic levitation amount becomes the minimum during seek in the first direction from the inner circumference to the outer circumference on the magnetic recording medium. Paying attention to the fact that as the seek speed (target speed) increases, the yaw angle also increases, and the rate of decrease in flying height also increases, and the seek direction during seek operation is the first direction from the inner circumference to the outer circumference on the magnetic recording medium. Direction or second from the outer circumference to the inner circumference
When seeking in the first direction, the maximum seek speed or target speed is limited so that the maximum seek speed or target speed does not exceed a predetermined limit speed (limit value). It is characterized by having done.

In the first configuration, the yaw angle increases as the seek speed increases, and the rate of decrease in the flying height also increases. In the first direction (that is, from the inner circumference to the outer circumference of the magnetic recording medium). When seeking, the maximum seek speed or target speed is limited so as not to exceed the limit value. As a result, it is possible to suppress the fluctuation of the yaw angle during the seek operation and suppress the decrease in the dynamic flying height of the head.

In the second configuration of the present invention, when seeking in the first direction, the maximum seek speed or target velocity is set smaller than in the case of seeking the same distance in the second direction. Is characterized by.

In the above-mentioned second structure, when seeking in the first direction (that is, from the inner circumference to the outer circumference of the magnetic recording medium) in which the seek speed acts to increase the yaw angle, the maximum seek speed or the target speed is obtained. Is set to a small value, the velocity vector component acting on the increase of the yaw angle is also reduced, the increase amount of the yaw angle can be reduced, and the rate of the dynamic levitation amount can be reduced. On the other hand, when seeking in the second direction (that is, from the outer circumference to the inner circumference) in which the seek speed acts in the direction of decreasing the yaw angle, the maximum seek speed or the target speed is larger than that when seeking in the first direction. Therefore, the minimum flying height can be kept large while maintaining the average access time.

A third structure of the present invention is the magnetic disk device, wherein the electromagnetic conversion portion of the magnetic head is biased toward the outer peripheral side of the magnetic recording medium from the center line of the magnetic head.
Pay attention to the fact that when seeking in the direction of, the roll moment applied during acceleration / deceleration of the head causes a decrease in the flying height, and when seeking in the first direction, the maximum seek speed or target acceleration exceeds the limit value. This is characterized in that the maximum seek acceleration or the target acceleration is limited so as not to exist.

In the third configuration, the maximum seek speed or the target acceleration does not exceed the limit value when seeking in the first direction in which the flying height decreases due to the effect of the roll moment applied when the head is accelerated or decelerated. Therefore, it is possible to suppress the influence of the roll moment and prevent the flying height of the head from decreasing.

A fourth structure of the present invention is the magnetic disk device in which the electromagnetic conversion portion of the magnetic head is biased toward the outer peripheral side of the magnetic recording medium with respect to the center line of the magnetic head.
Paying attention to the fact that the roll moment applied to the head increases due to the magnitude of the acceleration when seeking in the direction of (especially when seeking toward the outer periphery on the inner peripheral side), which causes a decrease in the flying height. When seeking in the direction of, the seek maximum acceleration or the target acceleration is set smaller than in the case of seeking the same distance in the second direction.

In the fourth structure, since the acceleration (seek maximum acceleration or target acceleration) when seeking in the first direction is set to a small value, the roll moment applied to the head is minimized, It is possible to secure the minimum flying height (dynamic flying height) of the head.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a magnetic disk device (HDD) according to an embodiment of the present invention.
In FIG. 1, reference numeral 1 is a head (magnetic head) having an electromagnetic conversion unit (transducer) not shown. Head 1
Is held by the rotary actuator 2 and moves (seeks) in the radial direction of the 2.5-inch disk 3, for example.
To do. The head 1 floats on the disk 3 by an air bearing with a minute gap maintained by the relative speed of the disk 3. The rotary actuator 2 is rotationally driven in the radial direction of the disk 3 by a voice coil motor (VCM) 4. Rotary actuator 2 in the present embodiment
The positional relationship with respect to the disk 3 is the same as the conventional one. Here, when the head 1 is located on the inner peripheral side of the disk 3 (for example, radial position 18.65 mm), the yaw angle is used in a state close to 0 °, and it is located on the outer peripheral side (for example, radial position 27.48 mm). In some cases, it is used with a yaw angle (about 10 °) (however, when not seeking). Also, head 1
The electromagnetic conversion unit (transducer) (not shown) included in
As in the conventional case, it is located at a position deviated to the outer peripheral side of the disk 3 from the center line of the head 1 (center line in the longitudinal direction of the slider portion of the head 1).

The disk 3 is a spindle motor (SP
M) 3a rotates at high speed. The disk 3 has a format structure in which a large number of tracks are formed on both sides and each track is divided into a plurality of sectors. Each sector is roughly divided into a servo area for recording servo data for head positioning control and a data area for recording normal data (user data).

The voice coil motor (VCM) 4 serves as a drive source for the head 1 and is driven by the drive current supplied from the VCM driver 5. The VCM driver 5
The voice coil motor (VCM) 4 is driven by the control of the head positioning control circuit 8 described later.

The data recording / reproducing circuit 6 provides a data reproducing function of reproducing data from a read signal read by the head 1 (the electromagnetic conversion section of the head 1) and a write current corresponding to the write data given from the controller 9. It has a function of recording data supplied to the head 1. Data reproduced by the data reproducing function of the data recording / reproducing circuit 6 is roughly classified into servo data and user data.

The servo data detection circuit 7 records data
Servo data is detected from the reproduction data obtained from the reproduction circuit 6, position information of the head 1 is generated based on this servo data, and this is output to the head positioning control circuit 8.

The head positioning control circuit 8 performs positioning control (speed control) for positioning the head 1 on the target cylinder under the control of the controller (HDC) 9 based on the position information provided from the servo data detection circuit 7. To do. The head positioning control circuit 8 is realized by a ROM that stores a microprogram and the like, and a CPU (microprocessor) that operates according to the microprogram.

The controller (HDC) 9 controls the interface with the host device 10. The controller 9 demodulates the read data reproduced by the data recording / reproducing circuit 6 and transfers the read data to the host device 10 in response to a read command from the host device 10, or in response to a write command from the host device 10. In addition to modulating the write data from the host device 10 and outputting it to the data recording / reproducing circuit 6, here, the target to which the head 1 should move based on a specified address (logical address) from the host device 10. The cylinder number is obtained and given to the head positioning control circuit 8.

Next, the operation of the configuration of FIG. 1 will be described with reference to the flowchart of FIG. 2, focusing on the positioning control (speed control) by the head positioning control circuit 8.

When the host device 10 requests read / write access or seek, the controller 9
A target cylinder number indicating a target cylinder to which the head 1 is to be moved is generated from the logical address included in the request, and is output to the head positioning control circuit 8.

In response to this, the head positioning control circuit 8 executes the movement control of the head 1 to move (seek) the head 1 to the target cylinder. At this time, a read signal read from the disk 3 by the head 1 (electromagnetic conversion section of the head 1) is given to the data recording / reproducing circuit 6.

The data recording / reproducing circuit 6 reproduces data from the read signal read by the head 1. The servo data detection circuit 7 detects servo data from the data reproduced by the data recording / reproducing circuit 6. Then, the servo data detection circuit 7 generates position information of the head 1 based on the detected servo data and outputs it to the head positioning control circuit 8.

When the head positioning control circuit 8 obtains the position information from the servo data detection circuit 7 (step S1),
The moving speed of the head 1 is detected based on this position information (step S2). That is, the head positioning control circuit 8
The moving speed is obtained by calculating the moving distance from the position obtained by the current servo data and the position obtained by the preceding servo data and dividing this by one sector time. The one-sector time is the time obtained by dividing the time required for the disk to rotate once by the number of sectors per track.

In the head positioning control circuit 8, the moving direction (seek direction) of the head 1 is either the direction from the inner circumference to the outer circumference of the disk 3 (ID → OD), or the direction from the outer circumference to the inner circumference ( It is determined whether OD → ID) (step S3).

The head positioning control circuit 8 detects the target speed for the target cylinder based on the seek direction determination result and the position information obtained from the servo data detection circuit 7. A seek speed pattern (speed profile curve) is used to detect (determine) the target speed. This seek speed pattern is different from the conventional one, and is prepared for two types, one for seek from the inner circumference to the outer circumference (for ID → OD) and one for seek when going from the outer circumference to the inner circumference (for OD → ID). ing.

An example of these two kinds of seek speed patterns (in the case of full track seek) is shown by a solid line in FIG. This Figure 3
For comparison, a conventional seek velocity pattern is shown in FIG. Regarding the speed represented by the ID → OD seek speed pattern, the maximum speed (maximum seek speed) is particularly smaller than the conventional speed, and the OD → ID seek speed pattern is conversely large. Please note. Here, the maximum seek speed B of the ID → OD seek speed pattern is set to be about 20% smaller than the maximum seek speed A of the OD → ID seek speed pattern.

The seek direction determination result in step S3 is used to determine whether to apply the ID → OD seek speed pattern or the OD → ID seek speed pattern for detecting the target speed.

That is, when the head positioning control circuit 8 determines the seek direction from the inner circumference to the outer circumference (ID → OD), after calculating the number of remaining cylinders from the current position of the head 1 to the target cylinder, The target speed required to move the number of remaining cylinders is obtained from the ID → OD seek speed pattern (step S4).

On the other hand, when the seek direction from the outer circumference to the inner circumference (OD → ID) is determined, the head positioning control circuit 8 calculates the number of remaining cylinders from the current position of the head 1 to the target cylinder, and then The target speed required to move the remaining cylinder number is obtained from the OD → ID seek speed pattern (step S5).

Here, the speed (especially the maximum speed) represented by the seek speed pattern for ID → OD is smaller than that of the conventional seek speed pattern as described above.
Speed indicated by ID seek speed pattern (especially maximum speed)
Is larger than the conventional seek speed pattern (see FIG. 3). Therefore, the target speed differs depending on the seek direction even when the moving distance (remaining number of cylinders) is the same. Set fast. This difference is particularly remarkable when the target speed is the maximum speed.

As described above, in this embodiment, the seek speed (target speed) when seeking from the inner circumference to the outer circumference is reduced, and the seek speed (target speed) when seeking from the outer circumference to the inner circumference is increased. There is.

By decreasing (suppressing) the seek speed (target speed), especially the maximum seek speed (maximum seek speed) when seeking toward the outer circumference, the velocity vector component that acts to increase the yaw angle is also reduced. Since the amount of increase in the yaw angle can be reduced as a result of reduction, the extent to which the flying height decreases (when seeking toward the outer circumference) can be reduced.

On the other hand, when seeking toward the inner circumference, the seek speed (target speed), especially the maximum seek speed (maximum seek speed) is increased (compared to the conventional one), but since it works in the direction of decreasing the yaw angle (see FIG. 13 type of θy → θy ″), the flying height increases and there is no problem. Moreover, by increasing the seek speed (target speed) when seeking toward the inner circumference, the seek speed when seeking toward the outer circumference ( Target speed)
The average access time can be maintained at the conventional level by compensating for the seek time delay due to the reduction of.

The above-mentioned seek speed pattern (speed profile curve) is not actually prepared, but instead, a correspondence table (seek speed) of the number of remaining cylinders (movement amount) and speed (target speed) is used. Table) is used. This table is stored in the ROM in advance.

When the head positioning control circuit 8 obtains the target speed (seek speed) of the head 1 in step S4 or step S5, the difference (signed difference) between the target speed and the moving speed obtained in step S2. ) Is taken (step S6).

Next, in the head positioning control circuit 8, the moving direction (seek direction) of the head 1 is the direction from the inner circumference to the outer circumference (ID → OD) of the disk 3, or the direction from the outer circumference to the inner circumference. It is again determined whether it is (OD → ID) (step S7).

The head positioning control circuit 8 detects the target acceleration (acceleration / deceleration amount to give) based on the seek direction determination result and the difference (error speed) between the target speed and the moving speed obtained in step S6. Detection (determination) of this target acceleration
For this, a seek acceleration pattern (acceleration profile curve) is used. Two types of seek acceleration patterns are prepared, one for seek (ID → OD) from the inner circumference to the outer circumference and one for seek (OD → ID) from the outer circumference to the inner circumference.

An example of these two kinds of seek acceleration patterns (in the case of full track seek) is shown by a solid line in FIG. In FIG. 4, a conventional seek speed pattern is shown by a broken line for comparison. Regarding the acceleration represented by the ID → OD seek acceleration pattern, the maximum acceleration (seek maximum acceleration) is smaller in absolute value than the conventional one, and the OD → ID seek speed pattern is large. Please note that

The seek direction determination result in step S7 is used to determine whether to apply the ID → OD seek acceleration pattern or the OD → ID seek acceleration pattern for detecting the target acceleration.

That is, when the head positioning control circuit 8 determines the seek direction from the inner circumference to the outer circumference (ID → OD), it corresponds to the difference (error speed) between the target speed and the moving speed obtained in step S6. The target acceleration (acceleration / deceleration amount to give) is detected (determined) from the ID → OD seek acceleration pattern and is output to the VCM driver 5 as a control amount (step S8).

On the other hand, when the seek direction (OD → ID) from the outer circumference to the inner circumference is determined, the head positioning control circuit 8 determines the difference (error speed) between the target speed and the moving speed obtained in step S6. A corresponding target acceleration (acceleration / deceleration amount that gives) is detected (determined) from the OD → ID seek acceleration pattern and is output to the VCM driver 5 as a control amount (step S9).

The absolute value of the acceleration (particularly the maximum acceleration) represented by the ID → OD seek acceleration pattern is smaller than that of the conventional seek acceleration pattern as described above, and the OD → ID seek acceleration pattern is obtained. On the contrary, the absolute value of the acceleration (in particular, the maximum acceleration) is larger than that of the conventional seek acceleration speed pattern (see FIG. 4). Therefore, the target acceleration differs depending on the seek direction even when the difference between the target speed and the moving speed (error speed) is the same, and when seeking from the inner circumference to the outer circumference, it is set smaller than in the past, and the seek from the outer circumference to the inner circumference is reduced. Sometimes it is set larger than the conventional one. This difference is particularly remarkable when the target acceleration is the maximum acceleration.

As described above, in this embodiment, the seek acceleration speed (target acceleration) when seeking from the inner circumference to the outer circumference.
Is decreased, and the seek acceleration (target acceleration) at the time of seeking from the outer circumference to the inner circumference is increased.

By the way, the seek acceleration causes the head 1 (slider portion thereof) to generate a roll moment to roll the head 1 as described in the section of [Problems to be Solved by the Invention]. The amount decreases. In particular, at the time of acceleration from the inner circumference to the outer circumference, the head 1 (slider part of the head) having the electromagnetic conversion part (transducer)
It is the worst because it rolls in the direction that the outer peripheral side goes down.

However, in the present embodiment, the seek acceleration (target acceleration), especially the maximum seek acceleration (maximum seek acceleration) at the time of seeking toward the outer circumference is reduced (suppressed) as described above (compared with the prior art), whereby Since the roll moment can be reduced, the minimum flying height (dynamic flying height) of the head 1 can be secured.

The above-described seek acceleration pattern is not actually prepared, but instead of this, a correspondence table (seek acceleration table) between the error velocity and the acceleration (target acceleration) is used. This table is stored in the ROM in advance.

The flying height characteristic at the time of seeking toward the outer circumference when the above-described series of positioning control (speed control) is applied is shown by a symbol a1 in FIG. For comparison, for seek acceleration, the same value is used when seeking to the outer circumference as when seeking to the inner circumference (that is, the same seek acceleration pattern as the conventional one is applied), and only for the seek speed, the outer circumference is used. The flying height characteristic (that is, the flying height characteristic in which only the influence of the seek speed is taken into consideration) at the time of seeking toward the outer circumference when a smaller value is used during the seek to is indicated by a2. In addition, a flying height characteristic (static flying height characteristic) in a non-seeked state (seek velocity = 0, seek acceleration = 0) is denoted by a3, and the same velocity control as that of the conventional one (that is, the same seek velocity pattern as the conventional one) And a seek acceleration pattern), the flying height characteristic at the time of seeking toward the outer circumference is indicated by reference symbol a4.

As is apparent from FIG. 5, in consideration of the influence of the seek speed and the seek acceleration, the flying height characteristics (dynamic flying height characteristics) in which a smaller value is applied when seeking to the outer circumference than when seeking to the inner circumference ) A1 has the smallest decrease in the flying height with respect to the static flying height characteristic a3. Also, the flying height characteristic (dynamic flying height characteristic) a2 considering only the influence of the seek speed is
The reduction amount of the flying height is smaller than that of the conventional flying height characteristic (dynamic flying height characteristic) a4. However, since the flying height characteristic a3 does not consider the influence of the seek acceleration, the amount of decrease of the flying height on the inner peripheral side is slightly larger than that of the flying height characteristic a1.

In the above, as the seek velocity pattern (the seek velocity table corresponding thereto) and the seek acceleration pattern (the seek acceleration table corresponding thereto), ID →
The case where two types of OD and OD → ID are prepared has been described, but the present invention is not limited to this. For example, OD
→ Only the seek speed pattern and seek acceleration pattern for ID are prepared, and the target speed and target acceleration when seeking in the ID → OD direction are also based on the seek speed pattern and seek acceleration pattern for OD → ID. The configuration may be determined. This will be described with reference to the flowchart of FIG.

First, the head positioning control circuit 8 determines the head 1 based on the position information obtained from the servo data detection circuit 7.
The moving speed of (steps S11, S1
2) The target speed required to move the head 1 from the current position to the target cylinder is OD → regardless of the seek direction.
Obtained from ID seek speed pattern (step S1)
3).

Next, in the head positioning control circuit 8, the moving direction (seek direction) of the head 1 is the direction from the inner circumference to the outer circumference of the disk 3 (ID → OD), or the direction from the outer circumference to the inner circumference. It is determined whether or not (OD → ID) (step S14).

If the seek is from the outer circumference to the inner circumference (head movement), the head positioning control circuit 8
Use the obtained target speed as it is.

On the other hand, if the seek is from the inner circumference to the outer circumference, the head positioning control circuit 8 checks whether or not the obtained target speed exceeds a predetermined limit value (step S15). This limit value matches the maximum speed of the ID → OD seek speed pattern in the above embodiment.

If the target speed does not exceed the limit value, the head positioning control circuit 8 uses the calculated target speed as it is.

On the other hand, if the calculated target speed exceeds the limit value, that is, if the seek is from the inner circumference to the outer circumference and the target speed exceeds the limit value, the head positioning control circuit 8 , It is determined that the yaw angle is significantly increased by the velocity vector corresponding to the velocity, and the flying height (dynamic flying height) of the head 1 is significantly reduced. In order to prevent this, the target speed is set to the limit value. (Step S16).

When the head positioning control circuit 8 determines the target speed as described above, it detects the difference (error speed) between this target speed and the moving speed obtained in step S12 (step S17).

Next, the head positioning control circuit 8 sets the target acceleration (acceleration / deceleration amount giving) corresponding to the difference between the target speed and the moving speed obtained in step S17 to the seek acceleration for OD → ID regardless of the seek direction. The pattern is detected (step S18).

Next, the head positioning control circuit 8 moves the head 1 in the moving direction (seek direction) as in step S14.
However, the direction from the inner circumference to the outer circumference of the disc 3 (ID → O
D) or the direction from the outer circumference to the inner circumference (OD
→ ID) is determined (step S19).

If the seek is from the outer circumference to the inner circumference, the head positioning control circuit 8 uses the obtained target acceleration as it is.

On the other hand, if the seek is from the inner circumference to the outer circumference, the head positioning control circuit 8 checks whether or not the calculated target acceleration exceeds a predetermined limit value (step S20). This limit value matches the maximum acceleration of the ID → OD seek acceleration pattern in the above embodiment.

If the target acceleration does not exceed the limit value, the head positioning control circuit 8 uses the calculated target acceleration as it is (however, the signs are reversed).

On the other hand, if the calculated target acceleration exceeds the limit value, that is, if the seek is from the inner circumference to the outer circumference and the target acceleration exceeds the limit value, the head positioning control circuit 8 It is determined that the roll moment increases due to the acceleration, and the flying height (dynamic flying height) of the head 1 decreases, and in order to prevent this, the target acceleration is corrected to the limit value (step S21). .

When the head positioning control circuit 8 determines the target acceleration as described above, it outputs this target acceleration (acceleration / deceleration amount to give) to the VCM driver 5 as a control amount (step S22).

In this method, in the range where the target velocity (target acceleration) does not exceed the limit value, even if seeking from the inner circumference to the outer circumference, the same target as when seeking from the outer circumference to the inner circumference at the same distance is obtained. Velocity (target acceleration with the same absolute value) is used. However, within the range where the target speed (target acceleration) does not exceed the limit value, even if the same target speed (target acceleration) is used regardless of the seek direction, there is no decrease in the head flying height when seeking from the inner circumference to the outer circumference. It is slight and does not pose a problem in practical use. In other words, when the target speed (target acceleration) does not exceed the limit value, that is, when the head 1 moves a relatively short distance, it is not always necessary to reduce the target speed (target acceleration). Therefore, using the above method, in such a case, it is possible to seek without limiting the target speed (target acceleration),
The seek time (access time) can be shortened without lowering the reliability of the device.

Further, in the above-described embodiment, the increase in the yaw angle at the seek time (specifically, at the seek time from the inner circumference to the outer circumference) which causes a decrease in the head flying height (dynamic flying height) is reduced. Although the seek speed (target speed) or seek acceleration (target acceleration) is reduced, the rotational speed of the disk (recording medium) may be increased to relatively reduce the seek speed.

In the above embodiment, the case where the head in which the electromagnetic conversion portion is located on the outer peripheral side is used has been described.
It is also applicable when using a head located on the inner peripheral side. However, if seek acceleration is considered in this case,
Contrary to the above embodiment, it is necessary to reduce the value of the target acceleration (seek maximum acceleration) at the time of seeking toward the inner circumference, but this direction acts so that the flying height increases with the seek speed. There is little effect considering acceleration.

[0094]

As described in detail above, according to the present invention, the yaw angle is increased during the seek operation or the roll moment applied to the head is suppressed only by controlling the speed or the acceleration when the head is sought. Since it is possible to suppress the reduction in the flying height of the head, it is possible to prevent the occurrence of troubles such as a head crash and improve the reliability of the device. Further, since the reduction in the flying height of the head can be suppressed, the flying height of the head can be reduced and the recording density can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining positioning control (speed control) by a head positioning control circuit 8 in the same embodiment.

FIG. 3 is a diagram showing an example of a seek speed pattern applied in the embodiment.

FIG. 4 is a diagram showing an example of a seek acceleration pattern applied in the embodiment.

FIG. 5 shows the flying height characteristics when seeking toward the outer periphery in the same embodiment, considering the flying height characteristics when seeking only the seek speed, the flying height characteristics when not seeking, and the seek speed and the seek acceleration. The figure shown in contrast with the flying height characteristic of the conventional method which is not performed.

FIG. 6 is a flowchart for explaining an operation in the case where only a seek speed pattern and a seek acceleration pattern for OD → ID are prepared and positioning control (speed control) is performed.

FIG. 7 is a diagram showing static flying height characteristics when a TF head is used in a conventional magnetic disk device.

FIG. 8 is a diagram showing static flying height characteristics when a TPC head is used in a conventional magnetic disk device.

FIG. 9 is a diagram showing dynamic flying height characteristics when seeking toward the outer circumference and seeking toward the inner circumference when a TF head is used in a conventional magnetic disk device, in comparison with static flying height characteristics.

FIG. 10 is a diagram showing dynamic flying height characteristics when seeking toward the outer circumference and seeking toward the inner circumference when a TPC head is used in a conventional magnetic disk device, in comparison with static flying height characteristics.

FIG. 11 is a diagram showing an example of a seek speed pattern applied in a conventional magnetic disk device.

FIG. 12 is a diagram showing an example of a seek acceleration pattern applied in a conventional magnetic disk device.

FIG. 13 is a diagram for explaining that the yaw angle changes depending on the seek speed.

FIG. 14 is a diagram showing the yaw angle dependence of the head flying height when a TF head is used in a conventional magnetic disk device.

FIG. 15 is a diagram showing the yaw angle dependence of the head flying height when a TPC head is used in a conventional magnetic disk device.

FIG. 16 is a diagram for explaining a roll moment M applied to the head during a seek operation.

[Explanation of symbols]

1 ... Head, 2 ... Rotary actuator, 3 ... Disk (magnetic recording medium), 3a ... Spindle motor (SP
M), 4 ... Voice coil motor (VCM), 5 ... VCM
Driver, 6 ... Data recording / reproducing circuit, 7 ... Servo data detection circuit, 8 ... Head positioning control circuit, 9 ... Controller, 10 ... Host device.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-135521 (JP, A) JP-A-4-339371 (JP, A) JP-A-59-171079 (JP, A) JP-A-4- 205866 (JP, A) JP-A-5-120822 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 21/08 G11B 21/16-21/26

Claims (16)

(57) [Claims] 1. A magnetic disk device comprising a head positioning control means for controlling the positioning of a magnetic head floating above a magnetic recording medium by means of an air bearing, wherein the head positioning control means has a seek direction during seek operation of the magnetic recording. the seek direction determining means for determining whether the second direction toward the inner circumference from a first direction or the outer periphery toward the outer periphery on the medium from the inner periphery, the first direction by the seek direction discrimination means Is determined
The head to seek in the first direction.
The maximum seek speed will not exceed the specified speed limit
And a head movement control means for limiting the maximum seek speed. 2. A magnetic disk device comprising a head positioning control means for controlling the positioning of a magnetic head floating above a magnetic recording medium by means of an air bearing, wherein the head positioning control means has a seek direction during seek operation of the magnetic recording. the seek direction determining means for determining whether the second direction toward the inner circumference from a first direction or the outer periphery toward the outer periphery on the medium from the inner periphery, the first direction by the seek direction discrimination means Is determined
The head to seek in the first direction.
In this case, make sure that the target speed does not exceed the specified speed limit.
And a head movement control means for limiting the target speed. 3. A magnetic head flying above a magnetic recording medium by an air bearing, wherein the magnetic recording medium is located from the center line of the magnetic head.
In a magnetic disk device having a head positioning control means for performing positioning control of a magnetic head in which an electromagnetic conversion portion exists at a position biased to the outer peripheral side of the body, the head positioning control means causes the seek direction during seek operation to be the magnetic recording. the seek direction determining means for determining whether the second direction toward the inner circumference from a first direction or the outer periphery toward the outer periphery on the medium from the inner periphery, the first direction by the seek direction discrimination means Is determined
The head to seek in the first direction.
If the maximum seek speed does not exceed the specified limit acceleration,
And a head movement control means for limiting the maximum seek acceleration. 4. A magnetic head flying above a magnetic recording medium by an air bearing, wherein the magnetic recording medium is located from the center line of the magnetic head.
In a magnetic disk device having a head positioning control means for performing positioning control of a magnetic head in which an electromagnetic conversion portion exists at a position biased to the outer peripheral side of the body, the head positioning control means causes the seek direction during seek operation to be the magnetic recording. the seek direction determining means for determining whether the second direction toward the inner circumference from a first direction or the outer periphery toward the outer periphery on the medium from the inner periphery, the first direction by the seek direction discrimination means Is determined
The head to seek in the first direction.
If the target acceleration does not exceed the prescribed limit acceleration,
And a head movement control means for limiting the target acceleration. 5. A magnetic disk device comprising a head positioning control means for controlling the positioning of a magnetic head floating above a magnetic recording medium by means of an air bearing, wherein the head positioning control means has a seek direction during seek operation of the magnetic recording. Seek direction determining means for determining whether it is a first direction from the inner circumference to the outer circumference or a second direction from the outer circumference to the inner circumference on the medium; and the first direction by the seek direction determining means. When the head is sought and the seek is performed in the first direction, the head movement control means for setting the seek maximum speed to be smaller than that in the case where the same distance is sought in the second direction. A magnetic disk device characterized in that. 6. A magnetic disk device comprising a head positioning control means for controlling the positioning of a magnetic head flying above a magnetic recording medium by means of an air bearing, wherein the head positioning control means has a seek direction during seek operation of the magnetic recording. Seek direction determining means for determining whether it is a first direction from the inner circumference to the outer circumference or a second direction from the outer circumference to the inner circumference on the medium; and the first direction by the seek direction determining means. When it is determined that the head seeks in the first direction, head movement control means for setting the target speed of the head to be smaller than in the case of seeking the same distance in the second direction. A magnetic disk device comprising: 7. A magnetic head flying above a magnetic recording medium by an air bearing, wherein the magnetic recording medium is located from the center line of the magnetic head.
In a magnetic disk device having a head positioning control means for performing positioning control of a magnetic head in which an electromagnetic conversion portion exists at a position biased to the outer peripheral side of the body, the head positioning control means causes the seek direction during seek operation to be the magnetic recording. Seek direction determining means for determining whether it is a first direction from the inner circumference to the outer circumference or a second direction from the outer circumference to the inner circumference on the medium; and the first direction by the seek direction determining means. When the head is sought in the first direction, the head movement control means for setting the seek maximum acceleration to be smaller than in the case where the same distance is sought in the second direction. A magnetic disk device characterized in that. 8. A magnetic head flying above a magnetic recording medium by an air bearing, wherein the magnetic recording medium is located from the center line of the magnetic head.
In a magnetic disk device having a head positioning control means for performing positioning control of a magnetic head in which an electromagnetic conversion portion exists at a position biased to the outer peripheral side of the body, the head positioning control means causes the seek direction during seek operation to be the magnetic recording. Seek direction determining means for determining whether it is a first direction from the inner circumference to the outer circumference or a second direction from the outer circumference to the inner circumference on the medium; and the first direction by the seek direction determining means. When the head is sought in the first direction, the head movement control means for setting the target acceleration of the head to be smaller than that in the case of seeking the same distance in the second direction. A magnetic disk device comprising: 9. A head movement control method at the time of seek applied to a magnetic disk device having a magnetic head that floats above the magnetic recording medium by an air bearing, wherein a seek direction at the time of seek operation is an inner circumference on the magnetic recording medium. From the outer circumference to the outer circumference or the second direction from the outer circumference to the inner circumference, and a case where the first direction is determined in this first step , Shi
The head maximum speed is restricted so that the maximum peak speed does not exceed a predetermined speed limit, and the head is moved to the first direction.
And a second step of causing the seek to proceed in the opposite direction . 10. A head movement control method during seek applied to a magnetic disk device having a magnetic head that floats above the magnetic recording medium by an air bearing, wherein the seek direction during seek operation is an inner circumference on the magnetic recording medium. From the outer circumference to the outer circumference or the second direction from the outer circumference to the inner circumference, and a case where the first direction is determined in this first step ,Eye
A second step of limiting the target speed so that the velocity does not exceed a predetermined speed limit and causing the head to seek in the first direction. Method. 11. A magnetic head which floats on a magnetic recording medium by an air bearing, wherein the magnetic recording is performed from a center line of the magnetic head.
In a head movement control method at the time of seek applied to a magnetic disk device having a magnetic head in which an electromagnetic conversion portion exists at a position deviated to the outer peripheral side of the medium, a seek direction at the seek operation is an inner peripheral direction on the magnetic recording medium. From the outer circumference to the outer circumference or the second direction from the outer circumference to the inner circumference, and a case where the first direction is determined in this first step , Shi
Make sure that the maximum acceleration does not exceed the specified acceleration limit.
Wherein said head places restrictions on the seek maximum acceleration a
A second step of seeking in the direction of 1. The head movement control method at the time of seeking. 12. A magnetic head which floats on a magnetic recording medium by an air bearing, wherein the magnetic recording is carried out from a center line of the magnetic head.
In a head movement control method at the time of seek applied to a magnetic disk device having a magnetic head in which an electromagnetic conversion portion exists at a position deviated to the outer peripheral side of the medium, a seek direction at the seek operation is an inner peripheral direction on the magnetic recording medium. From the outer circumference to the outer circumference or the second direction from the outer circumference to the inner circumference, and a case where the first direction is determined in this first step ,Eye
A second step of limiting the target acceleration so that the standard acceleration does not exceed a predetermined limit acceleration and causing the head to seek in the first direction. Head movement control method during seek. 13. A head movement control method at the time of seek applied to a magnetic disk device having a magnetic head flying above the magnetic recording medium by an air bearing, wherein a seek direction at the time of seek operation is an inner circumference on the magnetic recording medium. From the first direction toward the outer circumference or from the second direction toward the inner circumference from the outer circumference, and the first direction is determined in the first step, A second step of setting the seek maximum speed to be smaller when seeking the head in the first direction than in seeking the same distance in the second direction. Head movement control method during seek. 14. A head movement control method at the time of seek applied to a magnetic disk device having a magnetic head that floats above the magnetic recording medium by an air bearing, wherein the seek direction at the seek operation is an inner circumference on the magnetic recording medium. From the first direction toward the outer circumference or from the second direction toward the inner circumference from the outer circumference, and the first direction is determined in the first step, The second step of setting the target speed smaller when seeking the head in the first direction than in the case of seeking the same distance in the second direction. Head movement control method during seek. 15. A magnetic head flying over the magnetic recording medium by an air bearing said magnetic recording than the center line
In a head movement control method at the time of seek applied to a magnetic disk device having a magnetic head in which an electromagnetic conversion portion exists at a position deviated to the outer peripheral side of the medium, a seek direction at the seek operation is an inner peripheral direction on the magnetic recording medium. From the first direction toward the outer circumference or from the second direction toward the inner circumference from the outer circumference, and the first direction is determined in the first step, A second step of setting the seek maximum acceleration smaller when seeking the head in the first direction than when seeking the same distance in the second direction. Head movement control method during seek. 16. A magnetic head flying over the magnetic recording medium by an air bearing said magnetic recording than the center line
In a head movement control method at the time of seek applied to a magnetic disk device having a magnetic head in which an electromagnetic conversion portion exists at a position deviated to the outer peripheral side of the medium, a seek direction at the seek operation is an inner peripheral direction on the magnetic recording medium. From the first direction toward the outer circumference or from the second direction toward the inner circumference from the outer circumference, and the first direction is determined in the first step, A second step of setting the target acceleration smaller when seeking the head in the first direction than when seeking the same distance in the second direction. Head movement control method during seek.