JPH07113652B2 - Inspection method of magnetic disk device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inspection method for a magnetic disk device, and more particularly to an assembly defect, a defect, an abnormality, and a malfunction due to aging at the time of manufacturing an actuator of the magnetic disk device. The present invention relates to a magnetic disk device inspection method suitable for early detection.

[Conventional technology]

Magnetic disk devices tend to have large capacity and high density year after year,
With the increase of the linear recording density, the recording density in the track direction is becoming higher and higher. With this increase in density, an actuator for positioning the magnetic head on a desired track of the magnetic disk is required to have a high positioning accuracy on the order of submicron of 1 μm or less. In order to achieve this high positioning accuracy, it is necessary to develop an actuator with low vibration and low deformation. Further, the servo control circuit for controlling the positioning of the actuator is also required to perform high-precision servo control in consideration of frictional force received from the actuator rails and bearings and external force due to air flow. Therefore, as a conventional technique, for example, as described in Japanese Patent Laid-Open No. 57-6470, an external force value is stored in advance in a memory in accordance with a cylinder address (track address), and this value is read out at the time of access to external force. The method of correcting is done.

[Problems to be solved by the invention]

However, the above-mentioned prior art does not consider the change in external force over time. That is, even if the external force is not generated at first, the external force is generated when the mechanical parts such as the bearing for guiding the movement of the actuator are subsequently worn. However, in the above-mentioned conventional technique, since the external force correction value is a predetermined value, it is not possible to follow such a temporal change, which may cause a positioning error. Also,
Generally, most of the current magnetic disk devices have a closed structure for the purpose of dust prevention, so that the inside of the enclosure cannot be seen after assembly. As a result, there is a possibility that contact or interference between parts may occur due to defects during assembly, or that minute foreign matter (such as chips such as screws) may adhere to or mix with the actuator bearing, causing abnormal external force detection. is there. Generally, this kind of failure often occurs as a failure such as malfunction of the actuator over time, and it is necessary to detect it early. Further, it is desirable that such detection can be performed nondestructively at any time in the actual operating state of the magnetic disk device, but this cannot be performed by the conventional technology.

Therefore, the object of the present invention is to avoid an increase in the positioning error of the actuator by detecting an abnormal external force accompanied by a change with time due to actuator friction of the magnetic disk device even in an actual operating state at an early stage. Another object of the present invention is to provide a magnetic disk device inspection method for improving the reliability of the magnetic disk device.

[Means for solving problems]

In order to achieve the above object, in the inspection method of the magnetic disk device of the present invention, a detection means for detecting the fluctuation of the external force acting on the actuator by measuring the drive signal of the actuator generated by the magnetic head positioning servo control circuit is provided. The defect (defect, abnormality) of the actuator of the magnetic disk device is determined based on the detection result of the detecting means.

In a preferred embodiment, the above-mentioned detecting means is constructed so as to be sequentially carried out over all the tracks in the stationary state of the magnetic head for each track, and it is judged whether or not the tracks are defective by combining these.

[Action]

 Next, the operation based on the above configuration will be described.

The servo control circuit of the magnetic disk device controls the drive circuit so that the reference servo head has a zero positioning error at the desired track, and positions the actuator. Therefore, when there is no external force, the drive signal output of the actuator is almost zero.
On the other hand, even when external force acts on the actuator,
Similarly, the servo control circuit tries to position the servo head to zero error, and therefore generates a predetermined signal necessary for canceling the external force to the drive circuit of the actuator. The external force can be easily obtained based on the magnitude of the drive signal and the thrust of the actuator. Therefore, by measuring the magnitude of the drive signal, the presence or absence of external force and its magnitude can be known, and the abnormality of the actuator can be detected.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a magnetic disk device applied to the embodiment of the present invention, and FIG. 3 is a block diagram of a servo control circuit of the magnetic disk device in the embodiment of the present invention.

As shown in FIG. 2, the magnetic disk device applied to this embodiment includes a magnetic disk 1, a spindle 2, a magnetic head 3, and a carriage.
It is equipped with 4, guide rail 5, rail housing 6, bearing 7, coil 8, permanent magnet 9, and FPC10 (flexible printed circuit). Magnetic disk 1 is spindle 2
And is rotated by a motor (not shown). Further, the actuator for the magnetic disk device of this embodiment is
Carriage 4 with magnetic head 3 mounted, multiple bearings 7 for moving the carriage linearly, rail housing 6
A guide rail 5 that is held by the guide rail 5 and guides the bearing 7, and a coil 8 that is connected to the carriage 4 and serves as a movable portion of a linear motor (not shown). Further, a so-called voice coil motor (hereinafter referred to as VCM) is formed by the magnetic circuit including the coil 8 and the permanent magnet 9, and the carriage 4 is driven by a command of the control device 18 (see FIG. 1 described later) to move the magnetic head 3 to the magnetic head 3. A desired track of the magnetic disk 1 is accessed and a positioning operation is performed. Further, the FPC 10 is connected to the carriage 4 which is a movable part, and exchanges the read voltage of the magnetic head 3 and the drive signal of the power amplifier 16. Also,
In FIG. 3, the servo signal 11 read from the servo head 3a is amplified by a preamplifier 12 and then converted by a position demodulation circuit 13 into a position signal 13a. The position control circuit 14 sends a signal to the power amplifier control circuit 15 so that the position signal 13a becomes zero, and drives the VCM via the power amplifier 16. The current sense circuit 17 is a power amplifier.
The drive signal of 16 is detected, and the operation state of the power amplifier 16 is fed back to the power amplifier control circuit 15 so that an appropriate track follow operation can be performed.

1 is a block diagram of the external force measuring apparatus according to the embodiment of the present invention, and FIG. 4 shows a measurement flow chart of the external force measuring apparatus according to the embodiment of the present invention. First
In the figure, the entire servo control circuit of FIG. 3 is shown as a magnetic disk device MD and a current sense circuit 17. The magnetic disk device MD of this embodiment is connected to the control device 18 and performs an access operation according to a command from the connection device 18.
The magnitude of the external force is measured by a digital voltmeter 19 as a current sense voltage 17a which is the output of the current sense circuit 17 of the magnetic disk device. Further, the control device 18 and the digital voltmeter 19 are connected to the microcomputer 20 and issue an access command, transmit an external force measurement value, and the like according to a command from the microcomputer 20.

The external force is measured according to the flow chart shown in FIG. First, in order to initialize the measurement system, the internal memory (not shown) of the microcomputer 20 is cleared (41) The range of the digital voltmeter 19 is set, and the control device 18 is returned to the magnetic disk device.・ Two-zero instruction 42 is issued. When the return-to-zero is completed (43) and the magnetic disk device enters the track follow state, the zero track current sense voltage 17a is measured (44) and transmitted to the microcomputer 20 and stored in the internal memory (not shown). Stored in (45). Next, the first track is accessed (46), and the same operation is sequentially performed up to the innermost track, which is the maximum track (47 to 49). The measurement for each track is performed with the magnetic head resting on each track (track follow state). If the current sense voltage 17a is measured for all tracks, the external force value is calculated based on the force constant determined by the current sense voltage 17a and the VCM of the magnetic disk device (50), and the external force value is calculated for all tracks. It is printed out by the ivy printer 21.

5 (a) and 5 (b) are diagrams showing the results of measuring the external force in the embodiment of the present invention. The curve 22 in FIG. 5 (a) shows a normal case, and the curve 22a shows an abnormal case. Also, FIG. 5 (b)
Curves 22b and 22c of 2 indicate cases where both are abnormal. In the magnetic disk device of the linear access type as shown in FIG. 2, in a normal case, the leakage magnetic flux (not shown) generated from the permanent magnet 9 attracts the magnetic material connected to the actuator such as the bearing 7. However, since it acts as an external force, the absolute value of the external force generally becomes maximum at the zero track which is the outermost track where the bearing 7 is close to the permanent magnet 9 as shown in 22, and becomes smaller as the inner track moves away from the permanent magnet 9. . In addition, its polarity is a suction force and is negative. If the FPC 10 is in contact with and interferes with the permanent magnet 9 due to defective assembly, the reaction force due to the bending of the FPC 10 acts as an external force, so that the external force becomes large at the outer circumference track like 22a.
The polarity is positive in the direction that pushes the carriage 4 toward the inner track. Further, if foreign matter is mixed in the bearing 7 or if dust or the like is attached to the guide rail 5, a track for supporting the load of the carriage 4 at the defective portion due to rolling of the bearing 7 at the time of access. Since the external force changes rapidly at, the external force value becomes like 22b. When the rolling surface of the bearing 7 or the running surface of the guide rail 5 is abraded over time, the external force becomes large at the worn portion, so that the external force change with respect to the track position is 22c. Changes irregularly. Thus, the current sense voltage
By sequentially measuring 17a over all tracks, changes in external force due to wear of the mechanical parts, especially the actuator traveling system due to defects during assembly or changes with time can be found early. Such a defective assembly, defect, or abnormality can be found by the means for monitoring the characteristics shown in FIG. Further, it is also possible to automatically discriminate a defective product from the normal characteristic curve that deviates from the predetermined limit value. Although only the case where the external force measurement is performed on the linear access type magnetic disk device is disclosed here, it goes without saying that the same can be applied to the rotary access type device. In addition, it is desirable that the measurement in the embodiment of the present invention be performed immediately after assembly and during safety.

〔The invention's effect〕

As described in detail above, according to the inspection method of the magnetic disk device of the present invention, based on the result of detecting the fluctuation of the external force acting on the actuator by measuring the drive signal of the actuator generated by the magnetic head positioning servo control circuit. Since it is configured to determine whether the actuator is defective, it is possible to detect an external force abnormality due to a defective assembly of the magnetic disk device or a change with time of mechanical parts at any time early. It is possible to prevent the deterioration of the positioning accuracy and the positioning failure, and to improve the reliability of the magnetic disk device.

[Brief description of drawings]

FIG. 1 is a block diagram of an external force measuring apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of a magnetic disk device applied to the embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. A block diagram of a servo control circuit of a magnetic disk device applied, FIG. 4 is a flow chart showing an external force measuring method in one embodiment of the present invention, and FIGS. 5 (a) and 5 (b) are one embodiment of the present invention. FIG. 5 is an explanatory diagram showing a relationship between a track position and an external force value in FIG. 1 ... Magnetic disk, 3 ... Magnetic head, 4 ... Carriage, 5 ... Guide rail, 6 ... Rail housing,
7 ... Bearing, 8 ... Coil, 9 ... Permanent magnet, 10 ... Flexible print circuit, 15 ... Power amplifier control circuit, 16 ... Power amplifier, 17 ... Current sense circuit (variation detecting means), 18 ... Control device, 19 ... Digital voltmeter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Suzuki 2880 Kokufu, Odawara-shi, Kanagawa Stock company Hitachi Ltd. Odawara factory (72) Inventor Toneki Une 2880, Kozu, Odawara, Kanagawa Hitachi Odawara factory (72) Inventor Tomio Suzuki 2880, Kozu, Odawara-shi, Kanagawa Hitachi, Ltd. Odawara factory (72) Inventor Hiroshi Nishida 2880, Kozu, Odawara, Kanagawa Hitachi Ltd. Odawara factory (72) Inventor Hiroyuki Mitsuhashi 2880, Kozu, Odawara-shi, Kanagawa Within Hitachi Computer Equipment Co., Ltd. (72) Inventor Jiro Mochida 2880, Kozu, Odawara-shi, Kanagawa Hitachi Ltd. (72) Innovator Matsumoto, Tokuhiko Matsuda, Odawara-shi, Kanagawa 2880 Hitachi Computer Equipment Co., Ltd. (72) Inventor Eiji Sabota 2880 Kozu, Odawara-shi, Kanagawa Hitachi Computer Equipment Co., Ltd. (72) Inventor Toshihiko Saito 393 Totsuka-cho, Totsuka-ku, Yokohama, Kanagawa Hiritshonan Electronics Co., Ltd. 56) References JP-A-62-182674 (JP, A)

Claims (2)

[Claims] 1. An inspection system for a magnetic disk device, comprising: an actuator for moving a magnetic head mounted on a carriage to position the magnetic head at a desired track of a magnetic disk; and a servo control circuit for controlling the motion of the actuator. An inspection of a magnetic disk device, characterized by comprising detection means for detecting a fluctuation of an external force acting on the actuator by measuring a drive signal of the magnetic disk device, and determining a defect of the magnetic disk device based on a detection result of the detection means. method. 2. The inspection of the magnetic disk device according to claim 1, wherein the detection by the detection means is carried out every time the actuator is sequentially positioned on each track and brought into a track follow state. method.