JPH09203630A - Projection detection sensor, projection detection apparatus and projection detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a projection on a magnetic recording medium by detecting a change of a temperature due to an energy obtained when a resistance body butts against the projection and detecting the projection. SOLUTION: In order to manufacture a projection detection sensor 1, first, a Permalloy film is formed by vapor deposition at a rear end of a head slider 5. The Permalloy film is the etched by dry etching thereby to form a resistance body 4. Lead wires 2, 3 are formed at both ends of the Permalloy film. A sensor 1 is constituted in this manner. The sensor 1 utilizes an energy converter into heat among an energy of the resistance body 4 generated when the resistance body 4 butts against a projection on a magnetic disk 6. The resistance body 4 is exposed at a surface of the slider 5. Therefore, the energy generated when the resistance body 4 butts against the projection on the magnetic disk 6 is directly converted into heat by the resistance body 4 because of no intervening substance. A detecting sensitivity of the sensor 1 is accordingly enhanced, so that even a minute projection can be detected by the sensor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting a protrusion on a magnetic recording medium on which information such as data and programs is recorded and reproduced by magnetism, a device for detecting the protrusion, and a method for detecting the protrusion. .

[0002]

2. Description of the Related Art As a magnetic recording medium, there is, for example, a magnetic disk or a magnetic tape. Examples of a device that records information on a magnetic disk and reproduces the information recorded on the magnetic disk include a hard disk device and a flexible disk device. Magnetic films are formed on both surfaces of the magnetic disk built into the hard disk drive, and information is track-shaped on the magnetic film by a magnetic head mounted on a head slider floating above the surface of the magnetic disk. Information recorded and recorded in a track shape on the magnetic film is reproduced. The mechanism for driving the flying head slider on which the magnetic head is mounted and the drive for driving the magnetic disk are pre-installed inside the housing, so that data and the like are recorded at a relatively high density. It is also possible to access recorded data and the like at high speed.

Since the magnetic films formed on both surfaces of the magnetic disk are formed by sputtering or the like, projections may be formed on the surface of the magnetic film immediately after the film formation. These projections may adversely affect the recording and reproduction of information by the magnetic head mounted on the head slider, so it is necessary to remove the projections. Therefore, a head slider on which a waffle head having a filing function is mounted is arranged on the surface of the magnetic disk, and the waffle head is moved in the radial direction of the magnetic disk while rotating the magnetic disk to scrape off the protrusions. . After the protrusion removal is completed, a head slider on which the protrusion detection sensor is mounted is arranged on the surface of the magnetic disk, and the protrusion detection sensor is moved in the radial direction of the magnetic disk while rotating the magnetic disk. The presence or absence of protrusions that could not be removed is detected.

A piezoelectric element is used in the conventional protrusion detection sensor. Then, the protrusion detection method is such that the head slider on which the piezoelectric element is mounted is levitated on the magnetic disk at an arbitrary flying height, and vibration generated when the head slider collides with the protrusion higher than the flying height is generated by the piezoelectric element. The projection is detected by the output voltage from the piezoelectric element according to the degree of the collision. The vibration of the head slider at this time does not occur due to the loss of the flying stability of the head slider due to the protrusion, but in most cases, it is natural vibration that occurs when an impact is applied to the head slider. Therefore, the vibration frequency of the voltage observed from the piezoelectric element also becomes the natural frequency of the head slider.

[0005]

The above-described conventional method for detecting protrusions on a magnetic recording medium has the following three problems. The first problem is that it takes a long time for the vibration of the head slider to settle. This vibration settling time varies somewhat depending on the damping constant of the head slider, but is about 1.5 when the output voltage of the piezoelectric element disappears after the head slider collides with the protrusion.
ms. The rotation speed of the magnetic disk is about 3 when detecting protrusions.
Since it is 600 rpm, it is about 14 mm when the head slider is located near the radius of 25 mm of the magnetic disk.
While traveling, the protrusions cannot be detected during this period.

The second problem is that the detection sensitivity of the piezoelectric element is limited. The natural vibration of the head slider may be weak depending on the shape of the protrusion, and in this case, the weak natural vibration may not propagate to the piezoelectric element, so that the protrusion cannot be detected. When a protrusion that cannot be detected by such a piezoelectric element remains and collides with the magnetic head, the bulk inductive head does not damage the head itself, but the MR head using the magnetoresistive effect has a function. Since the film is exposed on the surface of the head slider, the head itself may be damaged.

A third problem is that, in the case of a magnetic disk radially divided into a data recording area and a control signal recording area by a concavo-convex portion formed on the surface, a non-protrusion is detected as a protrusion. Is. When the head slider flies over a magnetic disk on which irregularities are formed, the flying height of the head slider fluctuates when moving from the data recording area to the control signal recording area.
When the fluctuation of the flying height occurs, the head slider vibrates by receiving the acceleration from the magnetic disk, so that the piezoelectric element outputs a voltage and detects it as a protrusion.
Therefore, it is not possible to determine whether the output voltage is due to the collision between the head slider and the protrusion or the variation in the flying height of the head slider, and the protrusion cannot be detected. Generally, when discriminating a voltage, the magnitude, frequency, phase, etc. of the voltage are used. However, in the above case, the output voltage due to the collision between the head slider and the protrusion and the output voltage due to the change in the flying height of the head slider vary depending on the size of the protrusion and the shape of the control signal recording area. It is difficult to make a distinction based only on the magnitude, and it is also difficult to make a distinction based on the frequency, phase, etc. of the output voltage because both output voltages are waveforms that vibrate at the natural frequency of the head slider.

In view of the above points, an object of the present invention is to provide a protrusion detection sensor, a protrusion detection method, and a protrusion detection device capable of accurately detecting protrusions on a magnetic recording medium.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide a sensor for detecting a protrusion on a magnetic recording medium on which information is magnetically recorded and reproduced, by means of energy obtained when the protrusion collides. This is achieved by detecting a change in temperature and detecting the protrusion.

According to the above construction, the protrusion is detected by utilizing the thermal energy of the collision energy with the protrusion, so that the protrusion can be detected with high accuracy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. It is not limited to these forms unless otherwise stated.

FIG. 1 is a perspective view showing an embodiment of a protrusion detecting sensor of the present invention. The protrusion detection sensor 1 includes a resistor 4 which is an element in which lead wires 2 and 3 are connected to both ends.
Is provided at the rear end of the head slider 5. As the material of the resistor 4, for example, the thermal conductivity is 60.
Permalloy having a W / mK to 80 W / mK and a resistance value of 27Ω is used. As a material for the lead wires 2 and 3, for example, copper is used. The head slider 5 has a size of a general nano slider. When manufacturing such a protrusion detection sensor 1, first, permalloy is formed on the rear end of the head slider 5 by a vapor deposition method to have a film thickness of 60 nm, for example. Next, the permalloy film is etched to a length of 10 μm and a width of 2.5 μm by a dry etching method to form a resistor 4. Then, the lead wires 2 and 3 are formed of copper on both ends of the permalloy film to form the protrusion detection sensor 1.

The protrusion detecting sensor 1 utilizes the energy converted into heat, out of the energy obtained by the resistor 4 when the resistor 4 collides with the protrusion on the magnetic recording medium, for example, the magnetic disk 6. It is a thing. That is, since the energy converted into heat raises the temperature of the resistor 4 and raises the resistance of the resistor 4, the protrusion on the magnetic disk 6 is detected by detecting the change in the resistance value of the resistor 4. Can be detected. Here, the resistor 4 is exposed on the surface of the head slider 5. By doing so, the energy when the resistor 4 collides with the protrusion on the magnetic disk 6 is mediated. Without resistor 4
Since it is directly converted into heat by itself, the protrusion detection sensor 1
It is possible to increase the detection sensitivity of and detect even minute protrusions.

Although the resistor 4 is formed of a thin film, by doing so, the heat capacity of the resistor 4 is reduced, so that the resistance value of the resistor 4 is small even when a small amount of energy is applied to a minute protrusion. Changes, and the thermal diffusivity of the resistor 4 increases, so that the protrusion detection time, that is, the time from when the resistor 4 collides with the protrusion on the magnetic disk 6 until the resistor 4 stabilizes. Becomes shorter. Since the lead wires 2 and 3 are connected to both ends of the resistor body 4, a constant current source is connected to the lead wires 2 and 3 to supply a constant current to the resistor body 4, It is possible to detect a change in the resistance value of the device as a change in voltage.

First, the detection of protrusions on the magnetic disk 6 having a generally flat surface was examined. The magnetic disk 6 used had cylindrical bumps with a diameter of 30 μm and a height of 40 nm, and the radius of the magnetic disk 6 was 20 mm, 24 mm, and 28 m.
The bump disks are arranged linearly in the radial direction at each position of m. The flying height of the head slider 5 was changed by arranging the head slider 5 at a position where the radius of the bump disk was 28 mm and changing the relative speed between the head slider 5 and the bump disk. That is, the larger the relative speed between the head slider 5 and the bump disk, the larger the flying height of the head slider 5.

FIG. 2 is a diagram showing the relationship between the output voltage of the protrusion detection sensor 1 and the flying height of the head slider 5. As is apparent from FIG. 2, the output voltage of the protrusion detection sensor 1 becomes smaller when the flying height of the head slider 5 is larger than the height of the bump, and becomes smaller when the flying height of the head slider 5 is smaller than the height of the bump. Will be extremely large. The waveform of the output voltage of the protrusion detection sensor 1 is shown in FIG.
As shown in FIG. 3B, when the flying height of the head slider 5 is larger than the height of the bump, a downward convex waveform is generated, as shown in FIG.
As shown in, when the flying height of the head slider 5 is smaller than the height of the bump, the waveform is convex upward. This is for the following reason.

When the flying height of the head slider 5 is larger than the height of the bump, the resistor 4 does not collide with the bump, but when the resistor 4 passes over the bump, the resistor 4 and the bump disk surface are separated. The distance is reduced by the height of the bump. As a result, the thermal resistance between the resistor 4 and the bump disk becomes small, so that the heat of the resistor 4 is radiated to the bump disk side, and the resistance value of the resistor 4 becomes small. Therefore, the output voltage of the resistor 4 through which the constant current flows decreases. Also, when the flying height of the head slider 5 is smaller than the height of the bump, the resistor 4 collides with the bump, heat is generated in the resistor 4, and the resistance value of the resistor 4 increases. Therefore, the resistor 4 in which a constant current flows
The output voltage of is large. When the flying height of the head slider 5 and the height of the bump are substantially the same, it is considered that the effect of heat dissipation when approaching the bump and the effect of heat absorption when colliding with the bump are mixed. As described above, by using the resistor 4, it is possible to detect a protrusion on a magnetic disk whose surface is generally flat.

Next, the detection of protrusions on the magnetic disk 6 having an uneven surface is examined. The magnetic disk 6 used has an uneven portion (the black portion in FIG. 4B is convex) as in the plan view showing the entire shape of FIG. 4A and the plan view showing the partial shape of the surface of FIG. 4B. Is a magnetic disk 6 in which a data recording area (data zone) and a control signal recording area (servo zone) each of which is composed of a portion and a white portion indicate a concave portion are radially formed. The servo zone has a circular arc shape from the inner circumference to the outer circumference of the magnetic disk 6 corresponding to the skew angle of the magnetic head, and the depth of the recess is 2 per 64 per circumference.
It is formed to have a thickness of 00 nm. In the data zone, a concentric data track for recording data or the like is formed so as to have a track pitch of 4.8 μm and a track width of 3.8 μm. The head slider 5 was placed on the magnetic disk 6 at a protrusion having a height of 100 nm, and the head slider 5 was levitated by 50 nm.

FIG. 5 is a diagram showing the waveform of the output voltage of the protrusion detection sensor 1 at this time. Small waveforms appearing at both ends in FIG. 5 are waveforms of the output voltage of the protrusion detection sensor 1 when passing through the servo zone, and large waveforms appearing in the center of them are protrusion collisions on the magnetic disk 6 of the protrusion detection sensor 1. It is a waveform of the output voltage when. As described above, the magnitude of the output voltage of the protrusion detection sensor 1 is different between when the servo zone passes and when the protrusion collides, and becomes larger when the protrusion collides than when the servo zone passes. Further, the waveform of the output voltage of the protrusion detection sensor 1 is different between when the servo zone passes and when the protrusion collides.
As described above, by using the resistor 4, it is possible to detect the protrusion on the magnetic disk 6 having the uneven portion formed on the surface.

Here, the reason why the voltage is output even when the protrusion detection sensor 1 passes through the servo zone will be described. The gap between the resistor 4 and the magnetic disk 6 is equal to the flying height of the head slider 5 and is about 50 nm. Considering the dimension of the resistor 4 and the dimension of the gap, it is considered that the resistor 4 always radiates heat onto the magnetic disk 6 through this gap. In the servo zone and data zone,
The ratio of the uneven portions on the surface of the magnetic disk 6 under the head slider 5 is different. This means that the thermal resistances of the resistor 4 and the magnetic disk 6 are different. Generally, the ratio of the uneven portions is larger in the data zone. Therefore, the data zone has lower thermal resistance. As a result, when the protrusion detection sensor 1 passes through the servo zone, the resistance value of the resistor 4 is slightly increased and a voltage is output.

The increase in the resistance value of the resistor 4 when the protrusion detection sensor 1 passes through the servo zone is much smaller than the increase in the resistance value of the resistor 4 when the protrusion detection sensor 1 collides with the protrusion. This is because the surface of the resistor 4 facing the magnetic disk 6 is the surface of the ultrathin film resistor in the thickness direction. Considering that the thickness of the resistor 4 is on the order of nanometers, the output voltage due to the difference in thermal resistance due to the difference in the ratio of the uneven portions is smaller than the output voltage at the time of collision of the protrusion detection sensor 1. it is obvious. Therefore, by providing a slice level between the output voltage of the protrusion detection sensor 1 when the protrusion detection sensor 1 passes through the servo zone and the output voltage of the protrusion detection sensor 1 when the protrusion collision occurs, only the output voltage of the protrusion detection sensor 1 when the protrusion collision occurs. It is possible to determine Further, since the output voltage of the protrusion detection sensor 1 when it passes through the servo zone and the output voltage of the protrusion detection sensor 1 when it collides with the protrusion have different waveforms, the output voltage is passed through the signal processing circuit to obtain the protrusion voltage. It is possible to determine only the output voltage of the detection sensor 1 when the protrusion collides.

FIG. 6 is a block diagram showing a first embodiment of the projection detecting apparatus of the present invention for detecting a projection on a magnetic disk having an uneven surface. In the protrusion detection device 10, when the output voltage from the protrusion detection sensor 1 is input to and amplified by the voltage amplifier 11, and the amplified voltage is input to the voltage comparator 12 and is larger than a preset comparison reference voltage. It is designed to be output to.
Therefore, by setting the comparison reference voltage to be equal to or higher than the output voltage of the protrusion detection sensor 1 when the servo zone is passed and equal to or lower than the output voltage of the protrusion detection sensor 1 when the protrusion collides, the resistor 4 becomes a protrusion on the magnetic disk 6. The output can be obtained from the protrusion detection device 10 only when a collision occurs.

FIG. 7 is a diagram showing a waveform of the output voltage waveform of the protrusion detection sensor 1 shown in FIG. 5, which is band-pass filtered at a frequency between 100 kHz and 300 kHz. The first rising direction of the waveform of the output voltage when the protrusion detection sensor 1 shown in FIG.
As shown in (A), the projection detection sensor 1 has a negative direction.
The first rising direction of the waveform of the output voltage at the time of collision of the protrusions is the positive direction as shown in FIG. 7 (B). As described above, the initial rising direction of the waveform of the output voltage of the protrusion detection sensor 1 is different when the servo zone is passed and when the protrusion collides. As described above, by using the resistor 4, it is possible to detect the protrusion on the magnetic disk having the uneven portion formed on the surface.

FIG. 8 is a block diagram showing a second embodiment of the projection detecting apparatus of the present invention for detecting a projection on a magnetic disk having an uneven surface. In the protrusion detection device 20, the output voltage from the protrusion detection sensor 1 is input to and amplified by a voltage amplifier 21, and the amplified voltage is input to a bandpass filter 22 to be converted into a predetermined frequency band and a predetermined frequency band. The determined voltage is polarity determiner 2
3, the polarity is determined and the determination result is output. Therefore, based on the determination result, it is possible to determine whether the output voltage from the protrusion detection sensor 1 is generated when the servo zone passes or when the protrusion collides.

[0025]

As described above, according to the present invention,
Since protrusions on the magnetic recording medium can be detected with high accuracy, the accuracy of information recording and reproduction can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a protrusion detection sensor of the present invention.

FIG. 2 is a diagram showing the relationship between the output voltage of the protrusion detection sensor shown in FIG. 1 and the flying height of the head slider.

FIG. 3 is a diagram showing a waveform of an output voltage of the protrusion detection sensor shown in FIG.

FIG. 4 is a plan view showing the entire shape of the magnetic disk and a plan view showing a partial shape of the surface of the magnetic disk.

5 is a diagram showing a waveform of an output voltage of the protrusion detection sensor shown in FIG.

FIG. 6 is a block diagram showing a first embodiment of a protrusion detection device of the present invention.

7 is a diagram showing a waveform of a waveform of an output voltage of the protrusion detection sensor shown in FIG. 5, which is band-pass filtered at a frequency within a predetermined range.

FIG. 8 is a block diagram showing a second embodiment of the protrusion detection device of the present invention.

[Explanation of symbols]

1 ... Protrusion detection sensor, 2 ... Lead wire, 3 ...
Lead wire, 4 ... Resistor, 5 ... Head slider,
6 ... Magnetic disk, 10 ... Protrusion detection device, 11
... Voltage amplifier, 12 ... Voltage comparator, 20 ...
Protrusion detection device, 21 ... Voltage amplifier, 22 ... Band pass filter, 23 ... Polarity determination device

Claims (4)

[Claims] 1. A sensor for detecting a protrusion on a magnetic recording medium, on which information is magnetically recorded and reproduced, wherein the protrusion is detected by detecting a change in temperature due to energy obtained when the protrusion collides with the magnetic recording medium. A unique protrusion detection sensor. 2. A sensor for detecting a protrusion on a magnetic recording medium, on which information is magnetically recorded and reproduced, comprising an element whose resistance value changes due to a change in temperature due to energy obtained when the protrusion collides with the magnetic recording medium. A protrusion detection sensor characterized in that 3. A device for detecting a protrusion on a magnetic recording medium, on which information is magnetically recorded and reproduced, wherein the resistance value changes due to a change in temperature due to energy obtained when the protrusion collides, And a circuit for supplying a constant current to the element to detect a change in voltage corresponding to a change in the resistance value of the element. 4. A method for detecting a protrusion on a magnetic recording medium, on which information is magnetically recorded and reproduced, wherein a constant current is supplied to the protrusion detecting means to cause the protrusion detecting means to collide with the protrusion, and by the collision, The temperature of the protrusion detecting means is changed, the resistance value of the protrusion detecting means is changed by the temperature change, and the change in the voltage of the protrusion detecting means corresponding to the change in the resistance value is detected. A protrusion detection method, characterized in that the protrusion is detected by a change.