JPH04330608A - Detection of contact force for magnetic head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the contact force of a magnetic head, and more particularly, a method for detecting the contact force of a contact type magnetic head on a magnetic disk surface in a magnetic disk device used as an external storage device of a computer. Regarding.

0002

[Background Art] With the spread of computers, magnetic disk drives are required to have improved performance such as higher density, larger capacity, and smaller size, and research and development thereof has been active. There is a device that performs recording and reproduction using a flying magnetic head, and the slider 50 of the magnetic head has an air inflow end 50a that flies high when a magnetic disk 51 rotates, and an air outflow end where an electromagnetic transducer 52 is provided. 50b floats up a little. This flying height changes as shown in FIG. 8 according to the rotation of the disk. It is known that in order to improve the recording density of a magnetic disk, it is important to minimize the distance (ie, the flying height) between the magnetic disk and the magnetic head (electromagnetic transducer).

[0003]Contact type magnetic heads have therefore begun to be considered as the ultimate in minimum flying height. However, when recording and reproducing are carried out by bringing the magnetic head into contact with a magnetic disk, as in the case of a contact type magnetic head, the wear of the magnetic head progresses rapidly due to high-speed sliding as the magnetic disk rotates. For this reason, it is important to bring a smaller magnetic head into contact with the magnetic disk with a smaller load, and by detecting the contact force with high precision and controlling the spring pressure of the support spring based on this, the magnetic head can be brought into contact with the magnetic disk with a smaller load. It is necessary to record and play back by contacting the disc.

[0004] Conventionally, as a method of detecting the contact force of a magnetic head, a method is known in which a strain gauge is used to detect the force applied to the head arm when the disk rotates at low speed. This is a CSS (contact start
This is carried out for the purpose of investigating head damage during a stop.

[0005]

[Problem to be Solved by the Invention] Since strain gauges are configured to detect changes in resistance value due to changes in contact force, especially those with high sensitivity may fluctuate in measured values due to the temperature of the test environment and temperature changes. , there was a problem that detection accuracy decreased. In addition, strain gauges can measure if the head pressing force is about 10 g, but if the head pressing force is several tens of mg.
There was a problem in that it was impossible to measure things at a certain level. Furthermore, if the rigidity of the head arm system is lowered and the distortion is increased for detection, the response frequency will be lowered and it will be more likely to vibrate due to turbulence of airflow, etc., and in this case as well, there is a problem that the detection accuracy will be lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic head detection method that can detect the contact force of a low-load magnetic head with high precision without being affected by environmental temperature.

[0007]

[Means for Solving the Problems] FIG. 1 shows a diagram of the basic configuration of the present invention. The first invention shown in FIG. 4A measures the motor drive current I with the contact type magnetic head 4 in contact with the magnetic disk 1, and calculates (contact force F)=(frictional force W)/(friction coefficient μ) = (torque constant K)・(motor drive current I)/
The contact force F or friction force W is calculated from the relational expression of μ (disc radius R). The second invention shown in FIG. 2B is a method for cutting off the motor drive power after rotating the disk with the magnetic head 4 in contact with the magnetic disk 1, and reducing the number of stop times until the magnetic disk stops. The measured rotation stoppage is determined from the rotation stop time versus rotation characteristic (C) when the magnetic head is not in contact with the magnetic disk and the characteristic (D) when the magnetic head is not in contact, which have been determined in advance. Find the difference (S) between both characteristics over time and contact force F or friction force W.
Calculate.

[0008]

[Operation] Since the relationship between the rotational speed and the contact force is as shown in FIG. 3, the contact force F at that time can be calculated by determining the motor drive current I. Therefore, the contact force or friction force of a magnetic head with a low load of several tens of milligrams can be detected with high accuracy without being affected by environmental temperature or the like, compared to the conventional example in which the contact force was detected using a strain gauge. Further, since the relationship between the rotation stop time and the rotation speed is as shown in FIG. 6, the contact force can be calculated from the difference S between the characteristics C and D by detecting the rotation stop time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram illustrating a first embodiment of the present invention. In the figure, a magnetic disk 1 is rotated by a motor 3 that is supplied with power from a motor drive circuit 2 and driven. A magnetic head 4 is a rotating magnetic disk 1
Recording and playback are performed by contacting with a low load. 5 is a motor drive current measurement unit that measures the motor drive current I. Reference numeral 6 denotes a control unit that determines the contact force F or frictional force W based on the motor drive current I measured by the measurement unit 5.

In this case, in order to improve measurement accuracy, it is important to reduce as much as possible influences other than the contact force of the head. Specifically, in order to reduce friction between the rotating shaft of the disk 1 and the rotating shaft of the motor 3, an air bearing or a magnetic bearing may be used. Further, the disk 1 is preferably of small diameter or thin in order to reduce inertia.

[0011] Here, when the head pressing force is constant,
The relationship between rotational speed and contact force is as shown in FIG. That is, when the rotational speed of the disk 1 decreases (increases), while the pressing force of the magnetic head 4 remains constant, the flying force decreases (increases), so the contact force of the head against the disk surface gradually increases ( Decrease. Because of this relationship, in the first embodiment of the present invention, the head contact force F at that time is determined by detecting the motor drive current I when the disk is rotating at a predetermined rotational speed.

In FIG. 2, a motor drive current I supplied from a motor drive circuit 2 to a motor 3 is measured in a drive current measurement section 5, and a control section 6 calculates a contact force based on the measured motor drive current I. Find F or frictional force W. Therefore, if the friction coefficient between the magnetic disk 1 and the magnetic head 4 is μ, the torque is T, the torque constant is K, and the radius of the magnetic disk 1 is R, then F=W/μ

(1) T=WR=KI

The relational expression (2) is established, and by substituting equation (2) into equation (1), F=KI/μR

Equation (3) is obtained. Above (3)
In the equation, K, μ, and R are known, so if the motor drive current I can be measured, the contact force F can be determined, and the friction force W can be determined from the relationship in equation (1).

In this way, the contact force F can be calculated simply by determining the motor drive current and performing calculations in the control section 6 based on this.
, the contact force F of a magnetic head with a low load (pressure force) of several tens of milligrams can be detected without being affected by changes in environmental temperature or humidity, compared to conventional methods that use strain gauges to detect contact force. Can be detected with high precision.

The contact force F obtained in this manner is applied to a support spring (not shown) of the magnetic head 4 as a control signal, for example.
The magnetic head is controlled to be pressed with a smaller load by adjusting the amount of deformation of the support spring. Alternatively, the reliability is evaluated based on the obtained contact force.

[0015] Note that the disc rotation speed and motor drive current I
The relationship is as shown in FIG. If the case where the magnetic head 4 is not in contact with the disk 1 is characteristic A, and the case where it is in contact is characteristic B, then the difference Q at a certain number of rotations will be a value proportional to the contact force F. Therefore, the characteristic B, the difference Q, and the corresponding contact force F are stored in the control unit 6,
The control unit 6 may calculate the contact force F from the difference Q corresponding to the motor drive current I measured by the drive current measurement unit 5.

Furthermore, the contact force F at any rotational speed can be determined while changing the rotational speed of the disk 1.

FIG. 5 shows a block diagram illustrating a second embodiment of the present invention, in which the same components as those in FIG. 2 are given the same numbers. In FIG. 5, reference numeral 10 denotes a rotation stop time measurement unit that measures the time from when the power is turned off after the disk 1 is rotated at a predetermined rotation speed until it stops. Reference numeral 11 denotes a control unit, which determines the contact force F based on the rotation stop time measured in the measurement diagram 10.

Here, when the head pressing force is constant,
The relationship between rotation speed and rotation stop time is as shown in FIG. The second embodiment applies the phenomenon that the stop time is shortened by the contact force F (frictional force W), as shown in FIG. That is, when the magnetic head 4 is not in contact with the disk 1, the characteristic is C, and when it is in contact, the characteristic is D, and the difference S at a certain number of rotations is a value proportional to the contact force F. In this case, if we consider that viscous resistance (air resistance), which is proportional to the speed, is an important factor in reducing the rotation speed, the rotation speed stop time is
The display shows a straight line (characteristic C). However, while the magnetic head is sliding, a contact force F (frictional force W) is applied, and this contact force F increases as the number of rotations decreases, so that the rotation stop time becomes non-linear.

Therefore, the characteristic D, the difference S, and the corresponding contact force F are stored in the control section 11, and the control section 11
In this step, the contact force F is determined from the displacement amount S corresponding to the rotation stop time measured by the measurement unit 10.

[0020]

[Effects of the Invention] According to the present invention, since the motor drive current is detected and the contact force or frictional force is calculated from this, the contact force or the frictional force is also calculated from the rotation stop time. Therefore, compared to conventional methods using strain gauges, the contact force or frictional force of a low-load magnetic head can be detected with high precision without being affected by environmental temperature, etc., and is useful for reliability evaluation of contact-type magnetic heads, for example. I can make a big contribution.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a block diagram illustrating a first embodiment of the present invention.

FIG. 3 is a characteristic diagram of disk rotational speed versus contact force.

FIG. 4 is a characteristic diagram of disk rotation speed versus motor drive current.

FIG. 5 is a block diagram illustrating a second embodiment of the present invention.

FIG. 6 is a characteristic diagram of rotation stop time versus disk rotation speed.

FIG. 7 is a diagram illustrating a floating state of a floating magnetic head.

FIG. 8 is a characteristic diagram of disk rotational speed versus flying height in a flying magnetic head.

[Explanation of symbols]

1 Magnetic disk 2 Motor drive circuit 3 Motor 4 Magnetic head 5 Drive current measurement section 6,11 Control section 10 Rotation stop time measurement section

Claims (2)

[Claims] 1. A method for measuring the contact force of a contact magnetic head (4) with respect to a magnetic disk (1), wherein the contact force of the contact magnetic head (4) is in contact with the magnetic disk (1). Measure the motor drive current I required to rotate the disk, and calculate (contact force F) = (frictional force W) / (friction coefficient μ between the magnetic disk and the magnetic head).
)=(torque constant K)・(motor drive current I)/μ・(
A method for detecting a contact force of a magnetic head, characterized in that a contact force F or a friction force W is calculated from a relational expression of a disk radius R). 2. A method for measuring the contact force of a contact magnetic head (4) with respect to a magnetic disk (1), wherein the contact force of the contact magnetic head (4) is in contact with the magnetic disk (1). After rotating the disk, cut off the motor drive power, measure the rotation stop time until the magnetic disk stops, and calculate the rotation stop time compared to the previously determined rotation stop time when the magnetic head is not in contact with the magnetic disk. From the rotation speed characteristic (C) and the rotation stop time versus rotation speed characteristic (D) when the magnetic head is in contact with the magnetic disk, find the difference (S) between both characteristics in the rotation stop time measured above. A method for detecting a contact force of a magnetic head, the method comprising: calculating a contact force F or a friction force W.