JPH06111255A - Durability evaluation device for magnetic recording medium and magnetic head - Google Patents

Abstract

PURPOSE:To improve the durability performance of a magnetic recording medium and a magnetic head by providing a function for changing generated torque by detecting and controlling the angle, angular velocity, and application current of a spindle motor by forming a non-contact type encoder at one part of the rotary part of the spindle motor. CONSTITUTION:A black and white pattern 8 with 60 cycles in one periphery is provided at the upper surface outer periphery of a cap 7 where a magnetic recording medium 6 is fixed to a spindle motor 4, a small hole is made on a case 9, a detection edge 10 of an optical fiber of a photoelectric switch 12 is inserted and fixed, and then a pulse signal (60 pulses per revolution) corresponding to the revolution of the magnetic recording medium 6 is generated in an interface circuit 2. In an actual product, the magnetic recording device 6 is remodeled and used but the magnetic recording medium 6, a magnetic head mounting part 11, the case 9 etc., may be created newly for improving the ease of use and wide use as an evaluation device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an evaluation for observing and evaluating an increase in frictional force due to sliding of a magnetic recording medium and a magnetic head and an adsorption phenomenon, which are one of the serious quality problems in a magnetic recording apparatus. Involved in equipment.

[0002]

2. Description of the Related Art A magnetic recording apparatus is required to lower the flying height of a magnetic head with respect to a magnetic recording medium, that is, reduce spacing loss to achieve higher recording density. Therefore, high flatness,
Smoothness is required.

As described above, a magnetic recording medium having a surface closer to a mirror surface is desired to enable high recording density recording. On the other hand, the surface of the magnetic head in contact with the recording medium also has a stable flying characteristic. In order to obtain it, it is mirror-finished. Therefore, the frictional force increases or adsorption occurs as the magnetic recording medium slides on the magnetic head. It is known that this causes a force exceeding the torque of the spindle motor of the magnetic recording device, and the magnetic recording device becomes unbootable.

Needless to say, it is necessary to sufficiently understand the durability performance of the magnetic recording medium and the magnetic head in the magnetic recording device so that such a phenomenon does not occur in an actual use situation. In addition, it is important to analyze the phenomenon of trouble occurrence in detail and improve the performance of the magnetic recording medium and the magnetic head.

For this purpose, a device for evaluating the durability of the magnetic recording medium and the magnetic head has been proposed. These evaluation devices can be attached with any magnetic recording medium,
It has a rotating shaft that can imitate the start and stop operations of the magnetic recording device, and mounts the magnetic head by pressing it against the magnetic recording medium as in the mounted state, and by using a load cell or the like to slide the magnetic recording medium and magnetic head. The resulting frictional force can be measured. There is also an evaluation device that can set the environment such as temperature and humidity in order to approximate the actual usage state of the magnetic recording device.

With these evaluation devices, the change in the frictional force between the magnetic recording medium and the magnetic head with respect to the number of times of starting and stopping,
The relationship between the position on the magnetic recording medium and the frictional force, and the data such as the dynamic frictional force at the time of starting and stopping were collected to quantify the durability of the magnetic recording medium and the magnetic head.

[0007]

However, the above-described evaluation apparatus cannot make the factors affecting the frictional wear phenomenon the same as those of the actual magnetic recording apparatus. These phenomena are generally multi-factor multiple interactions, and it is very difficult to reproduce the same phenomenon in different devices. Therefore, in a conventional general-purpose evaluation device, the evaluation conditions are different, which may not be sufficient for evaluation.

For example, in an actual magnetic recording apparatus, in order to improve the volumetric efficiency, parts (magnetic recording medium, magnetic head, etc.) are housed in a very narrow area, and in order to prevent dust from entering,
It is almost sealed. On the other hand, a commercially available evaluation device has an arrangement with a margin to prevent deterioration of operability and is often an open system. Further, since the method of fixing the magnetic head in the evaluation device measures the frictional force with a load cell or the like, the measurement itself may affect the phenomenon. Further, the spindle that rotates the magnetic recording medium of the evaluation device often has a high torque and a large moment of inertia as compared with that of the magnetic recording device.

Due to such a difference, the durability of the actual magnetic recording device cannot be guaranteed by the general-purpose evaluation device, and in the end, a considerable number of actual devices are assembled and the start and stop are repeated.
Evaluating the quality of parts. However, the information obtained here is only the number of times the magnetic recording apparatus is stopped until the magnetic recording apparatus becomes unbootable, and there is a problem that it is far from being sufficient for investigating and improving the cause of failure.

The present invention has been made in view of these points, and it is highly reliable by measuring the frictional force acting on the magnetic recording medium and the magnetic head while maintaining the actual environment of the magnetic recording apparatus. It is an object of the present invention to provide a magnetic recording medium and a magnetic head durability evaluation apparatus that can obtain technically effective data.

[0011]

In order to achieve the above-mentioned object, a magnetic recording medium of a magnetic recording apparatus of the present invention and an apparatus for evaluating the durability of a magnetic head are not provided in a part of a rotating portion of a spindle motor. It is characterized by forming a contact encoder and having a function of detecting the angle and angular velocity of the spindle motor and a function of controlling the current applied to the spindle motor and changing the generated torque.

[0012]

According to the evaluation apparatus of the present invention having the above-mentioned structure, the durability of the magnetic recording medium and the magnetic head of the magnetic recording apparatus is extremely accurately, that is, close to the actual usage conditions of the actual product. Various technical data such as start / stop frequency vs. dynamic friction force, start / stop frequency vs. start torque, stop frequency by position of magnetic head on magnetic recording medium, start torque by position of magnetic head on magnetic recording medium Can be measured and quantified. As a result, the conditions of the magnetic recording medium and the magnetic head, which greatly affect the durability of the magnetic recording device, can be filled with data closer to the actual product, and ultimately the reliability of the magnetic recording device is improved. I can do things.

[0013]

Embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 5). Here, FIG. 1 to FIG. 3 are explanatory diagrams showing the configuration and function of the apparatus in one embodiment of the present invention, and FIG. 4 to FIG. 6 are explanatory diagrams showing the measuring method.

As shown in FIG. 1, the apparatus of this embodiment has the following features. Magnetic recording device (1) with some modifications.

2. An interface circuit (2) for extracting a signal from the magnetic recording device (1) and inputting it to a computer (3) or controlling the magnetic recording device (1) from the computer (3).

3. A computer (3) for controlling the magnetic recording device (1), processing measured signals, and displaying, recording, and outputting data. It consists of three blocks.

The magnetic recording device (1) is a magnetic recording device (1), which is originally a normal product, uses one 3.5-inch magnetic recording medium and uses two magnetic heads and has a storage capacity of 40 Mbytes. The following modifications have been made in order to use it as a durability evaluation device.

1) By supplying power (5,12V), the magnetic recording device (1) alone has a predetermined start / stop sequence (spindle motor (4) until the magnetic recording medium reaches 3200 rpm).
The spindle motor (4) for 10 seconds after stopping the energization to the spindle motor (4) when it reaches 3200 rpm. If the rotation speed (3200 rpm) was not reached within 10 seconds, the controller program of the magnetic recording device (1) was changed so as to stop the start-stop sequence.

2) Remove the spindle motor current limiting resistor (A) attached to the driver (5) of the spindle motor (4) so that the torque generated by the spindle motor (4) can be controlled from the computer (3). It was connected to the interface circuit (2).

3) The controller B of the magnetic recording apparatus (1) connected the energization command signal to the driver (5) of the spindle motor (4) to the interface circuit (2).

4) As shown in FIG. 2, a black and white pattern (8) of 60 cycles per revolution is formed on the outer periphery of the upper surface of the cap (7) which fixes the magnetic recording medium (6) to the spindle motor (4).
Then, a small hole is opened in the case (9), the detection end (10) of the optical fiber of the photoelectric switch (12) is inserted and fixed, and a pulse signal (1) corresponding to the rotation of the magnetic recording medium (6) is obtained.
The interface circuit (2) can generate 60 pulses of rotation.

5) As shown in FIG. 2, a black and white pattern (8) of one cycle per cycle is formed on the outer periphery of the upper surface of the cap (7) which fixes the magnetic recording medium (6) to the spindle motor (4).
Then, a small hole is made in the case (9), the detection end (10) of the optical fiber of the photoelectric switch (13) is inserted and fixed, and a pulse signal (1) corresponding to the rotation of the magnetic recording medium (6) is obtained.
The interface circuit (2) can generate one rotation pulse.

In this embodiment, the magnetic recording device (6) which is an actual product is remodeled and used, and this is the best from the point of the present invention, but the usability as an evaluation device, the versatility, etc. are improved. Therefore, the magnetic recording medium (6), the magnetic head mounting portion (11), the case (9), etc. may be newly prepared. However, it is necessary to avoid making a large change, and it is preferable to use at least the spindle motor (4) used in the product.

The interface circuit (2) was designed and manufactured so as to have the following five functions.

1) A power supply (5, 5) supplied to the magnetic recording device (1)
12V) is turned on and off according to a command from the computer (3).

2) The resistance value of the spindle motor current limiting resistance (A) of the magnetic recording device (1) is changed according to a command from the computer (3), and the spindle motor (4) of the magnetic recording device (1) is changed. Control the torque.

3) The spindle motor energization command signal of the magnetic recording device (1) is output to the computer (3).

4) The angle of the magnetic recording medium (6) at the moment is obtained from the two photoelectric switches (12) and (13) connected to the magnetic recording device (1) and output to the computer (3).

5) One photoelectric switch S (12) connected to the magnetic recording device (1) generates a voltage proportional to the angular velocity of the magnetic recording medium (6) and outputs it to the computer (3).

The mechanism for realizing each function will be described below.

Function 1) As shown in FIG. 3, the magnetic recording device (1) and the power source connected thereto are connected via relays (14) and (15).
The voltage (TTL level) of the I / O output of the computer (3) is passed through a relay drive circuit (19) that comprises the relays (14) and (15) with a transistor (16), a resistor (17) and a diode (18). ) To realize function 1).

Function 2) As shown in FIG. 3, five resistors (20) to (24) are connected in parallel, and four resistors (20) to (23) are connected to relays (25), respectively. ~ (28) are connected in series and placed. function
Similarly to 1), by connecting the relays (25) to (28) with the I / O output of the computer (3), the resistance circuit (2)
9) The resistance value at both ends can be changed. Further, if the ratio of the resistance values of the four resistors (20) to (23) is set to a power of 2, that is, 1: 2: 4: 8, the resistance value at both ends of the resistance circuit (29) is 4 Number of relays (25) ~ (2
8) can be operated to create 16 levels of resistance. According to such a circuit, when a constant voltage is applied to both ends, the current value becomes 16 steps of equal difference, and the remaining one resistor (2
In 4), the offset current value is simply determined.
If this is used as the spindle motor current limiting resistor (A) of the magnetic recording device (1) and the resistor (24) is a variable resistor, a spindle motor torque adjuster with a computer-controlled equality 16-step offset adjusting function is obtained.

In this embodiment, the resistances (20) to (23) are set to 18.2Ω, 9.1Ω, 4.55Ω and 2.275Ω, respectively.
The resistance (24) is a variable resistance of 0 to 5 KΩ. In addition, each relay (14), (1
5), the light emitting diode (30) in (25) to (28) ...
And relays (14), (15), (25) to (2
The state of 8) is designed to be visually confirmed.

In this embodiment, the relays (14), (1
5), the torque of the spindle motor (4) is changed stepwise by switching the resistance in (25) to (28), but the variable resistance may be controlled to be continuous. Further, torque control may be performed by current value control using a solid element such as an FET instead of a resistor.

Function 3) Since the spindle motor energization command signal of the magnetic recording apparatus (1) used in this embodiment is a TTL signal, it can be directly connected to the computer (3), but as much as possible, the magnetic recording apparatus ( Mediate with a transistor so as not to affect 1). In this embodiment, this signal is counted by the counter (32).
Is also output to monitor the number of times the magnetic recording device (1) is stopped.

Function 4) The output of the photoelectric switch (12) is input to the counter (33). The photoelectric switch (12) is a magnetic recording medium (6) 1
Since 60 pulses are output by rotation, the counter (33)
Will be incremented by one each time the magnetic recording medium (6) rotates 6 degrees. On the other hand, photoelectric switch (1
The output of 3) is input as a reset of the counter (33). The photoelectric switch (13) outputs one pulse at a predetermined angle (depending on the pattern on the cap) for one rotation of the magnetic recording medium (6), so that the counter (33) becomes zero at the predetermined angle. Therefore, the angle of the magnetic recording medium (6) is
It is a value obtained by multiplying the value of the counter (33) by 6. BCD output from the counter (33) to computer (3)
The computer (33) can detect the angle of the magnetic recording medium (6) by inputting the counter value.

In this embodiment, a photoelectric switch (1) is used to generate a pulse corresponding to the rotation of the spindle motor (4).
Although 2) and (13) are used, a magnetic sensor, a capacitance sensor or the like may be used as long as they are non-contact, instead of such an optical method.

Function 5) The output of the photoelectric switch (12) is input to the FV converter,
A voltage proportional to the angular velocity of the magnetic recording medium (6) is obtained. The computer (3), via the AD conversion board (E),
The angular velocity of the magnetic recording medium (6) can be detected. Since the angular velocity of the magnetic recording medium (6) is required at a relatively low rotation speed, the FV converter (C) needs to be particularly set to operate stably even in the low frequency region.

The computer (3) is connected to the interface circuit (2) through the general-purpose I / O board (D) and the AD conversion board (E), and has a function provided by the interface circuit (2) by a program. Utilizing this, the magnetic recording device (1) is controlled to detect necessary information, process the data, display and record.

In the apparatus of the present embodiment configured as described above, the starting torque (minimum value of torque required to start rotating the magnetic recording medium (6)) and dynamic friction force (magnetic recording) are as follows. The maximum value of the frictional force generated by the sliding of the medium (6) and the magnetic head (11 ') is measured.

The procedure for measuring the starting torque will be described with reference to FIG. FIG. 4 is a diagram showing a time change of each signal on the interface circuit (2) at the time of measuring the starting torque. The measurement is performed by the following procedures 1) to 4).

1. After the spindle motor (4) is stopped and before the next start, the torque set value (G) is set to the minimum. At this time, the energization command signal (K) is disabled (I). When the preset time has passed, the spindle motor (4)
Starts with the minimum torque, and at that moment, the energization command signal (K)
Becomes an enable (L). With that as a trigger, 2)
Move to.

2. When the angular velocity of the magnetic recording medium (6) is monitored and the value is zero, that is, if the spindle motor (4) does not rotate, the torque is held for a fixed time (0.3 seconds).

3. If the spindle motor (4) does not rotate during the torque holding time, increase the torque by one step and repeat from 2). If the magnetic recording device (1) does not rotate even at the maximum torque, it means that the magnetic recording device (1) cannot be started, and all evaluations are completed.

4. When the spindle motor (4) starts to rotate, the torque is increased to the normal set value (M) at once. This is to reduce the influence of the starting torque measurement itself on the durability of the magnetic recording medium (6) and the magnetic head (11 ') as much as possible (the torque of the spindle motor (4) is This is one of the important factors affecting the durability of 1) The start / stop of the spindle motor (4) when the torque is different causes the magnetic recording medium (6) and the magnetic head (11 ') to slide. Because the state is different, the progress of friction and wear is also different).

The torque at the moment when the spindle motor (4) starts to rotate is taken as the measured value of the starting torque.

Next, the procedure for measuring the dynamic friction force will be described with reference to FIGS. FIG. 5 is a diagram showing temporal changes in angular velocity and angular acceleration of the spindle motor (4) during one start-stop cycle. FIG. 6 is a diagram showing the relationship between the angular velocity and the angular acceleration at that time.

The dynamic frictional force is obtained from the difference in angular velocity profile during deceleration of the spindle motor (4) depending on the presence (N) and (O) of the magnetic head (11 ') as shown in FIG. The angular velocity profile during deceleration is the magnetic head (11
If it is not attached, it is mainly determined by three factors: coil loss due to induced current flowing in the coil of the spindle motor (4), bearing loss of the spindle motor (4), and wind loss due to rotation of the magnetic recording medium (6). These forces may be viewed as a function of angular velocity, being proportional to angular velocity at high revolutions and nearly constant at low revolutions. The magnetic head (11
Before mounting ´), measure and record the angular velocity profile during deceleration.

When the magnetic head (11 ') is mounted, in addition to the above three forces, there is a force due to the sliding of the magnetic recording medium (6) and the magnetic head (11'). by this,
The angular velocity profile changes as shown in the figure. When the spindle motor (4) is rotating at high speed, the magnetic head (11 ') is not in direct contact with the magnetic recording medium (6) due to the lift generated by the relative speed with the magnetic recording medium (6). Therefore, the magnetic head (1
There is no difference depending on the presence or absence of 1 '). When the rotation of the spindle motor (4) slows down, the magnetic head (11 ') comes into direct contact with the magnetic recording medium (6), and a frictional force is generated, and the magnetic head (11') is not mounted. The angular velocity of the spindle motor (4) decreases more quickly than

Each angular velocity profile is differentiated once to obtain an angular acceleration profile. These are quantities proportional to the force acting on the spindle motor (4). For comparison between the two, the angular acceleration profile is represented as a function of angular velocity as shown in FIG. Here, the magnetic head (11 ')
The difference (S) between the angular acceleration profile (Q) with and without the angular acceleration profile (R) represents the frictional force acting between the magnetic head (11 ') and the magnetic recording medium (6). And the maximum value is the measured value of the dynamic friction force.

In the present embodiment, the values measured as described above are further processed by a computer to determine the stop position frequency of the magnetic recording medium (6), the relationship between the stop position and the starting torque, the number of starting and stopping times and the starting torque, and the dynamic friction. We are looking for power relationships.

[0052]

As described above, according to the present invention,
The durability of the magnetic recording medium and the magnetic head in the magnetic recording device can be obtained as technically valuable data in a state very close to the actual product, and can be used for improving the durability performance of the magnetic recording medium and the magnetic head. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration and functions of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a magnetic recording device according to an embodiment of the present invention.

FIG. 3 is a power supply control of a magnetic recording apparatus according to an embodiment of the present invention,
It is explanatory drawing of the torque control circuit of a spindle motor.

FIG. 4 is an explanatory diagram of a starting torque measuring method according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a dynamic friction force measuring method according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a dynamic friction force measuring method according to an embodiment of the present invention.

[Explanation of symbols]

 1 magnetic recording device 2 interface circuit 3 computer 4 spindle motor 5 driver 6 magnetic recording medium 11 'magnetic head

Claims (1)

[Claims] 1. An apparatus for evaluating a magnetic recording device, comprising:
A non-contact encoder is formed in a part of the rotating portion of the spindle motor to have a function of detecting the angle and angular velocity of the spindle motor and a function of controlling the current applied to the spindle motor and changing the generated torque. A magnetic recording medium and a magnetic head durability evaluation device characterized by the above.