JPS6117203A - magnetic recording and reproducing device - 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 Field of the Invention The present invention relates to a magnetic recording and reproducing device such as a magnetic disk device and a magnetic tape device for recording and reproducing digital information.

Conventional configurations and their problems Reproducing recorded signals in the magnetic head of a magnetic recording and reproducing device that records and reproduces digital information is possible using a method that uses windings by applying the electromagnetic induction phenomenon and a method that uses magnetoelectric conversion elements such as magnetoresistive elements. There is a method to use.

FIG. 1 shows a magnetoresistive element head (hereinafter referred to as an MR head) belonging to the latter type of magnetic flux sensitive head. The configuration of this conventional example will be explained below with reference to FIG. 1.

In FIG. 1, numeral 1 is a magnetoresistive element, and since this magnetoresistive element 1 is usually required to have soft magnetic properties, permalloy is used. A current is applied to this magnetoresistive element 1 through a conductor 2. The magnetoresistive element 1 and the conductor 2 are formed on a block member 4 that moves relatively in proximity to or in contact with the recording medium 3, and further includes another block portion #1''.
It is held between 5 and 5.

Note that the structure usually includes means for applying a constant weak magnetic field to the magnetoresistive element 1 according to each element, but this explanation is omitted here.

Next, the operation of the above conventional example will be explained. Recording medium 3
When the magnetic head moves relative to the recording medium 3 in proximity to or in contact with the recording medium 3, the magneto-resistive element 1 receives a magnetic field change corresponding to the magnetization in the recording medium. As shown in FIG. 2, the magnetoresistive element 1 has a property that its resistance changes with respect to the magnetic field that it receives. As a result, if a constant current is applied to the magnetoresistive element 1,
Since the voltage across the element changes depending on the magnetization in the recording medium, this is used as a reproduction signal.

As described above, the reproduction output voltage of the MR head has the property of being proportional to the constant current value applied to the element.

However, in the above conventional example, since a constant current is always applied to the magnetoresistive element, if an excessive constant current is applied to the magnetoresistive element 1 for the purpose of obtaining a large reproduction output voltage, irregular low-frequency noise called thermal noise occurs. This has the drawback of causing an increase in the amount of damage caused by the magneto-resistance element 1, and even causing the magnetoresistive element 1 to melt. The above-mentioned thermal noise is generated because Joule heat generated in the magnetoresistive element 1 is randomly diffused when the recording medium and the MR head slide in contact with each other.

OBJECT OF THE INVENTION The present invention eliminates the drawbacks of the conventional example described above, and aims to increase the reproduction output voltage by increasing the constant current applied to the magnetoresistive element. The purpose is to avoid the risk of melting down the element.

Structure of the Invention In order to achieve the above-mentioned object, the present invention has a method in which the current applied to the magnetoresistive element is limited to only a necessary time, whereas in the conventional example, a current is constantly passed through the magnetoresistive element. This has the effect of suppressing the generation of Joule heat in the magnetoresistive element.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The third drawing shows the reproduction output voltage generated in response to the magnetic field received by the magnetoresistive element l from the recording medium 3 when the recording medium 3 moves relative to the MFt head, and FIG. 3(B) shows the reproduction output voltage generated inside the magnetic recording and reproducing apparatus. A timing chart shows a pulse signal called a window signal that is generated in response to a generated clock signal. It is the positive and negative maximum points that carry information in the reproduced output voltage of (A), and the window signal (B)
makes the demodulator circuit capable of detecting signals only near this maximum point.

In the present invention, as shown in FIG. 3(q), a current is applied to the magnetoresistive element in synchronization with the window signal (13)K.

Since the magnetoresistive element does not generate a reproduction output voltage in response to the magnetic field from the recording medium when no current is applied, a voltage is generated only in a part of the reproduction output voltage from the magnetoresistive element. However, the Nobuhide voltage from the magnetoresistive element has a waveform that preserves the positive and negative maximum points necessary for reproducing recorded information, and it is possible to correctly demodulate the digital signal.

Next, a signal demodulation method and a magnetoresistive element driving method will be explained with reference to the block diagram shown in FIG. 4.

In FIG. 4, the output of the head 6 using a magnetoresistive element is intermittently generated as shown in FIG. Therefore, this is amplified by the regenerative amplifier 7. After that, the output of the window comparator 8, the output of the peak detector consisting of the differentiating circuit 9 and the zero-cross detection circuit 10 are used to detect the peak position of the positive and negative head output voltages within an area exceeding a certain voltage. The signal is applied to the OR circuit 11 and is used as a demodulated signal. This demodulated signal is
Since the demodulated output is exactly the same as that obtained from a conventional recording/reproducing device, the window generating circuit 2 for generating the window signal from this signal may be the same as the conventional one. The above objective is achieved by applying the output of the window creation circuit 12 to the switching transistor 13 and continuing to apply current to the magnetoresistive element. In the present invention, compared to the conventional example in which a constant current is always applied to the magnetoresistive element, the Zeel heat generated from the magnetoresistive element is reduced by the period in which no current is applied. Conversely, if the heat generation of the magnetoresistive element is constant, a larger current can be applied when the time for applying current is limited than when a constant current is applied all the time.

As a result, as described above, the reproduced output voltage increases in proportion to the current applied to the element.

Therefore, a correct window signal cannot be generated.

Therefore, when the device is started, a constant current is temporarily applied to the magnetoresistive element at all times, but this does not pose any particular problem since the clock signal is generated immediately after the device is started.

In the above explanation, only the case where a magnetoresistive element is used is mentioned, but the present invention can be applied in exactly the same way even when a Hall element is used as the magnetoelectric conversion element.

Furthermore, the recording method to which the present invention is applied can be either longitudinal recording or perpendicular recording.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

(a) The configuration is simple because only the current applied to the magnetoresistive element is controlled.

(b) It can be realized using the conventional MR head and recording medium as they are.

(cl) Applicable regardless of the MR head, recording medium, and recording method.

[Brief explanation of drawings]

FIG. 1 is a transparent perspective view of a conventional MR head, FIG. 2 is a schematic diagram showing the operating principle of a magnetoresistive element, and FIG. 3 is a timing chart of signals of various parts of a magnetic recording/reproducing apparatus in an embodiment of the present invention. FIG. 4 is an electrical circuit diagram of the same embodiment. 6...Head, 7...Regenerative amplifier, 8...Window comparator, 9...Differential circuit, 10...Zencross detection circuit, 11...OR circuit, 12.Window creation circuit, 13.・Switch puffer transistor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure? Happy 2 Figure 3 Figure 4

Claims (1)

[Claims] The present invention is characterized in that the current applied to a magnetoresistive element of a magnetic head that detects a reproduced signal using a magnetoresistive effect is controlled in synchronization with a clock signal generated from the reproduced signal itself. magnetic recording and reproducing device.