JPH0981909A - Disk recording and reproducing device and read parameter adjusting method to be applied to the same device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make retry processings at the time of the generation of a read error efficient and also to reduce the generating of the read error at the time of a data reproducing by utilizing the sense current adjusting function of an MR head in a disk recording and reproducing device using the MR head. SOLUTION: When the read error is generated at the time of the data reproducing, after retry processings are repeated by a prescribed number of specified times, a CPU 11 execute retry processings by changing the sense current amounts of an MR head 2. When a normal data reproducing operation is executed by these retry processings, the CPU 11 stores the changed sense current amount in a memory 14. Consequently, the retry processings are eventually made efficient by reducing the number of wasteful retry processings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk recording / reproducing apparatus such as a hard disk device, and more particularly to a disk recording / reproducing apparatus using an MR head exclusively for reproduction.

[0002]

2. Description of the Related Art Conventionally, for example, a hard disk drive (HD)
The disk recording / reproducing apparatus such as D) uses a magnetic head (hereinafter simply referred to as a head) for a disk as a recording medium.
The data recording / reproducing operation is executed by.

In recent years, in particular, in an HDD having a small size and a high recording density, an inductive type thin film head is used for recording data, and a reproduction-only MR (magnetoretor) is used for reproducing data.
A recording / reproducing separated type (composite head structure type) head using a simultaneous head is drawing attention.

In particular, the MR head has the advantages of high sensitivity and reproduction output not depending on the running speed (peripheral speed) of the disk (a relatively high reproduction output can be obtained). It is one of the elements.

An MR head is a magnetoresistive element (MR element).
Is a magnetoresistive effect type head that detects the recording magnetic field generated on the surface of the disk as a change in resistance value by utilizing the anisotropic magnetoresistive effect.

As shown in FIG. 7A, the operating principle of the MR head is that the MR element (MR thin film) positioned closely on the track of the disk 1 (object of read access).
A sense current (I) is applied to the magnetic field 2 and the resistivity which changes according to the recording magnetic field (vertical magnetic field H) from the disk 1 is taken out as a voltage signal (V).

That is, the sense current (I) is a drive current for detecting a resistance change due to the recording magnetic field as a voltage change. The voltage signal (V) is amplified as a reproduction signal by a head amplifier and sent to a data reproduction circuit called a read channel.

Here, the resistivity ρ of the MR element 2 and the resistivity ρ
7B, in the magnetization M of the MR element 2 due to the maximum change amount Δρm, the sense current I, and the vertical magnetic field H, the angle formed by the direction of the sense current I and the direction of the magnetization M is θ.
Then, the following relational expression (1) is established. ρ = Δρm * cos ² θ (1).

Further, the MR head requires a bias magnetic field to enable a reproducing operation in a linear region. Figure 7
(C) and (D) are MR for the recording magnetic field H of the MR head.
It is a figure which shows the characteristic of resistance value. FIG. 7C shows the case where there is no bias magnetic field, and FIG. 7D shows the case where a bias magnetic field is applied.

In order to generate this bias magnetic field, a sense current (ie, bias current) is supplied to the MR element or a shunt of the sense current to a bias film adjacent to the MR element.

According to the operation principle of the MR head as described above, the sense current amount (sense current value) is one of the important parameters for determining the characteristics of the MR head. For this reason,
Conventionally, in the HDD manufacturing process, the sense current amount is set to an appropriate value according to the operating characteristics of the MR head. Specifically, the sense current amount that minimizes the asymmetry and noise level is set according to the vertical symmetry of the reproduction signal waveform of the MR head and the noise characteristic (Barkhausen noise).

The sense current amount is set to an optimum value for each MR head of the plurality of heads provided in the HDD,
It is usually a fixed value. Therefore, the sense current amount is generally not changed after the adjustment in the manufacturing process, that is, after the HDD is shipped as a product.

By the way, in the HDD, when data is reproduced,
If normal read data cannot be reproduced from the read signal from the head (a read error has occurred), normally again
The same data reproducing operation is executed. This is called a retry process.

In the retry process, the same data reproducing operation is repeatedly executed a prescribed number of times. Even if the retry process is executed a predetermined number of times, if a read error occurs, the error process is performed.

In the error processing, it is usually determined that a sector or track to be accessed on the disk has a defect, the use of the defective sector or the defective track is prohibited, and the alternative sector or the alternative track is assigned. There is. Further, there is a method of prohibiting the use of the data surface of the disk corresponding to the head when it is determined that the head is defective.

[0016]

As described above, a head using an MR head for data reproduction has attracted attention as a high recording density HDD. When a read error occurs during the data reproducing operation by the MR head, the retry process is conventionally executed a predetermined number of times.

As described above, in the MR head, the sense current value greatly affects the operating characteristics, and it is expected that the read error occurrence rate increases when the sense current value is an inappropriate value. Specifically, when the sense current value does not match the characteristics of the MR head, the read signal waveform asymmetry of the MR head and the noise level become large, which causes a read error. The sense current value of the MR head is set as a fixed value during the HDD manufacturing process.

However, when the ambient temperature of the HDD changes, M
When the resistance value of the R element fluctuates, the set sense current value is not necessarily the optimum value. In addition, the optimum value may not be set for some reason during the setting work in the manufacturing process. When the operating characteristics of the MR head are used as a factor, no matter how many times the retry process is repeated, a read error occurs and a normal data reproducing operation becomes impossible. Therefore, useless retry processing is repeated, resulting in a decrease in HDD operation efficiency.

An object of the present invention is to improve the efficiency of retry processing when a read error occurs in a disk recording / reproducing apparatus using an MR head, by utilizing the adjusting function of the sense current of the MR head, and to combine the data. This is to reduce the occurrence of read errors during reproduction.

[0020]

SUMMARY OF THE INVENTION A first aspect of the present invention is as follows.
When a read error occurs during data reproduction, the retry process is repeated a predetermined number of times, and then the control unit changes the sense current amount of the MR head via the sense current supply unit to execute the retry process. If a read error occurs even within the sense current adjustment range, set the sense current that minimizes the read error and
Perform retry processing to adjust the parameters of the write channel. When a normal data reproducing operation is executed by this retry processing, the changed sense current amount and parameter are stored in the memory.

As a result, the number of unnecessary retry processes can be reduced, and as a result, the efficiency of the retry process can be improved. Further, at the next data reproducing operation, it is possible to supply a new sense current amount and a parameter estimated to be proper values and significantly suppress the occurrence of a read error.

According to a second aspect of the present invention, a temperature detecting means for detecting a temperature change in the HDD is provided, and a read test operation is executed when it is detected that the temperature change exceeds an allowable range. And a read test means for determining a read error.

The control means changes the sense current amount through the adjusting function of the sense current supply means, re-executes the read test operation, and stores the changed sense current amount in the memory in the case of a normal read operation. To do.

As a result, when a read error occurs due to a change in the operating characteristics of the MR head due to a change in the ambient temperature of the HDD, a read test operation with adjustment of the sense current amount can be executed. . Therefore,
When a read error occurs, the efficiency of retry processing can be improved. Further, by storing a new sense current amount estimated to be an appropriate value, it becomes possible to significantly suppress the occurrence of subsequent read errors.

The third aspect of the present invention is particularly applied to a CDR type HDD, and when read errors occur frequently in a specific zone, it is estimated that the operating characteristic of the MR head is a factor,
The read test process is executed by using, for example, the innermost track in the zone. The sense current amount is adjusted through the adjusting function of the sense current supply means so that the reproduction signal waveform obtained by this read test process becomes normal.

Therefore, by setting the sense current amount to the optimum value, it is possible to eliminate the frequent occurrence of read errors in the zone due to the operating characteristics of the MR head.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an HDD relating to the first to third embodiments, and FIG. 2 is a conceptual diagram for explaining the format of a CDR type disc particularly relating to the third embodiment. 3 is a block diagram for explaining a read channel parameter changing process particularly related to the first embodiment, and FIG. 4 is a flowchart for explaining an operation related to the first embodiment. 5 is a flow chart for explaining the operation related to the second embodiment, and FIG. 6 is a flow chart for explaining the operation related to the third embodiment. (Configuration of HDD) HDD of the present embodiment
1 uses a recording / playback separation type head 4 in which a read-only MR head 2 and an inductive type thin film head 3 for recording operation are combined as shown in FIG. An apparatus using the disk 1 of FIG.

For the sake of convenience, the number of disks 1 is one. The heads 4 are arranged corresponding to both sides of the disk 1. The disk 1 is rotating at a high speed by a spindle motor 5. The head 4 is held by a head actuator 6, and is rotated by a voice coil motor (VCM) 7 in the radial direction of the disk 1.

Spindle motor (SPM) 5 and VCM 7
Are microcontrollers (CPU 11) 10
, A driving current is supplied from a VCM / SPM driver (double driver) 8 to drive the device.

The microcontroller 10 is the main controller of the HDD and controls the positioning of the head 4 (servo processing), the adjustment processing of the sense current amount of the MR head 2 related to this embodiment, and the parameter change of the read channel described later. Various control processes such as process, read test process, and retry process are executed.

The microcontroller 10 includes a microprocessor (CPU) 11, an A / D converter 12, and
And a D / A converter 13. The CPU 11 is a main component of the controller 10 and executes the various control processes described above.

The A / D converter 12 converts the burst signal (positional error signal) generated through the read channel (see FIG. 3) of the read / write circuit 15 into digital data. The CPU 11 uses the burst signal to execute position control for positioning the head 4 at the center of the target track.

The D / A converter 13 converts the operation control amount related to the positioning control of the head 4 calculated by the CPU 11 into an analog signal and outputs it to the VCM / SPM driver 8.

The memory 14 is accessed by the CPU 11 and stores sense current amount data SI and read channel parameter data PA as will be described later. The read / write circuit 15 is a circuit that processes a read / write signal of the HDD and has a read channel for reproducing the read signal output from the MR head 2 during data reproduction.

As shown in FIG. 3, the read channel 25 has a signal processing circuit such as a low pass filter (LPF) 25a and a pulse generation circuit, and reproduces read data including user data and servo data.

At the time of data recording, the read / write circuit 1
Reference numeral 5 converts the write data from the HDC 20 into a write signal (write current) and supplies it to the thin film head 3 via the head amplifier circuit 9.

The head amplifier circuit 9 has a read amplifier for amplifying the read signal from the MR head 2 and a write amplifier for amplifying the write signal. Further, the head amplifier circuit 9 includes a sense current source circuit for supplying a sense current of the MR head 2 related to this embodiment.

The read / write circuit 15 has an adjusting circuit for adjusting the sense current amount of the sense current source circuit according to the control of the CPU 11 (sense current amount data). H
The DC 16 has a function as an interface between the HDD and the host computer and a data controller of the HDD. The HDC 16 uses the buffer memory 17 to control transfer of recording / reproducing data to / from the read / write circuit 15. The HDC 16 has an ECC circuit and has a function of detecting a read error of read data.

Since the present embodiment is concerned with the data reproducing operation by the MR head 2 dedicated to reproduction, the description relating to the data recording operation and the servo processing (head positioning control) will be omitted. (Operation of the First Embodiment) This embodiment assumes an HDD which executes a retry process in which the same read operation is repeated when a read error occurs during data reproduction.

That is, when reproducing data, the MR head 2
Is positioned on the target track by the servo processing of the CPU 11, and the read operation of reading the recording data from the sector to be accessed is executed (step S1).

The read channel of the read / write circuit 15 reproduces read data (user data) from the read signal from the MR head 2 and outputs it to the HDC 16.
The HDC 16 checks by ECC processing whether the read data is normally output.

When a read error occurs due to this check processing, the CPU 11 executes retry processing (YES in step S2). The CPU 11 repeats the retry process a preset number of times (for example, 10 times) (steps S3 and S4).

When a read error occurs even after repeating the retry process a prescribed number of times, the CPU 11 estimates that the sense current amount of the MR head 2 is not an appropriate value, and executes a process of changing the sense current amount (step). YES in S4,
S5).

Specifically, the CPU 11 calculates the sense current amount data and outputs it to the adjusting circuit of the read / write circuit 15. With this adjusting circuit, the amount of sense current from the sense current source circuit of the head amplifier circuit 9 is adjusted, and M
It is supplied to the R head 2.

After changing the sense current amount, the CPU 11 executes the retry processing again (step S6).
The CPU 11 continues until normal read data is reproduced.
The retry process is repeated while changing the sense current amount.

When the normal read data is reproduced within the predetermined sense current amount range, the CPU 11 stores the sense current amount data at that time in the memory 14 (NO in step S7, S8). That is, the sense current amount when reproducing normal read data is reset as the optimum value for the corresponding MR head 2. Therefore, the memory 14 stores the sense current amount data for each MR head 2.

As a result, from the next read operation, C
The PU 11 controls the MR head 2 so as to supply the sense current of the sense current amount stored in the memory 14. On the other hand, if a read error occurs even in the retry process due to the change within the range of the predetermined sense current amount, C
The PU 11 shifts to the process of adjusting the read channel parameter together with the sense current amount (YE in step S7).
S, S9).

Here, the read channel is an external (CPU
LP required for read signal processing by input from 11)
An LSI having a function of adjusting parameters such as F. The parameters include the LPF cutoff frequency and the boost amount.

The CPU 11 repeats the retry process while changing the sense current amount and the read channel parameter up to a predetermined number of times (change range) until normal read data is reproduced (step S10).

When reproducing normal read data, C
The PU 11 stores the sense current amount and the parameter at that time in the memory 14 (NO in step S11, S13).
That is, reset the changed sense current amount as the optimum value,
Moreover, the changed parameter is also reset as the optimum value of the read channel.

If the occurrence of a read error does not disappear within the predetermined number of retry processings, the CPU 11
Shifts to predetermined error processing (YE in step S11)
S, S12). The error processing includes, for example, a defect processing for a defective track or a defective sector or the MR head 2
This is a process of treating the head 4 including the above as a defective head. Normally, use is prohibited in the case of a defective track or defective sector, and an alternative track or alternative sector is assigned. In the case of the defect processing of the MR head 2, the head 4
All the data surfaces of the disk 1 corresponding to are prohibited.

As described above, according to the present embodiment, a normal read operation cannot be executed even if the retry process is performed a predetermined number of times.
When a read error occurs, it is estimated that the sense current amount of the MR head 2 is not the optimum value, the sense current amount is changed, and the retry process is repeated. Then, when the normal read operation can be executed, the changed sense current amount is stored in the memory 14 as the optimum value, and is reset from the next read operation.

Therefore, it is possible to prevent the occurrence of a read error caused by the fact that the sense current amount of the MR head 2 is not set to the optimum value, and to eliminate the unnecessary repetition of the retry process.

Further, by changing the parameters of the read channel together with the amount of the sense current and executing the retry process, it is possible to greatly increase the probability that the read error caused by the complex factors can be eliminated. (Second Embodiment) In the second embodiment, when the ambient temperature of the HDD changes beyond the allowable range, the resistance characteristic which is the operation characteristic of the MR head 2 changes, and the initially set sense current amount is changed. As a result, the optimum value is not assumed.

In the second embodiment, as shown in FIG.
A temperature detection device (device using a thermistor or the like) 18 is arranged inside the DD to monitor the internal temperature of the HDD. The temperature detection device 18 outputs a detection signal to the microcontroller 10 when the temperature exceeds a preset reference temperature.

In response to the detection signal from the temperature detection device 18, the CPU 11 determines that the internal temperature of the HDD has changed beyond the allowable range, and executes the read test operation (YES in step S20, S21).

The read test operation is a process for actually reading the data from the disk 1 and inspecting whether or not the normal read data is reproduced, and whether or not the access being executed is stopped and executed. Or execute after completion. Further, for the inspection, either a method of reproducing test data prepared in advance and then reproducing the test data or a method of utilizing the actually recorded user data may be used.

When the CPU 11 does not find any abnormality in the read test operation, it naturally does not change the sense current amount of the MR head 2. When a read error occurs due to the read test operation, the CPU 11 changes the sense current amount as described above and executes the read test operation again (YES in step S22, S23). When the normal read operation is executed within the range of the read test operation of the predetermined number of times (that is, within the range of the sense current amount), the CPU 11 stores the sense current amount at that time in the memory 14 ( NO in step S24, N in step S22
O, S25). That is, the changed sense current amount is reset as the optimum value.

When the normal read operation cannot be executed within the prescribed number of times, the read test operation is repeated while changing the sense current amount and the read channel parameter as described above (steps S26 and S27). ).

When normal read data is reproduced, C
The PU 11 stores the sense current amount and the parameter at that time in the memory 14 (NO in step S28, S30).
That is, reset the changed sense current amount as the optimum value,
Moreover, the changed parameter is also reset as the optimum value of the read channel. If the read error does not disappear even after the read test operation is repeated a predetermined number of times, the CPU 11 shifts to a predetermined error process. The error processing is the same as in the case of the first embodiment described above.

As described above, according to this embodiment, the HDD
When the ambient temperature of the MR head changes, the resistance characteristic of the MR head 2 changes and the preset sense current amount becomes an improper value, and it is possible to prevent the occurrence of a read error due to that. Becomes

That is, when the read test operation is executed according to the detection of the temperature change and a read error occurs,
It is estimated that the improper value of the sense current amount of the MR head 2 is the cause, and the process of changing the sense current amount is executed. As a result, the sense current amount can be reset to the optimum value.

Further, when not only the sense current amount but also the read channel parameter becomes an inappropriate value due to temperature change, the read channel operation is executed by changing the read channel parameter as well, and the sense current amount is changed. At the same time, the read channel parameters can be reset to optimum values. Therefore, it is possible to prevent a situation in which a read error occurs due to multiple factors due to temperature changes. (Third Embodiment) In the third embodiment, as shown in FIG. 2, CDR (constant density re) is used.
It is assumed that the HDD uses the disk 1 of the disk format of the cording system and sets the sense current amount of the MR head 2 for each zone.

In the CDR system, as shown in FIG. 2, a large number of tracks on the disk 1 are divided into a plurality of zones 0-2, and the data recording / reproducing characteristics such as the data transfer rate are set for each zone 0-2. different.

In the HDD, data access is normally
Often executed sequentially within the zone. Therefore, it is highly possible that read errors due to the operating characteristics of the MR head 2 occur frequently in a specific zone.

Therefore, in the present embodiment, the number of read error occurrences is measured for each zone, and if the number of occurrences is more frequent than a predetermined reference value, the cause of the read error is the operating characteristic of the MR head 2. That is, it is estimated that there is a sense current amount.

Hereinafter, with reference to the flow chart of FIG.
This will be specifically described. The CPU 11 counts the number of read errors that have occurred during data reproduction for each zone and stores the count in the memory 14 or an internal register (step S40).

The CPU 11 compares the stored number of read errors with a predetermined reference value, and specifies a zone (here, zone 0) in which it is determined that the read errors occur frequently (step 0). S41).

In this zone 0, as shown in FIG. 2, the CPU 11 causes the head 4 to seek the innermost track TZ0 and causes the thin film head 3 to record the test data prepared in advance (steps S42 and S43).

Further, the CPU 11 causes the MR head 2 of the head 4 to execute a read operation for reading the test data (step S44). If no read error occurs due to this read operation, the MR head 2
The operating characteristic, that is, the sense current amount is determined to be an appropriate value, and is excluded from the cause of the read error.

When a read error occurs due to the read operation, the CPU 11 instructs the read / write circuit 15 to execute the adjustment process of the sense current amount (step S).
45, S46 NO).

Here, in this embodiment, as shown in FIG. 3, in the read channel 25 of the read / write circuit 15, the asymmetry of the read signal waveform is detected, and the sense current is eliminated so as to eliminate this asymmetry. A quantity adjusting circuit is provided.

The CPU 11 inputs the adjusted sense current amount from the read channel 25 and temporarily stores it in the internal register. Next, the CPU 11 causes the read channel 25
The adjustment processing of the parameters (cutoff frequency and boost amount) of the LPF 24a is executed (step S47). Here, as a matter of course, if the read error is eliminated by adjusting the amount of sense current, the parameter may remain at the initially set value.

When the CPU 11 finally determines the sense current amount and the parameter that will not cause a read error, they are stored in the memory 14 (step S49). That is, as shown in FIG. 3, in the memory 14, the sense current data storage memory 14a stores the sense current amount data SI0 for the zone 0, and the parameter data storage memory 14b stores the parameter data PA0 for the zone 0. Store.

The memory 14a, 14b stores sense current amount data and parameter data for each of the other zones. The CPU 11, for example, sets the sense current amount of the MR head 2 and the parameters of the read channel based on these data when the HDD is activated.

If the read error does not disappear even after the adjustment process of the sense current amount and the parameter is executed, the CPU 11 shifts to a predetermined error process (step S50). The error processing is the same as in the case of the first embodiment described above.

As described above, according to this embodiment, the zone where read errors frequently occur is specified, and the factors causing the read errors are estimated to be the sense current amount of the MR head 2 and the read channel parameters. The adjustment process of the sense current amount and the parameter is executed. In this case, only the sense current amount adjustment process may be performed.

In the case of the CDR type HDD, since there are many sequential accesses for each zone, when read errors occur frequently, it is highly likely that the operating characteristics of the MR head 2 and the inadequacy of the read channel parameters are the factors. . Therefore, in the present embodiment, by executing the adjustment process of the sense current amount and the parameter, the cause of the read error having a high probability is eliminated. As a result, the estimated factor can be eliminated before the retry process of the read operation is executed when a read error occurs, and as a result, it is highly possible that the read error can be eliminated by a small number of retry processes. In other words, it is possible to improve the efficiency of retry processing when a read error occurs.

[0079]

As described above in detail, according to the present invention, in the disk recording / reproducing apparatus using the MR head for data reproduction, the amount of sense current of the MR head during the retry process of the read operation when the read error occurs. It is possible to eliminate the occurrence of a read error due to the operating characteristics of the MR head by using the adjustment function of. Therefore, MR
When the operating characteristic of the head is a factor, useless retry processing can be reduced and the efficiency of retry processing can be improved. Therefore, it is possible to improve the operation efficiency of the device as a result.

When the ambient temperature of the device changes,
By executing the read test operation assuming the occurrence of a read error due to the operating characteristics of the MR head, the efficiency of the retry process can be similarly improved. In this case, an appropriate amount of sense current can be set according to the temperature state at that time.

Further, when applied to a CDR type HDD or the like, for a specific zone where read errors frequently occur,
A read test operation is executed assuming the operating characteristics of the MR head as a factor. That is, by the read test operation accompanied by the adjustment of the sense current amount, it is possible to eliminate the frequent occurrence of read errors in the zone due to the operating characteristics of the MR head.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an HDD related to the first to third embodiments.

FIG. 2 is a conceptual diagram for explaining the format of a CDR type disc related to the third embodiment.

FIG. 3 is a block diagram for explaining a read channel parameter changing process related to the first embodiment.

FIG. 4 is a flowchart for explaining an operation related to the first embodiment;

FIG. 5 is a flowchart for explaining an operation related to the second embodiment;

FIG. 6 is a flowchart for explaining an operation related to the third embodiment.

FIG. 7 is a diagram for explaining the operation principle of a conventional MR head.

[Explanation of symbols]

 1 ... Disk 2 ... MR head 3 ... Induction type thin film head 4 ... Head 5 ... Spindle motor 6 ... Head actuator 7 ... Voice coil motor 8 ... VCM / SPM driver 9 ... Head amplifier circuit (sense current source circuit) 10 ... Micro controller 11 ... CPU (control means) 14 ... Memory 15 ... Read / write circuit (sense current adjusting circuit) 16 ... Disk controller (HDC) 17 ... Buffer memory 18 ... Temperature detection device

Claims (6)

[Claims] 1. A disk recording / reproducing apparatus for reproducing data by using a reproduction-only MR head as a head for recording / reproducing data on / from a disk, wherein a sense current is supplied to the MR head during data reproduction. Means for adjusting the amount of sense current and a sense current supply means for adjusting the amount of sense current, and a reproducing process of a read signal output from the MR head at the time of data reproduction, and a parameter necessary for the reproducing process. A read signal processing means having an adjusting function, a retry processing means for executing a retry processing for repeating a data reproduction operation a predetermined prescribed number of times when a read error occurs during the data reproduction, and the retry processing of the prescribed number of times. If a read error occurs even after the end, the sense current is supplied via the adjustment function of the sense current supply means. And a control unit that stores the changed sense current amount in the case of normal read operation by changing the amount and executes the retry process, and adjusts the parameter of the read signal processing unit when a read error occurs. A disc recording / reproducing apparatus comprising: 2. A disk recording / reproducing apparatus for reproducing data by using a reproduction-dedicated MR head as a head for recording / reproducing data on / from the disk, the temperature detection for detecting a temperature change in the apparatus. Means, a means for supplying a sense current to the MR head at the time of data reproduction, and a sense current supplying means having an adjusting function for adjusting the amount of the sense current; and a temperature detecting means for allowing a temperature change in the apparatus. When it is detected that the range has been exceeded, a read test means for executing a data reproducing operation on the disk to judge the occurrence of a read error, and a read error occurred in the data reproducing operation by the read test means. Sometimes, the amount of sense current is changed through the adjusting function of the sense current supply means, and data read by the read test means is changed. It was re-execute the operation, the disk recording and reproducing apparatus characterized by comprising a control means for storing the sense current amount of change in the case of normal read operations. 3. A disk recording / reproducing apparatus for reproducing data by using a reproduction-dedicated MR head as a head for recording / reproducing data on / from the disk, the temperature detection for detecting a temperature change in the apparatus. Means for supplying a sense current to the MR head at the time of reproducing data, and sense current supplying means having an adjusting function for adjusting the amount of the sense current, and a read output from the MR head at the time of reproducing the data. Read signal processing means for executing signal reproduction processing and having a function of adjusting parameters required for reproduction processing; and when the temperature detection means detects that the temperature change in the apparatus exceeds the allowable range, A read test means for executing a data reproducing operation on the disc to determine the occurrence of a read error, and a data re-execution by the read test means. When a read error occurs in the operation, the sense current amount is changed through the adjusting function of the sense current supply means, and the data reproducing operation by the read test means is re-executed so that the read operation is changed normally. A disc recording / reproducing apparatus comprising: a control unit that stores a sense current amount and adjusts a parameter of the read signal processing unit when a read error occurs. 4. A disk recording / reproducing apparatus for reproducing data by using a reproduction-only MR head as a head for recording / reproducing data to / from a disk, wherein a sense current is supplied to the MR head during data reproduction. Means for adjusting the amount of the sense current, and a read error occurrence count for each predetermined zone on the disk when a read error occurs during the data reproduction. Then, a measuring unit that specifies a zone in which the number of read error occurrences exceeds a predetermined reference number of occurrences, and seeks the head to a specific track in the zone specified by the measuring unit to write test data, Read for reading test data by the MR head and generating a reproduced signal waveform corresponding to the test data Based on the reproduction signal waveform obtained by the test means and the read test means, the sense current amount is adjusted and adjusted by the adjustment function of the sense current supply means so that the reproduction signal waveform becomes normal. A disk recording / reproducing apparatus comprising: a control unit that stores the sensed current amount as a value corresponding to the specific zone. 5. A disk having a function of adjusting the amount of sense current supplied to the MR head as a read parameter by reproducing the data using a read-only MR head as a head for recording and reproducing the data on the disk. A read parameter adjusting method for a recording / reproducing apparatus, which detects a temperature change in the apparatus and, when the temperature change exceeds an allowable range, executes a test reproduction operation on the disk to detect a read error. A step of determining occurrence, a step of changing the sense current amount to re-execute the test reproduction operation when a read error occurs in the data reproduction operation, and a step of re-executing the test reproduction operation to perform normal read In the case of operation, the changed sense current amount is used as the sense current amount to be supplied to the MR head during data reproduction. And a step of storing as a read parameter adjusting method. 6. A disk having a function of adjusting the amount of sense current supplied to the MR head as a read parameter by reproducing the data by using a read-only MR head as a head for recording and reproducing data on the disk. A read parameter adjusting method for a recording / reproducing apparatus, wherein when a read error occurs during data reproduction, a step of measuring the number of read error occurrences for each predetermined zone on the disk; A step of specifying a zone exceeding the reference number of occurrences, and a test data is written by seeking the head to a specific track in the specified zone, and the test data is read by the MR head to correspond to the test data. To perform a read test process to generate the reproduced signal waveform A step of adjusting the sense current so that the reproduction signal waveform becomes normal based on the reproduction signal waveform obtained by a test process, and storing the adjusted sense current amount as a value corresponding to the specific zone. A read parameter adjusting method comprising: