JPH10260089A - Temperature measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly measure temperature of the extreme end of a magnetic head during regenerating magnetic record by arranging a magnetoresistance effect (MR) element on the extreme end part of the magnetic head. SOLUTION: This temperature measuring device is provided with a head piece 10 and a MR type temperature sensor part 30 (MR element) mounted thereon. For the head piece 10, a video head of 8mm VTR is used. Hereby, the same condition as the condition in which information of a magnetic tape is actually recorded and regenerated by the video of 8mm VTR reappears. The MR type temperature sensor part 30 is provided with a curved tape contact face 30A on the extreme end, and the radius of curvature of the tape contact face 30A is the same as the radius of curvature of the tape contact face 16 of the extreme end of the magnetic head of 8mm VTR. Substrates 41, 42 for outer terminal are mounted on the head piece 10, and the MR type temperature sensor part 30 and the substrates 41, 42 are electrically connected together through lead wires 43, 43. This can be applied to the magnetic head of the magnetic record regenerating device of a computer and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring device, and more particularly, to a temperature measuring device for measuring a temperature of a portion of a tip of a magnetic head of a magnetic recording / reproducing device which contacts or approaches a magnetic recording medium. .

[0002]

2. Description of the Related Art FIG. 7 is a diagram schematically showing a recording / reproducing section of a conventional 8 mm VTR. The drum of the recording / reproducing unit includes an upper rotating drum 1 and a lower fixed drum 2, and the video heads 10 </ b> A and 10 </ b> B rotate together with the rotating drum 1. The magnetic tape 20 runs while contacting the side surfaces of the drums 1 and 2. The running direction of the magnetic tape 20 is the video head 10A,
It is inclined with respect to the rotation plane of 10B, and this inclination angle is called a lead angle θ _L.

An example of an 8 mm VTR video head will be described with reference to FIG. FIG. 8A shows a MIG type (Metal-Inline-G
ap Type) video head. The MIG type video head has two cores 11 and 11 made of a single crystal of MnZn ferrite and a sputter film 12 of a sendust alloy inserted between them. The two cores 11 and 11 are joined by a glass 13. . Head gap 14
Is composed of an insulating film of silicon oxide (Si ₂ O ₃ ).

FIG. 8B shows an example of a laminated (laminated) video head. The laminated video head has a structure in which two laminated cores are joined by a glass 13, and each laminated core is a single-layer MnZn ferrite single crystal core 1.
1 and 11 and a sendust alloy or amorphous alloy core 15 interposed therebetween.

The video head has a curved tape contact surface 16 at the tip and a coil window 17 at the center. These video heads are mounted on a small rotating drum, for example, a drum having an outer diameter of 40 mm. In this case, the radius of curvature of the tape contact surface 16 is 6 to 8 mm. Thereby, when the magnetic tape 20 runs, the magnetic tape 20 and the tape contact surface 16 of the video head can appropriately contact each other.

FIG. 9 is a schematic view of a sectional structure of a coating type magnetic tape 20. The magnetic tape 20 is a base film 20
A and a magnetic material layer 20B. The magnetic material layer 20B is a mixture of a magnetic material, a binder, an abrasive, a lubricant, a dispersant, and the like at an appropriate ratio. Magnetic material cobalt, α iron ferromagnetic doped by nickel γFe ₂ O
_It has a structure covered with ₃ and further covered in a capsule shape with alumina.

The contact state between the tape contact surface 16 of the video head and the magnetic tape 20 will be described with reference to FIG. The tape contact surface 16 is polished with a lapping tape having an extremely fine abrasive, and is finished to have a predetermined surface roughness. When the magnetic tape 20 is in contact with the tape contact surface 16, a fringe pattern 21 appears on the surface of the magnetic tape 20 and can be observed. The fringe pattern 21 is ± 200 μm in the longitudinal direction of the tape around the head gap 14 and 55 μm in the width direction of the tape.
Appear over the region.

The fringe pattern is a light and dark stripe pattern obtained by an optical interference method, and the interval between the light and dark stripes is a quarter λ / 4 of the wavelength λ of the monochromatic light.

FIG. 11 schematically shows a contact state between the magnetic tape 20 and the tape contact surface 16 of the video head. The magnetic material layer 20 </ b> B side of the magnetic tape 20 contacts the tape contact surface 16. Friction heat is generated by friction between the running magnetic tape 20 and the tape contact surface 16 of the rotating video head. The heat of friction is determined by the coefficient of friction, the relative speed of the video head to the magnetic tape 20, the tensile stress of the magnetic tape 20, the contact pressure between the magnetic tape 20 and the tape contact surface 16 (the amount of head protrusion), and the like.

When the drum is composed of the rotating upper drum 1 and the fixed lower drum 2, an air film formed between the running magnetic tape 20 and the tape contact surface 16, a winding window communicating with the air film. The size and shape of 17 are also parameters for frictional heat.

However, as will be described below, the frictional heat changes over time when the magnetic tape 20 and the video head are used for a long time. The magnetic tape 20 and the tape contact surface 16 of the video head have minute irregularities.
When the tape is running, the two minute projections collide with each other, causing an adhesion phenomenon. As a result, the material of the magnetic material layer 20B of the magnetic tape 20 falls off from the coating film, and a part of the material stagnates between the magnetic tape 20 and the tape contact surface 16 or gathers in a minute concave portion of the tape contact surface 16, and Some scatter.

In a portion where the magnetic material layer 20B of the magnetic tape 20 and the material constituting the tape contact surface 16 of the video head are in direct contact locally, a flash temperature (Flash) is used.
A high temperature generation phenomenon called Temperature) occurs. The temperature at this time has not been measured, but is said to reach several hundred degrees.

The polymer material such as a binder, a lubricant, and a dispersant contained in the magnetic material layer 20B plastically flows at a high temperature, a part of which covers the magnetic material, and the other part is a minute concave portion of the magnetic tape 20. Flows to Thereby, the surface properties of the magnetic tape 20 change.

In this way, the friction between the magnetic tape 20 and the tape contact surface 16 of the video head changes the minute unevenness of the contact surface between them, and changes from point contact to surface contact when viewed microscopically. As a result, the coefficient of friction between the two increases, and the frictional heat also changes over time.

Assuming that the load of the magnetic tape 20 applied to the tape contact surface 16 of the video head is W and the dynamic friction coefficient is μ, the frictional force F is F = μW. Assuming that the relative speed of the magnetic tape 20 with respect to the tape contact surface 16 is v, the work performed by the frictional force is Fv = μWv. Assuming that all of this work changes into frictional heat, the frictional heat will be μWv / J.

The temperature of the tape contact surface 16 of the video head rises due to frictional heat. If the frictional heat is large, the local temperature rise ΔT is large, but the temperature rise ΔT is
It also changes depending on thermal properties such as thermal conductivity k and specific heat c.
However, the thermal conductivity k is the most important parameter. When the thermal conductivity is small, the temperature rise ΔT is large, and when the thermal conductivity is large, the temperature rise ΔT is small. For example, glass (k = 0.017) has a temperature rise ΔT about 10 times greater than copper (k = 0.92).

As a theoretical equation for determining the temperature at the contact point, the Jaeger equation is known. This equation is obtained based on abrasive wear (adhesion), and differs between a case where the sliding speed is high and a case where the sliding speed is low.

[0018]

ΔT _A = x ₁ ^1/2 μWv / 3.761J (1.1
25k ₂ x ₁ ^1/2 + k ₁ Wv) ΔT _B = μWv / 4.241J (k ₁ + k ₁ ) x ₁ = k ₁ / c ₁ d ₁

ΔT _A and ΔT _B are a temperature rise with respect to the ambient temperature when the sliding speed is high and a temperature rise with respect to the ambient temperature when the sliding speed is low, respectively. Subscript 1, 2
Represents solid 1 and solid 2. k ₁ , c ₁ and d ₁ are solid 1
, Specific heat and density. W is the load, μ is the coefficient of kinetic friction, and v is the relative velocity between solid 1 and solid 2.

[0020]

An increase in the temperature of the tape contact surface of the magnetic head affects the recording / reproducing function. For example, thermal induce noise occurs. On the tape contact surface of the magnetic head, a chemical reaction product called brown stain, white stain or the like whose surface properties have changed is generated. Further, a phenomenon called a clog or the like that a part of the magnetic material of the magnetic head adheres to the tape contact surface of the magnetic head occurs. These cause spacing loss.

In order to increase the recording density, the rotation frequency of the magnetic head also increases, and in recent years, it reaches 30 to 300 Hz. Accompanying this, the frictional heat also increases, and the temperature of the magnetic head becomes even higher.

On the other hand, a hard disk drive (HDD)
Even in a non-contact recording / reproducing system including a disk-type recording medium and a slider-type head as in an apparatus, the temperature at the tip of the head increases due to partial or temporary contact between the recording medium and the head during operation. When a high recording density is required, the gap between the disk-type recording medium and the slider-type head, the so-called flying height, is about 50 nm.
In addition, Proximity Recor
ding), the flying height is designed to be about 25 nm. Therefore, instantaneous contact between the recording medium and the head is inevitable, and frictional heat is generated.

By accurately measuring the temperature at the tip of the magnetic head during recording / reproducing, the interaction between the magnetic head and the recording medium becomes apparent, and the data necessary for designing a magnetic head capable of high recording density is obtained. Can be provided.

Conventionally, as a method of measuring temperature, there are known a contact type in which a sensor is brought into contact with an object to be measured and a non-contact type in which a sensor is measured without contacting the object. Contact sensors include thermocouples, thermistors, bolometers, and the like, and have the advantage of being inexpensive and having various measurement temperature ranges.

Non-contact sensors include quantum sensors such as MCT (Mercury Cadmium Tellurium) and InSb (Indiu
m Antimony). The quantum sensor is configured to excite the sensor with infrared energy radiated from an object. Since the output characteristics have wavelength dependence, it is possible to select a device having a sensor sensitivity suitable for the property of infrared radiation (temperature dependence).

However, the conventional temperature sensor has disadvantages of low sensitivity, low output voltage, detection disturbance due to system noise, and poor linearity of temperature versus output voltage. In addition, there is a drawback that the response speed is low and an instantaneous temperature change cannot be detected.

In the contact type, there is no device capable of accurately measuring the temperature in an extremely small area, for example, an area having a diameter of 50 μm. There is a drawback that the sensor needs to be brought into contact with the measurement target and is not suitable for a dynamic measurement target.

In view of the foregoing, it is an object of the present invention to provide a temperature measuring device and method for accurately measuring the temperature of the tip of a magnetic head of a magnetic recording / reproducing device.

In view of the foregoing, it is an object of the present invention to provide a temperature measuring apparatus and method for accurately measuring the temperature at the tip of a magnetic head during actual magnetic recording and reproduction.

[0030]

According to the present invention, the temperature measuring device is configured to measure the temperature of the tip of the magnetic head from the output signal of the MR element arranged at the tip of the magnetic head. In addition, a sensor unit including an MR element is disposed at the tip of the magnetic head, and the sensor unit has a tape contact surface having the same radius of curvature as the tape contact surface of the magnetic head.

According to the present invention, the magnetic head is a rotary magnetic head for reading magnetic data recorded on a magnetic tape type magnetic recording medium or a slider type magnetic head for reading magnetic data recorded on a magnetic disk type magnetic recording medium. Head.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a temperature measuring device according to the present invention will be described with reference to FIG. The temperature measuring device of the present embodiment has a headpiece 10 and a magnetoresistive effect (Magnetoresistance) mounted thereon.
Resistive Effect) type temperature sensor unit 30. The headpiece 10 is the conventional 8 mm described with reference to FIG.
A VTR video head may be used. Thereby, the same state as the state where the information on the magnetic tape is recorded and reproduced by the video head of the 8 mm VTR is actually reproduced.

However, a block having the same shape as the video head may be used instead of the video head of the 8 mm VTR. The video head of the conventional 8 mm VTR was removed, and a block having the same shape as the video head was mounted in place of the video head.
By mounting 0, the temperature measuring device of this example is formed.

The magnetoresistance effect type temperature sensor section 30 has a tape contact surface 30A curved at the tip, and the radius of curvature of the tape contact surface 30A is the same as the radius of curvature of the tape contact surface 16 at the tip of the 8 mm VTR magnetic head. It may be.

The headpiece 10 has a substrate 4 for external terminals.
1 and 42 are mounted, and the magnetoresistive effect type temperature sensor 30
And the substrates 41 and 42 are electrically connected by lead wires 43 and 43.

Referring to FIG. 2, an example of the configuration of the magnetoresistive effect type temperature sensor section 30 of this embodiment will be described. The magnetoresistive effect type temperature sensor section 30 includes magnetoresistive elements 31 and 32 and protectors 35 and 36 on both sides thereof.
Reference numerals 1 and 32 denote a magnetoresistive effect film (MR film) 31 and a SAL (Sof
t Adjacent Layer) 32 and a lead portion 33 made of a metal thin film.

The MR film 31 may be formed of Fe-Ni, and the SAL 32 may be formed of Fe-Ni-Ta. The lead part 33 is connected to a lead wire 43 connected to the substrates 41 and 42. Bias current I _B supplied via the lead portion 33. Bias current I _B, the shape of the magnetoresistive elements 31 and 32 is determined by the dimensions and the like, may for example be about 10mA.

Incidentally, the magnetoresistive effect type temperature sensor section 3 of this embodiment
Various types of magnetoresistive elements other than the example shown in FIG. As the thin film type magnetoresistive element, a GMR (Giant Magneto Resistive) element, a spin valve element, a semiconductor magnetoresistive element, or the like may be used.

The magnetoresistance effect is a phenomenon in which the electric resistance changes due to a magnetic field or magnetization, and the value of the specific resistance ρ changes depending on the inclination angle θ with respect to the magnetization vector M as expressed by the following equation. .

[0040]

Ρ = ρ ₁ sin ² θ + ρ ₂ cos ² θ = ρ ₁ + Δρ cos ² θ Δρ = ρ ₂ −ρ ₁

Here, θ is the inclination angle of the specific resistance ρ with respect to the magnetization vector M in the measurement direction, ρ ₁ is the specific resistance ρ when θ = 90 °, and ρ ₂ is the specific resistance ρ when θ = 0 °. is there.

FIG. 3 shows the characteristics of the rate of change Δρ / ρ of the specific resistance ρ. The rate of change Δρ / ρ of the specific resistance ρ changes according to the magnetic field H from the magnetic tape as shown. Normally, the magneto-resistance effect element, the DC bias magnetic field H _B is applied. Therefore, the magnetic field H from the magnetic tape is the DC bias magnetic field H _B
And the signal magnetic field H _{S is} the sum H _B + H _S.

By appropriately selecting the value of the DC bias magnetic field H _B , the magnetic field H changes in a region where the gradient of the curve of the change rate Δρ / ρ of the specific resistance ρ is relatively large. Therefore,
The sensitivity of the output signal V can be increased. Note that the rate of change Δρ / ρ of the specific resistance ρ is substantially equal to the rate of change ΔR / R of the resistance R.

FIG. 4 shows an example of the temperature characteristics of the magnetoresistance effect element. The rate of change of the resistance value with respect to the temperature change of the magnetoresistive element used in the experiment is ΔR / ΔT = 100 mmΩ / °
C. The resistance value at 25 ° C. is 45.7Ω.
Met. The relationship between the temperature t ° C and the output voltage v is expressed by the following equation. This magnetoresistive element has extremely good linearity in the measurement temperature range.

[0045]

## EQU3 ## v = 0.0011t + 0.4429

Referring to FIG. 5, a first example of the detection circuit of the temperature measuring device according to the present invention will be described. According to this example, the drive power for the motor of the rotary magnetic head is supplied via the rotary transformer 50, but the output signal of the temperature measuring device is transmitted to the outside using at least one channel of the rotary transformer 50. . The detection circuit of this example includes a signal generator 51 provided on the fixed side of the rotary transformer, a pulse shaping circuit 53 provided on the rotating side of the rotary transformer, a constant current pulse drive circuit 54, a Wheatstone bridge circuit 55, a differential amplifier. 56 and a current drive circuit 57.

The Wheatstone bridge circuit 55 is a bridge circuit including four resistors 55A, 55B, 55C, and 55D. One of the bridge circuits 55A is a magnetoresistive element included in the temperature measuring device of this embodiment. The output signal from the current drive circuit 57 is output from the fixed secondary coils 50a, 50a via the rotary transformer 50.

A second example of the detection circuit of the temperature measuring device according to the present invention will be described with reference to FIG. According to this example, the driving power of the motor of the rotary magnetic head is supplied via the rotary transformer 50, and the output signal of the temperature measuring device is transmitted to the outside via the wireless communication including the transmitter and the receiver. . The wireless communication may be a wireless communication system used in a mobile phone system. The detection circuit of this example includes a transmission block 80A provided on the rotary magnetic head side and a reception block 80B provided on the fixed side. Transmission block 8
0A is the substrate 41, 42 of the head piece 10 shown in FIG.
Has been implemented.

The transmission block 80A includes a constant current drive circuit 81, a magnetoresistive element 82, a differential amplifier 83, an AD converter 84, a QPS (Quadrature Phase Sift) modulator 85, and a transmitter 86. The receiving block 80B includes a receiver 87, a synchronous detection (orthogonal) detector 88, and a voltage / temperature converter 8
9 inclusive.

Power is supplied to the constant current drive circuit 81 of the transmission block 80A via the rotary transformer 50. Magnetoresistive element 8 of magnetoresistive sensor section 30
2 is driven by the drive current from the constant current drive circuit 81. The magnetoresistive element 82 is incorporated in a bridge circuit together with the other three resistors, as in the example shown in FIG. The output of the magnetoresistive element 82 is
3 and is supplied to an AD converter 84 to be converted into a digital signal. This digital signal is transmitted via the QPS modulator 85 and the transmitter 86.

The signal from the transmitter 86 is transmitted to the receiving block 8
OB is received by a receiver 87, subjected to quadrature synchronous detection by a synchronous detector 88, and converted into a temperature signal by a voltage-temperature converter 89.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to these examples, and various modifications can be made within the scope of the invention described in the claims. It will be understood by those skilled in the art.

In the above description, the recording / reproducing head for 8 mm video has been described as an example. However, the temperature measuring apparatus according to the present invention is applicable not only to the recording / reproducing head for 8 mm video but also to other types of VTRs. is there. Further, the temperature measuring apparatus according to the present invention is applicable not only to a recording medium of a magnetic tape type such as a VTR, but also to a case where recording and reproduction are performed from a recording medium of a disk type.

That is, the temperature measuring device according to the present invention is applicable to a magnetic recording / reproducing device such as a computer, for example, a magnetic head such as an HDD and a data streamer.

[0055]

According to the present invention, there is an advantage that the temperature of a magnetic head can be measured under the same conditions as those for recording and reproducing with an actual magnetic head.

According to the present invention, since the temperature is measured using the magnetoresistive element, there is an advantage that the temperature can be measured very accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a temperature measuring device according to the present invention.

FIG. 2 is an explanatory diagram for explaining a configuration of a magnetoresistive sensor unit of the temperature measuring device according to the present invention.

FIG. 3 is a diagram showing an output characteristic curve of a magnetoresistive element.

FIG. 4 is a diagram showing temperature characteristics of a magnetoresistive element.

FIG. 5 is a diagram showing an example of a detection circuit of the temperature measuring device according to the present invention.

FIG. 6 is a diagram showing another example of the detection circuit of the temperature measuring device according to the present invention.

FIG. 7 is a diagram showing the appearance of a conventional rotary drum type magnetic head of 8 mm VTR.

FIG. 8 is a diagram showing a configuration of a conventional 8 mm VTR video head.

FIG. 9 is a diagram showing a configuration example of a conventional magnetic tape.

FIG. 10 is a diagram showing a contact state between a tape contact surface of a video head and a magnetic tape.

FIG. 11 is a partially enlarged view schematically showing a state of contact between a tape contact surface of a video head and a magnetic tape.

[Explanation of symbols]

1, 2 drums, 10 headpieces, 10A, 1
0B video head, 11 ferrite core, 12
Sendust alloy film, 13 glass, 14 head gap, 15 Sendust alloy or amorphous alloy core, 16 tape contact surface, 17 window, 20 magnetic tape, 20A base film, 20B magnetic material, 21 fringe pattern, 30 MR sensor section, 30A tape Contact surface, 31 MR film, 32
SAL, 33 lead part, 41, 42 substrate, 43
Lead

Claims (7)

[Claims] 1. A temperature measuring device configured to measure a temperature of a tip portion of a magnetic head from an output signal of an MR element arranged at a tip portion of the magnetic head. 2. The temperature measuring device according to claim 1, wherein
A temperature measuring device, wherein a sensor unit including the MR element is arranged at a tip of the magnetic head, and the sensor unit has a tape contact surface having the same radius of curvature as a tape contact surface of the magnetic head. 3. A temperature measuring apparatus according to claim 1, wherein said magnetic head is a rotary magnetic head for reading magnetic data recorded on a magnetic tape type magnetic recording medium. apparatus. 4. The temperature measuring device according to claim 3,
A signal from the MR element is transmitted via a rotary transformer. 5. The temperature measuring device according to claim 3,
A temperature measuring device, wherein a signal from the MR element is transmitted via wireless communication between a transmitter disposed on the rotary magnetic head and an external receiver. 6. A temperature measuring apparatus according to claim 1, wherein said magnetic head is a slider type magnetic head for reading magnetic data recorded on a magnetic disk type magnetic recording medium. . 7. The temperature measuring device according to claim 1,
A temperature measuring device, wherein a head piece having the same outer shape as the magnetic head is used instead of the magnetic head.