JPH0454885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic encoder capable of detecting angle and position, and in particular to an improvement in the method of manufacturing its magnetic head.

A magnetic encoder places magnetic marks in a lattice pattern on the periphery or edge of a disk-shaped or strip-shaped magnetic medium.
A magnetic head is brought into contact with the code recording surface of a magnetic code disk or magnetic scale provided at a predetermined constant interval λ (distance between the north pole and the south pole), or is opposed to the code recording surface of the magnetic scale at a small distance, and The magnetic mark is read by moving or rotating the magnetic head in the length measurement direction.

In a conventionally known magnetoresistive element type magnetic head (hereinafter referred to as an MR head), the magnetic sensing part of the magnetic head is composed of a magnetoresistive element, and four or more magnetoresistive elements are used. In addition to forming a bridge with two resistors and two voltage dividing resistors,
The magnetoresistive elements are arranged with a desired spacing and a predetermined phase difference with respect to the magnetic mark spacing of the magnetic scale (for example, see Japanese Patent Application Laid-Open No. 141514/1983), and the relative movement of the two allows magnetic A magnetic field is applied to the magnetoresistive element at the mark part, and the unbalanced output of the bridge is differentially amplified by a DC difference amplifier.
The output of the differential amplifier and a constant DC voltage from a separately provided voltage generation circuit are input to a comparator circuit for waveform conversion consisting of a Schmitt trigger circuit, an operational amplifier, etc. The device was configured to output a voltage pulse corresponding to the magnetized element.

However, the conventional bridge type MR head has problems such as the complicated circuit configuration of the output detection circuit, low detection accuracy, and the need for time and effort to adjust the output detection circuit.

In other words, since the minute gap between the code recording surface of the magnetic scale and the MR head changes due to mechanical vibration or impact, the output characteristics of the voltage pulse (particularly the pulse time width, etc.) caused by magnetic code detection change. The duty factor changes, and such defects also occur due to changes in the magnetic flux of the magnetic mark due to changes in ambient temperature or changes over time.

Furthermore, the above-mentioned MR magnetic head has the problem that there are severe restrictions on the phase relationship of the magnetoresistive elements used, which limits the way they can be arranged.

The present invention has been made based on the above-mentioned viewpoints, and its purpose is to provide a simple configuration of an output detection circuit, high detection accuracy, and adjustment of the output detection circuit, etc., in a short time. The object of the present invention is to provide a method for efficiently manufacturing a user-friendly MR magnetic head circuit.

The above object is to insert a balance adjustment resistor on at least one side of the bridge in a magnetic encoder comprising a bridge-connected magnetoresistive element and a circuit for detecting a change in resistance of the magnetoresistive element. Then, the bridge circuit is balanced in a state where the elements of the bridge circuit are not magnetized, and the output voltage of the bridge circuit is guided to a comparator circuit to generate a voltage pulse corresponding to the unbalanced voltage generated when the magnetoresistive element is magnetized. This is achieved by a magnetic head configured to output .In the present invention, in manufacturing the magnetic head, a plurality of bridge-connected magnetoresistive elements formed as thin films on an insulating substrate are attached to a magnetic scale. At least two phases are formed along the direction of relative movement to the resistor, and in the operation of forming the resistor for balance adjustment, the thin film is formed in a comb-like shape from one side of the resistive material thin film formed in a strip shape on the insulating base inward. A plurality of first slits are formed in the thin film, and the thin film is cut out so as to extend substantially parallel to the inner side of the side opposite to the first slit to a position midway between the first slits. A large number of second slits are formed, and during balance adjustment, the thin film between the second slits is linearly removed in a direction substantially perpendicular to the second slits to sequentially connect the required number of second slits. By doing so, the required resistance value for balance adjustment can be obtained.

The magnetic head section consisting of the magnetoresistive element made of the magnetoresistive alloy described above and the bridge circuit of the magnetoresistive element, etc., is formed on a substrate coated with glass, ceramics, or the like, as will be described later. magnetoresistive alloys formed by thin film forming techniques such as vapor deposition and sputtering,
For example, about permalloy, an Fe-Ni alloy,
It is a thin film of about 500 Å, and the bridge circuit pattern shown in Figures 1 and 2, which will be described later, is formed by masking when forming the thin film by vapor deposition, or by masking after forming the thin film on the entire surface. After forming by removing unnecessary parts by electrolysis, chemical etching, photo etching, etc., or forming a thin film on the entire surface, scribing and drawing processing is performed by numerical control using tools such as diamond without masking. Alternatively, the pattern may be formed by drawing a target pattern through numerical control using a particle beam such as a laser beam or an electron beam instead of the above-mentioned tool.

Hereinafter, the details of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is an explanatory diagram of a one-phase magnetic head circuit for explaining the principle of a magnetic head circuit for a magnetic encoder manufactured by the method according to the present invention, and FIG. 2 is a similar diagram of a conventionally known magnetic head circuit for a magnetic encoder. FIG. 2 is an explanatory diagram of a one-phase magnetic head for explaining the principle.

In FIG. 1, 1a and 1b are magnetic marks regularly provided at predetermined intervals (λ) on a band-shaped linear scale or a disc-shaped magnetic scale (not shown).
1a is a north pole, 1b is a south pole, 2 is in a state close to the magnetic scale to the extent that it almost contacts,
This is a magnetic head circuit that moves relatively in the direction of a magnetic mark on a magnetic scale.

Thus, the magnetic head circuit 2
The bridge circuit consists of a magnetic head section consisting of a bridge circuit 3 made of a magnetoresistive element, and a comparator circuit 4 for waveform conversion consisting of a Schmitt trigger, an operational amplifier, etc., either integrated with the bridge circuit 3 or separate via a flexible lead wire. 3 is four magnetoresistive elements 3
1, 32, 33, and 34, and a balance adjustment resistor 35 inserted into both or one of the two pairs of opposite sides.

The known magnetic head circuit 5 shown in FIG.
It consists of

Note that terminal +B is a positive terminal of a bias constant voltage power supply, and G is a ground terminal.

Bridge-connecting magnetoresistive elements in this way distinguishes between changes in resistance due to temperature changes and changes in resistance due to magnetic marks 1, 1, and only changes in resistance due to magnetic marks 1, 1. This is to take it out.

When either magnetic head or magnetic head circuit is relatively moved along the magnetic scale, a magnetic field is sequentially and alternately applied by the magnetic marks 1, 1 to the magnetoresistive elements constituting the bridge circuit. Therefore, each bridge circuit terminal bd
In between, each time the magnetic head moves by one interval λ of the magnetic mask, one cycle (or, for example,
As described in Publication No. 58-35414, the configuration of the magnetic head circuit is different, but multiple cycles)
The unbalanced voltage varies alternately at a rate of .

In the known magnetic head circuit 5 shown in FIG. 2, this unbalanced voltage is amplified by the differential amplifier 7 and then supplied to the Schmitt trigger circuit 8. The magnetic head moves the magnetic mark 1 according to the signal output from 7.
Each time the distance moves, an output pulse is sent to one destination.

At first glance at the circuit shown in FIG. 2, it appears that the purpose can be achieved even without using the differential amplifier 7.

However, the resistance value of the magnetoresistive elements 61, 62, 63, and 64 constituting the bridge circuit 6 depends on the width of the element and the thickness of the thin film as a whole, as is clear from the above-mentioned manufacturing method of the magnetoresistive element. Since it is difficult to maintain a constant or predetermined value and cannot be accurately controlled during manufacturing, the balance of the bridge 6 is incomplete, and the voltage change that appears between the terminals BD of the bridge 6 is not always accurate to the magnetic mask 1,
1 and the magnetic head 5. Therefore, if this signal is directly input to the Schmitt trigger circuit 8, a voltage pulse detection signal having an accurate and uniform phase and duty factor will be generated for the magnetic marks at accurate intervals. can't get it.

Therefore, in order to obtain a correct and uniform signal, the pitch between each element must be set accurately and uniformly to a predetermined interval such as 1/2 of the magnetic mark interval λ or 1/4 λ as described in each of the above publications. First, the output of the bridge circuit 6 needs to be input to the differential amplifier 7 for differential amplification, convert it into a signal having a time, phase, or voltage level that correctly indicates the position of the magnetic mark, and then supply it to the Schmitt circuit 8. There is.

As shown in FIG. 1, the magnetic head circuit 2 of the magnetic head of the MR head includes magnetoresistive elements 31, 32,
33 and 34 and a resistor 35 inserted to adjust the balance of the bridge.
is configured.

And the resistance element 35 for the above-mentioned balance adjustment.
The resistance value of the magnetic head portion of the thin film bridge circuit consisting of the above-mentioned thin film magnetoresistive element is adjusted by means such as trimming with a laser or the like, as will be described later. No. 3 is one in which the balance is completely adjusted in a state in which all magnetoresistive elements are not magnetized.

Note that it is recommended that the balance adjustment resistor 35 be inserted not only on one side of the bridge, but also on one side of each pair of opposing sides, that is, on two sides. In this way, balance adjustment becomes even easier without creating a case where balance adjustment by trimming, which will be described later, is impossible.

In addition, in reality, a level adjustment resistor is formed as a thin film by vapor deposition or the like using the same alloy material as the magnetoresistive element on the same substrate as the magnetoresistive element of the magnetic head circuit.
Balance can be adjusted by trimming this with a laser or the like, by forming a thin film on a substrate separate from the magnetic head in the same way as above, or by configuring a trimming resistor circuit and trimming it. It may be configured to do so.

When the bridge circuit 3 of the magnetic head moves along the magnetic scale, a magnetic field is sequentially applied to each magnetoresistive element by the magnetic marks 1, 1, so that there is a gap between the terminals BD depending on the position of the magnetic head. Alternatingly varying unbalanced voltages are generated.

In the magnetic head manufactured by the method of the present invention, the bridge circuit 3 is perfectly balanced, so that the voltage appearing between the terminals b and d of the bridge circuit 3 will not be applied to the MR head due to impact or the like. It changes due to changes in the gap between the recording surface and the magnetic scale code, as well as changes in the magnetic field of the magnetic mark due to temperature and aging, and these changes are relative and do not accurately reflect the position of the magnetic mark. Therefore, when this is directly input to the comparator circuit 4 such as a Schmitt trigger, the characteristics of the output voltage pulse are constant and do not change even depending on the impact gap or changes over time. This feature allows the position of the magnetic head to be detected accurately at all times without causing any errors.

By configuring as in the present invention, the mutual spacing between the magnetoresistive elements of the magnetic head, for example, the distance between the magnetoresistive elements 33 and 34 relative to the magnetoresistive elements 31 and 32 can be reduced.
Since it is no longer necessary to strictly set the spacing, especially the phase difference, to 1/2 or 1/4 of the spacing λ between the magnetic marks, the present invention improves the degree of freedom in designing the magnetic head.

Next, the case of manufacturing a two-phase output bridge type MR magnetic head using the manufacturing method according to the present invention will be described with reference to FIGS. 3 to 7.

Figure 3 shows the principle magnetic head circuit connection of the two-phase output bridge type MR head.
31A, 32A, 33A, and 34A are magnetoresistive elements of the A-phase bridge circuit 3A connected to the bridge circuit, and 31B, 32B, and 34B are magnetoresistive elements of the B-phase bridge circuit 3B, and each magnetoresistive element is magnetically connected. As described above, the magnetic marks of the scale are arranged sequentially so as to have a phase difference of, for example, 1/2λ or 1/4λ with respect to the interval λ, and the corresponding magnetoresistive elements of the A phase and phase are /2λ: 1/4
When the phase difference is λ, or 1/4λ, the phase difference is 1/8λ. In addition, 35A-1, 35A-4 and 35B-1, 35B-4 are balance adjustment resistors 4A and 4B inserted in series with the corresponding magnetic resistance elements 31A, 34A and 31B, 34B of each phase, respectively.
is the output comparator circuit for each phase.

Therefore, the voltage between terminals +B and G is Vo, and the magnetoresistive elements 31A, 32A, 33A, 34A and 31
The resistance values of B, 32B, 33B, and 34B are R1, respectively.
A, R2A, R3A, R4A and R1B, R2
B, R3B, and R4B, the bridge circuit of each phase has R1A・R3A−R2A・R4A=0 R1B・R3B−R2B・R4B=0 when all the magnetoresistive elements are not magnetized. However, even if adjustment methods such as trimming are used, each strip-like minute magnetoresistive element formed by thin film forming means such as vapor deposition will not be accurate as planned. It is extremely rare to be configured to have a resistance value,
As mentioned above, the balance adjustment resistors 35A-1 and 3
5A-4, 35B-1, and 35B-4 are inserted and adjusted to balance each bridge circuit, so the respective resistance values after the above balance adjustment resistors are adjusted are R5A1, R5A4, and R5B1, R5B
4, the adjustment is made so that (R1A+R5A1)・R3A −R2A(R4A+R5A4)=0 (R1B+R5B1)・R3B −R2B(R4B+R5B4)=0.The adjustment is performed as follows. It is something.

That is, if the output voltages of terminals A ₁ , A ₂ and B ₁ , B ₂ of each phase are VA ₁ , VA ₂ and VB ₁ , VB ₂ , then VA ₁ = R2A/R1A+R2A・Vo VA ₂ = R3A/R3A+R4A・Vo VB ₁ = R2B/R1B+R2B・Vo VB ₂ = R3B/R3B+R4B・Vo. In this case, the above-mentioned balance adjustment resistors R5A1, R5A4 and R5B1, R5B4
Each resistance value of each corresponding magnetoresistive element 31A, 34
It is assumed that the resistance values of A, 31B, and 34B are initially set to sufficiently small values as will be described later.

Then, the output voltages of the respective output terminals A ₁ , A ₂ and B ₁ , B ₂ are measured as VA ₁ , VA ₂ and VB ₁ , VB ₂ ,
When comparing the output voltage for each phase, for example, VA ₁
> VA ₂ and VB ₁ < VB ₂ , in the A phase bridge, R2A/R1A + R2A > R3A/R3A + R4A, so as mentioned above, the balance adjustment The resistance value of the resistor 35A-1 is set to a predetermined resistance value R5A1 larger than the preset value, that is, the voltage is VA ₁ =VA ₂
Measure and adjust the voltage until B
In the phase bridge circuit, R2B/R1B+R2B<R3A/R3A+R4A, so the resistance value of the balance adjustment resistor 35A-4, which is also set to a small value in advance, is
The adjustment is completed by adjusting while measuring the voltage until it reaches a predetermined resistance value R5B4 that is larger than the preset value, that is, until the voltage becomes VB ₁ =VB ₂ .

FIG. 4 shows the A-phase and B-phase bridge circuits 3A and 3B and their respective magnetoresistive elements 31 in FIG.
A, 32A, 33A and 34A and 31B, 32
B, 33B and 34B and each balance adjustment 3
5A-1, 35A-4, 35B-1 and 35B-
4 is a plan view showing an example of the pattern and arrangement configuration of an embodiment formed on a substrate by thin film forming means such as vapor deposition according to the method of the present invention, FIG. 5 is a side view thereof, and FIG. An enlarged explanatory view of a part of the magnetoresistive element 31A and the balance adjustment resistor 35A-1, FIG. 7 shows the balance adjustment resistor 35A-1.
It is an enlarged view for explaining the manufacturing method.

4 to 6, numeral 10 is an insulating substrate made of glass or ceramics or coated with metal, and numeral 11 is an insulating substrate formed by vapor deposition, sputtering, etc. on the substrate 10. Metsuki or
The thickness of magnetoresistive alloys, such as permalloy, formed by thin film forming techniques such as CVD
It is a thin film of about 500 Å, and the pattern shown in the figure is formed by masking during thin film formation such as vapor deposition, by electrolytic etching, chemical etching, photo etching, etc. by masking after forming a thin film on the entire surface, or by forming a thin film on the entire surface. After forming, scribing and drawing processing is performed by numerical control using tools such as diamond without masking, or scribing removal drawing processing is performed by numerical control using particle beams such as laser beams and electron beams instead of the above tools. This is how it is formed.

The MR magnetic head using the AB two-phase output bridge type magnetoresistive element of this embodiment has magnetic marks 1a, 1b, . That is,
This kind of magnetic scale is used for each of the above magnetic marks 1
Each magnetoresistive element 3 is magnetized and recorded so that the center line of each of a, 1b, ... coincides with the radial direction of the magnetic scale disk.
1A, 32A, 33A and 34A and 31B,
32B, 33B, and 34B are arranged side by side so that they are in the normal direction on an arc of a certain curvature.

Each magnetoresistive element extends in the radial direction of the magnetic scale rotary disk, as shown in a partially enlarged view in FIG. It is constructed by connecting ten unit elements 31a in series in a staggered manner through lead portions 31b, with the line width of the element becoming narrower to about 0.015 mm as it approaches the center, and each unit element 3
In this embodiment, the distance P between the centers of the magnetic marks 1a is approximately 0.072 mm at the outer periphery and approximately 0.060 mm at the inner periphery, and the distance between the magnetic marks 1a and 1b is, for example, λ≒0.072 mm ( (approximately 0.060 mm on the inside), the values match (P=nλ of course), and furthermore, the distance between each unit element 31a and 32a of adjacent elements 31A and 32A is the same as that of this embodiment. So about
0.126mm (approximately 105mm on the inside), and the phase difference is (nλ+
3/4λ), that is, (nλ±1/4λ) (of course, it may be nλ±1/2λ). Also, although not shown, the B The phase unit element 31a' has an interval or phase difference of (nλ±
1/8λ).

In the illustrated embodiment, each of the balance adjustment resistors 35A-1, 35A-4, and 35B-
1, 35B-4 are each magnetoresistive element 31 as shown in the figure.
A, 34A and 31B, 34B each +B side terminal 3
Terminal portions 31C, 34C, 31 are formed on the thin film 11 portions in 1C, 34C, 31C', 34C' by etching or scribing drawing processing using the above-mentioned tool or particle beam when forming the thin film or after forming the thin film.
In order to form thin film conductive paths C' and 34C' in a zigzag pattern, the thin film 11 is formed in a zigzag pattern by removing it or leaving it absent.In the illustrated state, each balance adjustment resistor 35A- 1, 35A-4 and 3
The resistance values of 5B-1 and 35B-4 are sufficiently lower than those of the corresponding magnetoresistive elements 31A, 34A and 31B, 34B (in this example, they are made of the same alloy material as the magnetoresistive elements). composed of a thin film).

And in the figure, 31P, 34P, and 31
P′ and 34P′ are virtual machining start points, and the third
The voltages VA ₁ , VA ₂ and VB ₁ as explained in the figure,
While measuring VB ₂ , first, according to VA ₁ > VA ₂ , the thin film 11 is removed by laser processing along the broken line arrow from the processing start point 31P until VA ₁ ≒ VA ₂ , and then Next, in accordance with VB ₁ <VB ₂ , the thin film 11 is similarly removed by laser processing from the processing start point 34P' along the broken line arrow until VB ₁ ≈VB ₂ . That is, by this thin film removal process, a staggered thin film conductive path is formed with a predetermined length in the balance adjustment resistor holes 35A-1 and 35B-4. And resistances 35A-1, 35A-4 and 35B-1, 3 for balance adjustment
When the width and length of the lattice part without the thin film 11 of 5B-4 and the lattice part of the thin film 11 are set to values as shown in the figure, and the thin film 11 is removed by laser processing and processed by scribing, a magnetoresistive element is formed in the unit adjustment resistance section 31U. You can change the resistance by about 0.5% of the 31A resistance, so each balance adjustment resistor is 35A.
-1, 35A-4 and 35B-1, 35B-4, if 20 unit adjustment resistor parts 31U are configured in advance, adjustment of about 10% is possible, so it is almost sufficient. It is thought that.

Processing start points 31P, 34 for the above adjustment
Trimming processing from P, 31P', 34P' is
It goes without saying that the laser processing is not limited to numerical control, but may also be performed using other particle beams or mechanical tools, or may be performed using particle beams or etching in a masked state for each predetermined unit.

Although the method of manufacturing the magnetic head according to the present invention has been described above, the method of forming the balance adjusting resistor 35A-1 and the like will now be explained again with reference to the enlarged view of FIG.

That is, a large number of first slits 11c, 11c are formed by cutting the thin film in a comb-like shape toward the inside from one side 11a of the resistive material thin film 11 formed in a strip shape as a circuit conductor on the insulating substrate 10. , a large number of second slits 11d, 11d are formed by cutting out the thin film so as to extend substantially parallel to the first slits from the inside of the side 11b opposite to the first slit, and During adjustment, the thin film 1 between the second slits
1e and 11e are removed in a linear shape 11f in a direction substantially perpendicular to the second slits, and the required number of second slits are sequentially connected, so that the liquid flows in the region of the thin film portion 11g along the side 11b. By cutting off the current, the resistance value of the resistor 35A-1 is increased stepwise to obtain the required resistance value for balance adjustment.

Since the present invention is configured as described above, when the present invention is used, the configuration of the output detection circuit of the MR magnetic head can be simplified, and high detection accuracy can be obtained.
This makes it possible to provide a new MR magnetic head in large quantities at low cost that does not require much effort for adjustment.

Note that the configuration of the present invention is not limited to the above-mentioned embodiments; for example, the balance adjustment mechanism for adjusting the balance of the bridge may be configured as a thin film resistor on a substrate separate from the bridge type magnetic head. The design of each component can be changed freely within the scope of the purpose of the present invention, and the present invention encompasses all of them.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a one-phase magnetic head circuit for explaining the principle of a magnetic head circuit for a magnetic encoder manufactured by the method according to the present invention, and FIG. 2 is a similar diagram of a conventionally known magnetic head circuit for a magnetic encoder. An explanatory diagram of a one-phase magnetic head for explaining the principle, and FIGS. 3 to 7 are explanatory diagrams of a two-phase output bridge type MR magnetic head manufactured by the manufacturing method according to the present invention. 1, 1... Magnetic mark, 2, 5... Magnetic head, 3, 6... Bridge circuit, 31, 32, 3
3, 34, 61, 62, 63, 64... Magnetoresistive element, 35... Resistor for balance adjustment, 4, 8...
... Schmitt trigger circuit, 7... Differential amplifier.

Claims (1)

[Claims] 1. A magnetic head for a magnetic encoder that is moved relative to a magnetic scale provided with magnetic marks, the head comprising a plurality of bridge-connected magnetic resistors formed as a thin film on an insulating substrate. Motoko and
A method of manufacturing a magnetic head for a magnetic encoder having a balance adjustment resistor formed as a thin film on an insulating substrate and inserted into at least one side of the bridge, wherein the bridge-connected resistor is formed as a thin film on an insulating substrate. A plurality of magnetoresistive elements are formed in at least two phases along the direction of relative movement with respect to the magnetic scale, and in the above-mentioned operation of forming a resistor for balance adjustment, a thin film of resistance material formed in a strip shape on an insulating substrate is directed inward from one side. a plurality of first slits formed by cutting the thin film in a comb-like shape, and extending substantially parallel to the first slits from the inside of the side opposite to the one side to a position midway between the first slits. A large number of second slits are formed by omitting the thin film, and during balance adjustment, the thin film between the second slits is linearly removed in a direction substantially perpendicular to the second slits to obtain the required number of slits. A method of manufacturing a magnetic head for a magnetic encoder, characterized in that a required resistance value for balance adjustment is obtained by sequentially connecting the second slits of the head.