JP2004198253A - Scale of magnetic encoder, and magnetic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scale of a magnetic encoder having a simple structure, easy to manufacture and hardly generating warpage; and to provide a magnetic encoder provided with the scale and having high detection accuracy. <P>SOLUTION: This magnetic encoder 10 is provided with this scale 16 including: a substrate 12; and a plurality of scale coils (scale segments) 14 arranged side by side along a predetermined measurement track on the substrate 12. Magnetic glass is used for the material of the substrate 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic encoder scale and a magnetic encoder used in, for example, industrial equipment and transportation equipment.
[0002]
[Prior art]
Conventionally, as one means for detecting position, speed, and the like, a magnetic encoder provided with a scale including a substrate and a plurality of scale segments arranged side by side on the substrate along a predetermined measurement trajectory is known. It is known (for example, refer to Patent Document 1).
[0003]
The magnetic encoder has a magnetic flux generator for emitting magnetic flux to the scale segment, and a detector for detecting the magnetic flux returned by the scale coil, so that the magnetic encoder can move relative to the scale. A detection head is provided, and input and output of an electric signal are performed via the detection head.
[0004]
In order to perform high-precision detection with such a magnetic encoder, it is preferable that the gap between the scale and the detection head be kept within a predetermined minute range.
[0005]
The scale substrate is generally made of glass epoxy. Glass epoxy is obtained by impregnating an epoxy resin into a glass cloth in which glass fibers are woven in a cloth shape and hardening the glass cloth, and is excellent in strength and economy.
[0006]
However, the glass epoxy substrate is liable to warp, and the warp may cause the gap between the scale and the detection head to be too large or too small to lower the detection accuracy. Therefore, a substrate having high morphological stability is demanded. Even if the warp angle of the substrate is the same, if the scale is long, the gap between the scale and the detection head tends to be excessively large or small.
[0007]
In order to reduce such warpage of the scale, for example, a metal plate 108 is disposed on the glass epoxy substrate 104 of the scale 102 on the side opposite to the scale segment 106 as in a magnetic encoder 100 shown in FIG. The substrate 104 may be reinforced.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-317881
[Problems to be solved by the invention]
However, when the detection head 110 emits a magnetic flux to the scale segment 106, an eddy current is generated in the metal plate 108, which weakens the magnetic flux and lowers the detection accuracy.
[0010]
Further, there is a problem that turbulence (noise) of magnetic flux is generated due to an eddy current of the metal plate 108, and the S / N (Signal to Noise Ratio) ratio of the magnetic encoder is reduced.
[0011]
On the other hand, by forming the magnetic layer 112 between the substrate 104 and the metal plate 108 (or between the glass epoxy 104 and the scale segment 106), generation of eddy current can be prevented. However, there is a problem that the structure becomes complicated and the number of manufacturing steps increases.
[0012]
In particular, when the magnetic flux changes at a high frequency, it is necessary to form a layer of a soft magnetic material having a low conductivity, such as ferrite, on glass epoxy, but such a soft magnetic material is difficult to plate. Therefore, a dry process is required to form a thin film, and the number of manufacturing steps is greatly increased.
[0013]
The present invention has been made in view of the above problems, and has a magnetic encoder scale having a simple structure, easy to manufacture, and in which warping is unlikely to occur, and a high detection accuracy using the scale. It is an object to provide an expression encoder.
[0014]
[Means for Solving the Problems]
The present invention is directed to a magnetic encoder scale including a substrate and a plurality of scale segments arranged side by side along a predetermined measurement trajectory on the substrate, wherein the material of the substrate is magnetic glass. The present invention has solved the above-mentioned problem.
[0015]
Note that a large number of minute undulations may be formed on at least one surface of the substrate to form a rough surface, and the scale segment may be formed on the rough surface.
[0016]
Further, on at least one surface of the substrate, a base layer having at least one of zinc oxide, chromium and nickel chromium and having adhesion may be formed, and the scale segment may be formed on the base layer.
[0017]
In this case, it is preferable to divide the underlayer and form a plurality of layers.
[0018]
Further, it is preferable that the underlayer has the same shape as the plurality of scale segments.
[0019]
Further, the present invention has solved the above-mentioned problem by a magnetic encoder provided with any one of the scales described above.
[0020]
ADVANTAGE OF THE INVENTION According to this invention, simplification of the structure of a scale and simplification of manufacture can be aimed at, warpage can be reduced, and the detection accuracy of a magnetic encoder can be improved.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a side view schematically showing a structure of a magnetic encoder according to the present embodiment, FIG. 2 is a plan view showing a schematic structure of a scale of the magnetic encoder, and FIG. It is a bottom view which shows a schematic structure.
[0023]
The magnetic encoder 10 includes a scale 16 including a substrate 12 and a plurality of scale coils (scale segments) 14 arranged side by side on the substrate 12 along a predetermined measurement trajectory. It is characterized by glass.
[0024]
The other configuration is the same as that of the conventional magnetic encoder, and the description will be appropriately omitted.
[0025]
The magnetic encoder 10 has a magnetic flux generator 18 for emitting magnetic flux to the scale coil 14 and a detector 20 for detecting magnetic flux returned by the scale coil 12, and is movable along the scale 16. The detection head 22 is disposed so as to input and output electric signals via the detection head 22.
[0026]
The substrate 12 is an elongated rectangular plate-like body, and the material is magnetic glass as described above. Here, the magnetic glass refers to a low-melting glass that is dispersed and mixed with a soft magnetic material such as ferrite or terbium oxide that does not crystallize the low-melting glass and has poor reactivity with the low-melting glass. Is solidified. Specifically, for example, magnetic glass or the like manufactured by Sumita Optical Glass Co., Ltd. containing terbium oxide can be used.
[0027]
As a typical application of such a magnetic glass, a Faraday rotating glass having a function of rotating polarized light is conventionally known in the field of optics (for example, see JP-A-4-170338).
[0028]
The scale coil 14 has a configuration in which a plurality of first scale coils 24 and a plurality of second scale coils 26 are arranged side by side in the longitudinal direction on one surface of the substrate 12.
[0029]
The first scale coil 24 is an annular body in which a rectangular return part 24A and a rectangular receiving part 24B larger than the return part 24A form a loop, and the return part 24A is located near the center of the substrate 12 in the width direction. A plurality of receivers 24A are arranged at equal pitches along one end of the substrate 12 in the width direction.
[0030]
The second scale coil 26 is an annular body having the same shape as the first scale coil 24. They are arranged at the same pitch so that they are arranged every other. The second scale coil 26 is disposed so that the receiving portion 26B is along the other end in the width direction of the substrate 12, that is, along the side opposite to the side on which the receiving portion 24B of the first scale coil 24 is disposed. ing.
[0031]
A base layer 28 containing zinc oxide is formed on one surface of the substrate 12, and the scale coil 14 is formed on the base layer 28 by a plating method. The base layer 28 containing zinc oxide has good adhesion, and the provision of the base layer 28 enhances the adhesion between the scale coil 14 and the substrate 12. Here, “above the underlayer 28” means the surface of the underlayer 28, and is not limited to the case where it is arranged vertically above the underlayer 28 in actual use.
[0032]
The magnetic flux generator 18 includes a transmitting coil 30 disposed along both ends in the width direction of the substantially rectangular lower surface of the detection head 22 and a transmitter 32 for supplying a current of a predetermined frequency to the transmitting coil 30. It is configured to have.
[0033]
The transmitting coil 30 has the same rectangular shape as the rectangular first transmitting coil 30A disposed along one end in the width direction of the lower surface of the detection head 22 corresponding to the receiving section 24B of the first scale coil 24. Corresponding to the receiving section 26B of the second scale coil 26, the second transmitting coil 30B disposed along the other end in the width direction of the lower surface of the detection head 22 forms one loop. Have been. The transmitting coil 30 is configured such that the first transmitting coil 30A and the second transmitting coil 30B generate magnetic fluxes in opposite directions to the scale 14 when energized.
[0034]
The detection unit 20 includes a reception coil 34 disposed near the center of the lower surface of the detection head 22 in the width direction corresponding to the reception units 24A and 26A of the first scale coil 24 and the second scale coil 26, And a receiver 36 for detecting the voltage at 34.
[0035]
The receiving coil 34 has a first receiving coil 38 and a second receiving coil 40. The first receiving coil 38 forms a twisted pair, and a first loop 38A and a second loop 38B, which is reversely wound with respect to the first loop 38A, are continuous at an equal pitch every other along the measurement trajectory. ing. The pitch between the adjacent first loop 38A and the second loop 38B is equal to the pitch P between the adjacent first scale coil 24 and second scale coil 26 in the scale 16.
[0036]
The second receiving coil 40 also forms a twisted pair, and the first loop 40A and the second loop 40B, which is reversely wound with respect to the first loop 40A, are continuously arranged at an equal pitch every other along the measurement trajectory. I have. Note that the first receiving coil 38 and the second receiving coil 40 are arranged such that the first loop 38A and the first loop 40A are shifted by half the pitch P.
[0037]
The receiver 36 can individually detect terminal voltages of the first receiving coil 38 and the second receiving coil 40.
[0038]
Next, the operation of the magnetic encoder 10 will be described.
[0039]
First, when a current having a predetermined frequency is applied to the transmitting coil 30 from the transmitter 32 of the detection head 22, the first transmitting coil 30A and the second transmitting coil 30B generate magnetic flux, and these magnetic fluxes are supplied to the first scale coil. 24 and the second scale coil 26. The direction of the magnetic flux passing through the receiving unit 24B and the direction of the magnetic flux passing through the receiving unit 26B are opposite (opposite phase). As a result, an induced electromotive force is generated in the first scale coil 24 and the second scale coil 26, and a reverse current flows, and the return portions 24A and 26A emit magnetic fluxes in opposite directions.
[0040]
Here, since the material of the substrate 12 of the scale 16 is glass, even if a magnetic flux is emitted to the substrate 12, an eddy current is generated as in a substrate having a metal plate, and the magnetic flux is disturbed (noise). There is no.
[0041]
Also, since the substrate 12 has magnetism, the magnetic flux generated by the first transmitting coil 30A and the second transmitting coil 30B is reflected by the substrate 12, and the receiving units 24B and 26B receive strong magnetic flux. The magnetic flux returned by the return units 24A and 26A is strengthened.
[0042]
The magnetic flux generated by the first transmitting coil 30A and the second transmitting coil 30B also passes through the first receiving coil 38 and the second receiving coil 40, but the first receiving coil 38 is connected to the first loop 38A. The second loop 38B is reverse-wound, and the induced electromotive force is generated in each loop in the opposite direction and is canceled, so that the first transmitting coil 30A and the second transmitting coil 30B generate the first induced magnetic flux. No voltage is generated at both ends of the receiving coil 38. Similarly, no voltage is generated at both ends of the second receiving coil 40 due to the magnetic flux generated by the first transmitting coil 30A and the second transmitting coil 30B.
[0043]
The magnetic flux returned by the return units 24A and 26A passes through the first receiving coil 38 and the second receiving coil 40 of the detection head 22. In each loop of the first receiving coil 38 and the second receiving coil 40, a dielectric electromotive force corresponding to the magnitude of the returned magnetic flux is generated. As a result, the balance of the induced electromotive force in each loop of the first receiving coil 38 and the second receiving coil 40 is lost, and the receiver 36 reduces the terminal voltage of the first receiving coil 38 and the second receiving coil 40. Detect individually.
[0044]
When the detection head 22 moves along the scale 16, the terminal voltages of the first receiving coil 38 and the second receiving coil 40 change. For example, when the center of the first loop 38A of the first receiving coil 38 and the center of the return portion 24A of the first scale coil 24 approach, the center of the second loop 38B and the second scale coil 26 The center of the reply section 26A also approaches. At this time, the return portions 24A and 26A emit magnetic fluxes in opposite directions. However, since the first loop 38A and the second loop 38B are reversely wound, the first loop 38A and the second loop 38B have the same direction. A voltage is generated, and a maximum voltage is generated in the first receiving coil 38.
[0045]
When the detection head 22 moves by the pitch P with respect to the scale 16, a maximum voltage in the opposite direction is generated in the first receiving coil 38. When the detection head 22 moves along the scale 16 in this manner, a voltage corresponding to the amount of movement is generated at both ends of the first receiving coil 38. When the relationship between the amount of movement and the voltage is represented in an orthogonal graph, the shape becomes like a sine wave.
[0046]
Similarly, a voltage corresponding to the amount of movement is generated at both ends of the second reception coil 40, but the phase is shifted with respect to the voltage at both ends of the first reception coil 38.
[0047]
The amount of movement of the detection head 22 with respect to the scale 16 can be detected based on the voltage between both ends of the first reception coil 38 and the second reception coil 40.
[0048]
Since the substrate 12 of the scale 16 is made of glass, it has excellent morphological stability with respect to a substrate of a composite material such as glass epoxy, and the variation in the gap between the detection head 22 and the scale 16 is within a predetermined minute range. Can be easily stored.
[0049]
As described above, the gap between the detection head 22 and the scale 16 can be easily maintained in a preferable range, and the leakage and disturbance of the magnetic flux between the detection head 22 and the scale 16 can be suppressed. The encoder 10 has high detection accuracy and high reliability.
[0050]
In addition, the scale 16 is made of a single magnetic glass as the material of the substrate 12, and can be easily manufactured on a composite material substrate such as glass epoxy.
[0051]
Further, by forming the underlayer 28 on one surface of the substrate 12, the scale coil 14 can be easily formed on the underlayer 28 by a plating method, and the scale 16 is also easy to manufacture in this respect. Furthermore, the underlayer 28 containing zinc oxide can be easily etched, and the scale 16 can be easily manufactured in this respect as well.
[0052]
In the present embodiment, the scale 16 includes the first scale coil 24 and the second scale coil 26, but the present invention is not limited to this, and the shape and arrangement of the scale coil are particularly limited. The present invention is not limited thereto. For example, the present invention can be applied to a scale having a configuration in which a single type of coil is juxtaposed at equal pitches near the center of the scale. Further, the present invention is applicable to a scale having a configuration in which scale segments of a conductor such as a metal piece are juxtaposed at equal pitches, instead of the scale coil of a wire rod.
[0053]
In the present embodiment, the detection head 22 includes the first reception coil 38 and the second reception coil 40, but the present invention is not limited to this, and the detection head may be a single reception coil. The present invention is also applicable to a magnetic encoder provided with a magnetic head or a magnetic encoder provided with a detection head having three or more receiving coils. Further, the shapes of the receiving coil and the transmitting coil of the detection head are not particularly limited.
[0054]
Further, in the present embodiment, the substrate 12 of the scale 16 is a rectangular plate-like body corresponding to a linear measurement trajectory. However, the present invention is not limited to this. The present invention can be applied to a scale having another shape such as a cylindrical body corresponding to.
[0055]
Further, in the present embodiment, the magnetic encoder 10 has a configuration in which the detection head 22 moves with respect to the scale 16, but the present invention is not limited to this, and the scale may be moved with respect to the detection head. The present invention is also applicable to a magnetic encoder having a moving configuration.
[0056]
Further, in the present embodiment, the scale coil 14 is formed by a plating method on the base layer 28 including zinc oxide. However, the present invention is not limited to this, and the same good quality as zinc oxide is used. For example, a scale coil may be formed on the underlying layer by a plating method as an underlying layer having a configuration that includes another material such as chromium, nickel chrome, or the like, which has adhesion. Furthermore, good adhesion can be obtained even when a base layer containing titanium is formed, and the scale coil can be formed by a plating method.
[0057]
In the present embodiment, the underlayer 28 is formed uniformly on the entire surface of the substrate 12 (see FIG. 1), but the present invention is not limited to this, and as shown in FIG. A cut 28A may be formed in the base layer 28, and the base layer 28 may be divided into a plurality of parts and formed on the substrate 12. By doing so, the eddy current generated in the underlayer 28 due to the magnetic flux transmitted from the detection head 22 can be reduced. It is more preferable that the underlayer 28 has the same shape as the plurality of scale coils 14, as shown in FIG.
[0058]
As a manufacturing method, the base layer 28 may be formed uniformly on the entire surface of the substrate 12, then cut and formed, and the scale coil 14 may be plated. Alternatively, the underlayer 28 may be formed uniformly on the entire surface of the substrate 12, and the scale coil 14 may be plated, and then the cut 28A may be formed to divide the underlayer 28.
[0059]
Instead of the underlayer, a rough surface having a large number of minute undulations may be formed on the substrate, and a scale coil may be formed on the rough surface by plating. If a base layer is further formed on the rough surface and a scale coil is formed on the base layer, the scale coil can be more firmly fixed.
[0060]
In the present embodiment, the scale coil 14 is formed by a plating method, but the method of forming the scale coil is not particularly limited. When the plating method is not used, the underlayer 28 and the rough surface may be omitted.
[0061]
Further, in the present embodiment, a glass containing ferrite and terbium oxide is exemplified as the magnetic glass, but the material is not particularly limited as long as the glass is provided with magnetism.
[0062]
【The invention's effect】
As described above, according to the present invention, the material of the substrate 12 of the scale 16 is made of magnetic glass, thereby simplifying the structure of the scale, facilitating the manufacture, and suppressing the warpage of the scale. And an excellent effect that the detection accuracy of the magnetic encoder can be improved.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing an outline of the structure of a magnetic encoder according to an embodiment of the present invention. FIG. 2 is a plan view showing an enlarged scale structure of the magnetic encoder. FIG. FIG. 4 is an enlarged bottom view showing the structure of a detection head of the type encoder. FIG. 4 is a side view showing the structure of a magnetic encoder according to another embodiment of the present invention. FIG. FIG. 6 is a side view showing an example of the structure of a conventional magnetic encoder.
10, 100: magnetic encoder 12, 104: substrate 14, 106: scale coil (scale segment)
16, 102 Scale 18 Magnetic flux generator 20 Detectors 22, 110 Detection head 28 Base layer 28A Break

Claims (6)

In a scale of a magnetic encoder comprising a substrate and a plurality of scale segments arranged side by side along a predetermined measurement trajectory on the substrate,
A magnetic encoder scale, wherein the material of the substrate is magnetic glass. In claim 1,
At least one surface of the substrate is a rough surface on which a large number of minute undulations are formed, and the scale segment is formed on the rough surface. In claim 1 or 2,
At least one surface of the substrate includes one of zinc oxide, chromium, and nickel chromium, a base layer having adhesion is formed, and the scale segment is formed on the base layer. Magnetic encoder scale. In claim 3,
A scale for a magnetic encoder, wherein a plurality of the underlayers are formed separately. In claim 4,
The scale of the magnetic encoder, wherein the underlayer has the same shape as the plurality of scale segments. A magnetic encoder comprising the scale according to claim 1.

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