JP2002031546A - Magnetic encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce and error due to a cross talk between two kinds of cycles to improve measurement precision in a magnetic encoder detecting an absolute position on the basis of two kinds of cycle signals. SOLUTION: A first scale coil 14 is arranged in the measurement direction at a cycle λ1/2, and a second scale coil 16 is arranged symmetrically with respect to the axis of this arrangement. In this way, a magnetic field formed by the second scale coil 16 is cancelled in the first scale soil 14 arrangement area, so that a cross talk between these scale coils is reduced. A wiring line connecting the first and second scale coils 14, 16 together is formed into a coil type connection coil. The connection coils adjacent to each other in the measurement direction are arranged proximately, and magnetic fields formed by them have no positional information and have less influence on position measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of detecting a magnetic flux, which is formed by a scale coil and changes periodically in a measurement direction, by a detection coil relatively moving in the measurement direction with respect to the scale coil. The present invention relates to a magnetic encoder to be calculated.

[0002]

2. Description of the Related Art An encoder is known which detects a relative movement amount between two objects by using a periodic change of a predetermined physical quantity. The scale fixed to one of the relatively moving objects forms a periodic change in the moving direction of the predetermined physical quantity, and the sensor fixed to the other object detects this periodic change and counts the number of periods. , The relative movement amount is calculated.

The above-mentioned encoder can detect the relative movement amount of two objects, but cannot directly detect the relative position. That is, only the relative position at that time is detected as the movement amount from the reference position.
On the other hand, a plurality of scales having different periods are provided, and within a period corresponding to the least common multiple of the plurality of periods,
There is known an absolute encoder capable of detecting an absolute position.

On the other hand, there is known an encoder that uses light intensity, capacitance, and the like as physical quantities that change periodically.

[0005]

In an encoder capable of detecting an absolute position based on a plurality of cycles, it is necessary to prevent interference between the plurality of cycles.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce a measurement error due to interference between a plurality of cycles in a magnetic encoder capable of detecting an absolute position in a plurality of cycles using a magnetic flux as a physical quantity that changes in a cycle. I do.

[0007]

In order to solve the above-mentioned problems, in a magnetic encoder according to the present invention, considering the symmetry and periodicity of the coil, the detection signal has a period other than a desired period. The coils are arranged to prevent or reduce riding.

According to one aspect of the present invention, the first scale coil is arranged at a first period in the measurement direction, and the second scale coil is arranged at the left and right sides of the first scale coil in the measurement direction. It is arranged by. The second cycle has a value other than an integral multiple of the first cycle. Preferably, the second
Is a value close to twice the first period. The first scale coil is, for the second scale arranged on the left and right,
They are alternately coupled by coupling wiring. That is, the odd first scale coils are coupled to the second scale coil disposed on the left side, while the even first scale coils are coupled to the second scale coil on the right side. At this time, the left and right second scale coils are arranged symmetrically with respect to the axis of the arrangement of the first scale coils.

[0009] With this object arrangement, the influence from the left and right second scale coils is canceled out at the portion where the first scale coil is arranged, and interference is prevented or reduced.

Further, the coupling wiring may form a coil, and may be arranged so that coils adjacent to each other in the measurement direction are adjacent to each other. This allows
The change in the magnetic field formed by the coupling wiring in the measurement direction is reduced, and the magnetic field has no position information. Therefore,
The influence on the measurement of the position information is reduced.

[0011] Further, the coupling portion between the coupling wiring and the first scale coil may be arranged at a period twice as long as the first period on each of the left and right sides of the axis of the arrangement of the first scale coil. it can. Further, a coupling portion between the coupling wiring and the second scale coil may be arranged at the second period.

[0012]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of the present embodiment. A scale 10 extending in a measurement direction indicated by an arrow in the drawing and a slider 12 movable in the measurement direction are arranged integrally with the object to be measured or in a predetermined relationship. By detecting the relative movement amount or the relative position between the scale 10 and the slider 12, the movement amount or the position of the measuring object is detected. On the scale 10, a wiring pattern that repeats in a predetermined direction in the measurement direction is formed. Wiring pattern includes a first scale coils 14 arranged in a cycle lambda _1/2 in the measurement direction in a row, and the second scale coils 16 arranged in the respective period lambda ₂ on both sides of the first scale coils 14, the Connection wiring 1 for connecting the first and second scale coils 14 and 16
8 inclusive. On the other hand, a wiring pattern is also formed on the slider 12, and the first detection coil 20 is disposed at a position corresponding to the first scale coil 14, and the second detection coil 22 is disposed at a position corresponding to the second scale coil 16. Slider 1
2, a first excitation coil 24 is disposed at a position corresponding to the second scale coil 16, and a second excitation coil 26 is disposed at a position corresponding to the first scale coil 14.

A current of a predetermined frequency flows from the transmission control unit 28 to the first and second excitation coils 24 and 26, respectively. This current causes the scale coils 14, 16
A flowing current is generated in the inside, and the detection coils 20 and 22 receive a magnetic field due to the induced current. The reception control unit 30 calculates the amount of movement and the position of the slider 12 based on the intensity received by the detection coils 20 and 22.

FIG. 2 shows details of the wiring pattern. As described above, the first scale coils 14 are arranged in a line in the measurement direction at a period λ _1/2 . The second scale coil 16 has an axis 32 of the array of the first scale coil 14.
Are symmetrically arranged in two rows. In the following description, when it is necessary to distinguish the two rows of the second scale coils 16, the upper and lower parts in FIG. 2 are denoted by reference numerals 16 a and 16 b, respectively. The second scale coils 16 are arranged with a period λ ₂ in each row. Also,
Second scale coils 16a, 16b arranged on both sides
Are arranged at the same position in the measurement direction so that each pair forms a pair.

The first scale coil 14 and the second scale coil 16 are connected one-to-one by a connection wiring 18. The first scale coil 14 coupled to the second scale coil 16 on one side is one step as shown. In the following description, when it is necessary to distinguish the first scale coil 14 depending on the other party to be coupled, the one connected to the second scale coil 16a is denoted by reference numeral 14a and the one connected to the second scale coil 16b. Are described using reference numeral 14b. In FIG. 2, the odd-numbered first scale coil 14b from the left is coupled to the second scale coil 16b, and the even-numbered first scale coil 14a from the left is coupled to the second scale coil 16a. The first scale coils 14a, 14b will be located at each period lambda _1. Also, the period λ ₁ ,
λ ₂ is a close but unequal value.

The coupling wiring 18 is connected to the first scale coil 14
a and a wiring 18a connecting the second scale coil 16a to the second scale coil 16a;
First scale coil 14b and second scale coil 16b
Are connected to each other. Further, the coupling wiring 18
Are formed in a coil shape, and are arranged with a slight gap so that adjacent ones are adjacent to each other. The coil-shaped portion of the coupling wiring 18 is hereinafter referred to as a coupling coil 34, and the coupling coil corresponding to the coupling wiring 18a is denoted by reference numeral 34a, and the coupling coil corresponding to the coupling wiring 18b is denoted by reference numeral 34b.

The connection wiring 18 further includes a first connection portion 36 connecting the first scale coil 14 and the connection coil 34,
It has a second connecting portion 38 for connecting the second scale coil 16 and the coupling coil 34. First and second connection parts 36, 3
In FIG. 8 as well, those belonging to the coupling wiring 18a will be given the suffix a as needed, and those belonging to the coupling wiring 18b will be given the suffix b as well. As shown in figure, the first connecting portion 36a, 36b has a first scale coils 14a respectively, are arranged in the same period lambda ₁ and the sequence of 14b. The second connection portions 38a and 38b are also arranged at the same cycle λ ₂ as the arrangement of the second scale coils 16a and 16b, respectively. The first and second connecting portions 36 and 38 are preferably arranged such that the centers of the scale coils 14 and 16 to which they are connected and the centers of the connecting portions 36 and 38 coincide with the measurement direction. Note that the first and second connection portions 36,
38 is desirably formed to be short, and it is desirable that the distance between the paired wirings constituting the connection portion is also small. While the first and second connection portions 36 and 38 are shortened, the interval between the first and second scale coils 14 and 16 must have a predetermined value. The interval is formed widely.

The first and second exciting coils 24 and 26 of the slider 12 have a substantially rectangular shape. The first excitation coil 24 is disposed to face each of the second scale coils 16a and 16b, and the rectangular shape of the coil has a length of approximately 2λ _{2 in} the measurement direction. The second excitation coil 26 is disposed so as to face the first scale coil 14, and the rectangular shape of the coil is substantially two in the measurement direction.
λ ₁ length. First and second excitation coils 2
4 and 26 are separately supplied with electric power from the transmission control unit 28, whereby the first and second scale coils 14, 1
Current is induced in 6.

The first and second detection coils 20, 22 of the slider 12 are arranged at positions overlapping the second and first excitation coils 26, 24. However, electrical insulation is maintained. The first detection coil 20 has a shape in which four rhombuses or squares are connected, and portions where wires appear to intersect in the drawing are separated in a direction perpendicular to the paper surface, and insulation is secured. The four diamond-shaped parts are λ ₁ /
They are arranged in two cycles. Two second detection coils 22 are arranged corresponding to the first excitation coil 24. Further, like the first detection coil 20, it has a shape in which four rhombuses or squares are connected, and the portions that appear to intersect in the drawing are similarly insulated. Array period of the diamond twelfth detection coil 22 is lambda _2/2. As described above, current flows through the first and second detection coils 20 and 22 due to the magnetic field generated by the current flowing through the first and second scale coils 14 and 16. The position and the movement amount of the slider 12 are measured by detecting the current by the reception control unit 30 and measuring the intensity and the intensity change.

FIGS. 3 and 4 show the measurement principle of the magnetic encoder according to the present embodiment. FIG. 3 is a diagram for describing measurement relating to the first excitation coil 24 and the first detection coil 20. As shown, currents of opposite phases are applied to the two first exciting coils 24. As a result, a reverse current also flows through the second scale coils 16a and 16b. This current also flows through the first scale coils 14a, 14b coupled by the coupling wires 18a, 18b, and forms opposite magnetic fields alternately arranged in the measurement direction. The magnetic field induces alternating currents in the four rhombic portions of the first detection coil 20 alternately in the figure, but these currents are added together by the configuration of the rhombic portions as described above. Is done. The intensity of this current changes depending on the relative position of the first scale coil 14 and the first detection coil 20 in the measurement direction. That is, when the center of the rhombus of the first detection coil 20 coincides with the center of the first scale coil 14, the maximum value or the minimum value is obtained, and during that time, the value corresponds to the phase of these coils. This current value is substantially the wavelength lambda ₁ of the sine wave.

FIG. 4 is a diagram for explaining the measurement of the second exciting coil 26 and the second detecting coil 22. As shown, a current flows through the second excitation coil 26. As a result, currents in the same direction flow through the first scale coils 14a and 14b. This current is applied to the coupling wiring 18
a, the second scale coil 16 coupled at 18b
a, 16b, and form a magnetic field in the same direction. Second scale coils 16a, 1 adjacent in the measurement direction
A magnetic field opposite to the magnetic field formed in the coils 16a and 16b is formed in a portion between the coils 6a and 6b. Due to these magnetic fields, four diamond-shaped portions of the second detection coil 22
Alternately, currents in the opposite direction are induced in the figure, but these currents are added together by the configuration of the diamond-shaped portion as described above. The intensity of this current changes depending on the relative position of the second scale coil 16 and the second detection coil 22 in the measurement direction. That is, the center of the rhombus of the second detection coil 22 is
When the center coincides with the center of the second scale coil 16, the maximum value or the minimum value is taken, and during that time, the value is in accordance with the phase of these coils. This current value is almost the wavelength lambda ₂ of the sine wave.

As described above, two sine-wave signals that are close to each other but have different wavelengths λ ₁ and λ ₂ can be obtained according to the relative movement of the scale 12. The phase relationship between the two sinusoidal signals is a periodic function with the least common multiple λ of λ ₁ and λ ₂ as one wavelength. In other words, in the range of the wavelength Λ, λ ₁ , λ ₂
, The absolute position of the scale 12 can be uniquely determined. As for the measurement of the wavelength Λ or more, it is stored every time the wavelength Λ moves, and the amount of movement that does not reach one wavelength is calculated from the phase relationship between the two sine wave signals as described above, and these are added. , The total movement amount of the scale 12 is calculated.

In detecting these two wavelengths λ ₁ and λ ₂ , an error may occur due to the influence of the other. For example, in FIG. 3, the magnetic field generated by the second scale coil 16 may affect the first scale coil 14 and disturb the magnetic field due to the current flowing through the second scale coil 16. Further, a magnetic field is generated by the coupling wiring 18, which may affect the first and second scale coils 14 and 16.

A configuration for eliminating such mutual influence due to the detection of two wavelengths will be described below.

The second scale coils 16a and 16b are arranged symmetrically with respect to the axis 32 of the arrangement of the first scale coils as described above. Therefore, as shown in FIG. 3, when currents of opposite phases flow through the second scale coils 16a and 16b, the magnetic fields generated by these currents are canceled at the position of the axis 32 of symmetry. Therefore, the influence on the detection of the magnetic field formed by the first scale coil 14 is reduced.

The coupling coil 34 is formed in a substantially rectangular shape, and is disposed adjacent to each other in the measurement direction so that adjacent ones have a narrow interval. As a result, the magnetic field generated by the coupling coil 34 is uniform in the measurement direction, that is, has no positional information. Therefore, this magnetic field
Although it affects the first and second scale coils 14 and 16, the influence has no positional information, and therefore appears as direct current in the current induced in the first and second scale coils 14 and 16. This DC component can be eliminated by the signal processing system, and as a result, the influence of the coupling coil 34 is reduced.

Further, the first connection portions 36a and 36b are arranged at a period λ ₁ equal to the arrangement period of the first scale coils 14a and 14b, respectively.
The arrangement between 36b is shifted by λ _1/2 . Therefore, the period of the magnetic field formed by the first connection portions 36a and 36b matches the period of the magnetic field of the first scale coils 14a and 14b, and therefore, the first scale coils 14a and 14b
Distortion of the waveform of the magnetic field formed by 14b can be prevented.

The second connecting portions 38a and 38b are arranged at a period λ ₂ equal to the arrangement period of the second scale coils 16a and 16b, respectively.
It is arranged at a position symmetrical with respect to the axis 32 of the array. Like the first connection portions 36a and 36b, the second scale coil 16
Distortion of the waveform of the magnetic field formed by a and 16b can be prevented. In addition, since they are arranged at positions symmetrical with respect to the axis of the arrangement, the magnetic fields of the first scale coil 14 cancel each other out, so that the influence is small.

In each coil, the first and second
Since the scale coils 14 and 16 as well as the coupling wiring 18 are formed to have substantially the same shape, the inductance of each coil is substantially equal, and the change in the propagation time due to the floating circuit element is suppressed to a small extent.

With the above-described coil arrangement, so-called crosstalk, which is a magnetic field applied to the measurement of one cycle, which affects the measurement of the other cycle, can be suppressed, and the measurement accuracy is improved.

In this embodiment, an encoder having coils arranged in two types of cycles has been described. However, an encoder using coils having more types of cycles may be used.
It can be adapted as well.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a magnetic encoder according to an embodiment.

FIG. 2 is an explanatory diagram of a shape of a coil and the like.

FIG. 3 is an explanatory diagram of measurement relating to a wavelength λ ₁ .

FIG. 4 is an explanatory diagram of measurement relating to a wavelength λ ₂ .

[Explanation of symbols]

10 scale, 12 slider, 14 (14a, 14
b) 1st scale coil, 16 (16a, 16b)
2nd scale coil, 18 (18a, 18b) coupling wiring, 20 first detection coil, 22 second detection coil,
24 First excitation coil, 26 Second excitation coil, 28
Transmission control unit, 30 reception control unit, 32 axes of arrangement of first scale coil, 34 (34a, 34b) coupling coil,
36 (36a, 36b) first connection portion, 38 (38a,
38b) Second connection.

Claims (4)

[Claims] 1. A scale coil arranged in a predetermined pattern in a measurement direction, an excitation coil for exciting the scale coil, and the excited scale coil arranged so as to be movable in the measurement direction with respect to the scale coil. A detection coil that detects the magnetic flux of the scale coil, and a calculation unit that calculates a relative movement amount of the scale coil and the detection coil from a change in the detected magnetic flux, wherein the scale coil has a first direction in a measurement direction. A first scale coil arranged in a cycle, and a second scale coil arranged symmetrically with respect to an axis of the array of the first scale coil and having a cycle other than an integral multiple of the first cycle on each side of the axis. A second scale coil arranged at a period of 1 and the first and second scale coils are connected in a one-to-one relationship, and the first scale coil is connected to a second scale on the left and right of the axis. Having a coupling line for coupling alternating Rukoiru, magnetic encoder. 2. The magnetic encoder according to claim 1, wherein the coupling wiring forms a coupling coil wired such that adjacent ones are adjacent to each other. 3. The magnetic encoder according to claim 1, wherein the coupling portion between the coupling wire and the first scale coil is provided on each side of an axis of the array of the first scale coil.
A magnetic encoder, wherein the magnetic encoder is arranged in the measurement direction at a period twice as long as the first period, and the coupling portion between the coupling wiring and the second scale coil is arranged at the second period in the measurement direction. . 4. The magnetic encoder according to claim 1, wherein a value twice as long as said first period and said second period are close to each other.