JPH06241832A - Electromagnetic-induction linear scale - Google Patents

Abstract

PURPOSE:To provide an absolute electromagnetic-induction linear scale wherein the displacement of a slider can be measured wish high resolution without adjusting a zero point in a measurement. CONSTITUTION:In an electromagnetic-induction linear scale, a scale 1 on which exciting coils have been mounted and a slider 2 on which two sets of detection coils 4, 5 have been mounted in such a way that their phases are dislocated by a 1/4 pitch are arranged so as to be faced, and the linear displacement of the slider is measured. A first exciting coil 7 as well as a second exciting coil 8 and a third exciting coil 9 in which the distribution of coil-side lengths is changed relatively along the lengthwise direction of the scale 1 and which have been arranged by setting a phase difference of 180 deg. between both are mounted on the scale 1. Step positional information which has been found from induced voltages of the detection coils 4, 5 with reference to the second and third exciting coils 8, 9 is added to inside-pitch positional information which has been found from an induced voltage with reference to the first exciting coil 7. The displacement (absolute position) from the reference point of the slider 2 is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction type linear scale known as Inductosyn (trade name).

[0002]

2. Description of the Related Art An electromagnetic induction type linear scale called Inductosyn (trade name) is known as a linear displacement digital converter. Next, the configuration of the conventional magnetic induction type linear scale and its operating principle are shown in FIG.
This will be described in (a) to (c). First, in FIG.
1 is the scale of the length corresponding to the measurement length, 2 is the scale 1
Is a slider that moves in the direction of the arrow X along the axis of the scale 1. The scale 1 has exciting coils 3 arranged in a zigzag pattern at an equal pitch P.
However, the slider 2 has a spatial phase of 1/4 between them.
Two sets of detection coils 4 and 5 which are arranged in a zigzag pattern at a pitch P by shifting the pitch are mounted.

Here, when the slider 2 is displaced in the X direction while the exciting coil 3 is excited by the AC power source 6 at the frequency f ₁ , the detecting coils 4 and 5 are displaced as shown in FIG. A voltage Va that changes sinusoidally in response to
Vb is induced. Therefore, if the wave numbers of the induced voltages Va and Vb are counted by the signal processing circuit connected to the subsequent stage of the detection coil, the pitch P of the exciting coil 3 and the detection coils 4, 5 are counted.
From the wave number n of the induced voltage output from the output, the step position X1 of the slider 2 corresponding to an integral multiple of the coil pitch P is X1.
= P × n. In addition, induced voltages Va and V
Since there is a phase difference of 90 degrees in electrical angle between b, the moving direction of the slider 2 can be discriminated from the output voltage of the sine and cosine, and the induced voltages Va and Vb are combined to perform signal processing. As a result, the information on the in-pitch position obtained by multi-dividing the displacement for one pitch can be obtained. Here, the position in the pitch of the slider is ΔX, the vector sum of the voltages Va and Vb is V,
Assuming that θ is a phase within one pitch, from the diagram (c), Va = V cos θ, Vb = V sin θ, θ = (ΔX / P) ×
Since it is given as 360 °, the in-pitch position ΔX can be obtained from the values of the voltages Va and Vb. For example, when the coil pitch P = 1 mm and the electrical angle 360 ° is divided into 1000, a resolution of 1 μm can be obtained for ΔX. As a result, the linear displacement (absolute position from the reference point) X of the slider 2 can be obtained as X = X1 + ΔX.

[0004]

By the way, the above-mentioned magnetic induction type linear scale is an incremental type (a type which outputs the displacement increase / decrease of the slider from a certain point).
Therefore, when actually measuring the displacement of the slider (absolute position from the reference point), it is necessary to adjust the zero point each time the measurement is made to adjust the slider to the reference point, which is troublesome to handle and increases the resolution. When the coil pitch P is reduced as described above, the number of wave counts with respect to the amount of displacement of the slider increases, and thus high-speed processing of the output signal becomes difficult.

The present invention has been made in view of the above points, and an object of the present invention is to solve the above problems and to measure the displacement (absolute position) of a slider with high resolution without performing zero adjustment during measurement. It is to provide the absolute type magnetic induction type linear scale.

[0006]

In order to achieve the above object, the magnetic induction type linear scale of the present invention has a first exciting coil relative to the scale and a coil side length distribution along the longitudinal direction of the scale. 2nd and 3rd exciting coils which are arranged so that the phase difference between them is changed and arranged, and obtained from the induced voltage of the detecting coil corresponding to the exciting frequency of the 2nd and 3rd exciting coils. The displacement of the slider is measured by adding the information on the step position corresponding to an integral multiple of the coil pitch and the information on the in-pitch position obtained from the induced voltage of the detection coil corresponding to the excitation frequency of the first excitation coil. Shall be configured.

Further, as a concrete means of the linear scale, there is the following structure. (1) A phase difference of 180 degrees in electrical angle is set between the second exciting coil and the third exciting coil. (2) A phase difference of 90 degrees in electrical angle is set between the second exciting coil and the third exciting coil.

(3) Each exciting coil mounted on the scale,
Also, each detection coil mounted on the slider is formed as a thin film coil in which a magnetic plate is used as a substrate and is laminated thereon to form a pattern. (4) In the above item (3), a thin film magnetic layer is formed in the peripheral region of the thin film coil.

[0009]

In the above structure, when the first exciting coil mounted on the scale is excited at the frequency f ₁ and the second _and third exciting coils are excited at the frequency f ₂ , the first detecting coil mounted on the slider becomes the first The induced voltage of frequency f ₁ corresponding to the exciting coil and the voltage corresponding to the second and third exciting coils (exciting frequency f ₂ ) are simultaneously induced. here,
If a phase difference of 180 ° in electrical angle (reversing the flowing direction of the exciting current) is set between the coils so that the magnetic fluxes cancel each other out between the second exciting coil and the third exciting coil. A voltage corresponding to the difference in the coil side length distribution of the exciting coil is induced in the detection coil of the slider. Moreover, since the second and third exciting coils relatively change the distribution of the coil side length along the longitudinal direction of the scale, the induced voltage of the detecting coil is related so as to change depending on the step position of the slider. As a result, the step position of the slider (the position corresponding to the coil pitch number from the reference point) can be immediately obtained from the value of the induced voltage. That is, unlike the conventional configuration described in FIG. 5, it is not necessary to count the wave number of the output signal from the detection coil or perform zero adjustment.
The step position of the slider can be obtained immediately.

On the other hand, if a phase difference of 90 ° in electrical angle is set between the second exciting coil and the third exciting coil,
It is possible to further improve the detection accuracy of the above step position information by utilizing the phase of the voltage induced in the detection coil of the slider based on the same operation principle as described in FIG. 5 above. At the same time as above, the first detection coil of the slider is
Since the voltage corresponding to the exciting coil (exciting frequency f ₁ ) is induced, the information on the in-pitch position can be obtained based on this by the same operation principle as in FIG. Therefore, after the output signal of the frequency f _{1 and} the output signal of the frequency f ₂ are separated by the filter of the signal processing circuit connected to the latter stage of the slider, the information on the pitch position and the information on the step position are detected separately. ,
By adding the slider position and the in-pitch position, the linear displacement (absolute position) of the slider can be instantaneously measured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings of each embodiment, the same members corresponding to those in FIG. 4 are designated by the same reference numerals. Embodiment 1 First, in FIG. 1, two sets of detection coils 4 and 5 are spatially displaced from each other by 1/4 pitch in the same manner as in FIG. Is installed. On the other hand, in addition to the first exciting coil 7 arranged in a zigzag at the equal pitch P on the scale 1 as in the exciting coil 3 of FIG. 5, second and third exciting coils 8 and 9 arranged on the same plane are mounted. Has been done. Here, the patterns of the second exciting coil 8 and the third exciting coil 9 are patterned so that the distribution of the coil side lengths L1 and L2 relatively changes along the longitudinal direction of the scale 1 as shown in the figure ( In the illustrated example, the boundary line between the exciting coils 8 and 9 is an oblique straight line), and the exciting coils 8 are arranged.
And 9 have an electrical angle of 18 so that they cancel each other's magnetic flux.
A phase difference of 0 ° (reversing the flowing direction of the exciting current) is set.

With this structure, when the slider 2 is moved while the first exciting coil 7 is excited by the alternating current of the frequency f ₁ and the second and third exciting coils 8 and 9 of the frequency f ₂ , the slider 2 is detected. The coils 4 and 5 have induced voltages Va-1 and Vb-1 (frequency f ₁ ) generated by the first exciting coil 7 and induced voltages Va-2 and V generated by the second and third exciting coils 8 and 9 at the same time.
b-2 (frequency f ₂ ) is generated. Here, the induced voltage Va
-2, Vb-2 is a voltage value according to the difference between the coil side lengths L1 and L2 between the exciting coils 8 and 9, and the arrangement of the exciting coils 8 and 9 has a geometric pattern as shown in FIG. In Figure 2
As indicated by, the induced voltage changes in proportion to the displacement X of the slider 2 in proportion to the square of the position. Exciting coils 8 and 9
The induced voltages Va-2 and Vb-2 having characteristics different from those in FIG. 2 can be obtained by changing the pattern.

Therefore, in the signal processing circuit (not shown) connected to the latter stage of the slider 2, the output signals of the detection coils 4 and 5 are filtered by the voltages Va-1 and Vb of the frequency f _1.
-1 and the voltages Va-2 and Vb-2 of the frequency f ₂ are separated, and one of the induced voltages Va-1 and Vb-1 is processed in the same manner as described with reference to FIG. The information of the in-pitch position ΔX obtained by multi-dividing one pitch is obtained.
Further, based on the peak voltage value of either one of the induced voltages Va-2 and Vb-2, the step position X1 from the reference point of the slider 2 corresponding to the integral multiple of the coil pitch P (see FIG. (Corresponding to the step position obtained by counting the wave number described in 1)) is obtained. Then, by adding the information of the step position X1 and the information of the in-pitch position ΔX,
The displacement X (absolute position) of the slider 2 can be instantaneously measured with X = X1 + ΔX. Moreover, in this case, it is of course not necessary to adjust the zero point, and since it is not necessary to count the wave number as described in FIG. 5, the output signal can be processed at high speed.

Next, FIG. 3 shows a manufacturing process of the exciting coils 7, 8 and 9 mounted on the scale 1. (1) First, a rectangular magnetic plate (for example, a silicon steel plate) having a size of 20 × 5 × 0.1 mm is used as a magnetic substrate 10, and an aluminum oxide film 11 having a thickness of 0.2 μm is formed as an insulating layer on the upper surface side of the magnetic substrate 10. To form a film. (See FIG. 5A) (2) Subsequently, copper 12 having a film thickness of 10 μm is deposited on the aluminum oxide film 11 as a conductor layer. (See Fig. (B)) (3) Next, a silicon oxide film having a thickness of 0.2 µm is formed on the copper 11, an etching mask having a predetermined pattern is formed by a photo process, and ion beam etching is further performed. The exciting coils 8 and 9 shown in FIG. 1 are patterned. (See FIG. 7C) (4) Further, the polyimide resin 13 is applied on the exciting coils 8 and 9 to finish the surface flat. (Refer to FIG. (D)) (5) Next, copper of 10 μm in thickness is vapor-deposited and laminated on the layer of polyimide 13, and the exciting coil 7 in FIG. 1 is patterned in the same manner as in the step (3). Form.
(See Fig. (E)) (6) Finally, a film thickness of 0.2 on the excitation coil 7 as a protective layer.
A silicon oxide film 14 having a thickness of μm is formed by a sputtering method, and further, the silicon oxide film at the end of each coil is removed by dry etching to form a terminal portion, which is then plated with gold and then a wire 15 of a gold wire is bonded. To do. (Refer to the figure (f)) In addition, the detection coils 4 and 5 of the slider 2 in FIG. 1 are constructed by the same method as described above. By constructing each coil of the scale 1 and the slider 2 by applying the technique of the semiconductor manufacturing process as described above, it is possible to miniaturize the coil pitch and manufacture a linear scale having high resolution.

Second Embodiment Next, an embodiment different from the first embodiment is shown in FIG. That is, in this embodiment, with respect to the second and third exciting coils 8 and 9 (see FIG. 1) mounted on the scale 1, the exciting coils 8 and 9 are arranged on the same plane with a relative shift of 1/4 pitch. However, a phase difference of 90 ° in electrical angle is set between both coils. As described above, by arranging the second exciting coil 8 and the third exciting coil 9 with a phase angle of 90 ° in electrical angle, the voltage induced in the exciting coils 8 and 9 (Example 1) Using the phase between the induced voltages Va-2 and Vb-2 described in (see FIG. 5).
It is possible to further improve the detection accuracy of the step position information by performing the same operation principle as described above.

Further, the thin film magnetic layer 16 is formed in the peripheral region of the exciting coils 8 and 9 which are formed as thin film coils in this embodiment. With this configuration, the magnetic layer 16 serves as a yoke that enhances the degree of magnetic coupling between the scale 1 and the slider 2, so that the induced voltage of the detection coil mounted on the slider side increases. In order to construct the structure of FIG. 4 on a scale, a silicon oxide film is formed on the exciting coils 8 and 9 in place of polyimide resin by a thin sputtering method in the step (4) in the manufacturing process described in FIG. Then, a magnetic material, permalloy, is sputtered on top of it
After forming a film having a thickness of m and filling the concave groove remaining between the coil conductors with permalloy, the surface is ground to expose the conductor surfaces of the exciting coils 8 and 9, and the thin film magnetic layer 16 is formed in the peripheral region of the coils. Form. After that, a silicon oxide film is sputtered as an interlayer insulating layer to a thickness of 0.2 μm, and the silicon oxide film is sputtered on the insulating layer.
The scale 1 is completed by constructing the first excitation coil 7 in the same manner as in the manufacturing process of 1.

[0017]

As described above, according to the configuration of the present invention, when the displacement of the slider is measured, the zero point adjustment as in the conventional linear scale and the step of counting the wave number of the voltage induced in the detection coil of the slider are performed. Position information in the pitch obtained from the induced voltage of the detection coil corresponding to the first exciting coil mounted on the scale without the need to obtain the position, and the induced voltage corresponding to the second and third exciting coils separately from this Since the step position information obtained from the above is added, an absolute electromagnetic induction type linear scale capable of instantaneously measuring the linear displacement (absolute position) of the slider from the reference position can be provided.

Moreover, since it is not necessary to count the number of waves of the voltage induced in the detection coil of the slider in order to obtain the step position, the signal processing speed can be increased and the coil pitch can be sufficiently miniaturized to increase the resolution of the scale. it can. Further, by applying the semiconductor process technology, a linear scale with high pattern accuracy can be manufactured by constructing the excitation coil of the scale and the detection coil of the slider as a thin film coil, and a thin film magnetic layer is formed in the peripheral region of the thin film coil. By forming it, a large output signal is obtained from the detection coil of the slider, which is advantageous.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a linear scale according to a first embodiment of the present invention.

FIG. 2 is an operation principle diagram for obtaining step position information with the configuration of FIG.

FIG. 3 is an explanatory diagram of a manufacturing process of the scale in FIG. 1, and (a) to (f) are diagrams showing states in respective steps.

FIG. 4 is a plan view of a scale according to a second embodiment of the present invention.

FIG. 5 is a principle diagram of a configuration and an operation of a conventional electromagnetic induction type linear scale, (a) is a schematic diagram of a configuration circuit,
(B) is a diagram showing the relationship between the voltage induced in the detection coil of the slider and the displacement of the slider, and (c) is an explanatory diagram for obtaining in-pitch position information.

[Explanation of symbols]

1 Scale 2 Slider 4 Detection Coil 5 Detection Coil 7 First Excitation Coil 8 Second Excitation Coil 9 Third Excitation Coil 10 Magnetic Substrate 16 Magnetic Layer f ₁ Excitation Frequency of First Excitation Coil f ₂ Second, Second Excitation frequency of the excitation coil of 3

Claims (5)

[Claims] 1. A scale equipped with an exciting coil having a length corresponding to a measurement length, and a scale having a phase shifted by 1/4 pitch from each other.
In an electromagnetic induction linear scale in which a slider equipped with a pair of detection coils is arranged in close proximity to each other, and the linear displacement of the slider is measured based on the induced voltage of the detection coil, the scale includes a first excitation coil, The second and third exciting coils are arranged so that the distribution of the coil side lengths is relatively changed along the longitudinal direction of the scale and the phase difference is set between the second and third exciting coils. Information on the step position corresponding to an integral multiple of the coil pitch obtained from the induced voltage of the detection coil corresponding to the excitation frequency of, and the position within the pitch obtained from the induced voltage of the detection coil corresponding to the excitation frequency of the first excitation coil An electromagnetic induction type linear scale characterized in that the displacement of the slider is measured by adding the above information. 2. The linear scale according to claim 1, wherein
An electromagnetic induction type linear scale characterized in that a phase difference of 180 degrees in electrical angle is set between the second exciting coil and the third exciting coil. 3. The linear scale according to claim 1, wherein
An electromagnetic induction type linear scale characterized in that a phase difference of 90 degrees in electrical angle is set between the second exciting coil and the third exciting coil. 4. The linear scale according to claim 1, wherein
An electromagnetic induction type linear scale characterized in that each exciting coil of the scale and each detecting coil of the slider are thin film coils formed by laminating a magnetic plate as a substrate on which a pattern is formed. 5. The linear scale according to claim 4, wherein
An electromagnetic induction type linear scale characterized in that a thin film magnetic layer is formed around the thin film coil.