JPH03144306A - Length measuring device - Google Patents

Abstract

PURPOSE:To enable highly-precise and direct detection of a position even when a length-measuring device is made long, by a method wherein a standing wave of an electromagnetic wave is generated in a waveguide, the electromagnetic wave is taken out by a probe provided in a slider and a current is thereby detected. CONSTITUTION:An electromagnetic wave which has a wavelength lambda being 1/3 of the axial length l of a waveguide 12 is injected by an oscillator 11 into the waveguide 12 provided with a slit, so that a standing wave be generated therein. In a slider 13, on the other side, probes 14A to 14D are projected at an interval of lambda/8 and diodes 15A to 15D are connected to the respective end parts of the probes. Part of the electromagnetic wave is taken out by these probes 14A to 14D and detected by the diodes 15A to 15D and thereby detection currents Ia to Id being proportional substantially with the square of field strengths at the positions of the probes are obtained respectively. With these currents Ia to Id used, sine and cosine values corresponding to the amount of displacement of relative movement are obtained by a prescribed calculation formula, and by combining a prescribed counting circuit with this constitution, an absolute position is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a length measuring device suitable for measuring the position of a long stroke such as a large machine tool.

(Conventional technology) Conventionally, when directly measuring the linear position with a machine tool, etc.
Generally, optical or magnetic length measuring devices are used. These length measuring devices require a main scale provided with a fine grid pattern or a magnetization pattern with alternating polarities in a range larger than the length measurement stroke.

FIG. 5 is a perspective view showing an example of a conventional optical length measuring device and a block diagram showing an example of its detection circuit. A main scale 3 provided with a first grating 4 is fixed, an index scale 6 provided with a second grating 5 on the other member, a light emitting means composed of a light source 1 and a collimator lens 2, and a light receiving element 7. A slider having a photoelectric conversion means configured as shown in FIG. And'ff
The change in light amount caused by the relative movement between the Jl grating 4 and the second grating 5 is photoelectrically converted, and the obtained signal is sent to the amplifier circuit 8.
^, 8B, the interpolation circuit 9 and the counting circuit 10 convert the value into a digital value representing the amount of displacement of the relative movement, and the position of the moving axis is detected.

In such a length measuring device and its detection circuit, the phase of the second grating 5 provided on the index scale 6 with respect to the first grating 4 provided on the main scale 3 is determined by the pitch p of the first grating 4. For example, if it is 360 degrees, O',
Since it is divided into 90', 180', and 270°, amplifier circuit 08 and flB are connected to Z of main scale 3.
Corresponding to the displacement amount 2 in the direction, approximately the sine value 5 inches (2i
Z/p) and a two-phase detection signal that can be approximated by a cosine value cos (2rc Z/p) is output by differential amplification.

The interpolation circuit 9 performs arithmetic processing according to the following equation (1) using the two-phase detection signals from the amplifier circuits 8^ and 8B, and calculates an absolute value that represents the range of pitch p of the first grating 4 as a value from O to 255. Output position data PL.

When S = 5in (2yc Z/p) and C = cos (2kubo Z/p), the interpolation circuit 9 further performs the determination process of the following equation (2) to determine whether the up-count pulse is up or the down-count pulse 0. Output.

However, p is the previously detected PL. Then, the counting circuit 10 uses the up-count pulse UP or down-count pulse DP from the interpolation circuit 9 to set the up-count or down-count count value Pu, that is, the movement displacement to the first grid. The number of pitches ρ corresponding to 4 is output.

Absolute position data P obtained by the above processing
L and up-count or down-count count value PU
By combining these values, it is possible to obtain a value P2 that is a digital value of the displacement amount 2 of the relative movement.

The above explained an optical length measuring device, but in the case of a magnetic length measuring device, the main scale is made of ferromagnetic material, and the N and S poles are alternately magnetized instead of a grid on the main scale. A pattern is provided, and an MR element or the like having a pattern similar to the pattern on the index scale is used in place of the light receiving element and the index scale, so changes in magnetic intensity caused by relative movement of the main scale and the slider are converted into electrical signals. By converting it to , it is possible to obtain a signal equivalent to that of an optical length measuring device.

Therefore, the detection circuit of the magnetic type length measuring device has a configuration similar to that used in the optical type.

(Problems to be Solved by the Invention) The conventional optical length measuring instruments and magnetic length measuring instruments described above have a fine grating pattern or a sine pattern with alternating polarity in a range larger than the length measuring stroke of the main scale. Therefore, the longer the length of the main scale, the more difficult and time-consuming it is to manufacture, and the accuracy is also worse than that of a shorter main scale. In addition, if you try to widen the pattern repetition pitch to expand the range that can be absolutely detected and reduce the effort required for pattern formation, it may become difficult to obtain an output of 8, which is equivalent to the sine and cosine values for displacement, or the pattern repetition pitch There is also a problem in that as the pattern repetition pitch increases, the resolution accuracy per period of the pattern repetition pitch deteriorates.

The wooden invention was made due to the above-mentioned circumstances, and the purpose of the wooden invention was to be able to directly detect the position of long strokes with high precision,
Another object of the present invention is to provide a length measuring device that is easy to manufacture and inexpensive.

(Means for solving the problem) The wooden invention provides a long stroke position 51 for large machine tools, etc.
The present invention relates to a length measuring device suitable for measurement, and the object of the present invention is to include a waveguide provided with a slit in the axial direction, an oscillator that generates a standing electromagnetic wave within the waveguide, and the electric waveguide. This is achieved by providing a plurality of probes for extracting the 611 waves, a detector for detecting the current generated on each probe side, and a slider portion movable along the slit.

(Function) The length measuring device of the present invention uses a standing wave that makes the pattern of electromagnetic wave intensity change uniform with respect to the amount of displacement, so when the repeating pitch period of the electromagnetic wave intensity change is interpolated,
The resolution accuracy is high, and even if the repetition pitch is widened, the resolution accuracy hardly deteriorates. Furthermore, by utilizing this point and combining a plurality of length measuring devices of the invention with different wavelengths of the 7rim waves in the waveguide, it is possible to detect a long stroke with an absolute displacement amount.

(Example) Fig. 1 is a perspective view showing an example of the length measuring device of the present invention, and Fig. 2 (
^) is its X, -X, cross-sectional view, the same figure (It) is part 7,
, -7. , is a cross-sectional view. A wavelength λ of 1/3 of the axial length ρ of the waveguide I2 is transmitted into the waveguide 12 by an oscillator II connected to the other end side of the waveguide 12 with one end closed and a hole at the other end.
Electromagnetic waves such as microwaves are injected into the waveguide I2, thereby creating a TE as shown in FIG. 2(b). A standing wave of waves is created. In addition, slits are provided at the center of the upper surface of the waveguide 12 so as to influence the wall current in the axial direction (Z-axis direction) of the waveguide 12, and are spaced at intervals of λ/8. 4 wooden probes placed 14^,
One end of each of 14B, 14G, and 14D protrudes into the waveguide 12 through the slit of the waveguide 12, and each other end is connected to the diodes 15A, 15B, 15C, and 150. And each diode 15A, 158.15C, 15
D is a slider 13 made of a conductor movable along the slit and a support made of an insulator 168, 168.16 [;
, 160.

In such a configuration, the probes 14A-14D take out a portion of the 'rvLm wave in the waveguide 12, and the diode 15
Since the detection is performed at a portion close to the square characteristic of the nonlinear region of 8 to +50, it is necessary to obtain a detection current that is approximately proportional to the square of the electric field strength at the position of each probe 14A-140.

Here, the electric field strength E, Eb, Ee, Ea at the position of each probe 148, 14B, 14c, 140 is E, the reflection coefficient is E, the reflection coefficient is R, and the waveguide 12 is Assuming that the displacement amount of the relative movement of the slider 13 is 2, it is expressed by the following equation (3) from the standing wave relational expression.

From the above formula (3), each diode 15^, 15B, 15C
, 150 detected currents Ia, Ib, L,
Id is! , QCI E, l 2Ib ocll:b
12, 1cocll:c12. L"1E41'
If we set J: sl0CE, it is expressed by the following equation (4).

Next, the detection currents 1a, Ib, Ic, and Ia are increased by
I vessel 17A.

11 and ■ by 17B. , Ib and Id are differentially amplified, so their output voltages V, , Vb are expressed by the above equation (
4), it is expressed by the following equation (5).

Here, if V(X: tI'r, φ=π/4, then the signal of sine value and cosine value corresponding to the displacement amount 2 of the relative movement, which is the same as the optical length measuring device shown in Fig. 5) is obtained. Therefore, by combining the length measuring device of the present invention shown in FIG. 1 with the interpolation circuit 9 and counting circuit 10 shown in FIG. It can be detected by

FIG. 3 is a perspective view showing another example of the length measuring instrument of the present invention;
Figure (A) is a sectional view of Dh-12, Figure (B) is part 2.
3-13 sectional view. This length measuring device has a configuration in which two length measuring devices shown in Fig. 1 are arranged in parallel so that the axial directions of each waveguide are parallel, and each slider section is connected, and one oscillator 11A injects electromagnetic waves such as microwaves with a wavelength λ1, which is 1/8 of the axial length l of the waveguide 12A, into the waveguide 12^, and the other oscillator 11B injects the waveguide 12B into the waveguide 12B. '1FiIi waves such as microwaves having an axial length of 1 and a wavelength λ of 177.5 are injected.

Also, a probe 14 that takes out a part of the electromagnetic waves within the waveguide 12A.
^^, 14^B, 14AC, and 14^0 are arranged at intervals of λ^/8 in the axial direction of the waveguide 12^.
[Probes 148^, 1488 that take out part of the electromagnetic waves within 1
, 148G, 14BD are λ67 in the axial direction of the waveguide 12B.
They are arranged at intervals of 8.

In such a configuration, signals IAa, ■All+I proportional to the square of the electric field strength within the waveguides 12^ and 12B
Ae+IAd1 and r8a, tab, TBc, I
! Amplifiers 17^, 17 [1 and 5] shown in FIG.
By processing with the interpolation circuit 9 shown in the figure, absolute positions can be detected within the range of λA/2 and within the range of λ,/2, that is, within the range of 1/16 and within the range of fl/15. can. Here, it is assumed that the interpolation circuit 9 shown in FIG. 5 outputs the manually inputted sine and cosine values within one cycle as a numerical value from 0 to 255, and the absolute position fl within the range of It/L6 is calculated by Cheetara PAL ( (+ ≦PAL ≦255
(Q integer a) If the absolute position data within the range of J2/is is PaL (an integer of 0≦pat, ≦255), then by performing the following equation (7) with integer arithmetic, 1/16
It can be detected as J2/152/15.

In reality, the above equation (7) does not hold true unless the decomposition accuracy by interpolation of PAL and PBL is good, but this length measuring device calculates displacement from a standing wave of electromagnetic waves, which has a uniform intensity change pattern with respect to displacement. Due to indirect measurement, PAL
Even if the absolute detection range of PILL and PILL is widened, the decomposition accuracy by interpolation is good, and a wide area of the measurement range λ can be measured at an absolute position.

In the above-described embodiment, the number of length measuring devices arranged in parallel is two, but any number of length measuring devices may be arranged in parallel.

(Effects of the Invention) As described above, according to the length measuring device of the present invention, there is no need for a main scale with a fine grid pattern or a magnetized pattern with alternating polarity, so the length measuring device can be made longer. However, it has a simple structure and can be made at low cost. Furthermore, since the resolution accuracy due to interpolation is increased, a wide length measurement range can be detected at the absolute position l.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of the length measuring device of the present invention, and Fig. 2 (
A) is its X, -X, cross-sectional view, and the same figure (B) is its 2, -
2. 3 is a perspective view showing another example of the length measuring device of the present invention, and FIG. 4(A) is a Z2-22 sectional view thereof, and FIG.
B) is a 23-23 sectional view thereof, and FIG. 5 is a perspective view showing an example of a conventional length measuring device and its detection circuit. 1... Light source, 2... Collimator lens, 3... Main scale, 4.5... Grid, 6... Index scale, 7... Light receiving element, 8^, 8B, 17^,
17B... Amplifier, 9... Interpolation circuit, 10... Counting circuit, 11, 11^, IIB... Oscillator, 12.1
2A, 12B... Waveguide, 13... Slider, 14
A. 14B, 14C, 14D, 14^^, 14^B, 14^
C, 14AD, 14B^, 14BB. 14BC, 14BD... probe, 15A, 15B, 15
C, 15D...Diode, 16A, 16B, 16C
, 16D...Insulator.

Claims (1)

[Claims] 1. A waveguide provided with a slit in the axial direction, an oscillator that generates a standing electromagnetic wave within the waveguide, a plurality of probes for extracting the electromagnetic waves, and each probe. 1. A length measuring instrument comprising: a detector for detecting a current generated in the slit; and a slider section movable along the slit. 2. The length measuring instrument according to claim 1, wherein the four probes are arranged at intervals of 1/8 of the wavelength of the electromagnetic wave. 3. A plurality of the length measuring devices according to claim 1 are arranged in parallel so that the axial directions of the respective waveguides are parallel to each other, and each slider portion is mechanically coupled, and each oscillator is connected within each waveguide. A length measuring device that generates standing waves of electromagnetic waves with different wavelengths.