JPH02296108A - Position detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to detect the position of a core highly accurately by outputting the outputs of secondary coils sequentially with a switching means through a phase detector and an output correcting device, and detecting the position of the core. CONSTITUTION:A primary coil 14 is wound around a hollow bobbin 13. A plurality of three or more secondary coils 15 are wound in the divided pattern in the longitudinal direction in an overlapped pattern on the coil 14. A linear type differential transformer 16 having core which is movably inserted in the axial direction at the center of the bobbin 13 is provided. A switching means 17 switches the connections of the output lines from the coils 15. The adjacent two coils 15 of the transformer 16 are combined. When the phase of the amplitude voltage of the signal from the means 17 is equal to the phase of the reference signal from the coil 14, the voltage is rectified and outputted from a phase detector 7. When the phase is inverted, the polarity of the amplitude voltage is inverted. Then the voltage is rectified and outputted from the phase detector 7. The output from the detector 7 is compared with a predetermined command value. The output is corrected and the result is outputted from an output correcting device 19. The outputs of the coils 15 are sequentially outputted with the means 17 through the detector 7 and the device 19, and the position of the core 3 is detected.

Description

[Detailed Description of the Invention] [Summary] Regarding a position detection device using a direct-acting differential transformer (hereinafter referred to as a differential transformer), the present invention relates to a position detection device using a direct-acting differential transformer (hereinafter referred to as a differential transformer). A primary coil, and at least three or more coils that are overlapped on the primary coil and wound in sections in the longitudinal direction.
A linear differential transformer comprising a secondary coil and a core fitted in the center of a hollow bobbin so as to be movable in the axial direction, and two adjacent secondary coils of the linear differential transformer are combined. a switching means for sequentially switching the connections of the output wires, and if the amplitude voltage of the signal from the switching means has the same phase as the reference signal from the primary coil, it remains the same, and if the phase is reversed, the polarity of the amplitude voltage is reversed. a phase detector that rectifies and outputs the output, and an output correction device that compares the output from the phase detector with a predetermined target value, corrects it, and outputs it,
The switching means is configured to sequentially output the output of the secondary coil via the phase detector and the output correction device to detect the position of the core.

[Industrial application field]

The present invention relates to a position detection device using a differential transformer.

BACKGROUND OF THE INVENTION As linear motion stages such as steppers used in the manufacturing process of semiconductor integrated devices become more accurate and smaller, differential transformers are attracting attention as position detection devices.

Although a differential transformer is an analog output position detector, it has extremely high position detection resolution and can be miniaturized, so it is often used as a position detection means for linear motion stages with a small movable range. .

[Conventional technology]

As shown in FIGS. 7(a) and 7(b), the differential transformer 1 consists of an outer cylinder 2 around which a coil is wound, and a core 3 that is movable in the axial direction around the center of the outer cylinder 2.

That is, the central axis of the outer cylinder 2 is hollow, and the primary coil 4 is wound in the center thereof, and two secondary coils 5 and 6 are wound symmetrically on both sides of the primary coil 4.

On the other hand, the core 3 is made of a material with high magnetic permeability and has a cylindrical shape.

The secondary coils 5 and 6 are reversely connected as shown in the figure (C), and when AC voltage Ep is applied to the primary coil 4 in this state,
The magnetic flux that the secondary coils 5 and 6 receive from the primary coil 4 is
It acts on each secondary coil 5 and 6 through the core 3 to generate an electromotive force.

In the differential transformer 1 having such a configuration, as shown in FIG. 8, when the core 3 is at a symmetrical position between the secondary coils 5 and 6, the differential output voltage Es is Es,=Es.

So, when the core 3 shifts toward the secondary coil 5, Es, >
Esz, and conversely when there is a deviation, Es, <Es, and an output that changes linearly in proportion to the movement of the core 3 can be obtained.

As shown in the block diagram of FIG. 9, this output is output as is if the amplitude voltage is the same as the reference signal from the monthly coil 4 in phase detector 7, and if the phase is reversed, the amplitude voltage is output as is. The polarity is inverted and rectified, and the analog/digital converter 8 converts the signal into a digital signal.

This digital signal is input to the control section 9 of the computer, and the control section 9 compares it with the target value of the table 10 to move the stage 11 using the motor 12.

[Problem to be solved by the invention] In the case of the above position detection device, for example, the length measurement range is ±IO.
Even if it is as small as M, a resolution of 1/20,000 is required to measure, for example, 1 μ■, which requires advanced analog technology to handle minute level electrical signals and a differential transformer with high linearity. .

In recent years, there has been an increasing number of methods for converting measurement output into a digital signal using an analog/digital converter and importing it into a measurement or control computer.However, when measuring a wide range with high precision, high-resolution analog/digital conversion is required. There was a problem in that the resolution was insufficient even if a device was used.

Furthermore, when using a high-resolution analog/digital converter, there is a problem in that it requires expensive parts, advanced know-how, considerable averaging processing, etc. in order to prevent noise.

The present invention aims at wide-range and highly accurate position detection.

[Means to solve the problem]

In order to achieve the above object, in the present invention, as shown in the principle diagram of FIG. At least three or more secondary coils 1 wound with
5, a linear differential transformer 16 having a core 3 fitted in the center of the hollow bobbin 13 so as to be movable in the axial direction, and two adjacent secondary coils 15 of the linear differential transformer 16. If the amplitude voltage of the signal from the switching means 17 is the same as that of the reference signal from the primary coil 14, the phase may be reversed. For example, it is composed of a phase detector 7 that inverts the polarity of the amplitude voltage, rectifies it, and outputs it, and an output correction device 19 that compares the output from the phase detector 7 with a predetermined target value, corrects it, and outputs it, The switching means 17 sequentially outputs the output of the secondary coil 15 via the phase detector 18 and the output correcting device 19 to detect the position of the core 3.

[Effect]

Since the differential transformer 13 has many subdivided secondary coils compared to those of the prior art, the resolution is increased.
The output is sequentially switched and taken out by the switching means 17,
By outputting through the phase detector 18 and the output corrector, highly accurate position detection of the core becomes possible.

〔Example〕

FIGS. 2 to 6 show an embodiment of the present invention.

Identical parts are designated by the same reference numerals throughout the figures.

In the present invention, a linear differential transformer (hereinafter referred to as differential transformer) 16 as shown in FIGS. 2(a) and 2(b) is used.

That is, the differential transformer 16 has a structure that is an extension of the structure of the conventional differential transformer, and as shown in the cross-sectional view of FIG. A coil 14 and a plurality of two coils (both 3 or more) which are overlapped on the primary coil 14 and wound in sections in the longitudinal direction.
It comprises a secondary coil 15 and a core 3 fitted within the center of a hollow bobbin 13 so as to be movable in the axial direction.

In the figure, the secondary coil 15 is wound over the primary coil 14, but the primary coil 14 may be wound over the secondary coil 15.

In this embodiment, the number of secondary coils 15 is four, and the core length=secondary coil width:coil spacing is 6:4:l.

Further, the coils (a) and (C) of the secondary coil 15 are configured to output a voltage on the negative side when phase detection is performed, and the coil (b) and the same are configured to output voltage on the positive side when phase detection is performed.

As for the connection, as shown in the circuit diagram shown in the same figure, the terminal end and the starting end of each coil are connected, and an output line is provided at the connection part.

In such a differential transformer 16, as shown in FIG. FIGS. 3(1)), (C), and (d) show the relationship between the output voltage after phase detection depending on the position of the core 3 and each combination of the secondary coil 15, with the origin being taken as the origin.

For example, the output voltage when the core 3 is at the home position is 75% of the negative side maximum output in the case of the combination of secondary coils 15 (a) and (b), and the output voltage of the secondary coils 15 (b) and ( In the case of the combination C), it is 25% of the positive side maximum output, and in the case of the combinations (C) and (d) of the secondary coil 15, it is 0.

The dotted lines in FIGS. 3 Φ), (C), and (d) indicate the individual output voltages of each secondary coil 15, and the graph is obtained as a composite of the output voltages.

The parts with large slopes of the graphs in FIGS. 3(b), (C), and (d) are defined as the effective range of the linear differential transformer in the present invention.

Only the effective range of these outputs is extracted and shown.
It is a graph shown in FIG. 4(a).

In this example, the measurement sensitivity (the slope of the straight line) is 1.9 times longer than that measured in the same range using the conventional differential transformer shown in FIG.

Furthermore, if the number of secondary coils 15 is increased to 5, 6, 7, and 8, the number of secondary coils 15 will be 2.
It becomes 5 times, 3.1 times, 3.8 times, and 4.4 times better.

FIG. 5 is a configuration block diagram of a position detection device using the differential transformer 16 having such a configuration, in which the switching means 17
are switches for selecting two adjacent secondary coils 15 of the differential transformer 16, and are sequentially switched in accordance with commands from the control device 20.

The phase detector 7 is of the prior art and performs phase detection of the output of the secondary coil 15 selected by the switching means 17.

Analog/digital converter 8 is also of the prior art and converts the output of phase detector 7 into digital form.

This converted digital signal is output to the control device 20 and the output correction bag W, 20.

The control device 20 switches the switching means 17 as needed to determine which combination of secondary coils the core 3 is currently within the effective range of.

Then, the digital signal output from the analog/digital converter 8 is corrected in accordance with the current core position, and position information is output.

The correction at this time is performed by instructing the output correction device 19 based on a table that has been calibrated in advance using another measuring means.

When the secondary coils shown in FIGS. 2 and 3 are four differential transformers 16, the operation of the control device 20 is as shown in the flowchart shown in FIG. 6 to determine which combination of secondary coils is effective. Determine whether core 3 is within range.

As shown in the figure, first, the output voltage ■ of the combination of coils (a) and (b). , and the output voltage of the combination of coils (b) and (C) c, and the output voltage Vcd of the combination of coils (C) and (d), (t) Vbc>O and Vca=0, That is, when the output voltage of FIG. 3(C) is positive and the output voltage of FIG. 3(d) is 0, it is determined that the core position is within the effective range of FIG. 3(b).

(2) When v,b>o and VC,<Ol, that is, when the output voltage in FIG. 3(a) is positive and the output voltage in FIG. 3(d) is negative, the core position is at the third position. It is determined that it is within the effective range shown in Figure (C).

(3) When V, b=O and V, c<Ol, that is, when the output voltage in Fig. 3(a) is O and the output voltage in Fig. 3(C) is negative, the core position is It is determined that it is within the effective range shown in FIG. 3(d).

〔Effect of the invention〕

As explained above (according to the present invention, it is possible to measure a relatively wide range with high resolution without using a particularly high-resolution analog/digital converter, so the influence of noise can be reduced. It has great economic and industrial effects, such as lowering costs.

[Brief explanation of the drawing]

Figure 1 is a principle diagram of the position detection device of the present invention, Figure 2 (a)
is a cross-sectional view of the linear differential transformer used in the present invention, FIG. 2(C) is a circuit diagram of FIG. 3(a), and FIG. 3(a)
~(d) are charts showing the measured values of the linear differential transformer used in the present invention, and Figures 4(a) and (b) are the graphs showing the measured values of the linear differential transformer of the present invention and the conventional one. 5 is a configuration block diagram showing an embodiment of the position detection device of the present invention, FIG. 6 is an operation flowchart of the control device of FIG. 5, and FIG. 7(a) is a conventional linear differential A broken perspective view of the transformer, Figure 7 (with) is a sectional view of Figure 7 (a), Figure 7 (C) is a circuit diagram of Figure 7 (b), and Figure 8 is a conventional linear differential. FIG. 9 is a diagram showing the relationship between the position of the transformer core and the differential output voltage. FIG. 9 is a block diagram of the configuration of a conventional position detection device. In the figure, 3 is the core, 7 is the phase detector, 8 is the analog/digital converter, 13 is the hollow bobbin, 14 is the primary coil, 15 is the 2
16 is a linear differential transformer, 17 is a switching means, 19 is an output correction device, and 20 is a control device. /13 Medium γ Honbin Honmenmei f) La! Detection throw rn, ring diagram < d) (When 7A&:Coil width:]Ile spacing = 6:4:ft)
Figure 3: α0 [Cable diagram (CL) f Baro non-display diagram/b] (α) Subordinate flux f) Okichenbun, Katakane 5. Compare the measured values with the 0 term and 1 constant time of the present invention. Place detection device! Great celebration of J
．． Figure 77 Figure 5 Diagram of the conventional Hyakumuneri reed moving Torashimata's grinding machine Cross-section of the side (α) Suspicious! 0 movement 70-Nayat Figure 6 Figure 9

Claims (1)

[Claims] A primary coil (14) wound around a hollow bobbin (13);
A plurality of secondary coils (at least three or more) overlapped on the primary coil (14) and wound in sections in the longitudinal direction
a linear differential transformer (16) comprising: ) said secondary coil (15)
a switching means (17) for sequentially switching the connection of output lines of a combination of two adjacent output lines; A phase detector (7) that outputs the amplitude voltage as it is if they are the same, or inverts the polarity of the amplitude voltage if the phase is reversed and rectifies it. Compares the output from the phase detector (7) with a predetermined target value. and an output correction device (19) for correcting and outputting the output, and the switching means (17) sequentially outputs the secondary coil (15).
) to the phase detector (18) and the output correction device (
19), and detects the position of the core (3).