KR20170040320A - Position detection device - Google Patents

Abstract

The present invention relates to a sensor coil part having three or more sensor coils arranged in a longitudinal direction on concentric axes and excited by AC signals of the same frequency respectively and a sensor coil part for outputting a differential signal at both ends of each sensor coil A plurality of differential signal output means; a plurality of subtraction signal output means for subtracting a differential signal corresponding to the two sensor coils and outputting a subtraction signal; As a position signal that linearly changes by calculating the subtraction signal, the position of the measuring body in the axial direction of the measuring body when the measuring body including the material for changing the impedance of the measuring body moves along the concentric axis direction The position detecting apparatus according to any one of claims 1 to 3, Wherein the position detection means is based on a sensor coil specified by the coil identification means and the change of the plurality of subtraction signals is based on the position of the sensor coils of the plurality of sensor coils And the position signal is synthesized so as to be continuous in accordance with the arrangement order.

Description

[0001] POSITION DETECTION DEVICE [0002]

The present invention relates to a position detecting device for detecting a linear position (axial position) of a measuring body and outputting a position signal to the outside.

Various configurations have been proposed for a position detecting device for detecting the linear position of the measuring object and outputting the position signal to the outside. For example, Patent Document 1 discloses a sensor configured as follows. A plurality of voltage taps 7 are arranged so as to equally divide the voltage in the middle of the measuring coil 1 to which AC power is applied at both ends and the voltage at each voltage tap 7 is added by the addition amplifier 10 And outputs it. A ring 6 made of a material capable of changing the magnetoresistance (impedance) of the coil 1 is arranged on the outer periphery of the measurement coil 1 so as to be movable in the direction of the central axis of the measurement coil 1. The voltage of the voltage tap 7 changes because the impedance of the measurement coil 1 at the portion where the ring 6 is located changes. Since the total amount of weight to be applied varies depending on the position of the ring 6 in the measurement coil 1, the output voltage of the addition amplifier 10, which is the final output, changes, so that the position of the ring 6 can be detected .

Patent Document 2 discloses a position detecting device configured as follows. The magnetic responding member 11 made of a rod-like magnetic material is linearly displaced in accordance with the displacement of the detection target, with respect to the hollow portion of the cylindrical coil portion 10 made of six coil sections. The range of the length 4K corresponding to the four coil sections LA, LB, LC and LD of the coil section 10 is the effective detection range. The coils of each coil section are excited by a common AC signal sin? T, and the voltages V ?, VA, VB, VC, VD, V? Between the opposite ends of each coil section are detected.

As the degree of proximity or penetration of the magnetic response member 11 to each coil increases, the magnetic inductance of the coil increases and the voltage across each coil changes. When the detected voltages are input to the analog arithmetic circuits 20 and 21 in a predetermined combination, the detected voltages are added or subtracted according to a predetermined arithmetic expression to generate two AC output signals indicating sine and cosine function characteristics sin? sin? t and cos? sin? t are generated.

The phase angle? Of the sine and cosine functions, which are the amplitude components of the respective AC output signals, corresponds to the position of the detection object, and the phase angle? In the range of 90 degrees corresponds to the length K of one coil. The effective detection range of the length of 4K corresponds to the range of 0 to 360 degrees of the phase angle [theta], so that if the phase angle [theta] is detected, the absolute position of the detection object can be detected within the range of 4K.

Patent Document 1: Japanese Patent Publication No. Hei 8-12082 Patent Document 2: Japanese Patent No. 4464517

However, in the configuration of Patent Document 1, since the gain of the entire sensor is determined by the influence of the indefinite factor such as the characteristic of the ring 6, it is necessary to individually adjust the gain of the sensor. That is, there is a problem that it is difficult to obtain the absolute positional accuracy of the ring 6 on the principle of measurement. Further, since the detection value regarding the entire position detection range is constant, the resolution is deteriorated as the detection range is lengthened. Also, the temperature characteristic deteriorates in proportion to a longer detection range.

In the configuration of Patent Document 2, there is a restriction that the magnetism-responsive member 11 is required to be the same object at least for a length of 4K or more of the detection target range. Since the phase angle? Varies from 0 degrees to 360 degrees corresponding to the length 4K, the detection range of the absolute position is limited to the substantial length 4K. In order to detect the absolute position with respect to the range exceeding the length of 4K, an auxiliary structure for processing the position signal outputted by combining the basic structures is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a position detecting apparatus which is less restricted in the shape of a measuring object and can detect the absolute position easily over a longer range have.

In the position detecting device of the present invention,

A sensor coil part arranged so as to lie on the concentric axis in the longitudinal direction and having three or more sensor coils excited by AC signals of the same frequency,

A plurality of differential signal output means for outputting differential signals at both ends of each sensor coil,

A plurality of subtraction signal output means for subtracting a differential signal corresponding to the two sensor coils and outputting a subtraction signal,

The axial position of the measuring body when the measuring body, which is located on the outer circumferential side or the inner circumferential side of the sensor coil part and includes a material for changing the impedance of the sensor coil, moves along the concentric axis direction, And outputting the position signal as a linearly varying position signal,

And coil specifying means for specifying a sensor coil corresponding to a current position of the measuring object on the basis of a result of calculating a plurality of differential signals,

Characterized in that the position detecting means synthesizes a position signal so that the change of the plurality of subtraction signals continues in accordance with the arrangement order of the plurality of sensor coils based on the sensor coil specified by the coil specifying means do.

According to the position detecting device of the present invention, the position detecting means is based on the sensor coil specified by the coil specifying means, and outputs the position signal so that the change of the plurality of the subtracting signals continues in accordance with the arrangement order of the sensor coils Thus, the absolute position of the measuring object can be continuously output in accordance with the number of sensor coils arranged. Further, since the length of the measuring body may be equal to or larger than the axial length of at least one sensor coil, the constraint on the shape of the measuring body is smaller.

Fig. 1 is a functional block diagram showing an overall configuration of a position detecting device according to a first embodiment.
2 is a diagram showing a configuration example of an arithmetic circuit.
Fig. 3 is a diagram showing a modified example by a combination of an A / D converter and a multiplexer.
4 is a longitudinal side view of the coil sensor unit.
5 is an operation timing chart.
6 is an operation timing chart (1) for specifying a measurement interval.
7 is an operation timing chart (No. 2) for specifying a measurement period.
Fig. 8 is a functional block diagram showing a configuration of a coil sensor unit and an arithmetic circuit according to a second embodiment.
Fig. 9 shows a third embodiment of the present invention, and shows a modified example of a configuration for exciting a plurality of coils.
Fig. 10 is a functional block diagram showing the configuration of a coil sensor unit and an arithmetic circuit when there are two measuring objects.
11 is a functional block diagram showing the configuration of a coil sensor unit and a calculation circuit according to a fifth embodiment of the present invention.
12 is a longitudinal side view of the coil sensor unit.
Fig. 13 is a functional block diagram showing an overall configuration of a position detecting device according to a sixth embodiment of the present invention.
14 is an operation timing chart showing the seventh embodiment.
15 is an eighth embodiment and is a longitudinal side view of a coil sensor portion.
16 is a longitudinal side view of the rear end side of the coil sensor unit according to the ninth embodiment.
17 is a tenth embodiment and is a longitudinal side view of a part of a coil sensor portion.
18 is a eleventh embodiment and is a longitudinal side view showing a configuration in which a sensor coil part is disposed inside a rod reciprocating the cylinder part.

Carrying out the invention  Form for

(First Embodiment)

Hereinafter, the first embodiment will be described with reference to Figs. 1 to 7. Fig. 4 is a longitudinal side view showing a configuration example of the sensor unit. Hollow Cylinders A plurality of (for example, six) coils 3A to 3F are arranged on the outer circumferential side of the coil support 1 so as to be continuous in the axial direction with an insulating material 2 interposed therebetween. The coil supporter 1, the coil (sensor coil) 3 and the like are inserted into the hollow cylindrical sensor sleeve 4. The distal end portion (the left end side in the figure) of the sensor sleeve 4 is sealed by the distal end cover 5.

The rear end of the sensor sleeve 4 is connected to the distal end of the sensor case 6. The wirings 7 connected to both ends of the respective coils 3 are led to the inside of the sensor case 6 from the rear end thereof via the inside of the coil support body 1. Further, the wiring 7 may be surrounded by the outer side (surface) of the coil 3. A sensor lead-out cable 8 is connected to a lower portion of the sensor case 6 and a wire 10 drawn out from the detection circuit 9 shown in Fig. 1 is surrounded inside the sensor lead-out cable 8 . The wirings 7 and 10 are connected by soldering in the sensor case 6 and the rear end portion of the sensor case 6 is covered by the rear end cover 11. [ The above constitutes the sensor unit 12.

The measuring body 13 is ring-shaped and is arranged so that the outer peripheral side of the sensor sleeve 4 is linearly displaced in the axial direction. Since the measuring body 13 may be a member (material) that changes the impedance (inductance) of each coil 3, it may be either a magnetic material or a non-magnetic material. If the magnetic material is used for the measuring object 13, the impedance of the coil 3 is increased because the measuring object 13 is close to the object. If the non-magnetic material is used, the impedance is reversely lowered. The axial length of the measuring body 13 may be the same as the axial length (1 section) of at least one coil 3. Thus, the measuring body 13 may be of a very simple type such as a pipe made of a non-magnetic material, has an advantage of extremely low cost, and excellent in strength and environmental resistance.

Fig. 1 is a functional block diagram mainly showing the configuration of the detection circuit 9. Fig. One end of the coil 3A which is the upper end of the series circuit of the series circuit is oscillated and outputted from the oscillator 14 included in the detection circuit 9 and is connected through the excitation part 15 AC signal is applied. One end of the coil 3F, which is the lower end of the series circuit, is connected to the ground. The detection circuit 9 includes six differential amplifying circuits 16A to 16F (differential signal outputting means) corresponding to the coils 3A to 3F, respectively. The differential amplifying circuits 16A to 16F The terminals are connected to both ends of the corresponding coils 3A to 3F.

The differential amplifying circuits 16A to 16F output the both end voltages of the corresponding coils 3A to 3F as Va to Vf. In the next stage, five arithmetic circuits 17 (1) to 17 (5) (subtraction signal output means) are arranged, and voltages Va and Vb are inputted to input terminals X and Y of the arithmetic circuit 17 have. Similarly, the voltages Vb and Vc, the voltages Vc and Vd, the voltages Vd and Ve, and the voltages Ve and Vf are input to the input terminals X and Y of the arithmetic circuits 17 (2) to 17 (5), respectively. The differential amplifying circuits 16A to 16F and the arithmetic circuits 17 (1) to 17 (5) may be provided with a gain and a gain may be added so that the signal inputted to the A / The S / N ratio can be improved by increasing the level.

Fig. 2 shows an internal configuration example of the arithmetic circuit 17. In the configuration shown in Fig. 2A, the input terminal X is connected to the input terminal A of the computing unit 17c via the rectifying unit 17Xa and the low-pass filter (LPF) 17Xb. Similarly, the input terminal Y is connected to the input terminal B of the computing unit 17c via the rectifying unit 17Ya and the LPF 17Yb. In other words, the input signal is rectified by the rectifying section 17a, smoothed by the LPF 17b, and then input to the computing section 17c. The computing unit 17c outputs the subtraction result (A-B) of the signal given to the input terminals A and B.

In the configuration shown in Fig. 2B, a computing unit 17c is arranged at the initial stage, followed by a rectifying unit 17a and an LPF 17b. In the configuration shown in Fig. 2C, the computing unit 17c in (a) is replaced with a computing unit 17d. The arithmetic unit 17d outputs the result of subtracting the subtraction result AB by the addition value A + B, which is a so-called ratio metric (A + B) which eliminates the influence of the fluctuation of the reference voltage in the subsequent stage A / This is a configuration corresponding to the operation.

The calculation circuit 17 (1) outputs the signal Vab (= Va-Vb) as the calculation result. The operation circuit 17 (2) outputs the signal Vbc (= Vb-Vc) as the calculation result. Similarly, the arithmetic circuits 17 (3) to 17 (5) output the signals Vcd, Vde, and Vef as the calculation results, respectively. These calculation results are inputted to the controller 19 (position detecting means, coil specifying means) through the A / D converters 18 (1) to 18 (5), respectively.

3, the A / D converter 18 is used and the multiplexer 20 is disposed on the input side thereof, so that the controller 19 switches the signals Vab to Vef to time division May be input.

The controller 19 is constituted by a CPU, a microcomputer, a gate array or an FPGA (Field Programmable Gate Array), reads signals Vab to Vef through the A / D converter 18, I ask. The controller 19 is connected to a nonvolatile memory 21 such as a flash ROM and the controller 19 is based on information previously stored in the nonvolatile memory 21. The controller 19 is connected to the non- (Offset component, gain component), correction of linearity, correction of temperature drift characteristics, and the like.

The controller 19 outputs the obtained position of the measuring object 13 to the upper unit 23 via the external interface (I / F) The external (I / F) 22 includes a network I / F function in addition to outputting the position data in parallel, and it is also possible to connect to the network system.

The external device 25 is connected to the controller 19 via the contact output unit 24. [ The controller 19 outputs an ON / OFF signal (a contact open / close signal) to the external device 25 through the contact output unit 24, thereby realizing a limit switch function. The limit switch function is a function of turning on / off the contact of the contact output section 24 with the predetermined position of the measuring body 13 as a threshold.

The limit switch function is equivalent to a hardware operation (it operates as long as it is not damaged once set) when the position detecting device (sensor) is regarded as one device. For example, even if the transmission / reception of data with the upper unit 23 or the upper unit 23 is out of operation due to some improper operation, the limit switch function operates as prescribed by the position detecting device itself. Therefore, it is an element that improves the safety of the system, such as operating as a safety device. Since the position detecting device of the present embodiment is of the absolute type, the signal data of the position data is high, and it is easy to adapt to the requirement of high reliability required for the limit switch function.

The limit switch function can be turned ON / OFF corresponding to a plurality of positions within the detection range. 1, there is only one contact output unit 24 having a limit switch function, but a plurality of contact output units 24 may be used. The threshold value may be set to an arbitrary position as an input signal from the external I / F 22 or may be set by switching by the setting switch 26 or the like.

The limit switch function described above may be provided with a limited speed detection function for outputting an ON / OFF signal in accordance with, for example, a change in position per a predetermined time and a result of comparison with a predetermined threshold value. The limit speed detection function is a function for turning the output signal ON or OFF when the moving speed of the measuring body 13 becomes equal to or greater than a predetermined threshold value that is a reference (limit reference) Can be performed.

The detection circuit 9 receives the power supply from the external power supply 27 and generates an internal power supply 28 of, for example, a voltage of about 5 V by a power supply circuit (not shown) As shown in FIG. In addition, the sensor unit 12 and the detection circuit 9 constitute the position detection device 29.

Next, the operation of the present embodiment will be described with reference to Fig. When the impedance (inductance) of one coil 3 rises when the measuring body 13 moves along the sensor sleeve 4, the impedance of the other coil 3 falls. The detection circuit 9 performs differential signal processing on the signals of the two coils 3 in the same manner as the half bridge type differential transformer.

In order to change the impedance of the coil 3 as described above, the length dimension of the measuring body 13 is N times (N (length) of one section (the axial length of one coil 3) Is a natural number). Therefore, the coils 3 to be detected do not necessarily have a positional relationship that is adjacent to each other (for example, when N = 2, the differential signals are processed between the coils 3A to 3C). ).

Fig. 5 shows a signal change of each part when the measuring body 13 is displaced. In this example, the material of the measuring body 13 is a conductor of a non-magnetic material. It is to be noted that the length of the measuring body 13 is the same as one section of the coil 3. The coil 3A is located at the left end of the figure, and the coils 3B to 3D are arranged in succession in the rightward direction in the figure. If there are three or more coils 3, there is no upper limit. The coils 3A to 3D are all the same.

The signals Va to Vc are obtained by floating the signal level when the center portion of the measuring object 13 is located and vary in proportion to the impedance of the coil 3. [ In a state in which the measuring body 13 does not overlap any of the coils 3, each of the signals Va to Vc shows the maximum value (Vmax in Fig. 5).

When the measuring body 13 moves in the POS direction (right arrow direction) in Fig. 5 and starts to overlap with the coil 3A, the level of the signal Va gradually decreases. When the measuring body 13 further moves and its central portion is superposed on the center of the coil 3A, the level of the signal Va becomes the minimum value (Vmin in the figure). Thereafter, when the measuring body 13 also moves in the POS direction, the level of the signal Va starts rising again. When the overlap between the coil 3A and the measuring body 13 disappears, the signal Va returns to the maximum value. Thus, the range in which the signal Va varies depending on the position of the measuring body 13 is only a range overlapping with the coil 3A. The length of the range corresponds to two sections of the coil 3. Likewise, the levels of the signals Vb and Vc accompanying the passage of the measuring object 13 change.

Here, attention should be paid to " a measurement interval by coils A and B " (hereinafter referred to as a first measurement interval) shown in the figure. This section is a range in which the center of the measuring body 13 is located between the center of the coil 3A and the center of the coil 3B. When the measuring object 13 moves in the POS direction, the level of the signal Va gradually increases (monotonously increases) and the level of the signal Vb gradually decreases (monotonously decreases) within this range.

The calculated value " Va-Vb " in this range becomes a signal increasing at a constant slope. If the coils 3A and 3B have the same characteristics, the calculated value " Va-Vb " becomes zero at the center of the first measurement interval. This operating principle is the principle of operation of the differential transformer composed of the coils 3A and 3B and the measuring body 13. That is, according to this configuration, the calculation value " Va-Vb " acts as a sensor for detecting the POS moving position of the measuring body 13 in the first measuring period, As shown in FIG. Further, the fact that the operation principle is the same as that of the differential transformer means that the position detecting device 29 has the same merits as the differential transformer.

Similarly, in the "measurement interval by the coils B, C" (hereinafter referred to as the second measurement interval), the calculated value "Vb-Vc" Quot; Vc-Vd " changes with the movement of the measuring body 13 in the POS direction. Since each of the above-described measurement periods occurs in each section of the coil 3 with the movement of the measuring body 13, the corresponding calculated values are continuously read as position data that can be obtained adjacent to each other .

Here, when the measurement object 13 is in the first measurement interval, the calculation value " Va-Vb " is output as data indicating the position of the first end section (the measurement object 13 in the figure is the left end). When the measuring object 13 is in the second measurement interval, the calculation value " Vb-Vc " is added to the position data as the position data corresponding to the length of one interval as " offset ".

Similarly, when the number of measurement sections passed until then is N according to the measurement section in which the measuring object 13 is located, N times of the position data corresponding to the length of one section is added to the position data as " offset ". This state is shown in " waveform synthesis " in Fig. Thereby, the position data that linearly change (continuously changing) over a plurality of measurement intervals can be read out. As shown in Fig. 5, when the number of coils 3 is " 4 ", the number of sections in which positions can be measured is " 3 ". Similarly, when the sensor unit 12 is composed of N coils 3, the measurement range is the section of " N-1 ". In addition, the processing of adding the offset to the position data as described above can be easily realized when the controller 19 digitally processes the data.

Next, a description will be given of a method for the controller 19 to recognize in which measurement section the measuring body 13 is located. Quot; Va + Vb " shown in Fig. The calculated value " Va + Vb " holds the lowest value Vmin_ab when the measuring body 13 is positioned within the first measuring section operated as the differential transformer by the coils 3A and 3B. When the measuring body 13 is located in another section, the calculated value " Va + Vb " indicates a value higher than the minimum value Vmin_ab. Similarly, when the measuring object 13 is positioned within the second measurement interval, the calculated value " Vb + Vc " holds the lowest value Vmin_bc.

Since the first and second measurement periods are adjacent but do not overlap, the region where the calculation value " Va + Vb " and the calculation value " Vb + Vc " maintain the minimum values Vmin_ab and Vmin_bc, respectively, do not overlap. These calculated values are "Va + Vb", "Vb + Vc", "Vc + Vd", "Vd + Ve" And there are (N-1) the number of the coils 3 when there are N coils 3.

Therefore, in order to determine the measurement period (current measurement period) in which the measuring object 13 is located, the calculation values "Va + Vb" to "Vd + Ve" , And the section indicating the minimum value Vmin_ab or the like is the current measurement section. In the case where the measurement section 13 does not show the minimum value, it indicates that the measurement body 13 deviates from the measurable range. Therefore, the detection of the position error (dropout of the measurement body 13) Can be easily performed.

In the explanation up to this point, a value such as a calculation value "Va + Vb" is used for convenience. However, in the configuration shown in Fig. 1, the data read by the controller 19 are the subtraction values "Va-Vb" to "Vc-Vd" to be. To obtain the added value " Va + Vb ", an adder may be used separately. Hereinafter, a method of obtaining the additive value Va + Vb in the configuration of the detection circuit 9 shown in Fig. 1 will be described.

First, a signal CHK_AB corresponding to the additive value " Va + Vb " for discriminating the section of the first terminal (left end), i.e., the first measurement section, is obtained by the calculation of the following equation.

CHK_AB = (Va-Vb) -2 x (Vb-Vc)

        = (Va + Vb) - 2 x Vc

When the waveform of the signal CHK_AB shown in Fig. 6 is compared with the calculated value " Va + Vb " in Fig. 5, the characteristic that maintains the minimum value Vmin_ab 'in the first measurement interval coincides with each other. I know there is.

Next, the signal CHK_BC corresponding to the additive value " Vb + Vc " for discriminating the second measurement interval adjacent to the first end (left end) is obtained by the calculation of the following equation.

CHK_BC = (Vc-Vd) - (Va-Vb)

= (Vb + Vc) -Va-Vd

When the waveform of the signal CHK_BC shown in Fig. 6 is compared with the calculated value " Vb + Vc " in Fig. 5, the characteristic of maintaining the minimum value Vmin_bc 'in the second measurement interval also coincides. Then, the signals CHK_CD, CHK_DE (not shown) ... The same processing as that of the signal CHK_BC may be performed.

As described above, only the signal CHK_AB is different in operation, but the other operations can be obtained by the same operation as the signal CHK_BC. Although not shown, a signal obtained by performing the same calculation as that of the CHK_AB signal may be used for determination of the right end measurement region. Therefore, even if only the differential signal is input as data, a signal for determining the measurement section can be generated internally by the operation of the controller 19. [

In addition, in order to obtain a signal for determining the measurement section, the technique shown in Fig. 7 may be used. For example, the signal CHK_BC is obtained from the following equation.

CHK_BC = (Vc-Vd) (Va-Vb)

Since the obtained signal CHK_BC acquires a negative value only in the second measurement interval, it can be determined that the measurement object 13 is located in the second measurement interval.

In addition, for example, there is a possibility that an error is caused in discrimination between the second and third measurement sections, because the characteristics of the respective coils 3 are uneven. This corrects the non-uniformity, for example, in the case of the linearity correction or the like to be described separately, and it is possible to eliminate the section determination error due to the unevenness of the respective coils 3. In other words, even if it is judged erroneously with respect to the second measurement period in the region extremely close to the environment of the two measurement regions, for example, in the third measurement region, the calculated value " Vb-Vc " In the region of the 3 measurement interval, the value is not reduced sharply, so that the value finally calculated as the position data contains only an extremely small error, and practical problems are small.

The accuracy and resolution of position detection of the position detecting device 29 of the present embodiment can be considered as follows. First, the accuracy (linearity) within one section is high precision equivalent to that of the differential transformer. In addition, the detection accuracy is determined by the positional accuracy of each coil 3 in the axial direction, over the section of the plurality of coils 3. The coil 3 itself is wound in a state of being simple and easy to shape, and the coil protecting member 1 is also cylindrical. It is easy to improve the positional accuracy of the coil 3 by using a servo motor or a ball screw or the like having excellent positional accuracy while taking advantage of the characteristics of these members. Therefore, the sensor unit 12 can be manufactured so as to obtain a high accuracy with respect to the detection accuracy (including absolute position accuracy) over a plurality of coil sections.

With regard to the resolution, it is easy to treat the number of divisions (resolution) of one section of the coil 3 constantly. When the number of sections of the coil 3 is increased in order to widen the detection range, , The resolution (distance per bit of data) is constant.

The operation principle described so far is an application of a half bridge type differential transducer (DVRT) and has characteristics in accordance with the operation principle of the DVRT. On the other hand, if the primary coil and the secondary coil of the DVRT are separated from each other by a differential transformer (LVDT), the position detecting device 29 can also detect the primary coil And the N coils 3 are used as secondary coils, it can be handled as a sensor including the above-mentioned characteristics of the sensor (see the fifth embodiment).

Next, each member shown in Fig. 4 will be described.

<Coil 3>

As the material of the coil 3, a magnet wire whose surface is insulated may be used. Since one coil 3 is wound with any layer (possibly even one layer) and arranged at intervals of one section, the length of one coil 3 becomes one section or less. In addition, insulation can be enhanced by winding an insulator (insulating paper) around the outer periphery of the coil 3. The connection wiring 10 to the detection circuit 9 may be wound around the outer periphery of the coil 3.

&Lt; Coil support member (1), Insulator (2) &gt;

The coil supporting member 1 may be a voltage conductor, which fixes the magnetic shape of the coil 3 and fixes the relative positions of the plurality of coils 3. However, since it functions as a short coil, the impedance of the coil 3 . Therefore, when a conductor is used, it is preferable to use stainless steel or nickel alloy (Hastelloy, Inconel ... registered trademark) having high voltage resistance. Also, its thickness should be thinner. The coil supporting member 1 may be an insulator such as a resin.

It is also possible to use a magnetic material for the coil supporting member 1. In this case, the impedance of the coil 3 may be increased to further increase the sensitivity (the signal change may increase). However, it is necessary to pay attention to the temperature characteristics of the magnetic material. It is also possible to dispose the magnetic material on the inner periphery of the non-magnetic coil support material 1. [ The insulator 2 between the coil 3 and the coil supporting member 1 is not necessarily required because the coil member itself is insulated from the coil 3. However, And so on. When the coil 3 is formed by using a molding coil or the like, it is possible to make the coil supporting member 1 unnecessary.

<Sensor sleeve (4)>

The sensor sleeve 4 is not essential for the position detection operation. It is necessary to provide a mechanical protection of the coil part and a sealing structure. As shown in Fig. 4, when the measuring body 13 is located on the outer circumferential side, the sensor sleeve 4 needs a non-magnetic material. Since the sensor sleeve 4 itself also functions as a short coil, if the electric conductivity is low, the impedance of the coil 3 lowers and the signal change becomes small, which is not preferable. Therefore, a high electric conductivity is suitable. For example, an austenitic stainless steel, a nickel alloy (Hastelloy, Inconel ...) and the like can be used.

For the same reason, it is preferable that the thickness thereof is also thin. However, it is necessary to consider the balance with the mechanical strength. Particularly, when the sensor coil part 12 is, for example, A thickness that is not required is required. The sensor sleeve 4 can be made of a member made of a resinous material such as a glass epoxy resin reinforced or carbon fiber reinforced pipe and can be made lightweight and low in cost Do.

&Lt; Sensor case 6, front end cover 5, rear cover 11,

The sensor case 6, the front end cover 5 and the rear end cover 11 are members for fixing the relative positions of the coil supporting member 1 and the sensor sleeve 4 or for realizing a sealing structure , A magnetic material, a non-magnetic material, a conductor, and an insulator.

<Sensor pull-out cable (8)>

The sensor lead-out cable 8 is used to lead out the wiring 7 of the coil 3 to the outside of the sensor coil part 12 and to connect it to the detection circuit 9. The distal end of the lead-out cable 8 may be connected to the connector.

<Others>

An appropriate O-ring (packing) or the like can be used in order to increase airtightness and the like. In general, these materials are insulators and do not affect the position detecting operation, so that they can be arbitrarily installed at necessary positions. In addition, the joining between the members can be performed by a method such as adhesion, press fitting, welding, or screw fixing.

According to the present embodiment as described above, the plurality of coils 3 that are excited in the AC signal of the same frequency are arranged so as to lie on the concentric axis in the longitudinal direction to constitute the sensor coil part 12. [ The plurality of differential amplifying circuits 16 output differential signals at both ends of the respective coils 3 and the computing unit 17 subtracts the differential signals corresponding to the two coils 3 and outputs a subtraction signal to the controller 19 . The controller 19 is provided on the outer circumferential side of the sensor coil section 12 and includes a measuring body 13 when the measuring body 13 including a material for changing the impedance of the coil 3 moves along the concentric axis direction As a position signal linearly changing by calculating the subtracted signal.

At that time, the controller 19 specifies the coil 3 corresponding to the current position of the measuring body 13 on the basis of the result of calculating a plurality of differential signals. Specifically, a plurality of subtraction signals are calculated to obtain an addition signal of two differential signals, and the coil 3 corresponding to the current position of the measuring body 13 is specified based on the addition signal thereof. Alternatively, the coil 3 is specified on the basis of a result obtained by multiplying a plurality of subtraction signals. Then, based on the specified coil 3, a position signal is synthesized and output such that the change of the plurality of subtraction signals continues in accordance with the arrangement order of the plurality of coils 3.

Therefore, since the position signal can be continuously and linearly outputted in accordance with the number of arrangements of the coils 3, the position detection range of the measuring body 13 can be extremely simply expanded. Since the axial dimension of the measuring body 13 may be equal to or greater than the length of at least one coil 3, the constraint on the outer shape of the measuring body 13 is small and the degree of freedom in designing can be improved . Also, as in Patent Document 1, the gain of the position detecting device 29 is not affected by the characteristics of the measuring object 13, and the level of the position signal is proportional to the number of arrangements of the coils 3 , The resolution does not deteriorate even when the detection range is expanded, and the temperature characteristic does not deteriorate.

Since the detection circuit 9 includes an electronic limit switch function for outputting a switch signal for turning on and off the contact output section 24 at a preset position on the basis of the position signal, The position detection device 29 can perform the operation as prescribed by itself and can detect the position of the object to be measured (for example, 13), it is possible to improve the safety of the system.

Since the limit switch function includes the limit speed detection function for outputting the ON / OFF signal in accordance with the change of the position per a predetermined time and the result of the comparison with the predetermined threshold value, the moving speed of the measuring body 13 is too fast , It is possible to improve the safety by limiting the speed.

In order to specify the coil 3 corresponding to the current position of the measuring object 13, when obtaining the addition signals of the two differential signals, it is not necessary to necessarily obtain the addition signals from the results of calculating the plurality of subtraction signals , And the addition signal may be obtained by disposing a separate adder at the rear end of the differential amplification circuit 16.

(Second Embodiment)

8 shows the second embodiment, and the same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and the different parts will be described below. 8, the detection circuit 31 of the second embodiment includes a differential amplifier circuit 16G (differential signal output means, temperature detection means), an LPF 32, and an A / D converter 18 (6) Has been added. The repetitive input terminal of the differential amplifying circuit 16G is connected to one end (ground) of the coil 3F and the non-repetitive input terminal is connected to one end (a repeated input terminal of the differential amplifying circuit 16A) of the coil 3A . The output signal of the differential amplifying circuit 16G is input to the controller 19A (temperature detecting means, not shown) through the LPF 32 and the A / D converter 18 (6).

Next, the operation of the second embodiment will be described. With the above configuration added, the data read by the controller 19A through the A / D converter 18 (6) becomes a DC equivalent voltage applied to both ends of the series circuit of the coils 3A to 3F. Thereby, the controller 19A can measure and measure the temperature of the coil 3.

It is known that, in a general artificial cable used as a magnet wire, its resistance value changes at about -0.39% / DEG C depending on the temperature. The signal source 33 shown in the drawing corresponds to the oscillator circuit 14 and the exciter circuit 15 of the first embodiment but the signal source 33 is driven by the constant current so that the DC current component is always supplied to the coil 3 It is possible to make a flow. The voltage (DC component) across the series circuit of the coils 3A to 3F is proportional to the dc resistance of the series circuit. Therefore, the controller 19A can invert the temperature of the coil 3 from the data value read through the A / D converter 18 (6).

With this configuration, the temperature of the coil 3 can be accurately measured even when, for example, the sensor coil part 12 and the detection circuit 31 are disposed apart from each other. The measured temperature may be used to cancel the temperature drift caused by the coil 3. It is also possible to transmit the temperature information to the upper unit 23, and when a system including the sensor coil section 12 or the sensor coil section 12 is at an abnormal temperature and is left to stand, You may.

As described above, according to the second embodiment, the differential amplifier circuit 16G outputs differential signals at both ends of the sensor coil section 12. The controller 19A controls the sensor coil section 12) was detected. Therefore, a process for preventing the sensor coil portion 12 from becoming overheated can be performed.

(Third Embodiment)

The third embodiment shown in Fig. 9 shows a modification of the drive type of the sensor coil section 12. Fig. 9A, a signal source 33 (1) is connected to both ends of a series circuit of the coils 3A to 3C by using two signal sources 33 (1) and 33 (2) And connected to both ends of the series circuit of the coils (3D to 3F). In this case, it is not necessary to electrically connect the coils 3A to 3C and the coils 3D to 3F. It is also possible to operate even if the frequency and the phase relation between the signal source 33 (1) and the signal source 33 (2) are wrong. The advantage of driving the sensor coil part 12 in the two signal sources 33 (1) and 33 (2) is that the number of the coils 3 driven by one signal source 33 decreases, 3, it is possible to increase the current density and to improve the noise resistance and the influence of the external magnetic field.

Similarly, as shown in Fig. 9B, the coils 3 and the signal source 33 can be connected to each other one-to-one and can be driven individually. As shown in Fig. 9C, When connecting the signal source 33 (1) to the series circuit, one end of each coil 3A to 3C may be commonly connected and driven.

(Fourth Embodiment)

The fourth embodiment shown in Fig. 10 is a configuration in which two measuring bodies 13 (1) and 13 (2) are arranged in the sensor coil part 12. Fig. In the position detecting device 29, as described above, the range in which the measuring body 13 changes the characteristics of the coil 3 falls within a finite range from the point where the measuring body 13 is located. Therefore, as long as the two measuring bodies 13 (1) and 13 (2) are not close to a position where mutual influence on the impedance change of the coil 3 to be subjected to position detection is started, (1) and 13 (2) can be detected as independent phenomena. It is also possible to increase the number of the measuring bodies 13 to three or more. In the case where the plurality of measuring objects 13 are close to each other within the above-mentioned limit range, it is possible to detect them as measurement anomalies and issue a warning to the upper unit 23 or the like.

(Fifth Embodiment)

The fifth embodiment shown in Figs. 11 and 12 is a structure in which the primary coil is designed as described in the first embodiment. A primary coil (excitation coil) 42 is disposed opposite to the sensor coil section 41 with the coils 3A to 3F serving as secondary coils and a signal source 33 is connected to both ends of the primary coil 42 And supplies the AC signal. In this case, as shown in Fig. 12 corresponding to Fig. 4, the primary coil 42 is disposed inside the sensor sleeve 4. Fig. By constituting the sensor coil part 41 in this way, the position detecting device 43 can be a position sensor including the same features as the half bridge type differential transformer.

(Sixth Embodiment)

The position detection device 51 of the sixth embodiment shown in Fig. 13 includes the configuration of the detection circuit 38 of the second embodiment (it may be the detection circuit 9 of the first embodiment). In the sixth embodiment, data for correcting the linearity of the position detecting device 51 is stored in advance in the nonvolatile memory 21 (storage means), and when the position of the measuring object 13 is detected, (19B) corrects the linearity of the detection position using the data. Hereinafter, the acquisition of data used for the correction will be described.

First, a linear displacement detection sensor having excellent absolute value accuracy and linearity is prepared. Here, an optical linear scale 52 is used. (Not shown) that connects the detection head 53 of the linear scale 52 and the measuring object 13 and moves linearly. This movable stage is made movable from an external position at an arbitrary position.

The scale 54 of the optical linear scale 52 is installed so as to read sensor output data (position data) thereof accompanying the movement of the detection head 53. When the position data is outputted from the detection head 53, the controller 19B of the position detection device 51 reads the position data thereof through the correction I / F 54. In general, the position output of the optical sensor is the A / B phase output, but the correction I / F 54 is designed to read the absolute absolute position by inputting such two-phase output.

In the above-described installed state, the moving rod is gradually moved from one end of the sensor coil part 12 to the other end. At this time, the controller 19B obtains the absolute absolute position obtained by the optical linear scale 52 and the deviation of the position itself detected by the sensor coil part 12, And stores the deviation in the nonvolatile memory 21. For example, when the entire measurement range is output as 16-bit data, its data value indicates 0 to 65535. For example, when the deviations are stored for each data value 1024, deviation data of all 64 points are stored in the nonvolatile memory 21 as table values.

The process of storing the deviation data is performed when the position detecting device 51 is manufactured at the factory. Therefore, the correction data storage processing is performed by writing a correction-only program in the controller 19B or by starting the correction program written in advance (input by the setting switch 25 or the like) from the outside .

When the position detection device 51 actually detects the position of the measuring object 13 after the storage processing is completed and its position is, for example, between the above-mentioned 64 correction points, And interpolated correction data is calculated. By subtracting the correction data from the data before correction, position data corrected for linearity is calculated.

As described above, according to the sixth embodiment, the controller 19B includes the nonvolatile memory 21 in which the correction data for correcting the linearity of the position signal is stored in advance. When obtaining the position signal, To correct the linearity. Therefore, the position detection accuracy can be improved.

(Seventh Embodiment)

The seventh embodiment shown in Fig. 14 shows a detection state when the length of the measuring body 13A is twice the length of one section of the coil 3. Fig. In this case, the coil 3 as a differential transformer is constituted by two coils 3 across one, and the differential signals are (Va-Vc), (Vb-Vd) and (Vc-Ve). As shown in the figure, the first time is the "measurement period by the coils A, C" and then the "measurement period by the coils B, D". In such a case, the measurable range range is "N-2" when the number of coils 3 is N.

In addition, the sections showing the lowest value (L = Vmin) are shifted by one section for each of the addition signals Va + Vc, Vb + Vd and Va + Vc. Therefore, it is possible to specify the coil 3 (measurement section) corresponding to the current position of the measuring object 13A by referring to the change of these addition signals. That is, when the state in which the addition signal does not indicate the minimum value L is "x"

Added signal / measurement interval 3A and 3C 3D and 3D 3C and 3E

Va + Vc L L ×

Vb + Vd L L L

Va + Vc × L L

. For example, when the coils 3B and 3D are the measurement periods, the addition signals Va + Vc, Vb + Vd, and Va + Vc all show the minimum value L. Thereby, the measurement section can be specified.

Further, for example, the addition signal Va + Vc can be obtained by the following calculation.

(Va-Vc) +2 (Vc-Ve)

= Va-Vc + 2Vc-2Ve = (Va + Vc) -2Ve

Since the signal Ve is at the zero level in the section in which the added signal (Va + Vc) shows the minimum value, there is no influence of the second term.

(Eighth embodiment)

In the eighth embodiment shown in Fig. 15, the circumferential measuring body 55 is fixed to the tip end of the rod-shaped support body 56 whose diameter is smaller than that of the rod-like support body 56, and is displaced in the coil- Lt; / RTI &gt; In this case, the material of the coil supporting member 1 needs to be an insulator such as a non-magnetic material or resin for detecting a change in signal. In the case where a magnetic material is used, the impedance of the coil 3 can not be sufficiently influenced more than the change in impedance of the coil 3 by the measuring body 13 when the magnetic material is used, although the magnetic material, non-magnetic material, If fewer ones are used, error increases.

In this case, the distal end cover 5A has a through hole for introducing the measuring body 55 into the inside of the coil supporting member 1. [ The sensor case 6A also has a communicating portion 6B communicating with the hollow portion of the coil supporting member 1. The rear end cover 11A also has the same diameter as the communicating portion 6B And has a shape with a hole.

(Ninth embodiment)

The ninth embodiment shown in Fig. 16 has a configuration in which the detection circuit 9 is arranged in the internal space of the sensor case 6. Fig. In this case, the wiring 57 led out to the outside via the lead-out cable 8 becomes a power line connected to the external power source 27 or a connection line to the upper unit 23 and the external device 25. [ With this configuration, the position detecting device 29 can be made more compact. However, the heat-resistant temperature of the position detecting device 29 may be limited within the operable temperature range of the semiconductor device or the like mounted on the detecting circuit 9. [

(Tenth Embodiment)

The tenth embodiment shown in Fig. 17 shows a case where the coil 3 is wound in one layer. In the case of one-layer winding, the operation of winding the coil 3 may be such that the wire is always continuously wound in one direction and the tabs of the coils A to D are drawn out in the middle. Therefore, the workability is extremely good and the manufacturing process can be simplified.

(Eleventh Embodiment)

The tenth embodiment shown in Fig. 18 shows a configuration in which the sensor coil section 12 is arranged inside a rod 62 reciprocating inside the cylinder 61. Fig. The hole is opened in the diameter of the rod 62 so that the sensor sleeve 4 is not connected and the measuring body 13 is fixed to the inner wall end of the rod 62. [ The pressure of the cylinder is applied to the sleeve 4 of the sensor or the measuring body 13, but the sensor coil part 12 is structurally strong as described above, so that it is applicable. Only the metallic ring (measuring body 13) is coupled to the movable rod 62 and has extremely strong resistance to vibration and shock added to the rod 62. [ Also, the O-ring (packing) required for the cylinder 61, the oil port, and the like are not shown.

 The present invention is not limited to the embodiments described above or illustrated in the drawings, but may be modified or extended as follows.

The coil 3 may be directly wound around the coil support 1 made of an insulator.

4, it is not necessary that the coil supporting body 1 is hollow (pipe-shaped) unless the wiring of each coil 3 needs to be made through the inside of the coil supporting body 1. [

The electronic limit switch function and the limited speed detection function may be installed as needed.

As the temperature detecting means, a thermistor or the like may be used.

Industrial availability

INDUSTRIAL APPLICABILITY As described above, the position detecting apparatus according to the present invention is useful for detecting a linear movement position of a measuring object.

3 is a coil (sensor coil), 9 is a detecting circuit, 12 is a sensor coil part, 13 is a measuring object, 16 is a differential amplifying circuit (differential signal outputting means), 17 is an arithmetic circuit (Position detecting means, coil specifying means), and 28 denotes a position detecting device.

Claims (9)

A sensor coil part (12, 41) arranged so as to lie on a concentric axis in the longitudinal direction and having three or more sensor coils (3) excited by AC signals of the same frequency,
A plurality of differential signal output means (16) for outputting differential signals at both ends of each sensor coil (3)
A plurality of subtraction signal output means 17 for subtracting a differential signal corresponding to the two sensor coils 3 and outputting a subtraction signal,
When the measuring body (13, 55), which is located on the outer circumferential side or the inner circumferential side of the sensor coil part (12, 41) and includes a material for changing the impedance of the sensor coil (3) And position detecting means (19, 19A, 19B) for outputting the position of the measuring body (13) in the axial direction as a position signal linearly changing by calculating the subtracting signal,
And a coil specifying means (19, 19A, 19B) for specifying a sensor coil (3) corresponding to a current position of the measuring object (13, 55) based on a result of calculating a plurality of differential signals,
The position detecting means 19, 19A and 19B are constituted such that a change of a plurality of subtraction signals is based on the sensor coil 3 specified by the coil specifying means 19, 19A and 19B, (3), and outputs the synthesized position signal. The sensor coil (3) according to claim 1, wherein the coil specifying means (19, 19A, 19B) comprises a sensor coil (3) corresponding to a current position of the measuring object (13, Of the position detection device. The position detection device according to claim 2, wherein the coil specifying means (19, 19A, 19B) calculates a plurality of the subtraction signals to obtain an addition signal of two differential signals. 2. The apparatus according to claim 1, wherein the coil specifying means (19, 19A, 19B) is based on a result of multiplying a plurality of the subtraction signals, 3). The position detecting device according to any one of claims 1 to 4, wherein the sensor coil (3) is constituted by a one-layer winding. The sensor coil unit according to any one of claims 1 to 5, further comprising differential signal output means (16G) for outputting differential signals at both ends of the sensor coil unit (12) And a temperature detecting means (19A) for detecting the temperature of the object. 7. The method according to any one of claims 1 to 6,
The position detection means (19B) outputs the position signal as a linearly changing signal,
And storage means (21) in which correction data for correcting the linearity of the position signal is stored in advance,
Wherein the position detection means (19B) is configured to correct linearity using the correction data when calculating the position signal by calculating the subtraction signal. 8. The method according to any one of claims 1 to 7,
And an electronic limit switch function (19, 23) for outputting a switch signal to be turned on and off at a preset position on the basis of the position signal. 9. The electronic limit switch according to claim 8, wherein the electronic limit switch function further includes a limit speed detecting function (19, 23) for outputting a switch signal to be turned on and off when the amount of change of the position signal for a predetermined time exceeds a set change amount And the position detection device.

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