JP2001356179A - Conductor detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect surely passage of a conductor having a size over a prescribed length without being influenced by the size, the passing position, the passing speed or the like, and realizing expansion of a detection object and improvement of detection reliability. SOLUTION: In a cylindrical sensor body, a first toroidal coil 7 having a wound first coil 6 and a second toroidal coil 9 having a wound second coil 8 are arranged coaxially, and a hollow part on the inner circumferential side of the coils 6, 8 functions as a sensing area 10. A high-frequency current is supplied to the first coil 6 from a power supply device 19. When the conductor passing through the sensing area 10, becomes in the projected state from each end face part on both sides of the sensor body 2 in the supply state of the high-frequency current, capacitive coupling between each projection part of the conductor and the sensor body is generated, and a current is made to flow in the second coil 8 through the capacity, and the current is detected by a detection circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor detecting device for detecting passage of a conductor.

[0002]

For example, in a penetration type proximity sensor which detects a metal passing through a sensing area formed by a ring-shaped sensor section,
It is general to employ a circuit configuration as shown in FIG. That is, in FIG. 12, an oscillation circuit 2 having a resonance capacitor 2a is connected to both ends of a tightly wound loop coil 1. The oscillation circuit 2 oscillates at a constant frequency, and its oscillation output is provided to a detection / amplification circuit 3. When a metal detection target (hereinafter, referred to as a material) A passes through a sensing area in the loop coil 1, the conductance thereof increases, so that the oscillation condition (particularly Q) of the oscillation circuit 2 changes and the amplitude decreases. (Or stop the oscillation). Such a change in the amplitude is extracted by the detection / amplification circuit 3, and the comparison circuit 4 determines whether or not the amplitude has fallen below a predetermined threshold level. The passage detection signal is output through the circuit 5.

In the above-described penetrating type proximity sensor, generally, when the shape of the material A passing through the sensing area is small, only a very small signal change can be detected. On the other hand, the amplitude of the oscillation output of the oscillation circuit 2 is affected by the length of the sensor cable, the temperature drift of the circuit itself, and the forward voltage of the diode normally used in the detection / amplification circuit 3. There is a situation that the voltage level after detection also fluctuates due to the influence of the temperature characteristic of the drop, and it is inevitable that the DC operation includes uncertain and unstable factors. For this reason, the amplitude fluctuation due to the above uncertain and unstable element may be larger than the minute signal change when the material A passes through the sensing area, and the detection reliability is significantly increased. Will decrease. Therefore, the above configuration cannot cope with a case where detection of passage of a small material is required.

In order to cope with the above-described requirement of detecting the passage of a small material, conventionally, only a minute change in the output signal is detected at a stage subsequent to the detection / amplification circuit 3 as shown in FIG. Therefore, a differentiating circuit 6 for cutting a DC component is provided. However, with such a circuit configuration, the following new problems arise.

In other words, since it has a differentiation function, it does not essentially detect the presence or absence of a material, but outputs a pulse-like detection signal only when the front and rear ends of the material pass through the sensing area. However, it is impossible to detect the presence or absence of the material in the passage process, and for example, in a situation where the sensor power is turned on while the material is passing through the sensing area, the material cannot be detected. become. Furthermore, since the comparison input of the comparison circuit 4 is a differential signal, there is a situation that the hysteresis operation in the comparison circuit 4 cannot be set. For this reason, if the material to be detected vibrates in the sensing area, the output signal finally obtained may cause chattering due to the fluctuation in the amplitude of the oscillation output corresponding to the vibration, and the detection reliability may be reduced. Will decrease. Further, even when the passage of the same material is detected, the differential output value differs according to the passage speed of the material, so that the detection timing of the material may vary, and in such a case, the detection reliability is reduced. Sometimes. further,
Depending on the passing speed of the material, there is a case where a detection signal is output or a case where the detection signal is not output in accordance with the passage, and this also lowers the detection reliability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to ensure that a conductor having a dimension equal to or greater than a predetermined length can be passed without being affected by the size, the passing position, or the passing speed. It is an object of the present invention to provide a conductor detection device that can detect a conductor, and that can expand a detection target and improve detection reliability.

[0007]

To achieve the above object, the means described in claim 1 can be adopted. According to this means, in a state in which the high frequency current is supplied from the power supply device to the first coil wound around the first toroidal core, the first coil wound around the first coil and the second toroidal core are wound around the first coil. When the conductor to be detected does not exist in the sensing area formed in the inner hollow portion of the second coil,
Almost no current flows through the second coil.

On the other hand, in a state where a high-frequency current is supplied to the first coil, a conductor having a certain length enters the sensing area, and the conductor extends from each end face on both sides of the sensor body. When the conductor is in a protruding state, the protruding portions of the conductor and the portions on both ends of the sensor main body are coupled via a capacitor. Thereby, an induced current according to the alternating current flowing through the first coil flows through the coupling capacitance in the conductor.
Then, a current corresponding to the induced current is induced in the second coil, and the induced current is detected by the detection circuit.

That is, when the conductor passes through the sensing area, the first coil functions as a transmitting coil and the second coil functions as a receiving coil, so that the current detected by the detecting circuit is substantially reduced. The current rapidly increases from zero, and it is possible to reliably detect whether or not the conductor has passed through the sensing area based on such a current change. Moreover, when no conductor to be detected exists in the sensing area, almost no current flows through the second coil, so that a stable detection operation can be performed even when the detection sensitivity is increased. In addition, since the detection current of the detection circuit rapidly increases from almost zero as the conductor passes, complicated sensitivity adjustment can be omitted. Furthermore, if the conductor protrudes from each end face on both sides of the sensor body, an induced current will flow through the conductor, so that the conductor passes through the sensing area as in the conventional configuration using a differentiation circuit. There is no danger that detection of the presence or absence of the conductor becomes impossible.

In this case, if the material of the conductor is the same, the level of the current flowing through the second coil becomes substantially constant irrespective of the passing speed of the conductor. In addition, even when the position of the conductor passing through the sensing area changes, the fluctuation of the current level flowing through the second coil is small, and unlike the conventional configuration using a differentiating circuit, the signal processing circuit can be subjected to a hysteresis operation. Therefore, even when the conductor vibrates in the sensing area, chattering of the output signal can be prevented. As a result, a stable detection operation can be performed without being affected by the passing speed and the passing position of the conductor, and the detection reliability is improved. In addition, it is not necessary to consider the magnetic characteristics of the sensor main body for housing the first and second coils and the like and the characteristics of the structure disposed around the sensor main body, and the versatility is improved. Further, since the sensor body is made of metal, a structure that can easily clear the heat resistance can be reliably realized.

According to the second aspect of the present invention, the metal sensor main body is formed by fixing first and second annular end plates to both axial end surfaces of a cylindrical main body case. Therefore, it is possible to increase the coupling capacitance between the protruding portions of the conductor from the respective end surfaces on both sides of the sensor main body and the first and second annular end plates which are the both end side portions of the sensor main body. . As a result, the level of the induced current flowing in the conductor increases, and the detection sensitivity is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a longitudinal sectional structure of a sensor unit constituting a sensor head, and FIG. 2 shows a substantial part of the sensor unit and a configuration of a sensor output processing circuit. That is, in FIG. 1, a cylindrical sensor main body 2 constituting an outer shell of the sensor unit 1 is made of metal such as stainless steel, and has first and second ring-shaped groove portions at both axial end surfaces. A cylindrical main body case 3 formed concentrically with 3a and 3b, and first and second ring-shaped groove portions 3a and 3b on both axial end surfaces of the main body case 3, respectively.
First and second annular end plates 4 and 5 secured by, for example, screwing means (not shown) to close the opening of
And a configuration including

The first ring-shaped groove 3a has a first ring-shaped groove 3a.
The first toroidal core 7 with the coil 6 wound thereon is housed therein, and the second toroidal core 9 with the second coil 8 wound therein is housed in the second ring-shaped groove 3b. Is done. As a result, the first toroidal core 7 and the second toroidal core 9 are coaxially arranged, and the inner hollow portions of the first and second coils 6 and 8 (the center of the sensor main body 2). ) Function as the sensing area 10.

O-rings 11 and 12 for sealing are provided between the main body case 3 and the first annular end plate 4 at positions corresponding to the inner and outer peripheral edges of the first ring-shaped groove 3a.
O-rings 13 and 14 for sealing are interposed between the main body case 3 and the second annular end plate 5 at positions corresponding to the inner and outer peripheral edges of the second ring-shaped groove 3b. Is done. A cylindrical sleeve 15 made of an insulating material (for example, ceramic or resin) is provided on the inner peripheral edge of the sensor main body 2 so as to surround the sensing area 10, and the O-rings 11 and 1 are formed by the sleeve 15.
3 is prevented from falling off. O-rings 12 and 14
Are housed in ring-shaped grooves (without reference numerals) formed at positions outside the first and second ring-shaped grooves 3a and 3b on both axial end surfaces of the sensor main body 2. , Thereby preventing falling off.
Further, the first and second ring-shaped grooves 3a and 3b are filled with resin molding materials 16 and 17 as needed.

In FIG. 2, an output processing circuit 18 includes a power supply 19 for supplying a high-frequency current to the first coil 6 (illustrated in FIG. 2 with the number of turns omitted),
And a detection circuit 20 for detecting a current flowing through the coil 8 (the number of turns is omitted in FIG. 2). In this case, the detection circuit 20 includes an amplification circuit 20a that amplifies the voltage output from both ends of the second coil 8.
And a rectifier circuit 20b for rectifying the amplified output of the amplifier circuit 20a, and a comparator 20c for comparing the output voltage from the rectifier circuit 20b with a reference voltage Vs.

The operation of the above configuration is as follows.
That is, in a state where the high frequency current is supplied from the power supply device 19 to the first coil 6 wound around the first toroidal core 7, the first coil 6 is wound around the first coil 6 and the second toroidal core 9. When the conductor to be detected does not exist in the sensing area 10 formed in the inner hollow portion of the second coil 8, almost no current flows through the second coil 8.

On the other hand, when a high-frequency current is supplied to the first coil 6, a conductor 21 having a certain length enters the sensing area 10 as shown in FIG. When the projections 21 protrude from the respective end surfaces on both sides of the sensor main body 2, the respective protruding portions of the conductor 21 and the both end side portions (the first and second annular end plates 4 and 5) of the sensor main body 2 Are connected via the capacitors C1 and C2, and the stray capacitances C3 and C4 appear between the respective protruding portions of the conductor 21 and the ground.

As a result, an induced current corresponding to the high-frequency current flowing through the first coil 6 flows through the conductor 21 through the coupling capacitors C1 and C2 and the floating capacitors C3 and C4. Then, a current corresponding to the induced current is induced in the second coil 8, and the induced current is detected by the detection circuit 20. That is, when the conductor 21 passes through the sensing area 10 (actually, when the tip of the conductor 21 projects from the end surface of the sensor body 2), the first coil 6 functions as a transmission coil and , The second coil 8 functions as a receiving coil, and the current detected by the detection circuit 20 rapidly increases from almost zero. Based on such a current change, the conductor 21 is moved to the sensing area 10. Can be reliably and highly sensitively detected. In addition, when the conductor 21 to be detected does not exist in the sensing area 10, almost no current flows through the second coil 8, so that a stable detection operation can be performed even when the detection sensitivity is increased. Further, since the current detected by the detection circuit 20 rapidly increases from almost zero as the conductor 21 passes as described above, complicated sensitivity adjustment can be omitted. Furthermore, if the conductor 21 protrudes from each end face on both sides of the two sensor bodies, an induced current flows through the conductor 21, as in the conventional configuration using a differentiating circuit.
In the process in which the conductor 21 passes through the sensing area 10, there is no possibility that the presence or absence of the conductor cannot be detected.

In this case, if the materials of the conductors 21 are the same, the level of the current flowing through the second coil 8 becomes substantially constant irrespective of the passing speed of the conductor 21. In addition, even when the passing position of the conductor 21 in the sensing area 10 changes, the level of the current flowing through the second coil 8 fluctuates little, and unlike the conventional configuration using a differentiating circuit, detection for signal processing is performed. Since the comparator 20c in the circuit 20 can perform the hysteresis operation, even when the conductor 21 vibrates in the sensing area 10, chattering of the output signal can be prevented. As a result, conductor 2
1 can perform a stable detection operation without being affected by the passing speed, the passing position, and the like, and the detection reliability is improved. Moreover, it is not necessary to consider the magnetic characteristics of the sensor main body 2 and the characteristics of the structures disposed around the sensor main body 2, and the versatility is improved. Further, the sensor body 2
Since is made of metal, a structure that can easily clear the heat resistance can be reliably realized.

Whether or not the metal part of the sensor body 2 is a magnetic material is not related to the operation of the present embodiment. Therefore, as the material of the sensor body 2, an optimum material (for example, aluminum or iron) considering the environment and cost is used. But you can choose). Further, since the space between the main body case 3 constituting the sensor main body 2 and the first and second annular end plates 4 and 5 is sealed by the O-rings 11 to 14 having a simple structure, mechanical strength and corrosion resistance are improved. It is possible to make the structure excellent in the above. The cylindrical sleeve 15 made of an insulating material is provided to prevent the O-rings 11 and 13 from falling off and does not contribute to the detection of the conductor 21. Therefore, even if this portion is slightly deteriorated or deformed. There is no possibility that the detection characteristics and environmental resistance are affected.

As shown equivalently in FIG. 4, a current path route between the first coil 6 and the second coil 8 includes a capacitor C1, a resistor R of the conductor 21, and a capacitor C2 interposed in series. It will be in the state that was done. Thus, the capacitor C1
As a result, the impedance of the current path becomes very high. That is, for example,
The output frequency of the power supply 19 is 1 MHz, the capacitor C1
When the combined capacitance of C2 and C2 is 10 pF, the impedance of the current path is about 16 kΩ, and the resistance R of the conductor 21 can be substantially ignored. As a result, the detection operation of the conductor 21 can be performed without being greatly affected by the difference in the material (conductivity) of the conductor 21.

Therefore, as shown in FIG. 5, for example, even when the felt-tip pen 22 filled with the aqueous ink 22a as the conductor to be detected passes through the sensing area 10, an induced current flows through the aqueous ink 22a. As a result, the operation of detecting the aqueous ink 22a can be reliably performed as described above. Further, the presence or absence of a conductive liquid (water or an aqueous solution, food such as soy sauce, sauce, juice, sake, etc.) flowing inside a non-conductive pipe (for example, a resin pipe, a wooden pipe, or the like) can be reliably detected. .

As shown in FIG. 6, the sensing area 10 is connected to a conductor 23a, which is a conductor to be detected, by a resin 23.
If the conductor 23a is broken when the cable 23 covered with the cable 23b passes, when the broken part B is located near the center of the sensing area 10, the first coil 6 side 6, a coupling capacitance C6 shown in
Although a relatively large level of current flows through C7, only a very small current flows on the second coil 8 side due to the broken portion B of the conductive wire 23a. That is, on the second coil 8 side, the coupling capacitors C6 and C8 and the disconnection portion B shown in FIG.
Although the current flows through the coupling capacitance Cx, the capacitance C6, Cx, and C8 are interposed in series in the current path, so that their combined capacitance becomes extremely small, and the current becomes negligible. Become smaller.

As a result, in a state where the broken portion B of the cable 23 enters the sensing area 10, the induced current of the second coil 8 rapidly decreases, so that the detection state which has been in the detection state up to that point is obtained. The circuit 20 is inverted to the non-detection state. Therefore, according to the configuration of the present embodiment, disconnection detection of the covered cable 23 is also possible.

Here, even if a current flows through the coupling capacitance C5 shown in FIG. 3, no current flows through the second coil 8 in response thereto. Therefore, the passage of the conductor 21 can be detected only when the tip of the conductor 21 projects from the end surface of the sensor body 2 by a certain amount or more. For this reason, the following operation is obtained, and the following configuration is possible.

That is, as shown in FIG. 7, the sleeve 1 facing the inner peripheral surface of the sensor body 2, that is, the sensing area 10.
Even when the conductive liquid 24 such as water accumulates on the inner peripheral surface of 5, the risk of erroneously detecting the conductive liquid 24 is eliminated.
That is, in the state where the conductive liquid 24 is accumulated in this manner, a current indicated by I in FIG. 7 flows through the conductive liquid 24 in accordance with the energization of the first coil 6, but the current flows to the second coil 8 side. Since no electromotive force is generated in the located conductive liquid 24, no current flows. Therefore, as described above, the sleeve 1
Even when the conductive liquid 24 accumulates on the inner peripheral surface of the nozzle 5, there is no risk of erroneous detection.

The configuration of the present embodiment can be applied to abnormality detection of tools such as drills and end mills in NC machine tools. That is, as shown in FIG. 8, the drill 26 (corresponding to a conductor to be detected) chucked by the drill machine 25 is moved to a predetermined stop position in a preset check process. In this stop position, drill 2
When the length of the sensor body 6 is normal, the tip is set so as to protrude from the end of the sensor body 2 through the sensing area 10 of the sensor body 2. Accordingly, when the drill 26 is in a normal state, the detection circuit 20 comes to show a detection state when the drill 26 is moved to the stop position, but when the drill 26 is shortened due to breakage or the like, When the drill 26 is moved to the stop position, the detection circuit 20 does not exhibit a detection state, and thus the abnormality of the drill 26 can be reliably detected.

As shown in FIGS. 9 and 10, even when metal pipes 28 and 29 are provided on both sides of the sensor main body 2 to carry, for example, a conductive wire 27 which is a conductor to be detected, the conductive material is not electrically conductive. Passage detection of the wire 27 can be reliably performed. That is, in this case, as shown in FIG. 9, the capacitors C9 and C10 are provided between the sensor body 2 and the pipes 28 and 29.
However, in this state, no current flows through the sensor main body 2 as indicated by I 'in FIG. On the other hand, as shown in FIG. 10, when the conductive wire 27 passes through the sensing area 10, the coupling capacitor C is connected to the conductive wire 27.
9, C10 and the current flows through the coupling capacitors C11 and C12 between the conductive wire 27 and the pipes 28 and 29, and accordingly, the detection circuit 20 exhibits the detection state. Therefore, the detection of the conductive wire 27 can be reliably performed regardless of the presence or absence of the pipes 28 and 29. In this case, if the pipes 28 and 29 are configured to be grounded, a current having a level higher than the above-mentioned current flows through the C11 and C12, so that the sensitivity can be improved.

(Second Embodiment) FIG. 11 schematically shows the structure of a second embodiment of the present invention, and only the portions different from the first embodiment will be described below. That is, in the second embodiment, the sensor unit 1 is divided into two parts (only the portions corresponding to the first coil 6 and the first toroidal core 7 are “6 ′, 6 ″” and “7 ′,
7 ""), and the sensing area 10 can be arbitrarily opened and closed according to the rotation about the fulcrum S of each split part. According to this configuration, for example, disconnection detection of a long coated cable having both ends fixed by a structure can be performed extremely easily.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sensor unit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the entire configuration in substance.

FIG. 3 is a longitudinal sectional view for explaining an example of conductor detection;

FIG. 4 is an equivalent circuit diagram for explaining operation.

FIG. 5 is a longitudinal sectional view for explaining an example of conductor detection;

FIG. 6 is a longitudinal sectional view 3 for explaining an example of conductor detection;

FIG. 7 is a longitudinal sectional view for explaining the operation.

FIG. 8 is a longitudinal sectional view 4 for explaining an example of conductor detection;

FIG. 9 is a longitudinal sectional view showing an example of arrangement of sensor units.

FIG. 10 is a vertical sectional view for explaining an example of conductor detection;

FIG. 11 is a conceptual diagram of a main part showing a second embodiment of the present invention.

FIG. 12 is a circuit diagram showing a first conventional example.

FIG. 13 is a circuit diagram showing a second conventional example.

[Description of Signs] 1 is a sensor unit, 2 is a sensor main body, 3 is a main body case, 3a is a first ring-shaped groove, 3b is a second ring-shaped groove, 4 is a first annular end plate, and 5 is a first ring-shaped groove. 2, annular end plate, 6,
6 ', 6 "are first coils, 7, 7', 7" are first toroidal cores, 8 is second coils, 9 is second toroidal cores, 10 is sensing areas, 21 is conductors, 22a
Denotes an aqueous ink (conductor), 23a denotes a conductor (conductor), 26 denotes a drill (conductor), and 27 denotes a conductive wire (conductor).

Claims (2)

[Claims] 1. A conductor detecting device for detecting a conductor passing through a predetermined sensing area, comprising: a first and a second toroidal core arranged coaxially; and a first and a second toroidal. A first and a second coil wound around a core, and a hollow portion on an inner peripheral side functions as the sensing area; and the first and the second toroidal cores are the first and the second toroidal cores.
A cylindrical metal sensor main body for accommodating with the first coil, a power supply device for supplying a high-frequency current to the first coil, a detection circuit for detecting a current flowing through the second coil, A conductor detecting device configured to detect whether or not the conductor has passed through the sensing area based on a change in a detected current. 2. The sensor main body, wherein the first toroidal core in a state where the first coil is wound on both end surfaces in the axial direction and the second toroid in a state where the second coil is wound. A cylindrical main body case in which first and second ring-shaped grooves for accommodating the toroidal core are formed, respectively; and the first and second ring-shaped grooves on both axial end surfaces of the main body case, respectively. 2. The conductor detecting apparatus according to claim 1, further comprising first and second annular end plates fixed so as to close said opening.