JP2014188122A - Magnetic substance detection sensor, magnetic substance detection method, and magnetic substance detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic substance detection sensor for detecting a magnetic substance including an anastomosis needle, etc. and a magnetic fluid, capable of realizing both reduction of influence of the earth magnetism, etc. and increased detection sensitivity, and also achieving downsizing of the probe.SOLUTION: In a magnetic substance detection apparatus 1: an AC signal generating unit 2 outputs an excitation signal and excites a sensor unit 3; the sensor unit 3 outputs a detection signal; a signal detection unit 4 detects an amplitude change and phase change of the detection signal; and a signal processing unit 5 determines the presence of an anastomosis needle, etc. on the basis of the amplitude change and phase change of the detection signal. The sensor unit 3 is composed of a magnetic substance detection sensor 30, etc. The magnetic substance detection sensor 30 comprises: two terminals for inputting the excitation signal output from the AC signal generating unit 2; a coil for detecting a magnetic substance; and two terminals for outputting the detection signal to the signal detection unit 4. The magnetic substance detection sensor 30 inputs the excitation signal output from the AC signal generating unit 2, and outputs a change in the electromagnetic characteristic of the coil as the detection signal.

Description

  The present invention relates to a magnetic substance detection sensor or the like for detecting a magnetic substance in a body cavity or the like, and more specifically, administered to an anastomosis needle, a suture needle, a radiopaque steel wire gauze or a tumor lesion part remaining in a body cavity or the like. The present invention relates to a magnetic substance detection sensor or the like for detecting a magnetic fluid.

  In recent years, the remaining foreign body in which an anastomosis needle, a suture needle, a gauze, or the like is inadvertently placed in the body after surgery occupies the top of medical accidents related to surgery. In the medical field, prevention measures against remaining foreign bodies are an important issue. As a measure for preventing foreign body residues, counting operations are performed in the operating room to check whether surgical instruments and sanitary materials remain in the body. Counting is counting the number of surgical instruments and sanitary materials before the start of surgery and before the start of closure. In addition, as another preventive measure for remaining foreign matter in the body, there is a method of checking the presence or absence of an indwelling object by performing X-ray imaging or CT imaging after surgery. However, it cannot be said that the counting work alone is sufficiently reliable, and if there is a shortage, there is no means for finding where in the body cavity. In addition, X-ray imaging has a problem of X-ray exposure. Furthermore, an anastomosis needle used under a surgical microscope in neurosurgery is a very small needle having a diameter of 0.1 mm and a length of 3 mm, and may not be detected by X-ray photography or the like. Thus, sufficient preventive measures against the remaining foreign body have not been fully established.

  Further, regarding malignant tumor metastasis, it is known that tumor cells present in a lesion part metastasize via lymphatic vessels. The lymph node to which tumor cells that have entered the lymphatic vessels from the lesion first reach is called the sentinel lymph node. If there is no metastasis in the sentinel lymph node, the removal of the lymph node ahead becomes unnecessary, and the burden on patients such as edema and lymphedema, which are complications of the excision, can be reduced. In order to identify the position of the sentinel lymph node, a ferrofluid (for example, “Rezovist (registered trademark)”) is injected in the vicinity of the lesion, and after a predetermined time has passed, the ferrofluid staying in the sentinel lymph node is removed. A method of detecting by a detection device has been devised (see Patent Documents 1 and 2).

  The magnetic fluid detection devices described in Patent Documents 1 and 2 both detect magnetic fluid using a magnetic sensor. However, a magnetic fluid having no residual magnetic force cannot be detected with a magnetic sensor alone. Therefore, in the magnetic fluid detection devices described in Patent Documents 1 and 2, a magnet or electromagnet having a strong magnetic force is installed in the vicinity of the magnetic sensor to excite the magnetic fluid. In this method, the detection sensitivity of the magnetic fluid is proportional to the strength of the magnetic force of the exciting magnet for exciting the magnetic fluid.

Japanese Patent No. 3847694 Japanese Patent No. 3960558

  By the way, when a magnetic sensor is used, the detection signal changes depending on the direction of the magnetic sensor because it is affected by electromagnetic signals from devices using geomagnetism and general commercial power supply in addition to the magnetic fluid. Therefore, the magnetic fluid detection device described in Patent Document 1 uses two magnetic sensors and calculates the difference between detection signals from the two magnetic sensors, thereby affecting the influence of geomagnetism or the like that is far from the detection target. Is reduced.

  However, the magnetic fluid detection device described in Patent Document 1 needs to employ an exciting magnet that does not have a strong magnetic force in order to prevent the magnetic sensor from overflowing, resulting in a low detection sensitivity. Therefore, the magnetic fluid detection device described in Patent Document 2 has a configuration in which an exciting magnet having a strong magnetic force can be employed by devising the magnetic force lines from the exciting magnet not to reach the magnetic sensor. However, since the magnetic fluid detection device described in Patent Document 1 uses only one magnetic sensor in its configuration, it is affected by geomagnetism and the like.

  As described above, the magnetic fluid detection devices described in Patent Documents 1 and 2 cannot realize both reduction in influence of geomagnetism and the like and increase in detection sensitivity. In addition, since the magnetic fluid detection devices described in Patent Documents 1 and 2 require one or more magnetic sensors and one or more exciting magnets, there is a limit to miniaturization of a probe provided with them.

  Further, in the magnetic fluid detection devices described in Patent Documents 1 and 2, there is a possibility that the magnetic fluid is attracted to the exciting magnet in the probe, and the magnetic fluid is erroneously detected at a place different from the original.

  As described above, it is possible to detect both anastomosis needles and magnetic fluids, and to achieve both reduction in the influence of geomagnetism etc. and high detection sensitivity, and to reduce patient burden in endoscopic surgery etc. A detection sensor that can reduce the size of a probe so that a small incision is sufficient is desired.

  The present invention has been made in view of the above-described problems, and an object of the present invention is a magnetic body detection sensor for detecting a magnetic body containing an anastomosis needle or the like or a magnetic fluid, and reducing the influence of geomagnetism or the like. It is to provide a magnetic substance detection sensor or the like that can realize both high sensitivity and high detection sensitivity and can reduce the size of the probe. In particular, it is to provide a magnetic substance detection sensor or the like that can be used during surgery and that can be used in a narrow surgical field using, for example, endoscopic surgery or a surgical microscope.

  A first invention for achieving the above-described object is a magnetic body detection sensor for detecting a magnetic body, the core extending in a longitudinal direction, wound in the circumferential direction of the core, and the longitudinal center of the core A pair of coils arranged at substantially symmetrical positions with respect to the axis of symmetry, and an AC bridge circuit is constituted by the pair of elements and the pair of coils, and one of the four terminals of the AC bridge circuit. A magnetic substance detection sensor having two opposing terminals as excitation terminals and the other two opposing terminals as detection terminals. The magnetic substance detection sensor according to the first aspect of the present invention may further comprise an adjusting means for adjusting the amplitude of the detection signal output from the detection terminal. The AC bridge circuit is, for example, a Wheatstone bridge circuit applied to AC impedance measurement. The pair of elements is, for example, a resistor, a coil, a capacitor, or the like.

  2nd invention is a magnetic body detection sensor which detects a magnetic body, Comprising: It arrange | positions so that the longitudinal direction center of the said core may be a center position wound in the circumferential direction of the core extended in a longitudinal direction A first coil that is wound in the circumferential direction of the core, and a pair of second coils that are disposed at positions that are substantially symmetrical about the longitudinal center of the core as an axis of symmetry. A differential transformer circuit is configured by the coil and the pair of second coils, and a terminal connected to one of the first coil and the pair of second coils is used as an excitation terminal, and a terminal connected to the other is detected. A magnetic body, wherein the pair of second coils have opposite winding directions, and a relative positional relationship between the core, the first coil, and the pair of second coils is fixed. It is a detection sensor. The magnetic substance detection sensor according to the second invention may further comprise an adjusting means for adjusting the amplitude of the detection signal output from the detection terminal.

  A third invention is a magnetic body detection method for detecting the magnetic body using the magnetic body detection sensor of the first invention or the second invention, wherein the phase change of the detection signal output from the detection terminal and A magnetic substance detection method comprising: detecting the magnetic substance based on an amplitude change. In the magnetic body detection method of the third invention, the type of the magnetic body may be determined based on a ratio between the phase change and the amplitude change. The ratio between the phase change and the amplitude change is not greatly affected by the distance between the magnetic substance detection sensor and the detection target, and is a value specific to the magnetic substance that is the detection target. From this value, the type of the magnetic substance can be accurately determined. Can do.

  A fourth aspect of the invention is a magnetic body detection device that includes the magnetic body detection sensor according to the first or second aspect of the invention and detects the magnetic body, and outputs an excitation signal to the excitation terminal. And a signal detection unit for detecting a phase change and / or an amplitude change of the detection signal output from the detection terminal; and a signal output from the signal detection unit to process the phase change and / or the amplitude change. And a signal processing unit that detects the magnetic body based on the magnetic body detection device. The signal processing unit in the magnetic body detection device of the fourth invention may determine the type of the magnetic body based on a ratio between the phase change and the amplitude change.

  According to the present invention, a magnetic body detection sensor for detecting a magnetic body including an anastomosis needle or the like or a magnetic fluid, which can realize both reduction in influence of geomagnetism and the like and increase in detection sensitivity, and miniaturization of a probe. A magnetic substance detection sensor or the like can be provided. In addition, according to the present invention, it is possible to provide a magnetic body detection sensor or the like that can determine the type of a magnetic body to be detected.

Device configuration diagram of the magnetic body detection device in the first embodiment Sectional drawing of the magnetic body detection sensor in 1st Embodiment Circuit diagram of magnetic substance detection sensor in the first embodiment Sectional drawing of the magnetic body detection sensor in 2nd Embodiment Circuit diagram of magnetic substance detection sensor according to second embodiment Device configuration diagram of a magnetic body detection device according to a third embodiment Sectional drawing of the magnetic body detection sensor in 3rd Embodiment Device configuration diagram of a magnetic substance detection device according to a fourth embodiment Sectional drawing of the magnetic body detection sensor in 4th Embodiment Graph of amplitude change and phase change for each type of magnetic material in the fifth embodiment The figure explaining the principle of operation of the present invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A magnetic substance detection sensor, a magnetic substance detection method, and a magnetic substance detection device according to an embodiment of the present invention detect a magnetic substance from inside or outside a living body. The magnetic substance means a substance capable of being magnetized, and includes an anastomosis needle, a suture needle, a radiopaque steel wire gauze (hereinafter referred to as “anastomosis needle etc.”) and a tumor lesion part used for surgery. Including a ferrofluid to be administered. According to the magnetic body detection sensor or the like according to the embodiment of the present invention, it is not affected by geomagnetism and without using an exciting magnet (a magnet or an electromagnet having a strong magnetic force) for exciting a magnetic body to be detected. It is possible to detect the magnetic substance to be detected with high sensitivity. The magnetic body detection sensor or the like according to the embodiment of the present invention mainly detects a magnetic body in a body cavity, but is not limited to this. For example, it is possible to detect an anastomosis needle hidden in a gauze, a sterilized cloth, a surgical gown, or the like, or an anastomosis needle dropped on the floor.

<First Embodiment>
FIG. 1 is an apparatus configuration diagram of a magnetic body detection apparatus according to the first embodiment. The magnetic body detection device 1 includes an AC signal generation unit 2, a sensor unit 3, a signal detection unit 4, a signal processing unit 5, a sensor control unit 6, and the like.

  For example, when examining whether or not an anastomosis needle or the like is present in the body cavity, the operator activates the magnetic body detection device 1 and causes the sensor unit 3 to approach the search site. On the other hand, in the magnetic substance detection device 1, the AC signal generation unit 2 outputs an excitation signal to excite the sensor unit 3, the sensor unit 3 outputs a detection signal, and the signal detection unit 4 detects the amplitude of the detection signal. The change and the phase change are detected, and the signal processing unit 5 determines the presence and position of the anastomosis needle or the like based on the amplitude change and the phase change of the detection signal. The same applies to the identification of the position of the magnetic fluid administered to the tumor lesion.

  The AC signal generator 2 includes an oscillation circuit 21, an amplitude stabilization circuit 22, and the like. The oscillation circuit 21 oscillates a sine wave signal (an AC signal having an arbitrary frequency). The amplitude stabilization circuit 22 outputs the sine wave signal oscillated from the oscillation circuit 21 to the sensor unit 3 and the phase difference detection unit 43 with a constant amplitude. In this way, the AC signal generation unit 2 outputs an excitation signal for exciting the magnetic body detection sensor 30 of the sensor unit 3.

  Examples of the oscillation circuit 21 include a Wien bridge oscillation circuit, but other oscillation circuits may also be used. The frequency of the sine wave signal is arbitrary, but is preferably 50 Hz or more and 500 kHz or less, for example. When the frequency is too low, the response characteristic is deteriorated and the sensitivity is lowered. On the other hand, when the frequency is too high, the sensitivity increases, but erroneous detection is likely to occur.

  As described above, it is desirable that the oscillation circuit 21 oscillates a sine wave signal in order to stably and accurately measure the signal from the sensor unit 3. However, the oscillation circuit 21 may oscillate a signal including harmonics, and any waveform can be oscillated as long as the amplitude and phase difference can be measured by the signal detection unit 4 and the signal processing unit 5 described later. good. For example, even when a rectangular wave signal is output from the AC signal generating unit 2 to the sensor unit 3, the output signal of the sensor unit 3 is passed through a bandpass filter, and the same measurement as in the case of a sine wave signal is performed. be able to. However, there is more noise than when a sine wave signal is input to the sensor unit 3.

  The amplitude of the signal output from the sensor unit 3 is proportional to the amplitude of the signal input to the sensor unit 3 when there is no detection target magnetic body in the vicinity of the sensor unit 3. In order to stably detect the amplitude change due to the detection target, it is necessary to always make the amplitude of the signal input to the sensor unit 3 constant. Therefore, the amplitude stabilizing circuit 22 serves to make the amplitude of the signal input to the sensor unit 3 constant. Note that the phase change is less affected by fluctuations in the amplitude of the signal input to the sensor unit 3.

  The sensor unit 3 includes a magnetic body detection sensor 30 and the like. The magnetic body detection sensor 30 includes two terminals for inputting an excitation signal oscillated from the AC signal generation unit 2, a coil for detecting a magnetic body, and two terminals for outputting a detection signal to the signal detection unit 4. When the detection target is a conductive magnetic body (metal or the like), when the magnetic body detection sensor 30 approaches the metal, an eddy current is generated in the detection target, and the inductance and impedance of the coil are reduced. Further, when the relative permeability of the detection target is much larger than 1, the influence of the relative permeability is superior to the influence of the eddy current, and the inductance and impedance of the coil are increased. The magnetic body detection sensor 30 receives the excitation signal output from the AC signal generator 2, and outputs a change in the electromagnetic characteristics (inductance, impedance, etc.) of the coil depending on the detection target as a detection signal. Details of the magnetic body detection sensor 30 will be described later.

  The signal detection unit 4 includes a detection signal amplification unit 41, an amplitude detection unit 42, a phase difference detection unit 43, and the like. The detection signal amplifier 41 receives a signal from the sensor unit 3 and outputs a signal to the amplitude detector 42. The amplitude detector 42 receives a signal from the detection signal amplifier 41 and outputs an amplitude detection signal to the signal processor 5. The phase difference detection unit 43 inputs signals from the AC signal generation unit 2 and the sensor unit 3 and outputs a phase difference detection signal to the signal processing unit 5.

  The detection signal amplification unit 41 includes a differential amplification circuit 411, a band pass filter 412 and the like. The differential amplifier circuit 411 amplifies the difference between the detection signals from the two terminals output from the magnetic substance detection sensor 30. The band pass filter 412 passes only a frequency close to the frequency of the sine wave signal output from the AC signal generation unit 2 and outputs it to the amplitude detection unit 42 and the phase difference detection unit 43. In this way, the detection signal amplification unit 41 amplifies the detection signal output from the sensor unit 3.

  The detection signal amplifying unit 41 includes, for example, an instrumentation amplifier (a high-performance differential amplifier circuit capable of setting the amplification degree with a single resistor, for example, INA128). In the instrumentation amplifier, a series resonance circuit is inserted in a portion that determines the amplification factor, and the amplification factor is increased only in the vicinity of a frequency that matches the resonance frequency of the series resonance circuit. The function of the filter 412 can be provided. In addition, the detection signal amplifying unit 41 may be configured by any circuit as long as it has a high amplification factor amplification function and a band-pass filter function.

  The amplitude detection unit 42 includes an amplitude detection circuit 421 (including a rectifier circuit and a smoothing circuit), an amplifier circuit 422, and the like. The amplitude detection circuit 421 detects the amplitude of the detection signal output from the detection signal amplification unit 41. The amplification circuit 422 amplifies the amplitude detected by the amplitude detection circuit 421 by DC. In this way, the amplitude detector 42 detects the amplitude of the detection signal amplified by the detection signal amplifier 41.

  The amplitude detection unit 42 can be configured by, for example, a rectifier circuit using an operational amplifier, a smoothing circuit that shapes a waveform after rectification, and an amplifier circuit. In addition, the amplitude detector 42 may be configured by any circuit as long as it has a function of detecting an amplitude.

  The phase difference detection unit 43 includes an amplification circuit 431, an amplification circuit 432, a phase difference detection circuit 433, a smoothing circuit 434, and the like. The amplifying circuit 431 amplifies the signal output from the detection signal amplifying unit 41 to obtain a waveform close to a rectangular wave. The amplifying circuit 432 amplifies the signal output from the AC signal generating unit 2 to obtain a waveform close to a rectangular wave. The phase difference detection circuit 433 detects the phase difference between the signal amplified by the amplification circuit 431 and the signal amplified by the amplification circuit 432. The output of the phase difference detection circuit 433 is pulsed, and the pulse width indicates the phase difference. The smoothing circuit 434 converts this pulse signal into an analog signal proportional to the pulse width. This analog signal is sent to the signal processing unit 5 and processed by the AD conversion circuit 51. At this time, it is also possible to directly measure the pulse width from the pulse-like signal output from the phase difference detection circuit 433 by the computer 52 of the signal processing unit 5 without passing through the smoothing circuit 434.

  The phase difference detection unit 43 inputs, for example, signals output from the detection signal amplification unit 41 and the AC signal generation unit 2 to an exclusive OR circuit (for example, PLL IC 4046) and outputs from the exclusive OR circuit. The output signal can be smoothed with a resistor and a capacitor and output through a low-pass filter. In this case, the exclusive OR circuit plays a role of phase discrimination. In addition, the phase difference detection unit 43 may use a multiplication circuit, and may be configured with any circuit as long as the phase difference can be detected.

  The detection signal output from the detection signal amplifier 41 may be passed through a phase shifter circuit before being amplified. Since the output of the exclusive OR circuit is output as an absolute value with a phase difference of zero as a boundary, the phase change becomes discontinuous. Therefore, the phase may be shifted by passing through a phase shifter circuit to prevent discontinuity of the phase change. However, in a state in which the balance of the magnetic body detection sensor 30 is adjusted (showing a state in which the sensor unit 3 is adjusted so that the output of the amplitude detection unit 42 is minimized when there is no detection target in the vicinity of the sensor coil). Even in this case, the phase difference between the signal output from the AC signal generator 2 and the signal output from the sensor unit 3 should theoretically be zero, but does not actually become zero. There is also a phenomenon that the phase of the detection signal is shifted by the band-pass filter 412. Therefore, the phase shifter circuit is often unnecessary.

  The signal processing unit 5 includes an AD conversion circuit 51, a computer 52, a measurement data display circuit 53, an alarm output circuit 54, and the like. The AD conversion circuit 51 receives a signal from the signal detection unit 4 and outputs a signal to the computer 52. The computer 52 inputs a signal from the AD conversion circuit 51 and outputs a signal to the measurement data display circuit 53 and the alarm output circuit 54.

  The AD conversion circuit 51 performs analog-digital conversion on the amplitude signal and the phase difference signal output from the signal detection unit 4. The computer 52 controls the measurement data display circuit 53, the alarm output circuit 54, the sensor balance adjustment mechanism 61, and the like, and processes digital data input from the AD conversion circuit 51. The measurement data display circuit 53 displays the measurement results of the amplitude signal and the phase difference signal. The alarm output circuit 54 issues an alarm with light or sound when the amplitude signal or the phase difference signal is out of a predetermined range.

  The sensor control unit 6 includes a sensor balance adjustment mechanism 61 and the like. The sensor balance adjustment mechanism 61 adjusts the balance of the characteristics of the magnetic body detection sensor 30 according to the control of the computer 52. The sensor balance adjustment mechanism 61 includes, for example, a servo motor (not shown). In the first embodiment, the sensor balance adjustment mechanism 61 adjusts the resistance value of the adjustment trimmer resistor 37 illustrated in FIG. 3 when receiving the control signal of the computer 52. Note that manual adjustment may be used instead of computer-controlled adjustment using the sensor balance adjustment mechanism 61. In either case, when there is no detection target in the vicinity of the magnetic substance detection sensor 30, adjustment is made so that the output of the amplitude detector 42 is minimized.

  FIG. 2 is a cross-sectional view of the magnetic substance detection sensor according to the first embodiment. The magnetic body detection sensor 30 has a sensor cover 31 and is connected to the AC signal generation unit 2 and the signal detection unit 4 by a connection cable 7 extending from the rear end 312 of the sensor cover 31. The operator points the front end 311 of the sensor cover 31 in a direction in which the magnetic body to be detected can exist. For example, when detecting a magnetic body in the body cavity, the operator makes the front end 311 of the sensor cover 31 face the direction in which the detection target is supposed to exist.

  The sensor cover 31 includes a core 32, a coil bobbin 33, a pair of coils 34A and 34B, and the like. The core 32 is a rod that extends in the longitudinal direction X. Examples of the core 32 include a ferrite core. The coil bobbin 33 is a cylinder having a cylindrical hollow portion 331 extending in the longitudinal direction X, and the core 32 is located in the hollow portion 331. The virtual line 321 bisects the dimension of the core 32 in the longitudinal direction X. The coils 34 </ b> A and 34 </ b> B are wound in the circumferential direction of the coil bobbin 33 (core 32), and are disposed at positions that are substantially symmetric with respect to the longitudinal direction X center of the core 32, i.e., the virtual line 321. The coils 34A and 34B are wound around the core 32 in the same direction.

  The coil bobbin 33 has two recesses 332A and 332B. The recesses 332A and 332B are formed in an annular shape in the circumferential direction of the coil bobbin 33, and are positioned approximately symmetrically with the virtual line 321 as the axis of symmetry. The coil bobbin 33 is a resin having electrical insulation, and is preferably made of a material that hardly changes in expansion and contraction due to temperature. The coil bobbin 33 is for restricting the positions of the coils 34A and 34B and for positioning the core 32 inside the coils 34A and 34B. Any coil bobbin 33 may be used as long as it satisfies the above-described conditions. Further, the coils 34 </ b> A and 34 </ b> B may be directly wound around the core 32 without using the coil bobbin 33. In this case, the coil bobbin 33 is not required if there is a support body serving as a core for holding the coils 34A and 34B in the sensor cover 31.

  The coils 34A and 34B have the same number of turns, the length in the longitudinal direction X, the cross-sectional area orthogonal to the longitudinal direction X, and the winding direction. Since the coils 34A and 34B are wound around the recesses 332A and 332B, respectively, as described above, the coils 34A and 34B are disposed at substantially symmetrical positions with the longitudinal center X of the core 32 as the symmetry axis. . Accordingly, the impedances of the two coils 34A and 34B are substantially the same.

  The sensor cover 31 also includes a first terminal 361 to a fourth terminal 364 shown in FIG. The resistors 35 </ b> A and 35 </ b> B and the adjustment trimmer resistor 37 are preferably inside the sensor cover 31, but may be outside the sensor cover 31.

  FIG. 3 is a circuit diagram of the magnetic substance detection sensor in the first embodiment. In the magnetic body detection sensor 30 in the first embodiment, an RL AC bridge circuit is configured by a pair of resistors 35A and 35B and a pair of coils 34A and 34B. The RL AC bridge circuit is, for example, a Wheatstone bridge circuit applied to AC impedance measurement. The resistors 35A and 35B have substantially the same resistance value. As described above, the coils 34A and 34B have substantially the same impedance. The winding direction of the coils 34A and 34B (in FIG. 3, the winding start position is indicated by the “black circle” in the vicinity of each coil). A first terminal 361 is connected between the coil 34A and the resistor 35A. A second terminal 362 is connected between the coil 34A and the coil 34B. A third terminal 363 is connected between the coil 34B and the resistor 35B. A fourth terminal 364 is connected between the resistors 35 </ b> A and 35 </ b> B via an adjustment trimmer resistor 37. Therefore, the adjustment trimmer resistor 37 is located between the resistors 35A and 35B.

  A sine wave AC signal having an arbitrary frequency is applied between the second terminal 362 and the fourth terminal 364 by the oscillation circuit 21. The signal detection unit 4 detects amplitude and phase difference using detection signals from the first terminal 361 and the third terminal 363. It is also possible to apply a sine wave AC signal between the first terminal 361 and the third terminal 363 and detect the amplitude and phase difference from the second terminal 362 and the fourth terminal 364 using detection signals. That is, of the four terminals of the AC bridge circuit, one opposing two terminals can be used as excitation terminals, and the other two opposing terminals can be used as detection terminals. Hereinafter, in order to avoid confusion, a description will be given assuming that a sinusoidal AC signal is applied between the second terminal 362 and the fourth terminal 364 and a detection signal is detected from the first terminal 361 and the third terminal 363.

  Here, the magnetic body detection method in 1st Embodiment is demonstrated. As an advance preparation, the adjustment trimmer resistor 37 is adjusted in the absence of a magnetic substance in the surroundings, and the balance of the AC bridge circuit is adjusted so that the amplitude of the signal between the first terminal 361 and the third terminal 363 is minimized. It is desirable to adjust. Specifically, the resistance value of the adjustment trimmer resistor 37 is adjusted so that the amplitude of the signal between the first terminal 361 and the third terminal 363 is minimized by manual control of the operator or automatic control of the computer 52. To do.

  When the resistance value of the adjustment trimmer resistor 37 is adjusted, the amplitude of the signal between the first terminal 361 and the third terminal 363 should theoretically become zero. However, it is not actually zero. In this state, in the magnetic body detection sensor 30 according to the first embodiment, when the magnetic body to be detected approaches one of the coils 34A and 34B, the balance of the coils 34A and 34B is lost, and the phase of the AC bridge circuit changes. In addition, the amplitude may be further smaller than the amplitude adjusted for balance due to eddy current.

  Here, when the amplitude of the signal is minimum, it is desirable to adjust the phase difference so that −α <phase difference <α (α is a constant satisfying 0 degree <α <90 degrees). In other words, it is desirable to adjust so that the absolute value of the phase difference is equal to or less than the constant α. The reason will be described later with reference to FIG.

  When the operator activates the magnetic substance detection device 1, the oscillation circuit 21 applies a sine wave AC signal between the second terminal 362 and the fourth terminal 364. In this state, the operator directs the front end 311 of the magnetic body detection sensor 30 in a direction in which a detection target can exist. Then, the impedance of the coil 34A provided on the front end 311 side changes. The impedance of the coil 34B may change slightly. However, since the coil 34A is closer to the detection target than the coil 34B, the change in the impedance of the coil 34A is much larger than the change in the impedance of the coil 34B.

  When the impedance of the coil 34 </ b> A changes, the RL AC bridge circuit of the magnetic substance detection sensor 30 loses its balance, and the signal detected between the first terminal 361 and the third terminal 363 changes. Specifically, when the operator moves the front end portion 311 of the magnetic body detection sensor 30 closer to the detection target, the amplitude of the signal between the first terminal 361 and the third terminal 363 changes, and the second terminal 362. And the phase difference between the sine wave AC signal applied between the first terminal 364 and the fourth terminal 364 also changes.

  The signal detection unit 4 detects the amplitude of the detection signal output from the magnetic substance detection sensor 30 and outputs it to the signal processing unit 5. Further, the signal detection unit 4 detects a phase difference between the detection signal output from the magnetic substance detection sensor 30 and the oscillation signal output from the AC signal generation unit 2, and outputs it to the signal processing unit 5. The computer 52 of the signal processing unit 5 determines the presence / absence of the magnetic substance and the position identification based on the amplitude signal and the phase difference signal output from the signal detection unit 4. For example, when the amplitude signal and the phase difference signal exceed a predetermined threshold value, the computer 52 determines that a magnetic material is present, and transmits a control signal to the alarm output circuit 54 to issue an alarm with light or sound. To do. Further, for example, the computer 52 determines that the presence position of the magnetic body is close as the change in the amplitude signal and the phase difference signal increases, and a control signal indicating that the blinking of light is accelerated or the volume is increased. Is transmitted to the alarm output circuit 54.

  The signal detection unit 4 may detect either the amplitude signal or the phase difference signal, or may detect both. Further, the computer 52 of the signal processing unit 5 may make the determination based on either the amplitude signal or the phase difference signal, or may make the determination based on both. When the type of the magnetic material to be detected is clear, it may be selected whether to detect either the amplitude signal or the phase difference signal, or to detect both, depending on the type of the magnetic material to be detected. For example, if the magnetic substance to be detected is a magnetic fluid that is unlikely to generate eddy currents or a thin surgical needle, it is better to detect at least the phase difference signal. In this case, by further detecting the amplitude signal, it is easy to distinguish the magnetic fluid from other than the thin surgical needle. This is because even if the phase change is large, if the amplitude change is large, information indicating that there is a possibility other than a magnetic fluid or a thin surgical needle can be obtained.

  As described above, in the first embodiment, the magnetic body to be detected is detected by the magnetic body detection sensor 30 having the RL AC bridge circuit including the pair of coils 34A and 34B having substantially the same impedance and the pair of resistors 35A and 35B. To detect. Since the magnetic body detection sensor 30 in the first embodiment detects the influence of the relative permeability of the detection target and the eddy current generated in the detection target on the coils 34A and 34B, it is hardly affected by the geomagnetism. Therefore, the magnetic material can be detected stably. Further, since it is hardly affected by geomagnetism, it is not necessary to measure the difference between two sensors (magnetic sensor in the case of the prior art) as in the prior art, and the magnetic material can be detected with high sensitivity.

  Furthermore, in the prior art, in order to reduce the influence of geomagnetism, it is necessary to measure the difference using two magnetic sensors. Further, in the prior art, in order to detect an anastomosis needle or the like or magnetic fluid having no residual magnetic force by a magnetic sensor, an anastomosis needle or the like or an exciting magnet for exciting the magnetic fluid is required. Therefore, there is a limit to downsizing the sensor unit 3 (probe in the case of the prior art). On the other hand, in the first embodiment, since the magnetic body detection sensor 30 is mainly composed of the core 32 and the pair of coils 34A and 34B, the sensor unit 3 can be downsized.

  In addition, magnetic fluid has very high fluidity and is attracted to a magnet. Therefore, if a probe having an exciting magnet is kept close to the affected area for a long time as in the prior art, the magnetic fluid is attracted to the exciting magnet of the probe, and the magnetic fluid can be erroneously detected at a place different from the original. There is sex. On the other hand, in the first embodiment, there is no such worry because there is no strong exciting magnet inside the sensor unit 3.

  Further, since the magnetic body detection sensor 30 is mainly composed of the core 32 and the pair of coils 34A and 34B, there is little shot noise and 1 / f noise that are generated in the semiconductor magnetic sensor. Therefore, noise that affects the detection sensitivity is reduced, and the magnetic material can be detected with high sensitivity.

Second Embodiment
In the second embodiment, the same constituent elements as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed descriptions thereof are omitted. The first embodiment and the second embodiment are different in the configuration of the magnetic body detection sensor 30.

  FIG. 4 is a cross-sectional view of a magnetic substance detection sensor according to the second embodiment. Similar to the first embodiment, the magnetic body detection sensor 30 includes a sensor cover 31 and is connected to the AC signal generation unit 2 and the signal detection unit 4 by a connection cable 7 extending from the rear end 312 of the sensor cover 31. .

  The sensor cover 31 includes a core 32, a coil bobbin 33, a first coil 34C, a pair of second coils 34D and 34E, an adjustment core 38, and the like. The core 32 is a rod that extends in the longitudinal direction X. The coil bobbin 33 is a cylindrical body having a cylindrical hollow portion 331 extending in the longitudinal direction X, and the core 32 and the adjustment core 38 are located in the hollow portion 331. The core 32 is held by the coil bobbin 33 and the position is fixed. The virtual line 321 bisects the dimension of the core 32 in the longitudinal direction X. The first coil 34 </ b> C is wound in the circumferential direction of the coil bobbin 33 (core 32), and is arranged so that the longitudinal direction X center of the core 32, that is, the imaginary line 321 is the center position. The second coils 34 </ b> D and 34 </ b> E are wound in the circumferential direction of the coil bobbin 33 (core 32), and are disposed at positions that are substantially symmetric with respect to the longitudinal direction X center of the core 32, i.e., the virtual line 321. Accordingly, the first coil 34C is located between the pair of second coils 34D and 34E. In this way, the relative positional relationship between the core 32, the first coil 34C, and the pair of second coils 34D and 34E is fixed.

  The coil bobbin 33 has three concave portions 332C, 332D, and 332E. The recess 332 </ b> C is formed in an annular shape in the circumferential direction of the coil bobbin 33, and the virtual line 321 is the center position in the longitudinal direction X. The recesses 332D and 332E are formed in an annular shape in the circumferential direction of the coil bobbin 33, and are positioned substantially symmetrically with the virtual line 321 as the axis of symmetry. The coil bobbin 33 regulates the positions of the first coil 34C and the second coils 34D and 34E, positions the core 32 inside the first coil 34C and the second coils 34D and 34E, and fixes the relative positional relationship. Any material may be used as long as it satisfies the above conditions. Further, the first coil 34 </ b> C and the second coils 34 </ b> D and 34 </ b> E may be directly wound around the core 32 without using the coil bobbin 33. In this case, the coil bobbin 33 is not required if there is a support body serving as a core for holding the core 32, the first coil 34C, and the second coils 34D, 34E in the sensor cover 31.

  The second coils 34 </ b> D and 34 </ b> E have the same number of turns, a length, and a cross-sectional area perpendicular to the longitudinal direction X, and are opposite in winding direction. Since the first coil 34C and the second coils 34D and 34E are wound around the recesses 332C, 332D and 332E, respectively, as described above, the first coil 34C has the center position in the longitudinal direction X center of the core 32. The second coils 34 </ b> D and 34 </ b> E are arranged at positions that are substantially symmetric with respect to the longitudinal direction X center of the core 32 as an axis of symmetry. Therefore, the inductances of the coils are substantially the same.

  The adjustment core 38 adjusts the amplitude of the detection signal output from the sensor unit 3, is spaced apart from the core 32 in the longitudinal direction X, is positioned in the hollow portion 331 of the coil bobbin 33, and moves in the longitudinal direction X Is possible. The adjustment core 38 is located closer to the rear end 312 of the sensor cover 31 than the core 32. For example, when the coil bobbin 33 and the adjustment core 38 are threaded, the position of the adjustment core 38 can be adjusted by rotating the adjustment core 38. The adjustment core 38 can adjust the position in the longitudinal direction X by, for example, a servo motor (not shown). In the second embodiment, the sensor balance adjustment mechanism 61 of the sensor control unit 6 adjusts the position in the longitudinal direction X of the adjustment core 38 when receiving a control signal from the computer 52.

  The sensor cover 31 also includes a first terminal 361 to a fourth terminal 364 shown in FIG.

  FIG. 5 is a circuit diagram of a magnetic substance detection sensor according to the second embodiment. In the magnetic body detection sensor 30 according to the second embodiment, a differential transformer circuit is configured by the first coil 34C and the pair of second coils 34D and 34E. As described above, the second coils 34D and 34E have substantially the same inductance. The winding directions of the second coils 34D and 34E (in FIG. 5, the winding start position is indicated by the “black circle” in the vicinity of each coil) are opposite. A second terminal 362 and a fourth terminal 364 are connected to both ends of the first coil 34C. As for 2nd coil 34D, 34E, while one end part is connected, the 1st terminal 361 is connected to the other end part of 2nd coil 34D, and the 3rd terminal is connected to the other end part of 2nd coil 34E. 363 is connected.

  The fifth terminal 365 is a terminal located between the first terminal 361 and the third terminal 363. A signal (a signal detected from the third terminal 363 and the fifth terminal 365) induced to the second coil 34E by mutual induction in the absence of a magnetic substance in the surroundings is a signal (the first signal detected from the third terminal 363 and the fifth terminal 365). Compared with signals detected from the first terminal 361 and the fifth terminal 365), the amplitude is the same and the phase is shifted by 180 degrees. In this state, the signal detected from the first terminal 361 and the third terminal 363 is composed of the signal induced in the second coil 34E and the signal induced in the second coil 34D, and ideally becomes zero. . However, it never actually goes to zero.

  The circuit diagram of the differential transformer circuit shown in FIG. 5 is well known as a circuit diagram of a differential transformer circuit used as a displacement sensor. In the displacement sensor, the core at the center of the coil moves, and the displacement is measured. On the other hand, the magnetic body detection sensor 30 in the second embodiment has the core 32 fixed, and behaves as if the core 32 moves due to the influence of the magnetic body approaching the magnetic body detection sensor 30. Detecting the approach of a magnetic material.

  A sine wave AC signal having an arbitrary frequency is applied between the second terminal 362 and the fourth terminal 364 by the oscillation circuit 21. The signal detection unit 4 detects a detection signal from the first terminal 361 and the third terminal 363. It is also possible to apply a sine wave AC signal between the first terminal 361 and the third terminal 363 and detect the detection signal from the second terminal 362 and the fourth terminal 364. That is, two terminals connected to one of the first coil 34C and the pair of second coils 34D and 34E can be used as excitation terminals, and two terminals connected to the other can be used as detection terminals. Hereinafter, in order to avoid confusion, a description will be given assuming that a sinusoidal AC signal is applied between the second terminal 362 and the fourth terminal 364 and a detection signal is detected from the first terminal 361 and the third terminal 363.

  Here, the magnetic body detection method in 2nd Embodiment is demonstrated. As a preliminary preparation, the adjustment core 38 is adjusted in the absence of a magnetic substance in the surroundings, and the differential transformer circuit is balanced so that the amplitude of the signal between the first terminal 361 and the third terminal 363 is minimized. It is desirable to adjust. Specifically, the position of the adjustment core 38 in the longitudinal direction X is set so that the amplitude of the signal between the first terminal 361 and the third terminal 363 is minimized by manual control of the operator or automatic control of the computer 52. Adjust. Here, as in the first embodiment, when the amplitude of the signal is minimum, the phase difference is adjusted to satisfy −α <phase difference <α (α is a constant satisfying 0 degree <α <90 degrees). It is desirable to do. The reason will be described later with reference to FIG. After that, after the operator activates the magnetic body detection device 1, it is the same as the magnetic body detection method in the first embodiment.

  Examples of the adjustment core 38 include a ferrite core, a copper core, and an aluminum core. In the case of a ferrite core, the relative permeability is much larger than 1, and no eddy current is generated, so that the inductance of the second coil 34E can be adjusted. In the case of a copper core or an aluminum core, the relative permeability is close to 1 and an eddy current is generated. Therefore, the effect of the eddy current is greater than the relative permeability and the inductance of the second coil 34E can be adjusted to be reduced. . As described above, the material of the adjustment core 38 can be appropriately selected as necessary.

  As described above, in the second embodiment, the magnetic body to be detected by the magnetic body detection sensor 30 having the differential transformer circuit including the first coil 34C and the pair of second coils 34D and 34E having substantially the same inductance. Is detected. Similarly to the first embodiment, the magnetic body detection sensor 30 in the second embodiment also detects the influence of the relative permeability of the detection target on the first coil 34C and the second coils 34D and 34E, and therefore the influence of geomagnetism. Not receive. Therefore, the magnetic material can be detected stably. Further, since it is not affected by geomagnetism, it is not necessary to measure the difference between two sensors (magnetic sensor in the case of the prior art) as in the prior art, and the magnetic material can be detected with high sensitivity.

  In the second embodiment, the magnetic body detection sensor 30 is mainly composed of the core 32, the first coil 34C, and the pair of second coils 34D and 34E. Miniaturization is possible. Further, as in the first embodiment, noise that affects the detection sensitivity is reduced, and the magnetic material can be detected with high sensitivity.

<Third Embodiment>
In the third embodiment, the same constituent elements as those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and detailed description thereof is omitted. The first, second and third embodiments are mainly different in the configuration of the sensor control unit 6. The sensor control unit 6 of the third embodiment can be applied to any of the magnetic body detection sensors 30 of the first and second embodiments. Hereinafter, the magnetic body detection sensor 30 of the first embodiment will be described as an example.

  FIG. 6 is an apparatus configuration diagram of the magnetic body detection apparatus according to the third embodiment. When FIG. 1 and FIG. 6 are compared, the configurations of the sensor unit 3 and the sensor control unit 6 are different. In general, the sensor is affected by temperature changes. The magnetic body detection sensor 30 according to the present invention is no exception and is affected by a certain temperature change. Therefore, in the third embodiment, a mechanism for keeping the temperature in the sensor cover 31 constant is realized.

  The sensor unit 3 includes a temperature sensor 39 in addition to the magnetic body detection sensor 30. The temperature sensor 39 measures the temperature in the sensor cover 31 and transmits temperature data to the computer 52 of the signal processing unit 5.

  The sensor control unit 6 includes an air pump 62 and a heating device 63 in addition to the sensor balance adjustment mechanism 61. The air pump 62 sends air into the sensor cover 31 of the magnetic substance detection sensor 30. The heating device 63 heats the air sent into the sensor cover 31 by the air pump 62.

  FIG. 7 is a cross-sectional view of a magnetic substance detection sensor according to the third embodiment. The sensor cover 31 includes a ventilation pipe 313 serving as a passage for air sent from the outside by the air pump 62. The core 32 is provided with a ventilation hole 322 penetrating in the longitudinal direction X as an air passage. The coil bobbin 33 is formed with a vent hole 333 formed in an annular shape in the circumferential direction at a position radially outside the hollow portion 331 as an air passage. The cross section orthogonal to the longitudinal direction X of the ventilation hole 333 has a donut shape. Although not shown in FIG. 7, the rear end portion 312 of the sensor cover 31 is provided with an air sending hole and a discharge hole.

  In FIG. 7, the flow of air is illustrated by arrows. Air sent from a delivery hole (not shown) by the air pump 62 passes through the ventilation pipe 313, the ventilation hole 322 of the core 32, and the ventilation hole 333 of the coil bobbin 33 and exits from the discharge hole (not shown).

  Here, a method of detecting a magnetic material that keeps the temperature in the sensor cover 31 constant will be described. The temperature sensor 39 transmits temperature data to the computer 52 as needed. When detecting the change in the temperature data, the computer 52 transmits a control signal to the air pump 62 and the heating device 63 so as to send air at the set temperature into the sensor cover 31. The air pump 62 sends air into the sensor cover 31 of the magnetic body detection sensor 30 in accordance with a control signal from the computer 52. The heating device 63 heats the air sent into the sensor cover 31 by the air pump 62 in accordance with a control signal from the computer 52 so as to reach a set temperature. The set temperature is higher than the environmental temperature. In this manner, the magnetic body detection device 1 according to the third embodiment controls the air temperature to be constant by the heating device 63 based on the information of the temperature sensor 39, and air that is hotter than the ambient temperature in the sensor cover 31. Is circulated to keep the temperature in the sensor cover 31 constant.

  The reason why the set temperature is higher than the ambient temperature is that the amount of heat flowing out from the sensor cover 31 to the outside is equal to the amount of heat flowing into the sensor cover 31 by the air pump 62, and the sensor cover 31 is in a thermal equilibrium state. It is to make it. On the contrary, the same purpose can be achieved by setting the set temperature to a value lower than the ambient temperature. In this case, air at a lower temperature is sent from the air pump 62 into the sensor cover 31 to bring the sensor cover 31 into a thermal equilibrium state.

  Instead of the above-described method, the temperature in the sensor cover 31 can be kept constant by sending a large amount of air at a constant temperature from the air pump 62 at all times. In this case, the temperature sensor 39 need not be provided in the sensor cover 31.

  In the third embodiment, the temperature in the sensor cover 31 can be kept constant. Therefore, the magnetic body detection sensor 30 can detect the magnetic body with high sensitivity without being affected by the temperature change.

<Fourth embodiment>
In the fourth embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and detailed description thereof is omitted. The first, second and fourth embodiments mainly differ in the configuration of the sensor control unit 6. The sensor control unit 6 of the fourth embodiment can be applied to any of the magnetic body detection sensors 30 of the first and second embodiments. Hereinafter, the magnetic body detection sensor 30 of the first embodiment will be described as an example.

  FIG. 8 is a device configuration diagram of the magnetic body detection device according to the fourth embodiment. Comparing FIG. 1 and FIG. 8, the configuration of the sensor control unit 6 is different. In the third embodiment, a mechanism for keeping the temperature in the sensor cover 31 constant is realized. However, in the fourth embodiment, a mechanism for making it less susceptible to the temperature change in the sensor cover 31 is realized.

  The sensor control unit 6 includes an actuator 64 in addition to the sensor balance adjustment mechanism 61. The actuator 64 moves the coil bobbin 33 to a predetermined position in the longitudinal direction X. The coil bobbin 33 has the core 32 inside, and the coils 34A and 34B are wound in the circumferential direction. Therefore, if the position of the coil bobbin 33 in the longitudinal direction X moves, the longitudinal direction X of the core 32 and the coils 34A and 34B. The position of will also move.

  FIG. 9 is a cross-sectional view of a magnetic substance detection sensor according to the fourth embodiment. The actuator 64 includes a connecting portion 641 with the coil bobbin 33. The connecting portion 641 is connected to the rear end portion 335 of the coil bobbin 33. The coil bobbin 33 has a front end 334 that can be moved by the actuator 64 from the first measurement position P1 to the second measurement position P2. The position in the longitudinal direction X of the first measurement position P1 is closer to the front end 311 side of the sensor cover 31 than the position in the longitudinal direction X of the second measurement position P2. When detecting the magnetic body, the operator directs the front end 311 of the sensor cover 31 in the direction in which the magnetic body to be detected can exist, so that the first measurement position P1 is set to be detected more than the second measurement position P2. Close position.

  Here, a magnetic body detection method that is not affected by the temperature change in the sensor cover 31 will be described. When the operator activates the magnetic body detection device 1, the computer 52 transmits a control signal for moving the position of the front end 334 of the coil bobbin 33 to the first measurement position P <b> 1 to the actuator 64. The actuator 64 moves the front end 334 of the coil bobbin 33 to the first measurement position P1 in accordance with a control signal from the computer 52. As in the first embodiment, the computer 52 obtains sampling values (first detection signals) of the amplitude signal and the phase difference signal output from the signal detection unit 4.

  Next, the computer 52 transmits a control signal for moving the position of the front end portion 334 of the coil bobbin 33 to the second measurement position P <b> 2 to the actuator 64. The actuator 64 moves the front end 334 of the coil bobbin 33 to the second measurement position P2 in accordance with a control signal from the computer 52. Then, similarly to the first embodiment, the computer 52 obtains a sampling value (second detection signal) of the amplitude signal and the phase difference signal output from the signal detection unit 4.

  Next, the computer 52 calculates the difference between the sampling value (first detection signal) obtained at the first measurement position P1 and the sampling value (second detection signal) obtained at the second measurement position P2. Then, the computer 52 determines the presence / absence of the magnetic substance and the position identification based on the amplitude signal and the phase difference signal obtained by this calculation.

  The reason why the sensor cover 31 is not affected by the temperature change in this method will be described. Assuming that the influence of the temperature change in the sensor cover 31 in the measurement result is X, the sampling value S1 at the first measurement position P1 is S1 = A + X, where A is the influence by the magnetic substance. Here, the influence of the temperature change is independent of the influence of the magnetic substance. Similarly, the sampling value S2 at the second measurement position P2 is S2 = B + X, where B is the influence due to the magnetic material. Accordingly, when the difference between the sampling values is calculated, S1−S2 = (A + X) − (B + X) = A−B, which is a value that does not depend on X, which is an influence due to the temperature change. Therefore, it is not affected by temperature changes. Thus, in 4th Embodiment, since it is not influenced by the temperature change in the sensor cover 31, a magnetic body can be detected with high sensitivity.

<Fifth Embodiment>
In the fifth embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and detailed description thereof is omitted. The first, second and fifth embodiments are different in the determination process by the computer 52 of the signal processing unit 5. The determination process by the computer 52 of the fifth embodiment can be applied to any of the magnetic body detection sensors 30 of the first and second embodiments. Hereinafter, the magnetic body detection sensor 30 of the first embodiment will be described as an example.

  FIG. 10 is a graph of amplitude change and phase change for each type of magnetic material in the fifth embodiment. In the first embodiment, the computer 52 only determines the presence / absence of a magnetic body and the position identification. On the other hand, in the fifth embodiment, the computer 52 also performs detection type determination. FIG. 10 illustrates data serving as a determination criterion by the computer 52.

  FIG. 10 is a graph in which the horizontal axis represents phase change and the vertical axis represents amplitude change. In FIG. 10, the detection signal in the state where there is no detection target around the magnetic substance detection sensor 30 is used as a reference, and the point where the detection signal is plotted is the origin. In the process in which the magnetic detection sensor 30 approaches the detection target, when the detection target is far from the magnetic detection sensor 30, neither a phase change nor an amplitude change occurs, but the magnetic detection sensor 30 gradually becomes a detection target. When approaching, the phase change and amplitude change increase. FIG. 10 is a plot of this process for each type of magnetic material. As shown in FIG. 10, the amplitude change and the phase change are plotted on a substantially straight line. Further, the ratio between the phase change and the amplitude change is different for each type of detection target. Therefore, it is possible to determine the type of detection target based on the ratio between the phase change and the amplitude change.

  Here, the magnetic body detection method in 5th Embodiment is demonstrated. The computer 52 stores in advance the ratio of phase change to amplitude change for each type of magnetic material. The preparation and the operation from when the operator activates the magnetic body detection device 1 until the signal detection unit 4 outputs the amplitude signal and the phase difference signal to the signal processing unit 5 are the same as in the first embodiment. .

  The computer 52 of the signal processing unit 5 calculates the ratio between the phase change and the amplitude change based on the amplitude signal and the phase difference signal output from the signal detection unit 4. Next, the computer 52 searches for a value closest to the calculated value among the previously stored ratio values of the phase change and the amplitude change. If the error between the searched value and the calculated value is within a predetermined range, the computer 52 determines that there is a type of magnetic body corresponding to the searched value, and sets the type of the magnetic body. A control signal for display is transmitted to the measurement data display circuit 443. The measurement data display circuit 443 displays the type of the magnetic material according to the control signal from the computer 52. The computer 52 stores an alarm method for each magnetic material type in advance, and transmits a control signal to the alarm output circuit 534 to output an alarm by the alarm method corresponding to the magnetic material type. May be. As described above, in the fifth embodiment, the type of the detection target can also be determined.

  The fact that the phase change and the amplitude change are plotted on a substantially straight line means that the ratio between the phase change and the amplitude change does not change with respect to the distance between the magnetic substance detection sensor 30 and the detection target. That is, it means that the ratio between the phase change and the amplitude change is not easily affected by the distance between the magnetic substance detection sensor 30 and the detection target. Therefore, even if there are human factors of the operator or inclusions (skin, adipose tissue, sterilization bag, paint, insulation coating, etc.) between the magnetic substance detection sensor 30 and the detection target, it is highly accurate. The type of detection target can be determined.

  For example, in the case of stainless steel, since the phase change is small and the amplitude change is large, when the detection target is a stainless steel forceps or tweezers, the determination process based on the amplitude change can be detected more accurately than the phase change. Inferred. On the other hand, when the detection target is a magnetic fluid, the amplitude change is small and the phase change is large. Therefore, it is assumed that the determination process based on the phase change can be detected more accurately than the amplitude change. Accordingly, the computer 52 performs a determination process based on both the phase change and the amplitude change of the detection signal obtained from the magnetic substance detection sensor 30, thereby accurately detecting whatever magnetic substance is to be detected. can do.

<Operation Principle of the Present Invention>
The magnetic body detection sensor 30 in the first embodiment forms an AC bridge circuit, and the magnetic body detection sensor 30 in the second embodiment forms a differential transformer circuit. The AC bridge circuit and the differential transformer circuit are known techniques and are used for impedance measurement and displacement sensor, respectively. In the following, the difference between a magnetic substance detection sensor according to the present invention and an AC bridge circuit used for impedance measurement and a differential transformer circuit used for a displacement sensor will be described, and the operating principle of the present invention will be described.

  FIG. 11A is a graph of changes in amplitude and phase when the magnetic body detection sensor in the first embodiment and the second embodiment approaches the detection target. The horizontal axis represents a state in which the sensor circuit balance of the magnetic body detection sensor 30 is in balance (a state in which the magnetic body detection sensor 30 is adjusted so that the output of the amplitude detection unit 42 is minimized when there is no detection target in the vicinity). Indicates the amount of misalignment when the origin is used. The vertical axis represents the amplitude and phase when the origin is a state in which the sensor circuit balance of the magnetic substance detection sensor 30 is matched.

  The magnetic body detection sensors 30 in the first embodiment and the second embodiment have different circuits, but the output characteristics of the sensors are common. In an ideal state, the amplitude becomes zero in a state where the sensor circuit balance is suitable, and the amplitude becomes a linear graph with respect to the balance deviation. However, in actuality, even when the sensor circuit balance is in a proper state, such as the amplitude 101 shown in FIG. 11A, the sensor circuit output does not become zero and becomes flat when the sensor circuit balance is in proper state. Further, in an ideal state, the phase switches discontinuously between plus and minus when the sensor circuit balance is matched. However, in actuality, as in the phase 102 shown in FIG. 11A, the sensor circuit continuously changes in the vicinity of the state where the sensor circuit balance is matched.

  Below, the difference between the magnetic body detection sensor 30 in 2nd Embodiment and the well-known displacement sensor using a differential transformer circuit is demonstrated first.

  In a known displacement sensor, the balance of the circuit is intentionally broken by displacing the movable core, and the amplitude of the output signal is used as a value proportional to the displacement. That is, when an AC signal is input to the displacement sensor, the output amplitude increases in accordance with the circuit balance deviation. Here, both of the amplitudes increase with respect to the deviation between the positive and negative circuit balances when the circuit balance is matched. That is, it is noted that the known displacement sensor does not change in the direction in which the amplitude decreases. It is also noted that there is almost no amplitude change near the circuit balance. Regarding the phase change, if the phase with respect to the deviation of the circuit balance in the minus direction is +90 degrees, the phase with respect to the deviation of the circuit balance in the plus direction is −90 degrees. This phase change occurs continuously with the circuit balance being matched. A region 103 (shaded portion) shown in FIG. 11A is a region to be avoided when a differential transformer circuit is used as a displacement sensor because the amplitude change is small and the phase change is also unstable.

  On the other hand, the magnetic body detection sensor 30 in the second embodiment does not include a movable core. That is, the relative positional relationship between the core 32 and the first coil 34C and the second coils 34D and 34E is fixed. And the sensor output when a detection target approaches the core 32 vicinity is utilized for a magnetic body detection. Further, the magnetic body detection sensor 30 is formed by utilizing the characteristics of the region 103 shown in FIG. 11A that can be avoided in the differential transformer circuit for the displacement sensor. This area 103 is a range in which the ratio of phase change to the balance deviation (absolute value of the slope of the phase 102) is large. Therefore, a sudden phase change occurs with a slight change in the circuit balance, so that the sensor becomes very sensitive. Further, this region 103 has a characteristic that the amplitude change is very small. Note that the range of the region 103 can be changed as appropriate in consideration of the trade-off between sensitivity and erroneous detection.

  As described above, in the magnetic body detection sensor 30 in the second embodiment and the known displacement sensor using the differential transformer circuit, is the relative positional relationship between the core and the sensor coil fixed or changed? There is a difference. Further, the magnetic substance detection sensor 30 uses a sensor output in a range where the ratio of the phase change to the balance deviation is large, and a known displacement sensor using a differential transformer circuit avoids the sensor output in that range. There is a difference.

  Similarly, the magnetic substance detection sensor 30 in the first embodiment is different from a known AC bridge circuit for impedance measurement. In the magnetic body detection sensor 30 according to the first embodiment, a pair of coils 32 </ b> A and 32 </ b> B are wound around the same core 32. On the other hand, a known AC bridge circuit for impedance measurement has a plurality of physically independent coils because a coil with unknown impedance and a known coil are separately connected. In addition, the magnetic body detection sensor 30 in the first embodiment uses a sensor output in a range in which the ratio of the phase change with respect to the balance shift is large, like the magnetic body detection sensor 30 in the second embodiment. On the other hand, the known AC bridge circuit for impedance measurement only adjusts the circuit balance.

  Next, the operation principle of the magnetic body detection sensor 30 in the first embodiment and the second embodiment will be described in detail.

  If the magnetic body detection sensor 30 is brought close to the detection target in a state in which the sensor circuit balance of the region 103 is matched, an eddy current is generated in the detection target when the detection target is a conductive magnetic body. If it is the magnetic substance detection sensor 30 in the first embodiment, the impedance of the coil 34A on the front end 311 side is reduced by the eddy current, and if it is the magnetic substance detection sensor 30 in the second embodiment, it is detected by the eddy current. The inductance of the second coil 34D on the near front end 311 side decreases. Further, electric power is consumed by the eddy current generated in the detection target and the electrical resistance of the detection target, and the change in amplitude is smaller than the change in phase. For example, when the detection target is a small electrical resistance such as aluminum or copper, the decrease in the output signal amplitude is small, and when the detection target is a large electrical resistivity such as lead or white copper, the decrease in the output signal amplitude is large. . Further, for example, when an eddy current does not occur as in the case of ferrite as a detection target, the output signal amplitude of the circuit does not decrease, and a slight increase in amplitude corresponding to the balance shift in FIG.

  When the relative permeability of the detection target is much larger than 1, the influence of the relative permeability is larger than the influence of the decrease in impedance or inductance due to the eddy current. Accordingly, due to the high relative magnetic permeability, the impedance of the coil 34A on the front end 311 side increases in the case of the magnetic body detection sensor 30 in the first embodiment, and the detection occurs in the case of the magnetic body detection sensor 30 in the second embodiment. The inductance of the second coil 34D on the front end 311 side close to the object increases. For example, the relative permeability of aluminum or copper is approximately 1, whereas iron varies depending on the type, but is 2000 or more. For this reason, an increase in impedance and inductance due to relative permeability is superior to a decrease in impedance and inductance due to eddy current. Moreover, since iron is conductive, eddy current is generated and the amplitude decreases.

  For example, when the detection target is aluminum or copper, when the magnetic substance detection sensor 30 approaches the detection target, the amplitude decreases in FIG. 11A and the phase changes in the negative direction. On the other hand, when the detection target is iron, when the magnetic substance detection sensor 30 approaches the detection target, the amplitude decreases in FIG. 11A and the phase changes in the positive direction. As described above, there is a difference between the amplitude change and the phase change depending on the characteristics such as the relative permeability and electric resistivity of the detection target. By utilizing this characteristic, not only the presence and position of the magnetic material can be detected, but also the type of the magnetic material can be determined. As described above, FIG. 10 shows an actual measurement example for each type of magnetic material. It is noted that, except for ferrite, where eddy currents do not occur, the amplitude is further reduced from the balanced state of the sensor circuit. Note that the positive and negative phases are relative. If the phase change of aluminum or copper is the positive direction, the phase change of iron is in the negative direction.

  As described above, the magnetic body detection sensor 30 in the first embodiment and the second embodiment can detect the magnetic body with high sensitivity by utilizing the phenomenon in the unique region 103 that is conventionally avoided and used. At the same time, the type of the magnetic material can be determined.

  In addition, when the magnetic body detection sensor 30 further approaches the detection target and moves out of the region 103, the reduced amplitude is reversed and increases. Also, the phase change is very small.

  Next, the balance adjustment of the sensor circuit will be described. FIG. 11B shows a phase change in a state where the amplitude of the signal is adjusted to be the minimum. Ideally, the phase change should be zero when the signal amplitude is at a minimum, but in practice it is not. That is, it does not pass through the origin as in the phase 102 in FIG. 11A, and in fact, a shift occurs as in the phases 102a to 102d in FIG. If this deviation is too large, the magnetic substance detection sensor 30 will not function. For example, since the positive portion of the phase 102a is completely out of the region 103 and the negative portion of the phase 102d is completely out of the region 103, the magnetic substance cannot be detected with high sensitivity or erroneous detection occurs. On the other hand, in the phase 102b and the phase 102c, although the intersection with the vertical axis is deviated from the origin, the plus portion and the minus portion are almost included in the region 103. Can be detected. Therefore, when the amplitude of the signal is minimum, the magnetic material is adjusted with high sensitivity by adjusting the phase difference to satisfy −α <phase difference <α (α is a constant satisfying 0 ° <α <90 °). Can be detected. The constant α may be set as appropriate according to the sensitivity required for the magnetic substance detection sensor 30.

  As mentioned above, although preferred embodiment, such as a magnetic body detection sensor concerning the present invention, was described, referring to an accompanying drawing, the present invention is not limited to the above-mentioned example. For example, although the core 32 is exemplified by a ferrite core, it may be a core made of a silicon steel plate, or any other material that is suitable for the operating frequency of the magnetic substance detection sensor 30.

  In the above description, the coils 34A and 34B in the first embodiment have the same winding direction. However, even if the winding directions are opposite, the magnetic material can be detected. This can be explained as follows with reference to FIGS. In the magnetic body detection sensor 30 in the second embodiment, a similar sensor output can be obtained by supplying an AC signal to the fifth terminal 365 instead of the first coil 34C. When considering such a circuit, one end of the AC signal is the fifth terminal 365 and the other end is ground. The first terminal 361 and the third terminal 363 are input to the differential input amplifier, and these two inputs are substantially connected to the ground with a resistor interposed therebetween. Then, this circuit substantially becomes an AC bridge circuit shown in FIG. However, the winding directions of the pair of coils are opposite. That is, the coils 34A and 34B in the first embodiment can obtain the same sensor output as the magnetic body detection sensor 30 in the first embodiment and the second embodiment even if the winding direction is opposite. Can be detected. As can be understood from this description, the first embodiment and the second embodiment can be said to have the same basic technical idea because the same sensor output can be obtained although the configurations are different.

  In the above description, the adjustment trimmer resistor 37 is positioned between the two resistors 35A and 35B in the first embodiment. However, other adjustment means for adjusting the amplitude of the detection signal output from the detection terminal in order to adjust the balance of the AC bridge circuit are conceivable. For example, one of the resistors 35A and 35B may be the adjustment trimmer resistor 37. Further, the adjustment trimmer resistor 37 may be removed and the adjustment core 38 shown in FIG. 4 may be attached.

  In the above description, in the first embodiment, resistors 35A and 35B are used in addition to the coils 34A and 34B as elements constituting the AC bridge circuit. However, other elements that constitute the AC bridge circuit are conceivable. For example, a coil or a capacitor may be used instead of the resistors 35A and 35B. That is, the magnetic body detection sensor 30 according to the first embodiment may be configured as an AC bridge circuit including a pair of elements and a pair of coils. In addition, when using a capacitor | condenser, it is necessary to consider the resonant frequency by a coil and a capacitor | condenser.

1 .... Magnetic material detection device 2 .... AC signal generator 4 .... Signal detector 5 .......... .Signal processing unit 30 ......... magnetic substance detection sensor 32 ......... core 33 ......... coil bobbins 34A to 34E ... .. Coil 35A to 35B ..... Resistance 361 ........ First terminal 362 ........ Second terminal 363 ........ ..3rd terminal 364 ......... 4th terminal

Claims (8)

A magnetic substance detection sensor for detecting a magnetic substance,
A core extending in the longitudinal direction;
A pair of coils wound in a circumferential direction of the core and disposed at positions that are substantially symmetric with respect to the longitudinal center of the core;
With
An AC bridge circuit is composed of a pair of elements and the pair of coils,
Of the four terminals of the AC bridge circuit, one opposing two terminals serve as excitation terminals, and the other two opposing terminals serve as detection terminals. Adjusting means for adjusting the amplitude of the detection signal output from the detection terminal;
The magnetic body detection sensor according to claim 1, further comprising: A magnetic substance detection sensor for detecting a magnetic substance,
A core extending in the longitudinal direction;
A first coil wound in a circumferential direction of the core and disposed so that the longitudinal center of the core is a central position;
A pair of second coils wound in the circumferential direction of the core and disposed substantially symmetrically about the longitudinal center of the core as a symmetry axis;
With
A differential transformer circuit is composed of the first coil and the pair of second coils,
A terminal connected to one of the first coil and the pair of second coils is an excitation terminal, and a terminal connected to the other is a detection terminal.
The pair of second coils have opposite winding directions,
The magnetic body detection sensor, wherein a relative positional relationship between the core, the first coil, and the pair of second coils is fixed. Adjusting means for adjusting the amplitude of the detection signal output from the detection terminal;
The magnetic body detection sensor according to claim 3, further comprising: A magnetic body detection method for detecting the magnetic body using the magnetic body detection sensor according to claim 1,
A magnetic body detection method, comprising: detecting the magnetic body based on a phase change and / or an amplitude change of a detection signal output from the detection terminal.   6. The magnetic substance detection method according to claim 5, wherein the type of the magnetic substance is determined based on a ratio between the phase change and the amplitude change. A magnetic body detection device comprising the magnetic body detection sensor according to any one of claims 1 to 4 and detecting the magnetic body,
An AC signal generator for outputting an excitation signal to the excitation terminal;
A signal detector for detecting a phase change and / or an amplitude change of a detection signal output from the detection terminal;
A signal processing unit that processes a signal output from the signal detection unit and detects the magnetic body based on the phase change and / or the amplitude change;
The magnetic body detection device further comprising:   8. The magnetic body detection device according to claim 7, wherein the signal processing unit determines a type of the magnetic body based on a ratio between the phase change and the amplitude change.