WO2024201899A1 - 変位検出センサ及びセンサ装置 - Google Patents

変位検出センサ及びセンサ装置 Download PDF

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Publication number
WO2024201899A1
WO2024201899A1 PCT/JP2023/013198 JP2023013198W WO2024201899A1 WO 2024201899 A1 WO2024201899 A1 WO 2024201899A1 JP 2023013198 W JP2023013198 W JP 2023013198W WO 2024201899 A1 WO2024201899 A1 WO 2024201899A1
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Prior art keywords
coil
sensor
coil unit
coils
primary
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English (en)
French (fr)
Japanese (ja)
Inventor
智史 高塚
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NSD Corp
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NSD Corp
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Priority to JP2025509500A priority Critical patent/JPWO2024201899A1/ja
Priority to PCT/JP2023/013198 priority patent/WO2024201899A1/ja
Publication of WO2024201899A1 publication Critical patent/WO2024201899A1/ja
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques

Definitions

  • An embodiment of the present invention relates to a displacement detection sensor and a sensor device.
  • Reed switches operated by magnets have long been known as sensors for detecting the position of such linear displacement.
  • reed switches have issues such as being vulnerable to vibration because they have mechanical contacts, and being prone to unstable output and poor contact due to deterioration over time.
  • reed switches vary greatly from product to product, and are easily affected by disturbances caused by DC magnetic fields and by temperature.
  • reed switches are difficult to fine-tune because the contacts are binary, either on or off, and fine adjustments become even more difficult when there is not enough working space.
  • a differential transformer that does not have mechanical contacts is also known as a sensor that detects the position of a linear displacement.
  • a differential transformer has the advantage of good linearity of response and being able to continuously detect the position of a moving object because it is an absolute detection. Furthermore, because it has a differential configuration, it is easy to increase the sensitivity of the differential transformer, and it has excellent noise resistance and temperature characteristics.
  • the range in which the position of a moving object can be detected by a differential transformer is about half the total length of the differential transformer, that is, the length of the two differentially connected coils. For this reason, a differential transformer needs a coil that is at least twice the length of the moving range of the moving object, so the coil is long compared to the detection range of the moving object. Therefore, even if you try to replace a conventional reed switch with a differential transformer, it is difficult to secure the installation space.
  • the output characteristic of a differential transformer differs.
  • the slope of the change in output voltage of a differential transformer with a detection range of 200 mm is half the slope of the change in output voltage of a differential transformer with a detection range of 100 mm.
  • the embodiment of the present invention has been made in consideration of the above circumstances, and its purpose is to provide a displacement detection sensor and sensor device that can obtain the advantages of a differential transformer as described above when detecting only a specific range from both ends of the movement range, while allowing the circuit configuration to be standardized even when the movement ranges are different.
  • the displacement detection sensor of the embodiment is a sensor that detects two distant positions, and includes a primary coil unit that is excited by receiving power from a signal source, and a secondary coil unit that is arranged in a position where it is magnetically coupled to the primary coil unit.
  • the primary coil unit and the secondary coil unit are configured such that the inductance between the primary coil unit and the secondary coil unit changes when a measurement body made of a magnetic material or a non-magnetic material having electrical conductivity moves relative to the primary coil unit and the secondary coil unit.
  • One of the primary coil unit and the secondary coil unit is configured to have two coils that are arranged apart from each other and differentially connected.
  • the sensor device of this embodiment includes the above-mentioned displacement detection sensor and a converter that outputs a position signal indicating the position of the measurement object based on the induced electromotive force of the secondary coil unit and has a two-wire signal line.
  • FIG. 1 is a diagram illustrating an example of a circuit configuration when a detection result is output in analog form in a sensor device according to an embodiment
  • FIG. 1 is a diagram illustrating a detection principle of an example of a sensor according to an embodiment
  • FIG. 2 is a diagram showing the relationship between the amount of movement of the measuring body and the output of the sensor device of FIG. 1.
  • FIG. 1 is a diagram illustrating an example of a circuit configuration when a detection result is output digitally in a sensor device according to an embodiment
  • FIG. 5 is a diagram showing the relationship between the movement amount of the measuring body and the output of the sensor device of FIG.
  • FIG. 13 is a diagram illustrating a detection principle of another example of a sensor according to an embodiment.
  • FIG. 7 is a diagram showing the relationship between the amount of movement of a measuring object and output when the sensor of FIG. 6 is used in the sensor device of FIG. 1 or FIG. 4.
  • FIG. 1 is a schematic diagram showing an example of a mechanical configuration of a sensor according to an embodiment, in which a coil is formed by winding a wire around a coil holder;
  • FIG. 1 is a schematic diagram showing an example of a mechanical configuration of a sensor according to an embodiment, in which a coil is formed by a pattern provided on a printed circuit board;
  • FIG. 1 is a diagram illustrating an example of a converter in a sensor device according to an embodiment, which is configured as a two-wire converter;
  • FIG. 1 is a diagram illustrating a first example of a sensor unit using a sensor according to an embodiment
  • FIG. 13 is a diagram illustrating a second example of a sensor unit using a sensor according to an embodiment
  • FIG. 13 is a diagram illustrating a third example of a sensor unit using a sensor according to an embodiment.
  • the displacement detection sensor may be simply referred to as a sensor. Also, the same components are given the same reference numerals and the description will be omitted.
  • Sensor device A shown in FIG. 1 comprises a sensor 1, a signal source 2, and a converter 30A.
  • Sensor device A detects an object that moves back and forth linearly, such as a piston rod or a table, and detects two positions, such as both ends, within the range of movement of the object.
  • sensor 1 comprises a primary coil unit 10 and a secondary coil unit 20, and detects the position of a measurement body 4 attached to the object to be detected.
  • a coil unit is defined as a configuration including at least one coil.
  • the primary coil unit 10 is excited by receiving a signal output from the signal source 2.
  • the secondary coil unit 20 is disposed in a position where it is magnetically coupled to the primary coil unit 10.
  • One of the primary coil unit 10 and the secondary coil unit 20 is configured with two differentially connected coils.
  • a differentially connected coil is defined as a differential coil.
  • the primary coil unit 10 has two primary coils 11, 12.
  • the secondary coil unit 20 has two secondary coils 21, 22.
  • the primary coils 11, 12 and the secondary coils 21, 22 can be formed by winding a wire such as a magnet wire having an insulating coating on the outer circumferential surface.
  • the primary coil 11 and secondary coil 21, and the primary coil 12 and secondary coil 22 are each paired. Furthermore, the set of the primary coil 11 and secondary coil 21, and the set of the primary coil 12 and secondary coil 22 are arranged apart from each other. In the following description, one set of the primary coil 11 and secondary coil 21 may be referred to as the first coil set C1, and the other set of the primary coil 12 and secondary coil 22 may be referred to as the second coil set C2. Furthermore, the distance between the first coil set C1 and the second coil set C2 may be referred to as the coil gap length Y.
  • the two secondary coils 21 and 22 are arranged at a predetermined distance Y, i.e., the coil gap length Y, from each other.
  • the two secondary coils 21 and 22 are differentially connected and connected to the detection circuit 3 of the converter 30A, as shown in FIG. 1.
  • the two secondary coils 21 and 22 are differential coils.
  • the two primary coils 11 and 12 are arranged at a distance Y, i.e., the coil gap length Y, from each other, as with the secondary coils 21 and 22.
  • the two primary coils 11 and 12 are sum-connected and connected to the signal source 2.
  • Each coil 11, 12, 21, and 22 is formed, for example, in a ring or cylindrical shape.
  • the two coil sets C1 and C2 are arranged coaxially, i.e., in a straight line, and are configured so that the measurement object 4 can pass inside or outside each coil 11, 12, 21, and 22.
  • the two primary coils 11, 12 are arranged in positions facing the secondary coils 21, 22, which are differential coils, and are magnetically coupled to the facing secondary coils 21, 22. That is, the primary coil 11 and secondary coil 21 constituting the first coil set C1 are arranged in positions where they are magnetically coupled to each other. Similarly, the primary coil 12 and secondary coil 22 constituting the second coil set C2 are arranged in positions where they are magnetically coupled to each other. In this case, the two primary coils 11, 12 face the two secondary coils 21, 22, respectively.
  • a coil facing a differential coil is defined as an opposing coil. In this embodiment, the two primary coils 11, 12 are opposing coils.
  • each coil set C1, C2 the primary coils 11, 12 and the secondary coils 21, 22 are arranged overlapping each other in a direction perpendicular to the movement direction of the measurement object 4.
  • the primary coils 11 and 12 are arranged on the outer periphery side of the secondary coils 21 and 22.
  • the primary coils 11 and 12 may also be arranged on the inner periphery side of the secondary coils 21 and 22.
  • the signal source 2 is connected to the primary coils 11 and 12, and supplies power, i.e., voltage or current, to the primary coils 11 and 12 to drive the sensor 1.
  • the signal source 2 supplies, for example, an AC signal to the primary coils 11 and 12.
  • the converter 30A has a detection circuit 3 and is connected to the secondary coils 21 and 22, and outputs a position signal, for example a voltage, indicating the position of the measurement object 4 based on the induced electromotive force of the secondary coils 21 and 22.
  • the measuring body 4 is attached to the detection target and moves along each of the coils 11, 12, 21, 22 in accordance with the movement of the detection target.
  • the measuring body 4 is for changing the magnetic coupling of each of the coil sets C1, C2 by moving inside or outside each of the coils 11, 12, 21, 22.
  • the measuring body 4 is made of a magnetic material or a non-magnetic material having electrical conductivity.
  • the measuring body 4 is a magnetic material.
  • the measuring body 4 is placed outside each of the coils 11, 12, 21, 22, it is preferable that the measuring body 4 is a non-magnetic material having electrical conductivity such as copper, aluminum, or brass.
  • the length dimension of the first coil set C1 may be referred to as the first coil set length
  • the length dimension of the second coil set C2 may be referred to as the second coil set length.
  • the first coil set length and the second coil set length are both set to the same length dimension W.
  • the length dimension in the traveling direction of the measuring body 4 is also set to the same length dimension W as the first coil set length and the second coil set length.
  • the coil gap length Y is set, for example, longer than each coil set length W and the length dimension W of the measuring body 4.
  • the length dimension of the measuring body 4 does not necessarily have to be the same as the first coil set length and the second coil set length.
  • the coil gap length Y may be greater than 0, and although details will be described later, it may also be set shorter than each coil set length W and the length dimension W of the measuring body 4, for example, as shown in FIG. 6.
  • the outer end of the first coil set C1 on the left side of the paper in FIG. 2, i.e., the left end, is taken as the reference position 0.
  • the distance from the reference position 0 to the left end 401 of the measuring body 4 is taken as the movement amount P of the measuring body 4.
  • the movement amount P is the sum of the length dimension W of the measuring body 4 and the coil gap length Y, which is W + Y.
  • This configuration appears to be similar to a typical differential transformer. However, because a coil gap length Y is provided between the two secondary coils 21 and 22, which are differential coils, its behavior differs from that of a differential transformer.
  • the operating principle of the sensor 1 of this embodiment will be explained below with reference to FIG. 3.
  • FIG. 3 is a graph showing the relationship between the position of the measurement object 4 and the output voltage V.
  • the vertical axis of the graph in FIG. 3 is the output voltage V
  • the horizontal axis is the amount of movement P.
  • the amount of movement P 0.
  • the amount of change in inductance of the primary coil 11 and the secondary coil 21 in the first coil set C1 is maximum compared to the case where the measurement object 4 is not present inside the first coil set C1. That is, in this case, the two differentially connected secondary coils 21 and 22 are in the most unbalanced state, and as a result, the output voltage V becomes extremely maximum or extremely minimum.
  • the output voltage V is set to be extremely minimum when the measurement object 4 is stopped at the reference position 0.
  • the inductance in the first coil set C1 decreases from the maximum state if the measurement body 4 is a magnetic body, and increases from the minimum state if the measurement body 4 is a conductive non-magnetic body.
  • the inductance in the second coil set C2 does not change. This is because a coil gap length Y larger than the length dimension W of the measurement body 4 is set between the two secondary coils 21, 22, and the measurement body 4 does not penetrate into the inside of one secondary coil 22 while a part of the measurement body 4 is located inside the other secondary coil 21.
  • the inductance of the second coil set C2 increases if the measurement object 4 is magnetic, and decreases if the measurement object 4 is conductive non-magnetic.
  • the above operation can be summarized in terms of the range of the movement amount P of the measurement body 4 and the output voltage V as follows.
  • 0 ⁇ P ⁇ W The output voltage V is negative and increases as the amount of movement P increases.
  • W ⁇ P ⁇ Y The output voltage V is 0 and is unrelated to the amount of movement P.
  • Y ⁇ P ⁇ W+Y The output voltage V is positive and increases as the amount of movement P increases.
  • the ranges of 0 ⁇ P ⁇ W and Y ⁇ P ⁇ W+Y are the measurement ranges in which the position of the measured object 4 can be measured.
  • the sensor 1 described above is a sensor that detects two positions that are separated from each other.
  • the sensor 1 includes two differential coils 21, 22, opposing coils 11, 12, and a measuring body 4.
  • the differential coils 21, 22 are differentially connected to each other.
  • the opposing coils 11, 12 are disposed in positions that face the differential coils 21, 22, respectively, and are magnetically coupled to the differential coils 21, 22.
  • the measuring body 4 is made of a magnetic material or a non-magnetic material having electrical conductivity, and moves relative to the differential coils 21, 22 and the opposing coils 11, 12, changing the magnetic coupling between the differential coils 21, 22 and the opposing coils 11, 12 as it moves.
  • the two differential coils 21, 22 are disposed at a distance from each other that is, for example, equal to or greater than the length dimension W of the measuring body 4.
  • the detection range of the sensor 1 described above is a distance W from both ends of the moving range W+Y+W.
  • a sensor 1 when detecting only a predetermined range W from both ends of the moving range, it is possible to obtain the advantages of a differential transformer while standardizing the circuit configuration even when the moving ranges are different.
  • the above-mentioned sensor 1 has secondary coils 21, 22 differentially connected, it is possible to obtain characteristics in terms of disturbance noise and temperature characteristics that are equivalent or close to those of a general differential transformer.
  • the sensor 1 does not have mechanical contacts, there are fewer problems with malfunctions due to life span or vibration, and the effects of characteristic variations and deterioration over time are extremely small.
  • it is less susceptible to disturbance DC magnetic fields than methods that use magnets and reed switches.
  • temperature characteristics derived from magnetic components such as magnets such as deviations in the detection position due to temperature, are less likely to occur, and temperature correction is also possible.
  • the sensor 1 described above differs from a typical differential transformer mainly in the following two points.
  • the first point is that when the measurement object 4 is located inside the first coil set C1 or the second coil set C2, that is, in the range of 0 ⁇ P ⁇ W or Y ⁇ P ⁇ W+Y with respect to the amount of movement P, even if the inductance of one of the first coil set C1 or the second coil set C2 changes, the inductance of the other does not change.
  • the second point is that, with respect to the amount of movement P, a dead range appears in which the output voltage V is maintained at approximately 0 during the period W ⁇ P ⁇ Y.
  • the sensor device A having the above configuration can be modified as follows.
  • the signal source 2 is not limited to a voltage source, but may be a current source.
  • the primary coil unit 10 may be configured to apply signals to the two primary coils 11 and 12 independently, instead of the two primary coils 11 and 12 being summarily connected. Similar characteristics can be obtained even if the primary coils 11, 12 of the primary coil unit 10 are differentially connected and the secondary coils 21, 22 of the secondary coil unit 20 are summarily connected. Of the primary coil unit 10 and the secondary coil unit 20, the one that is not differentially connected may be formed over the entire length of the movement range of the measurement object 4, that is, over a length of 2W+Y.
  • the measuring body 4 may be made of any material as long as it can change the magnetic coupling, i.e., the inductance, of the coils 11, 12, 21, and 22.
  • the measuring body 4 may be made of a magnetic material or a non-magnetic material having electrical conductivity. If the measuring body 4 is made of a non-magnetic material, it can be made less susceptible to the effects of disturbance DC magnetic fields, which is a problem when a magnet and a reed switch are used.
  • the shape of the measuring body 4 may be a column, a cylinder, a rod, or a plate that passes through the inside of the coil sets C1 and C2, or a cylinder or a square tube that surrounds the outside of the coil sets C1 and C2. Furthermore, when the measuring body 4 is disposed on the outer periphery side of the coil sets C1 and C2, the measuring body 4 may be a plate.
  • the signal processing in the converter 30A can be not only analog processing, but also conversion to digital data by an A/D converter and then digital processing by a CPU, FPGA, or the like to convert the position signal into digital data.
  • Each of the coils 11, 12, 21, and 22 may be a coil using a magnet wire, or may be a spiral coil disposed on a printed circuit board.
  • the primary coil unit 10 and the secondary coil unit 20 may be configured as a half-bridge type coil instead of being separated from each other.
  • the sensor device B shown in FIG. 4 and FIG. 5 differs from the sensor device A in FIG. 1 in that it has a converter 30B instead of the converter 30A in FIG. 1, but the configuration of the sensor 1 is the same.
  • the detection range at both ends of the movement range of the measurement object 4 relative to the sensor 1 may be referred to as the starting side, where the amount of movement P is 0 ⁇ P ⁇ W, and the area where the amount of movement P is Y ⁇ P ⁇ W+Y, where the end side.
  • the converter 30B has a function of converting the analog signal output from the detection circuit 3, that is, the output voltage V, into a digital signal.
  • the converter 30B has, for example, two comparators 31 and 32. In the following description, one of the two comparators 31 and 32 may be referred to as the first comparator 31, and the other may be referred to as the second comparator 32.
  • the first comparator 31 corresponds to detection of the starting end side
  • the second comparator 32 corresponds to detection of the ending end side.
  • the output voltage V is connected to the inverting input
  • the first reference voltage Vref1 is connected to the non-inverting input
  • the second reference voltage Vref2 is connected to the inverting input.
  • the first reference voltage Vref1 and the second reference voltage Vref2 are reference voltages that can be adjusted by the user.
  • the output of the first comparator 31 is referred to as the first output Out1
  • the output of the second comparator 32 is referred to as the second output Out2.
  • the adjustment range Va1 of the first reference voltage Vref1 input to the first comparator 31 is preferably set slightly inside the voltage range that is actually output when the measured object 4 is detected at the starting end, in this case the voltage range from the minimum value to 0.
  • the adjustment range Va2 of the second reference voltage Vref2 input to the second comparator 32 is preferably set slightly inside the voltage range that is actually output when the measured object 4 is detected at the ending end, in this case the voltage range from 0 to the maximum value. This is to prevent errors in threshold determination due to temperature drift of the circuit and sensor 1, external noise, component variations, etc.
  • the user can set the first reference voltage Vref1 and the second reference voltage Vref2 to any value within the respective adjustment ranges Va1 and Va2. That is, the user can adjust the detection position Q1 on the starting side within the adjustment range H1 by adjusting the first reference voltage Vref1 within the adjustment range Va1. Similarly, the user can adjust the detection position Q2 on the terminal side within the adjustment range H2 by adjusting the second reference voltage Vref2 within the adjustment range Va2. That is, the sensor 1 can adjust the detection position Q1 on the starting side and the detection position Q2 on the terminal side individually by individually adjusting the first reference voltage Vref1 and the second reference voltage Vref2.
  • the first reference voltage Vref1 is set to the midpoint of the adjustment range Va1 of the first reference voltage Vref1.
  • the second reference voltage Vref2 is set to the midpoint of the adjustment range Va2 of the second reference voltage Vref2.
  • Sensor device B then outputs the detection results of the starting end and the ending end as binary values of 0 and 1, respectively. This makes it extremely easy for a higher-level device such as a PLC (Programmable Logic Controller) to import the position detection results output from sensor device B.
  • PLC Programmable Logic Controller
  • converter 30B which has the function of adjusting positions Q1 and Q2, is not built into sensor 1. Therefore, converter 30B can be installed in a location away from sensor 1, that is, in a location where it is easy for a person to work, and as a result, the workability related to adjustment can be improved.
  • the first output Out1 indicates the behavior of the measured body 4 at the starting end side
  • the second output Out2 indicates the behavior of the measured body 4 at the terminal end side.
  • the length dimension W of the coil sets C1, C2 coincides with the detection range at the starting end side and the terminal end side. In other words, a constant relationship is maintained between the length dimension W of the coil sets C1, C2 and the detection range at the starting end side and the terminal end side. Therefore, when designing the sensor 1, the length dimension W of the coil sets C1, C2 can be determined based on the detection range at the starting end side and the terminal end side, making it easier to design the sensor 1.
  • the coil gap length Y does not affect the output voltage V. Therefore, in the sensor 1 configured as described above, by changing the coil gap length Y without changing the length dimension W of the coil sets C1 and C2, it is possible to accommodate changes in the movement range of the measurement object 4 in the sensor 1, i.e., changes in the movement range of the detection target, without changing the position detection characteristics near both ends. In this case, for example, even if the coil gap length Y is changed without changing the length dimension W of the coil sets C1 and C2 in Figure 2, only the length of the dead zone W ⁇ P ⁇ Y shown in Figures 3 and 5 changes, and the output characteristics of the sensor 1 do not change in the range 0 ⁇ P ⁇ W and the range indicated by Y ⁇ P ⁇ W+Y.
  • the designer when designing sensor 1 to match the range of movement of the detection object, such as the stroke of a piston, i.e., the range of movement of the measurement body 4, the designer only needs to change the coil gap length Y to match that range of movement, and in this case, there is no need to change the circuit configuration of sensor device B. In other words, with the above configuration, the circuit configuration of sensor device B can be made common regardless of the range of movement of measurement body 4.
  • the number of turns and length dimension W of the coil units 10, 20 of the sensor 1 can be made the same regardless of the movement range of the measurement body 4, which reduces the design burden. Furthermore, by standardizing the circuit configuration of the sensor device B, even if the detection target of the sensor 1 and the movement range of the measurement body 4 are different in multiple sensor devices B, that is, even if the overall length of the sensor 1 is different, the adjustment work of the detection position Q1 on the starting side and the detection position Q2 on the terminal side can be made common. As a result, the burden on the worker who adjusts the detection positions Q1 and Q2 of the sensor device B can be reduced.
  • the length dimensions of the first coil set C1 and the second coil set C2 are the same, but if the inductances of the two coil sets C1 and C2 are set to approximately the same, the effect of a differential transformer can be obtained. In other words, the length dimensions of the first coil set C1 and the second coil set C2 may be different within a range in which the effect of a differential transformer can be obtained.
  • the length dimensions of the first coil set C1 and the second coil set C2 may also be set to different lengths.
  • the inductance can be made approximately the same by adjusting the number of turns of the first coil set C1 and the second coil set C2.
  • the detection ranges can be different at the starting end and the ending end, it is possible to respond more flexibly to mechanical reasons.
  • the coil gap length Y is longer than the coil set length W of each coil set C1, C2 and the length dimension W of the measurement body 4.
  • the coil gap length Y may be shorter than the coil set length W of each coil set C1, C2 and the length dimension W of the measurement body 4.
  • the inductance of coil set C1 gradually decreases if the measurement body 4 is a magnetic body, and gradually increases if the measurement body 4 is a conductive non-magnetic body. In contrast, the inductance of coil set C2 does not change.
  • the measurement body 4 overlaps both coil sets C1 and C2.
  • the inductance of coil set C1 gradually decreases if the measurement body 4 is magnetic, and gradually increases if the measurement body 4 is conductive non-magnetic.
  • the inductance of coil set C2 gradually increases if the measurement body 4 is magnetic, and gradually decreases if the measurement body 4 is conductive non-magnetic. For this reason, the amount of change in inductance of the coil unit 20 becomes larger, and as shown in FIG. 7, the slope of the graph of the amount of movement P - output voltage V is twice as large as when 0 ⁇ P ⁇ Y.
  • the measurement body 4 When the amount of movement P is W ⁇ P ⁇ W+Y, at least a portion of the measurement body 4 overlaps with the coil set C2, but the measurement body 4 does not overlap with the coil set C1. In this case, as the amount of movement P increases, the inductance of the coil set C2 gradually increases if the measurement body 4 is a magnetic body, and gradually decreases if the measurement body 4 is a conductive non-magnetic body. In contrast, the inductance of the coil set C1 does not change.
  • the range of 0 ⁇ P ⁇ W is the front end measurement range where the position of the measurement body 4 can be measured at the front end
  • the range of Y ⁇ P ⁇ W+Y is the rear end measurement range where the position of the measurement body 4 can be measured at the rear end.
  • the front end measurement range and the rear end measurement range overlap in the range of Y ⁇ P ⁇ W.
  • the resistance temperature coefficient ⁇ t in the above formula (1) is a coefficient that indicates the rate of change in resistance value per 1°C, and is 0.00393 for general copper.
  • the resistance value of each coil unit 10, 20 is determined by the specific resistivity and length of the winding used in each coil unit 10, 20, and is a value specific to the specifications of each coil unit 10, 20. Therefore, the current temperature of the coil unit 10, 20, that is, the temperature T of the sensor 1, can be measured based on the initial resistance value Rt of the coil unit 10, 20, the temperature t at the time of that resistance value Rt, and the current resistance value RT.
  • the above-mentioned function makes it possible to measure the internal temperature of the sensor 1, making it easier to perform temperature correction with higher accuracy.
  • the internal temperature of the sensor 1 can be measured, for example, as follows. First, a DC current is passed through both ends of either the primary coil unit 10 or the secondary coil unit 20. Next, the DC voltage across both ends of the coil units 10, 20 through which the DC current is passed is measured, and the current resistance value RT is measured based on the DC voltage. Then, the temperature T of the sensor 1 is calculated from the above formula (1) based on the preset resistance value Rt and temperature t.
  • a DC current is supplied to the primary coil unit 10 superimposed on the AC signal supplied from the signal source 2. Then, the voltage across both ends of the primary coil unit 10 is measured (in this case, the voltage converted to DC by filtering), and the resistance value of the primary coil unit 10 can be calculated by measuring the supplied DC current and the measured DC voltage.
  • a circuit for measuring the resistance value can be constructed using, for example, a four-wire wiring method.
  • each of the coils 11, 12, 21, and 22 is made of a winding such as a copper wire.
  • Sensor 1A in Figure 8 is equipped with a coil holder 13.
  • the coil holder 13 is configured, for example, in a cylindrical or square tube shape.
  • Each of the coils 11, 12, 21, and 22 is configured of a winding such as a copper wire, and is wound around the outer circumference of the coil holder 13.
  • the coil holder 13 has the function of maintaining the self-shape of each of the coils 11, 12, 21, and 22, and the function of fixing the relative positions.
  • the coil holder 13 may be made of a metal having electrical conductivity. However, if the coil holder 13 is made of a conductor, it will act as a short coil, lowering the inductance of each of the coils 11, 12, 21, and 22. Therefore, if a conductor is used for the coil holder 13, it is preferable to use a material with high electrical resistance, that is, stainless steel or nickel alloy, which flows a small current as a short coil. It is also preferable that the thickness of the coil holder 13 is thin.
  • the coil holder 13 may be made of an insulator such as resin.
  • the coil holder 13 may be made of a magnetic material.
  • a magnetic material for the coil holder 13 By using a magnetic material for the coil holder 13, the inductance of each of the coils 11, 12, 21, and 22 can be increased, thereby increasing the sensitivity, i.e., the signal change can be made larger.
  • attention must be paid to temperature characteristics, etc.
  • a non-magnetic material or an insulator is selected for the coil holder 13 in order to obtain a signal change.
  • Insulators may also be provided between the coil holder 13 and each of the coils 11, 12, 21, and 22.
  • the windings, i.e., magnet wires, that make up each of the coils 11, 12, 21, and 22 are insulated by an insulating coating or the like, so it is not necessary to provide insulators between the coil holder 13 and each of the coils 11, 12, 21, and 22.
  • the dielectric strength between the coil holder 13 and each of the coils 11, 12, 21, and 22 can be improved.
  • Sensor 1B shown in FIG. 9 is an example in which each coil 11, 12, 21, 22 is formed by a coil pattern provided on a printed circuit board.
  • the primary coil unit 10 and the secondary coil unit 20 of sensor 1B are formed by coil patterns provided in a spiral shape on printed circuit boards 41 and 42, respectively.
  • the pattern related to the primary coil unit 10 is shown in black, and the pattern related to the secondary coil unit 20 is shown in white.
  • Sensor 1B is formed by stacking a first layer board 41, a second layer board 42, a third layer board 43, and a fourth layer board 44. The patterns provided on each board 41, 42, 43, 44 are connected through through holes as necessary. Land patterns 511, 512, 521, 522 connected to each coil 11, 12, 21, 22 are provided on the first layer board 41.
  • the coil patterns of the primary coils 11 and 12 are provided on the first layer substrate 41, which is the outermost layer of the sensor 1B.
  • the land pattern 511 is connected to the primary coil 11, which is farther from the land pattern 511, of the two primary coils 11 and 12, via a connection pattern 531 provided on the first layer substrate 41 and a connection pattern 532 provided on the third layer substrate 43.
  • the two primary coils 11 and 12 are summatively connected to each other via a connection pattern 533 provided on the first layer substrate 41 and a connection pattern 534 provided on the third layer substrate 43.
  • the primary coil 12, which is closer to the land pattern 512, of the two primary coils 11 and 12, is connected to the land pattern 512 via a connection pattern 535 provided on the first layer substrate 41.
  • the coil patterns of the secondary coils 21 and 22 are provided on the second layer substrate 42.
  • the land pattern 521 is connected to the secondary coil 21 that is farther from the land pattern 521 of the two secondary coils 21 and 22 via a connection pattern 541 provided on the fourth layer substrate 44.
  • the two secondary coils 21 and 22 are differentially connected to each other via a connection pattern 542 provided on the second layer substrate 42 and a connection pattern 543 provided on the fourth layer substrate 44.
  • the secondary coil 22 that is closer to the land pattern 522 of the two secondary coils 21 and 22 is connected to the land pattern 522 via a connection pattern 544 provided on the second layer substrate 42.
  • each of the coils 11, 12, 21, and 22 as a coil pattern on the printed circuit boards 41 and 42, high-precision manufacturing techniques for printed circuit boards can be used.
  • This makes it possible to inexpensively manufacture sensor 1B with coil patterns of the same dimensions, i.e., with the same characteristics and little variation.
  • wiring can be performed simply by soldering signal wires to land patterns 511, 512, 521, and 522, for example, which provides good workability.
  • the coil length W and coil gap length Y of each of the coils 11, 12, 21, and 22 during the design of sensor 1B it is possible to change the design easily and accurately, since it is only necessary to change the layout data in CAD or the like.
  • sensor 1B is constructed by stacking four layers of printed circuit boards 41 to 44, but the inductance of coil units 10 and 20 can be easily increased by increasing the number of printed circuit boards on which the coil patterns of coils 11, 12, 21, and 22 are provided. In this case, no electronic components such as ICs or transistors are provided on each of printed circuit boards 41 to 44. Therefore, each of printed circuit boards 41 to 44 can be constructed thin, and as a result, even if the number of laminated printed circuit boards is increased, the thickness does not increase excessively, and the circuit boards can be constructed thin and compact.
  • the sensor 1B can be made lightweight and highly rigid. This eliminates the need to use reinforcing materials other than those used for the printed circuit boards 41-44, and makes the sensor 1B less likely to break and more reliable.
  • printed circuit boards are generally easy to process and can be made into any desired external shape relatively easily. This allows the external shape of the sensor 1B to be made into a shape that is easy to work with during assembly. For example, protrusions, recesses, and even spring structures for fitting the sensor 1B to an attachment target when attaching it can be easily provided on the printed circuit boards 41-44.
  • the converter 30B can be replaced with the converter 30C of FIG. 10.
  • the converter 30C of FIG. 10 is an example of a two-wire configuration that does not use a signal source 2 for driving the sensor.
  • the signal line connecting the converter 30C and the higher-level device 90 is configured as a two-wire system.
  • the converter 30C also functions as a signal source that supplies power to excite the primary coil unit 10.
  • the converter 30C in the example of FIG. 10 has, for example, an input terminal block 33, an output terminal block 34, a sensor internal circuit 35, a start output circuit 361, a end output circuit 362, transistors 371, 372, and non-polar circuits 381, 382.
  • the primary coil unit 10 and the secondary coil unit 20 are connected to each of the four terminals of the input terminal block 33.
  • Detectors 921, 922 of a higher-level device 90 are connected to each terminal of the output terminal block 34 via a terminal block 91 provided on the higher-level device 90.
  • the detectors 921, 922 are composed of, for example, photocouplers, and detect ON/OFF signals output from the output circuits 361, 362, respectively.
  • the detectors 921, 922 are configured as a two-wire system in which two signal lines 391, 392, 393, 394 are connected, respectively. For this reason, a conventional two-wire reed switch can be easily replaced with the sensor device B of this configuration.
  • the sensor internal circuit 35 has a drive circuit 351 that drives the sensor 1, and a comparison circuit 352.
  • the comparison circuit 352 has a function of detecting the sensor signal, comparing it with each reference voltage Vref1, Vref2, and sending an ON/OFF command of the contact output to the start output circuit 361 and the end output circuit 362.
  • the upper device 90 determines that the input is OFF. Even if this input is OFF, that is, the current is sufficiently small, the sensor device B of this embodiment, that is, the sensor 1 and the converter 30C are configured to operate.
  • the current value at which the host device 90 determines that the input is OFF varies depending on the specifications of the host device 90, but is often 1 mA or less.
  • the start end output circuit 361 and the end end output circuit 362 are circuits that turn on/off the contact output to the higher-level device 90 based on the ON/OFF command sent from the sensor internal circuit 35.
  • the start end output circuit 361 performs contact output on the start end side
  • the end end output circuit 362 performs contact output on the end end side.
  • the driving power for the sensor internal circuit 35 is supplied from the end end output circuit 362.
  • the non-polarity circuits 381 and 382 are designed to allow the polarity of the contact output current to be either a sink, which draws current from the higher-level device 90 to the converter 30C, or a source, which outputs current from the converter 30C to the higher-level device 90, and are configured, for example, with a bridge circuit using diodes.
  • the non-polarity circuits 381 and 382 can also be configured using FETs instead of diodes. Using FETs makes the circuit more complex, but the ON resistance can be reduced.
  • a sensor unit using sensor 1 uses sensor 1A shown in Fig. 8, and is an example in which a measuring body 4 is arranged on the outer periphery of sensor 1A.
  • Sensor unit 601 shown in Fig. 11 has sensor 1A, measuring body 4, sleeve 61, case 62, front end cover 63, rear end cover 64, and pull-out cable 65.
  • Coil holder 13 and coil units 10 and 20 are arranged inside sleeve 61.
  • measuring body 4 is arranged movably outside sleeve 61, i.e., outside coil units 10 and 20.
  • the example shown in Fig. 12 uses the sensor 1A shown in Fig. 8, and is an example in which a measuring body 4 is placed inside the sensor 1A.
  • the sensor unit 602 shown in Fig. 12 has the sensor 1A, measuring body 4, sleeve 61, case 62, front end cover 63, rear end cover 64, and pull-out cable 65.
  • the coil holder 13 and coil units 10 and 20 are placed inside the sleeve 61.
  • the measuring body 4 is also placed so that it can move inside the sleeve 61, that is, inside the coil units 10 and 20. In this case, the measuring body 4 is supported by the support body 5.
  • the example shown in Fig. 13 uses the sensor 1B shown in Fig. 9, and is an example in which the measuring body 4 is arranged outside the sensor 1B.
  • the sensor unit 603 shown in Fig. 13 has the sensor 1B, the measuring body 4, a sleeve 61, a case 62, a front end cover 63, a rear end cover 64, and a pull-out cable 65.
  • the sensor 1B is arranged inside the sleeve 61.
  • the measuring body 4 is arranged movably outside the sleeve 61, that is, outside the coil units 10 and 20.
  • the sleeve 61 is a configuration for sealing the sensors 1A, 1B to provide mechanical protection.
  • the sleeve 61 is made of a non-magnetic material.
  • the sleeve 61 is preferably made of a non-magnetic material with high electrical resistance, such as austenitic stainless steel or a nickel alloy.
  • the sleeve 61 is thin. However, it is necessary to consider the balance with the mechanical strength. In particular, when the sensor 1A is built into a hydraulic cylinder or the like, the sleeve 61 must be thick enough not to be damaged. In applications where large pressure is not applied or where waterproofing is not required, the sleeve 61 can be made of glass fiber reinforced resin or carbon fiber reinforced resin, which can achieve lighter weight and lower costs.
  • the pull-out cable 65 is for pulling the wiring of the coil units 10, 20 out of the case 62, and is connected to the detection circuit 3 or the sensor internal circuit 35 outside the case 62.
  • the end of the pull-out cable 65 may have a connector attached, for example.
  • the pull-out cable 65 is fixed to the case 62 by, for example, a cable gland 66. This cable gland 66 ensures waterproofing between the case 62 and the sheath of the pull-out cable 65.
  • the displacement detection sensor 1 is a sensor that detects two positions that are separated from each other.
  • the displacement detection sensor 1 includes a primary coil unit 10 and a secondary coil unit 20.
  • the primary coil unit 10 is excited by receiving power from the signal source 2, 30C.
  • the secondary coil unit 20 is disposed at a position where it is magnetically coupled to the primary coil unit 10.
  • the primary coil unit 10 and the secondary coil unit 20 change the inductance between the primary coil unit 10 and the secondary coil unit 20 when the measurement body 4, which is made of a magnetic material or a non-magnetic material having electrical conductivity, moves relative to the primary coil unit 10 and the secondary coil unit 20.
  • One of the primary coil unit 10 and the secondary coil unit 20 is configured to have two coils 21, 22 that are arranged apart from each other and are differentially connected.
  • the primary coil unit 10 and the secondary coil unit 20 are configured by coil patterns provided on printed circuit boards 41, 42, 43, and 44.
  • the primary coil unit 10 and the secondary coil unit 20 can be mass-produced with high precision and at low cost.
  • the sensor device B of the embodiment also includes a converter 30C that outputs a position signal indicating the position of the measurement object 4 based on the induced electromotive force of the secondary coil unit 20 and has a two-wire signal line. This allows a conventional two-wire reed switch to be easily replaced with the sensor device B of this configuration.
  • the sensor device B includes the above-mentioned displacement detection sensors 1, 1A, 1B and converters 30B, 30C.
  • the converters 30B, 30C can adjust the detection positions Q1, Q2 of the measurement object 4 by adjusting the reference voltages Vref1, Vref2. According to this, when adjusting the detection positions Q1, Q2, the operator only needs to adjust the values of the reference voltages Vref1, Vref2, and does not need to adjust the detection positions mechanically. Therefore, according to the sensor device B of this configuration, it is easier to adjust the detection position than, for example, a reed switch that has only two values of on and off contacts and requires mechanical adjustment.
  • the converters 30B, 30C are usually installed outside the device in which the displacement detection sensors 1, 1A, 1B are incorporated. Therefore, even if it is difficult to secure a working space around the displacement detection sensors 1, 1A, 1B, the detection positions Q1, Q2 can be adjusted at a location away from the displacement detection sensors 1, 1A, 1B. As a result, this configuration further improves the ease of adjusting detection positions Q1 and Q2.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
PCT/JP2023/013198 2023-03-30 2023-03-30 変位検出センサ及びセンサ装置 Pending WO2024201899A1 (ja)

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JP2025509500A JPWO2024201899A1 (enrdf_load_stackoverflow) 2023-03-30 2023-03-30
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5033672B1 (enrdf_load_stackoverflow) * 1967-11-08 1975-11-01
JPH01265112A (ja) * 1988-04-18 1989-10-23 Toshiba Corp 非接触型変位センサ
JPH0979809A (ja) * 1995-09-18 1997-03-28 Mikuni Corp 故障判定機能を有する磁気式位置センサ
JP2000088506A (ja) * 1998-07-10 2000-03-31 Omron Corp 磁気センサ
JP2002022402A (ja) * 2000-05-24 2002-01-23 Balluff Gmbh 位置測定システム

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5033672B1 (enrdf_load_stackoverflow) * 1967-11-08 1975-11-01
JPH01265112A (ja) * 1988-04-18 1989-10-23 Toshiba Corp 非接触型変位センサ
JPH0979809A (ja) * 1995-09-18 1997-03-28 Mikuni Corp 故障判定機能を有する磁気式位置センサ
JP2000088506A (ja) * 1998-07-10 2000-03-31 Omron Corp 磁気センサ
JP2002022402A (ja) * 2000-05-24 2002-01-23 Balluff Gmbh 位置測定システム

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