Displacement detection sensor and sensor device

Abstract

A displacement detection sensor (1, 1A, 1B) detects two separated positions, and is provided with: a primary coil unit (10) that is excited by receiving power supplied from a signal source (2, 30C); and a secondary coil unit (20) disposed at a position magnetically coupled to the primary coil unit. In the primary coil unit and the secondary coil unit, the inductances of the primary coil unit and the secondary coil unit are changed by relative movement of a measurement body (4) composed of a magnet or a non-magnet having conductivity with respect to the primary coil unit and the secondary coil unit. One of the primary coil unit and the secondary coil unit is configured so as to have two coils (21, 22) arranged apart from each other and connected in series in opposite directions.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a displacement detection sensor and a sensor device. BACKGROUND

[0002] In order to grasp the behavior of a moving body that performs linear displacement such as a piston rod of a cylinder, a table of a sliding table, and the like, the moving body is sometimes detected at both ends of a moving range. As a sensor that performs position detection of such linear displacement, for example, a magnetic reed switch that operates using a magnet has been known for a long time. However, the magnetic reed switch is not resistant to vibration because it has a mechanical contact, and in addition, there are problems in that output becomes unstable due to deterioration over time, or contact failure easily occurs. Furthermore, the magnetic reed switch has a large variation in each product, and is easily affected by disturbance caused by a direct current magnetic field, temperature, and the like. In addition, since the magnetic reed switch is a binary state of on and off of a contact, it is difficult to perform fine adjustment, and it is even more difficult to perform fine adjustment in a case where an operation space cannot be ensured.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2-3702;

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-91322. SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] Therefore, as a sensor that performs position detection of linear displacement, there is also known, for example, a differential transformer that does not have a mechanical contact. The differential transformer has good linearity of response, and in addition, since it is an absolute type detection, it has an advantage that it can continuously detect the position of a moving body. Also, the differential transformer is a differential structure, so it is easy to improve sensitivity, and in addition, it has excellent noise resistance characteristics and temperature characteristics. On the other hand, in the differential transformer, the range in which the position of the moving body can be detected is the full length of the differential transformer, that is, 1 / 2 of the length of two coils that are connected in reverse series. Therefore, the differential transformer requires a coil having a length of more than twice the moving range of the moving body, so the coil becomes longer compared to the detection range of the moving body. Therefore, even if it is intended to replace, for example, a conventional magnetic reed switch with a differential transformer, there are cases where it is difficult to ensure a setting space.

[0009] Further, the differential transformer has different slopes of the output voltage per unit length, which is an output characteristic of the differential transformer, with respect to a change in the detection position, when the detection ranges are different. For example, the slope of the change in the output voltage of the differential transformer having a detection range of 200 mm is 1 / 2 the slope of the change in the output voltage of the differential transformer having a detection range of 100 mm. Therefore, even when it is desired to detect only from both ends of the moving range of the moving body to a certain range, the conventional differential transformer needs to have a circuit structure including the differential transformer that is different for each moving range, and there is a case where it is difficult to commonize the circuit structure of the signal source, the detection circuit, and the like.

[0010] An embodiment of the present application is made in view of the above-described circumstances, and has an object to provide a displacement detection sensor and a sensor device that can obtain the advantages of the differential transformer described above while commonizing the circuit structure even when the moving ranges are different, in a case where detection is performed only from both ends of the moving range to a certain range.

[0011] Solution to the problem

[0012] The displacement detection sensor of the embodiment detects two separate positions, and has a primary coil unit that is excited by power supplied from a signal source, and a secondary coil unit that is disposed at a position magnetically coupled to the primary coil unit. In the primary coil unit and the secondary coil unit, the inductance of the primary coil unit and the secondary coil unit changes by relative movement of the primary coil unit and the secondary coil unit by a measurement body composed of a magnet or a non-magnet having electrical conductivity. One of the primary coil unit and the secondary coil unit is configured to have two coils disposed separately from each other and connected in reverse series.

[0013] The sensor device of the embodiment has the above-described displacement detection sensor, and a converter that outputs a position signal indicating the position of the measurement body based on the induced electromotive force of the secondary coil unit, the converter being configured so that the signal line is two-wire type. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A diagram schematically showing one example of a circuit structure in a case where an analog output is performed on a detection result, for the sensor device of the embodiment;

[0015] Figure 2 A diagram schematically showing a detection principle, for one example of the sensor of the embodiment;

[0016] Figure 3 A diagram showing the relationship between the movement amount of the measurement body and the output, for the sensor device of the embodiment; Figure 1 ​

[0017] Figure 4 FIG. 1 is a diagram schematically showing a circuit structure of a sensor device according to the embodiment, in a case where a detection result is output as a digital value;

[0018] Figure 5 FIG. 2 is a diagram schematically showing a detection principle of a sensor according to the embodiment; Figure 4

[0019] Figure 6 FIG. 3 is a diagram schematically showing a mechanical structure of a sensor according to the embodiment;

[0020] Figure 7 FIG. 4 is a diagram schematically showing a relationship between a moving amount of a measurement body and an output, in a case where a sensor according to the embodiment is used in a sensor device according to the embodiment; Figure 1 Figure 4 Figure 6

[0021] Figure 8

[0022] Figure 9

[0023] Figure 10

[0024] Figure 11 FIG. 7 is a diagram schematically showing a first example of a sensor unit using a sensor according to the embodiment;

[0025] Figure 12 FIG. 8 is a diagram schematically showing a second example of a sensor unit using a sensor according to the embodiment;

[0026] Figure 13 FIG. 9 is a diagram schematically showing a third example of a sensor unit using a sensor according to the embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, displacement detection sensors according to a plurality of embodiments and sensor devices having the displacement detection sensors will be described with reference to the drawings. Note that in the following description, the displacement detection sensors will be simply referred to as sensors. Further, the same reference numerals are assigned to the same structures, and the description will be omitted.

[0028] Figure 1 ​​​​​​​The illustrated sensor device A has a sensor 1, a signal source 2, and a converter 30A. The sensor device A detects, for example, two positions such as both end portions in a moving range of an object that is linearly reciprocally moved such as a piston rod, a work table, or the like, as a detection target. Also as Figure 2 As illustrated, the sensor 1 has a primary coil unit 10 and a secondary coil unit 20 that detect a position of a measurement body 4 mounted on a detection target. Note that, in this specification, a coil unit refers to a structure including at least one coil.

[0029] The primary coil unit 10 is excited by accepting a signal output from the signal source 2. The secondary coil unit 20 is disposed at a position magnetically coupled with the primary coil unit 10. One of the primary coil unit 10 and the secondary coil unit 20 is configured to have two coils that are connected in reverse series. In this specification, the coils connected in reverse series are defined as differential coils. In the case of the example illustrated in FIG. 1, 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 an electromagnetic wire having an insulating coating around an outer peripheral surface. Figure 1

[0030] The primary coil 11 and the secondary coil 21, and the primary coil 12 and the secondary coil 22 are paired, respectively. Further, the pair of the primary coil 11 and the secondary coil 21, and the pair of the primary coil 12 and the secondary coil 22 are disposed separately from each other. In the following description, the primary coil 11 and the secondary coil 21 of one pair are sometimes referred to as a first coil group Cl, and the primary coil 12 and the secondary coil 22 of the other pair are sometimes referred to as a second coil group C2. Further, a distance between the first coil group Cl and the second coil group C2 is sometimes referred to as a coil gap length Y.

[0031] The two secondary coils 21, 22 are disposed apart from each other by a prescribed distance Y, that is, a coil gap length Y. Also as Figure 1 illustrated, the two secondary coils 21, 22 are connected in reverse series and connected to a detection circuit 3 of the converter 30A. In this case, the two secondary coils 21, 22 are differential coils, respectively. Further, the two primary coils 11, 12 and the two secondary coils 21, 22 are disposed apart by the distance Y, that is, the coil gap length Y. Also, the two primary coils 11, 12 are connected in forward series and connected to the signal source 2. Each of the coils 11, 12, 21, 22 is formed, for example, in a ring shape or a cylindrical shape. Also, the two coil groups Cl, C2 are disposed on the same axis, that is, on a straight line, and configured to allow the measurement body 4 to pass through the inside or the outside of each of the coils 11, 12, 21, 22.

[0032] ​The two primary coils 11 and 12 are respectively arranged in positions facing the secondary coils 21 and 22, which serve as differential coils, and are magnetically coupled to the facing secondary coils 21 and 22. That is, the primary coil 11 and the secondary coil 21 that constitute the first coil group C1 are arranged in positions where they are magnetically coupled to each other. Similarly, the primary coil 12 and the secondary coil 22 that constitute the second coil group C2 are arranged in positions where they are magnetically coupled to each other. In this case, the two primary coils 11 and 12 are respectively facing the two secondary coils 21 and 22. In this specification, coils that face the differential coils are defined as facing coils. In the present embodiment, the two primary coils 11 and 12 are respectively facing coils. In each coil group C1 and C2, the primary coils 11 and 12 and the secondary coils 21 and 22 are arranged so as to overlap at right angles to the direction of movement of the measuring body 4. In the present embodiment, the primary coils 11 and 12 are arranged on the outer periphery of the secondary coils 21 and 22. In addition, the primary coils 11 and 12 may be arranged on the inner circumference side of the secondary coils 21 and 22 .

[0033] Signal source 2 is connected to primary coils 11 and 12 and supplies power, i.e., voltage or current, to primary coils 11 and 12 for driving sensor 1. Signal source 2 supplies, for example, an AC signal to primary coils 11 and 12. Converter 30A includes a detector circuit 3 and is connected to secondary coils 21 and 22. Based on the induced electromotive force of secondary coils 21 and 22, it outputs a position signal, such as a voltage, indicating the position of measuring body 4.

[0034] The measuring body 4 is mounted on the detection object and moves along the coils 11, 12, 21, and 22 as the detection object moves. The measuring body 4 is used to change the magnetic coupling of each coil group C1 and C2 by moving inside or outside each coil 11, 12, 21, and 22. The measuring body 4 is composed of a magnet or a non-magnetic material with conductivity. In the case where the measuring body 4 is arranged on the inside of each coil 11, 12, 21, and 22, the measuring body 4 is preferably a magnet. In addition, in the case where the measuring body 4 is arranged on the outside of each coil 11, 12, 21, and 22, the measuring body 4 is preferably a non-magnetic material with conductivity such as copper, aluminum, and brass.

[0035] exist Figure 2 In the structure, the length of the first coil group C1 is sometimes referred to as the first coil group length, and the length of the second coil group C2 is sometimes referred to as the second coil group length. Figure 2In the example, the length of the first coil group and the length of the second coil group are both set to the same length dimension W. In addition, in this embodiment, for the sake of simplicity, the length dimension of the traveling direction of the measuring body 4 is also set to the same length dimension W as the first coil group length and the second coil group length. In this case, the coil gap length Y is set to be, for example, longer than the length W of each coil group and the length dimension W of the measuring body 4. In addition, the length dimension of the measuring body 4 does not necessarily have to be the same as the first coil group length and the second coil group length. In addition, the coil gap length Y only needs to be greater than 0, and the details will be described later. For example Figure 6 As shown, it can be set shorter than the length W of each coil group and the length W of the measuring body 4.

[0036] In addition, in the following description, for convenience, Figure 2 The outer end of the first coil group C1 on the left side of the paper, that is, the left end, is set as reference position 0. Furthermore, the distance from reference position 0 to the left end 401 of the measuring body 4 is set as the movement amount P of the measuring body 4. In this case, when the left end 401 of the measuring body 4 coincides with reference position 0, that is, when the left end 401 of the measuring body 4 coincides with the outer end of the first coil group C1, the movement amount P = 0. Furthermore, when the right end 402 of the measuring body 4 coincides with the right end of the second coil group C2, that is, when the right end 402 of the measuring body 4 coincides with the outer end of the second coil group C2, the movement amount P becomes W + Y, which is the sum of the length W of the measuring body 4 and the coil gap length Y.

[0037] This structure looks similar to a common differential transformer. However, since a coil gap length Y is provided between the two secondary coils 21 and 22 as differential coils, the operation is different from that of a differential transformer. Figure 3 , the operating principle of the sensor 1 of this embodiment is described.

[0038] Figure 3 Graph showing the relationship between the position of the measuring body 4 and the output voltage V. Figure 3 The vertical axis of the graph represents output voltage V, and the horizontal axis represents movement P. When measuring body 4 is stopped at reference position 0, movement P = 0. In this case, the change in inductance between the primary coil 11 and the secondary coil 21 in the first coil group C1 is the largest, compared to the case where measuring body 4 is not inside the first coil group C1. In other words, in this case, the two secondary coils 21 and 22 connected in series in opposite directions become most unbalanced, resulting in the output voltage V being either extremely large or extremely small. Whether it reaches its maximum or extremely small value depends on factors such as whether measuring body 4 is a magnet or a conductive non-magnetic object and the polarity of detection circuit 3. Figure 3In the example of FIG. 6, for the sake of convenience, it is assumed that the output voltage V is minimum when the measurement body 4 is stopped at the reference position 0.

[0039] In Figure 2 In the example of FIG. 6, for the sake of convenience, it is assumed that the output voltage V is minimum when the measurement body 4 is stopped at the reference position 0.

[0040] When the measurement body 4 is further moved to become the movement amount P = W, the measurement body 4 moves out of the inside of the first coil group Cl, and does not affect the inductance of the first coil group Cl. As a result, the two secondary coils 21, 22 connected in reverse become the most balanced state, and as a result, as shown in the interval of W to Y in FIG. 6, the output voltage V = 0. Figure 3

[0041] When the measurement body 4 is further moved beyond the movement amount P = W, until the movement amount P = Y, both the first coil group Cl and the second coil group C2 remain in a state where the inductance is not affected by the measurement body 4, that is, a state where the output voltage V = 0. Then, when the movement amount P = Y, the front end 402 of the measurement body 4 in the direction of travel is at the same position as the left end of the second coil group C2. When the measurement body 4 is further moved beyond the movement amount P = Y, the measurement body 4 starts to intrude into the inside of the second coil group C2, and starts to affect the inductance of the second coil group C2.

[0042] In this case, when the movement of the measurement body 4 exceeds the movement amount P = Y, the inductance of the second coil group C2 increases when the measurement body 4 is a magnet, and decreases when the measurement body 4 is a non-magnetic body that is conductive. In addition, when the movement of the measurement body 4 exceeds the movement amount P = Y, the inductance of the first coil group Cl decreases when the measurement body 4 is a magnet, and increases when the measurement body 4 is a non-magnetic body that is conductive. Figure 3 In the example of FIG. 6, for the sake of convenience, it is assumed that the output voltage V is maximum when the measurement body 4 is stopped at the position of the movement amount P = W + Y.

[0043] In Figure 3 In the example of FIG. 6, with respect to the range of the movement amount P of the measurement body 4 and the output voltage V, the above-described operation is summarized as follows.

[0044] 0 ≤ P < W: The output voltage V is negative and increases as the movement amount P increases

[0045] W ≤ P ≤ Y: The output voltage V is 0 and is independent of the increase in the movement amount P ​

[0046] Y<P≤W+Y: The output voltage V is positive and increases as the movement amount P increases.

[0047] That is, in Figure 2 and Figure 3 In the example of FIG. 1 , the range of 0≤P<W and Y<P≤W+Y is referred to as the measurement range in which the position of the measuring body 4 can be measured.

[0048] The above-mentioned sensor 1 is a sensor that detects two separate positions. The sensor 1 has two differential coils 21, 22, opposing coils 11, 12, and a measuring body 4. The differential coils 21, 22 are connected in series in opposite directions. The opposing coils 11, 12 are respectively arranged at positions facing the differential coils 21, 22 and at positions magnetically coupled with the differential coils 21, 22. The measuring body 4 is composed of a magnet or a conductive non-magnetic body, and the differential coils 21, 22 and the opposing coils 11, 12 are moved relative to each other, and the magnetic coupling between the differential coils 21, 22 and the opposing coils 11, 12 changes with this movement. Moreover, the two differential coils 21, 22 are arranged in a manner such that they are separated from each other by a distance greater than the length dimension W of the measuring body 4.

[0049] like Figure 2 As shown, the sensor 1 described above uses the range from the ends of the movement range W+Y+W to a distance W as its detection range. With this sensor 1, the advantages of a differential transformer can be obtained by detecting only the range from the ends of the movement range to a predetermined range W, and even when the movement ranges are different, the circuit configuration can be standardized.

[0050] Specifically, in the aforementioned sensor 1, since secondary coils 21 and 22 are connected in series in opposite directions, characteristics similar to or similar to those of a conventional differential transformer can be achieved with respect to interference noise and temperature characteristics. In other words, since sensor 1 lacks mechanical contacts, issues with malfunction due to lifespan, vibration, and the like are minimized. Furthermore, the effects of characteristic deviations and degradation over time are minimal. Furthermore, compared to methods using magnets and reed switches, it is less susceptible to the effects of interfering DC magnetic fields. Furthermore, temperature characteristics of magnetic components such as magnets, such as temperature-related misalignment of the detection position, are less likely to occur, allowing for temperature correction.

[0051] Furthermore, the sensor 1 described above differs from conventional differential transformers primarily in the following two points. First, when the measuring body 4 is located inside either the first coil group C1 or the second coil group C2, that is, within the range of 0 ≤ P < W or Y < P ≤ W + Y for displacement P, even if the inductance of one of the first coil group C1 or the second coil group C2 changes, the inductance of the other does not change. Second, within the range of W ≤ P ≤ Y for displacement P, a non-inductive range in which the output voltage V remains substantially zero is observed.

[0052] Further, in the use of detecting the position near both ends of the sensor 1, when the moving amount P of the measurement body 4 is in the range of P < 0 or P > W + Y, that is, in the range where the measurement body 4 runs out of the coil groups C1, C2 to the left and right, an undesirable situation occurs. For example Figure 3 the position R1 is in Y < P < W + Y, and, on the contrary, the position R2 is in P > W + Y. In this case, the output voltages V of R1, R2 are both expressed as the same value, and the moving amount P cannot be determined from the output voltage V. Therefore, in the use of detecting the position near both ends of the sensor 1, it is preferable to set a mechanical restriction to restrict the movement of the measurement body 4 in the range of 0 < P < W + Y.

[0053] In addition, the sensor device A of the above-described structure can be changed in the following manner.

[0054] The signal source 2 is not limited to a voltage source, but can be a current source.

[0055] The primary coil unit 10 can also not be a structure in which the two primary coils 11, 12 are connected in series in the forward direction, but can be a structure in which signals are independently applied to the two primary coils 11, 12.

[0056] Even if it is a structure in which the primary coils 11, 12 of the primary coil unit 10 are connected in series in the reverse direction, and the secondary coils 21, 22 of the secondary coil unit 20 are connected in series in the forward direction, the same characteristics can be obtained.

[0057] The coil unit of one of the primary coil unit 10 and the secondary coil unit 20 which is not connected in series in the reverse direction can also be formed over the entire length of the moving range of the measurement body 4, that is, the length of 2W + Y.

[0058] The measurement body 4 can be a magnetic material or a non-magnetic material having electrical conductivity, as long as it can change the magnetic coupling of each coil 11, 12, 21, 22, that is, change the inductance. In the case where the measurement body 4 is composed of a non-magnetic material, it can be less affected by a disturbing direct-current magnetic field which becomes a problem in the case where a magnet and a reed switch are used.

[0059] Further, the shape of the measurement body 4 can be a cylinder, a cylinder, a rod, or a plate which passes through the inside of the coil groups C1, C2, or can be a cylinder or a square cylinder which surrounds the outside of the coil groups C1, C2. Furthermore, in the case where the measurement body 4 is disposed on the outer peripheral side of the coil groups C1, C2, the measurement body 4 can also be a plate.

[0060] The signal processing of the converter 30A is not only analog processing, but can also be digital processing using a CPU, an FPGA, or the like after being converted into digital data by an A / D converter, so that the position signal becomes digital data.

[0061] Each of the coils 11 , 12 , 21 , and 22 may be a coil using electromagnetic wire, or a spiral coil may be arranged on a printed circuit board.

[0062] The primary coil unit 10 and the secondary coil unit 20 may not be separated from each other but may have a half-bridge arm structure.

[0063] Next, refer to Figure 4 and Figure 5 , the sensor device B is described. Figure 4 and Figure 5 In the sensor device B shown, a converter 30B is provided instead of Figure 1 The converter 30A this point with Figure 1 The sensor device A is different, but the structure of sensor 1 is the same. It should be noted that in the following description, regarding the detection range at both ends of the movement range of the measuring body 4 relative to the sensor 1, the area within the range of movement P of 0 ≤ P < W is sometimes referred to as the starting end, and the area within the range of movement P of Y < P ≤ W + Y is sometimes referred to as the ending end. Converter 30B has the function of converting the analog signal output from detection circuit 3, that is, output voltage V, into a digital signal. Converter 30B includes, for example, two comparators 31 and 32. In the following description, one of the two comparators 31 and 31 is sometimes referred to as the first comparator 31, and the other as the second comparator 32.

[0064] exist Figure 4 In the example, the first comparator 31 corresponds to detection on the starting side, and the second comparator 32 corresponds to detection on the ending side. In the first comparator 31, the output voltage V is connected to the inverting input, and the first reference voltage Vref1 is connected to the non-inverting input. On the other hand, in the second comparator 32, the output voltage V is connected to the non-inverting input, and the second reference voltage Vref2 is connected to the inverting input. The first reference voltage Vref1 and the second reference voltage Vref2 are user-adjustable reference voltages. The output of the first comparator 31 is referred to as the first output Out1, and the output of the second comparator 32 is referred to as the second output Out2.

[0065] like Figure 5As shown, the adjustment range Va1 of the first reference voltage Vref1 inputted to the first comparator 31 is preferably set to the voltage range actually outputted when the measurand 4 is detected at the start end side, in this case, slightly inside the voltage range from the minimum value to 0. Similarly, the adjustment range Va2 of the second reference voltage Vref2 inputted to the second comparator 32 is preferably set to the voltage range actually outputted when the measurand 4 is detected at the end end side, in this case, slightly inside the voltage range from 0 to the maximum value. This is to prevent errors in threshold determination due to temperature drift of the circuit, the sensor 1, interference noise, variations in components, and the like.

[0066] The user can set the first reference voltage Vref1 and the second reference voltage Vref2 to arbitrary values within the respective adjustment ranges Va1, Va2. That is, the user can adjust the detection position Q1 at the start end 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 at the end end side within the adjustment range H2 by adjusting the second reference voltage Vref2 within the adjustment range Va2. That is, the sensor 1 can individually adjust the detection position Q1 at the start end side and the detection position Q2 at the end end side by individually adjusting the first reference voltage Vref1 and the second reference voltage Vref2. In Figure 5 In the example, the first reference voltage Vref1 is set at the middle point of the adjustment range Va1 of the first reference voltage Vref1. Similarly, the second reference voltage Vref2 is set at the middle point of the adjustment range Va2 of the second reference voltage Vref2.

[0067] When viewed from the start end side, in the case where the movement amount P of the measurand 4 is P = 0, that is, in the case where the measurand 4 is located at the start end of the detection range, the output voltage V is less than the first reference voltage Vref1. In this case, the first output Out1 = 1. Then, when the movement amount P of the measurand 4 exceeds the position Q1 corresponding to the first reference voltage Vref1, the output voltage V is greater than the first reference voltage Vref1. As a result, the first output Out1 = 0. That is, the relationship between the movement amount P of the measurand 4 and the first output Out1 is as follows.

[0068] 0 ≤ P ≤ Q1: First output Out1 = 1

[0069] Q1 < P ≤ W + Y: First output Out1 = 0

[0070] Further, when the terminal side is observed, the output voltage V is smaller than the second reference voltage Vref2 in a case where the movement amount P of the measuring body 4 does not exceed the position Q2 corresponding to the second reference voltage Vref2. In this case, the second output Out2 = 0. Then, when the movement amount P of the measuring body 4 is the position Q2 or more corresponding to the second reference voltage Vref2, the output voltage V is the second reference voltage Vref2 or more. Thus, the second output Out2 = 1. That is, the relationship between the movement amount P of the measuring body 4 and the second output Out2 is as follows.

[0071] 0 ≤ P < Q2: Second output Out2 = 0

[0072] Q2 ≤ P ≤ W + Y: Second output Out2 = 1

[0073] As such, the user can arbitrarily adjust the first reference voltage Vrefl and the second reference voltage Vref2 within the respective adjustment ranges Va1, Va2. Further, the sensor device B outputs the detection results of the start end side and the terminal side as binary outputs of 0 and 1, respectively. Therefore, a device such as a PLC (Programmable Logic Controller) at a higher level can extremely easily acquire the results of the position detection output from the sensor device B.

[0074] Further, in the sensor device B, the converter 30B having the adjustment function of the positions Ql, Q2 is not built in the sensor 1. Therefore, the converter 30B can be disposed at a place away from the sensor 1, that is, a place where a person easily operates, as a result of which the operability related to the adjustment can be improved.

[0075] Further, in the above-described structure, the first output Outl indicates the movement of the measuring body 4 at the start end side, and the second output Out2 indicates the movement of the measuring body 4 at the terminal side. In this case, the length dimension W of the coil groups Cl, C2 coincides with the detection ranges at the start end side and the terminal side. That is, the length dimension W of the coil groups Cl, C2 maintains a certain relationship with the detection ranges at the start end side and the terminal side. Therefore, when the sensor 1 is designed, the length dimension W of the coil groups Cl, C2 can be determined based on the detection ranges at the start end side and the terminal side, and thus the design of the sensor 1 becomes easy.

[0076] Here, the coil gap length Y has no influence on the output voltage V. Therefore, in the sensor 1 of the above-described structure, by changing the coil gap length Y without changing the length dimension W of the coil groups Cl, C2, it is possible to cope with the change in the movement range of the measuring body 4 in the sensor 1, that is, the change in the movement range of the detection object, without changing the position detection characteristics near both ends. In this case, for example, in a case where the movement range of the detection object is changed to a range of 0 to 100 mm, the coil gap length Y is changed to 10 mm, and the length dimension W of the coil groups Cl, C2 is changed to 90 mm. Figure 2In other words, even when the coil gap length Y is changed without changing the length dimension W of the coil sets C1, C2, only the non-induction range of W≤P≤Y changes, and the output characteristics of the sensor 1 do not change in the range indicated by 0≤P Figure 3 and Figure 5 The length of the non-induction range of W≤P≤Y shown in FIG. 6 changes, and the output characteristics of the sensor 1 do not change in the range indicated by 0≤P

[0077] Therefore, when the sensor 1 is designed in accordance with the moving range of the detection object, i.e., the moving range of the measurement body 4, the designer can change only the coil gap length Y in accordance with the moving range, and in this case, the circuit structure of the sensor device B does not need to be changed. That is, according to the above-described structure, the circuit structure of the sensor device B can be made common regardless of the moving range of the measurement body 4.

[0078] Further, since the number of turns and the length dimension W of the coil units 10, 20 in the sensor 1 can be made the same regardless of the moving range of the measurement body 4, the burden on the designer can be reduced. Moreover, by making the circuit structure of the sensor device B common, even in a plurality of sensor devices B, when the moving range of the detection object of the sensor 1 and the measurement body 4 are different, i.e., when the overall length of the sensor 1 is different, the adjustment operation of the detection position Q1 on the start end side and the detection position Q2 on the end end side can be made common. As a result, the burden on the operator who performs the adjustment operation of the detection positions Q1, Q2 of the sensor device B can be reduced.

[0079] Further, although in the above-described structure, the length dimensions of the first coil set C1 and the second coil set C2 are made the same, as long as the inductances of the two coil sets C1, C2 are set to the same degree, the effect as a differential transformer can be obtained. That is, the length dimensions of the first coil set C1 and the second coil set C2 can also be different within a range in which the effect as a differential transformer can be obtained.

[0080] Further, the length dimensions of the first coil set C1 and the second coil set C2 can also be set to different lengths. In this case, by adjusting the first coil set C1, the second coil set C2, and the number of turns, the inductances can be made the same degree. That is, since different detection ranges can be set on the start end side and the end end side, the mechanical situation can be dealt with more flexibly.

[0081] Further, although in the above description, the case where the coil gap length Y is longer than the coil group length W of each coil group C1, C2 and the length dimension W of the measurement body 4 is described, the coil gap length Y can be shorter than the coil group length W of each coil group C1, C2 and the length dimension W of the measurement body 4. Further, since in the case where the coil gap length Y = 0, it becomes a normal differential transformer itself, it is excluded from the scope of the present application. That is, the coil gap length Y can be at least greater than 0.

[0082] Figure 6 and Figure 7 The example shown in FIG. 6 is an example in the case where the coil gap length Y is set to be greater than 0 and be below the coil group length W of each coil group C1, C2 and the length dimension W of the measurement body 4, that is, in the range of 0 < Y ≤ W. In this case, there is no non-induction range where the output voltage V = 0. Also, as shown in FIG. 7, in a graph where the moving amount P is set to the horizontal axis and the output voltage V is set to the vertical axis, it becomes a shape approximating to an S-shaped curve. Figure 7

[0083] In the case where the moving amount P is 0 ≤ P < Y, although at least a part of the measurement body 4 overlaps with the coil group C1, the measurement body 4 does not overlap with the coil group C2. In this case, as the moving amount P increases, the inductance of the coil group C1 gradually decreases when the measurement body 4 is a magnet and gradually increases when the measurement body 4 is a non-magnetic body of electrical conductivity. On the contrary, the inductance of the coil group C2 does not change.

[0084] Further, in the case where the moving amount P is Y ≤ P ≤ W, the measurement body 4 overlaps with both of the coil groups C1, C2. In this case, as the moving amount P increases, the inductance of the coil group C1 gradually decreases when the measurement body 4 is a magnet and gradually increases when the measurement body 4 is a non-magnetic body of electrical conductivity. On the other hand, as the moving amount P increases, the inductance of the coil group C2 gradually increases when the measurement body 4 is a magnet and gradually decreases when the measurement body 4 is a non-magnetic body of electrical conductivity. Therefore, the amount of change in the inductance of the coil unit 20 becomes large, as shown in FIG. 8, the slope of the graph of the moving amount P - output voltage V becomes twice as compared to the case of 0 ≤ P < Y. Figure 7

[0085] Further, in the case where the moving amount P is W < P ≤ W + Y, at least a part of the measurement body 4 overlaps with the coil group C2, but the measurement body 4 does not overlap with the coil group C1. In this case, as the moving amount P increases, the inductance of the coil group C2 gradually increases when the measurement body 4 is a magnet and gradually decreases when the measurement body 4 is a non-magnetic body of electrical conductivity. On the contrary, the inductance of the coil group C1 does not change. As a result, in the case where the moving amount P is W < P ≤ W + Y, the inductance of the coil group C2 is greater than that of the coil group C1, and the inductance of the coil group C1 is smaller than that of the coil group C2. Figure 6 and Figure 7 ​​In the example of FIG. 6, the range of 0≤P

[0086] Next, the temperature correction of the sensor 1 will be described. In the wire winding for the primary coil units 10 and the secondary coil units 20, mainly copper is used. It is known that the resistance value of a conductor such as copper changes depending on the temperature of the conductor. The relationship between the "resistance value of a conductor" and the "temperature" is expressed by the following formula.

[0087] RT = Rt{1 + αt(T - t)} [Ω]... (1)

[0088] RT: resistance value of a conductor when the temperature is T [°C] [Ω]

[0089] Rt: resistance value at t [°C] [Ω]

[0090] αt: resistance temperature coefficient at t [°C] [ppm / °C]

[0091] The resistance temperature coefficient αt in the above formula (1) is a coefficient indicating the proportion of the change in the resistance value per 1 °C, and in the case of ordinary copper, it is 0.00393. Further, the resistance value of each coil unit 10, 20 is determined by the inherent resistivity of the wire winding used for each coil unit 10, 20 and the length of the wire winding, and is a value inherent to the specifications of each coil unit 10, 20. Therefore, based on the initial resistance value Rt of the coil unit 10, 20, the temperature t at which the resistance value Rt is measured, and the current resistance value RT, the temperature T of the coil unit 10, 20 at present, that is, the temperature T of the sensor 1 can be measured. Further, since the temperature inside the sensor 1 can be measured by the above function, it is easy to perform temperature correction with higher precision.

[0092] Specifically, the internal temperature of the sensor 1 can be measured, for example, in the following manner. First, a direct current is caused to flow through both ends of either the primary coil unit 10 or the secondary coil unit 20. Next, for the coil unit 10, 20 through which the direct current flows, the direct current voltage across both ends is measured, and based on the direct current voltage, the current resistance value RT is measured. Then, based on the resistance value Rt and the temperature t set in advance, the temperature T of the sensor 1 is calculated from the above formula (1).

[0093] In the aforementioned sensor devices A and B, for example, when measuring the internal temperature of sensor 1 using primary coil unit 10, a DC current is supplied to primary coil unit 10, superimposed on an AC signal supplied by signal source 2. The voltage across primary coil unit 10 is then measured, in this case, a filtered, DC-converted voltage. The supplied DC current and the measured DC voltage are then detected, allowing calculation of the resistance of primary coil unit 10. In this case, to accurately measure the DC resistance of primary coil unit 10, a circuit for measuring the resistance can be constructed using, for example, a four-wire wiring method.

[0094] Next, refer to Figure 8 and Figure 9 , the structure examples of each coil 11, 12, 21, 22 are described. Figure 8 The sensor 1 shown is sensor 1A. Figure 9 The sensor 1 shown is distinguished as sensor 1B. Figure 8 The sensor 1A shown is an example in which the coils 11 , 12 , 21 , and 22 are formed by winding copper wire or the like. Figure 8 The sensor 1A includes a coil holding body 13 . The coil holding body 13 is configured in a cylindrical or rectangular shape, for example. Each coil 11 , 12 , 21 , 22 is formed of a winding such as a copper wire and is wound around the outer circumference of the coil holding body 13 .

[0095] The coil holding body 13 has the function of maintaining the shape of each coil 11, 12, 21, 22, as well as the function of fixing the relative position. The coil holding body 13 can also be made of a conductive metal. However, when the coil holding body 13 is made of a conductor, the coil holding body 13 acts as a short-circuit coil, resulting in a reduction in the inductance of each coil 11, 12, 21, 22. Therefore, when a conductor is used for the coil holding body 13, it is preferred that a material with high electrical resistance be used, that is, stainless steel, nickel alloy, etc. with a small current flowing through it be used as a short-circuit coil. In addition, the thickness of the coil holding body 13 is also preferably thin. In addition, the coil holding body 13 can also be made of an insulator such as resin.

[0096] Furthermore, magnetic materials can also be used for the coil holder 13. Using magnetic materials for the coil holder 13 increases the inductance of each coil 11, 12, 21, and 22, thereby improving sensitivity and, in other words, increasing signal variation. Furthermore, when using magnetic materials for the coil holder 13, consideration must be given to temperature characteristics and other factors. Furthermore, in a configuration where the measuring body 4 passes within the inner circumference of the coil holder 13, a non-magnetic material or insulator should be used for the coil holder 13 to ensure a signal variation.

[0097] Further, an insulator can be provided between the coil holding body 13 and each of the coils 11, 12, 21, 22. The wire forming each of the coils 11, 12, 21, 22, that is, the electromagnetic wire is insulated by an insulating coating film or the like, and thus it is not necessary to necessarily provide an insulator between the coil holding body 13 and each of the coils 11, 12, 21, 22. However, by providing an insulator between the coil holding body 13 and each of the coils 11, 12, 21, 22, the insulation withstand voltage between the coil holding body 13 and each of the coils 11, 12, 21, 22 can be improved.

[0098] Figure 9 The illustrated sensor IB is an example in which each of the coils 11, 12, 21, 22 is formed of a coil pattern provided on a printed board. In the illustrated example, the primary coil unit 10 and the secondary coil unit 20 of the sensor IB are each formed of a coil pattern provided in a spiral shape on a printed board 41, 42. In the illustrated example, for convenience of explanation, a pattern related to the primary coil unit 10 is indicated by black fill, and a pattern related to the secondary coil unit 20 is indicated by white fill. The sensor IB 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 of the boards 41, 42, 43, 44 are connected by a via hole as necessary. Pad patterns 511, 512, 521, 522 connected to each of the coils 11, 12, 21, 22 are provided on the first layer board 41. Figure 9 Figure 9 In the illustrated example, for convenience of explanation, a pattern related to the primary coil unit 10 is indicated by black fill, and a pattern related to the secondary coil unit 20 is indicated by white fill. The sensor IB 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 of the boards 41, 42, 43, 44 are connected by a via hole as necessary. Pad patterns 511, 512, 521, 522 connected to each of the coils 11, 12, 21, 22 are provided on the first layer board 41.

[0099] The coil patterns of the primary coils 11, 12 are provided on the first layer board 41, which is the outermost layer of the sensor IB. The pad pattern 511 is connected to the primary coil 11, which is distal from the pad pattern 511, of the two primary coils 11, 12 via a connection pattern 531 provided on the first layer board 41 and a connection pattern 532 provided on the third layer board 43. Further, the two primary coils 11, 12 are connected in series in the forward direction with each other via a connection pattern 533 provided on the first layer board 41 and a connection pattern 534 provided on the third layer board 43. Moreover, the primary coil 12, which is proximal to the pad pattern 512, of the two primary coils 11, 12 is connected to the pad pattern 512 via a connection pattern 535 provided on the first layer board 41.

[0100] ​The coil pattern of the secondary coil 21, 22 is provided on the second layer substrate 42. The pad pattern 521 is connected to the secondary coil 21, which is distal from the pad pattern 521, of the two secondary coils 21, 22 via the connection pattern 541 provided on the fourth layer substrate 44. Further, the two secondary coils 21, 22 are reversely connected in series with each other via the connection pattern 542 provided on the second layer substrate 42 and the connection pattern 543 provided on the fourth layer substrate 44. Moreover, the secondary coil 22, which is proximal from the pad pattern 522, of the two secondary coils 21, 22 is connected to the pad pattern 522 via the connection pattern 544 provided on the second layer substrate 42.

[0101] In this way, by forming each coil 11, 12, 21, 22 as a coil pattern on the printed substrates 41, 42, it is possible to use the high-precision manufacturing technology of the printed substrates. Thus, it is possible to inexpensively manufacture the same size of coil pattern, that is, the sensor IB of the same characteristics and less variation. Further, when mounting the sensor IB, for example, wiring can be performed by soldering only the signal lines on the pad patterns 511, 512, 521, 522, and thus the operability is good. Further, when designing the sensor IB, when changing the coil length W and the coil gap length Y of each coil 11, 12, 21, 22, it is possible to simply and reliably perform design change by changing only the layout data such as CAD.

[0102] In addition, although in the example of Figure 9 the sensor IB is configured by laminating four printed substrates 41 to 44, it is possible to simply increase the inductance of the coil units 10, 20 by increasing the number of printed substrates provided with the coil pattern of the coils 11, 12, 21, 22. In this case, no electronic components such as ICs, transistors, and the like are provided on each printed substrate 41 to 44. Thus, it is possible to make each printed substrate 41 to 44 thin, and as a result, even if the number of laminated printed substrates is increased, the thickness does not become extremely large, and it is possible to configure a thin and compact structure.

[0103] Further, by using a printed substrate made of epoxy resin to which glass is added as the printed substrates 41 to 44, it is possible to make the sensor IB a light-weight and high-rigidity sensor. Thus, it is possible to make a structure that is not easily bent and has high reliability without using a reinforcing material or the like different from the printed substrates 41 to 44. Further, a printed substrate is generally highly workable, and it is possible to easily make a free shape. Thus, it is possible to make the shape of the sensor IB a shape that is good in operability at the time of assembly. For example, a protrusion, a recess, a spring structure, and the like that fit into a mounting object at the time of mounting the sensor IB can be easily provided on the printed substrates 41 to 44.

[0104] Further, in the example of Figure 4In the sensor device B, the converter 30B can also be replaced by Figure 10 a converter 30C. Figure 10 The converter 30C is an example of a two-wire structure that does not use the signal source 2 for driving the sensor. That is, the signal line connecting the converter 30C and the upper device 90 is a two-wire structure. In this case, the converter 30C also functions as a signal source for supplying power for exciting the primary coil unit 10.

[0105] Figure 10 The converter 30C is an example of a two-wire structure that does not use the signal source 2 for driving the sensor. That is, the signal line connecting the converter 30C and the upper device 90 is a two-wire structure. In this case, the converter 30C also functions as a signal source for supplying power for exciting the primary coil unit 10.

[0106] The upper device 90 is connected to the terminals of the output terminal row 34 via the terminal row 91 of the upper device 90, such as a PLC. The detection sections 921, 922 are configured by, for example, optocouplers, and detect the ON / OFF signals output from the output circuits 361, 362, respectively. In this case, the two-wire structure is configured such that two signal lines 391, 392, 393, 394 are connected to the detection sections 921, 922, respectively. Therefore, the conventional two-wire magnetic reed switch can be easily replaced by the sensor device B of the present structure.

[0107] The sensor internal circuit 35 has a drive circuit 351 for driving the sensor 1, and a comparison circuit 352. The comparison circuit 352 has a function of detecting the sensor signal, comparing the sensor signal with each reference voltage Vref1, Vref2, and sending an ON / OFF (open / close) instruction of the contact output to the start end output circuit 361 and the end end output circuit 362. In this case, in order to drive in the two-wire structure, it is necessary to reduce the consumption current of the sensor internal circuit 35. Specifically, it is necessary to suppress the consumption current of the sensor internal circuit 35 to be 1 mA or less. This consumption current is the current input from the signal line 392 or 394, and is the current flowing to the detection sections 921 and 922 of the upper device 90. If the current flowing to the detection sections 921 and 922 is sufficiently small, the upper device 90 determines that the input is OFF. The sensor device B of the present embodiment is configured such that the sensor 1 and the converter 30C can operate even in the case where the input is OFF, that is, the current is sufficiently small. The current value at which the input is determined to be OFF in the upper device 90 differs depending on the specifications of the upper device 90, but is mostly 1 mA or less.

[0108] The start end output circuit 361 and the terminal end output circuit 362 are circuits that output ON / OFF to the contacts of the upper device 90 based on the ON / OFF instruction sent from the sensor internal circuit 35. In this case, the start end output circuit 361 performs the contact output on the start end side, and the terminal end output circuit 362 performs the contact output on the terminal end side. Further, in the example of FIG. 6, the drive power of the sensor internal circuit 35 is supplied from the terminal end output circuit 362. Figure 10

[0109] The non-polarity circuits 381, 382 are used to make the polarity of the current of the contact output able to cope with either the sink type as a way of introducing current from the upper device 90 to the converter 30C, or the source type as a way of discharging current from the converter 30C to the upper device 90, for example, are composed of a bridge circuit of diodes. In addition, the non-polarity circuits 381, 382 can also be composed using FETs (field effect transistors) instead of diodes. In the case of using FETs, the circuit becomes complex, but the ON resistance can be reduced.

[0110] Next, with reference to Figures 11 to 13 , a sensor unit using the sensor 1 will be described. Figure 11 The example shown in FIG. 5 is an example in which the sensor 1A shown in FIG. 1 is used and the measurement body 4 is disposed on the outside of the sensor 1A. Figure 8 The example shown in FIG. 5 is an example in which the sensor 1A shown in FIG. 1 is used and the measurement body 4 is disposed on the outside of the sensor 1A. Figure 11 The sensor unit 601 shown in FIG. 6 has the sensor 1A, the measurement body 4, the sleeve 61, the housing 62, the top end cap 63, the rear end cap 64, and the lead cable 65. The coil holding body 13 and the coil units 10, 20 are disposed inside the sleeve 61. Further, the measurement body 4 is movably disposed on the outside of the sleeve 61, that is, on the outside of the coil units 10, 20.

[0111] Figure 12 The example shown in FIG. 7 is an example in which the sensor 1B shown in FIG. 2 is used and the measurement body 4 is disposed on the outside of the sensor 1B. Figure 8 The example shown in FIG. 7 is an example in which the sensor 1B shown in FIG. 2 is used and the measurement body 4 is disposed on the outside of the sensor 1B. Figure 12 The sensor unit 602 shown in FIG. 7 has the sensor 1A, the measurement body 4, the sleeve 61, the housing 62, the top end cap 63, the rear end cap 64, and the lead cable 65. The coil holding body 13, the coil units 10, 20 are disposed inside the sleeve 61. Further, the measurement body 4 is movably disposed on the inside of the sleeve 61, that is, on the inside of the coil units 10, 20. In this case, the measurement body 4 is supported by the support body 5.

[0112] Figure 13 The example shown in FIG. 7 is an example in which the sensor 1B shown in FIG. 2 is used and the measurement body 4 is disposed on the outside of the sensor 1B. Figure 9 The example shown in FIG. 7 is an example in which the sensor 1B shown in FIG. 2 is used and the measurement body 4 is disposed on the outside of the sensor 1B. Figure 13 ​The sensor unit 603 shown includes a sensor 1B, a measuring body 4, a sleeve 61, a housing 62, a top cover 63, a rear cover 64, and a lead cable 65. The sensor 1B is disposed inside the sleeve 61. The measuring body 4 is movably disposed outside the sleeve 61, that is, outside the coil units 10 and 20.

[0113] exist Figures 11 to 13 In the structure, the sleeve 61 is used to seal the sensors 1A and 1B to realize the mechanical protection structure. Figure 11 The sensor unit 601 and Figure 13 In the structure where the measuring body 4 is arranged outside the coil units 10 and 20, as in the sensor unit 603, the sleeve 61 is made of a non-magnetic material. In this case, even if the sleeve 61 is made of a non-magnetic material, when a highly conductive material is used, the sleeve 61 itself will work as a short-circuit coil. As a result, the inductance of the coil units 10 and 20 is reduced, and as a result, the change in inductance becomes smaller, that is, the change in signal becomes smaller. Therefore, in Figure 11 and Figure 13 In the example, the sleeve 61 is preferably made of a non-magnetic material having high electrical resistance, such as austenitic stainless steel or nickel alloy.

[0114] Furthermore, for the same reasons as above, the thickness of sleeve 61 is also preferably thin. However, a balance must be considered with mechanical strength. In particular, when sensor 1A is built into a hydraulic cylinder, sleeve 61 must be thick enough to prevent damage. For applications that do not apply high pressure or do not require waterproofing, sleeve 61 can be made of glass fiber reinforced resin or carbon fiber reinforced resin, thereby achieving lightweight and low-cost performance.

[0115] Lead-out cable 65 is used to lead the wiring of coil units 10 and 20 to the outside of housing 62, where it is connected to detection circuit 3 or sensor internal circuit 35. A connector, for example, may be attached to the end of lead-out cable 65. Lead-out cable 65 is secured to housing 62 via, for example, a cable connector 66. This cable connector 66 ensures waterproofing between housing 62 and the protective sheath of lead-out cable 65.

[0116] Furthermore, there is a gap inside the protective cover of the lead cable 65. Therefore, if the connector at the end of the lead cable 65 is not connected or the protective cover of the lead cable 65 is damaged, there is a risk that liquid may enter the housing 62 through the gap inside the protective cover of the lead cable 65. Therefore, the housing 62 may be filled with epoxy resin 67 or the like to prevent liquid from entering the housing 62 through the lead cable 65.

[0117] As explained above, the displacement detection sensor 1 is a sensor that detects two positions separately. The displacement detection sensor 1 has a primary coil unit 10 and a secondary coil unit 20. The primary coil unit 10 is excited by being supplied with power from the signal source 2, 30C. The secondary coil unit 20 is disposed at a position magnetically coupled to the primary coil unit 10. In the primary coil unit 10 and the secondary coil unit 20, the inductance of the primary coil unit 10 and the secondary coil unit 20 changes by relative movement of the primary coil unit 10 and the secondary coil unit 20 by the measuring body 4 composed of a magnet or a non-magnetic body having electrical conductivity. Also, one of the primary coil unit 10 and the secondary coil unit 20 is configured to have two coils 21, 22 disposed separately from each other and connected in reverse series.

[0118] Thus, it is possible to obtain the advantage of a differential transformer in a case where detection is performed only from both ends of the moving range of the detection object or the measuring body 4 to a prescribed range, that is, from both ends of the full length of the sensor 1 to a prescribed range, and the circuit structure can be commonized even in a case where the moving range of the detection object is different.

[0119] Further, in the displacement detection sensor IB, the primary coil unit 10 and the secondary coil unit 20 are composed of coil patterns provided on the printed boards 41, 42, 43, 44. Thus, by using the technology of the printed board, it is possible to mass-produce the primary coil unit 10 and the secondary coil unit 20 with high precision and at low cost.

[0120] Further, the sensor device B of the embodiment has a converter 30C that outputs a position signal indicating the position of the measuring body 4 based on the induced electromotive force of the secondary coil unit 20, the converter 30C being configured so that the signal line is two-wire type. Thus, it is possible to simply replace the conventional two-wire type magnetic switch with the sensor device B of the present structure.

[0121] Further, the sensor device B has the displacement detection sensors 1, 1A, 1B and the converters 30B, 30C described above. The converters 30B, 30C can adjust the detection positions Q1, Q2 of the measuring bodies 4 by adjusting the reference voltages Vref1, Vref2. Thus, when adjusting the detection positions Q1, Q2, the operator can adjust the values of the reference voltages Vref1, Vref2 only, and does not need to adjust the detection positions mechanically. Therefore, according to the sensor device B of the present structure, it is easier to adjust the detection positions than, for example, a magnetic reed switch which is binary only and needs mechanical adjustment of the detection positions. Further, generally, the converters 30B, 30C are provided outside of a device or the like in which the displacement detection sensors 1, 1A, 1B are assembled. Therefore, even in a case where it is difficult to secure an operation space around the displacement detection sensors 1, 1A, 1B, it is possible to adjust the detection positions Q1, Q2 at a place away from the displacement detection sensors 1, 1A, 1B. As a result, according to the present structure, the operability related to adjustment of the detection positions Q1, Q2 is further improved.

[0122] The embodiments described above are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. The present embodiments and modifications thereof are included within the scope and spirit of the invention, and are included within the scope of the invention and the equivalent thereof recited in the claims.

Claims

1. A displacement detecting sensor (1, 1A, 1B) which detects two positions separated from each other, comprising: a primary coil unit (10) which is excited by power supplied from a signal source (2, 30C); and a secondary coil unit (20) which is disposed at a position magnetically coupled with the primary coil unit, in which the inductance of the primary coil unit and the secondary coil unit changes by relative movement of the primary coil unit and the secondary coil unit by a measuring body (4) composed of a magnet or a non-magnetic body having electrical conductivity, one of the primary coil unit and the secondary coil unit is configured to have two coils (21, 22) disposed separated from each other and connected in reverse series.

2. The displacement detecting sensor according to claim 1, wherein the primary coil unit and the secondary coil unit are composed of coil patterns provided on printed boards (41, 42, 43, 44).

3. A sensor device (B) comprising: the displacement detecting sensor (1, 1A, 1B) according to claim 1 or 2; and a converter (30C) which outputs a position signal representing the position of the measuring body based on the induced electromotive force of the secondary coil unit, the converter (30C) being configured so that the signal line is two-wire type.

4. A sensor device (B) comprising: the displacement detecting sensor (1, 1A, 1B) according to claim 1 or 2; and a converter (30B, 30C) which is capable of adjusting the detection position (Ql, Q2) of the measuring body by adjusting a reference voltage (Vrefl, Vref2). ​ ​ ​ ​ ​ ​ ​ ​ ​

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