Position Sensor

Abstract

The present invention addresses the problem of providing a position sensor that can accurately measure the distance to an object to be measured. [Solution] The position sensor includes a detection coil disposed opposite the object to be measured, a temperature sensor, an oscillator, a processing unit, and a storage device. The oscillator outputs an oscillation signal having a frequency corresponding to the inductance of the detection coil. The temperature sensor outputs a measurement signal corresponding to the temperature of the detection coil. The storage device stores correlation data indicating the relationship between the distance between the object to be measured and the detection coil, the frequency, and the temperature of the detection coil. The processing unit receives the oscillation signal and the measurement signal, and outputs the distance based on the correlation data.

Description

[Technical Field]

[0001] The present invention relates to a position sensor. [Background technology]

[0002] A known sensor for measuring the distance to a measurement object made of metal or other material is a position sensor that uses a coil as the sensor unit and a self-excited oscillator connected to the coil. When the distance between the coil and the measurement object changes, the inductance of the coil changes, and the frequency of the AC signal output from the oscillator changes. By measuring the frequency fluctuation, it is possible to measure the distance from the coil to the measurement object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 3-109816 [Patent Document 2] Patent Publication No. 2021-076527 Summary of the Invention [Problem to be solved by the invention]

[0004] When the ambient temperature changes, not only does the resistance of the sensor coil change, but the shape also changes due to thermal expansion and contraction. As a result, the temperature change of the coil inductance becomes complex. Therefore, it is difficult to simply perform temperature compensation for position detection from the change in the coil resistance. It is possible to use two detection coils to cancel out fluctuations in the output signal due to temperature changes. However, the need for two detection coils complicates the structure of the position sensor. Furthermore, the two coils must be manufactured so that their electromagnetic properties have the same temperature characteristics, making it difficult to manufacture a position sensor capable of highly accurate position detection. As described above, conventional position sensors have a problem in that the inductance changes with the temperature change of the detection coil, making it difficult to perform highly accurate position detection.

[0005] In view of the above problems, an object of the present invention is to provide a position sensor that can accurately measure the distance to an object to be measured even in a situation where the temperature of the detection coil changes. [Means for solving the problem]

[0006] The position sensor according to the present invention comprises: The apparatus includes a detection coil arranged opposite to the object to be measured, a temperature sensor, an oscillator, a processing unit, and a storage device, the oscillator outputs an oscillation signal having a frequency corresponding to the inductance of the detection coil; the temperature sensor outputs a measurement signal corresponding to the temperature of the detection coil; the storage device stores correlation data indicating a relationship between the distance between the object to be measured and the detection coil, the frequency, and the temperature of the detection coil; The calculation processing unit receives the oscillation signal and the measurement signal, and outputs the distance based on the correlation data.

[0007] By providing a position sensor with this configuration, it is possible to provide a position sensor that can accurately measure the distance from the detection coil to the object to be measured even when the temperature of the detection coil changes.

[0008] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, further comprising a frequency divider; The oscillation signal from the oscillator may be divided in frequency by the frequency divider and output to the arithmetic processing device.

[0009] By using a position sensor with such a configuration, it is possible to adjust the detection sensitivity depending on the intended use and situation.

[0010] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, The frequency divider may output two or more output signals having different frequency division ratios to the arithmetic processing device.

[0011] By using a position sensor with such a configuration, it is possible to select an appropriate frequency division ratio and adjust the detection sensitivity.

[0012] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, The frequency divider may switch between two or more output signals having different frequency division ratios and output the signals to the arithmetic processing device.

[0013] By configuring the position sensor in this way, it is possible to obtain a position sensor with a simple configuration that allows sensitivity adjustment.

[0014] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, Further comprising a frequency measuring device; The frequency measuring device may output a measured value of the frequency of the oscillation signal to the processor.

[0015] By configuring the position sensor in this way, the noise resistance of the position sensor can be improved.

[0016] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, The detection coil, the temperature sensor, and the oscillator may be mounted on the same substrate.

[0017] By using a position sensor with such a configuration, the position sensor can be easily installed.

[0018] Furthermore, the position sensor according to the present invention has the above-mentioned configuration, the calculation processing unit calculates a predicted value of the temperature of the detection coil from the measurement signal; The predicted value may be used as the temperature of the detection coil, and the distance may be output based on the correlation data.

[0019] By using a position sensor with such a configuration, it is possible to calculate the distance to the object to be measured even when there is a difference between the temperature change of the detection coil and the temperature change measured by the temperature sensor.

[0020] The integrated sensor according to the present invention A pressure measurement module, a distance measurement module, and an analysis module are provided, the pressure measurement module outputs a signal having a first output frequency responsive to a fluid pressure to the analysis module; the distance measurement module outputs a signal having a second output frequency according to the distance to the object to the analysis module; the analysis module has first correlation data indicating a relationship between the first output frequency and the fluid pressure, and second correlation data indicating a relationship between the second output frequency and the distance; the analysis module calculates the fluid pressure based on the first correlation data and the first output frequency output by the pressure measurement module; The distance is calculated based on the second correlation data and the second output frequency output by the distance measurement module.

[0021] The position sensor according to the present invention can also be integrated with a pressure sensor, allowing the measurement of two different physical quantities, distance and pressure, and can be used, for example, to monitor and control hydraulic circuits. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a position sensor that can accurately measure the distance to an object to be measured even in a situation where the temperature of the detection coil changes. [Brief explanation of the drawings]

[0023] [Figure 1] Fig. 1(A) shows the main circuit configuration of a position sensor 100 of embodiment 1. Fig. 1(B) is a schematic diagram showing the relationship between a detection coil Ls and an object M to be measured. [Figure 2]Figure 2(A) shows an example of an oscillator circuit using two inverters, and Figure 2(B) shows an example of an oscillator circuit using a Schmitt trigger inverter. [Figure 3] Fig. 3(A) shows the main configuration of the position sensor 100 of embodiment 2. Fig. 3(B) shows a modified example of the position sensor 100 of embodiment 2. [Figure 4] 4A and 4B show the main configuration of the position sensor 100 of the third embodiment. [Figure 5] Fig. 5 shows the main circuit configuration of the position sensor 100 of embodiment 4. Fig. 5(A) is a plan view showing the first surface of the position sensor 100, and Fig. 5(B) is a plan view showing the second surface of the position sensor 100. Figs. 5(C) and (D) show modified examples of the position sensor 100. [Figure 6] Fig. 6(A) shows the main circuit configuration of the pressure sensor 600. Fig. 6(B) is a cross-sectional view showing a specific example of the configuration of the sensor module MS'. [Figure 7] FIG. 7(A) shows an oscillation circuit using two inverters IA1 and IA2, and FIG. 7(B) shows an oscillation circuit using a Schmitt trigger inverter IB1. [Figure 8] FIG. 8(A) shows the main configuration of a pressure sensor 600 according to the sixth embodiment, and FIG. 8(B) shows a modified example of the pressure sensor 600 according to the sixth embodiment. [Figure 9] FIG. 9 shows the main configuration of a pressure sensor 600 according to the seventh embodiment. [Figure 10] FIG. 10(A) is a cross-sectional view that schematically shows a compressor 300 incorporating the position sensor 100, and FIG. 10(B) is a top view of the cylinder bottom 41b. [Figure 11] 11(A) and (B) show an example of the configuration of the position sensor 100 incorporated into the compressor 300. [Figure 12] FIG. 12 shows a schematic circuit configuration of an integrated sensor 500 for measuring different physical quantities. [Figure 13] FIG. 13 is a cross-sectional view schematically showing a compressor 301 according to a ninth embodiment incorporating the position sensor 100. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are not intended to limit the scope of the present invention. Furthermore, the same or similar components will be designated by the same reference numerals, and their description may be omitted.

[0025] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0026] (Embodiment 1) The position sensor 100 of the first embodiment will be described below with reference to the drawings. FIG. 1A shows the main circuit configuration of a position sensor 100 according to the first embodiment. FIG. 1B is a schematic diagram showing the relationship between the detection coil Ls and the object M to be measured.

[0027] As shown in FIG. 1(A), the position sensor 100 includes a detection coil Ls, an oscillator 1 (detection oscillator), an analyzer 3, and a temperature sensor 6. Power is supplied from a power supply (not shown) to the oscillator 1, the analyzer 3, and the temperature sensor 6. The position sensor 100 may be provided with, for example, a battery as a power supply. Alternatively, an external power supply may be provided, and power may be supplied to the position sensor 100 from the power supply via a wire or wirelessly.

[0028] The detection coil Ls is connected to an oscillator 1. The oscillator 1 is a self-excited oscillator that outputs an AC signal (sometimes referred to as an oscillation signal) having an oscillation frequency that corresponds to the inductance of the detection coil Ls. The oscillator 1 can be, for example, a known LC oscillator. The oscillation signal output from the oscillator 1 is, for example, a square wave, a sine wave, or the like, and is preferably output as a square wave that can be easily processed by a digital circuit.

[0029] FIG. 2 shows a non-limiting example of oscillator 1. Oscillator 1 can be configured using, for example, an inverter. FIG. 2(A) shows an oscillator circuit using two inverters IA1 and IA2, and FIG. 2(B) shows an oscillator circuit using a Schmitt trigger inverter IB1. In the figure, symbol R indicates a resistor, and symbols D1 and D2 indicate diodes. Oscillator 1 is supplied with DC power from a power source PW. 2(A) and (B) can output a square wave (OUT) with a frequency that depends on the inductance of the detection coil Ls and the capacitance of the capacitor C. The capacitance of the capacitor C is fixed, and the frequency of the output signal changes according to changes in the inductance of the detection coil Ls. Unlike conventional position sensors that detect eddy current loss due to an object to be measured, the position sensor 100 does not require a signal source that applies an AC current to the detection coil Ls, which allows the position sensor 100 to be made smaller.

[0030] The analysis device 3 includes a processing unit 4 and a storage device 5. The analysis device 3 can be configured, for example, by a microcomputer having a CPU and memory. The storage device 5 can be, but is not limited to, a known storage device that can be written to and read from by, for example, electromagnetic means. The position sensor 100 may include a clock oscillator 8 for a clock signal of the analysis device 3. Alternatively, the analysis device 3 may have a built-in clock oscillator for the clock signal. If the analysis device 3 has a built-in clock oscillator, this contributes to the miniaturization of the position sensor 100. However, in general, the frequency of the output signal of the oscillator built into the analysis device 3 is subject to large temperature changes due to the influence of the environmental temperature of the analysis device 3. By providing a clock oscillator 8 outside the analysis device 3, for example by using a crystal oscillator, it is possible to reduce the temperature change of the clock signal frequency.

[0031] If the analyzer 3 has a built-in clock oscillator, the analyzer 3 may be placed in a stable temperature environment (an environment with a constant temperature) away from the detection coil Ls and oscillator 1 in order to reduce temperature changes in the clock signal. This makes it possible to stabilize the operation of the analyzer 3 even if the temperature around the object to be measured M (and the detection coil Ls) changes. Alternatively, only the clock oscillator 8 may be placed in an environment with a stable temperature (an environment with a constant temperature), or the clock oscillator 8 and the analysis device 3 may be placed in an environment with a stable temperature.

[0032] The temperature sensor 6 is disposed in proximity to the detection coil Ls and measures the temperature of the detection coil Ls. The output of the temperature sensor 6 (referred to as a measurement signal or temperature measurement signal) is input to the analysis device 3. The temperature sensor 6 is preferably disposed in contact with the detection coil Ls and directly measures the temperature of the detection coil Ls. A known temperature detector can be used as the temperature sensor 6. A contact-type temperature sensor using, but not limited to, a thermocouple, a thermistor, or the like can be used as the temperature sensor 6. Using a contact-type temperature sensor as the temperature sensor 6 can contribute to miniaturization of the position sensor 100. Note that a non-contact radiation temperature sensor may also be used as the temperature sensor 6.

[0033] As shown in FIG. 1B, the detection coil Ls is disposed facing the measurement object M, such as a metal. As indicated by the arrow in the figure, when the measurement object M moves, the distance D between the detection coil Ls and the measurement object M changes. The inductance of the detection coil Ls changes depending on the distance D. Therefore, the frequency F of the signal output from the oscillator 1 (sometimes referred to as the output frequency F) changes depending on the distance D.

[0034] The object to be measured M is not limited to metal, but may be any material that has magnetic responsiveness and that affects the inductance of the detection coil Ls disposed opposite to it.

[0035] The output of oscillator 1 is input to analysis device 3. A processing unit 4 of analysis device 3 can measure the output frequency F of oscillator 1. The processing unit 4 can measure the output frequency F, for example, by counting the number of peaks per unit time of the output signal from oscillator 1.

[0036] Correlation data indicating the relationship between the output frequency F of the oscillator 1 and the distance D is stored in the storage device 5 of the analysis device 3. The calculation processing device 4 can read the correlation data stored in the storage device 5 and calculate the distance D from the output frequency F and the correlation data. Therefore, temperature compensation can be performed on the measurement of the distance D. The analysis device 3 can output the calculated distance D as an analog signal or a digital signal from the analog signal line AO ​​or the digital signal line DO. The analysis device 3 may have both the analog signal line AO ​​and the digital signal line DO, or may have only one of the signal lines.

[0037] The detection coil Ls changes not only its electrical resistance but also its shape depending on the temperature, so the inductance of the detection coil Ls (and the output frequency F of the oscillator 1) changes depending on the temperature Ts of the detection coil Ls. As a result, the correlation between the distance D and the output frequency F also depends on the temperature Ts of the detection coil Ls. Therefore, the correlation data indicates the relationship between the distance D, the output frequency F, and the temperature Ts.

[0038] A method for acquiring the correlation data stored in the storage device 5 will be described below.

[0039] First, the temperature Ts of the detection coil Ls is kept constant (Ts = Ts1). The distance D between the measurement object M and the detection coil Ls is changed, and the output frequency F is measured. The temperature sensor 6 measures the temperature Ts1 of the detection coil Ls and outputs the temperature measurement value. The distance Di1 (i1=1 to n) is changed, and the output frequency Fi1 (i1=1 to n) is measured for each distance Di1. As a result, correlation data between the distance Di1 and the output frequency Fi1 at the temperature Ts1 can be obtained. Note that n is the number of measurement points, and is set in consideration of the expected movement range of the measurement target M, the required spatial resolution, the use of the position sensor 100, and the like.

[0040] Next, the temperature Ts of the detection coil Ls is changed and kept constant (Ts = Ts2), and correlation data between the distance Di2 (i2 = 1 to n) and the output frequency Fi2 is acquired. The temperature sensor 6 measures the temperature Ts2 of the detection coil Ls and outputs the temperature measurement value. Similarly, the temperature Ts of the detection coil Ls is changed, and k Distance Di k (i k =1~n) and output frequency Fi k Measure each temperature Ts k Distance Di k and output frequency Fi k Correlation data can be obtained. In addition, the distance Di k is preferably at each temperature Ts k (Di1=Di2=Di k )

[0041] The correlation data obtained in advance as described above is stored in the storage device 5. The correlation data is stored in, for example, a three-dimensional table (Ts k , Di k ,Fi k ) can be stored in the storage device 5. From the correlation data, regression analysis was used to calculate the temperature Ts k For each measurement, an approximation formula (for example, a polynomial) for calculating the distance D may be obtained using the output frequency F as a variable, and the approximation formula may be stored in the storage device 5. Alternatively, an approximation formula for calculating the distance D may be obtained using the temperature Ts and the output frequency F as variables, and the approximation formula may be stored in the storage device 5. For example, at each temperature Ts, an approximation formula for the distance D may be obtained as a polynomial with the output frequency F as a variable. Then, the coefficients of each degree of the obtained polynomial may be obtained as an approximation formula (e.g., a polynomial) with the temperature Ts as a variable. Each coefficient specifying the approximation formula may be stored in the storage device 5 as correlation data. The approximate formula is not limited to the above.

[0042] Furthermore, correlation data may be constructed by machine learning so that the distance D can be calculated from the temperature Ts and the output frequency F. For example, parameters that define the relationship between the distance D, the temperature Ts, and the output frequency F may be stored in the storage device 5 according to the universality theorem of neural networks. Specifically, for each temperature Ts k For each, the output frequency Fi k is the input layer, and the distance Di k may be used as the output layer, and the parameters of the neural network (weights and thresholds) may be stored as correlation data in the storage device 5. In particular, by using an easily calculated function (such as a linear function) such as a ramp function as the activation function, the distance D can be calculated by simple arithmetic operations using the acquired output frequency F. In this case, it is possible to employ an inexpensive microcomputer or the like as the analysis device 3 (or the calculation processing device 4), which can contribute to reducing manufacturing costs.

[0043] A method for the analysis device 3 to calculate the distance D from the detection coil Ls to the measurement object M will be described below.

[0044] First, the arithmetic processing unit 4 of the analysis device 3 acquires the temperature Ts from the temperature sensor 6 and the output frequency F from the oscillator 1 . Next, the calculation processing unit 4 reads out correlation data stored in the storage unit 5, which data indicates the relationship between the distance D, the temperature Ts, and the output frequency F. Next, the calculation processing device 4 can calculate the distance D from the acquired temperature Ts and output frequency F based on the correlation data. The calculated distance D is output from the analysis device 3 to the outside as a digital signal or an analog signal. The output signal including information on the distance D is input to, for example, an external computer (calculation device) or display device.

[0045] As described above, by using the correlation data, it is possible to measure the distance D with high accuracy even if the inductance of the detection coil Ls changes depending on the environmental temperature.

[0046] If the correlation data is saved as a table, the temperature Ts obtained and the temperature Ts in the vicinity (around) of the output frequency F are k and output frequency Fi k Distance Di from k The distance D corresponding to the temperature Ts and the output frequency F may be calculated by performing multiple calculations and interpolating the results.

[0047] When the ambient temperature changes, the temperature of the detection coil Ls approaches the ambient temperature over time. By arranging the temperature sensor 6 in contact with the detection coil Ls, the analysis device 3 can output an accurate distance D according to the temperature Ts even when the temperature Ts of the detection coil Ls changes.

[0048] Generally, a small temperature sensor 6 has a smaller heat capacity than the detection coil Ls. Therefore, when the temperature sensor 6 is not in contact with the detection coil Ls, there may be a difference between the temperature measured by the temperature sensor 6 and the temperature Ts of the detection coil Ls in response to changes in the ambient temperature. If the temperature measurement value of the temperature sensor 6 differs from the temperature Ts of the detection coil Ls, it may be difficult to accurately calculate the distance D. In this case, the temperature Ts of the detection coil Ls may be predicted from changes over time in the temperature measurement value of the temperature sensor 6. The temperature Ts of the detection coil Ls may be calculated using a function (referred to as a temperature prediction function) that predicts the temperature Ts of the detection coil Ls from the temperature measurement value of the temperature sensor 6. For example, the current temperature Ts of the detection coil Ls may be calculated as a predicted value as a function of multiple (past and current) temperature measurements taken by the temperature sensor 6 and the time change of the temperature measurements (for example, the time derivative of the temperature).

[0049] A temperature prediction function can be theoretically determined from the heat capacity of the temperature sensor 6 and the heat capacity of the detection coil Ls. The temperature prediction function may also be determined based on actual measurement data. For example, while changing the environmental temperature, actual measurement data consisting of the temperature Ts of the detection coil Ls and the temperature measurement value of the temperature sensor 6 placed at a distance from the detection coil Ls without contacting it can be obtained, and the temperature prediction function can be determined by regression analysis. Note that, to obtain the actual measurement data, the temperature Ts of the detection coil Ls may be measured using a separately prepared radiation thermometer or contact thermometer.

[0050] Furthermore, the current temperature Ts of the detection coil Ls may be predicted from the temperature measurement value of the temperature sensor 6 by machine learning. For example, a recurrent neural network may be used to calculate a predicted value of the current temperature Ts of the detection coil Ls from multiple (past and present) temperature measurement values ​​measured by the temperature sensor 6 at regular time intervals. The necessary parameters can be obtained using actual measurement data.

[0051] The analysis device 3 can calculate the distance D between the detection coil Ls and the object to be measured M based on the correlation data using the current temperature Ts (predicted value) of the detection coil Ls calculated from the temperature measurement value of the temperature sensor 6 and the acquired output frequency F.

[0052] By storing information about the position (position coordinates) of the detection coil Ls in the storage device 5, the analysis device 3 can read out the position information of the detection coil Ls and calculate the position of the measurement object M based on the position information and the distance D. Therefore, the position sensor 100 can also be configured to output the position of the measurement object M. The analysis device 3 can also calculate the velocity and acceleration of the object to be measured M from the change over time in the position of the object to be measured M. Therefore, the position sensor 100 can also be configured to output the velocity and acceleration of the object to be measured M.

[0053] (Embodiment 2) The position sensor 100 may include a frequency divider 2 to adjust the output frequency F from the oscillator 1. The frequency divider 2 allows the detection sensitivity of the position sensor 100 to be adjusted. FIG. 3A shows the main configuration of the position sensor 100 of the second embodiment, and FIG. 3B shows a modified example of the position sensor 100 of the second embodiment.

[0054] As shown in FIG. 3(A), the position sensor 100 further includes a frequency divider 2, and the output signal of the oscillator 1 is input to the frequency divider 2. The frequency divider 2 divides the output signal of the oscillator 1 and outputs N signals (referred to as frequency-divided signals) having different frequency division ratios (two or more) to the analysis device 3. For example, in the example shown in FIG. 3(A), AC signals (e.g., square wave signals) having different divided frequencies are output to the analysis device 3 via N=5 frequency-divided signal lines DL1, DL2, DL3, DL4, and DL5. Note that N is not limited to 5.

[0055] For example, without limitation, when an AC signal (or square wave signal) with a frequency of 100 kHz is input from oscillator 1 to divider 2, if the N=5 division ratios are 10, 100, 1000, 10000, and 100000, AC signals (or square wave signals) with frequencies of 10 kHz, 1 kHz, 100 Hz, 10 Hz, and 1 Hz are output to analysis device 3 from divided signal lines DL1, DL2, DL3, DL4, and DL5. The frequency divider 2 can be configured using a known frequency dividing circuit. For example, it is possible to output a rectangular wave from the oscillator 1 and divide it as a digital signal, or it is also possible to configure the frequency divider 2 using a logic IC.

[0056] Correlation data corresponding to each division ratio is stored in the storage device 5. The calculation processing device 4 reads out the correlation data corresponding to the division ratio from the storage device 5, and can calculate the distance D based on the correlation data using the divided frequency F' (output frequency F'), the temperature Ts, and the division ratio. The analysis device 3 can recognize the division ratio by identifying the divided signal line DLi (i = 1 to N) to which the AC signal (or square wave signal) is input. The correlation data according to the frequency division ratio can be created from the correlation data created by the method described in the first embodiment. Alternatively, only the reference correlation data before frequency division may be stored in the storage device 5, and the arithmetic processing device 4 may convert the frequency F' acquired from the frequency-divided signal lines DL1, DL2, DL3, DL4, and DL5 according to the frequency division ratio, and calculate the distance D using the above-mentioned reference correlation data.

[0057] In addition, multiple signals may be input to the analysis device 3 in parallel via multiple divided signal lines, or any one of the divided signal lines DL1 to DLN may be selected in a time-division manner to input an AC signal (or a rectangular wave signal).

[0058] The analysis device 3 can select a division ratio and adjust the acquired frequency F' in accordance with the moving speed and moving range of the measurement object M. As a result, the position detection sensitivity (spatial resolution, etc.) of the position sensor 100 can be adjusted. For example, if the moving speed of the object to be measured M is low, the division ratio can be set to a large value, for example, 100, to increase the spatial resolution (to decrease the frequency F'). Also, if the moving speed of the object to be measured M is high, the division ratio can be set to a small value, for example, 2, to decrease the spatial resolution (to increase the frequency F'). Note that the determination of the division ratio is not limited to the above example.

[0059] Furthermore, even when the moving speed of the measurement object M varies, it is possible to select an optimum division ratio and flexibly adjust the sensitivity (resolution) of the position sensor 100. For example, it is also possible to compare the values ​​of the distance D obtained with different division ratios and select the optimum division ratio (automatically or manually).

[0060] The operator may specify the division ratio to be selected for the analysis device 3. For example, the analysis device 3 may be configured so that the operator can specify the division ratio to be selected for the analysis device 3 from an IO port (not shown) of the analysis device 3. In this way, the sensitivity of the position sensor 100 can be adjusted depending on the application and situation.

[0061] As shown in FIG. 3B, the frequency divider 2 may have one frequency division signal line DL1 and may be configured to change the frequency division ratio. The division ratio can be switched according to the moving speed and moving range of the object M to be measured, and the AC signal of the oscillator 1 can be input to the analysis device 3. The analysis device 3 can calculate the distance D from the output frequency F' and temperature Ts according to the division ratio. The number of signal lines from the frequency divider 2 to the analyzer 3 is reduced, and the configuration of the position sensor 100 is simplified.

[0062] Furthermore, when the division ratio is high, there is no need to operate the analysis device 3 at a high frequency, so it is possible to contribute to power savings by reducing the operating speed of the analysis device 3 (reducing the clock frequency) according to the division ratio.

[0063] To change the output frequency, the oscillator 1 may be configured as an LC oscillator, and may be provided with a plurality of capacitors C having different capacitances, with the capacitors C being switchable by a switch. By changing the capacitance of the capacitor C, the output frequency of the oscillator 1 can be changed. However, the capacitance of the capacitor C may change depending on the ambient temperature, so it is necessary to obtain the temperature dependency of the output frequency F of the oscillator 1 for each of the multiple capacitors C provided. By using a configuration in which the output frequency F of the oscillator 1 is changed by the frequency divider 2, it is not necessary to obtain the temperature dependency of the output frequency F of the oscillator 1 for each of the plurality of capacitors C.

[0064] (Embodiment 3) The position sensor 100 may include a frequency measuring device 7 (counter) for measuring the output frequency F from the oscillator 1. 4A and 4B show the main configuration of the position sensor 100 of the third embodiment.

[0065] As shown in Fig. 4(A), the output of oscillator 1 is input to frequency measuring device 7. Frequency measuring device 7 can measure the frequency of the AC signal output from oscillator 1. Note that frequency measuring device 7 may also measure the total count number of peaks (rectangular waves) in a predetermined unit time. The frequency measuring device 7 can output the measured value of the frequency (or count value) to the analyzing device 3 as a digital signal. The analysis device 3 can calculate the distance D based on the correlation data using the output frequency F of the oscillator 1 acquired from the frequency measuring device 7 and the temperature Ts acquired from the temperature sensor 6. The frequency measuring device 7 can use a known circuit.

[0066] Since the analysis device 3 receives the value of the output frequency F as a digital value, it is less susceptible to the influence of noise compared to when the AC signal of the oscillator 1 is received directly. The detection coil Ls, oscillator 1, and frequency measuring device 7 can be arranged close to each other, and the frequency measuring device 7 can be arranged at a long distance from the analysis device 3. This can improve the noise resistance in communication between the detection coil Ls and the analysis device 3.

[0067] As shown in Fig. 4(B), a combination of a detection coil Ls, an oscillator 1, a temperature sensor 6, and a frequency measuring device 7 may be configured as a sensor module MS, and the outputs of multiple sensor modules MS may be input to a single analysis device 3. The example shown in Fig. 4(B) shows a configuration having two sensor modules MSa (first sensor module) and MSb (second sensor module). Note that the number of sensor modules MS is not limited to two. The sensor module MSa is composed of a detection coil Lsa, an oscillator 1a, a temperature sensor 6a, and a frequency measuring device 7a, and the sensor module MSb is composed of a detection coil Lsb, an oscillator 1b, a temperature sensor 6b, and a frequency measuring device 7b. The outputs from the sensor module MSa and the sensor module MSb are input to the analysis device 3. The outputs from the plurality of sensor modules MS may be input to the analysis device 3 in a time-division manner.

[0068] The position sensor 100 is capable of detecting the distance D to each of the plurality of measurement objects M. The position sensor 100 can output to the outside an output signal that combines, for each of a plurality of measurement objects M, an identification signal that identifies the measurement object M and the distance D to the measurement object M.

[0069] Instead of the frequency measuring device 7, the frequency divider 2 may be used. In an environment where the influence of noise is small, the frequency measuring device 7 may be omitted, and the sensor module MS (MSa, MSb) may be composed of the detection coil Ls, the oscillator 1, and the temperature sensor 6.

[0070] (Embodiment 4) The position sensor 100 of the fourth embodiment is configured by providing the detection coil Ls, the oscillator 1, the temperature sensor 6, the frequency divider 2, and the analyzer 3 on one substrate BS. That is, the sensor module MS can be incorporated into the substrate BS. Fig. 5 shows the main circuit configuration of the position sensor 100 of embodiment 4. Fig. 5(A) is a plan view showing the first surface of the position sensor 100, and Fig. 5(B) is a plan view showing the second surface of the position sensor 100. Figs. 5(C) and (D) show modified examples of the position sensor 100.

[0071] Note that the terms "first surface" and "second surface" are used for convenience, and one surface of the substrate BS that constitutes the support substrate of the position sensor 100 is referred to as the "first surface" and the other surface is referred to as the "second surface." In FIG. 5, the ground lines are omitted for the sake of visibility.

[0072] 5(A), a coil 9 is provided on a first surface of an insulating substrate BS (printed circuit board). The coil 9 constitutes a detection coil Ls. The coil 9 can be formed as a printed wiring by patterning a conductive film such as copper foil using a known printing technique, but is not limited to this. One end of the coil 9 is connected to a first connection hole 10 (first through-hole), and the other end is connected to a second connection hole 11 (second through-hole). The first connection hole 10 and the second connection hole 11 are through-holes that penetrate the substrate BS and are provided with a conductive material (e.g., copper) inside. The first connection hole 10 and the second connection hole 11 can electrically connect wiring and the like formed on the first and second surfaces of the substrate BS.

[0073] 5(B), an oscillator 1 and a frequency divider 2 are mounted on the second surface of the substrate BS, and a first wiring 12 and a second wiring 13 are provided. The first wiring 12 and the second wiring 13 can be configured as printed wiring using, for example, a known printing technique. The first connection hole 10 and the second connection hole 11 are electrically connected to the oscillator 1 via a first wiring 12 and a second wiring 13 . The output signal of oscillator 1 is input to frequency divider 2 via third wiring 14. The output frequency F of oscillator 1 is divided by frequency divider 2, and the output signal having output frequency F' is input to analysis device 3 via fourth wiring 15. If division of the output frequency F of the oscillator 1 is not necessary, the frequency divider 2 may be omitted.

[0074] The substrate BS is further equipped with a temperature sensor 6 and an analysis device 3. The temperature sensor 6 measures the temperature Ts of the detection coil Ls. The output of the temperature sensor 6 is input to the analysis device 3 via a fifth wiring 16. The calculation processing device 4 of the analysis device 3 uses the acquired output frequency F′ (or output frequency F) and temperature Ts, and utilizes the correlation data stored in the storage device 5 to calculate the distance D. The calculated distance D is output from the analysis device 3 (arithmetic processing device 4) as a digital signal or an analog signal.

[0075] 5(B), the temperature sensor 6 is mounted on the second surface, but it may be mounted on the first surface. The temperature sensor 6 is required only to be disposed close to the coil 9 and be able to measure the temperature of the coil 9. 5(A) and (B), the coil 9 is mounted on the first surface, and the oscillator 1, frequency divider 2, analyzer 3, and clock oscillator 8 are mounted on the second surface, but all of these components may be mounted on the first surface. If the analyzer 3 has a built-in oscillator that generates a clock signal, the clock oscillator 8 may be omitted.

[0076] The coil 9 may be formed on both the first and second surfaces. For example, a coil 9' having the same shape as the coil 9 may be formed on the second surface, and the coil 9 on the first surface and the coil 9' on the second surface may be electrically connected via a connection hole (through hole).

[0077] Each wiring is preferably formed as a printed wiring, but may be a lead wire or the like.

[0078] Since the components of the position sensor 100 are concentrated on the substrate BS, the position sensor 100 can be easily installed, and this can contribute to improving the degree of freedom in the installation location. A battery or the like may be mounted on the substrate BS as a power source. Furthermore, the analysis device 3 may output an output including the calculated distance D as a wireless signal. Similarly, in the following modified examples, a battery may be mounted on the substrate BS, further improving the degree of freedom in installing the position sensor 100.

[0079] As shown in FIG. 5(C), the detection coil Ls, the oscillator 1, and the temperature sensor 6 may be provided on the substrate BS, and the frequency divider 2 and the analyzer 3 may be provided outside the substrate BS. In this case, the third wiring 14 and the fifth wiring 16 may be configured as lead wires, or some of the third wiring 14 and the fifth wiring 16 may be configured as printed wiring on the substrate BS, and the other third wiring 14 and the fifth wiring 16 may be configured as lead wires, etc. The configuration of each wiring is not limited to the above example, and may be any configuration.

[0080] The oscillation frequency of the oscillator 1 also changes depending on the temperature, so by placing the detection coil Ls and the oscillator 1 in the same temperature environment, the distance D can be measured with high accuracy. Furthermore, it becomes possible to place the analyzer 3 (or the frequency divider 2 and the analyzer 3) in an environment with a stable temperature, and temperature fluctuations in the analyzer 3 can be prevented.

[0081] As described above, by mounting a battery or the like on the substrate BS, it is possible to independently operate the sensor modules MS each having a detection coil Ls, an oscillator 1, and a temperature sensor 6. Furthermore, by providing each sensor module MS with a detection coil Ls, an oscillator 1 corresponding to the detection coil Ls, and a temperature sensor 6, it is possible to maintain these components in the same temperature environment.

[0082] Furthermore, a storage device (referred to as an auxiliary storage device) may be implemented in the sensor module MS, and the output signal of the oscillator 1 may be stored as data together with the time in the auxiliary storage device. The analysis device 3 may read the output signal of the oscillator 1 stored in the auxiliary storage device and calculate the distance D for each corresponding time. For example, the sensor module MS may be placed facing the object to be measured, and the output signal from the oscillator 1 may be stored as data in an auxiliary storage device for a predetermined period of time. After the predetermined period has elapsed, the analysis device 3 may be connected to the auxiliary storage device, read out the data, and output and analyze the change in the distance D over the predetermined period. Furthermore, by operating the sensor module MS intermittently, it is possible to measure the change in the distance D over a long period of time. In this way, the position sensor 100 can be used not only to monitor the distance D in real time, but also to periodically observe the time transition of the distance D. Similarly, in other embodiments, the position sensor 100 can be used intermittently or continuously.

[0083] 5(D), the detection coil Ls, oscillator 1, temperature sensor 6, and frequency divider 2 may be provided on the substrate BS, and the analysis device 3 may be provided outside the substrate BS. In this case, the fourth wiring 15 and the fifth wiring 16 may be configured as lead wires, or some of the fourth wiring 15 and the fifth wiring 16 may be configured as printed wiring on the substrate BS, and the other fourth wiring 15 and the fifth wiring 16 may be configured as lead wires or the like. The configuration of each wiring is not limited to the above example, and may be any configuration.

[0084] The frequency divider 2 may be omitted, or a frequency measuring device 7 may be provided in place of the frequency divider 2.

[0085] As described above, the position sensor 100 can adopt various forms and can meet various needs regarding the position measurement of the measurement object M. The position sensor 100 may measure the position of the measurement object M continuously or may measure the position of the measurement object M intermittently. The position sensor 100 having the optimum configuration can be adopted as appropriate, taking into consideration the intended use, detection sensitivity, the environment in which the measurement object M is located, energy consumption, cost, and the like.

[0086] In any of the embodiments, when a plurality of detection coils Ls are arranged close to each other, one temperature sensor 6 may measure the temperatures of the plurality of detection coils Ls.

[0087] (Embodiment 5) In the pressure sensor 600 of the fifth embodiment, the resistance change of the strain gauge RG is converted into a change in the oscillation frequency, thereby making it possible to detect pressure. Hereinafter, the pressure sensor 600 of the fifth embodiment will be described with reference to the drawings. FIG. 6A shows the main circuit configuration of the pressure sensor 600. FIG. 6B is a schematic diagram showing a specific example of the configuration of the sensor module MS'.

[0088] 6(A), the pressure sensor 600 includes a sensor module MS' and an analysis module MA. The sensor module MS' includes a strain gauge RG and an oscillator 61 (also called a detection oscillator), and the analysis module MA includes an analysis device 63. The sensor module MS' and the analysis module MA are electrically connected by a sensor cable SC. The strain gauge RG is a measuring resistor whose resistance value changes in response to strain, and is, for example, a resistor made of a metal film or semiconductor film with a zigzag shape. A commercially available strain gauge can also be used as the strain gauge RG. The sensor module MS′ may include a temperature sensor 66 for measuring the temperature of the strain gauge RG. The temperature measurement value of the temperature sensor 66 is output to the analysis device 63.

[0089] The sensor module MS' and the analysis module MA are each supplied with power from a power supply (not shown). For example, a power line may be provided within the sensor cable SC, allowing power to be supplied to the sensor module MS' from an external power supply.

[0090] The strain gauge RG is connected to an oscillator 61 by a lead wire LW. The oscillator 61 outputs an AC signal (sometimes referred to as an oscillation signal) having an oscillation frequency according to the resistance value of the strain gauge RG, and the sensor module MS' constitutes a self-excited oscillator. The oscillator 61 can be, for example, a known RC type oscillator. The oscillation signal output from the oscillator 61 is, for example, a square wave, a sine wave, or the like, and is preferably output as a square wave that can be easily processed by a digital circuit.

[0091] FIG. 7 shows a non-limiting example of an oscillator 61. The oscillator 61 may be configured similarly to the oscillator 1 shown in FIG. 2. The oscillator 61 may be configured using, for example, an inverter. FIG. 7(A) shows an oscillator circuit using two inverters IA1 and IA2, and FIG. 7(B) shows an oscillator circuit using a Schmitt trigger inverter IB1. In the figure, the symbol R represents a resistor, and the symbols D1 and D2 represent diodes. The oscillator 61 is supplied with DC power from a power source PW. 7(A) and (B) can output a square wave with a frequency that corresponds to the resistance value of the strain gauge RG and the capacitance of the capacitor C. The capacitance of the capacitor C is fixed, and the frequency F' of the output signal changes in response to changes in the resistance value of the strain gauge RG.

[0092] An output signal from the oscillator 61 of the sensor module MS' is input to the analysis device 63 of the analysis module MA via the sensor cable SC. The analysis device 63 includes a processing unit 64 and a storage device 65. The analysis device 63 can be configured, for example, by a microcomputer having a CPU and memory. The storage device 65 can be, but is not limited to, a known storage device that can be written to and read from by, for example, electromagnetic means. It should be noted that communication between the sensor module MS' and the analysis module MA is not limited to wired communication via the sensor cable SC, but may be wireless communication.

[0093] The pressure sensor 600 may include a clock oscillator 68, such as a crystal oscillator, for a clock signal for the analysis device 63. Alternatively, the analysis device 63 itself may have a built-in clock oscillator 68.

[0094] The temperature sensor 66 is disposed in proximity to the strain gauge RG and measures the temperature of the strain gauge RG. The output of the temperature sensor 66 (sometimes referred to as a temperature measurement signal) is input to the analysis device 63. The temperature sensor 66 is disposed, for example, in contact with the first support part 21 that supports the diaphragm 24 described below. A known temperature sensor can be used as the temperature sensor 66. As the temperature sensor 66, a contact type temperature sensor using, but not limited to, a thermocouple, a thermistor, or the like can be used.

[0095] FIG. 6B is a schematic diagram showing a configuration corresponding to the sensor module MS' of the pressure sensor 600, hereinafter referred to as a pressure measurement module, and shows an example of a form applicable to an actual fluid pressure circuit or the like.

[0096] 6(B), the strain gauge RG is fixed to a diaphragm 24, which is a pressure receiving part, and the diaphragm 24 is fixed to the first support part 21. The diaphragm 24 may be formed integrally with the first support part 21. The first support portion 21 can be connected to, for example, a pipe or the like that constitutes a fluid circuit by a known joint or the like.

[0097] The pressure measurement module has a second support part 22, and the second support part 22 has a substrate 25 on which an oscillator 61 is mounted. The second support part 22 is fixed to the first support part 21. As a result, the strain gauge RG is housed in the space S surrounded by the first support portion 21 and the second support portion 22. The diaphragm 24 deforms in response to the pressure difference between the fluid pressure P applied to the diaphragm 24 and the internal pressure of the space S. The space S may be kept airtight and the internal pressure of the space S may be kept constant, or a through-hole communicating with the outside may be provided in the second support portion 22 to make the pressure the same as the surrounding environment. The first support portion 21 and the second support portion 22 may be fixed together by screws, crimping, or welding.

[0098] The strain gauge RG on the diaphragm 24 is electrically connected to the oscillator 61 by a lead wire LW. For example, the oscillator 61 may be provided on the surface of the substrate 25 facing the diaphragm 24 (referred to as the back surface), and the strain gauge RG and the oscillator 61 may be connected by a lead wire LW, or the oscillator 61 may be mounted on the surface opposite the back surface of the substrate 25 (referred to as the front surface), a through hole may be provided in the substrate 25, and the lead wire LW may be connected to the oscillator 61 through the through hole. A connector may be mounted on the substrate 25 to connect the lead wire LW to the oscillator 61 .

[0099] The first support part 21 may have a flange part 211. The position of the second support part 22 is determined by contacting the end part 221 of the second support part 22 with the flange part 211. The outer wall surface 21S of the first support part 21 and the inner wall surface 22S of the second support part 22 may be configured to contact each other to prevent the intrusion of foreign matter from the outside.

[0100] The pressure measurement module has a third support portion 23, and a cable through-hole 231 of the third support portion 23 supports the sensor cable SC. The sensor cable SC is connected to the output of the oscillator 61 and is connected to an analysis device 63 arranged outside the third support part 23 via a cable through-hole 231 . The third support part 23 is fixed to the second support part 22 so as to cover the substrate 25, and protects the oscillator 61. The sensor cable SC may be airtightly sealed in the cable through hole 231, and the space S may be kept airtight.

[0101] The pressure measurement module can be easily manufactured by assembling the second support part 22 and the third support part 23 to the first support part 21 and wiring the lead wires LW and the sensor cable SC.

[0102] 6(B), when the diaphragm 24 is deformed by the fluid pressure P (hereinafter referred to as pressure P), the resistance value of the strain gauge RG changes. As a result, the frequency F' of the signal output from the oscillator 1 (more specifically, referred to as output frequency F') changes according to the pressure P.

[0103] The output of oscillator 61 is input to analyzer 63. A processing unit 64 of analyzer 63 can measure the output frequency F' of oscillator 61. The processing unit 64 can measure the output frequency F', for example, by counting the number of peaks per unit time of the output signal from oscillator 61.

[0104] The storage device 65 of the analysis device 63 stores correlation data that indicates the relationship between the output frequency F' of the oscillator 61 and the pressure P. The calculation processing device 64 reads the correlation data and can calculate the pressure P from the output frequency F' and the correlation data.

[0105] The analysis device 63 can output the calculated pressure P as an analog signal or a digital signal from an analog signal line AO ​​or a digital signal line DO. The analysis device 63 may have both the analog signal line AO ​​and the digital signal line DO, or may have only one of the signal lines.

[0106] Furthermore, the resistance value of the strain gauge RG (and the output frequency F of the oscillator 61) changes depending on the temperature Tr of the strain gauge RG. As a result, the correlation between the pressure P and the output frequency F' also depends on the temperature Tr of the strain gauge RG. Therefore, the correlation data indicates the relationship between the pressure P, the output frequency F', and the temperature Tr. Based on the temperature measured by the temperature sensor 66, temperature compensation can be performed on the measurement of the pressure P.

[0107] The method of acquiring the correlation data stored in the storage device 65 is the same as that of the position sensor 100 using the detection coil Ls. By changing the pressure P and measuring the output frequency F' for each temperature Tr of the strain gauge RG, the correlation data between the pressure P and the output frequency F' at each temperature Tr can be acquired. In order to distinguish it from the correlation data for the position sensor 100, the correlation data for the position sensor 100 will be referred to as distance correlation data, and the correlation data for the pressure sensor 600 will be referred to as stress correlation data. Alternatively, an approximation formula that can approximate the correlation between the pressure P and the output frequency F′ may be found, and parameters that specify the approximation formula may be stored in the storage device 65 as stress correlation data.

[0108] Hereinafter, a method for the analysis device 63 to calculate the pressure P from the strain gauge RG will be described.

[0109] The arithmetic processing unit 64 of the analysis device 63 acquires the temperature Tr from the temperature sensor 66 and the output frequency F′ from the oscillator 61 . Next, the processing unit 64 reads out the stress correlation data stored in the storage unit 65 . Next, the calculation processing device 64 calculates the pressure P from the acquired temperature Tr and output frequency F' based on the stress correlation data. The calculated pressure P can be output from the analysis device 63 to the outside as a digital signal or an analog signal. The output signal including information on the pressure P is input to, for example, an external computer (e.g., a fluid control device, etc.) or a display device.

[0110] As described above, by using the stress correlation data, it is possible to measure the pressure P with high accuracy even when the resistance value of the strain gauge RG changes depending on the environmental temperature or the like.

[0111] In addition, if the stress correlation data is saved as a table, the temperature Tr obtained and the temperature Tr in the vicinity (before and after) of the output frequency F' are k and output frequency Fi k Pressure Pi kThe pressure P corresponding to the temperature Tr and the output frequency F may be calculated by calculating multiple values ​​and interpolating them.

[0112] As described above, the analysis device 63 can calculate the pressure P by digital processing and output it to the outside. Furthermore, the analysis device 63 can also perform temperature compensation for the measurement of the pressure P by digital processing. Therefore, the pressure sensor 600 can measure pressure with high accuracy and also enable temperature compensation without requiring a strain gauge with a complex circuit configuration for improving detection sensitivity or temperature compensation.

[0113] Generally, in a fluid pressure circuit, pressure sensors are installed at multiple positions to monitor the pressure of the fluid. The sensor module MS' (specifically, the pressure measurement module) and the analysis module MA are electrically connected by a sensor cable SC. Therefore, it is possible to install only the sensor modules MS' at multiple positions and aggregate the output signals from the multiple sensor modules MS' into a single independent analysis module MA. The analysis module MA can monitor the pressure at multiple positions simultaneously. Furthermore, by inputting the pressure at each position output from the analysis module MA to a fluid control device that controls the fluid pressure circuit, it is possible to contribute to the control of the fluid pressure circuit. By sharing the analysis module MA, the configuration of each sensor module MS' can be simplified, which can contribute to reducing the labor required for monitoring the overall pressure of a fluid pressure circuit or the like.

[0114] In the conventional method of converting the slight resistance change of a strain gauge into a voltage change, when the output voltage is transmitted through a signal cable, a voltage drop can occur within the signal cable, making it difficult to monitor the outputs of multiple pressure sensors remotely by collecting them into a single analysis device. As described above, the analysis module MA digitally processes the signals converted to frequencies by the sensor modules MS', making it possible to monitor the pressure values ​​measured by multiple sensor modules MS' from a location remote from the sensor modules MS'.

[0115] Furthermore, by providing the analysis module MA with an input signal selection circuit (such as a multiplexer) as an interface circuit, it is possible to select a specific sensor module MS' from the multiple sensor modules MS' and input the signal from the selected sensor module MS' to the analysis device 63. The analysis module MA can measure the pressure P at any specific position. For example, the fluid circuit control device can select input signals using a selection circuit in accordance with the control algorithm of the fluid pressure circuit, and obtain pressure measurement values ​​at required positions in the required order via the analysis module MA.

[0116] (Embodiment 6) Similar to the position sensor 100 of the second embodiment, the pressure sensor 600 may include a frequency divider 62 to adjust the output frequency F' from the oscillator 61. The frequency divider 62 makes it possible to adjust the detection sensitivity of the pressure sensor 600, and the same effects as those of the second embodiment can be obtained. FIG. 8(A) shows the main configuration of a pressure sensor 600 according to the sixth embodiment, and FIG. 8(B) shows a modified example of the pressure sensor 600 according to the sixth embodiment.

[0117] As shown in FIG. 8(A), the pressure sensor 600 further includes a frequency divider 62, and the output signal of the oscillator 61 is input to the frequency divider 62. The frequency divider 62 divides the output signal of the oscillator 61 and outputs N signals (referred to as frequency-divided signals) having different frequency division ratios (two or more) to the analysis device 63. For example, in the example shown in FIG. 8(A), AC signals (e.g., square wave signals) having different divided frequencies are output to the analysis device 63 via N=5 frequency-divided signal lines DL1, DL2, DL3, DL4, and DL5. Note that N is not limited to 5.

[0118] The storage device 65 stores stress correlation data corresponding to each division ratio. The calculation processing device 64 reads out the stress correlation data corresponding to the division ratio from the storage device 65, and can calculate the pressure P based on the correlation data using the divided frequency Fd' (output frequency Fd'), the temperature Tr, and the division ratio. The analysis device 63 can recognize the division ratio by identifying the divided signal line DLi (i = 1 to N) to which the AC signal (or square wave signal) is input.

[0119] In addition, multiple signals may be input to the analysis device 63 in parallel via multiple divided signal lines, or any one of the divided signal lines DL1 to DLN may be selected by time division to input an AC signal (or a rectangular wave signal).

[0120] The analysis device 63 can select a frequency division ratio and adjust the frequency Fd' to be acquired in accordance with the fluctuation range of the pressure P. As a result, the pressure detection sensitivity of the pressure sensor 600 can be adjusted.

[0121] By selecting an optimum division ratio, it is possible to flexibly adjust the sensitivity (resolution) of the pressure sensor 600. For example, it is also possible to compare the values ​​of pressure P obtained by different division ratios and select the optimum division ratio (automatically or manually).

[0122] The operator may specify the division ratio to be selected for the analysis device 63. For example, the analysis device 63 may be configured so that the operator can specify the division ratio to be selected for the analysis device 63 from an IO port (not shown) of the analysis device 63. In this way, the sensitivity of the pressure sensor 600 can be adjusted depending on the application and situation.

[0123] As shown in FIG. 8B, the frequency divider 62 may have one frequency division signal line DL1 and may be configured to change the frequency division ratio. The frequency division ratio can be switched according to the fluctuation range of the pressure P, and the AC signal of the oscillator 61 can be input to the analysis device 63. The analysis device 63 can calculate the pressure P from the output frequency Fd' and the temperature Tr according to the frequency division ratio. The number of signal lines from the frequency divider 62 to the analysis device 63 is reduced, and the configuration of the pressure sensor 600 is simplified.

[0124] (Embodiment 7) The sensor module MS′ of the pressure sensor 600 may include a frequency measuring device 67 (or a counter) for measuring the output frequency F′ from the oscillator 61. FIG. 9 shows the main configuration of a pressure sensor 600 according to the seventh embodiment.

[0125] 9, the output of oscillator 61 is input to frequency measuring device 67. Frequency measuring device 67 can measure the frequency of the AC signal output from oscillator 61. Note that frequency measuring device 67 may also measure the total count number of peaks (rectangular waves) in a predetermined unit time. The frequency measuring device 67 can output the measured frequency value to the analyzing device 63 as a digital signal. The analysis device 63 can calculate the pressure P based on the correlation data using the output frequency F′ of the oscillator 61 acquired from the frequency measuring device 67 and the temperature Tr acquired from the temperature sensor 66. The frequency measuring device 67 can be a known circuit.

[0126] Since the analyzer 63 receives the value of the output frequency F' as a digital value, it is less susceptible to the influence of noise compared to when it receives the AC signal of the oscillator 61 directly. Although the sensor module MS' is complicated, the sensor module MS' of the seventh embodiment can be suitably employed, for example, when the fluid pressure circuit is located in an environment where electrical noise is particularly large.

[0127] (Embodiment 8) FIG. 10(A) is a cross-sectional view that schematically shows a compressor 300 incorporating the position sensor 100, and FIG. 10(B) is a top view of the cylinder bottom 41b. The compressor 300 shown in Fig. 10 is an example of a reciprocating compressor. The compressor 300 has a cylinder 41, a piston 42, and a rod 43. The cylinder 41 has a cylinder top 41a and a cylinder bottom 41b. The portion of the cylinder 41 other than the cylinder top 41a and the cylinder bottom 41b may be referred to as a cylinder main body. The position sensor 100 may be incorporated into, for example, an actuator driven by fluid pressure.

[0128] 11(A) and (B) show an example of the configuration of the position sensor 100 incorporated into the compressor 300. 11(A), an oscillator 1 and a temperature sensor 6 are mounted on a substrate BS. The detection coil Ls and the oscillator 1 provided on the substrate BS constitute a sensor module MS. 11(B), an oscillator 1, a temperature sensor 6, and a frequency measuring device 7 are mounted on a substrate BS. The oscillator 1 and the frequency measuring device 7 constitute a sensor module MS. The temperature sensor 6 may not be mounted on the substrate BS but may be arranged separately, for example, near the detection coil Ls, and connected to the analysis device 3 independently of the sensor cable SC. For example, the temperature sensor 66 may be sealed in the coil support part 44 near the detection coil Ls.

[0129] The cylinder bottom 41b is provided with a coil support part 44, which seals the detection coil Ls and the substrate BS and fixes them to the cylinder bottom 41b. The coil support part 44 is made of, for example, a pressure-resistant molded resin, but the material of the coil support part 44 is not limited to resin. The detection coil Ls and the oscillator 1 are electrically connected by a lead wire LW (not shown).

[0130] 5(C) and 5(D), the detection coil Ls may be mounted on the substrate BS, and the detection coil Ls and the oscillator 1 may be connected using the first wiring 12 and the second wiring 13 arranged on the substrate BS as lead wires LW. The detection coil Ls may be integrated with the oscillator 1 and sealed in the coil support part 44.

[0131] The sensor cable SC is electrically connected to the oscillator 1 through an opening provided in the cylinder bottom 41b. The oscillation signal output from the oscillator 1 is output to an analysis module MA provided outside the cylinder 41 via a sensor cable SC.

[0132] The rod 43 is connected to the piston 42, and power is transmitted between the rod 43 and the piston 42. The piston 42 reciprocates within the cylinder 41 between a cylinder top 41a and a cylinder bottom 41b. The sensor module MS outputs an oscillation signal having a frequency that corresponds to the distance D between the metal piston 42 and the detection coil Ls. When a frequency measuring device 7 as shown in FIG. 11(B) is provided on the substrate BS, the frequency of the oscillation signal is output to the analysis module MA as a digital signal.

[0133] As the piston 42 approaches the cylinder bottom 41 b , the fluid between the piston 42 and the cylinder bottom 41 b is compressed and discharged through the pipe 45 . By providing a sensor module MS' (specifically, a pressure measurement module) for measuring the pressure P of the fluid in the pipe 45, the value of the pressure P of the discharged fluid can be measured. The position of the pipe 45 is not limited to the example shown in FIG. 10(A). In addition, in order to measure the pressure P inside the cylinder 41, a sensor module MS' may be provided on the coil support portion 44.

[0134] 12 is a schematic diagram showing the circuit configuration of an integrated sensor 500 for measuring different physical quantities. The position sensor 100 can be integrated with a pressure sensor 600 to form the integrated sensor 500. The integrated sensor 500 includes at least one sensor module MSa (hereinafter referred to as a first sensor module MSa), at least one sensor module MSb (hereinafter referred to as a second sensor module MSb), and an analysis module MA. The outputs of the first sensor module MSa and the second sensor module MSb are connected to the analysis module MA via a sensor cable SC. The first sensor module MSa is a sensor module for measuring pressure, ie, a pressure measurement module, and the second sensor module MSb is a sensor module for measuring distance, ie, a distance measurement module. From the first sensor module MSa and the second sensor module MSb, oscillation signals having frequencies corresponding to the respective physical quantities, specifically pressure and distance, are input to the analysis module MA. The first sensor module MSa and the second sensor module MSb can employ the sensor modules MS described in the above embodiments.

[0135] It should be noted that the physical quantity is reflected in the frequency, and the width of the voltage output from the first sensor module MSa and the second sensor module MSb is both set to a voltage that can be received by the analysis module MA.

[0136] The memory device 65 of the analysis device 63 constituting the analysis module MA stores first correlation data indicating the correlation between the first output frequency, which is the frequency of the first oscillation signal output from the first sensor module MSa, and the pressure, which is the object of measurement of the first sensor module MSa, and second correlation data indicating the correlation between the second output frequency, which is the frequency of the second oscillation signal output from the second sensor module MSb, and the distance, which is the object of measurement of the second sensor module MSb. That is, correlation data is stored for each of the sensor modules MSa and MSb.

[0137] The calculation processing device 64 constituting the analysis module MA can read the first correlation data and the second correlation data corresponding to the first output frequency and the second output frequency, and calculate the pressure and distance, which are physical quantities corresponding to the first sensor module MSa and the second sensor module MSb.

[0138] The first correlation data may be correlation data indicating the relationship between a first temperature measurement value, which is a measurement value of a first temperature sensor included in the first sensor module MSa, the first output frequency, and the fluid pressure P, and the second correlation data may be correlation data indicating the relationship between a second temperature measurement value, which is a measurement value of a second temperature sensor included in the second sensor module MSb, the second output frequency, and the distance D. The analysis module MA receives the first output frequency and the first temperature and the second output frequency and the second temperature as inputs, and can calculate temperature-corrected fluid pressure P and distance D based on the first correlation data and the second correlation data. The calculated distance D allows the position of the piston 42 relative to the detection coil Ls to be determined.

[0139] In this way, it is possible to digitally process the frequencies of the oscillation signals corresponding to the different physical quantities of the measurement target using a single analysis module MA, thereby realizing an integrated sensor 500. The output from the analysis module MA can also be output serially via a single output cable. For example, the measurement data may be output as a digital signal together with an identifier that identifies the physical quantity. The output signal from the first sensor module MSa and the output signal from the second sensor module MSb are input serially to one analysis module MA in a time-division manner, and the analysis module MA can calculate the pressure P and distance D using correlation data corresponding to each output signal.

[0140] The first sensor module MSa and the second sensor module MSb enable the common analysis module MA to measure both the pressure P of the fluid discharged from the compressor 300 and the distance D between the piston 42 and the cylinder bottom 41b. By using the integrated sensor 500, it becomes possible to measure the pressure in conjunction with the movement of the piston 42. As a result, it becomes possible to control the pressure of the fluid pressure circuit while checking whether the fluid pressure circuit is operating normally.

[0141] The number of first sensor modules MSa and second sensor modules MSb connected to the analysis module MA is arbitrary. The first sensor modules MSa and / or second sensor modules MSb can be provided at multiple locations in the fluid pressure circuit. It is also possible to select the first sensor module MSa and / or second sensor module MSb at the location to be measured using a selection circuit or the like according to the pressure control flow of the fluid pressure circuit, and measure the physical quantity in the analysis module MA. The fluid pressure and piston position can be measured together, and the state of the compressor 300 and the fluid pressure can be measured in association with each other, allowing the operating status of the fluid pressure circuit to be monitored in real time. The output from the analysis module MA can also be fed back to pressure control of the fluid pressure circuit. For example, it can also contribute to controlling the position and movement speed of the piston 42.

[0142] Since the integrated sensor 500 can output signals for a plurality of physical quantities to be measured through a single output cable, the number of output cables can be reduced. The integrated sensor 500 can be applied to fluid pressure devices having many actuators and sensors, such as robots, and can reduce the number of output cables, contributing to the miniaturization of the device.

[0143] (Embodiment 9) 13 is a cross-sectional view schematically illustrating a compressor 301 according to a ninth embodiment incorporating the position sensor 100. The compressor 301 is an example of a reciprocating compressor. Although the compressor 301 will be described as an example, it may also be an actuator driven by fluid pressure.

[0144] The compressor 301 has a cylinder 41, a piston 42, and a rod 43. The cylinder 41 has a cylinder top 41a and a cylinder bottom 41b. The portion of the cylinder 41 other than the cylinder top 41a and the cylinder bottom 41b is referred to as a cylinder main body. In the example shown in Fig. 13, the cylinder top 41a and the cylinder main body are integrally formed.

[0145] The cylinder bottom 41b is provided with a coil support portion 44. The coil support portion 44 supports the detection coil Ls. The detection coil Ls is configured, for example, in the shape of a hollow solenoid. A lead wire LW is connected to the detection coil Ls, and the lead wire LW is electrically connected via a coil support portion 44 to a second sensor module MSb, which is a distance measurement module.

[0146] The rod 43 is connected to the piston 42, and power is transmitted between the rod 43 and the piston 42. The piston 42 reciprocates within the cylinder 41 between a cylinder top 41a and a cylinder bottom 41b. When the piston 42 moves, pressure can be applied to a fluid, such as oil, water, or air, that fills the space between the piston 42 and the cylinder 41 . In the case of an actuator, the piston 42 moves due to the pressure of the fluid flowing in and out of the space between the piston 42 and the cylinder 41. (The same applies to the example of embodiment 8.)

[0147] The piston 42 is provided with a target TG made of metal, for example, copper. As the piston 42 moves, the target TG moves within the area surrounded by the detection coil Ls. The piston 42 is provided with an extension 46. The extension 46 is configured to surround the detection coil Ls, prevents the piston 42 from colliding with the detection coil Ls and damaging the detection coil Ls, and functions as a coil protector.

[0148] When the target TG moves, the inductance of the detection coil Ls changes depending on the position of the target TG. The second sensor module MSb outputs a second oscillation signal having a frequency corresponding to the inductance of the detection coil Ls to the analysis module MA via the sensor cable SC. As a result, the analysis module MA can calculate the distance between the piston 42 and the cylinder bottom 41b. The second sensor module MSb may be provided inside the coil support portion 44.

[0149] A first sensor module MSa, which is a pressure measurement module that measures the fluid pressure P, is provided in a pipe 45 that communicates with the space between the piston 42 and the cylinder 41. The pressure P in the space between the piston 42 and the cylinder 41 can be measured using the first sensor module MSa.

[0150] The first oscillation signal of the first sensor module MSa and the second oscillation signal of the second sensor module MSb can be output to the analysis module MA. With this configuration, the analysis module MA can simultaneously measure the position of the piston 42 and the fluid pressure P. The calculated position of the piston 42 and the fluid pressure P can be used to control the compressor 301. When the compressor 301 is used as an actuator, the calculated position of the piston 42 and the pressure P of the fluid can also be used to control the actuator. [Industrial Applicability]

[0151] According to the present invention, it is possible to obtain a position sensor that can accurately measure the position of a measurement object M in accordance with temperature changes in the environment in which the sensor is placed. Furthermore, it is possible to configure position sensors to suit various applications, and the industrial applicability is high. Furthermore, according to the present invention, a pressure sensor using a strain gauge can be provided, and further, different physical quantities such as pressure and distance can be easily measured using a single analysis module, making it possible to reduce the number of cables for the sensor output. The integrated sensor can be suitably used in robots and the like that require complex movements driven by fluid pressure, and can be used for a variety of purposes. [Explanation of symbols]

[0152] 100 Position Sensor 1. Oscillator (detection oscillator) 2 frequency divider 3 Analysis device 4. Processing Unit 5 Storage device 6 Temperature Sensor 7 Frequency measuring instrument (counter) 8 Clock oscillator 9 coils 10 First connection hole (first through hole) 11 Second connection hole (second through hole) 12 First Wire 13 Second wiring 14 Third Wire 15 Fourth Wire 16 The fifth wire 21 First support 211 Flange 21S Exterior wall surface 22 Second support 22S inner wall 23 Third support 231 Cable Through Hole 24 diaphragm 25 boards 41 cylinders 41a Cylinder top 41b Cylinder bottom 42 Piston 43 Rod 44 Coil support 45 Piping 46 Extension 61 Oscillator (detection oscillator) 62 Frequency divider 63 Analyzer 64 Processing Unit 65 Storage device 66 Temperature Sensor 67 Frequency measuring instrument (counter) 68 Clock Oscillator 300, 301 compressors 500 Integrated Sensors Ls detection coil M Measurement object IA1, IA2 inverters IB1 Schmitt Trigger Inverter C capacitor R resistor D1, D2 diodes PW power supply BS board (printed circuit board) Ts temperature F, F' output frequency D distance AO Analog signal line DO Digital signal line MS Sensor Module MSa sensor module (first sensor module) MSb Sensor Module (Second Sensor Module) MS' sensor module LW lead wire P fluid pressure RG strain gauge S space SC sensor cable TG Target Tr temperature

Claims

1. It comprises a detection coil positioned facing the object to be measured, a temperature sensor, an oscillator, a processing unit, and a memory device. The oscillator outputs an oscillation signal having a frequency corresponding to the inductance of the detection coil. The temperature sensor outputs a measurement signal corresponding to the temperature of the detection coil. The storage device holds correlation data showing the relationship between the distance between the object to be measured and the detection coil, the frequency, and the temperature of the detection coil. The arithmetic processing unit receives the oscillation signal and the measurement signal, and outputs the distance based on the correlation data. The detection coil, the temperature sensor, and the oscillator are mounted on the same circuit board. A position sensor characterized by the following features.

2. Furthermore, equipped with a frequency divider, The oscillation signal from the oscillator is divided by the frequency divider and output to the arithmetic processing unit. The position sensor according to claim 1, characterized by its features.

3. The position sensor according to claim 2, characterized in that the frequency divider outputs two or more output signals with different frequency division ratios to the arithmetic processing unit.

4. The position sensor according to claim 2, characterized in that the frequency divider switches between two or more output signals with different frequency division ratios and outputs them to the arithmetic processing unit.

5. Furthermore, equipped with a frequency measuring instrument, The position sensor according to claim 1, characterized in that the frequency measuring instrument outputs the measured value of the frequency of the oscillation signal to the arithmetic processing unit.

6. The processing unit calculates a predicted value for the temperature of the detection coil from the measurement signal. The predicted value is used as the temperature of the detection coil, and the distance is output based on the correlation data. The position sensor according to claim 1, characterized by its features.

7. It is equipped with a pressure measurement module, a distance measurement module, and an analysis module. The pressure measurement module outputs a signal having a first output frequency corresponding to the fluid pressure to the analysis module. The distance measurement module outputs a signal having a second output frequency corresponding to the distance to the object to the analysis module. The analysis module includes first correlation data showing the relationship between the first output frequency and the fluid pressure, and second correlation data showing the relationship between the second output frequency and the distance. The analysis module calculates the fluid pressure based on the first correlation data and the first output frequency output by the pressure measurement module. An integrated sensor characterized by calculating the distance based on the second correlation data and the second output frequency output by the distance measurement module.

8. A detection coil positioned facing the object to be measured, a temperature sensor, an oscillator, a processing unit, and a storage device, The oscillator outputs an oscillation signal having a frequency corresponding to the inductance of the detection coil. The temperature sensor outputs a measurement signal corresponding to the temperature of the detection coil. The storage device holds correlation data showing the relationship between the distance between the object to be measured and the detection coil, the frequency, and the temperature of the detection coil. The arithmetic processing unit receives the oscillation signal and the measurement signal, and outputs the distance based on the correlation data. Furthermore, equipped with a frequency divider, The oscillation signal from the oscillator is divided by the frequency divider and output to the arithmetic processing unit. The frequency divider outputs two or more output signals with different division ratios to the arithmetic processing unit. A position sensor characterized by the following features.

9. The position sensor according to claim 8, characterized in that the detection coil, the temperature sensor, and the oscillator are mounted on the same substrate.

10. The arithmetic processing unit calculates a predicted value for the temperature of the detection coil from the measurement signal, The predicted value is used as the temperature of the detection coil, and the distance is output based on the correlation data. The position sensor according to claim 8, characterized in that it is a position sensor.

Images