JP2002107250A - Pressure gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure gauge having compact and simple structure and allowing easy temperature characteristic compensation so as to detect a very small displacement corresponding to a pressure with high resolution. SOLUTION: A sensor coil L1 excited by an alternating current signal is arranged with no contact in the proximity of a magneto-responsive material 11, which is displaced in conjunction with a diaphragm 301 displaced by application of a pressure to be detected. A temperature compensation coil L2 is connected in series to the sensor coil L1, and from the connection point between them, an output varied according to an impedance change in the sensor coil is taken out for the sensor coil. When the output for the sensor coil and a predetermined reference voltage are computed, at least two alternating current output signals having a predetermined periodic amplitude function as an amplitude coefficient are generated. On the basis of the alternating current output signals, a very small displacement of the diaphragm is detected as a phase change, and a pressure can be detected with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure gauge and, more particularly, to a position detector of a type which outputs an output AC signal showing amplitude function characteristics of a plurality of phases based on excitation by a single-phase AC signal according to a detection target position. The present invention relates to a device using the device, and more particularly, to a device in which the configuration of a detection unit including a sensor coil is simplified.

[0002]

2. Description of the Related Art There is a differential transformer as a conventionally known inductive linear position detecting device. The differential transformer excites one primary winding in one phase, and performs differential operation in accordance with a linear position of an iron core interlocking with a detection target position at each arrangement position of two differentially connected secondary windings. This causes reluctance to change gradually, and the voltage amplitude level of the resulting one-phase inductive output AC signal indicates the linear position of the iron core. In this differential transformer, only in a range where two secondary windings provided so that an induced voltage changes differentially are provided, only in a range where the induced voltage value shows linearity with respect to a paired linear position. The linear position cannot be detected, and the function of the change of the induced voltage value versus the linear position does not change over one cycle of a periodic function (for example, a trigonometric function such as a sine function). Therefore, the only way to extend the detectable range is to increase the winding length and the core length. There is a natural limit and the size of the device is increased. Further, it is impossible to obtain an output indicating an electrical phase correlated with the position of the detection target straight line.
Further, the voltage amplitude level of the inductive output signal is easily affected not only by the linear position of the iron core but also by the surrounding environment such as a temperature change, so that there is a difficulty in accuracy.

On the other hand, there is also known a phase shift type inductive linear position detecting device which outputs an AC signal having an electric phase angle correlated with a linear position to be detected. For example, Japanese Patent Application Laid-Open Nos.
No. -106065, Japanese Patent Application Laid-Open No. 55-13891 and Japanese Utility Model Publication No. 1-25286. In this type of conventionally known phase-type inductive linear position detecting device, for example, two primary windings, which are displaced from each other with respect to the direction of linear displacement of the movable iron core linked to the position to be detected, are electrically connected to each other. Excitation is performed by two-phase alternating-current signals (for example, sin ωt and cos ωt), each of which is shifted in phase.
One secondary output signal is generated by synthesizing the secondary-side induction signal from the secondary winding. The electrical phase shift in the secondary output signal with respect to the excitation AC signal indicates the linear position of the iron core linked to the position to be detected.
Further, in the structure disclosed in Japanese Utility Model Publication No. 1-25862, a plurality of iron cores are intermittently repeated at a predetermined pitch to detect a linear position over a wider range than a range where primary and secondary windings are provided. Is possible.

[0004]

The above-described conventional phase-shift-type inductive linear position detecting device has many advantages over the differential transformer, but at least two advantages are obtained.
Since the phase AC signals (for example, sin ωt and cos ωt) must be prepared, there is a problem that the configuration of the excitation circuit becomes complicated. Another problem is that if the impedances of the primary and secondary windings change due to a temperature change or the like, an error occurs in the electrical phase shift in the secondary output signal. Further, when a plurality of iron cores are intermittently repeated at a predetermined pitch to enable linear position detection over a wider range than the range in which the primary and secondary windings are provided, the primary and secondary windings are provided. Is set to the range of the movable core 1
Since it must be provided in a range longer than the pitch length,
The size of the entire winding assembly has been increased, and there has been a limit to miniaturization of the detection device. That is, assuming that the length of one pitch of the iron core is P, in the case of the four-phase type, the arrangement interval of each phase winding must be at least “3P / 4”, and the total is “4P”, which is four times as large. × (3P / 4) = 3P ”
Therefore, the winding assembly must be provided over a range of at least three pitches of the movable core.

[0005] The above-described conventional apparatus has a complicated detector configuration. In order to solve this problem, the present applicant has disclosed in Japanese Patent Laid-Open No.
We have filed a patent application for -170372. However, in the pressure gauge disclosed in the prior application, since both the primary coil and the secondary coil are required as the coil configuration of the position detecting device, there is room for further improvement in promoting the miniaturization. Also, measures against a temperature drift in which the coil output voltage fluctuates according to a temperature change have not been sufficient.

The present invention has been made in view of the above points, and has as its object to provide a pressure gauge which has a small and simple structure and can easily compensate for temperature characteristics. It is another object of the present invention to provide a pressure gauge capable of detecting with high resolution even when the displacement of a detection target is minute.

[0007]

A pressure gauge according to the present invention comprises:
A diaphragm which is displaced by receiving a pressure as a detection target, a coil portion including a sensor coil which is excited by an AC signal, and a magnetic responsive material which is displaced relatively to the coil portion, A detection unit in which the relative position of the magnetically responsive substance is displaced in conjunction with the displacement of the diaphragm; a temperature compensation coil connected in series to the sensor coil; and a sensor compensation coil and the temperature compensation coil. A circuit for extracting an output voltage of the sensor coil that changes based on a change in impedance of the sensor coil from a connection point.

[0008] The magnetically responsive material may typically comprise at least one of a magnetic material (ferromagnetic material) and a nonmagnetic / good conductor (diamagnetic material). When the magnetically responsive substance is made of a magnetic material, as the degree of proximity of the member to the sensor coil increases, the self-inductance of the coil increases, and the electrical impedance of the coil increases. The resulting voltage, that is, the terminal voltage (or voltage drop) increases. Conversely, as the degree of proximity of the magnetically responsive substance to the coil decreases, the inductance of the sensor coil decreases, the electrical impedance of the sensor coil decreases, and the voltage generated in the coil, Voltage decreases. In this way, the voltage generated in the coil, that is, the inter-terminal voltage, increases or decreases while the relative position of the magnetic response member with respect to the sensor coil changes over a predetermined range with the displacement of the detection target. The material of the diaphragm itself may be made of a magnetically responsive material,
In that case, the magnetically responsive substance in the detection section refers to a diaphragm. When the material of the diaphragm is not made of a magnetically responsive material, a special magnetically responsive material is provided in the detection unit.

According to the present invention, there is provided a temperature compensating coil connected in series to the sensor coil, and the temperature is changed based on a change in impedance of the sensor coil from a connection point between the sensor coil and the temperature compensating coil. Since the output voltage of the sensor coil is taken out, the temperature drift can be appropriately canceled out by using the same coil, and the output voltage after temperature drift compensation can be taken out. Therefore, pressure detection data with temperature drift compensation can be easily obtained.

A pressure gauge according to another aspect of the present invention comprises a diaphragm which is displaced by receiving a pressure to be detected, a coil portion having a sensor coil which is excited by an AC signal, and a relative to the coil portion. A detection unit that includes a magnetically responsive material that is displaced in a vertical direction, and a relative position of the magnetically responsive material with respect to the coil unit is displaced in conjunction with the displacement of the diaphragm; An arithmetic circuit that generates at least two AC output signals having a predetermined periodic amplitude function as an amplitude coefficient by calculating an output voltage of the sensor coil and the reference voltage,
The periodic amplitude function of each of the AC output signals is different from that of the periodic characteristic by a predetermined phase.

For example, typically, as the relative position of the diaphragm or magnetically responsive material changes over a predetermined range, the voltage developed on the coil shows an incremental change curve from 0 to 90 degrees in the sine function. It can be compared to the function value change of the range. Here, the AC signal component is represented by sinωt, and the amplitude coefficient level value of the sensor coil output voltage Vx obtained corresponding to the position of the start of an appropriate section in the gradually changing curve indicated by the voltage between the terminals of the sensor coil is Pa Then, the coil output voltage Vx corresponding to the start position of the section can be expressed as Pa sinωt. If the amplitude coefficient level value of the sensor coil output voltage Vx obtained corresponding to the end position of the section is Pb, the sensor coil output voltage corresponding to the end position of the section can be expressed as Pb sinωt. You. Here, the value P of the coil output voltage Vx corresponding to the starting position
When an AC voltage having the same value as a sinωt is determined as a reference voltage Va and is subtracted from the sensor coil output voltage Vx, the amplitude coefficient of the sensor coil output voltage Vx becomes a function A
When expressed by (x), Vx−Va = A (x) sinωt−Pa sinωt = ｛A (x) −Pa｝ sinωt (1) At the beginning of the section, A (x) = Pa
Therefore, the amplitude coefficient “A (x) −
“Pa” becomes “0”. On the other hand, since A (x) = Pb at the end position of the section, the amplitude coefficient “A (x) −Pa” of the calculation result is “Pb−Pa”. Therefore, the amplitude coefficient “A (x) −Pa” of the calculation result shows a function characteristic that gradually increases from “0” to “Pb−Pa” within the range of the section. Here, since “Pb−Pa” is the maximum value, if this is equivalently considered as “1”,
The amplitude coefficient “A (x) −P” of the AC signal according to the above equation (1)
“a” is “0” to “1” within the range of the section.
And the function characteristic of this amplitude coefficient is
First quadrant of the sine function (that is, in the range of 0 to 90 degrees)
Can be compared to the characteristics of Therefore, the amplitude coefficient “A (x) −Pa” of the AC signal according to the above equation (1).
Is equivalent to sin θ (however, approximately 0 ° ≦ θ ≦ 90
°).

In a preferred embodiment, the circuit for generating the reference voltage generates first and second reference voltages, and the arithmetic circuit includes an output voltage of the sensor coil and the first and second reference voltages.
A first AC output signal having a first amplitude function as an amplitude coefficient by performing a predetermined first operation and a second operation using the second reference voltage and the second amplitude function, respectively. And a second AC output signal having the amplitude coefficient as an amplitude coefficient. In this case, the coil section may be composed of only the primary coil, so that the configuration can be simplified to a minimum. By using Va as the first reference voltage, it is possible to obtain, as the first amplitude function, a sine function having a characteristic substantially in the first quadrant (that is, a range from 0 to 90 degrees). .

Further, an AC voltage having the same value as the value Pb sinωt of the coil output voltage Vx corresponding to the end position of the section is defined as a second reference voltage Vb, and the difference between this and the coil output voltage Vx is obtained. Vb−Vx = Pb sinωt−A (x) sinωt = ｛Pb−A (x)｝ sinωt (2) At the beginning of the section, A (x) = Pa
Therefore, the amplitude coefficient “Pb−A
(x) "becomes" Pb-Pa ". On the other hand, at the end position of the section, since A (x) = Pb, the amplitude coefficient “Pb−A (x)” of this calculation result is “0”.
Therefore, the amplitude coefficient “Pb−A (x)” of the calculation result is obtained.
Indicates a function characteristic that gradually decreases from “Pb−Pa” to “0” within the range of the section. As before,
Assuming that “Pb−Pa” is equivalent to “1”, the amplitude coefficient “Pb−A (x)” of the AC signal according to the above equation (2).
Changes from “1” to “0” within the range of the section, and the function characteristic of the amplitude coefficient is changed to the characteristic of the first quadrant of the cosine function (that is, the range of 0 ° to 90 °). Can be compared. Therefore, the above equation (2)
The amplitude coefficient “Pb−A (x)” of the AC signal according to the following equation can be equivalently expressed as cos θ (however, approximately 0 ° ≦ θ ≦ 90 °). Note that the subtraction in Expression (2) may be “Vx−Vb”.

Thus, without using a secondary coil,
2 that indicates the amplitude according to the sine and cosine function characteristics according to the displacement of the diaphragm due to the pressure to be detected.
One AC output signal can be generated. For example, when the displacement of the diaphragm to be detected is represented by a phase angle θ when a predetermined detectable range is converted into a phase angle of 360 degrees, an AC output signal having an amplitude showing a sine function characteristic is approximately sin θ sinωt And an AC output signal having an amplitude indicating a cosine function characteristic can be represented by cos θ sin ωt. This is similar to the form of an output signal of a position detector called a resolver, and is extremely useful.
For example, the two AC output signals generated by the arithmetic circuit are input, and a phase value in the sine and cosine functions that defines the amplitude value is detected from a correlation between the amplitude values in the two AC output signals, It is preferable that the apparatus further includes an amplitude / phase converter that generates the position detection data of the detection target based on the detected phase value. Since the sine and cosine functions exhibit characteristics in a range of approximately one quadrant (90 degrees), the detectable position range is detected after being converted into a phase angle in a range of approximately 90 degrees.

As an example, the circuit for generating the reference voltage includes two coils connected in series so that an AC signal is applied, and the reference voltage is extracted from a connection point of the coils. . Thereby, the temperature drift of the reference voltage can be compensated, and the accurate analog operation can be performed in which both the output voltage and the reference voltage are subjected to the temperature drift compensation.

When a good conductor such as copper is used as the magnetically responsive material, the self-inductance of the coil decreases due to eddy current loss, and the voltage between the terminals of the coil increases as the magnetically responsive material approaches the coil. Will gradually decrease. Also in this case, it is possible to detect in the same manner as described above. It should be noted that a hybrid type combining a magnetic material (ferromagnetic material) and a nonmagnetic / good conductor (diamagnetic material) may be used.

In another embodiment, the magnetic responsive material may include a permanent magnet, and the coil may include a magnetic core. In this case, the corresponding portion of the magnetic core on the side of the coil becomes magnetically saturated or supersaturated according to the approach of the permanent magnet, and the magnetic responsive material, that is, the terminal of the coil is changed according to the relative displacement of the permanent magnet with respect to the coil. The voltage will gradually decrease.

Thus, according to the present invention, only the primary coil needs to be provided, and the secondary coil is unnecessary, so that it is possible to provide a position detecting device having a small and simple structure. In addition, both the output voltage and the reference voltage can be subjected to temperature drift-compensated accurate analog calculation,
Relative position detection excluding the influence of temperature change can be easily performed. Of course, the circuit that generates the reference voltage is not limited to a coil, and a voltage generation circuit having a suitable configuration such as a resistor may be used. Note that the number of coils and reference voltages is not limited to one or two, but may be more. Accordingly, the available phase angle range is set to substantially one quadrant (90
The degree is not limited to minutes, but can be further expanded.

[0019]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing one embodiment of a pressure gauge according to the present invention. The pressure gauge 300 is provided at a portion of the diaphragm 301 which is displaced by receiving a pressure P to be detected, and detects the expansion and contraction displacement of the membrane surface of the diaphragm 301 by a non-contact magnetic coupling method. The pressure P is measured. That is, the displacement of the membrane surface of the diaphragm 301 is detected, and the detected data is equivalently used as pressure detection data. The detecting unit of the pressure gauge 300 is provided with a coil unit 302 which is fixedly arranged in close proximity to the membrane surface of the diaphragm 301 in a non-contact manner.
And a magnetically responsive substance 11 that is displaced in conjunction with the film surface of the diaphragm 301. The coil unit 302 includes at least one sensor coil L1 that is excited by a predetermined reference AC signal.

The magnetic responsive material 11 is made of a magnetic material (ferromagnetic material) such as iron, for example, and the self-inductance of the coil L1 increases as the degree of proximity of the magnetic responsive material 11 to the sensor coil L1 increases. Then, the coil L
1 increases, and the voltage generated in the sensor coil L1, that is, the terminal voltage (or voltage drop) increases. Conversely, as the degree of proximity of the magnetically responsive substance 11 to the coil L1 decreases, the inductance of the sensor coil L1 decreases, and the electrical impedance of the sensor coil L1 decreases, which is generated in the coil L1. The voltage, that is, the voltage between terminals, decreases. In this manner, the voltage generated in the coil L1 while the relative position of the magnetically responsive substance 11 with respect to the sensor coil L1 changes over a predetermined range, that is, the voltage between the terminals, increases or decreases with the displacement of the detection target. become.
The material of the diaphragm 301 itself is the magnetically responsive substance 11
In that case, the diaphragm 301 itself is used as the magnetic responsive material 11 without adding the special magnetic responsive material 11. Diaphragm 30
If the material 1 is not made of the magnetically responsive substance 11,
A special magnetic responsive material 11 is provided on the surface of the diaphragm 301.
Affix.

In the coil section 10, a temperature compensating coil L2 is provided near the sensor coil L1, but both coils are magnetically shielded so that the influence of the displacement of the magnetically responsive substance 11 is reduced by the temperature compensating coil L2. To be affected. As shown in FIG. 2, the sensor coil L <b> 1 is excited at a constant voltage or a constant current by a predetermined one-phase AC signal (tentatively represented by sinωt) generated from the AC generation source 30. As described above, the inductance of the sensor coil L1 changes in accordance with the displacement of the magnetically responsive substance 11 in accordance with the position x of the diaphragm 301, and therefore is equivalently shown as a variable inductance element in the circuit of FIG. The temperature compensation coil L2 is connected in series to the sensor coil L1, and an output voltage Vx of the sensor coil L1 is taken out from the connection point. As described above, the temperature compensation coil L2 does not respond to the displacement of the magnetically responsive substance 11 and has a constant impedance (inductance). Therefore, the temperature compensation coil L2 is equivalently shown as a fixed inductance element in the circuit of FIG. I have. The temperature compensation coil L2 is preferably a coil element under the same conditions as the sensor coil L1 so as to exhibit the same temperature drift characteristics as the sensor coil L1 as much as possible, and is disposed under the same environment as possible. Is preferred. Sensor coil L1
The output voltage Vx of the sensor coil L1 is extracted from the voltage and the voltage division ratio of the temperature compensation coil L2.
The temperature drift characteristics of 1 and L2 are canceled out, and the output voltage Vx of the sensor coil L1 is accurately temperature-compensated.

FIG. 3A is a graph illustrating a voltage (vertical axis) generated in the sensor coil L1 corresponding to the displacement (horizontal axis x) of the diaphragm 301 due to the pressure P to be detected. A and b described on the horizontal axis x correspond to the start and end positions of the detectable range. Diaphragm 301
Is small, the detectable range is, for example, a very small range of about 1 to several mm. Position a
Is the position where the membrane surface of the diaphragm 301 is farthest from the sensor coil L1. At this position, the impedance of the sensor coil L1 is minimum, and the voltage generated in the coil L1 is at the minimum level (minimum amplitude coefficient). Position b
Is the position where the membrane surface of the diaphragm 301 is closest to the sensor coil L1. At this position, since the impedance of the sensor coil L1 is the maximum, the voltage generated in the coil L1 is at the maximum level (maximum amplitude coefficient).

As described above, the voltage generated in the sensor coil L1 gradually changes from the minimum value to the maximum value while the diaphragm 301, that is, the magnetic responsive material 11 moves from the position a to the position b. Assuming that the output voltage Vx of the coil L1 having the minimum value at the position a is Pa sinωt (Pa is the minimum impedance), this is set as the first reference voltage Va. That is, Va = Pa sin ωt. Further, the coil L1 having the maximum value at the position b
Is Pb sinωt (Pb sinωt)
Is the maximum impedance), which is set as the second reference voltage Vb. That is, Vb = Pb sin ωt. The reference voltages Va and Vb can be variably set. Thereby, the detection target ranges a and b can be variably set.

In FIG. 2, two coils La1 and La2 serve as circuits for generating the respective reference voltages Va and Vb.
And a circuit in which two coils Lb1 and Lb2 are connected in series. These circuits are driven by an AC signal from an AC generator 30. The reference voltage Va is taken out from the connection point between the coils La1 and La2,
The reference voltage Vb is extracted from a connection point between the coils Lb1 and Lb2. Coil La1, La2, coil Lb1, Lb
The impedance (inductance) of each pair of 2 is appropriately adjusted so that desired reference voltages Va and Vb are obtained. Since the reference voltage Va is extracted based on the voltage division ratio of the coils La1 and La2, the temperature drift characteristics of the coils La1 and La2 are canceled, and the temperature of the reference voltage Va is accurately compensated. Similarly, the coils Lb1 and Lb2
, The temperature drift characteristics of the coils Lb1 and Lb2 are cancelled, and the reference voltage Vb is accurately temperature-compensated.

The arithmetic circuit 31A subtracts the first reference voltage Va from the output voltage Vx of the sensor coil L1, and calculates the amplitude coefficient of the coil output voltage as a function A (x ) Is performed. At the start position a of the detection target section set by the first reference voltage Va, since A (x) = Pa, the amplitude coefficient “A (x) −Pa” of the calculation result is obtained.
Becomes "0". On the other hand, at the position b at the end of the detection target section, since A (x) = Pb, the amplitude coefficient “A (x) −Pa” of this calculation result is “Pb−Pa”. Therefore, the amplitude coefficient "A (x) -Pa"
"Indicates a function characteristic that gradually increases from" 0 "to" Pb-Pa "within the range of the detection target section. here,
Since “Pb−Pa” is the maximum value, if this is equivalently considered to be “1”, the amplitude coefficient “A (x) −Pa” of the AC signal according to the above equation is within the range of the detection target section. As shown in FIG. 3B, the amplitude characteristic changes from “0” to “1”.
(C), the characteristics of the sine function sin θ in the first quadrant (that is, in the range of 0 to 90 degrees) can be compared. Therefore, the amplitude coefficient “A (x) −Pa” of the AC signal according to the above equation can be equivalently expressed by using sin θ (however, approximately 0 ° ≦ θ ≦ 90 °). Note that FIG.
(B) and (C) show only the curve sinθ of the amplitude coefficient of the sine function characteristic with respect to the position x, but the actual output of the arithmetic circuit 31A is an AC signal sinθsinωt having an amplitude level corresponding to the amplitude coefficient sinθ. It is.

The arithmetic circuit 31B calculates the difference between the output voltage Vx of the sensor coil L1 and the second reference voltage Vb. Is performed. At the start position a of the detection target section,
Since A (x) = Pa, the amplitude coefficient “Pb−A (x)” of the calculation result is “Pb−Pa”. on the other hand,
At the end position b of the section set by the second reference voltage Vb, since A (x) = Pb, the amplitude coefficient “Pb−A (x)” of this calculation result is “0”. Therefore, the amplitude coefficient “Pb−A (x)” of the calculation result shows a function characteristic that gradually decreases from “Pb−Pa” to “0” within the range of the detection target section. As before,
Assuming that “Pb−Pa” is equivalent to “1”, the amplitude coefficient “Pb−A (x)” of the AC signal according to the above equation becomes as shown in FIG. To
The amplitude coefficient changes from “1” to “0”, and the function characteristic of the amplitude coefficient is changed to the characteristic in the first quadrant (that is, the range from 0 ° to 90 °) of the cosine function as shown in FIG. Can be compared. Therefore, the amplitude coefficient “Pb−A (x)” of the AC signal according to the above equation is equivalent to cos θ
(However, approximately 0 ° ≦ θ ≦ 90 °). Also in this case, FIGS. 3B and 3C show only the curve cos θ of the amplitude coefficient of the cosine function characteristic with respect to the position x, but the actual output of the arithmetic circuit 31B is the amplitude corresponding to the amplitude coefficient cos θ. AC signal with level c
os θ sin ωt. Note that the subtraction in the arithmetic circuit 31B may be “Vx−Vb”.

In this manner, two AC output signals sinθ each representing an amplitude according to the sine and cosine function characteristics according to the displacement of the diaphragm 301, that is, the position x to be detected.
sinωt and cosθsinωt can be generated. This is similar to the form of an output signal of a position detector generally called a resolver, and can be effectively used. For example, two resolver-type AC output signals generated by the arithmetic circuits 31A and 31B are input to a phase detection circuit (or amplitude-phase conversion means) 32, and the amplitude is determined from the correlation between the amplitude values of the two AC output signals. The sine and cosine functions sinθ and co defining the value
By measuring the phase value θ of sθ, the detection target position can be absolutely detected. As the phase detection circuit 32, for example, Japanese Patent Application Laid-Open No.
It is preferable to use a technique disclosed in JP-A-126809. For example, the first AC output signal sinθsinω
t is electrically shifted by 90 degrees to obtain an AC signal s
inθcosωt is generated, and the second AC output signal cosθsinωt is added / subtracted and combined to obtain sin
(Ωt + θ) and sin (ωt−θ), two AC signals (signals obtained by converting the phase component θ into an AC phase shift) that are phase-shifted in the leading and lagging directions according to θ, By measuring θ, stroke position detection data can be obtained. The phase detection circuit 32 may be configured by a dedicated circuit (for example, an integrated circuit device), or may perform a phase detection process by executing predetermined software using a programmable processor or a computer. . Alternatively, an R-D converter used for processing a known resolver output may be used as the phase detection circuit 32.
Further, the detection processing of the phase component θ in the phase detection circuit 32 is not limited to digital processing, but may be performed by analog processing using an integration circuit or the like. Further, after digital detection data indicating the rotation phase θ is generated by the digital phase detection processing, the digital detection data may be converted into analog data to obtain analog detection data indicating the rotation position θ. Of course, without providing the phase detection circuit 32, the output signals sinθsinωt and cosθsinωt of the arithmetic circuits 31A and 31B may be directly output.

As shown in FIG. 3B, an AC output signal sin θ sin ωt having sine and cosine function characteristics is provided.
And cos θ sinωt have a phase angle θ
Assuming that the correspondence between the detection target position x and the detection target position x has linearity, it does not show the true sine and cosine function characteristics as shown in FIG. However, the phase detection circuit 32 apparently performs the phase detection processing on the AC output signals sin θ sin ωt and cos θ sin ωt as those having amplitude characteristics of sine and cosine functions, respectively. As a result, the detected phase angle θ is
It will not show linearity. However, in the position detection, the non-linearity between the detection output data (the detected phase angle θ) and the actual detection target position is not a very important problem. In other words, it suffices if the position can be detected with a predetermined reproducibility. Also,
If necessary, the output data of the phase detection circuit 32 is subjected to data conversion using an appropriate data conversion table, so that accurate linearity can be easily provided between the detected output data and the actual detection target position. Can be done. Therefore, the amplitude characteristics of the sine and cosine functions referred to in the present invention do not have to indicate the true sine and cosine function characteristics, and as shown in FIG. In other words, what is necessary is just to show such a tendency. That is,
Any function similar to a trigonometric function such as sine may be used. In the example of FIG. 3B, the scale of the horizontal axis is assumed to be θ, and the scale of the horizontal axis is assumed to be x if the scale is formed of a required non-linear scale. In this case, even if it looks like a triangular wave, it can be said that θ is a sine function or a cosine function.

Here, further compensation of the temperature drift characteristic will be described. As described above, the output voltage Vx of the sensor coil L1 and the reference voltages Va and Vb are temperature drift-compensated, respectively.
Due to the difference calculation in B, even if there is a level fluctuation error in the same direction, this will also be canceled out, and the temperature drift characteristic will be more reliably compensated.

Each coil La1, La for generating a reference voltage
2, Lb1 and Lb2 use coils having characteristics equivalent to those of the sensor coil L1, and use these coils La1 and Lb2.
It is preferable to place them in the same temperature environment as a2, Lb1, Lb2 and the sensor coil L1 (that is, to arrange them relatively close to the sensor coil L1), but the present invention is not limited to this. This is because temperature drift compensation is achieved by series connection of each pair of coils and voltage extraction from the connection point as shown in FIG. Therefore, each coil La1, La2, Lb1, Lb2 for generating the reference voltage
May be provided on the circuit board side of the arithmetic circuits 31A and 31B.

In some embodiments, the temperature compensation coil L2 connected in series to the sensor coil L1 may be omitted. FIG. 4 is a circuit diagram showing one example thereof.
This is an example in which a circuit for generating a and Vb and a circuit for generating an output voltage Vx of the sensor coil L1 are modified. A resistor R1 is provided instead of the coil L2.
a2, resistance elements Ra and Rb are provided instead of the coil Lb2. In this case as well, by calculating the output voltage Vx of the sensor coil L1 and the reference voltages Va and Vb, FIG.
Detection can be performed by the same operation as described above.

FIG. 5 is a modification of FIG. 2, in which one reference voltage Vb is generated and the output voltage Vx of the sensor coil L1 is changed.
This is an example in which is calculated. As a circuit for generating the reference voltage VN, a circuit in which two coils Lb1 and Lb2 are connected in series is used. The arithmetic circuit 33A adds the output voltage Vx of the sensor coil L1 and the reference voltage Vb,
The output voltage Vx of the sensor coil L1 is calculated by the arithmetic circuit 33B.
From the reference voltage Vb. As a result, as the addition result Vx + Vb in the arithmetic circuit 33A, an output AC signal sinθ sinωt having an amplitude coefficient sin θ equivalent to an amplitude characteristic in a narrow range of less than 90 ° of the sine function sin θ is obtained. Further, as the subtraction result Vx-Vb in the arithmetic circuit 33B, an output AC signal cos θ sinωt having an amplitude coefficient cos θ that can be equivalently compared to an amplitude characteristic in a narrow range of less than 90 ° of the cosine function sin θ is obtained. Also in FIG. 5, there may be a modification in which a resistance element is used instead of the temperature compensation coils L2 and Lb2.

FIG. 6 shows an embodiment using a needle-shaped magnetically responsive substance 11 which projects perpendicularly from the film surface of the diaphragm 301. In this case, an impedance corresponding to the amount of penetration of the needle-shaped magnetically responsive substance 11 penetrating into the internal space of the sensor coil L1 is generated in the sensor operation coil L1. The shape, arrangement, and the like of the magnetically responsive material 11 may be appropriately designed. Of course, the magnetic responsive substance 11 may be fixed, and the sensor coil L1 may move together with the diaphragm 301.

In each of the above embodiments, the configuration for obtaining the position detection data is not limited to the configuration using the phase detection circuit 32 as shown in FIG. 2 and the like, and as shown in FIG.
The voltage detection circuit 40 may be used. FIG.
2A, the configuration other than the voltage detection circuit 40 is the same as that shown in FIG. In short, the voltage detection circuit 40
Then, an AC signal sinθ sinωt equivalently having an amplitude characteristic of a sine function output from the arithmetic circuit 31A is input to the rectifier circuit 41 to remove an AC signal component and to detect a DC detection voltage V1 that responds only to the amplitude voltage component sin θ. Occurs. Also, an AC signal cos θ sinωt equivalently having a cosine function amplitude characteristic output from the arithmetic circuit 31B
To the rectifier circuit 42 to remove the AC signal component and generate a DC detection voltage V2 that responds only to the amplitude voltage component cos θ. FIG. 7B shows a characteristic example of each of the detection voltages V1 and V2 shown with respect to the detection target position x. The reason why such characteristics are obtained is as described above with reference to FIG. In this way, two types of detection voltages V1 and V2 having exactly opposite characteristics can be obtained in analog form. To detect the detection target position x, one of the detection voltages V
It is sufficient to configure only one series of rectifier circuits so as to obtain only V1 and V2, but two types of detection voltages V1 and V2 having opposite characteristics are sufficient.
Are generated in parallel, redundancy can be provided. That is, when any failure occurs in one of the detection sequences, it is possible to appropriately cope with the failure.

FIG. 8 shows an example of a configuration in which a phase detection analog circuit 32A and a voltage detection circuit 40 are provided side by side so that either phase detection or voltage detection can be employed. FIG.
This is the same as the one in which a phase detection analog circuit 32A is added in FIG. Therefore, for the description of the configuration other than the phase detection analog circuit 32A, the description of FIGS. 2 and 7A is cited. Analog circuit for phase detection 3
2A, an AC signal A = sinθsi equivalently having a sine function amplitude characteristic output from the arithmetic circuit 31A
nωt is input to the phase shift circuit 19, and its electric phase is phase-shifted by a predetermined amount, for example, advanced by 90 degrees, to obtain a phase-shifted AC signal A ′ = sinθ · cosωt. In addition, the analog circuit 32A for phase detection includes an addition circuit 15 and a subtraction circuit 16,
In the adder circuit 15, the phase-shifted AC signal A ′ = sinθ · cosωt output from the phase shift circuit 19
And an AC signal B = cos θ sinωt equivalently output from the arithmetic circuit 31B and having an amplitude characteristic of a cosine function, and the added output is B + A ′ = cos θ · s
A first electrical AC signal Y1 can be obtained which can be represented by a simplified expression of inωt + sinθ · cosωt = sin (ωt + θ). In the subtraction circuit 16, the phase-shifted AC signal A '= sin
θ · cosωt and the output AC signal B from the arithmetic circuit 31B
= Cosθ · sinωt is subtracted, and the subtraction output is
BA ′ = cosθ · sinωt−sinθ · cosωt = sin (ω
t-θ), a second electrical AC signal Y2 represented by a simplified expression
Is obtained. Thus, the first electrical AC output signal Y1 = sin (ωt + θ) having the electrical phase angle (+ θ) shifted in the positive direction corresponding to the detection target position (x).
And a second electrical AC output signal Y2 = sin (ωt−θ) having a negatively shifted electrical phase angle (−θ) corresponding to the same detection target position (x). Each is obtained by a logical processing.

The output signals Y1 and Y2 of the adder circuit 15 and the subtractor circuit 16 are input to zero-cross detection circuits 17 and 18, respectively, where the respective zero-crosses are detected. As a method of detecting the zero cross, for example, a zero cross in which the amplitude values of the signals Y1 and Y2 change from the negative polarity to the positive polarity, that is, zero phase is detected. The zero-cross detection pulse, that is, the zero-phase detection pulse detected by each of the circuits 17 and 18 is output as latch pulses LP1 and LP2. Latch pulse LP
1 and LP2 are input to a phase shift measuring device (not shown). In this phase shift measuring device, the time difference from the 0 phase time point of the reference AC signal sinωt generated from the reference AC signal source 30 to the generation time point (rising trigger time point) of each of the latch pulses LP1 and LP2 is counted. The corresponding count value is detected as phase data of the phase angle (+ θ) shifted in the positive direction, and the count value corresponding to the latch pulse LP2 is detected as phase data of the phase angle (−θ) shifted in the negative direction. . The method of using the phase detection data of the phase angles + θ and −θ shifted in the positive direction and the negative direction is described in the above-mentioned prior application of the present applicant. It should just be used by the method.

When the oscillation circuit itself of the reference AC source 30 is provided on the side of the coil section 10, the reference AC signal generated from the reference AC source 30 is converted into a square wave conversion circuit as shown in FIG. 20 and the reference AC signal sinω
A square wave signal (pulse signal) synchronized with t is formed and input to the phase shift measuring device. In that case, in the phase shift measuring device, the input reference AC signal sinω
The clock pulse count is performed in synchronization with the rise of the square wave signal (pulse signal) synchronized with t, and the count value is latched at the time when each of the latch pulses LP1 and LP2 occurs (at the time of the rising trigger). As described above, the phase detection data of the phase angles + θ and −θ shifted in the positive direction and the negative direction can be obtained. Of course, the present invention is not limited to this. On the side of the phase shift measuring device, a square wave signal (pulse signal) synchronized with the reference AC signal sinωt is generated, and the circuit side of the coil unit 10 is generated based on the square wave signal (pulse signal). The analog reference signal sin
ωt may be generated. In that case, on the side of the phase shift measuring device, the output reference AC signal sinωt
The clock pulse count is performed in synchronization with the rise of the square wave signal (pulse signal) synchronized with the clock pulse, and the generation time of each latch pulse LP1, LP2 (the rise trigger time)
Then, a configuration for latching the count value may be adopted.
As the phase shift measuring device, a processor such as a CPU capable of processing a software program may be used. In the circuit of FIG. 7, instead of the output signal A of the arithmetic circuit 31A = sin θ sin ωt, the output signal A ′ = sin θ cos ωt from the phase shift circuit 19 is input as the signal input to the rectifier circuit 41 of the voltage detection circuit 40. You may do so.

As the magnetic responsive material 11, a non-magnetic and good conductor (ie, a diamagnetic material) such as copper may be used instead of the ferromagnetic material. In this case, the inductance of the coil decreases due to the eddy current loss, and the magnetic response member 11
, The voltage between the terminals of the coil decreases. Also in this case, the position detection operation can be performed in the same manner as described above. As the magnetic response member, a hybrid type in which a ferromagnetic material and a nonmagnetic / good conductor (that is, a diamagnetic material) are combined may be used. In addition, the shape of the magnetic response member 11 is arbitrary, and may be, for example, an appropriate gradually decreasing or increasing shape, and a pattern having the appropriate gradually decreasing or increasing shape is formed on the surface of a predetermined base material by plating or the like. It may be something. Further, the number of sensor coils L1 is not limited to one and may be plural.

[0039]

As described above, according to the present invention, only the primary coil needs to be provided, and the secondary coil is not required. Therefore, it is possible to provide a position detecting device having a compact and simple structure. A temperature compensation coil connected in series to the sensor coil, and an output of the sensor coil that changes based on a change in impedance of the sensor coil from a connection point between the sensor coil and the temperature compensation coil. Since the voltage is taken out, the temperature drift can be properly canceled out by using the same coil, and the temperature drift compensated output voltage can be taken out, and the minute displacement of the diaphragm according to the pressure to be detected can be accurately detected. It has an excellent effect that it can be detected.

Further, by utilizing a gradually increasing (or gradually decreasing) change characteristic of the coil output voltage generated in response to a minute displacement of the diaphragm in accordance with the pressure to be detected, this is calculated and combined with a reference voltage to obtain a position to be detected. Easily generates a plurality of AC output signals (for example, two AC output signals each indicating an amplitude according to the sine and cosine function characteristics), each of which indicates an amplitude according to a predetermined periodic function characteristic. There is an excellent effect that a minute displacement of the diaphragm can be accurately detected. In addition, when the reference voltage is generated, two coils connected in series so that an AC signal is applied, and the reference voltage is taken out from a connection point of the coils, thereby compensating for the temperature drift of the reference voltage. As a result, it is possible to perform an accurate analog operation in which both the output voltage and the reference voltage are temperature drift compensated, and it is possible to easily perform the position detection excluding the influence of the temperature change. Furthermore, by detecting a phase value in a predetermined periodic function (for example, a sine and cosine function) that defines the amplitude value from the correlation between the amplitude values of the plurality of AC output signals, even if the displacement of the detection target is minute, high resolution is obtained. Can be detected.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing one embodiment of a pressure gauge according to the present invention.

FIG. 2 is an electric circuit diagram related to a sensor coil of the pressure gauge according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a detection operation of the embodiment of FIG.

FIG. 4 is an electric circuit diagram related to a sensor coil showing a modified example of the pressure gauge according to one embodiment of the present invention.

FIG. 5 is an electric circuit diagram relating to a sensor coil showing another modified example of the pressure gauge according to one embodiment of the present invention.

FIG. 6 is a schematic sectional view showing another configuration example of the magnetic response member in the pressure gauge according to the present invention.

FIG. 7 is an electric circuit diagram relating to a sensor coil of the pressure gauge according to the present invention, which is configured to generate an analog DC voltage according to a detection position.

FIG. 8 is an electric circuit diagram relating to a sensor coil of the pressure gauge according to the present invention, which has both functions of voltage detection and phase detection.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Magnetic response material 30 AC generation source 31A, 31B, 33A, 33B Analog operation circuit 32 Phase detection circuit 300 Pressure gauge 301 Diaphragm 302 Coil part L1 Sensor coil L2 Temperature compensation coil La1, La2, Lb1, Lb2 For reference voltage generation Coil 40 Voltage detection circuit 41, 42 Rectifier circuit

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) G01L 19/04 G01L 19/04 F term (reference) 2F055 AA40 BB20 CC02 DD19 EE21 FF02 FF11 FF43 GG32 2F063 AA02 CA01 CC04 DA01 DA05 GA05 GA08 KA01 LA01 LA27 2F077 AA13 CC02 FF02 FF31 FF39 TT11 TT21 TT82 UU07 VV01

Claims (8)

[Claims] 1. A diaphragm which is displaced by receiving a pressure as a detection target, a coil portion in which a sensor coil excited by an AC signal is arranged, and a magnetic responsive material which is displaced relatively to the coil portion. A detecting unit in which the relative position of the magnetically responsive substance with respect to the coil unit is displaced in conjunction with the displacement of the diaphragm; a temperature compensating coil connected in series to the sensor coil; the sensor coil and the temperature A circuit for extracting an output voltage of the sensor coil that changes based on a change in impedance of the sensor coil from a connection point with the compensation coil. 2. A circuit for generating a reference voltage composed of an AC signal; and calculating an output voltage of the sensor coil and the reference voltage to generate at least an AC output signal having a predetermined periodic amplitude function as an amplitude coefficient. 2. The pressure gauge according to claim 1, further comprising an arithmetic circuit for generating two, wherein the periodic amplitude function of each of the AC output signals differs by a predetermined phase in its periodic characteristic. 3. A diaphragm which is displaced by receiving a pressure as a detection target, a coil portion in which a sensor coil excited by an AC signal is arranged, and a magnetic responsive material which is displaced relatively to the coil portion. A detection unit in which the relative position of the magnetically responsive substance with respect to the coil unit is displaced in conjunction with the displacement of the diaphragm; a circuit for generating a reference voltage composed of an AC signal; an output voltage of the sensor coil and the reference An arithmetic circuit that generates at least two AC output signals having a predetermined periodic amplitude function as an amplitude coefficient by calculating with a voltage, wherein the periodic amplitude function of each of the AC output signals has a predetermined cycle characteristic. A pressure gauge with a phase difference. 4. The circuit according to claim 2, wherein the circuit for generating the reference voltage includes two coils connected in series so that an AC signal is applied, and extracts the reference voltage from a connection point of the coils. 3. The pressure gauge according to 3. 5. The circuit for generating the reference voltage generates first and second reference voltages, and the arithmetic circuit calculates an output voltage of the sensor coil and the first and second reference voltages. By performing predetermined first and second calculations using the first AC output signal having the first amplitude function as an amplitude coefficient and the second AC output signal having the second amplitude function as an amplitude coefficient, respectively. 4. The pressure gauge according to claim 2, wherein the pressure gauge generates an AC output signal. 6. The first and second reference voltages define a specific phase section in the periodic characteristics of the first and second amplitude functions in the first and second AC output signals, 6. The pressure gauge according to claim 5, wherein by varying the first and second reference voltages, the correspondence between the specific phase section and the range of change in the relative position can be varied. 7. A circuit for generating the reference voltage includes a first circuit including two coils connected in series so that an AC signal is applied, and a circuit connected in series such that an AC signal is applied. A second circuit including two coils;
6. The pressure gauge according to claim 5, wherein said first reference voltage is taken out from a connection point of a coil of said circuit, and said second reference voltage is taken out from a connection point of a coil of said second circuit. 8. The two coils connected in series have a magnetic core, and the arrangement of the magnetic core with respect to each of the two coils is adjusted to adjust the impedance of the coil. 8. The pressure gauge according to claim 4, wherein a level of a reference voltage taken out from a connection point of the coil can be adjusted.