JP2001330408A - Rotational position detector for fluid pressure oscillating actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotational position detector which achieves an easier mounting, a smaller size, a saving of space, an obtaining of a stable output against temperature changes and a higher resistance to effect from an magnetic field of a magnet or the like in a type used for a fluid pressure oscillating actuator. SOLUTION: In the rotational position detector, a coiled conductor or magnetic element rotating with an output shaft of a fluid pressure oscillating actuator is arranged at a position where it is laminated with one coil or more than one coils arrayed as opposed to each other to vary the inductance of the coils thereby changing the time of charging or discharging a capacitor (2). Utilizing this fact, the cycle of the oscillation using a comparator (3) is changed to observe the cycle thereof thereby allowing the detection of the angle of the rotation of the output shaft in the fluid pressure oscillating actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch for outputting a voltage or a current corresponding to the rotational position of a fluid pressure oscillating type actuator, detecting the rotational position and judging whether or not the actuator is at a predetermined position. The present invention relates to a rotational position detector in a fluid pressure oscillating actuator that generates an output.

[0002]

2. Description of the Related Art Generally, as shown in FIGS. 2 and 3, a position detector for a fluid pressure oscillating type actuator has a magnet mounting stay (19) fixed to an output shaft (18) and a magnet (19). 20) is configured to rotate with the output shaft,
A magnetic sensor using a Hall element or the like that senses magnetic force (2
1) is fixed to the body of the fluid pressure oscillating actuator (17) via a magnetic sensor mounting stay (22). The detection position is adjusted while moving the position of the magnetic sensor (21), and fixed by tightening with a screw or the like.

[0003]

The above-described position detector for the fluid pressure oscillating actuator requires not only a structure for adjusting the mounting position of the magnetic sensor (21) but also a magnetic field. The size of the sensor (21) itself is also limited. For example, in the case of a fluid pressure oscillating actuator having an outer diameter of 28 mm, a mounting space of a maximum diameter of 28 mm and a length of about 30 mm is required. , Could not be used. When the fluid pressure oscillating actuator is installed in a narrow place, it is difficult to adjust the detection position later, and the tightening force when fixing the magnetic sensor (21) is reduced. There was also a problem of large and small, and if it was tightened excessively, it would cause a malfunction, and if it was insufficiently tightened, the position could shift. In addition, since the system is configured to sense the magnetic force of the magnet (20), if it is installed in close proximity, it is affected by a magnet mounted on an adjacent actuator, so that it has to be installed at a certain distance. . Further, it could not be used in an environment with a strong external magnetic field.

The present invention has been made in view of the above points, and can be easily mounted on a fluid pressure oscillating actuator, a detection position can be easily set, a small and space-saving, external magnetic field, It is an object of the present invention to provide a rotational position detector for a fluid pressure oscillating type actuator, which has less output fluctuation due to temperature.

[0005]

In order to achieve the above-mentioned object, a rotary position detector according to the present invention comprises one or two or more coils arranged opposite to each other and a spiral coil arranged in an overlapping portion thereof. And a displacement detection unit made of a magnetic material or a conductor, and an oscillation circuit unit made up of a resistor, a capacitor, and a comparator, an amplifier unit made up of a frequency-voltage conversion unit, and an output conversion unit.

[0006] The coil used for the displacement detection unit is one,
Alternatively, when two or more are connected in series and two or more are connected, they are arranged with a slight gap. These coils are air cores or cored coils having a magnetic core.

The magnetic or conductive material used in the displacement detecting section is a spiral shape fixed to the output shaft of the fluid pressure oscillating actuator, and the coil and the magnetic material are electrically connected within the operating angle of the fluid pressure oscillating actuator. Are formed so that the area of the overlapping portion does not take a binary value.

The resistor used in the oscillation circuit section is connected in series with the coil, one of which is connected to the comparator input side and the other is connected to the comparator output side.

The capacitor used in the oscillation circuit has one pole connected to the reference potential and the other pole connected to the input side of the comparator.

[0010] The comparator used in the oscillation circuit section is
This is an inverting output comparator with a threshold with hysteresis. When the input voltage rises from a low voltage, it is determined by the threshold on the high voltage side, and when the input voltage exceeds the threshold, a low level is output. When the input voltage falls from the high voltage side, it is determined by the threshold value on the low voltage side, and when the input voltage exceeds the threshold value, a high level is output.
Specifically, in addition to the comparator, an operational amplifier, a Schmitt inverter of a logic element, or the like can be used.

The frequency-voltage converter observes the output oscillated by the comparator and converts the frequency to a voltage.

The output converter outputs a voltage or current corresponding to the rotation angle of the output shaft of the fluid pressure oscillating actuator, or outputs the output of the fluid pressure oscillating actuator to a predetermined rotation angle. The switch output is generated by determining which side the shaft rotation angle is on.

[0013] Further, the coil used for the displacement detecting section is
By using a copper-nickel-manganese alloy wire (manganin wire) or a copper-nickel alloy wire as the conductive wire, it is possible to further reduce the fluctuation of the output value with respect to a temperature change.

In addition, by making the material of the spiral magnetic material disposed in the overlapping portion of the displacement detecting unit and the coil a 3% silicon iron, amorphous, or ferrite material, the output value changes with temperature change. It is possible to make it smaller.

[0015] Further, the material of the spiral conductor disposed in the overlapping portion of the displacement detection unit and the coil is made of a copper-nickel-manganese alloy, a copper-nickel alloy, or a nickel-chromium alloy, so that the temperature change can be prevented. On the other hand, it is possible to make the fluctuation of the output value smaller.

Further, by using a cored coil having a magnetic material as a core for the coil of the displacement detecting section, a coil having a smaller number of turns and a smaller diameter can be used.

Further, by making the material of the magnetic material used as the core of the cored coil 3% silicon iron, amorphous, or ferrite, it is possible to further reduce the fluctuation of the output value with respect to the temperature change. .

Furthermore, in order to compensate for the temperature change of the resistance value of the coil of the displacement detecting section, a thermistor having a negative temperature characteristic is connected in series with the coil, and is arranged in the vicinity of the coil. On the other hand, it is possible to make the fluctuation of the output value smaller.

In order to compensate for the temperature change of the inductance of the coil of the displacement detecting section, a thermistor having a negative temperature characteristic is connected in parallel with the coil and is arranged near the coil to prevent the temperature change. Thus, the fluctuation of the output value can be further reduced.

Further, when a fixed-time rectangular wave is generated at the rise and fall of the output of the comparator of the oscillation circuit section, the interval between the rectangular waves varies due to a change in the period. By doing so, it becomes possible to output a change in the oscillation cycle of the output of the comparator as a change in voltage, and it is possible to easily configure a frequency-voltage converter.

[0021]

When power is applied to the rotational position detector constructed as described above, when no charge is stored in the capacitor, the comparator outputs a high level because the input voltage of the comparator is low. Then, electric charges are stored in the capacitor at a speed determined by the impedance of the coil and the resistor.

Since the pole on the side where electric charge is stored in this capacitor is also connected to the input side of the comparator, the output of the comparator is inverted when a voltage exceeding the threshold value of the comparator is reached after a certain time. Level. The change in the voltage on the input side to the comparator at this time is in the direction of rising from the low voltage, and the determination is made based on the threshold value on the high voltage side.

When the output of the comparator goes low, the charge stored in the capacitor is discharged as soon as it is determined by the impedance of the coil and the resistor.

This discharge causes the voltage on the input side of the comparator to decrease. At this time, the change in the voltage is in the direction of falling from the high voltage, and the judgment is made based on the threshold value on the low voltage side. When the input voltage falls below the threshold, the output goes high and charge is stored in the capacitor. Thereafter, by repeating these series of operations, the output of the comparator continues to oscillate.

When the electric charge is stored in the capacitor when the power is turned on, a low level is output because the input of the comparator is at a high level. Therefore, when the capacitor starts discharging and the voltage becomes low until the voltage exceeds the low-voltage threshold of the comparator, the output of the comparator goes high. Therefore, when the voltage is increased until the capacitor is charged and exceeds the high-side threshold value of the comparator, the output of the comparator becomes low level, and thereafter, a series of these operations are repeated.

As described above, if the power is turned on regardless of the state of the capacitor, the output of the comparator becomes
Start oscillating.

The cycle of this oscillation is determined by the values of the coil, the resistor, and the capacitor. In the rotational position detector, the oscillation cycle of the output of the comparator is changed by changing the impedance of the coil.

In order to change the impedance of the coil, it is necessary to change the inductance of the coil. At the overlap portion with the coil, a method of rotating a spiral magnetic or conductive material is used.

In the method of rotating the spiral magnetic body at the overlapping portion with the coil, as the portion where the magnetic material and the coil overlap increases, the magnetic permeability near the coil increases, so that the magnetic flux passing through the coil increases. As a result, the inductance of the coil increases and the impedance increases as the overlap between the magnetic material and the coil increases, so that the time for charging and discharging the capacitor increases, and as a result, the period of oscillation of the output of the comparator increases. .

In the method of rotating a spiral conductor at a portion where the coil overlaps with the coil, the magnetic flux generated from the coil generates an eddy current on the surface of the conductor, and is converted into heat by the internal resistance of the portion, resulting in loss. As a result, the magnetic flux passing through the coil decreases. Therefore, the cycle of oscillation between the conductor and the output of the comparator is shortened.

In the method using a cored coil having a rod-shaped magnetic material as a core, the magnetic flux concentrates near the coil because the rod-shaped magnetic material is used as a core, so that the magnetic flux passing through the coil increases and the inductance of the coil increases. Is increased compared to the air-core coil. As a result, coil characteristics similar to those of air-core coils can be obtained with smaller coils, and if a spiral conductor is placed in the overlapping portion with the coil in this state, the magnetic flux generated by the coil generates eddy currents on the surface of the conductor However, it is converted into heat, resulting in loss, and reduces the magnetic flux passing through the coil, thereby reducing the inductance of the coil. Therefore, since the impedance also decreases, as the number of overlapping portions between the coil and the conductor increases, the time for charging and discharging the capacitor decreases, and as a result, the period of oscillation of the comparator decreases.

As described above, the displacement detecting section is formed by disposing a spiral magnetic body or a conductor at the overlapping portion with the coil. However, in the case of one coil, there is an advantage that the shape can be reduced in size. However, it is easily affected by a change in the distance between the coil and the spiral magnetic or conductive material. Therefore, it is necessary to make the product accuracy and assembly accuracy strict. Therefore, by arranging two coils facing each other, connecting them in series, and arranging a spiral magnetic or conductive material in the gap, the output changes even if the distance from the coil changes slightly. Characteristics can be obtained. Also, the number of coils may be any number.

As described above, by changing the inductance and impedance of the coil, the cycle of oscillation of the output of the comparator is changed, and by observing the cycle, the rotation angle of the output shaft of the fluid pressure oscillating actuator can be changed. To detect.

In order to enhance the stability of the rotational position detector against a change in temperature, it is necessary to stabilize the resistance value of the coil which is involved in the charging and discharging time of the capacitor. By using a copper-nickel-manganese alloy wire (manganin wire) or a copper-nickel alloy wire whose material has a stable resistance value against a change in temperature, fluctuations in output can be suppressed.

In order to increase the stability of the rotational position detector against a change in temperature, it is necessary to stabilize the inductance and impedance of the coil involved in charging and discharging of the capacitor. By using 3% silicon iron, amorphous, or ferrite, whose magnetic properties are stable with respect to a change in temperature, as the material of the magnetic material serving as the core, fluctuations in output can be suppressed.

In order to enhance the stability of the rotational position detector against a change in temperature, it is necessary to stabilize the inductance and the impedance of the coil involved in charging and discharging of the capacitor. By using 3% silicon iron, amorphous, or ferrite, whose magnetic properties are stable with respect to a change in temperature, as the material of the spiral magnetic body to be disposed, fluctuations in output can be suppressed.

In order to increase the stability of the rotational position detector against a change in temperature, it is necessary to stabilize the inductance and the impedance of the coil involved in charging and discharging of the capacitor. The fluctuation of output is suppressed by using a copper-nickel-manganese alloy, a copper-nickel alloy, or a nickel-chromium alloy, whose resistance value is stable with respect to temperature change, for the material of the spiral conductor arranged in be able to.

In order to enhance the stability of the rotational position detector against a change in temperature, there is a method for compensating for a change in the resistance value of the coil portion. A thermistor having a negative temperature characteristic is connected in series with the coil, By arranging it in the vicinity, it is possible to suppress a change in output with respect to a change in temperature of the position detection unit.

In order to enhance the stability of the rotational position detector against changes in temperature, there is a method of compensating for changes in inductance of the coil portion. A thermistor having a negative temperature characteristic is connected in parallel with the coil, and the vicinity of the coil is connected. , It is possible to suppress a change in output with respect to a change in temperature of the position detection unit.

Further, as a method for easily realizing the function in the frequency-voltage converter of the rotational position detector, when a rectangular wave having a fixed time is generated at the rising and falling of the output of the comparator, Since the change causes variations in the interval between the rectangular waves, integration of the rectangular waves can output a change in the oscillation cycle of the comparator as a change in voltage.

The rotation position detector is realized by the above-described operation. In particular, by selecting a coil as an air-core coil and selecting a non-magnetic material for a spiral conductor disposed at a portion where the coil overlaps with the coil, The rotational position detector is not particularly affected by external magnetism, especially DC magnetism by a magnet or the like.

Also, since the sensing is used within a small gap between the coil and the magnetic or conductive material, mutual interference occurs even if devices having similar position detectors are arranged in close proximity. Never.

[0043]

An embodiment will be described with reference to the drawings.
First, the overall configuration will be described. In FIG. 1, the output shaft (1) of the fluid pressure oscillating actuator (1) is provided in a gap between two coils (4) and (5) connected in series and arranged facing each other. A spiral conductor (9) fixed to 7) is inserted.

The coils (4) and (5) and the resistor (6) are connected in series between the input side and the output side of the inverted output comparator (3) having a threshold value having hysteresis. Further, the capacitor (2) is connected to the input side of the comparator (3), and the other pole of the capacitor (2) is connected to the reference potential.

Observing the output waveform of the comparator (3),
When a rectangular wave having a fixed time is generated at the rise and fall, the rectangular wave becomes uneven due to the change of the period. By integrating the rectangular wave, the change of the period of oscillation of the comparator (3), that is, The change in frequency can be output as a change in voltage.

This voltage is output to an output converter (16).
Output as a voltage or current multiplied by a certain ratio,
Alternatively, a specific rotation angle is set in advance, and a switch output is generated by determining which side of the rotation angle of the output shaft of the fluid pressure oscillation type actuator is located with respect to the predetermined rotation angle. Is a rotational position detector.

When a switch output is generated, the voltage obtained by converting the frequency is compared with a voltage level corresponding to a desired rotation angle of the switch output, and the high level and the low level of the switch output are changed. A configuration for outputting data is conceivable.

By making the coils (4) and (5) cored coils in the configuration of the rotational position detector, it is possible to reduce the size of the coil portion. For example, the embodiment shown in FIG. As described above, a small pneumatic oscillating actuator having an outer diameter of 28 mm can be easily incorporated.

In this embodiment, the spiral conductor (2) is connected to the output shaft (24) of the pneumatic oscillating actuator (23).
5) is fixed, and two coils (26) and (27) are arranged so as to sandwich the conductor (25). The rotation angle of a general pneumatic oscillating actuator is about 270 to 300 degrees at the maximum, and when rotated within that range, as shown in FIG. 5, the coils (26) and (27) and the conductor ( 25) The shape and arrangement are such that the polymerized portion gradually changes.

In the embodiment shown in FIG.
6) The material of the conductive wire used in (27) is changed in temperature by using a copper-nickel-manganese alloy wire (manganin wire) or a copper-nickel alloy wire having a stable resistance value against a change in temperature. Output fluctuations can be further reduced.

In the embodiment shown in FIG. 4, the material of the core made of the magnetic materials (28) and (29) is made of 3% silicon iron, amorphous or ferrite whose magnetic properties are stable against a change in temperature. As a result, a change in the output value due to a change in temperature can be further reduced.

In the embodiment shown in FIG. 4, the coils (26) and (2) are provided near the coils (26) and (27) to compensate for the temperature change of the resistance of the coils (26) and (27).
By connecting and storing a thermistor having a negative temperature characteristic in series with 7), a change in output value due to a change in temperature can be further reduced.

In the embodiment shown in FIG. 4, the coils (2) and (27) are provided near the coils (26) and (27) to compensate for the temperature change of the inductance of the coils (26) and (27).
6) By connecting and storing a thermistor having a negative temperature characteristic in parallel with (27), a change in output value due to a change in temperature can be further reduced.

However, it is desired to avoid using a thermistor in realizing a small and simple structure which is a feature of the rotational position detector. Therefore, the magnetic material (28) (2)
9) Using a 3% silicon iron, amorphous or ferrite material for the core, using a manganin wire for the coils (26) and (27), and further inserting a spiral conductor ( 25) is a copper-nickel-manganese alloy,
By using a material whose electrical resistance is stable against temperature changes, such as a copper-nickel alloy or a nickel-chromium alloy, it is possible to obtain an extremely stable output against temperature changes without using a thermistor. become.

In the configuration diagram shown in FIG. 1, the frequency-voltage converter (15) is a part that converts the oscillation frequency of the output of the comparator (3) into a voltage. In general, there are many methods called frequency-voltage conversion, and a method that can be easily realized by this rotational position detector will be described below.

At the rising and falling edges of the output waveform of the oscillating comparator (3), a rectangular wave of a fixed time is generated. When the oscillation cycle of the comparator (3) changes, the interval between the rectangular waves changes, so that the frequency can be converted into a voltage by integrating.

Next, temperature compensation using a thermistor will be described. In the configuration diagram shown in FIG.
The material of the conductive wire used for (5), the material of the core (10) in the case of a cored coil, the spiral magnetic body (8) inserted into the gap between the coils (4) and (5), and the conductor ( 9)
As described above, it is considered that the temperature compensating thermistors (11) and (12) are not necessary if they are configured with good temperature characteristics. However, the use environment, shape, and other factors of the rotational position detector are considered. When it is difficult to use a material having good temperature characteristics, it may be easier to perform temperature compensation using a thermistor. Further, by using a thermistor in addition to using a material having good temperature characteristics as described above, the temperature characteristics can be further improved.

The method of temperature compensation using a thermistor will be described as a result of experimentally determining a connection method. Copper wires are used for the coils (4) and (5), and iron is used for the core (10) of the cored coil. When used, the electric resistance of the copper wire changes by about 0.4% / ° C with respect to the temperature change, and the inductance of the cored coil changes by about 0.1 to 0.2% / ° C. The output voltage changes due to the influence.

Therefore, the temperature of the displacement detecting section (13) is changed in series and in parallel with the coils (4) and (5), that is, by attaching a variable resistor instead of the thermistors (11) and (12) in FIG. Then, the resistance of each variable resistor was found so that the same output voltage as that at the initial temperature could be obtained. Then, both variable resistors need to be adjusted according to the amount of overlap between the spiral conductor (9) inserted into the gap between the two coils (4) and (5) and the coils (4) and (5). The temperature could not be compensated over the entire detection range. That is, it has been found that the value to be compensated differs depending on the rotation angle.

For this reason, a similar experiment was performed using manganin wires for the coils (4) and (5). Then
Without changing the resistance value of the variable resistor connected in series with the coils (4) and (5), only the resistance value of the variable resistor connected in parallel with the coils (4) and (5) is changed. Temperature compensation could be performed for the entire detection range.

From the above, since the manganin wire has a very stable temperature coefficient of resistance of about 10 PPM / ° C.,
What is compensated by the variable resistors connected in parallel to the coils (4) and (5) can be said to be the change in inductance of the cored coil. The compensation performed by the variable resistors connected in series to the coils (4) and (5) requires no adjustment because of the change to the manganin wire.
This can be said to be the change in the resistance value of (5).

Further, since the resistance value of both variable resistors when the temperature is compensated is such that the resistance value decreases as the temperature rises, in order to perform this with a thermistor, a resistor having a negative temperature coefficient of resistance is required. It is necessary to change the resistance value in proportion to temperature.In actual use, a fixed resistance and a thermistor are connected in parallel, and the change in the resistance value in a curved line with respect to the temperature of the thermistor is straightened. Need to be done.

[0063]

Since the present invention is configured as described above, it has the following effects.

Since a rotational position detector having excellent temperature characteristics can be constituted only by the coil and the spiral magnetic or conductive material, the structure is very simple, and the oscillation circuit, the frequency-voltage converter, and the output Since the amplifier section including the conversion section can be configured very simply, it is easy to reduce the size as a whole.

In the case of the cored coil system, a sufficient output can be obtained even with a single reciprocating coil, so that the displacement detecting section is very small, and it is easy to manufacture. It is easy to attach to various devices.

The components mounted on the fluid pressure oscillating actuator are only a coil, a magnetic substance or a conductor disposed at a position overlapping with the coil, and if necessary, a thermistor only. Since the conversion unit and the amplifier unit including the output conversion unit can be installed at a remote place via an electric wire, when the rotation position detector is used in an application that generates a switch output for a specific rotation position, The switch output position can be adjusted at a location distant from the location where the fluid pressure oscillating actuator is installed, and the degree of freedom in installing the fluid pressure oscillating actuator is increased.

Since the sensing is performed within a small gap between the coil and the magnetic or conductive material, it is possible to install a fluid pressure oscillating actuator having a similar position detector in close proximity. Do not cause interference.

In the case of the air-core coil system, if a non-magnetic material is selected for the conductor disposed at the position where the coil overlaps with the coil,
Since all the components can be made of a non-magnetic material, and the output does not fluctuate even when the magnetism of a magnet or the like is brought close, it is more stable against external magnetism than a conventional position detector such as a Hall element.

In a position detector using a coil, a complicated circuit for temperature compensation, which is generally used, or a selection of constituent materials without using a coil for temperature compensation, etc., is used.
Since a stable output is obtained with respect to a change in temperature, the degree of freedom of the coil structure is high, and the coil can be easily mounted on a device.

Further, by simply connecting a thermistor in series with the coil or connecting a thermistor in parallel with the coil and disposing the thermistor in the vicinity of the coil, the stability due to a temperature change can be easily improved. There are many choices, and it is easy to respond to usage environment, size, shape, etc.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rotational position detector in a fluid pressure oscillating actuator.

FIG. 2 is a configuration diagram (plan view) of a fluid pressure swing type actuator using a conventional position detector.

FIG. 3 is a configuration diagram (a front view) of a fluid pressure oscillation type actuator using a conventional position detector.

FIG. 4 is a cross-sectional view when the rotational position detector is incorporated in a small pneumatic oscillating actuator.

FIG. 5 is a plan view showing shapes and arrangements of a spiral conductor or a magnetic body and a coil of the rotational position detector.

[Explanation of symbols]

 Reference Signs List 1, 17 Fluid pressure oscillating actuator 2 Capacitor 3 Comparator 4, 5 Coil 6 Resistance 7, 18, 24 Output shaft 8 Magnetic body (spiral) 9 Conductor (spiral) 10 Magnetic body (core) 11, 12 Thermistor DESCRIPTION OF SYMBOLS 13 Displacement detection part 14 Oscillation circuit part 15 Frequency voltage conversion part 16 Output conversion part 19 Magnet attachment stay 20 Magnet 21 Magnetic sensor 22 Magnetic sensor attachment stay 23 Pneumatic oscillating actuator 24 Output shaft 25 Spiral conductor 26, 27 Coil 28, 29 core

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) G01D 5/20 G01D 5/20 PF term (Reference) 2F063 AA35 BA30 CB01 CC02 DA05 EA03 GA07 GA08 KA01 LA04 LA05 LA13 LA30 2F077 CC02 FF03 FF13 TT02 TT22 TT35 TT36 TT82 UU03 3H081 AA21 BB01 GG06 GG15

Claims (9)

[Claims] 1. A rotary position detector in a fluid pressure oscillating actuator (1), wherein one of the poles is connected to a reference potential and the other pole is connected to a reference potential, and the other pole is provided with an inverted output having a threshold value having hysteresis. The output side of the comparator (3) is connected to the input side of the comparator (3), and one or two or more coils (4) (5) arranged opposite to each other
And the resistor (6) are connected in series to form a circuit connected to the input side of the comparator (3), so that the output of the comparator (3) is oscillated, and the fluid pressure oscillating actuator (1) By arranging the spiral magnetic body (8) or the conductor (9) so that the overlapping area with the coils (4) and (5) changes with the rotation of the output shaft (7), the coils (4) and ( By changing the inductance of (5) with the rotation of the output shaft (7) of the fluid pressure oscillating actuator (1), the impedance including the coils (4) and (5) and the resistance (6) changes, so that the capacitor is changed. Since the period of the charge and discharge of (2) changes and the period of the oscillation of the output of the comparator (3) changes, the output shaft of the fluid pressure oscillating actuator (1) is observed by observing the period. (7) Configured translocation can detect the rotational position detector. 2. The material of the conductive wire forming the coils (4) and (5) is selected from a copper-nickel-manganese alloy wire (manganin wire) or a copper The rotational position detector according to claim 1, wherein the rotational position detector is a nickel alloy wire. 3. The material of the spiral magnetic body (8) disposed in the overlapping portion of the coils (4) and (5) is made of 3% silicon iron, amorphous whose magnetic properties are stable against a change in temperature. The rotational position detector according to claim 1, wherein the rotational position detector is ferrite. 4. A copper-nickel-manganese alloy having a resistance value stable with respect to a change in temperature, wherein a material of a spiral conductor (9) disposed in an overlapping portion of the coils (4) and (5) is made of a material. 2. The rotation position detector according to claim 1, wherein the rotation position detector is made of a copper-nickel alloy or a nickel-chromium alloy. 5. The rotational position detector according to claim 1, wherein the coils (4) and (5) use a cored coil having a magnetic body (10) as a core. 6. A rotational position detector wherein the material of the magnetic material (10) according to claim 5 is 3% silicon iron, amorphous, or ferrite. 7. A thermistor (11) having a negative temperature characteristic for compensating for a temperature change in resistance of the coils (4) and (5).
Are connected in series with the coils (4) and (5), and the coils (4)
The rotational position detector according to claim 1, wherein the rotational position detector is arranged near (5). 8. A thermistor (12) having a negative temperature characteristic is connected in parallel with the coils (4) and (5) to compensate for a temperature change in inductance of the coils (4) and (5). The rotational position detector according to claim 1, wherein the rotational position detector is arranged near (5). 9. When a rectangular wave having a fixed time is generated at the rise and fall of the output of the comparator (3), the interval between the rectangular waves varies due to a change in the period, and therefore the rectangular wave is integrated. 2. The rotational position detector according to claim 1, wherein a change in the oscillation cycle of the output of the comparator can be output as a change in voltage.