JPH03189530A - Pressure detector - Google Patents

Abstract

PURPOSE:To accurate detect pressure by using a coil for magnetic field as a static magnetic field production source and providing a control circuit which outputs a signal corresponding to the value of a current applied to a moving coil. CONSTITUTION:When a pressure detector is fitted to a point at which pressure is to be detected, pressure fluid is admitted to a chamber 5 through an entrance 5a to apply pressure to a diaphragm 2, an operation body 7 is moved, and a control circuit 17 detects the movement from its reference position with a detection signal and controls the value of the current fed to the moving coil 12 so that an actuator 8 generates force resistance to the pressure that the diaphragm 2 receives. Further, the coil 10 for the magnetic field is used as the production source for a static magnetic field, so when a constant current is fed to the coil 10, the pressure in the chamber 5 can accurately be found according to the value of the current fed to the coil 12 without variation of magnetic flux due to temperature variation nor temperature compensation even if the environmental temperature of the installation place of the pressure detector varies.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pressure detector that detects the pressure of a fluid.

[Prior Art] Generally, when fluid is used, high-pressure fluid supplied from a fluid supply source is not used as is, but is used after being reduced to the working pressure at the final use part. For example, in a gas combustion system, a mechanical system operates based on the pressure balance between the gas supply source and the burner, which is the final use part, so that a constant secondary pressure is maintained even if the primary pressure changes. A governor is installed to Further, the pipe line is equipped with a pressure detector to detect pressure abnormalities and the like. The pressure detector includes one using a semiconductor pressure sensor, and a device that uses a diaphragm and detects pressure by detecting the amount of movement of the diaphragm.

However, the characteristics of conventional semiconductor pressure sensors vary greatly depending on temperature, and some change in the positive direction while others change in the negative direction, making temperature correction difficult. on the other hand,
Pressure detectors that use a diaphragm detect pressure based on the amount of movement of the diaphragm as pressure changes.
When there is a large pressure change, the pressure detector becomes large in size to allow for its movement, which poses a problem in that it requires a large installation space.

In order to solve the above problem, the applicant of the present application provided a diaphragm 32 in the housing 31 as shown in FIG. An actuating body 34 that moves integrally is provided, and a moving coil type actuator 35 is provided above the housing 31 to apply a force to the actuating body 34 that resists the pressure received by the diaphragm 32, and the current value applied to the moving coil 3G is adjusted. A pressure detector was previously proposed which was provided with a control circuit 37 that outputs a corresponding signal. This pressure detector prevents the actuating body 34 from moving together with the diaphragm 32 when the diaphragm 32 receives a force corresponding to the pressure of the fluid introduced into the chamber 33, thereby holding the actuating body 34 in a predetermined position. The current value applied to the moving coil 36 is adjusted so that the pressure is detected based on the current value.

[Problems to be Solved by the Invention] In the pressure detector, even if the measurement range of detected pressure becomes wider, the actuating body 34 hardly moves, and the moving coil 36
This can be dealt with by changing the current value applied to the circuit, and miniaturization is possible. However, in this pressure detector, a permanent magnet M is used as a source of static magnetic field acting on the moving coil 36.
are using. Generally, the magnetic flux of permanent magnets changes in response to temperature changes, and in the case of permanent magnets made of relatively inexpensive barium ferrite, the temperature change rate (%10C) of residual magnetism (B7) is -0.19. , the value is -0,043 even for a rare earth magnet with a small rate of temperature change. The ambient temperature of the permanent magnet when using the pressure detector is
In winter, considering changes in environmental temperature depending on the region and temperature rise due to heat generation when energizing the moving coil, 50~
There is a temperature change of 80°C, and the magnetic flux of the permanent magnet also changes by about 10 to 15% for barium ferrite magnets and about 2 to 3% for rare earth magnets. Therefore, even if the value of the current applied to the moving coil is the same, the amount of variation in the magnitude of the force acting on the actuating body 34 is large enough that it cannot be ignored, and temperature correction is required to perform accurate pressure detection. Become. Conventionally, temperature was detected using a thermistor, etc., and the deviation from the reference temperature was compensated for using a circuit configuration, but it was difficult to accurately measure the temperature change of the entire permanent magnet, and it was difficult to completely absorb the deviation due to temperature change. I couldn't.

Another problem is that the structure becomes complicated due to the circuit configuration for temperature compensation.

As a method of compensating for changes in magnetic flux due to changes in temperature of the permanent magnet, as shown in FIG. It is conceivable to provide a bypass member 38 of. When the bypass member 38 is provided in this way, the amount of magnetic flux passing through the bypass member 38 decreases as the temperature rises, so even if the magnetic flux of the permanent magnet M decreases as the temperature rises, the moving coil 36 and The amount of intersecting magnetic flux does not decrease significantly, and it is possible to compensate for changes in magnetic flux caused by changes in the temperature of the permanent magnet. However, it is difficult to perform complete temperature compensation because the rate of change in magnetic flux of the permanent magnet and change in magnetic permeability of the magnetic shunt alloy due to temperature change is not the same.

The present invention has been made in view of the above problems, and includes:
The purpose is to provide a pressure detector that can be used in various measurement ranges, can be made smaller, and is less susceptible to temperature changes in the environment in which it is used. A second object is to provide a pressure detector that exhibits the above-mentioned effects and that allows fine adjustment in a low current region, that is, in a state where the detected pressure value is small.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides an actuator that is movable integrally with respect to a diaphragm provided in a housing, and that resists the pressure received by the diaphragm. A control circuit is provided that uses a moving coil in the driving part of the actuator that generates force and acts on the actuating body, uses a magnetic field coil as a static magnetic field generation source, and outputs a signal corresponding to the current value applied to the moving coil. Established. Moreover, in order to achieve the second object, the magnetic field coil and the moving coil were connected in series.

[Operation] In the present invention, fluid pressure acts on the diaphragm, and the actuating body attempts to move integrally with the diaphragm in proportion to the pressure received by the diaphragm. A current is applied to hold the actuating body in a fixed position against pressure;
The actuating body is held in a fixed position. Then, fluid pressure is detected based on the current value. The force exerted on the actuating body by energizing the moving coil is determined by the magnitude of the static magnetic field and the magnitude of the energizing current value. Since the magnetic field coil is used as the source of the static magnetic field, the magnitude of the static magnetic field is not affected by temperature changes, and pressure is accurately detected based on the value of the current flowing to the moving coil.

In addition, when the magnetic field coil and the moving coil are connected in series, the actuator force changes in proportion to the square of the excitation current value, making it easy to make fine adjustments in the low current region, that is, when the detected pressure value is small. becomes.

[Example 1] An example embodying the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, the pressure detector has a casing 3 fixed to the upper part of a housing 1 with a diaphragm 2 in between, which is open at the top. The housing 1 is divided into two upper and lower chambers 5 and 6 by a thin partition plate 4, and the upper chamber 5 has an inlet 5a through which fluid is introduced. An actuating body 7 is fixed to the center of the diaphragm 2 so as to be linearly movable integrally with the diaphragm 2 in proportion to the pressure received by the diaphragm 2, that is, the pressure inside the chamber 5. An actuator 8 is installed in the upper part of the casing 3 to generate a force against the pressure received by the diaphragm 2 and to act on the actuating body 7.

The actuator 8 has a moving coil type configuration,
A yoke 9 having a shaft portion 9a at the center inside the casing 3
is fixed, and a magnetic field coil 10 is disposed outside the shaft portion 9a. At the center of the magnetic field coil IO, a plunger 11 having a moving coil 12 wound around a cylindrical coil winding part 11a is disposed so as to be movable along the shaft part 9a of the yoke 9, and its base end is It is disposed so as to be in contact with the tip of the actuating body 7. In addition, the magnetic field coil I
O and the moving coil 12 are each independently connected to each other so that they can be energized. Between the lower surface of the pressure receiving plate 2a of the diaphragm 2 and the lower part of the housing l, there is a space between the diaphragm 2 and the housing l against the weight of the actuating body 7, the plunger 11, etc. when the moving coil 12 is not energized. A spring 13 is interposed to maintain the boundary between the casing 3 and the casing 3 at a reference position.

A permanent magnet 1 is attached to the lower end of the actuating body 7 for detecting the position of the actuating body 7.
4 is buried and fixed. On the other hand, a magnetic sensor 16 is arranged on the substrate 15 housed in the lower chamber 6 at a position facing the permanent magnet 14 with the partition plate 4 in between. Further, a control circuit 17 is arranged on the substrate 15. Control circuit 1
7 detects the position of the plunger 11 based on the detection signal of the magnetic sensor 16, and controls the value of current applied to the moving coil 12 so as to maintain the plunger 11 at a constant position. Moreover, the control circuit 17
is designed to output a signal corresponding to the value of the current flowing to the moving coil 12.

Next, the operation of the apparatus configured as described above will be explained. When a pressure detector is attached to a location where pressure is to be detected, pressure fluid is introduced into the chamber 5 from the inlet 5a. When pressurized fluid is introduced into the chamber 5, the diaphragm 2 receives the pressure,
The actuating body 7 is about to move upward in FIG. 1 together with the diaphragm 2, and the permanent magnet 14 provided at the lower end of the actuating body 7
The distance between the magnetic sensor 16 and the magnetic sensor 16 is about to increase. On the other hand, the magnetic sensor 16 always detects the position of the actuating body 7 by detecting the strength of the magnetic field generated from the permanent magnet 14, and its detection signal is output to the control circuit 17.

When the actuating body 7 moves due to pressure applied to the diaphragm 2, the control circuit 17 detects the movement from the reference position based on the detection signal, and causes the actuator 8 to generate a force that resists the pressure received by the diaphragm 2. The value of current applied to the moving coil 12 is controlled. Therefore, the actuating body 7 receives the pressure of the diaphragm 2 and the moving coil 12.
It is held in a substantially constant position by opposing the extrusion force.

As a result of measuring the relationship between the pushing force of the plunger 11 and its stroke by changing the current value applied to the moving coil 12 while keeping the value of the current applied to the magnetic field coil 10 constant, it was found that even if the size of the stroke changed The extrusion force was almost constant. The current value applied to the magnetic field coil 10 is 200 mA.
Assuming that the current value to be applied to the moving coil 12 is 50m
Figure 2 shows the measurement results when the current was changed to A, 100mA, 200mA, and 250mA. Further, the relationship between the current value (exciting current value) to the moving coil 12 and the pushing force of the plunger 11 is a straight line.For example, if the stroke of the plunger 11 is 2 mm and the current value to be applied to the magnetic field coil IO is 300 mA. The relationship between the two is shown in Figure 3.

The pressure received by the diaphragm 2 is proportional to the pressure inside the chamber 5, and the value of the current applied to the moving coil 12 is controlled so that the pressure received by the diaphragm 2 is equal to the pushing force of the plunger 11.
The pressure inside the chamber 5 can be determined based on the current value.

A signal output from the control circuit 17 corresponding to the current value is normally sent to a control section of a pressure regulating valve that regulates the secondary pressure of the fluid, but a means for displaying the pressure based on the output signal may be provided. .

The pushing force of the plunger 11 is proportional to the value of the current flowing to the moving coil 12 when the magnitude of the static magnetic field of the magnetic field coil IO is constant. In conventional devices that use permanent magnets as sources of static magnetic fields, the magnetic flux changes due to temperature changes.
Correction was required due to temperature changes. However, since the device of the present invention uses the magnetic field coil IO as the source of the static magnetic field, if a constant current is applied to the magnetic field coil 10, there is no change in magnetic flux due to temperature changes, and the pressure sensor is installed at the location where the pressure detector is installed. Even if the environmental temperature of the chamber 5 changes, the pressure in the chamber 5 can be accurately determined based on the value of the current flowing to the moving coil 12 without performing temperature compensation.

Additionally, when the pressure ranges to be detected are significantly different, conventionally it was necessary to use a permanent magnet with a different strength of static magnetic field by changing the size and type of the magnet, but in the present invention, the magnetic field coil IO By changing the energizing current value, the strength of the static magnetic field can be easily changed, and the detection pressure range can be changed significantly without structural changes.

Further, even if a constant current is applied to the moving coil 12 and a current control is applied to the magnetic field coil IO, pressure detection similar to the above is possible.

Furthermore, when both chambers 5 and 6 are partitioned by a thin partition plate 4 as in the device of this embodiment, it becomes easy to bring the permanent magnet 14 for detecting the position of the actuating body 7 close to the magnetic sensor 16.
Since it is possible to use a permanent magnet with a weak magnetic force as the permanent magnet 14, it is possible to downsize or reduce manufacturing costs.

[Example 2] Next, a second embodiment will be described with reference to FIGS. 4 and 5.

The pressure detector of this embodiment differs from the device of the previous embodiment in that the magnetic field coil lO and the moving coil 12 constituting the actuator 8 are connected in series as shown in FIG. The configuration is basically the same.

When both coils 10 and 12 are connected in series, the relationship between the current value and the pushing force of the plunger 11 becomes a quadratic curve, and when the stroke of the plunger 11 is 2 mm, it becomes as shown in Fig. 5. .

As is clear from FIG. 5, in a range where the value of the current applied to the moving coil 12 is small, the change in the pushing force is smaller than the change in the current value. Note that the straight line shown by the broken line is the relationship between the current value applied to the moving coil 12 and the pushing force of the plunger 11 when both the coils 10 and 12 are connected to each other so that they can be energized independently. However, both coils 10.
When pure direct current is applied with 12 connected in series,
Since there is a magnetic path with an iron core on the side of the magnetic field coil 10, magnetic hysteresis occurs. The pushing force of the plunger 11, that is, the force of the moving coil 12, is an output based on Fleming's left-hand rule, so theoretically no hysteresis occurs, but due to the influence of the hysteresis of the magnetic field coil IO, as shown in FIG. Regarding the relationship between the applied current value and the pushing force of the plunger 11, the pushing force differs when the current increases (solid line) and when the current decreases (dashed line). Therefore, if only pure direct current is applied, the error will be large. In order to eliminate this error, the iron core material is made of a material with small magnetic hysteresis (for example, electromagnetic soft iron, silicon iron, etc.), magnetic annealing is performed, and the DC current of the moving coil 12 and the magnetic field coil 10 is
When a 200 Hz AC component is applied as a dither current superimposed on the driving DC current, the influence of hysteresis disappears, and the value becomes intermediate between the solid line and the dashed line shown in FIG. 5. The frequency of the AC component is determined in consideration of the shape of the actuator 8, the natural frequency of the movable part, and the like. As a result, when used under conditions where the pressure value to be detected is small,
Fine adjustment of the pushing force of the actuator 8, that is, the plunger 11 corresponding to the pressure received by the diaphragm 2 is facilitated, and the accuracy of the detected pressure is increased.

Note that the present invention is not limited to the above embodiments, and for example, as a means for detecting the position of the actuating body 7, as shown in FIG. A portion 11b is provided, and the tip thereof is connected to the position detection sensor 18.
It may also be detected by. As the position detection sensor, a known sensor such as a differential transformer, optical sensor, magnetic sensor, or ultrasonic sensor is used.

[Effects of the Invention] As described in detail above, according to the present invention, pressure can be accurately detected without temperature compensation in response to temperature changes in the usage environment, and even when the measurement range of detected pressure is wide, it is compact and compact. Moreover, by changing the value of current applied to the magnetic field coil in accordance with the magnitude of the detected pressure, it is possible to correspond to various ranges of measured pressure.

Further, in the invention as set forth in claim 2, even when the detected pressure is small, the acting force of the actuator can be easily finely adjusted in accordance with the pressure received by the diaphragm, and the pressure can be detected accurately.

[Brief explanation of drawings]

Figures 1 to 3 show the first embodiment, in which Figure 1 is a cross-sectional view of the pressure detector, and Figure 2 shows the value of the current flowing to the moving coil while the current flowing to the magnetic field coil is constant. A diagram showing the relationship between the stroke of the plunger and the extrusion force when the plunger is changed, Fig. 3 is a diagram showing the relationship between the current value applied to the moving coil and the extrusion force, and Figs. 4 and 5 are the second embodiment. Fig. 4 is a diagram showing the connection state between the magnetic field coil and the moving coil, Fig. 5 is a diagram showing the relationship between the current value applied to the moving coil and the pushing force, and Fig. 6 is a diagram showing the relationship between the current value applied to the moving coil and the pushing force. FIG. 7 is a sectional view of a modified example, FIG. 7 is a sectional view of a conventional device, and FIG. 8 is a partial sectional view of an improved device.

Claims (1)

[Claims] 1. A diaphragm (2) provided in the housing (1).
), an actuator (7) is provided so as to be movable integrally with respect to the diaphragm (2), and a drive unit of an actuator (8) generates a force that resists the pressure received by the diaphragm (2) and acts on the actuator (7). In addition to using a moving coil (12), a magnetic field coil (10) is used as a static magnetic field generation source, and a control circuit (17) is provided that outputs a signal corresponding to the current value applied to the moving coil (12). A pressure detector featuring: 2. The magnetic field coil (10) and the moving coil (1
2) is connected in series with the pressure sensor according to claim 1.