JPH02245630A - Pressure sensor - Google Patents

Abstract

PURPOSE:To measure a pressure at a high accuracy in a wide measurement range by varying an energizing force of a coil spring to change a bias pressure applied to a diaphragm. CONSTITUTION:A set output from a setting circuit 22 for setting an energizing force of a compression coil spring 9 variable is inputted into a control circuit 23 for controlling an angle of rotation of a stepping motor 14. Then, a signal is outputted to the motor 14 from the circuit 23 to control the angle of rotation of the motor 14 so that a set energizing force is obtained. In this manner, the energizing force of the spring 9 is controlled to reach a set value. In addition, an output from the circuit 22 is outputted to a second signal output circuit 25, with which 25 the energizing force of the spring 9 is converted into a pressure on a diaphragm surface and a voltage equivalent to the pressure is outputted to a circuit 21. Then, with the circuit 21, a signal from the circuit 25 is added to a signal from a conductive brush 17 to output a signal equivalent to a true pressure value a diaphragm 3 receives.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure sensor that detects fluid pressure, etc., and particularly relates to a pressure sensor that has a wide measurement range.

[Prior art 1] There are many types of pressure sensors depending on the purpose of use, but in a pressure sensor for detecting fluid pressure, a diaphragm that is displaced in response to pressure is generally supported by a biasing force such as a spring. When they are balanced, the pressure is detected from the amount of displacement.

[Issue to be solved by the invention Ill The environment in which pressure sensors are used differs depending on the purpose of use, but there are many cases where precise measurement accuracy and a wide measurement range are required.8 For example, in automobile cooling systems. When using pressure sensors in evaporators, expansion valves, etc., a very wide measurement range is required due to differences in operating conditions, weather environments, etc. Moreover, in order to accurately control cooling equipment, it is necessary to measure refrigerant pressure with high precision. Since the installation position of the senna varies depending on the residential environment, etc., the IP always has a wide measurement range (for example, 1000 c
(mAq) is required, and the height of the hot water level must be detected with an accuracy of LC layer unit.

In this way, when high measurement accuracy and a wide measurement range are required, conventionally it is necessary to provide a highly accurate detection means that detects the displacement of the diaphragm in units of, for example, 1/1000th of its total stroke. As a result, pressure sensors have become extremely expensive.

The present invention eliminates such drawbacks of the conventional technology, and provides a pressure sensor that does not require highly accurate detection of the displacement amount of the diaphragm and can measure a wide measurement range with high accuracy. The purpose is to

[Means for Solving the Problem] In order to achieve the above object, the pressure sensor of the present invention has the following features:
5. A diaphragm disposed to be displaced in response to the pressure of a fluid, a biasing means for biasing the diaphragm against the pressure of the fluid, and a biasing force for variably setting the biasing force of the biasing means. a setting device, a biasing force control device that controls the biasing force of the biasing device based on an output signal from the biasing force setting device, and a first signal output device that outputs a signal corresponding to the amount of displacement of the diaphragm; A second signal output means outputs a signal corresponding to the magnitude of the biasing force, and the output signal from the first signal output means is added to the output signal from the second signal output means. The present invention is characterized in that it includes an addition means for outputting a signal corresponding to the pressure value of the fluid.

Further, a diaphragm provided to be displaced in response to the pressure of a fluid, a biasing means for biasing the diaphragm against the pressure of the fluid, and a biasing force of the biasing means is electrically inputted. urging force control means controlled by a signal;
The present invention is characterized in that it is provided with signal output means for outputting a signal corresponding to the amount of displacement of the diaphragm.

[Operation 1] By changing the urging force applied to the diaphragm from the urging means by the urging force control means, a bias pressure corresponding to the urging force is applied to the diaphragm against the pressure of the fluid. Then, the pressure corresponding to the displacement of the diaphragm and the pressure corresponding to the biasing force (i.e. bias pressure) becomes the fluid pressure, and the output obtained by adding the signal corresponding to the two pressures is added as the fluid pressure. output from the means.

[Example] Examples will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the invention.

In the figure, reference numeral 1 denotes a housing, and a pressure-sensitive hole 2 formed in the center thereof is connected to a conduit containing a fluid to be measured. 3 is a diaphragm made of a flexible thin film, which airtightly fixes the housing l at the upper side;
It is displaced in the vertical direction in response to the pressure of the fluid entering the pressure sensitive chamber 4 from the pressure sensitive hole 2.

A pair of holders of the diaphragm 3 are sandwiched between upper and lower surfaces by plates 5 and 6, and the lower holder is sandwiched between plates 6 and 6.
An auxiliary coil spring 7 is provided between the housing 1 and the housing 1.
is compressed and interposed. A rod 8 is erected on the upper surface of the upper receiver u5 with its axis aligned with the diaphragm 3.

9 is a compression coil spring (biasing means) having a stronger elastic force than the auxiliary coil spring 7, and the elastic force of this compression coil spring 9 causes the spring receiver 10,
The diaphragm 3 is urged downward via the rod 8 and the receiver ff15. A movable spring receiver 11 that receives the upper end side of the compression coil spring 9 is threadedly engaged with a threaded rod 12 arranged so that its axis coincides with the rod 8, and moves forward and backward in the axial direction by rotation of the threaded rod 12. Note that the movable spring receiver 11 is provided with a rotation prevention means, but illustration thereof is omitted.

The threaded rod 12 is connected to the step motor 1 via a reduction gear group 13.
4 controls the rotation angle. Therefore, by controlling the rotation of the step motor 14, the biasing force of the compression coil spring 9 against the diaphragm 3 is controlled. By changing the biasing force of the compression coil spring 9, a bias pressure corresponding to the biasing force is applied to the diaphragm 3 against the pressure of the fluid. 15 is a cover.

A cylindrical body 1 provided between the housing 1 and the cover 15
6 is made of electrically insulating synthetic resin,
One end of a conductive brush 17 is fixed to the inner wall of the housing. The conductive brush 17 is made of a metal material with spring properties, and the second
As shown in the figure, the ring-shaped portion 17m at the center is formed with a small round protrusion 18 projecting downward. The conductive brush 17 is lightly urged downward so that the protrusion 18 always comes into contact with the stepped portion 8a formed at the base of the rod 8. Therefore, as the diaphragm 3 is displaced, the conductive brush 17 swings up and down using its root as a fulcrum.

20 is a resistor having a negative electrical resistivity, and a voltage is applied to both ends of the resistor. Even if the conductive brush 17 swings due to the movement of the diaphragm 3, the tip 17b of the conductive brush 17 always contacts the resistor 20. Therefore, the potential of the conductive brush 17 changes corresponding to the amount of displacement of the diaphragm 3, and that potential is input to the adding circuit 21. In this way, the first signal output circuit that outputs a signal (voltage value) corresponding to the amount of displacement of the diaphragm 3 is formed by the conductive brush 17 and the resistor 20.

FIG. 3 shows the relationship between the pressure inside the pressure-sensitive hole 2 (that is, the pressure applied to the diaphragm 3) and the potential of the conductive brush 17 (when the bias pressure is zero). According to the displacement, the contact position between the conductive brush 17 and the resistor 20 changes, the potential of the conductive brush 17 changes, and the pressure applied to the diaphragm 3 is detected.

The measurement range is, for example, 20 cmAq, and the measurement resolution, that is, the minimum measurable unit, is, for example, 1 cmAq.

Returning to FIG. 1, 22 is a setting circuit (biasing force setting means) that variably sets the biasing force of the compression coil spring 9. The setting here may be performed manually, but depending on the usage environment. The settings may be automatically set by inputting temperature, pressure, and other signals.

The setting output from the setting circuit 22 is input to a control circuit 23 that controls the rotation angle of the step motor 14. Then, the step motor 1 is moved so that the set biasing force is obtained.
A control signal for controlling the rotation angle of step motor 4 is output from control circuit 23 to step motor 14 . In this way, the biasing force of the compression coil spring 9 is controlled to the set value.

Further, the output from the setting circuit 22 is output to the second signal output circuit 25. The second signal output circuit 25 converts the biasing force of the compression coil spring 9 into pressure on the diaphragm surface, and adds a voltage corresponding to the pressure to the addition circuit 21.
Output to. Then, in the adding circuit 21, the signal from the second signal output circuit 24 and the signal from the conductive brush 17 of the first signal output circuit are added, and the diaphragm 3
A signal corresponding to the true pressure value being experienced by the sensor is output.

FIG. 4 shows the relationship between the pressure within the pressure-sensitive hole 2 (that is, the pressure received by the diaphragm 3) and the output signal of the adder circuit 21. B is a bias pressure given by the biasing force of the compression coil spring 9. When the biasing force of the compression coil spring 9 does not change, the output signal from the adder circuit 21 is.

Exactly the same as in Figure 3! It is possible to detect a range of 20 c·aq in units of 1 c·aq. However, by changing the bias pressure B, the output from the adder circuit 21 as a whole changes within the shaded area in FIG.
000 cmAq) can be detected in units of 1 cmAq.

FIG. 5 shows a second embodiment of the present invention, in which a DC motor 54 is used in place of the step motor. In this case, the variable resistor 55 to which a constant voltage is applied is linked with the movable spring receiver 11 to form a potentiometer, and an output signal corresponding to the biasing force of the compression coil spring 9 is obtained from the potentiometer, and the adder circuit 21 is input.

FIG. 6 shows a third embodiment of the present invention, in which a permanent magnet 62 is fixed to the tip of a leaf spring 61 instead of the conductive brush. A magnetoresistive element 63 is arranged opposite to the permanent magnet 62, and the permanent magnet 62 is displaced in accordance with the displacement of the diaphragm 3, thereby changing the resistance value of the magnetoresistive element 63. The output voltage to changes. A circuit for applying a voltage to the magnetoresistive element 63 and the like are not shown.

Further, in FIG. 6, 64 is an electromagnetic coil, 65 is a movable iron core, and 66 is an iron yoke.The electromagnetic force generated by passing a current through the electromagnetic coil 64 forces the diaphragm 3 through a rod 67. acts. This biasing force can be changed by changing the value of the current flowing through the electromagnetic coil 64. A control circuit 68 controls the current value of the electromagnetic coil 64 in accordance with an input signal from the setting circuit 22.

Note that all or part of each circuit in each of the above embodiments may be configured by a microcomputer.
It may also be incorporated as part of the functions of a microcomputer that performs various other controls.

[Effects of the Invention] According to the pressure sensor of the present invention, even if the range of pressure that can be measured from the amount of displacement of the diaphragm is narrow, it is possible to change the bias pressure applied to the diaphragm by changing the urging force of the coil spring. Therefore, it has the excellent effect of being able to measure pressure over a very wide range of measurement ranges and with high accuracy within a narrow range using the same measurement units.

3 and 4 are diagrams showing the measurement range of the example, FIG. 5 is a configuration diagram of the second embodiment, FIG. 6 is a block diagram of the third embodiment.

3... Diaphragm, 9... Compression coil spring, 11... Movable spring receiver, 12... Threaded rod, 14...
...Step motor, 17...Conductive brush, 20...
・Resistor, 21...addition circuit, 22...setting circuit,
23... Control circuit, 25... Second signal output circuit.

Agent: Patent Attorney Kazuon Mii

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a first embodiment of the present invention, Fig. 2 is a perspective view of a conductive brush of the embodiment, Fig. 4 is a)

Claims (2)

[Claims] (1) A diaphragm disposed to be displaced by the pressure of a fluid, a biasing means for biasing the diaphragm against the pressure of the fluid, and a biasing force of the biasing means being variably set. a biasing force setting means for controlling the biasing force of the biasing means based on an output signal from the biasing force setting means; and a first signal output for outputting a signal corresponding to the amount of displacement of the diaphragm. a second signal output means for outputting a signal corresponding to the magnitude of the biasing force; and a second signal output means for adding the output signal from the first signal output means and the output signal from the second signal output means. and an addition means for outputting a signal corresponding to the pressure value of the fluid. (2) A diaphragm disposed to be displaced in response to the pressure of a fluid, a biasing means for biasing the diaphragm against the pressure of the fluid, and a biasing force of the biasing means being applied electrically. A pressure sensor comprising: urging force control means controlled by an input signal; and signal output means outputting a signal corresponding to the amount of displacement of the diaphragm.