JPH10111163A - Submerging water pressure-type water level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a submerging water pressure-type water level sensor which is not operated erroneously or broken down due to dew condensation even in an environment, e.g. at a high open-air temperature and a low water temperature and which can be manufactured at a low cost. SOLUTION: In a water level sensor, a pressure detecting element 2 which is provided with a moving electrode 5 formed on a diaphragm 4 deformed by receiving an external pressure and with a fixed electrode 6 arranged so as to be separated from the moving electrode 5 and which detects the external pressure on the basis of a change in a capacitance due to a change in the gap 8 between both electrodes 5, 6 and a signal processing circuit part 3 which processes an output signal from the pressure detecting element 2 are housed inside a housing 1 so as to be airtight, and an air tube 13 by which the open air is introduced into the housing 1 is provided. In this case, the gap part 8 between both electrodes 5, 6 and the open end of the air tube 13 are connected airtightly by an intermediary tube 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a pump at a constant rate regardless of water depth by controlling a pump speed by measuring water depth such as a water level of a sewage treatment tank. The present invention relates to a submersible hydraulic pressure level sensor used for purposes such as generating an alarm when a certain level is reached.

[0002]

2. Description of the Related Art For example, as a sensor for detecting a water level of a water supply / drainage facility or the like, an air pump is provided, and a pressure detecting end is installed in the atmosphere to detect a water level. Sensors are generally and widely used (for example, see Japanese Patent Application Laid-Open No. 7-54394).

However, such a water level sensor employing the air purge method not only complicates the device but also has a problem in maintenance because the life of the air pump for air purge is relatively short. was there.

For this reason, in recent years, a submerged hydraulic pressure level sensor has been developed as a device capable of detecting the water level in a sewage treatment tank, other general water tanks, ponds, rivers, and the like with simpler equipment.

That is, as shown in FIG. 3, an opening 1a as a pressure detecting end is provided at a lower end surface of a substantially cylindrical housing 1, and a pressure detecting element 2 is provided while facing the opening 1a.
Is hermetically housed inside the housing 1 and
A signal processing circuit section 3 for amplifying, processing and transmitting the output signal from the pressure detecting element 2 is also housed in the housing 1 in a sealed manner.

Here, the pressure detecting element 2 is provided with a diaphragm 4 which is deformed by receiving pressure (water pressure) from the opening 1a, and a movable electrode 5 is provided on the diaphragm 4.
The fixed electrode 6 is fixed to the pedestal 7 so as to be spaced from the moving electrode 5 by a predetermined distance, whereby a gap 8 is formed between the electrodes 5 and 6.

[0007] Between the diaphragm 4 and the pedestal 7, a bonding glass 9 surrounding the electrodes 5 and 6 and maintaining the gap 8 is interposed.
Is provided with a through-hole 10 for communicating the inside of the housing 1 with the gap 8.

Further, a cable 11 is inserted through the upper end of the housing 1, and a lead wire 12 for taking out an output signal from the signal processing circuit unit 3 to the outside inside the cable 11.
And an air tube 13 for introducing air into the housing 1.
And are housed.

Then, the housing 1 is immersed in water, and the air is introduced from the air tube 13 to equalize the inside of the housing 1 and the gap 8 between the electrodes 5 and 6 with the atmospheric pressure. The water pressure acts on the lower surface of the diaphragm 4 from the opening 1a, and the internal pressure (atmospheric pressure) of the housing 1 acts on the upper surface of the diaphragm 4, and the balance of the forces deforms the diaphragm 4 to deform the two electrodes 5, 6. The gap 8 between them changes, and the water pressure is detected as a change in capacitance accompanying the change in the gap 8, and the water level is detected.

[0010]

However, in the conventional submerged water pressure type water level sensor, when the moisture of the air in the housing is condensed due to the decrease of the water temperature, the shrinkage of the air in the housing due to the temperature decrease. As a result, new outside air containing a large amount of moisture is introduced into the housing from the air tube, and water is accumulated in the housing due to dew condensation, thereby causing malfunction or failure of the internal signal processing circuit unit. There was such a problem.

In addition, the pressure detecting element is composed of a moving electrode formed on a diaphragm which is deformed by receiving an external pressure, and a fixed electrode which has a gap with the moving electrode. In the case of using a so-called capacitance element, which detects as a change in capacitance due to dew, a change in the dielectric constant occurs when dew condensation occurs between the two electrodes, resulting in abnormal detection sensitivity and a malfunction. Would.

That is, when the temperature of the air in the housing decreases with low water temperature, the air in the housing contracts as shown in the following equation (1), and new air is introduced into the housing through the air tube. Will be. Since the fresh air is also a source of moisture, dew condensation in the housing increases, which has caused an output abnormality inside the pressure detecting element and the signal processing circuit. pv = nRT (1) where, p: pressure, v: volume, n: number of moles, R: constant,
T: Absolute temperature

The present invention has been made in view of the above-mentioned circumstances, and does not cause malfunction or failure due to dew condensation even when used in an environment where the outside air temperature is high and the water temperature is low, and is manufactured at a low cost. An object of the present invention is to provide a submerged water pressure type water level sensor.

[0014]

A submerged hydraulic pressure level sensor according to the present invention comprises a movable electrode formed on a diaphragm which is deformed by receiving an external pressure, and a fixed electrode which is arranged at a distance from the movable electrode. A pressure detecting element for detecting an external pressure by a change in capacitance caused by a change in a gap between the two electrodes, and a signal processing circuit for processing an output signal from the pressure detecting element are hermetically housed in a housing. A movable electrode formed on a diaphragm that is deformed by receiving an external pressure, and a fixed electrode disposed apart from the moving electrode are provided, and the external pressure is detected by a change in capacitance caused by a change in a gap between the two electrodes. A submerged housing having a pressure sensing element and a signal processing circuit for processing an output signal from the pressure sensing element hermetically housed in a housing, and having an air tube for introducing air into the housing. In hydraulic water level sensor, characterized in that connecting the open end of the gap portion and the air tube between the two electrodes hermetically.

The gap between the two electrodes and the open end of the air tube are air-tightly connected via a relay tube.

According to the present invention thus constructed, the air introduced into the housing from the air tube acts directly on the diaphragm of the pressure detecting element from the relay tube to fill the entire area of the housing having a relatively large volume. Nothing. Therefore, even if the air temperature is lowered due to a low water temperature, the absolute amount of dew is reduced, and the respiratory action of the air is significantly reduced, so that a large amount of moisture cannot be supplied. Malfunctions and breakdowns can be prevented.

Further, a packing is interposed between the diaphragm and the housing, and the pressure detecting element,
The connection portion between the pressure detection circuit and the pressure detection element of the relay tube is integrally resin-sealed and housed in the housing.

[0018] Thereby, the penetration of water from the lower part of the housing is double-protected by the resin sealed with the packing to improve the watertightness, and moisture existing in the internal space of the housing is dew-condensed. Even in the case where a leak occurs at the cable outlet of the housing, the pressure detection element and the signal processing circuit can be protected by the sealed resin.

[0019]

FIG. 1 is a block diagram showing an embodiment of the present invention.
A description will be given based on FIG. The same or corresponding parts as those in the conventional example shown in FIG.

As shown in FIG. 1, an opening 1a is provided at the lower end surface, and a pressure detecting element 2 and a pressure detecting element 2 are provided inside a housing 1 made of, for example, a low-cost resin having excellent corrosion resistance. The output signal is amplified and signal-processed, and the signal processing circuit unit 3 having a protection circuit and the like is hermetically housed. Further, a cable 11 containing therein a lead wire 12 for taking out an output signal from the signal processing circuit unit 3 to the outside and an air tube 13 for introducing air into the housing 1 is inserted through the upper end of the housing 1. I have.

One end of a relay tube 20 is airtightly connected to the open end of the air tube 13, and the other end of the relay tube 20 is connected to a gap 8 between the electrodes 5 and 6 of the pressure detecting element 2. It is airtightly communicated inside.

That is, as shown in detail in FIG. 2, the pressure detecting element 2 is provided with a diaphragm 4 which is deformed by receiving a pressure from the opening 1a.
The movable electrode 5 is formed thereon, and the fixed electrode 6 is fixed to the pedestal 7 so as to be spaced apart from the movable electrode 5 by a predetermined distance, whereby a gap 8 is formed between the electrodes 5 and 6. However, a cylindrical projection 21 is provided on the upper surface of the pedestal 7, the other end of the relay tube 20 is air-tightly connected to the projection 21, and a through hole 22 is formed inside the projection 21. Is provided. Note that a bonding glass 9 for maintaining an interval is interposed between the diaphragm 4 and the pedestal 7.

With this configuration, the air introduced from the air tube 13 is supplied from the relay tube 20 into the gap 8 between the electrodes 5 and 6, and the diaphragm 4
Can be detected, and the air does not fill the entire area of the housing 1 having a relatively large volume, so that even if the water temperature decreases, the absolute dew condensation can be prevented. The volume can be reduced and the respiratory action of the air can be significantly reduced, eliminating the need to supply large amounts of moisture.

That is, the atmosphere is introduced from the air tube 13 into the space 8 between the electrodes 5 and 6 through the relay tube 20, and their volume is considerably smaller than the internal volume of the housing 1. The absolute amount of dew condensation can be reduced, and the introduction of new air due to air shrinkage can be reduced.

Furthermore, the lower end of the pressure detecting element 2, the signal processing circuit section 3, and the relay tube 20 are exposed in a state where the lower surface of the diaphragm 4 in FIG. The resin is integrally sealed by a block-shaped sealing resin 23. The lower surface of the sealing resin 23 is fixed to the inner peripheral surface of the lower end of the housing 1. Also,
O1 as a packing surrounds the periphery of the opening 1a of the housing 1 and is provided between the housing 1 and the diaphragm 4.
A ring 24 is interposed.

Thus, intrusion of water from the opening 1a of the housing 1 is double prevented by the O-ring 24 and the sealing resin 23 to improve watertightness. Further, even in the case where moisture existing in the internal space of the housing 1 is dew-condensed or a leak is generated at a lead-out portion of the cable 11 of the housing 1, the pressure detecting element 2 and the signal processing circuit portion are sealed by the sealing resin 23. 3 can be protected.

The outline of the method for manufacturing such a water level sensor is as follows. First, a housing 1 which is divided into upper and lower parts is prepared. Next, the pressure detecting element 2 is packed (O-ring) 2
4 is fixed to the inner peripheral surface of the lower end portion of the housing 1 by caulking. Next, the relay tube 20 is fitted and fixed to the projection 21 on the pedestal 7 to be connected to the through hole 22 communicating with the gap. Also, the circuit board of the signal processing circuit unit 3 is
And make the necessary circuit wiring connections.

Next, the pressure detecting element 2, the signal processing circuit 3
The resin-sealed body 23 is formed by housing the lower end side connection portion of the relay tube 20 in a cylindrical member (not shown) and pouring and heating a liquid resin. And
Connect the upper end of the relay tube 20 to the air tube 13 of the cable.
And the wiring connection between the cable 11 and the signal processing unit 3 is performed. Finally, the upper part and the lower part of the split housing 1 are fixed by ultrasonic welding or the like, and the water level sensor shown in FIG. 1 is completed.

In the above embodiment, the air tube and the through hole for introducing air into the gap between the electrodes are connected using the relay tube. However, the air tube is directly connected to the through hole in the gap between the electrodes. You may make it. As described above, various embodiments can be modified without departing from the spirit of the present invention.

[0030]

As described above, according to the present invention,
Even in an environment where the outside air temperature is high and the water temperature is low, the absolute amount of dew condensation inside the housing and the supply amount of air are reduced,
It is possible to prevent malfunction and failure of the pressure detection element and the signal processing circuit unit due to the dew condensation action. Furthermore, by sealing the pressure detection element, signal processing circuit, etc. together with resin together with watertight protection by packing, moisture existing in the internal space of the housing may condense or leak at the cable outlet of the housing. In the case where
The pressure detection element and the signal processing circuit can be protected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of the present invention.

FIG. 2 is an enlarged view of a pressure detecting element.

FIG. 3 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Pressure detection element 3 Signal processing circuit part 4 Diaphragm 5 Moving electrode 6 Fixed electrode 8 Void 11 Cable 13 Air tube 20 Relay tube 22 Through hole 23 Sealing resin 24 O-ring (packing)

Claims (3)

[Claims] A movable electrode formed on a diaphragm that is deformed by receiving an external pressure; and a fixed electrode disposed apart from the movable electrode, and a change in capacitance caused by a change in a gap between the two electrodes. A submerged type having a pressure detection element for detecting an external pressure by a pressure sensor and a signal processing circuit for processing an output signal from the pressure detection element in a housing, and having an air tube for introducing air into the housing. A submersible water level sensor, wherein a gap between the two electrodes and an open end of the air tube are hermetically connected. 2. The submerged hydraulic water level according to claim 1, wherein the gap between the two electrodes and the open end of the air tube are airtightly connected via a relay tube. Sensor. 3. A packing is interposed between the pressure detection element and the housing, and the pressure detection element, the pressure detection circuit, and the connection portion of the relay tube on the pressure detection element side are integrally resin-sealed to form a housing. The submerged water pressure type water level sensor according to claim 2, wherein the water level sensor is accommodated in the water pressure sensor.