JP2001296171A - Structure of liquid surface detection sensor in drain tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent liquid surface from being detected erroneously, when dust adheres to the root part of a sensor in a capacitance type liquid surface detection sensor for detecting the height of the drain liquid surface of a drain tank. SOLUTION: A sensor protection pipe 11, projecting horizontally from the wall surface 3a of a drain tank 3, is provided with a tip part 11a with a relatively small diameter, an inclined part 11b with a gradually increased diameter, and a root part 11c with a large diameter. A sensor body 10 is accommodated inside the tip part 11a, thus reducing the sensitivity of the sensor 10 to the root part of the protection pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present application relates to a structure of a liquid level detection sensor provided in a drain tank for controlling a drain trap for discharging a fixed amount of drain stored in the drain tank.

[0002]

2. Description of the Related Art In order to remove oil from drains generated by drain generators such as an air compressor to make treated water harmless to the environment, the generated drains are temporarily stored in a drain tank and connected to a discharge port. A technique is used in which a fixed amount of oil is sent to an oil / water separator by a drain discharge valve, and oil is adsorbed by an adsorbent or the like in the oil / water separator.

In this case, if the compressed air is discharged together with the drain when the drain discharge valve is opened, the pressure of the compressed air pipe is reduced and energy is lost. Therefore, a liquid level detection sensor is placed at an appropriate position in the drain tank. The valve is opened and closed at an appropriate timing based on a detection signal of a sensor. As the liquid level detection sensor for this purpose, a capacitance type sensor is often used because it has no trouble due to abrasion of the mechanism and can detect water and oil similarly.

FIG. 5 shows an example of a capacitance type liquid level detection sensor provided in a drain tank. The sensor body 10 includes an electrode (not shown) and a protection member made of a cylindrical straight tube type non-conductive material for protecting the sensor body. The pipe 11 is installed horizontally on the drain tank wall, and the liquid level is detected by detecting a change in the capacitance between the sensor body 10 and the drain tank wall.

[0005]

The above-mentioned capacitance type liquid level detecting sensor is provided so as to protrude horizontally from the wall of the drain tank. However, if foreign matter having a large relative dielectric constant adheres to the periphery of the cylindrical protective tube, the liquid is detected. Due to a change in capacitance, it was erroneously determined that drain water was present in the surroundings, and a detection signal was sometimes output even when the liquid level was lower than a specified detection position. In particular, since the base of the protective tube is close to the wall surface, the flow velocity of the drain is low, and the shape is also in the corner, so that dust, sludge (iron rust), oily solids, etc. are easily structurally adhered, and the liquid level due to these There were many detections. If the liquid level detection sensor detects the drain liquid level erroneously, the drain valve will be in a state almost normally open,
Since a large amount of compressed air is discharged, it has been a particular problem to prevent this.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a capacitance type liquid level detecting sensor for detecting a liquid level of a drain in a drain tank. The above-mentioned problem has been solved by providing the drain tank away from the wall surface. Further, in the invention of claim 2, the sensor protection tube is configured to be longer than the sensor main body, and the sensor main body is inserted only at the front end thereof. Each of the above-mentioned problems is solved by making them larger.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a sectional structure of a liquid level detection sensor of the present invention installed in a drain tank and a relationship between the liquid level detection sensor and peripheral devices. Reference numerals 1 and 2 denote an air compressor and an air dryer which form part of an air conditioner. Reference numeral 3 denotes a drain tank for temporarily storing the discharged drain. Since the drain pipe is directly connected to the upper portion from the drain outlet of the air dryer, the inside thereof has a high pressure due to the output of the air compressor. A known drain discharge valve 4 that opens and closes a drain pipe in a manner such as an electric type or a float type is connected to a discharge port of the drain tank 3, and a downstream side of the drain discharge valve 4 is further connected to an oil / water separator (not shown). I have.

At a predetermined position in the drain tank 3, there is provided a liquid level detection sensor 6 for detecting the upper limit height of the liquid level by a change in the surrounding capacitance, and a detection signal output line thereof is connected to a drain valve control device. 7 input terminals. The drain valve control device 7 calculates an appropriate drain discharge time according to a predetermined procedure, and outputs an open / close signal to the drain discharge valve 4. With this signal, the automatic valve mechanism of the drain discharge valve 4 operates to discharge a certain amount of drain.

[0009]

[Embodiment 1] The liquid level detecting sensor 6, which is a main part of the present invention, comprises a sensor body 10 composed of a copper wire coil and a protective tube 11, as shown in FIG. The protection tube 11 is made of a fluororesin, and is provided in this embodiment at a distance from the wall surface 3a of the drain tank 3. For example, the protection tube 11 projects downward from the upper surface of the drain tank and has a sensor main body 10 therein.
Is inserted. Since there is a distance between the sensor body 10 and the wall 3a of the drain tank 3, the wall 3a of the drain tank 3
Although it is less susceptible to foreign matter adhering to the surface, normal drain liquid level detection can be performed without any trouble. The shape of the protective tube 11 is not limited to this as long as the protective tube 11 is separated from the wall surface at the detection position to some extent, and may be provided so as to protrude upward from the bottom surface, or be inclined or bent.

[0010]

Embodiment 2 FIG. 3 shows a second embodiment of the liquid level detecting sensor 6 according to the present invention. The sensor protection tube 11 of the present embodiment is a cylindrical straight tube that protrudes horizontally from the wall surface 3a of the drain tank 3, and the sensor main body 10 is shorter than the protection tube 11, and is inserted into the tip of the protection tube 11. I have. Therefore, the protective tube 11
Even if foreign matter adheres to the base of the
Since there is a distance between 0 and 0, the change in capacitance is small, and there is little hindrance to liquid level detection. The rise in the liquid level can be detected as usual by a change in the capacitance at the center of the drain tank.

[0011]

Third Embodiment FIG. 4 shows a third embodiment of the liquid level detection sensor 6 according to the present invention. The sensor protection tube 11 of the present embodiment protrudes horizontally from the wall surface 3a of the drain tank 3, and has a tip portion 11a having a relatively small diameter and an inclined portion 11 having a gradually increasing diameter.
b and a root portion 11c having a large diameter. That is, the inner diameter of the root portion 11c is changed to the tip portion 1 where the sensor body 10 is provided.
1a is larger than the inner diameter. Protection tube tip 11
The sensor main body 10 is housed inside a. In a preferred embodiment, the inner diameter of the root portion 11c is 2-3 times the inner diameter of the tip portion 11a.
mm, the inner diameter of the tip 11a is 9 mm and the inner diameter of the root 11c is 18 mm. Providing the inclined portion 11b at the step between the distal end portion 11a and the root portion 11c has an effect of widening the corner and making it difficult for foreign matter to adhere as compared with the protection tube root.

Even if the sensor main body is mounted only at the tip of the protection tube and installed away from the side wall of the drain tank as in the second embodiment, the signal output line passing through the base of the protection tube does not have any sensitivity. However, in this embodiment, in the liquid level detection sensor 6 of the present invention, since the base diameter of the protection tube 11 is made larger than before, the distance between the sensor body 10 and the inside of the drain tank is widened, and the protection tube base portion is formed. Sensitivity of the sensor can be reduced. Therefore, even when dust or the like adheres to the vicinity of the base of the protection tube 11, the influence on the capacitance is small, and the dust is less likely to be affected. Since the diameter of the distal end portion of the protection tube is small, the sensitivity at the central portion of the drain tank is the same as the conventional one, and normal drain liquid level detection can be performed without any trouble.

Table 1 shows a comparison of the liquid level detection state between the conventional apparatus and the invention according to the third embodiment of the present invention, in which the same amount of dust adheres to the base of the protective tube.

[0014]

[Table 1]

[0015] Each of the experimental machines was 60 minutes from the bottom of the drain tank.
It is designed to detect when the drain liquid level exists at a height of about mm as the upper limit liquid level. Table 1 shows that when dust adheres to the base of the protective tube, the conventional liquid level detection sensor erroneously detects that there is a liquid level even at about 30 mm, and a large error occurs. With the liquid level detection sensor, 6
This indicates that a liquid level of about 0 mm is detected.

[0016]

According to the structure of the liquid level detection sensor of the present invention, even if dust adheres to the base of the sensor, the liquid level is not erroneously detected, and the normal liquid level detection has the same sensitivity as the conventional one. Further, it is possible to prevent the compressed air from being discharged together with the drain due to a malfunction of the drain discharge valve. Therefore, there is an effect that energy loss of the piping can be prevented with a simple configuration, and the frequency of maintenance can be reduced.

[Brief description of the drawings]

FIG. 1 shows an outline of a drain discharge mechanism using a liquid level detection sensor of the present invention.

FIG. 2 is a vertical sectional view of the liquid level detection sensor according to the first embodiment.

FIG. 3 is a longitudinal sectional view of a liquid level detection sensor according to a second embodiment.

FIG. 4 is a longitudinal sectional view of a liquid level detection sensor according to a third embodiment.

FIG. 5 is a longitudinal sectional view of a conventional liquid level detection sensor.

[Explanation of symbols]

 Reference Signs List 3 Drain tank 3a Wall surface 10 Sensor body 11 Protection tube 11a Tip 11b Inclined portion 11c Root

Claims (3)

[Claims] 1. A capacitance type liquid level detecting sensor for detecting a drain liquid level of a drain tank, wherein a sensor main body is provided apart from a wall surface of the drain tank. Structure of liquid level detection sensor. 2. A capacitance type liquid level detection sensor for detecting a liquid level of a drain in a drain tank, wherein a sensor protection tube is longer than the sensor main body, and the sensor main body is inserted only at a tip portion thereof. The structure of the liquid level detection sensor according to claim 1, wherein: 3. A capacitance type liquid level detecting sensor for detecting a liquid level of a drain in a drain tank, wherein a diameter of the sensor protection tube near a wall surface of the drain tank is larger than a tip portion. The structure of the liquid level detection sensor according to claim 1.