Automatic drain discharge device

Abstract

To provide an automatic drain discharge device capable of automatically discharging drain reliably without using an equalizing pipe and without performing periodic valve release, in a compressed air pressure circuit.SOLUTION: An automatic drain discharge device is composed of a drain discharge valve part, a water level sensor part, and a control part. In the drain discharge pipe that guides drain water from a compressed air pressure circuit to the drain discharge valve, the water level sensor is located closer to a drain discharge port of the device of the compressed air pressure circuit than a midpoint between the drain discharge valve and the drain discharge port of the device. The control part employs means for opening and closing the drain discharge valve part according to the detection of a water level by the water level sensor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an automatic drain discharge device, and more particularly to a technique for an automatic drain discharge device having a water level sensor separate from the main body. [Background technology]

[0002] Conventionally, one method for treating drainage accumulated in an air tank or the like provided in a compressor is to use an automatic drainage discharge device that automatically discharges the drainage. However, depending on the installation state of the automatic drain discharge device, air may remain in the portion where the water level is detected, causing so-called air binding, which may result in poor drain discharge.

[0003] Methods for avoiding air binding include installing a pressure equalizing pipe or periodically opening a valve for a certain period of time in addition to detecting the water level to eliminate air pockets. However, installing the equalizing pipe is time-consuming, and opening the valve for a certain period of time results in the unnecessary discharge of compressed air, resulting in a decrease in the efficiency of compressed air utilization. Therefore, there has been a demand for an automatic drain discharge device that can reliably discharge drain without using an equalizing pipe or periodically opening a valve.

[0004] Various techniques have been proposed to address such problems. For example, a device for automatically discharging drainage (see Patent Document 1) has been proposed and is a known technique. More specifically, in an automatic drainage device that is composed of an air compressor that produces compressed air, an air tank that generates drainage from compression, a drainage discharge valve that sends out the drainage using compressed air, and a drainage treatment device that turns the drainage into clean water, a drainage sensor is disposed somewhere between the air tank and the drainage discharge valve so as to obtain information from the drainage sensor for sending out the generated drainage from the drainage discharge valve, and a control unit is disposed to continuously send out compressed air for a certain period of time to move the drainage in the drainage treatment device. However, in order to discharge the drain, the compressed air must be discharged periodically, even for a short period of time, which reduces the utilization efficiency of the compressed air and does not yet solve the above problem. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3498260 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above problems, an object of the present invention is to provide an automatic drain discharge device in a compressed air circuit that can automatically discharge drain reliably without using an equalizing pipe or periodically opening a valve. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention comprises a drain discharge valve section, a water level sensor section, and a control section, and in the drain discharge pipe that leads drain water from a compressed air pressure circuit to the drain discharge valve, the water level sensor is located closer to the drain discharge outlet of the equipment of the compressed air pressure circuit than the midpoint between the drain discharge valve and the drain discharge port of the equipment, and the control section employs means for opening and closing the drain discharge valve section in response to the detection of the water level by the water level sensor.

[0008] The present invention also employs a means in which the equipment of the compressed air circuit is an air tank, the drain outlet is located at a lower part of the air tank, the drain pipe includes an elbow pipe, and the water level sensor unit is connected to an end of the elbow pipe.

[0009] Furthermore, the present invention employs a means in which the equipment of the compressed air circuit is an air tank, the drain outlet is located at the bottom of the air tank, the drain outlet pipe includes an elbow pipe, the water level sensor unit is located between the drain outlet and the end of the elbow pipe, and the water level sensor unit is interconnected in the vertical direction.

[0010] Furthermore, the present invention employs a means in which the drain water level sensor is of a resistive type or a capacitive type.

[0011] Furthermore, the present invention employs a means for the control unit to maintain the drain valve open for a fixed period of time after the water level sensor unit detects the water level and then stops detecting the water level.

[0012] In addition, in the present invention, the water level sensor unit is composed of a cylindrical sensor holder unit having a water level detection unit, two bushing units, and a sensor protection cover, and the sensor holder is sandwiched between the two bushing units. An O-ring is provided between the sensor holder and the bushing units, and the sensor holder is rotatable around the axis of the cylinder relative to the bushing units when installed. The sensor holder is covered with a sensor protection cover that is disposed so as to straddle the two bushing units, and the sensor holder is isolated from the outside air by the bushing units and the sensor protection cover, and the sensor protection cover employs a means for providing light blocking properties. Effect of the Invention

[0013] According to the automatic drain discharge device of the present invention, in an automatic drain discharge device that automatically discharges drain from a compressed air pressure circuit, the drain can be discharged reliably without using an equalizing pipe or periodically opening a valve, which contributes to improving the performance of the automatic drain discharge device. [Brief description of the drawings]

[0014] [Figure 1] 1 is a system diagram showing an embodiment of an automatic drain discharge device according to the present invention. [Diagram 2] 1 is a side view showing an embodiment of an automatic drain discharge device according to the present invention. [Diagram 3] 1 is an enlarged side view showing an embodiment of an automatic drain discharge device according to the present invention. [Figure 4] FIG. 4 is an explanatory diagram showing a water level sensor in the automatic drain discharge device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The automatic drain discharge device according to the present invention is most characterized in that it can reliably discharge drainage without using an equalizing pipe or periodically opening a valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an automatic drain discharge device according to the present invention will now be described with reference to the drawings.

[0016] The overall configuration and each part of the automatic drain discharge device shown below are not limited to the embodiments described below, but can be modified as appropriate within the scope of the technical idea of ​​the present invention, i.e., within the scope of shapes, dimensions, structures, etc. that can achieve the same functional effects.

[0017] The present invention will be described with reference to FIGS. FIG. 1 is a system diagram showing an embodiment of an automatic drain discharge device according to the present invention. FIG. 2 is a side view showing an embodiment of the automatic drain discharge device according to the present invention, where (a) shows an example of an air tank attached to an air compressor, and (b) shows an example of a standalone air tank. FIG. 3 is an enlarged side view showing an embodiment of the automatic drain discharge device according to the present invention, where (a) shows a case in which the water level sensor is placed downstream of the elbow pipe, and (b) shows a case in which the water level sensor is placed directly at the drain outlet of the air tank. FIG. 4 is an explanatory diagram showing a water level sensor in an automatic drain discharge device according to the present invention, where (a) is an oblique view of the water level sensor part, (b) is a side view of the water level sensor part, (c) is an AA cross-sectional view, (d) is a BB cross-sectional view, and (e) is an example in which the angle of the sensor holder and bushing is changed.

[0018] The automatic drain discharge device 1 is a device that discharges drain water in a compressed air pressure circuit. The automatic drain discharge device 1 comprises a drain discharge valve unit 11, a water level sensor unit 30, and a control unit 20. The drain discharge valve unit 11 and the control unit 20 are built into the automatic drain discharge device main body 10, which is a single housing. Roughly speaking, the water level of the drain 3 is detected by the water level sensor unit 30, and in response to that, the control unit 20 opens and closes the solenoid valve of the drain discharge valve unit 11. A commercial power source is used.

[0019] The drain discharge valve portion 11 is a portion that controls retention and discharge of the drain 12 . It is equipped with a solenoid valve for discharging the drain 12. It is connected to a drain discharge pipe 62, receives instructions from the control unit 20 via a drain discharge valve control line 22, and controls drain discharge by opening and closing the solenoid valve. The drain discharged from the drain discharge valve unit 11 is sent to a drain treatment device 80. The drain 12 is treated in the drain treatment device 80, and becomes clean water that can be freely disposed of.

[0020] The control unit 20 opens and closes the drain discharge valve unit 11 in response to the detection of the water level by the water level sensor unit 30. In detail, signals from sensor element A32 and sensor element B33 of the water level sensor section 30 are received via the water level detection line 21, the resistance value or capacitance value of the two elements is measured, and it is determined whether there is air or water between the two elements. If it is determined that there is water between the two elements, that is, if the water level exceeds the sensor, a command is sent via the drain valve control line 22 to the drain valve section 11 to open the valve. Also, if it is determined that there is air between the two elements, that is, if the water level does not exceed the sensor, an instruction is sent via the drain valve control line 22 to the drain valve section 11 to close the valve.

[0021] A relatively long drain discharge pipe 62 is provided between the water level sensor unit 30 and the drain discharge valve unit 11. Therefore, even if the water level at the water level sensor unit 30 falls below a specified level, it is considered that there is still a large amount of drain 12 in the drain discharge pipe 62, so the timing of closing the valve may be delayed. In other words, the control unit 20 may maintain the open state of the drain discharge valve unit 11 for a certain period of time after the water level is no longer detected by the water level sensor unit 30 after the water level is detected by the water level sensor unit 30. The certain period of time depends on the length of the drain discharge pipe 62, but is, for example, about one second.

[0022] The water level sensor section 30 is composed of a cylindrical sensor holder 31 having a sensor element, two bushing sections, and a sensor protection cover 50. The water level sensor unit 30 is attached to any position of the drain discharge pipe 62 to detect the water level of the drain in the drain discharge pipe 62. Detection is possible whether the sensor is disposed horizontally or vertically. However, taking into consideration the effect of air binding, the water level sensor unit 30 is positioned in the drain discharge pipe 62 closer to the drain discharge outlet 61 than the midpoint between the drain discharge outlet 61 of the air tank 60, which is a device of the compressed air pressure circuit, and the drain discharge valve unit 11. By arranging the water level sensor unit 30 in a position close to the drain outlet, the effect of air binding can be reduced. The detection method of the water level sensor unit 30 is a resistive method or a capacitive method. The capacitive method is convenient because it can measure even if the object to be measured is not a conductor, and it can detect regardless of the state of the drain 12.

[0023] The sensor holder 31 is a portion that holds the sensor element A 32 and the sensor element B 33. It is cylindrical and is suitably made of a material such as polyoxymethylene, because it has strength and fatigue resistance and is suitable as a portion that holds the sensor elements to be inserted into a pipe. A flat recess is made in a part of the side surface to fix the sensor element A32 and the sensor element B33. The water level detection line 21 is connected to the sensor element A32 and the sensor element B33 and extends to the control unit 20 of the automatic drain discharge device main body 10. The sensor element A32 and the sensor element B33 are screw-shaped, and the tip of the screw penetrates the inside of the sensor holder 31 and is structured to contact the drain 12 flowing inside the sensor holder 31. A seal washer 34 is sandwiched near the head of the sensor element A32 and the sensor element B33 to prevent the drain 12 and the compressed air 71 from leaking out from the gap of the hole. For the seal washer 34, a combination of ordinary steel and nitrile rubber is suitable for waterproofing.

[0024] The material of the sensor element A32 and the sensor element B33 is preferably stainless steel, since the parts that come into contact with water are less susceptible to corrosion. Sensor holder 31 is sandwiched between two bushing parts, bushing A 40 and bushing B 41, and an O-ring 35 is placed between sensor holder 31 and the bushing parts to improve the degree of sealing. Nitrile rubber is a suitable material for the O-ring. The bushing A40 and the bushing B41 are disposed on the inflow side and the outflow side of the water level sensor part 30, and are structured to sandwich the sensor holder 31. The bushing A40 and the bushing B41 have a threaded part that screws into the internal threaded part of the drain discharge pipe 62, and a flange 42, and the sensor holder 31 is sandwiched between the flange 42 of the bushing A40 and the bushing B41. The bushing A 40 and the bushing B 41 are fixed by four bolts 43 .

[0025] The sensor protection cover 50 is disposed in the circumferential direction along the flanges 42 of the bushings A40 and B41, and the water level sensor unit 30 is sealed by the bushings A40, B41 and the sensor protection cover 50 and isolated from the outside. By isolating the water level sensor part 30 from the outside, it is possible to prevent moisture such as condensation from accumulating around the water level sensor part 30, and to prevent malfunction of the sensor elements A32 and B33. Furthermore, if the material of the water level sensor part 30 is polyoxymethylene, it is preferable that the sensor protective cover 50 has light-shielding properties to prevent deterioration due to light and ultraviolet rays. In other words, the sensor holder 31 is covered with a sensor protection cover 50 that is positioned so as to straddle the two bushing portions, and the sensor holder 31 is isolated from the outside air by the bushing portions and the sensor protection cover 50, and the sensor protection cover 50 is waterproof and light-blocking.

[0026] When installed in the bushing portion, the sensor holder 31 is rotatable about the axis of the cylindrical shape of the sensor holder 31 . In more detail, since the sensor holder 31 is fixed to the bushings A40 and B41 only by O-rings, when installing the water level sensor unit 30, the mounting angle between the bushings A40 and B41 and the sensor holder 31 can be changed. Therefore, for example, when fixing the bushing A40 to the drain discharge pipe 62 during installation, even if the upper position of the bushing A40 changes depending on the amount of screwing of the threaded portion of the bushing A40 into the drain discharge pipe 62, the upper position of the water level sensor unit 30 can be adjusted to the optimal position by changing the rotational position of the water level sensor unit 30 relative to the bushing A40.

[0027] The system of this embodiment will be described with reference to FIG. The air compressor 70 generates compressed air and supplies the compressed air to each device in the compressed air pressure circuit. One of the devices in the compressed air pressure circuit is the air tank 60. Compressed air 71 generated by the air compressor 70 is stored in the air tank 60. The stored compressed air 71 is supplied to other devices as appropriate. When the air compressor 70 compresses air, moisture is also collected, increasing the water vapor density in the compressed air. Therefore, depending on the outside temperature, the water vapor in the air tank 60 condenses, forming drain 12, which accumulates in the lower part of the air tank 60. Since drain 12 can cause corrosion, it should be drained from the air tank 60 as soon as possible. A drain outlet 61 is provided at the bottom of the air tank 60, and the drain 12 is discharged from the drain outlet 61. The drain outlet 61 is connected to the water level sensor unit 30 and a drain outlet pipe 62, and the drain outlet pipe 62 is connected to the drain outlet valve unit 11 of the automatic drain outlet device main body 10 at the end of the drain outlet pipe 62. If the drain discharge valve section 11 is always open, the compressed air 71 in the air tank 60 will be discharged, so the drain discharge valve section 11 is opened when the drain 12 accumulates to a specified amount, and is closed when the drain 12 has been discharged.

[0028] The operation is as follows: When the drain discharge valve unit 11 is closed, the drain 12 accumulates in the water level sensor unit 30 and the drain discharge pipe 62, and the water level of the drain 12 rises and exceeds the water level detection level of the water level sensor unit 30. Then, a signal that the water level has exceeded a specified value is transmitted from the water level sensor unit 30 to the control unit 20 via the water level detection line 21. Based on the received information, the control unit 20 instructs the drain discharge valve unit 11 to open the valve via the drain discharge valve control line 22. When the drain discharge valve portion 11 is opened, the drain 12 accumulated in the drain discharge pipe 62 is discharged all at once, assisted by the pressure of the compressed air 71 in the air tank 60. At the time of discharge, a very small part of the compressed air 71 is also discharged. The drain 12 is passed through a drain treatment device 80, where foreign matter is separated from the drain 12 and the drain 12 is discharged as clean water. As the drain 12 is discharged, the water level of the drain 12 drops, and when the water level falls below the water level detection level of the water level sensor unit 30, a signal indicating that the water level is below a specified value is transmitted from the water level sensor unit 30 to the control unit 20 via the water level detection line 21. The drain discharge valve control line 22 instructs the drain discharge valve unit 11 to close the valve via the drain discharge valve control line 22. The drain discharge valve portion 11 is closed, and the compressed air 71 in the air tank 60 can be prevented from being discharged unnecessarily.

[0029] The positional relationship between the air tank 60, the water level detection line 21, and the automatic drain discharge device main body 10 will be described with reference to FIG. First, the conventional operation will be described with reference to FIG. Various drain discharge devices (also called drain traps) are used to process the drain 12 that accumulates in the air tank 60 configured in the air compressor 70 or in the air tank 60 installed midway through the piping, but in many cases there is not enough space between the drain outlet 61 of the air tank 60 and the floor surface. In this case, an elbow pipe 64 is connected to the drain outlet 61, and then a straight pipe 63 or a tube is connected to it, and the conventional automatic drain discharge device 90 is connected at a position away from the air tank 60. The conventional automatic drain discharge device 90 is a type in which a water level sensor is built into the main body. Drain 12 from the air tank 60 reaches the conventional automatic drain discharge device 90 via an elbow pipe 64, a straight pipe 63, etc. The drain discharge valve opens and closes according to the water level detected by the built-in water level sensor. However, depending on the connection conditions from the drain discharge port 61 of the air tank 60 to the conventional automatic drain discharge device 90, a phenomenon called air binding may occur, preventing the drain 12 from reaching the conventional automatic drain discharge device 90, and there may be cases where the water level sensor cannot detect the water level even though the drain 12 is present. Air binding occurs when an air layer in the drain discharge device cannot be properly removed. In the example of Fig. 2(c), drain 12 is collected in part A, but there is air in part B, and since the air has nowhere to go, the drain 12 is pushed by the air and cannot reach part B. Naturally, the drain 12 cannot reach the water level sensor, so the drain valve cannot be controlled to open.

[0030] Next, the positional relationship between the air tank 60, the water level detection line 21, and the automatic drain discharge device main body 10 in the present invention will be described with reference to FIGS. 2(a) and 2(b). In both Figures 2(a) and 2(b), there is no space between the drain outlet 61 of the air tank 60 and the floor surface. An elbow pipe 64 is connected to the drain outlet 61 of the air tank 60, then the water level sensor unit 30 is connected, and further, the water level sensor unit 30 is connected to the automatic drain discharge device main body 10 via a straight pipe 63 or a hose. In terms of the relationship between the water level sensor unit 30 and the elbow pipe 64, there is a drain outlet 61 at the bottom of the air tank 60, which is a device in the compressed air pressure circuit, and the drain outlet 61 is connected to the drain outlet 61, which is connected to the drain outlet pipe 61 including the elbow pipe 64, and the water level sensor unit 30 is connected to the end of the elbow pipe 64. The end of the elbow pipe 64 includes both the upstream and downstream sides of the pipe. The water level detection line 21 of the water level sensor unit 30 is connected to the control unit 20 of the automatic drain discharge device main body 10. The height of the floor surface on which the automatic drain discharge device main body 10 is placed may be the same as the floor surface of the air compressor 70, etc. (Figure 2(a)), or it may be higher than the floor surfaces of the air compressor 70, air tank 60, etc. (Figure 2(b)). The drain 12 flows from the drain outlet 61 into the water level sensor unit 30 and the straight pipe 63 . In the case of Fig. 2(b), even if the drain 12 is pushed back by air and cannot reach the automatic drain discharge device main body 10, as in the conventional case of Fig. 2(c), the water level sensor unit 30 located immediately below the drain discharge port 61 can accurately grasp the amount of drain 12, so when the amount of drain 12 reaches or exceeds the amount detected by the water level sensor unit 30, the drain discharge valve unit 11 opens and the drain 12 can be discharged. Similarly, in the case of Fig. 2(a), the drain can be discharged without any problems.

[0031] In this way, since the water level sensor unit 30 is located immediately below the air tank 60, it is possible to detect the water level of the drain 12 before the point where air binding occurs. Therefore, even if air binding occurs at a later stage, the water level sensor unit 30 will detect the presence of the drain 12, so a discharge operation will be performed and the drain can be discharged normally.

[0032] The horizontal and vertical arrangements of the water level sensor unit 30 will be described. In Fig. 2, the water level sensor unit 30 is disposed in a portion where the drain 12 flows horizontally. This is referred to as a horizontal arrangement. An enlarged view is shown in Fig. 3(a). In the horizontal arrangement, the water level sensor unit 30 is disposed between the elbow pipe 64 and the straight pipe 63. When the sensor element A 32 and the sensor element B 33 provided in the sensor holder 31 are connected by the drain 12, the sensor detects the water level. 3(a), the water level of the drain 12 is in a state where the sensor element A 32 is slightly in contact with the water level of the drain 12. The drain 12 is filled in the pipe by about 80%. Since the water surface 13 of the drain 12 extends in the longitudinal direction of the pipe, when the water surface becomes choppy, the water surface 13 and the sensor element A32 easily separate from each other. Therefore, the water level needs to be detected by multiple checks. Furthermore, when the water level is detected, there is often a gap in the upper part of the pipe that allows the compressed air 24 to pass through. In this case, when the drain discharge valve 11 is opened, the compressed air 71 may be discharged together with the drain 12. This may result in the compressed air 71 being discharged wastefully, resulting in a decrease in the efficiency of using the compressed air.

[0033] Next, the case of the vertical arrangement will be described with reference to FIG. In the horizontal arrangement, the water level sensor unit 30 is disposed between the drain outlet 61 and the elbow pipe 64. More specifically, a drain outlet 61 is provided at the bottom of an air tank 60, which is a device in a compressed air circuit, a drain outlet pipe 62 includes an elbow pipe 64, and the water level sensor unit 30 is located between the drain outlet 61 and the end of the elbow pipe 64, with the water level sensor unit 30 being interconnected in the vertical direction. In this structure, the sensor element A32 and the sensor element B33 of the water level sensor unit 30 are arranged in the horizontal direction. When the drain 12 fills the entire inside of the elbow pipe 64 which is the drain discharge pipe 62 and reaches near the middle of the water level sensor unit 30, the sensor detects the water level. The water surface 13 of the drain 12 barely ripples because its area is only the width of the pipe of the water level sensor unit 30. Therefore, the reliability of detection is higher than that of a horizontal arrangement. Therefore, the need for frequent detection checks is reduced. In addition, when the water level is detected, the inside of the drain discharge pipe including the elbow pipe 64 is almost filled with drain 12, so when the drain discharge valve section 11 is opened, there is little possibility that compressed air 71 will be discharged together with the drain 12. Therefore, the vertical arrangement can improve the efficiency of compressed air utilization compared to the horizontal arrangement.

[0034] Thus, the automatic drain discharge device of the present invention, which automatically discharges drain from a compressed air pressure circuit, can reliably discharge drain without using an equalizing pipe or periodically opening a valve, thereby contributing to improving the performance of the automatic drain discharge device.

[0035] In addition, by locating the water level sensor at the end of the elbow pipe, the distance between the water level sensor and the drain discharge valve can be increased, thereby making it possible to suppress the occurrence of air binding.

[0036] Furthermore, since the sensor holder is rotatable, the position of the water level sensor can be optimized when arranging the water level sensor, thereby ensuring the performance of the water level sensor.

[0037] Furthermore, by covering the sensor part with the sensor protective cover, it is possible to prevent the outside of the sensor from getting wet due to condensation, etc. Also, since the sensor protective cover has light-shielding properties, it is possible to prevent deterioration of the sensor holder due to external light. [Industrial Applicability]

[0038] INDUSTRIAL APPLICABILITY The automatic drain discharge device according to the present invention is understood to have great industrial applicability as a technique for improving the performance of an automatic drain discharge device for discharging drain from a compressed air pressure circuit. [Explanation of symbols]

[0039] 1 Automatic drain discharge device 10 Automatic drain discharge device body 11 Drain discharge valve 12 Drain 13 Water surface 20 Control section 21 Water level detection line 22 Drain discharge valve control line 30 Water level sensor 31 Sensor holder 32 Sensor element A 33 Sensor element B 34 Seal washer 35 O-ring 40 Bushing A 41 Bushing B 42 Flange 43 Volts 50 Sensor protection cover 60 Air Tank 61 Drain outlet 62 Drain discharge pipe 63 straight pipe 64 Elbow Pipe 70 Air Compressor 71 Compressed Air 80 Drainage treatment equipment 90 Conventional automatic drain discharge device

Claims

1. An automatic drain discharge device for discharging drain water in a compressed air pressure circuit, The drain valve unit, the water level sensor unit, and the control unit are included. a drain discharge pipe for leading the drain water from the compressed air pressure circuit to the drain discharge valve portion, the water level sensor portion being located closer to the drain discharge port of the equipment of the compressed air pressure circuit than a midpoint between the drain discharge port of the equipment of the compressed air pressure circuit and the drain discharge valve portion; The control unit opens and closes the drain valve unit in response to the detection of the water level by the water level sensor unit.

2. The device of the compressed air pressure circuit is an air tank, and the drain outlet is located at a lower part of the air tank.

2. The automatic drain discharge device according to claim 1, wherein the drain discharge pipe includes an elbow pipe, and the water level sensor unit is connected to an end of the elbow pipe.

3. The device of the compressed air pressure circuit is an air tank, and the drain outlet is located at a lower part of the air tank. The drain discharge pipe includes an elbow pipe, and the water level sensor unit is located between the drain discharge port and an end of the elbow pipe, 2. The automatic drain discharge device according to claim 1, wherein the water level sensor unit is connected to each other in the vertical direction.

4. 2. The automatic drain discharge device according to claim 1, wherein the detection method of the water level sensor unit is a resistance type or a capacitance type.

5. 2. The automatic drain discharge device according to claim 1, wherein the control unit maintains the drain discharge valve in an open state for a certain period of time after the water level sensor detects the water level and then stops detecting the water level.

6. The water level sensor unit includes a cylindrical sensor holder having a sensor element, two bushings, and a sensor protection cover. The sensor holder is sandwiched between the two bushings, and an O-ring is provided between the sensor holder and the bushings. the sensor holder is rotatable about the axis of the cylinder when installed relative to the bushing portion; the sensor holder is covered with the sensor protection cover arranged to straddle the two bushing portions, and the sensor holder is isolated from outside air by the bushing portions and the sensor protection cover; 2. The automatic drain discharge device according to claim 1, wherein the sensor protective cover has waterproof and light-shielding properties.

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