Pressure-sensing drain discharge structure

Abstract

To provide a drain discharge structure that indirectly grasps the load / unload state of a compression means based on the positive / negative of the detected pressure, and does not allow drain being discharged to flow back even when the pressure inside the intercooler becomes negative. [Solution] A drain discharge structure in a compressed air circuit having two or more compression means and an intercooler, comprising a drain delivery pipe, a branch joint branching from the drain delivery pipe, a drain trap, and pressure detection means, the drain trap having a storage section, a discharge section, and a control section, the control section performing pressure reduction valve opening control to open a solenoid valve for a predetermined short time at predetermined cycles, and performing drain discharge valve opening control to open the solenoid valve between upper limit detection and lower limit detection by upper limit detection means and lower limit detection means during periods other than the pressure reduction valve opening control, and employing means not performing pressure reduction valve opening control and drain discharge valve opening control when the detection result of the pressure detection means is negative pressure.

Description

[Technical Field]

[0001] The present invention relates to a drain discharge structure connected to an intercooler disposed downstream of a first compression means in a compressed air circuit having two or more compression means. [Background technology]

[0002] When compressing air, the higher its density, the better the compression efficiency. However, when air is compressed, its temperature rises and its density decreases. In other words, as the air temperature rises, the compression efficiency decreases. Furthermore, since the compressed air produced has limited uses when it is in a high temperature state, it is desirable that the air be cooled almost simultaneously with compression during the manufacturing process in the compression means.

[0003] 2. Description of the Related Art Conventionally, an oil cooling system has been known as a method for efficiently and simply cooling compressed air in a screw compression means among compression means. The screw compression means compresses the air by introducing air between the male and female screw structures, while the oil-cooled type cools the air by spraying oil to seal the gap between the screws. The oil is then continuously recovered by a recovery mechanism such as an oil separator and reused. However, oil-cooled compression means have a problem in that the sealing and cooling oil that is not captured and recovered by the oil separator flows back in the direction of the produced compressed air, i.e., into the compressed air pressure circuit. This means that the oil is contained in the drain generated when the temperature of the compressed air drops (i.e., drain derived from the moisture originally contained in the compressed air), and in order to remove this oil, it is necessary to provide an oil-water separation means.

[0004] One solution to the above problem is an oil-free compression means in which no oil comes into contact with the air during the compression stroke. However, since oil-free compression means are not cooled by oil, the temperature of the compressed air rises and compression efficiency decreases. Therefore, oil-free compression means are provided with multiple compression means to compress the air in sections, and the compressed air is cooled by an intercooler at a predetermined intermediate point in the compression stroke.

[0005] However, the amount of compressed air used in the compressed air pressure circuit that generates the compressed air varies depending on the purpose of the compressed air-using equipment connected downstream. When the amount of compressed air used is high, it is difficult to respond without increasing the amount produced by the compression means. Conversely, when the amount of compressed air used is low, not only is a large amount produced by the compression means wasted, but the excess compressed air accumulates in the compressed air pressure circuit, causing the pressure to rise above the predetermined appropriate pressure. Therefore, while it is possible to stop the operation of the compression means when the amount of compressed air used is low, an excessive starting current is required to start the compression means. This is not economical from the standpoint of device life and power efficiency, and is therefore difficult to adopt.

[0006] Therefore, rather than stopping the compression means, there is a technique in which the compression means is operated under no load (hereinafter, no load operation may be referred to as "unloaded" and loaded operation may be referred to as "loaded"), the compressed air intake port is closed or slightly opened, and the compressed air remaining in the compression means, or the compressed air that has flowed into the compression means from the intake port and been compressed by the compression means during unloading, is released via an air release valve, thereby canceling the effect. However, this technology also has the problem that the discharge port of the intercooler, which is arranged in the middle between the compression means, is on the suction side of the subsequent compression means, and therefore the compression action associated with the unloading of the subsequent compression means causes negative pressure on the discharge port side of the intercooler, and not only the drain generated within the intercooler but also the drain discharged from the intercooler to the outside via a drain trap or the like may flow back toward the subsequent compression means.

[0007] In order to solve the above problems in the compression means, technical proposals have been made in Japanese Patent Laid-Open Publication No. 09-79160 (Patent Document 1) and Japanese Patent No. 5706681 (Patent Document 2). That is, Patent Document 1 proposes a technique for maintaining a positive pressure state by switching a three-way solenoid valve during no-load operation of a two-stage dry compression means. Also, Patent Document 2 proposes a technique for improving reliability by controlling the suction amount at the start of a multi-stage compression means equipped with a suction throttle valve. However, the technical proposal in Patent Document 1 uses a three-way valve, which is more complex and more prone to failure than the two-way valves that have been used conventionally, which creates new problems such as interference with the stable supply of compressed air. Furthermore, the technical proposal in Patent Document 2 also uses a suction throttle valve with a complex control structure, as well as a three-way valve similar to that in Patent Document 1 as the piping branching structure, which can easily make the piping structure complex, resulting in problems such as increased time required for maintenance work and equipment maintenance.

[0008] In order to discharge the drain generated in the compressed air circuit to the outside, drain traps are provided that have discharge methods such as a solenoid valve type that opens and closes under timer control, or a float type that opens and closes a valve using a float that moves up and down depending on the amount of drain stored in a drain reservoir. However, timer-controlled drain traps have the problem that even if no drain is present, the solenoid valve opens and closes according to the timer setting, resulting in the release of unnecessary compressed air when the solenoid valve opens. Furthermore, with a float-type drain trap, the valve will not open unless a certain amount of drain has accumulated, which causes an airlock in the drain piping and the drain trap. If the inflow of drain stops, the float will not operate, and the valve will not open.

[0009] Therefore, the applicant of the present invention has developed a technique to solve the above problems with drain traps, and has proposed the technique described in Japanese Patent No. 5703519 (Patent Document 3). According to this technical proposal, it is possible to automatically eliminate airlock by providing a drain reservoir with an upper limit electrode, a lower limit electrode, and a common electrode, and by opening the valve for a predetermined short time at a predetermined cycle, and when a predetermined amount of drain has accumulated up to the upper limit electrode position, it is possible to discharge the drain down to the lower limit electrode position, which is an excellent effect.

[0010] However, according to the technical proposal in Patent Document 3, when this technology is applied to a multistage compression means (often an oil-free type), when the multistage compression means is unloaded and an intercooler arranged between the compression means becomes negative pressure, there is a problem, as already mentioned as a problem on the compression means side, in that the drain that is to be discharged to the outside flows back toward the compression means of the subsequent stage, and there is also a problem that the compressed air discharged together with the drain and the air near the discharge port enter the drain reservoir due to the negative pressure caused by unloading, and form bubbles that induce malfunction of the sensor in the drain reservoir. One way to solve these problems is to have the drain trap receive an operating status signal from the compression means and operate the drain trap only when drain is likely to be generated, but connecting this operating status signal to the drain trap would complicate the internal wiring and increase the risk of human error during equipment operation, maintenance, etc. Furthermore, if the circuit structure does not send an operating status signal from the compression means, there is also the problem that the drain trap cannot detect the condition on its own.

[0011] The applicant focused on pressure detection technology that can detect the pressure inside the piping in the above-mentioned multi-stage compressed air pressure circuit, and came up with the idea of ​​whether it might be possible to indirectly detect the load / unload state of the compression means. Based on this idea, the applicant developed a drain discharge structure that controls the opening and closing of a solenoid valve using positive and negative pressure by providing a pressure detection means connected to the control unit of the drain trap in the drain delivery pipe connected to the intercooler, and has come to propose the "pressure detection type drain discharge structure" of the present invention. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 09-79160 [Patent Document 2] Patent No. 5706681 [Patent Document 3] Patent No. 5703519 Summary of the Invention [Problem to be solved by the invention]

[0013] In view of the above problems, the present invention aims to provide a drain discharge structure that indirectly grasps the load / unload state of the compression means based on whether the detected pressure is positive or negative, and that does not allow the drain being discharged to flow back even when the pressure inside the intercooler becomes negative. [Means for solving the problem]

[0014] In order to solve the above problems, the present invention provides a drain discharge structure in a compressed air circuit having two or more compression means and an intercooler, the drain discharge structure comprising a drain delivery pipe, a branch joint branching from the drain delivery pipe, a drain trap, and pressure detection means, the drain delivery pipe delivers drain to the drain trap, and has a base end connected to an intercooler disposed downstream of a first compression means and a tip connected to the drain trap, the drain trap having a reservoir section that stores drain flowing in via the drain delivery pipe and has upper limit detection means and lower limit detection means that detect upper and lower limits of the drain water level, and an electromagnetic valve, The system is equipped with a discharge section that discharges the drain in the storage section by opening and closing the solenoid valve, and a control section that controls the opening and closing of the solenoid valve, and the pressure detection means detects the pressure in the drain delivery pipe and is provided in a pipe branching off from the drain delivery pipe via a branch joint, and the control section performs pressure reduction valve opening control that opens the solenoid valve for a predetermined short time at predetermined cycles, and performs drain discharge valve opening control that opens the solenoid valve between the upper limit detection and the lower limit detection by the upper limit detection means and the lower limit detection means during periods other than the pressure reduction valve opening control, and employs means that does not perform pressure reduction valve opening control and drain discharge open valve control when the detection result of the pressure detection means is negative pressure.

[0015] Furthermore, in the present invention, when the detection result of the pressure detection means is a negative pressure, the control section performs valve opening control of the solenoid valve for a predetermined time after the detection of the negative pressure.

[0016] Furthermore, the present invention employs a means in which the drain delivery pipe is provided with a downward slope from the intercooler side toward the drain trap side.

[0017] Furthermore, the present invention employs a means for indicating a positive pressure state (loaded state of the compressor) when a predetermined pressure is continuously detected for a predetermined time period with respect to the detection result (pressure detection signal) of the pressure detection means, and a negative pressure state (unloaded state of the compressor) when the predetermined pressure is not detected for a predetermined time period. [Effects of the Invention]

[0018] According to the pressure detection type drain discharge structure of the present invention, by employing a means for controlling opening and closing by the control unit depending on whether the pressure detection is positive or negative, it is possible to grasp the negative pressure in the drain delivery pipe caused by the unloading of the compression means and control the closing of the solenoid valve, and even if the pressure inside the intercooler becomes negative, it is possible to prevent the drain in the drain delivery pipe or drain trap from flowing back.

[0019] Furthermore, according to the pressure detection type drain discharge structure of the present invention, when positive pressure is detected by the pressure detection means, the water level is detected by the water level sensor, and discharge control is not performed when negative pressure is detected (unloaded state).Even if the water level fluctuates due to the negative pressure in the intercooler, detection is not performed by the water level sensor, and opening / closing control due to malfunction of the sensor can be prevented.

[0020] Furthermore, according to the pressure detection type drain discharge structure of the present invention, after detecting negative pressure, the solenoid valve is controlled to open for a predetermined period of time, thereby making it possible to discharge the drain stored inside the intercooler and in the storage section of the drain trap to the outside before the drain backflow occurs due to the negative pressure inside the intercooler.

[0021] Furthermore, according to the pressure-sensing drain discharge structure of the present invention, the drain discharge pipe is provided with a downward slope from the intercooler side to the drain trap side, so that the drain discharged from the intercooler flows down the slope towards the drain trap, preventing the drain from accumulating in the drain discharge pipe and making it difficult for the drain being discharged to flow back even when negative pressure occurs inside the intercooler.

[0022] Furthermore, according to the drain detection type drain discharge structure of the present invention, the detection result (pressure detection signal) from the pressure detection means is set to a positive pressure state (loaded state in the compressor) when a predetermined pressure is continuously detected for a predetermined time, and is set to a negative pressure state (unloaded state in the compressor) when the predetermined pressure is not detected for a predetermined time, thereby making it possible to prevent erroneous detection due to significant pressure fluctuations that occur mainly due to changes in the flow rate of the internal fluid when drain is discharged. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is an explanatory diagram showing an embodiment of a pressure detection type drain discharge structure according to the present invention. [Figure 2] 4 is a time chart showing the operation of the pressure detection type drain discharge structure according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The greatest feature of the pressure detection type drain discharge structure of the present invention is that a branch pipe and pressure detection means are provided in the drain delivery pipe connected to the intercooler and the drain trap, and the pressure detection means detects positive or negative pressure to control the opening and closing of the solenoid valve for drain discharge provided in the drain trap. Hereinafter, an embodiment of a pressure detection type drain discharge structure 1 according to the present invention will be described with reference to the drawings. The pressure-sensing drain discharge structure of the present invention is not limited to the embodiments described below, but can be modified as appropriate within the scope of the technical concept of the present invention, i.e., within the scope of the shape, dimensions, structure, etc. that can achieve the same functional effects. In addition, in the present invention, negative pressure indicates a pressure less than 0 Pa, and positive pressure indicates a pressure of 0 Pa or more.

[0025] FIG. 1 is an explanatory diagram showing an embodiment of a pressure detection type drain discharge structure 1 according to the present invention. The pressure-sensing drain discharge structure 1 is a structure for discharging drain generated in an intercooler 2 to the outside by a drain trap 20. The drain is sent from the intercooler 2 through a drain delivery pipe 10 to the drain trap 20, and is discharged to the outside when an electromagnetic valve 24 provided in the drain trap 20 is opened.

[0026] (Compression method) In the compressed air pressure circuit of the present invention, the compression means 3, which is a means for generating compressed air, is a device that compresses air and generates compressed air that has been pressurized to a predetermined pressure (e.g., 0.7 MPa), and there are no particular limitations on its specific structure as long as it uses conventionally known technology. A plurality of compression means 3 are disposed in the compressed air pressure circuit. By performing divided compression in sequence in a plurality of times using the plurality of compression means 3, it is possible to increase the compression efficiency. The first-stage compression means 3 draws in outside air from the suction port and compresses it, and then sends the air to the subsequent compression means 3, thereby performing divided compression. A throttle valve is provided at the suction port to control the intake and exhaust of outside air. Furthermore, the compressed air is cooled by the intercooler 2 at a predetermined intermediate point between the compression means 3, and the compressed air with a lowered temperature and increased density is sent to the compression means 3 at the subsequent stage. The compression means 3 arranged in the compressed air pressure circuit are linked together, and loading (loaded operation state) and unloading (unloaded operation state) are appropriately repeated depending on the usage status of the compressed air-using equipment 7 connected downstream of the compressed air pressure circuit. During unloading, the throttle valve is closed, and the intake of outside air into the compression means 3 is stopped or only a small amount of outside air is taken in.

[0027] (Plumbing) The various devices arranged in the compressed air pressure circuit (including the compression means 3, the intercooler 2, an air dryer, a cyclone separator, etc. as needed) are connected by piping, and compressed air is sent through the piping, enabling the compressed air-using equipment 7 connected in the subsequent stage of the compressed air pressure circuit to be used. There are no particular limitations on the length and diameter of the piping used, and these are set appropriately depending on the locations of various devices and the equipment 7 using compressed air.

[0028] (Intercooler) The intercooler 2 is used in a compressed air pressure circuit having two or more compression means 3, and cools the compressed air that flows in from the compression means 3A in the preceding stage and sends it to the compression means 3B in the subsequent stage. The specific structure of the intercooler 2 and the method of cooling the compressed air are not particularly limited, and it is sufficient to adopt a device using conventionally known technology, such as a water-cooling type or an air-cooling type. The intercooler 2 is also provided with an intake port 4 through which the compressed air generated by the compression means 3A in the preceding stage flows in, an outlet port 5 through which the cooled compressed air is sent to the compression means 3B in the following stage, and a drain outlet 6 through which drain generated when the compressed air is cooled is sent to a drain trap 20. As the intercooler 2 cools the compressed air, water vapor contained in the compressed air condenses on the inner walls of the intercooler 2, generating drainage. The generated drainage accumulates below the intercooler 2 due to its own weight and gravity, and is sent to a drain delivery pipe 10 from a drain delivery port 6 provided at a predetermined location on the bottom surface of the intercooler 2. When the intercooler 2 is unloaded, from the perspective of the compression means 3A, the intake of outside air stops or a small amount is taken in, but even if outside air is taken in, it is released from an outlet (not shown), so it appears to be at close to atmospheric pressure.However, from the perspective of the compression means 3B, it is the intake side, so in many cases the internal pressure actually becomes negative.

[0029] (Aftercooler) An aftercooler is used in a compressed air pressure circuit having two or more compression means 3, and cools the compressed air that flows in from a compression means 3B other than the front-stage compression means 3A, and sends it to the subsequent stage. The amount of drain generated in the aftercooler depends on the discharge pressure of the compression means 3A, but in many cases it is less than the amount of drain generated in the intercooler 2, which is the first stage cooling means. In other words, since a certain amount of drain has already been removed by the intercooler 2, it is possible to fully prevent backflow due to the negative pressure state that accompanies the unloading of the compression means 3B by providing a check valve or the like in the piping connecting the compression means 3B and the aftercooler.

[0030] (Drain delivery pipe) The drain delivery pipe 10 is a pipe for delivering drain that connects the intercooler 2 and the drain trap 20 . There are no particular limitations on the length or diameter of the drain delivery pipe 10. Furthermore, although not shown, when arranging the drain delivery pipe 10, it is also possible to employ a mode in which the drain delivery pipe 10 is provided with a downward slope from the intercooler 2 side toward the drain trap 20 side. By employing such a mode, the drain that flows in from the intercooler 2 flows down the slope efficiently into the drain trap 20, and the drain does not accumulate in the drain delivery pipe 10, allowing the drain to reliably flow into the drain trap 20. In addition, even when the pressure inside the intercooler 2 becomes negative due to the unloading state of the compression means 3, it is possible to prevent the drain in the drain delivery pipe 10 and the drain trap 20 from easily flowing back toward the intercooler 2. When the compression means 3 is unloaded, the drain in the drain delivery pipe 10 flows back into the intercooler 2, which is in a negative pressure state, and the delivery of drain into the drain delivery pipe 10 stops until the compression means 3 is loaded and the intercooler 2 is in a positive pressure state.

[0031] (Branch joint) The branch joint 13 is provided at a predetermined position on the drain delivery pipe 10 and is a joint that branches the compressed air that is delivered into the drain delivery pipe 10. The branch joint 13 is connected to a predetermined location such as a bent portion of the drain delivery pipe 10 or a joint between straight pipes, and by connecting the branch piping 14 described below to the branch port of the branch joint 13, the compressed air sent from the intercooler 2 toward the drain trap 20 is branched within the drain delivery pipe 10 and flows into the branch piping 14 side. There are no particular limitations on the specific structure of the branch joint 13, but a branch joint using conventionally known technology, such as a T-joint or Y-joint, may be selected. There are also no particular limitations on the location where the branch joint 13 is installed, but it is preferable to install it at a bent section of the drain delivery pipe 10 as shown in Figure 1 or at a joint between straight pipes, and to prevent the drain flowing through the drain delivery pipe 10 from accumulating in the branch pipe 14, it is preferable to install it so that the branch opening is upward or horizontal.

[0032] (Branch piping) The branch pipe 14 is a pipe that connects the branch joint 13 and the pressure detection means 11 . The branch pipe 14 has its base end connected to a branch joint 13 and its tip connected to a pressure detection means 11. The branch joint 13 sends the air inside the pipe branched from the drain delivery pipe 10 to the pressure detection means 11 to make the pressure inside the pipe the same, thereby detecting the pressure inside the drain delivery pipe 10. There is no particular limitation on the length or diameter of the branch pipe 14, but depending on the method of connection to the pressure detection means 11, a mode in which a plurality of pipes are connected as shown in FIG. 1 is also conceivable.

[0033] (Pressure detection means) The pressure detection means 11 is provided in a branch pipe 14 branched from the drain delivery pipe 10 via a branch joint 13, and is a sensor capable of detecting the pressure inside the drain delivery pipe 10. The pressure detection means 11 makes the pressure in the drain delivery pipe 10 and the branch pipe 14 the same by flowing the air in the drain delivery pipe 10 into the branch pipe 14 via the branch fitting 13, and by detecting this pressure, determines whether the pressure in the drain delivery pipe 10 is positive or negative. The pressure detection information (positive pressure / negative pressure) by the pressure detection means 11 is transmitted to the control unit 23 of the drain trap 20 via a wire (control line 12) connected to the control unit 23. The specific pressure detection method used by the pressure detection means 11 is not particularly limited, but for example, a detection method using a pressure switch, a semiconductor pressure sensor, or the like is adopted. Incidentally, when drain is discharged, the internal pressure of the drain delivery pipe 10, the branch joint 13, and the branch pipe 14 undergoes severe pressure and flow rate fluctuations due to the discharge flow of the internal fluid, which may result in erroneous detection by the pressure detection means 11. For this reason, it is desirable to control the detection result (pressure detection signal) of the pressure detection means 11 so that it indicates a positive pressure state (loaded state of the compression means 3) when a predetermined pressure is continuously detected for a predetermined time, and a negative pressure state (unloaded state of the compression means 3) when the predetermined pressure is not detected for a predetermined time. This control may be performed by the pressure detection means 11 or by the control unit 23 in the drain trap 20. The method for controlling this predetermined time may be a time constant based on CR or an interrupt timer control by a microcomputer. If the detection result of the pressure detection means 11 is negative pressure, the control unit 23 controls the solenoid valve to open for a predetermined time after detection, which can be said to be a double measure to prevent malfunction in terms of both signal and operation. Furthermore, it is even more desirable to reset the timer if detection ceases before the predetermined time is reached.

[0034] (Drain trap) The drain trap 20 discharges the drain that has flowed in through the drain delivery pipe 10 to the outside by opening and closing an electromagnetic valve 24 . The drain trap 20 is mainly composed of a storage section 21 for storing drainage, a discharge section 22 for discharging the drainage to the outside, and a control section 23 for controlling the discharge operation.

[0035] (Storage section) The storage section 21 is a section that temporarily stores the drainage that has flowed in until it is discharged, and is provided with a drain inlet 29 through which the drainage flows in and a drain outlet 30 through which the drainage flows out. The drain inlet 29 is connected to the tip of the drain delivery pipe 10, and the drain outlet 30 is connected to the discharge section 22 that discharges the drainage to the outside. The reservoir 21 is also provided with an upper limit detection means and a lower limit detection means for determining the upper and lower limits of the drain water level. The volume of the storage section 21 is not particularly limited, but it is appropriate to estimate the maximum amount of drainage in an assumed discharge interval generated in the intercooler 2 and set the volume to about 0.6 to 1.3 times that amount as a reference. This is because a volume that is too large leads to high costs, and conversely, a volume that is too small can lead to backflow of drainage due to poor discharge.

[0036] (Drain inlet) The drain inlet 29 is connected to the tip of the drain delivery pipe 10, and allows the drain that has flowed through the drain delivery pipe 10 to flow into the reservoir 21. There is no particular limitation on the diameter of the drain inlet 29, but by making it approximately the same diameter as the diameter of the drain delivery pipe 10 to be connected, it becomes possible to ensure smooth flow of drain into the reservoir 21. There are also no particular limitations on the installation location of the drain inlet 29, but it is preferable to install it in a location where backflow is unlikely to occur even when the drain is stored to its maximum capacity in the storage section 21, and it is preferable to install it, for example, above the side wall or on the top surface as shown in Figure 1.

[0037] (Drain outlet) The drain outlet 30 is connected to the discharge part 22 to allow the drain in the storage part 21 to flow out to the discharge part 22. There is no particular limitation on the diameter of the drain outlet 30, but it is determined based on the required drainage volume while taking into account the average drain inflow volume, so that even if drainage continuously flows in, it can be drained without overflowing the storage section 21. There are no particular limitations on the location where drain outlet 30 is provided, but in order to efficiently discharge the drain inside storage section 21, it is provided near the bottom surface of storage section 21. However, because foreign matter such as dust contained in the stored drain may have accumulated on the lowest surface of storage section 21, it is preferable to provide it at a position above the lowest surface, as shown in Figure 1.

[0038] (Discharge section) The discharge section 22 discharges the drain stored in the storage section 21 to the outside, and is mainly composed of a drain discharge port 32, a drain discharge pipe 31, and an electromagnetic valve 24. The drain discharge pipe 31 is a pipe for discharging the drain to the outside, and its base end is connected to the drain outlet 30 of the storage section 21 and its tip is connected to the drain discharge port 32. There is no particular limitation on the diameters of the drain outlet 32 ​​and the drain outlet pipe 31, but making them approximately the same diameter as the drain outlet 30 will contribute to smooth discharge of the drain.

[0039] (Upper limit detection means and lower limit detection means) The upper limit detection means and the lower limit detection means provided in the reservoir 21 detect the water level of the drain stored in the reservoir 21 . The specific configuration of the upper limit detection means and the lower limit detection means does not matter as long as they can detect the upper and lower limits, regardless of the type, such as capacitance type, resistance type, or float type. The detection results of the upper and lower limits detected by the upper limit detection means and the lower limit detection means are sent to the control unit 23 and used to control the opening and closing of the solenoid valve 24.

[0040] (Water level sensor) A possible embodiment is to use a water level sensor 25 as the upper limit detection means and lower limit detection means. The water level sensor 25 is capable of detecting the water level status within the reservoir 21 and is composed of three terminals, a common pole 26, a lower limit pole 27, and an upper limit pole 28, which apply an electrical signal, and is installed on each side wall of the reservoir 21. The water level sensor 25 applies a weak voltage from the terminal of the common pole 26 toward the inside of the drain, and detects the current water level status based on whether or not the lower limit pole 27 and the upper limit pole 28 detect a current through the drain. The results of the detection of the upper and lower limits by the water level sensor 25 are sent to the control unit 23 and used to control the opening and closing of the solenoid valve 24.

[0041] The water level sensor 25 is attached to the side wall of the reservoir 21 in the order of common electrode 26, lower limit electrode 27, and upper limit electrode 28 from the bottom. In this case, by providing the lower limit electrode 27 in a position above the drain outlet 30, it is possible to prevent compressed air from flowing into the drain outlet 30 in the open valve state. The installation position of the water level sensor 25 must be a certain distance away from the drain inlet 29. This is to prevent erroneous detection of drain caused by drain flowing in forcefully from the drain inlet 29 turning into a mist and coming into contact with the sensor.

[0042] (solenoid valve) The solenoid valve 24 is a valve element that can open and close the flow path of the drain discharge pipe 31, and is disposed at a predetermined intermediate position of the drain discharge pipe 31. The solenoid valve 24 is a drain discharge valve that opens or closes the drain discharge pipe 31 based on a valve opening instruction from the control unit 23 . There are no particular limitations on the specific structure of the solenoid valve 24, and it may be any structure that uses conventionally known technology. Whether the power source for the solenoid valve 24 is AC or DC can be determined appropriately depending on the embodiment.

[0043] (Control unit) The control unit 23 controls the opening and closing of the solenoid valve 24, and basic control modes include pressure reducing valve opening control and drain discharge valve opening control. The pressure reducing valve opening control is a control that opens the solenoid valve for a predetermined short time at predetermined intervals, for example, for 0.4 to 3 seconds every 1 to 5 minutes, for the purpose of reducing the internal pressure of the drain delivery pipe 10 that connects the intercooler 2 and the drain trap 20. The pressure reducing valve opening control is intended to evacuate and reduce the pressure in the drain delivery pipe 10 and the reservoir 21 to a pressure equal to or lower than the internal pressure of the intercooler 2, so the intervals and valve opening time can be determined by appropriate calculations based on the amount of drain, volume, internal pressure, and the fluid discharge capacity of the solenoid valve. Drain discharge valve opening control is a control that opens the solenoid valve between the upper limit detection and the lower limit detection by the upper limit detection means and the lower limit detection means during periods other than the above-mentioned pressure reduction valve opening control, with the aim of discharging the drain in the storage section 21 to the outside.

[0044] The control unit 23 is connected to a pressure detection means 11 disposed in the drain delivery pipe 10 via a control line 12 . The control unit 23 determines whether to execute or stop the pressure reduction valve opening control and the drain discharge valve opening control of the solenoid valve 24, based on the detection result in the drain delivery pipe 10 by the pressure detection means 11. Specifically, when positive pressure is detected, the pressure reduction valve opening control and the drain discharge valve opening control are executed, and when negative pressure is detected, the pressure reduction valve opening control and the drain discharge valve opening control are stopped. This means that when positive pressure is detected in the drain delivery pipe 10, it is determined that the compression means 3 is in a loaded state and a normal discharge operation is performed, and conversely, when negative pressure is detected, it is determined that the compression means 3 is in an unloaded state and the discharge operation is stopped, thereby preventing the drain in the storage unit 21 from flowing back into the intercooler 2, which is in a negative pressure state, and preventing external air from flowing back and entering through the drain discharge port 32.

[0045] (Control mode) The water level sensor 25 provided in the reservoir 21 is a lower-level judgment standard in the control unit 23, and is used as material for judging whether to open or close the solenoid valve 24 when a positive pressure is detected by the pressure detection means 11. Conversely, when a negative pressure is detected by the pressure detection means 11, the water level sensor 25 does not make an open / close judgment and only issues a valve close command. Therefore, even if the water level in the reservoir 21 fluctuates due to the negative pressure in the intercooler 2, the water level sensor 25 does not detect it, and it is possible to prevent the solenoid valve 24 from being controlled to open or close due to a malfunction of the water level sensor 25. In the control of opening and closing of the solenoid valve 24 by the control unit 23, when the pressure detection means 11 detects negative pressure, the solenoid valve 24 is controlled to be open for a predetermined time (several seconds) before issuing a command to close the solenoid valve 24. Adopt For example, the valve closing command is issued 3 to 30 seconds after the negative pressure is detected. By adopting such a configuration, the drain stored in the storage portion 21 can be discharged before the negative pressure in the intercooler 2 becomes large, thereby reducing the amount of drain in the storage portion 21.

[0046] (action / action) The main operations and actions of the pressure detection type drain discharge structure 1 consisting of the above components will be described with reference to Fig. 1. Here, the case where a water level sensor 25 is used as the upper limit detection means and the lower limit detection means will be described. The pressure-sensing drain discharge structure 1 has a compression means 3A, an intercooler 2, and a compression means 3B arranged via piping, and is provided with a drain trap 20 via a drain discharge pipe 10 to discharge drain from the intercooler 2. First, compressed air is generated by compression means 3A, sent through piping, and flows into intercooler 2 from intake port 4. At this time, the compressed air is at a high temperature and is cooled by intercooler 2. The compressed air that has flowed into intercooler 2 is cooled within said intercooler 2, whereby moisture (drainage) is separated and removed, and the air flows into compression means 3B from discharge port 5 through piping. Compression means 3B further compresses the compressed air that has flowed in, and sends it to equipment 7 that uses compressed air in the subsequent stage.

[0047] Next, the drain separated from the compressed air in the intercooler 2 flows into the drain trap 20 through the drain delivery pipe 10 from the drain delivery port 6 provided at the bottom of the intercooler 2. At this time, the pressure (positive pressure / negative pressure) in the drain delivery pipe 10 is detected by the pressure detection means 11, and the detection result is sent to the control unit 23. The drain that flows into the drain trap 20 is temporarily stored in the storage section 21. A water level sensor 25 is disposed in the drain storage section 21 as an upper limit detection means and a lower limit detection means, and detects the upper and lower limits of the water level of the stored drain and sends the detection results to the control section 23. When the pressure detection means 11 detects a positive pressure and the water level sensor 25 detects an upper limit of the drain stored in the storage section 21, the control section 23 performs drain discharge valve opening control. Specifically, when the solenoid valve 24 is opened, a flow path is formed from the drain outlet 30 to the drain discharge port 32 via the drain discharge pipe 31, and the drain is discharged to the outside. Furthermore, while the pressure detection means 11 is detecting a positive pressure, in addition to the drain discharge valve opening control, drain is also discharged when the solenoid valve 24 is opened by pressure reduction valve opening control.

[0048] Next, the control operation of the solenoid valve 24 by the control unit 23 will be described with reference to FIG. A branch pipe 14 connected to the drain delivery pipe 10 via a branch joint 13 is provided with a pressure detection means 11, which is an upper-level criterion, and transmits the results of pressure detection in the drain delivery pipe 10 to the control unit 23. Furthermore, a water level sensor 25, which is a lower-level criterion, is provided in the storage unit 21, and detects the upper and lower limits of the drain stored in the storage unit 21 and transmits the detection results to the control unit 23. First, the control operation of the control unit 23 performed during the period (ON period) when the positive pressure (ON) is detected by the pressure detection means 11 will be described. When a positive pressure (ON) is detected (T1) by the pressure detection means 11 that detects the pressure inside the drain delivery pipe 10, a detection result (ON) is sent to the control unit 23. The control unit 23 determines that the compression means 3 is in a loaded state based on the detection result (ON). Furthermore, because the pressure detection means 11, which is a higher-level determination criterion, is in the ON state, a minute-time pressure reduction valve opening control (MDT) that opens the solenoid valve 24 at regular intervals (CT) during the ON period, and a drain discharge valve opening control based on the detection result of the water level sensor 25, which is a lower-level determination criterion, is performed during periods other than the pressure reduction valve opening control.

[0049] (Drain discharge valve opening control) When the lower limit electrode 27 of the water level sensor 25 provided in the storage section 21 is ON (detected) and the upper limit electrode 28 is OFF (not detected) (T2), it is determined that the drain in the storage section 21 is being stored, and the solenoid valve 24 remains closed (T3). When the upper limit electrode 28 of the water level sensor 25 changes from OFF to ON (T4) due to the rise in the drain water level in the storage section 21 caused by the inflow and storage of drain, it is determined that the amount of drain stored has reached the upper limit, and an instruction to open the solenoid valve 24 is issued (T5) to lower the drain water level in the storage section 21. This instruction to open the valve continues until the lower limit electrode 27 changes from ON to OFF (T6). When the water level in the reservoir 21 drops due to the discharge of condensate caused by the opening of the solenoid valve 24 and the lower limit electrode 27 of the water level sensor 25 changes from ON to OFF (T6), it is determined that the amount of condensate stored in the reservoir 21 has reached the lower limit, and an instruction to close the solenoid valve 24 is issued to store the condensate (T7). This instruction to close the valve continues until the upper limit electrode 27 changes from OFF to ON.

[0050] Next, the control operation of the control unit 23 performed during the period (OFF period) in which the pressure detection means 11 detects negative pressure (OFF) will be described. When the pressure detection means 11 that detects the pressure inside the drain delivery pipe 10 detects a negative pressure (OFF) (T2), the detection result (OFF) is sent to the control unit 23. The control unit 23 that receives the detection result (OFF) determines that the compression means 3 is in an unloaded state, stops the pressure reduction valve opening control and the drain discharge valve opening control that were performed during the ON period, and issues a command to close the solenoid valve 24 (T9). After this valve closing command is issued, the solenoid valve 24 is maintained in a closed state until the pressure detection means 11 detects ON.

[0051] The basic configuration and operation / function of the pressure detection type drain discharge structure 1 according to the present invention have been described above, but the present invention is not limited to the configuration shown in the above embodiment or the drawings. For example, by transmitting a judgment signal indicating the loaded / unloaded state of the compression means 3 from the control unit 23 to a drain trap provided in an aftercooler after the compression means 3B, it becomes possible to control the opening and closing of the solenoid valve in the drain trap without measuring the amount of drain in the drain trap.

[0052] As described above, the pressure detection type drain discharge structure 1 of the present invention allows the control unit 23 to indirectly grasp the loaded / unloaded state of the compression means 3 based on the detection results of the pressure detection means 11 provided in the drain delivery pipe 10, and even when it is determined that the compression means 3 is in an unloaded state, the control unit 23 can stop the drain discharge, thereby preventing backflow of the drain. [Industrial Applicability]

[0053] The present invention can be used as a compressed air generator that excels in drain discharge in any field that requires multistage compressed air, such as food processing, electronic component manufacturing, car body painting, etc. Therefore, it is believed that the "pressure detection type drain discharge structure" of the present invention has great industrial applicability. [Explanation of symbols]

[0054] 1 Pressure-sensing drain discharge structure 2 intercooler 3 Compression methods 4 Intake port 5 Outlet 6 Drain outlet 7. Compressed air equipment 10 Drain delivery pipe 11 Pressure detection means 12 Control Line 13 Branch joint 14 Branch pipe 20 Drain trap 21 Storage section 22 Discharge section 23 Control Unit 24 Solenoid valve 25 Water level sensor 26 Common Pole 27 Lower limit 28 Upper Limit 29 Drain inlet 30 Drain outlet 31 Drain discharge pipe 32 Drain outlet

Claims

1. A drain discharge structure in a compressed air pressure circuit having two or more compression means and an intercooler, The system comprises a drain delivery pipe, a branch joint branching from the drain delivery pipe, a drain trap, and pressure detection means, the drain delivery pipe delivers the drain to the drain trap, and has a base end connected to an intercooler disposed downstream of the first compression means and a tip connected to the drain trap; The drain trap is provided with a storage section that stores drain flowing in through a drain delivery pipe and has upper limit detection means and lower limit detection means that detect upper and lower limits of the drain water level, a discharge section that has a solenoid valve and discharges the drain in the storage section by opening and closing the solenoid valve, and a control section that controls the opening and closing of the solenoid valve, The pressure detection means detects the pressure in the drain delivery pipe and is provided in a pipe branched from the drain delivery pipe via a branch joint, The control unit performs pressure reduction valve opening control to open the solenoid valve for a predetermined short time at each predetermined cycle, and performs drain discharge valve opening control to open the solenoid valve between the upper limit detection and the lower limit detection by the upper limit detection means and the lower limit detection means during periods other than the pressure reduction valve opening control, and when the detection result by the pressure detection means is negative pressure, performs valve opening control of the solenoid valve for a predetermined time after the detection of the negative pressure, and thereafter does not perform pressure reduction valve opening control or drain discharge valve opening control.

2. 2. The pressure-sensing drain discharge structure according to claim 1, wherein the drain delivery pipe is provided with a downward slope from the intercooler side to the drain trap side.

3. 3. The drain detection type drain discharge structure according to claim 1, wherein the detection result of the pressure detection means indicates a positive pressure state when a predetermined pressure is continuously detected for a predetermined time, and indicates a negative pressure state when the predetermined pressure is not detected for a predetermined time.

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