Drain detection type drain discharge structure

Abstract

Based on the presence or absence of the detected drain, indirectly grasp the load / unload state of the compression means, and provide a drain discharge structure that does not cause the drained drain during discharge to flow back even when the inside of the intercooler becomes negative pressure. 【Solution means】A drain discharge structure in a compressed air pressure circuit having two or more compression means and an intercooler, wherein a drain detection means is provided in a drain delivery pipe between the intercooler and the drain trap, and a control unit that controls an electromagnetic valve for drain discharge performs a decompression opening control to open the electromagnetic valve at a predetermined minute time at a predetermined cycle, and during a period other than the decompression opening control, performs a drain discharge opening control to open the electromagnetic valve between an upper limit detection and a lower limit detection by an upper limit detection means and a lower limit detection means, and when the detection result in the drain detection means is no drain, adopts means not to perform the decompression opening control and the drain discharge opening control.

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 pressure circuit having two or more compression means.

Background Art

[0002] When compressing air, the higher its density, the better the compression efficiency. However, when air is compressed, its temperature rises while its density decreases. That is, when the temperature of air rises, the compression efficiency decreases. In addition, since the use of the generated compressed air is limited 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] Conventionally, an oil-cooling type is known as an efficient and simple method for cooling compressed air in screw compression means among compression means. The screw compression means compresses by introducing air between male and female screw-shaped structures. In the oil-cooling type, cooling is performed by oil sprayed for sealing between the screws. And the oil is continuously recovered by a recovery mechanism such as an oil separator and reused. However, the oil-cooling type compression means has a problem that the sealing / cooling oil that has not been captured and recovered by the oil separator flows backward toward the direction in which the manufactured compressed air goes, that is, toward the compressed air pressure circuit side. That is, the drain generated by the temperature drop of the compressed air (that is, the drain derived from the moisture originally contained in the compressed air) contains the oil, and it was necessary to provide an oil-water separation means to remove the oil.

[0004] Examples of solutions to the above problems include oil-free compression means that do not allow any oil to come into contact with the air during the compression stroke. However, since the oil-free compression means is not cooled by oil, the temperature of the compressed air will rise as it is, resulting in a decrease in compression efficiency. Therefore, the oil-free compression means divides and compresses the air by arranging a plurality of compression means, and cools the compressed air by an intercooler at a predetermined intermediate point in the compression stroke.

[0005] By the way, since the amount of compressed air used varies depending on the application of the compressed air-using equipment connected to the subsequent stage of the compressed air pressure circuit that generates the compressed air, when the usage amount is large, it will be difficult to cope unless the production amount by the compression means is increased. Conversely, when the usage amount is small, not only is it wasteful that the production amount by the compression means is large, but there is also a problem that the surplus compressed air stays in the compressed air pressure circuit and the pressure rises above the predetermined appropriate pressure. Therefore, when the amount of compressed air used is small, it is conceivable to stop the operation of the compression means, but since an excessive starting current is required when starting the compression means, it is never economical from the viewpoints of device life and power efficiency, and it is difficult to adopt.

[0006] Therefore, instead of stopping the compression means, the suction port of the compressed air is closed or slightly opened for no-load operation (hereinafter, no-load operation may be referred to as "unloading" and load operation may be referred to as "loading"), and the compressed air remaining in the compression means, or the compressed air that flows into the compression means from the suction port and is compressed by the compression means during unloading, is exhausted through the exhaust valve to cancel its influence. However, this technology also has a problem that, in the intercooler arranged in the intermediate part between the compression means, since the discharge port is on the suction port side of the subsequent compression means, due to the compression action accompanying the unloading of the subsequent compression means, the discharge port side of the intercooler becomes negative pressure, and there is a risk that the drain generated in the intercooler will flow back to the subsequent compression means side, including the drain discharged to the outside through a drain trap or the like from the intercooler.

[0007] In order to solve the problems in the above compression means, technical proposals described in Japanese Patent Application Laid-Open No. 09-79160 (Patent Document 1) and Japanese Patent No. 5706681 (Patent Document 2) have been made. That is, Patent Document 1 is a technical proposal to maintain a positive pressure state by switching a three-way solenoid valve during the no-load operation of a two-stage dry compression means. Further, Patent Document 2 is a technical proposal to improve reliability by controlling the suction amount at the start of the compression means in a multi-stage compression means equipped with a suction throttle valve. However, according to the technical proposal of Patent Document 1 above, since a three-way valve that is more complex and has a higher possibility of failure than the two-way valve conventionally used is used, there is a problem that it hinders the stable supply of compressed air, and a new problem has occurred. Also, in the technical proposal of Patent Document 2 above, since a three-way valve similar to that of Patent Document 1 above is used as a piping branch structure together with a suction throttle valve with a complex control structure, the piping structure tends to become complex, and problems such as an increase in the time required for maintenance work and equipment maintenance also occur.

[0008] By the way, when discharging the drain generated from the compressed air pressure circuit to the outside, a drain trap having a discharge method such as a solenoid valve type in which opening and closing are performed by timer control, or a float type in which a float that moves up and down according to the amount of drain stored in the drain reservoir opens and closes the valve is provided. However, the timer-controlled drain trap has a problem that even when there is no drain, the opening and closing operation of the solenoid valve is performed as set by the timer, so that wasteful compressed air is discharged when the solenoid valve opens. Furthermore, the float type drain trap has a problem that since the valve is not opened unless a predetermined amount of drain is stored, an air lock occurs in the drain pipe and the drain trap, and the float does not operate when the inflow of drain stops, so the valve opening operation is not performed either.

[0009] Therefore, the applicant of the present application has developed a technology for solving the problems in the above drain trap and has made a technical proposal described in Japanese Patent No. 5703519 (Patent Document 3). According to such a technical proposal, it is equipped with a drain reservoir with an upper limit pole, a lower limit pole, and a common pole, and a solenoid valve. By opening the valve for a predetermined short time at a predetermined cycle, it is possible to automatically eliminate the air lock. When a predetermined amount of drain is stored up to the upper limit pole position, it has an excellent effect of discharging the drain up to the lower limit pole position.

[0010] However, according to the technical proposal of Patent Document 3 above, when applying the technology to multi-stage compression means (in many cases, oil-free type), when the multi-stage compression means becomes unloaded and the intercooler disposed between the compression means becomes negative pressure, as described above as a problem on the compression means side, there is a problem that the drain to be discharged to the outside flows back to the subsequent compression means side. Also, there is a problem that compressed air discharged together with the drain and air near the discharge port enter the drain reservoir due to the negative pressure caused by unloading and become bubbles, inducing malfunction of the sensor in the drain reservoir. To solve these problems, it is conceivable to operate the drain trap only in a state where drain can occur by receiving the operation state signal of the compression means. However, connecting the operation state signal to the drain trap will complicate the internal wiring, and increase the risk of human error in device operation, maintenance, etc. There was also a problem that if the circuit structure does not emit an operation state signal on the compression means side, the drain trap alone cannot detect it.

[0011] The applicant of the present application focused on a drain detection technology capable of grasping the water level of the drain in the above multi-stage compressed air pressure circuit, and under the idea of whether the load / unload state of the compression means can be indirectly grasped, a drain detection means connected to the control part of the drain trap is provided in the drain delivery pipe connected to the intercooler, and a drain discharge structure that controls the opening and closing of the solenoid valve according to the presence or absence of drain detection is developed, leading to the proposal of the "drain detection type drain discharge structure" according to the present invention.

Prior Art Documents

Patent Documents

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

[0013] In view of the above problems, the present invention indirectly grasps the load / unload state of the compression means based on the detected presence or absence of drain, and even when the inside of the intercooler becomes negative pressure, provides a drain discharge structure that does not cause the drain being discharged to flow backward. Means for Solving the Problems

[0014] In order to solve the above problems, the present invention provides a drain discharge structure in a compressed air pressure circuit having two or more compression means and an intercooler, which comprises a drain delivery pipe, a drain trap, and drain detection means. The drain delivery pipe is configured to deliver drain to the drain trap, with its proximal end connected to an intercooler disposed downstream of the first compression means and its distal end connected to the drain trap. The drain trap has a storage section for storing the drain flowing in through the drain delivery pipe and having upper limit detection means and lower limit detection means for detecting the upper and lower limits of the drain water level, a discharge section having a solenoid valve for discharging the drain in the storage section by opening and closing the solenoid valve, and a control section for controlling the opening and closing of the solenoid valve. The drain detection means is configured to detect the presence or absence of drain in the drain delivery pipe and is disposed at a predetermined intermediate position in the drain delivery pipe. The control section performs decompression opening control to open the solenoid valve for a predetermined short time at a predetermined cycle, and performs drain discharge opening control to open the solenoid valve between upper limit detection and lower limit detection by the upper limit detection means and the lower limit detection means during periods other than the decompression opening control. When the detection result by the drain detection means indicates no drain, the control section takes measures not to perform the decompression opening control and the drain discharge opening control.

[0015] Further, the present invention provides a means such that when the detection result by the drain detection means indicates no drain, the control section performs opening control of the solenoid valve for a predetermined time after the detection of no drain.

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

[0017] Moreover, the present invention provides a means for indicating a drain presence state (load state in the compressor) when drain is continuously detected for a predetermined time and a drain absence state (unload state in the compressor) when drain is not detected for a predetermined time, respectively, for the detection result (drain detection signal) by the drain detection means. Measures are taken.

Advantages of the Invention

[0018] According to the drain detection type drain discharge structure of the present invention, by adopting means for performing opening and closing control by a control unit according to the presence or absence of drain detection, it is possible to grasp the negative pressure caused by the unloading of the compression means or the decrease in the drain amount and perform closing control of the solenoid valve. Even when the inside of the intercooler becomes negative pressure, it is possible to prevent the drain in the drain delivery pipe or the drain trap from flowing backward.

[0019] Further, according to the drain detection type drain discharge structure of the present invention, when the presence of drain is detected by the drain detection means, by performing water level detection by the water level sensor, the discharge control at the time of detecting the absence of drain (unloading state) is stopped. Even if the water level fluctuates due to the negative pressure in the intercooler, the detection by the water level sensor is not performed, and it is possible to prevent the opening and closing control due to the malfunction of the sensor.

[0020] Furthermore, according to the drain detection type drain discharge structure of the present invention, after detecting the absence of drain, by performing opening control of the solenoid valve for a predetermined time, before the reverse flow of the drain due to the negative pressure in the intercooler occurs, it is possible to discharge the drain stored in the intercooler or the storage part of the drain trap to the outside.

[0021] And also, according to the drain detection type drain discharge structure of the present invention, since a downward slope is provided in the drain delivery pipe from the intercooler side toward the drain trap side, the drain discharged from the intercooler flows down toward the drain trap according to the slope, preventing the drain from staying in the drain delivery pipe. At the same time, even when the inside of the intercooler becomes negative pressure, it is possible to make the structure such that the drain being discharged is less likely to flow backward.

[0022] Furthermore, according to the drain detection type drain discharge structure of the present invention, regarding the detection result (drain detection signal) in the drain detection means, when drain is continuously detected for a predetermined time, it is determined that there is drain, and when drain is not detected for a predetermined time, it is determined that there is no drain. This makes it possible to prevent false detection caused by drain in a mist state due to a change in the flow rate of the internal fluid mainly during drain discharge.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0024] The drain detection type drain discharge structure according to the present invention is characterized in that drain detection means is provided in a drain delivery pipe connected to an intercooler and a drain trap, and the opening and closing of an electromagnetic valve for drain discharge provided in the drain trap is controlled by detecting the presence or absence of drain by the drain detection means. Hereinafter, an embodiment of the drain detection type drain discharge structure 1 according to the present invention will be described with reference to the drawings. Note that the drain detection type drain discharge structure according to the present invention is not limited to the embodiments described below, and can be appropriately changed within the scope of the technical idea of the present invention, that is, within the scope of shapes, dimensions, structures, etc. that can exhibit the same operational effects.

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

[0026] (Compression means) In the compressed air pressure circuit according to the present invention, the compression means 3, which is a means for generating compressed air, is a device that compresses air to generate compressed air whose pressure is increased to a predetermined air pressure (for example, 0.7 Mpa). There is no particular limitation on the specific structure thereof as long as it uses a conventionally known technique. A plurality of compression means 3 are arranged in the compressed air pressure circuit. By performing divided compression in multiple stages in order by the plurality of compression means 3, it becomes possible to improve the compression efficiency. The compression means 3 at the forefront sucks in outside air from the suction port, compresses it, and then supplies the compressed air to the subsequent compression means 3 in sequence, thereby performing divided compression. A throttle valve is arranged at the suction port to control the inflow and outflow of outside air. Also, at a predetermined intermediate position between the compression means 3, the compressed air is cooled by the intercooler 2, and the compressed air whose temperature has decreased and density has increased is supplied to the subsequent compression means 3. Each compression means 3 arranged in the compressed air pressure circuit is interlocked, and according to the usage status of the compressed air using device 7 connected to the subsequent stage of the compressed air pressure circuit, loading (load operation state) and unloading (no-load operation state) are appropriately repeated. During unloading, the throttle valve is closed, the intake of outside air by the compression means 3 stops, or a small amount of intake is performed.

[0027] (Piping) Among various devices arranged in the compressed air pressure circuit (including an air dryer, a cyclone separator, etc. as necessary in addition to the compression means 3 and the intercooler 2), they are connected by piping, and by sending compressed air through the piping, the compressed air using device 7 connected to the subsequent stage of the compressed air pressure circuit can be used. There is no particular limitation on the length and diameter of the piping used, and it is appropriately set according to the arrangement positions of various devices and the compressed air using device 7.

[0028] (Intercooler) The intercooler 2 is used in a compressed air pressure circuit having two or more compression means 3, cools the compressed air flowing in from the front-stage compression means 3A, and sends the air to the rear-stage compression means 3B. There are no particular limitations on the specific structure of the intercooler 2 or the method of cooling the compressed air. For example, an apparatus using a conventionally known technique such as a water-cooled type or an air-cooled type may be employed. The intercooler 2 is also provided with a suction port 4 for allowing the compressed air generated by the front-stage compression means 3A to flow in, a discharge port 5 for sending the cooled compressed air to the rear-stage compression means 3B, and a drain outlet 6 for sending the drain generated during the cooling of the compressed air to a drain trap 20. Due to the cooling action of the intercooler 2 on the compressed air, the water vapor contained in the compressed air condenses on the inner wall of the intercooler 2 or the like, generating drain. The generated drain accumulates below the intercooler 2 according to its own weight and gravity, and is sent from the drain outlet 6 provided at a predetermined position on the bottom surface of the intercooler 2 to a drain discharge pipe 10. During unload, when viewed from the side of the compression means 3A, the intake of outside air stops or a small amount of outside air is inhaled, but even if the outside air is inhaled, it is exhausted from a discharge port (not shown), so it seems to be near atmospheric pressure. However, when viewed from the side of the compression means 3B, since it is the suction side, in many cases, the inside is actually in a negative pressure state.

[0029] (Aftercooler) The aftercooler is used in a compressed air pressure circuit having two or more compression means 3, cools the compressed air flowing in from the compression means 3B other than the frontmost compression means 3A, and sends the air to the rear stage. Note that the amount of drain generated in the aftercooler depends on the discharge pressure of the compression means 3A. In many cases, however, it is less than the amount of drain generated by the intercooler 2, which is the primary cooling means. In other words, since a certain amount of drain has already been removed by the intercooler 2, it is quite possible to prevent backflow due to the negative pressure state associated with the unload of the compression means 3 by installing a check valve or the like in the pipe connecting the compression means 3B and the aftercooler.

[0030] (Drain discharge pipe) The drain discharge pipe 10 is a pipe for discharging drain that connects the intercooler 2 and the drain trap 20. The base end of the drain discharge pipe 10 is connected to the drain outlet 6 of the intercooler 2, and the tip end is connected to the drain inlet 29 of the drain trap 20, and discharges the drain generated in the intercooler 2 to the drain trap 20. There are no particular limitations on the length and diameter of the drain discharge pipe 10. Although not shown in the figure, when arranging the drain discharge pipe 10, a downward slope from the intercooler 2 side toward the drain trap 20 side may also be adopted. By adopting such a mode, the drain flowing in from the intercooler 2 can efficiently flow down to the drain trap 20 along the slope, and the drain can be surely made to flow into the drain trap 20 without staying in the drain discharge pipe 10. Also, even when the inside of the intercooler 2 becomes negative pressure due to the unload state of the compression means 3, it is possible to prevent the drain in the drain discharge pipe 10 and the drain trap 20 from easily flowing backward in the direction of the intercooler 2. The drain in the drain discharge pipe 10 during the unload of the compression means 3 will flow backward into the intercooler 2 in a negative pressure state, and the drain discharge into the drain discharge pipe 10 will stop until the compression means 3 is loaded and the inside of the intercooler 2 becomes a positive pressure state.

[0031] (Drain detection means) The drain detection means 11 is a sensor provided at a predetermined intermediate position in the drain discharge pipe 10 and capable of detecting the presence or absence of the inflowing drain. Note that the detection result of the presence or absence of drain by the drain detection means 11 is transmitted to the control unit 23 of the drain trap 20 via a wiring (control line 12) connected to the control unit 23. Regarding the specific drain detection method in the drain detection means 11, there is no particular limitation. For example, detection methods such as capacitance type, resistance type, and ultrasonic type are adopted. Also, there is no particular limitation on the installation location of the drain detection means 11. However, when it is installed at a straight pipe section extending vertically in the vicinity of the drain outlet 6 or the drain inlet 29, since the drain is in a state of falling by gravity, it is assumed that drain detection may be difficult depending on the installation location. Therefore, a mode of installing it at a straight pipe section extending horizontally in the middle, where the drain flows in a concentrated state in the drain delivery pipe 10, is preferable. Also, it is assumed that the farther away from the intercooler 2, the more the drain flattens and the form in which it is concentrated collapses, and in that case, it is conceivable that drain detection may become difficult. Therefore, a mode of installing the drain detection means 11 at a location as close as possible to the intercooler 2 side rather than the drain trap 20 side is preferable. In addition, inside the drain delivery pipe 10, when the drain is discharged, due to the discharge flow of the internal fluid, violent pressure fluctuations and flow velocity fluctuations occur, so there is a possibility that the drain becomes atomized and the drain detection means 11 causes false detection. Therefore, regarding the detection result (drain detection signal) in the drain detection means 11, when the drain is continuously detected for a predetermined time, it is desirable to control it to indicate a drain presence state (load state of the compression means 3), and when the drain is not detected for a predetermined time, it is desirable to control it to indicate a drain absence state (unload state of the compression means 3). This control may be performed by the drain detection means 11 or by the control unit 23 in the drain trap 20. Regarding the control method for the predetermined time, it may be a time constant by CR or an interrupt timer control of a microcomputer, but it may be approximately 0.1 to 3 seconds. Additionally, after the drain is discharged, even if the compression means 3 is in a load state, the drain detection signal may become a drain absence state once. However, since the control unit 23 performs the valve opening control of the electromagnetic valve for a predetermined time after detection, it will operate assuming that the load state continues in effect, and there will be no problem in terms of operation and function. Also, when the detection in the drain detection means 11 stops before reaching the predetermined time, a mode of resetting the timer once is still desirable.

[0032] (Drain trap) The drain trap 20 discharges the drain flowing in through the drain discharge pipe 10 to the outside by the opening and closing operation of the solenoid valve 24. The drain trap 20 mainly includes a storage part 21 for storing the drain, a discharge part 22 for discharging the drain to the outside, and a control part 23 for controlling the discharge operation.

[0033] (Storage part) The storage part 21 is a part for temporarily storing the inflowing drain until the discharge operation is performed, and is provided with a drain inlet 29 for allowing the drain to flow in and a drain outlet 30 for allowing the drain to flow out. The tip of the drain discharge pipe 10 is connected to the drain inlet 29, and the drain outlet 30 is connected to the discharge part 22 for discharging the drain to the outside. In addition, the storage part 21 is provided with an upper limit detection means and a lower limit detection means for determining the upper limit and the lower limit of the drain water level. Regarding the volume of the storage part 21, although it is not particularly limited, it is appropriate to estimate the maximum amount of drain in the assumed discharge interval generated in the intercooler 2 and set the volume to about 0.6 to 1.3 times based on that. This is because if the volume is too large, it will lead to high costs, and conversely, if the volume is too small, it may lead to backflow of the drain due to poor discharge.

[0034] (Drain inlet) The drain inlet 29 allows the drain flowing through the drain discharge pipe 10 to flow into the storage part 21 by connecting the tip of the drain discharge pipe 10. Although there is no particular limitation on the diameter of the drain inlet 29, by making it substantially the same diameter as the diameter of the connected drain discharge pipe 10, it is possible to smoothly allow the drain to flow into the storage part 21. In addition, there is no particular limitation on the installation position of the drain inlet 29 either, but a location where backflow is unlikely to occur even when the drain is stored up to the maximum capacity in the storage part 21 is preferable. For example, a mode of installation on the upper part of the side wall or a mode of installation on the top surface as shown in FIG. 1 is preferable.

[0035] (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. It is determined based on the required drainage volume while considering the average drain inflow volume, and it enables drainage without causing the storage part 21 to overflow even when the drain continuously flows in. There is no particular limitation on the installation position of the drain outlet 30 either. However, in order to efficiently discharge the drain in the storage part 21, it is provided near the bottom surface part of the storage part 21. However, since foreign matters such as dust contained in the stored drain may accumulate on the lowest surface part of the storage part 21, as shown in FIG. 1, a mode of being provided at a position above the lowest surface part is preferable.

[0036] (Discharge part) The discharge part 22 is for discharging the drain stored in the storage part 21 to the outside, and is mainly composed of a drain discharge port 32, a drain discharge pipe 31, and a solenoid valve 24. The drain discharge pipe 31 is a pipe for discharging the drain to the outside. Its proximal end is connected to the drain outlet 30 of the storage part 21, and its distal end is connected to the drain discharge port 32. There is no particular limitation on the diameters of the drain discharge port 32 and the drain discharge pipe 31. By making them approximately the same diameter as the drain outlet 30, it contributes to the smooth discharge of the drain.

[0037] (Upper limit detection means and lower limit detection means) The upper limit detection means and the lower limit detection means provided in the storage part 21 are for detecting the water level of the drain stored in the storage part 21. Regarding the specific configuration of the upper limit detection means and the lower limit detection means, regardless of the method such as a capacitance type, a resistance type, a float type, etc., it is sufficient if the upper limit and the lower limit can be detected. The detection results of the upper limit and the lower limit detected by the upper limit detection means and the lower limit detection means are sent to the control part 23 and used for the opening and closing control of the solenoid valve 24.

[0038] (Water level sensor) As the upper limit detection means and the lower limit detection means, a mode using the water level sensor 25 can be considered. The water level sensor 25 can grasp the water level situation in the storage unit 21, and is composed of three terminals, namely, a common electrode 26, a lower limit electrode 27, and an upper limit electrode 28 to which an electric signal is applied, and are respectively installed on the side wall of the storage unit 21. The water level sensor 25 applies a weak voltage from the terminal of the common electrode 26 into the drain, and grasps the current water level situation by the presence or absence of current detection through the drains of the lower limit electrode 27 and the upper limit electrode 28. The upper limit and lower limit detection results by the water level sensor 25 are sent to the control unit 23 and used for the opening and closing control of the electromagnetic valve 24.

[0039] The water level sensor 25 is attached to the side wall of the storage unit 21 in the order of the common electrode 26, the lower limit electrode 27, and the upper limit electrode 28 from the bottom. At this time, by providing the lower limit electrode 27 in a state above the drain outlet 30, it may be possible to suppress the inflow of compressed air into the drain outlet 30 in the valve open state. In addition, the mounting position of the water level sensor 25 needs to be at a certain distance from the drain inlet 29. This is to prevent the misdetection of the drain caused by the drain flowing in vigorously from the drain inlet 29 becoming a spray and touching the sensor.

[0040] (Electromagnetic valve) The electromagnetic valve 24 is a valve body 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 electromagnetic valve 24 is a drain discharge valve that opens or closes (closes) the inside of the drain discharge pipe 31, and opens and closes based on an opening instruction from the control unit 23. There is no particular limitation on the specific structure of the electromagnetic valve 24, and any conventionally known technology may be used. Also, whether the operating power supply of the electromagnetic valve 24 is AC or DC can be appropriately determined according to the embodiment.

[0041] (Control unit) The control unit 23 controls the opening and closing operation of the solenoid valve 24. As basic control modes, there are decompression valve opening control and drain discharge valve opening control. The decompression valve opening control is a control that opens the solenoid valve for a predetermined short time at a predetermined cycle for the purpose of decompressing the internal pressure of the drain delivery pipe 10 connecting the intercooler 2 and the drain trap 20. For example, it is a control that opens the solenoid valve for 0.4 to 3 seconds every 1 to 5 minutes. Since the decompression valve opening control is for degassing and decompressing the drain delivery pipe 10 and the storage unit 21 and once making it below the internal pressure of the intercooler 2, the interval and the valve opening time may be appropriately calculated based on the drain amount, volume, internal pressure, and the fluid discharge capacity of the solenoid valve. The 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 a period other than the above decompression valve opening control for the purpose of discharging the drain in the storage unit 21 to the outside.

[0042] The control unit 23 is connected via a control line 12 to the drain detection means 11 disposed in the drain delivery pipe 10. Based on the detection result in the drain delivery pipe 10 by the drain detection means 11, the control unit 23 determines whether to execute or stop the above-described decompression valve opening control and drain discharge valve opening control of the solenoid valve 24. Specifically, when the presence of drain is detected, the decompression valve opening control and the drain discharge valve opening control are executed, and when the absence of drain is detected, the decompression valve opening control and the drain discharge valve opening control are stopped. This is because when the presence of drain is detected in the drain delivery pipe 10, it is determined that the compression means 3 is in the loaded state and the normal discharge operation is performed. Conversely, when the absence of drain is detected, it is determined that the compression means 3 is in the unloaded state and the discharge operation is stopped, thereby preventing the drain in the storage unit 21 from flowing back into the intercooler 2 in a negative pressure state and also preventing the outside air from flowing back and entering through the drain outlet 32 accordingly.

[0043] (Control Mode) The water level sensor 25 provided in the storage unit 21 is a lower judgment criterion in the control unit 23 and is used as a material for determining the opening and closing of the solenoid valve 24 when the drain detection means 11 detects the presence of drain. Conversely, when the drain detection means 11 detects the absence of drain, the opening and closing judgment by the water level sensor 25 is not performed, and only a valve closing instruction is given. Therefore, even if the water level in the storage unit 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 opening and closing control of the solenoid valve 24 due to the malfunction of the water level sensor 25. In the opening and closing control of the solenoid valve 24 by the control unit 23, when the drain detection means 11 detects the absence of drain, it is also preferable to perform an opening valve control for a predetermined time (about several seconds) before giving a valve closing instruction to the solenoid valve 24. For example, the valve closing instruction is given 3 to 30 seconds after detecting the absence of drain. By adopting such a mode, it is possible to discharge the drain stored in the storage unit 21 before the negative pressure in the intercooler 2 increases, and reduce the amount of drain in the storage unit 21.

[0044] (Operation · Function) Regarding the drain detection type drain discharge structure 1 composed of the above components, its main operations and functions will be described based on FIG. 1. Here, the case where the water level sensor 25 is used as the upper limit detection means and the lower limit detection means will be described. The drain detection type drain discharge structure 1 is provided with a compression means 3A, an intercooler 2, and a compression means 3B via pipes, and is provided with a drain trap 20 via a drain delivery pipe 10 to discharge the drain in the intercooler 2. First, compressed air is generated by the compression means 3A, sent through a pipe, and flows into the intercooler 2 from the suction port 4. The compressed air at this time is at a high temperature and is cooled by the intercooler 2. The compressed air flowing into the intercooler 2 is cooled in the intercooler 2, so that moisture (drain) is separated and removed, and flows into the compression means 3B through a pipe from the discharge port 5. The compression means 3B further compresses the flowing compressed air and sends it to the subsequent compressed air using device 7.

[0045] Next, the drain separated from the compressed air by the intercooler 2 flows into the drain trap 20 from the drain outlet 6 provided at the lower part of the intercooler 2 through the drain delivery pipe 10. At this time, when the drain flowing into the drain delivery pipe 10 passes through the drain detection means 11, the inflow of the drain into the drain delivery pipe 10 is detected, and the detection result is transmitted to the control unit 23. The drain that has flowed 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 upper limit detection means and lower limit detection means, detects the upper limit and lower limit of the water level of the stored drain, and sends the detection result to the control unit 23. Then, when the presence of the drain is detected by the drain detection means 11 and the upper limit of the drain is detected by the water level sensor 25 in the storage section 21, the control unit 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 through the drain discharge pipe 31 to the drain discharge port 32, and the drain is discharged to the outside. Also, during the detection of the presence of the drain by the drain detection means 11, in addition to the drain discharge valve opening control, when the solenoid valve 24 is opened by the pressure reduction valve opening control, the drain is similarly discharged.

[0046] Subsequently, the control operation of the solenoid valve 24 by the control unit 23 will be described with reference to FIG. 2. The drain detection means 11, which is the upper judgment criterion, is provided in the drain delivery pipe 10, and transmits the result of drain detection accompanying the inflow of the drain to the control unit 23. Further, a water level sensor 25, which is the lower judgment criterion, is provided in the storage section 21, detects the upper limit and lower limit of the drain stored in the storage section 21, and transmits the detection result to the control unit 23. First, the control operation of the control unit 23 performed during the period (ON period) in which the presence (ON) of the drain is detected by the drain detection means 11 will be described. When the drain flowing into the drain delivery pipe 10 passes through the drain detection means 11, the drain detection means 11 turns ON (T1), and the detection result (ON) is transmitted to the control unit 23. The control unit 23 determines that the compression means 3 is in the loaded state based on the detection result (ON). Also, since the drain detection means 11, which is the upper determination criterion, is in the ON state, during the ON period, a decompression valve opening control (MDT) for opening the solenoid valve 24 for a short time at regular intervals (CT) is performed, and drain discharge valve opening control based on the detection result of the water level sensor 25, which is the lower determination criterion, is performed during the period other than the decompression valve opening control.

[0047] (Drain discharge valve opening control) When the lower limit pole 27 of the water level sensor 25 provided in the storage unit 21 is ON (detected) and the upper limit pole 28 is OFF (not detected) (T2), it is determined that the drain in the storage unit 21 is being stored, and the closed state of the solenoid valve 24 is continued (T3). When the water level of the drain in the storage unit 21 rises due to the inflow and storage of the drain, and the upper limit pole 28 of the water level sensor 25 changes from OFF to ON (T4), it is determined that the storage amount of the drain has reached the upper limit, and an opening instruction for the solenoid valve 24 is given to lower the drain water level in the storage unit 21 (T5). Note that this opening instruction will continue until the lower limit pole 27 changes from ON to OFF (T6). When the water level in the storage unit 21 drops due to the discharge of the drain by opening the solenoid valve 24, and the lower limit pole 27 of the water level sensor 25 changes from ON to OFF (T6), it is determined that the storage amount of the drain in the storage unit 21 has reached the lower limit, and a closing instruction for the solenoid valve 24 is given for drain storage (T7). This closing instruction will continue until the upper limit pole 27 changes from OFF to ON.

[0048] Next, the control operation of the control unit 23 performed during the detection period (OFF period) of no drain (OFF) by the drain detection means 11 will be described. Drain flowing into the drain delivery pipe 10 does not pass through the drain detection means 11, or the drain discharge from the intercooler 2 is blocked, causing the drain detection means 11 to turn OFF (T2), and the detection result (OFF) is transmitted to the control unit 23. Upon receiving the detection result (OFF), the control unit 23 determines that the compression means 3 is in the unloaded state, stops the decompression valve control and drain discharge valve control performed during the ON period, and issues a valve closing instruction for the solenoid valve 24 (T9). After this valve closing instruction, the closed valve state of the solenoid valve 24 will be maintained until the drain detection means 11 detects ON.

[0049] As described above, the basic configuration aspects and operations / functions of the drain detection type drain discharge structure 1 according to the present invention have been explained. However, the present invention is not limited to the configuration aspects shown in the above embodiments and drawings. For example, by also transmitting the load / unload state determination signal of the compression means 3 by the control unit 23 to the drain trap provided in the aftercooler after the compression means 3B, it becomes possible to perform opening / closing control of the solenoid valve in the drain trap without measuring the drain amount in the drain trap.

[0050] As described above, in the drain detection type drain discharge structure 1 according to the present invention, the control unit 23 can indirectly grasp the load / unload state of the compression means 3 based on the detection result of the drain detection means 11 provided in the drain delivery pipe 10. Even when the compression means 3 is determined to be in the unloaded state, the control unit 23 can prevent the backflow of drain by stopping the drain discharge.

Industrial Applicability

[0051] The present invention can be adopted as a compressed air generation device excellent in drain discharge in all fields that require multi-stage compressed air, such as food processing, electronic components, and vehicle body painting. Therefore, it is considered that the industrial applicability of the "drain detection type drain discharge structure" according to the present invention is great.

Explanation of Reference Numerals

[0052] 1 Drain detection type drain discharge structure 2 Intercooler 3 Compression means 4 Suction port 5 Discharge port 6 Drain outlet 7 Compressed air using equipment 10 Drain discharge pipe 11 Drain detection means 12 Control line 20 Drain trap 21 Storage part 22 Discharge part 23 Control part 24 Electromagnetic valve 25 Water level sensor 26 Common electrode 27 Lower limit electrode 28 Upper limit electrode 29 Drain inlet 30 Drain outlet 31 Drain discharge pipe 32 Drain exhaust port

Claims

1. A drain discharge structure in a compressed air pressure circuit having two or more compression means and an intercooler, comprising: a drain delivery pipe, a drain trap, and drain detection means; the drain delivery pipe is for delivering drain to the drain trap, with its proximal end connected to an intercooler disposed downstream of the first compression means and its distal end connected to the drain trap; the drain trap has a storage section for storing the drain flowing in through the drain delivery pipe and having upper limit detection means and lower limit detection means for detecting the upper and lower limits of the drain water level, a discharge section having a solenoid valve for discharging the drain in the storage section by opening and closing the solenoid valve, and a control section for controlling the opening and closing of the solenoid valve; the drain detection means is for detecting the presence or absence of drain in the drain delivery pipe and is disposed at a predetermined intermediate position in the drain delivery pipe; the control section performs decompression opening control for opening the solenoid valve for a predetermined short time at a predetermined cycle, and performs drain discharge opening control for opening the solenoid valve between upper limit detection and lower limit detection by the upper limit detection means and the lower limit detection means during a period other than the decompression opening control, and does not perform the decompression opening control and the drain discharge opening control when the detection result of the drain detection means is that there is no drain, characterized by a drain detection type drain discharge structure.

2. When the detection result of the drain detection means is that there is no drain, the control section performs opening control of the solenoid valve for a predetermined time after the detection of no drain, according to the drain detection type drain discharge structure described in Claim 1.

3. The drain delivery pipe is provided with a downward slope from the intercooler side toward the drain trap side, according to the drain detection type drain discharge structure described in Claim 1.

4. Regarding the detection result of the drain detection means, when drain is continuously detected for a predetermined time, it indicates a drain presence state, and when drain is not detected for a predetermined time, it indicates a drain absence state, according to the drain detection type drain discharge structure described in any one of Claims 1 to 3.

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