Lubricating oil recovery mechanism for oil-flooded screw compressor

Abstract

To collect a lubricant, which is leaked from a shaft seal device in a compressor main body of an oil-cooled screw compressor, while reducing an execution frequency of forced unload and under short-time forced unload.SOLUTION: A lubricant collection space 55 in which a lubricant passing a shaft seal device 54 is collected is provided in a compressor main body 50 of an oil-cooled screw compressor 1, the other end 20b of a drain passage 20 communicating one end 20a to the lubricant collection space 55 is communicated to a storage container 30 which is opened in atmospheric air. The other end of a collection passage 40 opening one end 40a in the vicinity of a bottom in the storage container 30 is communicated to a suction passage 62 of the compressor main body 50 at a secondary side of an air intake control valve 60. While the oil-cooled screw compressor 1 is in an unload operation state where the air intake control valve 60 is closed, the lubricant stagnated in the storage container 30 is collected by a negative pressure generated in the suction passage 62 at the secondary side of the air intake control valve 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil recovery mechanism for an oil-cooled screw compressor, and more specifically to a lubricating oil recovery mechanism for recovering lubricating oil that has leaked from the shaft seal of an oil-cooled screw compressor and returning it to the lubricating oil circulation system formed between the compressor body and receiver tank of the oil-cooled screw compressor. [Background technology]

[0002] An example of the configuration of the oil-cooled screw compressor 100 will be described with reference to FIG.

[0003] This oil-cooled screw compressor 100 comprises a compressor main body 150 that compresses the gas to be compressed together with lubricating oil supplied into the compression working space for lubrication, cooling, and sealing, and discharges it as a gas-liquid mixed fluid with the lubricating oil, a drive source 170 such as an engine or motor that drives this compressor main body 150 (a motor in the illustrated example), and a receiver tank 180 that introduces the compressed gas discharged as a gas-liquid mixed fluid from the compressor main body 150, separates the gas and liquid, and supplies the compressed gas after separating the lubricating oil to equipment such as an air work machine connected to the consumption side.

[0004] The lubricating oil separated from the compressed gas in this receiver tank 180 is configured to be supplied to the compression working space of the compressor main body 150 via an oil supply passage 190 equipped with an oil cooler 191 and an oil filter 192, using the pressure within the receiver tank 180, thereby forming a lubricating oil circulation system between the compressor main body 150 and the receiver tank 180.

[0005] In the compressor body 150 of this oil-cooled screw compressor 100, the gas to be compressed is compressed by the meshing and rotation of a pair of male and female screw rotors 157, 158 housed in a rotor chamber 156 formed in the casing 151, and therefore the rotational driving force generated by the driving source 170 such as the motor mentioned above must be transmitted to the screw rotors 157, 158 to cause the meshing and rotation mentioned above.

[0006] Therefore, in the compressor main body 150 described above, the rotor shaft of one of the pair of male and female screw rotors 157, 158 (in the illustrated example, the suction side rotor shaft of the male rotor 157) penetrates and protrudes through the casing 151 to form the drive shaft 152, and the output shaft of a drive source 170 such as a motor is connected to this drive shaft 152 directly or indirectly via a coupling, power transmission mechanism, speed increasing device, etc., so that the pair of male and female screw rotors 157, 158 can be meshed and rotated by the rotational driving force generated by the drive source 170.

[0007] In this way, in the compressor body 150 of the oil-cooled screw compressor 100, the drive shaft 152 protrudes through the casing 151, and therefore a shaft sealing device 154 consisting of a mechanical seal, oil seal, etc. is provided to prevent lubricating oil and compressed gas from leaking outside the machine through the outer periphery of the drive shaft 152.

[0008] As an example of the installation of such a shaft seal device 154, as shown in Figure 7, a seal chamber 153 is provided in the casing 151 so as to surround the drive shaft 152, and the shaft seal device 154 is housed in this seal chamber 153. By providing a bearing 159 that supports the drive shaft 152 adjacent to the rotor chamber side of this seal chamber 153, when lubricating oil is supplied from the receiver tank 180 into the seal chamber 153, the sliding parts of the shaft seal device 154 and the bearing 159 can be lubricated, and leakage of compressed gas and lubricating oil to the outside of the casing 151 can be prevented.

[0009] However, the shaft sealing device 154 such as the mechanical seal or oil seal described above cannot completely prevent leakage of lubricating oil, and slight leakage may occur.

[0010] Furthermore, if the sealing performance of the shaft seal device 154 deteriorates due to aging or other reasons, resulting in poor sealing, further leakage of lubricating oil may occur.

[0011] Therefore, in order to recover the lubricating oil that has passed through the shaft seal device 154, the compressor body 150 of the oil-cooled screw compressor 100 is provided with a lubricating oil collection space 155 that is located on the outside of the machine relative to the shaft seal device 154 as shown in Figure 7 and that collects the lubricating oil that has passed through the shaft seal device 154.

[0012] Various lubricant recovery mechanisms have been proposed to recover the lubricant collected in this lubricant collection space 155 and return it to the lubricant circulation system described above.

[0013] As an example of such a lubricating oil recovery mechanism 110, the oil-cooled screw compressor 100 shown in Figure 6 has a recovery flow path 120 whose one end 120a is connected to the aforementioned lubricating oil collection space 155 (see Figures 6 and 7), and the other end 120b of this recovery flow path 120 is connected to the intake flow path 162 of the compressor main body 150 on the secondary side of the intake control valve via an orifice or check valve (Patent Document 1, Claim 5,

[0055] ,

[0056] ; however, Patent Document 1 differs from the configuration in Figure 6 in that the recovery flow path is formed within the thickness of the casing.).

[0014] In the lubricating oil recovery mechanism 110 shown in Figure 6, which is configured as described above, when the oil-cooled screw compressor 100 transitions to unloaded operation with the intake control valve 160 closed, negative pressure is created in the intake passage 162 on the secondary side of the intake control valve 160, and the lubricating oil accumulated in the lubricating oil collection space 155 and the recovery passage 120 is sucked into the intake passage 162 by this negative pressure and recovered into the compressor main body 150.

[0015] As another example of the configuration of the lubricating oil recovery mechanism, the lubricating oil recovery mechanism 210 shown in Figure 8 has one end 220a of a discharge passage 220 connected to the lubricating oil collection space 155, the other end 220b of which is connected to a container 230 via a three-way switching valve, the bottom of which is connected to the suction passage 162 of the compressor main body 150 via a return passage 240, and the remaining port of the three-way switching valve is connected to a receiver tank 180 (see Figures 1 to 4 of Patent Document 2).

[0016] In the lubricating oil recovery mechanism 210 shown in Figure 8, when the communication between the discharge flow path 220 and the container 230 is blocked by operating the three-way switching valve, and the container 230 is pressurized by introducing compressed gas into the receiver tank 180, the lubricating oil accumulated in the container 230 is transported together with the compressed gas into the compressor main body 150 via the return flow path 240 and the intake flow path 162, thereby forcibly recovering the lubricating oil.

[0017] As another lubricating oil recovery mechanism, the lubricating oil recovery mechanism 310 shown in Figure 9 is provided with a mixer 350 consisting of an ejector, a venturi, etc., and has a driving flow inlet 351 of this mixer 350 connected to the receiver tank 180 via an on-off valve, an outlet 352 of the mixer 350 connected to the intake passage 162 of the compressor main body 150, and further has a suction port 353 of the mixer 350 connected to an outlet 331 provided at the bottom of a container 330 connected to the lubricating oil collection space 155 (see claim 1 and Figure 1 of Patent Document 3).

[0018] In the lubricating oil recovery mechanism 310 shown in Figure 9, when the on-off valve provided between the mixer 350 and the receiver tank 180 is opened and the compressed gas in the receiver tank 180 is introduced into the mixer 350 as the driving flow, the lubricating oil recovered in the container 330 is sucked into the mixer 350 and mixed with the compressed gas from the receiver tank 180, which is the driving flow, and is discharged from the outlet 352 of the mixer 350, so that the lubricating oil can be forcibly recovered into the compressor body 150 through the suction passage 162 connected to this outlet 352. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] WO2019 / 111661 publication [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-021757 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-146718 Summary of the Invention [Problem to be solved by the invention]

[0020] Of the conventional lubricating oil recovery mechanisms 110, 210, and 310 described above, the lubricating oil recovery mechanism 110 (Patent Document 1) described with reference to Figure 6 has a relatively simple configuration, but is able to recover lubricating oil that has passed through the shaft seal device 154 and accumulated in the lubricating oil collection space 155 and the recovery flow path 120 into the compression action space of the compressor main body 150.

[0021] However, since the lubricating oil recovery mechanism 110 shown in Figure 6 is designed to recover lubricating oil by utilizing the negative pressure in the intake passage 162 that occurs during unloaded operation with the intake control valve 160 closed (such a type of lubricating oil recovery mechanism that recovers lubricating oil by utilizing the negative pressure in the intake passage that occurs during unloaded operation will be referred to as the "negative pressure suction type" hereinafter), the lubricating oil that has accumulated in the lubricating oil collection space 155 and the recovery passage 120 will not be recovered unless the oil-cooled screw compressor 100 is switched to unloaded operation.

[0022] Therefore, in an oil-cooled screw compressor 100 equipped with a negative pressure suction type lubricating oil recovery mechanism 110, if loaded operation continues for a long period of time without transitioning to unloaded operation due to the continuous consumption of compressed gas, the lubricating oil that can no longer be held in the lubricating oil collection space 155 and the recovery flow path 120 will overflow and contaminate the inside of the soundproof box of the oil-cooled screw compressor 100.

[0023] Therefore, in order to prevent such leakage of lubricating oil, the oil-cooled screw compressor 100 equipped with a negative pressure suction type lubricating oil recovery mechanism 110 performs a process known as "forced unloading," in which the compressor forcibly switches to unload operation for a predetermined time required to recover the accumulated lubricating oil at predetermined intervals set by a timer or the like, regardless of the consumption state of compressed gas on the consumption side.

[0024] Although such forced unloading is effective in preventing lubricating oil leakage, the supply of compressed gas to the consumer side is temporarily stopped while forced unloading is being performed, which may temporarily interrupt work being carried out on the consumer side.Therefore, it is desirable to perform forced unloading as infrequently as possible and within as short a time as possible.

[0025] However, the amount of lubricating oil that can be stored in the lubricating oil collection space 155 and the recovery flow path 120 is relatively small, and leakage of lubricating oil that has passed through the shaft seal device 154 can occur even with a relatively short period of loaded operation.Therefore, in the oil-cooled screw compressor 100 equipped with the conventional negative pressure suction type lubricating oil recovery mechanism 110 described with reference to Figure 6, forced unloading had to be performed relatively frequently.

[0026] Furthermore, the lubricating oil collection space 155 located on the outside of the shaft seal device 154 is open to the atmosphere through a gap δ that occurs on the outer periphery of the drive shaft 152 (see Figure 7), so when the negative pressure generated in the intake passage 162 during unloading operation sucks in the lubricating oil in the recovery passage 120 and the lubricating oil collection space 155, outside air is sucked into the lubricating oil collection space 155 through the aforementioned gap δ.

[0027] As a result, air accounts for a large portion of the fluid sucked into and recovered by the compressor body 150 through the lubricating oil collection space 155, the recovery passage 120, and the suction passage 162, which reduces the efficiency of recovering the lubricating oil, and it takes a relatively long time to recover even a small amount of lubricating oil.

[0028] For this reason, in an oil-cooled screw compressor 100 equipped with the lubricating oil recovery mechanism 110 described with reference to Figure 6, the forced unloading time per cycle must be extended or forced unloading must be performed more frequently, otherwise leakage of lubricating oil cannot be prevented by short-term forced unloading.

[0029] In view of these points, in an oil-cooled screw compressor 100 equipped with a conventional negative pressure suction type lubricating oil recovery mechanism 110 as described with reference to Figure 6, for example, if forced unloading is to be completed within a relatively short time of one to several seconds per forced unload, it is necessary to perform forced unloading at a high frequency of approximately once every hour.Therefore, there is a demand for a lubricating oil recovery mechanism that can recover lubricating oil within a relatively short time even when forced unloading is performed less frequently.

[0030] On the other hand, in a configuration such as the lubricating oil recovery mechanisms 210, 310 described with reference to Figures 8 (Patent Document 2) and 9 (Patent Document 3), which uses the pressure of the compressed gas in the receiver tank 180 to transport the lubricating oil recovered in the containers 230, 330 and forcibly recover it (hereinafter, a lubricating oil recovery mechanism which uses the pressure in the receiver tank to recover lubricating oil will be referred to as a "compressed gas transport type"), the lubricating oil can be recovered in the compression action space of the compressor main body 150 not only during unloaded operation but also during loaded operation, so that the lubricating oil can be recovered without forcibly unloading and therefore without interrupting work being performed on the consumption side.

[0031] However, in the compressed gas conveying type lubricating oil recovery mechanisms 210, 310 shown in Figures 8 and 9, an electromagnetic valve such as a three-way switching valve or an on-off valve is provided in the flow path connected to the receiver tank 180, and the start and stop of the supply of compressed gas from the receiver tank 180 can be electrically controlled, and an electronic control means (controller) is required to electrically control the opening and closing of the electromagnetic valve based on, for example, a set time using a timer or the liquid level position of the lubricating oil detected by a liquid level detection means provided in the container 330.

[0032] Furthermore, the lubricating oil recovery mechanism 210 shown in Figure 8 employs a configuration in which compressed gas in the receiver tank 180 is introduced into the container 230 to pressurize and pump out the lubricating oil, so the container 230 must be configured as a pressure vessel that can withstand such pressure.Furthermore, the lubricating oil recovery mechanism 310 shown in Figure 9 requires a mixer for mixing the lubricating oil with the compressed gas.

[0033] As a result, when a compressed gas conveying type lubricating oil recovery mechanism 210, 310 is adopted, the device configuration becomes complex and the number of parts increases, which increases manufacturing costs and reduces the price competitiveness in the market of an oil-cooled screw compressor 100 equipped with such a lubricating oil recovery mechanism 210, 310.

[0034] Therefore, the present invention has been made in consideration of the drawbacks of the above-mentioned conventional technology, and aims to provide an oil-cooled screw compressor equipped with a lubricating oil recovery mechanism that can simplify the device configuration and make it available at low cost by adopting the above-mentioned "negative pressure suction type" configuration that recovers lubricating oil during unloading operation of the oil-cooled screw compressor, while also making it possible to reduce the forced unloading time per operation to a relatively short time (for example, about one second to several seconds) even when the frequency of forced unloading is reduced, preferably significantly reduced. [Means for solving the problem]

[0035] The means for solving the problems are described below together with the reference numerals used in the description of the embodiment of the invention. These reference numerals are intended to clarify the correspondence between the claims and the description of the embodiment of the invention, and needless to say, are not used to restrict the interpretation of the technical scope of the present invention.

[0036] In order to achieve the above object, the lubricating oil recovery mechanism 10 of the oil-flooded screw compressor of the present invention is as follows: In an oil-cooled screw compressor 1, a pair of male and female screw rotors 57, 58 (in FIG. 1, the female rotor 58 is hidden behind the male rotor 57) are housed in a rotor chamber 56 provided in a casing 51 so as to be able to mesh and rotate, and the compressor body 50 compresses a gas to be compressed together with lubricating oil introduced into a compression action space and discharges the compressed gas as a gas-liquid mixed fluid, the compressor body 50 having a drive shaft 52 penetrating and protruding through the casing 51, a shaft seal device 54 that seals a gap generated on the outer periphery of the drive shaft 52, and a lubricating oil collecting space 55 that is provided on the outer periphery of the drive shaft 52 at a position closer to the outer side of the casing 51 than the shaft seal device 54 and that collects the lubricating oil that has passed through the shaft seal device 54, a discharge flow path 20 whose one end 20a is connected to the lubricant oil collecting space 55; a storage container 30 that is open to the atmosphere and communicates with the other end 20b of the discharge flow path 20, and that introduces the lubricating oil collected in the lubricating oil collecting space 55 through the discharge flow path 20 and stores it; The lubricating oil stored in the storage container 30 During unloading operation, the negative pressure generated in the intake passage 62 of the compressor body 50 on the secondary side of the intake control valve 60 is utilized. A recovery flow path 40 is provided in the compression action space of the compressor body 50, One end 40a of the recovery flow path 40 is opened near the bottom of the storage container 30, and the other end 40b of the recovery flow path 40 is The aforementioned On the secondary side of the intake control valve 60 The aforementioned It is characterized in that it communicates with the intake passage 62 (see claim 1, Figs. 1 and 2).

[0037] The storage container 30 is configured to include a container body 31 and a lid body 32 that is detachably attached to an opening of the container body 31 and closes the opening, It is preferable to attach the discharge flow path 20 and the recovery flow path 40 to the lid body 32 so that the other end 20b of the discharge flow path 20 and the one end 40a of the recovery flow path 40 open within the storage container 30 (see claim 2, Figure 4).

[0038] In this case, it is preferable that the one end 40a of the recovery passage 40 is formed by an orifice 41c (see claim 3 and FIG. 4).

[0039] Furthermore, it is desirable that the orifice 41c be provided with a strainer 46 that covers the inlet of the orifice 41c (see claim 4 and FIG. 4).

[0040] The lid 32 of the storage container 30 is preferably a cap type, and in the illustrated embodiment, can be a screw cap type, and is configured to cover the opening of the container body 31 and the side wall of the container body 31 within a predetermined height range from the opening, A breathing hole 34 penetrating the side wall of the container body 31 may be provided at a position higher than the position of the bottom 33 of the lid body 32 attached to the container body 31 (see claim 5, Figure 4). [Effects of the Invention]

[0041] With the configuration of the present invention described above, the oil-cooled screw compressor equipped with the lubricating oil recovery mechanism 10 of the present invention can achieve the following significant effects.

[0042] The lubricating oil recovery mechanism 10 of the present invention recovers lubricating oil by utilizing the negative pressure in the intake passage 62 that is generated during unloading operation of the oil-cooled screw compressor 1 with the intake control valve 60 closed.By adopting the above-mentioned "negative pressure suction type" configuration, the device configuration can be made simpler than the "compressed gas conveying type" lubricating oil recovery mechanisms 210, 310 described with reference to Figures 8 and 9, and therefore can be provided at a lower cost.

[0043] Furthermore, compared to the conventional "negative pressure suction type" lubricant oil recovery mechanism 110 described with reference to Figure 6, by providing a storage container 30 within the lubricant oil recovery mechanism 10, it is possible to significantly increase the amount of lubricant oil stored compared to the conventional negative pressure suction type lubricant oil recovery mechanism 110, thereby significantly reducing the frequency of forced unloading.

[0044] Furthermore, by opening one end 40a of the recovery flow path 40 near the bottom of the storage container 30, when lubricating oil has accumulated in the storage container 30, the recovery flow path 40 can suck in only the lubricating oil without entraining air and recover it in the compression action space of the compressor main body 50.

[0045] As a result, the efficiency of lubricating oil recovery was significantly improved compared to when lubricating oil is recovered together with air, as in the conventional negative pressure suction type lubricating oil recovery mechanism 110 described with reference to Figure 6.

[0046] In this way, with the lubricating oil recovery mechanism 10 of the present invention, the amount of lubricating oil stored is increased and the efficiency of lubricating oil recovery is improved. In the conventional negative pressure suction type lubricating oil recovery mechanism 110 described with reference to Figure 6, in order to perform forced unloading in a relatively short time of one to several seconds, forced unloading had to be performed at intervals of approximately one hour. However, with the lubricating oil recovery mechanism of the present invention, even when forced unloading is performed at intervals of approximately every 10 hours, for example, it is possible to recover lubricating oil with forced unloading in a relatively short time of one to several seconds.

[0047] The storage container 30 is configured to consist of a container body 31 and a lid body 32 removably attached to the opening of the container body 31, and the discharge flow path 20 and the recovery flow path 40 are attached to the lid body 32 so that the other end 20b of the discharge flow path 20 and the one end 40a of the recovery flow path 40 open within the storage container 30.In this configuration, simply by attaching the lid part 32 to the container body 31, not only can the other end 20b of the discharge flow path 20 and the one end 40a of the recovery flow path 40 be opened at an appropriate position within the storage container 30, but also, simply by removing the lid part 32 from the container body 31, the other end 20b of the discharge flow path 20 and the one end 40a of the recovery flow path 40 can be removed from the storage container 30, making it easy to check for blockages in these parts and to remove any clogged foreign matter.

[0048] In particular, in a configuration in which one end 40a of the recovery flow path 40 is formed by an orifice 41c, and further in which a strainer 46 is provided to cover the entrance of this orifice 41c, the orifice 41c and strainer 46 can be removed from the storage container 30 simply by removing the lid body 32 from the container body 31, making it extremely easy to perform maintenance and replacement work on the strainer 46 and orifice 41c.

[0049] Furthermore, the lid 32 of the storage container 30 is formed as a cap type that covers from the opening of the container body 31 to the outer wall within a predetermined height range, and a breathing hole 34 that penetrates the side wall of the container body 31 is provided in the side wall at a position higher than the position of the bottom 33 of the lid 32 when attached to the container body 31.In this configuration, the inside of the storage container 30 is open to the atmosphere, but when the lid 32 is attached, the breathing hole 34 is hidden on the back side of the lid 32, making it difficult for foreign matter such as dust to enter the storage container 30 through the breathing hole 34. [Brief explanation of the drawings]

[0050] [Figure 1] 1 is an explanatory diagram of an oil-cooled screw compressor equipped with a lubricating oil recovery mechanism of the present invention. [Figure 2] Cross-sectional view of line II-II in Figure 1. [Figure 3] 1 is a perspective view of a main part of an oil-cooled screw compressor equipped with a lubricating oil recovery mechanism of the present invention. [Figure 4] FIG. [Figure 5] FIG. 10 is an explanatory diagram of a modified example of the storage container (an example in which a liquid level detection means is provided). [Figure 6] FIG. 1 is an explanatory diagram of an oil-flooded screw compressor equipped with a conventional lubricating oil recovery mechanism (negative pressure suction type). [Figure 7] FIG. 7 is an enlarged view of the portion VII in FIG. 6. [Figure 8] FIG. 1 is an explanatory diagram of an oil-flooded screw compressor equipped with another conventional lubricating oil recovery mechanism (compressed gas conveying type). [Figure 9] FIG. 10 is an explanatory diagram of an oil-flooded screw compressor equipped with yet another conventional lubricating oil recovery mechanism (compressed gas conveying type). DETAILED DESCRIPTION OF THE INVENTION

[0051] The configuration of the present invention will be described below with reference to the accompanying drawings.

[0052] [Overall configuration of oil-flooded screw compressor] FIG. 1 shows an example of the configuration of an oil-cooled screw compressor 1 equipped with a lubricating oil recovery mechanism 10 of the present invention.

[0053] Except for the structure of the lubricating oil recovery mechanisms 10, 110, the basic configuration of the oil-cooled screw compressor 1 to which the lubricating oil recovery mechanism 10 of the present invention is applied is the same as the configuration of the oil-cooled screw compressor 100 equipped with the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6, and the receiver tank 180, which is a common configuration with the oil-cooled screw compressor 100 described with reference to Figure 6, the oil supply flow path 190 that supplies the lubricating oil recovered in this receiver tank 180 to the compressor main body 50 (150), and the oil cooler 191 and oil filter 192 provided in the oil supply flow path 190 are omitted from Figure 1.

[0054] Furthermore, the compressor body 50 provided in the oil-cooled screw compressor 1 equipped with the lubricating oil recovery mechanism 10 of the present invention compresses the compressed gas, such as air, introduced through the intake passage 62 opened and closed by the intake control valve 60 together with the lubricating oil supplied to the compression action space, and discharges it as a gas-liquid mixed fluid with the lubricating oil, similar to the conventional oil-cooled screw compressor 100 described with reference to Figure 6.

[0055] Furthermore, the compressor body 50 is provided with a drive shaft 52 that protrudes through the casing 51, and a seal chamber 53 is provided on the outer periphery of the drive shaft 52, and a shaft sealing device 54 such as a mechanical seal or an oil seal is housed within this seal chamber 53 to seal the shaft.In addition, a lubricating oil collection space 55 is provided to collect the lubricating oil that has passed through the shaft sealing device 54, which is similar to the configuration of the oil-cooled screw compressor 100 equipped with the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6.

[0056] [Overall configuration of lubricating oil recovery mechanism] While the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6 has a structure in which the lubricating oil collection space 155 and the intake passage 162 on the secondary side of the intake control valve 160 are directly connected by the recovery passage 120, the lubricating oil recovery mechanism 10 of the present invention, as shown in Figure 1, is configured to have a discharge passage 20 whose one end 20a is connected to the lubricating oil collection space 55 and whose other end 20b is connected to the storage container 30, and a recovery passage 40 whose one end 40a opens near the bottom of the storage container 30 and whose other end 40b is connected to the intake passage 62 on the secondary side of the intake control valve 60, and is significantly different from the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6 in that the lubricating oil collection space 55 is connected to the intake passage 62 on the secondary side of the intake control valve 60 via the aforementioned storage container 30.

[0057] [Discharge flow path] The discharge flow path 20 constituting the lubricating oil recovery mechanism 10 of the present invention is a flow path that connects the lubricating oil collection space 55 described above and the storage container 30 described below. In the illustrated embodiment, this discharge flow path 20 is composed of a one-end side flow path 21 formed as a drilled hole that connects to the lubricating oil collection space 55 within the thickness of the casing 51 of the compressor body, an intermediate flow path 22 consisting of an external piping such as a nylon tube that is connected to this one-end side flow path 21, and an other-end side flow path 23 consisting of a nylon sleeve or the like that is connected to this intermediate flow path 22. By attaching this other-end side flow path 23 to the storage container 30 described below, the other end 20b of the discharge flow path 20 is opened within the storage container 30.

[0058] Of this discharge flow path 20, the intermediate flow path 22, which is provided as an external piping for the casing 51, can be formed from various known piping materials as long as they can introduce the lubricating oil collected in the lubricating oil collection space 55 into the storage container 30 described below, and can be formed from metal pipes as well as flexible tubes such as nylon tubes.

[0059] In addition, in a configuration in which the storage container 30 described below is composed of a container body 31 and a lid body 32 removably attached to the container body 31, and the discharge flow path 20 is attached to the lid body 32 so that the other end 20b of the discharge flow path 20 opens within the storage container 30, it is preferable to form the intermediate flow path 22 portion of the discharge flow path 20 using a flexible tube such as a nylon tube as shown in Figure 3, in order to make it easier to attach and remove the lid body 32.

[0060] [Storage container] The storage container 30 is an atmospherically open container that is positioned at a lower position than the lubricating oil collection space 55 and stores the lubricating oil from the lubricating oil collection space 55 that flows down through the discharge flow path 20.In the embodiment shown in Figure 4, this storage container 30 is composed of a container body 31 and a lid body 32 that is removably attached to the opening of the container body 31.

[0061] The capacity of the storage container 30 can be set appropriately depending on the usage conditions of the oil-cooled screw compressor 1, etc. For example, if the oil-cooled screw compressor 1 equipped with the lubricating oil recovery mechanism 10 of the present invention is used as factory equipment, etc., the capacity can be set to be able to store the amount of lubricating oil that would be discharged if full-load operation were continued without unloading operation during the operating hours of the factory, thereby making it unnecessary to switch to forced unloading during operating hours.

[0062] The inside of this storage container 30 is open to the atmosphere, and is not used under pressure like the recovery container of Patent Document 2 described with reference to Figure 8. Therefore, it does not require high rigidity, and relatively inexpensive containers such as flexible containers made of synthetic resin can be used.

[0063] Preferably, at least the container body 31 of this storage container 30 is made of a transparent or translucent material so that the amount of accumulated lubricating oil can be observed with the naked eye from the outside.

[0064] In the illustrated embodiment, a male thread is formed on the outer periphery of the neck portion of the aforementioned container body 31, and the lid body 32 is a screw cap type with a female thread formed on the inner periphery, so that the lid body 32 can be easily attached and detached by screwing it onto the container body 31.

[0065] When the lid body 32 is attached to the container body 31, a breathing hole 34 is formed in the side wall of the neck portion of the container body 31, which is higher than the bottom hem 33 of the lid body 32, and in the illustrated embodiment, in the side wall of the portion located slightly below the lower end of the male screw formation range, thereby opening the storage container 30 to the atmosphere.

[0066] By forming the breathing hole 34 in this way in the container body 31 in the part covered by the lid body 32, even when the inside of the storage container 30 is suctioned through the recovery flow path 40 described later, creating a negative pressure inside the storage container 30 and causing outside air to be sucked in through the breathing hole 34, it becomes difficult for foreign matter such as dust to be sucked in through this breathing hole 34.

[0067] The attachment of the other end 20b of the aforementioned discharge flow path 20 to the storage container 30 is not particularly limited as long as it is capable of recovering the lubricating oil introduced through the discharge flow path 20 into the storage container 30, but in this embodiment, a predetermined range on the other end 20b side of the discharge flow path 20 and a predetermined range on one end 40a side of the recovery flow path 40 described later are attached to the aforementioned lid body 32 provided on the storage container 30 so that the other end 20b of the discharge flow path 20 and one end 40a of the recovery flow path 40 described later open within the storage container 30.

[0068] In the embodiment shown in Figure 4, the aforementioned other end flow path 23 of the discharge flow path 20, formed by a nylon sleeve, is inserted into a through hole 35 provided in the lid body 32, and a pair of sleeve nuts 24a, 24b and a nylon washer 25 screwed onto male threads provided on the outer periphery of this nylon sleeve (other end flow path) 23 clamp the lid body 32 from above and below at the peripheral portion of the through hole 35, thereby attaching the other end flow path 23 of the discharge flow path 20 to the lid body 32 of the storage container 30, and is configured so that when the lid body 32 is attached to the container body 31, the other end 20b of the discharge flow path 20 opens at a predetermined height position within the storage container 30.

[0069] By connecting a nylon tube (intermediate flow path) 22 connected to a drilled hole (one end flow path) 21 provided in the casing 51 to the upper end of this nylon sleeve (other end side flow path) 23, an exhaust flow path 20 is formed, with one end 20a connected to the lubricant collection space 55 and the other end 20b opening inside the storage container 30.

[0070] In addition, as shown in FIG. 5, the storage container 30 may be provided with a liquid level detection means 37 such as a float switch so that the liquid level position of the lubricating oil stored in the storage container 30 can be detected. For example, when the liquid level of the lubricating oil stored in the storage container 30 reaches a predetermined upper limit level L MAX When it is detected that the oil level is at a predetermined lower limit level L, forced unloading is initiated. MIN If it is detected that the forced unloading is in progress, the forced unloading may be stopped.

[0071] [Recovery flow path] In this embodiment, the recovery flow path 40 that connects the storage container 30 and the intake flow path 62 on the secondary side of the intake control valve 60 is composed of a one-end side flow path 41 attached to the storage container 30 as shown in Figure 1, and a main flow path 42 made of a nylon tube or the like that connects this one-end side flow path 41 and the intake flow path 62.

[0072] One end 40a of this recovery passage 40 opens near the bottom of the storage container 30 as shown in Figure 4, and the other end 40b of this recovery passage 40 is connected to the intake passage 62 on the secondary side of the intake control valve 60.By doing so, during unloaded operation with the intake control valve 60 closed, the intake passage 62 on the secondary side of the intake control valve 60 becomes negative pressure, and the lubricating oil stored in the storage container 30 can be recovered into the compression action space of the compressor main body 50 via the recovery passage 40.

[0073] The material of the aforementioned main flow path 42 portion of this recovery flow path 40 is not particularly limited as long as it is capable of sucking and recovering the lubricating oil stored in the storage container 30 by the negative pressure of the suction flow path 62, and it may be formed from a metal pipe. However, in the configuration of this embodiment in which the one-end flow path 41 portion of the recovery flow path 40 is attached to the lid body 32 of the storage container 30, it is preferable to form at least the main flow path 42 portion of the recovery flow path 40 from a flexible tube such as a nylon tube as shown in Figure 3, similar to the aforementioned discharge flow path 20, so that it can be deformed when the lid body 32 is attached or detached from the container body 31.

[0074] In the embodiment shown in Figure 4, the flow path 41 at one end of this recovery flow path 40 is composed of a nylon sleeve 41a, a nylon tube 41b connected to the lower end of this nylon sleeve 41a, and an orifice 41c attached to the lower end of this nylon tube 41b, and therefore, in the illustrated embodiment, the lower end of this orifice 41c becomes one end 40a of the recovery flow path.

[0075] It is preferable to attach a strainer 46 to the entrance of this orifice 41c, that is, to the opening provided at one end 40a of the recovery passage 40, to prevent clogging of the orifice 41c due to the intake of foreign matter.

[0076] In the illustrated configuration, the aforementioned nylon sleeve 41a is inserted into a through hole 36 formed in the lid body 32 of the storage container 30, and is attached to the lid body 32 by clamping the lid body 32 from above and below at the peripheral portion of the through hole 36 with a pair of sleeve nuts 45a, 45b screwed onto male threads on the outer periphery of the nylon sleeve 41a.

[0077] In the illustrated embodiment, a flange nut is used as the lower sleeve nut 45b, thereby eliminating the need to attach a nylon washer, but similar to the attachment structure of the nylon sleeve (other end side flow path) 23 at the other end 20b of the discharge flow path 20, the lower sleeve nut 45b may be an ordinary nut with a nylon washer or the like sandwiched between the cover body 32 and the lower sleeve nut 45b, and the attachment structure of the nylon sleeve (other end side flow path) 23 at the other end 20b of the discharge flow path 20 may be modified to imitate the attachment structure of the nylon sleeve 41a that constitutes the one end side flow path 41 of the recovery flow path 40.

[0078] The nylon tube 41b mentioned above is attached to the lower end of the nylon sleeve 41a attached to the lid 32 of the storage container 30 in this manner via a connecting nut 47a, and an orifice 41c is attached to the lower end of this nylon tube 41b via a connecting nut 47b, so that the nylon sleeve 41a, nylon tube 41b, and orifice 41c form one end side flow path 41 of the recovery flow path 40 that is attached to the lid 32 of the storage container 30.

[0079] Furthermore, a strainer 46 is detachably attached to the orifice 41c that forms the lower end of the one-end flow path 41 so as to cover the inlet of the orifice 41c.

[0080] In this way, one end 40a of the recovery flow path 40 is formed by an orifice 41c, and a strainer 46 is attached to the inlet of this orifice 41c. In the event that the strainer 46 or orifice 41c becomes clogged, the strainer 46 or orifice 41c can be removed from the storage container 30 simply by removing the lid 32 from the container body 31 of the storage container 30, and the clogging can be easily eliminated or the strainer 46 or orifice 41c can be replaced.

[0081] In this way, the upper end of the nylon sleeve 41a attached to the lid 32 of the storage container 30 is connected to the intake flow path 62 on the secondary side of the intake control valve 60 via a main flow path 42 consisting of a nylon tube or the like equipped with a check valve 49, thereby forming the aforementioned recovery flow path 40, one end 40a of which opens near the bottom of the storage container 30 and the other end 40b of which is connected to the intake flow path 62 on the secondary side of the intake control valve 60.

[0082] In the embodiment shown in Figure 4, the strainer 46 and orifice 41c are configured to be provided at one end 40a of the recovery flow path 40, but the strainer 46 and orifice 41c may also be provided at a position other than the one end 40a of the recovery flow path 40 (for example, at an intermediate position of the recovery flow path 40) as shown in Figure 1.

[0083] [Effect, etc.] In the oil-cooled screw compressor 1 equipped with the lubricating oil recovery mechanism 10 of the present invention described above, while the oil-cooled screw compressor 1 is operating, a portion of the lubricating oil supplied to the seal chamber 53 lubricates the shaft seal device 54, then passes through the shaft seal device 54 and is collected in the lubricating oil collection space 55.

[0084] The lubricating oil collected in the lubricating oil collecting space 55 in this manner is recovered and stored in the storage container 30 via the discharge flow path 20, one end 20a of which is connected to the lubricating oil collecting space 55.

[0085] When the oil-cooled screw compressor 1 switches to unloaded operation with the intake control valve 60 closed and negative pressure is created in the intake passage 62 on the secondary side of the intake control valve 60, the lubricating oil accumulated in the storage container 30 is sucked into the intake passage 62 through the recovery passage 40 by this negative pressure, and is introduced into the compression action space of the compressor main body 50, thereby returning it to the lubricating oil circulation system.

[0086] In this way, the lubricating oil recovery mechanism 10 of the present invention is provided with a storage container 30 that stores the lubricating oil that has passed through the shaft seal device 54 and been collected in the lubricating oil collection space 55, making it possible to significantly increase the amount of lubricating oil that can be stored within the lubricating oil recovery mechanism 10 compared to the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6.

[0087] Furthermore, by temporarily storing the lubricating oil in the storage container 30, the opening (the entrance to the orifice 41c) provided at one end 40a of the recovery flow path 40 can be positioned submerged in the lubricating oil stored in the storage container 30, and only the lubricating oil can be sucked up without entraining air when the lubricating oil is sucked up.

[0088] As a result, the structure is such that the lubricating oil is recovered together with the air sucked in through the gap δ (see Figure 7) that occurs on the outer periphery of the drive shaft 152, and the lubricating oil can be recovered more efficiently than in the conventional negative pressure suction type lubricating oil recovery mechanism 110 described with reference to Figure 6.

[0089] That is, even if the amount (volume) of "fluid" that can be sucked into the suction passages 62, 162 and recovered per predetermined time (e.g., 1 second) via the recovery passages 40, 120 is the same in the lubricant recovery mechanism 10 of the present invention (see FIG. 1) and the conventional lubricant recovery mechanism 110 (see FIG. 6), in the conventional negative pressure suction type lubricant recovery mechanism 110 (FIG. 6), which recovers lubricant as a mixed fluid with air, air accounts for a large portion of the recovered fluid, and therefore lubricant is only recovered as part of the recovered fluid. In contrast, in the lubricant recovery structure 10 of the present invention, all of the recovered fluid is lubricant by recovering lubricant that does not contain air, and therefore the amount of "lubricant" recovered is significantly increased even if the amount of "fluid" that can be recovered per predetermined time (e.g., 1 second) is the same.

[0090] As a result, coupled with the small amount of lubricating oil that can be stored in the recovery flow path 120, in the oil-cooled screw compressor 100 equipped with the conventional lubricating oil recovery mechanism 110 described with reference to Figure 6, which recovers lubricating oil together with air, if lubricating oil was to be recovered by forced unloading for about 1 second, forced unloading had to be performed about once every hour. In contrast, in the oil-cooled screw compressor 1 equipped with the lubricating oil recovery mechanism 10 of the present invention, forced unloading is performed about every 10 hours as the amount of oil stored in the storage container 30 increases, so that even if the amount of lubricating oil recovered by each forced unloading increases by about 10 times, lubricating oil that does not contain air can be recovered, and the lubricating oil accumulated in the storage container can be recovered by performing forced unloading for about 1 second per time (or several seconds depending on the amount of storage), as in the conventional case. Therefore, even if the frequency of forced unloading is significantly reduced, the lubricating oil can be recovered by performing forced unloading for a relatively short time.

[0091] Such forced unloading may be configured to be performed for a set length of time at predetermined intervals set by a timer, for example. However, as explained with reference to Figure 5, in a configuration in which a liquid level detection means 37 such as a float switch that detects the liquid level position of the lubricating oil is provided in the storage container 30, forced unloading may be started and / or stopped based on the detection signal of this liquid level detection means 37.

[0092] When the forced unloading operation is started based on the position of the lubricating oil level detected by the level detection means 37, as an example, L in FIG. MAX Specifically, the upper limit level L is set as a position lower than the position where the ventilation hole 34 is formed by a predetermined margin. MAX It can be configured to initiate forced unloading when the liquid level reaches

[0093] By configuring in this manner, lubricating oil can be stored up to nearly the upper capacity of the storage container 30, thereby minimizing the frequency of forced unloading, while forced unloading can be started before the lubricating oil stored in the storage container 30 overflows from the storage container 30 through the ventilation hole 34, thereby reliably preventing leakage of lubricating oil.

[0094] In particular, in combination with the normal forced unloading that is performed at predetermined intervals based on the count by the timer, the liquid level detection means 37 detects the upper limit level L Max By configuring the device to transition to forced unloading when a malfunction is detected regardless of the count time of the timer, it is possible to prevent leakage of lubricating oil even if the amount of lubricating oil in the storage container 30 unintentionally increases, for example, when the amount of lubricating oil passing through the shaft seal device 54 increases due to deterioration over time, resulting in an accumulation of lubricating oil that could not be fully recovered by performing normal forced unloading.

[0095] On the other hand, when the forced unloading operation is stopped based on the position of the lubricating oil level detected by the level detection means 37, as an example, L in FIG. MINSpecifically, the lower limit level L is set at a position higher than the inlet position provided at the lower end of the orifice 41c by a predetermined margin. MIN The forced unloading may be stopped when the liquid level reaches the predetermined value.

[0096] The lubricant level is at the lower limit L MIN If forced unloading operation is continued with the liquid level falling below this level and the inlet portion of the orifice 41c exposed above the liquid level, air in the storage container 30 is sucked into the intake passage 62 on the secondary side of the intake control valve 60 via the recovery passage 40.

[0097] However, when the level of the lubricating oil in the reservoir 30 reaches the lower limit level L MIN By stopping the forced unloading when the lower limit level L is reached, it is possible to prevent air from being introduced into the compression action space of the compressor body 50. MIN By stopping the forced unloading, it is possible to prevent air from mixing into the compressed gas even when the lubricating oil recovery mechanism 10 of the present invention is adopted as the lubricating oil recovery mechanism 10 of an oil-cooled screw compressor 1 that compresses gases other than air, such as fuel gas.

[0098] The forced unloading may be started and stopped based on the detection signal of the liquid level detection means 37 described above. The forced unloading may also be started based on the detection signal of the liquid level detection means 37 when the liquid level detection means 37 detects the upper limit level L. MAX The forced unloading may be started when the liquid level detection means 37 detects the lower limit level L and stopped when a predetermined time is counted by a timer. Furthermore, the forced unloading may be started at every set time by the timer and stopped when the liquid level detection means 37 detects the lower limit level L. MIN Furthermore, it is possible to use a combination of timer control and control based on the detection signal of the liquid level detection means 37, and start and / or stop forced unloading when either the counting of a set time by the timer or the detection of the liquid level by the liquid level detection means 37 is met, and various combinations are possible. [Explanation of symbols]

[0099] 1. Oil-flooded screw compressor 10 Lubricant recovery mechanism 20 Discharge flow path 20a One end (of the discharge flow path) 20b other end (of discharge flow path) 21 One end side flow path (drilled hole) 22 Intermediate flow path (nylon tube) 23 Other end flow path (nylon sleeve) 24a, 24b Sleeve nuts 25 nylon washer 30 Storage container 31 Container body 32 Lid 33 Bottom edge (of the lid) 34 Breathing hole 35,36 Through holes 37 Liquid level detection means (float switch) 40 Recovery channel 40a One end (of the recovery channel) 40b other end (of the recovery flow path) 41 One end side flow path (of recovery flow path) 41a nylon sleeve 41b nylon tube 41c Orifice 42 Main flow path (nylon tube) 45a, 45b sleeve nuts 46 Strainer 47a, 47b Connecting nuts 49 Check valve 50 Compressor body 51 Casing 52 Drive shaft 53 Seal Chamber 54 Shaft sealing device 55 Lubricating oil collection space 56 Rotor Room 57,58 Screw rotor 60 Intake control valve 62 Suction flow path 70 Drive source (motor) 100 Oil-flooded screw compressor 110 Lubricant recovery mechanism 120 Recovery channel 120a One end (of the recovery channel) 120b other end (of recovery flow path) 130 Container 150 Compressor body 151 Casing 152 drive shaft 153 Seal Chamber 154 Shaft sealing device 155 Lubricating oil collection space 156 Rotor Room 157,158 Screw rotor 159 Bearings 160 Intake control valve 162 Suction flow path 170 Drive source (motor) 180 receiver tank 190 Oil supply channel 191 Oil cooler 192 Oil filter 210 Lubricating oil recovery mechanism 220 Discharge flow path 220a One end (of the discharge flow path) 220b other end (of discharge flow path) 230 Container 240 Return channel 310 Lubricant recovery mechanism 330 Container 331 Outlet 350 mixer 351 Driving flow inlet 352 Outlet 353 Intake port

Claims

1. An oil-cooled screw compressor is provided with a compressor body in which a pair of male and female screw rotors are housed in a rotor chamber provided in a casing so as to be able to mesh and rotate, and which compresses a gas to be compressed together with lubricating oil introduced into a compression action space and discharges the compressed gas as a gas-liquid mixed fluid, the compressor body being provided with a drive shaft that penetrates and protrudes through the casing, a shaft seal device that seals a gap that occurs on the outer periphery of the drive shaft, and a lubricating oil collecting space that is provided on the outer periphery of the drive shaft at a position closer to the outer side of the casing than the shaft seal device and that collects the lubricating oil that has passed through the shaft seal device, a discharge flow path having one end connected to the lubricant oil collecting space; a storage container that is open to the atmosphere and communicates with the other end of the discharge flow path, and that introduces the lubricating oil collected in the lubricating oil collecting space through the discharge flow path and stores the lubricating oil therein; a recovery flow path that recovers the lubricating oil stored in the storage container into a compression action space of the compressor body by utilizing negative pressure generated in the intake flow path of the compressor body on the secondary side of the intake control valve during unloading operation; The oil recovery mechanism for an oil-cooled screw compressor is characterized in that one end of the recovery passage is open near the bottom of the storage container, and the other end of the recovery passage is connected to the suction passage on the secondary side of the intake control valve.

2. The storage container includes a container body and a lid body that is detachably attached to an opening of the container body and closes the opening, The lubricating oil recovery mechanism for an oil-cooled screw compressor as described in claim 1, characterized in that the discharge flow path and the recovery flow path are attached to the lid so that the other end of the discharge flow path and the one end of the recovery flow path open within the storage container.

3. 3. The lubricating oil recovery mechanism for an oil-cooled screw compressor according to claim 2, wherein the one end of the recovery passage is formed by an orifice.

4. 4. The lubricating oil recovery mechanism for an oil-cooled screw compressor according to claim 3, further comprising a strainer for covering the inlet of said orifice.

5. the lid of the storage container is a cap type and is configured to cover an opening of the container body and a side wall of the container body within a predetermined height range from the opening, The lubricating oil recovery mechanism of the oil-cooled screw compressor according to any one of claims 2 to 4, characterized in that a breathing hole penetrating the side wall of the container body is provided in the side wall of the container body at a position higher than the bottom position of the lid body attached to the container body.

Images