Oil leakage recovery structure of shaft seal portion of screw compressor

Abstract

Provided is a leakage oil recovery structure for a shaft seal portion of a screw compressor that can effectively recover leaked oil. A shaft seal device (60) is used to seal between the inner periphery of a shaft hole (32) provided in a housing (30) and the outer periphery of a drive shaft (20), and an oil accumulation space (34) that recovers lubricating oil leaked from the shaft seal device is provided around the drive shaft at a position on the housing outer side relative to the shaft seal device. The shaft seal device side of the drive shaft in the portion disposed in the oil accumulation space (34) is a small diameter portion (Nd), the portion on the housing outer side is a large diameter portion (Wd), a step portion (23) is provided at the boundary portion between the small diameter portion (Nd) and the large diameter portion (Wd), the large diameter portion (Wd) on the housing (30) outer side relative to the step portion is provided with a tapered portion (24) that gradually decreases in diameter as it goes toward the housing (30) outer side, and the end portion (24a) of the large diameter side of the tapered portion (24) is disposed in the oil accumulation space (34).

Description

TECHNICAL FIELD

[0001] The present application relates to a leakage oil recovery structure of a shaft seal portion of a screw compressor, and more particularly, to a leakage oil recovery structure for recovering lubricating oil leaked from a shaft seal device in a shaft seal portion of a screw compressor provided with a shaft hole penetrating a casing of a compressor main body, a drive shaft inserted into the shaft hole, and a shaft seal device sealing a gap between the shaft hole and the drive shaft. BACKGROUND

[0002] In order to rotate the screw rotors 110, 111 housed in a rotor chamber 131 formed in the casing 130 by a rotational driving force generated by a driving source such as a motor, an engine, etc. not shown, the screw compressor 100 is provided with a shaft hole 132 penetrating the casing 130, and a drive shaft 120 communicating the inside and outside of the casing 130 via the shaft hole 132. Figure 6 As shown in the drawing, the screw compressor 100 is provided with a shaft hole 132 penetrating the casing 130, and a drive shaft 120 communicating the inside and outside of the casing 130 via the shaft hole 132.

[0003] In the illustrated example, the rotor shaft provided at the suction side of either one of the male rotor 110 and the female rotor 111 (the male rotor 110 in the illustrated example) is provided as a drive shaft main body 121, and a power transmission member 122 (a pulley in the illustrated example) such as a pulley, a sprocket, a gear, a coupling, etc. is attached to the end portion of the drive shaft main body 121 projecting to the outside of the casing 130, as the drive shaft 120 transmitting the rotational driving force of a driving source (not shown) such as an engine, a motor, etc. to the screw rotors 110, 111.

[0004] Thus, the shaft hole 132 into which the drive shaft 120 is inserted is formed as a penetration hole communicating the inside and outside of the casing 130, and therefore, in order to prevent the gas, lubricating oil, etc. compressed in the screw compressor 100 from leaking to the outside via the shaft hole 132, the gap between the inner periphery of the shaft hole 132 and the outer periphery of the drive shaft 120 is sealed by the shaft seal device 160.

[0005] As such a shaft seal device 160, a contact type shaft seal device (an oil seal 161 in the illustrated example) such as an oil seal, a mechanical seal, etc. is widely used, and therefore, in the case where the shaft seal device 160 is an oil seal 161, a small amount of lubricating oil is required to be supplied for lubricating the sealing lip portion in sliding contact with the outer periphery of the drive shaft 120, and in the case where the shaft seal device 160 is a mechanical seal, a small amount of lubricating oil is required to be supplied for lubricating the sliding contact surface of the stationary ring and the rotating ring.

[0006] Therefore, even in the case where the aforementioned shaft seal device 160 is provided, the small amount of lubricating oil for lubricating the sliding contact portion of the shaft seal device 160 is continuously leaked to the outside, and particularly, if the sliding contact surface of the shaft seal device 160 is worn with the passage of time, the amount of leaked lubricating oil increases.

[0007] Thus, due to the fact that a small amount of lubricating oil leaks out because of the provision of the shaft seal device 160, the power transmission member 122 at the position where the lubricating oil leaks out, and the equipment in the vicinity of the position where the lubricating oil leaks out are contaminated with the lubricating oil, and the like become undesirable.

[0008] In addition, due to the fact that the lubricating oil is lost in the circulation system because of the fact that the lubricating oil leaks out to the outside of the machine, if the amount of lubricating oil that leaks out increases, the lubricating oil that is lost needs to be frequently replenished to the circulation system, and the maintenance becomes complicated.

[0009] Thus, a screw compressor 100 that has a recovery structure that recovers the lubricating oil that leaks out from the shaft seal device 160 before the lubricating oil further leaks out to the outside of the machine has been proposed.

[0010] As one example of a screw compressor 100 that has such a lubricating oil recovery structure, the following structure is employed in the patent document 1 described later, that is, as shown in Figure 6 and Figure 7 the oil accumulation space 134 that recovers the lubricating oil that leaks out from the shaft seal device 160 is provided around the drive shaft 120 at a position on the outside of the housing 130 with respect to the shaft seal device 160.

[0011] Furthermore, as shown in Figure 7 the following structure is employed, that is, the portion of the drive shaft 120 that is disposed in the oil accumulation space 134 and that is disposed on the shaft seal device 160 side becomes a small-diameter portion Nd that has a relatively small outer diameter, the portion that is disposed on the outside of the housing 130 becomes a large-diameter portion Wd that has a relatively large outer diameter, a step portion 123 is provided at the boundary between the small-diameter portion Nd and the large-diameter portion Wd, in the example shown in the drawing, the portion of the collar 121a that is provided at the position where the lip portion of the shaft seal device 160 (the oil seal 161) is in sliding contact in the drive shaft main body 121 becomes the aforementioned small-diameter portion Nd, and the hub portion of the power transmission member 122 (the pulley) becomes the aforementioned large-diameter portion Wd, and thus the aforementioned step portion 123 can be provided without the addition of a new component, new machining of the drive shaft main body 121, and the like.

[0012] Patent Document 1: Japanese Patent Application Publication No. 2014-145315

[0013] As shown in the screw compressor 100 that has the aforementioned existing leaked oil recovery structure, according to the structure in which the aforementioned step portion 123 is provided in the portion of the drive shaft 120 that is disposed in the oil accumulation space, if the lubricating oil that leaks out from the shaft seal device 160 moves to the outside of the machine along the outer periphery of the drive shaft 120, the lubricating oil collides with the step portion 123 and is restricted from moving in the axial direction of the drive shaft 120.

[0014] Moreover, the lubricating oil that reaches the step portion 123 is changed in direction of movement to a direction orthogonal to the axial direction of the drive shaft 120 by centrifugal force accompanying rotation of the drive shaft 120 along the side surface 123a of the step portion 123, and if reaching the outer peripheral edge of the step portion 123, is scattered in the outer peripheral direction of the drive shaft, and thus the lubricating oil is drained at the step portion 123 of the drive shaft 120.

[0015] As a result, the majority of the lubricating oil that leaks from the shaft seal device 160 and moves along the surface of the drive shaft 120 to the outside of the machine is recovered into the oil accumulation space 134 at the step portion 123, and thus leakage of the lubricating oil to the outside of the machine is prevented.

[0016] In addition, the lubricating oil that is recovered into the oil accumulation space 134 is returned to the lubricating oil circulation system via the drain passage 135 that communicates with the oil accumulation space 134, and the amount of lubricating oil lost in the circulation system is reduced, and thus it is possible to reduce the frequency of replenishing lubricating oil and the like, and performance in maintenance is excellent.

[0017] Thus, according to the leaked oil recovery structure described in Patent Document 1 described above, it is possible to effectively recover the lubricating oil that leaks from the shaft seal device 160.

[0018] However, it was confirmed that even the screw compressor 100 provided with such a leaked oil recovery structure could not completely prevent leakage of the lubricating oil along the drive shaft 120, and although only a small amount, the lubricating oil still leaked to the outside of the machine, and contaminated the power transmission member 122 such as a belt wheel, and peripheral equipment, and could not completely overcome the problem of preventing leakage of the lubricating oil to the outside of the machine.

[0019] Therefore, upon investigating the reason why the lubricating oil still leaks to the outside of the machine in the structure in which the step portion 123 is provided to the drive shaft 120 in the oil accumulation space 134 as described above, it was considered that the reason was that the lubricating oil that reaches the surface of the large diameter portion Wd over the step portion 123 leaks to the outside of the machine, as described below.

[0020] That is, it was considered that the lubricating oil that reaches the step portion 123 of the drive shaft 120 via the shaft seal device 160 is almost entirely scattered in the outer peripheral direction along the side surface 123a of the step portion 123 by the action of centrifugal force, and thus is removed from the surface of the drive shaft 120, but the lubricating oil as a viscous fluid cannot be completely removed from the surface of the drive shaft 120 by the action of this centrifugal force, and a small amount of the lubricating oil remaining on the surface of the drive shaft 120 still reaches the surface of the large diameter portion Wd over the step portion 123.

[0021] In addition, when the screw compressor 100 is stopped, although the lubricating oil adhering to the outer periphery of the small diameter portion Nd of the drive shaft 120 flows downward due to gravity, at this time the lower end corner portion of the stepped portion 123 becomes the lowest position in the drive shaft 120, and thus the lubricating oil flowing down along the surface of the drive shaft 120 is accumulated in the lower end corner portion of the stepped portion 123.

[0022] Thus, although a part of the lubricating oil accumulated in the lower end corner portion of the stepped portion 123 falls as oil droplets to the lower side, the remaining lubricating oil reaches the surface of the large diameter portion Wd by going around the lower side of the lower end corner portion of the stepped portion 123.

[0023] Thus, according to the leakage oil recovery structure of the screw compressor 100 provided with the leakage oil recovery structure described with reference to Figure 6 and Figure 7 the leakage of the lubricating oil to the outside of the machine cannot be completely prevented, and a leakage oil recovery structure capable of more reliably recovering the lubricating oil leaked from the shaft seal device 160 in the oil accumulation space 134 and preventing the leakage of the lubricating oil to the outside of the machine is desired to be developed.

[0024] In addition, in the description made with reference to Figure 6 and Figure 7 the structure of the shaft hole 132 through which the rotor shaft of the screw rotor 110, 111 (the rotor shaft of the male rotor 110 in the illustrated example) of either the male or the female, to which the leakage oil recovery structure is provided, is described.

[0025] However, for example, in the case where the screw compressor 100 is provided with a speed-up device composed of a driving gear and a driven gear, if the structure is such that the rotor shaft is not directly provided to protrude to the outside of the casing, but the drive shaft connected to the rotor shaft via the speed-up device is provided to protrude to the outside of the casing, the shaft seal device also needs to be provided to seal the portion of the drive shaft of such a speed-up device provided to protrude to the outside of the casing, and the leakage oil recovery structure also needs to be provided to recover the lubricating oil leaked from the shaft seal device, and the problems of the foregoing prior art are not limited to the illustrated example, but the shaft seal portion in the shaft hole provided to protrude to the outside of the casing of the screw compressor is all subject to the above problems. SUMMARY

[0026] Therefore, the present application is completed in order to solve the above-described problems in the prior art, and aims to provide a leakage oil recovery structure of a shaft seal portion of a screw compressor, in which the shaft seal portion provided in the shaft hole of the screw compressor provided to protrude to the outside of the casing, the leakage of the lubricating oil to the outside of the machine can be more reliably prevented by effectively recovering the lubricating oil passing through the shaft seal device.

[0027] The following describes components for solving the problems in conjunction with reference signs used in the embodiments. The reference signs are added for the purpose of clarifying the correspondence between the claims and the description of the embodiments, and are not used for limiting the technical scope of the present application.

[0028] To achieve the above object, the shaft seal portion oil leakage recovery structure of the screw compressor 1 of the present application is characterized in that, in the shaft seal portion of the screw compressor 1 in which the gap between the inner periphery of the shaft hole 32 provided in the housing 30 and the outer periphery of the drive shaft 20 inserted into the shaft hole 32 is sealed by the shaft seal device 60, an oil accumulation space 34 that recovers the lubricating oil leaked from the shaft seal device 60 is provided around the drive shaft 20 at a position on the outside of the housing 30 with respect to the shaft seal device 60, and the outer diameter of a large diameter portion Wd, which is the portion disposed on the outside of the housing 30, is made larger than the outer diameter of a small diameter portion Nd, which is the portion disposed on the shaft seal device 60 side, in the drive shaft 20 in the portion disposed in the oil accumulation space 34, a step portion 23 is provided at the boundary between the small diameter portion Nd and the large diameter portion Wd, a tapered portion 24 is provided in the large diameter portion Wd on the outside of the housing 30 with respect to the step portion 23, the tapered portion 24 gradually decreases in diameter as it goes toward the outside of the housing 30, and at least the end portion 24a of the large diameter side of the tapered portion 24 is disposed in the oil accumulation space 34 (see FIG. 1). Figures 2-4 ).

[0029] Although it is possible that the end portion 24a of the large diameter side of the step portion 23 and the tapered portion 24 is disposed at a predetermined separation position (see Figure 2 and Figure 4 ), it is preferable that the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24 are disposed at the same position (see Figure 3 ).

[0030] It is more preferable that a discharge flow passage 35, of which the upper end communicates with the bottom of the oil accumulation space 34, is provided, and that the communication port 35a, through which the discharge flow passage 35 communicates with the oil accumulation space 34, is opened on the perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the end portion 24a of the large diameter side of the tapered portion 24 (see Figures 2-4 ).

[0031] It is more preferable that the center or the vicinity of the center of the communication port 35a is disposed on the perpendicular line VL (see Figure 3 ).

[0032] With regard to the large diameter portion Wd of the drive shaft 20, the mounting range of the cylindrical member 22 can be made to be the large diameter portion Wd by fitting the cylindrical member 22 to the drive shaft body 21 from the outside (see Figures 2-4 ).

[0033] In this case, it is preferable that a seal member 28 such as an O-ring is interposed between the outer periphery of the drive shaft body 21 and the inner periphery of the cylindrical member 22 (see Figure 4 ).

[0034] More preferably, the diameter of the large-diameter portion Wd at a position on the outer side of the housing 30 of the tapered portion 24 is formed to be larger than the diameter of the small-diameter side end portion 24b of the tapered portion 24, and a second step portion 26 is provided near the small-diameter side end portion 24b of the tapered portion 24 (see Figures 2-4 ).

[0035] Effects of the Invention

[0036] According to the screw compressor 1 of the leaked oil recovery structure of the present application described above, the following effects can be obtained.

[0037] The drive shaft 20 is provided with the aforementioned step portion 23, and the large-diameter portion Wd on the outer side of the housing 30 with respect to the step portion 23 is provided with the tapered portion 24 whose diameter gradually decreases toward the outer side of the housing 30, so that even if the lubricating oil that has not been removed at the step portion 23 and remains on the surface of the drive shaft 20, the lubricating oil cannot move toward the outside of the machine beyond the tapered portion 24 at the time of operation and at the time of stop of the screw compressor 1, and can be recovered into the oil accumulation space 34, so that the leakage of the lubricating oil that has passed through the shaft seal device 60 to the outside of the machine can be more effectively prevented.

[0038] That is, at the time of operation of the screw compressor 1, as shown in Figure 5A , the lubricating oil at the tapered portion 24 is subjected to a force that pushes it from the small-diameter side of the tapered portion 24 to the large-diameter side by the centrifugal force generated in conjunction with the rotation of the drive shaft 20.

[0039] Therefore, even if the lubricating oil that has reached the large-diameter portion Wd beyond the step portion 23, the lubricating oil cannot move toward the outside of the machine beyond the tapered portion 24, and can be prevented from leaking to the outside of the machine, and is scattered in the outward peripheral direction at the end portion 24a of the large-diameter side of the tapered portion 24 by the centrifugal force and recovered into the oil accumulation space 34.

[0040] In addition, if the screw compressor 1 is stopped and the drive shaft 20 is stopped from rotating, the lubricating oil that has leaked from the shaft seal device 60 and adheres to the surface of the small-diameter portion Nd of the drive shaft 20 flows down to the lower end corner portion of the step portion 23 and accumulates there due to the weight, as shown in Figure 5B , so that even if the lubricating oil goes beyond the step portion 23 and goes around to the large-diameter portion Wd, the lubricating oil cannot move from the large-diameter side to the small-diameter side toward the upward direction at the tapered portion 24, and thus the leakage of the lubricating oil beyond the tapered portion 24 to the outside of the machine can be prevented in this respect as well.

[0041] Although the step portion 23 and the end portion 24a of the large-diameter side of the tapered portion 24 can also be arranged at a predetermined interval as shown in Figure 2 and Figure 4 However, as shown in Figure 3 , according to the structure in which the step portion 23 and the end portion 24a of the large-diameter side of the tapered portion 24 are provided at the same position, the outer peripheral edge of the step portion 23 is formed as an acute angle and the lubricating oil cannot exert a tension, and when the drive shaft 20 rotates, the oil discharge property of the lubricating oil moved to the outer peripheral edge of the step portion 23 by the centrifugal force is improved, and the lubricating oil can be more easily recovered to the oil accumulation space 34.

[0042] Further, according to the structure in which the communication port 35a through which the discharge flow passage 35 and the oil accumulation space 34 communicate is provided on the perpendicular line VL orthogonal to the axis of the drive shaft 20 and passing through the end portion 24a of the large-diameter side of the tapered portion 24, it is more preferable that the center or the vicinity of the center of the communication port 35a is arranged on the perpendicular line VL, and when the screw compressor 1 is stopped, the lubricating oil accumulated between the step portion 23 and the end portion 24a of the large-diameter side of the tapered portion 24 and dripped can be smoothly recovered into the discharge flow passage 35.

[0043] In addition, according to the structure in which the large-diameter portion Wd of the aforementioned is formed by the cylindrical member 22 fitted outside the drive shaft body 21, it is not necessary to directly machine the drive shaft body 21, and by only installing the cylindrical member 22 in which the tapered portion 24 is formed in advance, the step portion 23 and the tapered portion 24 can be easily formed in the drive shaft 20.

[0044] In addition, according to the structure in which the sealing member 28 such as an O-ring is interposed between the outer periphery of the drive shaft body 21 and the inner periphery of the cylindrical member 22, it is also possible to reliably prevent the lubricating oil that has passed through the shaft seal device 60 from leaking to the outside of the machine by moving through the gap between the drive shaft body 21 and the cylindrical member 22.

[0045] Further, according to the structure in which the diameter of the large-diameter portion Wd at the position on the outside of the housing 30 of the tapered portion 24 is formed larger than the diameter of the end portion 24b of the small-diameter side of the tapered portion 24, and the second step portion 26 is provided near the end portion 24b of the small-diameter side of the tapered portion 24, even if the lubricating oil reaches the tapered portion 24, the lubricating oil is prevented from further moving to the outside of the machine at the second step portion 26, and it is possible to more reliably prevent the lubricating oil from leaking to the outside of the machine. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a reduced-scale sectional plan view of a screw compressor provided with the leaked oil recovery structure of the present application.

[0047] Figure 2 is an enlarged view of the arrow II portion of Figure 1

[0048] Figure 3 is an enlarged view of the arrow II portion of Figure 1

[0049] Figure 4 is an enlarged view of the arrow II portion of Figure 1

[0050] Figure 5A and Figure 5B is an explanatory view of the moving direction of the lubricating oil on the drive shaft, Figure 5A is the screw compressor in operation, Figure 5B is the screw compressor at stop.

[0051] Figure 6 is a reduced scale sectional plan view of the screw compressor provided with the conventional leaked oil recovery structure (corresponding to FIG. 1 of Patent Document 1). Figure 1

[0052] Figure 7 is an enlarged view of the shaft seal portion of the screw compressor of Figure 6

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054] 1 screw compressor

[0055] 10 male rotor

[0056] 11 female rotor

[0057] 20 drive shaft

[0058] 21 drive shaft main body (rotor shaft)

[0059] 22 cylindrical member

[0060] 23 step portion

[0061] 23a side surface (of the step portion)

[0062] 24 conical portion

[0063] 24a end portion on the large diameter side (of the conical portion)

[0064] 24b end portion on the small diameter side (of the conical portion)

[0065] 25 annular groove

[0066] 26 second step portion

[0067] 28 sealing member (O-ring) ​​​​​

[0068] 30 housing

[0069] 31 rotor chamber

[0070] 32 shaft hole

[0071] 33 bearing

[0072] 34 oil accumulation space

[0073] 35 discharge flow passage

[0074] 35a communication port

[0075] 60 shaft seal device

[0076] 61 oil seal

[0077] 100 screw compressor

[0078] 110 male rotor

[0079] 111 female rotor

[0080] 120 drive shaft

[0081] 121 drive shaft body (rotor shaft)

[0082] 121a collar

[0083] 122 power transmission member (pulley)

[0084] 123 stepped portion

[0085] 123a side surface (of the stepped portion)

[0086] 130 housing

[0087] 131 rotor chamber

[0088] 132 shaft hole

[0089] 134 oil accumulation space

[0090] 135 discharge flow passage

[0091] 160 shaft seal device

[0092] 161 oil seal

[0093] Nd small diameter portion

[0094] Wd large diameter portion

[0095] VL perpendicular line DETAILED DESCRIPTION

[0096] Next, embodiments of the present application will be described with reference to the drawings.

[0097] In Figure 1 the drawing, reference numeral 1 is a screw compressor provided with the leakage oil recovery structure of the present application at a shaft seal portion, the screw compressor 1 is provided with a housing 30 and a pair of screw rotors composed of a male rotor 10 and a female rotor 11, the housing 30 is provided with a rotor chamber 31 that houses the screw rotors 10, 11 in an engaged state.

[0098] An axial hole 32 is formed at an end portion of the suction side of the housing 30, the axial hole 32 is a through hole that receives a rotor shaft 21 of the male rotor 10 and projects the rotor shaft 21 outside the housing 30, and the rotor shaft 21 of the male rotor is inserted into the axial hole 32 as a drive shaft body 21 that is used to input a rotational driving force from a driving source not shown.

[0099] The drive shaft body 21 that is inserted into the axial hole 32 provided in the housing 30 is supported to be rotatable by a bearing 33 provided in the axial hole 32, and between the outer periphery of the drive shaft 20 and the inner periphery of the axial hole 32 at a position outside the bearing 33 with respect to the housing 30, a shaft seal device 60 such as an oil seal, a mechanical seal, or the like is provided to seal.

[0100] At a position further outside the housing 30 with respect to the shaft seal device 60, an oil accumulation space 34 is continuously formed in the axial hole 32 in the circumferential direction, the oil accumulation space 34 is used to recover lubricating oil that leaks through the shaft seal device 60.

[0101] In the oil accumulation space 34, as Figure 2 shown, a discharge flow path 35 is communicated at the bottom portion thereof, and the lubricating oil recovered into the oil accumulation space 34 can be discharged through the discharge flow path 35.

[0102] In at least the portion of the aforementioned drive shaft 20 that is housed in the oil accumulation space, a small diameter portion Nd having a relatively small outer diameter is provided at the shaft seal device 60 side, a large diameter portion Wd having a relatively large outer diameter than the small diameter portion Nd is provided at the outside of the housing 30, and a step portion 23 is formed at the boundary portion of the small diameter portion Nd and the large diameter portion Wd.

[0103] The large diameter portion Wd can be directly formed at the outer periphery of the drive shaft body 21 by cutting or the like, but in the present embodiment, a cylindrical member 22 is fitted to the drive shaft body 21, and the portion where the cylindrical member 22 is fitted becomes the aforementioned large diameter portion Wd.

[0104] The large diameter portion Wd can form a hub portion of a power transmission member such as a pulley, a sprocket, a gear, a coupling, or the like not shown that is mounted at the end portion of the drive shaft body 21 as the aforementioned cylindrical member 22, or a cylindrical spacer that is butted against the end surface of the hub portion of the power transmission member can be mounted and used as the aforementioned cylindrical member 22.

[0105] In the case where the cylindrical member 22 is fitted to the drive shaft body 21 to form the large-diameter portion Wd, it is preferable that, as shown in Figure 4 , an O-ring 28 is interposed between the outer periphery of the drive shaft body 21 and the inner periphery of the cylindrical member 22, the O-ring 28 being fitted to an annular groove 25 provided in the outer periphery of the drive shaft body 21 or the inner periphery of the cylindrical member 22 (in the illustrated example, the annular groove 25 provided in the inner periphery of the cylindrical member 22), thereby preventing the lubricating oil from leaking out via the space between the outer periphery of the drive shaft body 21 and the inner periphery of the cylindrical member 22.

[0106] In this large-diameter portion Wd, a tapered portion 24 is further provided at a position on the outer side of the housing 30 with respect to the aforementioned step portion 23, the tapered portion 24 being formed in a shape in which the outer diameter gradually decreases as it goes toward the outer side of the housing 30.

[0107] As shown in Figure 2 and Figure 4 , the end portion 24a of the large-diameter side of the tapered portion 24 can be provided at a predetermined separation position on the outer side of the housing 30 with respect to the aforementioned step portion 23, but can also be configured such that, as shown in Figure 3 , the formation position of the step portion 23 and the formation position of the end portion 24a of the large-diameter side of the tapered portion 24 are provided at a common position, and an acute-angle corner portion is formed in the outer peripheral edge of the step portion 23.

[0108] By being thus configured, the lubricating oil that reaches the outer peripheral edge of the step portion 23 due to centrifugal force when the drive shaft 20 is rotating does not develop tension and easily scatters in the outer peripheral direction, and thus the oil discharge performance of the drive shaft 20 can be further improved.

[0109] The tapered portion 24 is provided such that at least the end portion 24a of the large-diameter side thereof is disposed within the aforementioned oil accumulation space, and preferably, as shown in Figure 2 and Figure 4 , the tapered portion 24 is provided in such a manner that the communication port 35a, through which the oil accumulation space 34 and the discharge flow passage 35 communicate, is formed in a vertical line VL that is orthogonal to the axis of the drive shaft 20 and passes through the end portion 24a of the large-diameter side of the tapered portion 24.

[0110] More preferably, as shown in Figure 3 , the center or a position near the center of the communication port 35a is located on the vertical line VL.

[0111] By being thus formed, the lubricating oil that accumulates between the step portion 23 and the end portion 24a of the large-diameter side of the tapered portion 24 and drips down when the screw compressor 1 is stopped can be smoothly introduced into the discharge flow passage 35.

[0112] Although the other end of the discharge flow path 35 can be configured to communicate with a recovery container (not shown) disposed outside the housing 30 to recover the lubricating oil recovered into the oil accumulation space 34 to the recovery container, in the case where the screw compressor 1 is an oil-cooled screw compressor that compresses the compressed gas and the lubricating oil together for lubrication, cooling, and sealing of the compression action space, the other end of the discharge flow path 35 can also be communicated with the suction side of the screw compressor 1 to introduce the lubricating oil recovered into the oil accumulation space 34 into the compression action space via the suction side, and by so configuring, it is possible to return the lubricating oil leaked from the shaft seal device 60 to the lubricating oil circulation system again, reduce the amount of lubricating oil lost from the lubricating oil circulation system, and extend the replenishment period of the lubricating oil to improve maintainability.

[0113] Further, it is preferable that, in the large-diameter portion Wd, the diameter of a portion adjacent to the position of the tapered portion 24 on the outside of the housing 30 is formed larger than the diameter of the end portion 24b of the small-diameter side of the tapered portion 24, and a second step portion 26 is provided near the end portion 24b of the small-diameter side of the tapered portion 24.

[0114] As described above, according to the screw compressor 1 provided with the leaked oil recovery structure of the present application at the shaft seal portion, if the rotational driving force from a driving source such as a motor, an engine, or the like, not shown, is input to the driving shaft 20, the male and female pair of screw rotors 10, 11 starts to mesh and rotate, and starts to compress the compressed fluid.

[0115] Although the gap between the outer periphery of the driving shaft 20 and the inner periphery of the shaft hole 32 is sealed by the shaft seal device 60 (the oil seal 61 in the illustrated embodiment) such as an oil seal 61, a mechanical seal, or the like, without leaking the lubricating oil or the like, according to such a shaft seal device 60, since lubrication of the sliding contact surface requires lubricating oil, a small amount of lubricating oil leaks from the shaft seal device 60 and attempts to move toward the outside of the machine along the surface of the driving shaft 20.

[0116] However, in the screw compressor 1 provided with the leaked oil recovery structure of the present application, even if the lubricating oil moves toward the outside of the machine along the surface of the small-diameter portion Nd of the driving shaft 20, during operation of the screw compressor 1, that is, when the driving shaft 20 rotates, as shown in FIG. 6, the movement of the lubricating oil along the surface of the small-diameter portion Nd is restricted by the step portion 23. Figure 5A

[0117] Further, the following aspects are the same as the leaked oil recovery structure of Patent Document 1 described with reference to Figure 6 and Figure 7 the leaked oil recovery structure of Patent Document 1 described with reference to​

[0118] According to the leaked oil recovery structure of the present application, a tapered portion 24 is further provided at a position on the outer side of the housing 30 with respect to the aforementioned step portion 23, so that even if a part of the lubricating oil further reaches the outer periphery of the large diameter portion Wd beyond the step portion 23, it is thrown out at the tapered portion 24 by centrifugal force as Figure 5A indicated by the arrow, is subjected to a force to push the lubricating oil from the small diameter side of the tapered portion 24 back to the large diameter side, so the lubricating oil cannot move further to the outer side of the machine beyond the tapered portion 24.

[0119] As a result, the lubricating oil on the end portion 24a side of the large diameter side of the tapered portion 24, which is pushed back, is scattered in the outer peripheral direction between the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24, and is thereby recovered into the oil accumulation space 34.

[0120] In particular, as Figure 3 indicated, according to the structure in which the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24 are provided at the same position, by making the outer peripheral edge portion of the step portion 23 an acute angle, the lubricating oil which is pushed back at the tapered portion 24 is also easily removed from the surface of the drive shaft, and the lubricating oil can be more effectively recovered.

[0121] On the other hand, if the screw compressor 1 is stopped and the drive shaft 20 is stopped from rotating, the lubricating oil which leaks from the shaft seal device 60 and adheres to the outer periphery of the small diameter portion Nd of the drive shaft 20 is, as Figure 5B indicated, caused to flow down along the surface of the small diameter portion Nd by the weight.

[0122] At this time, the portion of the drive shaft 20 between the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24 is disposed at the lowest position in the drive shaft 20, so the lubricating oil which flows down by the weight is accumulated in the portion between the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24.

[0123] However, the lubricating oil thus accumulated cannot move in the direction of upward inclination from the large diameter side to the small diameter side at the tapered portion 24, so even when the screw compressor 1 is stopped, the lubricating oil is prevented from moving beyond the tapered portion 24 to the outer side of the machine.

[0124] Thus, the lubricating oil which is accumulated between the step portion 23 and the end portion 24a of the large diameter side of the tapered portion 24 when the screw compressor 1 is stopped eventually becomes oil droplets and falls downward, and is recovered into the oil accumulation space 34.

[0125] A communication port 35a is formed in the bottom of the oil accumulation space 34 to communicate with the discharge flow passage 35, and is formed so as to open on a perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the large-diameter side end portion of the tapered portion, and preferably so that the center of the communication port 35a or the vicinity thereof is located on the perpendicular line VL, so that the lubricating oil that has fallen can be smoothly introduced into the discharge flow passage 35.

[0126] Further, according to the structure in which the diameter of the large-diameter portion Wd of the tapered portion 24 with respect to the outside of the housing is larger than the diameter of the small-diameter side end portion 24b of the tapered portion 24, the second step portion 26 is provided on the small-diameter side end portion 24b side of the tapered portion 24, so that even if lubricating oil reaches the tapered portion 24, the lubricating oil can be prevented from further moving to the outside of the machine beyond the second step portion 26, and the leakage of the lubricating oil to the outside of the machine can be more reliably prevented.

Claims

1. A leakage oil recovery structure of a screw compressor, characterized by comprising: in a shaft seal portion of a screw compressor in which a space between an inner periphery of a shaft hole provided in a housing and an outer periphery of a drive shaft inserted into the shaft hole is sealed by a shaft seal device, an oil accumulation space in which lubricating oil leaked from the shaft seal device is recovered is provided around the drive shaft at a position on the outside of the housing with respect to the shaft seal device, and an outer diameter of a large diameter portion as a portion provided on the outside of the housing is made larger than an outer diameter of a small diameter portion as a portion provided on the shaft seal device side in the drive shaft in a portion provided in the oil accumulation space, a step portion is provided at a boundary portion between the small diameter portion and the large diameter portion, a tapered portion is provided in the large diameter portion on the outside of the housing with respect to the step portion, the tapered portion gradually reduces in diameter toward the outside of the housing, and at least an end portion of a large diameter side of the tapered portion is provided in the oil accumulation space. The step portion and the end portion of the large diameter side of the tapered portion are provided at the same position.

3. The leakage oil recovery structure of a screw compressor according to claim 1 or 2, characterized by comprising: an exhaust flow passage whose upper end communicates with a bottom portion of the oil accumulation space is provided, a communication port that communicates the exhaust flow passage with the oil accumulation space is opened on a perpendicular line that is orthogonal to an axis of the drive shaft and passes through an end portion of the large diameter side of the tapered portion. A center of the communication port or a vicinity thereof is provided on the perpendicular line. An installation range of a cylindrical member is made the large diameter portion by fitting the cylindrical member to the drive shaft main body. A seal member is interposed between an outer periphery of the drive shaft main body and an inner periphery of the cylindrical member.

2. The oil leakage recovery structure of a screw compressor according to claim 1, characterized by A diameter of the large diameter portion on the outside of the housing with respect to the tapered portion is made larger than a diameter of an end portion of a small diameter side of the tapered portion, and a second step portion is provided in a vicinity of the end portion of the small diameter side of the tapered portion. ​ ​ ​ 4. The oil leakage recovery structure of a screw compressor according to claim 3, characterized by ​ 5. The leakage oil recovery structure of a screw compressor according to claim 1 or 2, characterized in that, ​ 6. The oil leakage recovery structure of a screw compressor according to claim 5, characterized by ​ 7. The leakage oil recovery structure of a screw compressor according to claim 1 or 2, characterized in that, ​

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