CN114542505A - Leaked oil recovery structure of shaft seal part of screw compressor - Google Patents

Abstract

Provided is a leaked oil recovery structure for a shaft seal part of a screw compressor, which can effectively recover leaked oil. A gap between the inner periphery of a shaft hole (32) provided in a housing (30) and the outer periphery of a drive shaft (20) is sealed by a shaft seal device (60), and an oil accumulation space (34) for recovering lubricating oil leaking from the shaft seal device is provided around the drive shaft at a position outside the housing with respect to the shaft seal device. The shaft seal device side of the drive shaft arranged in the oil accumulation space (34) is a small diameter part (Nd), the part near the outer side of the housing is a large diameter part (Wd), a step part (23) is arranged at the boundary part of the small diameter part (Nd) and the large diameter part (Wd), a taper part (24) with the diameter gradually reduced towards the outer side of the housing (30) is arranged relative to the large diameter part (Wd) near the outer side of the housing (30) of the step part, and the end part (24a) of the taper part (24) on the large diameter side is arranged in the oil accumulation space (34).

Description

Leaked oil recovery structure of shaft seal part of screw compressor

Technical Field

The present invention relates to a leaked oil recovery structure of a shaft seal portion of a screw compressor, and more particularly, to a leaked oil recovery structure for recovering lubricating oil leaked from a shaft seal device in a shaft seal portion of a screw compressor including a shaft hole penetrating a casing of a compressor main body, a drive shaft inserted into the shaft hole, and a shaft seal device for sealing a gap between the shaft hole and the drive shaft.

Background

As shown in fig. 6, the screw compressor 100 is provided with a shaft hole 132 penetrating the casing 130 and a drive shaft 120 communicating the inside and the outside of the casing 130 through the shaft hole 132 in order to rotate the screw rotors 110 and 111 accommodated in a rotor chamber 131 formed in the casing 130 by a rotational drive force generated by a drive source such as a motor or an engine, not shown.

In the illustrated example, a rotor shaft provided on the suction side of either the male rotor 110 or the female rotor 111 (in the illustrated example, the male rotor 110) is 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, or a coupling is attached to an end portion of the drive shaft main body 121 that protrudes outside the housing 130, and serves as a drive shaft 120 that transmits the rotational drive force of a drive source (not illustrated) such as an engine or a motor to the screw rotors 111 and 112.

Since the shaft hole 132 into which the drive shaft 120 is inserted is formed as a through hole that penetrates the inside and the outside of the casing 130, 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 so that gas, lubricating oil, and the like compressed in the screw compressor 100 does not leak to the outside of the machine through the shaft hole 132.

As such a shaft sealing device 160, a contact type shaft sealing device (in the illustrated example, an oil seal 161) such as an oil seal or a mechanical seal is widely used, and therefore, in both cases where the shaft sealing device 160 is the oil seal 161, a small amount of lubricating oil needs to be supplied for lubrication in order to lubricate a seal lip portion which is in sliding contact with the outer periphery of the drive shaft 120, and where the shaft sealing device 160 is the mechanical seal, in order to lubricate a sliding contact surface between the stationary ring and the rotating ring.

Therefore, even when the shaft sealing device 160 is provided as described above, a small amount of lubricating oil used for lubricating the sliding contact portion of the shaft sealing device 160 continuously leaks out of the machine, and particularly, if the sliding contact surface of the shaft sealing device 160 is worn with the lapse of time, the amount of the leaked lubricating oil increases.

In this way, a small amount of lubricant leaks out due to the shaft seal device 160, and therefore, there is a problem that the power transmission member 122 at the lubricant leakage position and the devices around the lubricant leakage position are contaminated with the lubricant.

Further, since the lubricant oil leaks out of the machine and the lubricant oil is lost in the circulation system, if the amount of the leaked lubricant oil increases, the maintenance becomes complicated, for example, by frequently replenishing the lost lubricant oil to the circulation system.

Therefore, there has been proposed a screw compressor 100 having a recovery structure for recovering the lubricating oil leaked from the shaft seal device 160 before the lubricating oil further leaks to the outside of the machine.

As an example of a screw compressor 100 having such a lubricating oil recovery structure, patent document 1 described below employs a structure in which: as shown in fig. 6 and 7, an oil accumulation space 134 for collecting the lubricating oil leaked from the shaft seal device 160 is provided around the drive shaft 120 at a position outside the housing 130 with respect to the shaft seal device 160.

As shown in fig. 7, the following structure is adopted: the portion of the drive shaft 120 disposed in the oil accumulation space 134 on the side of the shaft seal device 160 is a small diameter portion Nd having a relatively small outer diameter, the portion disposed outside the housing 130 is a large diameter portion Wd having a relatively large outer diameter, and a stepped portion 123 is provided at the boundary portion between the small diameter portion Nd and the large diameter portion Wd, and in the illustrated example, the portion of the collar 121a provided at the position of the drive shaft body 121 where the lip of the shaft seal device 160 (oil seal 161) is in sliding contact is the small diameter portion Nd, and the hub portion of the power transmission member 122 (pulley) is the large diameter portion Wd, so that the stepped portion 123 can be provided without adding new parts, performing new processing of the drive shaft body 121, and the like.

Patent document 1: japanese patent laid-open No. 2014-145315

As in the screw compressor 100 having the conventional leaked oil recovery structure described above, according to the structure in which the stepped portion 123 described above is provided in the portion of the drive shaft 120 disposed in the oil accumulation space, if the lubricating oil leaked from the shaft seal 160 moves to the outside of the machine along the outer periphery of the drive shaft 120, the lubricating oil collides with the stepped portion 123 and is restricted from moving in the axial direction of the drive shaft 120.

The lubricating oil that has reached the stepped portion 123 receives centrifugal force accompanying rotation of the drive shaft 120, changes its moving direction along the side surface 123a of the stepped portion 123 to a direction orthogonal to the axial direction of the drive shaft 120, and if it reaches the outer peripheral edge of the stepped portion 123, it scatters in the outer peripheral direction of the drive shaft, and oil is drained from the drive shaft 120 at the stepped portion 123.

As a result, most of the lubricant that leaks from the shaft seal device 160 and moves to the outside of the machine along the surface of the drive shaft 120 is collected into the oil accumulation space 134 at the step portion 123, and the lubricant is prevented from leaking to the outside of the machine.

Further, the lubricating oil recovered to the oil accumulation space 134 is returned to the circulation system of the lubricating oil through the discharge flow passage 135 communicating with the oil accumulation space 134, and the amount of the lubricating oil lost in the circulation system is reduced, whereby the frequency of replenishing the lubricating oil can be reduced, and the performance in terms of maintenance is excellent.

Thus, according to the leaked oil recovery structure described in patent document 1, the lubricating oil leaked from the shaft seal device 160 can be effectively recovered.

However, the following cases were confirmed: even in the screw compressor 100 having such a leaked oil recovery structure, leakage of the lubricating oil along the drive shaft 120 cannot be completely prevented, and the lubricating oil leaks out of the machine even if it is in a small amount, and the power transmission member 122 such as a pulley and peripheral devices are contaminated, and the problem of preventing leakage of the lubricating oil out of the machine cannot be completely overcome.

Therefore, when the reason why the lubricating oil leaks out of the machine even in the configuration in which the stepped portion 123 is provided in the drive shaft 120 in the oil accumulation space 134 as described above is examined, it is considered that the lubricating oil that has reached the surface of the large diameter portion Wd over the stepped portion 123 leaks out of the machine as described below.

Namely, it is considered that the reason is: the lubricating oil that has passed through the shaft seal device 160 and reached the stepped portion 123 of the drive shaft 120 is scattered in the outer circumferential direction along the side surface 123a of the stepped portion 123 by the centrifugal force and removed from the surface of the drive shaft 120, but the lubricating oil that is a viscous fluid cannot be completely removed from the surface of the drive shaft 120 by the centrifugal force, and a small amount of lubricating oil remaining on the surface of the drive shaft 120 still reaches the surface of the large diameter portion Wd over the stepped portion 123.

Further, when the screw compressor 100 is stopped, the lubricating oil adhered to the outer periphery of the small diameter portion Nd of the drive shaft 120 flows downward due to its own weight, but at this time, the lower end corner portion of the stepped portion 123 becomes the lowest position in the drive shaft 120, and therefore 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.

In this way, although a part of the lubricating oil accumulated in the lower end corner portion of the stepped portion 123 drops downward as oil droplets, the remaining lubricating oil reaches the surface of the large-diameter portion Wd while bypassing the lower side of the lower end corner portion of the stepped portion 123.

As described above, according to the screw compressor 100 having the leaked oil recovery structure described with reference to fig. 6 and 7, the leakage of the lubricating oil to the outside of the machine cannot be completely prevented, and it is desired to develop a leaked oil recovery structure capable of recovering the lubricating oil leaked from the shaft seal device 160 more reliably in the oil accumulation space 134 and preventing the lubricating oil from leaking to the outside of the machine.

In the description with reference to fig. 6 and 7, the structure in which the leaked oil recovery structure is provided in the shaft hole 132 through which the rotor shaft of the male screw rotor 110 or 111 (in the illustrated example, the rotor shaft of the male rotor 110) of either the male or female screw rotor is inserted is described.

However, for example, in the case where the screw compressor 100 includes a speed increasing device including a drive gear and a driven gear, if the drive shaft coupled to the rotor shaft via the speed increasing device is provided so as to protrude outside the casing without directly protruding the rotor shaft to the outside of the casing, it is also necessary to provide a shaft seal device for sealing a portion where the drive shaft provided in the speed increasing device penetrates the casing, and it is also necessary to provide a leaked oil recovery structure for recovering the lubricating oil leaked from the shaft seal device.

Disclosure of Invention

Accordingly, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a structure for recovering leaked oil from a shaft seal portion of a screw compressor, which is provided in a shaft hole of the screw compressor penetrating a casing, and which can more reliably prevent the leakage of lubricating oil to the outside of the machine by effectively recovering the lubricating oil passing through the shaft seal device.

Hereinafter, the means for solving the problem will be described together with the reference numerals used in the embodiments. The reference numerals are attached to clarify the correspondence between the description of the claims and the description of the embodiments, and are not to be construed as limiting the technical scope of the present invention.

In order to achieve the above object, a structure for recovering leaked oil from a shaft seal portion of a screw compressor 1 according to the present invention is characterized in that in the shaft seal portion of the screw compressor 1 in which a gap between an inner periphery of a shaft hole 32 provided in a casing 30 and an outer periphery of a drive shaft 20 inserted into the shaft hole 32 is sealed by a shaft seal device 60, an oil accumulation space 34 for recovering the lubricant leaked from the shaft seal device 60 is provided around the drive shaft 20 at a position outside the casing 30 with respect to the shaft seal device 60, and in the drive shaft 20 disposed in the oil accumulation space 34, an outer diameter of a large diameter portion Wd disposed outside the casing 30 is made larger than an outer diameter of a small diameter portion Nd disposed on a side of the shaft seal device 60, and a stepped portion 23 is provided at a boundary portion between the small diameter portion Nd and the large diameter portion Wd, a tapered portion 24 is provided in the large diameter portion Wd located outside the housing 30 with respect to the stepped portion 23, the tapered portion 24 gradually decreases in diameter toward the outside of the housing 30, and at least a large diameter side end portion 24a of the tapered portion 24 is disposed in the oil accumulation space 34 (see fig. 2 to 4).

Although the step portion 23 and the end portion 24a on the large diameter side of the tapered portion 24 may be provided at predetermined spaced positions (see fig. 2 and 4), it is preferable that the step portion 23 and the end portion 24a on the large diameter side of the tapered portion 24 are provided at the same position (see fig. 3).

More preferably, a discharge flow passage 35 having an upper end communicating with the bottom of the oil accumulation space 34 is provided, and a communication port 35a for communicating the discharge flow passage 35 with the oil accumulation space 34 is opened on a perpendicular line VL perpendicular to the axis of the drive shaft 20 and passing through the end 24a on the large diameter side of the tapered portion 24 (see fig. 2 to 4).

More preferably, the center or the vicinity of the center of the communication port 35a is disposed on the perpendicular line VL (see fig. 3).

The large-diameter portion Wd of the drive shaft 20 can be formed in a range where the cylindrical member 22 is attached by fitting the cylindrical member 22 to the drive shaft main body 21 (see fig. 2 to 4).

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 main body 21 and the inner periphery of the cylindrical member 22 (see fig. 4).

More preferably, the diameter of the large diameter portion Wd of the tapered portion 24 at a position outside the housing 30 is formed larger than the diameter of the end portion 24b on the small diameter side of the tapered portion 24, and a second stepped portion 26 is provided near the end portion 24b on the small diameter side of the tapered portion 24 (see fig. 2 to 4).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the screw compressor 1 having the leaked oil recovery structure of the present invention described above, the following effects can be obtained.

By providing the stepped portion 23 described above on the drive shaft 20 and providing the tapered portion 24 whose diameter gradually decreases toward the outside of the casing 30 on the large diameter portion Wd located outside the casing 30 with respect to the stepped portion 23, even if there is lubricating oil remaining on the surface of the drive shaft 20 without being removed at the stepped portion 23, the lubricating oil cannot move to the outside of the machine beyond the tapered portion 24 both during operation and during stoppage of the screw compressor 1, and can be collected in the oil accumulation space 34, and the lubricating oil having passed through the shaft sealing device 60 can be more effectively prevented from leaking to the outside of the machine.

That is, when the screw compressor 1 is operated, as shown in fig. 5A, the lubricating oil in the tapered portion 24 receives a force of being pushed back from the small diameter side to the large diameter side of the tapered portion 24 by a centrifugal force generated along with the rotation of the drive shaft 20.

Therefore, even if there is any lubricating oil that has passed over the stepped portion 23 and reached the large diameter portion Wd side, the lubricating oil does not move outside the machine beyond the tapered portion 24, and can be prevented from leaking outside the machine, and is scattered in the outer circumferential direction by the centrifugal force at the large diameter side end portion 24a of the tapered portion 24 and recovered in the oil accumulation space 34.

Further, if the screw compressor 1 stops and the rotation of the drive shaft 20 stops, the lubricating oil that has leaked from the shaft seal device 60 and adhered to the surface of the small diameter portion Nd of the drive shaft 20 flows down due to its own weight and accumulates at the lower end corner portion of the stepped portion 23 as shown in fig. 5B, and even if the lubricating oil runs over the stepped portion 23 and winds around to the large diameter portion Wd side, the lubricating oil cannot move in the direction of rising from the large diameter side to the small diameter side at the tapered portion 24, and therefore, in this respect, the lubricating oil can be prevented from leaking outside the machine over the tapered portion 24.

Although the stepped portion 23 and the end portion 24a on the large diameter side of the tapered portion 24 can be arranged at a predetermined interval as shown in fig. 2 and 4, according to the configuration in which the stepped portion 23 and the end portion 24a on the large diameter side of the tapered portion 24 are provided at the same position as shown in fig. 3, the outer peripheral edge of the stepped portion 23 is formed at an acute angle and the lubricating oil cannot exert tension, and when the drive shaft 20 rotates, the oil drainage performance with respect to the lubricating oil that moves to the outer peripheral edge of the stepped portion 23 by the centrifugal force is improved, and the lubricating oil can be more easily collected into the oil accumulation space 34.

Further, according to the structure in which the communication port 35a communicating with the oil accumulation space 34 in the discharge flow passage 35 is opened in the vertical line VL perpendicular to the axis of the drive shaft 20 and passing through the large diameter side end portion 24a of the tapered portion 24, and more preferably, the structure in which the center or the vicinity of the center of the communication port 35a is disposed on the vertical line VL, the lubricating oil accumulated between the stepped portion 23 and the large diameter side end portion 24a of the tapered portion 24 and dropped can be smoothly collected into the discharge flow passage 35 when the screw compressor 1 is stopped.

Further, according to the configuration in which the large diameter portion Wd is formed by the cylindrical member 22 externally fitted to the drive shaft main body 21, the stepped portion 23 and the tapered portion 24 can be easily formed in the drive shaft 20 only by attaching the cylindrical member 22 in which the tapered portion 24 is formed in advance, without directly processing the drive shaft main body 21.

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

Further, according to the configuration in which the diameter of the large diameter portion Wd of the tapered portion 24 at the position outside the housing 30 is formed larger than the diameter of the end portion 24b on the small diameter side of the tapered portion 24, and the second stepped portion 26 is provided in the vicinity of the end portion 24b on the small diameter side of the tapered portion 24, even if the lubricating oil reaching the tapered portion 24 is generated, the lubricating oil is prevented from further moving to the outside of the machine at the second stepped portion 26, and the lubricating oil can be more reliably prevented from leaking to the outside of the machine.

Drawings

Fig. 1 is a reduced-scale cross-sectional plan view of a screw compressor provided with a leaked oil recovery structure according to the present invention.

Fig. 2 is an enlarged view of an arrow II portion of fig. 1.

Fig. 3 is an enlarged view showing a modification example of the arrow II portion of fig. 1.

Fig. 4 is an enlarged view showing another modification example of the arrow II portion of fig. 1.

Fig. 5A and 5B are explanatory views of the moving direction of the lubricating oil on the drive shaft, and fig. 5A is when the screw compressor is operating and fig. 5B is when the screw compressor is stopped.

Fig. 6 is a reduced-scale cross-sectional plan view of a screw compressor having a conventional leaked oil recovery structure (corresponding to fig. 1 of patent document 1).

Fig. 7 is an enlarged view of the shaft seal portion of the screw compressor of fig. 6.

Description of the reference numerals

1 screw compressor

10 male rotor

11 female rotor

20 drive shaft

21 Main body of drive shaft (rotor shaft)

22 cylindrical member

23 step part

23a (of the step part) side surface

24 taper part

24a (of the tapered portion) of the end portion on the large diameter side

24b (of the tapered portion) on the small diameter side

25 annular groove

26 second step part

28 sealing component (O-shaped ring)

30 casing

31 rotor chamber

32 axle hole

33 bearing

34 oil accumulation space

35 discharge flow passage

35a communication port

60 shaft seal device

61 oil seal

100 screw compressor

110 male rotor

111 female rotor

120 drive shaft

121 drive shaft main body (rotor shaft)

121a collar

122 power transmission parts (Belt wheel)

123 step part

123a (of step part) side surface

130 casing

131 rotor chamber

132 axle hole

134 oil accumulation space

135 discharge flow passage

160 shaft seal device

161 oil seal

Nd small diameter part

Wd major diameter part

Perpendicular to VL.

Detailed Description

Next, embodiments of the present invention will be described with reference to the drawings.

In fig. 1, reference numeral 1 denotes a screw compressor provided with a leakage oil recovery structure of the present invention in a shaft seal portion, and the screw compressor 1 includes a casing 30 and a pair of screw rotors including a male rotor 10 and a female rotor 11, and the casing 30 includes a rotor chamber 31 accommodating the screw rotors 10 and 11 in a meshing state.

A shaft hole 32 is formed at an end portion on the suction side of the casing 30, the shaft hole 32 being a through hole for receiving the rotor shaft 21 of the male rotor 10 and allowing the rotor shaft 21 to protrude outward from the casing 30, and the rotor shaft 21 of the male rotor is inserted into the shaft hole 32 as a drive shaft main body 21, the drive shaft main body 21 being used for inputting a rotational drive force from a drive source not shown.

The drive shaft main body 21 inserted into the shaft hole 32 provided in the housing 30 is rotatably supported by a bearing 33 provided in the shaft hole 32, and at a position outside the machine with respect to the bearing 33, between the outer periphery of the drive shaft 20 and the inner periphery of the shaft hole 32 is sealed by a known shaft seal device 60 such as an oil seal, a mechanical seal, or the like.

An oil accumulation space 34 is formed continuously in the axial hole 32 along the circumferential direction at a position outside the housing 30 with respect to the shaft seal device 60, and the oil accumulation space 34 collects the lubricating oil leaking through the shaft seal device 60.

As shown in fig. 2, a discharge flow passage 35 is communicated with the bottom of the oil accumulation space 34, and the lubricating oil collected in the oil accumulation space 34 can be discharged through the discharge flow passage 35.

In the drive shaft 20, at least in the portion accommodated in the oil accumulation space, a small diameter portion Nd having a relatively small outer diameter is provided on the shaft seal device 60 side, a large diameter portion Wd having a relatively larger outer diameter than the small diameter portion Nd is provided on the outer side of the housing 30, and a stepped portion 23 is formed at a boundary portion between the small diameter portion Nd and the large diameter portion Wd.

Although the large diameter portion Wd may be formed directly on the outer periphery of the drive shaft main body 21 by cutting or the like, in the present embodiment, the cylindrical member 22 is externally fitted to the drive shaft main body 21, so that the portion to which the cylindrical member 22 is attached becomes the large diameter portion Wd described above.

The large diameter portion Wd may be formed by the cylindrical member 22 described above by a boss portion of a power transmission member, not shown, such as a pulley, a sprocket, a gear, and a coupling, which is attached to an end portion of the drive shaft body 21, or may be formed by attaching a cylindrical spacer which abuts an end surface of the boss portion of the power transmission member, and forming the spacer as the cylindrical member 22 described above.

In the case where the cylindrical member 22 is externally fitted to the drive shaft main body 21 to form the large diameter portion Wd, as shown in fig. 4, it is preferable that an O-ring 28 is interposed between the outer periphery of the drive shaft main body 21 and the inner periphery of the cylindrical member 22, and the O-ring 28 is fitted into an annular groove 25 provided on the outer periphery of the drive shaft main body 21 or the inner periphery of the cylindrical member 22 (in the illustrated example, the annular groove 25 provided on the inner periphery of the cylindrical member 22), thereby preventing the lubricant from leaking between the outer periphery of the drive shaft main body 21 and the inner periphery of the cylindrical member 22.

The large diameter portion Wd is further provided with a tapered portion 24 at a position outside the housing 30 with respect to the stepped portion 23, and the tapered portion 24 is formed in a shape in which the outer diameter gradually decreases toward the outside of the machine.

As shown in fig. 2 and 4, the end 24a on the large diameter side of the tapered portion 24 may be provided at a predetermined position apart from the stepped portion 23 on the outer side of the housing 30, but may be configured as shown in fig. 3: the formation position of the stepped portion 23 and the formation position of the end portion 24a on the large diameter side of the tapered portion 24 are provided at a common position, and an acute-angled corner portion is formed at the outer peripheral edge of the stepped portion 23.

With this configuration, when the drive shaft 20 rotates, the lubricating oil reaching the outer peripheral edge of the stepped portion 23 due to the centrifugal force does not exert a tensile force and easily scatters in the outer peripheral direction, and therefore the oil discharge performance of the drive shaft 20 can be further improved.

The tapered portion 24 is provided so that at least the large-diameter-side end portion 24a thereof is disposed in the oil accumulation space, and preferably, as shown in fig. 2 and 4, the tapered portion 24 is provided so that a communication port 35a between the oil accumulation space 34 and the discharge flow passage 35 is opened in a perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the large-diameter-side end portion 24a of the tapered portion 24.

More preferably, as shown in fig. 3, the center or the vicinity of the center of the communication port 35a is located on the perpendicular line VL.

By forming in this manner, the lubricating oil that accumulates and drips between the step portion 23 and the large-diameter-side end portion 24a of the tapered portion 24 when the screw compressor 1 is stopped can be smoothly introduced into the discharge flow passage 35.

Although the other end of the discharge flow path 35 may be configured to communicate with a recovery tank (not shown) disposed outside the casing 30 and recover the lubricating oil recovered in the oil accumulation space 34 to the recovery tank, in the case where the screw compressor 1 is an oil-cooled screw compressor in which the compressed gas and the lubricating oil are compressed together for lubrication, cooling, and sealing of the compression operation space, the other end of the discharge flow path 35 may be configured to communicate with the suction side of the screw compressor 1 and the lubricating oil recovered in the oil accumulation space 34 may be introduced into the compression operation space via the suction side, whereby the lubricating oil leaking from the shaft seal device 60 can be returned to the circulation system of the lubricating oil again, the amount of lubricating oil lost from the circulation system of the lubricating oil can be reduced, and the replenishment cycle of the lubricating oil can be extended to improve the maintenance performance.

In the large diameter portion Wd, it is preferable that a portion adjacent to the tapered portion 24 at a position outside the housing 30 has a diameter larger than a diameter of the end portion 24b on the small diameter side of the tapered portion 24, and that the second stepped portion 26 is provided near the end portion 24b on the small diameter side of the tapered portion 24.

As described above, according to the screw compressor 1 including the leaked oil recovery structure of the present invention in the shaft seal portion, if a rotational driving force is input to the drive shaft 20 from a driving source such as a motor or an engine, not shown, the pair of male and female screw rotors 10 and 11 start to rotate in mesh with each other, and compression of the fluid to be compressed is started.

Although the gap between the outer periphery of the drive shaft 20 and the inner periphery of the shaft hole 32 is sealed by a sealing device 60 (an oil seal 61 in the illustrated embodiment) such as an oil seal 61 or a mechanical seal, and the like, and no lubricating oil or the like leaks, according to such a shaft seal device 60, a small amount of lubricating oil leaks from the shaft seal device 60 and attempts to move to the outside of the machine along the surface of the drive shaft 20 because the lubricating oil is required for lubrication of the sliding contact surface.

However, in the screw compressor 1 having the leaked oil recovery structure according to the present invention, even if the lubricant oil moves to the outside of the machine along the surface of the small diameter portion Nd of the drive shaft 20, the movement of the lubricant oil along the surface of the small diameter portion Nd is restricted by the step portion 23 during the operation of the screw compressor 1, that is, when the drive shaft 20 rotates, as shown in fig. 5A.

The following points are the same as the leaked oil recovery structure of patent document 1 described with reference to fig. 6 and 7, that is: the lubricating oil restricted from moving by the stepped portion 23 changes its moving direction along the side surface 23a of the stepped portion 23 to a direction orthogonal to the axis of the drive shaft by a centrifugal force generated along the rotation of the drive shaft 20, and is scattered in the outer circumferential direction from the peripheral edge portion of the stepped portion 23, and is collected in the oil accumulation space.

According to the leakage oil recovery structure of the present invention, since the tapered portion 24 is provided on the outside of the housing 30 with respect to the stepped portion 23, even if part of the lubricating oil further reaches the outer periphery of the large diameter portion Wd beyond the stepped portion 23, the lubricating oil receives a force to push the lubricating oil from the small diameter side to the large diameter side of the tapered portion 24 by centrifugal force as shown by the arrow in fig. 5A, and therefore the lubricating oil cannot move further to the outside of the machine beyond the tapered portion 24.

As a result, the lubricating oil pushed back to the large diameter side end 24a of the tapered portion 24 is scattered in the outer circumferential direction between the stepped portion 23 and the large diameter side end 24a of the tapered portion 24, and is collected in the oil accumulation space 34.

In particular, as shown in fig. 3, according to the configuration in which the stepped portion 23 and the end portion 24a on the large diameter side of the tapered portion 24 are provided at the same position, the outer peripheral edge portion of the stepped portion 23 is set to an acute angle, so that the lubricating oil pushed back by the tapered portion 24 is easily removed from the surface of the drive shaft, and the lubricating oil can be recovered more efficiently.

On the other hand, if the screw compressor 1 stops and the drive shaft 20 stops rotating, the lubricating oil that leaks from the shaft seal device 60 and adheres to the outer periphery of the small diameter portion Nd of the drive shaft 20 flows down along the surface of the small diameter portion Nd by its own weight as shown in fig. 5B.

At this time, the portion of the drive shaft 20 between the stepped portion 23 and the large diameter side end portion 24a of the tapered portion 24 is disposed at the lowest position in the drive shaft 20, and therefore the lubricating oil that flows down by its own weight is accumulated in the portion between the stepped portion 23 and the large diameter side end portion 24a of the tapered portion 24.

However, the lubricant oil thus accumulated cannot move in the direction of rising from the large diameter side to the small diameter side at the tapered portion 24, and therefore, even when the screw compressor 1 is stopped, the lubricant oil is prevented from moving outside the machine beyond the tapered portion 24.

As described above, the lubricating oil accumulated between the step portion 23 and the large diameter side end portion 24a of the tapered portion 24 at the time of stopping the screw compressor 1 finally drops as oil droplets and falls downward, and is collected into the oil accumulation space 34.

A communication port 35a communicating with the discharge flow path 35 is opened at the bottom of the oil accumulation space 34, and the communication port 35a is opened at a perpendicular line VL perpendicular to the axis of the drive shaft 20 and passing through the large-diameter side end portion of the tapered portion, and preferably, the center or the vicinity of the center of the communication port 35a is positioned on the perpendicular line VL, so that the lubricating oil falling down can be smoothly introduced into the discharge flow path 35.

Further, according to the configuration in which the diameter of the large diameter portion Wd outside the housing with respect to the tapered portion 24 is larger than the diameter of the end portion 24b on the small diameter side of the tapered portion 24, and the second step portion 26 is provided on the end portion 24b side on the small diameter side of the tapered portion 24, even if there is lubricating oil reaching 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 lubricating oil can be more reliably prevented from leaking to the outside of the machine.

Claims (7)

1. A leaked oil recovery structure of a screw compressor is characterized in that,

in a shaft seal part of a screw compressor for sealing a gap between an inner periphery of a shaft hole provided in a casing and an outer periphery of a drive shaft inserted into the shaft hole by a shaft seal device,

an oil accumulation space for collecting the lubricating oil leaked from the shaft seal device is provided around the drive shaft at a position outside the housing with respect to the shaft seal device, and the oil accumulation space is provided

In the drive shaft disposed in the oil accumulation space, the outer diameter of a large diameter portion disposed outside the housing is made larger than the outer diameter of a small diameter portion disposed on the shaft seal device side, and a stepped portion is provided at a boundary portion between the small diameter portion and the large diameter portion,

a tapered portion is provided on the large diameter portion on the outer side of the housing with respect to the stepped portion, the tapered portion gradually decreasing in diameter toward the outer side of the housing,

at least the end portion on the large diameter side of the tapered portion is disposed in the oil accumulation space.

2. The leaked oil collecting structure of a screw compressor according to claim 1, wherein the step portion and an end portion on a large diameter side of the tapered portion are provided at the same position.

3. The leaked oil recovering structure of a screw compressor according to claim 1 or 2,

a discharge flow passage with the upper end communicated with the bottom of the oil accumulation space is arranged,

a communication port that communicates the discharge flow passage with the oil accumulation space is opened on a perpendicular line that is orthogonal to an axis of the drive shaft and that passes through an end portion on the large diameter side of the tapered portion.

4. The leaked oil collecting structure of a screw compressor according to claim 3, wherein a center or a vicinity of a center of the communication port is arranged on the vertical line.

5. The leaked oil recovery structure of a screw compressor according to claim 1 or 2, wherein a cylindrical member is externally fitted to the drive shaft main body so that an attachment range of the cylindrical member is the large diameter portion.

6. The leaked oil recovery structure of a screw compressor according to claim 5, wherein a seal member is interposed between an outer periphery of the drive shaft main body and an inner periphery of the cylindrical member.

7. The leaked oil recovery structure of a screw compressor according to claim 1 or 2, wherein a diameter of the large diameter portion at a position of the tapered portion on an outer side of the housing is formed larger than a diameter of a small diameter side end portion of the tapered portion, and a second stepped portion is provided in a vicinity of the small diameter side end portion of the tapered portion.

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