Oil Leakage Recovery Structure of Screw Compressor

Abstract

To provide a leaking oil recovery structure of a screw compressor which can efficiently recover a leaking oil from a shaft seal part.SOLUTION: In a leaking oil recovery structure of a screw compressor, an area between a shaft hole 32 provided at a casing and a drive shaft 20 is sealed with a shaft seal device 60 and an oil recovery space 34 which recovers a lubrication oil leaking from the shaft seal device 60 is provided at a position located close to the outer side of the casing relative to the shaft seal device 60 and around the drive shaft 20. The drive shaft 20 includes: a small diameter part Nd provided at the shaft seal device 60 side; and a large diameter part Wd provided close to the outer side of the casing. A border 23 between the small diameter part Nd and the large diameter part Wd is disposed within the oil recovery space 34 and a cylindrical reversing part 24 protruding from an end surface 23a of the large diameter part Wd in the border 23 is provided. The reversing part 24 encloses an outer periphery of an end of the small diameter part ND to form an oil sump 26. A tip 24a side of the reversing part 24 is provided with an inclination part 25 having a shape in which an inner diameter gradually spreads toward the tip 24a side.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an oil leakage recovery structure for a screw compressor. More specifically, the present invention relates to an oil leakage recovery structure for recovering oil leaked from a shaft seal portion having a shaft hole penetrating a casing of a compressor 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 in a screw compressor.

Background Art

[0002] A configuration example of a screw compressor 100 will be described with reference to FIG. 6. The screw compressor 100 includes a shaft hole 132 penetrating a casing 130 and a drive shaft 120 communicating inside and outside the casing 130 through the shaft hole 132 in order to rotate screw rotors 110 and 111 accommodated in a rotor chamber 131 formed in the casing 130 by a rotational driving force generated by a drive source such as a motor or an engine (not shown).

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

[0004] As described above, since the shaft hole 132 into which the drive shaft 120 is inserted is formed as a through hole penetrating inside and outside the casing 130, the gap between the inner circumference of the shaft hole 132 and the outer circumference of the drive shaft 120 is sealed by a shaft seal device 160 so that the gas, lubricating oil, etc. compressed in the screw compressor 100 do not leak outside the machine through the shaft hole 132.

[0005] As such a shaft sealing device 160, since contact-type shaft sealing devices such as oil seals and mechanical seals (in the illustrated example, an oil seal 161) are widely used, when the shaft sealing device 160 is an oil seal 161, in order to lubricate the seal lip portion that slidably contacts the outer periphery of the drive shaft 120, and when it is a mechanical seal, in order to lubricate the sliding contact surface between the stationary ring and the rotating ring, in either case, it is necessary to supply and lubricate a small amount of lubricating oil.

[0006] Therefore, when the shaft sealing device 160 described above is a mechanical seal, a small amount of lubricating oil used for lubricating the sliding contact portion of the mechanical seal will continuously leak outside the machine. In particular, over time, due to wear and scratches on the sliding contact surface of the shaft sealing device 160, the amount of lubricating oil leaking will also increase.

[0007] Also, when the shaft sealing device 160 described above is an oil seal 161, although the oil seal 161 usually prevents the leakage of lubricating oil, leakage of lubricating oil may occur due to wear and scratches on the sliding surface over time.

[0008] Thus, since a small amount of lubricating oil may leak even by providing the shaft sealing device 160, inconveniences such as the power transmission means 122 at the lubricating oil leakage position and the equipment around it being contaminated by the lubricating oil may occur.

[0009] Also, since the lubricating oil is lost from the lubricating oil circulation system due to leakage outside the machine, if the amount of lubricating oil leakage increases, it is necessary to frequently replenish the lost lubricating oil to the circulation system, which is also troublesome in terms of maintenance. Therefore, a screw compressor 100 having a recovery structure for recovering the lubricating oil leaked from the shaft sealing device 160 before it further leaks outside the machine has also been proposed.

[0010] As an example of the screw compressor 100 equipped with such a lubricating oil recovery structure, Patent Document 1 cited below adopts a configuration in which, as shown in FIGS. 6 and 7, an oil recovery space 134 for recovering the lubricating oil leaked from the shaft seal device 160 is provided around the drive shaft 120 at a position closer to the outside of the casing 130 with respect to the shaft seal device 160.

[0011] Then, as shown in FIG. 7, among the portions of the drive shaft 120 disposed in the oil recovery space 134, the portion disposed on the shaft seal device 160 side is formed as a small-diameter portion Nd having a relatively small outer diameter, and the portion disposed closer to the outside of the casing 130 is formed as a large-diameter portion Wd having a relatively large outer diameter. A configuration is adopted in which a stepped portion 123 generated at the boundary between the small-diameter portion Nd and the large-diameter portion Wd is disposed in the oil recovery space 134. In the illustrated example, the attachment portion of the collar 121a provided at the position where the lip of the shaft seal device 160 (oil seal 161) slidably contacts the drive shaft body 121 is formed as the above-described small-diameter portion Nd, and the attachment portion of the boss portion of the power transmission means 122 (pulley) is formed as the above-described large-diameter portion Wd. Thus, the above-described stepped portion 123 can be provided without adding new parts or performing new machining on the drive shaft body 121.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0013] In the screw compressor 100 equipped with the conventional leaked oil recovery structure described above, in the configuration in which the above-described stepped portion 123 is provided in the portion of the drive shaft 120 disposed in the oil recovery space 134, even if the lubricating oil leaked from the shaft seal device 160 moves outside the machine along the outer periphery of the drive shaft 120 (the outer periphery of the small-diameter portion Nd), this lubricating oil collides with the stepped portion 123, thereby restricting the movement of the drive shaft 120 in the axial direction.

[0014] Then, the lubricating oil that has reached the stepped portion 123 is subjected to centrifugal force accompanying the rotation of the drive shaft 120, and changes its moving direction to a direction orthogonal to the axial direction of the drive shaft 120 along the end face 123a of the large-diameter portion Wd that forms the boundary with the small-diameter portion Nd. When it reaches the outer peripheral edge of the end face 123a, it becomes an oil droplet and scatters in the outer peripheral direction of the drive shaft, so that oil drainage of the drive shaft 120 is performed at the stepped portion 123.

[0015] As a result, most of the lubricating oil that leaks from the shaft seal device 160 and moves outside the machine along the surface of the drive shaft 120 is recovered into the oil recovery space 134 at the stepped portion 123, thereby preventing the leakage of the lubricating oil to the outside of the machine.

[0016] Also, by returning the lubricating oil recovered in the oil recovery space 134 to the lubricating oil circulation system through the discharge passage 135 communicating with the oil recovery space 134, the amount of lubricating oil lost from the circulation system can be reduced, and the maintenance aspect can be made excellent, such as reducing the replenishment frequency of the lubricating oil.

[0017] Thus, in the leaked oil recovery structure described in the above-mentioned Patent Document 1, the lubricating oil leaked from the shaft seal device 160 can be efficiently recovered.

[0018] However, even in the screw compressor 100 provided with such a leaked oil recovery structure, the leakage of the lubricating oil transmitted through the drive shaft 120 cannot be completely prevented, and there are still confirmed cases where a small amount of lubricating oil leaks to the outside of the machine and contaminates the power transmission means 122 such as a pulley and peripheral equipment. Therefore, the problem of preventing the leakage of the lubricating oil to the outside of the machine cannot be completely solved.

[0019] Therefore, even in the configuration in which the stepped portion 123 is provided on the drive shaft 120 in the oil recovery space 134 as described above, when considering the cause of the leakage of the lubricating oil to the outside of the machine, it is considered that the lubricating oil that has reached the surface of the large-diameter portion Wd beyond the stepped portion 123 leaks to the outside of the machine as follows.

[0020] That is, although most of the lubricating oil that has passed through the shaft seal device 160 and reached the stepped portion 123 of the drive shaft 120 is removed from the surface of the drive shaft 120 by being scattered in the outer circumferential direction along the end face 123a of the large-diameter portion Wd due to the action of centrifugal force, the lubricating oil, which is a viscous fluid, cannot be completely removed from the surface of the drive shaft 120 even by the action of this centrifugal force, and it is considered that the lubricating oil remaining slightly on the surface of the drive shaft 120 still reaches the surface of the large-diameter portion Wd beyond the stepped portion 123.

[0021] Further, when the screw compressor 100 stops, the lubricating oil adhering to the outer circumference of the small-diameter portion Nd of the drive shaft 120 flows downward due to its own weight. At this time, since the lower end corner portion of the stepped portion 123 is the lowest position in the drive shaft 120, the lubricating oil flowing down the surface of the drive shaft 120 accumulates at the lower end corner portion of the stepped portion 123.

[0022] Most of the lubricating oil accumulated at the lower end corner portion of the stepped portion 123 in this way falls downward as oil droplets, but it is considered that there is still a small amount of lubricating oil that 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, in the screw compressor 100 provided with the leaked oil recovery structure described with reference to FIGS. 6 and 7, leakage of lubricating oil to the outside of the machine cannot be completely prevented, and there is a demand for the development of a leaked oil recovery structure that can more reliably recover the lubricating oil leaked from the shaft seal device 160 in the oil recovery space 134 and prevent leakage to the outside of the machine.

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

[0025] However, for example, when the screw compressor 100 is provided with a speed increasing device composed of a driving gear and a driven gear, in a configuration where the rotor shaft is not directly projected outside the casing, but a driving shaft connected to the rotor shaft via the speed increasing device is projected outside the casing, it is necessary to similarly provide a shaft sealing device for sealing also at the portion where the driving shaft provided in such a 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 this shaft sealing device. The problems of the above-described conventional technology are not limited to the illustrated example, and can occur in general shaft sealing portions in the shaft holes provided through the casing of the screw compressor.

[0026] Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and in a shaft sealing portion provided in a shaft hole of a screw compressor provided through a casing, it is possible to more surely prevent leakage to the outside of the machine by efficiently recovering the lubricating oil that has passed through the shaft sealing device. An object of the present invention is to provide a leaked oil recovery structure in a shaft sealing portion of a screw compressor.

Means for Solving the Problem

[0027] Hereinafter, the means for solving the problem will be described together with the reference numerals used in the mode for carrying out the invention. This reference numeral is described for clarifying the correspondence between the description of the claims and the description of the mode for carrying out the invention, and needless to say, it is not used restrictively for interpreting the technical scope of the present invention.

[0028] In order to achieve the above object, the leaked oil recovery structure of the present invention is In a leaked oil recovery structure of a screw compressor 1 having a shaft sealing portion in which the interval between the inner periphery of a shaft hole 32 provided in a casing 30 and the outer periphery of a driving shaft 20 inserted into the shaft hole 32 is sealed by a shaft sealing device 60, An oil recovery space 34 for recovering the lubricating oil leaked from the shaft sealing device 60 is provided around the driving shaft 20 at a position closer to the outside of the casing 30 with respect to the shaft sealing device 60. On the drive shaft 20, a small-diameter portion Nd disposed on the shaft seal device 60 side and a large-diameter portion Wd having a diameter larger than the outer diameter of the small-diameter portion Nd and disposed closer to the outside of the casing 30 are continuously provided. The boundary 23 between the small-diameter portion Nd and the large-diameter portion Wd is disposed within the oil recovery space 34. On the end face 23a of the large-diameter portion Wd at the boundary 23, a cylindrical counter portion 24 with a tip 24a protruding toward the shaft seal device 60 side is provided. By surrounding the outer periphery of the end of the small-diameter portion Nd on the large-diameter portion Wd side with the counter portion 24 at a predetermined interval, an oil reservoir 26 is formed between the inner peripheral surface of the counter portion 24 and the outer peripheral surface of the small-diameter portion Nd of the portion surrounded by the counter portion 24. In a range from the tip 24a of the counter portion 24, an inclined portion 25 having a shape in which the inner diameter gradually widens as it approaches the tip 24a side from the end face 23a side is provided (Claim 1).

[0029] The inclined portion 25 provided on the counter portion 24 can be formed in a tapered shape in which the wall thickness gradually decreases toward the tip 24a (Claim 2).

[0030] A discharge flow path 35 having an upper end communicating with the bottom of the oil recovery space 34 is provided. The communication port 35a of the discharge flow path 35 with respect to the oil recovery space 34 may be opened on a perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the tip 24a of the counter portion 24 (Claim 3).

[0031] The large-diameter portion Wd is formed by externally fitting a cylindrical member 22 (see FIGS. 1 to 4), which is a boss of a power transmission means such as a pulley, sprocket, gear, coupling, etc., or a cylindrical member 22' (see FIG. 5) such as a spacer, to the drive shaft body 21. The counter portion 24 may be provided on the cylindrical members 22, 22' (Claim 4).

[0032] When forming the large-diameter portion Wd by attaching the cylindrical members 22, 22', it is preferable to sandwich a sealing material 28 such as an O-ring between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the opposing portion 24 on the end face 23a side of the large-diameter portion Wd, preferably in a state of being in contact with the end face 23a (see Claim 5: FIG. 4).

Effect of the Invention

[0033] In the screw compressor 1 having the oil leakage recovery structure of the present invention described above, the following effects could be obtained.

[0034] In the conventional oil leakage recovery structure described with reference to FIGS. 6 and 7, the lubricating oil that passed through the shaft seal device 160 leaked outside the machine by moving from the outer peripheral surface of the small-diameter portion Nd of the drive shaft 120 to the outer peripheral surface of the large-diameter portion Wd.

[0035] However, in the configuration of the present invention, a cylindrical opposing portion 24 is provided that protrudes the tip 24a toward the shaft seal device 60 from the end face 23a of the large-diameter portion Wd at the boundary 23 between the small-diameter portion Nd and the large-diameter portion Wd of the drive shaft 20, and the end portion of the small-diameter portion Nd on the large-diameter portion Wd side is surrounded with a predetermined interval. By forming an oil reservoir 26 between the inner peripheral surface of the opposing portion 24 and the outer peripheral surface of the small-diameter portion Nd of the portion surrounded by the opposing portion 24, even if there is lubricating oil that moves outside the machine along the surface of the small-diameter portion Nd of the drive shaft 20, this lubricating oil is surely collected in the oil reservoir 26, and thus cannot reach the outer periphery of the large-diameter portion Wd beyond this oil reservoir 26. As a result, it was possible to prevent the lubricating oil that passed through the shaft seal device 60 from moving outside the machine along the surface of the drive shaft 20 and leaking.

[0036] In this way, the movement to the outside of the machine is restricted, and the lubricating oil collected in the oil reservoir 26 is removed from the surface of the drive shaft 20 by being scattered in the outer peripheral direction as oil droplets from the tip 24a of the opposing portion 24 by the centrifugal force accompanying the rotation of the drive shaft 20. At the same time, the lubricating oil removed from the surface of the drive shaft 20 is recovered into the oil recovery space 34, and the lubricating oil recovered in the oil recovery space 34 can be recovered via the discharge flow path 35, for example, into a lubricating oil circulation system (not shown).

[0037] Moreover, since the oil reservoir 26 opens toward the shaft seal device 60 side (inside the casing), the oil droplets discharged and scattered from the oil reservoir 26 scatter to the side opposite to the gap Δ communicating with the space outside the casing, so that the scattered oil droplets do not leak through the gap Δ.

[0038] Since the inner peripheral surface of a predetermined range on the tip 24a side of the opposing portion 24 has an inclined portion 25 having an inclined shape in which the inner diameter gradually widens toward the tip 24a side, the lubricating oil collected in the oil reservoir 26 is guided by the inclination of this inclined portion 25 when receiving centrifugal force and smoothly moves to the tip 24a side of the opposing portion 24, so that the discharge of the lubricating oil from the oil reservoir 26 can also be easily performed.

[0039] In particular, in the configuration in which the inclined portion 25 is tapered so that the wall thickness decreases toward the tip 24a, the opposing portion 24 becomes thinnest at its tip 24a, so that the lubricating oil reaching the tip 24a of the opposing portion 24 cannot exert tension at this portion and scatters as oil droplets, thereby improving the oil drainage property. As a result, the leaked lubricating oil can be recovered more smoothly.

[0040] Further, the lubricating oil collected in the oil reservoir 26 formed between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the opposing portion 24 after passing through the shaft seal device 60 flows downward by its own weight when the screw compressor 1 stops and the drive shaft 20 stops rotating. Also during such movement of the lubricating oil, the lubricating oil cannot reach the large-diameter portion Wd beyond the oil reservoir 26 and falls as oil droplets from the tip portion of the opposing portion 24 disposed at the lowermost part when the drive shaft 20 stops rotating.

[0041] Since the inclined portion 25 of the opposing portion 24 disposed at the lowermost part has a shape inclined downward toward the tip 24a side, even when flowing down by its own weight in this way, the lubricating oil can be smoothly discharged from the tip 24a side of the opposing portion 24 and recovered into the oil recovery space 34.

[0042] In addition, in the configuration in which the inclined portion 25 is formed in a tapered shape that becomes thinner as it goes toward the tip 24a, it is possible to improve the oil drainage property of such lubricating oil that falls due to its own weight.

[0043] In the configuration in which the discharge passage 35 communicating with the bottom of the oil recovery space 34 is opened on the perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the tip 24a of the reversing portion 24, the lubricating oil dripping from the tip 24a of the reversing portion 24 can be directly dropped into the discharge passage 35, and the discharge of the lubricating oil from the oil recovery space 34 can be performed extremely smoothly.

[0044] In addition, in the configuration in which the large-diameter portion Wd described above is formed by the cylindrical members 22, 22' externally fitted to the drive shaft main body 21, it is not necessary to directly machine the drive shaft main body 21, and the reversing portion 24 can be easily provided on the drive shaft 20 simply by attaching the cylindrical members 22, 22' in which the reversing portion 24 has been formed in advance.

[0045] Also, in the configuration in which the sealing material 28 such as an O-ring is sandwiched between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the reversing portion 24 on the end face 23a side of the large-diameter portion Wd, even when the large-diameter portion Wd is formed by attaching the cylindrical members 22, 22' described above, it is possible to prevent the lubricating oil that has passed through the shaft seal device 60 from leaking to the outside of the machine through the gap between the drive shaft main body 21 and the cylindrical members 22, 22'.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0047] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0048] In FIG. 1, reference numeral 1 denotes a screw compressor having the oil leakage recovery structure of the present invention in the shaft seal portion. This screw compressor 1 includes a pair of screw rotors composed of a male rotor 10 and a female rotor 11 (the female rotor 11 is hidden on the back side of the paper surface of the male rotor 10), and a casing 30 having a rotor chamber 31 for accommodating the screw rotors 10 and 11 in a meshed state.

[0049] At the suction-side end of the casing 30, a shaft hole 32, which is a through hole for receiving the rotor shaft 21 of the male rotor 10 and projecting it outside the casing 30, is formed. In this shaft hole 32, the rotor shaft 21 of the male rotor is inserted as a drive shaft main body 21 for inputting a rotational driving force from a drive source (not shown).

[0050] The drive shaft main body 21 inserted into the shaft hole 32 provided in the casing 30 is rotatably supported by a bearing 33 provided in the shaft hole 32. Between the outer periphery of the drive shaft 20 and the inner periphery of the shaft hole 32 at a position outside the bearing 33, it is sealed by a known shaft seal device 60 such as an oil seal or a mechanical seal.

[0051] At a position closer to the outside of the casing 30 with respect to this shaft seal device 60, an oil recovery space 34 for recovering the lubricating oil leaked through the shaft seal device 60 is continuously formed in the circumferential direction in the shaft hole 32.

[0052] As shown in FIGS. 2 and 3, a discharge passage 35 communicates with the bottom of this oil recovery space 34, and is configured to be able to discharge the lubricating oil recovered in the oil recovery space 34 through this discharge passage 35.

[0053] The above-described drive shaft 20 is provided with a small-diameter portion Nd having a relatively small outer diameter on the side of the shaft seal device 60, and a large-diameter portion Wd having a relatively large outer diameter with respect to the small-diameter portion Nd is provided near the outside of the casing 30. The boundary 23 between this small-diameter portion Nd and the large-diameter portion Wd is accommodated in the above-described oil recovery space 34.

[0054] Either one or both of this small-diameter portion Nd and the large-diameter portion Wd may be directly formed on the outer periphery of the drive shaft main body 21 by cutting or the like. In this embodiment, a collar 21a is attached to the contact portion with the lip of the oil seal 61 which is the shaft seal device 60, and the attachment portion of this collar 21a is taken as the small-diameter portion Nd.

[0055] Also, in this embodiment, by externally fitting cylindrical members 22, 22' to the drive shaft main body 21, the portions where these cylindrical members 22, 22' are attached are taken as the above-described large-diameter portion Wd.

[0056] As shown in FIGS. 1 to 4, this large-diameter portion Wd can be, for example, a pulley attached to the end of the drive shaft main body 21, or a boss portion of a power transmission means such as a sprocket, a gear, or a coupling (in the embodiment shown in FIG. 1, it is the boss portion of the pulley). Taking this portion as the above-described cylindrical member 22, it can be made into the large-diameter portion Wd. Or, as shown in FIG. 5, a cylindrical spacer can be attached to the drive shaft main body 21 between the small-diameter portion Nd and the boss portion of the power transmission means, and taking this spacer as the cylindrical member 22', this portion can also be made into the large-diameter portion Wd.

[0057] On the end face 23a of the large-diameter portion Wd, a cylindrical abutting portion 24 is provided with its tip 24a protruding toward the shaft seal device 60. By this abutting portion 24, the outer periphery of the end portion on the large-diameter portion Wd side of the small-diameter portion Nd is surrounded with a predetermined interval, so that an oil reservoir 26 is formed between the inner peripheral surface of the abutting portion 24 and the outer peripheral surface of the small-diameter portion Nd of the portion surrounded by the abutting portion 24.

[0058] A predetermined range from the tip 24a of this abutting portion 24 is formed in a shape that gradually widens the inner diameter as it approaches the tip 24a side. As a result, an inclined portion 25 is provided in which the inner peripheral surface on the tip 24a side of the abutting portion 24 inclines in the axial direction of the drive shaft 20.

[0059] In the illustrated embodiment, this inclined portion 25 is provided in a range of about 1 / 2 of the total length of the abutting portion 24 from the tip 24a, but is not limited to this configuration. The inclined portion 25 may be formed in a wider or narrower range of the abutting portion 24, or may be formed over the entire length of the abutting portion 24.

[0060] By providing the inclined portion 25 in the abutting portion 24 in this way, the lubricating oil collected in the oil reservoir 26 formed between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the abutting portion 24 is guided to the inclined surface when receiving centrifugal force during the rotation of the drive shaft 20 and smoothly moves to the tip 24a side of the abutting portion 24.

[0061] In the illustrated embodiment, including the formation portion of the inclined portion 25 described above, the outer diameter of the abutting portion 24 is the same as the outer diameter of the large-diameter portion Wd over its entire length. As a result, in the formation portion of the inclined portion 25 described above, the abutting portion 24 has a tapered shape that gradually becomes thinner toward the tip 24a.

[0062] However, the shape of the abutting portion 24 is not limited to this, and the abutting portion 24 may be formed with an outer diameter smaller than the outer diameter of the large-diameter portion Wd. Also, the outer diameter of the abutting portion 24 does not necessarily have to be a constant diameter. For example, it may be formed in a shape that gradually expands the outer diameter toward the tip 24a side at the formation position of the inclined portion 25.

[0063] In addition, the adoption of a configuration in which the inclined portion 25 has the above-described tapered shape and the tip 24a of the counter portion 24 is made thin is preferable in that the lubricating oil reaching the tip 24a of the counter portion 24 is less likely to exert tension, thereby improving the oil drainage property at the tip 24a of the counter portion 24.

[0064] In the configuration provided with the discharge passage 35 that opens at the bottom of the oil recovery space 34 as described above, preferably, as shown in FIGS. 2 to 5, the communication port 35a of the discharge passage 35 opens in the oil recovery space 34 on the perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the tip 24a of the counter portion 24, and the position of the tip 24a of the counter portion 24 is designed.

[0065] By configuring in this way, the lubricating oil that has dripped downward from the tip 24a of the counter portion 24 when the screw compressor 1 stops can be directly introduced into the discharge passage 35, and the discharge of the lubricating oil from the oil recovery space 34 can be extremely smoothly performed.

[0066] The other end of the discharge passage 35 may be configured to communicate with a recovery container (not shown) disposed outside the casing 30 to recover the lubricating oil recovered in the oil recovery space 34 into this recovery container. However, when the screw compressor 1 is an oil-cooled screw compressor that compresses the gas to be compressed together with the lubricating oil for lubrication, cooling, and sealing of the compression working space, the other end of the discharge passage 35 may be communicated with the suction side of the screw compressor 1 so that the lubricating oil recovered in the oil recovery space 34 is introduced into the compression working space through the suction side. By configuring in this way, the lubricating oil leaked from the shaft seal device 60 can be returned to the lubricating oil circulation system again, the amount of lubricating oil lost from the lubricating oil circulation system can be reduced, the lubricating oil replenishment cycle can be lengthened, and the maintainability can be improved.

[0067] In the embodiment described with reference to FIGS. 1 to 4, an example is shown in which the cylindrical member 22 forming the large-diameter portion Wd is formed by the boss of the power transmission means (pulley) attached to the drive shaft main body 21. However, instead of this configuration, as shown in FIG. 5, a spacer provided with the above-described reaction portion 24 is separately attached between the boss of the power transmission means and the collar 21a forming the small-diameter portion Nd, and this spacer may be used as the cylindrical member 22' to form the large-diameter portion Wd.

[0068] By configuring in this way, in the screw compressor 1 in which a spacer is already attached between the collar 21a and the boss of the power transmission means, a screw compressor having the oil leakage recovery structure of the present invention can be obtained only by replacing the existing spacer with a spacer provided with the reaction portion 24.

[0069] As described above, in the configuration in which the cylindrical members 22 and 22' such as the boss of the power transmission member (see FIGS. 1 to 4) and the spacer (see FIG. 5) are externally fitted to the drive shaft main body 21 to form the large-diameter portion Wd, as shown in FIG. 4, at a position near the end face 23a of the large-diameter portion Wd, preferably in a state of being in contact with the end face 23a, the sealing material 28 such as an O-ring is preferably sandwiched between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the reaction portion 24. By configuring in this way, it is also possible to prevent the leakage of lubricating oil through the gap between the outer periphery of the drive shaft main body 21 and the inner periphery of the cylindrical members 22 and 22'.

[0070] As described above, in the screw compressor 1 having the oil leakage recovery structure of the present invention in the shaft seal portion, when a rotational driving force from a drive source such as a motor or an engine (not shown) is input to the drive shaft 20, the male and female screw rotors 10 and 11 start to mesh and rotate, and the compression of the fluid to be compressed is started.

[0071] The gap between the outer circumference of the drive shaft 20 and the inner circumference of the shaft hole 32 is sealed by a shaft seal device 60 such as an oil seal 61 or a mechanical seal (an oil seal 61 in the illustrated embodiment) so that lubricating oil or the like does not leak. However, in such a shaft seal device 60, since lubricating oil is required for lubricating the sliding contact surface, a small amount of lubricating oil leaks from the shaft seal device 60, travels along the surface of the drive shaft 20, and moves toward the outside of the machine.

[0072] However, in the screw compressor 1 provided with the leaked oil recovery structure of the present invention, since an oil reservoir 26 is formed between the outer peripheral surface of the small-diameter portion Nd and the inner peripheral surface of the opposing portion 24 at the boundary 23 between the small-diameter portion Nd and the large-diameter portion Wd, the lubricating oil that has passed through the shaft seal device 60 is collected in the oil reservoir 26 and cannot reach the outer peripheral surface of the large-diameter portion Wd beyond the oil reservoir 26, thereby preventing the leakage of lubricating oil to the outside of the machine.

[0073] Then, the lubricating oil collected in the oil reservoir 26 is guided by the inclination of the inner peripheral surface formed on the inclined portion 25 of the opposing portion 24 by the centrifugal force accompanying the rotation of the drive shaft 20 and moves toward the tip 24a side of the opposing portion 24. When it reaches the tip 24a, it becomes an oil droplet and scatters in the outer peripheral direction and is recovered into the oil recovery space 34.

[0074] In particular, in the configuration in which the inclined portion 25 described above has a tapered shape that gradually becomes thinner toward the tip, since the opposing portion 24 is thinnest at its tip 24a, the lubricating oil that has moved to the tip 24a is less likely to maintain tension and is likely to form an oil droplet.

[0075] As a result, the oil drainage property of the tip 24a of the opposing portion 24 is improved, and the recoverability of the lubricating oil can be further improved.

[0076] On the other hand, when the screw compressor stops, while the action of centrifugal force on the lubricating oil disappears, gravity acts and the lubricating oil collected in the oil reservoir 26 moves downward due to its own weight. However, even during such movement, the lubricating oil does not reach the outer peripheral surface of the large-diameter portion Wd beyond the oil reservoir 26.

[0077] Moreover, since the inclined portion 25 of the counter portion 24 is inclined downward toward the tip 24a at the lowermost position, the lubricating oil in the oil reservoir 26 is guided by this inclination and smoothly discharged from the tip 24a of the counter portion 24, falling downward as oil droplets and being collected in the oil recovery space 34.

[0078] In particular, in the configuration where the inclined portion 25 of the counter portion 24 is tapered, the oil drainage property during such falling due to its own weight can also be improved.

[0079] At the bottom of the oil recovery space 34, a communication port 35a with the discharge passage 35 is opened, and the lubricating oil collected in the oil recovery space 34 is discharged through this discharge passage 35.

[0080] In particular, in the configuration where the communication port 35a of the discharge passage 35 is opened on the perpendicular line VL that is orthogonal to the axis of the drive shaft 20 and passes through the tip 24a of the counter portion 24, when the drive shaft 20 stops rotating, the discharge passage 35 opens directly below the tip 24a of the counter portion 24 located at the lowermost part. Therefore, the lubricating oil that has fallen from the tip 24a of the counter portion 24 directly falls into the discharge passage 35, and the discharge of the lubricating oil from the oil recovery space 34 can be extremely smooth.

Explanation of Reference Numerals

[0081] 1 Screw Compressor 10 Male Rotor 11 Female Rotor 20 Drive Shaft 21 Drive Shaft Body (Rotor Shaft) 21a Curler 22 Cylindrical Member (Boss Portion of Pulley) 22’ Cylindrical Member (Spacer) 23 Boundary (Between Small-Diameter Portion and Large-Diameter Portion) 23a End Face (of Large-Diameter Portion) 24 Counter Portion 24a Tip (of Counter Portion) 25 Inclined Portion 26 Oil Reservoir 28 Sealing Material (O-Ring) 30 Casing 31 Rotor chamber 32 Shaft hole 33 Bearing 34 Oil recovery space 35 Discharge flow path 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 body (rotor shaft) 121a Curler 122 Power transmission means (pulley) 123 Step portion 123a End face (of large diameter portion) 130 Casing 131 Rotor chamber 132 Shaft hole 134 Oil recovery space 135 Discharge flow path 160 Shaft seal device 161 Oil seal Nd Small diameter portion Wd Large diameter portion VL Vertical line

Claims

1. In an oil leakage recovery structure of a screw compressor having a shaft seal portion in which 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 is sealed by a shaft seal device, an oil recovery space for recovering lubricating oil leaked from the shaft seal device is provided around the drive shaft at a position closer to the outside of the casing with respect to the shaft seal device, a small-diameter portion disposed on the shaft seal device side and a large-diameter portion having a diameter larger than the outer diameter of the small-diameter portion and disposed closer to the outside of the casing are continuously provided on the drive shaft, a boundary between the small-diameter portion and the large-diameter portion is disposed within the oil recovery space, and a cylindrical reverse portion protruding with its tip toward the shaft seal device side is provided on an end face of the large-diameter portion at the boundary. By surrounding an outer periphery of an end portion on the large-diameter portion side of the small-diameter portion with the reverse portion via a predetermined interval, an oil reservoir is formed between an inner peripheral surface of the reverse portion and an outer peripheral surface of the small-diameter portion of the portion surrounded by the reverse portion, An oil leakage recovery structure of a screw compressor, characterized in that an inclined portion having a shape in which an inner diameter gradually widens as approaching from the end face side to the tip side is provided in a predetermined range from the tip of the reverse portion.

2. The oil leakage recovery structure of the screw compressor according to claim 1, characterized in that the inclined portion provided on the reverse portion is formed in a tapered shape in which the wall thickness gradually decreases toward the tip.

3. A discharge flow path having an upper end communicating with a bottom portion of the oil recovery space is provided, The oil leakage recovery structure of the screw compressor according to claim 1 or 2, characterized in that a communication port of the discharge flow path with respect to the oil recovery space is opened on a perpendicular line that intersects an axis of the drive shaft and passes through the tip of the reverse portion.

4. The oil leakage recovery structure of the screw compressor according to any one of claims 1 to 3, characterized in that the large-diameter portion is formed by externally fitting a cylindrical member to a drive shaft body, and the reverse portion is provided on the cylindrical member.

5. The oil leakage recovery structure of the screw compressor according to claim 4, characterized in that a sealing material is sandwiched between an outer peripheral surface of the small-diameter portion and an inner peripheral surface of the reverse portion on the end face side of the large-diameter portion.

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