Oil-cooled screw compressor

Abstract

To provide an oil-cooled screw compressor capable of suppressing loss caused by stirring of lubricating oil by a bearing while avoiding unnecessary efficiency reduction of the compressor due to oil level control of the lubricating oil in a bearing chamber.SOLUTION: The oil-cooled screw compressor includes a screw rotor, a casing, a slide valve, and a slide valve guide. The casing includes a bearing chamber, a rotor chamber, a suction space, and a discharge space. When the slide valve moves toward the discharge space, the inlet of the bypass passage, which connects the rotor chamber and the suction space, opens in the inner wall surface of the rotor chamber. The slide valve guide has a guide surface and a first groove provided in the guide surface and communicating with the discharge space. The slide valve has a sliding surface facing the guide surface, and a second groove provided in the sliding surface. When the second groove faces the first groove and the through hole that opens in the inner surface of the casing while the inlet of the bypass passage is open, the communication passage including the first groove, the second groove, and the through hole allows the discharge space and the bearing chamber to communicate with each other.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present disclosure relates to an oil-flooded screw compressor. [Background technology]

[0002] In an oil-cooled screw compressor, lubricating oil is used to lubricate the screw rotor and the bearings that support the screw rotor. A portion of the lubricating oil is stored in the internal space of the casing, such as the bearing chamber that houses the bearing.

[0003] If the level of the lubricating oil in the bearing chamber becomes too high, part of the bearing will be submerged in the oil, and if the compressor is operated in this state, losses (churning losses) caused by the bearing stirring the lubricating oil will increase. Patent Document 1 describes a method for controlling the level of lubricating oil in a gear chamber, but not in a bearing chamber, by introducing a portion of the compressed high-pressure gas into the gear chamber and lowering the level of the lubricating oil in the gear chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 61-138891 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if the method of Patent Document 1 is used to control the oil level in the bearing chamber, high-pressure gas will continue to be introduced into the bearing chamber even after the oil level of the lubricating oil has been lowered, which will reduce the efficiency of the compressor.

[0006] In view of the above circumstances, at least some embodiments of the present invention aim to provide an oil-cooled screw compressor that can suppress losses (churning losses) caused by stirring of the lubricating oil by the bearings while avoiding unnecessary reduction in compressor efficiency due to oil level control of the lubricating oil in the bearing chamber. [Means for solving the problem]

[0007] An oil-flooded screw compressor according to at least some embodiments of the present invention comprises: a screw rotor; a casing including a bearing chamber that accommodates a bearing for rotatably supporting the screw rotor, a rotor chamber that accommodates the screw rotor, a suction space, and a discharge space; a slide valve that is movable in the axial direction of the screw rotor and that is provided so as to form a part of the inner wall surface of the rotor chamber; a slide valve guide provided in the discharge space to support an end of the slide valve protruding into the discharge space; Equipped with the slide valve is configured to open an inlet of a bypass passage communicating between the rotor chamber and the suction space to the inner wall surface of the rotor chamber when moving toward the discharge space, the slide valve guide has a guide surface that slidably guides the slide valve, and a first groove that is provided on the guide surface and communicates with the discharge space, The slide valve has a sliding surface that faces the guide surface of the slide valve guide on an outer surface of the slide valve, and a second groove that is provided on the sliding surface, When the inlet of the bypass passage is open and the second groove faces the first groove and a through hole that opens to the inner surface of the casing, a communication passage including the first groove, the second groove, and the through hole is configured to communicate the discharge space with the bearing chamber. [Effects of the Invention]

[0008] According to at least some embodiments of the present invention, when the inlet of the bypass passage is open, a portion of the compressed high-pressure gas in the discharge space is introduced into the bearing chamber via a communication passage including the first groove, the second groove, and the through-hole, thereby lowering the oil level of the lubricating oil in the bearing chamber. In contrast, when the inlet of the bypass passage is closed by the slide valve, the discharge space and the bearing chamber are not in communication, and the high-pressure gas in the discharge space is not introduced into the bearing chamber. Therefore, an oil-cooled screw compressor is provided that can suppress losses (churning losses) caused by the stirring of the lubricating oil by the bearings while avoiding unnecessary reduction in compressor efficiency due to oil level control of the lubricating oil in the bearing chamber. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a schematic cross-sectional view of a screw compressor according to an embodiment, showing a state in which a slide valve is completely accommodated in a slide valve accommodating chamber. [Figure 1B] 1 is a schematic cross-sectional view of a screw compressor according to an embodiment, showing a state in which a slide valve is maximally protruded into a discharge space. [Figure 2A] FIG. 1 is a partial cross-sectional view showing the internal structure of a screw compressor according to one embodiment. [Figure 2B] FIG. 4 is a partial cross-sectional view showing the internal structure of a screw compressor according to another embodiment. [Figure 3] FIG. 2 is a perspective view showing a portion of a sliding valve guide and a casing according to one embodiment. [Figure 4A] FIG. 2 is a plan view of a sliding valve guide according to one embodiment. [Figure 4B] FIG. 10 is a plan view of a slide valve guide according to another embodiment. [Figure 5] 1 is a view of a slide valve guide and a slide valve according to an embodiment, as viewed from a discharge space side. FIG. [Figure 6] FIG. 1 is a perspective view of a slide valve according to one embodiment. [Figure 7A] FIG. 2 is a perspective view showing a slide valve, a slide valve guide, and a portion of a casing according to an embodiment. [Figure 7B] FIG. 10 is a perspective view showing a slide valve, a slide valve guide, and a part of a casing according to another embodiment. [Figure 8A] 1 is a plan view of a slide valve, a slide valve chamber, and a slide valve guide according to an embodiment, showing the slide valve in a fully closed position. FIG. [Figure 8B] 10 is a plan view of a slide valve, a slide valve accommodating chamber, and a slide valve guide according to one embodiment, showing a state in which a second groove and a through hole face each other. FIG. [Figure 8C] 1 is a plan view of a slide valve, a slide valve accommodating chamber, and a slide valve guide according to one embodiment, showing a state immediately after the first groove and the second groove start to face each other. FIG. [Figure 8D] 1 is a plan view of a slide valve, a slide valve chamber, and a slide valve guide according to an embodiment, showing the slide valve in a fully open position. FIG. [Figure 9] FIG. 1 is a perspective view showing an internal structure of a screw compressor according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, etc. of components described as an embodiment or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention. In this specification, unless otherwise specified, the "axial direction" refers to the axial direction of the screw rotor, and the side in the axial direction where the suction space is located is called the suction side, and the side where the discharge space is located is called the discharge side.

[0011] Fig. 1A is a schematic cross-sectional view of a screw compressor according to one embodiment, showing a state in which a slide valve is completely accommodated in a slide valve accommodating chamber, and Fig. 1B is a schematic cross-sectional view of a screw compressor according to one embodiment, showing a state in which the slide valve is maximally protruded into a discharge space.

[0012] In some embodiments, the screw compressor 1 includes a screw rotor 10 and a casing 20 that covers at least the screw rotor 10, as shown in FIGS. 1A and 1B.

[0013] 1A and 1B, the screw rotor 10 is a pair of screw rotors consisting of a male rotor and a female rotor. The male rotor and the female rotor are arranged side by side in the depth direction of the paper on which FIGS. 1A and 1B are drawn. In this case, the male rotor and female rotor have helical teeth that mesh with each other. A plurality of tooth groove spaces are formed by the tooth grooves of the male rotor and female rotor and the inner wall surface of the casing 20 (the inner wall surface 21W of the rotor chamber 21, which will be described later). The rotating shaft 11 of the male rotor is connected to the output shaft of a drive source (not shown) and is driven to rotate by the drive source. The female rotor rotates following the rotation of the male rotor. The female rotor rotates in the opposite direction to the rotation of the male rotor. When the male rotor and female rotor rotate in a meshed state, the tooth groove spaces of the screw rotor 10 move axially from the suction side to the discharge side.

[0014] The casing 20 includes at least a bearing chamber 27, a rotor chamber 21 that accommodates the screw rotor 10, a suction space 22, and a discharge space 23. In the embodiment shown in FIGS. 1A and 1B, the casing 20 is made up of a plurality of casing parts 20A to 20D that form the bearing chamber 27, the discharge space 23, the rotor chamber 21, and the suction space 22, respectively. Specifically, the casing 20 is composed of a casing 20A that forms the bearing chamber 27, a casing 20B that forms the discharge space 23, a casing 20C that forms the rotor chamber 21, and a casing 20D that forms the suction space 22. The casings 20A to 20D are connected in series so as to be separable from one another by fastening members such as bolts. A portion of the inner wall surface of the casing 20C forms the inner wall surface 21W of the rotor chamber 21. As described above, the inner wall surface 21W of the rotor chamber 21, together with the tooth grooves of the screw rotor 10 (male rotor and female rotor), form a plurality of tooth groove spaces. In addition to the rotor chamber 21, the casing 20C also includes a slide valve accommodating chamber 24 for accommodating a slide valve 40 (described below). The slide valve accommodating chamber 24 is a portion of the internal space of the casing 20C that communicates with the rotor chamber 21 and the discharge space 23, respectively.

[0015] The bearing chamber 27 accommodates bearings 14 for rotatably supporting the screw rotor 10. In the embodiment shown in Figures 1A and 1B, the rotation shafts of the male rotor and the female rotor are rotatably supported by different bearings 14, respectively. In addition, lubricating oil is supplied into the bearing chamber 27 from a supply hole (not shown) provided in the casing 20A to lubricate the bearing 14. A part of the supplied lubricating oil is stored in the bearing chamber 27. The oil level in the bearing chamber 27 may vary depending on the operating state of the screw compressor 1.

[0016] Uncompressed low-pressure gas G0 flows into the suction space 22 from outside the screw compressor 1. The low-pressure gas G0 is sucked from the suction space 22 into the tooth groove space via the suction port 12. When the suction port 12 is closed during the process of movement of the tooth groove space accompanying the rotation of the screw rotor 10 (male rotor and female rotor), the volume of the sealed tooth groove space decreases and the gas G1 in the tooth groove space is compressed. When the tooth groove space reaches the discharge port 13 and the tooth groove space and the discharge space 23 communicate with each other, compressed high-pressure gas G2 is discharged into the discharge space 23 via the discharge port 13.

[0017] Lubricating oil flows into the discharge space 23. The lubricating oil that has lubricated the screw rotor 10 mixes with the gas G1 in the tooth groove space, is compressed, and is discharged from the discharge space 23 together with the compressed high-pressure gas G2 to the outside of the screw compressor 1. A portion of the lubricating oil is stored in the discharge space 23, and the oil level may vary depending on the operating state of the screw compressor 1.

[0018] As shown in FIGS. 1A and 1B, in some embodiments, the screw compressor 1 includes a slide valve 40 that is movable in the axial direction of the screw rotor 10 and a slide valve guide 50 that supports an end of the slide valve 40 in order to achieve a capacity control function.

[0019] The slide valve 40 is provided so as to form a part of the inner wall surface 21W of the rotor chamber 21. Specifically, the surface of the outer surface 43 of the slide valve 40 that faces the rotor chamber 21 is continuous with the inner wall surface of the casing 20C and forms the inner wall surface 21W of the rotor chamber 21 together with the inner wall surface of the casing 20C.

[0020] As described above, the slide valve 40 is movable in the axial direction of the screw rotor 10 and adjusts the opening area of ​​the inlet 33 of the bypass passage 30 according to its axial position, thereby controlling the capacity of the screw compressor 1.

[0021] 1A, the outer surface 43 of the slide valve 40 is continuous with the inner wall surface of the casing 20C over the entire area facing the rotor chamber 21, and together with the inner wall surface of the casing 20C forms the inner wall surface 21W of the rotor chamber 21. At this time, the slide valve 40 is completely accommodated in the slide valve accommodating chamber 24, and the inlet 33 of the bypass passage 30 (see FIG. 1B) is closed by the slide valve 40. In this manner, in the state shown in FIG. 1A where the slide valve 40 is completely accommodated in the slide valve accommodating chamber 24, the opening area of ​​the inlet 33 of the bypass passage 30 becomes zero. Hereinafter, the position of the slide valve 40 in this state in the x-coordinate system along the axial direction of the screw rotor 10 is defined as x=1, and is referred to as the fully closed position.

[0022] In contrast, when the slide valve 40 moves to the discharge side, as shown in Fig. 1B, the end of the slide valve 40 protrudes into the discharge space 23, and the inlet 33 of the bypass passage 30 opens to the inner wall surface 21W of the rotor chamber 21. When the slide valve 40 protrudes to the maximum extent into the discharge space 23 (see Fig. 1B), the opening area of ​​the inlet 33 of the bypass passage 30 becomes maximum. In this state, the position of the slide valve 40 in the x-coordinate system along the axial direction of the screw rotor 10 is set as the origin x=0, and is called the fully open position.

[0023] The bypass passage 30 communicates between the rotor chamber 21 and the suction space 22, and guides a portion of the gas G1 in the tooth groove space (return low-pressure gas G3) to the suction space 22. The return low-pressure gas G3 that flows into the bypass passage 30 via the inlet 33 is guided to the suction space 22, where it merges with the uncompressed low-pressure gas G0, and then passes through the suction port 12 again to enter the tooth groove space. The greater the flow rate of the return low-pressure gas G3, the smaller the flow rate of the low-pressure gas G0 drawn in from outside the screw compressor 1. 1A, when the slide valve 40 is in the fully closed position, the flow rate of the return low-pressure gas G3 is zero because the inlet 33 is closed by the slide valve 40. In contrast, as shown in FIG. 1B, when the slide valve 40 is in the fully open position, the flow rate of the return low-pressure gas G3 is at its maximum. In this way, the slide valve 40 can move axially within the range of 0≦x≦1, and the flow rate of the low-pressure gas G0 sucked in from outside the screw compressor 1 is adjusted by changing the opening area of ​​the inlet 33 of the bypass passage 30 depending on the position of the slide valve 40.

[0024] 1A and 1B, the slide valve 40 includes a suction-side end portion 45 disposed on the suction side and a discharge-side end portion 46 disposed on the discharge side. Furthermore, the slide valve 40 includes a sliding surface 44 as part of an outer surface 43 of the slide valve 40, which faces a guide surface 51 of a slide valve guide 50 described later. In the portion of the slide valve 40 accommodated in the slide valve accommodating chamber 24, the sliding surface 44 faces an inner wall surface 25 of the slide valve accommodating chamber 24. When the slide valve 40 moves to the discharge side, the suction side end 45 of the slide valve 40 forms part of the contour of the inlet 33 of the bypass passage 30 that opens to the inner wall surface 21W of the rotor chamber 21, as shown in FIG. 1B.

[0025] The slide valve 40 may constitute the capacity control device 2 of the screw compressor 1 together with other components. In addition to the slide valve 40, the capacity control device 2 includes a piston rod 41 connected to a suction side end 45 of the slide valve 40, and a piston 42 connected to the piston rod 41 on the opposite side of the slide valve 40. The piston 42 is housed in a cylinder chamber 26 formed in the casing 20D. Note that the capacity control device 2 may be hydraulically driven, and the slide valve 40 may move axially by the pressure of oil supplied into the cylinder chamber 26.

[0026] The slide valve guide 50 is provided in the discharge space 23 and supports the discharge side end 46 of the slide valve 40 that protrudes into the discharge space 23 . In the embodiment shown in FIGS. 1A and 1B, the slide valve guide 50 is provided below the movement path of the slide valve 40 in the discharge space 23 so as to support the discharge side end 46 of the slide valve 40 from below.

[0027] The slide valve guide 50 includes a guide surface 51 that slidably guides the slide valve 40. The guide surface 51 of the slide valve guide 50 faces the sliding surface 44 of the slide valve 40 when the slide valve 40 moves toward the discharge side. In addition to the guide surface 51, the slide valve guide 50 includes an intake end portion 54 disposed on the intake side and an exhaust end portion 55 disposed on the exhaust side. The slide valve guide 50 is provided so that the intake end portion 54 is adjacent to the casing 20C.

[0028] As described above, the capacity of the screw compressor 1 can be controlled by changing the opening area of ​​the inlet 33 of the bypass passage 30 using the slide valve 40 and the slide valve guide 50 depending on the position of the slide valve 40. In some embodiments, in conjunction with the above-described capacity control, the communication between the discharge space 23 and the bearing chamber 27 is utilized to control the level of the lubricating oil in the bearing chamber 27.

[0029] Hereinafter, a configuration for controlling the oil level of lubricating oil by communication between discharge space 23 and bearing chamber 27 will be described with reference to FIGS. 2A to 7B. FIG. 2A is a partial cross-sectional view showing the internal structure of a screw compressor according to one embodiment. FIG. 2B is a partial cross-sectional view showing the internal structure of a screw compressor according to another embodiment. FIG. 3 is a perspective view showing a slide valve guide and a portion of a casing according to one embodiment. FIG. 4A is a plan view of a slide valve guide according to one embodiment. FIG. 4B is a plan view of a slide valve guide according to another embodiment. FIG. 5 is a view of a slide valve guide and a slide valve according to one embodiment, as viewed from the discharge space side. FIG. 6 is a perspective view of a slide valve according to one embodiment. FIG. 7A is a perspective view showing a slide valve, a slide valve guide and a portion of a casing according to one embodiment. FIG. 7B is a perspective view showing a slide valve, a slide valve guide and a portion of a casing according to another embodiment. 7A and 7B, the screw rotor 10 is omitted. The slide valve 40 and the slide valve guide 50 are shown in half of the two vertically divided sections along the axial plane.

[0030] In some embodiments, as shown in Figures 2A and 2B, the slide valve guide 50 has a first groove 61 provided in the guide surface 51, and the slide valve 40 has a second groove 62 provided in the sliding surface 44.

[0031] In some embodiments, as shown in Figures 3 to 4B, the first groove 61 is formed along the circumferential direction of the guide surface 51 of the sliding valve guide 50. In the exemplary embodiment shown in Figure 3, the guide surface 51 is the inner peripheral surface of the half-pipe-shaped sliding valve guide 50. The sliding surface 44 of the sliding valve 40 facing the guide surface 51 is a curved surface complementary to the guide surface 51, as shown in Figure 6. In another embodiment, the first groove 61 is formed along a direction intersecting the circumferential direction of the guide surface 51 of the slide valve guide 50.

[0032] The first groove 61 communicates with the discharge space 23 . 3 and 4A, the first groove 61 is in communication with the discharge space 23 by opening to the discharge space 23 at the vertical upper end 52 of the guide surface 51 of the sliding valve guide 50. The first groove 61 is provided at the suction side end 54 of the sliding valve guide 50. 4B , the first groove 61 does not open directly to the discharge space 23, but communicates with the discharge space 23 via an internal flow path 56 of the sliding valve guide 50. The first groove 61 is provided on the discharge side of the suction side end 54 of the sliding valve guide 50.

[0033] In some embodiments, the first groove 61 communicates with the discharge space 23 above the center position of the guide surface 51 of the slide valve guide 50 in the vertical direction. That is, as shown in Fig. 5, the first groove 61 communicates with the discharge space 23 at a position z where z > (Z1 + Z2) / 2. Note that in Fig. 5, in the vertical z coordinate system, Z1 indicates the position of the lower end 53 of the guide surface 51, and Z2 indicates the position of the upper end 52 of the guide surface 51 (where Z2 > Z1). The center position of the guide surface 51 in the vertical direction is expressed as z = (Z1 + Z2) / 2. 5, the first groove 61 communicates with the discharge space 23 via an internal flow path 56 of the sliding valve guide 50. The internal flow path 56 of the sliding valve guide 50 opens to the outer surface of the sliding valve guide 50 at a position z where z>(Z1+Z2) / 2.

[0034] 6 to 7B, the second groove 62 is provided at a position closer to the discharge side than the suction side end 45 of the slide valve 40 and at a position closer to the suction side than the discharge side end 46 of the slide valve 40. As shown in FIGS. 7A and 7B, the axial length of the second groove 62 is longer than the axial length of the first groove 61. The axial length and circumferential length of the second groove 62 are each longer than the diameter of a through hole 68, which will be described later.

[0035] 7A, the second groove 62 is provided along the axial direction at the lowest position in the vertical direction on the sliding surface 44 of the slide valve 40. The second groove 62 has a rounded rectangular shape with semicircular ends. In another embodiment, as shown in FIG. 7B, the second groove 62 has a shape that combines a rounded rectangle arranged along the axial direction at the lowest position in the vertical direction on the sliding surface 44 of the slide valve 40 and a circumferential groove arranged along the circumferential direction of the sliding surface 44.

[0036] The casing 20 has a through hole 68 that opens to the inner surface of the casing 20. The through hole 68 opens to the inner surface of the casing 20 at a position that corresponds to the trajectory that the second groove 62 passes through as the slide valve 40 moves. 2A to 3, in some embodiments, the through-hole 68 is provided in a casing 20C that forms the slide valve accommodating chamber 24. The through-hole 68 opens at a position on the inner wall surface 25 of the slide valve accommodating chamber 24 closer to the discharge space 23.

[0037] In the exemplary embodiment shown in Figures 3 and 7A, the through hole 68 opens into the inner wall surface 25 at the lowest vertical position of the portion of the inner wall surface 25 of the slide valve accommodating chamber 24 that faces the sliding surface 44 of the slide valve 40. In another embodiment, as shown in FIG. 7B, the through hole 68 opens into the inner wall surface 25 above the lowest vertical position of the portion of the inner wall surface 25 of the slide valve accommodating chamber 24 that faces the sliding surface 44 of the slide valve 40.

[0038] 2A and 2B, when the inlet 33 of the bypass passage 30 is open, the second groove 62 faces the first groove 61 and the through-hole 68. That is, when the slide valve 40 is in at least a part of the position range of 0≦x<1, the second groove 62 faces the first groove 61 and the through-hole 68.

[0039] 7A and 7B , when the slide valve 40 is at least in the fully open position, the communication area between the second groove 62 and the first groove 61 and the communication area between the second groove 62 and the through-hole 68 are maximized. At this time, the second groove 62 faces at least a portion of the first groove 61, and further faces the entire opening of the through-hole 68 to the inner wall surface 25 of the slide valve accommodating chamber 24. In this case, the axial length of the second groove 62 is longer than the axial distance between the first groove 61 and the through-hole 68.

[0040] When the inlet 33 of the bypass passage 30 is open and the second groove 62 faces the first groove 61 and the through hole 68, the communication passage 60 including the first groove 61, the second groove 62, and the through hole 68 communicates between the discharge space 23 and the bearing chamber 27. When the discharge space 23 communicates with the bearing chamber 27, a portion of the high-pressure gas G2 in the discharge space 23 (bypass high-pressure gas G4) is introduced into the bearing chamber 27 via the communication passage 60 and the supply hole 28. When the bearing chamber 27 is not in communication with the discharge space 23, the bearing chamber 27 is a sealed space through which gas does not substantially flow in or out.

[0041] 2A and 2B, the communication passage 60 further includes an external passage L provided outside the screw compressor 1 as a passage for gas (bypass high-pressure gas G4) from the discharge space 23. A through-hole 68 penetrating the casing 20C is connected to the upstream end of the external passage L. A downstream end of the external passage L is connected to the supply hole 28 opening in the inner wall surface 27W of the bearing chamber 27. In another embodiment, an internal flow path of the casing 20 is provided which communicates with the through hole 68 blocked by a plug, and the bypass high-pressure gas G4 is introduced into the bearing chamber 27 via a communicating passage 60 which includes the through hole 68 and the internal flow path of the casing 20.

[0042] Next, with reference to FIGS. 8A to 8D, a process in which the second groove 62 faces the first groove 61 and the through-hole 68 as the slide valve 40 moves will be described. FIG. 8A is a plan view of a slide valve, a slide valve housing chamber, and a slide valve guide according to an embodiment, showing a state where the slide valve is in a fully closed position. FIG. 8B is a plan view of a slide valve, a slide valve housing chamber, and a slide valve guide according to an embodiment, showing a state where the second groove and the through hole are opposed to each other. FIG. 8C is a plan view of a slide valve, a slide valve housing chamber, and a slide valve guide according to an embodiment, showing a state immediately after the first groove and the second groove start to oppose each other. FIG. 8D is a plan view of a slide valve, a slide valve housing chamber, and a slide valve guide according to an embodiment, showing a state where the slide valve is in a fully open position.

[0043] When the slide valve 40 moves from the fully closed position (FIG. 8A) to the discharge side, the second groove 62 and the through hole 68 face each other (FIG. 8B). Until the slide valve 40 moves from the position shown in FIG. 8B to the fully open position shown in FIG. 8D, the communication area between the second groove 62 and the through hole 68 is always maximum. When the slide valve 40 moves further to the discharge side, the first groove 61 and the second groove 62 start to oppose each other. The position of the slide valve 40 at this time is referred to as the communication start position X*. From the communication start position X*, the communication between the discharge space 23 and the bearing chamber 27 through the communication passage 60 starts (FIG. 8C). As the slide valve 40 moves further to the discharge side, the communication area between the first groove 61 and the second groove 62 monotonically increases. As the communication area between the first groove 61 and the second groove 62 gradually increases (as x becomes smaller), the flow rate of the bypass high-pressure gas G4 flowing into the communication passage 60 increases. The communication area between the first groove 61 and the second groove 62 becomes maximum until the slide valve 40 reaches the fully open position from the communication start position X* (FIG. 8D).

[0044] In some embodiments, in order to achieve both the oil level control of the bearing chamber 27 and the high-efficiency operation of the screw compressor 1, when the slide valve 40 is at a position where 0 < x ≦ 0.1, the first groove 61, the second groove 62, and the through hole 68 are provided so as to start communication. That is, the communication start position X* may be 0 < X* ≦ 0.1.

[0045] 2B, the bearing chamber 27 accommodates a gear 15 in addition to the bearing 14. The gear 15 transmits a rotational driving force from a driving source (not shown) to the screw rotor 10. The bearing chamber 27 accommodates a drive gear 15A attached to a rotary shaft 16 connected to a drive source, and a driven gear 15B that meshes with the drive gear 15A. The driven gear 15B is attached to the rotary shaft 11 of the screw rotor 10. When the drive gear 15A is driven to rotate by the drive source, the driven gear 15B rotates following the drive gear 15A, and the rotational drive force is transmitted from the rotary shaft 11 to the screw rotor 10. In the embodiment shown in FIGS. 2A and 2B, the bearing chamber 27 is provided on the discharge side of the screw compressor 1, but in another embodiment, it may be provided on the suction side.

[0046] FIG. 9 is a perspective view showing the internal structure of a screw compressor according to one embodiment. In some embodiments, the screw compressor 1 further includes an oil return passage 70 that connects the bearing chamber 27 with a low-pressure space having a lower pressure than the discharge space 23. The oil return passage 70 has an inlet 71 and an outlet 72.

[0047] An inlet 71 of the oil return passage 70 opens into the inner wall surface 27W of the bearing chamber 27 at a position lower than the height position of the lower end of the bearing 14 in the vertical direction. 9, the inlet 71 of the oil return passage 70 opens to the surface of the casing 20B in the inner wall surface 27W of the bearing chamber 27. Furthermore, the inlet 71 of the oil return passage 70 opens to the inner wall surface 27W of the bearing chamber 27 at a position lower than the height position of the lower end of the gear 15 in the vertical direction.

[0048] An outlet 72 of the oil return passage 70 opens to the inner wall surface 21W of the rotor chamber 21 so as to communicate with the tooth groove space of the screw rotor 10 as a low-pressure space. In the embodiment shown in Fig. 9, the outlet 72 communicates with the tooth groove space located on the relatively low-pressure side before the volume is reduced.

[0049] The oil return passage 70 includes an internal passage 73 in the casing 20. The internal passage 73 is provided between the inlet 71 and the outlet 72 of the oil return passage 70, and extends inside the casing 20 toward the rotor chamber 21. In the embodiment shown in Fig. 9, the internal passage 73 is provided inside the walls of the casing 20B and the casing 20C.

[0050] In some embodiments, the internal passage 73 extends within the wall of the casing 20 between an inlet 71 of the oil return passage 70 and an outlet 72 of the oil return passage 70 located at a higher elevation than the inlet 71 .

[0051] In the embodiment shown in Figure 9, the internal flow path 73 includes a first internal flow path 74 extending at the same height as the inlet 71 of the oil return flow path 70, a second internal flow path 75 extending at the same height as the outlet 72 of the oil return flow path 70, and a step portion 76 for connecting the first internal flow path 74 and the second internal flow path 75. The first internal flow path 74 extends inside the wall of the casing 20B from the inlet 71 of the oil return flow path 70 to the step portion 76. The second internal flow path 75 extends inside the wall of the casing 20C from the step portion 76 to the outlet 72 of the oil return flow path 70. The step portion 76 may be formed by a flow path groove formed in the mating surfaces of the casings 20B and 20C. In this case, a sealing member such as a gasket may be used to prevent fluid leakage from the flow path groove (step portion 76) through minute gaps in the mating surfaces.

[0052] The characteristic configurations of the oil-cooled screw compressors according to the above-described embodiments can be summarized as follows.

[0053] [1] An oil-flooded screw compressor (1; 1A, 1B) according to at least some embodiments of the present invention is A screw rotor (10), a casing (20) including a bearing chamber (27) that accommodates bearings (14) for rotatably supporting the screw rotor (10), a rotor chamber (21) that accommodates the screw rotor (10), a suction space (22), and a discharge space (23); a slide valve (40) that is movable in the axial direction of the screw rotor (10) and that is provided so as to form a part of the inner wall surface (21W) of the rotor chamber (21); a slide valve guide (50) provided in the discharge space (23) for supporting an end (46) of the slide valve (40) protruding into the discharge space (23); Equipped with The slide valve (40) is configured to open an inlet (33) of a bypass passage (30) communicating between the rotor chamber (21) and the suction space (22) to an inner wall surface (21W) of the rotor chamber (21) when the slide valve (40) moves toward the discharge space (23). The slide valve guide (50) has a guide surface (51) that slidably guides the slide valve (40), and a first groove (61) that is provided in the guide surface (51) and communicates with the discharge space (23), The slide valve (40) has a sliding surface (44) on an outer surface (43) of the slide valve (40) that faces a guide surface (51) of the slide valve guide (50), and a second groove (62) provided in the sliding surface (44); When the inlet (33) of the bypass passage (30) is open, and the second groove (62) faces the first groove (61) and the through hole (68) opening to the inner surface of the casing (20), the communicating passage (60) including the first groove (61), the second groove (62), and the through hole (68) is configured to communicate the discharge space (23) with the bearing chamber (27).

[0054] According to the configuration [1], the slide valve (40), whose position is adjusted according to the operating state of the compressor (1; 1A, 1B), is provided with the second groove (62), and the first groove (61) and the through hole (68) are switched between communicating and not communicating with each other via the second groove (62) by moving the slide valve (40). Therefore, a part of the compressed high-pressure gas (G2) (bypass high-pressure gas G4) can be introduced into the bearing chamber (27) according to the operating state of the compressor (1; 1A, 1B). Here, the compressor (1; 1A, 1B) is generally started with the inlet (33) of the bypass passage (30) open to the inner wall surface (21W) of the rotor chamber (21). Therefore, as in the configuration [1] above, by communicating the discharge space (23) with the bearing chamber (27) through the communication passage (60) including the first groove (61), the second groove (62), and the through hole (68) only when the inlet (33) of the bypass passage (30) is open, the oil level of the lubricating oil in the bearing chamber (27) can be lowered during start-up, when the efficiency of the compressors (1; 1A, 1B) is less affected. Thus, it is possible to suppress loss (churning loss) due to the agitation of the lubricating oil by the bearings (14) while avoiding an unnecessary decrease in the efficiency of the compressors (1; 1A, 1B) due to the control of the oil level of the lubricating oil in the bearing chamber (27).

[0055] [2] In some embodiments, in the configuration of [1] above, The first groove (61) communicates with the discharge space (23) above the center of the guide surface (51) in the vertical direction.

[0056] When lubricating oil is stored in the discharge space (23), depending on the oil level of the lubricating oil, a portion of the guide surface (51) of the slide valve guide (50) below the center position in the vertical direction may be submerged in the lubricating oil surface. According to the configuration [2], the flow of the bypass high-pressure gas (G4) guided from the discharge space (23) to the bearing chamber (27) via the communicating passage (60) including the first groove (61) is less affected by the oil level of the lubricating oil, and the bypass high-pressure gas (G4) can be stably guided to the bearing chamber (27).

[0057] [3] In some embodiments, in the configuration of [1] or [2] above, The first groove (61) is formed along the circumferential direction of the guide surface (51) of the slide valve guide (50) and opens into the discharge space (23) at the vertical upper end (52) of the guide surface (51).

[0058] According to the configuration [3], the flow of the bypass high-pressure gas (G4) guided from the discharge space (23) to the bearing chamber (27) via the communicating passage (60) including the first groove (61) is less affected by the oil level of the lubricating oil, and the bypass high-pressure gas (G4) can be guided to the bearing chamber (27) more stably.

[0059] [4] In some embodiments, in any of the configurations [1] to [3] above, an oil return passage (70) that connects the bearing chamber (27) with a low-pressure space having a pressure lower than that of the discharge space (23); An inlet (71) of the oil return channel (70) opens into an inner wall surface (27W) of the bearing chamber (27) at a position lower than the height of the lower end of the bearing (14) in the vertical direction.

[0060] According to the configuration [4] described above, the introduction of the bypass high-pressure gas (G4) into the bearing chamber (27) causes a pressure difference between the bearing chamber (27) and the low-pressure space, which causes the lubricating oil to flow from the bearing chamber (27) to the low-pressure space through the oil return passage (70), and the level of the lubricating oil in the bearing chamber (27) drops. The drop in the lubricating oil level continues until it reaches the height of the inlet (71) of the oil return passage (70), which opens at a position lower than the height of the lower end of the bearing (14). This prevents the bearing (14) from being immersed in the lubricating oil, thereby more reliably suppressing loss (churning loss) due to the agitation of the lubricating oil by the bearing (14).

[0061] [5] In some embodiments, in the configuration of [4] above, An outlet (72) of the oil return passage (70) opens to an inner wall surface (21W) of the rotor chamber (21) so as to communicate with a tooth groove space of the screw rotor (10) as a low-pressure space, The oil return flow path (70) includes an internal flow path (73) of the casing (20) that is provided between the inlet (71) and the outlet (72) of the oil return flow path (70) and extends inside the wall of the casing (20) toward the rotor chamber (21).

[0062] According to the configuration [5], the lubricating oil in the bearing chamber (27) is returned to the tooth groove space, so that a decrease in the efficiency of the compressors (1; 1A, 1B) due to a rise in temperature on the suction side can be suppressed compared to when the lubricating oil is returned to the suction side of the compressors (1; 1A, 1B).

[0063] [6] In some embodiments, in the configuration of [5] above, The internal flow path (73) extends inside the wall of the casing (20) between an inlet (71) of the oil return flow path (70) and an outlet (72) of the oil return flow path (70) located higher than the inlet (71).

[0064] To achieve the technical advantage described in [4] above, the inlet 71 of the oil return passage 70 must open at a position lower than the height position of the lower end of the bearing 14. On the other hand, to achieve the technical advantage described in [5] above, the outlet 72 of the oil return passage 70 must be located within the height range of the tooth groove space. However, depending on the outer diameter of the bearing 14, there is not necessarily a common height position that satisfies both positional constraints at the same time, and it may be appropriate to locate the inlet 71 of the oil return passage 70 at a position lower than the outlet 72. In this regard, according to the configuration [6] above, the difference in elevation between the inlet (71) and outlet (72) of the oil return flow path (70), which is located at a relatively low position with respect to the outlet (72), can be absorbed by the internal flow path (73) of the casing (20), and therefore, the above-mentioned positional constraints of the inlet (71) and outlet (72) of the oil return flow path (70) can be simultaneously satisfied.

[0065] [7] In some embodiments, in any of the configurations [4] to [6] above, It is provided with a gear (15; 15A, 15B) that is housed in a bearing chamber (27) and transmits a rotational driving force from a driving source to a screw rotor (10). The inlet (71) of the oil return passage (70) opens on the inner wall surface (27W) of the bearing chamber (27) at a position below the height position of the lower end of the gear (15; 15A, 15B) in the vertical direction.

[0066] In the screw compressor (1; 1A, 1B), in order to transmit the rotational driving force from the driving source to the screw rotor (10), a power transmission gear (15; 15A, 15B) may be provided between the driving source and the screw rotor (10). Since the gear (15; 15A, 15B) is housed in the bearing chamber (27), if the oil level of the lubricating oil in the bearing chamber (27) becomes too high, a part of the gear (15; 15A, 15B) may be immersed in the oil level. When the compressor (1; 1A, 1B) is driven in that state, the loss (agitation loss) caused by the agitation of the lubricating oil by the gear (15; 15A, 15B) increases. According to the configuration of [7] above, the oil level of the lubricating oil in the bearing chamber (27) drops until it reaches the height of the inlet (71) of the oil return passage (70) that opens at a position below the height position of the lower end of the gear (15; 15A, 15B) due to the introduction of the bypass high-pressure gas (G4) into the bearing chamber (27). Therefore, it is possible to prevent the gear (15; 15A, 15B) from being immersed in the lubricating oil and more reliably suppress the loss (agitation loss) caused by the agitation of the lubricating oil by the gear (15; 15A, 15B).

[0067] [8] In some embodiments, in any of the configurations of [1] to [7] above, In a coordinate system along the axial direction of the screw rotor (10), taking the fully open position of the slide valve (40) where the opening area of the inlet (33) of the bypass passage (30) is maximum as the origin x = 0, and the fully closed position of the slide valve (40) where the opening area of the inlet (33) of the bypass passage (30) is zero as x = 1, When the slide valve (40) moves toward the fully open position, when the slide valve (40) is at a position of 0 < x ≤ 0.1, the first groove (61), the second groove (62), and the through hole (68) are configured to start communicating.

[0068] According to the configuration [8], the communication start position X* is limited to a position close to the fully open position of the slide valve (40) corresponding to the start of the compressor (1; 1A, 1B). This makes it possible to simultaneously achieve the introduction of the bypass high-pressure gas (G4) into the bearing chamber (27) at the start of the compressor (1; 1A, 1B), which suppresses the performance of the compressor (1; 1A, 1B), and the highly efficient operation of the compressor (1; 1A, 1B) at times other than the start of the compressor (1; 1A, 1B). That is, when the compressors (1; 1A, 1B) are operating at a low load (when the slide valve 40 is in a position where x≦0.1), including at the time of startup of the compressors (1; 1A, 1B), the first groove (61), the second groove (62), and the through-hole (68) are in communication with each other, so that the level of the lubricating oil in the bearing chamber (27) can be lowered during startup, when the efficiency of the compressors (1; 1A, 1B) is not significantly affected. On the other hand, when the amount of gas intake by the compressors (1; 1A, 1B) is relatively large (when the slide valve (40) is in a position where x>0.1), the second groove (62) does not connect the first groove (61) to the through-hole (68), so that highly efficient operation of the compressors (1; 1A, 1B) can be achieved during operation other than at the time of startup. [Explanation of symbols]

[0069] 1 (1A, 1B): Oil-flooded screw compressor (compressor) 10: Screw rotor 14: Bearing 15 (15A, 15B): Gear 20(20A-20D): Casing 21: Rotor room 21W: Inner wall surface 22: Suction space 23: Discharge space 27: Bearing chamber 27W: Inner wall surface 30: Bypass passage 33: Entrance 40: Slide valve 43:Outer surface 44: Sliding surface 46:Discharge side end 50: Slide valve guide 51: Guide surface 52: Upper end 60: Communication path 61: 1st groove 62: 2nd groove 68:Through hole 70: Oil return passage 71:Entrance 72: Exit 73: Internal flow path

Claims

1. a screw rotor; a casing including a bearing chamber that accommodates a bearing for rotatably supporting the screw rotor, a rotor chamber that accommodates the screw rotor, a suction space, and a discharge space; a slide valve that is movable in the axial direction of the screw rotor and that is provided so as to form a part of the inner wall surface of the rotor chamber; a slide valve guide provided in the discharge space to support an end of the slide valve protruding into the discharge space; Equipped with the slide valve is configured to open an inlet of a bypass passage communicating between the rotor chamber and the suction space to the inner wall surface of the rotor chamber when moving toward the discharge space, the slide valve guide has a guide surface that slidably guides the slide valve, and a first groove that is provided on the guide surface and communicates with the discharge space, The slide valve has a sliding surface that faces the guide surface of the slide valve guide on an outer surface of the slide valve, and a second groove that is provided on the sliding surface, When the inlet of the bypass passage is open, and the second groove faces the first groove and a through hole that opens to the inner surface of the casing, a communication passage including the first groove, the second groove, and the through hole communicates the discharge space with the bearing chamber. Oil-flooded screw compressor.

2. The first groove communicates with the ejection space above a center position of the guide surface in the vertical direction. The oil-flooded screw compressor according to claim 1.

3. The first groove is formed along the circumferential direction of the guide surface of the slide valve guide and opens into the discharge space at an upper end of the guide surface in the vertical direction. The oil-cooled screw compressor according to claim 1 or 2.

4. an oil return passage communicating the bearing chamber with a low-pressure space having a pressure lower than that of the discharge space; The inlet of the oil return passage opens to the inner wall surface of the bearing chamber at a position lower than the height position of the lower end of the bearing in the vertical direction. The oil-cooled screw compressor according to claim 1 or 2.

5. an outlet of the oil return passage opens to the inner wall surface of the rotor chamber so as to communicate with a tooth groove space of the screw rotor as the low-pressure space, the oil return flow path includes an internal flow path of the casing that is provided between the inlet and the outlet of the oil return flow path and extends inside the wall of the casing toward the rotor chamber, The oil-cooled screw compressor according to claim 4.

6. The internal flow passage extends within the wall of the casing between the inlet of the oil return flow passage and the outlet of the oil return flow passage located higher than the inlet. The oil-cooled screw compressor according to claim 5.

7. a gear housed in the bearing chamber for transmitting a rotational driving force from a driving source to the screw rotor; The inlet of the oil return passage opens into the inner wall surface of the bearing chamber at a position lower than the height position of the lower end of the gear in the vertical direction. The oil-cooled screw compressor according to claim 4.

8. In a coordinate system along the axial direction of the screw rotor, when the fully open position of the slide valve where the opening area of ​​the inlet of the bypass passage is maximum is defined as the origin x=0 and the fully closed position of the slide valve where the opening area of ​​the inlet of the bypass passage is zero is defined as x=1, When the slide valve moves toward the fully open position, the first groove, the second groove, and the through hole are configured to start communicating with each other when the slide valve is at a position of 0<x≦0.

1. The oil-cooled screw compressor according to claim 1 or 2.

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