Screw compressor and gas compression equipment

Abstract

A screw compressor is provided with: a screw rotor having a discharge-side end surface; a housing having a rotor-facing surface facing the discharge-side end surface, and an opening provided in the rotor-facing surface and communicating with a discharge space through which the gas compressed by the screw rotor is discharged; a spool valve, the position of which in the axial direction of the screw rotor is variable so as to change the internal volume ratio; and a movable plate disposed along an edge of the opening of the housing configured to block a portion of the opening, the movable plate configured to be movable between a first position in which the movable plate together with the edge of the opening forms a first profile of an axial discharge port, and a second position in which the movable plate together with the edge of the opening forms a second profile of the axial discharge port. And a second position, which is farther from the screw rotor in the axial direction than the first position, configured such that, when the movable piece is located at the second position, a second contour of the axial discharge port having an opening area larger than that of the first contour is formed by the opening.

Description

Technical Field

[0001] This disclosure relates to screw compressors and gas compression equipment. Background Technology

[0002] Positive displacement screw compressors have outstanding advantages such as simple structure and good durability, and are generally widely used.

[0003] As representative methods of capacity control in screw compressors, there are speed control and slide valve control. In large screw compressors, slide valve control is generally used for capacity control.

[0004] In the slide valve configuration, by moving the slide valve, which forms the rotor housing, axially along with the housing, the volume of the toothed space formed between the male and female rotors at the start of compression can be changed. This allows for stepless adjustment of the compressed gas capacity according to the load of the screw compressor.

[0005] On the other hand, screw compressors have a volume ratio Vi (= suction volume V1 / discharge volume V2) suitable for operating conditions, and the positions and shapes of the suction and discharge ports are determined in such a way that the discharge of compressed gas begins at the moment corresponding to the volume ratio Vi suitable for operating conditions. Most existing screw compressors have a fixed internal volume ratio Vi, and therefore have a discharge port with a shape selected based on the average internal volume ratio.

[0006] However, in a screw compressor equipped with the aforementioned slide valve, by moving the slide valve, the internal volume ratio (the ratio of the volume of the tooth space at the start of compression (when volume reduction begins) to the volume at the end of compression (when volume reduction ends)) also changes simultaneously.

[0007] Patent document 1 describes a screw compressor that has the aforementioned slide valve and is capable of adjusting the internal volume ratio.

[0008] Existing technical documents Patent documents Patent Document 1: International Publication No. 2016 / 147467 Summary of the Invention

[0009] (a) Technical problems to be solved However, when screw compressors are scaled up, if the internal volume ratio of the discharge port is to be maintained while increasing the size of the screw compressor, the area ratio of the discharge port to the displacement becomes smaller, and the gas velocity in the discharge port increases. Thus, if the gas velocity in the discharge port increases, the pressure in the tooth space rises due to the resistance to flow through the discharge port, resulting in overcompression, and therefore, discharge losses may increase.

[0010] On the other hand, by increasing the area of ​​the discharge port (low internal volume ratio), the increase in gas flow velocity in the discharge port can be suppressed, thus making it difficult to cause the aforementioned problem of increased discharge loss. However, in operating regions that require a high internal volume ratio, due to insufficient compression, the gas flowing back from the discharge side will be recompressed and discharged, so the discharge loss may still increase.

[0011] In view of the above, the object of at least one embodiment of the present invention is to provide a screw compressor and a gas compression device that can suppress discharge loss within a wide operating range (range of internal volume ratio).

[0012] (II) Technical Solution The screw compressor of at least one embodiment of the present invention comprises: A screw rotor having a discharge side end face; The housing has a rotor-opposing surface facing the discharge side end face and an opening disposed on the rotor-opposing surface and communicating with the discharge space, wherein the discharge space is for discharging gas compressed by the screw rotor; A slide valve, whose position is variable in the axial direction of the screw rotor to change the internal volume ratio; and A movable piece, disposed along the edge of the opening in the housing, is configured to block a portion of the opening. The movable plate is configured to move between a first position and a second position, wherein, in the first position, the movable plate, together with the edge of the opening, forms a first profile of an axial discharge port, and the second position is axially farther away from the screw rotor compared to the first position. The configuration is such that, when the movable piece is in the second position, a second profile of the axial discharge port is formed through the opening, with an opening area larger than the first profile.

[0013] Furthermore, the gas compression apparatus of at least one embodiment of the present invention includes: The aforementioned screw compressor is configured to compress gas; and An oil separator is used to separate the oil from the mixture of compressed gas and oil discharged from the screw compressor.

[0014] (III) Beneficial Effects According to at least one embodiment of the present invention, a screw compressor and a gas compression device are provided, which can suppress discharge loss over a wide operating range (range of internal volume ratio). Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a gas compression device according to one embodiment.

[0016] Figure 2 This is a schematic cross-sectional view of a screw compressor according to one embodiment.

[0017] Figure 3 It means Figure 2 The diagram shows the AA section of the screw compressor.

[0018] Figure 4 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment.

[0019] Figure 5 It means Figure 4 A schematic diagram showing the outline of the axial discharge port.

[0020] Figure 6 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment.

[0021] Figure 7 It means Figure 6 A schematic diagram showing the outline of the axial discharge port.

[0022] Figure 8 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment.

[0023] Figure 9 It means Figure 8 A schematic diagram showing the outline of the axial discharge port.

[0024] Figure 10 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment.

[0025] Figure 11 It means Figure 10 A schematic diagram showing the outline of the axial discharge port.

[0026] Figure 12 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment.

[0027] Figure 13 This is a schematic cross-sectional view showing the vicinity of the axial discharge port of a screw compressor according to one embodiment. Detailed Implementation

[0028] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the constituent components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0029] (Structure of gas compression equipment) Figure 1 This is a schematic diagram of a gas compression device including a screw compressor with some embodiments. As shown in the figure, the gas compression device 1 includes a screw compressor 2, an oil separator 4, a cooler 6, and a pump 8.

[0030] The screw compressor 2 is configured to compress and discharge the intake gas. The symbol Ps in the figure represents the intake pressure of the screw compressor 2, and the symbol Pd represents the discharge pressure of the screw compressor 2. Oil is supplied to the screw compressor 2 via the oil supply line 10 for cooling, lubrication, etc. The oil supplied to the screw compressor 2 is discharged together with the compressed gas.

[0031] Oil separator 4 is configured to separate oil from the mixture of compressed gas and oil discharged from screw compressor 2. The oil separated by oil separator 4 is then supplied back to screw compressor 2 via oil supply line 10. Typically, the oil separated by oil separator 4 is pressurized by pump 8 and supplied to screw compressor 2 via oil supply line 10. In this case, the pressure Poil of the oil supplied to screw compressor 2 is higher than the discharge pressure Pd (Poil = Pd + α). Alternatively, the oil separated by oil separator 4 can also be cooled by cooler 6 and then pressurized by pump 8.

[0032] (Structure of a screw compressor) Figure 2 This is a schematic cross-sectional view of a screw compressor according to one embodiment. Figure 3 It means Figure 2 The diagram shows the AA section of the screw compressor. Figure 2 and Figure 3 As shown, the screw compressor 2 includes: a pair of screw rotors (male rotor 15 and female rotor 17) including a pair of rotor shafts 14 and 16, and a housing 12 for housing the pair of screw rotors.

[0033] A pair of rotor shafts 14 and 16 are supported by radial bearing 18 and thrust bearing 20 respectively to enable rotation. Pressurized oil is supplied to each bearing via oil supply line 10.

[0034] The male rotor 15 and the female rotor 17 have helical teeth that mesh with each other. Through the meshing of the teeth of the male rotor 15 and the female rotor 17 and the housing 12, a plurality of tooth groove spaces are formed along the axial direction of the rotor shafts 14 and 16.

[0035] The rotor shaft 14 constituting the male rotor 15 is connected to the output shaft of a motor (not shown) and is configured to be driven by the motor's rotation. The female rotor 17, which meshes with the male rotor 15, is driven to rotate by the rotation of the male rotor 15. The female rotor 17 rotates in the opposite direction to the rotation of the male rotor 15. If the male rotor 15 and the female rotor 17 rotate in a meshing state, the tooth space moves axially from the suction side to the discharge side.

[0036] A shaft seal 24 is provided in the through portion of the rotor shaft 14 of the housing 12 to prevent gas leakage through the through portion. Pressurized oil can also be supplied to the shaft seal 24 via the oil supply line 10.

[0037] The oil supplied to the bearing and shaft seal 24 is discharged from the housing 12 and returned to the relatively low-pressure space of the screw rotor housing 12 via the return pipeline (not shown).

[0038] Gas is drawn into the toothed space through the intake space 41 formed within the housing 12 via the intake port 40. As the male rotor 15 and female rotor 17 rotate, the toothed space moves axially from the intake side towards the discharge side. During this process, if it reaches its maximum volume, the volume of the toothed space decreases after the intake port 40 is closed, thus compressing the gas within the toothed space. If the toothed space reaches the discharge port 42, which communicates with the discharge space 43 formed within the housing 12, the compressed gas within the toothed space is discharged into the discharge space via the discharge port 42. The discharge port 42 includes a radial discharge port 46 for radially discharging the compressed gas from the toothed space, and an axial discharge port 44 for axially discharging the compressed gas from the toothed space. Details regarding the discharge port 42 will be described below.

[0039] like Figure 2 As shown, the screw compressor 2 may also include a balance piston 28 disposed on at least one of a pair of rotor shafts 14, 15. Figure 2 In the exemplary embodiment shown, a balance piston 28 is provided at the suction side end of the rotor shaft 14 constituting the male rotor 15. Oil at a relatively high pressure from the oil supply line 10 is supplied to the balance piston chamber 29 facing the suction side end face of the balance piston 28. As a result, a force (a force in the axial direction from the suction side to the discharge side) acting in the opposite direction to the gas thrust load acting on the rotor shaft 14 (a thrust load acting on the rotor shaft 14 due to the difference between the suction pressure Ps and the discharge pressure Pd of the screw compressor 2, acting axially from the discharge side to the suction side) acts on the rotor shaft 14 via the end face of the balance piston 28. This reduces the load on the thrust bearing 20.

[0040] like Figure 2 As shown, the screw compressor 2 includes a slide valve 30 for adjusting the capacity according to the load of the screw compressor 2. In the illustrated embodiment, the slide valve 30 is driven by a hydraulic piston 32, which can change its axial position.

[0041] If the slide valve 30 is moved axially from the suction side to the discharge side, the bypass passage opens towards the toothed space during the compression stroke. Gas in the toothed space returns to the suction chamber as the screw rotor rotates, and compression in that toothed space begins when the bypass passage is closed. The closer the slide valve moves to the discharge side, the smaller the volume of the toothed space at the start of compression. Thus, by changing the axial position of the slide valve 30, the volume Vs of each toothed space at the start of compression (i.e., when the volume of each toothed space begins to decrease, and the suction port 40 is closed) can be varied. This changes the internal volume ratio Vi of the screw compressor 2 (the ratio Vs / Vd of the volume Vs at the start of compression in the toothed space to the volume Vd at the end of compression (when the volume of the toothed space ends to the end of compression, and the discharge port 42 is open)). In other words, the closer the slide valve 30 is to the discharge side, the smaller the volume Vs of the toothed space at the start of compression. Therefore, the fact that the slide valve 30 is located closer to the discharge side is the main reason why the internal volume ratio Vi (=Vs / Vd) is smaller.

[0042] As described above, discharge port 42 includes radial discharge port 46 and axial discharge port 44.

[0043] The radial discharge port 46 is formed by the cutout 31 of the slide valve 30. The opening area of ​​the radial discharge port 46 is largest when the slide valve 30 is axially closest to the suction side, and decreases as the slide valve 30 moves closer to the discharge side. Furthermore, when the slide valve 30 reaches a predetermined axial position, the radial discharge port 46 closes, and its opening area becomes zero. The smaller the opening area of ​​the radial discharge port 46, the smaller the volume Vd at the moment the discharge port 42 is open for each tooth space. Therefore, the decrease in the opening area of ​​the radial discharge port 46 by moving the slide valve 30 towards the discharge side is the main reason for the increase in the internal volume ratio Vi (=Vs / Vd).

[0044] The axial discharge port 44 is at least partially formed by an opening 52 provided on the end face of the housing 12 (see reference). Figure 3 An opening 52 is formed in the rotor-facing surface 50 (end face of housing 12) of housing 12 opposite to the discharge-side end face 48 of the screw rotor (male rotor 15 and female rotor 17), and is configured to communicate with the discharge space 43.

[0045] Here, Figure 4 and Figure 6 This is a schematic cross-sectional view showing the vicinity of the axial discharge port 44 of a screw compressor according to one embodiment, which is equivalent to... Figure 3 A diagram of the BB section. Figure 5 and Figure 7 They represent Figure 4 and Figure 6 A schematic diagram showing the outline of the axial discharge port 44. Figures 8-11This is a diagram showing the vicinity of the axial discharge port 44 of a screw compressor according to another embodiment, which is respectively compared with the above... Figures 4-7 The corresponding diagram. Furthermore, regarding... Figure 4 , Figure 6 , Figure 8 and Figure 10 and the following Figure 12 and Figure 13 These figures are cross-sectional views near the discharge port 42 on the male rotor 15 side. However, in these figures, the diagonal lines inside the screw rotor represent the tooth tips of the screw rotor around the axial discharge port. That is, these figures show the case where the volume of the tooth space gradually decreases towards the discharge port 42.

[0046] like Figure 3 ,as well as Figure 4 , Figure 6 , Figure 8 as well as Figure 10 As shown, in some embodiments, the screw compressor 2 includes a movable piece 54 disposed along the edge of the opening 52 provided in the housing 12. The movable piece 54 is capable of blocking a portion of the opening 52.

[0047] The movable plate 54 includes a first end face 54a and a second end face 54b as two axial end faces. The first end face 54a is the end face opposite to the discharge side end face 48 of the screw rotor (male rotor 15 and female rotor 17), and the second end face 54b is the end face on the opposite side of the first end face 54a in the axial direction.

[0048] exist Figures 4-11 In the exemplary embodiment shown, the movable piece 54 includes a piston 56 capable of moving forward and backward in the axial direction. The piston 56 is inserted into an axially extending hole 68 provided in the housing 12, and is prevented from dislodging from the hole 68 by means of a plug 66.

[0049] exist Figures 4-7 In the exemplary embodiment shown, the first end face 54a and the second end face 54b of the movable piece 54 are formed by the two end faces of the piston 56.

[0050] exist Figures 8-11 In the exemplary embodiment shown, the movable plate 54 includes, in addition to the piston 56 which is capable of moving forward and backward in the axial direction, a plate-shaped member 78 mounted on the axial suction side end of the piston 56. The first end face 54a of the movable plate 54 is formed by the axial suction side end face of the plate-shaped member 78, and the second end face 54b of the movable plate 54 is formed by the axial discharge side end face of the piston 56.

[0051] The movable piece 54 is configured to be able to be in a first position in the axial direction (see reference). Figures 4-5 as well as Figures 8-9) and a second position that is axially further away from the screw rotor than the first position (refer to Figures 6-7 as well as Figures 10-11 The movable piece 54 in the second position moves between the two positions. That is, the movable piece 54 in the second position is located axially closer to the discharge side compared to the movable piece 54 in the first position.

[0052] For example, Figures 4-5 and Figures 8-9 As shown, the outline of the axial discharge port 44, i.e., the first outline 101, when the movable piece 54 is in the first position, is formed by the movable piece 54 and the edge of the opening 52 provided in the housing 12 (see reference). Figure 5 and Figure 9 That is, the movable piece 54 in the first position blocks a portion of the opening 52 provided in the housing 12, so the opening area of ​​the axial discharge port 44 with the first profile 101 is smaller than the opening area of ​​the opening 52 of the housing 12. In addition, when the movable piece 54 is in the first position, the first end face 54a of the movable piece 54 is flush with the rotor opposing surface 50 of the housing 12.

[0053] In addition, for example, Figures 6-7 and Figures 10-11 As shown, when the movable piece 54 is in the second position, the outline of the axial discharge port 44, i.e., the second outline 102, is formed by the edge of the opening 52 provided in the housing 12 (see reference). Figure 7 and Figure 11 That is, the opening area of ​​the axial discharge port 44 with the second profile 102 is larger than the opening area of ​​the axial discharge port 44 with the first profile 101 described above. In addition, when the movable piece 54 is in the second position, the first end face 54a of the movable piece 54 is located axially closer to the discharge side compared with the rotor opposing surface 50 of the housing 12.

[0054] exist Figures 4-7 In the exemplary embodiment shown, when the movable plate 54 is in the first position described above, the end face of the piston 56 on the suction side (the first end face 54a of the movable plate 54) in the axial direction is flush with the rotor-opposing surface 50 of the housing 12 (see reference). Figure 4 ), and piston 56 forms part of the first profile 101 (see reference). Figure 5 ).

[0055] exist Figures 8-11 In the exemplary embodiment shown, when the movable plate 54 is in the first position described above, the end face of the axially inclined plate-shaped member 78 on the suction side (the first end face 54a of the movable plate 54) is flush with the rotor-opposing surface 50 of the housing 12 (see reference). Figure 8 ), and the plate-shaped member 78 forms part of the first profile 101 (see reference). Figure 9 ).

[0056] In the above embodiment, the movable piece 54, which is disposed along the edge of the opening 52 of the housing 12 forming the axial discharge port 44, can move between a first position in the axial direction and a second position further away from the screw rotors (male rotor 15 and female rotor 17) than the first position. Furthermore, when the movable piece 54 is in the second position, the opening area of ​​the axial discharge port 44 is larger than when it is in the first position. Therefore, under operating conditions where the internal volume ratio Vi of the screw compressor 2 is relatively high (e.g., when the slide valve 30 is axially located closer to the suction side), by placing the movable piece 54 in the second position, the opening area of ​​the axial discharge port 44 can be made larger, suppressing the increase in gas flow velocity in the discharge port 42 and thus suppressing the increase in discharge loss. Conversely, under operating conditions where the internal volume ratio Vi of the screw compressor 2 is relatively low (e.g., when the slide valve 30 is axially located closer to the discharge side), by placing the movable piece 54 in the first position, the opening area of ​​the axial discharge port 44 can be made smaller, suppressing the increase in discharge loss caused by undercompression. Therefore, according to the above embodiment, by switching the position of the movable piece 54 between the first position and the second position according to the internal volume ratio Vi, discharge loss can be suppressed within a wide operating range (internal volume ratio Vi).

[0057] Furthermore, in the above embodiment, the movable plate 54 includes a piston 56 capable of moving forward and backward in the axial direction. That is, the movable plate 54 (piston 56) moves forward and backward in a direction orthogonal to the discharge side end face 48 of the screw rotor, thus making it difficult for interference between the movable plate 54 and the screw rotor to occur, and suppressing damage caused by contact between the two.

[0058] In addition, Figures 4-7 In the exemplary embodiment shown, when the movable plate 54 including the piston 56 is in the first position, the end face of the piston 56 (the first end face 54a of the movable plate 54) is flush with the rotor opposing surface 50 of the housing 12, and the piston 56 itself forms the outline (first outline) of the axial discharge port 44. Therefore, the screw compressor 2 including the movable plate 54 can be realized with a simple structure.

[0059] In addition, Figures 8-11 In the exemplary embodiment shown, when the movable plate 54, including the plate-shaped member 78 mounted at the end of the piston 56, is in the first position, the end face of the plate-shaped member 78 (the first end face 54a of the movable plate 54) is flush with the rotor-opposing surface 50 of the housing 12, and the plate-shaped member 78 forms the outline (first outline) of the axial discharge port 44. Here, since the plate-shaped member 78 can be a member of any shape, by making the shape of the plate-shaped member 78 appropriate, it is easy to make the shape of the first outline of the axial discharge port 44 an optimal shape that adapts to the tooth shape of the screw rotor, etc.

[0060] In some implementations, such as Figure 4 , Figure 6 , Figure 8 as well as Figure 10 As shown, the piston 56 has: a first portion 58; and a second portion 60, which is axially adjacent to the first portion 58, located axially on the discharge side of the first portion 58, and has a larger diameter than the first portion 58. A step portion 61 is formed axially between the first portion 58 and the second portion 60, which restricts the movement of the piston 56 from the second position toward the first position (i.e., axially from the discharge side toward the suction side).

[0061] Furthermore, in the illustrated embodiment, a position limiting surface 76 is provided on the housing 12 facing the discharge side in the axial direction. The position of the piston 56 in the axial direction is limited by the surface of the second part 60 of the piston 56 forming the step portion 61 abutting against the position limiting surface 76.

[0062] By providing the aforementioned stepped portion 61, the movement of the piston 56 from the second position toward the first position is restricted, thus preventing the end face of the piston 56 (the first end face 54a of the movable piece 54) from protruding from the rotor-opposing surface 50 of the housing 12 toward the screw rotor side. Therefore, contact between the piston 56 and the discharge-side end face 48 of the screw rotor can be suppressed.

[0063] In some implementations, such as Figure 4 , Figure 6 , Figure 8 as well as Figure 10 As shown, the screw compressor 2 includes a connecting passage 74 that connects the rear side space 72 exposed on the second end face 54b of the movable plate 54 to the discharge space 43. In the illustrated embodiment, the rear side space 72 is formed between the second end face 54b of the movable plate 54 and the plug 66.

[0064] In addition, such as Figure 4 , Figure 6 , Figure 8 as well as Figure 10 As shown, a force-applying component 62 (e.g., a spring) may also be provided between the movable plate 54 (piston 56) and the plug 66 in the axial direction. This force-applying component 62 is used to apply a preload to the movable plate 54 in the axial direction from the discharge side to the suction side (i.e., from the movable plate 54 towards the screw rotor).

[0065] According to the above embodiment, the first end face 54a of the movable piece 54 faces the toothed space in front of the axial discharge port 44 (i.e., the toothed space before discharge), and the second end face 54b of the movable piece 54 faces the back side space 72 that communicates with the discharge space 43. Therefore, the movable piece 54 can be automatically driven by the pressure difference between the toothed space in front of the axial discharge port 44 and the discharge space 43.

[0066] That is, under operating conditions where the internal volume ratio Vi is relatively low, the toothed space in front of the axial discharge port 44 has a pressure equal to or lower than that of the discharge space 43. At this time, the movable piece 54 is located in the first position due to the pressure difference acting on the two end faces (the first end face 54a and the second end face 54b). On the other hand, under operating conditions where the internal volume ratio Vi is relatively high, the toothed space in front of the axial discharge port 44 becomes a high pressure compared to the discharge space 43. Therefore, due to the pressure difference acting on the first end face 54a and the second end face 54b, a force from the first end face 54a toward the second end face 54b acts on the movable piece 54, and thus the movable piece 54 is located in the second position.

[0067] Thus, according to the above embodiment, the movable piece 54 can be automatically and appropriately driven based on the pressure difference acting on its two end faces (first end face 54a and second end face 54b), so that the movable piece 54 is in a first position when the internal volume ratio Vi is relatively low, and in a second position when the internal volume ratio Vi is relatively high. Therefore, discharge loss can be suppressed over a wide operating range (internal volume ratio Vi).

[0068] Figure 12 and Figure 13 These are schematic cross-sectional views of the vicinity of the axial discharge port 44 of a screw compressor according to one embodiment, showing... Figures 4-11 The illustrated embodiment is a variation. Furthermore, Figure 12 as well as Figure 13 Is with Figure 4 The corresponding diagram (including the diagram of the movable piece 54 in the first position) is omitted, as is the diagram including the movable piece 54 in the second position. Figure 6 (Corresponding diagram). In Figure 12 and Figure 13 In the text, for annotations with... Figures 4-11 Elements with the same symbol as those shown are omitted from the description to avoid repetition.

[0069] exist Figure 12 and Figure 13In the illustrated embodiment, the aforementioned connecting passage 74 is not provided. Instead, the screw compressor 2 of this embodiment includes, on the back side space 72 facing the second end face 54b of the movable plate 54, a high-pressure line 82 for introducing a high-pressure fluid with a higher pressure than the discharge space 43 and a valve 84 provided in the high-pressure line 82. Furthermore, in the illustrated embodiment, the high-pressure fluid from the high-pressure line 82 is introduced into the back side space 72 via an internal flow path 80 provided in the housing 12.

[0070] In one embodiment, oil pressurized by pump 8 in oil supply line 10 (pressure: Pd+α) can also be supplied to the rear side space 72 via high pressure line 82.

[0071] In the above embodiment, by appropriately operating the valve 84, high-pressure fluid can be introduced into the back side space 72 exposed on the second end face 54b of the movable piece 54 via the high-pressure line 82. This allows the movable piece 54 to be forcibly moved from the second position to the first position.

[0072] For example, even when the load on the screw compressor 2 is relatively high and the pressure in the toothed space in front of the axial discharge port 44 is relatively high, the high-pressure fluid from the high-pressure line 82 can be introduced into the back side space 72 by appropriately operating the valve 84 as needed, forcibly moving the movable plate 54 from the second position to the first position, thereby narrowing the opening area of ​​the axial discharge port 44 and increasing the internal volume ratio Vi.

[0073] exist Figure 12 In the exemplary embodiment shown, a throttling orifice 88 is also provided to connect the aforementioned rear side space 72 and the discharge space 43.

[0074] In the above embodiment, the back side space 72 is connected to the discharge space 43 via the throttle orifice 88. Therefore, during the period when the valve 84 is opened and high-pressure fluid is supplied from the high-pressure line 82 to the back side space 72, the pressure in the back side space 72 can be maintained at an appropriate pressure higher than that in the discharge space 43, thus maintaining the movable piece in the first position. In addition, the high-pressure oil in the back side space 72 is appropriately discharged to the discharge space 43 via the throttle orifice 88. Furthermore, during the period when the valve 84 is closed and the supply of high-pressure fluid from the high-pressure line 82 to the back side space 72 is stopped, the pressure in the back side space 72 is equal to the pressure in the discharge space 43. Therefore, as already explained, the movable piece 54 can be automatically driven to move between the first position and the second position by utilizing the pressure difference between the toothed space in front of the axial discharge port 44 and the discharge space 43 (i.e., the pressure difference acting on the first end face 54a and the second end face 54b of the movable piece 54).

[0075] exist Figure 13In the exemplary embodiment shown, the screw compressor 2 includes a low-pressure line 90 connected to a low-pressure source with a lower pressure than the discharge space 43. Furthermore, the valve 84 is configured to switch the connection of the back-side space 72 between the high-pressure line 82 and the low-pressure line 90.

[0076] The aforementioned low-pressure source can be gas with an intake pressure of Ps, and the low-pressure line 90 can also be a branch line from the intake line (not shown) used to introduce intake gas (pressure: Ps) into the screw compressor 2. Additionally, the aforementioned valve 84 can also include a three-way valve disposed between the rear side space 72 and the high-pressure line 82 and the low-pressure line 90.

[0077] In the above embodiment, by appropriately operating the valve 84, the connection object of the back side space 72 exposed on the second end face 54b of the movable plate 54 can be switched between the high-pressure line 82 and the low-pressure line 90. By connecting the back side space 72 to the high-pressure line 82, high-pressure fluid can be introduced into the back side space 72, forcibly moving the movable plate 54 from the second position to the first position. Similarly, by connecting the back side space 72 to the low-pressure line 90, low-pressure fluid from a low-pressure source can be introduced into the back side space 72, forcibly moving the movable plate 54 from the first position to the second position. That is, depending on the operating condition of the screw compressor 2, the operating valve 84 switches the connection object of the back side space 72 between the high-pressure line 82 and the low-pressure line 90, thereby appropriately changing the position of the movable plate 54 between the first and second positions. Therefore, more flexible operation of the screw compressor 2 is possible, and discharge losses can be easily suppressed over a wide operating range (internal volume ratio).

[0078] Thus, according to Figure 12 and Figure 13 The exemplary embodiment shown enables more flexible operation of the screw compressor 2 and easily suppresses discharge losses over a wide operating range (internal volume ratio).

[0079] The contents described in the above embodiments are as follows.

[0080] [1] The screw compressor 2 of at least one embodiment of the present invention comprises: The screw rotor (e.g., male rotor 15 and female rotor 17) has a discharge side end face 48; The housing 2 has a rotor-opposing surface 50 facing the discharge side end face, and an opening 52 disposed on the rotor-opposing surface and communicating with the discharge space 43, wherein the discharge space 43 is for discharging gas compressed by the screw rotor; A slide valve 30, whose position in the axial direction of the screw rotor is variable to change the internal volume ratio; and A movable piece 54, which is disposed along the edge of the opening of the housing, is configured to block part of the opening. The movable piece is configured to move between a first position and a second position, wherein, in the first position, the movable piece, together with the edge of the opening, forms a first profile 101 of an axial discharge port 44, and the second position is axially farther away from the screw rotor compared to the first position. The configuration is such that, when the movable piece is in the second position, a second profile 102 of the axial discharge port is formed through the opening, with an opening area larger than that of the first profile.

[0081] In the structure described above [1], the movable piece, which is provided along the edge of the opening of the housing forming the axial discharge port, can move between a first position in the axial direction and a second position further away from the screw rotor than the first position. Moreover, when the movable piece is in the second position, the opening area of ​​the axial discharge port is larger than when it is in the first position. Therefore, under operating conditions where the internal volume ratio of the screw compressor is relatively high, by placing the movable piece in the second position, the opening area of ​​the axial discharge port can be made relatively large, suppressing the increase in gas flow velocity in the discharge port and thus suppressing the increase in discharge loss. In addition, under operating conditions where the internal volume ratio of the screw compressor is relatively low, by placing the movable piece in the first position, the opening area of ​​the axial discharge port can be made relatively small, suppressing the increase in discharge loss caused by undercompression. Therefore, according to the structure described above [1], by switching the position of the movable piece between the first and second positions according to the internal volume ratio, discharge loss can be suppressed over a wide operating range (internal volume ratio).

[0082] [2] In some embodiments, in the structure described in [1] above, The movable plate includes a piston 56 capable of moving forward and backward in the axial direction.

[0083] Based on the structure described above [2], a screw compressor containing the movable plate described above [1] can be realized with a simple structure using a piston that can move forward and backward in the axial direction.

[0084] [3] In some embodiments, in the structure described in [2] above, The screw compression mechanism becomes, When the movable plate is in the first position, the end face of the piston in the axial direction (e.g., the first end face 54a of the movable plate 54) is flush with the rotor-opposing surface of the housing, and the piston forms part of the first profile.

[0085] According to the structure described above [3], when the movable plate including the piston is in the first position, the end face of the piston is flush with the rotor opposing surface of the housing, and the piston itself forms the outline of the axial discharge port (first outline). Therefore, a screw compressor containing the movable plate described above [1] can be realized with a simple structure.

[0086] [4] In some embodiments, in the structure described in [2] above, The movable plate includes a plate-shaped component 78, which is mounted on the axial end of the piston. The screw compression mechanism becomes, When the movable piece is in the first position, the end face of the plate-like member in the axial direction (e.g., the first end face 54a of the movable piece 54) is flush with the rotor-opposing surface of the housing, and the plate-like member forms part of the first profile.

[0087] According to the structure described above [4], when the movable plate including the plate-shaped member mounted on the end of the piston is in the first position, the end face of the plate-shaped member is flush with the rotor-opposing surface of the housing, and the plate-shaped member forms the outline (first outline) of the axial discharge port. Here, since the plate-shaped member can be any shape, it is easy to make the shape of the first outline of the axial discharge port into an optimal shape that adapts to the tooth shape of the screw rotor, etc.

[0088] [5] In some embodiments, in any of the structures described in [2] to [4] above, The piston has: Part 1, 58; and The second part 60, which is disposed axially across the first part on the side opposite to the screw rotor, and has a larger diameter than the first part. The screw compressor restricts the movement of the piston from the second position toward the first position by means of a stepped portion 61 formed by the first portion and the second portion.

[0089] According to the structure described above [5], the piston's movement from the second position to the first position is restricted by the stepped portion of the piston, thus preventing the piston's end face from protruding from the rotor-opposing surface of the housing towards the screw rotor side. Therefore, contact between the piston and the end face of the screw rotor can be suppressed.

[0090] [6] In some embodiments, in any of the structures described in [1] to [5] above, The movable plate has a first end face 54a opposite to the screw rotor, and a second end face 54b on the axial side opposite to the first end face. The screw compressor has a connecting passage 74 that connects the rear side space 72 exposed on the second end face to the discharge space.

[0091] According to the structure described above [6], the first end face of the movable piece faces the toothed space in front of the axial discharge port (i.e., the toothed space before discharge), and the second end face of the movable piece faces the back side space communicating with the discharge space. Therefore, the movable piece can be automatically driven by the pressure difference between the toothed space and the discharge space. That is, the movable piece can be automatically and appropriately driven according to the pressure difference, so that the movable piece is in the first position when the internal volume ratio is relatively low, and in the second position when the internal volume ratio is relatively high.

[0092] [7] In some embodiments, in any of the structures described in [1] to [5] above, The movable plate has a first end face 54a opposite to the screw rotor, and a second end face 54b on the axial side opposite to the first end face. The screw compressor includes: High-pressure conduit 82, used to introduce a high-pressure fluid with a higher pressure than the discharge space into the rear side space 72 exposed on the second end face; and Valve 84 is disposed between the rear side space and the high-pressure pipeline.

[0093] According to the structure described above [7], by appropriately operating the valve, high-pressure fluid can be introduced into the back side space exposed on the second end face of the movable plate through the high-pressure pipeline, thereby forcibly moving the movable plate from the second position to the first position. Therefore, for example, even when the load of the screw compressor is relatively high and the pressure of the toothed space in front of the axial discharge port is relatively high, high-pressure fluid can be introduced into the back side space by operating the valve as needed, forcibly moving the movable plate from the second position to the first position, thereby narrowing the opening area of ​​the discharge port and increasing the internal volume ratio. Therefore, the screw compressor can be operated more flexibly, and discharge losses can be easily suppressed in a wide range of operating areas (internal volume ratio).

[0094] [8] In some embodiments, in the structure described in [7] above, It has a throttling orifice 88 that connects the back side space exposed on the second end face to the discharge space.

[0095] According to the structure described above [8], since the back side space is connected to the discharge space via the throttle orifice, when the valve is opened and high-pressure fluid is supplied from the high-pressure line to the back side space, the pressure in the back side space can be maintained at an appropriate pressure higher than that in the discharge space, thus keeping the movable piece in the first position. In addition, when the valve is closed and the supply of high-pressure fluid from the high-pressure line to the back side space is stopped, the pressure in the back side space is equal to the pressure in the discharge space. Therefore, similar to the description in [6] above, the movable piece can be automatically driven by the pressure difference between the toothed space in front of the axial discharge port and the discharge space.

[0096] [9] In some embodiments, in the structure described in [7] above, It includes a low-pressure line 90, which is connected to a low-pressure source with a lower pressure than the discharge space. The valve is configured to switch the connection of the rear-side space between the high-pressure line and the low-pressure line.

[0097] According to the structure described above [9], by appropriately operating the valve, the connection object of the back side space exposed on the second end face of the movable plate can be switched between the high-pressure pipeline and the low-pressure pipeline. Here, by connecting the back side space to the high-pressure pipeline, high-pressure fluid can be introduced into the back side space, forcibly moving the movable plate from the second position to the first position, and by connecting the back side space to the low-pressure pipeline, low-pressure fluid from the low-pressure source can be introduced into the back side space, forcibly moving the movable plate from the first position to the second position. That is, depending on the operating condition of the screw compressor, the operating valve switches the connection object of the back side space between the high-pressure pipeline and the low-pressure pipeline, thereby appropriately changing the position of the movable plate between the first position and the second position. Therefore, the screw compressor can be operated more flexibly, and discharge losses can be easily suppressed within a wide operating range (internal volume ratio).

[0098]

[10] The gas compression apparatus 1 according to at least one embodiment of the present invention includes: The screw compressor 2 described in any one of [1] to [9] above is configured to compress gas; and Oil separator 4 is used to separate the oil from the mixture of compressed gas and oil discharged from the screw compressor described above.

[0099] In the structure described above

[10] , the movable piece, which is provided along the edge of the opening of the housing forming the discharge port, can move axially between a first position and a second position further away from the screw rotor than the first position. Moreover, when the movable piece is in the second position, the opening area of ​​the axial discharge port is larger than when it is in the first position. Therefore, under operating conditions where the internal volume ratio of the screw compressor is relatively high, by placing the movable piece in the second position, the opening area of ​​the axial discharge port can be made relatively large, suppressing the increase in gas flow velocity in the discharge port and suppressing the increase in discharge loss. In addition, under operating conditions where the internal volume ratio of the screw compressor is relatively low, by placing the movable piece in the first position, the opening area of ​​the axial discharge port can be made relatively small, suppressing the increase in discharge loss caused by undercompression. Therefore, according to the structure described above

[10] , by switching the position of the movable piece between the first and second positions according to the internal volume ratio, discharge loss can be suppressed over a wide operating range (internal volume ratio).

[0100] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and also includes modifications to the above embodiments and appropriate combinations of these embodiments.

[0101] In this specification, expressions such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," which indicate relative or absolute configuration, do not only refer to configuration in a strict sense, but also to a state of relative displacement of angle or distance with tolerance or to the extent that the same function can be obtained.

[0102] For example, expressions such as "same," "equal," and "homogeneous" that indicate that things are in an equal state do not only mean that they are strictly equal, but also that there is a difference in degree or that they can achieve the same function.

[0103] Furthermore, in this specification, the terms "quadrilateral shape," "cylindrical shape," etc., which refer to shapes, not only refer to shapes in a strictly geometric sense, but also to shapes that include concave and convex parts, chamfered parts, etc., within the range that can achieve the same effect.

[0104] Furthermore, in this specification, the expressions "have," "possess," "comprise," "include," or "have" one of the constituent elements are not exclusive expressions that exclude the existence of other constituent elements.

[0105] Explanation of reference numerals in the attached figures 1. Gas compression equipment 2 Screw compressor 4. Oil separator 6. Cooler 8 pumps 10. Oil supply lines 12. Shell 14 Rotor shaft 15 Male Rotor 16 Rotor shafts 17. Female rotor 18 Radial bearings 20 Thrust bearing 24 Shaft seal 28 Balanced Piston 29 Balanced piston chamber 30 Spool valve 31 Incision 32 Hydraulic Piston 40 Suction Port 41. Inhalation Space 42 Discharge Port 43 Exhaust space 44 Axial discharge port 46 Radial discharge port 48 Discharge side end face 50 Rotor Opposite Face 52 Opening 54 movable pieces 54a First end face 54b Second end face 56 Pistons 58 Part 1 60 Part Two 61 Steps 62 Force-applying components 66. Stopper 68 holes 72 Rear Side Space 74 Connecting Paths 76 Position-restricted surfaces 78 Plate-shaped components 80 Internal flow path 82 High-pressure pipeline 84 valve 88 throttle orifice 90 Low-pressure pipeline 101 First Outline 102 Second Outline Pd discharge pressure Ps Inhalation pressure

Claims

1. A screw compressor, comprising: A screw rotor having a discharge side end face; The housing has a rotor-opposing surface facing the discharge side end face, and an opening disposed on the rotor-opposing surface and communicating with the discharge space, wherein, The discharge space is for discharging the gas compressed by the screw rotor; A slide valve, whose position in the axial direction of the screw rotor is variable to change the internal volume ratio; as well as A movable piece, disposed along the edge of the opening in the housing, is configured to block a portion of the opening. The movable plate is configured to move between a first position and a second position, wherein, in the first position, the movable plate, together with the edge of the opening, forms a first profile of an axial discharge port, and the second position is axially farther away from the screw rotor compared to the first position. The configuration is such that, when the movable piece is in the second position, a second profile of the axial discharge port is formed through the opening, with an opening area larger than the first profile.

2. The screw compressor according to claim 1, characterized in that, The movable plate includes a piston capable of moving forward and backward in the axial direction.

3. The screw compressor according to claim 2, characterized in that, The piston is configured such that, when the movable plate is in the first position, the end face of the piston in the axial direction is flush with the rotor-opposing surface of the housing, and the piston forms part of the first profile.

4. The screw compressor according to claim 2, characterized in that, The movable plate includes a plate-like component mounted on the axial end of the piston. The screw compression mechanism is configured such that, when the movable plate is in the first position, the end face of the plate-shaped member in the axial direction is flush with the rotor-opposing surface of the housing, and the plate-shaped member forms part of the first profile.

5. The screw compressor according to any one of claims 2 to 4, characterized in that, The piston has: Part One; and The second part, which is disposed axially on the opposite side of the screw rotor, separated from the first part, and has a larger diameter than the first part. The step portion formed by the first part and the second part restricts the movement of the piston from the second position toward the first position.

6. The screw compressor according to any one of claims 1 to 4, characterized in that, The movable plate has a first end face opposite to the screw rotor and a second end face on the axial direction opposite to the first end face. It has a connecting passage that connects the exposed rear side space of the second end face with the discharge space.

7. The screw compressor according to any one of claims 1 to 4, characterized in that, The movable plate has a first end face opposite to the screw rotor and a second end face on the axial direction opposite to the first end face. The screw compressor includes: A high-pressure pipeline for introducing a high-pressure fluid with a higher pressure than the discharge space into the rear-side space exposed at the second end face; and A valve is disposed between the rear side space and the high-pressure pipeline.

8. The screw compressor according to claim 7, characterized in that, It has a throttling orifice that connects the rear side space exposed on the second end face to the discharge space.

9. The screw compressor according to claim 7, characterized in that, It includes a low-pressure pipeline connected to a low-pressure source with a lower pressure than that of the discharge space. The valve is configured to switch the connection of the rear-side space between the high-pressure line and the low-pressure line.

10. A gas compression device, comprising: The screw compressor according to any one of claims 1 to 4 is configured to compress a gas; and An oil separator is used to separate the oil from the mixture of compressed gas and oil discharged from the screw compressor.

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