Multi-stage compressor and method for recovery of gear chamber internal pressure in multi-stage compressor

Abstract

To reduce the gear chamber internal pressure of a multi-stage compressor to extend the service life of an oil seal.SOLUTION: A lubricating oil recovery passage 5 is provided that provides communication between an oil reservoir 75 at the bottom of a gear chamber 71, which is formed in a gear casing 70 attached to the suction side ends of a low-pressure stage compressor body 20 and a high-pressure stage compressor body 30, and a lubrication oil recovery port 29 provided in the low-pressure stage compressor body 20, to recover lubrication oil in the gear chamber 71 into the low-pressure stage compressor body 20 by utilizing a pressure within the gear chamber 71. At least one communication hole 28 is provided in the end wall (inlet casing) 53 covering the suction side end of a low-pressure stage cylinder 22 at a position higher than a liquid level in the oil reservoir 75, to provide communication between the space within the gear chamber 71 and a suction space 27 formed in the low-pressure stage compressor body 20. As a result, compressed gas in the gear chamber 71 is recovered into the suction space 27 of the low-pressure stage compressor body 20, which is under negative pressure, thereby reducing the pressure in the gear chamber.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a multi-stage compressor capable of recovering internal pressure in a gear chamber, and a method for recovering internal pressure in a gear chamber in the multi-stage compressor. [Background technology]

[0002] A multi-stage compressor is a compressor in which the discharge port of the low-pressure stage compressor body is connected to the intake port of the high-pressure stage compressor body via an intermediate stage flow path, so that the compressed gas generated in the low-pressure stage compressor body can be introduced into the high-pressure stage compressor body via the intermediate stage flow path and further compressed, and is used in applications where high-pressure compressed gas is required.

[0003] As an example of the configuration of such a multi-stage compressor, an example of the configuration of a multi-stage compressor described in Patent Document 1, which will be described later, is shown in FIG.

[0004] The multi-stage compressor 100 shown in FIG. 10 comprises a cylinder casing 111 in which a low-pressure stage cylinder 122 and a high-pressure stage cylinder 132 are formed in parallel, end covers 151, 152 that cover the discharge side end of the cylinder casing 111, and a gear casing 170 that covers the suction side end of the cylinder casing 111, and a pair of male and female screw rotors 123, 124; 133, 134 (the screw rotors 124, 134 are hidden on the back side of the screw rotors 123, 133 in the figure) are meshed with each other in the low-pressure stage cylinder 122 and the high-pressure stage cylinder 132, respectively. The low-pressure stage compressor body 120 and the high-pressure stage compressor body 130 are formed by rotatably housing the screw rotors 123a, 124a; 133a, 134a of the screw rotors 123, 124; 133, 134 with bearings 161, 164 provided in the end covers 151, 152, and by rotatably supporting the discharge side rotor shafts 123a, 124a; 133a, 134a of the screw rotors 123, 124; 133, 134 with bearings 163, 166 provided in shaft holes formed in the suction side end wall 153 of the cylinder casing 111.

[0005] Of the suction side rotor shafts 123b, 124b; 133b, 134b, the rotor shafts (in the illustrated example, the suction side rotor shafts 123b, 133b of the male rotors 123, 133) that penetrate the suction side end wall 153 of the cylinder casing 111 and protrude into a gear chamber 171 formed in the gear casing 170 are respectively attached to driven gears 182, 183, and a drive gear 181 attached to an input shaft 190 inserted into the gear chamber 171 through a shaft hole 172 that penetrates the thickness of the gear casing 170. By providing this, when the input shaft 190 is rotated by a driving source such as a motor or engine (not shown), the drive gear 181 attached to the input shaft 190 rotates the driven gears 182, 183 attached to the rotor shafts 123b, 133b, thereby allowing both the low-pressure stage compressor body 120 and the high-pressure stage compressor body 130 to rotate, and in the example shown, the driven gears 182, 183 are formed to have a smaller diameter than the drive gear 181, thereby giving the aforementioned gear mechanism 180 the function of a speed-up device (Figure 1 of Patent Document 1).

[0006] In the multi-stage compressor 100 of Figure 10, the intermediate stage flow path 140 that connects the discharge port 125 of the low-pressure stage compressor main body 120 and the intake port 136 of the high-pressure stage compressor main body 130 is formed as a space independent of the gear chamber 171. However, with the aim of making the multi-stage compressor more compact, multi-stage compressors have also been proposed that adopt a configuration in which the discharge port of the low-pressure stage compressor main body and the intake port of the high-pressure stage compressor main body are connected via the intermediate stage flow path and the space within the gear chamber (see Figure 1 of Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-110760 [Patent Document 2] Japanese Patent Application Publication No. 9-53583 Summary of the Invention [Problem to be solved by the invention]

[0008] In the configuration of the multi-stage compressor described in Patent Document 2 mentioned above, the discharge port of the low-pressure stage compressor body and the intake port of the high-pressure stage compressor body are connected via the intermediate stage flow path and the space within the gear chamber, so the pressure within the gear chamber is approximately the same as the pressure within the intermediate stage flow path, resulting in a relatively high pressure.

[0009] Furthermore, in the multi-stage compressor 100 of Patent Document 1 described with reference to Figure 10, the gear chamber 171 is formed as a chamber partitioned from the low-pressure stage compressor main body 120, the high-pressure stage compressor main body 130, and the intermediate stage flow path 140, but since the suction side rotor shaft 133b of the high-pressure stage compressor main body 130 protrudes into the gear chamber 171 through a shaft hole (bearing chamber in which the bearing 166 is accommodated) formed in the suction side end wall 153 of the cylinder casing 111, the space within the gear chamber 171 is connected to the suction side space of the high-pressure stage compressor main body 130 through this shaft hole.

[0010] Therefore, even in the configuration of the multi-stage compressor described in Patent Document 1, which was explained with reference to Figure 10, the pressure inside the gear chamber 171 is approximately the same as the pressure in the bearing chamber (the part where the bearing 166 is housed) on the suction side of the high-pressure stage compressor main body 130, and is therefore relatively high.

[0011] In addition, in the configurations of the multi-stage compressors of either of Patent Documents 1 and 2 mentioned above, when pressurized oil is introduced into the gear chamber 171 to supply oil to the gear mechanism 180 housed in the gear chamber 171, the pressure in the gear chamber 171 can also increase due to the introduction of this pressurized oil.

[0012] In this way, when the pressure inside the gear chamber 171 is high, if a lip seal is used as the oil seal 173 that seals the gap between the outer periphery of the input shaft 190 and the shaft hole 172, the pressure inside the gear chamber 171 increases the force pressing the lip of the lip seal against the outer periphery of the input shaft 190, thereby increasing the contact area between the lip seal and the input shaft 190.

[0013] When the input shaft 190 is rotated with the contact area increased in this way, the increased frictional resistance causes the lip seal to wear out in a relatively short period of time, or it may seize up and lose its sealing ability early, requiring frequent replacement, which complicates maintenance work and increases running costs.

[0014] One way to solve this problem is to construct the oil seal 173 using a mechanical seal instead of the lip seal mentioned above, but since mechanical seals are expensive and heavy, using a mechanical seal would increase the manufacturing cost of the multi-stage compressor 100 and could be a factor in increasing the weight of the multi-stage compressor 100 as a whole.

[0015] Therefore, even if a contact seal such as a lip seal is used as the oil seal 173 that seals the gap between the shaft hole 172 provided in the gear casing 170 and the input shaft 190, it is desirable to keep the pressure inside the gear chamber 171 as low as possible so as to extend the life of the oil seal 173.

[0016] On the other hand, since lubricating oil is supplied to the gear mechanism 180 (drive gear 181 and driven gears 182, 183) housed in the gear chamber, the bearing 167 supporting the input shaft 190, etc., the lubricating oil supplied to these parts accumulates in the gear chamber 171, and therefore it is necessary to discharge the lubricating oil introduced into the gear chamber 171 from the gear chamber 171 and recover it in the lubricating oil circulation system.

[0017] In this way, when the configuration for recovering the lubricating oil in the gear chamber 171 is such that, for example, the bottom of the gear chamber 171 communicates with the inside of the low-pressure stage compressor main body 120 (not shown) via a lubricating oil recovery passage (not shown) and the lubricating oil is recovered using the pressure in the gear chamber 171, if the pressure in the gear chamber 171 is reduced excessively, the lubricating oil cannot be smoothly discharged from the gear chamber 171, and the driven gear 183 of the high-pressure stage compressor main body 130 stirs the oil surface, increasing the power of the compressor. Also, there is a possibility that insufficient or insufficient supply of lubricating oil to the low-pressure stage compressor main body 120 will occur.

[0018] Therefore, when adopting a configuration that provides the aforementioned lubricating oil recovery path (not shown), even if the pressure in the gear chamber 171 is reduced for the purpose of protecting the oil seal 173, etc., it is necessary to adjust the pressure in the gear chamber 171 after the reduction, taking into consideration the balance between the two, so as not to hinder the discharge of lubricating oil from the gear chamber 171 or the supply of oil to the low-pressure stage compressor body.

[0019] Furthermore, if the pressure inside the gear chamber 171 is simply to be reduced, it is possible to reduce the pressure by releasing the compressed gas inside the gear chamber 171 into the atmosphere, for example.

[0020] However, if the pressure in the gear chamber 171 is reduced by releasing it into the atmosphere, the pressure energy of the compressed gas in the gear chamber 171 will be wasted, so it is desirable to recover the pressure in the gear chamber 171 so that it can be used to improve the performance of the multi-stage compressor.

[0021] The present invention has been made based on the points of view described above, and its first object is to provide a multi-stage compressor that can recover the internal pressure of the gear chamber and reduce the pressure inside the gear chamber with a relatively simple configuration, and a method for recovering pressure inside the gear chamber in a multi-stage compressor.

[0022] Furthermore, the second object of the present invention is to provide a multi-stage compressor that can easily perform fine adjustment of the gear chamber pressure, and a method for recovering gear chamber pressure in a multi-stage compressor, thereby making it possible to easily reduce the pressure in the gear chamber while maintaining the internal pressure in the gear chamber required for recovering the lubricating oil, even when a configuration is adopted in which the pressure in the gear chamber is used to recover the lubricating oil in the gear chamber.

[0023] Furthermore, a third object of the present invention is to provide a multi-stage compressor and a method for recovering pressure inside the gear chamber of a multi-stage compressor, in which the internal pressure of the gear chamber recovered as described above can be utilized to improve the performance of the multi-stage compressor. [Means for solving the problem]

[0024] The means for solving the problems are described below together with the reference numerals used in the description of the embodiment of the invention. These reference numerals are intended to clarify the correspondence between the claims and the description of the embodiment of the invention, and needless to say, are not used to restrict the interpretation of the technical scope of the present invention.

[0025] In order to achieve the above object, the multi-stage compressor 1 of the present invention comprises: The low-pressure stage cylinder 22 and the high-pressure stage cylinder 32 provided in the cylinder casing 11 (21, 31) are provided with male rotors 23, 33 and female rotors 24, 34, respectively, which are meshed and rotatably accommodated therein, thereby forming an oil-cooled low-pressure stage compressor body 20 and a high-pressure stage compressor body 30 that compress the gas to be compressed together with lubricating oil, and also forming a gear chamber 71 in a gear casing 70 attached to the suction side end of the cylinder casing 11 (21, 31). The suction side rotor shaft of the low-pressure stage compressor body 20 (the suction side rotor shaft 23b of the male rotor 23 in the illustrated example) protrudes into the gear chamber 71 through an end wall (inlet casing) 53 that covers the suction side end of the low-pressure stage cylinder 22. ), driven gears 82, 83 respectively attached to the suction side rotor shaft of the high-pressure stage compressor main body 30 (in the illustrated example, the suction side rotor shaft 33b of the male rotor 33) which penetrates the end wall 54 covering the suction side end of the high-pressure stage cylinder 32 and protrudes into the gear chamber 71, and a gear mechanism 80 consisting of a drive gear 81 attached to an input shaft 90 which penetrates the gear casing 70 and is inserted into the gear chamber 71 is housed in the gear chamber 71, and the low-pressure stage compressor main body 20 and the high-pressure stage compressor main body 30 can both be rotated by the rotation of the input shaft 90, and an oil reservoir 75 for lubricating oil introduced into the gear chamber 71 is formed at the bottom of the gear chamber 71, The low-pressure stage compressor body 20 is provided with a lubricating oil recovery port 29 communicating with the inside of the low-pressure stage compressor body 20, and a lubricating oil recovery passage 5 is provided that connects the oil reservoir 75 at the bottom of the gear chamber 71 with the lubricating oil recovery port 29, The end wall (inlet casing) 53 covering the suction side end of the low-pressure stage cylinder 22 is characterized in that it has at least one communication hole 28 that connects the space within the gear chamber 71 to the suction space 27 formed within the low-pressure stage compressor main body 20 at a position higher than the liquid level of the oil reservoir 75 (Claim 1, Figure 2).

[0026] In the multi-stage compressor 1 having the above configuration, the communication hole 28 can be made to open near the bottom of the suction space 27 on the lower end side of either the male rotor 23 or the female rotor 24 of the low-pressure stage compressor main body 20, or both (Claim 2: see Figures 2 to 6).

[0027] In addition, in a configuration in which a shield 45 is provided in the low-pressure stage compressor body 20 below the intake port 26 to cover the meshing portion between the male rotor 23 and the female rotor 24, and a support 46 is provided on the upper inner wall of the low-pressure stage cylinder 22 to suspend the end 45a of the shield 45 on the gear chamber 71 side, The communication hole 28 opening toward the support 46 may be provided in the end wall (inlet casing) 53 at a position higher than the meshing portion of the male rotor 23 and the female rotor 24 (Claim 3: see Figures 7 and 8).

[0028] Further, the gear chamber pressure recovery method in the multistage compressor 1 of the present invention is as follows: The low-pressure stage cylinder 22 and the high-pressure stage cylinder 32 provided in the cylinder casing 11 (21, 31) are provided with male rotors 23, 33 and female rotors 24, 34, respectively, which are meshed and rotatably accommodated therein, thereby forming an oil-cooled low-pressure stage compressor body 20 and a high-pressure stage compressor body 30 that compress the gas to be compressed together with lubricating oil, and also forming a gear chamber 71 in a gear casing 70 attached to the suction side end of the cylinder casing 11 (21, 31). The suction side rotor shaft of the low-pressure stage compressor body 20 (in the illustrated example, the suction side rotor shaft 23 of the male rotor 23) protrudes into the gear chamber 71 through an end wall (inlet casing) 53 that covers the suction side end of the low-pressure stage cylinder 22. b), driven gears 82, 83 respectively attached to the suction side rotor shaft of the high-pressure stage compressor body 30 (in the illustrated example, the suction side rotor shaft 33b of the male rotor 33) which penetrates the end wall 54 covering the suction side end of the high-pressure stage cylinder 32 and protrudes into the gear chamber 71, and a gear mechanism 80 consisting of a drive gear 81 attached to an input shaft 90 which penetrates the gear casing 70 and is inserted into the gear chamber 71 is housed in the gear chamber 71, and the low-pressure stage compressor body 20 and the high-pressure stage compressor body 30 can both be rotated by the rotation of the input shaft 90, and an oil reservoir 75 for lubricating oil introduced into the gear chamber is formed at the bottom of the gear chamber 71, The low-pressure stage compressor body 20 is provided with a lubricating oil recovery port 29 communicating with the inside of the low-pressure stage compressor body 20, and a lubricating oil recovery passage 5 is provided that connects the oil reservoir 75 at the bottom of the gear chamber 71 with the lubricating oil recovery port 29, The end wall (inlet casing) 53 covering the suction side end of the low-pressure stage cylinder 22 is provided with at least one communication hole 28 that connects the space within the gear chamber 71 to the suction space 27 formed within the low-pressure stage compressor main body 20 at a position higher than the liquid level of the oil reservoir 75, thereby allowing the compressed gas in the gear chamber 71 to be recovered into the suction space 27 of the low-pressure stage compressor main body 20 (Claim 4).

[0029] In the gear chamber pressure recovery method in a multi-stage compressor of the above configuration, the compressed gas in the gear chamber 71 may be recovered by opening the communication hole 28 near the bottom of the suction space 27 at the lower end side of either the male rotor 23 or the female rotor 24 of the low-pressure stage compressor main body 20, or both (Claim 5: see Figures 2 to 6).

[0030] In addition, in a configuration in which a shield 45 is provided in the low-pressure stage compressor body 20 below the intake port 26 to cover the meshing portion between the male rotor 23 and the female rotor 24, and a support 46 is provided on the upper inner wall of the low-pressure stage cylinder 22 to suspend the end 45a of the shield 45 on the gear chamber 71 side, The communication hole 28, which opens toward the support 46, may be provided in the end wall (inlet casing) 53 at a position higher than the meshing portion of the male rotor 23 and the female rotor 24, thereby recovering the compressed gas in the gear chamber 71 (Claim 6: see Figures 7 and 8).

[0031] In any of the above methods, the amount of compressed gas recovered to the suction space 27 of the low-pressure stage compressor main body 20 can be adjusted by selecting one or a combination of the size, number, and position of the communication holes 28 formed in the end wall (inlet casing) 53 covering the suction side end of the low-pressure stage cylinder 22 (Claims 7 and 8). [Effects of the Invention]

[0032] With the configuration of the present invention described above, the present invention can achieve the following significant effects.

[0033] At least one communication hole 28 is provided in the end wall (inlet casing) 53 covering the suction end of the low-pressure stage cylinder 22, at a position higher than the liquid level of the oil reservoir 75 formed at the bottom of the gear chamber 71, connecting the space within the gear chamber 71 with the suction space 27 of the low-pressure stage compressor main body 20, thereby making it possible to reduce the pressure within the gear chamber 71 by recovering the compressed gas within the gear chamber 71 into the suction space 27 of the low-pressure stage compressor main body 20.

[0034] As a result, even when a lip seal is used as the oil seal 73 that seals the gap between the shaft hole 72 provided in the gear casing 70 and the input shaft 90, the life of the oil seal 73 can be extended.

[0035] Furthermore, by recovering the internal pressure of the gear chamber 71 as described above by providing a communication hole 28 in the end wall (inlet casing) 53 covering the suction end of the low-pressure stage cylinder 22, it is possible to finely adjust the amount of compressed gas recovered in the suction space 27 by selecting one or a combination of the size of the communication holes 28 provided in the end wall (inlet casing) 53, the number of holes to be formed, and the position of the holes to be formed.This makes it possible to easily adjust the pressure in the gear chamber 71 to be reduced while maintaining the pressure in the gear chamber 71 necessary for recovering the lubricating oil in the gear chamber 71 by the lubricating oil recovery path 5.

[0036] In addition, lubricating oil, for example, supplied to bearings 63, accumulates at the bottom of suction space 27, and the rotating rotors 23, 24 scoop up and splash this accumulated lubricating oil, causing the lubricating oil to adhere to the surfaces of the rotors 23, 24 and being introduced into the compression action space, which is also used for lubricating, cooling, and sealing the low-pressure stage compressor main body 20.However, in a configuration in which the above-mentioned communication hole 28 is opened near the bottom of suction space 27 at the lower end side of either the male rotor 23 or the female rotor 24, or both, the lubricating oil that has accumulated at the bottom of suction space 27 can be splashed by the compressed gas that is introduced and sprayed into suction space 27 through the communication hole 28.

[0037] As a result, the lubricating oil scattered by the compressed gas introduced from the gear chamber 71 can be used to lubricate the rotors 23, 24 and seal the compression action space, while the rotational resistance of the rotors 23, 24 is reduced by eliminating the need to scoop up the lubricating oil, thereby reducing the fuel consumption and power consumption required to drive the multi-stage compressor 1.

[0038] Furthermore, if the aforementioned communication hole 28 is provided only on the lower end side of either the male rotor 23 or the female rotor 24, it is possible to reduce the internal pressure of the gear chamber 71 to a lower pressure by connecting the communication hole 28 to the suction space 27 at the lower end side of the male rotor 23, where a greater negative pressure is generated compared to the lower end side of the female rotor 24.

[0039] Furthermore, since the male rotor 23 has a larger diameter than the female rotor 24, the inner diameter of the low-pressure stage cylinder 22 is also larger on the male rotor 23 side, and the bottom of the suction space 27 on the lower end side of the male rotor 23 is positioned lower than the suction space 27 on the lower end side of the female rotor 24.

[0040] As a result, more lubricating oil accumulates at the bottom of the suction space 27 on the lower end side of the male rotor 23 than on the lower end side of the female rotor 24, so when the rotors 23, 24 rotate, the male rotor 23 experiences greater rotational resistance.Therefore, if the communication hole 28 is provided only on the lower end side of either the male rotor 23 or the female rotor 24, adopting a configuration in which the communication hole 28 is opened on the lower end side of the male rotor 23 to splash out the lubricating oil accumulated in this part can more efficiently reduce the rotational resistance of the rotors 23, 24.

[0041] Furthermore, in a configuration in which a shield 45 is provided in the low-pressure stage compressor main body 20 below the intake port 26 to cover the meshing portion between the male rotor 23 and the female rotor 24, and a support 46 is provided to suspend the gear chamber 71 side end 45a of this shield 45 from the upper inner wall of the low-pressure stage cylinder 22, as shown in Figure 9 (A), the support 46 provides resistance to the flow of compressed gas toward the gear chamber 71 side within the intake space 27, causing a vortex to occur on the back side of the support 46 (the gear chamber 71 side of the support 46), and the generation of this vortex reduces the intake efficiency of the low-pressure stage compressor main body 20.

[0042] In contrast, in a configuration in which the aforementioned communication hole 28 is connected to the suction space 27 so as to open toward the support 46 at a position higher than the meshing position of the male rotor 23 and the female rotor 24, the compressed gas introduced and ejected into the suction space 27 through the communication hole 28 stirs the air on the back side of the support 46 (the gear chamber 71 side of the support 46), suppressing the generation of vortices (see Figure 9 (B)), thereby improving the intake efficiency of the low-pressure stage compressor main body 20. [Brief explanation of the drawings]

[0043] [Figure 1] 1 is a schematic explanatory diagram of a multi-stage compressor according to the present invention; [Figure 2] 1 is a cross-sectional view of a multi-stage compressor according to the present invention. [Figure 3] 2 is a cross-sectional view of a main portion of a low-pressure stage compressor body according to an embodiment of the present invention. FIG. [Figure 4] FIG. 4 is an explanatory diagram of the positions where communication holes are formed in the embodiment of FIG. 3. [Figure 5] FIG. 4 is a cross-sectional view of a main portion of a low-pressure stage compressor body according to another embodiment of the present invention. [Figure 6] FIG. 6 is an explanatory diagram of the positions where communication holes are formed in the embodiment of FIG. 5. [Figure 7] FIG. 10 is a cross-sectional view of a main portion of a low-pressure stage compressor body according to still another embodiment of the present invention. [Figure 8] FIG. 8 is an explanatory diagram of the positions where communication holes are formed in the embodiment of FIG. 7. [Figure 9] This is an analytical image (left) and a schematic diagram (right) of the flow of intake gas in the main body of a low-pressure compressor equipped with a shield and support below the intake port. (A) shows the state where gear chamber pressure is not being recovered to the intake space, and (B) shows the state where gear chamber pressure is being recovered through a communication hole that opens toward the support. [Figure 10] 1 is a cross-sectional view of a conventional multi-stage compressor (corresponding to FIG. 1 of Patent Document 1). DETAILED DESCRIPTION OF THE INVENTION

[0044] The configuration of the multi-stage compressor of the present invention will be described below with reference to the accompanying drawings.

[0045] In Figures 1 and 2, symbol 1 is a multi-stage compressor of the present invention, and this multi-stage compressor 1 is equipped with a low-pressure stage compressor main body 20 and a high-pressure stage compressor main body 30, both of which are oil-cooled types that compress the gas to be compressed together with lubricating oil, and is configured so that the discharge port 25 of the low-pressure stage compressor main body 20 is connected to the intake port 36 of the high-pressure stage compressor main body 30 via an intermediate stage flow path 40, thereby allowing the compressed gas generated in the low-pressure stage compressor main body 20 to be further compressed in the high-pressure stage compressor main body 30.

[0046] The compressed gas discharged from the high-pressure stage compressor main body 30 as a gas-liquid mixed fluid with lubricating oil is introduced into a receiver tank 7 connected to the discharge port 35 of the high-pressure stage compressor main body 30, where it is separated into lubricating oil and compressed gas, and the compressed gas after the lubricating oil has been separated can be supplied to the consumer side.

[0047] On the other hand, the lubricating oil recovered in the receiver tank 7 passes through an oil cooler 8a and an oil filter 8b provided in the oil supply flow path 8, and then is introduced into an oil supply port 9 provided in the low-pressure stage compressor main body 20, and is introduced through the oil supply port 9 into the compression action space after the intake air is trapped in the low-pressure stage compressor main body 20, and is used for lubricating, cooling, and sealing the low-pressure stage compressor main body 20, and a portion of the lubricating oil is also introduced into the gear chamber 71 to supply oil to the gear mechanism 80.

[0048] As shown in Figure 2, this multi-stage compressor 1 has a cylinder casing 11 in which a low-pressure stage cylinder 22 and a high-pressure stage cylinder 32 are formed, and the low-pressure stage cylinder 22 and high-pressure stage cylinder 32 formed within this cylinder casing 11 respectively house male rotors 23, 33 and female rotors 24, 34 in a meshed and rotatable manner, thereby forming the low-pressure stage compressor main body 20 and high-pressure stage compressor main body 30.

[0049] In the embodiment shown in Figure 2, a low-pressure stage cylinder casing 21 having a low-pressure stage cylinder 22 formed therein and a high-pressure stage cylinder casing 31 having a high-pressure stage cylinder 32 formed therein are provided separately, and the cylinder casing 11 is formed by arranging the low-pressure stage cylinder casing 21 and the high-pressure stage cylinder casing 31 in parallel, but it is also possible to adopt a configuration in which both a low-pressure stage cylinder 122 and a high-pressure stage cylinder 132 are provided within a single cylinder casing 111, as in the conventional multi-stage compressor 100 described with reference to Figure 10, and the configuration of the cylinder casing 11 is not limited to the configuration shown in Figure 1.

[0050] In the illustrated embodiment, the low-pressure stage compressor body 20 is composed of the low-pressure stage cylinder casing 21 with the low-pressure stage cylinder 22 formed therein, an end cover 51 covering the discharge end of the low-pressure stage cylinder casing 21, an inlet casing 53 forming an end wall covering the suction end of the low-pressure stage cylinder casing 21, and a male rotor 23 and a female rotor 24 (in FIG. 1, the female rotor 24 is hidden behind the male rotor 23) that are accommodated in the low-pressure stage cylinder 22 so as to be able to mesh and rotate. With the male rotor 23 and female rotor 24 housed in the low-pressure stage cylinder casing 21, an end cover 51 is attached to the discharge side end of the low-pressure stage cylinder casing 21 and an inlet casing 53 is attached to the suction side end, so that the discharge side rotor shafts 23a (24a) of the male rotor 23 and female rotor 24 of the low-pressure stage compressor main body 20 are rotatably supported by bearings 61, 62 provided in the end cover 51, and the suction side rotor shafts 23b (24b) of the male rotor 23 and female rotor 24 of the low-pressure stage compressor main body 20 are rotatably supported by bearing 63 provided in the inlet casing 53.

[0051] In addition, the aforementioned high-pressure stage compressor body 30 is composed of a high-pressure stage cylinder casing 31 in which a high-pressure stage cylinder 32 is formed in the illustrated embodiment, an end cover 52 that covers the discharge side end of the high-pressure stage cylinder casing 31, and a male rotor 33 and a female rotor 34 (in Figure 1, the female rotor 34 is hidden behind the male rotor 33) that are meshed and rotatably housed within the high-pressure stage cylinder 32 formed within the high-pressure stage cylinder casing 31, and the male rotor 33 and the female rotor 34 are housed within the high-pressure stage cylinder casing 31. By attaching the end cover 52 to the discharge side end of the high-pressure stage cylinder casing 31 with the rotor 34 housed therein, the discharge side rotor shaft 33a (34a) of the male rotor 33 and female rotor 34 of the high-pressure stage compressor main body 30 is rotatably supported by bearings 64, 65 provided on the end cover 52, and the suction side rotor shaft 33b (34b) of the male rotor 33 and female rotor 34 of the high-pressure stage compressor main body 30 is rotatably supported by bearing 66 provided on the end wall 54 that closes the suction side end of the high-pressure stage cylinder casing 31.

[0052] A gear casing 70 is attached to the suction side end of the cylinder casing 11, which in the illustrated embodiment is the suction side end of each of the low-pressure stage cylinder casing 21 and the high-pressure stage cylinder casing 31, and a gear chamber 71 is formed within this gear casing 70 to accommodate a gear mechanism 80 for transmitting rotational driving force from a driving source (engine, motor, etc.) not shown to the low-pressure stage compressor main body 20 and the high-pressure stage compressor main body 30.

[0053] Into this gear chamber 71, the suction side rotor shaft of the low-pressure stage compressor main body 20 (in the illustrated example, the suction side rotor shaft 23b of the male rotor 23) protrudes, penetrating the inlet casing 53 of the low-pressure stage compressor main body 20, and the suction side rotor shaft of the high-pressure stage compressor main body 30 (in the illustrated example, the suction side rotor shaft 33b of the male rotor 33) protrudes, penetrating the suction side end wall 54 of the high-pressure stage cylinder casing 31, and driven gears 82, 83 are attached to these two rotor shafts 23b, 33b, respectively.

[0054] In addition, an input shaft 90 is inserted into the gear chamber 71, via a shaft hole 72 that penetrates the gear casing 70, and is connected to a drive source such as an engine or motor (not shown). A drive gear 81 that meshes with the driven gears 82 and 83 mentioned above is attached to this input shaft 90, and the gear mechanism 80 consisting of this drive gear 81 and driven gears 82 and 83 is configured so that when the input shaft 90 is rotated, both the low-pressure stage compressor main body 20 and the high-pressure stage compressor main body 30 can be rotated.

[0055] In the illustrated embodiment, the driving gear 81 has a larger diameter than the driven gears 82 and 83, thereby giving the gear mechanism 80 the function of a speed increasing device that increases the rotation of the driving source input via the input shaft 90 and transmits it to the low-pressure stage compressor main body 20 and the high-pressure stage compressor main body 30.

[0056] An intake port 26 is provided at the upper part of the low-pressure stage cylinder casing 21 at a midpoint in the longitudinal direction, and an unloader valve 2 is attached to this intake port 26 to control the opening and closing of the intake port 26.

[0057] In addition, within the low-pressure stage compressor body 20, an intake space 27 is formed between the upper outer periphery of the male rotor 23 and female rotor 24 on the intake side and the inner wall of the low-pressure stage cylinder 22, and between the intake side end faces of the male rotor 23 and female rotor 24 and the inlet casing 53, for introducing gas intake from the intake port 26 into the compression action space.

[0058] Therefore, when the rotors 23, 24 of the low-pressure stage compressor main body 20 are rotated with the unloader valve 2 open, the compressed gas sucked in through the unloader valve 2 and the intake port 26 is introduced into the compression action space (not shown) formed by the meshing of the male rotor 23 and the female rotor 24 through the intake space 27 provided in the low-pressure stage compressor main body 20, and is compressed together with the lubricating oil supplied to the compression action space after the intake air is trapped through the oil supply port 9, and the compressed gas generated in this way in the low-pressure stage compressor main body 20 as a gas-liquid mixed fluid with the lubricating oil is introduced into the intake port 36 of the high-pressure stage compressor main body 30 through the discharge port 25 and intermediate stage flow path 40 of the low-pressure stage compressor main body 20, and is configured to be compressed in the high-pressure stage compressor main body 30.

[0059] The gap between the shaft hole 72 in the gear casing 70 and the outer periphery of the aforementioned input shaft 90 is sealed by an oil seal (a lip seal in the illustrated embodiment) 73 provided on the outside of the machine for the bearing 67 that supports the input shaft 90, thereby preventing the lubricating oil supplied to the bearing 67 from leaking outside the machine.

[0060] In addition, an oil supply space 74 is formed between the bearing 67 and the oil seal 73 in the shaft hole 72 into which the input shaft 90 is inserted, and the bearing 67 can be lubricated by spraying lubricating oil toward the bearing 67 through this oil supply space 74, and the lubricating oil that has lubricated the bearing 67 is configured to pass through the bearing 67 and be introduced into the gear chamber 71.

[0061] Furthermore, as shown in Figure 1, some of the lubricating oil recovered in the receiver tank 7 is introduced into the gear chamber 71 to supply oil to the gear mechanism 80 housed within the gear chamber 71.The lubricating oil introduced into the gear chamber 71 in this way lubricates the gear mechanism 80, and then falls to the bottom of the gear chamber 71, forming an oil reservoir 75 at the bottom of the gear chamber 71.

[0062] Therefore, the multi-stage compressor 1 of the present invention is provided with a lubricating oil recovery passage 5 for recovering the lubricating oil accumulated at the bottom of the gear chamber 71.

[0063] One end 5a of this lubricating oil recovery passage 5 is connected to the bottom (oil reservoir 75) of the gear chamber 71, and the other end 5b is connected to a lubricating oil recovery port 29 provided in the low-pressure stage compressor main body 20.

[0064] This lubricating oil recovery port 29 is provided in communication with the part of the space within the low-pressure stage compressor body 20, including the suction space 27, which is at a lower pressure than the inside of the gear chamber 71, thereby enabling the recovery of lubricating oil that has accumulated within the gear chamber 71.

[0065] However, if the space within the low-pressure stage compressor main body 20 is connected to the suction space 27 and the lubricating oil within the gear chamber 71 is recovered into the suction space 27, the intake efficiency of the low-pressure stage compressor main body 20 will deteriorate, and the volumetric efficiency will also deteriorate due to the intake air expanding due to the heat of the lubricating oil.Therefore, it is preferable that the lubricating oil recovery port 29 be directly connected to the part of the compression space of the low-pressure stage compressor main body 20 that is at a lower pressure than the gear chamber 71, and in the present embodiment shown in Figure 1, the lubricating oil recovery port 29 is connected to the working space of the low-pressure stage compressor main body 20 at a position closer to the suction side than the oil supply port 9 described above.

[0066] This allows the lubricating oil in the gear chamber 71 to be recovered into the low-pressure stage compressor body 20 by utilizing the pressure in the gear chamber 71 .

[0067] The end wall 54 covering the suction side of the high-pressure stage cylinder casing 31 has an axial hole 55 passing through it, and the suction side rotor shaft 33b of the male rotor 33 of the high-pressure stage compressor main body 30 protrudes into the gear chamber 71 through this axial hole 55.Since the suction side of the high-pressure stage compressor main body 30 is connected to the space within the gear chamber 71 through this axial hole 55, the pressure within the gear chamber 71 is higher than the pressure on the suction side of the low-pressure stage compressor main body 20.

[0068] Furthermore, as shown in Figure 1, a portion of the lubricating oil recovered in the receiver tank 7 is pumped into the gear chamber 71 via the oil supply passage 8 by the pressure in the receiver tank 7, and the pressure in the gear chamber 71 is also increased by the oil supply via the oil supply passage 8.

[0069] As a result, when the bottom of the gear chamber 71, which is under relatively high pressure, is connected to the lubricating oil recovery port 29 of the low-pressure stage compressor main body 20 via the lubricating oil recovery path 5, the lubricating oil that has accumulated at the bottom of the gear chamber 71 is pushed out of the gear chamber 71 by the pressure within the gear chamber 71 and introduced into the lubricating oil recovery port 29 of the low-pressure stage compressor main body 20.

[0070] However, in the multi-stage compressor 1 configured as described above, if the pressure in the gear chamber 71 becomes too high, the force pressing the oil seal (lip seal) 73 that seals the gap between the shaft hole 72 provided in the gear casing 70 and the input shaft 90 against the outer periphery of the input shaft 90 (force in the direction indicated by the arrow in the enlarged view of Figure 2) increases, and the contact area between the lip seal 73 and the input shaft 90 increases, increasing frictional resistance.As a result, the lip seal 73 becomes more susceptible to wear and seizure, shortening the life of the lip seal 73.

[0071] Therefore, in the multi-stage compressor 1 of the present invention, in order to reduce the pressure in the gear chamber 71 to a degree that does not hinder the recovery of lubricating oil by the lubricating oil recovery path 5, at least one communication hole 28 is provided in the end wall (inlet casing) 53 covering the suction side end of the low-pressure stage cylinder 22 at a position higher than the liquid level of the oil reservoir 75 formed at the bottom of the gear chamber 71, connecting the space in the gear chamber 71 to the suction space 27 formed in the low-pressure stage compressor main body 20.

[0072] In this way, by connecting the space within the gear chamber 71 with the suction space 27 of the low-pressure stage compressor main body 20 at a position higher than the liquid level of the oil reservoir 75 formed at the bottom of the gear chamber 71, the compressed gas within the gear chamber 71 can be introduced into the suction space 27 of the low-pressure stage compressor main body 20, which is at negative pressure, thereby reducing the pressure within the gear chamber 71 and extending the life of the lip seal 73 that seals the gap between the shaft hole 72 provided in the gear casing 70 and the input shaft 90.

[0073] The suction space 27 of the low-pressure stage compressor main body 20 is also formed in the gap between the suction side end faces of the male rotor 23 and the female rotor 24 and the inlet casing (end wall) 53, so that lubricating oil for supplying oil to the bearings 63 accumulates at the bottom of the suction space 27 located on the lower end side of the male rotor 23 and the female rotor 24.

[0074] Therefore, in the multi-stage compressor 1 of the present invention, the communication hole 28 is opened near the bottom of the suction space 27 at the lower end side of either the male rotor 23 or the female rotor 24, or both, so that the jet of compressed fluid introduced into the suction space 27 through the communication hole 28 can cause the lubricating oil accumulated at the bottom of the suction space 27 to be splashed and sprayed toward the rotors 23, 24.

[0075] If the communication hole 28 is not provided in such a position, the lower end sides of the rotors 23, 24 will be immersed in the lubricating oil accumulated at the bottom of the suction space 27 and will be in contact with the lubricating oil, and as the rotors 23, 24 rotate, they will come into contact with the lubricating oil accumulated at the bottom of the suction space 27 and stir it up, resulting in the rotors 23, 24 being subjected to large rotational resistance.

[0076] In contrast, in a configuration in which a communication hole 28 is opened near the bottom of the suction space 27 provided on the lower end side of the rotors 23, 24, the compressed gas ejected into the suction space through the communication hole 28 blows the lubricating oil accumulated at the bottom of the suction space 27 toward the rotors 23, 24, so that the rotors 23, 24 no longer scoop up the lubricating oil, thereby reducing the rotational resistance of the rotors 23, 24. On the other hand, the lubricating oil is sprayed toward the rotors 23, 24 along with the compressed gas injected through the communication hole 28 and introduced into the compression action space before the intake air is trapped, and the lubricating oil sprayed in this way, together with the lubricating oil introduced into the action space through the lubricating oil recovery port 29 and the oil supply port 9, is then used to lubricate the rotors 23, 24 and seal the compression action space.

[0077] In this way, when the communication hole 28 is connected at the bottom of the suction space 27 provided on the lower end side of the rotors 23, 24, the communication hole 28 may be opened near the bottom of the suction space 27 on the lower end side of the female rotor 24 as shown in Figures 3 and 4, or the communication hole 28 may be opened near the bottom of the suction space 27 on the lower end side of the male rotor 23 as shown in Figures 5 and 6, and such a communication hole 28 may be provided only on either the lower end side of the female rotor 24 or the lower end side of the male rotor 23, or may be provided on both the lower end side of the female rotor 24 and the lower end side of the male rotor 23.

[0078] When the communication hole 28 is provided only on one side, either the lower end side of the female rotor 24 or the lower end side of the male rotor 23, it is preferable to adopt a configuration in which the communication hole 28 is provided on the lower end side of the male rotor 23, as shown in Figures 5 and 6.

[0079] In a configuration in which a communication hole 28 communicating with the suction space 27 is provided at the lower end side of the male rotor 23, a greater negative pressure (lower pressure) is generated in the suction space 27 on the male rotor 23 side compared to the suction space 27 on the female rotor 24 side. Therefore, if the size and number of communication holes 28 to be formed are the same, communicating the gear chamber 71 with the suction space 27 at the lower end side of the male rotor 23 is preferable in terms of protecting the oil seal (lip seal) 73, as the pressure within the gear chamber 71 can be reduced to a lower pressure, compared to communicating with the suction space 27 at the lower end side of the female rotor 24.

[0080] Furthermore, as shown in Figure 6, since the rotor diameter of the male rotor 23 is larger than that of the female rotor 24, the bottom of the suction space 27 is also located lower on the male rotor 23 side, and the lower end of the male rotor 23 is in contact with more lubricating oil than the female rotor 24.

[0081] Therefore, when rotating, the male rotor 23 experiences greater rotational resistance than the female rotor 24, so by connecting the communication hole 28 to the suction space 27 at the lower end side of the male rotor 23 and blowing away the lubricating oil that has accumulated at the lower end side of the male rotor 23, the rotational resistance that the rotors 23, 24 experience when rotating can be more efficiently reduced.

[0082] In this way, in the multi-stage compressor 1 of the present invention, the pressure in the gear chamber 71 is reduced by providing the communication holes 28 that connect the gear chamber 71 to the suction space 27 of the low-pressure stage compressor main body 20 in the suction side end wall (inlet casing) 53 of the low-pressure stage compressor main body 20.Therefore, by selecting one or a combination of the size (hole diameter) of the communication holes 28 to be formed, the number of holes to be formed, and the position of formation (selecting whether to connect the holes to the suction space on the male rotor side or the female rotor side), the pressure in the gear chamber 71 can be accurately reduced to the target pressure, and it is easy to adjust the pressure in the gear chamber 71 to be reduced to as low a pressure as possible without causing poor recovery of lubricating oil by the lubricating oil recovery path 5 or insufficient oil supply to the low-pressure stage compressor main body 20 by reducing the pressure in the gear chamber 71 excessively.

[0083] In the configuration of the multi-stage compressor 1 described above with reference to Figures 1 to 6, the above-mentioned communication hole 28 is connected to the suction space 27 at the lower end side of the rotors 23, 24 of the low-pressure stage compressor main body 20.

[0084] In contrast to this, in the embodiment shown in FIGS. 7 and 8, a configuration is adopted in which the aforementioned communication holes 28 communicate with the suction space 27 on the upper end side of the rotors 23, 24 of the low-pressure stage compressor body 20.

[0085] The configuration in which the communication hole 28 is provided at this position is preferably adopted in a multi-stage compressor 1 having a low-pressure stage compressor body 20 equipped with a shield 45 that covers the meshing portion of the male rotor 23 and female rotor 24 below the intake port 26 of the low-pressure stage compressor body 20, and a support 46 that suspends the end 45a of this shield 45 on the gear chamber 71 side from the upper inner wall of the low-pressure stage cylinder 22, as shown in Figures 7 and 8, in which case the communication hole 28 is configured to open toward the support 46 above the meshing position of the male rotor 23 and female rotor 24.

[0086] Here, in the configuration of the low-pressure stage compressor main body 20 shown in Figure 8, if the male rotor 23 is rotated clockwise and the female rotor 24 is rotated counterclockwise, there is a risk that the lubricating oil adhering to the rotors 23, 24 will splash upward and fly out of the intake port 26 if a shield 45 is not provided.

[0087] In addition, as the male rotor 23 and the female rotor 24 rotate, an upward gas flow occurs above the meshing portion of the male rotor 23 and the female rotor 24, and if the aforementioned shield 45 is not provided, this upward gas flow will obstruct the downward flow of compressed gas attempting to flow into the low-pressure stage cylinder 22 through the intake port 26.

[0088] In response to this, by providing a shield 45 above the meshing portion of the male rotor 23 and the female rotor 24, preferably a shield 45 having a V-shaped bottom surface as shown in Figure 8, the lubricating oil that splashes upward as the rotors 23, 24 rotate can be made to collide with the bottom surface of the shield 45, preventing it from reaching the intake port 26, and the gas flow that flows upward at the meshing portion as the rotors 23, 24 rotate can be made to collide with the bottom surface of the shield 45 and guided in the left-right direction of the page in Figure 8, thereby preventing the flow of compressed gas that is sucked into the low-pressure stage cylinder 22 through the intake port 26 from being obstructed.

[0089] However, when such a shield 45 or support 46 is provided, as shown in Figure 9(A), the gas sucked into the low-pressure stage compressor main body 20 through the intake port 26 flows through the intake space 27 while colliding with the support 46, and vortices are generated on the male rotor 23 side and the female rotor 24 side on the back side of the support 46 (the gear chamber 71 side of the support 46), and the generation of these two vortices reduces the intake efficiency of the low-pressure stage compressor main body 20.

[0090] In contrast to this, in a configuration in which the communication hole 28 provided in the inlet casing (end wall) 53 covering the suction side of the low-pressure stage cylinder 22 is opened toward the aforementioned support 46 at a position above the meshing portion of the male rotor 23 and female rotor 24 as shown in Figures 7 and 8, the compressed gas in the gear chamber 71 is injected toward the support 46 through the communication hole 28, and the generation of vortices on the back side of the support 46 (the gear chamber 71 side of the support 46) is suppressed as shown in Figure 9 (B), the vortex that had been generated on the male rotor 23 side disappears, and the vortex itself generated on the back side of the support 46 (the gear chamber 71 side of the support 46) becomes smaller, thereby improving the intake efficiency of the low-pressure stage compressor main body 20 equipped with the aforementioned shield 45 and support 46.

[0091] In addition, this configuration in which a communication hole 28 opening toward the aforementioned support 46 is provided at a position above the meshing portion of the male rotor 23 and female rotor 24 may be adopted alone, but it may also be provided together with a communication hole 28 that communicates with the suction space 27 at the lower end side of the rotors 23, 24, as explained with reference to Figures 2 to 6. [Explanation of symbols]

[0092] 1 Multi-stage compressor 2 Unloader valve 5 Lubricating oil recovery channel 5a One end (of lubricating oil recovery passage) 5b Other end (of lubricating oil recovery path) 7. Receiver Tank 8 Oil supply passage 8a Oil cooler 8b Oil filter 9 Fuel filler 11 Cylinder casing 20 Low-pressure stage compressor body 21 Low-pressure stage cylinder casing 22 Low-pressure stage cylinder 23 Osrota 23a Discharge side rotor shaft (male rotor) 23b Intake side rotor shaft (male rotor) 24 Mesrota 24a Discharge side rotor shaft (female rotor) 24b Intake side rotor shaft (female rotor) 25 Outlet 26 Air intake 27 Inhalation space 28 Communication hole 29 Lubricating oil recovery port 30 High-pressure stage compressor body 31 High-pressure stage cylinder casing 32 High-pressure stage cylinder 33 Osrota 33a Discharge side rotor shaft (male rotor) 33b Intake side rotor shaft (male rotor) 34 Mesrota 34a Discharge side rotor shaft (female rotor) 34b Intake side rotor shaft (female rotor) 35 Discharge port 36 Air intake 40 Intermediate stage flow path 45 Shield 45a Gear chamber side end (of shield) 46 Post 51,52 End cover 53 Inlet casing (end wall) 54 End Wall 55 shaft hole 61, 62, 63, 64, 65, 66, 67 Bearings 70 Gear casing 71 Gear room 72 Shaft hole 73 Oil seal (lip seal) 74 Refueling space 75 Oil Puddle 80 Gear mechanism (speed increasing device) 81 Drive gear 82,83 Driven gear 90 Input shaft 100 Multi-stage compressor 111 Cylinder casing 120 Low-pressure stage compressor body 122 Low-pressure stage cylinder 123,124 Screw rotor (low pressure stage compressor body) 123a, 124a Discharge side rotor shaft (of the low pressure stage compressor body) 123b, 124b Intake side rotor shaft (low pressure stage compressor body) 125 Discharge port 130 High-pressure stage compressor body 132 High-pressure stage cylinder 133, 134 Screw rotor (of the high-pressure stage compressor body) 133a, 134a Discharge side rotor shaft (of the high pressure stage compressor body) 133b, 134b Intake side rotor shaft (of high pressure stage compressor body) 136 Air intake 140 Intermediate stage flow path 151,152 End cover 153 End Wall 161,163,164,166,167 Bearings 170 Gear casing 171 Gear room 172 Shaft hole 173 Oil seal 180 Gear mechanism (speed increasing device) 181 Drive gear 182,183 Driven gear 190 input shaft

Claims

1. A male rotor and a female rotor are meshed and rotatably housed in each of the low-pressure stage cylinder and the high-pressure stage cylinder provided in the cylinder casing, thereby forming an oil-cooled low-pressure stage compressor body and a high-pressure stage compressor body that compress the gas to be compressed together with lubricating oil, and a gear chamber is formed in a gear casing attached to the suction side end of the cylinder casing. The suction side rotor shaft of the low-pressure stage compressor body, which penetrates the end wall covering the suction side end of the low-pressure stage cylinder and protrudes into the gear chamber, and the high-pressure stage cylinder a gear mechanism including a driven gear attached to the suction side rotor shaft of the high-pressure stage compressor body that penetrates an end wall covering the suction side end of a rotor and protrudes into the gear chamber, and a drive gear attached to an input shaft that penetrates the gear casing and is inserted into the gear chamber, and the low-pressure stage compressor body and the high-pressure stage compressor body can both be rotated by rotation of the input shaft, and an oil sump for lubricating oil introduced into the gear chamber is formed at the bottom of the gear chamber, The low-pressure stage compressor body is provided with a lubricating oil recovery port communicating with the inside of the low-pressure stage compressor body, and a lubricating oil recovery passage communicating the oil reservoir at the bottom of the gear chamber with the lubricating oil recovery port is provided, a gear chamber that is provided in the end wall covering the suction side end of the low-pressure stage cylinder and that is positioned higher than the liquid level of the oil reservoir and that communicates with a suction space formed in the low-pressure stage compressor body;

2. 2. The multi-stage compressor according to claim 1, wherein the communication hole is opened near the bottom of the suction space at the lower end side of either or both of the male rotor and the female rotor of the low-pressure stage compressor body.

3. a shield covering an engaging portion between the male rotor and the female rotor is provided below an intake port in the low-pressure stage compressor body, and a support column for suspending an end portion of the shield on the gear chamber side is provided on an upper inner wall of the low-pressure stage cylinder; 3. A multi-stage compressor according to claim 1, wherein the communication hole opening toward the support is provided in the end wall at a position higher than the meshing portion of the male rotor and the female rotor.

4. A male rotor and a female rotor are meshed and rotatably housed in each of the low-pressure stage cylinder and the high-pressure stage cylinder provided in the cylinder casing, thereby forming an oil-cooled low-pressure stage compressor body and a high-pressure stage compressor body that compress the gas to be compressed together with lubricating oil, and a gear chamber is formed in a gear casing attached to the suction side end of the cylinder casing, and a suction side rotor shaft of the low-pressure stage compressor body that protrudes into the gear chamber 71 through the end wall covering the suction side end of the low-pressure stage cylinder and a gear chamber is formed in the high-pressure stage cylinder. a gear mechanism including a driven gear attached to a suction side rotor shaft of the high-pressure stage compressor body that penetrates an end wall covering the suction side end of a compressor casing and protrudes into the gear chamber, and a drive gear attached to an input shaft that penetrates the gear casing and is inserted into the gear chamber, is housed in the gear chamber, and both the low-pressure stage compressor body and the high-pressure stage compressor body can be rotated by rotation of the input shaft, and an oil sump for lubricating oil introduced into the gear chamber is formed at the bottom of the gear chamber, The low-pressure stage compressor body is provided with a lubricating oil recovery port communicating with the inside of the low-pressure stage compressor body, and a lubricating oil recovery passage communicating the oil reservoir at the bottom of the gear chamber with the lubricating oil recovery port is provided, A gear chamber pressure recovery method in a multi-stage compressor, characterized in that the compressed gas in the gear chamber is recovered into the suction space of the low-pressure stage compressor main body by providing at least one communication hole in the end wall covering the suction side end of the low-pressure stage cylinder at a position higher than the liquid level of the oil reservoir, which communicates the space in the gear chamber with the suction space formed in the low-pressure stage compressor main body.

5. 5. The method for recovering pressure inside a gear chamber in a multi-stage compressor according to claim 4, wherein the compressed gas inside the gear chamber is recovered by opening the communication hole near the bottom of the suction space at the lower end side of either the male rotor or the female rotor, or both, of the low-pressure stage compressor body.

6. a shield covering an engaging portion between the male rotor and the female rotor is provided below an intake port in the low-pressure stage compressor body, and a support column for suspending an end portion of the shield on the gear chamber side is provided on an upper inner wall of the low-pressure stage cylinder; 6. A method for recovering pressure inside a gear chamber in a multi-stage compressor according to claim 4 or 5, characterized in that the communication hole opening toward the support is provided in the end wall at a position higher than the meshing portion of the male rotor and the female rotor, thereby recovering compressed gas inside the gear chamber.

7. 6. A method for recovering pressure inside a gear chamber in a multi-stage compressor according to claim 4 or 5, characterized in that the amount of compressed gas recovered to the suction space of the low-pressure stage compressor body is adjusted by selecting one or a combination of the size, number, and position of the communication holes provided in the end wall covering the suction side end of the low-pressure stage cylinder.

8. 7. A method for recovering pressure inside a gear chamber in a multi-stage compressor according to claim 6, characterized in that the amount of compressed gas recovered to the suction space of the low-pressure stage compressor body is adjusted by selecting one or a combination of the size, number, and position of the communication holes provided in the end wall covering the suction side end of the low-pressure stage cylinder.

Images