Positive displacement compressor

Abstract

Provided is a positive displacement compressor comprising: a screw compressor (2), which is a compressor main body that compresses a gas together with a liquid in compression chambers (25, 26); a first liquid flow path (6) that causes a first liquid, which is a liquid separated by a first gas-liquid separator (5) that separates the liquid from the compressed gas discharged from the screw compressor (2), to flow through a supply port (6c) in the compression chambers (25, 26); and a second liquid flow path (9) that causes a second liquid, which is a liquid separated by a second gas-liquid separator (7) for further separating the liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator (5), to flow through a communication port (9b) communicating with the first liquid flow path (6). The communication port (9b) is positioned below the supply port (6c).

Description

Positive displacement compressor

[0001] The present invention relates to a positive displacement compressor.

[0002] A positive displacement compressor is developed, which includes a first gas-liquid separator that separates liquid contained in the compressed gas discharged from a compressor body that compresses gas while supplying liquid therein, and a second gas-liquid separator that further separates liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator.

[0003] For example, Patent Document 1 discloses an air compression system including an oil-gas separation container (first gas-liquid separator) that separates oil from the gas discharged from the second-stage compressor head, and a gas separation cartridge (second gas-liquid separator) that further separates oil from the gas from which the oil has been separated by the oil-gas separation container.

[0004] Japanese Patent Application Publication No. 2024-523270

[0005] The air compression system of Patent Document 1 includes an oil return pipeline (first liquid flow path) that circulates the oil (liquid) separated by the oil-gas separation container (first gas-liquid separator) to the first and second stage compressor heads (compressor body), and a removal pipeline (second liquid flow path) that is connected via a connection part to the oil return pipeline (first liquid flow path) and circulates the oil (liquid) separated by the gas separation cartridge (second gas-liquid separator) to the oil return pipeline (first liquid flow path). Thereby, the liquid separated by the second gas-liquid separator flows into the first liquid flow path from the second liquid flow path via the connection part, and together with the liquid separated by the first gas-liquid separator, flows into the compressor body from the first liquid flow path.

[0006] On the other hand, since it is difficult to separate all the gas from the liquid in the second gas-liquid separator, the liquid flowing into the first liquid flow path from the second liquid flow path via the connection part may contain gas (bubbles of compressed gas).

[0007] Furthermore, if the flow rate of the fluid returned from the second liquid passage to the compressor body (this flow rate is determined by the pressure difference between the connection point between the compressor body and the first liquid passage and the second gas-liquid separator, and the flow resistance in the second liquid passage) is greater than the amount of oil flowing from the first gas-liquid separator to the second gas-liquid separator, then compressed gas will also flow into the second liquid passage along with the oil. As a result, compressed gas may be introduced into the first liquid passage and the compressor body in addition to the oil.

[0008] If compressed gas flows from the second liquid passage into the first liquid passage as well as oil, depending on the relative heights of the connection between the first liquid passage and the compressor body and the connection between the first and second liquid passages, compressed gas may accumulate in the first liquid passage. When compressed gas accumulates in the first liquid passage, the cross-sectional area through which oil can flow in that area decreases, increasing flow resistance and reducing the oil flow rate. In other words, the amount of oil supplied to the compressor body decreases, which may lead to a decline in cooling, sealing, and lubrication performance in the compressor body.

[0009] The object of the present invention is to provide a positive displacement compressor that can suppress the accumulation of gas that flows from the second gas-liquid separator into the first liquid flow path via the second liquid flow path within the first liquid flow path.

[0010] The present invention includes several means for solving the above problems, but to give one example, it comprises a compressor body that compresses gas together with liquid in a compression chamber, a first liquid passage that flows a first liquid, which is a liquid separated by a first gas-liquid separator that separates liquid from compressed gas discharged from the compressor body, to a supply port that opens into the compression chamber or a bearing chamber in which the bearing is housed, and a second liquid passage that flows a second liquid, which is a liquid separated by a second gas-liquid separator that further separates liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator, to a communication port that communicates with the first liquid passage, wherein the communication port is located below the supply port.

[0011] According to the present invention, it is possible to suppress the accumulation of gas contained in the second liquid at the supply port that supplies fluid from the communication port where the second liquid flow path communicates with the first liquid flow path to the compression chamber or bearing chamber of the compressor body. Therefore, it is possible to suppress deterioration of the compressor's performance due to a decrease in the amount of liquid flowing into the compressor body. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

[0012] This is a schematic diagram showing the configuration of a positive displacement compressor according to the first embodiment of the present invention. This is a cross-sectional view of the compressor body and electric motor provided in the positive displacement compressor according to the first embodiment of the present invention. This is a cross-sectional view taken along the line III-III in Figure 2. This is a cross-sectional view of the compressor body and electric motor provided in the positive displacement compressor according to the second embodiment of the present invention. This is a cross-sectional view taken along the line V-V in Figure 4. This is a cross-sectional view of the compressor body and electric motor provided in the positive displacement compressor according to the third embodiment of the present invention, in which the supply port of the first liquid passage opens into the low-pressure side bearing chamber. This is a cross-sectional view taken along the line VII-VII in Figure 6. This is a cross-sectional view of the compressor body and electric motor provided in the positive displacement compressor according to another embodiment of the third embodiment of the present invention, in which the supply port of the first liquid passage opens into the high-pressure side bearing chamber. This is a cross-sectional view taken along the line IX-IX in Figure 8. This is a cross-sectional view of the compressor body and electric motor provided in the positive displacement compressor according to another embodiment of the present invention. This is a cross-sectional view taken along the line XI-XI in Figure 10.

[0013] The configuration and operation of positive displacement compressors according to the first to third embodiments of the present invention will be described below with reference to the drawings. In each figure, the same reference numerals indicate the same parts.

[0014] (First Embodiment) Figure 1 is a schematic diagram showing the configuration of a positive displacement compressor according to the first embodiment of the present invention.

[0015] A positive displacement compressor is a compressor that compresses a gas by mechanically changing a fixed space (volume). The positive displacement compressor according to this embodiment is an air compressor 1 that compresses a gas (air) by changing the volume of the compression chamber as a male rotor and a female rotor rotate while meshing together.

[0016] As shown in Figure 1, the air compressor 1 comprises a screw compressor 2, which is the compressor body that compresses air (gas) together with lubricating oil (liquid) in the compression chamber; an electric motor 3; an intake filter 4; a first gas-liquid separator 5; a first liquid passage 6; a second gas-liquid separator 7; a compressed gas passage 8; and a second liquid passage 9. The first gas-liquid separator 5 and the second gas-liquid separator 7 may be provided outside the air compressor 1.

[0017] The screw compressor (compressor body) 2 is a device that draws in air through the intake filter 4, generates compressed gas, and discharges the compressed gas to the first gas-liquid separator 5 via the discharge channel 2a. The electric motor 3 is a device that drives the screw compressor 2. Details of the screw compressor 2 and the electric motor 3 will be described later.

[0018] The intake filter 4 is a component for removing impurities and foreign matter contained in the gas (in this embodiment, air) that is drawn in from the outside by the screw compressor 2.

[0019] The first gas-liquid separator 5 is a device that separates liquid (in this embodiment, lubricating oil) from compressed gas (in this embodiment, compressed air) discharged from the screw compressor 2, and is, for example, a swirling separation type gas-liquid separator. (Hereinafter, the liquid (lubricating oil) separated by the first gas-liquid separator 5 will be referred to as the "first liquid.") A swirling separation type gas-liquid separator is a device that separates lubricating oil from compressed gas by centrifugal force, and has a swirling channel (not shown) inside that swirls the compressed gas, and the separated first liquid is stored in a tank 5a at the bottom of the first gas-liquid separator 5.

[0020] In addition, it is preferable that the screw compressor 2, being a heavy component, is positioned below the air compressor 1, while the first gas-liquid separator 5 is positioned above or beside the air compressor 1.

[0021] The first liquid passage 6 is a passage for circulating the first liquid from the tank 5a to the screw compressor 2, supplying the first liquid stored in the tank 5a to the screw compressor 2. Downstream of the first liquid passage 6, there is a supply port for supplying the first liquid to the compression chamber for compressing gas or the bearing chamber for housing bearings, which are provided in the screw compressor 2.

[0022] Preferably, the first liquid flow path 6 is provided with a liquid cooler 6a for cooling the first liquid and an oil filter 6b located downstream of the liquid cooler 6a for removing impurities from the first liquid.

[0023] The second gas-liquid separator 7 is a device (for example, an oil separator) that separates the liquid (lubricating oil) contained in the compressed gas from which the first liquid has been separated. The liquid separated by the second gas-liquid separator 7 (hereinafter referred to as the second liquid) is, for example, a mist-like lubricating oil component.

[0024] Furthermore, it is preferable that the second gas-liquid separator 7 is positioned on top of the first gas-liquid separator 5 or formed integrally with the first gas-liquid separator 5.

[0025] Compressed gas, from which the first liquid has been separated in the first gas-liquid separator 5, flows into the second gas-liquid separator 7 from the top of the first gas-liquid separator 5. Then, for example, the second liquid contained in the compressed gas is filtered by a filter installed in the second gas-liquid separator 7, and the second liquid is separated from the compressed gas.

[0026] The second liquid separated in the second gas-liquid separator 7 flows into the second liquid flow path 9, and the compressed gas from which the second liquid has been separated in the second gas-liquid separator 7 flows into the compressed gas flow path 8.

[0027] The compressed gas flow path 8 is a flow path that circulates the compressed gas, from which the second liquid has been separated in the second gas-liquid separator 7, to external equipment that consumes compressed gas, and preferably includes an aftercooler 8a for cooling the compressed gas.

[0028] The aftercooler 8a is a device for cooling compressed gas, for example, by heat exchange with cooling air induced by a cooling fan.

[0029] The second liquid channel 9 is a channel through which the second liquid, separated from the compressed gas in the second gas-liquid separator 7, flows in from a connection part 9a that connects to the first liquid channel 6. The connection part 9a is provided with a communication port 9b (see Figure 2) through which the second liquid channel 9 communicates with the first liquid channel.

[0030] Figure 2 is a cross-sectional view of the compressor body and electric motor included in the positive displacement compressor according to this embodiment. Figure 3 is a cross-sectional view taken along line III-III in Figure 2.

[0031] The screw compressor 2 comprises a screw rotor 21, a casing 22 that houses the screw rotor 21, a bearing 23 that rotatably supports the screw rotor 21, and a shaft seal component 24 that seals the gap between the screw rotor 21 and the casing 22.

[0032] The screw rotor 21 is a helical component for drawing in, compressing, and discharging gas, and comprises a male rotor 21a and a female rotor 21b (see Figure 3) whose twisted teeth (lobes) interlock and rotate with each other.

[0033] The casing 22 is a rigid body for sealing the space in which the suction, compression, and discharge processes take place from the outside, and comprises a suction passage 22a, a discharge passage 22b, an operating space 22c, a low-pressure side bearing chamber 22d, and a high-pressure side bearing chamber 22e.

[0034] The suction passage 22a is a passage through which gas is drawn in via the suction filter 4. The discharge passage 22b is a passage through which compressed gas is discharged from the screw compressor 2 to the discharge passage 2a.

[0035] The working space 22c is a space that covers the helical portion of the screw rotor 21 and, as shown in Figure 3, comprises a male cylindrical inner surface 22f facing the tip of the teeth 21c of the male rotor 21a and a female cylindrical inner surface 22g facing the tip of the teeth 21d of the female rotor 21b. The male cylindrical inner surface 22f is formed such that the gap between it and the tip of the teeth 21c of the male rotor 21a is several μm to several mm. Similarly, the female cylindrical inner surface 22g is formed such that the gap between it and the tip of the teeth 21d of the female rotor 21b is several μm to several mm.

[0036] These gaps are sealed by the lubricating oil (first liquid or first liquid mixed with second liquid) that flows from the first liquid passage 6 into the screw compressor 2. As a result, a male compression chamber 25, which is the space surrounded by the inner surface 22f of the male cylinder and the tooth groove 21f of the male rotor 21a, and a female compression chamber 26, which is the space surrounded by the inner surface 22g of the female cylinder and the tooth groove 21g of the female rotor 21b, are formed within the working space 22c.

[0037] The compression chambers 25 and 26 are spaces through which the screw rotor 21 rotates, drawing in gas from the suction passage 22a, compressing it, and discharging the compressed gas into the discharge passage 22b.

[0038] Returning to Figure 2, the low-pressure side bearing chamber 22d is the space on the suction passage 22a side that houses the low-pressure side bearings 23a and 23b and the shaft seal component 24, which will be described later. Lubricating oil (first liquid or first liquid mixed with the second liquid) is supplied to the low-pressure side bearing chamber 22d via the first liquid passage 6.

[0039] The high-pressure side bearing chamber 22e is the space on the discharge channel 22b side that houses the high-pressure side bearings 23c and 23d, which will be described later. Lubricating oil (first liquid or first liquid mixed with the second liquid) is also supplied to the high-pressure side bearing chamber 22e via the first liquid channel 6.

[0040] The bearing 23 is a component that rotatably supports the screw rotor 21 (male rotor 21a and female rotor 21b), and comprises low-pressure side bearings 23a, 23b and high-pressure side bearings 23c, 23d.

[0041] The low-pressure side bearings 23a and 23b are bearings that rotatably support the shaft portion of the screw rotor 21 on the suction passage 22a side, and are housed in the low-pressure side bearing chamber 22d. Preferably, cylindrical roller bearings that can support a large radial load, have low friction, and can rotate at high speeds are used for the low-pressure side bearings 23a and 23b.

[0042] The high-pressure side bearings 23c and 23d are bearings that rotatably support the shaft portion on the discharge passage 22b side of the screw rotor 21 and are housed in the high-pressure side bearing chamber 22e. Preferably, the high-pressure side bearings 23c and 23d are a combination of cylindrical roller bearings that can support a large radial load, have low friction and can rotate at high speeds, and deep groove ball bearings that can support radial loads and light thrust loads, can rotate at high speeds, and produce less noise and vibration.

[0043] The shaft seal component 24 is a component that seals the gap between the flow path 22h of the casing 22 and the shaft portion 21e of the male rotor 21a that protrudes from the flow path 22h of the casing 22. Oil seals, mechanical seals, and the like are used for the shaft seal component 24.

[0044] The electric motor 3 is a power source for rotating the screw rotor 21 to compress gas. In the electric motor 3 of the present embodiment, a rotor 3a is coupled to the shaft portion 21e on the suction side of the male rotor 21a to rotationally drive the male rotor 21a.

[0045] The male rotor 21a rotationally driven by the electric motor 3 rotationally drives the female rotor 21b. When the male rotor 21a and the female rotor 21b rotate, the compression chambers 25 and 26 change in shape during the suction stroke of sucking in gas, the compression stroke of compressing the gas, and the discharge stroke of discharging the compressed gas.

[0046] The portion where the suction stroke is performed in the compression chambers 25 and 26 is surrounded by the male-side cylindrical inner surface 22f or the female-side cylindrical inner surface 22g, the tooth groove 21f of the male rotor 21a or the tooth groove 21g of the female rotor 21b, and the discharge end surface 22i of the working space 22c, and communicates with the suction flow path 22a. Therefore, gas flows into the portion where the suction stroke is performed in the compression chambers 25 and 26 from the suction flow path 22a.

[0047] The portion where the compression stroke is performed in the compression chambers 25 and 26 is surrounded by the male-side cylindrical inner surface 22f or the female-side cylindrical inner surface 22g, the tooth groove 21f of the male rotor 21a or the tooth groove 21g of the female rotor 21b, the suction end surface 22j and the discharge end surface 22i of the working space 22c, and is sealed. Therefore, in the portion where the compression stroke is performed in the compression chambers 25 and 26, the gas in the compression chambers 25 and 26 is compressed by the rotational drive of the male rotor 21a and the female rotor 21b.

[0048] The portion where the discharge stroke is performed in the compression chambers 25 and 26 is surrounded by the male-side cylindrical inner surface 22f or the female-side cylindrical inner surface 22g, the tooth groove 21f of the male rotor 21a or the tooth groove 21g of the female rotor 21b, and the suction end surface 22j of the working space 22c, and communicates with the discharge flow path 22b. Therefore, in the portion where the discharge stroke is performed in the compression chambers 25 and 26, the compressed gas in the compression chambers 25 and 26 is discharged from the discharge flow path 22b.

[0049] The first liquid channel 6 communicates with the compression chamber 25 via a first liquid channel 6d provided in the casing 22. Therefore, the lubricating oil (first liquid mixed with the first or second liquid) that is separated by the first gas-liquid separator 5 and flows through the first liquid channel 6 is supplied to the compression chamber 25 from a supply port 6c that opens into the compression chamber 25.

[0050] Figure 3 shows an embodiment in which the supply port 6c opens into the male compression chamber 25. However, the invention is not limited to this, and the supply port 6c may also open into the female compression chamber 26.

[0051] The supply port 6c is preferably opened to the portion of the compression chambers 25 and 26 where the compression stroke takes place. The reason for this is that the gas contained in the second liquid is compressed in the compressor body and becomes hot. Therefore, if the second liquid is mixed with the gas drawn in by the compressor body (hereinafter referred to as intake air), the gas contained in the second liquid expands in the intake air, reducing the amount of intake air drawn in from the outside. Also, if the gas contained in the second liquid is mixed with the intake air, the intake air expands due to the heat of the gas contained in the second liquid, and its density decreases. This reduces the mass flow rate of the compressed air.

[0052] However, in this embodiment, the air compressor 1 has a supply port 6c that opens to the portion of the compression chambers 25 and 26 where the compression stroke takes place. Therefore, gas contained in the second liquid does not mix with the intake air, which suppresses a decrease in the amount of intake air and suppresses a decrease in the mass flow rate of compressed air.

[0053] Furthermore, it is preferable that the supply port 6c opens into the compression chambers 25 and 26, where the compression stroke takes place, and where the pressure is lower than that within the first liquid flow path 6. This makes it possible to suppress the inflow of compressed gas from the supply port 6c into the first liquid flow path 6.

[0054] Furthermore, the second liquid channel 9 communicates with the first liquid channel 6 via a communication port 9b provided at the end of the second liquid channel 9c (see Figure 3) located in the casing 22. Therefore, the second liquid, which is separated by the second gas-liquid separator 7 and flows through the second liquid channel 9, flows into the first liquid channel 6 through the communication port 9b of the second liquid channel 9 that communicates with the first liquid channel 6.

[0055] On the other hand, if gas contained in the second fluid flowing into the first liquid flow path 6 from the communication port 9b accumulates in the flow path from the communication port 9b to the supply port 6c, there is a risk that the amount of first liquid flowing into the compression chambers 25 and 26 will decrease. For this reason, the communication port 9b of the second liquid flow path 9, which communicates with the first liquid flow path 6, is located below the supply port 6c that opens into the compression chambers 25 and 26. As a result, even if gas contained in the second liquid is mixed into the first liquid flowing through the first liquid flow path 6 as the second liquid flows into the first liquid flow path 6 from the communication port 9b, the communication port 9b is located below the supply port 6c, so it is possible to suppress the accumulation of the mixed gas in the flow path from the communication port 9b to the supply port 6c due to buoyancy.

[0056] Furthermore, it is preferable that the gradient of the first liquid flow path 6 is an upward gradient from the communication port 9b to the supply port 6c. Upward gradient flow paths include flow paths with a constant gradient from the communication port 9b to the supply port 6c, flow paths with a monotonically increasing gradient, and flow paths that extend vertically, such as the first liquid flow path 6d from the communication port 9b to the supply port 6c in Figure 3 (in this case, the gradient is infinite). It is preferable that the flow path has no horizontally extending portion between the communication port 9b and the supply port 6c. If the first liquid flow path 6 is shaped in this way, even if gas is introduced from the communication port 9b, the gas can be easily guided to the supply port 6c by buoyancy, and the accumulation of the gas in the first liquid flow path 6 can be suppressed.

[0057] Furthermore, it is preferable that the air compressor 1 includes a third liquid passage that branches off from the first liquid passage 6 upstream of the communication port 9b and supplies the first liquid to the bearing chambers 22d and 22e. Moreover, it is preferable that the third liquid passage branches off from the first liquid passage 6 below the communication port 9b.

[0058] In this embodiment, the third liquid flow path is formed by a flow path provided in the casing 22. Specifically, as shown in Figure 2, the third liquid flow path on the suction flow path 22a side is formed by a third liquid flow path 22k that branches off from the first liquid flow path 6d upstream and below the communication port 9b and communicates with a supply port 6e that supplies liquid to the low-pressure side bearing chamber 22d.

[0059] Furthermore, the third liquid flow path on the discharge flow path 22b side is formed by a third liquid flow path 22l that branches off from the first liquid flow path 6d upstream and below the communication port 9b and communicates with a supply port 6f that supplies liquid to the high-pressure side bearing chamber 22e. This prevents the second liquid from mixing with the liquid supplied to the low-pressure side bearing chamber 22d and the high-pressure side bearing chamber 22e.

[0060] Furthermore, it is preferable that the air compressor 1 is equipped with a fourth liquid passage through which the lubricating oil (first liquid) that has flowed into the bearing chambers 22d and 22e flows out into the compression chambers 25 and 26 during the suction stroke.

[0061] In this embodiment, the fourth liquid passage is formed by a passage provided in the casing 22. Specifically, the fourth liquid passage on the suction passage 22a side is formed by a fourth liquid passage 22n that connects the space 22m communicating with the compression chambers 25 and 26 in the suction stroke to the bottom of the low-pressure side bearing chamber 22d. The fourth liquid passage on the discharge passage 22b side is formed by a fourth liquid passage 22o that connects the compression chambers 25 and 26 in the suction stroke to the bottom of the high-pressure side bearing chamber 22e.

[0062] By providing fourth liquid passages 22n and 22o, it is possible to prevent the liquid supplied to the bearing chambers 22d and 22e from accumulating in the bearing chambers 22d and 22e, thereby hindering the operation of the bearings and shaft seal components and preventing power loss.

[0063] Furthermore, by having the fourth liquid channels 22n and 22o communicate with the compression chambers 25 and 26 during the suction stroke, it is possible to suppress the inflow of compressed gas from the compression chambers 25 and 26 into the fourth liquid channels 22n and 22o.

[0064] [Effects] The positive displacement compressor (air compressor 1) according to this embodiment comprises a screw compressor 2, which is the compressor body that compresses air (gas) together with lubricating oil (liquid) in compression chambers 25 and 26; a first liquid flow path 6 that circulates the first liquid, which is the liquid separated by a first gas-liquid separator 5 that separates liquid from the compressed gas discharged from the screw compressor (compressor body) 2, to a supply port 6c that opens into the compression chambers 25 and 26; and a second liquid flow path 9 that circulates the second liquid, which is the liquid separated by a second gas-liquid separator 7 that further separates liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator 5, to a communication port 9b that communicates with the first liquid flow path 6, wherein the communication port 9b is located below the supply port 6c.

[0065] As a result, even if gas contained in the second liquid is mixed into the first liquid flowing through the first liquid flow path 6 by the second liquid flowing through the first liquid flow path 6, the communication port 9b is located below the supply port 6c, so the mixed gas is prevented from accumulating in the flow path from the communication port 9b to the supply port 6c due to buoyancy. This prevents deterioration of cooling, sealing, lubrication, and other performance in the air compressor 1 due to a decrease in the amount of first liquid flowing into the screw compressor 2.

[0066] Furthermore, in the positive displacement compressor (air compressor 1) according to this embodiment, it is preferable that the gradient of the first liquid flow path 6 is an upward gradient from the communication port 9b to the supply port 6c. This makes it possible to suppress the accumulation of air contained in the second liquid in the flow path from the communication port 9b to the supply port 6c of the first liquid flow path 6.

[0067] Furthermore, the positive displacement compressor (air compressor 1) according to this embodiment preferably includes a third liquid passage (third liquid passages 22k, 22l) that branches off from the first liquid passage 6 upstream of the communication port 9b and supplies the first liquid to the bearing chambers 22d, 22e. This prevents the second liquid from flowing into the bearing chambers 22d, 22e and suppresses the flow of gas contained in the second liquid into the bearing chambers 22d, 22e. Therefore, even if the liquid accumulated in the bearing chambers 22d, 22e flows out to the part of the compression chambers 25, 26 where the intake stroke is performed, a decrease in the intake volume can be suppressed, and a decrease in the mass flow rate of compressed air can be suppressed.

[0068] Furthermore, it is preferable that the third liquid channel (third liquid channels 22k, 22l) branches off from the first liquid channel 6 below the communication port 9b. This prevents gas contained in the second liquid that flows into the first liquid channel 6 from the communication port 9b from flowing back into the third liquid channel (third liquid channels 22k, 22l).

[0069] (Second Embodiment) Figure 4 is a cross-sectional view of the screw compressor (compressor body) 202 and electric motor 3 provided in the positive displacement compressor (air compressor) according to the second embodiment. Figure 5 is a cross-sectional view of Figure 4 along the line V-V. The differences between the screw compressor (compressor body) 202 of this embodiment and the screw compressor (compressor body) 2 of the first embodiment are as follows.

[0070] Firstly, the first liquid flow path 206 is provided with a liquid storage section 206g for storing at least the first liquid separated by the first gas-liquid separator 5.

[0071] Secondly, in addition to the supply port 6c that opens to the male compression chamber 25, there is also a supply port 206c (see Figure 5) that opens to the female compression chamber 26.

[0072] Thirdly, in addition to third liquid channels 22k and 22l that supply the first liquid to the bearing 23 of the male rotor 21a, there are also third liquid channels 222k and 222l (not shown) that supply the first liquid to the bearing 23 of the female rotor 21b.

[0073] The liquid storage section 206g is provided in the first liquid flow path 206 and is a space having a larger cross-sectional area than the cross-sectional area of ​​the first liquid flow path 206. In this embodiment, the liquid storage section 206g is provided in the middle of the first liquid flow path 206d provided in the casing 222 and is a space having a larger cross-sectional area than the cross-sectional area of ​​the first liquid flow path 206d.

[0074] Furthermore, as shown in Figure 5, the casing 222 of this embodiment is provided with a first liquid flow path 206e that connects the liquid storage section 206g and the female compression chamber 26, and a supply port 206c that opens into the female compression chamber 26.

[0075] Furthermore, the casing 222 is provided with a third liquid passage 22k for supplying the first liquid to the low-pressure bearing 23 of the male rotor 21a, and a third liquid passage 222k for supplying the first liquid to the low-pressure bearing 23 of the female rotor 21b, both of which are in communication with the liquid reservoir 206g.

[0076] Furthermore, the casing 222 is provided with a third liquid channel 22l for supplying the first liquid to the high-pressure bearing 23 of the male rotor 21a, and a third liquid channel 222l (not shown) for supplying the first liquid to the high-pressure bearing 23 of the female rotor 21b, both of which are in communication with the liquid reservoir 206g.

[0077] Alternatively, a second liquid channel 9c may be connected to the liquid storage section 206g, and a communication port 209b may be provided. In this case, the first liquid and the second liquid are stored in the liquid storage section 206g. Therefore, it is preferable that the third liquid channel branches off from the first liquid channel 206 below the communication port 209b and supplies the first liquid to the bearing chambers 22d and 22e. In this embodiment, the third liquid channels 22k, 222k, 22l, and 222l are connected to the liquid storage section 206g below the communication port 209b. This makes it possible to suppress the inflow of gas contained in the second liquid into the third liquid channel.

[0078] [Effect] In the positive displacement compressor (air compressor) according to this embodiment, it is preferable that the first liquid passage 206 is provided with a liquid storage section 206g for storing at least the first liquid. This makes it possible to reduce the size of the tank for storing the first liquid in the first gas-liquid separator 5 without reducing the amount of lubricating oil in the air compressor.

[0079] Furthermore, in the positive displacement compressor according to this embodiment, it is preferable that a communication port 209b is provided in the liquid storage section 206g, and that a third liquid flow path (third liquid flow paths 22k, 222k, 22l, 222l) is provided that branches off from the first liquid flow path 206 below the communication port 209b and supplies liquid to the bearing chambers 22d, 22e. This makes it possible to suppress the flow of gas contained in the second liquid that flows into the first liquid flow path 206 (liquid storage section 206g in this embodiment) from the communication port 209b into the third liquid flow path (third liquid flow paths 22k, 222k, 22l, 222l).

[0080] (Third Embodiment) Figure 6 is a cross-sectional view of a compressor body (screw compressor) and electric motor in a positive displacement compressor (air compressor) according to the third embodiment of the present invention, in which the supply port of the first liquid passage opens into the low-pressure side bearing chamber. Figure 7 is a cross-sectional view taken along the line VII-VII in Figure 6. Figure 8 is a cross-sectional view of a compressor body (screw compressor) and electric motor in another positive displacement compressor (air compressor) according to another embodiment of the third embodiment of the present invention, in which the supply port of the first liquid passage opens into the high-pressure side bearing chamber. Figure 9 is a cross-sectional view taken along the line IX-IX in Figure 8.

[0081] The screw compressor (compressor body) 302 of this embodiment differs from the screw compressor (compressor body) 202 of the second embodiment in the following ways.

[0082] Firstly, the supply ports 306e and 306f of the first liquid passage 306 open into the bearing chambers 22d and 22e, and the first liquid passage 306 circulates the first liquid into the bearing chambers 22d and 22e.

[0083] Secondly, there are fourth liquid passages 322n, 322p (see Figure 7), 322o, and 322r (see Figure 9) that allow the liquid accumulated in the bearing chambers 22d and 22e to flow out from the bearing chambers 22d and 22e to the compression chambers 25 and 26.

[0084] Thirdly, it is equipped with a fifth liquid channel 322q that branches off from the first liquid channel 306 upstream of the communication port 309b and supplies the first liquid to the compression chambers 25 and 26.

[0085] First, a screw compressor (compressor body) 302a, in which the supply port of the first liquid flow path 306 opens into the low-pressure side bearing chamber 22d, will be explained using Figures 6 and 7.

[0086] The first liquid channel 306 communicates with the low-pressure side bearing chamber 22d via the first liquid channel 306d (including the liquid storage section 206g) and the first liquid channel 322k provided in the casing 322a. Therefore, the first liquid (lubricating oil) separated by the first gas-liquid separator 5 and flowing through the first liquid channel 306 is supplied to the low-pressure side bearing chamber 22d from the supply port 306e that opens into the low-pressure side bearing chamber 22d.

[0087] Furthermore, the second liquid channel 309 communicates with the first liquid channel 322k via a communication port 309b provided at the end of the second liquid channel 309c (see Figure 7) located in the casing 322. Therefore, the second liquid, which is separated by the second gas-liquid separator 7 and flows through the second liquid channel 309, flows into the first liquid channel 322k through the communication port 309b that connects the second liquid channel 309 to the first liquid channel 306.

[0088] On the other hand, if gas contained in the second fluid flowing into the first liquid flow path 306 from the communication port 309b accumulates in the flow path from the communication port 309b to the supply port 306e, there is a risk that the amount of the first liquid flowing into the low-pressure side bearing chamber 22d will decrease. For this reason, the communication port 309b of the second liquid flow path 309, which communicates with the first liquid flow path 322k, is located below the supply port 306e that opens into the low-pressure side bearing chamber 22d.

[0089] Furthermore, it is preferable that a fourth liquid passage is provided to allow the liquid accumulated in the low-pressure side bearing chamber 22d to flow out of the low-pressure side bearing chamber 22d. In this embodiment, the fourth liquid passage is a passage provided in the casing 322, which is the fourth liquid passage 322n, 322p (see Figure 7), and connects the bottom of the low-pressure side bearing chamber 22d with the compression chambers 25, 26. As a result, the lubricating oil (first liquid or first liquid mixed with the second liquid) accumulated at the bottom of the low-pressure side bearing chamber 22d flows out into the compression chambers 25, 26.

[0090] Furthermore, it is preferable that the fourth liquid passage communicates with the portion of the compression chambers 25 and 26 where the compression stroke takes place. This allows the liquid accumulated at the bottom of the low-pressure bearing chamber 22d to flow out to the portion of the compression chambers 25 and 26 where the compression stroke takes place.

[0091] Specifically, the fourth liquid passage 322n on the male rotor 21a side opens to the bottom of the low-pressure bearing chamber 22d and to the portion of the compression chambers 25 and 26 on the male rotor 21a side where the compression stroke takes place. The fourth liquid passage 322p on the female rotor 21b side opens to the bottom of the low-pressure bearing chamber 22d and to the compression chamber 26 on the female rotor 21b side where the compression stroke occurs.

[0092] Furthermore, it is preferable to have a fifth liquid channel that branches off from the first liquid channel 306 upstream of the communication port 309b and supplies the first liquid to the compression chambers 25 and 26. In this embodiment, the fifth liquid channel is a fifth liquid channel 322q provided in the casing 322, and connects the liquid storage section 206g with the compression chambers 25 and 26. As a result, the first liquid accumulated in the liquid storage section 206g flows out into the compression chambers 25 and 26.

[0093] Next, a screw compressor (compressor body) 302b, in which the supply port of the first liquid flow path 306 opens into the high-pressure side bearing chamber 22e, will be described using Figures 8 and 9.

[0094] The first liquid channel 306 communicates with the high-pressure side bearing chamber 22e via the first liquid channel 306d (including the liquid storage section 206g) and the first liquid channel 322l provided in the casing 322b. Therefore, the first liquid (lubricating oil) separated by the first gas-liquid separator 5 and flowing through the first liquid channel 306 is supplied to the high-pressure side bearing chamber 22e from the supply port 306f that opens into the high-pressure side bearing chamber 22e.

[0095] Furthermore, the second liquid channel 309 communicates with the first liquid channel 322l via a communication port 309b provided at the end of the second liquid channel 309c, which is provided in the casing 322. As a result, the second liquid, which is separated by the second gas-liquid separator 7 and flows through the second liquid channel 309, flows into the first liquid channel 322l from the communication port 309b, which communicates with the first liquid channel 306 in the second liquid channel 309.

[0096] On the other hand, if gas contained in the second fluid flowing into the first liquid flow path 306 from the communication port 309b accumulates in the flow path from the communication port 309b to the supply port 306f, there is a risk that the amount of the first liquid flowing into the high-pressure side bearing chamber 22e will decrease. For this reason, the communication port 309b of the second liquid flow path 309, which communicates with the first liquid flow path 322l, is located below the supply port 306f that opens into the low-pressure side bearing chamber 22d.

[0097] Furthermore, it is preferable that a fourth liquid passage is provided to allow the liquid accumulated in the high-pressure side bearing chamber 22e to flow out of the high-pressure side bearing chamber 22e. In this embodiment, the fourth liquid passage is a fourth liquid passage 322o, 322s (not shown) provided in the casing 322, which connects the bottom of the high-pressure side bearing chamber 22e with the compression chambers 25, 26. As a result, the lubricating oil (first liquid or first liquid mixed with the second liquid) accumulated at the bottom of the high-pressure side bearing chamber 22e flows out into the compression chambers 25, 26.

[0098] Furthermore, it is preferable that the fourth liquid passage communicates with the portion of the compression chambers 25 and 26 where the compression stroke takes place. This allows the liquid accumulated at the bottom of the high-pressure side bearing chamber 22e to flow out to the portion of the compression chambers 25 and 26 where the compression stroke takes place.

[0099] Specifically, the fourth liquid passage 322o on the male rotor 21a side opens to the bottom of the high-pressure bearing chamber 22e and to the portion of the compression chambers 25 and 26 on the male rotor 21a side where the compression stroke takes place. The fourth liquid passage 322s (not shown) on the female rotor 21b side opens to the bottom of the high-pressure bearing chamber 22e and to the compression chamber 26 on the female rotor 21b side where the compression stroke occurs.

[0100] Furthermore, it is preferable to have a fifth liquid channel that branches off from the first liquid channel 306 upstream of the communication port 309b and supplies the first liquid to the compression chambers 25 and 26. In this embodiment, the fifth liquid channel is a fifth liquid channel 322q provided in the casing 322, and connects the liquid storage section 206g with the compression chambers 25 and 26. As a result, the first liquid accumulated in the liquid storage section 206g flows out into the compression chambers 25 and 26.

[0101] [Effects] The positive displacement compressor (air compressor) according to this embodiment comprises a screw compressor 302, which is the compressor body that compresses air (gas) together with lubricating oil (liquid) in compression chambers 25 and 26; a first liquid passage 306 that circulates the first liquid, which is the liquid separated by a first gas-liquid separator 5 that separates liquid from the compressed gas discharged from the screw compressor 302, to supply ports 306e and 306f that open to bearing chambers 22d and 22e; and a second liquid passage 309 that circulates the second liquid, which is the liquid separated by a second gas-liquid separator 7 that further separates liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator 5, to a communication port 309b that communicates with the first liquid passage 306, wherein the communication port 309b is located below the supply ports 306e and 306f.

[0102] As a result, even if gas contained in the second liquid is mixed into the first liquid flowing through the first liquid flow path 306 by the second liquid flowing through the first liquid flow path 306, the communication port 309b is located below the supply ports 306e and 306f. Therefore, the mixed gas is prevented from accumulating in the flow path from the communication port 309b to the supply ports 306e and 306f due to buoyancy. This prevents deterioration of cooling, sealing, lubrication, and other performance aspects of the air compressor due to a decrease in the amount of first liquid flowing into the screw compressor 2.

[0103] Furthermore, in the positive displacement compressor according to this embodiment, it is preferable that the supply ports 306e and 306f open into the bearing chambers 22d and 22e, and that a fourth liquid flow path 322n, 322p, 322o, and 322s is provided to allow the liquid accumulated in the bearing chambers 22d and 22e to flow out from the bearing chambers 22d and 22e to the compression chambers 25 and 26.

[0104] Since the supply ports 306e and 306f open into the bearing chambers 22d and 22e, the gas contained in the second liquid flowing from the second liquid flow path 309 into the first liquid flow path 306 flows into the bearing chambers 22d and 22e.

[0105] On the other hand, since the bearing chambers 22d and 22e are provided with fourth liquid channels 322n, 322p, 322o, and 322s that allow liquid accumulated in the bearing chambers 22d and 22e to flow out, the internal pressure of the bearing chambers 22d and 22e is lower than the internal pressure of the first liquid channel 306. As a result, the gas that flows into the bearing chambers 22d and 22e expands, increasing the internal pressure of the bearing chambers 22d and 22e.

[0106] When the internal pressure of the bearing chambers 22d and 22e increases, the amount of liquid flowing out from the fourth liquid passages 322n, 322p, 322o, and 322s increases, and the amount of liquid stored in the bearing chambers 22d and 22e can be reduced. This suppresses the stirring of the liquid by the bearings and shaft seal components, thereby reducing power loss.

[0107] Furthermore, the positive displacement compressor according to this embodiment preferably includes a fifth liquid passage 322q that branches off from the first liquid passage 306 upstream of the communication port 309b and supplies the first liquid to the compression chambers 25 and 26. This prevents the second liquid from flowing into the compression chambers 25 and 26 from the fifth liquid passage 322q, preventing gas contained in the second liquid from mixing with the intake air, thus suppressing a decrease in the amount of intake air and suppressing a decrease in the mass flow rate of compressed air.

[0108] Furthermore, in the positive displacement compressor according to this embodiment, it is preferable that the fourth liquid passages 322n, 322p, 322o, and 322s communicate with the portion of the compression chambers 25 and 26 in which the compression stroke is performed. This suppresses the inflow of the second liquid into the intake air, prevents gas contained in the second liquid from mixing with the intake air, suppresses a decrease in the amount of intake air, and suppresses a decrease in the mass flow rate of compressed air.

[0109] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail for the purpose of explaining the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0110] Furthermore, embodiments of the present invention may also be as follows. That is, the above describes an embodiment in which a screw-type compressor is used in the compressor body of a positive displacement compressor. However, the invention is not limited thereto, and other types, for example, a piston-type compressor, may be used in the compressor body of a positive displacement compressor. Also, the above describes an embodiment in which lubricating oil is used as the liquid. However, the invention is not limited thereto, and other liquids, for example, a refrigerant or water, may be used. Also, the above describes an embodiment in which the first liquid passages 6, 206, and 306 are provided below the casings 22, 222, and 322, and the first liquid passages 6d, 206d, and 306d within the casings 22, 222, and 322 extend upward from the lower part of the casings 22, 222, and 322. However, the invention is not limited thereto, and for example, as shown in Figures 10 and 11, the first liquid passage 406 is provided on the side of the casing 422, and the first liquid passage 406d within the casing 422 may extend laterally from the side of the casing 422 and then extend upward.

[0111] 1...Air compressor, 2, 202, 302, 302a, 302b...Screw compressor, 22d, 22e...Bearing chamber, 22k, 22l...Third liquid passage, 22n, 22o, 322n, 322o, 322p, 322r, 322s...Fourth liquid passage, 25, 26...Compression chamber, 5...First gas-liquid separator, 6, 6d, 206, 206d, 306, 306d, 322k, 322l...First liquid passage, 6c, 6e, 6f, 206c, 306e, 306f...Supply port, 206g...Liquid storage section, 7...Second gas-liquid separator, 9, 9c, 309...Second liquid passage, 9b, 209b, 309b...Communication port, 322q...Fifth liquid passage

Claims

1. A positive displacement compressor comprising: a compressor body that compresses gas together with liquid in a compression chamber; a first liquid passage that circulates a first liquid, which is a liquid separated by a first gas-liquid separator that separates liquid from compressed gas discharged from the compressor body, to a supply port opening to the compression chamber or a bearing chamber housing a bearing; and a second liquid passage that circulates a second liquid, which is a liquid separated by a second gas-liquid separator that further separates liquid from the compressed gas from which the liquid has been separated by the first gas-liquid separator, to a communication port communicating with the first liquid passage, wherein the communication port is located below the supply port.

2. A positive displacement compressor according to claim 1, characterized in that the gradient of the first liquid flow path is an upward gradient from the communication port to the supply port.

3. A positive displacement compressor according to claim 1, wherein the supply port is open to the compression chamber and comprises a third liquid passage that branches off from the first liquid passage upstream of the communication port and supplies the first liquid to the bearing chamber.

4. A positive displacement compressor according to claim 3, characterized in that the third liquid passage branches off from the first liquid passage below the communication port.

5. A positive displacement compressor according to claim 1, characterized in that the supply port opens into the bearing chamber, and a fourth liquid flow path is provided for the liquid accumulated in the bearing chamber to flow out from the bearing chamber to the compression chamber.

6. A positive displacement compressor according to claim 5, characterized in that it comprises a fifth liquid passage that branches off from the first liquid passage upstream of the communication port and supplies the first liquid to the compression chamber.

7. A positive displacement compressor according to claim 6, characterized in that the fourth liquid passage communicates with the portion of the compression chamber in which the compression stroke is performed.

8. A positive displacement compressor according to claim 1, characterized in that the supply port opens to a portion of the compression chamber where the compression stroke is performed.

9. A positive displacement compressor according to claim 1, characterized in that the first liquid flow path is provided with at least a liquid storage section for storing the first liquid.

10. A positive displacement compressor according to claim 9, wherein the liquid reservoir is provided with the communication port, the supply port opens into the compression chamber, and a third liquid flow path branches off from the first liquid flow path below the communication port and supplies liquid to the bearing chamber.

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