Two-stage oil-free screw compressor

Abstract

To simplify a configuration of an oil flow passage in a two-stage oil-free screw compressor.SOLUTION: A two-stage oil-free screw compressor 1 comprises: a low-pressure stage casing 31 that defines a low-pressure stage compression chamber R1 for compressing fluid; a low-pressure stage compressor body 30 having a low-pressure stage cooling jacket 32 provided in the low-pressure stage casing 31; a high-pressure stage casing 41 that defines a high-pressure stage compression chamber R2 for compressing compressed air discharged from the low-pressure stage compressor body 30; a high-pressure stage compressor body 40 having a high-pressure stage cooling jacket 42 provided in the high-pressure stage casing 41; an oil cooler 52 that cools oil; and an oil flow path 3 in which the high-pressure stage cooling jacket 42, the oil cooler 52, and the low-pressure stage cooling jacket 32 are connected in series in this order and through which the oil flows.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a two-stage oil-free screw compressor.

Background Art

[0002] A two-stage oil-free screw compressor has a low-pressure stage compressor main body and a high-pressure stage compressor main body, and compresses air in two stages. The low-pressure stage compressor main body and the high-pressure stage compressor main body have a pair of male and female screw rotors that can rotate in a non-contact and oil-free manner. In a two-stage oil-free screw compressor, oil is not supplied to the compression chamber, but oil is supplied to drive mechanisms such as gears and bearings that drive the pair of male and female screw rotors. Since the oil is heated to a high temperature under the influence of compression heat, it is cooled by an oil cooler. For example, Patent Document 1 discloses such a two-stage oil-free screw compressor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the two-stage oil-free screw compressor of Patent Document 1, the oil flow path branches from the oil cooler to the low-pressure stage compressor main body and the high-pressure stage compressor main body. Therefore, the configuration of the oil flow path becomes complicated, and it is considered that a large amount of power is required to flow the oil due to the complicated flow.

[0005] An object of the present invention is to simplify the configuration of the oil flow path in a two-stage oil-free screw compressor.

Means for Solving the Problems

[0006] The present invention is A low-pressure stage compressor body having a low-pressure stage casing that defines a low-pressure stage compression chamber for compressing the inhaled fluid, and a low-pressure stage cooling jacket provided in the low-pressure stage casing, A high-pressure stage compressor body having a high-pressure stage casing that defines a high-pressure stage compression chamber for compressing the compressed fluid discharged from the low-pressure stage compressor body, and a high-pressure stage cooling jacket provided in the high-pressure stage casing, An oil cooler to cool the oil, The high-pressure stage cooling jacket, the oil cooler, and the low-pressure stage cooling jacket are connected in series in this order, and the oil passage through which the oil flows is We provide a two-stage oil-free screw compressor equipped with [specific features / features].

[0007] In this configuration, the oil flow path is connected in series with the high-pressure stage cooling jacket, oil cooler, and low-pressure stage cooling jacket in that order, allowing the oil flow path to be configured as a single, unbranched route. Therefore, the configuration of the oil flow path can be simplified, and the power required to circulate the oil can be reduced. This also allows for a reduction in the capacity of the oil pump, which powers the oil flow, compared to cases where the oil flow path branches.

[0008] The oil cooler may have an oil inlet at one end and an oil outlet at the other end in the longitudinal direction. The high-pressure stage compressor body may be positioned closer to the oil inlet than to the oil outlet. The low-pressure stage compressor body may be positioned closer to the oil outlet than to the oil inlet.

[0009] This configuration allows for shorter piping in the oil flow path between the low-pressure stage compressor body (low-pressure stage cooling jacket) and the oil cooler, as well as shorter piping in the oil flow path between the high-pressure stage compressor body (high-pressure stage cooling jacket) and the oil cooler, thus enabling a shorter oil flow path configuration.

[0010] The aforementioned two-stage oil-free screw compressor is A low-pressure stage gas cooler for cooling the compressed air discharged from the low-pressure stage compressor body, A high-pressure stage gas cooler cools the compressed air discharged from the high-pressure stage compressor body. You may also want to prepare for this, The low-pressure stage compressor body may be positioned closer to the oil cooler than the low-pressure stage gas cooler. The high-pressure stage compressor body may be positioned closer to the oil cooler than the high-pressure stage gas cooler.

[0011] This configuration allows the low-pressure and high-pressure stage compressors to be positioned closer to the oil cooler than the low-pressure and high-pressure stage gas coolers. In other words, when considering whether to shorten the compressed air passage or the oil passage, the choice is made to shorten the oil passage. This reduces the power required to circulate the oil.

[0012] The aforementioned two-stage oil-free screw compressor may further comprise the low-pressure stage compressor body, the high-pressure stage compressor body, the oil cooler, the low-pressure stage gas cooler, and an outer casing housing the low-pressure stage gas cooler. The oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler may be arranged horizontally and be air-cooled heat exchangers through which cooling air passes vertically. The oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler may be positioned directly below the exhaust port provided on the upper wall of the outer casing.

[0013] With this configuration, the cooling air passing vertically through the oil cooler, low-pressure stage gas cooler, and high-pressure stage gas cooler does not interfere with each other, resulting in high cooling efficiency. In addition, the cooling air that has become hot after passing through the oil cooler, low-pressure stage gas cooler, and high-pressure stage gas cooler is immediately exhausted through the exhaust port, thus suppressing the temperature rise inside the outer casing.

[0014] The aforementioned two-stage oil-free screw compressor is The low-pressure stage compressor body and the motor that drives the high-pressure stage compressor body, A gear case that stores a gear for transmitting driving force from the motor to the low-pressure stage compressor body and the high-pressure stage compressor body, An oil filter that is arranged adjacent to the gear case and filters the oil that has come out of the low-pressure stage cooling jacket, and may further be provided. In the oil flow path, the gear case may be arranged downstream of the oil filter.

[0015] According to this configuration, clean oil filtered of foreign matter by the oil filter can be supplied to the gear case (the gears inside), so that failures of the drive mechanism due to foreign matter can be suppressed. Also, since the oil filter is arranged adjacent to the gear case, the oil flow path can be configured to be short. Here, "adjacent" includes not only the case of being located next to but also the case of being directly in contact.

Effects of the Invention

[0016] According to the present invention, in a two-stage oil-free screw compressor, the configuration of the oil flow path can be simplified.

Brief Description of the Drawings

[0017] [Figure 1] Perspective view of a two-stage oil-free screw compressor according to an embodiment. [Figure 2] Perspective view of the two-stage oil-free screw compressor viewed from a different angle from FIG. 1. [Figure 3] Front view of the two-stage oil-free screw compressor of FIG. 1. [Figure 4] Right side view of the two-stage oil-free screw compressor of FIG. 1. [Figure 5] Schematic configuration diagram of the compressed air flow path, the oil flow path, and the cooling air flow path.

Modes for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0019] Referring to Figures 1-4, the two-stage oil-free screw compressor 1 compresses the fluid in two stages. In the following explanation, air will be used as an example of the fluid to be compressed, but any fluid can be compressed, not just air.

[0020] In Figures 1-4, the X direction represents the left-right direction (arrows pointing to the right), the Y direction represents the front-back direction (arrows pointing forward), and the Z direction represents the up-down direction (arrows pointing upward). However, these directional designations are for illustrative purposes only.

[0021] In the two-stage oil-free screw compressor 1 of this embodiment, each component is housed in an outer casing 10. The outer casing 10 is also commonly referred to as a package. In Figures 1 to 4, the outer casing 10 is partially shown with dashed lines to indicate its interior.

[0022] The outer casing 10 constitutes the outer surface of the two-stage oil-free screw compressor 1. For example, the outer casing 10 is a metal box with an outer rectangular parallelepiped shape. The outer casing 10 has an upper wall 11 and a lower wall 12 that face each other in the vertical direction, a left wall 14 and a right wall 13 that face each other in the left-right direction, and a front wall 16 and a rear wall 15 that face each other in the front-rear direction. The right wall 13 is provided with an intake port 13a (see the tip of the dashed-dotted arrow indicating airflow) for drawing in air to be compressed. The left wall 14 is provided with an outlet (not shown) for discharging compressed air. The lower part of the left wall 14 is provided with an intake port 14a (see the tip of the dashed-dotted arrow indicating airflow) for drawing in cooling air. The upper wall 11 is provided with an exhaust port 11a (see the base of the dashed-dotted arrow indicating airflow) for exhausting the high-temperature cooling air.

[0023] A motor 20 is located in the lower center of the outer casing 10. Cooling air drawn in from the intake port 14a is blown towards the motor 20 by a fan (not shown), thereby cooling the motor 20.

[0024] A gearbox 21, which houses gears, is mechanically connected to the motor 20. The gearbox 21 is positioned adjacent to the motor 20. The low-pressure stage compressor body 30 and the high-pressure stage compressor body 40 are also mechanically connected to the gearbox 21. The driving force of the motor 20 is transmitted to the low-pressure stage compressor body 30 and the high-pressure stage compressor body 40 via the gears in the gearbox 21. The lower part of the gearbox 21 is an oil reservoir 21a where oil, which will be described later, is stored.

[0025] The low-pressure stage compressor body 30 and the high-pressure stage compressor body 40 are arranged side-by-side adjacent to each other on the side of the gearbox 21. The low-pressure stage compressor body 30 and the high-pressure stage compressor body 40 are arranged in the front-to-back direction in the lower left side of the outer casing 10, such that their axial direction (the direction in which the rotation axis of the screw rotor, described later, extends) coincides with the left-to-right direction.

[0026] The low-pressure stage compressor body 30 is the part that performs the first stage of compression, and it increases the pressure of atmospheric air to a certain extent. The low-pressure stage compressor body 30 is fluidly connected to an intake port 13a provided on the right wall 13. The low-pressure stage compressor body 30 has a low-pressure stage casing 31 that defines a low-pressure stage compression chamber R1 for compressing the inhaled air, and a low-pressure stage cooling jacket 32 ​​provided on the low-pressure stage casing 31, which has a cooling function due to the flow of cooling oil. The low-pressure stage casing 31 is also provided with a low-pressure stage intake port 33 for suction and a low-pressure stage discharge port 34 for discharge. The oil inlet and oil outlet of the low-pressure stage cooling jacket 32 ​​are located on the side of the low-pressure stage casing 31, close to the front wall 16.

[0027] A pair of male and female screw rotors are arranged in the low-pressure stage compression chamber R1. The pair of male and female screw rotors are rotatably supported by bearings. The pair of male and female screw rotors are driven by a motor 20 via gears housed in a gearbox 21 to compress the air drawn into the low-pressure stage compression chamber R1. Here, the gears in the gearbox 21 and the bearings supporting the pair of male and female screw rotors are also referred to as the drive mechanism. In the two-stage oil-free screw compressor 1, oil is not supplied to the low-pressure stage compression chamber R1, but lubricating oil is supplied to the drive mechanism and cooling oil is supplied to the low-pressure stage cooling jacket 32. The same applies to the high-pressure stage compressor body 40 described below.

[0028] The high-pressure stage compressor body 40 is the part that performs the second stage of compression, further increasing the pressure of air that is already at a pressure higher than atmospheric pressure. The high-pressure stage compressor body 40 has a high-pressure stage casing 41 that defines a high-pressure stage compression chamber R2 for compressing the compressed air discharged from the low-pressure stage compressor body 30, and a high-pressure stage cooling jacket 42 provided in the high-pressure stage casing 41, which has a cooling function due to the flow of cooling oil. The high-pressure stage casing 41 is also provided with a high-pressure stage intake port 43 for suction and a high-pressure stage discharge port 44 for discharge. The oil inlet and oil outlet of the high-pressure stage cooling jacket 42 are located on the side of the high-pressure stage casing 41, close to the rear wall 15.

[0029] A pair of male and female screw rotors are arranged in the high-pressure stage compression chamber R2. The pair of male and female screw rotors are rotatably supported by bearings. The pair of male and female screw rotors are driven by a motor 20 via gears housed in a gearbox 21 to compress the air drawn into the high-pressure stage compression chamber R2.

[0030] The low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 are located in the upper part of the outer casing 10. The low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 are arranged horizontally (more specifically, left-to-right) directly below the exhaust port 11a of the upper wall 11. The high-pressure stage gas cooler 51, the low-pressure stage gas cooler 50, and the oil cooler 52 are arranged in this order from left to right. Therefore, the low-pressure stage compressor body 30 is located closer to the oil cooler 52 than to the low-pressure stage gas cooler 50. The high-pressure stage compressor body 40 is located closer to the oil cooler 52 than to the high-pressure stage gas cooler 51.

[0031] In this embodiment, the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 are air-cooled heat exchangers through which cooling air passes vertically. In Figures 1 to 4, the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 are schematically shown as roughly rectangular parallelepipeds, but in reality, they are configured so that air can pass from bottom to top.

[0032] The low-pressure stage gas cooler 50 is fluidically connected to the low-pressure stage compressor body 30 and the high-pressure stage compressor body 40. The low-pressure stage gas cooler 50 has an air inlet 50a for the compressed air to be cooled at one end (the front end in this embodiment) and an air outlet 50b for the compressed air to be cooled at the other end (the rear end in this embodiment). Compressed air discharged from the low-pressure stage compressor body 30 enters the low-pressure stage gas cooler 50 through the air inlet 50a, is cooled by the low-pressure stage gas cooler 50, exits the low-pressure stage gas cooler 50 through the air outlet 50b, and flows to the high-pressure stage compressor body 40.

[0033] The high-pressure stage gas cooler 51 is fluidically connected to the high-pressure stage compressor body 40 and a discharge port (not shown). The high-pressure stage gas cooler 51 has, in the longitudinal direction (front-to-back direction in this embodiment), an air outlet 51b for the compressed air to be cooled at one end (front end in this embodiment) and an air inlet 51a for the compressed air to be cooled at the other end (rear end in this embodiment). Compressed air discharged from the high-pressure stage compressor body 40 enters the high-pressure stage gas cooler 51 through the air inlet 51a, is cooled by the high-pressure stage gas cooler 51, exits the high-pressure stage gas cooler 51 through the air outlet 51b, and is sent to a desired destination through the discharge port of the outer casing 10.

[0034] The oil cooler 52 is fluidly connected to the low-pressure stage cooling jacket 32 ​​and the high-pressure stage cooling jacket 42. The oil cooler 52 has an oil inlet 52a at one end (the rear end in this embodiment) and an oil outlet 52b at the other end (the front end in this embodiment) in the longitudinal direction (front-to-back direction). In this embodiment, the high-pressure stage compressor body 40 is positioned closer to the oil inlet 52a than to the oil outlet 52b. The low-pressure stage compressor body 30 is positioned closer to the oil outlet 52b than to the oil inlet 52a. Oil coming out of the high-pressure stage cooling jacket 42 of the high-pressure stage compressor body 40 enters the oil cooler 52 through the oil inlet 52a. The oil is cooled by the oil cooler 52 and flows out of the oil outlet 52b to the low-pressure stage cooling jacket 32 ​​of the low-pressure stage compressor body 30. In other words, the high-pressure stage cooling jacket 42, the oil cooler 52, and the low-pressure stage cooling jacket 32 ​​are connected in series in this order, forming a part of the oil flow path 3 through which the oil flows. In this embodiment, the oil cooler 52 is provided only between the high-pressure stage cooling jacket 42 and the low-pressure stage cooling jacket 32; that is, there is no oil cooler upstream of the high-pressure stage cooling jacket 42.

[0035] An oil filter 60 is positioned adjacent to the low-pressure stage compressor body 30. The oil filter 60 filters the oil discharged from the low-pressure stage cooling jacket 32, removing foreign matter from the oil. The oil filter 60 is positioned adjacent to the gearbox 21, and the oil discharged from the oil filter 60 is supplied to the gearbox 21 to lubricate the aforementioned drive mechanism. That is, in the oil passage 3, the gearbox 21 is positioned downstream of the oil filter 60. In this embodiment, no intervening material is provided between the gearbox 21 and the oil filter 60.

[0036] The flow of oil in this oil passage 3 is carried out by an oil pump 70 located near the rear wall 15 in the lower part of the outer casing 10. The oil pump 70 is located below the motor 20 and near the gearbox 21. The oil pump 70 is fluidically connected to the oil reservoir 21a and the high-pressure stage cooling jacket 42. Oil flows from the oil reservoir 21a through the oil pump 70 to the high-pressure stage cooling jacket 42.

[0037] In the vertical direction, the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 are all located above the motor 20, and a duct 80 is positioned between the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 and the motor 20. In the illustrated example, the duct 80 is a rectangular tube extending in the vertical direction, but the rear surface is partially transparent so that the interior can be seen.

[0038] A blower fan 81 is located inside the duct 80. The blower fan 81 blows cooling air drawn into the interior of the outer casing 10 from the intake port 14a upwards. Thus, the blower fan 81 blows cooling air through the duct 80 to the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52.

[0039] Referring to Figure 5, the two-stage oil-free screw compressor 1 having the above configuration includes a compressed air passage 2, an oil passage 3, and a cooling air passage 4. In Figure 5, the compressed air passage 2 is indicated by a dashed line arrow, the oil passage 3 is indicated by a dashed line arrow, and the cooling air passage 4 is indicated by a thick line arrow.

[0040] In the compressed air passage 2, air from outside the outer casing 10 flows from the intake port 13a to the low-pressure stage intake port 33 of the low-pressure stage compressor body 30. The air is drawn into the low-pressure stage compressor body 30 from the low-pressure stage intake port 33, compressed in the low-pressure stage compression chamber R1, and discharged as compressed air from the low-pressure stage discharge port 34. The compressed air discharged from the low-pressure stage discharge port 34 is hot due to the heat of compression. The hot compressed air flows to the low-pressure stage gas cooler 50 and is cooled by the low-pressure stage gas cooler 50. The cooled compressed air flows to the high-pressure stage intake port 43 of the high-pressure stage compressor body 40. The compressed air is drawn into the high-pressure stage compressor body 40 from the high-pressure stage intake port 43, compressed in the high-pressure stage compression chamber R2, and discharged from the high-pressure stage discharge port 44. The compressed air discharged from the high-pressure stage discharge port 44 is hot due to the heat of compression. The high-temperature compressed air flows to the high-pressure stage gas cooler 51, is cooled by the high-pressure stage gas cooler 51, and is then sent to the desired destination.

[0041] In the oil flow path 3, the oil stored in the oil reservoir 21a flows from the oil pump 70 to the high-pressure stage cooling jacket 42, cooling the high-pressure stage compressor body 40. The oil that exits the high-pressure stage cooling jacket 42 is hot. The hot oil flows to the oil cooler 52, where it is cooled. The cooled oil flows to the low-pressure stage cooling jacket 32, cooling the low-pressure stage compressor body 30. The oil that exits the low-pressure stage cooling jacket 32 ​​is hot, but it is cooler than the oil that exits the high-pressure stage cooling jacket 42 and still has cooling capacity. The oil that exits the low-pressure stage cooling jacket 32 ​​flows to the oil filter 60. The oil has impurities removed by the oil filter 60 and flows to the gearbox 21. The oil that enters the gearbox 21 lubricates the drive mechanism. The oil used for lubrication is stored in the oil reservoir 21a of the gearbox 21 and flows to the oil pump 70. The oil then flows again from the oil pump 70 to the high-pressure stage cooling jacket 42, cooling the high-pressure stage compressor body 40, and the flow continues in the same manner thereafter. In this way, the oil passage 3 is configured to circulate in a single passage without branching. That is, the oil passage 3 is configured to supply the oil sent from the oil pump 70 to various lubrication points that require cooling or lubrication, and then return it to the oil reservoir 21a of the gearbox 21.

[0042] In the cooling air passage 4, cooling air from outside the outer casing 10 is drawn in through the intake port 14a and blown toward the motor 20 by the motor fan to cool the motor 20. The cooling air that has cooled the motor 20 is blown upward through the duct 80 by the blower fan 81 and passes through the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52. In the low-pressure stage gas cooler 50, the cooling air cools the compressed air discharged from the low-pressure stage compressor body 30. In the high-pressure stage gas cooler 51, the cooling air cools the compressed air discharged from the high-pressure stage compressor body 40. In the oil cooler 52, the cooling air cools the oil. The cooling air that has passed through the low-pressure stage gas cooler 50, the high-pressure stage gas cooler 51, and the oil cooler 52 is hot. The hot cooling air is exhausted outside the outer casing 10 through the exhaust port 11a.

[0043] The two-stage oil-free screw compressor 1 of this embodiment provides the following effects.

[0044] Since the oil passage 3 is connected in series with respect to the high-pressure stage cooling jacket 42, the oil cooler 52, and the low-pressure stage cooling jacket 32, the oil passage 3 can be configured as a single, unbranched route. Therefore, the configuration of the oil passage 3 can be simplified, and the power required to circulate the oil can be reduced. This also allows for a reduction in the capacity of the oil pump 70, which powers the oil circulation, compared to the case where the oil passage has branches.

[0045] Furthermore, since the piping constituting the oil passage 3 between the low-pressure stage compressor body 30 (low-pressure stage cooling jacket 32) and the oil cooler 52, and the piping constituting the oil passage between the high-pressure stage compressor body 40 (high-pressure stage cooling jacket 42) and the oil cooler 52 can be shortened, the oil passage 3 can be configured to be shorter.

[0046] Furthermore, the low-pressure stage compressor body 30 and the high-pressure stage compressor body 40 can be positioned closer to the oil cooler 52 than the low-pressure stage gas cooler 50 and the high-pressure stage gas cooler 51. In other words, when considering whether to shorten the compressed air passage 2 or the oil passage 3, the choice is made to shorten the oil passage 3. This reduces the power required to circulate the oil.

[0047] Furthermore, since the oil filter 60 filters out impurities, clean oil can be supplied to the gearbox 21 (the internal gears), which helps to suppress failures of the drive mechanism caused by impurities. Also, because the oil filter 60 is located adjacent to the gearbox 21, the oil passage 3 can be made shorter.

[0048] Furthermore, since the oil cooler 52, the low-pressure stage gas cooler 50, and the high-pressure stage gas cooler 51 are arranged horizontally, the cooling air passing through them vertically does not interfere with each other. Therefore, high cooling efficiency can be achieved. In addition, the cooling air that has become hot after passing through the oil cooler 52, the low-pressure stage gas cooler 50, and the high-pressure stage gas cooler 51 is immediately exhausted from the exhaust port 11a, thus suppressing the temperature rise inside the outer casing.

[0049] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be implemented with various modifications within the scope of this invention.

[0050] This disclosure may include the following aspects: (Aspect 1) A low-pressure stage compressor body having a low-pressure stage casing that defines a low-pressure stage compression chamber for compressing the inhaled fluid, and a low-pressure stage cooling jacket provided in the low-pressure stage casing, A high-pressure stage compressor body having a high-pressure stage casing that defines a high-pressure stage compression chamber for compressing the compressed fluid discharged from the low-pressure stage compressor body, and a high-pressure stage cooling jacket provided in the high-pressure stage casing, The low-pressure stage compressor body and the motor that drives the high-pressure stage compressor body, An oil cooler to cool the oil, The low-pressure stage compressor body, the high-pressure stage compressor body, the motor, and the outer casing housing the oil cooler, The high-pressure stage cooling jacket, the oil cooler, and the low-pressure stage cooling jacket are connected in series in this order, and the oil passage through which the oil flows is A two-stage oil-free screw compressor equipped with [feature name / feature name]. (Aspect 2) The oil cooler has an oil inlet at one end and an oil outlet at the other end in the longitudinal direction. The high-pressure stage compressor body is positioned closer to the oil inlet than to the oil outlet. The two-stage oil-free screw compressor according to embodiment 1, wherein the low-pressure stage compressor body is located closer to the oil outlet than to the oil inlet. (Aspect 3) A low-pressure stage gas cooler for cooling the compressed air discharged from the low-pressure stage compressor body, A high-pressure stage gas cooler cools the compressed air discharged from the high-pressure stage compressor body. Furthermore, The low-pressure stage compressor body is positioned closer to the oil cooler than the low-pressure stage gas cooler. A two-stage oil-free screw compressor according to embodiment 1 or 2, wherein the high-pressure stage compressor body is located closer to the oil cooler than the high-pressure stage gas cooler. (Aspect 4) The oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler are arranged horizontally and are air-cooled heat exchangers through which cooling air passes vertically. The two-stage oil-free screw compressor according to embodiment 3, wherein the oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler are located directly below an exhaust port provided on the upper wall of the outer casing. (Aspect 5) A gearbox housing gears that transmit driving force from the motor to the low-pressure stage compressor body and the high-pressure stage compressor body, An oil filter is positioned adjacent to the gearbox and removes impurities from the oil coming out of the low-pressure stage cooling jacket. Furthermore, A two-stage oil-free screw compressor according to any one of embodiments 1 to 4, wherein the gearbox is located downstream of the oil filter in the oil passage. [Explanation of Symbols]

[0051] 1. Two-stage oil-free screw compressor 2 Compressed air passage 3 Oil flow path 4. Cooling air passage 10 Outer box 11 Upper wall 11a Exhaust port 12 Lower wall 13 Right wall 13a Inlet 14 Left wall 14a Inlet 15 Back wall 16 Front wall 20 motors 21 Gearbox 21a Oil storage section 30 Low-pressure stage compressor unit 31 Low-pressure stage casing 32 Low-pressure stage cooling jacket 33 Low-pressure stage air intake 34 Low-pressure discharge port 40 High-pressure stage compressor unit 41 High-pressure stage casing 42 High-Pressure Stage Cooling Jacket 43 High-pressure stage air intake 44 High-pressure stage discharge port 50 Low-Pressure Stage Gas Cooler 50a air inlet 50b Air outlet 51 High-pressure stage gas cooler 51a Air Inlet 51b Air outlet 52 Oil cooler 52a Oil inlet 52b oil outlet 60 Oil filter 70 Oil pump 80 duct 81 Blower fan R1 Low-pressure stage compression chamber R2 High-pressure stage compression chamber

Claims

1. A low-pressure stage compressor body having a low-pressure stage casing that defines a low-pressure stage compression chamber for compressing the inhaled fluid, and a low-pressure stage cooling jacket provided in the low-pressure stage casing, A high-pressure stage compressor body having a high-pressure stage casing that defines a high-pressure stage compression chamber for compressing the compressed fluid discharged from the low-pressure stage compressor body, and a high-pressure stage cooling jacket provided in the high-pressure stage casing, An oil cooler to cool the oil, The high-pressure stage cooling jacket, the oil cooler, and the low-pressure stage cooling jacket are connected in series in this order, and the oil passage through which the oil flows is Equipped with, The oil cooler has an oil inlet at one end and an oil outlet at the other end in the longitudinal direction. The high-pressure stage compressor body is positioned closer to the oil inlet than to the oil outlet. The low-pressure stage compressor body is a two-stage oil-free screw compressor, positioned closer to the oil outlet than to the oil inlet.

2. A low-pressure stage gas cooler for cooling the compressed air discharged from the low-pressure stage compressor body, A high-pressure stage gas cooler cools the compressed air discharged from the high-pressure stage compressor body. Furthermore, The low-pressure stage compressor body is positioned closer to the oil cooler than the low-pressure stage gas cooler. The two-stage oil-free screw compressor according to claim 1, wherein the high-pressure stage compressor body is positioned closer to the oil cooler than the high-pressure stage gas cooler.

3. The low-pressure stage compressor body, the high-pressure stage compressor body, the oil cooler, the low-pressure stage gas cooler, and the outer casing housing the high-pressure stage gas cooler are further comprising: The oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler are arranged horizontally and are air-cooled heat exchangers through which cooling air passes vertically. The two-stage oil-free screw compressor according to claim 2, wherein the oil cooler, the low-pressure stage gas cooler, and the high-pressure stage gas cooler are located directly below an exhaust port provided on the upper wall of the outer casing.

4. The low-pressure stage compressor body and the motor that drives the high-pressure stage compressor body, A gearbox housing gears that transmit driving force from the motor to the low-pressure stage compressor body and the high-pressure stage compressor body, An oil filter is positioned adjacent to the gearbox and filters the oil that has come out of the low-pressure stage cooling jacket. Furthermore, The two-stage oil-free screw compressor according to claim 1, wherein the gearbox is located downstream of the oil filter in the oil passage.

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