Oil-injected compressor

Abstract

An oil-injected compressor 1 includes: an oil-injected compressor body 100; a centrifugal separation part 11 for separating oil from fluid discharged by the compressor body 100; an oil tank 12 for storing the oil separated by the centrifugal separation part 11; a heat exchanger 31 for cooling the oil; and a buffer tank 34 separate from the oil tank 12, the compressor body 100 and the heat exchanger 31, and for storing the oil.

Description

Oil-lubricated compressor

[0001] The present disclosure relates to oil-lubricated compressors.

[0002] In an oil-lubricated compressor, oil is supplied to the compressor body for lubrication, cooling, sealing, etc. The oil supplied to the compressor body is recovered, cooled, and then supplied to the compressor body again. In this way, the oil circulates in an oil-lubricated compressor (see, for example, Patent Document 1).

[0003] International Publication No. 2019 / 093181

[0004] The amount of oil held by the entire compressor is closely related to the rate of oil deterioration. If the amount of oil held by the entire compressor becomes small, the oil circulation speed increases, and the oil usage frequency increases, which can lead to early oil deterioration. Therefore, in oil-lubricated compressors, a certain amount of oil must be held by the entire compressor to prevent early oil deterioration.

[0005] Oil coolers (heat exchangers) used to cool oil have various capacities and oil storage capacities, even when selected for the same heat exchange capacity (cooling capacity). For example, shell-and-tube heat exchangers have a large volume, resulting in a large oil storage capacity. Plate and finned-tube heat exchangers, for example, have a small volume, resulting in a small oil storage capacity. On the other hand, because oil coolers (heat exchangers) are selected based on the required heat exchange capacity (cooling capacity), using a relatively small heat exchanger with good heat exchange performance results in a small oil storage capacity. This reduces the overall oil storage capacity of the compressor, potentially leading to rapid oil degradation. Therefore, when selecting a heat exchanger, it is necessary to balance the heat exchange capacity and oil storage capacity. It is also necessary to ensure an appropriate oil storage capacity for the entire compressor, taking into account the rate of oil degradation.

[0006] An object of the present disclosure is to ensure an appropriate amount of oil is retained throughout an oil-injected compressor.

[0007] The present disclosure provides an oil-lubricated compressor including an oil-lubricated compressor body, an oil separation section that separates oil from a fluid discharged by the compressor body, a first reservoir section that stores the oil separated by the oil separation section, a heat exchanger that cools the oil, and a second reservoir section that is separate from the first reservoir section, the compressor body, and the heat exchanger and stores the oil.

[0008] This configuration allows oil to be stored not only in the first reservoir but also in the second reservoir, making it easy to ensure an appropriate oil reserve amount sufficient to prevent early oil deterioration. Furthermore, compared to a single large reservoir, this configuration allows for greater flexibility in installation and reduces installation costs because installation can be performed without increasing the package size. Furthermore, a relatively small heat exchanger with good heat exchange performance can be used to cool the oil. Furthermore, the second reservoir can be added while using the existing compressor body and heat exchanger.

[0009] The second reservoir may be provided in the oil flow path upstream of the compressor body and downstream of the heat exchanger.

[0010] This configuration allows the oil cooled by the heat exchanger to be stored in the second reservoir. This allows the necessary amount of low-temperature oil to be maintained and supplied to the compressor body in a timely manner. Furthermore, since the second reservoir is located downstream of the heat exchanger, a small amount of oil fills the second reservoir due to back pressure during startup, ensuring an uninterrupted supply of oil to the compressor body when the three-way valve is switched.

[0011] The second reservoir may be provided in the oil flow path upstream of the heat exchanger and downstream of the first reservoir.

[0012] According to this configuration, the oil stored in the second reservoir can be cooled by the heat exchanger before being supplied to the compressor body, thereby ensuring that cooled oil is supplied from the heat exchanger to the compressor body.

[0013] The second reservoir may have an inlet for the oil from the first reservoir provided on a lower surface thereof, and may be located at a higher position than the first reservoir.

[0014] With this configuration, the oil stored in the second storage section can be easily returned to the first storage section using potential energy when the oil-lubricated compressor is stopped, allowing oil to be changed without leaving degraded oil in the second storage section.

[0015] According to the present disclosure, in an oil-injected compressor, an appropriate amount of oil can be secured throughout the compressor.

[0016] An overall system diagram of an oil-lubricated compressor according to a first embodiment. A system diagram schematically showing an oil circulation system of the oil-lubricated compressor according to the first embodiment. An overall system diagram of an oil-lubricated compressor according to a second embodiment. A system diagram schematically showing an oil circulation system of the oil-lubricated compressor according to the second embodiment.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0018] First Embodiment Fig. 1 shows a system diagram of an oil-lubricated compressor 1 according to a first embodiment. In this embodiment, the components of the oil-lubricated compressor 1 are arranged in a box-shaped package exterior 2. The oil-lubricated compressor 1 has an oil-lubricated compressor main body 100, which draws in air from the outside, compresses it internally, and discharges the compressed air. Here, the object to be compressed by the compressor main body 100 will be described using air as an example, but this is not particularly limited, and any fluid may be compressed.

[0019] The compressor body 100 of this embodiment has a compression section 120 and a motor 130 that drives the compression section 120 .

[0020] The compression section 120 is a part that has a compression function. The exterior of the compression section 120 is formed by a rotor casing 121. The rotor casing 121 is provided with a suction port 121a and a discharge port 121b. In this embodiment, the compressor body 100 is of a screw type, and a screw rotor 122 is housed in the rotor casing 121. However, the type of the compressor body 100 is not particularly limited and may be any type that requires oil supply.

[0021] The oil-lubricated compressor 1 has a compressed air supply system including a compressor body 100 and an oil separator / recovery device 10. In addition to the oil separator / recovery device 10, the compressed air supply system is provided with a pressure-maintaining check valve 21 and a gas cooler 22.

[0022] The oil separator / recovery device 10 is connected to the pressure-maintaining check valve 21 through a pipe 5b. The compressed air from which oil has been separated in the oil separator / recovery device 10 flows to the pressure-maintaining check valve 21 through the pipe 5b.

[0023] The pressure-maintaining check valve 21 has the function of maintaining a constant pressure inside the oil tank (first reservoir) 12 (described later). The pressure-maintaining check valve 21 is connected to the gas cooler 22 through the pipe 5c, and the compressed air whose pressure has been adjusted by the pressure-maintaining check valve 21 flows to the gas cooler 22 through the pipe 5c.

[0024] The gas cooler 22 is an air-cooled heat exchanger. Here, the high-temperature compressed air flowing in from the pipe 5c is cooled by ambient air at room temperature. However, the gas cooler 22 is not limited to this air-cooled heat exchanger and may be any other type. The gas cooler 22 is connected to the dryer 23 through the pipe 5d, and the compressed air cooled and dehumidified by the dryer 23 flows to any destination through the pipe 5e. However, regardless of the presence or absence of the dryer 23, the compressed air may also flow directly from the gas cooler 22 through the pipe 5e to any destination.

[0025] The oil-lubricated compressor 1 also has an oil circulation system including the compressor body 100 and the oil separator / recovery device 10. In addition to the oil separator / recovery device 10, the oil circulation system is provided with a heat exchanger 31, an oil filter 32, a three-way valve 33, and a buffer tank (second reservoir) 34.

[0026] The oil separator / recovery device 10 has a centrifugal separation section (oil separation section) 11 , an oil tank (first storage section) 12 , and a separator 13 .

[0027] The centrifugal separator 11 separates oil from the compressed air by centrifugal separation. The oil separated by the centrifugal separator 11 is stored in the oil tank 12. The centrifugal separator 11 is an example of an oil separator, but the embodiment is not particularly limited. Any embodiment of the oil separator may be adopted as long as it has the function of separating oil.

[0028] The separator 13 performs a second separation of oil from the compressed air from which the oil has been primarily separated in the centrifugal separation unit 11. The oil separated by the separator 13 is returned to the oil tank 12 or the compressor body 100. The separator 13 may be an example of the oil separation unit. A pipe 5b extends from the separator 13 and is connected to the pressure-maintaining check valve 21 described above.

[0029] The oil tank 12 is a portion for storing oil and is, for example, a metal tank. An oil temperature sensor 41 is attached to the oil tank 12, and the oil temperature sensor 41 can measure the oil temperature inside the oil tank 12.

[0030] The oil tank 12 is connected to the heat exchanger 31 through a pipe 6a, and the oil stored in the oil tank 12 flows to the heat exchanger 31 through the pipe 6a.

[0031] The heat exchanger 31 is an oil cooler that cools oil with a low-temperature fluid. The low-temperature fluid may be, for example, a gas such as air, or a liquid such as water. That is, the heat exchanger 31 may be either an air-cooled or water-cooled type. The heat exchanger 31 may be, for example, a plate-type heat exchanger formed by stacking multiple heat transfer plates, or may be, for example, a fin-tube-type heat exchanger formed by attaching multiple fins to tubes. The heat exchanger 31 is connected to the buffer tank 34 via the pipe 6b, and the oil cooled by the heat exchanger 31 flows into the buffer tank 34 via the pipe 6b.

[0032] The buffer tank 34 is a portion for storing oil and is, for example, a metal tank. The buffer tank 34 is separate from the oil tank 12. The buffer tank 34 is also separate from the compressor main body 100 and the heat exchanger 31. The buffer tank 34 is provided with an inlet 34a and an outlet 34b, and can store oil supplied through the inlet 34a to a certain depth.

[0033] The supply of oil to the buffer tank 34 and the oil tank 12 does not require an oil pump, and the oil is circulated by the differential pressure from the oil separator / recovery device 10. However, an oil pump may be provided in the pipe 6c and controlled by the control device 50 described below. Alternatively, for example, the control device 50 may receive the oil temperature from the oil temperature sensor 41 and control the rotation speed of the oil pump based on the received oil temperature.

[0034] In this embodiment, the outlet 34b of the buffer tank 34 is located on the bottom surface of the buffer tank 34 so that oil can flow into the oil tank 12 when the compressor is stopped. The oil inlet 34a for the buffer tank 34 is located above the outlet 34b and at a position that ensures sufficient storage capacity for the buffer tank 34. Since the outlet 34b is located on the bottom surface of the buffer tank 34, the oil is supplied to the compressor body 100 from the outlet 34b as soon as it flows into the buffer tank 34, eliminating time loss. In order to use potential energy to allow the oil to flow in this way, the outlet 34b of the buffer tank 34 can be located at a higher position than the oil tank 12 and the compressor body 100.

[0035] Alternatively, the inlet 34a of the buffer tank 34 may be located at a lower position than the outlet 34b. Also, the inlet 34a of the buffer tank 34 may be located at a higher position than the oil tank 12. This makes it easy to return the oil stored in the buffer tank 34 to the oil tank 12 using potential energy when the oil-lubricated compressor 1 is stopped, and oil can be changed without degraded oil remaining in the buffer tank 34. Furthermore, the oil filter 32, which will be described later, may be located at a higher position than the three-way valve 33. This ensures that the oil is returned to the oil tank 12 when the compressor is stopped, suppresses oil from flowing into the compressor main body 100, and suppresses an increase in starting torque when the compressor is restarted.

[0036] Furthermore, a valve may be provided in the pipe 6c, and the amount of oil flowing out of the buffer tank 34 may be adjusted by controlling the valve using a control device 50 described below. An oil level gauge may be provided in the buffer tank 34, and the amount of oil flowing to the compressor body 100 may be adjusted by adjusting the opening of the valve according to the amount of oil stored in the buffer tank 34. Furthermore, for example, the control device 50 may receive the oil temperature from the oil temperature sensor 41, and control the opening of the valve based on the received oil temperature.

[0037] The capacity of the buffer tank 34 can be set appropriately depending on the amount of oil required. The buffer tank 34 may have a volume approximately equal to that of the oil tank 12. Alternatively, the buffer tank 34 may have a volume larger or smaller than that of the oil tank 12. The buffer tank 34 is connected to the compressor body 100 via pipes 6c and 6d, and the oil stored in the buffer tank 34 flows to the compressor body 100 via pipes 6c and 6d. The pipes 6c and 6d are connected via an oil filter 32.

[0038] The oil filter 32 is a filter that filters out unwanted substances such as dust from the oil. The oil filter 32 is connected to the compressor body 100 via the pipe 6d, and the oil from which unwanted substances have been removed by the oil filter 32 flows to the compressor body 100 via the pipe 6d.

[0039] A three-way valve 33 is attached to the pipes 6a and 6c, and the pipes 6a and 6c are connected via the three-way valve 33. The three-way valve 33 allows the oil stored in the oil tank 12 to selectively bypass the heat exchanger 31 and the buffer tank 34 (i.e., without passing through the heat exchanger 31 and the buffer tank 34) and flow to the oil filter 32.

[0040] The three-way valve 33 may also function as a temperature control valve. In this case, the three-way valve 33 is controlled according to the temperature of the oil passing through the three-way valve 33. Specifically, when the oil temperature is below a predetermined threshold, the three-way valve 33 operates to allow oil to flow from the oil tank 12 to the oil filter 32, bypassing the heat exchanger 31 and the buffer tank 34. When the oil temperature is equal to or higher than the predetermined threshold, the three-way valve 33 operates to allow oil to flow from the oil tank 12 to the oil filter 32, passing through the heat exchanger 31 and the buffer tank 34. This allows the oil to pass through the heat exchanger 31 only when cooling of the oil is necessary, thereby avoiding unnecessary cooling.

[0041] The compressor body 100 is provided with a rotor oil supply port 121c for supplying oil to the screw rotor 122. The rotor oil supply port 121c is a hole provided in the rotor casing 121 and communicates with the screw rotor 122. Oil from which impurities have been removed by the oil filter 32 flows through the rotor oil supply port 121c into the rotor casing 121 via the pipe 6d and is supplied to the screw rotor 122 and is used for lubricating, cooling, sealing, and the like of the screw rotor 122.

[0042] Although not shown in detail, oil from which unnecessary substances have been removed by an oil filter 32 is also supplied to the bearings 125 and 126 and the motor 130 .

[0043] The oil supplied to the screw rotor 122 and the oil supplied to the bearings 125, 126 is discharged from the discharge port 121b together with the compressed air and flows through the pipe 5a to the oil separator / recovery device 10. In this way, the oil is circulated.

[0044] The oil-injected compressor 1 has a control device 50. The control device 50 is configured with hardware such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory), as well as software implemented therein. The control device 50 controls each component of the oil-injected compressor 1.

[0045] Referring to FIG. 2, the oil circulation system will be described using a schematic diagram for easier explanation.

[0046] Oil discharged from the compressor main body 100 together with compressed air flows through the pipe 5a to the oil tank 12 of the oil separator / recovery device 10. Next, the oil flows from the oil tank 12 through the pipe 6a to the three-way valve 33. The three-way valve 33 performs selective operation related to the bypass described above. That is, the oil flows from the oil tank 12 through the pipe 6a and the three-way valve 33 to the heat exchanger 31, from the heat exchanger 31 through the pipe 6b to the buffer tank 34, and from the buffer tank 34 through the pipes 6c and 6d to the compressor main body 100. Alternatively, the oil flows from the oil tank 12 to the compressor main body 100, sequentially through the pipe 6a, the three-way valve 33, and the pipes 6c and 6d. Particularly in this embodiment, the buffer tank 34 is provided upstream of the compressor main body 100 and downstream of the heat exchanger 31 in the oil flow path.

[0047] The oil-injected compressor 1 of this embodiment provides the following advantageous effects.

[0048] Since oil is stored not only in the oil tank 12 but also in the buffer tank 34, it is possible to easily and inexpensively secure an appropriate amount of oil to be stored in the entire compressor to prevent early deterioration of the oil. Furthermore, compared to providing one large storage section, there is a high degree of freedom in installation and costs can be reduced.

[0049] Furthermore, the existing compressor body 100 and heat exchanger 31 can be used as they are, and the buffer tank 34 can be additionally provided.

[0050] According to the oil-injected compressor 1 of this embodiment, the oil cooled by the heat exchanger 31 can be stored in the buffer tank 34. Therefore, even when a heat exchanger 31 with good heat exchange performance, i.e., a relatively small heat exchanger 31, is used, the required amount of low-temperature oil can be held and low-temperature oil can be supplied in a timely manner to the compressor main body 100. Furthermore, because the buffer tank 34 is provided downstream of the heat exchanger 31, a small amount of oil is filled in the buffer tank 34 due to the effect of back pressure at startup, and oil can be supplied to the compressor main body 100 without interruption when the three-way valve 33 is switched.

[0051] 3 and 4, the oil-injected compressor 1 of the second embodiment is different from the first embodiment in that the positions of the heat exchanger 31 and the buffer tank 34 in the oil circulation system are interchanged. Other than this, the compressor 1 is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

[0052] In this embodiment, oil discharged from the compressor main body 100 flows through the pipe 5a to the oil tank 12 of the oil separator / recovery device 10. Next, the oil flows from the oil tank 12 through the pipe 6a to the three-way valve 33. The three-way valve 33 performs selective bypass operation. That is, the oil flows from the three-way valve 33 through the pipe 6a to the buffer tank 34, from the buffer tank 34 through the pipe 6b to the heat exchanger 31, and from the heat exchanger 31 through the pipes 6c and 6d to the compressor main body 100. Alternatively, the oil flows from the oil tank 12 to the compressor main body 100 through the pipes 6a, 6c, and 6d without being cooled by the heat exchanger 31. Particularly in this embodiment, the buffer tank 34 is provided upstream of the heat exchanger 31 and downstream of the oil tank 12 in the oil flow path.

[0053] In this embodiment, the oil inlet 34a to the buffer tank 34 is located on the bottom surface of the buffer tank 34 so that oil can flow into the oil separator / recovery device 10 when the compressor 100 is stopped. The buffer tank 34 is also located at a higher position than the compressor body 100. The oil outlet 34b from the buffer tank 34 is located above the inlet 34a and at a position that ensures sufficient storage capacity in the buffer tank 34, since the oil level will never be higher than the outlet 34b. The buffer tank 34 may also be located at a higher position than the oil tank 12. This makes it easy to return the oil stored in the buffer tank 34 to the oil tank 12 using potential energy when the oil-lubricated compressor 1 is stopped, allowing for oil change without degraded oil remaining in the buffer tank 34.

[0054] According to the oil-lubricated compressor 1 of this embodiment, the oil stored in the buffer tank 34 can be cooled by the heat exchanger 31. Therefore, cooled oil (oil immediately after cooling) can be reliably supplied from the heat exchanger 31 to the compressor body 100.

[0055] In addition, the oil stored in the buffer tank 34 can be returned to the oil tank 12 using potential energy when the oil-lubricated compressor 1 stops, allowing oil to be changed without degraded oil remaining in the buffer tank 34.

[0056] Although specific embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and can be implemented with various modifications within the scope of the present invention.

[0057] In the above embodiment, examples have been described in which the heat exchanger 31 is a plate-type heat exchanger or a fin-tube-type heat exchanger, but the type of heat exchanger 31 is not limited to these, and other types of heat exchangers may also be used.

[0058] This application claims priority from Japanese Patent Application No. 2024-108989, filed July 5, 2024. Japanese Patent Application No. 2024-108989 is incorporated herein by reference.

[0059] REFERENCE SIGNS LIST 1 Oil-lubricated compressor 2 Package exterior 5a to 5e Piping 6a to 6d Piping 10 Oil separator / recovery device 11 Centrifugal separation section (oil separation section) 12 Oil tank (first storage section) 13 Separator 21 Pressure-retaining check valve 22 Gas cooler 23 Dryer 31 Heat exchanger 32 Oil filter 33 Three-way valve 34 Buffer tank (second storage section) 34a Inlet 34b Outlet 41 Oil temperature sensor 50 Control device 100 Compressor body 120 Compression section 121 Rotor casing 121a Suction port 121b Discharge port 121c Rotor oil supply port 122 Screw rotor 125, 126 Bearing 130 Motor

Claims

1. An oil-lubricated compressor comprising: an oil-lubricated compressor body; an oil separation section that separates oil from a fluid discharged by the compressor body; a first reservoir section that stores the oil separated by the oil separation section; a heat exchanger that cools the oil; and a second reservoir section that is separate from the first reservoir section, the compressor body, and the heat exchanger and stores the oil.

2. The oil-injected compressor according to claim 1, wherein the second reservoir is provided in the oil flow path upstream of the compressor body and downstream of the heat exchanger.

3. The oil-injected compressor according to claim 1, wherein the second reservoir is provided upstream of the heat exchanger and downstream of the first reservoir in the oil flow path.

4. An oil-injected compressor according to claim 3, wherein the second reservoir has an inlet for the oil from the first reservoir on its underside and is located at a higher position than the first reservoir.

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