Oil-fed compressor

Abstract

To provide an oil feeding type compressor which enables reduction of an amount of compressed air discharged during recovery of oil separated by a second oil separator to inhibit deterioration of compression efficiency.SOLUTION: An oil feeding type compressor includes: a compressor body 2 that compresses gas while injecting oil; a first oil separator 6 that separates oil from the compressed gas discharged from the compressor body 2; a second oil separator 8 that further separates oil from the compressed gas from which the oil has been separated by the first oil separator 6, and has a storage unit 8bd to store the separated oil; a discharge pipe system 9 through which the compressed gas from which the oil has been separated by the second oil separator 8 flows; an oil discharging path 10 that discharges the oil stored in the storage unit 8bd from the storage unit 8bd; a valve body 10a that is provided in the oil discharging path 10; and a control unit 11 that controls the degree of opening of the valve body 10a on the basis of time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an oil-fed compressor.

Background Art

[0002] An oil-fed compressor drives the compressor body and compresses the air sucked from the intake side of the compressor body after mixing it with lubricating oil to a predetermined pressure. The compressed air in a gas-liquid mixture is separated from oil (primary separation) by an oil separator (first oil separator), and further separated from oil (secondary separation) by an oil separation element (second oil separator), and then flows into a discharge flow path through a cooler or the like.

[0003] Also, the oil separated in the first oil separator is recovered in an oil tank provided at the lower part of the first oil separator. The oil in the oil tank is pumped to the intake side of the compressor body by the pressure of the compressed air in the oil tank and refluxed to the compressor body.

[0004] On the other hand, an oil-fed compressor that refluxes the oil separated in the second oil separator to the compressor body is disclosed in, for example, Patent Document 1. The oil-fed compressor of Patent Document 1 pumps the oil that has dropped to an element head provided below the second oil separator to the intake side of the compressor body from an oil recovery hole formed in the element head by the pressure of the compressed air and refluxes it to the compressor body.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, the oil recovered from such an oil recovery hole is discharged by the pressure of the compressed air in the second oil separator. However, there is a possibility that the compressed gas discharged together with such oil may waste some of the compressed air generated by the compressor body, which is one of the factors reducing the compressor efficiency.

[0007] Here, in order to reduce the discharge amount of compressed air during oil recovery, it is conceivable to reduce the pipe diameter of the reflux path for refluxing oil from the oil recovery hole to the compressor body or to provide an orifice for restricting the flow of oil in the reflux path (further reducing the orifice diameter, etc.). However, there is a concern that the pipe may be clogged and the recovery may be poor, and it can be said that there is a certain limit to reducing the diameter.

[0008] In particular, in a small oil-injected compressor, since the amount of discharged air is small, the amount of oil recovered from the oil recovery hole also tends to be small. Therefore, even if the diameter of the reflux path is reduced, etc., the discharge amount of compressed air is relatively large, and there is a possibility that the deterioration of the compressor performance cannot be improved.

[0009] Also, in a configuration where the compressor body can perform variable speed operation, for example, when using an electric motor (electric motor) having a power conversion device (inverter) as the drive source of the compressor body, during low load operation, since the amount of discharged air is small and the amount of compressed air discharged does not change even though the amount of oil recovered from the oil recovery hole is small, the compressor performance tends to deteriorate.

[0010] This problem has been made in view of the above problems, and an object is to provide an oil-injected compressor that can suppress the amount of compressed air discharged during the recovery of the oil separated by the second oil separator and suppress the decrease in compression efficiency.

Means for Solving the Problem

[0011] To achieve the above object, the present invention includes a compressor body that compresses a gas while injecting oil, and separates oil from the compressed gas discharged from the compressor body A first oil separator that separates oil, and further separates oil from the compressed gas from which oil has been separated by the first oil separator, having a storage section for storing the separated oil SecondAn oil separator, an oil discharge path for discharging the oil stored in the storage section from the storage section, a valve body provided in the oil discharge path, and a control section that executes valve body control for controlling the opening degree of the valve body based on the integrated value of the load factor and the operation time of the compressor body.

[0012] Furthermore, the present invention includes a compressor body that compresses a gas while injecting oil, a first oil separator that separates oil from the compressed gas discharged from the compressor body, and a second oil separator that further separates oil from the compressed gas from which oil has been separated by the first oil separator and has a storage section for storing the separated oil, a discharge piping system through which the compressed gas from which oil has been separated by the second oil separator flows, an oil discharge path for discharging the oil stored in the storage section from the storage section, a valve body provided in the oil discharge path, and a control section that controls the opening degree of the valve body based on the load factor and time of the compressor body.

[0013] Furthermore, the present invention includes a compressor body that compresses a gas while injecting oil, a first oil separator that separates oil from the compressed gas discharged from the compressor body, and a second oil separator that further separates oil from the compressed gas from which oil has been separated by the first oil separator and has a storage section for storing the separated oil, a discharge piping system through which the compressed gas from which oil has been separated by the second oil separator flows, an oil discharge path for discharging the oil stored in the storage section from the storage section, a valve body provided in the oil discharge path, a pressure sensor for detecting the pressure of the discharge piping system, and a control section that controls the opening degree of the valve body based on time, and the control section controls the timing for reducing the opening degree of the valve body based on the detection pressure by the pressure sensor during the opening of the valve body.

Advantages of the Invention

[0014] According to the present invention, in an oil-injected compressor, it is possible to suppress the amount of compressed air discharged during the recovery of the oil separated by the second oil separator and suppress a decrease in compression efficiency.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] Hereinafter, with reference to the drawings, the configuration and operation of the oil-fed compressor according to the first to third embodiments of the present invention will be described. In each figure, the same reference numerals denote the same parts.

[0017] (First Embodiment) FIG. 1 is a schematic diagram showing the configuration of an oil-fed compressor 1A according to the first embodiment of the present invention. The oil-fed compressor 1A includes a compressor body 2, an electric motor 3, an intake filter 4, an intake valve 5, a first oil separator 6, an oil supply system 7, a second oil separator (oil separator) 8, a discharge piping system 9, an oil discharge path 10, and a control unit 11.

[0018] The compressor body 2 is the part that generates compressed air, and has a pair of screw rotors 2a, 2b that mesh with each other (only one of the pair is shown in Fig. 1) and a casing (not shown) that houses the pair of screw rotors 2a, 2b. A compression chamber (not shown), which is a closed space, is formed by the combination of the meshing of the pair of screw rotors 2a, 2b and the casing.

[0019] The electric motor 3 is the driving source for the screw rotors 2a, 2b of the compressor body 2. As the pair of screw rotors 2a, 2b are driven by the electric motor 3, the compression chamber moves in the axial direction of the screw rotors 2a, 2b (the left direction in Fig. 1), and continuously performs the processes of sucking, compressing, and discharging air. Therefore, the compression chamber sucks air through the suction filter 4 and the suction valve 5 provided on the suction side of the compressor body 2, compresses the air, and discharges the compressed air to the first oil separator 6 provided on the discharge side of the compressor body 2. Also, oil is supplied from the oil supply system 7 to the compression chamber for cooling the heat generated when compressing air, sealing the compression chamber, and lubricating the screw rotors 2a, 2b.

[0020] The first oil separator 6 is, for example, a swirl separation type gas-liquid separator that primarily separates oil from compressed air by centrifugal separation. A swirl flow path (not shown) for swirling the compressed air is formed inside the first oil separator 6. The oil separated primarily is stored in the oil tank 6a at the lower part of the first oil separator 6.

[0021] The oil supply system 7 is a pipe or the like that connects the oil tank 6a and the compressor body 2, and injects the oil stored in the oil tank 6a into the compression chamber of the compressor body 2 due to the pressure difference between the compressed air in the first oil separator 6 and the air sucked into the compressor body 2. Note that one or more holes for injecting oil into the compression chamber are provided downstream of the oil supply system 7, and oil is injected or sprayed into the compression chamber from one or more holes. When oil is injected from a plurality of holes, the oil injected from each of the plurality of holes may be collided to atomize the oil.

[0022] The fuel supply system 7 is provided with an oil cooler 7a for cooling the oil, and an oil filter 7b disposed downstream of the oil cooler 7a for removing impurities in the oil. The oil cooler 7a cools the oil by heat exchange with the cooling air induced by the cooling fan 13 that rotates the fan motor 12.

[0023] The oil separator 8 secondary-separates the mist-like oil content contained in the compressed air from which the oil has been primarily separated, communicates with the upper part of the first oil separator 6, and receives the compressed air from which the oil has been primarily separated by the first oil separator 6.

[0024] The oil separator 8 is provided with an element 8a which is a filter for filtering the mist-like oil content contained in the primarily separated compressed air, a head 8b having a recess (not shown) into which the lower part of the element 8a is fitted, and a case 8c that covers the element 8a and is coupled to the head 8b.

[0025] The element 8a is, for example, a cylindrical filter made of a non-woven fabric, a metal with a mesh structure, or a combination thereof, etc., with open upper and lower ends. The lower end is fitted into the recess of the head 8b, and the side surface and the upper end are covered by the case 8c.

[0026] The head 8b is a component for allowing the compressed air from which the oil has been primarily separated to flow into one side (the outer peripheral side in this embodiment) of the element 8a, and discharging the compressed air from which the oil has been secondary-separated by the element 8a from the other side (the inner peripheral side in this embodiment) of the element 8a. The head 8b is provided with, for example, a recess into which the lower part of the element 8a is fitted, an introduction flow path 8ba, a discharge pipe 8bb, a derivation flow path 8bc, a storage part 8bd, a discharge hole (not shown), and a discharge flow path 8be.

[0027] The introduction flow path 8ba communicates with the first oil separator 6 and is a flow path through which the compressed air from which oil has been primarily separated in the first oil separator 6 flows into the element 8a. The discharge pipe 8bb extends upward from the center of the head 8b, and the opening at the upper end is located inside the element 8a placed on the head 8b. Note that it is preferable that the opening of the discharge pipe 8bb be positioned near the upper end of the element 8a so that the oil that has been secondarily separated and dripped does not get caught up in the air flow of the compressed air and flow into the discharge piping system 9.

[0028] The derivation flow path 8bc is a flow path that communicates with the discharge pipe 8bb and the discharge piping system 9. The compressed air from which oil has been secondarily separated in the element 8a is discharged into the discharge piping system 9 via the discharge pipe 8bb and the derivation flow path 8bc.

[0029] The storage section 8bd is a section that stores the oil that has been filtered and separated from the compressed air by the element 8a and drips from the element 8a. For example, it is formed around the discharge pipe 8bb by the bottom surface and the inner wall of the recess of the head 8b and the outer peripheral wall of the discharge pipe 8bb that extends upward from the bottom surface of the recess. Note that there is a risk that the oil stored in the storage section 8bd may be lifted up by the air flow of the compressed air that has passed through the element 8a and discharged together with the compressed air from the opening of the discharge pipe 8bb. Therefore, a cylindrical shielding plate (not shown) that contacts the lower part of the inner peripheral surface of the element 8a is provided in the storage section 8bd so that the air flow of the compressed air passing through the element 8a does not lift up the oil stored in the storage section 8bd.

[0030] The discharge hole is a hole provided in the lower part (the bottom in this embodiment) of the storage section 8bd and communicates with the discharge flow path 8be. The discharge flow path 8be is a flow path that communicates the storage section 8bd and the oil discharge path 10 via the discharge hole, and causes the oil accumulated in the storage section 8bd to be sent to the oil discharge path 10 by the pressure of the compressed air in the oil separator 8.

[0031] The case 8c is a cylinder having a top plate and an open lower end, covers the element 8a, and the lower end is joined to the head 8b. The portion where the head 8b and the case 8c are joined is sealed so that compressed air and oil do not leak out.

[0032] The discharge piping system 9 is a pipe or the like that is connected to the outlet flow path 8bc of the oil separator 8 and discharges the compressed air from which oil has been secondarily separated by the oil separator 8 to the user side. The discharge piping system 9 is provided with a check valve 9a located on the downstream side of the oil separator 8, a pressure sensor 9b located between the oil separator 8 and the check valve 9a, and an aftercooler 9c located on the downstream side of the check valve 9a for cooling the compressed air.

[0033] The check valve 9a prevents the compressed air from flowing backward from the user side to the oil separator 8. The pressure sensor 9b detects the pressure of the compressed air discharged from the oil separator 8. The aftercooler 9c cools the compressed air by heat exchange with the cooling air induced by the cooling fan 13. Therefore, cooled compressed air is supplied to the user.

[0034] The oil discharge path 10 is a pipe or the like that connects the storage part 8bd and the compressor main body 2 via the discharge flow path 8be of the head 8b. The oil stored in the storage part 8bd is pressed by the air pressure of the compressed air in the oil separator 8 and discharged from the oil discharge path 10 through the discharge hole and the discharge flow path 8be. In this embodiment, the oil discharge path 10 is connected to the suction side of the compressor main body 2 so that the oil discharged from the oil discharge path 10 is recovered by the compressor main body 2. A valve body 10a is provided in the oil discharge path 10 so that the oil discharge path 10 can be opened and closed.

[0035] The valve body 10a is a solenoid valve, and its opening degree is controlled based on time by the control unit 11. For example, a normally open type ON-OFF solenoid valve is used for the solenoid valve of the valve body 10a. In this embodiment, an example of using a normally open type ON-OFF solenoid valve as the valve body 10a is shown, but it is not limited thereto. For example, a valve body 10a that enables three-stage or more control including an intermediate stage "open (including slightly open)" or "closed (including slightly closed)" state can also be used. That is, depending on the opening degree of the valve body 10a, the flow of the stored oil can be configured to be permitted (partially permitted) or restricted (partially prohibited).

[0036] The control unit 11 is a part that controls various operations of the oil-fed compressor 1A. In the control unit 11, for example, various controls of the oil-fed compressor 1A are realized by the cooperation of the CPU and the program. Note that a part of it may have an analog configuration. In the present embodiment, the control unit 11 includes a user interface (not shown) that can input a pressure set value and various set values, and based on the input values, controls the supply power to the electric motor 3 and the fan motor 12 and the opening degree of the valve body 10a.

[0037] Next, the opening degree control of the valve body 10a by the control unit 11 of the present embodiment will be described with reference to FIG. 2. FIG. 2 is a time chart of the opening degree control of the valve body 10a by the control unit 11 of the oil-fed compressor 1A according to the present embodiment.

[0038] The control unit 11 repeats holding the valve body 10a at the first opening degree during the first period Tc and holding the valve body 10a at a second opening degree larger than the first opening degree during the second period To after the elapse of the first period Tc. Specifically, as shown in FIG. 2, during the first period Tc, the control unit 11 transmits an ON signal to the valve body 10a and holds the valve body 10a in the "closed" state. Then, during the second period To after the elapse of the first period Tc, the control unit 11 turns off the signal transmission to the valve body 10a and holds the valve body 10a in the "open" state. Further, during the first period Tc after the elapse of the second period To, the control unit 11 transmits an ON signal to the valve body 10a and holds the valve body 10a in the "closed" state, and repeats these controls. Note that since the valve body 10a is a normally open type ON-OFF solenoid valve, when the power is lost, the valve body 10a is held in the "open" state, and it is possible to suppress the oil that has been secondarily separated by the element 8a and dripped from overflowing from the storage portion 8bd.

[0039] Also, the first period Tc is the time until a predetermined amount of oil accumulates in the storage portion 8bd, and the second period To is the time until the predetermined amount of oil accumulated in the storage portion 8bd in the first period Tc is discharged from the storage portion 8bd. Note that the predetermined amount of oil accumulated in the storage portion 8bd can be set to, for example, an amount that can suppress the backflow of the oil accumulated in the storage portion 8bd and the inflow into the discharge pipe 8bb.

[0040] Also, the first period Tc is, for example, the time measured until the oil accumulates in the storage section 8bd up to the predetermined amount, and the second period To is, for example, the time measured until the predetermined amount of oil is discharged from the storage section 8bd. The measured first period Tc and second period To are input to and stored in the control unit 11. The control unit 11 controls the opening degree of the valve body 10a based on the stored first period Tc and second period To.

[0041] Therefore, during the first period Tc, the valve body 10a of the oil-feed compressor 1A is "closed", and the oil is stored in the storage section 8bd up to the predetermined amount. Also, during the second period To after the first period Tc has elapsed, the valve body 10a of the oil-feed compressor 1A is "opened", and the predetermined amount of oil stored in the storage section 8bd is discharged to the suction side of the compressor main body 2 through the discharge hole, the discharge flow path 8be, and the oil discharge path 10.

[0042] In addition, it is preferable that the second period To be set to be equal to or longer than the time measured until the predetermined amount of oil is discharged from the storage section 8bd. The reasons are as follows. First, due to deterioration of the oil or the like, the flow velocity of the oil flowing through the discharge hole, the discharge flow path 8be, and the oil discharge path 10 may become slow, and the time until the predetermined amount of oil is discharged from the storage section 8bd may become longer than the measured time. Second, the element 8a may become clogged over time, the amount of oil that can be held may decrease, the amount of oil dripping from the element 8a per unit time may increase, and the amount of oil accumulating in the storage section 8bd may increase.

[0043] [Effect] The oil-feed compressor 1A according to the present embodiment includes a compressor main body 2 that compresses a gas while injecting oil, a first oil separator 6 that separates oil from the compressed gas discharged from the compressor main body 2, a second oil separator 8 that further separates oil from the compressed gas from which oil has been separated by the first oil separator 6 and stores the separated oil, a discharge piping system 9 through which the compressed gas from which oil has been recovered by the second oil separator 8 flows, an oil discharge path 10 that discharges the oil stored in the storage section 8bd from the storage section 8bd, a valve body 10a provided in the oil discharge path 10, and a control unit 11 that controls the opening degree of the valve body 10a based on time.

[0044] Previously, for example, an orifice with a constant opening degree was provided in the oil discharge path 10 for discharging the oil in the storage part 8bd, and the oil was continuously discharged together with the compressed air. However, in the oil-fed compressor 1A of the present embodiment configured as described above, the opening degree of the valve body 10a provided in the oil discharge path can be controlled (changed) based on time. And in the oil-fed compressor 1A of the present embodiment, if control is performed to increase the time during which the opening degree of the valve body 10a is kept smaller than the opening degree of the orifice (the valve body 10a may be closed), the discharge amount of the compressed air through the oil discharge path 10 can be reduced compared to the prior art, and as a result, a decrease in the compression efficiency of the oil-fed compressor 1A can be suppressed.

[0045] Also, in the oil-fed compressor 1A of the present embodiment, even when the amount of compressed air discharged decreases due to miniaturization of the air compressor and the amount of dripping oil further decreases, the first period Tc can be lengthened and the opening degree of the valve body 10a can be made smaller until oil accumulates in the storage part 8bd. And after oil accumulates in the storage part 8bd, the opening degree of the valve body 10a can be increased to discharge the oil accumulated in the storage part 8bd within a predetermined time. Therefore, the amount of compressed air discharged together with the oil can be reduced, and a decrease in the compression efficiency of the oil-fed compressor can be suppressed.

[0046] Also, in the oil-fed compressor 1A of the present embodiment, even when the compressor body is under low load, the discharge amount of compressed air is reduced, and the amount of dripping oil decreases, the first period Tc can be lengthened and the opening degree of the valve body 10a can be made smaller until oil accumulates in the storage part 8bd. And after oil accumulates in the storage part 8bd, the opening degree of the valve body 10a can be increased to discharge the oil accumulated in the storage part 8bd within a predetermined time. Therefore, the amount of compressed air discharged together with the oil can be reduced, and a decrease in the compression efficiency of the oil-fed compressor can be suppressed.

[0047] Further, the control unit 11 of the oil-injected compressor 1A according to the present embodiment repeats holding the valve body 10a at the first opening degree during the first period Tc and holding the valve body 10a at a second opening degree larger than the first opening degree during the second period To after the elapse of the first period Tc. Therefore, it is possible to suppress the oil discharge path 10 from being clogged and unable to discharge oil.

[0048] Further, the control unit 11 of the oil-injected compressor 1A according to the present embodiment closes the valve body 10a at the first opening degree and opens the valve body 10a at the second opening degree. Therefore, after the oil is stored in the storage unit 8bd, the oil stored in the storage unit 8bd can be discharged. Accordingly, it is possible to reduce the amount of compressed air discharged together with the oil and suppress a decrease in the compression efficiency of the oil-injected compressor.

[0049] Further, the control unit 11 of the oil-injected compressor 1A according to the present embodiment controls the second period To to be longer than the time for discharging the oil accumulated in the storage unit 8bd during the first period Tc. Thereby, the oil accumulated in the storage unit 8bd during the first period Tc can be discharged during the second period To, and it is possible to suppress the oil from remaining in the storage unit 8bd. Therefore, it is possible to suppress the oil from overflowing from the storage unit 8bd.

[0050] Further, the valve body 10a of the oil-injected compressor 1A according to the present embodiment uses a normally open ON-OFF solenoid valve. Therefore, it is possible to simplify the control of the flow rate of the oil flowing through the oil discharge path 10 by the control unit 11. Further, even when the valve body 10a cannot be controlled due to a power loss or the like, the valve is in the "open" state, the oil accumulates in the storage unit 8bd, and it is possible to suppress the oil from overflowing from the storage unit 8bd.

[0051] Further, the oil discharge path 10 of the oil-injected compressor 1A according to the present embodiment has a downstream opening communicating with the low-pressure side of the compressor body 2, and discharges the oil secondarily separated from the compressed gas by the second oil separator 8 to the low-pressure side of the compressor body 2. Therefore, the oil separated by the second oil separator 8 is not discharged to the outside and can be reused for compressing the gas by the compressor body 2.

[0052] Further, the second oil separator 8 of the oil-injected compressor 1A of the present embodiment includes a cylindrical case 8c with a closed upper end and an open lower end, a cylindrical filter (element 8a) located inside the case 8c and having open upper and lower ends, and a discharge pipe 8bb extending upward from below the filter and having an open upper end located inside the filter and communicating with the discharge piping system 9. Therefore, the filter (element 8a) can be lifted upward by removing the case 8c and can be easily replaced.

[0053] Further, the first oil separator 6 of the oil-injected compressor 1A of the present embodiment is a gas-liquid separator using a swirl separation method. The gas-liquid separator using the swirl separation method has a simple structure and can suppress costs.

[0054] (Second Embodiment) FIG. 3 is a schematic diagram showing the configuration of an oil-injected compressor 1B according to the second embodiment of the present invention. The oil-injected compressor 1B according to the present embodiment is different from the oil-injected compressor 1A according to the first embodiment in the following points.

[0055] First, the oil-injected compressor 1B is provided with a variable speed mechanism in the electric motor 3. That is, while the oil-injected compressor 1A according to the first embodiment is under constant speed control, the oil-injected compressor 1B according to the present embodiment is under variable speed control.

[0056] Further, since the oil-injected compressor 1B according to the present embodiment is provided with a variable speed mechanism in the electric motor 3, the amount of oil accumulated in the storage portion 8bd changes depending on the load factor (rotation speed ÷ maximum rotation speed × 100%) of the compressor body 2. Therefore, while the control unit 11 of the oil-injected compressor 1A according to the first embodiment controls the opening degree of the valve body 10a based on time, the control unit 11 of the oil-injected compressor 1B according to the present embodiment controls the opening degree of the valve body 10a based on the load factor and time of the compressor body 2.

[0057] The variable speed mechanism provided in the electric motor 3 is, for example, an inverter 20. The inverter 20 is electrically connected to the electric motor 3 and the control unit 11 and converts the electric power supplied to the electric motor 3 according to the command of the control unit 11.

[0058] The control unit 11 changes the amount of power supplied from the inverter 20 to the motor 3 according to the set pressure of the user based on, for example, the detected pressure of the pressure sensor 9b, and performs variable speed control of the compressor main body 2. The variable speed control includes proportional control (P control), proportional integral control (PI control), PID control obtained by adding derivative control (D control) to PI control, no-load operation control, and the like.

[0059] Note that the no-load operation control has the following methods. For example, when the detected pressure of the pressure sensor 9b is equal to or higher than the set pressure of the user, the intake valve 5 is set to "closed" to limit the amount of air sucked into the compressor main body 2. Also, when the detected pressure of the pressure sensor 9b is equal to or higher than the set pressure of the user, the intake valve 5 is set to "closed" and the motor 3 is lowered to a predetermined rotational speed (for example, the lowest rotational speed that can secure and maintain the set pressure of the user).

[0060] The inverter 20 of the oil-injected compressor 1B according to the present embodiment changes the amount of power supplied to the motor 3 by the above-described control method and the like, and controls the load factor of the compressor main body 2. Although the embodiment in which the oil-injected compressor 1B is variably speed-controlled by the inverter 20 has been shown, the oil-injected compressor 1B may be variably speed-controlled by other methods.

[0061] In the oil-injected compressor 1B according to the present embodiment, the load factor of the compressor main body 2 is changed according to the set pressure of the user, and the amount of compressed air discharged is changed. Therefore, the amount of oil accumulated in the storage portion 8bd after secondary separation by the oil separator 8 changes depending on the load factor of the compressor main body 2 during control. Therefore, if the opening degree of the valve body 10a is controlled based on time, when the compressor main body 2 has a low load factor, the amount of oil accumulated in the storage portion 8bd decreases, and the amount of compressed air discharged together with the oil increases. In order to suppress such an increase in the amount of compressed air, the opening degree of the valve body 10a is controlled according to the load factor of the compressor main body 2.

[0062] FIG. 4 is a graph showing changes over time in the load factor of the compressor main body 2 and a time chart of the opening degree control of the valve body 10a by the control unit 11 for the oil-injected compressor 1B according to the present embodiment.

[0063] The amount of oil stored in the storage section 8bd can be estimated from the load factor and the operating time of the compressor body 2. Therefore, the control unit 11 of the present embodiment controls the opening degree of the valve body 10a based on the load factor and the operating time of the compressor body 2.

[0064]

[0063] Specifically, while the integrated values A1, A2, A3, and A4 of the product of the load factor and the operating time of the compressor body 2 are less than a predetermined value, the valve body 10a is held at the first opening degree. Then, when the integrated values A1, A2, A3, and A4 of the product of the load factor and the operating time of the compressor body 2 reach the predetermined value, the valve body 10a is held at a second opening degree larger than the first opening degree for a predetermined period To.

[0065] In addition, when the integrated value of the product of the load factor and the operating time of the compressor body 2 reaches the predetermined value, the amount of oil accumulated in the storage section 8bd can be made equal to or less than the amount that can suppress the backflow of the oil and the inflow into the discharge pipe 8bb (the allowable capacity of the storage section 8bd). Further, the predetermined period To is preferably set to be equal to or longer than the time measured until a predetermined amount of oil stored in the storage section 8bd is discharged. The reason is the same as the reason for the second period To of the first embodiment described above.

[0066] [Effect] The oil-injected compressor 1B according to the present embodiment includes a compressor body 2 that compresses a gas while injecting oil, a first oil separator 6 that separates oil from the compressed gas discharged from the compressor body 2, a second oil separator 8 that further separates oil from the compressed gas from which oil has been separated by the first oil separator 6 and stores the separated oil, a discharge piping system 9 through which the compressed gas from which oil has been separated by the second oil separator 8 flows, an oil discharge path 10 that discharges the oil stored in the storage section 8bd from the storage section 8bd, a valve body 10a provided in the oil discharge path 10, and a control unit 11 that controls the opening degree of the valve body 10a based on the load factor and the time of the compressor body 2.

[0067] The oil quantity stored in the storage section 8bd can be estimated from the load factor of the compressor main body 2 and the time. Therefore, in the oil-feed compressor 1B of the present embodiment configured as described above, for example, as the oil quantity estimated from the load factor and the time increases, if the timing to release the valve body 10a from the closed state is controlled, it is possible to prevent oil from overflowing beyond the allowable capacity of the storage section 8bd and reduce the discharge amount of compressed air through the oil discharge path 10 compared to the past. Thereby, a decrease in the compression efficiency of the oil-feed compressor can be suppressed. Open Also, the control unit 11 of the oil-feed compressor 1B according to the present embodiment holds the valve body 10a at the first opening degree while the integrated values A1, A2, A3, A4 of the product of the load factor of the compressor main body 2 and the operation time are less than a predetermined value, and holds the valve body 10a at a second opening degree larger than the first opening degree for a predetermined period when the integrated value of the product of the load factor of the compressor main body 2 and the operation time reaches the predetermined value. Therefore, it is possible to suppress the oil discharge path 10 from being clogged and unable to discharge oil.

[0068] Moreover, in the oil-feed compressor 1B according to the present embodiment, the amount of oil accumulated in the storage section 8bd until the integrated values A1, A2, A3, A4 of the product of the load factor of the compressor main body 2 and the operation time reach a predetermined value is equal to or less than the allowable capacity of the oil stored in the storage section 8bd. Therefore, it is possible to suppress oil from overflowing from the storage section 8bd.

[0069] Furthermore, in the oil-feed compressor 1B according to the present embodiment, the predetermined period To for holding the valve body 10a at a second opening degree larger than the first opening degree is a period longer than the time for discharging the amount of oil accumulated in the storage section 8bd until the integrated value of the product of the load factor of the compressor main body 2 and the operation time reaches a predetermined value. Thereby, the oil accumulated in the storage section 8bd until the integrated values A1, A2, A3, A4 of the product of the load factor of the compressor main body 2 and the operation time reach a predetermined value can be discharged during the predetermined period To, and it is possible to suppress oil from remaining in the storage section 8bd. Therefore, it is possible to suppress oil from overflowing from the storage section 8bd.

[0070]

[0071] ​In addition, the control unit 11 of the oil-fed compressor 1B according to the present embodiment closes the valve body 10a at the first opening degree and opens the valve body 10a at the second opening degree. Therefore, after the oil is stored in the storage unit 8bd, the oil accumulated in the storage unit 8bd can be discharged. Accordingly, the amount of compressed air discharged together with the oil can be reduced, and a decrease in the compression efficiency of the oil-fed compressor can be suppressed.

[0072] (Third Embodiment) FIGS. 1 and 3 are schematic views showing the configuration of an oil-fed compressor 1C according to the third embodiment of the present invention. FIG. 5 is a graph showing changes over time in the detected pressure of the pressure sensor 9b and a time chart of the opening degree control of the valve body 10a by the control unit 11 for the oil-fed compressor 1C according to the third embodiment of the present invention. FIG. 6 is a graph showing changes over time in the load factor of the compressor body 2, a graph showing changes over time in the detected pressure of the pressure sensor 9b, and a time chart of the opening degree control of the valve body 10a by the control unit 11 for the oil-fed compressor 1C according to the third embodiment of the present invention.

[0073] In the oil-fed compressor 1C according to the present embodiment, the control unit 11 Open is different from the oil-fed compressors 1A and 1B according to the first and second embodiments in that the timing for reducing the opening degree of the valve body 10a is controlled based on the detected pressure by the pressure sensor 9b during the opening of the valve body 10a.

[0074] Specifically, the control unit 11 of the oil-fed compressors 1A and 1B according to the first and second embodiments holds the valve body 10a at a second opening degree larger than the first opening degree during the period To, and controls the valve body 10a to a first opening degree smaller than the second opening degree after the period To has elapsed. On the other hand, the control unit 11 of the oil-fed compressor 1C according to the present embodiment reduces the opening degree of the valve body 10a at the timing when the decrease (P1 - P2) in the detected pressure of the pressure sensor 9b that detects the pressure in the discharge piping system 9 during the opening of the valve body 10a reaches a predetermined value ΔP.

[0075] That is, the control unit 11 of the oil-fed compressor 1C controls the valve body 10a to a first opening degree smaller than the second opening degree at the timing when the decrease (P1 - P2) in the detected pressure of the pressure sensor 9b reaches a predetermined value ΔP while holding the valve body 10a at the second opening degree.

[0076] Therefore, in the control unit 11 of the oil-lubricated compressors 1A and 1B according to the first and second embodiments, the period To during which the valve element 10a is held at the second opening is a set predetermined time. In contrast, the control unit 11 of the oil-lubricated compressor 1C controls the period (To1 to To3) during which the valve element 10a is held at the second opening based on the fact that the pressure in the discharge piping system 9 decreases as a result of the compressed air being discharged after the oil accumulated in the storage unit 8bd is discharged.

[0077] 5 shows a case where the period during which the valve element 10a is held at the first opening is controlled based on time, similar to the oil-injected compressor 1A of the first embodiment. Also, FIG 6 shows a case where the period during which the valve element 10a is held at the first opening is controlled based on the load factor of the compressor body 2 and time, similar to the oil-injected compressor 1B of the second embodiment.

[0078] Furthermore, the oil-lubricated compressor 1C can control the control unit 11 to detect and notify a blockage in the oil discharge path 10 based on a decrease (P1-P2) in the pressure detected by the pressure sensor 9b.

[0079] That is, the control unit 11 notifies an abnormality when the period from when the valve body 10a is opened to the second degree until the decrease in pressure detected by the pressure sensor 9b (P1-P2) reaches a predetermined value ΔP exceeds a predetermined period.

[0080] In order to prevent malfunction, the following can be done. The control unit 11 controls the valve body 10a. Open During release, the number of times that the ratio ((P1-P2) / To) of the decrease in pressure (P1-P2) detected by the pressure sensor 9b to the elapsed time To does not reach a predetermined value is recorded. If the number of times reaches the predetermined number, an abnormality is reported.

[0081] In addition, various means and devices can be used to report an abnormality, such as displaying a warning on a display device provided in the control unit 11, activating a warning light to emit light, or emitting an alarm sound from a speaker.

[0082] [effect] The oil-lubricated compressor 1C according to this embodiment includes a compressor body 2 that compresses gas while injecting oil, a first oil separator 6 that separates oil from the compressed gas discharged from the compressor body 2, a second oil separator 8 that further separates oil from the compressed gas from which the oil has been separated in the first oil separator 6 and has a storage section 8bd that stores the separated oil, a discharge piping system 9 through which the compressed gas from which the oil has been recovered in the second oil separator 8 flows, an oil discharge path 10 that discharges the oil stored in the storage section 8bd from the storage section 8bd, a valve body 10a provided in the oil discharge path 10, a pressure sensor 9b for detecting the pressure of the discharge piping system 9, and a control unit 11 that controls the opening degree of the valve body 10a based on time, and the control unit 11 controls the timing of narrowing the opening degree of the valve body 10a based on the detected pressures P1 and P2 by the pressure sensor 9b while the valve body 10a is open.

[0083] In the oil-injected compressor 1C configured as above, the valve body 10a Open When the oil is released, the amount of oil in the reservoir 8bd decreases and the pressure detected by the pressure sensor 9b decreases. Open By controlling the timing of narrowing the opening of the valve body 10a based on the pressure detected by the pressure sensor 9b during the oil discharge, it is possible to prevent the valve body 10a from continuing to be open wastefully after the remaining amount of oil in the storage section 8bd becomes zero. This makes it possible to reduce the amount of compressed air discharged through the oil discharge path 10 compared to before, thereby suppressing a decrease in the compression efficiency of the oil-lubricated compressor.

[0084] In addition, the control unit 11 of the oil-injected compressor 1C according to this embodiment controls the valve body 10a. Open When the drop in pressure (P1-P2) detected by the pressure sensor 9b during discharge reaches a predetermined value ΔP, the opening of the valve body 10a is narrowed. Therefore, even if the oil discharge path 10 is clogged with foreign matter, reducing the flow path area and causing the drainage time of the oil accumulated in the reservoir 8bd to be longer than normal, the oil accumulated in the reservoir 8bd can be reliably drained.

[0085] In addition, the control unit 11 of the oil-injected compressor 1C according to this embodiment controls the valve body 10a. OpenWhen the detected pressure drop (P1 - P2) by the pressure sensor 9b in the middle reaches a predetermined value ΔP, the valve body 10a is closed. Therefore, the amount of compressed air discharged from the oil discharge path 10 can be reduced compared to the past, and a decrease in the compression efficiency of the oil-injected compressor can be suppressed.

[0086] Also, the control unit 11 of the oil-injected compressor 1C according to the present embodiment opens the valve body 10a after closing the valve body 10a for a predetermined period, and when the detected pressure drop (P1 - P2) by the pressure sensor 9b during the opening of the valve body 10a reaches a predetermined value ΔP, the valve body 10a is closed. Therefore, after storing oil in the storage unit 8bd, the oil accumulated in the storage unit 8bd can be discharged. Accordingly, the amount of compressed air discharged from the oil discharge path can be reduced compared to the past, and a decrease in the compression efficiency of the oil-injected compressor can be suppressed.

[0087] Further, in the oil-injected compressor 1C according to the present embodiment, the predetermined period for closing the valve body 10a varies depending on the load factor of the compressor main body 2. Therefore, even if the oil-injected compressor is under variable speed control, after storing a predetermined amount of oil in the storage unit 8bd, the oil can be discharged from the storage unit 8bd, the number of oil discharges can be reduced, the discharge of compressed air accompanying the oil discharge can be reduced compared to the past, and a decrease in the compression efficiency of the oil-injected compressor can be suppressed.

[0088] Also, the control unit 11 of the oil-injected compressor 1C according to the present embodiment, when the valve body 10a is Open opened, if the period from when the valve body 10a is opened until the detected pressure drop (P1 - P2) by the pressure sensor 9b reaches a predetermined value ΔP exceeds a predetermined period, an abnormality is reported. Thereby, clogging of the oil discharge path 10 can be detected and the user can be notified of this.

[0089] Also, the control unit 11 of the oil-injected compressor 1C according to the present embodiment, during the Open opening of the valve body 10a, records the number of times the rate of decrease in the detected pressure by the pressure sensor 9b with respect to the elapsed time does not reach a predetermined value, and if the number of times reaches a predetermined number, an abnormality is reported. Thereby, it is possible to suppress erroneously detecting clogging of the oil discharge path 10 and accurately notify the user of the clogging of the oil discharge path 10.

[0090] Further, the pressure sensor 9b of the oil-injected compressor 1C according to the present embodiment is provided near the location where the discharge piping system 9 is connected to the second oil separator 8. Thereby, a pressure drop in the second oil separator 8 can be quickly detected.

[0091] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, or replace other configurations for a part of the configuration of each embodiment.

[0092] Also, each of the above configurations, functions, etc. may be realized in hardware by designing a part or all of them, for example, by an integrated circuit. Further, each of the above configurations, functions, etc. may be realized in software by a processor (microcomputer) interpreting and executing a program for realizing each function. Information such as programs, tables, files, etc. for realizing each function can be stored in a memory, a recording device such as a hard disk or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

[0093] Note that the embodiments of the present invention may also be in the following aspects. Each of the oil-injected compressors 1A and 1B according to the first and second embodiments can incorporate the control of the oil-injected compressor 1C according to the third embodiment.

[0094] Also, in the first to third embodiments, the case where the compressor main body 2 is a screw rotor type and includes a pair of screw rotors 2a and 2b has been described as an example, but the present invention is not limited thereto. The compressor main body may include, for example, one screw rotor (including a combined gate rotor type) and a plurality of gate rotors. Further, the compressor main body may be of another positive displacement type other than the screw rotor type (specifically, other rotary types such as scroll type or claw type, or reciprocating type, etc.).

[0095] Also, in the first to third embodiments, the case where the electric motor 3 is used as the drive source has been described as an example, but the present invention is not limited thereto, and for example, an internal combustion engine or an engine using natural energy such as wind power or hydraulic power can also be applied.

[0096] Also, in the first to third embodiments, the case where the inverter 20 is used as the variable speed mechanism has been described as an example, but the present invention is not limited thereto. For example, when the drive source is an internal combustion engine, a transmission gear or a fuel supply control device can be used as the variable speed mechanism. Further, when the drive source is an engine using natural energy such as wind power or hydraulic power, a transmission gear or a clutch mechanism can be used as the variable speed mechanism.

[0097] Also, in the first to third embodiments, the case where air is used as the gas to be compressed has been described as an example, but the present invention is not limited thereto, and other gases, for example, nitrogen, may also be used.

[0098] Also, in the first to third embodiments, the case where the control unit 11 is provided in the oil-injected compressor has been described as an example, but the present invention is not limited thereto, and the oil-injected compressor may be remotely controlled by wire or wirelessly by a control device separated from the oil-injected compressor. Further, some controls may be performed by the control unit 11 in the oil-injected compressor, and other controls may be performed by the remote control device.

Explanation of Reference Numerals

[0099] 1A, 1B, 1C… Oil-fed compressor, 2… Compressor body, 3… Electric motor, 6… First oil separator, 8… Second oil separator (oil separator), 8a… Element, 8b… Head, 8ba… Introduction flow path, 8bb… Discharge pipe, 8bc… Derivation flow path, 8bd… Storage part, 8be… Discharge flow path, 8c… Case, 9… Discharge piping system, 9a… Check valve, 9b… Pressure sensor, 10… Oil discharge path, 10a… Valve body, 11… Control unit, 20… Inverter

Claims

1. An oil-injected compressor comprising: a compressor body that compresses gas while injecting oil; a first oil separator that separates oil from the compressed gas discharged from the compressor body; a second oil separator having a storage section that further separates oil from the compressed gas from which oil has been separated by the first oil separator and stores the separated oil; an oil discharge path that discharges the oil stored in the storage section from the storage section; a valve body provided in the oil discharge path; and a control unit that executes valve body control for controlling the opening degree of the valve body based on an integrated value of the product of the load factor and the operating time of the compressor body.

2. The oil-injected compressor according to claim 1, wherein the control unit holds the valve body at a first opening degree while the integrated value of the product of the load factor and the operating time of the compressor body is less than a predetermined value, and holds the valve body at a second opening degree greater than the first opening degree for a predetermined period when the integrated value of the product of the load factor and the operating time of the compressor body is greater than or equal to the predetermined value.

3. The oil-injected compressor according to claim 2, wherein the control unit closes the valve body at the first opening degree and opens the valve body at the second opening degree.

4. The oil-injected compressor according to claim 1, wherein the control unit controls the opening degree of the valve body based on the amount of oil estimated to be stored in the storage section from the load factor and the operating time of the compressor body.

5. The oil-injected compressor according to claim 2, wherein the predetermined period is longer than the time required to discharge the oil accumulated in the storage section until the integrated value becomes greater than or equal to the predetermined value.

6. The oil-injected compressor according to claim 1, further comprising a discharge piping system through which the compressed gas from which oil has been separated by the second oil separator flows; and a pressure sensor for detecting the pressure of the discharge piping system, wherein the valve body control in the control unit controls the opening degree of the valve body based on the detection pressure of the pressure sensor during the opening of the valve body in addition to the integrated value of the product of the load factor and the time of the compressor body.

7. The oil-injected compressor according to claim 6, wherein the control unit reduces the opening degree of the valve body when the decrease in the detection pressure by the pressure sensor during the opening of the valve body reaches a predetermined value.

8. The oil-injected compressor according to claim 6, The control unit is an oil-fed compressor that closes the valve body after closing it for a predetermined period, and closes the valve body when the detected pressure by the pressure sensor during the opening of the valve body drops to a predetermined value.

9. The oil-fed compressor according to claim 2, wherein the control unit changes the predetermined period based on the load factor of the compressor body.

10. The oil-fed compressor according to claim 6, wherein the control unit reports an abnormality when the period from when the valve body is opened until the detected pressure of the pressure sensor drops to a predetermined pressure exceeds a predetermined period.

11. The oil-fed compressor according to claim 6, wherein the control unit records the number of times the rate of decrease in the detected pressure of the pressure sensor with respect to the elapsed time while the valve body is open does not reach a predetermined value, and reports an abnormality when the number of times reaches a predetermined number.

12. The oil-fed compressor according to claim 6, wherein the pressure sensor is provided near the location where the discharge piping system is connected to the second oil separator.

13. The oil-fed compressor according to claim 1, wherein the oil discharge path has a downstream opening communicating with the low-pressure side of the compressor body, and discharges the oil separated from the compressed gas by the second oil separator to the low-pressure side of the compressor body.

14. The oil-fed compressor according to claim 6, wherein the second oil separator has a cylindrical case with a closed upper end and an open lower end, a cylindrical filter located inside the case with open upper and lower ends, and a discharge pipe extending upward from below the filter with the upper end opening located inside the filter and communicating with the discharge piping system.

15. The oil-fed compressor according to claim 1, wherein the first oil separator has a swirl separation type gas-liquid separator that separates oil from the compressed air discharged from the compressor body.

16. The oil-fed compressor according to claim 1, wherein the control unit opens the valve body from the closed state before the amount of oil estimated to be stored in the storage unit exceeds the allowable amount of oil stored in the storage unit.

Images