Liquid-feed screw compressor

Abstract

To provide a liquid supply type screw compressor that can properly adjust an oil supply amount irrespective of set pressure.SOLUTION: A compressor includes: a route 45a for supplying lubricant to a workspace 313 of pressure P3; a route 45c for supplying lubricant to a workspace 311 of pressure P1; an oil supply selector valve 42 capable of sequentially moving to a first valve element position of bringing the routes 45a, 45c into (open, close) state, a second valve element position of bringing them into (open, open) state, and a third valve element position of bringing them into (close, open) state; and a drive mechanism for driving the oil supply selector valve 42 with force FR by an elastic body 43 and force FL by discharge pressure. When (first discharge pressure)≥(discharge pressure)>(second discharge pressure) is met, the oil supply selector valve 42 is driven to the third valve element position, when (prescribed pressure)>(discharge pressure)>(first discharge pressure) is met, the oil supply selector valve 42 is driven to the second valve element position, and when (discharge pressure)≥(prescribed pressure) is met, the oil supply selector valve 42 is driven to the first valve element position.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid feed screw compressor. [Background technology]

[0002] Some screw compressors are of a liquid-supply type, in which a liquid is supplied into the working chamber during the compression stroke for purposes such as sealing the internal gap between the screw rotor and the casing, cooling the compressed gas, and lubricating sliding parts. The liquid used is often lubricating oil, for example. In such oil-supply screw compressors, lubricating oil is mixed into the compressed gas discharged, so a separator is used to separate the lubricating oil from the compressed gas. The lubricating oil separated by the separator is self-circulated by utilizing the pressure difference between the discharge pressure generated by the compressor itself and the pressure in the working space of the compressor body, and is then supplied back to the compressor body (see, for example, Patent Document 1).

[0003] A typical screw compressor is connected to a customer's facility that uses compressed air via an air tank and various filters. In this case, the pressure in the air tank fluctuates depending on the amount of air used, so it is common to control the screw compressor to switch between loaded and unloaded operation or stop it based on information obtained from a pressure detection device attached to the compressor.

[0004] For example, in the case of capacity control of a constant speed machine in which the rotational speed of the motor that drives the compressor body is constant, compressed air is filled into the air tank and control is performed to maintain the pressure based on the pressure at which load operation switches to no-load operation (hereinafter referred to as the upper limit pressure) and the pressure at which no-load operation switches to load operation (hereinafter referred to as the return pressure).

[0005] In the case of capacity control of a variable speed machine in which the rotational speed of the motor that drives the compressor body is variable, the rotational speed of the motor is changed to maintain a preset pressure (hereinafter referred to as the control pressure), and compressed air is filled into the air tank, thereby controlling the pressure to be maintained.

[0006] These upper limit pressure, return pressure, control pressure, etc. can be changed from the factory settings (hereinafter referred to as the rated state) according to the customer's equipment. Therefore, in an oil-lubricated screw compressor in which oil is supplied by differential pressure, the amount of lubricating oil supplied to the compressor body will vary according to these settings. In other words, the optimal oil supply position when the customer is using the compressor may be different from the oil supply position set to maximize efficiency in the rated state.

[0007] Patent Document 1 discloses a method for an oil-lubricated screw compressor, which is configured with a normal oil supply line for the compressor body and a separate oil supply line equipped with an oil supply valve, reducing power loss by supplying oil in consideration of rated conditions and suppressing water condensation by supplying oil in consideration of water condensation. In Patent Document 1, the temperature of the lubricating oil in the oil tank is measured, and if the temperature of the lubricating oil is higher than a predetermined temperature, oil is supplied from both the oil supply line located in the low-pressure working space of the compressor body and the oil supply line located in the high-pressure working space via the oil supply valve. On the other hand, if the temperature of the lubricating oil in the oil tank is lower than a predetermined temperature, the oil supply valve is closed and oil is supplied only through the oil supply line located in the low-pressure working space of the compressor body, reducing power loss and suppressing water condensation by supplying oil in consideration of water condensation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6843033 Summary of the Invention [Problem to be solved by the invention]

[0009] However, although Patent Document 1 discloses that the amount of oil supplied to the compressor body is adjusted in rated operation to reduce power loss, it does not disclose a method for adjusting the amount of oil supplied to the compressor body taking into account the customer's usage conditions. [Means for solving the problem]

[0010] A liquid feed screw compressor according to an aspect of the present invention includes a compressor body accommodating a screw rotor, and a coolant path that separates coolant from discharge gas discharged from the compressor body and returns the coolant to the compressor body, and supplies liquid using a differential pressure between a working space pressure in the compressor body and a coolant pressure in the coolant path. The liquid feed screw compressor includes a first supply passage that supplies coolant from the coolant path to a first working space where the working space pressure is a first pressure, and a second supply passage that supplies coolant from the coolant path to a second working space where the working space pressure is a second pressure lower than the first pressure. a third supply passage that supplies the coolant from the coolant path to a third working space, the working space pressure of which is greater than the second pressure and less than the first pressure; the cooling fluid pressure adjusting mechanism includes a valve element that is slidably movable in order among a first valve element position that opens the first supply channel and closes the second supply channel, a second valve element position that opens the first supply channel and the second supply channel, and a third valve element position that closes the first supply channel and opens the second supply channel; and a drive mechanism that slides and drives the valve element by a first biasing force from the first valve element position to the third valve element position due to an elastic force of an elastic body and a second biasing force from the third valve element position to the first valve element position due to a discharge pressure of the discharge gas, wherein the drive mechanism slides and drives the valve element to the third valve element position when the discharge pressure is equal to or less than a first discharge pressure at which the cooling fluid pressure becomes the first pressure and is greater than a second discharge pressure at which the cooling fluid pressure becomes the second pressure, and slides and drives the valve element to the second valve element position when the discharge pressure is greater than the first discharge pressure and is less than a predetermined pressure that is greater than the first discharge pressure, and slides and drives the valve element to the first valve element position when the discharge pressure is equal to or greater than the predetermined pressure. The third supply passage always supplies the coolant regardless of the valve position of the valve body. . According to another aspect of the present invention, there is provided a liquid feed screw compressor comprising: a compressor body accommodating a screw rotor; and a coolant path for separating coolant from discharge gas discharged from the compressor body and returning the coolant to the compressor body, the liquid feed screw compressor supplying liquid based on the differential pressure between the working space pressure of the compressor body and the coolant pressure of the coolant path, the liquid feed screw compressor further comprising: a pressure detection device for detecting the pressure of the discharge gas; a first supply path for supplying coolant from the coolant path to a first working space where the working space pressure is a first pressure; and a second supply path for supplying coolant from the coolant path to a second working space where the working space pressure is a second pressure lower than the first pressure. a third supply passage that supplies the coolant from the coolant path to a third working space, the working space pressure of which is greater than the second pressure and less than the first pressure; The cooling system includes a valve element movable between a first valve element position that opens the first supply path and closes the second supply path and a second valve element position that closes the first supply path and opens the second supply path, a drive device that moves the valve element, and a control device that controls movement of the valve element by the drive device based on a pressure detection value of the pressure detection device, wherein the control device moves the valve element to the first valve element position when the coolant pressure based on the pressure detection value is greater than the first pressure, and moves the valve element to the second valve element position when the coolant pressure based on the pressure detection value is equal to or less than the first pressure and greater than a second pressure. The third supply passage always supplies the coolant regardless of the valve position of the valve body. . [Effects of the Invention]

[0011] According to the present invention, the amount of oil supplied to the compressor body can be appropriately adjusted regardless of the pressure used by the customer, and the reliability of the compressor body can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing an example of a system diagram of a liquid feed screw compressor according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing a switching device for lubricating oil circulated and supplied to the compressor body. [Figure 3] FIG. 3 is a PV diagram illustrating the suction process, compression process, and discharge process of the compressor body. [Figure 4]FIG. 4 is an enlarged view of the area in which the switching device of FIG. 2 is provided. [Figure 5] FIG. 5 is a diagram showing the slide position of the oil supply switching valve when the discharge pressure is lower than the discharge pressure upper limit value. [Figure 6] FIG. 6 is a diagram showing a second embodiment of a liquid feed screw compressor according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. Furthermore, in the following description, identical or similar elements and processes are given the same reference numerals, and duplicate explanations may be omitted. Note that the content described below merely shows an example of an embodiment of the present invention, and the present invention is not limited to the following embodiment, and can be implemented in various other forms.

[0014] (First embodiment) Fig. 1 is a diagram showing an example of a system diagram of a liquid feed type screw compressor 100 according to the first embodiment. In a liquid feed type screw compressor, water, oil, or the like is used as the liquid to be supplied, but the following description will be given taking as an example a case where lubricating oil is used as the coolant. Note that, hereinafter, the liquid feed type screw compressor 100 will be simply referred to as the compressor 100.

[0015] Although not shown, the compressor 100 is provided with a housing that reduces noise generated from the compressor main body 3. Intake gas (e.g., air) passes through an opening provided in the housing, an intake filter 1, and an intake throttle valve 2, and is sucked into the compressor main body 3, where it is compressed to a predetermined pressure. The compressor main body 3 is driven to rotate by a main electric motor 4. Electric power is supplied to the main electric motor 4 from a control device 9 mounted on a compressor control board.

[0016] Compressed gas (e.g., compressed air) compressed by compressor main body 3 has lubricating oil contained in the compressed gas separated in oil separator 5, and after passing through pressure regulating check valve 6, aftercooler 7, and a dryer (not shown), etc., the gas is stored in storage tank 10 installed downstream of the compressor. The pressure value of the compressed gas supplied from compressor 100 is detected by pressure detection device 11 and displayed on a display unit (not shown) provided on control device 9. The compressed gas stored in storage tank 10 is used as a gas source for customer equipment.

[0017] The pressure value detected by the pressure detection device 11 is lower than the discharge pressure of the compressor main body 3 due to pressure loss when the compressed gas passes through the oil separator 5 and the aftercooler 7. Operation of the screw compressor is controlled based on the pressure value obtained by the pressure detection device 11. In the example shown in FIG. 1, the pressure detection device 11 is installed between the aftercooler 7 and the storage tank 10, but the installation location is not limited to this and the device may be installed anywhere from the compressor main body 3 to the storage tank 10.

[0018] Meanwhile, the lubricating oil separated in the oil separator 5 is sent to the oil cooler 8 via the temperature control valve 12 and cooled. Thereafter, after passing through an oil filter and the like (not shown), it is returned to the compressor body 3 via a return pipe 13 of the lubricating oil path and supplied to the rotor, bearings, and the like housed inside the compressor body 3. The temperature control valve 12 controls the amount of lubricating oil that bypasses the oil cooler 8, thereby maintaining a constant temperature of the lubricating oil supplied to the compressor body 3. In this way, the lubricating oil circulates through the lubricating oil path of the compressor 100.

[0019] Generally, there are two main types of control methods for the compressor 100. The first is constant speed control, in which the rotation speed of the main motor 4 is kept constant, and the second is variable speed control, in which the rotation speed of the main motor 4 is varied. Constant speed control is a control method that maintains pressure by opening and closing the suction throttle valve 2 so that the pressure detection value obtained from the pressure detection device 11 falls within a preset range of upper limit pressure and return pressure, and by repeating loaded and unloaded operation. On the other hand, variable speed control is a control method that adjusts the rotation speed of the main motor 4 connected to the control device 9 so that the pressure value obtained from the pressure detection device 11 becomes a preset control pressure.

[0020] Furthermore, a design point called the rated state is set for the compressor 100. The rated state is a state in which the compressor body 3 discharges a specified amount of gas at a specified pressure. The oil supply position a in the compressor body 3 for the lubricating oil that has returned to the compressor body 3 through the lubricating oil path is predetermined to be the most efficient position in the rated state.

[0021] FIG. 2 is a diagram showing a switching device 40 for lubricating oil circulated and supplied to the compressor main body 3. In this embodiment, the switching device 40 is provided integrally with the casing of the compressor main body 3. The compressor 100 of this embodiment is a twin-shaft screw rotor compressor, and a pair of screw rotors consisting of a female rotor 31 with multiple spiral grooves and a male rotor (not shown) are provided within the rotor casing 30. In FIG. 2, the pair of screw rotors are arranged along the front-to-back direction of the page. The female rotor 31 is rotatably supported by bearings 33 and 34 provided in a bearing casing 32 and a bearing 35 provided in the rotor casing 30. The female rotor 31 is rotationally driven by the main motor 4 shown in FIG. 1.

[0022] An intake port 300 is formed at the top of the rotor casing 30 in the illustration, and an exhaust port 301 is formed in the bearing casing 32. In the compressor 100, a closed working space is formed by the combination of the meshing of the female rotor 31 and the male rotor and the rotor casing 30, and as the rotor rotates, the working space moves from the intake side (right side in the illustration) to the discharge side (left side in the illustration). During the movement process, there are times when it is connected only to the intake port 300 (suction process), times when it is not connected to either the intake port 300 or the discharge port 301 and the volume of the working space decreases (compression process), and times when it is connected only to the discharge port 301 (discharge process), and the processes of suction, compression, and discharge of gas such as air are performed continuously.

[0023] A portion of the lubricating oil returning through the return pipe 13 shown in FIG. 1 is supplied into the rotor casing 30 via the switching device 40. In this embodiment, the switching device 40 is integrally formed with the rotor casing 30, but it may be formed separately. The switching device 40 defines a valve chamber 41. The valve chamber 41 is provided with an oil supply switching valve 42 that slides left and right within the valve chamber 41. The valve chamber 41 is divided by the oil supply switching valve 42 into an elastic body chamber 411, an oil passage chamber 412, and a control chamber 413. An elastic body 43, such as a spring, is disposed in the elastic body chamber 411. Return lubricating oil is supplied to the oil passage chamber 412 via the return pipe 13. Discharge gas from the discharge port 301 is supplied to the control chamber 413 via a piping path 46. In this embodiment, the piping path 46 connects the control chamber 413 to the discharge port 301 of the compressor main body 3, but it may be connected anywhere between the compressor main body 3 and the pressure regulating check valve 6.

[0024] The elastic body chamber 411 is in communication with the surrounding outside air, and its internal pressure is maintained at atmospheric pressure. The oil supply switching valve 42 is urged rightward in the figure by the elastic force of the elastic body 43, and is also urged leftward in the figure by the pressure of the discharge gas from the control chamber 413. Therefore, the oil supply switching valve 42 slides left and right depending on the magnitude of the discharge gas pressure. Three working space oil supply paths 45a, 45b, and 45c are formed in the valve body chamber 41, which communicate with different working spaces within the rotor casing 30. The working space oil supply path 45a, the working space oil supply path 45b, and the working space oil supply path 45c are provided in order of decreasing working space pressure.

[0025] FIG. 3 is a PV diagram illustrating the suction process, compression process, and discharge process of the compressor main body 3, with the horizontal axis representing the working space volume V and the vertical axis representing the working space pressure P. In FIG. 3, curve L(ABC1) represents the PV diagram in the rated state, and curve L(ABD1) represents the PV diagram when the set pressure is lower than the rated state. C1 is the set pressure in the rated state, and the discharge pressure is controlled to be C1. D1 is the set pressure when the set pressure is lower than the rated state. In the following description, the compressor 100 is set between set pressure C1 and set pressure D1. Therefore, pressures C1 and D1 may also be referred to as the upper limit C1 and lower limit D1 of the discharge pressure.

[0026] Oil-lubricated screw compressors, which use differential pressure lubrication, utilize the pressure difference between the discharge pressure of the compressor body 3 and the pressure in the working space that supplies oil to the compressor body 3 for self-circulation lubrication. The pressure of the return lubricating oil at the oil supply port a in Figure 1 (hereinafter referred to as the oil supply pressure) drops due to pressure loss ΔP as the lubricating oil passes through the oil separator 5, oil cooler 8, and oil filter (not shown), resulting in pressure values ​​C2 and D2 lower than the discharge pressures C1 and D1. Therefore, when the pressure in the working space to be lubricated is equal to the oil supply pressures C2 and D2, no differential pressure for oil supply occurs, and C2 and D2 represent the oil supply limit pressures. The working space volumes E and F correspond to the oil supply pressures C2 and D2 and indicate the oil supply limit positions. When the set pressure is set to the upper discharge pressure limit C1, the oil supply range of the working space volume at rated operation is section BE. When the set pressure is set to the lower discharge pressure limit D1, the oil supply range is section BF. In the following description, the fuel supply pressure C2 at the discharge pressure upper limit C1 may be referred to as the fuel supply pressure upper limit, and the fuel supply pressure D2 at the discharge pressure lower limit D1 may be referred to as the fuel supply pressure lower limit.

[0027] Incidentally, if the set pressure is set to the lower limit of discharge pressure D1, the oil supply pressure will be the lower limit of oil supply pressure D2. Therefore, if the oil supply position is set near the oil supply limit position at point E, taking into account the highest efficiency at rated conditions, oil will not be able to be supplied to the working space within section EF, reducing rotor reliability. Conversely, if the oil supply position is set within section BF, taking into account a condition where the set pressure is lower than the rated condition, the amount of lubricating oil supplied will be excessive at discharge pressure C1 and oil supply pressure D1 at the rated condition, resulting in power loss and reduced performance.

[0028] On the other hand, in this embodiment, the switching device 40 as shown in FIG. 2 is provided, so that the occurrence of the above-mentioned problem can be prevented. FIG. 4 is an enlarged view of the area in FIG. 2 where the switching device 40 is provided. Note that in FIG. 4, the female rotor 31 is shown schematically with the working spaces instead of the rotor tooth shape shown in FIG. 2. The band-shaped areas indicated by the reference numerals 311, 312, and 313 represent the working spaces. The working space oil supply paths 45a, 45b, and 45c are connected to different working spaces 313, 312, and 311, respectively. The working space 311 has a pressure P1 and a volume V1. Similarly, the working space 312 has a pressure P2 and a volume V2, and the working space 313 has a pressure P3 and a volume V3.

[0029] The number of working spaces formed corresponds to the number of threads in the screw rotor, and as described above, the working spaces move from the right to the left as the rotor rotates. Figure 4 shows the position of each working space at a given moment, and as the female rotor 31 rotates over time, the working spaces 311, 312, and 313 move leftward as shown in the figure. In other words, the hatched area marked G represents gas trapped in the working space, and the working space in which this gas G is trapped moves leftward as the rotor rotates.

[0030] When the working space containing gas G moves to a position indicated by reference numeral 311 where the working space communicates with working space oil supply path 45c, the gas G reaches a pressure of P1 and a volume of V1. The term working space 311 refers to the working space that has moved to a position where it communicates with working space oil supply path 45c. Similarly, when the working space containing gas G moves to a position called working space 312, the gas G reaches a pressure of P2 and a volume of V2, and the working space communicates with working space oil supply path 45b. Furthermore, when the working space containing gas G moves to a position called working space 313, the gas G reaches a pressure of P3 and a volume of V3, and the working space communicates with working space oil supply path 45a. Points H1, H2, and H3 on the PV diagram shown in FIG. 3 correspond to these states.

[0031] As shown in Fig. 3, the pressure P3 in the operating space 313 is greater than the oil supply pressure D2 at the lower limit value D1 of the discharge pressure, and the pressures P1 and P2 in the operating spaces 311 and 312 are lower than the oil supply pressure D2. That is, the operating space oil supply paths 45b and 45c are formed to communicate with the operating spaces 312 and 311 within the oil supply possible range BF at the lower limit value D2 of the oil supply pressure when the set pressure is set to the lower limit value D1 of the discharge pressure.

[0032] When the valve body diameters of the oil supply switching valve 42 that partitions the valve body chamber 41 are the same, a rightward force FR and a leftward force FL due to the gas pressure in the control chamber 413 act on the oil supply switching valve 42 of the switching device 40. The gas pressure in the control chamber 413 is the discharge pressure of the compressor main body 3. Then, the oil supply switching valve 42 slides and moves to a position where the force FR and the force FL are balanced. The leftward movement of the oil supply switching valve 42 is restricted by the locking portion 44a shown in Fig. 4, and the rightward movement is restricted by the locking portion 44b shown in Fig. 4. Therefore, the movement range of the oil supply switching valve 42 is from the locking portion 44a to the locking portion 44b. The spring constant of the elastic body 43 is set such that FR(44a) < FL(C1) is satisfied when the oil supply switching valve 42 is in contact with the locking portion 44a, and FR(44b) > FL(D1) is satisfied when the oil supply switching valve 42 is in contact with the locking portion 44b. That is, the spring constant of the elastic body 43 is set such that FL(C1) > FR(44a) > FR(44b) > FL(D1).

[0033] Next, referring to Figs. 3 to 5, the operation of the switching device 40, that is, the relationship between the gas pressure in the control chamber 413 (that is, the discharge pressure of the compressor main body 3) and the slide position of the oil supply switching valve 42 will be described. Fig. 4 shows the slide position of the oil supply switching valve 42 when the discharge pressure of the compressor main body 3 is the upper limit value C1 of the discharge pressure. Fig. 5 shows the slide position of the oil supply switching valve 42 when the discharge pressure is lower than the upper limit value C1 of the discharge pressure.

[0034] First, when the discharge pressure of the compressor body 3 is at the discharge pressure upper limit C1, compressed gas at pressure C1 is supplied to the control chamber 413, and the oil supply switching valve 42 abuts against the locking portion 44a, as shown in FIG. 4. That is, in the rated state, the working space oil supply passage 45c is blocked by the oil supply switching valve 42, and the working space oil supply passages 45a and 45b are open. As shown in FIG. 3, when the discharge pressure is at the discharge pressure upper limit C1, the pressure in the oil passage chamber 412, i.e., the return lubricant oil supply pressure C2, is in the following order relative to the pressures P1, P2, and P3 in the working spaces 311, 312, and 313: C2 > P3 > P2 > P1. Therefore, the lubricant oil in the oil passage chamber 412 flows into the working spaces 313 and 312 via the working space oil supply passages 45a and 45b.

[0035] Next, consider the case where the discharge pressure drops from the discharge pressure upper limit C1 to pressure J1. In this case, as shown in the upper part of FIG. 5, the oil supply changeover valve 42 is in a state where the working space oil supply passage 45c is about to switch from a closed state to a state where it begins to open. When the discharge pressure is lower than J1 and higher than K1, the working space oil supply passages 45a, 45b, and 45c are open, as shown in the middle part of FIG. 5. Then, when the discharge pressure further drops to K1, the working space oil supply passage 45a is closed by the oil supply changeover valve 42, and the working space oil supply passages 45b and 45c are opened, as shown in the lower part of FIG. 5. Although not shown, when the discharge pressure further drops, the oil supply changeover valve 42 moves further to the right in the figure while the working space oil supply passages 45b and 45c remain open, and the oil supply changeover valve 42 is locked by the locking portion 44b. Therefore, when the discharge pressure lower limit value D1 is equal to the fuel supply pressure lower limit value D2, the fuel supply switching valve 42 is locked by the locking portion 44b.

[0036] When the discharge pressure is J1, the oil supply pressure is J2. When the discharge pressure is K1, the oil supply pressure is K2. When the discharge pressure is D1, the oil supply pressure is D2. The pressure in the working space 313 is pressure P3 in state H3 in FIG. 3. When C1 ≥ discharge pressure > K1, the oil supply pressure is C2 ≥ oil supply pressure > K2 > P3, so that the differential pressure (= oil supply pressure - P3) for supplying lubricating oil to the working space 313 can be reliably secured. On the other hand, when K1 ≥ discharge pressure ≥ D1, the oil supply pressure is K2 ≥ oil supply pressure ≥ D2. However, because the working space oil supply path 45a that supplies lubricating oil to the working space 313 is blocked by the oil supply switching valve 42, the compressed gas in the working space 313 does not flow back into the oil passage chamber 412 even if the oil supply pressure drops below the pressure P3 in the working space 313.

[0037] In the compressor 100, which supplies oil using the differential pressure between the working space pressure of the compressor body 3 and the oil supply pressure, this embodiment is configured so that the state in which return lubricating oil is supplied from the working space oil supply paths 45a, 45b to the working spaces 313, 312 achieves an optimal oil supply state in the rated state (discharge pressure C1). When the discharge pressure is lower than the discharge pressure upper limit value C1, the oil supply switching valve 42 is slidably driven in accordance with the discharge pressure to switch the working spaces to which lubricating oil is supplied as shown in Fig. 5 between (working spaces 312, 313) and (working spaces 311, 312, 313) and (working spaces 311, 312), thereby enabling an appropriate supply of lubricating oil according to the discharge pressure.

[0038] For example, consider a configuration that does not include the switching device 40 and supplies lubricant to the working spaces 312 and 313 regardless of the magnitude of the discharge pressure. If a user changes the set pressure from the upper discharge pressure limit C1 to the lower discharge pressure limit D1, the oil supply pressure D2 becomes lower than the pressure P3 of the working space 313. As a result, a problem occurs in which the lubricant cannot be supplied appropriately. On the other hand, in this embodiment, when the discharge pressure reaches the lower discharge pressure limit D1, the switching device 40 closes the working space oil supply path 45a and opens the working space oil supply path 45c, thereby stopping the supply of lubricant to the working space 313 and supplying lubricant to the new working space 311, which has a lower pressure. As a result, it is possible to maintain an appropriate supply of lubricant based on the pressure difference, thereby improving the reliability of the compressor body 3.

[0039] As described above, in the liquid feed screw compressor of this embodiment, regardless of the customer's usage state, the oil feed switching valve 42 can be slid in accordance with the discharge pressure of the compressor body 3, thereby adjusting the amount of oil fed to the compressor body 3. This makes it possible to provide an oil feed screw compressor with improved reliability of the compressor body 3.

[0040] (Second embodiment) 6 is a diagram showing a second embodiment of a liquid feed screw compressor according to the present invention. Comparing a compressor body 3B of the second embodiment with the above-described compressor body 3, the method of driving the oil supply switching valve 42 in a switching device 40B is different, and the oil supply switching valve 42 is slidably driven by a driving device 18 such as a motor. The driving device 18 is controlled by a control device 9 based on a pressure value relating to the discharge pressure detected by a pressure detection device 11. The other configurations are the same as those of the first embodiment described above.

[0041] Similar to the above-described first embodiment, the valve body chamber 41 is partitioned by the fuel supply switching valve 42 into an elastic body chamber 411B, an oil passage chamber 412, and a control chamber 413B. However, the piping path 46 shown in FIG. 2 has been deleted. The elastic body chamber 411B and the control chamber 413B communicate with the oil passage chamber 412, and the elastic body chamber 411B, the oil passage chamber 412, and the control chamber 413B are all at the same pressure. The other configurations are the same as those of the first embodiment, and the description thereof is omitted. Note that the locking portions 44a and 44b may or may not be provided.

[0042] Next, the switching operation by the fuel supply switching valve 42 will be described. As described above, the pressure detection device 11 is provided to detect the pressure of the compressed gas discharged from the compressor main body 3B. However, a pressure value lower by the pressure loss in the path from the discharge port 301 of the compressor main body 3B to the pressure detection device 11 is detected for the discharge pressure at the discharge port 301. The control device 9 calculates the value obtained by adding the pressure loss component to the pressure detection value as the discharge pressure, and controls the slide drive of the fuel supply switching valve 42 by the drive device 18 based on the calculated discharge pressure.

[0043] When the discharge pressure satisfies the condition "pressure C1 ≥ (discharge pressure) ≥ J1", the control device 9 positions the fuel supply switching valve 42 at the position shown in FIG. 4. When the discharge pressure is "J1 > (discharge pressure) > K1", the fuel supply switching valve 42 is slid rightward in the figure from the position shown in FIG. 4 in response to the pressure drop. In that case, the arrangement shown in FIG. 4 is adopted when the discharge pressure = J1, and the arrangement shown in the lower part of FIG. 5 is adopted when the discharge pressure = K1. Further, when the discharge pressure becomes lower than K1, the fuel supply switching valve 42 is slid to a position where the working space fuel supply passage 45a is completely closed and the working space fuel supply passage 45c is completely opened.

[0044] Also in the second embodiment, the fuel supply switching valve 42 is moved according to the magnitude of the discharge pressure, and the working space for fuel supply is switched so that the differential pressure for fuel supply does not become zero or less. As a result, it is possible to maintain the lubricating oil supply by the differential pressure in an appropriate state, and the reliability of the compressor main body 3B can be improved.

[0045] When the oil supply switching valve 42 is slid using the drive device 18, it is also possible to rapidly change the open / closed state of the working space oil supply paths 45a, 45b, 45c in a stepwise manner from (open, open, closed) to (closed, open, open) when the discharge pressure is within the range of "pressure C1 ≥ (discharge pressure) ≥ J1." However, if the state is changed in a stepwise manner, the amount of oil supply may change suddenly, causing a sudden change in the load. Therefore, it is preferable to gradually change from the (open, open, closed) state to (closed, open, open) in accordance with the change in discharge pressure as described above, which can prevent a sudden change in the amount of oil supply.

[0046] As another operation method, the oil supply switching valve 42 may be positioned at a position corresponding to a pressure set by a user. The user inputs set pressure information to the control device 9. The relationship between the set pressure in the control device 9 and the position of the oil supply switching valve 42 may be the same as the relationship between the discharge pressure and the slide position described above, or the open / closed states of the working space oil supply paths 45a, 45b, 45c may be (open, open, closed) when the set pressure is "C1 ≧ set pressure ≧ predetermined value," and the open / closed states of the working space oil supply paths 45a, 45b, 45c may be (closed, open, open) when the set pressure is "predetermined value ≧ set pressure ≧ D1."

[0047] In the first and second embodiments described above, oil is used as the liquid to be supplied, but other liquids (for example, water) may be used. Also, while the left and right valve bodies of the oil supply switching valve 42 have the same diameter, they may be configured to have different diameters. In the first and second embodiments, the oil supply path 45b is configured to always communicate with the working space 312 and supply oil, but this may be omitted if the amount of oil supplied is sufficient.

[0048] In the first and second embodiments described above, the return lubricating oil is supplied to the female rotor 31 of a twin screw compressor having male and female screw rotors via the switching devices 40, 40B, but the present invention can also be applied to a configuration in which oil is supplied to the male rotor. Furthermore, the present invention is not limited to a twin screw configuration and can be similarly applied to a liquid feed type screw compressor having a single screw configuration.

[0049] In the first and second embodiments described above, the oil supply switching valve 42 is used to switch between opening and closing the working space oil supply path 45a and the working space oil supply path 45c, which communicate with two working spaces having different pressures. However, the oil supply switching valve 42 may be used to switch between opening and closing three or more working space oil supply paths. Also, the switching devices 40 and 40B are configured as switching valves with a sliding valve body. However, various configurations are possible, not limited to the sliding type.

[0050] According to the first and second embodiments of the present invention described above, the following advantageous effects are achieved.

[0051] (C1) As shown in Figures 1 to 5, the liquid feed screw compressor 100 includes a compressor body 3 accommodating a screw rotor, and a return pipe 13 that separates lubricating oil from the discharge gas discharged from the compressor body 3 and returns the lubricating oil to the compressor body 3, and supplies oil by the differential pressure between the working space pressure of the compressor body 3 and the oil supply pressure. The liquid feed screw compressor 100 has a working space oil supply passage 45a that supplies lubricating oil from the return pipe 13 to the working space 313 where the working space pressure is pressure P3, a working space oil supply passage 45c that supplies lubricating oil from the return pipe 13 to the working space 311 where the working space pressure is pressure P1 lower than the pressure P3, a first valve body position shown in the upper part of Figure 5 where the working space oil supply passage 45a is opened and the working space oil supply passage 45c is closed, and a second valve body position shown in the middle part of Figure 5 where the working space oil supply passage 45a and the working space oil supply passage 45c are closed. The oil supply switching valve 42 is provided with a valve body chamber 41 which constitutes a drive mechanism that slides the oil supply switching valve 42 by a first biasing force FR in the direction from the first valve body position to the third valve body position due to the elastic force of the elastic body 43, and a second biasing force FL in the direction from the third valve body position to the first valve body position due to the discharge pressure. When the discharge pressure of the discharge gas is equal to or less than the discharge pressure K1 at which the oil pressure becomes pressure P3 and is greater than the discharge pressure P0 at which the oil pressure becomes pressure P1, the oil supply switching valve 42 is slidably driven to the third valve body position (see the lower part of Figure 5), when the discharge pressure is greater than the discharge pressure K1 and less than a predetermined pressure J1 that is greater than the discharge pressure K1, the oil supply switching valve 42 is slidably driven to the second valve body position (see the middle part of Figure 5), and when the discharge pressure is equal to or greater than the predetermined pressure J1, the oil supply switching valve 42 is slidably driven to the first valve body position (see the upper part of Figure 5).

[0052] As described above, in the liquid feed screw compressor 100 in which liquid is fed by the pressure difference between the working space pressure of the compressor body 3 and the oil feed pressure, the oil feed switching valve 42 is slidably driven in accordance with the magnitude of the discharge pressure, and the working space to which lubricating oil is fed is switched from (working space 312, 313) to (working space 311, 312, 313) to (working space 311, 312) as shown in FIG. 5, thereby making it possible to maintain the supply of lubricating oil by the pressure difference in an appropriate state, thereby improving the reliability of the compressor body 3.

[0053] (C2) As shown in Figures 1, 3 to 6, the liquid feed screw compressor 100 includes a compressor body 3B containing a screw rotor, and a return pipe 13 that separates lubricating oil from discharge gas discharged from the compressor body 3B and returns the lubricating oil to the compressor body 3B, and supplies oil by the differential pressure between the working space pressure of the compressor body 3B and the oil supply pressure of the return pipe 13. The compressor includes a pressure detection device 11 that detects the pressure of the discharge gas, a working space oil supply passage 45a that supplies lubricating oil from the return pipe 13 to the working space 313 where the working space pressure is pressure P3, a working space oil supply passage 45c that supplies lubricating oil from the return pipe 13 to the working space 311 where the working space pressure is pressure P1 lower than pressure P3, a first valve body position shown in the upper part of Figure 5 that opens the working space oil supply passage 45a and closes the working space oil supply passage 45c, and a second valve body position shown in the lower part of Figure 5 that closes the working space oil supply passage 45a and closes the working space oil supply passage 45c. a drive unit 18 that moves the fuel supply switch valve 42; and a control device 9 that controls the movement of the fuel supply switch valve 42 by the drive unit 18 based on the pressure detection value of the pressure detection device 11. The control device 9 moves the fuel supply switch valve 42 to the first valve body position when the supply oil pressure based on the pressure detection value is greater than pressure P3, and moves the fuel supply switch valve 42 to the second valve body position when the supply oil pressure based on the pressure detection value is equal to or less than pressure P3 and greater than pressure P1.

[0054] As described above, the oil supply switching valve 42 is moved to the first valve element position or the second valve element position depending on the magnitude of the discharge pressure, thereby switching the working space to which oil is supplied so that the differential pressure for oil supply does not become equal to or less than zero. As a result, it is possible to maintain an appropriate state of lubricating oil supply due to the differential pressure, thereby improving the reliability of the compressor main body 3B.

[0055] (C3) In the above (C2), as shown in Figures 1 and 3 to 6, when the oil supply pressure based on the pressure detection value is greater than pressure P3 and less than a predetermined oil supply pressure J2 greater than pressure P3, the control device 9 moves the oil supply switching valve 42 to the third valve element position (see the middle part of Figure 5) which opens the working space oil supply passage 45a and the working space oil supply passage 45c. In the configuration of the above (C2), by providing a third valve element position between the first valve element position and the second valve element position which opens the working space oil supply passage 45a and the working space oil supply passage 45c, it is possible to suppress a sudden change in the amount of lubricating oil supplied.

[0056] (C4) The liquid feed screw compressor according to any one of (C1) to (C3) above, further comprising a working space oil supply path 45b for supplying lubricating oil from the return pipe 13 to the working space 312 where the working space pressure is higher than pressure P1 and lower than pressure P3, as shown in Fig. 2, so that lubricating oil is always supplied by the working space oil supply path 45b regardless of the position of the valve disc of the oil supply switching valve 42. By providing the working space oil supply path 45b, it is possible to cope with cases where a larger amount of oil is required to be supplied.

[0057] The above-described embodiments and various modifications are merely examples, and the present invention is not limited to these details as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the present invention is not limited to these details. Other aspects conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0058] 1...suction filter, 2...suction throttle valve, 3, 3B...compressor body, 4...main motor, 5...oil separator, 6...pressure regulating check valve, 7...aftercooler, 8...oil cooler, 9...control device, 10...storage tank, 11...pressure detection device, 12...temperature control valve, 13...return pipe, 18...drive device, 30...rotor casing, 31...female rotor, 32...bearing casing, 33-35...bearings , 40, 40B...switching device, 41...valve body chamber, 42...oil supply switching valve, 43...elastic body, 44a, 44b...engaging portion, 45a, 45b, 45c...working space oil supply path, 46...piping path, 100...liquid feed type screw compressor, 300...suction port, 301...discharge port, 311 to 313...working space, 411, 411B...elastic body chamber, 412...oil passage chamber, 413, 413B...control chamber

Claims

1. A liquid feed screw compressor includes a compressor body containing a screw rotor, and a coolant path that separates coolant from discharge gas discharged from the compressor body and returns the coolant to the compressor body, and supplies liquid using a differential pressure between a working space pressure in the compressor body and a coolant pressure in the coolant path, a first supply passage for supplying the coolant from the coolant path to a first working space having a working space pressure of a first pressure; a second supply passage for supplying the coolant from the coolant path to a second working space, the working space pressure of which is a second pressure lower than the first pressure; a third supply passage that supplies the coolant from the coolant path to a third working space, the working space pressure of which is greater than the second pressure and less than the first pressure; a valve body that is slidably movable in order between a first valve body position that opens the first supply path and closes the second supply path, a second valve body position that opens the first supply path and the second supply path, and a third valve body position that closes the first supply path and opens the second supply path; a drive mechanism that slides and drives the valve body by a first biasing force in a direction from the first valve body position to the third valve body position due to an elastic force of an elastic body, and a second biasing force in a direction from the third valve body position to the first valve body position due to a discharge pressure of the discharge gas, The drive mechanism includes: When the discharge pressure is equal to or lower than a first discharge pressure at which the cooling liquid pressure becomes the first pressure and is higher than a second discharge pressure at which the cooling liquid pressure becomes the second pressure, the valve body is slidably driven to the third valve body position, When the discharge pressure is greater than the first discharge pressure and less than a predetermined pressure greater than the first discharge pressure, the valve body is slidably driven to the second valve body position, When the discharge pressure is equal to or greater than the predetermined pressure, the valve body is slidably driven to the first valve body position, The third supply passage constantly supplies the coolant regardless of the position of the valve body of the liquid feed screw compressor.

2. A liquid feed screw compressor includes a compressor body containing a screw rotor, and a coolant path that separates coolant from discharge gas discharged from the compressor body and returns the coolant to the compressor body, and supplies liquid using a differential pressure between a working space pressure in the compressor body and a coolant pressure in the coolant path, a pressure detection device for detecting the pressure of the discharge gas; a first supply passage for supplying the coolant from the coolant path to a first working space having a working space pressure of a first pressure; a second supply passage for supplying the coolant from the coolant path to a second working space, the working space pressure of which is a second pressure lower than the first pressure; a third supply passage that supplies the coolant from the coolant path to a third working space, the working space pressure of which is greater than the second pressure and less than the first pressure; a valve body that is movable between a first valve body position that opens the first supply path and closes the second supply path and a second valve body position that closes the first supply path and opens the second supply path; a drive device that moves the valve body; a control device that controls movement of the valve element by the drive device based on a pressure detection value of the pressure detection device, The control device When the coolant pressure based on the pressure detection value is greater than the first pressure, the valve body is moved to the first valve body position; When the coolant pressure based on the pressure detection value is equal to or less than the first pressure and is greater than the second pressure, the valve element is moved to the second valve element position; The third supply passage constantly supplies the coolant regardless of the position of the valve body of the liquid feed screw compressor.

3. 3. The liquid feed screw compressor according to claim 2, the control device, when the coolant pressure based on the pressure detection value is higher than the first pressure and lower than a predetermined coolant pressure that is higher than the first pressure, slides the valve element to a third valve element position to open the first supply path and the second supply path.

Images