1、英文原文Lubricant supply system and operating method of multisystem lubrication screw compressorSekiya; Yoshimitsu (Moriya, JP)AbstractAn oil refrigeration screw compressor being applied to a refrigeration system etc., in which the problem of strength reduction of a bearing material under high temperatu
2、res and that of lifetime reduction of the bearing material due to viscosity lowering of lubricant are solved. A lubricant supply system to a compressor body is divided into a bearing oil supply system for supplying lubricant to each bearing of the compressor body at low pressure and into a temperatu
3、re control oil supply system for supplying lubricant into the compressor body at high pressure. The bearing oil supply system is a closed circuit oil supply system comprising an oil supply tank, an oil cooler, and an oil supply pump, and the temperature control oil supply system is a closed circuit
4、oil supply system comprising an oil separator and an oil cooler. BEST MODE FOR EMBODIMENT OF THE INVENTION Preferred embodiment of the present invention will now be detailed with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, material
5、s, relative positions and so forth of the constituent parts in the embodiments shall be interpreted as illustrative only not as limitative of the scope of the present invention. FIG. 1 is a schematic illustration of an example of lube oil supply line of the screw compressor according to the present
6、invention in a perspective view. In FIG. 1, reference numeral I is an oil supply line for controlling temperature, lube oil is supplied through this line to be injected from a slide valve toward screw rotors b consisting of a male rotor and a female rotor in order to control temperature of the compr
7、essed fluid discharged from the compressor together with the compressed fluid. Reference numeral II is a bearing lubricating oil supply line, lube oil is supplied through this line to sleeve bearings d and thrust bearings e of rotor shafts c, to a balance piston g for reducing thrust load, and to an
8、 oil seal h, and flows out to a return path II which communicates to an oil supply tank not shown in the drawing. Reference numeral III is an oil supply line for supplying oil to a hydraulic piston p for driving the slide valve a. This line is a closed line provided separately from the line I and II
9、 which are related to the present invention, The line III is not related to the invention, so explanation is omitted. By providing the oil supply lines I and II separately from each other in the invention, the compressor can be operated at optimal conditions concerning temperature, pressure, and flo
10、w rate of lube oil supplied via each of the oil supply lines, and the objects of the present invention can be attained. Next, in FIG. 2 showing the lube oil supply system of the first embodiment of the invention, reference numeral 1 is a screw compressor, 2 is a screw rotor of a pair of male and fem
11、ale screw rotors supported rotatably in the rotor casing of the compressor 1, 3 is a slide valve for injecting lube oil to the rotor 2 in the rotor casing. Reference numeral 1a is a suction port of fluid f to be compressed, 1b is a discharge port of compressed fluid f, and 2a is a shaft part of the
12、rotor 2.The fluid f to be compressed is sucked from the suction port 1a into the compressor 1 and compressed as the rotors 2 rotate to be discharged in a pressurized state together with lube oil mixed in it. The mixed lube oil is separated from the compressed gas in an oil separator 4. The separated
13、 lube oil is cooled in an oil cooler 5, filtered through a filter 6 to remove foreign matter, and again returned to the slide valve 3. This closed circulation circuit composes the temperature control, oil supply line I and shown by a broken line. Reference numeral 7 is an oil supply tank in which lu
14、be oil is reserved, the oil reserved in the oil supply tank 7 is supplied by means of an oil supply pump 8 to rotor bearing parts of the compressor via an oil cooler and a filter 10. The lube oil supplied to the rotor bearing parts is recovered to the oil supply tank 7 passing through a return path
15、L.sub.3. This closed circuit composes the bearing lubricating oil supply line II and shown by a solid line. The oil supply tank 7 is provided with a liquid-level meter 13 for detecting oil levels and a liquid level transmitter 11 for sending oil levels detected by the liquid-level meter 13 to an oil
16、-level control operator 12. A temperature control valve 14 is provided in the upstream of the oil cooler 9, a branch path L.sub.1 branches from the temperature control valve 14, and a branch path L.sub.2 equipped with a pressure regulator valve 15 branches from the branch path L.sub.1 for allowing a
17、 part of the lube oil from the oil supply pump 8 to be returned to the oil supply tank 7. A path L.sub.4 is provided which communicates the gas zone in the upper part of the oil supply tank 7 to a position near the suction port 1a, a pressure regulator valve 16 is provided in the path L.sub.4, and a
18、 path L.sub.5 having a flow regulator valve 17 is provided for allowing the lube oil in the oil supply line II to be supplied to the position near the suction port 1a. A path L.sub.6 is provided to the temperature control oil supply line I for supplying a part of the lube oil to in the line to the o
19、il supply tank 7, and a filter 18 and a flow regulator valve 19 are provided in the path L.sub.6. A temperature control valve 20 is provided in the downstream of the oil cooler 5, and a path L.sub.7 branches from the temperature control valve 20. The oil separator 4 is provided with a liquid-level m
20、eter 22 for detecting oil levels and a liquid-level switch 21 for allowing an alarm to be sounded when the detected oil level has lowered to a limit level. Reference numerals 23, 24, and 25 are temperature detectors for detecting and transmitting signals of detected temperatures, and reference numer
21、al 26, 27, 28, and 29 are pressure detectors for detecting pressure and transmitting signals of detected pressures provided to each of the paths respectively. Reference numeral 30 is a flow detector, 31 is a control operator for determining oil pressure adequate or optimal for the bearing lubricatin
22、g oil supply line II based on the pressure difference between the upstream and downstream zone of the oil supply pump 8 and on the pressure difference between the temperature control oil supply line I and bearing lubricating oil supply line II, and for controlling the pressure regulator valve 15 so
23、that said adequate oil pressure is realized in the bearing lubricating oil supply line II. Reference numerals 32, 33, 34, and 35 are non-return valves, and 36 is a manual valve. FIG. 3A shows arrangement of rotors and bearing parts of the first embodiment shown in FIG. 1. In the drawing, lube oil in
24、jected into the rotor room to control temperature of compressed fluid f is indicated by I, and lube oil supplied to lubricate bearings is indicated by II. In FIG. 3A, reference numeral 2 is a pair of male and female rotors, each of the rotors 2 is supported by journal bearings 42 at its shaft parts
25、2a extending from both ends thereof. Reference numerals 41 are oil seals, 43 are thrust bearings. Reference numeral 44 is a mechanical oil seal. FIG. 3B and FIG. 3C are respectively an enlarged sectional view of the journal bearing indicated by an arrow B and arrow C in FIG. 3A. In FIG. 3B and FIG.
26、3C, an oil groove 45, 46 is provided in each of the journal bearings for returning lube oil to the oil supply tank 7 via the oil return path L.sub.3. Journal bearings of this type may be used together with the oil seals 41 or without the oil seals 41. In the first embodiment shown in FIG. 2 and FIG.
27、 3A, lube oil supplied via the temperature control oil supply line I and via the bearing lubricating oil supply line II inevitably mix with each other, so preferably lube oil of the same kind is used for the lines I and II. Lube oil for controlling temperature can be injected into the rotor room by
28、utilizing pressure difference between the discharge pressure at the discharge port 1b and the pressure in the rotor space under compression process. As to temperature of oil, temperature of the oil supplied via the temperature control oil supply line I and that supplied via the bearing lubricating o
29、il supply line II can be made different, for the two lines I and II are separate lines. It is effective, for example, to raise the temperature of the oil injected into the rotor room for temperature control in order to prevent occurrence of condensation of the gas compressed in the compressor by dec
30、reasing or stopping oil flow and decrease the temperature of the oil supplied to the bearings in order to secure proper viscosity of the lube oil. Herewith, aforementioned problems in the prior art, that is, reduction in strength of slide bearings due to heat generation by friction and reduction in
31、bearing life due to lowering in viscosity of lube oil, can be prevented. According to the embodiment, injection oil supplied to the rotor room can be raised in temperature or decreased in flow rate for the purpose of preventing occurrence of condensation of compressed fluid, so the amount of lube oi
32、l mixed in the fluid can be reduced. Therefore, the oil separator in the temperature control oil supply line I can be small sized and oil separation efficiency can be increased. Further, intrusion of foreign matter contained in the fluid f to be compressed to the bearing lubricating oil supply line
33、II can be suppressed to the minimum. On the other hand, the amount (flow rate) of lube oil for lubricating rotor bearings can be reduced to the minimum and its temperature can be lowered below permissible temperature for bearing lubrication. Therefore, it is made possible to adopt low viscosity lube
34、 oil, for example, mineral oil, and also to maintain the compressed gas in high temperature without excessively cooled by lube oil. Further, by providing the path L.sub.3 in the bearing lubricating oil supply line II in order to recover the lube oil after lubricating bearings of the compressor 1 to
35、the oil supply tank 7 and the path L.sub.6 in the temperature control oil supply line I in order to supply a part of the lube oil separated in the oil separator 4 and cooled by the oil cooler 5, lube oil in both lines including lube oil leaked between both lines can be eventually recovered to the oi
36、l supply tank 7 in the bearing lubricating oil supply line II, so a little leakage between both lines is acceptable. The same lube oil must be used for both lines, for lube oil in both lines mixes with each other.As shown in FIG. 3, by adopting slide bearings for supporting rotatably the rotors 2 an
37、d providing grooves 45 and 46 respectively near the rotor end face side end of each slide bearing to allow lube oil to be accumulated therein so that the lube oil accumulated in the groove is introduced to the lube oil recovery path L.sub.3 of low pressure, supply and recovery of lube oil for lubric
38、ating the bearings can be performed easily and positively, and leakage of lube oil from bearing space into the rotor casing or on the contrary from the rotor casing into the bearing space can be suppressed to the minimum while allowing the leakage of a certain amount of lube oil. That is, leakage of
39、 lube oil can be suppressed by allowing lube oil to accumulate transiently in the grooves and recovering again to another low pressure lube oil recovering path. By this, lube oil leakage between both lines I and II can be minimized. Further, by providing the path L.sub.4 for communicating the gas zo
40、ne in the oil supply tank 7 in the bearing lubricating oil supply line II to a position near the suction port 1a and attaching the pressure regulator valve 16 to the path L.sub.4, pressure of the gas zone in the oil supply tank 7 in the bearing lubricating oil supply line II can be made to be at a p
41、ressure the same as suction pressure of fluid f to be compressed or intermediate pressure between suction and discharge pressure, so pressure rise in the oil supply tank 7 in the bearing lubricating oil supply line II when starting operation of the compressor 1 can be prevented, and it is made possi
42、ble that oil injection into the rotor room can be performed by pressure difference between discharge pressure detected by the pressure detector (26) and suction pressure detected by the pressure detector (28), that is, oil supply by pressure difference in operation can be adopted. Further, by provid
43、ing the branch path L.sub.2 for returning lube oil in the downstream of the oil supply pump 8 to the oil supply tank 7, attaching the pressure regulator valve 15 to the branch path L.sub.2, and providing the control operator 31 for controlling the opening of the pressure regulator valve 15 based on
44、the pressure difference between oil pressure in the downstream and upstream of the oil supply pump 8 (pressure difference between the pressure detected by the pressure detector 27 and that detected by the pressure detector 28) and the pressure difference between discharge gas pressure in the tempera
45、ture control oil supply line I (pressure detected by the pressure detector 26) and oil pressure in the downstream of the oil supply pump 8 (pressure detected by the pressure detector 27), a rapid pressure rise in the lube oil recovery path L.sub.2 when staring operation of the compressor can be alle
46、viated. Further, by providing the oil-level meter 11 to the oil supply tank 7 in the bearing lubricating oil supply line II, providing the path L.sub.5 for returning lube oil from the oil supply tank 7 to the temperature control oil supply line I, providing the flow regulator valve 17 to the path L.
47、sub.5, providing the flow regulator valve 19 to the path L.sub.6 in the temperature control oil supply line I to recover a part of lube oil to the oil supply tank 7, the flow regulator valves 17 and 19 being controlled based on the oil level detected by the oil-level meter 11, and providing the cont
48、rol operator 12 for controlling the level of the oil in the oil supply tank 7 in a predetermined range, the level of the oil in the oil supply tank 7 can be maintained in a prescribed range and variation of the oil level caused by oil leak between the bearing lubricating oil supply line II and tempe
49、rature control oil supply line I etc. can be suppressed. Further, by providing the branch path L.sub.1 for allowing the lube oil discharged from the oil pump 8 to bypass the oil cooler 9 in the bearing lubricating oil supply line II, attaching the temperature control valve 14 for controlling lube oil temperature to the branch path L.sub.1, and controlling temperature of lube oil supplied to the bearings of the rotors by controlling the opening of the temperature control valve 14, lube oil of low temperature and high viscosity can be supplied to the bearings of the rotors. Further, by adopting
