SCREW COMPRESSOR MEANS FOR LUBRICATION OF A ROTOR BEARING

Abstract: A screw compressor means for lubrication of a rotor bearing on the compressor's low pressure side, which is supplied with refrigerant droplets containing oil accompanying the inlet gas. This kind of lubrication is usually carried out by permitting a limited amount of gas and oil to flow from the high pressure side to the low pressure side via the bearings located on the low pressure side, and further to the inlet. By this working mode compressor capacity as well as compression work deposited is lost. This is avoided when the compressor means according to the invention is provided with a special, smaller inlet channel (7), which via the rotor bearing (3) opens out in a specific inlet port (8) located at an expanding rotor thread presenting a lower pressure than the inlet (6) pressure of the compressor.

Description: SCREW COMPRESSOR MEANS FOR LUBRICATION OF A ROTOR BEARING This invention relates to a screw compressor means for lubrication of a rotor bearing on the compressor's low pressure side, which is supplied with a refrigerant con¬ taining oil for lubrication of the compressor's working chamber. In a refrigeration compressor which is run with circula¬ ting oil, the rotors are lubricated with help of the oil- enriched refrigerant droplets which accompany the inflowing gas. After completed compression, a certain amount of the gas and oil is allowed to escape along the high pressure side's rotor axis, through the bearings and finally arrive at a closed thread with lower pressure than that present at the corresponding bearing. There is no such usable pressure difference for the low pressure bearings. Gas and oil are therefore usually allowed to pass through a longitudinal boring through the rotor axis from the high pressure side to the low pressure side, through the low pressure rotor bearings and to the inlet. By this both compressor capacity and compression work from the returning gas stream is lost. Furthermore, a certain amount of heating of the bearing occurs. The object of this invention is to achieve an improved lubrication of the bearings on the low pressure side. This has, according to the invention, been achieved by means of the features specified by the following patent claims. Normally, an expanding thread is placed in the compres¬ sor in immediate connection to the compressor's inlet. By separating, in accordance with the invention, the inlet port into two ports, the possibility of two suction levels is achieved simply. The thread's first suction takes place, therefore, through the specifically arranged port, by which a lower pressure level is obtained than the pressure level that occurs at the compressor's inlet. A flow of gas and oil through the bearings on the low pressure side can thereby be achieved. This flow cools the bearings by its low temperature and lubricates the bearings by means of accompanying oil-enriched refrigerant droplets. The invention is now explained further with reference to the attached drawing, in which Fig. 1 schematically illustrates, as an example, a longitudinal section of an embodiment of a means in accordance with the invention, and Fig. 2 schematically shows a specific, axial inlet port. Figure 1 shows the low pressure end of a rotor 1 in a screw compressor. This end of the rotor has a shaft 2 which, by means of a bearing 3 is journalled in a chamber 4 in the end wall 5 of the compressor housing. The compressor's inlet channel is_ ^ denoted 6 and com¬ municates with the chamber 4 via short passages 7 which open out at the inner end wall of the bearing 3. Between the chamber 4 and a specific inlet port 8 in the compressor housing there is a channel 9. The port 8 is so designed that, during the first expansion of the thread, a lower pressure is produced here rather than at the compressor's ordinary inlet. This lower pressure is transmitted through the channel 9 to the chamber 4, by which refrigerant and oil will be moved by suction from the inlet 6 via the channels 7, the bearing 3, the channel 9 to the port 8. Preferably, the refrigerant is conducted in liquid form to the channels 7 from a point on the low pressure side, i.e. after an expansion valve in the cooling circuit where en¬ richment of refrigerant liquid and oil can take place. Also a buffer chamber forming a part of the inlet channel is advisable. Moreover or as an alternative the specific inlet port may be designed as an axial port 8' in the low pressure end wall 10, as shown in Fig. 2, the usual axial inlet port 11 being divided into two parts on opposite sides of the spe¬ cific port 8' , which should be connected to the channel 9 in Fig. 1 (not shown).

Claims: CLAIMS 1. A screw compressor means for lubrication of a rotor bearing (3) on the compressor's low pressure side, which is supplied with a refrigerant containing oil for lubrication of the compressor's working chamber, characterized in that the compressor is provided with a special, smaller inlet channel (7, 9), which via the above mentioned rotor bear¬ ings (3) opens out in a specific inlet port (8, 8') located at an expanding rotor thread with lower pressure than the compressor's inlet pressure. 2. A means according to claim 1 characterized in that one side of the above mentioned bearing (3) is connected to the compressor's inlet channel (6) close to the main inlet port (11). 3. A means according to claim 1 or 2 characterized in that the special, smaller inlet channel (7, 9) passes oil mixed with refrigerant in liquid form through said bearing

Inventors: PAMLIN ROLAND, SJOEHOLM LARS, PAMLIN, ROLAND, SJOEHOLM, LARS
Applicants: SVENSKA ROTOR MASKINER AB
Application year: 1986
Main classification: F04C29
IPC codes: F04C18, F04C29