EP0105315B1

EP0105315B1 - Compressor of hermetical type

Info

Publication number: EP0105315B1
Application number: EP83901250A
Authority: EP
Inventors: Rune Glanvall
Original assignee: Stal Refrigeration AB
Current assignee: Stal Refrigeration AB
Priority date: 1982-04-13
Filing date: 1983-03-31
Publication date: 1987-01-07
Also published as: JPH056037B2; EP0105315A1; JPS59500572A; SE450150B; SE8202299L; WO1983003641A1; DE3368965D1

Abstract

A compressor of hermetical type in which the electric driving motor (16) is enclosed in a chamber (29), which is flowed through by the compressed medium, is driven by the driving motor via a gear drive (24, 23) enclosed in gear space (22) which is drained to an intermediate pressure in the compressor. Due to this fact the gear drive (24, 23) and adjacent bearings (6, 11, 20) are lubricated by oil of that pressure prevailing in the oil separator (31) of the compressor, whereby an oil pump can be spared.

Description

The invention relates to a hermetical compressor of rotational type according to the introductory part of claim 1. Such a compressor is known from Figure 2 of the DE-A-2 914 726.
The compressor disclosed in the DE-A-2914726 is of a so called hermetical type in which the compressor and its driving motor are enclosed in a housing from which no rotating parts project. Such compressors are easy to tighten and are used in those cases in which the compressed medium is not allowed to leak out of the compressor.
The electric driving motor needs cooling, and in the known compressor this is brought about by conducting the warm, compressed medium which is sufficiently cold for cooling the driving motor through the same.
In the known apparatus the gear wheels are arranged for adapting the number of revolutions of the driving motor to an optimum number. of revolutions of the compressor rotors. The known compressor has that disadvantage that lubricating points in the compressor require an oil pressure that is higher than the final pressure of the compressed medium, which requires a special oil pump. Examples of such lubricating points are the bearing of the driven screw rotor 16 in the wall towards the motor room 8, and the bearing of the two ends of the motor shaft 2, outside which lubricating points the mentioned final pressure exists and thus the oil has to be supplied with a pressure higher than the mentioned final pressure.
From the GB-A-2 059 511 an open-air com- ^pressor is known, the driving motor of which is connected via gear wheels to the shaft of one of two screw-shaped compressor rotors meshing with one another. The driving motor is surrounded by the open air and sucks in the air to be compressed with the help of a fan. This compressor unit is of a special compact design, incorporating in one constructional unit an air filter, an oil separator and a cooler for the compressed air. The gear wheels between compressor and driving motor are housed in a chamber that is closed towards the open air and thereby towards the driving motor. This gear chamber is supplied with lubricating oil via a pipe opening into the gear chamber, and the gear chamber is connected via a second pipe to a compartment of the pressure chamber in which the pressure is lower than in the gear chamber. The bearings on the pressure side of the compressor rotors are lubricated by oil, being injected at an intermediate point between the inlet and the outlet of the compressor and being squeeezed through the bearings whereupon the oil is led back to the pressureless outside of one of the rotors.
From the SE-A-422350 a compressor is known where lubrication of the rotor bearings is achieved by feeding oil at output pressure of the compressor to grooves surrounding the bearings and by discharging the oil after being squeezed through the bearing surfaces via a pipe to a point in the compressor chamber positioned between the inlet and the outlet of the compressor.
The invention aims at developing a hermetical compressor of the above-mentioned kind, which is constructively simple and where an oil pump for supplying oil to the compressor for lubricating, cooling and tightening purposes can be spared.
In order to achieve this aim the invention suggests a hermetical compressor according to the introductory part of claim 1, which is characterized by the features of the characterizing part of claim 1.
Further developments of the invention are characterized by the features of the additional claims.
In the compressor unit according to the invention oil having an initial pressure equal to the final pressure of the compressed medium, i.e. equal to the pressure in the motor chamber, is forced to circulate through the shaft bearings being adjacent to the gear chamber, and through the gear chamber and lubricate and cool the mentioned shaft bearings and the gear wheels in the gear chamber.
It shall also be remarked that it is previously known by for instance Swedish patent publication No. 369,097 to lubricate and cool a bearing of a motor rotor in an electric driving motor for driving a compressor and where the driving motor is under the final pressure of the compressed medium without using a special oil pump, oil having the final pressure of the compressed medium being forced to circulate through the mentioned bearing and is sucked out of the bearing by a pressure that is lower than the final pressure of the compressed medium. The oil, however, is not sucked out into such a gear chamber that among other things characterizes the present invention and, therefore, has nothing to do with the characterizing new thing in the present invention.
The oil which is mixed with outleaking, gaseous medium can, of course, be sucked away from the gear space to the suction side of the compressor, but hereby the ability of the compressor to suck in medium from outside will be correspondingly deteriorated.
The ability of the compressor to suck in medium from outside, however, will not be deteriorated if, according to a further development of the invention, the outlet from the gear space communicates with a working chamber in the rotor space having a pressure lying between the inlet pressure and the outlet pressure of the compressor.
According to a further development of the invention the motor rotor with the shaft and gear wheels belonging to it is journalled only in the wall between the motor chamber and the gear space.
Hereby is obtained a very simple and space- saving bearing of the motor rotor.
When the peripheral speed of the gear wheels is high it is not sufficient to have the gear wheels rotating in an oil bath - the oil will be thrown away from the gear wheels and the lubrication becomes incomplete - and, therefore, oil has to be sprayed towards the gear wheels, preferably at the tooth engagement.
Such a high peripheral speed mentioned can very well appear in a compressor according to the present invention.
Therefore, another further development of the invention is characterized by a nozzle which is directed towards the engagement between the gear wheels for lubricating this by oil.
Hereby, it is possible by the present invention to spray oil towards the engagement of the teeth without aid of a special oil pump.
An embodiment of a compressor according to the invention is disclosed in the accompanying drawings, the figure of which shows a longitudinal section of a screw compressor having two rotors, one of which via a pair of gear wheels is driven by the rotor of an electric motor.
A compressor house is indicated by 1 and in this house two cooperating, helicoidal rotors 2, 3 are arranged and journalled. The rotor 2 is by means of two shaft spindles 4, 5 journalled in radial direction by plain bearings 6, 7 and in axial direction by a rolling bearing 8. The rotor 3 is by means of two shaft spindels 9, 10 journalled in radial direction by plain bearings 11, 12 and in axial direction by a rolling bearing 13.
The compressor house 1 is by means of screws 14 built together with a motor house 15, in which an electric driving motor 16 is arranged. The motor 16 comprises a stationary part, the stator 17, and a rotating part, the rotor 18. The rotor 18 comprises a shaft 19, which is journalled in the motor house 15 in radial direction by a plain bearing 20 and in axial direction by a rolling bearing 21.
Between the compressor house 1 and the motor house 15 is formed a gear space 22 into which the shaft spindle 9 and the shaft 19 project and are drivably connected to each other by means of gear wheels 23 and 24, of which the gear wheel 23 is fastened on the shaft spindle 9 and the gear wheel 24 on the shaft 19.
The compressor rotors 2 and 3, which in a known way form a working chamber 26 between themselves and the compressor house 1, suck a medium into a working chamber through an inlet 25, which medium shall be compressed, whereafter during the rotation of the rotors 2, 3 the working chamber is closed towards the inlet 25. The volume of the working chamber is reduced thereafter, the medium being compressed, whereafter the working chamber is opened towards an outlet 27, through which the compressed medium is let out of the compressor house 1.
The outlet 27 communicates with an inlet 28 of a motor chamber 29 in the motor house 15, in which the driving motor 16 is arranged. The compressed medium streams through the motor chamber 29 and cools the driving motor 16, whereafter the compressed medium is delivered via an outlet 30 to an oil separator 31, in which oil is separated from the medium before it is delivered outwards through an outlet 32, for instance to a cooling circuit.
The rotating parts of the compressor are lubricated, cooled and tightened by oil which is supplied from the oil separator 31 with an initial pressure that is equal to the final pressure of the compressed medium.
The bearings 7 and 12 are supplied with oil from the oil separator 31 via a line 33, which oil is sucked away from the lower ends of the bearings 7, 12 through a channel 34 and from the upper ends of the bearings 7, 12 through a channel 35.
The bearings 8 and 13 are supplied with oil during the passage of the oil from the upper ends of the bearings 7, 12 to the channel 35.
The oil is sucked from the channels 34, 35 together with the medium, that leaks out from the working chambers and is taken care of by the channel 34, into a channel 36 and is sucked therefrom in by an opening 37 of a working chamber 26 having an intermediate pressure, which working chamber 26 neither communicates with the inlet 25 nor with the outlet 27.
Oil is supplied to the bearings 6 and 11 from the oil separator 31 via a line 38, which oil is sucked away from the upper ends of the bearings 6, 11 through channel 39 that communicates with the opening 37, which channel 39 also takes care of the medium leaking out from the working chambers 26 of the compressor.
From the lower ends of the bearings 6, 11 the oil is sucked down into the gear space 22, which communicates with the opening 37 via an outlet 49 and the channel 36.
Oil is supplied to the gear wheels by a nozzle 40, which communicates with the line 38 and which sprays oil on the teeth of the gear wheels 23, 24 at their tooth engagement.
Oil is supplied to the bearing 20 by a line 41 ending in two positions 42, 43 along the shaft 19, wherefrom the oil is streaming along the shaft 19 to positions 44, 45, 46 which communicate with the opening 37 via the bearing 21, which is thereby supplied with oil and the gear chamber 22. Medium leaking out from the motor chamber 29 along the shaft 19 is via the position 46 directly conducted up into the gear chamber 22 and due to this fact does not jeopardize the lubrication of the shaft 19.
The compressor rotors 2, 3 are supplied with oil for lubrication, tightening and cooling by a line 47.
The oil being supplied by the compressor can for instance be cooled by means of a cooler 48 or by spraying refrigerant into the compressor such that due to this fact the final temperature of the compressed medium and therewith the temperature of the oil obtain a suitable low value.

Claims

1. Hermatical compressor of rotational type having an electric driving motor (16) with a rotor (18), which compressor comprises a compressor housing (1) enclosing a rotor space in which a compressor rotor (3) is arranged for sucking a medium into the compressor housing through an inlet (25) in the same, compressing the medium, and delivering the compressed medium through an outlet (27) in the compressor housing to an inlet (28) in a motor housing (15), the motor housing enclosing a motor chamber (29) in which the driving motor (16) is arranged, the motor chamber (29) having an outlet (30) for the compressed medium, the compressor housing (1) and the motor housing (15) being built together into a unit, and the rotor (18) of the driving motor driving the compressor rotor (3) via engagement between a gear wheel (24) on a shaft (19) of the rotor and a gear wheel (23) on a shaft (9) of the compressor rotor, the gear wheels being arranged in a gear space (22) separated from the compressor rotor space by a wall in which the shaft (9) of the compressor rotor (3) is journalled in bearings lubricated by oil, characterized in that the gear space (22) is separated from the motor chamber (29) by a wall in which the shaft (19) of the motor rotor (18) is journalled in bearings lubricated by oil, that the gear space (22) is kept under a pressure which is lower than that in the motor chamber (29) such that oil from the adjacent bearings (6, 11) of the compressor rotor (3) and the adjacent bearings (20, 21) of the motor rotor (18) is sucked into the gear space (22) and from there is removed through an outlet (49) from the gear space, that the gear space outlet communicates with a working chamber in the rotor space having a pressure lying between the inlet pressure and the outlet pressure of the compressor, and that the lubricating oil is supplied to the bearings at a pressure substantially equal to the compressor outlet pressure.

2. Compressor according to claim 1, characterized in that the motor rotor (18) with shaft (19) and gear wheel (24) belonging to it is journalled only in the wall between the motor chamber (29) and the gear space (22).

3. Compressor according to claim 1 or 2, characterized in that a nozzle (40) is directed towards the engagement between the gear wheels (23,24) for lubricating this by means of oil.