EP0030619B1 - Rotor compressor, especially screw rotor compressor, with lubricant supply to and drainage thereof from the bearings - Google Patents

Description

The invention relates to a rotary compressor, in particular a screw rotor compressor, in which each end of the shaft of the or each rotor is mounted in the housing by means of a radial sliding bearing and is surrounded by a shaft seal between the latter and the working space of the compressor, and a lubricating oil circuit is provided for bearing lubrication, with a lubricating oil container from which from which the lubricating oil is fed to the bearings via an oil pump and lines and into which the lubricating oil that flows from each bearing into a storage space on the side of the bearing facing away from the working space flows back via oil return channels.

A compressor of this type is known from DE-OS 2 441 520, in which the annular drainage space is part of an elaborate sealing arrangement of great length, which has the purpose of sucking unfiltered outside air into the working space of the compressor and the leakage of lubricant. and to avoid coolant from the compressor working space along the shaft. For this purpose, the sealing arrangement has, in addition to the drainage space, further annular spaces, one of which is acted upon as a barrier pressure space by a compressed gas source, in particular by the compressor outlet. The annular drainage space opens up to the outside, and this means that the quantities of gas entering the drainage space from the barrier pressure space are lost. This means that such a sealing arrangement can only be used if the compressor compresses air or a compressed air source is available, because corresponding losses of another gas compressed by the compressor, e.g. B. a refrigerant would not be portable. But even when compressing air, the losses via the barrier pressure chamber must be as low as possible so as not to impair the efficiency of the compressor too much. The seal arrangement must therefore meet high tightness requirements. This means a large overall length of the sealing arrangement, particularly at higher working pressures of the compressor. Seals with a large overall length mean larger bearing distances, which can result in impermissibly high deflections and bending stresses in the rotor even at relatively low loads.

There is a particular problem with compressors that compress refrigerants. On the one hand, the refrigerant must remain in the closed process cycle under all circumstances and must not escape in small quantities. On the other hand, the refrigerant dissolves in the lubricating oil at higher pressure and impermissibly reduces its lubricating ability. In the magazine Betriebsstechnik, 1969, Issue 12, p.303, Figure 3, shaft seals for a screw compressor are shown, with which any contact between the compressed gas and the lubricating oil circuit is to be prevented. This objective results in seals of undesirably large axial length, since several sealing points in the form of carbon rings or the like, which seal as well as possible, must be arranged one behind the other. In the left embodiment in Figure 3, three annular chambers are provided to collect any leakage gas, of which the first or inner chamber is connected to the suction side of another compressor process, while the middle chamber is connected to an ejector and the outer chamber is free of the atmosphere. All leakage gas is thus lost from the circuit containing the screw compressor and either loads another compressor circuit or the propellant gas with which the ejector is operated, or the atmosphere. This solution is completely unsuitable for compressing refrigerants. In the right embodiment of Figure 3, the inner and middle chamber are closed and the outer chamber is connected to the suction line of the first compressor stage. All leakage gas therefore remains in the compressor circuit and is not lost. However, in order to prevent any contact between the leakage gas and the lubricating oil circuit, a length-increasing seal with sealing oil supply is arranged between the outer chamber and the bearing. Part of the sealing oil gets into the outer chamber, is drawn off together with the leak gas and must be separated from the leak gas by a cyclone separator. If a refrigerant is compressed, parts of it will dissolve in the sealing oil so that it is lost for reuse.

The invention has for its object to provide a rotary compressor of the type mentioned, in particular for refrigerant compression, in which a very simple, cheap and space-saving seal arrangement between the work space and the bearing can be used and still both a leakage gas loss and an impairment of the lubricating oil circuit by under Pressure dissolving gas is avoided.

This is achieved according to the invention in a compressor of the type mentioned above in that a pressure compensation connection is provided between the lubricating oil circuit and the suction side of the compressor, through which the entire lubricating oil circuit on the suction side of the oil pump is essentially under the suction pressure of the compressor, and that between the The shaft seal and the bearing are arranged in a drainage space surrounding the shaft in a ring shape to collect lubricating oil escaping from the bearing on this side and any leakage gas that passes through the shaft seal, which is connected to the associated storage space via a drainage channel and thereby also under the suction pressure of the compressor stands.

This has the advantage that the Drainage spaces prevent both the passage of leakage gas to the bearing and the passage of bearing lubricant into the working space of the compressor, but on the other hand the lubricant and gas leaks into the drainage space are unproblematic because these gas and liquid quantities are returned to the compressor or the lubricant circuit to be led back. It can therefore be tolerated relatively large leaks of compressed gas and possibly also injected coolant and lubricant from the work space into the annular drainage space, and it follows that only a relatively very simple, short and cheap seal between the work space and the drainage space essentially only needs to exert throttling action, must be arranged.

In contrast to the prior art, the contact between leakage gas and the lubricants in the circuit is therefore consciously accepted in the drainage rooms. However, since these drainage spaces, also on the pressure side of the compressor, are under the compressor suction pressure, there is no fear of the refrigerant dissolving in the lubricant even when compressing refrigerants, since this only occurs at higher pressures. According to the invention, however, the entire lubricant circuit is completely separated from the compressed gas stream, and the leakage gas only comes into contact with the lubricant under low pressure. The small proportions of leakage gas that dissolve in the lubricant at this low pressure have the opportunity in the lubricating oil tank to escape again.

A second circuit for a coolant and sealant can be provided, which is fed to the working space of the compressor and is separated from the compressed gas stream by a separator connected to the pressure side of the compressor. A connecting line with a valve can be provided between the separator and the separating container of the lubricant circuit, which valve can be controlled by a level switch on the separating container.

• Fig. 1 zeigt einen Längsschnitt durch einen Schraubenverdichter sowie das Fließschema des zugehörigen Ölkreislaufs gemäß einer Ausführungsform der Erfindung.
• Fig. 2 zeigt in ähnlicher Darstellung wie Fig. 1 eine zweite Ausführungsform mit vereinfachtem Ölkreislauf.

Embodiments of the invention are explained in more detail with reference to the drawings.

• Fig. 1 shows a longitudinal section through a screw compressor and the flow diagram of the associated oil circuit according to an embodiment of the invention.
• Fig. 2 shows in a similar representation as Fig. 1, a second embodiment with a simplified oil circuit.

According to FIG. 1, the compressor has a housing 10, in the working space 12 of which two rotors 14 are mounted next to one another, which engage in one another with helically arranged ribs and grooves. Only one of these rotors 14 is visible in the drawing. The shaft 16 of the rotor is supported at both ends by means of radial sliding bearings 18 and also at the end on the pressure side by means of an axial roller bearing 20. The shaft of one rotor, the main rotor, is driven by a drive (not shown), and the main rotor drives the secondary rotor by direct meshing engagement or also by means of a synchronous gear (not shown). The gas to be compressed, in particular a refrigerant such as difluoromonochloromethane, which in this case is under the evaporator pressure, is sucked in via the suction line 22 and the suction nozzle 24, compressed in the working chamber 12 by the rotors 14 and via the pressure nozzle 26 and the pressure line 28 as The separator and storage container serving pressure container 30 is supplied, from where it passes through the separating filter 32 and the pipeline 34 to the consumer and, in the case of refrigerants, to the condenser.

In the lower part of the pressure vessel 30 there is oil or another liquid suitable as a coolant, sealant and lubricant, which is supplied to the working space 12 by means of the line 36 via a cooler 38, a throttle element 40 and the housing bore 42 in order to close the rotors cool, seal against each other and against the housing and lubricate on their meshing flanks. This oil is discharged together with the compressed gas stream via the pressure port 26 and the pressure line 28 and separated from the gas stream in the container 30 and returned to the sump 44.

To lubricate the bearings 18, oil is removed from a closed reservoir 46 via a pump 48 and a cooler 50 and fed to the lubricant bores of the bearings 18 via the line 52 and the housing channels 54. From these lubricant holes, the oil enters the bearing gap in both axial directions. A portion of the oil passes directly from the bearing gap into the oil collecting spaces 56, 58, which are connected to one another by a longitudinal channel 60 in the housing 10. The portion of the oil which occurs in the direction of the working space passes from the respective bearing 18 into an annular oil collecting groove 62 which is arranged as a drainage space between each bearing 18 and a sealing element 64 and is connected to the associated oil collecting space 56 and 58 by a channel 66 in each case is. The oil collecting space 56 is connected to the reservoir 46 via an outlet channel 68. The gas space of the reservoir 46 is also connected to the suction line 22 via a compensating line 70. As a result, the reservoir 46, the spaces 56, 58 and the oil collecting grooves 62 are under the low suction pressure of the compressor. The oil collecting groove 62, which is under low pressure and is arranged between each bearing 18 and the working space 12, effectively leaks oil from the bearing 18 to the working space 12 or vice versa, leaks gas from the working space 12 to the bearing 18 largely prevented. The additional sealing elements 64 are therefore not particularly demanding, it can be simple and very short elements such. B. act short labyrinths or swim rings. These can also be supplied with oil and lubricant pressure through appropriate housing bores, as shown for the pressure-side sealing element.

Since the reservoir 46 is under the low suction pressure of the compressor, the oil therein can only contain relatively small amounts of a soluble gas, e.g. B. refrigerant, dissolved. During e.g. B. in the reservoir pressure container 30 under the high compensation pressure of the compressor of z. B. 20 bar and a temperature of z. B. 70 ° C up to 30% refrigerant can be solved, the corresponding proportion in the reservoir 46 at a pressure of z. B. 5 bar and a temperature of 70 ° C significantly less than 5%, which practically does not affect the viscosity of the oil.

Since oil leaks from the lubricant circuit into the coolant and sealant circuit and vice versa can occur in the described compressor via the bearings and the working space of the compressor, the oil quantity in the reservoir 46 is automatically kept constant. A level switch 74 with lower and upper limit contact controls on the one hand a solenoid valve 76, which connects the line 36 to the reservoir 46, and also a solenoid valve 78, which connects the line 52 to the suction line 22 of the compressor. As soon as the oil level in the container 46 has dropped too much, i. H. If too much oil has come from the low-pressure to the high-pressure circuit, the solenoid valve 76 is opened and oil can get into the container 46 from the pressure container 30. If the oil level in the container 46 rises excessively, the valve 78 opens and excess oil from the container 46 enters the suction line and from there with the gas through the compressor into the reservoir pressure container 30.

2 shows a simplified embodiment for those applications in which there is no risk of the viscosity of the oil being reduced by dissolved gas because of low working pressures or with gases which are not soluble in oil. In this case, the same compressor design as in Fig. 1 can be used without structural changes. The reservoir 46 of FIG. 1 and the associated lines u. The like. Is omitted and the outlet opening 68 of the oil collecting space 56, which is no longer required, is closed with a stopper 80. Instead, one of two bores 82, 84 is optionally opened, which connect the longitudinal channel 60 to the intake port 24 or the working chamber 12 of the compressor and of which the other bore or, when used according to FIG. 1, both bores with suitable ones Stopper 86 are closed. All of the lubricating oil from the bearings 18 now passes through the respectively opened bore 82 or 84 into the compression space, from where it reaches the supply pressure container 30 with the compressed gas via the pressure line 28 and is separated off. From its oil sump 44, the oil is then passed as a lubricant via lines 90, 92 to bearings 18 and further via line 94 into the working space of the compressor for lubricating and cooling the rotor flanks. A significant advantage in this embodiment, which is also brought about by the oil collecting grooves or drainage spaces 62, is that a separate oil pump for the supply of lubricant is not required. Since it is ensured that the spaces 62, 56, 58 adjacent to the bearings 18 are always under the pressure of the suction side of the compressor, the resulting differential pressure between the pressure container 30 and the lubrication or injection points on the compressor is sufficient to the compressor to supply with oil without fear of gas breakthrough to the bearings due to the relatively low lubricant pressure in the bearing.

Claims (4)

1. A rotary compressor, in particular a screw compressor, wherein each end of the shaft (16) of the or each rotor (14) is mounted in the housing (10) by means of a radial plane bearing (18) and between the latter and the working chamber (12) of the compressor each end of the shaft is surrounded by a shaft seal (64) and for bearing lubrication a lubricating-oil circuit is provided, having a lubricating-oil reservoir (46) from which the lubricating oil is fed to the bearings (18) via an oil pump (48) and pipes (52) and into which the lubricating oil that drains from each bearing into a storage space (56, 58) on the side of the bearing remote from the working chamber (12) flows back via oil return passages (60, 68), characterised in that between the lubricating-oil circuit (46, 52, 56, 58, 60, 68) and the intake side of the compressor there is provided a presure-balancing connection (70), as a result of which the entire lubricating-oil circuit on the inlet side of the oil pump (48) is substantially under the intake pressure of the compressor, and in that between each shaft seal (64) and bearing (18) there is disposed a drainage space (62) annularly surrounding the shaft and serving to collect lubricating oil escaping from the bearing (18) at that end as well as any gas which may have leaked through the shaft seal (64), which drainage space is connected via a drainage duct (66) with the associated storage space (56, 58) and thereby is likewise under the intake pressure of the compressor.

2. A compressor according to Claim 1, characterised in that the pressure-balancing connection from each drainage space (62) extends via the drainage duct (66), the associated storage space (56, 58), the lubricating-oil return passage (60) and also the closed gas chamber of the lubricating-oil reservoir (46) which is connected via a balancing duct (70) with the intake duct (22) of the compressor.

3. A compressor according to Claim 1 or 2, characterised in that, for optional return of oil and any gas which may have leaked, either into the gas chamber of the lubricating-oil reservoir (46) or, by-passing the lubricating-oil reservoir, directly into the intake connection (24) or the working chamber (12) of the compressor, selectively closable openings (68, 82, 84) are provided between, on the one hand, the lubricating-oil return passage (60) or a respective storage space (56) and, on the other hand, the lubricating-oil reservoir (46), or the intake connection (24) or the working chamber (12) of the compressor.

4. A compressor according to one of Claims 1 to 3, with a further oil circuit for feeding coolant and sealing agent into the working chamber of the compressor, which further circuit has a separating vessel (30) connected to the compressor outlet (28) for lubricant entrained by the gas flow and an oil pipe (36, 42) leading from the separating vessel (30) into the working chamber (12) of the compressor, characterised in that the separating vessel (30) is connected with the lubricating-oil reservoir (46) via a connecting pipe (36) with a valve (76) which is controllable by means of a level switch (74) in the lubricating-oil reservoir (46).

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