EP0000131B1 - Process and apparatus for the lubrication of compressors - Google Patents

Description

The present invention relates to a method of lubricating compressors, in particular of the helical type.

It also relates to a device for implementing said method.

• En premier lieu, une fonction dé ftuide caloporteur pour éliminer les calories résultant de la compression du fluide, l'air par exemple.
• En deuxième lieu, une fonction d'étanchéité et cela en constituant des joints visqueux au niveau des diverses lignes de fuite et de jeux internes.
• En troisième lieu, la fonction de lubrification proprement dite des divers organes tels que roulements, paliers, trains d'engrenage, joints d'étanchéité frottants et autres.

We know that in compressors, the oil conveyed in the lubrication circuits assumes several main functions:

• Firstly, a heat transfer fluid function to eliminate the calories resulting from the compression of the fluid, air for example.
• Secondly, a sealing function by constituting viscous seals at the level of the various lines of flight and internal clearances.
• Thirdly, the actual lubrication function of the various organs such as bearings, bearings, gear trains, friction seals and others.

As regards in particular the function of heat transfer fluid, it is easily understood that the quantity of oil necessary for this purpose is a function of the quantity of calories to be removed, since the temperature of the mixture of air and oil discharged from the compressor must be within a well-defined temperature range, in order to avoid water condensation in the oil tank on the one hand, and auto-ignition of the air-oil mixture on the other.

So in idling mode the amount of calories to be evacuated is less than in laden mode and the oil requirements are reduced.

We know how to overcome this problem by providing two separate lubrication circuits for the two regimes (see for example French patents 1,429,488 and 1,574,479). However, this leads to complex and expensive devices, which comprise for the secondary circuit an auxiliary tank, at least one oil circulation pump, valves and throttles for regulating the oil flow, etc.

The object of the invention is to simplify the auxiliary circuit and, therefore, to make it less expensive and more reliable.

The subject of the invention is therefore a method of lubricating a compressor with a fluid of the type comprising a compression chamber in which at least two rotors are driven in rotation by at least one gear and each rotate on two end bearings , said bearings and gear being housed in flanges acting as scrolls, namely a suction flange and a delivery flange, said gear being linked to a driving shaft, the sealing of said shaft being ensured, suction side, by a seal with friction grain, characterized in that, under operating conditions under load, said compression chamber, said bearings, said gear, as well as said friction grain seal are supplied with oil from a separating tank and under high pressure and substantially equal to that prevailing in said separator tank, while under idling conditions said compression chamber and said bearings housed in said delivery flange ent are supplied with oil from said separator tank but under low pressure, the bearings, said gear, as well as said friction grain seal housed in said suction flange being independently supplied with oil coming directly from the exhaust or discharge of the compressor and at a pressure slightly higher than atmospheric pressure.

The invention also relates to a device for implementing the method according to claim 1, characterized in that it comprises two circuits, a main circuit and a secondary circuit, said main circuit comprising a pipe having its source in said separator tank of oil and subdivided into three branches, a first branch supplying said compression chamber, a second branch supplying said bearings, said gear and said friction grain seal housed in said suction flange via a valve, and a third branch supplying said bearings housed in said delivery flange, said secondary circuit comprising a pipe originating directly from the compressor exhaust, leading to a valve, then subdivided into two branches, a first branch supplying the bearings and the gear housed in said suction flange, by means of a valve, e t a second bypass supplying the rubbing grain seal.

• La figure 1 représente un compresseur lubrifié selon l'art antérieur.
• La figure 2 représente à titre purement illustratif mais nullement limitatif un compresseur lubrifié selon l'invention.

The drawbacks of the prior art and the advantages of the present invention will be better illustrated by the description which follows, description given with reference to the appended drawings in which:

• Figure 1 shows a lubricated compressor according to the prior art.
• Figure 2 shows purely by way of illustration but in no way limiting a lubricated compressor according to the invention.

The compressor lubricated in the known manner and represented in FIG. 1 therefore comprises a compression block 1 in which two helical rotors rotate, a male rotor 2 and a female rotor 3, the male rotor 2 being driven by means of a motor 4 and by means of a gear 5 cooperating with a universal joint 6, housings such as 7 ensuring sealing

Atmospheric air enters the block 1 via a filter 8 and after compression escapes through a line 9. This line 9 opens into an oil separator tank 10 above, of course, the oil level 11. Compressed air is therefore evacuated to the place of use via the pipe 12 according to the arrows, after having abandoned the oil particles entrained at the level of a filter 13.

• . En régime de marche à pleine charge, l'huile comprimée par l'air débouchant de la canalisation 9 emprunte la canalisation 14 puis est refroidie dans un refroidisseur 15 et cela par cheminement dans un serpentin 16 refroidi par un ventilateur à air 17 entraîné par le moteur 4. L'huile ainsi refroidie emprunte alors la canalisation 18 pour déboucher dans le bloc de compression 1 où elle s'échauffe par suite de la compression de l'air qui la refoule ensuite dans la canalisation 9 et ainsi de suite.
• En régime de marche à vide on conçoit aisément que les besoins en huile sont réduits. En effet, si la quantité d'huile nécessaire aux fonctions d'étanchéité et de lubrification des organes est pratiquement indépendante du régime de marche, par contre la quantité d'huile nécessaire pour la fonction caloporteur peut être réduite en régime de marche à vide.

Lubrication is ensured as follows:

• . In operating mode at full load, the oil compressed by the air emerging from the line 9 borrows the line 14 then is cooled in a cooler 15 and this by routing in a coil 16 cooled by an air fan 17 driven by the engine 4. The oil thus cooled then borrows the line 18 to open into the compression block 1 where it heats up as a result of the compression of the air which then discharges it into the line 9 and so on.
• Under no-load conditions it is easy to see that the oil requirements are reduced. In fact, if the quantity of oil necessary for the sealing and lubrication functions of the members is practically independent of the running speed, on the other hand the quantity of oil required for the heat transfer function can be reduced in idling operating conditions.

For this purpose, the suction 8 is therefore partially obstructed in order to reduce the pressure in the separator tank 10 and consequently the compression power.

However, the subjection resulting from the need to obtain sufficient oil circulation in order to ensure the sealing and lubrication functions limits such a reduction in pressure, so that in idle mode the compressor still consumes 35 to 40% of its power under load, approximately.

The Applicant has therefore sought to remedy such a drawback and to significantly reduce the power consumed when idling, and this by implementing a simple, inexpensive and reliable additional lubrication circuit.

We will therefore describe, with reference to FIG. 2, such a lubrication process, as well as the implementation device, applied to an air compressor, and this is purely illustrative but in no way limiting.

The compressor shown in FIG. 2 comprises a casing 20 or compression block inside which two rotors move in rotation, a male rotor 21 and a female rotor 22 of helical type. These rotors rotate on ball or roller bearings, namely bearings 23 and 24 for the male rotor 21 and bearings 25 and 26 for the female rotor 22. Such bearings are housed in flanges 27 and 28, the flange 27 acting as a suction scroll, while the flange 28 assumes the role of discharge or exhaust scroll.

The male rotor 21 has a shaft end (not shown) on which a multiplier gear train 29 is keyed linked to a driving shaft 30 journalled on bearings 31 and 32, the seal being ensured by means of a seal grain rubbing 33.

Having thus described a compressor, known per se, we will now highlight the invention, the advantages of which will emerge from the present description.

• En premier lieu, le bloc de compression 20 et cela par un débit d'huile variable en fonction de la puissance de compression (fonction caloporteur) mais minimal en vue d'assurer l'étanchéité.
• En deuxième lieu, les paliers et roulements 23,24,25,26,31 et 32.
• En troisième lieu, le train d'engrenage multiplicateur 29.

It is therefore seen with reference to FIG. 2 that the members which must be lubricated at all times are the following:

• First, the compression block 20 and this by a variable oil flow depending on the compression power (coolant function) but minimal in order to ensure sealing.
• Second, the bearings and bearings 23,24,25,26,31 and 32.
• Third, the multiplier gear train 29.

Finally, the rubbing grain seal 33.

The oil flow required for these latter members must of course be substantially constant.

In view of the above considerations, and in accordance with the invention, two lubrication circuits are used, a main circuit and a secondary or additional circuit.

• Une première dérivation 40a alimentant le bloc de compression 20.
• Une deuxième dérivation 40b alimentant les roulements et paliers 23, 25, 31 le train d'engrenage 29 et le joint frottant 33 par l'intermédiaire de conduits tels que 41.

The main circuit comprises a pipe 40 originating from the separating tank, not shown, but similar to that referenced 10 in FIG. 1. This pipe 40 is subdivided at point A into 3 branches or branches:

• A first branch 40a supplying the compression block 20.
• A second bypass 40b supplying the bearings and bearings 23, 25, 31 the gear train 29 and the friction seal 33 via conduits such as 41.

• Une troisième dérivation 40c alimentant les paliers 24 et 26 par l'intermédiaire d'un conduit 42.

This bypass 40b can be opened or closed by a valve V2.

• A third branch 40c supplying the bearings 24 and 26 via a conduit 42.

• Une première dérivation 43a alimentant les roulements et paliers 23, 25, 31, le train d'engrenage 29 par l'intermédiare des conduits 41, cette canalisation étant ouverte ou fermée par une vanne V3.
• Une deuxième dérivation 43b alimentant le joint frottant 33 ainsi que le roulement 32.

The secondary circuit comprises a pipe 43 taking its source from the discharge scroll at B or the compressor exhaust. This pipe 43 leads to a valve V1 controlled by the oil pressure existing at point C. From the valve V1, said pipe 43 is subdivided into two branches or branches:

• A first bypass 43a supplying the bearings and bearings 23, 25, 31, the gear train 29 via the conduits 41, this pipe being opened or closed by a valve V3.
• A second branch 43b supplying the friction seal 33 as well as the bearing 32.

• Lorsque la compresseur fonctionne en régime de charge, la pression dans la réservoir séparateur où prend sa source la canalisation 40 est élevée, soit 7 à 10 bars selon le débit. Au point A ainsi qu'au point B la pression est également élevée, tout au plus inférieure de 200 gr/cm² à celle régnant dans ledit réservoir séparateur. Il en résulte que l'huile emprunte les derivations 40a, 40b et 40c et alimente la chambre de compression 20 ainsi que les divers roulements paliers, train d'engrenage et joint frottant précédemment décrits, selon un débit élevé, tant du côté aspiration que du côté refoulement.

The device according to the invention operates as follows:

• When the compressor is operating in load mode, the pressure in the separating tank where the line 40 originates is high, ie 7 to 10 bars depending on the flow rate. At point A as well as at point B the pressure is also high, at most 200 gr / cm ² lower than that prevailing in said tank separator. As a result, the oil borrows the branches 40a, 40b and 40c and feeds the compression chamber 20 as well as the various bearing bearings, gear train and friction seal described above, at a high flow rate, both on the suction side and on the discharge side.

Of course, the pressure drops in said branches are predetermined so that the oil flow is sufficient.

When the compressor is running empty, the pressure in the separator tank is relatively low and at point B it is about 20gr / cm ² higher than atmospheric pressure. It is also weak at point C. Consequently the valve V1 opens and the oil conveyed by the pressure prevailing at point B, opens the valve V3 and lubricates the various organs on the suction side by means of branches 43a and 43b.

At the same time, the valve V2 is closed, but the oil still feeds the compression chamber 20 as well as the various organs on the discharge side by the branches 40a and 40c according to, of course, a low flow rate which is nevertheless sufficient. It will be noted that the secondary lubrication circuit has a high conductance, taking into account the relatively low pressure prevailing at point B.

When the compressor resumes its load regime again, the valves V1 and V3 close, the valve V2 opens and so on.

It can therefore be seen that such lubrication according to the invention makes it possible, when idling, to supply the organs situated on the suction side with oil at a low pressure, however sufficient, which results in a significant saving in the power of compression.

Such an advantage is of course impossible to obtain with conventional lubrication systems which work in idle mode at discharge pressures of 3 to 4 bars, which reduces consumption by only 35 to 40% compared to that in charge. On the contrary, according to the invention, the discharge pressure is, thanks to the secondary circuit, reduced to a value slightly higher than atmospheric pressure, hence a significant reduction in compression power and consumption which is no longer only 12 to 15% of the power under load.

In other words, compared to conventional machines the no-load power is divided by a coefficient at least equal to 2.5.

Of course, the invention is in no way limited to the embodiment which has just been described, but on the contrary it covers all the variants within the reach of those skilled in the art.

Claims (4)

1. A method of lubricating a fluid compressor of the type comprising a compression chamber (20), in which at least two rotors (21, 22) are driven by at least one gear train (29) and rotate each on two end bearings (23, 24, 25, 26), said bearings and gear train being housed in volute casings (27, 28), that is a suction casing (27) and an exhaust casing (28), said gear train (29) being coupled to a drive shaft (30), gas-tightness of the shaft being obtained on the suction side of a friction seal (33), characterized by the fact that, when operating under load, said compression chamber (20), said end bearings (23, 24, 25, 26), said gear train (29) and said friction seal (33) are supplied with oil from an oil separation tank (10) under a high pressure, which is substantially equal to the pressure in said tank, whereas when operating under no load conditions, said compression chamber (20), the end bearings (24, 26) in the exhaust casing (28) are supplied with oil from said oil separation tank (10) under a low pressure, the end bearings (23, 25), said gear train (29) and said friction seal (33) in said suction casing (27) being independently supplied with oil directly from the exhaust side of the compressor and under a pressure which is slightly higher than atmosphere pressure.

2. A device for the realization of the method according to claim 1, characterized by the fact that it comprises two circuits, a main circuit and a secondary circuit, said main circuit comprising a pipe (40) originating from said oil separation tank (10) and being subdivided into three branches, a first branch (40a) for feeding said compression chamber (20), a second branch (40b) for feeding by means of a valve (V2) said bearings (23, 25), said gear train (29) and said friction seal (33) housed in said suction casing (27), and a third branch (40c) for feeding said L ₃arings (24, 26) housed in said exhaust casing (28), said secondary circuit comprising a pipe (43) originating directly from the discharge end of the compressor, passing a valve (V1), then being subdivided into two branches, the first branch (43a) for feeding the bearings (23, 25) and the gear train (29) housed in said suction casing (27), by means of a valve (V3), and a second branch (43b) for feeding particularly the friction seal.

3. A device according to claim 2, characterized by the fact that said valves (V1, V2, V3) are oil pressure commanded valves dependent upon the operational mode of the compressor, so that when the compressor operates under load, the valve (V2) of the second branch (40b) of the main circuit is open, whereas the valve (V1) of the pipe (43) of the secondary circuit is closed, and that when the compressor operates under no load, the valve (V2) of the second branch (40b) of the main circuit is closed, whereas the valves (V1, V3) of the pipe (43) and of the first branch (43a) of the secondary circuit are open.

4. A device according to one of the claims 2 and 3, characterized by the fact that said secondary circuit presents a high conductance.

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