EP4015823A1 - Rotary piston engine unit with lubricant supply device - Google Patents

Abstract

The invention relates to a rotary piston machine unit with a dry-running, two-shaft rotary piston machine and a lubricant supply device, the lubricant supply device having an electrically driven lubricant pump.

Description

technical field

The invention relates to a rotary piston machine unit with a dry-running, two-shaft rotary piston machine and a lubricant supply device.

State of the art

Rotary piston machines, in particular screw compressors and positive displacement blowers of the Roots type, but also rotary piston expansion machines, are usually primarily fitted with roller bearings up to differential pressures of around 15 bar and speeds of up to around 20,000 rpm. The high radial forces that occur as a result of the compression or expansion process are absorbed by cylindrical roller bearings, for example. In the case of twisted rotors (eg in screw compressors), a pressure gradient also develops in the axial direction, which also causes axial forces to occur in the bearings. Additional axial forces can also be caused, for example, by helical gears mounted on the rotor shafts. These highly stressed bearings must be adequately supplied with lubricating oil.

The bearings and the synchronizing wheels of such rotary piston machines are typically supplied with oil in one of three ways mentioned below.

In particular for relatively slowly rotating rotary piston machines, such as rotary piston blowers of the Roots type, splash disks or splash rings or the like are often used, which absorb oil from an oil sump and throw it off tangentially, whereby the entire oil chamber is filled with an oil-air aerosol, but also individual ones Drain drops from housing parts and indefinitely but adequately lubricate the bearings and gears. In this context, the EP 1 855 009 B1 known, which relates to a dry-running rotary piston machine with spray discs.

However, it has been shown that the quantity of oil conveyed by splash rings and splash discs decreases sharply at high engine speeds or peripheral speeds, so that when there is a high demand for lubricating oil of all things, little of it is supplied, although the power consumption of the splash discs and rings and thus the heat input into the oil continue to rise. Even at particularly low speeds, the oil flow rate is often too low. With the help of certain measures, such as the toothing of spray discs, which gives them the appearance of circular saw blades, or the additional setting of these teeth, the conveying effect can be significantly increased and still be sufficient even at high speeds, but the power consumption of such spray discs is also clear elevated.

Typically, therefore, at least at higher shaft speeds, oil pumps are used, which are often mechanically driven directly by one of the two shafts of the twin-shaft rotary engine. The size of the oil pump must be dimensioned in such a way that even at all operating points of the rotary piston machine with the lowest permissible speed sufficient oil is pumped. This often means that at higher speeds, much more oil is pumped than is required. The use of an oil pump has advantages in that larger quantities of oil can be sprayed through nozzles into the bearings or at other lubrication points. With large amounts of oil at high speeds, however, this causes large flow losses, which is why so-called overflow regulators are often used to limit the outlet pressure of the oil pump. Even if the power consumption of the pump is limited by the overflow controller, it requires an unnecessarily large amount of power at high speeds, which significantly worsens the overall efficiency of the rotary piston machine or the rotary piston machine unit.

In order to avoid the disadvantages of a mechanically driven oil pump, those that are driven by a separate electric motor, usually at a constant speed, are also used. The size of the oil pump must be dimensioned in such a way that sufficient oil is pumped at all operating points of the rotary piston machine, and is therefore based on the operating points with the highest speed. In most cases, this improves the overall efficiency of the rotary piston machine and oil pump, although it must be taken into account that the efficiency of small electric motors, such as those used to drive oil pumps separately, is significantly lower than that of larger electric motors that drive rotary piston machines together with mechanically coupled ones drive oil pumps.

subject of the invention

One aim of the invention is to provide a rotary piston machine assembly with a lubricant supply device, the lubricant supply device itself consuming as little power as possible, which on the one hand increases the overall efficiency of the rotary piston machine assembly improved and on the other hand the average lubricant temperature should be reduced. Furthermore, the operational safety should be increased and the service life of the lubricant and the bearings should be increased.

According to the invention, a rotary piston machine unit with the features according to claim 1 is provided. Preferred embodiments are set out in the dependent claims. Furthermore, the invention relates to the use of a lubricant supply device for a rotary piston machine.

A rotary piston engine unit includes, in addition to other components, such as a main drive motor or a lubricant supply device, as a mechanical unit, a rotary engine. In so-called "dry-running" rotary piston machines, the profiled areas of the rotors have no contact with one another due to the synchronization of the rotors by a synchronization gear arranged outside the pumping chamber.

The rotors of the rotary piston machine are thus arranged for non-contact running. However, the design as a dry-running rotary piston machine does not rule out the possibility of liquid media being injected, e.g. to achieve cooling during operation.

Such a rotary piston machine usually comprises two rotors which are mounted in a housing via shafts and bearing arrangements and which mesh with one another in opposite directions in order to define a pumping chamber together with the housing. One of the bearing arrangements of each shaft is designed as a fixed bearing arrangement in the axial direction. The task of the synchronizing gears is to allow the pair of rotors to rotate in opposite directions with as little play as possible but without contact. Here, the synchronous wheels transmit a significant torque.

The bearings and/or synchromesh must be supplied with lubricant. The lubricated spaces, in which the bearing arrangements and the synchronizing wheels are located, are separated from the pumping space by means of shaft seals, some of which are quite complex, so that the pumped medium does not come into contact with oil.

The rotary piston machine unit comprises a dry-running, two-shaft rotary piston machine and a lubricant supply device, the lubricant supply device comprising an electrically driven lubricant pump. The lubricant pump can be operated with a control voltage of the rotary piston machine unit, the control voltage being <50 V.

A third voltage supply level can be avoided in this way, particularly in the case of rotary piston engines with lower power, so that it is possible to use only the voltage levels that are already present in the rotary engine unit for the main drive motor and for the control voltage.

The lubricant pump is preferably an oil pump. A mineral lubricating oil or else a synthetic lubricating oil can be used as a lubricant, for example.

In particular, it is provided that the rotary piston machine assembly has a control voltage power pack, which provides an electrical supply to a control device of the rotary piston machine assembly, and in particular to the lubricant pump.

The lubricant pump of the lubricant supply device has the advantage that a continuous supply of lubricant is ensured is, the complexity of the structure of the rotary piston machine unit is not increased by the operation by means of the control voltage of the rotary piston machine.

It is preferred that the control voltage is DC. This means that the control voltage that is usual for rotary piston machine units can be used.

It is preferably provided that the electric lubricant pump driven by the control voltage is a displacement pump. With displacement pumps, the lubricant can also be pumped at higher pressures.

A preferred embodiment of a positive displacement lubricant pump is the gear pump.

According to a particularly preferred embodiment, the lubricant pump is an oscillating armature pump with an upstream pulse width modulator (PWM). An efficiency advantage can be achieved by using the oscillating armature pump, since such a lubricant pump has a lower power consumption in comparison to other pumps and to spray disks or the like.

Tests have shown that oscillating armature pumps work reliably and permanently even when using hot lubricant or oil as the medium, deliver a sufficient flow rate and consume very little power. For example, only about 50 W are required for the supply of lubricant to a rotary piston machine unit with a rated output of 55 kW.

Oscillating piston pumps are also referred to as oscillating piston pumps or solenoid pumps or oscillating piston pumps. The working principle of such pumps is based on a piston which is attracted by a magnetic field against the force of a spring and thus performs a lifting movement. To When the magnetic field is switched off, the piston is moved back in the other direction by the spring force. Oscillating armature pumps are, for example, in AT 275329B , EP 0 288 216 B1 or EP 1 818 538 B1 disclosed.

The generation of a periodically present and non-existent magnetic field is usually realized by means of a coil through which current periodically flows.

In the case of alternating current, only one diode is used for this purpose, which blocks the second half-wave in each case. With direct current (DC), an electronic circuit is required which, for example, generates square-wave pulses. Such circuits are often referred to as pulse width modulators (PWM). Nowadays, DC voltage is used almost exclusively as the control voltage in rotary piston machine aggregates.

According to a further embodiment, it is therefore provided that the lubricant pump is set up to be operated with a control voltage of <30 V (in particular DC), e.g. 24 V (in particular DC). In particular, a pulse width modulator (PWM) can receive direct current (DC) that is converted into square wave pulses.

It is preferred that the rotary engine unit has a lubricant cooler to cool the lubricant. In this case, the lubricant cooler is arranged in particular on an outlet side of the lubricant pump. This has the advantage that the lubricant, which is still heated, is pumped through the lubricant pump, thus enabling a higher volume flow.

Furthermore, it is preferred that the rotary piston machine unit has a lubricant filter with which the circulating lubricant can be cleaned. It is particularly preferred to provide the lubricant filter on an inlet side of the lubricant pump. Thus, the pump protected. In addition, the lubricant on the inlet side has a lower viscosity due to the heated condition, so that the flow of the lubricant through the lubricant filter is less affected.

The lubricant cooler and/or the lubricant filter also contribute to ensuring that the lubricant has a relatively long service life. A permanent and reliable supply of lubricant can thus be provided. The use of a lubricant cooler and/or lubricant filter is not possible when using splash disks, splash rings or the like.

The rotary piston machine unit preferably has an inlet line for conveying a lubricant from the lubricant pump to the bearings and a synchronization gear of the rotary piston machine and a return line for conveying a lubricant from the bearings and a synchronization gear of the rotary piston machine to the lubricant pump.

Furthermore, it is preferred that the rotary piston machine is a screw compressor.

The invention also relates to the use of a lubricant pump for supplying lubricant to a dry-running rotary piston machine, the lubricant pump being operated with a control voltage of the rotary piston machine, the control voltage being <50 V. In this context, it is preferred that aspects that are used for the aforementioned rotary piston machine unit or that are described in the subclaims are also used in the context of using a lubricant pump.

Brief description of the drawings

1

shows a perspective view of a rotary piston machine with a lubricant supply device as part of a rotary piston machine unit according to an embodiment of the invention.

2

Fig. 12 is a circuit diagram showing a lubricant supply device according to the embodiment of the invention.

Detailed Description of the Preferred Embodiment

A preferred embodiment of the invention is clearly described below with reference to a circuit diagram. Although the embodiment is to be understood purely as an example, individual features can also be used to specify the invention specified in the claims.

A lubricant supply device 10 according to the embodiment is integrated in a screw compressor unit 1 (as an example of a rotary engine unit). The screw compressor unit 1 comprises a screw compressor 100 (as an example of a rotary machine) and a main drive motor 101 used to drive the rotors of the screw compressor 100 . The main drive motor 101 is supplied with a three-phase operating voltage of 400 V AC. The rotors of the screw compressor 100 are arranged to run without contact and are synchronized by means of a synchromesh gear.

The bearings and the synchronization gear are supplied with lubricant, in particular lubricating oil. The lubricant supply device 10 according to the embodiment is used for this.

The lubricant supply device 10 comprises an inflow line 11, which conducts a flow of lubricant to the screw compressor 100, and a return line 12, which is connected to the screw compressor 100 on a return side. Between the return line 12 and the feed line 11, the lubricant pump 14 is arranged, which is designed according to the embodiment as an oscillating armature pump.

The lubricant pump 14 is preceded by a lubricant filter 13 which cleans the lubricant supplied from the return line 12 . Starting from the lubricant filter 13, the lubricant flows through a first connecting line 16 to the lubricant pump 14, which further conveys the lubricant. A supply line 18 is provided in the area of the first connecting line 16 in order to supply lubricant to the lubricant circuit or to remove it from the lubricant circuit.

The lubricant delivered by the lubricant pump 14 is supplied to a lubricant cooler 15 via a second connecting line 17 in order to cool the lubricant after it has left the lubricant pump 14 . An outlet of the lubricant cooler 15 communicates with the supply line 11 through which the lubricant is supplied to the screw compressor 100 . In 1 not visible but in 2 shown, the lubricant is distributed within the screw compressor on both bearing sides of the rotors.

A coupling line 19 is provided on the screw compressor 100 in order to supply the returning lubricant from a bearing side (in 1 the drive side) to another bearing side of the screw compressor 100 to lead. The other side of the bearing of the screw compressor 100 is with the Return line 12 in connection to close the lubricant circuit.

The lubricant pump 14 is operated with a control voltage for the screw compressor unit 1 of 24 V DC. To operate the lubricant pump 14, a pulse width modulator (PWM) 21 is provided for this purpose, which is preceded by a power pack 20. In industrial applications, the power pack 20 is usually supplied with an operating voltage of 400 V AC and converts the operating voltage of 400 V AC into direct voltage (typically 24 V DC).

The power pack 20 provides, among other things, an electrical supply to a control device 22 of the rotary piston engine unit 1 and in particular to the lubricant pump 14 .

The pulse width modulator 21 receives the direct current (DC) provided by the power pack 20 and converts it into square-wave pulses. A coil of the lubricant pump 14 is periodically excited by means of the pulses, the magnetic field of which acts on an oscillatingly mounted armature. The lubricant pump thus operates at the frequency of the voltage supplied by the pulse width modulator 21 .

Claims (15)

Rotary piston machine unit (1) with a dry-running, two-shaft rotary piston machine (100) and a lubricant supply device (10), the lubricant supply device (10) comprising an electrically driven lubricant pump (14), characterized in that the lubricant pump (14) is connected to a control voltage of the rotary piston machine unit ( 1) can be operated with the control voltage being < 50 V. Rotary piston engine unit (1) according to Claim 1, characterized in that the control voltage is direct voltage. Rotary piston engine unit (1) according to Claim 1 or 2, characterized in that the lubricant pump (14) is a displacement pump. Rotary piston engine unit (1) according to any one of the preceding claims, characterized in that the lubricant pump (14) is an oscillating armature pump. Rotary piston engine unit (1) according to Claim 4, characterized in that the lubricant pump (14) is an oscillating armature pump with an upstream pulse width modulator (21). Rotary piston engine unit (1) according to one of Claims 1-3, characterized in that the lubricant pump (14) is a gear pump. Rotary piston engine unit (1) according to any one of the preceding claims, characterized in that the rotary engine unit (1) is designed for a connected load of ≦110 kW, preferably ≦60 kW. Rotary piston engine unit (1) according to one of the preceding claims, characterized in that the control voltage is <30 V. Rotary piston engine unit (1) according to one of the preceding claims, further comprising a lubricant cooler (15) which is arranged in particular on an outlet side of the lubricant pump (14). Rotary piston engine unit (1) according to one of the preceding claims, further comprising a lubricant filter (13) which is arranged in particular on an inlet side of the lubricant pump (14). Rotary piston machine unit (1) according to one of the preceding claims, comprising an inlet line (11) for conveying a lubricant from the lubricant pump (14) to a bearing and/or a synchronization gear of the rotary piston machine (100) and a return line (12) for conveying a lubricant from a bearing and/or a synchronization gear of the rotary piston machine (100) to the lubricant pump (14). Rotary piston machine unit (1) according to one of the preceding claims, wherein the rotary piston machine (100) is a twin-shaft screw compressor. Use of a lubricant pump (14) for supplying lubricant to a dry-running rotary piston machine (100), the lubricant pump (14) being connected to a control voltage of Rotary piston engine unit (1) is operated, the control voltage being <50 V, preferably <30 V. Use according to claim 13, wherein the lubricant pump (14) is operated with direct current. Use according to one of claims 13-14, wherein the lubricant pump (14) is an oscillating armature pump, preferably an oscillating armature pump with an upstream pulse width modulator (21).

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