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EP-4739916-A1 - OIL CIRCUIT FOR SUPPLYING A COMPRESSOR COMPRESSING IN AN OIL-FREE MANNER, AND METHOD FOR CONTROLLING AN OIL PARAMETER FOR THE OIL SUPPLY OF A COMPRESSOR OF THIS TYPE

EP4739916A1EP 4739916 A1EP4739916 A1EP 4739916A1EP-4739916-A1

Abstract

The invention relates to an oil circuit (200) for supplying an oil-free compressor (100), to a compressor (100) of this type, and to a method for controlling an oil parameter for the oil supply of an oil-free compressor (100). The oil supply is used to lubricate and cool at least one bearing (55a, 55b), a drive and/or a gearing of the compressor (100). The oil circuit (200) comprises: an oil reservoir (1); an oil pump (3) for pumping oil from the oil reservoir (1) to the compressor (100) through an oil supply line (4, 4a, 4b, 4c) which connects an oil pump outlet (42) to at least one oil inlet (19, 19a, 19b) of the compressor (100); an oil cooler (6) which is located downstream of the oil pump (3) in a section of the oil supply line (4, 4a, 4b, 4c); an oil recirculation line (14, 14a, 14b) which branches off from the oil supply line (4a) downstream of the oil pump (3) and upstream of the oil cooler (6) and leads to the oil reservoir (1); and a valve (20), preferably an overflow valve, for controlling an oil flow in the oil circulation line (14, 14a, 14b).

Inventors

  • SIMROSS, DIRK
  • SCHMIDT, STEPHAN
  • Rosenkranz, Benjamin

Assignees

  • Kaeser Kompressoren SE

Dates

Publication Date
20260513
Application Date
20240625

Claims (15)

  1. 1. Oil circuit (200) for supplying an oil-free compressor (100), in particular at least one bearing (55a, 55b), a drive and/or a gear of the compressor (100), with oil, wherein the oil circuit (200) comprises: - an oil reservoir (1); - an oil pump (3) for conveying oil from the oil reservoir (1) to the compressor (100), in particular to the at least one bearing (55a, 55b), a drive and/or a gear of the compressor (100), through an oil supply line (4, 4a, 4b, 4c) which connects an oil pump outlet (42) to at least one oil inlet (19, 19a, 19b) of the compressor (100); - an oil cooler (6) arranged downstream of the oil pump (3) in a section of the oil supply line (4, 4a, 4b, 4c); - an oil recirculation line (14, 14a, 14b) which branches off from the oil supply line (4a) downstream of the oil pump (3) and upstream of the oil cooler (6) and leads to the oil reservoir (1); - a valve (20), preferably an overflow valve, for regulating an oil flow in the oil recirculation line (14, 14a, 14b).
  2. 2. Oil circuit (200) according to claim 1, wherein the oil circuit (200) comprises an oil filter (7) which is arranged in a section of the oil supply line (4, 4a, 4b, 4c) upstream, preferably immediately upstream, of the oil inlet (19, 19a, 19b) of the compressor (100) and preferably downstream of the oil cooler (6), wherein the oil circuit (200) preferably comprises a bypass line (15) bypassing the oil filter (7) with a differential pressure limiting valve (43).
  3. 3. Oil circuit (200) according to claim 1 or 2, wherein for regulating an oil flow in the oil recirculation line (14, 14a, 14b) at least one oil parameter (P2, TI, T2, VI), in particular an oil pressure (P2), an oil temperature (TI, T2) and/or an oil flow (VI), of the oil in the oil supply line (4c) downstream of the oil filter (7) and/or in the oil supply line (4b) downstream of the oil cooler (6) can be tapped, wherein preferably an oil injection pressure at the oil inlet (19, 19a, 19b) of the compressor (100) and/or an oil injection flow downstream of the branch point (9) can be tapped.
  4. 4. Oil circuit (200) according to one of the preceding claims, wherein the valve (20), preferably overflow valve, is designed to regulate the oil flow in the oil recirculation line (14, 14a, 14b) based on an oil pressure (P2) tapped as a control pressure in the oil supply line (4, 4a, 4b, 4c), preferably downstream of the oil filter (7) and/or downstream of the oil cooler (6), preferably in such a way that the tapped oil pressure (P2) adjusts to a preferably variably adjustable, predetermined target oil pressure (P2 So n), wherein in particular a control connection (30) of the valve (20) is connected to the oil supply line (4, 4a, 4b, 4c) via a hydraulic control line (11) downstream of the oil filter (7) and/or downstream of the oil cooler (6).
  5. 5. Oil circuit (200) according to one of the preceding claims, in particular according to claim 4, wherein the valve (20) is designed to variably specify the desired oil pressure (P2soii) by adjusting a spring preload of a spring element (22) of the valve (20), wherein preferably a closure body (27) for a flow opening (31) of the valve (20) is subjected to the adjusted spring preload.
  6. 6. Oil circuit (200) according to one of the preceding claims, in particular according to one of claims 4 or 5, wherein the control line (11) is connected to a damping chamber of the valve (20) and/or the control line (11), preferably upstream of the control connection (30), has a throttle section (12), wherein the damping chamber and/or the throttle section (12) are in particular for Damping a movement of a closure body (27) of the valve (20).
  7. 7. Oil circuit (200) according to one of the preceding claims, in particular according to one of claims 4 to 6, wherein the valve (20), preferably overflow valve, has a closure body (27) for changing at least one flow opening (29) of the valve (20), wherein the closure body (27) is displaceably guided in a valve housing (21), preferably in a valve insert (28), such that the closure body (27) is subjected to a closing force by a spring element (22), with a preferably adjustable spring preload, wherein a control pressure applied to a control connection (30) of the valve (20) exerts an opening force on the closure body (27) that counteracts the closing force.
  8. 8. Oil circuit (200) according to one of the preceding claims, in particular according to one of claims 1 to 3, wherein a sensor (8, 13, 41, 44) for detecting an oil parameter (P2, TI, T2, VI) of the oil in the oil supply line (4, 4a, 4b, 4c), preferably a pressure sensor (8) for detecting an oil pressure (P2), a temperature sensor (13, 44) for detecting an oil temperature (TI, T2) and/or a flow sensor (41) for detecting an oil flow (VI), is provided downstream of the oil filter (7) and/or downstream of the oil cooler (6), which is preferably connected to a control unit (40) in a signal-transmitting manner.
  9. 9. Oil circuit (200) according to one of the preceding claims, in particular according to claim 8, wherein the valve (20) comprises a control unit (40) and/or is designed for connection to a control unit (40), preferably of the compressor (100), wherein the control unit (40) is designed to control an actuator (35) of the valve (20) based on at least one detected oil parameter (P2, TI, T2, VI), preferably based on at least one detected oil pressure (P2) and/or oil flow (VI), for regulating the oil flow in the oil recirculation line (14, 14a, 14b) in such a way that the detected oil parameter (P2, VI) corresponds to a predetermined target oil parameter (P2 S oii, Vlsoii), preferably a target oil pressure (P2 So n) and/or a target oil flow (Vlsoii).
  10. 10. Oil circuit (200) according to one of the preceding claims, in particular according to one of claims 8 or 9, wherein the target oil parameter (P2 SO II, Vlsoii), preferably target oil pressure (P2 So n) and/or target oil flow (Vlsoii), can be specified, preferably variably, depending on at least one of the following operating parameters, preferably automatically by a control unit (40): - a determined, preferably measured, oil temperature of the oil in the oil circuit (200), in particular oil temperature (TI, T2) of the oil in the oil supply line (4, 4c) downstream of the oil filter (7) and/or in the oil supply line (4, 4b) downstream of the oil cooler (6); - a temperature-dependent determined, preferably measured, viscosity of the oil, in particular in the oil supply line (4, 4a, 4b, 4c); - a specific, preferably measured, bearing temperature of the at least one bearing (55a, 55b); - a predetermined or measured drive speed of a drive of the compressor (100) and/or a predetermined or measured speed of the compressor (100); - a predetermined or determined, preferably measured, final compression pressure of a compressing gas produced by the compressor (100), preferably a screw compressor, in particular the compressed air produced; - an operating state of the compressor (100), in particular idle or load operation.
  11. 11. Oil circuit (200) according to one of the preceding claims, in particular according to one of claims 8 to 10, wherein the control unit (40) is designed to regulate the oil flow in the oil recirculation line (14, 14a, 14b) through the valve (20) during a cold start of the oil circuit (200), in particular during a cold start of the compressor (100), such that a predetermined maximum permissible oil filter differential pressure across the oil filter (7) is not exceeded, wherein a differential pressure sensor is preferably provided across the oil filter (7) for determining the oil filter differential pressure by the control unit (40) and/or a first oil pressure (PI) which is detected downstream of the oil pump (3) and upstream of the oil filter (7), preferably by a pressure sensor (5), and a second oil pressure (P2) is detected downstream of the oil filter (7) and upstream of an oil inlet (19, 19a, 19b), preferably by a pressure sensor (8).
  12. 12. Oil circuit (200) according to one of the preceding claims, wherein the valve (20), preferably overflow valve, is designed as a proportional valve, wherein the closure body (27) has a plurality of flow openings (29) with an opening cross-section that changes in the axial direction of the closure body (27), which in particular define a defined flow characteristic of the valve (20), preferably a linear or equal percentage flow characteristic.
  13. 13. Oil-free compressor (100), preferably a screw compressor, for generating compressed gas, preferably compressed air, for a consumer, comprising an oil circuit (200) for supplying the compressor (100) with oil according to one of claims 1 to 12, wherein the compressor (100) and the oil pump (3) preferably have a coupled drive, in particular are driven by a common drive unit.
  14. 14. Method for controlling an oil parameter, preferably oil pressure and/or oil flow, for the oil supply of an oil-free compressor, in particular a compressor (100) according to claim 13, in particular at least one bearing (55a, 55b), a drive and/or a transmission of the compressor (100), comprising the following steps: - conveying oil in an oil circuit (200), in particular according to one of claims 1 to 12, with an oil pump (3) from an oil reservoir (1) to at least one oil inlet (19, 19a, 19b) of the compressor (100) through an oil supply line (4, 4a, 4b, 4c) which connects an oil pump outlet (42) to the at least one oil inlet (19, 19a, 19b) of the compressor (100), wherein downstream of the oil pump (3) in a an oil cooler (6) is arranged in a section of the oil supply line (4, 4a, 4b, 4c); - preferably tapping an oil parameter (P2, TI, T2, VI) downstream of an oil filter (7) and/or downstream of the oil cooler (6); - recirculating oil to the oil reservoir (1) through an oil recirculation line (14, 14a, 14b) which branches off from the oil supply line (4, 4a, 4b, 4c) downstream of the oil pump (3) and upstream of the oil cooler (6) and leads to the oil reservoir (1); - Actuating a valve (20), preferably an overflow valve, in particular based on the tapped oil parameter (P2, TI, T2, VI), for regulating an oil flow in the oil recirculation line (14, 14a, 14b), preferably in such a way that the oil parameter (P2, VI) approximates a predetermined target oil parameter (P2 S oii, Vlsoii).
  15. 15. The method according to claim 14, wherein the target oil parameter (P2 S oii, Vlsoii), preferably target oil pressure (P2 So n) and/or target oil flow (Vlsoii), is predetermined, preferably variably, depending on at least one of the following operating parameters, preferably by a control unit (40): - a determined, preferably measured, oil temperature of the oil in the oil circuit (200), in particular oil temperature (TI, T2) of the oil in the oil supply line (4, 4a, 4b, 4c) downstream of the oil filter (7) and/or in the oil supply line downstream of the oil cooler (6); - a temperature-dependent determined, preferably measured, viscosity of the oil, in particular in the oil supply line (4, 4a, 4b, 4c); - a specific, preferably measured, bearing temperature of the at least one bearing (55a, 55b); - a predetermined or measured drive speed of a drive of the compressor (100) and/or a predetermined or measured speed of the compressor (100); - a predetermined or determined, preferably measured, final compression pressure of a pressure vessel (100) generated by the compressor (100), preferably screw compressor, the compressed gas produced, in particular the compressed air produced; - an operating state of the compressor (100), in particular idle or load operation.

Description

Oil circuit for supplying an oil-free compressor and method for controlling an oil parameter for the oil supply of such a compressor Description The invention relates to an oil circuit for supplying oil to an oil-free compressor for producing compressed gas, preferably compressed air, for a consumer. The invention also relates to an oil-free compressor and a method for controlling an oil parameter for the oil supply to such a compressor. Oil-free compressors (oil-free compressors) are sometimes also referred to as dry-compressing compressors (compressors) or dry compressors. They are mainly used for applications in which the provision of oil-free compressed process gas, in particular oil-free compressed air, is important, such as in the food or pharmaceutical industries. Unlike oil-injected compressors, in which the oil injected into the compressor elements can serve not only to lubricate and cool the compressor elements but also to seal them, with oil-free compressors no oil should get into the compression chamber and further into the compressed gas produced. Oil-free compressors are often used with rotating compressor elements, such as oil-free screw compressors. Oil-free compressors often have oil lubrication and cooling for the bearings of the compressor rotor shaft. Due to the high rotation speeds of rotating compressor elements (compressor rotors), the bearings must be supplied with a sufficient oil flow for cooling, with heat generated in the bearings being dissipated by the oil supplied via an oil circuit. In oil-free screw compressors, the compressor stages and the oil pump are often driven by a common drive motor. This has led to The result is that the oil volume flow delivered by the oil pump is usually too high, depending on the operating point of the compressor. Depending on the operating conditions, in particular the temperature of the oil, the oil flow delivered by the oil pump sometimes exceeds the cooling requirements of the compressor more and sometimes less. In addition, the oil flow required for sufficient cooling in speed-controlled compressors depends on the drive speed. Oil circuits for supplying the bearings of oil-free compressors are generally known from the state of the art; these use an oil cooler to cool the oil and an oil filter to clean the oil that is fed to the compressor. Solutions are also known that use overflow valves to return excessive oil volume flow to the oil tank. EP 3 392 478 A1 describes an oil-free compressor with an oil circuit, where the oil pump of the oil circuit is driven by the motor of the compressor element. One of the problems described is that an oil cooler designed for maximum speed cools the oil too much at low machine speeds, which leads to large temperature differences during operation, which are disadvantageous. In addition, a large oil cooler is required, which is designed for the entire oil volume flow at maximum speed. It is therefore proposed to arrange an oil cooler and a bypass valve in a bypass pipe, which could also be referred to as an oil recirculation line. According to EP 3 392 478 A1, this makes it possible to achieve a more constant oil temperature and a smaller dimensioning of the oil cooler. Other known solutions have the disadvantage of increased construction costs due to the use of several separate valves in the oil supply line. In addition, there is often a risk that an oil filter will be damaged by a pressure difference that is too high, particularly during cold starts ("overrun"). A corresponding over-dimensioning of the oil filter requires increased pump performance. A corresponding under-dimensioning of the oil pump in order to avoid overloading the oil filter may pose a problem at other operating points of the oil circuit. There is no sufficient oil volume flow available. State-of-the-art oil circuits often have the disadvantage that the oil pump consumes an unnecessarily high amount of power, namely when an unnecessarily large amount of oil is pumped at an unnecessarily high pressure. The present invention has the object of providing an oil circuit for supplying an oil-free compressor with oil, a corresponding compressor and a method for operating an oil circuit of the compressor, which overcome at least one of the disadvantages mentioned. In particular, the oil circuit should be operable with low energy consumption and should be as simple as possible. In addition, a high level of operational reliability and the lowest possible maintenance effort should be achieved. This task is solved in each case by a sophisticated oil circuit, a sophisticated oil-free compressor and a sophisticated process. In particular, the object is achieved by an oil circuit for supplying an oil-free compressor, in particular at least one bearing, a drive and/or a gear of the compressor, with oil, wherein the oil circuit comprises: - an oil reservoir; - an oil pump for pumping oil from the oil reservoir to the compressor, in particular to the at l