Method for monitoring the oil level of an oil-lubricated compressor, an oil level monitoring system for carrying out said method, and a compressor system equipped with such an oil level monitoring system

Abstract

A method for oil level monitoring of an oil-lubricated compressor includes the following steps: reading at least one oil level sensor (21, 21a, 21b) at which an oil level representative of the compressor oil level is detected, checking fulfillment of at least one preset verification criterion to verify the read oil level, and forwarding an oil level signal if the read oil level fulfills at least one forwarding criterion (10a, 10b) and at least one verification criterion according to reaching or falling below a predetermined oil level.

Description

[Technical field]

[0001] The present invention relates to a method for oil level monitoring in an oil-lubricated compressor, an oil level monitoring system for implementing said method, as well as a compressor system equipped with such an oil level monitoring system.

[0002] For example, currently, the oil level of oil-lubricated compressors for rail vehicles is checked manually at regular intervals to avoid consequent damage and / or malfunctions due to insufficient oil level. This is coupled with a corresponding maintenance effort and can ultimately lead to compressor damage due to overheating caused by this in the event of unexpected oil shortage outside the maintenance interval. However, manual checking of the oil level is fundamentally prone to errors, since readings are sometimes taken incorrectly or even inadvertently not taken at all.

[0003] Reading errors may also be promoted by not observing a specific process for reading the oil level, such as compressor warm-up, shutdown, respecting waiting periods and then performing the reading. The oil level gauge provided for the reading is usually a sight glass or a sight tube on an oil container with a predefined indicating level, whereby reading errors may also occur due to the individual viewing angle or access means.

[0004] Therefore, in light of the above, an object of the present invention is to provide a method for oil level monitoring of an oil-lubricated compressor, an oil level monitoring system for carrying out the method, and a compressor system equipped with such an oil level monitoring system, which enable cost-effective, automated and reliable oil level monitoring.

[0005] This problem is solved by a method for oil level monitoring in an oil-lubricated compressor, an oil level monitoring system for implementing the method, as well as a compressor system equipped with such an oil level monitoring system according to the independent claims. Preferred further developments of the invention are contained in the dependent claims.

[0006] According to the present invention, a method for oil level monitoring of an oil lubricated compressor comprises the following steps: - reading at least one oil level sensor, the oil level being representative of the compressor oil level; - checking for fulfilment of at least one predefined validation criterion to validate the read oil level; - forwarding the oil level signal if the read oil level satisfies at least one forwarding criterion and at least one validation criterion according to reaching or falling below a predetermined oil level.

[0007] The oil level representing the compressor oil level here may be the oil level of the compressor itself or may be an oil level corresponding to the oil level of the compressor. For example, a percentage of oil from the compressor may be diverted for oil level monitoring to allow detection independent of compressor operation and / or structural frame conditions.

[0008] The oil level can be detected either analogically or digitally. Analogue oil level detection is understood to mean a quantitative detection, which determines, for example, a specific filling level or filling amount. In contrast, with digital detection it is also possible to determine whether qualitative oil level characteristics, such as compliance with a minimum oil level, are met.

[0009] A check of at least one validation criterion is used for validating the read oil level, where this validation criterion does not involve an evaluation of the read oil level itself, but rather an evaluation of the suitability of the read oil level for forwarding the oil level signal, as long as corresponding predefined forwarding criteria are fulfilled. The forwarding criterion thus corresponds to the information content of the oil level signal to be forwarded, whereas the validation criterion verifies the applicability of the information or at least a sufficient probability thereof.

[0010] Thus, according to the method, the forwarding of the oil level signal is associated with the fulfillment of at least one validation criterion as well as a forwarding criterion according to the reaching or falling below a predetermined oil level. Here, the oil level signal must be distinguished from the signal originally read from the oil level sensor, i.e. the sensor signal. Insofar as the oil level signal does not need to contain information apart from the sensor signal, for example the sensor signal can be directly processed during forwarding as the oil level signal, it corresponds to the sensor signal. However, in many cases it may be advantageous if information derived from the sensor information, rather than the sensor information itself, is forwarded as the oil level signal. In such a case the content of the oil level signal deviates from the content of the sensor signal. This sensor signal can therefore be converted into an oil level signal.

[0011] The method is particularly applicable in a suitable manner to oil-lubricated compressors for rail vehicles.

[0012] In one embodiment of the method, the transfer criterion corresponds to a low oil level and / or a critical oil level.

[0013] In the event of a low oil level, the compressor can still continue to operate for a certain operating duration without the possibility of compressor damage, for example due to overheating. The transfer of a corresponding oil level signal therefore allows the oil refill to be scheduled within a still permissible operating duration. In the event of a critical oil level, a stop of the compressor operation is recommended, since the possibility of damage resulting from further operation of the compressor can no longer be excluded. Therefore, preferably, not only a distinction is made between a low oil level and a critical oil level, but also, in particular, a correspondingly different oil level signal is transferred.

[0014] In particular, the verification criteria correspond to at least one of a time criterion, according to which an oil level corresponding to the transfer criterion is read over a predetermined period of time, a frequency criterion, according to which there are a predetermined number of individual reading processes that satisfy the transfer criterion, and / or an operating state criterion, according to which a predetermined operating state is established.

[0015] As already mentioned above, at least one validation criterion is used to check the suitability of the oil level signal for transfer when the transfer criterion is fulfilled. For example, the oil level corresponding to the transfer criterion is not the actual oil level, which may only occur for a short time, but may be due to vibrations of the oil container or other frame conditions not due to the oil level. In order to reduce the probability of arriving at an erroneous inverse inference from temporary fluctuations in the oil level to the actual oil level, for example a time criterion can be used as validation criterion. To fulfill the time criterion, it is checked whether the oil level corresponding to the transfer criterion is read continuously or at least with a predetermined frequency over a predetermined period of time.

[0016] Alternatively or additionally, a frequency criterion can also be taken into account as a verification criterion, in which there is a predetermined number of individual reading processes that fulfill the transfer criterion. A reading process corresponds here to a reading over a predetermined period of time of at least one oil level sensor. A reading process that fulfills the transfer criterion is present if the oil level that corresponds to the transfer criterion is read continuously or at least with a predetermined frequency over the individual reading processes. In other words, the frequency criterion corresponds to a predetermined number of fulfilled time criteria. It can be assumed that in order to fulfill the frequency criterion, a predetermined number of reading processes, for example five reading processes, that fulfill the transfer criterion must be present, either directly following each other or within a predetermined period of time.

[0017] Alternatively or additionally, an operating state criterion can also be defined as a verification criterion, according to which a predefined operating state is established. It is thus checked whether the compressor is in a predefined operating state during the reading of the at least one oil level sensor. For example, the operating state criterion is considered to be fulfilled only if the compressor is operating or stopped. If the operation of the compressor is assumed as an operating state criterion, a predefined output phase of the compressor operation can also be additionally assumed. Since the start-up phase must be taken into account when the compressor is operating, or the stop-up phase must be taken into account when the compressor is stopped, it can furthermore be advantageous to take into account not only the operating state itself, but also the corresponding time component for the achievement of a stable operating state, for example "the compressor continues to operate for ... seconds" or "the compressor remains stopped for ... seconds", when defining the operating state criterion.

[0018] The probability of a reliable measurement of the oil level can be increased through the combination of various validation criteria.

[0019] In a development of the method, the pressure sensor is read for determining the predetermined operating state.

[0020] The predefined operating state can here correspond to a defined pressure window, the presence of which is determined via the pressure sensor. The term "pressure window" refers to a pressure range that corresponds to a decompressed or reduced pressure state of the compressor after a predefined time has elapsed. The interrogation of the pressure sensor can ensure, for example, that the oil level in a warmed-up but switched-off compressor state is detected by at least one oil level sensor, in which case operation does not last longer than a defined duration.

[0021] According to one embodiment, the step of reading the at least one oil level sensor occurs prior to checking the at least one predetermined validation criterion.

[0022] Thus, the check of the at least one pre-set validation criterion is only performed if the reading of the oil level sensor results in the fulfillment of the transfer criterion, so that data retrieval and processing can be reduced to a minimum.

[0023] Alternatively, however, the checking of at least one predefined validation criterion can precede the reading of the oil level sensor. For example, if an operating state criterion is used as validation criterion, the transfer of the oil level signal can in any case only take place upon the reaching of a predefined operating state. Thus, a pre-emptive reading of the oil level, at least in the sense of the method described herein, does not necessarily lead to results that can be used in all method embodiments.

[0024] In the check of a number of verification criteria, for example, an operating state criterion can be checked first, and in the presentation of the corresponding operating state criterion, an oil level sensor reading can be performed, and a check of further verification criteria, such as a time criterion, can be associated with the fulfillment of a transfer criterion. The selection of the verification criterion and / or the selection of the order of the method steps can also be made depending on the operating state. Thus, not only the various verification criteria and / or the order of the method steps can be defined, but also the transfer criteria, in order to be able to perform an oil level monitoring that is adapted to them in the respective operating states, both during operation of the compressor and when the compressor is switched off, and thus a gap-free oil level monitoring.

[0025] In one embodiment, two oil level sensors are read.

[0026] Reading at least two oil level sensors can be advantageous, for example, if several oil levels define a transfer criterion or different transfer criteria, in which case several oil levels are not detectable via one oil level sensor or the detection should be mapped redundantly. For example, one oil level sensor can be used for each of the respective oil levels, if both low and critical oil levels are to be conditional on the transfer of one or the respective oil level signal upon corresponding additional fulfillment of the verification criterion to be applied. If the additional oil level detection is not coverable via one oil level sensor, besides the use of additional oil level sensors, different detection parameters such as measurement sensitivity, reaction time, measurement principle, etc. can also be adapted as required via independent detection.

[0027] In particular, a float is used as the oil level sensor.

[0028] The float or a functional unit interacting therewith, e.g. a float switch operable by the float, provides a cost-effective implementation of an oil level monitoring system. In particular, by associating at least one verification criterion with the oil level monitoring, the application of floats, which otherwise usually involves significant uncertainties, is improved in its reliability.

[0029] In a further development, depending on the transfer criterion, the oil level signal is transferred as a message to a monitoring unit, in particular a cab, and / or to a control device and / or a maintenance device, and / or, in particular in the case of a critical oil level, as a control parameter for the compressor control device.

[0030] The oil level signal can trigger optical, acoustic and / or haptic signals in the form of messages via the monitoring unit. For example, explicit text messages such as "low oil level" or "critical oil level" are displayed to the operator via the cab display and / or a corresponding warning light is activated. In particular in crisis situations such as critical oil levels, an acoustic signal can be alternatively or supplementarily output in order to increase the probability of being perceived independently of the gaze direction. The monitoring unit may be part of a maintenance system, whereby maintenance intervals are adapted depending on the transferred oil level signal and / or corresponding maintenance instructions, such as for example "top up oil" for the upcoming maintenance, are stored in a maintenance protocol.

[0031] However, depending on the forwarding criterion of the oil level signal, the control parameters for the compressor control device can also be adapted so that the probability of malfunction or resulting damage due to compressor overheating or other oil shortage consequences is reduced. For example, the maximum power of the compressor can be throttled back to ensure that temporary emergency operation is possible with still remaining oil. In the case of a critical oil level, it is also possible to envisage a complete shutdown of the compressor operation.

[0032] According to one embodiment, the method is performed during shutdown of the oil-lubricated compressor.

[0033] This allows finding stable and particularly constant conditions necessary for reliable detection of the oil level. As mentioned above, the start-up of the compressor can be interrupted in so far as it is better to assume a stop of the compressor operation upon the transfer of a corresponding oil level signal. The compressor is thus not switched off here during continued operation. In other words, the compressor is only started if there is no transfer of an oil level signal. In particular, this can be assumed as a transfer criterion for the critical oil level.

[0034] In this connection, it should be noted that the transfer criterion, for example a low or critical oil level, can be adapted to the frame criterion. For example, if a relatively long travel distance is referenced to the oil level monitoring via the navigation system or a relatively long duration until the next maintenance interval is stored, a higher oil level can already form the transfer criterion than in the case of a relatively short distance or a relatively short duration until the next maintenance interval.

[0035] The present invention, in another aspect, provides an oil level monitoring system for carrying out the above method, the oil level monitoring system comprising: at least one oil level sensor for detecting an oil level in an oil container of the compressor, the oil level being representative of the compressor oil level; an evaluation unit for reading the sensor signals of the at least one oil level sensor, in which at least one transfer criterion as well as at least one verification criterion are stored, Here, the evaluation unit relates to an oil level monitoring system, wherein the evaluation unit is configured to forward the oil level signal if at least one forwarding criterion and at least one validation criterion are fulfilled according to the read oil level.

[0036] The fulfillment of the verification criteria is checked via the evaluation unit itself, for example via evaluation of the oil level read in the sense of the aforementioned time and / or frequency criteria, and via a corresponding comparison of the evaluation results with the stored verification criteria. However, such evaluation results, or operating states with respect to the operating state criteria, can also be transmitted to the evaluation unit for comparison with stored values ​​and / or states.

[0037] In a further development, the oil level monitoring system comprises a pressure sensor, in particular a pressure sensor which can be arranged on an oil container representing the compressor oil level, via which a pressure representative of the operating state of the compressor can be detected, and the evaluation unit takes into account at least the detected pressure as a verification criterion.

[0038] The detection of the pressure representative of the operating state of the compressor and its consideration as a verification criterion involves the procedure described in the present method. For this purpose, the pressure sensor is preferably placed on an oil container representative of the compressor oil level in order to minimize interference due to distance. The oil level in the oil container corresponds to the oil level of the compressor. This is fulfilled, for example, when the oil container is the oil container of the compressor or when the oil level of the oil container is in communication with the compressor so that it can be used to describe the oil level of the compressor. Therefore, the expression "oil container representative of the compressor oil level" is used in relation to the oil container.

[0039] In particular, the at least one oil level sensor is a float.

[0040] The advantage of the float as an oil level sensor arises analogously to the embodiment already carried out for the method.

[0041] According to one embodiment, the evaluation unit is arranged to distinguish between at least two transfer criteria and to transfer different oil level signals depending on the transfer criteria.

[0042] For example, reaching or falling below a first limit value of the oil level corresponding to a low oil level is established as a first transfer criterion. Reaching or falling below a second limit value of the oil level corresponding to a critical oil level is established as a second transfer criterion. This second limit value is in this case lower than the first limit value. If the first limit value is reached or fallen below and if at least one verification criterion assigned to the first transfer criterion is fulfilled, the evaluation unit transfers, for example, an oil level signal "low oil level" as a corresponding message to the cab of the rail vehicle and / or to the maintenance device as an application example. If the read oil level reaches or falls below a second limit value while simultaneously fulfilling a verification criterion respectively assigned to the second limit value, the evaluation unit transfers, for example, an oil level signal "critical oil level" as a corresponding message to the cab of the rail vehicle and / or to the maintenance device as an application example. Alternatively or additionally, the evaluation unit can also transfer the oil level signal as a control parameter to the compressor control device, so that the compressor power can be proactively reduced or the compressor operation can be stopped completely.

[0043] In a further aspect, the present invention relates to a compressor system equipped with an oil level monitoring system as described above, wherein the compressor system has an oil reservoir representative of the compressor oil level, and wherein at least one oil level sensor is particularly centrally located within the oil reservoir.

[0044] The positioning of the oil level sensor influences the probability of detection of temporary fluctuations of the oil level present in the oil container relative to the actual oil level. If a float is arranged as an oil level sensor, for example, at the edge of the oil container, the oil level fluctuations will have a larger amplitude in the sense of fluid movement at the edge of the oil container, thereby resulting in a larger uncertainty regarding the distinction between temporary level fluctuations and the actual oil level. A possible central arrangement, i.e. in an area with relatively small level fluctuations or level fluctuation amplitudes, can therefore reduce the possible distinction uncertainty. As a result, it is also possible in this respect to reduce at least one verification criterion to fewer requirements. Alternatively or additionally, however, the oil container may be configured as a container that is sufficiently decoupled from the fluctuations in order to maintain a low degree of undesired influence on the oil level detection. Since such a decoupling of fluctuations must be performed for the compressor, it can be envisaged here in particular to perform the oil level detection via a separate oil container. A separate oil container, whose oil level corresponds to the compressor oil level, can be decoupled from the fluctuations as a smaller unit with less effort.

[0045] In a further development, the compressor system has a control device to which the oil level signal is forwarded by the evaluation unit, whereby the control device controls the operation of the compressor in dependence on the oil level signal.

[0046] Thus, as already explained with respect to the method and the oil level monitoring system, the compressor can be controlled depending on the oil level signal, for example to reduce oil consumption in case of low oil levels or to completely prevent potentially damaging operation in case of subsequent, particularly critical, oil levels. The control device can thus, for example, switch the compressor into a lower oil consumption operating mode or stop the operation of the compressor.

[0047] The invention will now be explained in more detail based on embodiments with reference to the accompanying drawings. [Brief description of the drawings]

[0048] [Figure 1] 1 is a schematic diagram of an oil level monitoring system in accordance with an exemplary embodiment of the present invention; [Diagram 2] 4 is a flow chart of a method for oil level monitoring according to a first embodiment of the method. [Diagram 3] 4 is a flow chart of a method for oil level monitoring according to a second embodiment of the method. [Figure 4] 4 is a flow chart of a method for oil level monitoring according to a third embodiment of the method.

[0049] FIG. 1 shows an oil level monitoring system 1 for implementing a method for oil level monitoring of an oil-lubricated compressor for rail vehicles based on oil level monitoring of an oil-lubricated compressor, as is also applicable for the embodiment of the method shown in FIGS. 2 to 4. The oil level monitoring system 1 comprises an oil level sensor 21 arranged in an oil container 20, which represents the oil level of the oil-lubricated compressor. The oil level sensor 21 is configured here as a float. Furthermore, the oil level monitoring system 1 has an evaluation unit 30, which is connected in signal technology with the oil level sensor 21 via a signal line 40. The signal technology connection can also be formed via a wireless transmission method. In the illustrated embodiment, the evaluation unit 30 is supplied not only with the sensor signal of the oil level sensor 21, but also with the sensor signal of the pressure sensor 22 arranged in the oil container 20, in order to be able to derive the operating state of the compressor via the detected pressure. Here again, the signal technology connection is made, by way of example, via a further signal line 40.

[0050] Furthermore, in FIG. 1, a low oil level 10a is indicated via a dashed line. The dashed-dotted line 10b represents the critical state 10b. According to the depicted depiction of the oil level sensor 21, the oil 10 in the oil container 20 has a low oil level 10a. By establishing the transfer criterion as reaching or falling below the low oil level 10a, this transfer criterion is therefore fulfilled in the depicted state. This is checked by the evaluation unit 30 by a comparison of the sensor signal of the oil level sensor 21 with stored limit values ​​for the transfer criterion, or the oil level sensor itself transmits a corresponding positive value to the effect of fulfillment of the transfer criterion. For this purpose, the oil level sensor can have an own data processing unit. If the oil level sensor 21 is configured in a digital manner, i.e., for example, if a signal is only transmitted in the event of fulfillment of the transfer criterion, the application of the sensor signal to the evaluation unit 30 can have sufficient information content.

[0051] However, since the fulfillment of the transfer criterion by the read oil level itself may not yet be sufficient to reliably indicate the actual oil level, the evaluation unit 30 additionally checks a predefined verification criterion. In the illustrated embodiment of the oil level monitoring system 1, for example, the sensor signal of the pressure sensor 22 is used by the evaluation unit to detect whether the compressor is stopped. Only if the transfer criterion is fulfilled by the sensor signal of the oil level sensor 21 simultaneously with the presentation of a pressure signal that fulfills the corresponding verification criterion, the oil level signal is transferred from the evaluation unit 30 via a further signal line 40 to the cab 50. There, for example, a message "low oil level" then appears on a corresponding display device. As this will become clear on the basis of the description of the further figures, the verification criterion is not limited here to operating state criteria that can be checked by the pressure sensor 21, but can alternatively or additionally also be imaged, for example, a time criterion or a frequency criterion.

[0052] Figure 2 shows a flowchart of a method for oil level monitoring according to a first embodiment of the present method. Here, first, the oil level sensor 21 is read. If the transferred criterion "low oil level" for the read oil level is met, that is, if it has reached or fallen below a predetermined limit value corresponding to this transferred criterion, the fulfillment of the defined verification criterion is checked. Otherwise, the oil level sensor is read again. In the illustrated embodiment of the present method, when a low oil level is read, first, it is checked whether the time criterion is met. This time criterion is here a continuous measurement of a low oil level, i.e., an oil level that meets the transferred criterion, over x seconds, i.e., a predetermined duration or minimum duration. If this time criterion is met, a frequency criterion is checked as a further verification criterion, and otherwise, the evaluation is interrupted and the oil level sensor is read again. According to the frequency criterion applied here, it is checked whether there are a predetermined number k of successful measurements. The evaluation unit 30 is here programmed to recognize an instantaneous change in the oil level read over a duration of t < x*ms as an oil level measurement error and not to evaluate it. The frequency criterion is considered fulfilled when an oil level that meets the transferred criterion, i.e., here a low oil level, is read a predetermined number k, for example 5 times, within a preset period. However, the frequency criterion may be defined such that for its fulfillment, the time criterion needs to be met sequentially a predetermined number of times or within a predetermined period. When the frequency criterion is met, an oil level signal "low oil level" is transferred. According to this oil level signal, for example, a corresponding message "low oil level" is displayed on the display of the driver's cab 50. The oil level signal can alternatively or additionally be transferred to a maintenance device, which then stores the replenishment of oil for each compressor as a maintenance operation in a maintenance protocol. The maintenance device can, in one embodiment, also adapt the maintenance time, for example advance it, depending on the oil level signal.

[0053] FIG. 3 shows a flow chart of a method for oil level monitoring according to a second embodiment of the method. The second embodiment of the method differs from the first embodiment of the method in that two transfer criteria are distinguished. Reaching or falling below a first limit value of the oil level, which corresponds to a low oil level, is determined as the first transfer criterion. Reaching or falling below a second limit value of the oil level, which corresponds to a critical oil level, is determined as the second transfer criterion. The second limit value is here lower than the first limit value. In the illustrated flow chart for the purpose of illustration, two digital oil level sensors 21a, 21b are read. The reading of the first oil level sensor 21a corresponds here to the first transfer criterion, i.e. the check of the low oil level, and the reading of the second oil level sensor 21b corresponds to the second transfer criterion, i.e. the check of the critical oil level. Alternatively, however, an analogue oil level sensor can also be read, via which both the low and the critical oil levels can then be detected. Thus, instead of the oil level sensors 21a, 21b, analogue oil level sensors can be used. Regardless of the number of oil level sensors used, it is first checked here whether a critical oil level exists according to the read oil level, i.e. whether the second limit value has been reached or is below it. If a critical oil level is not detected, the further course of the method shown in FIG. 3 corresponds to the first embodiment of the method according to FIG. 2. If a critical oil level is detected according to the read oil level of the oil level sensor 21b, the time and frequency criteria are also checked in addition for the presentation of the second transfer criterion, analogous to the further method for low oil level. In the second exemplary embodiment of the method, the time and frequency criteria for the transfer criteria "critical oil level" and "low oil level" up to the respective limit value and thus the oil level to be referred to are the same. However, in a further variant of the method, the verification criteria can also be defined independently of one another. At a critical oil level, the oil level signal "critical oil level" is transferred as long as the relevant time and frequency criteria are fulfilled. This "critical oil level" is now also transferred, for example, to the cab 50 for display.Furthermore, the oil level signal can also be forwarded to the compressor control device in order to prevent further operation of the compressor in this case or to switch to another operating mode.

[0054] FIG. 4 shows a flow chart of a method for oil level monitoring according to a third embodiment of the method. The third embodiment of the method according to FIG. 4 differs from the second embodiment of the method according to FIG. 3 by an additional reading of the pressure sensor 22. The pressure to be checked corresponds to an operating state criterion as a further verification criterion. For example, the target area is defined as the pressure area present at the time of the compressor's stop state. The oil level monitoring according to the second embodiment of the method is continued only if the read pressure of the pressure sensor 22 is within the predefined target area. In other words, the fulfillment of the operating state criterion is a prerequisite for a further check of the transfer criteria, as well as for the respective time criterion and the respective frequency criterion. If the pressure is outside the predefined target area, the sensor value is further read until the operating state criterion corresponding to the pressure is fulfilled.

[0055] The invention is not limited to the described embodiment. For example, even if the operating state criterion in the third embodiment of the method is checked, for example, on the basis of pressure measurements, the respective operating state of the compressor can also be transferred via the compressor control device to the evaluation unit 30 and evaluated accordingly. Furthermore, the evaluation unit 30 can be part of the compressor control device. [Explanation of symbols]

[0056] 1 Oil level monitoring system 10. Oil 10a low oil level 10b Critical oil level 20 Oil container 21, 21a, 21b Oil level sensor 22 Pressure Sensor 30 Evaluation Units 40 Signal Line 50 Cab

Claims

1. A method for oil level monitoring of an oil-lubricated compressor, performed during shutdown of the oil-lubricated compressor, comprising the following steps: reading at least one oil level sensor (21, 21a, 21b) from which an oil level representative of a compressor oil level is detected; - checking for fulfilment of at least one pre-defined validation criterion to validate the read oil level; and transferring the oil level signal if the read oil level satisfies at least one transfer criterion (10a, 10b) and at least one verification criterion according to reaching or falling below a predetermined oil level, the verification criteria correspond to at least one of a time criterion, during which an oil level corresponding to the transfer criterion (10a, 10b) is read over a predetermined period (x), a frequency criterion, during which there is a predetermined number (k) of individual reading processes that satisfy the transfer criterion (10a, 10b), and an operating state criterion, during which a predetermined operating state of the oil-lubricated compressor is established; The method of claim 1, wherein the operating condition criteria is considered to be met only if the oil-lubricated compressor is shut down.

2. The method according to claim 1, wherein the transfer criteria (10a, 10b) correspond to a low oil level (10a) and / or a critical oil level (10b).

3. The method of claim 1 or 2, wherein a pressure sensor (22) is read to determine the predetermined operating condition.

4. 4. The method according to claim 1, wherein the step of reading the at least one oil level sensor (21, 21a, 21b) is performed before checking at least one pre-set verification criterion.

5. 5. The method according to claim 1, wherein two oil level sensors (21a, 21b) are read.

6. 6. The method according to claim 1, wherein a float is used as the oil level sensor (21, 21a, 21b).

7. 7. The method according to claim 1, wherein, depending on the transfer criteria (10a, 10b), the oil level signal is transferred as a message to a monitoring unit (50), in particular to a cab, and / or to a control device and / or a maintenance device, and / or, in particular in the case of a critical oil level according to claim 2, as a control parameter for a control device of the compressor.

8. The method of claim 1 , wherein the method is performed during shutdown of the oil-lubricated compressor.

9. An oil level monitoring system (1) for implementing the method according to any one of claims 1 to 8, said oil level monitoring system (1) comprising: at least one oil level sensor (21, 21a, 21b) for detecting an oil level representative of the compressor oil level of the oil (10) in an oil container (20) of the compressor; an evaluation unit (30) for reading the sensor signals of at least one oil level sensor (21, 21a, 21b), in which at least one transfer criterion (10a, 10b) as well as at least one verification criterion are stored, The evaluation unit (30) is configured to forward an oil level signal if the at least one forwarding criterion (10a, 10b) and the at least one verification criterion are fulfilled according to the read oil level.

10. 10. The oil level monitoring system (1) according to claim 9, further comprising a pressure sensor (22), in particular a pressure sensor (22) that can be arranged on an oil container (20) representing the compressor oil level, via which a pressure representative of the operating state of the compressor can be detected, and the evaluation unit (30) takes into account at least the detected pressure as a verification criterion.

11. The oil level monitoring system (1) according to claim 9 or 10, wherein the at least one oil level sensor (21, 21a, 21b) is a float.

12. The oil level monitoring system (1) according to any one of claims 9 to 11, wherein the evaluation unit (30) is configured to distinguish between at least two transfer criteria (10a, 10b) and to transfer different oil level signals depending on the transfer criteria (10a, 10b).

13. A compressor system equipped with an oil level monitoring system (1) according to any one of claims 9 to 12, the compressor system having an oil container (20) representative of the compressor oil level, and at least one oil level sensor (21, 21a, 21b) being arranged in particular centrally in the oil container (20).

14. 14. The compressor system according to claim 13, further comprising a control device to which an oil level signal is transferred by the evaluation unit (30), the control device controlling the operation of the compressor in dependence on the oil level signal.

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