Method for oil level monitoring of an oil-lubricated compressor, oil level monitoring system for performing the method, and compressor system having such an oil level monitoring system

Abstract

The invention relates to a method for oil level monitoring of an oil-lubricated compressor, comprising the steps of reading at least one oil level sensor (21, 21a, 21b), detecting an oil level representative of the compressor oil level by means of the at least one oil level sensor, checking whether at least one predetermined verification criterion for verifying the read oil level is fulfilled, and forwarding an oil level signal if the read oil level fulfils at least one forwarding criterion (10a, 10b) depending on reaching or falling below a predetermined oil level and the at least one verification criterion is fulfilled.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for oil level monitoring of an oil-lubricated compressor, to an oil level monitoring system for carrying out the method, and to a compressor system having such an oil level monitoring system. BACKGROUND

[0002] For example, the oil level of oil-lubricated compressors for rail vehicles is currently regularly manually checked in order to avoid subsequent damage and / or operating malfunctions due to an insufficient oil level. This is associated with a corresponding maintenance outlay and can possibly result in damage to the compressor due to overheating caused thereby, especially in the event of unexpected oil loss outside the maintenance intervals. However, the manual checking of the oil level is also essentially prone to faults since the reading can not be carried out correctly or even unintentionally.

[0003] In addition, reading errors can be caused by the fact that the specific procedure for reading the oil level is not followed, for example the hot running of the compressor, the stopping, the waiting time being observed and then the reading being carried out. The oil level indicator provided for the reading is usually an observation glass or an observation tube on the oil container which has a certain indication height. Reading errors can thus also be caused by the individual viewing angle or proximity. SUMMARY

[0004] In view of the above, it is therefore the task of the present invention 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 having such an oil level monitoring system, in order to enable low-cost automatic and reliable oil level monitoring.

[0005] The stated task is solved by 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 having such an oil level monitoring system

[0006] According to the invention, the method for oil level monitoring of an oil-lubricated compressor comprises the steps of:

[0007] - reading at least one oil level sensor by means of which an oil level representative of the oil level of the compressor is detected,

[0008] - checking whether at least one predetermined verification criterion for verifying the read oil level is fulfilled, and

[0009] - forwarding an oil level signal if the read oil level fulfils at least one forwarding criterion depending on the oil level being at or below a predetermined oil level and fulfils the at least one verification criterion.

[0010] The oil level representative of the compressor oil level can be the oil level of the compressor itself or an oil level corresponding to the oil level of the compressor. For example, a portion of the oil can be tapped off from the compressor for oil level monitoring in order to achieve a detection independent of the compressor operation and / or the structural framework conditions.

[0011] The detection of the oil level can be carried out in an analog manner and in a digital manner. Analog oil level detection is understood to mean a quantitative detection, i.e. for example a specific filling height or filling volume is ascertained. In contrast thereto, according to digital detection, it is also possible to determine only whether a qualitative oil level feature is fulfilled, for example a minimum oil level is adhered to, respectively.

[0012] The checking of the at least one verification criterion serves to verify the read oil level. Here, the verification criterion is not used to evaluate the read oil level itself, but rather to evaluate the suitability of the read oil level for forwarding the oil level signal, as soon as the corresponding predetermined forwarding criterion is fulfilled. The forwarding criterion thus corresponds to the information content of the oil level signal to be forwarded, whereas the verification criterion verifies the availability of the information or at least a sufficient probability of the information.

[0013] According to the method, the forwarding of the oil level signal is thus limited not only to the fulfillment of the at least one verification criterion, but also to the fulfillment of the forwarding criterion according to the reaching or undershooting of a predetermined oil level. Here, the oil level signal is first to be distinguished from the reading signal of the oil level sensor, i.e. the sensor signal. If the oil level signal does not necessarily contain information different from the sensor signal, for example because the sensor signal can be processed directly as the oil level signal upon forwarding, the oil level signal corresponds to the sensor signal. However, in many cases it is advantageous for information derived therefrom to be forwarded as the oil level signal, instead of the sensor information itself. In this case, the content of the oil level signal deviates from the content of the sensor signal. The sensor signal can thus be converted into the oil level signal.

[0014] The method can be used particularly advantageously for oil-lubricated compressors of rail vehicles.

[0015] In a design variant of the method, the forwarding criterion corresponds to a low oil level and / or a critical oil level.

[0016] In the case of a low oil level, the compressor can also continue to be operated for a certain operating duration without the possibility of damage to the compressor, for example due to overheating. By forwarding the corresponding oil level signal, it is thus possible to plan a replenishment of oil within a still tolerable operating duration. In the case of a critical oil level, a subsequent damage cannot be ruled out any more upon continued operation of the compressor, so that an interruption of the compressor operation is recommended. It is therefore preferred not only to distinguish between a low oil level and a critical oil level, but also to forward different oil level signals accordingly, in particular.

[0017] In particular, the verification criteria correspond to at least one of a time criterion, a frequency criterion and / or a running state criterion, in which in the time criterion the oil level corresponding to the forwarding criterion is read over a predetermined period of time, in which in the frequency criterion there is a predetermined number of individual reading processes which satisfy the forwarding criterion, in which in the running state criterion a predetermined running state is determined.

[0018] As has already been explained above, at least one verification criterion is used to check the suitability of the oil level signal for forwarding in the case of a satisfied forwarding criterion. For example, the oil level corresponding to the forwarding criterion can only occur briefly and not be due to an actual oil level, but rather due to a vibration of the oil container or other non-oil level-related framework conditions. In order to reduce the probability of false conclusions about the actual oil level due to temporary fluctuations of the oil gauge, for example a time criterion can be used as a verification criterion. In order to satisfy the time criterion, it is checked whether the oil level corresponding to the forwarding criterion is read continuously over a predetermined period of time or at least with a predetermined frequency.

[0019] Alternatively or in addition, as a verification criterion a frequency criterion can also be considered, in which a predetermined number of individual reading processes which satisfy the forwarding criterion occur. A reading process here corresponds to a reading of the at least one oil level sensor over a predetermined period of time. If the oil level corresponding to the forwarding criterion is read continuously via the individual reading processes or at least with a predetermined frequency, there is a reading process which satisfies the forwarding criterion. In other words, the frequency criterion corresponds to a predetermined number of satisfied time criteria. In order to satisfy the frequency criterion it can be provided that the predetermined number of reading processes which satisfy the forwarding criterion, for example five reading processes, must directly follow one another or must occur within a predetermined period of time.

[0020] Furthermore, alternatively or in addition, a running state criterion can also be defined as a verification criterion, in which a predetermined running state is determined. It is thus checked whether the compressor is in a predetermined running state during the reading of the at least one oil level sensor. For example, the running state criterion is only considered to be satisfied if the compressor is running or stopped. If the running of the compressor is taken as a running state criterion, it is also possible to take a determined power level of the compressor running as a prerequisite. Since start-up phases are to be taken into account when the compressor is running or stop phases are to be taken into account when the compressor is set, it is furthermore advantageous when defining the running state criterion not only the running state itself, but also a corresponding time component for the attainment of a stable running state is taken into account, for example "the compressor has been running for... seconds" or "the compressor has been stopped for... seconds".

[0021] By combining the individual verification criteria, the probability of reliably measuring the oil level can be increased.

[0022] In an improved version of the method, in order to determine the predetermined running state, a pressure sensor is read.

[0023] Here, the predetermined operating state can correspond to a defined pressure window, the presence of which is ascertained by means of the pressure sensor. The term "pressure window" refers to a pressure range corresponding to a pressure- relieved or pressure-reduced state of the compressor after a predetermined time. By querying the pressure sensor it can be ensured that, for example, in a warm but switched-off state of the compressor, the oil level is detected by at least one oil level sensor, wherein the operating state does not exceed the defined duration prematurely.

[0024] According to the design, the step of reading at least one oil level sensor is carried out before checking at least one preset verification criterion.

[0025] Thus, the checking of at least one preset verification criterion is only carried out if the reading of the oil level sensor leads to the fulfillment of the forwarding criterion. The data ascertainment and processing can thus be minimized.

[0026] Alternatively, however, the checking of at least one preset verification criterion can also be provided before the reading of the oil level sensor. If, for example, an operating state criterion is considered as a verification criterion, the forwarding of the oil level signal can only be carried out at all when the predetermined operating state is reached. Thus, at least the prior reading of the oil level in the sense of the method described here does not lead to a usable result in every design of the method.

[0027] In the checking of a plurality of verification criteria, for example, an operating state criterion can first be checked, the reading of the oil level sensor is carried out when the respective operating state criterion is present and the checking of further verification criteria, such as a time criterion, is associated with the fulfillment of the forwarding criterion. The selection of the verification criteria and / or the selection of the order of the method steps can also be carried out depending on the operating state. Thus, different verification criteria and / or orders of the method steps can be defined not only during the operation of the compressor but also when the compressor is switched off, or else the forwarding criterion is defined, so that in each operating state an oil level monitoring can be carried out which is adapted thereto and thus seamless.

[0028] In an embodiment, two oil level sensors are read.

[0029] The reading of at least two oil level sensors is advantageous, for example, in the case of a plurality of oil level definitions of the forwarding criterion or different forwarding criteria, wherein a plurality of oil levels cannot be detected by one oil level sensor or the detection should be redundantly mapped. For example, if a low oil level and a critical oil level both lead to the forwarding of one or a respective oil level signal, respectively, in the case of the additional fulfillment of the verification criteria to be used, an oil level sensor can be used for each respective oil level. In addition to 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 by means of independent detection when the additional oil level detection cannot be covered by the oil level sensor.

[0030] In particular, the float serves as an oil level sensor.

[0031] The float or rather the functional unit cooperating therewith, for example a float switch, which can be actuated by the float, provides a cost-effective implementation of the oil level monitoring. By virtue of the inclusion of at least one verification criterion for the oil level monitoring, the application of the float, which would otherwise generally have a significant uncertainty with regard to its reliability, is improved.

[0032] In the improvement, the oil level signal is forwarded as a message to a monitoring unit, in particular to a bridge and / or to a control and / or maintenance device, in accordance with the forwarding criterion, and / or the oil level signal is forwarded as a control parameter for a control device of the compressor, in particular in the case of a critical oil level.

[0033] The oil level signal can trigger an optical, acoustic and / or haptic signal in the sense of a message by the monitoring unit. For example, an explicit text message, such as "low oil level" or "critical oil level", is displayed to the operator by means of a display in the bridge and / or a corresponding warning light is activated. In the case of a critical situation, for example in the case of a critical oil level, an acoustic signal can alternatively or additionally be output in order to increase the probability of perception independently of the direction of observation. The monitoring unit can also be part of a maintenance system, so that the maintenance intervals are adjusted in accordance with the forwarded oil level signal and / or a corresponding maintenance instruction, for example "refill oil", is saved in the maintenance protocol for the next maintenance.

[0034] However, in accordance with the forwarding criterion of the oil level signal, a control parameter for a control device of the compressor can also be adjusted, so that the probability of operating faults or consequential damage due to overheating of the compressor or other consequences of a lack of oil is reduced. For example, the maximum compressor power can be limited in order to ensure that the remaining oil also enables a temporary emergency operation. In the case of a critical oil level, it can also be provided that the compressor operation is completely stopped.

[0035] According to the design, the method is carried out during a stop of the oil-lubricated compressor.

[0036] It is thereby possible to encounter stable, in particular constant, conditions required for reliably detecting the oil level. If, as described above, a stop of the compressor operation is to be provided upon forwarding of the corresponding oil level signal, the start of the compressor can be interrupted. The compressor is therefore not switched off during the continuous operation. In other words, the compressor is only started when there is no oil level signal forwarding. This is provided as a forwarding criterion, in particular for a critical oil level.

[0037] To this it is to be added that the forwarding criterion, such as a low oil level or a critical oil level, can be adapted to the frame criterion. If, for example, the oil level monitoring or the relatively long duration until the next maintenance interval is monitored or stored by means of a navigation system for a relatively long driving section, a higher oil level can already form the forwarding criterion compared to the case of a relatively short section or a short duration until the next maintenance interval.

[0038] In another aspect, the application relates to an oil level monitoring system for carrying out the above-mentioned method, having

[0039] at least one oil level sensor for detecting an oil level of oil in an oil container of the compressor, the oil level representing the compressor oil level; and

[0040] an evaluation unit for reading a sensor signal of the at least one oil level sensor, in which at least one forwarding criterion and at least one verification criterion are stored,

[0041] wherein the evaluation unit is configured to forward an oil level signal when the at least one forwarding criterion is met and the at least one verification criterion is met in accordance with the read oil level.

[0042] The fulfillment of the verification criterion is checked by the evaluation unit itself, for example by evaluating the read oil level in the sense of the above-mentioned time criterion and / or frequency criterion and comparing the evaluation result accordingly with the stored verification criterion. However, such an evaluation result or also the operating state with regard to the operating state criterion can otherwise also be transmitted to the evaluation unit for comparison with the stored values and / or states.

[0043] In an improvement, the oil level monitoring system has a pressure sensor, in particular a pressure sensor which can be arranged on the oil container representing the compressor oil level, by means of which a pressure representing 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.

[0044] The detection of a pressure representing the operating state of the compressor and the taking into account thereof as a verification criterion is associated with the method described with regard to the method. For this purpose, the pressure sensor is preferably arranged on the oil container representing the compressor oil level in order to be able to minimize interference influences with regard to the distance. The oil level in the oil container corresponds to the oil level in the compressor. This is the case, for example, if the oil container is the oil container of the compressor or the oil level of the oil container is connected to the compressor, so that the oil level of the oil container can be used for the specification of the oil level with regard to the compressor. Accordingly, with regard to the oil container, the expression "oil container representing the compressor oil level" is used.

[0045] In particular, the at least one oil level sensor is a float.

[0046] The advantages of the float as oil level sensor are similar to those already derived for the embodiments of the method.

[0047] According to an embodiment, the evaluation unit is configured in such a way that it distinguishes between at least two forwarding criteria and forwards different oil level signals depending on the forwarding criteria.

[0048] For example, a first limit value, which is reached or undershot, corresponding to an oil level of a low oil level, is determined as a first forwarding criterion. A second limit value, which is reached or undershot, corresponding to an oil level of a critical oil level, is determined as a second forwarding criterion. Here, the second limit value is lower than the first limit value. In the event of reaching or undershooting the first limit value and at least one verification criterion assigned to the first forwarding criterion being fulfilled, the evaluation unit forwards, for example, the oil level signal "oil level low" 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 undershoots the second limit value in the case of simultaneously fulfilling the verification criteria assigned to the second limit value, respectively, the evaluation unit forwards, for example, the oil level signal "oil level critical" as a corresponding message to the cab of the rail vehicle and / or to the maintenance device. Alternatively or additionally, the evaluation unit can also forward the oil level signal as a control parameter to the control device of the compressor, so that the power of the compressor can be limited in advance or the operation of the compressor can be stopped completely.

[0049] In another aspect, the application relates to a compressor system having the above-mentioned oil level monitoring system, wherein the compressor system has an oil container representing the compressor oil level, and wherein the at least one oil level sensor is arranged in the oil container, in particular centrally.

[0050] The positioning of the oil level sensor influences the probability of detecting temporary fluctuations of the oil level with respect to the actual oil level, which is present in the oil container. If the float as oil level sensor is arranged, for example, on the edge of the oil container, the oil level fluctuations in the sense of fluid movements on the oil container edge will lead to a greater amplitude and thus to a greater uncertainty in terms of distinguishing between temporary oil level movements and the actual oil level. By means of an as central as possible arrangement, i.e. in a region with a relatively small oil level movement or oil level fluctuation amplitude, it is thus possible to reduce the possible unreliability of the distinction. Via this, it is also possible to reduce the at least one verification criterion to a smaller requirement. Alternatively or additionally, however, the oil container can also be configured as a container which is largely decoupled from fluctuations in order to keep the undesired influence on the oil level detection small. In order to have to decouple the compressor from such fluctuations, it can be provided here that the oil level detection is carried out by means of a separate oil container. The separate oil container, the oil level of which corresponds to the compressor oil level, can be decoupled from the fluctuations as a smaller unit with less outlay.

[0051] In a refinement, the compressor system has a control device to which the oil level signal is forwarded by the evaluation unit, wherein the control device controls the operation of the compressor as a function of the oil level signal.

[0052] As already described with respect to the method and the oil level monitoring system, the compressor can thus be controlled as a function of the oil level signal in order to reduce the oil consumption, for example, or also to completely inhibit an operation which can cause damage at such an oil level, in particular at a critical oil level. The control device can thus switch the compressor, for example, to an operating mode with less oil consumption or bring the compressor to a standstill. BRIEF DESCRIPTION OF DRAWINGS

[0053] The application is explained in more detail below with the aid of embodiments with reference to the drawings. The drawings show in detail:

[0054] Figure 1 is a schematic diagram of an oil level monitoring system according to an exemplary embodiment of the application.

[0055] Figure 2 shows a flowchart of a method for oil level monitoring according to a first method design.

[0056] Figure 3 shows a flowchart of a method for oil level monitoring according to a second method design.

[0057] Figure 4 shows a flowchart of a method for oil level monitoring according to a third method design. DETAILED DESCRIPTION

[0058] Figure 1 An oil level monitoring system 1 is shown for carrying out a method for monitoring the oil level of an oil-lubricated compressor by means of oil level monitoring of an oil-lubricated compressor for a rail vehicle, as it can also be used in the method designs shown in Figures 2 to 4 The oil level monitoring system 1 comprises an oil level sensor 20 which is arranged in an oil container 20 which represents the oil level of the oil-lubricated compressor. The oil level sensor 20 is configured as a float here. Furthermore, the oil level monitoring system 1 has an evaluation unit 30 which is connected signal-technically to the oil level sensor 21 by means of a signal line 40. The signal-technical connection can also be configured by means of a wireless transmission. In the embodiment shown, not only the sensor signal of the oil level sensor 21 but also the sensor signal of a pressure sensor 22 which is arranged on the oil container 20 in order to be able to deduce the operating state of the compressor from the pressure detected is supplied to the evaluation unit 30. The signal-technical connection is exemplarily realized by means of a further signal line 40 here.

[0059] Furthermore, in Figure 1The low oil level 10a is indicated by a dashed line. The dotted line 10b represents a critical state 10b. According to the illustrated diagram of the oil level sensor 21, the oil 10 in the oil container 20 has a low oil level 10a. The forwarding criterion is therefore determined as reaching or falling below the low oil level 10a, which is met in the illustrated state. This is checked by the evaluation unit 30 either by comparing the sensor signal of the oil level sensor 21 with the stored limit value for the forwarding criterion or by the oil level sensor itself delivering a corresponding positive value in the sense of meeting the forwarding criterion. To this end, the oil level sensor can have its own data processing unit. If the oil level sensor 21 is configured digitally, i.e. only ever sends one signal in the case of meeting the forwarding criterion, for example, the application of the sensor signal on the evaluation unit 30 can have sufficient information content.

[0060] However, since the meeting of the forwarding criterion by the read oil level itself is not yet sufficient to reliably state the actual oil level, the evaluation unit 30 additionally checks a predetermined verification criterion. In the illustrated embodiment of the oil level monitoring system 1, the sensor signal of the pressure sensor 22 is used by the evaluation unit, for example, in order to detect whether the compressor is stopped. First, in the case of the sensor signal of the oil level sensor 21 simultaneously meeting the forwarding criterion, the oil level signal is forwarded from the evaluation unit 30 to the bridge 50 via a further signal line 40 with the presentation of a pressure signal meeting the corresponding verification criterion. There, a message "low oil level", for example, is displayed on a corresponding display device. As this is also shown by means of the further figures, the verification criterion is not limited to the operating state criterion which can be checked here by the pressure sensor 21, but can alternatively or additionally, for example, reflect a time criterion or a frequency criterion.

[0061] Figure 2A flow chart of a method for oil level monitoring according to a first method design is shown. Here, the oil level sensor 21 is first read. If the oil level read meets the forwarding criterion "low oil level", that is, reaches or falls below a predetermined limit value corresponding to the forwarding criterion, it is checked whether the defined verification criterion is met. Otherwise, the oil level sensor is read further. In the shown method design, it is first checked upon reading a low oil level whether the time criterion is met. The time criterion here is a continuous measurement of the low oil level, that is, of the oil level meeting the forwarding criterion, within x seconds, that is, within a predetermined or minimum duration. If the time criterion is met, the frequency criterion is checked as a further verification criterion, or otherwise the evaluation is interrupted and the reading of the oil level sensor is continued. According to the frequency criterion check applied here, it is checked whether there are a predetermined number k of successful measurements. The evaluation unit 30 is programmed here such that the evaluation unit recognizes a temporal change in the oil level read over a duration t < x*ms as an oil level measurement error and does not analyze the temporal change. The frequency criterion is considered to be met if the oil level meeting the forwarding criterion, that is, here the low oil level, is read a predetermined number k, for example, five times, within a preset time period. However, the frequency criterion can also be defined such that, in order to meet the frequency criterion, the time criterion must be given successively a certain number of times or within a predetermined time period. If the frequency criterion is met, the oil level signal "low oil level" is forwarded. According to the oil level signal, a corresponding "low oil level" message is displayed, for example, on a display of the driver's cab 50. Alternatively or additionally, the oil level signal can also be forwarded to a maintenance device, which then stores the replenishment of oil in a maintenance protocol for the corresponding compressor as a maintenance work. The maintenance device can also adjust, for example, advance a maintenance time point according to the oil level signal in the design.

[0062] Figure 3A flow chart of a method for oil level monitoring according to a second method design is shown. The second method design differs from the first method design in that two forwarding criteria are distinguished. A first limit value, which is reached or undershot, corresponding to the oil level of a low oil level, is determined as a first forwarding criterion. A second limit value, which is reached or undershot, corresponding to the oil level of a critical oil level, is determined as a second forwarding criterion. Here, the second limit value is lower than the first limit value. In the flow chart shown here for this purpose, two digital oil level sensors 21a, 21b are read. The reading of the first oil level sensor 21a here corresponds to checking the first forwarding criterion, i.e. the low oil level, and the reading of the second oil level sensor 21b corresponds to checking the second forwarding criterion, i.e. the critical oil level. Alternatively, however, an analog oil level sensor can also be read, by means of which both the low oil level and the critical oil level can be detected. Thus, an analog oil level sensor can be used instead of the oil level sensors 21a, 21b. Irrespective of the number of oil level sensors used, it is now first checked whether, depending on the oil level read, a critical oil level is present, i.e. the second limit value is reached or undershot. If no critical oil level is detected, then in the case of a low oil level, i.e. if the first limit value is reached or undershot, the time criterion and the frequency criterion are checked in the same way as in the further method for a low oil level, with the exception that the second forwarding criterion is present. In the exemplary second method design, the time criterion and the frequency criterion of the forwarding criteria "oil level critical" and "oil level low" are identical, apart from the respective limit values and thus the oil levels to be taken into account. In a further method variant, however, the verification criteria can also be defined independently of one another. If the respective time criterion and the frequency criterion are fulfilled in the case of a critical oil level, the oil level signal "oil level critical" is forwarded. This is here, for example, also forwarded to the bridge 50 for display. In addition, the oil level signal can also be forwarded to the control device of the compressor in order to inhibit the continued operation of the compressor or to switch to another operating mode in this case. Figure 3 The further method flow shown in Figure 2 corresponds to the first method design according to If a critical oil level is detected depending on the oil level read by the oil level sensor 21b, then in analogy to the further method for a low oil level, apart from the second forwarding criterion, the time criterion and the frequency criterion are also checked. In the exemplary second method design, the time criterion and the frequency criterion of the forwarding criteria "oil level critical" and "oil level low" are identical, apart from the respective limit values and thus the oil levels to be taken into account. In a further method variant, however, the verification criteria can also be defined independently of one another. If the respective time criterion and the frequency criterion are fulfilled in the case of a critical oil level, the oil level signal "oil level critical" is forwarded. This is here, for example, also forwarded to the bridge 50 for display. In addition, the oil level signal can also be forwarded to the control device of the compressor in order to inhibit the continued operation of the compressor or to switch to another operating mode in this case.

[0063] Figure 4 A flow chart of a method for oil level monitoring according to a third method design is shown. The third method design according to Figure 4 corresponds to the first method design according to Figure 3The second method design differs. The pressure to be checked corresponds to a running state criterion as a further verification criterion. For example, a nominal range is defined as the pressure range in the presence of a compressor standstill. Only if the reading pressure of the pressure sensor 22 lies in the predetermined nominal range, the oil level monitoring is continued according to the second method design. In other words, the fulfillment of the running state criterion is a prerequisite for the continuation of the check of the forwarding criterion and the result of the respective time criterion and the respective frequency criterion. If the pressure lies outside the preset nominal range, the sensor value is continued to be read until the running state criterion corresponding to the pressure is fulfilled.

[0064] The application is not limited to the described embodiments. Even if the running state criterion is checked exemplarily by means of a pressure measurement, for example in the third method design, the individual running states of the compressor can be forwarded to the evaluation unit 30 by the control device of the compressor and evaluated accordingly. Furthermore, the evaluation unit 30 can also be part of the control device of the compressor.

[0065] List of reference signs

[0066] 1 oil level monitoring system

[0067] 10 oil

[0068] 10a low oil level

[0069] 10b critical oil level

[0070] 20 oil container

[0071] 21, 21a, 21b oil level sensor

[0072] 22 pressure sensor

[0073] 30 evaluation unit

[0074] 40 signal line

[0075] 50 bridge

Claims

1. A method for monitoring the oil level in an oil-lubricated compressor, the method comprising the following steps: - Read at least one oil level sensor (21, 21a, 21b) to detect the oil level representing the compressor oil level. - Check whether at least one preset verification criterion is met for verifying the read oil level, and - If the read oil level meets at least one forwarding criterion (10a, 10b) based on reaching or falling below a predetermined oil level and also meets the at least one verification criterion, then forward the oil level signal; The verification criteria correspond to at least one time criterion, frequency criterion, and / or operating status criterion. In the at least one time criterion, the oil level corresponding to the forwarding criteria (10a, 10b) is read at least at a predetermined frequency over a predetermined time period (x). In the frequency criterion, there are a predetermined number (k) of individual reading processes that satisfy the forwarding criteria (10a, 10b). In the operating status criterion, a predetermined operating status is determined.

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

3. The method according to claim 1, wherein, The pressure sensor (22) is read in order to determine the intended operating state.

4. The method according to any one of claims 1 to 3, wherein, Before checking the preset verification criteria, the reading step of the at least one oil level sensor (21, 21a, 21b) is performed.

5. The method according to any one of claims 1 to 3, wherein, Read the data from the two oil level sensors.

6. The method according to any one of claims 1 to 3, wherein, The floats are used as oil level sensors (21, 21a, 21b).

7. The method according to any one of claims 1 to 3, wherein, According to the forwarding standards (10a, 10b), the oil level signal is forwarded as a message to the monitoring unit (50), and / or the oil level signal is forwarded as a control parameter for the compressor control device.

8. The method according to any one of claims 1 to 3, wherein, According to the aforementioned forwarding standards (10a, 10b), the oil level signal is forwarded as a message to the driver's console and / or to the control and / or maintenance devices.

9. The method according to any one of claims 1 to 3, wherein, The method is performed during a shutdown of the oil-lubricated compressor.

10. An oil level monitoring system (1) for performing the method according to any one of claims 1 to 9, the oil level monitoring system comprising: - At least one oil level sensor (21, 21a, 21b) for detecting the oil level (10) in the oil container (20) of the compressor, said oil level representing the compressor oil level; and - An evaluation unit (30) for reading sensor signals from at least one oil level sensor (21, 21a, 21b), wherein the evaluation unit stores at least one forwarding standard (10a, 10b) and at least one verification standard. in, The evaluation unit (30) is configured to forward the oil level signal when the oil level read satisfies at least one forwarding criterion (10a, 10b) and at least one verification criterion. The verification criteria correspond to at least one time criterion, frequency criterion, and / or operating status criterion. In the at least one time criterion, the oil level corresponding to the forwarding criteria (10a, 10b) is read at least at a predetermined frequency over a predetermined time period (x). In the frequency criterion, there are a predetermined number (k) of individual reading processes that satisfy the forwarding criteria (10a, 10b). In the operating status criterion, a predetermined operating status is determined.

11. The oil level monitoring system (1) according to claim 10, wherein, The oil level monitoring system (1) has a pressure sensor (22) that can detect the pressure representing the operating status of the compressor, and the evaluation unit (30) considers the detected pressure as a verification standard at least.

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

13. The oil level monitoring system (1) according to claim 10 or 11, wherein, The evaluation unit (30) is configured such that it distinguishes at least two forwarding standards (10a, 10b) and forwards different oil level signals according to each of the forwarding standards (10a, 10b).

14. The oil level monitoring system (1) according to claim 11, wherein, The pressure sensor (22) can be placed on the oil container (20) that represents the compressor oil level.

15. A compressor system having an oil level monitoring system (1) according to any one of claims 10 to 14, the compressor system having an oil container (20) representing the compressor oil level, wherein, The at least one oil level sensor (21, 21a, 21b) is arranged in the oil container (20).

16. The compressor system according to claim 15, wherein, The at least one oil level sensor (21, 21a, 21b) is centrally located in the oil container (20).

17. The compressor system according to claim 15 or 16, wherein, The compressor system has a control device, and the oil level signal is forwarded to the control device through the evaluation unit (30), and the control device controls the operation of the compressor according to the oil level signal.

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