DE102020128686A1 - Oil mist detector and method for checking the functionality of an oil mist detector - Google Patents

Abstract

In summary, to improve the reliability of the optical detection of fine oil mist (2) using an oil mist detector (1), it is proposed that a test gas be fed into an interior space (4) by means of a test gas feed (41) provided or at least controlled by the oil mist detector (1). is flushed in and then a gas sample of the test gas is removed from the interior (4) again through a gas sampling device (29) of the oil mist detector (1) in order to measure it optically with the aid of the oil mist detector (1). The test gas preferably follows a flow path to an optical measuring chamber (5) of the oil mist detector (1), which a gas sample takes from the interior (4) in normal operation of the oil mist detector (1), starting from an intake opening (8).

Description

The invention relates to an oil mist detector for detecting and/or analyzing oil-air mixtures. Such mixtures can exist as a potentially explosive mixture or as a (also sub-explosive) mixture with a characterized mixing ratio. These mixtures, which often take the form of dispersions of fine oil droplets in air, are also known as oil mist or aerosols.

For the detection and/or analysis of the oil-air mixture, in particular potentially explosive fine oil mist, the oil mist detector has a measuring chamber that forms at least one optical measuring section for the optical detection of an oil mist. With the help of the measuring chamber, the oil mist detector can thus detect potentially explosive mixtures or oil mist, issue a corresponding warning signal and thus ensure increased operational safety.

In particular, the oil mist detector can be designed in such a way that it can be used in a crankcase of a piston machine (such as an internal combustion engine or a compressor) in order to be able to detect fine oil droplets arising in the crankcase at an early stage, since these can form an explosive mixture with air in the Crank space can form.

Furthermore, the invention relates to a method for checking the function of such an oil mist detector.

The detection and analysis of oil droplets in air using light is generally known. In particular, oil mist detectors are known which can detect oil mist as described above by means of transmitted light and/or scattered light measurements.

The formation or detection of small oil droplets within a monitored space such as an engine compartment is relevant in that the presence of such oil droplets indicates that an engine failure is to be expected in the near future. In the worst case, it can happen that the oil droplets ignite on surfaces heated by friction or other sources of ignition, thus triggering an explosion in the monitored room. Similar dangers also occur, for example, in systems in the process industry, and here too an oil mist detector according to the invention can be used to monitor a room.

A distinction can be made between mechanically generated oil mist, which consists of relatively large oil droplets with a diameter of 50 µm or more, and fine oil mist, which is caused by evaporation due to hot surfaces or in some other way, with this type of mist typically having a droplet size of less than 10 microns, for example from 1-5 microns. These small droplets are very dangerous as they can form potentially explosive mixtures, particularly easily in air.

In typical application situations, however, both these small droplets and the large oil droplets form and together form an inhomogeneous oil-air mixture that must be examined optically.

Against this background, the invention has set itself the task of making the detection of such potentially explosive oil-air mixtures more reliable with the aid of an oil mist detector, in particular when they occur in internal combustion engines. In particular, the invention is intended to ensure that the oil mist detector is functioning correctly and to make it easy to check.

To solve this problem, the features of claim 1 are provided according to the invention in an oil mist detector. In particular, it is therefore proposed according to the invention to solve the problem with an oil mist detector of the type mentioned at the outset that the oil mist detector is set up for insertion into a housing that delimits an interior space and is set up to introduce a test gas from the outside into the interior space. This controlled introduction can be done, for example, by switching a test gas inlet valve of the test gas supply. This means that the oil mist detector can be set up in particular to regulate a test gas flow through the test gas feed. The interior can thus in particular be a room that is monitored by the oil mist detector (“monitored room”).

In this case, for easy retrofitting of the oil mist detector, it is preferable if the oil mist detector forms a test gas feed. By manually and/or automatically controlling the test gas supply, the oil mist detector can introduce a test gas into the interior from the outside, in particular through the housing. As a result, an artificial test gas atmosphere can be created in the interior and this can then be measured optically with the oil mist detector as a test.

In other words, the oil mist detector can thus be set up to automatically, esp especially as part of a test operation, to supply a test gas to the interior via the test gas supply. The oil mist detector can then pick up this test gas again and measure it optically, in particular to carry out a self-test.

However, the injection of test gas is primarily used to test the safety monitoring function. The operator should be able to bring this in at any time, even without the system being informed. For example, the entire signal chain - including outside of the oil mist detector - of the triggered alarm can be checked.

The advantage here is that the oil mist detector can optically measure the test gas introduced by it into the interior for test purposes in order to check the correct functioning of the optical detection taking place in the measuring chamber. The oil mist detector can thus check its own correct functioning independently, in particular automatically, by means of an optical test gas measurement.

According to a preferred embodiment, the measuring chamber is arranged outside of the interior when the oil mist detector is inserted into said housing, preferably in a sealed manner. Because this is advantageous in order to service the measuring chamber, in particular to clean it, without having to remove the oil mist detector from the housing for this purpose.

The oil mist detector preferably also has its own gas conveying device for actively taking gas samples from the interior. Because this makes it possible to easily retrofit the oil mist detector to existing combustion engines. The gas delivery device can preferably be designed as an electric gas delivery pump, in particular configured as a suction pump.

Alternatively, the oil mist detector can also be based on a working principle that does not require a gas conveying device. The working principle can, for example, be based on diffusion or be otherwise passive. In this case, too, it is advantageous to be able to add a test gas via an access opening to the crank chamber, which is necessary for the measurement anyway.

Furthermore, the oil mist detector can have a gas extraction device, which is led through an opening in the housing into the interior when the oil mist detector is inserted into the housing. In other words, the oil mist detector can thus have a gas extraction device which is set up to extract gas samples from the interior and through the housing. With the gas sampling device and the gas conveying device, gas samples can thus be taken from the interior and conveyed into the measuring chamber, which is preferably arranged outside the interior, in order to be measured there.

As will be explained in more detail, it is crucial for a high level of functional reliability of the subsequent normal measurement of gas samples from the interior using the oil mist detector that the gas sample of the test gas travels the same distance from the interior into the measuring chamber as one does in normal operation gas sample from the interior examined with the oil mist detector. It is therefore preferable if, during the test gas measurement, the respective (test) gas sample always passes the gas extraction device of the oil mist detector and is conveyed into the measuring chamber by the gas delivery device.

In addition, the oil mist detector then does not have to be removed for a function test as described above using a test gas sample, but a test of the correct functioning of the oil mist detector can be carried out when it is installed (in the housing).

In other words, the invention thus proposes that, in order to achieve the object mentioned at the outset, the oil mist detector is set up to introduce a test gas from the outside into said interior space by means of the test gas supply, in order to then supply a sample of this test gas through the gas extraction device of the oil mist detector using the gas conveying device removed and optically measured in the measuring chamber.

In normal operation of the oil mist detector, on the other hand, gas samples of a gas atmosphere present or just emerging in the interior, i.e. in particular an oil mist occurring in the interior, can be taken by the gas sampling device with the aid of the gas delivery device and fed to the measuring chamber for optical measurement.

The test gas supply line is preferably designed on the oil mist detector in such a way that, when the oil mist detector is inserted into the housing, it is routed through the opening into the interior, through which the gas extraction device is also routed. In other words, it can preferably be provided that the test gas supply is designed as a single compact unit together with the other components of the oil mist detector. This assembly can be used in said housing, with compo nents how the measuring chamber can be arranged outside the housing / the interior.

For ease of assembly, it is particularly preferable if the test gas supply is integrated into the gas extraction device explained above.

In yet other configurations, depending on the application, it can be advantageous to arrange the test gas feed separately from the rest of the oil mist detector. In this case, the oil mist detector can, for example, only access the test gas supply in a controlling manner, for example via a corresponding control line, in order to initiate the flow of the test gas into the interior. In this case, the test gas supply and said gas extraction device can be guided into the interior at different points.

In both cases - integration of the test gas supply into the gas extraction device or separate design - it is of great advantage for a high level of reliability of the functional test of the oil mist detector if the test gas supply is designed in such a way that in a test measurement operation the test gas sample follows the same path from the interior to travels to the measuring chamber like a gas sample, which is taken from the interior by the oil mist detector during normal measuring operation and optically measured. This path can run through the gas extraction device. This approach ensures that the functioning of the oil mist detector is checked, which is relevant for the actual subsequent measurement task. For example, a blockage within the gas sampling device can be detected using the test gas and not just the correct functioning of the optical measurement in the measuring chamber.

The gas extraction device can be designed, for example, in the form of an intake pipe or hose and/or preferably protrude into the interior in the installation situation. As a result, a gas sample can be taken with the gas sampling device precisely at a desired point within the interior.

Due to the test gas supply when the oil mist detector is installed in the housing, the gas sampling device of the oil mist detector can thus be used to take gas samples from both a gas atmosphere in the interior and gas samples from the test gas fed into the interior via the test gas supply and from the interior and to the measuring chamber. These gas samples can then be measured optically in the measuring chamber. As a result, a safety check of the correct functioning of the oil mist detector can be carried out at continuous intervals, particularly during ongoing operation, with the aid of the test gas, as will be explained in more detail with regard to the method according to the invention.

A particularly suitable application of such an oil mist detector provides that the oil mist detector is set up for insertion into a crankcase housing, which delimits a crankcase of an internal combustion engine. As a result, the formation of fine oil mist in the crankcase can be monitored in real time with practically no time delay (for example, except for a constant time delay between the actual condition in the crankcase and the measured value representing the condition of about one second). In this case, the gas sampling device can be guided through an opening in the crankcase into the crankcase, in particular protrude into the crankcase when the oil mist detector is inserted into the crankcase. The ability to early detect oil droplets forming in the crankcase with the oil mist detector is important because these oil droplets can form a potentially explosive mixture with air.

• So schlägt eine besonders bevorzugte Ausgestaltung zur Erhöhung der Sicherheit des Betriebs des Ölnebeldetektors vor, dass der Ölnebeldetektor dazu eingerichtet ist, einen Selbsttest seiner Funktionsweise auf Basis einer an einer Gasprobe des Testgases vorgenommenen optischen Messung in der Messkammer auszuführen. Hierbei ist es bevorzugt, wenn der Ölnebeldetektor zusätzlich zur Ausgabe eines Benutzerhinweises eingerichtet ist, welcher das Ergebnis des Selbsttests wiedergibt. Ein Benutzer kann dann nämlich anhand des Benutzerhinweises entscheiden, ob der Ölnebeldetektor noch sicher arbeitet oder aber ausgetauscht / gewartet werden muss.

According to the invention, the object can also be achieved by further advantageous embodiments:

• A particularly preferred embodiment to increase the reliability of the operation of the oil mist detector proposes that the oil mist detector be set up to carry out a self-test of its functioning based on an optical measurement made on a gas sample of the test gas in the measuring chamber. In this case, it is preferred if the oil mist detector is additionally set up to output user information, which reflects the result of the self-test. A user can then use the user information to decide whether the oil mist detector is still working reliably or whether it needs to be replaced/maintained.

Put simply, the oil mist detector can thus independently check whether the measuring chamber detects test gas as soon as this is introduced into the interior via the test gas supply. If this is the case, the result of the self-test is positive because the test gas must have been transported properly from the interior into the measuring chamber by the gas delivery device. Such a self-test can thus be used to check whether the gas extraction device and/or the gas delivery device and/or the measuring chamber is/are working properly.

The measuring chamber is preferably connected to an intake duct. The intake channel can open into an intake opening. The suction opening can in turn be formed by the gas extraction device and/or can be arranged in the interior when installed.

According to a preferred embodiment, the intake opening is thus located inside the interior, ie in particular inside the crank chamber described above, when the oil mist detector is inserted into said housing, in particular into said crank chamber housing.

The measuring chamber, in turn, can preferably be arranged outside of the interior space/crank space. This is advantageous, for example, in order to ensure the requirements for temperature stability of the optical measurement.

Gas samples can thus be conducted from the interior through the housing into the measuring chamber by means of the intake channel.

In order to enable a test gas measurement that comes as close as possible to an actual measurement, it is advantageous if the test gas supply ends in the area of the suction opening, preferably in the immediate vicinity of the suction opening. This is because a test gas, which is supplied via the test gas supply into the interior/crank space, can be removed from the interior/crank space through the intake opening.

In particular, this means that when the oil mist detector is installed in the housing/crankcase, a test gas introduced via the test gas supply follows the same path into the measuring chamber, which takes a gas sample that is taken by the oil mist detector in normal operation from the interior/crankcase by means of the Gas sampling device is removed.

With the oil mist detector designed according to the invention and by means of the test gas, it can thus be checked whether the sampling device can forward test gas from the crank interior to the measuring chamber. Because, for example, if the gas sampling device is partially closed, it can happen that the measurement results of the oil mist detector deny a detection of fine oil mist, although such is currently occurring in the interior. Such incorrect measurement results can be avoided by regularly carrying out test gas measurements. In this case, the test gas can be selected in such a way that when the oil mist detector is functioning properly, ie in particular when the gas extraction device is functioning properly, the oil mist detector can optically detect the presence of the test gas in the measuring chamber. As a result, conclusions can be drawn that the test gas was properly conveyed from the gas conveying device through the gas sampling device into the measuring chamber.

It is also possible to detect unsuitable installation positions. This is due to the fact that there are areas in the crankcase where significant amounts of splash oil from the plain bearings accumulate, so-called "oil discs". The splashing oil can negatively affect the measurement accuracy through the sampling device. Since the invention enables a test to be carried out during normal operation without the engine having to be stopped, it is also possible to detect an inoperability or reduced operability due to an unsuitable installation position, which would first become apparent during operation.

Another particularly preferred, because it is robust, embodiment provides that the gas extraction device has a first channel for supplying a stream of test gas (test gas stream) into the interior/crankcase, in particular to the intake opening, and a second channel for removing a gas sample from the interior/crankcase into the measuring chamber. In such a configuration, it is preferable if the second channel connects the suction opening to the measuring chamber and/or forms the suction channel explained above.

Furthermore, it can be advantageous if the first and the second channel are formed together. For example, a single duct can first be used as a supply line for the test gas into the interior and then as a discharge duct to discharge the test gas from the interior—like a normal gas sample in normal operation—and conduct it to the measuring chamber. Provision can also be made here for the gas sample to reach the measuring chamber as a result of turbulence in the crankcase or as a result of diffusion.

However, the first channel is preferably separated from the second channel, for example by means of a partition. In this case, a continuous flow of test gas can be conducted into the interior via the first channel, while the test gas is conducted from the interior into the measuring chamber by means of the second channel in order to be measured there.

Provision can also be made for the first channel to open into the second channel, preferably at a distance from an intake opening, for example the one already mentioned. A space-saving configuration can thus be provided.

In one embodiment of the invention, it can be provided that a return duct is formed, with which the measurement gas taken via the intake duct is returned to the crank chamber. This means that the sample gas cannot escape from the monitored area. In this case, the first channel can, for example, be designed completely or partially separately from the return channel or correspond to it.

However, it is particularly favorable if the first channel and the second channel are formed completely separately. This enables a functional test of the entire second channel and thus a full functional test of the oil mist detector. It is particularly favorable here if a suction opening of the second channel is arranged at an end (distal or facing away from the measuring chamber) of the first channel than at a return opening of a return channel. A (desired) fluidic short circuit between the first channel and the second channel can thus be achieved, which should be avoided during normal operation between the second channel and the return channel in order to detect the gas actually present in the crankcase.

Furthermore, it can be advantageous in certain applications if the test gas supply, i.e. in particular the gas sampling device explained above, if the test gas supply is integrated into it, has an outer diameter that can be guided through a ¾ inch thread. In this case, existing systems can be converted particularly easily in order to be able to use the advantages of the invention.

In order to achieve the above object, the features of the independent method claim are also provided according to the invention. In order to achieve the object of a method for checking the function of an oil mist detector of the type described above, it is therefore proposed according to the invention that the oil mist detector introduces a test gas in a controlled manner into an interior monitored by the oil mist detector, in particular by activating an inlet valve of a test gas feed. This monitored interior can in particular be the interior/crank space described above.

In addition, the oil mist detector can form the test gas supply itself, as has already been explained, which makes retrofitting much easier, since no separate test gas supply is designed and therefore no major adjustments have to be made.

Furthermore, it can be provided that a gas sample of the test gas is taken from the interior by means of a gas delivery device provided by the oil mist detector and that the gas sample is then optically measured by the oil mist detector in the measuring chamber in a test measurement. As a result, the advantages of the invention described above can be realized.

The correct functioning of the oil mist detector can then preferably be checked on the basis of a measurement result from this test measurement, particularly preferably by the oil mist detector itself. Because, as already described above, this can output a corresponding user message. This allows the oil mist detector to inform the user of the functional check result.

It is therefore particularly favorable if an oil mist detector according to the invention, in particular as described above or according to one of the protection claims directed to an oil mist detector, is used in the method according to the invention.

A further development of this method provides that a gas sample of the test gas is conveyed by means of the gas delivery device of the oil mist detector through a gas sampling device of the oil mist detector into the measuring chamber, with gas samples passing through this gas sampling device from the interior into the measuring chamber during normal operation of the oil mist detector. As a result, not only the correct functioning of the measuring chamber and/or the gas delivery device, but also the correct passage of gas samples through the gas sampling device can be checked with the aid of the test gas measurement.

It is preferred here if the test gas is flushed into the interior through the test gas supply during a test measurement at a predetermined volume rate. The test result can then be determined depending on whether a minimum quantity/minimum concentration of test gas can be detected in the measuring chamber. This is because it can be checked whether the gas extraction device allows a minimum volume flow of test gas to pass.

The invention will now be described in more detail using an exemplary embodiment, but is not limited to this exemplary embodiment. Further developments of the invention can be obtained from the following description of a preferred exemplary embodiment in conjunction with the general description, the claims and the drawings.

In the following description, elements that have the same function are given the same reference numbers even if their design or shape differs.

• 1 einen erfindungsgemäßen Ölnebeldetektor mit demontiertem Gehäuse, wobei die sonst im Gehäuse verbauten Leiterplatten und deren Befestigung nicht dargestellt sind,
• 2 den Ölnebeldetektor aus 1 mit aufgesetztem Gehäuse,
• 3 eine Gasfördervorrichtung des Ölnebeldetektors aus 1 in Form einer Ansaugpumpe in ausgebautem Zustand (vgl. 1, rechte Darstellung),
• 4 den Ölnebeldetektor aus 2 eingesetzt in ein Kurbelraumgehäuse eines Verbrennungsmotors,
• 5 eine Gasentnahmevorrichtung des Ölnebeldetektors aus 1 und 2 betrachtet von schräg oben,
• 6 die Gasentnahmevorrichtung aus 5 betrachtet von schräg unten,
• 7 eine frontale Ansicht von vorne auf die Gasentnahmevorrichtung aus 5,
• 8 einen Längsschnitt durch die Gasentnahmevorrichtung aus 5,
• 9 eine Ansicht von schräg vorne auf die Vorderseite des Ölnebeldetektors aus 1 mit abgesetztem Gehäuse, ohne Leiterplatten und bei abgenommener Gasentnahmevorrichtung,
• 10 eine Ansicht von schräg hinten auf die Rückseite des Ölnebeldetektors aus 9,
• 11 eine Draufsicht auf die Vorderseite des Ölnebeldetektors bei abgenommenem Deckel,
• 12 eine Seitenansicht von unten auf den Ölnebeldetektor mit abgesetztem Gehäuse,
• 13 eine Draufsicht auf die Rückseite des Ölnebeldetektors, mit einer Detailansicht in einer tieferen Ebene (schraffierte Flächen),
• 14 die Detailansicht aus 13 in einer vergrößerten Darstellung mit einer Illustration verschiedener Teilgasströme und einer weiteren vergrößerten Detailansicht der Gasströmungen im Bereich des Bypasses und der Messkammer.
• 15 den Ölnebeldetektor aus 2 mit abgenommenem Spannelement,
• 16 eine Seitenansicht des Ölnebeldetektors aus 2 mit einer teilweisen Schnittansicht im Bereich der Gasfördervorrichtung,
• 17 die Gasfördervorrichtung aus 3 in einer Schnittdarstellung mit einer gegenüber 3 um 90° um eine Längsachse gedrehten Schnittebene,
• 18 die Gasfördervorrichtung aus 3 und 17 in einer perspektivischen Ansicht von vorne, und
• 19 eine weitere mögliche Ausgestaltung einer Gasentnahmevorrichtung des Ölnebeldetektors.

It shows:

• 1 an oil mist detector according to the invention with the housing dismantled, the printed circuit boards otherwise installed in the housing and their attachment being not shown,
• 2 off the oil mist detector 1 with attached housing,
• 3 a gas delivery device of the oil mist detector 1 in the form of a suction pump when removed (cf. 1 , right illustration),
• 4 off the oil mist detector 2 used in a crankcase of an internal combustion engine,
• 5 a gas sampling device of the oil mist detector 1 and 2 viewed from above,
• 6 the gas extraction device 5 viewed from below,
• 7 a frontal view from the front of the gas extraction device 5 ,
• 8th a longitudinal section through the gas sampling device 5 ,
• 9 an oblique view of the front of the oil mist detector 1 with separate housing, without printed circuit boards and with the gas sampling device removed,
• 10 a rear view of the oil mist detector 9 ,
• 11 a top view of the front of the oil mist detector with the cover removed,
• 12 a side view from below of the oil mist detector with separate housing,
• 13 a top view of the rear of the oil mist detector, with a detailed view at a lower level (shaded areas),
• 14 the detail view 13 in an enlarged representation with an illustration of different partial gas flows and a further enlarged detailed view of the gas flows in the area of the bypass and the measuring chamber.
• 15 off the oil mist detector 2 with removed clamping element,
• 16 shows a side view of the oil mist detector 2 with a partial sectional view in the area of the gas conveying device,
• 17 the gas delivery device 3 in a sectional view with a opposite 3 cutting plane rotated by 90° around a longitudinal axis,
• 18 the gas delivery device 3 and 17 in a perspective view from the front, and
• 19 another possible embodiment of a gas sampling device of the oil mist detector.

the 2 shows an oil mist detector according to the invention with attached housing, while 1 shows the oil mist detector with separate housing and without printed circuit board(s), once with the gas delivery device 27 installed (left) and once with the gas delivery device 27 removed (right).

As in 4 is illustrated, the oil mist detector 1 is for insertion into a crankcase 3 of a (in 4 not illustrated in more detail) configured as an internal combustion engine designed piston machine. For this purpose, the oil mist detector 1 has a gas sampling device 29 on a measuring part 70 (cf 4 ), which can be passed through the crankcase housing 3 into the crankcase 4 of the internal combustion engine in order to be able to take a gas sample there. The measuring part 70 remains outside of the crankcase 4, which is monitored with the oil mist detector 1.

Like in the 15 illustrated, the gas extraction device 29 is designed to be removable in order to be able to clean it. By means of an interface 58 formed on the housing 39 of the oil mist detector (cf 9 ) and a separate clamping element 63 (cf 2 and 15 ) the gas extraction device 29 can be mounted securely and sealingly on the oil mist detector 1.

The particular advantage of this approach is that the oil mist detector 1, i.e. in particular the 11 shown measuring chamber 5 and in 1 and 3 shown gas delivery device 27 of the oil mist detector 1, are accessible from the outside. In addition, the oil mist detector 1 can be detached while the gas extraction device 29 remains inserted in the crankcase 3.

The gas conveying device 27 of the oil mist detector 1, which is shown in 4 The installation situation shown is arranged on the outside in relation to the crank chamber 4, is used to take gas samples from the crank chamber 4. With the help of the gas conveying device 27, which is designed as a motor-driven gas conveying pump 28, as in 3 can be seen, the oil mist detector 1 can thus a gas sample depending on Actively remove measurement requirements from the crankcase 4. The gas sample is passed through the in 4 ring-shaped intake opening 8 of the gas extraction device 29 to be recognized and sucked in through an intake channel 7 configured in an intake pipe 30 of the gas extraction device 29, which in 8th is illustrated in more detail, from the crankcase 4 through the crankcase housing 3 and into a measuring chamber 5 of the oil mist detector 1 which is arranged outside of the crankcase 4 and which in 9 you can see.

A return flow 65 is returned to the crank chamber 4 through a return channel 67 via a return opening 66 . In this case, the return opening 66 faces away from the suction opening 8 in order to avoid a fluidic short circuit, ie the direct suction of the gas that emerges from the return opening 66 .

As the 3 and 13 show, the gas feed pump 28 for conveying the gas flow 13 has a fan blade arrangement 31 which is driven by an electric drive motor 32 . The gas feed pump 28 thus forms a radial fan together with a wall 68 of the receptacle 37 . The gas feed pump 28 is also designed as a suction pump, since it is placed downstream of the junction 24 for gas and thus sucks in the gas flow 13 through the gas extraction device 29 from the crankcase 4 . This is advantageous since the gas flow 13 only comes into contact with the fan blade arrangement 31 after it has passed the measuring chamber 5 . This can prevent the size distribution of the oil droplets from being falsified by an interaction with the rotating fan blade arrangement 31 .

This approach makes it possible to optically detect an oil mist 2 arising in the crankcase 4 , ie an aerosol of extremely fine oil droplets, with the oil mist detector 1 . This is because the oil mist 2 can be conveyed into the measuring chamber 5 as part of the gas sample using the gas sampling device 29 and can be optically measured there. The formation of fine oil mist 2 in the crankcase 4 can thus be monitored with the oil mist detector 1 .

For this purpose, in the measuring chamber 5 of the oil mist detector 1, as shown in the detailed view of 13 is clearly visible, an optical measuring section 6 for the optical detection of the oil mist 2 conveyed into the measuring chamber 5 is formed. More precisely, the measuring chamber 5 has an optical measuring arrangement 44 . This includes light sources 45 in the form of LEDs and light detectors 46 in the form of photodiodes and is set up to carry out a transmitted light measurement and a scattered light measurement on the gas sample located in the measuring chamber 5 . Because how easy it is in the detailed view of the 13 as can be seen, a first optical measuring section 6 is designed for a first transmitted light measurement, and a second optical measuring section 72 for a second redundant transmitted light measurement of the same gas volume. Besides are like that 14 Illustrated, formed four further optical measuring sections 73, 74, 75 and 76, which are provided for a respective scattered light measurement. All of these six measurement sections 6,72,73,74,75 and 76 can be evaluated simultaneously.

For transmitted light measurement, the optical measuring arrangement 44 comprises a first pair of functions 47 consisting of a light source 45 and a light detector 46, as well as a second such pair of functions 48, which is designed analogously (cf. 13 and 14 ). The light sources 45 and light detectors 46 of the two function pairs 47, 48 are each aligned in such a way that the light source 45 of the first function pair 47 forms the first optical measuring path 6 with the light detector 46 of the second function pair 48, while the light source 45 of the second function pair 48 the light detector 46 of the first pair of functions 47 forms the second optical measurement path 72 . In this case, the two optical measurement paths 6 and 72 run in opposite directions and cover the same measurement path through the measurement chamber 5 . In other words, the first and the second optical measuring section 6 and 72, or the first pair of functions 47 and the second pair of functions 48, thus form a redundant bidirectional measuring pair. The first and the second optical measuring section 6, 72 run in mutually opposite directions and parallel to one another, as can be seen in the view in FIG 14 well recognized.

In 13 and 14 It can also be seen that the two pairs of functions 47, 48 are each structurally designed as a unit. In this case, each of the units is inserted into a respective receptacle 49 of the measuring chamber 5 . In 14 It is also easy to see that the two receptacles 49 of the pairs of functions 47, 48 are opposite one another in such a way that the first and second optical measuring section 6, 72 run through the middle of the measuring chamber 5.

by means of a 14 Illustrated further light detector 52, which forms a line of sight 53 at an angle of more than 10° in relation to the first optical measuring section 6, scattered light, more precisely light which the light source 45 of the left function pair 47 emits and which is scattered back on oil droplets in the measuring chamber 5 will, detect. A second scattered light detector 71 is also formed next to it. This also forms a line of sight that forms an angle of more than 10° with the first optical measuring section 6 . However, this second further light detector receives 71 forward scattered light, which was originally emitted by the light source 45 of the left function pair 47.

In relation to the light source 45 of the second right function pair 48, the first further light detector 52 receives forward-scattered light (measurement section 73) and the second further light detector 71 receives back-scattered light (measurement section 74). Conversely, the light detector 52 receives light scattered backwards from the left light source 45 (measuring section 75) and the light detector 71 receives light scattered forward from the left light source 45 (measuring section 76). In other words, the light detectors 52 and 71 thus form a redundant measurement pair for (multiple) redundant scattered light measurements with forward and backward scattered light.

The second further light detector 71 is thus provided for carrying out a second scattered light measurement, namely using light which the light source 45 of the second function pair 48 emits. This second scattered light measurement is redundant to the first scattered light measurement possible by means of the first further light detector 52 using light which the light source 45 of the first functional pair 47 emits. For example, with respect to light emitted from the left light source 45, the detector 71 can measure forward scattered light and at the same time the other detector 52 can measure forward scattered light from the right light source 45.

In order to be able to benefit from the redundancy provided by the measuring arrangement 44, the oil mist detector 1 has a calculation unit which is set up to evaluate two independent transmitted light measurements using the first and second optical measuring sections 6, 72, in particular simultaneously. A diode-specific contamination is constantly determined and taken into account in later calculations. This function can be used to increase the maintenance/cleaning interval.

Alternatively, or if the contamination is too great, the calculation unit discards measurement results if the measurement signals from the first and second optical measurement sections 6, 72 deviate too greatly from one another.

In other words, the calculation unit thus carries out a plausibility check of the transmitted light measurement using measurement data obtained with the second optical measurement section 72 , specifically in relation to measurement data which were obtained with the first optical measurement section 6 . In addition, the calculation unit can also perform a plausibility check on one of the scattered light measurements in an analogous manner, for example using measurement data obtained with the second scattered light measurement 73/75, specifically in relation to measurement data that were obtained with the first scattered light measurement 74/76 (either for forward or backward scattered light).

The calculation unit, which is designed in the form of an electronics unit, is also set up to calculate light absorption based on the two redundant transmitted light measurements using the optical measuring sections 6 and 72 and a scattered light intensity based on the multiple redundant scattered light measurements (using forward and backward scattered light ) to be determined quantitatively with the aid of the optical measuring sections 73 and 74. From such quantitative measurements, conclusions can be drawn about the concentration of the oil mist 2 in the measuring chamber 5. In particular, it can be determined, at least indirectly, whether the oil mist 2 has oil droplets that can form a potentially explosive oil-air mixture in the monitored space 4 , even if the exact size of the oil droplets remains unknown.

The calculation unit is also able, on the basis of the determined light absorption and the determined scattered light intensity, to distinguish measurement signals that can be assigned to a water content of the gas sample in the measurement chamber 5 from measurement signals that correspond to a proportion of an aerosol of oil droplets, in particular less than 10 μm Diameter that can be assigned to the gas sample. For this purpose, the calculation unit uses the determined scattered light intensity to differentiate between the two measurement signals, which are generated by the water content or the oil-aerosol content.

In order to ensure safe operation of the internal combustion engine (as an example of a piston engine that can be monitored with the oil mist detector 1), the calculation unit emits a corresponding warning signal if it detects the presence of said aerosol of oil droplets on the basis of the determined light absorption and/or the determined scattered light intensity closes. In such a case, the operation of the internal combustion engine can be stopped.

The calculation unit thus implements a method according to the invention for detecting the oil mist 2 in the measuring chamber 5, in which the two measuring sections 6 and 72 are evaluated simultaneously or alternately for a redundant transmitted light measurement, while an additional scattered light measurement is also carried out, either using light from the first measuring section 6 or 72 and one or both of the other light detectors 52 and 71, and the detection of the oil mist 2 is based on the transmitted light measurement and the scattered light measurement.

As already described, the diode-specific contamination is recognized and taken into account in the measurement. This extends maintenance intervals, increases accuracy and/or eliminates false alarms.

In this method, the calculation unit also uses the two other light detectors 52 and 71 simultaneously or alternately in order to make the scattered light measurement redundant. The other optical measuring sections 73 and 74 are used for this, which are 14 are illustrated and which each run at an angle of more than 10° to the first or second measurement section 6/72.

The oil mist detector 1 also has other features that may have their own inventive quality. In order to enable the most accurate possible measurement of the critical small oil droplets with a diameter of less than 10 µm in the measuring chamber 5, these must be separated from larger oil droplets, which may also be in the gas sample or may only be present during the transport of the gas sample due to condensation or agglomeration processes form by the oil mist detector 1 can be separated.

For this purpose it is provided, as can be clearly seen from the 13 and 14 can be understood to form a bypass 11 which guides a first part of the gas flow 13 flowing into the oil mist detector 1 via the gas extraction device 29 as a first partial gas flow 14 past the measuring chamber 5 . This part of the gas sample or the gas flow 13 does not even get into the measuring chamber 5 and does not disturb the optical measurement there.

A closer look at the 13 and 14 shows that the measuring chamber 5 is connected to the previously explained intake channel 7 by means of a gas supply line 9 . The intake channel 7 extends from the intake opening 8 of the gas extraction device 29 in the crankcase 4 (cf. 4 ) along the intake pipe 30 (cf. 8th ) through the in 13 recognizable second suction opening 69 into an antechamber 50 and from there to the gas supply 9 and the bypass 11.

The antechamber 50 serves as a type of calming zone in which turbulence in the gas flow 13 can be reduced. As a result, a first separation of larger oil particles takes place in the antechamber 50 . These can then be fed back into the gas extraction device 29 via the suction opening 69, following gravity, and from there via the in 6 recognizable outflow openings 57 flow back into the interior space 4 (monitored with the oil mist detector 1). Responsible for this calming of the gas flow 13 is the enlarged flow cross section of the antechamber 50 compared to the adjoining section of the intake channel 7.

Furthermore, a gas discharge 10 is designed as a channel for discharging gas from the measuring chamber 5. The gas discharge 10 extends from the measuring chamber 5 to the gas conveying device 27 (cf. 14 ). From there, the recombined gas stream 13 is further through the in 11 , 13 and 14 recognizable first outlet opening 54a in an outlet channel 55 of the gas extraction device 29 (cf 5 and 6 ) and from there on to an openings 54b and 66 arranged in the crankcase 4 - in the installation situation - which in 6 are easy to recognize. The outlet channel 55 also forms two further outflows 57 through which oil can flow back from the oil mist detector 1 into the crankcase 4 (cf. 6 ).

With the help of the oil mist detector 1, a gas flow circuit is thus formed which - driven by the gas conveying device 27 of the oil mist detector 1 - leads from the crankcase 4 through the gas extraction device 29 into the oil mist detector 1 and then again through the gas extraction device 29 - in the example via a separate return channel 67 - back to the crank room 4.

The bypass 11 provided serves to discharge gas from the intake duct 7, bypassing the measuring chamber 5, into the outlet duct 55 and from there back into the crankcase 4. This can be implemented particularly easily if - as shown in the exemplary embodiment of the figures - the bypass 11 connects the gas inlet 9 to the gas outlet 10 .

As can be seen from the illustration of the various gas flows within the oil mist detector 1 14 can be seen, the gas flow 13 flowing in through the gas extraction device 29 is thus divided into the first partial gas flow 14, which flows through the bypass 11, and a remaining partial gas flow 15, which flows through the gas inlet 9 into the measuring chamber 5 and from there into the gas outlet 10 , divided up. Shortly after the bypass 11, these two partial gas flows 14, 15 are then at the in 13 illustrated union point 24 are brought together again before they are conveyed back into the gas extraction device 29 as a common recombined gas stream 13 from the gas conveying device 27 . In order to allow as little turbulence as possible to occur during this combination, the angle between the mean flow direction of the first partial gas flow 14 and the second partial gas flow 15 at the combining point 24 can be less than 60°, for example.

The intake port 7 branches at the in 13 and 14 illustrated branch point 12 thus into the gas supply 9 and the bypass 11. As a result, the first partial gas flow 14, which flows through the intake opening 8 and the intake channel 7, through the bypass 11 and past the measuring chamber 5 into the gas discharge 10.

In contrast, the second, remaining partial gas flow 15 of the gas flow 13 flowing through the intake channel 7 is conducted through the gas supply 9 into the measuring chamber 5 .

The division of the inflowing gas stream 13 into the two partial gas streams 14 and 15 pursues the goal of separating larger oil droplets into the bypass 11 and primarily guiding smaller oil droplets, which are relevant to the risk of explosion, into the measuring chamber 5 so that they can escape there - undisturbed by the larger oil droplets - can be precisely measured.

For this purpose, the gas supply 9 branches at the branching point 12 from the intake port 7, based on the 4 installation situation shown, upwards. As a result, oil droplets entering the measuring chamber 5 must therefore migrate against the force of gravity, which is more likely for smaller oil droplets than for larger oil droplets.

Separating the large oil droplets also has the advantage that contamination of the measuring chamber/diodes is reduced, which considerably extends the maintenance/cleaning intervals. In certain applications, reliable operation of the oil mist detector 1 can be guaranteed for weeks.

In other words, in the installation situation, the gas supply 9 leads the second partial gas flow 15 against the force of gravity and—on closer inspection 14 - Also against a flow direction 16c of the first partial gas flow 14 from the intake port 7 from. This means that the first partial gas flow 14 has predominantly larger oil droplets, in particular with a diameter of at least 10 μm, while the second partial gas flow 15 has predominantly smaller oil droplets with a diameter of less than 10 μm.

In order to improve the separation of the larger oil droplets from the smaller oil droplets, an acceleration section 17 is additionally formed in the intake channel 7 before the branching point 12 (cf. 10 ). As the 14 shows by means of the arrows of different strengths, which represent flow velocities of different magnitudes, the acceleration section 17 is used to accelerate the gas flow 13 along the in 13 illustrated acceleration direction 18 after it has passed the antechamber 50. As a result, the first part of the gas stream 13, which finally reaches the bypass 11, is accelerated in particular.

The acceleration ensures that the larger oil droplets in particular achieve a high level of kinetic energy, so that they initially continue to fly in a straight line until they hit the in 14 illustrated deflection surface 21 meet. The deflection surface 21 forms a kind of catch funnel 22 which collects the heavy oil droplets and directs them into the bypass 11 . For this purpose, the deflection surface 21 assumes an acute angle of less than 90° with the direction of acceleration 18 .

The acceleration section 17 and the bypass 11 thus form an inertial separator which separates heavy oil droplets or other dirt into the bypass 11 and thus prevents them from contaminating the measuring chamber.

The small and therefore lighter oil droplets, on the other hand, can change their direction more easily because they have a comparatively low kinetic energy, and are therefore preferably separated into the gas feed 9 before the deflection surface 21 and thus reach the measuring chamber 5.

Good to see in the 10 and 13 is that the acceleration section 17 forms a rise 19 in the installation situation in the direction of the gas flow 13 . Thus, the heavier oil droplets in the area of the branching point 12 preferably collect on the lower channel floor of the intake channel 7 and migrate along the rise 19 to the bypass 11.

In addition, it is advantageous for efficient separation of the smaller oil droplets if - as in 13 shown, the gas supply 9 at the branch point 12 from the intake port 7, based on the in 4 illustrated installation situation, branches off upwards. For better understanding, it should be mentioned here again that the measuring chamber 5 is the highest in the installation situation (cf. 4 ), so that the gas inlet 9 and the gas outlet 10 open into the measuring chamber 5 from below (cf. 13 ), like a comparison of the 4 , 11 and 13 illustrated. This has the advantage, among other things, that when the gas flow 13 dries up, liquid oil residues that are deposited in the gas inlet 9 and/or the gas outlet 10 can flow back into the intake duct 7 and/or the outlet duct 55 due to the force of gravity and therefore cannot flow back accumulate in the measuring chamber 5. At the in 13 shown embodiment while the oil residues flow due to the heavy force against the illustrated direction of acceleration 18 and against the rise 19.

As in the 11 , 13 and 14 As can be seen, the gas supply 9 thus discharges the second partial gas flow 15 from the gas flow 13 flowing through the intake channel 7 counter to the direction of acceleration 18 and also counter to the direction of the rise 19 . Here the gas supply 9 branches off from the acceleration section 17 at an acute angle relative to the direction of acceleration 18 . Like the flow arrows in 14 To illustrate, this means that the oil droplets that follow the second partial gas flow 15 experience a direction reversal in relation to the original direction of acceleration 18 . However, this reversal of direction is very improbable for heavier oil droplets with high kinetic energy, so that they reach the gas feed 9 less frequently or not at all.

Furthermore, in the 11 , 13 and 14 to see that a flow cross section increases in the direction of the gas supply 9 in the area of the branching point 12 compared to the flow cross section of the adjoining intake port 7, as can be seen from the two double arrows in FIG 13 is illustrated.

In 11 and 13 It can also be seen that an impact surface 20 is formed in the gas flow direction 16a in front of the acceleration section 17 in such a way that the gas flow 13 flowing through the antechamber 50 undergoes a direction reversal 23 at the impact surface 20 before passing through the acceleration section 17. As a result, all the oil droplets experience a change in direction in order to then be accelerated in the direction of acceleration 18 .

The second partial gas flow 15 is conveyed through the measuring chamber 5 with the aid of a Venturi nozzle 25, which is formed by means of a cross-sectional constriction 26 in the area of the bypass 11, as shown in FIG 13 and 14 illustrated. As a result, the second partial gas flow 15 is conveyed through the measuring chamber 5 by means of a pressure difference generated by the Venturi nozzle 25, because as in 14 can be seen from the flow arrows, the gas flow rate is highest in the area of the cross-sectional constriction 26 .

In order to achieve this high flow speed of the first partial gas flow 14 in the area of the bypass 11, the gas supply 9 is designed in comparison to the bypass 11 in such a way that it has a higher flow resistance. This ensures that an average flow rate through the bypass 11 exceeds an average flow rate through the measuring chamber 5 .

Here, the Venturi nozzle 25 interacts with the higher flow resistance in order to generate a stable flow through the measuring chamber 5 .

The device features explained above thus enable a method for the detection and/or analysis of potentially explosive oil-air mixtures in a monitored space 4, in particular in crankcases or other interior spaces of internal combustion engines, compressors and other piston machines, in which a gas sample is taken with the aid of the gas delivery device 27 of the oil mist detector 1 is removed from the monitored space 4 / interior through a suction opening 8 of the oil mist detector 1 arranged in the monitored space 4 / interior. The combustion engine does not have to be specially adapted for this. Because the only requirement for this is that the piston machine, in particular the internal combustion engine or the compressor, offers a passage through which the gas extraction device 29 of the oil mist detector 1 can be guided from the outside into the interior and then sealed.

If a bypass 11 as described above is implemented, the gas sample in the oil mist detector 1 can also be divided into at least two partial gas flows 14, 15, so that a first partial gas flow 14 is guided through the bypass 11, bypassing the measuring chamber 5, while a second, in particular remaining , Partial gas flow 15 is guided through a gas supply 9 into the measuring chamber 5 .

The measures described above can be used to ensure that smaller oil droplets with a diameter of less than 10 µm contained in the gas sample are separated from the first partial gas flow 14 or the inflowing gas flow 13 in such a way that a relative proportion of these smaller Oil droplets in the second partial gas flow 15 is increased compared to a relative proportion of these smaller oil droplets in the gas sample. In other words, the relative proportion of larger oil droplets in the measuring chamber 5 is lower than in the gas sample originally taken from the interior, which is advantageous for a precise measurement of said smaller oil droplets, since the larger oil droplets no longer interfere with the transmitted or scattered light measurements be able.

Coming back again to the optical measuring arrangement 44 explained at the outset, it can be said that in the embodiment of the oil mist detector 1 shown in the figures is: a first pair of functions 47 from a light source 45 and a detector 46 combined to form a first removable structural unit; an opposite second functional pair 48 from a light source 45 and a detector 46 combined to form a second removable structural unit; and two separate scattered light detectors 52 and 71 arranged at a distance from one another, with the two pairs of functions 47, 48 realizing two redundant transmitted light measurements 6, 72 and the two scattered light detectors 52, 71 each realizing a scattered light measurement 73/74 with light which is emitted by one of the pairs of functions 47 / 48 was emitted and scattered on a gas sample located in the measuring chamber 5. In this way, two, in particular two, redundant scattered light measurements can be evaluated simultaneously, and the two opposing transmitted light measurements 6, 72 can also be evaluated simultaneously. It was also explained that a respective line of sight 53 of the respective scattered light detector 52/71 can enclose an angle of at least 10° with a line which connects the first pair of functions 47 to the second pair of functions 48 . This imaginary line forms an axis of the two transmitted light measurements 6 and 72.

In order to improve the measurement reliability and measurement accuracy of an oil mist detector 1 for the detection and/or analysis of potentially explosive oil-air mixtures, it is therefore proposed that the oil mist detector 1 internally has a bypass 11, with which a first partial gas flow 14, which compared to one through an intake opening 8 gas flow 13 sucked in by the oil mist detector 1 has an increased relative proportion of larger oil droplets with a diameter of at least 10 µm, is guided past an optical measuring chamber 5, so that a second, in particular residual, partial gas flow 15, which is measured optically in the measuring chamber 5, primarily has smaller oil droplets of less than 10 µm in diameter. This can increase the safety and accuracy in the detection of these smaller oil droplets with a diameter of less than 10 µm, which can lead to the formation of potentially explosive mixtures. It is also proposed to use a combination of a redundant transmitted light measurement 6, 72 and a multiply redundant scattered light measurement 73/74, 75/76 for the optical detection of the smaller oil droplets. The contamination is reduced by the bypass 11 . This significantly improves security against false alarms, improves measurement accuracy and extends cleaning intervals.

how to get in 1 well recognised, the gas delivery device 27 for actively taking gas samples is integrated into the oil mist detector 1 . The gas delivery device 27, which is designed as an electric gas delivery pump 28 with an electric drive motor 32, has - as 3 to recognize - a fan blade assembly 31 for conveying the gas stream 13 on. This fan blade arrangement 31 is arranged in the intake duct 7 , which in turn is connected to the measuring chamber 5 via the gas discharge 10 . In other words, in the embodiment shown in the figures, the intake duct 7 comprises the gas inlet 9, the gas outlet 10 and also the bypass 11 described above and thus extends from the antechamber 50 to the fan blade arrangement 31.

As in 15 As can be seen, the electric drive motor 32 of the gas feed pump 28 is arranged outside of the intake duct 7 in order to prevent sparks that can arise at the drive motor 32 from leading to a gas explosion within the oil mist detector 1 .

In order to cause as little gas loss as possible from the intake duct 7, a first seal 33a is formed between the fan blade arrangement 31 and the drive motor 32 with the aid of an elastomer ring (cf. 3 ). This seal 33a thus seals off the intake channel 7 from the drive motor 32 . The seal 33a is designed as a shaft sealing ring, which is pushed over the shaft 64, which transmits the drive torque of the drive motor 32 to the fan blade arrangement 31 (cf. 3 and 17 ) .

A clearance 35 is formed in the gas leakage direction behind the gasket 33a (See also 16 ), that is between the seal 33a and the drive motor 32. This intermediate space 35 is formed by a cartridge housing 36 of the gas delivery device 27/the gas delivery pump 28. In addition, the intermediate space 35 is sealed off from the drive motor 32 by means of a further seal 33b (cf 3 and 17 ), which prevents the gas that has passed the first seal 33a, for example due to a defect in the seal 33a, from being able to advance to the drive motor 32. The seal 33b is also designed as a shaft sealing ring, which is pushed over the shaft 64 (cf. 3 and 17 ).

The entire gas delivery device 27/gas delivery pump 28 can be inserted with the cartridge housing 36 into a receptacle 37 provided for this purpose on the oil mist detector 1, as shown in 1 is illustrated. It is also possible to replace the cartridge housing 36 and thus the drive motor 32 without dismantling the oil mist detector 1 and without removing the oil mist detector 1 from the crankcase housing 3, so that the gas delivery device 27 can be serviced particularly easily and quickly.

Since it cannot be ruled out that gas will leak out of the intake channel 7 through the first seal 33a (or a seal 33c) into the intermediate space 35 during operation, this is vented to the outside by means of a vent 34, as in FIGS 17 and 18 can be seen. The ventilation 34 is formed by means of a ventilation opening 38 in the cartridge housing 36, which is designed to correspond to a ventilation opening 60 in the receptacle 37 (cf. 16 and 18 ). The vent opening 60 in turn communicates with the in the 9 , 11 and 15 Vent opening 62 to be seen, which is covered by the clamping element 63 but not closed, so that venting to the environment is realized even when the gas extraction device 29 is attached. Thus, the intermediate space 35 is vented to the outside through the vent openings 38 and 60 when the Gas delivery device 27 is used with the cartridge housing 36 in the receptacle 37.

The cartridge housing 36 thus also forms the ventilation of the intermediate space 35 . Gases that have passed through the first seal 33a (or the seal 33c), starting from the intake channel 7, are thus discharged through the ventilation 34 to the outside into the receptacle 37 and from there into the environment, as indicated by the dashed line in FIG 16 is illustrated. As a result, they do not reach the electric drive motor 32 and the explosion safety is thus guaranteed.

With these precautions, a very reliable method for detecting explosive oil-air mixtures in an interior of an internal combustion engine can thus be implemented with the aid of an oil mist detector 1 . In this case, a gas sample is first taken from the interior with the aid of the gas conveying device 27 , the gas sample being sucked in by means of a fan blade arrangement 31 which is arranged in the intake duct 7 . As a result, the gas sample reaches the measuring chamber 5 of the oil mist detector. Gas from the intake duct 7, which escapes from the intake duct 7 in the direction of the drive motor 32 of the gas conveying device 27, in particular through the first seal 33a (or the seal 33c), is discharged to the outside by means of the previously described vent 34. As a result, an explosive mixture can no longer form in the immediate vicinity of the electric drive motor 32, in particular due to the second seal 33b (or a seal 33d).

In summary, to improve the handling and the operational reliability of an optical oil mist detector 1 for the optical detection of fine oil mist 2, it is proposed that a gas sample to be examined optically be conveyed from the oil mist detector 1 to a measuring chamber 5 by means of an electric gas feed pump 28 and that an electric drive motor 32 of the gas feed pump 28 is decoupled from an intake duct 7 of the oil mist detector 1 by means of an intermediate space 35 that is vented to the outside, through which the gas sample is fed by means of the gas feed pump 28 .

The oil mist detector 1 illustrated in the figures is not only set up for insertion into a housing 3, which delimits an interior space 4, as in 4 illustrated, but also to control a test gas supply 41, so as to introduce a test gas from the outside into the interior 4. As will be explained below, this functionality serves to enable a test measurement, with the aid of which the correct functioning of the oil mist detector 1 can be reliably checked.

• Die Gasentnahmevorrichtung 29 bietet einen ersten Kanal 42, der als Einlasskanal 51 für ein Testgas dient. Indem der Ölnebeldetektor 1 das in den 5, 6 und 8 erkennbare Einlassventil 56 für das Testgas ansteuert, kann der Ölnebeldetektor 1 somit einen (mit Pfeilen in 8 illustrierten) Testgasstrom 59 durch das Einlassventil 56 und den Einlasskanal 51 bis in den Innenraum 4 bewirken. Hierbei endet der Einlasskanal 51 gerade im Bereich der Einlassöffnung 8 der Gasentnahmevorrichtung 29. Dies bewirkt, dass das Testgas durch die Einlassöffnung 8 und einen sich anschließenden zweiten Kanal 43, als Teil des zuvor erläuterten Ansaugkanals 7, strömen kann und damit denselben Weg bis zur Messkammer 5 zurück legt, den eine Gasprobe im normalen Messbetrieb von dem Kurbelinnenraum 4 bis zur Messkammer 5 zurücklegt.

In the example shown in the figures, the oil mist detector 1, more precisely its gas extraction device 29, forms the test gas supply 41 itself, as shown in FIG 8th is clearly visible:

• The gas sampling device 29 offers a first channel 42, which serves as an inlet channel 51 for a test gas. By the oil mist detector 1 in the 5 , 6 and 8th detectable inlet valve 56 for the test gas, the oil mist detector 1 can thus have a (with arrows in 8th illustrated) cause test gas flow 59 through the inlet valve 56 and the inlet channel 51 into the interior 4. In this case, the inlet channel 51 ends precisely in the area of the inlet opening 8 of the gas sampling device 29. This means that the test gas can flow through the inlet opening 8 and a subsequent second channel 43, as part of the intake channel 7 explained above, and thus the same way to the measuring chamber 5 covers the distance covered by a gas sample from the crank interior 4 to the measuring chamber 5 in normal measuring operation.

While the first duct 42 is used to supply a defined test gas flow 5 into the interior 4, the purpose of the second duct 43 is to discharge the test gas sample from the interior 4 into the external measuring chamber 5. The second duct 43 connects the suction opening 8 with the measuring chamber 5 thus also forms the previously explained intake channel 7 . In 8th It can also be seen that the first channel 42 and the second channel 43 are separated by a dividing wall 61 so that test gas can be flushed into the interior space 4 through the test gas supply 41 in particular in continuous operation at a predetermined volume rate.

Because, as already explained, the oil mist detector 1 also has a gas delivery device 27 in the form of an electric gas delivery pump 28 for actively removing gas samples from the interior 4, as well as said gas removal device 29 4 until 8th illustrated gas sampling device 29, which is set up for taking gas samples from the interior 4 and through the housing 3, the test gas flowing through the test gas supply 41 into the interior 4 can thus be removed again and transferred to the measuring chamber 5 for an optical test measurement there to be performed on the test gas. The test gas is sucked in via the gas feed pump 28 in exactly the same way as a gas sample which is taken from the interior 4 with the aid of the gas sampling device 29 in normal operation.

How to look well in the longitudinal section view of the 8th recognizes, the test gas supply line 41 configured by means of the inlet channel 51 and the inlet valve 56 is configured in such a way that in a test measurement mode the test gas travels the same path from the interior 4 to the measurement chamber 5 through the gas extraction device 29 as a gas sample, which in normal measurement mode is removed from the Oil mist detector 1 is removed from the interior 4 and measured optically.

the 19 shows another possible embodiment of the gas sampling device 29, wherein compared to 8th in 19 the test gas stream 59 is directed into the interior 4 from left to right. In contrast to the design according to 8th is in 19 provided that the first channel 42 of the gas extraction device 29 is connected to the suction opening 8 in such a way that the test gas flow 59, after passing through the suction opening 8, takes exactly the same path into the measuring chamber 5 that the gas flow 13 actually to be measured takes in normal operation of the oil mist detector 1 returns. This ensures that the supply of the test gas and the test gas measurement carried out with it checks whether the path from the suction opening 8 to the measuring chamber 5 is completely free.

The design of 19 is thus characterized in that the test gas supply 41, more precisely its first channel 42, is also formed by the suction opening 8. This ensures that the test gas stream 59 , after passing through the suction opening 8 , travels the same path into the measuring chamber 5 as a gas sample which is taken from the monitored interior 4 with the aid of the gas sampling device 29 during normal operation. If, for example, the suction opening 8 is blocked, this can be detected with a test gas measurement. With a configuration as in 8th On the other hand, there is a risk that the test gas flow 59, starting from the first channel 42, can still get into the measuring chamber 5 if the suction opening 8 is blocked. In other words, with an embodiment as in 19 illustrates a higher level of security in terms of checking the functionality of the oil mist detector 1 achievable compared to the embodiment according to FIG 8th , in which a blockage within the second channel 43 (e.g. due to a liquid oil accumulation) can be detected, but not necessarily a blockage of the suction opening 8.

As previously explained, the measuring chamber 5 is connected to the intake duct 7, which - like the 5 , 6 and 8th illustrate - in the suction opening 8, which is located in the installation situation within the interior 4, while the measuring chamber 5 is arranged outside of the interior 4 opens. The test gas supply 41 now opens out in the area of the intake opening 8, as can be seen in 8th well recognized. At the outlet point, the test gas flow thus combines with the previously explained gas flow 13 (or replaces it in test measurement operation), which originates from the area surrounding the suction opening 8 . This configuration has the advantage that test gas fed into the interior 4 via the test gas supply 41, ie in particular the inlet channel 51, can be removed from the interior 4 again with the oil mist detector 1 through the suction opening 8. This means that it can be specifically checked whether the gas sampling device 29 can actually forward a gas sample from the interior 4 to the measuring chamber 5 . In contrast to an only external supply of test gas to the measuring chamber 5, not only the correct functioning of the measuring chamber, but also the correct functioning of the transport of gas samples from the interior through the gas extraction device 29 into the measuring chamber 5 can be checked in the said test mode will. This increases the reliability of the function check.

Due to the fact that the test gas supply 41 is integrated into the gas extraction device 29, only one passage 40 has to be provided in the housing 3. Here, the gas extraction device 29 is designed in such a way that it fits through the opening 40 with a ¾ inch thread. Thus, the measuring arrangement can easily be retrofitted to an existing machine, as such access openings are common.

In addition, the oil mist detector 1 can automatically carry out a self-test of its functioning on the basis of an optical measurement carried out on a gas sample of the test gas in the measuring chamber 5 . The oil mist detector gives 1 also the result of the self-test in the form of a user note and saves this in an internal memory.

With the embodiment of the oil mist detector 1 shown in the figures, a method for checking the function of the oil mist detector 1 can thus be implemented, in which the oil mist detector 1 introduces the test gas into the interior 4 monitored by the oil mist detector 1 by actuating the inlet valve 56 of the test gas feed 41. The oil mist detector 1 then removes test gas from the interior 4 again with the aid of its gas conveying device 27 and then measures it optically in the measuring chamber 5 as part of the previously discussed test measurement. In doing so, the oil mist detector 1 checks its own correct functioning based on a measurement result of this test measurement. For example, the oil mist detector 1 can check whether a minimum quantity/minimum concentration of test gas can be detected in the measuring chamber for a volume rate of the test gas flow 59 set by it. If this is the case, it can be concluded that the gas extraction device 29 allows a minimum volume flow of test gas to pass that is necessary for safe operation.

In this method, the gas delivery device 27 delivers test gas through the gas extraction device 29 into the measuring chamber 5 along the same path along which gas samples from the atmosphere of the interior 4 reach the measuring chamber 5 during normal operation.

In order to improve the reliability of the optical detection of fine oil mist 2 using an oil mist detector 1, it is therefore proposed that a test gas be flushed into an interior space 4 by means of a test gas supply 41 provided or at least controlled by the oil mist detector 1 and then a gas sample of the test gas be passed through a Gas sampling device 29 of the oil mist detector 1 is taken through again from the interior 4 in order to measure it optically with the help of the oil mist detector 1. Here, the test gas preferably follows a flow path up to an optical measuring chamber 5 of the oil mist detector 1 , which a gas sample from the interior 4 takes in normal operation of the oil mist detector 1 starting from an intake opening 8 .

Reference List

1

oil mist detector

2

oil mist

3

Housing (especially crankcase housing)

4

Interior (especially crankcase)

5

measuring chamber

6

optical measuring section

7

intake duct

8th

intake port

9

gas supply

10

gas evacuation

11

bypass

12

branch point

13

gas flow (through 7)

14

first partial gas flow (of 13, is led past 5)

15

second partial gas stream (from 13, enters 5)

16a

Flow Direction (of 13)

16b

Flow Direction (of 13)

16c

Flow Direction (of 13)

16d

Flow Direction (of 13)

16e

Flow Direction (of 13)

17

Acceleration Section (of 7)

18

Acceleration Direction (of 17)

19

rise

20

baffle

21

deflection surface

22

drogue

23

reversal of direction

24

merging office

25

venturi nozzle

26

constriction

27

gas conveying device

28

gas pump

29

gas sampling device

30

intake pipe

31

fan blade assembly

32

Drive Motor (of 27)

33a

(first) seal

33b

(second) seal

33c

poetry

33d

poetry

34

ventilation

35

intermediate space (ventilated from the outside)

36

cartridge case (of 32)

37

Recording (for 36)

38

Air Vent (of 36)

39

Housing

40

Implementation (in 3 for 29)

41

test gas supply

42

first channel (of 29)

43

second channel (of 29)

44

optical measuring arrangement

45

light source

46

light detector

47

first pair (of 45 and 46)

48

second pair (from 45 and 46)

49

Recording (for 47/48/52/71)

50

antechamber

51

inlet channel (for test gas)

52

additional light detector (for scattered light measurement)

53

line of sight (of 52)

54a

(first) outlet opening

54b

(second) outlet opening

55

exit channel

56

inlet valve (for test gas)

57

outflow opening

58

Interface (for 29)

59

test gas flow

60

Air Vent (of 37)

61

partition wall

62

vent hole

63

clamping element

64

Wave

65

return current

66

return port

67

return channel

68

wall of 37

69

Intake opening from 70

70

measuring part

71

additional light detector (for scattered light measurement)

72

optical measuring section

73

optical measuring section

74

optical measuring section

75

optical measuring section

76

optical measuring section

Claims (15)

Oil mist detector (1) for the detection and/or analysis of oil-air mixtures, with - a measuring chamber (5) which forms at least one optical measuring section (6, 72) for the optical detection of an oil mist (2), characterized in that - that the oil mist detector (1) is set up for insertion into a housing (3) which delimits an interior space (4), and - that the oil mist detector (1) is set up to introduce a test gas from the outside into the interior space (4). Oil mist detector (1) after claim 1 , wherein the oil mist detector (1) forms a test gas supply (41). Oil mist detector (1) after claim 1 or 2 , wherein the oil mist detector (1) has a gas delivery device (27), preferably designed as an electric gas delivery pump (28), for actively taking gas samples from the interior (4). Oil mist detector (1) according to one of the preceding claims, in which the oil mist detector (1) has a gas extraction device (29), for example in the form of an intake pipe (30), which can be fed through an opening (40) in the housing (3) into the interior ( 4) is performed when the oil mist detector (1) is inserted into the housing (3) and/or is set up to take gas samples from the interior (4) and through the housing (3). Oil mist detector (1) according to one of the preceding claims, wherein the oil mist detector (1) is set up to introduce a test gas from the outside into the interior (4) by means of the test gas supply (41) in order to subsequently draw a sample of this test gas through the gas sampling device (29) removed by means of the gas conveying device (27) and measured optically in the measuring chamber (5), which is preferably arranged outside the interior (4). Oil mist detector (1) according to one of the preceding claims, wherein the test gas supply (41) is integrated into the gas sampling device (29) and/or - wherein the test gas supply (41) is designed such that in a test measurement operation the test gas sample follows the same path from the interior ( 4) to the measuring chamber (5), in particular through the gas extraction device (29), as a gas sample that is taken from the interior (4) by the oil mist detector (1) during normal measurement operation and measured optically. Oil mist detector (1) according to one of the preceding claims, wherein the oil mist detector (1) is set up to carry out a self-test of its functioning on the basis of an optical measurement carried out on a gas sample of the test gas in the measuring chamber (5), - Preferably, wherein the oil mist detector (1) is set up to issue a user notice, which reflects the result of the self-test. Oil mist detector (1) according to one of the preceding claims, wherein the measuring chamber (5) is connected to an intake channel (7) which opens into an intake opening (8), - preferably wherein the suction opening (8) is located within the interior (4) when the oil mist detector (1) is inserted into the housing (3) and/or - wherein the measuring chamber (5) is arranged outside of the interior (4). Oil mist detector (1) according to one of the preceding claims, wherein the test gas supply (41) opens out in the area of the suction opening (8), - in particular so that via the test gas supply (41) into the interior (4) supplied test gas can be removed from the interior (4) through the suction opening (8) and / or - So that the test gas can be used to check whether the gas sampling device (29) can forward a gas sample from the interior (4) to the measuring chamber (5). Oil mist detector (1) according to any one of the preceding claims, wherein the gas sampling device (29) - A first channel (42) for supplying a test gas flow (5) into the interior (4), in particular to the suction opening (8), and - a second channel (43) for discharging a gas sample from the interior (4) into the measuring chamber (5), - preferably wherein the second channel (43) connects the suction opening (8) to the measuring chamber (5) and/or forms the suction channel (7) and/or - The first and the second channel (42, 43) being formed together or the first channel (42) being separated from the second channel (43), in particular by means of a partition (61). An oil mist detector (1) according to any one of the preceding claims wherein the test gas supply (41) and/or the extraction device (29) is/are adapted to pass through a ¾ inch diameter opening. Method for checking the function of an oil mist detector (1), in particular according to one of the preceding claims, with a measuring chamber (5) which forms at least one optical measuring section (6, 72) for the optical detection of an oil mist (2), characterized in that - the oil mist detector (1) introducing a test gas in a controlled manner into an interior (4) monitored by the oil mist detector (1), preferably by actuating an inlet valve (56) of a test gas feed (41). procedure according to claim 12 , wherein the test gas is introduced into the interior (4) through a test gas supply (41) formed by the oil mist detector (1). procedure according to Claim 13 or 14 , wherein a gas sample of the test gas is taken from the interior (4) by means of a gas delivery device (27) provided by the oil mist detector (1), - in particular wherein the gas sample is then optically detected by the oil mist detector (1) in the measuring chamber (5) in the frame a test measurement is measured, - preferably wherein the correct functioning of the oil mist detector (1) is checked on the basis of a measurement result of this test measurement. procedure according to Claim 14 , wherein - a gas sample of the test gas is conveyed by means of the gas delivery device (27) through a gas extraction device (29) of the oil mist detector (1) into the measuring chamber (5), through which gas samples from the interior (4) are taken during normal operation of the oil mist detector (1) in reach the measuring chamber (5), - in particular with the test gas being flushed into the interior (4) at a predetermined volume rate through the test gas supply (41) during the test measurement.

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