DE102020128688B4 - Oil mist detector with gas pumping device - Google Patents

Abstract

Oil mist detector (1) for detecting and/or analyzing oil-air mixtures (oil mist), in particular for use in a crankcase housing (3) which delimits a crankcase (4) of a piston engine, with a measuring chamber (5) which is at least forms an optical measuring section (6, 72) for the optical detection of an oil mist (2), characterized in that the oil mist detector (1) has an electric gas feed pump (28) for actively taking gas samples, which is integrated in the oil mist detector (1). ,- wherein the gas feed pump (28) has a fan blade arrangement (31) which is arranged in an intake duct (7) which is connected to the measuring chamber (5),- wherein an electric drive motor (32) of the gas feed pump (28) outside of the intake duct (7) and- wherein a seal (33a) is formed between the fan blade arrangement (31) and the drive motor (32) and- a ventilated intermediate space (35) is formed between the seal (33a) and the drive motor (32), and - That the intermediate space (35) is sealed by means of a further seal (33b) in relation to the drive motor (32).

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.

The invention also relates to a piston engine, which can be designed in particular as a compressor or internal combustion engine, with a crankcase housing that delimits a crankcase, and with an oil mist detector as described above.

Finally, the invention relates to a method for detecting potentially explosive oil-air mixtures in an interior or monitored space, in particular in a crankcase of a piston machine (such as an internal combustion engine), using an oil mist detector that has a measuring chamber that has an optical measuring section for the optical Detection and / or analysis of an oil mist forms.

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.

Oil mist detectors for detecting potentially explosive mixtures are about out DE 10 78 788 A , KR 10 0 629 915 B1 or off JP 2005- 30 945 A previously known, the oil mist detectors also each have a gas feed pump with a rotating fan blade arrangement in order to be able to suck gas samples into the oil mist detector.

Against this background, the invention has set itself the task of providing improved handling of oil mist detectors as described at the outset, while at the same time ensuring a high level of operational reliability.

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 has a gas delivery device, designed as an electric gas delivery pump, for actively taking gas samples, which is integrated in the oil mist detector. In order to increase the explosion safety, it is also provided that the gas feed pump has a fan blade arrangement which is arranged in an intake channel which is connected to the measuring chamber. In this case, an electric drive motor of the gas feed pump is arranged outside of the intake duct and a seal is formed between the fan blade arrangement and the drive motor, as well as a ventilated intermediate space between the seal and the drive motor. Finally, the gap is by means of a wide Ren seal sealed against the drive motor.

The advantage of such an embodiment is that gas samples can be easily removed from the interior of an internal combustion engine using the oil mist detector, without the internal combustion engine having to have special devices for this purpose. As a result, optical monitoring of the operation of an internal combustion engine can be implemented particularly easily by retrofitting an oil mist detector according to the invention.

In other words, with the help of the gas delivery device of the oil mist detector, a gas sample can be taken from an interior of an internal combustion engine and then optically characterized in the measuring chamber. As a result, the formation of potentially explosive oil-air mixtures in the interior of the internal combustion engine can be repeatedly, in particular continuously, monitored during operation of the internal combustion engine. With an oil mist detector according to the invention, safety during operation of the internal combustion engine can thus be guaranteed in a particularly simple manner.

As already mentioned, to increase the reliability of the operation of the oil mist detector, it is provided that the gas feed pump has a fan blade arrangement that is arranged in an intake duct of the oil mist detector, which is connected to the measuring chamber, and that an electric drive motor of the gas feed pump is arranged outside of the intake duct. This can prevent the potentially explosive gas mixtures, especially when operating on the gas engine, from coming into contact in the intake duct with the electric drive motor of the gas feed pump, which could lead to explosions, for example if sparks occur in the drive motor.

A gas flow can be generated by means of the fan blade arrangement arranged in the intake duct, so that gas mixtures can be conveyed into the measuring chamber in order to be able to examine them optically there. In this case, the fan blade arrangement can preferably be arranged downstream of the measuring chamber. In this case, the gas feed pump can thus be operated as a suction pump in the oil mist detector, which feeds gas from the suction channel into the optical measuring chamber and then out of it.

Furthermore, to increase safety, it is provided that at least one seal, in particular with the aid of an elastomer, is formed between the fan blade arrangement and the drive motor. By means of the seal, gas can be effectively prevented from jumping out of the intake duct to the electric drive motor of the gas feed pump. The seal can thus preferably seal off the intake port. For this purpose, the seal can in particular seal off a drive shaft, by means of which the fan blade arrangement is driven by the drive motor.

A further advantageous embodiment proposes that, in relation to a gas stream flowing through the intake channel, a vent be formed behind the previously explained seal. Through this vent, gases that pass through the seal from the intake port can be discharged to the outside. This can ensure that these gases do not reach the electric drive motor despite passing through the seal. By venting these gases from the oil mist detector, the formation of an explosive mixture in the immediate vicinity of the electric drive motor can be effectively prevented.

As already mentioned, a ventilated space is formed between the seal and the drive motor in order to increase the explosion safety of the oil mist detector. Here, the explosion safety is increased again, since the intermediate space is sealed off from the drive motor by means of an additional seal. Because this effectively prevents a leakage of explosive gas from the ventilated space to the drive motor as a possible source of ignition.

According to an advantageous embodiment, the gas delivery device has a housing in the form of a cartridge, ie a cartridge housing, for this purpose. This cartridge housing can be inserted into a receptacle of the oil mist detector provided for this purpose. The cartridge housing can be characterized, for example, in that it has a cylindrical outer contour and/or forms an interior space through which a drive axle of the drive motor is guided to the fan blade arrangement.

The advantage of this configuration is that the cartridge housing can also form the ventilation of the intermediate space. For this purpose, a ventilation opening of the cartridge housing can be designed to correspond to a ventilation opening of the receptacle for the cartridge housing. In this case, gas can thus be discharged to the outside from an interior space of the cartridge housing through the vent opening of the cartridge housing and the vent opening of the receptacle.

A particularly safe guarantee of this venting function can be guaranteed in an embodiment of the oil mist detector, in which said ventilated space through the Belüf tion opening of the cartridge housing and the vent opening of the receptacle is vented to the outside as soon as the gas delivery device together with the cartridge housing is inserted into the receptacle. Such a configuration offers the advantage that when replacing, for example, the drive motor together with the cartridge housing, the correct functioning of the ventilation function does not have to be checked in a complex manner, since the ventilation is automatically ensured. For this purpose, in particular, a guide structure can be formed on the oil mist detector, more precisely on the receptacle, which guides the cartridge housing when it is inserted and thus specifies an alignment of the cartridge housing in which the venting function is ensured.

A further simplification in the maintenance of the oil mist detector and thus improved handling of the same is achieved if the drive motor and/or the cartridge housing can be exchanged without dismantling or removing the oil mist detector. Because in this case the oil mist detector, especially if it is used in a housing of an internal combustion engine, can remain in place if the drive motor has to be replaced in the event of a defect.

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 detecting potentially explosive oil-air mixtures of the type described above, the invention proposes in particular that a gas sample be taken from the interior through an intake opening of the oil mist detector using an electric gas feed pump of the oil mist detector. The gas sample can then be optically measured outside of the interior in the measuring chamber. In other words, in this method the measuring chamber of the oil mist detector is preferably arranged outside of the interior.

This method describes a simple way of using the method to increase operational safety without major retrofitting of an existing internal combustion engine by detecting explosive oil-air mixtures inside an interior of the internal combustion engine with the external oil mist detector. In order to avoid an unwanted deflagration or even an explosion inside the oil mist detector, it is also proposed to convey the gas sample into the measuring chamber by means of a fan blade arrangement which is arranged in an intake duct of the oil mist detector. It is particularly preferred here if the gas sample is sucked into the measuring chamber by means of the fan blade arrangement. In this case, the gas sample only interacts with the fan blade arrangement after it has passed the measurement chamber, so that an original size distribution of oil droplets in the gas sample is initially retained.

In the method according to the invention, gas which escapes in the direction of an electric drive motor of the gas delivery device/gas delivery pump through a seal and out of the intake channel is discharged to the outside by means of a vent from an intermediate space located between the seal and the drive motor. In this case, the intermediate space is sealed off from the drive motor by means of a further seal, so that gas which has passed through the (first) seal cannot advance to the drive motor. As already explained, this means that no explosive mixture can form in the immediate vicinity of the electric drive motor. This decisively improves the explosion safety when using the method. In particular, as described above, this ventilation can take place through a ventilation opening of a cartridge housing of the drive motor.

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.

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 view 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 actively remove a gas sample from the crankcase 4 depending on the measuring requirement. 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 . Here, the return opening 66 is turned away from the suction port 8 to a fluidic short circuit, so the immediacy bare aspiration of the gas exiting the return port 66 to avoid.

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 71 receives forward-scattered light, which was originally emitted by the light source 45 of the left-hand pair of functions 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 functional 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 be of 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 larger oil droplets in the bypass 11 separate and primarily smaller oil droplets, which are relevant to the risk of explosion, into the measuring chamber 5, so that they can be precisely measured there - undisturbed by the larger oil droplets.

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 years.

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 In the embodiment shown, the oil residues flow off due to gravity 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 increase 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 . This reversal of direction is for heavier oil droplets with high However, kinetic energy is very improbable, so that it gets into the gas supply 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 to the optical measuring arrangement 44 explained at the outset, it can be said that the embodiment of the oil mist detector 1 shown in the figures provides: a first pair of functions 47 consisting of 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, the two pairs of functions 47, 48 realizing two redundant transmitted light measurements 6, 72 and
the two scattered light detectors 52, 71 each carry out a scattered light measurement 73/74 with light which was emitted by one of the function pairs 47/48 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 doing 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 summary, 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 proposed that the oil mist detector 1 has a bypass 11 internally, 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 conveying device 27 is inserted 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 zurücklegt, 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 travels that a gas sample travels 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, is by means of the inlet port 51 and the inlet valve 56 is configured such 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 is taken from the interior 4 by the oil mist detector 1 in normal measurement operation and is 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 the 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 sampling device 29 into the measuring chamber 5 can be checked in the said test mode will. This increases the security of the 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 . Here, the oil mist detector 1 also outputs the result of the self-test in the form of user information and stores this in an internal memory.

With the embodiment of the oil mist detector 1 shown in the figures, a method for the safety check of the oil mist detector 1 can thus be implemented, in which the oil mist detector 1 introduces the test gas into the interior space 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 is detected in the measuring chamber for a volume rate of the test gas flow 59 set by it can be. 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 sampling 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)5

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 (8)

Oil mist detector (1) for detecting and/or analyzing oil-air mixtures (oil mist), in particular for use in a crankcase housing (3) which delimits a crankcase (4) of a piston engine, having - a measuring chamber (5) which is at least forms an optical measuring section (6, 72) for the optical detection of an oil mist (2), characterized in that - the oil mist detector (1) has an electric gas feed pump (28) for actively taking gas samples, which is integrated in the oil mist detector (1). , - wherein the gas feed pump (28) has a fan blade arrangement (31) which is arranged in an intake duct (7) which is connected to the measuring chamber (5), - wherein an electric drive motor (32) of the gas feed pump (28) outside of the Intake duct (7) is arranged and - wherein a seal (33a) between the fan blade arrangement (31) and the drive motor (32) and - a ventilated intermediate space (35) between the seal (33a) and the drive motor (32) i st, and - that the intermediate space (35) is sealed by means of a further seal (33b) relative to the drive motor (32). Oil mist detector (1) after claim 1 , wherein the seal (33a) seals the intake port (7) and/or - wherein, based on a gas flow (13) flowing through the intake port (7), a vent (34) is formed behind the seal (33a). Oil mist detector (1) after claim 2 , whereby through the ventilation (34) gases which, starting from the intake duct (7) pass the seal (33a), can be discharged to the outside, - in particular so that these gases do not reach the electric drive motor (32). Oil mist detector (1) according to one of the preceding claims, wherein the gas conveying device (27) has a cartridge housing (36), - In particular, wherein the cartridge housing (36) is inserted into a receptacle (37) of the oil mist detector (1). Oil mist detector (1) after claim 4 , wherein the cartridge housing (36) forms the ventilation of the intermediate space (35), wherein a ventilation opening (38) of the cartridge housing (36) is designed to correspond to a ventilation opening (60) of the receptacle (37). Oil mist detector (1) according to one of Claims 4 or 5 , wherein the intermediate space (35) is vented to the outside through the ventilation opening (38) of the cartridge housing (36) and the ventilation opening (60) of the receptacle (37) when the gas delivery device (27) together with the cartridge housing (36) is inserted into the receptacle ( 37) is used. Oil mist detector (1) according to one of the preceding claims, in which the drive motor (32) and/or the cartridge housing (36) is/are replaceable without disassembling or removing the oil mist detector (1). Method for detecting potentially explosive oil-air mixtures in an interior, in particular a crankcase (4), of an internal combustion engine with the aid an oil mist detector (1), in particular according to one of Claims 1 until 7 , which has a measuring chamber (5) which forms an optical measuring section (6) for the optical detection of an oil mist (2), characterized in that a gas sample is drawn in through an intake opening (8) of the oil mist detector ( 1) is removed from the interior, - the gas sample being conveyed, preferably sucked, into the measuring chamber (5) by means of a fan blade arrangement (31) which is arranged in an intake duct (7) of the oil mist detector (1), and - wherein Gas which escapes in the direction of an electric drive motor (32) of the gas feed pump (28) through a seal (33a) out of the intake duct (7) by means of a vent (34) from a pressure chamber between the seal (33a) and the drive motor (32 ) located intermediate space (35) is discharged to the outside, the intermediate space (35) being sealed off from the drive motor (32) by means of a further seal (33b), so that gas which has passed through the seal (33a) does not can advance up to the drive motor (32).

Images