DE202021103938U1 - Filter monitoring system - Google Patents

Abstract

Filter monitoring system (1) for monitoring the condition of a filter (4) in a fluid channel (20), in particular an HVAC fluid channel, which is located in a vehicle,
having a differential pressure sensor (10),
characterized,
that the filter monitoring system (1) is designed to be arranged on the fluid channel (20) in such a way that the differential pressure _{sensor (10) has a pressure difference ΔP between a pressure (P 1} ) of a channel fluid (2) flowing through the fluid channel (20) in one downstream of the filter (4) located area (21) of the fluid channel (20) and a pressure (P ₀ ) of an ambient fluid (3) in an area (30) outside the fluid channel (20).

Description

TECHNICAL AREA

The present invention relates to a filter monitoring system for monitoring the condition of a filter in a fluid channel.

STATE OF THE ART

Filters are often indispensable for removing particles from fluids, including gases and liquids. Air filters, for example, are essential components of HVAC (heating, ventilation, air conditioning) systems, while fuel filters are used in burners and engines, among other things.

Blockages of such a filter usually have undesirable consequences, such as increased energy consumption, overheating and / or other damage.

It is therefore desirable to recognize the clogging of a filter at an early stage so that the filter can be cleaned or replaced in good time.

Many systems for monitoring the condition of a filter are known from the prior art.

For example, the US 7,594,960 B2 a system for monitoring the condition of an air filter. The system includes a mechanical force measuring device located on the downstream side of the filter. The filter flexes in response to flow through the filter, thereby exerting a force on the force measuring device, the force increasing as the filter becomes clogged.

US 9,120,043 B2 discloses a filter life sensor within an air handling system. The air treatment system includes an airflow inlet, an airflow outlet, and a filter disposed between the airflow inlet and the airflow outlet. The filter sensor arrangement comprises a bypass, which connects the airflow inlet with the airflow outlet, and a dielectric vibration sensor next to the bypass. A stream of air flowing through the bypass increases the frequency and amplitude of the oscillation.

US 2006/0259273 A1 discloses a filter monitoring system that uses a differential pressure sensor to provide a continuous signal output proportional to a pressure drop across a filter element. A system that monitors pressure drop across a filter is also in WO 2015/078672 A1 disclosed.

In such monitoring systems, a first pressure connection is located upstream of the filter element and a second pressure connection is located downstream of the filter element. Particles can therefore penetrate the differential pressure sensor through the first pressure connection and contaminate it, which can impair the function of the differential pressure sensor. The problem is particularly serious with dynamic differential pressure sensors that measure the differential pressure by monitoring a fluid flow through a sensor channel. Dynamic differential pressure sensors quickly become inoperable if particles pass through the sensor channel. It may therefore be necessary to use static differential pressure sensors instead of dynamic differential pressure sensors. Static differential pressure sensors that are able to detect sufficiently small pressure differences are, however, relatively expensive.

DISCLOSURE OF THE INVENTION

In a first aspect, it is an object of the present invention to specify a filter monitoring system which prevents contamination of the differential pressure sensor, enables simple system integration and does not hinder replacement and cleaning of the filter.

This object is achieved by a filter monitoring system according to claim 1. Further embodiments are given in the dependent claims.

A filter monitoring system for monitoring the condition of a filter in a fluid channel, in particular an HVAC fluid channel, which is located in a vehicle, is therefore disclosed,
having a differential pressure sensor,
wherein the filter monitoring system is designed to be arranged on the fluid channel in such a way that the differential pressure sensor determines a pressure difference between a pressure of a channel fluid flowing through the fluid channel in an area of the fluid channel downstream of the filter and a pressure of an ambient fluid in an area outside the fluid channel.

The fact that a pressure difference is determined between the pressure of the channel fluid in an area of the fluid channel downstream of the filter and the pressure of the ambient fluid in an area outside the fluid channel prevents particles from entering the differential pressure sensor from an area upstream of the filter and contaminate it can. The latter would be the case, for example, in an arrangement which would provide for a determination of a pressure difference between the pressure of the channel fluid in a region of the fluid channel located downstream of the filter and the pressure of the channel fluid in a region of the fluid channel located upstream of the filter. In addition, the proposed filter monitoring system enables a particularly simple arrangement on the fluid channel, because only a single access opening is required in a boundary wall of the fluid channel.

The differential pressure sensor preferably has a first pressure connection and a second pressure connection, the first pressure connection and the second pressure connection being located outside the fluid channel when the filter monitoring system is arranged on the fluid channel as intended. Furthermore, the filter monitoring system preferably comprises a housing which protrudes into an access opening in a boundary wall of the fluid channel. The housing preferably has a connecting channel which fluidly connects the first pressure connection to the region of the fluid channel located downstream of the filter. The housing also preferably connects the second pressure connection fluidically with the environment, i.e. with the area outside the fluid channel in which the ambient fluid is located.

Ideally, the filter monitoring system has a protective filter which is arranged in such a way that the ambient fluid can only pass through the protective filter from the area located outside the fluid channel into the second pressure connection of the differential pressure sensor.

Such a protective filter can prevent particles from the ambient fluid from getting into the differential pressure sensor. In contrast to the flow rate of the channel fluid through the filter in the fluid channel, the ambient fluid has a very low flow rate through the protective filter, as a result of which the dirt filter is only slightly and slowly soiled.

The differential pressure sensor is preferably a dynamic differential pressure sensor with a sensor channel extending between the first pressure port and the second pressure port, wherein the differential pressure sensor can be configured to determine the pressure difference between the first pressure port and the second pressure port by allowing a sensor fluid flow through measures the sensor channel, the sensor fluid flow being caused by the pressure difference between the pressure of the ambient fluid and the pressure of the channel fluid.

The sensor channel has a cross-sectional area which is orders of magnitude smaller than the cross-sectional area of the fluid channel through which the channel fluid flows, e.g. smaller by at least a factor of 1,000. Accordingly, the flow rate through the sensor channel is orders of magnitude smaller than the flow rate through the fluid channel.

The filter monitoring system is preferably designed such that the first pressure connection of the differential pressure sensor extends perpendicular to a longitudinal direction of the fluid channel or a flow direction of the channel fluid defined thereby when the filter monitoring system is arranged on the fluid channel as intended. In particular, the housing of the filter monitoring system can be designed in such a way that it accommodates the differential pressure sensor in a corresponding orientation.

The differential pressure sensor is preferably designed in a design in which the second pressure connection extends parallel to the first pressure connection, the first pressure connection and the second pressure connection both pointing in the direction of the fluid channel when the filter monitoring system is arranged as intended on the fluid channel. The housing of the filter monitoring system can accordingly be designed to accommodate a differential pressure sensor of this type. Such an arrangement of the pressure connections is widespread in differential pressure sensors. Since the filter monitoring system provides such an arrangement of the pressure connections (which, for example, requires a corresponding design of the housing), commercially available differential pressure sensors can be used. This can further reduce the costs of the filter monitoring system.

The housing can have a sealing surface which is designed to rest on an outside of a boundary wall of the fluid channel. The housing can also have a connection device, via which connection device the housing can be connected to the boundary wall of the fluid channel. This connecting device can in particular be a bayonet connection. The connecting device can have an anti-rotation pin which is designed to engage in a recess on the outside of the boundary wall, as a result of which the filter monitoring system is prevented from being accidentally rotated.

The differential pressure sensor can be attached to a printed circuit board that is held in the housing of the filter monitoring system. The housing can in particular comprise a first housing part and a second housing part. The first The housing part can serve to connect the differential pressure sensor to the fluid channel. For this purpose, the first housing part can protrude into the access opening in the boundary wall of the fluid channel and have the above-mentioned connecting channel, which fluidly connects the first pressure connection to the region of the fluid channel located downstream of the filter. The first housing part also preferably connects the second pressure connection fluidically with the environment, ie with the area outside the fluid channel in which the ambient fluid is located. Furthermore, the first housing part can have the sealing surface mentioned above, as well as the connection device, via which connection device the first housing can be connected to the boundary wall of the fluid channel.

The second housing part, on the other hand, can serve to protect the circuit board. For this purpose, the second housing part can have a receptacle for the printed circuit board. The circuit board can be held in the receptacle by a holding device in order to prevent it from accidentally falling out. The second housing part, the printed circuit board with the differential pressure sensor and the first housing part can preferably be connected to one another in such a way that the first pressure connection of the differential pressure sensor is inserted into the connecting channel of the first housing part like a plug and that the second pressure connection comes to lie opposite a housing opening in the first housing part , through which an exchange of the ambient fluid can take place.

Ideally, the housing opening in the first housing part is spanned by the protective filter, wherein the protective filter can optionally be clamped in the first housing part by a removable protective filter holder. The protective filter can optionally also be designed as a removable filter membrane, which makes cleaning or replacement easier.

The printed circuit board can have a plug connection on a side opposite the differential pressure sensor, the second housing part surrounding this plug connection in such a way that a guide for a counterpart to the plug connection is thereby formed. For example, a plug connection with 3 contact pins is particularly suitable for implementing a LIN interface. Plug connections with 4 contact pins - e.g. for an I2C interface - are also conceivable.

The pressure difference determined by the differential pressure sensor depends on the one hand on the flow rate of the duct fluid through the filter and accordingly on the degree of clogging of the filter, on the other hand the determined pressure difference is also dependent on the absolute pressure of the ambient fluid.

Since the absolute pressure of the ambient fluid can often only be regulated with difficulty or not at all, for example in the case of the absolute pressure of the ambient air in a vehicle, it is desirable to be able to determine this absolute pressure of the ambient fluid. The pressure difference determined by the differential pressure sensor can be compensated with regard to the absolute pressure of the ambient fluid in such a way that a compensated parameter results which indicates the degree of clogging of the filter independently of the pressure of the ambient fluid and thus enables the output of a reliable and accurate status signal.

The filter monitoring system can therefore have an absolute pressure sensor for determining the absolute pressure of the ambient fluid. This absolute pressure sensor is preferably arranged inside the housing, but can also be located outside the housing.

Instead of the absolute pressure sensor or in addition to the absolute pressure sensor, the filter monitoring system can have an interface for receiving GPS data from which the absolute pressure of the ambient fluid can be determined.

The filter monitoring system can also have an interface for receiving a signal from an engine control unit of the vehicle, the absolute pressure of the ambient fluid being able to be determined from the signal.

• In einem ersten Schritt können vordefinierte Parameter eingestellt werden, welche zur einer bekannten Durchflussrate des Kanalfluids führen. Die vordefinierten Parameter können insbesondere im Falle eines HLK-Systems in einem Fahrzeug beispielsweise Default-Zustände von Fenstern, HLK-Klappen oder eines HLK-Gebläses sein.
• In einem zweiten Schritt kann die Druckdifferenz anhand eines Filterüberwachungssystem ermittelt werden, welches einen Differenzdrucksensor aufweist, wobei das Filterüberwachungssystem dazu ausgebildet ist, derart am Fluidkanal angeordnet zu werden, dass der Differenzdrucksensor eine Druckdifferenz zwischen einem Druck eines den Fluidkanal durchströmenden Kanalfluids in einem sich stromabwärts des Filters befindenden Bereich des Fluidkanals und einem Druck eines Umgebungsfluids in einem Bereich ausserhalb des Fluidkanals ermittelt.
• In einem dritten Schritt, welcher vorzugsweise zeitgleich zum zweiten Schritt erfolgt, kann optional der absolute Druck des Umgebungsfluids anhand eines Absolutdrucksensors, GPS-Daten oder eines Signals aus einer Motorkontrolleinheit ermittelt werden.
• In einem vierten Schritt kann optional aus der Druckdifferenz und aus dem absoluten Druck eine Kenngrösse, die hinsichtlich des absoluten Drucks kompensiert ist, ermittelt werden. Das Filterüberwachungssystem kann eine Signalverarbeitungseinrichtung aufweisen, welche dazu ausgebildet ist, eine solche Kenngrösse zu berechnen.
• Diese Kenngrösse kann anschliessend optional in einem fünften Schritt mit einem Referenzwert verglichen werden. Dieser Referenzwert kann z.B. in einer Tabelle gespeichert sein, welche beispielsweise in der Signalverarbeitungseinrichtung hinterlegt ist.
• Das Verfahren kann zudem einen Referenzmessschritt aufweisen, bei dem ein Referenzwert für die besagten vordefinierten Parameter nach Einsetzen eines neuen oder frisch gereinigten Filters in den Fluidkanal ermittelt wird.
• In einem sechsten Schritt kann optional ein Zustandssignal ausgegeben werden, welches angibt, wie stark die ermittelte Kenngrösse vom Referenzwert abweicht und/oder ob der Filter ausgetauscht bzw. gereinigt werden sollte.

A method for determining the status of a filter in a fluid channel, in particular an HVAC fluid channel in a vehicle, can thus have the following steps:

• In a first step, predefined parameters can be set which lead to a known flow rate of the channel fluid. In particular in the case of an HVAC system in a vehicle, the predefined parameters can be, for example, default states of windows, HVAC flaps or an HVAC fan.
• In a second step, the pressure difference can be determined using a filter monitoring system which has a differential pressure sensor, the filter monitoring system being designed to be arranged on the fluid channel in such a way that the differential pressure sensor shows a pressure difference between a pressure of a channel fluid flowing through the fluid channel in a downstream of the Filter located area of the fluid channel and a pressure of an ambient fluid is determined in an area outside the fluid channel.
• In a third step, which preferably takes place at the same time as the second step, the absolute pressure of the ambient fluid can optionally be determined using an absolute pressure sensor, GPS data or a signal from an engine control unit.
• In a fourth step, a parameter that is compensated with regard to the absolute pressure can optionally be determined from the pressure difference and the absolute pressure. The filter monitoring system can have a signal processing device which is designed to calculate such a parameter.
• This parameter can then optionally be compared with a reference value in a fifth step. This reference value can be stored, for example, in a table which is stored, for example, in the signal processing device.
• The method can also have a reference measuring step in which a reference value for the said predefined parameters is determined after a new or freshly cleaned filter has been inserted into the fluid channel.
• In a sixth step, a status signal can optionally be output which indicates how much the determined parameter deviates from the reference value and / or whether the filter should be replaced or cleaned.

It is advantageous that the absolute pressure of the ambient fluid in such a method is only used to compensate for atmospheric fluctuations and thus has to be determined much less precisely than if the absolute pressure of the ambient fluid had to be measured explicitly to determine the pressure difference. Simple and inexpensive absolute pressure sensors can thus be used to determine the absolute pressure of the ambient fluid in the aforementioned method.

In a second aspect, it is an object of the present invention to provide an HVAC system in which the clogging state of a filter is easily monitored.

The HVAC system has a fluid channel and a filter which is arranged in the fluid channel. Furthermore, the HVAC system has a filter monitoring system of the type mentioned above, the filter monitoring system being attached to the fluid channel in such a way that the differential pressure sensor shows a pressure difference between a pressure of a channel fluid flowing through the fluid channel in a region of the fluid channel downstream of the filter and a pressure of a Ambient fluids determined in an area outside the fluid channel.

Figure list

• 1 in stark schematischer Weise ein Filterüberwachungssystem nach dem Stand der Technik;
• 2 ein Diagramm zur Veranschaulichung der Abhängigkeit des Druckabfalls über einem Filter von der Durchflussrate für einen neuen Filter und für einen verstopften Filter;
• 3 in stark schematischer Weise ein Filterüberwachungssystem gemäss einer ersten Ausführungsform der vorliegenden Erfindung;
• 4 eine detaillierte Schnittansicht der ersten Ausführungsform der vorliegenden Erfindung;
• 5 eine Ausführungsform eines Differenzdrucksensors in perspektivischer Ansicht;
• 6 den Aufbau des Filterüberwachungssystems der 4 in einer perspektivischen Explosionsansicht;
• 7a eine erste perspektivische Ansicht des Filterüberwachungssystems der 4;
• 7b eine zweite perspektivische Ansicht des Filterüberwachungssystems der 4;
• 7c eine perspektivische Ansicht des zweiten Gehäuseteils des Filterüberwachungssystems der 4 inklusive einer Leiterplatte, an welcher ein Differenzdrucksensor angebracht ist;
• 8a in stark schematischer Weise ein Filterüberwachungssystem gemäss einer zweiten Ausführungsform der vorliegenden Erfindung;
• 8b in stark schematischer Weise ein Filterüberwachungssystem gemäss einer dritten Ausführungsform der vorliegenden Erfindung;
• 8c in stark schematischer Weise ein Filterüberwachungssystem gemäss einer vierten Ausführungsform der vorliegenden Erfindung;
• 9 ein Flussdiagramm, das ein Verfahren gemäss einer Ausführungsform der vorliegenden Erfindung illustriert.

Preferred embodiments of the invention are described below with reference to the drawings, which are only used for explanation and are not to be interpreted as restrictive. In the drawings show:

• 1 in a highly schematic manner, a filter monitoring system according to the prior art;
• 2 a diagram to illustrate the dependence of the pressure drop across a filter on the flow rate for a new filter and for a clogged filter;
• 3 in a highly schematic manner a filter monitoring system according to a first embodiment of the present invention;
• 4th Fig. 3 is a detailed sectional view of the first embodiment of the present invention;
• 5 an embodiment of a differential pressure sensor in a perspective view;
• 6th the structure of the filter monitoring system of 4th in an exploded perspective view;
• 7a a first perspective view of the filter monitoring system of FIG 4th ;
• 7b a second perspective view of the filter monitoring system of FIG 4th ;
• 7c a perspective view of the second housing part of the filter monitoring system of FIG 4th including a circuit board to which a differential pressure sensor is attached;
• 8a in a highly schematic manner, a filter monitoring system according to a second embodiment of the present invention;
• 8b in a highly schematic manner, a filter monitoring system according to a third embodiment of the present invention;
• 8c in a highly schematic manner, a filter monitoring system according to a fourth embodiment of the present invention;
• 9 a flow chart illustrating a method according to an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

State-of-the-art filter monitoring system

1 shows in a highly schematic manner a filter monitoring system according to the prior art. One filter 4th is in a fluid channel 20th arranged. The filter 4th is fluid-tight in the fluid channel 20th attached so that a channel fluid 2 the filter 4th flows through. The filter 4th spans the cross section of the fluid channel 20th to remove particles from the channel fluid 2 to stop.

A differential pressure sensor 10 has a first, downstream of the filter 4th arranged pressure connection 11 and a second, upstream of the filter 4th arranged pressure connection 12th . The first pressure connection 11 is the static fluid pressure P ₁ downstream of the filter 4th suspended while the second pressure port 12th the static fluid pressure P ₂ upstream of the filter 4th is exposed. The differential pressure sensor 10 measures the pressure drop ΔP = P ₂ -P ₁ across the filter 4th .

The pressure drop ΔP depends on the flow rate Q of the channel fluid 2 through the fluid channel 20th at a given flow rate Q but also on the degree of contamination of the filter 4th , as in 2 is shown schematically. A clean filter 4th leads to a lower pressure drop ΔP as a dirty filter 4th . The degree of contamination of the filter 4th can therefore be done by measuring the pressure drop ΔP be monitored. In particular, for a given flow rate Q, a difference δ between the pressure drop across the (potentially) clogged filter ΔP _v and a reference measurement of the pressure drop across a clean filter ΔP _s can be formed, i.e. δ = ΔP _v - ΔP _s , with a warning signal being triggered can, this difference δ should exceed a specified threshold value.

Filter monitoring system according to a first embodiment

3 represents a filter monitoring system in a highly schematic manner 1 according to a first embodiment of the present invention. Instead of the fluid pressure P ₂ upstream of the filter 4th is the second pressure connection 12th of the differential pressure sensor 10 a print P ₀ an ambient fluid 3 in one area 30th outside of the fluid channel 20th exposed. Because the first pressure connection 11 the pressure P ₁ downstream of the filter 4th is exposed, the differential pressure sensor determines 10 now the pressure difference ΔP = P ₀ -P ₁ . The installation of such a filter monitoring system 1 on a fluid channel 20th is in contrast to the arrangement in 1 Simplified, because here only one of the two pressure connections through a boundary wall 24 of the fluid channel 20th fluidically therethrough with the fluid channel 20th needs to be connected.

In 4th the first embodiment of the present invention is illustrated in a sectional view. It should be noted that the dimensions of the fluid channel 20th and the filter 4th compared to the dimensions of the filter monitoring system 1 in 4th are not shown to scale. The fluid channel can in particular be an HVAC channel in a vehicle, which typically has a cross section in the range of, for example, 400 to 800 cm ² . The filter monitoring system 1 comprises a housing, the housing being a first housing part 40 and a second housing part 50 having. This in 4th The housing shown preferably has an extension of less than 5 cm in all spatial directions. When the filter monitoring system 1 as intended (ie as shown here) on the fluid channel 20th is arranged, the first housing part protrudes 40 into an access opening 22nd in a boundary wall 24 of the fluid channel 20th into it, the first housing part 40 a sealing surface 42 having which on an outside of the fluid channel 20th rests. The first housing part 40 also has a connecting device 43 on, in particular as shown here, a bayonet connection via which the first housing part 40 with the fluid channel 20th connected is. A rotation lock pin 44 reaches into a recess 23 on the outside of the fluid channel 20th which prevents the filter monitoring system from accidentally twisting. The differential pressure sensor 10 is on a circuit board 60 attached, which of the second 50 Housing part is surrounded. The second part of the housing 50 who have favourited Circuit Board 60 with the differential pressure sensor 10 and the first housing part 40 are connected to one another in such a way that the first pressure connection 11 of the differential pressure sensor 10 like a plug into a connecting channel 41 of the first housing part 40 inserts, the connecting channel 41 the first pressure connection 11 of the differential pressure sensor 10 with an area downstream of the filter 21 of the fluid channel 20th fluidically connects. One is concerned with the first pressure connection 11 extending sealing ring 55 ensures a tight insertion of the first pressure connection 11 in the connection channel 41 . The circuit board 60 points to one of the differential pressure sensor 10 opposite side a plug connection 61 (here a LIN connector). The second part of the housing 50 surrounds this plug connection 61 so that this gives a guide 54 for a counterpart to the plug connection 61 is formed. The connecting channel 41 and the first pressure connection 11 are perpendicular to a longitudinal direction of the fluid channel 20th or a direction of flow of the channel fluid defined thereby 2 (see arrow in 4th ) arranged when the filter monitoring system is intended to be attached to the fluid channel, as is the case here 20th is arranged. The second pressure connection 12th runs parallel to the first pressure connection 11 and, like the first pressure connection, points in the direction of the fluid channel. The second pressure connection is also located in a housing opening 46 in the first part of the housing 40 opposite to. A protective filter 52 spans this housing opening 46 in the first part of the housing 40 , the protection filter 52 here from a removable protective filter holder 53 is clamped in the first housing part. The ambient fluid 3 in this case passes through the protective filter 52 through from one outside the fluid channel 20th located area 30th into the second pressure connection 12th .

In the preferred embodiment shown here, the differential pressure sensor is 10 a dynamic differential pressure sensor with one sensor channel 13th that is between the first pressure port 11 and the second pressure connection 12th extends, the differential pressure sensor 10 is configured to have a pressure differential ΔP between the first pressure port 11 and the second pressure connection 12th determined by having a sensor fluid flow 14th through the sensor channel 13th measures. The sensor fluid flow 14th is determined by the differential pressure between the pressure P ₀ of the ambient fluid 3 and the pressure P ₁ of the channel fluid 2 caused. Is the pressure P ₁ is lower than the pressure P ₀ which is usually the case as long as the channel fluid 2 is sucked in by a fan arranged downstream of the filter, the sensor fluid flow 14th indicated by the dashed arrow in 4th indicated direction.

In 5 is an embodiment of the differential pressure sensor 10 seen in perspective view. This embodiment corresponds to the embodiment of the differential pressure sensor 10 , what a 4th as part of the filter monitoring system 1 can be seen in the sectional view. The differential pressure sensor 10 has a sensor housing 15th in which the sensor channel 13th is trained. In the sensor channel 13th a microthermal sensor element is arranged. The microthermal sensor element comprises a heating element, a first temperature sensor upstream of the heating element and a second temperature sensor downstream of the heating element in relation to the sensor fluid flow. For determining the sensor fluid flow through the sensor channel 13th the heating element is heated and the temperature difference between the first and second temperature sensors is determined. With a given heating power, the temperature difference in the steady state is an indicator of the sensor fluid flow through the sensor channel. Because the sensor fluid flow depends on the pressure difference between the first pressure port 11 and the second pressure connection 12th depends, the temperature difference between the first and the second temperature sensor is also an indicator of the pressure difference between these pressure connections 11 , 12th . A control circuit is provided to supply the heating element with power and to process the temperature signals from the temperature sensors. The control circuit can be integrated together with the heating element and the temperature sensors on a common substrate, e.g. B. based on CMOS technology. For a possible structure and mode of operation of the microthermal sensor element, see EP1426740A2 referenced. The two pressure connections 11 , 12th are aligned parallel to each other and extend from the housing 15th away in the same direction. A differential pressure sensor of this type is detailed in the publication EP 3032 227B1 the disclosure of which is incorporated herein by reference in its entirety. The second pressure connection 12th can for example also through a simple opening in the housing 15th of the differential pressure sensor must be replaced. For the embodiment of the filter monitoring system of 4th it is sufficient that the differential pressure sensor has a single plug-like pressure connection.

6th shows the structure of the filter monitoring system according to the in 4th shown preferred embodiment in a perspective exploded view. As can be seen particularly well in this exploded view, the protective filters are 52 and the protective filter holder 53 in this preferred embodiment both are removable. Can also be seen clearly on the outside of the first housing part 40 attached locking tabs 45 which are designed to each extend around one on an outside of the second housing part 50 attached knobs 56 to extend when the first housing part 40 and the second housing part 50 are nested to form a locking connection.

7a and 7b are perspective views of the filter monitoring system 1 , here the first housing part 40 and the second housing part 50 are nested. In the in 7a selected view are the sealing surface 42 , the bayonet connection 43 , as well as the anti-rotation pin 44 clearly visible. In 7b it can be seen that the second housing part is a guide 54 for the counterpart to the plug connection 61 forms.

7c shows a perspective view of the second housing part 50 . The second housing part has a receptacle for the circuit board 60 on. The circuit board 60 at which the differential pressure sensor 10 is attached, is held by a holding device 51 in the receptacle.

Filter monitoring system according to further embodiments

the 8a until 8c show further embodiments of a filter monitoring system 1 according to the present invention, wherein in addition to the pressure difference ΔP also the absolute pressure P ₀ of the ambient fluid 3 is determined. The filter monitoring system 1 also has a signal processing device 100 on, which is designed to be used by the differential pressure sensor 10 determined pressure difference ΔP such in terms of absolute pressure P ₀ to compensate that one compensated (ie from absolute pressure P ₀ the ambient fluid independent) parameter results.

In the in 8a The second embodiment, shown schematically, has the filter monitoring system 1 an absolute pressure sensor 70 to determine the absolute pressure P ₀ of the ambient fluid 3 on. This is preferably arranged within the housing.

In the in 8b The third embodiment, shown schematically, has the filter monitoring system 1 an interface 101 for receiving GPS data from a GPS receiver 80 on from which the absolute pressure P ₀ of the ambient fluid 3 is determinable.

In the in 8c The fourth embodiment, shown schematically, has the filter monitoring system 1 an interface 102 to receive a signal from an engine control unit 90 of the vehicle, with the absolute pressure from the signal P ₀ of the ambient fluid 3 is determinable.

Use of the filter monitoring system

9 shows a method for determining the state of a filter in a fluid channel, in particular an HVAC fluid channel in a vehicle, which is based on the use of the filter monitoring system according to the second, third or fourth embodiment of the present invention. In a first step 201, predefined parameters are set which lead to a known flow rate Q of the channel fluid. In particular in the case of an HVAC system in a vehicle, the predefined parameters can be, for example, default states of windows, HVAC flaps or an HVAC fan. In a second step 202, the pressure difference ΔP determined using the differential pressure sensor in the filter monitoring system. In a third step 203, which ideally takes place at the same time as the second step 202, the absolute pressure is set P ₀ of the ambient fluid is determined using an absolute pressure sensor, GPS data or a signal from an engine control unit. In a fourth step 204, the pressure difference becomes ΔP and the absolute pressure P ₀ one in terms of absolute pressure P ₀ compensated parameter determined. This parameter is then compared in a fifth step 205 with a reference value that has been determined for the said predefined parameters as the filter 4th was new or freshly cleaned. This reference value can be taken from a table, for example, which is stored in the signal processing device 100 can be saved. In a sixth step 206, a status signal is output which indicates how much the determined normalized parameter deviates from the reference value and / or whether the filter should be replaced or cleaned.

Considerations for the dimensioning of the filter monitoring system

For an HVAC fluid duct in a vehicle, the differential pressure is ΔP at a flow rate of the duct fluid (in this case air) of Q = 300 m ³ / h with a new filter ΔP = 50-100 Pa, while with a clogged filter a pressure difference of ΔP = 200-300 Pa typically occurs. Ideally, the differential pressure sensor is able to determine pressure differences in a measuring range of 10-300 Pa with an accuracy of 10-20 Pa. Dynamic differential pressure sensors based on microthermal sensor elements are particularly suitable for achieving such an accuracy in this low measuring range. For a possible structure and mode of operation of a microthermal sensor element, see EP1426740A2 referenced. Differential pressure sensors that have such microthermal sensor elements are in EP 3 032 227 B1 disclosed.

List of reference symbols

1

Filter monitoring system

2

Channel fluid

3rd

Ambient fluid

4th

filter

10

Differential pressure sensor

11

first pressure connection

12th

second pressure connection

13th

Sensor channel

14th

Sensor fluid flow

15th

Sensor housing

20th

Fluid channel

21

Area of the fluid channel downstream of the filter

22nd

Access opening

23

deepening

24

Boundary wall

30th

Area outside the fluid channel

40

first housing part

41

Connection channel

42

Sealing surface

43

Connecting device

44

Anti-rotation pin

45

Locking tabs

46

Housing opening

50

second housing part

52

Protection filter

53

Protective filter holder

54

guide

55

Sealing ring

56

Knobs

60

Circuit board

61

Plug connection

70

Absolute pressure sensor

80

GPS receiver

90

Engine control unit

100

Signal processing device

101

interface

102

interface

P0

Ambient fluid pressure

P1

Channel fluid pressure

ΔP

Pressure difference

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 7594960 B2 [0006]
• US 9120043 B2 [0007]
• US 2006/0259273 A1 [0008]
• WO 2015/078672 A1 [0008]
• EP 1426740 A2 [0042, 0051]
• EP 3032227 B1 [0042, 0051]

Claims (15)

Filter monitoring system (1) for monitoring the condition of a filter (4) in a fluid channel (20), in particular an HVAC fluid channel, which is located in a vehicle, having a differential pressure sensor (10), characterized in that the filter monitoring system (1) for this purpose is designed to be arranged on the fluid channel (20) in such a way that the differential pressure _{sensor (10) has a pressure difference ΔP between a pressure (P 1} ) of a channel fluid (2) flowing through the fluid channel (20) in a channel fluid (2) located downstream of the filter (4) Area (21) of the fluid channel (20) and a pressure (P ₀ ) of an ambient fluid (3) in an area (30) outside the fluid channel (20). Filter monitoring system according to Claim 1 , wherein the differential pressure sensor (10) has a first pressure connection (11) and a second pressure connection (12), the first pressure connection (11) and the second pressure connection (12) being outside the fluid channel (20) when the filter monitoring system (1 ) is arranged as intended on the fluid channel (20), the filter monitoring system (1) comprising a housing which protrudes into an access opening (22) in a boundary wall (24) of the fluid channel (20), the housing having a connecting channel (41), which fluidly connects the first pressure connection (11) to the area (21) of the fluid channel (20) located downstream of the filter (4), and wherein the housing connects the second pressure connection (12) to the area (30) outside the fluid channel (20) ) fluidically connects. Filter monitoring system according to Claim 2 , wherein the filter monitoring system (1) has a protective filter (52) which is arranged in such a way that the ambient fluid (3) only through the protective filter (52) from the area (30) located outside the fluid channel (20) into the second Pressure connection (12) of the differential pressure sensor (10) arrives. Filter monitoring system according to one of the Claims 2 or 3 , wherein the differential pressure sensor (10) is a dynamic differential pressure sensor with a sensor channel (13) which extends between the first pressure port (11) and the second pressure port (12), wherein the differential pressure sensor (10) is configured to measure the pressure difference ΔP between the first pressure connection (11) and the second pressure connection (12) is determined by measuring a sensor fluid flow (14) through the sensor channel (13), the sensor fluid flow (14) being determined by the pressure difference ΔP between the pressure (P ₀ ) of the Ambient fluid (3) and the pressure (P ₁ ) of the channel fluid (2) is caused. Filter monitoring system according to one of the Claims 2 - 4th , the filter monitoring system (1) being designed in such a way that the first pressure connection (11) of the differential pressure sensor (10) extends perpendicular to a longitudinal direction of the fluid channel (20) or a flow direction of the channel fluid (3) defined thereby when the filter monitoring system ( 1) is arranged as intended on the fluid channel (20), and in particular the housing of the filter monitoring system (1) is designed in such a way that it receives the differential pressure sensor in a corresponding orientation. Filter monitoring system according to one of the Claims 2 - 5 , wherein the differential pressure sensor (10) is designed in a design in which the second pressure connection (12) extends parallel to the first pressure connection (11), the first pressure connection (11) and the second pressure connection (12) both in the direction of the fluid channel (20) when the filter monitoring system (1) is arranged as intended on the fluid channel (20), and the housing of the filter monitoring system (1) is designed to accommodate a differential pressure sensor (10) configured in this design. Filter monitoring system according to one of the Claims 2 - 6th , wherein the housing has a sealing surface (42) which is designed to rest on an outside of a boundary wall (24) of the fluid channel (20), the housing having a connecting device (43), in particular a bayonet connection, via which connecting device ( 43) the housing can be connected to the delimitation wall (24) of the fluid channel (20), and the connecting device (43) optionally has an anti-rotation pin (44) which is designed to be inserted into a recess (23) on the outside of the delimitation wall ( 24) intervene. Filter monitoring system according to one of the Claims 2 - 7th , wherein the differential pressure sensor (10) is attached to a printed circuit board (60), wherein the housing of the filter monitoring system (1) comprises a first housing part (40) and a second housing part (50), the first housing part (40) the connection channel (41 ), which fluidly connects the first pressure connection (11) to the area (21) of the fluid channel (20) located downstream of the filter (4), the first housing part (40) connecting the second pressure connection (12) to the area (30) ) fluidically connects outside the fluid channel (20), the second housing part (50) having a receptacle for the circuit board (60), the circuit board (60) is optionally held in the receptacle by a holding device (51), and wherein the second housing part (50), the circuit board (60) with the differential pressure sensor (10) and the first housing part (40) can be connected to one another in such a way that the first pressure connection (11) of the differential pressure sensor (10) fits like a plug into the connecting channel (41) of the first housing part (40) and that the second pressure connection (12) comes to lie opposite a housing opening (46) in the first housing part (40) , through which an exchange of the ambient fluid (3) takes place. Filter monitoring system according to Claim 8 in combination with Claim 3 , the housing opening (46) in the first housing part (40) being spanned by the protective filter (52), the protective filter (52) optionally being clamped in the first housing part (40) by a removable protective filter holder (53). Filter monitoring system according to Claim 8 or 9 , wherein the circuit board (60) has a plug connection (61), in particular a LIN-compatible plug connection, on a side opposite the differential pressure sensor (10), and wherein the second housing part (50) surrounds this plug connection (61) in such a way that a Guide (54) is formed for a counterpart to the plug connection (61). Filter monitoring system according to one of the preceding claims, wherein the filter monitoring system (1) has an absolute pressure sensor (70) for determining the absolute pressure P _{0 of} the ambient fluid (3). Filter monitoring system according to Claim 11 , wherein the absolute pressure sensor (70) is arranged within the housing. Filter monitoring system according to one of the preceding claims, wherein the filter monitoring system (1) has an interface (101) for receiving GPS data from which the absolute pressure P _{0 of} the ambient fluid (3) can be determined. Filter monitoring system according to one of the preceding claims, wherein the filter monitoring system (1) has an interface (102) for receiving a signal from an engine control unit (90) of the vehicle, the absolute pressure P _{0 of} the ambient fluid (3) being determinable from the signal. An HVAC system comprising: a fluid channel (20); a filter (4) which is arranged in the fluid channel (20), and a filter monitoring system (1) with a differential pressure sensor (10) according to one of the preceding claims, wherein the filter monitoring system (1) is attached to the fluid channel (20) in such a way that the differential pressure sensor (10) a pressure difference ΔP between a pressure (P ₁ ) of a channel fluid (2) flowing through the fluid channel (20) in an area (21) of the fluid channel (20) located downstream of the filter (4) and a pressure (P ₀ ) of an ambient fluid (3) in an area (30) outside the fluid channel (20).

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