DE102017202584A1 - Fuel filter device for an internal combustion engine - Google Patents

Abstract

The invention relates to a fuel filter device (1) for an internal combustion engine. The fuel filter device (1) comprises a ring filter element (2), through which a fuel (8) can flow, which separates a raw side (3) from a clean side (4). The fuel filter device (1) further comprises a water separator (6) having an electric coalescer (5) with two electrodes (10, 11) for coalescing water (7) contained in the fuel (8) and an end separator (16) for depositing the water Has water (7) from the fuel (8). The electric coalescer (5) is arranged to determine at least one dielectric property of the fuel (8) passed through the electric coalescer (5).

Description

The present invention relates to a fuel filter device for an internal combustion engine and an internal combustion engine having such a fuel filter device.

In modern fuel supply systems, water separators are usually used in the associated fuel filter devices in order to lower as far as possible a water content contained in the fuel. If the water contained in the fuel is not separated and separated, it can lead to undesired corrosion, abrasion, material embrittlement and cavitation in the following units. Likewise, an increased proportion of water in the fuel supply system leads to a growth promotion of microorganisms, which cause a mucus of the fuel filter device and can cause increased corrosion on the filter housing. As a water separator so-called coalescers are usually used, which coalesce the smallest portions of water to larger water droplets and deposit them by gravity from the fuel-water emulsion. If necessary for the separation of water, a so-called end separator consisting of a hydrophobic tissue can also filter out the drops of water contained in the fuel-water emulsion. The water separated in this way is then collected in separate water collecting chambers, from which it is drained periodically or at the latest when a filter element is replaced.

Against this background is from the DE 10 2010 062 813 A1 a filter device for an internal combustion engine of a motor vehicle, in particular a fuel or lubricant filter, with a filter housing and a arranged in this and in the radial direction from a raw side to a clean side perfused ring filter element known. On the clean side of the filter element and below it, a water separator is arranged, which has a continuous from radially outside to radially inward for fuel / lubricant, hydrophobic and extending in the axial direction of the filter element, annular membrane. This is a classic coalescer, which in combination with an end separator should improve the water separation efficiency.

However, diesel fuels from various countries of origin not only contain water that separates, but also often vary greatly in their composition and properties. Substances are often added in addition to the requirements of the various fields of application and the legislative requirements. In addition, a wide variety of environmental conditions during storage of the fuels act on these. The sum of these factors leads to different fuel qualities with different fuel properties. For example, low quality fuels can significantly reduce the life of fuel supply system and engine components. The diesel engine combustion process and the resulting emissions are also dependent on the fuel quality. Adding fossil diesel fuel biodiesel (FAME) can reduce CO ₂ emissions. However, the beneficial, emission-reducing effect of the FAME admixture has a significant disadvantage. Consequences, which are caused by the emergence of aging products of biofuel, have a detrimental effect on the entire fuel supply system. The oxidative aging of blended fuels with biogenic content causes an increase in the viscosity of the fuel fluid, a reduction in the lubricity thereof, and can lead to precipitation formation, in which the aging products accumulate as sediment. The resulting aging products are mostly oligomers, which are polar substances and thus do not go in the non-polar fuel in solution. As a result, among other things, the functionality of fuel filters can be affected, but also in the diesel engine combustion of the mixed fuels unwanted by-products can be generated. Furthermore, biodiesel components that enter the engine oil can negatively affect its properties and also accelerate its aging.

The present invention therefore deals with the problem of providing a fuel filter device with an improved embodiment, which achieves good separation values for the water contained in the fuel and by means of which information about the further composition of the fuel can be obtained simultaneously.

This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The basic idea of the invention is therefore to use an electric coalescer not only for separating water, but also to form it in addition to determining at least one dielectric property of the fuel carried by the coalescer.

Dielectric properties, such as the relative permittivity of a fuel - also known to those skilled in the art as "relative dielectric conductivity" - may, especially if the fuel is a diesel fuel, be used as an indicator of the quality of the fuel.

The information obtained about the prevailing fuel properties can then be used as the basis for adjusting the combustion strategy of internal combustion engines. An optimization of the engine management can be achieved, for example, by adjusting the timing of the engine valves to the cetane number or by varying and adjusting the injection cycles. Different compositions of the fuel imply different energy contents of the fluid mixture, which in turn results in an unreasonable combustion of unnecessary fuel consumption, which can be avoided by a fuel quality-based engine control - in particular with regard to the valve timing, the control of the injection or Nacheinspritzung. The thus also controllable emission quality represents another claim to the fuel quality sensors.

Regardless of the foregoing advantages, which result from the determination of at least one dielectric property of the fuel, the use of an electric coalescer in a fuel filter device also permits effective separation of water from the fuel passed through the coalescer. Compared to conventional coalescers with corresponding coalescer materials, an electrical coalescer is subject to little or no wear and thus can remain there throughout the life of the fuel filter device. As a result, in particular the maintenance costs for such a fuel filter device can be significantly reduced. In addition, an electric coalescer has a greater insensitivity to the composition of the fuel, other additives and water, without affecting the coalescer efficiency. In addition, it is of particular advantage that an electric coalescer offers the possibility of influencing the specific parameters of the coalescing process, for example the drop movement or droplet formation, individually. Of particular advantage in the inventive arrangement of the two electrodes of the electric Koaleszers is also that they can be arranged at previously unoccupied points, whereby the fuel filter device according to the invention can be constructed extremely compact.

By dispersing water into fuel, a water-fuel emulsion is generated. It is a binary system, the essential feature of which is the formation of a miscibility gap that extends over almost the entire concentration range. Due to the thermodynamic instability of the system, this aims at a state that represents a minimum in terms of energy. The separation of the two phases is thus accelerated until finally there is complete phase separation. In order to intensify the demulsification process in a water-in-fuel emulsion, the beneficial effect of the presence of an electric field is now utilized. The process of droplet coalescence is forced by the polarizing effect of the applied electric field. The forces occurring in the electric field cause an increase in the mobility of the water droplets, this consequently leads to a higher collision rate, which in turn has a positive effect on the droplet coalescence. The drops thus combine to form larger drops and flow together. If the drops are correspondingly large, gravity outweighs and the specific denser water phase decreases.

A fuel filter device according to the invention for an internal combustion engine comprises a ring filter element, through which fuel can pass, for separating dirt particles from the fuel, which separates a raw side from a clean side. The fuel filter device further comprises a water separator, which in turn comprises an electric coalescer with two electrodes for coalescing water contained in the fuel and an end separator for separating the water from the fuel.

According to the invention, the electric coalescer is designed to determine at least one dielectric property of the fuel carried by the coalescer.

According to a preferred embodiment, the electric coalescer is arranged on the clean side of the ring filter element. In this embodiment, the two electrodes extend along a longitudinal direction, which preferably extends coaxially to a filter axis or a central longitudinal axis of the ring filter element. The two electrodes thus limit a flow path through which the fuel can flow, in which the two electrodes form with the fuel an electrical capacitor whose capacitance depends on the dielectric properties of the fuel. Said dielectric properties, in particular the dielectric property of the fuel, can thus be determined by a simple capacitive measurement.

Particularly advantageously, the at least one dielectric property of the fuel comprises or is its relative dielectric conductivity. This can be particularly easily quantified by means of capacitive measurement, so that even simple The quality of the fuel present can be determined.

According to a preferred embodiment, the electrical coalescer has an electrical measuring device for determining the dielectric properties, in particular the relative dielectric conductivity, of the fuel carried by the coalescer. The two electrodes of the electric coalescer are part of the electrical measuring device in this embodiment. By means of the electrical measuring device can thus be carried out using the two electrodes in a particularly simple manner, the capacitive measurement for determining the relative dielectric conductivity of the fuel.

In a preferred embodiment, the two electrodes and the fuel guided through the flow path together form an electrical capacitor with a complex impedance, which can be determined by means of the electrical measuring device.

Suitably, the electrical measuring device comprises an electrical voltage source which generates an electrical output voltage and is electrically connected to the two electrodes. Preferably, the generated electrical output voltage may be an alternating electrical voltage. By means of such a voltage source, the desired separation of water from the fuel can be achieved in the electric coalescer on the one hand. On the other hand, it is possible to generate the required for carrying out the previously capacitive measurement voltage. This eliminates the provision of two separate electrical voltage sources to provide both functions, which does not significantly simplify the construction of the measuring device and thus leads to cost advantages.

Furthermore, according to a further preferred embodiment, the electrical measuring device may comprise an electrical voltage measuring unit, which may be designed in particular as a voltmeter. In this embodiment, the electrical voltage measuring unit of the fuel guided through the flow path is electrically connected to the two electrodes, so that the electrical voltage dropping across the fuel can be detected to determine the complex electrical impedance of the fuel.

The electrical measuring device expediently also comprises an evaluation unit cooperating with the electrical voltage source and with the electrical voltage measuring unit. The evaluation unit is in this case designed such that the complex impedance of the fuel can be determined by evaluating the voltage drop across the fuel as a function of the electrical output voltage which is provided by the electrical voltage source. From the complex impedance, the desired relative dielectric conductivity of the fuel can then be calculated.

In a further advantageous development, the electrical measuring device comprises a control unit cooperating with the electrical voltage source, by means of which the electrical output voltage generated by the electrical voltage source can be varied. In this way, the electric coalescer can be switched over between a first operating state in which it interacts with the final separator as a water separator for the fuel carried by the coalescer, and a second operating state in which it receives the at least one dielectric property of the one produced by the coalescer guided fuel determined.

In an advantageous development, the electrical voltage source in the first operating state generates an electrical output voltage that is different from the electrical output voltage generated in the second operating state. In a particularly preferred variant, at least the electrical output voltage generated by the electrical voltage source in the second operating state is an electrical alternating voltage. In this way, the coalescer can be used on the one hand for its actual determination, ie, in conjunction with the final separator, the separation of water from the fuel. On the other hand, by switching from the first to the second operating state, it is also possible to obtain information on the quality of the fuel by determining the dielectric property (s) of the fuel.

In a further advantageous development, the fuel filter device is designed to flow through with a fuel whose dielectric conductivity has at most a predetermined maximum value. In this development, at least one of the two electrodes has an electrode insulation whose dielectric conductivity has a greater value than said predetermined maximum value. Preferably, this value is at least twice, most preferably at least five times the predetermined maximum value. Particularly preferred applies above for both electrodes. By said measures, a displacement of the electric field is achieved in the flowing through the electric coalescer fuel. This in turn is accompanied by an increased electrical voltage drop across the fuel, so that the complex impedance of the fuel can be determined with increased accuracy.

In another advantageous development, a first of the two electrodes is an internal electrode and a second of the two electrodes is an external electrode. In this development, the two electrodes together limit the flow path designed as an annular channel for flowing through with the fuel. Preferably, the external electrode is electrically connected to an electrical ground potential or at least connected to such. As a result, susceptibility can be avoided or at least reduced, which are caused by external electrical and magnetic fields.

Suitably, at least one electrode may be designed as two-component injection-molded electrodes. In this case, an electrically conductive plastic forms an inner component. Said inner component is encased externally by a second, electrically insulating outer component. Particularly expedient both electrodes are formed as described above.

In an advantageous development, the two electrodes for limiting the annular channel are each tubular. In the installed state, this annular channel particularly preferably has tangentially directed inflow openings arranged at the top, which force a helical flow of the fuel in the annular channel. This leads to an increased cross-section of the water separator.

The invention further relates to an internal combustion engine with a previously presented fuel filter device. The above-explained advantages of the fuel filter device are therefore also transferred to the internal combustion engine according to the invention.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

Corresponding 1 which is a sectional view through a fuel filter device according to the invention 1 shows, the fuel filter device 1 for an otherwise not shown internal combustion engine, a ring filter element 2 on, this is a raw page 3 from a clean side 4 separates and thus flows through in the present case from outside to inside.

In addition, a water separator 6 provided that an electric coalescer 5 with two electrodes 10 . 11 and an end separator 16 for separating the water 7 from the fuel 8th includes.

The electric coalescer 5 serves for depositing a polar phase, in particular for separating off water 7 , from the fuel 8th , In the example scenario, the water separator 6 with the electric coalescer 5 on the clean side 4 within the ring filter element 2 arranged.

Considering the fuel filter device 1 according to the 1 , so you can tell that the two electrodes 10 . 11 are tubular and have a flow path 21 in the form of an annular channel 12 limit, in the installed state of the fuel filter device 1 arranged above, tangentially directed inlet openings 13 which has a helical flow of fuel 8th in the ring channel 12 force.

Like the representation of the 1 clearly demonstrated, a first of the two electrodes 10 an internal electrode and a second of the two electrodes 11 an external electrode. The internal electrode 10 and the external electrode 11 limit together as the ring channel 12 trained flow path 21 for flowing through with fuel 8th , The two electrodes 10 . 11 can be designed as two-component injection-molded electrodes. In this case, an electrically conductive plastic form an inner component of the respective injection-molded electrode, which is encased externally by a second, electrically insulating outer component. It proves to be advantageous if the external electrode 11 electrically with an electrical ground potential 15 connected is.

The through the fuel filter device 1 and its ring filter element 2 from the raw side 3 to the clean side 4 flowing fuel 8th is initially along the outside electrode 11 deflected upwards until it reaches the inflow openings 13 reached. Since these are in the tangential direction in the annular channel 12 open, is the through the inlet openings 13 in the ring channel 12 incoming fuel 8th forced a helical flow or a helical flow, resulting in a prolonged contact with the two electrodes 10 . 11 and connected with it leads to an improved water separation. The heavier water droplets 7 are due to the adjusting centrifugal forces to the outside to the outside electrode 11 thrown and flow down along this. At the bottom of the internal electrode 10 is an end separator 16 provided, which has a sound beaker-like intermediate piece 17 into the internal electrode 10 passes. On the intermediate piece 17 are again flow guide 18 , For example, ribs arranged, which on the one hand further increase the coalescence and on the other hand, the already coalesced water droplets 7 radially outward in the direction of a housing wall 19 fling. From there they can then, following the direction of gravity, down into one below the end separator 16 located water collection room 20 fall. The fuel 8th whereas it passes through the final separator 16 through and flows through a through the hollow internal electrode 10 formed pure channel 30 up from the fuel filter device 1 out. The final separator 16 can also be equipped with a hydrophobic sieve. Such a hydrophobic screen may comprise textile fibers or a textile membrane.

The electric coalescer 5 is in the fuel filter device according to the invention 1 not only for separating water 7 from the fuel 8th educated; Rather, it is also used to determine at least one dielectric property of the coalescer 5 furnished fuel. This dielectric property can be the relative dielectric conductivity ε _{r of} the fuel 8th be. To determine the dielectric property, the two electrodes extend 10 . 11 along a longitudinal direction L coaxial with a filter axis 9 of the ring filter element 2 - In the example scenario, the filter axis 9 a central longitudinal axis 14 the cylindrical ring filter element 2 - runs. The two electrodes 10 . 11 limit the flow path 21 or the annular channel 12 laterally.

For determining the relative dielectric conductivity ε _r of the coalescer 5 guided fuel 8th owns the electric coalescer 5 an electrical measuring device 22 , The two electrodes 10 . 11 of the electric coalescer 5 are part of this electrical measuring device 22 ,

The two electrodes 10 . 11 and the through the flow path 21 or the annular channel 12 guided fuel 8th together form an electrical capacitor 25 with a complex electrical impedance Z out, by means of the electrical measuring device 22 can be determined. For this purpose, the electrical measuring device includes 22 an electrical voltage source 23 which generates an electrical output voltage V ₀ and via electrical conduction paths 26 electrically with the two electrodes 10 . 11 connected is. Between the electrical voltage source 23 and the electrodes 10 . 11 can be arranged further electrical and / or electronic components, which in the 1 for the sake of clarity is not shown. The electrical output voltage V ₀ is preferably an alternating electrical voltage for the determination of the complex impedance.

The electrical measuring device 22 further comprises an electrical voltage measuring unit 24 , which can be designed as a voltmeter. For determining the complex impedance Z des through the flow path 21 or the annular channel 12 guided fuel 8th is the electric voltage measuring unit 24 via electrical conduction paths 27 high impedance with the two electrodes 10 . 11 connected. By means of the electric voltage measuring unit 24 Can the fuel 8th falling voltage V are detected. From the electrical voltage V in turn, the complex impedance Z and from this the sought relative dielectric conductivity ε _{r of} the fuel 8th be calculated. In this case, the electrical measuring device comprises 22 one with the electrical voltage source 23 and with the electric voltage measuring unit 24 cooperating evaluation unit 28 , The evaluation unit 28 is now realized in such a way that by evaluation of the fuel 8th decreasing electrical voltage V as a function of that of the electrical voltage source 23 generated electrical voltage V _0, the complex impedance Z of the fuel 8th can be calculated. From the complex impedance Z can then the capacity of the fuel 8th and from this the relative dielectric conductivity ε _{r of} the fuel 8th be determined.

The electrical measuring device 21 includes accordingly 1 one with the electrical voltage source 23 cooperating control unit 29 , The control unit 29 can be the electrical power source 23 in such a way that the means of which the electrical output voltage V ₀ generated by the electrical voltage source can be varied. In this way, the electric coalescer 5 between a first operating state, in which he together with the Endabscheider 16 as a water separator 6 for that by the electric coalescer 5 guided fuel 8th acts, and be switched to a second operating state in which it has the at least one dielectric property of the electrical Koaleszer 5 guided fuel 8th certainly. In the first operating state generates the electrical voltage source 23 an electrical output voltage V ₀ , which is different from the electrical output voltage V ₀ generated in the second operating state. This electrical output voltage V ₀ may be a DC electrical voltage or an AC electrical voltage or a Combination of both. In particular, a pulsed DC voltage is conceivable. For the determination of the complex impedance Z, it is advantageous if that of the electrical voltage source 23 in the second operating state generated electrical output voltage is an electrical alternating voltage.

The fuel filter device 1 is preferred for flowing through with a fuel 8th equipped, the dielectric conductivity ε _{r has} at most a predetermined maximum value. At least one of the two electrodes 10 . 11 in this case has an electrode insulation whose dielectric conductivity has a greater value than the predetermined maximum value described above. By means of this measure it is ensured that the at the electrodes 10 . 11 generated electric field in the flow path 21 is pushed into it, causing the complex impedance Z of the fuel 8th can be measured with very high accuracy.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102010062813 A1 [0003]

Claims (16)

Fuel filter device (1) for an internal combustion engine, with a ring filter element (2) permeable by fuel (8) for separating dirt particles from the fuel, which separates a raw side (3) from a clean side (4), - With a water separator (6) having an electric Koaleszer (5) with two electrodes (10, 11) for coalescing in the fuel (8) contained water (7) and an Endabscheider (16) for separating the water (7) comprising fuel (8), - Wherein the electrical coalescer (5) is arranged to determine at least one dielectric property of the guided through the electric coalescer (5) fuel (8). Fuel filter device according to Claim 1 , characterized in that the electric coalescer (5) is arranged on the clean side (4) of the ring filter element (2), wherein the two electrodes (10, 11) extend along a longitudinal direction (L) which is preferably coaxial to a filter axis (10). 9) or a central longitudinal axis (14) of the ring filter element and delimiting a flow path (21) through which the fuel (8) can flow. Fuel filter device according to Claim 1 or 2 , characterized in that the at least one dielectric property is the relative dielectric conductivity (ε _r ) of the fuel (8). Fuel filter device according to one of the preceding claims, characterized in that the electrical coalescer (5) for determining the dielectric properties, in particular the relative dielectric conductivity (ε _r ), of the fuel (8) guided through the electric coalescer (5) comprises an electrical measuring device ( 22), wherein the two electrodes (10, 11) are part of the electrical measuring device (22). Fuel filter device according to Claim 4 , characterized in that the two electrodes (10, 11) and the through the flow path (21) guided fuel (8) together form an electrical capacitor (25) having a complex electrical impedance (Z) by means of the electrical measuring device (22 ) is determinable. Fuel filter device according to Claim 4 or 5 , characterized in that the electrical measuring device (22) comprises an electrical voltage source (23) which generates an electrical output voltage (V ₀ ) and is electrically connected to the two electrodes (10, 11). Fuel filter device according to Claim 6 , characterized in that the electrical output voltage (V ₀ ) is an electrical alternating voltage. Fuel filter device according to one of Claims 4 to 7 , characterized in that the electrical measuring device (22) comprises an electrical voltage measuring unit (24), in particular a voltmeter, which for determining the complex impedance (Z) of the guided through the flow path (21) fuel (8) electrically with the two electrodes (10, 11) is connected and by means of which the fuel (8) falling electrical voltage (V) can be detected. Fuel filter device according to one of Claims 6 to 8th , characterized in that the electrical measuring device (22) comprises an evaluation unit (28) cooperating with the electrical voltage source (23) and with the electrical voltage measuring unit (24), designed such that by determining the electrical voltage dropping on the fuel (8) ( V) the complex impedance of the fuel (Z) and from this the relative dielectric conductivity (ε _r ) of the fuel (8) can be determined. Fuel filter device according to one of Claims 6 to 9 , characterized in that the electrical measuring device (22) comprises a with the electrical voltage source (23) cooperating control unit (29), by means of which of the electrical voltage source (23) generated electrical output voltage (V ₀ ) is variable, so that the electric Coalescer (5) between a first operating state in which it acts together with the Endabscheider (16) as a water separator (7) for the guided through the electric Koaleszer (5) fuel (8), and a second operating state in which he at least a dielectric property of the fuel (8) guided by the electric coalescer (5) is adjustable. Fuel filter device according to one of Claims 6 to 10 , characterized in that the electrical voltage source (23) in the first operating state generates an electrical output voltage (V ₀ ) which is different from the electrical output voltage (V ₀ ) generated in the second operating state, wherein preferably at least the electrical output voltage generated in the second operating state ( V ₀ ) is an electrical alternating voltage. Fuel filter device according to one of the preceding claims, characterized in that - the fuel filter device (1) is designed to flow through with a fuel (8) whose dielectric conductivity (ε _r ) has at most a predetermined maximum value, - at least one of the two electrodes (10, 11) has an electrode insulation whose dielectric conductivity has a greater value has as the predetermined maximum value and preferably at least twice, most preferably at least five times the predetermined maximum value. Fuel filter device according to one of the preceding claims, characterized in that a first of the two electrodes (10) is an internal electrode and a second of the two electrodes (11) is an external electrode which together form the flow path (21) designed as an annular channel (12). for flowing through with fuel (8) limit, wherein the external electrode (11) with an electrical ground potential (15) is connectable or connected. Fuel filter device according to one of the preceding claims, characterized in that at least one electrode (10, 11), preferably both electrodes (10, 11), is designed as a two-component injection-molded electrodes, wherein an electrically conductive plastic is an internal component formed, which is externally covered by a second, electrically insulating outer component, Fuel filter device according to one of the preceding claims, characterized in that the two electrodes (10,11) for defining the annular channel (12) are each tubular, wherein the preferably in the installed state above arranged tangentially directed inflow openings (13) having a helical Force flow of the fuel (8) in the annular channel (12). Internal combustion engine with a fuel filter device (1) according to one of the preceding claims.

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