EP3877746A1

EP3877746A1 - Particle sensor and method for operating same

Info

Publication number: EP3877746A1
Application number: EP19787230.2A
Authority: EP
Inventors: Andy Tiefenbach; Christopher Henrik SCHITTENHELM
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-11-06
Filing date: 2019-10-14
Publication date: 2021-09-15
Also published as: DE102018218918A1; WO2020094335A1

Abstract

The invention relates to a particle sensor comprising a particle charging device for charging particles in a fluid flow flowing in the region of the particle sensor, the particle charging device having at least one corona electrode for producing a corona discharge. The particle sensor has a control device which is designed to supply a variable electrical potential to the at least one corona electrode.

Description

description

title

Particle sensor and operating method therefor

State of the art

The disclosure relates to a particle sensor with a particle charging device for charging particles in a fluid stream flowing in the area of the particle sensor.

The disclosure further relates to an operating method for such a particle sensor.

Disclosure of the invention

Preferred embodiments relate to a particle sensor with a particle charging device for charging particles in a fluid stream flowing in the area of the particle sensor, the particle charging device having at least one corona electrode for generating a corona discharge, the particle sensor having a control device which is designed to do this to apply at least one corona electrode with a variable electrical potential. This advantageously provides the possibility of using different particle charging devices

Operate corona voltages, which can affect the charging of particles. In this way, the operation of the particle charging device or the particle sensor on different ones can be advantageous

Operating states of a target system for the particle sensor (e.g. a

Exhaust system of an internal combustion engine) can be adapted or a measurement accuracy of the particle sensor can be increased.

For example, the fluid flow can be an exhaust gas flow from an internal combustion engine of a motor vehicle. For example, it can the particles are soot particles, such as those generated in the course of combustion of fuel by an internal combustion engine.

In a preferred embodiment, the particle sensor has a

Base body or a substrate element. The is particularly preferred

Base body formed from an essentially planar ceramic substrate. The base body can, for example, be essentially cuboid

Have basic shape with a width and a length, with a

Height dimension in terms of width and length is comparatively small. Furthermore, the particle charging device is preferably on a first one

Arranged outer surface of the base body.

In a further advantageous embodiment, the

Particle charger by generating a corona discharge an electrical charge of particles or particles in general, e.g. also of gases from the fluid flow or exhaust gas flow in a room around the

Corona electrode. On the one hand, particles are charged directly when flowing through a space in the area of the first surface in which the corona discharge takes place. On the other hand, particles are charged via charged particles of the gas or exhaust gas stream, the gas or exhaust gas stream being charged directly when flowing through the space in the region of the high-voltage electrode. Overall, this improves the effectiveness of the charging. In a preferred embodiment, the corona electrode has at least one needle-shaped area or tip.

In a further embodiment, the particle charging device has a counter electrode to the corona electrode. In the present case, a counter electrode is understood to mean an electrode which is different from the corona electrode and which can be acted upon with a different electrical potential with respect to the corona electrode. For example, the counter electrode to the corona electrode can be connected to a reference potential, such as a ground potential, for example, or it can be fixed to a reference potential

Circuit node to be connected. In further embodiments, the corona electrode can have a positive or negative electrical potential applied to the counter electrode. In a further embodiment, the counterelectrode is particularly preferably likewise arranged on the first surface, which results in a particularly simple construction and efficient manufacture of the particle sensor.

The counter electrode is particularly preferably completely on the first

Surface arranged.

In further preferred embodiments it is provided that the

Particle charger at least one further electrode, e.g. has the counter-electrode to the corona electrode already mentioned above, the control device being designed to carry out the at least one

Corona electrode and the at least one further electrode (e.g.

Counter electrode) with a variable electrical voltage, the

hereinafter also referred to as "corona tension".

In further preferred embodiments it is provided that the

Control device is designed to change a polarity of the changeable electrical potential and / or the changeable electrical voltage. This results in further degrees of freedom for the operation of the particle sensor.

In further preferred embodiments it is provided that the

Control device is designed to receive first data from at least one external unit and to change the electrical potential or the electrical voltage, in particular corona voltage, as a function of the first data. For example, the external unit can be a control unit of an internal combustion engine, in whose exhaust system the particle sensor is used.

In further preferred embodiments it is provided that a) the particle sensor has at least one sensor electrode, the

Control device is designed to evaluate a signal from the sensor electrode, and / or wherein the particle sensor has at least one ion trap, in particular in the form of a trapezoidal electrode, the control device being designed to provide the ion trap with a predeterminable (possibly also temporally variable) electrical potential or to apply a predeterminable electrical voltage. As a result, the control device can advantageously simultaneously provide a changeable corona voltage or one effect the corresponding changeable potential for the corona electrode and evaluate the other parameters of the particle sensor mentioned or

provide.

In further preferred embodiments it is provided that the

Control device is designed to act on the corona electrode at least temporarily with a DC voltage of different magnitude, for example in the form of a stepped DC voltage, with a respective amount corresponding to a step of the stepped DC voltage

DC voltage is set for a predeterminable time, and in further preferred embodiments the same or different predefinable times can be provided for different DC voltage levels.

In further preferred embodiments it is provided that the

Control device is designed to act on the corona electrode at least temporarily with a voltage which changes at least approximately linearly over time. In further preferred embodiments, for example, a desired gradient (measure of the change in voltage over time) can be set.

In further preferred embodiments it is provided that the

Control device is designed to apply a pulsed voltage to the corona electrode at least temporarily.

Further preferred embodiments relate to a method for operating a particle sensor with a particle charging device

Charging particles in a fluid stream flowing in the area of the particle sensor, the particle charging device at least one

Corona electrode for generating a corona discharge, the particle sensor having a control device, wherein the control device acts on the at least one corona electrode with a variable electrical potential.

In further preferred embodiments it is provided that the

Particle charging device has at least one further electrode, the control device acting on the at least one corona electrode and the at least one further electrode with a variable electrical voltage. In further preferred embodiments it is provided that the

Control device receives first data from at least one external unit and changes the electrical potential or the corona voltage depending on the first data.

Further preferred embodiments relate to the use of at least one particle sensor according to the embodiments and / or at least one method according to the embodiments for determining a number of particles of different sizes in the fluid flow.

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are shown in the figures of the drawing. All of the described or illustrated features, alone or in any combination, form the subject matter of the invention, regardless of their

Summary in the claims or their relationship and regardless of their wording or representation in the description or in the drawing.

The drawing shows:

FIG. 1 schematically shows a side view of a first embodiment of the particle sensor according to the invention,

Figure 2,

3, 4, 5 schematically each show the arrangement of the particle sensor according to

1 in a target system,

Figure 6 to

12 each schematically shows a time course of operating variables of preferred embodiments, and

FIG. 13 schematically shows a simplified flow diagram of a method according to further preferred embodiments. FIG. 1 schematically shows a side view of a first embodiment of the particle sensor 100 according to the invention. The particle sensor 100 has a preferably planar base body 102, which is formed, for example, by a substrate made of an electrically non-conductive material, such as, for example

Ceramic material can be formed. In the present case, the base body 102 has a vertical thickness in FIG. 1, which is preferably smaller, in particular significantly smaller (for example by at least approximately 80% smaller) than a length extending along the x-axis and smaller than one perpendicular in FIG. 1 Ready area extending to the drawing plane.

The particle sensor 100 has a particle charging device 110

electrical charging of particles which are located in a fluid stream A1 flowing in the area of the particle sensor 100, the

Particle charger 110 has at least one corona electrode 1 12 for generating a corona discharge C. Furthermore, the particle sensor 100 has a control device 120 which is designed to apply a variable electrical potential to the at least one corona electrode 112, cf. the supply line 121a. This advantageously provides the possibility of operating the particle charging device 110 at least at times with different corona voltages Uc, as a result of which charging of particles can be influenced. In this way, the operation of the particle charging device 110 or the particle sensor 100 can advantageously be based on different operating states of a target system for the

Particle sensor 100 (e.g. an exhaust system of an internal combustion engine) can be adapted or a measurement accuracy of the particle sensor 100 can be increased.

For example, the fluid flow A1 can be an exhaust gas flow from an internal combustion engine of a motor vehicle. For example, the particles can be soot particles, such as those that arise during the combustion of fuel by an internal combustion engine.

In further preferred embodiments, the

Particle charger 110 by generating the corona discharge C an electrical charge of particles or generally particles, e.g. also of gases from the fluid flow A1 or exhaust gas flow in a room around the

Corona electrode 112. On the one hand, particles are directly at the Flowing through a space located in the area of the surface 102a in which the corona discharge C takes place. On the other hand, particles are charged via charged particles of the gas or exhaust gas stream A1, the gas or exhaust gas stream A1 being charged directly when flowing through the space in the region of the high-voltage electrode 1 12. Overall, this improves the effectiveness of the charging. In a preferred one

In one embodiment, the corona electrode 1 12 has at least one needle-shaped area or tip 1 12 ′.

In a further embodiment, the particle charging device 110 has an optional counter electrode 114 to the corona electrode 112. In the present case, a counter electrode is understood to mean an electrode which is different from the corona electrode 112 and which can be acted upon with a different electrical potential with respect to the corona electrode 112, cf. the optional supply line 121 b. For example, the counter electrode 114 to the corona electrode 112 can have a reference potential such as, for example

Ground potential are set or be firmly connected to a circuit node having the reference potential. With others

In embodiments, the corona electrode 1 12 can be acted upon by the control device 120 at least temporarily with a positive or negative electrical potential with respect to the counter electrode.

In a further embodiment, the counterelectrode 114 is also particularly preferably arranged on the surface 102a, which results in a particularly simple construction and efficient manufacture of the particle sensor 100.

In further preferred embodiments it is provided that the

Particle charger at least one further electrode, e.g. the above-mentioned counter electrode 1 14 to the corona electrode 112, wherein the control device 120 is designed to control the at least one corona electrode 1 12 and the at least one further electrode 1 14 (for example counter electrode) with a variable electrical voltage Uc, which also below is referred to as "corona tension".

In further preferred embodiments it is provided that the

Control device 120 is designed to polarity of the changeable electrical potential and / or the changeable electrical voltage Uc to change. This results in further degrees of freedom for the operation of the particle sensor 100.

In further preferred embodiments it is provided that the

Control device 120 is designed to receive first data D1 from at least one optional external unit 200 and to change the electrical potential or the electrical voltage Uc as a function of the first data D1. For example, the external unit 200 may be one

Act control unit of an internal combustion engine, in whose exhaust system the particle sensor 100 is used. A data connection between the

Control device 120 and external unit 200 can be implemented, for example, via a CAN bus and / or a comparable data connection.

In further preferred embodiments it is provided that the

Particle sensor 100 has at least one optional sensor electrode 130, the control device 120 in particular being designed to evaluate a signal S1 from the sensor electrode 130, for example in order to determine a number and / or concentration of particles (in particular charged by means of the particle charging device 110). The at least one is preferred

Sensor electrode 130 is also arranged on the surface 102a of the substrate 102.

In further preferred embodiments it is provided that the

Particle sensor 100 has at least one optional ion trap 140, in particular in the form of a trapezoidal electrode, the control device 120 in particular being designed to apply a predeterminable electrical potential or a predeterminable electrical voltage to the ion trap 140.

The optional trapezoidal electrode 140 is provided for deflecting charged particles of the fluid flow A1, which, for example, by means of the

Particle charger 1 10 have been generated further upstream with respect to fluid flow A1. For example, trapezoidal electrode 140,

in particular by the control device 120, with the same (or a different) electrical potential as the corona electrode 1 12, cf. the supply line 121c. Particles charged by trapezoidal electrode 140, in particular ions, can be particularly advantageous from the

Fluid flow A1 are deflected or "captured" so that it does not close of the optional sensor electrode 130 arranged further downstream.

By means of the above optional measures 130, 140, 121c, S1, the control device 120 can advantageously provide a

cause changeable corona voltage or a corresponding changeable potential for the corona electrode 112 and evaluate the other parameters of the particle sensor mentioned (signal S1) or provide (voltage for the trapeze electrode 140).

The sensor electrode 130 is provided for acquiring information S1 about an electrical charge current, which is caused by charged particles from the fluid flow A1. For example, these can be particles which have been electrically charged further upstream with respect to the fluid flow A1 by means of the particle charging device 110 or by means of the corona discharge C generated by them. Preferably, only comparatively heavy charged particles reach the sensor electrode 130 in the downstream direction because, as already described above, comparatively light charged particles such as ions are deflected or captured by the optional trapeze electrode 140. Thereby, the sensor electrode 130 enables e.g. by means of a measurement of the charge influence caused by the

Charged particles flowing past sensor electrode 130 is effected, the determination of a concentration of the charged particles in the fluid stream A1. For example, as already mentioned, the fluid flow A1 can be an exhaust gas flow from an internal combustion engine (not shown). For example, the particles can be soot particles, such as those that arise during the combustion of fuel by an internal combustion engine.

In further embodiments, it is conceivable not to provide an optional sensor electrode 130. In these variants of the invention, the so-called “escaping current” principle can be used to measure a charge current of the charged particles. For this purpose, the complete system containing the particle sensor 100 can preferably be isolated from the outside (in particular, this makes the counter electrode 1 14 of the corona electrode 1 12 and any optional counter electrode for the trapeze electrode “virtual”), and an electrical current is measured , which the charged particles in the form of their electrical charge from the otherwise electrically isolated and therefore Remove the closed System 100. For example, the electrical current under consideration flows from the corona electrode 112 through the corona discharge C into the counter electrode 114, and the trapeze electrode 140 or its counter electrode, not shown here, traps the remaining ions. The current generated by the charged particles must be added to the counter electrode 114 again so that its electrical potential remains constant. It is known as the "escaping current" and is a measure of the concentration of charged particles.

In the embodiment shown in FIG. 1, an electrically conductive element (not shown) can be used as the counter electrode for the trapeze electrode 140.

for example, a metal sheet can be provided, which is arranged (against) above the surface 102a. In some embodiments, e.g. a protective tube surrounding the particle sensor 100 (not shown in FIG. 1) made of an electrically conductive material or with an electrically conductive surface which is present at least in sections serves as a counter electrode for the optional trapeze electrode 130.

FIG. 2 schematically shows the arrangement of the particle sensor 100 according to FIG. 1 in a target system Z, which in the present case is an exhaust tract of an internal combustion engine, for example a motor vehicle. A

Exhaust gas flow is designated in the present case with the reference symbol A2. Also shown is a protective tube arrangement composed of two tubes R1, R2 arranged concentrically to one another, the particle sensor 100 being arranged in the inner tube R1 in such a way that its surface 102a runs essentially parallel to a longitudinal axis LA of the inner tube R1. Due to the

Different lengths and the arrangement of the tubes R1, R2 relative to each other results in a suction by the Venturi effect, in which the

Exhaust gas flow A2 causes a fluid flow P1 or A1 out of the inner tube R1 in FIG. 2 in the vertical direction upwards. The further arrows P2, P3, P4 indicate the continuation of this fluid flow caused by the Venturi effect through an intermediate space between the two tubes R1, R2 to the surroundings of the protective tube arrangement. Overall, the arrangement shown in FIG. 2 results in a comparatively uniform overflow of the particle sensor 100 or its first surface 102a aligned along the fluid flow A1, which enables efficient detection of particles located in the fluid flow A1, P1. About that In addition, the particle sensor 100 is protected from direct contact with the main exhaust gas stream A2. The elements 100, R1, R2 thus advantageously provide a sensor device 1000 for determining a particle concentration in the exhaust gas A2.

The reference symbol R2 'indicates an optional electrical connection of the outer tube R2 and / or the inner tube R1 with a reference potential such as, for example, the ground potential, so that the tube or both tubes in question advantageously simultaneously with their fluidic conducting function as an electrical counterelectrode, for example for the optional one Trapel electrode 130 (and / or for the corona electrode 112), see FIG. 1, can be used.

FIG. 3 schematically shows an exhaust pipe R and parts of the sensor device 1000 according to FIG. 2 in the exhaust pipe R. In particular, FIG. 3 again shows the particle sensor 100 within the protective pipe arrangement R1, R2 (FIG. 2). The particle sensor 100 is thus in the protective tube arrangement

aligned so that its surface 102a extends along the x-axis, whereas the flow direction of the exhaust gas A2 in the exhaust pipe R is aligned parallel to the y-axis.

FIG. 4 schematically shows a further preferred configuration in which the arrangement of the corona needle 112 'on a ceramic carrier 102 can be seen, as well as the protective tubes R2, R3 already described above with reference to FIG. 2. A holder 1002 is provided on the left in FIG. 4, to which the protective tubes R2, R3 and the carrier 102 can be fastened.

FIG. 5 schematically shows a further preferred configuration. Visible is the exhaust pipe R with particles P in the exhaust gas flow A1, the particle sensor 100, and in the present case by means of a data connection (e.g. connecting lines) 121 with the particle sensor 100 or with at least one of its components 110,

1 12, 1 14, 130, 140 connected control device 120. The control device 120 can also be seen by means of a CAN bus connection 122 with the

Control unit 200a connected, which is, for example, a control unit of an internal combustion engine of a motor vehicle, which generates the exhaust gas flow A1. In further preferred embodiments it is provided that the

Control device 120 (FIG. 1) is designed to at least temporarily apply a different amount of DC voltage to the corona electrode 112, for example in the form of a stepped DC voltage, cf. Curve K1 from FIG. 6, wherein a respective amount of the DC voltage corresponding to a step Uo, Ui, U2, U3, U _{4 of} the stepped DC voltage K1 is set for a predeterminable time, with others being preferred

Embodiments for different DC voltage levels Uo, Ui, U2, U3, U _{4 the} same (as shown by way of example in FIG. 6) or different (not shown) predeterminable times T01, T12, T23, T34 can be provided.

In further preferred embodiments, the polarity of the corona voltage Uc (FIG. 1) can also be changed, cf. e.g. curve K2 from FIG. 7, in which the gradation described above with reference to FIG. 6 is combined with a change in polarity.

In further preferred embodiments it is provided that the

Control device 120 (FIG. 1) is designed to act upon corona electrode 112 at least temporarily with a voltage that changes at least approximately linearly over time, cf. e.g. Curve K3 from FIG. 8. In further preferred embodiments, for example, a desired gradient (measure of the change in voltage over time, “steepness”) can be set, in particular also varied over time, cf. the

Time ranges T1, T2.

In further preferred embodiments it is provided that the

Control device 120 is designed to apply a pulsed voltage to the corona electrode 1 12 (FIG. 1) at least temporarily, cf. Curve K4 from FIG. 9. An amount (and / or a polarity) of the voltage for the respective pulses p01, p02, p03 can be specified, for example, as a function of a respective operating point of the exhaust system or of the internal combustion engine containing the particle sensor 100 and by the control device 120 can be set.

FIG. 10 shows, by way of example, a further chronological course of the corona voltage predetermined by the control device 120, cf. Curve K5, in which depending on different operating points (eg signaled by the external unit 200 (FIG. 1) using the data D1) a sawtooth

Voltage profile with different gradients is given in certain areas, cf. the different operating points BP1, BP2, BP3.

FIG. 1 shows an example of a further chronological course of the corona voltage predetermined by the control device 120, cf. Curve K6, in which, depending on different operating phases BPH1, BPH2 (e.g. again signaled by the external unit 200 (FIG. 1) using the data D1), differently pulsed DC voltages are provided. FIG. 12 shows a comparable embodiment with the two different ones

Operating phases BPH1 ″, BPH2 ″, in addition to the voltage curve according to FIG. 11, a change in the polarity of the voltage curve K7 between the operating phases BPH1 ″, BPH2 ″ is also provided.

Further preferred embodiments relate to a method for operating a particle sensor 100 (FIG. 1), cf. 13. In step 300, the control device 120 applies a first electrical potential to the at least one corona electrode 112, and in the subsequent optional step 310, the control device 120 applies a second electrical potential to the at least one corona electrode 112, which is generated by the first potential is different.

Further preferred embodiments relate to the use of at least one particle sensor 100 according to the embodiments and / or at least one method according to the embodiments for determining a number of particles of different sizes in the fluid stream A1 (FIG. 1).

The principle according to the embodiments advantageously enables a targeted variation of the corona voltage Uc, in particular when the particle sensor 100 is in operation, as a result of which a precision in determining a number or concentration of the particles can be increased compared to conventional systems.

In general, the particle sensor 100 can e.g. be used to determine soot mass in the exhaust tract of an internal combustion engine, e.g. to

Monitoring of diesel particle filters or comparable particle filters for petrol-powered vehicles. A disadvantage of conventional systems in particular that, due to the principle, the electrical charge of a comparatively small number of small, but differently sized, particles is measured, which results in very small measuring currents (eg signal S1 from sensor electrode 130).

In particular, the particles P to be measured (Fig. 5) have different sizes in the range of e.g. a few nanometers (nm) to typically about 300 nm and carry different positive or negative, natural electrical charges or are neutral. According to investigations by the applicant, the collective of these particles P has a size distribution and a charge distribution which depend on many boundary conditions: from an operating point of the internal combustion engine which generates the exhaust gas stream A1, from an application of this internal combustion engine, from the type and operation of the exhaust gas aftertreatment components used, such as Catalysts on the exhaust side, for example are arranged in front of a particle filter, the aging of this entire facility and other points such as the ambient temperature.

All of these influences have a negative effect on the accuracy of the conventional particle sensors and, in the known approaches, cannot be compensated for, or possibly only with extremely high application effort, and then only partially.

Furthermore, in the known systems only the entire collective of particles P is always recorded as a sum signal, and in particular the corresponding number of particles cannot be selectively determined for a specific, limited size range of particles. Especially for the direct monitoring of particle filters of vehicles with

So far, the known systems have not yet provided a suitable solution for gasoline internal combustion engines, where the number of small particles is of particular relevance.

The principle described above by way of example with reference to FIGS. 1 to 13 according to the embodiments advantageously enables the aforementioned

Compensating factors influencing the accuracy of a measurement of particles and thus increasing the signal quality. Furthermore, using the principle according to the embodiments, not only one Detect particle number for the collective of all occurring particles P, but selectively one or more specific size number distributions in

Sub-areas, i.e. defined sub-areas from the total area of the particle collective to be recorded, e.g. determine the number of small particles in the range from 1 nm to 23 nm or the range above from 23 nm to 40 nm, etc. This can advantageously be achieved by at least temporarily varying the corona voltage Uc or the electrical potential with which the corona electrode 112 is applied.

Using the principle according to FIGS

Embodiments e.g. a certain voltage profile can be specified in a controlled manner, cf. e.g. the exemplary curves K1, K2, K3 from Fig. 6, 7, 8, or it can even be dependent on predetermined boundary conditions e.g.

from a vehicle control unit (VCU) 200, 200a the currently pending

Corona voltage Uc (Fig. 1) can be adjusted in height and / or polarity, particularly depending on e.g. of certain operating states BP1, BP2 (Fig.

9) of the vehicle or the internal combustion engine. This information can be signaled to the control device 120, for example, by means of the first data D1 (FIG. 1), which thereupon shows the height and / or polarity of the

Corona voltage Uc can set or change.

Thus, in further preferred embodiments, a selective, preferred electrical loading of the particles P (FIG. 5) as a function of the size / diameter / surface and pre-loading is made from the

Combustion process enables. This defined variation in the electrical loading conditions enables the size distribution of the particles to be measured selectively in further preferred embodiments. This then makes it possible, for example, to determine the transmission behavior or the efficiency of a particle filter in a size-selective manner, which significantly improves

Depicts monitoring function or depth.

Furthermore, legislators could also set particle number limit values for internal combustion engines in a size-selective manner, for example, to require targeted monitoring of particularly harmful particles in a certain size window, i.e. a defined sub-area of the particle collective, in particular the small particles based on the available knowledge, e.g. by specifying a specific one Limit for that particular Size class. Such monitoring can also be carried out efficiently using the principle according to the embodiments.

In further preferred embodiments, a measurement or

Determination of signals S1 by the measuring electrodes 130 takes place quickly (i.e. with a high measuring rate) or in real time, the corona voltage Uc preferably being varied during a phase of constant operating conditions of the exhaust gas stream A1 or of the vehicle generating the exhaust gas stream A1 or of the internal combustion engine , e.g. for recording e.g. 3 or more specific size classes from the collective, cf. for example curve K5 from FIG. 10.

The respective measured currents or amounts of charge (signal S1) of the

Sensing electrodes 130 are then e.g. compared with results from a previous measurement under similar operating conditions or with corresponding values, e.g. are stored in a model, e.g. was determined for a limit filter. Alternatively or additionally, the measuring time for a certain size class of particles can be extended, in particular during constant operating conditions, in order to increase the accuracy by averaging.

The principle according to the embodiments for the selective detection of the number of certain small particles has proven to be particularly advantageous. Thus, the principle according to the embodiments can not only e.g. for the

Monitoring of diesel particle filters but in particular also of comparable filters of vehicles with gasoline internal combustion engines can be used in a particularly effective manner, as well as for many others

Fields of application.

Using the principle according to the embodiments, detection of aging / drift of processes / components, e.g.

Fuel injection processes are realized, e.g. if in certain

Size ranges under certain repetitive operating conditions or phases Changes in the number occur in one or more, certain size ranges and thereby a delimitation

a possible change in the transmission behavior of the particle filter in this size range can be ensured, for example by the evaluation the temporal behavior of the change.

In further advantageous embodiments, based on a discernible drift in a predetermined size range of particles

Adaptation e.g. the combustion process parameters of the internal combustion engine are carried out in order to counteract this drift, that is to say to compensate for this.

Furthermore, in further preferred embodiments, an optional ion trap 140 (FIG. 1) placed downstream of the corona electrode 1 12, in which, if applicable, also a variation of the operating voltage at certain

Operating points is used. Thus, a correlation to the approach described above can be established to the

To further increase signal sharpness, e.g. to reduce the background loading of the particles by taking size-selective particles from the fluid stream A1 (that is, by means of the ion trap 140).

As already described above, a time profile of the potential of the corona electrode 112 or the corona voltage Uc can be specified, for example in accordance with a predefinable time pattern, that is to say in a controlled manner. A coupling of the corona voltage Uc to current operating conditions of those generating the exhaust gas flow A1 can also be preferred

Internal combustion engine or the exhaust system, i.e. the time course of the corona voltage Uc e.g. as a function of current operating conditions or operating parameters of the internal combustion engine producing the exhaust gas stream A1, which e.g. about the

Engine control unit 200, 200a are provided in the form of the first data D1.

In further preferred embodiments, it is provided that time ranges with constant operating conditions of the internal combustion engine are used in order to set successive voltage jumps of different magnitude and / or polarity for the corona voltage Uc during such time ranges (for example operating phase BPH1, BPH2 from FIG. 11), which means, for example, different size classes all particles P can be detected. For example, the length (duration) of the voltage jumps and their time intervals are specifically set. Since, in further preferred embodiments, the particle sensor 100 measures quasi in real time (e.g. Detection and evaluation of the signal S1 of the sensor electrode 130, for example

preferably also by means of the control device 120), preferably short, constant operating phases BPH1, BPH2 of e.g. just a few seconds for a precise determination of particle numbers or particle concentrations of different particle size classes.

In further preferred embodiments, the amount of corona voltage Uc can typically be in the range from several 100 volts (V) to several kV (kilovolts). The corona voltage Uc can e.g. are generated directly by or in the control device 120 or by an external voltage source which can be controlled by means of the control device 120 in the sense of the principle according to the embodiments.

In further preferred embodiments, the adaptation or variation of the corona voltage Uc specifically controls a unipolar diffusion charge for ionizing existing, gaseous air or exhaust gas components, and thus the resultant from the combustion process

Charge carrier distribution of the particle collective P to be measured, which ultimately arrives at the relevant measuring point, typically behind a particle filter, is deliberately disrupted or changed. The following

Acquisition electrodes 130, the measured current (signal S1, Fig. 1) or a certain detected amount of charge over a certain period of time at a certain operating point for different values of the corona voltage is determined and compared with each other or compared with previous conditions in analog operating conditions. Alternatively or additionally, a comparison is made with values that e.g. have been determined for a limit filter or a new filter and are stored in a map or model.

Investigations by the applicant have shown that the probability of taking up charge carriers of the particles depends, among other things, on the size and the loading of the particles P. It may also matter which air or exhaust gas molecules are ionized in which form and how high their number is. In a further preferred embodiment, a desired plasma can be set by a specific adaptation of the corona voltage according to magnitude and polarity, ie either a negative or positive corona C, for example nitrogen can be ionized in a targeted manner or oxygen which is in a subsequent step, transfer their loads to certain particles and adjust the resulting load in a targeted manner.

In further preferred embodiments, a number of the ions generated is controlled with a certain value over the duration of the applied non-vanishing corona voltage. The existing charge carrier distribution of the collective of particles P can thus be deliberately disrupted. This disturbance of the present size distribution can occur in the entire conceivable range, i.e. that all particles have taken up their maximum possible negative charge or have taken up their maximum possible positive charge, as well as all mixed forms of differently charged states or partially charged states and also states with a certain proportion on electrically neutral particles, whereby this can preferably be done depending on the size, that is to say showing or hiding specific size ranges. Neutral particles are not detected by the downstream measuring electrode 130.

In further preferred embodiments, the optional trapeze electrode 140 (Fig. 1), which forms the ion trap, can also be operated with a variable adjustable voltage supply, e.g. to specifically eliminate electrically charged particles up to a certain size from the fluid flow A1 (“measurement flow”). In this respect, the above statements regarding the

Potential or the corona voltage for the trapeze electrode 140 accordingly.

Claims

Expectations

1. Particle sensor (100) with a particle charging device (110) for

Charging of particles (P) in a fluid stream (A1) flowing in the area of the particle sensor (100), the particle charging device (1 10) having at least one corona electrode (1 12) for generating a corona discharge (C), the particle sensor ( 100) a

Control device (120) which is designed to apply a variable electrical potential to the at least one corona electrode (112).

2. Particle sensor (100) according to claim 1, wherein the

Particle charging device (1 10) has at least one further electrode (1 14), and wherein the control device (120) is designed to supply the at least one corona electrode (112) and the at least one further electrode (1 14) with a variable electrical voltage (Uc ) to act upon.

3. Particle sensor (100) according to at least one of the above

Claims, wherein the control device (120) is designed to change a polarity of the variable electrical potential and / or the variable electrical voltage.

4. Particle sensor (100) according to at least one of the above

Claims, wherein the control device (120) is designed to receive first data (D1) from at least one external unit (200) and the electrical potential or the electrical voltage in

Change dependency of the first data (D1).

5. Particle sensor (100) according to at least one of the above

Claims, wherein a) the particle sensor (100) at least one

Has sensor electrode (130), and wherein the control device (120) is designed to evaluate a signal (S1) of the sensor electrode (130), and / or wherein the particle sensor (100) at least one Ion trap (140), in particular in the form of a trapezoidal electrode, wherein the control device (120) is designed to act upon the ion trap (140) with a predeterminable electrical potential or a predefinable electrical voltage.

6. Particle sensor (100) according to at least one of the above

Claims, wherein the control device (120) is designed to act on the corona electrode (1 12) at least temporarily with a DC voltage of different magnitude.

7. Particle sensor (100) according to at least one of the above

Claims, wherein the control device (120) is designed to act on the corona electrode (1 12) at least temporarily with a voltage which changes at least approximately linearly over time.

8. Particle sensor (100) according to at least one of the above

Claims, wherein the control device (120) is designed to apply a pulsed voltage to the corona electrode (1 12) at least temporarily.

9. Method for operating a particle sensor (100) with a

Particle charging device (1 10) for charging particles in a fluid stream (A1) flowing in the area of the particle sensor (100), the particle charging device (1 10) having at least one corona electrode (1 12) for generating a corona discharge (C), wherein the

Particle sensor (100) has a control device (120), the control device (120) acting on the at least one corona electrode (1 12) with a variable electrical potential (300, 310).

10. The method according to claim 9, wherein the particle charging device (1 10) has at least one further electrode (114), and wherein the

Control device (120) acts on the at least one corona electrode (1 12) and the at least one further electrode (1 14) with a variable electrical voltage (Uc).

1 1. The method according to at least one of claims 9 to 10, wherein the control device (120) receives first data (D1) from at least one external unit (200) and changes the electrical potential depending on the first data (D1).

12. Use of at least one particle sensor (100) according to at least one of claims 1 to 8 and / or at least one method according to at least one of claims 9 to 11 for determining a number of particles (P) of different sizes in the fluid stream (A1).