WO2020127617A1

WO2020127617A1 - Particle sensor and method for operating same

Info

Publication number: WO2020127617A1
Application number: PCT/EP2019/086142
Authority: WO
Inventors: Simon Schneider; Radoslav Rusanov
Original assignee: Robert Bosch Gmbh
Priority date: 2018-12-20
Filing date: 2019-12-19
Publication date: 2020-06-25
Also published as: DE102018222534A1; EP3899487A1

Abstract

The invention relates to a particle sensor comprising a particle charging device for charging particles in a fluid flow, said particle charging device having a corona electrode for generating a corona discharge, and the particle sensor being designed to apply a pulsed control signal to the 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.

The disclosure further relates to an operating method for such

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, the particle charging device having a corona electrode for generating a corona discharge, and the particle sensor being designed to apply a pulsed control signal to the corona electrode. As a result, ions can be generated efficiently, by means of which the particles of the fluid flow can be electrically charged, and at the same time, the pulsed control signal avoids an undesirably strong influence on charged particles, in particular by means of the particle charging device, of electrically charged particles. In particular, some may be preferred

Embodiments are avoided by the pulsed control signal to unnecessarily influence a trajectory of the charged particles by the corona discharge, which could possibly influence the determination of information about the charged particles or particles.

The control signal is particularly preferably selected in further embodiments such that individual pulses of the control signal each result in a (likewise pulsed) corona discharge in the area of the corona electrode, which however, is not maintained due to the pulsed drive signal. Rather, the named corona discharge ends when a corresponding pulse of the control signal ends. In other words, in further preferred embodiments, an ignition frequency of the corona discharge can correspond to the pulse frequency of the pulsed control signal (and an ignition duration or burning duration of the corona discharge can generally correspond to the pulse width of individual pulses of the control signal). Investigations by the applicant have shown that, in further preferred embodiments, a sufficient number of ions can advantageously be generated by means of the pulsed corona discharge in order to electrically charge particles of the fluid flow, without, however, significantly influencing a trajectory of the charged particles by the corona discharge.

For example, the fluid flow 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. The principle according to the embodiments can be used both for sensing and as a solid

trained particles (e.g. soot particles, as they are contained in an exhaust gas stream of an internal combustion engine) as well as for sensing e.g. liquid particles (e.g. aerosol) can be used.

In further preferred embodiments it is provided that the

Particle sensor has a sensor unit for determining information about charged particles, in particular about particles charged by means of the particle charging device, the sensor unit in particular being designed to determine the information about charged particles by means of the principle of influence and / or by means of the escaping current principle.

In further preferred embodiments, in which the principle of influence can be used to determine the information about charged particles, the sensor unit has at least one sensing electrode, which is preferably arranged downstream of the particle charging device with respect to the fluid flow. Particles which are electrically charged by means of the particle charging device move past the sensing electrode, as a result of which a corresponding electrical signal results from the sensing electrode due to influence. The signal can are evaluated in order to obtain information about a number and / or concentration of the particles or the like in the fluid stream.

In further preferred embodiments, in which the escaping current principle can be used to determine the information about charged particles, the system containing the particle sensor or at least some components of the particle sensor can face the outside (or in relation to a target system into which the Particle sensor or the components are or will be installed) are electrically isolated, and an electrical current is measured, which the charged particles carry out in the form of their electrical charge from the otherwise electrically insulated and therefore closed system. For example, in some embodiments, the electrical current under consideration can flow from the corona electrode through the

Corona discharge flows into a counter electrode, and an optional trap electrode captures remaining ions (which, for example, did not contribute to the electrical charging of particles), which were generated by the corona discharge. The current which is generated by the charged particles must be added to the counterelectrode again so that their electrical potential remains constant, for example equal to a first predefinable reference potential such as the ground potential. This current is known as the "escaping current" and is a measure of the concentration of charged particles. The counter electrode can therefore be e.g. can also be seen as a virtual ground electrode.

However, the principle according to the embodiments is not limited to the evaluation principles mentioned above (influence principle, escaping current principle), but rather can, according to further preferred embodiments, be combined with all evaluation principles in which

Information regarding electrically charged particles can be evaluated.

In further preferred embodiments it is provided that the

Drive signal pulses with a maximum pulse width of 100 milliseconds, ms, or less. This results in pulse-like occurrences

Corona discharges in the area of the corona electrode

Particle charging device, which can be used for electrically charging the particles, but the trajectory of the charged particles is not essential or to a lesser extent - compared to a stationary corona discharge.

In further preferred embodiments it is provided that the

Control signal has pulses with a maximum pulse width of 10 ms or less, preferably 3 ms or less. This also enables reliable electrical charging of the particles, but the trajectory of the charged particles is influenced to an even lesser extent than with larger pulse widths.

In further preferred embodiments, it is provided that a minimum pulse width of the pulses of the drive signal is 10 microseconds, ps, or more. This advantageously ensures that a sufficient number of ions are generated by means of the pulsed corona discharge in order to bring about a reliable electrical charging of particles in the fluid stream.

In further preferred embodiments, it is provided that a minimum pulse width of the pulses of the drive signal is 100 ps or more, preferably 1000 ps or more.

In further preferred embodiments it is provided that a

Pulse pause between two successive pulses of the control signal is greater than a flight time of particles through a charging zone in the area of the corona discharge.

In further preferred embodiments it is provided that the

Particle sensor is designed to determine a first variable and / or to receive it from an external unit, the first variable being a

Characterized the velocity of the particles in the fluid flow. As a result, the operation of the particle sensor and / or the particle charging device can be controlled particularly precisely, in particular adapted to the speed of the particles in the fluid flow. With some preferred

In embodiments, the particle sensor or the particle charging device and / or a control device assigned to it or itself can determine the first variable. In other preferred embodiments, the particle sensor or the particle charging device and / or a control device assigned to it or it can receive the first variable from the external unit. At In other preferred embodiments, the external unit can be, for example, a control unit of the target system, for example a control unit of an internal combustion engine of a motor vehicle, in the exhaust tract of which the particle sensor can be used.

In further preferred embodiments it is provided that the

Particle sensor is designed to determine at least one of the following elements depending on the first variable: a) a minimum pulse width of the pulses of the control signal, b) a maximum pulse width of the pulses of the

Control signal, c) a minimal pulse pause between two

successive pulses of the control signal, d) a maximum pulse pause between two successive pulses of the control signal, the particle sensor in particular being designed to use the corona electrode as a function of the determined element or elements

head for. As a result, operation of the particle sensor and / or the particle charging device can be adapted particularly precisely to the

Velocity of the particles in the fluid flow, that is, for example, to a current exhaust gas velocity of an internal combustion engine to which the particle sensor is assigned.

For example, with comparatively low exhaust gas velocities (corresponding to a comparatively low value of the first variable), a maximum pulse width of the control signal for the corona electrode for generating the corona discharge can be chosen to be comparatively small, because the particles to be electrically charged by means of the particle charging device remain in the area of influence of the electric field for a comparatively long time the corona electrode, which could undesirably distract them. in the

In contrast, at comparatively high exhaust gas speeds, a maximum pulse width of the control signal for the corona electrode for generating the corona discharge can be selected to be comparatively large because the particles are comparatively short in the area of influence of the electrical field of the corona electrode, so that they can be deflected less strongly as a result.

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

Charging particles in a fluid stream, the particle charging device has a corona electrode for generating a corona discharge, the particle sensor acting on the corona electrode with a pulsed control signal.

In further preferred embodiments, the pulsed control signal has one or more pulses with a predefinable pulse width and / or predefinable pulse pauses between successive pulses, which also, e.g.

periodically, can be repeated.

In further preferred embodiments it is provided that the

Control signal pulses with a maximum pulse width of 100 milliseconds, ms, or less, in particular 10 ms or less, preferably 3 ms or less, and / or wherein a minimum pulse width of the pulses of

Drive signal is 10 microseconds, ps, or more, especially 100 ps or more, preferably 1000 ps or more.

In further preferred embodiments it is provided that the

Particle sensor determines a first variable and / or receives it from an external unit, the first variable characterizing a speed of the particles in the fluid flow, the particle sensor in particular

Control signal, in particular a time profile of the control signal, determined as a function of the first variable.

In further preferred embodiments it is provided that a

Corona current, which is used to generate the corona electrode

Corona discharge is supplied as a function of a speed of the fluid flow and / or one or the pulse width and / or as a function of a pulse pause between two successive pulses.

is set. It can thereby be achieved in further preferred embodiments that the electrical charging of the particles does not depend on these parameters and only comparatively slightly.

Further preferred embodiments relate to the use of the particle sensor according to the embodiments and / or the method according to the embodiments to determine information relating to particles (e.g. particle concentration, number of particles) in an exhaust gas stream

Internal combustion engine, in particular a motor vehicle. The principle according to the Embodiments can be used both for sensing as a solid

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 features described or illustrated form the subject matter of the invention, independently or in any combination

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

The drawing shows:

Figure 1 schematically shows a side view of a particle sensor according to

preferred embodiments,

Figure 2 schematically shows a side view of a particle sensor according to

further preferred embodiments,

FIG. 3 schematically shows the arrangement of the particle sensor according to FIG. 2

in a target system,

Figure 4 schematically shows a side view of details of a particle sensor

according to further preferred embodiments,

Figure 5 schematically shows a control signal according to other preferred

Embodiments,

FIG. 6 schematically shows a transit time of particles according to further preferred embodiments,

FIG. 7A schematically shows a simplified flow diagram of a method according to preferred embodiments, FIG. 7B schematically shows a simplified flow diagram of a method according to further preferred embodiments, and

FIG. 8 schematically shows a block diagram of a control device according to further preferred embodiments.

FIG. 1 schematically shows a side view of a particle sensor 100 according to preferred embodiments. The particle sensor 100 has one

Particle charging device 110, which is designed to electrically charge particles P of a fluid stream A1, as a result of which charged particles P 'are obtained. For this purpose, the particle charging device 110 has a corona electrode 112 for at least temporarily generating a corona discharge 114. In preferred embodiments, the particle sensor 100 is designed to apply a pulsed control signal ASC to the corona electrode 112, which leads to a corona discharge 114 (“pulsed corona discharge”) on the corona electrode 112 only temporarily, in particular in accordance with the pulse pattern of the control signal ASC builds up.

For example, the fluid flow A1 can be an exhaust gas flow (or a part of the exhaust gas flow) of an internal combustion engine of a motor vehicle. For example, the particles P, P ″ can be soot particles, such as those that arise during the combustion of fuel by an internal combustion engine. The principle according to the embodiments can be used both for sensing particles formed as solids (e.g.

Soot particles, as they are contained in an exhaust gas stream of an internal combustion engine) as well as for sensing e.g. liquid particles (e.g. aerosol) can be used.

In further preferred embodiments it is provided that the

Particle sensor 100 has a sensor unit 120 for determining information about charged particles P ″, in particular about by means of the

Particle charging device 110 charged particles P ', in particular the sensor unit 120 being designed to determine the information about charged particles P' by means of the principle of influence and / or by means of the escaping current principle. In further preferred embodiments, in which the principle of influence can be used to determine the information about charged particles P ′, the sensor unit 120 has at least one sensing electrode 122, which is preferably arranged downstream of the particle charging device 110 with respect to the fluid flow A1, cf. the schematic side view of the particle sensor 100a according to FIG. 2. In this embodiment, the particle sensor 100a has a presently planar carrier element 102, which is, for example, a substrate (optionally laminate, having several layers) made of a ceramic material. The carrier element 102 has a length L and a thickness d1, which is preferably substantially smaller than the length L. These are on a first surface 102a of the carrier element 102

Particle charging device 110 and further components 112, 122 of the particle sensor 100a are arranged.

By means of the particle charging device 110, electrically charged particles P 'move past the sensing electrode 122 along the horizontal coordinate axis x in FIG. 2, as a result of which a corresponding electrical signal on the sensing electrode 122 is caused by the influence of influence

("Mirror charge principle") results. The signal from the sensing electrode 122 can be evaluated in order to obtain information about a number and / or concentration of the particles P ′ or the like in the fluid stream A1.

In further preferred embodiments, the particle sensor 100a has a counter electrode 114a for the corona electrode 112, the

Counter electrode 114a as shown in FIG. 2 is also arranged on the first surface 102a of the carrier element 102. With other preferred

The counter electrode 114a can also be embodied outside of the embodiment

Carrier element 102 may be arranged, for example on a protective tube R1, which is described below with reference to Figure 3.

In further preferred embodiments, the particle sensor 100a has an optional trap electrode 124, which serves to deflect (“trapping”) charged particles of the fluid stream A1. Excess ions that have been generated by means of the particle charging device 110 can thus be removed from the fluid stream A1, for example, so that they do not contribute to the measurement by the sensing electrode 122. The optional trap electrode 124 is preferred with respect to the flow direction x between the particle charging device 110 and the optional sensing electrode 122. In further preferred embodiments, a counter electrode (not shown) can also be provided for the trap electrode 124. In further preferred embodiments, the protective tube R1 (FIG. 3) already mentioned above can also serve, for example, as a counter electrode for the trap electrode 124.

In further preferred embodiments, in which the escaping current principle can be used to determine the information about charged particles P ′, the system containing the particle sensor 100a or at least some components 102, 110, 112 of the particle sensor 100a can be electrically external be isolated and there will be an electric current

measured which the charged particles P 'in the form of their electrical

Remove the charge from the otherwise electrically insulated and therefore closed system. For example, the electrical current under consideration can flow from the corona electrode 112 through the corona discharge 114 into one or the counter electrode 114a, and the optional trap electrode 124 captures the remaining ions. The current, which is generated by the charged particles P '(and leaves the sensor with the fluid flow A1), must

Counter electrode 114a is added again so that its electrical potential remains constant, for example equal to a first predeterminable reference potential such as the ground potential. This current is known as the "escaping current" and is a measure of the concentration of charged particles.

Information regarding electrically charged particles can be evaluated.

FIG. 3 schematically shows the arrangement of the particle sensor 100a according to FIG. 2 in a target system Z, which is, for example, an exhaust tract of an internal combustion engine of a motor vehicle. An exhaust gas flow in the exhaust tract is designated by the reference symbol A2 in the present case. Also shown is a protective tube arrangement composed of two tubes R1, R2 arranged concentrically to one another, the particle sensor 100a being arranged in the inner tube R1 such that its first surface 102a essentially runs parallel to a longitudinal axis LA of the inner tube R1, also compare the vertical coordinate axis x in FIG. 3. With other preferred

In embodiments, the lengths and the relative arrangement of the tubes R1, R2 to one another are selected such that the Venturi effect results in suction, in which the exhaust gas flow A2 causes a fluid flow P1 or A1 out of the inner tube R1 in FIG. 3 in a vertical direction 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. 3 results in a comparatively uniform overflow of the particle sensor 100a or its first surface 102a aligned along the fluid flow P1 (in particular in the sense of a laminar flow), which enables efficient detection of particles in the fluid flow A1, P1 P enables. In addition, the particle sensor 100a is protected from direct contact with the main exhaust gas flow A2.

In the configuration shown by way of example in FIG. 3, the inner tube R1 can be designed, for example, to be electrically conductive, and the counter electrode 114a described above with reference to FIG

Represent corona electrode 114 and / or for the optional trap electrode 124.

The reference symbol R2 'indicates an optional electrical connection of the outer pipe R2 and / or the inner pipe R1 with a reference potential such as the ground potential, so that the pipe in question or both pipes advantageously simultaneously with their fluidic conducting function as an electrical counterelectrode, for example for the trap -Electrode 124 (and / or for the corona electrode 114), compare FIGS. 1, 2, can be used.

The block arrow P5 symbolizes in FIG. 3 an optional fresh gas supply, in particular fresh air supply, which is preferred in some

Embodiments may be desired, with other preferred ones

However, embodiments are not provided.

FIG. 4 schematically shows a side view of details of a particle sensor 100, 100a according to further preferred embodiments. Different flight paths (trajectories) T1, T2 of particles of the Fluid flow A1 (FIG. 1) in the area of the corona discharge 114. Also shown is a corona electrode 112 'arranged on the carrier element 102' and a counter electrode 114a 'assigned to the corona electrode 112', which is, for example, an inner surface of the inner tube R1 Figure 3 acts. An electrical field 114 'is formed between the electrodes 112', 114a ', which can influence a trajectory T1, T2 of a charged particle P' (FIG. 1). An ion drift takes place in the electrical field 114 'from the corona electrode 112' to the counter electrode 114a ', as a result of which particles P can be electrically charged. The charged particles P 'experience a through the electric field 114' of the corona discharge 114

(Unwanted) deflection in the direction of the counter electrode 114a '.

The first trajectory T1 results, for example, from a comparatively massive (heavy) and / or comparatively fast charged particle. In this case, the electric field 114 ″ caused by the corona discharge 114 has a comparatively small influence on the first trajectory T1. The second trajectory T2 results, for example, in the case of a comparatively low-mass (light) and / or comparatively slow charged particle, in which the electric field 114 ', as can be seen in FIG

causes a comparatively strong influence on the second trajectory T2. This can be undesirable in further preferred embodiments, because in this way in particular comparatively slow and / or comparatively light charged particles can be detected with insufficient accuracy or possibly no longer at all. This can be the case, for example, when the second trajectory T2 is influenced in such a way that the charged particle in question no longer reaches the area of the sensor unit 120 (FIG. 1) or sensing electrode 122 (FIG. 2), but for example strikes the counter electrode 114a '(undesired "trapping" of the charged particle P' by the electric field of the corona discharge 114, to be distinguished from a possibly desired trapping of excess ions from the

Corona discharge 114 using the optional trap electrode 124).

In further preferred embodiments, therefore, a pulsed

Control of the corona electrode 112 (FIG. 1), that is to say the application of a pulsed control signal ASC to the corona electrode 112, is proposed, as is described below by way of example with reference to FIG. 5. FIG. 5 shows an example of a temporal course of a pulsed Control signal ASC for the corona electrode 112 of the particle sensor 100,

100a, which causes a corresponding, pulse-wise occurrence of the corona discharge 114 (FIG. 1), which essentially correlates in time with the individual pulses 1, 2 (FIG. 5). The time course ASC characterizes e.g. a time course of an electrical voltage or an electrical potential with which the corona electrode 112 is applied.

A first pulse 1 begins at time t01 and ends at time t02, which results in a pulse width PB, and a subsequent second pulse 2 begins at time t03 and ends at time t04. Outside the pulses 1, 2 mentioned, the control signal ASC has no non-vanishing value. A pulse amplitude is plotted on the vertical axis PA. In further preferred embodiments, the pulse amplitude PA for the individual pulses 1, 2 is selected such that a corona discharge 114 occurs at the corona electrode 112 within the relevant pulse width PB (ie during the occurrence of a pulse 1, 2). A pulse pause PP is defined between the successive pulses 1, 2, which in the present case results from the time difference between the times t03, t02.

In other preferred embodiments, a value for the

Control signal ASC during at least one pulse pause PP can also be specified so that it is slightly below an ignition voltage for the corona discharge 114 (not shown), e.g. by a predeterminable threshold value lower than the ignition voltage. This ensures that the corona discharge 114 is not already ignited during the pulse pause PP by the control signal ASC thus specified. Furthermore, this will result in

Connection to the pulse pause PP, e.g. at time t03, the corona discharge 114 can be rapidly ignited because the value of the

Control signal ASC must be increased comparatively slightly (e.g. to the amplitude value of pulse 2) in order to ignite the corona discharge 114.

In further preferred embodiments, different pulses 1,

2 also have different pulse widths and / or pulse amp situations.

In further preferred embodiments it is provided that the

Control signal ASC pulses 1, 2 with a maximum pulse width PB of 100 milliseconds, ms, or less. This results in a pulse Corona discharges 114 occurring in the area of the corona electrode 112 (FIG. 1) of the particle charging device 110, which can be used for electrically charging the particles P, but the flight path T1, T2 (FIG. 4) of the charged particles P '(FIG. 1) is not essential affect.

In further preferred embodiments it is provided that the

Control signal ASC pulses 1, 2 having a maximum pulse width PB of 10 ms or less, preferably 3 ms or less. This can also result in a reliable electrical charging of the particles P, but the trajectory of the charged particles P 'is influenced to an even lesser extent by the corona discharge 114 than in the case of larger pulse widths.

It is provided in further preferred embodiments that a minimum pulse width PB of the pulses 1, 2 of the control signal ASC 10

Microseconds, ps, or more. This advantageously ensures that a sufficient number of ions are generated by means of the pulsed corona discharge 114 in order to bring about a reliable electrical charging of particles P in the fluid stream A1 (FIG. 1).

In further preferred embodiments it is provided that a minimum pulse width PB of the pulses 1, 2 of the control signal is 100 ps or more, preferably 1000 ps or more.

In further preferred embodiments it is provided that a

Pulse pause PP between two successive pulses 1, 2 of the

Control signal ASC is greater than a flight time of particles through a charging zone in the region 114 'of the corona discharge 114.

FIG. 6 schematically shows a transit time t_t of particles P through a region of the electric field 114 ′ of the corona discharge 114 (FIG. 4) according to further preferred embodiments, plotted against an exhaust gas velocity vex, which for example the exhaust gas flow A2 (FIG. 3) or the fluid flow A1 in the area of the particle sensor. The transit time t_t indicates how long a particle P is in the area of the electric field 114 'as a function of the exhaust gas velocity vex, wherein its trajectory can be influenced as already described. It can be seen from FIG. 6 that the transit time t_t decreases sharply as the exhaust gas velocity vex increases. According to investigations by the applicant, there is a typical maximum transit time t_max for each particle size of the particles P, above which there is a significant trapping (trapping of the particles, analogous to the effect of the optional trap electrode 124, FIG. 2) of the particles of this size in the range

Corona discharge 114 occurs. Therefore, in particular, the case may arise that comparatively slow and / or light electrically charged particles P 'are already trapped by the electric field of the corona discharge 114, as a result of which they are no longer accessible for measurement or evaluation by the sensor unit 120 . This may be the case with other preferred ones

Embodiments can be avoided by the pulsed actuation of the corona electrode 112 already described above with reference to FIG. 5.

According to further investigations by the applicant, the transit time t_t (FIG. 6) can have an influence on the electrical charge of the charged particles P ′, so that in some embodiments a sensor signal determined by the optional sensor unit 120 (FIG. 1) is dependent on the

Exhaust gas velocity vex.

In further preferred embodiments, the operation of the

Particle sensor 100, 100a a maximum time or transit time t_max can be specified in which the particles P of the fluid stream A1 may be exposed to the electric field 114 '(FIG. 4) of the corona discharge 114, so that little or no trapping of the particles (for example max. 50 %) occurs through the electric field 114 'of the corona discharge 114.

In further preferred embodiments, the maximum time t_max can be selected so that even the smallest particles still to be measured (e.g.

having a maximum length extension of 10 nm (nanometers) or 23 nm, for example predeterminable depending on the target system or a planned application of the particle sensor), the corona discharge 114 does not trap, or does not trap too strongly.

Then, in further preferred embodiments, a (minimum and / or maximum) pulse width PB (FIG. 5) for the pulsed actuation of the corona electrode 112 by means of the pulses 1, 2 as a function of the maximum time t_max can be determined. For example, in further preferred embodiments, the maximum time t_max can assume values in the range of 0.1 ms <t_max <10ms or 1 ms <t_max <3ms. With other preferred

In embodiments, a pulse width PB is determined or specified which is less than the maximum time t_max.

In further preferred embodiments it can be provided that the corona current with which the corona electrode 112 is used to generate the

Corona discharge 114 is supplied, as a function of the maximum time t_max and / or as a function of the selected pulse width PB and / or as a function of the selected pulse pause PP. The charging efficiency for the electrical charging of the particles P of the fluid stream A1 can thus advantageously be influenced. Another is advantageous

Embodiments because of the comparatively short pulse duration or

Pulse widths PB are not expected to reduce the lifespan of the corona electrode 112 due to corona currents which may be increased according to some embodiments.

In further preferred embodiments, a value is selected for the pulse pauses PP between two successive pulses 1, 2, which is greater than or equal to a typical transit time t_t (FIG. 6) of the particles under consideration through the spatial area of the electric field 114 ′ of the corona discharge 114. In further preferred embodiments, the pulse pause PP can therefore be advantageous depending on a current exhaust gas velocity or

Flow rate of the fluid flow A1 can be selected.

In further preferred embodiments it is provided that the

Particle sensor 100, 100a is designed to determine a first variable and / or to receive it from an external unit, the first variable characterizing a speed of the particles P (FIG. 1) in the fluid stream A1. As a result, the operation of the particle sensor and / or the

Particle charging device can be controlled and / or regulated particularly precisely, in particular to be adapted to the speed of the particles in the fluid stream A1 or the exhaust gas speed vex, see also reference symbol A2 according to FIG. 3. In further preferred embodiments, the particle sensor or the particle charging device 110 and / or one assigned to it or it

Control device itself determine the first size. In other preferred embodiments, the particle sensor or the particle charging device and / or a control device assigned to it or it can receive the first variable from the external unit. In further preferred embodiments, the external unit can be, for example, a control device of the target system, for example a control device of a

Internal combustion engine of a motor vehicle, in the exhaust tract of which

Particle sensor can be used.

FIG. 8 schematically shows a simplified block diagram of a

Control device 1100 according to further preferred embodiments.

For example, the control device 1100 can be designed to control the operation of the particle charging device 110 from FIG. 1. In particular, the control device 1100 can be designed to apply the pulsed control signal ASC to the corona electrode 112. In further preferred embodiments, the control device 1100 is designed to:

Corona electrode 112 in the sense of the pulsed control signal ASC with a corresponding time profile of an electrical voltage and / or an electrical current.

The control device 1100 has at least one computing device 1102, at least one storage device 1104 assigned to the computing device 1102 for at least temporarily storing a computer program PRG, the computer program PRG being designed in particular to control the operation of the particle charging device 110. Under the control of the

Computer program PRG can be implemented in further preferred embodiments, for example the method according to the embodiments, in particular also the determination of a pulse width PB and / or pulse pause PP and / or to be used for controlling the corona electrode 112

Pulse amplitude PA.

In further preferred embodiments, the computing device 1102 has at least one of the following elements: a microprocessor, a microcontroller, a digital signal processor (DSP), a programmable logic module (for example FPGA, field programmable gate array), an ASIC (application specific integrated circuit), a hardware circuit. Combinations of these are also conceivable in further preferred embodiments.

In further preferred embodiments, the memory device 1104 has at least one of the following elements: a volatile memory 1104a, in particular working memory (RAM), a non-volatile memory 1104b, in particular flash EEPROM. The computer program PRG is preferably stored in the non-volatile memory 1104b.

In further preferred embodiments, the control device 1100 is designed for the first variable G1, which has already been described above, and which represents the speed of the particles P in the fluid stream A1 or the

Characterized exhaust gas velocity to determine. As an alternative or in addition, the control device 1100 can be designed to receive the first variable G1 from an external unit 300, for example a control device for a

Internal combustion engine of a motor vehicle, in the exhaust tract Z (FIG. 3) of which the particle sensor 100, 100a according to the embodiments is used. The control device 1100 can, for example, store the first variable G1 at least temporarily in the working memory 1104a.

A data exchange with the external unit 300 can take place, for example, via a preferably bidirectional data interface 1106. The corona electrode 112 can be actuated with the pulsed actuation signal ASC, for example, via a control interface 1108, the one

can provide corresponding electrical voltage and / or a corresponding electrical current for controlling the corona electrode 114.

In further preferred embodiments it is provided that the

Particle sensor 100, 100a is designed to determine at least one of the following elements as a function of the first variable: a) a minimum pulse width PB (FIG. 5) of pulses 1, 2 of the control signal ASC, b) a maximum pulse width of the pulses of the control signal , c) a minimum pulse pause PP between two successive pulses of the control signal, d) a maximum pulse pause between two successive pulses of the

Control signal, e) a pulse amplitude or a corona current, wherein in particular, the particle sensor is designed to adapt the corona electrode 112 as a function of the element determined (that is to say, for example, with the minimum and / or maximum pulse width PB and / or the minimum and / or maximum pulse pause PP and / or pulse amplitude PA as a function of the first variable G1 ) head for. In this way, operation of the particle sensor 100, 100a and / or the particle charging device 110 can be adapted particularly precisely to the speed of the particles P in the fluid stream A1, that is to say, for example, to a current exhaust gas speed vex of an internal combustion engine to which the particle sensor is assigned.

For example, at comparatively low exhaust gas velocities vex (corresponding to a comparatively low value of the first variable G1), a maximum pulse width PB of the control signal ASC for the corona electrode 112 for generating the corona discharge 114 can be chosen to be comparatively small because the particles to be electrically charged by means of the particle charging device 110 are comparatively small long in the area of influence of the electric field 114 'of the corona electrode 112, as a result of which they could be undesirably deflected. Optionally, with other preferred ones

Embodiments in these cases, the corona current may be increased above a nominal value in order to enable sufficient ionization or electrical charging of the particles despite the comparatively small pulse width PB.

In contrast to this, at comparatively high exhaust gas velocities vex, a maximum pulse width PB of the control signal for the corona electrode for generating the corona discharge can be selected to be comparatively large because the particles are comparatively short in the area of influence of the electrical field of the corona electrode, so that they are deflected less as a result can. Accordingly, in further preferred embodiments, the corona current can be set, for example, to the nominal value described above or to a lower value, because a reliable electrical charging of the particles is ensured due to the larger pulse width PB increased transit time.

Further preferred embodiments relate to a method for operating a particle sensor 100, 100a, in particular according to FIGS

Embodiments. FIG. 7A schematically shows a simplified one Flow chart. In step 200, the particle sensor 100, 100a applies a pulsed control signal ASC to the corona electrode 112 (FIG. 5). In the subsequent optional step 202, information relating to the charged particles P ′ can be determined, for example, by the optional sensor unit 120, for example by means of the principle of influence and / or by means of the escaping current principle and / or by means of another principle that relates to a Evaluation of electrically charged particles P 'is based.

FIG. 7B schematically shows a simplified flow diagram according to further preferred embodiments. In step 210, the particle sensor determines (for example by means of the control device 1100, FIG. 8) the first variable G1, which is the

Characterized the speed of the particles P in the fluid flow A1. Alternatively or additionally, the particle sensor receives the first variable G1 in step 210 from an external unit 300 (FIG. 8). In step 212 (FIG. 7B), the particle sensor determines (or calculates or forms) the control signal ASC, in particular the time profile of the control signal ASC, as a function of the first variable G1. Alternatively or additionally, the control signal ASC can be determined in step 212 as a function of a particle size or particle mass of interest. In the subsequent, optional step 214, the corona electrode 112 is actuated with the pulsed actuation signal ASC, which was previously determined in step 212.

Further preferred embodiments relate to the use of the particle sensor according to the embodiments and / or the method according to the embodiments to determine information relating to particles P (e.g. particle concentration, number of particles) in an exhaust gas stream A1, A2 of an internal combustion engine, in particular a motor vehicle. The principle according to the embodiments can be used both for sensing and as a solid

formed particles P (e.g. soot particles as they are contained in an exhaust gas stream of an internal combustion engine) as well as for sensing e.g. liquid particles P (e.g. aerosol) can be used.

Some preferred embodiments enable the following advantages: no or less trapping of small particles in the area of the

Corona discharge 114, no or less dependence of the charge of the particles P on the exhaust gas velocity vex. The principle according to others preferred embodiments advantageously enables a particularly precise and uniform electrical charging of the particles P.

In further preferred embodiments, the particle sensor can be used in particular in the area of particle filters for internal combustion engines, in particular diesel particle filters (DPF) and / or gasoline particle filters (GPF), in particular for realizing a diagnosis, for example on-board diagnosis (OBD).

Claims

Expectations

1. Particle sensor (100; 100a) with a particle charging device (110) for charging particles (P) in a fluid stream (A1), the

Particle charging device (110) has a corona electrode (112) for generating a corona discharge (114), and wherein the particle sensor (100; 100a) is designed to apply a pulsed control signal (ASC) to the corona electrode (112).

2. Particle sensor (100; 100a) according to claim 1, wherein the control signal (ASC) pulses (1, 2) with a maximum pulse width (PB) of 100

Milliseconds, ms, or less.

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

Claims, wherein the control signal (ASC) has pulses (1, 2) with a maximum pulse width (PB) of 10 ms or less, preferably 3 ms or less.

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

Claims, wherein a minimum pulse width (PB) of the pulses (1, 2) of the drive signal (ASC) is 10 microseconds, ps, or more.

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

Claims, wherein a minimum pulse width (PB) of the pulses (1, 2) of the control signal (ASC) is 100 ps or more, preferably 1000 ps or more.

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

Claims, wherein a pulse pause (PP) between two successive pulses (1, 2) of the control signal (ASC) is greater than a flight time of particles through a charging zone in the area (114 ') of the

Corona discharge (114).

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

Claims, wherein the particle sensor (100; 100a) is designed to determining the first variable (G1) and / or receiving it from an external unit (300), the first variable (G1) characterizing a velocity of the particles (P) in the fluid stream (A1).

8. particle sensor (100; 100a) according to claim 7, wherein the particle sensor (100;

100a) is designed to determine (210) at least one of the following elements as a function of the first variable (G1): a) a minimum pulse width (PB) of the pulses (1, 2) of the control signal (ASC), b) a maximum Pulse width (PB) of the pulses (1, 2) of the control signal (ASC), c) a minimum pulse pause (PP) between two successive pulses (1, 2) of the control signal (ASC), d) a maximum pulse pause (PP) between two successive pulses (1, 2) of the control signal (ASC), the particle sensor (100; 100a) in particular being designed to control (214) the corona electrode (112) as a function of the determined element.

9. Particle sensor (100; 100a) according to at least one of the above

Claims, wherein the particle sensor (100; 100a) has a sensor unit (120) for determining information about charged particles (P '), the sensor unit (120) in particular being designed to transmit the information about charged particles (P') by means of the To determine the principle of influence and / or by means of the escaping-current principle.

10. Method for operating a particle sensor (100; 100a) with a

Particle charging device (110) for charging particles in a fluid stream (A1), the particle charging device (110) being a

Corona electrode (112) for generating a corona discharge (114), wherein the particle sensor (100; 100a) acts on the corona electrode (112) with a pulsed control signal (ASC) (200).

11. The method according to claim 10, wherein the control signal (ASC) has pulses (1, 2) with a maximum pulse width (PB) of 100 milliseconds, ms, or less, in particular 10 ms or less, preferably 3 ms or less, and / or wherein a minimum pulse width (PB) of the pulses (1, 2) of the drive signal (ASC) is 10 microseconds, ps, or more, in particular 100 ps or more, preferably 1000 ps or more.

12. The method according to at least one of claims 10 to 11, wherein the

Particle sensor (100; 100a) determines (210) and / or a first variable (G1) receives (210) from an external unit (300), the first variable (G1) characterizing a speed of the particles (P) in the fluid stream (A1), the particle sensor (100; 100a) in particular the control signal (ASC), in particular determines (212) a time profile of the control signal (ASC), depending on the first variable (G1).

13. The method according to at least one of claims 10 to 12, wherein a

Corona current, with which the corona electrode (112) is supplied for the generation of the corona discharge (114), as a function of a speed (vex) of the fluid flow (A1) and / or one or the pulse width (PB) and / or as a function of a pulse pause (PP) between two successive pulses (1, 2) is specified or set.