DE102009000077A1 - Particle sensor for detecting conductive particles in gas flow, has measuring cell and electrode system with one electrode, another electrode and semi-conducting or small conducting material - Google Patents

Abstract

The particle sensor has a measuring cell (1) and an electrode system with an electrode (1a), another electrode (1b) and a semi-conducting or small conducting material (1c). The former electrode and the latter electrode of an electrode system are electrically connected by a semi-conducting or small conducting material. Another measuring cell (2) is provided with another electrode system. An independent claim is also included for a method for detecting conductive particles in a gas flow.

Description

State of the art

The The present invention relates to a particle sensor with reference measuring cell and a method of detecting conductive particles in a gas stream with such a particle sensor.

In Future must be the soot emissions during the Driving operation of a motor vehicle after passing through the engine or a diesel particulate filter (DPF) by law Regulation monitors and the functionality of this monitoring be ensured (on-board diagnostics - OBD). About that In addition, a load forecast of diesel particulate filters makes sense for a high system security with few efficient, fuel to achieve saving regeneration cycles and more cost-effective Filter materials, such as cordierite to use.

One possibility for this is offered by resistive particle sensors, which make use of a change in resistance of an interdigital (comb-like, interlocking) electrode structure due to particle attachment for the detection of particles, in particular soot. Due to the mode of operation, resistive particle sensors arrange themselves according to the collecting principles (cf. DE 10149333 A1 . WO 2003006976 A2 ).

Currently Resistive particle sensors are known in which two or more metallic electrodes are formed, which under the influence an electrical measuring voltage accumulating conductive Particles, in particular carbon black particles, short circuit the electrodes and so with increasing amount of particles on the sensor surface a decreasing resistance, or an increasing current at a constant applied voltage, measurable between the electrodes becomes.

to Regeneration after particle attachment become such particle sensors conventionally with the aid of an integrated heating device of released particles freed.

The Time between the end of regeneration and the measurement of a current, which is big enough to be safely resolved and Reliable detection is called blind time.

Most of time However, particle sensors have a simple, only slightly dissolving Electronics on. As the single contribution of a single particle bridge to the total current of the measuring cell only a few nA small, must correspondingly many particle bridges are closed, reliable for particle sensors with simple electronics Measurement with a sufficiently high signal, for example of a few μA, to deliver. Particle sensors with simple electronics therefore exhibit usually a long blind time. The use of high-resolution On the other hand, electronics usually causes high costs.

moreover Particle sensors are often behind a diesel particulate filter used where the blind time due to the low particle concentration is especially big.

Disclosure of the invention

object the present invention is a, in particular resistive, particle sensor, for the detection of conductive particles in a gas stream, which a first measuring cell and a second measuring cell, wherein the second measuring cell is configured shielded from particles, wherein the first measuring cell has a first electrode system with at least one first and a second electrode and a first, semiconducting or low conductive material, wherein the first and second Electrode of the first electrode system over the first, semiconducting or low-conductivity material electrically conductively connected or are connected, wherein the second measuring cell, in particular reference measuring cell, a second electrode system having at least a first and a first electrode system second electrode and a second, semiconducting or low conductivity Material, wherein the first and second electrode of the second electrode system via the second, semiconducting or low conductivity material electrically are conductively connected or connected.

• – eine hohe Genauigkeit und kurze Blindzeit aufweist,
• – einfach und kostengünstig, beispielsweise durch ein Siebdruckverfahren, herstellbar ist,
• – eine rußfreie Funktionsprüfung im Anschluss an das Herstellungsverfahren erlaubt,
• – eigendiagnosefähig und kalibrierungsfähig ist,
• – keine Temperaturkorrektur benötigt,
• – eine Temperaturmessung ermöglicht, und
• – die Verwendung einer Vielzahl von halbleitenden oder gering leitenden Materialien erlaubt, da die Leitfähigkeit des halbleitenden oder gering leitenden Materials keinen oder nur geringen Einfluss auf den erforderlichen Messbereich hat, welcher hauptsächlich von dem Partikelsignal bestimmt wird, auf welches die Elektronik optimiert werden kann.

The particle sensor according to the invention has the advantages that this

• - has high accuracy and short blind time,
• Is easy and inexpensive, for example by a screen printing process, can be produced,
• - allows a soot-free functional test following the manufacturing process,
• Is self-diagnostic capable and capable of calibration,
• - no temperature correction needed,
• - allows a temperature measurement, and
• - allows the use of a plurality of semiconducting or low-conductivity materials, since the conductivity of the semiconducting or low-conductivity material has little or no effect on the required measuring range, which is mainly determined by the particle signal to which the electronics can be optimized.

The shielding of the second measuring cell from particles can be carried out in several ways in the context of the present invention. For example, the shield may be provided by an insulating layer over the second measuring cell or by the arranging the first measuring cell on the second measuring cell.

in the Within a preferred embodiment of the present invention Invention, the particle sensor therefore comprises a first insulating layer, wherein the first insulating layer over the second measuring cell is arranged. In this way it can be ensured that the second measuring cell is shielded from particles or a first measuring cell arranged on the second measuring cell of this is isolated.

information like "on", "over" or "under" should in the Frame of the present invention for the description of an arrangement of several elements and not to describe an orientation serve with respect to the direction of gravity.

in the Within the scope of a further preferred embodiment of the The present invention is the first electrode system as an interdigital electrode system from at least two intermeshing, comb-like electrodes and / or the second electrode system as an interdigital electrode system from at least two intermeshing, comb-like electrodes educated. In this way, the accuracy of the particle sensor continue to be increased.

The semiconducting material may, for example, from a temperature of ≥ 400 ° C, for example of ≥ 500 ° C, in particular of ≥ 550 ° C; and / or from a voltage level of ≥ 1 V applied to the semiconducting material, for example of ≥ 30 V, in particular of ≥ 50 V; and / or from a frequency of a voltage applied to the semiconducting material of ≥ 1 s ^-1 , for example of ≥ 300 s ^-1 , in particular of ≥ 5000 s ^-1 ; and / or only at one polarity of a voltage / current applied to the semiconductive material; electrically conductive or have a specific electrical conductivity of ≥ 10 ^-5 S / m, for example, of ≥ 10 ^-3 S / m, in particular of ≥ 0.1 S / m.

For example, the semiconductive material may be a delafosit, for example, CuAlO ₂ , silicon carbide, nitride bonded silicon carbide, nitrided silicon aluminum carbide, stabilized, doped or undoped ruthenium oxide, stabilized, doped or undoped indium oxide, stabilized or doped zirconia, stabilized or doped alumina, stabilized, doped or undoped zinc oxide , in particular undoped ruthenium dioxide, tin doped indium oxide, yttrium stabilized zirconia, iron, manganese and / or magnesium stabilized alumina and / or zinc oxide, or a mixture thereof.

The low-conductivity material may, for example, have a specific conductivity at room temperature of ≥ 10 ^-8 S / m to ≦ 10 ² S / m.

For example For example, the low conductivity material may be a matrix material, for example Alumina and / or glass, its conductivity, for example, by the incorporation of elemental platinum, ruthenium dioxide, Iron oxide, manganese oxide, titanium dioxide, silicon dioxide, calcium oxide and / or magnesium, was targeted.

in the Within the scope of a further preferred embodiment of the present invention is the first and / or second, semiconducting or low-conductive material, in particular in each case as a layer, in particular Self-diagnosis layer, formed.

in the Within the scope of the present invention, the layer, in particular Self-diagnostic layer, from the first, semiconducting or low conductive material both above and below the first Electrode system may be arranged. Likewise, the layer, in particular Self-diagnosis layer, from the second, semiconducting or low conductive material both above and below the second electrode system be arranged.

in the Within a particularly preferred embodiment of the present invention, the first and second measuring cell are substantially identically designed. This is especially true for the implementation of the later explained inventive method proved to be advantageous.

in the Under the present invention, the first and second measuring cell be arranged side by side or on different, for example, on opposite sides, in particular arranged on the front and back, the particle sensor or the first measuring cell can be above the second measuring cell be arranged. Preferably, in an arrangement of the first measuring cell on the second measuring cell, the first insulating layer between the arranged first and second measuring cell.

in the Within the scope of a further preferred embodiment of the Present invention are the first electrode of the first electrode system and the first electrode of the second electrode system via a supply line connected to a common contact. To this Way, these electrodes can be connected together to ground and contacts and leads are advantageously saved become.

In order to ensure that the first and second measuring cells have a similar or identical temperature, the first and second measuring cells are preferably arranged spatially close to one another net.

in the Frame of a further, particularly preferred embodiment According to the present invention, the particle sensor has one, in particular wheatstone or Thomson's bridge circuit. Preferably the first electrode system as a resistor in the first branch of the bridge circuit and the second electrode system as a parallel resistor connected in the second branch of the bridge circuit. The others Resistors of the bridge circuit can be both constant and variable resistors. Of the Using a bridge circuit has the advantage that the accuracy the determination of the voltage and thus the determination of the amount of particles increases and the blind time is shortened. About that In addition, a bridge circuit allows recalibration and measuring range extension or adaptation, for example by adjusting the resistances of the bridge circuit.

Of the Particle sensor according to the invention can further insulation layers exhibit. For example, the inventive Particle sensor comprise a second insulating layer, wherein the arranged first and second measuring cell on the second insulating layer are. In addition, the inventive Particle sensor a, in particular integrated heating device for Include regeneration of the particle sensor.

• – der Strom- und/oder die Spannung an der ersten Messzelle gemessen wird, und
• – gleichzeitig der Strom- und/oder die Spannung an der zweiten Messzelle gemessen wird, und
• – durch Vergleichen, insbesondere durch die Differenz, der Strom- und/oder Spannungssignale an der ersten und zweiten Messzelle die Partikelmenge bestimmt wird.

Another object of the present invention is a method for the detection of conductive particles in a gas stream with a particle sensor according to the invention, in which

• - the current and / or voltage at the first measuring cell is measured, and
• - At the same time the current and / or voltage is measured at the second measuring cell, and
• - By comparing, in particular by the difference, the current and / or voltage signals at the first and second measuring cell, the amount of particles is determined.

By Compare or the formation of the difference between the two Current and / or voltage signals is advantageously a correction of Temperature-dependent basic flow is no longer necessary.

Farther represents a high ground conductivity of the semiconducting or low-conductivity materials no problem for the measuring electronics in terms of measuring range and resolution, because by the comparison or subtraction of the base current no longer included in the measurement.

There only one with the first measuring cell through the second measuring cell should flow identical basic current, may be a deviation the two currents or voltages advantageously either - as already explained on particle accumulation - or attributed to a defect in the measuring cells become.

in the Frame of a preferred embodiment of the invention The method therefore becomes substantially particle-bridge free Condition of the particle sensor, for example during or directly after the regeneration of the particle sensor or directly after the production of the particle sensor, by comparing the current and / or voltage signals at the first and second measuring cell Function of the measuring cells determined, and with different power and / or Voltage signals at the first and second measuring cell, the particle sensor recalibrated or a defect of the particle sensor is output. By a recalibration can advantageously be an exchange of a Partially defective particle sensor can be avoided.

in the Frame of a particularly preferred embodiment of the inventive method is the voltage at the first and second measuring electrodes by one, in particular Wheatstone or Thomson bridge circuit measured.

• – eine höhere Genauigkeit bei der Bestimmung der Partikelmenge, insbesondere während des Anfangs der Signalbildung, erzielt werden kann,
• – die Blindzeit verkürzt werden kann, was insbesondere für den Einsatz in Werkstattmessgeräten und Kraftfahrzeugen im Kurzstreckenbetrieb mit Fahrzeiten unter 20 Minuten vorteilhaft ist, und
• – eine Neukalibrierung und Messbereichserweiterung beziehungsweise -anpassung durchgeführt werden kann.

The measurement of the voltage through a bridge circuit has the advantages that

• A higher accuracy in the determination of the amount of particles can be achieved, in particular during the beginning of the signal formation,
• - The blind time can be shortened, which is particularly advantageous for use in workshop measuring instruments and motor vehicles in short-distance operation with travel times under 20 minutes, and
• - A recalibration and measuring range extension or adaptation can be performed.

Out the current or voltage signal at the second measuring cell In addition, advantageously with knowledge of temperature-dependent conductivity of the semiconducting or low-conductivity material determines the temperature of the measuring cell and used for example for temperature correction of the particle signal become.

in the Frame of a further preferred embodiment of the inventive method is therefore from the Current and / or voltage signal of the second measuring cell determines the temperature. Optionally, the determination of the amount of particles according to be temperature corrected.

Another object of the present invention is the use of an inventive Particle sensor and / or method in a workshop measuring device for exhaust gas examination or in a measuring device for air quality control or in a soot particle sensor for "on board diagnosis" (OBD), and / or for monitoring the operation of an internal combustion engine, such as a diesel engine, or an incinerator , For example, a heating system, and / or to monitor the functioning of a particulate filter and / or monitoring the load condition of a particulate filter, such as a diesel particulate filter (DPF), or for monitoring of chemical manufacturing processes, exhaust systems and / or exhaust aftertreatment systems.

drawings

Further Advantages and advantageous embodiments of the invention Item are illustrated by the drawings and in the explained below description. It should be noted, that the drawings are descriptive and not intended to limit the invention in any way. It demonstrate:

1 a schematic plan view of a first embodiment of a particle sensor according to the invention, the first and second measuring cell are arranged side by side;

2 a schematic cross section through a second embodiment of a particle sensor according to the invention, the first measuring cell is arranged on the second measuring cell, wherein the semiconducting or low-conductivity layers are respectively arranged over the electrode systems;

3 a schematic cross-section through a third embodiment of a particle sensor according to the invention, the first measuring cell is arranged on the second measuring cell, wherein the semiconducting or low-conductivity layers are respectively arranged below the electrode systems;

4 a schematic structure of a structure of a Wheatstone bridge circuit; and

5 a graph illustrating the current signal and the diagonal voltage of a Wheatstone bridge of a berußenden measuring cell.

1 shows that a particle sensor according to the invention is a first measuring cell 1 and a second measuring cell 2 includes. The first measuring cell 1 has a first electrode system with at least one first 1a and a second 1b Electrode and a first, semiconducting or low-conductivity material 1c on, with the first 1a and second 1b Electrode of the first electrode system via the first, semiconducting or low-conductivity material 1c electrically conductively connected or connected. The second measuring cell 2 is designed as a reference measuring cell and has a second electrode system with at least a first 2a and a second 2 B Electrode and a second, semiconducting or low-conductivity material 2c on, with the first 2a and second 2 B Electrode of the second electrode system via the second, semiconducting or low-conductivity material 2c electrically conductively connected or connected.

As part of the in 1 The first embodiment shown are the first 1 and second 2 Measuring cell arranged side by side. In the process, the second measuring cell becomes 2 through one on the second measuring cell 2 arranged first insulation layer 3 shielded from particles.

In addition, in the context of in 1 shown first embodiment, both the first semiconducting or low-conductivity material 1c as well as second semiconducting or low conductive material 2c each formed as a layer (self-diagnosis layer). The dinging of the layers 1c . 2c in 1 represent the layers 1c . 2c can be arranged both above and below the corresponding electrode system.

1 continues to show that the first 1 and second 2 Measuring cell in the context of the present invention are preferably configured substantially identical.

In addition, shows 1 in that both the first electrode system and the second electrode system as interdigital electrode system comprise at least two intermeshing comb-like electrodes 1a . 1b . 2a . 2 B can be trained. 1 further shows that the particle sensor leads 1d . 1e . 2d . 2e for contacting the electrodes 1a . 1b . 2a . 2 B can have.

Further shows 1 in that the particle sensor according to the invention has a second, below the first 1 and second 2 Measuring cell arranged insulation layer 4 may include.

As part of the in 2 the second embodiment shown is the first measuring cell 1 above the second measuring cell 2 arranged. Here is the first insulation layer 3 between the first 1 and the second 2 Measuring cell arranged. In addition, shows 2 in that, in the context of the second embodiment, the layer of the first, semiconductive or low-conductivity material 1c above the first electrode system and the layer from the second, semiconducting or low-conductivity material 2c is arranged above the second electrode system.

As part of the in 3 the third embodiment shown is the first measuring cell 1 also above the second measuring cell 2 arranged and between the first 1 and the second 2 Measuring cell, a first insulation layer 3 arranged. Unlike the second, in 2 shown embodiment is within the scope of in 3 shown third embodiment, the layer of the first, semiconducting or low-conductivity material 1c under the first electrode system and the layer of the second, semiconductive or low-conductivity material 2c arranged under the second electrode system.

4 shows the schematic structure of a Wheatstone bridge circuit. In the context of the present invention, the first 1 and second 2 Measuring cell preferably connected such that the resistance of the first measuring cell 1 the resistance R3 and the resistance of the second measuring cell 2 corresponds to the resistor R1. Now changes the resistance R3 of the first measuring cell 1 (For particle accumulation of ∞ coming to values in the range of a few MΩ or kΩ), the measured diagonal voltage U _{D changes} according to Equation 1:

If the two measuring cells 1 . 2 , For example, due to spatial proximity to each other, are at the same temperature, can advantageously account for a temperature correction for the Grundleitfähigkeit the semiconducting or low-conductivity materials.

Of the ideal measuring range may be beyond the design of other three resistors are set. Variable resistances advantageously allow a continuous Adaptation during operation to the current operating point.

5 shows a simulated graph to illustrate the difference between the current signal (conventional measuring method) 5 and the diagonal voltage of a Wheatstone bridge 6 a signaling measuring cell.

When Output parameters for this simulation was Equation 1, wherein the berußende measuring cell in place of the resistor R3 has been set. The resistors R1 and R2 had one Value of 1 kΩ each, R4 was set to 100 MΩ.

While When the current signal rises to 10 nA, the voltage changes at the bridge around well measurable 1 V. At a current increase in the automotive sector still very poorly measurable 100 nA, the bridge voltage is about 7 V. It offers the bridge voltage a significantly better detectable signal, that much more sensitive to a change in resistance The measuring cell by particle accumulation reacts as the previously used current signal.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10149333 A1 [0003]
• WO 2003006976 A2 [0003]

Claims (14)

Particle sensor for the detection of conductive particles in a gas stream, comprising - a first measuring cell ( 1 ), comprising - a first electrode system having at least a first ( 1a ) and a second ( 1b ) Electrode and - a first, semiconducting or low-conductivity material ( 1c ), the first ( 1a ) and second ( 1b ) Electrode of the first electrode system via the first, semiconducting or low-conductivity material ( 1c ) are electrically conductively connected or connected, and - a second measuring cell ( 2 ) - a second electrode system having at least a first ( 2a ) and a second ( 2 B ) Electrode and - a second, semiconducting or low-conductivity material ( 2c ), the first ( 2a ) and second ( 2 B ) Electrode of the second electrode system via the second, semiconducting or low-conductivity material ( 2c ) are electrically conductively connected or connected, wherein the second measuring cell ( 2 ) is configured shielded by particles. Particle sensor according to claim 1, characterized in that the particle sensor further comprises a first insulating layer ( 3 ), wherein the first insulation layer ( 3 ) above the second measuring cell ( 2 ) is arranged. Particle sensor according to claim 1 or 2, characterized in that the first electrode system as an interdigital electrode system consists of at least two intermeshing, comb-like electrodes ( 1a . 1b ) is formed and / or the second electrode system as an interdigital electrode system of at least two intermeshing, comb-like electrodes ( 2a . 2 B ) is trained. Particle sensor according to one of claims 1 to 3, characterized in that the first, semiconducting or low-conductivity material ( 1c ) is formed as a layer and / or the second, semiconducting or low-conductivity material ( 2c ) is formed as a layer. Particle sensor according to one of claims 1 to 4, characterized in that the layer of the first, semiconducting or low-conductivity material ( 1c ) above or below the first electrode system and / or the layer of the second, semiconductive or low-conductivity material ( 2c ) is disposed above or below the second electrode system. Particle sensor according to one of claims 1 to 5, characterized in that the first ( 1 ) and second ( 2 ) Measuring cell are designed substantially identical. Particle sensor according to one of claims 1 to 6, characterized in that - the first ( 1 ) and second ( 2 ) Measuring cell are arranged side by side, or - the first measuring cell ( 1 ) above the second measuring cell ( 2 ), wherein the first insulation layer ( 3 ) between the first ( 1 ) and the second ( 2 ) Measuring cell is arranged, or - the two measuring cells ( 1 . 2 ) are arranged on different sides of the particle sensor. Particle sensor according to one of claims 1 to 7, characterized in that the first electrode ( 1a ) of the first electrode system and the first electrode ( 2a ) of the second electrode system are connected via a supply line to a common contact. Particle sensor according to one of the claims 1 to 8, characterized in that the particle sensor one, in particular Wheatstone or Thomson bridge circuit. Particle sensor according to one of the claims 1 to 9, characterized in that the first electrode system as a resistor in the first branch of a bridge circuit and the second electrode system as a parallel resistor are connected in the second branch of the bridge circuit. Method for detecting conductive particles in a gas stream with a particle sensor according to one of claims 1 to 10, in which - the current and / or the voltage at the first measuring cell ( 1 ), and - at the same time the current and / or the voltage at the second measuring cell ( 2 ), and - by comparing the current and / or voltage signals at the first ( 1 ) and second ( 2 ) Measuring cell the amount of particles is determined. Method according to claim 11, characterized in that the voltage at the first ( 1 ) and second ( 2 ) Measuring cell is measured by a, in particular Wheatstone or Thomson bridge circuit. A method according to claim 11 or 12, characterized in that in a substantially particle bridge-free state of the particle sensor, by comparing the current and / or voltage signals at the first ( 1 ) and second ( 2 ) Measuring cell the function of the measuring cells ( 1 . 2 ), and for different current and / or voltage signals at the first ( 1 ) and second ( 2 ) Measuring cell, - the particle sensor is recalibrated or - a defect of the particle sensor is output. Method according to one of claims 11 to 13, characterized in that from the current and / or voltage signal at the second measuring cell ( 2 ) the temperature is determined.