WO2019129411A1

WO2019129411A1 - Control unit for operating a single-cell wideband oxygen sensor and a binary sensor

Info

Publication number: WO2019129411A1
Application number: PCT/EP2018/079007
Authority: WO
Inventors: Fabian Baumann
Original assignee: Robert Bosch Gmbh
Priority date: 2017-12-28
Filing date: 2018-10-23
Publication date: 2019-07-04
Also published as: DE102017223843A1

Abstract

The invention relates to a control unit (10) for operating a single-cell wideband oxygen sensor (12) and a binary sensor (14), in particular in an exhaust gas after-treatment system of an internal combustion engine. The control unit (10) has three or four connections (IPE, APE, RE, MES) for electrically contacting the single-cell wideband oxygen sensor (12) and the binary sensor (14). A first connection (IPE) of the connections (IPE, APE, RE, MES) is designed in such a way that the single-cell wideband oxygen sensor (12) and the binary sensor (14) can be electrically contacted together at the first connection (IPE).

Description

description

title

Control unit for operating a single cell broadband lambda probe and a

jump probe

State of the art

Methods and devices for detecting at least a portion of a gas component from a gas mixture in a measuring gas space are known from the prior art. The invention will be described in the following without limitation of other possible embodiments substantially with reference to methods and apparatus which for quantitative and / or qualitative detection of at least one gas component of a

Serve gas mixture in a sample gas space. The gas is in particular an exhaust gas of an internal combustion engine, in which

Measuring gas chamber in particular around an exhaust tract. The device is preferably a lambda probe. Such lambda probes are described for example in Konrad Reif (ed.), Sensors in the motor vehicle, 2nd edition, Springer Vieweg, pages 160-165.

Lambda probes, in particular so-called universal lambda probes, balance two streams of material, in particular oxygen streams, between a cavity of the device and the sample gas space. One of the streams is driven by concentration differences through a diffusion barrier. Another stream is via a solid state electrolyte and two

Electrodes, in particular two pumping electrodes, which form a pumping cell, driven driven by an impressed pumping current. The pump cell is preferably heated by at least one heater.

The pumping current can be regulated in such a way that a constant and very low oxygen concentration is established in the cavity. On Concentration profile over a diffusion barrier is uniquely determined by a constant control point in the cavity, in particular a constant setpoint voltage, resulting in an oxygen concentration and by an exhaust gas oxygen concentration. An influx of

Oxygen molecules from the sample gas space to the cavity adjusts according to this unique concentration profile and corresponds to the regulated pumping current. Therefore, the pumping current serves as a measured value for the oxygen concentration in the measuring gas space, in particular for the oxygen concentration on the exhaust gas side.

Different variants of lambda probes are known from the prior art. In particular, with regard to the possibilities with regard to the control of the probes, two-point lambda probes differ from broadband lambda probes.

The two-point lambda probes compare the residual oxygen content in the exhaust gas with the oxygen content of a reference gas atmosphere, which may be in the interior of the sensor device as circulating air, and indicate whether in the exhaust gas, a so-called "rich mixture" with a lambda value Lambda <1 or a so-called "lean mixture" with a lambda value of lambda> 1 is present. Here lambda denotes the ratio between the current air / fuel ratio and the stoichiometric air / fuel ratio. Due to the construction of the two-point lambda probe occurs in the characteristic of the two-point lambda probe, however, a jump in the probe voltage at lambda = 1, so that the two-point lambda probe only allows control of the composition of the mixture to a lambda value of lambda = 1 , For this reason, such lambda probes are also referred to as jump probes.

In contrast, by means of the broadband lambda probe, the oxygen concentration in the exhaust gas can be determined over a large lambda range and from this the air-fuel ratio in the combustion chamber of the internal combustion engine can be concluded. The broadband lambda probe can therefore not only determine the lambda value in the stoichiometric point at lambda = 1, but also in the lean mixture as well as in the rich mixture. Determine the value of the oxygen concentration in the exhaust gas of the internal combustion engine. To control broadband lambda probes

Usually subjected to a fixed pumping voltage, what as

"Limiting current principle" is called.

With regard to their construction, broadband lambda probes according to the limiting current principle with a cell, which is also referred to as a "pumping cell", differ from broadband lambda probes with two cells, which are commonly used

Wear the terms "pump cell" and "reference cell". The

In this case, a broadband lambda probe with a cell has two electrodes arranged on a solid electrolyte, one electrode (outer pumping electrode) passing into a reference gas via a reference or exhaust air channel and the other electrode (inner pumping electrode) passing into the measurement gas or exhaust gas via a diffusion barrier , According to the limiting current principle, a fixed pumping voltage is applied to the pumping cell, which comprises the two electrodes. In contrast, to determine the lambda value in broadband lambda probes according to the limiting current principle with two cells, a first electrode, which is arranged behind a diffusion barrier in the exhaust gas and therefore also referred to as "inner pumping electrode" IPN, and a second electrode, which is commonly referred to as Reference electrode "RE" is used since it is arranged in a reference air channel.

Usually, the lambda probes with a corresponding

Control unit in the form of an integrated circuit (IC) connected. Thus, by means of such a control unit, a broadband lambda probe can be operated and monitored with the aid of a single ASIC (Application Specific Integrated Circuit). This ASIC serves in particular for the provision of a regulated pumping current (Ip) and its detection, for detecting the

Sensor internal resistance (Ri) for temperature monitoring of the sensor as well as for monitoring and, if necessary, the protection of all sensor cables.

Despite the advantages brought about by the aforementioned control units, they still need to be improved. So can with known integrated

Evaluation blocks ("lambda ASICs") per ASIC exactly one

Broadband lambda probe or a combination of broadband lambda probe and a jump probe operated. In the latter case, an extra interface is kept in the ASIC for the jump probe.

Disclosure of the invention

Therefore, a control unit and a sensor system are proposed which at least largely avoid the disadvantages of the known control units. In particular, the proposed control unit allows the operation of a combination of single-cell broadband lambda probe and jump probe, without the number of interfaces or connections of the ASIC must be changed.

A control unit according to the invention for operating a unicellular

Broadband lambda probe and a jumping probe, especially in one

Exhaust after-treatment system of an internal combustion engine, has to

electrically contacting the unicellular broadband lambda probe and the jump probe 3 or 4 ports on. A first terminal of the terminals is formed such that the unicellular broadband lambda probe and the

Jump probe are electrically contacted together at the first terminal. By means of the control unit according to the invention can be a unicellular

Broadband lambda probe and a jump probe using a single ASIC (Application Specific Integrated Circuit) and monitor.

This ASIC serves, in particular, for providing a regulated pump current (Ip) and its detection, for detecting the internal sensor resistance (Ri) for temperature monitoring of the probes and for monitoring and possibly protecting all sensor lines.

In a further development, the control unit further comprises a first electrical current source for producing a readiness for operation of the unicellular

A broadband lambda probe, in particular for establishing the reference of the single-cell broadband lambda probe, and a second electrical current source for producing an operational readiness of the jump probe, wherein the first electrical current source differs from the second electrical current source, wherein a second terminal of the terminals with the first electrical

Power source is electrically contacted and a third connection of the connections with the second electrical power source is electrically contacted. As a result, the unicellular broadband lambda probe and the jump probe can be supplied and controlled separately with electric current. Thus, the first electric current source is designed to allow a technically positive electric current to flow from the second terminal to the first terminal via the single-celled broadband lambda probe. However, the first electric current source can also lower a technically negative electric current from the first terminal to the second terminal. The second electric current source is configured to allow a technically positive electric current to flow from the third terminal to the first terminal via the jump probe.

In one development, the unicellular broadband lambda probe has a

Pump cell having an outer pumping electrode and an inner pumping electrode, wherein the first terminal for electrically contacting the jumping probe and the inner pumping electrode is formed. This makes it particularly easy to contact the two probes electrically and drive reliably.

In a further development, the second connection of the connections to

electrically contacting the outer pumping electrode formed. This makes it particularly easy to contact the two probes electrically and drive reliably.

In a further development, the jump probe for electrical contacting has a positive pole and a positive pole, the first terminal being designed to make electrical contact with the negative terminal of the jumping probe. This makes it particularly easy to contact the two probes electrically and drive reliably.

In a further development, the third connection of the connections for electrically contacting the positive pole of the jump probe is formed.

In a further development, the control unit has four connections, wherein a fourth connection of the connections for electrically contacting the single-cell broadband lambda probe is formed. This makes it particularly easy to contact the two probes electrically and drive reliably. A sensor system according to the invention, in particular for operation in an exhaust aftertreatment system, comprises a single-cell broadband lambda probe, a jumping probe and a control unit according to the invention. In this case, the first connection of the connections with the single-cell broadband lambda probe and the jump probe is electrically contacted together.

Power source is electrically contacted and a third terminal of the terminals is electrically contacted with the second electrical power source.

In one development, the unicellular broadband lambda probe has a

Pump cell with an outer pumping electrode and an inner pumping electrode, wherein the first connection with the jump probe and the inner

Pump electrode is electrically contacted.

In a development, the second connection of the connections is electrically contacted with the outer pumping electrode.

In a further development, the jump probe for electrical contacting has a positive pole and a negative pole, wherein the first terminal is electrically contacted with the negative pole of the jump probe.

In a further development, the third connection of the connections is electrically contacted with the positive pole of the jump probe.

In a further development, the control unit has four connections, wherein a fourth connection of the connections is electrically contacted with the single-cell broadband lambda probe. Under a control unit is within the scope of the present invention

basically to understand any controller capable of controlling a single cell broadband lambda probe and a jump probe, one such

Control unit can be designed as an integrated circuit (IC).

Under a single-cell broadband lambda probe is in the context of the present invention, a broadband lambda probe with only a single

To understand electrochemical cell in the form of a pump cell having two separated by a solid electrolyte electrodes. The

Broadband lambda probe with one cell thus has two on one

Solid electrolyte arranged electrodes, wherein an electrode (outer

Pump electrode) via a reference or exhaust duct into a reference gas ranges and the other electrode (inner pumping electrode) via a diffusion barrier into the sample gas or exhaust gas ranges. The unicellular broadband lambda probe works according to the limiting current principle. According to the limiting current principle, a fixed pumping voltage is applied to the pumping cell, which comprises the two electrodes.

In the context of the present invention, a jump probe is to be understood as meaning a lambda probe operating on the Nernst principle. Jump probes are also referred to as two-point lambda probes. The two-point lambda probes compare the residual oxygen content in the exhaust gas with the oxygen content of a reference gas atmosphere, which may be in the interior of the sensor device as circulating air, and indicate whether in the exhaust gas, a so-called "rich mixture" with a lambda value Lambda <1 or a so-called "lean mixture" with a lambda value of lambda> 1 is present. Here lambda denotes the ratio between the current air / fuel ratio and the stoichiometric air / fuel ratio. Due to the construction of the two-point lambda probe occurs in the characteristic of the two-point lambda probe, however, a jump in the probe voltage at lambda = 1, so that the two-point lambda probe only allows control of the composition of the mixture to a lambda value of lambda = 1 , For this reason, such lambda probes are also called

Jump sensors are called. In the context of the present invention, a solid electrolyte is to be understood as meaning a body or article having electrolytic properties, that is to say having ion-conducting properties. In particular, it may be a ceramic solid electrolyte. This also includes the raw material of a solid electrolyte and therefore the formation as a so-called green compact or browning, which only becomes a solid electrolyte after sintering.

In particular, the solid electrolyte may be formed as a solid electrolyte layer or from a plurality of solid electrolyte layers. In the context of the present invention, a layer is to be understood as a uniform mass in the areal extent of a certain height which lies above, below or between other elements.

An electrode in the context of the present invention is generally understood to mean an element which is capable of contacting the solid electrolyte in such a way that a current can be maintained by the solid electrolyte and the electrode. Accordingly, the electrode may comprise an element to which the ions can be incorporated in the solid electrolyte and / or removed from the solid electrolyte. Typically, the electrodes comprise a noble metal electrode, which may, for example, be deposited on the solid electrolyte as a metal-ceramic electrode or otherwise be in communication with the solid electrolyte. Typical electrode materials are platinum cermet electrodes. However, other precious metals, such as gold or palladium, are in principle applicable.

In the context of the present invention, a heating element is to be understood as meaning an element which is suitable for heating the solid electrolyte and the electrodes to at least their functional temperature and preferably to their temperature

Operating temperature is used. The functional temperature is the temperature at which the solid electrolyte becomes conductive to ions and which is approximately 350 ° C. Of this, the operating temperature is to be distinguished, which is the temperature at which the sensor element is usually operated and which is higher than the operating temperature. The operating temperature may be, for example, from 700 ° C to 950 ° C. The heating element may comprise a heating area and at least one feed track. Under a heating area is under the The present invention is intended to understand the region of the heating element which overlaps with an electrode in the layer structure along a direction perpendicular to the surface of the sensor element. Usually it heats up

Heating area during operation stronger than the supply line, so that they are distinguishable. The different heating can for example be realized in that the heating area has a higher electrical resistance than the supply track. The heating area and / or the supply line are formed, for example, as an electrical resistance path and heat up by applying an electrical voltage. The heating element may for example be made of a platinum cermet.

The terms "first," "second," "third," and "fourth" are used in the present invention only to distinguish the corresponding components and are not intended to indicate a particular order or weighting.

A basic idea of the present invention is to design the control unit in such a way that a single-cell broadband lambda probe and a jump probe share a connection in common. As a result, the number of ports compared to conventional control units remain unchanged.

The control unit according to the invention or the sensor system offer the following advantages. Costs for a microcontroller resource and discrete components are saved. The temperature measurement of the jump probe is faster and thus provides a more accurate useful signal than in a discretely constructed

Evaluation module. The evaluation of jump probes from different manufacturers is possible via a corresponding software configuration. With the

Control unit is the usual lambda probe assembly in Gasoline systems consisting of a single-cell broadband lambda probe before the catalyst and a jump probe after the catalyst covered. However, the control unit can also be used in diesel systems. Fewer components have to be equipped and tested. Development costs are lower as development and protection of only one ASIC is required.

Brief description of the drawings Further optional details and features of the invention will become apparent from the following description of preferred embodiments, which are shown schematically in the figures.

Show it:

Figure 1 is a block diagram of a control unit for operating a single-cell broadband lambda probe and a jump probe and

Figure 2 is a block diagram of a sensor system.

Embodiments of the invention

FIG. 1 shows a block diagram of a control unit 10 for operating a single-cell broadband lambda probe 12 and a jump probe 14 (FIG. 2). The control unit is based in its function on an evaluation module for a two-line broadband lambda probe, by the applicant under the

Designation CJ135 is sold. The controller 10 is therefore signal coupled to the single cell broadband lambda probe 12 and the jump probe 14, as will be described in more detail below. In addition, there is a signal connection to an external microcontroller 16.

The control unit 10 comprises an analog-to-digital converter 18, a filter 20 and an SPI (Serial Peripheral Interface) shift register 22. By means of the analog-to-digital converter 18, those of the unicellular

Broadband lambda probe 12 and the jump probe 14 supplied analog

Measurement data digitized for digital further processing. By means of the filter 20, preferably a low-pass filter, the signal noise of the measurement signals supplied by the single-cell broadband lambda probe and the jump probe is reduced. The thus filtered digital data is transmitted to the microcontroller 16.

The control unit 10 further comprises a switching matrix 24, which is operated by means of a control module 26 and is fed by a current generator 28. By means of the switching matrix 24, the inputs of the control unit 10 and flexibly adapt or change the type of evaluation of the measuring signals. A not shown in detail Lambda controller is located in this case in

Microcontroller 16 and the pumping current regulator are implemented in the control unit 10.

2 shows a block diagram of a sensor system 30. The sensor system comprises the control unit 10, the unicellular broadband lambda probe 12 and the jump probe 14. The control unit 10 has three or four connections for electrically contacting the single-cell broadband lambda probe 12 and the jump probe 14. In the embodiment shown, the control unit 10 has four ports IPE, APE, RE, MES. A first terminal IPE of the terminals IPE, APE, RE, MES is designed such that the single-cell broadband lambda probe 12 and the jump probe 14 are electrically contactable together at the first terminal IPE, as will be described in more detail below.

The single-cell broadband lambda probe 12 has a pumping cell 32 with an outer pumping electrode 34 and an inner pumping electrode 36, which are separated from one another by a solid electrolyte 38 shown as an electrical resistance. The jump probe 14 has a positive pole 40 and a negative pole 42 for electrical contacting, which are connected via a solid electrolyte 44 shown as an electrical resistance.

The first terminal IPE is configured to electrically contact the jump probe 14 and the inner pumping electrode 36. Furthermore, the first terminal IPE is designed to electrically contact the negative pole 42 of the jump probe 14. Thus, the first terminal IPE is electrically contacted via a first connecting line 46 both to the inner pumping electrode 36 and to the negative pole 42. The first terminal IPE is further connected to a controller, not shown in more detail, of the control unit 10, which regulates a virtual electrical ground to a constant electrical voltage. The second terminal APE is designed to electrically contact the outer pumping electrode 34. Thus, the second terminal APE is electrically contacted to the outer pumping electrode 34 via a second connecting line 48. The third terminal RE is for electrically contacting the positive pole 40 of the jump probe 14 educated. Thus, the third terminal RE is electrically contacted to the positive pole 40 via a third connecting line 50. The optional fourth connection MES is designed for electrically contacting the single-cell broadband lambda probe 12. So the fourth connection is MES with the unicellular

Broadband lambda probe 12 electrically contacted via a fourth connecting line 52. More specifically, the fourth lead 52 is connected to an optional sense resistor 54 of the single cell broadband lambda probe 12.

The control unit 10 further comprises a first electrical power source 56 for establishing a readiness for operation of the single-cell broadband lambda probe 12 and a second electric current source 58 for producing a

Operational readiness of the jump probe 14. The first electrical current source 56 is in particular for establishing the reference of the unicellular

The second electric current source 58 serves in particular for inflating the oxygen reference for the jump probe 14. The first electric current source 56 differs from the second electric current source 58. The first electric current source 56 is electrically contacted with the second terminal APE. The second electric current source 58 is electrically contacted with the third terminal RE. The first electric current source 56 is designed to allow a technically positive electric current to flow from the second terminal APE to the first terminal IPE via the unicellular broadband lambda probe 12. However, the first electric current source 56 can also lower a technically negative electric current from the first terminal IPE to the second terminal APE, for example in the case of rich exhaust gas. The second electric current source 58 is designed to allow a technically positive electric current to flow from the third terminal RE to the first terminal IPE via the jump probe 14.

Claims

claims

First control unit (10) for operating a single-cell broadband lambda probe (12) and a jump probe (14), in particular in one

Exhaust after-treatment system of an internal combustion engine, wherein the control unit (10) for electrically contacting the unicellular

Broadband lambda probe (12) and the jump probe (14) has three or four terminals (IPE, APE, RE, MES), wherein a first terminal (IPE) of the terminals (IPE, APE, RE, MES) is formed such that the unicellular Broadband lambda probe (12) and the jump probe (14) are electrically contacted together at the first port (IPE).

2. Control unit (10) according to claim 1, further comprising a first

electrical current source (56) for establishing readiness of the single-cell broadband lambda probe (12), in particular for establishing the reference of the single-cell broadband lambda probe (12), and a second electrical current source (58) for establishing operational readiness of the jump probe (14), wherein the first electric power source (56) is different from the second electric power source (58), wherein a second terminal (APE) of the terminals (IPE, APE, RE, MES) is electrically contacted with the first electric power source (56) and a third terminal (RE ) of the terminals (IPE, APE, RE, MES) is electrically contacted with the second electrical power source (58).

3. Control unit (10) according to claim 2, wherein the unicellular

Broadband lambda probe (12) a pumping cell (32) with an outer

Pump electrode (34) and an inner pumping electrode (36), wherein the first terminal (IPE) for electrically contacting the jump probe (14) and the inner pumping electrode (36) is formed.

4. Control unit (10) according to claim 3, wherein the second terminal (APE) of the terminals (IPE, APE, RE, MES) is designed for electrically contacting the outer pumping electrode (34).

5. control unit (10) according to one of claims 2 to 4, wherein the jump probe (14) for electrical contacting a plus pole (40) and a negative pole (42), wherein the first terminal (IPE) for electrically contacting the negative pole (42 ) of the jump probe (14) is formed.

6. Control unit (10) according to claim 5, wherein a third terminal (RE) of the terminals (IPE, APE, RE, MES) for electrically contacting the

Positive pole (40) of the jump probe (14) is formed.

7. Control unit (10) according to one of claims 1 to 6, wherein the control unit (10) has four terminals (IPE, APE, RE, MES), wherein a fourth terminal (MES) of the terminals (IPE, APE, RE, MES ) for electrically contacting the single-cell broadband lambda probe (12) is formed.

8. sensor system (30), in particular for operation in one

Exhaust after-treatment system comprising a unicellular

A broadband lambda probe (12), a jump probe (14) and a control unit (10) according to any one of claims 1 to 7, wherein the first terminal (IPE) of the terminals (IPE, APE, RE, MES) is connected to the single cell broadband lambda probe (12) and the jump probe (14) is electrically contacted together.

9. sensor system (30) according to claim 8, wherein the control unit (10) further comprises a first electrical power source (56) for producing a

Operational readiness of the unicellular broadband lambda probe (12),

in particular for establishing the reference of the unicellular

Broadband lambda probe (12), and a second electrical current source (58) for establishing a ready state of the jumping probe (14), wherein the first electric current source (56) differs from the second electric current source (58), wherein a second terminal (APE) the terminals (IPE, APE, RE, MES) are electrically contacted with the first electrical power source (56) and a third terminal (RE) of the terminals (IPE, APE, RE, MES) is electrically contacted with the second electrical power source (58).

10. Sensor system (30) according to claim 8 or 9, wherein the unicellular

Broadband lambda probe (12) a pumping cell (32) with an outer

Pump electrode (34) and an inner pumping electrode (36), wherein the first terminal (IPE) with the jump probe (14) and the inner

Pump electrode (36) is electrically contacted.

11. The sensor system (30) of claim 10, wherein the second terminal (APE) of the terminals (IPE, APE, RE, MES) is electrically contacted with the outer pumping electrode (34).

12. Sensor system (30) according to any one of claims 8 to 11, wherein the

Jump probe (14) for electrical contacting has a positive pole (40) and a negative pole (42), wherein the first terminal (IPE) with the negative terminal (42) of the jump probe (14) is electrically contacted.

13. Sensor system (30) according to claim 12, wherein the third terminal (RE) of the terminals (IPE, APE, RE, MES) with the positive pole (40) of the jump probe (14) is electrically contacted.

14. Sensor system (30) according to any one of claims 8 to 13, wherein the

Control unit (10) has four terminals (IPE, APE, RE, MES), wherein a fourth terminal (MES) of the terminals (IPE, APE, RE, MES) is electrically contacted with the single-cell broadband lambda probe (12).