DE102016202854A1 - Method and device for operating a lambda probe in an exhaust passage of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating a lambda probe (20) in an exhaust passage (12) of an internal combustion engine (10), wherein the lambda probe (20) is arranged in the exhaust passage (12) upstream of a catalytic converter (14), wherein the lambda probe (20 ) has a heating element (22), wherein the operating temperature of the lambda probe (20) by means of a heating controller (24) of the heating element (22) is set, and wherein an exhaust gas temperature of the internal combustion engine (10) by an internal resistance of the lambda probe (20) is determined characterized in that a reference temperature is determined by means of a temperature sensor (16), at the determined reference temperature an internal resistance (Ri) of the heating element (22) is measured, the heating element (22) is acted upon by a defined heating voltage, a step response of the internal resistance of the heating element (22) is evaluated and based on the step response, an adaptation of the heating resistor (Rh) of the heating element (22). The invention further relates to a device for carrying out such a method and to a control device (18) for carrying out such a method, in which a program code is stored on a machine-readable carrier and the method is executed when the program is executed on the control device (18) ,

Description

The invention relates to a method for operating a lambda probe in an exhaust passage of an internal combustion engine and to an apparatus for carrying out such a method according to the preambles of the independent claims.

In motor vehicles with an internal combustion engine, in particular with a petrol engine, today three-way catalytic converters for exhaust aftertreatment standard. The internal combustion engines are controlled by lambda probes alternately by a stoichiometric combustion air ratio, so that such three-way catalysts can develop their maximum efficiency with respect to the conversion of harmful exhaust gas components. In this case, a temperature measurement in the exhaust passage can provide important information about the condition of the exhaust system. Thus, for example, by a temperature measurement in the exhaust passage, an intervention in the engine control of the engine take place in order to avoid overheating of components for exhaust aftertreatment of the internal combustion engine. Furthermore, the lambda control can be improved via the temperature measurement in such a way that the measuring accuracy of the lambda probes increases and thus the internal combustion engine can be regulated in a narrower window by a stoichiometric combustion air ratio. This reduces the raw emissions of the internal combustion engine and thus the total emissions of the motor vehicle. Temperature sensors are known from the prior art, which measure an exhaust gas temperature and send this information to the engine control unit of the internal combustion engine. However, these sensors are relatively expensive, so that efforts have already been made in the past to determine the exhaust gas temperature via the heating resistance of a heated lambda probe.

From the DE 10 2008 011 833 A1 a method is known for controlling a lambda-controlled exhaust system of an internal combustion engine, wherein the exhaust system has at least one catalytic converter and at least one heating element for heating the lambda probe to an operating temperature. It is envisaged that the performance of the heating element is determined and at least one corrected control parameter is used by the heating element control for controlled heating of the heating element.

The invention is based on the object to further improve such a method and to allow using the already existing on the motor vehicle temperature sensors improved information about the temperature in the exhaust duct.

The object is achieved by an inventive method for operating a lambda probe in an exhaust passage of an internal combustion engine, wherein the lambda probe is arranged in the exhaust passage upstream of a catalyst, wherein the lambda probe has a heating element, wherein the operating temperature of the lambda probe is adjusted by means of a heating controller of the heating element, wherein an exhaust gas temperature of the internal combustion engine is determined by an internal resistance of the lambda probe, and wherein by means of a temperature sensor, a reference temperature is determined at the determined reference temperature an internal resistance of the heating element is measured, the heating element is acted upon by a defined heating voltage, evaluated a step response of the internal resistance of the heating element is carried out and based on the step response, an adaptation of the heating resistor of the heating element. As a result, individual compensation of the component spreads of the heating resistor of the lambda probes is possible so that lambda probes-individually a temperature-resistance curve of the lambda probe can be calculated and thus an improved determination of the temperature in the exhaust duct based on the internal resistance of the respective lambda probe is possible.

According to an advantageous embodiment of the method it is provided that at a first time a first resistance of the heating element and at a later time a second resistance of the heating element is evaluated. By a two-fold evaluation of the internal resistance of the heating element, a simple creation of a correction function of the lambda probe is possible.

Preferably, the adaptation of the resistor takes place as a function of three resistance measurements of the heating element, wherein a first resistance measurement takes place at a temperature determined by the temperature sensor and two further resistance measurements are carried out at unknown temperatures and based on the measured internal resistance R _i a lambda probe individual heating resistor R _h for the Heating element of the lambda probe is calculated. There are thus three temperature measurements, one at the known temperature and two at unknown temperatures. A relationship between the internal resistance R _i and the heating resistor R _h can be established in order to infer the size of the lambda probe-individual heating resistor R _h or a deviation from a heating resistor of a standard lambda probe. As a result, component variations in the heating resistor can be compensated and thus an improved model for calculating the exhaust gas temperature can be provided.

According to an advantageous embodiment of the method is provided that as Reference temperature is the ambient temperature is provided. In general, a sensor for detecting the ambient temperature is present on motor vehicles, for example, to provide the driver via a display with this information, to regulate the heating or air conditioning of the vehicle or to warn the driver against black ice. By means of such a temperature sensor and an accurate temperature measurement, the exhaust gas temperature model can be made plausible by a sensor value, which improves the modeling over the entire exhaust system of the internal combustion engine.

In a preferred embodiment of the invention, it is provided that an adapted heating resistor R _{h is} stored in a control unit of the internal combustion engine. Thus, the corrected heating resistor is available for the further operation of the internal combustion engine and does not have to be constantly redetermined. In addition, the measurement for correcting the heating resistor R _h can be repeated at regular intervals in order to compensate for an aging of the lambda probe or a change in the heating resistance over the duration of the lambda probe.

In a further preferred embodiment of the invention, it is provided that the method is started or carried out before a starting process of the internal combustion engine. Before the start of the internal combustion engine or after a longer standstill of the internal combustion engine or the motor vehicle, the temperature of the lambda probe substantially corresponds to the ambient temperature. Thus, the internal resistance R _{i of} the heating resistance of the lambda probe can be determined at a precisely known temperature, whereby a stable support point for the model for the calculation of the exhaust gas temperature is formed.

According to a preferred embodiment of the method it is provided that the method is started by a door contact switch, a buckle sensor or a sensor for detecting a seat occupancy of a motor vehicle. Before starting a motor vehicle, the driver usually opens the driver's door, sits on the driver's seat, closes the belt and starts the vehicle and thus the internal combustion engine. Thus, a door contact switch, a buckle sensor or a sensor for detecting a seat occupancy of the driver's seat are well suited to start before starting the engine, a corresponding method. In this case, appropriate warning devices are usually present both for a non-closed door contact or for a non-applied seat belt, the signal can be easily forwarded to the control unit of the internal combustion engine to start the process.

According to the invention, a device for correcting a characteristic curve of a lambda probe in an exhaust duct of an internal combustion engine is proposed, wherein a catalytic converter is arranged in the exhaust duct, wherein in the flow direction of an exhaust gas of the internal combustion engine through the exhaust duct upstream of the catalyst, the lambda sensor is arranged, wherein the operating temperature of the lambda probe means a heating controller of the heating element is adjustable, wherein an exhaust gas temperature of the internal combustion engine can be determined by an internal resistance of the lambda probe, wherein a temperature sensor is provided for determining a reference temperature, and wherein the device comprises a control unit. By such a device can be carried out in a simple manner described in the preceding sections method. With such a device, an improved calculation of the temperature in the exhaust duct based on the heating resistance of the lambda probe can be done.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a motor vehicle with a device according to the invention for operating a lambda probe

2 a flowchart for carrying out a method according to the invention.

1 shows a motor vehicle 32 with an internal combustion engine 10 , The internal combustion engine 32 has an exhaust duct 12 in which a catalyst 14 , preferably a three-way catalyst is arranged. The internal combustion engine 10 is about one in the exhaust gas flow direction of an exhaust gas of the internal combustion engine 10 upstream of the catalyst 14 arranged lambda probe 20 through a control unit 18 adjustable, the internal combustion engine 10 preferably operated alternately with low excess air and low fuel surplus by a stoichiometric combustion air ratio. The lambda probe 20 is preferably designed as a broadband probe and has a controllable heating element 22 , preferably a heating resistor. For controlling the heating element 22 is a heating controller 24 provided which, for example, in the control unit 18 of internal combustion engine 10 can be integrated or formed as a separate component.

On the motor vehicle 32 is a temperature sensor 16 arranged, with which a, preferably substantially constant temperature, in particular the ambient temperature, can be detected. On the motor vehicle 32 are also sensors 26 . 28 . 30 installed, which as a door contact switch 26 , as a belt buckle sensor 28 or as a sensor 30 are designed to detect the seat occupancy.

In operation of the internal combustion engine 10 becomes the lambda probe 20 both via the hot exhaust gas of the internal combustion engine and via the heating element 22 heated and regulated to a predefined operating temperature. With hot exhaust gas is basically the heating power requirement to the electric heating element 22 low, because a larger heat flow through the exhaust gas to the lambda probe 20 is supplied. The electric heating element 22 based on ohmic resistance. The applied voltage U is quadratically proportional to the heating power of the heating element 22 , The heating resistor R _{h of} the heating element 22 determines how much voltage must be applied to regulate the target temperature. The target value of this regulation is the internal resistance R _{i of} the heating element 22 the lambda probe 20 ,

The functional relationship can be described as follows: P _h = U * I = U ² / R _h

Where P _{h is} the heating power, U is the heating voltage, I is the flowing current and R _{h is} the heating resistor.

The heating resistor is subject to manufacturing tolerances, so that during operation of the lambda probe 20 different heating powers are required to achieve the target internal resistance R _i . These tolerances must be adapted. Therefore, an adjustment to existing temperature sensors 16 helpful. This is preferred in cold and stationary internal combustion engine 10 performed via a sensor for detecting the ambient temperature. The control unit 18 can for example via a door contact sensor 26 start an adaptation routine, with a defined heating voltage U _h to the lambda probe 20 is brought and the step response of the internal resistance R _{i of} the heating element 22 is evaluated. The gradient of the internal resistance R _i is at lambda probes 20 with lower heating resistance R _{h of} the heating element 22 higher than with lambda probes 20 with maximum permissible heating resistance.

The temperature of the lambda probe is proportional to the internal resistance R _{i of} the heating element 22 , The following applies: T ~ R _i , where R _{i is} the internal resistance of the heating element 22 and T is the temperature of the lambda probe 20 is.

The internal resistance R _i is also proportional to the introduced heating power P _h . The following applies: R _i ~ P _h . This is the temperature at the lambda probe 20 inversely proportional to the heating resistance R _h . The following applies: T ~ U ² / R _h ~ R _i

In 2 is a flow diagram of a method according to the invention for operating a lambda probe 20 shown.

In a first step < 100 > the ambient temperature is determined by the temperature sensor 16 measured. In a second process step < 110 > is carried out a measurement of the internal resistance R _i at time t ₀ , ie at ambient temperature and before the lambda probe 20 or the heating element are acted upon by a defined heating voltage. In a further process step < 120 > is a defined heating voltage U _h on the heating element 22 with cold lambda probe 20 given. At a first time t ₁ takes place in a method step < 130 > a second measurement of the internal resistance R _{i of} the heating element 22 , After expiry of a further delay time takes place at a second, later time t _2, a new measurement of the internal resistance R _{i of} the heating element 22 , In a following process step < 140 > The adaptation routine is terminated and the learned, adapted value of the heating voltage R _h in the control unit 18 saved.

By making three measurements of the internal resistance R _i , one at a known (ambient) temperature and two more at unknown temperatures, a relationship between R _i and R _h can be made to the size of the adapted heating resistor R _h or the distance to a standardized heating element 22 close.

In operation of the internal combustion engine 10 becomes the lambda probe 20 both with the electric heating element 22 as well as by the exhaust gas of the internal combustion engine 10 heated. With the known and adapted heating resistor R _{h of} the heating element 22 and the applied heating voltage U _h can thus clearly and reliably to the temperature of the exhaust gas at the lambda probe 20 getting closed. This will be the disadvantages of an unadapted heating element 22 overcome and thus achieved greater accuracy in the temperature determination. Through a more accurate temperature determination via this method, the exhaust gas temperature model can provide an additional sensor value for plausibility which improves modeling throughout the exhaust system.

LIST OF REFERENCE NUMBERS

10

Internal combustion engine

12

exhaust duct

14

catalyst

16

temperature sensor

18

control unit

20

lambda probe

22

heating element

24

Heating controller

26

Door switch

28

Buckle sensor

30

Sensor for detecting seat occupancy

32

motor vehicle

I

amperage

P _h

heating capacity

R _h

heating resistor

R _i

internal resistance

T

temperature

U

tension

t ₀

Measuring time before applying the heating voltage

t ₁

first time of measurement

t ₂

second measuring time

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008011833 A1 [0003]

Claims (10)

Method for operating a lambda probe ( 20 ) in an exhaust duct ( 12 ) an internal combustion engine ( 10 ), wherein the lambda probe ( 20 ) in the exhaust duct ( 12 ) upstream of a catalyst ( 14 ), wherein the lambda probe ( 20 ) a heating element ( 22 ), wherein the operating temperature of the lambda probe ( 20 ) by means of a heating controller ( 24 ) of the heating element ( 22 ), and wherein an exhaust gas temperature of the internal combustion engine ( 10 ) by an internal resistance of the lambda probe ( 20 ), characterized in that by means of a temperature sensor ( 16 ) a reference temperature is determined, at the determined reference temperature an internal resistance (R _i ) of the heating element ( 22 ), the heating element ( 22 ) is applied with a defined heating voltage (U _h ), a step response of the internal resistance (R _i ) of the heating element ( 22 ) is evaluated and based on the step response, an adaptation of the heating resistor (R _h ) of the heating element ( 22 ) he follows. A method according to claim 1, characterized in that at a first time (t ₁ ) a first resistance of the heating element ( 22 ) and at a later time (t ₂ ) a second resistance of the heating element ( 22 ) is evaluated. A method according to claim 2, characterized in that the adaptation of the resistance in dependence on three resistance measurements of the heating element ( 22 ), wherein a first resistance measurement at a by the temperature sensor ( 16 ) and two further resistance measurements are carried out at unknown temperatures and based on the measured internal resistance (R _i ) a probe-individual heating resistor (R _h ) for the heating element ( 22 ) the lambda probe ( 20 ) is calculated. Method according to one of claims 1 to 3, characterized in that the ambient temperature is selected as the reference temperature. Method according to one of claims 1 to 4, characterized in that an adapted heating resistor (R _h ) in a control unit ( 18 ) of the internal combustion engine ( 10 ) is stored. Method according to one of claims 1 to 5, characterized in that the method before a starting operation of the internal combustion engine ( 10 ) is started or carried out. A method according to claim 6, characterized in that the method by a door contact switch ( 26 ), a buckle sensor ( 28 ) or a sensor ( 30 ) for detecting a seat occupancy of a motor vehicle ( 32 ) is started. Control unit ( 18 ) with a program code which is stored on a machine-readable carrier, for carrying out a method according to one of claims 1 to 7, when the program is stored on a computing device, in particular on a control device ( 18 ) of the internal combustion engine ( 10 ), is performed. Device for correcting a characteristic curve of a lambda probe ( 20 ) in an exhaust duct ( 12 ) an internal combustion engine ( 10 ), wherein in the exhaust duct ( 12 ) a catalyst ( 14 ) is arranged, wherein in the flow direction of an exhaust gas of the internal combustion engine ( 10 ) through the exhaust duct ( 12 ) upstream of the catalyst ( 14 ) the lambda probe ( 20 ), wherein the operating temperature of the lambda probe ( 20 ) by means of a heating controller ( 24 ) of the heating element ( 22 ) is adjustable, wherein an exhaust gas temperature of the internal combustion engine ( 10 ) by an internal resistance of the lambda probe ( 20 ) can be determined, characterized in that a temperature sensor ( 16 ) is provided for determining a reference temperature and that the device is a control device ( 18 ), wherein the device is arranged to perform a method according to one of claims 1 to 7. Apparatus according to claim 9, characterized in that the lambda probe ( 20 ) is designed as a broadband probe.

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