WO2017194570A1

WO2017194570A1 - Method for determining a water content in the exhaust gas of a drive system

Info

Publication number: WO2017194570A1
Application number: PCT/EP2017/061106
Authority: WO
Inventors: Florian Stief; Markus Willimowski
Original assignee: Robert Bosch Gmbh
Priority date: 2016-05-12
Filing date: 2017-05-10
Publication date: 2017-11-16
Also published as: CN109072799A; KR20190006995A; DE102016208161A1; CN109072799B; KR102256491B1

Abstract

The invention relates to a method for determining a water content (w) in the exhaust gas of a drive system in a motor vehicle. Here, a water injection system injects water into an air/fuel mixture. Furthermore, at least one lambda sensor is arranged in an exhaust tract of the drive system. The method comprises the following steps: Firstly, the water injection is deactivated (204). By increasing (205) a pumping voltage (U_P) in the lambda sensor, an electrolysis (206) of water vapour occurs. In a reference measurement (207), a first oxygen content, arising from the electrolysis (206) of the water vapour, of the exhaust gas is determined (208) by means of the lambda sensor, and from this, a nominal water quantity (W_N) is determined (208). Subsequently, a predefined water quantity is injected (209, 213) into the air/fuel mixture. This is followed by an actual measurement (211, 216) in which a second oxygen content, arising from the electrolysis (210, 215), of the exhaust gas is determined by means of the lambda sensor at a predefined operating point. Furthermore, a difference (Δ) between the second oxygen content and the first oxygen content is calculated (212, 217), and this is used together with the nominal water quantity (W_N) to calculate (213, 218) the water content (w).

Description

Description title

Method for determining a water content in the exhaust gas of a drive system

The present invention relates to a method for determining a

Water content in the exhaust gas of a drive system. Furthermore, the present invention relates to a computer program that executes each step of the method when running on a computing device and to a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control device which is set up to carry out the method.

State of the art

Nowadays, by injecting water into one

Air / fuel mixture changed various engine parameters. For example, thus the ignition timing can be changed in the engine. The water is injected via a water injection, which is upstream of the

Internal combustion engine is injected into the intake system. In addition, systems are known in which the injection of water injects water directly into the cylinders of the internal combustion engine. Since the amount of water has an influence on the one hand on the performance of the vehicle, on the other hand on the composition of the exhaust gas, a monitoring of the water injection system is necessary. On top of that, the influence on the composition means that the legislator demands a diagnosis of the system. Usually, electrical diagnoses of the individual water injection components are used, but these only include electrical faults, such as electrical faults. a line drop, recognize.

In addition, further components of the exhaust gas are monitored in the exhaust tract. Among other things, this includes an oxygen content, which is monitored by means of Lambda sensors, which are arranged in the exhaust tract. DE 10 2010 021 281 AI relates to a system for an exhaust gas sensor, for example, an oxygen sensor with an exhaust system of a

Combustion engine is connected. Furthermore, the document relates to a method in which the exhaust gas sensor, in addition to an amount of oxygen additionally indicates an amount of water in the fuel. A pumping current can be varied, whereby it can be selected which of the above-mentioned components are determined. To determine the amount of water, the pumping current is increased, so that the amount of oxygen contained in water molecules can be measured by the exhaust gas sensor.

Disclosure of the invention

The method relates to a water injection system, as well as to an exhaust tract of a drive system in a motor vehicle. The drive system comprises an internal combustion engine, as well as an intake tract and the aforementioned exhaust tract, both of which are connected to the internal combustion engine. in the

Exhaust tract downstream of the internal combustion engine at least one lambda sensor is arranged, with which it is possible to determine an amount of oxygen in the exhaust gas. The water injection system is upstream of one

Internal combustion engine arranged on the intake manifold and arranged to inject a predetermined amount of water in the air / fuel mixture. Consequently, an air / fuel mixture with a fixed reaches

Water content of the internal combustion engine. The injected water has both influence on different engine parameters and thus on a performance of the motor vehicle, as well as on the exhaust gas. Therefore, monitoring the injected water quantity and the water injection itself is of great importance. In the process, the existing lambda sensors are used to determine the water content of the exhaust gas and thus to detect a system error of the water injection. Thereby can

if necessary, countermeasures are initiated.

Initially, in the process, the water injection is turned off. This makes it possible to carry out a reference measurement of ambient humidity. Subsequently, the pumping voltage of the lambda sensor is increased, whereby an electrolysis of water vapor takes place. The water is split into hydrogen and oxygen. A resulting first oxygen content is now determined in the reference measurement by the lambda sensor and further calculates a nominal water quantity. This gives the current

Amount of water in the system without additional injection of water.

Subsequently, a predetermined amount of water in the

Lufl fuel mixture injected. In an actual measurement, at a

predetermined operating point, a second oxygen content is determined, which is also caused by the electrolysis of the water, as described above. This second oxygen content is composed of the first

Oxygen content, which corresponds to the amount of water in the ambient air, and the oxygen, which corresponds to the additional injected water. Forming a difference between the second and the first oxygen content, one obtains a statement about the oxygen content, the injected by the

Water has formed. The water content, however, is calculated from the difference and the nominal water quantity, which is determined from the reference measurement

According to a further aspect of the method, provision may be made for using further measured quantities in order to achieve a desired water content in the

Determine exhaust gas. From a comparison between the desired

Water content and the above calculated water content in the exhaust gas can be determined too low and / or high water content in the exhaust gas. In addition, a malfunction of the water injection system can be diagnosed.

For example, these parameters are engine temperature, shutdown time and / or

Ambient temperature, as well as a control of the water injection. The advantage is that it is possible on the basis of this information to take appropriate measures to achieve the desired water content.

Preferably, the information is used to control the water injection. If the water content in the exhaust gas is too low, the

Water injection are readjusted accordingly and the injected amount of water can be increased. On the other hand, if the water content in the exhaust gas is too high, the water injection can be switched off. This allows the injected amount of water can be optimized via the water injection and adapted to the conditions of the motor vehicle.

Preferably, in a diagnosis of a malfunction of

Water injection to be informed a driver of the motor vehicle. This can then, for example, commission a review and possibly a repair in a workshop.

According to one aspect, it may be provided that the actual measurement of the oxygen content resulting from the electrolysis of the water vapor is carried out at a plurality of predetermined operating points. Preferably, these differ by the predetermined injection quantities of water. For example, a maximum amount of water (full amount) can be injected and an actual measurement can be performed. Subsequently, the injected amount of water can be halved (half amount) and also an actual measurement can be performed. Forming the difference in each case from the full quantity with the nominal water quantity and from the half quantity with the nominal water quantity, the accuracy of the statements can be increased.

In an advantageous embodiment of the method can be provided that additional steps are performed before the electrolysis of the water vapor to ensure a constant quality of the exhaust gas during the measurements, since during the measurements, the lambda sensors are used and for this purpose the lambda control briefly except Force is set. For this purpose, on the one hand an adaptation of the lambda sensor is performed, on the other hand, it is checked whether a lambda control has settled.

In addition, the operating parameters for a diagnosis are queried. If the operating parameters for a diagnosis are met, the procedure is initiated as described above. Otherwise the diagnosis will not be carried out.

In another aspect, operating points needed for diagnostics may be adjusted by an electronic controller should they not be powered up by the driver. As a result, the diagnosis can be started specifically. The computer program is set up to perform each step of the method, in particular when it is performed on a computing device or controller. It allows the implementation of the method in a conventional electronic control unit without having to make any structural changes. For this it is on the machine-readable

Storage medium stored.

By putting the computer program on a conventional

Electronic control unit, the electronic control unit is obtained, which is adapted to control the determination of the water content in the exhaust gas by means of the method described above.

BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

FIG. 1 schematically shows a drive system and an intake tract with water injection arranged thereon and an exhaust tract with the lambda sensor arranged therein, which can be controlled by means of the method according to the invention.

FIG. 2a shows a first part of a flow chart of a

Embodiment of the method according to the invention.

FIG. 2b shows a second part of the flowchart, which is the continuation of the first part of FIG. 2a, of an embodiment of the invention

inventive method. Embodiment of the invention

In Figure 1, a drive system 100 is shown, the an internal combustion engine 110, and a Ansaugtraktl20 and an exhaust tract 130, which with the

Combustion engine 110 are connected includes. A water injection 121 is at the intake tract 120, upstream of the internal combustion engine 110 arranged. This injects a predetermined amount of water in the

Intake tract 20. In the exhaust tract 130, at least one lambda sensor 131 is arranged downstream of the internal combustion engine 110, so that the exhaust gas flows past it. With the lambda sensor 131, it is possible to use a

To measure oxygen content in the exhaust gas. The present embodiment of the method according to the invention discloses a possibility with this lambda sensor 131 also to measure a water content w in the exhaust gas. An electronic control unit 140 is connected to the internal combustion engine 110, the water injection 121 and the lambda sensor 131 and can control and monitor them.

Figures 2a and 2b show a flow diagram of the embodiment of the method according to the invention. With reference to FIG. 2a, an adaptation 200 of the lambda sensor 131 in the system is carried out at the beginning of the method. Depending on the condition, it is possible for the system to perform a lambda control 202 in which the water content is varied by injecting the water injection 121 to adapt it to the conditions. In order for the method according to the invention to proceed correctly, it is provided that the

Lambda control 202 is completed, which is checked in a second step 201. If the lambda control 202 has not been completed, the method is ended 227. Furthermore, a query 203 of the

Operating parameters for the diagnosis started. If these are not fulfilled, the procedure is also ended. 227. If the above conditions are fulfilled, the diagnosis of the

Water injection 121, by turning off 204 of these. Next, an increase 205 of the pump voltage UP of the lambda sensor 131 takes place. This leads to electrolysis 206 of the water vapor, so that water is split into hydrogen and oxygen. In a reference measurement 207, a first oxygen content is measured that has been produced by the electrolysis 206. This first oxygen content is dependent on the ambient humidity or the water content due to external influences. From the first oxygen content, a nominal water quantity W can then be determined 208, which includes the influences mentioned above. To monitor the water injection 121, an injection 209 of a full amount is initiated. This means that the water injection 121 injects a maximum amount of water into the intake tract 120. Since there continues to be a raised pumping voltage UP of the lambda sensor 131, the additionally injected amount of water is split by an electrolysis 210, corresponding to the electrolysis 206, into oxygen and hydrogen. Thus, a second oxygen content in an actual measurement 211 of the full amount can be determined. The second oxygen content comprises on the one hand the first

Oxygen content and additionally the oxygen content, due to the

Injection 209 of the full amount of water has arisen. By calculating 212 the difference Δ between the actual measurement 211 and the reference measurement 207, a calculation 213 of the water content w in the exhaust gas can be carried out with the aid of this difference Δ and the nominal water quantity WN. In a further step, the method according to the invention provides, in addition to the actual measurement 211 of the full quantity, to examine a further quantity of water. For this purpose, an injection 214 of a half amount corresponding to half the amount of water of the full amount, initiated. The injected half-amount is, by an electrolysis 215, according to the electrolysis 210, split into oxygen and hydrogen. Equivalent to the actual measurement 211 of the full quantity, a second oxygen content is determined in the actual measurement 216 of the half-quantity. In the same

As described above, a difference Δ of the actual measurement 216 and the reference measurement 207 is calculated 217. This difference Δ is also used with the nominal water quantity W in order to determine the water content w in the exhaust gas. By multiple actual measurements at different predetermined injection quantities a higher accuracy is given.

The flowchart is continued in FIG. 2b. From the actual measurement 211 of the full quantity and the actual measurement 216 of the half quantity, in FIG. 2 a, a calculated water content w is thus determined. In a further step 220, a desired water content is determined where other measurands 219 are included. These measurement variables 219 include, inter alia, an engine temperature, a shutdown time and an ambient temperature, as well as a triggering of the water injection 121. In a query 221, the

Ratio between calculated water content w and desired

Water content where checked. In the event that the calculated amount of water w is smaller than the desired amount of water where, a readjustment 222 of the water injection 121 is performed, in which the injected amount of water is increased. Subsequently, a fault memory entry 223 is created and the process is terminated 227. If it is determined in the query 221 that the calculated water content w is greater than the desired water content where, a shutdown 224 of the water injection 121 is performed, resulting in a

Reduction of the water content w in the exhaust gas leads. Then one

Error memory entry 223 is applied and the process is terminated 227. In the case of the calculated water content w having the desired water content where, the process is terminated immediately 227. Moreover, by comparing the calculated water content w with the desired water content where, a malfunction of the water injection 121 diagnosed, this is certified in a query 225 of the malfunction and informed the driver 226. If there is no malfunction of the water injection 121, the process is terminated 227.

Claims

claims

1. A method for determining a water content (w) in the exhaust gas of a drive system (100) in a motor vehicle, wherein a

Water injection system (121) injects water into an air / fuel mixture and at least one lambda sensor (131) in an exhaust tract

(130) of the drive system (100), comprising the following steps:

- switching off (204) the water injection (121);

Electrolysis (206) of water vapor by lifting (205) a

Pump voltage (UP) in lambda sensor (131);

Reference measurement (207) of one of the electrolysis (206) of the

Water vapor resulting first oxygen content of the exhaust gas through the lambda sensor (131) and therefrom determination of a nominal water quantity (WN);

- injecting (209) a predetermined injection quantity of water into the air / fuel mixture;

- actual measurement (211) of a second oxygen content of the exhaust gas resulting from the electrolysis (210) of the water vapor by the lambda sensor (131) at a predetermined operating point;

Calculating (212) a difference (Δ) between the second

Oxygen content and the first oxygen content;

- Calculation (213) of the water content (w) from the difference (Δ) and the nominal water quantity (WN).

2. The method of claim 1, wherein with the aid of further measured quantities (219) a desired water content in the exhaust gas is determined and from a comparison between the desired water content (where) and calculated water content (w) in the exhaust too low and / or high water content (w) is determined in the exhaust gas and / or a malfunction of the water injection system (121) is diagnosed (225).

The method of claim 2, wherein at too low a water content w, the water injection (121) is readjusted (222) and at high water content (w) a shutdown (224) of the water injection (121) takes place and a fault memory entry (223) is applied

The method of claim 2 or 3, wherein a driver of the motor vehicle is informed (226) when a malfunction of the water injection (121) is diagnosed (225).

Method according to one of the preceding claims, wherein the actual measurement (211, 216) of the oxygen content resulting from the electrolysis (210, 215) of the water vapor is predetermined at several

Operating points is performed, which differ by predetermined injection amounts of water.

Method according to one of the preceding claims, wherein the following steps are carried out before the electrolysis of the water vapor:

- Adaptation of the lambda sensor (200);

- checking (201) whether a lambda control (202) has been completed;

- query the operating parameters for a diagnosis (203).

Computer program which is set up every step of the

Method according to one of claims 1 to 6 perform.

Machine-readable storage medium on which a

Computer program according to claim 7 is stored.

Electronic control unit (140) which is set up to carry out a determination of the water content w in the exhaust gas of a drive system (100) by means of a method according to one of claims 1 to 6.