KR102601386B1 - Method for operating a hydraulic system - Google Patents

Abstract

The present invention includes a pressure sensor 22 for measuring the measured system pressure (p _sens ); a transfer pump (21) for providing pressure (p _ist ) in the hydraulic system (9); Metering supply valve 32 for metering injection of liquid medium; and a controller (R) for controlling the pressure (p _ist ) in the hydraulic system (9), comprising: a first operating state of the hydraulic system (9); At S _Norm ), the controller (R) receives the system pressure (p _sens ) measured by the pressure sensor 22 and sends an operation request to the transfer pump 21 under comparison with the pressure set value (p _soll ), In a further operating state (S _Err ) of the hydraulic system (9), the request for operation of the transfer pump (21) is determined taking into account the pressure model value (p _mod ).

Description

{METHOD FOR OPERATING A HYDRAULIC SYSTEM}

The present invention relates to a method of operating a hydraulic system, particularly an SCR exhaust gas aftertreatment system. The present invention also relates to a computer program that executes each step of the above method when executed on a computer, and a machine-readable storage medium storing the computer program. Finally, the invention relates to an electronic control device configured to carry out the above method.

In particular, in automobiles, an SCR catalytic converter (SCR: S elective C catalytic Reduction ) is placed in the exhaust gas area of the automobile, which reduces nitrogen oxides (NOx) contained in the exhaust gas of the internal combustion engine to nitrogen in the presence of a reducing agent. Methods and devices for operating the organ are known. Thereby, the proportion of nitrogen oxides in the exhaust gas can be significantly reduced. DE 103 46 220 A1 describes the basic principles. Ammonia (NH ₃ ) is required for the reaction to proceed. As a reducing agent, NH ₃ separation reagents that are added and mixed into the exhaust gas are used. Typically, for this purpose, 32.5% urea solution, commercially available as AdBlue® and metered into the exhaust gas line upstream of the SCR catalytic converter, is used.

The reducing agent solution is usually provided in a reducing agent tank in an automobile. For transport and metering of urea solution, usually a transport pump; pressure line; Metering supply module with metering supply valve; And a metering and supply system including the necessary sensor device and electronic control device is provided. The transfer pump transfers the urea solution from the reductant tank into the metering supply module via a pressure line. For metering on demand, the requested and required mass and/or volume of reducing agent solution is metered into the exhaust gas line via a metering valve.

Typically, pressure sensors are used to monitor system pressure.

In addition, DE 10 2012 214 369 A1 includes an exhaust gas aftertreatment assembly; It relates to a method for metering and injecting a reducing agent into the exhaust gas line of an internal combustion engine including a reducing agent tank. Here, the controller controls the system pressure by matching the system pressure through pressurization of the transfer pump through comparison of the pressure value detected by the pressure sensor and the pressure set value.

In principle, it may be desirable to provide redundant detection of the prevailing pressure in the SCR exhaust gas aftertreatment system, so that operation of the SCR aftertreatment system with improved reliability can be ensured.

According to the invention, a pressure sensor for measuring the system pressure to be measured; a transfer pump for providing pressure in the hydraulic system; A metering supply valve for metering liquid media, especially reagents, into the exhaust gas line of an internal combustion engine; and a controller for controlling the pressure in the hydraulic system. Pressure is received and an actuating request is sent to the transfer pump under comparison with the pressure set value. In the further operating state of the hydraulic system, an actuating request is made to the transfer pump under consideration of the pressure model value calculated from the pressure model. do.

The reason why it is desirable to provide overlapping pressure model values provided in addition to the pressure values detected by the sensor within the scope of control is that although validation of the pressure values detected by the sensor can be performed, in case of failure of the pressure sensor This is because control functions can also be performed. This significantly improves system precision and operational reliability in the event of an error.

In one preferred embodiment of the method herein, the measured system pressure corresponds to the pressure within the SCR exhaust gas aftertreatment system. This embodiment is advantageous because the pressure in the exhaust gas aftertreatment system can be derived very simply when there is a direct relationship between the measured system pressure and the pressure in the SCR exhaust gas aftertreatment system. Additionally, through a corresponding correction using the correction coefficient, errors due to the system can be corrected and a corresponding correction of the pressure sensor can be performed.

In another preferred embodiment, the first operating state of the hydraulic system is a regular operation mode of the hydraulic system, in which control of the pressure is based on the system pressure measured via a sensor; An additional operating state of the SCR exhaust gas aftertreatment system is that the pressure within the SCR exhaust gas aftertreatment system is detected redundantly from the pressure model value to the measured system pressure of the pressure sensor, so that the SCR exhaust gas aftertreatment system operates. It is a state of being. Redundant detection of system pressure based on the model has the advantage of enabling validation of sensor-based pressure so that sensor malfunctions can be inferred in some cases. It is also possible to use pressure model values during control, which is desirable because the resulting pressure values used for pressure control are improved based on measured pressure and model-based pressure. Pressure values in the model are calculated using sensor values in normal operating mode and can be stored in the control unit, in particular within the scope of the pressure compensation characteristic curve.

In another preferred embodiment of the invention, pressure control of the SCR exhaust gas aftertreatment system is carried out in case of failure of the pressure sensor. In case of failure of the pressure sensor, the measured system pressure can no longer be used reliably and therefore control is no longer possible in principle in conventional systems. Here, failures can include sensor deterioration and even complete failure. However, on the other hand, within the scope of the invention, a model-based variable of pressure can be provided, and the corresponding control of the SCR exhaust gas aftertreatment system can now be carried out based on this model-based variable instead of the pressure value detected by the sensor. . In this case, a model-based value replaces the value detected by the pressure sensor, and through comparison of the pressure setpoint with the model value, a control deviation is calculated, based on which a control intervention in the transfer pump is triggered and the As a result, the system pressure is adjusted.

In another preferred embodiment of the invention, for the calculation of pressure model values, one or more operating variables of the SCR exhaust gas aftertreatment system are used. In another preferred embodiment, the calculation of the pressure model value is performed based on the current characteristics of the transfer pump of the SCR exhaust gas aftertreatment system and/or the drive characteristics of one or more metering supply valves. In principle, it is desirable to recourse to physical system variables, for example the current characteristics of the transfer pump or the actuation characteristics of the individual metering supply valves, since these system variables can reproduce the system pressure of the SCR exhaust gas aftertreatment system. This is because it enables possible calculations.

In another preferred embodiment, in a first operating state of the hydraulic system, a pressure model is learned by comparing the pressure model values with the system pressure measured by the pressure sensor. This method step is desirable because the pressure model can be learned according to the measured pressure values of the hydraulic system, thereby allowing the pressure model to be well matched to the actual pressure conditions in the system. The pressure model can be adjusted based on pressure sensor values and learned during operation, especially during normal operating mode. The learned pressure model can be reflected in particular in the scope of a pressure correction characteristic curve, and the pressure correction characteristic curve can be stored, for example, in a higher-level control device.

Additionally, the subject matter of the present invention is a computer program configured to perform each step of the method herein and a machine-readable storage medium on which the computer program is executed. Furthermore, the object of the present invention is an electronic control device configured to correspondingly execute the above-described method. Preferably, the present method is implemented in the form of a computer program stored in the form of software in a data storage medium, especially a memory, and provided to a control device for executing the present method, or an integrated circuit, especially an ASIC, is provided. The reason is that this approach incurs particularly low costs, especially if the execution-side control unit exists anyway as it is also used for other tasks. Storage media suitable for providing computer programs are, in particular, magnetic, optical and electronic memories, which have been known many times from the prior art.

Further advantages and configurations of the present invention are set forth in the specification and accompanying drawings.

Embodiments of the invention are illustrated in the drawings and are described in more detail below.

Figure 1 shows an SCR system comprising a pressure sensor in a pressure line, where pressure control is implemented according to embodiments of the method according to the invention.
Figure 2 is a schematic control circuit diagram of a transfer pump according to the first embodiment.
3 is a schematic control circuit diagram of a transfer pump according to another embodiment.
Figure 4 is a flow chart of the embodiment according to Figure 2.
Figure 5 is a flow chart of the embodiment according to Figure 3;

A hydraulic system 9, particularly an SCR exhaust gas aftertreatment system 100, for an SCR catalytic converter in an automobile (not shown) is shown in FIG. 1 . The SCR exhaust gas after-treatment system 100 includes a reducing agent tank 10 for a reducing agent solution, a transfer module 20, and a metering supply module 30. From the reductant tank 10 a suction line 11 leads to the transfer pump 21 of the transfer module 20 . The liquid reductant solution reaches the pressure line 31 via the filter 25 and through the outlet to the metering supply valve 32 of the metering supply module 30 and, if necessary, upstream of the SCR catalytic converter to the internal combustion engine ( It is metered and injected into the exhaust gas line (not shown). Additionally, from the transfer module 20 a return line 12 containing a throttle valve 23 can lead back into the reducing agent tank 10 (shown in dashed lines). In this case, the SCR exhaust gas after-treatment system 100 may be connected to the surroundings through the return line 12. A 4/2 direction control valve 24 is disposed on the transfer pump 21, and the transfer direction of the transfer pump 21 can be adjusted by the 4/2 direction control valve. In the transfer mode, the transfer pump 21 transfers the reducing agent solution from the reducing agent tank 10 to the metering supply module 30. In re-suction mode, the reductant solution can be transferred back from the SCR system into the reductant tank 10 via the suction line 11.

Additionally, a pressure sensor 22 is provided on the discharge side of the transfer pump 21 between the transfer pump and the metering supply valve 30. In one embodiment, pressure sensor 22 is located within transfer module 20 and is assigned to filter 25. Here, the pressure sensor 22 is designed as a relative pressure sensor and measures the relative pressure p of the SCR system in relation to the ambient pressure. In another embodiment, pressure sensor 22 may also be configured as an absolute pressure sensor (not shown) to measure absolute pressure within the SCR system. The pressure sensor 22 is connected to an electronic control device 40 in the form of a controller R, which receives the measured pressure values. Additionally, the electronic control device 40 in the form of a controller (R) can be connected to and control the transfer pump 21, the 4/2 direction control valve 24, and the metering supply valve 32.

In principle, the method of operation of the exhaust gas after-treatment system 100 described above and the SCR exhaust gas after-treatment system 100 described below includes a metering supply valve ( It can also be expanded to a system comprising one or more additional metering modules 32a with 32b). In principle, the invention is not limited to the above-described embodiments. Therefore, the method as a whole includes: a transfer pump; pressure lines; metering supply elements; liquid storage tank; one or more pressure sensors; And it can be applied to all hydraulic systems, including a control architecture of the system that allows at least controlling a transfer pump and in which model-based pressure values can be calculated.

A first embodiment of a method for controlling an SCR exhaust aftertreatment system 100 is shown as a control circuit diagram in FIG. 2 and as a flow chart in FIG. 4. In the SCR exhaust gas aftertreatment system 100, the actual pressure p _ist in the pressure line 31 is supplied from the transfer pump 21 (Q _SP ) and through one or more metering supply valves 32, 32a. Adjusted based on the amount of liquid discharged (Q _DV ). From this, the amount of pressure change per time is calculated according to the following relationship,

,

In the above relational expression, V is the volume of the relevant system, and B is a variable proportional to the compression module.

The actual pressure p _ist and its time curve are detected via the pressure sensor 22 (see step 110a). In principle, the actual pressure p _ist can be deduced directly from the measured pressure value p _sens of the sensor 22 . However, in this case, even when converting the measured pressure value (p _sens ) to the actual pressure (p _ist ), in some cases, error sources caused by the system are removed and correction, especially the correction of the pressure sensor 22, is ensured. For this reason, a correction factor may be considered.

In step 120a, the measured pressure values p _sens are received by the controller R, which calculates the control deviation Δp = p _soll - p _sens (step 130a). Then, based on the control deviation Δp, the controller R causes a control intervention U in the transfer pump 21 (step 140a), thereby aiming at maintaining the system pressure p _ist With this, the pumping liquid introduction (Q _SP ) into the system 100 is performed. The above-described control is subject to a first operating state S _Norm of the SCR exhaust gas aftertreatment system 100 , which represents the normal operating mode 105 . In this case, pressure control is effected based on the measurements of the pressure sensor. Additionally, the measured values of the sensor 22 can be used for learning a pressure model (P _Model ). Through comparison of the sensor pressure value (p _sens ) with the model-based system pressure (p _mod ), the pressure model (P _Model ) is optimized during operation and is correspondingly taken into account when calculating the control deviation (Δp) (see step 130a). (see step 135a in FIG. 4). In particular, in order to check the correct functioning of the pressure sensor 22, it is also possible to verify the validity of the pressure (p _sens ) detected by the pressure sensor 22 according to the model-based system pressure (p _mod ). Consideration of the pressure model (P _Model ) during pressure control and/or validation of the model-based system pressure (p _mod ) using sensor pressure values (p _sens ) can be performed in the category of additional operating states (S _Err ).

In the control device 40 or controller R, a pressure model (P _Model ), for example the current characteristic (I _SP ) of the transfer pump 21 during operation and/or the actuation of one or more metering valves 32, 32a. Based on observations of physical variables such as properties, an algorithm can be implemented to calculate model-based system pressure (p _mod ).

The control of the SCR exhaust gas aftertreatment system 100 can also be carried out in the scope of the alternative 106 of the additional operating state S _Err (see Figure 5). In this case, control of the system pressure (p _ist ) can only be performed based on the model (P _Model ) and the model-based pressure value (p _mod ), since the model-based system pressure (p _mod ) is the sensor pressure. This is because the value (p _sens ) exists redundantly. This has the advantage that, in addition to validation, the system can be operated even if, for example, the pressure sensor 22 fails or no longer functions properly due to a defect. In this case, the control deviation related to pressure control is calculated according to Δp = p _soll - p _mod .

Within the scope of this further embodiment of the present method, initially the operational reliability of the pressure sensor 22 is checked or queried (see 110b). This can be done through the above-described validation of the measured pressure (p _sens ) based on the model-based system pressure (p _mod ). Alternatively, the operational reliability can also be determined in such a way that, for example, the pressure sensor 22 detects the reducing agent pressure and the pressure measured by the pressure sensor is compared with a reference pressure, for example an ambient pressure. Through this comparison, it can be confirmed whether the pressure sensor 22 is functioning correctly, for example when the internal combustion engine is started and the reductant tank is emptied. In a first step, the reducing agent pressure can be compared with the ambient pressure via the pressure sensor 22 upon starting of the internal combustion engine. If the measured reducing agent pressure is different from the ambient pressure, a malfunction of the pressure sensor 22 can be inferred.

If the pressure sensor 22 is functioning correctly, the process continues, as shown in Figure 4 (see 105). If a defect in the pressure sensor 22 exists, a control deviation is calculated based on the model-based pressure value (p _mod ) in the range of alternative pressure controls (see step 135b). Then, based on the alternatively calculated control deviation (Δp = p _soll - p _mod ), the controller (R) causes a control intervention (U) for the transfer pump (21) (step 140b), thereby causing the system Pumping liquid introduction (Q _SP ) into system 100 is performed for the purpose of maintaining pressure (p _ist ). If the pressure sensor 22 is faulty, the branch with the pressure model P _Model can be connected directly to the control circuit influenced by the controller R, for example by means of the switching element S (see Figure 3). .

Claims (11)

A pressure sensor (22) for measuring the measured system pressure (p _sens ); a transfer pump (21) for providing pressure (p _ist ) in the hydraulic system (9); Metering supply valve 32 for metering injection of liquid medium; A method of operating a hydraulic system (9) comprising a controller (R) for controlling the pressure (p _ist ) in the hydraulic system (9),
In the first operating state (S _Norm ) of the hydraulic system (9), the controller (R) receives the system pressure (p _sens ) measured by the pressure sensor 22 and compares it with the pressure setpoint (p _soll ). An operation request is sent to the pump 21, and in the additional operating state (S _Err ) of the hydraulic system (9), the operation request is sent to the transfer pump (21) under consideration of the pressure model value (p _mod ) calculated from the pressure model (P _Model ). The operation request is determined,
In the first operating state (S _Norm ) of the hydraulic system 9, the pressure model (P _Model ) compares the pressure model value (p _mod ) with the system pressure (p _sens ) measured based on the pressure sensor 22. Learn how hydraulic systems work. 2. Method according to claim 1, wherein the hydraulic system (9) is an SCR exhaust gas aftertreatment system (100) and the liquid medium is metered in the form of a reagent into the exhaust gas line of the internal combustion engine. 3. The system according to claim 1 or 2, wherein the measured system pressure (p _sens ) corresponds to the pressure (p _{ist) in the hydraulic system (9) or the pressure (p ist )} in the hydraulic system (9) is measured. A method of operating a hydraulic system, characterized in that it is determined from pressure (p _sens ) and a correction coefficient. 3. The method according to claim 1 or 2, wherein in a first operating state (S _Norm ) of the hydraulic system (9) the normal operating mode of the hydraulic system (9) is carried out and a further operating state (S) of the hydraulic system (9) is carried out. _Err ) is characterized in that it represents a state in which the pressure (p _ist ) in the hydraulic system 9 is redundantly determined with respect to the measured system pressure (p _sens ) of the pressure sensor 22 from the pressure model value (p _mod ). How a hydraulic system works. 3. The method of claim 1 or 2, wherein in a further operating state (S _Err ) of the hydraulic system (9), pressure control of the hydraulic system (9) is carried out in case of failure of the pressure sensor (22), wherein the hydraulic system (9) 9) A method of operating a hydraulic system, wherein the pressure (p _ist ) is determined from the pressure model value (p _mod ) instead of the measured system pressure (p _sens ) of the pressure sensor (22). 3. Method according to claim 1 or 2, wherein at least one operating variable of the hydraulic system (9) is used for the calculation of the pressure model value (p _mod ). 7. Method according to claim 6, wherein at least one current characteristic (I _SP ) of the transfer pump (21) is used for the calculation of the pressure model value (p _mod ). delete A computer program stored on a machine-readable storage medium and configured to perform each step of the method according to claim 1 or 2. A machine-readable storage medium storing the computer program according to claim 9. Electronic control device (40) configured to carry out the method according to claim 1 or 2.

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