DE102015200724A1 - Hydraulic dosing system, in particular an internal combustion engine of a motor vehicle and method for its operation - Google Patents

Abstract

The present invention relates to a hydraulic metering system, in particular an internal combustion engine of a motor vehicle, in which at least one feed pump (125, 130) for conveying a fluid (115) and at least one pressure sensor (135) for determining the hydraulic pressure in the metering system are arranged it is provided that the at least one feed pump (125, 130) is functionally inseparably connected to the pressure sensor (135) and that the pressure sensor (135) has a data interface (140) for data transmission of characteristic values of the at least one feed pump (125, 130) to a Control unit (145).

Description

The invention relates to a hydraulic or fluidic metering system, in particular an internal combustion engine of a motor vehicle, in which at least one feed pump for conveying a fluid and at least one pressure sensor for determining the hydraulic pressure in the metering system are arranged, and a method for its operation, according to the preambles of respective independent claims. Furthermore, the invention relates to a computer program, a machine-readable data carrier for storing the computer program and an electronic control unit, by means of which the method according to the invention can be carried out.

State of the art

In order to limit pollutant emissions from motor vehicles, the permissible limit values are being reduced further and further worldwide. In the coming years, new emission legislation (Euro 6, from September 2014) as well as new test cycles (WLTP: Worldwide Harmonized Light Duty Test Procedure or RDE: Real Driving Emission, expected from 2017) will further reduce the permissible values. Compliance with these limits will only be possible for all vehicle classes with active exhaust aftertreatment.

The Denoxtronic is used to inject AdBlue, a urea-water solution (HWL) of 32.5% urea in water, into the exhaust stream upstream of an SCR catalyst. The urea is converted into ammonia by thermolysis and hydrolysis. In the SCR catalytic converter, the ammonia reduces the nitrogen oxides to water and nitrogen.

Modern diesel engines have 96% lower NOx emissions than a typical diesel engine from 1990. The Selective Catalytic Reduction (SCR) system with Applicant's Denoxtronic urea dosing system reduces these raw emissions by up to 95%. Instead of the diversity of variants of the first generation Denoxtronic 3.1, the second generation (Denoxtronic 5.x) has a standardized supply module, which is welded to the respective vehicle manufacturer via a standardized mechanical interface with the AdBlue tank. This enables robust and economical solutions. The Denoxtronic 5.x comes with dosing modules for use in the underbody (passively cooled with air) or in the engine compartment (actively cooled with engine cooling water).

The current Denoxtronic 5.x (simplified in the following "DNOX5.x" system), which was designed for use in passenger cars and light-duty vehicles, includes a volumetric delivery pump or delivery module. The system is operated purely controlled and has by design, especially during the Dosiermittelbetriebs not a return for unused AdBlue solution in said tank. Due to the also known tight tolerances with respect to the flow rate per delivery stroke, it is possible to operate such a system without a pressure sensor without significantly deteriorate the dosing accuracy. However, such systems without pressure sensor operated with volumetric pilot control disadvantageously have a relatively large pressure range, which results inter alia by the production-related stroke / quantity tolerance of the feed pump. Correspondingly tighter tolerances would significantly increase the production costs of the feed pump.

Future DNOX systems for the aforementioned motor vehicle classes (DNOX5V) will be equipped with a pressure sensor in order to keep the system pressure within the narrowest possible pressure range. This has the advantage that the effectiveness of the dosage or dosing spray no longer needs to be secured in all pressure ranges and for all motor vehicle series by means of complex vehicle measurements. The feed pump used in future DNOX systems essentially corresponds to the feed pump used in previous and present day DNOX systems, i. a volumetric reciprocating pump with an analogous design principle or analogous operation. Therefore, the knowledge of the stroke volume can continue to be used advantageously for the determination of the (delivery pump) mass flow.

Out DE 10 2011 003 327 A1 shows a method for detecting the loading state of a filter in an SCR dosing system, in which a pressure sensor is arranged in a pump unit. The pump unit comprises in terms of pressure conveying direction a feed pump, a fine filter and on the clean side of the filter said pressure sensor. The delivery pump is combined together with the pressure sensor in a structural unit.

Disclosure of the invention

The invention is based on the idea that in a affected here with a feed pump and a pressure sensor equipped hydraulic or fluid metering, in particular a named DNOX system, said tight tolerances in the stroke volumes of the feed pump with the least possible negative influences on the Quantity accuracy and can be met with the lowest possible production costs. In addition, the system performance of the dosing system on the basis of as accurate as possible known delivery pump characteristic can be improved.

The invention proposes, in particular, in a pump module with at least one said feed pump, a production functionally inseparable or at least only irreversibly separably connected or permanently installed pressure sensor via a data interface for digital data transmission to an evaluation / control electronics of the hydraulic dosing system or a corresponding control unit electrically or connect data technology. Said manufacturing-related functional non-separability or functionally only irreversibly possible separability of the pressure sensor and the delivery pump preferably corresponds to a mechanical connection which, after separation of the two components, leads to a permanent non-functionality of the overall system, e.g. in a connection by means of welding, predetermined breaking points, in an encapsulated construction, or the like.

In particular, pump characteristic values are transmitted to said electronics or the control unit of the dosing system via said data interface of the pressure sensor. The pressure sensor therefore preferably has its own data memory for storing these characteristic values.

The pressure sensor is thus connected after the production of the pump module as a non-replaceable component fixed to the manufactured pump module. The relevant characteristic values of the delivery pump, which are determined during the production of the pump module, e.g. the pump-specific specific actual displacement volume in dependence on at least two different pressure values or on the drive frequency of the pump module or the delivery pump, as well as other characteristics necessary for the overall functionality of the hydraulic dosing system, e.g. Pump-specific resistance values of one or more arranged in the pump module or in the feed pump solenoid coils are permanently stored in the pressure sensor. In addition, corresponding characteristic values of an existing return pump in the pressure sensor can be stored permanently.

The aforementioned digital data interface or signal transmission is preferably a SENT interface known per se (SENT = "Single Edge Nibble Transmission"), which is particularly suitable for use in an internal combustion engine of a motor vehicle for the reasons described below.

The mentioned characteristics of the feed pump are transmitted in the case of a said SENT interface by means of a corresponding SENT transmission protocol to the respective control unit. This transmission can take place both cyclically and once after every engine start. In the event of a necessary component replacement of the pump module, the permanently connected pressure sensor is always exchanged, as a result of which, in particular, it is effectively prevented that the assignment of the delivery pump and the return suction pump to its characteristic data is lost or can be reversed.

The SENT transmission protocol has the further advantage that the transmission signals of this protocol are known to be very insensitive to disturbances that occur more frequently in the present motor vehicle field. One of the reasons for this lies in the way the signal is evaluated. Because not the entire waveform is used in detection, but only the voltage drop ("single edge"), since only one signal edge is used. In particular, the time difference between the falling edges is determined. In addition, the SENT protocol does not require special receivers, so conventional signal processors can be used.

By means of the method according to the invention, the effects of manufacturing tolerances of the stroke volume of the feed pump on the operation of the pump can advantageously be minimized, since individual characteristic values are stored in the permanently assigned pressure sensor for the respective feed pump and are thus known. As a result, thus the production costs of a feed pump can be significantly reduced. In addition, since the stroke volume of a feed pump permanently installed in the metering system is precisely known as a function of the hydraulic pressure in the metering system, considerably smaller metering quantity deviations on a fluid substance to be metered can be realized by means of the invention compared with the prior art.

In addition, according to the invention, newly manufactured pump modules or a metering system having such a pump module have virtually no component tolerance any more since the corresponding tolerance values are stored as characteristic values in the pressure sensor. In this way, the system functionality of the dosing system can be considerably simplified, since a dosing quantity monitoring (CDM) can be carried out considerably more simply or even completely dispensed with. Also, a known suction pump can be controlled more accurately at a known stroke volume in a system emptying, resulting in a further improvement in the performance of the dosing.

In addition, a named component exchange can be made without simultaneously System-related learning values must be reset manually via an external (workshop) tester. The detection of a pump replacement can advantageously be carried out by checking the pump characteristic data mentioned or a clear production identification stored in the sensor, for example at each system start of the metering system or the underlying motor vehicle. In this case, a comparison of the pump characteristic values last transferred by means of the SENT interface as well as the production identification with currently transmitted pump characteristic values as well as the production identification can be carried out. If the comparison shows that these characteristic values do not match or lie outside an empirically specified difference value, it can be assumed that a component replacement has taken place in the meantime. As a result, such a component exchange is automatically recognizable by a control device or a corresponding control program.

The invention can be used in all fluidic or hydraulic dosing systems in which an inventive permanent connection between a pressure sensor with digital signal transmission to clearly assigned feed pumps, in particular volumetric reciprocating pumps and / or corresponding return pumps consists. A preferred field of use is future Applicant's Denoxtronic dosing systems (e.g., "DNOX5V") which are to be used in both passenger cars and light commercial vehicles.

The computer program according to the invention is set up to carry out each step of the method, in particular if it runs on a computing device or a control device. It allows the implementation of the method according to the invention on an electronic control unit, without having to make structural changes to this. For this purpose, the machine-readable data carrier is provided on which the computer program according to the invention is stored. By loading the computer program according to the invention on an electronic control unit, the electronic control unit according to the invention is obtained, which is set up to control a hydraulic dosing system affected here by means of the method according to the invention.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a block diagram of a metering system according to the invention.

2 shows an embodiment of the method according to the invention with reference to a flowchart.

Description of exemplary embodiments

This in 1 A hydraulic metering system for metering in urea-water solution (HWL) into a motor vehicle SCR catalyst system (not shown) comprises a metering module 100 with a clocked controllable metering valve 105 , That in a tank 110 stored HWL fluid 115 is by means of a pump module 120 , via a discharge line 117 , a main 118 and a supply line 119 , the dosing module 100 fed. The pump module 120 includes a feed pump 125 and a return pump 130 , which with one in the area of the main line 118 also in the pump module 120 arranged pressure sensor 135 , For example, by an appropriate encapsulated construction or the like, are inextricably linked. The return pump 130 is with one of the main line 118 outgoing return line 131 connected, being about in the tank 110 excess fluid to be returned via one with the tank 110 connected or in the tank 110 opening return line 132 to be led. The abbreviation PL stands for "pressure line". The pressure line (PL) in the present case comprises the supply line 119 as well as the hydraulic connection between the pump module 120 and the dosing module 100 ,

The pressure sensor 135 is in the embodiment via a named SENT interface 140 with a control unit or a control unit 145 connected by data or signal technology and transmits relevant pump characteristics of the feed pump for operation 125 and the return pump 130 to a in the control unit 145 provided control program. This is already the case when manufacturing the pump module 120 Determined characteristics of the feed pump 125 , For example, the actual stroke volume in accordance with the pump individually as a function of at least two different pressure values, and possibly corresponding characteristic values of the return pump 130 , in the pressure sensor 135 permanently stored (preferably in a specially provided there for data storage) and are therefore always to the control unit 145 transferable.

The formed in the present embodiment as a diaphragm pump feed pump 125 sucks the HWL fluid 115 from the tank 110 and conveys it pressurized into the main pipe 118 in which the system pressure required for the atomization of 4.5 to 8.5 bar is present. The dosing module 100 measures the amount of HWL required for NOx reduction and atomizes it into the exhaust stream (not shown) before the SCR catalyst. The control of the dosing and heating strategy as well as an on-board diagnosis is carried out by a (not shown) engine control unit or the in 1 shown (dosing) control unit 145 , With the processing of the current engine operating data and all required sensor data, the amount of the reducing agent is tuned in a conventional manner by means of a control exactly to the operating point of the internal combustion engine and the catalyst-specific properties for maximum nitrogen oxide.

It should be noted that the said metering valve 105 for Dosiermittelbetrieb via a control line 107 from the controller 145 is driven in a conventional manner.

In the tank 110 is a sensor 150 arranged, which via a signal or control line 155 with the control unit 145 connected is. The sensors 150 serves in particular to a possibly present low level of the fluid 115 to the control unit 145 so that the driver can refill the fluid if necessary. Over two further signal or control lines 160 . 165 are also the pump 125 and the return pump 130 with the control unit 145 connected to the two pumps 125 . 130 to control for the dosing in a conventional manner.

One known, per se known SENT interface represents a unidirectional, asynchronous voltage interface, which requires three conductors, namely a supply voltage of 5V, a signal voltage of <0.5V for the low level and> 4.1V for the high level , as well as a ground line. Data is transmitted in units of 4 bits (= 1 "nibble"), for which the time between two falling edges ("falling edge") of a constant amplitude modulated signal voltage is evaluated. An entire data frame comprises 24 bits for measurement data, three nibbles each for two measurement channels, e.g. for pressure and temperature, a nibble for CRC error detection and a nibble for status and communication. In total, eight nibbles are thus transferred with each data transfer.

Furthermore, a further serial transport stream is provided via 2 bits of the "status and communication" nibble, via which additional messages with a correspondingly slower transmission rate can be transmitted (so-called "slow-channel mode"). Such a message consists of an identifier (ID), a value, and a CRC checksum over the message. The transmission is either 4-bit ID and 8-bit data in 16 consecutive data frames ("Short-Message Format"), or 8-bit ID and 12-bit data in 18 consecutive data frames ("Enhanced-Message Format").

Possible contents of said measured data are preferably static values such as a type code of the pressure sensor 135 , a manufacturer identifier, a sensor characteristic (ie assignment of the actual measured values to physical quantities), and / or variable values such as an error code or a temperature value. In this way, moreover, automatic detection of sensor variants or detection of incorrect connection can take place.

After starting by putting the dosing system into operation, in the present embodiment of an SCR system 200 the in 2 The routine shown is first checked 205 , whether the data transmission of said characteristics of pressure sensor 135 to the control unit 145 is completely completed. This query or check is made until this condition is met, ie in step 205 at a test result "j".

After complete transmission of the characteristic values or characteristic data 205 from the pressure sensor 135 creates the control unit 145 in step 210 a characteristic curve for the feed pump 125 , or in the case of said two pumps, a characteristic curve for the feed pump 125 and a named characteristic drive signal for the return pump 130 , In the characteristic curve for the feed pump 125 are preferably values of the stroke volume of the feed pump 125 depending on the hydraulic pressure, preferably in the main line 118 of the pump module 120 is present and by means of the pressure sensor 135 is detected. On the basis of this characteristic will be in step 220 over the control line 107 the metering valve 105 of the dosing module 100 as well as via the control line 160 the delivery pump 125 for dosing agent operation by the controller 145 Optimized controlled.

To the mentioned process steps 200 to 220 Optionally, the following can be indicated by the dashed line 225 delimited further steps 230 to 250 connect or parallel to the steps mentioned 200 to 220 be executed.

After complete transmission of the characteristic data from the pressure sensor 135 , be in step 230 the transmitted characteristics of the feed pump 125 and / or the return pump 130 with im Control unit non-volatile stored SENT comparison characteristics of the pump module from a previous commissioning of the SCR system retrieved and in the subsequent step 240 compared to each other. Returns the comparison 240 in that these values do not match or are outside an empirically predetermined difference value (in test step 240 the result "j"), it is concluded that in the meantime a component exchange has taken place.

The last-mentioned test result can be found in the control unit 145 in step 250 be used to further stored systemic learning values in the control unit 145 other components, eg the dosing module 100 , if provided a functional coupling of such a component to the pump module 120 is present. Furthermore, in step 250 the previously in the control unit 145 stored SENT characteristics of the pump module 120 by the currently transmitted characteristic values in the non-volatile memory of the control unit 145 stored at a possibly next exchange event of the pump module 120 be able to recognize automatically in the manner described.

The method described can be implemented in the form of a control program for an electronic control unit for controlling an internal combustion engine or in the form of one or more corresponding electronic control units (ECUs).

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 102011003327 A1 [0007]

Claims (11)

Hydraulic metering system, in particular an internal combustion engine of a motor vehicle, in which at least one feed pump ( 125 . 130 ) for conveying a fluid ( 115 ) and at least one pressure sensor ( 135 ) are arranged for determining the hydraulic pressure in the metering system, characterized in that the at least one feed pump ( 125 . 130 ) with the pressure sensor ( 135 ) is functionally inseparably connected and that the pressure sensor ( 135 ) a data interface ( 140 ) for data transmission of characteristic values of the at least one feed pump ( 125 . 130 ) to a control unit ( 145 ) having. Hydraulic dosing system according to claim 1, characterized in that the pressure sensor ( 135 ) arranged data interface ( 140 ) is formed by a digital SENT interface. Hydraulic dosing system according to claim 1 or 2, characterized in that the characteristic values of the at least one feed pump ( 125 . 130 ) by in the production of at least one feed pump ( 125 . 130 ) are formed pump-individual values of the stroke volume in dependence on at least two pressure values. Hydraulic dosing system according to one of the preceding claims, characterized in that the characteristic values of the at least one feed pump ( 125 . 130 ) by in the production of at least one feed pump ( 125 . 130 ) detected individual pump resistance values of at least one magnetic coil of the feed pump ( 125 . 130 ) are formed. Hydraulic dosing system according to one of the preceding claims, characterized in that the pressure sensor ( 135 ) a data memory for storing the characteristic values of the at least one feed pump ( 125 . 130 ) having. Hydraulic dosing system according to one of the preceding claims, characterized in that the at least one feed pump ( 125 . 130 ) and the pressure sensor ( 135 ) in a pump module ( 120 ) are encapsulated. Method for operating a hydraulic metering system according to one of the preceding claims, characterized in that the characteristic values of the at least one feed pump ( 125 . 130 ) after a start of the internal combustion engine or cyclically recurring to a control unit ( 145 ) and that the dosing system is controlled by the control unit on the basis of the transmitted characteristic values ( 145 ) is operated. A method according to claim 7, characterized in that already to the control unit ( 145 ) are compared with newly transferred characteristic values ( 240 ) and depending on the result of the comparison ( 240 ) on an interim replacement of the at least one feed pump ( 125 . 130 ) or one of its components is closed. Computer program that is set up to perform each step of a method according to one of claims 7 or 8. Machine-readable data carrier on which a computer program according to claim 9 is stored. Electronic control device, which is set up, a hydraulic dosing system, in particular an internal combustion engine of a motor vehicle, in which at least one feed pump ( 125 . 130 ) for conveying a fluid ( 115 ) and at least one pressure sensor ( 135 ) are arranged to determine the hydraulic pressure in the metering system, by means of a method according to one of claims 7 or 8 to control.

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