DE102015216016A1 - A method of controlling a combustion engine having a fuel pressure sensor - Google Patents

Abstract

Disclosed is a method of operating an internal combustion engine having a fuel pressure accumulator, a control unit, at least one injection valve, a fuel pressure accumulator and a low pressure sensor and a low pressure pump which is adapted to generate a fuel pressure in the fuel accumulator, the low pressure sensor prevailing in the fuel pressure accumulator Detects fuel pressure and the control unit forms control signals for the low-pressure pump in dependence on the fuel pressure. When the internal combustion engine is running, operating parameters that affect the fuel pressure in the fuel pressure accumulator are detected. The operability of the low pressure sensor is checked, and then, when the low pressure sensor is operational, a pressure reading of the low pressure sensor is detected and used as the actual value for controlling the fuel pressure. The method is characterized in that when the low-pressure sensor is not functional, stored for the detected operating parameters and determined from previous runs of the control loop replacement value of the control of the low-pressure pump influencing variable read from a substitute value memory and for the formation of a drive signal for the Low pressure pump is used. Another independent claim is directed to a programmed for performing process control device.

Description

State of the art

The present invention relates to a method for operating an internal combustion engine according to the preamble of claim 1. The invention further relates to a control device having the features of the independent device claim.

Such a method and such a control device is for example from the DE 102 48 627 A1 known. This document shows an internal combustion engine which can be operated both with a port fuel injection (PFI) of fuel and with direct injection of fuel into the combustion chamber. The intake manifold injection takes place with a comparatively low injection pressure. Here, the injection only has to overcome the pressure prevailing in the intake manifold, which is less than about 1 bar without charging. The associated fuel system is therefore also referred to as a low pressure system. The direct injection takes place with a comparatively higher injection pressure, since the injection takes place here against the higher, prevailing in the combustion chamber pressure. The associated fuel system is therefore also referred to as a high-pressure system.

Basically, low-pressure systems with and without return system, in which the delivery of the low-pressure pump is not regulated, as well as demand-controlled systems, in which the promotion of the low-pressure pump is controlled, distinguished from each other. With non-demand-controlled low-pressure systems with return, more fuel is pumped into the fuel pressure accumulator than flows from there via the injection valves. The excess amount flows back through a arranged on the fuel pressure accumulator pressure control valve and a return line to the tank. In non-demand-controlled low-pressure systems without return, the pressure regulating valve is located in the tank. Therefore, the return line can be omitted.

The demand-controlled low-pressure systems are becoming more and more important, since they are more favorable in terms of their total energy consumption. In the demand-controlled system, only the amount of fuel consumed by the engine and necessary to set the desired pressure is pumped by the fuel pump into the fuel pressure accumulator. The pressure is controlled by the control unit of the internal combustion engine in a closed loop, wherein the current fuel pressure is detected via the low pressure sensor. A mechanical pressure regulator is not available with these systems. To adjust the delivery rate, the operating voltage of the low-pressure pump is set via a clock module controlled by the control unit. The pressure relief valve is used to prevent a fuel pressure increase to undesirably high values during a fuel cut or after the engine is stopped.

A combination of PFI and DI allows the benefits of both injection modes to be used for optimal mixture formation and combustion. At full load and fast speed and / or load changes of the internal combustion engine, the DI injection system is more advantageous (eg with regard to avoiding knocking), and in the partial load range, the PFI injection system is more advantageous (for example, by the number of particles and the amount of unburned hydrocarbons in the exhaust gas to keep low.

As a low pressure system from which a higher injection pressure in the high pressure system generating high pressure pump is fed, the already existing low pressure system of the intake manifold injection is used. In the event of a defect of the low-pressure pump, the entire fuel supply then drops, which causes the vehicle to remain lying. In the above-mentioned prior art, the PFI is generally turned off in another error in the low-pressure system and the low-pressure pump is set to full delivery. The fuel pressure in the low pressure system is then determined by the pressure relief valve, also referred to as the spill valve. For example, this pressure is around 9 bar and has a rough tolerance of +/- 1 bar.

The injection then takes place solely via the DI injection valves. In contrast to the accuracy of the PFI, the DI does not suffer from inaccuracies resulting from the tolerance of the pressure relief valve of the low pressure system. This is due to the fact that in the high-pressure system, a separate high-pressure control takes place, so that the injection pressure-dependent injection quantity accuracy is ensured in the DI. The reason for the shutdown of the PFI is in the lack of accurate information of the low pressure value of the fuel for the determination of the driving periods of the PFI injectors. With the same activation duration, the injected fuel quantity changes with changes in the injection pressure. The higher the pressure, the greater the injected fuel quantity.

An examination of the functionality of a low pressure sensor is for example from the DE 102 48 627 A1 known.

Disclosure of the invention

From the above-mentioned prior art, the present invention differs in its method aspects by the characterizing features of claim 1. In their Device aspects, the present invention differs from this prior art by the characterizing features of the independent device claim.

Due to these features, failure of the low pressure sensor will no longer automatically shut off the PFI. The shutdown can be avoided. In contrast to the prior art, in which the PFI is switched off in case of a fault of the low pressure sensor and in which the fuel metering then takes place only via the DI, the advantages of an availability of the advantages of the PFI remain even with a defective low pressure sensor in the invention. Since drifts, in particular changes in the fuel quantities injected via the PFI injection valves as a function of the actuation periods of the injection valves, change only slowly over the course of several operating hours until the next service requested by an error message, the low-pressure system operates with an accuracy in this time Accuracy of a faultless low pressure system with closed pressure control loop comes much closer than an operation in which the low pressure is limited by a large pressure tolerances (usually +/- 1 bar at about 9 bar opening pressure) mechanical pressure relief valve. In particular, the maps in which split factors are stored for the quantities of fuel to be metered in via the PFI and the DI can thus continue to be used even in the event of an error. This has a positive effect on consumption, exhaust emissions (e.g., HC, NOx, particulates, etc.) and noise emissions.

A preferred embodiment is characterized in that the correction value formed with functional low-pressure sensor is not used for the formation of the substitute value, as a complete test of the functionality of the low-pressure sensor takes.

It is also preferred that the substitute value is formed from at least one correction value formed in the case of a functioning low-pressure sensor.

Furthermore, it is preferred that a respective new substitute value is formed on the basis of an average value of correction values formed when the low-pressure sensor is functioning.

It is also preferable that a base value of a new substitute value is formed on the basis of the latest correction value that satisfies the condition to have been formed when the low-pressure sensor is functioning.

It is further preferred that a new substitute value be formed by weighted association of the old substitute value with the new substitute value.

It is also preferred that a correction value averaged from earlier correction values formed as control manipulated variables is formed as substitute value.

It is also preferable that the substitute value is formed from earlier activation signals of the low-pressure pump.

With regard to the controller aspects of the invention, it is preferred that the controller is adapted to perform at least one of the preferred embodiments of the method.

Further advantages will be apparent from the dependent claims, the description and the attached figures.

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

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. In this case, the same reference numerals in different figures denote the same or at least functionally comparable elements. In each case, in schematic form:

1 the technical environment of the invention in the form of a DI and PFI-capable internal combustion engine with control unit, sensors and injectors; and

2 a flowchart as an embodiment of a method according to the invention.

1 shows in detail an internal combustion engine 10 with a control unit 12 , various sensors 14 . 16 and a fuel supply system. The fuel supply system has a low pressure system and a high pressure system.

The low pressure system has a low pressure accumulator 18 with a fuel temperature sensor 14 , at least one hydraulic with the low-pressure accumulator and electrically with the controller 12 connected low-pressure injection valve 20 , a pressure relief valve connected hydraulically to the low pressure accumulator 22 , one hydraulically with the low pressure accumulator 18 and electrically with the controller 12 connected low pressure sensor 16 and one hydraulically with the low pressure accumulator 18 and electrically with the controller 12 connected low pressure pump 24 as well as a fuel tank 26 on.

The low pressure pump 24 is in the fuel tank 26 and lies in the fuel when the tank is full. It is designed to remove fuel from the fuel tank 26 in the low-pressure accumulator 18 to promote and thus produce a fuel pressure in the low-pressure accumulator. The low pressure pump is preferably an electric fuel pump having a BLDC motor (brushless DC motor). As a result, there are advantages in terms of accuracy, space, life and noise due to the actively controlled field commutation.

The low pressure sensor 16 is set up in the low-pressure accumulator 18 to capture prevailing fuel pressure. The low pressure sensor 16 is located, for example, in the low pressure line, which is the low pressure pump 24 hydraulically with the low-pressure accumulator 18 combines. The pressure relief valve 22 is adapted to the fuel pressure in the low-pressure accumulator 18 to limit to a predetermined maximum value, and the controller 12 is designed to promote the low pressure pump 24 in response to the pressure prevailing in the fuel pressure accumulator to control and driving pulses for the at least one low-pressure injection valve 20 as a function of a value for the pressure prevailing in the low-pressure accumulator fuel pressure. The low-pressure injection valve injects fuel from the low-pressure accumulator in the opened state 18 in a suction pipe 28 one that passes through an inlet valve 30 from a combustion chamber 32 the internal combustion engine can be disconnected and connected.

The high-pressure system additionally has a high-pressure fuel accumulator 34 , at least one hydraulically with the high-pressure fuel storage 34 and electrically with the controller 12 connected high-pressure injection valve 37 and a hydraulic with the high-pressure fuel storage 34 and one electrically with the controller 12 connected high-pressure pump 36 on. The control unit 12 controls an electric valve of the high-pressure pump 36 on, which is hydraulically located between the low pressure accumulator and the pump inlet of the high pressure pump. Controlled opening and closing of the valve control the amount of fuel to be compressed by the pump piston of the high-pressure pump and thus the pressure in the high-pressure accumulator.

The high pressure pump 36 is set up by the low pressure pump 24 extracted fuel from the low pressure system to compress and in the high-pressure fuel storage 34 to promote and thus a high fuel pressure in the high-pressure fuel storage 34 to create. The high pressure system may include other components such as a high pressure fuel sensor and / or a high pressure control valve. For example, the fuel pressure prevailing in the high pressure system is intermediate 100 bar and 200 bar. The pressure prevailing in the low-pressure system fuel pressure, however, is less than 10 bar.

Overall, the fuel supply system fulfills the purpose of supplying the fuel to be metered to the combustion chamber with a defined pressure to the injection valves 20 and 37 to promote. The injectors 20 and 37 inject the fuel into the intake manifold (PFI) or directly into the combustion chamber (DI). For the PFI, the fuel is pumped from the tank to the injectors by the low pressure pump. The injection pressure is regulated and is normally 3 to 4 bar. The normal case is characterized in particular by a functional low-pressure sensor 22 out. One from the control unit 12 controlled ignition device 33 serves to ignite the combustion chamber fillings. One from the control unit 12 controlled fault lamp 35 is used to indicate a fault to the driver and / or workshop personnel. The control unit is preferably a control unit that controls the injection and the ignition of the internal combustion engine and the low-pressure pump and the high-pressure pump. The control unit has in particular a substitute value memory 12.1 on.

2 shows a flowchart of a processed by the controller program as an embodiment of a method according to the invention.

The functions associated with the blocks can be processed in the order that results from the representation of the 2 results. Some of the functions can also be processed in a different order.

The individual blocks of the program are partly individual steps and partly subprogram modules, which can also comprise several steps.

The block 100 represents a higher-level main program for controlling the internal combustion engine. In the main program, for example, the driver's request for torque in driving pulses for the injectors 20 . 37 and the igniter 33 implemented. From this main program is repeated in the presence of predetermined conditions, for example, whenever in the main program no program parts must be processed, which have a higher priority, in the step 102 branched, are detected in the predetermined operating parameters BPM, which directly or indirectly influence the pressure prevailing in the fuel pressure accumulator pressure. These operating parameters preferably comprise at least the pro Working cycle and combustion chamber of the internal combustion engine via the injectors 20 . 37 metered amount of fuel, the fuel temperature and the vehicle electrical system voltage. This list is not meant to be exhaustive.

The mentioned amount of fuel is in the control unit 12 As the control unit also has the task of determining the drive pulse widths for the various injection valves 20 . 37 This determination is preceded by a calculation of the associated fuel mass. The fuel quantity results in particular, but not only, from the current torque requirements for the internal combustion engine. Other influencing variables may arise, for example, in particular from exhaust gas regulations. The quantities of fuel to be injected tend to reduce the pressure in the fuel pressure accumulator 18 one.

The fuel temperature in the fuel pressure accumulator 18 is preferred with the fuel temperature sensor 14 measured or, if such a sensor is not present, calculated from other operating parameters of the internal combustion engine. A temperature sensor used for the measurement is preferably in or at the fuel pressure accumulator in thermal contact with the fuel in the fuel pressure accumulator. The fuel temperature affects the density of the fuel. The higher the fuel temperature, the higher will be the pressure in general.

The vehicle electrical system voltage has a particular effect on the delivery rate of the electrically driven low-pressure pump. The lower the vehicle electrical system voltage that varies during operation of the internal combustion engine, the lower the delivery rate will be, which tends to have a negative effect on the pressure in the fuel pressure accumulator. The vehicle electrical system voltage is known in the control unit. It is preferred with one in the control unit 12 arranged voltmeter detected.

From these operating parameters is in step 103 a base value B of a drive signal AS for the low-pressure pump 24 educated. This is done in the control unit 12 accessed in the form of maps and / or stored in the form of calculation rules relationships.

In step 104 is the ruling in the fuel pressure accumulator fuel pressure p with the low pressure sensor 14 detected.

In step 106 An examination of the functionality of the low-pressure sensor is carried out 16 , A test of the low pressure sensor is known. As an example, here on the above-mentioned DE 102 48 627 A1 directed. The detected pressure p is compared, for example, with an expected value formed for the current operating conditions. Deviations that go beyond a plausible difference are considered errors. If a target value can no longer be adjusted in the pressure control loop, this is alternatively or additionally also rated as an error. Alternatively or additionally, an implausible drive signal for the low-pressure pump, for example a drive signal which generates a high delivery rate with a low fuel requirement of the internal combustion engine, is also regarded as an error. It is also preferred that such errors initially only apply as presumptions of error, which must be secured by further measurement results. Such hedging is preferably carried out by a mixture control loop. An erroneously too low pressure measurement leads to the consideration of the measured pressure in the control of the injectors to the fact that too much fuel is metered, resulting in an opposite reaction of the mixture control loop. A presumed error is in one embodiment only as an error when it is confirmed by such a reaction of the mixture control loop.

The test may be divided into several passes of the method, so that a definite result may only be present after expiration of a time period that is required for error detection. Such a period of time can extend over many process cycles, in particular, when a suspected error must first be confirmed by a reaction of a mixture control loop.

From the step 106 becomes a branching step 108 reached, in which the result of said review is queried. As long as the test of functioning in step 106 does not result in a malfunction of the low pressure sensor, the low pressure sensor is considered functional. In this case, the process branches in the steps 110 ,

In step 110 a correction value K is formed on the basis of the detected pressure in the fuel pressure sensor. The correction value is formed in a subprogram of the main program programmed as a controller 100 such that the as the actual value with the low pressure sensor 14 measured pressure value p is compared with a desired value and that the correction value, which is included later in the formation of the drive signal for the low-pressure pump, a deviation of the actual value of the desired value at least in the time average, that is, apart from possibly occurring control oscillations reduced. In other words, if the actual value is smaller than the target value, a correction value increasing the base value is determined. If the actual value is greater than the setpoint value, a correction value that reduces the basic value is determined.

Subsequently, the thus determined new correction value K_neu is stored together with the operating parameters BPM recorded in the same process run in the control unit. This is done in the step 112 , The storage takes place for example by reading into a shift register of the control unit 12 , Reading into the shift register is one example of the more general idea of securing newly determined correction values for replacement value generation. The time for which the correction values are saved is at least as long as a period of time which is at least required for a reliable detection of a defective low-pressure sensor.

In step 114 is a determined in the past correction value, which is hereinafter referred to different from a newly determined correction value as K_alt, in a substitute value memory of the control unit 12 written. The substitute value memory is preferably a specific area of a read / write memory of the controller 12 , This is done together with the set of operating parameters BPM that had been captured in the same process run.

The saving of correction values dependent on operating parameters can be realized, for example, in tabular form. The table is structured like a matrix of rows and columns. Each matrix element represents a specific speed range and a specific torque range. The speed ranges are arranged in the columns, for example, and the torque ranges are preferably arranged in the rows. If the speed is in a certain range and the torque is within a certain range, the correction value is assigned to the associated matrix element. For very small areas, a lot of memory is needed. For the accuracy increases. Coarser subdivision requires less memory. For the accuracy decreases.

This writing into the substitute value memory occurs only when at least as much time has elapsed since the determination of the correction value and the associated values of the operating parameters as would have been necessary for the detection of a defective low-pressure sensor and only if no error of the low-pressure sensor during this time has been detected. This condition is met in one embodiment in that the shift register the data stored when reading a new data set (correction value plus operating parameters) each shift a memory space, and for each record has so many memory locations that once read at the input of the shift register data set after Expiration of said minimum time appears at the output of the shift register and thus can be taken over into the substitute value memory of the control unit.

If the low-pressure sensor is working properly, it will be in step 116 a control signal AS for the low-pressure pump by linking the currently determined correction value K_neu linked to the currently determined for the detected operating parameters BPM base value B. In the subsequent step 118 is the drive signal AS for controlling the low-pressure pump 24 output and that program returns to the step 100 , so return to the main program, so that the low pressure with properly functioning low pressure sensor 16 is regulated in a closed loop.

Results in the step 108 On the other hand, if the low-pressure sensor is tested for malfunction of the low-pressure sensor, the program branches to the step 120 , In this step 120 is a previously determined for the same operating parameters correction value K_alt read from the substitute value memory. The substitute value memory is here the same memory area in the step 114 obtained substitute values K_alt be enrolled. In step 122 the drive signal is then determined as a function of the current operating parameters and the previously learned substitute value K_alt of the correction value K. The determination is made as they are in the step 116 he follows. The difference between the two steps is only that the determination in step 116 in response to a determined at functioning low pressure sensor correction value K_neu, and in step 122 in the case of a non-functional low-pressure sensor as a function of a correction value learned earlier in the case of a functional low-pressure sensor.

The correction values represent control interventions with which predetermined base values of control signals are corrected. In an alternative embodiment, instead of correction values, complete control signals are determined as substitute values, stored and used in the event of an error.

A preferred embodiment provides that in step 114 Substitute values to be stored in the substitute value memory with substitute values already stored for the same set of operating parameters, be it correction values or actuation signals, are linked to each other via a weighting in order to filter out disturbances. In the simplest case, this is done by a moving averaging. The weighting factor in this case is 1/2 and the combination is additive. The weighting factors may also differ from 1/2, for example, to give more weight to older stored values, or, for example, younger ones to weight stored values more strongly. In the new condition of the low-pressure sensor and the low-pressure pump, predetermined, preferably neutral, initial values are written into the substitute value memory instead of the substitute values to be obtained later during operation of the internal combustion engine, so that the predetermined basic value is not changed in this case.

The values to be stored during the generation of substitute values to be stored in the shift register or also in another buffer, be it correction values or triggering signals, are stored back to the past as far back as the error detection method requires for error detection. If an error is detected, discard the values cached in the cache because they may already be faulty.

Also conceivable are numerical methods, for example Gaussian processes, which in the fault-free case, ie functional low-pressure sensor, the relationship between the relevant operating parameters such as the fuel temperature, the PFI injection quantities and the DI injection quantities, the vehicle electrical system voltage, with the low-pressure pump directly or is driven indirectly, with the correction value or the drive signal online, so learning during operation of the internal combustion engine. Learning the substitute values for correction values or drive signals represents learning or training a computational model in an error-free phase of the low-pressure sensor. In the event of an error, the learned substitute values representing a trained model are then used. In case of error, the error lamp 35 from the control unit 12 switched on and the driver is the error in the fuel system displayed.

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 10248627 A1 [0002, 0008, 0040]

Claims (10)

Method for operating an internal combustion engine ( 10 ), which except a fuel pressure accumulator ( 18 ) a control device ( 12 ), at least one hydraulically connected to the fuel pressure accumulator and electrically connected to the control unit injection valve ( 20 . 37 ), a hydraulically connected to the fuel pressure accumulator and electrically connected to the controller low pressure sensor ( 16 ) and a hydraulically connected to the fuel pressure accumulator and electrically connected to the controller low pressure pump ( 24 ), wherein the low pressure pump is adapted to promote fuel in the fuel accumulator and thus to generate a fuel pressure in the fuel accumulator, the low pressure sensor is adapted to detect the pressure prevailing in the fuel pressure accumulator fuel pressure, and the control device is adapted to control signals for the Low-pressure pump as a function of a value for the pressure prevailing in the fuel pressure accumulator, in which method when the internal combustion engine operating parameters that affect the fuel pressure in the fuel pressure accumulator are detected, the functioning of the low-pressure sensor is checked ( 106 . 108 ) and when the low pressure sensor is operative, a pressure reading of the low pressure sensor is detected and used as feedback in a closed loop for fuel pressure control, characterized in that, if the low pressure sensor is inoperative, one stored for the sensed operating parameters determined from previous runs of the control loop replacement value of the control of the low-pressure pump influencing variable from a substitute value memory ( 12.1 ) and used for the formation of a drive signal for the low-pressure pump. A method according to claim 1, characterized in that the correction value formed in functioning low-pressure sensor is not used for the formation of the substitute value as long as a complete test of the functionality of the low-pressure sensor takes. Method according to Claim 2, characterized in that the substitute value is formed from at least one correction value formed in the case of a functioning low-pressure sensor. A method according to claim 3, characterized in that a respective new substitute value is formed on the basis of an average value of correction values formed in functional low-pressure sensor. Method according to one of the preceding claims, characterized in that a base value of a new substitute value is formed on the basis of the most recent correction value which satisfies the condition to have been formed when the low-pressure sensor is functioning. Method according to the immediately preceding claim, characterized in that a new substitute value is formed by weighted association of the old substitute value with the new substitute value. Method according to the immediately preceding claim, characterized in that a correction value averaged from previous correction values formed as control manipulated variables is formed as substitute value. Method according to one of the claims, characterized in that a value formed from a substitute value formed from previous activation signals of the low-pressure pump is used as substitute value. Control unit ( 12 ) of an internal combustion engine ( 10 ), which except a fuel pressure accumulator ( 18 ) a control device ( 12 ), at least one hydraulically with the fuel pressure accumulator ( 18 ) and electrically connected to the control unit injection valve ( 20 . 37 ), a hydraulically connected to the fuel pressure accumulator and electrically connected to the controller low pressure sensor ( 16 ) and a hydraulically connected to the fuel pressure accumulator and electrically connected to the controller low pressure pump ( 24 ), wherein the low pressure pump is adapted to promote fuel in the fuel accumulator and thus to generate a fuel pressure in the fuel accumulator, the low pressure sensor is adapted to detect the pressure prevailing in the fuel pressure accumulator fuel pressure, and the control device is adapted to control signals for the Low-pressure pump to form depending on a value for the pressure prevailing in the fuel pressure accumulator, and to detect when the internal combustion engine operating parameters that affect the fuel pressure in the fuel pressure accumulator to check the functioning of the low pressure sensor ( 106 . 108 and when the low pressure sensor is operable to detect a pressure reading of the low pressure sensor and to use it as an actual value in a closed loop for control of the fuel pressure, characterized in that the controller is adapted to in particular programmed to perform a method with the features of claim 1. Control unit ( 12 ) according to claim 10, characterized in that it is set up, in particular programmed to perform a method according to one of claims 2 to 9.

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