DE102013110169A1 - Method for determining an accumulator pressure and method for controlling a fuel pump - Google Patents

Abstract

The present disclosure relates to a method of estimating a fuel pressure (Pr *) in a high pressure accumulator (104). It further relates to a control method for a high-pressure pump (102). In a fuel delivery system (100), fuel is pressurized by a high pressure pump (102), stored in a high pressure accumulator (104), and injected through at least one fuel injector (108) on an internal combustion engine. If there is no valid accumulator pressure (Pr) reading, the fuel pressure may be iteratively estimated in response to a pressure change determined based on a pump characteristic (134) and an injector characteristic (132) ,

Description

The invention relates to a method for determining an accumulator pressure and a method for controlling a fuel pump which compresses a possibly supplied by a tank via a low-pressure pump fuel to a high pressure of, for example, 1,000 to 3,000 bar and fed to a high-pressure accumulator. Such a fuel pump (hereinafter referred to as high-pressure pump) is known in practice. It is used in a fuel delivery system that provides high pressure fuel for a direct injection internal combustion engine.

1 shows a fuel delivery system according to the prior art. It comprises an electronic control unit (ECU) which generates a control signal (tpcv) for the high-pressure pump ( 102 ) and a control signal (Tinj) for one or more fuel injectors ( 108 ). The of the high-pressure pump ( 102 ) fuel is stored in an accumulator ( 104 ) (also called common rail) cached. From the accumulator, the one or more fuel injectors ( 108 ).

Within the ECU is an engine control logic ( 120 ), which determines a target injection quantity (Qi_t) and a target accumulator pressure (Pr_t). The determination of these setpoints happens, for example, in response to a driver's request and a current operating mode (operation mode) of the internal combustion engine. The driver's request may include a demand torque and / or a demand speed. The setpoint for the accumulator pressure can be obtained for example from a setpoint characteristic map which selects a suitable accumulator pressure as a function of the operating state of the engine and / or the driver's request. This may preferably be a characteristic map which contains an assignment of an accumulator pressure setpoint value to a rotational speed and an injection quantity.

The ECU further comprises injection control logic ( 122 ) as well as a pump control logic ( 124 ). The injection control logic determines a drive duration (Tinj) to activate a fuel injection. By determining the activation duration, the actual fuel injection quantity of the injector (in dependence on a momentary accumulator pressure Pr) is determined ( 108 ). The injection control logic ( 122 ) can control the injection quantity in a closed loop, as known for example from the system "iArt" (sales name). The pump control logic ( 124 ) sets a drive timing (tpcv) for the high pressure pump ( 102 ) after closing the inlet valve ( 110 ) during a lifting phase of a compression means ( 114 ) he follows. The earlier the inlet valve ( 110 ) is closed during the lifting phase, ie during the upward movement of the compression means after reaching the bottom dead center, the more fuel is in the compression chamber ( 112 ) and pressurized. The later the inlet valve ( 110 ) is closed, the more fuel is again from the compression chamber during the beginning of the lifting phase of the compression means ( 112 ) through the inlet valve ( 110 ), so that after closing the inlet valve ( 110 ) only a smaller amount of fuel in the compression chamber ( 112 ) is present. The pressurized fuel is passed through an exhaust valve ( 116 ) to a high-pressure accumulator ( 104 ) fed out. There is a pressure sensor ( 126 ) which detects the actual accumulator pressure (Pr). The difference (dPr) between the target accumulator pressure (Pr_t) and the actual accumulator pressure (Pr) is the control deviation after which the drive timing (tpcv) is set.

It is an object of the present invention to provide a method for determining, in particular for estimating an accumulator pressure and a method for controlling a high-pressure pump, which can operate without a measurement signal for the accumulator pressure. The invention solves this problem with the characterizing features in the independent claims.

In accordance with this disclosure, a method of estimating fuel pressure in the high pressure accumulator is provided in which the currently estimated fuel pressure in the high pressure accumulator is iteratively calculated in response to an estimated pressure change from a known starting value. The pressure change relates to an increase and / or a decrease in the fuel pressure in the high-pressure accumulator as a result of a pump delivery and a fuel injection. The pressure change is determined on the basis of a characteristic for the pumping promotion and a characteristic for a fuel injection.

The method of determining the fuel pressure may be performed in parallel to the regular operation of the fuel delivery system and the estimated fuel pressure may be compared to a measured fuel pressure. When an unexpectedly large difference between the actual value and the estimated value of the fuel pressure occurs, an abnormal condition of the fuel delivery system can be determined from this difference. This may, for example, concern a too low pumping rate or too high or too low an injection quantity of fuel. Based on the detected anomaly can Safety measures, such as a warning to the driver or a restriction of engine operation are triggered.

Hereinafter, the term "accumulator pressure" is used as a short name for the fuel pressure in the high-pressure accumulator of the fuel delivery system.

The method for estimating the fuel pressure can be carried out, in particular, if there is no valid measured value for the accumulator pressure from the pressure sensor, for example because the sensor is defective or there is a signal disturbance. In such a case, the operation of the engine may be continued based on the estimated accumulator pressure, and advantageously no immediate decommissioning of the vehicle and no massive limitation of the operating condition is required. As a result, critical driving conditions can be avoided and road safety can be increased. It also increases customer satisfaction if the vehicle can still be driven to the next workshop after an error has occurred.

The present disclosure also relates to a control method for a high pressure pump in the aforementioned fuel delivery system according to the independent claim.

In the dependent claims further advantageous embodiments of the invention are given.

The invention is illustrated by way of example and schematically in the drawings. They show in detail:

1 a fuel delivery system including a high pressure pump, a high pressure accumulator, a fuel injector and an electronic control unit according to the prior art;

2 : a fuel delivery system analogous to 1 wherein a method of estimating accumulator pressure in a first embodiment is performed;

3 : a map for a pump model showing an association between a drive timing of a high pressure pump, a pump delivery rate, and an accumulator pressure;

4 a first map showing an association between a leakage amount, an injection amount, and a battery pressure, and a second map showing an association between an injection amount, an injector drive duration, and a battery pressure;

5 : A fuel delivery system analogous to 2 wherein a refined method of estimating accumulator pressure according to a second embodiment is performed;

6 3 is a flowchart illustrating an exemplary operation of a fuel delivery system with accumulator pressure estimation.

2 shows a fuel delivery system ( 100 ), which is essentially the system 1 equivalent. It has motor control logic ( 120 ), which in response to a desired torque (demand torque), a desired speed (demand speed) and an operating mode (operation mode) of the internal combustion engine, a target injection quantity (Qi_t) and a target accumulator pressure (Pr_t) established.

It is also an injection control logic ( 122 ), which operates here however in the open control loop, ie without a feedback about an actual fuel injection quantity. The injection control logic ( 122 Further, the target accumulator pressure (Pr_t) is supplied directly as an input. It sets the injector drive duration (Tinj) in dependence on the target injection quantity (Qi_t) and the target accumulator pressure (Pr_t). The injector ( 108 ) is energized as a function of this activation period (Tinj) (for example. Through a corresponding Bestromungsprofil). The drive duration (Tinj) represents the actual drive duration. It is set in the energization profile as an actual period of time between an increase in the injector injection drive current to start an injection and a zero decrease in the injection current to terminate the injection.

The injector drive duration (Tinj) is an injector characteristic ( 132 ) supplied as input. The injector characteristic ( 132 ), an estimated pumping rate (Qpump *) continues to be supplied. The detection of the estimated pumping rate will be explained below.

The injector characteristic ( 132 ) estimates a fuel pressure (Pr *) in the high-pressure accumulator on the basis of the aforementioned input variables ( 104 ) (= estimated accumulator pressure Pr *) after execution or during the execution of an injection based on a pressure change caused by the fuel injection.

The injector characteristic ( 132 ) is preferably created on the basis of measured or modeled values for the aforementioned variables and stored as a map. Further details on the content and the creation of the injector characteristic ( 132 ) are described below.

The estimated accumulator pressure (Pr *) may be determined by a PT1 filter ( 138 ) (= Deadtime member) are smoothed. The PT1 filter ( 138 ) the output signal of the injector characteristic ( 132 ) supplied as a raw signal. At the output of the PT1 filter then there is the smoothed signal of the estimated accumulator pressure (Pr *).

The estimated accumulator pressure (Pr *) is subtracted from the target accumulator pressure (Pr_t), resulting in the estimated differential pressure (dPr *). This is a pump control logic ( 124 ). The pump control logic ( 124 ) may be formed substantially as a PID controller according to the prior art. It sets the control timing (tpcv) for the control valve ( 110 ) of the high-pressure pump ( 102 ) firmly.

The high pressure pump ( 102 ) has an adjustable pumping rate (Qpump). The adjustment of the pumping rate is made by specifying a timing (= control timing tpcv) for closing the control valve ( 110 ). Such a control valve is also referred to in practice as a pre-stroke control valve. It controls the release of a connection between the pump inlet and the compression chamber ( 112 ) of the high pressure pump.

If necessary, fuel is supplied to the pump inlet via an upstream low-pressure pump (centrifugal pump). This fuel can be used when the inlet valve ( 110 ) into the compression chamber ( 112 ). When the compression agent ( 114 ) decreases when the inlet valve is open, increases the effective volume of the compression chamber ( 112 ), and there is fuel in the compression chamber ( 112 sucked in). When the inlet valve ( 110 ) remains open and the compression means ( 114 ) then executes a stroke movement, reduces the effective volume of the compression chamber ( 112 ) and fuel is directed towards the pump inlet from the compression chamber ( 112 ).

Once the inlet valve ( 110 ) during the lifting movement of the compression means ( 114 ) is closed, is the amount of in the compression chamber ( 112 ) enclosed fuel. This is then due to the further stroke movement of the compression means ( 114 ) is pressurized. Once the pressure in the compression chamber ( 112 ) is higher than the back pressure in the supply line to the high pressure accumulator ( 104 ) (plus the switching pressure of the passive exhaust valve ( 116 )), the exhaust valve opens ( 116 ) and the high pressure fuel is fed to the high pressure accumulator where it is stored.

The delivery of fuel from the high-pressure pump depends on the course of the lifting movement of the compression means. It takes place until the compression agent ( 114 ) has reached the top dead center. Once the compression agent ( 114 ) again performs a downward movement, the pressure in the compression chamber ( 112 ) again against the pressure in the high-pressure accumulator, so that the exhaust valve ( 116 ) closes. At the same time or shortly thereafter, the inlet valve opens ( 110 ) (self-opening valve) or it is opened (double-actuated valve), so that again fuel from the pump inlet into the compression chamber ( 112 ) and the next pump cycle begins.

From the aforementioned kinematics of the high-pressure pump ( 102 ) it can be seen that the exit quantity of the high-pressure pump ( 102 ) substantially from the drive timing of the control valve ( 110 ) depends. The compression means is preferably driven via a cam drive with one or more drive cams for the lifting and lowering movement. The drive timing indicates a point in time or an angular position for closing the control valve ( 110 ) within the stroke movement of the compression means ( 114 ) in front. It preferably relates to a time duration or a corresponding angular interval of the drive cam which has been active since the beginning of the lifting movement (ie since the bottom dead center has been reached by the compression means (FIG. 114 )) until the controlled closing of the control valve ( 110 ) elapses.

The estimated accumulator pressure (Pr *) and the actuation timing (tpcv) are assigned to a pump characteristic ( 134 ). On the basis of the aforementioned values, this determines an estimated pumping rate (Qpump *). The creation and content of a pump characteristic ( 134 ) will be explained below.

This in 2 illustrated information flow diagram is provided for a stationary control of the accumulator pressure. In steady-state control, the cycle average of the accumulator pressure is maintained at a constant level. In the duration of a delivery cycle of the fuel delivery system can be provided that for each fuel injection, a predetermined number of Pumpförderungen by the high-pressure pump ( 102 ) is provided. If a plurality of injections are carried out on the injector during a working cycle, it can accordingly be provided that a predetermined number of pumping deliveries are provided for each injection cycle.

The high pressure pump ( 102 ) delivers during stationary operation during a delivery cycle exactly the amount of fuel in the high-pressure accumulator ( 104 ) passing through the injector ( 108 ) is consumed. When the fuel economy and the After delivery of fuel within a cycle are identical, a constant pressure level in the high-pressure accumulator (on average 104 ) held. It should be noted that a high pressure accumulator ( 104 ) depending on the operating mode of the internal combustion engine to pressures between 500 bar and 3,000 bar can be controlled (transient operation), while pressure changes due to a single Pumpfördervorgangs and a single injection cycle in the range of 0 to 15 bar.

In the mentioned stationary case, the pumping rate is by definition identical to the fuel consumption at the injector (injector consumption). Accordingly, the output value of the pump characteristic ( 134 ), namely the estimated pumping rate (Qpump *), directly to the injector characteristic ( 132 ) and is there as an input.

The creation and content of an injector characteristic ( 132 ) and a pump characteristic ( 134 ) explained. The explanations relate to a fuel injector ( 108 ), whose valve needle is actuated indirectly via a servo valve. The servo valve has an electric actuator, via whose energization it is activated. The servo valve further includes a control chamber arranged in the opening direction of the needle valve. In the control chamber, fuel supplied from an injector inlet can be stored. The control chamber is held on the accumulator pressure with the servo valve deactivated. The pressure in the control chamber supports the valve body of the injector in the closing direction.

On the other hand, the fuel stored in the control chamber can be discharged to a fuel return line. The return line is connected to the fuel tank.

Upon activation, the servo valve releases communication between the control chamber and the fuel return line. As a result, the pressure in the control chamber drops. At the needle valve then falls a rear support away, so that only acts on the valve seat side also applied fuel pressure. This causes an opening of the needle valve and thus an injection from the injector. Such an injector is known in practice.

The aforementioned indirectly actuated injector with a servo valve and other known types of injectors have leakage currents that occur with each fuel injection and depend essentially on the fuel pressure in the high pressure accumulator (Pr) (= feed pressure of the injector) and the duration of the injection. A leakage current is a loss of fuel. Thus, an injector consumes not only the amount of fuel injected, but also the amount of leakage.

4 shows two maps for the aforementioned indirectly actuated injector ( 108 ). The first map on the left shows an association between a leakage rate (loss output in volume per unit time), an injection amount (expressed as drive time (Tinj) or injection amount, and accumulator pressure (Pr).) The second map shown on the right shows an association between an injector drive duration (Tinj), an injection amount, and an accumulator pressure (Pr) 4 maps shown can be determined, for example, by tests at the manufacturer. Alternatively, they can be created or adjusted while an injector is running. Finally, such maps can be created based on simulation models. Corresponding maps can also be made by a person skilled in the art for other forms of injectors ( 108 ) or created in any other way.

The in the 2 and 5 illustrated injector characteristic ( 132 ) is created based on an injector model with one or more injector consumption maps, as shown in FIG 4 is shown. From these characteristics, a pressure change due to a fuel injection can be read with a known actuation duration (Tinj) of the injector and known injector consumption, and thus an estimated accumulator pressure (Pr *) can be calculated.

3 FIG. 12 is a map showing an association between a delivery quantity, a PCV activation timing (tpcv), and an accumulator pressure Pr. Such a map can also be created by experiments or based on a simulation model. It may alternatively or additionally be created or adapted during operation of a high pressure pump on the vehicle.

5 shows an information flow diagram analogous to 2 , with the following changes 2 be explained.

In the information flowchart according to 5 is additionally a memory effect model ( 136 ) available. To this memory model ( 136 ), the estimated accumulator pressure (Pr *) and the estimated differential pressure (dPr *) are fed as input variables. The memory effect model ( 136 ) represents a relationship between a pressure change in the high-pressure accumulator ( 104 ) and a supply or removal of fuel. The memory effect model ( 136 ) may include, for example, a map in which an association between an output accumulator pressure (Pr), a supplied or withdrawn amount of fuel and a pressure changes generated thereby is reproduced. Alternatively, the memory effect model may include a formula in which the aforementioned relationship is calculated based on the compression modulus of the fuel.

The memory effect model ( 136 ) calculates the estimated transient pump delivery rate (Qtrans *). The transient pumping rate is that amount of fuel that must be supplied to the high pressure accumulator to increase the fuel pressure above the cycle average. When there is a transient operation of the fuel delivery system, not only is so much fuel pumped through the high pressure pump ( 102 ) to the high pressure accumulator ( 104 ), as within the cycle through the injector ( 108 ) is consumed (static Pumpfördermenge), but it is additionally fed the transient flow rate (Qtrans *). The total pumping rate (Qpump) is thus composed of the static pumping rate (Qstatic) and the transient pumping rate (Qtrans).

The memory effect model ( 136 ) estimates the transient fraction of the pumping rate as estimated transient pumping rate (Qtrans *). This is deducted from the total pumping rate (Qpump *), which results in the stationary proportion of the pumping rate (Qstatic *). The stationary pumping rate (Qstatic *) is by definition (even in non-stationary operation of the conveyor system ( 100 )) during a delivery cycle equal to the injector consumption. Correspondingly, the estimated stationary pumping rate (Qstatic *) is in the 5 the injector characteristic ( 132 ) supplied as input.

At the in 2 and 5 In the information flow diagrams shown, a recursive calculation is performed in which the estimated accumulator pressure (Pr *) is determined on the basis of, among other things, its own value at a preceding calculation interval. In other words, the value of the estimated accumulator pressure (Pr *) is circulated within the information flow. In order for such accumulator pressure estimation to be possible, it must be iteratively executed at certain time intervals, and an element for delaying an estimated value in the next computation cycle is required (at an arbitrarily arbitrary position) within the information flow. Such an element is in the 2 and 5 as a "cycle delay" element ( 130 ). Via the cycle delay element ( 130 ), a starting value for the iterative calculation of the accumulator pressure can also be specified. This starting value is preferably a last valid measured value of a pressure sensor on the high-pressure accumulator ( 104 ). Alternatively, such a starting value may be an initial estimated value taken from a map for engine operating conditions.

The determination of an estimated accumulator pressure (Pr *) and the determination of an estimated pump delivery rate (Qpump) can be carried out in mutually time-independent computing processes. Depending on the choice of characteristics ( 132 . 134 ), the calculations of the estimated accumulator pressure (Pr *) and the estimated pump delivery rate (Qpump *) during a delivery cycle can be calculated only once (global determination) or several times (detail determination). Preferably, the calculations are performed at a common clock rate.

It is preferable, according to the present disclosure, that an estimation of the accumulator pressure (Pr *) based on the actual driving duration (Tinj) of the fuel injector ( 108 ) he follows. In this way, a particularly accurate and oriented to the actual physical processes calculation done. Alternatively, a desired drive duration can be used, which is present for example as a variable in the electronic control unit. Accordingly, it is preferably provided that a calculation of the estimated pump delivery rate (Qpump *) based on an actual actuation timing (tpcv) of the high-pressure pump ( 102 ) he follows. Alternatively, a desired drive timing may be used, which may also be present as a variable within the electronic control unit.

In 6 is the course of a method for estimating a fuel pressure (Pr *) and a control method for a high pressure pump ( 102 ) according to the present disclosure. It is assumed that a high-pressure pump ( 102 ) is driven in normal operation in a closed loop based on a detected actual accumulator pressure (Pr). It is further assumed that an injector ( 108 ) is driven based on the actual accumulator pressure (Pr) and possibly in a closed loop as a function of an actual injection quantity (see. 1 ).

In the 6 The process sequence shown is executed when, according to step (S100), the invalidation of a measured value of the accumulator pressure (Pr) is detected. Then, according to step (S102), the injector control logic for control is changed over in response to the target accumulator pressure (Pr_t) and thus to open-loop control. Furthermore, if necessary, a stationary operation for the fuel delivery system ( 100 ), in which the accumulator pressure is maintained at a constant cycle average.

In the subsequent step (S104), the target values for the next calculation cycle are determined. Ie. In particular, the target injection quantity (Qi_t) and the target accumulator pressure (Pr_t) are determined.

The estimated accumulator pressure (Pr *) is usually determined after the in 6 determined sequence determined. However, a start value for the accumulator pressure (Pr *) may be determined according to step (S106) based on the injector characteristic (FIG. 132 ) be determined. To estimate the value in the next iteration, the procedure described below is performed.

Subsequently or in parallel to step (S106), the estimated pumping rate (Qpump *) is determined in step (S108). The determination is made based on the accumulator pressure (Pr / Pr *) and the drive timing (tpcv) of the high pressure pump. The determination may be based on the pump characteristic in accordance with 3 be executed relationship shown.

In the first embodiment of the method after the determination of an invalid measured value for the accumulator pressure (Pr), the estimated pump delivery rate (Qpump *) can be determined on the basis of the last valid measured value (Pr (t-1)). In all subsequent steps, the determination can be based on the last estimated value for the pumping rate (Qpump *) from the previous calculation cycle.

The in 6 illustrated step (S110) is optional and relates to in 5 additionally provided memory effect model ( 136 ). According to step (S110), the estimated transient pumping rate (Qtrans *) is determined based on the accumulator pressure (Pr / Pr *) and the pressure difference (dPr / dPr *). The transient pumping rate can be done either based on an actual reading (as a seed) or on an estimated value for the gauge pressure as well as the pressure difference.

When step (S110) is executed, step () is executed. 112 ) after estimating the steady-state portion of the pumping rate (Qstatic *) based on the estimated (total) pumping rate (Qpump *) and the estimated transient pumping rate (Qtrans *).

When the steps (S110, S112) are executed, a new accumulator pressure (Pr *) is subsequently estimated at step (S114) (for example, in accordance with FIG 4 ) based on the estimated steady-state pumping rate (Q-static *) and the actual driving time (T-inj) of the injector. The estimated stationary pumping rate (Q-static *) is in a fixed ratio to the injection quantity. In the stationary case, the stationary pumping rate (Q-static *) must be equal to the new delivery rate of the pump minus a leakage quantity. It can be separately determined each time the method is performed, whether or not steps (S110) to (S114) should be executed.

If during the execution of the method it is determined that a valid value for the accumulator pressure (Pr) is present again, it is possible to return to the regular method for controlling the high-pressure pump (FIG. 102 ) are switched to a closed loop.

Further developments and modifications of the present disclosure are possible in various ways. In particular, all of the features described or shown in relation to the respective embodiments can be combined with one another in any desired manner, replaced with one another, supplemented or omitted.

The injector characteristic ( 132 ) and / or the pump characteristic ( 134 ) can each be created for a steady-state cycle average of the accumulator pressure (Pr). Alternatively or additionally, they can be created in great detail both for an initial value before an injection or before a pump delivery or a final pressure after an injection or after a pump delivery.

It can be provided that the accumulator pressure (Pr) is lowered to a lower level in the event of failure of the accumulator pressure sensor. The lowering may be accomplished in any manner, for example, by suspending pumping of fuel through the high pressure pump for a reasonable number of pumping intervals or by venting fuel from the accumulator. The reduction can be done, for example, from a normal operating pressure level of 3000 bar to a reduced pressure level of at most 2000 bar.

A preferred variant for lowering the operating pressure level is to select from the setpoint map, from which the setpoint values for the accumulator pressure originate, an area with a lower operating pressure for the operation of the engine. Alternatively or additionally, the limiting valve described below can be used to lower the operating pressure.

A limiting valve may be arranged on the high-pressure accumulator which opens when excess pressure is exceeded and excess fuel from the high-pressure accumulator (FIG. 104 ) and, for example, returns to a tank. The limiting valve can possibly be controlled and for quickly reducing the pressure in a high-pressure accumulator ( 104 ) to be activated. It can be provided in particular that the limiting valve has an adjustable limit pressure.

An initial value for the accumulator pressure estimation may also be set by activating the limit valve to set a definable limit pressure, discharging a corresponding required amount of fuel from the high pressure accumulator. This limit pressure can be taken as the starting value for the accumulator pressure estimation (Pr *). Subsequently, the limiting pressure for the limiting valve can be increased again and the accumulator pressure (Pr *) estimate and the high-pressure pump control ( 102 ) can be continued according to the indicated method. By such a measure, the open loop control of the one or more injectors ( 108 ) as well as the high-pressure pump ( 102 ) are recalibrated during the unavailability of a valid accumulator pressure reading so that the accuracy of the calculated values required for the control is restored.

In carrying out the methods indicated here, the estimated accumulator pressure (Pr *) can also be used as an input to the injection control logic ( 122 ), so that they can be operated in a closed loop.

For the control disclosed here, it can advantageously be utilized that estimation errors tend to correct themselves. For example, if the estimated accumulator pressure (Pr *) is less than the actual (unknown) accumulator pressure (Pr), under fixed specification of the pump driver, too little (a reduced amount) of fuel will be delivered or increased if the injection timing is fixed much (an excess amount of) injected fuel, and vice versa. The surplus and shortage quantities can balance each other out. Thus, the estimated accumulator pressure (Pr *) converges toward the actual accumulator pressure (Pr) in case of misjudgment.

A plausibility check of the estimated value (Pr *) for the accumulator pressure can take place via a comparison of setpoint and actual values of the engine performance parameters. For example, a method for torque estimation and / or torque prediction may be performed for the internal combustion engine. Such a method is for example from the DE 10 2008 005 154 A1 known. If the actual value (Pr) of the accumulator pressure over several iterations is higher than the estimated value (Pr *), a torque increased over the predicted value would result due to the excess amount of injected fuel. The difference between estimated / predicted torque and measured torque may be used to correct the accumulator pressure estimate (Pr *).

LIST OF REFERENCE NUMBERS

100

 Fuel delivery system - Fuel supply system

102

 High pressure pump - High pressure pump

104

Accumulator / Common Rail - Accumulator / Common Rail

106

 Electronic control unit (ECU) - Electronic Control Device (ECU)

108

 Injector - Injector

110

 Pre-Stroke Control Valve (PCV) / Inlet Control Valve - Pre-Stroke Control Valve (PCV) / Inlet Control Valve

112

 Compression chamber - Compression chamber

114

 Compression / Plunger / Plunger - Compression means / Plunger / Piston

116

 Exhaust Valve (passive) - Outlet Valve (passive)

120

 Engine control logic - Engine control logic

122

 Injector control logic - Injector control logic

124

 Pump control logic - Pump control logic

126

 Pressure sensor - Pressure sensor

130

 Delay unit -Delay unit

132

Injector Characteristics / Injector Map - Injector characteristic

134

 Pump characteristics / Pump characteristics - Pump characteristics

136

 Memory Effect Model - Storage effect model

pr

 actual accumulator pressure / rail pressure - Actual accumulator pressure / rail pressure

Pr *

 estimated accumulator pressure / rail pressure - Estimated accumulator pressure / rail pressure

Pr_t

 Target accumulator pressure / rail pressure - Target accumulator pressure / rail pressure

Qi_t

 Target injection quantity - Target injection quantity

Tinj

 Injector drive duration - Injector activation duration

tpcv

 Target Activation Timing - Target activation timing

dPr

 Pressure difference measured - Pressure difference measured

dPr *

 Pressure difference estimated - Pressure difference estimated

QPUMP *

 Estimated (total) pumping rate - Estimated (overall) pump delivery quantity

Qstatic *

Estimated Static Pumping Rate - Estimated static pump delivery quantity

Qtrans *

 Estimated transient pump delivery rate - Estimated transient pump delivery quantity

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 102008005154 A1 [0067]

Claims (10)

Method for estimating a fuel pressure (Pr *) in a high pressure accumulator ( 104 ) (Accumulator pressure), whereby fuel in a fuel delivery system ( 100 ) from a high pressure pump ( 102 ) is pressurized in the high pressure accumulator ( 104 ) and by at least one fuel injector ( 108 ), characterized in that the accumulator pressure (Pr *) is calculated iteratively as a function of an estimated pressure change starting from a previously known starting value (Pr (t-1)), this estimated pressure change being based on a characteristic ( 134 ) for pumping the high-pressure pump ( 102 ) and a characteristic ( 132 ) for fuel injection by the at least one fuel injector ( 108 ) is determined. Method according to claim 1, characterized in that the high pressure pump ( 102 ) and the at least one fuel injector ( 108 ) in normal operation in a closed loop based on a measured accumulator pressure (Pr) are driven, wherein the estimation method for the accumulator pressure is executed when no valid value for the accumulator pressure (Pr) is present. Method according to at least one of claims 1 or 2, characterized in that the characteristic ( 134 ) for a pump delivery, an association between an accumulator pressure (Pr), a drive timing (tpcv) of the high-pressure pump ( 102 ) and a discharge amount (Qpump) of the high-pressure pump ( 102 ) contains. Method according to one of the preceding claims, characterized in that the characteristic ( 132 ) for a fuel injection, an association between an accumulator pressure (Pr), a drive duration (Tinj) of the fuel injector ( 108 ) and an injection quantity of the fuel injector ( 108 ) contains. Method according to claim 4, characterized in that the characteristic ( 132 ) for fuel injection further includes an assignment to a leakage amount. Method according to one of the preceding claims, characterized in that the estimation of the fuel pressure (Pr *) based on an actual driving timing (tpcv) of the high-pressure pump ( 102 ) and / or an actual drive duration (Tinj) of the fuel injector ( 108 ) he follows. Method according to one of the preceding claims, characterized in that the last valid measured value (Pr (t-1)) of the accumulator pressure sensor is the starting value for the estimation of the accumulator pressure (Pr *). Method according to one of the preceding claims, characterized in that a starting value for the estimation of the accumulator pressure (Pr *) is predetermined by setting a limit pressure to which the actual pressure (Pr) in the accumulator ( 104 ) is discharged by means of a pressure relief valve. Method according to one of the preceding claims, characterized in that a plausibility check and if necessary. Adaptation of the estimated value (Pr *) for the accumulator pressure via a comparison of desired and actual values of the engine performance parameters, in particular based on a comparison of an estimated or predicted engine torque with a measured engine torque. Control method for a high-pressure pump ( 102 ), which pressurizes fuel and to a high-pressure accumulator ( 104 ), wherein the pumping rate (Qpump) of the high-pressure pump ( 102 ) via a control valve ( 110 , PCV), which controls the release of a connection between a pump inlet and a compression chamber ( 112 ), characterized in that the discharge amount of the high pressure pump is controlled in response to a pressure difference (dPr *) between a target accumulator pressure (Pr_t) and an estimated accumulator pressure (Pr *) in a closed loop, so that the estimated Accumulator pressure (Pr *) follows the target accumulator pressure (Pr_t), wherein the estimated accumulator pressure (Pr *) is estimated by a method according to one of the preceding claims.

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