EP1529948B1 - Pre-controlling process of a variable lift fuel pump in an Internal combustion engine - Google Patents

Abstract

Process for pre-controlling a reciprocating fuel pump of a vehicle comprises from the starting values determining the fuel volume removal from a high pressure rail by the injection valve per stroke of the pump, determining the fuel volume necessary for a change of theoretical pressure in the high pressure rail per stroke of the pump, and determining the volume loss by a non-optimum degree of delivery based on the formation of steam bubbles in the fuel. Preferred Features: The reciprocating pump is driven by a camshaft of an internal combustion engine.

Description

The invention relates to a method for piloting a stroke-piston fuel pump of an internal combustion engine, in particular of a motor vehicle, wherein the internal combustion engine has a high-pressure rail and associated injection valves, according to the preamble of claim 1.

An amount set mechanism of a reciprocating piston fuel pump for a fuel supply of an internal combustion engine determines an amount of fuel that is compressed in the reciprocating piston fuel pump and pushed into a high-pressure rail. In a motor fire device, a Regetatgorithmus is implemented, which calculates the opening and closing times or angles of the quantity control of the pump. These opening and closing times are output in the form of an electrical signal to the bulkhead. For optimal combustion and combustion mixture formation in a combustion chamber of the internal combustion engine, the fuel pressure and the amount of fuel available for injection in the high-pressure rail must be provided as accurately as possible.

In a known algorithm for controlling the quantity control station, a pilot control and a controller are provided.

That's how it shows DE 102 36 654 A1 a possibility of preventing pressure control problems caused by a deviation of a feedback control amount. The target fuel pressure is calculated and the pump discharge volume is calculated as an optimum value taking into account the pressure deviation between the actual fuel pressure and the target fuel pressure. The US Pat. No. 644 66 10 B1 describes, moreover, the regulation of the fuel pressure in the form that the delivered fuel quantity is equal to the algebraic sum of an amount of fuel to be injected into the combustion space and a necessary amount of fuel to correct the pressure deviation between the measured fuel pressure and a desired fuel pressure, whereby also the operating parameters of the Electrovalve be considered.

• Die Toleranzlagenstreuung der Pumpe in der Serie.
• Fehler in den Vorsteuerkennfeldern.
• Physikalische Abhängigkeiten, wie beispielsweise Temperaturabhängigkeiten.

In the pre-control, the time duration for the control with limited accuracy is determined. Input signals of the precontrol are the nominal values for fuel pressure and quantity. On the basis of these setpoints, maps are addressed in which a control angle is stored. These maps do not simulate the physical conditions in the reciprocating piston power pump, but are empirically determined on pumps selected by way of example. By using a controller, it is possible to correct the control period of the quantity control station determined in the pilot control. The controller works on the basis of a pressure detection with a sensor in the high pressure rail. This controller is designed as a PI controller. This correction is necessary because the following relationships can not be taken into account by the pilot control maps:

• Tolerance distribution of the pump in the series.
• Error in the pilot control maps.
• Physical dependencies, such as temperature dependencies.

The more accurately the pilot control maps correspond to the real conditions, the smaller the interventions of the controller are.

The invention has for its object to provide a method of the above type with respect. Control of the quantity of the hub piston-fuel pump to achieve a high accuracy with respect. To provide the fuel injection quantity and the fuel injection pressure in the high-pressure rail to improve and to make it more robust against disturbances.

This object is achieved by a method of o.g. Art solved with the features characterized in claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

For this it is inventively provided that from the input values fuel volume vevphh from the high pressure rail through the injectors per stroke of the piston-stroke fuel pump, vdaavst fuel volume , which is required for a change of the desired pressure Δ p _{soll_rail} in the high-pressure _rail per stroke of the reciprocating piston fuel pump vkdavst , which requires the piston of the reciprocating piston fuel pump to compress the fuel from low pressure to high pressure rail pressure per stroke of the reciprocating piston fuel pump, and volume loss vvlfghdp due to non-optimal delivery due to vapor bubble formation in the fuel per stroke of the stroke Piston Fuel Pump Closing and opening times for an amount set point of the Hub Piston Kraftstoffpümpe be determined.

Fig. 1

ein schematisches Schaltbild eines bekannten, rücklauffreien Kraftstoffsystems,

Fig. 2

ein schematisches Schaltbild der Funktionsweise einer Hub-Kolben-Kraftstoffpumpe zur Veranschaulichung des erfindungsgemäßen Verfahrens und

Fig. 3

ein Kennfeld für die Kompressibilität des Kraftstoffs in Abhängigkeit von Druck und Temperatur.

Fig. 4

eine schematische Darstellung der Ansteuerung eines Mengenstellwerkes einer Hub-Kolben-Kraftstoffpumpe,

This has the advantage that a higher accuracy is achieved with less application effort and better diagnostic capability, with different pump concepts can be realized.
Further features, advantages and advantageous embodiments of the invention will become apparent from the dependent claims, and from the following description of the invention with reference to the accompanying drawings. These show in

Fig. 1

a schematic diagram of a known, non-return fuel system,

Fig. 2

a schematic diagram of the operation of a reciprocating-piston fuel pump to illustrate the method according to the invention and

Fig. 3

a map for the compressibility of the fuel as a function of pressure and temperature.

Fig. 4

a schematic representation of the control of a quantity control station of a reciprocating piston fuel pump,

Fig. 1 FIG. 10 illustrates a non-return fuel system including a fuel tank 10, an electric fuel pump 12, a fuel filter 14, a high-pressure pump (HDP) 16 with tonnage control, a high-pressure rail 18, multiple high-pressure injection valves (HDEV) 20, a return line 22 , a pressure relief valve (DBV) 24, an engine control unit (ECU) 26, a low pressure sensor 28, a high pressure sensor 30 and a power output stage 32 for driving the fuel pump 12. Line 34 separates the fuel system into a high pressure side 36 and a low pressure side 36. EKP) 12 serves as a prefeed pump for the Hub Piston Fuel Pump (HDP) 16. The Hub Piston Fuel Pump (HDP) 16 adjusts the fuel pressure in the rail or high pressure rail 18. The high-pressure injection valves 20 are supplied with fuel from the high-pressure rail 20. Fuel flows back via the return line 22 when the pressure in the high-pressure rail exceeds a safety-critical limit value. This can only occur in the event of a fault. A non-illustrated leakage line of the Hub Piston Fuel Pump (HDP) 16 discharges fuel that escapes in the Hub Piston Fuel Pump (HDP) 16 between the piston and cylinder. However, this amount is relatively small.

The stroke piston fuel pump 16 includes, as shown Fig. 2 can be seen, a piston 40 in a cylinder 42 which performs a lifting movement. This lifting movement is divided into a downward and upward movement. In the downward movement, a displacement with fuel from the fuel tank 10 of the low-pressure system 38 is filled with fuel. In the upward movement, the compression of the fuel takes place. A quantity control in the form of a quantity control valve 44 separates the compression space from the supply side and low pressure side 38, respectively, during a predetermined part of the upstroke. During that portion of the upward movement of the piston 40 to be used to compress the fuel, the quantity interlocking 44 disconnects the displacement Hub piston fuel pump 16 and supply line 46. During that portion of the upward movement of the piston 40, which is not to be used for compression of the fuel, the quantity control 44 opens the connection between the displacement of the reciprocating piston fuel pump 16 and the supply line 46th The result is a closing interval, which lies in the compression stroke of the reciprocating piston fuel pump 16.

The position of the interval in the compression stroke is in principle freely selectable. Usually either the closing or the opening time is set to one of the dead centers of the movement of the piston 40. With both concepts it is possible to set the effective compression stroke. The displacement is connected to the high pressure rail 18 of the high pressure system 36 via a check valve 48. As soon as the pressure in the displacement of the lift-piston fuel pump 16 becomes greater than the pressure in the high-pressure rail 18, the compressed fuel flows from the displacement of the lift-piston fuel pump 16 into the high-pressure rail 18. Fig. 1 ) outputs the switching pulse to the quantity control valve (44) of the quantity control station. The duration of this switching pulse determines the effective stroke taking into account the piston speed and piston position.

Fig. 4 illustrates the control of Mengenesteitwerkes 44 with the two different concepts. For this purpose, a graph 50 illustrates the movement of the piston 40 between a top dead center 52 and a bottom dead center 54, wherein a filling 56 and a compression 58 cyclically alternate. According to a first concept with closing interval at the beginning of the compression stroke 58, as indicated by arrows 60 (compression phase according to concept I), graph 62 shows a drive signal for the quantity control valve 44 between 0V and 12V, a graph 64 a state of the quantity control valve 44 between "open" 66, and "closed" 68 and a graph 70 a pressure in the compression chamber, the stroke-piston fuel pump 16 between a low pressure P _low-pressure 72 in the low pressure system 38 and a high pressure p _HD-rail 74 in the high-pressure system 36 or high-pressure rail 18. According to a second concept with closing interval at the end of the compression stroke 58, as indicated by arrows 76 (compression phase according to concept II), graph 78 shows a drive signal for the quantity control valve 44 between 0V and 12V, a graph 80 shows a state of the quantity control valve 44 between "open" 82 and "closed 84 and a graph 86 a pressure in the compression space of the reciprocating piston fuel pump 16 between a P low-pressure _low-pressure 88 in the low pressure system 38 and a high pressure p _HD-rail 90 in the high-pressure system 36 or high-pressure rail 18th

The closing interval 60 or 76 of the quantity-adjusting mechanism 44 lies between the bottom dead center 54 and the top dead center 52 of the piston 40 of the reciprocating piston fuel pump 16 relative to a piston 40 moving upward in the cylinder 42. In principle, it does not matter if the closing interval immediately after passing through the bottom dead center 54 begins (concept I, arrow 60) or ends with reaching the top dead center 52 (concept II, arrow 76). Both concepts lead to pressure build-up. For energetic reasons, however, the second concept (arrow 76) is to be preferred. The compression process 60 or 76 is triggered by closing the quantity control station 44 with upwardly moving piston 40. The volume of fuel in the compression space at this moment is at approximately low pressure level. By the upward movement of the piston 40, the pressure increases. If the pressure in the compression chamber of the reciprocating piston fuel pump 16 rises above the pressure p _HD-rail prevailing in the high-pressure _rail 18 , then the check valve 48 opens and the fuel flows out of the compression space of the reciprocating piston fuel pump 16 into the high-pressure _rail 18. Dies takes place as long as the pressure in the compression chamber above the pressure p _{HD rail is maintained} in the high-pressure _rail 18. The effective compression stroke is ended by opening the quantity-adjusting mechanism 44 or as soon as the piston 40 reaches its top dead center 52. Depending on the pump design and concept, a residual volume at the end of the compression process 58 may remain in the compression space of the reciprocating piston fuel pump 16.

wobei V ₀ ein Ausgangsvolumen [mm³]; Δp eine Druckänderung [bar], χ eine Kompressibilitätszahl [1/bar] und ΔV eine Volumenänderung [mm³] ist. Die eine Kompressibilitätszahl χ [1/bar] für das zu komprimierende Fluid ergibt sich in Abhängigkeit von Temperatur und Druck aus einer Kennlinienschar gemäß Fig. 3. Die Fig. 3 zeigt auf einer horizontalen Achse 92 einen Druck in [bar] und auf einer vertikalen Achse 94 die Kompressibilität in [E-4/bar]. Die Kennlinien entsprechen von oben nach unten einer Temperatur von 413K, 393K, 373K,353K, 333K, 313K, 293K, 273K, 253K und 233K. Die Kompressibilität ist empirisch ermittelt und bezieht sich bei dem dargesteltten Beispiel auf Superbenzin, das bei 15°C und 1 bar die Dichte ρ =0,7647 g/cm³ aufweist.The fuel, for example petrol, changes its volume under pressure. This volume change results $$\mathrm{\Delta }V={\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="imgf0003.png"\; state="\{\{state\}\}">V</figure-callout>}}_0*\mathrm{\Delta }p*\chi$$

where V _{0 is} an initial volume [mm ³ ]; Δ p is a pressure change [bar], χ is a compressibility number [1 / bar] and Δ V is a volume change [mm ³ ]. The one compressibility number χ [1 / bar] for the fluid to be compressed results in dependence on temperature and pressure from a family of curves according to Fig. 3 , The Fig. 3 shows on a horizontal axis 92 a pressure in [bar] and on a vertical axis 94 the compressibility in [E-4 / bar]. The curves correspond from top to bottom to a temperature of 413K, 393K, 373K, 353K, 333K, 313K, 293K, 273K, 253K and 233K. The compressibility is determined empirically and refers in the example shown to super-grade petrol which has the density ρ = 0.7647 g / cm ³ at 15 ° C. and 1 bar.

According to the invention, the variables used for calculating the volume change in the compression of fuel, the pressure change, temperature change, output volume, output pressure and output temperature and a compressibility map of the fuel grade used.

wobei ρ_Kraftstoff eine Dichte des Kraftstoffes in [g/mm³], ρ_norm eine Dichte des Kraftstoffes unter Normbedingungen in [g/mm³], p_Kraftstoff ein Druck des Kraftstoffes [bar], ], p_norm ein Normdruck in [bar] und χ_Kraftstoff eine Kompressibilität des Kraftstoffes ist. Dieser Zusammenhang ist gültig für Kraftstoff in flüssiger Form.For the calculation of the density change by compression, the density of the fuel for the respective operating point is first calculated. The density depends on the compressibility and the pressure according to the following formula: $${\rho }_{\mathit{fuel}}=\frac{\rho }{\left(1-\left(p_{\mathit{rail}}-p_{\mathit{standard}}\right)*{\chi }_{\mathit{Kail}}\right)}$$

where ρ _{fuel is} a density of the fuel in [g / mm ³ ], ρ _{norm is} a density of the fuel under standard conditions in [g / mm ³ ], p _{fuel is} a pressure of the fuel [bar],], p _{norm is} a standard pressure in [bar ] and χ _{fuel is} a compressibility of the fuel. This relationship applies to fuel in liquid form.

$$t_{\mathit{emotr}}=f\left(\left(t_{\mathit{mot}}-t_{\mathit{krailnp}}\right);Q_{\mathit{Kraftstoff}}\right)$$

$$t_{\mathit{krailnp}}=f\left(\left(p_{\mathit{rail}}-p_{\mathit{Niederdruckseite}}\right)\right)$$

$$t_{\mathit{eulr}}=f\left(t_{\mathit{Umgebung}};v_{\mathit{Fahrzeug}}\right)$$

Sizes that can not be measured directly must be modeled using models. This relates to the temperature in the present application. For the determination of the compressibility it is necessary to model the temperature of the fuel at two points of the fuel system, namely the temperature of the fuel _flowing into the compression _space t _flvrhdp and the temperature of the fuel in the high-pressure _rail t _krail . For t _flvrhdp a map is addressed, which is empirically determined in the experiment. The temperature t _{krail of} the fuel in the high-pressure _rail 18 depends on various influencing variables. The starting point is the inlet _temperature t _{flvrhdp of} the fuel in the lift-piston fuel pump 16. The fuel flows through first the lift-piston fuel pump 16, the fuel line and then the high-pressure rail 18. There is a heat transfer due to the contact of the fuel with the inner surfaces of the fuel-carrying components instead. The source of heat is the engine block or the ambient air in the engine compartment as well as the compression work in the reciprocating piston fuel pump 16. These heat _inputs bear the following names t _emotr , t _eulr and t _krailnp . The fuel flows into the compression _space via the open quantity control 44 at the temperature t _flvrhdp . There, the fuel is compressed and flows through the check valve 48 in the high-pressure _rail 18. By this thermodynamic process takes place a temperature _entry t _krailnp in the fuel. For t _krail applies: $$t_{\mathit{Krail}}=t_{\mathit{flvhdp}}+t_{\mathit{emotr}}+t_{\mathit{eulr}}+t_{\mathit{krailnp}}$$

$$t_{\mathit{emotr}}=f\left(\left(t_{\mathit{mot}}-t_{\mathit{krailnp}}\right);Q_{\mathit{fuel}}\right)$$

$$t_{\mathit{krailnp}}=f\left(\left(p_{\mathit{rail}}-p_{\mathit{Low\; pressure\; side}}\right)\right)$$

$$t_{\mathit{eulr}}=f\left(t_{\mathit{Surroundings}};v_{\mathit{vehicle}}\right)$$

The dependencies of t _emotr , t _eulr and t _krailnp are determined empirically and stored in curves and _maps .

By means of a low-pass filter, the dynamic behavior of the temperature t _krail in the high-pressure _rail 18 is detected. The time behavior of the filter is determined as a function of the fuel _{mass flow} Q _fuel ) and of the difference between t _mot and t _krailnp .

According to the invention, the pilot control of the stroke piston fuel pump 16 is based on the calculation of the stroke volume of the piston 40 which is to be used for the compression of the fuel. This stroke volume is defined by closing and opening times of the quantity control station 44 taking into account the pump geometry. The volume of fuel to be compressed results from the requirements of the engine control 26 with respect to target fuel pressure in the high-pressure rail 18 and fuel quantity and the current operating parameters, such as temperature and actual pressures.

$$\mathit{kmphvst}=\frac{\mathit{dmkrhdev}}{\mathit{ishdpvst}}$$

$$\mathit{ishdpvst}=\mathit{nmv}*\mathit{nahdpanz}$$

$${\rho }_{\mathit{kravst}}=\frac{{\rho }_{\mathit{rohnvst}}}{1-\left(\left(p_{\mathit{rail}}-p_{\mathit{norm}}\right)*{\chi }_{\mathit{Krail}}\right)}$$

wobei

νeνphh =

Kraftstoffvolumenentnahme aus dem Hochdruckrail durch die Einspritzventile in [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

kmphνst =

Kraftstoffmassenentnahme durch die Einspritzventile aus dem Hochdruckrail pro Hub der Hub-Kolben-Kraftstoffpumpe in [g/Hub der Hub-Kolben-Kraftstoffpumpe].

ρ_krarνst =

Dichte des Kraftstoffes bei Ausströmen aus dem Hochdruckrail 18 in [g/mm³].

ρ_rohnνst =

Normdichte des Kraftstoffes (sortenabhängig) in [g/mm³].

p_rail =

Druck im Hochdruckrail 18 in [bar].

p_norm =

Normdruck in [bar].

χ_Krail =

Kompressibilität des Kraftstoffes im Hochdruckrail in [1/bar].

dmkrhdeν =

Kraftstoffmenge durch die Hochdruckeinspritzventile (HDEV) 20 berechnet aus Ventilöffnungszeiten in [g/min].

ishdpνst =

Anzahl der Lastspiele der Hub-Kolben-Kraftstoffpumpe pro min in [1/min].

nnw =

Nockenwellendrehzahl in [1/min].

nahdpanz =

Anzahl der Nocken auf der Nockenwelle für den Antrieb der Hub-Kolben-Kraftstoffpumpe [dimensionslos].

The volume of fuel removed from the high-pressure rail 20 by the high-pressure injection valves must be returned to the high-pressure rail 18 by the stroke piston fuel pump 16. The volume taken from the high-pressure rail 18 vevphh 96 ( FIG. Fig. 2 ) results from: $$\mathit{vevphh}=\frac{\mathit{krnphvst}}{{\rho }_{\mathit{kharvst}}}$$

$$\mathit{kmphvst}=\frac{\mathit{dmkrhdev}}{\mathit{ishdpvst}}$$

$$\mathit{ishdpvst}=\mathit{nmv}*\mathit{nahdpanz}$$

$${\rho }_{\mathit{kravst}}=\frac{{\rho }_{\mathit{rohnvst}}}{1-\left(\left(p_{\mathit{rail}}-p_{\mathit{standard}}\right)*{\chi }_{\mathit{Krail}}\right)}$$

in which

νeνphh =

Fuel volume extraction from the high-pressure rail through the injection valves in [mm ³ / stroke stroke piston fuel pump].

kmphvst =

Fuel mass extraction by the injection valves from the high-pressure rail per stroke of the reciprocating piston fuel pump in [g / stroke of the reciprocating piston fuel pump].

ρ _krarvst =

Density of the fuel when flowing out of the high-pressure rail 18 in [g / mm ³ ].

ρ _rohnvst =

Standard density of the fuel (depending on the grade) in [g / mm ³ ].

p _rail =

Pressure in the high-pressure rail 18 in [bar].

p _norm =

Standard pressure in [bar].

_{Krail logo CNRS logo INIST}

Compressibility of the fuel in the high-pressure rail in [1 / bar].

dmkrhdeν =

Fuel quantity through High Pressure Injection Valves (HDEV) 20 calculated from valve opening times in [g / min].

ishdpvst =

Number of load cycles of the reciprocating piston fuel pump per minute in [1 / min].

nnw =

Camshaft speed in [1 / min].

close - up

Number of cams on the camshaft for driving the reciprocating piston fuel pump [dimensionless].

wobei

νdaaνst =

Volumen Kraftstoff für Druckauf- und -abbau pro Hub der Hub-Kolben-Kraftstoffpumpe [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

Δp_{soll_rail} =

Solldruckveränderung pro Hub der Hub-Kolben-Kraftstoffpumpe [bar/Hub Hub-Kolben-Kraftstoffpumpe].

V_HDRL =

Volumen des gesamten Hochdruckbereiches bestehend aus Hochdruckrail und Hochdruckleitungen in [mm³].

χ_Krail =

Kompressibilität des Kraftstoffes im Hochdruckrail in [1/bar].

An increase in the pressure in the high-pressure rail 18 leaves only about an additional fuel volume νdaaνst 98 ( Fig. 2 )the rich. With a positive target pressure gradient, therefore, an additional amount of fuel must be pumped into the high-pressure rail 18. Because this additional amount is not taken from the high pressure rail 18, there is an increase in pressure in the high pressure rail 18. If the pressure in the high pressure rail 18, however, reduce the high pressure rail 18, a smaller fuel volume must be supplied, as this has been removed by the high pressure injection valves 20 , This smaller volume results with a negative target pressure gradient. In this case, the calculated volume gets a negative sign. From a technical point of view, this relationship can be captured as follows: $$\mathit{vdaavst}=\mathrm{\Delta }{p}_{\mathit{soll\_rail}}*V_{\mathit{HDRL}}*{\chi }_{\mathit{Krail}}$$

in which

νdaaνst =

Volume Fuel for pressure buildup and release per stroke of Hub Piston Fuel Pump [mm ³ / Hub Hub Piston Fuel Pump].

Δp _{soll_rail} =

Target pressure change per stroke of the Hub Piston Fuel Pump [bar / Hub Hub Piston Fuel Pump].

V _HDRL =

Volume of the entire high-pressure area consisting of high-pressure rail and high-pressure lines in [mm ³ ].

_{Krail logo CNRS logo INIST}

Compressibility of the fuel in the high-pressure rail in [1 / bar].

Here Ap _{soll_rail} is defined as follows: Δ p _{soll_rail>} 0 meant that the nominal pressure gradient is positive and Ap _{soll_rail} <0 meant the nominal pressure gradient däß negative.

$$V_{komp}=vevphh+vdaavst+vtotraum$$

wobei

νkdaνst =

Volumen für Kompression bis Druckausgleich zwischen Kompressionsraum in der Hub-Kolben-Kraftstoffpumpe 16 und dem Hochdruckrail 18 in [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

χ_Khdp =

Kompressibilität des Kraftstoffs bei Einströmen in den Kompressionsraum der Hub-Kolben-Kraftstoffpumpe in [1/bar].

V_komp =

Kraftstoffvolumen das sich bei Druckausgleich im Kompressionsraum der Hub-Kolben-Kraftstoffpumpe befindet in [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

νdaaνst =

Volumen Kraftstoff für Druckauf- und -abbau pro Hub der Hub-Kolben-Kraftstoffpumpe [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

νeνphh =

Kraftstoffvolumenentnahme aus dem Hochdruckrail durch die Einspritzventile in [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

νtotraum =

Kraftstoffvolumen im Kompressionsraum der Hub-Kolben-Kraftstoffpumpe 16 bei Ende des Kompressionsvorganges in [mm³/Hub Hub-Kolben-Kraftstoffpumpe].

Next, a volume change νkdaνst 100 ( Fig. 2 ) by compression. When the compression process begins, the fuel is initially at low pressure level. By the piston 40 moving upwards, there is an increase in pressure. Only when pressure equalization between the compression space of the reciprocating piston fuel pump 16 and the high-pressure rail 18, opens the intervening check valve 48. The stroke volume, which requires the piston for the compression of low pressure to rail pressure level, is due to the compressibility of the fuel , According to the invention, this stroke volume is taken into account in the calculation of the activation of the quantity control station 44 and is added to the previously calculated volumes νeνphh (fuel volume extraction from the high-pressure rail through the injection valves) and νdaaνst (volume of fuel for pressure buildup and reduction in the high-pressure rail 18 ). This additional volume is calculated as follows: $$\mathit{vkdavst}=\frac{{\chi }_{\mathit{KHDP}}*\mathrm{\Delta }p*V_{\mathit{comp}}}{1-\mathrm{\Delta }p*{\chi }_{\mathit{KHDP}}}$$

$$V_{kOmp}=vevpHH+vdaavst+vtOtraum$$

in which

νkdaνst =

Volume for compression to pressure equalization between compression space in the reciprocating piston fuel pump 16 and the high-pressure rail 18 in [mm ³ / stroke stroke piston fuel pump].

_Khdp =

Compressibility of the fuel flowing into the compression space of the reciprocating piston fuel pump in [1 / bar].

V _comp =

Fuel volume in the compression chamber of the reciprocating piston fuel pump is in [mm ³ / Hub Hub Piston Fuel Pump].

νdaaνst =

Volume Fuel for pressure buildup and release per stroke of Hub Piston Fuel Pump [mm ³ / Hub Hub Piston Fuel Pump].

νeνphh =

Fuel volume extraction from the high-pressure rail through the injection valves in [mm ³ / stroke stroke piston fuel pump].

νtotraum =

Fuel volume in the compression chamber of the stroke piston fuel pump 16 at the end of the compression process in [mm ³ / Hub Hub Piston Fuel Pump].

wobei

V_{Kompressionsraum} =

Volumen des Kompressionsraumes der Hub-Kolben-Kraftstoffpumpe 16 in [mm³].

When the bulkhead 44 closes at the bottom dead center of the piston 40 of the reciprocating piston fuel pump 16 (see arrow 60 in FIG Fig. 4 According to concept I) and the pressure build-up begins, the entire fuel in the compression space of the reciprocating piston fuel pump 16 must always be brought from low pressure to rail pressure level. For pump concepts, which always close at the bottom dead center of the piston 40 of the reciprocating piston fuel pump 16, the quantity control unit 44 and adjust their capacity with a variable opening time of the quantity control 44, νkdaνst (volume for compression to pressure equalization between compression space in the lifting Piston fuel pump 16 and the high-pressure rail 18) alternatively represent something simpler: $$\mathit{vkdavst}={\chi }_{\mathit{KHDP}}*\mathrm{\Delta }p*V_{\mathit{compression\; chamber}}$$

in which

V _compression space

Volume of the compression space of the reciprocating piston fuel pump 16 in [mm ³ ].

vvlfghdp =

Volumenverlust durch nicht optimalen Liefergrad aufgrund von Dampfblasenbil- dung im Kraftstoff pro Hub der Hub-Kolben-Kraftstoffpumpe [mm³].

Ifgrhdp =

Liefergrad bei der Befüllung des Kompressionsraumes der Hub-Kolben-Kraftstoffpumpe [dimensionslos]. Definition: $$0<lfgrhdp<1$$

• 0 = keine Füllung
• 1 = 100% Führung

$$lfgrhdp=f\left(kmeshdp;tfvrhdp\right)*f\left(nmot;p_{niederdruck}\right)$$

kmeshdp =

Kraftstoffmasse, die durch das Mengenstellwerk in das Hochdruckrail pro Hub einströmt in [g/hub Hub-Koben-Kraftstoffpumpe].

tflvrhdp =

Temperatur des Kraftstoffes beim Einströmen in den Kompressionsraum in [°C].

nmot =

Motordrehzahl in [1/min].

p_niederdruck =

Kraftstoffdruck auf einer Niederdruckseite in [kPa].

The filling of the compression space of the lift-piston fuel pump 16 takes place while the piston 40 moves downward. It must be replenished as much fuel in the compression chamber, as previously in the compression stroke has been discharged into the high-pressure rail 18. However, dynamic flow effects can cause the filling not to be uniform. Due to high flow velocities and not optimal inflow channels Occasionally zones with low pressure levels are created. In these zones it can happen that the fuel passes under the influence of temperature from the liquid to the gaseous phase. This includes an increase in volume. The resulting vapor bubbles are either already in the compression space of the reciprocating piston fuel pump 16 or are entrained by the fuel flow and thus get into the compression chamber. Under pressure increase by the incipient compression process, these bubbles form back. It comes to a reduction in volume. The stroke volume required by the piston 40 of the lift-piston power fuel pump 16 when the quantity control station 44 is closed in order to compensate for this volume change is referred to below as vvlfghdp . This volume vvlfghdp 102 ( Fig. 2 ) is considered according to the invention in the determination of the total volume to be compressed.

vvlfghdp =

Volume loss due to less than optimal delivery due to vapor formation in the fuel per stroke of the reciprocating piston fuel pump [mm ³ ].

Ifgrhdp =

Degree of delivery when filling the compression space of the reciprocating piston fuel pump [dimensionless]. Definition: $$0<lfGrHdp<1$$

• 0 = no filling
• 1 = 100% leadership

$$lfGrHdp=f\left(kmesHdp;tfvrHdp\right)*f\left(nmOt;p_{niederdruck}\right)$$

kmeshdp =

Fuel mass flowing into the high-pressure rail per stroke through the metering station in [g / stroke Hub-Koben fuel pump].

tflvrhdp =

Temperature of the fuel flowing into the compression chamber in [° C].

nmot =

Engine speed in [rpm].

p _{low pressure}

Fuel pressure on a low pressure side in [kPa].

With kmeshdp, tjlvrhdp, nmot and p _low pressure maps are addressed, which are empirically determined in the experiment.

wobei

νkhdpνst =

Pro Hub der Hub-Kolben-Kraftstoffpumpe zu komprimierendes Gesamtvolumen [mm³].

The total volume to be compressed results from the addition of the above determined volumes according to: $$\mathit{vkhdpvst}\mathit{=}\mathit{vevphh}\mathit{+}\mathit{vkdavst}\mathit{+}\mathit{vdaavst}\mathit{+}\mathit{vvlfghdp}$$

in which

νkhdpvst =

For each stroke of the reciprocating piston fuel pump, the total volume to be compressed [mm ³ ].

wobei

skhdp =

Kompressionshub des Kolbens der Hub-Kolben-Kraftstoffpumpe, der für das zu komprimierende Gesamtvolumen νkhdpνst erforderlicher ist [mm].

νkhdpνst =

Pro Hub der Hub-Kolben-Kraftstoffpumpe zu komprimierendes Gesamtvolumen [mm³].

r_Kolben =

Radius des Kolbens der Hub-Kolben-Kraftstoffpumpe [mm].

mit $$\mathit{dwmsvsvg}=\mathit{Erhebungskurve\_Nocken}\left(\mathit{skhdp}\right)$$

wobei die Funktion Erhebungskurve_Nocken(skhdp) die Geometrie der steigenden Flanke der Antriebsnockens für die Hub-Kolben-Kraftstoffpumpe in Form einer Kennlinie beschreibt. Adressiert wird diese Kennlinie mit dem erforderlichen Kompressionshub skhdp in [mm]. Über die Geometrie ergibt sich mit dwmsνsνg der notwendige Kurbelwinkel, den das Mengenstellwerk geschlossen sein muß, damit der Kolben der Hub-Kolben-Kraftstoffpumpe den erforderlichen Kompressionshub skhdp ausführen kann, mit

dwmsνsνg =

Deltakurbelwinkel, den das Mengenstellwerk geschlossen bleibt in [°KW].

In many applications, the lift-piston fuel pump is driven by a cam on a camshaft of the internal combustion engine. The shaft is connected in angular synchronism with the driving crankshaft. The strokes of the piston of the reciprocating piston fuel pump in such a case are angularly synchronized with the crankshaft. The control of the quantity control station then takes place in an advantageous manner depending on the crank angle. Here, the closing and opening angle of the quantity control gear is determined based on the crank angle. To implement the total volume to be compressed in a crankshaft-synchronous driving the quantity control station, the connection of the reciprocating-piston fuel pump is detected formula technically. For this purpose, the gear ratio and the number of cams on the camshaft, which are assigned to the stroke-piston fuel pump to pay attention. The actual stroke movement is determined by the geometric shape of the cam. The distance traveled results in conjunction with the diameter of the piston, the stroke volume of the lift-piston fuel pump. The result is the following formula: $$\mathit{skhdp}=\frac{\mathit{vkhdpvst}}{\pi *{\mathrm{<figure-callout\; id="2"\; label="r\; piston"\; filenames="imgf0003.png"\; state="\{\{state\}\}">r\; </figure-callout>}}_{\mathit{piston}}^{\mathit{}}}$$

in which

skhdp =

Compression stroke of the piston of the reciprocating piston fuel pump required for the total volume to be compressed νkhdpνst [mm].

νkhdpvst =

For each stroke of the reciprocating piston fuel pump, the total volume to be compressed [mm ³ ].

r _piston =

Radius of the piston of the reciprocating piston fuel pump [mm].

With $$\mathit{dwmsvsvg}=\mathit{Erhebungskurve\_Nocken}\left(\mathit{skhdp}\right)$$

wherein the function Erhebungskurve_Nocken (skhdp) describes the geometry of the rising edge of the drive cam for the stroke-plunger fuel pump in the form of a characteristic curve. This characteristic curve is addressed with the required compression stroke skhdp in [mm]. About the geometry results with dwmsνsνg the necessary crank angle, the quantity control must be closed so that the piston of the reciprocating piston fuel pump can perform the required compression stroke skhdp , with

dwmsνsνg =

Deltakurbelwinkel, the quantity control station remains closed in [° KW].

The delta crank angle dwmsνsνg refers to that part of the rising edge of the drive cam for the reciprocating piston fuel pump that is conceptually used for the compression interval.

LIST OF REFERENCE NUMBERS

10

Fuel tank

12

Fuel pump

14

Fuel filter

16

Hub Piston Fuel Pump or High Pressure Pump (HDP)

18

High-pressure rail

20

High Pressure Injection Valves (HDEV)

22

Return line

24

Pressure relief valve (DBV)

26

Engine control unit / ECU)

28

Low Pressure Sensor

30

High pressure sensor

32

power output stage

34

line

36

High pressure side

38

Low pressure side

40

piston

42

cylinder

44

Quantity switch / quantity control valve

46

supply line

48

check valve

50

Graph: the movement of the piston 40

52

Top Dead Center

54

bottom dead center

56

filling

58

compression

60

Arrow: Compression phase according to Concept I

62

Graph: Control signal for quantity control valve 44 (Concept I)

64

Graph: State of quantity control valve 44 (Concept I)

66

Condition: "open" (Concept I)

68

Condition: "closed" (Concept I)

70

Graph: Pressure in the compression space of the reciprocating piston fuel pump 16 (Concept I)

72

Low pressure p _{low pressure} (Concept I)

74

High pressure p _HD-rail (Concept I)

76

Arrow: Compression phase according to Concept II

78

Graph: Control signal for quantity control valve 44 (Concept II)

80

Graph: State of quantity control valve 44 (Concept II)

82

Condition: "open" (Concept II)

84

Condition: "closed" (Concept II)

86

Graph: Pressure in the compression space of the reciprocating piston fuel pump 16 (Concept II).

88

Low pressure p _{low pressure} (Concept II)

90

High pressure p _{HD rail} (Concept II)

92

horizontal axis

94

vertical axis

96

vevphh

98

vdaavst

100

vkdavst

102

vvlfghdp

dmkrhdev

Amount of fuel flowing in through the injectors in [g / min] calculated from valve opening times.

dwmsvsvg

Deltakurbelwinkel, the quantity control station remains closed in [° KW]. Survey curve_cock ( skhdp ) Characteristic describing a geometry of a rising flank of a drive cam of the camshaft for the reciprocating piston fuel pump for the required compression stroke skhdp .

ishdpvst

Number of load cycles of the reciprocating piston fuel pump per minute in [1 / min].

kmeshdp

Fuel mass that flows through the metering station into the high-pressure rail per stroke in [g / stroke stroke-piston fuel pump].

kmphvst

Fuel mass extraction through the injection valves from the high-pressure rail per stroke of the reciprocating piston fuel pump in [g / Hub Hub-Koiben-Kraftstoffpumpe].

lfgrhdp

Degree of delivery when filling the compression space of the reciprocating piston fuel pump [dimensionless].

nahdpanz

Number of cams on the camshaft for driving the reciprocating piston fuel pump [dimensionless].

nmot

Engine speed in [rpm].

nnw

Camshaft speed in [1 / min].

p _{low pressure}

Fuel pressure on a low pressure side in [kPa].

p _norm

Standard pressure in [bar].

p _rail

Pressure in the high-pressure rail in [bar].

Δ p

Pressure change in [bar].

Δp _{soll_rail}

Changing the setpoint pressure in the high-pressure rail [bar / stroke-piston-fuel pump].

Q _fuel )

Kraftstoffmassenfluß

r _piston

Radius of the piston of the reciprocating piston fuel pump [mm].

ρ _krarvst

Density of the fuel when flowing out of the high pressure rail in [g / mm ³ ].

ρ _rohnvst

Standard density of the fuel (depending on the grade) in [g / mm ³ ].

skhdp

Compression stroke, which is more necessary for the total volume to be compressed νkhdpνst [mm].

t _emotr

Temperature engine block [° C].

t _eulr

Ambient air temperature in the engine compartment [° C].

tflνrhdp

Temperature of the fuel flowing into the compression chamber in [° C].

t _Krail

Temperature in the high-pressure rail 18 [° C].

t _krailnp

Temperature due to compression work in reciprocating piston fuel pump 16 [° C].

V _HDRL

Volume of the entire high-pressure area consisting of high-pressure rail and high-pressure lines in [mm ³ ].

V _comp

Fuel volume in the compression chamber at pressure compensation in [mm ³ / Hub Hub Piston Fuel Pump].

V _{compression space}

Volume of the compression space of the reciprocating piston fuel pump in [mm ³ ].

νdaaνst

Fuel volume, which is required for a change in the setpoint pressure Δp _{soll_rail} in the high-pressure _rail , in [mm ³ / stroke stroke piston fuel pump].

νeνphh

Fuel volume extraction from the high-pressure rail through the injection valves in [mm ³ / stroke stroke piston fuel pump].

νkdaνst

Stroke volume which the piston of the reciprocating piston fuel pump requires to compress the fuel from low pressure to high pressure rail pressure in [mm ³ / stroke stroke piston fuel pump].

νkhdpνst

For each stroke of the reciprocating piston fuel pump, the total volume to be compressed [mm ³ ].

vtotraum

Fuel volume in the compression chamber of the reciprocating piston fuel pump at the end of the compression process in [mm ³ / stroke stroke piston fuel pump].

vvlfghdp

Volume loss due to less than optimal delivery due to vapor formation in the fuel per stroke of the reciprocating piston fuel pump [mm ³ ].

_Khdp

Compressibility of the fuel flowing into the compression space of the reciprocating piston fuel pump in [1 / bar].

χ _Krail

Compressibility of the fuel in the high-pressure rail in [1 / bar].

Claims (13)

1. Method for the pilot control of a reciprocating piston fuel pump of an internal combustion engine, particularly of a motor vehicle, the internal combustion engine comprising a high-pressure rail and injection valves connected thereto, characterized in that closing and opening times for a fuel feed control mechanism of the reciprocating piston fuel pump are determined from the input values for the fuel volumetric withdrawal for, a fuel volume vdaavst, which is needed for a variation of the set-point pressure Δp_{soll_rail} in the high-pressure rail per stroke of the reciprocating piston fuel pump, for a swept volume vkdavst, which the piston of the reciprocating piston fuel pump needs for compression of the fuel from low pressure to the pressure in the high-pressure rail per stroke of the reciprocating piston fuel pump, and the volumetric loss vvlfghdp through non-optimal volumetric efficiency due to vapour bubble formation in the fuel per stroke of the reciprocating piston fuel pump, closing and opening times are determined for a fuel feed control mechanism of the reciprocating piston fuel pump.
2. Method according to Claim 1, characterized in that a total volume vkhdpvst to be compressed per stroke of the reciprocating piston fuel pump is calculated as the sum of: $$vkhdpvst=vevphh+vkdavst+vdaavst+vvlfghdp\mathrm{.}$$

   
3. Method according to Claim 2, characterized in that from the total volume vkhdpvst to be compressed a compression stroke skhdp of the piston of the reciprocating piston fuel pump required for this is calculated according to $$\mathit{skhdp}\mathit{=}\frac{\mathit{vkhdpvst}}{\mathit{\pi }\mathit{*}{\mathit{r}}_{\mathit{Kolben}}^2}$$

   

   
   where r_Kolben is a radius of the piston of the reciprocating piston fuel pump.
4. Method according to Claim 3, characterized in that the reciprocating piston fuel pump is driven by a camshaft of the internal combustion engine, closing and opening times being determined as a delta crank angle dwmsvsvg, for which the fuel feed control mechanism remains closed, according to $$dwmsvsvg=Erhebungskurve\_Nocken\left(skhdp\right),$$

   

   
   the function Erhebungskurve_Nocken (skhdp) describing a geometry of a rising flank of a drive cam of the camshaft for the reciprocating piston fuel pump in the form of a characteristic curve for the required compression stroke skhdp.
5. Method according to at least one of the preceding claims, characterized in that the fuel volumetric withdrawal vevphh is calculated according to $$\mathit{vevphh}\mathit{=}\frac{\mathit{kmphvst}}{{\mathit{\rho }}_{\mathit{krarvst}}}$$

   

   
   where kmphvst is a fuel mass withdrawal by the injection valves from the high-pressure rail per stroke of the reciprocating piston fuel pump and ρ_krarvst is a density of the fuel as it flows out of the high-pressure rail.
6. Method according to Claim 5, characterized in that the fuel volumetric withdrawal kmphvst is calculated according to $$\mathit{kmphvst}\mathit{=}\frac{\mathit{dmkrhdev}}{\mathit{ishdpvst}},$$

   

   
   where dmkrhdev is a quantity of fuel flowing through the injection valves calculated from valve opening times and ishdpvst is a number of load cycles of the reciprocating piston fuel pump per min.
7. Method according to Claim 6, characterized in that the number of load cycles of the reciprocating piston fuel pump ishdpvst is calculated according to $$ishdpvst=nnw*nahdpanz$$

   

   
   where nnw is a camshaft speed and nahdpanz is a number of cams on the camshaft for driving the reciprocating piston fuel pump.
8. Method according to at least one of Claims 5 to 7, characterized in that ρ_krarvst is calculated according to $${\rho }_{\mathit{krarvst}}=\frac{{\rho }_{\mathit{rohnvst}}}{1-\left(\left({\mathit{p}}_{\mathit{rail}}\mathit{-}{\mathit{p}}_{\mathit{norm}}\right)*{\chi }_{\mathit{Krail}}\right)},$$

   

   
   where ρ_rohnvst is a standard density of the fuel, p_rail is a pressure in the high-pressure rail, P_norm is a standard pressure and χ_Krail is a compressibility of the fuel in the high-pressure rail.
9. Method according to at least one of the preceding claims, characterized in that the fuel volume vdaavst is calculated according to $$\mathit{vdaavst}=\mathrm{\Delta }{p}_{\mathit{soll\_rail}}*V_{\mathit{HDRL}}*{\chi }_{\mathit{Krail}},$$

   

   
   where Δp_{soll_rail} is a variation of the set-point pressure in the high-pressure rail, V_HDRL is a volume of the total high-pressure area comprising the high-pressure rail and the high-pressure lines and χ_Krail is a compressibility of the fuel in the high-pressure rail.
10. Method according to Claim 9, characterized in that Δp_{soll_rail} is greater than 0 when a set-point pressure gradient is positive, and in that Δp_{soll_rail} is less than 0 when a set-point pressure gradient is negative.
11. Method according to at least one of the preceding claims, characterized in that the swept volume vkdavst is calculated according to $$\mathit{vkdavst}=\frac{{\chi }_{\mathit{Khdp}}*\mathrm{\Delta }p*V_{\mathit{komp}}}{1-\mathrm{\Delta }p*{\chi }_{\mathit{Khdp}}},$$

    

    
    where χ_Khdp is a compressibility of the fuel as it flows into the compression chamber of the reciprocating piston fuel pump, Δp is a pressure variation and V_komp is a fuel volume, which is present during pressure equalization in the compression chamber.
12. Method according to Claim 11, characterized in that the fuel volume V_komp is calculated according to $$V_{komp}=vevphh+vdaavst+vtotraum,$$

    

    
    where vtotraum is a fuel volume in the compression chamber of the reciprocating piston fuel pump at the end of the compression process.
13. Method according to at least one of Claims 1 to 10, characterized in that the fuel feed control mechanism is closed at a bottom dead centre of the piston of the reciprocating piston fuel pump, the swept volume vkdavst being calculated according to $$\mathit{vkdavst}\mathit{=}{\mathit{\chi }}_{\mathit{Khdp}}\mathit{*}\mathrm{\Delta }p\mathit{*}{\mathit{V}}_{\mathit{Kompressionsraum}},$$

    

    
    where V_{Kompressionsraum} is a volume of the compression chamber of the reciprocating piston fuel pump, Δp is a pressure variation and χ_Khdp is a compressibility of the fuel as it flows into the compression chamber of the reciprocating piston fuel pump.

Images