WO2011134853A1

WO2011134853A1 - Method for operating an internal combustion engine, and internal combustion engine

Info

Publication number: WO2011134853A1
Application number: PCT/EP2011/056288
Authority: WO
Inventors: Thomas Kraft; Tobias Ritsch; Sandra Mueller; Wolfgang Stapf; Hans Riepl
Original assignee: Continental Automotive Gmbh
Priority date: 2010-04-27
Filing date: 2011-04-20
Publication date: 2011-11-03
Also published as: DE102010018467A1; DE102010018467B4

Abstract

The invention relates to a method for operating an internal combustion engine and to an internal combustion engine. The internal combustion engine has an injection system with a common-rail system and a stop & start functionality. Using the method, the specific E modulus of the fuel that is used for operating the internal combustion engine is ascertained by a targeted analysis of injection impulses, and the expected pressure build-up value of the injection system during the start phase of the internal combustion engine is obtained therefrom. If the ascertained expected pressure build-up value does not correspond to a sufficient pressure build-up, the stop & start function is deactivated in order to ensure consistent starting conditions.

Description

description

Method for operating an internal combustion engine and internal combustion engine

The present invention relates to a method for operating an internal combustion engine with a common rail injection system and a stop-start functionality.

Due to the increasingly important CC> 2 requirements, automobile manufacturers are trying to reduce CC> 2 emissions in all areas. For this purpose, the so-called Stop & Start strategy was developed. This causes the engine to be switched off, for example, if you have to stop at a traffic light. As soon as z. B. the accelerator pedal is reactivated to continue, automatically restarts the engine. It is important that the time between activation and engine startup is as short as possible and also reproducible (constant). While it was still required in EUR05 applications to achieve the injection release for the 3 engine TDC, the release for the release of the 2 engine TDC is now required for EUR06 applications. In the worst case, this means for a 4-cylinder engine, a crank angle of z. B. 215 ° (nominal engine stop position 90 ° BTDC (bottom dead center) + 50 ° tolerance, worst case stop position corresponds to 220 ° crankshaft minus 5 ° crankshaft for the first pilot injection). When using such a stop-and-start strategy in an internal combustion engine provided with an injection system, in particular in injection systems with leakage-prone injectors, the pressure build-up in the injection system is of crucial importance. With a reproducible, ie constant pressure build-up can be achieved a constant period of time until reaching the injection release pressure and thus the starting or restarting of the engine. The present invention is based on the object

To provide method for operating an internal combustion engine, with which the stop-start functionality of the internal combustion engine can be optimized, in particular with respect to a reproducible (constant) time between activation and restart of the engine.

This object is achieved by a method for operating an internal combustion engine having a common-rail injection system and a stop-start functionality, comprising the following steps:

Defined setting of an injection test pulse during nearly constant rail pressure; Determining the resulting pressure drop (Δρ) in the rail or in the entire hydraulic high-pressure volume (V);

Determining the specific modulus of elasticity of the fuel used for operating the internal combustion engine from the specific pressure drop (Δρ), the total hydraulic high pressure volume (V) of the injection system and the volume extraction (Δν) from the high pressure volume;

Determining the anticipated pressure buildup value of the injection system during the starting phase of the internal combustion engine from the determined modulus of elasticity, the total hydraulic high pressure volume (V) and the delivery rate of the high pressure pump of the injection system; and Use the specific estimated pressure build-up value to control Stop & Start functionality.

With the method according to the invention, the anticipated pressure buildup value of the injection system is determined. This anticipated pressure buildup value plays a significant role in the Stop & Start functionality employed, as noted above, and can be used to control, adjust or optimize it. In particular, a reproducible (constant) period of time can be achieved until the injection release pressure is reached and thus the engine is started or restarted. If an insufficient presumed pressure build-up value is determined, for example, the Stop & Start function can be deactivated to avoid starting times of different lengths. In particular, deactivation of the stop-and-start function may take place if an insufficient presumed pressure build-up value for reaching the second engine TDC is determined.

The pressure build-up in a common-rail injection system is i.a. from the delivery volume of the high pressure pump of the injection system, the size of the entire hydraulic high pressure volume thereof, the leakage of the injectors used, the fuel temperature and the fuel used and thus of the modulus of elasticity. Physically, this can be detected by the formula Δρ = Ε * Δν / ν. This makes it clear that the pressure build-up in the system depends crucially on the modulus of elasticity (elastic modulus) of the fuel used.

With the method according to the invention, the estimated pressure build-up value is now determined by determining the modulus of elasticity of the fuel used for the system used in each case. In this case, a defined spark test pulse set during almost constant rail pressure. This happens during a non-promotion of the high-pressure pump of the injection system. "Nearly constant" here means that the rail pressure is not quite constant due to the permanent leaching of the system.This test pulse can be determined during a nearly constant rail pressure (during non-production The pressure drop is determined (via the rail pressure sensor) and the modulus Δρ = Ε * Δν / ν is used to determine the modulus of elasticity The injection timing of the injector and the corresponding Ti-map for the injector can also be used to determine the volume extraction (AV) from the high-pressure volume.The Ti-Map indicates the quantities of fuel depending on pressure, temperature and Ansteuerzeit injected and thus removed from the entire hydraulic high pressure volume.

From the determined in this way specific modulus of elasticity, the total hydraulic high pressure volume (V) and the capacity of the high pressure pump used can also be determined (calculated) over the relationship Δρ = Ε * Δν / ν the expected pressure build-up value, especially for a

Crank angle of 215 ° in a four-cylinder engine. Δν (volume change in the entire hydraulic high-pressure system) depends on the pump delivery rate (no injection yet takes place).

According to the invention, the stop-and-start functionality is preferably optimized in such a way that it is deactivated when a prospective pressure build-up value which is insufficient for the restart is determined, in particular when a insufficient pressure is detected for the second engine TDC. In this way, different start times can be avoided. In general, a deactivation of the Stop & Start function can be carried out with a low modulus of elasticity of the fuel or with a low presumed pressure build-up value in order to be able to ensure consistent starting conditions.

The method according to the invention can be used in particular for injectors which are subject to leakage but also leak-free.

The invention further relates to an internal combustion engine having a common rail injection system with a high-pressure pump and a stop-start functionality and a controller for these systems, wherein the controller is designed to carry out a method of the type described above. The injection system of the internal combustion engine is designed such that an injection test pulse can be set in a defined manner during a constant rail pressure.

The invention will be explained below with reference to an embodiment in conjunction with the drawings in detail. Show it:

Figure 1 is a diagram crank angle pressure, which shows the example of pressure buildup of an injection system in the starting phase;

Figure 2 is a diagram in which the rail pressure and the In jector voltage are shown, wherein the fall from the rail pressure ge by a test pulse shows is; FIG. 3 shows an example of a Ti-map for an injector type at a defined temperature;

FIG. 4 is a flow chart of the method; and

Figure 5 shows the schematic structure of an internal combustion engine.

With the method according to the invention, the anticipated pressure build-up value in the injection system during the starting phase of an internal combustion engine is determined from the modulus of elasticity of the fuel and the delivery rate of the high-pressure pump of the injection system. FIG. 1 shows such an exemplary pressure build-up. At a crank angle of z. B. 215 ° is in the system a pressure of z. B. reached 82.3 bar. If the presumed pressure buildup value determined according to the invention is below the necessary injection release pressure of the injectors, deactivation of the stop & start function takes place in order to be able to ensure consistent start conditions.

To determine the probable pressure increase value of the system, the specific modulus of elasticity of the fuel used for operating the internal combustion engine is determined. This is calculated from the pressure drop Δρ in the rail, which results from a defined injection test pulse during almost constant rail pressure.

FIG. 2 shows the effect of an injection test pulse on the pressure drop Δρ in the rail. The modulus Δρ = Ε * Δν / ν is used to calculate the modulus of elasticity. Δρ is here, as stated above, obtained by targeted evaluation of such Einspritzitztestimpulsen (measurement via the rail pressure sensor). The entire high pressure hydraulic volume (V) of the injection system is known. ΔΥ, ie the volume extraction from the high-pressure volume through the injection performed, is obtained from the drive time of the injector and the Ti-map for the injector. This value Δν can be corrected by the known amounts of the permanent leakage and the switching leakage of the injectors for the respective operating states. To determine the volume extraction from the entire hydraulic high-pressure volume, the valid for the respective rail pressure and the fuel temperature in the rail Ti-map is used. To determine the fuel temperature in the rail, the TFU model of the ECU is used. The so-called TFU model calculated by various temperature sensors, eg. B. inlet, cooling water, etc., operating point dependent, that is, depending on z. B. rail pressure, etc., the temperature in the rail or in the entire hy-draulic high-pressure volume.

FIG. 3 shows a Ti map for an injector type at a defined temperature (injection quantity as a function of the rail pressure) for eleven different actuation times ti in ms. After calculating the modulus of elasticity in the manner described above is also on the relationship Δρ = Ε * Δν / ν and the capacity of the high-pressure pump used in the injection system and the value V of the expected pressure build-up value after a crank angle of z. B. 215 ° precalculated. If the calculated expected pressure build-up value is below the

Injection release pressure of the injectors, the Stop & Start function is deactivated in order to be able to ensure consistent starting conditions in this way. FIG. 4 shows a flowchart of the method performed. In a first step, a test pulse is set. In a second step, the calculation of the modulus of elasticity follows the pressure drop Δρ. In a further step, the expected pressure build-up value is then calculated. Is the calculated If the expected pressure increase above the injection release pressure of the injector, the Stop & Start function is activated. If the expected pressure build-up value is below the injection enable pressure of the injector, the Stop & Start function is deactivated.

Figure 5 shows the schematic structure of an internal combustion engine, in which the inventive method is applied. The internal combustion engine has an engine block 2 with a cylinder head 3, an exhaust tract 4 and a suction pipe 7. In the engine block 2 is a combustion chamber 9 with a piston 11 disposed therein, which is connected via a connecting rod 10 with a crankshaft 8. Furthermore, an intake valve 12, an exhaust valve 13 and a Kraftstoffeinspritzven- valve 18 are shown. The exhaust tract 4 contains a catalytic converter 23 and an exhaust gas probe 38. The crankshaft 8 is assigned a crankshaft angle sensor 36.

The internal combustion engine further has an injection system to which the aforementioned injector 39 with fuel injection valve 18 belongs. The injection system has a common rail 5, from which a high-pressure fuel line 27 leads to the injector 39. The common rail 5 is supplied with fuel from a fuel tank 24 via a low pressure fuel passage 30, a flow control valve 21, a high pressure pump 6, and a pressure control valve 20. A rail pressure sensor 26 measures the pressure prevailing in the common rail. Via a leakage line 40, fuel is returned from the injector 39 and the pressure regulating valve 20 to the fuel tank 24.

The internal combustion engine further comprises a control device 25, which controls the operation of the injection system in response to various signal inputs 28, for example from Rail pressure sensor 26, controls. The control device 25 controls the volume flow control valve 21, the high pressure pump 6, the pressure control valve 20 and the injector 39 via signal outputs 29. The control device 25 is further designed such that the method illustrated in the flowchart of FIG. 4 is hereby carried out. In other words, the control device 25 controls the injector 39 so as to set a test pulse, and performs the calculation of the modulus of elasticity on the pressure drop as well as the calculation of the provisional pressure buildup value. Further, it performs a comparison of the calculated preliminary pressure increase value with the injection release pressure of the injector and activates and deactivates the stop-start function of the internal combustion engine.

Claims

claims

1. A method for operating an internal combustion engine with a common rail injection system and a stop

Start-up functionality, comprising the steps of: defining an injection test pulse during near-constant rail pressure;

Determining the resulting pressure drop (Δρ) in the rail or in the entire hydraulic high-pressure volume;

Determining the specific modulus of elasticity of the fuel used to operate the internal combustion engine from the determined pressure drop (Δρ), the total hydraulic high pressure volume (V) of the injection system and the volume extraction (Δν) from the high pressure volume;

Determining the anticipated pressure buildup value of the injection system during the starting phase of the internal combustion engine from the determined modulus of elasticity, the total hydraulic high pressure volume (V) and the delivery rate of the high pressure pump of the injection system; and

Use the specific estimated pressure build-up value to control Stop & Start functionality. A method according to claim 1, characterized in that the stop & start functionality is deactivated when a not sufficient for restarting expected Druckauf Auwert is determined

A method according to claim 2, characterized in that the stop & start functionality is deactivated when an insufficient pressure build-up value for the second engine TDC is determined.

Method according to one of the preceding claims, characterized in that it is used for operating an internal combustion engine with leakage-laden injectors.

Method according to one of the preceding claims, characterized in that it is used for setting a constant period of time until reaching the injection release pressure for the restart.

Method according to one of the preceding claims, characterized in that the volume extraction (AV) is determined from the high pressure volume from the present for the special injector Ti map.

Method according to one of the preceding claims, characterized in that the prospective pressure build-up value from the relationship Δρ = Ε * Δν / ν is determined.

Internal combustion engine with a common-rail injection system with a high-pressure pump and a stop-start functionality and a controller for the Systems, characterized in that the controller is designed to carry out a method according to one of the preceding claims.