Method and device for operating an internal combustion engine and carrying out a correction of the fuel injection quantity by correlation of a fuel pressure change
The disclosure relates to a method for operating an internal combustion engine which has at least one injector and in which a correction of fuel injection quantity is implemented. For the correction of the fuel injection quantity, different properties of the injector in the ballistic working range thereof and in the linear working range thereof are evaluated. A total injection quantity of the injector demanded in an operating cycle is divided into a number of smaller, equal partial injection quantities implemented as partial pulses, and an evaluation of the pressure drops triggered by the partial pulses is performed in the correction of the fuel injection quantity. The disclosure furthermore relates to a device for operating an internal combustion engine which has at least one injector and in which a correction of the fuel injection quantity is implemented.
1. A method for operating an internal combustion engine having at least one injector, the method comprising:
evaluating different properties of the at least one injector in a ballistic working range and in a linear working range;
dividing a total injection quantity of the injector demanded in an operating cycle into a number of smaller, identical partial injection quantities;
implementing the number of smaller, identical partial injection quantities as partial pulses;
detecting an error in an opening behavior of the injector in the ballistic working range of the injector;
measuring a pressure drop triggered by each partial pulse;
determining a sum of the pressure drops triggered by the partial pulses;
comparing a sum of the pressure drops triggered by each partial pulse with a stored nominal pressure drop for a required total injection quantity; and
implementing a correction of a fuel injection quantity based on pressure drops triggered by the partial pulses;
wherein the error in the opening behavior of the injector is determined based on a difference between an expected pressure drop dp X of a single pulse X with a mass dm x and a measured pressure drop dp i,m that results at the number i in a sequence of all partial pulses XE with a mass dm XE,i and a total mass dm XE , as well as based on a fuel density ρ(p,T), a pressurized system volume V, and a bulk modulus B s (p,T) of the fuel.
2. The method of claim 1 , further comprising:
measuring the pressure drop triggered by a partial pulse; and
determining a sum of the pressure drops triggered by the partial pulses.
3. The method of claim 1 , wherein the error in the opening behavior of the injector is determined according to the following correlation:
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4. The method of claim 1 , further comprising:
detecting an error in a flow behavior of the injector in the linear working range of the injector.
5. The method of claim 1 , further comprising:
determining errors in an opening behavior and in a flow behavior of the injector for a plurality of different total injection quantities and respective associated different partial injection quantities.
6. The method of claim 1 , further comprising:
performing an offset correction for an operating point of the injector is by adapting a control duration of a determined characteristic curve to a predefined nominal characteristic curve.
7. The method of claim 6 , further comprising:
determining a deviation of a gradient of a determined fuel injection quantity characteristic curve in relation to a nominal fuel injection quantity characteristic curve; and
correcting the determined deviation by a gradient correction of the determined fuel injection quantity characteristic curve.
8. The method of claim 7 , wherein the correction for the ballistic working range and for the linear working range of the injector takes place separately.
9. A method for operating an internal combustion engine having at least one injector, the method comprising:
evaluating different properties of the at least one injector in a ballistic working range and in a linear working range;
dividing a total injection quantity of the injector demanded in an operating cycle into a number of smaller, identical partial injection quantities;
implementing the number of smaller, identical partial injection quantities as partial pulses;
detecting an error in an opening behavior of the injector in the ballistic working range of the injector;
detecting an error in a flow behavior of the injector in the linear working range of the injector; and
implementing a correction of a fuel injection quantity based on pressure drops triggered by the partial pulses,
wherein the error in the flow behavior of the injector is determined based on a difference between a theoretical pressure drop dp X of a single pulse X with a mass dm x and a difference between a pressure drop dp x,m in the case of a real, erroneous mass dm x,r being dispensed as a single pulse in linear injector operation and a measured pressure drop dp i,m that results at the number i in a sequence of all partial pulses XE with a mass dm XE,i , and a total mass dm XE , and based on a fuel density ρ(p,T), a pressurized system volume V, and a bulk modulus B s (p,T) of the fuel.
10. A device for carrying out a method for operating an internal combustion engine having at least one injector, the device comprising:
a control unit configured for controlling the method for operating an internal combustion engine having at least one injector, the method comprising:
evaluating different properties of the at least one injector in a ballistic working range and in a linear working range;
dividing a total injection quantity of the injector demanded in an operating cycle into a number of smaller, identical partial injection quantities;
implementing the number of smaller, identical partial injection quantities as partial pulses;
detecting an error in an opening behavior of the injector in the ballistic working range of the injector;
detecting an error in a flow behavior of the injector in the linear working range of the injector; and
implementing a correction of a fuel injection quantity based on pressure drops triggered by the partial pulses;
wherein the error in the flow behavior of the injector is determined based on a difference between a theoretical pressure drop dp X of a single pulse X with a mass dm x and a difference between a pressure drop dp x,m in the case of a real, erroneous mass dm x,r being dispensed as a single pulse in linear injector operation and a measured pressure drop dp i,m that results at the number i in a sequence of all partial pulses XE with a mass dm XE,i , and a total mass dm XE , and based on a fuel density ρ(p,T), a pressurized system volume V, and a bulk modulus B s (p,T) of the fuel.
11. The device of claim 10 , wherein the method further comprises:
measuring the pressure drop triggered by a partial pulse; and
determining a sum of the pressure drops triggered by the partial pulses.
12. The device of claim 10 , wherein the method further comprises:
measuring the pressure drop triggered by each partial pulse; and
determining a sum of the pressure drops triggered by the partial pulses.
13. The device of claim 12 , wherein the method further comprises:
comparing a sum of the pressure drops triggered by each partial pulse with a stored nominal pressure drop for the required total injection quantity.
14. The device of claim 10 , wherein the error in the flow behavior of the injector is determined according to the following correlation:
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=
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-
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15. A device for carrying out a method for operating an internal combustion engine having at least one injector, the device comprising:
a control unit configured for controlling the method for operating an internal combustion engine having at least one injector, the method comprising:
evaluating different properties of the at least one injector in a ballistic working range and in a linear working range;
dividing a total injection quantity of the injector demanded in an operating cycle into a number of smaller, identical partial injection quantities;
implementing the number of smaller, identical partial injection quantities as partial pulses; and
implementing a correction of a fuel injection quantity based on pressure drops triggered by the partial pulses;
detecting an error in an opening behavior of the injector in the ballistic working range of the injector;
measuring the pressure drop triggered by each partial pulse;
determining a sum of the pressure drops triggered by the partial pulses;
comparing a sum of the pressure drops triggered by each partial pulse with a stored nominal pressure drop for the required total injection quantity,
wherein the error in the opening behavior of the injector is determined based on a difference between an expected pressure drop dp X of a single pulse X with a mass dm x and a measured pressure drop dp i,m that results at the number i in a sequence of all partial pulses XE with a mass dm XE,i and a total mass dm XE , as well as based on a fuel density ρ(p,T), a pressurized system volume V, and a bulk modulus B s (p,T) of the fuel.