Method for estimating quantity of fuel injected

1. A method for estimating a quantity of fuel injected into an internal combustion engine with a number of cylinders, comprising the steps of:

a) Injection and combustion of a test quantity of fuel in a cylinder of the internal combustion engine during a phase of deactivated fuel feed,

b) Determining a segment time T(k) of the internal combustion engine from signals of a crankshaft sensor,

c) Calculating the test torque C(k) generated by the combustion of the test quantity from a numerically determined second temporal derivation of the segment time T(k) and

d) Determining a size of the test quantity from the test torque C(k) calculated, based on a test quantity-test torque characteristic map.

2. The method as claimed in claim 1 , comprising the further step of:

Injection and combustion of a series of test quantities in one or in a plurality of phases of interrupted fuel feed of the internal combustion engine and

Calculating an average value of the test torque C(k) from the test torques which have been determined for each test quantity injected.

3. The method as claimed in claim 1 , comprising the further step of:

Calculating the test torque from the difference between the test torque after the injection of the test quantity and the test torque before the injection of the test quantity.

4. The method as claimed in claim 2 , comprising the further step of:

Recursive updating of the average value of the test torque with each further series of injected test quantities.

5. A method for estimating a quantity of fuel injected into an internal combustion engine, comprising the steps of:

a) Injection of a test quantity of fuel into a cylinder of the internal combustion engine during a phase of deactivated fuel feed,

b) Igniting the injected test quantity,

b) Determining a segment time T(k) from signals of a crankshaft sensor,

c) Calculating a test torque C(k) generated by the combustion of the test quantity from a numerically determined second temporal derivation of the segment time T(k) and

d) Determining a size of the test quantity from the test torque C(k), based on a test quantity-test torque characteristic map.

6. The method as claimed in claim 5 , comprising the further steps of:

Injection and combustion of a series of test quantities in one or in a plurality of phases of interrupted fuel feed of the internal combustion engine, and

Calculating an average value of the test torque C(k) from the test torques which have been determined for each test quantity injected.

7. The method as claimed in claim 5 , comprising the further step of:

Calculating the test torque from the difference between the test torque after the injection of the test quantity and the test torque before the injection of the test quantity.

8. The method as claimed in claim 7 , comprising the further step of:

Recursive updating of the average value of the test torque with each further series of injected test quantities.

9. A system for estimating a quantity of fuel injected into an internal combustion engine with a number of cylinders, comprising:

a) Means for Injecting and combusting of a test quantity of fuel in a cylinder of the internal combustion engine during a phase of deactivated fuel feed,

b) Means for determining a segment time T(k) of the internal combustion engine from signals of a crankshaft sensor,

c) Means for calculating the test torque C(k) generated by the combustion of the test quantity from a numerically determined second temporal derivation of the segment time T(k), and

d) Means for determining a size of the test quantity from the test torque C(k) calculated, based on a test quantity-test torque characteristic map.

10. The system as claimed in claim 9 , further comprising:

Means for injecting and combusting of a series of test quantities in one or in a plurality of phases of interrupted fuel feed of the internal combustion engine, and

Means for calculating an average value of the test torque C(k) from the test torques which have been determined for each test quantity injected.

11. The system as claimed in claim 9 , further comprising:

Means for calculating the test torque from the difference between the test torque after the injection of the test quantity and the test torque before the injection of the test quantity.

12. The system as claimed in claim 11 , further comprising:

Means for recursive updating of the average value of the test torque with each further series of injected test quantities.