Measuring and testing – Vehicle chassis – Steering
Reexamination Certificate
2000-08-30
2002-06-11
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Vehicle chassis
Steering
Reexamination Certificate
active
06401527
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for determining the actual torque developed by an internal combustion engine by evaluating the trace of the rotational speed (rpm) of the crankshaft of the engine.
BACKGROUND OF THE INVENTION
It is known to provide a transducer disc or a transducer wheel having markings on the crankshaft of an internal combustion engine for detecting the position of the crankshaft. The transducer disc or transducer wheel is scanned by a fixed pickup. The transducer wheel is configured, for example, as a transducer toothed wheel having teeth as markings on the periphery of the transducer wheel. The pickup is configured, for example, as an inductive pickup wherein voltage pulses are induced by the teeth which run past with a rotation of the crankshaft and of the transducer toothed wheel. The time-dependent spacings of the voltage pulses or of the teeth of the transducer toothed wheel (the so-called tooth times) are measured. From the measured tooth times, the trace of the rpm of the crankshaft is then determined. In a subsequent evaluation step, the trace of the actual torque, which is developed by the engine, is determined from the trace of the rpm.
The actual torque of the engine is transmitted to a central control unit of the engine for optimizing the power characteristic, the noise performance and the exhaust gas performance of the engine. In conventional internal combustion engines having intake manifold injection, the air charge of the cylinders of the engine is measured for determining the actual torque developed by the engine. The actual torque can, however, be determined only in conventional engines which are operated with lambda=1 (wherein the air/fuel mixture is in the ratio of 1:1). In internal combustion engines of newer types and especially for so-called lean engines and stratified charge engines (direct injecting internal combustion engines; gasoline or diesel engines), which are operated up to lambda=10 (air/fuel mixture in the ratio of 10:1), the air charge of the cylinders remains constant and only the fuel quantity, which is injected into the cylinders, is varied. Therefore, the actual torque of the engine cannot be determined for the air charge of the cylinder in engines of the newer type. For this reason, the actual torque is determined, for example, from the rpm of the crankshaft of the engine.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of the above-mentioned kind which is so configured and improved that it operates simply and quickly and especially requires little computing power.
The method of the invention is for determining the actual torque (M_act) developed by an internal combustion engine by evaluating the trace of the rpm (n) of the crankshaft of the engine. The method includes the steps: determining the mean rpm (n_) from a trace of the rpm (n) in a work stroke of a piston of the engine; determining a first area (F
1
) between the trace of the rpm (n) in the first half of the work stroke and the mean rpm (n
13
); determining a second area (F
2
) between the trace of the rpm (n) in the second half of the work stroke and the mean rpm (n
13
); determining an index (A) for the actual torque (M_act) from one of: the difference of the first area (F
1
) and the second area (F
2
) or from the ratio of the first area (F
1
) to the second area (F
2
); and, determining the actual torque (M_act) developed by the engine from the index (A) for the actual torque (M_act).
In the method according to the invention, preferably an inductive rpm transducer is utilized. The rpm transducer includes, on the one hand, a transducer toothed wheel, which is assigned to the crankshaft of the engine, and, on the other hand, a fixed inductive pickup. Voltage pulses are induced in the pickup by the teeth which run by during a rotation of the crankshaft and of the transducer toothed wheel. The time-dependent intervals of the voltage pulses (that is, the teeth of the transducer toothed wheel), the so-called tooth times, are measured. The trace of the rpm of the crankshaft is then determined from the tooth times and the total number of teeth of the transducer toothed wheel. The trace of the rpm is plotted against the teeth of the transducer toothed wheel.
In the method of the invention, the rotational irregularity of the crankshaft is determined from the areas between the rpm trace and a mean rpm and is applied to determine the actual torque developed by the engine. In this way, an index for the actual torque can be determined in a simple manner and without a great complexity as to computations. This index is then converted into the actual torque developed by the engine. The actual torque can be determined with high accuracy from the area between the rpm trace and the mean rpm.
Each of the cylinders of the engine executes a work stroke during a two-time rotation of the crankshaft. Accordingly, the number of the teeth of the transducer toothed wheel included in a work stroke of a cylinder results from the quotient of the two-fold tooth number of the transducer toothed wheel and the number of the cylinders of the engine. When utilizing a 60-2 toothed wheel in a twelve cylinder engine, the result is that the work stroke of a cylinder includes ten teeth (2*60 teeth/12 cylinders=10). A 60-2 toothed wheel has 60 teeth on its periphery and two teeth thereof are only imaginary, that is, they are not actually configured and define gaps.
In the method of the invention, the difference (that is, the ratio of the first and the second areas in the first and second halves of the work strokes) are applied as characteristic variable. In the above-mentioned example, the first half of the work stroke therefore corresponds to five teeth of the transducer toothed wheel and the second half of the work stroke corresponds to the next five teeth. Starting from the first tooth of the transducer toothed wheel, the first half of the work stroke includes therefore the teeth
1
to
5
and the second half of the work stroke includes the teeth
6
to
10
. Starting from any desired tooth of the transducer toothed wheel, the work stroke can include any desired ten teeth. The first area and the second area can include a desired interval within the five teeth of the transducer toothed wheel. However, it is important that, in the determination of the index of the actual torque, for all work strokes, the same intervals are applied for the first area and the second area.
According to a preferred embodiment of the invention, it is suggested that the first area include the entire area between the trace of the rpm in the first half of the work stroke and the mean rpm. The first area is therefore determined in the complete interval of half the work stroke. In the above example, the interval, in which the first area is determined, includes all five teeth of the first half of the work stroke.
According to another preferred embodiment of the invention, it is proposed that the first area includes the area between the trace of the rpm in the first half of the work stroke and the mean rpm within one interval. The interval can have any desired magnitude within the particular half of the work stroke.
Likewise, and in accordance with another preferred embodiment of the invention, it is proposed that the second area include the total area between the trace of the rpm in the second half of the work stroke and the mean rpm.
Likewise, it is suggested in accordance with another preferred embodiment of the invention that the second area include the area between the trace of the rpm in the second half of the work stroke and the mean rpm within an interval.
The second embodiment of the method of the invention includes the steps of: determining a first extreme (E
1
) of the maximum rpm (n) in a work stroke of a cylinder of the engine; determining a second extreme (E
2
) of the minimum rpm (n) in a work stroke; determining an index (A) for the actual torque (M_act) from one of the difference of the first extreme (E
1
) and the second extreme (E
Fuller Benjamin R.
Ottesen Walter
Robert & Bosch GmbH
Stevens Maurice
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