Measuring and testing – Test stand – For engine
Reexamination Certificate
1999-06-14
2001-09-11
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Test stand
For engine
Reexamination Certificate
active
06286365
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of determining respective segment times between corresponding pairs of equally spaced marks provided on a rotating body, especially a transducer disk, connected to a camshaft of an internal combustion engine.
2. Prior Art
For regulating internal combustion engines, the rpm of the crankshaft and/or camshaft of the engine is always needed. From the position of these shafts, when trigger signals for certain components must be generated can be determined. For example, the time when current must be supplied to a particular injection valve so that the most optimal possible combustion event can proceed in the associated cylinder is dependent on the position of the crankshaft and/or camshaft of a Diesel engine.
To determine the angular position of the crankshaft and/or camshaft of an internal combustion engine, sensors are typically used that each scan a transducer wheel connected to the crankshaft and the camshaft, respectively. The two transducer wheels typically have a characteristic sequence of angle markings or slits on their circumference. As these angle markings or slits move past the stationary sensors, voltages are induced in the sensors, and from the course of these voltages over time, the surface area of the applicable transducer disk can be derived. The sensor voltages are typically converted into square-wave signals to make them easier to evaluate. The position of each of the signal edges corresponds to a certain rpm of the crankshaft or camshaft.
In Diesel engines currently in use, the transducer disk connected to the crankshaft, in a rotating cylinder engine, has 60-3·2 teeth, and the distribution of the teeth or angle markings is such that three gaps are formed, and between each two gaps there are 18 teeth, spaced apart by equal angles from one another. The disk connected to the camshaft has six slits, for six cylinders, and the slits are spaced apart by equal angles. A seventh slit is disposed between the first and second slits and serves as a reference marking; it is only slightly distant from the first slit, for instance by a camshaft angle of 15°.
When the engine is started, it is brought to a starting rpm with the aid of a starter. The crankshaft and the camshaft then rotate at a relatively constant rpm; it is well known that the crankshaft rotates at twice the speed of the camshaft. No later than after one revolution of the camshaft, a synchronization can be effected, since the seventh tooth is recognized as the synchronizing tooth. From this instant on, during normal operation, the correct injection can be begun. The requisite trigger signals are output by the engine control unit, which processes the output signals of the sensors. For instance, the engine control unit trips the delivery of current to the injection valves or the onset of pumping at the correct instant, thus enabling optimal regulation of the engine. Since the transducer disk on the crankshaft has many teeth, a signal is produced that has pulses in rapid succession; exact engine regulation is thus possible, in the normal situation. If under unfavorable conditions the crankshaft sensor fails, emergency operation should be possible with the camshaft sensor alone.
SUMMARY OF THE INVENTION
It is an object of the present invention to enable reliable starting and continued operation of the engine without a crankshaft signal, especially in starting. It is also the object of the invention however, to disclose a general method in which reliable engine regulation, especially in starting, can be performed using a relatively coarse angle signal.
This object is attained by a method for determining segment times required for controlling an internal combustion engine provided with a camshaft, the method comprising the steps of:
a) providing a transducer disk connected to the camshaft with a plurality of markings on it which are equally spaced from each other around the transducer disk so that the transducer disk rotates with the camshaft;
b) measuring respective segment times between corresponding pairs of the markings on the transducer disk by means of a camshaft sensor;
c) triggering corresponding fuel injection events and thus combustion events in the internal combustion engine in order to trip acceleration events at a substantially constant camshaft rotation speed; and
d) determining, in response to the triggering of step c), a resulting acceleration quotient for a current segment time, this acceleration quotient equaling the current segment time divided by a formerly measured segment time immediately prior to the current segment time; and
e) correcting a following segment time obtained during the measuring by means of the acceleration quotient for the current segment time.
The method however is not performed when the internal combustion engine has a crankshaft with a crankshaft sensor for measuring crankshaft rotation speed and a crankshaft sensor signal from the crankshaft sensor is detected.
The method according to the invention for determining segment times has the advantage that in conjunction with a conventional internal combustion engine control unit, it enables reliable engine regulation even in the absence of a crankshaft sensor signal, and that particularly in starting it enables fast, accurate determination of trigger pulses. In simple engines that have only a transducer disk connected to the camshaft, fast and reliable regulation is also possible, and again this is especially true for starting.
These advantages are attained in that the segment times, which are determined in accordance with the chronological spacing between two markings spaced apart by the same angle from one another; in starting, at a substantially constant rpm, a first acceleration event is first tripped, and the associated segment time T
k
and the associated acceleration quotient Q
k
are calculated, and after that two further acceleration events are tripped, and the first acceleration event is taken into account by means of the first, adapted acceleration quotient, while the second acceleration event is determined from a newly determined segment time. After that, three successive acceleration events are tripped, and the rpm change in the first two acceleration events is determined with the aid of the acceleration quotient, while the third acceleration event is again determined from the associated segment time. After that, a dynamic correction of the expected segment times can be performed.
Further advantages of the invention are attained by the provisions recited in the dependent claims. It is especially advantageous that the acceleration phases are tripped by supplying current to the selectable injection valve or injection valves. In conventional engines, the method of the invention can advantageously be performed as an emergency operation provision, if the crankshaft incremental sensor is defective. In simple systems, which have only a low-resolution transducer, an improvement in the accuracy of control is achieved with the method of the invention, because acceleration-dictated changes in the rpm can be detected and compensated for or adapted.
REFERENCES:
patent: 5325833 (1994-07-01), Fukui et al.
patent: 5377535 (1995-01-01), Angermaier et al.
patent: 5554802 (1996-09-01), Fukui et al.
Lang Tobias
Zimmermann Michael
Davis Octavia
Fuller Benjamin R.
Robert & Bosch GmbH
Striker Michael J.
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