Internal-combustion engines – High tension ignition system – Having specific trigger circuitry
Patent
1983-01-27
1984-10-09
Nelli, Raymond A.
Internal-combustion engines
High tension ignition system
Having specific trigger circuitry
123414, F02P 304, F02P 100
Patent
active
044755260
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to inductive transducers used in motor vehicle ignition systems, and more particularly to an improved circuit for deriving a digital output from the signal produced by the transducer.
It is known, especially in ignition systems, to use inductive transducer arrangements, which supply voltages dependent on rotary speed. These voltages are delivered to a threshold stage, which furnishes a signal train dependent on rotary speed. As the rotary speed increases, the amplitude of the voltage emitted by the transducer normally increases as well. At a constant threshold value of the threshold stage, the range of shaft angle at which the threshold value is exceeded varies as a consequence of the increase in amplitude. The result is that the ignition system in which the transducer arrangement is used exhibits an inherent systematic error.
THE INVENTION
The apparatus according to the invention and having means for shifting the transducer voltage signal, in accordance with amplitude, before the voltage signal is applied to the input of the threshold stage has the advantage over the prior art that, as a result of the shift in voltage of the transducer signal, the thus-modified input signal of the threshold stage crosses over or under the threshold value at the same rotary angle despite varying amplitudes of the transducer voltages. An inherent systematic error on the part of the ignition system is thereby avoided or sharply reduced.
DRAWINGS
FIG. 1, a circuitry realization of the exemplary embodiment;
FIG. 2, voltage courses for the apparatus according to the invention, plotted in accordance with time; and
FIG. 3, transducer voltages and the output voltage of the threshold stage, plotted in accordance with the rotary angle.
DETAILED DESCRIPTION
An inductive transducer arrangement 1, which can preferably be connected with the crankshaft or camshaft of an internal combustion engine or with some other shaft of an engine, is connected via a low-pass filter 2 with the cathode of a first diode 3 and the anode of a second diode 4, a first resistor 5 and a second resistor 6. Taken in order from the anode of the first diode 3, a first capacitor 7 is connected to ground, and a first discharge resistor 8 is located parallel to it. A third resistor 9 which is connected with the first resistor 5 is also connected with the anode of the first diode 3. The junction A of these two resistors 5, 9 is connected via a third diode 10 with the input of a threshold stage 11 embodied as a Schmitt trigger; the anode of the third diode is located at the junction A and the cathode is located at the input of the Schmitt trigger 11. Taken in order from the cathode of the second diode 4, a second capacitor 12 is connected to ground, and a second discharge resistor 13 is located parallel to it. The cathode of the second diode 4 is furthermore connected via a fourth resistor 14 with the second resistor 6. The junction B of these two resistors 6, 14 is connected via a fourth diode 15 to the input of the Schmitt trigger 11, and the cathode of the fourth diode 15 is located at the junction and the anode is located at the input of the Schmitt trigger 11. The junctions between the first and third resistors 5, 9 and between the second and fourth resistors 6, 14 are connected to ground via protective diodes 16-19. The resistors 9 and 14 are approximately twice as large as the resistors 5 and 6.
As shown in FIGS. 2 and 3, by means of the inductive transducer arrangement 1, an alternating voltage is generated in accordance with the rotary speed; this voltage is shown in FIG. 2 plotted in accordance with time and in FIG. 3 in accordance with the rotary angle. The transducer voltage is carried via the low-pass filter 2, in order to eliminate the high-frequency peaks. The first capacitor 7 charges via the first diode 3 to approximately the negative peak value of the transducer voltage and then discharges, with the first discharge resistor 8 and the third resistor 9 determining the discharge speed. The discharging pro
REFERENCES:
patent: 3943896 (1976-03-01), Green et al.
patent: 4271812 (1981-06-01), Bodig et al.
patent: 4308848 (1982-01-01), Pfaff et al.
patent: 4367721 (1983-01-01), Boyer
patent: 4398516 (1983-08-01), Momoyama
Nelli Raymond A.
Robert & Bosch GmbH
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