Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1986-05-02
1988-10-11
Wolfe, Jr., Willis R.
Internal-combustion engines
Charge forming device
Fuel injection system
361153, F02D 500, G05F 158
Patent
active
047763140
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to a switching circuit for controlling the current through a consumer in accordance with the type of the preamble of the main claim.
A current controlled end stage for electromagnetic consumers is known from U.S. Pat. No. 4,492,913, whereby a field effect transistor assumes the function of the switching and the current measuring. Thereby, the voltage is simulated with the assistance of a capacitor which is connected parallel to the field effect transistor in accordance with the described exemplified embodiment.
It now had been shown that the described circuit does not provide an optimum behavior in conjunction with its resistance against short circuiting. For example, during a through switched field effect transistor and a sudden short circuit of the field effect transistor to the battery voltage a much too long reaction time of the circuit results until the switching off of the field effect transistor, so that the same is thermically severely overloaded.
ADVANTAGES OF THE INVENTION
In contrast to the described state of the art the switching circuit, in accordance with the invention, for controlling the current through an electrical consumer, in particular an electromagnetic consumer with the features of the main claim is advantageous in that substantially shorter reaction times are possible in the switching circuit after short circuits. This is obtained in accordance with the invention that the switching circuit can feed a current through the electrical consumer only with the assistance of a forced switching on.
Thereby, it is particularly advantageous to realize the forced switching on by means of a capacitor. Further advantageous embodiments and improvements of the device stated in the main claim in accordance with the invention are made possible by the measures stated in the subclaims.
DRAWING
One exemplified embodiment of the invention is illustrated in the drawing and explained in detail in the following description. The single FIGURE in the drawing illustrates a diagram of the switching circuit in accordance with the invention.
DESCRIPTION OF THE EXEMPLIFIED EMBODIMENT
The described exemplified embodiment relates to a switching circuit for controlling the current through an electrical consumer. In particular, the switching circuit in accordance with the invention is suitable for controlling and/or regulating the current through an electromagnetic consumer, for example, a magnetic valve. The described switching circuit may be used, for example, in conjunction with internal combustion engines, in particular during the injection of the fuel into the combustion chamber of the internal combustion engine with the assistance of a magnetic valve. However, in principal the switching circuit in accordance with the invention is not limited to these specific applications, but may be used in all cases where rapid reactions are required with respect to short circuits and overloads.
The single FIGURE of the drawing illustrates a realisation of the switching circuit in accordance with the invention. An electromagnetic consumer 10 and a field effect transistor 11 form a series circuit, whereby the electromagnetic consumer 10 is connected to a battery voltage U.sub.Batt and the field effect transistor 11 to ground. It is also possible to use a bipolar transistor instead of the field effect transistor. From the connecting point of the electromagnetic consumer 10 and the field effect transistor 11, a series circuit of a diode 12 and a reversely connected Zener diode 13 leads to the control terminal of the field effect transistor 11. A resistor 14 is connected with the battery voltage U.sub.Batt and through a further resistor 15 with the mentioned control terminal of the field effect transistor 11, the connection point of resistors 14 and 15 is connected with the output of an operation amplifier 16. From the connecting point of the electromagnetic consumer 10 and the field effect transistor 11 a feedback resistor 17 is connected to the inverting input of the operation amp
REFERENCES:
patent: 4328526 (1982-05-01), Dilger et al.
patent: 4454558 (1984-06-01), Huddart
patent: 4485342 (1984-11-01), Hill et al.
patent: 4492913 (1985-01-01), Arnold et al.
Krauter Immanuel
Van Belzen David
Robert & Bosch GmbH
Striker Michael J.
Wolfe, Jr. Willis R.
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