Abstract An internal combustion engine speed limit circuit for preventing the engine speed from exceeding a predetermined maximum. A monostable multivibrator circuit, responsive to the engine ignition signals, produces a series of equally spaced electrical pulses at a repetition rate proportional to engine speed. These signals base bias a charge circuit transistor conductive to periodically establish a charge circuit for a capacitor and a base drive circuit for two transistors connected in Darlington pair which, while conducting, divert base drive current from a control transistor through the current carrying electrodes thereof, thereby maintaining the control transistor not conductive. While the charge circuit transistor is not conducting during the spaces between the electrical pulses, the discharge of the capacitor supplies the base drive current for the transistors of the Darlington pair to maintain these devices conductive and, consequently, the control transistor not conductive. As the speed of the motor increases, the duration of each one of the series of electrical pulses decreases until, at the predetermined engine speed, the electrical pulses are no longer produced, consequently, the charging circuit for the capacitor is no longer periodically established. The charge upon the capacitor dissipates through the base-emitter electrodes of the transistors of the Darlington pair until it has reduced to a predetermined minimum at which insufficient base drive current is supplied thereby to maintain the Darlington pair conductive. Base drive current is then supplied to the control transistor which conducts through the collector-emitter electrodes thereof to disenable the ignition system of the engine.
Inventors
👤 J Shearer
👤 R Richards
👤 Masters P Le
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-25 12:10
CPC Classifications
F; F02; F02P; F02P9/00; F02P9/002; F02P9/005
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
191 words
An internal combustion engine speed limit circuit for preventing the engine speed from exceeding a predetermined maximum comprising in combination with the engine ignition system which produces ignition signals in tiMed relationship with the engine and a source of direct current supply potential, a monostable multivibrator circuit responsive to said ignition signals for producing a series of equally spaced electrical pulses at a repetition rate proportional to engine speed, a capacitor, a charge circuit through which said capacitor is charged across said source of direct current supply potential, a first transistor having two current carrying electrodes connected in series in said charge circuit responsive to each one of said series of electrical pulses for establishing said charge circuit for the duration of each of said electrical pulses, a high impedance discharge circuit for said capacitor, and a second transistor having two current carrying electrodes which is maintained not conductive while said capacitor is discharging and is rendered conductive through said current carrying electrodes when the charge upon said capacitor has reduced to a predetermined minimum for disenabling the ignition system of the engine when the engine speed reaches a predetermined maximum.
Claim 2
Dependent Claim
191 words
An internal combustion engine speed limit circuit for preventing the engine speed from exceeding a predetermined maximum comprising in combination with the engine ignition system which produces ignition signals in tiMed relationship with the engine and a source of direct current supply potential, a monostable multivibrator circuit responsive to said ignition signals for producing a series of equally spaced electrical pulses at a repetition rate proportional to engine speed, a capacitor, a charge circuit through which said capacitor is charged across said source of direct current supply potential, a first transistor having two current carrying electrodes connected in series in said charge circuit responsive to each one of said series of electrical pulses for establishing said charge circuit for the duration of each of said electrical pulses, a high impedance discharge circuit for said capacitor, and a second transistor having two current carrying electrodes which is maintained not conductive while said capacitor is discharging and is rendered conductive through said current carrying electrodes when the charge upon said capacitor has reduced to a predetermined minimum for disenabling the ignition system of the engine when the engine speed reaches a predetermined maximum.