Electronic governor having an overspeed preventing circuit for internal combustion engines

Claim 1

An electronic governor for an internal combustion engine comprising a comparison circuit for comparing a first input voltage proportional to the rotational speed of the engine and a second input voltage related to the position of an accelerator operating lever and for producing an output voltage in accordance therewith, means for connecting the output of said comparison circuit to the control coil of a fuel regulating rod of a fuel injection pump so that the position of the fuel regulating rod is electromagnetically controlled in accordance with the electromagnetic force generated by the control coil responsive to the output of said comparison circuit, and an overspeed circuit for preventing engine overspeed including a further, separate voltage generating circuit for generating a D.C. output voltage proportional to the rotational speed of the engine and means for connecting the output of said D. C. voltage generating circuit to said control coil so as to produce an electromagnetic force which acts in an opposite direction to the said electromagnetic force produced by the output of said comparison circuit when the rotational speed of the engine exceeds a predetermined value, said connecting means including means responsive to said D.C. voltage for disconnecting said comparison circuit from said control coil and for connecting said D.C. voltage generating circuit to said control coil when said D.C. output voltage of said voltage generating circuit exceeds a predetermined value, said switching means comprising a relay and first and second pairs of switching contacts controlled by said relay, said first pair of contacts being closed responsive to the energization of said relay to connect the output of said comparison circuit to said control coil and the second pair of relay contacts being closed responsive to the de-energization of said relay to connect said voltage generating circuit to said control coil, and said voltage generating circut including sensing coil means for sensing the rotational speed of the engine and for producing an output voltage in accordance therewith, means for converting the output voltage produced by said sensing coil means into a corresponding D.C. voltage, and transistor amplifier means including a first transistor, connected to said converting means, which conducts responsive to the said D.C. voltage produced by said converting means exceeding a predetermined value and a second, normally conducting transistor which is rendered nonconducting when said first transistor conducts, and means for connecting said second transistor in series with said relay so that said relay is de-energized when said second transistor is rendered non-conducting.