US 4,336,778 A · Safety limiter for engine speed

Abstract

A safety system for limiting the speed of a fuel powered engine, particularly an internal combustion engine of a vehicle or machine, preferably by controlling the engine ignition. The system is especially useful for vehicles such as snowmobiles, motorcycles, power boats, and the like. An alternating or pulsed electrical output directly proportional to engine rpm is detected and the rpm is limited to one of two or more different levels, depending upon the condition of a programming switch or switches, in this embodiment a throttle switch. An upper level limits engine speed to a safe rpm in the event of load removal, such as when a drive belt breaks or a gear change is missed. Engine speed is limited to a lower level if the throttle switch indicates idle rpm is desired and if the engine does not begin to decelerate from a higher rpm within a predetermined time, regardless of the actual throttle condition. In drives utilizing automatic drive clutches, the lower level of rpm is below the engine speed necessary to engage the clutch.

Claims22

Dependent claims

A method of controlling the operating speed of an internal combustion engine having an electrical ignition, an operator-actuated throttle control and means for sensing operator force upon the throttle control, and that drives a load through a centrifugal clutch, comprising the steps of:

sensing during engine operation lack of deceleration of the engine speed upon removal of actuating force from the throttle control, and interrupting the ignition in the absence of sensed deceleration upon removal of actuating force from the throttle control until the engine speed is below that necessary to engage the centrifugal clutch.

In a system for controlling the speed of an engine, a control circuit for connection among an alternator driven by the engine, an engine ignition circuit, and a switch sensitive to the position of a throttle actuator for the engine, said circuit comprising:

a power supply with an input and an output, the input coupled to the alternator and the output forming a power source,
pulse conditioning means including first means to compare two inputs, one from the power supply output and the other from the alternator, and to produce output pulses of a frequency proportional to engine speed,
means to convert an input pulse frequency to a voltage the level of which is proportional to the frequency and including second means to compare two inputs, one from said pulse conditioning means and the other from its own output through a feedback circuit to produce a sawtooth voltage waveform,
means to monitor the voltage from said second means, including third means to compare two inputs, one from said second means and the other from both said second means and a time delay circuit, to produce output pulses when said engine is running at a constant speed or accelerating, but not when decelerating,
means for detecting the voltage level of the output from the frequency-to-voltage converting means, said means including fourth means to compare two inputs, one from the power supply and the other from the frequency-to-voltage converting means to produce an output when the voltage output of the frequency-to-voltage converting means reaches a predetermined level, and including means to change the level of the said other input through operation of said switch, thereby changing the output required from said frequency-to-voltage converter to produce an output from the voltage level detecting means,
circuit means connecting the output of the monitor means to the said other input to the frequency-to-voltage converter to short the said other input to ground when no output is produced by said third means, to prevent any output from said fourth means from being produced,
means for interrupting said ignition in response to an output from said fourth means,
said time delay circuit including means to delay transmission of the output from said fourth means to the ignition interrupting means and means to produce an output that is coupled to said one input of said third means, and
feedback means to couple said output from the time delay circuit to the said one input of said third means.

6 more elements

Dependencies are inferred from the claim text.

Safety limiter for engine speed

Life of this patent

Safety limiter for engine speed

Life of this patent

Abstract

Claims22