Abstract The disclosed devices comprise a monostable multivibrator applied with periodic trigger pulses resulting from the rotation of the engine. If the engine has a speed of rotation less than a predetermined speed a voltage charged on a capacitor within the pulse period in the stable state of the multivibrator reaches a breakdown voltage of a Zener diode to produce an output from the latter. Otherwise the voltage across the capacitor does not reach the breakdown voltage to produce no output from the diode. Two capacitors may charge or discharge with different time constants in the stable state of the multivibrator while one of the capacitors is disabled in accordance with whether the actual speed is higher or lower than the predetermined speed.
A number-of-rotations detection device comprising, a rotation pulse generator circuit for periodically generating pulses in dependence upon the rotational movement Of a rotary member, means in said pulse generator circuit causing said pulses to have a duration dependent upon the number of rotations per unit time of the rotary number, means for integrating each of the pulses for at least the duration of each pulse to produce an amplitude dependent on the pulse duration and for returning the amplitude to zero value, means for detecting whether the amplitude of the integrated pulses is above or below a predetermined value to determine whether the number of rotations per unit time of the rotary member is above or below a predetermined value, said means for integrating including a plurality of pulse generator means for generating a plurality of sloped pulses different in rate of change in voltage from one another during the periods of the first-mentioned pulses, a selection switch for selecting sloped pulses, and voltage detection means receptive of the sloped pulses selected by the selection switch to produce an output in response to the applied sloped pulses having a voltage exceeding a predetermined magnitude.
Claim 2
Dependent Claim
194 words
A number-of-rotations detection device comprising, a rotation pulse generator circuit for periodically generating pulses in dependence upon the rotational movement Of a rotary member, means in said pulse generator circuit causing said pulses to have a duration dependent upon the number of rotations per unit time of the rotary number, means for integrating each of the pulses for at least the duration of each pulse to produce an amplitude dependent on the pulse duration and for returning the amplitude to zero value, means for detecting whether the amplitude of the integrated pulses is above or below a predetermined value to determine whether the number of rotations per unit time of the rotary member is above or below a predetermined value, said means for integrating including a plurality of pulse generator means for generating a plurality of sloped pulses different in rate of change in voltage from one another during the periods of the first-mentioned pulses, a selection switch for selecting sloped pulses, and voltage detection means receptive of the sloped pulses selected by the selection switch to produce an output in response to the applied sloped pulses having a voltage exceeding a predetermined magnitude.
Claim 3
Dependent Claim
28 words
A number-of-rotation detection device as claimed in claim 1, wherein the selection switch comprises means controlled in response to an operating state of an associated internal combustion engine.
Claim 4
Dependent Claim
26 words
A number-of-rotation detection device as claimed in claim 1, wherein the selection switch means is controlled in response to an output from said voltage detection means.