Engine operating time hour meter

An engine operating time measuring apparatus is provided for use with an engine having an internal magneto-type electrical generator providing an ignition voltage. The engine operating time measuring apparatus includes power supply circuitry coupled to the electrical generator of the monitored engine for supplying operating power to the apparatus in response to generated ignition voltage. Timing circuitry is responsive to the operating power supplying circuitry for generating a clock signal. A counter is responsive to the clock signal for counting the generated clock signal to identify the engine operating time.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to hour meters for recording the operating 
time of monitored engines, and more particularly to an improved engine 
operating time recording apparatus having operating power completely 
derived from an internal magneto-type electrical generator of a monitored 
engine. 
2. Description of the Prior Art 
Hour meters are commonly used to measure the running or operating time of 
various equipment for scheduling preventive maintenance. Disadvantages of 
known mechanical hour meters include the imprecise recording of time and 
unreliability. Other known hour meters for recording the operating time of 
monitored engines utilize a battery direct current (DC) source, as is 
available in many vehicles such as automobiles. Alternatively known hour 
meters use an alternating current (AC) source. However, an AC source or a 
battery is not included with many small engine applications, such as in 
lawn mowers or pumps. 
In small engine applications, typically an electronic ignition control 
system is used in conjunction with an internal magneto-type electrical 
generator of the engine. For example, the ignition control system can be 
operatively positioned adjacent a flywheel of the engine being controlled. 
The ignition control system provides a high voltage, such as in a 
secondary winding of an ignition coil, to fire a spark plug or spark plugs 
associated with the engine. Typically the engine flywheel carries a 
permanent magnet that energizes a stator core of the ignition control 
system upon rotation of the flywheel for generating various electrical 
control pulses. 
It is desirable to provide an hour meter for recording the operating time 
of small engines that is completely powered by an internal magneto-type 
electrical generator of a monitored engine and that is reliable and 
accurate. 
SUMMARY OF THE INVENTION 
Among the important objects of the present invention are to provide an 
improved hour meter for recording the operating time of a monitored 
engine; to provide such an hour meter that is a simple arrangement and 
economical to manufacture; and to provide such an hour meter that 
overcomes many of the disadvantages of known hour meters. 
In brief, the objects and advantages of the present invention are achieved 
by an engine operating time measuring apparatus for use with an engine 
having an internal magneto-type electrical generator providing an ignition 
voltage. The engine operating time measuring apparatus includes power 
supply circuitry coupled to the electrical generator of the monitored 
engine for supplying operating power to the apparatus. Timing circuitry is 
responsive to the operating power supplying circuitry for generating a 
clock signal. A counter is responsive to the clock signal for counting the 
generated clock signal to identify the engine operating time. 
In accordance with a feature of the invention, the operating power for the 
engine operating time measuring apparatus or hour meter is completely 
derived from the monitored engine. The power supply circuitry includes a 
charging capacitor for storing energy in response to induced voltages 
resulting, for example, from a rotating magnetic field of the monitored 
engine. A crystal controlled oscillator circuit and a stepping motor can 
be included in the timing circuitry for generating a clock movement signal 
that is applied to a mechanical counter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, in FIG. 1 there is illustrated an engine 
powered hour meter arranged in accordance with the principles of the 
present invention and designated as a whole by the reference character 10. 
A conventional engine 11 is shown with the engine powered hour meter 10, 
although it should be understood that the engine powered hour meter 10 
advantageously can be used for various applications with any engine having 
an internal magneto-type electrical generator. 
Referring also to FIG. 2, there is shown a schematic diagram representation 
of the engine powered hour meter 10. Among its primary components, the 
engine powered hour meter 10 includes an operating power supply circuit 12 
for providing DC operating power to the meter 10 when the monitored engine 
11 is operating, a crystal controlled oscillator circuit 14 operatively 
connected to the power supply circuit 12 for providing a stable 
predetermined frequency signal or clock signal, a motor 16 for providing a 
clock movement signal in response to the clock signal output of the 
oscillator circuit 14 and a mechanical counter 18 operatively driven by 
the clock movement signal of motor 16. 
A parallel combination of the operating power supply circuit 12 and an 
engine enable switch 20 energizes the operating power supply circuit 12 
when the engine 11 is operating. Engine enable switch 20 is connected 
between ground potential indicated at a line G and an enable input E of an 
electronic ignition control module 22 used in conjunction with the 
monitored engine 11. The electronic ignition control module 22 includes 
conventional connections to a spark plug indicated by 22P, an ignition 
coil indicated by 22C, the engine enable switch 20 indicated by 22E and 
ground potential indicated by 22G. 
With the engine enable switch 20 opened, then engine 11 can operate. Engine 
11 can be stopped by closing the engine enable switch 20 so that the 
enable input E is connected to ground potential G. The operating power 
supply circuit 12 includes a plurality of diodes 24, 26, 28, 30 and 32 
coupled in series across the engine enable switch 20, a current limiting 
resistor 34 series-connected between diodes 30 and 32, and a charging 
capacitor 36 connected between a junction 33 of diode 32 and resistor 34 
and the enable input E of an electronic ignition module 22. Diode 32 is 
arranged cathode to anode between the junction 33 and ground potential G 
to provide the proper polarity of power to an integrated circuit 
oscillator device 50. 
FIG. 3A illustrates a typical voltage waveform generally designated by 40 
at a circuit point corresponding to the enable input E when the engine 11 
is operating. The voltage waveform 40 includes a periodic positive and 
negative pulse 42A and 42B, for example, corresponding to an ignition 
firing signal. Typically the positive pulse 42A is used to fire a spark 
plug associated with the monitored engine 11 and the negative pulse 42B is 
unused in conventional operation of the engine 11. 
In accordance with an important aspect of the present invention, an 
operating power supply for the hour meter 10 is derived from an ignition 
firing signal, such as the periodic negative pulses 42B. In operation, the 
periodic negative pulses 42B are applied via the series connected diodes 
24, 26, 28, 30, 32 and resistor 34 for charging the energy storage 
capacitor 36. A reference voltage level of approximately 2.8 volts is 
provided by the series connected diodes 24, 26, 28, 30. 
FIG. 3B provides a graphical representation of the voltage waveform 
generally designated by 44 corresponding to the voltage across the series 
connected diodes 24, 26, 28, 30. Voltage waveform 44 has a peak voltage 
level indicated by 44A of approximately 2.8 volts generally coinciding 
with the charging pulses 42B of waveform 40 in FIG. 3A. Voltage waveform 
44 has a minimum voltage level indicated by 44B of approximately 2.2 volts 
representing the discharge of the energy storage capacitor 36 between the 
charging pulses 42B with the engine 11 operating. 
The crystal controlled oscillator circuit 14 is energized responsive to the 
voltage waveform 44 of the power supply circuit 12 to provide a stable 
clock signal at a line 48. Oscillator circuit 14 includes the integrated 
circuit oscillator device 50 arranged for providing, for example, a 1 Hz 
bipolar drive signal at its output 48 used to directly drive motor 16. 
Coupled to the integrated circuit oscillator device 50 are an external 
crystal 52 having a selected resonant operating frequency, such as a 
37.768 KHz, and a trimmer capacitor 54. Various commercially available 
devices having low power consumption characteristics, such as a CMOS 
integrated circuit device type CD22777, manufactured and sold by RCA 
Corp., can be used for the integrated circuit oscillator device 50. 
Motor 16 advantageously is provided by a stepping motor having low power 
consumption characteristics. The 1 Hz bipolar drive signal at line 48 is 
applied to directly drive the motor 16. An output of one revolution per 
two drive the motor 16. An output of one revolution per two second time 
interval or 30 RPM (revolutions per minute) is provided with the applied 1 
Hz bipolar drive signal and the motor 16 having a rated step of 180 
degrees. A gear train assembly 58 adjusts the frequency of the motor drive 
movement to provide a selected frequency drive movement indicated at a 
line 60 that is applied to the mechanical counter 18. 
Referring again to FIG. 1, mechanical counter 18 is operatively driven by 
the motor 16 via the gear train assembly 58. Mechanical counter 18 
includes a plurality of dial display elements 62.sub.1 -62.sub.N, together 
indicative of cumulative operating time for the engine 11. For example, 
each incremental movement of the dial display element 62.sub.1 can 
indicate 1/10 hour, 62.sub.2 indicating 1 hour increments and being 
incremented one time after 10 increments or one complete rotation of 
display element 62.sub.1. This action continues for each of the sequential 
dial display elements through display element 62.sub.N included in the 
counter 18. 
While the invention has been described with reference to details of the 
illustrated embodiment, these details are not intended to limit the scope 
of the invention as defined in the appended claims.