METHOD FOR MONITORING AND CONTROLLING ENGINE SPEED

• US 20130106118A1
• Filed: 10/25/2012
• Published: 05/02/2013
• Est. Priority Date: 10/27/2011
• Status: Active Grant

• Current Assignee: Briggs & Stratton LLC (Briggs & Stratton Corporation)
• Original Assignee: Briggs & Stratton Corporation
• Inventors: Koenen, Robert J., Raasch, Jason J.
• Granted Patent: US 9,628,009 B2
• Time in Patent Office: Days
• US Class Current: 290/40.B
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator

Abstract

A generator having an electronic governor for controlling the speed of an engine to generate an output voltage from an alternator is disclosed. The generator includes an alternator coupled to an engine to generate an output voltage. The variable speed of the engine allows the alternator to generate a variable output voltage. An electronic governor monitors a time period between voltage benchmarks on the output voltage. The electronic governor compares the monitored time period to a reference time period and adjusts the position of the throttle based upon the comparison between the monitored time period and the reference time period. The reference time period is set based upon the desired output voltage frequency. In an alternate embodiment, the electronic governor senses the current draw from the alternator and adjusts the position of the throttle to prevent changes in the frequency of the output voltage

Claims

1. A generator system, comprising:

an engine having a drive shaft and a throttle;

an alternator having a rotor disposed on a rotor shaft, wherein the drive shaft of the engine is coupled to the rotor shaft of the alternator such that the engine drives the alternator to generate a variable output voltage; and

an electronic governor operable to monitor the output voltage and adjust the throttle to control the speed of the engine in response to changes in the monitored output voltage.

2. The generator system of claim 1 wherein the electronic governor monitors voltage benchmarks on the output voltage and adjusts the throttle based on the monitored voltage benchmark.

3. The generator system of claim 2 wherein the voltage benchmarks are zero crossings of the output voltage.

4. The generator system of claim 2 wherein the electronic governor monitors a time period between the voltage benchmarks and adjusts the throttle to keep the time period generally constant.

5. The generator system of claim 1 wherein the electronic governor includes a voltage sensing circuit operable to determine the time period between voltage benchmarks on the output voltage.

6. The generator system of claim 5 wherein the electronic governor further comprises an engine control unit connected to the voltage sensing circuit and the throttle, wherein the engine control circuit adjusts the position of the throttle based on the time period sensed by the voltage sensing circuit.

7. The generator system of claim 1, wherein the electronic governor monitors an output current drawn from the alternator and adjusts the throttle to control the speed of the engine based on both the monitored output current draw and changes in the monitored output voltage.

8. The generator system of claim 7 wherein the electronic governor includes a current sensor coupled to an engine control unit, wherein the engine control unit adjusts the position of the throttle to control the speed of the engine.

9. A method of controlling a generator having an engine, an engine throttle, and an alternator, the alternator having a rotor and a rotor shaft coupled to a drive shaft of the engine, comprising:

monitoring a time period between voltage benchmarks of the output voltage;

comparing the monitored time period to a reference time period between the voltage benchmarks; and

adjusting the position of the throttle to increase or decrease the speed of the engine based upon the comparison between the monitored time period and the reference time period.

10. The method of claim 9 further comprising the step of setting a reference time period based upon the desired frequency of the output voltage and the type of voltage benchmark.

11. The method of claim 10 wherein the voltage benchmark is a zero crossing of the output voltage.

12. The method of claim 10 wherein the voltage benchmark is a peak value of the output voltage.

13. The method of claim 9 wherein the position of the throttle is adjusted when the monitored time period varies from the reference time period by more than a desired tolerance.

14. The method of claim 13 wherein the desired tolerance is a percentage of the reference time period.

15. The method of claim 9 further comprising the step of determining a desired frequency for the output voltage from the alternator and determining a reference time period based upon the desired output frequency.

16. A method of controlling a generator having an engine, an engine throttle, and an alternator, the alternator having a rotor and a rotor shaft coupled to a drive shaft of the engine, comprising:

monitoring for a change in the amount of current drawn from the alternator; and

adjusting the position of the throttle to increase or decrease the speed of the engine based upon an increase or a decrease in the amount of current drawn from the alternator by electric loads.

17. The method of claim 16 further comprising the step of positioning a current sensing element to determine the amount of current drawn from the alternator.

18. The method of claim 16 further comprising the steps of:

monitoring the frequency of the output voltage; and

operating the engine to generate the output voltage at the desired frequency.