Control system for an electric motor having an integral flywheel rotor

• US 6,369,532 B2
• Filed: 02/01/2001
• Issued: 04/09/2002
• Est. Priority Date: 02/24/2000
• Status: Expired due to Fees

• Current Assignee: Briggs & Stratton Corporation
• Original Assignee: Briggs & Stratton Corporation
• Inventors: Koenen, Robert, Wesenberg, Scott
• Primary Examiner(s): Donels, Jeffrey
• Assistant Examiner(s): Duda, Rina I.
• Application Number:
  US09/773,410
• Publication Number:
  US 20020005699A1
• Time in Patent Office: 432 Days
• Field of Search: 318/150, 318/161, 180/165, 180/65.2, 180/65.3, 310/74, 310/153, 290/27, 290/28, 290/48, 290/40.A
• US Class Current: 318/150
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32

Abstract

A control system for an electric motor having an integral flywheel rotor. The motor includes a stator mounted co-axially with the engine crankshaft and a rotor surrounding the stator. A sensor is positioned near the rotor for sensing its rotational speed. The sensor is coupled to a controller. The controller is operable to deliver an output signal to the stator to start the internal combustion engine. While the engine is starting, the processor steps the starter motor from a low speed to a high speed. Once the engine has started and is rotating at a speed greater than a trigger speed, the processor delivers another output signal such that the motor is commutated at a speed that is less than the speed of the rotor to generate a speed slip. By commutating the motor in this manner, it acts as a generator. The speed slip is regulated when the motor is generating electric power so that the motor produces a constant output voltage.

Claims

1. A control system for an electric motor having a stator and an integral flywheel-rotor with a plurality of position indicators, the system comprising:

a sensor that generates a signal based on the movement of the position indicators of the rotor; and

a controller coupled to the sensor to receive the signal and operable to deliver an output signal to the stator such that the motor is stepped from a low rotational speed to a high rotational speed in a series of increments, wherein the controller checks the rotational speed of the rotor before stepping the motor to the next increment.

2. A control system as claimed in claim 1, wherein the controller steps the motor from the low rotational speed to the high rotational speed in discrete increments.

3. A control system as claimed in claim 1, further comprising a starter switch coupled to the controller, and wherein the controller steps the motor from the low rotational speed to the high rotational speed after the starter switch is engaged.

4. A control system as claimed in claim 1, further comprising an ignition system coupled to the controller, and wherein the controller is operable to generate an ignition signal based on the signal of the sensor.

5. A control system as claimed in claim 1, wherein the controller checks the rotational speed of the rotor to determine whether the engine has a rotational speed greater than a rotational speed indicative of engine starting.

6. A control system as claimed in claim 5, wherein each increment of rotational speed has a distinct speed indicative of engine starting.

7. A control system as claimed in claim 1, wherein the motor includes at least one winding, wherein the control system further comprises a second sensor that generates a signal based on a current flow from the stator to a power source, and wherein the controller checks the current to determine whether the motor has started.

8. A control system for a motor having a stator and an integral flywheel rotor, the system comprising:

a sensor that generates a signal based on the rotation of the rotor; and

a controller coupled to the sensor to receive the signal, and operable to deliver an output signal to the stator such that the motor is commutated at a rotational speed that is less than the rotational speed of the rotor to generate a slip and to vary the slip such that the motor generates a substantially constant voltage.

9. A system as claimed in claim 8, wherein the controller is also operable to deliver an output signal to the stator such that the motor is stepped from a low rotational speed to a high rotational speed.

10. A control system as claimed in claim 9, wherein the controller steps the motor from the low rotational speed to the high rotational speed in discrete increments.

11. A control system as claimed in claim 9, further comprising a starter switch coupled to the controller, and wherein the controller steps the motor from the low rotational speed to the high rotational speed after the starter switch is engaged.

12. A control system as claimed in claim 8, further comprising an ignition system coupled to the controller, and wherein the controller is operable to generate an ignition signal based on the signal of the sensor.

13. A control system for a motor having a stator and a rotor, the system comprising:

a sensor generating a signal based on the speed of the rotor; and

a controller coupled to the sensor and operable to deliver an output signal to the stator when the speed of the rotor is below a predetermined speed such that the motor is stepped from a low speed to a high speed, the high speed being less than or equal to the predetermined speed, and to deliver another output signal when the speed of the rotor is equal to or above the predetermined speed such that the motor is commutated at a speed that is less than the speed of the rotor to generate a slip.

14. A control system as claimed in claim 13, wherein the controller commutates the motor to vary the slip such that the motor generates a substantially constant voltage.

15. A control system as claimed in claim 13, wherein the controller steps the motor from the low speed to the high speed in 100 revolutions per minute increments.

16. A control system as claimed in claim 13, further comprising a starter switch coupled to the controller, and wherein the controller steps the motor from the low speed to the high speed after the starter switch is engaged.

17. A control system as claimed in claim 13, further comprising an ignition system coupled to the controller and wherein the controller is operable to generate an ignition signal based on the signal of the sensor.

18. A control system as claimed in claim 13, wherein the slip speed is controlled in a manner to produce a substantially constant output voltage.

19. A method of controlling a motor for an internal combustion engine, the motor having a stator, a rotor magnetically interacting with the stator, and a starter switch, the method comprising

sensing the rotational speed of the rotor;

sensing engagement of the starter switch;

delivering an output signal to the stator to step the starter motor from a low rotational speed to a high rotational speed after the starter switch is engaged;

sensing starting of the internal combustion engine; and

commutating the motor after the internal combustion engine is started and, when the rotational speed of the rotor is equal to or above a predetermined rotational speed, commutating the motor such that the motor is commutated at a rotational speed that is less than the rotational speed of the rotor.

20. A method as claimed in claim 19, wherein the sensing starting step includes sensing a current flow from the motor to a power source.

21. A method as claimed in claim 19, wherein the sensing starting step includes determining whether the sensed rotational speed of the rotor is greater than a rotational speed indicative of starting.

23. A method as claimed in claim 19, wherein the commutating step includes establishing a desired output voltage for the motor.

24. A method as claimed in claim 23, wherein the commutating step further motor includes checking the actual output voltage of the motor.

25. A method as claimed in claim 24, wherein the commutating step further includes determining the difference between the desired output voltage and the actual output voltage.

26. A method as claimed in claim 25, wherein the commutating step further includes calculating a regulation adjustment based at least in part on the difference between the desired output voltage and the actual output voltage.

27. A method as claimed in claim 26, wherein the commutating step further includes estimating a future rotational speed of the rotor.

28. A method as claimed in claim 27, wherein the commutating step further includes calculating a new commutating speed by subtracting the estimated future rotational speed by the regulation adjustment.

22. A method as claimed in 21, wherein the rotational speed indicative of starting is distinct for each step rotational speed.

29. A method of controlling a starter motor for an internal combustion engine, the starter motor having a stator and an integral flywheel rotor magnetically interacting with the stator, the method comprising

sensing starting of the internal combustion engine;

and

commutating the starter motor after the internal combustion engine is started and, when the speed of the rotor is equal to or above a predetermined speed, commutating the starter motor such that the starter motor is commutated at a speed that is less than the speed of the rotor.

30. A method as claimed in claim 29, wherein the commutating step includes:

establishing a desired output voltage for the starter motor;

checking the actual output voltage of the starter motor;

calculating a commutation frequency based at least in part on the difference between the desired output voltage for the starter motor and the actual output voltage of the starter motor; and

delivering a current with the commutation frequency to the stator.

31. A method as claimed in claim 30, wherein the calculating includes estimating a future speed of the rotor.