HOUSEHOLD APPLIANCE INCLUDING A FAN SPEED CONTROLLER

• US 20100092275A1
• Filed: 10/09/2008
• Published: 04/15/2010
• Est. Priority Date: 10/09/2008
• Status: Active Grant

• Current Assignee: BSH Home Appliances Corporation (Robert Bosch GmbH)
• Original Assignee: BSH Home Appliances Corporation (Robert Bosch GmbH)
• Inventors: Savitz, George
• Granted Patent: US 8,836,257 B2
• Time in Patent Office: Days
• US Class Current: 415/1
• CPC Class Codes: F24C 15/325 electrically-heated
• CPC Class Codes: F24C 7/08 Arrangement or mounting of control or safety devices
• CPC Class Codes: H02P 25/04 Single phase motors, e.g. capacitor motors
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/26 Arrangements for controlling single phase motors

Abstract

A household appliance including a fan speed controller, and a method of controlling fan speed of a household appliance, are provided. The system includes a fan speed controller that cut a voltage to the fan motor, measures an electromotive force (EMF) of the fan motor at a predetermined time after the cutting of the voltage to the fan motor, and compares the measured electromotive force (EMF) to a table.

Claims

1. A method of controlling a fan motor of a household appliance, the method comprising:

cutting a voltage to the fan motor;

measuring an electromotive force (EMF) of the fan motor at a predetermined time after the cutting of the voltage to the fan motor; and

comparing the measured electromotive force (EMF) to a table.

2. The method according to claim 1, wherein the fan motor is an AC inductive motor.

3. The method according to claim 1, wherein the table is a software table or database.

4. The method according to claim 1, wherein the table is specific to the fan motor being used.

5. The method according to claim 1, wherein the table includes a threshold value.

6. The method according to claim 5,

wherein the threshold value includes a first threshold for a high speed mode, and

wherein the threshold value includes a second threshold for a low speed mode.

7. The method according to claim 5, wherein the threshold value is based on the household appliance.

8. The method according to claim 1, further comprising:

determining one of;

whether the fan motor was running at a time of the cutting of the voltage to the fan motor based on the comparison of the measured electromotive force (EMF) to the table;

a speed of the fan motor at a time of the cutting of the voltage to the fan motor based on the comparison of the measured electromotive force (EMF) to the table; and

whether the fan motor is operating below a predetermined or threshold value at a time of the cutting of the voltage to the fan motor based on the comparison of the measured electromotive force (EMF) to the table.

9. The method according to claim 8, further comprising:

outputting a first signal indicating that the fan motor is operating properly if the operation of the fan motor is equal to or greater than the predetermined or threshold value; and

outputting a second signal indicating that the fan motor is operating improperly if the operation of the fan motor is less than the predetermined or threshold value.

10. The method according to claim 9,

wherein the first signal is a first Hall effect mimicking signal, and

wherein the second signal is a second Hall effect mimicking signal.

11. The method according to claim 9, wherein the household appliance is a cooking appliance.

12. The method according to claim 11, further comprising one of:

turning the voltage to the fan motor back on based on the outputting of the first signal;

sending a signal to cut a voltage to a heating element of the cooking appliance based on the outputting of the second signal;

sending a signal to terminate a heating cycle of the cooking appliance based on the outputting of the second signal; and

sending a signal to default the fan motor to a high speed setting based on the outputting of the second signal.

13. The method according to claim 12, further comprising:

setting a timer upon turning the voltage to the fan motor back on based on the outputting of the first signal; and

re-cutting the voltage to the fan motor after the timer has expired.

14. The method according to claim 1, further comprising:

turning the voltage to the fan motor back on.

15. The method according to claim 14,

wherein the voltage is periodically cut and turned back on, and

wherein the electromotive force (EMF) is measured during periods when the voltage is cut.

16. The method according to claim 1,

wherein a microcontroller performs the comparing of the measured electromotive force (EMF) to the table, and

wherein the method includes normalizing the measured electromotive force (EMF) of the fan motor to be within an operating range of a microcontroller.

17. The method according to claim 1, further comprising:

powering the fan motor in a full-on state to provide a high speed mode; and

cutting a leading edge of a power signal to the fan motor to reduce an amount of on-time of the fan motor and provide a low speed mode.

18. A method of controlling a fan motor of a household appliance, the method comprising:

periodically cutting a voltage to the fan motor;

measuring an electromotive force (EMF) of the fan motor at a predetermined period of time after the cutting of the voltage to the fan motor; and

comparing the measured electromotive force (EMF) to a table to determine if the fan motor is operating properly,

wherein, if the fan motor is determined to be operating properly, the method includes outputting a first signal and turning the voltage to the fan motor back on, and

wherein, if the fan motor is determined to be operating improperly, the method includes;

outputting a second signal; and

one of cutting a voltage to a heating element of the household appliance and setting the fan motor to a high speed setting.

19. A household appliance including a sensorless fan speed controller, the household appliance comprising:

a housing having an interior cavity;

a fan;

a fan motor rotatably coupled to the fan; and

a fan controller that monitors operation of the fan based on electromotive force (EMF) conditions of the fan motor.

20. The household appliance according to claim 19, wherein the fan motor is an AC inductive motor.

21. The household appliance according to claim 19, wherein the fan controller cuts a voltage to the fan motor, measures an electromotive force (EMF) of the fan motor during a motor off time, and compares the measured electromotive force (EMF) to a table.

22. The household appliance according to claim 19, wherein the fan controller includes:

a speed sensing module that measures the electromotive force (EMF) of the fan motor;

a microcontroller that receives the measured electromotive force (EMF) from the speed sensing module and compares the measured electromotive force (EMF) to a table.

23. The household appliance according to claim 22, wherein the speed sensing module normalizes the measured electromotive force (EMF) of the fan motor to be within an operating range of the microcontroller.

24. The household appliance according to claim 19, wherein the fan controller determines one of:

whether the fan motor was running based on the electromotive force (EMF) conditions of the fan motor,

a speed of the fan motor based on the electromotive force (EMF) conditions of the fan motor, and

whether the fan motor was operating below a predetermined or threshold value based on the electromotive force (EMF) conditions of the fan motor.

25. The household appliance according to claim 19,

wherein the fan controller outputs a first signal indicating that the fan motor is operating properly if the electromotive force (EMF) conditions of the fan motor are equal to or greater than a predetermined or threshold value, and

wherein the fan controller outputs a second signal indicating that the fan motor is operating improperly if the electromotive force (EMF) conditions of the fan motor are less than a predetermined or threshold value.

26. The household appliance according to claim 20, wherein the AC inductive motor is a two-speed AC inductive motor.