Household appliance including a fan speed controller

• US 8,836,257 B2
• Filed: 10/09/2008
• Issued: 09/16/2014
• 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
• Primary Examiner(s): Ismail, Shawki S
• Assistant Examiner(s): Carrasquillo, Jorge L
• Application Number:
  US12/248,417
• Publication Number:
  US 20100092275A1
• Time in Patent Office: 2,168 Days
• Field of Search: 318/494, 318/767, 318/772, 318/400.35, 318/400.34, 318/400.32, 318/599, 318/727, 318/799, 318/801, 318/802, 318/400.33, 318/400.16, 318/400.23, 318/400.26, 318/400.24, 318/400.36, 318/443, 318/102, 318/444, 318/144, 318/750, 318/756, 415/1, 417/410
• US Class Current: 318/400.32
• 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 providing sensorless control of a fan motor of a household appliance, the method comprising:

cutting a voltage to the fan motor of the household appliance;

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, and based on the comparison to the table, 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; and

based on the determining, generating, by a microcontroller of the household appliance, a mimicking signal that mimics a Hall effect square wave signal and outputting, by the microcontroller, the mimicking signal that mimics the Hall effect square wave signal.

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

3. The household appliance according to claim 2, wherein the AC inductive motor is a two-speed AC inductive motor.

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

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

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

7. The method according to claim 6,

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.

8. The method according to claim 6, wherein the threshold value is based on the household appliance.

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

based on the determining, outputting, by the microcontroller, a first mimicking signal that mimics a first Hall effect square wave signal to the fan motor controller 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

based on the determining, outputting, by the microcontroller, a second mimicking signal that mimics a second Hall effect square wave signal to the fan motor controller 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 household appliance is a cooking appliance.

11. The method according to claim 9, further comprising one of:

turning the voltage to the fan motor back on based on the outputting of the first mimicking signal that mimics the first Hall effect square wave signal;

sending a signal to cut a voltage to a heating element of the cooking appliance based on the outputting of the second mimicking signal that mimics the second Hall effect square wave signal;

sending a signal to terminate a heating cycle of the cooking appliance based on the outputting of the second mimicking signal that mimics the second Hall effect square wave signal; and

sending a signal to default the fan motor to a high speed setting based on the outputting of the second mimicking signal that mimics the second Hall effect square wave signal.

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

setting a timer upon turning the voltage to the fan motor back on based on the outputting of the first mimicking signal that mimics the first Hall effect square wave signal; and

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

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

turning the voltage to the fan motor back on.

14. The method according to claim 13,

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.

15. The method according to claim 1,

wherein the 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 the microcontroller.

16. 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.

17. 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, based on the comparing, generating, by a microcontroller of the household appliance, a first mimicking signal that mimics a first Hall effect square wave signal and outputting, by the microcontroller, the first mimicking signal that mimics the first Hall effect square wave 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

based on the comparing, generating, by the microcontroller, a second mimicking signal that mimics a second Hall effect square wave signal and outputting, by the microcontroller, the second mimicking signal that mimics the second Hall effect square wave signal indicating that the fan motor is operating improperly if the operation of the fan motor is less than the predetermined or threshold value.

18. 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;

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

a microcontroller,

wherein the sensorless fan controller monitors operation of the fan by;

cutting a voltage to the fan motor of the household appliance;

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, and based on the comparison to the table, 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; and

wherein the microcontroller generates, based on the determining by the sensorless fan controller, a mimicking signal that mimics a Hall effect square wave signal, and wherein the microcontroller outputs the mimicking signal that mimics the Hall effect square wave signal.

19. The household appliance according to claim 18, wherein the sensorless fan controller includes:

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

wherein the microcontroller receives the measured electromotive force (EMF) from the speed sensing module.

20. The household appliance according to claim 19, wherein the speed sensing module normalizes the measured electromotive force (EMF) of the fan motor to be within an operating range of the microcontroller.

21. The household appliance according to claim 18,

wherein the microcontroller outputs a first mimicking signal that mimics a first Hall effect square wave 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 microcontroller outputs a second mimicking signal that mimics a second Hall effect square wave 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.