Method of determining a relative speed between independently driven members in an image forming apparatus

1. A method of determining a relative speed between two separately driven members in an image forming apparatus, comprising the steps of:

transporting a print medium using a print media transport assembly including a first nip, said print media transport assembly operable at a first transport speed;

driving a rotatable member associated with a second nip using an electric motor at a second transport speed which is independent from said first transport speed;

transferring the print medium between said first nip and said second nip;

detecting an electrical characteristic of said motor when the print medium is present in each of said first nip and said second nip; and

determining a relative speed between said first transport speed and said second transport speed.

2. The method of claim 1 , including the steps of, prior to said determining step:

transporting an other print medium using said print media transport assembly at said first transport speed;

driving said rotatable member using said electric motor at a third transport speed which is different from said second transport speed;

transferring the other print medium between said first nip and said second nip;

detecting said electrical characteristic of said motor when the print medium is present in each of said first nip and said second nip; and

comparing said electrical characteristic from said second detecting step with said electrical characteristic from said first detecting step;

wherein said determining step is dependent upon said comparing step.

3. The method of claim 2 , wherein said detecting steps include the substep of:

monitoring a pulse width modulation setting of said motor for each of said first detecting step and said second detecting step;

the method further includes a step of calculating a numerical analysis data fit using a rise in said pulse width modulation setting associated with each of said first detecting step and said second detecting step; and

wherein said determining step is dependent upon said calculated data fit.

4. The method of claim 3 , wherein said data fit is a linear regression data fit.

5. The method of claim 1 , including the step of setting said second transport speed at a predetermined value below said first transport speed.

6. The method of claim 5 , wherein said second transport speed is set at a value which is approximately 0.75% less than said first transport speed.

7. The method of claim 1 , wherein said detecting step includes the substeps of:

monitoring a pulse width modulation setting of said motor;

detecting a rise in said pulse width modulation setting associated with said second transport speed being faster than said first transport speed.

8. The method of claim 7 , including the further substep of setting a threshold value for said rise in pulse width modulation setting.

9. The method of claim 8 , wherein said threshold value is set at an approximately 15% rise in said pulse width modulation setting.

10. The method of claim 1 , wherein said detecting step includes the substep of monitoring one of a pulse width modulation setting of said motor, an electrical current supplied to said motor, and an encoder speed associated with said motor.

11. The method of claim 1 , wherein said motor comprises one of a fuser motor located downstream from said first nip, and a bump-align motor located upstream from said first nip.

12. The method of claim 1 , wherein said rotatable member comprises one of a fuser roll and a bump-align roll.

13. The method of claim 1 , wherein said first nip is defined in part by a print media transport belt.

14. The method of claim 1 , wherein said paper transport assembly and said rotatable member are mechanically decoupled.

15. A method of operating an image forming apparatus, comprising the steps of:

transporting a first print medium, comprising the substeps of:

transporting the first print medium using a print media transport assembly at a first transport speed to a first nip;

transporting the first print medium to a second nip at a second transport speed associated with an electric motor, said second transport speed being independent from said first transport speed;

detecting an electrical characteristic of said motor when the first print medium is present in each of said first nip and said second nip; and

transporting a second print medium, comprising the substeps of:

transporting the second print medium using said print media transport assembly at said first transport speed to said first nip;

transporting the second print medium to said second nip at a third transport speed associated with said electric motor, said third transport speed being independent from said first transport speed;

detecting an electrical characteristic of said motor when the second print medium is present in each of said first nip and said second nip;

comparing said electrical characteristic from said second detecting step with said electrical characteristic from said first detecting step;

determining whether at least one of said second transport speed and said third transport speed is faster than said first transport speed.

16. The method of claim 15 , wherein said detecting steps include the substeps of:

monitoring a pulse width modulation setting of said motor for each of said first detecting step and said second detecting step; and

calculating a numerical analysis data fit using a rise in said pulse width modulation setting associated with each of said first detecting step and said second detecting step; and

wherein said determining step is dependent upon said calculated data fit.

17. The method of claim 16 , wherein said data fit is a linear regression data fit.

18. The method of claim 15 , including the step of setting said second transport speed at a predetermined value below said first transport speed.

19. The method of claim 18 , wherein said second transport speed is set at a value which is approximately 0.75% less than said first transport speed.

20. The method of claim 15 , wherein said detecting steps include the substeps of:

monitoring a pulse width modulation setting of said motor; and

detecting a rise in said pulse width modulation setting.

21. The method of claim 20 , including the further substep of setting a threshold value for said rise in pulse width modulation setting.

22. The method of claim 21 , wherein said threshold value is set at a 15% rise in said pulse width modulation setting.

23. The method of claim 15 , wherein said detecting step includes the substep of monitoring one of a pulse width modulation setting of said motor, an electrical current supplied to said motor, and an encoder speed associated with said motor.

24. The method of claim 15 , wherein said motor comprises one of a fuser motor located downstream from said first nip, and a bump-align motor located upstream from said first nip.

25. The method of claim 15 , further including a rotatable member defining one of said first nip and said second nip, said rotatable member comprising one of a fuser roll and a bump-align motor.

26. The method of claim 15 , wherein said first nip is defined in part by a print media transport belt.

27. A method of operating an electrophotographic printer, comprising the steps of:

transporting a print medium through a first nip at a first transport speed using a first rotatable member;

driving a second rotatable member associated with a second nip using an electric motor at a second transport speed which is independent from said first transport speed;

transferring the print medium between said first nip and said second nip; and

detecting an electrical characteristic of said motor when the print medium is present in said second nip.