Transfer print voltage adjustment based on temperature, humidity, and transfer feedback voltage

1. An electrophotographic image forming device comprising:

an image forming unit comprising a first component and a second component disposed to transfer a toner image therebetween;

a first sensing unit operative to detect transfer feedback voltage of a feedback loop comprising an interface between the first component and the second component;

a second sensing unit operative to detect dry-bulb temperature and relative humidity used to calculate wet-bulb temperature therefrom; and

a controller operative to adjust transfer voltage bias jointly using both the to wet-bulb temperature measurement and the detected transfer feedback voltage.

2. The device of claim 1 wherein the transfer feedback voltage of the feedback loop is detected by determining a voltage produced by passing a known current through one of the first component or the second component.

3. The device of claim 1 wherein the transfer feedback voltage comprises a resistance-capacitance characteristic of the feedback loop.

4. The device of claim 1 wherein the controller is further operative to adjust the transfer bias in response to a device throughput.

5. The device of claim 1 further comprising a memory device for storing a lookup table comprising adjustment values corresponding to wet-bulb temperature values and measured transfer feedback voltage.

6. The device of claim 1 wherein the wet-bulb temperature is calculated using the following equation:

Z=AX 2 +BY 2 +CXY+DX+EY+F

where:

A is about −0.00079;

B is about −0.00047;

C is about 0.00479;

D is about 0.59473;

E is about 0.10035;

F is about −6.32789;

X is the dry-bulb temperature in ° C.;

Y is the relative humidity as a percentage; and

Z is the wet-bulb temperature in ° C.

7. The device of claim 1 wherein the wet-bulb temperature is calculated from temperature sensor measurements and humidity sensor measurements.

8. The device of claim 1 wherein the relative humidity is measured using a humidity sensor.

9. A method of adjusting an operating parameter in an image forming device, the method comprising:

periodically determining a transfer feedback voltage of a feedback loop comprising an interface between a first component and a second component of image forming unit, wherein the transfer feedback voltage of the feedback loop is used in setting an operating parameter for the image forming device;

determining a wet-bulb temperature used in setting an operating parameter for the image forming device;

determining an adjusted transfer voltage bias using both the wet-bulb temperature and the detected transfer feedback voltage; and

setting an operating parameter for the image forming device using the adjusted transfer voltage bias;

wherein determining the transfer feedback voltage of the feedback loop comprises determining a voltage required to pass a known current through one of the first or the second component.

10. The method of claim 9 wherein the second component is a transfer member.

11. The method of claim 9 wherein the first component is a photoconductive member.

12. The method of claim 9 wherein the wet-bulb temperature is calculated as a function of dry-bulb temperature and relative humidity.

13. The method of claim 12 wherein the relative humidity is measured using a humidity sensor.

14. The method of claim 9 wherein the wet-bulb temperature is calculated from temperature sensor measurements and humidity sensor measurements.

15. The method of claim 9 wherein the wet-bulb temperature is substantially equal to a calculated value determined by the equation: Z=−0.00079X 2 −0.00047Y 2 +0.00479XY+0.59473X+0.10035Y−6.32789, where X is the dry-bulb temperature in ° C., Y is the relative humidity as a percentage, and Z is the wet-bulb temperature in ° C.

16. A method of adjusting a transfer voltage bias in an image forming device, the method comprising:

periodically measuring a transfer feedback voltage for a feedback loop comprising an interface between a transfer member and a photoconductive member, the transfer feedback voltage determined by passing a known current through the interface between a transfer member and a photoconductive member;

determining a wet-bulb temperature;

storing a set of transfer bias values, each corresponding to different ranges of wet-bulb temperatures and measured transfer feedback voltages;

determining an adjusted transfer feedback voltage based on a transfer bias value that corresponds to both the wet-bulb temperature and the measured transfer feedback voltage; and

setting the transfer voltage bias applied to the transfer member during subsequent print jobs using the adjusted transfer feedback voltage.

17. The method of claim 16 wherein the wet-bulb temperature is calculated as a function of dry-bulb temperature and relative humidity which are measured using a temperature sensor and a humidity sensor, respectively.

18. The method of claim 16 wherein determining an adjusted transfer feedback voltage comprises calculating the adjusted transfer feedback voltage using an equation with the measured transfer feedback voltage and the wet-bulb temperature being independent variables.

19. The method of claim 16 , wherein determining the adjusted transfer feedback voltage comprises reading the magnitude of feedback voltage transfer adjustment from a lookup table.

20. The method of claim 16 wherein the wet-bulb temperature is determined by the equation: Z=−0.00079X 2 −0.00047Y 2 +0.00479XY+0.59473X+0.10035Y−6.32789, where X is the dry-bulb temperature in ° C., Y is the relative humidity as a percentage, and Z is the wet-bulb temperature in ° C.