Methods for determining when to transition between color printing and black-only printing in an image forming device

1. A method for determining when to deactivate a color cartridge in an image forming device, comprising:

activating the color cartridge;

calculating a first test value as a number of sequential black-only images in an examined portion of a print queue, starting with a current image;

calculating a second test value as a sum of the first test value and a number of sequential black-only images immediately preceding the current image in an examined portion of a print history;

selecting a predetermined trigger value based on a printing state of the image forming device, a run mode of the image forming device, and whether the examined portion of the print queue includes a color image;

when the examined portion of the print queue includes a color image, comparing the first test value to the predetermined trigger value;

when the examined portion of the print queue includes all black-only images, comparing the second test value to the predetermined trigger value; and

deactivating the color cartridge based on the comparison of the first or second test value to the predetermined trigger value.

2. The method of claim 1 , wherein selecting the predetermined trigger value based on the printing state of the image forming device comprises selecting the predetermined trigger value based on whether the image forming device is operating in a color state or a black-only state.

3. The method of claim 1 , wherein selecting the predetermined trigger value based on the run mode of the image forming device comprises selecting the predetermined trigger value based on whether the image forming device is operating in simplex, duplex, or idle mode, the idle mode including interpage gaps equal to or greater than an amount of time required to deactivate the color cartridge.

4. The method of claim 1 , wherein deactivating the color cartridge based on the comparison of the first or second test value to the predetermined trigger value comprises deactivating the color cartridge when either the first or second test value is greater than or equal to the predetermined trigger value.

5. The method of claim 1 , wherein when calculating the first and second test values and the image forming device is operating in a duplex mode in which both images of a first duplex sheet are printed before printing either image of a second duplex sheet, each duplex sheet is counted as two color images if at least one image is a color image.

6. The method of claim 1 , wherein when calculating the first and second test values and the image forming device is operating in a duplex mode in which at least one image of a second duplex sheet is printed prior to printing both images of a first duplex sheet, the first and second duplex sheets are counted as four color images if at least one image is a color image.

7. The method of claim 1 , further comprising:

determining an interpage gap between the current image and a next image in the examined portion of the print queue;

comparing the interpage gap to an amount of time required to deactivate the color cartridge; and

deactivating the color cartridge when the interpage gap is greater than or equal to the time required to deactivate the color cartridge and all the images in the examined portion of the print queue are black-only images.

8. The method of claim 1 , further comprising recalculating the first and second test values after printing each image.

9. The method of claim 1 , further comprising after deactivating the color cartridge, activating the color cartridge when the next image to be printed in the examined portion of the print queue is a color image.

10. A method for determining when to deactivate a color cartridge in an image forming device, comprising:

activating the color cartridge;

counting a sequential number of black-only images immediately preceding a current image in an examined portion of a print history;

counting a sequential number of black-only images in an examined portion of a print queue, starting with a current image;

determining if the examined portion of the print queue includes a color image;

determining a printing state of the image forming device;

determining a run mode of the image forming device;

selecting a trigger value based on whether the examined portion of the print queue includes a color image, the printing state, and the run mode; and

determining when to deactivate the color cartridge based on a comparison of at least one of the number of sequential black-only images in the examined portion of the print history and the number of sequential black-only images in the examined portion of the print queue, with the trigger value.

11. The method of claim 10 , wherein determining the printing state comprises determining whether the image forming device is operating in a color state or a black-only state.

12. The method of claim 10 , wherein determining the run mode comprises determining whether the image forming device is operating in a simplex, duplex, or idle mode.

13. The method of claim 10 , wherein determining when to deactivate the color cartridge comprises determining when to deactivate the color cartridge based on a comparison of the number of sequential black-only images in the examined portion of the print queue with the trigger value, when the examined portion of the print queue includes a color image.

14. The method of claim 10 , wherein determining when to deactivate the color cartridge comprises determining when to deactivate the color cartridge based on a comparison of a sum of the number of sequential black-only images immediately preceding the current image in the examined portion of the print history and the number of sequential black-only images in the examined portion of the print queue with the trigger value, when the examined portion of the print queue includes all black-only images.

15. The method of claim 10 , further comprising after deactivating the color cartridge, activating the color cartridge when the next image to be printed in the examined portion of the print queue is a color image.

16. A method for determining when to deactivate a color cartridge in an image forming device, comprising:

activating the color cartridge;

determining whether an examined portion of a print queue includes a color image;

when the examined portion of the print queue includes a color image, calculating a first test value as a number of sequential black-only images in the examined portion of the print queue beginning with a first image in the examined portion of the print queue;

comparing the first test value with a first trigger value and deactivating the color cartridge when the first test value is greater than or equal to the first trigger value;

when the examined portion of the print queue includes all black-only images, calculating a second test value as a sum of the first test value and a number of sequential black-only images immediately preceding the first image in an examined portion of a print history; and

comparing the second test value with a second trigger value and deactivating the color cartridge when the second test value is greater than or equal to the second trigger value.

17. The method of claim 16 , wherein comparing the first and second test values with the first and second trigger values comprises comparing the first and second test values with the first and second trigger values selected based on one or more factors including a printing state and a run mode of the image forming device.

18. The method of claim 17 , wherein selecting the first and second trigger values based on the printing state comprises selecting the first and second trigger values based on whether the image forming device is operated in a color state or black-only state.

19. The method of claim 17 , wherein selecting the first and second trigger values based on the run mode comprises selecting the first and second trigger values based on whether the image forming device is operating in a simplex, duplex, or idle mode.

20. The method of claim 16 , further comprising after deactivating the color cartridge, activating the color cartridge when the first image in the examined portion of the print queue is a color image.