Image forming device
View Patent ↗An image forming device has multiple image forming units that form developing agent images, an intermediate transfer member to which developing agent images are transferred from selected image forming units, and a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium, using a voltage supplied from a voltage supply unit. The voltage supply unit varies the voltage supplied to the transfer member, either before or after or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium, according to the number of selected image forming units or their disposition.
1. An image forming device comprising:
a plurality of image forming units for forming developing agent images;
an intermediate transfer member to which the developing agent images are transferred from selected ones of the image forming units;
a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium to form an image on the recording medium; and
a voltage supply unit for supplying a voltage to the transfer member,
wherein the voltage supply unit varies the voltage supplied to the transfer member, either before or after the developing agent images are transferred from the intermediate transfer member to the recording medium or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium, responsive to the number or disposition of the selected image forming units, and
wherein the voltage supply unit supplies the transfer member with a voltage of a normal polarity when more than one of the image forming units are selected, and supplies the transfer member with a voltage of a reverse polarity, opposite to the normal polarity, when only one of the image forming units is selected.
2. The image forming device of claim 1 , wherein:
the image forming units use respective developing agents with respective normal electrical charge characteristics, a proportion of developing agent charged to a reverse polarity reverse to the normal charge characteristic also being present in each of the image forming units;
the plurality of image forming units include a first image forming unit that forms a developing agent image of a first color and at least one second image forming unit that forms a developing agent image of a second color different from the first color, the first image forming unit having a highest proportion of developing agent charged to the reverse polarity; and
the plurality of image forming units are disposed in such a way that the developing agent image formed by at least one second image forming unit is transferred to the intermediate transfer member after the developing agent image formed by the first image forming unit is transferred to the intermediate transfer member.
3. The image forming device of claim 2 , wherein the first color is white.
4. The image forming device of claim 1 , wherein:
the image forming units use respective developing agents with a normal electrical charge characteristic, a proportion of developing agent charged to a reverse polarity reverse to the normal electrical charge characteristic also being present in each of the image forming units;
the plurality of image forming units include a first image forming unit that forms a developing agent image of a first color and at least one second image forming unit that forms a developing agent image of a second color different from the first color, the first image forming unit having a highest proportion of developing agent charged to the reverse polarity;
when the selected image forming units are disposed in such a way that the developing agent image formed by the first image forming unit is transferred last to the intermediate transfer member, the voltage supply unit supplies the transfer member with a voltage having a polarity reverse to the normal electrical charge characteristic of the developing agents; and
when the selected image forming units are disposed in such a way that the developing agent image formed by at least one second image forming unit is transferred to the intermediate transfer member after the developing agent image formed by the first image forming unit is transferred to the intermediate transfer member, the voltage supply unit supplies the transfer member with a voltage having a polarity matching the normal electrical charge characteristic of the developing agents.
5. The image forming device of claim 4 , wherein the disposition of the plurality of image forming units can be changed.
6. The image forming device of claim 4 , wherein the first color is white.
7. The image forming device of claim 1 , further comprising a control unit for selecting the image forming units that transfer developing agent images to the intermediate transfer body from among the plurality of image forming units, responsive to colors of the image formed on the recording medium.
8. The image forming device of claim 7 , the plurality of image forming units including respective image carriers on which the developing agent images are formed, the image forming device further comprising:
a displacement unit for changing the position of each of the image carriers between a first position at which image transfer to the intermediate transfer member is carried out and a second position at which image transfer to the intermediate transfer member is not carried out,
wherein the displacement unit places the image carriers in the selected image forming units in the first position, and places the image carriers in image forming units other than the selected image forming units in the second position.
9. The image forming device of claim 8 , wherein the image carriers make contact with the intermediate transfer member in the first position and do not make contact with the intermediate transfer member in the second position.
10. An image forming device comprising:
a plurality of image forming units for forming developing agent images;
an intermediate transfer member to which the developing agent images are transferred from selected ones of the image forming units;
a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium to form an image on the recording medium; and
a voltage supply unit for supplying a voltage to the transfer member,
wherein the voltage supply unit varies the voltage supplied to the transfer member, either before or after the developing agent images are transferred from the intermediate transfer member to the recording medium or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium, responsive to the number or disposition of the selected image forming units, and
wherein the voltage supply unit increases an absolute value of the voltage supplied to the transfer member as the number of selected image forming units increases.
11. The image forming device of claim 10 , wherein the voltage supply unit supplies the transfer member with a voltage of a normal polarity when more than one of the image forming units are selected, and supplies the transfer member with a voltage of a reverse polarity, opposite to the normal polarity, when only one of the image forming units is selected.
12. The image forming device of claim 10 , wherein the disposition of the plurality of image forming units can be changed.
13. The image forming device of claim 10 , further comprising a control unit for selecting the image forming units that transfer developing agent images to the intermediate transfer body from among the plurality of image forming units, responsive to colors of the image formed on the recording medium.
14. The image forming device of claim 10 , the plurality of image forming units including respective image carriers on which the developing agent images are formed, the image forming device further comprising:
a displacement unit for changing the position of each of the image carriers between a first position at which image transfer to the intermediate transfer member is carried out and a second position at which image transfer to the intermediate transfer member is not carried out,
wherein the displacement unit places the image carriers in the selected image forming units in the first position, and places the image carriers in image forming units other than the selected image forming units in the second position.
15. An image forming device comprising:
a plurality of image forming units for forming developing agent images;
an intermediate transfer member to which the developing agent images are transferred from selected ones of the image forming units;
a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium to form an image on the recording medium; and
a voltage supply unit for supplying a voltage to the transfer member,
wherein the voltage supply unit varies the voltage supplied to the transfer member, either before or after the developing agent images are transferred from the intermediate transfer member to the recording medium or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium, responsive to the number or disposition of the selected image forming units, and
wherein the voltage supply unit supplies the transfer member with a voltage of a reverse polarity, opposite to the normal polarity of developing agent of white, when only one of the image forming units is selected and the selected image forming unit forms a developing agent image of white.
16. The image forming device of claim 15 , wherein the disposition of the plurality of image forming units can be changed.
17. The image forming device of claim 15 , further comprising a control unit for selecting the image forming units that transfer developing agent images to the intermediate transfer body from among the plurality of image forming units, responsive to colors of the image formed on the recording medium.
18. The image forming device of claim 15 , the plurality of image forming units including respective image carriers on which the developing agent images are formed, the image forming device further comprising:
a displacement unit for changing the position of each of the image carriers between a first position at which image transfer to the intermediate transfer member is carried out and a second position at which image transfer to the intermediate transfer member is not carried out,
wherein the displacement unit places the image carriers in the selected image forming units in the first position, and places the image carriers in image forming units other than the selected image forming units in the second position.
19. The image forming device of claim 15 , wherein the voltage supply unit increases an absolute value of the voltage supplied to the transfer member as the number of selected image forming units increases.
20. An image forming device comprising:
a plurality of image forming units for forming developing agent images;
an intermediate transfer member to which the developing agent images are transferred from selected ones of the image forming units;
a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium to form an image on the recording medium; and
a voltage supply unit for supplying a voltage to the transfer member,
wherein when only one of the image forming units is selected, the voltage supply unit supplies a voltage different from a voltage supplied when more than one of the image forming units are selected, either before or after the developing agent images are transferred from the intermediate transfer member to the recording medium or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium.
21. The image forming device of claim 20 , wherein, when only one of the image forming units is selected and the selected image forming unit forms a developing agent image of white, the voltage supply unit supplies a voltage different from a voltage which is supplied when more than one of the image forming units are selected.