Image forming apparatus

Abstract

Assume that a paper feed width of a sheet of paper of a predetermined size that is smaller than the maximum paper feed width W is W1. Then, when a sheet of paper having a width larger than the paper feed width W1 is transported, to stabilize the transportation thereof, first, second, and third fans 26a to 26c are all so rotated as to stick the entire sheet of paper to a transportation unit 25. On the other hand, when a sheet of paper having a width equal to or smaller than the paper feed width W1 is transported, only the first and third fans 26a and 26c are made to rotate to prevent an increase in the temperature of non-paper feeding areas 30a and 30b formed at the edges of a fuser roller pair 14a.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional view showing the structure near the image forming portion and the fuser of the image forming apparatus according to one embodiment of the present invention;

FIG. 2 is a perspective view, as seen from the paper transportation path side (the right of FIG. 1), of the transportation unit;

FIG. 3 is a perspective view, as seen from the duplex-printing paper transportation path side (the left of FIG. 1), of the transportation unit;

FIG. 4 is a perspective view showing a state in which the transportation unit and the duplexer are separated from each other;

FIG. 5 is a schematic plan view showing the positional relationship between the fans and the fuser;

FIG. 6 is a schematic plan view showing an example in which the shutter mechanisms are provided in the air guide paths;

FIG. 7 is a block diagram showing the control mechanism of the image forming apparatus of the present invention;

FIG. 8 is a flow chart showing an example of the procedure performed during image formation for controlling the driving of the fans;

FIG. 9 is a flow chart showing another example of the procedure performed during image formation for controlling the driving of the fans;

FIG. 10 is a schematic diagram showing the entire structure of a conventional image forming apparatus; and

FIG. 11 is a graph showing how the fusing temperatures of a paper feeding area and a non-paper feeding area change when printing is continuously performed.

Claims

1. An image forming apparatus comprising: a transportation unit that has transfer means transferring a toner image formed on an image carrier to a recording medium, and that carries and transports the recording medium;a fuser that fuses the toner image transferred by the transfer means to the recording medium;a plurality of fans that are provided across a transportation width of the transportation unit for sticking the recording medium on the transportation unit onto a transporting surface by depressurizing;an air guide path through which an air inflow side of each fan communicates with an inside of the fuser; andcontrol means that controls a rotation of the fans in such a way that, when more than a predetermined number of recording mediums having a width equal to or smaller than a predetermined width are transported within a predetermined time, a rotation of the fan communicating through the air guide path with a paper feeding area located inside the fuser and a rotation of the fan communicating through the air guide path with a non-paper feeding area located inside the fuser are separately controlled.

2. The image forming apparatus of claim 1, wherein when more than a predetermined number of recording mediums having a width equal to or smaller than the predetermined width are transported within a predetermined time, the control means rotates only the fan communicating with the non-paper feeding area located inside the fuser.

3. The image forming apparatus of claim 1, wherein when more than a predetermined number of recording mediums having a width equal to or smaller than the predetermined width are transported within a predetermined time, the control means makes a rotation speed of the fan communicating with the paper feeding area located inside the fuser slower than a rotation speed of the fan communicating with the non-paper feeding area.

4. The image forming apparatus of claim 1, wherein there is provided opening/closing means that opens/closes the air guide path, andwhen a recording medium that is wider than the predetermined width is transported, the control means causes the opening/closing means to close the air guide path.

5. The image forming apparatus of claim 2, wherein there is provided opening/closing means that opens/closes the air guide path, andwhen a recording medium that is wider than the predetermined width is transported, the control means causes the opening/closing means to close the air guide path.

6. The image forming apparatus of claim 3, wherein there is provided opening/closing means that opens/closes the air guide path, andwhen a recording medium that is wider than the predetermined width is transported, the control means causes the opening/closing means to close the air guide path.

7. The image forming apparatus of claim 1, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing paper transportation path.

8. The image forming apparatus of claim 2, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing paper transportation path.

9. The image forming apparatus of claim 3, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing paper transportation path.

10. The image forming apparatus of claim 4, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing papertransportation path.

11. The image forming apparatus of claim 5, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing paper transportation path.

12. The image forming apparatus of claim 6, wherein there is provided a duplex-printing paper transportation path that re-transports to the transfer means a recording medium that has passed through the fuser at a time of duplex printing, andan air outflow side of each fan communicates with the duplex-printing paper transportation path.