JPH04164742A - Paper transfer guide plate - Google Patents

Abstract

PURPOSE:To provide a transfer guide at a proper position to a fixing part without paper being crumpled even at a low temperature by making a conductive guide plate own the identical electric potential to a frame or no electric conductivity when paper is transferred onto the conductive guide plate, and enters he fixing part. CONSTITUTION:A paper entry detection sensor 20 detects that the end of paper 2 enters a nip part 12c between a fixing roller 12a and a pressurizing roller 12b. As a result, a control part 18 restrains attraction force from becoming higher than it needs due to static electricity between the paper 2 and the conductive guide plate 11A. Moreover, the paper is made to enter the nip part 12c of a fixing part 12 at an exact position to prevent the paper from being crumpled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a paper conveyance guide plate from a transfer section to a fixing section in an image forming apparatus such as a printer or a copying machine.

(Prior Art) FIG. 7 shows a schematic diagram of the configuration of a laser printer as an example of an image forming apparatus. To give an overview of the operation of this laser printer, sheets 2 placed on a paper feed tray 1 are picked up one by one by a pickup roller 3, conveyed to a pair of registration rollers 5 by a grip roller 4,
Here, take the timing and insert the photoconductor (○PC) belt 6.
Transport to.

On the other hand, the PC belt 6 is rotated in the direction of the arrow by a main motor (not shown), its surface is charged by a charger 7, and then scanned with a laser spot L modulated by an optical unit 8 for image writing to generate electrostatic charges. Form a latent image. Then, a developing unit 9 applies toner to this latent image to make it visible.

Further, this toner image is transferred by the transfer charger 10 onto the paper 2 conveyed by the pair of registration rollers 5, and transferred to the fixing section 12 via the conductive guide plate 11.
(the fixing roller 12a and the pressure roller 12b), and is heated and fixed by the fixing roller 12a.

The paper that has left the fixing section is conveyed upward by a paper ejection roller 13 and ejected to a paper ejection tray 15 provided on the top surface of the printer 14.

Note that after the visible image has been transferred, the OPC belt 6 is cleaned of residual toner by a cleaning unit 16, and a static elimination lamp 17
receives static elimination action.

FIG. 8 is an explanatory diagram of the process in each part of FIG. is charged with a (-) charge. In the exposure process (2), the laser beam (spot L) from the laser diode 8a in the optical unit 8 is irradiated onto the surface of the PC belt 6 via the mirror 8b. On the surface of the OPC belt, where the laser beam hits, the resistance value decreases and the charged charges escape. Therefore, (-) charges remain where the laser beam does not hit. The area where this charge remains becomes an image called the electrostatic latent image.

Next, in the development process (3), the toner L of (+) potential is attached to the electrostatic latent image ((-) charge) on the surface of the PC belt 6 by the development roller 9a of the development unit 9, and the toner is developed. Change to In the transfer process (4), transfer charger 1
When a high (-) voltage is applied from the power back 10b to the 0 tungsten wire IOa, the toner adhering to the PC belt 6 also moves to the paper 2.

Returning to FIG. 7, when the paper 2 carrying a (-) charge passes over the conductive guide plate 11, an attractive force due to static electricity acts between the paper 2 and the guide plate, suppressing the flapping of the paper 2 and fixing it. It smoothly enters the protrusion between the roller 12a and the pressure roller 12b. Further, in the transfer charger lO, the OPC belt 6 and the paper 2 are fed together, so that the image on the PC belt is transferred onto the paper without shifting.

(Problem to be solved by the invention) By the way, when the humidity is low like in winter, the paper 2 has
Electric charge is more likely to remain, and more suction force than necessary is generated between the paper and the conductive guide plate, causing the paper to stick to the guide plate and hindering paper movement, causing wrinkles on the paper, and causing damage to the transfer charger. There was a speed discrepancy between the paper speed and the OPC belt during transfer, resulting in image misalignment.

In order to prevent such paper from wrinkling, it has been proposed to use a non-conductive guide plate instead of the conductive guide plate 11, but according to this, the attraction force is reduced due to static electricity. Because the paper does not work, the paper becomes too free, and the paper sometimes enters the nip between the fixing roller and the pressure roller in the fixing unit at an arbitrary position without being placed on the guide plate, causing jams and wrinkles.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a guide plate which eliminates the problems of the conventional guide plate and allows paper to be conveyed to the fixing unit at the correct position without wrinkles even in low humidity.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the objects, the invention as set forth in claim (1) provides a paper conveyance guide plate from the transfer section to the fixing section on the transfer section side. A conductive guide plate installed on the conductive guide plate and a non-conductive guide plate installed on the fixing unit side constitute a paper transport guide plate between the transfer unit and the fixing unit, and the paper is placed on the conductive guide plate. The present invention is characterized in that when the paper is transported and enters the fixing section, the conductive guide plate is at the same potential as the frame or is electrically non-conductive.

Further, in the invention described in claim (2), in the paper conveyance guide plate from the transfer section to the fixing section, the conductive guide plate installed on the transfer section side has several slits in the paper conveyance direction. , the non-conductive guide plate installed on the fixing unit side has several ribs protruding from the slit of the conductive guide plate to the guide surface, and the paper is conveyed onto the conductive guide plate, and the paper is conveyed onto the conductive guide plate. When entering the fixing section, the ribs of the non-conductive guide plate pass through the slits of the conductive guide plate and protrude onto the guide surface.

Further, in the invention described in claim (3), in the paper conveyance guide plate from the transfer unit to the fixing unit, a conductive guide plate is formed between the transfer unit side and the fixing unit, and a conductive guide plate near the conductive guide plate is provided. The humidity detection element establishes electrical continuity between the conductive guide plate and the frame when the humidity is below a predetermined value, and does not establish electrical continuity between the conductive guide plate and the frame when the humidity is above a predetermined value. It is characterized by

(Function) In the invention described in claim (1) of the present invention, the paper transferred in the transfer section is controlled to have an appropriate electrostatic attraction force on the conductive guide plate, and the paper is transferred on the non-conductive guide plate. When the paper is transported and enters the nip between the fixing roller and the pressure roller of the fixing unit, the electrically conductive guide plate is made to have the same potential as the frame or is electrically non-conductive, so that the paper and the conductive guide plate are separated. This suppresses the excessive suction force caused by static electricity, which prevents wrinkles from occurring without interfering with paper movement.

Further, in the invention described in claim (2), the paper transferred in the transfer section is controlled by an appropriate electrostatic attraction force on the conductive guide plate, and the paper is moved between the fixing roller and the pressure roller of the fixing section. When the paper enters the nip, it passes through the slit of the conductive guide plate, the ribs of the non-conductive guide plate located at the lower position protrude, guide the paper, and create a gap between the conductive guide plate and the paper. Reduces suction power and prevents paper from wrinkling.

Furthermore, the invention as claimed in claim (3) establishes electrical continuity with the frame when the humidity near the conductive guide plate is below a predetermined value, and establishes electrical continuity with the frame when the humidity is above the predetermined value. When the humidity is lower than a predetermined value, the suction force between the paper and the conductive guide plate is suppressed to prevent the paper from wrinkling.

(Embodiment) FIG. 1 shows a control system according to an embodiment of the invention described in claim (1) of the present invention. In the figure, IIA is a conductive guide plate formed of a metal material installed downstream of the transfer charger 10 in the conveyance direction (arrow A) of the paper 2, and 11B is a conductive guide plate whose conveyance surface is the same as that of the conductive guide plate 11A. This is a non-conductive guide plate made of an insulating material, and is installed upstream of the sheet 2 of the fixing unit 12 . 18 is the conductive guide plate 11A
20 is a paper entry detection sensor installed near the entry of the paper 2 into the fixing unit 12, and the controller 18 controls the conductive guide plate 11A. Used for timing detection.

FIG. 2 is an exploded perspective view showing the arrangement of the conductive guide plate 11A and the non-conductive guide plate 11B of FIG. 1, and the non-conductive guide plate 11B is attached to the stay 19A of the printer body.

In this embodiment, the paper entry detection sensor 2o detects the paper 2
When detecting that the tip of the conductive guide plate 11A enters the nip 12c between the fixing roller 12a and the pressure roller 12b, the control unit 18 moves the conductive guide plate 11A to the frame 19 (in FIG. 2, the stay 19A) based on this detection signal. ) or are electrically non-conductive, suppressing the excessive attraction force due to static electricity between the paper 2 and the conductive guide plate 11A, and moving the paper toward the nip portion 12c of the fixing unit 12 without interfering with the movement of the paper. Insert the paper in the correct position to prevent wrinkles from forming on the paper.

FIG. 3 shows an exploded perspective view of a conductive guide plate 11A according to another embodiment of the present invention, which is fixed to the printer main body with non-conductive screws lla via insulators llb. Then, the switch 21 is turned on and off by a signal from the control unit 18, and the conductive guide plate l
Electrical continuity between the IA and the frame 19 is turned on and off. That is, when the paper entry detection sensor 20 detects that the paper 2 has entered the nip section 12c of the fixing section 12, as in FIGS. 1 and 2, the control section 18 turns off the switch based on this detection signal, and Frame 1 with sex guide plate 11A
By electrically separating the sheet 2 from the conductive guide plate 9, the suction force between the sheet 2 and the conductive guide plate is eliminated, allowing the sheet to enter the nip portion at the correct position without interfering with the sheet, thereby causing wrinkles. I can guide you without any trouble.

FIG. 4 shows a control system of an embodiment according to the invention set forth in claim (2) of the present invention. In the figure, reference numeral 22 denotes a drive unit for the non-conductive guide plate 11B, which is moved in the direction of arrow B (upward in the figure) by a signal from the control unit 18.

FIG. 5 shows an exploded perspective view showing the structure of the conductive guide plate 11A and the non-conductive guide plate 11B shown in FIG. Same figure (
In 1), the conductive guide plate 11A has several slits lie in the paper 2 transport direction (arrow C), and the ribs lld of the non-conductive guide plate 11B pass through the slits llc, and the conductive guide plate 11A It is configured to protrude toward the guide surface of. Arrow B on the second non-conductive guide plate 11B
The lifting mechanism in the direction is composed of a stopper 24 that engages with the switching knob 23, and its inclined surface 24a (enlarged view (2)
) locks the lifting portion 11e of the non-conductive guide plate 11B. Further, a support shaft ILg is inserted through a shaft hole 11f serving as a pivot axis of the non-conductive guide plate 11B, and both end shafts of the support shaft 11g are fixed to the frame 19.

Now, the paper entry detection sensor 20 detects that the paper 2 is in the fixing section 12.
When detecting the entry into the nip portion 12c, the control section 18 outputs a signal to the drive section 22 based on the detection signal. The driving part 22 lifts the non-conductive guide plate 11B by pulling the switching knob 23 shown in FIG. 5 in the direction of the arrow.
The stopper 24 of the ie is released, and the non-conductive guide plate 11B is rotated in the direction of arrow B about the support shaft 11g.

As a result, the rib lid passes through the slit llc of the conductive guide plate 11A, and the sheet 2 is guided by the rib lid. As a result, the paper smoothly enters the nip portion 12c at the correct position without being affected by the attraction force with the conductive guide plate 11A.

When the end of the paper 2 is detected by the paper entry detection sensor 20, the control unit 18 controls the drive unit 2 based on the detection signal.
2 to return the switching knob 23 to small in the opposite direction of the arrow and lock it with the stopper 24.
The non-conductive guide plate 11B returns to its original position, and the knob lid descends from the slit llc to prepare for the next paper guide. The above-mentioned operation of the non-conductive guide plate 11B is performed each time the paper 2 enters the fixing section, but it may also be performed only when the control section 18 determines that the humidity is low based on a detection signal from a humidity detection sensor, which will be described later. .

FIG. 6 shows a control system of an embodiment according to the invention set forth in claim (3) of the present invention. In the figure, 25 is the conductive guide plate 1
A humidity detection sensor is installed near 1A, and its detection signal is input to the control unit 18. The control unit 18 establishes electrical continuity between the conductive guide plate and the frame when the humidity is below a predetermined value, and prevents electrical continuity between the conductive guide plate and the frame when the humidity is above a predetermined value. Control.

In this way, when the humidity is low in winter, the suction force of the paper to the conductive guide plate 11A can be suppressed, and the paper can smoothly enter the nip portion of the fixing section at a fixed position without wrinkles.

The present invention may be implemented by a combination of the above-mentioned embodiments.
For example, the humidity detection sensor shown in Fig. 6 may be replaced with the humidity detection sensor shown in Fig. 1 or 4 above.
It connects to the control unit shown in the figure, and determines whether the humidity shown in Figure 6 is above a predetermined value based on the detection signal from the humidity detection sensor.
It is effective to control each of the conductive guide plate and the non-conductive guide plate at the bottom.

(Effects of the Invention) As explained above, the present invention allows the paper guide plate installed between the transfer section and the fixing section in an image forming apparatus to have an appropriate suction force against the paper, which is affected by the surrounding humidity. With this configuration, wrinkles do not occur on the paper at the fixing section, and image shift at the transfer section due to wrinkles is prevented.

[Brief explanation of the drawing]

FIG. 1 is an exploded view showing the control system of the embodiment according to the invention described in claim (1) of the present invention, and FIG. 2 is an exploded view showing the arrangement of the conductive guide plate and the non-conductive guide plate of FIG. FIG. 3 is an exploded perspective view of a conductive guide plate according to another embodiment, FIG. 4 is a diagram showing a control system of an embodiment according to claim (2) of the present invention, and FIG. is an exploded perspective view showing the configuration of the conductive guide plate and the non-conductive guide plate shown in FIG. 4, FIG.
The figure is a schematic diagram of the configuration of a laser printer as an example of an image forming apparatus, and FIG. 8 is an explanatory diagram of processes in each part of FIG. 7. 2...Paper, 6...Photoconductor (OPC) belt,
10...Transfer charger, IIA...Conductive guide plate, IIB...Non-conductive guide plate, lla...
Non-conductive screw, llb... insulator, llc
...slit, lid...rib, lie...lifting part, llf...shaft hole, Ilg...support shaft, 12.
...Fixing section, 12a...Fixing roller, 12b...
Pressure roller, 12c...Nip portion, 18...Control unit, 19...Frame of printer body, 19A...
・Stay, 20... Paper entry detection sensor, 21...
・Switch, 22... Drive unit, 23... Switching knob,
24... Stopper, 24a... Inclined surface, 25...
・Humidity detection sensor. Figure 1 Figure 4 Figure 2 Sweat

Claims (3)

[Claims] (1) In the guide plate for transporting paper from the transfer section to the fixing section, a conductive guide plate installed on the transfer section side and a non-conductive guide plate installed on the fixing section side connect the transfer section and the fixing section. A paper transport guide plate between the frames is configured, and when the paper is transported onto the conductive guide plate and the paper enters the fixing section, the conductive guide plate is placed at the same potential as the frame or electrically non-conductive. A paper conveyance guide plate characterized by: (2) In the paper conveyance guide plate from the transfer section to the fixing section, the conductive guide plate installed on the transfer section side has several slits in the paper conveyance direction, and the non-conductive guide plate installed on the fixing section side has several slits in the paper conveyance direction. The conductive guide plate has several ribs protruding from the slit of the conductive guide plate to the guide surface, and when the paper is conveyed onto the conductive guide plate and enters the fixing section, the non-conductive guide plate 1. A paper conveyance guide plate, wherein a rib of the conductive guide plate passes through a slit of the conductive guide plate and projects onto a guide surface. (3) In the paper conveyance guide plate from the transfer unit to the fixing unit, a conductive guide plate is formed between the transfer unit side and the fixing unit,
A humidity detection element near the conductive guide plate establishes electrical continuity between the conductive guide plate and the frame when the humidity is below a predetermined value, and connects the conductive guide plate with the frame when the humidity is above a predetermined value. A paper conveyance guide plate characterized by not having electrical continuity.