JP2929035B2 - Paper transport guide device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial application field) The present invention relates to a guide device for conveying a sheet 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 configuration diagram of a laser printer as an example of an image forming apparatus. An outline of the operation of the laser printer will be described. Sheets 2 placed on a sheet feed tray 1 are picked up one by one by a pickup roller 3.
The sheet is conveyed to a pair of registration rollers 5 by a grip roller 4, and is conveyed to a photoreceptor (OPC) belt 6 at a proper timing.

On the other hand, the OPC belt 6 is driven to rotate in the direction of the arrow by a main motor (not shown), the surface of the OPC belt 6 is charged by the charging charger 7, and then scanned by the laser spot L modulated by the optical unit 8 for writing an image. Form an image. Then, the latent image is visualized by attaching toner with the developing unit 9.

Further, the toner image is transferred by the transfer charger 10 onto the sheet 2 conveyed by the registration roller pair 5 and is transferred via the conductive guide plate 11 to the fixing unit 12 (fixing roller 12a and pressure roller 12b). To the fixing roller 12
Heat and fix by a. The sheet exiting the fixing section is transported upward by a sheet discharge roller 13 and discharged to a sheet discharge tray 15 provided on the upper surface of the printer 14.

After the transfer of the visible image, the OPC belt 6 is cleaned by a cleaning unit 16 to remove residual toner, and is subjected to a charge removing operation by a charge removing lamp 17.

FIG. 8 is an explanatory view of the process in each part of FIG. 7. In the charging process (1), when a high voltage is applied from the power pack 7b to the tungsten wire 7a of the charging charger 7, the surface of the OPC belt 6 is The charge of (−) is charged. In the exposure process (2), the laser beam (spot L) from the laser diode 8a in the optical unit 8
Is irradiated on the surface of the OPC belt 6 via the mirror 8b. O
On the surface of the PC belt, where the laser beam hits, the resistance decreases and the charged charges escape. Therefore, where the laser beam does not hit, the charge (-) remains. The place where the charge remains is an image called the electrostatic latent image.

Next, in a developing process (3), a toner t of (+) potential is adhered to the electrostatic latent image ((−) charge) on the surface of the OPC belt 6 by a developing roller 9a of a developing unit 9 to form a toner visible image. Change. In the transfer process (4), when a high voltage (−) is applied from the power pack 10b to the tungsten wire 10a of the transfer charger 10, the toner t attached on the OPC belt 6 moves to the paper 2.

Referring back to FIG. 7, when the sheet 2 on which the (−) charge is passed passes over the conductive guide plate 11, a suction force due to static electricity acts between the guide plate 11 and the sheet 2 to prevent the sheet 2 from fluttering and fix. It smoothly enters between the roller 12a and the pressure roller 12b (nip portion). Further, in the transfer charger 10, the OPC belt 6 and the paper 2 are fed together, and the image on the OPC belt is transferred onto the paper without shifting.

(Problems to be Solved by the Invention) By the way, when the humidity is low as in winter, electric charges are more likely to remain on the paper 2 and an unnecessary suction force is generated between the paper and the conductive guide plate. Paper was stuck on the guide plate and the movement of the paper was hindered, causing wrinkles on the paper and causing a speed gap between the paper speed at the time of transfer with the transfer charger and the OPC belt, resulting in image displacement. .

In order to prevent such paper from wrinkling,
It has also been proposed to use a non-conductive guide plate in place of the conductive guide plate 11, but according to this, the paper becomes too free because the suction force does not work due to static electricity, and the paper does not rest on the guide plate. In some cases, the paper may enter the nip portion between the fixing roller and the pressure roller of the fixing unit at an arbitrary position, causing jams and wrinkles.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a guide plate that solves such a problem of the conventional guide plate and that can guide a sheet at a correct position in a fixing unit without wrinkling even in a low humidity.

(Means for Solving the Problems) In order to solve the above problems and achieve the object, the invention described in claim (1) is arranged between a transfer unit and a fixing unit,
A sheet transport guide plate configured by a conductive guide plate installed on the transfer unit side, and a non-conductive guide plate installed on the fixing unit side; and the fixing unit provided near the fixing unit. A paper entering detection unit that detects a sheet entering the paper, and a control unit that makes the conductive guide plate have the same potential as the frame or electrically non-conductive based on a detection signal of the paper entering detection unit. Features.

The invention according to claim (2) is a conductive guide plate disposed between the transfer section and the fixing section, installed on the transfer section side and having several slits in the sheet conveyance direction, and on the fixing section side. A sheet conveyance guide plate provided with a non-conductive guide plate having a plurality of ribs provided in the sheet conveyance direction and provided near the fixing unit to detect a sheet entering the fixing unit; A sheet entry detection unit, and a control unit that moves the non-conductive guide plate so that the ribs pass through slits of the conductive guide plate and project to the guide surface based on a detection signal of the sheet entry detection unit. It is characterized by having.

The invention according to claim (3) is configured by a conductive guide plate disposed between the transfer unit and the fixing unit and disposed on the transfer unit side, and a non-conductive guide plate disposed on the fixation unit side. A sheet conveyance guide plate, a paper entry detection unit provided near the fixing unit and detecting a sheet entering the fixing unit, a humidity detection element provided near the conductive guide plate, Based on a detection element and a detection signal of the paper entry detection unit, before the sheet enters the fixing unit, if the humidity is equal to or less than a predetermined value, the conductive guide plate is electrically connected to a frame, and the humidity is controlled. A control unit for controlling the conductive guide plate so as not to be electrically connected to the frame when the value is equal to or more than a predetermined value.

(Operation) According to the invention described in claim (1) of the present invention, the paper transferred by the transfer unit is controlled on a conductive guide plate by an appropriate attraction force due to static electricity, and the paper is transferred onto the non-conductive guide plate. Immediately before entering the nip portion between the fixing roller and the pressure roller of the fixing unit, the sheet entry detection unit detects the sheet, and the conductive guide plate is connected to the frame based on a detection signal from the sheet entry detection unit. By making the same potential or electrically non-conductive,
It suppresses unnecessary suction force due to static electricity between the paper and the conductive guide plate. As a result, the load on the paper when the paper comes into contact with the fixing roller is reduced, thereby suppressing the adverse effect on the toner image on the paper. Wrinkles are prevented without hindering the movement of the robot.

Further, according to the invention described in claim (2), the paper transferred by the transfer unit is controlled by an appropriate suction force by static electricity on the conductive guide plate, and the paper is moved between the fixing roller and the pressure roller of the fixing unit. Immediately before entering the nip portion, the sheet entry detection unit detects the sheet, passes through the slit of the conductive guide plate based on the detection signal from the sheet entry detection unit, and the rib of the non-conductive guide plate at the lower position is By projecting and guiding the paper, the suction force between the conductive guide plate and the paper is suppressed, and as a result, the load on the paper when the paper contacts the fixing roller is reduced, and the toner image on the paper is reduced. Reduce the negative impact on
Moreover, the paper is prevented from being wrinkled.

Further, the invention according to claim (3) provides an electrical connection with the frame when the humidity near the conductive guide plate is equal to or lower than a predetermined value, and an electrical connection with the frame when the humidity is equal to or higher than the predetermined value. When the humidity is lower than the specified 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 present invention. In the figure, 11A is the transfer charger 1
A conductive guide plate 11B formed of a metal material and disposed downstream of the sheet 2 in the conveying direction (arrow A) is a non-conductive material formed of an insulating material having the same conveying surface as the conductive guide plate 11A. A conductive guide plate is provided upstream of the fixing unit 12 where the paper 2 enters. Reference numeral 18 designates the conductive guide plate 11A as a frame 19.
And a control unit 20 for controlling the conductive guide plate 11A by the control unit 18 to detect the control timing of the conductive guide plate 11A. Used for

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. The non-conductive guide plate 11B is attached to a stay 19A of the printer body.

In the case of the embodiment of the present invention, as is apparent from FIG. 1, the leading edge of the paper 2 is detected by the paper entering detection sensor 20 immediately before entering the nip portion 12c between the fixing roller 12a and the pressing roller 12b. When paper is detected, the control unit 18
Connects the conductive guide plate 11A to the frame 19 (in FIG.
9A), the nip portion 12c of the fixing section 12 is prevented without suppressing the suction force more than necessary due to the static electricity between the sheet 2 and the conductive guide plate 11A. At the correct position to prevent paper wrinkles. Further, since the suction force is suppressed immediately before the paper enters the nip portion 12c, the load applied to the paper when the leading end of the paper contacts the fixing roller 12a is reduced, and the adverse effect on the toner image on the paper is reduced. be able to.

FIG. 3 is an exploded perspective view of a conductive guide plate 11A according to another embodiment of the present invention. The conductive guide plate 11A is fixed to a printer main body via an insulator 11b with non-conductive screws 11a. Then, the switch 21 is turned on and off by a signal from the control unit 18, and the conductive guide plate 11A and the frame 1 are turned on.
Turns on and off the electrical continuity with 9. That is, similarly to FIGS. 1 and 2, the paper 2 is
When the paper entry detection sensor 20 detects that the paper 2 has entered the controller 2, the controller 18 turns off the switch in response to the detection signal, and electrically disconnects the conductive guide plate 11A from the frame 19, whereby the paper 2 and the paper 2 are electrically connected. By eliminating the suction force with the guide plate, the paper can be guided at a correct position without obstructing the paper from entering the nip portion, and can be guided without generating wrinkles.

FIG. 4 shows a control system according to an embodiment of the present invention. In the figure, 22 is a non-conductive guide plate
The drive unit of 11B moves in the direction of arrow B (upward in the drawing) according to the signal of the control unit 18.

FIG. 5 is an exploded perspective view showing the configuration of the conductive guide plate 11A and the non-conductive guide plate 11B shown in FIG. In FIG. 1A, the conductive guide plate 11A has several slits 11c in the direction of conveyance of the sheet 2 (arrow C), and the rib 11d of the non-conductive guide plate 11B passes through the slit 11c. It is configured to protrude to the guide surface of the guide plate 11A. The lifting mechanism of the non-conductive guide plate 11B in the direction of arrow B is constituted by a stopper 24 which engages with the switching knob 23, and the non-conductive guide plate 11B is lifted by its inclined surface 24a (enlarged view (2)). The part 11e is locked. A support shaft 11g is inserted into a shaft hole 11f serving as a rotation base shaft of the non-conductive guide plate 11B, and both end shafts of the support shaft 11g are fixed to the frame 19.

Now, the nip portion of the fixing unit 12 is detected by the paper entry detection sensor 20.
When a sheet immediately before entering 12c is detected, the control unit 18 outputs a signal to the drive unit 22 based on the detection signal. Drive unit 22
The stopper 24 of the lifting portion 11e of the non-conductive guide plate 11B is released by pulling the switching knob 23 shown in FIG. 5 in the direction of arrow D, and the non-conductive guide plate 11B is moved in the direction of arrow B with the support shaft 11g as a base axis. Is rotated. Thus, the rib 11d passes through the slit 11c of the conductive guide plate 11A, and guides the sheet 2 by the rib 11d. As a result, the paper is
It smoothly enters the nip portion 12c at the correct position without being affected by the suction force with 11A. Also, since the suction force is suppressed immediately before the paper enters the nip portion 12c, the load applied to the paper when the leading edge of the paper contacts the fixing roller 12a is reduced,
The adverse effect on the toner image on the paper can be reduced.

When the trailing end of the paper 2 is detected by the paper entering detection sensor 20, the control unit 18 controls the driving unit 22 based on the detection signal, and returns the switching knob 23 to the direction D 'opposite to the direction of arrow D to stop the stopper. By locking with 24, the non-conductive guide plate 11B returns, the knob 11d descends from the slit 11c, and shifts to the preparation of the next paper guide. The above non-conductive guide plate
Although the operation of 11B is performed every time the paper 2 enters the fixing unit, the operation may be performed only when the control unit 18 determines that the humidity is low based on a detection signal of a humidity detection sensor described later.

FIG. 6 shows a control system according to an embodiment of the present invention. In the figure, 25 is the conductive guide plate 11
The detection signal is input to the control unit 18 by a humidity detection sensor installed near A. The controller 18 electrically connects the conductive guide plate to the frame when the humidity is equal to or lower than a predetermined value, and prevents the conductive guide plate from electrically connecting to the frame when the humidity is equal to or higher than the predetermined value. Control. In this way, the suction force of the sheet to the conductive guide plate 11A can be suppressed when the humidity in winter is low, and the sheet can smoothly enter the fixed position without causing wrinkles into the nip portion of the fixing unit.

The present invention may be a combination of the above embodiments, for example, by connecting the humidity detection sensor of FIG. 6 to the control unit shown in FIG. 1 or FIG. 4, based on a detection signal from the humidity detection sensor, It is effective to control each of the conductive guide plate and the non-conductive guide plate depending on whether the total humidity in FIG. 6 is above or below a predetermined value.

(Effect of the Invention) As described above, according to the present invention, the guide force of the sheet provided between the transfer unit and the fixing unit in the image forming apparatus can be appropriately adjusted by the suction force for the sheet affected by ambient humidity. With such a configuration, there is no wrinkling of the sheet at the fixing unit, and the image is prevented from shifting at the transfer unit due to the wrinkling. In addition, the suction force is adjusted immediately before the paper enters the fixing unit, so that before the paper enters the fixing unit, the paper is prevented from fluttering by the suction force between the paper and the conductive guide plate, and the paper enters the fixing unit. By reducing the suction force between the sheet and the conductive guide plate immediately before the fixing, the load on the sheet when the sheet comes into contact with the fixing roller is reduced, the adverse effect on the toner image on the sheet is suppressed, and the fixing unit is further reduced. While the paper is entering, the adverse effect due to the excessive suction force between the sheet and the conductive guide plate is prevented.

[Brief description of the drawings]

FIG. 1 is a view showing a control system according to an embodiment of the present invention, and FIG. 2 is an exploded view showing an arrangement of a conductive guide plate and a non-conductive guide plate in FIG. FIG. 3 is an exploded perspective view of a conductive guide plate of another embodiment, FIG. 4 is a diagram showing a control system of an embodiment according to the invention described in 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. 6 is a view showing a control system according to the invention of claim (3) of the present invention, and FIG.
FIG. 7 is a schematic diagram of a laser printer as an example of an image forming apparatus, and FIG. 8 is an explanatory diagram of a process in each unit in FIG. 2 paper, 6 photoconductor (OPC) belt, 10 transfer charger, 11A conductive guide plate, 11B non-conductive guide plate, 11a non-conductive screw, 11b insulator , 11c ... slit, 11d ... rib, 11e ... lifting part, 11f ... shaft hole, 11g ... support shaft, 12 ... fixing part, 12a ...
... fixing roller, 12b ... pressure roller, 12c ... nip,
18 ... Control unit, 19 ... Frame of printer body, 19A ...
... Stay, 20 ... Paper entry detection sensor, 21 ... Switch, 22 ... Driver, 23 ... Switch knob, 24 ... Stopper, 24a ... Slope surface, 25 ... Humidity detection sensor.

Claims (3)

(57) [Claims] 1. A sheet conveyance guide disposed between a transfer unit and a fixing unit and configured by a conductive guide plate installed on the transfer unit side and a non-conductive guide plate installed on the fixation unit side. A sheet, a sheet entering detection unit provided near the fixing unit, and detecting a sheet entering the fixing unit. The conductive guide plate is set at the same potential as a frame or based on a detection signal of the sheet entry detecting unit. A sheet conveyance guide device, comprising: a control unit that electrically disconnects the sheet. A conductive guide plate disposed between the transfer unit and the fixing unit, the conductive guide plate being provided on the transfer unit side and having several slits in a sheet conveyance direction; A sheet conveyance guide plate configured by a non-conductive guide plate having several ribs in the conveyance direction, and a sheet entry detection unit that is provided near the fixing unit and detects a sheet entering the fixing unit. A control unit configured to move the non-conductive guide plate so that the rib passes through a slit of the conductive guide plate and projects to a guide surface based on a detection signal of the paper entry detection unit. Characteristic paper transport guide device. 3. A sheet conveyance guide disposed between a transfer unit and a fixing unit, and configured by a conductive guide plate installed on the transfer unit side and a non-conductive guide plate installed on the fixation unit side. A sheet, a sheet entry detection unit provided near the fixing unit and detecting a sheet entering the fixing unit, a humidity detection element provided near the conductive guide plate, the humidity detection element and the sheet Based on the detection signal of the entry detection unit, before the paper enters the fixing unit, if the humidity is equal to or less than a predetermined value, the conductive guide plate is electrically connected to a frame, and the humidity is equal to or more than a predetermined value. A control unit for controlling the conductive guide plate so as not to be electrically connected to the frame.