JP3599301B2 - Transfer device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of a conveying device in a device having a recording paper conveying mechanism, such as an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile machine.
[0002]
[Prior art]
In an electrophotographic image forming apparatus, a toner image obtained by developing an electrostatic latent image on a photoreceptor with toner from a developing device is transferred onto a recording sheet, guided to a fixing device to perform fixing, and then discharged. ing. When transporting the recording paper from the transfer position to the fixing device, various considerations have been made so as not to deteriorate the unfixed transfer image formed on one side of the recording paper. Has been proposed.
For example, Japanese Patent Application Laid-Open No. 3-92869 discloses a method in which a recording sheet after transfer is conveyed along a conveyance guide plate while the non-transfer surface side is sucked by a fan. Japanese Patent Application Laid-Open Publication No. H11-163,087 discloses a device that electrically conveys a non-transfer surface after being attracted by an endless belt (or by negative pressure using a fan). However, when a fan is used as in the method described in JP-A-3-92869, (1) the cost of the fan is high, (2) noise is generated when the fan is operated, and (3) whether the fan is close to the fan. As a result, there is a problem in that a difference in suction force is generated, and the recording paper is not suctioned with an equal force.
Further, in the case of carrying by suction using a belt as in the technique described in JP-A-4-314075, (1) the cost of the belt is high, (2) rollers for rotating the belt are required, and the cost is increased. There is a problem that the space for incorporating the unit is large.
Further, in an image forming apparatus having a configuration in which a transfer unit such as a transfer roller is disposed on a lateral side surface of the photosensitive drum and the recording paper is conveyed to a fixing device positioned on the upper side in the vertical direction, the image forming apparatus passes the transfer position. If the recording paper is tilted toward the transfer surface, the unfixed toner image may be disturbed (rubbed) by hitting a guide plate or the like located on the same side. The device has not been proposed before.
That is, of the guide plates that guide the recording paper conveyed upward from the transfer position in the past, the guide plate on the side facing the back surface (non-transfer surface) of the recording paper stabilizes the recording paper at the entrance of the fixing device. Since the recording paper is inclined in a direction approaching the back surface of the recording paper to guide the recording paper, the recording paper falls down toward the guide plate located on the front surface (transfer surface) side, and the toner image is easily rubbed.
Also, when the leading end of the recording paper is nipped into the nip of two rollers constituting the fixing device and pulled in, the trailing end of the recording paper is still nipped by the nip between the transfer roller and the photosensitive drum. In this case, if the recording paper is strongly pulled by the fixing device, the transfer performance deteriorates. Therefore, the linear speed of the fixing roller constituting the fixing device is set to be lower than the linear speed of the transfer roller. As a result, the recording paper portion located between the fixing device and the transfer position swells in either direction.
However, conventionally, since the guide plate on the back surface side of the recording paper is close to the path of the recording paper, the recording paper is likely to swell to the front surface side. As a result, the recording paper comes into sliding contact with the guide plate located on the front surface side, and the toner image is formed. This has led to disturbed situations.
[0003]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to provide a guide plate for guiding a recording sheet in a conveying device that conveys a recording sheet that has passed a transfer position toward a fixing device located above the transfer position. The recording paper can be stably conveyed at low cost without disturbing the unfixed toner image by simply devising the orientation of the sheet and adding a conductive member (the power source can be shared with the separation electrode and the like). It is to provide a transport device.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is to provide a recording paper having a toner image transferred on a surface thereof at a transfer position formed between an image carrier for carrying a toner image and a transfer unit in a substantially vertical direction. An image forming apparatus having a configuration in which the toner image is fixed by being conveyed through a conveyance path into a fixing device located above a transfer position, and is disposed between the transfer position and the fixing device, and is recorded. a conveyance guide plates you guide the rear surface of paper, the conveying guide plate and the conductive member that is grounded is provided in a portion, opposite polarity of the bias to the bias applied to the transfer means relative to the conductive member And a control unit for controlling the power supply, wherein the control unit applies a constant voltage or a constant current to the conductive member, and a state in which the conductive member is grounded. And use the optional switch Rutotomoni, application of the bias to the conductive member and controls the power supply so as to perform immediately after the transcription termination by the transfer means.
According to a second aspect of the present invention, a recording sheet on which a toner image has been transferred onto a surface at a transfer position formed between an image bearing member for carrying a toner image and a transfer unit passes through a substantially vertical conveyance path, and is transferred to a transfer position. An image forming apparatus having a configuration in which the toner image is fixed by being conveyed into a fixing device positioned above the image forming apparatus, wherein the conveying device is disposed between the transfer position and the fixing device and guides the back surface of the recording paper. A guide plate, a conductive member provided on a part of the conveyance guide plate and grounded, a separation electrode disposed adjacent to the downstream side of the transfer unit, a power supply for applying a bias to the separation electrode, and a power supply. A control unit that controls the bias applied to the separation electrode between at least the rear end of the recording paper and the other front part of the recording paper , and controls the bias applied to the rear end. The applied bias to the front part Characterized in that it also has large Ri.
According to a third aspect of the present invention, in the first or second aspect, the transport guide plate is a transport guide plate that is inclined so as to expand in a direction away from a recording sheet to be transported toward the upper end. Features.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a schematic view of a first embodiment of the present invention . A transfer roller (transfer means) 2 is in contact with the outer periphery of a drum-shaped image carrier (photoconductor) 1, and the image carrier 1 and the transfer roller When the recording paper 3 passes through the nip portion (transfer position) with the recording paper 2, the toner image on the image carrier 1 is transferred onto the recording paper 3 by the transfer bias from the transfer roller 2. Reference numeral 4 denotes a separation electrode for applying a bias for separating recording paper adsorbed on the surface of the image carrier 1 by transfer, 5 denotes a transport guide plate facing the non-transfer surface side of the recording paper, and 6 denotes an upper guide plate. Reference numeral 7 denotes a pre-fixing guide plate, and 8 denotes a fixing device (fixing roller 8a and pressure roller 8b. This image forming unit arranges the transfer roller 2 on the side surface of the image carrier 1 to convey the recording paper. The direction is set to be upward (substantially vertical direction), and therefore, the fixing device 8 is also located above the transfer position.
The conventional transport guide plate 5 is disposed so as to be inclined toward the back surface of the recording paper with respect to the traveling direction of the recording paper sent out from the transfer position, but the transport guide plate 5 inclined to the recording paper side is used. When the recording paper has a tendency to curl toward the front side, the unfixed toner image slides on the upper guide plate 6 and the like, and a situation occurs in which the image is disturbed. In particular, when the recording paper is nipped at the same time by the nip portion of the fixing device and the nip portion of the transfer roller 2 as described above, the direction in which the recording paper bends due to the linear velocity difference from the fixing roller 8a is changed by the toner image. Since the toner image easily swells toward the transfer surface (front surface), the toner image may rub against the guide plate 6.
[0006]
On the other hand, in the embodiment shown in FIG. 1, in the straight line connecting the transfer position and the entrance of the fixing device 8, or in the advancing direction (latent direction) of the recording paper when it is sent out from the nip between the image carrier 1 and the transfer roller 2. With respect to the direction perpendicular to the line connecting the center of the image bearing member 1 and the transfer roller 2), the upper end of the transport guide plate 5 is sufficiently inclined so as to expand in a direction away from the back surface of the recording paper as shown in the figure. Let me. In other words, the recording paper is inclined so as to move away from the back surface (non-transfer surface of the image) of the recording paper toward the upper end side of the conveyance guide plate 5. The bending direction is likely to swell to the opposite side (back side) from the front surface, and it is possible to prevent the toner image from rubbing against the upper guide plate 6. In this figure, the transport guide plate 5 is inclined linearly, but may be slightly curved.
As described above, in the present embodiment, the recording paper 3 on which the toner image has been transferred from the latent image carrier 1 by the transfer roller 2 is perpendicular to a line connecting the latent image carrier 1 and the center of the transfer roller 2. At this time, the conveyance guide plate 5 is conveyed upward because the angle of the conveyance guide plate 5 is open in a direction away from the conveyance direction of the recording paper 3 (the angle θ exceeds 0 degree). The recording paper 3 is always easily swelled toward the back side, that is, the conveyance guide plate 5 side, and easily falls down, and it is possible to prevent the toner image on the recording paper surface from rubbing against the upper guide plate 6.
[0007]
Next, FIG. 2 is a schematic view of a second embodiment of the present invention . This embodiment shows one example of the surface (surface in contact with the recording paper) of a transport guide plate 5 made of resin, low-conductive metal, or the like. It is characteristic that the portion is formed of a conductive member 10 such as a metal having high conductivity, and the conductive member 10 is connected to the ground 11. That is, although the recording paper 3 after being transferred at the transfer position is charged, the recording paper 3 is grounded by using a part of the transport guide plate 5 located on the back side as a conductive member 10 and grounding the conductive member. A potential difference is generated between the paper 3 and the transport guide plate 5. As a result, the back surface of the recording paper can be positively attracted to the conveyance guide plate 5, so that the situation in which the toner image is rubbed by bending of the recording paper or jumping of the rear end due to curl or the like can be prevented. The effect of preventing the rear end from jumping up due to the curl is an effect provided in all the following embodiments as well.
In this embodiment, since the recording paper 3 is positively sucked toward the transport guide plate 5 by utilizing the potential difference, the transport guide plate 5 is separated from the recording paper back surface as shown in FIG. Not tilted in the direction.
[0008]
Next, FIG. 3 shows a third embodiment of the present invention . In this embodiment, as shown in FIG. 1, a transport mechanism in which the transport guide plate 5 is inclined in a direction away from the recording paper is shown in FIG. As described above, the conductive member 10 is provided on a part of the transport guide plate 5 and is grounded. According to this embodiment, the function of promoting the swelling and swelling of the recording paper toward the back side due to the inclination of the transport guide plate 5 and the function of attracting the recording paper due to the potential difference allow the swelling and swelling of the recording paper toward the front side. Can be more effectively prevented.
[0009]
FIG. 4 is a schematic diagram of the fourth, fifth, sixth, seventh, and eighth embodiments of the present invention. First, in the fourth embodiment, the transfer bias applied at the transfer position from the power supply 12 (which can also be used as the separation electrode 11 and the like) connected to the conductive member 10 provided on the transport guide plate 5 to the conductive member 10 is described. Is characterized in that a bias of opposite polarity is applied. According to this embodiment, the conductive member 10 is added to the transport guide plate 5 and connected to the power supply 12, and a bias having a polarity opposite to the transfer bias is applied to the conductive member 10 to transport the recording paper and the recording paper. The potential difference between the guide plates can be further increased, and the force for attracting the recording paper to the transport guide plate can be increased. As a result, it is possible to more reliably prevent the toner image on the recording paper surface from rubbing against the front guide plate 6 or the like as compared with the case of the third embodiment.
This embodiment is also applicable to the conveyance guide plate having a small inclination shown in FIG. 2 or the conveyance device having the conventional conveyance guide plate 5 (this point is also applicable to all the following embodiments). ).
[0010]
In the fifth embodiment, the reverse bias applied from the power supply 12 shown in FIG. 4 is controlled at a constant voltage. According to this embodiment, the electric field intensity of the conductive member 10 can be kept constant by setting the bias applied to the conductive member 10 to a constant voltage. Can be secured.
[0011]
Next, the sixth embodiment is characterized in that a reverse-polarity bias to the conductive member 10 is applied by constant current control. When the recording paper is dry, the insulating property is high. Therefore, there is no problem even if the bias applied to the conductive member 10 is controlled by a constant voltage. Is applied, the current flowing into the transfer position via the recording paper increases, and the transfer current is canceled, thereby deteriorating the transfer performance. Therefore, in this embodiment, the bias applied to the conductive member 10 is set to a constant current to prevent the current from flowing into the transfer position via the recording paper having increased conductivity due to moisture absorption at high temperature and high humidity. And a stable image can be obtained.
[0012]
Next, the features of the seventh embodiment corresponding to the first and second aspects are that a control method for applying a constant voltage (or a constant current) to the conductive member 10 of the transport guide plate 5 and the ground 11 are used. The point is that both methods of grounding the conductive member 10 can be arbitrarily selected and switched. For example, the conductive member 10 is normally connected to the ground 11, but immediately after the transfer of the toner image from the latent image carrier 1 to the recording paper 3, a bias is applied to the conductive member 10 to 3 is controlled to return to the ground state after passing through the conductive member 10. Such control is performed by controlling the power supply 12 by a control unit (CPU, RAM, ROM, etc., not shown) (this point also applies to the following embodiment).
According to this embodiment, by applying the bias to the conductive member 10 after the transfer, it is possible to minimize the influence of the bias applied to the conductive member on the transferred image.
[0013]
Next, an eighth embodiment corresponding to claims 3 and 4 relates to a recording paper when the recording paper 3 transferred at the nip portion between the transfer roller 2 and the image carrier 1 passes through the separation electrode 4. 3 is characterized in that the intensity (voltage or current) of the bias applied to the separation electrode 4 is switched between the rear end portion in the transport direction and the other portion. More specifically, by increasing the value of the applied bias with respect to the trailing edge of the recording paper, the trailing edge of the recording paper is attracted to the separation electrode 4 side. 5 (having a potential difference due to the ground or a potential difference due to a bias from the power supply). As a result, it is possible to particularly effectively prevent the upward jump toward the upper guide plate 6 and the deterioration of the image quality of the rear end portion, which are likely to occur when the rear end portion of the recording paper leaves the transfer position. As described above, in the present embodiment, the value of the bias applied to the separation electrode is switched between the rear end portion of the recording paper and the other front portion, so that the influence of the separation bias on the image is reduced. The rear end can be particularly effectively prevented from jumping. The bias applied to the second half and the first half of the recording paper may be switched.
The eighth embodiment can be used in combination with the fourth , fifth , sixth or seventh embodiment. In each of the above-described embodiments, the upward suction of the rear end of the recording sheet is suppressed by sequentially sucking the recording sheet toward the rear from the leading end of the recording sheet. It is possible to further enhance the effect of preventing a jump.
In each of the above embodiments, the photoconductor drum is used as the image carrier and the transfer roller is used as the transfer unit. However, this is an example, and the photoconductor belt is used as the image carrier, and the corona charger is used as the transfer unit. May be used.
[0014]
【The invention's effect】
As described above, the present invention relates to a conveyance device for conveying a recording sheet that has passed a transfer position toward a fixing device positioned above the transfer position. Only by adding members (because the power supply can be shared with the separation electrode and the like), the recording paper can be stably transported at low cost without disturbing the unfixed toner image.
That is, in the conveying device of the present invention, the recording paper conveyed into the fixing device via a conveying path extending in a substantially vertical direction from a nip portion (transfer position) between the photosensitive drum and the transfer roller is transferred to the back surface of the recording paper. The transport guide plate that guides from the side is expanded so as to be more distant from the recording paper toward the upper end. Can be done.
In addition, since the bending of the recording paper caused by the linear velocity difference between the fixing roller and the transfer roller swells on the opposite side (back side) of the toner image, the toner image is prevented from being rubbed with the upper guide plate and the like, so that the image is not disturbed. Has the effect of doing
Further, by applying the bias to the conductive member after the transfer, the adverse effect on the transferred image can be minimized.
Further, switching the intensity of the bias applied to the separation electrode at the rear end portion and the other of the front edge of the recording sheet, by strongly applying bias to the rear end, it has a small influence on the image of the separation bias This prevents the trailing edge of the recording paper from jumping up.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a main part of a transport device according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a main configuration of a transfer device according to another embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating a main configuration of a transfer device according to another embodiment of the present invention.
FIG. 4 is a schematic diagram showing a main configuration of a transfer device according to another embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 image carrier (photoreceptor), 2 transfer roller, 3 recording paper, 4 separation electrode, 5 transport guide plate, 6 upper guide plate, 7 pre-fixing guide plate, 8 fixing device (fixing roller 8a, pressure roller 8b) , 10 conductive members, 11 ground, 12 power supply.

Claims (3)

A fixing device located above a transfer position via a substantially vertical conveyance path for a recording paper having a toner image transferred to a surface at a transfer position formed between an image carrier for carrying a toner image and a transfer unit and transported within an image forming apparatus having a configuration for fixing the toner image, and the conveyance guide plates you guide the back surface of the recording paper is disposed between the transfer position and the fixing device, the A conductive member provided on a part of the transport guide plate and grounded, a power supply for applying a bias having a polarity opposite to a bias applied to the transfer unit to the conductive member, and a control unit for controlling the power supply, In those equipped with
The control unit arbitrarily selects and uses a bias application state in which a constant voltage or a constant current is applied to the conductive member and a state in which the conductive member is grounded, and applies the bias to the conductive member as described above. A transfer device for controlling a power supply so as to perform the transfer immediately after the transfer by a transfer unit is completed. A fixing device located above a transfer position via a substantially vertical conveyance path for a recording paper having a toner image transferred to a surface at a transfer position formed between an image carrier for carrying a toner image and a transfer unit An image forming apparatus having a configuration in which the toner image is conveyed into the image forming apparatus, wherein the conveying guide plate is disposed between the transfer position and the fixing device and guides the back side of the recording paper; A conductive member provided on a part of the plate and grounded; a separation electrode disposed adjacent to the downstream side of the transfer unit; a power supply for applying a bias to the separation electrode; and a control unit for controlling the power supply. In the provided,
The control unit switches the bias value applied to the separation electrode between at least the rear end of the recording paper and the other front part, and sets the bias applied to the rear end to be larger than the bias applied to the front part. Characteristic transport device. 3. The transport device according to claim 1 , wherein the transport guide plate is a transport guide plate that is inclined so as to expand in a direction away from a recording sheet being transported toward an upper end portion . 4.

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