JP2005070198A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has a paper feed means, arranged at a corner thereof, to reduce the amount of projection of a paper feed tray and which is compact and is superior in feeding, ejection, and loadability of recording materials and has a functional external design. <P>SOLUTION: The image forming apparatus forms images by a means of forming electrostatic latent images on an image carrier, a means of developing electrostatic latent images into toner images, a means of transferring toner images to recording materials, a means of feeding recording materials, a means of guiding recording materials to transfer areas of toner images, and image forming means of fixing toner images, respectively. In this image forming device, the feed means for feeding an approximately horizontally arranged recording material, an image carrier, and a fixing means are arranged consecutively in approximately the perpendicular direction, and the recording material to be carried to transfer areas of toner images is guided to the transfer areas, after passing at least once a space in the side which includes the transfer means, out of spaces divided by a tangential plane, at a point where the image carrier and the transfer means come closest to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a laser printer, a facsimile machine, and a copying machine that forms an image by using an electrostatic recording system such as an electrophotographic system. The present invention relates to a small-sized output device that is close in feeding and discharging positions, and excellent in usability, and an image forming apparatus that saves installation space.

  FIG. 8 shows an example of the arrangement of a small personal LBP using an electrophotographic system. An outline of the image forming process will be described with reference to FIG.

  In FIG. 8, reference numeral 31 denotes an organic photosensitive drum as an image carrier, which is rotationally controlled at a predetermined peripheral speed (process speed) in the direction of the arrow by a motor and drive transmission means (not shown). The surface of the photosensitive drum 31 is uniformly charged by a charging roller 33 which is a charging member, and then the intensity of the laser beam is modulated according to image information output from the laser exposure device 50 via a reflection mirror 49. As a result of the exposure, an electrostatic latent image is formed on the surface.

  The electrostatic latent image is developed as a toner image by the developing device 34. The recording material S is arranged in a substantially vertical direction on the paper feed tray T1 and is fed by a paper feed means including a lift plate LP2, a paper feed roller 35, a separation pad 36, and the like, and is formed by a photosensitive drum 31 and a transfer roller 39. To the transfer area. The toner image is transferred onto the recording material S by applying a transfer bias by a power supply unit (not shown) to a transfer roller 39 as a transfer unit.

  The toner image transferred to the recording material S is fixed by a fixing device including a heating roller 41 and a pressure roller, and then output onto the paper discharge tray T2.

  The laser beam printer (LBP) of this configuration is configured so that the recording material conveyance path is substantially U-shaped as indicated by A2 in the figure. For this reason, the paper supply / discharge direction is substantially vertical, and the installation area and the depth dimension (d2) when the printer is installed can be reduced.

  In addition, minimizing the length from paper feed to paper discharge has the advantage that the paper path can be shortened and the time required from paper feed to output can be shortened. With respect to the length dimension (h2), a projecting portion shown in P2-in and P2-out is generated by a tray for supporting a recording material or paper at the paper feed port T1 and the paper discharge port T2, thereby stabilizing the design. Lack of feeling and smoothness.

  In addition, since the paper supply / discharge tray is open vertically upward, dust and foreign matter can easily enter the paper feed port, and dust and foreign matter can be transported along with the paper during printing. There is a risk of damaging your body.

  Furthermore, if the paper is stood at the paper supply / discharge port for a long time, the paper is bent by the influence of gravity and is likely to be deformed. When the paper is deformed at the paper feed port, paper jams and paper wrinkles are likely to occur. Since the paper ejection slot stands against the tray with heat after fixing, the paper that is ejected tends to be asymmetrically deformed in the vertical direction unless it is removed from the tray for a short time or immediately. Will occur.

  As a printer engine configuration for solving the above problem, as shown in FIG. 9, a recording material S is horizontally loaded in a dedicated paper cassette 71, and the fed recording material is conveyed and an electrostatic latent image on the photosensitive drum 51 is obtained. In addition, many LBPs having a structure for forming and outputting a toner image, transferring and fixing a toner image onto a recording material, and outputting the same have been commercialized.

  The printer that transports the recording material in an S-shape as indicated by an arrow A3 in the drawing can be configured to have a substantially rectangular parallelepiped appearance, so that there are few protrusions from the exterior, and it is smooth and stable. It is easy to make the appearance design.

JP 2001-206590 A

  However, in order to horizontally arrange the recording material and transfer the recording material from the supply and discharge to the transfer and from the fixing to the paper discharge, the installation area becomes considerably larger than that of the apparatus employing the U-shaped path, Costs also increase.

  If the transport speed is the same because the paper path becomes longer, the time required from paper feeding to paper ejection becomes longer than that of the apparatus employing the U-shaped path, especially after sending a print command to the printer, The first printout time (FPOT) until the print is output tends to be long, and in order to shorten it, it is necessary to increase the absolute value of the conveyance speed. In order to increase the conveyance speed, it is necessary to increase the scanning speed of the laser scanner, the output of the fixing device, and the like, resulting in a high cost configuration.

  As a configuration for compromising the above problem, as shown in FIG. 5, after the recording material is horizontally arranged, the recording material is guided to the transfer portion without being reversed, and the toner image is transferred and fixed on the recording material. An output device has also been proposed. An arrow A4 indicates the recording material conveyance path in this example.

  The printer having the above-described configuration requires a smaller installation area than an S-pass printer, and the paper path can be shortened, so that the engine can be made smaller and the cost can be kept low.

  On the other hand, since the external size of the printer is relatively small with respect to the size of the recording material, it is impossible to prevent the paper feed tray and the paper discharge tray from protruding from the engine exterior. However, in contrast to the U-pass printer in which the tray and the recording material protrude in a substantially vertical direction, the paper path has a C-shaped configuration. Since it protrudes in the horizontal direction, the occurrence of habit or deformation due to leaving the recording material on the paper feed tray or paper discharge tray can be suppressed.

  However, in order to suppress the installation area of the C-shaped path printer main body and the protruding amount of the paper feed tray, it is necessary to dispose the paper feeding means at one corner of the printer main body. When the recording material enters, the recording material enters from the transfer member side, so that the toner is likely to be scattered.

  The reason why the toner scattering changes in the recording material entering direction when electrostatically transferring the toner image formed on the drum type photoreceptor will be described with reference to FIGS.

  In FIGS. 6 and 7, reference numeral 90 denotes a photosensitive drum, which is driven to rotate in the direction of an arrow, and is uniformly charged to a negative polarity by a charging unit (not shown), so that a negative toner is reversely developed on the exposed portion. A transfer roller 95 is driven to rotate in the direction of the arrow, and a positive transfer bias is applied to the cored bar. N is the close contact drawn from the point where the photosensitive drum is closest to the transfer roller, and S is the conveyance direction of the recording material. A bias having a polarity opposite to that of the toner is applied to the transfer roller 95, and an electric field E is formed between the surface of the transfer roller and the photosensitive drum as shown by a dotted line in the figure, and the toner t having a negative charge is The image is transferred to the recording material S by the electric field force acting in the reverse direction of the electric field E toward the transfer roller from the photoconductor.

  6 shows a state in which the recording material S has entered the transfer nip from the space on the transfer roller side, and FIG. 7 shows a state in which the recording material S has entered the transfer nip from the space on the photosensitive drum side.

  As shown in FIG. 6, when the recording material enters the transfer nip from the transfer roller side, the toner is easily transferred from the photoreceptor to the recording material by the force of the electric field before the recording material comes into close contact with the photosensitive drum. Under the influence of vibrations and speed changes that occur when the recording material is conveyed, subtle deviations and scattering are likely to occur at the transfer position.

  FIG. 7 shows a case where the recording material enters the transfer nip from the photosensitive drum side. In this case, it is easy to keep the recording material in close contact with the photosensitive drum in a region where the electric field force acts on the toner on the photosensitive member. Therefore, a transfer image with little transfer toner scattering and transfer deviation can be obtained.

  Therefore, an image forming apparatus that electrostatically transfers a toner image from a photosensitive member on a drum to a recording material generally adopts a configuration in which the recording material enters from the photosensitive drum side, but the C path is adopted. In the image forming apparatus, when the recording material is caused to enter from the photosensitive drum side, there is a drawback in that the position of the sheet feeding unit must be arranged in the direction in which the sheet feeding tray projects.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. The object of the present invention is to arrange a paper feeding means at one corner of the image forming apparatus so as to keep the projection amount of the paper feeding tray small, and to record in a compact manner. An object of the present invention is to provide an image forming apparatus which is excellent in material supply / discharge and stackability and has a functional appearance design.

  To achieve the above object, the present invention provides means for forming an electrostatic latent image on an image carrier, means for developing the electrostatic latent image as a toner image, and means for transferring the toner image to a recording material. And an image for forming an image by executing each of the image forming means for fixing the toner image transferred onto the recording material, the means for feeding the recording material, the means for guiding the recording material to the transfer area of the toner image, and the toner image transferred onto the recording material. In the forming apparatus, a sheet feeding unit that feeds a recording material arranged substantially horizontally, an image carrier, and a fixing unit are continuously arranged in a substantially vertical direction, respectively, and the recording material conveyed to the transfer area of the toner image When the space is divided by the tangential plane of the point where the image carrier is closest to the transfer means, the image carrier is guided to the transfer area after passing through the space including the transfer means at least once.

  According to the present invention, the means for feeding the recording material arranged in the substantially horizontal direction, the image carrier and the fixing device are continuously arranged in the substantially vertical direction, and the recording is carried to the transfer area of the toner image. The material is supplied by adopting a configuration in which when the space is divided by the tangential plane of the point where the image carrier is closest to the transfer means, the material is guided to the transfer area after passing through the space on the side including the transfer means at least once. By disposing paper means at one corner of the image forming apparatus, it is possible to keep the amount of protrusion of the paper feed tray small. At the same time, it is possible to provide an image forming apparatus that is compact, has a stable supply and discharge of recording materials, and has a stable appearance and a functional appearance design.

  Further, a guide member for guiding the recording material is disposed between the paper feeding means and the transfer means, and the guide member is configured to be movable by a pressure that contacts the recording material, thereby allowing the recording material to enter the transfer area. In this case, the toner can enter from the photosensitive drum side to suppress toner scattering and deviation.

  Further, the guide member has a configuration in which the ground resistance changes according to a change in the position of the contact surface with the recording material, and has a means for detecting the change in the ground resistance. The configuration is such that changes can be made. The stiffness of the recording material to be passed is detected by the change in grounding resistance of the guide member, and the curl amount of the thin paper is reduced by changing the conditions such as distinguishing the thick paper from the thin paper and changing the fixing temperature. Further, it is possible to improve the fixability of the thick paper.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
FIG. 1 is a cross-sectional view of a main part of an electrophotographic laser beam printer (LBP) to which the present invention is applied. FIG. 2 is a paper conveyance path and conveyance from paper feeding to toner image transfer, fixing, and paper ejection in the LBP. It is a figure showing the positional relationship of each roller, a guide, etc. in connection with.

  In FIG. 1, 1 is a photosensitive drum having an organic photosensitive layer formed on the surface, 2 is a cleaning blade, 3 is a charging roller, 20 is a laser exposure device, and 4 is a developing device. The toner image formed thereon is transferred onto the recording material S guided to the nip portion between the photosensitive drum 1 and the transfer roller 9.

  Reference numeral 15 denotes a paper feed tray, 16 denotes a stopper for pressing the rear end of the recording material sheet S, and 17 denotes a rotation shaft. When the recording material is not arranged on the paper feed tray 15, the paper feed tray 15 is folded around this axis. It is configured to be able to. LP1 is a lift plate, 5 is a paper feed roller, 6 is a separation pad, 7 is a registration roller, 8 is a transfer entrance guide, 9 is a transfer roller, 10 is a static eliminating needle, 11 is a fixing roller, 12 is a discharge roller, and 13 is a discharge roller. This is a paper discharge extension tray.

  The recording material S is fed and conveyed one by one by the operation of the lift plate, the paper feed roller 5 and the separation pad 6, and after the toner image is transferred, it is fixed and output onto the paper discharge tray 13.

  In the present embodiment, the recording material is arranged substantially horizontally on the paper feed tray 15 and connects the paper feed position to the transfer position and the fixing position to the paper discharge position with the shortest paths, and each section. By bending the direction with an R path having an angle close to 45 ° to 90 °, the paper feed tray 15 and the paper discharge tray 13 are arranged substantially horizontally, so that the paper can be deformed and fed on the tray, The first printout time is shortened by preventing the dust and foreign matter from falling and connecting the paper path from paper supply to paper discharge at the shortest distance. An arrow A1 indicates the conveyance path of the recording material, and in this embodiment, it is a C-shaped paper path.

  FIG. 2 shows the positional relationship between the transport rollers and guides of the LBP shown in this embodiment, and the members described in FIG. 1 are assigned the same numbers. An arrow Y is an extension of the pad surface of the separation pad, and the recording material is conveyed in the direction of the arrow after feeding. G is a guide connecting the separation pad and the registration roller 7, and has a role of changing the conveyance direction of the recording material after feeding and guiding it to the registration roller 7. A line segment l is a conveying direction of the registration roller pair, a line segment m is a tangent line drawn at a point F where the image carrier 1 is closest to the transfer roller 9, and C is an intersection of l and m.

  As shown in FIG. 2, in the present embodiment, the recording material passes through the space on the transfer roller side among the spaces divided by the tangent m and is guided to the transfer unit. That is, P1-in which is the amount of protrusion of the paper feed tray in FIG. 1 by bringing the paper feed roller 5, separation pad 6 and registration roller 7 close to or included in the divided space side including the transfer roller. It becomes possible to suppress the length dimension of.

  However, if the recording material enters the transfer portion from the transfer roller side with the tangent line F as a reference, the toner image will not scatter very well for the reason described above. Is configured to be able to enter the transfer portion.

  With the above-described configuration, in the compact image forming apparatus that connects the recording material feeding, the toner image transfer, fixing, and the paper ejection in almost the shortest distance, the protrusion of the paper feeding tray and the paper ejection tray is suppressed as much as possible. By arranging the paper feed tray and paper discharge tray almost horizontally, there is little risk of deformation or habits even if the recording material is placed on the tray for a long time, and dust and It is possible to provide an image forming apparatus with high print quality with no fear of foreign matter falling, and less toner scattering and image displacement.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS.

In this embodiment, the recording material is detected by detecting the strength and thickness of the recording material by adopting a configuration in which the height of the guide surface that guides the recording material to the transfer portion is variable depending on the contact pressure with the recording material. By automatically selecting the fixing temperature according to the thickness of the toner, curling is suppressed while maintaining the fixing property of the toner image, and toner scattering on plain paper having a basis weight of about 80 g / m ² or less is suppressed and 100 g / m It is characterized by stabilizing the paper transportability of ^two or more thick papers, postcards, envelopes and the like.

3 is a diagram showing a main section of a conveying member from feeding to discharging when conveying plain paper of 80 g / m ² or less, and FIG. 4 shows cardboard, postcards and envelopes of 100 g / m ² or more. It is a figure showing the main section of a conveyance member from paper feed to paper discharge at the time of carrying.

In FIG. 3, reference numeral 80 denotes a transfer entrance guide made of stainless steel, which is supported by a spring member (not shown) and is rotatable in the direction of the transfer roller 9 about W, and is grounded through a resistor R1. Has been. Reference numeral 81 denotes a contact, which forms a path to be grounded via resistors R2 and R3 when the guide 80 is rotated to the transfer roller side by the conveyance pressure of the recording material. However, when plain paper of 80 g / m ² or less is conveyed, the contact 81 does not form an electrical path with the bias power source 91 via the guide 80, the recording material, and the transfer roller as shown in the figure. Therefore, the potential V0 between R2 and R3 is 0V. The same members as those described in the first embodiment are given the same numbers.

FIG. 4 shows that the guide surface of the entrance guide 80 moves toward the transfer roller 9 when transporting thick paper of 100 g / m ² or more, a postcard, and an envelope, so that the transfer roller, It shows a case where an electrical path to the ground via the recording material, guide 80, contact 81, and resistors R2 and R3 is formed. In this case, a voltage V1 is induced between the resistors R2 and R3. R1 and R2 were set to 10 MΩ and 20 MΩ, respectively, and a paper having a basis weight of 128 g / m ² was passed through the core metal of the transfer roller 9 with a bias of 2.2 kV in a 23 ° C./60% RH environment. However, V1 was about 4V.

The voltage induced between the resistors R2 and R3 is A / D converted and detected by a CPU in a DC controller (not shown). When the voltage between R2 and R3 is 0V, the recording material passed between the registration roller 7 and the transfer roller 9 is identified as a recording material of 80 g / m ² or less, and the surface temperature of the heating roller 12 is set to 160. Fix at a temperature of ℃. When voltage V1 is induced between R2 and R3, it is recognized that thick paper has been passed, and fixing is performed by adjusting the surface temperature of the heating roller 12 to 175 ° C., thereby satisfying the fixability of the thick paper. .

In general, an electrophotographic apparatus that does not detect the thickness and basis weight of the recording material controls the temperature of the heating roller 12 at a fixing temperature that can satisfy the fixing property even with a paper having a basis weight of about 100 to 150 g / m ^2. Therefore, the amount of heat applied by fixing to a recording material that is relatively frequently used in an office of about 60 to 75 g / m ² is slightly high.

By applying the present invention, it becomes possible to reduce the amount of heat applied to a recording material of about 60 to 75 g / m ² while maintaining the fixing property. Can be achieved.

  The present invention can be applied to an arbitrary image forming apparatus such as a laser printer, a facsimile, or a copying machine that forms an image using an electrostatic recording system such as an electrophotographic system.

It is a structure sectional view of the LBP principal part concerning Embodiment 1 of the present invention. It is a figure showing arrangement | positioning of the member in connection with conveyance of a recording material in LBP which concerns on Embodiment 1 of this invention. It is a figure showing arrangement | positioning of the member in connection with conveyance of a recording material in LBP which concerns on Embodiment 2 of this invention. It is a figure showing the mode of the member in connection with conveyance at the time of letting thick paper pass in Embodiment 2 of this invention, especially a transfer entrance guide part. It is a composition sectional view of the LBP principal part used as a comparative example to an embodiment of the invention. FIG. 4 is a conceptual diagram for explaining how toner is transferred when a recording material enters a transfer nip portion from the transfer roller side. FIG. 4 is a conceptual diagram for explaining how toner is transferred when a recording material enters the transfer nip portion from the photosensitive drum side. It is a principal part cross-section block diagram which shows an example of LBP whose conveyance path of a recording material is U-shaped. It is a principal part cross-section block diagram which shows an example of LBP whose conveyance path of a recording material is S shape.

Explanation of symbols

1, 31, 51, 90, 100 Organic photosensitive drum 3, 103, 33, 53 Charging roller 20, 120, 49, 69 Laser exposure device 4, 104, 34, 54 Developer 5, 105, 35, 55 Feed roller 6, 106, 36, 56 Separation pad 7, 107, 57 Registration roller 8, 108, 38, 58, 80 Transfer entrance guide 9, 109, 95, 39, 59 Transfer roller 11, 111, 41, 61 Fixing roller 13, 113, 43 Paper discharge tray 15 Paper feed tray 81 Contact LP1 Lift plate S Recording material A1 LBP paper transport path A2 LBP paper transport path taking U-shaped paper path A3 LBP paper taking S-shaped paper path Transport route A4 LBP paper transport route

Claims (5)

Means for forming an electrostatic latent image on the image carrier, means for developing the electrostatic latent image as a toner image, means for transferring the toner image to a recording material, means for feeding the recording material, In an image forming apparatus for forming an image by executing a means for guiding a recording material to a transfer area of the toner image and each image forming means for fixing the toner image transferred on the recording material.
The sheet feeding means for feeding the recording material arranged substantially horizontally, the image carrier and the fixing means are arranged continuously in a substantially vertical direction, and the recording material conveyed to the transfer area of the toner image is image-bearing. An image forming apparatus characterized in that, when a space is divided by a tangential plane of a point closest to the transfer means, the image is guided to the transfer area after passing through the space on the side including the transfer means at least once.   The sheet feeding means is at least constituted by a combination of a sheet feeding roller and a separation pad, and the image carrier is a photosensitive drum having a photosensitive layer formed on a cylindrical cylinder. The image forming apparatus according to 1.   The guide member for guiding the recording material is disposed between the paper feeding means and the transfer means, and the contact surface of the guide member is movable by the pressure that contacts the recording material. The image forming apparatus according to 1 or 2.   4. The image forming apparatus according to claim 3, wherein the grounding resistance of the guide member for guiding the recording material to the transfer region is changed by a change in position of a surface in contact with the recording material.   5. The image forming apparatus according to claim 4, wherein the image forming process condition is changed by detecting a change in grounding resistance of a guide member that guides the recording material to a transfer area.

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