JP2004077868A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a transfer means which prevents a heavy transfer material (e.g., cardboard, paper with a tab, and a post card) and a self-weight transfer material (e.g., long-size copying paper) from having transfer spring on their rear ends in a transfer material conveyance direction. <P>SOLUTION: In the image forming apparatus, a guide means for feeding a transfer material between a photoreceptor drum and the transfer means is provided with a transfer material support member which can be lengthened/shortened in the transfer material conveyance direction. The lengthening/shortening the transfer material support member in the transfer material conveyance direction is controlled by a control means based upon the weight, material quality, etc., of the transfer material. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine, and relates to a transfer material guiding method for transferring a toner image formed on an image carrier onto a transfer material.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, an image is formed on a transfer material through steps of charging, exposing, developing, transferring, separating and fixing.
[0003]
For example, a charging unit, an image exposing unit, and a developing unit are provided on the periphery of the image bearing member such as a photosensitive drum, and a latent image is formed by performing image exposure on the charged photosensitive drum by the charging unit. After the latent image is developed into a toner image by a developing unit, the toner image on the photosensitive drum is transferred to a transfer material in a transfer unit.
[0004]
The transfer unit serving as a transfer unit is disposed to face the photosensitive drum carrying the toner image, and at the time of image transfer, a bias voltage having a polarity opposite to that of the toner forming the image on the photosensitive drum is applied to transfer the image from the transfer electrode to the periphery of the photosensitive drum. A transfer area including a transfer point at the shortest distance of corona discharge to the surface is formed, and the transfer material is brought into close contact with the peripheral surface of the photosensitive drum by electrostatic attraction to transfer the toner image, and the rotation of the photosensitive drum is performed. The sheet is conveyed synchronously and the transfer to the rear end of the transfer material is sequentially performed.
[0005]
In this case, the transfer material is fed from a paper feed tray or a manual feed portion, is sent to a pre-transfer roller, passes through a narrow gap for enhancing the adhesion between the leading end of the entrance guide plate and the photosensitive drum, and passes through the transfer portion. Sent to
[0006]
The distance between the leading end of the approach guide plate and the photosensitive drum is usually set to 0.5 to 0.6 mm, which is a distance capable of coping with various thicknesses of the transfer material.
[0007]
However, compared to ordinary copy paper (50~60g / ^{m 2} paper with basis weight) (about 200 g / ^{m 2} paper with basis weight) thick with a thickness of, tabbed sheet (or also referred to as index sheets. Basis weight in 150 to 200 g / ^{m 2} paper), postcard (130~300g / ^{m 2} paper with basis weight) and long size copy paper (A3 size, 11 × 17 inch (1 inch 2.54 cm)) such as a transfer material In the above, due to the influence of the bending of the transfer material due to its own weight and the stiffness due to the rigidity, the followability of the rear end of the transfer material to the curvature of the cylindrical photosensitive drum is insufficient, and the adhesion is lacking. Separation discharge occurs between the photosensitive drum and the transfer material, and transfer repelling is likely to occur.
[0008]
In particular, a transfer material that requires an image up to near the transfer material end face, for example, (1) transfer to a tab portion of tabbed paper and (2) transfer of a single color or a pattern to a peripheral edge of a postcard shown in FIG. Some measure is required for the transfer cissing at the rear end (with respect to the feed direction). The arrow indicates the transfer material transport direction.
[0009]
As a method of solving this, when the tip of the approach guide plate is further brought closer to the transfer point, the transfer efficiency due to corona discharge decreases, and the transfer of the toner image formed on the photosensitive drum to the transfer material becomes insufficient, This results in poor transfer due to missing images.
[0010]
Further, even if the transfer current applied to the transfer electrode is increased beyond a specified value in order to increase the electrostatic attraction force, the effective electric field between the transfer material and the toner on the photosensitive drum is reduced, and transfer repelling is prevented. Was difficult.
[0011]
[Problems to be solved by the invention]
For this reason, the present invention has been made in view of the above points, and improves the transfer performance of the rear end portion of a thick paper, a tabbed paper, a postcard, and a long-size regular paper without lowering the transfer efficiency. It is an object of the present invention to provide an image forming apparatus capable of performing such operations.
[0012]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0013]
(1) Image formation in which a toner image formed on an image carrier is electrostatically transferred to a transfer material supplied from a paper supply unit, guided by a guide unit, and sent between the image carrier and the transfer unit. An image forming apparatus, wherein the guide means is provided with a transfer material supporting member that can expand and contract in the transfer material transfer direction.
[0014]
(2) The image forming apparatus according to (1), wherein the transfer material supporting member is provided on a back surface side of the transfer material with respect to a toner receiving side.
[0015]
(3) The shoe according to (1), wherein a tip shoe is fixed to the tip of the transfer material supporting member and on a side facing the peripheral surface of the image carrier, and the shoe is made of an elastic material. Image forming device.
[0016]
(4) An image in which the toner image formed on the image carrier is supplied and conveyed from a paper feeding unit, and is electrostatically transferred to a transfer material guided between the image carrier and the transfer unit by being guided by the guide unit. In the forming apparatus, an extensible transfer material support member is provided at the end of the transfer means in the transfer material transfer direction of the guide means, and the expansion and contraction of the transfer material support member in the transfer material transport direction is based on information such as the basis weight and material of the transfer material. An image forming apparatus, which is controlled by a control unit to execute the image forming apparatus.
[0017]
(5) The expansion and contraction of the transfer material support member in the transfer material transport direction is such that when the rear end of the transfer material reaches the transfer point, the transfer material support member is extended, and when the rear end of the transfer material passes through the transfer point, the transfer material support member is initially expanded. The image forming apparatus according to (4), wherein the image forming apparatus is controlled by a control unit to return to the position.
[0018]
(6) The distance between the leading end in the transfer material transport direction and the transfer point on the image carrier when the transfer material supporting member is extended is in the range of 0.5 to 2 mm. An image forming apparatus according to claim 1.
[0019]
(7) The image forming apparatus according to any one of (4) to (6), wherein the leading end of the transfer material supporting member in the transfer material transport direction extends to a position where the leading end contacts the peripheral surface of the image carrier. apparatus.
[0020]
(8) The advancing angle of the transfer material support member to the peripheral surface of the image carrier in the transfer material transport direction is between 15 ° and 60 ° with respect to the tangential direction at the point where the tip of the transfer material support member is at the peripheral surface of the image carrier. The image forming apparatus according to any one of (4) to (7), wherein:
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an embodiment of the present invention will be described below with reference to the drawings.
[0022]
FIG. 1 is a front view of an image forming apparatus having a plurality of paper feed trays.
As shown in the figure, an apparatus denoted by reference numeral 1 is an image forming apparatus of a digital system, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer material transport unit D as a transfer material transport unit. Etc.
[0023]
An automatic document feeder for automatically transporting a document is provided above the image reading unit A, and the documents placed on the document table 11 are separated one by one by a document separation roller H and separated. The original is transported to the reading position 13a via the original transport roller 12, and the image is read.
[0024]
The document for which reading of the document has been completed is discharged onto the document discharge tray 14 by the document conveying roller 12 and the document discharge roller G.
[0025]
At this time, a first mirror, which will be described later, is in a fixed position immediately below the reading position 13a, and the second mirror unit 16 is also fixed at a position for maintaining a predetermined optical path length (a position on the left side from the position shown).
[0026]
On the other hand, when the image of the original placed on the platen glass 13 is read by the speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped second image is read. It is read by the movement of the second mirror unit 16 composed of the second mirror and the third mirror in the same direction at the speed v / 2.
[0027]
The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17.
[0028]
The linear optical image formed on the image sensor CCD is sequentially converted into an electric signal (luminance signal), A / D converted, and subjected to processing such as density conversion and filter processing in the image processing unit B. After that, the image data is temporarily stored in a memory.
[0029]
In the image forming section C, as an image forming unit, a photoreceptor drum 21, a charger 22 serving as a charging unit, a developing unit 23, and a transfer for transferring an image charged on the photoreceptor drum 21 to a transfer material P are provided on the outer periphery thereof. Means 24, a separating means 25 for separating the transfer material P which is in close contact with the photosensitive drum 21, a belt carrying section 45 as a carrying means, a cleaning means 26 for the photosensitive drum 21, and a PCL (precharge lamp) as a charge removing means. 27 are arranged in the order of operation.
[0030]
The photoreceptor drum 21 is formed by coating a photoconductive compound on a drum base, and for example, an organic photoreceptor is preferably used, and is driven and rotated clockwise as indicated by an arrow.
[0031]
After the rotating photosensitive drum 21 is uniformly charged by the charger 22, image exposure based on the image signal called from the memory of the image processing unit B is performed by the exposure optical system 30 as image exposure means. .
[0032]
An exposure optical system 30 serving as an image exposure unit serving as a writing unit uses a laser diode (not shown) as a light emission light source, passes through a rotating polygon mirror 31, an fθ lens 34, a cylindrical lens 35, and a reflection mirror 32 to the photosensitive drum 21. On the other hand, image exposure in the main operation direction is performed at a position Ao indicated by an arrow, and a latent image is formed on the photosensitive drum 21 through sub-scanning by rotation of the photosensitive drum 21.
[0033]
The latent image on the photosensitive drum 21 is reversely developed by the developing device 23, and a visible toner image is formed on the surface of the photosensitive drum 21.
[0034]
On the other hand, in the transfer material transporting section D, paper feed trays 71 and 72 are provided below the image forming section C as transfer material storing means for storing transfer materials P of different sizes, the same size, or different types of paper and basis weight. The transfer material P in the paper feed tray 71 (72, 73) selected from any of them is further conveyed by the guide roller 43, temporarily stopped by the registration roller pair 44, and The sheet is re-supplied by the rotation of the registration roller pair 44, and is guided to the transfer area via the pre-transfer roller 43a, the sheet supply path 46, the entrance guide plate 47 constituting guide means, and the like.
[0035]
Also, various kinds of paper (normal copy paper, high-weight paper, etc.) can be passed through the manual feed unit 48.
[0036]
The toner image on the photosensitive drum 21 is transferred onto the transfer material P at the transfer position Bo (arrow position) via the transfer means 24, and then the transfer material P is separated from the surface of the photosensitive drum 21 by the action of the separation means 25. After the separation, the sheet is conveyed toward the fixing unit 50 by the belt conveying unit 45.
[0037]
The fixing unit 50 has a fixing roller 51 and a pressure roller 52. When the transfer material P passes between the fixing roller 51 and the pressure roller 52, a heating and pressing action is given to the transfer material P. The image is fused to the transfer material P.
[0038]
The transfer material P on which the toner image has been fixed is conveyed by a fixing discharge roller 63 and discharged onto a discharge tray 64.
[0039]
On the other hand, the photosensitive drum 21 from which the transfer material P has been separated is rubbed on the surface of the photosensitive drum 21 by the cleaning means 26 to remove and clean the residual toner, thereby forming a toner image of the next original image. Continue or stop and wait.
[0040]
When the formation of the toner image of the next document image is subsequently performed, the entire surface of the photosensitive drum 21 is uniformly exposed by the PCL 27 to erase the history remaining on the photosensitive drum 21. You.
[0041]
FIG. 2 is a schematic configuration diagram of a portion including the transfer unit 24, the entrance guide plate 47, and the like in the image forming unit C.
[0042]
The toner image formed on the photoconductor drum 21 by toner having a polarity opposite to the potential of the photoconductor drum 21 and the toner image is sent out from the paper feed tray 71 (72, 73) or the manual feed portion 48, and the registration roller pair 44 (see FIG. 1) and the transfer material P conveyed on the entrance guide plate 47 by the pre-transfer roller 43a in synchronism with the paper feed timing and sent to the transfer section 24a in synchronism.
[0043]
The high-voltage power supply 81 operates according to a command from the control unit 80, and a high voltage is applied to the transfer electrode 24c disposed in the back plate 24b, thereby generating corona discharge.
[0044]
Due to the corona discharge, a potential having a polarity opposite to that of the toner is applied from the back surface of the transfer material P, and the transfer material P is electrostatically attracted to the photosensitive drum 21, and the toner image on the photosensitive drum 21 is transferred onto the transfer material P. Transfer is started.
[0045]
Subsequently, the transfer of the toner image onto the transfer material P is performed, and the control unit 80 determines that the rear end of the transfer material in the feed direction has reached the transfer point a (from the registration roller driving unit 82 that drives the registration roller pair 44). Can be determined from the count of the carry amount of the above).
[0046]
The transfer point a is near the intersection on the peripheral surface of the photosensitive drum 21 connecting the rotation center c of the photosensitive drum 21 and the transfer electrode 24c, that is, the shortest distance between the transfer electrode 24c and the peripheral surface of the photosensitive drum 21. Point. Although FIG. 2 shows a cross section, it actually covers the width in the transfer material transport direction and has a linear shape.
[0047]
At the same time that the control means 80 determines that the rear end of the transfer material feed direction has reached the transfer point a, the transfer material P such as thick paper, tabbed paper, and long size paper, and the basis weight and material of the transfer material P Is selected and input in advance in the operation unit S and stored in the control unit 80. If the transfer material P in which the transfer is being performed corresponds to the selected and input in advance and stored in the control unit 80, the control unit 80 If it is determined, the driving device 47a that expands and contracts the transfer material supporting member 47b attached to the entrance guide plate 47 is operated according to a command from the control means 80.
[0048]
By the operation of the driving device 47a, the transfer material supporting member 47b retracted to the initial position d extends to a position b in contact with the peripheral surface of the photosensitive drum 21, and the transfer material P is electrostatically attracted to the photosensitive drum 21. Therefore, the transfer material supporting member 47b stops while pressing the rear end of the transfer material back surface while bending so as to flutter in the rotation direction of the photosensitive drum 21 as shown in FIG.
[0049]
The extended end of the transfer material supporting member 47b is always downstream from the end of the entry guide plate 47 closest to the transfer electrode.
[0050]
As a result, as shown in FIG. 3, the approach angle θ between the transfer material P during transfer and the tangential direction XX of the photosensitive drum 21 at the position b where the tip of the transfer material support member contacts the peripheral surface of the photosensitive drum 21. = 15 ° to 60 °, the transfer material supporting member 47b is curved in the rotation direction of the photosensitive drum 21 as shown in FIG. Meanwhile, an appropriate pressing force is applied to the back surface of the transfer material by the tip shoe 47c fixed to the tip portion.
[0051]
When the entry angle θ of the transfer material support member 47b is less than 15 °, a space for mounting the transfer material support member 47b cannot be taken, and when the entry angle θ is 60 ° or more, the transfer material support member 47b with respect to the back surface of the transfer material. 47b becomes difficult to bend in the rotation direction of the photosensitive drum 21 and is difficult to adopt.
[0052]
The material of the transfer material supporting member 47b is an insulating material that hardly affects the potential in the corona discharge region, and has a suitable pressing force (that is, ensures the adhesion of the transfer material P, The pressing force applied from the back side of the transfer material 47b does not have a pressing force enough to reduce the electrostatic attraction force between the photosensitive drum 21 and the transfer material P). (Polyethylene terephthalate) film (thickness: 0.18 mm) is employed.
[0053]
The PET film is a member that covers the maximum width of the transfer material conveyance and has a shape that is long in the direction perpendicular to the paper surface, and a tip shoe 47c is fixed to the tip of the PET film as shown in FIG.
[0054]
The tip shoe 47c is fixed to the end of the transfer material support member 47b facing the peripheral surface of the photosensitive drum 21 so as to cover the maximum transfer width of the transfer material of the PET film.
[0055]
Further, when the rear end of the transfer material is separated from the front end of the transfer material support member 47b, the front end of the transfer material support member 47b pressing the back surface of the transfer material may slide on the peripheral surface of the photosensitive drum 21. In this case, urethane rubber is used as the material of the tip shoe 47c so as not to damage the peripheral surface of the photosensitive drum 21.
[0056]
Other than urethane rubber, fluorine rubber, chloroprene rubber, butadiene rubber, etc. are known, but urethane rubber is useful in that it has particularly excellent wear resistance compared to other rubbers, and is used for a long time. It is possible and the urethane rubber hardness is optimally 50 to 90 (JISA scale).
[0057]
By pressing the transfer material supporting member 47b against the back surface of the transfer material, the adhesion of the rear end portion of the transfer material is increased to prevent the occurrence of transfer cissing, and the transfer material such as thick paper, tabbed paper, postcard, and long copy paper is used. The image quality at the rear end can be ensured.
[0058]
The reaching point b (see FIG. 2) when the transfer material supporting member 47b extends is a distance L (see FIG. 2) from the transfer point a to the corona discharge region generated from the transfer electrode 24c so as not to affect the toner transfer. 2) is adjusted in the range of 0.5 to 2 mm.
[0059]
Thereby, it is possible to secure the image up to the rear end of the transfer image in the transport direction.
On the other hand, when L is closer to the transfer point a than 0.5 mm, the transfer efficiency due to corona discharge decreases, and the transfer of the toner image formed on the peripheral surface of the photosensitive drum 21 to the transfer material P becomes insufficient. Transfer failure due to image omission is likely to occur, and if L is more than 2 mm away from the transfer point a, the adhesion to the rear end of the transfer material will be insufficient, and transfer repelling will easily occur, and both are difficult to apply. .
[0060]
The front end of the transfer material support member 47b presses the rear end of the transfer material P in the transport direction from the back surface, and the adhesion of the rear end of the transfer material P to the peripheral surface of the photosensitive drum 21 is increased. Transfer repelling at the rear end of P can be prevented.
[0061]
Subsequently, the toner image formed on the photosensitive drum 21 is accurately transferred onto the transfer material P while being pressed against the transfer material supporting member 47b from the back surface to the rear end of the transfer material P.
[0062]
In this manner, the toner image on the photosensitive drum 21 is transferred to the transfer material P having poor adhesion at the rear end in the transfer material transport direction, such as thick paper, tabbed paper, postcard, and long size paper. No transfer repelling or the like occurs to the rear end, and the image can be transferred without deteriorating the image quality.
[0063]
Then, the control means 80 determines that the trailing end of the transfer material passes the transfer point a from the count of the transport amount from the registration roller driving section 82, and a command is issued from the control means 80 to the driving device 47a to transfer the image. The material support member 47b returns to the initial setting position d.
[0064]
【The invention's effect】
Adhesion at the rear end of the transfer section in the transfer material transport direction is improved, transfer cissing can be prevented, and the quality of the transferred image can be improved.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram as an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration and control explanatory diagram of an image forming unit.
FIG. 3 is an enlarged view of a rear end portion of a transfer material in an image forming unit.
FIG. 4 is an example of a transfer material according to the present invention.
[Explanation of symbols]
1 Image Forming Apparatus 21 Photoconductor Drum 24 Transfer Means 24a Transfer Section 24c Transfer Electrode 47 Entry Guide Plate 47a Drive Device 47b Transfer Material Support Member 47c Tip Shoe 80 Control Means 82 Registration Roller Drive Section a Transfer Point P Transfer Material S Operation Section

Claims (8)

In an image forming apparatus, a toner image formed on an image carrier is supplied from a paper supply unit, and is electrostatically transferred to a transfer material that is guided by a guide unit and fed between the image carrier and the transfer unit. An image forming apparatus comprising: a guide member provided with a transfer material supporting member that can expand and contract in a transfer material transfer direction. The image forming apparatus according to claim 1, wherein the transfer material supporting member is provided on a back surface side of the transfer material with respect to a toner receiving side. 2. The image forming apparatus according to claim 1, wherein a front end shoe is fixed to a front end portion of the transfer material supporting member and a side opposite to a peripheral surface of the image carrier, and the shoe is an elastic material. . 2. Description of the Related Art In an image forming apparatus, a toner image formed on an image carrier is supplied and conveyed from a paper feeding unit, and is electrostatically transferred to a transfer material guided between guide members by the guide means. An extendable transfer material support member is provided at the end of the guide means in the transfer material transfer direction, and the expansion and contraction of the transfer material support member in the transfer material transport direction is performed based on information such as the basis weight and material of the transfer material. An image forming apparatus characterized in that the image forming apparatus is controlled by a control unit. The expansion and contraction of the transfer material support member in the transfer material transport direction is such that when the rear end of the transfer material reaches the transfer point, the transfer material support member is extended, and returns to the initial position when the rear end of the transfer material passes through the transfer point. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is controlled by a control unit. 5. The image forming apparatus according to claim 4, wherein a distance between a leading end of the transfer material transporting direction in the transfer material transport direction and a transfer point on the image carrier when the transfer material support member extends is in a range of 0.5 to 2 mm. Image forming device. The image forming apparatus according to claim 4, wherein a front end of the transfer material supporting member in the transfer material transport direction extends to a position where the front end contacts the peripheral surface of the image carrier. The angle at which the transfer material supporting member enters the peripheral surface of the image carrier in the transfer material transport direction is between 15 ° and 60 ° with respect to the tangential direction at the point where the tip of the transfer material support member is at the peripheral surface of the image carrier. The image forming apparatus according to any one of claims 4 to 7, wherein:

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