JP2007232788A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that executes a toner consumption mode, the apparatus being designed to improve margin for trouble caused by paper powder mixed in, by detecting an amount of attached a toner in the middle and at the ends of development, thereby precisely detecting a decrease in an amount of scooped developer. <P>SOLUTION: The image forming apparatus includes a toner recycle means having a shutter mechanism capable of switching between a toner recycle path and a toner disposal path during the recycling of recovered toner, the toner disposal path being used for removing matter mixed in, except the toner. The image forming apparatus also has a means for exerting a mode by which all toner being conveyed in a developing means is discharged when a toner disposal setting has been separately set. The image forming apparatus is provided with a developing means by which an amount of the toner attached to a toner image formed on the image carrier as a reference density patch is detected in the middle and at the ends in the longitudinal direction of development, and switching between the recycle and disposal of the recovered toner is controlled based on the detected toner density. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a collected toner recycling mechanism of an electrophotographic image forming apparatus, and more particularly to an image forming apparatus having switching control between recycled toner recycling and toner discarding.

Conventionally, as a condition of the forced toner consumption mode, a toner having a small particle size or fine powder is selectively consumed by setting the potential difference between the latent image potential and the developing bias to a predetermined value or less. In the forced toner consumption mode, the toner recycling is performed. There has been proposed an image forming apparatus in which the switching means of the apparatus is set to discard the collected toner to prevent the quality deterioration of the recycled toner (for example, see Patent Document 1).
However, when trying to wipe out the paper dust in the developing device using this forced toner consumption mode, a large amount of paper dust is present in the vicinity of the stationary developer in the developing device, so the paper dust in the developing device is wiped out. It is difficult to do.

In addition, in order to avoid image defects due to insufficient charging of toner, an image forming apparatus that regulates the amount of collected toner to be recycled immediately after turning on the power of the image forming apparatus or after a certain period of time after being left for a long time has been proposed (for example, Patent Documents). 2).
However, in this image forming apparatus, it is difficult for image forming apparatuses that output a large amount of images per day, such as a high-speed copying machine, to prevent image leakage due to paper dust, which is a problem of the present case.

Further, an image forming apparatus that creates a reference density toner image (hereinafter referred to as “reference density patch”) for toner density control in the developing device is widely known.
An image forming apparatus has been proposed in which a density detection mechanism that detects a reference density patch can be detected in a variable area, a reference density patch can be created in an arbitrary image formation area, and the toner adhesion amount in that area can be known. (For example, refer to Patent Document 3).
Further, there has been proposed an image forming apparatus that creates conditions for forcibly generating background stains, detects the toner adhesion amount on the surface of the image carrier, and controls the recycling amount of the collected toner based on the result (for example, (See Patent Document 4).
JP 2005-91395 A JP 2003-295728 A Japanese Patent Laid-Open No. 11-24383 JP 2004-45889 A

  However, in recent years, transfer paper (recycled paper, transfer paper containing a large amount of impurities, etc.) that is considered to have a relatively large amount of paper powder is applied to the transfer paper used in the copying machine in terms of environment and cost. There are many. Most of the untransferred toner contains paper powder, and the recycled toner tends to agglomerate around the paper powder. For this reason, in an image forming apparatus that can recycle toner, there is a difference in the degree to which the environment, toner, and paper type are used. The amount of developer pumped up (the amount of developer passing through the photosensitive member-developing sleeve nip) is insufficient, resulting in problems such as image loss and toner scattering. It is also known that, after toner recycling for a certain period of time, discarding the collected toner while the toner in the toner conveyance path and the hopper makes a round can prevent the above-mentioned problem that occurs with time to some extent. However, applying the same toner recycling control to all papers is disadvantageous for a user who uses transfer paper with relatively little paper dust because it discards (recycled) toner more than necessary. If the amount of paper dust can be quantified by some means, fine control is possible. However, it is difficult to quantify the true amount of paper dust because the surrounding dust or the like adsorbs to the paper dust itself.

  Further, since a large amount of paper dust in the developing device is present in the vicinity of the immobile developer, it is difficult to remove it completely only by recycling control of the collected toner. In order to remove paper dust near the immobile developer, the toner concentration is lowered from the normal level by using a forced toner consumption mode, etc., the developer fluidity is improved, and the paper dust remaining in the developing device is removed from the developing device together with the toner. It needs to be easily discharged.

  The present invention has been made in consideration of the above-described circumstances, and uses a toner recycling apparatus controlled to discard the collected toner while the toner in the toner conveyance path and the hopper makes a round (or more than one round), and the recycled toner In an image forming apparatus that executes a mode in which the toner in the developing device is consumed at a predetermined timing when discarding is set, the toner adhering amount is detected at the center position and the end position of the developing length, and the amount of developer pumped up is accurately determined. The purpose is to detect a drop and to improve the margin for malfunction due to paper dust mixing.

  In order to solve the above problem, the invention according to claim 1 is a shutter mechanism capable of switching to a toner recycling path and a toner discarding path for removing contaminants other than toner during recycling of the collected toner. And a reference density formed on the image carrier in an image forming apparatus having a unit for executing a mode for discharging all of the toner being conveyed in the developing unit when the toner discarding setting is set separately. Image forming having developing means for detecting the toner adhesion amount of the toner image formed as a patch at the center position and the end position of the development longitudinal direction and controlling switching between recycling and discarding of the collected toner based on the detected toner density Features the device.

  The invention according to claim 2 is characterized in that the width of the reference density patch at the longitudinal end of the developing means is narrower than the width of the reference density patch at the center.

  According to a third aspect of the present invention, the developer holding surface shape of the developer amount regulating member at the longitudinal end of the developing means is developed more than the developer holding surface shape at the longitudinal end of the developing means. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus has a surface shape capable of holding a large amount of the agent.

  According to a fourth aspect of the present invention, the corner R of the tip of the developer amount regulating member at the longitudinal end of the developing means is made larger than the angle R of the developer amount regulating member at the center. The image forming apparatus is characterized.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the angle R of the tip end portion of the development amount regulating member at the longitudinal end portion of the developing means is 0.5 mm or more. Features.

  Further, in the invention described in claim 6, the surface shape of the conveying member that conveys the developer at the longitudinal end of the developing means to the developing region is such that the fixing force to the developer at the longitudinal end and the center of the developing means is The image forming apparatus according to claim 1, wherein the longitudinal end of the developing means is larger.

  According to a seventh aspect of the present invention, the image forming apparatus according to the sixth aspect is characterized in that the surface roughness of the conveying member that conveys the developer at the longitudinal end of the developing means to the developing area is rougher than the central portion. To do.

  Further, the invention according to claim 8 is an image forming apparatus to which a developing device having a groove horizontally with respect to the longitudinal direction of the developing means of a conveying member that conveys the developer of the developing means to a developing region is applied. The image forming apparatus according to claim 6, wherein the depth of the groove at the longitudinal end portion is shallower than the central portion.

  According to the present invention, there is provided a toner recycling means having a shutter mechanism capable of switching between a toner recycling path and a toner discarding path for removing contaminants other than toner during recycling of the collected toner, and is set separately. In the image forming apparatus having means for executing a mode for discharging all of the toner being conveyed in the developing means when the toner discard setting is performed, the toner adhesion amount of the toner image formed as the reference density patch formed on the image carrier is determined. An image forming apparatus comprising: a developing unit that detects at a center position and an end position of the development longitudinal direction and controls switching between recycling and discarding of the collected toner based on the detected toner density; By detecting the toner adhesion amount at the position and end position, it is possible to detect a decrease in the developer pumping amount with good accuracy, It is possible to improve the margin for engagement.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The configuration of the first embodiment of the image forming apparatus of the present invention is shown in FIG. The document placed on the contact glass 1 is decomposed into a large number of pixels after the image on the document is read, and the laser beam 2 irradiated corresponding to the density of each pixel is applied by the scorotron charger 3 or the like. A latent image is formed on the uniformly charged photosensitive drum 4. The linear velocity of the photosensitive member is as high as 500 mm / sec, for example, and the ratio of the developing sleeve linear velocity to the photosensitive member linear velocity (developing sleeve linear velocity / photosensitive member linear velocity) is 1.9.
The latent image formed on the photosensitive drum 4 is developed by the developing device 5 (here, a two-component developing system). For development, a developer-regulated amount of developer is conveyed to the photoreceptor-developing sleeve nip by a developing roller consisting of a fixed magnet and a rotating aluminum developing sleeve, and the latent image is electrostatically charged with the following conditions: It is done by attaching by force.

  For example, in the latent image, the potential (VL) of the image saturation density portion is 100V, the potential of the image white portion (VD) is 970V, and the developing bias of the image portion is 530V. The developing bias is applied to the developing sleeve by a developing bias power pack (not shown).

  Further, in this example, the toner is a polyester resin, CCA is a quaternary ammonium salt, carbon black is used as colored particles, an average of 0.7% hydrophobic silica and 0.3% titanium oxide as an external additive. A pulverized toner having a particle size of 9.5 μm is used. The toner start-off temperature is 105 ° C. (toner with a very low melting point). The outflow start point was measured using an elevated flow tester manufactured by Shimadzu. The measurement conditions were [die diameter: 1.0 mm, load: 20.0 kg, heating rate: 6.0 deg / min]. The carrier used is a magnetite core coating carrier, the toner q / m (the amount of charge per unit weight) is 20 to 35 μC / g, and the mixing ratio of the toner and the carrier is 2 to 4% by weight.

  In this embodiment, a reference density patch latent image is written by a laser beam every predetermined number of printed sheets, a development bias of the patch is applied, and a reference density toner image (hereinafter referred to as density) with a predetermined development potential (280 V in this embodiment). A patch) is developed. The reflection density of the density patch is detected by a reflection density sensor, and the toner 7 in the toner hopper 6 is replenished so that the reflection density falls within a certain range. The reflection density (Vsp) of the density patch is detected by the reflection density sensor. The background density (Vsg0) is detected when no drum is attached to the drum at the time of drum start-up (before development start-up) for one job. The target value Vref of the magnetic permeability sensor is determined from the ratio between the sensor output (Vsp) of the reflection density of the density patch and the reflection density (Vsg0) of the background. The magnetic permeability sensor detects the magnetic permeability of the developer (Vt: Vt increases as the developer toner concentration decreases). When Vref−Vt ≦ 0, toner is replenished, and as the absolute value of Vref−Vt (| Vref−Vt |) increases, that is, as the negative value of Vref−Vt increases, the toner replenishment amount increases. When Vref−Vt> 0 (considering that the toner density is sufficiently high), toner supply is not performed.

  The transfer belt 9 is charged by the bias roller 10, and the toner image formed on the photosensitive drum 4 by electrostatic force is transferred to the transfer paper 11 conveyed to the transfer belt 9. The remaining transfer residual toner that has been transferred is scraped off by the cleaning blade 12 and directly conveyed to the hopper 6 by the conveying screw 13. New toner from a toner bottle (not shown) is sent to the hopper 6 and mixed with the recycled toner conveyed from the conveying screw in the hopper 6. The toner recycling mechanism (hereinafter referred to as “recycling mechanism”) includes a cleaning blade 12, a conveying screw 13, and a shutter mechanism 14.

FIG. 2 shows the shutter mechanism 14 (solenoid power ON state) of the toner recycling apparatus. As shown in FIG. 2, the shutter mechanism 14 used in the image forming apparatus of the present invention includes a waste toner collection receiving unit 141, a shutter 142, a solenoid 143, and a collection port 144. That is, the shutter mechanism has a collection port 144 for collecting the waste toner in the recycling conveyance path, and the shutter 142 is positioned along the collection port 144. The shutter 142 is slid by the solenoid 143 along the recycling conveyance path as shown in FIGS. As shown in FIG. 2A, when the solenoid 143 is turned on, the collection port 144 is shut off by the shutter 142, and the collected toner is recycled to the developing device via the conveying screw 13 as it is.
Also, as shown in FIG. 7B, when the power supply of the solenoid 143 is turned off, the collection port 144 is opened, and the collected toner is collected as waste toner through the waste toner collection path 15. If this configuration is employed, the shutter mechanism position is always on the collected toner disposal side when the solenoid power is OFF. Therefore, even if the power is turned ON / OFF while the collected toner is discarded, the collected toner is not supplied to the recycling path, and the toner core and paper dust can be cleaned.

  FIG. 3 shows a flowchart of the toner forced consumption mode. In this embodiment, the toner consumption pattern is created until the detected value of the reference density patch becomes a predetermined value (for example, Vsp = 1.0) or more. When Vsp = 1.0 or more, the toner replenishment operation is executed for a certain period of time until the detected value of the reference density patch (reference density toner image) becomes a predetermined value (Vsp = 0.3) or less. Replace. The toner forced consumption mode is activated when the setting of the toner recycling mechanism is set to the collected toner recycling and the predetermined number of printed sheets (for example, 5 kp = 5000 sheets) is reached.

  In the second embodiment, the reflection density sensor detects density patches (reference density toner images) at two or more locations in the development longitudinal direction, and the difference (ΔVsp) in the detected value is used as a substitute characteristic value for the decrease in the pumping amount of the developer. To do. In this embodiment, when the ΔVsp value is 0.1 or more, the toner recycling apparatus is set to the collected toner discard side (toner is discarded), and when it is less than 0.1, the collected toner is set to the recycling side (toner is not changed). It was decided to recycle).

  FIG. 4 shows a result of confirming an image defect (occurrence of white blur in a black solid image) when the toner recycling apparatus is controlled based on the ΔVsp value of the development longitudinal center position and the development longitudinal end position. The evaluation is performed by visually observing the image, and the best is rank 5 and the worst is rank 1. If the toner recycling device is not controlled, it will be below the acceptable level (rank 3.5) when printing 100kp or more (100,000 sheets), but if the recycling device is controlled, the acceptable level will be sufficiently satisfied over a long period of 250kp or more. can do. In the second embodiment, the threshold value ΔVsp for recycling control is set to 0.13. Furthermore, it is possible to increase the sensitivity to the shortage of the developer pumping amount due to paper jams by reducing the developer pumping amount by narrowing the developer regulation width at the end portion where the margin of paper jam is the smallest.

  FIG. 5 is a cross-sectional view of a developing device using a doctor that has been subjected to sandblasting only at both longitudinal ends of the device. The developer is transferred from the paddle 21 to the developing sleeve 19, the amount of the developer is regulated to a fixed amount by the doctor 20, and the developer passing therethrough is conveyed to the developing region. In this embodiment, the surface roughness Rz at both ends is about 10. When the surface of the doctor 20 is roughened, stagnation occurs due to the flow of developer passing therethrough. As a result, the developer at the end becomes difficult to move, and a foreign matter such as paper dust is likely to adhere to the doctor 20. FIG. 6 shows the result of confirming a white blank image by applying this developing device to this embodiment. When sandblasting is applied to both longitudinal ends of the doctor 20, the rank of 4.5 or higher is maintained over a long period of 250 kp. From this result, it can be seen that when sandblasting is applied to both longitudinal ends of the doctor's device, white missing images due to paper jams are detected at an early stage, and the collected toner is set to the discard setting to prevent problems with the entire image. .

  FIG. 7 shows an enlarged view of the doctor in which the angle R at the distal end of the doctor at both ends of the apparatus is larger than that at the center. In Example 4, the angle R at the tip of the doctor was 0.3 mm at the longitudinal center of the apparatus and 0.5 mm at both ends. When the angle R at the tip of the doctor is increased, stagnation occurs in the developer flow near the doctor, and foreign matters such as paper dust easily adhere to the doctor. FIG. 8 shows the result of applying this doctor to the present embodiment and confirming the white blank image. When the angle R at the tip of the doctor at both ends of the apparatus is larger than the center, white blank images are hardly generated over a long period of 250 kp. From this result, if the angle R at the tip of the doctor at both ends of the device is larger than the center, a white missing image due to paper jam is detected early and the collected toner is discarded to prevent problems with the entire image. I understand that.

  FIG. 9 shows the relationship between the angle R at the tip of the doctor and the number of white blank NG (less than 3.5 rank) generated. Printing was performed by setting all the collected toners to be recycled with the same angle R throughout the length of the doctor. From this result, it is understood that a white blank image can be confirmed at an early stage by setting at least the corner R portion of the doctor tip to 0.5 mm or more.

  A stainless steel developing sleeve was prepared, and a TiN (titanium nitride) coat was applied to the surface except for both ends of the developing longitudinal direction. Toner is hard to adhere to the TiN coated surface. In Example 6, a paper passing experiment using a developing sleeve was performed, and the result of confirming a white blank image is shown in FIG. From this result, it became possible to detect the white spots due to the sticking of the doctor paper powder at an early stage by changing the surface physical properties at the longitudinal center and the end of the developing sleeve, and to prevent the entire image from being enlarged. This is because, when TiN coating is not applied to both ends of the developing sleeve, the toner adheres to that portion and the developer conveying ability on the surface of the sleeve is reduced, so that an early detection of a white blank image is possible. I think that is due to that.

  FIG. 11 shows the result of confirming a white-spotted image in the case where sandblasting is applied to the development longitudinal end portion on the surface of the aluminum development sleeve. In Example 7, the surface roughness of the central portion is Ra = 0.4, Ry = 3, Rz = 2, and Ra = 5, Ry = 30, Rz = 20 at both ends. The progress of the white missing image is faster, but it is superior to the white missing image as compared with the case where the entire surface of the sleeve is the same. This is because the rougher the surface, the more easily the toner adheres to the irregularities on the surface. As a result, the toner adheres to the developing sleeve and the developer conveying ability decreases, and white missing images are detected at both ends. The sensitivity is thought to have improved.

  FIG. 12 to FIG. 13 show the surface of the aluminum developing sleeve, in which a groove is dug to the depth d in a horizontal direction with respect to the development longitudinal direction. In Example 8, the depth of the groove at the development longitudinal center was 0.3 mm, and the depth of the grooves at both ends was 0.15. The deeper the groove of the developing sleeve, the higher the developer conveying ability on the surface of the developing sleeve can be expected. FIG. 14 shows the result of confirming a white blank image using this developing sleeve. Due to the same groove depth on the entire surface, an improvement in margin can be seen with respect to the white missing image.

1 is a cross-sectional view illustrating a configuration example of an image forming apparatus equipped with a toner recycling apparatus of the present invention. 4A and 4B are schematic diagrams of a shutter mechanism of the toner recycling apparatus of the present invention, in which FIG. 4A shows a state where the shutter is closed, and FIG. 4B shows a state where the shutter is opened. 6 is a flowchart in a toner forced consumption mode of the toner recycling apparatus of the present invention. It is explanatory drawing which shows the generation | occurrence | production result of the image defect by the recycling control of the toner recycling apparatus of this invention. FIG. 3 is a cross-sectional view of a doctor in which only the both ends of the longitudinal direction of the toner recycling apparatus of the present invention are sandblasted. It is explanatory drawing which shows the result of having confirmed the white blank image by applying the developing device of this invention. FIG. 4 is an enlarged cross-sectional view in which a corner R of a doctor tip at both longitudinal end portions of the toner recycling apparatus of the present invention is larger than a central portion. It is a figure which shows the result of having confirmed the white blank image by applying the doctor of the toner recycling apparatus of this invention to a present Example. FIG. 6 is a diagram illustrating a relationship between a corner R of a doctor tip and the number of white spots NG generated in the toner recycling apparatus of the present invention. FIG. 6 is a view showing a result of confirming a white blank image by performing a paper passing experiment using a developing sleeve provided with a TiN coat of the toner recycling apparatus of the present invention. It is a figure which shows the white blank evaluation in the paper passing experiment using the developing sleeve which formed the groove | channel in the developing longitudinal direction surface of the toner recycling apparatus of this invention. FIG. 4 is a perspective view in which a groove is formed on the surface of the developing sleeve of the toner recycling apparatus of the present invention. FIG. 3 is a cross-sectional view of a developing sleeve in which a groove is formed in the developing sleeve of the toner recycling apparatus of the present invention. It is a figure of white spot evaluation using the groove formation development sleeve of the toner recycling device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contact glass 2 Laser beam 3 Scorotron charger 4 Photosensitive drum 5 Developing device 6 Toner hopper 7 Toner 9 Transfer belt 11 Transfer paper 12 Cleaning blade 13 Conveying screw 14 Shutter mechanism 142 Shutter 143 Solenoid 144 Collection port 19 Developing sleeve 20 Doctor 21 Paddle 22 Paddle short part 23 Paddle center part 24 Sleeve groove

Claims (8)

  It has toner recycling means equipped with a shutter mechanism that can be switched to a toner recycling path and a toner discarding path for removing contaminants other than toner during recycling of the collected toner, and development is performed when toner discarding is set separately. In an image forming apparatus having a means for executing a mode for discharging all of the toner being conveyed in the means, the toner adhesion amount of the toner image formed as a reference density patch formed on the image carrier is determined by the development longitudinal center position. And an image forming apparatus having a developing unit that controls switching between recycling and discarding of the collected toner based on the detected toner density.   2. The image forming apparatus according to claim 1, wherein the width of the reference density patch at the longitudinal end of the developing unit is narrower than the width of the reference density patch at the center.   The developer holding surface shape of the developer amount regulating member at the longitudinal end portion of the developing means is such that the longitudinal end portion of the developing means can hold a larger amount of developer than the developer holding surface shape at the central portion. The image forming apparatus according to claim 1, wherein:   4. The image forming apparatus according to claim 3, wherein an angle R of a tip end portion of the developer amount regulating member at a longitudinal end portion of the developing unit is made larger than an angle R of the developer amount regulating member at the center portion.   5. The image forming apparatus according to claim 4, wherein the angle R of the tip end portion of the development amount regulating member at the longitudinal end portion of the developing means is 0.5 mm or more.   The surface shape of the conveying member that conveys the developer at the longitudinal end of the developing unit to the developing area is such that the fixing force to the developer at the developing unit longitudinal end and the center is greater at the developing unit longitudinal end. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 6, wherein a surface roughness of a conveying member that conveys the developer at a longitudinal end of the developing unit to a developing region is rougher than that of a central portion.   In the image forming apparatus to which the developing device having a groove horizontally with respect to the longitudinal direction of the developing unit of the conveying member for conveying the developer of the developing unit to the developing region is applied, the groove depth at the longitudinal end of the developing device is set to The image forming apparatus according to claim 6, wherein the image forming apparatus is shallower.

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