JP2009122447A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent nonuniformity of toner distribution in a developing unit in its longitudinal direction, resulting from nonuniform consumption of toner in the longitudinal direction of the developing unit. <P>SOLUTION: In a toner supply device that supplies toner to the main body of a developing device, a toner supply area is divided into two separate areas, and toner is selectively supplied to one of the separate toner supply areas, which has a smaller quantity of toner in it in the longitudinal direction of the main body of the developing device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer that forms an image using a developer, and more particularly, development that replenishes the developer to a developing apparatus that has consumed the developer by development. The present invention relates to an agent supply device.

  2. Description of the Related Art Conventionally, as a developer replenishing method in an electrophotographic image forming apparatus such as a copying machine, there is a method of supplying a developer from a developer replenishing device to a developing device.

  The developing device has a remaining amount detection sensor for detecting the remaining amount of developer in the developing device main body, and this sensor detects when the amount of developer near the remaining amount detection sensor becomes a predetermined amount or less. To do.

  On the other hand, the developer replenishing device has a developer conveying member (for example, a screw) that stirs and conveys the replenishing developer accommodated in the main body of the replenishing device (toner hopper), and is based on the output of the developer detection sensor described above. Then, the developer is replenished to the developing device by rotationally driving the screw via a driving source such as a motor.

  As described above, the developer toner replenished to one end in the width direction of the developing container is transported in the longitudinal direction of the developing sleeve by the rotationally driven transport screw.

  A toner regulating wall is provided in the toner conveyance path in order to supply toner substantially uniformly in the sleeve direction of the developing container.

  The toner dropped from the toner conveyance path is agitated and conveyed by various means, supplied to the developing sleeve, and used for developing the latent image formed on the photosensitive drum.

  When a large number of originals whose image density is significantly deviated along the longitudinal direction is output continuously using the apparatus having the above-described configuration, the toner consumption is deviated in the longitudinal direction. The amount of toner is significantly larger or smaller than the amount of toner remaining in the developing device detected by the remaining amount detection sensor, and the toner supply to the developing sleeve cannot keep up with its consumption, resulting in white spots in the image. On the other hand, since the toner is supplied even though the toner is sufficiently contained, the toner in the portion is compressed, resulting in a decrease in fluidity and causing a coating failure on the developing sleeve.

In order to solve such a situation, even when the developer consumption distribution is remarkably biased, there is a proposal for means for supplying toner corresponding to this distribution. (For example, see Patent Document 1)
In this conventional example, the supply distribution according to the developer consumption distribution can be realized by changing the distribution sequence of the positions where the developer falls by changing the driving sequence (speed, timing) of the conveying screw.
Japanese Patent Laid-Open No. 11-160988 (FIGS. 6 and 14)

  However, using the device configured as described above and switching the screw rotation speed and operation sequence to control the longitudinal distribution of developer replenishment, the environment such as temperature and humidity in the developer replenisher differs, and the toner itself The developer replenishment distribution in the longitudinal direction of the developer changes even in the same sequence because the degree of aggregation of the developer, the adhesive force, and the like change due to the change in the charged state.

  More specifically, toner conveyance by the screw conveys the toner by the combined force of the drag force and gravity received from the helical slope of the screw and the toner regulating wall. The toner picked up by the screw at the time of conveyance is replenished into the developing means main body by dropping in order from the lower part of the toner regulating wall.

  Here, when the cohesion degree, viscoelasticity, adhesion force, etc. of the toner itself change, the height of the wall to be carried changes, and the distribution of the fall amount in the longitudinal direction changes under the influence of temperature and humidity.

  As a result, the replenishment does not proceed as intended, and the non-uniform state of the toner in the developing device cannot be resolved.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A toner replenishing means for replenishing magnetic toner to a developing device having a developing member;
A toner container for containing toner;
A magnet roller provided in the toner container and supported in a rotatable manner having substantially the same length as the developing member of the developing device;
Driving means for rotating the magnet roller;
A regulating member that coats the magnetic roller with a certain thickness of magnetic toner;
A scraping member that scrapes off a certain amount of the coated toner layer, and the positional relationship between the regulating member and the scraping member is substantially vertical through the axis of the magnet roller in the cross-sectional shape at the center in the longitudinal direction of the magnet roller. It has a mirror image relationship with the spreading plane,
An image forming apparatus characterized in that a rotation direction of a magnet roller can be selected selectively.

  According to the present invention, in a toner replenishing device that replenishes toner to the developing device main body, the toner replenishing area is divided into two parts, and the toner in the developing device is selectively replenished to the side of the developing device main body where the toner is low. Unevenness of the longitudinal distribution of the amount can be improved.

  Further, the toner cohesion and adhesive force change due to changes in the temperature and humidity of the use environment, and there is no occurrence of uneven supply in the longitudinal direction of the toner.

Example 1
FIG. 1 is a sectional view of a copying machine which is an image forming apparatus embodying the present invention. An image forming process in this apparatus will be briefly described.

  An electrostatic latent image is formed by irradiating an image exposure 180 of the original on the photosensitive drum 110 charged to a predetermined potential by the charging roller 170, and is generated due to a potential difference between the developing sleeve 121 and the electrostatic latent image on the photosensitive drum l10. The electrostatic latent image is developed by moving the toner from the developing sleeve 121 to the photosensitive drum 110 by the applied electric field.

  On the other hand, the transfer material P sent from the paper feed cassette is conveyed between the transfer roller 130 and the photosensitive drum 110, and the development on the photosensitive drum 110 is pressed against the transfer material P by the transfer bias applied to the transfer roller 130. Is transcribed.

  The transfer material P receives the electrostatic force of the separation static elimination needle 140 and the curvature of the photosensitive drum 110, is separated from the photosensitive drum 110, conveyed, and the transferred image is fixed by heat and pressure by the fixing device 150. The transfer residual toner remaining on the photosensitive drum 110 after the transfer material P is separated is scraped off and cleaned by the cleaning device 160. A copy image of the original is formed by the above series of operations.

  The potential measuring wire 10 is a means for measuring an average potential of an electrostatic latent image formed by image exposure.

  As shown in FIG. 2, the potential measuring wire 10 is disposed so as to face the photosensitive drum 110 and is divided into two in the longitudinal direction, and each of them functions independently.

  When an electrostatic latent image is formed on the photosensitive drum 110 and reaches the potential measuring wire 10, an electric charge corresponding to the electrostatic latent image is induced on each potential measuring wire 10. The potential is measured by a separately provided potential sensor.

  3 is a top view of the toner replenishing means, FIG. 4 is a longitudinal sectional view of the toner container at the top of the toner replenishing means, and FIG. 5 is a sectional view perpendicular to the longitudinal direction of the developing device and the toner replenishing means. The replenishment process is performed as follows according to the signal detected by the residual detection sensor 124.

  The toner delivery screw 201 disposed in the toner container 200 of FIG. 4 is driven, the toner is conveyed by the screw 201, and the toner is discharged from the toner discharge port 202. The toner is supplied into the toner replenishing means from the front side (near 127) of the developing device 120 and transferred to the toner stirring member 125.

  The toner agitating member 125 is driven to rotate, and the amount of toner is made uniform in the longitudinal direction by rotating the agitating member 125.

  Further, the magnetic toner is adsorbed to the toner stirring member 125 and the magnet roller 126 shown in FIG.

  In FIG. 10, the magnet roller 126 is rotatably supported. The drive system 118 that transmits the drive to the magnet roller 126 has a control unit that can select an arbitrary direction for the rotation direction of the magnet roller 126.

  Around the magnet roller, toner coat portions 117a and 117b and toner scraping portions 116a and 116b, which are attached to or integrally formed with the toner container, are disposed.

  As the magnet roller 126 rotates, the toner coating portions 117a and 117b coat the toner on the magnet roller 126 with a constant thickness t1.

  If the rotation of the magnet roller 126 is continued as it is, the toner coated to a certain thickness t1 reaches the toner scraping portions 116a and 116b fixed at a position separated from the magnet roller by a distance t2, and the coated toner is removed (t1- Scrape off by the thickness of t2). Since the shapes of the coat part and the scraping part are not affected by temperature, humidity, etc., the longitudinal distribution of the scraping amount does not change between the pair of coat parts and the scraping part. Even if physical properties such as the degree of aggregation of the toner change, the drop amount distribution in the longitudinal direction is not affected. Moreover, since the scraping portion is in a non-contact state with the magnet roller, it is not subjected to stress such as being crushed at the time of scraping.

  The toner scraped off is supplied into the developing device main body 120 and used for development. In the present invention, the magnet roller 126 having substantially the same length as the developing area is provided, and the toner coat portion and the toner scraping portion provided in the toner container are arranged symmetrically with respect to the substantially central portion as a boundary.

  Accordingly, in the region b having the cross section b (FIG. 5-b), the toner falls when the magnet roller 126 is rotated in the right direction. On the other hand, in the area a having the cross-section a (FIG. 5-a), the toner having a thickness t2 coated on the magnet roller is not scraped off from the magnet roller and does not fall in the toner coat portion separated by the distance t1. Conversely, when the magnet roller 126 is rotated counterclockwise, the toner does not fall in the area b, but the toner falls in the area a. In summary, when the magnet roller 126 is rotated to the right, the toner falls and is replenished only to the region b, and when the magnet roller 126 is rotated to the left, only the region a is dropped.

  The toner residual detection sensor 124 is embedded in the wall on the front side of the developing device 120 so that the surface of the piezoelectric device is slightly recessed from the inner wall surface of the developing device 120, and the presence or absence of toner is determined by the piezoelectric device. Is.

  FIG. 4 is a longitudinal sectional view of the toner container 200. The toner stocked in the toner container 200 rotates the toner delivery screw 20l in accordance with a signal from the toner residual detection sensor 124 in the developing device 120, and sends a certain amount of toner to the opening 127 of the developing device 120.

  In the present embodiment, positively charged toner having an average particle diameter of 8 μm is used, the developing sleeve 121 is made of stainless steel, and the developing sleeve 121 is provided with a magnet roll and developed by a magnetic blade 128 facing the developing sleeve 121. The toner coat amount on the sleeve 121 is magnetically regulated, and the developing bias has a frequency of 2400 hz, an amplitude of 1. A superimposition of an AC component of З kVpp and a development DC bias (center value -290 V) that changes the potential contrast was used.

  The photosensitive drum 110 is charged to −680 V by a charging roller 170, and normal development is performed on the latent image. The process speed is 200 mm / sec, and the developing sleeve 121 rotates with a peripheral speed difference of 150%.

  Under the given process conditions, the toner consumption is estimated by knowing the DC component of the output developing bias and the potential on the photosensitive drum 110.

  These relationships are stored in a read only memory (ROM). In this example, as shown in FIG. 2, the potential on the photosensitive drum 110 is measured by the potential measuring wire 10 divided into two in the longitudinal direction, and by referring to the data stored in the ROM, the developing device corresponding to the divided area The toner consumption amount in 120 can be known.

  In addition, a memory for accumulating and storing toner consumption distribution data obtained here is provided. After changing the original, the potential on the photosensitive drum 110 is measured with a latent image for the first copy operation.

  If there is no significant difference between the areas obtained by dividing the sum in the main scanning direction into two in the longitudinal direction, the data obtained here is discarded, but if a certain difference occurs, it is stored in the memory. This data is weighted according to how many originals have been output.

  Although not shown in this example, various other conditions may be added to the weighting. During the copying operation, the toner in the developing device 120 is consumed, and when the amount of toner in the vicinity of the toner residual detection sensor 124 falls below a predetermined amount, the toner residual detection sensor 124 emits a signal to perform the replenishment operation. In this example, when the replenishment operation is performed by a signal from the toner residual detection sensor 124, the toner replenishment operation is performed based on the accumulated toner consumption amount distribution.

  That is, in the case of the toner consumption distribution as shown in FIG. 6B, the rotation of the magnet roller is controlled at the ratio of the left rotation 1 to the right rotation 3 until the toner remaining detection sensor 124 detects the presence of toner. continue.

  In the above-described apparatus, a multi-sheet copying operation was performed when the uniform replenishment operation was performed as usual using the original of FIG. 7 and when the replenishment operation described in the present embodiment was performed. As shown in the figure, the image density on the far side R is considerably higher than that on the near side F, and the difference in toner consumption is also large.

  The toner residual detection sensor 124 is installed on the front side in the longitudinal direction. At the end of 100 sheets, there is a sufficient amount of toner on the front side and the replenishment operation does not start, but the amount of toner near the developing sleeve 121 on the back side is considerably small. When the copying operation was continued, the replenishment operation started at the time of 180 sheets. However, when uniform replenishment as shown in FIG. 6A was performed, white spots occurred at the back side at the time of 200 sheets.

  If toner is uniformly present in the developing device 120, even if a solid black image is continuously copied, the amount of toner exceeding the toner consumption is set to be replenished almost uniformly to each part. Although this does not happen, the amount of toner in the developing device 120 is considerably biased at the start of replenishment, and this problem may occur in uniform toner replenishment. However, when this embodiment is used, the apparatus shown in FIG. 2 that averages the potential of the latent image formed on the photosensitive drum l10 by image exposure of the original shown in FIG. The average potential at each position on the near side was detected as -650V and -300V, respectively.

  Since this document provides data with a constant potential in the main scanning direction, it is determined that toner consumption is biased by integrating the data. If an appropriate image density as shown in FIG. 8 is dispersed, it is determined that there is no unknown distribution in consumption by integrating the image density. When the document of FIG. 7 was output continuously, the replenishment operation started with about 180 sheets as in the above example.

  Since it is determined that the toner consumption amount is biased, the replenishment operation in FIG. 6B is started, and more toner is replenished to the back side where the toner consumption amount is large. Since the toner is replenished to the near side little by little, when the toner is replenished in the vicinity of the residual toner detection sensor 124 and the replenishment operation is stopped, the toner distribution in the developing device 120 is substantially uniform and white spots occur. A good image could be output.

  In this embodiment, for detecting the longitudinal distribution of the toner consumption, the potential on the photosensitive member is measured and the toner consumption is estimated by the distribution of the charge amount. Is obtained. For example, using the fact that the laser irradiation time of a laser scanning device for forming an electrostatic latent image on a photoreceptor is proportional to the toner consumption, the longitudinal distribution of the toner consumption is obtained by obtaining the longitudinal distribution of the laser irradiation time. Recognize. The laser irradiation time from the laser scanner 250 is measured by the image processing controller 251 and accumulated in a memory to predict the toner consumption. Also, as shown in FIG. 11, by providing the toner residual detection sensors 124 and 129 on the walls at both ends in the longitudinal direction of the developing container, it is possible to determine the toner consumption distribution with or without actual toner.

  FIG. 9 is a block diagram for explaining the operation of the toner supply device of the present invention.

1 is a cross-sectional view showing an outline of an electrophotographic image forming apparatus employing the present invention. The above is a perspective view of the drum potential measuring device of the modeling device. FIG. 3 is a top view of the toner supply device of the present invention. FIG. 3 is a cross-sectional view of a toner container that supplies toner to the toner supply device of the present invention. FIG. 3 is a cross-sectional view of the toner supply device of the present invention. FIG. 7 is an explanatory diagram of toner supply amount distribution. It is Example 1 of a formed image. It is Example 2 of a formed image. FIG. 6 is a block diagram for explaining the operation of the toner supply device of the present invention. FIG. 4 is a partially enlarged view illustrating a toner coat portion and a scraping portion of the toner supply device. FIG. 7 is a diagram illustrating a state of toner in a developing device when there is a bias in toner consumption in the longitudinal direction.

Explanation of symbols

110 photoconductor
116a, b Toner scraper
117a, b Toner coat
118 Magnetic roller drive means
119 Toner supply means
120 Developer
121 Developer
124 Toner level sensor
126 Magnet roller
200 Toner container

Claims (6)

A toner replenishing means for replenishing magnetic toner to a developing device having a developing member;
A toner container for containing toner;
A magnet roller provided in the toner container and supported in a rotatable manner having substantially the same length as the developing member of the developing device;
Driving means for rotating the magnet roller;
A regulating member that coats the magnetic roller with a certain thickness of magnetic toner;
It has a scraping member that scrapes off a certain amount of the coated toner layer, and the positional relationship between the regulating member and the scraping member spreads in the vertical direction through the axis of the magnet roller in the cross-sectional shape at the center in the longitudinal direction of the magnet roller. Mirror image of the plane,
An image forming apparatus, wherein a rotation direction of a magnet roller can be selectively selected.   It has a means for estimating the toner consumption distribution of the developing member from one end to the center in the longitudinal direction of the developing member and from the center to the other end, and selectively rotates the magnet roller according to the estimated consumption. The image forming apparatus according to claim 1, wherein:   3. The image forming apparatus according to claim 2, wherein the toner consumption amount distribution estimating unit includes a potential measuring unit divided in the longitudinal direction.   The image forming apparatus according to claim 2, wherein the toner consumption amount distribution estimating unit measures a longitudinal direction writing distribution of the latent image writing unit.   The image forming apparatus according to claim 1, wherein a toner scraping unit is not in contact with the magnet roller.   3. The image forming apparatus according to claim 2, wherein the toner consumption distribution estimating means is a sensor for detecting presence / absence of toner provided on the front side and the back side in the longitudinal direction of the developing device.

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