JP2009058552A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of efficiently discharging deteriorated toner from a developing device to an electrostatic latent image carrier while suppressing lowering of image productivity. <P>SOLUTION: The image forming apparatus P obtains degree of degradation of toner in the developing device 4 when forming an electrostatic latent image for forcibly consuming toner on an electrostatic latent image carrier 1 in a toner forcible consumption mode, and selects the electrostatic latent image for forcibly consuming toner in accordance with the obtained degree of degradation of the toner out of a plurality of predetermined electrostatic latent images for forcibly consuming toner (solid pattern, dot pattern, line pattern and combination of solid pattern and dot pattern or the like) to discharge the deteriorated toner in accordance with the degree of degradation of the toner from both viewpoints of suppression of the lowering of the image productivity and efficient discharge of the deteriorated toner, and then forms the electrostatic latent image for forcibly consuming toner of the selected pattern. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multi-function machine combining two or more of these.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine combining two or more of these, the surface of the electrostatic latent image carrier is charged by a charging device, and image exposure is performed on the charging area from the exposure device. In general, an electrostatic latent image is formed, and the electrostatic latent image is developed with a developing device to form a toner image, and the toner image can be transferred to a transfer medium.

  Here, the “transfer object” is generally a recording medium such as a recording sheet in a monochrome image forming apparatus, and the toner image on the electrostatic latent image carrier is primary as in a color image forming apparatus. When an intermediate transfer member to be transferred is employed, it can be said that both the intermediate transfer member and the recording medium on which the toner image is secondarily transferred from the intermediate transfer member are transferred members.

  A developing device in such an image forming apparatus generally includes a developer carrying member that carries the developer and conveys the electrostatic latent image on the electrostatic latent image carrying member to a developing area for developing. And a developer regulating member for regulating the thickness of the developer on the developer carrying member while being conveyed to the developing region.

  In such a developing device, the toner that has not been consumed for development among the toner supplied to the developing region returns to the developing device, shows movement according to the structure of the developing device, and is conveyed toward the developing region again. However, the toner that returns to the developing device without being consumed in the developing area is repeatedly subjected to stress, and the external additive such as a fluidizing agent (such as silica) added to the toner is peeled off from the toner. Or become embedded in the toner, resulting in a deteriorated toner with low developability, that is, a deteriorated toner such as a toner charged in the opposite polarity to the normal charge or a weakly charged toner with a normal charge but a low charge amount. .

  In particular, if many images with low coverage, in other words, images with a low printing rate (images with a low ratio of the toner-attached area in the image-formable area) are continuously formed, toner consumption is required for the number of images formed. Since the amount is small, the same toner in the developing device is repeatedly stressed as the developing device is driven, so that toner deterioration becomes remarkable. As the toner in the developing device deteriorates, the quality of the toner image formed thereafter deteriorates.

Therefore, for example, in Japanese Patent Application Laid-Open No. 2001-75438, the average developer consumption amount of printed sheets is obtained from the consumption amount of developer and the number of printed sheets, and when this value is a predetermined value or less, the developer carrier (developing sleeve) ) Is forcibly consumed on the photoreceptor.
Japanese Patent Application Laid-Open No. 2000-206770 also describes forced toner consumption, and DC bias is applied to the developer carrying member (developing roller) during image formation, but DC bias is applied to the developer carrying member during forced toner consumption. The document describes that an AC bias including a component is applied and toner is forcibly consumed in a line pattern or a staggered pattern.

JP 2001-75438 A JP 2000-206770 A

  However, when forcibly consuming toner for discharging deteriorated toner in this way, if solid development is performed on the electrostatic latent image carrier, the time required for forced consumption of a predetermined amount of toner can be shortened. Although it is possible to suppress a decrease in image productivity (for example, the number of images formed per unit time), the amount of deteriorated toner that is reversely charged or only weakly charged even at regular charge is the amount of forced toner consumption. It is relatively small, and the deteriorated toner discharge efficiency is poor.

  Therefore, paying attention to the fact that the deteriorated toner tends to adhere more to the vicinity of the edge portion of the electrostatic latent image for forced toner consumption for attaching the toner, the latent image for the solid image is the electrostatic latent image for forced toner consumption. Other latent images, such as electrostatic latent images for halftone images, electrostatic latent images for line images, and the like, which form a latent image that contains more of the area near the edge portion where the deteriorated toner tends to adhere than the solid latent image. Thus, it is conceivable to forcibly consume the toner.

  However, in this case, the time required to forcibly consume a predetermined amount of toner is longer than that in the case of forming a solid latent image or a solid image, and the image productivity is lowered accordingly.

Therefore, the present invention
An electrostatic latent image bearing member, a charging device for charging the surface of the electrostatic latent image bearing member, and an image exposure is performed on a charging area of the surface of the electrostatic latent image bearing member charged by the charging device to form an electrostatic latent image. An exposure device and a developing device that develops the electrostatic latent image to form a toner image, the toner image can be transferred to a transfer target, the developing device includes at least one, and at least one developing device For non-image formation, a forced toner consumption mode for discharging the deteriorated toner in the developing device to an electrostatic latent image carrier corresponding to the developing device can be set. In this mode, the electrostatic latent image carrying An electrostatic latent image for forced toner consumption is formed on the latent electrostatic image bearing member on an exposure device corresponding to the body, and the electrostatic latent image for forced toner consumption is developed by the developing device to perform forced toner consumption. An image forming device that uses forced toner consumption Compared to the case where the forced toner consumption is always performed only by forming a solid image on the electrostatic latent image carrier, the deteriorated toner can be efficiently discharged onto the electrostatic latent image carrier. Compared with the case where forced toner consumption is always performed only by forming an image such as a halftone image other than a solid image on an electrostatic latent image carrier, an image forming apparatus capable of suppressing a decrease in image productivity is provided. The issue is to provide.

To solve the above problems, the present invention,
An electrostatic latent image bearing member, a charging device for charging the surface of the electrostatic latent image bearing member, and an image exposure is performed on a charging area of the surface of the electrostatic latent image bearing member charged by the charging device to form an electrostatic latent image. An exposure device and a developing device that develops the electrostatic latent image to form a toner image, the toner image can be transferred to a transfer target, the developing device includes at least one, and at least one developing device For non-image formation, a forced toner consumption mode for discharging the deteriorated toner in the developing device to an electrostatic latent image carrier corresponding to the developing device can be set. In this mode, the electrostatic latent image carrying An electrostatic latent image for forced toner consumption is formed on the latent electrostatic image bearing member on an exposure device corresponding to the body, and the electrostatic latent image for forced toner consumption is developed by the developing device to perform forced toner consumption. An image forming apparatus in the toner forced consumption mode; When the electrostatic latent image for forced toner consumption is formed on the electrostatic latent image carrier by the exposure device, the degree of deterioration of the toner in the developing device subject to forced toner consumption is obtained, and the reduction in image productivity and the efficiency of the deteriorated toner are determined. From the two types of electrostatic latent image patterns for forced toner consumption for discharging the deteriorated toner determined in advance according to the deterioration degree of the toner in the developing device from both viewpoints of the general release, according to the obtained toner deterioration degree An image forming apparatus is provided that selects an electrostatic latent image pattern for forced toner consumption and forms an electrostatic latent image for forced toner consumption of the selected pattern.

According to the image forming apparatus of the present invention,
In the forced toner consumption mode, when the electrostatic latent image for forced toner consumption is formed on the electrostatic latent image carrier by the exposure device, the degree of deterioration of the toner in the developing device subject to forced toner consumption is obtained.
Further, a plurality of types of electrostatic latent images for forced toner consumption for deteriorating the deteriorated toner determined in advance according to the degree of deterioration of the toner in the developing device from the viewpoints of suppressing the decrease in image productivity and efficiently discharging the deteriorated toner. From the patterns, an electrostatic latent image pattern for forced toner consumption according to the obtained degree of toner deterioration is selected, and an electrostatic latent image for forced toner consumption of the selected pattern is formed.

  Accordingly, when forced toner consumption is performed, the deteriorated toner is discharged onto the electrostatic latent image carrier more efficiently than when forced toner consumption is performed only by forming a solid image on the electrostatic latent image carrier. In addition, when the toner is forcibly consumed, the image productivity is reduced as compared with the case where the toner is forcibly consumed only by forming an image such as a halftone image other than a solid image on the electrostatic latent image carrier. Can be suppressed.

  Here, for example, as described above, the toner deterioration rate of the developing device becomes significant when the formation of an image with a low printing rate is repeated. The toner deterioration degree can be obtained by obtaining the toner deterioration degree corresponding to the obtained toner consumption rate from among the plurality of ranks of toner deterioration degree predetermined according to the toner consumption rate of the developing device.

The image forming apparatus according to the present invention may include a toner replenishing device that replenishes toner to a developing device subject to forced toner consumption.
When the toner replenishing device is provided as described above, the degree of deterioration of the toner in the developing device as a whole may change depending on the amount of toner replenished from the toner replenishing device to the developing device. is there.
More specifically, when the toner in the developing device has deteriorated at a low toner consumption rate, if new toner is replenished from the toner replenishing device into the developing device, the development is performed according to the combination of the toner consumption rate and the toner replenishment amount The charge amount of the new and old mixed toner in the apparatus as a whole may be reduced, or the charge potential width may be broadened, resulting in an increase in the degree of toner deterioration.
For example, when the toner replenishment amount is small when the toner consumption rate is low, the deterioration degree of the toner is still low as a whole of the new and old mixed toner, but when the toner replenishment amount increases while the toner consumption rate is low, the total amount of the old and new mixed toner As a result, the degree of toner deterioration may increase.

  Therefore, when a toner replenishing device is provided, the toner consumption rate of the developing device and the toner replenishing amount from the toner replenishing device to the developing device are obtained to determine the degree of toner deterioration in the developing device. Of the plurality of ranks of toner deterioration determined in advance according to the combination of the toner consumption rate of the apparatus and the toner replenishment amount to the developing device, the toner deterioration degree according to the determined combination of the toner consumption rate and the toner replenishment amount You may ask for.

  In any case, the toner consumption rate of the developing device is, for example, the ratio of the size of the region to which the developing toner is attached to the size of the entire image formable region in the predetermined number of image formations immediately before the calculation of the toner consumption rate. Alternatively, it can be obtained as a ratio of the total number of developed toner attached pixels to the total number of pixels in a predetermined number of image forming sheets immediately before the toner consumption rate calculation.

As explained above, according to the present invention,
An electrostatic latent image bearing member, a charging device for charging the surface of the electrostatic latent image bearing member, and an image exposure is performed on a charging area of the surface of the electrostatic latent image bearing member charged by the charging device to form an electrostatic latent image. An exposure device and a developing device that develops the electrostatic latent image to form a toner image, the toner image can be transferred to a transfer target, the developing device includes at least one, and at least one developing device For non-image formation, a forced toner consumption mode for discharging the deteriorated toner in the developing device to an electrostatic latent image carrier corresponding to the developing device can be set. In this mode, the electrostatic latent image carrying An electrostatic latent image for forced toner consumption is formed on the latent electrostatic image bearing member on an exposure device corresponding to the body, and the electrostatic latent image for forced toner consumption is developed by the developing device to perform forced toner consumption. An image forming device that uses forced toner consumption Compared to the case where the forced toner consumption is always performed only by forming a solid image on the electrostatic latent image carrier, the deteriorated toner can be efficiently discharged onto the electrostatic latent image carrier. Compared with the case where the forced toner consumption is always performed only by forming an image such as a halftone image other than a solid image on the electrostatic latent image carrier, it is possible to suppress a decrease in image productivity. It is possible to provide an image forming apparatus capable of suppressing degradation of image productivity and efficiently discharging deteriorated toner to an electrostatic latent image carrier.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a tandem type full color printer. The printer P has a drive roller 81 and an endless intermediate transfer belt 8 wound around a roller 82 facing the drive roller 81. The transfer belt 8 is rotated counterclockwise (arrow direction in the figure) α in the figure by a driving roller 81 driven by a belt driving unit (not shown).

  The driving roller 81 is faced with a cleaning device 83 for cleaning secondary transfer residual toner on the transfer belt 8 and the secondary transfer roller 9 is faced. The toner or the like collected by the cleaning device 83 is sent to a waste container by a conveying means (not shown).

  The surface layer portion of the secondary transfer roller 9 is formed of an elastic material, and is pressed against a portion of the intermediate transfer belt 8 supported by the driving roller 81 by a pressing unit (not shown), and a nip is formed between the secondary transfer roller 9 and the intermediate transfer belt 8. And can be rotated following the rotation of the intermediate transfer belt 8 or following the movement of the recording medium S fed into the nip as will be described later. A secondary transfer bias can be applied to the secondary transfer roller 9 from a power supply (not shown).

  A fixing device FX is disposed above the intermediate transfer belt 8 and the secondary transfer roller 9, a timing roller pair TR is disposed below, and a recording medium S such as recording paper is accommodated below the fixing device FX. The recording medium storage cassette 10 is disposed.

The fixing device FX includes a fixing heating roller incorporating a heat source such as a halogen lamp heater and a pressure roller pressed against the fixing heating roller.
The recording medium S accommodated in the recording medium accommodating cassette 10 can be pulled out one by one by the medium supply roller 101 and supplied to the timing roller pair TR.

  Between the rollers 81 and 82 around which the intermediate transfer belt 8 is wound, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the rollers 82 to 81 are moved along the transfer belt 8. Black image forming portions K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photosensitive member 1 as an image carrier, and a charger 2, an exposure device 3, a developing device 4, and a primary transfer around the photosensitive member. The roller 5, the cleaning device 6, and the static eliminator 7 are arranged in this order.

The primary transfer roller 5 faces the photoreceptor 1 with the transfer belt 8 in between, and rotates as the belt travels. A primary transfer bias for primary transfer of a toner image formed on the photoreceptor 1 to the belt 8 can be applied to the primary transfer roller 5 from a power supply (not shown).
The exposure apparatus 3 can perform image exposure by dot (point) exposure on the photosensitive member 1 by blinking of a laser beam in accordance with image information provided from a personal computer (not shown) or the like.

The photoconductor 1 in each image forming unit is a negatively chargeable photoconductor here, and can be driven to rotate clockwise in the drawing by a photoconductor drive motor (not shown).
The charger 2 in each image forming unit is not limited to this, but is a scorotron charger in this example, and a charging voltage is applied from a power supply (not shown) at a predetermined timing.

  The developing device 4 in each image forming unit is also shown in FIG. 2 and is not limited to this, but in this example, a developer (mainly a non-magnetic toner (in this example, a negatively charged non-magnetic toner)) is mainly used. A so-called one-component developer) can be used to reversely develop the electrostatic latent image formed on the photoreceptor 1 with a developing roller 41 to which a developing bias is applied from a power supply (not shown). The developing device 4 will be further described later.

  FIG. 5 is a block diagram showing an outline of the control circuit of the printer of FIG. Each unit in the printer operates at a predetermined timing under the instruction of the control unit Cont that controls the operation of the entire printer.

According to this printer, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 8 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotated in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the yellow region for the yellow image is transferred from the exposure device 3 to the charged area. Image exposure is performed, and a yellow electrostatic latent image is formed on the photoreceptor 1. This electrostatic latent image is developed by a developing roller 41 to which a developing bias of a developing device 4 having yellow toner is applied to become a visible yellow toner image, and the toner image is transferred onto a transfer belt 8 by a primary transfer roller 5. Primary transfer is performed. At this time, a primary transfer bias is applied to the primary transfer roller 5 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 8. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 8. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 8.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 8 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 8 moves toward the secondary transfer roller 9 by the rotation of the transfer belt 8.

  On the other hand, the recording medium S is pulled out from the recording medium accommodating cassette 10 by the medium supply roller 101, supplied to the timing roller pair TR, and is on standby.

  Thus, the recording medium S waiting at the timing roller pair TR is supplied to the nip portion between the transfer belt 8 and the secondary transfer roller 9 in accordance with the multiple toner image sent by the intermediate transfer belt 8. The multiple toner image is secondarily transferred onto the recording medium S by a secondary transfer roller 9 to which a secondary transfer bias is applied from a power supply (not shown). Thereafter, the recording medium S is passed through the fixing device FX, where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray DT by the discharge roller pair DR.

  In the primary transfer of the toner image to the belt 8, transfer residual toner or the like remaining on the photoreceptor 1 is cleaned by the cleaning device 6, and secondary transfer residual toner or the like remaining on the belt 8 by the secondary transfer is cleaned by the cleaning device 83. It is cleaned with. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  As described above, an image is formed, but the developing device 4 in each of the image forming units Y, M, C, and K is configured as shown in FIGS. 2 and 3, and an instruction from the control unit Cont. The toner supply from the toner supply device 40 can be received.

  FIG. 2 shows an outline of a cross-sectional structure of the developing device 4, and FIG. 3 shows an outline of an internal structure when the developing device 4 is viewed from behind (when viewed from the side opposite to the photoreceptor 1). However, the positions of the developing roller 41 and the supply roller 42 are indicated by chain lines).

Each developing device 4 includes an upper chamber 4U and a lower chamber 4L, and a partition 4W is formed between the upper and lower chambers.
The lower chamber 4L is provided with a developing roller 41 facing the photoreceptor 1 and a toner supply roller 42 for supplying toner to the developing roller 41. The photoreceptor 1 and the developing roller 41 face each other with a slight developing gap. The toner supply roller 42 is a roller having at least a surface layer portion made of a foamed elastic material, and is in contact with the developing roller 41. Both the developing roller 41 and the toner supply roller 42 are rotated counterclockwise in FIG. 2 by a developing roller drive motor (not shown). The developing roller 41 is used for developing the latent image on the photosensitive member in a state in which a developing bias (a bias in which an AC voltage is superimposed on a DC voltage) is applied from a power supply (not shown).

  In addition to the supply roller 42, the first and second toner regulating blades 43 and 44 and the charge removal member 45 are in contact with the developing roller 41. The toner regulating blades 43 and 44 are supplied onto the developing roller 41 by the supply roller 42, regulate the layer thickness of the toner conveyed toward the developing region to a predetermined level, and frictionally charge the toner. The neutralization member 45 neutralizes the toner that returns to the developing device without being consumed in the development area. The supply roller 42 also peels off the toner returning into the developing device from the developing roller 41.

  An upper toner conveying screw 46 is provided in the upper chamber 4U of the developing device, and a lower toner conveying screw 47 is provided above the lower chamber 4L. As shown in FIG. 3, in the partition wall 4W between the upper and lower chambers, a toner circulation opening P1 is formed in the vicinity of one end portion, and a toner circulation opening P2 is formed in the other end portion.

  The screws 46 and 47 are rotationally driven by a driving motor (not shown) (which may be the developing roller driving motor), so that the toner circulates in the developing device 4. More specifically, some toner in the lower chamber 4L is used for development, while the lower toner conveying screw 47 conveys the toner from the lower region of the one partition opening P1 toward the partition opening P2, and the upper chamber passes through the opening. 4U is supplied to the upper toner conveying screw 46 from the opening P2 toward the opening P1, and circulates so as to move from the opening P1 to the lower chamber 4L.

  The upper toner conveying screw 46 extends further outward (to the left in the drawing) from the partition opening P1, and the portion includes screw blades that convey toner from the side opposite to the opening P2 to the opening P1. . The toner can be supplied to this portion from a toner supply device 40 (not shown in FIG. 1).

  The toner replenishing device 40 replenishes toner under the instruction of the control unit Cont. The controller Cont causes the replenishing device 40 to replenish the insufficient toner amount derived from the toner amount detected by the developing device toner amount detecting device 48.

  In this example, the toner amount detection device 48 includes a light emitting element and a light receiving element. The light emitting element is turned on according to an instruction from the control unit Cont, and the light receiving element passes through a light guide member (not shown) from the light emitting element. Outputs a voltage according to the amount of light coming in. That is, the output voltage of the light receiving element is the detection output of the toner amount detection device 48, and this is input to the controller Cont as toner amount information in the developing device.

  The toner replenished from the toner replenishing device 40 is sent to the partition opening P1 in the upper chamber 4U, and is mixed with the toner circulated and transported in the upper chamber 4U from the partition opening P2 to the partition opening P1. However, it is dropped from the opening P1 to the lower chamber 4L, and is used for development while being circulated and agitated with the existing toner in the developing device.

  In the printer P, a toner forced consumption mode for discharging the deteriorated toner in the developing device 4 to the photosensitive member 1 corresponding to the developing device at a predetermined timing during non-image formation is set by the control unit Cont.

  Here, “at the time of non-image formation” is a time other than “at the time of image formation” in which an image to be transferred and output to the recording medium S is formed using at least one of the image forming portions Y to K. Examples of the timing for setting the forced toner consumption mode include the end of a print (image formation) job.

In the printer P, the forced toner consumption mode is performed for the developing device 4 in each of the image forming units Y, M, C, and K.
In the toner forced consumption mode, the controller Cont first obtains the degree of deterioration of the toner in the developing device as follows for each developing device 4.

  That is, the controller Cont obtains the toner consumption rate of the developing device 4 and the toner replenishment amount from the toner replenishing device 40 to the developing device at a predetermined toner forced consumption mode execution timing at the time of non-image formation. Then, the toner consumption rate and the toner determined from the plurality of ranks of toner deterioration determined in advance according to the combination of the toner consumption rate and the toner replenishment amount for the developing device 4 and stored in the control unit Cont. The degree of toner deterioration corresponding to the combination of replenishment amounts is obtained.

With respect to the “toner consumption rate”, the control unit Cont knows the number of all known pixels (image formation equivalent to one recording medium can be formed) immediately before the toner consumption rate is calculated. It can be obtained as a ratio [%] of the number of pixels to which the developing toner adheres to the known total number of pixels in the region × the predetermined number of image formations).
The number of pixels to which the developing toner has adhered is determined by counting the number of times the control unit Cont has exposed the photosensitive member 1 with dots (points) by the exposure device 3 based on image information from a computer or the like, using a dot counter in the control unit Cont. Be grasped.

  Regarding the “toner replenishment amount” by the toner replenishment device 40, the controller Cont commands the toner replenishment device 40 to replenish toner in the image formation of a predetermined number of image formations (for example, 100 sheets) immediately before the toner replenishment amount is obtained. Based on the toner replenishment motor drive signal at that time, it is grasped in the controller Cont.

  In addition, the control unit Cont includes a plurality of types of forced toner consumption for discharging a deteriorated toner determined in advance according to the degree of deterioration of the toner in the developing device from the viewpoint of suppressing the decrease in image productivity and efficiently discharging the deteriorated toner. An electrostatic latent image pattern is set.

  For example, as described below, solid toner image formation in which image productivity is prioritized over efficient discharge of deteriorated toner according to the combination of the toner consumption rate of the developing device 4 and the toner replenishment amount to the developing device It is set so that a solid pattern is selected, or a halftone dot pattern (or line pattern) that enables efficient discharge of deteriorated toner is selected.

Toner consumption rate Toner replenishment electrostatic latent image pattern for forced toner consumption
(1) Less than 2% Less than 1g Solid image solid pattern (See Fig. 5) (2) Less than 2% 1g or more and less than 3g Halftone dot pattern (also Linen pattern) (See Figs. 6 and 7)
(3) Less than 2% 3g or more Halftone dot pattern (also line pattern)
(4) 2% or more and less than 1 g Solid pattern (see Fig. 5)
(5) 2% or more 1g or more and less than 3g Solid pattern
(6) 2% or more 3g or more Halftone dot pattern (also line pattern) (See Fig. 6 and Fig. 7)

  Further, for example, as described below, a solid toner image in which image productivity is prioritized over efficient discharge of deteriorated toner according to the combination of the toner consumption rate of the developing device 4 and the toner replenishment amount to the developing device. A combined pattern of a solid pattern and a halftone dot pattern (or a line pattern) that allows a solid pattern for formation to be selected, or enables efficient discharge of deteriorated toner while maintaining image productivity as much as possible. Can be set to be selected.

Toner consumption rate Toner replenishment electrostatic latent image pattern for forced toner consumption
(1) Less than 2% Less than 1g Solid pattern for solid images (See Fig. 5) (2) Less than 2% 1g or more and less than 3g Solid pattern + halftone dot pattern (or line pattern) (See Figs. 8 and 9)
(3) Less than 2% 3g or more Solid pattern + halftone dot pattern (also line pattern) (See Fig. 8 and Fig. 9)
(4) 2% or more and less than 3% Less than 1g Solid pattern (see Fig. 5)
(5) 2% or more and less than 3% 1g or more and less than 3g Solid pattern + halftone dot pattern (also line pattern) (See Fig. 8 and Fig. 9)
(6) 2% or more and less than 3% 3g or more Solid pattern + halftone dot pattern (also line pattern) (See Fig. 8 and Fig. 9)
(7) 3% or more and less than 1 g Solid pattern (See Fig. 5)
(8) 3% or more 1 g or more and less than 3 g Solid pattern
(9) 3% or more 3g or more Solid pattern + halftone dot pattern (also line pattern) (See Fig. 8 and Fig. 9)

  As described above, the control unit Cont obtains the toner deterioration level based on the toner consumption rate and the toner replenishment amount, and sets the electrostatic forced image pattern for forced toner consumption corresponding to the obtained toner deterioration degree to the predetermined value. A plurality of types of electrostatic latent image patterns for forced toner consumption are selected, an electrostatic latent image for forced toner consumption of the selected pattern is formed on the photosensitive member 1 by the exposure device 3, and the electrostatic latent image is developed. The toner is developed in the device 4 and the toner in the developing device 4 is forcibly consumed, thereby releasing the deteriorated toner.

  In the printer P, the forced consumption toner image formed on the photoreceptor 1 is transferred to the intermediate transfer belt 8 and removed and cleaned from the belt 8 by the cleaning device 83. At this time, the secondary transfer roller 9 is separated from the belt 8 by driving means (not shown).

  Thus, when the forced toner consumption is always performed, the deteriorated toner can be efficiently discharged to the photosensitive member 1 as compared with the case where the forced toner consumption is performed only by forming a solid image on the photosensitive member 1. Compared with the case where the forced toner consumption is always performed only by forming an image such as a halftone dot image other than a solid image on the photosensitive member 1 when the consumption is performed, a decrease in image productivity can be suppressed.

  Next, using a tandem type full-color printer magicolor5570 manufactured by Konica Minolta Business Technologies, Inc., and for a cyan toner developing device, a blank recording paper is used as a recording medium, and the printing rate during image formation is 0% printing, that is, a blank paper. As a development, an image forming operation is performed for 5000 sheets, toner is forcibly consumed once every 100th image forming sheet, toner fogging on the 5000th recording sheet is evaluated, and image production is performed every 1000 sheets during that time. [Image / Minute] and average image productivity for all 5000 sheets were determined. The results are shown in Table 1. In Table 1, “K” represents “1000 sheets”, for example, “5K” represents “5000 sheets”. Note that toner fog on the photoreceptor 1 in white paper development is mainly caused by the degree of deterioration of the entire toner in the developing device (deterioration degree based on a combination of the toner consumption rate and the toner replenishment amount).

In Table 1, “forced consumption rate” represents how much of a print area rate is used for forced toner consumption for a white solid image. That is, the greater the percentage, the greater the forced toner consumption.
In the forced consumption pattern control field,
Control 1 is a solid pattern (FIG. 5) or a dot pattern (FIG. 6).
Control 2 is a solid pattern (FIG. 5) or a line pattern (FIG. 7).
Control 3 is a combination of a solid pattern and a halftone dot pattern (FIG. 8)
Control 4 is a combination of a solid pattern and a line pattern (FIG. 9).
Forcible consumption is performed in such a pattern, and the amount of consumption is the amount including the toner adhered to the blank paper portion in the case of a halftone dot pattern or a line pattern.

  Fogging evaluation is a transparent tape (commonly known as cellophane tape) having a pressure-sensitive adhesive layer on one side after the formation of 5000 images and forcibly stopping the printer during white solid development. And the tape was affixed to a blank recording paper, and the transmission density was measured with a transmission density meter CR-241 manufactured by Minolta Co., Ltd. and evaluated.

As an evaluation at this time, ranking is performed by c *, and the average value of the c * values of three points in the longitudinal direction of the photosensitive member (photosensitive member width direction) which is the photosensitive member rotation axis direction is ranked as follows. Was in a good state in which fog was substantially absent.
Rank 1: c * 7 or more Rank 2: c * 6 or more and less than 7 Rank 3: c * 5 or more and less than 6 Rank 4: c * 4 or more and less than 5 Rank 5: Less than c * 4

  Note that c * represents the color saturation obtained from a * and b * indicating chromaticity in the Lab display method known per se [JIS (JISZ8729)], which is a color display method. Focusing on the above, evaluation is performed by assigning a fog rank according to the value of c * using the fact that c * increases as fog toner increases.

As for image productivity, average productivity was 22.5 sheets / minute or more.
Under each condition, the amount of fog on the photoconductor and image productivity when a white solid image was formed on 5000 sheets was used as a criterion. Those that are not are marked as bad “x”.

  As can be seen from Table 1, when the forced toner consumption is performed, the deteriorated toner can be efficiently discharged to the photoreceptor 1 as compared with the case where the forced toner consumption is always performed only by forming a solid image on the photoreceptor 1. (Thus, fog can be reduced). Also, when the forced toner consumption is performed, the forced toner consumption is always compared with the case where only the formation of an image such as a halftone image other than a solid image is performed on the photoreceptor 1. It can be seen that a decrease in image productivity can be suppressed.

  The printer described above is a tandem type full-color printer, but the present invention can also be applied to a monochrome image forming apparatus, and can be applied to other types of multicolor image forming apparatuses (for example, so-called four-cycle type full-color printers). Is also applicable.

  INDUSTRIAL APPLICABILITY The present invention can be used to provide an image forming apparatus capable of efficiently discharging deteriorated toner from a developing device to an electrostatic latent image carrier while suppressing a decrease in image productivity.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an outline of a cross-sectional structure of a developing device in the image forming apparatus of FIG. 1. It is a figure which shows the outline of an internal structure when the developing device of FIG. 2 is seen from back. FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus in FIG. 1. FIG. 6 is a diagram illustrating an example (solid pattern) of a forced toner consumption pattern. FIG. 6 is a diagram illustrating another example of a forced toner consumption pattern (halftone dot pattern). FIG. 10 is a diagram illustrating still another example (line pattern) of a pattern of forced toner consumption. FIG. 10 is a diagram illustrating still another example (solid + halftone dot pattern) of a toner forced consumption pattern. FIG. 10 is a diagram illustrating still another example (solid + line pattern) of a toner forced consumption pattern.

Explanation of symbols

Y Yellow image forming portion M Magenta image forming portion C Cyan image forming portion K Black image forming portion 1 Photoconductor 2 Charging device 3 Image exposure device 4 Developing device 41 Developing roller 42 Toner supply roller 43, 44 Toner regulating blade 45 Static elimination member 4U Upper chamber 4L Lower chamber 4W Partition P1, P2 Partition opening 46 Upper toner conveying screw 47 Lower toner conveying screw 40 Toner replenishing device 48 Toner amount detecting device 5 in developing device Primary transfer roller 6 Cleaning device 8 Intermediate transfer belt 81 Drive roller 82 opposing roller 83 cleaner 9 secondary transfer roller 10 recording medium supply cassette 101 recording medium supply roller TR timing roller pair FX fixing device DR recording medium discharge roller pair DT recording medium discharge tray S recording medium Cont control unit

Claims (2)

  An electrostatic latent image bearing member, a charging device for charging the surface of the electrostatic latent image bearing member, and an image exposure is performed on a charging area of the surface of the electrostatic latent image bearing member charged by the charging device to form an electrostatic latent image. An exposure device and a developing device that develops the electrostatic latent image to form a toner image, the toner image can be transferred to a transfer target, the developing device includes at least one, and at least one developing device For non-image formation, a forced toner consumption mode for discharging the deteriorated toner in the developing device to an electrostatic latent image carrier corresponding to the developing device can be set. In this mode, the electrostatic latent image carrying An electrostatic latent image for forced toner consumption is formed on the latent electrostatic image bearing member on an exposure device corresponding to the body, and the electrostatic latent image for forced toner consumption is developed by the developing device to perform forced toner consumption. An image forming apparatus that is in the toner forced consumption mode. Then, when the electrostatic latent image for forced toner consumption is formed on the electrostatic latent image carrier by the exposure device, the deterioration degree of the toner in the developing device subject to the forced toner consumption is obtained, the reduction in image productivity is reduced, and the efficiency of the deteriorated toner From the two types of electrostatic latent image patterns for forced toner consumption for discharging the deteriorated toner determined in advance according to the deterioration degree of the toner in the developing device from both viewpoints of the general release, according to the obtained toner deterioration degree An electrostatic latent image pattern for forced toner consumption is selected, and an electrostatic latent image for forced toner consumption of the selected pattern is formed.   A toner replenishing device that replenishes toner to the developing device subject to forced toner consumption, and in determining the degree of deterioration of the toner in the developing device, the toner consumption rate of the developing device and the toner replenishing device to the developing device; The toner consumption rate and the toner replenishment amount are determined from a plurality of ranks of toner deterioration determined in advance according to the combination of the toner consumption rate of the developing device and the toner replenishment amount to the developing device. The image forming apparatus according to claim 1, wherein a toner deterioration degree corresponding to the combination of the toners is obtained.