JP7183661B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, an image forming apparatus has a developing device that develops an electrostatic latent image held on a photosensitive drum with a developer containing toner. There is also a configuration in which toner is replenished by pressing. In such an image forming apparatus, a technique disclosed in, for example, Japanese Patent Laid-Open No. 2002-300000 has already been proposed as a technique for determining that a toner replenishment abnormality has occurred.

Japanese Patent Application Laid-Open No. 2002-200000 discloses a replenishing means for replenishing toner to a developing device according to a detection result of a detecting means for detecting information on the amount of toner in the developing device, and an obtaining means for obtaining replenishment time during which the toner is replenished by the replenishing device. and a first calculating means for calculating the number of dots of an image to be formed, wherein the toner is replenished based on the number of dots of the image calculated by the first calculating means and the replenishment time acquired by the acquiring means. It is constructed such that it is determined by the determination means whether or not an abnormality has occurred.

Japanese Patent No. 5866899

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of judging the occurrence of an abnormality in toner density detection by a toner density detection means caused by a change in the fluidity of a developer in a developing means. be.

In the first aspect of the invention, developing means for developing an electrostatic latent image with a developer containing toner;
density detection means for detecting the toner density in the developing means;
replenishing means for replenishing toner to the developing means based on the image density of the electrostatic latent image and the detection result of the density detecting means;
Determining whether or not there is a detection abnormality in the density detection means based on each integrated value obtained by integrating the image density of the electrostatic latent image and the replenishment time of the replenishment means over a first period and updating each second period. and
a resolution means for executing an operation to resolve the detection abnormality of the density detection means when the determination means determines that there is a detection abnormality of the density detection means;
After the canceling means has executed the operation of canceling the detection abnormality of the density detecting means, the image density of the electrostatic latent image and the replenishing time of the replenishing means are integrated over a third period shorter than the first period. prohibiting means for prohibiting an image forming operation when the determining means determines that there is a detection abnormality in the density detecting means based on each integrated value;
and an image forming apparatus.

In the invention described in claim 2, developing means for developing an electrostatic latent image with a developer containing toner;
density detection means for detecting the toner density in the developing means;
replenishing means for replenishing toner to the developing means based on the image density of the electrostatic latent image and the detection result of the density detecting means;
Determining whether or not there is a detection abnormality in the density detection means based on each integrated value obtained by integrating the image density of the electrostatic latent image and the replenishment time of the replenishment means over a first period and updating each second period. and
a resolution means for executing an operation to resolve the detection abnormality of the density detection means when the determination means determines that there is a detection abnormality of the density detection means;
After the canceling means has executed the operation of canceling the detection abnormality of the density detecting means, the image density of the electrostatic latent image and the replenishing time of the replenishing means are integrated over a fourth period longer than the first period. and an instruction unit for instructing replacement of the developer in the developing unit when the determination unit determines that there is a detection abnormality in the density detection unit based on each integrated value.

(3) The image forming apparatus according to (1) or (2), wherein the canceling means drives the conveying means for conveying the developer in the developing means at a speed lower than a normal driving speed. It is a device.

A fourth aspect of the present invention is the image forming apparatus according to the first or second aspect , wherein the canceling means performs an operation of forcibly consuming the toner in the developing means.

In a fifth aspect of the present invention, when the determination means determines that there is a detection abnormality in the density detection means, a notification means for notifying a user of the detection abnormality in the density detection means;
selection means for allowing a user to select whether or not to execute an operation for resolving the detection abnormality of the density detection means;
5. The image forming apparatus according to claim 1, comprising:

The invention recited in claim 6 is the image forming apparatus according to any one of claims 1 to 5, wherein the second period is shorter than the first period .

According to the first aspect of the present invention, it is possible to determine whether the toner concentration detecting means has detected an abnormality in the toner concentration due to a change in the fluidity of the developer in the developing means.
According to the first aspect of the present invention, it is possible to eliminate the detection abnormality of the density detection means at an early stage compared to the case where the elimination means for executing the operation for eliminating the detection abnormality of the density detection means is not provided. .
According to the first aspect of the present invention, it is possible to prevent the image forming operation from being continued when the detection abnormality of the density detection means is not resolved.

According to the second aspect of the present invention, it is possible to determine whether the toner concentration detecting means has detected an abnormality in the toner concentration due to a change in the fluidity of the developer in the developing means.
According to the second aspect of the present invention, it is possible to eliminate the detection abnormality of the density detection means at an early stage compared to the case where the elimination means for executing the operation for eliminating the detection abnormality of the density detection means is not provided. .
According to the second aspect of the present invention, when detection abnormality of the density detection means occurs due to deterioration of the developer, the detection abnormality of the density detection means can be reliably eliminated.

According to the invention recited in claim 3, the solving means consumes less toner than when the conveying means for conveying the developer in the developing means is not driven at a speed slower than the normal driving speed. Abnormal detection of the concentration detection means can be eliminated.

According to the fourth aspect of the present invention, the canceling means reduces detection abnormality of the density detecting means due to deterioration of the developer compared to the case where the operation of forcibly consuming the toner in the developing means is not executed. can be resolved.

According to the fifth aspect of the present invention, the user can select whether or not to execute the operation to eliminate the detection abnormality of the density detection means, thereby improving the convenience.

According to the sixth aspect of the present invention , the first period is set relatively long so that detection abnormality of the concentration detection means can be accurately determined, and the second period is set relatively short. As a result, it is possible to quickly determine detection abnormality of the concentration detection means.

1 is a configuration diagram showing a color image forming apparatus as an example of an image forming apparatus according to Embodiment 1 of the present invention; FIG. 1 is a configuration diagram showing a main part of a color image forming apparatus as an example of an image forming apparatus according to Embodiment 1 of the present invention; FIG. 3 is a cross-sectional view showing a developing device; FIG. 1 is a block diagram showing a control device of a color image forming apparatus as an example of an image forming apparatus according to Embodiment 1 of the present invention; FIG. FIG. 4 is a schematic diagram showing a method of calculating an integrated value over a plurality of pages of recording paper; 4 is a flowchart showing a toner replenishment control operation; 4 is a flow chart showing the operation of the image forming apparatus according to Embodiment 1 of the present invention; 5 is a graph showing the relationship between the integrated value of toner replenishment time and the integrated value of image density. 8 is a flow chart showing the operation of the image forming apparatus according to Embodiment 2 of the present invention; 8 is a flow chart showing the operation of the image forming apparatus according to Embodiment 3 of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 shows an overall outline of a color image forming apparatus as an example of the image forming apparatus according to the first embodiment, and FIG. 2 shows a control device of the color image forming apparatus according to the first embodiment. In the drawing, arrow X indicates the width direction along the horizontal direction, Y indicates the depth direction along the horizontal direction, and Z indicates the vertical direction.

<Overall Configuration of Color Image Forming Apparatus>
The color image forming apparatus 1 is configured as, for example, a color printer. This color image forming apparatus 1, as shown in FIG. 1, includes an image forming device 20 as an example of a plurality of image forming means for forming toner images developed with toner constituting a developer. The image forming devices 20 are four image forming devices 20Y, 20M, 20C, and 20K that respectively form four-color toner images of yellow (Y), magenta (M), cyan (C), and black (K). It is configured. These four image forming devices 20 (Y, M, C, K) are arranged in a row while being inclined with respect to the horizontal direction X in the internal space of the device main body 1a. The apparatus main body 1a is formed of a support structure member, an exterior cover, and the like.

Each image forming device 20 (Y, M, C, K) includes a photosensitive drum 21 as an example of a rotating image holding means, as shown in FIG. Around the photoreceptor drum 21, a charging device 22 for charging a peripheral surface (image holding surface) of the photoreceptor drum 21 on which an image can be formed (image holding surface) to a required potential, and a The exposure device 23 as an example of an electrostatic latent image forming means that forms an electrostatic latent image (for each color) with a potential difference by irradiating light based on image information (signal) and the electrostatic latent image correspond to each other. Developing device 24 as an example of developing means for forming a toner image by developing with toner of developer of each color (Y, M, C, K), and primary transfer means for transferring each toner image to intermediate transfer device 30 A primary transfer device 25 as an example, and a drum cleaning device 26 as an example of cleaning means for removing and cleaning adherents such as toner remaining on the image holding surface of the photosensitive drum 21 after the primary transfer. are placed.

The photoreceptor drum 21 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar base material to be grounded. The photoreceptor drum 21 rotates in the direction indicated by the arrow A when a driving force is transmitted from a driving device (not shown).

The charging device 22 is composed of a contact-type charging roll arranged in contact with the photosensitive drum 21 . A charging voltage is supplied to the charging device 22 . As the charging voltage, when the developing device 24 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 24 is supplied. A cleaning roll 221 that cleans the surface of the charging device 22 is arranged in contact with the back side of the charging device 22 .

The exposure device 23 irradiates the photosensitive drum 21 with light according to image information from LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photosensitive drum 21 to form an electrostatic latent image. It consists of an LED print head or the like that forms a When a latent image is formed, image information (signals) input to the color image forming apparatus 1 by arbitrary means is sent to the exposing device 23 via an image processing device (not shown). The exposure device 23 irradiates the circumferential surface of the photosensitive drum 21 after it has been charged with a laser beam configured in accordance with image information input to the color image forming apparatus 1 to generate an electrostatic charge. A material that forms a latent image may also be used.

Each of the developing devices 24 (Y, M, C, K), as shown in FIG. 1, holds the developer inside a device housing 240 having an opening and a developer storage chamber. A developing roll 241 that conveys the developer to a developing area facing the body drum 21 , an agitating supply member 242 and agitating conveying member 243 such as a screw auger that conveys the developer while agitating the developer so that it passes through the developing roll 241 , and held by the developing roll 241 . A layer thickness regulating member 244 for regulating the amount (layer thickness) of the developer applied is arranged. A developing voltage is supplied to the developing device 24 between the developing roller 241 and the photosensitive drum 21 from a power supply device (not shown). Further, the developing roll 241, the agitating supply member 242, and the agitating/conveying member 243 are rotated in desired directions by transmission of a driving force from a driving device (not shown). Further, as the four-color developers (Y, M, C, K), a two-component developer containing non-magnetic toner and a magnetic carrier made of a magnetic material such as iron or ferrite is used. The developing device 24 will be detailed later.

Yellow (Y), magenta (M), cyan (C) and black (K) developers disposed above the intermediate transfer device 30 are supplied to the respective developing devices 24 (Y, M, C, K). The toner cartridges 245 (Y, M, C, K), which are examples of storage containers, are configured to supply toner of corresponding colors through toner supply devices 246 (Y, M, C, K). there is The toner supply devices 246 (Y, M, C, K) are individually driven by drive motors 247 (Y, M, C, K) as an example of drive means. The black (K) toner cartridge 245K is set to have a larger outer diameter (volume) than the other toner cartridges in consideration of the high frequency of use of black (K) toner.

The primary transfer device 25 is a contact type transfer device having a primary transfer roll that rotates in contact with the circumferential surface of the photosensitive drum 21 via the intermediate transfer belt 31 at the primary transfer position T1 and is supplied with a voltage for primary transfer. is. As the primary transfer voltage, a DC voltage or current having a polarity opposite to the charging polarity of the toner is supplied from a high-voltage power source (not shown).

The drum cleaning device 26 includes a cleaning blade 261 disposed inside a container-shaped main body 260 for cleaning by removing deposits such as residual toner, and a cleaning blade 261 for collecting deposits such as toner removed by the cleaning blade 261 (not shown). It consists of a delivery member 262, such as a screw auger, which is conveyed for delivery to the collection system.

The intermediate transfer device 30 is arranged to exist above each image forming device 20 (Y, M, C, K). The intermediate transfer device 30 includes an intermediate transfer belt 31 that circulates in the direction indicated by an arrow B while passing a primary transfer position T1 between the photosensitive drum 21 and the primary transfer device 25 (primary transfer roll); A plurality of belt support rolls 32 to 35 that hold the belt 31 in a desired state from its inner circumference and support it so as to be circulating, and an outer peripheral surface (image holding surface) of the intermediate transfer belt 31 supported by the belt support roll 35. ) side of the intermediate transfer belt 31 for secondary transfer of the toner image on the intermediate transfer belt 31 onto the recording paper 6, and It is mainly composed of a belt cleaning device 36 for cleaning by removing adhering matter such as toner and paper dust.

The belt support roll 32 is configured as a drive roll, the belt support roll 33 is configured as a leveling roll that holds the running position of the intermediate transfer belt 31, the belt support roll 34 is configured as a tensioning roll, and the belt support roll 35 is configured as a roll. It is configured as a backup roll for secondary transfer.

As shown in FIG. 1, the secondary transfer device 40 rotates at a secondary transfer position T2, which is the outer peripheral surface portion of the intermediate transfer belt 31 supported by the belt support roll 35 in the intermediate transfer device 30. A roll 41 is provided. The secondary transfer roll 41 or the belt support roll 35 of the intermediate transfer device 30 is supplied with a DC voltage having the same or opposite polarity as the charging polarity of the toner as a secondary transfer voltage.

The fixing device 50 includes a belt-shaped or roll-shaped heating rotator 51 that is heated by a heating means such as electromagnetic induction heating or a heat source so that the surface temperature is maintained at a predetermined temperature, and the heating rotator 51 . It is constructed by arranging a roll-type or belt-type pressurizing rotating body 52 or the like that contacts and rotates with a required pressure. In this fixing device 50, the contact portion where the heating rotator 51 and the pressurizing rotator 52 are in contact serves as a fixing processing portion for performing required fixing processing (heating and pressing).

The sheet feeding device 60 is arranged to exist below the image forming devices 20 (Y, M, C, K). The paper feeding device 60 includes a single (or a plurality of) paper containers 62 that contain recording paper 6 of a desired size and type while being stacked on a stacking plate 61 , and the recording paper 6 from the paper container 62 . It is mainly composed of a feeding device 63 that feeds out one sheet at a time.

As the recording paper 6, for example, thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or an OHP sheet made of a transparent film-like medium made of synthetic resin (such as PET). etc. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 6 is as smooth as possible. A so-called thick paper having a relatively large basis weight can also be suitably used.

Between the paper feeding device 60 and the secondary transfer device 40, there are a pair of (or a plurality of) paper transport rolls 64 for transporting the recording paper 6 fed from the paper feeding device 60 to the secondary transfer position T2, and a transport guide material. A paper feed transport path 67 composed of 65 and 66 is provided. A pair of paper transport rolls 64 arranged at a position immediately before the secondary transfer position T2 in the paper feed transport path 67 is configured, for example, as rolls (registration rolls) for adjusting the transport timing of the recording paper 6 .

Between the secondary transfer device 40 and the fixing device 50, there is provided a paper transport path 69 including a transport guide member 68 for transporting the recording paper 6 fed from the secondary transfer device 40 to the fixing device 50. It is

On the downstream side of the fixing device 50, there is a pair of paper transport rolls 71 and a paper ejection unit for ejecting the recording paper 6 on which the toner image has been fixed by the fixing device 50 to a paper ejection unit 70 arranged in the upper portion of the apparatus main body 1a. A discharge transport path 75 having a roll pair 72, transport guide members 73 and 74, and the like is provided.

In FIG. 1, reference numeral 100 designates a control device as an example of control means for overall control of the operation of the color image forming apparatus 1. As shown in FIG. The control device 100 will be detailed later.

<Basic Operation of Color Image Forming Apparatus>
A basic image forming operation of the color image forming apparatus 1 will be described below.

Here, when the four image forming devices 20 (Y, M, C, K) are used to form a full-color image formed by combining toner images of four colors (Y, M, C, K), image forming operation will be described. It should be noted that when forming an image combining single-color or multi-color toner images using one or more of the four image forming devices 20 (Y, M, C, BK), The image forming operation is basically the same.

When the color image forming apparatus 1 receives command information requesting an image forming operation (printing), the controller 100 controls four image forming devices 20 (Y, M, C, K), an intermediate transfer device 30, The secondary transfer device 40, fixing device 50, etc. are started.

In each imaging device 20 (Y, M, C, K), as shown in FIG. 1, each photosensitive drum 21 first rotates in the direction indicated by arrow A, and each charging device 22 rotates each photosensitive drum. The surface of the body drum 21 is charged to a desired polarity (negative polarity in the first embodiment) and potential. Subsequently, the exposure device 23 converts information of an image input to the color image forming apparatus 1 into each color component (Y, M, C, K) for the surface of the photosensitive drum 21 after charging. Light emitted based on image signals is applied to form an electrostatic latent image of each color component, which is composed of a required potential difference, on its surface.

Subsequently, each developing device 24 (Y, M, C, K) charges the electrostatic latent image of each color component formed on the photosensitive drum 21 with a corresponding color charged to a required polarity (negative polarity). (Y, M, C, BK) toners are supplied and electrostatically adhered to each other for development. By this development, the electrostatic latent image of each color component formed on each photosensitive drum 21 is visualized as a four-color (Y, M, C, K) toner image developed with the corresponding color toner. become.

Subsequently, when the toner images of the respective colors formed on the photosensitive drums 21 of the image forming devices 20 (Y, M, C, K) are conveyed to the primary transfer position T1, the primary transfer device 25 transfers the toner images of the respective colors. are primarily transferred onto the intermediate transfer belt 31 rotating in the direction indicated by the arrow B of the intermediate transfer device 30 so as to be superimposed in order.

In each image forming device 20 (Y, M, C, K) after primary transfer, the drum cleaning device 26 cleans the surface of the photoreceptor drum 21 by scraping off the adhering matter. As a result, each image forming device 20 (Y, M, C, K) is ready for the next image forming operation.

Subsequently, in the intermediate transfer device 30, the toner image primarily transferred by the rotation of the intermediate transfer belt 31 is held and conveyed to the secondary transfer position T2. On the other hand, the paper feeding device 60 feeds out the required recording paper 6 to the paper feeding path 67 in accordance with the image forming operation. In the paper feed path 67, a paper feed roll pair 64 serving as a registration roll feeds and supplies the recording paper 6 to the secondary transfer position T2 in accordance with the transfer timing.

At the secondary transfer position T2, the secondary transfer roll 41 collectively secondary-transfers the toner images on the intermediate transfer belt 31 onto the recording paper 6 . In the intermediate transfer device 30 after the secondary transfer is finished, the belt cleaning device 36 removes and cleans the surface of the intermediate transfer belt 31 after the secondary transfer by removing adherents such as toner remaining on the surface.

Subsequently, the recording paper 6 on which the toner image has been secondarily transferred is separated from the intermediate transfer belt 31 and the secondary transfer roll 40 and then transported along the paper transport path 69 to the fixing device 50 . In the fixing device 50, the necessary fixing processing (heating and pressurization) to fix the unfixed toner image on the recording paper 6 . After fixing, the recording paper 6 is discharged by the paper discharge roll pair 72 via the discharge transport path 75 to the discharge accommodating section 70 provided in the upper part of the apparatus main body 1a.

Through the above operation, a full-color image formed by combining toner images made up of four color toners T (Y, M, C, K) is output.

<Structure of Developing Device>
The developing device 24 used in the color image forming apparatus 1 according to the first embodiment employs a so-called two-component developing method. The yellow (Y), magenta (M), cyan (C) and black (K) developing devices 24 (Y, M, C, K) are similarly constructed. Here, the configuration of the developing device 24 will be described using the yellow (Y) developing device 24Y as an example.

As shown in FIG. 2, the developing device 24Y includes a device housing 240 as an example of a developing device main body having an opening 240a in a developing area facing the photosensitive drum 21. As shown in FIG. A developing roller 241 as an example of a developer holding unit is arranged in an opening 240 a of the device housing 240 . The developing roll 241 is arranged in a fixed state inside, and is a magnet roll 241a as an example of a columnar or cylindrical magnetic member magnetized with a magnetic pole of a required polarity at a required position along the circumferential direction; A cylindrical developer that is rotatably arranged on the outer periphery of the magnet roll 241a and conveys the developer 4 attracted by the magnetic force of the magnet roll 241a along the circumferential direction so as to pass through the development area facing the photosensitive drum 21. and a developing sleeve 241b as an example of a conveying member.

The apparatus housing 240 includes a first developer accommodating portion 248 arranged at a position adjacent to and obliquely below the developing roll 241 to accommodate the developer 4 , and a partition wall 249 on the rear side of the first developer accommodating portion 248 . and a second developer accommodating portion 250 arranged adjacent to each other. The first and second developer accommodating portions 248 and 250 are formed such that the lower half portions of their cross-sectional shapes are cylindrical. The second developer containing portion 250 communicates with the first developer containing portion 248 through communication ports 251 and 252 at both ends along the axial direction.

The two-component developer 4 is accommodated in the first and second developer accommodating portions 248 and 250, respectively. As shown in FIG. 3, the first developer container 248 has a spiral first developer agitating device that conveys the developer 4 in a predetermined axial direction (for example, from left to right in FIG. 3). A stirring supply member 242 is arranged as an example of a conveying means. The agitation supply member 242 has a rotating shaft 242a formed in a columnar or cylindrical shape by injection molding using a synthetic resin, and a helical conveying blade 242b integrally formed on the outer circumference of the rotating shaft 242a. It is a so-called screw auger that is formed to be rotatable with the auger. In order to improve the agitating and conveying property of the developer 4, the conveying blades 242b are provided on the outer periphery of the rotary shaft 242a over two lines with phases different by 180 degrees. The agitation supply member 242 is a supply auger having a supply function of supplying the developer 4 to the developing roller 241 in addition to a toner agitation and mixing function. The developer 4 conveyed by the agitation supply member 242 is conveyed in the opposite direction (from the right side to the left side in the drawing) to the agitation conveyance member 243 at the downstream end portion along the conveying direction of the agitation supply member 242 . A reverse transfer blade 242c is provided short along the axial direction.

Further, in the second developer container 250, a second developer agitating and conveying means as an example of a spiral second developer agitating and conveying means for conveying the developer 4 in a predetermined axial direction (for example, from right to left in FIG. 3) is provided. A stirring and conveying member 243 is arranged. The agitating and conveying member 243 has a rotating shaft 243a formed in a columnar or cylindrical shape by injection molding or the like using synthetic resin, and a helical conveying blade 243b integrally formed on the outer circumference of the rotating shaft 243a. It is a so-called screw auger that is formed to be rotatable with the auger. The conveying blades 243b are provided on the outer periphery of the rotating shaft 243a in two lines with phases different by 180 degrees in order to improve the conveyability of the developer 4 as well. The agitating/conveying member 243 is an admix auger mainly intended to agitate and mix the developer 4 accommodated in the second developer accommodating portion 250 and the replenished toner.

The developer 4 transported by the agitating/conveying member 243 is conveyed in the opposite direction (from left to right in the drawing) to the agitating/supplying member 242 at the downstream end along the conveying direction of the agitating/conveying member 243 . A reverse conveying blade 243c is provided to deliver the sheet. In addition, the upstream end of the agitating/conveying member 243 along the conveying direction extends longer than the agitating/supplying member 242 . The extended end of the agitating/conveying member 243 constitutes a conveying portion 243 d that conveys toner supplied from the toner cartridge 245 via the toner supply device 246 into the device housing 240 .

The first and second developer containing portions 248 and 250 form a developer transport path through which the developer 4 circulates through communication ports 251 and 252 opened in the partition wall 249 . The developer 4 contained in the first and second developer containing portions 248 and 250 is circulated and transported in the developer transport path while being agitated and mixed by a pair of spiral agitation supply member 242 and agitation transport member 243. .

Further, a toner concentration sensor 254 as an example of a toner concentration detecting means for detecting the toner concentration in the developer 4 is arranged downstream from the center of the second developer container 150 along the direction of conveyance of the developer 4 . It is The agitating/conveying member 243 is provided with a retention member (not shown) such as a paddle formed in a flat plate shape along the axial direction for retaining the developer 4 at a position facing the toner density sensor 254 as required. The toner concentration sensor 254 is arranged to contact the outer wall of the device housing 240 forming the second developer containing portion 250, as shown in FIG. As the toner density sensor 254, for example, one that detects the toner density in the developer 4 by utilizing the change in the magnetic permeability of the developer 4 accompanying the change in the toner density in the developer 4 is used. The toner density sensor 254 changes the frequency and voltage of the output signal according to the toner density in the developer 4 . As the toner concentration sensor 254, any type of sensor can be adopted as long as it can detect the toner concentration in the developer 4. FIG.

The toner supplied from the toner cartridge 245 to the device housing 240 of the developing device 24 through the toner supply device 246 is transported into the device housing 240 by the transport portion 243d of the stirring transport member 243, as shown in FIG. be done. The toner conveyed inside the developing device 24 is agitated and mixed with the developer 4 accommodated inside the device housing 240 while being conveyed along the axial direction by the agitating and conveying member 243 and the agitating and supplying member 242 . At the same time, the toner is triboelectrically charged to a required polarity (negative polarity). The developer 4 transported to the agitation supply member 242 is transferred from the agitation supply member 242 to the developing roller 241 as shown in FIG. The amount (layer thickness) of the developer 4 held on the surface of the developing roller 241 is regulated by the layer thickness regulating member 244 as the developing sleeve 241b rotates, and the developer 4 faces the surface of the photosensitive drum 21 for development. transported to the area. On the surface of the photosensitive drum 21, toner is attached to the electrostatic latent image formed according to the image information from the developer 4 held on the surface of the developing roll 241, and the electrostatic latent image is developed on the photosensitive drum 21. be.

<Configuration of Characteristic Portion of Color Image Forming Apparatus>
By the way, in the color image forming apparatus 1 configured as described above, as shown in FIGS. It is configured to detect by H.254. In the developing device 24 , the developer 4 staying near the toner density sensor 254 may increase due to changes in the fluidity of the developer 4 or the like.

For example, in a high-humidity environment, the chargeability of the toner that is agitated and conveyed by the agitating and conveying member 242 and the agitating and conveying member 243 in the developing device 24 and is triboelectrically charged deteriorates. When the chargeability of the toner is lowered, the electrostatic repulsive force acting between toner particles is reduced, and the amount of toner electrostatically adhering to the outer periphery of the carrier is increased. As a result, the fluidity of the developer 4 may decrease and the amount of the developer 4 remaining near the toner concentration sensor 254 may increase.

On the other hand, in a low-humidity environment, the chargeability of the toner that is agitated and conveyed by the agitating and conveying member 242 and the agitating and conveying member 243 in the developing device 24 and is triboelectrically charged is improved. When the chargeability of the toner is improved, the electrostatic repulsive force acting between toner particles increases, and the amount of toner electrostatically adhering to the outer periphery of the carrier decreases. As a result, the fluidity of the developer 4 is improved, and the amount of the developer 4 remaining near the toner concentration sensor 254 is reduced.

Further, in the developing device 24, if the developer 4 is continuously agitated and conveyed in a state where the toner consumption amount per unit time is small, as in the case where low-density images are continuously developed over a plurality of sheets of recording paper 6, In addition, the external additive added to the surface of the toner to adjust the chargeability and fluidity is peeled off or buried in the toner, and the external additive does not exhibit its original function, and the developer 4 deteriorates and fluidity is reduced. may decrease.

As a result, in the developing device 24 , when the fluidity of the developer 4 decreases and the developer 4 stays near the toner density sensor 254 , the toner density near the toner density sensor 254 is not the average toner density in the developing device 24 . In other words, the local toner concentration of the developer 4 stagnating in the area is detected. Therefore, if the toner density sensor 254 detects the local toner density of the developer 4 and a detection abnormality occurs, there is a problem in the toner replenishment control for replenishing toner to the inside of the developing device 24 based on the detection result of the toner density sensor 254. occurs.

For example, if the developer 4 with a toner concentration lower than the average toner concentration in the developing device 24 stays near the toner concentration sensor 254 , the toner concentration sensor 254 detects that the toner concentration is lower than the average toner concentration in the developing device 24 . Detect concentration. Therefore, if the toner replenishment time is calculated based on the detection result of the toner concentration sensor 254 in the toner replenishment control, the toner replenishment time is calculated to be excessively longer than the actual one.

Conversely, if the developer 4 having a toner concentration higher than the average toner concentration in the developing device 24 stays near the toner concentration sensor 254, the toner concentration sensor 254 detects that the toner concentration is higher than the average toner concentration in the developing device 24. Detect toner density. Therefore, if the toner replenishment time is calculated based on the detection result of the toner concentration sensor 254 in the toner replenishment control, the toner replenishment time is calculated to be shorter than the actual one.

As a result, in the developing device 24, the toner may be supplied excessively or insufficiently, and the density of the toner image may not match the target density, resulting in image defects.

Therefore, in the first embodiment, the image density of the electrostatic latent image and the replenishing time of the toner replenishing device are integrated over the first period, and based on each integrated value updated every second period, the toner density is calculated. It is configured to have a judgment means for judging the presence or absence of detection abnormality of the sensor 254 .

Here, the detection abnormality of the toner concentration sensor 254 means that the toner concentration sensor 254 does not detect the average toner concentration in the developing device 24 due to the deterioration of developer fluidity, etc., as described above. , means to detect the local toner density of the developer 4 staying in the vicinity of the toner density sensor 254 .

FIG. 4 is a block diagram showing the control device of the color image forming apparatus according to the first embodiment.

As shown in FIG. 4 , the control device 100 includes a control section 101 as an example of determination means, a storage section 102 , an operation section 103 and a communication section 104 .

The control unit 101 has a CPU (Central Processing Unit) 101a and a RAM (Random Access Memory) 101b. The control unit 101 executes a program stored in the storage unit 102 to control the image forming operation in the color image forming apparatus 1 and also controls the storage unit 102 , the operation unit 103 , or the communication unit 104 . In the image forming operation controlled by the controller 101, the yellow (Y), magenta (M), cyan (C) and black (K) toner supply devices 246 (Y, M, C, K) are controlled to A toner replenishment operation for replenishing toner to each developing device 24 (Y, M, C, K) is also included.

The control unit 101 also includes image density detection means, first toner replenishment time calculation means, and second toner replenishment time calculation means realized by executing a program pre-stored in the storage unit 102, as described below. It has functions as calculation means, integration means, drive control means, and determination means.

Image Density Detecting Means The image density detecting means converts image information input to the color image forming apparatus 1 into an image of each color component of yellow (Y), magenta (M), cyan (C), and black (K) at the time of image formation. An image of image information converted into respective color components of yellow (Y), magenta (M), cyan (C), and black (K) based on image information output from an image processing device (not shown) that converts each into information. It is a function to detect each density.

Further, the control unit 101 sets the image density of the image information converted into each color component of yellow (Y), magenta (M), cyan (C), and black (K) to a predetermined number N (positive integer ) as the average image density between pages.

More specifically, the image processing apparatus implemented by the control unit 101 executing a program includes an image information storage unit and a RIP (Raster Image Processing) processing unit. The image information storage unit temporarily and sequentially stores image information to be subjected to RIP processing, which is image information transmitted from a client terminal such as a user's personal computer. The image information storage unit is composed of part of the storage unit 102, for example. Here, the image information includes image data described in PDL (Page Description Language) (hereinafter referred to as “PDL data”) and print control information. The print control information is, for example, information regarding the number of copies to be printed and the type of recording paper 6 .

The RIP processing unit reads and interprets PDL data among the print data stored in the image information storage unit, and generates raster data for each page. The raster data generated by the RIP processor is sent to the exposure devices 23 (Y, M, C, K) of the color image forming apparatus 1, respectively.

The image density detection means has a function as a counter, and counts the number of effective pixels and the image density of the image data output to the exposure device 23 (Y, M, C, K). Here, the number of effective pixels is the number of pixels forming the electrostatic latent image formed on the photosensitive drum 21 by the exposure of the exposure device 23 (that is, the number of pixels to be developed with toner). Also, the image density is the density of the image corresponding to each pixel. The image density is expressed by, for example, 256 gradations.

For example, the image density detecting means counts the image density of image information formed in an image of one page in 256 gradations for each pixel, and cumulatively calculates the image density formed in all pixels of the image of one page. To detect.

Then, as shown in FIG. 5, the image density detection means performs the operation of cumulatively counting the image density formed in all the pixels of the image of one page over N pages. The image density detection means detects (calculates) the average value of the image densities by dividing the total image density of the image data counted over the N pages by N. Here, the image density detection means calculates the image density of the image per page and the average value of the image density over N pages for each of the yellow (Y), magenta (M), cyan (C) and black (K) color components. to detect. The detected image density of images per page and the average value of image densities over N pages are stored in the RAM 101 b or the storage unit 102 .

First toner replenishment time calculation means The first toner replenishment time calculation means calculates an image of each color component of yellow (Y), magenta (M), cyan (C) and black (K) detected by the image density detection means. This is a function of calculating the first toner supply time t1 corresponding to each color of yellow (Y), magenta (M), cyan (C) and black (K) based on the average value of density. The first toner supply time t1 is calculated, for example, using a predetermined relational expression based on the average image density. Further, the first toner supply time t1 may of course be obtained by referring to a table stored in advance in the storage unit based on the average value of the image density.

Second Toner Replenishment Time Calculation Means Further, the second toner replenishment time calculation means calculates the yellow (Y), magenta (M), cyan (C) and black (K) developing devices 24 (Y, M, C). , K), the second toner supply time t2 for each color of yellow (Y), magenta (M), cyan (C), and black (K) is calculated based on the detection result from the toner density sensor 254. It is a function to The second toner supply time t2 is calculated using a predetermined relational expression based on the toner concentration value detected by the toner concentration sensor 254, for example. Further, the second toner replenishment time t2 may of course be obtained by referring to a table pre-stored in the storage section based on the detected value of the toner density sensor 254. FIG.

Integrating Means The accumulating means is literally a function for sequentially accumulating input values. The accumulator has a function of accumulating the replenishment times t1 and t2 calculated by the first and second toner replenishment time calculators. That is, the integrating means calculates the first toner replenishment time t1, which is the result of calculation by the first toner replenishment time calculation means, and the second toner replenishment time t2, which is the result of calculation by the second toner replenishment time calculation means. Multiply (add). The integrating means obtains the integrated toner supply time (t1+t2) for each color component of yellow (Y), magenta (M), cyan (C) and black (K).

Further, the accumulating means has a function of accumulating the obtained toner replenishment time (t1+t2) over a predetermined number of pages, and a function of accumulating the image density over a predetermined number of pages N as an example of the first period. also has Further, the integrating means has a function of updating the integrated value for each page as an example of the second period. The second period is not limited to one page, and may be multiple pages. However, in order to perform control based on the latest value of the toner replenishment time (t1+t2), it is desirable to set the second period to one page.

Drive Control Means The drive control means controls the yellow (Y), magenta (M), cyan (C) and black (K) toner supply devices 246 (Y, M) for the toner supply time (t1+t2) accumulated by the accumulation means. , C, and K) to drive the motors 247 respectively.

Determining Means The determining means is based on an integrated value obtained by integrating the toner supply time (t1+t2) accumulated by the integrating means over a predetermined number N of pages, and an integrated value obtained by integrating the image density over a predetermined number N of pages. This is a function to determine whether the ratio (slope) of the integrated value of toner replenishment time to the integrated value of image density is abnormal or not. be.

Resolution Mode Execution Unit The resolution mode execution unit is a function that executes a resolution operation (solution mode) for eliminating detection abnormality of the toner concentration sensor 254 when the determination result by the determination unit is determined to be abnormal.

<Operation of Characteristic Portion of Color Image Forming Apparatus>
As shown in FIG. 1, the color image forming apparatus 1, according to image information input from a client terminal such as a personal computer (not shown) to the color image forming apparatus 1 via the communication unit 104 (FIG. 4), (Y), magenta (M), cyan (C), and black (K) image forming devices 20 (Y, M, C, K) form toner images of corresponding colors. At that time, the image information input to the color image forming apparatus 1 is converted into image information corresponding to each of yellow (Y), magenta (M), cyan (C), and black (K) by an image processing apparatus (not shown). be done.

The developing devices 24 of the yellow (Y), magenta (M), cyan (C), and black (K) image forming devices 20 (Y, M, C, K) are, as shown in FIG. By executing the developing process for developing the electrostatic latent image formed on the drum 21 , the toner in the developer 4 in the device housing 240 increases the image density of the electrostatic latent image formed on the photosensitive drum 21 . Consumed by attaching according to

The control unit 101 of the color image forming apparatus 1 executes a toner replenishment control operation at a predetermined timing.

As shown in FIG. 6, when the control unit 101 starts the toner replenishment control operation, each image of yellow (Y), magenta (M), cyan (C) and black (K) averaged over a predetermined number of pages N is displayed. After detecting the density (step 101), the first toner supply time t1 for each of yellow (Y), magenta (M), cyan (C) and black (K) is calculated according to the image density (step 102). ).

Here, when the detected image density is lower than the threshold value, the first toner replenishing time t1, which is the driving time of the toner replenishing device 246, is calculated shorter than the reference driving time. Further, when the detected image density is higher than the threshold value, the first toner replenishing time T1, which is the driving time of the toner replenishing device 246, is calculated to be longer than the reference driving time. Specifically, in order not to cause a delay in the toner replenishment control operation, as described above, the average image density of the most recent predetermined pages N is calculated, and based on the calculated average image density, to calculate the first toner supply time t1.

When the control unit 101 starts the toner replenishment control operation, the toner density sensor 254 detects the toner density in each developing device 24 for yellow (Y), magenta (M), cyan (C), and black (K). (step 103), and the second toner supply time T2 is calculated from the relationship between the toner density detected by the toner density sensor 254 and the target toner density (step 104).

Here, if the toner density detected by the toner density sensor 254 is lower than the target toner density, a second toner replenishment time t2 is calculated to replenish the toner so as to achieve the target toner density. Further, when the toner density detected by the toner density sensor 254 is higher than the target toner density, the second toner supply time t2 is calculated as a negative value. Furthermore, when the toner density detected by the toner density sensor 254 is equal to the target toner density, the second toner supply time t2 is calculated as zero.

Next, the controller 101 integrates the first toner replenishment time t1 and the second toner replenishment time t2 for yellow (Y), magenta (M), cyan (C), and black (K) (step 105).

After that, the controller 101 controls to drive the toner replenishing device 246 for the accumulated toner replenishing time (t1+t2) (step 106), and terminates the toner replenishing control operation. Specifically, as shown in FIG. 4, the controller 101 supplies yellow (Y), magenta (M), cyan (C), and black (K) toners for the accumulated toner supply time (t1+t2). A drive signal is output through a drive circuit (not shown) to drive the drive motor 247 of the supply device 246 .

As described above, the control unit 101 of the color image forming apparatus 1 executes the toner replenishment control operation so that the yellow (Y), magenta (M), cyan (C), and black (K) developing devices 24 (Y, M, C, K) are replenished with toner of corresponding colors from the toner cartridges 245 (Y, M, C, K) by the toner replenishing device 246 (Y, M, C, K).

However, in the developing device 24 (Y, M, C, K), the toner concentration sensor 254 may detect the toner concentration abnormally due to changes in the fluidity of the developer 4 or the like.

For example, in a high-humidity environment, the fluidity of the developer 4 may decrease and the developer 4 may stay near the toner density sensor 254 . Further, if the developing device 24 continuously agitates and conveys the developer 4 in a state where the toner consumption amount per unit time is small, the developer 4 may be deteriorated and the fluidity may also be lowered.

As a result, as shown in FIG. 3, when the fluidity of the developer 4 decreases and the developer 4 stays near the toner concentration sensor 254, the average toner concentration in the developing device 24 is Instead, the local toner density of the developer 4 remaining near the toner density sensor 254 is detected.

In the color image forming apparatus 1, as shown in FIG. 6, when the second toner replenishment time t2 is calculated based on the detection result of the toner density sensor 254 in the toner replenishment control, the second toner replenishment time T2 is It may be under-calculated or over-calculated.

Then, in the developing device 24, the toner is supplied excessively or insufficiently, and the density of the toner image does not match the target density, which may cause an image defect.

As shown in FIG. 7, when the operation of forming an image on one page of the recording paper 6 is completed (step 201), the control unit 101 executes the toner replenishment control operation as shown in FIG. 6 (step 202). ).

After that, the control unit 101 integrates the image density for one page of the recording paper 6 on which the image is formed (step 203). At the same time, the controller 101 detects the toner density in each developing device 24 by the toner density sensor 254, and calculates the second toner supply time T2 from the relationship between the toner density detected by the toner density sensor 254 and the target toner density. do.

Then, the controller 101 integrates the first toner replenishment time t1 and the second toner replenishment time t2 corresponding to the image density for one page (step 204).

After that, the control unit 101 adds 1 to the number of pages to count up (step 205), and determines whether or not the counted number of pages has reached a predetermined number of pages N (step 205). 206).

When the control unit 101 determines that the counted number of pages has not reached the predetermined number of pages N, it starts the image forming operation based on the image information of the next page (step 207). Return to 201.

On the other hand, when the controller 101 determines that the counted number of pages has reached the predetermined number of pages N, it determines whether or not the integrated value of the toner replenishment time with respect to the integrated value of the image density is abnormal (step 208).

Here, whether or not the integrated value of the toner replenishment time with respect to the integrated value of the image density is abnormal is determined as shown in FIG. That is, the ratio (slope) of the integrated value of the toner replenishment time to the integrated value of the image density increases in proportion to the integrated value of the toner replenishment time as the integrated value of the image density increases in an ideal state.

However, as described above, the amount of toner replenished inside the developing device 24 per unit time when the toner replenishing device 246 is driven is not always constant. and changes in characteristics such as toner fluidity over time.

Therefore, the ratio (gradient) of the integrated value of the toner replenishment time to the integrated value of the image density is a straight line in which the integrated value of the toner replenishment time increases proportionally as the integrated value of the image density increases, as shown in FIG. It may deviate slightly from L. Therefore, a certain amount of allowable width _LH and _LL is recognized on both sides of the case of direct proportion, and if it is within the allowable width W, it is determined to be within the normal range.

On the other hand, in the developing device 24, for example, when the developer 4 having a toner concentration lower than the average toner concentration stays near the toner concentration sensor 254, the toner concentration sensor 254 detects a toner concentration lower than the average toner concentration. will be detected. Therefore, if the toner replenishment time is calculated based on the detection result of the toner density sensor 254, the second toner replenishment time t2 will be calculated excessively.

Conversely, when the developer 4 having a toner concentration higher than the average toner concentration stays near the toner concentration sensor 254, the toner concentration sensor 254 detects a toner concentration higher than the average toner concentration in the developing device 24. . Therefore, if the toner replenishment time is calculated based on the detection result of the toner density sensor 254, the toner replenishment time will be calculated too short.

As a result, the ratio (slope) of the integrated value of the toner replenishment time to the integrated value of the image density becomes excessive or insufficient, as shown in _FIG . will be out of _L. When the ratio (gradient) of the integrated value of the toner replenishment time to the integrated value of the image density is out of the range of the allowable width W, the controller 101 determines that the toner concentration sensor 254 has detected an abnormality.

Note that when the ratio (slope) of the integrated value of the toner replenishment time to the integrated value of the image density is in the vicinity of the allowable widths _LH and _LL as shown in FIG. The operation of determining whether or not the toner concentration sensor 254 has detected abnormality may be repeated a plurality of times, and finally it may be determined whether or not the toner concentration sensor 254 has detected abnormality.

After that, when the control unit 101 determines that the ratio (slope) of the integrated value of the toner replenishment time to the load value of the image density is not abnormal but normal, it resets the load value of the image density and the integrated value of the toner replenishment time. is reset to zero (step 209), and the image forming operation for the next page is started (step 209).

On the other hand, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the stacking value of the image density is abnormal, the controller 101 executes the abnormality resolution mode (step 210).

In the abnormality resolution mode, the control unit 101 changes the rotational speeds of the agitation supply member 242 and the agitation conveyance member 243 of the developing device 24 to slower speeds than during normal development, and drives them for a predetermined time. Execute velocity drive mode.

At the time of development, the agitating supply member 242 and the agitating conveying member 243 of the developing device 24 are rotationally driven at a normal rotational speed. and the developer 4 tends to stay. Therefore, in the developing device 24, by executing the low-speed drive mode, the agitating operation is performed at a speed lower than the normal rotation speed, thereby weakening the centrifugal force caused by the rotation of the agitating and conveying member 243. By exerting the conveying force of the agitating and conveying member 243 on the developer 4 that is held down and stagnated by the wall surface of , it is possible to break the stagnation of the developer 4 .

In addition, the abnormality resolution mode is not limited to the case where the agitation supply member 242 and the agitation conveyance member 243 are driven at a low speed. A toner band, which is a toner image, may be formed to forcibly consume the toner in the developing device 24 .

This operation has the effect of increasing or decreasing the amount of developer in the developing device 24 by refreshing the toner in the developing device 24 (the operation of forcibly consuming and supplying toner). The effect of breaking down retention is exhibited.

As described above, in Embodiment 1, the ratio (slope) of the load value of the image density and the integrated value of the toner replenishment time is within the required range W If it is within the range, it is determined to be normal, and it can be seen that the toner concentration sensor 254 has not detected an abnormality. If the integrated value of the image density loading value and the toner replenishment time is outside the required range W for the ideal case, it is determined that the toner density sensor 254 has detected an abnormality. be able to.

Then, when the controller 101 determines that the toner concentration sensor 254 has detected abnormality, the abnormal detection state occurring in the toner concentration sensor 254 is eliminated by executing the abnormality elimination mode.

[Embodiment 2]
FIG. 9 is a flow chart showing control operations of a color image forming apparatus as an example of the image forming apparatus according to the second embodiment. In the second embodiment, the image density of the electrostatic latent image and the replenishment time of the replenishment means are maintained for a third period shorter than the first period after the resolving means performs the operation of resolving the detection abnormality of the density detection means. The image forming apparatus further includes prohibiting means for prohibiting the image forming operation when the determining means determines that there is a detection abnormality in the density detecting means based on each accumulated integrated value.

In the second embodiment, the control unit 101, which also functions as an example of prohibiting means, executes the following toner replenishment operation.

As shown in FIG. 9, when the operation of forming an image on one page of the recording paper 6 is completed (step 301), the control unit 101 executes the toner replenishment control operation as shown in FIG. 6 (step 302). ).

After that, the control unit 101 integrates the image density for one page of the recording paper 6 on which the image is formed (step 303). At the same time, the control unit 101 detects the toner density in each developing device 24 by the toner density sensor 254, and calculates the second toner supply time t2 from the relationship between the toner density detected by the toner density sensor 254 and the target toner density. do.

Then, the controller 101 integrates the first toner replenishment time t1 and the second toner replenishment time t2 corresponding to the image density for one page (step 304).

After that, the control unit 101 adds 1 to the number of pages to count up (step 305), and determines whether or not the counted number of pages has reached a predetermined number of pages N (step 305). 306).

Then, when the control unit 101 determines that the counted number of pages has not reached the predetermined number of pages N, an example of a second period after the abnormality resolution mode is executed and which is smaller than the predetermined number of pages N is It is determined whether or not the predetermined number of pages M has been reached (step 307).

On the other hand, when the controller 101 determines that the counted number of pages has reached the predetermined number of pages N, it determines whether or not the integrated value of the toner replenishment time with respect to the integrated value of the image density is abnormal (step 308).

After that, when the control unit 101 determines that the ratio (slope) of the integrated value of the toner replenishment time to the load value of the image density is not abnormal but normal, it resets the load value of the image density and the integrated value of the toner replenishment time. is returned to zero (step 309), and the process proceeds to step 307.

Further, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the load value of the image density is abnormal, the controller 101 executes the abnormality resolution mode (step 310 ), and then proceeds to step 307 .

In step 307, the control unit 101 determines whether or not the predetermined number of pages M, which is smaller than the predetermined number of pages N, has been reached after executing the abnormality resolution mode.

When the controller 101 determines that the abnormality resolution mode is not executed or that the predetermined number of pages M, which is smaller than the predetermined number of pages N, is not reached, the control unit 101 starts the image forming operation based on the image information of the next page ( step 311) and return to step 301;

On the other hand, when the control unit 101 determines that the predetermined number of pages M, which is smaller than the predetermined number of pages N, has been reached after executing the abnormality resolution mode, the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number M of pages. is abnormal (step 312).

When the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number M of pages is not abnormal, it starts the image forming operation based on the image information of the next page (step 311). Return to step 301 .

Further, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number M of pages is abnormal, it prohibits the printing operation (step 313). Then, the control unit 101 displays a message to call a service engineer on the display unit 103b.

Here, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number M of pages is abnormal, the printing operation is prohibited because the abnormality resolution mode is executed in step 310. However, if the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number M of pages smaller than the predetermined number N of pages is determined to be abnormal, the cause of the abnormality is the developing device 24 itself, or This is because it is not appropriate to determine that the toner replenishing device 246 or the toner concentration sensor 254 itself has failed and to continue the printing operation.

As described above, in the second embodiment, it is possible to determine that the development device 24 itself, the toner replenishing device 246, or the toner density sensor 254 itself is malfunctioning, in addition to the detection abnormality of the toner density sensor 254. .

[Embodiment 3]
FIG. 10 is a flow chart showing control operations of a color image forming apparatus as an example of the image forming apparatus according to the third embodiment. In the third embodiment, the image density of the electrostatic latent image and the replenishment time of the replenishment means are maintained for a fourth period longer than the first period after the resolving means performs the operation of resolving the detection abnormality of the density detection means. An instruction means is provided for instructing a toner replacement operation in the developing means when the judgment means judges that there is a detection abnormality in the density detection means based on each accumulated integrated value.

In the third embodiment, the control section 101 executes the toner supply operation as follows.

As shown in FIG. 10, when the operation of forming an image on one page of the recording paper 6 is completed (step 401), the control unit 101 executes the toner replenishment control operation as shown in FIG. 6 (step 402). ).

After that, the control unit 101 integrates the image density for one page of the recording paper 6 on which the image is formed (step 403). At the same time, the control unit 101 detects the toner density in each developing device 24 by the toner density sensor 254, and calculates the second toner supply time t2 from the relationship between the toner density detected by the toner density sensor 254 and the target toner density. do.

Then, the controller 101 integrates the first toner replenishment time t1 and the second toner replenishment time t2 corresponding to the image density for one page (step 404).

Thereafter, the control unit 101 adds 1 to the number of pages to count up (step 405), and determines whether or not the counted number of pages has reached a predetermined number of pages N (step 405). 406).

Then, when the control unit 101 determines that the counted number of pages has not reached the predetermined number of pages N, an example of a fourth period after the execution of the abnormality resolution mode and greater than the predetermined number of pages N is It is determined whether or not a predetermined number of pages P has been reached (step 407).

On the other hand, when the controller 101 determines that the counted number of pages has reached the predetermined number of pages N, it determines whether or not the integrated value of the toner replenishment time with respect to the integrated value of the image density is abnormal (step 408).

After that, when the control unit 101 determines that the ratio (slope) of the integrated value of the toner replenishment time to the integrated value of the image density is not abnormal but normal, it resets the stacked value of the image density and the integrated value of the toner replenishment time. is reset to zero (step 409), and the process proceeds to step 407.

Further, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density is abnormal, the controller 101 executes the abnormality resolution mode (step 410 ), and then proceeds to step 407 .

In step 407, the control unit 101 determines whether or not the predetermined number of pages P, which is larger than the predetermined number of pages N, has been reached after executing the abnormality resolution mode.

When the control unit 101 determines that the abnormality resolution mode is not executed or that the predetermined number of pages P, which is greater than the predetermined number of pages N, is not reached, the control unit 101 starts the image forming operation based on the image information of the next page ( step 411), and return to step 401;

On the other hand, when the controller 101 determines that the predetermined number of pages P, which is greater than the predetermined number of pages N, has been reached after executing the abnormality resolution mode, the controller 101 integrates the toner replenishment time with respect to the integrated value of the image density for the predetermined number P of pages. It is determined whether the value is abnormal (step 412).

When the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number of pages P is not abnormal, it starts the image forming operation based on the image information of the next page (step 411). Return to step 401 .

Further, when the controller 101 determines that the integrated value of the toner replenishment time with respect to the integrated value of the image density for the predetermined number of pages P is abnormal, the controller 101 executes the developer replacement operation (step 413). The developer replacement operation is performed by displaying a message prompting a service engineer to perform the developer replacement operation in the developing device 24 on the display unit 103b.

However, the printing operation may be continued until a service engineer is called and the toner replacement operation is executed. At this time, a message urging the service engineer to be called and the toner replacement operation to be performed is displayed on the display unit 103b, and a confirmation button for confirming that the user is to perform the toner replacement operation is displayed on the display unit 103b. The print operation may be continued only when the button is operated.

As described above, in the third embodiment, after the abnormality resolution mode is executed, it is determined that the predetermined number of pages P, which is greater than the predetermined number of pages N, is reached, and furthermore, the image density integrated value between the predetermined number of pages P is determined. If it is determined that the integrated value of the toner replenishment time is abnormal, it is assumed that the developer 4 has deteriorated, and the toner replacement operation is executed.

Therefore, the developing device 24 replaces the deteriorated developer 4 inside with the developer 4 containing new carrier and toner to normalize the fluidity of the developer 4, and the toner density sensor 254 detects an abnormality. is avoided.

In the above embodiment, a full-color image forming apparatus having yellow (Y), magenta (M), cyan (C), and black (K) image forming devices 10 (Y, M, C, K) is described. Although described, it goes without saying that the same can be applied to a monochrome image forming apparatus including only the black (K) image forming apparatus 10K.

In the above-described embodiment, the image density of the electrostatic latent image and the replenishing time of the replenishing means are integrated so as to be obtained from the number of pages of the recording paper 6. It may be configured to be calculated based on the integrated value of the number of revolutions of the developing roll of the apparatus.

Reference Signs List 1: image forming apparatuses 20Y to 20K: full-color image forming apparatus 21: photosensitive drum 24: developing device 100: control device 101: control section 254: toner density sensor

Claims (6)

a developing means for developing the electrostatic latent image with a developer containing toner;
density detection means for detecting the toner density in the developing means;
replenishing means for replenishing toner to the developing means based on the image density of the electrostatic latent image and the detection result of the density detecting means;
Determining whether or not there is a detection abnormality in the density detection means based on each integrated value obtained by integrating the image density of the electrostatic latent image and the replenishment time of the replenishment means over a first period and updating each second period. and
a resolution means for executing an operation to resolve the detection abnormality of the density detection means when the determination means determines that there is a detection abnormality of the density detection means;
After the canceling means has executed the operation of canceling the detection abnormality of the density detecting means, the image density of the electrostatic latent image and the replenishing time of the replenishing means are integrated over a third period shorter than the first period. prohibiting means for prohibiting an image forming operation when the determining means determines that there is a detection abnormality in the density detecting means based on each integrated value;
image forming apparatus. a developing means for developing the electrostatic latent image with a developer containing toner;
density detection means for detecting the toner density in the developing means;
replenishing means for replenishing toner to the developing means based on the image density of the electrostatic latent image and the detection result of the density detecting means;
Determining whether or not there is a detection abnormality in the density detection means based on each integrated value obtained by integrating the image density of the electrostatic latent image and the replenishment time of the replenishment means over a first period and updating each second period. and
a resolution means for executing an operation to resolve the detection abnormality of the density detection means when the determination means determines that there is a detection abnormality of the density detection means;
After the canceling means has executed the operation of canceling the detection abnormality of the density detecting means, the image density of the electrostatic latent image and the replenishing time of the replenishing means are integrated over a fourth period longer than the first period. and an instruction unit for instructing replacement of the developer in the developing unit when the determination unit determines that there is a detection abnormality in the density detection unit based on each integrated value. 3. The image forming apparatus according to claim 1 , wherein said solving means drives the conveying means for conveying the developer in said developing means at a speed slower than a normal driving speed. 3. The image forming apparatus according to claim 1 , wherein said canceling means executes an operation of forcibly consuming toner in said developing means. notification means for notifying a user of the detection abnormality of the density detection means when the determination means determines that there is a detection abnormality of the density detection means;
selection means for allowing a user to select whether or not to execute an operation for resolving the detection abnormality of the density detection means;
5. The image forming apparatus according to claim 1, comprising: 6. The image forming apparatus according to claim 1, wherein said second period is shorter than said first period .

Images