JP7367452B2 - Image forming device and method of controlling the image forming device - Google Patents

Description

The present disclosure relates to an image forming apparatus and a method of controlling the image forming apparatus, and particularly relates to detection of toner concentration.

When the two-component developer in the developing device is left for a long time, its bulk becomes lower (bulk density becomes larger) than when it is sufficiently stirred, and for this reason, the output characteristics of the toner concentration detection sensor ( The relationship between the toner concentration of the developer in the developing device and the output value of the toner concentration detection sensor may change depending on the state of the developer in the developing device. In other words, even if the toner concentration of the developer in the developing device is the same, the toner concentration detection sensor detects that the toner concentration of the developer that has been left for a long time is lower than the toner concentration of the developer that has been sufficiently stirred. There is a possibility of detection.

As a preventive measure against this phenomenon, there is a known technology that detects the toner concentration after optimizing the bulk density of the toner by stirring the developing device for a predetermined period of time during warm-up, depending on the length of time the developing device is left and the humidity. (See Patent Document 1).

However, the warm-up operation is extended by the stirring time, resulting in extra waiting time for the user. Therefore, in order to accurately detect toner density, the following correction technique is known.

For example, a method has been proposed in which the input voltage of a toner concentration detection sensor is offset for a predetermined number of sheets after being left for a long time (see Patent Document 2).

Another method is to memorize input voltages for toner concentrations in multiple absolute humidity environments in advance, and calculate the toner concentration by performing linear interpolation using the difference between the detected absolute humidity and the previously memorized input voltages. A method has been proposed (see Patent Document 3).

As yet another method, since the supply amount of new toner is not stable, a method has been proposed in which the toner empty notification is not notified for a predetermined period of time or for a predetermined number of sheets after the new toner is installed (see Patent Document 4).

Japanese Patent Application Publication No. 11-212343 Japanese Patent Application Publication No. 2008-116757 Japanese Patent Application Publication No. 2008-122466 Japanese Patent Application Publication No. 2003-215902

However, since the amount of toner settling in the developing device varies depending on the humidity and the length of time it has been left in the developing device, there is a possibility that the toner density cannot be corrected completely and a density abnormality is falsely detected. You may end up in a prohibited state.

The present disclosure has been made in view of the above-mentioned background, and an object of the present disclosure is to provide an image forming apparatus and a control method for the image forming apparatus that prevent false detection of toner density abnormality using a simple method. .

An image forming apparatus according to one aspect includes an image carrier on which an electrostatic latent image is formed, a developing device that develops the electrostatic latent image on the image carrier into a toner image, and a toner concentration of a developer in the developing device. A toner concentration detection section detects the toner concentration, a flow section that flows the developer in the developing device, a stop period acquisition section that acquires the stop period during which the flow section was stopped, and a stop period acquisition section that obtains the stop period. and a toner concentration abnormality determination section that determines whether the toner concentration detected by the toner concentration detection section is within a predetermined range depending on the length.

Preferably, the toner concentration abnormality determination section determines whether the toner concentration detected by the toner concentration detection section is within a predetermined range when the suspension period acquired by the suspension period acquisition section is less than a predetermined period; If the stop period acquired by the stop period acquisition section is longer than the predetermined period, it is not determined whether the toner concentration detected by the toner concentration detection section is within the predetermined range.

Preferably, the apparatus further includes a period adjustment section that adjusts the predetermined period based on predetermined conditions.
Preferably, the device further includes an environmental information acquisition unit that acquires humidity or temperature. The period adjustment section adjusts the predetermined period based on the humidity or temperature acquired by the environmental information acquisition section.

Preferably, the apparatus further includes an operation period acquisition section that acquires an operation period during which the flow section was in an operation state. The period adjustment section adjusts the predetermined period based on the operation period acquired by the operation period acquisition section.

Preferably, the image forming apparatus further includes a toner concentration storage section that stores the toner concentration when the flow section is stopped. The period adjustment section adjusts the predetermined period based on the toner concentration stored in the toner concentration storage section.

Preferably, the toner concentration abnormality determination section determines the toner concentration abnormality after causing the developer in the developing device to flow in the flow section if the stop period acquired by the stop period acquisition section is longer than a predetermined period.

Preferably, the image forming apparatus further includes a print forming section that transfers the developed toner image onto a recording medium and outputs it. If the toner concentration abnormality determining section determines that the toner concentration detected by the toner concentration detecting section is not within a predetermined range, the print forming section does not transfer the developed toner image to the recording medium and output it.

Preferably, a plurality of image carriers are provided. A plurality of developing devices are provided, each corresponding to a plurality of image carriers. A plurality of toner density detection sections are provided, each corresponding to a plurality of developing devices. A plurality of flow sections are provided, each corresponding to a plurality of developing devices. A plurality of stop period acquisition sections are provided respectively corresponding to the plurality of flow sections. A plurality of toner concentration abnormality determination sections are provided respectively corresponding to the plurality of stop period acquisition sections. Each toner concentration abnormality determination section determines whether the toner concentration detected by the corresponding toner concentration detection section is within a predetermined range when the stop period acquired by the corresponding stop period acquisition section is less than a predetermined period. However, if the stop period acquired by the corresponding stop period acquisition section is longer than the predetermined period, it is not determined whether the toner concentration detected by the corresponding toner concentration detection section is within the predetermined range.

Preferably, the developer is a two-component developer containing toner and a magnetic carrier.
An image including an image carrier on which an electrostatic latent image is formed according to a certain aspect, a developing device that develops the electrostatic latent image on the image carrier into a toner image, and a fluidizing section that causes developer in the developing device to flow. A method for controlling a forming device, which includes the steps of: detecting the toner concentration of a developer in a developing device; obtaining a stop period in which a flow section is in a stopped state; , and determining whether the detected toner concentration is within a predetermined range.

These and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings.

FIG. 1 is a diagram illustrating the appearance of an image forming apparatus 1 based on an embodiment. FIG. 1 is a diagram illustrating functional blocks of an image forming apparatus 1 based on an embodiment. FIG. 4 is a diagram illustrating the configuration of a developing device 412 according to the embodiment. FIG. 3 is a functional block diagram for executing toner concentration detection control according to the embodiment. FIG. 3 is a diagram illustrating a relationship between a stop period and a toner density level in an image forming apparatus according to an embodiment. FIG. 3 is a flow diagram illustrating toner density detection control processing in the image forming apparatus according to the embodiment. FIG. 7 is a diagram illustrating the relationship between humidity and toner density level in an image forming apparatus according to Modification 1 of the embodiment. FIG. 7 is a diagram illustrating a relationship between a stop period and a toner density level in an image forming apparatus according to a second modification of the embodiment. FIG. 7 is a diagram illustrating a relationship between a stop period and a toner density level in an image forming apparatus according to a third modification of the embodiment.

Hereinafter, embodiments of the technical idea according to the present disclosure will be described with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

In the following embodiments, the image forming apparatus includes, for example, an MFP, a printer, a copier, or a facsimile.

FIG. 1 is a diagram illustrating the appearance of an image forming apparatus 1 based on the embodiment.
FIG. 2 is a diagram illustrating functional blocks of the image forming apparatus 1 based on the embodiment.

Referring to FIGS. 1 and 2, an image forming apparatus 1 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. The image forming apparatus 1 primarily transfers each color toner image of C (cyan), M (magenta), Y (yellow), and K (black) formed on the photoreceptor drum 413 to an intermediate transfer belt 421, and An image is formed by superimposing the four-color toner images on the transfer belt 421 and then performing secondary transfer onto recording paper.

The image forming apparatus 1 includes a tandem system in which photosensitive drums 413 corresponding to four colors of CMYK are arranged in series in the running direction of an intermediate transfer belt 421, and toner images of each color are sequentially transferred to the intermediate transfer belt 421 in one step. method is adopted.

The image forming apparatus 1 includes an image reading section 10, an operation display section 20, an image processing section 30, an image forming section 40, a transport section 50, a fixing section 60, and a control section 70.

The control unit 70 includes a CPU (Central Processing Unit) 71, a ROM (Read Only Memory) 72, a RAM (Random Access Memory) 73, a clock 74, and the like.

The CPU 71 reads a program according to the processing content from the ROM 72, loads it into the RAM 73, and controls the operation of each block of the image forming apparatus 1 in cooperation with the loaded program. At this time, various data stored in the storage unit 82 are referred to.

The storage unit 82 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

The control unit 70 sends and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 81. conduct.

For example, the control unit 70 receives image data transmitted from an external device, and forms an image on recording paper based on this image data (input image data). The communication unit 81 is configured by a communication control card such as a LAN card, for example.

The image reading unit 10 includes an automatic document feeding device 11 called an ADF (Auto Document Feeder), a document image scanning device (scanner) 12, and the like. The automatic document feeder 11 uses a conveyance mechanism to convey the document D placed on the document tray and sends it to the document image scanning device 12 .

The automatic document feeder 11 can continuously read images of a document D placed on a document tray.

The document image scanning device 12 optically scans the document conveyed onto the contact glass from the automatic document feeder 11 or the document placed on the contact glass, and converts the reflected light from the document into a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a and the original image is read.

The image reading section 10 generates input image data based on the reading result by the document image scanning device 12. This input image data is subjected to predetermined image processing in the image processing section 30.

The operation display unit 20 is configured of, for example, a liquid crystal display (LCD) having a touch panel, and functions as a display unit 21 and an operation unit 22.

The display unit 21 displays various operation screens, image status display, operating status of each function, etc. in accordance with display control signals input from the control unit 70. Note that the display section 21 functions as a notification section.

The operation unit 22 includes various operation keys such as a numeric keypad and a start key. The operation unit 22 receives various input operations by the user and outputs operation signals corresponding to the input operations to the control unit 70. Note that the operation signal may be output from an external device to the control unit 70 via the communication unit 81.

The image processing unit 30 includes a circuit and the like that performs digital image processing on input image data according to initial settings or user settings. The image processing unit 30 also includes a circuit that performs gradation image processing on input image data. The image processing unit 30 also performs various correction processes such as color correction, compression processing, etc. in addition to gradation correction on input image data. The image forming section 40 is controlled based on the image data that has undergone these processes.

The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K, and an intermediate transfer unit 42 for forming images using colored toners of Y component, M component, C component, and K component based on input image data. and a toner image density detection sensor 43.

The image forming units 41Y, 41M, 41C, and 41K for the Y component, M component, C component, and K component have the same configuration except for the color of the toner used. For convenience of illustration and explanation, common components are indicated by the same reference numerals, and when they are distinguished from each other, they are indicated by the same symbols Y, M, and when they are distinguished, they are indicated by Y, M, C, K is also shown here.

In FIG. 1, only the components of the image forming unit 41Y for the Y component are numbered, and in the other FIG. 1, only the components of the image forming unit 41Y for the Y component are numbered, and other image forming Reference numerals are omitted for the components of the units 41M, 41C, and 41K.

Next, the configuration of the image forming unit 41 will be explained using the image forming unit 41Y. The image forming unit 41Y includes an exposure device 411, a developing device 412, a photosensitive drum 413 (image carrier), a charging device 414, a cleaning device 415, and the like.

The photosensitive drum 413 includes, for example, an undercoat layer (UCL), a charge generation layer, and a charge transport layer on the circumferential surface of an aluminum conductive cylinder (aluminum tube). This is a negatively charged organic photoconductor (OPC) in which a transport layer (transport layer) and an overcoat layer (OCL) are sequentially laminated. Note that the photoreceptor drum 413 may be a belt-shaped photoreceptor instead of a roller-shaped photoreceptor.

The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The charging method of the charging device 414 may be either a contact roller charging method or a non-contact corona charging method.

The exposure device 411 includes, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to a Y component image. Positive charges are generated in the charge generation layer of the photoreceptor drum 413 and transported to the surface of the charge transport layer, thereby neutralizing the surface charges (negative charges) of the photoreceptor drum 413. An electrostatic latent image of the Y component is formed on the surface of the photoreceptor drum 413 due to the potential difference with the surroundings.

The developing device 412 contains a Y component developer. The developer is a two-component developer consisting of toner of small particle size and carrier. As shown in FIG. 3, the developing device 412 causes the Y component toner to adhere to the surface of the photoreceptor drum 413 by rotationally driving the developing roller 108. Thereby, the developing device 412 visualizes the electrostatic latent image and forms a toner image. The toner particles used in the developing device 412 are usually prepared by mixing a coloring agent in a binder resin and, if necessary, adding a charge control agent, a release agent, etc., and granulating them to a predetermined particle size. The particle size is made to be about 3 to 15 [μm] by coating with external additives. Generally known methods such as a pulverization method, an emulsion polymerization method, and a suspension polymerization method are used for granulating the toner particles.

The cleaning device 415 has a drum cleaning blade that comes into sliding contact with the surface of the photoreceptor drum 413. Transfer residual toner remaining on the surface of the photoreceptor drum 413 after the primary transfer is removed by a drum cleaning blade. Note that the cleaning device 415 may be a cleaning means of a composite cleaning method using a combination of a cleaning brush, a cleaning roller, or other means. Alternatively, a cleanerless method may be used in which the cleaning device 415 is eliminated and the developing device 412 collects the residual toner after transfer.

The intermediate transfer unit 42 includes an intermediate transfer belt 421 serving as an intermediate transfer body, a primary transfer roller 422, a secondary transfer roller 423, a drive roller 424, a driven roller 425, a cleaning device 426, and the like.

The intermediate transfer belt 421 is an endless belt, and is stretched around a driving roller 424 and a driven roller 425. The intermediate transfer belt 421 runs at a constant speed in the direction of arrow A due to the rotation of the drive roller 424. When the intermediate transfer belt 421 is brought into pressure contact with the photoreceptor drum 413 by the primary transfer roller 422, toner images of each color are primarily transferred onto the intermediate transfer belt 421 in a superimposed manner. Then, when the intermediate transfer belt 421 is pressed against the recording paper S by the secondary transfer roller 423, the toner image primarily transferred to the intermediate transfer belt 421 is secondarily transferred to the recording paper S. Note that instead of the transfer method using the intermediate transfer belt 421, a transfer charger, a transfer roller, or the like may be used as the transfer means. A direct transfer method in which the toner image is directly transferred from the photosensitive drum 413 to the recording paper S may also be used.

The belt cleaning device 426 has a belt cleaning blade that comes into sliding contact with the surface of the intermediate transfer belt 421. Transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer is scraped off and removed by a belt cleaning blade. Note that the belt cleaning device 426 may be a cleaning means of a composite cleaning method using a combination of a cleaning brush, a cleaning roller, or other means.

As shown in FIG. 1, the toner image density detection sensor 43 faces the intermediate transfer belt 421 on the downstream side in the rotational direction of the intermediate transfer belt 421 from the secondary transfer position where the toner image is secondarily transferred onto the recording paper S. will be placed.

For example, two toner image density detection sensors 43 are arranged to face each other on both sides of the intermediate transfer belt 421 in the width direction (that is, the direction perpendicular to the rotational direction of the intermediate transfer belt 421, the main scanning direction). The toner image density detection sensor 43 is used when generating gradation correction data. The gradation correction data generation process is performed, for example, when the power switch is turned on, every time a predetermined number of prints are executed, when the amount of fluctuation in the surrounding environment (temperature, humidity, etc.) of the device exceeds a predetermined range, or when a malfunction occurs. This is executed when recovering from a problem or when executing image stabilization control to stably reproduce an input image as an output image.

The toner image density detection sensor 43 is formed in a non-image forming area of the intermediate transfer belt 421 (on both sides of the intermediate transfer belt 421 in the width direction) so as to face the toner image density detection sensor 43 as the intermediate transfer belt 421 rotates. The density of the patch image for gradation correction is detected, and the detected density is output to the control unit 70. The size of the patch image is, for example, 20 [mm] in the main scanning direction x 18 [mm] in the sub-operation direction.

The toner image density detection sensor 43 includes a light emitting element such as a light emitting diode (LED) and a light receiving element such as a photodiode (PD), and detects the toner adhesion amount (density) of a patch image. A reflective optical sensor for detection can be applied. As the amount of toner adhering to the patch image formed on the intermediate transfer belt 421 increases, the amount of light received by the light receiving element decreases, the amount of reflected light decreases, and the sensor output value output from the toner image density detection sensor 43 decreases. . Conversely, the smaller the amount of toner adhering to the patch image formed on the intermediate transfer belt 421, the more the amount of light received by the light receiving element increases, the more the amount of reflected light increases, and the sensor output value output from the toner image density detection sensor 43 increases. becomes larger.

Note that the arrangement position of the toner image density detection sensor 43 is not limited to the above-described embodiment. For example, the toner image density detection sensor 43 may be placed upstream of the secondary transfer position in the rotational direction of the intermediate transfer belt 421. In short, it is sufficient that the toner image density detection sensor 43 is arranged so as to be able to detect the amount of toner adhering to the patch image formed on the intermediate transfer belt 421. In addition, when the intermediate transfer belt 421 is made of a translucent material, the toner image density detection sensor 43 may be a transmissive type in which a light emitting element and a light receiving element are arranged opposite to each other with the intermediate transfer belt 421 interposed therebetween. Optical sensors can be applied.

The fixing section 60 is configured using a belt heating method. The fixing section 60 has an upper pressure section and a lower pressure section that form a fixing nip section. The upper pressure section includes a heating roller and a fixing roller. An endless fixing belt is stretched between the heating roller and the fixing roller with a predetermined belt tension. The lower pressure section has a pressure roller. The pressure roller is pressed against the fixing roller with a predetermined fixing load via the fixing belt. In this way, a fixing nip portion is formed between the fixing roller and the pressure roller, which pinches and conveys the recording paper S. The fixing unit 60 fixes the toner image on the recording paper S by heating and pressurizing the transported recording paper S at a fixing nip. Note that the fixing unit 60 may be configured using a roller heating method, or may be a non-contact type fixing means that heats the recording paper S in a non-contact manner using a heat source such as a heating lamp or a heater.

The transport section 50 includes a paper feed section 51, a transport mechanism 52, a paper discharge section 53, and the like. The three paper feed tray units 51a to 51c constituting the paper feed section 51 are preset with recording paper S (for example, standard paper or special paper) that is identified based on the basis weight, size, etc. of the recording paper. It is stored by type.

The recording sheets S stored in the paper feed tray units 51a to 51c are fed out one by one from the top, and conveyed to the image forming section 40 by a conveyance mechanism 52 equipped with a plurality of conveyance rollers such as registration rollers 52a. . At this time, the inclination of the fed recording paper S is corrected and the conveyance timing is adjusted by the registration section provided with the registration rollers 52a. Then, in the image forming section 40, the toner image on the intermediate transfer belt 421 is secondarily transferred all at once onto the image forming surface of the recording paper S, and a fixing process is performed in the fixing section 60. The recording paper S on which the fixing process has been performed is discharged to the outside of the image forming apparatus 1 by a paper discharge section 53 that includes a paper discharge roller 53a.

[Configuration of developing device 412]
FIG. 3 is a diagram illustrating the configuration of the developing device 412 according to the embodiment.

As shown in FIG. 3, the developing device 412 includes a housing 101 (developer storage section) that stores developer. The interior of the housing 101 is divided by a partition wall 102 into an agitation tank 103 and a supply tank 104, which contain a developer containing toner and carrier. The stirring screw 105 is disposed in the stirring tank 103, and stirs the toner and carrier while conveying them to the left in the figure, thereby triboelectrically charging the toner. The supply screw 106 is disposed within the supply tank 104 and supplies the developer containing charged toner to the developing roller 108 while conveying it rightward in the figure.

In the developing roller 108, a sleeve roller rotates around a fixedly arranged magnet roller, and developer is supplied to the outer peripheral surface of the sleeve roller by a supply screw 106. When the developer supplied to the outer peripheral surface of the sleeve roller moves on the outer peripheral surface of the sleeve roller, the carrier forms a magnetic brush due to the magnetic force of the magnetic poles provided on the magnet roller. The toner adhering to the magnetic brush adheres to the electrostatic latent image on the photoreceptor drum 413. That is, the electrostatic latent image on the photoreceptor drum 413 is developed with toner.

The magnet roller has five magnetic poles N1, S1, N2, N3, and S2 along the rotation direction of the sleeve roller. Among these magnetic poles, the main magnetic pole N1 is arranged at a position facing the photosensitive drum 413. The same polar parts N2 and N3, which generate a repulsion magnetic field for peeling off the developer on the sleeve roller, are arranged at opposing positions inside the developing device 412. The direction of rotation of the sleeve roller is set to be the same as the direction of rotation of the photoreceptor drum 413 (that is, opposite to each other at the opposing portion of the sleeve roller and the photoreceptor drum 413).

The supply screw 106 and the stirring screw 105 are spiral screws each provided with helical blades 110 and 112 having a predetermined helical pitch over almost the entire area of the shaft (rotating shaft).

The developing roller 108, the supply screw 106, and the stirring screw 105 are arranged so that their rotation axes are parallel to each other.

Communication ports 114 and 116 are provided at both ends of the partition wall 102 for transferring developer between the stirring tank 103 and the supply tank 104. This creates a circulation path in which the developer housed inside the housing 101 circulates between the stirring tank 103 and the supply tank 104 through the communication ports 114 and 116 while being stirred by the stirring screw 105 and the supply screw 106. It is formed.

Note that the circulation path formed inside the housing 101 may be a vertical or triaxial circulation path.

A toner replenishment port 122 is provided on the upstream side of the stirring tank 103 in the developer transport direction.

The toner supply port 122 receives toner supply via a toner hopper 124 filled with toner. Note that the toner hopper 124 may be filled with carrier in addition to toner, and may be configured to be supplied with toner and carrier together. A toner concentration detection sensor 140 that detects the toner concentration (ratio of toner in the developer) in the housing 101 is provided at the bottom of the stirring tank 103 on the downstream side in the developer transport direction.

The toner concentration detection sensor 140, also called a TCR sensor, outputs the detected toner concentration to the control unit 70. Specifically, the toner concentration detection sensor 140 outputs a sensor signal including a count value proportional to the magnitude of the toner concentration. The control unit 70 can specify the magnitude of the toner concentration from the count value included in the sensor signal output from the toner concentration detection sensor 140.

The toner concentration detection sensor 140 is a magnetic sensor that detects the toner concentration from the amount of carrier in a unit volume by measuring changes in the magnetic permeability of the developer using the fact that the carrier is a paramagnetic material.

The toner concentration detection sensor 140 detects a change in the inductance of the two coils due to a change in magnetic permeability as a toner concentration. Note that the toner density detection sensor 140 is not limited to a magnetic sensor, and a reflective optical sensor similar to the toner image density detection sensor 43 can be used.

The shaft of the supply screw 106 extends further downstream in the developer transport direction than the communication port 116 , and the downstream end of the shaft in the developer transport direction is connected to the supply tank 104 in the developer transport direction. It is located within the developer discharge section 126 that protrudes toward the downstream side. On the shaft of the supply screw 106, a counter-wound spiral blade 128 whose spiral direction is opposite to that of the spiral blade 110 is provided on the downstream side in the developer transport direction.

The reversely wound spiral blade 128 has a smaller helical pitch than the helical pitch of the spiral blade 110. The reverse spiral blade 128 regulates the conveyance of the developer in the developer conveyance direction of the supply screw 106 and sends the developer to the communication port 116 .

The shaft of the supply screw 106 located in the developer discharge section 126 is provided with a helical blade 130 having the same spiral direction as the helical blade 110 and a smaller helical pitch than the helical blade 110.

A developer discharge port 132 for discharging the developer is provided on the bottom surface of the developer discharge section 126.

The spiral blade 130 sends the developer that has moved beyond the reversely wound spiral blade 128 to the developer discharge port 132 .

A developer recovery container 134 is attached to the developer discharge port 132 . As in the present embodiment, the developer discharge port 132 is located at a position (in the developer transport direction) where the supplied toner is sufficiently mixed with the developer in the housing 101 so that the supplied toner is not discharged immediately. It is desirable to provide it at the most downstream position).

The counterwound spiral blade 128, the spiral blade 130, and the developer discharge portion 126 of the supply screw 106 constitute a trickle discharge mechanism that discharges excess developer from the developer discharge port 132 when the amount of developer in the housing 101 increases.

Note that the developer discharge mechanism may be configured such that the height of the housing 101 is lowered by the developer discharge port 132 and the excess developer in the housing 101 is discharged from the developer discharge port 132. good.

[Toner supply operation control]
The control unit 70 detects the count value of the toner concentration detection sensor 140, calculates the toner concentration, and determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range. Note that it may be determined whether or not the toner concentration is equal to or higher than a predetermined toner concentration. If the toner concentration is not higher than the predetermined toner concentration, a toner replenishment control signal requesting toner replenishment is output to the toner hopper 124. As a result, toner is replenished from the toner hopper 124 to the toner supply port 122 . If the toner concentration is equal to or higher than a predetermined toner concentration, no toner replenishment control signal is output.

When the toner is developed from the developing roller 108 onto the photosensitive drum 413, the toner density decreases, but since it takes time for the toner density detection sensor 140 to detect it, toner is replenished according to the input image data. First, the image reading section 10 generates input image data based on the reading result by the document image scanning device 12. Next, the image processing section 30 performs various digital image processing on the input image data generated by the image reading section 10, and outputs the image signal after the image processing as output image information. Next, the control unit 70 calculates the amount of toner consumed in the image forming process by the image forming unit 40 based on the output image information output from the image processing unit 30. Finally, the control unit 70 outputs a toner replenishment control signal requesting replenishment of toner to the toner hopper 124 according to the calculated toner consumption amount.

As a result, toner is replenished from the toner hopper 124 to the toner supply port 122 .

Note that in the present embodiment, the control unit 70 calculates the consumption amount of each color toner of Y component, M component, C component, and K component based on the output image information, and calculates the consumption amount corresponding to the calculated consumption amount. The developing device 412 is controlled to be supplied with the same amount of toner.

[Checking the operation of toner replenishment]
The control unit 70 determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range. Note that it may be determined whether or not the toner concentration is equal to or higher than a predetermined toner concentration (lower limit of toner concentration that is allowable). If the result of this determination is that the toner concentration is equal to or higher than the predetermined toner concentration, the control unit 70 determines that the toner replenishment operation has been performed normally. Then, the toner supply confirmation operation ends.

On the other hand, if the toner concentration detected by the toner concentration detection sensor 140 is not higher than the predetermined toner concentration, the control unit 70 determines that the toner replenishment operation is not performed normally, and repairs the toner replenishment mechanism or repairs the toner hopper 124. The display unit 21 displays a message that the toner bottle provided above the toner bottle that supplies toner to the toner hopper 124 needs to be replaced (toner replenishment error), and the toner replenishment confirmation operation ends. Note that the control section 70 may output audio information indicating a toner replenishment error to the speaker, or may display an abnormality in toner concentration on the display section 21 and interrupt image printing.

[Toner density detection control]
FIG. 4 is a functional block diagram for executing toner concentration detection control according to the embodiment.

Referring to FIG. 4, the CPU 71 includes a stop period acquisition section 90, an operation period acquisition section 92, a period adjustment section 94, a toner concentration abnormality determination section 96, an environmental information acquisition section 98, and a toner concentration storage section 99. including.

The stop period acquisition unit 90 obtains the stop period of the stirring screw 105 of the developing device 412. Specifically, the stop period acquisition unit 90 periodically (every 10 ms) monitors the state of the developing device 412 and obtains the period in which the stirring screw 105 is in the stop state. For example, the stop period acquisition section 90 periodically monitors the state of the developing device 412, uses the clock 74 to store the time when the developing device 412 stops in the storage section 82, etc., and stores the time when the developing device 412 stops operating next time. The stop period of the stirring screw 105 of the developing device 412 may be obtained based on the difference from the time.

The operation period acquisition unit 92 acquires the operation period of the stirring screw 105 of the developing device 412. Specifically, the operating period acquisition unit 92 periodically (every 10 ms) monitors the state of the developing device 412 and obtains the period of the operating state of the stirring screw 105. For example, the operating period acquisition section 92 periodically monitors the state of the developing device 412, stores the time when the developing device 412 starts operating in the storage section 82, etc. using the clock 74, and calculates the difference from the current time. The operating period of the stirring screw 105 of the developing device 412 may be obtained based on the difference between the time when the developing device 412 starts operating and the time when the stirring screw 105 of the developing device 412 stops. The operating period may also be obtained by

The toner concentration abnormality determining section 96 determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range. Note that it may be determined whether or not the toner concentration is equal to or higher than a predetermined toner concentration (lower limit of toner concentration that is allowable).

Further, in this example, the toner concentration abnormality determination section 96 determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range, depending on the length of the suspension period acquired by the suspension period acquisition section 90. to judge. More specifically, when the stop period acquired by the stop period acquisition section 90 is less than a predetermined period, the toner concentration abnormality determination section 96 determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range. If the stop period acquired by the stop period acquisition unit 90 is equal to or longer than a predetermined period, it is not determined whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range.

The environmental information acquisition unit 98 acquires environmental information such as the temperature and/or humidity around the developing device 412 using a thermometer, a hygrometer, or the like.

The toner concentration storage section 99 stores the toner concentration detected by the toner concentration detection sensor 140 before the developing device 412 is in a stopped state in the storage section 82 or the like.

The period adjustment section 94 adjusts the value of the predetermined period determined by the toner concentration abnormality determination section 96 based on a predetermined condition.

FIG. 5 is a diagram illustrating the relationship between the stop period and the toner density level in the image forming apparatus according to the embodiment.

As shown in FIG. 5, the longer the period when the developing device 412 is stopped, the lower the toner concentration becomes.

The toner concentration detection sensor 140 detects that even if the toner concentration of the developer in the developing device 412 is the same, the toner concentration of the developer that has been left for a long time is lower than the toner concentration of the developer that has been sufficiently stirred. To detect.

Therefore, in this example, if the agitation screw 105 of the developing device 412 is stopped for a long time, the toner concentration determination process is not executed because the toner concentration may not be detected with high accuracy.

FIG. 6 is a flow diagram illustrating toner density detection control processing in the image forming apparatus according to the embodiment.

Referring to FIG. 6, control unit 70 determines whether or not image forming apparatus 1 is powered on (step S0).

In step S0, when the image forming apparatus 1 is powered on (YES in step S0), the control unit 70 obtains a flow stop period (step S2). The stop period acquisition unit 90 obtains the stop period of the stirring screw 105 of the developing device 412. The stop period acquisition unit 90 acquires current time information from the clock 74. The stop period acquisition unit 90 acquires information on the previous time when the developing device 412 was stopped, which is stored in the storage unit 82 or the like. Then, the stop period obtaining unit 90 obtains the stop period of the stirring screw 105 of the developing device 412 based on the difference between the time when the developing device 412 stopped and the current time information stored in the storage unit 82 or the like.

Next, the control unit 70 sets a period serving as a determination threshold (step S8). The period adjustment unit 94 sets a period that becomes a determination threshold. For example, the predetermined period serving as the determination threshold may be set to 10 hours. The predetermined period can be adjusted based on predetermined conditions.

Next, the control unit 70 detects toner density (step S10). The toner concentration detection sensor 140 detects the toner concentration of the developing device 412.

Next, the control unit 70 determines whether the period during which the stirring screw 105 of the developing device 412 is stopped is longer than the period of the determination threshold (step S12). The toner concentration abnormality determination unit 96 determines whether the stop period acquired by the stop period acquisition unit 90 is longer than a predetermined period (10 hours).

In step S12, if the control unit 70 determines that the stop period of the stirring screw 105 of the developing device 412 is not longer than the determination threshold period (NO in step S12), the process proceeds to step S22. In step S22, the control unit 70 determines whether the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range (step S22). If the toner concentration abnormality determination unit 96 determines that the stop period acquired by the stop period acquisition unit 90 is not longer than the predetermined period (10 hours), the toner concentration abnormality determination unit 96 determines that the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range. Determine whether it fits or not. That is, in this case, normal toner density detection control is executed.

Next, in step S22, if the control unit 70 determines that the toner concentration detected by the toner concentration detection sensor 140 is within the predetermined range (YES in step S22), the process proceeds to step S16. When the toner concentration abnormality determination unit 96 determines that the toner concentration detected by the toner concentration detection sensor 140 is within a predetermined range, the toner concentration abnormality determination unit 96 continues its operation without proceeding to abnormality processing because it is normal. That is, in this case, normal toner density detection control is executed.

On the other hand, if the control unit 70 determines in step S22 that the toner concentration detected by the toner concentration detection sensor 140 is not within the predetermined range (NO in step S22), the process proceeds to step S26. In step S26, the control unit 70 executes toner density abnormality processing. Specifically, when the toner concentration abnormality determination unit 96 determines that there is an abnormality, it is necessary to repair the toner replenishment mechanism or replace the toner bottle provided above the toner hopper 124 that supplies toner to the toner hopper 124. The display unit 21 may also display a message to the effect (toner replenishment error). Alternatively, even if audio information indicating a toner replenishment error is output to the speaker, the toner concentration abnormality determination unit 96 displays the toner concentration abnormality on the display unit 21 and instructs the image forming unit 40 to interrupt image printing. It's okay. Thereby, if it is determined that the toner density is not within a predetermined range, the developed toner image may not be transferred to the recording medium and output.

Then, the process ends (end).
On the other hand, in step S12, if the control unit 70 determines that the stop period of the stirring screw 105 of the developing device 412 is longer than the period of the determination threshold value (YES in step S12), the controller 70 controls the stirring screw 105 of the developing device 412 to A flow operation period is acquired (step S13). The operation period acquisition section 92 acquires the flow operation period of the stirring screw 105 of the development device 412 based on the difference between the time when the development device 412 starts operating and the current time, which is stored in the storage section 82 or the like.

Next, the control unit 70 determines whether the period of flow operation by the stirring screw 105 of the developing device 412 is longer than the period of the return threshold (step S14). The toner concentration abnormality determination section 96 determines whether the fluid operation period acquired by the operation period acquisition section 92 is longer than a predetermined period (10 minutes) that is the period of the recovery threshold.

If the control unit 70 determines that the period of flow operation by the stirring screw 105 of the developing device 412 is longer than the return threshold period (YES in step S14), the process proceeds to step S22, and the control unit 70 detects the toner concentration. It is determined whether the toner concentration detected by the sensor 140 is within a predetermined range (step S22). The same applies to subsequent processing. That is, if the period of flow operation by the stirring screw 105 of the developing device 412 is longer than the period of the return threshold, it is determined that the developer has been sufficiently stirred by the stirring screw 105 of the developing device 412, and therefore, normally The toner density abnormality determination process is executed.

On the other hand, in step S14, if the control unit 70 determines that the period of flow operation by the stirring screw 105 of the developing device 412 is not longer than the period of the return threshold, the control unit 70 does not execute the toner concentration abnormality determination process. The process advances to step S16. In other words, in this example, if the period of flow operation by the stirring screw 105 of the developing device 412 is not longer than the period of the return threshold, it is determined that the developer is not sufficiently stirred, so that normal toner is not used. Does not perform density abnormality determination processing.

In step S16, the control unit 70 determines whether the developer is flowing (step S16). Specifically, the control unit 70 determines whether the stirring screw 105 of the developing device 412 is operating.

If the control unit 70 determines that the developer is flowing (YES in step S16), it measures the flow time (step S18). Specifically, the operating period acquisition unit 92 uses the clock 74 to store the time when the developing device 412 starts operating in the storage unit 82 or the like.

Then, the process advances to the next step S20, and it is determined whether or not the process has ended (step S20).

If it is determined in step S20 that the process has not been completed (NO in step S20), the process returns to step S10 and the above process is repeated.

On the other hand, if it is determined in step S20 that the process has ended (YES in step S20), the process ends (end).
On the other hand, if the control unit 70 determines in step S16 that the developer is not flowing (NO in step S16), it stores the stop time (step S28). The stop period acquisition unit 90 uses the clock 74 to store the time when the developing device 412 stops in the storage unit 82 or the like.

Then, the process proceeds to step S20, and it is determined whether the process has ended (step S20). Since the subsequent processing is the same as that described above, detailed description thereof will not be repeated.

If the agitation screw 105 of the developing device 412 is stopped for a long time due to this process, the toner concentration determination process is not executed because the toner concentration may not be detected with high accuracy. With this simple method, it is possible to prevent false detection of toner concentration abnormality.

In this example, a case has been described in which the above processing is executed when the power is turned on, but the present invention is not limited to this, and can be similarly applied to, for example, a return from sleep or an error return.

(Modification 1)
FIG. 7 is a diagram illustrating the relationship between humidity and toner density level in an image forming apparatus according to Modification 1 of the embodiment.

As shown in FIG. 7, the toner concentration detection sensor 140 detects that the higher the humidity, the more the toner concentration of the developer in the developing device 412 is the same, compared to the toner concentration of the developer when the humidity is low. Detection is low. Note that the same applies to temperature.

Therefore, environmental information such as humidity or temperature may be acquired and a period serving as a determination threshold may be set based on the environmental information. Specifically, the period adjustment unit 94 may adjust the predetermined period to be shorter than 10 hours if the environmental information is obtained and the environment is high temperature and humidity, for example.

Through this process, it is possible to further suppress false detection of toner concentration by taking environmental information into consideration.

(Modification 2)
FIG. 8 is a diagram illustrating the relationship between the stop period and the toner density level in the image forming apparatus according to the second modification of the embodiment.

As shown in FIG. 8, two types of characteristics are shown, and the dotted line waveform is the characteristic when the developer flowing period of the developing device 412 is long. The solid line waveform is a characteristic when the developer flowing period of the developing device 412 is short.

Even if the toner concentration of the developer in the developing device 412 is the same, the toner concentration detection sensor 140 compares the toner concentration of the developer that has been left for a long time (long stop period) with the toner concentration of the developer that has been sufficiently stirred. The toner concentration is detected to be low compared to the toner concentration.

On the other hand, regarding the toner concentration of the developer whose stop period is long, if the flow period of the developer in the developing device 412 before stopping is long, the flowing period of the developer in the developing device 412 before stopping is short. The degree of change is smaller than that of the state.

Therefore, information on the flow period of the developer in the developing device 412 before it is stopped may be obtained, and the period serving as the determination threshold may be set based on the information on the flow period. Specifically, the period adjustment unit 94 acquires information on the flow period of the developer in the developing device 412 and sets the predetermined period to a period longer than 10 hours if the flow period is long, for example. You may adjust it so that

Through this process, it is possible to further suppress false detection of toner concentration by considering the period during which the developer in the developing device 412 flows before it is stopped.

(Modification 3)
FIG. 9 is a diagram illustrating the relationship between the stop period and the toner density level in the image forming apparatus according to the third modification of the embodiment.

As shown in FIG. 9, two types of characteristics are shown, and the dotted line waveform is the characteristic when the toner concentration of the developer in the developing device 412 is high. The solid line waveform is a characteristic when the toner concentration of the developer in the developing device 412 is low.

Even if the toner concentration of the developer in the developing device 412 is the same, the toner concentration detection sensor 140 compares the toner concentration of the developer that has been left for a long time (long stop period) with the toner concentration of the developer that has been sufficiently stirred. The toner concentration is detected to be low compared to the toner concentration.

On the other hand, when the toner concentration of the developer in the developing device 412 is high and when the toner concentration of the developer in the developing device 412 is low, the toner concentration of the developer in the developing device 412 is different. When the value is high, the degree of change is smaller than when the toner concentration of the developer in the developing device 412 is low.

Therefore, the information on the toner concentration value of the developer may be acquired, and the period serving as the determination threshold may be set based on the information on the toner concentration value of the developer. Specifically, the period adjustment section 94 acquires the toner concentration information stored by the toner concentration storage section 99 in the storage section 82 or the like. The period adjustment unit 94 acquires information on the toner concentration value of the developer and adjusts the predetermined period to be longer than 10 hours, for example, when the toner concentration value of the developer is high. Good too.

Through this process, it is possible to further suppress erroneous detection of toner concentration by taking into consideration information on the value of toner concentration of the developer.

As described above, since the developing device 412 is provided for each of the image forming units 41Y, 41M, 41C, and 41K, the above processing can be executed for each image forming unit.

Furthermore, if it is determined that some of the image forming units 41 are abnormal in toner density, the image forming process may be executed except for the image forming units 41 that are determined to be abnormal. For example, if it is determined that there is an abnormality in the toner density of the Y component developing device 412, color printing may be prohibited and printing may be enabled in a mode in which only monochrome printing is performed.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

Reference Signs List 1 image forming device, 10 image reading section, 11 automatic document feeder, 12 document image scanning device, 21 display section, 22 operation section, 30 image processing section, 40 image forming section, 41 image forming unit, 42 intermediate transfer unit , 43 toner image density detection sensor, 50 transport unit, 51 paper feed unit, 52 transport mechanism, 53 paper discharge unit, 60 fixing unit, 70 control unit, 72 ROM, 73 RAM, 74 clock, 81 communication unit, 82 storage unit , 90 stop period acquisition section, 92 operation period acquisition section, 94 period adjustment section, 96 toner concentration abnormality determination section, 98 environmental information acquisition section, 99 toner concentration storage section.

Claims (8)

an image carrier on which an electrostatic latent image is formed;
a developing device that develops the electrostatic latent image on the image carrier into a toner image;
a toner concentration detection section that detects the toner concentration of the developer in the developing device;
a fluidizing section that fluidizes the developer in the developing device;
a stop period acquisition unit that obtains a previous stop period during which the flow section was in a stopped state ;
a toner concentration abnormality determination unit that determines whether the toner concentration detected by the toner concentration detection unit is within a predetermined range;
The toner concentration abnormality determination section includes:
When the stop period acquired by the stop period acquisition section is less than a predetermined period, it is determined whether the toner concentration detected by the toner concentration detection section is within a predetermined range, and the stop period acquired by the stop period acquisition section is determined. If the stop period is longer than a predetermined period, it is not determined whether the toner concentration detected by the toner concentration detection section is within a predetermined range;
a period adjustment unit that adjusts the predetermined period based on predetermined conditions;
further comprising a toner concentration storage section that stores the toner concentration before the flow section is in a stopped state,
In the image forming apparatus, the period adjustment section adjusts the predetermined period based on the toner concentration stored in the toner concentration storage section . It further includes an environmental information acquisition unit that acquires humidity or temperature,
The image forming apparatus according to claim 1, wherein the period adjustment section adjusts the predetermined period based on humidity or temperature acquired by the environmental information acquisition section. further comprising an operation period acquisition unit that acquires an operation period during which the flow section was in an operation state before the image forming apparatus stopped ,
The image forming apparatus according to claim 1, wherein the period adjustment section adjusts the predetermined period based on the operation period acquired by the operation period acquisition section. The toner concentration abnormality determining section determines whether there is a toner concentration abnormality after causing the developer in the developing device to flow in the flowing section when the stop period obtained by the stop period obtaining section is longer than a predetermined period. The image forming apparatus according to claim 1. It further includes a print forming section that transfers and outputs the developed toner image to a recording medium,
The image forming unit according to claim 1, wherein the print forming unit suspends processing when the toner density abnormality determining unit determines that the toner density detected by the toner density detecting unit is not within a predetermined range. Device. A plurality of the image carriers are provided,
A plurality of the developing devices are provided, each corresponding to the plurality of image carriers,
A plurality of the toner concentration detection sections are provided respectively corresponding to the plurality of developing devices,
A plurality of said flow parts are provided respectively corresponding to said plurality of developing devices,
A plurality of stop period acquisition units are provided, each of which corresponds to a plurality of flow parts and obtains a previous stop period during which the corresponding flow part was in a stopped state,
A plurality of toner concentration abnormality determination units are provided, each corresponding to a plurality of stop period acquisition units,
If the stop period acquired by the corresponding stop period acquisition section is less than a predetermined period, each of the toner concentration abnormality determination sections determines whether the toner concentration detected by the corresponding toner concentration detection section is within a predetermined range. If the stop period acquired by the corresponding stop period acquisition section is equal to or longer than a predetermined period, it is determined whether the toner concentration detected by the corresponding toner concentration detection section is within a predetermined range. The image forming apparatus according to claim 1, wherein the image forming apparatus does not make any judgment. 7. The image forming apparatus according to claim 1, wherein the developer in the developing device is a two-component developer containing toner and a magnetic carrier. Image formation including an image carrier on which an electrostatic latent image is formed, a developing device that develops the electrostatic latent image on the image carrier into a toner image, and a fluidizing section that causes developer in the developing device to flow. A method for controlling a device, the method comprising:
detecting the toner concentration of the developer in the developing device;
obtaining a previous stop period during which the flow section was in a stop state;
a step of determining whether the detected toner concentration is within a predetermined range;
In the step of determining, if the obtained stop period is less than a predetermined period, it is judged whether the detected toner concentration is within a predetermined range, and if the obtained stop period is greater than or equal to the predetermined period, the detected toner concentration is determined to be within a predetermined range. without determining whether the toner density is within a predetermined range.
adjusting the predetermined period based on predetermined conditions;
storing the toner concentration before the flow section is in a stopped state;
The method for controlling an image forming apparatus further comprises the step of adjusting the predetermined period based on the stored toner density.

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