JP5652162B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, as the image forming apparatus, for example, an electrostatic latent image formed on the surface of a photosensitive drum is visualized using a toner by a developing device, and the toner image is recorded directly or via an intermediate transfer member. Some are configured to form an image by transferring and fixing on a sheet.

  By the way, in such an image forming apparatus, when an image with a low image density is formed frequently, the toner in the developing device is hardly consumed and the time in which the toner stays inside becomes long, and the toner is excessively charged by friction. Deteriorated image quality, such as the amount of toner that is electrostatically attached to the electrostatic latent image formed on the surface of the photosensitive drum and develops the electrostatic latent image is reduced, and the image density is reduced. Cause.

  In view of this, for example, Japanese Patent Application Laid-Open No. 2004-1706604, Japanese Patent Application Laid-Open No. 2008-76428, or Japanese Patent Application Laid-Open No. 2009-265604 can be used as a technique that can suppress image quality deterioration due to developer deterioration in the image forming apparatus. Have already been proposed.

An image forming apparatus according to the above Japanese Patent Application Laid-Open No. 2004-170660 includes a latent image carrier for holding an electrostatic latent image on its outer peripheral surface,
Charging means for uniformly charging the surface of the latent image carrier;
Exposure means for exposing the surface of the uniformly charged latent image carrier to form an electrostatic latent image; and
At least a developer storage section for storing a developer for developing an electrostatic latent image, an agitating / conveying means for agitating / conveying the stored developer, and the developer being held in a developable state Developing means provided with a developer carrier to be supplied to the image carrier;
A transfer means for transferring the toner image on the latent image carrier visualized by the developing means onto the image carrier;
In an image forming apparatus using a two-component developer containing a magnetic carrier and a non-magnetic toner,
The developing means includes a plurality of types of developer characteristic measuring means, and is configured to measure the degree of deterioration of the developer by comparing detection outputs from the respective measuring means.

Further, a developing device according to the above-mentioned Japanese Patent Application Laid-Open No. 2008-76428 includes a storage unit that stores a developer including toner and a carrier,
A developer carrying member carrying the developer;
In a developing device provided with stirring and conveying means for conveying the developer in the container while stirring,
The detection unit is configured to detect the volume of the developer stored in the storage unit.

Furthermore, an image forming method according to the above-mentioned JP2009-265604A includes an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier,
A developing step of forming a toner image on the electrostatic latent image;
An image forming method comprising: a transfer step of forming an electric field between the electrostatic latent image carrier and the intermediate transfer member to transfer the toner image to the intermediate transfer member;
The image forming method includes:
A first detection step of detecting an image density of an image transferred with a predetermined reference electric field;
A second detection step of detecting an image density of an image transferred with an electric field lower or higher than the reference electric field,
After the first detection step and the second detection step, a processing step for processing the deteriorated toner is performed based on the image density detected in each detection step.

JP 2004-170660 A JP 2008-76428 A JP 2009-265604 A

  Incidentally, the problem to be solved by the present invention is to provide an image forming apparatus capable of determining the deterioration state of the developer and maintaining good image quality.

According to the first aspect of the present invention, there is provided an image forming unit that forms an image by forming an electrostatic latent image on an image holding member into a visible image using a developer by a developing unit, and a toner in the developing unit. A toner density detecting means for detecting density, an image density detecting means for detecting the density of a toner image for image density detection formed by the image forming means, a detection result of the toner density detecting means, and the image density detecting means. On the basis of the detection result, a control means for controlling image forming conditions so that a predetermined image density is obtained by the image forming means, and a toner density in the developing means detected by the toner density detecting means. and a predetermined concentration or more, and based on by that control to the control means, the image forming operation by the image forming condition corresponding to the control state when the toner is deteriorated To continue order determined time or more, a recovery means for performing recovery operation to recover the quality of an image formed by said image forming means, selection means for selecting the image quality mode, selected by said selection means An image forming system comprising: a second changing unit configured to change at least one of an image forming condition corresponding to a control state when the toner is deteriorated or the predetermined time based on an image quality mode. Device.

According to a second aspect of the present invention, there is provided an environment detection unit that detects an environmental condition in which the image forming apparatus is installed;
2. The apparatus according to claim 1, further comprising: a first changing unit that changes the predetermined density and the predetermined image forming condition based on a detection result of the environment detection unit. An image forming apparatus.

The image forming condition controlled by the control unit may be at least one of the developing condition of the developing unit of the image forming unit or the toner density in the developing unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

According to a fourth aspect of the present invention, the image forming condition controlled by the control unit is a transfer bias of a transfer unit that transfers a toner image formed by the image forming unit. Item 3. The image forming apparatus according to any one of Items 1 to 2 .

Further, the invention described in claim 5 is characterized in that the recovery operation executed by the recovery means is a forced consumption operation for forcibly consuming the developer of the developing means. The image forming apparatus according to any one of the above.

According to the first aspect of the present invention, the execution condition of the image quality recovery operation can be changed according to the selected image quality mode.

  In addition, according to the invention described in claim 2, it is possible to determine the deterioration state of the developer and maintain good image quality even when the environment changes compared to the case where the present configuration is not provided. .

According to the second aspect of the present invention, it is possible to execute an image quality restoration operation suitable for the selected image quality mode even if the environment changes.

Furthermore, according to the invention described in claim 3 , a predetermined image density can be obtained.

Further, according to the invention described in claim 4, the image density can be obtained predetermined.

Further, according to the fifth aspect of the present invention, the forced consumption operation suitable for the selected image quality mode can be executed even when an image with a low image density is frequently formed.

It is explanatory drawing which shows operation | movement of the image forming apparatus which concerns on Embodiment 1 of this invention. 1 is a configuration diagram illustrating a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention; FIG. It is a block diagram which shows an image formation part. FIG. 3 is a configuration diagram illustrating a toner patch. 5 is a graph showing a relationship between a developing electric field and a toner patch density. 6 is a graph showing a relationship between a toner charge amount and a developing electric field. 6 is a graph showing the relationship between toner density and toner charge amount. 6 is a graph showing a relationship between toner density and a developing electric field. 1 is a block diagram showing a control device of an image forming apparatus according to Embodiment 1 of the present invention. 3 is a graph showing a relationship between a surface potential of a photosensitive drum and a developing bias voltage. It is explanatory drawing which shows the recovery operation performed in the image forming apparatus which concerns on Embodiment 1 of this invention. 5 is a graph showing a relationship between a transfer electric field and a toner patch density. 3 is a flowchart showing the operation of the image forming apparatus according to Embodiment 1 of the present invention. 3 is a flowchart showing the operation of the image forming apparatus according to Embodiment 1 of the present invention. 3 is a flowchart showing the operation of the image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows the image forming apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the control apparatus of the image forming apparatus which concerns on Embodiment 2 of this invention. It is a graph which shows control operation of the image forming apparatus concerning Embodiment 2 of this invention. It is a block diagram which shows the control apparatus of the image forming apparatus which concerns on Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 shows a tandem full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. The tandem full-color printer includes an image reading device and is configured to function as a full-color copier. However, the tandem full-color printer may not include the image reading device. In addition, this full-color printer has a high productivity, which is the number of recording sheets on which image formation is possible per unit time. For example, 100 sheets per minute on an A4 size LEF (Long Edge Feed) recording sheet. An image can be formed to some extent. However, the present invention is not limited to a high-speed tandem image forming apparatus.

  In FIG. 2, reference numeral 1 denotes a main body of the image forming apparatus, and an image reading device 4 that reads an image of the document 2 is disposed at one upper end (left end in the illustrated example) of the image forming apparatus main body 1. ing. The image reading device 4 illuminates a document 2 placed on a platen glass 5 while being pressed by a document pressing member 3 with a light source 6, and reflects a reflected light image from the document 2 with a full rate mirror 7 and a half rate mirror 8. The image reading element 11 reads the image of the document 2 at a predetermined dot density by performing scanning exposure on the image reading element 11 made of a CCD or the like through a reduction optical system including the image forming lens 10 and the image forming lens 10. It is configured.

  The image of the document 2 read by the image reading device 4 is sent to the image processing device 12 as, for example, three-color image data of red (R), green (G), and blue (B) (each 8 bits), In this image processing device 12, predetermined image processing such as shading correction, position shift correction, lightness / color space conversion, gamma correction, frame removal, color / moving editing, etc. is performed on the image data of the document 2. The In addition, image data that has been subjected to predetermined image processing by the image processing device 12 as described above is similarly processed by the image processing device 12 to yellow (Y), magenta (M), cyan (C), black (K) ( Each image data is converted into 4-bit image data of 8 bits). Of course, the image data input to the image processing device 12 may be sent from a personal computer or the like via a communication line (not shown).

  By the way, this embodiment is configured to include a plurality of image forming means for forming images using toners having different colors.

  That is, inside the image forming apparatus main body 1 according to this embodiment, as shown in FIG. 2, as a plurality of image forming means, yellow (Y), magenta (M), cyan (C), black (K The image forming units 13Y, 13M, 13C, and 13K corresponding to each color are arranged in parallel at a certain interval along the horizontal direction, and these image forming units 13Y, 13M, 13C, and 13K are arranged in parallel. For example, a specific color image forming unit 13CT that forms an image using transparent toner (CT) is disposed at an equal interval from the other image forming units. As described above, the transparent toner image forming unit 13CT is arranged on the upstream side so that an image made of transparent toner used for giving gloss to a full-color image is a full-color image on the recording medium. This is because the image is transferred and fixed on the surface of the image. Further, by disposing the transparent toner image forming unit 13CT on the upstream side, when the transparent toner image is not formed, downstream yellow (Y), magenta (M), cyan (C), black (K The image forming operation can be started immediately in each of the image forming units 13Y, 13M, 13C, and 13K), and even if the image forming unit 13CT of transparent toner is arranged, it is desirable that the productivity is not lowered.

  The arrangement order of the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, and 13K and the transparent toner image forming unit 13CT is shown in the drawing. The transparent toner image forming unit 13CT may be used instead of the transparent toner image forming unit 13CT, or a plurality of specific toners such as color toners having different densities may be used together with the transparent toner image forming unit 13CT. A color image forming unit may also be arranged. In addition, one or a plurality of specific color image forming units may be mounted on the main body of the image forming apparatus so as to be exchangeable with other image forming units as necessary.

  Examples of the transparent toner include resins constituting toners used in the other image forming portions 13Y, 13M, 13C, and 13K of yellow (Y), magenta (M), cyan (C), and black (K). What remove | excluded the pigment as a coloring agent from material is used. The image processing apparatus 12 outputs image data corresponding to the transparent toner to the transparent toner image forming unit 13CT. The image data corresponding to the transparent toner is, for example, one that forms a transparent toner image uniformly at a predetermined image density on the entire surface of the recording medium, or yellow (Y), magenta (M), cyan (C). , One that forms a transparent toner image uniformly at a predetermined image density only in an area where image data of each color of black (K) exists, or yellow (Y), magenta (M), cyan (C) The transparent toner image may be uniformly formed at a predetermined image density only in an area where no image data of each color of black (K) exists.

These five image forming units 13CT , 13Y, 13M , 13C, and 13K are basically the same except for the type of toner to be used, as shown in FIG. 2, and are roughly driven at a predetermined rotational speed along the direction of arrow A. A photosensitive drum 15 as an image holding member, a scorotron 16 as a primary charging means for uniformly charging the surface of the photosensitive drum 15, and an image corresponding to each color on the surface of the photosensitive drum 15. Then, an image exposure device 14 as a latent image forming means for forming an electrostatic latent image, and a developing device 17 as a developing means for developing the electrostatic latent image formed on the photosensitive drum 15 with a corresponding color toner. And a cleaning device 18 and a primary transfer roll 26 as transfer means for transferring a toner image formed on the photosensitive drum 15 onto an intermediate transfer belt 25 described later.

  As shown in FIG. 2, the image exposure device 14 modulates the semiconductor laser 19 according to the image data, and emits a laser beam LB from the semiconductor laser 19 according to the image data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflecting mirrors 20 and 21, and the focal length is adjusted according to the scanning angle by an unshown f-θ lens. Then, scanning exposure is performed on the photosensitive drum 15 as an image holding member through a plurality of reflecting mirrors 23 and 24 and the like.

From the image processing device 12, the image forming unit 13CT for each color of transparent toner (CT), yellow (Y), magenta, cyan (C), and black (K) is provided. , 13Y, 13M , 13C, 13K image exposure device 14CT , 14Y, 14M , 14C, and 14K, image data corresponding to each color is sequentially output. These image exposure apparatuses 14CT , 14Y, 14M , 14C, and 14K, the laser light LB emitted in accordance with the image data corresponds to the corresponding photosensitive drum 15CT. , 15Y, 15M , 15C, 15K are exposed to scanning along the main scanning direction, and the photosensitive drum 15CT is exposed. , 15Y, 15M , 15C, and 15K, electrostatic latent images are formed. Each of the photosensitive drums 15CT , 15Y, 15M , 15C, and 15K, the electrostatic latent image is developed by the developing device 17CT. , 17Y, 17M , 17C, and 17K, the toner images are developed as transparent toner (CT), yellow (Y), magenta, cyan (C), and black (K) toner images, respectively.

Development device 17CT , 17Y, 17M 17C and 17K, as shown in FIG. 3, for example, a two-component developing device in which a two-component developer 171 composed of toner and carrier (magnetic particles) is accommodated in the developing device main body 170 is used. It is done. The toner is supplied from the toner cartridges 175CT to 175K (see FIG. 2) to the inside of the developing device main body 170 at a predetermined timing. The toner supplied into the developing device main body 170 is agitated with the developer 171 in the developing device main body 170 by the two agitators 172 and 173 for stirring and conveying the developer, is frictionally charged, and circulates. In the meantime, the developer 171 is supplied to the developing roll 174 in a state where the layer thickness of the developer 171 is regulated by a layer thickness regulating member (not shown), and as a magnetic brush of the developer 171 formed on the surface of the developing roll 174 15 is conveyed to a developing area facing the surface of the photosensitive drum 15, and is used for developing the electrostatic latent image formed on the surface of the photosensitive drum 15.

Each developing device 17CT of the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) , 17Y, 17M 17C and 17K, as shown in FIG. 3, a toner concentration sensor 175 as a toner concentration detecting means for detecting the toner concentration of the two-component developer 171 is provided at the bottom of the developing device main body 170. As the toner density sensor 175, for example, the density of toner as a nonmagnetic material contained in the two-component developer 171 is detected by detecting the magnetic permeability of the two-component developer 171 accommodated in the developing device main body 170. The one that detects is used. However, the toner density sensor 175 may be of any other type as long as the toner density in the developing device main body 170 can be detected.

  The transparent toner (CT), yellow (Y), and magenta (M) are sequentially formed on the photosensitive drums 15CT, 15Y, 15M, 15C, and 15K of the image forming units 13CT, 13Y, 13M, 13C, and 13K. , Cyan (C), and black (K) toner images, as shown in FIG. 2, are intermediate transfer images as intermediate transfer members disposed below the image forming units 13CT, 13Y, 13M, 13C, and 13K. Primary transfer is performed on the belt 25 in a state of being superposed on each other by primary transfer rolls 26CT, 26Y, 26M, 26C, and 26K.

  The intermediate transfer belt 25 includes a driving roll 27, a tension applying roll 28, a driven roll 29, a driven roll 30, a back support roll 31 of the secondary transfer unit, and a plurality of rolls including a driven roll 32. The photosensitive drums 15CT, 15Y, 15M, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C, 15C It is driven to circulate at a predetermined speed substantially equal to the rotational speed (circumferential speed) of 15K. As the intermediate transfer belt 25, for example, a flexible synthetic resin film such as polyimide or polyamideimide formed in an endless belt shape is used.

  The transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 25 are intermediately transferred to the back support roll 31. The recording sheet 34, which is secondarily transferred onto a recording sheet 34 as a recording medium and transferred onto the recording sheet 34 as a recording medium by the secondary transfer roll 33 that is in pressure contact with the transfer belt 25, and the toner images of the respective colors are transferred, is transported in a double series. It is conveyed to a fixing device 37 by belts 35 and 36. The recording paper 34 onto which the toner images of the respective colors have been transferred is subjected to a fixing process with heat and pressure by a heating belt 38 and a pressure roll 39 of a fixing device 37, and in the case of single-sided printing, the image forming apparatus main body as it is. 1 is discharged onto a discharge tray 40 provided outside of 1.

  As shown in FIG. 2, the recording paper 34 is, for example, one of a plurality of paper feed trays 41, 42 having a desired size and material, a paper feed roll 43, and a pair of paper transport rolls 44. , 45 are temporarily transported to the registration roll 47 via the paper transport path 46 and stopped. The recording paper 34 supplied from one of the paper feed trays 41 and 42 is sent out to the secondary transfer position of the intermediate transfer belt 25 by a registration roll 47 that is rotationally driven at a predetermined timing.

  Further, when images are formed on both sides of the recording paper 34 by the image forming apparatus, the recording paper 34 on which the image is fixed on one side by the fixing device 37 is not discharged out of the apparatus as it is, but a switching gate (not shown). As a result, the transport path of the recording paper 34 is switched downward and transported to the reverse paper transport path 48 once. Then, the recording paper 34 conveyed to the reversing paper conveyance path 48 is reversed, with the conveyance direction reversed, through the double-sided paper conveyance path 49 and the normal paper conveyance path 46. In this state, the sheet is conveyed again to the secondary transfer position of the intermediate transfer belt 25 and an image is formed on the back surface, and then subjected to a fixing process with heat and pressure by the heating belt 38 and the pressure roll 39 of the fixing device 37. Then, the image is discharged onto a discharge tray 40 provided outside the image forming apparatus main body 1.

  Note that the surface of the photosensitive drum 16 after the primary transfer of the toner image is completed is cleaned by the cleaning device 18. The intermediate transfer belt 25 after the secondary transfer of the toner image is cleaned by a belt cleaning device 50 whose surface is disposed in the vicinity of the drive roll 27.

  In the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, 13M, 13C, and 13K, as shown in FIG. At a predetermined timing, toner images for detecting the image density of transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) (hereinafter referred to as “toner patches”). 70CT, 70Y, 70M, 70C, and 70K are formed, for example, in a halftone having an image density of about 50% or over a plurality of densities of 30% and 60%. These transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) toner patches 70CT, 70Y, 70M, 70C, and 70K are primarily transferred onto the intermediate transfer belt 25. In the state of primary transfer by the transfer rolls 25CT, 25Y, 25M, 25C, and 25K, as shown in FIG. 2, the black (K) image forming unit 13K has the downstream side along the moving direction of the intermediate transfer belt 25. It is detected by an image density sensor 103 arranged so as to face the intermediate transfer belt 25.

  As the image density sensor 103, for example, the light emitted from the light emitting element is irradiated on the surface of the intermediate transfer belt 25, and the transparent toner (CT), yellow (Y), magenta transferred onto the intermediate transfer belt 25 is used. The light receiving element receives the reflected light of at least one of or both of diffuse reflection and regular reflection from the toner patches 70CT, 70Y, 70M, 70C, and 70K of the respective colors (M), cyan (C), and black (K). Thus, the toner patches 70CT, 70Y, 70M, 70C, and 70K configured to detect the image density are used.

By the way, in the image forming apparatus configured as described above, the transparent toner (CT), yellow (Y), magenta, cyan (C), and black (K) image forming units 13CT. , 13Y, 13M , 13C, 13K, at least one image forming unit 13CT , 13Y, 13M 13C and 13K, for example, if the frequency with which an image with a low image density is formed is high, the toner in the developing device 17 of the corresponding image forming unit 13 is hardly consumed and stays in the developing device main body 170. Becomes longer, the toner is excessively frictionally charged and deteriorates, the amount of toner contributing to the development of the electrostatic latent image formed on the surface of the photosensitive drum 15 is reduced, and the image density is lowered. It causes image quality degradation.

  As described above, when the toner is excessively frictionally charged and deteriorates, as shown in FIG. 5, the toner charge 70CT, 70Y, and 70M for detecting the image density is large because the charge amount due to the frictional charging of the toner is large. , 70C, and 70K are formed on the photosensitive drums 15CT, 15Y, 15M, 15C, and 15K, the larger the toner deterioration state, the larger the charge amount of the toner, and the toner patches 70CT, 70Y, and 70M having the target density. , 70C, and 70K require a large developing electric field.

  As described above, the amount of charge of the toner that accompanies deterioration due to excessive frictional charging of the toner, and the development required to develop the toner patches 70CT, 70Y, 70M, 70C, and 70K having the target density. As shown in FIG. 6, the electric field has a relationship corresponding to a substantially linear shape.

  Further, as shown in FIG. 7, the charge amount of the toner described above varies depending on the toner concentration in the developing device main body 170 depending on the toner deterioration state, and when the toner deterioration state is small, When the toner concentration in the developing device main body 170 increases, the amount of charged electric charge of the toner decreases relatively rapidly. However, even if the toner concentration in the developing device main body 170 increases as the toner deteriorates, the toner concentration increases. The amount by which the amount of charged electric charge decreases is reduced.

Accordingly, the developing devices 17CT for the transparent toner (CT), yellow (Y), magenta, cyan (C), and black (K) are provided. , 17Y, 17M , 17C, and 17K, as shown in FIG. 8, the developing electric field required to obtain the density of the toner patches 70CT, 70Y, 70M, 70C, and 70K of the target value, and each developing device main body 170 in the developing electric field Even when the toner density is detected and the development electric field and the toner density are adjusted, the development electric field required to obtain the density of the target toner patches 70CT, 70Y, 70M, 70C, and 70K is high, and the development electric field 1, when the toner density in each developing device main body 170 is high and continues for a predetermined period or longer as shown in FIG. 1, it is determined that the developer 171 containing toner is in a deteriorated state. Can do.

  In FIG. 8, the hatched area indicates a developing electric field and toner density area where image quality is poor.

  FIG. 9 is a block diagram showing a control circuit of the image forming apparatus according to this embodiment.

  In FIG. 9, reference numeral 100 denotes a control circuit as a control unit composed of a CPU, MCU, or the like that controls the image forming operation of the image forming apparatus. The control circuit 100 is, for example, according to a program stored in the ROM 101. Based on the control data stored in the NVRAM (nonvolatile memory) 102, the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, It also has a function as a control means for controlling the image forming conditions of the respective color toner images in 13M, 13C, and 13K.

  Reference numerals 13CT, 13Y, 13M, 13C, and 13K denote the above-described transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units, respectively. .

  Further, 175CT, 175Y, 175M, 175C, and 175K are transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, 13M, and 13C, respectively. , 13K developing devices 17CT, 17Y, 17M, 17C, and 17K, and toner concentration sensors that detect toner concentrations in the developing devices 17CT, 17Y, 17M, 17C, and 17K are shown.

  Reference numeral 103 denotes a toner patch 70CT formed by the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, 13M, 13C, and 13K. , 70Y, 70M, 70C, and 70K are image density sensors that detect the density on the intermediate transfer belt 25.

  Further, as described above, the control circuit 100 controls the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, 13M, and 13C. The control circuit 100 controls the developing device 17CT based on the detection results of the toner density sensors 175CT, 175Y, 175M, 175C, and 175K and the detection result of the image density sensor 103. , 17Y, 17M, 17C, 17K so that a predetermined image density can be obtained, or the developing conditions of the developing devices 17CT, 17Y, 17M, 17C, 17K, or the developing devices 17CT, 17Y, 17M, 17C, 17K. It also has a function as a control means for controlling at least one of the toner concentrations in the developing device main body 170. .

  That is, the control circuit 100, as shown in FIG. 10, based on the detection result of the image density sensor 103, the transparent toner (CT), yellow (Y), magenta (M), cyan (C), black (K ) Of the respective color toner patches 70CT, 70Y, 70M, 70C, and 70K so as to be equal to a predetermined target density value (target value), the developing devices 17CT, 17Y, 17M, 17C, and 17K. The development state in FIG. 1, for example, the development bias value is controlled.

  In each of the developing devices 17CT, 17Y, 17M, 17C, and 17K, as shown in FIG. 10, an electrostatic latent image formed on the surface of the photosensitive drum 15 is applied to a developing roll 174 by applying a developing bias voltage. Further, reversal development is performed using a negatively charged toner.

  At this time, as shown in FIG. 10, a developing bias voltage controlled by the control circuit 100 is applied to the developing roll 174 of each of the developing devices 17CT, 17Y, 17M, 17C, and 17K, and the photosensitive drum 15 The electrostatic latent image formed on the surface of the photosensitive drum 15 is negatively charged by the developing electric field that is the difference between the exposure portion potential, which is the image portion of the electrostatic latent image formed on the surface, and the developing bias voltage. The toner is reversed and developed with the toner.

  The negative developing bias voltage applied to the developing roll 175 is such that the higher the voltage value (absolute value) of the developing bias voltage, the more photosensitive the toner held as the magnetic brush of the developer 171 on the surface of the developing roll 175. Since the electric field (developing electric field) to be moved toward the photosensitive drum 15 is increased, the electrostatic latent image formed on the surface of the photosensitive drum 15 is developed by controlling the voltage value (absolute value) of the developing bias voltage. The amount of toner, that is, the image density can be controlled.

The transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT, 13Y, 13M, 13C, and 13K are used as means for controlling the image density. Is not limited to controlling the developing bias voltage, but as shown in FIG. 10, in order to control the exposure portion potential that is the image portion of the electrostatic latent image formed on the surface of the photosensitive drum 15, The intensity or area (in the case of area gradation) of the laser beam LB in the image exposure device 14 may be controlled, or the surface potential (V _H ) of the photosensitive drum 15 may be controlled.

  In addition, the control circuit 100 performs each of the image forming sections 13CT, 13Y, 13M, 13C, and 13K for transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K). The developing device 17CT, 17Y, 17M, 17C, or 17K also has a function as a cumulative driving time calculation unit that calculates a cumulative driving time during image formation.

  Further, as shown in FIG. 1, the control circuit 100 determines in advance the toner density in each developing device 17CT, 17Y, 17M, 17C, 17K detected by the toner density sensors 175CT, 175Y, 175M, 175C, 175K. The state in which the developing conditions of the developing devices 17CT, 17Y, 17M, 17C, and 17K after the optimization controlled by the control circuit 100 are equal to or higher than the predetermined developing conditions is predetermined. If any one of the image forming units 13CT, 13Y, 13M, 13C, and 13K is determined to have exceeded the specified time, the image formed by each corresponding image forming unit 13CT, 13Y, 13M, 13C, and 13K It also has a function as a recovery means for executing a recovery operation for recovering the image quality.

  As the recovery operation for recovering the image quality of the image, for example, as shown in FIG. 11, after completion of the image forming operation for forming a series of images 60 or at a predetermined timing such as in the middle of the image forming operation, A predetermined length along the moving direction of the intermediate transfer belt 25 at a predetermined image density (for example, about 50 to 60%) by the image forming units 13CT, 13Y, 13M, 13C, and 13K that satisfy the conditions. The belt-like toner images 62Y, 62M, 62C, 62K, 62CT, 62 of the respective colors of yellow (Y), magenta (M), cyan (C), black (K), transparent toner (CT), and spare (#) are provided. # (Hereinafter referred to as “toner band”) is formed, and the toner bands 62Y, 62M, 62C, 62K, 62CT, 62 # are transferred onto the intermediate transfer belt 25. It is implemented by executing the forced operation of consuming the determined image forming portion of the developer to be deteriorated. The operation of forming the toner bands 62Y, 62M, 62C, 62K, 62CT, 62 # is basically executed under the same conditions as the normal image forming operation, but the toner bands 62Y, 62M, 62C, 62K, 62CT, Of course, as long as 62 # can be formed, it may be executed under conditions different from the normal image forming operation. The toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # transferred onto the intermediate transfer belt 25 are formed without passing the recording paper 34, and are removed by the cleaning device 50 for the intermediate transfer belt 25. The

  The toner bands 62Y, 62M, 62C, 62K, 62CT, 62 # are transferred to the toner band panel 63 set corresponding to the image panel 61, as shown in FIG. A toner image having a predetermined length L along the rotation direction of the photosensitive drum 15 is formed at a predetermined image density (for example, 50 to 60%) over the entire width in the longitudinal direction. The length L of the toner image may be variable so that it can be set as appropriate.

  If any one of the image forming units 13CT, 13Y, 13M, 13C, and 13K does not satisfy the toner band forming conditions, the areas of the opened toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # are displayed. Alternatively, other color toner bands may be formed.

  More specifically, as shown in FIG. 11, the toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # are, for example, yellow, magenta, cyan, and cyan from the head along the traveling direction of the toner band panel 63. It is formed in the order of black, transparent toner, and preliminary. A patch region 64 for forming a patch for detecting image density and image position is provided at the tip of the toner band panel 63. The toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # are formed with a gap 65 required to switch the voltage applied to the primary transfer roll 26 on the downstream side of the patch region 64.

  The toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # are set to, for example, an image density of about 50% or 60%. However, the present invention is not limited to this. Of course, it is also good.

  In the above embodiment, the control operation executed by the control circuit 100 to obtain the target image density is performed by transferring the toner images formed by the image forming units 13CT, 13Y, 13M, 13C, and 13K to the intermediate transfer belt. 24 may be configured to control the transfer bias voltage applied to the primary transfer rolls 26CT, 26Y, 26M, 26C, and 26K to be transferred onto the recording medium 24.

  That is, by controlling the transfer electric field determined by the transfer bias voltage applied to the primary transfer rolls 26CT, 26Y, 26M, 26C, and 26K, as shown in FIG. As the densities of 70CT, 70Y, 70M, 70C, and 70K, it is possible to control so as to obtain a target density (target value).

  In the above configuration, in the image forming apparatus according to this embodiment, it is possible to determine the deterioration state of the developer and maintain good image quality as follows.

  That is, in the image forming apparatus, as shown in FIG. 2, for example, based on the image data input to the image processing apparatus 12, transparent toner (CT), yellow (Y), magenta (M), cyan (C ) And black (K) image forming portions 13CT, 13Y, 13M, 13C, and 13K, toner images of respective colors are formed, and transparent toner formed by these image forming portions 13CT, 13Y, 13M, 13C, and 13K. The toner images of each color (CT), yellow (Y), magenta (M), cyan (C), and black (K) are transferred onto the intermediate transfer belt 25 in a multiple manner, and then from the intermediate transfer belt 25. Secondary transfer is performed collectively on the recording paper 34.

  In the image forming apparatus, as shown in FIG. 2, toners of colors according to image data such as transparent toner (CT), yellow (Y), magenta (M), cyan (C), black (K), etc. The recording sheet 34 onto which the image has been transferred undergoes a fixing process by the fixing device 37 and is discharged onto a discharge tray 40 provided outside the image forming apparatus main body 1.

  At this time, in the image forming apparatus, as shown in FIG. 13, the control circuit 100 sets the transparent toner (CT), yellow (Y) with the flag for determining whether or not the recovery operation can be performed set to “0”. ), Magenta (M), cyan (C), and black (K) image forming sections 13CT, 13Y, 13M, 13C, and 13K, a printing operation is executed (step 101), and a predetermined number of recording sheets 34 are obtained. The image density adjustment operation of the toner patches 70CT, 70Y, 70M, 70C, and 70K is started at a predetermined timing such as after the image is printed (step 102).

  In this toner patch density adjustment operation, as shown in FIG. 4, the transparent toner (CT), yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13CT and 13Y are formed. , 13M, 13C, and 13K, toner patches 70CT, 70Y, 70M, 70C, and 70K of the respective colors are formed, transferred onto the intermediate transfer belt 25, and then the toner patches 70CT, 70Y, 70M, and 70C by the image density sensor 103. , An image density of 70K is detected.

  Then, as shown in FIG. 13, the control circuit 100 determines whether or not the image densities (current values) of the toner patches 70CT, 70Y, 70M, 70C, and 70K are less than a predetermined target value ( Step 103), when it is determined that the density of the toner patches 70CT, 70Y, 70M, 70C, and 60K is less than the target value, it is determined whether or not the developing electric field is less than the upper limit value (Step 104). . Further, when the control circuit 100 determines that the developing electric field is less than the upper limit value, as shown in FIG. 10 according to the difference between the image density of the toner patches 70CT, 70Y, 70M, 70C, and 70K and the target value. After the operation for controlling the developing bias voltage to increase the developing electric field (step 106), it is determined whether or not the developing electric field is less than [upper limit value−set value 1] (step 107). ). Note that the developing electric field is set so that, for example, a value larger than the upper limit value cannot be obtained.

  If the control circuit 100 determines that the image densities (current values) of the toner patches 70CT, 70Y, 70M, 70C, and 70K are equal to or higher than a predetermined target value (step 103), the toner patches 70CT and 70Y are detected. After the operation of controlling the developing bias voltage so as to lower the developing electric field according to the difference between the image density of 70M, 70C, and 70K and the target value (step 105), as shown in FIG. It is determined whether or not the developing electric field is less than [upper limit value−setting value 1] (step 107).

  Next, when the control circuit 100 determines that the developing electric field is less than [upper limit value−set value 1], the flag is set to “0” (step 108), and the developing electric field is set to [upper limit value− If it is determined that the value is equal to or greater than the set value 1], the flag is set to “1” (step 109).

  Thereafter, the control circuit 100 determines whether the toner density is less than the upper limit value (step 110). If it is determined that the toner density is less than the upper limit value, it determines whether the developing electric field is near the upper limit value. A determination is made (step 111). Here, whether or not the developing electric field is in the vicinity of the upper limit value is determined depending on whether or not the developing electric field is equal to or greater than the threshold value of the developing electric field, as shown in FIG. When the control circuit 100 determines that the developing electric field is close to the upper limit value, the corresponding developing device 17 is replenished with toner from the toner cartridge 175 and the operation of increasing the toner density is executed (step 112). ), It is determined whether or not the toner density is near the upper limit (step 113). Here, whether or not the toner density is near the upper limit value is determined by whether or not the toner density is equal to or higher than a threshold value of the toner density, for example, as shown in FIG.

  When the control circuit 100 determines that the toner density is equal to or higher than the upper limit value (step 110) or is determined to be near the upper limit value (step 113), the flag is a value obtained by multiplying the flag by 1. [Flag * 1] is set (Step 114), and if it is determined that the toner density is not close to the upper limit value, the flag is set to [Flag * 0] obtained by multiplying the flag by 0 (Step 115). The image density adjustment operation based on the density detection of the toner patches 70CT, 70Y, 70M, 70C, and 70K is completed (step 116), and the process returns to step 101.

  Here, in the control circuit 100, if the flag is set to “0” in step 108, even if it is determined that the toner density is equal to or higher than the upper limit value or near the upper limit value, In 114, since the flag is set to a value obtained by multiplying the flag by 1 [flag * 1], the flag becomes “0” * 1 = 0.

  On the other hand, the control circuit 100 determines that the flag is “1” in step 109, and sets the flag to a value obtained by multiplying the flag by 1 [flag * 1] in step 114. Is “1” * 1 = 1.

  Therefore, the control circuit 100 determines in step 107 that the developing electric field is equal to or greater than [upper limit value−set value 1]. In step 109, the flag is set to “1”. The flag is set to a value obtained by multiplying the flag by 1 [flag * 1] only when the toner density is determined to be equal to or higher than the upper limit value or when it is determined in step 113 that the toner density is close to the upper limit value. Therefore, the flag is “1” * 1 = 1.

  On the other hand, in the control circuit 100, as shown in FIG. 15, a subroutine for determining whether or not to start the recovery operation of the deteriorated toner is executed in parallel.

  In the subroutine for determining whether or not to start the recovery operation of the deteriorated toner, as shown in FIG. 15, it is determined whether or not the flag is 1 by the control circuit 100 (step 201), and the flag is “1”. Is determined, the short Δ cumulative drive time which is a predetermined unit drive time is added to the cumulative drive time of the developing device 17 for which the flag is determined to be “1” (step 202). If is not 1, the cumulative drive time is cleared (step 203).

  Thereafter, the control circuit 100 determines whether or not the accumulated drive time exceeds the set value (step 204). If it is determined that the accumulated time does not exceed the set value, the control circuit 100 returns to step 201 and accumulates. If it is determined that the time exceeds the set value, the control circuit 1000 determines that the toner is in a deteriorated state, and a recovery operation for the deteriorated toner is started (step 205).

  As the recovery operation of the deteriorated toner, for example, in the image forming units 13CT, 13Y, 13M, 13C, and 13K that satisfy the above-described conditions, intermediate transfer is performed at a predetermined image density (for example, about 50 to 60%). Toner bands of yellow (Y), magenta (M), cyan (C), black (K), transparent toner (CT), and spare (#) colors over a predetermined length along the moving direction of the belt 25. The operation formed by 62Y, 62M, 62C, 62K, 62CT, 62 # is executed.

  As described above, the toner bands 62Y, 62M, 62C, 62K, 62CT, and 62 # of the respective colors are formed by the image forming units 13CT, 13Y, 13M, 13C, and 13K that satisfy the conditions, thereby deteriorating the developing device main body 171. The developed developer (toner) is forcibly consumed, and new toner is supplied from the corresponding toner cartridge 174 to the inside of the developing device main body 171. Therefore, the developing device 17CT, 17Y, 17M, 17C, 17K The development characteristics of the toner can be restored, and the image quality can be maintained satisfactorily.

Embodiment 2
FIG. 16 shows a second embodiment of the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. In the second embodiment, the image forming apparatus is installed. An environmental detection means for detecting an environmental condition to be performed, and a first changing means for changing the predetermined density and the predetermined development condition based on a detection result of the environmental detection means. It is configured.

  That is, in the second embodiment, as shown in FIG. 16, an environmental sensor as an environment detection unit that detects temperature and humidity as the environmental conditions of the environment in which the image forming apparatus is installed inside the image forming apparatus main body 1. 200 is arranged.

  Then, as shown in FIG. 17, the control circuit 100 changes the predetermined density and the predetermined development condition based on at least one of the temperature and humidity of the installation environment detected by the environmental sensor 200. 1 is also configured to function as a change means.

  When the control circuit 100 determines that the environment is a low temperature and low humidity environment based on the temperature and humidity detection results detected by the environment sensor 200, for example, the toner density in the developing device 17 is set to a predetermined density. When it is determined that the developing condition of the developing device 17 controlled by the control circuit 100 is equal to or higher than a predetermined developing condition, a predetermined toner density is obtained as shown in FIG. A value larger than that of the first embodiment is adopted, and a value larger than that of the first embodiment (a value having a large absolute value) is adopted as a predetermined developing condition.

  On the other hand, when the control circuit 100 determines that the environment is a high temperature and high humidity environment based on the temperature and humidity detection results detected by the environment sensor 200, the toner density in the developing device 17 is determined in advance. When it is determined that the developing condition of the developing device 17 that is equal to or higher than the predetermined density and that is controlled by the control circuit 100 is equal to or higher than the predetermined developing condition, the predetermined toner density is set as the predetermined toner density. A value smaller than that of the first embodiment is adopted, and a value smaller than that of the first embodiment (a value having a small absolute value) is adopted as a predetermined developing condition.

  As described above, in the second embodiment, it is possible to maintain good image quality even when the environmental condition varies.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Embodiment 3
FIG. 19 shows a third embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the third embodiment, the image quality mode desired by the user is shown. And a second changing unit that changes at least one of the predetermined image forming condition or the predetermined time based on the image quality mode selected by the selecting unit. It is configured.

  That is, in the third embodiment, as shown in FIG. 19, a user interface 300 is provided as a selection means for selecting the image quality mode desired by the user. By selecting one of the priority modes, the control circuit 100 functions as a second changing unit that changes the content of the operation to be executed according to either the image quality priority mode or the productivity priority mode selected by the user. Is configured to do.

  In the control circuit 100, as shown in FIG. 19, when the user selects the image quality priority mode by the user interface 300, the setting value for determining whether or not the cumulative driving time of the developing device exceeds the set value. The value is changed to a time shorter than that in the first embodiment, and the recovery operation is executed relatively frequently.

  In the control circuit 100, simultaneously with the change of the setting value described above, the time for forming the toner band as the recovery operation is set to be relatively long, and sufficient recovery operation is executed to maintain good image quality. It is supposed to be.

  On the other hand, in the control circuit 100, as shown in FIG. 19, when the user selects the productivity priority mode by the user interface 300, it is determined whether or not the cumulative driving time of the developing device exceeds the set value. The installation value is changed to a time longer than that in the first embodiment, and the number of times of executing the recovery operation is relatively reduced.

  On the other hand, in the control circuit 100, simultaneously with the change of the setting value described above, the time for forming the toner band as the recovery operation is set to be relatively short, the recovery operation is reduced, and the image quality is kept good to some extent. However, it has come to satisfy productivity.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

  In the above-described embodiment, an image forming apparatus including a plurality of image forming units that form images of different colors has been described. However, the present invention is not limited to this, and an image forming apparatus 1 Needless to say, the present invention can also be applied to an image forming apparatus having only one image forming unit or a so-called four-cycle image forming apparatus that sequentially forms images of different colors on one image carrier.

  13CT, 13Y, 13M, 13C, and 13K: Transparent toner, yellow (Y), magenta (M), cyan (C), and black (K) image forming units, 15CT, 15Y, 15M, 15C, and 15K: photoconductor Drum, 100: control circuit, 103: image density sensor, 175: toner density sensor.

Claims (5)

An image forming means for forming an image by making the electrostatic latent image on the image carrier visible by a developing means using a developer; and
Toner density detecting means for detecting the toner density in the developing means;
Image density detecting means for detecting the density of a toner image for image density detection formed by the image forming means;
Control means for controlling image forming conditions so that a predetermined image density is obtained by the image forming means based on the detection result of the toner density detecting means and the detection result of the image density detecting means;
The toner density toner density in the developing unit sensed by the sensing means is a predetermined concentration or more, and based on by that control to the control means, the image corresponding to the control state when the toner is deteriorated A recovery means for executing a recovery operation for recovering the image quality of the image formed by the image forming means when the image forming operation according to the forming condition is continued for a predetermined time or more ;
A selection means for selecting an image quality mode;
A second changing unit that changes at least one of an image forming condition corresponding to a control state when the toner is deteriorated or the predetermined time based on the image quality mode selected by the selecting unit . An image forming apparatus. Environmental detection means for detecting environmental conditions in which the image forming apparatus is installed;
2. The apparatus according to claim 1, further comprising: a first changing unit that changes the predetermined density and the predetermined image forming condition based on a detection result of the environment detection unit. Image forming apparatus. 3. The image according to claim 1, wherein the image forming condition controlled by the control unit is at least one of a developing condition of the developing unit of the image forming unit or a toner density in the developing unit. Forming equipment. 3. The image formation according to claim 1, wherein the image forming condition controlled by the control unit is a transfer bias of a transfer unit that transfers a toner image formed by the image forming unit. apparatus. The image forming apparatus according to claim 1, wherein the recovery operation executed by the recovery unit is a forced consumption operation for forcibly consuming the developer of the developing unit.

Images