JP5040604B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Some image forming apparatuses such as printers and copiers perform adjustments to stably maintain image quality. Such adjustment is typically for reproducing the density of an image as intended, and is called “setup” or “calibration”. In the case of a color image forming apparatus using a plurality of colors, it is also common to adjust the color misregistration (registration misalignment). Hereinafter, such adjustments are collectively referred to as “image quality adjustment”.

In an electrophotographic color image forming apparatus, a technique is known in which only necessary image quality adjustment is performed in order to suppress toner and power consumption and extend the life of the apparatus. For example, in an image forming apparatus that uses only black toner, only black image quality adjustment is performed and image quality adjustment for other colors is not performed (see Patent Documents 1 and 2). In such a case, the electrophotographic image forming apparatus may be configured such that some of the members relating to other colors are not operated at all depending on the configuration.
JP 2004-109321 A JP 2005-249873 A

However, if there is a color for which neither image formation nor image quality adjustment is performed for a long period of time, many inconveniences arise. For example, if only a specific color is used for a long period of time, when trying to use another color, the image quality of that color will be significantly reduced or the time required for adjusting the image quality of that color will be less than usual. May be longer. Further, since the adjustment amount itself by the image quality adjustment becomes large, there is a possibility that the target adjustment cannot be sufficiently performed. In addition, if there is a member that does not operate for a long period of time, an excessive load may be applied to a specific member, or dust may accumulate on a specific portion of the member.
The present invention has been made in view of such circumstances, and an object of the present invention is to suppress deterioration in image quality of other colors as compared with the conventional case when priority is given to the use of a specific color.

An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium using at least one of a first color and a second color different from the first color, and the first color A first priority mode that prioritizes use; a selection unit that selects either the second color or a second priority mode that prioritizes the use of the first and second colors; and the selection unit selects Image forming control means for operating the image forming means in accordance with the priority mode performed to execute image formation; a first adjustment mode for adjusting the image quality of the first color before, during or after image formation; Image quality adjustment control means for operating the image forming means to execute image quality adjustment according to either a second color or a second adjustment mode for adjusting the image quality of the first and second colors. adjustment control means, the image forming hands Recently, when the image has been formed using the second color, or the elapsed time since the image quality adjustment in the second adjustment mode has been performed is equal to or greater than a predetermined threshold, The image quality adjustment is executed in the second adjustment mode, and the threshold value when the first priority mode is selected is greater than the threshold value when the second priority mode is selected, and the selection When the first priority mode is selected by the means, the second image quality adjustment execution frequency in the second adjustment mode is not zero, and the second priority mode is selected in the second priority mode. The image quality adjustment is executed such that the image quality adjustment is performed less frequently than the adjustment mode of the image quality adjustment mode.

Alternatively, the image forming apparatus according to the present invention, an image forming means for forming an image on a recording medium using at least one of a second color different from the first color and the first color, the first A selection unit that selects one of a first priority mode that prioritizes use of a color, and a second priority mode that prioritizes use of the second color or the first and second colors; and the selection unit An image forming control unit that causes the image forming unit to operate in accordance with the priority mode selected by the image forming unit, and a first adjustment mode that performs image quality adjustment of the first color before, during, or during image formation. Image quality adjustment control means for operating the image forming means to execute image quality adjustment according to either the second color or the second adjustment mode for adjusting the image quality of the first and second colors, The image quality adjustment control means is A threshold value that determines the number of times that the image forming unit has recently formed an image using the second color or formed an image on the recording medium after performing image quality adjustment in the second adjustment mode. When the image quality adjustment in the second adjustment mode is executed in response to the above, the threshold value when the first priority mode is selected is the threshold value when the second priority mode is selected Ri Ah at larger than the threshold value, rather than the execution frequency of the image quality adjustment is 0 according to the first and the second adjustment mode when the priority mode has been selected in by said selecting means, and said second priority mode A configuration may be adopted in which image quality adjustment is executed so that the frequency of image quality adjustment in the second adjustment mode is lower than when the image is selected.

  In the image forming apparatus according to the present invention, the image forming unit includes a first member used for forming the first color image, and a first member used for forming the second color image. Different second members, and when the second priority mode is selected by the selecting means, the second member is set in the same state as the first member, and the second means is selected by the selecting means. When the first priority mode is selected, a configuration in which the second member is different from the first member may be employed.

  The image forming apparatus according to the present invention preferably has a configuration in which the first color is black or a configuration in which the second color is a so-called special color in a general configuration.

  According to the present invention, when priority is given to the use of a specific color, it is possible to suppress deterioration in image quality of other colors than before.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an electrophotographic image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 of the present embodiment includes a control unit 100, an image forming unit 200, a sensor unit 600, an operation unit 300, a communication unit 400, and a storage unit 500.

  The control unit 100 includes an arithmetic device such as a CPU (Central Processing Unit) and an ASIC (Application Specific Integrated Circuit) and a memory, and controls the operation of the image forming apparatus 10. The control unit 100 acquires image data from the communication unit 400 or the storage unit 500, executes appropriate image processing on the image data, and supplies the image data to the image forming unit 200. In addition, the control unit 100 acquires the current time or stores the past time, and at a predetermined timing based on these, the image forming unit 200 forms an image with an intended image quality. It has the function to control each part. In the present embodiment, the image data has a gradation value of 8 bits (256 gradations), and represents “white” (state in which no toner is present) when “0”, and so-called “255”. Assume that a solid image is represented.

  The image forming unit 200 forms an image corresponding to the supplied image data on a sheet. The image forming unit 200 forms an image by an electrophotographic process, and the electrophotographic process includes steps such as charging, exposure, development, transfer, and fixing. The image forming unit 200 of the present embodiment can use yellow (Y), magenta (M), cyan (C), and black (K) toners, and forms an image using at least one of these. . Further, the image forming unit 200 of the present embodiment forms an image with a two-component developer, that is, a developer in which a toner and a carrier are mixed. The sensor unit 600 includes a sensor that detects a state of image formation performed by the image forming unit 200, and supplies information indicating the detection result to the control unit 100.

  The operation unit 300 includes operation elements such as buttons, and supplies operation information representing the operation content to the control unit 100 in accordance with a user operation. This operation information includes information related to the priority mode described later. Note that the operation unit 300 may include a configuration in which an operation is received from a user by a touch panel display device instead of a specific button or the like. The communication unit 400 includes an interface for transmitting and receiving data to and from a communication device that is an external device, and acquires image data from the external device. Further, the communication unit 400 may acquire data corresponding to the operation information described above from an external device. The storage unit 500 includes a storage device such as an HDD (Hard Disk Drive) and stores image data.

  FIG. 2 is a diagram illustrating the configuration of the image forming unit 200 and the sensor unit 600. As shown in the figure, the image forming unit 200 includes photosensitive drums 210Y, 210M, 210C, and 210K, charging devices 220Y, 220M, 220C, and 220K, an exposure device 230, and developing devices 240Y, 240M, 240C, and 240K. An intermediate transfer belt 250, a plurality of rotating rolls 251, primary transfer rolls 260Y, 260M, 260C, and 260K, a secondary transfer roll 270, a backup roll 271, a plurality of transport rolls 280, and a fixing device 290. Is provided.

  Of the reference numerals of the image forming unit 200, those with an alphabet (Y, M, C, or K) at the end indicate a part related to image formation of a color corresponding to the alphabet. For example, the photosensitive drum 210Y, the charging device 220Y, and the developing device 240Y form a yellow toner image in cooperation with the exposure device 230, the intermediate transfer belt 250, and the like. In addition, each reference numeral that is different only in the alphabet at the end represents the same basic configuration although the position and toner used are different. Therefore, when it is not necessary to particularly distinguish each of the configurations, description of alphabets at the end of the reference numerals such as “photosensitive drum 210” and “charging device 220” is omitted.

  The photosensitive drum 210 is a cylindrical member having a photoconductive film laminated on the surface. When the photosensitive drum 210 is in contact with the intermediate transfer belt 250, the photosensitive drum 210 is rotated in the direction of arrow A in FIG. The charging device 220 charges the photoconductive film of the photosensitive drum 210 to a predetermined potential. The exposure device 230 controls the exposure amount by the control unit 100, and irradiates light (that is, exposure) to the photosensitive drum 210 charged to a predetermined potential to form an electrostatic latent image corresponding to the exposure light. Here, the exposure amount refers to the amount of light per unit time or unit area when the exposure apparatus 230 performs exposure. The developing device 240 includes means for supplying toner, and visualizes (that is, develops) the electrostatic latent image formed on the photosensitive drum 210 with the toner. The developing device 240 generates a predetermined potential difference with the photosensitive drum 210, and moves the charged toner to the surface of the photosensitive drum 210 by this potential difference.

  The intermediate transfer belt 250 is an endless belt-like member, and moves so as to rotate in the direction of arrow B in the drawing while being in contact with the rotary roll 251, the primary transfer roll 260 and the backup roll 271. The rotary roll 251 is a cylindrical member that supports the movement of the intermediate transfer belt 250 and rotates around the center of the cylinder. The rotating roll 251 includes a rotating roll itself that is rotated by a driving unit and a rotating roll 251 that rotates as the intermediate transfer belt 250 moves. Further, the rotary roll 251 may have a function of adjusting the tension acting on the intermediate transfer belt 250. The primary transfer roll 260 is a cylindrical member that faces the photosensitive drum 210 with the intermediate transfer belt 250 interposed therebetween. A potential difference is generated between the primary transfer roll 260 and the toner on the surface of the photosensitive drum 210. Transfer to the surface of the belt 250. The secondary transfer roll 270 is a cylindrical member that faces the backup roll 271 with the intermediate transfer belt 250 interposed therebetween. A potential difference is generated between the secondary transfer roll 270 and the toner on the surface of the intermediate transfer belt 250 on the sheet surface. Transcript. The transport roll 280 is a cylindrical member that transports the paper to a position where the secondary transfer roll 270 performs transfer, and transports the paper onto which the toner has been transferred to the position where the fixing device 290 is provided. The fixing device 290 heats and pressurizes the sheet on which the toner is transferred, and fixes the toner on the sheet. That is, the paper transport path is as indicated by the broken arrow C in the figure.

  The primary transfer rolls 260 </ b> Y, 260 </ b> M, and 260 </ b> C of the present embodiment are configured to be able to contact and separate from the intermediate transfer belt 250. Further, the photosensitive drums 210Y, 210M, and 210C of the present embodiment are configured to be separated from the intermediate transfer belt 250 when the primary transfer rolls 260Y, 260M, and 260C are separated from the intermediate transfer belt 250, respectively. .

  FIG. 3 is a diagram illustrating a contact / separation state of the photosensitive drum 210 (210Y, 210M, or 210C) and the primary transfer roll 260 (260Y, 260M, or 260C). The photosensitive drum 210 and the primary transfer roll 260 are in contact with the intermediate transfer belt 250 as shown in FIG. 3A when image formation is performed. In addition, the photosensitive drum 210 and the primary transfer roll 260 are separated from the intermediate transfer belt 250 as shown in FIG. 3B when image formation is not performed. In the following, the former state is referred to as “contact state” and the latter state is referred to as “retract state”. Switching between the contact state and the retract state is performed by changing the position of at least one of the photosensitive drum 210 and the primary transfer roll 260. At this time, a part of the rotating roll 251 may be moved so as to change the tension acting on the intermediate transfer belt 250, so that the contact / separation state can be switched more easily.

  FIG. 4 is a diagram showing the configuration of the sensor unit 600 from the direction of the arrow D in FIG. As shown in FIG. 2, the sensor unit 600 is provided between the contact portion of the photosensitive drum 210 and the contact portion of the backup roll 271 in the track of the intermediate transfer belt 250. As shown in FIG. 4, the sensor unit 600 includes a density sensor 610 and color misregistration sensors 620 and 630.

  The density sensor 610 is an optical sensor facing the intermediate transfer belt 250, and detects an image formed on the intermediate transfer belt 250 by irradiating the intermediate transfer belt 250 with light and receiving the reflected light. The color misregistration sensors 620 and 630 are sensors provided near both ends of the intermediate transfer belt 250, respectively. The color misregistration sensors 620 and 630 are optical sensors similar to the density sensor 610, but use of detection results is different. The density sensor 610 is a sensor for detecting the density (optical density) of each image formed on the intermediate transfer belt 250, and the color shift sensors 620 and 630 are the shifts of the images formed on the intermediate transfer belt 250. It is a sensor for detecting. The image read by the sensor unit 600 will be described later.

  The configuration of the image forming apparatus 10 is as described above. Under this configuration, the image forming apparatus 10 forms an image corresponding to the image data on a sheet. The image forming apparatus 10 according to the present embodiment is configured to be able to execute image formation with a single black color and image formation with a full color using all colors. Which image formation is performed by the image forming apparatus 10 is determined based on image data. In other words, the image data of the present embodiment is data that can identify whether the image data is formed in single color or full color. However, the configuration may be such that the user can select whether to form an image in single color or full color.

  Further, the image forming apparatus 10 operates according to the determined priority mode. Here, the priority mode is a mode for determining whether to give priority to single color or full color in image formation. Information indicating the priority mode is stored in the memory of the control unit 100. The control unit 100 reads the contents of the memory when the operation is started by turning on the power or the like, determines the priority mode, and selects which priority mode the image forming unit 200 is to operate. In addition, the control unit 100 can change the priority mode at an arbitrary timing according to a user operation or the like. When the priority mode is changed, the control unit 100 rewrites information indicating the priority mode stored in the memory.

  There are two types of priority modes in the present embodiment: “monochrome priority mode” and “color priority mode”. The monochrome priority mode is a priority mode that prioritizes image formation with a single black color, and the color priority mode is a priority mode that prioritizes image formation with a full color.

  In the monochrome priority mode, the control unit 100 of the image forming apparatus 10 causes the photosensitive drums 210Y, 210M, and 210C and the primary transfer rolls 260Y, 260M, and 260C to be retracted. By doing so, the image forming apparatus 10 is in a state in which yellow, magenta, and cyan image formation cannot be performed. Further, the photosensitive drum 210 is stopped from rotating by being separated from the intermediate transfer belt 250, and the surface wear is suppressed as compared with the case where the photosensitive drum 210 is always rotating. Even in the black and white priority mode, all of the photosensitive drum 210 and the primary transfer roll 260 are in contact with each other when performing full color image quality adjustment, which will be described later.

  On the other hand, in the color priority mode, the control unit 100 brings all of the photosensitive drum 210 and the primary transfer roll 260 into contact. By doing so, the image forming apparatus 10 can be in a state in which color image formation can be performed more quickly than in the case where the photosensitive drum 210 and the primary transfer roll 260 are in the retracted state.

  Further, the image forming apparatus 10 according to the present embodiment performs image quality adjustment at an appropriate timing regardless of which priority mode is selected. There are two types of image quality adjustment executed in the present embodiment: density adjustment and color misregistration adjustment. In the density adjustment, an image having a predetermined density formed by the image forming unit 200 is detected by the density sensor 610, and when the detected density and the intended density (determined density) do not match, these are matched. In addition, the charging potential of the photosensitive drum 210 and the exposure amount of the exposure device 230 are corrected. The color misregistration adjustment is performed when an image having a predetermined shape formed by the image forming unit 200 is detected by the color misregistration sensors 620 and 630, and the detected shape does not match the intended shape (determined density). The timing of image formation for each color is corrected so that they match. There are two types of density adjustment, one for adjusting only black and the other for adjusting all colors of toner. On the other hand, the color misregistration is adjusted only for all the colors of the toner.

FIG. 5 is a diagram illustrating an image formed on the intermediate transfer belt 250 when image quality adjustment is performed. FIG. 5A shows an image used for full-color image quality adjustment, and FIG. 5B shows an image used for black image quality adjustment. In FIG. 5A, images formed in the vicinity of both ends of the intermediate transfer belt 250 are images for color misregistration adjustment, and are formed at positions that can be read by the color misregistration sensors 620 and 630. Each of the images I1, I2, I3, and I4 includes a plurality of straight lines that use yellow, magenta, cyan, and black in a single color, and the straight lines having different colors are formed at equal intervals and in parallel. It is an image. That is, when the straight lines that are the detection results of the images I1, I2, I3, and I4 are not equally spaced or parallel, it indicates that a color shift has occurred.
On the other hand, the image formed near the center of the intermediate transfer belt 250 is an image for density adjustment, and is formed at a position that can be read by the density sensor 610. Each of the images IY, IM, IC, and IK is an image that includes a plurality of rectangles each using a single color of yellow, magenta, cyan, or black, and is formed so that each rectangle has a predetermined density. That is, when the rectangles that are the detection results of the images IY, IM, IC, and IK are different from the determined density, it indicates that the image is not formed with the intended shading.

  On the other hand, the image used for monochrome image quality adjustment is only the image IK, as shown in FIG. In monochromatic image quality adjustment, images corresponding to the above-described images IY, IM, and IC are unnecessary. In addition, since there is no color shift in monochromatic image formation, images corresponding to the above-described images I1, I2, I3, and I4 are unnecessary. Therefore, the process for forming an image used for monochromatic image quality adjustment is completed in a shorter time than the process for forming an image used for full color image quality adjustment.

  The image forming apparatus 10 according to the present embodiment performs any of the image quality adjustments described above at a predetermined timing with a certain time as a reference. The control unit 100 of the image forming apparatus 10 operates the image forming unit 200 in one of an adjustment mode of a first adjustment mode for adjusting the image quality of a single color and a second adjustment mode for adjusting the image quality of a full color. The reference time point in image quality adjustment is, for example, when the power is turned on. At this time, the control unit 100 changes the image quality adjustment execution mode according to the selected priority mode. Specifically, the control unit 100 reduces the frequency of full color image quality adjustment executed in the monochrome priority mode to less than the frequency of full color image quality adjustment executed in the color priority mode. However, the control unit 100 does not execute full color image quality adjustment at all when the monochrome priority mode is selected for a long period of time.

  FIG. 6 is a flowchart illustrating processing when the control unit 100 of the image forming apparatus 10 executes image quality adjustment. As shown in the figure, first, the control unit 100 calculates a time (ΔT_FC) that has elapsed since the most recent full-color image formation (step S1). The control unit 100 calculates the above-described ΔT_FC by subtracting the time (PrevTime_FC) when image formation was performed in full color at the end (that is, immediately before) from the current time (NowTime). In order to realize this, the control unit 100 stores the time when image formation is performed in full color each time, and sets the latest one as PrevTime_FC. Next, the control unit 100 determines the selected priority mode (step S2), and executes different processing when the monochrome priority mode is selected and when the color priority mode is selected.

  When the color priority mode is selected (step S2: NO), the control unit 100 compares ΔT_FC with a predetermined threshold (T_FC), and determines whether ΔT_FC is equal to or greater than T_FC (step S3). Here, T_FC is a threshold value for determining whether or not to perform full color image quality adjustment in the color priority mode. When ΔT_FC is equal to or greater than T_FC (step S3: YES), the control unit 100 causes the image forming unit 200 to perform full color image quality adjustment (step S4). On the other hand, when ΔT_FC is less than T_FC (step S3: NO), the control unit 100 ends the process without executing any image quality adjustment.

  When the monochrome priority mode is selected (step S2: YES), the control unit 100 compares ΔT_FC with a predetermined threshold (T_BWFC) and determines whether ΔT_FC is equal to or greater than T_BWFC (step S5). Here, T_BWFC is a threshold value for determining whether or not to perform full color image quality adjustment in the monochrome priority mode. However, T_BWFC is larger than T_FC described above. When ΔT_FC is equal to or greater than T_BWFC (step S5: YES), the control unit 100 causes the image forming unit 200 to perform full color image quality adjustment (step S4). On the other hand, when ΔT_FC is less than T_BWFC (step S5: NO), the control unit 100 executes a process for determining whether or not to perform monochrome image quality adjustment.

  When ΔT_FC is less than T_BWFC, the control unit 100 calculates the time (ΔT_BW) that has elapsed since the most recent black monochrome image formation (step S6). The control unit 100 calculates the above-described ΔT_BW by subtracting the time (PrevTime_BW) when image formation was performed in a single color last (that is, immediately before) from the current time (NowTime). In order to realize this, the control unit 100 stores the time when image formation is performed in a single color each time, and sets the latest one as PrevTime_BW.

  Next, the control unit 100 compares ΔT_BW with a predetermined threshold value (T_BW) and determines whether ΔT_BW is equal to or greater than T_BW (step S7). Here, T_BW is a threshold value for determining whether or not to perform monochrome image quality adjustment in the monochrome priority mode. When T_BW is greater than or equal to T_BW (step S7: YES), the control unit 100 causes the image forming unit 200 to perform monochrome image quality adjustment (step S8). On the other hand, when ΔT_BW is less than T_BW (step S7: NO), the control unit 100 ends the process without executing any image quality adjustment.

  The processing executed by the control unit 100 when executing image quality adjustment is as described above. By this processing, the image forming apparatus 10 performs both single color image quality adjustment and full color image quality adjustment in the monochrome priority mode, and performs only full color image quality adjustment in the color priority mode. Further, the image forming apparatus 10 performs full-color image quality adjustment in the color priority mode more frequently than in the monochrome priority mode.

FIG. 7 is a diagram illustrating the execution timing of image quality adjustment in accordance with each priority mode. In this example, T_BW = T_FC, and this time is t. Further, it is assumed that T_BWFC is three times T_FC, that is, 3t. For convenience of explanation, it is assumed here that PrevTime_BW = PrevTime_FC.
According to this example, in the black and white priority mode, the image forming apparatus 10 executes image quality adjustment once every time t, and full-color image quality adjustment (FC in the figure) is performed once every three times. The other two times, monochrome image quality adjustment (BW in the figure) is executed. Further, in the color priority mode, the image forming apparatus 10 performs full color image quality adjustment once every time t. That is, according to this example, the image quality adjustment is performed at the same time interval in each priority mode, and the frequency of full-color image quality adjustment in the black and white priority mode is once for every three executions in the color priority mode. Done.

  As described above, the image forming apparatus 10 according to the present embodiment performs full-color image quality adjustment in the black and white priority mode less frequently than in the color priority mode. It is possible to suppress the use of toners of colors other than. An image forming apparatus often does not perform full-color image formation depending on the user's application. In such a user, black is used for actual image formation (forming an image other than an image for image quality adjustment). There are cases where almost no other color toner is used. In such a case, when image quality adjustment is performed without distinction as in the priority mode of the present embodiment, toner other than black is hardly used for actual image formation, except for black. In some cases, the toner of this color will soon disappear. On the other hand, according to the image forming apparatus 10 of the present embodiment, the full-color image quality adjustment is performed in the black and white priority mode at a longer time interval than in the color priority mode, so that the reduction in toner of colors other than black is reduced. Is possible.

  Further, in the image forming apparatus 10 of the present embodiment, even when the black and white priority mode, that is, the priority mode that prioritizes the use of black is selected, the full color image quality adjustment is not performed at all, but the color priority mode is set. It is appropriately executed with a lower frequency than the selected case. Therefore, even when only black single-color image formation is executed, the image quality of the other colors (yellow, magenta, and cyan) does not deteriorate significantly, and a constant quality is maintained. In addition, according to the image forming apparatus 10, even when the monochrome priority mode is selected and the photosensitive drum 210 and the primary transfer roll 260 that are not used are in a retracted state and stopped operating, the contact state is reached at an appropriate timing. Therefore, it is possible to suppress an excessive load on the photosensitive drum 210 and accumulation of dust at a specific location. That is, according to the image forming apparatus 10 of the present embodiment, priority is given to the use of a single black color, and even when it is frequently used, it is possible to suppress degradation in image quality of other colors.

[Modification]
The present invention is not limited to the above-described embodiment, and may be implemented in other forms. For example, the following modifications can be applied to the present invention. Note that the following modifications may be combined as appropriate.

(1) Modification 1
The above-described embodiment is an example when the “first color” in the present invention is black and the “second color” is other colors (at least one of yellow, magenta, and cyan). The present invention is also applicable to other color combinations. The present invention can also be applied to, for example, an image forming apparatus that uses a so-called spot color. Here, the special color means a color different from a normal color (generally, yellow, magenta, cyan, and black), and a color that cannot be reproduced using a normal color or difficult to reproduce. It is used when you want to reproduce colors. The special colors of the electrophotographic image forming apparatus include, for example, red, green, orange, fluorescent color, metallic color, white, clear (color reproduced using so-called transparent toner) and the like.

  FIG. 8 shows a configuration applicable to the present invention, and shows the configuration of an image forming unit that uses one special color in addition to four colors of yellow, magenta, cyan, and black. In the following, the same reference numerals as those in the above-described embodiment are used for the same configurations as those in the above-described embodiment.

  The image forming unit 200a in FIG. 8 is mainly different from the image forming unit 200 in FIG. 2 in that a photosensitive drum 210S, a charging device 220S, a developing device 240S, and a primary transfer roll 260S are provided. . Further, the image forming unit 200a has different configurations of the exposure device 230, the intermediate transfer belt 250, and the like according to the difference between the main differences. The photosensitive drum 210S, the charging device 220S, the developing device 240S, and the primary transfer roll 260S are all members used for spot color image formation. Note that an image forming apparatus according to this modification, that is, an image forming apparatus that includes the image forming unit 200a instead of the image forming unit 200 of the image forming apparatus 10 is hereinafter referred to as an “image forming apparatus 20”. It is distinguished from the image forming apparatus 10.

  The image forming apparatus 20 according to this modification operates by selecting either “normal priority mode” or “spot color priority mode” as the priority mode. The normal priority mode is a priority mode that prioritizes normal colors, that is, yellow, magenta, cyan, and black, over the spot color, and the spot color priority mode is a priority mode that prioritizes the combination of the normal color and the spot color. . In the normal priority mode, the image forming unit 200a places the photosensitive drum 210S and the primary transfer roll 260S in the retracted state, and does not allow image formation with a special color until an image needs to be formed with the special color.

  Further, the image forming apparatus 20 according to the present modification operates in either the “normal adjustment mode” or the “spot color adjustment mode” as the adjustment mode. The normal adjustment mode is an adjustment mode for executing image quality adjustment of only normal colors not including a spot color, and is the same as the “color adjustment mode” in the above-described embodiment. In the special color adjustment mode, image quality adjustment for both normal colors and special colors is performed.

  FIG. 9 is a diagram illustrating an image formed on the intermediate transfer belt 250 when image quality adjustment including a spot color is executed. The difference between the image shown in FIG. 5 and the image shown in FIG. 5A is that the images I1, I2, I3, and I4 for color misregistration adjustment also include straight lines of special colors, and density adjustment. The special image IS is also included in the image for this purpose.

  Based on the above configuration, the image forming apparatus 20 performs image quality adjustment at an appropriate timing. When the normal priority mode is selected, the image forming apparatus 20 executes the image quality adjustment including the spot color less frequently than when the spot color priority mode is selected. However, as in the above-described embodiment, the image forming apparatus 20 does not perform image quality adjustment including a spot color at all even when the normal priority mode is selected. That is, the execution frequency of image quality adjustment including a spot color when the normal priority mode is selected is not zero.

(2) Modification 2
The first color and the second color in the present invention are not limited to the example described above, and can be selected as appropriate. Further, each of the first color and the second color may be one color, or may be regarded as a group of a plurality of colors. For example, when the amount of magenta toner used is larger than the amount of cyan and yellow toner used, the first color may be black and magenta, and the second color may be cyan and yellow.

(3) Modification 3
The criterion for executing image quality adjustment is not limited to the elapsed time since the image formation was executed. For example, in step S1 described above, instead of the time (ΔT_FC) that has elapsed since the last full color image formation was performed (ΔT_FC), the time that has elapsed since the last full color image adjustment was performed, The number of times image formation has been performed after the image formation is performed in step S1 and the number of sheets on which images have been formed after the full-color image formation has been recently performed are calculated and compared with a predetermined threshold value. Thus, it may be determined whether or not to perform full color image quality adjustment.
In addition, for example, it may be determined whether or not to perform full-color image quality adjustment using, for example, the number of rotations of the photosensitive drums 210 for each color, the amount of toner used for each color, or the like.

(4) Modification 4
The image quality adjustment in the present invention is not limited to the above-described density adjustment and color shift adjustment. For example, in the density adjustment, instead of reading the image formed on the intermediate transfer belt 250, the image formed on the paper may be read, or the potential of the exposed portion of the photosensitive drum 210 is measured. May be. Also, the image for color misregistration adjustment need not be a plurality of parallel straight lines, and an image having a predetermined shape may be formed with a plurality of colors, or an image such as a so-called registration mark (trim mark). May be.

  Further, the image quality adjustment in the present invention may be performed by only one of density adjustment and color misregistration adjustment, or may be performed by another adjustment different from both density adjustment and color misregistration adjustment. In short, various adjustments are included in the image quality adjustment according to the present invention as long as the adjustment is repeatedly performed to maintain the image quality at a certain level or improve the image quality.

(5) Modification 5
In the above-described embodiment, in the black and white priority mode (first priority mode), the photosensitive drums 210 other than black and the primary transfer roll 260 are in the retracted state, but the operation performed in the first priority mode is another operation. It is good. For example, an operation of separating a certain member in contact with the photosensitive drum 210 may be used. The member to be separated may be a part of the developing device 240 (developing roll), or may be a charging roll when the charging device 220 is a contact roller charging method. Further, when a cleaning member (such as a blade) for removing excess toner remaining on the photosensitive drum 210 is in contact, it may be separated.

(6) Modification 6
In the present invention, the image quality adjustment execution timing is not limited to when the power is turned on. For example, when the image forming apparatus can take a normal state and a state in which power consumption is suppressed more than the normal state (so-called sleep state or the like), the process shown in FIG. 6 is executed at the timing when the state is switched. May be. If the image formation is not hindered, the process shown in FIG. 6 may be executed at an arbitrary timing before or after the image formation. Further, depending on the configuration of the image forming apparatus, image quality adjustment can be performed simultaneously with image formation during image formation.

  FIG. 10 is a diagram showing a configuration for simultaneously executing image formation and image quality adjustment. In the figure, Ia indicates an image for one sheet formed according to image data, and Ib and Ic indicate images for image quality adjustment. As described above, if the width of the intermediate transfer belt 250 is sufficiently larger than the width of one sheet and an image for adjusting image quality can be formed on both ends of the image of one sheet, it corresponds to the image data. It is possible to form an image for adjusting image quality while executing image formation, and to adjust the image quality of the image formed thereafter.

(7) Modification 7
The image forming apparatus according to the present invention is not limited to the one described in the above-described embodiment as long as it is an electrophotographic system. The present invention may be applied to, for example, an image forming apparatus that does not use an intermediate transfer belt, or may be applied to a color image forming apparatus that uses different numbers of toner colors. Further, the recording medium on which an image is formed with toner is not limited to paper, and various materials and shapes capable of fixing toner can be used.

1 is a block diagram illustrating a configuration of an image forming apparatus according to the present invention. It is a figure which shows the structure of an image formation part and a sensor part. It is a figure which shows the contact / separation state of a photoconductive drum and a primary transfer roll. It is a figure which shows the structure of a sensor part. FIG. 6 is a diagram illustrating an image formed on an intermediate transfer belt when image quality adjustment is performed. 6 is a flowchart illustrating processing when the image forming apparatus executes image quality adjustment. It is a figure which illustrates the execution timing of image quality adjustment in the case of responding to each priority mode. It is a figure which shows the modification of an image formation part. FIG. 6 is a diagram illustrating an image formed on an intermediate transfer belt when image quality adjustment including a spot color is executed. It is a figure which shows the structure for performing image formation and image quality adjustment simultaneously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20 ... Image forming apparatus, 100 ... Control part, 200, 200a ... Image forming part, 210 ... Photosensitive drum, 220 ... Charging device, 230 ... Exposure apparatus, 240 ... Developing apparatus, 250 ... Intermediate transfer belt, 251 ... Rotating roll, 260 ... primary transfer roll, 270 ... secondary transfer roll, 271 ... backup roll, 280 ... transport roll, 290 ... fixing device, 300 ... operation unit, 400 ... communication unit, 500 ... storage unit, 600 ... sensor unit

Claims (2)

Image forming means for forming an image on a recording medium using at least one of a first color and a second color different from the first color;
Selection means for selecting one of the first priority mode that prioritizes use of the first color and the second priority mode that prioritizes use of the second color or the first and second colors; ,
Image formation control means for operating the image forming means according to the priority mode selected by the selection means to execute image formation;
Before, during or after image formation, a first adjustment mode for adjusting the image quality of the first color and a second adjustment mode for adjusting the image quality of the second color or the first and second colors. Image quality adjustment control means for operating the image forming means to perform image quality adjustment by any of the above,
The image quality adjustment control means includes
The elapsed time since the image forming unit recently formed an image using the second color or performed image quality adjustment in the second adjustment mode has exceeded a predetermined threshold. Triggered by the image quality adjustment in the second adjustment mode,
The threshold value when the first priority mode is selected is greater than the threshold value when the second priority mode is selected;
The execution frequency of image quality adjustment by the second adjustment mode when the first priority mode is selected by the selection means is not zero, and the second priority mode is selected. An image forming apparatus, wherein the image quality adjustment is executed so that the image quality adjustment is executed less frequently than in the second adjustment mode. Image forming means for forming an image on a recording medium using at least one of a first color and a second color different from the first color;
Selection means for selecting one of the first priority mode that prioritizes use of the first color and the second priority mode that prioritizes use of the second color or the first and second colors; ,
Image formation control means for operating the image forming means according to the priority mode selected by the selection means to execute image formation;
Before, during or after image formation, a first adjustment mode for adjusting the image quality of the first color and a second adjustment mode for adjusting the image quality of the second color or the first and second colors. Image quality adjustment control means for operating the image forming means to perform image quality adjustment by any of the above,
The image quality adjustment control means includes
The number of times the image forming unit has recently formed an image using the second color or formed an image on the recording medium after performing image quality adjustment in the second adjustment mode is determined. The image quality adjustment in the second adjustment mode is executed when the threshold value is exceeded,
The threshold value when the first priority mode is selected is greater than the threshold value when the second priority mode is selected;
The execution frequency of image quality adjustment by the second adjustment mode when the first priority mode is selected by the selection means is not zero, and the second priority mode is selected. An image forming apparatus, wherein the image quality adjustment is executed so that the image quality adjustment is executed less frequently than in the second adjustment mode.

Images