JP5040168B2 - Image forming apparatus and control method thereof - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer, and a control method thereof.

  In recent years, image forming apparatuses such as copiers and printers are required to adjust image quality with high accuracy as the image forming speed increases. A typical image quality adjustment is image density. In general, as a method for adjusting the image density, a method of changing a set value of a potential for determining a developing electric field, a method of changing a target value of a toner concentration (TC) in a developing device, an input image density and an output image There is a method of changing LUT (Look Up Table) data indicating density correlation (density conversion condition).

  Among these, with respect to a technique for adjusting the image density by changing LUT data, for example, a technique described in Patent Document 1 is known. In this prior art, the density of the input image is divided into three ranges (low density range, medium density range, and high density range), and the strength level can be set in seven levels from +3 to -3 in each density range. It has a configuration.

JP 2000-98801 A

  However, each of the above three density adjustment methods has advantages and disadvantages, and any method is used to adjust the image density, which has some disadvantages.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of adjusting an image density more appropriately than in the related art.

The image forming apparatus according to the present invention is obtained by charging a photosensitive member whose surface potential changes by exposure, exposing the photosensitive member to write an electrostatic latent image, and developing the electrostatic latent image with toner. Image forming unit for transferring the toner image to a recording medium, a first method, and a second method in which the response of density change is slower than in the first method and the image quality defect is smaller than in the first method. A density adjustment control unit that adjusts the density of the toner image by any one of the methods, and a reception unit that receives an instruction to adjust the image density, and the density adjustment control unit follows the adjustment instruction received by the reception unit. After adjusting the density of the toner image by the first method, based on the environment of the apparatus or the value of time-lapse information , the larger the degree of deterioration in image quality, the more the adjustment amount by the first method. Key Migration adjustment amount to shift is determined the transition adjustment amount to be greater, and wherein only the transition adjustment amount from the first method that shifts the adjustment to the second method.

  According to the image forming apparatus of the present invention, the image density can be adjusted by taking advantage of the first method and the second method. For this reason, it is possible to adjust the image density more appropriately than in the past.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration example of a full-color image forming apparatus to which the present invention is applied. The illustrated image forming apparatus forms a color or monochrome image on a recording medium according to an electrophotographic process. Here, as an example of the recording medium, an image is formed on a sheet (synonymous with a sheet) such as plain paper or coated paper. The image forming apparatus has a double-sided image forming function (double-sided printing function, double-sided copying function, etc.) for forming an image on both sides (first side and second side) of a sheet as a recording medium. Yellow (Y), The four-tandem machine configuration includes four image forming units 1, 2, 3, and 4 corresponding to magenta (M), cyan (C), and black (K) colors.

  Each of the image forming units 1, 2, 3, and 4 is configured using a photosensitive drum, a charger, an exposure device, a developing device, a transfer device, a drum cleaner, a static eliminator, and the like. The charger charges the surface of the photosensitive drum to a uniform potential level. The exposure device forms an electrostatic latent image on the surface of the photosensitive drum by exposing and scanning the surface of the photosensitive drum charged by the charger with a laser beam. The developing device develops the electrostatic latent image formed on the surface of the photosensitive drum into a toner image using a two-component developer composed of toner and carrier. The transfer device transfers (primary transfer) the toner image developed by the developing device to the intermediate transfer belt 5. The drum cleaner removes unnecessary toner remaining on the surface of the photosensitive drum without being transferred to the intermediate transfer belt 5. The static eliminator removes unnecessary charges on the surface of the photosensitive drum.

  The intermediate transfer belt 5 is an image carrier that carries a toner image transferred onto a sheet. The intermediate transfer belt 5 is an endless belt member and is stretched in a loop shape by a plurality of belt support rolls. In the middle of the loop of the intermediate transfer belt 5, in addition to the four image forming units 1, 2, 3, and 4 described above, a patch density sensor 6 and a transfer roll 7 are disposed. In the case where a toner image is directly transferred from a photosensitive drum to a sheet without using an intermediate transfer belt, the photosensitive drum serves as an image carrier.

  The patch density sensor 6 is disposed downstream of the final-stage image forming unit 4 in the rotation direction (traveling direction) of the intermediate transfer belt 5. The patch density sensor 6 detects the density of the toner patch formed on the intermediate transfer belt 5. The patch density sensor 6 is composed of, for example, a reflective optical sensor including a light emitting element and a light receiving element, and irradiates the surface of the intermediate transfer belt 5 with sensor light emitted from the light emitting element, and reflects light from the sensor (normal light). The density of the toner patch is detected by receiving the reflected light or diffuse reflected light) by the light receiving element. Incidentally, the toner patch is formed on the intermediate transfer belt 5 by using the respective image forming units 1, 2, 3, and 4 in order to appropriately control the density of the image finally output on the paper. It is a patch image.

  The transfer roll 7 is disposed downstream of the above-described patch density sensor 6 in the rotation direction of the intermediate transfer belt 5. The transfer roll 7 is for transferring (secondary transfer) the toner image carried on the intermediate transfer belt 5 to a sheet. The vacuum conveyance unit 8 conveys the sheet on which the toner image has been transferred by the transfer roll 7 to the fixing device 9 while being vacuum-sucked from the back side (the side opposite to the transfer surface of the toner image). The fixing device 9 fixes the toner image transferred onto the sheet by the transfer roll 7 on the sheet. In the fixing device 9, the sheet is conveyed while being nipped by a heating roll and a pressure belt (or a pressure roll) that is in pressure contact with the heating roll, so that a toner image is applied to the sheet by a heating action and a pressure action applied to the nip portion. It is the structure which fixes. Further, a release agent such as amine oil or silicone oil is applied to the heating roll of the fixing device 9.

  The plurality of paper trays 10, 11, 12, and 13 are for storing sheets of a predetermined size in a stacked state. The paper stored in each of the paper trays 10, 11, 12, and 13 is transported by a paper transport device having a plurality of transport rolls. Further, the sheets stored in the sheet trays 10, 11, 12, and 13 are supplied to the sheet conveying path by the corresponding sheet feeding mechanisms and are conveyed along the sheet conveying path by the sheet conveying apparatus. A paper aligning unit 14 is provided in the middle of the paper transport path. For example, the sheet aligning unit 14 performs skew correction for correcting the inclination of the sheet with respect to the sheet conveying direction, lead registration correction for correcting the positional deviation of the sheet in the sheet conveying direction (sub-scanning direction), and a direction orthogonal to the sheet conveying direction (main scanning). Direction misalignment of the paper in the direction of the paper, such as side registration correction that corrects the misalignment of the paper in the direction).

  On the other hand, on the paper discharge side of the fixing device 9, the paper transport path is branched into a transport path leading to the discharge tray 15 and a transport path leading to the reversing unit 16 and the re-transport unit 17. The discharge tray 15 is a tray for finally discharging a sheet on which an image is formed on one side or both sides. The reversing unit 16 is for reversing the paper on the paper transport path. The re-conveying unit 17 is for conveying the paper reversed by the reversing unit 16 toward the image transfer position again. A curl correction unit 18 is provided in the middle of the conveyance path leading to the discharge tray 15. The curl correction unit 18 corrects paper curl that occurs when the fixing device 9 fixes the toner image.

  In addition, an operation panel 19 serving as a UI (user interface) is provided on the upper portion of the image forming apparatus main body. The operation panel 19 corresponds to the “accepting means” in the present invention, and is configured using, for example, a display unit including a touch panel display and an operation unit having various operation buttons and keys. is there. The operation panel 19 is operated by the user in order to set the density of the output image, the number of output sheets, the number of output copies, the paper size, etc., and instruct the start of the image forming operation.

  Next, a procedure for forming an image on a sheet using the image forming apparatus having the above configuration will be described. First, when the user gives an instruction to start image formation on the operation panel 19 (pressing the star button), the photosensitive drums and the intermediate transfer belt 5 of the four image forming units 1, 2, 3, 4 start to rotate. At the same time, yellow, magenta, cyan, and black toner images are sequentially superimposed and transferred onto the intermediate transfer belt 5 by driving the image forming units 1, 2, 3, and 4. Incidentally, when a black and white image is formed on a sheet, only the black toner image is transferred onto the intermediate transfer belt 5 by the image forming unit 4. The toner image thus formed on the intermediate transfer belt 5 is sent to the image transfer position (position where the transfer roll 7 is disposed) by the rotation of the intermediate transfer belt 5.

  On the other hand, paper used for image formation is fed from a paper tray selected by the user on the operation panel 19 or a paper tray selected by an automatic tray selection function provided in the image forming apparatus. Therefore, for example, if the user selects the paper tray 11, the paper stored in the paper tray 11 is sent out to the paper transport path. The paper thus sent out to the paper transport path is sent to the image transfer position in a state where the positional alignment is corrected by the paper aligning unit 14. At this time, the sheet is fed in accordance with the timing at which the toner image reaches the image transfer position.

  At the image transfer position, the sheet is nipped by the intermediate transfer belt 5 and the transfer roll 7, and when passing through the nip position, the toner image on the intermediate transfer belt 5 is transferred to the first surface of the sheet. Thereafter, the sheet is fed into the fixing device 9 where the toner image is fixed and then discharged to the discharge tray 15 through the curl correction unit 18. Further, a sheet to be subjected to double-sided image formation processing (double-sided printing, double-sided copying, etc.) is sent again from the fixing unit 9 to the image transfer position through the reversing unit 16, the re-conveying unit 17, and the paper aligning unit 14, where After the toner image is transferred to the second surface, the paper is discharged to the discharge tray 15 through the fixing device 9 and the curl correction unit 18.

  FIG. 2 is a block diagram showing the configuration of the control system of the image forming apparatus according to the embodiment of the present invention. In the figure, the main control unit 21 includes a density adjustment control unit 22, a sensor control unit 23, a toner supply control unit 24, a memory control unit 25, an image formation control unit 26, and a panel control unit 27. Is. In addition to the above-described patch density sensor 6, fixing device 9, and operation panel 19, the main control unit 21 includes a toner density sensor (TC sensor) 28, a potential sensor 29, a memory 30, a toner supply motor 31, a charger 32, The exposure device 33, the developing device 34, and the transfer device 35 are electrically connected. Among these, the toner density sensor 28, the potential sensor 30, the toner replenishing motor 32, the charger 33, the exposure device 34, the developing device 35, and the transfer device 36 are individually provided for each of the image forming units 1, 2, 3, and 4 described above. It is provided.

  The density adjustment control unit 22 controls processing related to image density adjustment (image density adjustment processing). The image density described here refers to the density of an image transferred to a sheet from the intermediate transfer belt 5 serving as an image carrier (hereinafter also referred to as “image density on the sheet”). The image density can be adjusted by a plurality of different methods, and there are various methods for adjusting the image density, and three density adjustment methods are exemplified here.

  In the first density adjustment method, development is performed based on a potential difference between an exposure potential when an electrostatic latent image is formed on the photosensitive drum by the exposure device 32 and a development potential when the electrostatic latent image is developed by the development device 34. Since the strength of the electric field is determined, the image density is adjusted by changing the setting values of the exposure potential and the development bias potential. The advantage of the first density adjustment method is that the image density can be quickly adjusted by changing the potential setting. The disadvantages of the first density adjustment method are as follows. In other words, the range of potential that can be set appropriately changes depending on the environment in which the device is used (temperature, humidity, etc.) and deterioration of the photoreceptor over time (thickness reduction, etc.). There is a risk that image quality defects such as fogging and carrier outflow may occur, and depending on the set potential, the life of the photoreceptor may be shortened in the long run. Further, depending on the toner density in the developing device 34, there is a saturation point where the image density does not change any more even if the set potential is changed.

  As shown in FIG. 3, the second density adjustment method is such that the relationship between the input image density and the output image density is changed, for example, from the relationship shown by the solid line in the figure to the relationship shown by the two-dot chain line (on the low density side). This is a method of adjusting the image density by changing the LUT data so that the output density is low and the output density is high on the high density side. The advantages of the second density adjustment method are that the image density can be quickly adjusted by changing the data of the LUT, and that image quality deterioration such as toner fog or carrier outflow does not occur because the density adjustment is performed by image processing. The disadvantage of the second density adjustment method is that when the density of an image output on paper at an output image density of 100% (hereinafter also referred to as “maximum output density”) becomes lower than a desired density, the paper is further increased. Since the upper image density cannot be increased and the density change amount per 1% of the input image density changes depending on the state of the apparatus at that time, the image density gradually changes when the LUT of the same data is continuously used. The point is that

  The third density adjustment method is a method of adjusting the image density by changing the target value of the toner density (TC) so that the toner density level controlled in the developing device 34 is changed. The advantage of the third density adjustment method is that the density of the image formed on the sheet can be changed reliably. The disadvantage of the third density adjustment method is that when the toner density in the developing device is changed, it is necessary to supply or consume more toner. Therefore, after changing the target value of the toner density, In fact, it takes time until the toner density in the developing device 34 is adjusted to the target density.

  These three density adjustment methods are relatively faster in response to output density change than in the first method, which is relatively fast in response to output density change, due to the difference in response (fast and slow) in output density change. The second method is slow. Responsiveness of the output density change is the length of operation time required for the density of the output image to change (up and down) to the target density after the density adjustment control unit 22 actually adjusts the image density (changes the adjustment parameter). It depends on the situation.

  The first method with relatively fast output density change responsiveness includes a first density adjustment method for changing the set value of the potential that determines the development electric field, and an LUT that indicates the correlation between the input image density and the output image density. A second density adjustment method for changing data is included. Further, the second method in which the response of the output density change is relatively slow includes a third density adjustment method for changing the target value of the toner density (TC) in the developing device. The adjustment of the image density by the density adjustment control unit 22 is appropriately adopted from the above three density adjustment methods.

  The sensor control unit 23 controls the patch density sensor 6, the toner density sensor 28, and the potential sensor 29 described above. The toner concentration sensor 28 detects the toner concentration (TC) in the developing device 34, more specifically, the toner mixing ratio of the two-component developer composed of toner and carrier (the mixing ratio of the toner with respect to the developer). . The potential sensor 29 detects the surface potential of the photosensitive drum.

  The toner supply control unit 24 controls the toner supply to the developing device 34 by driving the toner supply motor 31. More specifically, the toner replenishment control unit 24 drives the toner replenishment motor 31 so that the detected value of the toner density detected by the toner density sensor 28 coincides with the target toner density value 37, so that the per unit time. The toner replenishment amount is controlled. By such toner supply control, the toner density in the developing device 34 is kept constant at the target toner density.

  The memory control unit 25 reads and writes data (information) with respect to the memory 30. The memory 30 is configured using a nonvolatile memory such as an EPROM (Electrically Erasable Programmable Read-Only Memory). The memory 30 stores various control data relating to image formation, and includes a patch density target value 36, a toner density target value 38, a potential target value 38, and LUT data 39.

  The patch density target value 36 indicates a target patch density value when the toner density on the intermediate transfer belt 5 is controlled based on the density of the toner patch detected by the patch density sensor 6. The toner density target value 37 indicates a target toner density (TC) value when the toner supply control unit 24 controls toner supply based on the toner density detected by the toner density sensor 28. The potential target value 38 indicates a target photoreceptor potential value when the photoreceptor potential is controlled based on the surface potential of the photoreceptor drum detected by the potential sensor 29. The LUT data 39 indicates LUT data indicating the correlation between the input image density and the output image density.

  The image forming control unit 26 controls the image forming operation based on the electrophotographic process with the charging device 32, the exposure device 33, the developing device 34, the transfer device 35, and the fixing device 9 as control targets. The panel control unit 27 controls the operation panel 19, and more specifically controls input processing on the operation panel 19 and display processing on the operation panel 19.

  FIG. 4 is a flowchart showing a procedure of image density adjustment processing performed by the density adjustment control unit 22. First, an image density adjustment instruction is received by the operation panel 19 (step S1). For example, as shown in FIG. 5, an image density adjustment instruction displays an operation screen for image density adjustment on the display unit (touch panel) of the operation panel 19, and the user instructs a desired density level on the operation screen. It is done by doing. The operation screen is provided with a “density increase” button 41, a “density decrease” button 42, an “apply” button 43, an image density setting display section 44, and an “end adjustment” button 45. ing. An instruction to adjust the image density from the user is accepted by selecting (pressing) the “increase density” button 41 or the “decrease density” button 42 and then pressing the “apply” button 43. In this operation screen, each time the “increase density” button 41 or the “decrease density” button 42 is pressed once, the level of the image density setting display section 44 is +1 level or − Each level changes. The image density adjustment instruction may be performed collectively as an instruction common to each color of YMCK, or may be performed individually for each color. Further, the input image density range may be divided into a plurality of density ranges (for example, a high density range, a medium density range, and a low density range) and may be performed individually for each density range.

  When an image density adjustment instruction is received through the operation panel 19 in this way, the density adjustment control unit 22 determines whether or not it is necessary to increase the maximum image density in order to adjust the image density according to the adjustment instruction (step). S2). For example, if there is an adjustment instruction to further increase the density of the solid image after outputting a solid image having an output image density of 100% to the paper, it is determined that the maximum image density needs to be increased. Otherwise, it is determined that there is no need to increase the maximum image density. If it is determined that the maximum image density needs to be increased, the image density is adjusted by the first density adjustment method, that is, the method for changing the set value of the potential (step S3), and the maximum image density is increased. If it is determined that it is not necessary, the image density is adjusted by the second density adjustment method, that is, the method of changing the data of the LUT (step S4). Both the first density adjustment method and the second density adjustment method correspond to the “first method” in the present invention.

  Thereafter, when the user gives an instruction to adjust the image density again on the operation screen (see FIG. 5) (Yes in step S5), the process returns to step S1 and the same processing is repeated. Thereby, depending on the content of the image density adjustment instruction received in step S1, the image density is adjusted only by the first density adjustment method (step S3) or the second density adjustment method (step S4). The image density may be adjusted by both the first density adjustment method and the second density adjustment method.

  If the “end adjustment” button 45 is pressed by the user on the operation screen (Yes in step S6), the image density adjustment amount D determined at that time is detected (step S7). The image density adjustment amount D corresponds to the image density adjustment amount changed by changing the set value of the potential when the density adjustment according to the image density adjustment instruction is performed only in step S3. When the density adjustment is performed only in step S4 in accordance with the image density adjustment instruction, it corresponds to the image density adjustment amount changed by changing the LUT data, and is performed in both steps S3 and S4. If this is the case, the adjustment amount at each step is added. When an image density adjustment instruction is received during the image forming job, it may be determined that the image density adjustment is completed (Yes in step S6) when the image forming job is completed.

  Next, when the image density adjustment amount D detected earlier is transferred to the image density adjustment amount by the second method (third density adjustment method) at least a part of the adjustment amount is actually transferred. An adjustment amount (hereinafter referred to as “transition adjustment amount”) D ′ is determined (step S8). Shifting the image density adjustment amount means that if the image density adjustment amount adjusted by a certain method is D, at least a part D ′ of the adjustment amount is transferred to the image density adjustment amount by another method (sorting). ). In this case, the shift adjustment amount D ′ may be a part or all of the image density adjustment amount D detected in step S <b> 7.

  As an example, the image density adjustment instruction received on the operation panel 19 is an instruction to increase the image density setting by +3 level from the current state, and in accordance with the instruction, the first density adjustment method (the potential set value is changed). When the image density is adjusted to be increased by +3 level by the change method), for example, the +2 level image density adjustment is determined as the shift adjustment amount among the +3 level image density adjustments. Accordingly, the adjustment amount of +2 level image density is transferred (sorted) to the adjustment amount of the third density adjustment method (method of changing the target value of toner density). As a result, the image density adjustment by the first density adjustment method is reduced from the +3 level to the +1 level.

  In determining the shift adjustment amount D ′, it is desirable to change the shift adjustment amount D ′ in accordance with the environment (temperature, humidity, etc.) of the apparatus or time-lapse information. For example, considering the case where the environment of the apparatus is humidity, toner fog and carrier outflow are likely to occur when the humidity increases. Considering the case where the time information of the apparatus is the number of image forming cycles, the photosensitive film of the photosensitive drum gradually becomes thinner due to friction and wear as the number of image forming cycles increases. Then, even if the same potential is set, the developing electric field becomes strong, so that carriers can easily fly. In such a case, it is preferable to transfer the image density adjustment amount to the image density adjustment amount by the third density adjustment method as much as possible out of the image density adjustment amount by the first density adjustment method. It will be a thing.

  Subsequently, the number of transition processes N is set based on the transition adjustment amount D 'determined in step S8 (step S9). The transfer process is the adjustment of the image density by the first method (first density adjustment method, second density adjustment method), and the adjustment of the image density by the second method (third density adjustment method). This is the process performed to shift to. The number N of transfer processes is set to, for example, one time, three times, five times, seven times, or ten times depending on whether the shift adjustment amount D ′ is large or small. That is, when the transition adjustment amount D ′ is less than the first amount, the number of transition processes is set to one (N = 1), and the transition adjustment amount D ′ is greater than or equal to the first amount and less than the second amount. In this case, the number of migration processes is set to 3 (N = 3). When the shift adjustment amount D ′ is equal to or greater than the second amount and less than the third amount, the number of shift processes is set to 5 (N = 5), and the shift adjustment amount D ′ is equal to or greater than the third amount. In this case, the number of migration processes is set to 7 (N = 7).

  When the transition processing count N is set in this way, first, in order to shift the image density adjustment corresponding to D ′ / N to the image density adjustment by the second method, the third density adjustment method, that is, development. The image density is adjusted by an amount corresponding to D ′ / N by a method of changing the target value of the toner density (TC) in the container (step S10). The third density adjustment method corresponds to the “second method” in the present invention. Next, as the image density adjustment amount corresponding to D ′ / N is shifted, the first method is adapted so that the image density adjustment amount by the first method is reduced by the amount corresponding to D ′ / N. The adjusted image density adjustment parameters (potential setting value, LUT data) are corrected (step S11).

  Thereafter, the value of N is decremented by 1 (step S12). Next, it is confirmed whether or not the value of N has become 0 (zero), that is, whether or not the transition processing for the number of times set in step S9 has been completed (step S13), and when completed (when N = 0). A series of processing is finished as it is. If the set number of transition processes have not been completed (if N ≠ 0), the set number of transition processes are repeatedly executed while controlling the transition process interval in step S14. The transition process interval is an interval from the previous transition process to the current transition process.

  In step S14, it is determined whether or not it is time to execute the migration process. Specifically, for example, whether or not the elapsed time since the previous transition processing has reached a predetermined time, or whether or not the number of image formations processed since the previous transition processing has reached a predetermined number Alternatively, it is determined whether or not the execution timing of the transfer process has come, depending on whether or not the number of image forming jobs executed since the previous transfer process has reached a predetermined number. If it is determined in step S14 that the execution timing of the transition process has come (for example, if it is determined that the elapsed time since the previous transition process has reached a predetermined time, or after the previous transition process has been performed) If it is determined that the number of processed image forming sheets has reached a predetermined number, or if it is determined that the number of image forming jobs performed after the previous transition processing has reached a predetermined number of times), the process proceeds to step S10 again. . As a result, the transition process (the processes in steps S10 and S11) is repeated for the number N of times set in step S9.

  As described above, in the image forming apparatus according to the embodiment of the present invention, the first method (first density adjustment method, second density adjustment method) according to the image density adjustment instruction received from the user via the operation panel 19. After adjusting the image density, the control is performed so that at least a part of the image density adjustment by the first method is transferred to the image density adjustment by the second method (third density adjustment method). The image density can be adjusted by taking advantage of the first method and the second method.

  That is, by applying the first density adjustment method or the second density adjustment method, which has relatively fast response to the output density change, to the first method, the density can be immediately adjusted according to the image density adjustment instruction. A changed image (for example, a sample of density) can be output to a sheet. In addition, when the first density adjustment method (the method for changing the potential setting value) is applied to the first method to adjust the image density, there is a risk of image quality deterioration due to toner fog or carrier outflow. In this case, at least part of the image density adjustment by the first method (first density adjustment method) is transferred to the image density adjustment by the second method (third density adjustment method). While maintaining the image density as it is, the set value of the potential can be changed so that the image quality does not deteriorate. In addition, when the image density is adjusted by applying the second density adjustment method (method for changing LUT data) to the first method, the image density of the first method (second density adjustment method) is adjusted. By shifting at least a part of the adjustment to the image density adjustment by the second method (third density adjustment method), the image density output on the paper can be stabilized over a long period of time.

  As a result, the user does not know which adjustment parameter (potential setting value, LUT data, toner density target value) to change when adjusting the image density, and simply increases or decreases the image density from the current level. By simply instructing whether to do so, an image reflecting the instruction can be output on a sheet. Also, by adjusting the image density adjustment by the first method to the image density adjustment by the second method, the setting of the adjustment parameter can be optimized while maintaining the image density desired by the user. it can. For this reason, it is possible to set an image density adjustment parameter under conditions that the apparatus side considers optimal for the long term.

  In addition, the image density adjustment by the first method (first density adjustment method, second density adjustment method) is shifted to the image density adjustment by the second method (third density adjustment method). The transition adjustment amount can be appropriately set by changing the transition adjustment amount to be performed according to the environment (temperature, humidity, etc.) of the apparatus or time-dependent information (number of image forming cycles, etc.). Furthermore, by setting the number of migration processes based on this migration adjustment amount, if the migration adjustment amount is large, the migration process number is set accordingly, and if the migration adjustment amount is small, the migration process number is set accordingly. Can be set less. For this reason, it is possible to average the adjustment amount of the image density transferred in one transfer process or to limit the maximum adjustment amount.

  Further, by performing the transfer process in a plurality of times, the slowness of the response of the output density change, which is a disadvantage of the third density adjustment method, can be obtained by using the advantages of the first density adjustment method and the second density adjustment method. The amount of adjustment of the image density can be gradually shifted while compensating for the response speed of the output density change. Further, by controlling the transition processing interval based on the elapsed time from the previous transition processing, the number of image formations, or the number of image formation jobs, the transition processing interval can be adjusted appropriately.

  FIG. 6 is a flowchart showing a procedure of image density adjustment processing performed by the density adjustment control unit 22 when an image density adjustment instruction is received during an image forming job. First, when an image forming job is started, an image density adjustment instruction wait state is entered (step S21). When image formation is completed in this state (Yes in step S22), the image forming job is finished as it is. On the other hand, if an image density adjustment instruction is given by the user before the end of image formation, the adjustment instruction is accepted by the operation panel 19 (step S23). In this case, the presence / absence of an image density adjustment instruction may be determined based on whether the “apply” button 43 is pressed on the operation screen illustrated in FIG. The image density adjustment instruction may be accepted when the “apply” button 43 is pressed on the operation screen.

  When an image density adjustment instruction is actually received, the number of remaining sheets that have not been subjected to image formation at that time is confirmed, and whether or not the confirmed remaining number is equal to or greater than a predetermined number. Is determined (step S24). If the remaining number is less than the predetermined number, the image density is adjusted by the first method (first density adjustment method or second density adjustment method) (step S25). If the remaining number is equal to or greater than the predetermined number, the image density is adjusted by the second method (third density adjustment method) (step S26). Thereafter, the process returns to step S21.

  In step S24, if the remaining number is equal to or greater than the predetermined number, the image density is adjusted by the first method (the first density adjustment method or the second density adjustment method), and then the image density is set. It is also possible to control so that at least a part of the adjustment is transferred to the adjustment of the image density by the second method (third density adjustment method).

  Specifically, when the remaining number is equal to or greater than the predetermined number in step S24, first, for example, as shown in FIG. 7, first method (first density adjustment method or second density adjustment method). To adjust the image density (step S27). Next, part or all of the image density adjustment by the first method is determined as the shift adjustment amount (step S28). Next, the image density is adjusted by the second method (third density adjustment method) according to the shift adjustment amount (step S29). Next, the image density adjustment parameter corresponding to the first method is corrected so that the image density adjustment amount by the first method is reduced by the amount shifted to the second method (step S30). Thereafter, the process returns to step S21. Also in this case, similarly to the processing flow of FIG. 4 described above, it is possible to set the number of migration processes based on the migration adjustment amount, or to perform the migration process in multiple steps.

  Thus, when an image density adjustment instruction is received on the operation panel 19 during an image forming job, the image is determined depending on whether or not the remaining number of images that have not been formed in the image forming job currently being processed is equal to or greater than a predetermined number. By changing the density adjustment method, the image density adjustment method can be appropriately switched depending on whether the number of remaining sheets is large or small.

  That is, when the remaining number is small, the density is changed immediately according to the image density adjustment instruction by adjusting the image density by applying the first method that is relatively responsive to the output density change. Images can be output on paper. Further, when the remaining number is large, the image density is adjusted by the second method in which the response of the output density change is relatively slow, so that the image density does not deteriorate due to the fogging of the toner or the outflow of the carrier. The image density on the paper can be changed reliably according to the adjustment instruction.

  If the remaining number is sufficient, first, the image density is adjusted by the first method, and then the image density adjustment by the first method is shifted to the image density adjustment by the second method. As a result, the adjustment parameter setting can be optimized while maintaining the image density desired by the user until the image forming job is completed.

  In the above-described embodiment, the tandem image forming apparatus including a plurality of image forming units has been described as an example. However, the present invention is not limited thereto, and the single drum image forming apparatus including one image forming unit is used. The same applies to the apparatus. In the above embodiment, the intermediate transfer method using the intermediate transfer member (intermediate transfer belt 5) has been described as an example. However, the present invention is not limited to this, and an image (toner image) is directly transferred from the photosensitive member to the sheet. It can also be applied to a direct transfer system. Furthermore, as a method for adjusting the image density, a method other than the first density adjustment method, the second density adjustment method, and the third density adjustment method described above can be applied.

1 is a schematic diagram illustrating a configuration example of a full-color image forming apparatus to which the present invention is applied. FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus according to the embodiment of the present invention. It is a figure which shows the correlation of input image density and output image density. It is a flowchart which shows the procedure of an image density adjustment process. It is a figure which shows an example of the operation screen for image density adjustment. 6 is a flowchart illustrating a procedure of image density adjustment processing during an image forming job. 12 is a flowchart illustrating another procedure of image density adjustment processing during an image forming job.

Explanation of symbols

  1, 2, 3, 4 ... Image forming unit, 5 ... Intermediate transfer belt, 6 ... Patch density sensor, 7 ... Transfer roll, 19 ... Operation panel, 22 ... Density adjustment controller

Claims (7)

The photosensitive member whose surface potential is changed by exposure is charged, the photosensitive member is exposed to write an electrostatic latent image, and the electrostatic latent image is developed with toner, and the toner image obtained is transferred to a recording medium. An image forming unit;
The density of the toner image is adjusted by either the first method or the second method, which has a slower response to density change than the first method and has fewer image quality defects than the first method. Density adjustment control means;
Receiving means for receiving an image density adjustment instruction,
The density adjustment control means adjusts the density of the toner image by the first method in accordance with the adjustment instruction received by the receiving means, and then determines the degree of deterioration in image quality based on the environment of the apparatus or the value of time-lapse information. The shift adjustment amount is determined so that the shift adjustment amount to be shifted to the adjustment by the second method out of the adjustment amount by the first method is larger, and the first method is determined by the shift adjustment amount. The image forming apparatus is characterized in that the adjustment is shifted from the first method to the second method. 2. The image according to claim 1, wherein the density adjustment control unit executes a transition process for shifting the adjustment from the first method to the second method by the shift adjustment amount in a plurality of times. Forming equipment. The density adjustment control unit determines the number of times of the transfer process so that the number of times of the shift adjustment increases as the shift adjustment amount increases, and executes the shift process by an adjustment amount obtained by dividing the shift adjustment amount by the number of times. The image forming apparatus according to claim 2. The density adjustment control unit controls the interval of the transition process based on an elapsed time from the previous transition process, the number of image formations, or the number of image formation jobs. The image forming apparatus described. When the density adjustment control unit receives an adjustment instruction from the reception unit during execution of an image forming job and the remaining number of images that have not been formed in the image forming job is less than a predetermined number, The image forming apparatus according to claim 1, wherein the density of the toner image is adjusted by a first method. When the density adjustment control unit receives an adjustment instruction from the reception unit during execution of an image forming job, and the remaining number of images that have not been formed in the image forming job is equal to or greater than a predetermined number, The adjustment is shifted from the first method to the second method by the shift adjustment amount after adjusting the density of the toner image by the first method. The image forming apparatus described. The photosensitive member whose surface potential is changed by exposure is charged, the photosensitive member is exposed to write an electrostatic latent image, and the electrostatic latent image is developed with toner, and the toner image obtained is transferred to a recording medium. When an image density adjustment instruction is received in an image forming apparatus having an image forming unit, after adjusting the density of the toner image by the first method, the image quality is determined based on the environment of the apparatus or the value of time-lapse information . As the degree of decrease is larger, among the adjustment amounts by the first method, the adjustment by the second method is slower in response to density change than the first method and has fewer image quality defects than the first method. Control of the image forming apparatus, wherein the shift adjustment amount is determined so that the shift adjustment amount to be transferred is increased, and the adjustment is shifted from the first method to the second method by the shift adjustment amount. Method.

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